draft-ietf-nfsv4-minorversion1-PAv8.txt   2009-12-17-2-TO-rfc5661.txt 
NFSv4 S. Shepler Network Working Group S. Shepler, Ed.
Internet-Draft M. Eisler Request for Comments: 5661 Storspeed, Inc.
Intended status: Standards Track D. Noveck Category: Standards Track M. Eisler, Ed.
Expires: June 9, 2010 Editors D. Noveck, Ed.
December 06, 2009 NetApp
October 2009
NFS Version 4 Minor Version 1
draft-ietf-nfsv4-minorversion1-PAv8.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Network File System (NFS) Version 4 Minor Version 1 Protocol
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Abstract
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at This document describes the Network File System (NFS) version 4 minor
http://www.ietf.org/ietf/1id-abstracts.txt. version 1, including features retained from the base protocol (NFS
version 4 minor version 0, which is specified in RFC 3530) and
protocol extensions made subsequently. Major extensions introduced
in NFS version 4 minor version 1 include Sessions, Directory
Delegations, and parallel NFS (pNFS). NFS version 4 minor version 1
has no dependencies on NFS version 4 minor version 0, and it is
considered a separate protocol. Thus, this document neither updates
nor obsoletes RFC 3530. NFS minor version 1 is deemed superior to
NFS minor version 0 with no loss of functionality, and its use is
preferred over version 0. Both NFS minor versions 0 and 1 can be
used simultaneously on the same network, between the same client and
server.
The list of Internet-Draft Shadow Directories can be accessed at Status of This Memo
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on June 9, 2010. This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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described in the BSD License.
This document describes NFS version 4 minor version one, including
features retained from the base protocol (NFS version 4 minor version
zero which is specified in RFC3530) and protocol extensions made
subsequently. Major extensions introduced in NFS version 4 minor
version one include: Sessions, Directory Delegations, and parallel
NFS (pNFS). NFS version 4 minor version one has no dependencies on
NFS version 4 minor version zero, and is considered a separate
protocol. Thus this document neither updates nor obsoletes RFC3530.
NFS minor version one is deemed superior to NFS minor version zero
with no loss of functionality, and its use is preferred over version
zero. Both NFS minor version zero and one can be used simultaneously
on the same network, between the same client and server.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1].
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 11
1.1. The NFS Version 4 Minor Version 1 Protocol . . . . . . . 12 1.1. The NFS Version 4 Minor Version 1 Protocol . . . . . . . 11
1.2. Scope of this Document . . . . . . . . . . . . . . . . . 12 1.2. Requirements Language . . . . . . . . . . . . . . . . . 11
1.3. NFSv4 Goals . . . . . . . . . . . . . . . . . . . . . . 12 1.3. Scope of This Document . . . . . . . . . . . . . . . . . 11
1.4. NFSv4.1 Goals . . . . . . . . . . . . . . . . . . . . . 13 1.4. NFSv4 Goals . . . . . . . . . . . . . . . . . . . . . . 11
1.5. General Definitions . . . . . . . . . . . . . . . . . . 13 1.5. NFSv4.1 Goals . . . . . . . . . . . . . . . . . . . . . 12
1.6. Overview of NFSv4.1 Features . . . . . . . . . . . . . . 16 1.6. General Definitions . . . . . . . . . . . . . . . . . . 13
1.6.1. RPC and Security . . . . . . . . . . . . . . . . . . 16 1.7. Overview of NFSv4.1 Features . . . . . . . . . . . . . . 15
1.6.2. Protocol Structure . . . . . . . . . . . . . . . . . 17 1.7.1. RPC and Security . . . . . . . . . . . . . . . . . . 15
1.6.3. File System Model . . . . . . . . . . . . . . . . . 17 1.7.2. Protocol Structure . . . . . . . . . . . . . . . . . 16
1.6.4. Locking Facilities . . . . . . . . . . . . . . . . . 19 1.7.3. File System Model . . . . . . . . . . . . . . . . . 16
1.7. Differences from NFSv4.0 . . . . . . . . . . . . . . . . 20 1.7.4. Locking Facilities . . . . . . . . . . . . . . . . . 18
2. Core Infrastructure . . . . . . . . . . . . . . . . . . . . . 21 1.8. Differences from NFSv4.0 . . . . . . . . . . . . . . . . 19
2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 21 2. Core Infrastructure . . . . . . . . . . . . . . . . . . . . . 20
2.2. RPC and XDR . . . . . . . . . . . . . . . . . . . . . . 21 2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 20
2.2.1. RPC-based Security . . . . . . . . . . . . . . . . . 21 2.2. RPC and XDR . . . . . . . . . . . . . . . . . . . . . . 20
2.3. COMPOUND and CB_COMPOUND . . . . . . . . . . . . . . . . 24 2.2.1. RPC-Based Security . . . . . . . . . . . . . . . . . 20
2.4. Client Identifiers and Client Owners . . . . . . . . . . 25 2.3. COMPOUND and CB_COMPOUND . . . . . . . . . . . . . . . . 23
2.4.1. Upgrade from NFSv4.0 to NFSv4.1 . . . . . . . . . . 29 2.4. Client Identifiers and Client Owners . . . . . . . . . . 24
2.4.2. Server Release of Client ID . . . . . . . . . . . . 29 2.4.1. Upgrade from NFSv4.0 to NFSv4.1 . . . . . . . . . . 28
2.4.3. Resolving Client Owner Conflicts . . . . . . . . . . 30 2.4.2. Server Release of Client ID . . . . . . . . . . . . 28
2.5. Server Owners . . . . . . . . . . . . . . . . . . . . . 31 2.4.3. Resolving Client Owner Conflicts . . . . . . . . . . 29
2.6. Security Service Negotiation . . . . . . . . . . . . . . 31 2.5. Server Owners . . . . . . . . . . . . . . . . . . . . . 30
2.6.1. NFSv4.1 Security Tuples . . . . . . . . . . . . . . 32 2.6. Security Service Negotiation . . . . . . . . . . . . . . 30
2.6.2. SECINFO and SECINFO_NO_NAME . . . . . . . . . . . . 32 2.6.1. NFSv4.1 Security Tuples . . . . . . . . . . . . . . 31
2.6.3. Security Error . . . . . . . . . . . . . . . . . . . 32 2.6.2. SECINFO and SECINFO_NO_NAME . . . . . . . . . . . . 31
2.7. Minor Versioning . . . . . . . . . . . . . . . . . . . . 37 2.6.3. Security Error . . . . . . . . . . . . . . . . . . . 31
2.8. Non-RPC-based Security Services . . . . . . . . . . . . 39 2.7. Minor Versioning . . . . . . . . . . . . . . . . . . . . 36
2.8.1. Authorization . . . . . . . . . . . . . . . . . . . 39 2.8. Non-RPC-Based Security Services . . . . . . . . . . . . 38
2.8.2. Auditing . . . . . . . . . . . . . . . . . . . . . . 39 2.8.1. Authorization . . . . . . . . . . . . . . . . . . . 38
2.8.3. Intrusion Detection . . . . . . . . . . . . . . . . 40 2.8.2. Auditing . . . . . . . . . . . . . . . . . . . . . . 38
2.9. Transport Layers . . . . . . . . . . . . . . . . . . . . 40 2.8.3. Intrusion Detection . . . . . . . . . . . . . . . . 39
2.9.1. REQUIRED and RECOMMENDED Properties of Transports . 40 2.9. Transport Layers . . . . . . . . . . . . . . . . . . . . 39
2.9.2. Client and Server Transport Behavior . . . . . . . . 41 2.9.1. REQUIRED and RECOMMENDED Properties of Transports . 39
2.9.3. Ports . . . . . . . . . . . . . . . . . . . . . . . 42 2.9.2. Client and Server Transport Behavior . . . . . . . . 40
2.10. Session . . . . . . . . . . . . . . . . . . . . . . . . 42 2.9.3. Ports . . . . . . . . . . . . . . . . . . . . . . . 41
2.10.1. Motivation and Overview . . . . . . . . . . . . . . 42 2.10. Session . . . . . . . . . . . . . . . . . . . . . . . . 41
2.10.2. NFSv4 Integration . . . . . . . . . . . . . . . . . 44 2.10.1. Motivation and Overview . . . . . . . . . . . . . . 41
2.10.3. Channels . . . . . . . . . . . . . . . . . . . . . . 45 2.10.2. NFSv4 Integration . . . . . . . . . . . . . . . . . 43
2.10.4. Server Scope . . . . . . . . . . . . . . . . . . . . 46 2.10.3. Channels . . . . . . . . . . . . . . . . . . . . . . 44
2.10.5. Trunking . . . . . . . . . . . . . . . . . . . . . . 49 2.10.4. Server Scope . . . . . . . . . . . . . . . . . . . . 45
2.10.6. Exactly Once Semantics . . . . . . . . . . . . . . . 52 2.10.5. Trunking . . . . . . . . . . . . . . . . . . . . . . 48
2.10.7. RDMA Considerations . . . . . . . . . . . . . . . . 67 2.10.6. Exactly Once Semantics . . . . . . . . . . . . . . . 51
2.10.8. Sessions Security . . . . . . . . . . . . . . . . . 70 2.10.7. RDMA Considerations . . . . . . . . . . . . . . . . 66
2.10.9. The Secret State Verifier (SSV) GSS Mechanism . . . 75 2.10.8. Session Security . . . . . . . . . . . . . . . . . . 69
2.10.10. Security Considerations for RPCSEC_GSS when using 2.10.9. The Secret State Verifier (SSV) GSS Mechanism . . . 74
the SSV Mechanism . . . . . . . . . . . . . . . . . 79 2.10.10. Security Considerations for RPCSEC_GSS When Using
2.10.11. Session Mechanics - Steady State . . . . . . . . . . 81 the SSV Mechanism . . . . . . . . . . . . . . . . . 78
2.10.12. Session Inactivity Timer . . . . . . . . . . . . . . 82 2.10.11. Session Mechanics - Steady State . . . . . . . . . . 80
2.10.13. Session Mechanics - Recovery . . . . . . . . . . . . 83 2.10.12. Session Inactivity Timer . . . . . . . . . . . . . . 81
2.10.14. Parallel NFS and Sessions . . . . . . . . . . . . . 88 2.10.13. Session Mechanics - Recovery . . . . . . . . . . . . 82
3. Protocol Constants and Data Types . . . . . . . . . . . . . . 88 2.10.14. Parallel NFS and Sessions . . . . . . . . . . . . . 87
3.1. Basic Constants . . . . . . . . . . . . . . . . . . . . 88 3. Protocol Constants and Data Types . . . . . . . . . . . . . . 87
3.2. Basic Data Types . . . . . . . . . . . . . . . . . . . . 89 3.1. Basic Constants . . . . . . . . . . . . . . . . . . . . 87
3.3. Structured Data Types . . . . . . . . . . . . . . . . . 91 3.2. Basic Data Types . . . . . . . . . . . . . . . . . . . . 88
4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . . . 99 3.3. Structured Data Types . . . . . . . . . . . . . . . . . 90
4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . . . 98
4.1. Obtaining the First Filehandle . . . . . . . . . . . . . 99 4.1. Obtaining the First Filehandle . . . . . . . . . . . . . 99
4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . 99 4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . 99
4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . 100 4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . 99
4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . 100 4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . 100
4.2.1. General Properties of a Filehandle . . . . . . . . . 101 4.2.1. General Properties of a Filehandle . . . . . . . . . 100
4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . 101 4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . 101
4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . 102 4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . 101
4.3. One Method of Constructing a Volatile Filehandle . . . . 103 4.3. One Method of Constructing a Volatile Filehandle . . . . 102
4.4. Client Recovery from Filehandle Expiration . . . . . . . 103 4.4. Client Recovery from Filehandle Expiration . . . . . . . 103
5. File Attributes . . . . . . . . . . . . . . . . . . . . . . . 104 5. File Attributes . . . . . . . . . . . . . . . . . . . . . . . 104
5.1. REQUIRED Attributes . . . . . . . . . . . . . . . . . . 105 5.1. REQUIRED Attributes . . . . . . . . . . . . . . . . . . 105
5.2. RECOMMENDED Attributes . . . . . . . . . . . . . . . . . 106 5.2. RECOMMENDED Attributes . . . . . . . . . . . . . . . . . 105
5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 106 5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 106
5.4. Classification of Attributes . . . . . . . . . . . . . . 108 5.4. Classification of Attributes . . . . . . . . . . . . . . 107
5.5. Set-Only and Get-Only Attributes . . . . . . . . . . . . 109 5.5. Set-Only and Get-Only Attributes . . . . . . . . . . . . 108
5.6. REQUIRED Attributes - List and Definition References . . 109 5.6. REQUIRED Attributes - List and Definition References . . 108
5.7. RECOMMENDED Attributes - List and Definition 5.7. RECOMMENDED Attributes - List and Definition
References . . . . . . . . . . . . . . . . . . . . . . . 110 References . . . . . . . . . . . . . . . . . . . . . . . 109
5.8. Attribute Definitions . . . . . . . . . . . . . . . . . 112 5.8. Attribute Definitions . . . . . . . . . . . . . . . . . 111
5.8.1. Definitions of REQUIRED Attributes . . . . . . . . . 112 5.8.1. Definitions of REQUIRED Attributes . . . . . . . . . 111
5.8.2. Definitions of Uncategorized RECOMMENDED 5.8.2. Definitions of Uncategorized RECOMMENDED
Attributes . . . . . . . . . . . . . . . . . . . . . 114 Attributes . . . . . . . . . . . . . . . . . . . . . 113
5.9. Interpreting owner and owner_group . . . . . . . . . . . 120 5.9. Interpreting owner and owner_group . . . . . . . . . . . 120
5.10. Character Case Attributes . . . . . . . . . . . . . . . 122 5.10. Character Case Attributes . . . . . . . . . . . . . . . 122
5.11. Directory Notification Attributes . . . . . . . . . . . 123 5.11. Directory Notification Attributes . . . . . . . . . . . 122
5.12. pNFS Attribute Definitions . . . . . . . . . . . . . . . 123 5.12. pNFS Attribute Definitions . . . . . . . . . . . . . . . 122
5.13. Retention Attributes . . . . . . . . . . . . . . . . . . 125 5.13. Retention Attributes . . . . . . . . . . . . . . . . . . 124
6. Access Control Attributes . . . . . . . . . . . . . . . . . . 128 6. Access Control Attributes . . . . . . . . . . . . . . . . . . 127
6.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . 128 6.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . 127
6.2. File Attributes Discussion . . . . . . . . . . . . . . . 129 6.2. File Attributes Discussion . . . . . . . . . . . . . . . 128
6.2.1. Attribute 12: acl . . . . . . . . . . . . . . . . . 129 6.2.1. Attribute 12: acl . . . . . . . . . . . . . . . . . 128
6.2.2. Attribute 58: dacl . . . . . . . . . . . . . . . . . 144 6.2.2. Attribute 58: dacl . . . . . . . . . . . . . . . . . 144
6.2.3. Attribute 59: sacl . . . . . . . . . . . . . . . . . 144 6.2.3. Attribute 59: sacl . . . . . . . . . . . . . . . . . 144
6.2.4. Attribute 33: mode . . . . . . . . . . . . . . . . . 144 6.2.4. Attribute 33: mode . . . . . . . . . . . . . . . . . 144
6.2.5. Attribute 74: mode_set_masked . . . . . . . . . . . 145 6.2.5. Attribute 74: mode_set_masked . . . . . . . . . . . 144
6.3. Common Methods . . . . . . . . . . . . . . . . . . . . . 146 6.3. Common Methods . . . . . . . . . . . . . . . . . . . . . 145
6.3.1. Interpreting an ACL . . . . . . . . . . . . . . . . 146 6.3.1. Interpreting an ACL . . . . . . . . . . . . . . . . 145
6.3.2. Computing a Mode Attribute from an ACL . . . . . . . 147 6.3.2. Computing a Mode Attribute from an ACL . . . . . . . 146
6.4. Requirements . . . . . . . . . . . . . . . . . . . . . . 148 6.4. Requirements . . . . . . . . . . . . . . . . . . . . . . 147
6.4.1. Setting the mode and/or ACL Attributes . . . . . . . 148 6.4.1. Setting the Mode and/or ACL Attributes . . . . . . . 148
6.4.2. Retrieving the mode and/or ACL Attributes . . . . . 150 6.4.2. Retrieving the Mode and/or ACL Attributes . . . . . 149
6.4.3. Creating New Objects . . . . . . . . . . . . . . . . 150 6.4.3. Creating New Objects . . . . . . . . . . . . . . . . 150
7. Single-server Namespace . . . . . . . . . . . . . . . . . . . 154 7. Single-Server Namespace . . . . . . . . . . . . . . . . . . . 154
7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 155 7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 154
7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 155 7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 154
7.3. Server Pseudo File System . . . . . . . . . . . . . . . 155 7.3. Server Pseudo File System . . . . . . . . . . . . . . . 155
7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 156 7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 155
7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . 156 7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . 155
7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . 157 7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . 156
7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 157 7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 156
7.8. Security Policy and Namespace Presentation . . . . . . . 157 7.8. Security Policy and Namespace Presentation . . . . . . . 157
8. State Management . . . . . . . . . . . . . . . . . . . . . . 158 8. State Management . . . . . . . . . . . . . . . . . . . . . . 158
8.1. Client and Session ID . . . . . . . . . . . . . . . . . 159 8.1. Client and Session ID . . . . . . . . . . . . . . . . . 158
8.2. Stateid Definition . . . . . . . . . . . . . . . . . . . 160 8.2. Stateid Definition . . . . . . . . . . . . . . . . . . . 159
8.2.1. Stateid Types . . . . . . . . . . . . . . . . . . . 160 8.2.1. Stateid Types . . . . . . . . . . . . . . . . . . . 159
8.2.2. Stateid Structure . . . . . . . . . . . . . . . . . 161 8.2.2. Stateid Structure . . . . . . . . . . . . . . . . . 161
8.2.3. Special Stateids . . . . . . . . . . . . . . . . . . 163 8.2.3. Special Stateids . . . . . . . . . . . . . . . . . . 162
8.2.4. Stateid Lifetime and Validation . . . . . . . . . . 164 8.2.4. Stateid Lifetime and Validation . . . . . . . . . . 163
8.2.5. Stateid Use for I/O Operations . . . . . . . . . . . 167 8.2.5. Stateid Use for I/O Operations . . . . . . . . . . . 166
8.2.6. Stateid Use for SETATTR Operations . . . . . . . . . 168 8.2.6. Stateid Use for SETATTR Operations . . . . . . . . . 167
8.3. Lease Renewal . . . . . . . . . . . . . . . . . . . . . 168 8.3. Lease Renewal . . . . . . . . . . . . . . . . . . . . . 167
8.4. Crash Recovery . . . . . . . . . . . . . . . . . . . . . 171 8.4. Crash Recovery . . . . . . . . . . . . . . . . . . . . . 170
8.4.1. Client Failure and Recovery . . . . . . . . . . . . 171 8.4.1. Client Failure and Recovery . . . . . . . . . . . . 170
8.4.2. Server Failure and Recovery . . . . . . . . . . . . 172 8.4.2. Server Failure and Recovery . . . . . . . . . . . . 171
8.4.3. Network Partitions and Recovery . . . . . . . . . . 177 8.4.3. Network Partitions and Recovery . . . . . . . . . . 176
8.5. Server Revocation of Locks . . . . . . . . . . . . . . . 182 8.5. Server Revocation of Locks . . . . . . . . . . . . . . . 181
8.6. Short and Long Leases . . . . . . . . . . . . . . . . . 183 8.6. Short and Long Leases . . . . . . . . . . . . . . . . . 182
8.7. Clocks, Propagation Delay, and Calculating Lease 8.7. Clocks, Propagation Delay, and Calculating Lease
Expiration . . . . . . . . . . . . . . . . . . . . . . . 183 Expiration . . . . . . . . . . . . . . . . . . . . . . . 182
8.8. Obsolete Locking Infrastructure From NFSv4.0 . . . . . . 184 8.8. Obsolete Locking Infrastructure from NFSv4.0 . . . . . . 183
9. File Locking and Share Reservations . . . . . . . . . . . . . 185 9. File Locking and Share Reservations . . . . . . . . . . . . . 184
9.1. Opens and Byte-Range Locks . . . . . . . . . . . . . . . 185 9.1. Opens and Byte-Range Locks . . . . . . . . . . . . . . . 184
9.1.1. State-owner Definition . . . . . . . . . . . . . . . 185 9.1.1. State-Owner Definition . . . . . . . . . . . . . . . 184
9.1.2. Use of the Stateid and Locking . . . . . . . . . . . 185 9.1.2. Use of the Stateid and Locking . . . . . . . . . . . 185
9.2. Lock Ranges . . . . . . . . . . . . . . . . . . . . . . 188 9.2. Lock Ranges . . . . . . . . . . . . . . . . . . . . . . 188
9.3. Upgrading and Downgrading Locks . . . . . . . . . . . . 189 9.3. Upgrading and Downgrading Locks . . . . . . . . . . . . 188
9.4. Stateid Seqid Values and Byte-Range Locks . . . . . . . 189 9.4. Stateid Seqid Values and Byte-Range Locks . . . . . . . 189
9.5. Issues with Multiple Open-Owners . . . . . . . . . . . . 190 9.5. Issues with Multiple Open-Owners . . . . . . . . . . . . 189
9.6. Blocking Locks . . . . . . . . . . . . . . . . . . . . . 190 9.6. Blocking Locks . . . . . . . . . . . . . . . . . . . . . 190
9.7. Share Reservations . . . . . . . . . . . . . . . . . . . 191 9.7. Share Reservations . . . . . . . . . . . . . . . . . . . 191
9.8. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . 192 9.8. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . 192
9.9. Open Upgrade and Downgrade . . . . . . . . . . . . . . . 193 9.9. Open Upgrade and Downgrade . . . . . . . . . . . . . . . 192
9.10. Parallel OPENs . . . . . . . . . . . . . . . . . . . . . 194 9.10. Parallel OPENs . . . . . . . . . . . . . . . . . . . . . 193
9.11. Reclaim of Open and Byte-Range Locks . . . . . . . . . . 194 9.11. Reclaim of Open and Byte-Range Locks . . . . . . . . . . 194
10. Client-Side Caching . . . . . . . . . . . . . . . . . . . . . 195 10. Client-Side Caching . . . . . . . . . . . . . . . . . . . . . 194
10.1. Performance Challenges for Client-Side Caching . . . . . 195 10.1. Performance Challenges for Client-Side Caching . . . . . 195
10.2. Delegation and Callbacks . . . . . . . . . . . . . . . . 196 10.2. Delegation and Callbacks . . . . . . . . . . . . . . . . 196
10.2.1. Delegation Recovery . . . . . . . . . . . . . . . . 198 10.2.1. Delegation Recovery . . . . . . . . . . . . . . . . 198
10.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . 201 10.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . 200
10.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . 201 10.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . 201
10.3.2. Data Caching and File Locking . . . . . . . . . . . 202 10.3.2. Data Caching and File Locking . . . . . . . . . . . 202
10.3.3. Data Caching and Mandatory File Locking . . . . . . 204 10.3.3. Data Caching and Mandatory File Locking . . . . . . 203
10.3.4. Data Caching and File Identity . . . . . . . . . . . 204 10.3.4. Data Caching and File Identity . . . . . . . . . . . 204
10.4. Open Delegation . . . . . . . . . . . . . . . . . . . . 205 10.4. Open Delegation . . . . . . . . . . . . . . . . . . . . 205
10.4.1. Open Delegation and Data Caching . . . . . . . . . . 208 10.4.1. Open Delegation and Data Caching . . . . . . . . . . 207
10.4.2. Open Delegation and File Locks . . . . . . . . . . . 209 10.4.2. Open Delegation and File Locks . . . . . . . . . . . 209
10.4.3. Handling of CB_GETATTR . . . . . . . . . . . . . . . 209 10.4.3. Handling of CB_GETATTR . . . . . . . . . . . . . . . 209
10.4.4. Recall of Open Delegation . . . . . . . . . . . . . 212 10.4.4. Recall of Open Delegation . . . . . . . . . . . . . 212
10.4.5. Clients that Fail to Honor Delegation Recalls . . . 214 10.4.5. Clients That Fail to Honor Delegation Recalls . . . 214
10.4.6. Delegation Revocation . . . . . . . . . . . . . . . 215 10.4.6. Delegation Revocation . . . . . . . . . . . . . . . 215
10.4.7. Delegations via WANT_DELEGATION . . . . . . . . . . 215 10.4.7. Delegations via WANT_DELEGATION . . . . . . . . . . 216
10.5. Data Caching and Revocation . . . . . . . . . . . . . . 216 10.5. Data Caching and Revocation . . . . . . . . . . . . . . 216
10.5.1. Revocation Recovery for Write Open Delegation . . . 217 10.5.1. Revocation Recovery for Write Open Delegation . . . 217
10.6. Attribute Caching . . . . . . . . . . . . . . . . . . . 217 10.6. Attribute Caching . . . . . . . . . . . . . . . . . . . 218
10.7. Data and Metadata Caching and Memory Mapped Files . . . 219 10.7. Data and Metadata Caching and Memory Mapped Files . . . 220
10.8. Name and Directory Caching without Directory 10.8. Name and Directory Caching without Directory
Delegations . . . . . . . . . . . . . . . . . . . . . . 222 Delegations . . . . . . . . . . . . . . . . . . . . . . 222
10.8.1. Name Caching . . . . . . . . . . . . . . . . . . . . 222 10.8.1. Name Caching . . . . . . . . . . . . . . . . . . . . 222
10.8.2. Directory Caching . . . . . . . . . . . . . . . . . 223 10.8.2. Directory Caching . . . . . . . . . . . . . . . . . 224
10.9. Directory Delegations . . . . . . . . . . . . . . . . . 224 10.9. Directory Delegations . . . . . . . . . . . . . . . . . 224
10.9.1. Introduction to Directory Delegations . . . . . . . 224 10.9.1. Introduction to Directory Delegations . . . . . . . 225
10.9.2. Directory Delegation Design . . . . . . . . . . . . 225 10.9.2. Directory Delegation Design . . . . . . . . . . . . 226
10.9.3. Attributes in Support of Directory Notifications . . 226 10.9.3. Attributes in Support of Directory Notifications . . 227
10.9.4. Directory Delegation Recall . . . . . . . . . . . . 226 10.9.4. Directory Delegation Recall . . . . . . . . . . . . 227
10.9.5. Directory Delegation Recovery . . . . . . . . . . . 227 10.9.5. Directory Delegation Recovery . . . . . . . . . . . 227
11. Multi-Server Namespace . . . . . . . . . . . . . . . . . . . 227 11. Multi-Server Namespace . . . . . . . . . . . . . . . . . . . 228
11.1. Location Attributes . . . . . . . . . . . . . . . . . . 228 11.1. Location Attributes . . . . . . . . . . . . . . . . . . 228
11.2. File System Presence or Absence . . . . . . . . . . . . 228 11.2. File System Presence or Absence . . . . . . . . . . . . 228
11.3. Getting Attributes for an Absent File System . . . . . . 229 11.3. Getting Attributes for an Absent File System . . . . . . 230
11.3.1. GETATTR Within an Absent File System . . . . . . . . 230 11.3.1. GETATTR within an Absent File System . . . . . . . . 230
11.3.2. READDIR and Absent File Systems . . . . . . . . . . 231 11.3.2. READDIR and Absent File Systems . . . . . . . . . . 231
11.4. Uses of Location Information . . . . . . . . . . . . . . 231 11.4. Uses of Location Information . . . . . . . . . . . . . . 232
11.4.1. File System Replication . . . . . . . . . . . . . . 232 11.4.1. File System Replication . . . . . . . . . . . . . . 232
11.4.2. File System Migration . . . . . . . . . . . . . . . 233 11.4.2. File System Migration . . . . . . . . . . . . . . . 233
11.4.3. Referrals . . . . . . . . . . . . . . . . . . . . . 234 11.4.3. Referrals . . . . . . . . . . . . . . . . . . . . . 234
11.5. Location Entries and Server Identity . . . . . . . . . . 236 11.5. Location Entries and Server Identity . . . . . . . . . . 236
11.6. Additional Client-side Considerations . . . . . . . . . 236 11.6. Additional Client-Side Considerations . . . . . . . . . 236
11.7. Effecting File System Transitions . . . . . . . . . . . 237 11.7. Effecting File System Transitions . . . . . . . . . . . 237
11.7.1. File System Transitions and Simultaneous Access . . 238 11.7.1. File System Transitions and Simultaneous Access . . 238
11.7.2. Simultaneous Use and Transparent Transitions . . . . 239 11.7.2. Simultaneous Use and Transparent Transitions . . . . 239
11.7.3. Filehandles and File System Transitions . . . . . . 242 11.7.3. Filehandles and File System Transitions . . . . . . 242
11.7.4. Fileids and File System Transitions . . . . . . . . 242 11.7.4. Fileids and File System Transitions . . . . . . . . 242
11.7.5. Fsids and File System Transitions . . . . . . . . . 243 11.7.5. Fsids and File System Transitions . . . . . . . . . 243
11.7.6. The Change Attribute and File System Transitions . . 244 11.7.6. The Change Attribute and File System Transitions . . 244
11.7.7. Lock State and File System Transitions . . . . . . . 244 11.7.7. Lock State and File System Transitions . . . . . . . 245
11.7.8. Write Verifiers and File System Transitions . . . . 249 11.7.8. Write Verifiers and File System Transitions . . . . 249
11.7.9. Readdir Cookies and Verifiers and File System 11.7.9. Readdir Cookies and Verifiers and File System
Transitions . . . . . . . . . . . . . . . . . . . . 249 Transitions . . . . . . . . . . . . . . . . . . . . 249
11.7.10. File System Data and File System Transitions . . . . 249 11.7.10. File System Data and File System Transitions . . . . 249
11.8. Effecting File System Referrals . . . . . . . . . . . . 251 11.8. Effecting File System Referrals . . . . . . . . . . . . 251
11.8.1. Referral Example (LOOKUP) . . . . . . . . . . . . . 251 11.8.1. Referral Example (LOOKUP) . . . . . . . . . . . . . 251
11.8.2. Referral Example (READDIR) . . . . . . . . . . . . . 255 11.8.2. Referral Example (READDIR) . . . . . . . . . . . . . 255
11.9. The Attribute fs_locations . . . . . . . . . . . . . . . 257 11.9. The Attribute fs_locations . . . . . . . . . . . . . . . 257
11.10. The Attribute fs_locations_info . . . . . . . . . . . . 260 11.10. The Attribute fs_locations_info . . . . . . . . . . . . 260
11.10.1. The fs_locations_server4 Structure . . . . . . . . . 264 11.10.1. The fs_locations_server4 Structure . . . . . . . . . 264
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12.2. pNFS Definitions . . . . . . . . . . . . . . . . . . . . 277 12.2. pNFS Definitions . . . . . . . . . . . . . . . . . . . . 277
12.2.1. Metadata . . . . . . . . . . . . . . . . . . . . . . 278 12.2.1. Metadata . . . . . . . . . . . . . . . . . . . . . . 278
12.2.2. Metadata Server . . . . . . . . . . . . . . . . . . 278 12.2.2. Metadata Server . . . . . . . . . . . . . . . . . . 278
12.2.3. pNFS Client . . . . . . . . . . . . . . . . . . . . 278 12.2.3. pNFS Client . . . . . . . . . . . . . . . . . . . . 278
12.2.4. Storage Device . . . . . . . . . . . . . . . . . . . 278 12.2.4. Storage Device . . . . . . . . . . . . . . . . . . . 278
12.2.5. Storage Protocol . . . . . . . . . . . . . . . . . . 279 12.2.5. Storage Protocol . . . . . . . . . . . . . . . . . . 279
12.2.6. Control Protocol . . . . . . . . . . . . . . . . . . 279 12.2.6. Control Protocol . . . . . . . . . . . . . . . . . . 279
12.2.7. Layout Types . . . . . . . . . . . . . . . . . . . . 280 12.2.7. Layout Types . . . . . . . . . . . . . . . . . . . . 280
12.2.8. Layout . . . . . . . . . . . . . . . . . . . . . . . 280 12.2.8. Layout . . . . . . . . . . . . . . . . . . . . . . . 280
12.2.9. Layout Iomode . . . . . . . . . . . . . . . . . . . 281 12.2.9. Layout Iomode . . . . . . . . . . . . . . . . . . . 281
12.2.10. Device IDs . . . . . . . . . . . . . . . . . . . . . 281 12.2.10. Device IDs . . . . . . . . . . . . . . . . . . . . . 282
12.3. pNFS Operations . . . . . . . . . . . . . . . . . . . . 283 12.3. pNFS Operations . . . . . . . . . . . . . . . . . . . . 283
12.4. pNFS Attributes . . . . . . . . . . . . . . . . . . . . 284 12.4. pNFS Attributes . . . . . . . . . . . . . . . . . . . . 284
12.5. Layout Semantics . . . . . . . . . . . . . . . . . . . . 284 12.5. Layout Semantics . . . . . . . . . . . . . . . . . . . . 284
12.5.1. Guarantees Provided by Layouts . . . . . . . . . . . 284 12.5.1. Guarantees Provided by Layouts . . . . . . . . . . . 284
12.5.2. Getting a Layout . . . . . . . . . . . . . . . . . . 285 12.5.2. Getting a Layout . . . . . . . . . . . . . . . . . . 285
12.5.3. Layout Stateid . . . . . . . . . . . . . . . . . . . 286 12.5.3. Layout Stateid . . . . . . . . . . . . . . . . . . . 286
12.5.4. Committing a Layout . . . . . . . . . . . . . . . . 287 12.5.4. Committing a Layout . . . . . . . . . . . . . . . . 287
12.5.5. Recalling a Layout . . . . . . . . . . . . . . . . . 290 12.5.5. Recalling a Layout . . . . . . . . . . . . . . . . . 290
12.5.6. Revoking Layouts . . . . . . . . . . . . . . . . . . 299 12.5.6. Revoking Layouts . . . . . . . . . . . . . . . . . . 299
12.5.7. Metadata Server Write Propagation . . . . . . . . . 299 12.5.7. Metadata Server Write Propagation . . . . . . . . . 299
12.6. pNFS Mechanics . . . . . . . . . . . . . . . . . . . . . 299 12.6. pNFS Mechanics . . . . . . . . . . . . . . . . . . . . . 299
12.7. Recovery . . . . . . . . . . . . . . . . . . . . . . . . 301 12.7. Recovery . . . . . . . . . . . . . . . . . . . . . . . . 301
12.7.1. Recovery from Client Restart . . . . . . . . . . . . 301 12.7.1. Recovery from Client Restart . . . . . . . . . . . . 301
12.7.2. Dealing with Lease Expiration on the Client . . . . 301 12.7.2. Dealing with Lease Expiration on the Client . . . . 301
12.7.3. Dealing with Loss of Layout State on the Metadata 12.7.3. Dealing with Loss of Layout State on the Metadata
Server . . . . . . . . . . . . . . . . . . . . . . . 302 Server . . . . . . . . . . . . . . . . . . . . . . . 302
12.7.4. Recovery from Metadata Server Restart . . . . . . . 303 12.7.4. Recovery from Metadata Server Restart . . . . . . . 303
12.7.5. Operations During Metadata Server Grace Period . . . 305 12.7.5. Operations during Metadata Server Grace Period . . . 305
12.7.6. Storage Device Recovery . . . . . . . . . . . . . . 305 12.7.6. Storage Device Recovery . . . . . . . . . . . . . . 305
12.8. Metadata and Storage Device Roles . . . . . . . . . . . 306 12.8. Metadata and Storage Device Roles . . . . . . . . . . . 306
12.9. Security Considerations for pNFS . . . . . . . . . . . . 306 12.9. Security Considerations for pNFS . . . . . . . . . . . . 306
13. NFSv4.1 as a Storage Protocol in pNFS: the File Layout Type . 307 13. NFSv4.1 as a Storage Protocol in pNFS: the File Layout Type . 307
13.1. Client ID and Session Considerations . . . . . . . . . . 307 13.1. Client ID and Session Considerations . . . . . . . . . . 308
13.1.1. Sessions Considerations for Data Servers . . . . . . 310 13.1.1. Sessions Considerations for Data Servers . . . . . . 310
13.2. File Layout Definitions . . . . . . . . . . . . . . . . 310 13.2. File Layout Definitions . . . . . . . . . . . . . . . . 310
13.3. File Layout Data Types . . . . . . . . . . . . . . . . . 311 13.3. File Layout Data Types . . . . . . . . . . . . . . . . . 311
13.4. Interpreting the File Layout . . . . . . . . . . . . . . 315 13.4. Interpreting the File Layout . . . . . . . . . . . . . . 315
13.4.1. Determining the Stripe Unit Number . . . . . . . . . 315 13.4.1. Determining the Stripe Unit Number . . . . . . . . . 315
13.4.2. Interpreting the File Layout Using Sparse Packing . 316 13.4.2. Interpreting the File Layout Using Sparse Packing . 316
13.4.3. Interpreting the File Layout Using Dense Packing . . 318 13.4.3. Interpreting the File Layout Using Dense Packing . . 318
13.4.4. Sparse and Dense Stripe Unit Packing . . . . . . . . 320 13.4.4. Sparse and Dense Stripe Unit Packing . . . . . . . . 320
13.5. Data Server Multipathing . . . . . . . . . . . . . . . . 322 13.5. Data Server Multipathing . . . . . . . . . . . . . . . . 322
13.6. Operations Sent to NFSv4.1 Data Servers . . . . . . . . 323 13.6. Operations Sent to NFSv4.1 Data Servers . . . . . . . . 323
13.7. COMMIT Through Metadata Server . . . . . . . . . . . . . 325 13.7. COMMIT through Metadata Server . . . . . . . . . . . . . 325
13.8. The Layout Iomode . . . . . . . . . . . . . . . . . . . 327 13.8. The Layout Iomode . . . . . . . . . . . . . . . . . . . 327
13.9. Metadata and Data Server State Coordination . . . . . . 327 13.9. Metadata and Data Server State Coordination . . . . . . 327
13.9.1. Global Stateid Requirements . . . . . . . . . . . . 327 13.9.1. Global Stateid Requirements . . . . . . . . . . . . 327
13.9.2. Data Server State Propagation . . . . . . . . . . . 328 13.9.2. Data Server State Propagation . . . . . . . . . . . 328
13.10. Data Server Component File Size . . . . . . . . . . . . 330 13.10. Data Server Component File Size . . . . . . . . . . . . 330
13.11. Layout Revocation and Fencing . . . . . . . . . . . . . 331 13.11. Layout Revocation and Fencing . . . . . . . . . . . . . 331
13.12. Security Considerations for the File Layout Type . . . . 331 13.12. Security Considerations for the File Layout Type . . . . 332
14. Internationalization . . . . . . . . . . . . . . . . . . . . 332 14. Internationalization . . . . . . . . . . . . . . . . . . . . 333
14.1. Stringprep profile for the utf8str_cs type . . . . . . . 333 14.1. Stringprep Profile for the utf8str_cs Type . . . . . . . 334
14.2. Stringprep profile for the utf8str_cis type . . . . . . 335 14.2. Stringprep Profile for the utf8str_cis Type . . . . . . 335
14.3. Stringprep profile for the utf8str_mixed type . . . . . 336 14.3. Stringprep Profile for the utf8str_mixed Type . . . . . 336
14.4. UTF-8 Capabilities . . . . . . . . . . . . . . . . . . . 337 14.4. UTF-8 Capabilities . . . . . . . . . . . . . . . . . . . 338
14.5. UTF-8 Related Errors . . . . . . . . . . . . . . . . . . 338 14.5. UTF-8 Related Errors . . . . . . . . . . . . . . . . . . 338
15. Error Values . . . . . . . . . . . . . . . . . . . . . . . . 338 15. Error Values . . . . . . . . . . . . . . . . . . . . . . . . 339
15.1. Error Definitions . . . . . . . . . . . . . . . . . . . 339 15.1. Error Definitions . . . . . . . . . . . . . . . . . . . 339
15.1.1. General Errors . . . . . . . . . . . . . . . . . . . 341 15.1.1. General Errors . . . . . . . . . . . . . . . . . . . 341
15.1.2. Filehandle Errors . . . . . . . . . . . . . . . . . 343 15.1.2. Filehandle Errors . . . . . . . . . . . . . . . . . 343
15.1.3. Compound Structure Errors . . . . . . . . . . . . . 344 15.1.3. Compound Structure Errors . . . . . . . . . . . . . 344
15.1.4. File System Errors . . . . . . . . . . . . . . . . . 346 15.1.4. File System Errors . . . . . . . . . . . . . . . . . 346
15.1.5. State Management Errors . . . . . . . . . . . . . . 348 15.1.5. State Management Errors . . . . . . . . . . . . . . 348
15.1.6. Security Errors . . . . . . . . . . . . . . . . . . 348 15.1.6. Security Errors . . . . . . . . . . . . . . . . . . 349
15.1.7. Name Errors . . . . . . . . . . . . . . . . . . . . 349 15.1.7. Name Errors . . . . . . . . . . . . . . . . . . . . 350
15.1.8. Locking Errors . . . . . . . . . . . . . . . . . . . 350 15.1.8. Locking Errors . . . . . . . . . . . . . . . . . . . 350
15.1.9. Reclaim Errors . . . . . . . . . . . . . . . . . . . 351 15.1.9. Reclaim Errors . . . . . . . . . . . . . . . . . . . 352
15.1.10. pNFS Errors . . . . . . . . . . . . . . . . . . . . 352 15.1.10. pNFS Errors . . . . . . . . . . . . . . . . . . . . 353
15.1.11. Session Use Errors . . . . . . . . . . . . . . . . . 353 15.1.11. Session Use Errors . . . . . . . . . . . . . . . . . 354
15.1.12. Session Management Errors . . . . . . . . . . . . . 355 15.1.12. Session Management Errors . . . . . . . . . . . . . 355
15.1.13. Client Management Errors . . . . . . . . . . . . . . 355 15.1.13. Client Management Errors . . . . . . . . . . . . . . 355
15.1.14. Delegation Errors . . . . . . . . . . . . . . . . . 356 15.1.14. Delegation Errors . . . . . . . . . . . . . . . . . 356
15.1.15. Attribute Handling Errors . . . . . . . . . . . . . 356 15.1.15. Attribute Handling Errors . . . . . . . . . . . . . 357
15.1.16. Obsoleted Errors . . . . . . . . . . . . . . . . . . 357 15.1.16. Obsoleted Errors . . . . . . . . . . . . . . . . . . 357
15.2. Operations and their valid errors . . . . . . . . . . . 358 15.2. Operations and Their Valid Errors . . . . . . . . . . . 358
15.3. Callback operations and their valid errors . . . . . . . 375 15.3. Callback Operations and Their Valid Errors . . . . . . . 375
15.4. Errors and the operations that use them . . . . . . . . 378 15.4. Errors and the Operations That Use Them . . . . . . . . 378
16. NFSv4.1 Procedures . . . . . . . . . . . . . . . . . . . . . 394 16. NFSv4.1 Procedures . . . . . . . . . . . . . . . . . . . . . 394
16.1. Procedure 0: NULL - No Operation . . . . . . . . . . . . 394 16.1. Procedure 0: NULL - No Operation . . . . . . . . . . . . 394
16.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 395 16.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 395
17. Operations: REQUIRED, RECOMMENDED, or OPTIONAL . . . . . . . 406 17. Operations: REQUIRED, RECOMMENDED, or OPTIONAL . . . . . . . 406
18. NFSv4.1 Operations . . . . . . . . . . . . . . . . . . . . . 409 18. NFSv4.1 Operations . . . . . . . . . . . . . . . . . . . . . 409
18.1. Operation 3: ACCESS - Check Access Rights . . . . . . . 409 18.1. Operation 3: ACCESS - Check Access Rights . . . . . . . 409
18.2. Operation 4: CLOSE - Close File . . . . . . . . . . . . 415 18.2. Operation 4: CLOSE - Close File . . . . . . . . . . . . 415
18.3. Operation 5: COMMIT - Commit Cached Data . . . . . . . . 416 18.3. Operation 5: COMMIT - Commit Cached Data . . . . . . . . 416
18.4. Operation 6: CREATE - Create a Non-Regular File Object . 419 18.4. Operation 6: CREATE - Create a Non-Regular File Object . 419
18.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting 18.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting
Recovery . . . . . . . . . . . . . . . . . . . . . . . . 422 Recovery . . . . . . . . . . . . . . . . . . . . . . . . 422
18.6. Operation 8: DELEGRETURN - Return Delegation . . . . . . 423 18.6. Operation 8: DELEGRETURN - Return Delegation . . . . . . 423
18.7. Operation 9: GETATTR - Get Attributes . . . . . . . . . 423 18.7. Operation 9: GETATTR - Get Attributes . . . . . . . . . 423
18.8. Operation 10: GETFH - Get Current Filehandle . . . . . . 425 18.8. Operation 10: GETFH - Get Current Filehandle . . . . . . 425
18.9. Operation 11: LINK - Create Link to a File . . . . . . . 426 18.9. Operation 11: LINK - Create Link to a File . . . . . . . 426
18.10. Operation 12: LOCK - Create Lock . . . . . . . . . . . . 429 18.10. Operation 12: LOCK - Create Lock . . . . . . . . . . . . 429
18.11. Operation 13: LOCKT - Test For Lock . . . . . . . . . . 433 18.11. Operation 13: LOCKT - Test for Lock . . . . . . . . . . 434
18.12. Operation 14: LOCKU - Unlock File . . . . . . . . . . . 434 18.12. Operation 14: LOCKU - Unlock File . . . . . . . . . . . 435
18.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . . . 436 18.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . . . 437
18.14. Operation 16: LOOKUPP - Lookup Parent Directory . . . . 437 18.14. Operation 16: LOOKUPP - Lookup Parent Directory . . . . 438
18.15. Operation 17: NVERIFY - Verify Difference in 18.15. Operation 17: NVERIFY - Verify Difference in
Attributes . . . . . . . . . . . . . . . . . . . . . . . 439 Attributes . . . . . . . . . . . . . . . . . . . . . . . 440
18.16. Operation 18: OPEN - Open a Regular File . . . . . . . . 440 18.16. Operation 18: OPEN - Open a Regular File . . . . . . . . 441
18.17. Operation 19: OPENATTR - Open Named Attribute 18.17. Operation 19: OPENATTR - Open Named Attribute
Directory . . . . . . . . . . . . . . . . . . . . . . . 459 Directory . . . . . . . . . . . . . . . . . . . . . . . 460
18.18. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access . 460 18.18. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access . 462
18.19. Operation 22: PUTFH - Set Current Filehandle . . . . . . 462 18.19. Operation 22: PUTFH - Set Current Filehandle . . . . . . 463
18.20. Operation 23: PUTPUBFH - Set Public Filehandle . . . . . 462 18.20. Operation 23: PUTPUBFH - Set Public Filehandle . . . . . 464
18.21. Operation 24: PUTROOTFH - Set Root Filehandle . . . . . 464 18.21. Operation 24: PUTROOTFH - Set Root Filehandle . . . . . 466
18.22. Operation 25: READ - Read from File . . . . . . . . . . 465 18.22. Operation 25: READ - Read from File . . . . . . . . . . 466
18.23. Operation 26: READDIR - Read Directory . . . . . . . . . 467 18.23. Operation 26: READDIR - Read Directory . . . . . . . . . 469
18.24. Operation 27: READLINK - Read Symbolic Link . . . . . . 471 18.24. Operation 27: READLINK - Read Symbolic Link . . . . . . 472
18.25. Operation 28: REMOVE - Remove File System Object . . . . 472 18.25. Operation 28: REMOVE - Remove File System Object . . . . 473
18.26. Operation 29: RENAME - Rename Directory Entry . . . . . 474 18.26. Operation 29: RENAME - Rename Directory Entry . . . . . 476
18.27. Operation 31: RESTOREFH - Restore Saved Filehandle . . . 478 18.27. Operation 31: RESTOREFH - Restore Saved Filehandle . . . 479
18.28. Operation 32: SAVEFH - Save Current Filehandle . . . . . 479 18.28. Operation 32: SAVEFH - Save Current Filehandle . . . . . 480
18.29. Operation 33: SECINFO - Obtain Available Security . . . 480 18.29. Operation 33: SECINFO - Obtain Available Security . . . 481
18.30. Operation 34: SETATTR - Set Attributes . . . . . . . . . 484 18.30. Operation 34: SETATTR - Set Attributes . . . . . . . . . 485
18.31. Operation 37: VERIFY - Verify Same Attributes . . . . . 487 18.31. Operation 37: VERIFY - Verify Same Attributes . . . . . 488
18.32. Operation 38: WRITE - Write to File . . . . . . . . . . 488 18.32. Operation 38: WRITE - Write to File . . . . . . . . . . 489
18.33. Operation 40: BACKCHANNEL_CTL - Backchannel Control . . 492 18.33. Operation 40: BACKCHANNEL_CTL - Backchannel Control . . 494
18.34. Operation 41: BIND_CONN_TO_SESSION - Associate 18.34. Operation 41: BIND_CONN_TO_SESSION - Associate
Connection with Session . . . . . . . . . . . . . . . . 494 Connection with Session . . . . . . . . . . . . . . . . 495
18.35. Operation 42: EXCHANGE_ID - Instantiate Client ID . . . 497 18.35. Operation 42: EXCHANGE_ID - Instantiate Client ID . . . 498
18.36. Operation 43: CREATE_SESSION - Create New Session and 18.36. Operation 43: CREATE_SESSION - Create New Session and
Confirm Client ID . . . . . . . . . . . . . . . . . . . 515 Confirm Client ID . . . . . . . . . . . . . . . . . . . 516
18.37. Operation 44: DESTROY_SESSION - Destroy a Session . . . 525 18.37. Operation 44: DESTROY_SESSION - Destroy a Session . . . 526
18.38. Operation 45: FREE_STATEID - Free Stateid with No 18.38. Operation 45: FREE_STATEID - Free Stateid with No
Locks . . . . . . . . . . . . . . . . . . . . . . . . . 527 Locks . . . . . . . . . . . . . . . . . . . . . . . . . 528
18.39. Operation 46: GET_DIR_DELEGATION - Get a directory 18.39. Operation 46: GET_DIR_DELEGATION - Get a Directory
delegation . . . . . . . . . . . . . . . . . . . . . . . 528 Delegation . . . . . . . . . . . . . . . . . . . . . . . 529
18.40. Operation 47: GETDEVICEINFO - Get Device Information . . 532 18.40. Operation 47: GETDEVICEINFO - Get Device Information . . 533
18.41. Operation 48: GETDEVICELIST - Get All Device Mappings 18.41. Operation 48: GETDEVICELIST - Get All Device Mappings
for a File System . . . . . . . . . . . . . . . . . . . 535 for a File System . . . . . . . . . . . . . . . . . . . 536
18.42. Operation 49: LAYOUTCOMMIT - Commit Writes Made Using 18.42. Operation 49: LAYOUTCOMMIT - Commit Writes Made Using
a Layout . . . . . . . . . . . . . . . . . . . . . . . . 536 a Layout . . . . . . . . . . . . . . . . . . . . . . . . 537
18.43. Operation 50: LAYOUTGET - Get Layout Information . . . . 540 18.43. Operation 50: LAYOUTGET - Get Layout Information . . . . 541
18.44. Operation 51: LAYOUTRETURN - Release Layout 18.44. Operation 51: LAYOUTRETURN - Release Layout
Information . . . . . . . . . . . . . . . . . . . . . . 549 Information . . . . . . . . . . . . . . . . . . . . . . 551
18.45. Operation 52: SECINFO_NO_NAME - Get Security on 18.45. Operation 52: SECINFO_NO_NAME - Get Security on
Unnamed Object . . . . . . . . . . . . . . . . . . . . . 553 Unnamed Object . . . . . . . . . . . . . . . . . . . . . 556
18.46. Operation 53: SEQUENCE - Supply Per-Procedure 18.46. Operation 53: SEQUENCE - Supply Per-Procedure
Sequencing and Control . . . . . . . . . . . . . . . . . 554 Sequencing and Control . . . . . . . . . . . . . . . . . 557
18.47. Operation 54: SET_SSV - Update SSV for a Client ID . . . 560 18.47. Operation 54: SET_SSV - Update SSV for a Client ID . . . 563
18.48. Operation 55: TEST_STATEID - Test Stateids for 18.48. Operation 55: TEST_STATEID - Test Stateids for
Validity . . . . . . . . . . . . . . . . . . . . . . . . 563 Validity . . . . . . . . . . . . . . . . . . . . . . . . 565
18.49. Operation 56: WANT_DELEGATION - Request Delegation . . . 564 18.49. Operation 56: WANT_DELEGATION - Request Delegation . . . 567
18.50. Operation 57: DESTROY_CLIENTID - Destroy a Client ID . . 568 18.50. Operation 57: DESTROY_CLIENTID - Destroy a Client ID . . 571
18.51. Operation 58: RECLAIM_COMPLETE - Indicates Reclaims 18.51. Operation 58: RECLAIM_COMPLETE - Indicates Reclaims
Finished . . . . . . . . . . . . . . . . . . . . . . . . 568 Finished . . . . . . . . . . . . . . . . . . . . . . . . 571
18.52. Operation 10044: ILLEGAL - Illegal operation . . . . . . 571 18.52. Operation 10044: ILLEGAL - Illegal Operation . . . . . . 574
19. NFSv4.1 Callback Procedures . . . . . . . . . . . . . . . . . 571 19. NFSv4.1 Callback Procedures . . . . . . . . . . . . . . . . . 574
19.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . 572 19.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . 575
19.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . . 572 19.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . . 575
20. NFSv4.1 Callback Operations . . . . . . . . . . . . . . . . . 576 20. NFSv4.1 Callback Operations . . . . . . . . . . . . . . . . . 579
20.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . . . 576 20.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . . . 579
20.2. Operation 4: CB_RECALL - Recall a Delegation . . . . . . 577 20.2. Operation 4: CB_RECALL - Recall a Delegation . . . . . . 580
20.3. Operation 5: CB_LAYOUTRECALL - Recall Layout from 20.3. Operation 5: CB_LAYOUTRECALL - Recall Layout from
Client . . . . . . . . . . . . . . . . . . . . . . . . . 578 Client . . . . . . . . . . . . . . . . . . . . . . . . . 581
20.4. Operation 6: CB_NOTIFY - Notify Client of Directory 20.4. Operation 6: CB_NOTIFY - Notify Client of Directory
Changes . . . . . . . . . . . . . . . . . . . . . . . . 582 Changes . . . . . . . . . . . . . . . . . . . . . . . . 585
20.5. Operation 7: CB_PUSH_DELEG - Offer Previously 20.5. Operation 7: CB_PUSH_DELEG - Offer Previously
Requested Delegation to Client . . . . . . . . . . . . . 586 Requested Delegation to Client . . . . . . . . . . . . . 589
20.6. Operation 8: CB_RECALL_ANY - Keep Any N Recallable 20.6. Operation 8: CB_RECALL_ANY - Keep Any N Recallable
Objects . . . . . . . . . . . . . . . . . . . . . . . . 587 Objects . . . . . . . . . . . . . . . . . . . . . . . . 590
20.7. Operation 9: CB_RECALLABLE_OBJ_AVAIL - Signal 20.7. Operation 9: CB_RECALLABLE_OBJ_AVAIL - Signal
Resources for Recallable Objects . . . . . . . . . . . . 590 Resources for Recallable Objects . . . . . . . . . . . . 593
20.8. Operation 10: CB_RECALL_SLOT - Change Flow Control 20.8. Operation 10: CB_RECALL_SLOT - Change Flow Control
Limits . . . . . . . . . . . . . . . . . . . . . . . . . 591 Limits . . . . . . . . . . . . . . . . . . . . . . . . . 594
20.9. Operation 11: CB_SEQUENCE - Supply Backchannel 20.9. Operation 11: CB_SEQUENCE - Supply Backchannel
Sequencing and Control . . . . . . . . . . . . . . . . . 592 Sequencing and Control . . . . . . . . . . . . . . . . . 595
20.10. Operation 12: CB_WANTS_CANCELLED - Cancel Pending 20.10. Operation 12: CB_WANTS_CANCELLED - Cancel Pending
Delegation Wants . . . . . . . . . . . . . . . . . . . . 594 Delegation Wants . . . . . . . . . . . . . . . . . . . . 597
20.11. Operation 13: CB_NOTIFY_LOCK - Notify Client of 20.11. Operation 13: CB_NOTIFY_LOCK - Notify Client of
Possible Lock Availability . . . . . . . . . . . . . . . 595 Possible Lock Availability . . . . . . . . . . . . . . . 598
20.12. Operation 14: CB_NOTIFY_DEVICEID - Notify Client of 20.12. Operation 14: CB_NOTIFY_DEVICEID - Notify Client of
Device ID Changes . . . . . . . . . . . . . . . . . . . 597 Device ID Changes . . . . . . . . . . . . . . . . . . . 600
20.13. Operation 10044: CB_ILLEGAL - Illegal Callback 20.13. Operation 10044: CB_ILLEGAL - Illegal Callback
Operation . . . . . . . . . . . . . . . . . . . . . . . 599 Operation . . . . . . . . . . . . . . . . . . . . . . . 602
21. Security Considerations . . . . . . . . . . . . . . . . . . . 599 21. Security Considerations . . . . . . . . . . . . . . . . . . . 602
22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 601 22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 604
22.1. Named Attribute Definitions . . . . . . . . . . . . . . 601 22.1. Named Attribute Definitions . . . . . . . . . . . . . . 604
22.1.1. Initial Registry . . . . . . . . . . . . . . . . . . 602 22.1.1. Initial Registry . . . . . . . . . . . . . . . . . . 605
22.1.2. Updating Registrations . . . . . . . . . . . . . . . 602 22.1.2. Updating Registrations . . . . . . . . . . . . . . . 605
22.2. Device ID Notifications . . . . . . . . . . . . . . . . 602 22.2. Device ID Notifications . . . . . . . . . . . . . . . . 605
22.2.1. Initial Registry . . . . . . . . . . . . . . . . . . 603 22.2.1. Initial Registry . . . . . . . . . . . . . . . . . . 606
22.2.2. Updating Registrations . . . . . . . . . . . . . . . 604 22.2.2. Updating Registrations . . . . . . . . . . . . . . . 607
22.3. Object Recall Types . . . . . . . . . . . . . . . . . . 604 22.3. Object Recall Types . . . . . . . . . . . . . . . . . . 607
22.3.1. Initial Registry . . . . . . . . . . . . . . . . . . 605 22.3.1. Initial Registry . . . . . . . . . . . . . . . . . . 608
22.3.2. Updating Registrations . . . . . . . . . . . . . . . 605 22.3.2. Updating Registrations . . . . . . . . . . . . . . . 608
22.4. Layout Types . . . . . . . . . . . . . . . . . . . . . . 605 22.4. Layout Types . . . . . . . . . . . . . . . . . . . . . . 608
22.4.1. Initial Registry . . . . . . . . . . . . . . . . . . 606 22.4.1. Initial Registry . . . . . . . . . . . . . . . . . . 609
22.4.2. Updating Registrations . . . . . . . . . . . . . . . 607 22.4.2. Updating Registrations . . . . . . . . . . . . . . . 610
22.4.3. Guidelines for Writing Layout Type Specifications . 607 22.4.3. Guidelines for Writing Layout Type Specifications . 610
22.5. Path Variable Definitions . . . . . . . . . . . . . . . 608 22.5. Path Variable Definitions . . . . . . . . . . . . . . . 611
22.5.1. Path Variables Registry . . . . . . . . . . . . . . 608 22.5.1. Path Variables Registry . . . . . . . . . . . . . . 612
22.5.2. Values for the ${ietf.org:CPU_ARCH} Variable . . . . 610 22.5.2. Values for the ${ietf.org:CPU_ARCH} Variable . . . . 613
22.5.3. Values for the ${ietf.org:OS_TYPE} Variable . . . . 611 22.5.3. Values for the ${ietf.org:OS_TYPE} Variable . . . . 614
23. References . . . . . . . . . . . . . . . . . . . . . . . . . 612 23. References . . . . . . . . . . . . . . . . . . . . . . . . . 615
23.1. Normative References . . . . . . . . . . . . . . . . . . 612 23.1. Normative References . . . . . . . . . . . . . . . . . . 615
23.2. Informative References . . . . . . . . . . . . . . . . . 614 23.2. Informative References . . . . . . . . . . . . . . . . . 617
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 616 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 619
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 618
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 619
1. Introduction 1. Introduction
1.1. The NFS Version 4 Minor Version 1 Protocol 1.1. The NFS Version 4 Minor Version 1 Protocol
The NFS version 4 minor version 1 (NFSv4.1) protocol is the second The NFS version 4 minor version 1 (NFSv4.1) protocol is the second
minor version of the NFS version 4 (NFSv4) protocol. The first minor minor version of the NFS version 4 (NFSv4) protocol. The first minor
version, NFSv4.0 is described in [30]. It generally follows the version, NFSv4.0, is described in [30]. It generally follows the
guidelines for minor versioning model listed in Section 10 of RFC guidelines for minor versioning that are listed in Section 10 of RFC
3530. However, it diverges from guidelines 11 ("a client and server 3530. However, it diverges from guidelines 11 ("a client and server
that supports minor version X must support minor versions 0 through that support minor version X must support minor versions 0 through
X-1"), and 12 ("no features may be introduced as mandatory in a minor X-1") and 12 ("no new features may be introduced as mandatory in a
version"). These divergences are due to the introduction of the minor version"). These divergences are due to the introduction of
sessions model for managing non-idempotent operations and the the sessions model for managing non-idempotent operations and the
RECLAIM_COMPLETE operation. These two new features are RECLAIM_COMPLETE operation. These two new features are
infrastructural in nature and simplify implementation of existing and infrastructural in nature and simplify implementation of existing and
other new features. Making them anything but REQUIRED would add other new features. Making them anything but REQUIRED would add
undue complexity to protocol definition and implementation. NFSv4.1 undue complexity to protocol definition and implementation. NFSv4.1
accordingly updates the Minor Versioning guidelines (Section 2.7). accordingly updates the minor versioning guidelines (Section 2.7).
As a minor version, NFSv4.1 is consistent with the overall goals for As a minor version, NFSv4.1 is consistent with the overall goals for
NFSv4, but extends the protocol so as to better meet those goals, NFSv4, but extends the protocol so as to better meet those goals,
based on experiences with NFSv4.0. In addition, NFSv4.1 has adopted based on experiences with NFSv4.0. In addition, NFSv4.1 has adopted
some additional goals, which motivate some of the major extensions in some additional goals, which motivate some of the major extensions in
NFSv4.1. NFSv4.1.
1.2. Scope of this Document 1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1].
1.3. Scope of This Document
This document describes the NFSv4.1 protocol. With respect to This document describes the NFSv4.1 protocol. With respect to
NFSv4.0, this document does not: NFSv4.0, this document does not:
o describe the NFSv4.0 protocol, except where needed to contrast o describe the NFSv4.0 protocol, except where needed to contrast
with NFSv4.1. with NFSv4.1.
o modify the specification of the NFSv4.0 protocol. o modify the specification of the NFSv4.0 protocol.
o clarify the NFSv4.0 protocol. o clarify the NFSv4.0 protocol.
1.3. NFSv4 Goals 1.4. NFSv4 Goals
The NFSv4 protocol is a further revision of the NFS protocol defined The NFSv4 protocol is a further revision of the NFS protocol defined
already by NFSv3 [31]. It retains the essential characteristics of already by NFSv3 [31]. It retains the essential characteristics of
previous versions: easy recovery; independence of transport previous versions: easy recovery; independence of transport
protocols, operating systems and file systems; simplicity; and good protocols, operating systems, and file systems; simplicity; and good
performance. NFSv4 has the following goals: performance. NFSv4 has the following goals:
o Improved access and good performance on the Internet. o Improved access and good performance on the Internet
The protocol is designed to transit firewalls easily, perform well The protocol is designed to transit firewalls easily, perform well
where latency is high and bandwidth is low, and scale to very where latency is high and bandwidth is low, and scale to very
large numbers of clients per server. large numbers of clients per server.
o Strong security with negotiation built into the protocol. o Strong security with negotiation built into the protocol
The protocol builds on the work of the ONCRPC working group in The protocol builds on the work of the ONCRPC working group in
supporting the RPCSEC_GSS protocol. Additionally, the NFSv4.1 supporting the RPCSEC_GSS protocol. Additionally, the NFSv4.1
protocol provides a mechanism to allow clients and servers the protocol provides a mechanism to allow clients and servers the
ability to negotiate security and require clients and servers to ability to negotiate security and require clients and servers to
support a minimal set of security schemes. support a minimal set of security schemes.
o Good cross-platform interoperability. o Good cross-platform interoperability
The protocol features a file system model that provides a useful, The protocol features a file system model that provides a useful,
common set of features that does not unduly favor one file system common set of features that does not unduly favor one file system
or operating system over another. or operating system over another.
o Designed for protocol extensions. o Designed for protocol extensions
The protocol is designed to accept standard extensions within a The protocol is designed to accept standard extensions within a
framework that enable and encourages backward compatibility. framework that enables and encourages backward compatibility.
1.4. NFSv4.1 Goals 1.5. NFSv4.1 Goals
NFSv4.1 has the following goals, within the framework established by NFSv4.1 has the following goals, within the framework established by
the overall NFSv4 goals. the overall NFSv4 goals.
o To correct significant structural weaknesses and oversights o To correct significant structural weaknesses and oversights
discovered in the base protocol. discovered in the base protocol.
o To add clarity and specificity to areas left unaddressed or not o To add clarity and specificity to areas left unaddressed or not
addressed in sufficient detail in the base protocol. However, as addressed in sufficient detail in the base protocol. However, as
stated in Section 1.2, it is not a goal to clarify the NFSv4.0 stated in Section 1.3, it is not a goal to clarify the NFSv4.0
protocol in the NFSv4.1 specification. protocol in the NFSv4.1 specification.
o To add specific features based on experience with the existing o To add specific features based on experience with the existing
protocol and recent industry developments. protocol and recent industry developments.
o To provide protocol support to take advantage of clustered server o To provide protocol support to take advantage of clustered server
deployments including the ability to provide scalable parallel deployments including the ability to provide scalable parallel
access to files distributed among multiple servers. access to files distributed among multiple servers.
1.5. General Definitions 1.6. General Definitions
The following definitions are provided for the purpose of providing The following definitions provide an appropriate context for the
an appropriate context for the reader. reader.
Byte This document defines a byte as an octet, i.e. a datum exactly Byte: In this document, a byte is an octet, i.e., a datum exactly 8
8 bits in length. bits in length.
Client The "client" is the entity that accesses the NFS server's Client: The client is the entity that accesses the NFS server's
resources. The client may be an application which contains the resources. The client may be an application that contains the
logic to access the NFS server directly. The client may also be logic to access the NFS server directly. The client may also be
the traditional operating system client that provides remote file the traditional operating system client that provides remote file
system services for a set of applications. system services for a set of applications.
A client is uniquely identified by a Client Owner. A client is uniquely identified by a client owner.
With reference to file locking, the client is also the entity that With reference to byte-range locking, the client is also the
maintains a set of locks on behalf of one or more applications. entity that maintains a set of locks on behalf of one or more
This client is responsible for crash or failure recovery for those applications. This client is responsible for crash or failure
locks it manages. recovery for those locks it manages.
Note that multiple clients may share the same transport and Note that multiple clients may share the same transport and
connection and multiple clients may exist on the same network connection and multiple clients may exist on the same network
node. node.
Client ID A 64-bit quantity used as a unique, short-hand reference Client ID: The client ID is a 64-bit quantity used as a unique,
to a client supplied Verifier and client owner. The server is short-hand reference to a client-supplied verifier and client
responsible for supplying the client ID. owner. The server is responsible for supplying the client ID.
Client Owner The client owner is a unique string, opaque to the Client Owner: The client owner is a unique string, opaque to the
server, which identifies a client. Multiple network connections server, that identifies a client. Multiple network connections
and source network addresses originating from those connections and source network addresses originating from those connections
may share a client owner. The server is expected to treat may share a client owner. The server is expected to treat
requests from connections with the same client owner as coming requests from connections with the same client owner as coming
from the same client. from the same client.
File System The collection of objects on a server (as identified by File System: The file system is the collection of objects on a
the major identifier of a Server Owner, which is defined later in server (as identified by the major identifier of a server owner,
this section), that share the same fsid attribute (see which is defined later in this section) that share the same fsid
Section 5.8.1.9). attribute (see Section 5.8.1.9).
Lease An interval of time defined by the server for which the client Lease: A lease is an interval of time defined by the server for
is irrevocably granted a lock. At the end of a lease period the which the client is irrevocably granted locks. At the end of a
lock may be revoked if the lease has not been extended. The lock lease period, locks may be revoked if the lease has not been
must be revoked if a conflicting lock has been granted after the extended. A lock must be revoked if a conflicting lock has been
lease interval. granted after the lease interval.
All leases granted by a server have the same fixed interval. Note A server grants a client a single lease for all state.
that the fixed interval was chosen to alleviate the expense a
server would have in maintaining state about variable length
leases across server failures.
Lock The term "lock" is used to refer to byte-range (in UNIX Lock: The term "lock" is used to refer to byte-range (in UNIX
environments, also known as record) locks, share reservations, environments, also known as record) locks, share reservations,
delegations, or layouts unless specifically stated otherwise. delegations, or layouts unless specifically stated otherwise.
Secret State Verifier (SSV) The SSV is a unique secret key shared Secret State Verifier (SSV): The SSV is a unique secret key shared
between a client and server. The SSV serves as the secret key for between a client and server. The SSV serves as the secret key for
an internal (that is, internal to NFSv4.1) GSS mechanism (the SSV an internal (that is, internal to NFSv4.1) Generic Security
GSS mechanism, see Section 2.10.9). The SSV GSS mechanism uses Services (GSS) mechanism (the SSV GSS mechanism; see
the SSV to compute Message Integrity Code (MIC) and Wrap tokens. Section 2.10.9). The SSV GSS mechanism uses the SSV to compute
See Section 2.10.8.3 for more details on how NFSv4.1 uses the SSV message integrity code (MIC) and Wrap tokens. See
and the SSV GSS mechanism. Section 2.10.8.3 for more details on how NFSv4.1 uses the SSV and
the SSV GSS mechanism.
Server The "Server" is the entity responsible for coordinating Server: The Server is the entity responsible for coordinating client
client access to a set of file systems and is identified by a access to a set of file systems and is identified by a server
Server owner. A server can span multiple network addresses. owner. A server can span multiple network addresses.
Server Owner The "Server Owner" identifies the server to the client. Server Owner: The server owner identifies the server to the client.
The server owner consists of a major and minor identifier. When The server owner consists of a major identifier and a minor
the client has two connections each to a peer with the same major identifier. When the client has two connections each to a peer
identifier, the client assumes both peers are the same server (the with the same major identifier, the client assumes that both peers
server namespace is the same via each connection), and assumes and are the same server (the server namespace is the same via each
lock state is sharable across both connections. When each peer connection) and that lock state is sharable across both
has both the same major and minor identifier, the client assumes connections. When each peer has both the same major and minor
each connection might be associable with the same session. identifiers, the client assumes that each connection might be
associable with the same session.
Stable Storage Stable storage is storage from which data stored by Stable Storage: Stable storage is storage from which data stored by
an NFSv4.1 server can be recovered without data loss from multiple an NFSv4.1 server can be recovered without data loss from multiple
power failures (including cascading power failures, that is, power failures (including cascading power failures, that is,
several power failures in quick succession), operating system several power failures in quick succession), operating system
failures, and/or hardware failure of components other than the failures, and/or hardware failure of components other than the
storage medium itself (such as disk, nonvolatile RAM, flash storage medium itself (such as disk, nonvolatile RAM, flash
memory, etc.). memory, etc.).
Some examples of stable storage that are allowable for an NFS Some examples of stable storage that are allowable for an NFS
server include: server include:
1. Media commit of data, that is, the modified data has been 1. Media commit of data; that is, the modified data has been
successfully written to the disk media, for example, the disk successfully written to the disk media, for example, the disk
platter. platter.
2. An immediate reply disk drive with battery-backed on- drive 2. An immediate reply disk drive with battery-backed, on-drive
intermediate storage or uninterruptible power system (UPS). intermediate storage or uninterruptible power system (UPS).
3. Server commit of data with battery-backed intermediate storage 3. Server commit of data with battery-backed intermediate storage
and recovery software. and recovery software.
4. Cache commit with uninterruptible power system (UPS) and 4. Cache commit with uninterruptible power system (UPS) and
recovery software. recovery software.
Stateid A 128-bit quantity returned by a server that uniquely Stateid: A stateid is a 128-bit quantity returned by a server that
defines the open and locking state provided by the server for a uniquely defines the open and locking states provided by the
specific open-owner or lock-owner/open-owner pair for a specific server for a specific open-owner or lock-owner/open-owner pair for
file and type of lock. a specific file and type of lock.
Verifier A 64-bit quantity generated by the client that the server Verifier: A verifier is a 64-bit quantity generated by the client
can use to determine if the client has restarted and lost all that the server can use to determine if the client has restarted
previous lock state. and lost all previous lock state.
1.6. Overview of NFSv4.1 Features 1.7. Overview of NFSv4.1 Features
To provide a reasonable context for the reader, the major features of The major features of the NFSv4.1 protocol will be reviewed in brief.
the NFSv4.1 protocol will be reviewed in brief. This will be done to This will be done to provide an appropriate context for both the
provide an appropriate context for both the reader who is familiar reader who is familiar with the previous versions of the NFS protocol
with the previous versions of the NFS protocol and the reader that is and the reader who is new to the NFS protocols. For the reader new
new to the NFS protocols. For the reader new to the NFS protocols, to the NFS protocols, there is still a set of fundamental knowledge
there is still a set of fundamental knowledge that is expected. The that is expected. The reader should be familiar with the External
reader should be familiar with the XDR and RPC protocols as described Data Representation (XDR) and Remote Procedure Call (RPC) protocols
in [2] and [3]. A basic knowledge of file systems and distributed as described in [2] and [3]. A basic knowledge of file systems and
file systems is expected as well. distributed file systems is expected as well.
In general this specification of NFSv4.1 will not distinguish those In general, this specification of NFSv4.1 will not distinguish those
features added in minor version one from those present in the base features added in minor version 1 from those present in the base
protocol but will treat NFSv4.1 as a unified whole. See Section 1.7 protocol but will treat NFSv4.1 as a unified whole. See Section 1.8
for a summary of the differences between NFSv4.0 and NFSv4.1. for a summary of the differences between NFSv4.0 and NFSv4.1.
1.6.1. RPC and Security 1.7.1. RPC and Security
As with previous versions of NFS, the External Data Representation As with previous versions of NFS, the External Data Representation
(XDR) and Remote Procedure Call (RPC) mechanisms used for the NFSv4.1 (XDR) and Remote Procedure Call (RPC) mechanisms used for the NFSv4.1
protocol are those defined in [2] and [3]. To meet end-to-end protocol are those defined in [2] and [3]. To meet end-to-end
security requirements, the RPCSEC_GSS framework [4] is used to extend security requirements, the RPCSEC_GSS framework [4] is used to extend
the basic RPC security. With the use of RPCSEC_GSS, various the basic RPC security. With the use of RPCSEC_GSS, various
mechanisms can be provided to offer authentication, integrity, and mechanisms can be provided to offer authentication, integrity, and
privacy to the NFSv4 protocol. Kerberos V5 is used as described in privacy to the NFSv4 protocol. Kerberos V5 is used as described in
[5] to provide one security framework. With the use of RPCSEC_GSS, [5] to provide one security framework. With the use of RPCSEC_GSS,
other mechanisms may also be specified and used for NFSv4.1 security. other mechanisms may also be specified and used for NFSv4.1 security.
To enable in-band security negotiation, the NFSv4.1 protocol has To enable in-band security negotiation, the NFSv4.1 protocol has
operations which provide the client a method of querying the server operations that provide the client a method of querying the server
about its policies regarding which security mechanisms must be used about its policies regarding which security mechanisms must be used
for access to the server's file system resources. With this, the for access to the server's file system resources. With this, the
client can securely match the security mechanism that meets the client can securely match the security mechanism that meets the
policies specified at both the client and server. policies specified at both the client and server.
NFSv4.1 introduces parallel access (see Section 1.6.2.2), which is NFSv4.1 introduces parallel access (see Section 1.7.2.2), which is
called pNFS. The security framework described in this section is called pNFS. The security framework described in this section is
significantly modified by the introduction of pNFS (see significantly modified by the introduction of pNFS (see
Section 12.9), because data access is sometimes not over RPC. The Section 12.9), because data access is sometimes not over RPC. The
level of significance varies with the Storage Protocol (see level of significance varies with the storage protocol (see
Section 12.2.5) and can be as low as zero impact (see Section 13.12). Section 12.2.5) and can be as low as zero impact (see Section 13.12).
1.6.2. Protocol Structure 1.7.2. Protocol Structure
1.6.2.1. Core Protocol 1.7.2.1. Core Protocol
Unlike NFSv3, which used a series of ancillary protocols (e.g. NLM, Unlike NFSv3, which used a series of ancillary protocols (e.g., NLM,
NSM, MOUNT), within all minor versions of NFSv4 a single RPC protocol NSM (Network Status Monitor), MOUNT), within all minor versions of
is used to make requests to the server. Facilities that had been NFSv4 a single RPC protocol is used to make requests to the server.
separate protocols, such as locking, are now integrated within a Facilities that had been separate protocols, such as locking, are now
single unified protocol. integrated within a single unified protocol.
1.6.2.2. Parallel Access 1.7.2.2. Parallel Access
Minor version one supports high-performance data access to a Minor version 1 supports high-performance data access to a clustered
clustered server implementation by enabling a separation of metadata server implementation by enabling a separation of metadata access and
access and data access, with the latter done to multiple servers in data access, with the latter done to multiple servers in parallel.
parallel.
Such parallel data access is controlled by recallable objects known Such parallel data access is controlled by recallable objects known
as "layouts", which are integrated into the protocol locking model. as "layouts", which are integrated into the protocol locking model.
Clients direct requests for data access to a set of data servers Clients direct requests for data access to a set of data servers
specified by the layout via a data storage protocol which may be specified by the layout via a data storage protocol which may be
NFSv4.1 or may be another protocol. NFSv4.1 or may be another protocol.
Because the protocols used for parallel data access are not Because the protocols used for parallel data access are not
necessarily RPC-based, the RPC-based security model (Section 1.6.1) necessarily RPC-based, the RPC-based security model (Section 1.7.1)
is obviously impacted (see Section 12.9). The degree of impact is obviously impacted (see Section 12.9). The degree of impact
varies with the Storage Protocol (see Section 12.2.5) used for data varies with the storage protocol (see Section 12.2.5) used for data
access, and can be as low as zero (see Section 13.12). access, and can be as low as zero (see Section 13.12).
1.6.3. File System Model 1.7.3. File System Model
The general file system model used for the NFSv4.1 protocol is the The general file system model used for the NFSv4.1 protocol is the
same as previous versions. The server file system is hierarchical same as previous versions. The server file system is hierarchical
with the regular files contained within being treated as opaque byte with the regular files contained within being treated as opaque byte
streams. In a slight departure, file and directory names are encoded streams. In a slight departure, file and directory names are encoded
with UTF-8 to deal with the basics of internationalization. with UTF-8 to deal with the basics of internationalization.
The NFSv4.1 protocol does not require a separate protocol to provide The NFSv4.1 protocol does not require a separate protocol to provide
for the initial mapping between path name and filehandle. All file for the initial mapping between path name and filehandle. All file
systems exported by a server are presented as a tree so that all file systems exported by a server are presented as a tree so that all file
systems are reachable from a special per-server global root systems are reachable from a special per-server global root
filehandle. This allows LOOKUP operations to be used to perform filehandle. This allows LOOKUP operations to be used to perform
functions previously provided by the MOUNT protocol. The server functions previously provided by the MOUNT protocol. The server
provides any necessary pseudo file systems to bridge any gaps that provides any necessary pseudo file systems to bridge any gaps that
arise due to unexported gaps between exported file systems. arise due to unexported gaps between exported file systems.
1.6.3.1. Filehandles 1.7.3.1. Filehandles
As in previous versions of the NFS protocol, opaque filehandles are As in previous versions of the NFS protocol, opaque filehandles are
used to identify individual files and directories. Lookup-type and used to identify individual files and directories. Lookup-type and
create operations translate file and directory names to filehandles create operations translate file and directory names to filehandles,
which are then used to identify objects in subsequent operations. which are then used to identify objects in subsequent operations.
The NFSv4.1 protocol provides support for persistent filehandles, The NFSv4.1 protocol provides support for persistent filehandles,
guaranteed to be valid for the lifetime of the file system object guaranteed to be valid for the lifetime of the file system object
designated. In addition it provides support to servers to provide designated. In addition, it provides support to servers to provide
filehandles with more limited validity guarantees, called volatile filehandles with more limited validity guarantees, called volatile
filehandles. filehandles.
1.6.3.2. File Attributes 1.7.3.2. File Attributes
The NFSv4.1 protocol has a rich and extensible file object attribute The NFSv4.1 protocol has a rich and extensible file object attribute
structure, which is divided into REQUIRED, RECOMMENDED, and named structure, which is divided into REQUIRED, RECOMMENDED, and named
attributes (see Section 5). attributes (see Section 5).
Several (but not all) of the REQUIRED attributes are derived from the Several (but not all) of the REQUIRED attributes are derived from the
attributes of NFSv3 (see the definition of the fattr3 data type in attributes of NFSv3 (see the definition of the fattr3 data type in
[31]). An example of a REQUIRED attribute is the file object's type [31]). An example of a REQUIRED attribute is the file object's type
(Section 5.8.1.2) so that regular files can be distinguished from (Section 5.8.1.2) so that regular files can be distinguished from
directories (also known as folders in some operating environments) directories (also known as folders in some operating environments)
and other types of objects. REQUIRED attributes are discussed in and other types of objects. REQUIRED attributes are discussed in
Section 5.1. Section 5.1.
An example of three RECOMMENDED attributes are acl, sacl, and dacl. An example of three RECOMMENDED attributes are acl, sacl, and dacl.
These attributes define an Access Control List (ACL) on a file object These attributes define an Access Control List (ACL) on a file object
(Section 6). An ACL provides directory and file access control (Section 6). An ACL provides directory and file access control
beyond the model used in NFSv3. The ACL definition allows for beyond the model used in NFSv3. The ACL definition allows for
specification of specific sets of permissions for individual users specification of specific sets of permissions for individual users
and groups. In addition, ACL inheritance allows propagation of and groups. In addition, ACL inheritance allows propagation of
access permissions and restriction down a directory tree as file access permissions and restrictions down a directory tree as file
system objects are created. RECOMMENDED attributes are discussed in system objects are created. RECOMMENDED attributes are discussed in
Section 5.2. Section 5.2.
A named attribute is an opaque byte stream that is associated with a A named attribute is an opaque byte stream that is associated with a
directory or file and referred to by a string name. Named attributes directory or file and referred to by a string name. Named attributes
are meant to be used by client applications as a method to associate are meant to be used by client applications as a method to associate
application-specific data with a regular file or directory. NFSv4.1 application-specific data with a regular file or directory. NFSv4.1
modifies named attributes relative to NFSv4.0 by tightening the modifies named attributes relative to NFSv4.0 by tightening the
allowed operations in order to prevent the development of non- allowed operations in order to prevent the development of non-
interoperable implementations. Named attributes are discussed in interoperable implementations. Named attributes are discussed in
Section 5.3. Section 5.3.
1.6.3.3. Multi-server Namespace 1.7.3.3. Multi-Server Namespace
NFSv4.1 contains a number of features to allow implementation of NFSv4.1 contains a number of features to allow implementation of
namespaces that cross server boundaries and that allow and facilitate namespaces that cross server boundaries and that allow and facilitate
a non-disruptive transfer of support for individual file systems a non-disruptive transfer of support for individual file systems
between servers. They are all based upon attributes that allow one between servers. They are all based upon attributes that allow one
file system to specify alternate or new locations for that file file system to specify alternate or new locations for that file
system. system.
These attributes may be used together with the concept of absent file These attributes may be used together with the concept of absent file
systems, which provide specifications for additional locations but no systems, which provide specifications for additional locations but no
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o Location attributes may be provided for present file systems to o Location attributes may be provided for present file systems to
provide the locations of alternate file system instances or provide the locations of alternate file system instances or
replicas to be used in the event that the current file system replicas to be used in the event that the current file system
instance becomes unavailable. instance becomes unavailable.
o Location attributes may be provided when a previously present file o Location attributes may be provided when a previously present file
system becomes absent. This allows non-disruptive migration of system becomes absent. This allows non-disruptive migration of
file systems to alternate servers. file systems to alternate servers.
1.6.4. Locking Facilities 1.7.4. Locking Facilities
As mentioned previously, NFS v4.1 is a single protocol which includes As mentioned previously, NFSv4.1 is a single protocol that includes
locking facilities. These locking facilities include support for locking facilities. These locking facilities include support for
many types of locks including a number of sorts of recallable locks. many types of locks including a number of sorts of recallable locks.
Recallable locks such as delegations allow the client to be assured Recallable locks such as delegations allow the client to be assured
that certain events will not occur so long as that lock is held. that certain events will not occur so long as that lock is held.
When circumstances change, the lock is recalled via a callback When circumstances change, the lock is recalled via a callback
request. The assurances provided by delegations allow more extensive request. The assurances provided by delegations allow more extensive
caching to be done safely when circumstances allow it. caching to be done safely when circumstances allow it.
The types of locks are: The types of locks are:
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o File delegations, which are recallable locks that assure the o File delegations, which are recallable locks that assure the
holder that inconsistent opens and file changes cannot occur so holder that inconsistent opens and file changes cannot occur so
long as the delegation is held. long as the delegation is held.
o Directory delegations, which are recallable locks that assure the o Directory delegations, which are recallable locks that assure the
holder that inconsistent directory modifications cannot occur so holder that inconsistent directory modifications cannot occur so
long as the delegation is held. long as the delegation is held.
o Layouts, which are recallable objects that assure the holder that o Layouts, which are recallable objects that assure the holder that
direct access to the file data may be performed directly by the direct access to the file data may be performed directly by the
client and that no change to the data's location inconsistent with client and that no change to the data's location that is
that access may be made so long as the layout is held. inconsistent with that access may be made so long as the layout is
held.
All locks for a given client are tied together under a single client- All locks for a given client are tied together under a single client-
wide lease. All requests made on sessions associated with the client wide lease. All requests made on sessions associated with the client
renew that lease. When leases are not promptly renewed locks are renew that lease. When the client's lease is not promptly renewed,
subject to revocation. In the event of server restart, clients have the client's locks are subject to revocation. In the event of server
the opportunity to safely reclaim their locks within a special grace restart, clients have the opportunity to safely reclaim their locks
period. within a special grace period.
1.7. Differences from NFSv4.0 1.8. Differences from NFSv4.0
The following summarizes the major differences between minor version The following summarizes the major differences between minor version
one and the base protocol: 1 and the base protocol:
o Implementation of the sessions model (Section 2.10). o Implementation of the sessions model (Section 2.10).
o Parallel access to data (Section 12). o Parallel access to data (Section 12).
o Addition of the RECLAIM_COMPLETE operation to better structure the o Addition of the RECLAIM_COMPLETE operation to better structure the
lock reclamation process (Section 18.51). lock reclamation process (Section 18.51).
o Enhanced delegation support as follows. o Enhanced delegation support as follows.
* Delegations on directories and other file types in addition to * Delegations on directories and other file types in addition to
regular files (Section 18.39, Section 18.49). regular files (Section 18.39, Section 18.49).
* Operations to optimize acquisition of recalled or denied * Operations to optimize acquisition of recalled or denied
delegations (Section 18.49, Section 20.5, Section 20.7). delegations (Section 18.49, Section 20.5, Section 20.7).
* Notifications of changes to files and directories * Notifications of changes to files and directories
(Section 18.39, Section 20.4). (Section 18.39, Section 20.4).
* A method to allow a server to indicate it is recalling one or * A method to allow a server to indicate that it is recalling one
more delegations for resource management reasons, and thus a or more delegations for resource management reasons, and thus a
method to allow the client to pick which delegations to return method to allow the client to pick which delegations to return
(Section 20.6). (Section 20.6).
o Attributes can be set atomically during exclusive file create via o Attributes can be set atomically during exclusive file create via
the OPEN operation (see the new EXCLUSIVE4_1 creation method in the OPEN operation (see the new EXCLUSIVE4_1 creation method in
Section 18.16). Section 18.16).
o Open files can be preserved if removed and the hard link count o Open files can be preserved if removed and the hard link count
("hard link" is defined in an Open Group [6] standard) goes to ("hard link" is defined in an Open Group [6] standard) goes to
zero thus obviating the need for clients to rename deleted files zero, thus obviating the need for clients to rename deleted files
to partially hidden names -- colloquially called "silly rename" to partially hidden names -- colloquially called "silly rename"
(see the new OPEN4_RESULT_PRESERVE_UNLINKED reply flag in (see the new OPEN4_RESULT_PRESERVE_UNLINKED reply flag in
Section 18.16). Section 18.16).
o Improved compatibility with Microsoft Windows for Access Control o Improved compatibility with Microsoft Windows for Access Control
Lists (Section 6.2.3, Section 6.2.2, Section 6.4.3.2). Lists (Section 6.2.3, Section 6.2.2, Section 6.4.3.2).
o Data retention (Section 5.13). o Data retention (Section 5.13).
o Identification of the implementation of the NFS client and server o Identification of the implementation of the NFS client and server
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NFSv4.1 relies on core infrastructure common to nearly every NFSv4.1 relies on core infrastructure common to nearly every
operation. This core infrastructure is described in the remainder of operation. This core infrastructure is described in the remainder of
this section. this section.
2.2. RPC and XDR 2.2. RPC and XDR
The NFSv4.1 protocol is a Remote Procedure Call (RPC) application The NFSv4.1 protocol is a Remote Procedure Call (RPC) application
that uses RPC version 2 and the corresponding eXternal Data that uses RPC version 2 and the corresponding eXternal Data
Representation (XDR) as defined in [3] and [2]. Representation (XDR) as defined in [3] and [2].
2.2.1. RPC-based Security 2.2.1. RPC-Based Security
Previous NFS versions have been thought of as having a host-based Previous NFS versions have been thought of as having a host-based
authentication model, where the NFS server authenticates the NFS authentication model, where the NFS server authenticates the NFS
client, and trusts the client to authenticate all users. Actually, client, and trusts the client to authenticate all users. Actually,
NFS has always depended on RPC for authentication. One of the first NFS has always depended on RPC for authentication. One of the first
forms of RPC authentication, AUTH_SYS, had no strong authentication, forms of RPC authentication, AUTH_SYS, had no strong authentication
and required a host-based authentication approach. NFSv4.1 also and required a host-based authentication approach. NFSv4.1 also
depends on RPC for basic security services, and mandates RPC support depends on RPC for basic security services and mandates RPC support
for a user-based authentication model. The user-based authentication for a user-based authentication model. The user-based authentication
model has user principals authenticated by a server, and in turn the model has user principals authenticated by a server, and in turn the
server authenticated by user principals. RPC provides some basic server authenticated by user principals. RPC provides some basic
security services which are used by NFSv4.1. security services that are used by NFSv4.1.
2.2.1.1. RPC Security Flavors 2.2.1.1. RPC Security Flavors
As described in section 7.2 "Authentication" of [3], RPC security is As described in Section 7.2 ("Authentication") of [3], RPC security
encapsulated in the RPC header, via a security or authentication is encapsulated in the RPC header, via a security or authentication
flavor, and information specific to the specified security flavor. flavor, and information specific to the specified security flavor.
Every RPC header conveys information used to identify and Every RPC header conveys information used to identify and
authenticate a client and server. As discussed in Section 2.2.1.1.1, authenticate a client and server. As discussed in Section 2.2.1.1.1,
some security flavors provide additional security services. some security flavors provide additional security services.
NFSv4.1 clients and servers MUST implement RPCSEC_GSS. (This NFSv4.1 clients and servers MUST implement RPCSEC_GSS. (This
requirement to implement is not a requirement to use.) Other requirement to implement is not a requirement to use.) Other
flavors, such as AUTH_NONE, and AUTH_SYS, MAY be implemented as well. flavors, such as AUTH_NONE and AUTH_SYS, MAY be implemented as well.
2.2.1.1.1. RPCSEC_GSS and Security Services 2.2.1.1.1. RPCSEC_GSS and Security Services
RPCSEC_GSS ([4]) uses the functionality of GSS-API [7]. This allows RPCSEC_GSS [4] uses the functionality of GSS-API [7]. This allows
for the use of various security mechanisms by the RPC layer without for the use of various security mechanisms by the RPC layer without
the additional implementation overhead of adding RPC security the additional implementation overhead of adding RPC security
flavors. flavors.
2.2.1.1.1.1. Identification, Authentication, Integrity, Privacy 2.2.1.1.1.1. Identification, Authentication, Integrity, Privacy
Via the GSS-API, RPCSEC_GSS can be used to identify and authenticate Via the GSS-API, RPCSEC_GSS can be used to identify and authenticate
users on clients to servers, and servers to users. It can also users on clients to servers, and servers to users. It can also
perform integrity checking on the entire RPC message, including the perform integrity checking on the entire RPC message, including the
RPC header, and the arguments or results. Finally, privacy, usually RPC header, and on the arguments or results. Finally, privacy,
via encryption, is a service available with RPCSEC_GSS. Privacy is usually via encryption, is a service available with RPCSEC_GSS.
performed on the arguments and results. Note that if privacy is Privacy is performed on the arguments and results. Note that if
selected, integrity, authentication, and identification are enabled. privacy is selected, integrity, authentication, and identification
If privacy is not selected, but integrity is selected, authentication are enabled. If privacy is not selected, but integrity is selected,
and identification are enabled. If integrity and privacy are not authentication and identification are enabled. If integrity and
selected, but authentication is enabled, identification is enabled. privacy are not selected, but authentication is enabled,
RPCSEC_GSS does not provide identification as a separate service. identification is enabled. RPCSEC_GSS does not provide
identification as a separate service.
Although GSS-API has an authentication service distinct from its Although GSS-API has an authentication service distinct from its
privacy and integrity services, GSS-API's authentication service is privacy and integrity services, GSS-API's authentication service is
not used for RPCSEC_GSS's authentication service. Instead, each RPC not used for RPCSEC_GSS's authentication service. Instead, each RPC
request and response header is integrity protected with the GSS-API request and response header is integrity protected with the GSS-API
integrity service, and this allows RPCSEC_GSS to offer per-RPC integrity service, and this allows RPCSEC_GSS to offer per-RPC
authentication and identity. See [4] for more information. authentication and identity. See [4] for more information.
NFSv4.1 client and servers MUST support RPCSEC_GSS's integrity and NFSv4.1 client and servers MUST support RPCSEC_GSS's integrity and
authentication service. NFSv4.1 servers MUST support RPCSEC_GSS's authentication service. NFSv4.1 servers MUST support RPCSEC_GSS's
privacy service. NFSv4.1 clients SHOULD support RPCSEC_GSS's privacy privacy service. NFSv4.1 clients SHOULD support RPCSEC_GSS's privacy
service. service.
2.2.1.1.1.2. Security mechanisms for NFSv4.1 2.2.1.1.1.2. Security Mechanisms for NFSv4.1
RPCSEC_GSS, via GSS-API, normalizes access to mechanisms that provide RPCSEC_GSS, via GSS-API, normalizes access to mechanisms that provide
security services. Therefore NFSv4.1 clients and servers MUST security services. Therefore, NFSv4.1 clients and servers MUST
support the Kerberos V5 security mechanism. support the Kerberos V5 security mechanism.
The use of RPCSEC_GSS requires selection of: mechanism, quality of The use of RPCSEC_GSS requires selection of mechanism, quality of
protection (QOP), and service (authentication, integrity, privacy). protection (QOP), and service (authentication, integrity, privacy).
For the mandated security mechanisms, NFSv4.1 specifies that a QOP of For the mandated security mechanisms, NFSv4.1 specifies that a QOP of
zero (0) is used, leaving it up to the mechanism or the mechanism's zero is used, leaving it up to the mechanism or the mechanism's
configuration to map QOP zero to an appropriate level of protection. configuration to map QOP zero to an appropriate level of protection.
Each mandated mechanism specifies minimum set of cryptographic Each mandated mechanism specifies a minimum set of cryptographic
algorithms for implementing integrity and privacy. NFSv4.1 clients algorithms for implementing integrity and privacy. NFSv4.1 clients
and servers MUST be implemented on operating environments that comply and servers MUST be implemented on operating environments that comply
with the REQUIRED cryptographic algorithms of each REQUIRED with the REQUIRED cryptographic algorithms of each REQUIRED
mechanism. mechanism.
2.2.1.1.1.2.1. Kerberos V5 2.2.1.1.1.2.1. Kerberos V5
The Kerberos V5 GSS-API mechanism as described in [5] MUST be The Kerberos V5 GSS-API mechanism as described in [5] MUST be
implemented with the RPCSEC_GSS services as specified in the implemented with the RPCSEC_GSS services as specified in the
following table: following table:
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4 == RPCSEC_GSS service 4 == RPCSEC_GSS service
5 == NFSv4.1 clients MUST support 5 == NFSv4.1 clients MUST support
6 == NFSv4.1 servers MUST support 6 == NFSv4.1 servers MUST support
1 2 3 4 5 6 1 2 3 4 5 6
------------------------------------------------------------------ ------------------------------------------------------------------
390003 krb5 1.2.840.113554.1.2.2 rpc_gss_svc_none yes yes 390003 krb5 1.2.840.113554.1.2.2 rpc_gss_svc_none yes yes
390004 krb5i 1.2.840.113554.1.2.2 rpc_gss_svc_integrity yes yes 390004 krb5i 1.2.840.113554.1.2.2 rpc_gss_svc_integrity yes yes
390005 krb5p 1.2.840.113554.1.2.2 rpc_gss_svc_privacy no yes 390005 krb5p 1.2.840.113554.1.2.2 rpc_gss_svc_privacy no yes
Note that the number and name of the pseudo flavor is presented here Note that the number and name of the pseudo flavor are presented here
as a mapping aid to the implementor. Because the NFSv4.1 protocol as a mapping aid to the implementor. Because the NFSv4.1 protocol
includes a method to negotiate security and it understands the GSS- includes a method to negotiate security and it understands the GSS-
API mechanism, the pseudo flavor is not needed. The pseudo flavor is API mechanism, the pseudo flavor is not needed. The pseudo flavor is
needed for the NFSv3 since the security negotiation is done via the needed for the NFSv3 since the security negotiation is done via the
MOUNT protocol as described in [33]. MOUNT protocol as described in [33].
At the time NFSv4.1 was specified, AES with HMAC-SHA1 was a REQUIRED At the time NFSv4.1 was specified, the Advanced Encryption Standard
algorithm set for Kerberos V5. In contrast, when NFSv4.0 was (AES) with HMAC-SHA1 was a REQUIRED algorithm set for Kerberos V5.
specified, weaker algorithm sets were REQUIRED for Kerberos V5, and In contrast, when NFSv4.0 was specified, weaker algorithm sets were
were REQUIRED in the NFSv4.0 specification, because the Kerberos V5 REQUIRED for Kerberos V5, and were REQUIRED in the NFSv4.0
specification at the time did not specify stronger algorithms. The specification, because the Kerberos V5 specification at the time did
NFSv4.1 specification does not specify REQUIRED algorithms for not specify stronger algorithms. The NFSv4.1 specification does not
Kerberos V5, and instead, the implementor is expected to track the specify REQUIRED algorithms for Kerberos V5, and instead, the
evolution of the Kerberos V5 standard if and when stronger algorithms implementor is expected to track the evolution of the Kerberos V5
are specified. standard if and when stronger algorithms are specified.
2.2.1.1.1.2.1.1. Security Considerations for Cryptographic Algorithms 2.2.1.1.1.2.1.1. Security Considerations for Cryptographic Algorithms
in Kerberos V5 in Kerberos V5
When deploying NFSv4.1, the strength of the security achieved depends When deploying NFSv4.1, the strength of the security achieved depends
on the existing Kerberos V5 infrastructure. The algorithms of on the existing Kerberos V5 infrastructure. The algorithms of
Kerberos V5 are not directly exposed to or selectable by the client Kerberos V5 are not directly exposed to or selectable by the client
or server, so there is some due diligence required by the user of or server, so there is some due diligence required by the user of
NFSv4.1 to ensure that security is acceptable where where needed. NFSv4.1 to ensure that security is acceptable where needed.
2.2.1.1.1.3. GSS Server Principal 2.2.1.1.1.3. GSS Server Principal
Regardless of what security mechanism under RPCSEC_GSS is being used, Regardless of what security mechanism under RPCSEC_GSS is being used,
the NFS server, MUST identify itself in GSS-API via a the NFS server MUST identify itself in GSS-API via a
GSS_C_NT_HOSTBASED_SERVICE name type. GSS_C_NT_HOSTBASED_SERVICE GSS_C_NT_HOSTBASED_SERVICE name type. GSS_C_NT_HOSTBASED_SERVICE
names are of the form: names are of the form:
service@hostname service@hostname
For NFS, the "service" element is For NFS, the "service" element is
nfs nfs
Implementations of security mechanisms will convert nfs@hostname to Implementations of security mechanisms will convert nfs@hostname to
various different forms. For Kerberos V5 the following form is various different forms. For Kerberos V5, the following form is
RECOMMENDED: RECOMMENDED:
nfs/hostname nfs/hostname
2.3. COMPOUND and CB_COMPOUND 2.3. COMPOUND and CB_COMPOUND
A significant departure from the versions of the NFS protocol before A significant departure from the versions of the NFS protocol before
NFSv4 is the introduction of the COMPOUND procedure. For the NFSv4 NFSv4 is the introduction of the COMPOUND procedure. For the NFSv4
protocol, in all minor versions, there are exactly two RPC protocol, in all minor versions, there are exactly two RPC
procedures, NULL and COMPOUND. The COMPOUND procedure is defined as procedures, NULL and COMPOUND. The COMPOUND procedure is defined as
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of facilities exist to pass results from one operation to another. of facilities exist to pass results from one operation to another.
Once an operation returns a failing result, the evaluation ends and Once an operation returns a failing result, the evaluation ends and
the results of all evaluated operations are returned to the client. the results of all evaluated operations are returned to the client.
With the use of the COMPOUND procedure, the client is able to build With the use of the COMPOUND procedure, the client is able to build
simple or complex requests. These COMPOUND requests allow for a simple or complex requests. These COMPOUND requests allow for a
reduction in the number of RPCs needed for logical file system reduction in the number of RPCs needed for logical file system
operations. For example, multi-component lookup requests can be operations. For example, multi-component lookup requests can be
constructed by combining multiple LOOKUP operations. Those can be constructed by combining multiple LOOKUP operations. Those can be
further combined with operations such as GETATTR, READDIR, or OPEN further combined with operations such as GETATTR, READDIR, or OPEN
plus READ to do more complicated sets of operations without incurring plus READ to do more complicated sets of operation without incurring
additional latency. additional latency.
NFSv4.1 also contains a considerable set of callback operations in NFSv4.1 also contains a considerable set of callback operations in
which the server makes an RPC directed at the client. Callback RPCs which the server makes an RPC directed at the client. Callback RPCs
have a similar structure to that of the normal server requests. In have a similar structure to that of the normal server requests. In
all minor versions of the NFSv4 protocol there are two callback RPC all minor versions of the NFSv4 protocol, there are two callback RPC
procedures, CB_NULL and CB_COMPOUND. The CB_COMPOUND procedure is procedures: CB_NULL and CB_COMPOUND. The CB_COMPOUND procedure is
defined in an analogous fashion to that of COMPOUND with its own set defined in an analogous fashion to that of COMPOUND with its own set
of callback operations. of callback operations.
The addition of new server and callback operations within the The addition of new server and callback operations within the
COMPOUND and CB_COMPOUND request framework provides a means of COMPOUND and CB_COMPOUND request framework provides a means of
extending the protocol in subsequent minor versions. extending the protocol in subsequent minor versions.
Except for a small number of operations needed for session creation, Except for a small number of operations needed for session creation,
server requests and callback requests are performed within the server requests and callback requests are performed within the
context of a session. Sessions provide a client context for every context of a session. Sessions provide a client context for every
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Unlike NFSv4.0, the only NFSv4.1 operations possible before a client Unlike NFSv4.0, the only NFSv4.1 operations possible before a client
ID is established are those needed to establish the client ID. ID is established are those needed to establish the client ID.
A sequence of an EXCHANGE_ID operation followed by a CREATE_SESSION A sequence of an EXCHANGE_ID operation followed by a CREATE_SESSION
operation using that client ID (eir_clientid as returned from operation using that client ID (eir_clientid as returned from
EXCHANGE_ID) is required to establish and confirm the client ID on EXCHANGE_ID) is required to establish and confirm the client ID on
the server. Establishment of identification by a new incarnation of the server. Establishment of identification by a new incarnation of
the client also has the effect of immediately releasing any locking the client also has the effect of immediately releasing any locking
state that a previous incarnation of that same client might have had state that a previous incarnation of that same client might have had
on the server. Such released state would include all lock, share on the server. Such released state would include all byte-range
reservation, layout state, and where the server is not supporting the lock, share reservation, layout state, and -- where the server
CLAIM_DELEGATE_PREV claim type, all delegation state associated with supports neither the CLAIM_DELEGATE_PREV nor CLAIM_DELEG_CUR_FH claim
the same client with the same identity. For discussion of delegation types -- all delegation state associated with the same client with
state recovery, see Section 10.2.1. For discussion of layout state the same identity. For discussion of delegation state recovery, see
recovery see Section 12.7.1. Section 10.2.1. For discussion of layout state recovery, see
Section 12.7.1.
Releasing such state requires that the server be able to determine Releasing such state requires that the server be able to determine
that one client instance is the successor of another. Where this that one client instance is the successor of another. Where this
cannot be done, for any of a number of reasons, the locking state cannot be done, for any of a number of reasons, the locking state
will remain for a time subject to lease expiration (see Section 8.3) will remain for a time subject to lease expiration (see Section 8.3)
and the new client will need to wait for such state to be removed, if and the new client will need to wait for such state to be removed, if
it makes conflicting lock requests. it makes conflicting lock requests.
Client identification is encapsulated in the following Client Owner Client identification is encapsulated in the following client owner
data type: data type:
struct client_owner4 { struct client_owner4 {
verifier4 co_verifier; verifier4 co_verifier;
opaque co_ownerid<NFS4_OPAQUE_LIMIT>; opaque co_ownerid<NFS4_OPAQUE_LIMIT>;
}; };
The first field, co_verifier, is a client incarnation verifier. The The first field, co_verifier, is a client incarnation verifier. The
server will start the process of canceling the client's leased state server will start the process of canceling the client's leased state
if co_verifier is different than what the server has previously if co_verifier is different than what the server has previously
recorded for the identified client (as specified in the co_ownerid recorded for the identified client (as specified in the co_ownerid
field). field).
The second field, co_ownerid is a variable length string that The second field, co_ownerid, is a variable length string that
uniquely defines the client so that subsequent instances of the same uniquely defines the client so that subsequent instances of the same
client bear the same co_ownerid with a different verifier. client bear the same co_ownerid with a different verifier.
There are several considerations for how the client generates the There are several considerations for how the client generates the
co_ownerid string: co_ownerid string:
o The string should be unique so that multiple clients do not o The string should be unique so that multiple clients do not
present the same string. The consequences of two clients present the same string. The consequences of two clients
presenting the same string range from one client getting an error presenting the same string range from one client getting an error
to one client having its leased state abruptly and unexpectedly to one client having its leased state abruptly and unexpectedly
cancelled. cancelled.
o The string should be selected so that subsequent incarnations o The string should be selected so that subsequent incarnations
(e.g. restarts) of the same client cause the client to present the (e.g., restarts) of the same client cause the client to present
same string. The implementor is cautioned from an approach that the same string. The implementor is cautioned from an approach
requires the string to be recorded in a local file because this that requires the string to be recorded in a local file because
precludes the use of the implementation in an environment where this precludes the use of the implementation in an environment
there is no local disk and all file access is from an NFSv4.1 where there is no local disk and all file access is from an
server. NFSv4.1 server.
o The string should be the same for each server network address that o The string should be the same for each server network address that
the client accesses. This way, if a server has multiple the client accesses. This way, if a server has multiple
interfaces, the client can trunk traffic over multiple network interfaces, the client can trunk traffic over multiple network
paths as described in Section 2.10.5. (Note: the precise opposite paths as described in Section 2.10.5. (Note: the precise opposite
was advised in the NFSv4.0 specification [30].) was advised in the NFSv4.0 specification [30].)
o The algorithm for generating the string should not assume that the o The algorithm for generating the string should not assume that the
client's network address will not change, unless the client client's network address will not change, unless the client
implementation knows it is using statically assigned network implementation knows it is using statically assigned network
addresses. This includes changes between client incarnations and addresses. This includes changes between client incarnations and
even changes while the client is still running in its current even changes while the client is still running in its current
incarnation. Thus with dynamic address assignment, if the client incarnation. Thus, with dynamic address assignment, if the client
includes just the client's network address in the co_ownerid includes just the client's network address in the co_ownerid
string, there is a real risk that after the client gives up the string, there is a real risk that after the client gives up the
network address, another client, using a similar algorithm for network address, another client, using a similar algorithm for
generating the co_ownerid string, would generate a conflicting generating the co_ownerid string, would generate a conflicting
co_ownerid string. co_ownerid string.
Given the above considerations, an example of a well generated Given the above considerations, an example of a well-generated
co_ownerid string is one that includes: co_ownerid string is one that includes:
o If applicable, the client's statically assigned network address. o If applicable, the client's statically assigned network address.
o Additional information that tends to be unique, such as one or o Additional information that tends to be unique, such as one or
more of: more of:
* The client machine's serial number (for privacy reasons, it is * The client machine's serial number (for privacy reasons, it is
best to perform some one way function on the serial number). best to perform some one-way function on the serial number).
* A MAC address (again, a one way function should be performed). * A Media Access Control (MAC) address (again, a one-way function
should be performed).
* The timestamp of when the NFSv4.1 software was first installed * The timestamp of when the NFSv4.1 software was first installed
on the client (though this is subject to the previously on the client (though this is subject to the previously
mentioned caution about using information that is stored in a mentioned caution about using information that is stored in a
file, because the file might only be accessible over NFSv4.1). file, because the file might only be accessible over NFSv4.1).
* A true random number. However since this number ought to be * A true random number. However, since this number ought to be
the same between client incarnations, this shares the same the same between client incarnations, this shares the same
problem as that of using the timestamp of the software problem as that of using the timestamp of the software
installation. installation.
o For a user level NFSv4.1 client, it should contain additional o For a user-level NFSv4.1 client, it should contain additional
information to distinguish the client from other user level information to distinguish the client from other user-level
clients running on the same host, such as a process identifier or clients running on the same host, such as a process identifier or
other unique sequence. other unique sequence.
The client ID is assigned by the server (the eir_clientid result from The client ID is assigned by the server (the eir_clientid result from
EXCHANGE_ID) and should be chosen so that it will not conflict with a EXCHANGE_ID) and should be chosen so that it will not conflict with a
client ID previously assigned by the server. This applies across client ID previously assigned by the server. This applies across
server restarts. server restarts.
In the event of a server restart, a client may find out that its In the event of a server restart, a client may find out that its
current client ID is no longer valid when it receives an current client ID is no longer valid when it receives an
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a server restart. When the existing client ID is presented to a a server restart. When the existing client ID is presented to a
server as part of creating a session and that client ID is not server as part of creating a session and that client ID is not
recognized, as would happen after a server restart, the server will recognized, as would happen after a server restart, the server will
reject the request with the error NFS4ERR_STALE_CLIENTID. reject the request with the error NFS4ERR_STALE_CLIENTID.
In the case of the session being persistent, the client will re- In the case of the session being persistent, the client will re-
establish communication using the existing session after the restart. establish communication using the existing session after the restart.
This session will be associated with the existing client ID but may This session will be associated with the existing client ID but may
only be used to retransmit operations that the client previously only be used to retransmit operations that the client previously
transmitted and did not see replies to. Replies to operations that transmitted and did not see replies to. Replies to operations that
the server previously performed will come from the reply cache, the server previously performed will come from the reply cache;
otherwise NFS4ERR_DEADSESSION will be returned. Hence, such a otherwise, NFS4ERR_DEADSESSION will be returned. Hence, such a
session is referred to as "dead". In this situation, in order to session is referred to as "dead". In this situation, in order to
perform new operations, the client needs to establish a new session. perform new operations, the client needs to establish a new session.
If an attempt is made to establish this new session with the existing If an attempt is made to establish this new session with the existing
client ID, the server will reject the request with client ID, the server will reject the request with
NFS4ERR_STALE_CLIENTID. NFS4ERR_STALE_CLIENTID.
When NFS4ERR_STALE_CLIENTID is received in either of these When NFS4ERR_STALE_CLIENTID is received in either of these
situations, the client needs to obtain a new client ID by use of the situations, the client needs to obtain a new client ID by use of the
EXCHANGE_ID operation, then use that client ID as the basis of a new EXCHANGE_ID operation, then use that client ID as the basis of a new
session, and then proceed to any other necessary recovery for the session, and then proceed to any other necessary recovery for the
server restart case (See Section 8.4.2). server restart case (see Section 8.4.2).
See the descriptions of EXCHANGE_ID (Section 18.35) and See the descriptions of EXCHANGE_ID (Section 18.35) and
CREATE_SESSION (Section 18.36) for a complete specification of these CREATE_SESSION (Section 18.36) for a complete specification of these
operations. operations.
2.4.1. Upgrade from NFSv4.0 to NFSv4.1 2.4.1. Upgrade from NFSv4.0 to NFSv4.1
To facilitate upgrade from NFSv4.0 to NFSv4.1, a server may compare a To facilitate upgrade from NFSv4.0 to NFSv4.1, a server may compare a
client_owner4 in an EXCHANGE_ID with an nfs_client_id4 established value of data type client_owner4 in an EXCHANGE_ID with a value of
using the SETCLIENTID operation of NFSv4.0. A server that does so data type nfs_client_id4 that was established using the SETCLIENTID
will allow an upgraded client to avoid waiting until the lease (i.e. operation of NFSv4.0. A server that does so will allow an upgraded
the lease established by the NFSv4.0 instance client) expires. This client to avoid waiting until the lease (i.e., the lease established
requires the client_owner4 be constructed the same way as the by the NFSv4.0 instance client) expires. This requires that the
nfs_client_id4. If the latter's contents included the server's value of data type client_owner4 be constructed the same way as the
network address (per the recommendations of the NFSv4.0 specification value of data type nfs_client_id4. If the latter's contents included
[30]), and the NFSv4.1 client does not wish to use a client ID that the server's network address (per the recommendations of the NFSv4.0
prevents trunking, it should send two EXCHANGE_ID operations. The specification [30]), and the NFSv4.1 client does not wish to use a
first EXCHANGE_ID will have a client_owner4 equal to the client ID that prevents trunking, it should send two EXCHANGE_ID
nfs_client_id4. This will clear the state created by the NFSv4.0 operations. The first EXCHANGE_ID will have a client_owner4 equal to
the nfs_client_id4. This will clear the state created by the NFSv4.0
client. The second EXCHANGE_ID will not have the server's network client. The second EXCHANGE_ID will not have the server's network
address. The state created for the second EXCHANGE_ID will not have address. The state created for the second EXCHANGE_ID will not have
to wait for lease expiration, because there will be no state to to wait for lease expiration, because there will be no state to
expire. expire.
2.4.2. Server Release of Client ID 2.4.2. Server Release of Client ID
NFSv4.1 introduces a new operation called DESTROY_CLIENTID NFSv4.1 introduces a new operation called DESTROY_CLIENTID
(Section 18.50) which the client SHOULD use to destroy a client ID it (Section 18.50), which the client SHOULD use to destroy a client ID
no longer needs. This permits graceful, bilateral release of a it no longer needs. This permits graceful, bilateral release of a
client ID. The operation cannot be used if there are sessions client ID. The operation cannot be used if there are sessions
associated with the client ID, or state with an unexpired lease. associated with the client ID, or state with an unexpired lease.
If the server determines that the client holds no associated state If the server determines that the client holds no associated state
for its client ID (associated state includes unrevoked sessions, for its client ID (associated state includes unrevoked sessions,
opens, locks, delegations, layouts, and wants), the server MAY choose opens, locks, delegations, layouts, and wants), the server MAY choose
to unilaterally release the client ID in order to conserve resources. to unilaterally release the client ID in order to conserve resources.
If the client contacts the server after this release, the server MUST If the client contacts the server after this release, the server MUST
ensure the client receives the appropriate error so that it will use ensure that the client receives the appropriate error so that it will
the EXCHANGE_ID/CREATE_SESSION sequence to establish a new client ID. use the EXCHANGE_ID/CREATE_SESSION sequence to establish a new client
The server ought to be very hesitant to release a client ID since the ID. The server ought to be very hesitant to release a client ID
resulting work on the client to recover from such an event will be since the resulting work on the client to recover from such an event
the same burden as if the server had failed and restarted. Typically will be the same burden as if the server had failed and restarted.
a server would not release a client ID unless there had been no Typically, a server would not release a client ID unless there had
activity from that client for many minutes. As long as there are been no activity from that client for many minutes. As long as there
sessions, opens, locks, delegations, layouts, or wants, the server are sessions, opens, locks, delegations, layouts, or wants, the
MUST NOT release the client ID. See Section 2.10.13.1.4 for a server MUST NOT release the client ID. See Section 2.10.13.1.4 for
discussion on releasing inactive sessions. discussion on releasing inactive sessions.
2.4.3. Resolving Client Owner Conflicts 2.4.3. Resolving Client Owner Conflicts
When the server gets an EXCHANGE_ID for a client owner that currently When the server gets an EXCHANGE_ID for a client owner that currently
has no state, or that has state, but the lease has expired, the has no state, or that has state but the lease has expired, the server
server MUST allow the EXCHANGE_ID, and confirm the new client ID if MUST allow the EXCHANGE_ID and confirm the new client ID if followed
followed by the appropriate CREATE_SESSION. by the appropriate CREATE_SESSION.
When the server gets an EXCHANGE_ID for a new incarnation of a client When the server gets an EXCHANGE_ID for a new incarnation of a client
owner that currently has an old incarnation with state and an owner that currently has an old incarnation with state and an
unexpired lease, the server is allowed to dispose of the state of the unexpired lease, the server is allowed to dispose of the state of the
previous incarnation of the client owner if one of the following are previous incarnation of the client owner if one of the following is
true: true:
o The principal that created the client ID for the client owner is o The principal that created the client ID for the client owner is
the same as the principal that is sending the EXCHANGE_ID the same as the principal that is sending the EXCHANGE_ID
operation. Note that if the client ID was created with operation. Note that if the client ID was created with
SP4_MACH_CRED state protection (Section 18.35), the principal MUST SP4_MACH_CRED state protection (Section 18.35), the principal MUST
be based on RPCSEC_GSS authentication, the RPCSEC_GSS service used be based on RPCSEC_GSS authentication, the RPCSEC_GSS service used
MUST be integrity or privacy, and the same GSS mechanism and MUST be integrity or privacy, and the same GSS mechanism and
principal MUST be used as that used when the client ID was principal MUST be used as that used when the client ID was
created. created.
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client ID was created. client ID was created.
If none of the above situations apply, the server MUST return If none of the above situations apply, the server MUST return
NFS4ERR_CLID_INUSE. NFS4ERR_CLID_INUSE.
If the server accepts the principal and co_ownerid as matching that If the server accepts the principal and co_ownerid as matching that
which created the client ID, and the co_verifier in the EXCHANGE_ID which created the client ID, and the co_verifier in the EXCHANGE_ID
differs from the co_verifier used when the client ID was created, differs from the co_verifier used when the client ID was created,
then after the server receives a CREATE_SESSION that confirms the then after the server receives a CREATE_SESSION that confirms the
client ID, the server deletes state. If the co_verifier values are client ID, the server deletes state. If the co_verifier values are
the same, (e.g. the client is either updating properties of the the same (e.g., the client either is updating properties of the
client ID (Section 18.35), or the client is attempting trunking client ID (Section 18.35) or is attempting trunking (Section 2.10.5),
(Section 2.10.5) the server MUST NOT delete state. the server MUST NOT delete state.
2.5. Server Owners 2.5. Server Owners
The Server Owner is similar to a Client Owner (Section 2.4), but The server owner is similar to a client owner (Section 2.4), but
unlike the Client Owner, there is no shorthand server ID. The Server unlike the client owner, there is no shorthand server ID. The server
Owner is defined in the following data type: owner is defined in the following data type:
struct server_owner4 { struct server_owner4 {
uint64_t so_minor_id; uint64_t so_minor_id;
opaque so_major_id<NFS4_OPAQUE_LIMIT>; opaque so_major_id<NFS4_OPAQUE_LIMIT>;
}; };
The Server Owner is returned from EXCHANGE_ID. When the so_major_id The server owner is returned from EXCHANGE_ID. When the so_major_id
fields are the same in two EXCHANGE_ID results, the connections each fields are the same in two EXCHANGE_ID results, the connections that
EXCHANGE_ID were sent over can be assumed to address the same Server each EXCHANGE_ID were sent over can be assumed to address the same
(as defined in Section 1.5). If the so_minor_id fields are also the server (as defined in Section 1.6). If the so_minor_id fields are
same, then not only do both connections connect to the same server, also the same, then not only do both connections connect to the same
but the session can be shared across both connections. The reader is server, but the session can be shared across both connections. The
cautioned that multiple servers may deliberately or accidentally reader is cautioned that multiple servers may deliberately or
claim to have the same so_major_id or so_major_id/so_minor_id; the accidentally claim to have the same so_major_id or so_major_id/
reader should examine Section 2.10.5 and Section 18.35 in order to so_minor_id; the reader should examine Sections 2.10.5 and 18.35 in
avoid acting on falsely matching Server Owner values. order to avoid acting on falsely matching server owner values.
The considerations for generating a so_major_id are similar to that The considerations for generating a so_major_id are similar to that
for generating a co_ownerid string (see Section 2.4). The for generating a co_ownerid string (see Section 2.4). The
consequences of two servers generating conflicting so_major_id values consequences of two servers generating conflicting so_major_id values
are less dire than they are for co_ownerid conflicts because the are less dire than they are for co_ownerid conflicts because the
client can use RPCSEC_GSS to compare the authenticity of each server client can use RPCSEC_GSS to compare the authenticity of each server
(see Section 2.10.5). (see Section 2.10.5).
2.6. Security Service Negotiation 2.6. Security Service Negotiation
With the NFSv4.1 server potentially offering multiple security With the NFSv4.1 server potentially offering multiple security
mechanisms, the client needs a method to determine or negotiate which mechanisms, the client needs a method to determine or negotiate which
mechanism is to be used for its communication with the server. The mechanism is to be used for its communication with the server. The
NFS server may have multiple points within its file system namespace NFS server may have multiple points within its file system namespace
that are available for use by NFS clients. These points can be that are available for use by NFS clients. These points can be
considered security policy boundaries, and in some NFS considered security policy boundaries, and, in some NFS
implementations are tied to NFS export points. In turn the NFS implementations, are tied to NFS export points. In turn, the NFS
server may be configured such that each of these security policy server may be configured such that each of these security policy
boundaries may have different or multiple security mechanisms in use. boundaries may have different or multiple security mechanisms in use.
The security negotiation between client and server SHOULD be done The security negotiation between client and server SHOULD be done
with a secure channel to eliminate the possibility of a third party with a secure channel to eliminate the possibility of a third party
intercepting the negotiation sequence and forcing the client and intercepting the negotiation sequence and forcing the client and
server to choose a lower level of security than required or desired. server to choose a lower level of security than required or desired.
See Section 21 for further discussion. See Section 21 for further discussion.
2.6.1. NFSv4.1 Security Tuples 2.6.1. NFSv4.1 Security Tuples
An NFS server can assign one or more "security tuples" to each An NFS server can assign one or more "security tuples" to each
security policy boundary in its namespace. Each security tuple security policy boundary in its namespace. Each security tuple
consists of a security flavor (see Section 2.2.1.1), and if the consists of a security flavor (see Section 2.2.1.1) and, if the
flavor is RPCSEC_GSS, a GSS-API mechanism OID, a GSS-API quality of flavor is RPCSEC_GSS, a GSS-API mechanism Object Identifier (OID), a
protection, and an RPCSEC_GSS service. GSS-API quality of protection, and an RPCSEC_GSS service.
2.6.2. SECINFO and SECINFO_NO_NAME 2.6.2. SECINFO and SECINFO_NO_NAME
The SECINFO and SECINFO_NO_NAME operations allow the client to The SECINFO and SECINFO_NO_NAME operations allow the client to
determine, on a per filehandle basis, what security tuple is to be determine, on a per-filehandle basis, what security tuple is to be
used for server access. In general, the client will not have to use used for server access. In general, the client will not have to use
either operation except during initial communication with the server either operation except during initial communication with the server
or when the client crosses security policy boundaries at the server. or when the client crosses security policy boundaries at the server.
However, the server's policies may also change at any time and force However, the server's policies may also change at any time and force
the client to negotiate a new security tuple. the client to negotiate a new security tuple.
Where the use of different security tuples would affect the type of Where the use of different security tuples would affect the type of
access that would be allowed if a request was sent over the same access that would be allowed if a request was sent over the same
connection used for the SECINFO or SECINFO_NO_NAME operation (e.g. connection used for the SECINFO or SECINFO_NO_NAME operation (e.g.,
read-only vs. read-write) access, security tuples that allow greater read-only vs. read-write) access, security tuples that allow greater
access should be presented first. Where the general level of access access should be presented first. Where the general level of access
is the same and different security flavors limit the range of is the same and different security flavors limit the range of
principals whose privileges are recognized (e.g. allowing or principals whose privileges are recognized (e.g., allowing or
disallowing root access), flavors supporting the greatest range of disallowing root access), flavors supporting the greatest range of
principals should be listed first. principals should be listed first.
2.6.3. Security Error 2.6.3. Security Error
Based on the assumption that each NFSv4.1 client and server MUST Based on the assumption that each NFSv4.1 client and server MUST
support a minimum set of security (i.e., Kerberos V5 under support a minimum set of security (i.e., Kerberos V5 under
RPCSEC_GSS), the NFS client will initiate file access to the server RPCSEC_GSS), the NFS client will initiate file access to the server
with one of the minimal security tuples. During communication with with one of the minimal security tuples. During communication with
the server, the client may receive an NFS error of NFS4ERR_WRONGSEC. the server, the client may receive an NFS error of NFS4ERR_WRONGSEC.
This error allows the server to notify the client that the security This error allows the server to notify the client that the security
tuple currently being used contravenes the server's security policy. tuple currently being used contravenes the server's security policy.
The client is then responsible for determining (see Section 2.6.3.1) The client is then responsible for determining (see Section 2.6.3.1)
what security tuples are available at the server and choosing one what security tuples are available at the server and choosing one
which is appropriate for the client. that is appropriate for the client.
2.6.3.1. Using NFS4ERR_WRONGSEC, SECINFO, and SECINFO_NO_NAME 2.6.3.1. Using NFS4ERR_WRONGSEC, SECINFO, and SECINFO_NO_NAME
This section explains of the mechanics of NFSv4.1 security This section explains the mechanics of NFSv4.1 security negotiation.
negotiation.
2.6.3.1.1. Put Filehandle Operations 2.6.3.1.1. Put Filehandle Operations
The term "put filehandle operation" refers to PUTROOTFH, PUTPUBFH, The term "put filehandle operation" refers to PUTROOTFH, PUTPUBFH,
PUTFH, and RESTOREFH. Each of the subsections herein describes how PUTFH, and RESTOREFH. Each of the subsections herein describes how
the server handles a subseries of operations that starts with a put the server handles a subseries of operations that starts with a put
filehandle operation. filehandle operation.
2.6.3.1.1.1. Put Filehandle Operation + SAVEFH 2.6.3.1.1.1. Put Filehandle Operation + SAVEFH
The client is saving a filehandle for a future RESTOREFH, LINK, or The client is saving a filehandle for a future RESTOREFH, LINK, or
RENAME. SAVEFH MUST NOT return NFS4ERR_WRONGSEC. To determine RENAME. SAVEFH MUST NOT return NFS4ERR_WRONGSEC. To determine
whether the put filehandle operation returns NFS4ERR_WRONGSEC or not, whether or not the put filehandle operation returns NFS4ERR_WRONGSEC,
the server implementation pretends SAVEFH is not in the series of the server implementation pretends SAVEFH is not in the series of
operations and examines which of the situations described in the operations and examines which of the situations described in the
other subsections of Section 2.6.3.1.1 apply. other subsections of Section 2.6.3.1.1 apply.
2.6.3.1.1.2. Two or More Put Filehandle Operations 2.6.3.1.1.2. Two or More Put Filehandle Operations
For a series of N put filehandle operations, the server MUST NOT For a series of N put filehandle operations, the server MUST NOT
return NFS4ERR_WRONGSEC to the first N-1 put filehandle operations. return NFS4ERR_WRONGSEC to the first N-1 put filehandle operations.
The N'th put filehandle operation is handled as if it is the first in The Nth put filehandle operation is handled as if it is the first in
a subseries of operations. For example if the server received PUTFH, a subseries of operations. For example, if the server received a
PUTROOTFH, LOOKUP, then the PUTFH is ignored for NFS4ERR_WRONGSEC COMPOUND request with this series of operations -- PUTFH, PUTROOTFH,
LOOKUP -- then the PUTFH operation is ignored for NFS4ERR_WRONGSEC
purposes, and the PUTROOTFH, LOOKUP subseries is processed as purposes, and the PUTROOTFH, LOOKUP subseries is processed as
according to Section 2.6.3.1.1.3. according to Section 2.6.3.1.1.3.
2.6.3.1.1.3. Put Filehandle Operation + LOOKUP (or OPEN of an Existing 2.6.3.1.1.3. Put Filehandle Operation + LOOKUP (or OPEN of an Existing
Name) Name)
This situation also applies to a put filehandle operation followed by This situation also applies to a put filehandle operation followed by
a LOOKUP or an OPEN operation that specifies an existing component a LOOKUP or an OPEN operation that specifies an existing component
name. name.
In this situation, the client is potentially crossing a security In this situation, the client is potentially crossing a security
policy boundary, and the set of security tuples the parent directory policy boundary, and the set of security tuples the parent directory
supports may differ from those of the child. The server supports may differ from those of the child. The server
implementation may decide whether to impose any restrictions on implementation may decide whether to impose any restrictions on
security policy administration. There are at least three approaches security policy administration. There are at least three approaches
(sec_policy_child is the tuple set of the child export, (sec_policy_child is the tuple set of the child export,
sec_policy_parent is that of the parent). sec_policy_parent is that of the parent).
a) sec_policy_child <= sec_policy_parent (<= for subset). This (a) sec_policy_child <= sec_policy_parent (<= for subset). This
means that the set of security tuples specified on the security means that the set of security tuples specified on the security
policy of a child directory is always a subset of that of its policy of a child directory is always a subset of its parent
parent directory. directory.
b) sec_policy_child ^ sec_policy_parent != {} (^ for intersection, (b) sec_policy_child ^ sec_policy_parent != {} (^ for intersection,
{} for the empty set). This means that the security tuples {} for the empty set). This means that the set of security
specified on the security policy of a child directory always has a tuples specified on the security policy of a child directory
non empty intersection with that of the parent. always has a non-empty intersection with that of the parent.
c) sec_policy_child ^ sec_policy_parent == {}. This means that (c) sec_policy_child ^ sec_policy_parent == {}. This means that the
the set of tuples specified on the security policy of a child set of security tuples specified on the security policy of a
directory may not intersect with that of the parent. In other child directory may not intersect with that of the parent. In
words, there are no restrictions on how the system administrator other words, there are no restrictions on how the system
may set up these tuples. administrator may set up these tuples.
In order for a server to support approaches (b) (for the case when a In order for a server to support approaches (b) (for the case when a
client chooses a flavor that is not a member of sec_policy_parent) client chooses a flavor that is not a member of sec_policy_parent)
and (c), the put filehandle operation cannot return NFS4ERR_WRONGSEC and (c), the put filehandle operation cannot return NFS4ERR_WRONGSEC
when there is a security tuple mismatch. Instead, it should be when there is a security tuple mismatch. Instead, it should be
returned from the LOOKUP (or OPEN by existing component name) that returned from the LOOKUP (or OPEN by existing component name) that
follows. follows.
Since the above guideline does not contradict approach (a), it should Since the above guideline does not contradict approach (a), it should
be followed in general. Even if approach (a) is implemented, it is be followed in general. Even if approach (a) is implemented, it is
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the client's only recourse is to send the put filehandle operation, the client's only recourse is to send the put filehandle operation,
LOOKUPP, GETFH sequence of operations with every security tuple it LOOKUPP, GETFH sequence of operations with every security tuple it
supports. supports.
Regardless of whether SECINFO_NO_NAME is supported, an NFSv4.1 server Regardless of whether SECINFO_NO_NAME is supported, an NFSv4.1 server
MUST NOT return NFS4ERR_WRONGSEC in response to a put filehandle MUST NOT return NFS4ERR_WRONGSEC in response to a put filehandle
operation if the operation is immediately followed by a LOOKUPP. operation if the operation is immediately followed by a LOOKUPP.
2.6.3.1.1.5. Put Filehandle Operation + SECINFO/SECINFO_NO_NAME 2.6.3.1.1.5. Put Filehandle Operation + SECINFO/SECINFO_NO_NAME
A security sensitive client is allowed to choose a strong security A security-sensitive client is allowed to choose a strong security
tuple when querying a server to determine a file object's permitted tuple when querying a server to determine a file object's permitted
security tuples. The security tuple chosen by the client does not security tuples. The security tuple chosen by the client does not
have to be included in the tuple list of the security policy of the have to be included in the tuple list of the security policy of
either parent directory indicated in the put filehandle operation, or either the parent directory indicated in the put filehandle operation
the child file object indicated in SECINFO (or any parent directory or the child file object indicated in SECINFO (or any parent
indicated in SECINFO_NO_NAME). Of course the server has to be directory indicated in SECINFO_NO_NAME). Of course, the server has
configured for whatever security tuple the client selects, otherwise to be configured for whatever security tuple the client selects;
the request will fail at RPC layer with an appropriate authentication otherwise, the request will fail at the RPC layer with an appropriate
error. authentication error.
In theory, there is no connection between the security flavor used by In theory, there is no connection between the security flavor used by
SECINFO or SECINFO_NO_NAME and those supported by the security SECINFO or SECINFO_NO_NAME and those supported by the security
policy. But in practice, the client may start looking for strong policy. But in practice, the client may start looking for strong
flavors from those supported by the security policy, followed by flavors from those supported by the security policy, followed by
those in the REQUIRED set. those in the REQUIRED set.
The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC to a put The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC to a put
filehandle operation that is immediately followed by SECINFO or filehandle operation that is immediately followed by SECINFO or
SECINFO_NO_NAME. The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC SECINFO_NO_NAME. The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC
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2.6.3.1.1.6. Put Filehandle Operation + Nothing 2.6.3.1.1.6. Put Filehandle Operation + Nothing
The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC. The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC.
2.6.3.1.1.7. Put Filehandle Operation + Anything Else 2.6.3.1.1.7. Put Filehandle Operation + Anything Else
"Anything Else" includes OPEN by filehandle. "Anything Else" includes OPEN by filehandle.
The security policy enforcement applies to the filehandle specified The security policy enforcement applies to the filehandle specified
in the put filehandle operation. Therefore the put filehandle in the put filehandle operation. Therefore, the put filehandle
operation MUST return NFS4ERR_WRONGSEC when there is a security tuple operation MUST return NFS4ERR_WRONGSEC when there is a security tuple
mismatch. This avoids the complexity adding NFS4ERR_WRONGSEC as an mismatch. This avoids the complexity of adding NFS4ERR_WRONGSEC as
allowable error to every other operation. an allowable error to every other operation.
A COMPOUND containing the series put filehandle operation + A COMPOUND containing the series put filehandle operation +
SECINFO_NO_NAME (style SECINFO_STYLE4_CURRENT_FH) is an efficient way SECINFO_NO_NAME (style SECINFO_STYLE4_CURRENT_FH) is an efficient way
for the client to recover from NFS4ERR_WRONGSEC. for the client to recover from NFS4ERR_WRONGSEC.
The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC to any operation The NFSv4.1 server MUST NOT return NFS4ERR_WRONGSEC to any operation
other than a put filehandle operation, LOOKUP, LOOKUPP, and OPEN (by other than a put filehandle operation, LOOKUP, LOOKUPP, and OPEN (by
component name). component name).
2.6.3.1.1.8. Operations after SECINFO and SECINFO_NO_NAME 2.6.3.1.1.8. Operations after SECINFO and SECINFO_NO_NAME
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SECINFO and SECINFO_NO_NAME consume the current filehandle (note that SECINFO and SECINFO_NO_NAME consume the current filehandle (note that
this is a change from NFSv4.0). This leaves no current filehandle this is a change from NFSv4.0). This leaves no current filehandle
for READ to use, and READ returns NFS4ERR_NOFILEHANDLE. for READ to use, and READ returns NFS4ERR_NOFILEHANDLE.
2.6.3.1.2. LINK and RENAME 2.6.3.1.2. LINK and RENAME
The LINK and RENAME operations use both the current and saved The LINK and RENAME operations use both the current and saved
filehandles. Technically, the server MAY return NFS4ERR_WRONGSEC filehandles. Technically, the server MAY return NFS4ERR_WRONGSEC
from LINK or RENAME if the security policy of the saved filehandle from LINK or RENAME if the security policy of the saved filehandle
rejects the security flavor used in the COMPOUND request's rejects the security flavor used in the COMPOUND request's
credentials. However, if the server does so, and if there is no credentials. If the server does so, then if there is no intersection
intersection between the security policies of saved and current between the security policies of saved and current filehandles, this
filehandles, this means it will be impossible for the client to means that it will be impossible for the client to perform the
perform the intended LINK or RENAME operation. intended LINK or RENAME operation.
For example, suppose the client sends this COMPOUND request: For example, suppose the client sends this COMPOUND request:
SEQUENCE, PUTFH bFH, SAVEFH, PUTFH aFH, RENAME "c" "d", where SEQUENCE, PUTFH bFH, SAVEFH, PUTFH aFH, RENAME "c" "d", where
filehandles bFH and aFH refer to different directories. Suppose no filehandles bFH and aFH refer to different directories. Suppose no
common security tuple exists between the security policies of aFH and common security tuple exists between the security policies of aFH and
bFH. If the client sends the request using credentials acceptable to bFH. If the client sends the request using credentials acceptable to
bFH's security policy but not aFH's policy, then the PUTFH aFH bFH's security policy but not aFH's policy, then the PUTFH aFH
operation will fail with NFS4ERR_WRONGSEC. After a SECINFO_NO_NAME operation will fail with NFS4ERR_WRONGSEC. After a SECINFO_NO_NAME
request, the client sends SEQUENCE, PUTFH bFH, SAVEFH, PUTFH aFH, request, the client sends SEQUENCE, PUTFH bFH, SAVEFH, PUTFH aFH,
RENAME "c" "d", using credentials acceptable to aFH's security RENAME "c" "d", using credentials acceptable to aFH's security policy
policy, but not bFH's policy. The server returns NFS4ERR_WRONGSEC on but not bFH's policy. The server returns NFS4ERR_WRONGSEC on the
the RENAME operation. RENAME operation.
To prevent a client from starting endless cycle of a request To prevent a client from an endless sequence of a request containing
containing LINK or RENAME, followed by a request containing LINK or RENAME, followed by a request containing SECINFO_NO_NAME or
SECINFO_NO_NAME or SECINFO, the server MUST detect when the security SECINFO, the server MUST detect when the security policies of the
policies of the current and saved filehandles have no mutually current and saved filehandles have no mutually acceptable security
acceptable security tuple, and MUST NOT return NFS4ERR_WRONGSEC from tuple, and MUST NOT return NFS4ERR_WRONGSEC from LINK or RENAME in
LINK or RENAME in that situation. Instead the server MUST do one of that situation. Instead the server MUST do one of two things:
two things:
o The server can return NFS4ERR_XDEV. o The server can return NFS4ERR_XDEV.
o The server can allow the security policy of the current filehandle o The server can allow the security policy of the current filehandle
to override that of the saved filehandle, and so return NFS4_OK. to override that of the saved filehandle, and so return NFS4_OK.
2.7. Minor Versioning 2.7. Minor Versioning
To address the requirement of an NFS protocol that can evolve as the To address the requirement of an NFS protocol that can evolve as the
need arises, the NFSv4.1 protocol contains the rules and framework to need arises, the NFSv4.1 protocol contains the rules and framework to
allow for future minor changes or versioning. allow for future minor changes or versioning.
The base assumption with respect to minor versioning is that any The base assumption with respect to minor versioning is that any
future accepted minor version will be documented in one or more future accepted minor version will be documented in one or more
standards track RFCs. Minor version zero of the NFSv4 protocol is Standards Track RFCs. Minor version 0 of the NFSv4 protocol is
represented by [30], and minor version one is represented by this represented by [30], and minor version 1 is represented by this RFC.
document [[Comment.1: RFC Editor: change "document" to "RFC" when we The COMPOUND and CB_COMPOUND procedures support the encoding of the
publish]]. The COMPOUND and CB_COMPOUND procedures support the minor version being requested by the client.
encoding of the minor version being requested by the client.
The following items represent the basic rules for the development of The following items represent the basic rules for the development of
minor versions. Note that a future minor version may modify or add minor versions. Note that a future minor version may modify or add
to the following rules as part of the minor version definition. to the following rules as part of the minor version definition.
1. Procedures are not added or deleted 1. Procedures are not added or deleted.
To maintain the general RPC model, NFSv4 minor versions will not To maintain the general RPC model, NFSv4 minor versions will not
add to or delete procedures from the NFS program. add to or delete procedures from the NFS program.
2. Minor versions may add operations to the COMPOUND and 2. Minor versions may add operations to the COMPOUND and
CB_COMPOUND procedures. CB_COMPOUND procedures.
The addition of operations to the COMPOUND and CB_COMPOUND The addition of operations to the COMPOUND and CB_COMPOUND
procedures does not affect the RPC model. procedures does not affect the RPC model.
* Minor versions may append attributes to the bitmap4 that * Minor versions may append attributes to the bitmap4 that
represents sets of attributes and the fattr4 that represents represents sets of attributes and to the fattr4 that
sets of attribute values. represents sets of attribute values.
This allows for the expansion of the attribute model to allow This allows for the expansion of the attribute model to allow
for future growth or adaptation. for future growth or adaptation.
* Minor version X must append any new attributes after the last * Minor version X must append any new attributes after the last
documented attribute. documented attribute.
Since attribute results are specified as an opaque array of Since attribute results are specified as an opaque array of
per-attribute XDR encoded results, the complexity of adding per-attribute, XDR-encoded results, the complexity of adding
new attributes in the midst of the current definitions would new attributes in the midst of the current definitions would
be too burdensome. be too burdensome.
3. Minor versions must not modify the structure of an existing 3. Minor versions must not modify the structure of an existing
operation's arguments or results. operation's arguments or results.
Again the complexity of handling multiple structure definitions Again, the complexity of handling multiple structure definitions
for a single operation is too burdensome. New operations should for a single operation is too burdensome. New operations should
be added instead of modifying existing structures for a minor be added instead of modifying existing structures for a minor
version. version.
This rule does not preclude the following adaptations in a minor This rule does not preclude the following adaptations in a minor
version. version:
* adding bits to flag fields such as new attributes to * adding bits to flag fields, such as new attributes to
GETATTR's bitmap4 data type and providing corresponding GETATTR's bitmap4 data type, and providing corresponding
variants of opaque arrays, such as a notify4 used together variants of opaque arrays, such as a notify4 used together
with such bitmaps. with such bitmaps
* adding bits to existing attributes like ACLs that have flag * adding bits to existing attributes like ACLs that have flag
words words
* extending enumerated types (including NFS4ERR_*) with new * extending enumerated types (including NFS4ERR_*) with new
values values
* adding cases to a switched union * adding cases to a switched union
4. Minor versions must not modify the structure of existing 4. Minor versions must not modify the structure of existing
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This prevents the potential reuse of a particular operation This prevents the potential reuse of a particular operation
"slot" in a future minor version. "slot" in a future minor version.
6. Minor versions must not delete attributes. 6. Minor versions must not delete attributes.
7. Minor versions must not delete flag bits or enumeration values. 7. Minor versions must not delete flag bits or enumeration values.
8. Minor versions may declare an operation MUST NOT be implemented. 8. Minor versions may declare an operation MUST NOT be implemented.
Specifying an operation MUST NOT be implemented is equivalent to Specifying that an operation MUST NOT be implemented is
obsoleting an operation. For the client, it means that the equivalent to obsoleting an operation. For the client, it means
operation MUST NOT be sent to the server. For the server, an that the operation MUST NOT be sent to the server. For the
NFS error can be returned as opposed to "dropping" the request server, an NFS error can be returned as opposed to "dropping"
as an XDR decode error. This approach allows for the the request as an XDR decode error. This approach allows for
obsolescence of an operation while maintaining its structure so the obsolescence of an operation while maintaining its structure
that a future minor version can reintroduce the operation. so that a future minor version can reintroduce the operation.
1. Minor versions may declare an attribute MUST NOT be 1. Minor versions may declare that an attribute MUST NOT be
implemented. implemented.
2. Minor versions may declare a flag bit or enumeration value 2. Minor versions may declare that a flag bit or enumeration
MUST NOT be implemented. value MUST NOT be implemented.
9. Minor versions may downgrade features from REQUIRED to 9. Minor versions may downgrade features from REQUIRED to
RECOMMENDED, or RECOMMENDED to OPTIONAL. RECOMMENDED, or RECOMMENDED to OPTIONAL.
10. Minor versions may upgrade features from OPTIONAL to RECOMMENDED 10. Minor versions may upgrade features from OPTIONAL to
or RECOMMENDED to REQUIRED. RECOMMENDED, or RECOMMENDED to REQUIRED.
11. A client and server that supports minor version X SHOULD support 11. A client and server that support minor version X SHOULD support
minor versions 0 (zero) through X-1 as well. minor versions zero through X-1 as well.
12. Except for infrastructural changes, a minor version must not 12. Except for infrastructural changes, a minor version must not
introduce REQUIRED new features. introduce REQUIRED new features.
This rule allows for the introduction of new functionality and This rule allows for the introduction of new functionality and
forces the use of implementation experience before designating a forces the use of implementation experience before designating a
feature as REQUIRED. On the other hand, some classes of feature as REQUIRED. On the other hand, some classes of
features are infrastructural and have broad effects. Allowing features are infrastructural and have broad effects. Allowing
infrastructural features to be RECOMMENDED or OPTIONAL infrastructural features to be RECOMMENDED or OPTIONAL
complicates implementation of the minor version. complicates implementation of the minor version.
13. A client MUST NOT attempt to use a stateid, filehandle, or 13. A client MUST NOT attempt to use a stateid, filehandle, or
similar returned object from the COMPOUND procedure with minor similar returned object from the COMPOUND procedure with minor
version X for another COMPOUND procedure with minor version Y, version X for another COMPOUND procedure with minor version Y,
where X != Y. where X != Y.
2.8. Non-RPC-based Security Services 2.8. Non-RPC-Based Security Services
As described in Section 2.2.1.1.1.1, NFSv4.1 relies on RPC for As described in Section 2.2.1.1.1.1, NFSv4.1 relies on RPC for
identification, authentication, integrity, and privacy. NFSv4.1 identification, authentication, integrity, and privacy. NFSv4.1
itself provides or enables additional security services as described itself provides or enables additional security services as described
in the next several subsections. in the next several subsections.
2.8.1. Authorization 2.8.1. Authorization
Authorization to access a file object via an NFSv4.1 operation is Authorization to access a file object via an NFSv4.1 operation is
ultimately determined by the NFSv4.1 server. A client can ultimately determined by the NFSv4.1 server. A client can
predetermine its access to a file object via the OPEN (Section 18.16) predetermine its access to a file object via the OPEN (Section 18.16)
and the ACCESS (Section 18.1) operations. and the ACCESS (Section 18.1) operations.
Principals with appropriate access rights can modify the Principals with appropriate access rights can modify the
authorization on a file object via the SETATTR (Section 18.30) authorization on a file object via the SETATTR (Section 18.30)
operation. Attributes that affect access rights include: mode, operation. Attributes that affect access rights include mode, owner,
owner, owner_group, acl, dacl, and sacl. See Section 5. owner_group, acl, dacl, and sacl. See Section 5.
2.8.2. Auditing 2.8.2. Auditing
NFSv4.1 provides auditing on a per file object basis, via the acl and NFSv4.1 provides auditing on a per-file object basis, via the acl and
sacl attributes as described in Section 6. It is outside the scope sacl attributes as described in Section 6. It is outside the scope
of this specification to specify audit log formats or management of this specification to specify audit log formats or management
policies. policies.
2.8.3. Intrusion Detection 2.8.3. Intrusion Detection
NFSv4.1 provides alarm control on a per file object basis, via the NFSv4.1 provides alarm control on a per-file object basis, via the
acl and sacl attributes as described in Section 6. Alarms may serve acl and sacl attributes as described in Section 6. Alarms may serve
as the basis for intrusion detection. It is outside the scope of as the basis for intrusion detection. It is outside the scope of
this specification to specify heuristics for detecting intrusion via this specification to specify heuristics for detecting intrusion via
alarms. alarms.
2.9. Transport Layers 2.9. Transport Layers
2.9.1. REQUIRED and RECOMMENDED Properties of Transports 2.9.1. REQUIRED and RECOMMENDED Properties of Transports
NFSv4.1 works over RDMA and non-RDMA-based transports with the NFSv4.1 works over Remote Direct Memory Access (RDMA) and non-RDMA-
following attributes: based transports with the following attributes:
o The transport supports reliable delivery of data, which NFSv4.1 o The transport supports reliable delivery of data, which NFSv4.1
requires but neither NFSv4.1 nor RPC has facilities for ensuring. requires but neither NFSv4.1 nor RPC has facilities for ensuring
[34] [34].
o The transport delivers data in the order it was sent. Ordered o The transport delivers data in the order it was sent. Ordered
delivery simplifies detection of transmit errors, and simplifies delivery simplifies detection of transmit errors, and simplifies
the sending of arbitrary sized requests and responses, via the the sending of arbitrary sized requests and responses via the
record marking protocol [3]. record marking protocol [3].
Where an NFSv4.1 implementation supports operation over the IP Where an NFSv4.1 implementation supports operation over the IP
network protocol, any transport used between NFS and IP MUST be among network protocol, any transport used between NFS and IP MUST be among
the IETF-approved congestion control transport protocols. At the the IETF-approved congestion control transport protocols. At the
time this document was written, the only two transports that had the time this document was written, the only two transports that had the
above attributes were TCP and SCTP. To enhance the possibilities for above attributes were TCP and the Stream Control Transmission
interoperability, an NFSv4.1 implementation MUST support operation Protocol (SCTP). To enhance the possibilities for interoperability,
over the TCP transport protocol. an NFSv4.1 implementation MUST support operation over the TCP
transport protocol.
Even if NFSv4.1 is used over a non-IP network protocol, it is Even if NFSv4.1 is used over a non-IP network protocol, it is
RECOMMENDED that the transport support congestion control. RECOMMENDED that the transport support congestion control.
It is permissible for a connectionless transport to be used under It is permissible for a connectionless transport to be used under
NFSv4.1, however reliable and in-order delivery of data combined with NFSv4.1; however, reliable and in-order delivery of data combined
congestion control by the connectionless transport is REQUIRED; as a with congestion control by the connectionless transport is REQUIRED.
consequence UDP by itself MUST NOT be used as an NFSv4.1 transport. As a consequence, UDP by itself MUST NOT be used as an NFSv4.1
NFSv4.1 assumes that a client transport address and server transport transport. NFSv4.1 assumes that a client transport address and
address used to send data over a transport together constitute a server transport address used to send data over a transport together
connection, even if the underlying transport eschews the concept of a constitute a connection, even if the underlying transport eschews the
connection. concept of a connection.
2.9.2. Client and Server Transport Behavior 2.9.2. Client and Server Transport Behavior
If a connection-oriented transport (e.g. TCP) is used, the client If a connection-oriented transport (e.g., TCP) is used, the client
and server SHOULD use long lived connections for at least three and server SHOULD use long-lived connections for at least three
reasons: reasons:
1. This will prevent the weakening of the transport's congestion 1. This will prevent the weakening of the transport's congestion
control mechanisms via short lived connections. control mechanisms via short-lived connections.
2. This will improve performance for the WAN environment by 2. This will improve performance for the WAN environment by
eliminating the need for connection setup handshakes. eliminating the need for connection setup handshakes.
3. The NFSv4.1 callback model differs from NFSv4.0, and requires the 3. The NFSv4.1 callback model differs from NFSv4.0, and requires the
client and server to maintain a client-created backchannel (see client and server to maintain a client-created backchannel (see
Section 2.10.3.1) for the server to use. Section 2.10.3.1) for the server to use.
In order to reduce congestion, if a connection-oriented transport is In order to reduce congestion, if a connection-oriented transport is
used, and the request is not the NULL procedure, used, and the request is not the NULL procedure:
o A requester MUST NOT retry a request unless the connection the o A requester MUST NOT retry a request unless the connection the
request was sent over was lost before the reply was received. request was sent over was lost before the reply was received.
o A replier MUST NOT silently drop a request, even if the request is o A replier MUST NOT silently drop a request, even if the request is
a retry. (The silent drop behavior of RPCSEC_GSS [4] does not a retry. (The silent drop behavior of RPCSEC_GSS [4] does not
apply because this behavior happens at the RPCSEC_GSS layer, a apply because this behavior happens at the RPCSEC_GSS layer, a
lower layer in the request processing). Instead, the replier lower layer in the request processing.) Instead, the replier
SHOULD return an appropriate error (see Section 2.10.6.1) or it SHOULD return an appropriate error (see Section 2.10.6.1), or it
MAY disconnect the connection. MAY disconnect the connection.
When sending a reply, the replier MUST send the reply to the same When sending a reply, the replier MUST send the reply to the same
full network address (e.g. if using an IP-based transport, the source full network address (e.g., if using an IP-based transport, the
port of the requester is part of the full network address) that the source port of the requester is part of the full network address)
requester sent the request from. If using a connection-oriented from which the requester sent the request. If using a connection-
transport, replies MUST be sent on the same connection the request oriented transport, replies MUST be sent on the same connection from
was received from. which the request was received.
If a connection is dropped after the replier receives the request but If a connection is dropped after the replier receives the request but
before the replier sends the reply, the replier might have an pending before the replier sends the reply, the replier might have a pending
reply. If a connection is established with the same source and reply. If a connection is established with the same source and
destination full network address as the dropped connection, then the destination full network address as the dropped connection, then the
replier MUST NOT send the reply until the requester retries the replier MUST NOT send the reply until the requester retries the
request. The reason for this prohibition is that the requester MAY request. The reason for this prohibition is that the requester MAY
retry a request over a different connection that is associated with retry a request over a different connection (provided that connection
the session. is associated with the original request's session).
When using RDMA transports there are other reasons for not tolerating When using RDMA transports, there are other reasons for not
retries over the same connection: tolerating retries over the same connection:
o RDMA transports use "credits" to enforce flow control, where a o RDMA transports use "credits" to enforce flow control, where a
credit is a right to a peer to transmit a message. If one peer credit is a right to a peer to transmit a message. If one peer
were to retransmit a request (or reply), it would consume an were to retransmit a request (or reply), it would consume an
additional credit. If the replier retransmitted a reply, it would additional credit. If the replier retransmitted a reply, it would
certainly result in an RDMA connection loss, since the requester certainly result in an RDMA connection loss, since the requester
would typically only post a single receive buffer for each would typically only post a single receive buffer for each
request. If the requester retransmitted a request, the additional request. If the requester retransmitted a request, the additional
credit consumed on the server might lead to RDMA connection credit consumed on the server might lead to RDMA connection
failure unless the client accounted for it and decreased its failure unless the client accounted for it and decreased its
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shortfalls with practical solutions: shortfalls with practical solutions:
o EOS is enabled by a reply cache with a bounded size, making it o EOS is enabled by a reply cache with a bounded size, making it
feasible to keep the cache in persistent storage and enable EOS feasible to keep the cache in persistent storage and enable EOS
through server failure and recovery. One reason that previous through server failure and recovery. One reason that previous
revisions of NFS did not support EOS was because some EOS revisions of NFS did not support EOS was because some EOS
approaches often limited parallelism. As will be explained in approaches often limited parallelism. As will be explained in
Section 2.10.6, NFSv4.1 supports both EOS and unlimited Section 2.10.6, NFSv4.1 supports both EOS and unlimited
parallelism. parallelism.
o The NFSv4.1 client (defined in Section 1.5, Paragraph 2) creates o The NFSv4.1 client (defined in Section 1.6, Paragraph 2) creates
transport connections and provides them to the server to use for transport connections and provides them to the server to use for
sending callback requests, thus solving the firewall issue sending callback requests, thus solving the firewall issue
(Section 18.34). Races between responses from client requests, (Section 18.34). Races between responses from client requests and
and callbacks caused by the requests are detected via the callbacks caused by the requests are detected via the session's
session's sequencing properties which are a consequence of EOS sequencing properties that are a consequence of EOS
(Section 2.10.6.3). (Section 2.10.6.3).
o The NFSv4.1 client can associate an arbitrary number of o The NFSv4.1 client can associate an arbitrary number of
connections with the session, and thus provide trunking connections with the session, and thus provide trunking
(Section 2.10.5). (Section 2.10.5).
o The NFSv4.1 client and server produces a session key independent o The NFSv4.1 client and server produces a session key independent
of client and server machine credentials which can be used to of client and server machine credentials which can be used to
compute a digest for protecting critical session management compute a digest for protecting critical session management
operations (Section 2.10.8.3). operations (Section 2.10.8.3).
o The NFSv4.1 client can also create secure RPCSEC_GSS contexts for o The NFSv4.1 client can also create secure RPCSEC_GSS contexts for
use by the session's backchannel that do not require the server to use by the session's backchannel that do not require the server to
authenticate to a client machine principal (Section 2.10.8.2). authenticate to a client machine principal (Section 2.10.8.2).
A session is a dynamically created, long-lived server object created A session is a dynamically created, long-lived server object created
by a client, used over time from one or more transport connections. by a client and used over time from one or more transport
Its function is to maintain the server's state relative to the connections. Its function is to maintain the server's state relative
connection(s) belonging to a client instance. This state is entirely to the connection(s) belonging to a client instance. This state is
independent of the connection itself, and indeed the state exists entirely independent of the connection itself, and indeed the state
whether the connection exists or not. A client may have one or more exists whether or not the connection exists. A client may have one
sessions associated with it so that client-associated state may be or more sessions associated with it so that client-associated state
accessed using any of the sessions associated with that client's may be accessed using any of the sessions associated with that
client ID, when connections are associated with those sessions. When client's client ID, when connections are associated with those
no connections are associated with any of a client ID's sessions for sessions. When no connections are associated with any of a client
an extended time, such objects as locks, opens, delegations, layouts, ID's sessions for an extended time, such objects as locks, opens,
etc. are subject to expiration. The session serves as an object delegations, layouts, etc. are subject to expiration. The session
representing a means of access by a client to the associated client serves as an object representing a means of access by a client to the
state on the server, independent of the physical means of access to associated client state on the server, independent of the physical
that state. means of access to that state.
A single client may create multiple sessions. A single session MUST A single client may create multiple sessions. A single session MUST
NOT serve multiple clients. NOT serve multiple clients.
2.10.2. NFSv4 Integration 2.10.2. NFSv4 Integration
Sessions are part of NFSv4.1 and not NFSv4.0. Normally, a major Sessions are part of NFSv4.1 and not NFSv4.0. Normally, a major
infrastructure change such as sessions would require a new major infrastructure change such as sessions would require a new major
version number to an ONC RPC program like NFS. However, because version number to an Open Network Computing (ONC) RPC program like
NFSv4 encapsulates its functionality in a single procedure, COMPOUND, NFS. However, because NFSv4 encapsulates its functionality in a
and because COMPOUND can support an arbitrary number of operations, single procedure, COMPOUND, and because COMPOUND can support an
sessions have been added to NFSv4.1 with little difficulty. COMPOUND arbitrary number of operations, sessions have been added to NFSv4.1
includes a minor version number field, and for NFSv4.1 this minor with little difficulty. COMPOUND includes a minor version number
version is set to 1. When the NFSv4 server processes a COMPOUND with field, and for NFSv4.1 this minor version is set to 1. When the
the minor version set to 1, it expects a different set of operations NFSv4 server processes a COMPOUND with the minor version set to 1, it
than it does for NFSv4.0. NFSv4.1 defines the SEQUENCE operation, expects a different set of operations than it does for NFSv4.0.
which is required for every COMPOUND that operates over an NFSv4.1 defines the SEQUENCE operation, which is required for every
established session, with the exception of some session COMPOUND that operates over an established session, with the
administration operations, such as DESTROY_SESSION (Section 18.37). exception of some session administration operations, such as
DESTROY_SESSION (Section 18.37).
2.10.2.1. SEQUENCE and CB_SEQUENCE 2.10.2.1. SEQUENCE and CB_SEQUENCE
In NFSv4.1, when the SEQUENCE operation is present, it MUST be the In NFSv4.1, when the SEQUENCE operation is present, it MUST be the
first operation in the COMPOUND procedure. The primary purpose of first operation in the COMPOUND procedure. The primary purpose of
SEQUENCE is to carry the session identifier. The session identifier SEQUENCE is to carry the session identifier. The session identifier
associates all other operations in the COMPOUND procedure with a associates all other operations in the COMPOUND procedure with a
particular session. SEQUENCE also contains required information for particular session. SEQUENCE also contains required information for
maintaining EOS (see Section 2.10.6). Session-enabled NFSv4.1 maintaining EOS (see Section 2.10.6). Session-enabled NFSv4.1
COMPOUND requests thus have the form: COMPOUND requests thus have the form:
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"callback_ident", which is superfluous in NFSv4.1 and MUST be ignored "callback_ident", which is superfluous in NFSv4.1 and MUST be ignored
by the client. CB_SEQUENCE has the same information as SEQUENCE, and by the client. CB_SEQUENCE has the same information as SEQUENCE, and
also includes other information needed to resolve callback races also includes other information needed to resolve callback races
(Section 2.10.6.3). (Section 2.10.6.3).
2.10.2.2. Client ID and Session Association 2.10.2.2. Client ID and Session Association
Each client ID (Section 2.4) can have zero or more active sessions. Each client ID (Section 2.4) can have zero or more active sessions.
A client ID and associated session are required to perform file A client ID and associated session are required to perform file
access in NFSv4.1. Each time a session is used (whether by a client access in NFSv4.1. Each time a session is used (whether by a client
sending a request to the server, or the client replying to a callback sending a request to the server or the client replying to a callback
request from the server), the state leased to its associated client request from the server), the state leased to its associated client
ID is automatically renewed. ID is automatically renewed.
State such as share reservations, locks, delegations, and layouts State (which can consist of share reservations, locks, delegations,
(Section 1.6.4) is tied to the client ID. Client state is not tied and layouts (Section 1.7.4)) is tied to the client ID. Client state
to any individual session. Successive state changing operations from is not tied to any individual session. Successive state changing
a given state owner MAY go over different sessions, provided the operations from a given state owner MAY go over different sessions,
session is associated with the same client ID. A callback MAY arrive provided the session is associated with the same client ID. A
over a different session than from the session that originally callback MAY arrive over a different session than that of the request
acquired the state pertaining to the callback. For example, if that originally acquired the state pertaining to the callback. For
session A is used to acquire a delegation, a request to recall the example, if session A is used to acquire a delegation, a request to
delegation MAY arrive over session B if both sessions are associated recall the delegation MAY arrive over session B if both sessions are
with the same client ID. Section 2.10.8.1 and Section 2.10.8.2 associated with the same client ID. Sections 2.10.8.1 and 2.10.8.2
discuss the security considerations around callbacks. discuss the security considerations around callbacks.
2.10.3. Channels 2.10.3. Channels
A channel is not a connection. A channel represents the direction A channel is not a connection. A channel represents the direction
ONC RPC requests are sent. ONC RPC requests are sent.
Each session has one or two channels: the fore channel and the Each session has one or two channels: the fore channel and the
backchannel. Because there are at most two channels per session, and backchannel. Because there are at most two channels per session, and
because each channel has a distinct purpose, channels are not because each channel has a distinct purpose, channels are not
assigned identifiers. assigned identifiers.
The fore channel is used for ordinary requests from the client to the The fore channel is used for ordinary requests from the client to the
server, and carries COMPOUND requests and responses. A session server, and carries COMPOUND requests and responses. A session
always has a fore channel. always has a fore channel.
The backchannel used for callback requests from server to client, and The backchannel is used for callback requests from server to client,
carries CB_COMPOUND requests and responses. Whether there is a and carries CB_COMPOUND requests and responses. Whether or not there
backchannel or not is a decision by the client, however many features is a backchannel is a decision made by the client; however, many
of NFSv4.1 require a backchannel. NFSv4.1 servers MUST support features of NFSv4.1 require a backchannel. NFSv4.1 servers MUST
backchannels. support backchannels.
Each session has resources for each channel, including separate reply Each session has resources for each channel, including separate reply
caches (see Section 2.10.6.1). Note that even the backchannel caches (see Section 2.10.6.1). Note that even the backchannel
requires a reply cache (or at least, a slot table in order to detect requires a reply cache (or, at least, a slot table in order to detect
retries) because some callback operations are nonidempotent. retries) because some callback operations are nonidempotent.
2.10.3.1. Association of Connections, Channels, and Sessions 2.10.3.1. Association of Connections, Channels, and Sessions
Each channel is associated with zero or more transport connections Each channel is associated with zero or more transport connections
(whether of the same transport protocol or different transport (whether of the same transport protocol or different transport
protocols). A connection can be associated with one channel or both protocols). A connection can be associated with one channel or both
channels of a session; the client and server negotiate whether a channels of a session; the client and server negotiate whether a
connection will carry traffic for one channel or both channels via connection will carry traffic for one channel or both channels via
the CREATE_SESSION (Section 18.36) and the BIND_CONN_TO_SESSION the CREATE_SESSION (Section 18.36) and the BIND_CONN_TO_SESSION
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SEQUENCE is transmitted on a different connection, the connection is SEQUENCE is transmitted on a different connection, the connection is
automatically associated with the fore channel of the session automatically associated with the fore channel of the session
specified in the SEQUENCE operation. specified in the SEQUENCE operation.
A connection's association with a session is not exclusive. A A connection's association with a session is not exclusive. A
connection associated with the channel(s) of one session may be connection associated with the channel(s) of one session may be
simultaneously associated with the channel(s) of other sessions simultaneously associated with the channel(s) of other sessions
including sessions associated with other client IDs. including sessions associated with other client IDs.
It is permissible for connections of multiple transport types to be It is permissible for connections of multiple transport types to be
associated with the same channel. For example both a TCP and RDMA associated with the same channel. For example, both TCP and RDMA
connection can be associated with the fore channel. In the event an connections can be associated with the fore channel. In the event an
RDMA and non-RDMA connection are associated with the same channel, RDMA and non-RDMA connection are associated with the same channel,
the maximum number of slots SHOULD be at least one more than the the maximum number of slots SHOULD be at least one more than the
total number of RDMA credits (Section 2.10.6.1. This way if all RDMA total number of RDMA credits (Section 2.10.6.1). This way, if all
credits are used, the non-RDMA connection can have at least one RDMA credits are used, the non-RDMA connection can have at least one
outstanding request. If a server supports multiple transport types, outstanding request. If a server supports multiple transport types,
it MUST allow a client to associate connections from each transport it MUST allow a client to associate connections from each transport
to a channel. to a channel.
It is permissible for a connection of one type of transport to be It is permissible for a connection of one type of transport to be
associated with the fore channel, and a connection of a different associated with the fore channel, and a connection of a different
type to be associated with the backchannel. type to be associated with the backchannel.
2.10.4. Server Scope 2.10.4. Server Scope
Servers each specify a server scope value in the form of an opaque Servers each specify a server scope value in the form of an opaque
string eir_server_scope returned as part of the results of an string eir_server_scope returned as part of the results of an
EXCHANGE_ID operation. The purpose of the server scope is to allow a EXCHANGE_ID operation. The purpose of the server scope is to allow a
group of servers to indicate to clients that a set of servers sharing group of servers to indicate to clients that a set of servers sharing
the same server scope value have arranged to use compatible values of the same server scope value has arranged to use compatible values of
otherwise opaque identifiers. Thus the identifiers generated by one otherwise opaque identifiers. Thus, the identifiers generated by one
server of that set may be presented to another of that same scope. server of that set may be presented to another of that same scope.
The use of such compatible values does not imply that a value The use of such compatible values does not imply that a value
generated by one server will always be accepted by another. In most generated by one server will always be accepted by another. In most
cases, it will not. However, a server will not accept a value cases, it will not. However, a server will not accept a value
generated by another inadvertently. When it does accept it, it will generated by another inadvertently. When it does accept it, it will
be because it is recognized as valid and carrying the same meaning as be because it is recognized as valid and carrying the same meaning as
on another server of the same scope. on another server of the same scope.
When servers are of the same server scope, this compatibility of When servers are of the same server scope, this compatibility of
values applies to the follow identifiers: values applies to the follow identifiers:
o Filehandle values. A filehandle value accepted by two servers of o Filehandle values. A filehandle value accepted by two servers of
the same server scope denotes the same object. A write done to the same server scope denotes the same object. A WRITE operation
one server is reflected immediately in a read done to the other sent to one server is reflected immediately in a READ sent to the
and locks obtained on one server conflict with those requested on other, and locks obtained on one server conflict with those
the other. requested on the other.
o Session ID values. A session ID value accepted by two servers of o Session ID values. A session ID value accepted by two servers of
the same server scope denotes the same session. the same server scope denotes the same session.
o Client ID values. A client ID value accepted as valid by two o Client ID values. A client ID value accepted as valid by two
servers of the same server scope is associated with two clients servers of the same server scope is associated with two clients
with the same client owner and verifier. with the same client owner and verifier.
o State ID values when the corresponding client ID is recognized as o State ID values. A state ID value is recognized as valid when the
valid. If the same stateid value is accepted as valid on two corresponding client ID is recognized as valid. If the same
servers of the same scope and the client IDs on the two servers stateid value is accepted as valid on two servers of the same
represent the same client owner and verifier, then the two stateid scope and the client IDs on the two servers represent the same
values designate the same set of locks and are for the same file client owner and verifier, then the two stateid values designate
the same set of locks and are for the same file.
o Server owner values. When the server scope values are the same, o Server owner values. When the server scope values are the same,
server owner value may be validly compared. In cases where the server owner value may be validly compared. In cases where the
server scope are different, server owner values are treated as server scope values are different, server owner values are treated
different even if they contain all identical bytes. as different even if they contain all identical bytes.
The co-ordination among servers required to provide such The coordination among servers required to provide such compatibility
compatibility can be quite minimal, and limited to a simple partition can be quite minimal, and limited to a simple partition of the ID
of the ID space. The recognition of common values requires space. The recognition of common values requires additional
additional implementation, but this can be tailored to the specific implementation, but this can be tailored to the specific situations
situations in which that recognition is desired. in which that recognition is desired.
Clients will have occasion to compare the server scope values of Clients will have occasion to compare the server scope values of
multiple servers under a number of circumstances, each of which will multiple servers under a number of circumstances, each of which will
be discussed under the appropriate functional section. be discussed under the appropriate functional section:
o When server owner values received in response to EXCHANGE_ID o When server owner values received in response to EXCHANGE_ID
operations sent to multiple network addresses are compared for the operations sent to multiple network addresses are compared for the
purpose of determining the validity of various forms of trunking, purpose of determining the validity of various forms of trunking,
as described in Section 2.10.5. as described in Section 2.10.5.
o When network or server reconfiguration causes the same network o When network or server reconfiguration causes the same network
address to possibly be directed to different servers, with the address to possibly be directed to different servers, with the
necessity for the client to determine when lock reclaim should be necessity for the client to determine when lock reclaim should be
attempted, as described in Section 8.4.2.1 attempted, as described in Section 8.4.2.1.
o When file system migration causes the transfer of responsibility o When file system migration causes the transfer of responsibility
for a file system between servers and the client needs to for a file system between servers and the client needs to
determine whether state has been transferred with the file system determine whether state has been transferred with the file system
(as described in Section 11.7.7) or whether the client needs to (as described in Section 11.7.7) or whether the client needs to
reclaim state on a similar basis as in the case of server restart, reclaim state on a similar basis as in the case of server restart,
as described in Section 8.4.2. as described in Section 8.4.2.
When two replies from EXCHANGE_ID each from two different server When two replies from EXCHANGE_ID, each from two different server
network addresses have the same server scope, there are a number of network addresses, have the same server scope, there are a number of
ways a client can validate that the common server scope is due to two ways a client can validate that the common server scope is due to two
servers cooperating in a group. servers cooperating in a group.
o If both EXCHANGE_ID requests were sent with RPCSEC_GSS o If both EXCHANGE_ID requests were sent with RPCSEC_GSS
authentication and the server principal is the same for both authentication and the server principal is the same for both
targets, the equality of server scope is validated. It is targets, the equality of server scope is validated. It is
RECOMMENDED that two servers intending to share the same server RECOMMENDED that two servers intending to share the same server
scope also share the same principal name. scope also share the same principal name.
o The client may accept the appearance of the second server in o The client may accept the appearance of the second server in the
fs_locations or fs_locations_info attribute for a relevant file fs_locations or fs_locations_info attribute for a relevant file
system. For example, if there is a migration event for a system. For example, if there is a migration event for a
particular file system or there are locks to be reclaimed on a particular file system or there are locks to be reclaimed on a
particular file system, the attributes for that particular file particular file system, the attributes for that particular file
system may be used. The client sends the GETATTR request to the system may be used. The client sends the GETATTR request to the
first server for the fs_locations or fs_locations_info attribute first server for the fs_locations or fs_locations_info attribute
with RPCSEC_GSS authentication. It may need to do this in advance with RPCSEC_GSS authentication. It may need to do this in advance
of the need to verify the common server scope. If the client of the need to verify the common server scope. If the client
successfully authenticates the reply to GETATTR, and the GETATTR successfully authenticates the reply to GETATTR, and the GETATTR
request and reply containing the fs_locations or fs_locations_info request and reply containing the fs_locations or fs_locations_info
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MAY allow network addresses for different servers to use client ID MAY allow network addresses for different servers to use client ID
trunking. trunking.
Clients may use either form of trunking as long as they do not, when Clients may use either form of trunking as long as they do not, when
trunking between different server network addresses, violate the trunking between different server network addresses, violate the
servers' mandates as to the kinds of trunking to be allowed (see servers' mandates as to the kinds of trunking to be allowed (see
below). With regard to callback channels, the client MUST allow the below). With regard to callback channels, the client MUST allow the
server to choose among all callback channels valid for a given client server to choose among all callback channels valid for a given client
ID and MUST support trunking when the connections supporting the ID and MUST support trunking when the connections supporting the
backchannel allow session or client ID trunking to be used for backchannel allow session or client ID trunking to be used for
callbacks callbacks.
Session trunking is essentially the association of multiple Session trunking is essentially the association of multiple
connections, each with potentially different target and/or source connections, each with potentially different target and/or source
network addresses, to the same session. When the target network network addresses, to the same session. When the target network
addresses (server addresses) of the two connections are the same, the addresses (server addresses) of the two connections are the same, the
server MUST support such session trunking. When the target network server MUST support such session trunking. When the target network
addresses are different, the server MAY indicate such support using addresses are different, the server MAY indicate such support using
the data returned by the EXCHANGE_ID operation (see below). the data returned by the EXCHANGE_ID operation (see below).
Client ID trunking is the association of multiple sessions to the Client ID trunking is the association of multiple sessions to the
same client ID. Servers MUST support client ID trunking for two same client ID. Servers MUST support client ID trunking for two
target network addresses whenever they allow session trunking for target network addresses whenever they allow session trunking for
those same two network addresses. In addition, a server MAY, by those same two network addresses. In addition, a server MAY, by
presenting the same major server owner ID (Section 2.5), and server presenting the same major server owner ID (Section 2.5) and server
scope (Section 2.10.4) allow an additional case of client ID scope (Section 2.10.4), allow an additional case of client ID
trunking. When two servers return the same major server owner and trunking. When two servers return the same major server owner and
server scope, it means that the two servers are cooperating on server scope, it means that the two servers are cooperating on
locking state management which is a prerequisite for client ID locking state management, which is a prerequisite for client ID
trunking. trunking.
Understanding and distinguishing when the client is allowed to use Distinguishing when the client is allowed to use session and client
session and client ID trunking requires understanding how the results ID trunking requires understanding how the results of the EXCHANGE_ID
of the EXCHANGE_ID (Section 18.35) operation identify a server. (Section 18.35) operation identify a server. Suppose a client sends
Suppose a client sends EXCHANGE_ID over two different connections EXCHANGE_IDs over two different connections, each with a possibly
each with a possibly different target network address but each different target network address, but each EXCHANGE_ID operation has
EXCHANGE_ID operation has the same value in the eia_clientowner the same value in the eia_clientowner field. If the same NFSv4.1
field. If the same NFSv4.1 server is listening over each connection, server is listening over each connection, then each EXCHANGE_ID
then each EXCHANGE_ID result MUST return the same values of result MUST return the same values of eir_clientid,
eir_clientid, eir_server_owner.so_major_id and eir_server_scope. The eir_server_owner.so_major_id, and eir_server_scope. The client can
client can then treat each connection as referring to the same server then treat each connection as referring to the same server (subject
(subject to verification, see Paragraph 8 later in this section), and to verification; see Section 2.10.5.1 later in this section), and it
it can use each connection to trunk requests and replies. The can use each connection to trunk requests and replies. The client's
client's choice is whether session trunking or client ID trunking choice is whether session trunking or client ID trunking applies.
applies.
Session Trunking. If the eia_clientowner argument is the same in two Session Trunking. If the eia_clientowner argument is the same in two
different EXCHANGE_ID requests, and the eir_clientid, different EXCHANGE_ID requests, and the eir_clientid,
eir_server_owner.so_major_id, eir_server_owner.so_minor_id, and eir_server_owner.so_major_id, eir_server_owner.so_minor_id, and
eir_server_scope results match in both EXCHANGE_ID results, then eir_server_scope results match in both EXCHANGE_ID results, then
the client is permitted to perform session trunking. If the the client is permitted to perform session trunking. If the
client has no session mapping to the tuple of eir_clientid, client has no session mapping to the tuple of eir_clientid,
eir_server_owner.so_major_id, eir_server_scope, eir_server_owner.so_major_id, eir_server_scope, and
eir_server_owner.so_minor_id, then it creates the session via a eir_server_owner.so_minor_id, then it creates the session via a
CREATE_SESSION operation over one of the connections, which CREATE_SESSION operation over one of the connections, which
associates the connection to the session. If there is a session associates the connection to the session. If there is a session
for the tuple, the client can send BIND_CONN_TO_SESSION to for the tuple, the client can send BIND_CONN_TO_SESSION to
associate the connection to the session. associate the connection to the session.
Of course, if the client does not desire to use session trunking, Of course, if the client does not desire to use session trunking,
it is not required to do so. It can invoke CREATE_SESSION on the it is not required to do so. It can invoke CREATE_SESSION on the
connection. This will result in client ID trunking as described connection. This will result in client ID trunking as described
below. It can also decide to drop the connection if it does not below. It can also decide to drop the connection if it does not
choose to use trunking. choose to use trunking.
Client ID Trunking. If the eia_clientowner argument is the same in Client ID Trunking. If the eia_clientowner argument is the same in
two different EXCHANGE_ID requests, and the eir_clientid, two different EXCHANGE_ID requests, and the eir_clientid,
eir_server_owner.so_major_id, and eir_server_scope results match eir_server_owner.so_major_id, and eir_server_scope results match
in both EXCHANGE_ID results, then the client is permitted to in both EXCHANGE_ID results, then the client is permitted to
perform client ID trunking (regardless whether the perform client ID trunking (regardless of whether the
eir_server_owner.so_minor_id results match). The client can eir_server_owner.so_minor_id results match). The client can
associate each connection with different sessions, where each associate each connection with different sessions, where each
session is associated with the same server. session is associated with the same server.
The client completes the act of client ID trunking by invoking The client completes the act of client ID trunking by invoking
CREATE_SESSION on each connection, using the same client ID that CREATE_SESSION on each connection, using the same client ID that
was returned in eir_clientid. These invocations create two was returned in eir_clientid. These invocations create two
sessions and also associate each connection with its respective sessions and also associate each connection with its respective
session. The client is free to choose not to use client ID session. The client is free to decline to use client ID trunking
trunking by simply dropping the connection at this point. by simply dropping the connection at this point.
When doing client ID trunking, locking state is shared across When doing client ID trunking, locking state is shared across
sessions associated with that same client ID. This requires the sessions associated with that same client ID. This requires the
server to coordinate state across sessions. server to coordinate state across sessions.
The client should be prepared for the possibility that The client should be prepared for the possibility that
eir_server_owner values may be different on subsequent EXCHANGE_ID eir_server_owner values may be different on subsequent EXCHANGE_ID
requests made to the same network address, as a result of various requests made to the same network address, as a result of various
sorts of reconfiguration events. When this happens and the changes sorts of reconfiguration events. When this happens and the changes
result in the invalidation of previously valid forms of trunking, the result in the invalidation of previously valid forms of trunking, the
client should cease to use those forms, either by dropping client should cease to use those forms, either by dropping
connections or by adding sessions. For a discussion of lock reclaim connections or by adding sessions. For a discussion of lock reclaim
as it relates to such reconfiguration events, see Section 8.4.2.1. as it relates to such reconfiguration events, see Section 8.4.2.1.
2.10.5.1. Verifying Claims of Matching Server Identity
When two servers over two connections claim matching or partially When two servers over two connections claim matching or partially
matching eir_server_owner, eir_server_scope, and eir_clientid values, matching eir_server_owner, eir_server_scope, and eir_clientid values,
the client does not have to trust the servers' claims. The client the client does not have to trust the servers' claims. The client
may verify these claims before trunking traffic in the following may verify these claims before trunking traffic in the following
ways: ways:
o For session trunking, clients SHOULD reliably verify if o For session trunking, clients SHOULD reliably verify if
connections between different network paths are in fact associated connections between different network paths are in fact associated
with the same NFSv4.1 server and usable on the same session, and with the same NFSv4.1 server and usable on the same session, and
servers MUST allow clients to perform reliable verification. When servers MUST allow clients to perform reliable verification. When
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ID was created. Mutual authentication via RPCSEC_GSS assures the ID was created. Mutual authentication via RPCSEC_GSS assures the
client that the connection is associated with the correct session client that the connection is associated with the correct session
of the correct server. of the correct server.
o For client ID trunking, the client has at least two options for o For client ID trunking, the client has at least two options for
verifying that the same client ID obtained from two different verifying that the same client ID obtained from two different
EXCHANGE_ID operations came from the same server. The first EXCHANGE_ID operations came from the same server. The first
option is to use RPCSEC_GSS authentication when sending each option is to use RPCSEC_GSS authentication when sending each
EXCHANGE_ID operation. Each time an EXCHANGE_ID is sent with EXCHANGE_ID operation. Each time an EXCHANGE_ID is sent with
RPCSEC_GSS authentication, the client notes the principal name of RPCSEC_GSS authentication, the client notes the principal name of
the GSS target. If the EXCHANGE_ID results indicate client ID the GSS target. If the EXCHANGE_ID results indicate that client
trunking is possible, and the GSS targets' principal names are the ID trunking is possible, and the GSS targets' principal names are
same, the servers are the same and client ID trunking is allowed. the same, the servers are the same and client ID trunking is
allowed.
The second option for verification is to use SP4_SSV protection. The second option for verification is to use SP4_SSV protection.
When the client sends EXCHANGE_ID it specifies SP4_SSV protection. When the client sends EXCHANGE_ID, it specifies SP4_SSV
The first EXCHANGE_ID the client sends always has to be confirmed protection. The first EXCHANGE_ID the client sends always has to
by a CREATE_SESSION call. The client then sends SET_SSV. Later be confirmed by a CREATE_SESSION call. The client then sends
the client sends EXCHANGE_ID to a second destination network SET_SSV. Later, the client sends EXCHANGE_ID to a second
address different from the one the first EXCHANGE_ID was sent to. destination network address different from the one the first
The client checks that each EXCHANGE_ID reply has the same EXCHANGE_ID was sent to. The client checks that each EXCHANGE_ID
eir_clientid, eir_server_owner.so_major_id, and eir_server_scope. reply has the same eir_clientid, eir_server_owner.so_major_id, and
If so, the client verifies the claim by sending a CREATE_SESSION eir_server_scope. If so, the client verifies the claim by sending
operation to the second destination address, protected with a CREATE_SESSION operation to the second destination address,
RPCSEC_GSS integrity using an RPCSEC_GSS handle returned by the protected with RPCSEC_GSS integrity using an RPCSEC_GSS handle
second EXCHANGE_ID. If the server accepts the CREATE_SESSION returned by the second EXCHANGE_ID. If the server accepts the
request, and if the client verifies the RPCSEC_GSS verifier and CREATE_SESSION request, and if the client verifies the RPCSEC_GSS
integrity codes, then the client has proof the second server knows verifier and integrity codes, then the client has proof the second
the SSV, and thus the two servers are co-operating for the server knows the SSV, and thus the two servers are cooperating for
purposes of specifying server scope and client ID trunking. the purposes of specifying server scope and client ID trunking.
2.10.6. Exactly Once Semantics 2.10.6. Exactly Once Semantics
Via the session, NFSv4.1 offers Exactly Once Semantics (EOS) for Via the session, NFSv4.1 offers exactly once semantics (EOS) for
requests sent over a channel. EOS is supported on both the fore and requests sent over a channel. EOS is supported on both the fore
back channels. channel and backchannel.
Each COMPOUND or CB_COMPOUND request that is sent with a leading Each COMPOUND or CB_COMPOUND request that is sent with a leading
SEQUENCE or CB_SEQUENCE operation MUST be executed by the receiver SEQUENCE or CB_SEQUENCE operation MUST be executed by the receiver
exactly once. This requirement holds regardless of whether the exactly once. This requirement holds regardless of whether the
request is sent with reply caching specified (see request is sent with reply caching specified (see
Section 2.10.6.1.3). The requirement holds even if the requester is Section 2.10.6.1.3). The requirement holds even if the requester is
sending the request over a session created between a pNFS data client sending the request over a session created between a pNFS data client
and pNFS data server. To understand the rationale for this and pNFS data server. To understand the rationale for this
requirement, divide the requests into three classifications: requirement, divide the requests into three classifications:
o Nonidempotent requests. o Non-idempotent requests.
o Idempotent modifying requests. o Idempotent modifying requests.
o Idempotent non-modifying requests. o Idempotent non-modifying requests.
An example of a non-idempotent request is RENAME. Obviously if a An example of a non-idempotent request is RENAME. Obviously, if a
replier executes the same RENAME request twice, and the first replier executes the same RENAME request twice, and the first
execution succeeds, the re-execution will fail. If the replier execution succeeds, the re-execution will fail. If the replier
returns the result from the re-execution, this result is incorrect. returns the result from the re-execution, this result is incorrect.
Therefore, EOS is required for nonidempotent requests. Therefore, EOS is required for non-idempotent requests.
An example of an idempotent modifying request is a COMPOUND request An example of an idempotent modifying request is a COMPOUND request
containing a WRITE operation. Repeated execution of the same WRITE containing a WRITE operation. Repeated execution of the same WRITE
has the same effect as execution of that write a single time. has the same effect as execution of that WRITE a single time.
Nevertheless, enforcing EOS for WRITEs and other idempotent modifying Nevertheless, enforcing EOS for WRITEs and other idempotent modifying
requests is necessary to avoid data corruption. requests is necessary to avoid data corruption.
Suppose a client sends WRITE A to a noncompliant server that does not Suppose a client sends WRITE A to a noncompliant server that does not
enforce EOS, and receives no response, perhaps due to a network enforce EOS, and receives no response, perhaps due to a network
partition. The client reconnects to the server and re-sends WRITE A. partition. The client reconnects to the server and re-sends WRITE A.
Now, the server has outstanding two instances of A. The server can be Now, the server has outstanding two instances of A. The server can be
in a situation in which it executes and replies to the retry of A, in a situation in which it executes and replies to the retry of A,
while the first A is still waiting in the server's internal I/O while the first A is still waiting in the server's internal I/O
system for some resource. Upon receiving the reply to the second system for some resource. Upon receiving the reply to the second
attempt of WRITE A, the client believes its write is done so it is attempt of WRITE A, the client believes its WRITE is done so it is
free to send WRITE B which overlaps the range of A. When the original free to send WRITE B, which overlaps the byte-range of A. When the
A is dispatched from the server's I/O system, and executed (thus the original A is dispatched from the server's I/O system and executed
second time A will have been written), then what has been written by (thus the second time A will have been written), then what has been
B can be overwritten and thus corrupted. written by B can be overwritten and thus corrupted.
An example of an idempotent non-modifying request is a COMPOUND An example of an idempotent non-modifying request is a COMPOUND
containing SEQUENCE, PUTFH, READLINK and nothing else. The re- containing SEQUENCE, PUTFH, READLINK, and nothing else. The re-
execution of a such a request will not cause data corruption, or execution of such a request will not cause data corruption or produce
produce an incorrect result. Nonetheless, to keep the implementation an incorrect result. Nonetheless, to keep the implementation simple,
simple, the replier MUST enforce EOS for all requests whether the replier MUST enforce EOS for all requests, whether or not
idempotent and non-modifying or not. idempotent and non-modifying.
Note that true and complete EOS is not possible unless the server Note that true and complete EOS is not possible unless the server
persists the reply cache in stable storage, unless the server is persists the reply cache in stable storage, and unless the server is
somehow implemented to never require a restart (indeed if such a somehow implemented to never require a restart (indeed, if such a
server exists, the distinction between a reply cache kept in stable server exists, the distinction between a reply cache kept in stable
storage versus one that is not is one without meaning). See storage versus one that is not is one without meaning). See
Section 2.10.6.5 for a discussion of persistence in the reply cache. Section 2.10.6.5 for a discussion of persistence in the reply cache.
Regardless, even if the server does not persist the reply cache, EOS Regardless, even if the server does not persist the reply cache, EOS
improves robustness and correctness over previous versions of NFS improves robustness and correctness over previous versions of NFS
because the legacy duplicate request/reply caches were based on the because the legacy duplicate request/reply caches were based on the
ONC RPC transaction identifier (XID). Section 2.10.6.1 explains the ONC RPC transaction identifier (XID). Section 2.10.6.1 explains the
shortcomings of the XID as a basis for a reply cache and describes shortcomings of the XID as a basis for a reply cache and describes
how NFSv4.1 sessions improve upon the XID. how NFSv4.1 sessions improve upon the XID.
2.10.6.1. Slot Identifiers and Reply Cache 2.10.6.1. Slot Identifiers and Reply Cache
The RPC layer provides a transaction ID (XID), which, while required The RPC layer provides a transaction ID (XID), which, while required
to be unique, is not convenient for tracking requests for two to be unique, is not convenient for tracking requests for two
reasons. First, the XID is only meaningful to the requester; it reasons. First, the XID is only meaningful to the requester; it
cannot be interpreted by the replier except to test for equality with cannot be interpreted by the replier except to test for equality with
previously sent requests. When consulting an RPC-based duplicate previously sent requests. When consulting an RPC-based duplicate
request cache, the opaqueness of the XID requires a computationally request cache, the opaqueness of the XID requires a computationally
expensive lookup (often via a hash that includes XID and source expensive lookup (often via a hash that includes XID and source
address). NFSv4.1 requests use a non-opaque slot ID which is an address). NFSv4.1 requests use a non-opaque slot ID, which is an
index into a slot table, which is far more efficient. Second, index into a slot table, which is far more efficient. Second,
because RPC requests can be executed by the replier in any order, because RPC requests can be executed by the replier in any order,
there is no bound on the number of requests that may be outstanding there is no bound on the number of requests that may be outstanding
at any time. To achieve perfect EOS using ONC RPC would require at any time. To achieve perfect EOS, using ONC RPC would require
storing all replies in the reply cache. XIDs are 32 bits; storing storing all replies in the reply cache. XIDs are 32 bits; storing
over four billion (2^32) replies in the reply cache is not practical. over four billion (2^32) replies in the reply cache is not practical.
In practice, previous versions of NFS have chosen to store a fixed In practice, previous versions of NFS have chosen to store a fixed
number of replies in the cache, and use a least recently used (LRU) number of replies in the cache, and to use a least recently used
approach to replacing cache entries with new entries when the cache (LRU) approach to replacing cache entries with new entries when the
is full. In NFSv4.1, the number of outstanding requests is bounded cache is full. In NFSv4.1, the number of outstanding requests is
by the size of the slot table, and a sequence ID per slot is used to bounded by the size of the slot table, and a sequence ID per slot is
tell the replier when it is safe to delete a cached reply. used to tell the replier when it is safe to delete a cached reply.
In the NFSv4.1 reply cache, when the requester sends a new request, In the NFSv4.1 reply cache, when the requester sends a new request,
it selects a slot ID in the range 0..N, where N is the replier's it selects a slot ID in the range 0..N, where N is the replier's
current maximum slot ID granted to the requester on the session over current maximum slot ID granted to the requester on the session over
which the request is to be sent. The value of N starts out as equal which the request is to be sent. The value of N starts out as equal
to ca_maxrequests - 1 (Section 18.36), but can be adjusted by the to ca_maxrequests - 1 (Section 18.36), but can be adjusted by the
response to SEQUENCE or CB_SEQUENCE as described later in this response to SEQUENCE or CB_SEQUENCE as described later in this
section. The slot ID must be unused by any of the requests which the section. The slot ID must be unused by any of the requests that the
requester has already active on the session. "Unused" here means the requester has already active on the session. "Unused" here means the
requester has no outstanding request for that slot ID. requester has no outstanding request for that slot ID.
A slot contains a sequence ID and the cached reply corresponding to A slot contains a sequence ID and the cached reply corresponding to
the request sent with that sequence ID. The sequence ID is a 32 bit the request sent with that sequence ID. The sequence ID is a 32-bit
unsigned value, and is therefore in the range 0..0xFFFFFFFF (2^32 - unsigned value, and is therefore in the range 0..0xFFFFFFFF (2^32 -
1). The first time a slot is used, the requester MUST specify a 1). The first time a slot is used, the requester MUST specify a
sequence ID of one (1) (Section 18.36). Each time a slot is reused, sequence ID of one (Section 18.36). Each time a slot is reused, the
the request MUST specify a sequence ID that is one greater than that request MUST specify a sequence ID that is one greater than that of
of the previous request on the slot. If the previous sequence ID was the previous request on the slot. If the previous sequence ID was
0xFFFFFFFF, then the next request for the slot MUST have the sequence 0xFFFFFFFF, then the next request for the slot MUST have the sequence
ID set to zero (i.e. (2^32 - 1) + 1 mod 2^32). ID set to zero (i.e., (2^32 - 1) + 1 mod 2^32).
The sequence ID accompanies the slot ID in each request. It is for The sequence ID accompanies the slot ID in each request. It is for
the critical check at the replier: it used to efficiently determine the critical check at the replier: it used to efficiently determine
whether a request using a certain slot ID is a retransmit or a new, whether a request using a certain slot ID is a retransmit or a new,
never-before-seen request. It is not feasible for the requester to never-before-seen request. It is not feasible for the requester to
assert that it is retransmitting to implement this, because for any assert that it is retransmitting to implement this, because for any
given request the requester cannot know whether the replier has seen given request the requester cannot know whether the replier has seen
it unless the replier actually replies. Of course, if the requester it unless the replier actually replies. Of course, if the requester
has seen the reply, the requester would not retransmit. has seen the reply, the requester would not retransmit.
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executed to completion, the replier returns the cached reply. See executed to completion, the replier returns the cached reply. See
Section 2.10.6.2 for direction on how the replier deals with Section 2.10.6.2 for direction on how the replier deals with
retries of requests that are still in progress. retries of requests that are still in progress.
o A misordered retry, in which the sequence ID is less than o A misordered retry, in which the sequence ID is less than
(accounting for sequence wraparound) that previously seen in the (accounting for sequence wraparound) that previously seen in the
slot. The replier MUST return NFS4ERR_SEQ_MISORDERED (as the slot. The replier MUST return NFS4ERR_SEQ_MISORDERED (as the
result from SEQUENCE or CB_SEQUENCE). result from SEQUENCE or CB_SEQUENCE).
o A misordered new request, in which the sequence ID is two or more o A misordered new request, in which the sequence ID is two or more
than (accounting for sequence wraparound) than that previously than (accounting for sequence wraparound) that previously seen in
seen in the slot. Note that because the sequence ID MUST the slot. Note that because the sequence ID MUST wrap around to
wraparound to zero (0) once it reaches 0xFFFFFFFF, a misordered zero once it reaches 0xFFFFFFFF, a misordered new request and a
new request and a misordered retry cannot be distinguished. Thus, misordered retry cannot be distinguished. Thus, the replier MUST
the replier MUST return NFS4ERR_SEQ_MISORDERED (as the result from return NFS4ERR_SEQ_MISORDERED (as the result from SEQUENCE or
SEQUENCE or CB_SEQUENCE). CB_SEQUENCE).
Unlike the XID, the slot ID is always within a specific range; this Unlike the XID, the slot ID is always within a specific range; this
has two implications. The first implication is that for a given has two implications. The first implication is that for a given
session, the replier need only cache the results of a limited number session, the replier need only cache the results of a limited number
of COMPOUND requests . The second implication derives from the of COMPOUND requests. The second implication derives from the first,
first, which is that unlike XID-indexed reply caches (also known as which is that unlike XID-indexed reply caches (also known as
duplicate request caches - DRCs), the slot ID-based reply cache duplicate request caches - DRCs), the slot ID-based reply cache
cannot be overflowed. Through use of the sequence ID to identify cannot be overflowed. Through use of the sequence ID to identify
retransmitted requests, the replier does not need to actually cache retransmitted requests, the replier does not need to actually cache
the request itself, reducing the storage requirements of the reply the request itself, reducing the storage requirements of the reply
cache further. These facilities make it practical to maintain all cache further. These facilities make it practical to maintain all
the required entries for an effective reply cache. the required entries for an effective reply cache.
The slot ID, sequence ID, and session ID therefore take over the The slot ID, sequence ID, and session ID therefore take over the
traditional role of the XID and source network address in the traditional role of the XID and source network address in the
replier's reply cache implementation. This approach is considerably replier's reply cache implementation. This approach is considerably
more portable and completely robust - it is not subject to the more portable and completely robust -- it is not subject to the
reassignment of ports as clients reconnect over IP networks. In reassignment of ports as clients reconnect over IP networks. In
addition, the RPC XID is not used in the reply cache, enhancing addition, the RPC XID is not used in the reply cache, enhancing
robustness of the cache in the face of any rapid reuse of XIDs by the robustness of the cache in the face of any rapid reuse of XIDs by the
requester. While the replier does not care about the XID for the requester. While the replier does not care about the XID for the
purposes of reply cache management (but the replier MUST return the purposes of reply cache management (but the replier MUST return the
same XID that was in the request), nonetheless there are same XID that was in the request), nonetheless there are
considerations for the XID in NFSv4.1 that are the same as all other considerations for the XID in NFSv4.1 that are the same as all other
previous versions of NFS. The RPC XID remains in each message and previous versions of NFS. The RPC XID remains in each message and
needs to be formulated in NFSv4.1 requests as in any other ONC RPC needs to be formulated in NFSv4.1 requests as in any other ONC RPC
request. The reasons include: request. The reasons include:
o The RPC layer retains its existing semantics and implementation. o The RPC layer retains its existing semantics and implementation.
o The requester and replier must be able to interoperate at the RPC o The requester and replier must be able to interoperate at the RPC
layer, prior to the NFSv4.1 decoding of the SEQUENCE or layer, prior to the NFSv4.1 decoding of the SEQUENCE or
CB_SEQUENCE operation. CB_SEQUENCE operation.
o If an operation is being used that does not start with SEQUENCE or o If an operation is being used that does not start with SEQUENCE or
CB_SEQUENCE (e.g. BIND_CONN_TO_SESSION), then the RPC XID is CB_SEQUENCE (e.g., BIND_CONN_TO_SESSION), then the RPC XID is
needed for correct operation to match the reply to the request. needed for correct operation to match the reply to the request.
o The SEQUENCE or CB_SEQUENCE operation may generate an error. If o The SEQUENCE or CB_SEQUENCE operation may generate an error. If
so, the embedded slot ID, sequence ID, and session ID (if present) so, the embedded slot ID, sequence ID, and session ID (if present)
in the request will not be in the reply, and the requester has in the request will not be in the reply, and the requester has
only the XID to match the reply to the request. only the XID to match the reply to the request.
Given that well formulated XIDs continue to be required, this begs Given that well-formulated XIDs continue to be required, this begs
the question why SEQUENCE and CB_SEQUENCE replies have a session ID, the question: why do SEQUENCE and CB_SEQUENCE replies have a session
slot ID and sequence ID? Having the session ID in the reply means ID, slot ID, and sequence ID? Having the session ID in the reply
the requester does not have to use the XID to lookup the session ID, means that the requester does not have to use the XID to look up the
which would be necessary if the connection were associated with session ID, which would be necessary if the connection were
multiple sessions. Having the slot ID and sequence ID in the reply associated with multiple sessions. Having the slot ID and sequence
means the requester does not have to use the XID to lookup the slot ID in the reply means that the requester does not have to use the XID
ID and sequence ID. Furthermore, since the XID is only 32 bits, it to look up the slot ID and sequence ID. Furthermore, since the XID
is too small to guarantee the re-association of a reply with its is only 32 bits, it is too small to guarantee the re-association of a
request ([37]); having session ID, slot ID, and sequence ID in the reply with its request [37]; having session ID, slot ID, and sequence
reply allows the client to validate that the reply in fact belongs to ID in the reply allows the client to validate that the reply in fact
the matched request. belongs to the matched request.
The SEQUENCE (and CB_SEQUENCE) operation also carries a The SEQUENCE (and CB_SEQUENCE) operation also carries a
"highest_slotid" value which carries additional requester slot usage "highest_slotid" value, which carries additional requester slot usage
information. The requester MUST always indicate the slot ID information. The requester MUST always indicate the slot ID
representing the outstanding request with the highest-numbered slot representing the outstanding request with the highest-numbered slot
value. The requester should in all cases provide the most value. The requester should in all cases provide the most
conservative value possible, although it can be increased somewhat conservative value possible, although it can be increased somewhat
above the actual instantaneous usage to maintain some minimum or above the actual instantaneous usage to maintain some minimum or
optimal level. This provides a way for the requester to yield unused optimal level. This provides a way for the requester to yield unused
request slots back to the replier, which in turn can use the request slots back to the replier, which in turn can use the
information to reallocate resources. information to reallocate resources.
The replier responds with both a new target highest_slotid, and an The replier responds with both a new target highest_slotid and an
enforced highest_slotid, described as follows: enforced highest_slotid, described as follows:
o The target highest_slotid is an indication to the requester of the o The target highest_slotid is an indication to the requester of the
highest_slotid the replier wishes the requester to be using. This highest_slotid the replier wishes the requester to be using. This
permits the replier to withdraw (or add) resources from a permits the replier to withdraw (or add) resources from a
requester that has been found to not be using them, in order to requester that has been found to not be using them, in order to
more fairly share resources among a varying level of demand from more fairly share resources among a varying level of demand from
other requesters. The requester must always comply with the other requesters. The requester must always comply with the
replier's value updates, since they indicate newly established replier's value updates, since they indicate newly established
hard limits on the requester's access to session resources. hard limits on the requester's access to session resources.
However, because of request pipelining, the requester may have However, because of request pipelining, the requester may have
active requests in flight reflecting prior values, therefore the active requests in flight reflecting prior values; therefore, the
replier must not immediately require the requester to comply. replier must not immediately require the requester to comply.
o The enforced highest_slotid indicates the highest slot ID the o The enforced highest_slotid indicates the highest slot ID the
requester is permitted to use on a subsequent SEQUENCE or requester is permitted to use on a subsequent SEQUENCE or
CB_SEQUENCE operation. The replier's enforced highest_slotid CB_SEQUENCE operation. The replier's enforced highest_slotid
SHOULD be no less than the highest_slotid the requester indicated SHOULD be no less than the highest_slotid the requester indicated
in the SEQUENCE or CB_SEQUENCE arguments. in the SEQUENCE or CB_SEQUENCE arguments.
A requester can be intransigent with respect to lowering its A requester can be intransigent with respect to lowering its
highest_slotid argument to a Sequence operation, i.e. the highest_slotid argument to a Sequence operation, i.e. the
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highest_slotid argument to be higher than the target highest_slotid argument to be higher than the target
highest_slotid. This can be considered particularly egregious highest_slotid. This can be considered particularly egregious
behavior when the replier knows there are no outstanding requests behavior when the replier knows there are no outstanding requests
with slot IDs higher than its target highest_slotid. When faced with slot IDs higher than its target highest_slotid. When faced
with such intransigence, the replier is free to take more forceful with such intransigence, the replier is free to take more forceful
action, and MAY reply with a new enforced highest_slotid that is action, and MAY reply with a new enforced highest_slotid that is
less than its previous enforced highest_slotid. Thereafter, if less than its previous enforced highest_slotid. Thereafter, if
the requester continues to send requests with a highest_slotid the requester continues to send requests with a highest_slotid
that is greater than the replier's new enforced highest_slotid, that is greater than the replier's new enforced highest_slotid,
the server MAY return NFS4ERR_BAD_HIGH_SLOT, unless the slot ID in the server MAY return NFS4ERR_BAD_HIGH_SLOT, unless the slot ID in
the request is greater than the new enforced highest_slotid, and the request is greater than the new enforced highest_slotid and
the request is a retry. the request is a retry.
The replier SHOULD retain the slots it wants to retire until the The replier SHOULD retain the slots it wants to retire until the
requester sends a request with a highest_slotid less than or equal requester sends a request with a highest_slotid less than or equal
to the replier's new enforced highest_slotid. to the replier's new enforced highest_slotid.
The requester can also be intransigent with respect to sending The requester can also be intransigent with respect to sending
non-retry requests that have a slot ID that exceeds the replier's non-retry requests that have a slot ID that exceeds the replier's
highest_slotid. Once the replier has forcibly lowered the highest_slotid. Once the replier has forcibly lowered the
enforced highest_slotid, the requester is only allowed to send enforced highest_slotid, the requester is only allowed to send
retries on slots that exceed the replier's highest_slotid. If a retries on slots that exceed the replier's highest_slotid. If a
request is received with a slot ID that is higher than the new request is received with a slot ID that is higher than the new
enforced highest_slotid, and the sequence ID is one higher than enforced highest_slotid, and the sequence ID is one higher than
what is in the slot's reply cache, then the server can both retire what is in the slot's reply cache, then the server can both retire
the slot and return NFS4ERR_BADSLOT (however the server MUST NOT the slot and return NFS4ERR_BADSLOT (however, the server MUST NOT
do one and not the other). The reason it is safe to retire the do one and not the other). The reason it is safe to retire the
slot is because that by using the next sequence ID, the requester slot is because by using the next sequence ID, the requester is
is indicating it has received the previous reply for the slot. indicating it has received the previous reply for the slot.
o The requester SHOULD use the lowest available slot when sending a o The requester SHOULD use the lowest available slot when sending a
new request. This way, the replier may be able to retire slot new request. This way, the replier may be able to retire slot
entries faster. However, where the replier is actively adjusting entries faster. However, where the replier is actively adjusting
its granted highest_slotid, it will not be able to use only the its granted highest_slotid, it will not be able to use only the
receipt of the slot ID and highest_slotid in the request. Neither receipt of the slot ID and highest_slotid in the request. Neither
the slot ID nor the highest_slotid used in a request may reflect the slot ID nor the highest_slotid used in a request may reflect
the replier's current idea of the requester's session limit, the replier's current idea of the requester's session limit,
because the request may have been sent from the requester before because the request may have been sent from the requester before
the update was received. Therefore, in the downward adjustment the update was received. Therefore, in the downward adjustment
case, the replier may have to retain a number of reply cache case, the replier may have to retain a number of reply cache
entries at least as large as the old value of maximum requests entries at least as large as the old value of maximum requests
outstanding, until it can infer that the requester has seen a outstanding, until it can infer that the requester has seen a
reply containing the new granted highest_slotid. The replier can reply containing the new granted highest_slotid. The replier can
infer that requester as seen such a reply when it receives a new infer that the requester has seen such a reply when it receives a
request with the same slot ID as the request replied to and the new request with the same slot ID as the request replied to and
next higher sequence ID. the next higher sequence ID.
2.10.6.1.1. Caching of SEQUENCE and CB_SEQUENCE Replies 2.10.6.1.1. Caching of SEQUENCE and CB_SEQUENCE Replies
When a SEQUENCE or CB_SEQUENCE operation is successfully executed, When a SEQUENCE or CB_SEQUENCE operation is successfully executed,
its reply MUST always be cached. Specifically, session ID, sequence its reply MUST always be cached. Specifically, session ID, sequence
ID, and slot ID MUST be cached in the reply cache. The reply from ID, and slot ID MUST be cached in the reply cache. The reply from
SEQUENCE also includes the highest slot ID, target highest slot ID, SEQUENCE also includes the highest slot ID, target highest slot ID,
and status flags. Instead of caching these values, the server MAY and status flags. Instead of caching these values, the server MAY
re-compute the values from the current state of the fore channel, re-compute the values from the current state of the fore channel,
session and/or client ID as appropriate. Similarly, the reply from session, and/or client ID as appropriate. Similarly, the reply from
CB_SEQUENCE includes a highest slot ID and target highest slot ID. CB_SEQUENCE includes a highest slot ID and target highest slot ID.
The client MAY re-compute the values from the current state of the The client MAY re-compute the values from the current state of the
session as appropriate. session as appropriate.
Regardless of whether a replier is re-computing highest slot ID, Regardless of whether or not a replier is re-computing highest slot
target slot ID, and status on replies to retries or not, the ID, target slot ID, and status on replies to retries, the requester
requester MUST NOT assume the values are being re-computed whenever MUST NOT assume that the values are being re-computed whenever it
it receives a reply after a retry is sent, since it has no way of receives a reply after a retry is sent, since it has no way of
knowing whether the reply it has received was sent by the server in knowing whether the reply it has received was sent by the replier in
response to the retry, or is a delayed response to the original response to the retry or is a delayed response to the original
request. Therefore, it may be the case that highest slot ID, target request. Therefore, it may be the case that highest slot ID, target
slot ID, or status bits may reflect the state of affairs when the slot ID, or status bits may reflect the state of affairs when the
request was first executed. Although acting based on such delayed request was first executed. Although acting based on such delayed
information is valid, it may cause the receiver to do unneeded work. information is valid, it may cause the receiver of the reply to do
Requesters MAY choose to send additional requests to get the current unneeded work. Requesters MAY choose to send additional requests to
state of affairs or use the state of affairs reported by subsequent get the current state of affairs or use the state of affairs reported
requests, in preference to acting immediately on data which may be by subsequent requests, in preference to acting immediately on data
out of date. that might be out of date.
2.10.6.1.2. Errors from SEQUENCE and CB_SEQUENCE 2.10.6.1.2. Errors from SEQUENCE and CB_SEQUENCE
Any time SEQUENCE or CB_SEQUENCE return an error, the sequence ID of Any time SEQUENCE or CB_SEQUENCE returns an error, the sequence ID of
the slot MUST NOT change. The replier MUST NOT modify the reply the slot MUST NOT change. The replier MUST NOT modify the reply
cache entry for the slot whenever an error is returned from SEQUENCE cache entry for the slot whenever an error is returned from SEQUENCE
or CB_SEQUENCE. or CB_SEQUENCE.
2.10.6.1.3. Optional Reply Caching 2.10.6.1.3. Optional Reply Caching
On a per-request basis the requester can choose to direct the replier On a per-request basis, the requester can choose to direct the
to cache the reply to all operations after the first operation replier to cache the reply to all operations after the first
(SEQUENCE or CB_SEQUENCE) via the sa_cachethis or csa_cachethis operation (SEQUENCE or CB_SEQUENCE) via the sa_cachethis or
fields of the arguments to SEQUENCE or CB_SEQUENCE. The reason it csa_cachethis fields of the arguments to SEQUENCE or CB_SEQUENCE.
would not direct the replier to cache the entire reply is that the The reason it would not direct the replier to cache the entire reply
request is composed of all idempotent operations [34]. Caching the is that the request is composed of all idempotent operations [34].
reply may offer little benefit. If the reply is too large (see Caching the reply may offer little benefit. If the reply is too
Section 2.10.6.4), it may not be cacheable anyway. Even if the reply large (see Section 2.10.6.4), it may not be cacheable anyway. Even
to idempotent request is small enough to cache, unnecessarily caching if the reply to idempotent request is small enough to cache,
the reply slows down the server and increases RPC latency. unnecessarily caching the reply slows down the server and increases
RPC latency.
Whether the requester requests the reply to be cached or not has no Whether or not the requester requests the reply to be cached has no
effect on the slot processing. If the results of SEQUENCE or effect on the slot processing. If the results of SEQUENCE or
CB_SEQUENCE are NFS4_OK, then the slot's sequence ID MUST be CB_SEQUENCE are NFS4_OK, then the slot's sequence ID MUST be
incremented by one. If a requester does not direct the replier to incremented by one. If a requester does not direct the replier to
cache the reply, the replier MUST do one of following: cache the reply, the replier MUST do one of following:
o The replier can cache the entire original reply. Even though o The replier can cache the entire original reply. Even though
sa_cachethis or csa_cachethis are FALSE, the replier is always sa_cachethis or csa_cachethis is FALSE, the replier is always free
free to cache. It may choose this approach in order to simplify to cache. It may choose this approach in order to simplify
implementation. implementation.
o The replier enters into its reply cache a reply consisting of the o The replier enters into its reply cache a reply consisting of the
original results to the SEQUENCE or CB_SEQUENCE operation, and original results to the SEQUENCE or CB_SEQUENCE operation, and
with the next operation in COMPOUND or CB_COMPOUND having the with the next operation in COMPOUND or CB_COMPOUND having the
error NFS4ERR_RETRY_UNCACHED_REP. Thus if the requester later error NFS4ERR_RETRY_UNCACHED_REP. Thus, if the requester later
retries the request, it will get NFS4ERR_RETRY_UNCACHED_REP. If a retries the request, it will get NFS4ERR_RETRY_UNCACHED_REP. If a
replier receives a retried Sequence operation where the reply to replier receives a retried Sequence operation where the reply to
the COMPOUND or CB_COMPOUND was not cached, then the replier, the COMPOUND or CB_COMPOUND was not cached, then the replier,
* MAY return NFS4ERR_RETRY_UNCACHED_REP in reply to a Sequence * MAY return NFS4ERR_RETRY_UNCACHED_REP in reply to a Sequence
operation if the Sequence operation is not the first operation operation if the Sequence operation is not the first operation
(granted, a requester that does so is in violation of the (granted, a requester that does so is in violation of the
NFSv4.1 protocol). NFSv4.1 protocol).
* MUST NOT return NFS4ERR_RETRY_UNCACHED_REP in reply to a * MUST NOT return NFS4ERR_RETRY_UNCACHED_REP in reply to a
Sequence operation if the Sequence operation is the first Sequence operation if the Sequence operation is the first
operation. operation.
o If the second operation is an illegal operation, or an operation o If the second operation is an illegal operation, or an operation
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operation if the Sequence operation is not the first operation operation if the Sequence operation is not the first operation
(granted, a requester that does so is in violation of the (granted, a requester that does so is in violation of the
NFSv4.1 protocol). NFSv4.1 protocol).
* MUST NOT return NFS4ERR_RETRY_UNCACHED_REP in reply to a * MUST NOT return NFS4ERR_RETRY_UNCACHED_REP in reply to a
Sequence operation if the Sequence operation is the first Sequence operation if the Sequence operation is the first
operation. operation.
o If the second operation is an illegal operation, or an operation o If the second operation is an illegal operation, or an operation
that was legal in a previous minor version of NFSv4 and MUST NOT that was legal in a previous minor version of NFSv4 and MUST NOT
be supported in current minor version (e.g. SETCLIENTID), the be supported in the current minor version (e.g., SETCLIENTID), the
replier MUST NOT ever return NFS4ERR_RETRY_UNCACHED_REP. Instead replier MUST NOT ever return NFS4ERR_RETRY_UNCACHED_REP. Instead
the replier MUST return NFS4ERR_OP_ILLEGAL, or NFS4ERR_BADXDR, or the replier MUST return NFS4ERR_OP_ILLEGAL or NFS4ERR_BADXDR or
NFS4ERR_NOTSUPP as appropriate. NFS4ERR_NOTSUPP as appropriate.
o If the second operation can result in another error status, the o If the second operation can result in another error status, the
replier MAY return a status other than NFS4ERR_RETRY_UNCACHED_REP, replier MAY return a status other than NFS4ERR_RETRY_UNCACHED_REP,
provided the operation is not executed in such a way that the provided the operation is not executed in such a way that the
state of the replier is changed. Examples of such an error status state of the replier is changed. Examples of such an error status
include: NFS4ERR_NOTSUPP returned for an operation that is legal include: NFS4ERR_NOTSUPP returned for an operation that is legal
but not REQUIRED in the current minor versions, and thus not but not REQUIRED in the current minor versions, and thus not
supported by the replier; NFS4ERR_SEQUENCE_POS; and supported by the replier; NFS4ERR_SEQUENCE_POS; and
NFS4ERR_REQ_TOO_BIG. NFS4ERR_REQ_TOO_BIG.
The discussion above assumes that the retried request matches the The discussion above assumes that the retried request matches the
original one. Section 2.10.6.1.3.1 discusses what the replier might original one. Section 2.10.6.1.3.1 discusses what the replier might
do, and MUST do when original and retried requests do not match. do, and MUST do when original and retried requests do not match.
Since the replier may only cache a small amount of the information Since the replier may only cache a small amount of the information
that would be required to determine whether this is a case of a false that would be required to determine whether this is a case of a false
retry, the replier may send to the client, any of the following retry, the replier may send to the client any of the following
responses: responses:
o The cached reply to the original request (if the replier has o The cached reply to the original request (if the replier has
cached it in its entirety, and the users of the original request cached it in its entirety and the users of the original request
and retry match). and retry match).
o A reply that consists only of the Sequence operation with the o A reply that consists only of the Sequence operation with the
error NFS4ERR_FALSE_RETRY. error NFS4ERR_FALSE_RETRY.
o A reply consisting of the response to Sequence with the status o A reply consisting of the response to Sequence with the status
NFS4_OK, together with the second operation as it appeared in the NFS4_OK, together with the second operation as it appeared in the
retried request with an error of NFS4ERR_RETRY_UNCACHED_REP or retried request with an error of NFS4ERR_RETRY_UNCACHED_REP or
other error as described above. other error as described above.
o A reply that consists of the response to Sequence with the status o A reply that consists of the response to Sequence with the status
NFS4_OK, together with the second operation as it appeared in the NFS4_OK, together with the second operation as it appeared in the
original request with an error of NFS4ERR_RETRY_UNCACHED_REP or original request with an error of NFS4ERR_RETRY_UNCACHED_REP or
other error as described above. other error as described above.
2.10.6.1.3.1. False Retry 2.10.6.1.3.1. False Retry
If a requester sent a Sequence operation with a slot ID and sequence If a requester sent a Sequence operation with a slot ID and sequence
ID that are in the reply cache, but the replier detected that the ID that are in the reply cache but the replier detected that the
retried request is not the same as the original request, including a retried request is not the same as the original request, including a
retry that has different operations or different arguments in the retry that has different operations or different arguments in the
operations from the original, and a retry that uses a different operations from the original and a retry that uses a different
principal in the RPC request's credential field that translates to a principal in the RPC request's credential field that translates to a
different user, then this is a false retry. When the replier detects different user, then this is a false retry. When the replier detects
a false retry, it is permitted to (but not always obligated to) a false retry, it is permitted (but not always obligated) to return
return NFS4ERR_FALSE_RETRY in response to the Sequence operation when NFS4ERR_FALSE_RETRY in response to the Sequence operation when it
it detects a false retry. detects a false retry.
Translations of particularly privileged user values to other users Translations of particularly privileged user values to other users
due to the lack of appropriately secure credentials, as configured on due to the lack of appropriately secure credentials, as configured on
the replier, should be applied before determining whether the users the replier, should be applied before determining whether the users
are the same or different. If the replier determines the users are are the same or different. If the replier determines the users are
different between the original request and a retry, then the replier different between the original request and a retry, then the replier
MUST return NFS4ERR_FALSE_RETRY. MUST return NFS4ERR_FALSE_RETRY.
If an operation of the retry is an illegal operation, or an operation If an operation of the retry is an illegal operation, or an operation
that was legal in a previous minor version of NFSv4 and MUST NOT be that was legal in a previous minor version of NFSv4 and MUST NOT be
supported in current minor version (e.g. SETCLIENTID), the replier supported in the current minor version (e.g., SETCLIENTID), the
MAY return NFS4ERR_FALSE_RETRY (and MUST do so if the users of the replier MAY return NFS4ERR_FALSE_RETRY (and MUST do so if the users
original request and retry differ). Otherwise, the replier MAY of the original request and retry differ). Otherwise, the replier
NFS4ERR_OP_ILLEGAL, or NFS4ERR_BADXDR, or NFS4ERR_NOTSUPP as MAY return NFS4ERR_OP_ILLEGAL or NFS4ERR_BADXDR or NFS4ERR_NOTSUPP as
appropriate. Note that the handling is in contrast for how replier appropriate. Note that the handling is in contrast for how the
deals with retries requests with no cached reply. The difference is replier deals with retries requests with no cached reply. The
due to NFS4ERR_FALSE_RETRY being a valid error for only Sequence difference is due to NFS4ERR_FALSE_RETRY being a valid error for only
operations, whereas NFS4ERR_RETRY_UNCACHED_REP is a valid error for Sequence operations, whereas NFS4ERR_RETRY_UNCACHED_REP is a valid
all operations except illegal operations and operations that MUST NOT error for all operations except illegal operations and operations
be supported in the current minor version of NFSv4. that MUST NOT be supported in the current minor version of NFSv4.
2.10.6.2. Retry and Replay of Reply 2.10.6.2. Retry and Replay of Reply
A requester MUST NOT retry a request, unless the connection it used A requester MUST NOT retry a request, unless the connection it used
to send the request disconnects. The requester can then reconnect to send the request disconnects. The requester can then reconnect
and re-send the request, or it can re-send the request over a and re-send the request, or it can re-send the request over a
different connection that is associated with the same session. different connection that is associated with the same session.
If the requester is a server wanting to re-send a callback operation If the requester is a server wanting to re-send a callback operation
over the backchannel of a session, the requester of course cannot over the backchannel of a session, the requester of course cannot
reconnect because only the client can associate connections with the reconnect because only the client can associate connections with the
backchannel. The server can re-send the request over another backchannel. The server can re-send the request over another
connection that is bound to the same session's backchannel. If there connection that is bound to the same session's backchannel. If there
is no such connection, the server MUST indicate that the session has is no such connection, the server MUST indicate that the session has
no backchannel by setting the SEQ4_STATUS_CB_PATH_DOWN_SESSION flag no backchannel by setting the SEQ4_STATUS_CB_PATH_DOWN_SESSION flag
bit in the response to the next SEQUENCE operation from the client. bit in the response to the next SEQUENCE operation from the client.
The client MUST then associate a connection with the session (or The client MUST then associate a connection with the session (or
destroy the session). destroy the session).
Note that it is not fatal for a requester to retry without a Note that it is not fatal for a requester to retry without a
disconnect between the request and retry. However the retry does disconnect between the request and retry. However, the retry does
consume resources, especially with RDMA, where each request, retry or consume resources, especially with RDMA, where each request, retry or
not, consumes a credit. Retries for no reason, especially retries not, consumes a credit. Retries for no reason, especially retries
sent shortly after the previous attempt, are a poor use of network sent shortly after the previous attempt, are a poor use of network
bandwidth and defeat the purpose of a transport's inherent congestion bandwidth and defeat the purpose of a transport's inherent congestion
control system. control system.
A requester MUST wait for a reply to a request before using the slot A requester MUST wait for a reply to a request before using the slot
for another request. If it does not wait for a reply, then the for another request. If it does not wait for a reply, then the
requester does not know what sequence ID to use for the slot on its requester does not know what sequence ID to use for the slot on its
next request. For example, suppose a requester sends a request with next request. For example, suppose a requester sends a request with
sequence ID 1, and does not wait for the response. The next time it sequence ID 1, and does not wait for the response. The next time it
uses the slot, it sends the new request with sequence ID 2. If the uses the slot, it sends the new request with sequence ID 2. If the
replier has not seen the request with sequence ID 1, then the replier replier has not seen the request with sequence ID 1, then the replier
is not expecting sequence ID 2, and rejects the requester's new is not expecting sequence ID 2, and rejects the requester's new
request with NFS4ERR_SEQ_MISORDERED (as the result from SEQUENCE or request with NFS4ERR_SEQ_MISORDERED (as the result from SEQUENCE or
CB_SEQUENCE). CB_SEQUENCE).
RDMA fabrics do not guarantee that the memory handles (Steering Tags) RDMA fabrics do not guarantee that the memory handles (Steering Tags)
within each RPC/RDMA "chunk" ([8]) are valid on a scope outside that within each RPC/RDMA "chunk" [8] are valid on a scope outside that of
of a single connection. Therefore, handles used by the direct a single connection. Therefore, handles used by the direct
operations become invalid after connection loss. The server must operations become invalid after connection loss. The server must
ensure that any RDMA operations which must be replayed from the reply ensure that any RDMA operations that must be replayed from the reply
cache use the newly provided handle(s) from the most recent request. cache use the newly provided handle(s) from the most recent request.
A retry might be sent while the original request is still in progress A retry might be sent while the original request is still in progress
on the replier. The replier SHOULD deal with the issue by returning on the replier. The replier SHOULD deal with the issue by returning
NFS4ERR_DELAY as the reply to SEQUENCE or CB_SEQUENCE operation, but NFS4ERR_DELAY as the reply to SEQUENCE or CB_SEQUENCE operation, but
implementations MAY return NFS4ERR_MISORDERED. Since errors from implementations MAY return NFS4ERR_MISORDERED. Since errors from
SEQUENCE and CB_SEQUENCE are never recorded in the reply cache, this SEQUENCE and CB_SEQUENCE are never recorded in the reply cache, this
approach allows the results of the execution of the original request approach allows the results of the execution of the original request
to be properly recorded in the reply cache (assuming the requester to be properly recorded in the reply cache (assuming that the
specified the reply to be cached). requester specified the reply to be cached).
2.10.6.3. Resolving Server Callback Races 2.10.6.3. Resolving Server Callback Races
It is possible for server callbacks to arrive at the client before It is possible for server callbacks to arrive at the client before
the reply from related fore channel operations. For example, a the reply from related fore channel operations. For example, a
client may have been granted a delegation to a file it has opened, client may have been granted a delegation to a file it has opened,
but the reply to the OPEN (informing the client of the granting of but the reply to the OPEN (informing the client of the granting of
the delegation) may be delayed in the network. If a conflicting the delegation) may be delayed in the network. If a conflicting
operation arrives at the server, it will recall the delegation using operation arrives at the server, it will recall the delegation using
the backchannel, which may be on a different transport connection, the backchannel, which may be on a different transport connection,
perhaps even a different network, or even a different session perhaps even a different network, or even a different session
associated with the same client ID associated with the same client ID.
The presence of a session between the client and server alleviates The presence of a session between the client and server alleviates
this issue. When a session is in place, each client request is this issue. When a session is in place, each client request is
uniquely identified by its { session ID, slot ID, sequence ID } uniquely identified by its { session ID, slot ID, sequence ID }
triple. By the rules under which slot entries (reply cache entries) triple. By the rules under which slot entries (reply cache entries)
are retired, the server has knowledge whether the client has "seen" are retired, the server has knowledge whether the client has "seen"
each of the server's replies. The server can therefore provide each of the server's replies. The server can therefore provide
sufficient information to the client to allow it to disambiguate sufficient information to the client to allow it to disambiguate
between an erroneous or conflicting callback race condition. between an erroneous or conflicting callback race condition.
For each client operation which might result in some sort of server For each client operation that might result in some sort of server
callback, the server SHOULD "remember" the { session ID, slot ID, callback, the server SHOULD "remember" the { session ID, slot ID,
sequence ID } triple of the client request until the slot ID sequence ID } triple of the client request until the slot ID
retirement rules allow the server to determine that the client has, retirement rules allow the server to determine that the client has,
in fact, seen the server's reply. Until the time the { session ID, in fact, seen the server's reply. Until the time the { session ID,
slot ID, sequence ID } request triple can be retired, any recalls of slot ID, sequence ID } request triple can be retired, any recalls of
the associated object MUST carry an array of these referring the associated object MUST carry an array of these referring
identifiers (in the CB_SEQUENCE operation's arguments), for the identifiers (in the CB_SEQUENCE operation's arguments), for the
benefit of the client. After this time, it is not necessary for the benefit of the client. After this time, it is not necessary for the
server to provide this information in related callbacks, since it is server to provide this information in related callbacks, since it is
certain that a race condition can no longer occur. certain that a race condition can no longer occur.
The CB_SEQUENCE operation which begins each server callback carries a The CB_SEQUENCE operation that begins each server callback carries a
list of "referring" { session ID, slot ID, sequence ID } triples. If list of "referring" { session ID, slot ID, sequence ID } triples. If
the client finds the request corresponding to the referring session the client finds the request corresponding to the referring session
ID, slot ID and sequence ID to be currently outstanding (i.e. the ID, slot ID, and sequence ID to be currently outstanding (i.e., the
server's reply has not been seen by the client), it can determine server's reply has not been seen by the client), it can determine
that the callback has raced the reply, and act accordingly. If the that the callback has raced the reply, and act accordingly. If the
client does not find the request corresponding the referring triple client does not find the request corresponding to the referring
to be outstanding (including the case of a session ID referring to a triple to be outstanding (including the case of a session ID
destroyed session), then there is no race with respect to this referring to a destroyed session), then there is no race with respect
triple. The server SHOULD limit the referring triples to requests to this triple. The server SHOULD limit the referring triples to
that refer to just those that apply to the objects referred to in the requests that refer to just those that apply to the objects referred
CB_COMPOUND procedure. to in the CB_COMPOUND procedure.
The client must not simply wait forever for the expected server reply The client must not simply wait forever for the expected server reply
to arrive before responding to the CB_COMPOUND that won the race, to arrive before responding to the CB_COMPOUND that won the race,
because it is possible that it will be delayed indefinitely. The because it is possible that it will be delayed indefinitely. The
client should assume the likely case that the reply will arrive client should assume the likely case that the reply will arrive
within the average round trip time for COMPOUND requests to the within the average round-trip time for COMPOUND requests to the
server, and wait that period of time. If that period of time expires server, and wait that period of time. If that period of time
it can respond to the CB_COMPOUND with NFS4ERR_DELAY. expires, it can respond to the CB_COMPOUND with NFS4ERR_DELAY.
There are other scenarios under which callbacks may race replies. There are other scenarios under which callbacks may race replies.
Among them are pNFS layout recalls as described in Section 12.5.5.2. Among them are pNFS layout recalls as described in Section 12.5.5.2.
2.10.6.4. COMPOUND and CB_COMPOUND Construction Issues 2.10.6.4. COMPOUND and CB_COMPOUND Construction Issues
Very large requests and replies may pose both buffer management Very large requests and replies may pose both buffer management
issues (especially with RDMA) and reply cache issues. When the issues (especially with RDMA) and reply cache issues. When the
session is created, (Section 18.36), for each channel (fore and session is created (Section 18.36), for each channel (fore and back),
back), the client and server negotiate the maximum sized request they the client and server negotiate the maximum-sized request they will
will send or process (ca_maxrequestsize), the maximum sized reply send or process (ca_maxrequestsize), the maximum-sized reply they
they will return or process (ca_maxresponsesize), and the maximum will return or process (ca_maxresponsesize), and the maximum-sized
sized reply they will store in the reply cache reply they will store in the reply cache (ca_maxresponsesize_cached).
(ca_maxresponsesize_cached).
If a request exceeds ca_maxrequestsize, the reply will have the If a request exceeds ca_maxrequestsize, the reply will have the
status NFS4ERR_REQ_TOO_BIG. A replier MAY return NFS4ERR_REQ_TOO_BIG status NFS4ERR_REQ_TOO_BIG. A replier MAY return NFS4ERR_REQ_TOO_BIG
as the status for first operation (SEQUENCE or CB_SEQUENCE) in the as the status for the first operation (SEQUENCE or CB_SEQUENCE) in
request (which means no operations in the request executed, and the the request (which means that no operations in the request executed
state of the slot in the reply cache is unchanged), or it MAY opt to and that the state of the slot in the reply cache is unchanged), or
return it on a subsequent operation in the same COMPOUND or it MAY opt to return it on a subsequent operation in the same
CB_COMPOUND request (which means at least one operation did execute COMPOUND or CB_COMPOUND request (which means that at least one
and the state of the slot in reply cache does change). The replier operation did execute and that the state of the slot in the reply
SHOULD set NFS4ERR_REQ_TOO_BIG on the operation that exceeds cache does change). The replier SHOULD set NFS4ERR_REQ_TOO_BIG on
ca_maxrequestsize. the operation that exceeds ca_maxrequestsize.
If a reply exceeds ca_maxresponsesize, the reply will have the status If a reply exceeds ca_maxresponsesize, the reply will have the status
NFS4ERR_REP_TOO_BIG. A replier MAY return NFS4ERR_REP_TOO_BIG as the NFS4ERR_REP_TOO_BIG. A replier MAY return NFS4ERR_REP_TOO_BIG as the
status for first operation (SEQUENCE or CB_SEQUENCE) in the request, status for the first operation (SEQUENCE or CB_SEQUENCE) in the
or it MAY opt to return it on a subsequent operation (in the same request, or it MAY opt to return it on a subsequent operation (in the
COMPOUND or CB_COMPOUND reply). A replier MAY return same COMPOUND or CB_COMPOUND reply). A replier MAY return
NFS4ERR_REP_TOO_BIG in the reply to SEQUENCE or CB_SEQUENCE, even if NFS4ERR_REP_TOO_BIG in the reply to SEQUENCE or CB_SEQUENCE, even if
the response would still exceed ca_maxresponsesize. the response would still exceed ca_maxresponsesize.
If sa_cachethis or csa_cachethis are TRUE, then the replier MUST If sa_cachethis or csa_cachethis is TRUE, then the replier MUST cache
cache a reply except if an error is returned by the SEQUENCE or a reply except if an error is returned by the SEQUENCE or CB_SEQUENCE
CB_SEQUENCE operation (see Section 2.10.6.1.2). If the reply exceeds operation (see Section 2.10.6.1.2). If the reply exceeds
ca_maxresponsesize_cached, (and sa_cachethis or csa_cachethis are ca_maxresponsesize_cached (and sa_cachethis or csa_cachethis is
TRUE) then the server MUST return NFS4ERR_REP_TOO_BIG_TO_CACHE. Even TRUE), then the server MUST return NFS4ERR_REP_TOO_BIG_TO_CACHE.
if NFS4ERR_REP_TOO_BIG_TO_CACHE (or any other error for that matter) Even if NFS4ERR_REP_TOO_BIG_TO_CACHE (or any other error for that
is returned on a operation other than first operation (SEQUENCE or matter) is returned on an operation other than the first operation
CB_SEQUENCE), then the reply MUST be cached if sa_cachethis or (SEQUENCE or CB_SEQUENCE), then the reply MUST be cached if
csa_cachethis are TRUE. For example, if a COMPOUND has eleven sa_cachethis or csa_cachethis is TRUE. For example, if a COMPOUND
operations, including SEQUENCE, the fifth operation is a RENAME, and has eleven operations, including SEQUENCE, the fifth operation is a
the tenth operation is a READ for one million bytes, the server may RENAME, and the tenth operation is a READ for one million bytes, the
return NFS4ERR_REP_TOO_BIG_TO_CACHE on the tenth operation. Since server may return NFS4ERR_REP_TOO_BIG_TO_CACHE on the tenth
the server executed several operations, especially the non-idempotent operation. Since the server executed several operations, especially
RENAME, the client's request to cache the reply needs to be honored the non-idempotent RENAME, the client's request to cache the reply
in order for correct operation of exactly once semantics. If the needs to be honored in order for the correct operation of exactly
client retries the request, the server will have cached a reply that once semantics. If the client retries the request, the server will
contains results for ten of the eleven requested operations, with the have cached a reply that contains results for ten of the eleven
tenth operation having a status of NFS4ERR_REP_TOO_BIG_TO_CACHE. requested operations, with the tenth operation having a status of
NFS4ERR_REP_TOO_BIG_TO_CACHE.
A client needs to take care that when sending operations that change A client needs to take care that when sending operations that change
the current filehandle (except for PUTFH, PUTPUBFH, PUTROOTFH and the current filehandle (except for PUTFH, PUTPUBFH, PUTROOTFH, and
RESTOREFH) that it not exceed the maximum reply buffer before the RESTOREFH), it not exceed the maximum reply buffer before the GETFH
GETFH operation. Otherwise the client will have to retry the operation. Otherwise, the client will have to retry the operation
operation that changed the current filehandle, in order to obtain the that changed the current filehandle, in order to obtain the desired
desired filehandle. For the OPEN operation (see Section 18.16), filehandle. For the OPEN operation (see Section 18.16), retry is not
retry is not always available as an option. The following guidelines always available as an option. The following guidelines for the
for the handling of filehandle changing operations are advised: handling of filehandle-changing operations are advised:
o Within the same COMPOUND procedure, a client SHOULD send GETFH o Within the same COMPOUND procedure, a client SHOULD send GETFH
immediately after a current filehandle changing operation. A immediately after a current filehandle-changing operation. A
client MUST send GETFH after a current filehandle changing client MUST send GETFH after a current filehandle-changing
operation that is also non-idempotent (e.g., the OPEN operation), operation that is also non-idempotent (e.g., the OPEN operation),
unless the operation is RESTOREFH. RESTOREFH is an exception, unless the operation is RESTOREFH. RESTOREFH is an exception,
because even though it is non-idempotent, the filehandle RESTOREFH because even though it is non-idempotent, the filehandle RESTOREFH
produced originated from an operation that is either idempotent produced originated from an operation that is either idempotent
(e.g. PUTFH, LOOKUP), or non-idempotent (e.g. OPEN, CREATE). If (e.g., PUTFH, LOOKUP), or non-idempotent (e.g., OPEN, CREATE). If
the origin is non-idempotent, then because the client MUST send the origin is non-idempotent, then because the client MUST send
GETFH after the origin operation, the client can recover if GETFH after the origin operation, the client can recover if
RESTOREFH returns an error. RESTOREFH returns an error.
o A server MAY return NFS4ERR_REP_TOO_BIG or o A server MAY return NFS4ERR_REP_TOO_BIG or
NFS4ERR_REP_TOO_BIG_TO_CACHE (if sa_cachethis is TRUE) on a NFS4ERR_REP_TOO_BIG_TO_CACHE (if sa_cachethis is TRUE) on a
filehandle changing operation if the reply would be too large on filehandle-changing operation if the reply would be too large on
the next operation. the next operation.
o A server SHOULD return NFS4ERR_REP_TOO_BIG or o A server SHOULD return NFS4ERR_REP_TOO_BIG or
NFS4ERR_REP_TOO_BIG_TO_CACHE (if sa_cachethis is TRUE) on a NFS4ERR_REP_TOO_BIG_TO_CACHE (if sa_cachethis is TRUE) on a
filehandle changing non-idempotent operation if the reply would be filehandle-changing, non-idempotent operation if the reply would
too large on the next operation, especially if the operation is be too large on the next operation, especially if the operation is
OPEN. OPEN.
o A server MAY return NFS4ERR_UNSAFE_COMPOUND to a non-idempotent o A server MAY return NFS4ERR_UNSAFE_COMPOUND to a non-idempotent
current filehandle changing operation, if it looks at the next current filehandle-changing operation, if it looks at the next
operation (in the same COMPOUND procedure) and finds it is not operation (in the same COMPOUND procedure) and finds it is not
GETFH. The server SHOULD do this if it is unable to determine in GETFH. The server SHOULD do this if it is unable to determine in
advance whether the total response size would exceed advance whether the total response size would exceed
ca_maxresponsesize_cached or ca_maxresponsesize. ca_maxresponsesize_cached or ca_maxresponsesize.
2.10.6.5. Persistence 2.10.6.5. Persistence
Since the reply cache is bounded, it is practical for the reply cache Since the reply cache is bounded, it is practical for the reply cache
to persist across server restarts. The replier MUST persist the to persist across server restarts. The replier MUST persist the
following information if it agreed to persist the session (when the following information if it agreed to persist the session (when the
session was created; see Section 18.36): session was created; see Section 18.36):
o The session ID. o The session ID.
o The slot table including the sequence ID and cached reply for each o The slot table including the sequence ID and cached reply for each
slot. slot.
The above are sufficient for a replier to provide EOS semantics for The above are sufficient for a replier to provide EOS semantics for
any requests that were sent and executed before the server restarted. any requests that were sent and executed before the server restarted.
If the replier is a client then there is no need for it to persist If the replier is a client, then there is no need for it to persist
any more information, unless the client will be persisting all other any more information, unless the client will be persisting all other
state across client restart. In which case, the server will never state across client restart, in which case, the server will never see
see any NFSv4.1-level protocol manifestation of a client restart. If any NFSv4.1-level protocol manifestation of a client restart. If the
the replier is a server, with just the slot table and session ID replier is a server, with just the slot table and session ID
persisting, any requests the client retries after the server restart persisting, any requests the client retries after the server restart
will return the results that are cached in reply cache. and any new will return the results that are cached in the reply cache, and any
requests (i.e. the sequence ID is one (1) greater than the slot's new requests (i.e., the sequence ID is one greater than the slot's
sequence ID) MUST be rejected with NFS4ERR_DEADSESSION (returned by sequence ID) MUST be rejected with NFS4ERR_DEADSESSION (returned by
SEQUENCE). Such a session is considered dead. A server MAY re- SEQUENCE). Such a session is considered dead. A server MAY re-
animate a session after a server restart so that the session will animate a session after a server restart so that the session will
accept new requests as well as retries. To re-animate a session the accept new requests as well as retries. To re-animate a session, the
server needs to persist additional information through server server needs to persist additional information through server
restart: restart:
o The client ID. This is a prerequisite to let the client to create o The client ID. This is a prerequisite to let the client create
more sessions associated with the same client ID as the more sessions associated with the same client ID as the re-
animated session.
o The client ID's sequence ID that is used for creating sessions o The client ID's sequence ID that is used for creating sessions
(see Section 18.35 and Section 18.36). This is a prerequisite to (see Sections 18.35 and 18.36). This is a prerequisite to let the
let the client create more sessions. client create more sessions.
o The principal that created the client ID. This allows the server o The principal that created the client ID. This allows the server
to authenticate the client when it sends EXCHANGE_ID. to authenticate the client when it sends EXCHANGE_ID.
o The SSV, if SP4_SSV state protection was specified when the client o The SSV, if SP4_SSV state protection was specified when the client
ID was created (see Section 18.35). This lets the client create ID was created (see Section 18.35). This lets the client create
new sessions, and associate connections with the new and existing new sessions, and associate connections with the new and existing
sessions. sessions.
o The properties of the client ID as defined in Section 18.35. o The properties of the client ID as defined in Section 18.35.
A persistent reply cache places certain demands on the server. The A persistent reply cache places certain demands on the server. The
execution of the sequence of operations (starting with SEQUENCE) and execution of the sequence of operations (starting with SEQUENCE) and
placement of its results in the persistent cache MUST be atomic. If placement of its results in the persistent cache MUST be atomic. If
a client retries an sequence of operations that was previously a client retries a sequence of operations that was previously
executed on the server the only acceptable outcomes are either the executed on the server, the only acceptable outcomes are either the
original cached reply or an indication that client ID or session has original cached reply or an indication that the client ID or session
been lost (indicating a catastrophic loss of the reply cache or a has been lost (indicating a catastrophic loss of the reply cache or a
session that has been deleted because the client failed to use the session that has been deleted because the client failed to use the
session for an extended period of time). session for an extended period of time).
A server could fail and restart in the middle of a COMPOUND procedure A server could fail and restart in the middle of a COMPOUND procedure
that contains one or more non-idempotent or idempotent-but-modifying that contains one or more non-idempotent or idempotent-but-modifying
operations. This creates an even higher challenge for atomic operations. This creates an even higher challenge for atomic
execution and placement of results in the reply cache. One way to execution and placement of results in the reply cache. One way to
view the problem is as a single transaction consisting of each view the problem is as a single transaction consisting of each
operation in the COMPOUND followed by storing the result in operation in the COMPOUND followed by storing the result in
persistent storage, then finally a transaction commit. If there is a persistent storage, then finally a transaction commit. If there is a
failure before the transaction is committed, then the server rolls failure before the transaction is committed, then the server rolls
back the transaction. If server itself fails, then when it restarts, back the transaction. If the server itself fails, then when it
its recovery logic could roll back the transaction before starting restarts, its recovery logic could roll back the transaction before
the NFSv4.1 server. starting the NFSv4.1 server.
While the description of the implementation for atomic execution of While the description of the implementation for atomic execution of
the request and caching of the reply is beyond the scope of this the request and caching of the reply is beyond the scope of this
document, an example implementation for NFSv2 [38] is described in document, an example implementation for NFSv2 [38] is described in
[39]. [39].
2.10.7. RDMA Considerations 2.10.7. RDMA Considerations
A complete discussion of the operation of RPC-based protocols over A complete discussion of the operation of RPC-based protocols over
RDMA transports is in [8]. A discussion of the operation of NFSv4, RDMA transports is in [8]. A discussion of the operation of NFSv4,
including NFSv4.1, over RDMA is in [9]. Where RDMA is considered, including NFSv4.1, over RDMA is in [9]. Where RDMA is considered,
this specification assumes the use of such a layering; it addresses this specification assumes the use of such a layering; it addresses
only the upper layer issues relevant to making best use of RPC/RDMA. only the upper-layer issues relevant to making best use of RPC/RDMA.
2.10.7.1. RDMA Connection Resources 2.10.7.1. RDMA Connection Resources
RDMA requires its consumers to register memory and post buffers of a RDMA requires its consumers to register memory and post buffers of a
specific size and number for receive operations. specific size and number for receive operations.
Registration of memory can be a relatively high-overhead operation, Registration of memory can be a relatively high-overhead operation,
since it requires pinning of buffers, assignment of attributes (e.g. since it requires pinning of buffers, assignment of attributes (e.g.,
readable/writable), and initialization of hardware translation. readable/writable), and initialization of hardware translation.
Preregistration is desirable to reduce overhead. These registrations Preregistration is desirable to reduce overhead. These registrations
are specific to hardware interfaces and even to RDMA connection are specific to hardware interfaces and even to RDMA connection
endpoints, therefore negotiation of their limits is desirable to endpoints; therefore, negotiation of their limits is desirable to
manage resources effectively. manage resources effectively.
Following basic registration, these buffers must be posted by the RPC Following basic registration, these buffers must be posted by the RPC
layer to handle receives. These buffers remain in use by the RPC/ layer to handle receives. These buffers remain in use by the RPC/
NFSv4.1 implementation; the size and number of them must be known to NFSv4.1 implementation; the size and number of them must be known to
the remote peer in order to avoid RDMA errors which would cause a the remote peer in order to avoid RDMA errors that would cause a
fatal error on the RDMA connection. fatal error on the RDMA connection.
NFSv4.1 manages slots as resources on a per session basis (see NFSv4.1 manages slots as resources on a per-session basis (see
Section 2.10), while RDMA connections manage credits on a per Section 2.10), while RDMA connections manage credits on a per-
connection basis. This means that in order for a peer to send data connection basis. This means that in order for a peer to send data
over RDMA to a remote buffer, it has to have both an NFSv4.1 slot, over RDMA to a remote buffer, it has to have both an NFSv4.1 slot and
and an RDMA credit. If multiple RDMA connections are associated with an RDMA credit. If multiple RDMA connections are associated with a
a session, then if the total number of credits across all RDMA session, then if the total number of credits across all RDMA
connections associated with the session is X, and the number slots in connections associated with the session is X, and the number of slots
the session is Y, then the maximum number of outstanding requests is in the session is Y, then the maximum number of outstanding requests
lesser of X and Y. is the lesser of X and Y.
2.10.7.2. Flow Control 2.10.7.2. Flow Control
Previous versions of NFS do not provide flow control; instead they Previous versions of NFS do not provide flow control; instead, they
rely on the windowing provided by transports like TCP to throttle rely on the windowing provided by transports like TCP to throttle
requests. This does not work with RDMA, which provides no operation requests. This does not work with RDMA, which provides no operation
flow control and will terminate a connection in error when limits are flow control and will terminate a connection in error when limits are
exceeded. Limits such as maximum number of requests outstanding are exceeded. Limits such as maximum number of requests outstanding are
therefore negotiated when a session is created (see the therefore negotiated when a session is created (see the
ca_maxrequests field in Section 18.36). These limits then provide ca_maxrequests field in Section 18.36). These limits then provide
the maxima which each connection associated with the session's the maxima within which each connection associated with the session's
channel(s) must remain within. RDMA connections are managed within channel(s) must remain. RDMA connections are managed within these
these limits as described in section 3.3 ("Flow Control"[[Comment.2: limits as described in Section 3.3 of [8]; if there are multiple RDMA
RFC Editor: please verify section and title of the RPCRDMA document connections, then the maximum number of requests for a channel will
which is currently at be divided among the RDMA connections. Put a different way, the onus
http://tools.ietf.org/html/draft-ietf-nfsv4-rpcrdma-08#section-3.3]]) is on the replier to ensure that the total number of RDMA credits
of [8]; if there are multiple RDMA connections, then the maximum across all connections associated with the replier's channel does
number of requests for a channel will be divided among the RDMA exceed the channel's maximum number of outstanding requests.
connections. Put a different way, the onus is on the replier to
ensure that total number of RDMA credits across all connections
associated with the replier's channel does exceed the channel's
maximum number of outstanding requests.
The limits may also be modified dynamically at the replier's choosing The limits may also be modified dynamically at the replier's choosing
by manipulating certain parameters present in each NFSv4.1 reply. In by manipulating certain parameters present in each NFSv4.1 reply. In
addition, the CB_RECALL_SLOT callback operation (see Section 20.8) addition, the CB_RECALL_SLOT callback operation (see Section 20.8)
can be sent by a server to a client to return RDMA credits to the can be sent by a server to a client to return RDMA credits to the
server, thereby lowering the maximum number of requests a client can server, thereby lowering the maximum number of requests a client can
have outstanding to the server. have outstanding to the server.
2.10.7.3. Padding 2.10.7.3. Padding
Header padding is requested by each peer at session initiation (see Header padding is requested by each peer at session initiation (see
the ca_headerpadsize argument to CREATE_SESSION in Section 18.36), the ca_headerpadsize argument to CREATE_SESSION in Section 18.36),
and subsequently used by the RPC RDMA layer, as described in [8]. and subsequently used by the RPC RDMA layer, as described in [8].
Zero padding is permitted. Zero padding is permitted.
Padding leverages the useful property that RDMA preserve alignment of Padding leverages the useful property that RDMA preserve alignment of
data, even when they are placed into anonymous (untagged) buffers. data, even when they are placed into anonymous (untagged) buffers.
If requested, client inline writes will insert appropriate pad bytes If requested, client inline writes will insert appropriate pad bytes
within the request header to align the data payload on the specified within the request header to align the data payload on the specified
boundary. The client is encouraged to add sufficient padding (up to boundary. The client is encouraged to add sufficient padding (up to
the negotiated size) so that the "data" field of the NFSv4.1 WRITE the negotiated size) so that the "data" field of the WRITE operation
operation is aligned. Most servers can make good use of such is aligned. Most servers can make good use of such padding, which
padding, which allows them to chain receive buffers in such a way allows them to chain receive buffers in such a way that any data
that any data carried by client requests will be placed into carried by client requests will be placed into appropriate buffers at
appropriate buffers at the server, ready for file system processing. the server, ready for file system processing. The receiver's RPC
The receiver's RPC layer encounters no overhead from skipping over layer encounters no overhead from skipping over pad bytes, and the
pad bytes, and the RDMA layer's high performance makes the insertion RDMA layer's high performance makes the insertion and transmission of
and transmission of padding on the sender a significant optimization. padding on the sender a significant optimization. In this way, the
In this way, the need for servers to perform RDMA Read to satisfy all need for servers to perform RDMA Read to satisfy all but the largest
but the largest client writes is obviated. An added benefit is the client writes is obviated. An added benefit is the reduction of
reduction of message round trips on the network - a potentially good message round trips on the network -- a potentially good trade, where
trade, where latency is present. latency is present.
The value to choose for padding is subject to a number of criteria. The value to choose for padding is subject to a number of criteria.
A primary source of variable-length data in the RPC header is the A primary source of variable-length data in the RPC header is the
authentication information, the form of which is client-determined, authentication information, the form of which is client-determined,
possibly in response to server specification. The contents of possibly in response to server specification. The contents of
COMPOUNDs, sizes of strings such as those passed to RENAME, etc. all COMPOUNDs, sizes of strings such as those passed to RENAME, etc. all
go into the determination of a maximal NFSv4.1 request size and go into the determination of a maximal NFSv4.1 request size and
therefore minimal buffer size. The client must select its offered therefore minimal buffer size. The client must select its offered
value carefully, so as not to overburden the server, and vice- versa. value carefully, so as to avoid overburdening the server, and vice
The benefit of an appropriate padding value is higher performance. versa. The benefit of an appropriate padding value is higher
[[Comment.3: RFC editor please keep this diagram on one page.]] performance.
Sender gather: Sender gather:
|RPC Request|Pad bytes|Length| -> |User data...| |RPC Request|Pad bytes|Length| -> |User data...|
\------+----------------------/ \ \------+----------------------/ \
\ \ \ \
\ Receiver scatter: \-----------+- ... \ Receiver scatter: \-----------+- ...
/-----+----------------\ \ \ /-----+----------------\ \ \
|RPC Request|Pad|Length| -> |FS buffer|->|FS buffer|->... |RPC Request|Pad|Length| -> |FS buffer|->|FS buffer|->...
In the above case, the server may recycle unused buffers to the next In the above case, the server may recycle unused buffers to the next
posted receive if unused by the actual received request, or may pass posted receive if unused by the actual received request, or may pass
the now-complete buffers by reference for normal write processing. the now-complete buffers by reference for normal write processing.
For a server which can make use of it, this removes any need for data For a server that can make use of it, this removes any need for data
copies of incoming data, without resorting to complicated end-to-end copies of incoming data, without resorting to complicated end-to-end
buffer advertisement and management. This includes most kernel-based buffer advertisement and management. This includes most kernel-based
and integrated server designs, among many others. The client may and integrated server designs, among many others. The client may
perform similar optimizations, if desired. perform similar optimizations, if desired.
2.10.7.4. Dual RDMA and Non-RDMA Transports 2.10.7.4. Dual RDMA and Non-RDMA Transports
Some RDMA transports (e.g., RFC5040 [10]), permit a "streaming" (non- Some RDMA transports (e.g., RFC 5040 [10]) permit a "streaming" (non-
RDMA) phase, where ordinary traffic might flow before "stepping up" RDMA) phase, where ordinary traffic might flow before "stepping up"
to RDMA mode, commencing RDMA traffic. Some RDMA transports start to RDMA mode, commencing RDMA traffic. Some RDMA transports start
connections always in RDMA mode. NFSv4.1 allows, but does not connections always in RDMA mode. NFSv4.1 allows, but does not
assume, a streaming phase before RDMA mode. When a connection is assume, a streaming phase before RDMA mode. When a connection is
associated with a session, the client and server negotiate whether associated with a session, the client and server negotiate whether
the connection is used in RDMA or non-RDMA mode (see Section 18.36 the connection is used in RDMA or non-RDMA mode (see Sections 18.36
and Section 18.34). and 18.34).
2.10.8. Sessions Security 2.10.8. Session Security
2.10.8.1. Session Callback Security 2.10.8.1. Session Callback Security
Via session / connection association, NFSv4.1 improves security over Via session / connection association, NFSv4.1 improves security over
that provided by NFSv4.0 for the backchannel. The connection is that provided by NFSv4.0 for the backchannel. The connection is
client-initiated (see Section 18.34), and subject to the same client-initiated (see Section 18.34) and subject to the same firewall
firewall and routing checks as the fore channel. At the client's and routing checks as the fore channel. At the client's option (see
option (see Section 18.35), connection association is fully Section 18.35), connection association is fully authenticated before
authenticated before being activated (see Section 18.34). Traffic being activated (see Section 18.34). Traffic from the server over
from the server over the backchannel is authenticated exactly as the the backchannel is authenticated exactly as the client specifies (see
client specifies (see Section 2.10.8.2). Section 2.10.8.2).
2.10.8.2. Backchannel RPC Security 2.10.8.2. Backchannel RPC Security
When the NFSv4.1 client establishes the backchannel, it informs the When the NFSv4.1 client establishes the backchannel, it informs the
server of the security flavors and principals to use when sending server of the security flavors and principals to use when sending
requests. If the security flavor is RPCSEC_GSS, the client expresses requests. If the security flavor is RPCSEC_GSS, the client expresses
the principal in the form of an established RPCSEC_GSS context. The the principal in the form of an established RPCSEC_GSS context. The
server is free to use any of the flavor/principal combinations the server is free to use any of the flavor/principal combinations the
client offers, but it MUST NOT use unoffered combinations. This way, client offers, but it MUST NOT use unoffered combinations. This way,
the client need not provide a target GSS principal for the the client need not provide a target GSS principal for the
backchannel as it did with NFSv4.0, nor the server have to implement backchannel as it did with NFSv4.0, nor does the server have to
an RPCSEC_GSS initiator as it did with NFSv4.0 [30]. implement an RPCSEC_GSS initiator as it did with NFSv4.0 [30].
The CREATE_SESSION (Section 18.36) and BACKCHANNEL_CTL The CREATE_SESSION (Section 18.36) and BACKCHANNEL_CTL
(Section 18.33) operations allow the client to specify flavor/ (Section 18.33) operations allow the client to specify flavor/
principal combinations. principal combinations.
Also note that the SP4_SSV state protection mode (see Section 18.35 Also note that the SP4_SSV state protection mode (see Sections 18.35
and Section 2.10.8.3) has the side benefit of providing SSV-derived and 2.10.8.3) has the side benefit of providing SSV-derived
RPCSEC_GSS contexts (Section 2.10.9). RPCSEC_GSS contexts (Section 2.10.9).
2.10.8.3. Protection from Unauthorized State Changes 2.10.8.3. Protection from Unauthorized State Changes
As described to this point in the specification, the state model of As described to this point in the specification, the state model of
NFSv4.1 is vulnerable to an attacker that sends a SEQUENCE operation NFSv4.1 is vulnerable to an attacker that sends a SEQUENCE operation
with a forged session ID and with a slot ID that it expects the with a forged session ID and with a slot ID that it expects the
legitimate client to use next. When the legitimate client uses the legitimate client to use next. When the legitimate client uses the
slot ID with the same sequence number, the server returns the slot ID with the same sequence number, the server returns the
attacker's result from the reply cache which disrupts the legitimate attacker's result from the reply cache, which disrupts the legitimate
client and thus denies service to it. Similarly an attacker could client and thus denies service to it. Similarly, an attacker could
send a CREATE_SESSION with a forged client ID to create a new session send a CREATE_SESSION with a forged client ID to create a new session
associated with the client ID. The attacker could send requests associated with the client ID. The attacker could send requests
using the new session that change locking state, such as LOCKU using the new session that change locking state, such as LOCKU
operations to release locks the legitimate client has acquired. operations to release locks the legitimate client has acquired.
Setting a security policy on the file that requires RPCSEC_GSS
Setting a security policy on the file which requires RPCSEC_GSS
credentials when manipulating the file's state is one potential work credentials when manipulating the file's state is one potential work
around, but has the disadvantage of preventing a legitimate client around, but has the disadvantage of preventing a legitimate client
from releasing state when RPCSEC_GSS is required to do so, but a GSS from releasing state when RPCSEC_GSS is required to do so, but a GSS
context cannot be obtained (possibly because the user has logged off context cannot be obtained (possibly because the user has logged off
the client). the client).
NFSv4.1 provides three options to a client for state protection which NFSv4.1 provides three options to a client for state protection,
are specified when a client creates a client ID via EXCHANGE_ID which are specified when a client creates a client ID via EXCHANGE_ID
(Section 18.35). (Section 18.35).
The first (SP4_NONE) is to simply waive state protection. The first (SP4_NONE) is to simply waive state protection.
The other two options (SP4_MACH_CRED and SP4_SSV) share several The other two options (SP4_MACH_CRED and SP4_SSV) share several
traits: traits:
o An RPCSEC_GSS-based credential is used to authenticate client ID o An RPCSEC_GSS-based credential is used to authenticate client ID
and session maintenance operations, including creating and and session maintenance operations, including creating and
destroying a session, associating a connection with the session, destroying a session, associating a connection with the session,
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might have to be the same as the one that acquired the state). might have to be the same as the one that acquired the state).
However, the client might not have an RPCSEC_GSS context for such However, the client might not have an RPCSEC_GSS context for such
a principal, and might not be able to create such a context a principal, and might not be able to create such a context
(perhaps because the user has logged off). When the client (perhaps because the user has logged off). When the client
establishes SP4_MACH_CRED or SP4_SSV protection, it can specify a establishes SP4_MACH_CRED or SP4_SSV protection, it can specify a
list of operations that the server MUST allow using the machine list of operations that the server MUST allow using the machine
credential (if SP4_MACH_CRED is used) or the SSV credential (if credential (if SP4_MACH_CRED is used) or the SSV credential (if
SP4_SSV is used). SP4_SSV is used).
The SP4_MACH_CRED state protection option uses a machine credential The SP4_MACH_CRED state protection option uses a machine credential
where the principal that creates the client ID, MUST also be the where the principal that creates the client ID MUST also be the
principal that performs client ID and session maintenance operations. principal that performs client ID and session maintenance operations.
The security of the machine credential state protection approach The security of the machine credential state protection approach
depends entirely on safe guarding the per-machine credential. depends entirely on safe guarding the per-machine credential.
Assuming a proper safe guard, using the per-machine credential for Assuming a proper safeguard using the per-machine credential for
operations like CREATE_SESSION, BIND_CONN_TO_SESSION, operations like CREATE_SESSION, BIND_CONN_TO_SESSION,
DESTROY_SESSION, and DESTROY_CLIENTID will prevent an attacker from DESTROY_SESSION, and DESTROY_CLIENTID will prevent an attacker from
associating a rogue connection with a session, or associating a rogue associating a rogue connection with a session, or associating a rogue
session with a client ID. session with a client ID.
There are at least three scenarios for the SP4_MACH_CRED option: There are at least three scenarios for the SP4_MACH_CRED option:
1. That the system administrator configures a unique, permanent per- 1. The system administrator configures a unique, permanent per-
machine credential for one of the mandated GSS mechanisms (e.g., machine credential for one of the mandated GSS mechanisms (e.g.,
if Kerberos V5 is used, a "keytab" containing a principal derived if Kerberos V5 is used, a "keytab" containing a principal derived
from a client host name could be used). from a client host name could be used).
2. The client is used by a single user, and so the client ID and its 2. The client is used by a single user, and so the client ID and its
sessions are used by just that user. If the user's credential sessions are used by just that user. If the user's credential
expires, then session and client ID maintenance cannot occur, but expires, then session and client ID maintenance cannot occur, but
since the client has a single user, only that user is since the client has a single user, only that user is
inconvenienced. inconvenienced.
3. The physical client has multiple users, but the client 3. The physical client has multiple users, but the client
implementation has a unique client ID for each user. This is implementation has a unique client ID for each user. This is
effectively the same as the second scenario, but a disadvantage effectively the same as the second scenario, but a disadvantage
is that each user needs to be allocated at least one session is that each user needs to be allocated at least one session
each, so the approach suffers from lack of economy. each, so the approach suffers from lack of economy.
The SP4_SSV protection option uses the SSV (Section 1.5), via The SP4_SSV protection option uses the SSV (Section 1.6), via
RPCSEC_GSS and the SSV GSS mechanism (Section 2.10.9) to protect RPCSEC_GSS and the SSV GSS mechanism (Section 2.10.9), to protect
state from attack. The SP4_SSV protection option is intended for the state from attack. The SP4_SSV protection option is intended for the
situation comprised of a client that has multiple active users, and a situation comprised of a client that has multiple active users and a
system administrator who wants to avoid the burden of installing a system administrator who wants to avoid the burden of installing a
permanent machine credential on each client. The SSV is established permanent machine credential on each client. The SSV is established
and updated on the server via SET_SSV (see Section 18.47). To and updated on the server via SET_SSV (see Section 18.47). To
prevent eavesdropping, a client SHOULD send SET_SSV via RPCSEC_GSS prevent eavesdropping, a client SHOULD send SET_SSV via RPCSEC_GSS
with the privacy service. Several aspects of the SSV make it with the privacy service. Several aspects of the SSV make it
intractable for an attacker to guess the SSV, and thus associate intractable for an attacker to guess the SSV, and thus associate
rogue connections with a session, and rogue sessions with a client rogue connections with a session, and rogue sessions with a client
ID: ID:
o The arguments to and results of SET_SSV include digests of the old o The arguments to and results of SET_SSV include digests of the old
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operation or before the second CREATE_SESSION operation on a operation or before the second CREATE_SESSION operation on a
client ID. If it does not, the SSV mechanism will not generate client ID. If it does not, the SSV mechanism will not generate
tokens (Section 2.10.9). A client SHOULD send SET_SSV as soon as tokens (Section 2.10.9). A client SHOULD send SET_SSV as soon as
a session is created. a session is created.
o A SET_SSV request does not replace the SSV with the argument to o A SET_SSV request does not replace the SSV with the argument to
SET_SSV. Instead, the current SSV on the server is logically SET_SSV. Instead, the current SSV on the server is logically
exclusive ORed (XORed) with the argument to SET_SSV. Each time a exclusive ORed (XORed) with the argument to SET_SSV. Each time a
new principal uses a client ID for the first time, the client new principal uses a client ID for the first time, the client
SHOULD send a SET_SSV with that principal's RPCSEC_GSS SHOULD send a SET_SSV with that principal's RPCSEC_GSS
credentials, with the RPCSEC_GSS service set to credentials, with RPCSEC_GSS service set to RPC_GSS_SVC_PRIVACY.
RPC_GSS_SVC_PRIVACY.
Here are the types of attacks that can be attempted by an attacker Here are the types of attacks that can be attempted by an attacker
named Eve on a victim named Bob, and how SP4_SSV protection foils named Eve on a victim named Bob, and how SP4_SSV protection foils
each attack: each attack:
o Suppose Eve is the first user to log into a legitimate client. o Suppose Eve is the first user to log into a legitimate client.
Eve's use of an NFSv4.1 file system will cause the legitimate Eve's use of an NFSv4.1 file system will cause the legitimate
client to create a client ID with SP4_SSV protection, specifying client to create a client ID with SP4_SSV protection, specifying
that the BIND_CONN_TO_SESSION operation MUST use the SSV that the BIND_CONN_TO_SESSION operation MUST use the SSV
credential. Eve's use of the file system also causes an SSV to be credential. Eve's use of the file system also causes an SSV to be
created. The SET_SSV operation that creates the SSV will be created. The SET_SSV operation that creates the SSV will be
protected by the RPCSEC_GSS context created by the legitimate protected by the RPCSEC_GSS context created by the legitimate
client which uses Eve's GSS principal and credentials. Eve can client, which uses Eve's GSS principal and credentials. Eve can
eavesdrop on the network while her RPCSEC_GSS context is created, eavesdrop on the network while her RPCSEC_GSS context is created
and the SET_SSV using her context is sent. Even if the legitimate and the SET_SSV using her context is sent. Even if the legitimate
client sends the SET_SSV with RPC_GSS_SVC_PRIVACY, because Eve client sends the SET_SSV with RPC_GSS_SVC_PRIVACY, because Eve
knows her own credentials, she can decrypt the SSV. Eve can knows her own credentials, she can decrypt the SSV. Eve can
compute an RPCSEC_GSS credential that BIND_CONN_TO_SESSION will compute an RPCSEC_GSS credential that BIND_CONN_TO_SESSION will
accept, and so associate a new connection with the legitimate accept, and so associate a new connection with the legitimate
session. Eve can change the slot ID and sequence state of a session. Eve can change the slot ID and sequence state of a
legitimate session, and/or the SSV state, in such a way that when legitimate session, and/or the SSV state, in such a way that when
Bob accesses the server via the same legitimate client, the Bob accesses the server via the same legitimate client, the
legitimate client will be unable to use the session. legitimate client will be unable to use the session.
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Once the legitimate client establishes an SSV over the new session Once the legitimate client establishes an SSV over the new session
using Bob's RPCSEC_GSS context, Eve can use the new session via using Bob's RPCSEC_GSS context, Eve can use the new session via
the legitimate client, but she cannot disrupt Bob. Moreover, the legitimate client, but she cannot disrupt Bob. Moreover,
because the client SHOULD have modified the SSV due to Eve using because the client SHOULD have modified the SSV due to Eve using
the new session, Bob cannot get revenge on Eve by associating a the new session, Bob cannot get revenge on Eve by associating a
rogue connection with the session. rogue connection with the session.
The question is how did the legitimate client detect that Eve has The question is how did the legitimate client detect that Eve has
hijacked the old session? When the client detects that a new hijacked the old session? When the client detects that a new
principal, Bob, wants to use the session, it SHOULD have sent a principal, Bob, wants to use the session, it SHOULD have sent a
SET_SSV, which leads to following sub-scenarios: SET_SSV, which leads to the following sub-scenarios:
* Let us suppose that from the rogue connection, Eve sent a * Let us suppose that from the rogue connection, Eve sent a
SET_SSV with the same slot ID and sequence ID that the SET_SSV with the same slot ID and sequence ID that the
legitimate client later uses. The server will assume the legitimate client later uses. The server will assume the
SET_SSV sent with Bob's credentials is a retry, and return to SET_SSV sent with Bob's credentials is a retry, and return to
the legitimate client the reply it sent Eve. However, unless the legitimate client the reply it sent Eve. However, unless
Eve can correctly guess the SSV the legitimate client will use, Eve can correctly guess the SSV the legitimate client will use,
the digest verification checks in the SET_SSV response will the digest verification checks in the SET_SSV response will
fail. That is an indication to the client that the session has fail. That is an indication to the client that the session has
apparently been hijacked. apparently been hijacked.
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with the same slot ID and sequence that the legitimate client with the same slot ID and sequence that the legitimate client
uses for its SET_SSV. The server returns to the legitimate uses for its SET_SSV. The server returns to the legitimate
client the response it sent Eve. The client sees that the client the response it sent Eve. The client sees that the
response is not at all what it expects. The client assumes response is not at all what it expects. The client assumes
either session hijacking or a server bug, and either way either session hijacking or a server bug, and either way
destroys the old session. destroys the old session.
o Eve associates a rogue connection with the session as above, and o Eve associates a rogue connection with the session as above, and
then destroys the session. Again, Bob goes to use the server from then destroys the session. Again, Bob goes to use the server from
the legitimate client, which sends a SET_SSV using Bob's the legitimate client, which sends a SET_SSV using Bob's
credentials. The client receives an error that indicates the credentials. The client receives an error that indicates that the
session does not exist. When the client tries to create a new session does not exist. When the client tries to create a new
session, this will fail because the SSV it has does not match that session, this will fail because the SSV it has does not match that
the server has, and now the client knows the session was hijacked. which the server has, and now the client knows the session was
The legitimate client establishes a new client ID. hijacked. The legitimate client establishes a new client ID.
o If Eve creates a connection before the legitimate client o If Eve creates a connection before the legitimate client
establishes an SSV, because the initial value of the SSV is zero establishes an SSV, because the initial value of the SSV is zero
and therefore known, Eve can send a SET_SSV that will pass the and therefore known, Eve can send a SET_SSV that will pass the
digest verification check. However because the new connection has digest verification check. However, because the new connection
not been associated with the session, the SET_SSV is rejected for has not been associated with the session, the SET_SSV is rejected
that reason. for that reason.
In summary, an attacker's disruption of state when SP4_SSV protection In summary, an attacker's disruption of state when SP4_SSV protection
is in use is limited to the formative period of a client ID, its is in use is limited to the formative period of a client ID, its
first session, and the establishment of the SSV. Once a non- first session, and the establishment of the SSV. Once a non-
malicious user uses the client ID, the client quickly detects any malicious user uses the client ID, the client quickly detects any
hijack and rectifies the situation. Once a non-malicious user hijack and rectifies the situation. Once a non-malicious user
successfully modifies the SSV, the attacker cannot use NFSv4.1 successfully modifies the SSV, the attacker cannot use NFSv4.1
operations to disrupt the non-malicious user. operations to disrupt the non-malicious user.
Note that neither the SP4_MACH_CRED nor SP4_SSV protection approaches Note that neither the SP4_MACH_CRED nor SP4_SSV protection approaches
prevent hijacking of a transport connection that has previously been prevent hijacking of a transport connection that has previously been
associated with a session. If the goal of a counter threat strategy associated with a session. If the goal of a counter-threat strategy
is to prevent connection hijacking, the use of IPsec is RECOMMENDED. is to prevent connection hijacking, the use of IPsec is RECOMMENDED.
If a connection hijack occurs, the hijacker could in theory change If a connection hijack occurs, the hijacker could in theory change
locking state and negatively impact the service to legitimate locking state and negatively impact the service to legitimate
clients. However if the server is configured to require the use of clients. However, if the server is configured to require the use of
RPCSEC_GSS with integrity or privacy on the affected file objects, RPCSEC_GSS with integrity or privacy on the affected file objects,
and if EXCHGID4_FLAG_BIND_PRINC_STATEID capability (Section 18.35), and if EXCHGID4_FLAG_BIND_PRINC_STATEID capability (Section 18.35) is
is in force, this will thwart unauthorized attempts to change locking in force, this will thwart unauthorized attempts to change locking
state. state.
2.10.9. The Secret State Verifier (SSV) GSS Mechanism 2.10.9. The Secret State Verifier (SSV) GSS Mechanism
The SSV provides the secret key for a GSS mechanism internal to The SSV provides the secret key for a GSS mechanism internal to
NFSv4.1 that NFSv4.1 uses for state protection. Contexts for this NFSv4.1 that NFSv4.1 uses for state protection. Contexts for this
mechanism are not established via the RPCSEC_GSS protocol. Instead, mechanism are not established via the RPCSEC_GSS protocol. Instead,
the contexts are automatically created when EXCHANGE_ID specifies the contexts are automatically created when EXCHANGE_ID specifies
SP4_SSV protection. The only tokens defined are the PerMsgToken SP4_SSV protection. The only tokens defined are the PerMsgToken
(emitted by GSS_GetMIC) and the SealedMessage token (emitted by (emitted by GSS_GetMIC) and the SealedMessage token (emitted by
GSS_Wrap). GSS_Wrap).
The mechanism OID for the SSV mechanism is: The mechanism OID for the SSV mechanism is
iso.org.dod.internet.private.enterprise.Michael Eisler.nfs.ssv_mech iso.org.dod.internet.private.enterprise.Michael Eisler.nfs.ssv_mech
(1.3.6.1.4.1.28882.1.1). While the SSV mechanism does not define any (1.3.6.1.4.1.28882.1.1). While the SSV mechanism does not define any
initial context tokens, the OID can be used to let servers indicate initial context tokens, the OID can be used to let servers indicate
that the SSV mechanism is acceptable whenever the client sends a that the SSV mechanism is acceptable whenever the client sends a
SECINFO or SECINFO_NO_NAME operation (see Section 2.6). SECINFO or SECINFO_NO_NAME operation (see Section 2.6).
The SSV mechanism defines four subkeys derived from the SSV value. The SSV mechanism defines four subkeys derived from the SSV value.
Each time SET_SSV is invoked the subkeys are recalculated by the Each time SET_SSV is invoked, the subkeys are recalculated by the
client and server. The calculation of each of the four subkeys client and server. The calculation of each of the four subkeys
depends on each of the four respective ssv_subkey4 enumerated values. depends on each of the four respective ssv_subkey4 enumerated values.
The calculation uses the HMAC [11], algorithm, using the current SSV The calculation uses the HMAC [11] algorithm, using the current SSV
as the key, the one way hash algorithm as negotiated by EXCHANGE_ID, as the key, the one-way hash algorithm as negotiated by EXCHANGE_ID,
and the input text as represented by the XDR encoded enumeration and the input text as represented by the XDR encoded enumeration
value for that subkey of data type ssv_subkey4. If the length of the value for that subkey of data type ssv_subkey4. If the length of the
output of the HMAC algorithm exceeds the length of key of encryption output of the HMAC algorithm exceeds the length of key of the
algorithm (which is also negotiated by EXCHANGE_ID), then the subkey encryption algorithm (which is also negotiated by EXCHANGE_ID), then
MUST be truncated from the HMAC output, i.e. if the subkey is of N the subkey MUST be truncated from the HMAC output, i.e., if the
bytes long, then the first N bytes of the HMAC output MUST be used subkey is of N bytes long, then the first N bytes of the HMAC output
for the subkey. The specification of EXCHANGE_ID states that the MUST be used for the subkey. The specification of EXCHANGE_ID states
length of the output of the HMAC algorithm MUST NOT be less than that the length of the output of the HMAC algorithm MUST NOT be less
length of subkey needed for the encryption algorithm (see than the length of subkey needed for the encryption algorithm (see
Section 18.35). Section 18.35).
/* Input for computing subkeys */ /* Input for computing subkeys */
enum ssv_subkey4 { enum ssv_subkey4 {
SSV4_SUBKEY_MIC_I2T = 1, SSV4_SUBKEY_MIC_I2T = 1,
SSV4_SUBKEY_MIC_T2I = 2, SSV4_SUBKEY_MIC_T2I = 2,
SSV4_SUBKEY_SEAL_I2T = 3, SSV4_SUBKEY_SEAL_I2T = 3,
SSV4_SUBKEY_SEAL_T2I = 4 SSV4_SUBKEY_SEAL_T2I = 4
}; };
The subkey derived from SSV4_SUBKEY_MIC_I2T is used for calculating The subkey derived from SSV4_SUBKEY_MIC_I2T is used for calculating
message integrity codes (MICs) that originate from the NFSv4.1 message integrity codes (MICs) that originate from the NFSv4.1
client, whether as part of a request over the fore channel, or a client, whether as part of a request over the fore channel or a
response over the backchannel. The subkey derived from response over the backchannel. The subkey derived from
SSV4_SUBKEY_MIC_T2I is used for MICs originating from the NFSv4.1 SSV4_SUBKEY_MIC_T2I is used for MICs originating from the NFSv4.1
server. The subkey derived from SSV4_SUBKEY_SEAL_I2T is used for server. The subkey derived from SSV4_SUBKEY_SEAL_I2T is used for
encryption text originating from the NFSv4.1 client and the subkey encryption text originating from the NFSv4.1 client, and the subkey
derived from SSV4_SUBKEY_SEAL_T2I is used for encryption text derived from SSV4_SUBKEY_SEAL_T2I is used for encryption text
originating from the NFSv4.1 server. originating from the NFSv4.1 server.
The PerMsgToken description is based on an XDR definition: The PerMsgToken description is based on an XDR definition:
/* Input for computing smt_hmac */ /* Input for computing smt_hmac */
struct ssv_mic_plain_tkn4 { struct ssv_mic_plain_tkn4 {
uint32_t smpt_ssv_seq; uint32_t smpt_ssv_seq;
opaque smpt_orig_plain<>; opaque smpt_orig_plain<>;
}; };
/* SSV GSS PerMsgToken token */ /* SSV GSS PerMsgToken token */
struct ssv_mic_tkn4 { struct ssv_mic_tkn4 {
uint32_t smt_ssv_seq; uint32_t smt_ssv_seq;
opaque smt_hmac<>; opaque smt_hmac<>;
}; };
The field smt_hmac is an HMAC calculated by using the subkey derived The field smt_hmac is an HMAC calculated by using the subkey derived
from SSV4_SUBKEY_MIC_I2T or SSV4_SUBKEY_MIC_T2I as the key, the one from SSV4_SUBKEY_MIC_I2T or SSV4_SUBKEY_MIC_T2I as the key, the one-
way hash algorithm as negotiated by EXCHANGE_ID, and the input text way hash algorithm as negotiated by EXCHANGE_ID, and the input text
as represented by data of type ssv_mic_plain_tkn4. The field as represented by data of type ssv_mic_plain_tkn4. The field
smpt_ssv_seq is the same as smt_ssv_seq. The field smpt_orig_plain smpt_ssv_seq is the same as smt_ssv_seq. The field smpt_orig_plain
is the "message" input passed to GSS_GetMIC() (see Section 2.3.1 of is the "message" input passed to GSS_GetMIC() (see Section 2.3.1 of
[7]). The caller of GSS_GetMIC() provides a pointer to a buffer [7]). The caller of GSS_GetMIC() provides a pointer to a buffer
containing the plain text. The SSV mechanism's entry point for containing the plain text. The SSV mechanism's entry point for
GSS_GetMIC() encodes this into an opaque array, and the encoding will GSS_GetMIC() encodes this into an opaque array, and the encoding will
include an initial four byte length, plus any necessary padding. include an initial four-byte length, plus any necessary padding.
Prepended to this will be the XDR encoded value of smpt_ssv_seq thus Prepended to this will be the XDR encoded value of smpt_ssv_seq, thus
making up an XDR encoding of a value of data type ssv_mic_plain_tkn4, making up an XDR encoding of a value of data type ssv_mic_plain_tkn4,
which in turn is the input into the HMAC. which in turn is the input into the HMAC.
The token emitted by GSS_GetMIC() is XDR encoded and of XDR data type The token emitted by GSS_GetMIC() is XDR encoded and of XDR data type
ssv_mic_tkn4. The field smt_ssv_seq comes from the SSV sequence ssv_mic_tkn4. The field smt_ssv_seq comes from the SSV sequence
number which is equal to 1 after SET_SSV (Section 18.47) is called number, which is equal to one after SET_SSV (Section 18.47) is called
the first time on a client ID. Thereafter, the SSV sequence number the first time on a client ID. Thereafter, the SSV sequence number
is incremented on each SET_SSV. Thus smt_ssv_seq represents the is incremented on each SET_SSV. Thus, smt_ssv_seq represents the
version of the SSV at the time GSS_GetMIC() was called. As noted in version of the SSV at the time GSS_GetMIC() was called. As noted in
Section 18.35, the client and server can maintain multiple concurrent Section 18.35, the client and server can maintain multiple concurrent
versions of the SSV. This allows the SSV to be changed without versions of the SSV. This allows the SSV to be changed without
serializing all RPC calls that use the SSV mechanism with SET_SSV serializing all RPC calls that use the SSV mechanism with SET_SSV
operations. Once the HMAC is calculated, it is XDR encoded into operations. Once the HMAC is calculated, it is XDR encoded into
smt_hmac, which will include an initial four byte length, and any smt_hmac, which will include an initial four-byte length, and any
necessary padding. Prepended to this will be the XDR encoded value necessary padding. Prepended to this will be the XDR encoded value
of smt_ssv_seq. of smt_ssv_seq.
The SealedMessage description is based on an XDR definition: The SealedMessage description is based on an XDR definition:
/* Input for computing ssct_encr_data and ssct_hmac */ /* Input for computing ssct_encr_data and ssct_hmac */
struct ssv_seal_plain_tkn4 { struct ssv_seal_plain_tkn4 {
opaque sspt_confounder<>; opaque sspt_confounder<>;
uint32_t sspt_ssv_seq; uint32_t sspt_ssv_seq;
opaque sspt_orig_plain<>; opaque sspt_orig_plain<>;
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The ssct_ssv_seq field has the same meaning as smt_ssv_seq. The ssct_ssv_seq field has the same meaning as smt_ssv_seq.
The ssct_encr_data field is the result of encrypting a value of the The ssct_encr_data field is the result of encrypting a value of the
XDR encoded data type ssv_seal_plain_tkn4. The encryption key is the XDR encoded data type ssv_seal_plain_tkn4. The encryption key is the
subkey derived from SSV4_SUBKEY_SEAL_I2T or SSV4_SUBKEY_SEAL_T2I, and subkey derived from SSV4_SUBKEY_SEAL_I2T or SSV4_SUBKEY_SEAL_T2I, and
the encryption algorithm is that negotiated by EXCHANGE_ID. the encryption algorithm is that negotiated by EXCHANGE_ID.
The ssct_iv field is the initialization vector (IV) for the The ssct_iv field is the initialization vector (IV) for the
encryption algorithm (if applicable) and is sent in clear text. The encryption algorithm (if applicable) and is sent in clear text. The
content and size of the IV MUST comply with specification of the content and size of the IV MUST comply with the specification of the
encryption algorithm. For example, the id-aes256-CBC algorithm MUST encryption algorithm. For example, the id-aes256-CBC algorithm MUST
use a 16 byte initialization vector (IV) which MUST be unpredictable use a 16-byte initialization vector (IV), which MUST be unpredictable
for each instance of a value of type ssv_seal_plain_tkn4 that is for each instance of a value of data type ssv_seal_plain_tkn4 that is
encrypted with a particular SSV key. encrypted with a particular SSV key.
The ssct_hmac field is the result of computing an HMAC using value of The ssct_hmac field is the result of computing an HMAC using the
the XDR encoded data type ssv_seal_plain_tkn4 as the input text. The value of the XDR encoded data type ssv_seal_plain_tkn4 as the input
key is the subkey derived from SSV4_SUBKEY_MIC_I2T or text. The key is the subkey derived from SSV4_SUBKEY_MIC_I2T or
SSV4_SUBKEY_MIC_T2I, and the one way hash algorithm is that SSV4_SUBKEY_MIC_T2I, and the one-way hash algorithm is that
negotiated by EXCHANGE_ID. negotiated by EXCHANGE_ID.
The sspt_confounder field is a random value. The sspt_confounder field is a random value.
The sspt_ssv_seq field is the same as ssvt_ssv_seq. The sspt_ssv_seq field is the same as ssvt_ssv_seq.
The field sspt_orig_plain field is the original plaintext and is the The field sspt_orig_plain field is the original plaintext and is the
"input_message" input passed to GSS_Wrap() (see Section 2.3.3 of "input_message" input passed to GSS_Wrap() (see Section 2.3.3 of
[7]). As with the handling of the plaintext by the SSV mechanism's [7]). As with the handling of the plaintext by the SSV mechanism's
GSS_GetMIC() entry point, the entry point for GSS_Wrap() expects a GSS_GetMIC() entry point, the entry point for GSS_Wrap() expects a
pointer to the plaintext, and will XDR encode an opaque array into pointer to the plaintext, and will XDR encode an opaque array into
sspt_orig_plain representing the plain text, along with the other sspt_orig_plain representing the plain text, along with the other
fields of an instance of data type ssv_seal_plain_tkn4. fields of an instance of data type ssv_seal_plain_tkn4.
The sspt_pad field is present to support encryption algorithms that The sspt_pad field is present to support encryption algorithms that
require inputs to be in fixed sized blocks. The content of sspt_pad require inputs to be in fixed-sized blocks. The content of sspt_pad
is zero filled except for the length. Beware that the XDR encoding is zero filled except for the length. Beware that the XDR encoding
of ssv_seal_plain_tkn4 contains three variable length arrays, and so of ssv_seal_plain_tkn4 contains three variable-length arrays, and so
each array consumes four bytes for an array length, and each array each array consumes four bytes for an array length, and each array
that follows the length is always padded to a multiple of four bytes that follows the length is always padded to a multiple of four bytes
per the XDR standard. per the XDR standard.
For example suppose the encryption algorithm uses 16 byte blocks, and For example, suppose the encryption algorithm uses 16-byte blocks,
the sspt_confounder is three bytes long, and the sspt_orig_plain and the sspt_confounder is three bytes long, and the sspt_orig_plain
field is 15 bytes long. The XDR encoding of sspt_confounder uses field is 15 bytes long. The XDR encoding of sspt_confounder uses
eight bytes (4 + 3 + 1 byte pad), the XDR encoding of sspt_ssv_seq eight bytes (4 + 3 + 1 byte pad), the XDR encoding of sspt_ssv_seq
uses four bytes, the XDR encoding of sspt_orig_plain uses 20 bytes (4 uses four bytes, the XDR encoding of sspt_orig_plain uses 20 bytes (4
+ 15 + 1 byte pad), and the smallest XDR encoding of the sspt_pad + 15 + 1 byte pad), and the smallest XDR encoding of the sspt_pad
field is four bytes. This totals 36 bytes. The next multiple of 16 field is four bytes. This totals 36 bytes. The next multiple of 16
is 48, thus the length field of sspt_pad needs to be set to 12 bytes, is 48; thus, the length field of sspt_pad needs to be set to 12
or a total encoding of 16 bytes. The total number of XDR encoded bytes, or a total encoding of 16 bytes. The total number of XDR
bytes is thus 8 + 4 + 20 + 16 = 48. encoded bytes is thus 8 + 4 + 20 + 16 = 48.
GSS_Wrap() emits a token that is an XDR encoding of a value of data GSS_Wrap() emits a token that is an XDR encoding of a value of data
type ssv_seal_cipher_tkn4. Note that regardless whether the caller type ssv_seal_cipher_tkn4. Note that regardless of whether or not
of GSS_Wrap() requests confidentiality or not, the token always has the caller of GSS_Wrap() requests confidentiality, the token always
confidentiality. This is because the SSV mechanism is for has confidentiality. This is because the SSV mechanism is for
RPCSEC_GSS, and RPCSEC_GSS never produces GSS_wrap() tokens without RPCSEC_GSS, and RPCSEC_GSS never produces GSS_wrap() tokens without
confidentiality. confidentiality.
There is one SSV per client ID. There is a single GSS context for a There is one SSV per client ID. There is a single GSS context for a
client ID / SSV pair. All SSV mechanism RPCSEC_GSS handles of a client ID / SSV pair. All SSV mechanism RPCSEC_GSS handles of a
client ID / SSV pair share the same GSS context. SSV GSS contexts do client ID / SSV pair share the same GSS context. SSV GSS contexts do
not expire except when the SSV is destroyed (causes would include the not expire except when the SSV is destroyed (causes would include the
client ID being destroyed or a server restart). Since one purpose of client ID being destroyed or a server restart). Since one purpose of
context expiration is to replace keys that have been in use for "too context expiration is to replace keys that have been in use for "too
long" hence vulnerable to compromise by brute force or accident, the long", hence vulnerable to compromise by brute force or accident, the
client can replace the SSV key by sending periodic SET_SSV client can replace the SSV key by sending periodic SET_SSV
operations, by cycling through different users' RPCSEC_GSS operations, which is done by cycling through different users'
credentials. This way the SSV is replaced without destroying the RPCSEC_GSS credentials. This way, the SSV is replaced without
SSV's GSS contexts. destroying the SSV's GSS contexts.
SSV RPCSEC_GSS handles can be expired or deleted by the server at any SSV RPCSEC_GSS handles can be expired or deleted by the server at any
time and the EXCHANGE_ID operation can be used to create more SSV time, and the EXCHANGE_ID operation can be used to create more SSV
RPCSEC_GSS handles. Expiration of SSV RPCSEC_GSS handles does not RPCSEC_GSS handles. Expiration of SSV RPCSEC_GSS handles does not
imply that the SSV or its GSS context have expired. imply that the SSV or its GSS context has expired.
The client MUST establish an SSV via SET_SSV before the SSV GSS The client MUST establish an SSV via SET_SSV before the SSV GSS
context can be used to emit tokens from GSS_Wrap() and GSS_GetMIC(). context can be used to emit tokens from GSS_Wrap() and GSS_GetMIC().
If SET_SSV has not been successfully called, attempts to emit tokens If SET_SSV has not been successfully called, attempts to emit tokens
MUST fail. MUST fail.
The SSV mechanism does not support replay detection and sequencing in The SSV mechanism does not support replay detection and sequencing in
its tokens because RPCSEC_GSS does not use those features (See its tokens because RPCSEC_GSS does not use those features (See
Section 5.2.2 "Context Creation Requests" in [4]). However, Section 5.2.2, "Context Creation Requests", in [4]). However,
Section 2.10.10 discusses special considerations for the SSV Section 2.10.10 discusses special considerations for the SSV
mechanism when used with RPCSEC_GSS. mechanism when used with RPCSEC_GSS.
2.10.10. Security Considerations for RPCSEC_GSS when using the SSV 2.10.10. Security Considerations for RPCSEC_GSS When Using the SSV
Mechanism Mechanism
When a client ID is created with SP4_SSV state protection (see When a client ID is created with SP4_SSV state protection (see
Section 18.35), the client is permitted to associate multiple Section 18.35), the client is permitted to associate multiple
RPCSEC_GSS handles with the single SSV GSS context (see RPCSEC_GSS handles with the single SSV GSS context (see
Section 2.10.9). Because of the way RPCSEC_GSS (both version 1 and Section 2.10.9). Because of the way RPCSEC_GSS (both version 1 and
version 2, see [4] and [12]) calculate the verifier of the reply, version 2, see [4] and [12]) calculate the verifier of the reply,
special care must be taken by the implementation of the NFSv4.1 special care must be taken by the implementation of the NFSv4.1
client to prevent attacks by a man-in-the-middle. The verifier of an client to prevent attacks by a man-in-the-middle. The verifier of an
RPCSEC_GSS reply is the output of GSS_GetMIC() applied to the input RPCSEC_GSS reply is the output of GSS_GetMIC() applied to the input
skipping to change at page 81, line 21 skipping to change at page 80, line 21
(RPCSEC_GSS contexts and backchannel connections). If these (RPCSEC_GSS contexts and backchannel connections). If these
resources vanish, the server takes action as specified in resources vanish, the server takes action as specified in
Section 2.10.13.2. Section 2.10.13.2.
2.10.11.2. Obligations of the Client 2.10.11.2. Obligations of the Client
The client SHOULD honor the following obligations in order to utilize The client SHOULD honor the following obligations in order to utilize
the session: the session:
o Keep a necessary session from going idle on the server. A client o Keep a necessary session from going idle on the server. A client
that requires a session, but nonetheless is not sending operations that requires a session but nonetheless is not sending operations
risks having the server destroy the session. This is because risks having the session be destroyed by the server. This is
sessions consume resources, and resource limitations may force the because sessions consume resources, and resource limitations may
server to cull an inactive session. A server MAY consider a force the server to cull an inactive session. A server MAY
session to be inactive if the client has not used the session consider a session to be inactive if the client has not used the
before the session inactivity timer (Section 2.10.12) has expired. session before the session inactivity timer (Section 2.10.12) has
expired.
o Destroy the session when not needed. If a client has multiple o Destroy the session when not needed. If a client has multiple
sessions, one of which has no requests waiting for replies, and sessions, one of which has no requests waiting for replies, and
has been idle for some period of time, it SHOULD destroy the has been idle for some period of time, it SHOULD destroy the
session. session.
o Maintain GSS contexts and RPCSEC_GSS handles for the backchannel. o Maintain GSS contexts and RPCSEC_GSS handles for the backchannel.
If the client requires the server to use the RPCSEC_GSS security If the client requires the server to use the RPCSEC_GSS security
flavor for callbacks, then it needs to be sure the RPCSEC_GSS flavor for callbacks, then it needs to be sure the RPCSEC_GSS
handles and/or their GSS contexts that are handed to the server handles and/or their GSS contexts that are handed to the server
via BACKCHANNEL_CTL or CREATE_SESSION are unexpired. via BACKCHANNEL_CTL or CREATE_SESSION are unexpired.
o Preserve a connection for a backchannel. The server requires a o Preserve a connection for a backchannel. The server requires a
backchannel in order to gracefully recall recallable state, or backchannel in order to gracefully recall recallable state or
notify the client of certain events. Note that if the connection notify the client of certain events. Note that if the connection
is not being used for the fore channel, there is no way for the is not being used for the fore channel, there is no way for the
client tell if the connection is still alive (e.g., the server client to tell if the connection is still alive (e.g., the server
restarted without sending a disconnect). The onus is on the restarted without sending a disconnect). The onus is on the
server, not the client, to determine if the backchannel's server, not the client, to determine if the backchannel's
connection is alive, and to indicate in the response to a SEQUENCE connection is alive, and to indicate in the response to a SEQUENCE
operation when the last connection associated with a session's operation when the last connection associated with a session's
backchannel has disconnected. backchannel has disconnected.
2.10.11.3. Steps the Client Takes To Establish a Session 2.10.11.3. Steps the Client Takes to Establish a Session
If the client does not have a client ID, the client sends EXCHANGE_ID If the client does not have a client ID, the client sends EXCHANGE_ID
to establish a client ID. If it opts for SP4_MACH_CRED or SP4_SSV to establish a client ID. If it opts for SP4_MACH_CRED or SP4_SSV
protection, in the spo_must_enforce list of operations, it SHOULD at protection, in the spo_must_enforce list of operations, it SHOULD at
minimum specify: CREATE_SESSION, DESTROY_SESSION, minimum specify CREATE_SESSION, DESTROY_SESSION,
BIND_CONN_TO_SESSION, BACKCHANNEL_CTL, and DESTROY_CLIENTID. If opts BIND_CONN_TO_SESSION, BACKCHANNEL_CTL, and DESTROY_CLIENTID. If it
for SP4_SSV protection, the client needs to ask for SSV-based opts for SP4_SSV protection, the client needs to ask for SSV-based
RPCSEC_GSS handles. RPCSEC_GSS handles.
The client uses the client ID to send a CREATE_SESSION on a The client uses the client ID to send a CREATE_SESSION on a
connection to the server. The results of CREATE_SESSION indicate connection to the server. The results of CREATE_SESSION indicate
whether the server will persist the session reply cache through a whether or not the server will persist the session reply cache
server restart or not, and the client notes this for future through a server that has restarted, and the client notes this for
reference. future reference.
If the client specified SP4_SSV state protection when the client ID If the client specified SP4_SSV state protection when the client ID
was created, then it SHOULD send SET_SSV in the first COMPOUND after was created, then it SHOULD send SET_SSV in the first COMPOUND after
the session is created. Each time a new principal goes to use the the session is created. Each time a new principal goes to use the
client ID, it SHOULD send a SET_SSV again. client ID, it SHOULD send a SET_SSV again.
If the client wants to use delegations, layouts, directory If the client wants to use delegations, layouts, directory
notifications, or any other state that requires a backchannel, then notifications, or any other state that requires a backchannel, then
it needs to add a connection to the backchannel if CREATE_SESSION did it needs to add a connection to the backchannel if CREATE_SESSION did
not already do so. The client creates a connection, and calls not already do so. The client creates a connection, and calls
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protection when it called EXCHANGE_ID, then the client SHOULD specify protection when it called EXCHANGE_ID, then the client SHOULD specify
that the backchannel use RPCSEC_GSS contexts for security. that the backchannel use RPCSEC_GSS contexts for security.
If the client wants to use additional connections for the If the client wants to use additional connections for the
backchannel, then it needs to call BIND_CONN_TO_SESSION on each backchannel, then it needs to call BIND_CONN_TO_SESSION on each
connection it wants to use with the session. If the client wants to connection it wants to use with the session. If the client wants to
use additional connections for the fore channel, then it needs to use additional connections for the fore channel, then it needs to
call BIND_CONN_TO_SESSION if it specified SP4_SSV or SP4_MACH_CRED call BIND_CONN_TO_SESSION if it specified SP4_SSV or SP4_MACH_CRED
state protection when the client ID was created. state protection when the client ID was created.
At this point the session has reached steady state. At this point, the session has reached steady state.
2.10.12. Session Inactivity Timer 2.10.12. Session Inactivity Timer
The server MAY maintain a session inactivity timer for each session. The server MAY maintain a session inactivity timer for each session.
If the session inactivity timer expires, then the server MAY destroy If the session inactivity timer expires, then the server MAY destroy
the session. To avoid losing a session due to inactivity, the client the session. To avoid losing a session due to inactivity, the client
MUST renew the session inactivity timer. The length of session MUST renew the session inactivity timer. The length of session
inactivity timer MUST NOT be less than the lease_time attribute inactivity timer MUST NOT be less than the lease_time attribute
(Section 5.8.1.11). As with lease renewal (Section 8.3), when the (Section 5.8.1.11). As with lease renewal (Section 8.3), when the
server receives a SEQUENCE operation, it resets the session server receives a SEQUENCE operation, it resets the session
inactivity timer, and MUST NOT allow the timer to expire while the inactivity timer, and MUST NOT allow the timer to expire while the
rest of the operations in the COMPOUND procedure's request are still rest of the operations in the COMPOUND procedure's request are still
executing. Once the last operation has finished, the server MUST set executing. Once the last operation has finished, the server MUST set
the session inactivity timer to expire no sooner that the sum of the the session inactivity timer to expire no sooner than the sum of the
current time and the value of the lease_time attribute. current time and the value of the lease_time attribute.
2.10.13. Session Mechanics - Recovery 2.10.13. Session Mechanics - Recovery
2.10.13.1. Events Requiring Client Action 2.10.13.1. Events Requiring Client Action
The following events require client action to recover. The following events require client action to recover.
2.10.13.1.1. RPCSEC_GSS Context Loss by Callback Path 2.10.13.1.1. RPCSEC_GSS Context Loss by Callback Path
If all RPCSEC_GSS handles granted by the client to the server for If all RPCSEC_GSS handles granted by the client to the server for
callback use have expired, the client MUST establish a new handle via callback use have expired, the client MUST establish a new handle via
BACKCHANNEL_CTL. The sr_status_flags field of the SEQUENCE results BACKCHANNEL_CTL. The sr_status_flags field of the SEQUENCE results
indicates when callback handles are nearly expired, or fully expired indicates when callback handles are nearly expired, or fully expired
(see Section 18.46.3). (see Section 18.46.3).
2.10.13.1.2. Connection Loss 2.10.13.1.2. Connection Loss
If the client loses the last connection of the session, and if wants If the client loses the last connection of the session and wants to
to retain the session, then it needs to create a new connection, and retain the session, then it needs to create a new connection, and if,
if, when the client ID was created, BIND_CONN_TO_SESSION was when the client ID was created, BIND_CONN_TO_SESSION was specified in
specified in the spo_must_enforce list, the client MUST use the spo_must_enforce list, the client MUST use BIND_CONN_TO_SESSION
BIND_CONN_TO_SESSION to associate the connection with the session. to associate the connection with the session.
If there was a request outstanding at the time the of connection If there was a request outstanding at the time of connection loss,
loss, then if client wants to continue to use the session it MUST then if the client wants to continue to use the session, it MUST
retry the request, as described in Section 2.10.6.2. Note that it is retry the request, as described in Section 2.10.6.2. Note that it is
not necessary to retry requests over a connection with the same not necessary to retry requests over a connection with the same
source network address or the same destination network address as the source network address or the same destination network address as the
lost connection. As long as the session ID, slot ID, and sequence ID lost connection. As long as the session ID, slot ID, and sequence ID
in the retry match that of the original request, the server will in the retry match that of the original request, the server will
recognize the request as a retry if it executed the request prior to recognize the request as a retry if it executed the request prior to
disconnect. disconnect.
If the connection that was lost was the last one associated with the If the connection that was lost was the last one associated with the
backchannel, and the client wants to retain the backchannel and/or backchannel, and the client wants to retain the backchannel and/or
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reconnect, and if it does, it MUST associate the connection to the reconnect, and if it does, it MUST associate the connection to the
session and backchannel via BIND_CONN_TO_SESSION. The server SHOULD session and backchannel via BIND_CONN_TO_SESSION. The server SHOULD
indicate when it has no callback connection via the sr_status_flags indicate when it has no callback connection via the sr_status_flags
result from SEQUENCE. result from SEQUENCE.
2.10.13.1.3. Backchannel GSS Context Loss 2.10.13.1.3. Backchannel GSS Context Loss
Via the sr_status_flags result of the SEQUENCE operation or other Via the sr_status_flags result of the SEQUENCE operation or other
means, the client will learn if some or all of the RPCSEC_GSS means, the client will learn if some or all of the RPCSEC_GSS
contexts it assigned to the backchannel have been lost. If the contexts it assigned to the backchannel have been lost. If the
client wants to the retain the backchannel and/or not put recallable client wants to retain the backchannel and/or not put recallable
state subjection to revocation, the client needs to use state subject to revocation, the client needs to use BACKCHANNEL_CTL
BACKCHANNEL_CTL to assign new contexts. to assign new contexts.
2.10.13.1.4. Loss of Session 2.10.13.1.4. Loss of Session
The replier might lose a record of the session. Causes include: The replier might lose a record of the session. Causes include:
o Replier failure and restart o Replier failure and restart.
o A catastrophe that causes the reply cache to be corrupted or lost o A catastrophe that causes the reply cache to be corrupted or lost
on the media it was stored on. This applies even if the replier on the media on which it was stored. This applies even if the
indicated in the CREATE_SESSION results that it would persist the replier indicated in the CREATE_SESSION results that it would
cache. persist the cache.
o The server purges the session of a client that has been inactive o The server purges the session of a client that has been inactive
for a very extended period of time. for a very extended period of time.
o As a result of configuration changes among a set of clustered o As a result of configuration changes among a set of clustered
servers, a network address previously connected to one server servers, a network address previously connected to one server
becomes connected to a different server which has no knowledge of becomes connected to a different server that has no knowledge of
the session in question. Such a configuration change will the session in question. Such a configuration change will
generally only happen when the original server ceases to function generally only happen when the original server ceases to function
for a time. for a time.
Loss of reply cache is equivalent to loss of session. The replier Loss of reply cache is equivalent to loss of session. The replier
indicates loss of session to the requester by returning indicates loss of session to the requester by returning
NFS4ERR_BADSESSION on the next operation that uses the session ID NFS4ERR_BADSESSION on the next operation that uses the session ID
that refers to the lost session. that refers to the lost session.
After an event like a server restart, the client may have lost its After an event like a server restart, the client may have lost its
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SEQUENCE. If BIND_CONN_TO_SESSION or SEQUENCE returns SEQUENCE. If BIND_CONN_TO_SESSION or SEQUENCE returns
NFS4ERR_BADSESSION, the client knows the session is not available to NFS4ERR_BADSESSION, the client knows the session is not available to
it when communicating with that network address. If the connection it when communicating with that network address. If the connection
survives session loss, then the next SEQUENCE operation the client survives session loss, then the next SEQUENCE operation the client
sends over the connection will get back NFS4ERR_BADSESSION. The sends over the connection will get back NFS4ERR_BADSESSION. The
client again knows the session was lost. client again knows the session was lost.
Here is one suggested algorithm for the client when it gets Here is one suggested algorithm for the client when it gets
NFS4ERR_BADSESSION. It is not obligatory in that, if a client does NFS4ERR_BADSESSION. It is not obligatory in that, if a client does
not want to take advantage of such features as trunking, it may omit not want to take advantage of such features as trunking, it may omit
parts of it. However, it is a useful example which draws attention parts of it. However, it is a useful example that draws attention to
to various possible recovery issues: various possible recovery issues:
1. If the client has other connections to other server network 1. If the client has other connections to other server network
addresses associated with the same session, attempt a COMPOUND addresses associated with the same session, attempt a COMPOUND
with a single operation, SEQUENCE, on each of the other with a single operation, SEQUENCE, on each of the other
connections. connections.
2. If the attempts succeed, the session is still alive, and this is 2. If the attempts succeed, the session is still alive, and this is
a strong indicator the server's network address has moved. The a strong indicator that the server's network address has moved.
client might send an EXCHANGE_ID on the connection that returned The client might send an EXCHANGE_ID on the connection that
NFS4ERR_BADSESSION to see if there are opportunities for client returned NFS4ERR_BADSESSION to see if there are opportunities for
ID trunking (i.e. the same client ID and so_major are returned). client ID trunking (i.e., the same client ID and so_major are
The client might use DNS to see if the moved network address was returned). The client might use DNS to see if the moved network
replaced with another, so that the performance and availability address was replaced with another, so that the performance and
benefits of session trunking can continue. availability benefits of session trunking can continue.
3. If the SEQUENCE requests fail with NFS4ERR_BADSESSION then the 3. If the SEQUENCE requests fail with NFS4ERR_BADSESSION, then the
session no longer exists on any of the server network addresses session no longer exists on any of the server network addresses
the client has connections associated with that session ID. It for which the client has connections associated with that session
is possible the session is still alive and available on other ID. It is possible the session is still alive and available on
network addresses. The client sends an EXCHANGE_ID on all the other network addresses. The client sends an EXCHANGE_ID on all
connections to see if the server owner is still listening on the connections to see if the server owner is still listening on
those network addresses. If the same server owner is returned, those network addresses. If the same server owner is returned
but a new client ID is returned, this is a strong indicator of a but a new client ID is returned, this is a strong indicator of a
server restart. If both the same server owner and same client ID server restart. If both the same server owner and same client ID
are returned, then this is a strong indication that the server are returned, then this is a strong indication that the server
did delete the session, and the client will need to send a did delete the session, and the client will need to send a
CREATE_SESSION if it has no other sessions for that client ID. CREATE_SESSION if it has no other sessions for that client ID.
If a different server owner is returned, the client can use DNS If a different server owner is returned, the client can use DNS
to find other network addresses. If it does not, or if DNS does to find other network addresses. If it does not, or if DNS does
not find any other addresses for the server, then the client will not find any other addresses for the server, then the client will
be unable to provide NFSv4.1 service, and fatal errors should be be unable to provide NFSv4.1 service, and fatal errors should be
returned to processes that were using the server. If the client returned to processes that were using the server. If the client
is using a "mount" paradigm, unmounting the server is advised. is using a "mount" paradigm, unmounting the server is advised.
4. If the client knows of no other connections associated with the 4. If the client knows of no other connections associated with the
session ID, and server network addresses that are, or have been session ID and server network addresses that are, or have been,
associated with the session ID, then the client can use DNS to associated with the session ID, then the client can use DNS to
find other network addresses. If it does not, or if DNS does not find other network addresses. If it does not, or if DNS does not
find any other addresses for the server, then the client will be find any other addresses for the server, then the client will be
unable to provide NFSv4.1 service, and fatal errors should be unable to provide NFSv4.1 service, and fatal errors should be
returned to processes that were using the server. If the client returned to processes that were using the server. If the client
is using a "mount" paradigm, unmounting the server is advised. is using a "mount" paradigm, unmounting the server is advised.
If there is a reconfiguration event which results in the same network If there is a reconfiguration event that results in the same network
address being assigned to servers where the eir_server_scope value is address being assigned to servers where the eir_server_scope value is
different, it cannot be guaranteed that a session ID generated by the different, it cannot be guaranteed that a session ID generated by the
first will be recognized as invalid by the first. Therefore, in first will be recognized as invalid by the first. Therefore, in
managing server reconfigurations among servers with different server managing server reconfigurations among servers with different server
scope values, it is necessary to make sure that all clients have scope values, it is necessary to make sure that all clients have
disconnected from the first server before effecting the disconnected from the first server before effecting the
reconfiguration. Nonetheless, clients cannot assume that servers reconfiguration. Nonetheless, clients should not assume that servers
will always adhere to this requirement; clients MUST be prepared to will always adhere to this requirement; clients MUST be prepared to
deal with unexpected effects of server reconfigurations. Even where deal with unexpected effects of server reconfigurations. Even where
a session ID is inappropriately recognized as valid, it is likely a session ID is inappropriately recognized as valid, it is likely
that either the connection will not be recognized as valid, or that a either that the connection will not be recognized as valid or that a
sequence value for a slot will not be correct. Therefore, when a sequence value for a slot will not be correct. Therefore, when a
client receives results indicating such unexpected errors, the use of client receives results indicating such unexpected errors, the use of
EXCHANGE_ID to determine the current server configuration is EXCHANGE_ID to determine the current server configuration is
RECOMMENDED. RECOMMENDED.
A variation on the above is that after a server's network address A variation on the above is that after a server's network address
moves, there is no NFSv4.1 server listening. E.g. no listener on moves, there is no NFSv4.1 server listening, e.g., no listener on
port 2049, the NFSv4 server returns NFS4ERR_MINOR_VERS_MISMATCH, the port 2049. In this example, one of the following occur: the NFSv4
NFS server returns a PROG_MISMATCH error, the RPC listener on 2049 server returns NFS4ERR_MINOR_VERS_MISMATCH, the NFS server returns a
returns PROG_MISMATCH, or attempts to re-connect to the network PROG_MISMATCH error, the RPC listener on 2049 returns PROG_UNVAIL, or
address timeout. These SHOULD be treated as equivalent to SEQUENCE attempts to reconnect to the network address timeout. These SHOULD
returning NFS4ERR_BADSESSION for these purposes. be treated as equivalent to SEQUENCE returning NFS4ERR_BADSESSION for
these purposes.
When the client detects session loss, it needs to call CREATE_SESSION When the client detects session loss, it needs to call CREATE_SESSION
to recover. Any non-idempotent operations that were in progress to recover. Any non-idempotent operations that were in progress
might have been performed on the server at the time of session loss. might have been performed on the server at the time of session loss.
The client has no general way to recover from this. The client has no general way to recover from this.
Note that loss of session does not imply loss of lock, open, Note that loss of session does not imply loss of byte-range lock,
delegation, or layout state because locks, opens, delegations, and open, delegation, or layout state because locks, opens, delegations,
layouts are tied to the client ID and depend on the client ID, not and layouts are tied to the client ID and depend on the client ID,
the session. Nor does loss of lock, open, delegation, or layout not the session. Nor does loss of byte-range lock, open, delegation,
state imply loss of session state, because the session depends on the or layout state imply loss of session state, because the session
client ID; loss of client ID however does imply loss of session, depends on the client ID; loss of client ID however does imply loss
lock, open, delegation, and layout state. See Section 8.4.2. A of session, byte-range lock, open, delegation, and layout state. See
session can survive a server restart, but lock recovery may still be Section 8.4.2. A session can survive a server restart, but lock
needed. recovery may still be needed.
It is possible CREATE_SESSION will fail with NFS4ERR_STALE_CLIENTID It is possible that CREATE_SESSION will fail with
(e.g. the server restarts and does not preserve client ID state). If NFS4ERR_STALE_CLIENTID (e.g., the server restarts and does not
so, the client needs to call EXCHANGE_ID, followed by CREATE_SESSION. preserve client ID state). If so, the client needs to call
EXCHANGE_ID, followed by CREATE_SESSION.
2.10.13.2. Events Requiring Server Action 2.10.13.2. Events Requiring Server Action
The following events require server action to recover. The following events require server action to recover.
2.10.13.2.1. Client Crash and Restart 2.10.13.2.1. Client Crash and Restart
As described in Section 18.35, a restarted client sends EXCHANGE_ID As described in Section 18.35, a restarted client sends EXCHANGE_ID
in such a way it causes the server to delete any sessions it had. in such a way that it causes the server to delete any sessions it
had.
2.10.13.2.2. Client Crash with No Restart 2.10.13.2.2. Client Crash with No Restart
If a client crashes and never comes back, it will never send If a client crashes and never comes back, it will never send
EXCHANGE_ID with its old client owner. Thus the server has session EXCHANGE_ID with its old client owner. Thus, the server has session
state that will never be used again. After an extended period of state that will never be used again. After an extended period of
time and if the server has resource constraints, it MAY destroy the time, and if the server has resource constraints, it MAY destroy the
old session as well as locking state. old session as well as locking state.
2.10.13.2.3. Extended Network Partition 2.10.13.2.3. Extended Network Partition
To the server, the extended network partition may be no different To the server, the extended network partition may be no different
from a client crash with no restart (see Section 2.10.13.2.2). from a client crash with no restart (see Section 2.10.13.2.2).
Unless the server can discern that there is a network partition, it Unless the server can discern that there is a network partition, it
is free to treat the situation as if the client has crashed is free to treat the situation as if the client has crashed
permanently. permanently.
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in Section 2.10.6.2. Note that it is not necessary to retry requests in Section 2.10.6.2. Note that it is not necessary to retry requests
over a connection with the same source network address or the same over a connection with the same source network address or the same
destination network address as the lost connection. As long as the destination network address as the lost connection. As long as the
session ID, slot ID, and sequence ID in the retry match that of the session ID, slot ID, and sequence ID in the retry match that of the
original request, the callback target will recognize the request as a original request, the callback target will recognize the request as a
retry even if it did see the request prior to disconnect. retry even if it did see the request prior to disconnect.
If the connection lost is the last one associated with the If the connection lost is the last one associated with the
backchannel, then the server MUST indicate that in the backchannel, then the server MUST indicate that in the
sr_status_flags field of every SEQUENCE reply until the backchannel sr_status_flags field of every SEQUENCE reply until the backchannel
is reestablished. There are two situations each of which use is re-established. There are two situations, each of which uses
different status flags: no connectivity for the session's different status flags: no connectivity for the session's backchannel
backchannel, and no connectivity for any session backchannel of the and no connectivity for any session backchannel of the client. See
client. See Section 18.46 for a description of the appropriate flags Section 18.46 for a description of the appropriate flags in
in sr_status_flags. sr_status_flags.
2.10.13.2.5. GSS Context Loss 2.10.13.2.5. GSS Context Loss
The server SHOULD monitor when the number RPCSEC_GSS contexts The server SHOULD monitor when the number RPCSEC_GSS handles assigned
assigned to the backchannel reaches one, and when that one context is to the backchannel reaches one, and when that one handle is near
near expiry (i.e. between one and two periods of lease time), expiry (i.e., between one and two periods of lease time), and
indicate so in the sr_status_flags field of all SEQUENCE replies. indicate so in the sr_status_flags field of all SEQUENCE replies.
The server MUST indicate when all of the backchannel's assigned The server MUST indicate when all of the backchannel's assigned
RPCSEC_GSS handles have expired via the sr_status_flags field of all RPCSEC_GSS handles have expired via the sr_status_flags field of all
SEQUENCE replies. SEQUENCE replies.
2.10.14. Parallel NFS and Sessions 2.10.14. Parallel NFS and Sessions
A client and server can potentially be a non-pNFS implementation, a A client and server can potentially be a non-pNFS implementation, a
metadata server implementation, a data server implementation, or two metadata server implementation, a data server implementation, or two
or three types of implementations. The EXCHGID4_FLAG_USE_NON_PNFS, or three types of implementations. The EXCHGID4_FLAG_USE_NON_PNFS,
EXCHGID4_FLAG_USE_PNFS_MDS, and EXCHGID4_FLAG_USE_PNFS_DS flags (not EXCHGID4_FLAG_USE_PNFS_MDS, and EXCHGID4_FLAG_USE_PNFS_DS flags (not
mutually exclusive) are passed in the EXCHANGE_ID arguments and mutually exclusive) are passed in the EXCHANGE_ID arguments and
results to allow the client to indicate how it wants to use sessions results to allow the client to indicate how it wants to use sessions
created under the client ID, and to allow the server to indicate how created under the client ID, and to allow the server to indicate how
it will allow the sessions to be used. See Section 13.1 for pNFS it will allow the sessions to be used. See Section 13.1 for pNFS
sessions considerations. sessions considerations.
3. Protocol Constants and Data Types 3. Protocol Constants and Data Types
The syntax and semantics to describe the data types of the NFSv4.1 The syntax and semantics to describe the data types of the NFSv4.1
protocol are defined in the XDR RFC4506 [2] and RPC RFC1831 [3] protocol are defined in the XDR RFC 4506 [2] and RPC RFC 5531 [3]
documents. The next sections build upon the XDR data types to define documents. The next sections build upon the XDR data types to define
constants, types and structures specific to this protocol. The full constants, types, and structures specific to this protocol. The full
list of XDR data types is in [13]. list of XDR data types is in [13].
3.1. Basic Constants 3.1. Basic Constants
const NFS4_FHSIZE = 128; const NFS4_FHSIZE = 128;
const NFS4_VERIFIER_SIZE = 8; const NFS4_VERIFIER_SIZE = 8;
const NFS4_OPAQUE_LIMIT = 1024; const NFS4_OPAQUE_LIMIT = 1024;
const NFS4_SESSIONID_SIZE = 16; const NFS4_SESSIONID_SIZE = 16;
const NFS4_INT64_MAX = 0x7fffffffffffffff; const NFS4_INT64_MAX = 0x7fffffffffffffff;
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o NFS4_FHSIZE is the maximum size of a filehandle. o NFS4_FHSIZE is the maximum size of a filehandle.
o NFS4_VERIFIER_SIZE is the fixed size of a verifier. o NFS4_VERIFIER_SIZE is the fixed size of a verifier.
o NFS4_OPAQUE_LIMIT is the maximum size of certain opaque o NFS4_OPAQUE_LIMIT is the maximum size of certain opaque
information. information.
o NFS4_SESSIONID_SIZE is the fixed size of a session identifier. o NFS4_SESSIONID_SIZE is the fixed size of a session identifier.
o NFS4_INT64_MAX is the maximum value of a signed 64 bit integer. o NFS4_INT64_MAX is the maximum value of a signed 64-bit integer.
o NFS4_UINT64_MAX is the maximum value of an unsigned 64 bit o NFS4_UINT64_MAX is the maximum value of an unsigned 64-bit
integer. integer.
o NFS4_INT32_MAX is the maximum value of a signed 32 bit integer. o NFS4_INT32_MAX is the maximum value of a signed 32-bit integer.
o NFS4_UINT32_MAX is the maximum value of an unsigned 32 bit o NFS4_UINT32_MAX is the maximum value of an unsigned 32-bit
integer. integer.
o NFS4_MAXFILELEN is the maximum length of a regular file. o NFS4_MAXFILELEN is the maximum length of a regular file.
o NFS4_MAXFILEOFF is the maximum offset into a regular file. o NFS4_MAXFILEOFF is the maximum offset into a regular file.
3.2. Basic Data Types 3.2. Basic Data Types
These are the base NFSv4.1 data types. These are the base NFSv4.1 data types.
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| | Used for file/directory attributes. | | | Used for file/directory attributes. |
| bitmap4 | typedef uint32_t bitmap4<>; | | bitmap4 | typedef uint32_t bitmap4<>; |
| | Used in attribute array encoding. | | | Used in attribute array encoding. |
| changeid4 | typedef uint64_t changeid4; | | changeid4 | typedef uint64_t changeid4; |
| | Used in the definition of change_info4. | | | Used in the definition of change_info4. |
| clientid4 | typedef uint64_t clientid4; | | clientid4 | typedef uint64_t clientid4; |
| | Shorthand reference to client identification. | | | Shorthand reference to client identification. |
| count4 | typedef uint32_t count4; | | count4 | typedef uint32_t count4; |
| | Various count parameters (READ, WRITE, COMMIT). | | | Various count parameters (READ, WRITE, COMMIT). |
| length4 | typedef uint64_t length4; | | length4 | typedef uint64_t length4; |
| | The length of a byte range within a file. | | | The length of a byte-range within a file. |
| mode4 | typedef uint32_t mode4; | | mode4 | typedef uint32_t mode4; |
| | Mode attribute data type. | | | Mode attribute data type. |
| nfs_cookie4 | typedef uint64_t nfs_cookie4; | | nfs_cookie4 | typedef uint64_t nfs_cookie4; |
| | Opaque cookie value for READDIR. | | | Opaque cookie value for READDIR. |
| nfs_fh4 | typedef opaque nfs_fh4<NFS4_FHSIZE>; | | nfs_fh4 | typedef opaque nfs_fh4<NFS4_FHSIZE>; |
| | Filehandle definition. | | | Filehandle definition. |
| nfs_ftype4 | enum nfs_ftype4; | | nfs_ftype4 | enum nfs_ftype4; |
| | Various defined file types. | | | Various defined file types. |
| nfsstat4 | enum nfsstat4; | | nfsstat4 | enum nfsstat4; |
| | Return value for operations. | | | Return value for operations. |
| offset4 | typedef uint64_t offset4; | | offset4 | typedef uint64_t offset4; |
| | Various offset designations (READ, WRITE, LOCK, | | | Various offset designations (READ, WRITE, LOCK, |
| | COMMIT). | | | COMMIT). |
| qop4 | typedef uint32_t qop4; | | qop4 | typedef uint32_t qop4; |
| | Quality of protection designation in SECINFO. | | | Quality of protection designation in SECINFO. |
| sec_oid4 | typedef opaque sec_oid4<>; | | sec_oid4 | typedef opaque sec_oid4<>; |
| | Security Object Identifier. The sec_oid4 data | | | Security Object Identifier. The sec_oid4 data |
| | type is not really opaque. Instead it contains an | | | type is not really opaque. Instead, it contains |
| | ASN.1 OBJECT IDENTIFIER as used by GSS-API in the | | | an ASN.1 OBJECT IDENTIFIER as used by GSS-API in |
| | mech_type argument to GSS_Init_sec_context. See | | | the mech_type argument to GSS_Init_sec_context. |
| | [7] for details. | | | See [7] for details. |
| sequenceid4 | typedef uint32_t sequenceid4; | | sequenceid4 | typedef uint32_t sequenceid4; |
| | Sequence number used for various session | | | Sequence number used for various session |
| | operations (EXCHANGE_ID, CREATE_SESSION, | | | operations (EXCHANGE_ID, CREATE_SESSION, |
| | SEQUENCE, CB_SEQUENCE). | | | SEQUENCE, CB_SEQUENCE). |
| seqid4 | typedef uint32_t seqid4; | | seqid4 | typedef uint32_t seqid4; |
| | Sequence identifier used for file locking. | | | Sequence identifier used for locking. |
| sessionid4 | typedef opaque sessionid4[NFS4_SESSIONID_SIZE]; | | sessionid4 | typedef opaque sessionid4[NFS4_SESSIONID_SIZE]; |
| | Session identifier. | | | Session identifier. |
| slotid4 | typedef uint32_t slotid4; | | slotid4 | typedef uint32_t slotid4; |
| | Sequencing artifact for various session | | | Sequencing artifact for various session |
| | operations (SEQUENCE, CB_SEQUENCE). | | | operations (SEQUENCE, CB_SEQUENCE). |
| utf8string | typedef opaque utf8string<>; | | utf8string | typedef opaque utf8string<>; |
| | UTF-8 encoding for strings. | | | UTF-8 encoding for strings. |
| utf8str_cis | typedef utf8string utf8str_cis; | | utf8str_cis | typedef utf8string utf8str_cis; |
| | Case-insensitive UTF-8 string. | | | Case-insensitive UTF-8 string. |
| utf8str_cs | typedef utf8string utf8str_cs; | | utf8str_cs | typedef utf8string utf8str_cs; |
| | Case-sensitive UTF-8 string. | | | Case-sensitive UTF-8 string. |
| utf8str_mixed | typedef utf8string utf8str_mixed; | | utf8str_mixed | typedef utf8string utf8str_mixed; |
| | UTF-8 strings with a case sensitive prefix and a | | | UTF-8 strings with a case-sensitive prefix and a |
| | case insensitive suffix. | | | case-insensitive suffix. |
| component4 | typedef utf8str_cs component4; | | component4 | typedef utf8str_cs component4; |
| | Represents path name components. | | | Represents path name components. |
| linktext4 | typedef utf8str_cs linktext4; | | linktext4 | typedef utf8str_cs linktext4; |
| | Symbolic link contents ("symbolic link" is | | | Symbolic link contents ("symbolic link" is |
| | defined in an Open Group [14] standard). | | | defined in an Open Group [14] standard). |
| pathname4 | typedef component4 pathname4<>; | | pathname4 | typedef component4 pathname4<>; |
| | Represents path name for fs_locations. | | | Represents path name for fs_locations. |
| verifier4 | typedef opaque verifier4[NFS4_VERIFIER_SIZE]; | | verifier4 | typedef opaque verifier4[NFS4_VERIFIER_SIZE]; |
| | Verifier used for various operations (COMMIT, | | | Verifier used for various operations (COMMIT, |
| | CREATE, EXCHANGE_ID, OPEN, READDIR, WRITE) | | | CREATE, EXCHANGE_ID, OPEN, READDIR, WRITE) |
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3.3. Structured Data Types 3.3. Structured Data Types
3.3.1. nfstime4 3.3.1. nfstime4
struct nfstime4 { struct nfstime4 {
int64_t seconds; int64_t seconds;
uint32_t nseconds; uint32_t nseconds;
}; };
The nfstime4 data type gives the number of seconds and nanoseconds The nfstime4 data type gives the number of seconds and nanoseconds
since midnight or 0 hour January 1, 1970 Coordinated Universal Time since midnight or zero hour January 1, 1970 Coordinated Universal
(UTC). Values greater than zero for the seconds field denote dates Time (UTC). Values greater than zero for the seconds field denote
after the 0 hour January 1, 1970. Values less than zero for the dates after the zero hour January 1, 1970. Values less than zero for
seconds field denote dates before the 0 hour January 1, 1970. In the seconds field denote dates before the zero hour January 1, 1970.
both cases, the nseconds field is to be added to the seconds field In both cases, the nseconds field is to be added to the seconds field
for the final time representation. For example, if the time to be for the final time representation. For example, if the time to be
represented is one-half second before 0 hour January 1, 1970, the represented is one-half second before zero hour January 1, 1970, the
seconds field would have a value of negative one (-1) and the seconds field would have a value of negative one (-1) and the
nseconds fields would have a value of one-half second (500000000). nseconds field would have a value of one-half second (500000000).
Values greater than 999,999,999 for nseconds are invalid. Values greater than 999,999,999 for nseconds are invalid.
This data type is used to pass time and date information. A server This data type is used to pass time and date information. A server
converts to and from its local representation of time when processing converts to and from its local representation of time when processing
time values, preserving as much accuracy as possible. If the time values, preserving as much accuracy as possible. If the
precision of timestamps stored for a file system object is less than precision of timestamps stored for a file system object is less than
defined, loss of precision can occur. An adjunct time maintenance defined, loss of precision can occur. An adjunct time maintenance
protocol is RECOMMENDED to reduce client and server time skew. protocol is RECOMMENDED to reduce client and server time skew.
3.3.2. time_how4 3.3.2. time_how4
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3.3.7. fattr4 3.3.7. fattr4
struct fattr4 { struct fattr4 {
bitmap4 attrmask; bitmap4 attrmask;
attrlist4 attr_vals; attrlist4 attr_vals;
}; };
The fattr4 data type is used to represent file and directory The fattr4 data type is used to represent file and directory
attributes. attributes.
The bitmap is a counted array of 32 bit integers used to contain bit The bitmap is a counted array of 32-bit integers used to contain bit
values. The position of the integer in the array that contains bit n values. The position of the integer in the array that contains bit n
can be computed from the expression (n / 32) and its bit within that can be computed from the expression (n / 32), and its bit within that
integer is (n mod 32). integer is (n mod 32).
0 1 0 1
+-----------+-----------+-----------+-- +-----------+-----------+-----------+--
| count | 31 .. 0 | 63 .. 32 | | count | 31 .. 0 | 63 .. 32 |
+-----------+-----------+-----------+-- +-----------+-----------+-----------+--
3.3.8. change_info4 3.3.8. change_info4
struct change_info4 { struct change_info4 {
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struct netaddr4 { struct netaddr4 {
/* see struct rpcb in RFC 1833 */ /* see struct rpcb in RFC 1833 */
string na_r_netid<>; /* network id */ string na_r_netid<>; /* network id */
string na_r_addr<>; /* universal address */ string na_r_addr<>; /* universal address */
}; };
The netaddr4 data type is used to identify network transport The netaddr4 data type is used to identify network transport
endpoints. The r_netid and r_addr fields respectively contain a endpoints. The r_netid and r_addr fields respectively contain a
netid and uaddr. The netid and uaddr concepts are defined in [15]. netid and uaddr. The netid and uaddr concepts are defined in [15].
The netid and uaddr formats for TCP over IPv4 and TCP over IPv6 are The netid and uaddr formats for TCP over IPv4 and TCP over IPv6 are
defined in [15], specifically Tables 2 and 3 and Sections 4.2.3.3 and defined in [15], specifically Tables 2 and 3 and Sections 5.2.3.3 and
4.2.3.4. 5.2.3.4.
3.3.10. state_owner4 3.3.10. state_owner4
struct state_owner4 { struct state_owner4 {
clientid4 clientid; clientid4 clientid;
opaque owner<NFS4_OPAQUE_LIMIT>; opaque owner<NFS4_OPAQUE_LIMIT>;
}; };
typedef state_owner4 open_owner4; typedef state_owner4 open_owner4;
typedef state_owner4 lock_owner4; typedef state_owner4 lock_owner4;
The state_owner4 data type is the base type for the open_owner4 The state_owner4 data type is the base type for the open_owner4
Section 3.3.10.1 and lock_owner4 Section 3.3.10.2. (Section 3.3.10.1) and lock_owner4 (Section 3.3.10.2.
3.3.10.1. open_owner4 3.3.10.1. open_owner4
This data type is used to identify the owner of open state. This data type is used to identify the owner of OPEN state.
3.3.10.2. lock_owner4 3.3.10.2. lock_owner4
This structure is used to identify the owner of byte-range locking This structure is used to identify the owner of byte-range locking
state. state.
3.3.11. open_to_lock_owner4 3.3.11. open_to_lock_owner4
struct open_to_lock_owner4 { struct open_to_lock_owner4 {
seqid4 open_seqid; seqid4 open_seqid;
stateid4 open_stateid; stateid4 open_stateid;
seqid4 lock_seqid; seqid4 lock_seqid;
lock_owner4 lock_owner; lock_owner4 lock_owner;
}; };
This data type is used for the first LOCK operation done for an This data type is used for the first LOCK operation done for an
open_owner4. It provides both the open_stateid and lock_owner such open_owner4. It provides both the open_stateid and lock_owner, such
that the transition is made from a valid open_stateid sequence to that the transition is made from a valid open_stateid sequence to
that of the new lock_stateid sequence. Using this mechanism avoids that of the new lock_stateid sequence. Using this mechanism avoids
the confirmation of the lock_owner/lock_seqid pair since it is tied the confirmation of the lock_owner/lock_seqid pair since it is tied
to established state in the form of the open_stateid/open_seqid. to established state in the form of the open_stateid/open_seqid.
3.3.12. stateid4 3.3.12. stateid4
struct stateid4 { struct stateid4 {
uint32_t seqid; uint32_t seqid;
opaque other[12]; opaque other[12];
}; };
This data type is used for the various state sharing mechanisms This data type is used for the various state sharing mechanisms
between the client and server. The client never modifies a value of between the client and server. The client never modifies a value of
data type stateid. The starting value of the seqid field is data type stateid. The starting value of the "seqid" field is
undefined. The server is required to increment the seqid field by undefined. The server is required to increment the "seqid" field by
one (1) at each transition of the stateid. This is important since one at each transition of the stateid. This is important since the
the client will inspect the seqid in OPEN stateids to determine the client will inspect the seqid in OPEN stateids to determine the order
order of OPEN processing done by the server. of OPEN processing done by the server.
3.3.13. layouttype4 3.3.13. layouttype4
enum layouttype4 { enum layouttype4 {
LAYOUT4_NFSV4_1_FILES = 0x1, LAYOUT4_NFSV4_1_FILES = 0x1,
LAYOUT4_OSD2_OBJECTS = 0x2, LAYOUT4_OSD2_OBJECTS = 0x2,
LAYOUT4_BLOCK_VOLUME = 0x3 LAYOUT4_BLOCK_VOLUME = 0x3
}; };
This data type indicates what type of layout is being used. The file This data type indicates what type of layout is being used. The file
server advertises the layout types it supports through the server advertises the layout types it supports through the
fs_layout_type file system attribute (Section 5.12.1). A client asks fs_layout_type file system attribute (Section 5.12.1). A client asks
for layouts of a particular type in LAYOUTGET, and processes those for layouts of a particular type in LAYOUTGET, and processes those
layouts in its layout-type-specific logic. layouts in its layout-type-specific logic.
The layouttype4 data type is 32 bits in length. The range The layouttype4 data type is 32 bits in length. The range
represented by the layout type is split into three parts. Type 0x0 represented by the layout type is split into three parts. Type 0x0
is reserved. Types within the range 0x00000001-0x7FFFFFFF are is reserved. Types within the range 0x00000001-0x7FFFFFFF are
globally unique and are assigned according to the description in globally unique and are assigned according to the description in
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The device address is used to set up a communication channel with the The device address is used to set up a communication channel with the
storage device. Different layout types will require different data storage device. Different layout types will require different data
types to define how they communicate with storage devices. The types to define how they communicate with storage devices. The
opaque da_addr_body field is interpreted based on the specified opaque da_addr_body field is interpreted based on the specified
da_layout_type field. da_layout_type field.
This document defines the device address for the NFSv4.1 file layout This document defines the device address for the NFSv4.1 file layout
(see Section 13.3), which identifies a storage device by network IP (see Section 13.3), which identifies a storage device by network IP
address and port number. This is sufficient for the clients to address and port number. This is sufficient for the clients to
communicate with the NFSv4.1 storage devices, and may be sufficient communicate with the NFSv4.1 storage devices, and may be sufficient
for other layout types as well. Device types for object storage for other layout types as well. Device types for object-based
devices and block storage devices (e.g., SCSI volume labels) are storage devices and block storage devices (e.g., Small Computer
defined by their respective layout specifications. System Interface (SCSI) volume labels) are defined by their
respective layout specifications.
3.3.16. layout_content4 3.3.16. layout_content4
struct layout_content4 { struct layout_content4 {
layouttype4 loc_type; layouttype4 loc_type;
opaque loc_body<>; opaque loc_body<>;
}; };
The loc_body field is interpreted based on the layout type The loc_body field is interpreted based on the layout type
(loc_type). This document defines the loc_body for the NFSv4.1 file (loc_type). This document defines the loc_body for the NFSv4.1 file
layout type is defined; see Section 13.3 for its definition. layout type; see Section 13.3 for its definition.
3.3.17. layout4 3.3.17. layout4
struct layout4 { struct layout4 {
offset4 lo_offset; offset4 lo_offset;
length4 lo_length; length4 lo_length;
layoutiomode4 lo_iomode; layoutiomode4 lo_iomode;
layout_content4 lo_content; layout_content4 lo_content;
}; };
The layout4 data type defines a layout for a file. The layout type The layout4 data type defines a layout for a file. The layout type
specific data is opaque within lo_content. Since layouts are sub- specific data is opaque within lo_content. Since layouts are sub-
dividable, the offset and length together with the file's filehandle, dividable, the offset and length together with the file's filehandle,
the client ID, iomode, and layout type, identify the layout. the client ID, iomode, and layout type identify the layout.
3.3.18. layoutupdate4 3.3.18. layoutupdate4
struct layoutupdate4 { struct layoutupdate4 {
layouttype4 lou_type; layouttype4 lou_type;
opaque lou_body<>; opaque lou_body<>;
}; };
The layoutupdate4 data type is used by the client to return updated The layoutupdate4 data type is used by the client to return updated
layout information to the metadata server via the LAYOUTCOMMIT layout information to the metadata server via the LAYOUTCOMMIT
(Section 18.42) operation. This data type provides a channel to pass (Section 18.42) operation. This data type provides a channel to pass
layout type specific information (in field lou_body) back to the layout type specific information (in field lou_body) back to the
metadata server. E.g., for the block/volume layout type this could metadata server. For example, for the block/volume layout type, this
include the list of reserved blocks that were written. The contents could include the list of reserved blocks that were written. The
of the opaque lou_body argument are determined by the layout type. contents of the opaque lou_body argument are determined by the layout
The NFSv4.1 file-based layout does not use this data type; if type. The NFSv4.1 file-based layout does not use this data type; if
lou_type is LAYOUT4_NFSV4_1_FILES, the lou_body field MUST have a lou_type is LAYOUT4_NFSV4_1_FILES, the lou_body field MUST have a
zero length. zero length.
3.3.19. layouthint4 3.3.19. layouthint4
struct layouthint4 { struct layouthint4 {
layouttype4 loh_type; layouttype4 loh_type;
opaque loh_body<>; opaque loh_body<>;
}; };
The layouthint4 data type is used by the client to pass in a hint The layouthint4 data type is used by the client to pass in a hint
about the type of layout it would like created for a particular file. about the type of layout it would like created for a particular file.
It is the data type specified by the layout_hint attribute described It is the data type specified by the layout_hint attribute described
in Section 5.12.4. The metadata server may ignore the hint, or may in Section 5.12.4. The metadata server may ignore the hint or may
selectively ignore fields within the hint. This hint should be selectively ignore fields within the hint. This hint should be
provided at create time as part of the initial attributes within provided at create time as part of the initial attributes within
OPEN. The loh_body field is specific to the type of layout OPEN. The loh_body field is specific to the type of layout
(loh_type). The NFSv4.1 file-based layout uses the (loh_type). The NFSv4.1 file-based layout uses the
nfsv4_1_file_layouthint4 data type as defined in Section 13.3. nfsv4_1_file_layouthint4 data type as defined in Section 13.3.
3.3.20. layoutiomode4 3.3.20. layoutiomode4
enum layoutiomode4 { enum layoutiomode4 {
LAYOUTIOMODE4_READ = 1, LAYOUTIOMODE4_READ = 1,
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3.3.21. nfs_impl_id4 3.3.21. nfs_impl_id4
struct nfs_impl_id4 { struct nfs_impl_id4 {
utf8str_cis nii_domain; utf8str_cis nii_domain;
utf8str_cs nii_name; utf8str_cs nii_name;
nfstime4 nii_date; nfstime4 nii_date;
}; };
This data type is used to identify client and server implementation This data type is used to identify client and server implementation
details. The nii_domain field is the DNS domain name that the details. The nii_domain field is the DNS domain name with which the
implementer is associated with. The nii_name field is the product implementor is associated. The nii_name field is the product name of
name of the implementation and is completely free form. It is the implementation and is completely free form. It is RECOMMENDED
RECOMMENDED that the nii_name be used to distinguish machine that the nii_name be used to distinguish machine architecture,
architecture, machine platforms, revisions, versions, and patch machine platforms, revisions, versions, and patch levels. The
levels. The nii_date field is the timestamp of when the software nii_date field is the timestamp of when the software instance was
instance was published or built. published or built.
3.3.22. threshold_item4 3.3.22. threshold_item4
struct threshold_item4 { struct threshold_item4 {
layouttype4 thi_layout_type; layouttype4 thi_layout_type;
bitmap4 thi_hintset; bitmap4 thi_hintset;
opaque thi_hintlist<>; opaque thi_hintlist<>;
}; };
This data type contains a list of hints specific to a layout type for This data type contains a list of hints specific to a layout type for
helping the client determine when it should send I/O directly through helping the client determine when it should send I/O directly through
the metadata server versus the storage devices. The data type the metadata server versus the storage devices. The data type
consists of the layout type (thi_layout_type), a bitmap (thi_hintset) consists of the layout type (thi_layout_type), a bitmap (thi_hintset)
describing the set of hints supported by the server (they may differ describing the set of hints supported by the server (they may differ
based on the layout type), and a list of hints (thi_hintlist), whose based on the layout type), and a list of hints (thi_hintlist) whose
content is determined by the hintset bitmap. See the mdsthreshold content is determined by the hintset bitmap. See the mdsthreshold
attribute for more details. attribute for more details.
The thi_hintset field is a bitmap of the following values: The thi_hintset field is a bitmap of the following values:
+-------------------------+---+---------+---------------------------+ +-------------------------+---+---------+---------------------------+
| name | # | Data | Description | | name | # | Data | Description |
| | | Type | | | | | Type | |
+-------------------------+---+---------+---------------------------+ +-------------------------+---+---------+---------------------------+
| threshold4_read_size | 0 | length4 | The file size below which | | threshold4_read_size | 0 | length4 | If a file's length is |
| | | | it is RECOMMENDED to read | | | | | less than the value of |
| | | | data through the MDS. | | | | | threshold4_read_size, |
| threshold4_write_size | 1 | length4 | The file size below which | | | | | then it is RECOMMENDED |
| | | | it is RECOMMENDED to | | | | | that the client read from |
| | | | write data through the | | | | | the file via the MDS and |
| | | | MDS. | | | | | not a storage device. |
| threshold4_write_size | 1 | length4 | If a file's length is |
| | | | less than the value of |
| | | | threshold4_write_size, |
| | | | then it is RECOMMENDED |
| | | | that the client write to |
| | | | the file via the MDS and |
| | | | not a storage device. |
| threshold4_read_iosize | 2 | length4 | For read I/O sizes below | | threshold4_read_iosize | 2 | length4 | For read I/O sizes below |
| | | | this threshold it is | | | | | this threshold, it is |
| | | | RECOMMENDED to read data | | | | | RECOMMENDED to read data |
| | | | through the MDS | | | | | through the MDS. |
| threshold4_write_iosize | 3 | length4 | For write I/O sizes below | | threshold4_write_iosize | 3 | length4 | For write I/O sizes below |
| | | | this threshold it is | | | | | this threshold, it is |
| | | | RECOMMENDED to write data | | | | | RECOMMENDED to write data |
| | | | through the MDS | | | | | through the MDS. |
+-------------------------+---+---------+---------------------------+ +-------------------------+---+---------+---------------------------+
3.3.23. mdsthreshold4 3.3.23. mdsthreshold4
struct mdsthreshold4 { struct mdsthreshold4 {
threshold_item4 mth_hints<>; threshold_item4 mth_hints<>;
}; };
This data type holds an array of elements of data type This data type holds an array of elements of data type
threshold_item4, each of which is valid for a particular layout type. threshold_item4, each of which is valid for a particular layout type.
An array is necessary because a server can support multiple layout An array is necessary because a server can support multiple layout
types for a single file. types for a single file.
4. Filehandles 4. Filehandles
The filehandle in the NFS protocol is a per server unique identifier The filehandle in the NFS protocol is a per-server unique identifier
for a file system object. The contents of the filehandle are opaque for a file system object. The contents of the filehandle are opaque
to the client. Therefore, the server is responsible for translating to the client. Therefore, the server is responsible for translating
the filehandle to an internal representation of the file system the filehandle to an internal representation of the file system
object. object.
4.1. Obtaining the First Filehandle 4.1. Obtaining the First Filehandle
The operations of the NFS protocol are defined in terms of one or The operations of the NFS protocol are defined in terms of one or
more filehandles. Therefore, the client needs a filehandle to more filehandles. Therefore, the client needs a filehandle to
initiate communication with the server. With the NFSv3 protocol initiate communication with the server. With the NFSv3 protocol (RFC
(RFC1813 [31]), there exists an ancillary protocol to obtain this 1813 [31]), there exists an ancillary protocol to obtain this first
first filehandle. The MOUNT protocol, RPC program number 100005, filehandle. The MOUNT protocol, RPC program number 100005, provides
provides the mechanism of translating a string based file system path the mechanism of translating a string-based file system pathname to a
name to a filehandle which can then be used by the NFS protocols. filehandle, which can then be used by the NFS protocols.
The MOUNT protocol has deficiencies in the area of security and use The MOUNT protocol has deficiencies in the area of security and use
via firewalls. This is one reason that the use of the public via firewalls. This is one reason that the use of the public
filehandle was introduced in RFC2054 [42] and RFC2055 [43]. With the filehandle was introduced in RFC 2054 [42] and RFC 2055 [43]. With
use of the public filehandle in combination with the LOOKUP operation the use of the public filehandle in combination with the LOOKUP
in the NFSv3 protocol, it has been demonstrated that the MOUNT operation in the NFSv3 protocol, it has been demonstrated that the
protocol is unnecessary for viable interaction between NFS client and MOUNT protocol is unnecessary for viable interaction between NFS
server. client and server.
Therefore, the NFSv4.1 protocol will not use an ancillary protocol Therefore, the NFSv4.1 protocol will not use an ancillary protocol
for translation from string based path names to a filehandle. Two for translation from string-based pathnames to a filehandle. Two
special filehandles will be used as starting points for the NFS special filehandles will be used as starting points for the NFS
client. client.
4.1.1. Root Filehandle 4.1.1. Root Filehandle
The first of the special filehandles is the ROOT filehandle. The The first of the special filehandles is the ROOT filehandle. The
ROOT filehandle is the "conceptual" root of the file system name ROOT filehandle is the "conceptual" root of the file system namespace
space at the NFS server. The client uses or starts with the ROOT at the NFS server. The client uses or starts with the ROOT
filehandle by employing the PUTROOTFH operation. The PUTROOTFH filehandle by employing the PUTROOTFH operation. The PUTROOTFH
operation instructs the server to set the "current" filehandle to the operation instructs the server to set the "current" filehandle to the
ROOT of the server's file tree. Once this PUTROOTFH operation is ROOT of the server's file tree. Once this PUTROOTFH operation is
used, the client can then traverse the entirety of the server's file used, the client can then traverse the entirety of the server's file
tree with the LOOKUP operation. A complete discussion of the server tree with the LOOKUP operation. A complete discussion of the server
name space is in the Section 7. namespace is in Section 7.
4.1.2. Public Filehandle 4.1.2. Public Filehandle
The second special filehandle is the PUBLIC filehandle. Unlike the The second special filehandle is the PUBLIC filehandle. Unlike the
ROOT filehandle, the PUBLIC filehandle may be bound or represent an ROOT filehandle, the PUBLIC filehandle may be bound or represent an
arbitrary file system object at the server. The server is arbitrary file system object at the server. The server is
responsible for this binding. It may be that the PUBLIC filehandle responsible for this binding. It may be that the PUBLIC filehandle
and the ROOT filehandle refer to the same file system object. and the ROOT filehandle refer to the same file system object.
However, it is up to the administrative software at the server and However, it is up to the administrative software at the server and
the policies of the server administrator to define the binding of the the policies of the server administrator to define the binding of the
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4.2. Filehandle Types 4.2. Filehandle Types
In the NFSv3 protocol, there was one type of filehandle with a single In the NFSv3 protocol, there was one type of filehandle with a single
set of semantics. This type of filehandle is termed "persistent" in set of semantics. This type of filehandle is termed "persistent" in
NFSv4.1. The semantics of a persistent filehandle remain the same as NFSv4.1. The semantics of a persistent filehandle remain the same as
before. A new type of filehandle introduced in NFSv4.1 is the before. A new type of filehandle introduced in NFSv4.1 is the
"volatile" filehandle, which attempts to accommodate certain server "volatile" filehandle, which attempts to accommodate certain server
environments. environments.
The volatile filehandle type was introduced to address server The volatile filehandle type was introduced to address server
functionality or implementation issues which make correct functionality or implementation issues that make correct
implementation of a persistent filehandle infeasible. Some server implementation of a persistent filehandle infeasible. Some server
environments do not provide a file system level invariant that can be environments do not provide a file-system-level invariant that can be
used to construct a persistent filehandle. The underlying server used to construct a persistent filehandle. The underlying server
file system may not provide the invariant or the server's file system file system may not provide the invariant or the server's file system
programming interfaces may not provide access to the needed programming interfaces may not provide access to the needed
invariant. Volatile filehandles may ease the implementation of invariant. Volatile filehandles may ease the implementation of
server functionality such as hierarchical storage management or file server functionality such as hierarchical storage management or file
system reorganization or migration. However, the volatile filehandle system reorganization or migration. However, the volatile filehandle
increases the implementation burden for the client. increases the implementation burden for the client.
Since the client will need to handle persistent and volatile Since the client will need to handle persistent and volatile
filehandles differently, a file attribute is defined which may be filehandles differently, a file attribute is defined that may be used
used by the client to determine the filehandle types being returned by the client to determine the filehandle types being returned by the
by the server. server.
4.2.1. General Properties of a Filehandle 4.2.1. General Properties of a Filehandle
The filehandle contains all the information the server needs to The filehandle contains all the information the server needs to
distinguish an individual file. To the client, the filehandle is distinguish an individual file. To the client, the filehandle is
opaque. The client stores filehandles for use in a later request and opaque. The client stores filehandles for use in a later request and
can compare two filehandles from the same server for equality by can compare two filehandles from the same server for equality by
doing a byte-by-byte comparison. However, the client MUST NOT doing a byte-by-byte comparison. However, the client MUST NOT
otherwise interpret the contents of filehandles. If two filehandles otherwise interpret the contents of filehandles. If two filehandles
from the same server are equal, they MUST refer to the same file. from the same server are equal, they MUST refer to the same file.
Servers SHOULD try to maintain a one-to-one correspondence between Servers SHOULD try to maintain a one-to-one correspondence between
filehandles and files but this is not required. Clients MUST use filehandles and files, but this is not required. Clients MUST use
filehandle comparisons only to improve performance, not for correct filehandle comparisons only to improve performance, not for correct
behavior. All clients need to be prepared for situations in which it behavior. All clients need to be prepared for situations in which it
cannot be determined whether two filehandles denote the same object cannot be determined whether two filehandles denote the same object
and in such cases, avoid making invalid assumptions which might cause and in such cases, avoid making invalid assumptions that might cause
incorrect behavior. Further discussion of filehandle and attribute incorrect behavior. Further discussion of filehandle and attribute
comparison in the context of data caching is presented in the comparison in the context of data caching is presented in
Section 10.3.4. Section 10.3.4.
As an example, in the case that two different path names when As an example, in the case that two different path names when
traversed at the server terminate at the same file system object, the traversed at the server terminate at the same file system object, the
server SHOULD return the same filehandle for each path. This can server SHOULD return the same filehandle for each path. This can
occur if a hard link (see [6]) is used to create two file names which occur if a hard link (see [6]) is used to create two file names that
refer to the same underlying file object and associated data. For refer to the same underlying file object and associated data. For
example, if paths /a/b/c and /a/d/c refer to the same file, the example, if paths /a/b/c and /a/d/c refer to the same file, the
server SHOULD return the same filehandle for both path name server SHOULD return the same filehandle for both pathnames'
traversals. traversals.
4.2.2. Persistent Filehandle 4.2.2. Persistent Filehandle
A persistent filehandle is defined as having a fixed value for the A persistent filehandle is defined as having a fixed value for the
lifetime of the file system object to which it refers. Once the lifetime of the file system object to which it refers. Once the
server creates the filehandle for a file system object, the server server creates the filehandle for a file system object, the server
MUST accept the same filehandle for the object for the lifetime of MUST accept the same filehandle for the object for the lifetime of
the object. If the server restarts, the NFS server MUST honor the the object. If the server restarts, the NFS server MUST honor the
same filehandle value as it did in the server's previous same filehandle value as it did in the server's previous
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NFS server MUST honor the same filehandle as the old NFS server. NFS server MUST honor the same filehandle as the old NFS server.
The persistent filehandle will be become stale or invalid when the The persistent filehandle will be become stale or invalid when the
file system object is removed. When the server is presented with a file system object is removed. When the server is presented with a
persistent filehandle that refers to a deleted object, it MUST return persistent filehandle that refers to a deleted object, it MUST return
an error of NFS4ERR_STALE. A filehandle may become stale when the an error of NFS4ERR_STALE. A filehandle may become stale when the
file system containing the object is no longer available. The file file system containing the object is no longer available. The file
system may become unavailable if it exists on removable media and the system may become unavailable if it exists on removable media and the
media is no longer available at the server or the file system in media is no longer available at the server or the file system in
whole has been destroyed or the file system has simply been removed whole has been destroyed or the file system has simply been removed
from the server's name space (i.e. unmounted in a UNIX environment). from the server's namespace (i.e., unmounted in a UNIX environment).
4.2.3. Volatile Filehandle 4.2.3. Volatile Filehandle
A volatile filehandle does not share the same longevity A volatile filehandle does not share the same longevity
characteristics of a persistent filehandle. The server may determine characteristics of a persistent filehandle. The server may determine
that a volatile filehandle is no longer valid at many different that a volatile filehandle is no longer valid at many different
points in time. If the server can definitively determine that a points in time. If the server can definitively determine that a
volatile filehandle refers to an object that has been removed, the volatile filehandle refers to an object that has been removed, the
server should return NFS4ERR_STALE to the client (as is the case for server should return NFS4ERR_STALE to the client (as is the case for
persistent filehandles). In all other cases where the server persistent filehandles). In all other cases where the server
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particular file system. This attribute is a bitmask with the particular file system. This attribute is a bitmask with the
following values: following values:
FH4_PERSISTENT The value of FH4_PERSISTENT is used to indicate a FH4_PERSISTENT The value of FH4_PERSISTENT is used to indicate a
persistent filehandle, which is valid until the object is removed persistent filehandle, which is valid until the object is removed
from the file system. The server will not return from the file system. The server will not return
NFS4ERR_FHEXPIRED for this filehandle. FH4_PERSISTENT is defined NFS4ERR_FHEXPIRED for this filehandle. FH4_PERSISTENT is defined
as a value in which none of the bits specified below are set. as a value in which none of the bits specified below are set.
FH4_VOLATILE_ANY The filehandle may expire at any time, except as FH4_VOLATILE_ANY The filehandle may expire at any time, except as
specifically excluded (i.e. FH4_NO_EXPIRE_WITH_OPEN). specifically excluded (i.e., FH4_NO_EXPIRE_WITH_OPEN).
FH4_NOEXPIRE_WITH_OPEN May only be set when FH4_VOLATILE_ANY is set. FH4_NOEXPIRE_WITH_OPEN May only be set when FH4_VOLATILE_ANY is set.
If this bit is set, then the meaning of FH4_VOLATILE_ANY is If this bit is set, then the meaning of FH4_VOLATILE_ANY is
qualified to exclude any expiration of the filehandle when it is qualified to exclude any expiration of the filehandle when it is
open. open.
FH4_VOL_MIGRATION The filehandle will expire as a result of a file FH4_VOL_MIGRATION The filehandle will expire as a result of a file
system transition (migration or replication), in those case in system transition (migration or replication), in those cases in
which the continuity of filehandle use is not specified by which the continuity of filehandle use is not specified by handle
_handle_ class information within the fs_locations_info attribute. class information within the fs_locations_info attribute. When
When this bit is set, clients without access to fs_locations_info this bit is set, clients without access to fs_locations_info
information should assume filehandles will expire on file system information should assume that filehandles will expire on file
transitions. system transitions.
FH4_VOL_RENAME The filehandle will expire during rename. This FH4_VOL_RENAME The filehandle will expire during rename. This
includes a rename by the requesting client or a rename by any includes a rename by the requesting client or a rename by any
other client. If FH4_VOLATILE_ANY is set, FH4_VOL_RENAME is other client. If FH4_VOL_ANY is set, FH4_VOL_RENAME is redundant.
redundant.
Servers which provide volatile filehandles that may expire while open Servers that provide volatile filehandles that can expire while open
require special care as regards handling of RENAMEs and REMOVEs. require special care as regards handling of RENAMEs and REMOVEs.
This situation can arise if FH4_VOL_MIGRATION or FH4_VOL_RENAME is This situation can arise if FH4_VOL_MIGRATION or FH4_VOL_RENAME is
set, if FH4_VOLATILE_ANY is set and FH4_NOEXPIRE_WITH_OPEN not set, set, if FH4_VOLATILE_ANY is set and FH4_NOEXPIRE_WITH_OPEN is not
or if a non-readonly file system has a transition target in a set, or if a non-read-only file system has a transition target in a
different _handle _ class. In these cases, the server should deny a different handle class. In these cases, the server should deny a
RENAME or REMOVE that would affect an OPEN file of any of the RENAME or REMOVE that would affect an OPEN file of any of the
components leading to the OPEN file. In addition, the server should components leading to the OPEN file. In addition, the server should
deny all RENAME or REMOVE requests during the grace period, in order deny all RENAME or REMOVE requests during the grace period, in order
to make sure that reclaims of files where filehandles may have to make sure that reclaims of files where filehandles may have
expired do not do a reclaim for the wrong file. expired do not do a reclaim for the wrong file.
Volatile filehandles are especially suitable for implementation of Volatile filehandles are especially suitable for implementation of
the pseudo file systems used to bridge exports. See Section 7.5 for the pseudo file systems used to bridge exports. See Section 7.5 for
a discussion of this. a discussion of this.
4.3. One Method of Constructing a Volatile Filehandle 4.3. One Method of Constructing a Volatile Filehandle
A volatile filehandle, while opaque to the client could contain: A volatile filehandle, while opaque to the client, could contain:
[volatile bit = 1 | server boot time | slot | generation number] [volatile bit = 1 | server boot time | slot | generation number]
o slot is an index in the server volatile filehandle table o slot is an index in the server volatile filehandle table
o generation number is the generation number for the table entry/ o generation number is the generation number for the table entry/
slot slot
When the client presents a volatile filehandle, the server makes the When the client presents a volatile filehandle, the server makes the
following checks, which assume that the check for the volatile bit following checks, which assume that the check for the volatile bit
has passed. If the server boot time is less than the current server has passed. If the server boot time is less than the current server
boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return
NFS4ERR_BADHANDLE. If the generation number does not match, return NFS4ERR_BADHANDLE. If the generation number does not match, return
skipping to change at page 103, line 36 skipping to change at page 103, line 18
When the client presents a volatile filehandle, the server makes the When the client presents a volatile filehandle, the server makes the
following checks, which assume that the check for the volatile bit following checks, which assume that the check for the volatile bit
has passed. If the server boot time is less than the current server has passed. If the server boot time is less than the current server
boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return
NFS4ERR_BADHANDLE. If the generation number does not match, return NFS4ERR_BADHANDLE. If the generation number does not match, return
NFS4ERR_FHEXPIRED. NFS4ERR_FHEXPIRED.
When the server restarts, the table is gone (it is volatile). When the server restarts, the table is gone (it is volatile).
If volatile bit is 0, then it is a persistent filehandle with a If the volatile bit is 0, then it is a persistent filehandle with a
different structure following it. different structure following it.
4.4. Client Recovery from Filehandle Expiration 4.4. Client Recovery from Filehandle Expiration
If possible, the client SHOULD recover from the receipt of an If possible, the client SHOULD recover from the receipt of an
NFS4ERR_FHEXPIRED error. The client must take on additional NFS4ERR_FHEXPIRED error. The client must take on additional
responsibility so that it may prepare itself to recover from the responsibility so that it may prepare itself to recover from the
expiration of a volatile filehandle. If the server returns expiration of a volatile filehandle. If the server returns
persistent filehandles, the client does not need these additional persistent filehandles, the client does not need these additional
steps. steps.
For volatile filehandles, most commonly the client will need to store For volatile filehandles, most commonly the client will need to store
the component names leading up to and including the file system the component names leading up to and including the file system
object in question. With these names, the client should be able to object in question. With these names, the client should be able to
recover by finding a filehandle in the name space that is still recover by finding a filehandle in the name space that is still
available or by starting at the root of the server's file system name available or by starting at the root of the server's file system
space. namespace.
If the expired filehandle refers to an object that has been removed If the expired filehandle refers to an object that has been removed
from the file system, obviously the client will not be able to from the file system, obviously the client will not be able to
recover from the expired filehandle. recover from the expired filehandle.
It is also possible that the expired filehandle refers to a file that It is also possible that the expired filehandle refers to a file that
has been renamed. If the file was renamed by another client, again has been renamed. If the file was renamed by another client, again
it is possible that the original client will not be able to recover. it is possible that the original client will not be able to recover.
However, in the case that the client itself is renaming the file and However, in the case that the client itself is renaming the file and
the file is open, it is possible that the client may be able to the file is open, it is possible that the client may be able to
recover. The client can determine the new path name based on the recover. The client can determine the new path name based on the
processing of the rename request. The client can then regenerate the processing of the rename request. The client can then regenerate the
new filehandle based on the new path name. The client could also use new filehandle based on the new path name. The client could also use
the compound operation mechanism to construct a set of operations the COMPOUND procedure to construct a series of operations like:
like:
RENAME A B RENAME A B
LOOKUP B LOOKUP B
GETFH GETFH
Note that the COMPOUND procedure does not provide atomicity. This Note that the COMPOUND procedure does not provide atomicity. This
example only reduces the overhead of recovering from an expired example only reduces the overhead of recovering from an expired
filehandle. filehandle.
5. File Attributes 5. File Attributes
To meet the requirements of extensibility and increased To meet the requirements of extensibility and increased
interoperability with non-UNIX platforms, attributes need to be interoperability with non-UNIX platforms, attributes need to be
handled in a flexible manner. The NFSv3 fattr3 structure contains a handled in a flexible manner. The NFSv3 fattr3 structure contains a
fixed list of attributes that not all clients and servers are able to fixed list of attributes that not all clients and servers are able to
support or care about. The fattr3 structure can not be extended as support or care about. The fattr3 structure can not be extended as
new needs arise and it provides no way to indicate non-support. With new needs arise and it provides no way to indicate non-support. With
the NFSv4.1 protocol, the client is able query what attributes the the NFSv4.1 protocol, the client is able to query what attributes the
server supports and construct requests with only those supported server supports and construct requests with only those supported
attributes (or a subset thereof). attributes (or a subset thereof).
To this end, attributes are divided into three groups: REQUIRED, To this end, attributes are divided into three groups: REQUIRED,
RECOMMENDED, and named. Both REQUIRED and RECOMMENDED attributes are RECOMMENDED, and named. Both REQUIRED and RECOMMENDED attributes are
supported in the NFSv4.1 protocol by a specific and well-defined supported in the NFSv4.1 protocol by a specific and well-defined
encoding and are identified by number. They are requested by setting encoding and are identified by number. They are requested by setting
a bit in the bit vector sent in the GETATTR request; the server a bit in the bit vector sent in the GETATTR request; the server
response includes a bit vector to list what attributes were returned response includes a bit vector to list what attributes were returned
in the response. New REQUIRED or RECOMMENDED attributes may be added in the response. New REQUIRED or RECOMMENDED attributes may be added
to the NFSv4 protocol as part of a new minor version by publishing a to the NFSv4 protocol as part of a new minor version by publishing a
standards-track RFC which allocates a new attribute number value and Standards Track RFC that allocates a new attribute number value and
defines the encoding for the attribute. See Section 2.7 for further defines the encoding for the attribute. See Section 2.7 for further
discussion. discussion.
Named attributes are accessed by the new OPENATTR operation, which Named attributes are accessed by the new OPENATTR operation, which
accesses a hidden directory of attributes associated with a file accesses a hidden directory of attributes associated with a file
system object. OPENATTR takes a filehandle for the object and system object. OPENATTR takes a filehandle for the object and
returns the filehandle for the attribute hierarchy. The filehandle returns the filehandle for the attribute hierarchy. The filehandle
for the named attributes is a directory object accessible by LOOKUP for the named attributes is a directory object accessible by LOOKUP
or READDIR and contains files whose names represent the named or READDIR and contains files whose names represent the named
attributes and whose data bytes are the value of the attribute. For attributes and whose data bytes are the value of the attribute. For
skipping to change at page 105, line 27 skipping to change at page 105, line 16
| LOOKUP | "foo" | ; look up file | | LOOKUP | "foo" | ; look up file |
| GETATTR | attrbits | | | GETATTR | attrbits | |
| OPENATTR | | ; access foo's named attributes | | OPENATTR | | ; access foo's named attributes |
| LOOKUP | "x11icon" | ; look up specific attribute | | LOOKUP | "x11icon" | ; look up specific attribute |
| READ | 0,4096 | ; read stream of bytes | | READ | 0,4096 | ; read stream of bytes |
+----------+-----------+---------------------------------+ +----------+-----------+---------------------------------+
Named attributes are intended for data needed by applications rather Named attributes are intended for data needed by applications rather
than by an NFS client implementation. NFS implementors are strongly than by an NFS client implementation. NFS implementors are strongly
encouraged to define their new attributes as RECOMMENDED attributes encouraged to define their new attributes as RECOMMENDED attributes
by bringing them to the IETF standards-track process. by bringing them to the IETF Standards Track process.
The set of attributes which are classified as REQUIRED is The set of attributes that are classified as REQUIRED is deliberately
deliberately small since servers need to do whatever it takes to small since servers need to do whatever it takes to support them. A
support them. A server should support as many of the RECOMMENDED server should support as many of the RECOMMENDED attributes as
attributes as possible but by their definition, the server is not possible but, by their definition, the server is not required to
required to support all of them. Attributes are deemed REQUIRED if support all of them. Attributes are deemed REQUIRED if the data is
the data is both needed by a large number of clients and is not both needed by a large number of clients and is not otherwise
otherwise reasonably computable by the client when support is not reasonably computable by the client when support is not provided on
provided on the server. the server.
Note that the hidden directory returned by OPENATTR is a convenience Note that the hidden directory returned by OPENATTR is a convenience
for protocol processing. The client should not make any assumptions for protocol processing. The client should not make any assumptions
about the server's implementation of named attributes and whether the about the server's implementation of named attributes and whether or
underlying file system at the server has a named attribute directory not the underlying file system at the server has a named attribute
or not. Therefore, operations such as SETATTR and GETATTR on the directory. Therefore, operations such as SETATTR and GETATTR on the
named attribute directory are undefined. named attribute directory are undefined.
5.1. REQUIRED Attributes 5.1. REQUIRED Attributes
These MUST be supported by every NFSv4.1 client and server in order These MUST be supported by every NFSv4.1 client and server in order
to ensure a minimum level of interoperability. The server MUST store to ensure a minimum level of interoperability. The server MUST store
and return these attributes and the client MUST be able to function and return these attributes, and the client MUST be able to function
with an attribute set limited to these attributes. With just the with an attribute set limited to these attributes. With just the
REQUIRED attributes some client functionality may be impaired or REQUIRED attributes some client functionality may be impaired or
limited in some ways. A client may ask for any of these attributes limited in some ways. A client may ask for any of these attributes
to be returned by setting a bit in the GETATTR request and the server to be returned by setting a bit in the GETATTR request, and the
must return their value. server MUST return their value.
5.2. RECOMMENDED Attributes 5.2. RECOMMENDED Attributes
These attributes are understood well enough to warrant support in the These attributes are understood well enough to warrant support in the
NFSv4.1 protocol. However, they may not be supported on all clients NFSv4.1 protocol. However, they may not be supported on all clients
and servers. A client may ask for any of these attributes to be and servers. A client may ask for any of these attributes to be
returned by setting a bit in the GETATTR request but must handle the returned by setting a bit in the GETATTR request but must handle the
case where the server does not return them. A client MAY ask for the case where the server does not return them. A client MAY ask for the
set of attributes the server supports and SHOULD NOT request set of attributes the server supports and SHOULD NOT request
attributes the server does not support. A server should be tolerant attributes the server does not support. A server should be tolerant
of requests for unsupported attributes and simply not return them of requests for unsupported attributes and simply not return them
rather than considering the request an error. It is expected that rather than considering the request an error. It is expected that
servers will support all attributes they comfortably can and only servers will support all attributes they comfortably can and only
fail to support attributes which are difficult to support in their fail to support attributes that are difficult to support in their
operating environments. A server should provide attributes whenever operating environments. A server should provide attributes whenever
they don't have to "tell lies" to the client. For example, a file they don't have to "tell lies" to the client. For example, a file
modification time should be either an accurate time or should not be modification time should be either an accurate time or should not be
supported by the server. This will not always be comfortable to supported by the server. At times this will be difficult for
clients but the client is better positioned decide whether and how to clients, but a client is better positioned to decide whether and how
fabricate or construct an attribute or whether to do without the to fabricate or construct an attribute or whether to do without the
attribute. attribute.
5.3. Named Attributes 5.3. Named Attributes
These attributes are not supported by direct encoding in the NFSv4 These attributes are not supported by direct encoding in the NFSv4
protocol but are accessed by string names rather than numbers and protocol but are accessed by string names rather than numbers and
correspond to an uninterpreted stream of bytes which are stored with correspond to an uninterpreted stream of bytes that are stored with
the file system object. The name space for these attributes may be the file system object. The name space for these attributes may be
accessed by using the OPENATTR operation. The OPENATTR operation accessed by using the OPENATTR operation. The OPENATTR operation
returns a filehandle for a virtual "named attribute directory" and returns a filehandle for a virtual "named attribute directory", and
further perusal and modification of the name space may be done using further perusal and modification of the name space may be done using
operations that work on more typical directories. In particular, operations that work on more typical directories. In particular,
READDIR may be used to get a list of such named attributes and LOOKUP READDIR may be used to get a list of such named attributes, and
and OPEN may select a particular attribute. Creation of a new named LOOKUP and OPEN may select a particular attribute. Creation of a new
attribute may be the result of an OPEN specifying file creation. named attribute may be the result of an OPEN specifying file
creation.
Once an OPEN is done, named attributes may be examined and changed by Once an OPEN is done, named attributes may be examined and changed by
normal READ and WRITE operations using the filehandles and stateids normal READ and WRITE operations using the filehandles and stateids
returned by OPEN. returned by OPEN.
Named attributes and the named attribute directory may have their own Named attributes and the named attribute directory may have their own
(non-named) attributes. Each of these objects MUST have all of the (non-named) attributes. Each of these objects MUST have all of the
REQUIRED attributes and may have additional RECOMMENDED attributes. REQUIRED attributes and may have additional RECOMMENDED attributes.
However, the set of attributes for named attributes and the named However, the set of attributes for named attributes and the named
attribute directory need not be as large as, and typically will not attribute directory need not be, and typically will not be, as large
be as large as that for other objects in that file system. as that for other objects in that file system.
Named attributes and the named attribute directory may be the target Named attributes and the named attribute directory might be the
of delegations (in the case of the named attribute directory these target of delegations (in the case of the named attribute directory,
will be directory delegations). However, since granting of these will be directory delegations). However, since granting
delegations or not is within the server's discretion, a server need delegations is at the server's discretion, a server need not support
not support delegations on named attributes or the named attribute delegations on named attributes or the named attribute directory.
directory.
It is RECOMMENDED that servers support arbitrary named attributes. A It is RECOMMENDED that servers support arbitrary named attributes. A
client should not depend on the ability to store any named attributes client should not depend on the ability to store any named attributes
in the server's file system. If a server does support named in the server's file system. If a server does support named
attributes, a client which is also able to handle them should be able attributes, a client that is also able to handle them should be able
to copy a file's data and metadata with complete transparency from to copy a file's data and metadata with complete transparency from
one location to another; this would imply that names allowed for one location to another; this would imply that names allowed for
regular directory entries are valid for named attribute names as regular directory entries are valid for named attribute names as
well. well.
In NFSv4.1, the structure of named attribute directories is In NFSv4.1, the structure of named attribute directories is
restricted in a number of ways, in order to prevent the development restricted in a number of ways, in order to prevent the development
of non-interoperable implementations in which some servers support a of non-interoperable implementations in which some servers support a
fully general hierarchical directory structure for named attributes fully general hierarchical directory structure for named attributes
while others support a limited set, but fully adequate to the while others support a limited but adequate structure for named
feature's goals. In such an environment, clients or applications attributes. In such an environment, clients or applications might
might come to depend on non-portable extensions. The restrictions come to depend on non-portable extensions. The restrictions are:
are:
o CREATE is not allowed in a named attribute directory. Thus, such o CREATE is not allowed in a named attribute directory. Thus, such
objects as symbolic links and special files are not allowed to be objects as symbolic links and special files are not allowed to be
named attributes. Further, directories may not be created in a named attributes. Further, directories may not be created in a
named attribute directory so no hierarchical structure of named named attribute directory, so no hierarchical structure of named
attributes for a single object is allowed. attributes for a single object is allowed.
o If OPENATTR is done on a named attribute directory or on a named o If OPENATTR is done on a named attribute directory or on a named
attribute, the server MUST return NFS4ERR_WRONG_TYPE. attribute, the server MUST return NFS4ERR_WRONG_TYPE.
o Doing a RENAME of a named attribute to a different named attribute o Doing a RENAME of a named attribute to a different named attribute
directory or to an ordinary (i.e. non-named-attribute) directory directory or to an ordinary (i.e., non-named-attribute) directory
is not allowed. is not allowed.
o Creating hard links between named attribute directories or between o Creating hard links between named attribute directories or between
named attribute directories and ordinary directories is not named attribute directories and ordinary directories is not
allowed. allowed.
Names of attributes will not be controlled by this document or other Names of attributes will not be controlled by this document or other
IETF standards track documents. See Section 22.1 for further IETF Standards Track documents. See Section 22.1 for further
discussion. discussion.
5.4. Classification of Attributes 5.4. Classification of Attributes
Each of the REQUIRED and RECOMMENDED attributes can be classified in Each of the REQUIRED and RECOMMENDED attributes can be classified in
one of three categories: per server (i.e. the value of the attribute one of three categories: per server (i.e., the value of the attribute
will be the same for all file objects that share the same server will be the same for all file objects that share the same server
owner; see Section 2.5 for a definition of server owner), per file owner; see Section 2.5 for a definition of server owner), per file
system (i.e. the value of the attribute will be the same for some or system (i.e., the value of the attribute will be the same for some or
all file objects that share the same fsid attribute (Section 5.8.1.9) all file objects that share the same fsid attribute (Section 5.8.1.9)
and Server Owner), or per file system object. Note that it is and server owner), or per file system object. Note that it is
possible that some per file system attributes may vary within the possible that some per file system attributes may vary within the
file system, depending on the value of the "homogeneous" file system, depending on the value of the "homogeneous"
(Section 5.8.2.16) attribute. Note that the attributes (Section 5.8.2.16) attribute. Note that the attributes
time_access_set and time_modify_set are not listed in this section time_access_set and time_modify_set are not listed in this section
because they are write-only attributes corresponding to time_access because they are write-only attributes corresponding to time_access
and time_modify, and are used in a special instance of SETATTR. and time_modify, and are used in a special instance of SETATTR.
o The per server attribute is: o The per-server attribute is:
lease_time lease_time
o The per file system attributes are: o The per-file system attributes are:
supported_attrs, suppattr_exclcreat, fh_expire_type, supported_attrs, suppattr_exclcreat, fh_expire_type,
link_support, symlink_support, unique_handles, aclsupport, link_support, symlink_support, unique_handles, aclsupport,
cansettime, case_insensitive, case_preserving, cansettime, case_insensitive, case_preserving,
chown_restricted, files_avail, files_free, files_total, chown_restricted, files_avail, files_free, files_total,
fs_locations, homogeneous, maxfilesize, maxname, maxread, fs_locations, homogeneous, maxfilesize, maxname, maxread,
maxwrite, no_trunc, space_avail, space_free, space_total, maxwrite, no_trunc, space_avail, space_free, space_total,
time_delta, change_policy, fs_status, fs_layout_type, time_delta, change_policy, fs_status, fs_layout_type,
fs_locations_info, fs_charset_cap fs_locations_info, fs_charset_cap
o The per file system object attributes are: o The per-file system object attributes are:
type, change, size, named_attr, fsid, rdattr_error, filehandle, type, change, size, named_attr, fsid, rdattr_error, filehandle,
acl, archive, fileid, hidden, maxlink, mimetype, mode, acl, archive, fileid, hidden, maxlink, mimetype, mode,
numlinks, owner, owner_group, rawdev, space_used, system, numlinks, owner, owner_group, rawdev, space_used, system,
time_access, time_backup, time_create, time_metadata, time_access, time_backup, time_create, time_metadata,
time_modify, mounted_on_fileid, dir_notif_delay, time_modify, mounted_on_fileid, dir_notif_delay,
dirent_notif_delay, dacl, sacl, layout_type, layout_hint, dirent_notif_delay, dacl, sacl, layout_type, layout_hint,
layout_blksize, layout_alignment, mdsthreshold, retention_get, layout_blksize, layout_alignment, mdsthreshold, retention_get,
retention_set, retentevt_get, retentevt_set, retention_hold, retention_set, retentevt_get, retentevt_set, retention_hold,
mode_set_masked mode_set_masked
For quota_avail_hard, quota_avail_soft, and quota_used see their For quota_avail_hard, quota_avail_soft, and quota_used, see their
definitions below for the appropriate classification. definitions below for the appropriate classification.
5.5. Set-Only and Get-Only Attributes 5.5. Set-Only and Get-Only Attributes
Some REQUIRED and RECOMMENDED attributes are set-only, i.e. they can Some REQUIRED and RECOMMENDED attributes are set-only; i.e., they can
be set via SETATTR but not retrieved via GETATTR. Similarly, some be set via SETATTR but not retrieved via GETATTR. Similarly, some
REQUIRED and RECOMMENDED attributes are get-only, i.e. they can be REQUIRED and RECOMMENDED attributes are get-only; i.e., they can be
retrieved GETATTR but not set via SETATTR. If a client attempts to retrieved via GETATTR but not set via SETATTR. If a client attempts
set a get-only attribute or get a set-only attributes, the server to set a get-only attribute or get a set-only attributes, the server
MUST return NFS4ERR_INVAL. MUST return NFS4ERR_INVAL.
5.6. REQUIRED Attributes - List and Definition References 5.6. REQUIRED Attributes - List and Definition References
The list of REQUIRED attributes appears in Table 2. The meaning of The list of REQUIRED attributes appears in Table 2. The meaning of
the columns of the table are: the columns of the table are:
o Name: the name of attribute o Name: The name of the attribute.
o Id: the number assigned to the attribute. In the event of o Id: The number assigned to the attribute. In the event of
conflicts between the assigned number and [13], the latter is conflicts between the assigned number and [13], the latter is
likely authoritative, but should be resolved with Errata to this likely authoritative, but should be resolved with Errata to this
document and/or [13]. See [44] for the Errata process. document and/or [13]. See [44] for the Errata process.
o Data Type: The XDR data type of the attribute. o Data Type: The XDR data type of the attribute.
o Acc: Access allowed to the attribute. R means read-only (GETATTR o Acc: Access allowed to the attribute. R means read-only (GETATTR
may retrieve, SETATTR may not set). W means write-only (SETATTR may retrieve, SETATTR may not set). W means write-only (SETATTR
may set, GETATTR may not retrieve). R W means read/write (GETATTR may set, GETATTR may not retrieve). R W means read/write (GETATTR
may retrieve, SETATTR may set). may retrieve, SETATTR may set).
o Defined in: the section of this specification that describes the o Defined in: The section of this specification that describes the
attribute. attribute.
+--------------------+----+------------+-----+------------------+ +--------------------+----+------------+-----+------------------+
| Name | Id | Data Type | Acc | Defined in: | | Name | Id | Data Type | Acc | Defined in: |
+--------------------+----+------------+-----+------------------+ +--------------------+----+------------+-----+------------------+
| supported_attrs | 0 | bitmap4 | R | Section 5.8.1.1 | | supported_attrs | 0 | bitmap4 | R | Section 5.8.1.1 |
| type | 1 | nfs_ftype4 | R | Section 5.8.1.2 | | type | 1 | nfs_ftype4 | R | Section 5.8.1.2 |
| fh_expire_type | 2 | uint32_t | R | Section 5.8.1.3 | | fh_expire_type | 2 | uint32_t | R | Section 5.8.1.3 |
| change | 3 | uint64_t | R | Section 5.8.1.4 | | change | 3 | uint64_t | R | Section 5.8.1.4 |
| size | 4 | uint64_t | R W | Section 5.8.1.5 | | size | 4 | uint64_t | R W | Section 5.8.1.5 |
skipping to change at page 112, line 4 skipping to change at page 111, line 21
| time_access_set | 48 | settime4 | W | Section 5.8.2.38 | | time_access_set | 48 | settime4 | W | Section 5.8.2.38 |
| time_backup | 49 | nfstime4 | R W | Section 5.8.2.39 | | time_backup | 49 | nfstime4 | R W | Section 5.8.2.39 |
| time_create | 50 | nfstime4 | R W | Section 5.8.2.40 | | time_create | 50 | nfstime4 | R W | Section 5.8.2.40 |
| time_delta | 51 | nfstime4 | R | Section 5.8.2.41 | | time_delta | 51 | nfstime4 | R | Section 5.8.2.41 |
| time_metadata | 52 | nfstime4 | R | Section 5.8.2.42 | | time_metadata | 52 | nfstime4 | R | Section 5.8.2.42 |
| time_modify | 53 | nfstime4 | R | Section 5.8.2.43 | | time_modify | 53 | nfstime4 | R | Section 5.8.2.43 |
| time_modify_set | 54 | settime4 | W | Section 5.8.2.44 | | time_modify_set | 54 | settime4 | W | Section 5.8.2.44 |
+--------------------+----+----------------+-----+------------------+ +--------------------+----+----------------+-----+------------------+
Table 3 Table 3
* fs_locations_info4 * fs_locations_info4
5.8. Attribute Definitions 5.8. Attribute Definitions
5.8.1. Definitions of REQUIRED Attributes 5.8.1. Definitions of REQUIRED Attributes
5.8.1.1. Attribute 0: supported_attrs 5.8.1.1. Attribute 0: supported_attrs
The bit vector which would retrieve all REQUIRED and RECOMMENDED The bit vector that would retrieve all REQUIRED and RECOMMENDED
attributes that are supported for this object. The scope of this attributes that are supported for this object. The scope of this
attribute applies to all objects with a matching fsid. attribute applies to all objects with a matching fsid.
5.8.1.2. Attribute 1: type 5.8.1.2. Attribute 1: type
Designates the type of an object in terms of one of a number of Designates the type of an object in terms of one of a number of
special constants: special constants:
o NF4REG designates a regular file. o NF4REG designates a regular file.
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o NF4FIFO designates a fifo special file. o NF4FIFO designates a fifo special file.
o NF4ATTRDIR designates a named attribute directory. o NF4ATTRDIR designates a named attribute directory.
o NF4NAMEDATTR designates a named attribute. o NF4NAMEDATTR designates a named attribute.
Within the explanatory text and operation descriptions, the following Within the explanatory text and operation descriptions, the following
phrases will be used with the meanings given below: phrases will be used with the meanings given below:
o The phrase "is a directory" means that the object is of type o The phrase "is a directory" means that the object's type attribute
NF4DIR or of type NF4ATTRDIR. is NF4DIR or NF4ATTRDIR.
o The phrase "is a special file" means that the object is of one of o The phrase "is a special file" means that the object's type
the types NF4BLK, NF4CHR, NF4SOCK, or NF4FIFO. attribute is NF4BLK, NF4CHR, NF4SOCK, or NF4FIFO.
o The phrase "is an ordinary file" means that the object is of type o The phrases "is an ordinary file" and "is a regular file" mean
NF4REG or of type NF4NAMEDATTR. that the object's type attribute is NF4REG or NF4NAMEDATTR.
5.8.1.3. Attribute 2: fh_expire_type 5.8.1.3. Attribute 2: fh_expire_type
Server uses this to specify filehandle expiration behavior to the Server uses this to specify filehandle expiration behavior to the
client. See Section 4 for additional description. client. See Section 4 for additional description.
5.8.1.4. Attribute 3: change 5.8.1.4. Attribute 3: change
A value created by the server that the client can use to determine if A value created by the server that the client can use to determine if
file data, directory contents or attributes of the object have been file data, directory contents, or attributes of the object have been
modified. The server may return the object's time_metadata attribute modified. The server may return the object's time_metadata attribute
for this attribute's value but only if the file system object can not for this attribute's value, but only if the file system object cannot
be updated more frequently than the resolution of time_metadata. be updated more frequently than the resolution of time_metadata.
5.8.1.5. Attribute 4: size 5.8.1.5. Attribute 4: size
The size of the object in bytes. The size of the object in bytes.
5.8.1.6. Attribute 5: link_support 5.8.1.6. Attribute 5: link_support
True, if the object's file system supports hard links. TRUE, if the object's file system supports hard links.
5.8.1.7. Attribute 6: symlink_support 5.8.1.7. Attribute 6: symlink_support
True, if the object's file system supports symbolic links. TRUE, if the object's file system supports symbolic links.
5.8.1.8. Attribute 7: named_attr 5.8.1.8. Attribute 7: named_attr
True, if this object has named attributes. In other words, object TRUE, if this object has named attributes. In other words, object
has a non-empty named attribute directory. has a non-empty named attribute directory.
5.8.1.9. Attribute 8: fsid 5.8.1.9. Attribute 8: fsid
Unique file system identifier for the file system holding this Unique file system identifier for the file system holding this
object. fsid contains major and minor components each of which are of object. The fsid attribute has major and minor components, each of
data type uint64_t. which are of data type uint64_t.
5.8.1.10. Attribute 9: unique_handles 5.8.1.10. Attribute 9: unique_handles
True, if two distinct filehandles guaranteed to refer to two TRUE, if two distinct filehandles are guaranteed to refer to two
different file system objects. different file system objects.
5.8.1.11. Attribute 10: lease_time 5.8.1.11. Attribute 10: lease_time
Duration of leases at server in seconds. Duration of the lease at server in seconds.
5.8.1.12. Attribute 11: rdattr_error 5.8.1.12. Attribute 11: rdattr_error
Error returned from an attempt to retrieve attributes during a Error returned from an attempt to retrieve attributes during a
READDIR operation. READDIR operation.
5.8.1.13. Attribute 19: filehandle 5.8.1.13. Attribute 19: filehandle
The filehandle of this object (primarily for READDIR requests). The filehandle of this object (primarily for READDIR requests).
5.8.1.14. Attribute 75: suppattr_exclcreat 5.8.1.14. Attribute 75: suppattr_exclcreat
The bit vector which would set all REQUIRED and RECOMMENDED The bit vector that would set all REQUIRED and RECOMMENDED attributes
attributes that are supported by the EXCLUSIVE4_1 method of file that are supported by the EXCLUSIVE4_1 method of file creation via
creation via the OPEN operation. The scope of this attribute applies the OPEN operation. The scope of this attribute applies to all
to all objects with a matching fsid. objects with a matching fsid.
5.8.2. Definitions of Uncategorized RECOMMENDED Attributes 5.8.2. Definitions of Uncategorized RECOMMENDED Attributes
The definitions of most of the RECOMMENDED attributes follow. The definitions of most of the RECOMMENDED attributes follow.
Collections that share a common category are defined in other Collections that share a common category are defined in other
sections. sections.
5.8.2.1. Attribute 14: archive 5.8.2.1. Attribute 14: archive
True, if this file has been archived since the time of last TRUE, if this file has been archived since the time of last
modification (deprecated in favor of time_backup). modification (deprecated in favor of time_backup).
5.8.2.2. Attribute 15: cansettime 5.8.2.2. Attribute 15: cansettime
True, if the server able to change the times for a file system object TRUE, if the server is able to change the times for a file system
as specified in a SETATTR operation. object as specified in a SETATTR operation.
5.8.2.3. Attribute 16: case_insensitive 5.8.2.3. Attribute 16: case_insensitive
True, if file name comparisons on this file system are case TRUE, if file name comparisons on this file system are case
insensitive. insensitive.
5.8.2.4. Attribute 17: case_preserving 5.8.2.4. Attribute 17: case_preserving
True, if file name case on this file system is preserved. TRUE, if file name case on this file system is preserved.
5.8.2.5. Attribute 60: change_policy 5.8.2.5. Attribute 60: change_policy
A value created by the server that the client can use to determine if A value created by the server that the client can use to determine if
some server policy related to the current file system has been some server policy related to the current file system has been
subject to change. If the value remains the same then the client can subject to change. If the value remains the same, then the client
be sure that the values of the attributes related to fs location and can be sure that the values of the attributes related to fs location
the fss_type field of the fs_status attribute have not changed. On and the fss_type field of the fs_status attribute have not changed.
the other hand, a change in this value does necessarily imply a On the other hand, a change in this value does necessarily imply a
change in policy. It is up to the client to interrogate the server change in policy. It is up to the client to interrogate the server
to determine if some policy relevant to it has changed. See to determine if some policy relevant to it has changed. See
Section 3.3.6 for details. Section 3.3.6 for details.
This attribute MUST change when the value returned by the This attribute MUST change when the value returned by the
fs_locations or fs_locations_info attribute changes, when a file fs_locations or fs_locations_info attribute changes, when a file
system goes from read-only to writable or vice versa, or when the system goes from read-only to writable or vice versa, or when the
allowable set of security flavors for the file system or any part allowable set of security flavors for the file system or any part
thereof is changed. thereof is changed.
5.8.2.6. Attribute 18: chown_restricted 5.8.2.6. Attribute 18: chown_restricted
If TRUE, the server will reject any request to change either the If TRUE, the server will reject any request to change either the
owner or the group associated with a file if the caller is not a owner or the group associated with a file if the caller is not a
privileged user (for example, "root" in UNIX operating environments privileged user (for example, "root" in UNIX operating environments
or in Windows 2000 the "Take Ownership" privilege). or, in Windows 2000, the "Take Ownership" privilege).
5.8.2.7. Attribute 20: fileid 5.8.2.7. Attribute 20: fileid
A number uniquely identifying the file within the file system. A number uniquely identifying the file within the file system.
5.8.2.8. Attribute 21: files_avail 5.8.2.8. Attribute 21: files_avail
File slots available to this user on the file system containing this File slots available to this user on the file system containing this
object - this should be the smallest relevant limit. object -- this should be the smallest relevant limit.
5.8.2.9. Attribute 22: files_free 5.8.2.9. Attribute 22: files_free
Free file slots on the file system containing this object - this Free file slots on the file system containing this object -- this
should be the smallest relevant limit. should be the smallest relevant limit.
5.8.2.10. Attribute 23: files_total 5.8.2.10. Attribute 23: files_total
Total file slots on the file system containing this object. Total file slots on the file system containing this object.
5.8.2.11. Attribute 76: fs_charset_cap 5.8.2.11. Attribute 76: fs_charset_cap
Character set capabilities for this file system. See Section 14.4. Character set capabilities for this file system. See Section 14.4.
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Full function file system location. See Section 11.10 for more Full function file system location. See Section 11.10 for more
details. details.
5.8.2.14. Attribute 61: fs_status 5.8.2.14. Attribute 61: fs_status
Generic file system type information. See Section 11.11 for more Generic file system type information. See Section 11.11 for more
details. details.
5.8.2.15. Attribute 25: hidden 5.8.2.15. Attribute 25: hidden
True, if the file is considered hidden with respect to the Windows TRUE, if the file is considered hidden with respect to the Windows
API. API.
5.8.2.16. Attribute 26: homogeneous 5.8.2.16. Attribute 26: homogeneous
True, if this object's file system is homogeneous, i.e. are per file TRUE, if this object's file system is homogeneous; i.e., all objects
system attributes the same for all file system's objects. in the file system (all objects on the server with the same fsid)
have common values for all per-file-system attributes.
5.8.2.17. Attribute 27: maxfilesize 5.8.2.17. Attribute 27: maxfilesize
Maximum supported file size for the file system of this object. Maximum supported file size for the file system of this object.
5.8.2.18. Attribute 28: maxlink 5.8.2.18. Attribute 28: maxlink
Maximum number of links for this object. Maximum number of links for this object.
5.8.2.19. Attribute 29: maxname 5.8.2.19. Attribute 29: maxname
Maximum file name size supported for this object. Maximum file name size supported for this object.
5.8.2.20. Attribute 30: maxread 5.8.2.20. Attribute 30: maxread
Maximum read size supported for this object. Maximum amount of data the READ operation will return for this
object.
5.8.2.21. Attribute 31: maxwrite 5.8.2.21. Attribute 31: maxwrite
Maximum write size supported for this object. This attribute SHOULD Maximum amount of data the WRITE operation will accept for this
be supported if the file is writable. Lack of this attribute can object. This attribute SHOULD be supported if the file is writable.
lead to the client either wasting bandwidth or not receiving the best Lack of this attribute can lead to the client either wasting
performance. bandwidth or not receiving the best performance.
5.8.2.22. Attribute 32: mimetype 5.8.2.22. Attribute 32: mimetype
MIME body type/subtype of this object. MIME body type/subtype of this object.
5.8.2.23. Attribute 55: mounted_on_fileid 5.8.2.23. Attribute 55: mounted_on_fileid
Like fileid, but if the target filehandle is the root of a file Like fileid, but if the target filehandle is the root of a file
system, this attribute represents the fileid of the underlying system, this attribute represents the fileid of the underlying
directory. directory.
UNIX-based operating environments connect a file system into the UNIX-based operating environments connect a file system into the
namespace by connecting (mounting) the file system onto the existing namespace by connecting (mounting) the file system onto the existing
file object (the mount point, usually a directory) of an existing file object (the mount point, usually a directory) of an existing
file system. When the mount point's parent directory is read via an file system. When the mount point's parent directory is read via an
API like readdir(), the return results are directory entries, each API like readdir(), the return results are directory entries, each
with a component name and a fileid. The fileid of the mount point's with a component name and a fileid. The fileid of the mount point's
directory entry will be different from the fileid that the stat() directory entry will be different from the fileid that the stat()
system call returns. The stat() system call is returning the fileid system call returns. The stat() system call is returning the fileid
of the root of the mounted file system, whereas readdir() is of the root of the mounted file system, whereas readdir() is
returning the fileid stat() would have returned before any file returning the fileid that stat() would have returned before any file
systems were mounted on the mount point. systems were mounted on the mount point.
Unlike NFSv3, NFSv4.1 allows a client's LOOKUP request to cross other Unlike NFSv3, NFSv4.1 allows a client's LOOKUP request to cross other
file systems. The client detects the file system crossing whenever file systems. The client detects the file system crossing whenever
the filehandle argument of LOOKUP has an fsid attribute different the filehandle argument of LOOKUP has an fsid attribute different
from that of the filehandle returned by LOOKUP. A UNIX-based client from that of the filehandle returned by LOOKUP. A UNIX-based client
will consider this a "mount point crossing". UNIX has a legacy will consider this a "mount point crossing". UNIX has a legacy
scheme for allowing a process to determine its current working scheme for allowing a process to determine its current working
directory. This relies on readdir() of a mount point's parent and directory. This relies on readdir() of a mount point's parent and
stat() of the mount point returning fileids as previously described. stat() of the mount point returning fileids as previously described.
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the same as that of the fileid attribute. the same as that of the fileid attribute.
The mounted_on_fileid attribute is RECOMMENDED, so the server SHOULD The mounted_on_fileid attribute is RECOMMENDED, so the server SHOULD
provide it if possible, and for a UNIX-based server, this is provide it if possible, and for a UNIX-based server, this is
straightforward. Usually, mounted_on_fileid will be requested during straightforward. Usually, mounted_on_fileid will be requested during
a READDIR operation, in which case it is trivial (at least for UNIX- a READDIR operation, in which case it is trivial (at least for UNIX-
based servers) to return mounted_on_fileid since it is equal to the based servers) to return mounted_on_fileid since it is equal to the
fileid of a directory entry returned by readdir(). If fileid of a directory entry returned by readdir(). If
mounted_on_fileid is requested in a GETATTR operation, the server mounted_on_fileid is requested in a GETATTR operation, the server
should obey an invariant that has it returning a value that is equal should obey an invariant that has it returning a value that is equal
to the file object's entry in the object's parent directory, i.e. to the file object's entry in the object's parent directory, i.e.,
what readdir() would have returned. Some operating environments what readdir() would have returned. Some operating environments
allow a series of two or more file systems to be mounted onto a allow a series of two or more file systems to be mounted onto a
single mount point. In this case, for the server to obey the single mount point. In this case, for the server to obey the
aforementioned invariant, it will need to find the base mount point, aforementioned invariant, it will need to find the base mount point,
and not the intermediate mount points. and not the intermediate mount points.
5.8.2.24. Attribute 34: no_trunc 5.8.2.24. Attribute 34: no_trunc
If this attribute is TRUE, then if the client uses a file name longer If this attribute is TRUE, then if the client uses a file name longer
than name_max, an error will be returned instead of the name being than name_max, an error will be returned instead of the name being
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5.8.2.26. Attribute 36: owner 5.8.2.26. Attribute 36: owner
The string name of the owner of this object. The string name of the owner of this object.
5.8.2.27. Attribute 37: owner_group 5.8.2.27. Attribute 37: owner_group
The string name of the group ownership of this object. The string name of the group ownership of this object.
5.8.2.28. Attribute 38: quota_avail_hard 5.8.2.28. Attribute 38: quota_avail_hard
The value in bytes which represents the amount of additional disk The value in bytes that represents the amount of additional disk
space beyond the current allocation that can be allocated to this space beyond the current allocation that can be allocated to this
file or directory before further allocations will be refused. It is file or directory before further allocations will be refused. It is
understood that this space may be consumed by allocations to other understood that this space may be consumed by allocations to other
files or directories. files or directories.
5.8.2.29. Attribute 39: quota_avail_soft 5.8.2.29. Attribute 39: quota_avail_soft
The value in bytes which represents the amount of additional disk The value in bytes that represents the amount of additional disk
space that can be allocated to this file or directory before the user space that can be allocated to this file or directory before the user
may reasonably be warned. It is understood that this space may be may reasonably be warned. It is understood that this space may be
consumed by allocations to other files or directories though there is consumed by allocations to other files or directories though there is
a rule as to which other files or directories. a rule as to which other files or directories.
5.8.2.30. Attribute 40: quota_used 5.8.2.30. Attribute 40: quota_used
The value in bytes which represent the amount of disc space used by The value in bytes that represents the amount of disk space used by
this file or directory and possibly a number of other similar files this file or directory and possibly a number of other similar files
or directories, where the set of "similar" meets at least the or directories, where the set of "similar" meets at least the
criterion that allocating space to any file or directory in the set criterion that allocating space to any file or directory in the set
will reduce the "quota_avail_hard" of every other file or directory will reduce the "quota_avail_hard" of every other file or directory
in the set. in the set.
Note that there may be a number of distinct but overlapping sets of Note that there may be a number of distinct but overlapping sets of
files or directories for which a quota_used value is maintained. files or directories for which a quota_used value is maintained,
E.g. "all files with a given owner", "all files with a given group e.g., "all files with a given owner", "all files with a given group
owner". etc. The server is at liberty to choose any of those sets owner", etc. The server is at liberty to choose any of those sets
when providing the content of the quota_used attribute, but should do when providing the content of the quota_used attribute, but should do
so in a repeatable way. The rule may be configured per file system so in a repeatable way. The rule may be configured per file system
or may be "choose the set with the smallest quota". or may be "choose the set with the smallest quota".
5.8.2.31. Attribute 41: rawdev 5.8.2.31. Attribute 41: rawdev
Raw device identifier; the UNIX device major/minor node information. Raw device number of file of type NF4BLK or NF4CHR. The device
If the value of type is not NF4BLK or NF4CHR, the value returned number is split into major and minor numbers. If the file's type
SHOULD NOT be considered useful. attribute is not NF4BLK or NF4CHR, the value returned SHOULD NOT be
considered useful.
5.8.2.32. Attribute 42: space_avail 5.8.2.32. Attribute 42: space_avail
Disk space in bytes available to this user on the file system Disk space in bytes available to this user on the file system
containing this object - this should be the smallest relevant limit. containing this object -- this should be the smallest relevant limit.
5.8.2.33. Attribute 43: space_free 5.8.2.33. Attribute 43: space_free
Free disk space in bytes on the file system containing this object - Free disk space in bytes on the file system containing this object --
this should be the smallest relevant limit. this should be the smallest relevant limit.
5.8.2.34. Attribute 44: space_total 5.8.2.34. Attribute 44: space_total
Total disk space in bytes on the file system containing this object. Total disk space in bytes on the file system containing this object.
5.8.2.35. Attribute 45: space_used 5.8.2.35. Attribute 45: space_used
Number of file system bytes allocated to this object. Number of file system bytes allocated to this object.
5.8.2.36. Attribute 46: system 5.8.2.36. Attribute 46: system
This attribute is TRUE if this file is a "system" file with respect This attribute is TRUE if this file is a "system" file with respect
to the Windows operating environment. to the Windows operating environment.
5.8.2.37. Attribute 47: time_access 5.8.2.37. Attribute 47: time_access
The time_access attribute represents the time of last access to the The time_access attribute represents the time of last access to the
object by a read that was satisfied by the server. The notion of object by a READ operation sent to the server. The notion of what is
what is an "access" depends on server's operating environment and/or an "access" depends on the server's operating environment and/or the
the server's file system semantics. For example, for servers obeying server's file system semantics. For example, for servers obeying
POSIX semantics, time_access would be updated only by the READ and Portable Operating System Interface (POSIX) semantics, time_access
READDIR operations and not any of the operations that modify the would be updated only by the READ and READDIR operations and not any
content of the object [16], [17], [18]. Of course, setting the of the operations that modify the content of the object [16], [17],
corresponding time_access_set attribute is another way to modify the [18]. Of course, setting the corresponding time_access_set attribute
time_access attribute. is another way to modify the time_access attribute.
Whenever the file object resides on a writable file system, the Whenever the file object resides on a writable file system, the
server should make best efforts to record time_access into stable server should make its best efforts to record time_access into stable
storage. However, to mitigate the performance effects of doing so, storage. However, to mitigate the performance effects of doing so,
and most especially whenever the server is satisfying the read of the and most especially whenever the server is satisfying the read of the
object's content from its cache, the server MAY cache access time object's content from its cache, the server MAY cache access time
updates and lazily write them to stable storage. It is also updates and lazily write them to stable storage. It is also
acceptable to give administrators of the server the option to disable acceptable to give administrators of the server the option to disable
time_access updates. time_access updates.
5.8.2.38. Attribute 48: time_access_set 5.8.2.38. Attribute 48: time_access_set
Set the time of last access to the object. SETATTR use only. Sets the time of last access to the object. SETATTR use only.
5.8.2.39. Attribute 49: time_backup 5.8.2.39. Attribute 49: time_backup
The time of last backup of the object. The time of last backup of the object.
5.8.2.40. Attribute 50: time_create 5.8.2.40. Attribute 50: time_create
The time of creation of the object. This attribute does not have any The time of creation of the object. This attribute does not have any
relation to the traditional UNIX file attribute "ctime" or "change relation to the traditional UNIX file attribute "ctime" or "change
time". time".
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5.8.2.42. Attribute 52: time_metadata 5.8.2.42. Attribute 52: time_metadata
The time of last metadata modification of the object. The time of last metadata modification of the object.
5.8.2.43. Attribute 53: time_modify 5.8.2.43. Attribute 53: time_modify
The time of last modification to the object. The time of last modification to the object.
5.8.2.44. Attribute 54: time_modify_set 5.8.2.44. Attribute 54: time_modify_set
Set the time of last modification to the object. SETATTR use only. Sets the time of last modification to the object. SETATTR use only.
5.9. Interpreting owner and owner_group 5.9. Interpreting owner and owner_group
The RECOMMENDED attributes "owner" and "owner_group" (and also users The RECOMMENDED attributes "owner" and "owner_group" (and also users
and groups within the "acl" attribute) are represented in terms of a and groups within the "acl" attribute) are represented in terms of a
UTF-8 string. To avoid a representation that is tied to a particular UTF-8 string. To avoid a representation that is tied to a particular
underlying implementation at the client or server, the use of the underlying implementation at the client or server, the use of the
UTF-8 string has been chosen. Note that section 6.1 of RFC2624 [45] UTF-8 string has been chosen. Note that Section 6.1 of RFC 2624 [45]
provides additional rationale. It is expected that the client and provides additional rationale. It is expected that the client and
server will have their own local representation of owner and server will have their own local representation of owner and
owner_group that is used for local storage or presentation to the end owner_group that is used for local storage or presentation to the end
user. Therefore, it is expected that when these attributes are user. Therefore, it is expected that when these attributes are
transferred between the client and server that the local transferred between the client and server, the local representation
representation is translated to a syntax of the form "user@ is translated to a syntax of the form "user@dns_domain". This will
dns_domain". This will allow for a client and server that do not use allow for a client and server that do not use the same local
the same local representation the ability to translate to a common representation the ability to translate to a common syntax that can
syntax that can be interpreted by both. be interpreted by both.
Similarly, security principals may be represented in different ways Similarly, security principals may be represented in different ways
by different security mechanisms. Servers normally translate these by different security mechanisms. Servers normally translate these
representations into a common format, generally that used by local representations into a common format, generally that used by local
storage, to serve as a means of identifying the users corresponding storage, to serve as a means of identifying the users corresponding
to these security principals. When these local identifiers are to these security principals. When these local identifiers are
translated to the form of the owner attribute, associated with files translated to the form of the owner attribute, associated with files
created by such principals they identify, in a common format, the created by such principals, they identify, in a common format, the
users associated with each corresponding set of security principals. users associated with each corresponding set of security principals.
The translation used to interpret owner and group strings is not The translation used to interpret owner and group strings is not
specified as part of the protocol. This allows various solutions to specified as part of the protocol. This allows various solutions to
be employed. For example, a local translation table may be consulted be employed. For example, a local translation table may be consulted
that maps between a numeric identifier to the user@dns_domain syntax. that maps a numeric identifier to the user@dns_domain syntax. A name
A name service may also be used to accomplish the translation. A service may also be used to accomplish the translation. A server may
server may provide a more general service, not limited by any provide a more general service, not limited by any particular
particular translation (which would only translate a limited set of translation (which would only translate a limited set of possible
possible strings) by storing the owner and owner_group attributes in strings) by storing the owner and owner_group attributes in local
local storage without any translation or it may augment a translation storage without any translation or it may augment a translation
method by storing the entire string for attributes for which no method by storing the entire string for attributes for which no
translation is available while using the local representation for translation is available while using the local representation for
those cases in which a translation is available. those cases in which a translation is available.
Servers that do not provide support for all possible values of the Servers that do not provide support for all possible values of the
owner and owner_group attributes, SHOULD return an error owner and owner_group attributes SHOULD return an error
(NFS4ERR_BADOWNER) when a string is presented that has no (NFS4ERR_BADOWNER) when a string is presented that has no
translation, as the value to be set for a SETATTR of the owner, translation, as the value to be set for a SETATTR of the owner,
owner_group, or acl attributes. When a server does accept an owner owner_group, or acl attributes. When a server does accept an owner
or owner_group value as valid on a SETATTR (and similarly for the or owner_group value as valid on a SETATTR (and similarly for the
owner and group strings in an acl), it is promising to return that owner and group strings in an acl), it is promising to return that
same string when a corresponding GETATTR is done. Configuration same string when a corresponding GETATTR is done. Configuration
changes (including changes from the mapping of the string to the changes (including changes from the mapping of the string to the
local representation) and ill-constructed name translations (those local representation) and ill-constructed name translations (those
that contain aliasing) may make that promise impossible to honor. that contain aliasing) may make that promise impossible to honor.
Servers should make appropriate efforts to avoid a situation in which Servers should make appropriate efforts to avoid a situation in which
these attributes have their values changed when no real change to these attributes have their values changed when no real change to
ownership has occurred. ownership has occurred.
The "dns_domain" portion of the owner string is meant to be a DNS The "dns_domain" portion of the owner string is meant to be a DNS
domain name. For example, user@example.org. Servers should accept domain name, for example, user@example.org. Servers should accept as
as valid a set of users for at least one domain. A server may treat valid a set of users for at least one domain. A server may treat
other domains as having no valid translations. A more general other domains as having no valid translations. A more general
service is provided when a server is capable of accepting users for service is provided when a server is capable of accepting users for
multiple domains, or for all domains, subject to security multiple domains, or for all domains, subject to security
constraints. constraints.
In the case where there is no translation available to the client or In the case where there is no translation available to the client or
server, the attribute value will be constructed without the "@". server, the attribute value will be constructed without the "@".
Therefore, the absence of the @ from the owner or owner_group Therefore, the absence of the @ from the owner or owner_group
attribute signifies that no translation was available at the sender attribute signifies that no translation was available at the sender
and that the receiver of the attribute should not use that string as and that the receiver of the attribute should not use that string as
a basis for translation into its own internal format. Even though a basis for translation into its own internal format. Even though
the attribute value can not be translated, it may still be useful. the attribute value cannot be translated, it may still be useful. In
In the case of a client, the attribute string may be used for local the case of a client, the attribute string may be used for local
display of ownership. display of ownership.
To provide a greater degree of compatibility with NFSv3, which To provide a greater degree of compatibility with NFSv3, which
identified users and groups by 32-bit unsigned user identifiers and identified users and groups by 32-bit unsigned user identifiers and
group identifiers, owner and group strings that consist of decimal group identifiers, owner and group strings that consist of decimal
numeric values with no leading zeros can be given a special numeric values with no leading zeros can be given a special
interpretation by clients and servers which choose to provide such interpretation by clients and servers that choose to provide such
support. The receiver may treat such a user or group string as support. The receiver may treat such a user or group string as
representing the same user as would be represented by an NFSv3 uid or representing the same user as would be represented by an NFSv3 uid or
gid having the corresponding numeric value. A server is not gid having the corresponding numeric value. A server is not
obligated to accept such a string, but may return an NFS4ERR_BADOWNER obligated to accept such a string, but may return an NFS4ERR_BADOWNER
instead. To avoid this mechanism being used to subvert user and instead. To avoid this mechanism being used to subvert user and
group translation, so that a client might pass all of the owners and group translation, so that a client might pass all of the owners and
groups in numeric form, a server SHOULD return an NFS4ERR_BADOWNER groups in numeric form, a server SHOULD return an NFS4ERR_BADOWNER
error when there is a valid translation for the user or owner error when there is a valid translation for the user or owner
designated in this way. In that case, the client must use the designated in this way. In that case, the client must use the
appropriate name@domain string and not the special form for appropriate name@domain string and not the special form for
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layout_blksize, and WRITE operations with a data argument of size layout_blksize, and WRITE operations with a data argument of size
that is a whole multiple of layout_blksize. that is a whole multiple of layout_blksize.
5.12.4. Attribute 63: layout_hint 5.12.4. Attribute 63: layout_hint
The layout_hint attribute (see Section 3.3.19) may be set on newly The layout_hint attribute (see Section 3.3.19) may be set on newly
created files to influence the metadata server's choice for the created files to influence the metadata server's choice for the
file's layout. If possible, this attribute is one of those set in file's layout. If possible, this attribute is one of those set in
the initial attributes within the OPEN operation. The metadata the initial attributes within the OPEN operation. The metadata
server may choose to ignore this attribute. The layout_hint server may choose to ignore this attribute. The layout_hint
attribute is a sub-set of the layout structure returned by LAYOUTGET. attribute is a subset of the layout structure returned by LAYOUTGET.
For example, instead of specifying particular devices, this would be For example, instead of specifying particular devices, this would be
used to suggest the stripe width of a file. The server used to suggest the stripe width of a file. The server
implementation determines which fields within the layout will be implementation determines which fields within the layout will be
used. used.
5.12.5. Attribute 64: layout_type 5.12.5. Attribute 64: layout_type
This attribute lists the layout type(s) available for a file. The This attribute lists the layout type(s) available for a file. The
value returned by the server is for informational purposes only. The value returned by the server is for informational purposes only. The
client will use the LAYOUTGET operation to obtain the information client will use the LAYOUTGET operation to obtain the information
needed in order to perform I/O. For example, the specific device needed in order to perform I/O, for example, the specific device
information for the file and its layout. information for the file and its layout.
5.12.6. Attribute 68: mdsthreshold 5.12.6. Attribute 68: mdsthreshold
This attribute is a server provided hint used to communicate to the This attribute is a server-provided hint used to communicate to the
client when it is more efficient to send READ and WRITE operations to client when it is more efficient to send READ and WRITE operations to
the metadata server or the data server. The two types of thresholds the metadata server or the data server. The two types of thresholds
described are file size thresholds and I/O size thresholds. If a described are file size thresholds and I/O size thresholds. If a
file's size is smaller than the file size threshold, data accesses file's size is smaller than the file size threshold, data accesses
SHOULD be sent to the metadata server. If an I/O request has a SHOULD be sent to the metadata server. If an I/O request has a
length that is below the I/O size threshold, the I/O SHOULD be sent length that is below the I/O size threshold, the I/O SHOULD be sent
to the metadata server. Each threshold type is specified separately to the metadata server. Each threshold type is specified separately
for READ and WRITE. for read and write.
The server MAY provide both types of thresholds for a file. If both The server MAY provide both types of thresholds for a file. If both
file size and I/O size are provided, the client SHOULD reach or file size and I/O size are provided, the client SHOULD reach or
exceed both thresholds before sending its READ or WRITE operations to exceed both thresholds before sending its read or write requests to
the data server. Alternatively, if only one of the specified the data server. Alternatively, if only one of the specified
thresholds are reached or exceeded, the I/O requests are sent to the thresholds is reached or exceeded, the I/O requests are sent to the
metadata server. metadata server.
For each threshold type, a value of 0 indicates no READ or WRITE For each threshold type, a value of zero indicates no READ or WRITE
should be sent to the metadata server, while a value of all 1s should be sent to the metadata server, while a value of all ones
indicates all READS or WRITES should be sent to the metadata server. indicates that all READs or WRITEs should be sent to the metadata
server.
The attribute is available on a per filehandle basis. If the current The attribute is available on a per-filehandle basis. If the current
filehandle refers to a non-pNFS file or directory, the metadata filehandle refers to a non-pNFS file or directory, the metadata
server should return an attribute that is representative of the server should return an attribute that is representative of the
filehandle's file system. It is suggested that this attribute is filehandle's file system. It is suggested that this attribute is
queried as part of the OPEN operation. Due to dynamic system queried as part of the OPEN operation. Due to dynamic system
changes, the client should not assume that the attribute will remain changes, the client should not assume that the attribute will remain
constant for any specific time period, thus it should be periodically constant for any specific time period; thus, it should be
refreshed. periodically refreshed.
5.13. Retention Attributes 5.13. Retention Attributes
Retention is a concept whereby a file object can be placed in an Retention is a concept whereby a file object can be placed in an
immutable, undeletable, unrenamable state for a fixed or infinite immutable, undeletable, unrenamable state for a fixed or infinite
duration of time. Once in this "retained" state, the file cannot be duration of time. Once in this "retained" state, the file cannot be
moved out of the state until the duration of retention has been moved out of the state until the duration of retention has been
reached. reached.
When retention is enabled, retention MUST extend to the data of the When retention is enabled, retention MUST extend to the data of the
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If the client sets rs_enable to TRUE, then it is enabling retention If the client sets rs_enable to TRUE, then it is enabling retention
on the file object with the begin time of retention starting from the on the file object with the begin time of retention starting from the
server's current time and date. The duration of the retention can server's current time and date. The duration of the retention can
also be provided if the rs_duration array is of length one. The also be provided if the rs_duration array is of length one. The
duration is the time in seconds from the begin time of retention, and duration is the time in seconds from the begin time of retention, and
if set to RET4_DURATION_INFINITE, the file is to be retained forever. if set to RET4_DURATION_INFINITE, the file is to be retained forever.
If retention is enabled, with no duration specified in either this If retention is enabled, with no duration specified in either this
SETATTR or a previous SETATTR, the duration defaults to zero seconds. SETATTR or a previous SETATTR, the duration defaults to zero seconds.
The server MAY restrict the enabling of retention or the duration of The server MAY restrict the enabling of retention or the duration of
retention on the basis of the ACE4_WRITE_RETENTION ACL permission. retention on the basis of the ACE4_WRITE_RETENTION ACL permission.
The enabling of retention MUST NOT prevent the enabling of event- The enabling of retention MUST NOT prevent the enabling of event-
based retention nor the modification of the retention_hold attribute. based retention or the modification of the retention_hold attribute.
The following rules apply to both the retention_set and retentevt_set The following rules apply to both the retention_set and retentevt_set
attributes. attributes.
o As long as retention is not enabled, the client is permitted to o As long as retention is not enabled, the client is permitted to
decrease the duration. decrease the duration.
o The duration can always be set to an equal or higher value, even o The duration can always be set to an equal or higher value, even
if retention is enabled. Note that once retention is enabled, the if retention is enabled. Note that once retention is enabled, the
actual duration (as returned by the retention_get or retentevt_get actual duration (as returned by the retention_get or retentevt_get
attributes, see Section 5.13.1 or Section 5.13.3), is constantly attributes; see Section 5.13.1 or Section 5.13.3) is constantly
counting down to zero (one unit per second), unless the duration counting down to zero (one unit per second), unless the duration
was set to RET4_DURATION_INFINITE. Thus it will not be possible was set to RET4_DURATION_INFINITE. Thus, it will not be possible
for the client to precisely extend the duration on a file that has for the client to precisely extend the duration on a file that has
retention enabled. retention enabled.
o While retention is enabled, attempts to disable retention or o While retention is enabled, attempts to disable retention or
decrease the retention's duration MUST fail with the error decrease the retention's duration MUST fail with the error
NFS4ERR_INVAL. NFS4ERR_INVAL.
o If the principal attempting to change retention_set or o If the principal attempting to change retention_set or
retentevt_set does not have ACE4_WRITE_RETENTION permissions, the retentevt_set does not have ACE4_WRITE_RETENTION permissions, the
attempt MUST fail with NFS4ERR_ACCESS. attempt MUST fail with NFS4ERR_ACCESS.
5.13.3. Attribute 71: retentevt_get 5.13.3. Attribute 71: retentevt_get
Get the event-based retention duration, and if enabled, the event- Gets the event-based retention duration, and if enabled, the event-
based retention begin time of the file object. This attribute is based retention begin time of the file object. This attribute is
like retention_get but refers to event-based retention. The event like retention_get, but refers to event-based retention. The event
that triggers event-based retention is not defined by the NFSv4.1 that triggers event-based retention is not defined by the NFSv4.1
specification. specification.
5.13.4. Attribute 72: retentevt_set 5.13.4. Attribute 72: retentevt_set
Set the event-based retention duration, and optionally enable event- Sets the event-based retention duration, and optionally enables
based retention on the file object. This attribute corresponds to event-based retention on the file object. This attribute corresponds
retentevt_get, is like retention_set, but refers to event-based to retentevt_get and is like retention_set, but refers to event-based
retention. When event based retention is set, the file MUST be retention. When event-based retention is set, the file MUST be
retained even if non-event-based retention has been set, and the retained even if non-event-based retention has been set, and the
duration of non-event-based retention has been reached. Conversely, duration of non-event-based retention has been reached. Conversely,
when non-event-based retention has been set, the file MUST be when non-event-based retention has been set, the file MUST be
retained even if event-based retention has been set, and the duration retained even if event-based retention has been set, and the duration
of event-based retention has been reached. The server MAY restrict of event-based retention has been reached. The server MAY restrict
the enabling of event-based retention or the duration of event-based the enabling of event-based retention or the duration of event-based
retention on the basis of the ACE4_WRITE_RETENTION ACL permission. retention on the basis of the ACE4_WRITE_RETENTION ACL permission.
The enabling of event-based retention MUST NOT prevent the enabling The enabling of event-based retention MUST NOT prevent the enabling
of non-event-based retention nor the modification of the of non-event-based retention or the modification of the
retention_hold attribute. retention_hold attribute.
5.13.5. Attribute 73: retention_hold 5.13.5. Attribute 73: retention_hold
Get or set administrative retention holds, one hold per bit position. Gets or sets administrative retention holds, one hold per bit
position.
This attribute allows one to 64 administrative holds, one hold per This attribute allows one to 64 administrative holds, one hold per
bit on the attribute. If retention_hold is not zero, then the file bit on the attribute. If retention_hold is not zero, then the file
MUST NOT be deleted, renamed, or modified, even if the duration on MUST NOT be deleted, renamed, or modified, even if the duration on
enabled event or non-event-based retention has been reached. The enabled event or non-event-based retention has been reached. The
server MAY restrict the modification of retention_hold on the basis server MAY restrict the modification of retention_hold on the basis
of the ACE4_WRITE_RETENTION_HOLD ACL permission. The enabling of of the ACE4_WRITE_RETENTION_HOLD ACL permission. The enabling of
administration retention holds does not prevent the enabling of administration retention holds does not prevent the enabling of
event-based or non-event-based retention. event-based or non-event-based retention.
If the principal attempting to change retention_hold does not have If the principal attempting to change retention_hold does not have
ACE4_WRITE_RETENTION_HOLD permissions, the attempt MUST fail with ACE4_WRITE_RETENTION_HOLD permissions, the attempt MUST fail with
NFS4ERR_ACCESS. NFS4ERR_ACCESS.
6. Access Control Attributes 6. Access Control Attributes
Access Control Lists (ACLs) are file attributes that specify fine Access Control Lists (ACLs) are file attributes that specify fine-
grained access control. This chapter covers the "acl", "dacl", grained access control. This section covers the "acl", "dacl",
"sacl", "aclsupport", "mode", "mode_set_masked" file attributes, and "sacl", "aclsupport", "mode", and "mode_set_masked" file attributes
their interactions. Note that file attributes may apply to any file and their interactions. Note that file attributes may apply to any
system object. file system object.
6.1. Goals 6.1. Goals
ACLs and modes represent two well established models for specifying ACLs and modes represent two well-established models for specifying
permissions. This chapter specifies requirements that attempt to permissions. This section specifies requirements that attempt to
meet the following goals: meet the following goals:
o If a server supports the mode attribute, it should provide o If a server supports the mode attribute, it should provide
reasonable semantics to clients that only set and retrieve the reasonable semantics to clients that only set and retrieve the
mode attribute. mode attribute.
o If a server supports ACL attributes, it should provide reasonable o If a server supports ACL attributes, it should provide reasonable
semantics to clients that only set and retrieve those attributes. semantics to clients that only set and retrieve those attributes.
o On servers that support the mode attribute, if ACL attributes have o On servers that support the mode attribute, if ACL attributes have
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o On servers that support the mode attribute, if the ACL attributes o On servers that support the mode attribute, if the ACL attributes
have been previously set on an object, either explicitly or via have been previously set on an object, either explicitly or via
inheritance: inheritance:
* Setting only the mode attribute should effectively control the * Setting only the mode attribute should effectively control the
traditional UNIX-like permissions of read, write, and execute traditional UNIX-like permissions of read, write, and execute
on owner, owner_group, and other. on owner, owner_group, and other.
* Setting only the mode attribute should provide reasonable * Setting only the mode attribute should provide reasonable
security. For example, setting a mode of 000 should be enough security. For example, setting a mode of 000 should be enough
to ensure that future opens for read or write by any principal to ensure that future OPEN operations for
fail, regardless of a previously existing or inherited ACL. OPEN4_SHARE_ACCESS_READ or OPEN4_SHARE_ACCESS_WRITE by any
principal fail, regardless of a previously existing or
inherited ACL.
o NFSv4.1 may introduce different semantics relating to the mode and o NFSv4.1 may introduce different semantics relating to the mode and
ACL attributes, but it does not render invalid any previously ACL attributes, but it does not render invalid any previously
existing implementations. Additionally, this chapter provides existing implementations. Additionally, this section provides
clarifications based on previous implementations and discussions clarifications based on previous implementations and discussions
around them. around them.
o On servers that support both the mode and the acl or dacl o On servers that support both the mode and the acl or dacl
attributes, the server must keep the two consistent with each attributes, the server must keep the two consistent with each
other. The value of the mode attribute (with the exception of the other. The value of the mode attribute (with the exception of the
three high order bits described in Section 6.2.4), must be three high-order bits described in Section 6.2.4) must be
determined entirely by the value of the ACL, so that use of the determined entirely by the value of the ACL, so that use of the
mode is never required for anything other than setting the three mode is never required for anything other than setting the three
high order bits. See Section 6.4.1 for exact requirements. high-order bits. See Section 6.4.1 for exact requirements.
o When a mode attribute is set on an object, the ACL attributes may o When a mode attribute is set on an object, the ACL attributes may
need to be modified so as to not conflict with the new mode. In need to be modified in order to not conflict with the new mode.
such cases, it is desirable that the ACL keep as much information In such cases, it is desirable that the ACL keep as much
as possible. This includes information about inheritance, AUDIT information as possible. This includes information about
and ALARM ACEs, and permissions granted and denied that do not inheritance, AUDIT and ALARM ACEs, and permissions granted and
conflict with the new mode. denied that do not conflict with the new mode.
6.2. File Attributes Discussion 6.2. File Attributes Discussion
6.2.1. Attribute 12: acl 6.2.1. Attribute 12: acl
The NFSv4.1 ACL attribute contains an array of access control entries The NFSv4.1 ACL attribute contains an array of Access Control Entries
(ACEs) that are associated with the file system object. Although the (ACEs) that are associated with the file system object. Although the
client can read and write the acl attribute, the server is client can set and get the acl attribute, the server is responsible
responsible for using the ACL to perform access control. The client for using the ACL to perform access control. The client can use the
can use the OPEN or ACCESS operations to check access without OPEN or ACCESS operations to check access without modifying or
modifying or reading data or metadata. reading data or metadata.
The NFS ACE structure is defined as follows: The NFS ACE structure is defined as follows:
typedef uint32_t acetype4; typedef uint32_t acetype4;
typedef uint32_t aceflag4; typedef uint32_t aceflag4;
typedef uint32_t acemask4; typedef uint32_t acemask4;
struct nfsace4 { struct nfsace4 {
acetype4 type; acetype4 type;
aceflag4 flag; aceflag4 flag;
acemask4 access_mask; acemask4 access_mask;
utf8str_mixed who; utf8str_mixed who;
}; };
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typedef uint32_t acemask4; typedef uint32_t acemask4;
struct nfsace4 { struct nfsace4 {
acetype4 type; acetype4 type;
aceflag4 flag; aceflag4 flag;
acemask4 access_mask; acemask4 access_mask;
utf8str_mixed who; utf8str_mixed who;
}; };
To determine if a request succeeds, the server processes each nfsace4 To determine if a request succeeds, the server processes each nfsace4
entry in order. Only ACEs which have a "who" that matches the entry in order. Only ACEs that have a "who" that matches the
requester are considered. Each ACE is processed until all of the requester are considered. Each ACE is processed until all of the
bits of the requester's access have been ALLOWED. Once a bit (see bits of the requester's access have been ALLOWED. Once a bit (see
below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it is no longer below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it is no longer
considered in the processing of later ACEs. If an ACCESS_DENIED_ACE considered in the processing of later ACEs. If an ACCESS_DENIED_ACE
is encountered where the requester's access still has unALLOWED bits is encountered where the requester's access still has unALLOWED bits
in common with the "access_mask" of the ACE, the request is denied. in common with the "access_mask" of the ACE, the request is denied.
When the ACL is fully processed, if there are bits in the requester's When the ACL is fully processed, if there are bits in the requester's
mask that have not been ALLOWED or DENIED, access is denied. mask that have not been ALLOWED or DENIED, access is denied.
Unlike the ALLOW and DENY ACE types, the ALARM and AUDIT ACE types do Unlike the ALLOW and DENY ACE types, the ALARM and AUDIT ACE types do
not affect a requester's access, and instead are for triggering not affect a requester's access, and instead are for triggering
events as a result of a requester's access attempt. Therefore, AUDIT events as a result of a requester's access attempt. Therefore, AUDIT
and ALARM ACEs are processed only after processing ALLOW and DENY and ALARM ACEs are processed only after processing ALLOW and DENY
ACEs. ACEs.
The NFSv4.1 ACL model is quite rich. Some server platforms may The NFSv4.1 ACL model is quite rich. Some server platforms may
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When the ACL is fully processed, if there are bits in the requester's When the ACL is fully processed, if there are bits in the requester's
mask that have not been ALLOWED or DENIED, access is denied. mask that have not been ALLOWED or DENIED, access is denied.
Unlike the ALLOW and DENY ACE types, the ALARM and AUDIT ACE types do Unlike the ALLOW and DENY ACE types, the ALARM and AUDIT ACE types do
not affect a requester's access, and instead are for triggering not affect a requester's access, and instead are for triggering
events as a result of a requester's access attempt. Therefore, AUDIT events as a result of a requester's access attempt. Therefore, AUDIT
and ALARM ACEs are processed only after processing ALLOW and DENY and ALARM ACEs are processed only after processing ALLOW and DENY
ACEs. ACEs.
The NFSv4.1 ACL model is quite rich. Some server platforms may The NFSv4.1 ACL model is quite rich. Some server platforms may
provide access control functionality that goes beyond the UNIX-style provide access-control functionality that goes beyond the UNIX-style
mode attribute, but which is not as rich as the NFS ACL model. So mode attribute, but that is not as rich as the NFS ACL model. So
that users can take advantage of this more limited functionality, the that users can take advantage of this more limited functionality, the
server may support the acl attributes by mapping between its ACL server may support the acl attributes by mapping between its ACL
model and the NFSv4.1 ACL model. Servers must ensure that the ACL model and the NFSv4.1 ACL model. Servers must ensure that the ACL
they actually store or enforce is at least as strict as the NFSv4 ACL they actually store or enforce is at least as strict as the NFSv4 ACL
that was set. It is tempting to accomplish this by rejecting any ACL that was set. It is tempting to accomplish this by rejecting any ACL
that falls outside the small set that can be represented accurately. that falls outside the small set that can be represented accurately.
However, such an approach can render ACLs unusable without special However, such an approach can render ACLs unusable without special
client-side knowledge of the server's mapping, which defeats the client-side knowledge of the server's mapping, which defeats the
purpose of having a common NFSv4 ACL protocol. Therefore servers purpose of having a common NFSv4 ACL protocol. Therefore, servers
should accept every ACL that they can without compromising security. should accept every ACL that they can without compromising security.
To help accomplish this, servers may make a special exception, in the To help accomplish this, servers may make a special exception, in the
case of unsupported permission bits, to the rule that bits not case of unsupported permission bits, to the rule that bits not
ALLOWED or DENIED by an ACL must be denied. For example, a UNIX- ALLOWED or DENIED by an ACL must be denied. For example, a UNIX-
style server might choose to silently allow read attribute style server might choose to silently allow read attribute
permissions even though an ACL does not explicitly allow those permissions even though an ACL does not explicitly allow those
permissions. (An ACL that explicitly denies permission to read permissions. (An ACL that explicitly denies permission to read
attributes should still be rejected.) attributes should still be rejected.)
The situation is complicated by the fact that a server may have The situation is complicated by the fact that a server may have
multiple modules that enforce ACLs. For example, the enforcement for multiple modules that enforce ACLs. For example, the enforcement for
NFSv4.1 access may be different from, but not weaker than, the NFSv4.1 access may be different from, but not weaker than, the
enforcement for local access, and both may be different from the enforcement for local access, and both may be different from the
enforcement for access through other protocols such as SMB. So it enforcement for access through other protocols such as SMB (Server
may be useful for a server to accept an ACL even if not all of its Message Block). So it may be useful for a server to accept an ACL
modules are able to support it. even if not all of its modules are able to support it.
The guiding principle with regard to NFSv4 access is that the server The guiding principle with regard to NFSv4 access is that the server
must not accept ACLs that appear to make access to the file more must not accept ACLs that appear to make access to the file more
restrictive than it really is. restrictive than it really is.
6.2.1.1. ACE Type 6.2.1.1. ACE Type
The constants used for the type field (acetype4) are as follows: The constants used for the type field (acetype4) are as follows:
const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000; const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;
const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001; const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;
const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002; const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;
const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003; const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;
Only the ALLOWED and DENIED bits types may be used in the dacl Only the ALLOWED and DENIED bits may be used in the dacl attribute,
attribute, and only the AUDIT and ALARM bits may be used in the sacl and only the AUDIT and ALARM bits may be used in the sacl attribute.
attribute. All four are permitted in the acl attribute. All four are permitted in the acl attribute.
+------------------------------+--------------+---------------------+ +------------------------------+--------------+---------------------+
| Value | Abbreviation | Description | | Value | Abbreviation | Description |
+------------------------------+--------------+---------------------+ +------------------------------+--------------+---------------------+
| ACE4_ACCESS_ALLOWED_ACE_TYPE | ALLOW | Explicitly grants | | ACE4_ACCESS_ALLOWED_ACE_TYPE | ALLOW | Explicitly grants |
| | | the access defined | | | | the access defined |
| | | in acemask4 to the | | | | in acemask4 to the |
| | | file or directory. | | | | file or directory. |
| ACE4_ACCESS_DENIED_ACE_TYPE | DENY | Explicitly denies | | ACE4_ACCESS_DENIED_ACE_TYPE | DENY | Explicitly denies |
| | | the access defined | | | | the access defined |
| | | in acemask4 to the | | | | in acemask4 to the |
| | | file or directory. | | | | file or directory. |
| ACE4_SYSTEM_AUDIT_ACE_TYPE | AUDIT | LOG (in a system | | ACE4_SYSTEM_AUDIT_ACE_TYPE | AUDIT | Log (in a |
| | | dependent way) any | | | | system-dependent |
| | | access attempt to a | | | | way) any access |
| | | file or directory | | | | attempt to a file |
| | | which uses any of | | | | or directory that |
| | | the access methods | | | | uses any of the |
| | | access methods |
| | | specified in | | | | specified in |
| | | acemask4. | | | | acemask4. |
| ACE4_SYSTEM_ALARM_ACE_TYPE | ALARM | Generate a system | | ACE4_SYSTEM_ALARM_ACE_TYPE | ALARM | Generate an alarm |
| | | ALARM (system | | | | (in a |
| | | dependent) when any | | | | system-dependent |
| | | way) when any |
| | | access attempt is | | | | access attempt is |
| | | made to a file or | | | | made to a file or |
| | | directory for the | | | | directory for the |
| | | access methods | | | | access methods |
| | | specified in | | | | specified in |
| | | acemask4. | | | | acemask4. |
+------------------------------+--------------+---------------------+ +------------------------------+--------------+---------------------+
The "Abbreviation" column denotes how the types will be referred to The "Abbreviation" column denotes how the types will be referred to
throughout the rest of this chapter. throughout the rest of this section.
6.2.1.2. Attribute 13: aclsupport 6.2.1.2. Attribute 13: aclsupport
A server need not support all of the above ACE types. This attribute A server need not support all of the above ACE types. This attribute
indicates which ACE types are supported for the current file system. indicates which ACE types are supported for the current file system.
The bitmask constants used to represent the above definitions within The bitmask constants used to represent the above definitions within
the aclsupport attribute are as follows: the aclsupport attribute are as follows:
const ACL4_SUPPORT_ALLOW_ACL = 0x00000001; const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;
const ACL4_SUPPORT_DENY_ACL = 0x00000002; const ACL4_SUPPORT_DENY_ACL = 0x00000002;
const ACL4_SUPPORT_AUDIT_ACL = 0x00000004; const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;
const ACL4_SUPPORT_ALARM_ACL = 0x00000008; const ACL4_SUPPORT_ALARM_ACL = 0x00000008;
Servers which support either the ALLOW or DENY ACE type SHOULD Servers that support either the ALLOW or DENY ACE type SHOULD support
support both ALLOW and DENY ACE types. both ALLOW and DENY ACE types.
Clients should not attempt to set an ACE unless the server claims Clients should not attempt to set an ACE unless the server claims
support for that ACE type. If the server receives a request to set support for that ACE type. If the server receives a request to set
an ACE that it cannot store, it MUST reject the request with an ACE that it cannot store, it MUST reject the request with
NFS4ERR_ATTRNOTSUPP. If the server receives a request to set an ACE NFS4ERR_ATTRNOTSUPP. If the server receives a request to set an ACE
that it can store but cannot enforce, the server SHOULD reject the that it can store but cannot enforce, the server SHOULD reject the
request with NFS4ERR_ATTRNOTSUPP. request with NFS4ERR_ATTRNOTSUPP.
Support for any of the ACL attributes is optional (albeit, Support for any of the ACL attributes is optional (albeit
RECOMMENDED). However, a server that supports either of the new ACL RECOMMENDED). However, a server that supports either of the new ACL
attributes (dacl or sacl) MUST allow use of the new ACL attributes to attributes (dacl or sacl) MUST allow use of the new ACL attributes to
access all of the ACE types which it supports. In other words, if access all of the ACE types that it supports. In other words, if
such a server supports ALLOW or DENY ACEs, then it MUST support the such a server supports ALLOW or DENY ACEs, then it MUST support the
dacl attribute, and if it supports AUDIT or ALARM ACEs, then it MUST dacl attribute, and if it supports AUDIT or ALARM ACEs, then it MUST
support the sacl attribute. support the sacl attribute.
6.2.1.3. ACE Access Mask 6.2.1.3. ACE Access Mask
The bitmask constants used for the access mask field are as follows: The bitmask constants used for the access mask field are as follows:
const ACE4_READ_DATA = 0x00000001; const ACE4_READ_DATA = 0x00000001;
const ACE4_LIST_DIRECTORY = 0x00000001; const ACE4_LIST_DIRECTORY = 0x00000001;
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ACE4_READ_NAMED_ATTRS ACE4_READ_NAMED_ATTRS
Operation(s) affected: Operation(s) affected:
OPENATTR OPENATTR
Discussion: Discussion:
Permission to read the named attributes of a file or to lookup Permission to read the named attributes of a file or to lookup
the named attributes directory. OPENATTR is affected when it the named attribute directory. OPENATTR is affected when it is
is not used to create a named attribute directory. This is not used to create a named attribute directory. This is when
when 1.) createdir is TRUE, but a named attribute directory 1) createdir is TRUE, but a named attribute directory already
already exists, or 2.) createdir is FALSE. exists, or 2) createdir is FALSE.
ACE4_WRITE_NAMED_ATTRS ACE4_WRITE_NAMED_ATTRS
Operation(s) affected: Operation(s) affected:
OPENATTR OPENATTR
Discussion: Discussion:
Permission to write the named attributes of a file or to create Permission to write the named attributes of a file or to create
a named attribute directory. OPENATTR is affected when it is a named attribute directory. OPENATTR is affected when it is
used to create a named attribute directory. This is when used to create a named attribute directory. This is when
createdir is TRUE and no named attribute directory exists. The createdir is TRUE and no named attribute directory exists. The
ability to check whether or not a named attribute directory ability to check whether or not a named attribute directory
exists depends on the ability to look it up, therefore, users exists depends on the ability to look it up; therefore, users
also need the ACE4_READ_NAMED_ATTRS permission in order to also need the ACE4_READ_NAMED_ATTRS permission in order to
create a named attribute directory. create a named attribute directory.
ACE4_EXECUTE ACE4_EXECUTE
Operation(s) affected: Operation(s) affected:
READ READ
OPEN OPEN
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Permission to delete a file or directory within a directory. Permission to delete a file or directory within a directory.
See Section 6.2.1.3.2 for information on ACE4_DELETE and See Section 6.2.1.3.2 for information on ACE4_DELETE and
ACE4_DELETE_CHILD interact. ACE4_DELETE_CHILD interact.
ACE4_READ_ATTRIBUTES ACE4_READ_ATTRIBUTES
Operation(s) affected: Operation(s) affected:
GETATTR of file system object attributes GETATTR of file system object attributes
VERIFY VERIFY
NVERIFY NVERIFY
READDIR READDIR
Discussion: Discussion:
The ability to read basic attributes (non-ACLs) of a file. On The ability to read basic attributes (non-ACLs) of a file. On
a UNIX system, basic attributes can be thought of as the stat a UNIX system, basic attributes can be thought of as the stat-
level attributes. Allowing this access mask bit would mean the level attributes. Allowing this access mask bit would mean
entity can execute "ls -l" and stat. If a READDIR operation that the entity can execute "ls -l" and stat. If a READDIR
requests attributes, this mask must be allowed for the READDIR operation requests attributes, this mask must be allowed for
to succeed. the READDIR to succeed.
ACE4_WRITE_ATTRIBUTES ACE4_WRITE_ATTRIBUTES
Operation(s) affected: Operation(s) affected:
SETATTR of time_access_set, time_backup, SETATTR of time_access_set, time_backup,
time_create, time_modify_set, mimetype, hidden, system time_create, time_modify_set, mimetype, hidden, system
Discussion: Discussion:
Permission to change the times associated with a file or Permission to change the times associated with a file or
directory to an arbitrary value. Also permission to change the directory to an arbitrary value. Also permission to change the
mimetype, hidden and system attributes. A user having mimetype, hidden, and system attributes. A user having
ACE4_WRITE_DATA or ACE4_WRITE_ATTRIBUTES will be allowed to set ACE4_WRITE_DATA or ACE4_WRITE_ATTRIBUTES will be allowed to set
the times associated with a file to the current server time. the times associated with a file to the current server time.
ACE4_WRITE_RETENTION ACE4_WRITE_RETENTION
Operation(s) affected: Operation(s) affected:
SETATTR of retention_set, retentevt_set. SETATTR of retention_set, retentevt_set.
Discussion: Discussion:
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NONE NONE
Discussion: Discussion:
Permission to use the file object as a synchronization Permission to use the file object as a synchronization
primitive for interprocess communication. This permission is primitive for interprocess communication. This permission is
not enforced or interpreted by the NFSv4.1 server on behalf of not enforced or interpreted by the NFSv4.1 server on behalf of
the client. the client.
Typically, the ACE4_SYNCHRONIZE permission is only meaningful Typically, the ACE4_SYNCHRONIZE permission is only meaningful
on local file systems, i.e. file systems not accessed via on local file systems, i.e., file systems not accessed via
NFSv4.1. The reason that the permission bit exists is that NFSv4.1. The reason that the permission bit exists is that
some operating environments, such as Windows, use some operating environments, such as Windows, use
ACE4_SYNCHRONIZE. ACE4_SYNCHRONIZE.
For example, if a client copies a file that has For example, if a client copies a file that has
ACE4_SYNCHRONIZE set from a local file system to an NFSv4.1 ACE4_SYNCHRONIZE set from a local file system to an NFSv4.1
server, and then later copies the file from the NFSv4.1 server server, and then later copies the file from the NFSv4.1 server
to a local file system, it is likely that if ACE4_SYNCHRONIZE to a local file system, it is likely that if ACE4_SYNCHRONIZE
was set in the original file, the client will want it set in was set in the original file, the client will want it set in
the second copy. The first copy will not have the permission the second copy. The first copy will not have the permission
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except in the previously discussed cases of execute and read. For except in the previously discussed cases of execute and read. For
example, suppose a server cannot distinguish overwriting data from example, suppose a server cannot distinguish overwriting data from
appending new data, as described in the previous paragraph. If a appending new data, as described in the previous paragraph. If a
client submits an ALLOW ACE where ACE4_APPEND_DATA is set but client submits an ALLOW ACE where ACE4_APPEND_DATA is set but
ACE4_WRITE_DATA is not (or vice versa), the server should either turn ACE4_WRITE_DATA is not (or vice versa), the server should either turn
off ACE4_APPEND_DATA or reject the request with NFS4ERR_ATTRNOTSUPP. off ACE4_APPEND_DATA or reject the request with NFS4ERR_ATTRNOTSUPP.
6.2.1.3.2. ACE4_DELETE vs. ACE4_DELETE_CHILD 6.2.1.3.2. ACE4_DELETE vs. ACE4_DELETE_CHILD
Two access mask bits govern the ability to delete a directory entry: Two access mask bits govern the ability to delete a directory entry:
ACE4_DELETE on the object itself (the "target"), and ACE4_DELETE on the object itself (the "target") and ACE4_DELETE_CHILD
ACE4_DELETE_CHILD on the containing directory (the "parent"). on the containing directory (the "parent").
Many systems also take the "sticky bit" (MODE4_SVTX) on a directory Many systems also take the "sticky bit" (MODE4_SVTX) on a directory
to allow unlink only to a user that owns either the target or the to allow unlink only to a user that owns either the target or the
parent; on some such systems the decision also depends on whether the parent; on some such systems the decision also depends on whether the
target is writable. target is writable.
Servers SHOULD allow unlink if either ACE4_DELETE is permitted on the Servers SHOULD allow unlink if either ACE4_DELETE is permitted on the
target, or ACE4_DELETE_CHILD is permitted on the parent. (Note that target, or ACE4_DELETE_CHILD is permitted on the parent. (Note that
this is true even if the parent or target explicitly denies one of this is true even if the parent or target explicitly denies one of
these permissions.) these permissions.)
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Any non-directory file in any sub-directory will get this ACE Any non-directory file in any sub-directory will get this ACE
inherited. inherited.
ACE4_DIRECTORY_INHERIT_ACE ACE4_DIRECTORY_INHERIT_ACE
Can be placed on a directory and indicates that this ACE should be Can be placed on a directory and indicates that this ACE should be
added to each new directory created. added to each new directory created.
If this flag is set in an ACE in an ACL attribute to be set on a If this flag is set in an ACE in an ACL attribute to be set on a
non-directory file system object, the operation attempting to set non-directory file system object, the operation attempting to set
the ACL SHOULD fail with NFS4ERR_ATTRNOTSUPP. the ACL SHOULD fail with NFS4ERR_ATTRNOTSUPP.
ACE4_NO_PROPAGATE_INHERIT_ACE
Can be placed on a directory. This flag tells the server that
inheritance of this ACE should stop at newly created child
directories.
ACE4_INHERIT_ONLY_ACE ACE4_INHERIT_ONLY_ACE
Can be placed on a directory but does not apply to the directory; Can be placed on a directory but does not apply to the directory;
ALLOW and DENY ACEs with this bit set do not affect access to the ALLOW and DENY ACEs with this bit set do not affect access to the
directory, and AUDIT and ALARM ACEs with this bit set do not directory, and AUDIT and ALARM ACEs with this bit set do not
trigger log or alarm events. Such ACEs only take effect once they trigger log or alarm events. Such ACEs only take effect once they
are applied (with this bit cleared) to newly created files and are applied (with this bit cleared) to newly created files and
directories as specified by the above two flags. directories as specified by the ACE4_FILE_INHERIT_ACE and
ACE4_DIRECTORY_INHERIT_ACE flags.
If this flag is present on an ACE, but neither If this flag is present on an ACE, but neither
ACE4_DIRECTORY_INHERIT_ACE nor ACE4_FILE_INHERIT_ACE is present, ACE4_DIRECTORY_INHERIT_ACE nor ACE4_FILE_INHERIT_ACE is present,
then an operation attempting to set such an attribute SHOULD fail then an operation attempting to set such an attribute SHOULD fail
with NFS4ERR_ATTRNOTSUPP. with NFS4ERR_ATTRNOTSUPP.
ACE4_NO_PROPAGATE_INHERIT_ACE
Can be placed on a directory. This flag tells the server that
inheritance of this ACE should stop at newly created child
directories.
ACE4_INHERITED_ACE
Indicates that this ACE is inherited from a parent directory. A
server that supports automatic inheritance will place this flag on
any ACEs inherited from the parent directory when creating a new
object. Client applications will use this to perform automatic
inheritance. Clients and servers MUST clear this bit in the acl
attribute; it may only be used in the dacl and sacl attributes.
ACE4_SUCCESSFUL_ACCESS_ACE_FLAG ACE4_SUCCESSFUL_ACCESS_ACE_FLAG
ACE4_FAILED_ACCESS_ACE_FLAG ACE4_FAILED_ACCESS_ACE_FLAG
The ACE4_SUCCESSFUL_ACCESS_ACE_FLAG (SUCCESS) and The ACE4_SUCCESSFUL_ACCESS_ACE_FLAG (SUCCESS) and
ACE4_FAILED_ACCESS_ACE_FLAG (FAILED) flag bits may be set only on ACE4_FAILED_ACCESS_ACE_FLAG (FAILED) flag bits may be set only on
ACE4_SYSTEM_AUDIT_ACE_TYPE (AUDIT) and ACE4_SYSTEM_ALARM_ACE_TYPE ACE4_SYSTEM_AUDIT_ACE_TYPE (AUDIT) and ACE4_SYSTEM_ALARM_ACE_TYPE
(ALARM) ACE types. If during the processing of the file's ACL, (ALARM) ACE types. If during the processing of the file's ACL,
the server encounters an AUDIT or ALARM ACE that matches the the server encounters an AUDIT or ALARM ACE that matches the
principal attempting the OPEN, the server notes that fact, and the principal attempting the OPEN, the server notes that fact, and the
presence, if any, of the SUCCESS and FAILED flags encountered in presence, if any, of the SUCCESS and FAILED flags encountered in
the AUDIT or ALARM ACE. Once the server completes the ACL the AUDIT or ALARM ACE. Once the server completes the ACL
processing, it then notes if the operation succeeded or failed. processing, it then notes if the operation succeeded or failed.
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ALARM, we consider an ACCESS operation to be a "failure" if it ALARM, we consider an ACCESS operation to be a "failure" if it
fails to return a bit that was requested and supported. fails to return a bit that was requested and supported.
ACE4_IDENTIFIER_GROUP ACE4_IDENTIFIER_GROUP
Indicates that the "who" refers to a GROUP as defined under UNIX Indicates that the "who" refers to a GROUP as defined under UNIX
or a GROUP ACCOUNT as defined under Windows. Clients and servers or a GROUP ACCOUNT as defined under Windows. Clients and servers
MUST ignore the ACE4_IDENTIFIER_GROUP flag on ACEs with a who MUST ignore the ACE4_IDENTIFIER_GROUP flag on ACEs with a who
value equal to one of the special identifiers outlined in value equal to one of the special identifiers outlined in
Section 6.2.1.5. Section 6.2.1.5.
ACE4_INHERITED_ACE
Indicates that this ACE is inherited from a parent directory. A
server that supports automatic inheritance will place this flag on
any ACEs inherited from the parent directory when creating a new
object. Client applications will use this to perform automatic
inheritance. Clients and servers MUST clear this bit in the acl
attribute; it may only be used in the dacl and sacl attributes.
6.2.1.5. ACE Who 6.2.1.5. ACE Who
The "who" field of an ACE is an identifier that specifies the The "who" field of an ACE is an identifier that specifies the
principal or principals to whom the ACE applies. It may refer to a principal or principals to whom the ACE applies. It may refer to a
user or a group, with the flag bit ACE4_IDENTIFIER_GROUP specifying user or a group, with the flag bit ACE4_IDENTIFIER_GROUP specifying
which. which.
There are several special identifiers which need to be understood There are several special identifiers that need to be understood
universally, rather than in the context of a particular DNS domain. universally, rather than in the context of a particular DNS domain.
Some of these identifiers cannot be understood when an NFS client Some of these identifiers cannot be understood when an NFS client
accesses the server, but have meaning when a local process accesses accesses the server, but have meaning when a local process accesses
the file. The ability to display and modify these permissions is the file. The ability to display and modify these permissions is
permitted over NFS, even if none of the access methods on the server permitted over NFS, even if none of the access methods on the server
understands the identifiers. understands the identifiers.
+---------------+--------------------------------------------------+ +---------------+--------------------------------------------------+
| Who | Description | | Who | Description |
+---------------+--------------------------------------------------+ +---------------+--------------------------------------------------+
| OWNER | The owner of the file | | OWNER | The owner of the file. |
| GROUP | The group associated with the file. | | GROUP | The group associated with the file. |
| EVERYONE | The world, including the owner and owning group. | | EVERYONE | The world, including the owner and owning group. |
| INTERACTIVE | Accessed from an interactive terminal. | | INTERACTIVE | Accessed from an interactive terminal. |
| NETWORK | Accessed via the network. | | NETWORK | Accessed via the network. |
| DIALUP | Accessed as a dialup user to the server. | | DIALUP | Accessed as a dialup user to the server. |
| BATCH | Accessed from a batch job. | | BATCH | Accessed from a batch job. |
| ANONYMOUS | Accessed without any authentication. | | ANONYMOUS | Accessed without any authentication. |
| AUTHENTICATED | Any authenticated user (opposite of ANONYMOUS) | | AUTHENTICATED | Any authenticated user (opposite of ANONYMOUS). |
| SERVICE | Access from a system service. | | SERVICE | Access from a system service. |
+---------------+--------------------------------------------------+ +---------------+--------------------------------------------------+
Table 4 Table 4
To avoid conflict, these special identifiers are distinguished by an To avoid conflict, these special identifiers are distinguished by an
appended "@" and should appear in the form "xxxx@" (with no domain appended "@" and should appear in the form "xxxx@" (with no domain
name after the "@"). For example: ANONYMOUS@. name after the "@"), for example, ANONYMOUS@.
The ACE4_IDENTIFIER_GROUP flag MUST be ignored on entries with these The ACE4_IDENTIFIER_GROUP flag MUST be ignored on entries with these
special identifiers. When encoding entries with these special special identifiers. When encoding entries with these special
identifiers, the ACE4_IDENTIFIER_GROUP flag SHOULD be set to zero. identifiers, the ACE4_IDENTIFIER_GROUP flag SHOULD be set to zero.
6.2.1.5.1. Discussion of EVERYONE@ 6.2.1.5.1. Discussion of EVERYONE@
It is important to note that "EVERYONE@" is not equivalent to the It is important to note that "EVERYONE@" is not equivalent to the
UNIX "other" entity. This is because, by definition, UNIX "other" UNIX "other" entity. This is because, by definition, UNIX "other"
does not include the owner or owning group of a file. "EVERYONE@" does not include the owner or owning group of a file. "EVERYONE@"
skipping to change at page 145, line 22 skipping to change at page 144, line 39
const MODE4_WGRP = 0x010; /* write permission: group */ const MODE4_WGRP = 0x010; /* write permission: group */
const MODE4_XGRP = 0x008; /* execute permission: group */ const MODE4_XGRP = 0x008; /* execute permission: group */
const MODE4_ROTH = 0x004; /* read permission: other */ const MODE4_ROTH = 0x004; /* read permission: other */
const MODE4_WOTH = 0x002; /* write permission: other */ const MODE4_WOTH = 0x002; /* write permission: other */
const MODE4_XOTH = 0x001; /* execute permission: other */ const MODE4_XOTH = 0x001; /* execute permission: other */
Bits MODE4_RUSR, MODE4_WUSR, and MODE4_XUSR apply to the principal Bits MODE4_RUSR, MODE4_WUSR, and MODE4_XUSR apply to the principal
identified in the owner attribute. Bits MODE4_RGRP, MODE4_WGRP, and identified in the owner attribute. Bits MODE4_RGRP, MODE4_WGRP, and
MODE4_XGRP apply to principals identified in the owner_group MODE4_XGRP apply to principals identified in the owner_group
attribute but who are not identified in the owner attribute. Bits attribute but who are not identified in the owner attribute. Bits
MODE4_ROTH, MODE4_WOTH, MODE4_XOTH apply to any principal that does MODE4_ROTH, MODE4_WOTH, and MODE4_XOTH apply to any principal that
not match that in the owner attribute, and does not have a group does not match that in the owner attribute and does not have a group
matching that of the owner_group attribute. matching that of the owner_group attribute.
Bits within the mode other than those specified above are not defined Bits within a mode other than those specified above are not defined
by this protocol. A server MUST NOT return bits other than those by this protocol. A server MUST NOT return bits other than those
defined above in a GETATTR or READDIR operation, and it MUST return defined above in a GETATTR or READDIR operation, and it MUST return
NFS4ERR_INVAL if bits other than those defined above are set in a NFS4ERR_INVAL if bits other than those defined above are set in a
SETATTR, CREATE, OPEN, VERIFY or NVERIFY operation. SETATTR, CREATE, OPEN, VERIFY, or NVERIFY operation.
6.2.5. Attribute 74: mode_set_masked 6.2.5. Attribute 74: mode_set_masked
The mode_set_masked attribute is a write-only attribute that allows The mode_set_masked attribute is a write-only attribute that allows
individual bits in the mode attribute to be set or reset, without individual bits in the mode attribute to be set or reset, without
changing others. It allows, for example, the bits MODE4_SUID, changing others. It allows, for example, the bits MODE4_SUID,
MODE4_SGID, and MODE4_SVTX to be modified while leaving unmodified MODE4_SGID, and MODE4_SVTX to be modified while leaving unmodified
any of the nine low-order mode bits devoted to permissions. any of the nine low-order mode bits devoted to permissions.
In such instances that the nine low-order bits are left unmodified, In such instances that the nine low-order bits are left unmodified,
then neither the acl nor the dacl attribute should be automatically then neither the acl nor the dacl attribute should be automatically
modified as discussed in Section 6.4.1. modified as discussed in Section 6.4.1.
The mode_set_masked attribute consists of two words each in the form The mode_set_masked attribute consists of two words, each in the form
of a mode4. The first consists of the value to be applied to the of a mode4. The first consists of the value to be applied to the
current mode value and the second is a mask. Only bits set to one in current mode value and the second is a mask. Only bits set to one in
the mask word are changed (set or reset) in the file's mode. All the mask word are changed (set or reset) in the file's mode. All
other bits in the mode remain unchanged. Bits in the first word that other bits in the mode remain unchanged. Bits in the first word that
correspond to bits which are zero in the mask are ignored, except correspond to bits that are zero in the mask are ignored, except that
that undefined bits are checked for validity and can result in undefined bits are checked for validity and can result in
NFS4ERR_INVAL as described below. NFS4ERR_INVAL as described below.
The mode_set_masked attribute is only valid in a SETATTR operation. The mode_set_masked attribute is only valid in a SETATTR operation.
If it is used in a CREATE or OPEN operation, the server MUST return If it is used in a CREATE or OPEN operation, the server MUST return
NFS4ERR_INVAL. NFS4ERR_INVAL.
Bits not defined as valid in the mode attribute are not valid in Bits not defined as valid in the mode attribute are not valid in
either word of the mode_set_masked attribute. The server MUST return either word of the mode_set_masked attribute. The server MUST return
NFS4ERR_INVAL if any of those are on in a SETATTR. If the mode and NFS4ERR_INVAL if any such bits are set to one in a SETATTR. If the
mode_set_masked attributes are both specified in the same SETATTR, mode and mode_set_masked attributes are both specified in the same
the server MUST also return NFS4ERR_INVAL. SETATTR, the server MUST also return NFS4ERR_INVAL.
6.3. Common Methods 6.3. Common Methods
The requirements in this section will be referred to in future The requirements in this section will be referred to in future
sections, especially Section 6.4. sections, especially Section 6.4.
6.3.1. Interpreting an ACL 6.3.1. Interpreting an ACL
6.3.1.1. Server Considerations 6.3.1.1. Server Considerations
The server uses the algorithm described in Section 6.2.1 to determine The server uses the algorithm described in Section 6.2.1 to determine
whether an ACL allows access to an object. However, the ACL might whether an ACL allows access to an object. However, the ACL might
not be the sole determiner of access. For example: not be the sole determiner of access. For example:
o In the case of a file system exported as read-only, the server may o In the case of a file system exported as read-only, the server may
deny write permissions even though an object's ACL grants it. deny write access even though an object's ACL grants it.
o Server implementations MAY grant ACE4_WRITE_ACL and ACE4_READ_ACL o Server implementations MAY grant ACE4_WRITE_ACL and ACE4_READ_ACL
permissions to prevent a situation from arising in which there is permissions to prevent a situation from arising in which there is
no valid way to ever modify the ACL. no valid way to ever modify the ACL.
o All servers will allow a user the ability to read the data of the o All servers will allow a user the ability to read the data of the
file when only the execute permission is granted (i.e. If the ACL file when only the execute permission is granted (i.e., if the ACL
denies the user the ACE4_READ_DATA access and allows the user denies the user the ACE4_READ_DATA access and allows the user
ACE4_EXECUTE, the server will allow the user to read the data of ACE4_EXECUTE, the server will allow the user to read the data of
the file). the file).
o Many servers have the notion of owner-override in which the owner o Many servers have the notion of owner-override in which the owner
of the object is allowed to override accesses that are denied by of the object is allowed to override accesses that are denied by
the ACL. This may be helpful, for example, to allow users the ACL. This may be helpful, for example, to allow users
continued access to open files on which the permissions have continued access to open files on which the permissions have
changed. changed.
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beyond an ordinary user. The superuser may be able to read or beyond an ordinary user. The superuser may be able to read or
write data or metadata in ways that would not be permitted by the write data or metadata in ways that would not be permitted by the
ACL. ACL.
o A retention attribute might also block access otherwise allowed by o A retention attribute might also block access otherwise allowed by
ACLs (see Section 5.13). ACLs (see Section 5.13).
6.3.1.2. Client Considerations 6.3.1.2. Client Considerations
Clients SHOULD NOT do their own access checks based on their Clients SHOULD NOT do their own access checks based on their
interpretation the ACL, but rather use the OPEN and ACCESS operations interpretation of the ACL, but rather use the OPEN and ACCESS
to do access checks. This allows the client to act on the results of operations to do access checks. This allows the client to act on the
having the server determine whether or not access should be granted results of having the server determine whether or not access should
based on its interpretation of the ACL. be granted based on its interpretation of the ACL.
Clients must be aware of situations in which an object's ACL will Clients must be aware of situations in which an object's ACL will
define a certain access even though the server will not enforce it. define a certain access even though the server will not enforce it.
In general, but especially in these situations, the client needs to In general, but especially in these situations, the client needs to
do its part in the enforcement of access as defined by the ACL. To do its part in the enforcement of access as defined by the ACL. To
do this, the client MAY send the appropriate ACCESS operation prior do this, the client MAY send the appropriate ACCESS operation prior
to servicing the request of the user or application in order to to servicing the request of the user or application in order to
determine whether the user or application should be granted the determine whether the user or application should be granted the
access requested. For examples in which the ACL may define accesses access requested. For examples in which the ACL may define accesses
that the server doesn't enforce see Section 6.3.1.1. that the server doesn't enforce, see Section 6.3.1.1.
6.3.2. Computing a Mode Attribute from an ACL 6.3.2. Computing a Mode Attribute from an ACL
The following method can be used to calculate the MODE4_R*, MODE4_W* The following method can be used to calculate the MODE4_R*, MODE4_W*,
and MODE4_X* bits of a mode attribute, based upon an ACL. and MODE4_X* bits of a mode attribute, based upon an ACL.
First, for each of the special identifiers OWNER@, GROUP@, and First, for each of the special identifiers OWNER@, GROUP@, and
EVERYONE@, evaluate the ACL in order, considering only ALLOW and DENY EVERYONE@, evaluate the ACL in order, considering only ALLOW and DENY
ACEs for the identifier EVERYONE@ and for the identifier under ACEs for the identifier EVERYONE@ and for the identifier under
consideration. The result of the evaluation will be an NFSv4 ACL consideration. The result of the evaluation will be an NFSv4 ACL
mask showing exactly which bits are permitted to that identifier. mask showing exactly which bits are permitted to that identifier.
Then translate the calculated mask for OWNER@, GROUP@, and EVERYONE@ Then translate the calculated mask for OWNER@, GROUP@, and EVERYONE@
into mode bits for, respectively, the user, group, and other, as into mode bits for, respectively, the user, group, and other, as
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The same user confusion seen when fetching the mode also results if The same user confusion seen when fetching the mode also results if
setting the mode does not effectively control permissions for the setting the mode does not effectively control permissions for the
owner, group, and other users; this motivates some of the owner, group, and other users; this motivates some of the
requirements that follow. requirements that follow.
6.4. Requirements 6.4. Requirements
The server that supports both mode and ACL must take care to The server that supports both mode and ACL must take care to
synchronize the MODE4_*USR, MODE4_*GRP, and MODE4_*OTH bits with the synchronize the MODE4_*USR, MODE4_*GRP, and MODE4_*OTH bits with the
ACEs which have respective who fields of "OWNER@", "GROUP@", and ACEs that have respective who fields of "OWNER@", "GROUP@", and
"EVERYONE@" so that the client can see semantically equivalent access "EVERYONE@". This way, the client can see if semantically equivalent
permissions exist whether the client asks for owner, owner_group and access permissions exist whether the client asks for the owner,
mode attributes, or for just the ACL. owner_group, and mode attributes or for just the ACL.
In this section, much is made of the methods in Section 6.3.2. Many In this section, much is made of the methods in Section 6.3.2. Many
requirements refer to this section. But note that the methods have requirements refer to this section. But note that the methods have
behaviors specified with "SHOULD". This is intentional, to avoid behaviors specified with "SHOULD". This is intentional, to avoid
invalidating existing implementations that compute the mode according invalidating existing implementations that compute the mode according
to the withdrawn POSIX ACL draft (1003.1e draft 17), rather than by to the withdrawn POSIX ACL draft (1003.1e draft 17), rather than by
actual permissions on owner, group, and other. actual permissions on owner, group, and other.
6.4.1. Setting the mode and/or ACL Attributes 6.4.1. Setting the Mode and/or ACL Attributes
In the case where a server supports the sacl or dacl attribute, in In the case where a server supports the sacl or dacl attribute, in
addition to the acl attribute, the server MUST fail a request to set addition to the acl attribute, the server MUST fail a request to set
the acl attribute simultaneously with a dacl or sacl attribute. The the acl attribute simultaneously with a dacl or sacl attribute. The
error to be given is NFS4ERR_ATTRNOTSUPP. error to be given is NFS4ERR_ATTRNOTSUPP.
6.4.1.1. Setting mode and not ACL 6.4.1.1. Setting Mode and not ACL
When any of the nine low-order mode bits are subject to change, When any of the nine low-order mode bits are subject to change,
either because the mode attribute was set or because the either because the mode attribute was set or because the
mode_set_masked attribute was set and the mask included one or more mode_set_masked attribute was set and the mask included one or more
bits from the nine low-order mode bits, and no ACL attribute is bits from the nine low-order mode bits, and no ACL attribute is
explicitly set, the acl and dacl attributes must be modified in explicitly set, the acl and dacl attributes must be modified in
accordance with the updated value of those bits. This must happen accordance with the updated value of those bits. This must happen
even if the value of the low-order bits is the same after the mode is even if the value of the low-order bits is the same after the mode is
set as before. set as before.
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ACE4_READ_DATA. ACE4_READ_DATA.
2. If MODE4_WGRP is not set, entities explicitly listed in the ACL 2. If MODE4_WGRP is not set, entities explicitly listed in the ACL
other than OWNER@ and EVERYONE@ SHOULD NOT be granted other than OWNER@ and EVERYONE@ SHOULD NOT be granted
ACE4_WRITE_DATA or ACE4_APPEND_DATA. ACE4_WRITE_DATA or ACE4_APPEND_DATA.
3. If MODE4_XGRP is not set, entities explicitly listed in the ACL 3. If MODE4_XGRP is not set, entities explicitly listed in the ACL
other than OWNER@ and EVERYONE@ SHOULD NOT be granted other than OWNER@ and EVERYONE@ SHOULD NOT be granted
ACE4_EXECUTE. ACE4_EXECUTE.
Access mask bits other those listed above, appearing in ALLOW ACEs, Access mask bits other than those listed above, appearing in ALLOW
MAY also be disabled. ACEs, MAY also be disabled.
Note that ACEs with the flag ACE4_INHERIT_ONLY_ACE set do not affect Note that ACEs with the flag ACE4_INHERIT_ONLY_ACE set do not affect
the permissions of the ACL itself, nor do ACEs of the type AUDIT and the permissions of the ACL itself, nor do ACEs of the type AUDIT and
ALARM. As such, it is desirable to leave these ACEs unmodified when ALARM. As such, it is desirable to leave these ACEs unmodified when
modifying the ACL attributes. modifying the ACL attributes.
Also note that the requirement may be met by discarding the acl and Also note that the requirement may be met by discarding the acl and
dacl, in favor of an ACL that represents the mode and only the mode. dacl, in favor of an ACL that represents the mode and only the mode.
This is permitted, but it is preferable for a server to preserve as This is permitted, but it is preferable for a server to preserve as
much of the ACL as possible without violating the above requirements. much of the ACL as possible without violating the above requirements.
Discarding the ACL makes it effectively impossible for a file created Discarding the ACL makes it effectively impossible for a file created
with a mode attribute to inherit an ACL (see Section 6.4.3). with a mode attribute to inherit an ACL (see Section 6.4.3).
6.4.1.2. Setting ACL and not mode 6.4.1.2. Setting ACL and Not Mode
When setting the acl or dacl and not setting the mode or When setting the acl or dacl and not setting the mode or
mode_set_masked attributes, the permission bits of the mode need to mode_set_masked attributes, the permission bits of the mode need to
be derived from the ACL. In this case, the ACL attribute SHOULD be be derived from the ACL. In this case, the ACL attribute SHOULD be
set as given. The nine low-order bits of the mode attribute set as given. The nine low-order bits of the mode attribute
(MODE4_R*, MODE4_W*, MODE4_X*) MUST be modified to match the result (MODE4_R*, MODE4_W*, MODE4_X*) MUST be modified to match the result
of the method Section 6.3.2. The three high-order bits of the mode of the method in Section 6.3.2. The three high-order bits of the
(MODE4_SUID, MODE4_SGID, MODE4_SVTX) SHOULD remain unchanged. mode (MODE4_SUID, MODE4_SGID, MODE4_SVTX) SHOULD remain unchanged.
6.4.1.3. Setting both ACL and mode 6.4.1.3. Setting Both ACL and Mode
When setting both the mode (includes use of either the mode attribute When setting both the mode (includes use of either the mode attribute
or the mode_set_masked attribute) and the acl or dacl attributes in or the mode_set_masked attribute) and the acl or dacl attributes in
the same operation, the attributes MUST be applied in this order: the same operation, the attributes MUST be applied in this order:
mode (or mode_set_masked), then ACL. The mode-related attribute is mode (or mode_set_masked), then ACL. The mode-related attribute is
set as given, then the ACL attribute is set as given, possibly set as given, then the ACL attribute is set as given, possibly
changing the final mode, as described above in Section 6.4.1.2. changing the final mode, as described above in Section 6.4.1.2.
6.4.2. Retrieving the mode and/or ACL Attributes 6.4.2. Retrieving the Mode and/or ACL Attributes
This section applies only to servers that support both the mode and This section applies only to servers that support both the mode and
ACL attributes. ACL attributes.
Some server implementations may have a concept of "objects without Some server implementations may have a concept of "objects without
ACLs", meaning that all permissions are granted and denied according ACLs", meaning that all permissions are granted and denied according
to the mode attribute, and that no ACL attribute is stored for that to the mode attribute and that no ACL attribute is stored for that
object. If an ACL attribute is requested of such a server, the object. If an ACL attribute is requested of such a server, the
server SHOULD return an ACL that does not conflict with the mode; server SHOULD return an ACL that does not conflict with the mode;
that is to say, the ACL returned SHOULD represent the nine low-order that is to say, the ACL returned SHOULD represent the nine low-order
bits of the mode attribute (MODE4_R*, MODE4_W*, MODE4_X*) as bits of the mode attribute (MODE4_R*, MODE4_W*, MODE4_X*) as
described in Section 6.3.2. described in Section 6.3.2.
For other server implementations, the ACL attribute is always present For other server implementations, the ACL attribute is always present
for every object. Such servers SHOULD store at least the three high- for every object. Such servers SHOULD store at least the three high-
order bits of the mode attribute (MODE4_SUID, MODE4_SGID, order bits of the mode attribute (MODE4_SUID, MODE4_SGID,
MODE4_SVTX). The server SHOULD return a mode attribute if one is MODE4_SVTX). The server SHOULD return a mode attribute if one is
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6.4.3. Creating New Objects 6.4.3. Creating New Objects
If a server supports any ACL attributes, it may use the ACL If a server supports any ACL attributes, it may use the ACL
attributes on the parent directory to compute an initial ACL attributes on the parent directory to compute an initial ACL
attribute for a newly created object. This will be referred to as attribute for a newly created object. This will be referred to as
the inherited ACL within this section. The act of adding one or more the inherited ACL within this section. The act of adding one or more
ACEs to the inherited ACL that are based upon ACEs in the parent ACEs to the inherited ACL that are based upon ACEs in the parent
directory's ACL will be referred to as inheriting an ACE within this directory's ACL will be referred to as inheriting an ACE within this
section. section.
Implementors should standardize on what the behavior of CREATE and Implementors should standardize what the behavior of CREATE and OPEN
OPEN must be depending on the presence or absence of the mode and ACL must be depending on the presence or absence of the mode and ACL
attributes. attributes.
1. If just the mode is given in the call: 1. If just the mode is given in the call:
In this case, inheritance SHOULD take place, but the mode MUST be In this case, inheritance SHOULD take place, but the mode MUST be
applied to the inherited ACL as described in Section 6.4.1.1, applied to the inherited ACL as described in Section 6.4.1.1,
thereby modifying the ACL. thereby modifying the ACL.
2. If just the ACL is given in the call: 2. If just the ACL is given in the call:
In this case, inheritance SHOULD NOT take place, and the ACL as In this case, inheritance SHOULD NOT take place, and the ACL as
defined in the CREATE or OPEN will be set without modification, defined in the CREATE or OPEN will be set without modification,
and the mode modified as in Section 6.4.1.2 and the mode modified as in Section 6.4.1.2.
3. If both mode and ACL are given in the call: 3. If both mode and ACL are given in the call:
In this case, inheritance SHOULD NOT take place, and both In this case, inheritance SHOULD NOT take place, and both
attributes will be set as described in Section 6.4.1.3. attributes will be set as described in Section 6.4.1.3.
4. If neither mode nor ACL are given in the call: 4. If neither mode nor ACL is given in the call:
In the case where an object is being created without any initial In the case where an object is being created without any initial
attributes at all, e.g. an OPEN operation with an opentype4 of attributes at all, e.g., an OPEN operation with an opentype4 of
OPEN4_CREATE and a createmode4 of EXCLUSIVE4, inheritance SHOULD OPEN4_CREATE and a createmode4 of EXCLUSIVE4, inheritance SHOULD
NOT take place (note that EXCLUSIVE4_1 is a better choice of NOT take place (note that EXCLUSIVE4_1 is a better choice of
createmode4, since it does permit initial attributes). Instead, createmode4, since it does permit initial attributes). Instead,
the server SHOULD set permissions to deny all access to the newly the server SHOULD set permissions to deny all access to the newly
created object. It is expected that the appropriate client will created object. It is expected that the appropriate client will
set the desired attributes in a subsequent SETATTR operation, and set the desired attributes in a subsequent SETATTR operation, and
the server SHOULD allow that operation to succeed, regardless of the server SHOULD allow that operation to succeed, regardless of
what permissions the object is created with. For example, an what permissions the object is created with. For example, an
empty ACL denies all permissions, but the server should allow the empty ACL denies all permissions, but the server should allow the
owner's SETATTR to succeed even though WRITE_ACL is implicitly owner's SETATTR to succeed even though WRITE_ACL is implicitly
denied. denied.
In other cases, inheritance SHOULD take place, and no In other cases, inheritance SHOULD take place, and no
modifications to the ACL will happen. The mode attribute, if modifications to the ACL will happen. The mode attribute, if
supported, MUST be as computed in Section 6.3.2, with the supported, MUST be as computed in Section 6.3.2, with the
MODE4_SUID, MODE4_SGID and MODE4_SVTX bits clear. If no MODE4_SUID, MODE4_SGID, and MODE4_SVTX bits clear. If no
inheritable ACEs exist on the parent directory, the rules for inheritable ACEs exist on the parent directory, the rules for
creating acl, dacl or sacl attributes are implementation defined. creating acl, dacl, or sacl attributes are implementation
If either the dacl or sacl attribute is supported, then the defined. If either the dacl or sacl attribute is supported, then
ACL4_DEFAULTED flag SHOULD be set on the newly created the ACL4_DEFAULTED flag SHOULD be set on the newly created
attributes. attributes.
6.4.3.1. The Inherited ACL 6.4.3.1. The Inherited ACL
If the object being created is not a directory, the inherited ACL If the object being created is not a directory, the inherited ACL
SHOULD NOT inherit ACEs from the parent directory ACL unless the SHOULD NOT inherit ACEs from the parent directory ACL unless the
ACE4_FILE_INHERIT_FLAG is set. ACE4_FILE_INHERIT_FLAG is set.
If the object being created is a directory, the inherited ACL should If the object being created is a directory, the inherited ACL should
inherit all inheritable ACEs from the parent directory, those that inherit all inheritable ACEs from the parent directory, that is,
have ACE4_FILE_INHERIT_ACE or ACE4_DIRECTORY_INHERIT_ACE flag set. those that have the ACE4_FILE_INHERIT_ACE or
If the inheritable ACE has ACE4_FILE_INHERIT_ACE set, but ACE4_DIRECTORY_INHERIT_ACE flag set. If the inheritable ACE has
ACE4_DIRECTORY_INHERIT_ACE is clear, the inherited ACE on the newly ACE4_FILE_INHERIT_ACE set but ACE4_DIRECTORY_INHERIT_ACE is clear,
created directory MUST have the ACE4_INHERIT_ONLY_ACE flag set to the inherited ACE on the newly created directory MUST have the
prevent the directory from being affected by ACEs meant for non- ACE4_INHERIT_ONLY_ACE flag set to prevent the directory from being
directories. affected by ACEs meant for non-directories.
When a new directory is created, the server MAY split any inherited When a new directory is created, the server MAY split any inherited
ACE which is both inheritable and effective (in other words, which ACE that is both inheritable and effective (in other words, that has
has neither ACE4_INHERIT_ONLY_ACE nor ACE4_NO_PROPAGATE_INHERIT_ACE neither ACE4_INHERIT_ONLY_ACE nor ACE4_NO_PROPAGATE_INHERIT_ACE set),
set), into two ACEs, one with no inheritance flags, and one with into two ACEs, one with no inheritance flags and one with
ACE4_INHERIT_ONLY_ACE set. (In the case of a dacl or sacl attribute, ACE4_INHERIT_ONLY_ACE set. (In the case of a dacl or sacl attribute,
both of those ACEs SHOULD also have the ACE4_INHERITED_ACE flag set.) both of those ACEs SHOULD also have the ACE4_INHERITED_ACE flag set.)
This makes it simpler to modify the effective permissions on the This makes it simpler to modify the effective permissions on the
directory without modifying the ACE which is to be inherited to the directory without modifying the ACE that is to be inherited to the
new directory's children. new directory's children.
6.4.3.2. Automatic Inheritance 6.4.3.2. Automatic Inheritance
The acl attribute consists only of an array of ACEs, but the sacl The acl attribute consists only of an array of ACEs, but the sacl
(Section 6.2.3) and dacl (Section 6.2.2) attributes also include an (Section 6.2.3) and dacl (Section 6.2.2) attributes also include an
additional flag field. additional flag field.
struct nfsacl41 { struct nfsacl41 {
aclflag4 na41_flag; aclflag4 na41_flag;
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cleared in the acl). cleared in the acl).
Together these features allow a server to support automatic Together these features allow a server to support automatic
inheritance, which we now explain in more detail. inheritance, which we now explain in more detail.
Inheritable ACEs are normally inherited by child objects only at the Inheritable ACEs are normally inherited by child objects only at the
time that the child objects are created; later modifications to time that the child objects are created; later modifications to
inheritable ACEs do not result in modifications to inherited ACEs on inheritable ACEs do not result in modifications to inherited ACEs on
descendants. descendants.
However, the dacl and sacl provide an OPTIONAL mechanism which allows However, the dacl and sacl provide an OPTIONAL mechanism that allows
a client application to propagate changes to inheritable ACEs to an a client application to propagate changes to inheritable ACEs to an
entire directory hierarchy. entire directory hierarchy.
A server that supports this performs inheritance at object creation A server that supports this performs inheritance at object creation
time in the normal way, and SHOULD set the ACE4_INHERITED_ACE flag on time in the normal way, and SHOULD set the ACE4_INHERITED_ACE flag on
any inherited ACEs as they are added to the new object. any inherited ACEs as they are added to the new object.
A client application such as an ACL editor may then propagate changes A client application such as an ACL editor may then propagate changes
to inheritable ACEs on a directory by recursively traversing that to inheritable ACEs on a directory by recursively traversing that
directory's descendants and modifying each ACL encountered to remove directory's descendants and modifying each ACL encountered to remove
any ACEs with the ACE4_INHERITED_ACE flag and to replace them by the any ACEs with the ACE4_INHERITED_ACE flag and to replace them by the
new inheritable ACEs (also with the ACE4_INHERITED_ACE flag set). It new inheritable ACEs (also with the ACE4_INHERITED_ACE flag set). It
uses the existing ACE inheritance flags in the obvious way to decide uses the existing ACE inheritance flags in the obvious way to decide
which ACEs to propagate. (Note that it may encounter further which ACEs to propagate. (Note that it may encounter further
inheritable ACEs when descending the directory hierarchy, and that inheritable ACEs when descending the directory hierarchy and that
those will also need to be taken into account when propagating those will also need to be taken into account when propagating
inheritable ACEs to further descendants.) inheritable ACEs to further descendants.)
The reach of this propagation may be limited in two ways: first, The reach of this propagation may be limited in two ways: first,
automatic inheritance is not performed from any directory ACL that automatic inheritance is not performed from any directory ACL that
has the ACL4_AUTO_INHERIT flag cleared; and second, automatic has the ACL4_AUTO_INHERIT flag cleared; and second, automatic
inheritance stops wherever an ACL with the ACL4_PROTECTED flag is inheritance stops wherever an ACL with the ACL4_PROTECTED flag is
set, preventing modification of that ACL and also (if the ACL is set set, preventing modification of that ACL and also (if the ACL is set
on a directory) of the ACL on any of the object's descendants. on a directory) of the ACL on any of the object's descendants.
This propagation is performed independently for the sacl and the dacl This propagation is performed independently for the sacl and the dacl
attributes; thus the ACL4_AUTO_INHERIT and ACL4_PROTECTED flags may attributes; thus, the ACL4_AUTO_INHERIT and ACL4_PROTECTED flags may
be independently set for the sacl and the dacl, and propagation of be independently set for the sacl and the dacl, and propagation of
one type of acl may continue down a hierarchy even where propagation one type of acl may continue down a hierarchy even where propagation
of the other acl has stopped. of the other acl has stopped.
New objects should be created with a dacl and a sacl that both have New objects should be created with a dacl and a sacl that both have
the ACL4_PROTECTED flag cleared and the ACL4_AUTO_INHERIT flag set to the ACL4_PROTECTED flag cleared and the ACL4_AUTO_INHERIT flag set to
the same value as that on, respectively, the sacl or dacl of the the same value as that on, respectively, the sacl or dacl of the
parent object. parent object.
Both the dacl and sacl attributes are RECOMMENDED, and a server may Both the dacl and sacl attributes are RECOMMENDED, and a server may
support one without supporting the other. support one without supporting the other.
A server that supports both the old acl attribute and one or both of A server that supports both the old acl attribute and one or both of
the new dacl or sacl attributes must do so in such a way as to keep the new dacl or sacl attributes must do so in such a way as to keep
all three attributes consistent with each other. Thus the ACEs all three attributes consistent with each other. Thus, the ACEs
reported in the acl attribute should be the union of the ACEs reported in the acl attribute should be the union of the ACEs
reported in the dacl and sacl attributes, except that the reported in the dacl and sacl attributes, except that the
ACE4_INHERITED_ACE flag must be cleared from the ACEs in the acl. ACE4_INHERITED_ACE flag must be cleared from the ACEs in the acl.
And of course a client that queries only the acl will be unable to And of course a client that queries only the acl will be unable to
determine the values of the sacl or dacl flag fields. determine the values of the sacl or dacl flag fields.
When a client performs a SETATTR for the acl attribute, the server When a client performs a SETATTR for the acl attribute, the server
SHOULD set the ACL4_PROTECTED flag to true on both the sacl and the SHOULD set the ACL4_PROTECTED flag to true on both the sacl and the
dacl. By using the acl attribute, as opposed to the dacl or sacl dacl. By using the acl attribute, as opposed to the dacl or sacl
attributes, the client signals that it may not understand automatic attributes, the client signals that it may not understand automatic
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Finally, in the case where the request that creates a new file or Finally, in the case where the request that creates a new file or
directory does not also set permissions for that file or directory, directory does not also set permissions for that file or directory,
and there are also no ACEs to inherit from the parent's directory, and there are also no ACEs to inherit from the parent's directory,
then the server's choice of ACL for the new object is implementation- then the server's choice of ACL for the new object is implementation-
dependent. In this case, the server SHOULD set the ACL4_DEFAULTED dependent. In this case, the server SHOULD set the ACL4_DEFAULTED
flag on the ACL it chooses for the new object. An application flag on the ACL it chooses for the new object. An application
performing automatic inheritance takes the ACL4_DEFAULTED flag as a performing automatic inheritance takes the ACL4_DEFAULTED flag as a
sign that the ACL should be completely replaced by one generated sign that the ACL should be completely replaced by one generated
using the automatic inheritance rules. using the automatic inheritance rules.
7. Single-server Namespace 7. Single-Server Namespace
This chapter describes the NFSv4 single-server namespace. Single- This section describes the NFSv4 single-server namespace. Single-
server namespaces may be presented directly to clients, or they may server namespaces may be presented directly to clients, or they may
be used as a basis to form larger multi-server namespaces (e.g. site- be used as a basis to form larger multi-server namespaces (e.g.,
wide or organization-wide) to be presented to clients, as described site-wide or organization-wide) to be presented to clients, as
in Section 11. described in Section 11.
7.1. Server Exports 7.1. Server Exports
On a UNIX server, the namespace describes all the files reachable by On a UNIX server, the namespace describes all the files reachable by
pathnames under the root directory or "/". On a Windows server the pathnames under the root directory or "/". On a Windows server, the
namespace constitutes all the files on disks named by mapped disk namespace constitutes all the files on disks named by mapped disk
letters. NFS server administrators rarely make the entire server's letters. NFS server administrators rarely make the entire server's
file system namespace available to NFS clients. More often portions file system namespace available to NFS clients. More often, portions
of the namespace are made available via an "export" feature. In of the namespace are made available via an "export" feature. In
previous versions of the NFS protocol, the root filehandle for each previous versions of the NFS protocol, the root filehandle for each
export is obtained through the MOUNT protocol; the client sent a export is obtained through the MOUNT protocol; the client sent a
string that identified the export name within the namespace and the string that identified the export name within the namespace and the
server returned the root filehandle for that export. The MOUNT server returned the root filehandle for that export. The MOUNT
protocol also provided an EXPORTS procedure that enumerated server's protocol also provided an EXPORTS procedure that enumerated the
exports. server's exports.
7.2. Browsing Exports 7.2. Browsing Exports
The NFSv4.1 protocol provides a root filehandle that clients can use The NFSv4.1 protocol provides a root filehandle that clients can use
to obtain filehandles for the exports of a particular server, via a to obtain filehandles for the exports of a particular server, via a
series of LOOKUP operations within a COMPOUND, to traverse a path. A series of LOOKUP operations within a COMPOUND, to traverse a path. A
common user experience is to use a graphical user interface (perhaps common user experience is to use a graphical user interface (perhaps
a file "Open" dialog window) to find a file via progressive browsing a file "Open" dialog window) to find a file via progressive browsing
through a directory tree. The client must be able to move from one through a directory tree. The client must be able to move from one
export to another export via single-component, progressive LOOKUP export to another export via single-component, progressive LOOKUP
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In the case of NFSv3, an automounter on the client can obtain a In the case of NFSv3, an automounter on the client can obtain a
snapshot of the server's namespace using the EXPORTS procedure of the snapshot of the server's namespace using the EXPORTS procedure of the
MOUNT protocol. If it understands the server's pathname syntax, it MOUNT protocol. If it understands the server's pathname syntax, it
can create an image of the server's namespace on the client. The can create an image of the server's namespace on the client. The
parts of the namespace that are not exported by the server are filled parts of the namespace that are not exported by the server are filled
in with directories that might be constructed similarly to an NFSv4.1 in with directories that might be constructed similarly to an NFSv4.1
"pseudo file system" (see Section 7.3) that allows the user to browse "pseudo file system" (see Section 7.3) that allows the user to browse
from one mounted file system to another. There is a drawback to this from one mounted file system to another. There is a drawback to this
representation of the server's namespace on the client: it is static. representation of the server's namespace on the client: it is static.
If the server administrator adds a new export the client will be If the server administrator adds a new export, the client will be
unaware of it. unaware of it.
7.3. Server Pseudo File System 7.3. Server Pseudo File System
NFSv4.1 servers avoid this namespace inconsistency by presenting all NFSv4.1 servers avoid this namespace inconsistency by presenting all
the exports for a given server within the framework of a single the exports for a given server within the framework of a single
namespace, for that server. An NFSv4.1 client uses LOOKUP and namespace for that server. An NFSv4.1 client uses LOOKUP and READDIR
READDIR operations to browse seamlessly from one export to another. operations to browse seamlessly from one export to another.
Where there are portions of the server namespace that are not Where there are portions of the server namespace that are not
exported, clients require some way of traversing those portions to exported, clients require some way of traversing those portions to
reach actual exported file systems. A technique that servers may use reach actual exported file systems. A technique that servers may use
to provide for this is to bridge unexported portion of the namespace to provide for this is to bridge the unexported portion of the
via a "pseudo file system" that provides a view of exported namespace via a "pseudo file system" that provides a view of exported
directories only. A pseudo file system has a unique fsid and behaves directories only. A pseudo file system has a unique fsid and behaves
like a normal, read-only file system. like a normal, read-only file system.
Based on the construction of the server's namespace, it is possible Based on the construction of the server's namespace, it is possible
that multiple pseudo file systems may exist. For example, that multiple pseudo file systems may exist. For example,
/a pseudo file system /a pseudo file system
/a/b real file system /a/b real file system
/a/b/c pseudo file system /a/b/c pseudo file system
/a/b/c/d real file system /a/b/c/d real file system
Each of the pseudo file systems is considered a separate entity and Each of the pseudo file systems is considered a separate entity and
therefore MUST have its own fsid, unique among all the fsids for that therefore MUST have its own fsid, unique among all the fsids for that
server. server.
7.4. Multiple Roots 7.4. Multiple Roots
Certain operating environments are sometimes described as having Certain operating environments are sometimes described as having
"multiple roots". In such environments individual file systems are "multiple roots". In such environments, individual file systems are
commonly represented by disk or volume names. NFSv4 servers for commonly represented by disk or volume names. NFSv4 servers for
these platforms can construct a pseudo file system above these root these platforms can construct a pseudo file system above these root
names so that disk letters or volume names are simply directory names names so that disk letters or volume names are simply directory names
in the pseudo root. in the pseudo root.
7.5. Filehandle Volatility 7.5. Filehandle Volatility
The nature of the server's pseudo file system is that it is a logical The nature of the server's pseudo file system is that it is a logical
representation of file system(s) available from the server. representation of file system(s) available from the server.
Therefore, the pseudo file system is most likely constructed Therefore, the pseudo file system is most likely constructed
dynamically when the server is first instantiated. It is expected dynamically when the server is first instantiated. It is expected
that the pseudo file system may not have an on disk counterpart from that the pseudo file system may not have an on-disk counterpart from
which persistent filehandles could be constructed. Even though it is which persistent filehandles could be constructed. Even though it is
preferable that the server provide persistent filehandles for the preferable that the server provide persistent filehandles for the
pseudo file system, the NFS client should expect that pseudo file pseudo file system, the NFS client should expect that pseudo file
system filehandles are volatile. This can be confirmed by checking system filehandles are volatile. This can be confirmed by checking
the associated "fh_expire_type" attribute for those filehandles in the associated "fh_expire_type" attribute for those filehandles in
question. If the filehandles are volatile, the NFS client must be question. If the filehandles are volatile, the NFS client must be
prepared to recover a filehandle value (e.g. with a series of LOOKUP prepared to recover a filehandle value (e.g., with a series of LOOKUP
operations) when receiving an error of NFS4ERR_FHEXPIRED. operations) when receiving an error of NFS4ERR_FHEXPIRED.
Because it is quite likely that servers will implement pseudo file Because it is quite likely that servers will implement pseudo file
systems using volatile filehandles, clients need to be prepared for systems using volatile filehandles, clients need to be prepared for
them, rather than assuming that all filehandles will be persistent. them, rather than assuming that all filehandles will be persistent.
7.6. Exported Root 7.6. Exported Root
If the server's root file system is exported, one might conclude that If the server's root file system is exported, one might conclude that
a pseudo file system is unneeded. This not necessarily so. Assume a pseudo file system is unneeded. This is not necessarily so.
the following file systems on a server: Assume the following file systems on a server:
/ fs1 (exported) / fs1 (exported)
/a fs2 (not exported) /a fs2 (not exported)
/a/b fs3 (exported) /a/b fs3 (exported)
Because fs2 is not exported, fs3 cannot be reached with simple Because fs2 is not exported, fs3 cannot be reached with simple
LOOKUPs. The server must bridge the gap with a pseudo file system. LOOKUPs. The server must bridge the gap with a pseudo file system.
7.7. Mount Point Crossing 7.7. Mount Point Crossing
The server file system environment may be constructed in such a way The server file system environment may be constructed in such a way
that one file system contains a directory which is 'covered' or that one file system contains a directory that is 'covered' or
mounted upon by a second file system. For example: mounted upon by a second file system. For example:
/a/b (file system 1) /a/b (file system 1)
/a/b/c/d (file system 2) /a/b/c/d (file system 2)
The pseudo file system for this server may be constructed to look The pseudo file system for this server may be constructed to look
like: like:
/ (place holder/not exported) / (place holder/not exported)
/a/b (file system 1) /a/b (file system 1)
/a/b/c/d (file system 2) /a/b/c/d (file system 2)
It is the server's responsibility to present the pseudo file system It is the server's responsibility to present the pseudo file system
that is complete to the client. If the client sends a lookup request that is complete to the client. If the client sends a LOOKUP request
for the path "/a/b/c/d", the server's response is the filehandle of for the path /a/b/c/d, the server's response is the filehandle of the
the root of the file system "/a/b/c/d". In previous versions of the root of the file system /a/b/c/d. In previous versions of the NFS
NFS protocol, the server would respond with the filehandle of protocol, the server would respond with the filehandle of directory
directory "/a/b/c/d" within the file system "/a/b". /a/b/c/d within the file system /a/b.
The NFS client will be able to determine if it crosses a server mount The NFS client will be able to determine if it crosses a server mount
point by a change in the value of the "fsid" attribute. point by a change in the value of the "fsid" attribute.
7.8. Security Policy and Namespace Presentation 7.8. Security Policy and Namespace Presentation
Because NFSv4 clients possess the ability to change the security Because NFSv4 clients possess the ability to change the security
mechanisms used, after determining what is allowed, by using SECINFO mechanisms used, after determining what is allowed, by using SECINFO
and SECINFO_NONAME, the server SHOULD NOT present a different view of and SECINFO_NONAME, the server SHOULD NOT present a different view of
the namespace based on the security mechanism being used by a client. the namespace based on the security mechanism being used by a client.
skipping to change at page 158, line 30 skipping to change at page 157, line 39
shared resource. Suppose the security policy for /a/b/ shared resource. Suppose the security policy for /a/b/
MySecretProject is Kerberos with integrity and it is desired to limit MySecretProject is Kerberos with integrity and it is desired to limit
knowledge of the existence of this file system. In this case, the knowledge of the existence of this file system. In this case, the
server should apply the same security policy to /a/b. This allows server should apply the same security policy to /a/b. This allows
for knowledge of the existence of a file system to be secured when for knowledge of the existence of a file system to be secured when
desirable. desirable.
For the case of the use of multiple, disjoint security mechanisms in For the case of the use of multiple, disjoint security mechanisms in
the server's resources, applying that sort of policy would result in the server's resources, applying that sort of policy would result in
the higher-level file system not being accessible using any security the higher-level file system not being accessible using any security
flavor, which would make that higher-level file system inaccessible. flavor. Therefore, that sort of configuration is not compatible with
Therefore, that sort of configuration is not compatible with hiding hiding the existence (as opposed to the contents) from clients using
the existence (as opposed to the contents) from clients using
multiple disjoint sets of security flavors. multiple disjoint sets of security flavors.
In other circumstances, a desirable policy is for the security of a In other circumstances, a desirable policy is for the security of a
particular object in the server's namespace should include the union particular object in the server's namespace to include the union of
of all security mechanisms of all direct descendants. A common and all security mechanisms of all direct descendants. A common and
convenient practice, unless strong security requirements dictate convenient practice, unless strong security requirements dictate
otherwise, is to make all of the pseudo file system accessible by all otherwise, is to make the entire the pseudo file system accessible by
of the valid security mechanisms. all of the valid security mechanisms.
Where there is concern about the security of data on the network, Where there is concern about the security of data on the network,
clients should use strong security mechanisms to access the pseudo clients should use strong security mechanisms to access the pseudo
file system in order to prevent man-in-the-middle attacks. file system in order to prevent man-in-the-middle attacks.
8. State Management 8. State Management
Integrating locking into the NFS protocol necessarily causes it to be Integrating locking into the NFS protocol necessarily causes it to be
stateful. With the inclusion of such features as share reservations, stateful. With the inclusion of such features as share reservations,
file and directory delegations, recallable layouts, and support for file and directory delegations, recallable layouts, and support for
mandatory byte-range locking, the protocol becomes substantially more mandatory byte-range locking, the protocol becomes substantially more
dependent on proper management of state than the traditional dependent on proper management of state than the traditional
combination of NFS and NLM [46]. These features include expanded combination of NFS and NLM (Network Lock Manager) [46]. These
locking facilities, which provide some measure of interclient features include expanded locking facilities, which provide some
exclusion, but the state also offers features not readily providable measure of inter-client exclusion, but the state also offers features
using a stateless model. There are three components to making this not readily providable using a stateless model. There are three
state manageable: components to making this state manageable:
o Clear division between client and server o clear division between client and server
o Ability to reliably detect inconsistency in state between client o ability to reliably detect inconsistency in state between client
and server and server
o Simple and robust recovery mechanisms o simple and robust recovery mechanisms
In this model, the server owns the state information. The client In this model, the server owns the state information. The client
requests changes in locks and the server responds with the changes requests changes in locks and the server responds with the changes
made. Non-client-initiated changes in locking state are infrequent. made. Non-client-initiated changes in locking state are infrequent.
The client receives prompt notification of such changes and can The client receives prompt notification of such changes and can
adjust its view of the locking state to reflect the server's changes. adjust its view of the locking state to reflect the server's changes.
Individual pieces of state created by the server and passed to the Individual pieces of state created by the server and passed to the
client at its request are represented by 128-bit stateids. These client at its request are represented by 128-bit stateids. These
stateids may represent a particular open file, a set of byte-range stateids may represent a particular open file, a set of byte-range
locks held by a particular owner, or a recallable delegation of locks held by a particular owner, or a recallable delegation of
privileges to access a file in particular ways, or at a particular privileges to access a file in particular ways or at a particular
location. location.
In all cases, there is a transition from the most general information In all cases, there is a transition from the most general information
which represents a client as a whole to the eventual lightweight that represents a client as a whole to the eventual lightweight
stateid used for most client and server locking interactions. The stateid used for most client and server locking interactions. The
details of this transition will vary with the type of object but it details of this transition will vary with the type of object but it
always starts with a client ID. always starts with a client ID.
8.1. Client and Session ID 8.1. Client and Session ID
A client must establish a client ID (see Section 2.4) and then one or A client must establish a client ID (see Section 2.4) and then one or
more sessionids (see Section 2.10) before performing any operations more sessionids (see Section 2.10) before performing any operations
to open, lock, delegate, or obtain a layout for a file object. Each to open, byte-range lock, delegate, or obtain a layout for a file
session ID is associated with a specific client ID, and thus serves object. Each session ID is associated with a specific client ID, and
as a shorthand reference to an NFSv4.1 client. thus serves as a shorthand reference to an NFSv4.1 client.
For some types of locking interactions, the client will represent For some types of locking interactions, the client will represent
some number of internal locking entities called "owners", which some number of internal locking entities called "owners", which
normally correspond to processes internal to the client. For other normally correspond to processes internal to the client. For other
types of locking-related objects, such as delegations and layouts, no types of locking-related objects, such as delegations and layouts, no
such intermediate entities are provided for, and the locking-related such intermediate entities are provided for, and the locking-related
objects are considered to be transferred directly between the server objects are considered to be transferred directly between the server
and a unitary client. and a unitary client.
8.2. Stateid Definition 8.2. Stateid Definition
When the server grants a lock of any type (including opens, byte- When the server grants a lock of any type (including opens, byte-
range locks, delegations, and layouts) it responds with a unique range locks, delegations, and layouts), it responds with a unique
stateid, that represents a set of locks (often a single lock) for the stateid that represents a set of locks (often a single lock) for the
same file, of the same type, and sharing the same ownership same file, of the same type, and sharing the same ownership
characteristics. Thus opens of the same file by different open- characteristics. Thus, opens of the same file by different open-
owners each have an identifying stateid. Similarly, each set of owners each have an identifying stateid. Similarly, each set of
byte-range locks on a file owned by a specific lock-owner has its own byte-range locks on a file owned by a specific lock-owner has its own
identifying stateid. Delegations and layouts also have associated identifying stateid. Delegations and layouts also have associated
stateids by which they may be referenced. The stateid is used as a stateids by which they may be referenced. The stateid is used as a
shorthand reference to a lock or set of locks and given a stateid the shorthand reference to a lock or set of locks, and given a stateid,
server can determine the associated state-owner or state-owners (in the server can determine the associated state-owner or state-owners
the case of an open-owner/lock-owner pair) and the associated (in the case of an open-owner/lock-owner pair) and the associated
filehandle. When stateids are used, the current filehandle must be filehandle. When stateids are used, the current filehandle must be
the one associated with that stateid. the one associated with that stateid.
All stateids associated with a given client ID are associated with a All stateids associated with a given client ID are associated with a
common lease which represents the claim of those stateids and the common lease that represents the claim of those stateids and the
objects they represent to be maintained by the server. See objects they represent to be maintained by the server. See
Section 8.3 for a discussion of leases. Section 8.3 for a discussion of the lease.
The server may assign stateids independently for different clients. The server may assign stateids independently for different clients.
A stateid with the same bit pattern for one client may designate an A stateid with the same bit pattern for one client may designate an
entirely different set of locks for a different client. The stateid entirely different set of locks for a different client. The stateid
is always interpreted with respect to the client ID associated with is always interpreted with respect to the client ID associated with
the current session. Stateids apply to all sessions associated with the current session. Stateids apply to all sessions associated with
the given client ID and the client may use a stateid obtained from the given client ID, and the client may use a stateid obtained from
one session on another session associated with the same client ID. one session on another session associated with the same client ID.
8.2.1. Stateid Types 8.2.1. Stateid Types
With the exception of special stateids (see Section 8.2.3), each With the exception of special stateids (see Section 8.2.3), each
stateid represents locking objects of one of a set of types defined stateid represents locking objects of one of a set of types defined
by the NFSv4.1 protocol. Note that in all these cases, where we by the NFSv4.1 protocol. Note that in all these cases, where we
speak of guarantee, it is understood there are situations such as a speak of guarantee, it is understood there are situations such as a
client restart, or lock revocation, that allow the guarantee to be client restart, or lock revocation, that allow the guarantee to be
voided. voided.
o Stateids may represent opens of files. o Stateids may represent opens of files.
Each stateid in this case represents the open state for a given Each stateid in this case represents the OPEN state for a given
client ID/open-owner/filehandle triple. Such stateids are subject client ID/open-owner/filehandle triple. Such stateids are subject
to change (with consequent incrementing of the stateid's seqid) in to change (with consequent incrementing of the stateid's seqid) in
response to OPENs that result in upgrade and OPEN_DOWNGRADE response to OPENs that result in upgrade and OPEN_DOWNGRADE
operations. operations.
o Stateids may represent sets of byte-range locks. o Stateids may represent sets of byte-range locks.
All locks held on a particular file by a particular owner and all All locks held on a particular file by a particular owner and
gotten under the aegis of a particular open file are associated gotten under the aegis of a particular open file are associated
with a single stateid with the seqid being incremented whenever with a single stateid with the seqid being incremented whenever
LOCK and LOCKU operations affect that set of locks. LOCK and LOCKU operations affect that set of locks.
o Stateids may represent file delegations, which are recallable o Stateids may represent file delegations, which are recallable
guarantees by the server to the client, that other clients will guarantees by the server to the client that other clients will not
not reference, or will not modify a particular file, until the reference or modify a particular file, until the delegation is
delegation is returned. In NFSv4.1, file delegations may be returned. In NFSv4.1, file delegations may be obtained on both
obtained on both regular and non-regular files. regular and non-regular files.
A stateid represents a single delegation held by a client for a A stateid represents a single delegation held by a client for a
particular filehandle. particular filehandle.
o Stateids may represent directory delegations, which are recallable o Stateids may represent directory delegations, which are recallable
guarantees by the server to the client, that other clients will guarantees by the server to the client that other clients will not
not modify the directory, until the delegation is returned. modify the directory, until the delegation is returned.
A stateid represents a single delegation held by a client for a A stateid represents a single delegation held by a client for a
particular directory filehandle. particular directory filehandle.
o Stateids may represent layouts, which are recallable guarantees by o Stateids may represent layouts, which are recallable guarantees by
the server to the client, that particular files may be accessed the server to the client that particular files may be accessed via
via an alternate data access protocol at specific locations. Such an alternate data access protocol at specific locations. Such
access is limited to particular sets of byte ranges and may access is limited to particular sets of byte-ranges and may
proceed until those byte ranges are reduced or the layout is proceed until those byte-ranges are reduced or the layout is
returned. returned.
A stateid represents the set of all layouts held by a particular A stateid represents the set of all layouts held by a particular
client for a particular filehandle with a given layout type. The client for a particular filehandle with a given layout type. The
seqid is updated as the layouts of that set changes with layout seqid is updated as the layouts of that set of byte-ranges change,
stateid changing operations such as LAYOUTGET and LAYOUTRETURN. via layout stateid changing operations such as LAYOUTGET and
LAYOUTRETURN.
8.2.2. Stateid Structure 8.2.2. Stateid Structure
Stateids are divided into two fields, a 96-bit "other" field Stateids are divided into two fields, a 96-bit "other" field
identifying the specific set of locks and a 32-bit "seqid" sequence identifying the specific set of locks and a 32-bit "seqid" sequence
value. Except in the case of special stateids (see Section 8.2.3), a value. Except in the case of special stateids (see Section 8.2.3), a
particular value of the "other" field denotes a set of locks of the particular value of the "other" field denotes a set of locks of the
same type (for example byte-range locks, opens, delegations, or same type (for example, byte-range locks, opens, delegations, or
layouts), for a specific file or directory, and sharing the same layouts), for a specific file or directory, and sharing the same
ownership characteristics. The seqid designates a specific instance ownership characteristics. The seqid designates a specific instance
of such a set of locks, and is incremented to indicate changes in of such a set of locks, and is incremented to indicate changes in
such a set of locks, either by the addition or deletion of locks from such a set of locks, either by the addition or deletion of locks from
the set, a change in the byte-range they apply to, or an upgrade or the set, a change in the byte-range they apply to, or an upgrade or
downgrade in the type of one or more locks. downgrade in the type of one or more locks.
When such a set of locks is first created the server returns a When such a set of locks is first created, the server returns a
stateid with seqid value of one. On subsequent operations which stateid with seqid value of one. On subsequent operations that
modify the set of locks the server is required to increment the seqid modify the set of locks, the server is required to increment the
field by one (1) whenever it returns a stateid for the same state- "seqid" field by one whenever it returns a stateid for the same
owner/file/type combination and there is some change in the set of state-owner/file/type combination and there is some change in the set
locks actually designated. In this case the server will return a of locks actually designated. In this case, the server will return a
stateid with an other field the same as previously used for that stateid with an "other" field the same as previously used for that
state-owner/file/type combination, with an incremented seqid field. state-owner/file/type combination, with an incremented "seqid" field.
This pattern continues until the seqid is incremented past This pattern continues until the seqid is incremented past
NFS4_UINT32_MAX, and one (not zero) is the next seqid value. NFS4_UINT32_MAX, and one (not zero) is the next seqid value.
The purpose of the incrementing of the seqid is to allow the server The purpose of the incrementing of the seqid is to allow the server
to communicate to the client the order in which operations that to communicate to the client the order in which operations that
modified locking state associated with a stateid have been processed modified locking state associated with a stateid have been processed
and to make it possible for the client to send requests that are and to make it possible for the client to send requests that are
conditional on the set of locks not having changed since the stateid conditional on the set of locks not having changed since the stateid
in question was returned. in question was returned.
Except for layout stateids (Section 12.5.3) when a client sends a Except for layout stateids (Section 12.5.3), when a client sends a
stateid to the server, it has two choices with regard to the seqid stateid to the server, it has two choices with regard to the seqid
sent. It may set the seqid to zero to indicate to the server that it sent. It may set the seqid to zero to indicate to the server that it
wishes the most up-to-date seqid for that stateid's "other" field to wishes the most up-to-date seqid for that stateid's "other" field to
be used. This would be the common choice in the case of a stateid be used. This would be the common choice in the case of a stateid
sent with a READ or WRITE operation. It also may set a non-zero sent with a READ or WRITE operation. It also may set a non-zero
value in which case the server checks if that seqid is the correct value, in which case the server checks if that seqid is the correct
one. In that case the server is required to return one. In that case, the server is required to return
NFS4ERR_OLD_STATEID if the seqid is lower than the most current value NFS4ERR_OLD_STATEID if the seqid is lower than the most current value
and NFS4ERR_BAD_STATEID if the seqid is greater than the most current and NFS4ERR_BAD_STATEID if the seqid is greater than the most current
value. This would be the common choice in the case of stateids sent value. This would be the common choice in the case of stateids sent
with a CLOSE or OPEN_DOWNGRADE. Because OPENs may be sent in with a CLOSE or OPEN_DOWNGRADE. Because OPENs may be sent in
parallel for the same owner, a client might close a file without parallel for the same owner, a client might close a file without
knowing that an OPEN upgrade had been done by the server, changing knowing that an OPEN upgrade had been done by the server, changing
the lock in question. If CLOSE were sent with a zero seqid, the OPEN the lock in question. If CLOSE were sent with a zero seqid, the OPEN
upgrade would be cancelled before the client even received an upgrade would be cancelled before the client even received an
indication that an upgrade had happened. indication that an upgrade had happened.
When a stateid is sent by the server to client as part of a callback When a stateid is sent by the server to the client as part of a
operation, it is not subject to checking for a current seqid and callback operation, it is not subject to checking for a current seqid
returning NFS4ERR_OLD_STATEID. This is because the client is not in and returning NFS4ERR_OLD_STATEID. This is because the client is not
a position to know the most up-to-date seqid and thus cannot verify in a position to know the most up-to-date seqid and thus cannot
it. Unless specially noted, the seqid value for a stateid sent by verify it. Unless specially noted, the seqid value for a stateid
the server to the client as part of a callback is required to be zero sent by the server to the client as part of a callback is required to
with NFS4ERR_BAD_STATEID returned if it is not. be zero with NFS4ERR_BAD_STATEID returned if it is not.
In making comparisons between seqids, both by the client in In making comparisons between seqids, both by the client in
determining the order of operations and by the server in determining determining the order of operations and by the server in determining
whether the NFS4ERR_OLD_STATEID is to be returned, the possibility of whether the NFS4ERR_OLD_STATEID is to be returned, the possibility of
the seqid being swapped around past the NFS4_UINT32_MAX value needs the seqid being swapped around past the NFS4_UINT32_MAX value needs
to be taken into account. When two seqid values are being compared, to be taken into account. When two seqid values are being compared,
the total count of slots for all sessions associated with the current the total count of slots for all sessions associated with the current
client is used to do this. When one seqid value is less that this client is used to do this. When one seqid value is less than this
total slot count and another seqid value is greater than total slot count and another seqid value is greater than
NFS4_UINT32_MAX minus the total slot count, the former is to be NFS4_UINT32_MAX minus the total slot count, the former is to be
treated as lower than the later, despite the fact that it is treated as lower than the latter, despite the fact that it is
numerically greater. numerically greater.
8.2.3. Special Stateids 8.2.3. Special Stateids
Stateid values whose "other" field is either all zeros or all ones Stateid values whose "other" field is either all zeros or all ones
are reserved. They may not be assigned by the server but have are reserved. They may not be assigned by the server but have
special meanings defined by the protocol. The particular meaning special meanings defined by the protocol. The particular meaning
depends on whether the "other" field is all zeros or all ones and the depends on whether the "other" field is all zeros or all ones and the
specific value of the "seqid" field. specific value of the "seqid" field.
The following combinations of "other" and "seqid" are defined in The following combinations of "other" and "seqid" are defined in
NFSv4.1: NFSv4.1:
o When "other" and "seqid" are both zero, the stateid is treated as o When "other" and "seqid" are both zero, the stateid is treated as
a special anonymous stateid, which can be used in READ, WRITE, and a special anonymous stateid, which can be used in READ, WRITE, and
SETATTR requests to indicate the absence of any open state SETATTR requests to indicate the absence of any OPEN state
associated with the request. When an anonymous stateid value is associated with the request. When an anonymous stateid value is
used, and an existing open denies the form of access requested, used and an existing open denies the form of access requested,
then access will be denied to the request. This stateid MUST NOT then access will be denied to the request. This stateid MUST NOT
be used on operations to data servers (Section 13.6). be used on operations to data servers (Section 13.6).
o When "other" and "seqid" are both all ones, the stateid is a o When "other" and "seqid" are both all ones, the stateid is a
special read bypass stateid. When this value is used in WRITE or special READ bypass stateid. When this value is used in WRITE or
SETATTR, it is treated like the anonymous value. When used in SETATTR, it is treated like the anonymous value. When used in
READ, the server MAY grant access, even if access would normally READ, the server MAY grant access, even if access would normally
be denied to READ requests. This stateid MUST NOT be used on be denied to READ operations. This stateid MUST NOT be used on
operations to data servers. operations to data servers.
o When "other" is zero and "seqid" is one, the stateid represents o When "other" is zero and "seqid" is one, the stateid represents
the current stateid, which is whatever value is the last stateid the current stateid, which is whatever value is the last stateid
returned by an operation within the COMPOUND. In the case of an returned by an operation within the COMPOUND. In the case of an
OPEN, the stateid returned for the open file, and not the OPEN, the stateid returned for the open file and not the
delegation is used. The stateid passed to the operation in place delegation is used. The stateid passed to the operation in place
of the special value has its "seqid" value set to zero, except of the special value has its "seqid" value set to zero, except
when the current stateid is used by the operation CLOSE or when the current stateid is used by the operation CLOSE or
OPEN_DOWNGRADE. If there is no operation in the COMPOUND which OPEN_DOWNGRADE. If there is no operation in the COMPOUND that has
has returned a stateid value, the server MUST return the error returned a stateid value, the server MUST return the error
NFS4ERR_BAD_STATEID. As illustrated in Figure 6, if the value of NFS4ERR_BAD_STATEID. As illustrated in Figure 6, if the value of
a current stateid is a special stateid, and the stateid of an a current stateid is a special stateid and the stateid of an
operation's arguments has "other" set to zero, and "seqid" set to operation's arguments has "other" set to zero and "seqid" set to
one, then the server MUST return the error NFS4ERR_BAD_STATEID. one, then the server MUST return the error NFS4ERR_BAD_STATEID.
o When "other" is zero and "seqid" is NFS4_UINT32_MAX, the stateid o When "other" is zero and "seqid" is NFS4_UINT32_MAX, the stateid
represents a reserved stateid value defined to be invalid. When represents a reserved stateid value defined to be invalid. When
this stateid is used, the server MUST return the error this stateid is used, the server MUST return the error
NFS4ERR_BAD_STATEID. NFS4ERR_BAD_STATEID.
If a stateid value is used which has all zero or all ones in the If a stateid value is used that has all zeros or all ones in the
"other" field, but does not match one of the cases above, the server "other" field but does not match one of the cases above, the server
MUST return the error NFS4ERR_BAD_STATEID. MUST return the error NFS4ERR_BAD_STATEID.
Special stateids, unlike other stateids, are not associated with Special stateids, unlike other stateids, are not associated with
individual client IDs or filehandles and can be used with all valid individual client IDs or filehandles and can be used with all valid
client IDs and filehandles. In the case of a special stateid client IDs and filehandles. In the case of a special stateid
designating the current stateid, the current stateid value designating the current stateid, the current stateid value
substituted for the special stateid is associated with a particular substituted for the special stateid is associated with a particular
client ID and filehandle, and so, if it is used where current client ID and filehandle, and so, if it is used where the current
filehandle does not match that associated with the current stateid, filehandle does not match that associated with the current stateid,
the operation to which the stateid is passed will return the operation to which the stateid is passed will return
NFS4ERR_BAD_STATEID. NFS4ERR_BAD_STATEID.
8.2.4. Stateid Lifetime and Validation 8.2.4. Stateid Lifetime and Validation
Stateids must remain valid until either a client restart or a server Stateids must remain valid until either a client restart or a server
restart or until the client returns all of the locks associated with restart or until the client returns all of the locks associated with
the stateid by means of an operation such as CLOSE or DELEGRETURN. the stateid by means of an operation such as CLOSE or DELEGRETURN.
If the locks are lost due to revocation, as long as the client ID is If the locks are lost due to revocation, as long as the client ID is
valid, the stateid remains a valid designation of that revoked state valid, the stateid remains a valid designation of that revoked state
until the client frees it by using FREE_STATEID. Stateids associated until the client frees it by using FREE_STATEID. Stateids associated
with byte-range locks are an exception. They remain valid even if a with byte-range locks are an exception. They remain valid even if a
LOCKU frees all remaining locks, so long as the open file with which LOCKU frees all remaining locks, so long as the open file with which
they are associated remains open, unless the client does a they are associated remains open, unless the client frees the
FREE_STATEID to cause the stateid to be freed. stateids via the FREE_STATEID operation.
It should be noted that there are situations in which the client's It should be noted that there are situations in which the client's
locks become invalid, without the client requesting they be returned. locks become invalid, without the client requesting they be returned.
These include lease expiration and a number of forms of lock These include lease expiration and a number of forms of lock
revocation within the lease period. It is important to note that in revocation within the lease period. It is important to note that in
these situations, the stateid remains valid and the client can use it these situations, the stateid remains valid and the client can use it
to determine the disposition of the associated lost locks. to determine the disposition of the associated lost locks.
An "other" value must never be reused for a different purpose (i.e. An "other" value must never be reused for a different purpose (i.e.,
different filehandle, owner, or type of locks) within the context of different filehandle, owner, or type of locks) within the context of
a single client ID. A server may retain the "other" value for the a single client ID. A server may retain the "other" value for the
same purpose beyond the point where it may otherwise be freed but if same purpose beyond the point where it may otherwise be freed, but if
it does so, it must maintain "seqid" continuity with previous values. it does so, it must maintain "seqid" continuity with previous values.
One mechanism that may be used to satisfy the requirement that the One mechanism that may be used to satisfy the requirement that the
server recognize invalid and out-of-date stateids is for the server server recognize invalid and out-of-date stateids is for the server
to divide the "other" field of the stateid into two fields. to divide the "other" field of the stateid into two fields.
o An index into a table of locking-state structures. o an index into a table of locking-state structures.
o A generation number which is incremented on each allocation of a o a generation number that is incremented on each allocation of a
table entry for a particular use. table entry for a particular use.
And then store in each table entry, And then store in each table entry,
o The client ID with which the stateid is associated. o the client ID with which the stateid is associated.
o The current generation number for the (at most one) valid stateid o the current generation number for the (at most one) valid stateid
sharing this index value. sharing this index value.
o The filehandle of the file on which the locks are taken. o the filehandle of the file on which the locks are taken.
o An indication of the type of stateid (open, byte-range lock, file o an indication of the type of stateid (open, byte-range lock, file
delegation, directory delegation, layout). delegation, directory delegation, layout).
o The last "seqid" value returned corresponding to the current o the last "seqid" value returned corresponding to the current
"other" value. "other" value.
o An indication of the current status of the locks associated with o an indication of the current status of the locks associated with
this stateid. In particular, whether these have been revoked and this stateid, in particular, whether these have been revoked and
if so, for what reason. if so, for what reason.
With this information, an incoming stateid can be validated and the With this information, an incoming stateid can be validated and the
appropriate error returned when necessary. Special and non-special appropriate error returned when necessary. Special and non-special
stateids are handled separately. (See Section 8.2.3 for a discussion stateids are handled separately. (See Section 8.2.3 for a discussion
of special stateids.) of special stateids.)
Note that stateids are implicitly qualified by the current client ID, Note that stateids are implicitly qualified by the current client ID,
as derived from the client ID associated with the current session. as derived from the client ID associated with the current session.
Note however, that the semantics of the session will prevent stateids Note, however, that the semantics of the session will prevent
associated with a previous client or server instance from being stateids associated with a previous client or server instance from
analyzed by this procedure. being analyzed by this procedure.
If server restart has resulted in an invalid client ID or a session If server restart has resulted in an invalid client ID or a session
ID which is invalid, SEQUENCE will return an error and the operation ID that is invalid, SEQUENCE will return an error and the operation
that takes a stateid as an argument will never be processed. that takes a stateid as an argument will never be processed.
If there has been a server restart where there is a persistent If there has been a server restart where there is a persistent
session, and all leased state has been lost, then the session in session and all leased state has been lost, then the session in
question will, although valid, be marked as dead, and any operation question will, although valid, be marked as dead, and any operation
not satisfied by means of the reply cache will receive the error not satisfied by means of the reply cache will receive the error
NFS4ERR_DEADSESSION, and thus not be processed as indicated below. NFS4ERR_DEADSESSION, and thus not be processed as indicated below.
When a stateid is being tested, and the "other" field is all zeros or When a stateid is being tested and the "other" field is all zeros or
all ones, a check that the "other" and "seqid" fields match a defined all ones, a check that the "other" and "seqid" fields match a defined
combination for a special stateid is done and the results determined combination for a special stateid is done and the results determined
as follows: as follows:
o If the "other" and "seqid" fields do not match a defined o If the "other" and "seqid" fields do not match a defined
combination associated with a special stateid, the error combination associated with a special stateid, the error
NFS4ERR_BAD_STATEID is returned. NFS4ERR_BAD_STATEID is returned.
o If the special stateid is one designating the current stateid, and o If the special stateid is one designating the current stateid and
there is a current stateid, then the current stateid is there is a current stateid, then the current stateid is
substituted for the special stateid and the checks appropriate to substituted for the special stateid and the checks appropriate to
non-special stateids in performed. non-special stateids are performed.
o If the combination is valid in general but is not appropriate to o If the combination is valid in general but is not appropriate to
the context in which the stateid is used (e.g. an all-zero stateid the context in which the stateid is used (e.g., an all-zero
is used when an open stateid is required in a LOCK operation), the stateid is used when an OPEN stateid is required in a LOCK
error NFS4ERR_BAD_STATEID is also returned. operation), the error NFS4ERR_BAD_STATEID is also returned.
o Otherwise, the check is completed and the special stateid is o Otherwise, the check is completed and the special stateid is
accepted as valid. accepted as valid.
When a stateid is being tested, and the "other" field is neither all When a stateid is being tested, and the "other" field is neither all
zeros or all ones, the following procedure could be used to validate zeros nor all ones, the following procedure could be used to validate
an incoming stateid and return an appropriate error, when necessary, an incoming stateid and return an appropriate error, when necessary,
assuming that the "other" field would be divided into a table index assuming that the "other" field would be divided into a table index
and an entry generation. and an entry generation.
o If the table index field is outside the range of the associated o If the table index field is outside the range of the associated
table, return NFS4ERR_BAD_STATEID. table, return NFS4ERR_BAD_STATEID.
o If the selected table entry is of a different generation than that o If the selected table entry is of a different generation than that
specified in the incoming stateid, return NFS4ERR_BAD_STATEID. specified in the incoming stateid, return NFS4ERR_BAD_STATEID.
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associated with the current session, return NFS4ERR_BAD_STATEID. associated with the current session, return NFS4ERR_BAD_STATEID.
o If the stateid represents revoked state, then return o If the stateid represents revoked state, then return
NFS4ERR_EXPIRED, NFS4ERR_ADMIN_REVOKED, or NFS4ERR_DELEG_REVOKED, NFS4ERR_EXPIRED, NFS4ERR_ADMIN_REVOKED, or NFS4ERR_DELEG_REVOKED,
as appropriate. as appropriate.
o If the stateid type is not valid for the context in which the o If the stateid type is not valid for the context in which the
stateid appears, return NFS4ERR_BAD_STATEID. Note that a stateid stateid appears, return NFS4ERR_BAD_STATEID. Note that a stateid
may be valid in general, as would be reported by the TEST_STATEID may be valid in general, as would be reported by the TEST_STATEID
operation, but be invalid for a particular operation, as, for operation, but be invalid for a particular operation, as, for
example, when a stateid which doesn't represent byte-range locks example, when a stateid that doesn't represent byte-range locks is
is passed to the non-from_open case of LOCK or to LOCKU, or when a passed to the non-from_open case of LOCK or to LOCKU, or when a
stateid which does not represent an open is passed to CLOSE or stateid that does not represent an open is passed to CLOSE or
OPEN_DOWNGRADE. In such cases, the server MUST return OPEN_DOWNGRADE. In such cases, the server MUST return
NFS4ERR_BAD_STATEID. NFS4ERR_BAD_STATEID.
o If the "seqid" field is not zero, and it is greater than the o If the "seqid" field is not zero and it is greater than the
current sequence value corresponding the current "other" field, current sequence value corresponding to the current "other" field,
return NFS4ERR_BAD_STATEID. return NFS4ERR_BAD_STATEID.
o If the "seqid" field is not zero, and it is less than the current o If the "seqid" field is not zero and it is less than the current
sequence value corresponding the current "other" field, return sequence value corresponding to the current "other" field, return
NFS4ERR_OLD_STATEID. NFS4ERR_OLD_STATEID.
o Otherwise, the stateid is valid and the table entry should contain o Otherwise, the stateid is valid and the table entry should contain
any additional information about the type of stateid and any additional information about the type of stateid and
information associated with that particular type of stateid, such information associated with that particular type of stateid, such
as the associated set of locks, such as open-owner and lock-owner as the associated set of locks, e.g., open-owner and lock-owner
information, as well as information on the specific locks, such as information, as well as information on the specific locks, e.g.,
open modes and byte ranges. open modes and byte-ranges.
8.2.5. Stateid Use for I/O Operations 8.2.5. Stateid Use for I/O Operations
Clients performing I/O operations need to select an appropriate Clients performing I/O operations need to select an appropriate
stateid based on the locks (including opens and delegations) held by stateid based on the locks (including opens and delegations) held by
the client and the various types of state-owners sending the I/O the client and the various types of state-owners sending the I/O
requests. SETATTR operations which change the file size are treated requests. SETATTR operations that change the file size are treated
like I/O operations in this regard. like I/O operations in this regard.
The following rules, applied in order of decreasing priority, govern The following rules, applied in order of decreasing priority, govern
the selection of the appropriate stateid. In following these rules, the selection of the appropriate stateid. In following these rules,
the client will only consider locks of which it has actually received the client will only consider locks of which it has actually received
notification by an appropriate operation response or callback. Note notification by an appropriate operation response or callback. Note
that the rules are slightly different in the case of I/O to data that the rules are slightly different in the case of I/O to data
servers when file layouts are being used (see Section 13.9.1). servers when file layouts are being used (see Section 13.9.1).
o If the client holds a delegation for the file in question, the o If the client holds a delegation for the file in question, the
delegation stateid SHOULD be used. delegation stateid SHOULD be used.
o Otherwise, if the lock-owner corresponding entity (e.g. process) o Otherwise, if the entity corresponding to the lock-owner (e.g., a
sending the I/O has a lock stateid for the associated open file, process) sending the I/O has a byte-range lock stateid for the
then the lock stateid for that lock-owner and open file SHOULD be associated open file, then the byte-range lock stateid for that
used. lock-owner and open file SHOULD be used.
o If there is no lock stateid, then the open stateid for the open o If there is no byte-range lock stateid, then the OPEN stateid for
file in question SHOULD be used. the open file in question SHOULD be used.
o Finally, if none of the above apply, then a special stateid SHOULD o Finally, if none of the above apply, then a special stateid SHOULD
be used. be used.
Ignoring these rules may result in situations in which the server Ignoring these rules may result in situations in which the server
does not have information necessary to properly process the request. does not have information necessary to properly process the request.
For example, when mandatory byte-range locks are in effect, if the For example, when mandatory byte-range locks are in effect, if the
stateid does not indicate the proper lock-owner, via a lock stateid, stateid does not indicate the proper lock-owner, via a lock stateid,
a request might be avoidably rejected. a request might be avoidably rejected.
The server however should not try to enforce these ordering rules and The server however should not try to enforce these ordering rules and
should use whatever information is available to proper process I/O should use whatever information is available to properly process I/O
requests. In particular, when a client has a delegation for a given requests. In particular, when a client has a delegation for a given
file, it SHOULD take note of this fact in processing a request, even file, it SHOULD take note of this fact in processing a request, even
if it is sent with a special stateid. if it is sent with a special stateid.
8.2.6. Stateid Use for SETATTR Operations 8.2.6. Stateid Use for SETATTR Operations
Because each operation is associated with a session ID and from that Because each operation is associated with a session ID and from that
the clientid can be determined, operations do not need to include a the clientid can be determined, operations do not need to include a
stateid for the server to be able to determine whether they should stateid for the server to be able to determine whether they should
cause a delegation to be recalled or are to be treated as done within cause a delegation to be recalled or are to be treated as done within
the scope of the delegation. the scope of the delegation.
In the case of SETATTR operations, a stateid is present. In cases In the case of SETATTR operations, a stateid is present. In cases
other than those which set the file size, the client may send either other than those that set the file size, the client may send either a
a special stateid or, when a delegation is held for the file in special stateid or, when a delegation is held for the file in
question, a delegation stateid. While the server SHOULD validate the question, a delegation stateid. While the server SHOULD validate the
stateid and may use the stateid to optimize the determination as to stateid and may use the stateid to optimize the determination as to
whether a delegation is held, it SHOULD note the presence of a whether a delegation is held, it SHOULD note the presence of a
delegation even when a special stateid is sent, and MUST accept a delegation even when a special stateid is sent, and MUST accept a
valid delegation stateid when sent. valid delegation stateid when sent.
8.3. Lease Renewal 8.3. Lease Renewal
Each client/server pair, as represented by a client ID, has a single Each client/server pair, as represented by a client ID, has a single
lease. The purpose of the lease is to allow the client to indicate lease. The purpose of the lease is to allow the client to indicate
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used for one of those connections. used for one of those connections.
o Transport retransmission delays might become so large as to o Transport retransmission delays might become so large as to
approach or exceed the length of the lease period. This may be approach or exceed the length of the lease period. This may be
particularly likely when the server is unresponsive due to a particularly likely when the server is unresponsive due to a
restart; see Section 8.4.2.1. If the client implementation is not restart; see Section 8.4.2.1. If the client implementation is not
careful, transport retransmission delays can result in the client careful, transport retransmission delays can result in the client
failing to detect a server restart before the grace period ends. failing to detect a server restart before the grace period ends.
The scenario is that the client is using a transport with The scenario is that the client is using a transport with
exponential back off, such that the maximum retransmission timeout exponential back off, such that the maximum retransmission timeout
exceeds the both the grace period and the lease_time attribute. A exceeds both the grace period and the lease_time attribute. A
network partition causes the client's connection's retransmission network partition causes the client's connection's retransmission
interval to back off, and even after the partition heals, the next interval to back off, and even after the partition heals, the next
transport-level retransmission is sent after the server has transport-level retransmission is sent after the server has
restarted and its grace period ends. restarted and its grace period ends.
The client MUST either recover from the ensuing NFS4ERR_NO_GRACE The client MUST either recover from the ensuing NFS4ERR_NO_GRACE
errors, or it MUST ensure that despite transport level errors or it MUST ensure that, despite transport-level
retransmission intervals that exceed the lease_time, nonetheless a retransmission intervals that exceed the lease_time, a SEQUENCE
SEQUENCE operation is sent that renews the lease before operation is sent that renews the lease before expiration. The
expiration. The client can achieve this by associating a new client can achieve this by associating a new connection with the
connection with the session, and sending a SEQUENCE operation on session, and sending a SEQUENCE operation on it. However, if the
it. However, if the attempt to establish a new connection is attempt to establish a new connection is delayed for some reason
delayed for some reason (e.g. exponential backoff of the (e.g., exponential backoff of the connection establishment
connection establishment packets), the client will have to abort packets), the client will have to abort the connection
the connection establishment attempt before the lease expires, and establishment attempt before the lease expires, and attempt to
attempt to re-connect. reconnect.
If the server renews the lease upon receiving a SEQUENCE operation, If the server renews the lease upon receiving a SEQUENCE operation,
the server MUST NOT allow the lease to expire while the rest of the the server MUST NOT allow the lease to expire while the rest of the
operations in the COMPOUND procedure's request are still executing. operations in the COMPOUND procedure's request are still executing.
Once the last operation has finished, and the response to COMPOUND Once the last operation has finished, and the response to COMPOUND
has been sent, the server MUST set the lease to expire no sooner than has been sent, the server MUST set the lease to expire no sooner than
the sum of current time and the value of the lease_time attribute. the sum of current time and the value of the lease_time attribute.
A client ID's lease can expire when it has been at least the lease A client ID's lease can expire when it has been at least the lease
interval (lease_time) since the last lease-renewing SEQUENCE interval (lease_time) since the last lease-renewing SEQUENCE
operation was sent on any of the client ID's sessions and there are operation was sent on any of the client ID's sessions and there are
no active COMPOUND operations on any such sessions. no active COMPOUND operations on any such sessions.
Because the SEQUENCE operation is the basic mechanism to renew a Because the SEQUENCE operation is the basic mechanism to renew a
lease, and because if must be done at least once for each lease lease, and because it must be done at least once for each lease
period, it is the natural mechanism whereby the server will inform period, it is the natural mechanism whereby the server will inform
the client of changes in the lease status that the client needs to be the client of changes in the lease status that the client needs to be
informed of. The client should inspect the status flags informed of. The client should inspect the status flags
(sr_status_flags) returned by sequence and take the appropriate (sr_status_flags) returned by sequence and take the appropriate
action (see Section 18.46.3 for details). action (see Section 18.46.3 for details).
o The status bits SEQ4_STATUS_CB_PATH_DOWN and o The status bits SEQ4_STATUS_CB_PATH_DOWN and
SEQ4_STATUS_CB_PATH_DOWN_SESSION indicate problems with the SEQ4_STATUS_CB_PATH_DOWN_SESSION indicate problems with the
backchannel which the client may need to address in order to backchannel that the client may need to address in order to
receive callback requests. receive callback requests.
o The status bits SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRING and o The status bits SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRING and
SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRED indicate problems with GSS SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRED indicate problems with GSS
contexts or RPCSEC_GSS handles for the backchannel which the contexts or RPCSEC_GSS handles for the backchannel that the client
client may have to address to allow callback requests to be sent might have to address in order to allow callback requests to be
to it. sent.
o The status bits SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED, o The status bits SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED,
SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED, SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED,
SEQ4_STATUS_ADMIN_STATE_REVOKED, and SEQ4_STATUS_ADMIN_STATE_REVOKED, and
SEQ4_STATUS_RECALLABLE_STATE_REVOKED notify the client of lock SEQ4_STATUS_RECALLABLE_STATE_REVOKED notify the client of lock
revocation events. When these bits are set, the client should use revocation events. When these bits are set, the client should use
TEST_STATEID to find what stateids have been revoked and use TEST_STATEID to find what stateids have been revoked and use
FREE_STATEID to acknowledge loss of the associated state. FREE_STATEID to acknowledge loss of the associated state.
o The status bit SEQ4_STATUS_LEASE_MOVE indicates that o The status bit SEQ4_STATUS_LEASE_MOVE indicates that
responsibility for lease renewal has been transferred to one or responsibility for lease renewal has been transferred to one or
more new servers. more new servers.
o The status bit SEQ4_STATUS_RESTART_RECLAIM_NEEDED indicates that o The status bit SEQ4_STATUS_RESTART_RECLAIM_NEEDED indicates that
due to server restart the client must reclaim locking state. due to server restart the client must reclaim locking state.
o The status bit SEQ4_STATUS_BACKCHANNEL_FAULT indicates the server o The status bit SEQ4_STATUS_BACKCHANNEL_FAULT indicates that the
has encountered an unrecoverable fault with the backchannel (e.g. server has encountered an unrecoverable fault with the backchannel
it has lost track of a sequence ID for a slot in the backchannel). (e.g., it has lost track of a sequence ID for a slot in the
backchannel).
8.4. Crash Recovery 8.4. Crash Recovery
A critical requirement in crash recovery is that both the client and A critical requirement in crash recovery is that both the client and
the server know when the other has failed. Additionally, it is the server know when the other has failed. Additionally, it is
required that a client sees a consistent view of data across server required that a client sees a consistent view of data across server
restarts. All READ and WRITE operations that may have been queued restarts. All READ and WRITE operations that may have been queued
within the client or network buffers must wait until the client has within the client or network buffers must wait until the client has
successfully recovered the locks protecting the READ and WRITE successfully recovered the locks protecting the READ and WRITE
operations. Any that reach the server before the server can safely operations. Any that reach the server before the server can safely
determine that the client has recovered enough locking state to be determine that the client has recovered enough locking state to be
sure that such operations can be safely processed must be rejected. sure that such operations can be safely processed must be rejected.
This will happen because either: This will happen because either:
o The state presented is no longer valid since it is associated with o The state presented is no longer valid since it is associated with
a now invalid client ID. In this case the client will receive a now invalid client ID. In this case, the client will receive
either an NFS4ERR_BADSESSION or NFS4ERR_DEADSESSION error, and any either an NFS4ERR_BADSESSION or NFS4ERR_DEADSESSION error, and any
attempt to attach a new session to that invalid client ID will attempt to attach a new session to that invalid client ID will
result in an NFS4ERR_STALE_CLIENTID error. result in an NFS4ERR_STALE_CLIENTID error.
o Subsequent recovery of locks may make execution of the operation o Subsequent recovery of locks may make execution of the operation
inappropriate (NFS4ERR_GRACE). inappropriate (NFS4ERR_GRACE).
8.4.1. Client Failure and Recovery 8.4.1. Client Failure and Recovery
In the event that a client fails, the server may release the client's In the event that a client fails, the server may release the client's
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discussed in Section 8.3, when a client has not failed and re- discussed in Section 8.3, when a client has not failed and re-
establishes its lease before expiration occurs, requests for establishes its lease before expiration occurs, requests for
conflicting locks will not be granted. conflicting locks will not be granted.
To minimize client delay upon restart, lock requests are associated To minimize client delay upon restart, lock requests are associated
with an instance of the client by a client-supplied verifier. This with an instance of the client by a client-supplied verifier. This
verifier is part of the client_owner4 sent in the initial EXCHANGE_ID verifier is part of the client_owner4 sent in the initial EXCHANGE_ID
call made by the client. The server returns a client ID as a result call made by the client. The server returns a client ID as a result
of the EXCHANGE_ID operation. The client then confirms the use of of the EXCHANGE_ID operation. The client then confirms the use of
the client ID by establishing a session associated with that client the client ID by establishing a session associated with that client
ID (see Section 18.36.3 for a description how this is done). All ID (see Section 18.36.3 for a description of how this is done). All
locks, including opens, byte-range locks, delegations, and layouts locks, including opens, byte-range locks, delegations, and layouts
obtained by sessions using that client ID are associated with that obtained by sessions using that client ID, are associated with that
client ID. client ID.
Since the verifier will be changed by the client upon each Since the verifier will be changed by the client upon each
initialization, the server can compare a new verifier to the verifier initialization, the server can compare a new verifier to the verifier
associated with currently held locks and determine that they do not associated with currently held locks and determine that they do not
match. This signifies the client's new instantiation and subsequent match. This signifies the client's new instantiation and subsequent
loss (upon confirmation of the new client ID) of locking state. As a loss (upon confirmation of the new client ID) of locking state. As a
result, the server is free to release all locks held which are result, the server is free to release all locks held that are
associated with the old client ID which was derived from the old associated with the old client ID that was derived from the old
verifier. At this point conflicting locks from other clients, kept verifier. At this point, conflicting locks from other clients, kept
waiting while the lease had not yet expired, can be granted. In waiting while the lease had not yet expired, can be granted. In
addition, all stateids associated with the old client ID can also be addition, all stateids associated with the old client ID can also be
freed, as they are no longer reference-able. freed, as they are no longer reference-able.
Note that the verifier must have the same uniqueness properties as Note that the verifier must have the same uniqueness properties as
the verifier for the COMMIT operation. the verifier for the COMMIT operation.
8.4.2. Server Failure and Recovery 8.4.2. Server Failure and Recovery
If the server loses locking state (usually as a result of a restart), If the server loses locking state (usually as a result of a restart),
it must allow clients time to discover this fact and re-establish the it must allow clients time to discover this fact and re-establish the
lost locking state. The client must be able to re-establish the lost locking state. The client must be able to re-establish the
locking state without having the server deny valid requests because locking state without having the server deny valid requests because
the server has granted conflicting access to another client. the server has granted conflicting access to another client.
Likewise, if there is a possibility that clients have not yet re- Likewise, if there is a possibility that clients have not yet re-
established their locking state for a file, and that such locking established their locking state for a file and that such locking
state might make it invalid to perform READ or WRITE operations, for state might make it invalid to perform READ or WRITE operations. For
example through the establishment of mandatory locks, the server must example, if mandatory locks are a possibility, the server must
disallow READ and WRITE operations for that file. disallow READ and WRITE operations for that file.
A client can determine that loss of locking state has occurred via A client can determine that loss of locking state has occurred via
several methods. several methods.
1. When a SEQUENCE (most common) or other operation returns 1. When a SEQUENCE (most common) or other operation returns
NFS4ERR_BADSESSION, this may mean the session has been destroyed, NFS4ERR_BADSESSION, this may mean that the session has been
but the client ID is still valid. The client sends a destroyed but the client ID is still valid. The client sends a
CREATE_SESSION request with the client ID to re-establish the CREATE_SESSION request with the client ID to re-establish the
session. If CREATE_SESSION fails with NFS4ERR_STALE_CLIENTID, session. If CREATE_SESSION fails with NFS4ERR_STALE_CLIENTID,
the client must establish a new client ID (see Section 8.1) and the client must establish a new client ID (see Section 8.1) and
re-establish its lock state with the new client ID, after the re-establish its lock state with the new client ID, after the
CREATE_SESSION operation succeeds (see Section 8.4.2.1). CREATE_SESSION operation succeeds (see Section 8.4.2.1).
2. When a SEQUENCE (most common) or other operation on a persistent 2. When a SEQUENCE (most common) or other operation on a persistent
session returns NFS4ERR_DEADSESSION, this indicates that a session returns NFS4ERR_DEADSESSION, this indicates that a
session is no longer usable for new, i.e. not satisfied from the session is no longer usable for new, i.e., not satisfied from the
reply cache, operations. Once all pending operations are reply cache, operations. Once all pending operations are
determined to be either performed before the retry or not determined to be either performed before the retry or not
performed, the client sends a CREATE_SESSION request with the performed, the client sends a CREATE_SESSION request with the
client ID to re-establish the session. If CREATE_SESSION fails client ID to re-establish the session. If CREATE_SESSION fails
with NFS4ERR_STALE_CLIENTID, the client must establish a new with NFS4ERR_STALE_CLIENTID, the client must establish a new
client ID (see Section 8.1) and re-establish its lock state after client ID (see Section 8.1) and re-establish its lock state after
the CREATE_SESSION, with the new client ID, succeeds, the CREATE_SESSION, with the new client ID, succeeds
(Section 8.4.2.1). (Section 8.4.2.1).
3. When a operation, neither SEQUENCE nor preceded by SEQUENCE (for 3. When an operation, neither SEQUENCE nor preceded by SEQUENCE (for
example, CREATE_SESSION, DESTROY_SESSION) returns example, CREATE_SESSION, DESTROY_SESSION), returns
NFS4ERR_STALE_CLIENTID. The client MUST establish a new client NFS4ERR_STALE_CLIENTID, the client MUST establish a new client ID
ID (Section 8.1) and re-establish its lock state (Section 8.1) and re-establish its lock state (Section 8.4.2.1).
(Section 8.4.2.1).
8.4.2.1. State Reclaim 8.4.2.1. State Reclaim
When state information and the associated locks are lost as a result When state information and the associated locks are lost as a result
of a server restart, the protocol must provide a way to cause that of a server restart, the protocol must provide a way to cause that
state to be re-established. The approach used is to define, for most state to be re-established. The approach used is to define, for most
types of locking state (layouts are an exception), a request whose types of locking state (layouts are an exception), a request whose
function is to allow the client to re-establish on the server a lock function is to allow the client to re-establish on the server a lock
first obtained from a previous instance. Generally these requests first obtained from a previous instance. Generally, these requests
are variants of the requests normally used to create locks of that are variants of the requests normally used to create locks of that
type and are referred to as "reclaim-type" requests and the process type and are referred to as "reclaim-type" requests, and the process
of re-establishing such locks is referred to as "reclaiming" them. of re-establishing such locks is referred to as "reclaiming" them.
Because each client must have an opportunity to reclaim all of the Because each client must have an opportunity to reclaim all of the
locks that it has without the possibility that some other client will locks that it has without the possibility that some other client will
be granted a conflicting lock, a special period called the "grace be granted a conflicting lock, a "grace period" is devoted to the
period" is devoted to the reclaim process. During this period, reclaim process. During this period, requests creating client IDs
requests creating client IDs and sessions are handled normally, but and sessions are handled normally, but locking requests are subject
locking requests are subject to special restrictions. Only reclaim- to special restrictions. Only reclaim-type locking requests are
type locking requests are allowed, unless the server can reliably allowed, unless the server can reliably determine (through state
determine (through state persistently maintained across restart persistently maintained across restart instances) that granting any
instances), that granting any such lock cannot possibly conflict with such lock cannot possibly conflict with a subsequent reclaim. When a
a subsequent reclaim. When a request is made to obtain a new lock request is made to obtain a new lock (i.e., not a reclaim-type
(i.e. not a reclaim-type request) during the grace period and such a request) during the grace period and such a determination cannot be
determination cannot be made, the server must return the error made, the server must return the error NFS4ERR_GRACE.
NFS4ERR_GRACE.
Once a session is established using the new client ID, the client Once a session is established using the new client ID, the client
will use reclaim-type locking requests (e.g. LOCK requests with will use reclaim-type locking requests (e.g., LOCK operations with
reclaim set to TRUE and OPEN operations with a claim type of reclaim set to TRUE and OPEN operations with a claim type of
CLAIM_PREVIOUS; see Section 9.11) to re-establish its locking state. CLAIM_PREVIOUS; see Section 9.11) to re-establish its locking state.
Once this is done, or if there is no such locking state to reclaim, Once this is done, or if there is no such locking state to reclaim,
the client sends a global RECLAIM_COMPLETE operation, i.e. one with the client sends a global RECLAIM_COMPLETE operation, i.e., one with
the rca_one_fs argument set to FALSE, to indicate that it has the rca_one_fs argument set to FALSE, to indicate that it has
reclaimed all of the locking state that it will reclaim. Once a reclaimed all of the locking state that it will reclaim. Once a
client sends such a RECLAIM_COMPLETE operation, it may attempt non- client sends such a RECLAIM_COMPLETE operation, it may attempt non-
reclaim locking operations, although it may get NFS4ERR_GRACE errors reclaim locking operations, although it might get an NFS4ERR_GRACE
the operations until the period of special handling is over. See status result from each such operation until the period of special
Section 11.7.7 for a discussion of the analogous handling lock handling is over. See Section 11.7.7 for a discussion of the
reclamation in the case of file systems transitioning from server to analogous handling lock reclamation in the case of file systems
server. transitioning from server to server.
During the grace period, the server must reject READ and WRITE During the grace period, the server must reject READ and WRITE
operations and non-reclaim locking requests (i.e. other LOCK and OPEN operations and non-reclaim locking requests (i.e., other LOCK and
operations) with an error of NFS4ERR_GRACE, unless it can guarantee OPEN operations) with an error of NFS4ERR_GRACE, unless it can
that these may be done safely, as described below. guarantee that these may be done safely, as described below.
The grace period may last until all clients which are known to The grace period may last until all clients that are known to
possibly have had locks have done a global RECLAIM_COMPLETE possibly have had locks have done a global RECLAIM_COMPLETE
operation, indicating that they have finished reclaiming the locks operation, indicating that they have finished reclaiming the locks
they held before the server restart. This means that a client which they held before the server restart. This means that a client that
has done a RECLAIM_COMPLETE must be prepared to receive an has done a RECLAIM_COMPLETE must be prepared to receive an
NFS4ERR_GRACE when attempting to acquire new locks. In order for the NFS4ERR_GRACE when attempting to acquire new locks. In order for the
server to know that all clients with possible prior lock state have server to know that all clients with possible prior lock state have
done a RECLAIM_COMPLETE, the server must maintain in stable storage a done a RECLAIM_COMPLETE, the server must maintain in stable storage a
list of clients which may have such locks. The server may also list clients that may have such locks. The server may also terminate
terminate the grace period before all clients have done a global the grace period before all clients have done a global
RECLAIM_COMPLETE. The server SHOULD NOT terminate the grace period RECLAIM_COMPLETE. The server SHOULD NOT terminate the grace period
before a time equal to the lease period in order to give clients an before a time equal to the lease period in order to give clients an
opportunity to find out about the server restart, as a result of opportunity to find out about the server restart, as a result of
sending requests on associated sessions with a frequency governed by sending requests on associated sessions with a frequency governed by
the lease time. Note that when a client does not send such requests the lease time. Note that when a client does not send such requests
(or they are sent by the client but not received by the server), it (or they are sent by the client but not received by the server), it
is possible for the grace period to expire before the client finds is possible for the grace period to expire before the client finds
out that the server restart has occurred. out that the server restart has occurred.
Some additional time in order to allow a client to establish a new Some additional time in order to allow a client to establish a new
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to guarantee that no possible conflict could arise between a to guarantee that no possible conflict could arise between a
potential reclaim locking request and the READ or WRITE operation. potential reclaim locking request and the READ or WRITE operation.
If the server is unable to offer that guarantee, the NFS4ERR_GRACE If the server is unable to offer that guarantee, the NFS4ERR_GRACE
error must be returned to the client. error must be returned to the client.
For a server to provide simple, valid handling during the grace For a server to provide simple, valid handling during the grace
period, the easiest method is to simply reject all non-reclaim period, the easiest method is to simply reject all non-reclaim
locking requests and READ and WRITE operations by returning the locking requests and READ and WRITE operations by returning the
NFS4ERR_GRACE error. However, a server may keep information about NFS4ERR_GRACE error. However, a server may keep information about
granted locks in stable storage. With this information, the server granted locks in stable storage. With this information, the server
could determine if a regular lock or READ or WRITE operation can be could determine if a locking, READ or WRITE operation can be safely
safely processed. processed.
For example, if the server maintained on stable storage summary For example, if the server maintained on stable storage summary
information on whether mandatory locks exist, either mandatory byte- information on whether mandatory locks exist, either mandatory byte-
range locks, or share reservations specifying deny modes, many range locks, or share reservations specifying deny modes, many
requests could be allowed during the grace period. If it is known requests could be allowed during the grace period. If it is known
that no such share reservations exist, OPEN request that do not that no such share reservations exist, OPEN request that do not
specify deny modes may be safely granted. If, in addition, it is specify deny modes may be safely granted. If, in addition, it is
known that no mandatory byte-range locks exist, either through known that no mandatory byte-range locks exist, either through
information stored on stable storage or simply because the server information stored on stable storage or simply because the server
does not support such locks, READ and WRITE requests may be safely does not support such locks, READ and WRITE operations may be safely
processed during the grace period. Another important case is where processed during the grace period. Another important case is where
it is known that no mandatory byte-range locks exist, either because it is known that no mandatory byte-range locks exist, either because
the server does not provide support for them, or because their the server does not provide support for them or because their absence
absence is known from persistently recorded data. In this case, READ is known from persistently recorded data. In this case, READ and
and WRITE operations specifying stateids derived from reclaim-type WRITE operations specifying stateids derived from reclaim-type
operation may be validly processed during the grace period because operations may be validly processed during the grace period because
the fact of the valid reclaim ensures that no lock subsequently of the fact that the valid reclaim ensures that no lock subsequently
granted can prevent the I/O. granted can prevent the I/O.
To reiterate, for a server that allows non-reclaim lock and I/O To reiterate, for a server that allows non-reclaim lock and I/O
requests to be processed during the grace period, it MUST determine requests to be processed during the grace period, it MUST determine
that no lock subsequently reclaimed will be rejected and that no lock that no lock subsequently reclaimed will be rejected and that no lock
subsequently reclaimed would have prevented any I/O operation subsequently reclaimed would have prevented any I/O operation
processed during the grace period. processed during the grace period.
Clients should be prepared for the return of NFS4ERR_GRACE errors for Clients should be prepared for the return of NFS4ERR_GRACE errors for
non-reclaim lock and I/O requests. In this case the client should non-reclaim lock and I/O requests. In this case, the client should
employ a retry mechanism for the request. A delay (on the order of employ a retry mechanism for the request. A delay (on the order of
several seconds) between retries should be used to avoid overwhelming several seconds) between retries should be used to avoid overwhelming
the server. Further discussion of the general issue is included in the server. Further discussion of the general issue is included in
[47]. The client must account for the server that can perform I/O [47]. The client must account for the server that can perform I/O
and non-reclaim locking requests within the grace period as well as and non-reclaim locking requests within the grace period as well as
those that cannot do so. those that cannot do so.
A reclaim-type locking request outside the server's grace period can A reclaim-type locking request outside the server's grace period can
only succeed if the server can guarantee that no conflicting lock or only succeed if the server can guarantee that no conflicting lock or
I/O request has been granted since restart. I/O request has been granted since restart.
A server may, upon restart, establish a new value for the lease A server may, upon restart, establish a new value for the lease
period. Therefore, clients should, once a new client ID is period. Therefore, clients should, once a new client ID is
established, refetch the lease_time attribute and use it as the basis established, refetch the lease_time attribute and use it as the basis
for lease renewal for the lease associated with that server. for lease renewal for the lease associated with that server.
However, the server must establish, for this restart event, a grace However, the server must establish, for this restart event, a grace
period at least as long as the lease period for the previous server period at least as long as the lease period for the previous server
instantiation. This allows the client state obtained during the instantiation. This allows the client state obtained during the
previous server instance to be reliably re-established. previous server instance to be reliably re-established.
The possibility exists, that because of server configuration events, The possibility exists that, because of server configuration events,
the client will be communicating with a server different than the one the client will be communicating with a server different than the one
on which the locks were obtained, as shown by the combination of on which the locks were obtained, as shown by the combination of
eir_server_scope and eir_server_owner. This leads to the issue of if eir_server_scope and eir_server_owner. This leads to the issue of if
and when the client should attempt to reclaim locks previously and when the client should attempt to reclaim locks previously
obtained on what is being reported as a different server. The rules obtained on what is being reported as a different server. The rules
to resolve this question are as follows: to resolve this question are as follows:
o If the server scope is different the client should not attempt to o If the server scope is different, the client should not attempt to
reclaim locks. In this situation no lock reclaim is possible. reclaim locks. In this situation, no lock reclaim is possible.
Any attempt to re-obtain the locks with non-reclaim operations is Any attempt to re-obtain the locks with non-reclaim operations is
problematic since there is no guarantee that the existing problematic since there is no guarantee that the existing
filehandles will be recognized by the new server, or that if filehandles will be recognized by the new server, or that if
recognized, they denote the same objects. It is best to treat the recognized, they denote the same objects. It is best to treat the
locks as having been revoked by the reconfiguration event. locks as having been revoked by the reconfiguration event.
o If the server scope is the same, the client should attempt to o If the server scope is the same, the client should attempt to
reclaim locks, even if the eir_server_owner value is different. reclaim locks, even if the eir_server_owner value is different.
In this situation, it is the responsibility of the server to In this situation, it is the responsibility of the server to
return NFS4ERR_NO_GRACE if it cannot provide correct support for return NFS4ERR_NO_GRACE if it cannot provide correct support for
lock reclaim operations, including the prevention of edge lock reclaim operations, including the prevention of edge
conditions. conditions.
The eir_server_owner field is not used in making this determination. The eir_server_owner field is not used in making this determination.
Its function is to specify trunking possibilities for the client (see Its function is to specify trunking possibilities for the client (see
Section 2.10.5) and not to control lock reclaim. Section 2.10.5) and not to control lock reclaim.
8.4.2.1.1. Security Considerations for State Reclaim 8.4.2.1.1. Security Considerations for State Reclaim
During the grace period, a client can reclaim state it believes or During the grace period, a client can reclaim state that it believes
asserts it had before the server restarted. Unless the server or asserts it had before the server restarted. Unless the server
maintained a complete record of all the state the client had, the maintained a complete record of all the state the client had, the
server has little choice but to trust the client. (Of course if the server has little choice but to trust the client. (Of course, if the
server maintained a complete record, then it would not have to force server maintained a complete record, then it would not have to force
the client to reclaim state after server restart.) While the server the client to reclaim state after server restart.) While the server
has to trust the client to tell the truth, such trust does not have has to trust the client to tell the truth, such trust does not have
any negative consequences for security. The fundamental rule for the any negative consequences for security. The fundamental rule for the
server when processing reclaim requests is that it MUST NOT grant the server when processing reclaim requests is that it MUST NOT grant the
reclaim if an equivalent non-reclaim request would not be granted reclaim if an equivalent non-reclaim request would not be granted
during steady-state due to access control or access conflict issues. during steady state due to access control or access conflict issues.
For example an OPEN request during a reclaim will be refused with For example, an OPEN request during a reclaim will be refused with
NFS4ERR_ACCESS if the principal making the request does not have NFS4ERR_ACCESS if the principal making the request does not have
access to open the file according to the discretionary ACL access to open the file according to the discretionary ACL
(Section 6.2.2) on the file. (Section 6.2.2) on the file.
Nonetheless, it is possible that client operating in error or Nonetheless, it is possible that a client operating in error or
maliciously could, during reclaim, prevent another client from maliciously could, during reclaim, prevent another client from
reclaiming access to state. For example, an attacker could send an reclaiming access to state. For example, an attacker could send an
OPEN reclaim operation with a deny mode that prevents another client OPEN reclaim operation with a deny mode that prevents another client
from reclaiming the open state it had before the server restarted. from reclaiming the OPEN state it had before the server restarted.
The attacker could perform the same denial of service during steady The attacker could perform the same denial of service during steady
state prior to server restart, as long as the the attacker had state prior to server restart, as long as the attacker had
permissions. Given that the attack vectors are equivalent, the grace permissions. Given that the attack vectors are equivalent, the grace
period does not offer any additional opportunity for denial of period does not offer any additional opportunity for denial of
service, and any concerns about this attack vector, whether during service, and any concerns about this attack vector, whether during
grace or steady state are addressed the same way: use RPCSEC_GSS for grace or steady state, are addressed the same way: use RPCSEC_GSS for
authentication, and limit access to the file only to principals the authentication and limit access to the file only to principals that
owner of the file trusts. the owner of the file trusts.
Note that if prior to restart the server had client IDs with the Note that if prior to restart the server had client IDs with the
EXCHGID4_FLAG_BIND_PRINC_STATEID (Section 18.35) capability set, then EXCHGID4_FLAG_BIND_PRINC_STATEID (Section 18.35) capability set, then
the server SHOULD record in stable storage the client owner and the the server SHOULD record in stable storage the client owner and the
principal that established the client ID via EXCHANGE_ID. If the principal that established the client ID via EXCHANGE_ID. If the
server does not, then there is a risk a client will be unable to server does not, then there is a risk a client will be unable to
reclaim state if it does not have a credential for a principal that reclaim state if it does not have a credential for a principal that
was originally authorized to establish the state. was originally authorized to establish the state.
8.4.3. Network Partitions and Recovery 8.4.3. Network Partitions and Recovery
If the duration of a network partition is greater than the lease If the duration of a network partition is greater than the lease
period provided by the server, the server will not have received a period provided by the server, the server will not have received a
lease renewal from the client. If this occurs, the server may free lease renewal from the client. If this occurs, the server may free
all locks held for the client, or it may allow the lock state to all locks held for the client or it may allow the lock state to
remain for a considerable period, subject to the constraint that if a remain for a considerable period, subject to the constraint that if a
request for a conflicting lock is made, locks associated with an request for a conflicting lock is made, locks associated with an
expired lease do not prevent such a conflicting lock from being expired lease do not prevent such a conflicting lock from being
granted but MUST be revoked as necessary so as not to interfere with granted but MUST be revoked as necessary so as to avoid interfering
such conflicting requests. with such conflicting requests.
If the server chooses to delay freeing of lock state until there is a If the server chooses to delay freeing of lock state until there is a
conflict, it may either free all of the clients locks once there is a conflict, it may either free all of the client's locks once there is
conflict, or it may only revoke the minimum set of locks necessary to a conflict or it may only revoke the minimum set of locks necessary
allow conflicting requests. When it adopts the finer-grained to allow conflicting requests. When it adopts the finer-grained
approach, it must revoke all locks associated with a given stateid, approach, it must revoke all locks associated with a given stateid,
even if the conflict is with only a subset of locks. even if the conflict is with only a subset of locks.
When the server chooses to free all of a client's lock state, either When the server chooses to free all of a client's lock state, either
immediately upon lease expiration, or a result of the first attempt immediately upon lease expiration or as a result of the first attempt
to obtain a conflicting a lock, the server may report the loss of to obtain a conflicting a lock, the server may report the loss of
lock state in a number of ways. lock state in a number of ways.
The server may choose to invalidate the session and the associated The server may choose to invalidate the session and the associated
client ID. In this case, once the client can communicate with the client ID. In this case, once the client can communicate with the
server, it will receive an NFS4ERR_BADSESSION error. Upon attempting server, it will receive an NFS4ERR_BADSESSION error. Upon attempting
to create a new session, it would get an NFS4ERR_STALE_CLIENTID. to create a new session, it would get an NFS4ERR_STALE_CLIENTID.
Upon creating the new client ID and new session the client will Upon creating the new client ID and new session, the client will
attempt to reclaim locks. Normally, the server will not allow the attempt to reclaim locks. Normally, the server will not allow the
client to reclaim locks, because the server will not be in its client to reclaim locks, because the server will not be in its
recovery grace period. recovery grace period.
Another possibility is for the server to maintain the session and Another possibility is for the server to maintain the session and
client ID but for all stateids held by the client to become invalid client ID but for all stateids held by the client to become invalid
or stale. Once the client can reach the server after such a network or stale. Once the client can reach the server after such a network
partition, the status returned by the SEQUENCE operation will partition, the status returned by the SEQUENCE operation will
indicate a loss of locking state, i.e. the flag indicate a loss of locking state; i.e., the flag
SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED will be set in sr_status_flags. SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED will be set in sr_status_flags.
In addition, all I/O submitted by the client with the now invalid In addition, all I/O submitted by the client with the now invalid
stateids will fail with the server returning the error stateids will fail with the server returning the error
NFS4ERR_EXPIRED. Once the client learns of the loss of locking NFS4ERR_EXPIRED. Once the client learns of the loss of locking
state, it will suitably notify the applications that held the state, it will suitably notify the applications that held the
invalidated locks. The client should then take action to free invalidated locks. The client should then take action to free
invalidated stateids, either by establishing a new client ID using a invalidated stateids, either by establishing a new client ID using a
new verifier or by doing a FREE_STATEID operation to release each of new verifier or by doing a FREE_STATEID operation to release each of
the invalidated stateids. the invalidated stateids.
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the following: the following:
1. Client A acquires a lock. 1. Client A acquires a lock.
2. Client A and server experience mutual network partition, such 2. Client A and server experience mutual network partition, such
that client A is unable to renew its lease. that client A is unable to renew its lease.
3. Client A's lease expires, and the server releases the lock. 3. Client A's lease expires, and the server releases the lock.
4. Client B acquires a lock that would have conflicted with that of 4. Client B acquires a lock that would have conflicted with that of
Client A. client A.
5. Client B releases its lock. 5. Client B releases its lock.
6. Server restarts. 6. Server restarts.
7. Network partition between client A and server heals. 7. Network partition between client A and server heals.
8. Client A connects to new server instance and finds out about 8. Client A connects to a new server instance and finds out about
server restart. server restart.
9. Client A reclaims its lock within the server's grace period. 9. Client A reclaims its lock within the server's grace period.
Thus, at the final step, the server has erroneously granted client Thus, at the final step, the server has erroneously granted client
A's lock reclaim. If client B modified the object the lock was A's lock reclaim. If client B modified the object the lock was
protecting, client A will experience object corruption. protecting, client A will experience object corruption.
The second known edge condition arises in situations such as the The second known edge condition arises in situations such as the
following: following:
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9. Client A connects to new server instance and finds out about 9. Client A connects to new server instance and finds out about
server restart. server restart.
10. Client A reclaims its lock within the server's grace period. 10. Client A reclaims its lock within the server's grace period.
As with the first edge condition, the final step of the scenario of As with the first edge condition, the final step of the scenario of
the second edge condition has the server erroneously granting client the second edge condition has the server erroneously granting client
A's lock reclaim. A's lock reclaim.
Solving the first and second edge conditions requires that the server Solving the first and second edge conditions requires either that the
either always assumes after it restarts that some edge condition server always assumes after it restarts that some edge condition
occurs, and thus return NFS4ERR_NO_GRACE for all reclaim attempts, or occurs, and thus returns NFS4ERR_NO_GRACE for all reclaim attempts,
that the server record some information in stable storage. The or that the server record some information in stable storage. The
amount of information the server records in stable storage is in amount of information the server records in stable storage is in
inverse proportion to how harsh the server intends to be whenever inverse proportion to how harsh the server intends to be whenever
edge conditions arise. The server that is completely tolerant of all edge conditions arise. The server that is completely tolerant of all
edge conditions will record in stable storage every lock that is edge conditions will record in stable storage every lock that is
acquired, removing the lock record from stable storage only when the acquired, removing the lock record from stable storage only when the
lock is released. For the two edge conditions discussed above, the lock is released. For the two edge conditions discussed above, the
harshest a server can be, and still support a grace period for harshest a server can be, and still support a grace period for
reclaims, requires that the server record in stable storage some reclaims, requires that the server record in stable storage some
minimal information. For example, a server implementation could, for minimal information. For example, a server implementation could, for
each client, save in stable storage a record containing: each client, save in stable storage a record containing:
o the co_ownerid field from the client_owner4 presented in the o the co_ownerid field from the client_owner4 presented in the
EXCHANGE_ID operation. EXCHANGE_ID operation.
o a boolean that indicates if the client's lease expired or if there o a boolean that indicates if the client's lease expired or if there
was administrative intervention (see Section 8.5) to revoke a was administrative intervention (see Section 8.5) to revoke a
byte-range lock, share reservation, or delegation and there has byte-range lock, share reservation, or delegation and there has
been no acknowledgement, via FREE_STATEID, of such revocation. been no acknowledgment, via FREE_STATEID, of such revocation.
o a boolean that indicates whether the client may have locks that it o a boolean that indicates whether the client may have locks that it
believes to be reclaimable in situations which the grace period believes to be reclaimable in situations in which the grace period
was terminated, making the server's view of lock reclaimability was terminated, making the server's view of lock reclaimability
suspect. The server will set this for any client record in stable suspect. The server will set this for any client record in stable
storage where the client has not done a suitable RECLAIM_COMPLETE storage where the client has not done a suitable RECLAIM_COMPLETE
(global or file system-specific depending on the target of the (global or file system-specific depending on the target of the
lock request) before it grants any new (i.e. not reclaimed) lock lock request) before it grants any new (i.e., not reclaimed) lock
to any client. to any client.
Assuming the above record keeping, for the first edge condition, Assuming the above record keeping, for the first edge condition,
after the server restarts, the record that client A's lease expired after the server restarts, the record that client A's lease expired
means that another client could have acquired a conflicting byte- means that another client could have acquired a conflicting byte-
range lock, share reservation, or delegation. Hence the server must range lock, share reservation, or delegation. Hence, the server must
reject a reclaim from client A with the error NFS4ERR_NO_GRACE. reject a reclaim from client A with the error NFS4ERR_NO_GRACE.
For the second edge condition, after the server restarts for a second For the second edge condition, after the server restarts for a second
time, the indication that the client had not completed its reclaims time, the indication that the client had not completed its reclaims
at the time at which the grace period ended means that the server at the time at which the grace period ended means that the server
must reject a reclaim from client A with the error NFS4ERR_NO_GRACE. must reject a reclaim from client A with the error NFS4ERR_NO_GRACE.
When either edge condition occurs, the client's attempt to reclaim When either edge condition occurs, the client's attempt to reclaim
locks will result in the error NFS4ERR_NO_GRACE. When this is locks will result in the error NFS4ERR_NO_GRACE. When this is
received, or after the client restarts with no lock state, the client received, or after the client restarts with no lock state, the client
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reclaims of share reservations, byte-range locks, and delegations): reclaims of share reservations, byte-range locks, and delegations):
1. Reject all reclaims with NFS4ERR_NO_GRACE. This is extremely 1. Reject all reclaims with NFS4ERR_NO_GRACE. This is extremely
unforgiving, but necessary if the server does not record lock unforgiving, but necessary if the server does not record lock
state in stable storage. state in stable storage.
2. Record sufficient state in stable storage such that all known 2. Record sufficient state in stable storage such that all known
edge conditions involving server restart, including the two noted edge conditions involving server restart, including the two noted
in this section, are detected. It is acceptable to erroneously in this section, are detected. It is acceptable to erroneously
recognize an edge condition and not allow a reclaim, when, with recognize an edge condition and not allow a reclaim, when, with
sufficient knowledge it would be allowed. The error the server sufficient knowledge, it would be allowed. The error the server
would return in this case is NFS4ERR_NO_GRACE. Note it is not would return in this case is NFS4ERR_NO_GRACE. Note that it is
known if there are other edge conditions. not known if there are other edge conditions.
In the event that, after a server restart, the server determines In the event that, after a server restart, the server determines
that there is unrecoverable damage or corruption to the there is unrecoverable damage or corruption to the information in
information in stable storage, then for all clients and/or locks stable storage, then for all clients and/or locks that may be
which may be affected, the server MUST return NFS4ERR_NO_GRACE. affected, the server MUST return NFS4ERR_NO_GRACE.
A mandate for the client's handling of the NFS4ERR_NO_GRACE error is A mandate for the client's handling of the NFS4ERR_NO_GRACE error is
outside the scope of this specification, since the strategies for outside the scope of this specification, since the strategies for
such handling are very dependent on the client's operating such handling are very dependent on the client's operating
environment. However, one potential approach is described below. environment. However, one potential approach is described below.
When the client receives NFS4ERR_NO_GRACE, it could examine the When the client receives NFS4ERR_NO_GRACE, it could examine the
change attribute of the objects the client is trying to reclaim state change attribute of the objects for which the client is trying to
for, and use that to determine whether to re-establish the state via reclaim state, and use that to determine whether to re-establish the
normal OPEN or LOCK requests. This is acceptable provided the state via normal OPEN or LOCK operations. This is acceptable
client's operating environment allows it. In other words, the client provided that the client's operating environment allows it. In other
implementor is advised to document for his users the behavior. The words, the client implementor is advised to document for his users
client could also inform the application that its byte-range lock or the behavior. The client could also inform the application that its
share reservations (whether they were delegated or not) have been byte-range lock or share reservations (whether or not they were
lost, such as via a UNIX signal, a GUI pop-up window, etc. See delegated) have been lost, such as via a UNIX signal, a Graphical
Section 10.5 for a discussion of what the client should do for User Interface (GUI) pop-up window, etc. See Section 10.5 for a
dealing with unreclaimed delegations on client state. discussion of what the client should do for dealing with unreclaimed
delegations on client state.
For further discussion of revocation of locks see Section 8.5. For further discussion of revocation of locks, see Section 8.5.
8.5. Server Revocation of Locks 8.5. Server Revocation of Locks
At any point, the server can revoke locks held by a client and the At any point, the server can revoke locks held by a client, and the
client must be prepared for this event. When the client detects that client must be prepared for this event. When the client detects that
its locks have been or may have been revoked, the client is its locks have been or may have been revoked, the client is
responsible for validating the state information between itself and responsible for validating the state information between itself and
the server. Validating locking state for the client means that it the server. Validating locking state for the client means that it
must verify or reclaim state for each lock currently held. must verify or reclaim state for each lock currently held.
The first occasion of lock revocation is upon server restart. Note The first occasion of lock revocation is upon server restart. Note
that this includes situations in which sessions are persistent and that this includes situations in which sessions are persistent and
locking state is lost. In this class of instances, the client will locking state is lost. In this class of instances, the client will
receive an error (NFS4ERR_STALE_CLIENTID) on an operation that takes receive an error (NFS4ERR_STALE_CLIENTID) on an operation that takes
client ID, usually as part of recovery in response to a problem with client ID, usually as part of recovery in response to a problem with
the current session) and the client will proceed with normal crash the current session), and the client will proceed with normal crash
recovery as described in the Section 8.4.2.1. recovery as described in the Section 8.4.2.1.
The second occasion of lock revocation is the inability to renew the The second occasion of lock revocation is the inability to renew the
lease before expiration, as discussed in Section 8.4.3. While this lease before expiration, as discussed in Section 8.4.3. While this
is considered a rare or unusual event, the client must be prepared to is considered a rare or unusual event, the client must be prepared to
recover. The server is responsible for determining the precise recover. The server is responsible for determining the precise
consequences of the lease expiration, informing the client of the consequences of the lease expiration, informing the client of the
scope of the lock revocation decided upon. The client then uses the scope of the lock revocation decided upon. The client then uses the
status information provided by the server in the SEQUENCE results status information provided by the server in the SEQUENCE results
(field sr_status_flags, see Section 18.46.3) to synchronize its (field sr_status_flags, see Section 18.46.3) to synchronize its
locking state with that of the server, in order to recover. locking state with that of the server, in order to recover.
The third occasion of lock revocation can occur as a result of The third occasion of lock revocation can occur as a result of
revocation of locks within the lease period, either because of revocation of locks within the lease period, either because of
administrative intervention, or because a recallable lock (a administrative intervention or because a recallable lock (a
delegation or layout) was not returned within the lease period after delegation or layout) was not returned within the lease period after
having been recalled. While these are considered rare events, they having been recalled. While these are considered rare events, they
are possible and the client must be prepared to deal with them. When are possible, and the client must be prepared to deal with them.
either of these events occur, the client finds out about the When either of these events occurs, the client finds out about the
situation through the status returned by the SEQUENCE operation. Any situation through the status returned by the SEQUENCE operation. Any
use of stateids associated with locks revoked during the lease period use of stateids associated with locks revoked during the lease period
will receive the error NFS4ERR_ADMIN_REVOKED or will receive the error NFS4ERR_ADMIN_REVOKED or
NFS4ERR_DELEG_REVOKED, as appropriate. NFS4ERR_DELEG_REVOKED, as appropriate.
In all situations in which a subset of locking state may have been In all situations in which a subset of locking state may have been
revoked, which include all cases in which locking state is revoked revoked, which include all cases in which locking state is revoked
within the lease period, it is up to the client to determine which within the lease period, it is up to the client to determine which
locks have been revoked and which have not. It does this by using locks have been revoked and which have not. It does this by using
the TEST_STATEID operation on the appropriate set of stateids. Once the TEST_STATEID operation on the appropriate set of stateids. Once
the set of revoked locks has been determined, the applications can be the set of revoked locks has been determined, the applications can be
notified, and the invalidated stateids can be freed and lock notified, and the invalidated stateids can be freed and lock
revocation acknowledged by using FREE_STATEID. revocation acknowledged by using FREE_STATEID.
8.6. Short and Long Leases 8.6. Short and Long Leases
When determining the time period for the server lease, the usual When determining the time period for the server lease, the usual
lease tradeoffs apply. Short leases are good for fast server lease tradeoffs apply. A short lease is good for fast server
recovery at a cost of increased operations to effect lease renewal recovery at a cost of increased operations to effect lease renewal
(when there are no other operations during the period to effect lease (when there are no other operations during the period to effect lease
renewal as a side-effect). Long leases are certainly kinder and renewal as a side effect). A long lease is certainly kinder and
gentler to servers trying to handle very large numbers of clients. gentler to servers trying to handle very large numbers of clients.
The number of extra requests to effect lock renewal drops in inverse The number of extra requests to effect lock renewal drops in inverse
proportion to the lease time. The disadvantages of long leases proportion to the lease time. The disadvantages of a long lease
include the possibility of slower recovery after certain failures. include the possibility of slower recovery after certain failures.
After server failure, a longer grace period may be required when some After server failure, a longer grace period may be required when some
clients do not promptly reclaim their locks and do a global clients do not promptly reclaim their locks and do a global
RECLAIM_COMPLETE. In the event of client failure, there can be a RECLAIM_COMPLETE. In the event of client failure, the longer period
longer period for leases to expire thus forcing conflicting requests for a lease to expire will force conflicting requests to wait longer.
to wait.
Long leases are practical if the server can store lease state in A long lease is practical if the server can store lease state in
stable storage. Upon recovery, the server can reconstruct the lease stable storage. Upon recovery, the server can reconstruct the lease
state from its stable storage and continue operation with its state from its stable storage and continue operation with its
clients. clients.
8.7. Clocks, Propagation Delay, and Calculating Lease Expiration 8.7. Clocks, Propagation Delay, and Calculating Lease Expiration
To avoid the need for synchronized clocks, lease times are granted by To avoid the need for synchronized clocks, lease times are granted by
the server as a time delta. However, there is a requirement that the the server as a time delta. However, there is a requirement that the
client and server clocks do not drift excessively over the duration client and server clocks do not drift excessively over the duration
of the lease. There is also the issue of propagation delay across of the lease. There is also the issue of propagation delay across
the network which could easily be several hundred milliseconds as the network, which could easily be several hundred milliseconds, as
well as the possibility that requests will be lost and need to be well as the possibility that requests will be lost and need to be
retransmitted. retransmitted.
To take propagation delay into account, the client should subtract it To take propagation delay into account, the client should subtract it
from lease times (e.g. if the client estimates the one-way from lease times (e.g., if the client estimates the one-way
propagation delay as 200 milliseconds, then it can assume that the propagation delay as 200 milliseconds, then it can assume that the
lease is already 200 milliseconds old when it gets it). In addition, lease is already 200 milliseconds old when it gets it). In addition,
it will take another 200 milliseconds to get a response back to the it will take another 200 milliseconds to get a response back to the
server. So the client must send a lease renewal or write data back server. So the client must send a lease renewal or write data back
to the server at least 400 milliseconds before the lease would to the server at least 400 milliseconds before the lease would
expire. If the propagation delay varies over the life of the lease expire. If the propagation delay varies over the life of the lease
(e.g. the client is on a mobile host), the client will need to (e.g., the client is on a mobile host), the client will need to
continuously subtract the increase in propagation delay from the continuously subtract the increase in propagation delay from the
lease times. lease times.
The server's lease period configuration should take into account the The server's lease period configuration should take into account the
network distance of the clients that will be accessing the server's network distance of the clients that will be accessing the server's
resources. It is expected that the lease period will take into resources. It is expected that the lease period will take into
account the network propagation delays and other network delay account the network propagation delays and other network delay
factors for the client population. Since the protocol does not allow factors for the client population. Since the protocol does not allow
for an automatic method to determine an appropriate lease period, the for an automatic method to determine an appropriate lease period, the
server's administrator may have to tune the lease period. server's administrator may have to tune the lease period.
8.8. Obsolete Locking Infrastructure From NFSv4.0 8.8. Obsolete Locking Infrastructure from NFSv4.0
There are a number of operations and fields within existing There are a number of operations and fields within existing
operations that no longer have a function in NFSv4.1. In one way or operations that no longer have a function in NFSv4.1. In one way or
another, these changes are all due to the implementation of sessions another, these changes are all due to the implementation of sessions
which provides client context and exactly once semantics as a base that provide client context and exactly once semantics as a base
feature of the protocol, separate from locking itself. feature of the protocol, separate from locking itself.
The following NFSv4.0 operations MUST NOT be implemented in NFSv4.1. The following NFSv4.0 operations MUST NOT be implemented in NFSv4.1.
The server MUST return NFS4ERR_NOTSUPP if these operations are found The server MUST return NFS4ERR_NOTSUPP if these operations are found
in an NFSv4.1 COMPOUND. in an NFSv4.1 COMPOUND.
o SETCLIENTID since its function has been replaced by EXCHANGE_ID. o SETCLIENTID since its function has been replaced by EXCHANGE_ID.
o SETCLIENTID_CONFIRM since client ID confirmation now happens by o SETCLIENTID_CONFIRM since client ID confirmation now happens by
means of CREATE_SESSION. means of CREATE_SESSION.
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o OPEN_CONFIRM because state-owner-based seqids have been replaced o OPEN_CONFIRM because state-owner-based seqids have been replaced
by the sequence ID in the SEQUENCE operation. by the sequence ID in the SEQUENCE operation.
o RELEASE_LOCKOWNER because lock-owners with no associated locks do o RELEASE_LOCKOWNER because lock-owners with no associated locks do
not have any sequence-related state and so can be deleted by the not have any sequence-related state and so can be deleted by the
server at will. server at will.
o RENEW because every SEQUENCE operation for a session causes lease o RENEW because every SEQUENCE operation for a session causes lease
renewal, making a separate operation superfluous. renewal, making a separate operation superfluous.
Also, there are a number of fields, present in existing operations Also, there are a number of fields, present in existing operations,
related to locking that have no use in minor version one. They were related to locking that have no use in minor version 1. They were
used in minor version zero to perform functions now provided in a used in minor version 0 to perform functions now provided in a
different fashion. different fashion.
o Sequence ids used to sequence requests for a given state-owner and o Sequence ids used to sequence requests for a given state-owner and
to provide retry protection, now provided via sessions. to provide retry protection, now provided via sessions.
o Client IDs used to identify the client associated with a given o Client IDs used to identify the client associated with a given
request. Client identification is now available using the client request. Client identification is now available using the client
ID associated with the current session, without needing an ID associated with the current session, without needing an
explicit client ID field. explicit client ID field.
Such vestigial fields in existing operations have no function in Such vestigial fields in existing operations have no function in
NFSv4.1 and are ignored by the server. Note that client IDs in NFSv4.1 and are ignored by the server. Note that client IDs in
operations new to NFSv4.1 (such as CREATE_SESSION and operations new to NFSv4.1 (such as CREATE_SESSION and
DESTROY_CLIENTID) are not ignored. DESTROY_CLIENTID) are not ignored.
9. File Locking and Share Reservations 9. File Locking and Share Reservations
To support Win32 share reservations it is necessary to provide To support Win32 share reservations, it is necessary to provide
operations which atomically open or create files. Having a separate operations that atomically open or create files. Having a separate
share/unshare operation would not allow correct implementation of the share/unshare operation would not allow correct implementation of the
Win32 OpenFile API. In order to correctly implement share semantics, Win32 OpenFile API. In order to correctly implement share semantics,
the previous NFS protocol mechanisms used when a file is opened or the previous NFS protocol mechanisms used when a file is opened or
created (LOOKUP, CREATE, ACCESS) need to be replaced. The NFSv4.1 created (LOOKUP, CREATE, ACCESS) need to be replaced. The NFSv4.1
protocol defines an OPEN operation which is capable of atomically protocol defines an OPEN operation that is capable of atomically
looking up, creating, and locking a file on the server. looking up, creating, and locking a file on the server.
9.1. Opens and Byte-Range Locks 9.1. Opens and Byte-Range Locks
It is assumed that manipulating a byte-range lock is rare when It is assumed that manipulating a byte-range lock is rare when
compared to READ and WRITE operations. It is also assumed that compared to READ and WRITE operations. It is also assumed that
server restarts and network partitions are relatively rare. server restarts and network partitions are relatively rare.
Therefore it is important that the READ and WRITE operations have a Therefore, it is important that the READ and WRITE operations have a
lightweight mechanism to indicate if they possess a held lock. A lightweight mechanism to indicate if they possess a held lock. A
byte-range lock request contains the heavyweight information required LOCK operation contains the heavyweight information required to
to establish a lock and uniquely define the owner of the lock. establish a byte-range lock and uniquely define the owner of the
lock.
9.1.1. State-owner Definition 9.1.1. State-Owner Definition
When opening a file or requesting a byte-range lock, the client must When opening a file or requesting a byte-range lock, the client must
specify an identifier which represents the owner of the requested specify an identifier that represents the owner of the requested
lock. This identifier is in the form of a state-owner, represented lock. This identifier is in the form of a state-owner, represented
in the protocol by a state_owner4, a variable-length opaque array in the protocol by a state_owner4, a variable-length opaque array
which, when concatenated with the current client ID uniquely defines that, when concatenated with the current client ID, uniquely defines
the owner of lock managed by the client. This may be a thread ID, the owner of a lock managed by the client. This may be a thread ID,
process ID, or other unique value. process ID, or other unique value.
Owners of opens and owners of byte-range locks are separate entities Owners of opens and owners of byte-range locks are separate entities
and remain separate even if the same opaque arrays are used to and remain separate even if the same opaque arrays are used to
designate owners of each. The protocol distinguishes between open- designate owners of each. The protocol distinguishes between open-
owners (represented by open_owner4 structures) and lock-owners owners (represented by open_owner4 structures) and lock-owners
(represented by lock_owner4 structures). (represented by lock_owner4 structures).
Each open is associated with a specific open-owner while each byte- Each open is associated with a specific open-owner while each byte-
range lock is associated with a lock-owner and an open-owner, the range lock is associated with a lock-owner and an open-owner, the
latter being the open-owner associated with the open file under which latter being the open-owner associated with the open file under which
the LOCK operation was done. Delegations and layouts, on the other the LOCK operation was done. Delegations and layouts, on the other
hand, are not associated with a specific owner but are associated hand, are not associated with a specific owner but are associated
with the client as a whole (identified by a client ID). with the client as a whole (identified by a client ID).
9.1.2. Use of the Stateid and Locking 9.1.2. Use of the Stateid and Locking
All READ, WRITE and SETATTR operations contain a stateid. For the All READ, WRITE, and SETATTR operations contain a stateid. For the
purposes of this section, SETATTR operations which change the size purposes of this section, SETATTR operations that change the size
attribute of a file are treated as if they are writing the area attribute of a file are treated as if they are writing the area
between the old and new size (i.e. the range truncated or added to between the old and new sizes (i.e., the byte-range truncated or
the file by means of the SETATTR), even where SETATTR is not added to the file by means of the SETATTR), even where SETATTR is not
explicitly mentioned in the text. The stateid passed to one of these explicitly mentioned in the text. The stateid passed to one of these
operations must be one that represents an open, a set of byte-range operations must be one that represents an open, a set of byte-range
locks, or a delegation, or it may be a special stateid representing locks, or a delegation, or it may be a special stateid representing
anonymous access or the special bypass stateid. anonymous access or the special bypass stateid.
If the state-owner performs a READ or WRITE in a situation in which If the state-owner performs a READ or WRITE operation in a situation
it has established a byte-range lock or share reservation on the in which it has established a byte-range lock or share reservation on
server (any OPEN constitutes a share reservation) the stateid the server (any OPEN constitutes a share reservation), the stateid
(previously returned by the server) must be used to indicate what (previously returned by the server) must be used to indicate what
locks, including both byte-range locks and share reservations, are locks, including both byte-range locks and share reservations, are
held by the state-owner. If no state is established by the client, held by the state-owner. If no state is established by the client,
either byte-range lock or share reservation, a special stateid for either a byte-range lock or a share reservation, a special stateid
anonymous state (zero as "other" and "seqid") is used. (See for anonymous state (zero as the value for "other" and "seqid") is
Section 8.2.3 for a description of 'special' stateids in general.) used. (See Section 8.2.3 for a description of 'special' stateids in
Regardless whether a stateid for anonymous state or a stateid general.) Regardless of whether a stateid for anonymous state or a
returned by the server is used, if there is a conflicting share stateid returned by the server is used, if there is a conflicting
reservation or mandatory byte-range lock held on the file, the server share reservation or mandatory byte-range lock held on the file, the
MUST refuse to service the READ or WRITE operation. server MUST refuse to service the READ or WRITE operation.
Share reservations are established by OPEN operations and by their Share reservations are established by OPEN operations and by their
nature are mandatory in that when the OPEN denies READ or WRITE nature are mandatory in that when the OPEN denies READ or WRITE
operations, that denial results in such operations being rejected operations, that denial results in such operations being rejected
with error NFS4ERR_LOCKED. Byte-range locks may be implemented by with error NFS4ERR_LOCKED. Byte-range locks may be implemented by
the server as either mandatory or advisory, or the choice of the server as either mandatory or advisory, or the choice of
mandatory or advisory behavior may be determined by the server on the mandatory or advisory behavior may be determined by the server on the
basis of the file being accessed (for example, some UNIX-based basis of the file being accessed (for example, some UNIX-based
servers support a "mandatory lock bit" on the mode attribute such servers support a "mandatory lock bit" on the mode attribute such
that if set, byte-range locks are required on the file before I/O is that if set, byte-range locks are required on the file before I/O is
possible). When byte-range locks are advisory, they only prevent the possible). When byte-range locks are advisory, they only prevent the
granting of conflicting lock requests and have no effect on READs or granting of conflicting lock requests and have no effect on READs or
WRITEs. Mandatory byte-range locks, however, prevent conflicting I/O WRITEs. Mandatory byte-range locks, however, prevent conflicting I/O
operations. When they are attempted, they are rejected with operations. When they are attempted, they are rejected with
NFS4ERR_LOCKED. When the client gets NFS4ERR_LOCKED on a file it NFS4ERR_LOCKED. When the client gets NFS4ERR_LOCKED on a file for
knows it has the proper share reservation for, it will need to send a which it knows it has the proper share reservation, it will need to
LOCK request on the region of the file that includes the region the send a LOCK operation on the byte-range of the file that includes the
I/O was to be performed on, with an appropriate locktype (i.e. byte-range the I/O was to be performed on, with an appropriate
READ*_LT for a READ operation, WRITE*_LT for a WRITE operation). locktype field of the LOCK operation's arguments (i.e., READ*_LT for
a READ operation, WRITE*_LT for a WRITE operation).
Note that for UNIX environments that support mandatory file locking,
the distinction between advisory and mandatory locking is subtle. In
fact, advisory and mandatory byte-range locks are exactly the same in
so far as the APIs and requirements on implementation. If the
mandatory lock attribute is set on the file, the server checks to see
if the lock-owner has an appropriate shared (read) or exclusive
(write) byte-range lock on the region it wishes to read or write to.
If there is no appropriate lock, the server checks if there is a Note that for UNIX environments that support mandatory byte-range
conflicting lock (which can be done by attempting to acquire the locking, the distinction between advisory and mandatory locking is
conflicting lock on behalf of the lock-owner, and if successful, subtle. In fact, advisory and mandatory byte-range locks are exactly
release the lock after the READ or WRITE is done), and if there is, the same as far as the APIs and requirements on implementation. If
the server returns NFS4ERR_LOCKED. the mandatory lock attribute is set on the file, the server checks to
see if the lock-owner has an appropriate shared (READ_LT) or
exclusive (WRITE_LT) byte-range lock on the byte-range it wishes to
READ from or WRITE to. If there is no appropriate lock, the server
checks if there is a conflicting lock (which can be done by
attempting to acquire the conflicting lock on behalf of the lock-
owner, and if successful, release the lock after the READ or WRITE
operation is done), and if there is, the server returns
NFS4ERR_LOCKED.
For Windows environments, byte-range locks are always mandatory, so For Windows environments, byte-range locks are always mandatory, so
the server always checks for byte-range locks during I/O requests. the server always checks for byte-range locks during I/O requests.
Thus, the NFSv4.1 LOCK operation does not need to distinguish between Thus, the LOCK operation does not need to distinguish between
advisory and mandatory byte-range locks. It is the NFSv4.1 server's advisory and mandatory byte-range locks. It is the server's
processing of the READ and WRITE operations that introduces the processing of the READ and WRITE operations that introduces the
distinction. distinction.
Every stateid which is validly passed to READ, WRITE or SETATTR, with Every stateid that is validly passed to READ, WRITE, or SETATTR, with
the exception of special stateid values, defines an access mode for the exception of special stateid values, defines an access mode for
the file (i.e. READ, WRITE, or READ-WRITE) the file (i.e., OPEN4_SHARE_ACCESS_READ, OPEN4_SHARE_ACCESS_WRITE, or
OPEN4_SHARE_ACCESS_BOTH).
o For stateids associated with opens, this is the mode defined by o For stateids associated with opens, this is the mode defined by
the original OPEN which caused the allocation of the open stateid the original OPEN that caused the allocation of the OPEN stateid
and as modified by subsequent OPENs and OPEN_DOWNGRADEs for the and as modified by subsequent OPENs and OPEN_DOWNGRADEs for the
same open-owner/file pair. same open-owner/file pair.
o For stateids returned by byte-range lock requests, the appropriate o For stateids returned by byte-range LOCK operations, the
mode is the access mode for the open stateid associated with the appropriate mode is the access mode for the OPEN stateid
lock set represented by the stateid. associated with the lock set represented by the stateid.
o For delegation stateids the access mode is based on the type of o For delegation stateids, the access mode is based on the type of
delegation. delegation.
When a READ, WRITE, or SETATTR (which specifies the size attribute) When a READ, WRITE, or SETATTR (that specifies the size attribute)
is done, the operation is subject to checking against the access mode operation is done, the operation is subject to checking against the
to verify that the operation is appropriate given the stateid with access mode to verify that the operation is appropriate given the
which the operation is associated. stateid with which the operation is associated.
In the case of WRITE-type operations (i.e. WRITEs and SETATTRs which In the case of WRITE-type operations (i.e., WRITEs and SETATTRs that
set size), the server MUST verify that the access mode allows writing set size), the server MUST verify that the access mode allows writing
and MUST return an NFS4ERR_OPENMODE error if it does not. In the and MUST return an NFS4ERR_OPENMODE error if it does not. In the
case, of READ, the server may perform the corresponding check on the case of READ, the server may perform the corresponding check on the
access mode, or it may choose to allow READ on opens for WRITE only, access mode, or it may choose to allow READ on OPENs for
to accommodate clients whose write implementation may unavoidably do OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
reads (e.g. due to buffer cache constraints). However, even if READs implementation may unavoidably do reads (e.g., due to buffer cache
are allowed in these circumstances, the server MUST still check for constraints). However, even if READs are allowed in these
locks that conflict with the READ (e.g. another open specify denial circumstances, the server MUST still check for locks that conflict
of READs). Note that a server which does enforce the access mode with the READ (e.g., another OPEN specified OPEN4_SHARE_DENY_READ or
check on READs need not explicitly check for conflicting share OPEN4_SHARE_DENY_BOTH). Note that a server that does enforce the
reservations since the existence of OPEN for read access guarantees access mode check on READs need not explicitly check for conflicting
that no conflicting share reservation can exist. share reservations since the existence of OPEN for
OPEN4_SHARE_ACCESS_READ guarantees that no conflicting share
reservation can exist.
The read bypass special stateid (all bits of "other" and "seqid" set The READ bypass special stateid (all bits of "other" and "seqid" set
to one) indicates a desire to bypass locking checks. The server MAY to one) indicates a desire to bypass locking checks. The server MAY
allow READ operations to bypass locking checks at the server, when allow READ operations to bypass locking checks at the server, when
this special stateid is used. However, WRITE operations with this this special stateid is used. However, WRITE operations with this
special stateid value MUST NOT bypass locking checks and are treated special stateid value MUST NOT bypass locking checks and are treated
exactly the same as if a special stateid for anonymous state were exactly the same as if a special stateid for anonymous state were
used. used.
A lock may not be granted while a READ or WRITE operation using one A lock may not be granted while a READ or WRITE operation using one
of the special stateids is being performed and the scope of the lock of the special stateids is being performed and the scope of the lock
to be granted would conflict with the READ or WRITE operation. This to be granted would conflict with the READ or WRITE operation. This
can occur when: can occur when:
o A mandatory byte range lock is requested with range that conflicts o A mandatory byte-range lock is requested with a byte-range that
with the range of the READ or WRITE operation. For the purposes conflicts with the byte-range of the READ or WRITE operation. For
of this paragraph, a conflict occurs when a shared lock is the purposes of this paragraph, a conflict occurs when a shared
requested and a WRITE operation is being performed, or an lock is requested and a WRITE operation is being performed, or an
exclusive lock is requested and either a READ or a WRITE operation exclusive lock is requested and either a READ or a WRITE operation
is being performed. is being performed.
o A share reservation is requested which denies reading and or o A share reservation is requested that denies reading and/or
writing and the corresponding operation is being performed. writing and the corresponding operation is being performed.
o A delegation is to be granted and the delegation type would o A delegation is to be granted and the delegation type would
prevent the I/O operation, i.e. READ and WRITE conflict with a prevent the I/O operation, i.e., READ and WRITE conflict with an
write delegation and WRITE conflicts with a read delegation. OPEN_DELEGATE_WRITE delegation and WRITE conflicts with an
OPEN_DELEGATE_READ delegation.
When a client holds a delegation, it needs to ensure that the stateid When a client holds a delegation, it needs to ensure that the stateid
sent conveys the association of operation with the delegation, to sent conveys the association of operation with the delegation, to
avoid the delegation from being avoidably recalled. When the avoid the delegation from being avoidably recalled. When the
delegation stateid, or a stateid open associated with that delegation stateid, a stateid open associated with that delegation,
delegation, or a stateid representing byte-range locks derived form or a stateid representing byte-range locks derived from such an open
such an open is used, the server knows that the READ, WRITE, or is used, the server knows that the READ, WRITE, or SETATTR does not
SETATTR does not conflict with the delegation, but is sent under the conflict with the delegation but is sent under the aegis of the
aegis of the delegation. Even though it is possible for the server delegation. Even though it is possible for the server to determine
to determine from the client ID (via the session ID) that the client from the client ID (via the session ID) that the client does in fact
does in fact have a delegation, the server is not obliged to check have a delegation, the server is not obliged to check this, so using
this, so using a special stateid can result in avoidable recall of a special stateid can result in avoidable recall of the delegation.
the delegation.
9.2. Lock Ranges 9.2. Lock Ranges
The protocol allows a lock-owner to request a lock with a byte range The protocol allows a lock-owner to request a lock with a byte-range
and then either upgrade, downgrade, or unlock a sub-range of the and then either upgrade, downgrade, or unlock a sub-range of the
initial lock, or a range that consists of a range which overlaps, initial lock, or a byte-range that overlaps -- fully or partially --
fully or partially, that initial lock or a combination of a set of either with that initial lock or a combination of a set of existing
existing locks for the same lock-owner. It is expected that this locks for the same lock-owner. It is expected that this will be an
will be an uncommon type of request. In any case, servers or server uncommon type of request. In any case, servers or server file
file systems may not be able to support sub-range lock semantics. In systems may not be able to support sub-range lock semantics. In the
the event that a server receives a locking request that represents a event that a server receives a locking request that represents a sub-
sub-range of current locking state for the lock-owner, the server is range of current locking state for the lock-owner, the server is
allowed to return the error NFS4ERR_LOCK_RANGE to signify that it allowed to return the error NFS4ERR_LOCK_RANGE to signify that it
does not support sub-range lock operations. Therefore, the client does not support sub-range lock operations. Therefore, the client
should be prepared to receive this error and, if appropriate, report should be prepared to receive this error and, if appropriate, report
the error to the requesting application. the error to the requesting application.
The client is discouraged from combining multiple independent locking The client is discouraged from combining multiple independent locking
ranges that happen to be adjacent into a single request since the ranges that happen to be adjacent into a single request since the
server may not support sub-range requests and for reasons related to server may not support sub-range requests for reasons related to the
the recovery of file locking state in the event of server failure. recovery of byte-range locking state in the event of server failure.
As discussed in Section 8.4.2, the server may employ certain As discussed in Section 8.4.2, the server may employ certain
optimizations during recovery that work effectively only when the optimizations during recovery that work effectively only when the
client's behavior during lock recovery is similar to the client's client's behavior during lock recovery is similar to the client's
locking behavior prior to server failure. locking behavior prior to server failure.
9.3. Upgrading and Downgrading Locks 9.3. Upgrading and Downgrading Locks
If a client has a write lock on a byte-range, it can request an If a client has a WRITE_LT lock on a byte-range, it can request an
atomic downgrade of the lock to a read lock via the LOCK request, by atomic downgrade of the lock to a READ_LT lock via the LOCK
setting the type to READ_LT. If the server supports atomic operation, by setting the type to READ_LT. If the server supports
downgrade, the request will succeed. If not, it will return atomic downgrade, the request will succeed. If not, it will return
NFS4ERR_LOCK_NOTSUPP. The client should be prepared to receive this NFS4ERR_LOCK_NOTSUPP. The client should be prepared to receive this
error, and if appropriate, report the error to the requesting error and, if appropriate, report the error to the requesting
application. application.
If a client has a read lock on a byte-range, it can request an atomic If a client has a READ_LT lock on a byte-range, it can request an
upgrade of the lock to a write lock via the LOCK request by setting atomic upgrade of the lock to a WRITE_LT lock via the LOCK operation
the type to WRITE_LT or WRITEW_LT. If the server does not support by setting the type to WRITE_LT or WRITEW_LT. If the server does not
atomic upgrade, it will return NFS4ERR_LOCK_NOTSUPP. If the upgrade support atomic upgrade, it will return NFS4ERR_LOCK_NOTSUPP. If the
can be achieved without an existing conflict, the request will upgrade can be achieved without an existing conflict, the request
succeed. Otherwise, the server will return either NFS4ERR_DENIED or will succeed. Otherwise, the server will return either
NFS4ERR_DEADLOCK. The error NFS4ERR_DEADLOCK is returned if the NFS4ERR_DENIED or NFS4ERR_DEADLOCK. The error NFS4ERR_DEADLOCK is
client sent the LOCK request with the type set to WRITEW_LT and the returned if the client sent the LOCK operation with the type set to
server has detected a deadlock. The client should be prepared to WRITEW_LT and the server has detected a deadlock. The client should
receive such errors and if appropriate, report the error to the be prepared to receive such errors and, if appropriate, report the
requesting application. error to the requesting application.
9.4. Stateid Seqid Values and Byte-Range Locks 9.4. Stateid Seqid Values and Byte-Range Locks
When a lock or unlock request is done, passing a stateid, the stateid When a LOCK or LOCKU operation is performed, the stateid returned has
returned has the same "other" value and a "seqid" value that is the same "other" value as the argument's stateid, and a "seqid" value
incremented to reflect the occurrence of the lock or unlock request. that is incremented (relative to the argument's stateid) to reflect
The server MUST increment the value of the "seqid" field whenever the occurrence of the LOCK or LOCKU operation. The server MUST
there is any change to the locking status of any byte offset as increment the value of the "seqid" field whenever there is any change
described by any of locks covered by the stateid. A change in to the locking status of any byte offset as described by any of the
locking status includes a change from locked to unlocked or the locks covered by the stateid. A change in locking status includes a
reverse or a change from being locked for read to being locked for change from locked to unlocked or the reverse or a change from being
write or the reverse. locked for READ_LT to being locked for WRITE_LT or the reverse.
When there is no such change, as, for example when a range already When there is no such change, as, for example, when a range already
locked for write is locked again for write, the server MAY increment locked for WRITE_LT is locked again for WRITE_LT, the server MAY
the "seqid" value. increment the "seqid" value.
9.5. Issues with Multiple Open-Owners 9.5. Issues with Multiple Open-Owners
When the same file is opened by multiple open-owners, a client will When the same file is opened by multiple open-owners, a client will
have multiple open stateids for that file, each associated with a have multiple OPEN stateids for that file, each associated with a
different open-owner. In that case, there can be multiple LOCK and different open-owner. In that case, there can be multiple LOCK and
LOCKU requests for the same lock-owner sent using the different open LOCKU requests for the same lock-owner sent using the different OPEN
stateids, and so a situation may arise in which there are multiple stateids, and so a situation may arise in which there are multiple
stateids, each representing byte-range locks on the same file and stateids, each representing byte-range locks on the same file and
held by the same lock-owner but each associated with a different held by the same lock-owner but each associated with a different
open-owner. open-owner.
In such a situation, the locking status of each byte (i.e. whether it In such a situation, the locking status of each byte (i.e., whether
is locked, the read or write mode of the lock and the lock-owner it is locked, the READ_LT or WRITE_LT type of the lock, and the lock-
holding the lock) MUST reflect the last LOCK or LOCKU operation done owner holding the lock) MUST reflect the last LOCK or LOCKU operation
for the lock-owner in question, independent of the stateid through done for the lock-owner in question, independent of the stateid
which the request was sent. through which the request was sent.
When a byte is locked by the lock-owner in question, the open-owner When a byte is locked by the lock-owner in question, the open-owner
to which that lock is assigned SHOULD be that of the open-owner to which that byte-range lock is assigned SHOULD be that of the open-
associated with the stateid through which the last LOCK of that byte owner associated with the stateid through which the last LOCK of that
was done. When there is a change in the open-owner associated with byte was done. When there is a change in the open-owner associated
locks for the stateid through which a LOCK or LOCKU was done, the with locks for the stateid through which a LOCK or LOCKU was done,
"seqid" field of the stateid MUST be incremented, even if the the "seqid" field of the stateid MUST be incremented, even if the
locking, in terms of lock-owners has not changed. When there is a locking, in terms of lock-owners has not changed. When there is a
change to the set of locked bytes associated with a different stateid change to the set of locked bytes associated with a different stateid
for the same lock-owner, i.e. associated with a different open-owner, for the same lock-owner, i.e., associated with a different open-
the "seqid" value for that stateid MUST NOT be incremented. owner, the "seqid" value for that stateid MUST NOT be incremented.
9.6. Blocking Locks 9.6. Blocking Locks
Some clients require the support of blocking locks. While NFSv4.1 Some clients require the support of blocking locks. While NFSv4.1
provides a callback when a previously unavailable lock becomes provides a callback when a previously unavailable lock becomes
available, this is an OPTIONAL feature and clients cannot depend on available, this is an OPTIONAL feature and clients cannot depend on
its presence. Clients need to be prepared to continually poll for its presence. Clients need to be prepared to continually poll for
the lock. This presents a fairness problem. Two of the lock types, the lock. This presents a fairness problem. Two of the lock types,
READW and WRITEW, are used to indicate to the server that the client READW_LT and WRITEW_LT, are used to indicate to the server that the
is requesting a blocking lock. When the callback is not used, the client is requesting a blocking lock. When the callback is not used,
server should maintain an ordered list of pending blocking locks. the server should maintain an ordered list of pending blocking locks.
When the conflicting lock is released, the server may wait for the When the conflicting lock is released, the server may wait for the
period of time equal to lease_time for the first waiting client to period of time equal to lease_time for the first waiting client to
re-request the lock. After the lease period expires, the next re-request the lock. After the lease period expires, the next
waiting client request is allowed the lock. Clients are required to waiting client request is allowed the lock. Clients are required to
poll at an interval sufficiently small that it is likely to acquire poll at an interval sufficiently small that it is likely to acquire
the lock in a timely manner. The server is not required to maintain the lock in a timely manner. The server is not required to maintain
a list of pending blocked locks as it is used to increase fairness a list of pending blocked locks as it is used to increase fairness
and not correct operation. Because of the unordered nature of crash and not correct operation. Because of the unordered nature of crash
recovery, storing of lock state to stable storage would be required recovery, storing of lock state to stable storage would be required
to guarantee ordered granting of blocking locks. to guarantee ordered granting of blocking locks.
Servers may also note the lock types and delay returning denial of Servers may also note the lock types and delay returning denial of
the request to allow extra time for a conflicting lock to be the request to allow extra time for a conflicting lock to be
released, allowing a successful return. In this way, clients can released, allowing a successful return. In this way, clients can
avoid the burden of needlessly frequent polling for blocking locks. avoid the burden of needless frequent polling for blocking locks.
The server should take care in the length of delay in the event the The server should take care in the length of delay in the event the
client retransmits the request. client retransmits the request.
If a server receives a blocking lock request, denies it, and then If a server receives a blocking LOCK operation, denies it, and then
later receives a nonblocking request for the same lock, which is also later receives a nonblocking request for the same lock, which is also
denied, then it should remove the lock in question from its list of denied, then it should remove the lock in question from its list of
pending blocking locks. Clients should use such a nonblocking pending blocking locks. Clients should use such a nonblocking
request to indicate to the server that this is the last time they request to indicate to the server that this is the last time they
intend to poll for the lock, as may happen when the process intend to poll for the lock, as may happen when the process
requesting the lock is interrupted. This is a courtesy to the requesting the lock is interrupted. This is a courtesy to the
server, to prevent it from unnecessarily waiting a lease period server, to prevent it from unnecessarily waiting a lease period
before granting other lock requests. However, clients are not before granting other LOCK operations. However, clients are not
required to perform this courtesy, and servers must not depend on required to perform this courtesy, and servers must not depend on
them doing so. Also, clients must be prepared for the possibility them doing so. Also, clients must be prepared for the possibility
that this final locking request will be accepted. that this final locking request will be accepted.
When server indicates, via the flag OPEN4_RESULT_MAY_NOTIFY_LOCK, When a server indicates, via the flag OPEN4_RESULT_MAY_NOTIFY_LOCK,
that CB_NOTIFY_LOCK callbacks will be done for the current open file, that CB_NOTIFY_LOCK callbacks might be done for the current open
the client should take notice of this, but, since this is a hint, file, the client should take notice of this, but, since this is a
cannot rely on a CB_NOTIFY_LOCK always being done. A client may hint, cannot rely on a CB_NOTIFY_LOCK always being done. A client
reasonably reduce the frequency with which it polls for a denied may reasonably reduce the frequency with which it polls for a denied
lock, since the greater latency that might occur is likely to be lock, since the greater latency that might occur is likely to be
eliminated given a prompt callback, but it still needs to poll. When eliminated given a prompt callback, but it still needs to poll. When
it receives a CB_NOTIFY_LOCK it should promptly try to obtain the it receives a CB_NOTIFY_LOCK, it should promptly try to obtain the
lock, but it should be aware that other clients may polling and the lock, but it should be aware that other clients may be polling and
server is under no obligation to reserve the lock for that particular that the server is under no obligation to reserve the lock for that
client. particular client.
9.7. Share Reservations 9.7. Share Reservations
A share reservation is a mechanism to control access to a file. It A share reservation is a mechanism to control access to a file. It
is a separate and independent mechanism from byte-range locking. is a separate and independent mechanism from byte-range locking.
When a client opens a file, it sends an OPEN operation to the server When a client opens a file, it sends an OPEN operation to the server
specifying the type of access required (READ, WRITE, or BOTH) and the specifying the type of access required (READ, WRITE, or BOTH) and the
type of access to deny others (deny NONE, READ, WRITE, or BOTH). If type of access to deny others (OPEN4_SHARE_DENY_NONE,
the OPEN fails the client will fail the application's open request. OPEN4_SHARE_DENY_READ, OPEN4_SHARE_DENY_WRITE, or
OPEN4_SHARE_DENY_BOTH). If the OPEN fails, the client will fail the
application's open request.
Pseudo-code definition of the semantics: Pseudo-code definition of the semantics:
if (request.access == 0) { if (request.access == 0) {
return (NFS4ERR_INVAL) return (NFS4ERR_INVAL)
} else { } else {
if ((request.access & file_state.deny)) || if ((request.access & file_state.deny)) ||
(request.deny & file_state.access)) { (request.deny & file_state.access)) {
return (NFS4ERR_SHARE_DENIED) return (NFS4ERR_SHARE_DENIED)
} }
skipping to change at page 192, line 38 skipping to change at page 192, line 19
const OPEN4_SHARE_DENY_NONE = 0x00000000; const OPEN4_SHARE_DENY_NONE = 0x00000000;
const OPEN4_SHARE_DENY_READ = 0x00000001; const OPEN4_SHARE_DENY_READ = 0x00000001;
const OPEN4_SHARE_DENY_WRITE = 0x00000002; const OPEN4_SHARE_DENY_WRITE = 0x00000002;
const OPEN4_SHARE_DENY_BOTH = 0x00000003; const OPEN4_SHARE_DENY_BOTH = 0x00000003;
9.8. OPEN/CLOSE Operations 9.8. OPEN/CLOSE Operations
To provide correct share semantics, a client MUST use the OPEN To provide correct share semantics, a client MUST use the OPEN
operation to obtain the initial filehandle and indicate the desired operation to obtain the initial filehandle and indicate the desired
access and what access, if any, to deny. Even if the client intends access and what access, if any, to deny. Even if the client intends
to use a special stateid for anonymous state or read bypass, it must to use a special stateid for anonymous state or READ bypass, it must
still obtain the filehandle for the regular file with the OPEN still obtain the filehandle for the regular file with the OPEN
operation so the appropriate share semantics can be applied. For operation so the appropriate share semantics can be applied. Clients
clients that do not have a deny mode built into their open that do not have a deny mode built into their programming interfaces
programming interfaces, deny equal to NONE should be used. for opening a file should request a deny mode of
OPEN4_SHARE_DENY_NONE.
The OPEN operation with the CREATE flag, also subsumes the CREATE The OPEN operation with the CREATE flag also subsumes the CREATE
operation for regular files as used in previous versions of the NFS operation for regular files as used in previous versions of the NFS
protocol. This allows a create with a share to be done atomically. protocol. This allows a create with a share to be done atomically.
The CLOSE operation removes all share reservations held by the open- The CLOSE operation removes all share reservations held by the open-
owner on that file. If byte-range locks are held, the client SHOULD owner on that file. If byte-range locks are held, the client SHOULD
release all locks before sending a CLOSE operation. The server MAY release all locks before sending a CLOSE operation. The server MAY
free all outstanding locks on CLOSE but some servers may not support free all outstanding locks on CLOSE, but some servers may not support
the CLOSE of a file that still has byte-range locks held. The server the CLOSE of a file that still has byte-range locks held. The server
MUST return failure, NFS4ERR_LOCKS_HELD, if any locks would exist MUST return failure, NFS4ERR_LOCKS_HELD, if any locks would exist
after the CLOSE. after the CLOSE.
The LOOKUP operation will return a filehandle without establishing The LOOKUP operation will return a filehandle without establishing
any lock state on the server. Without a valid stateid, the server any lock state on the server. Without a valid stateid, the server
will assume the client has the least access. For example, a file will assume that the client has the least access. For example, if
opened with deny READ/WRITE using a filehandle obtained through one client opened a file with OPEN4_SHARE_DENY_BOTH and another
LOOKUP could only be read using the special read bypass stateid and client accesses the file via a filehandle obtained through LOOKUP,
could not be written at all because it would not have a valid stateid the second client could only read the file using the special read
and the special anonymous stateid would not be allowed access. bypass stateid. The second client could not WRITE the file at all
because it would not have a valid stateid from OPEN and the special
anonymous stateid would not be allowed access.
9.9. Open Upgrade and Downgrade 9.9. Open Upgrade and Downgrade
When an OPEN is done for a file and the open-owner for which the open When an OPEN is done for a file and the open-owner for which the OPEN
is being done already has the file open, the result is to upgrade the is being done already has the file open, the result is to upgrade the
open file status maintained on the server to include the access and open file status maintained on the server to include the access and
deny bits specified by the new OPEN as well as those for the existing deny bits specified by the new OPEN as well as those for the existing
OPEN. The result is that there is one open file, as far as the OPEN. The result is that there is one open file, as far as the
protocol is concerned, and it includes the union of the access and protocol is concerned, and it includes the union of the access and
deny bits for all of the OPEN requests completed. The open is deny bits for all of the OPEN requests completed. The OPEN is
represented by a single stateid whose "other" values matches that of represented by a single stateid whose "other" value matches that of
the original open, and whose "seqid" value is incremented to reflect the original open, and whose "seqid" value is incremented to reflect
the occurrence of the upgrade. The increment is required in cases in the occurrence of the upgrade. The increment is required in cases in
which the "upgrade" results in no change to the open mode (e.g. an which the "upgrade" results in no change to the open mode (e.g., an
OPEN is done for read when the existing open file is opened for read- OPEN is done for read when the existing open file is opened for
write). Only a single CLOSE will be done to reset the effects of OPEN4_SHARE_ACCESS_BOTH). Only a single CLOSE will be done to reset
both OPENs. The client may use the stateid returned by the OPEN the effects of both OPENs. The client may use the stateid returned
effecting the upgrade or with a stateid sharing the same "other" by the OPEN effecting the upgrade or with a stateid sharing the same
field and a seqid of zero, although care needs to be taken as far as "other" field and a seqid of zero, although care needs to be taken as
upgrades which happen while the CLOSE is pending. Note that the far as upgrades that happen while the CLOSE is pending. Note that
client, when sending the OPEN operation, may not know that the same the client, when sending the OPEN, may not know that the same file is
file is in fact being opened. The above only applies if both OPENs in fact being opened. The above only applies if both OPENs result in
result in the OPENed object being designated by the same filehandle. the OPENed object being designated by the same filehandle.
When the server chooses to export multiple filehandles corresponding When the server chooses to export multiple filehandles corresponding
to the same file object and returns different filehandles on two to the same file object and returns different filehandles on two
different OPENs of the same file object, the server MUST NOT "OR" different OPENs of the same file object, the server MUST NOT "OR"
together the access and deny bits and coalesce the two open files. together the access and deny bits and coalesce the two open files.
Instead the server must maintain separate OPENs with separate Instead, the server must maintain separate OPENs with separate
stateids and will require separate CLOSEs to free them. stateids and will require separate CLOSEs to free them.
When multiple open files on the client are merged into a single open When multiple open files on the client are merged into a single OPEN
file object on the server, the close of one of the open files (on the file object on the server, the close of one of the open files (on the
client) may necessitate change of the access and deny status of the client) may necessitate change of the access and deny status of the
open file on the server. This is because the union of the access and open file on the server. This is because the union of the access and
deny bits for the remaining opens may be smaller (i.e. a proper deny bits for the remaining opens may be smaller (i.e., a proper
subset) than previously. The OPEN_DOWNGRADE operation is used to subset) than previously. The OPEN_DOWNGRADE operation is used to
make the necessary change and the client should use it to update the make the necessary change and the client should use it to update the
server so that share reservation requests by other clients are server so that share reservation requests by other clients are
handled properly. The stateid returned has the same "other" field as handled properly. The stateid returned has the same "other" field as
that passed to the server. The "seqid" value in the returned stateid that passed to the server. The "seqid" value in the returned stateid
MUST be incremented, even is situation in which there is no change MUST be incremented, even in situations in which there is no change
the access and deny bits for the file. to the access and deny bits for the file.
9.10. Parallel OPENs 9.10. Parallel OPENs
Unlike the case of NFSv4.0, in which OPEN operations for the same Unlike the case of NFSv4.0, in which OPEN operations for the same
open-owner are inherently serialized because of the owner-based open-owner are inherently serialized because of the owner-based
seqid, multiple OPENs for the same open-owner may be done in seqid, multiple OPENs for the same open-owner may be done in
parallel. When clients do this, they may encounter situations in parallel. When clients do this, they may encounter situations in
which, because of the existence of hard links, two OPEN operations which, because of the existence of hard links, two OPEN operations
may turn out to open the same file, with a later OPEN performed being may turn out to open the same file, with a later OPEN performed being
an upgrade of the first, with this fact only visible to the client an upgrade of the first, with this fact only visible to the client
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were performed by examining the stateids returned by the OPENs. were performed by examining the stateids returned by the OPENs.
Stateids that share a common value of the "other" field can be Stateids that share a common value of the "other" field can be
recognized as having opened the same file, with the order of the recognized as having opened the same file, with the order of the
operations determinable from the order of the "seqid" fields, mod any operations determinable from the order of the "seqid" fields, mod any
possible wraparound of the 32-bit field. possible wraparound of the 32-bit field.
When the possibility exists that the client will send multiple OPENs When the possibility exists that the client will send multiple OPENs
for the same open-owner in parallel, it may be the case that an open for the same open-owner in parallel, it may be the case that an open
upgrade may happen without the client knowing beforehand that this upgrade may happen without the client knowing beforehand that this
could happen. Because of this possibility, CLOSEs and could happen. Because of this possibility, CLOSEs and
OPEN_DOWNGRADEs, should generally be sent with a non-zero seqid in OPEN_DOWNGRADEs should generally be sent with a non-zero seqid in the
the stateid, to avoid the possibility that the status change stateid, to avoid the possibility that the status change associated
associated with an open upgrade is not inadvertently lost. with an open upgrade is not inadvertently lost.
9.11. Reclaim of Open and Byte-Range Locks 9.11. Reclaim of Open and Byte-Range Locks
Special forms of the LOCK and OPEN operations are provided when it is Special forms of the LOCK and OPEN operations are provided when it is
necessary to re-establish byte-range locks or opens after a server necessary to re-establish byte-range locks or opens after a server
failure. failure.
o To reclaim existing opens, an OPEN operation is performed using a o To reclaim existing opens, an OPEN operation is performed using a
CLAIM_PREVIOUS. Because the client, in this type of situation, CLAIM_PREVIOUS. Because the client, in this type of situation,
will have already opened the file and have the filehandle of the will have already opened the file and have the filehandle of the
target file, this operation requires that the current filehandle target file, this operation requires that the current filehandle
be the target file, rather than a directory and no file name is be the target file, rather than a directory, and no file name is
specified. specified.
o To reclaim byte-range locks, a LOCK operation with the reclaim o To reclaim byte-range locks, a LOCK operation with the reclaim
parameter set to true is used. parameter set to true is used.
Reclaims of opens associated with delegations are discussed in Reclaims of opens associated with delegations are discussed in
Section 10.2.1. Section 10.2.1.
10. Client-Side Caching 10. Client-Side Caching
Client-side caching of data, of file attributes, and of file names is Client-side caching of data, of file attributes, and of file names is
essential to providing good performance with the NFS protocol. essential to providing good performance with the NFS protocol.
Providing distributed cache coherence is a difficult problem and Providing distributed cache coherence is a difficult problem, and
previous versions of the NFS protocol have not attempted it. previous versions of the NFS protocol have not attempted it.
Instead, several NFS client implementation techniques have been used Instead, several NFS client implementation techniques have been used
to reduce the problems that a lack of coherence poses for users. to reduce the problems that a lack of coherence poses for users.
These techniques have not been clearly defined by earlier protocol These techniques have not been clearly defined by earlier protocol
specifications and it is often unclear what is valid or invalid specifications, and it is often unclear what is valid or invalid
client behavior. client behavior.
The NFSv4.1 protocol uses many techniques similar to those that have The NFSv4.1 protocol uses many techniques similar to those that have
been used in previous protocol versions. The NFSv4.1 protocol does been used in previous protocol versions. The NFSv4.1 protocol does
not provide distributed cache coherence. However, it defines a more not provide distributed cache coherence. However, it defines a more
limited set of caching guarantees to allow locks and share limited set of caching guarantees to allow locks and share
reservations to be used without destructive interference from client reservations to be used without destructive interference from client-
side caching. side caching.
In addition, the NFSv4.1 protocol introduces a delegation mechanism In addition, the NFSv4.1 protocol introduces a delegation mechanism,
which allows many decisions normally made by the server to be made which allows many decisions normally made by the server to be made
locally by clients. This mechanism provides efficient support of the locally by clients. This mechanism provides efficient support of the
common cases where sharing is infrequent or where sharing is read- common cases where sharing is infrequent or where sharing is read-
only. only.
10.1. Performance Challenges for Client-Side Caching 10.1. Performance Challenges for Client-Side Caching
Caching techniques used in previous versions of the NFS protocol have Caching techniques used in previous versions of the NFS protocol have
been successful in providing good performance. However, several been successful in providing good performance. However, several
scalability challenges can arise when those techniques are used with scalability challenges can arise when those techniques are used with
very large numbers of clients. This is particularly true when very large numbers of clients. This is particularly true when
clients are geographically distributed which classically increases clients are geographically distributed, which classically increases
the latency for cache revalidation requests. the latency for cache revalidation requests.
The previous versions of the NFS protocol repeat their file data The previous versions of the NFS protocol repeat their file data
cache validation requests at the time the file is opened. This cache validation requests at the time the file is opened. This
behavior can have serious performance drawbacks. A common case is behavior can have serious performance drawbacks. A common case is
one in which a file is only accessed by a single client. Therefore, one in which a file is only accessed by a single client. Therefore,
sharing is infrequent. sharing is infrequent.
In this case, repeated reference to the server to find that no In this case, repeated references to the server to find that no
conflicts exist is expensive. A better option with regards to conflicts exist are expensive. A better option with regards to
performance is to allow a client that repeatedly opens a file to do performance is to allow a client that repeatedly opens a file to do
so without reference to the server. This is done until potentially so without reference to the server. This is done until potentially
conflicting operations from another client actually occur. conflicting operations from another client actually occur.
A similar situation arises in connection with file locking. Sending A similar situation arises in connection with byte-range locking.
file lock and unlock requests to the server as well as the read and Sending LOCK and LOCKU operations as well as the READ and WRITE
write requests necessary to make data caching consistent with the operations necessary to make data caching consistent with the locking
locking semantics (see Section 10.3.2) can severely limit semantics (see Section 10.3.2) can severely limit performance. When
performance. When locking is used to provide protection against locking is used to provide protection against infrequent conflicts, a
infrequent conflicts, a large penalty is incurred. This penalty may large penalty is incurred. This penalty may discourage the use of
discourage the use of file locking by applications. byte-range locking by applications.
The NFSv4.1 protocol provides more aggressive caching strategies with The NFSv4.1 protocol provides more aggressive caching strategies with
the following design goals: the following design goals:
o Compatibility with a large range of server semantics. o Compatibility with a large range of server semantics.
o Providing the same caching benefits as previous versions of the o Providing the same caching benefits as previous versions of the
NFS protocol when unable to support the more aggressive model. NFS protocol when unable to support the more aggressive model.
o Requirements for aggressive caching are organized so that a large o Requirements for aggressive caching are organized so that a large
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Recallable delegation of server responsibilities for a file to a Recallable delegation of server responsibilities for a file to a
client improves performance by avoiding repeated requests to the client improves performance by avoiding repeated requests to the
server in the absence of inter-client conflict. With the use of a server in the absence of inter-client conflict. With the use of a
"callback" RPC from server to client, a server recalls delegated "callback" RPC from server to client, a server recalls delegated
responsibilities when another client engages in sharing of a responsibilities when another client engages in sharing of a
delegated file. delegated file.
A delegation is passed from the server to the client, specifying the A delegation is passed from the server to the client, specifying the
object of the delegation and the type of delegation. There are object of the delegation and the type of delegation. There are
different types of delegations but each type contains a stateid to be different types of delegations, but each type contains a stateid to
used to represent the delegation when performing operations that be used to represent the delegation when performing operations that
depend on the delegation. This stateid is similar to those depend on the delegation. This stateid is similar to those
associated with locks and share reservations but differs in that the associated with locks and share reservations but differs in that the
stateid for a delegation is associated with a client ID and may be stateid for a delegation is associated with a client ID and may be
used on behalf of all the open-owners for the given client. A used on behalf of all the open-owners for the given client. A
delegation is made to the client as a whole and not to any specific delegation is made to the client as a whole and not to any specific
process or thread of control within it. process or thread of control within it.
The backchannel is established by CREATE_SESSION and The backchannel is established by CREATE_SESSION and
BIND_CONN_TO_SESSION, and the client is required to maintain it. BIND_CONN_TO_SESSION, and the client is required to maintain it.
Because the backchannel may be down, even temporarily, correct Because the backchannel may be down, even temporarily, correct
protocol operation does not depend on them. Preliminary testing of protocol operation does not depend on them. Preliminary testing of
backchannel functionality by means of a CB_COMPOUND procedure with a backchannel functionality by means of a CB_COMPOUND procedure with a
single operation, CB_SEQUENCE, can be used to check the continuity of single operation, CB_SEQUENCE, can be used to check the continuity of
the backchannel. A server avoids delegating responsibilities until the backchannel. A server avoids delegating responsibilities until
it has determined that the backchannel exists. Because the granting it has determined that the backchannel exists. Because the granting
of a delegation is always conditional upon the absence of conflicting of a delegation is always conditional upon the absence of conflicting
access, clients MUST NOT assume that a delegation will be granted and access, clients MUST NOT assume that a delegation will be granted and
they MUST always be prepared for OPENs, WANT_DELEGATIONs, and they MUST always be prepared for OPENs, WANT_DELEGATIONs, and
GET_DIR_DELEGATIONs to be processed without any delegations being GET_DIR_DELEGATIONs to be processed without any delegations being
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backchannel functionality by means of a CB_COMPOUND procedure with a backchannel functionality by means of a CB_COMPOUND procedure with a
single operation, CB_SEQUENCE, can be used to check the continuity of single operation, CB_SEQUENCE, can be used to check the continuity of
the backchannel. A server avoids delegating responsibilities until the backchannel. A server avoids delegating responsibilities until
it has determined that the backchannel exists. Because the granting it has determined that the backchannel exists. Because the granting
of a delegation is always conditional upon the absence of conflicting of a delegation is always conditional upon the absence of conflicting
access, clients MUST NOT assume that a delegation will be granted and access, clients MUST NOT assume that a delegation will be granted and
they MUST always be prepared for OPENs, WANT_DELEGATIONs, and they MUST always be prepared for OPENs, WANT_DELEGATIONs, and
GET_DIR_DELEGATIONs to be processed without any delegations being GET_DIR_DELEGATIONs to be processed without any delegations being
granted. granted.
Once granted, a delegation behaves in many ways like a lock. There
is an associated lease that is subject to renewal together with all
of the other leases held by that client.
Unlike locks, an operation by a second client to a delegated file Unlike locks, an operation by a second client to a delegated file
will cause the server to recall a delegation through a callback. For will cause the server to recall a delegation through a callback. For
individual operations, we will describe, under IMPLEMENTATION, when individual operations, we will describe, under IMPLEMENTATION, when
such operations are required to effect a recall. A number of points such operations are required to effect a recall. A number of points
should be noted, however. should be noted, however.
o The server is free to recall a delegation whenever it feels it is o The server is free to recall a delegation whenever it feels it is
desirable and may do so even if no operations requiring recall are desirable and may do so even if no operations requiring recall are
being done. being done.
o Operations done outside the NFSv4 protocol, due to, for example, o Operations done outside the NFSv4.1 protocol, due to, for example,
access by other protocols, or by local access, also need to result access by other protocols, or by local access, also need to result
in delegation recall when they make analogous changes to file in delegation recall when they make analogous changes to file
system data. What is crucial is if the change would invalidate system data. What is crucial is if the change would invalidate
the guarantees provided by the delegation. When this is possible, the guarantees provided by the delegation. When this is possible,
the delegation needs to be recalled and MUST be returned or the delegation needs to be recalled and MUST be returned or
revoked before allowing the operation to proceed. revoked before allowing the operation to proceed.
o The semantics of the file system are crucial in defining when o The semantics of the file system are crucial in defining when
delegation recall is required. If a particular change within a delegation recall is required. If a particular change within a
specific implementation causes change to a file attribute, then specific implementation causes change to a file attribute, then
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the server should allow sufficient time for the delegation to be the server should allow sufficient time for the delegation to be
returned since it may involve numerous RPCs to the server. If the returned since it may involve numerous RPCs to the server. If the
server is able to determine that the client is diligently flushing server is able to determine that the client is diligently flushing
state to the server as a result of the recall, the server may extend state to the server as a result of the recall, the server may extend
the usual time allowed for a recall. However, the time allowed for the usual time allowed for a recall. However, the time allowed for
recall completion should not be unbounded. recall completion should not be unbounded.
An example of this is when responsibility to mediate opens on a given An example of this is when responsibility to mediate opens on a given
file is delegated to a client (see Section 10.4). The server will file is delegated to a client (see Section 10.4). The server will
not know what opens are in effect on the client. Without this not know what opens are in effect on the client. Without this
knowledge the server will be unable to determine if the access and knowledge, the server will be unable to determine if the access and
deny state for the file allows any particular open until the deny states for the file allow any particular open until the
delegation for the file has been returned. delegation for the file has been returned.
A client failure or a network partition can result in failure to A client failure or a network partition can result in failure to
respond to a recall callback. In this case, the server will revoke respond to a recall callback. In this case, the server will revoke
the delegation which in turn will render useless any modified state the delegation, which in turn will render useless any modified state
still on the client. still on the client.
10.2.1. Delegation Recovery 10.2.1. Delegation Recovery
There are three situations that delegation recovery needs to deal There are three situations that delegation recovery needs to deal
with: with:
o Client restart o client restart
o Server restart o server restart
o Network partition (full or backchannel-only) o network partition (full or backchannel-only)
In the event the client restarts, the failure to renew the lease will In the event the client restarts, the failure to renew the lease will
result in the revocation of byte-range locks and share reservations. result in the revocation of byte-range locks and share reservations.
Delegations, however, may be treated a bit differently. Delegations, however, may be treated a bit differently.
There will be situations in which delegations will need to be There will be situations in which delegations will need to be re-
reestablished after a client restarts. The reason for this is the established after a client restarts. The reason for this is that the
client may have file data stored locally and this data was associated client may have file data stored locally and this data was associated
with the previously held delegations. The client will need to with the previously held delegations. The client will need to re-
reestablish the appropriate file state on the server. establish the appropriate file state on the server.
To allow for this type of client recovery, the server MAY extend the To allow for this type of client recovery, the server MAY extend the
period for delegation recovery beyond the typical lease expiration period for delegation recovery beyond the typical lease expiration
period. This implies that requests from other clients that conflict period. This implies that requests from other clients that conflict
with these delegations will need to wait. Because the normal recall with these delegations will need to wait. Because the normal recall
process may require significant time for the client to flush changed process may require significant time for the client to flush changed
state to the server, other clients need be prepared for delays that state to the server, other clients need be prepared for delays that
occur because of a conflicting delegation. This longer interval occur because of a conflicting delegation. This longer interval
would increase the window for clients to restart and consult stable would increase the window for clients to restart and consult stable
storage so that the delegations can be reclaimed. For open storage so that the delegations can be reclaimed. For OPEN
delegations, such delegations are reclaimed using OPEN with a claim delegations, such delegations are reclaimed using OPEN with a claim
type of CLAIM_DELEGATE_PREV or CLAIM_DELEG_PREV_FH (See Section 10.5 type of CLAIM_DELEGATE_PREV or CLAIM_DELEG_PREV_FH (see Sections 10.5
and Section 18.16 for discussion of open delegation and the details and 18.16 for discussion of OPEN delegation and the details of OPEN,
of OPEN respectively). respectively).
A server MAY support claim types of CLAIM_DELEGATE_PREV and A server MAY support claim types of CLAIM_DELEGATE_PREV and
CLAIM_DELEG_PREV_FH, and if it does, it MUST NOT remove delegations CLAIM_DELEG_PREV_FH, and if it does, it MUST NOT remove delegations
upon a CREATE_SESSION that confirms a client ID created by upon a CREATE_SESSION that confirm a client ID created by
EXCHANGE_ID, and instead MUST, for a period of time no less than that EXCHANGE_ID. Instead, the server MUST, for a period of time no less
of the value of the lease_time attribute, maintain the client's than that of the value of the lease_time attribute, maintain the
delegations to allow time for the client to send CLAIM_DELEGATE_PREV client's delegations to allow time for the client to send
requests. The server that supports CLAIM_DELEGATE_PREV and/or CLAIM_DELEGATE_PREV and/or CLAIM_DELEG_PREV_FH requests. The server
CLAIM_DELEG_PREV_FH MUST support the DELEGPURGE operation. that supports CLAIM_DELEGATE_PREV and/or CLAIM_DELEG_PREV_FH MUST
support the DELEGPURGE operation.
When the server restarts, delegations are reclaimed (using the OPEN When the server restarts, delegations are reclaimed (using the OPEN
operation with CLAIM_PREVIOUS) in a similar fashion to byte-range operation with CLAIM_PREVIOUS) in a similar fashion to byte-range
locks and share reservations. However, there is a slight semantic locks and share reservations. However, there is a slight semantic
difference. In the normal case if the server decides that a difference. In the normal case, if the server decides that a
delegation should not be granted, it performs the requested action delegation should not be granted, it performs the requested action
(e.g. OPEN) without granting any delegation. For reclaim, the (e.g., OPEN) without granting any delegation. For reclaim, the
server grants the delegation but a special designation is applied so server grants the delegation but a special designation is applied so
that the client treats the delegation as having been granted but that the client treats the delegation as having been granted but
recalled by the server. Because of this, the client has the duty to recalled by the server. Because of this, the client has the duty to
write all modified state to the server and then return the write all modified state to the server and then return the
delegation. This process of handling delegation reclaim reconciles delegation. This process of handling delegation reclaim reconciles
three principles of the NFSv4.1 protocol: three principles of the NFSv4.1 protocol:
o Upon reclaim, a client reporting resources assigned to it by an o Upon reclaim, a client reporting resources assigned to it by an
earlier server instance must be granted those resources. earlier server instance must be granted those resources.
o The server has unquestionable authority to determine whether o The server has unquestionable authority to determine whether
delegations are to be granted and, once granted, whether they are delegations are to be granted and, once granted, whether they are
to be continued. to be continued.
o The use of callbacks is not to be depended upon until the client o The use of callbacks should not be depended upon until the client
has proven its ability to receive them. has proven its ability to receive them.
When a client needs to reclaim a delegation and there is no When a client needs to reclaim a delegation and there is no
associated open, the client may use the CLAIM_PREVIOUS variant of the associated open, the client may use the CLAIM_PREVIOUS variant of the
WANT_DELEGATION operation. However, since the server is not required WANT_DELEGATION operation. However, since the server is not required
to support this operation, an alternative is to reclaim via a dummy to support this operation, an alternative is to reclaim via a dummy
open together with the delegation using an OPEN of type OPEN together with the delegation using an OPEN of type
CLAIM_PREVIOUS. The dummy open file can be released using a CLOSE to CLAIM_PREVIOUS. The dummy open file can be released using a CLOSE to
re-establish the original state to be reclaimed, a delegation without re-establish the original state to be reclaimed, a delegation without
an associated open. an associated open.
When a client has more than a single open associated with a When a client has more than a single open associated with a
delegation, state for those additional opens can be established using delegation, state for those additional opens can be established using
OPEN operations of type CLAIM_DELEGATE_CUR. When these are used to OPEN operations of type CLAIM_DELEGATE_CUR. When these are used to
establish opens associated with reclaimed delegations, the server establish opens associated with reclaimed delegations, the server
MUST allow them when made within the grace period. MUST allow them when made within the grace period.
When a network partition occurs, delegations are subject to freeing When a network partition occurs, delegations are subject to freeing
by the server when the lease renewal period expires. This is similar by the server when the lease renewal period expires. This is similar
to the behavior for locks and share reservations. For delegations, to the behavior for locks and share reservations. For delegations,
however, the server may extend the period in which conflicting however, the server may extend the period in which conflicting
requests are held off. Eventually the occurrence of a conflicting requests are held off. Eventually, the occurrence of a conflicting
request from another client will cause revocation of the delegation. request from another client will cause revocation of the delegation.
A loss of the backchannel (e.g. by later network configuration A loss of the backchannel (e.g., by later network configuration
change) will have the same effect. A recall request will fail and change) will have the same effect. A recall request will fail and
revocation of the delegation will result. revocation of the delegation will result.
A client normally finds out about revocation of a delegation when it A client normally finds out about revocation of a delegation when it
uses a stateid associated with a delegation and receives one of the uses a stateid associated with a delegation and receives one of the
errors NFS4ERR_EXPIRED, NFS4ERR_ADMIN_REVOKED, or errors NFS4ERR_EXPIRED, NFS4ERR_ADMIN_REVOKED, or
NFS4ERR_DELEG_REVOKED. It also may find out about delegation NFS4ERR_DELEG_REVOKED. It also may find out about delegation
revocation after a client restart when it attempts to reclaim a revocation after a client restart when it attempts to reclaim a
delegation and receives that same error. Note that in the case of a delegation and receives that same error. Note that in the case of a
revoked write open delegation, there are issues because data may have revoked OPEN_DELEGATE_WRITE delegation, there are issues because data
been modified by the client whose delegation is revoked and may have been modified by the client whose delegation is revoked and
separately by other clients. See Section 10.5.1 for a discussion of separately by other clients. See Section 10.5.1 for a discussion of
such issues. Note also that when delegations are revoked, such issues. Note also that when delegations are revoked,
information about the revoked delegation will be written by the information about the revoked delegation will be written by the
server to stable storage (as described in Section 8.4.3). This is server to stable storage (as described in Section 8.4.3). This is
done to deal with the case in which a server restarts after revoking done to deal with the case in which a server restarts after revoking
a delegation but before the client holding the revoked delegation is a delegation but before the client holding the revoked delegation is
notified about the revocation. notified about the revocation.
10.3. Data Caching 10.3. Data Caching
When applications share access to a set of files, they need to be When applications share access to a set of files, they need to be
implemented so as to take account of the possibility of conflicting implemented so as to take account of the possibility of conflicting
access by another application. This is true whether the applications access by another application. This is true whether the applications
in question execute on different clients or reside on the same in question execute on different clients or reside on the same
client. client.
Share reservations and byte-range locks are the facilities the Share reservations and byte-range locks are the facilities the
NFSv4.1 protocol provides to allow applications to coordinate access NFSv4.1 protocol provides to allow applications to coordinate access
by using mutual exclusion facilities. The NFSv4.1 protocol's data by using mutual exclusion facilities. The NFSv4.1 protocol's data
caching must be implemented such that it does not invalidate the caching must be implemented such that it does not invalidate the
assumptions that those using these facilities depend upon. assumptions on which those using these facilities depend.
10.3.1. Data Caching and OPENs 10.3.1. Data Caching and OPENs
In order to avoid invalidating the sharing assumptions that In order to avoid invalidating the sharing assumptions on which
applications rely on, NFSv4.1 clients should not provide cached data applications rely, NFSv4.1 clients should not provide cached data to
to applications or modify it on behalf of an application when it applications or modify it on behalf of an application when it would
would not be valid to obtain or modify that same data via a READ or not be valid to obtain or modify that same data via a READ or WRITE
WRITE operation. operation.
Furthermore, in the absence of open delegation (see Section 10.4), Furthermore, in the absence of an OPEN delegation (see Section 10.4),
two additional rules apply. Note that these rules are obeyed in two additional rules apply. Note that these rules are obeyed in
practice by many NFSv3 clients. practice by many NFSv3 clients.
o First, cached data present on a client must be revalidated after o First, cached data present on a client must be revalidated after
doing an OPEN. Revalidating means that the client fetches the doing an OPEN. Revalidating means that the client fetches the
change attribute from the server, compares it with the cached change attribute from the server, compares it with the cached
change attribute, and if different, declares the cached data (as change attribute, and if different, declares the cached data (as
well as the cached attributes) as invalid. This is to ensure that well as the cached attributes) as invalid. This is to ensure that
the data for the OPENed file is still correctly reflected in the the data for the OPENed file is still correctly reflected in the
client's cache. This validation must be done at least when the client's cache. This validation must be done at least when the
client's OPEN operation includes DENY=WRITE or BOTH thus client's OPEN operation includes a deny of OPEN4_SHARE_DENY_WRITE
terminating a period in which other clients may have had the or OPEN4_SHARE_DENY_BOTH, thus terminating a period in which other
opportunity to open the file with WRITE access. Clients may clients may have had the opportunity to open the file with
choose to do the revalidation more often (i.e. at OPENs specifying OPEN4_SHARE_ACCESS_WRITE/OPEN4_SHARE_ACCESS_BOTH access. Clients
DENY=NONE) to parallel the NFSv3 protocol's practice for the may choose to do the revalidation more often (i.e., at OPENs
benefit of users assuming this degree of cache revalidation. specifying a deny mode of OPEN4_SHARE_DENY_NONE) to parallel the
NFSv3 protocol's practice for the benefit of users assuming this
degree of cache revalidation.
Since the change attribute is updated for data and metadata Since the change attribute is updated for data and metadata
modifications, some client implementors may be tempted to use the modifications, some client implementors may be tempted to use the
time_modify attribute and not the change attribute to validate time_modify attribute and not the change attribute to validate
cached data, so that metadata changes do not spuriously invalidate cached data, so that metadata changes do not spuriously invalidate
clean data. The implementor is cautioned in this approach. The clean data. The implementor is cautioned in this approach. The
change attribute is guaranteed to change for each update to the change attribute is guaranteed to change for each update to the
file, whereas time_modify is guaranteed to change only at the file, whereas time_modify is guaranteed to change only at the
granularity of the time_delta attribute. Use by the client's data granularity of the time_delta attribute. Use by the client's data
cache validation logic of time_modify and not change runs the risk cache validation logic of time_modify and not change runs the risk
of the client incorrectly marking stale data as valid. Thus any of the client incorrectly marking stale data as valid. Thus, any
cache validation approach by the client MUST include the use of cache validation approach by the client MUST include the use of
the change attribute. the change attribute.
o Second, modified data must be flushed to the server before closing o Second, modified data must be flushed to the server before closing
a file OPENed for write. This is complementary to the first rule. a file OPENed for OPEN4_SHARE_ACCESS_WRITE. This is complementary
If the data is not flushed at CLOSE, the revalidation done after to the first rule. If the data is not flushed at CLOSE, the
client OPENs as file is unable to achieve its purpose. The other revalidation done after the client OPENs a file is unable to
aspect to flushing the data before close is that the data must be achieve its purpose. The other aspect to flushing the data before
committed to stable storage, at the server, before the CLOSE close is that the data must be committed to stable storage, at the
operation is requested by the client. In the case of a server server, before the CLOSE operation is requested by the client. In
restart and a CLOSEd file, it may not be possible to retransmit the case of a server restart and a CLOSEd file, it may not be
the data to be written to the file. Hence, this requirement. possible to retransmit the data to be written to the file, hence,
this requirement.
10.3.2. Data Caching and File Locking 10.3.2. Data Caching and File Locking
For those applications that choose to use file locking instead of For those applications that choose to use byte-range locking instead
share reservations to exclude inconsistent file access, there is an of share reservations to exclude inconsistent file access, there is
analogous set of constraints that apply to client side data caching. an analogous set of constraints that apply to client-side data
These rules are effective only if the file locking is used in a way caching. These rules are effective only if the byte-range locking is
that matches in an equivalent way the actual READ and WRITE used in a way that matches in an equivalent way the actual READ and
operations executed. This is as opposed to file locking that is WRITE operations executed. This is as opposed to byte-range locking
based on pure convention. For example, it is possible to manipulate that is based on pure convention. For example, it is possible to
a two-megabyte file by dividing the file into two one-megabyte manipulate a two-megabyte file by dividing the file into two one-
regions and protecting access to the two regions by file locks on megabyte ranges and protecting access to the two byte-ranges by byte-
bytes zero and one. A lock for write on byte zero of the file would range locks on bytes zero and one. A WRITE_LT lock on byte zero of
represent the right to do READ and WRITE operations on the first the file would represent the right to perform READ and WRITE
region. A lock for write on byte one of the file would represent the operations on the first byte-range. A WRITE_LT lock on byte one of
right to do READ and WRITE operations on the second region. As long the file would represent the right to perform READ and WRITE
as all applications manipulating the file obey this convention, they operations on the second byte-range. As long as all applications
will work on a local file system. However, they may not work with manipulating the file obey this convention, they will work on a local
the NFSv4.1 protocol unless clients refrain from data caching. file system. However, they may not work with the NFSv4.1 protocol
unless clients refrain from data caching.
The rules for data caching in the file locking environment are: The rules for data caching in the byte-range locking environment are:
o First, when a client obtains a file lock for a particular region, o First, when a client obtains a byte-range lock for a particular
the data cache corresponding to that region (if any cache data byte-range, the data cache corresponding to that byte-range (if
exists) must be revalidated. If the change attribute indicates any cache data exists) must be revalidated. If the change
that the file may have been updated since the cached data was attribute indicates that the file may have been updated since the
obtained, the client must flush or invalidate the cached data for cached data was obtained, the client must flush or invalidate the
the newly locked region. A client might choose to invalidate all cached data for the newly locked byte-range. A client might
of non-modified cached data that it has for the file but the only choose to invalidate all of the non-modified cached data that it
requirement for correct operation is to invalidate all of the data has for the file, but the only requirement for correct operation
in the newly locked region. is to invalidate all of the data in the newly locked byte-range.
o Second, before releasing a write lock for a region, all modified o Second, before releasing a WRITE_LT lock for a byte-range, all
data for that region must be flushed to the server. The modified modified data for that byte-range must be flushed to the server.
data must also be written to stable storage. The modified data must also be written to stable storage.
Note that flushing data to the server and the invalidation of cached Note that flushing data to the server and the invalidation of cached
data must reflect the actual byte ranges locked or unlocked. data must reflect the actual byte-ranges locked or unlocked.
Rounding these up or down to reflect client cache block boundaries Rounding these up or down to reflect client cache block boundaries
will cause problems if not carefully done. For example, writing a will cause problems if not carefully done. For example, writing a
modified block when only half of that block is within an area being modified block when only half of that block is within an area being
unlocked may cause invalid modification to the region outside the unlocked may cause invalid modification to the byte-range outside the
unlocked area. This, in turn, may be part of a region locked by unlocked area. This, in turn, may be part of a byte-range locked by
another client. Clients can avoid this situation by synchronously another client. Clients can avoid this situation by synchronously
performing portions of write operations that overlap that portion performing portions of WRITE operations that overlap that portion
(initial or final) that is not a full block. Similarly, invalidating (initial or final) that is not a full block. Similarly, invalidating
a locked area which is not an integral number of full buffer blocks a locked area that is not an integral number of full buffer blocks
would require the client to read one or two partial blocks from the would require the client to read one or two partial blocks from the
server if the revalidation procedure shows that the data which the server if the revalidation procedure shows that the data that the
client possesses may not be valid. client possesses may not be valid.
The data that is written to the server as a prerequisite to the The data that is written to the server as a prerequisite to the
unlocking of a region must be written, at the server, to stable unlocking of a byte-range must be written, at the server, to stable
storage. The client may accomplish this either with synchronous storage. The client may accomplish this either with synchronous
writes or by following asynchronous writes with a COMMIT operation. writes or by following asynchronous writes with a COMMIT operation.
This is required because retransmission of the modified data after a This is required because retransmission of the modified data after a
server restart might conflict with a lock held by another client. server restart might conflict with a lock held by another client.
A client implementation may choose to accommodate applications which A client implementation may choose to accommodate applications that
use byte-range locking in non-standard ways (e.g. using a byte-range use byte-range locking in non-standard ways (e.g., using a byte-range
lock as a global semaphore) by flushing to the server more data upon lock as a global semaphore) by flushing to the server more data upon
an LOCKU than is covered by the locked range. This may include a LOCKU than is covered by the locked range. This may include
modified data within files other than the one for which the unlocks modified data within files other than the one for which the unlocks
are being done. In such cases, the client must not interfere with are being done. In such cases, the client must not interfere with
applications whose READs and WRITEs are being done only within the applications whose READs and WRITEs are being done only within the
bounds of byte-range locks which the application holds. For example, bounds of byte-range locks that the application holds. For example,
an application locks a single byte of a file and proceeds to write an application locks a single byte of a file and proceeds to write
that single byte. A client that chose to handle a LOCKU by flushing that single byte. A client that chose to handle a LOCKU by flushing
all modified data to the server could validly write that single byte all modified data to the server could validly write that single byte
in response to an unrelated unlock. However, it would not be valid in response to an unrelated LOCKU operation. However, it would not
to write the entire block in which that single written byte was be valid to write the entire block in which that single written byte
located since it includes an area that is not locked and might be was located since it includes an area that is not locked and might be
locked by another client. Client implementations can avoid this locked by another client. Client implementations can avoid this
problem by dividing files with modified data into those for which all problem by dividing files with modified data into those for which all
modifications are done to areas covered by an appropriate byte-range modifications are done to areas covered by an appropriate byte-range
lock and those for which there are modifications not covered by a lock and those for which there are modifications not covered by a
byte-range lock. Any writes done for the former class of files must byte-range lock. Any writes done for the former class of files must
not include areas not locked and thus not modified on the client. not include areas not locked and thus not modified on the client.
10.3.3. Data Caching and Mandatory File Locking 10.3.3. Data Caching and Mandatory File Locking
Client side data caching needs to respect mandatory file locking when Client-side data caching needs to respect mandatory byte-range
it is in effect. The presence of mandatory file locking for a given locking when it is in effect. The presence of mandatory byte-range
file is indicated when the client gets back NFS4ERR_LOCKED from a locking for a given file is indicated when the client gets back
READ or WRITE on a file it has an appropriate share reservation for. NFS4ERR_LOCKED from a READ or WRITE operation on a file for which it
When mandatory locking is in effect for a file, the client must check has an appropriate share reservation. When mandatory locking is in
for an appropriate file lock for data being read or written. If a effect for a file, the client must check for an appropriate byte-
lock exists for the range being read or written, the client may range lock for data being read or written. If a byte-range lock
satisfy the request using the client's validated cache. If an exists for the range being read or written, the client may satisfy
appropriate file lock is not held for the range of the read or write, the request using the client's validated cache. If an appropriate
the read or write request must not be satisfied by the client's cache byte-range lock is not held for the range of the read or write, the
and the request must be sent to the server for processing. When a read or write request must not be satisfied by the client's cache and
read or write request partially overlaps a locked region, the request the request must be sent to the server for processing. When a read
should be subdivided into multiple pieces with each region (locked or or write request partially overlaps a locked byte-range, the request
not) treated appropriately. should be subdivided into multiple pieces with each byte-range
(locked or not) treated appropriately.
10.3.4. Data Caching and File Identity 10.3.4. Data Caching and File Identity
When clients cache data, the file data needs to be organized When clients cache data, the file data needs to be organized
according to the file system object to which the data belongs. For according to the file system object to which the data belongs. For
NFSv3 clients, the typical practice has been to assume for the NFSv3 clients, the typical practice has been to assume for the
purpose of caching that distinct filehandles represent distinct file purpose of caching that distinct filehandles represent distinct file
system objects. The client then has the choice to organize and system objects. The client then has the choice to organize and
maintain the data cache on this basis. maintain the data cache on this basis.
In the NFSv4.1 protocol, there is now the possibility to have In the NFSv4.1 protocol, there is now the possibility to have
significant deviations from a "one filehandle per object" model significant deviations from a "one filehandle per object" model
because a filehandle may be constructed on the basis of the object's because a filehandle may be constructed on the basis of the object's
pathname. Therefore, clients need a reliable method to determine if pathname. Therefore, clients need a reliable method to determine if
two filehandles designate the same file system object. If clients two filehandles designate the same file system object. If clients
were simply to assume that all distinct filehandles denote distinct were simply to assume that all distinct filehandles denote distinct
objects and proceed to do data caching on this basis, caching objects and proceed to do data caching on this basis, caching
inconsistencies would arise between the distinct client side objects inconsistencies would arise between the distinct client-side objects
which mapped to the same server side object. that mapped to the same server-side object.
By providing a method to differentiate filehandles, the NFSv4.1 By providing a method to differentiate filehandles, the NFSv4.1
protocol alleviates a potential functional regression in comparison protocol alleviates a potential functional regression in comparison
with the NFSv3 protocol. Without this method, caching with the NFSv3 protocol. Without this method, caching
inconsistencies within the same client could occur and this has not inconsistencies within the same client could occur, and this has not
been present in previous versions of the NFS protocol. Note that it been present in previous versions of the NFS protocol. Note that it
is possible to have such inconsistencies with applications executing is possible to have such inconsistencies with applications executing
on multiple clients but that is not the issue being addressed here. on multiple clients, but that is not the issue being addressed here.
For the purposes of data caching, the following steps allow an For the purposes of data caching, the following steps allow an
NFSv4.1 client to determine whether two distinct filehandles denote NFSv4.1 client to determine whether two distinct filehandles denote
the same server side object: the same server-side object:
o If GETATTR directed to two filehandles returns different values of o If GETATTR directed to two filehandles returns different values of
the fsid attribute, then the filehandles represent distinct the fsid attribute, then the filehandles represent distinct
objects. objects.
o If GETATTR for any file with an fsid that matches the fsid of the o If GETATTR for any file with an fsid that matches the fsid of the
two filehandles in question returns a unique_handles attribute two filehandles in question returns a unique_handles attribute
with a value of TRUE, then the two objects are distinct. with a value of TRUE, then the two objects are distinct.
o If GETATTR directed to the two filehandles does not return the o If GETATTR directed to the two filehandles does not return the
fileid attribute for both of the handles, then it cannot be fileid attribute for both of the handles, then it cannot be
determined whether the two objects are the same. Therefore, determined whether the two objects are the same. Therefore,
operations which depend on that knowledge (e.g. client side data operations that depend on that knowledge (e.g., client-side data
caching) cannot be done reliably. Note that if GETATTR does not caching) cannot be done reliably. Note that if GETATTR does not
return the fileid attribute for both filehandles, it will return return the fileid attribute for both filehandles, it will return
it for neither of the filehandles, since the fsid for both it for neither of the filehandles, since the fsid for both
filehandles is the same. filehandles is the same.
o If GETATTR directed to the two filehandles returns different o If GETATTR directed to the two filehandles returns different
values for the fileid attribute, then they are distinct objects. values for the fileid attribute, then they are distinct objects.
o Otherwise they are the same object. o Otherwise, they are the same object.
10.4. Open Delegation 10.4. Open Delegation
When a file is being OPENed, the server may delegate further handling When a file is being OPENed, the server may delegate further handling
of opens and closes for that file to the opening client. Any such of opens and closes for that file to the opening client. Any such
delegation is recallable, since the circumstances that allowed for delegation is recallable since the circumstances that allowed for the
the delegation are subject to change. In particular, the server may delegation are subject to change. In particular, if the server
receive a conflicting OPEN from another client, the server must receives a conflicting OPEN from another client, the server must
recall the delegation before deciding whether the OPEN from the other recall the delegation before deciding whether the OPEN from the other
client may be granted. Making a delegation is up to the server and client may be granted. Making a delegation is up to the server, and
clients should not assume that any particular OPEN either will or clients should not assume that any particular OPEN either will or
will not result in an open delegation. The following is a typical will not result in an OPEN delegation. The following is a typical
set of conditions that servers might use in deciding whether OPEN set of conditions that servers might use in deciding whether an OPEN
should be delegated: should be delegated:
o The client must be able to respond to the server's callback o The client must be able to respond to the server's callback
requests. If a backchannel has been established, the server will requests. If a backchannel has been established, the server will
send a CB_COMPOUND request, containing a single operation, send a CB_COMPOUND request, containing a single operation,
CB_SEQUENCE, for a test of backchannel availability. CB_SEQUENCE, for a test of backchannel availability.
o The client must have responded properly to previous recalls. o The client must have responded properly to previous recalls.
o There must be no current open conflicting with the requested o There must be no current OPEN conflicting with the requested
delegation. delegation.
o There should be no current delegation that conflicts with the o There should be no current delegation that conflicts with the
delegation being requested. delegation being requested.
o The probability of future conflicting open requests should be low o The probability of future conflicting open requests should be low
based on the recent history of the file. based on the recent history of the file.
o The existence of any server-specific semantics of OPEN/CLOSE that o The existence of any server-specific semantics of OPEN/CLOSE that
would make the required handling incompatible with the prescribed would make the required handling incompatible with the prescribed
handling that the delegated client would apply (see below). handling that the delegated client would apply (see below).
There are two types of open delegations, read and write. A read open There are two types of OPEN delegations: OPEN_DELEGATE_READ and
delegation allows a client to handle, on its own, requests to open a OPEN_DELEGATE_WRITE. An OPEN_DELEGATE_READ delegation allows a
file for reading that do not deny read access to others. Multiple client to handle, on its own, requests to open a file for reading
read open delegations may be outstanding simultaneously and do not that do not deny OPEN4_SHARE_ACCESS_READ access to others. Multiple
conflict. A write open delegation allows the client to handle, on OPEN_DELEGATE_READ delegations may be outstanding simultaneously and
its own, all opens. Only one write open delegation may exist for a do not conflict. An OPEN_DELEGATE_WRITE delegation allows the client
given file at a given time and it is inconsistent with any read open to handle, on its own, all opens. Only OPEN_DELEGATE_WRITE
delegations. delegation may exist for a given file at a given time, and it is
inconsistent with any OPEN_DELEGATE_READ delegations.
When a client has a read open delegation, it is assured that neither When a client has an OPEN_DELEGATE_READ delegation, it is assured
the contents, the attributes (with the exception of time_access), nor that neither the contents, the attributes (with the exception of
the names of any links to the file will change without its knowledge, time_access), nor the names of any links to the file will change
so long as the delegation is held. When a client has a write open without its knowledge, so long as the delegation is held. When a
delegation, it may modify the file data locally since no other client client has an OPEN_DELEGATE_WRITE delegation, it may modify the file
will be accessing the file's data. The client holding a write data locally since no other client will be accessing the file's data.
delegation may only locally affect file attributes which are The client holding an OPEN_DELEGATE_WRITE delegation may only locally
intimately connected with the file data: size, change, time_access, affect file attributes that are intimately connected with the file
time_metadata, and time_modify. All other attributes must be data: size, change, time_access, time_metadata, and time_modify. All
reflected on the server. other attributes must be reflected on the server.
When a client has an open delegation, it does not need to send OPENs When a client has an OPEN delegation, it does not need to send OPENs
or CLOSEs to the server. Instead the client may update the or CLOSEs to the server. Instead, the client may update the
appropriate status internally. For a read open delegation, opens appropriate status internally. For an OPEN_DELEGATE_READ delegation,
that cannot be handled locally (opens for write or that deny read opens that cannot be handled locally (opens that are for
access) must be sent to the server. OPEN4_SHARE_ACCESS_WRITE/OPEN4_SHARE_ACCESS_BOTH or that deny
OPEN4_SHARE_ACCESS_READ access) must be sent to the server.
When an open delegation is made, the reply to the OPEN contains an When an OPEN delegation is made, the reply to the OPEN contains an
open delegation structure which specifies the following: OPEN delegation structure that specifies the following:
o the type of delegation (read or write). o the type of delegation (OPEN_DELEGATE_READ or
OPEN_DELEGATE_WRITE).
o space limitation information to control flushing of data on close o space limitation information to control flushing of data on close
(write open delegation only, see Section 10.4.1). (OPEN_DELEGATE_WRITE delegation only; see Section 10.4.1)
o an nfsace4 specifying read and write permissions. o an nfsace4 specifying read and write permissions
o a stateid to represent the delegation for READ and WRITE. o a stateid to represent the delegation
The delegation stateid is separate and distinct from the stateid for The delegation stateid is separate and distinct from the stateid for
the OPEN proper. The standard stateid, unlike the delegation the OPEN proper. The standard stateid, unlike the delegation
stateid, is associated with a particular lock-owner and will continue stateid, is associated with a particular lock-owner and will continue
to be valid after the delegation is recalled and the file remains to be valid after the delegation is recalled and the file remains
open. open.
When a request internal to the client is made to open a file and an When a request internal to the client is made to open a file and an
open delegation is in effect, it will be accepted or rejected solely OPEN delegation is in effect, it will be accepted or rejected solely
on the basis of the following conditions. Any requirement for other on the basis of the following conditions. Any requirement for other
checks to be made by the delegate should result in open delegation checks to be made by the delegate should result in the OPEN
being denied so that the checks can be made by the server itself. delegation being denied so that the checks can be made by the server
itself.
o The access and deny bits for the request and the file as described o The access and deny bits for the request and the file as described
in Section 9.7. in Section 9.7.
o The read and write permissions as determined below. o The read and write permissions as determined below.
The nfsace4 passed with delegation can be used to avoid frequent The nfsace4 passed with delegation can be used to avoid frequent
ACCESS calls. The permission check should be as follows: ACCESS calls. The permission check should be as follows:
o If the nfsace4 indicates that the open may be done, then it should o If the nfsace4 indicates that the open may be done, then it should
skipping to change at page 207, line 52 skipping to change at page 207, line 37
The use of a delegation together with various other forms of caching The use of a delegation together with various other forms of caching
creates the possibility that no server authentication and creates the possibility that no server authentication and
authorization will ever be performed for a given user since all of authorization will ever be performed for a given user since all of
the user's requests might be satisfied locally. Where the client is the user's requests might be satisfied locally. Where the client is
depending on the server for authentication and authorization, the depending on the server for authentication and authorization, the
client should be sure authentication and authorization occurs for client should be sure authentication and authorization occurs for
each user by use of the ACCESS operation. This should be the case each user by use of the ACCESS operation. This should be the case
even if an ACCESS operation would not be required otherwise. As even if an ACCESS operation would not be required otherwise. As
mentioned before, the server may enforce frequent authentication by mentioned before, the server may enforce frequent authentication by
returning an nfsace4 denying all access with every open delegation. returning an nfsace4 denying all access with every OPEN delegation.
10.4.1. Open Delegation and Data Caching 10.4.1. Open Delegation and Data Caching
An OPEN delegation allows much of the message overhead associated An OPEN delegation allows much of the message overhead associated
with the opening and closing files to be eliminated. An open when an with the opening and closing files to be eliminated. An open when an
open delegation is in effect does not require that a validation OPEN delegation is in effect does not require that a validation
message be sent to the server. The continued endurance of the "read message be sent to the server. The continued endurance of the
open delegation" provides a guarantee that no OPEN for write and thus "OPEN_DELEGATE_READ delegation" provides a guarantee that no OPEN for
no write has occurred. Similarly, when closing a file opened for OPEN4_SHARE_ACCESS_WRITE/OPEN4_SHARE_ACCESS_BOTH, and thus no write,
write and if write open delegation is in effect, the data written has occurred. Similarly, when closing a file opened for
does not have to be written to the server until the open delegation OPEN4_SHARE_ACCESS_WRITE/OPEN4_SHARE_ACCESS_BOTH and if an
is recalled. The continued endurance of the open delegation provides OPEN_DELEGATE_WRITE delegation is in effect, the data written does
a guarantee that no open and thus no read or write has been done by not have to be written to the server until the OPEN delegation is
recalled. The continued endurance of the OPEN delegation provides a
guarantee that no open, and thus no READ or WRITE, has been done by
another client. another client.
For the purposes of open delegation, READs and WRITEs done without an For the purposes of OPEN delegation, READs and WRITEs done without an
OPEN are treated as the functional equivalents of a corresponding OPEN are treated as the functional equivalents of a corresponding
type of OPEN. Although client SHOULD NOT use special stateids when type of OPEN. Although a client SHOULD NOT use special stateids when
an open exists, delegation handling on the server can use the client an open exists, delegation handling on the server can use the client
ID associated with the current session to determine if the operation ID associated with the current session to determine if the operation
has been done by the holder of the delegation, in which case, no has been done by the holder of the delegation (in which case, no
recall is necessary, or by another client, in which case the recall is necessary) or by another client (in which case, the
delegation must be recalled and I/O not proceed until the delegation delegation must be recalled and I/O not proceed until the delegation
is recalled or revoked. is recalled or revoked).
With delegations, a client is able to avoid writing data to the With delegations, a client is able to avoid writing data to the
server when the CLOSE of a file is serviced. The file close system server when the CLOSE of a file is serviced. The file close system
call is the usual point at which the client is notified of a lack of call is the usual point at which the client is notified of a lack of
stable storage for the modified file data generated by the stable storage for the modified file data generated by the
application. At the close, file data is written to the server and application. At the close, file data is written to the server and,
through normal accounting the server is able to determine if the through normal accounting, the server is able to determine if the
available file system space for the data has been exceeded (i.e. available file system space for the data has been exceeded (i.e., the
server returns NFS4ERR_NOSPC or NFS4ERR_DQUOT). This accounting server returns NFS4ERR_NOSPC or NFS4ERR_DQUOT). This accounting
includes quotas. The introduction of delegations requires that a includes quotas. The introduction of delegations requires that an
alternative method be in place for the same type of communication to alternative method be in place for the same type of communication to
occur between client and server. occur between client and server.
In the delegation response, the server provides either the limit of In the delegation response, the server provides either the limit of
the size of the file or the number of modified blocks and associated the size of the file or the number of modified blocks and associated
block size. The server must ensure that the client will be able to block size. The server must ensure that the client will be able to
write modified data to the server of a size equal to that provided in write modified data to the server of a size equal to that provided in
the original delegation. The server must make this assurance for all the original delegation. The server must make this assurance for all
outstanding delegations. Therefore, the server must be careful in outstanding delegations. Therefore, the server must be careful in
its management of available space for new or modified data taking its management of available space for new or modified data, taking
into account available file system space and any applicable quotas. into account available file system space and any applicable quotas.
The server can recall delegations as a result of managing the The server can recall delegations as a result of managing the
available file system space. The client should abide by the server's available file system space. The client should abide by the server's
state space limits for delegations. If the client exceeds the stated state space limits for delegations. If the client exceeds the stated
limits for the delegation, the server's behavior is undefined. limits for the delegation, the server's behavior is undefined.
Based on server conditions, quotas or available file system space, Based on server conditions, quotas, or available file system space,
the server may grant write open delegations with very restrictive the server may grant OPEN_DELEGATE_WRITE delegations with very
space limitations. The limitations may be defined in a way that will restrictive space limitations. The limitations may be defined in a
always force modified data to be flushed to the server on close. way that will always force modified data to be flushed to the server
on close.
With respect to authentication, flushing modified data to the server With respect to authentication, flushing modified data to the server
after a CLOSE has occurred may be problematic. For example, the user after a CLOSE has occurred may be problematic. For example, the user
of the application may have logged off the client and unexpired of the application may have logged off the client, and unexpired
authentication credentials may not be present. In this case, the authentication credentials may not be present. In this case, the
client may need to take special care to ensure that local unexpired client may need to take special care to ensure that local unexpired
credentials will in fact be available. This may be accomplished by credentials will in fact be available. This may be accomplished by
tracking the expiration time of credentials and flushing data well in tracking the expiration time of credentials and flushing data well in
advance of their expiration or by making private copies of advance of their expiration or by making private copies of
credentials to assure their availability when needed. credentials to assure their availability when needed.
10.4.2. Open Delegation and File Locks 10.4.2. Open Delegation and File Locks
When a client holds a write open delegation, lock operations are When a client holds an OPEN_DELEGATE_WRITE delegation, lock
performed locally. This includes those required for mandatory file operations are performed locally. This includes those required for
locking. This can be done since the delegation implies that there mandatory byte-range locking. This can be done since the delegation
can be no conflicting locks. Similarly, all of the revalidations implies that there can be no conflicting locks. Similarly, all of
that would normally be associated with obtaining locks and the the revalidations that would normally be associated with obtaining
flushing of data associated with the releasing of locks need not be locks and the flushing of data associated with the releasing of locks
done. need not be done.
When a client holds a read open delegation, lock operations are not When a client holds an OPEN_DELEGATE_READ delegation, lock operations
performed locally. All lock operations, including those requesting are not performed locally. All lock operations, including those
non-exclusive locks, are sent to the server for resolution. requesting non-exclusive locks, are sent to the server for
resolution.
10.4.3. Handling of CB_GETATTR 10.4.3. Handling of CB_GETATTR
The server needs to employ special handling for a GETATTR where the The server needs to employ special handling for a GETATTR where the
target is a file that has a write open delegation in effect. The target is a file that has an OPEN_DELEGATE_WRITE delegation in
reason for this is that the client holding the write delegation may effect. The reason for this is that the client holding the
have modified the data and the server needs to reflect this change to OPEN_DELEGATE_WRITE delegation may have modified the data, and the
the second client that submitted the GETATTR. Therefore, the client server needs to reflect this change to the second client that
holding the write delegation needs to be interrogated. The server submitted the GETATTR. Therefore, the client holding the
OPEN_DELEGATE_WRITE delegation needs to be interrogated. The server
will use the CB_GETATTR operation. The only attributes that the will use the CB_GETATTR operation. The only attributes that the
server can reliably query via CB_GETATTR are size and change. server can reliably query via CB_GETATTR are size and change.
Since CB_GETATTR is being used to satisfy another client's GETATTR Since CB_GETATTR is being used to satisfy another client's GETATTR
request, the server only needs to know if the client holding the request, the server only needs to know if the client holding the
delegation has a modified version of the file. If the client's copy delegation has a modified version of the file. If the client's copy
of the delegated file is not modified (data or size), the server can of the delegated file is not modified (data or size), the server can
satisfy the second client's GETATTR request from the attributes satisfy the second client's GETATTR request from the attributes
stored locally at the server. If the file is modified, the server stored locally at the server. If the file is modified, the server
only needs to know about this modified state. If the server only needs to know about this modified state. If the server
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stored locally at the server. If the file is modified, the server stored locally at the server. If the file is modified, the server
only needs to know about this modified state. If the server only needs to know about this modified state. If the server
determines that the file is currently modified, it will respond to determines that the file is currently modified, it will respond to
the second client's GETATTR as if the file had been modified locally the second client's GETATTR as if the file had been modified locally
at the server. at the server.
Since the form of the change attribute is determined by the server Since the form of the change attribute is determined by the server
and is opaque to the client, the client and server need to agree on a and is opaque to the client, the client and server need to agree on a
method of communicating the modified state of the file. For the size method of communicating the modified state of the file. For the size
attribute, the client will report its current view of the file size. attribute, the client will report its current view of the file size.
For the change attribute, the handling is more involved. For the change attribute, the handling is more involved.
For the client, the following steps will be taken when receiving a For the client, the following steps will be taken when receiving an
write delegation: OPEN_DELEGATE_WRITE delegation:
o The value of the change attribute will be obtained from the server o The value of the change attribute will be obtained from the server
and cached. Let this value be represented by c. and cached. Let this value be represented by c.
o The client will create a value greater than c that will be used o The client will create a value greater than c that will be used
for communicating modified data is held at the client. Let this for communicating that modified data is held at the client. Let
value be represented by d. this value be represented by d.
o When the client is queried via CB_GETATTR for the change o When the client is queried via CB_GETATTR for the change
attribute, it checks to see if it holds modified data. If the attribute, it checks to see if it holds modified data. If the
file is modified, the value d is returned for the change attribute file is modified, the value d is returned for the change attribute
value. If this file is not currently modified, the client returns value. If this file is not currently modified, the client returns
the value c for the change attribute. the value c for the change attribute.
For simplicity of implementation, the client MAY for each CB_GETATTR For simplicity of implementation, the client MAY for each CB_GETATTR
return the same value d. This is true even if, between successive return the same value d. This is true even if, between successive
CB_GETATTR operations, the client again modifies in the file's data CB_GETATTR operations, the client again modifies the file's data or
or metadata in its cache. The client can return the same value metadata in its cache. The client can return the same value because
because the only requirement is that the client be able to indicate the only requirement is that the client be able to indicate to the
to the server that the client holds modified data. Therefore, the server that the client holds modified data. Therefore, the value of
value of d may always be c + 1. d may always be c + 1.
While the change attribute is opaque to the client in the sense that While the change attribute is opaque to the client in the sense that
it has no idea what units of time, if any, the server is counting it has no idea what units of time, if any, the server is counting
change with, it is not opaque in that the client has to treat it as change with, it is not opaque in that the client has to treat it as
an unsigned integer, and the server has to be able to see the results an unsigned integer, and the server has to be able to see the results
of the client's changes to that integer. Therefore, the server MUST of the client's changes to that integer. Therefore, the server MUST
encode the change attribute in network order when sending it to the encode the change attribute in network order when sending it to the
client. The client MUST decode it from network order to its native client. The client MUST decode it from network order to its native
order when receiving it and the client MUST encode it network order order when receiving it, and the client MUST encode it in network
when sending it to the server. For this reason, change is defined as order when sending it to the server. For this reason, change is
an unsigned integer rather than an opaque array of bytes. defined as an unsigned integer rather than an opaque array of bytes.
For the server, the following steps will be taken when providing a For the server, the following steps will be taken when providing an
write delegation: OPEN_DELEGATE_WRITE delegation:
o Upon providing a write delegation, the server will cache a copy of o Upon providing an OPEN_DELEGATE_WRITE delegation, the server will
the change attribute in the data structure it uses to record the cache a copy of the change attribute in the data structure it uses
delegation. Let this value be represented by sc. to record the delegation. Let this value be represented by sc.
o When a second client sends a GETATTR operation on the same file to o When a second client sends a GETATTR operation on the same file to
the server, the server obtains the change attribute from the first the server, the server obtains the change attribute from the first
client. Let this value be cc. client. Let this value be cc.
o If the value cc is equal to sc, the file is not modified and the o If the value cc is equal to sc, the file is not modified and the
server returns the current values for change, time_metadata, and server returns the current values for change, time_metadata, and
time_modify (for example) to the second client. time_modify (for example) to the second client.
o If the value cc is NOT equal to sc, the file is currently modified o If the value cc is NOT equal to sc, the file is currently modified
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In the case that the file attribute size is different than the In the case that the file attribute size is different than the
server's current value, the server treats this as a modification server's current value, the server treats this as a modification
regardless of the value of the change attribute retrieved via regardless of the value of the change attribute retrieved via
CB_GETATTR and responds to the second client as in the last step. CB_GETATTR and responds to the second client as in the last step.
This methodology resolves issues of clock differences between client This methodology resolves issues of clock differences between client
and server and other scenarios where the use of CB_GETATTR break and server and other scenarios where the use of CB_GETATTR break
down. down.
It should be noted that the server is under no obligation to use It should be noted that the server is under no obligation to use
CB_GETATTR and therefore the server MAY simply recall the delegation CB_GETATTR, and therefore the server MAY simply recall the delegation
to avoid its use. to avoid its use.
10.4.4. Recall of Open Delegation 10.4.4. Recall of Open Delegation
The following events necessitate recall of an open delegation: The following events necessitate recall of an OPEN delegation:
o Potentially conflicting OPEN request (or READ/WRITE done with o potentially conflicting OPEN request (or a READ or WRITE operation
"special" stateid) done with a special stateid)
o SETATTR sent by another client o SETATTR sent by another client
o REMOVE request for the file o REMOVE request for the file
o RENAME request for the file as either source or target of the o RENAME request for the file as either the source or target of the
RENAME RENAME
Whether a RENAME of a directory in the path leading to the file Whether a RENAME of a directory in the path leading to the file
results in recall of an open delegation depends on the semantics of results in recall of an OPEN delegation depends on the semantics of
the server's file system. If that file system denies such RENAMEs the server's file system. If that file system denies such RENAMEs
when a file is open, the recall must be performed to determine when a file is open, the recall must be performed to determine
whether the file in question is, in fact, open. whether the file in question is, in fact, open.
In addition to the situations above, the server may choose to recall In addition to the situations above, the server may choose to recall
open delegations at any time if resource constraints make it OPEN delegations at any time if resource constraints make it
advisable to do so. Clients should always be prepared for the advisable to do so. Clients should always be prepared for the
possibility of recall. possibility of recall.
When a client receives a recall for an open delegation, it needs to When a client receives a recall for an OPEN delegation, it needs to
update state on the server before returning the delegation. These update state on the server before returning the delegation. These
same updates must be done whenever a client chooses to return a same updates must be done whenever a client chooses to return a
delegation voluntarily. The following items of state need to be delegation voluntarily. The following items of state need to be
dealt with: dealt with:
o If the file associated with the delegation is no longer open and o If the file associated with the delegation is no longer open and
no previous CLOSE operation has been sent to the server, a CLOSE no previous CLOSE operation has been sent to the server, a CLOSE
operation must be sent to the server. operation must be sent to the server.
o If a file has other open references at the client, then OPEN o If a file has other open references at the client, then OPEN
operations must be sent to the server. The appropriate stateids operations must be sent to the server. The appropriate stateids
will be provided by the server for subsequent use by the client will be provided by the server for subsequent use by the client
since the delegation stateid will no longer be valid. These OPEN since the delegation stateid will no longer be valid. These OPEN
requests are done with the claim type of CLAIM_DELEGATE_CUR. This requests are done with the claim type of CLAIM_DELEGATE_CUR. This
will allow the presentation of the delegation stateid so that the will allow the presentation of the delegation stateid so that the
client can establish the appropriate rights to perform the OPEN. client can establish the appropriate rights to perform the OPEN.
(see the Section 18.16 which describes the OPEN" operation for (see Section 18.16, which describes the OPEN operation, for
details.) details.)
o If there are granted file locks, the corresponding LOCK operations o If there are granted byte-range locks, the corresponding LOCK
need to be performed. This applies to the write open delegation operations need to be performed. This applies to the
case only. OPEN_DELEGATE_WRITE delegation case only.
o For a write open delegation, if at the time of recall the file is o For an OPEN_DELEGATE_WRITE delegation, if at the time of recall
not open for write, all modified data for the file must be flushed the file is not open for OPEN4_SHARE_ACCESS_WRITE/
to the server. If the delegation had not existed, the client OPEN4_SHARE_ACCESS_BOTH, all modified data for the file must be
would have done this data flush before the CLOSE operation. flushed to the server. If the delegation had not existed, the
client would have done this data flush before the CLOSE operation.
o For a write open delegation when a file is still open at the time o For an OPEN_DELEGATE_WRITE delegation when a file is still open at
of recall, any modified data for the file needs to be flushed to the time of recall, any modified data for the file needs to be
the server. flushed to the server.
o With the write open delegation in place, it is possible that the o With the OPEN_DELEGATE_WRITE delegation in place, it is possible
file was truncated during the duration of the delegation. For that the file was truncated during the duration of the delegation.
example, the truncation could have occurred as a result of an OPEN For example, the truncation could have occurred as a result of an
UNCHECKED with a size attribute value of zero. Therefore, if a OPEN UNCHECKED with a size attribute value of zero. Therefore, if
truncation of the file has occurred and this operation has not a truncation of the file has occurred and this operation has not
been propagated to the server, the truncation must occur before been propagated to the server, the truncation must occur before
any modified data is written to the server. any modified data is written to the server.
In the case of write open delegation, file locking imposes some In the case of OPEN_DELEGATE_WRITE delegation, byte-range locking
additional requirements. To precisely maintain the associated imposes some additional requirements. To precisely maintain the
invariant, it is required to flush any modified data in any region associated invariant, it is required to flush any modified data in
for which a write lock was released while the write delegation was in any byte-range for which a WRITE_LT lock was released while the
effect. However, because the write open delegation implies no other OPEN_DELEGATE_WRITE delegation was in effect. However, because the
locking by other clients, a simpler implementation is to flush all OPEN_DELEGATE_WRITE delegation implies no other locking by other
modified data for the file (as described just above) if any write clients, a simpler implementation is to flush all modified data for
lock has been released while the write open delegation was in effect. the file (as described just above) if any WRITE_LT lock has been
released while the OPEN_DELEGATE_WRITE delegation was in effect.
An implementation need not wait until delegation recall (or deciding An implementation need not wait until delegation recall (or the
to voluntarily return a delegation) to perform any of the above decision to voluntarily return a delegation) to perform any of the
actions, if implementation considerations (e.g. resource availability above actions, if implementation considerations (e.g., resource
constraints) make that desirable. Generally, however, the fact that availability constraints) make that desirable. Generally, however,
the actual open state of the file may continue to change makes it not the fact that the actual OPEN state of the file may continue to
worthwhile to send information about opens and closes to the server, change makes it not worthwhile to send information about opens and
except as part of delegation return. Only in the case of closing the closes to the server, except as part of delegation return. An
open that resulted in obtaining the delegation would clients be exception is when the client has no more internal opens of the file.
likely to do this early, since, in that case, the close once done In this case, sending a CLOSE is useful because it reduces resource
will not be undone. Regardless of the client's choices on scheduling utilization on the client and server. Regardless of the client's
these actions, all must be performed before the delegation is choices on scheduling these actions, all must be performed before the
returned, including (when applicable) the close that corresponds to delegation is returned, including (when applicable) the close that
the open that resulted in the delegation. These actions can be corresponds to the OPEN that resulted in the delegation. These
performed either in previous requests or in previous operations in actions can be performed either in previous requests or in previous
the same COMPOUND request. operations in the same COMPOUND request.
10.4.5. Clients that Fail to Honor Delegation Recalls 10.4.5. Clients That Fail to Honor Delegation Recalls
A client may fail to respond to a recall for various reasons, such as A client may fail to respond to a recall for various reasons, such as
a failure of the backchannel from server to the client. The client a failure of the backchannel from server to the client. The client
may be unaware of a failure in the backchannel. This lack of may be unaware of a failure in the backchannel. This lack of
awareness could result in the client finding out long after the awareness could result in the client finding out long after the
failure that its delegation has been revoked, and another client has failure that its delegation has been revoked, and another client has
modified the data for which the client had a delegation. This is modified the data for which the client had a delegation. This is
especially a problem for the client that held a write delegation. especially a problem for the client that held an OPEN_DELEGATE_WRITE
delegation.
Status bits returned by SEQUENCE operations help to provide an Status bits returned by SEQUENCE operations help to provide an
alternate way of informing the client of issues regarding the status alternate way of informing the client of issues regarding the status
of the backchannel and of recalled delegations. When the backchannel of the backchannel and of recalled delegations. When the backchannel
is not available, the server returns the status bit is not available, the server returns the status bit
SEQ4_STATUS_CB_PATH_DOWN on SEQUENCE operations. The client can SEQ4_STATUS_CB_PATH_DOWN on SEQUENCE operations. The client can
react by attempting to re-establish the backchannel and by returning react by attempting to re-establish the backchannel and by returning
recallable objects if a backchannel cannot be successfully re- recallable objects if a backchannel cannot be successfully re-
established. established.
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down status and re-establish the backchannel. down status and re-establish the backchannel.
When delegations are revoked, the server will return with the When delegations are revoked, the server will return with the
SEQ4_STATUS_RECALLABLE_STATE_REVOKED status bit set on subsequent SEQ4_STATUS_RECALLABLE_STATE_REVOKED status bit set on subsequent
SEQUENCE operations. The client should note this and then use SEQUENCE operations. The client should note this and then use
TEST_STATEID to find which delegations have been revoked. TEST_STATEID to find which delegations have been revoked.
10.4.6. Delegation Revocation 10.4.6. Delegation Revocation
At the point a delegation is revoked, if there are associated opens At the point a delegation is revoked, if there are associated opens
on the client, these opens may or may not be revoked. If no lock or on the client, these opens may or may not be revoked. If no byte-
open is granted that is inconsistent with the existing open, the range lock or open is granted that is inconsistent with the existing
stateid for the open may remain valid, and be disconnected from the open, the stateid for the open may remain valid and be disconnected
revoked delegation, just as would be the case if the delegation were from the revoked delegation, just as would be the case if the
returned. delegation were returned.
For example, if an OPEN for read-write with DENY=NONE is associated For example, if an OPEN for OPEN4_SHARE_ACCESS_BOTH with a deny of
with the delegation, granting of another such OPEN to a different OPEN4_SHARE_DENY_NONE is associated with the delegation, granting of
client will revoke the delegation but need not revoke the OPEN, since another such OPEN to a different client will revoke the delegation
no lock inconsistent with that OPEN has been granted. On the other but need not revoke the OPEN, since the two OPENs are consistent with
hand, if an OPEN denying write is granted, then the existing open each other. On the other hand, if an OPEN denying write access is
must be revoked. granted, then the existing OPEN must be revoked.
When opens and/or locks are revoked, the applications holding these When opens and/or locks are revoked, the applications holding these
opens or locks need to be notified. This notification usually occurs opens or locks need to be notified. This notification usually occurs
by returning errors for READ/WRITE operations or when a close is by returning errors for READ/WRITE operations or when a close is
attempted for the open file. attempted for the open file.
If no opens exist for the file at the point the delegation is If no opens exist for the file at the point the delegation is
revoked, then notification of the revocation is unnecessary. revoked, then notification of the revocation is unnecessary.
However, if there is modified data present at the client for the However, if there is modified data present at the client for the
file, the user of the application should be notified. Unfortunately, file, the user of the application should be notified. Unfortunately,
it may not be possible to notify the user since active applications it may not be possible to notify the user since active applications
may not be present at the client. See Section 10.5.1 for additional may not be present at the client. See Section 10.5.1 for additional
details. details.
10.4.7. Delegations via WANT_DELEGATION 10.4.7. Delegations via WANT_DELEGATION
In addition to providing delegations as part of the reply to OPEN In addition to providing delegations as part of the reply to OPEN
operations, servers MAY provide delegations separate from open, via operations, servers MAY provide delegations separate from open, via
the OPTIONAL WANT_DELEGATION operation. This allows delegations to the OPTIONAL WANT_DELEGATION operation. This allows delegations to
be obtained in advance of an OPEN that might benefit from them, for be obtained in advance of an OPEN that might benefit from them, for
objects which are not a valid target of OPEN, or to deal with cases objects that are not a valid target of OPEN, or to deal with cases in
in which a delegation has been recalled and the client wants to make which a delegation has been recalled and the client wants to make an
an attempt to re-establish it if the absence of use by other clients attempt to re-establish it if the absence of use by other clients
allows that. allows that.
The WANT_DELEGATION operation may be performed on any type of file The WANT_DELEGATION operation may be performed on any type of file
object other than a directory. object other than a directory.
When a delegation is obtained using WANT_DELEGATION, any open files When a delegation is obtained using WANT_DELEGATION, any open files
for the same filehandle held by that client are to be treated as for the same filehandle held by that client are to be treated as
subordinate to the delegation, just as if they had been created using subordinate to the delegation, just as if they had been created using
an OPEN of type CLAIM_DELEGATE_CUR. They are otherwise unchanged as an OPEN of type CLAIM_DELEGATE_CUR. They are otherwise unchanged as
to seqid, access and deny modes, and the relationship with byte-range to seqid, access and deny modes, and the relationship with byte-range
locks. Similarly, existing byte-range locks subordinate to an open locks. Similarly, because existing byte-range locks are subordinate
which becomes subordinate to a delegation, become indirectly to an open, those byte-range locks also become indirectly subordinate
subordinate to that new delegation. to that new delegation.
The WANT_DELEGATION operation provides for delivery of delegations The WANT_DELEGATION operation provides for delivery of delegations
via callbacks, when the delegations are not immediately available. via callbacks, when the delegations are not immediately available.
When a requested delegation is available, it is delivered to the When a requested delegation is available, it is delivered to the
client via a CB_PUSH_DELEG operation. When this happens, open files client via a CB_PUSH_DELEG operation. When this happens, open files
for the same filehandle become subordinate to the new delegation at for the same filehandle become subordinate to the new delegation at
the point at which the delegation is delivered , just as if they had the point at which the delegation is delivered , just as if they had
been created using an OPEN of type CLAIM_DELEGATE_CUR. Similarly, been created using an OPEN of type CLAIM_DELEGATE_CUR. Similarly,
for existing byte-range locks subordinate to an open. this occurs for existing byte-range locks subordinate to an open.
10.5. Data Caching and Revocation 10.5. Data Caching and Revocation
When locks and delegations are revoked, the assumptions upon which When locks and delegations are revoked, the assumptions upon which
successful caching depend are no longer guaranteed. For any locks or successful caching depends are no longer guaranteed. For any locks
share reservations that have been revoked, the corresponding state- or share reservations that have been revoked, the corresponding
owner needs to be notified. This notification includes applications state-owner needs to be notified. This notification includes
with a file open that has a corresponding delegation which has been applications with a file open that has a corresponding delegation
revoked. Cached data associated with the revocation must be removed that has been revoked. Cached data associated with the revocation
from the client. In the case of modified data existing in the must be removed from the client. In the case of modified data
client's cache, that data must be removed from the client without it existing in the client's cache, that data must be removed from the
being written to the server. As mentioned, the assumptions made by client without being written to the server. As mentioned, the
the client are no longer valid at the point when a lock or delegation assumptions made by the client are no longer valid at the point when
has been revoked. For example, another client may have been granted a lock or delegation has been revoked. For example, another client
a conflicting lock after the revocation of the lock at the first may have been granted a conflicting byte-range lock after the
client. Therefore, the data within the lock range may have been revocation of the byte-range lock at the first client. Therefore,
modified by the other client. Obviously, the first client is unable the data within the lock range may have been modified by the other
to guarantee to the application what has occurred to the file in the client. Obviously, the first client is unable to guarantee to the
case of revocation. application what has occurred to the file in the case of revocation.
Notification to a state-owner will in many cases consist of simply Notification to a state-owner will in many cases consist of simply
returning an error on the next and all subsequent READs/WRITEs to the returning an error on the next and all subsequent READs/WRITEs to the
open file or on the close. Where the methods available to a client open file or on the close. Where the methods available to a client
make such notification impossible because errors for certain make such notification impossible because errors for certain
operations may not be returned, more drastic action such as signals operations may not be returned, more drastic action such as signals
or process termination may be appropriate. The justification for or process termination may be appropriate. The justification here is
this is that an invariant for which an application depends on may be that an invariant on which an application depends may be violated.
violated. Depending on how errors are typically treated for the Depending on how errors are typically treated for the client-
client operating environment, further levels of notification operating environment, further levels of notification including
including logging, console messages, and GUI pop-ups may be logging, console messages, and GUI pop-ups may be appropriate.
appropriate.
10.5.1. Revocation Recovery for Write Open Delegation 10.5.1. Revocation Recovery for Write Open Delegation
Revocation recovery for a write open delegation poses the special Revocation recovery for an OPEN_DELEGATE_WRITE delegation poses the
issue of modified data in the client cache while the file is not special issue of modified data in the client cache while the file is
open. In this situation, any client which does not flush modified not open. In this situation, any client that does not flush modified
data to the server on each close must ensure that the user receives data to the server on each close must ensure that the user receives
appropriate notification of the failure as a result of the appropriate notification of the failure as a result of the
revocation. Since such situations may require human action to revocation. Since such situations may require human action to
correct problems, notification schemes in which the appropriate user correct problems, notification schemes in which the appropriate user
or administrator is notified may be necessary. Logging and console or administrator is notified may be necessary. Logging and console
messages are typical examples. messages are typical examples.
If there is modified data on the client, it must not be flushed If there is modified data on the client, it must not be flushed
normally to the server. A client may attempt to provide a copy of normally to the server. A client may attempt to provide a copy of
the file data as modified during the delegation under a different the file data as modified during the delegation under a different
name in the file system name space to ease recovery. Note that when name in the file system name space to ease recovery. Note that when
the client can determine that the file has not been modified by any the client can determine that the file has not been modified by any
other client, or when the client has a complete cached copy of file other client, or when the client has a complete cached copy of the
in question, such a saved copy of the client's view of the file may file in question, such a saved copy of the client's view of the file
be of particular value for recovery. In other case, recovery using a may be of particular value for recovery. In another case, recovery
copy of the file based partially on the client's cached data and using a copy of the file based partially on the client's cached data
partially on the server copy as modified by other clients, will be and partially on the server's copy as modified by other clients will
anything but straightforward, so clients may avoid saving file be anything but straightforward, so clients may avoid saving file
contents in these situations or mark the results specially to warn contents in these situations or specially mark the results to warn
users of possible problems. users of possible problems.
Saving of such modified data in delegation revocation situations may Saving of such modified data in delegation revocation situations may
be limited to files of a certain size or might be used only when be limited to files of a certain size or might be used only when
sufficient disk space is available within the target file system. sufficient disk space is available within the target file system.
Such saving may also be restricted to situations when the client has Such saving may also be restricted to situations when the client has
sufficient buffering resources to keep the cached copy available sufficient buffering resources to keep the cached copy available
until it is properly stored to the target file system. until it is properly stored to the target file system.
10.6. Attribute Caching 10.6. Attribute Caching
This section pertains to the caching of a file's attributes on a This section pertains to the caching of a file's attributes on a
client when that client does not hold a delegation on the file. client when that client does not hold a delegation on the file.
The attributes discussed in this section do not include named The attributes discussed in this section do not include named
attributes. Individual named attributes are analogous to files and attributes. Individual named attributes are analogous to files, and
caching of the data for these needs to be handled just as data caching of the data for these needs to be handled just as data
caching is for ordinary files. Similarly, LOOKUP results from an caching is for ordinary files. Similarly, LOOKUP results from an
OPENATTR directory are to be cached on the same basis as any other OPENATTR directory (as well as the directory's contents) are to be
pathnames and similarly for directory contents. cached on the same basis as any other pathnames.
Clients may cache file attributes obtained from the server and use Clients may cache file attributes obtained from the server and use
them to avoid subsequent GETATTR requests. Such caching is write them to avoid subsequent GETATTR requests. Such caching is write
through in that modification to file attributes is always done by through in that modification to file attributes is always done by
means of requests to the server and should not be done locally and means of requests to the server and should not be done locally and
cached. The exception to this are modifications to attributes that should not be cached. The exception to this are modifications to
are intimately connected with data caching. Therefore, extending a attributes that are intimately connected with data caching.
file by writing data to the local data cache is reflected immediately Therefore, extending a file by writing data to the local data cache
in the size as seen on the client without this change being is reflected immediately in the size as seen on the client without
immediately reflected on the server. Normally such changes are not this change being immediately reflected on the server. Normally,
propagated directly to the server but when the modified data is such changes are not propagated directly to the server, but when the
flushed to the server, analogous attribute changes are made on the modified data is flushed to the server, analogous attribute changes
server. When open delegation is in effect, the modified attributes are made on the server. When OPEN delegation is in effect, the
may be returned to the server in reaction to a CB_RECALL call. modified attributes may be returned to the server in reaction to a
CB_RECALL call.
The result of local caching of attributes is that the attribute The result of local caching of attributes is that the attribute
caches maintained on individual clients will not be coherent. caches maintained on individual clients will not be coherent.
Changes made in one order on the server may be seen in a different Changes made in one order on the server may be seen in a different
order on one client and in a third order on a different client. order on one client and in a third order on another client.
The typical file system application programming interfaces do not The typical file system application programming interfaces do not
provide means to atomically modify or interrogate attributes for provide means to atomically modify or interrogate attributes for
multiple files at the same time. The following rules provide an multiple files at the same time. The following rules provide an
environment where the potential incoherences mentioned above can be environment where the potential incoherencies mentioned above can be
reasonably managed. These rules are derived from the practice of reasonably managed. These rules are derived from the practice of
previous NFS protocols. previous NFS protocols.
o All attributes for a given file (per-fsid attributes excepted) are o All attributes for a given file (per-fsid attributes excepted) are
cached as a unit at the client so that no non-serializability can cached as a unit at the client so that no non-serializability can
arise within the context of a single file. arise within the context of a single file.
o An upper time boundary is maintained on how long a client cache o An upper time boundary is maintained on how long a client cache
entry can be kept without being refreshed from the server. entry can be kept without being refreshed from the server.
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containing RPC. This includes directory operations that update containing RPC. This includes directory operations that update
attributes indirectly. This is accomplished by following the attributes indirectly. This is accomplished by following the
modifying operation with a GETATTR operation and then using the modifying operation with a GETATTR operation and then using the
results of the GETATTR to update the client's cached attributes. results of the GETATTR to update the client's cached attributes.
Note that if the full set of attributes to be cached is requested by Note that if the full set of attributes to be cached is requested by
READDIR, the results can be cached by the client on the same basis as READDIR, the results can be cached by the client on the same basis as
attributes obtained via GETATTR. attributes obtained via GETATTR.
A client may validate its cached version of attributes for a file by A client may validate its cached version of attributes for a file by
fetching just both the change and time_access attributes and assuming fetching both the change and time_access attributes and assuming that
that if the change attribute has the same value as it did when the if the change attribute has the same value as it did when the
attributes were cached, then no attributes other than time_access attributes were cached, then no attributes other than time_access
have changed. The reason why time_access is also fetched is because have changed. The reason why time_access is also fetched is because
many servers operate in environments where the operation that updates many servers operate in environments where the operation that updates
change does not update time_access. For example, POSIX file change does not update time_access. For example, POSIX file
semantics do not update access time when a file is modified by the semantics do not update access time when a file is modified by the
write system call [18]. Therefore, the client that wants a current write system call [18]. Therefore, the client that wants a current
time_access value should fetch it with change during the attribute time_access value should fetch it with change during the attribute
cache validation processing and update its cached time_access. cache validation processing and update its cached time_access.
The client may maintain a cache of modified attributes for those The client may maintain a cache of modified attributes for those
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file object. If an NFS client is caching the content of a file file object. If an NFS client is caching the content of a file
object, whether it is a regular file, directory, or symbolic link, object, whether it is a regular file, directory, or symbolic link,
the client SHOULD NOT update the time_access attribute (via SETATTR the client SHOULD NOT update the time_access attribute (via SETATTR
or a small READ or READDIR request) on the server with each read that or a small READ or READDIR request) on the server with each read that
is satisfied from cache. The reason is that this can defeat the is satisfied from cache. The reason is that this can defeat the
performance benefits of caching content, especially since an explicit performance benefits of caching content, especially since an explicit
SETATTR of time_access may alter the change attribute on the server. SETATTR of time_access may alter the change attribute on the server.
If the change attribute changes, clients that are caching the content If the change attribute changes, clients that are caching the content
will think the content has changed, and will re-read unmodified data will think the content has changed, and will re-read unmodified data
from the server. Nor is the client encouraged to maintain a modified from the server. Nor is the client encouraged to maintain a modified
version of time_access in its cache, since this would mean that the version of time_access in its cache, since the client either would
client will either eventually have to write the access time to the eventually have to write the access time to the server with bad
server with bad performance effects, or it would never update the performance effects or never update the server's time_access, thereby
server's time_access, thereby resulting in a situation where an resulting in a situation where an application that caches access time
application that caches access time between a close and open of the between a close and open of the same file observes the access time
same file observes the access time oscillating between the past and oscillating between the past and present. The time_access attribute
present. The time_access attribute always means the time of last always means the time of last access to a file by a read that was
access to a file by a read that was satisfied by the server. This satisfied by the server. This way clients will tend to see only
way clients will tend to see only time_access changes that go forward time_access changes that go forward in time.
in time.
10.7. Data and Metadata Caching and Memory Mapped Files 10.7. Data and Metadata Caching and Memory Mapped Files
Some operating environments include the capability for an application Some operating environments include the capability for an application
to map a file's content into the application's address space. Each to map a file's content into the application's address space. Each
time the application accesses a memory location that corresponds to a time the application accesses a memory location that corresponds to a
block that has not been loaded into the address space, a page fault block that has not been loaded into the address space, a page fault
occurs and the file is read (or if the block does not exist in the occurs and the file is read (or if the block does not exist in the
file, the block is allocated and then instantiated in the file, the block is allocated and then instantiated in the
application's address space). application's address space).
As long as each memory mapped access to the file requires a page As long as each memory-mapped access to the file requires a page
fault, the relevant attributes of the file that are used to detect fault, the relevant attributes of the file that are used to detect
access and modification (time_access, time_metadata, time_modify, and access and modification (time_access, time_metadata, time_modify, and
change) will be updated. However, in many operating environments, change) will be updated. However, in many operating environments,
when page faults are not required these attributes will not be when page faults are not required, these attributes will not be
updated on reads or updates to the file via memory access (regardless updated on reads or updates to the file via memory access (regardless
whether the file is local file or is being access remotely). A of whether the file is local or is accessed remotely). A client or
client or server MAY fail to update attributes of a file that is server MAY fail to update attributes of a file that is being accessed
being accessed via memory mapped I/O. This has several implications: via memory-mapped I/O. This has several implications:
o If there is an application on the server that has memory mapped a o If there is an application on the server that has memory mapped a
file that a client is also accessing, the client may not be able file that a client is also accessing, the client may not be able
to get a consistent value of the change attribute to determine to get a consistent value of the change attribute to determine
whether its cache is stale or not. A server that knows that the whether or not its cache is stale. A server that knows that the
file is memory mapped could always pessimistically return updated file is memory-mapped could always pessimistically return updated
values for change so as to force the application to always get the values for change so as to force the application to always get the
most up to date data and metadata for the file. However, due to most up-to-date data and metadata for the file. However, due to
the negative performance implications of this, such behavior is the negative performance implications of this, such behavior is
OPTIONAL. OPTIONAL.
o If the memory mapped file is not being modified on the server, and o If the memory-mapped file is not being modified on the server, and
instead is just being read by an application via the memory mapped instead is just being read by an application via the memory-mapped
interface, the client will not see an updated time_access interface, the client will not see an updated time_access
attribute. However, in many operating environments, neither will attribute. However, in many operating environments, neither will
any process running on the server. Thus NFS clients are at no any process running on the server. Thus, NFS clients are at no
disadvantage with respect to local processes. disadvantage with respect to local processes.
o If there is another client that is memory mapping the file, and if o If there is another client that is memory mapping the file, and if
that client is holding a write delegation, the same set of issues that client is holding an OPEN_DELEGATE_WRITE delegation, the same
as discussed in the previous two bullet items apply. So, when a set of issues as discussed in the previous two bullet points
server does a CB_GETATTR to a file that the client has modified in apply. So, when a server does a CB_GETATTR to a file that the
its cache, the reply from CB_GETATTR will not necessarily be client has modified in its cache, the reply from CB_GETATTR will
accurate. As discussed earlier, the client's obligation is to not necessarily be accurate. As discussed earlier, the client's
report that the file has been modified since the delegation was obligation is to report that the file has been modified since the
granted, not whether it has been modified again between successive delegation was granted, not whether it has been modified again
CB_GETATTR calls, and the server MUST assume that any file the between successive CB_GETATTR calls, and the server MUST assume
client has modified in cache has been modified again between that any file the client has modified in cache has been modified
successive CB_GETATTR calls. Depending on the nature of the again between successive CB_GETATTR calls. Depending on the
client's memory management system, this weak obligation may not be nature of the client's memory management system, this weak
possible. A client MAY return stale information in CB_GETATTR obligation may not be possible. A client MAY return stale
whenever the file is memory mapped. information in CB_GETATTR whenever the file is memory-mapped.
o The mixture of memory mapping and file locking on the same file is o The mixture of memory mapping and byte-range locking on the same
problematic. Consider the following scenario, where a page size file is problematic. Consider the following scenario, where a
on each client is 8192 bytes. page size on each client is 8192 bytes.
* Client A memory maps first page (8192 bytes) of file X * Client A memory maps the first page (8192 bytes) of file X.
* Client B memory maps first page (8192 bytes) of file X * Client B memory maps the first page (8192 bytes) of file X.
* Client A write locks first 4096 bytes * Client A WRITE_LT locks the first 4096 bytes.
* Client B write locks second 4096 bytes * Client B WRITE_LT locks the second 4096 bytes.
* Client A, via a STORE instruction modifies part of its locked * Client A, via a STORE instruction, modifies part of its locked
region. byte-range.
* Simultaneous to client A, client B executes a STORE on part of * Simultaneous to client A, client B executes a STORE on part of
its locked region. its locked byte-range.
Here the challenge is for each client to resynchronize to get a Here the challenge is for each client to resynchronize to get a
correct view of the first page. In many operating environments, the correct view of the first page. In many operating environments, the
virtual memory management systems on each client only know a page is virtual memory management systems on each client only know a page is
modified, not that a subset of the page corresponding to the modified, not that a subset of the page corresponding to the
respective lock regions has been modified. So it is not possible for respective lock byte-ranges has been modified. So it is not possible
each client to do the right thing, which is to only write to the for each client to do the right thing, which is to write to the
server that portion of the page that is locked. For example, if server only that portion of the page that is locked. For example, if
client A simply writes out the page, and then client B writes out the client A simply writes out the page, and then client B writes out the
page, client A's data is lost. page, client A's data is lost.
Moreover, if mandatory locking is enabled on the file, then we have a Moreover, if mandatory locking is enabled on the file, then we have a
different problem. When clients A and B execute the STORE different problem. When clients A and B execute the STORE
instructions, the resulting page faults require a byte-range lock on instructions, the resulting page faults require a byte-range lock on
the entire page. Each client then tries to extend their locked range the entire page. Each client then tries to extend their locked range
to the entire page, which results in a deadlock. Communicating the to the entire page, which results in a deadlock. Communicating the
NFS4ERR_DEADLOCK error to a STORE instruction is difficult at best. NFS4ERR_DEADLOCK error to a STORE instruction is difficult at best.
If a client is locking the entire memory mapped file, there is no If a client is locking the entire memory-mapped file, there is no
problem with advisory or mandatory byte-range locking, at least until problem with advisory or mandatory byte-range locking, at least until
the client unlocks a region in the middle of the file. the client unlocks a byte-range in the middle of the file.
Given the above issues the following are permitted: Given the above issues, the following are permitted:
o Clients and servers MAY deny memory mapping a file they know there o Clients and servers MAY deny memory mapping a file for which they
are byte-range locks for. know there are byte-range locks.
o Clients and servers MAY deny a byte-range lock on a file they know o Clients and servers MAY deny a byte-range lock on a file they know
is memory mapped. is memory-mapped.
o A client MAY deny memory mapping a file that it knows requires o A client MAY deny memory mapping a file that it knows requires
mandatory locking for I/O. If mandatory locking is enabled after mandatory locking for I/O. If mandatory locking is enabled after
the file is opened and mapped, the client MAY deny the application the file is opened and mapped, the client MAY deny the application
further access to its mapped file. further access to its mapped file.
10.8. Name and Directory Caching without Directory Delegations 10.8. Name and Directory Caching without Directory Delegations
The NFSv4.1 directory delegation facility (described in Section 10.9 The NFSv4.1 directory delegation facility (described in Section 10.9
below) is OPTIONAL for servers to implement. Even where it is below) is OPTIONAL for servers to implement. Even where it is
implemented, it may not be always be functional because of resource implemented, it may not always be functional because of resource
availability issues or other constraints. Thus, it is important to availability issues or other constraints. Thus, it is important to
understand how name and directory caching are done in the absence of understand how name and directory caching are done in the absence of
directory delegations. Those topics are discussed in the next in directory delegations. These topics are discussed in the next two
Section 10.8.1. subsections.
10.8.1. Name Caching 10.8.1. Name Caching
The results of LOOKUP and READDIR operations may be cached to avoid The results of LOOKUP and READDIR operations may be cached to avoid
the cost of subsequent LOOKUP operations. Just as in the case of the cost of subsequent LOOKUP operations. Just as in the case of
attribute caching, inconsistencies may arise among the various client attribute caching, inconsistencies may arise among the various client
caches. To mitigate the effects of these inconsistencies and given caches. To mitigate the effects of these inconsistencies and given
the context of typical file system APIs, an upper time boundary is the context of typical file system APIs, an upper time boundary is
maintained on how long a client name cache entry can be kept without maintained for how long a client name cache entry can be kept without
verifying that the entry has not been made invalid by a directory verifying that the entry has not been made invalid by a directory
change operation performed by another client. change operation performed by another client.
When a client is not making changes to a directory for which there When a client is not making changes to a directory for which there
exist name cache entries, the client needs to periodically fetch exist name cache entries, the client needs to periodically fetch
attributes for that directory to ensure that it is not being attributes for that directory to ensure that it is not being
modified. After determining that no modification has occurred, the modified. After determining that no modification has occurred, the
expiration time for the associated name cache entries may be updated expiration time for the associated name cache entries may be updated
to be the current time plus the name cache staleness bound. to be the current time plus the name cache staleness bound.
When a client is making changes to a given directory, it needs to When a client is making changes to a given directory, it needs to
determine whether there have been changes made to the directory by determine whether there have been changes made to the directory by
other clients. It does this by using the change attribute as other clients. It does this by using the change attribute as
reported before and after the directory operation in the associated reported before and after the directory operation in the associated
change_info4 value returned for the operation. The server is able to change_info4 value returned for the operation. The server is able to
communicate to the client whether the change_info4 data is provided communicate to the client whether the change_info4 data is provided
atomically with respect to the directory operation. If the change atomically with respect to the directory operation. If the change
values are provided atomically, the client has a basis for values are provided atomically, the client has a basis for
determining, given proper care, whether other clients are modifying determining, given proper care, whether other clients are modifying
the directory is question. the directory in question.
The simplest way to enable the client to make this determination is The simplest way to enable the client to make this determination is
for the client to serialize all changes made to a specific directory. for the client to serialize all changes made to a specific directory.
When this is done, and the server provides before and after values of When this is done, and the server provides before and after values of
the change attribute atomically, the client can simply compare the the change attribute atomically, the client can simply compare the
after value of the change attribute from one operation on a directory after value of the change attribute from one operation on a directory
with the before value on the next subsequent operation modifying that with the before value on the subsequent operation modifying that
directory. When these are equal, the client is assured that no other directory. When these are equal, the client is assured that no other
client is modifying the directory in question. client is modifying the directory in question.
When such serialization is not used, and there may be multiple When such serialization is not used, and there may be multiple
simultaneous outstanding operations modifying a single directory sent simultaneous outstanding operations modifying a single directory sent
from a single client, making this sort of determination can be more from a single client, making this sort of determination can be more
complicated, since two such operations which are recognized as complicated. If two such operations complete in a different order
complete in a different order than they were actually performed, than they were actually performed, that might give an appearance
might give an appearance consistent with modification being made by consistent with modification being made by another client. Where
another client. Where this appears to happen, the client needs to this appears to happen, the client needs to await the completion of
await the completion of all such modifications that were started all such modifications that were started previously, to see if the
previously, to see if the outstanding before and after change numbers outstanding before and after change numbers can be sorted into a
can be sorted into a chain such that the before value of one change chain such that the before value of one change number matches the
number matches the after value of a previous one, in a chain after value of a previous one, in a chain consistent with this client
consistent with this client being the only one modifying the being the only one modifying the directory.
directory.
In either of these cases, the client is able to determine whether the In either of these cases, the client is able to determine whether the
directory is being modified by another client. If the comparison directory is being modified by another client. If the comparison
indicates that the directory was updated by another client, the name indicates that the directory was updated by another client, the name
cache associated with the modified directory is purged from the cache associated with the modified directory is purged from the
client. If the comparison indicates no modification, the name cache client. If the comparison indicates no modification, the name cache
can be updated on the client to reflect the directory operation and can be updated on the client to reflect the directory operation and
the associated timeout extended. The post-operation change value the associated timeout can be extended. The post-operation change
needs to be saved as the basis for future change_info4 comparisons. value needs to be saved as the basis for future change_info4
comparisons.
As demonstrated by the scenario above, name caching requires that the As demonstrated by the scenario above, name caching requires that the
client revalidate name cache data by inspecting the change attribute client revalidate name cache data by inspecting the change attribute
of a directory at the point when the name cache item was cached. of a directory at the point when the name cache item was cached.
This requires that the server update the change attribute for This requires that the server update the change attribute for
directories when the contents of the corresponding directory is directories when the contents of the corresponding directory is
modified. For a client to use the change_info4 information modified. For a client to use the change_info4 information
appropriately and correctly, the server must report the pre and post appropriately and correctly, the server must report the pre- and
operation change attribute values atomically. When the server is post-operation change attribute values atomically. When the server
unable to report the before and after values atomically with respect is unable to report the before and after values atomically with
to the directory operation, the server must indicate that fact in the respect to the directory operation, the server must indicate that
change_info4 return value. When the information is not atomically fact in the change_info4 return value. When the information is not
reported, the client should not assume that other clients have not atomically reported, the client should not assume that other clients
changed the directory. have not changed the directory.
10.8.2. Directory Caching 10.8.2. Directory Caching
The results of READDIR operations may be used to avoid subsequent The results of READDIR operations may be used to avoid subsequent
READDIR operations. Just as in the cases of attribute and name READDIR operations. Just as in the cases of attribute and name
caching, inconsistencies may arise among the various client caches. caching, inconsistencies may arise among the various client caches.
To mitigate the effects of these inconsistencies, and given the To mitigate the effects of these inconsistencies, and given the
context of typical file system APIs, the following rules should be context of typical file system APIs, the following rules should be
followed: followed:
o Cached READDIR information for a directory which is not obtained o Cached READDIR information for a directory that is not obtained in
in a single READDIR operation must always be a consistent snapshot a single READDIR operation must always be a consistent snapshot of
of directory contents. This is determined by using a GETATTR directory contents. This is determined by using a GETATTR before
before the first READDIR and after the last of READDIR that the first READDIR and after the last READDIR that contributes to
contributes to the cache. the cache.
o An upper time boundary is maintained to indicate the length of o An upper time boundary is maintained to indicate the length of
time a directory cache entry is considered valid before the client time a directory cache entry is considered valid before the client
must revalidate the cached information. must revalidate the cached information.
The revalidation technique parallels that discussed in the case of The revalidation technique parallels that discussed in the case of
name caching. When the client is not changing the directory in name caching. When the client is not changing the directory in
question, checking the change attribute of the directory with GETATTR question, checking the change attribute of the directory with GETATTR
is adequate. The lifetime of the cache entry can be extended at is adequate. The lifetime of the cache entry can be extended at
these checkpoints. When a client is modifying the directory, the these checkpoints. When a client is modifying the directory, the
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are other clients modifying the directory. If it is determined that are other clients modifying the directory. If it is determined that
no other client modifications are occurring, the client may update no other client modifications are occurring, the client may update
its directory cache to reflect its own changes. its directory cache to reflect its own changes.
As demonstrated previously, directory caching requires that the As demonstrated previously, directory caching requires that the
client revalidate directory cache data by inspecting the change client revalidate directory cache data by inspecting the change
attribute of a directory at the point when the directory was cached. attribute of a directory at the point when the directory was cached.
This requires that the server update the change attribute for This requires that the server update the change attribute for
directories when the contents of the corresponding directory is directories when the contents of the corresponding directory is
modified. For a client to use the change_info4 information modified. For a client to use the change_info4 information
appropriately and correctly, the server must report the pre and post appropriately and correctly, the server must report the pre- and
operation change attribute values atomically. When the server is post-operation change attribute values atomically. When the server
unable to report the before and after values atomically with respect is unable to report the before and after values atomically with
to the directory operation, the server must indicate that fact in the respect to the directory operation, the server must indicate that
change_info4 return value. When the information is not atomically fact in the change_info4 return value. When the information is not
reported, the client should not assume that other clients have not atomically reported, the client should not assume that other clients
changed the directory. have not changed the directory.
10.9. Directory Delegations 10.9. Directory Delegations
10.9.1. Introduction to Directory Delegations 10.9.1. Introduction to Directory Delegations
Directory caching for the NFSv4.1 protocol, as previously described, Directory caching for the NFSv4.1 protocol, as previously described,
is similar to file caching in previous versions. Clients typically is similar to file caching in previous versions. Clients typically
cache directory information for a duration determined by the client. cache directory information for a duration determined by the client.
At the end of a predefined timeout, the client will query the server At the end of a predefined timeout, the client will query the server
to see if the directory has been updated. By caching attributes, to see if the directory has been updated. By caching attributes,
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In addition to asking for delegations, a client can also ask for In addition to asking for delegations, a client can also ask for
notifications for certain events. These events include changes to notifications for certain events. These events include changes to
the directory's attributes and/or its contents. If a client asks for the directory's attributes and/or its contents. If a client asks for
notification for a certain event, the server will notify the client notification for a certain event, the server will notify the client
when that event occurs. This will not result in the delegation being when that event occurs. This will not result in the delegation being
recalled for that client. The notifications are asynchronous and recalled for that client. The notifications are asynchronous and
provide a way of avoiding recalls in situations where a directory is provide a way of avoiding recalls in situations where a directory is
changing enough that the pure recall model may not be effective while changing enough that the pure recall model may not be effective while
trying to allow the client to get substantial benefit. In the trying to allow the client to get substantial benefit. In the
absence of notifications, once the delegation is recalled the client absence of notifications, once the delegation is recalled the client
has to refresh its directory cache which might not be very efficient has to refresh its directory cache; this might not be very efficient
for very large directories. for very large directories.
The delegation is read-only and the client may not make changes to The delegation is read-only and the client may not make changes to
the directory other than by performing NFSv4.1 operations that modify the directory other than by performing NFSv4.1 operations that modify
the directory or the associated file attributes so that the server the directory or the associated file attributes so that the server
has knowledge of these changes. In order to keep the client has knowledge of these changes. In order to keep the client's
namespace synchronized with the server, the server will, if the namespace synchronized with the server, the server will notify the
client has requested notifications, notify the client holding the delegation-holding client (assuming it has requested notifications)
delegation of the changes made as a result. This is to avoid any of the changes made as a result of that client's directory-modifying
need for subsequent GETATTR or READDIR calls to the server. If a operations. This is to avoid any need for that client to send
single client is holding the delegation and that client makes any subsequent GETATTR or READDIR operations to the server. If a single
changes to the directory (i.e. the changes are made via operations client is holding the delegation and that client makes any changes to
sent though a session associated with the client ID holding the the directory (i.e., the changes are made via operations sent on a
delegation), the delegation will not be recalled. Multiple clients session associated with the client ID holding the delegation), the
may hold a delegation on the same directory, but if any such client delegation will not be recalled. Multiple clients may hold a
modifies the directory, the server MUST recall the delegation from delegation on the same directory, but if any such client modifies the
the other clients, unless those clients have made provisions to be directory, the server MUST recall the delegation from the other
notified of that sort of modification. clients, unless those clients have made provisions to be notified of
that sort of modification.
Delegations can be recalled by the server at any time. Normally, the Delegations can be recalled by the server at any time. Normally, the
server will recall the delegation when the directory changes in a way server will recall the delegation when the directory changes in a way
that is not covered by the notification, or when the directory that is not covered by the notification, or when the directory
changes and notifications have not been requested. If another client changes and notifications have not been requested. If another client
removes the directory for which a delegation has been granted, the removes the directory for which a delegation has been granted, the
server will recall the delegation. server will recall the delegation.
10.9.3. Attributes in Support of Directory Notifications 10.9.3. Attributes in Support of Directory Notifications
See Section 5.11 for a description of the attributes associated with See Section 5.11 for a description of the attributes associated with
directory notifications. directory notifications.
10.9.4. Directory Delegation Recall 10.9.4. Directory Delegation Recall
The server will recall the directory delegation by sending a callback The server will recall the directory delegation by sending a callback
to the client. It will use the same callback procedure as used for to the client. It will use the same callback procedure as used for
recalling file delegations. The server will recall the delegation recalling file delegations. The server will recall the delegation
when the directory changes in a way that is not covered by the when the directory changes in a way that is not covered by the
notification. However the server need not recall the delegation if notification. However, the server need not recall the delegation if
attributes of an entry within the directory change. attributes of an entry within the directory change.
If the server notices that handing out a delegation for a directory If the server notices that handing out a delegation for a directory
is causing too many notifications to be sent out, it may decide not is causing too many notifications to be sent out, it may decide to
to hand out delegations for that directory, or recall those already not hand out delegations for that directory and/or recall those
granted. If a client tries to remove the directory for which a already granted. If a client tries to remove the directory for which
delegation has been granted, the server will recall all associated a delegation has been granted, the server will recall all associated
delegations. delegations.
The implementation sections for a number of operations describe The implementation sections for a number of operations describe
situations in which notification or delegation recall would be situations in which notification or delegation recall would be
required under some common circumstances. In this regard, a similar required under some common circumstances. In this regard, a similar
set of caveats to those listed in Section 10.2 apply. set of caveats to those listed in Section 10.2 apply.
o For CREATE, see Section 18.4.4. o For CREATE, see Section 18.4.4.
o For LINK, see Section 18.9.4. o For LINK, see Section 18.9.4.
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o For REMOVE, see Section 18.25.4. o For REMOVE, see Section 18.25.4.
o For RENAME, see Section 18.26.4. o For RENAME, see Section 18.26.4.
o For SETATTR, see Section 18.30.4. o For SETATTR, see Section 18.30.4.
10.9.5. Directory Delegation Recovery 10.9.5. Directory Delegation Recovery
Recovery from client or server restart for state on regular files has Recovery from client or server restart for state on regular files has
two main goals, avoiding the necessity of breaking application two main goals: avoiding the necessity of breaking application
guarantees with respect to locked files and delivery of updates guarantees with respect to locked files and delivery of updates
cached at the client. Neither of these goals applies to directories cached at the client. Neither of these goals applies to directories
protected by read delegations and notifications. Thus, no provision protected by OPEN_DELEGATE_READ delegations and notifications. Thus,
is made for reclaiming directory delegations in the event of client no provision is made for reclaiming directory delegations in the
or server restart. The client can simply establish a directory event of client or server restart. The client can simply establish a
delegation in the same fashion as was done initially. directory delegation in the same fashion as was done initially.
11. Multi-Server Namespace 11. Multi-Server Namespace
NFSv4.1 supports attributes that allow a namespace to extend beyond NFSv4.1 supports attributes that allow a namespace to extend beyond
the boundaries of a single server. It is RECOMMENDED that clients the boundaries of a single server. It is RECOMMENDED that clients
and servers support construction of such multi-server namespaces. and servers support construction of such multi-server namespaces.
Use of such multi-server namespaces is OPTIONAL however, and for many Use of such multi-server namespaces is OPTIONAL, however, and for
purposes, single-server namespace are perfectly acceptable. Use of many purposes, single-server namespaces are perfectly acceptable.
multi-server namespaces can provide many advantages, however, by Use of multi-server namespaces can provide many advantages, however,
separating a file system's logical position in a namespace from the by separating a file system's logical position in a namespace from
(possibly changing) logistical and administrative considerations that the (possibly changing) logistical and administrative considerations
result in particular file systems being located on particular that result in particular file systems being located on particular
servers. servers.
11.1. Location Attributes 11.1. Location Attributes
NFSv4.1 contains RECOMMENDED attributes that allow file systems on NFSv4.1 contains RECOMMENDED attributes that allow file systems on
one server to be associated with one or more instances of that file one server to be associated with one or more instances of that file
system on other servers. These attributes specify such file system system on other servers. These attributes specify such file system
instances by specifying a server address target (either as a DNS name instances by specifying a server address target (either as a DNS name
representing one or more IP addresses or as a literal IP address) representing one or more IP addresses or as a literal IP address)
together with the path of that file system within the associated together with the path of that file system within the associated
single-server namespace. single-server namespace.
The fs_locations_info RECOMMENDED attribute allows specification of The fs_locations_info RECOMMENDED attribute allows specification of
one or more file system instance locations where the data one or more file system instance locations where the data
corresponding to a given file system may be found. This attribute corresponding to a given file system may be found. This attribute
provides to the client, in addition to information about file system provides to the client, in addition to information about file system
instance locations, significant information about the various file instance locations, significant information about the various file
system instance choices (e.g. priority for use, writability, system instance choices (e.g., priority for use, writability,
currency, etc.). It also includes information to help the client currency, etc.). It also includes information to help the client
efficiently effect as seamless a transition as possible among efficiently effect as seamless a transition as possible among
multiple file system instances, when and if that should be necessary. multiple file system instances, when and if that should be necessary.
The fs_locations RECOMMENDED attribute is inherited from NFSv4.0 and The fs_locations RECOMMENDED attribute is inherited from NFSv4.0 and
only allows specification of the file system locations where the data only allows specification of the file system locations where the data
corresponding to a given file system may be found. Servers SHOULD corresponding to a given file system may be found. Servers SHOULD
make this attribute available whenever fs_locations_info is make this attribute available whenever fs_locations_info is
supported, but client use of fs_locations_info is to be preferred. supported, but client use of fs_locations_info is to be preferred.
11.2. File System Presence or Absence 11.2. File System Presence or Absence
A given location in an NFSv4.1 namespace (typically but not A given location in an NFSv4.1 namespace (typically but not
necessarily a multi-server namespace) can have a number of file necessarily a multi-server namespace) can have a number of file
system instance locations associated with it (via the fs_locations or system instance locations associated with it (via the fs_locations or
fs_locations_info attribute). There may also be an actual current fs_locations_info attribute). There may also be an actual current
file system at that location, accessible via normal namespace file system at that location, accessible via normal namespace
operations (e.g. LOOKUP). In this case, the file system is said to operations (e.g., LOOKUP). In this case, the file system is said to
be "present" at that position in the namespace and clients will be "present" at that position in the namespace, and clients will
typically use it, reserving use of additional locations specified via typically use it, reserving use of additional locations specified via
the location-related attributes to situations in which the principal the location-related attributes to situations in which the principal
location is no longer available. location is no longer available.
When there is no actual file system at the namespace location in When there is no actual file system at the namespace location in
question, the file system is said to be "absent". An absent file question, the file system is said to be "absent". An absent file
system contains no files or directories other than the root. Any system contains no files or directories other than the root. Any
reference to it, except to access a small set of attributes useful in reference to it, except to access a small set of attributes useful in
determining alternate locations, will result in an error, determining alternate locations, will result in an error,
NFS4ERR_MOVED. Note that if the server ever returns the error NFS4ERR_MOVED. Note that if the server ever returns the error
NFS4ERR_MOVED, it MUST support the fs_locations attribute and SHOULD NFS4ERR_MOVED, it MUST support the fs_locations attribute and SHOULD
support the fs_locations_info and fs_status attributes. support the fs_locations_info and fs_status attributes.
While the error name suggests that we have a case of a file system While the error name suggests that we have a case of a file system
which once was present, and has only become absent later, this is that once was present, and has only become absent later, this is only
only one possibility. A position in the namespace may be permanently one possibility. A position in the namespace may be permanently
absent with the set of file system(s) designated by the location absent with the set of file system(s) designated by the location
attributes being the only realization. The name NFS4ERR_MOVED attributes being the only realization. The name NFS4ERR_MOVED
reflects an earlier, more limited conception of its function, but reflects an earlier, more limited conception of its function, but
this error will be returned whenever the referenced file system is this error will be returned whenever the referenced file system is
absent, whether it has moved or not. absent, whether it has moved or not.
Except in the case of GETATTR-type operations (to be discussed Except in the case of GETATTR-type operations (to be discussed
later), when the current filehandle at the start of an operation is later), when the current filehandle at the start of an operation is
within an absent file system, that operation is not performed and the within an absent file system, that operation is not performed and the
error NFS4ERR_MOVED returned, to indicate that the file system is error NFS4ERR_MOVED is returned, to indicate that the file system is
absent on the current server. absent on the current server.
Because a GETFH cannot succeed if the current filehandle is within an Because a GETFH cannot succeed if the current filehandle is within an
absent file system, filehandles within an absent file system cannot absent file system, filehandles within an absent file system cannot
be transferred to the client. When a client does have filehandles be transferred to the client. When a client does have filehandles
within an absent file system, it is the result of obtaining them when within an absent file system, it is the result of obtaining them when
the file system was present, and having the file system become absent the file system was present, and having the file system become absent
subsequently. subsequently.
It should be noted that because the check for the current filehandle It should be noted that because the check for the current filehandle
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information, as discussed below. information, as discussed below.
The RECOMMENDED file system attribute fs_status can be used to The RECOMMENDED file system attribute fs_status can be used to
interrogate the present/absent status of a given file system. interrogate the present/absent status of a given file system.
11.3. Getting Attributes for an Absent File System 11.3. Getting Attributes for an Absent File System
When a file system is absent, most attributes are not available, but When a file system is absent, most attributes are not available, but
it is necessary to allow the client access to the small set of it is necessary to allow the client access to the small set of
attributes that are available, and most particularly those that give attributes that are available, and most particularly those that give
information about the correct current locations for this file system, information about the correct current locations for this file system:
fs_locations and fs_locations_info. fs_locations and fs_locations_info.
11.3.1. GETATTR Within an Absent File System 11.3.1. GETATTR within an Absent File System
As mentioned above, an exception is made for GETATTR in that As mentioned above, an exception is made for GETATTR in that
attributes may be obtained for a filehandle within an absent file attributes may be obtained for a filehandle within an absent file
system. This exception only applies if the attribute mask contains system. This exception only applies if the attribute mask contains
at least one attribute bit that indicates the client is interested in at least one attribute bit that indicates the client is interested in
a result regarding an absent file system: fs_locations, a result regarding an absent file system: fs_locations,
fs_locations_info, or fs_status. If none of these attributes is fs_locations_info, or fs_status. If none of these attributes is
requested, GETATTR will result in an NFS4ERR_MOVED error. requested, GETATTR will result in an NFS4ERR_MOVED error.
When a GETATTR is done on an absent file system, the set of supported When a GETATTR is done on an absent file system, the set of supported
attributes is very limited. Many attributes, including those that attributes is very limited. Many attributes, including those that
are normally REQUIRED, will not be available on an absent file are normally REQUIRED, will not be available on an absent file
system. In addition to the attributes mentioned above (fs_locations, system. In addition to the attributes mentioned above (fs_locations,
fs_locations_info, fs_status), the following attributes SHOULD be fs_locations_info, fs_status), the following attributes SHOULD be
available on absent file systems, in the case of RECOMMENDED available on absent file systems. In the case of RECOMMENDED
attributes at least to the same degree that they are available on attributes, they should be available at least to the same degree that
present file systems. they are available on present file systems.
change_policy: This attribute is useful for absent file systems and change_policy: This attribute is useful for absent file systems and
can be helpful in summarizing to the client when any of the can be helpful in summarizing to the client when any of the
location-related attributes changes. location-related attributes change.
fsid: This attribute should be provided so that the client can fsid: This attribute should be provided so that the client can
determine file system boundaries, including, in particular, the determine file system boundaries, including, in particular, the
boundary between present and absent file systems. This value must boundary between present and absent file systems. This value must
be different from any other fsid on the current server and need be different from any other fsid on the current server and need
have no particular relationship to fsids on any particular have no particular relationship to fsids on any particular
destination to which the client might be directed. destination to which the client might be directed.
mounted_on_fileid: For objects at the top of an absent file system mounted_on_fileid: For objects at the top of an absent file system,
this attribute needs to be available. Since the fileid is one this attribute needs to be available. Since the fileid is within
which is within the present parent file system, there should be no the present parent file system, there should be no need to
need to reference the absent file system to provide this reference the absent file system to provide this information.
information.
Other attributes SHOULD NOT be made available for absent file Other attributes SHOULD NOT be made available for absent file
systems, even when it is possible to provide them. The server should systems, even when it is possible to provide them. The server should
not assume that more information is always better and should avoid not assume that more information is always better and should avoid
gratuitously providing additional information. gratuitously providing additional information.
When a GETATTR operation includes a bit mask for one of the When a GETATTR operation includes a bit mask for one of the
attributes fs_locations, fs_locations_info, or fs_status, but where attributes fs_locations, fs_locations_info, or fs_status, but where
the bit mask includes attributes which are not supported, GETATTR the bit mask includes attributes that are not supported, GETATTR will
will not return an error, but will return the mask of the actual not return an error, but will return the mask of the actual
attributes supported with the results. attributes supported with the results.
Handling of VERIFY/NVERIFY is similar to GETATTR in that if the Handling of VERIFY/NVERIFY is similar to GETATTR in that if the
attribute mask does not include fs_locations, fs_locations_info, or attribute mask does not include fs_locations, fs_locations_info, or
fs_status, the error NFS4ERR_MOVED will result. It differs in that fs_status, the error NFS4ERR_MOVED will result. It differs in that
any appearance in the attribute mask of an attribute not supported any appearance in the attribute mask of an attribute not supported
for an absent file system (and note that this will include some for an absent file system (and note that this will include some
normally REQUIRED attributes), will also cause an NFS4ERR_MOVED normally REQUIRED attributes) will also cause an NFS4ERR_MOVED
result. result.
11.3.2. READDIR and Absent File Systems 11.3.2. READDIR and Absent File Systems
A READDIR performed when the current filehandle is within an absent A READDIR performed when the current filehandle is within an absent
file system will result in an NFS4ERR_MOVED error, since, unlike the file system will result in an NFS4ERR_MOVED error, since, unlike the
case of GETATTR, no such exception is made for READDIR. case of GETATTR, no such exception is made for READDIR.
Attributes for an absent file system may be fetched via a READDIR for Attributes for an absent file system may be fetched via a READDIR for
a directory in a present file system, when that directory contains a directory in a present file system, when that directory contains
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case, the handling is as follows: case, the handling is as follows:
o If the attribute set requested includes one of the attributes o If the attribute set requested includes one of the attributes
fs_locations, fs_locations_info, or fs_status, then fetching of fs_locations, fs_locations_info, or fs_status, then fetching of
attributes proceeds normally and no NFS4ERR_MOVED indication is attributes proceeds normally and no NFS4ERR_MOVED indication is
returned, even when the rdattr_error attribute is requested. returned, even when the rdattr_error attribute is requested.
o If the attribute set requested does not include one of the o If the attribute set requested does not include one of the
attributes fs_locations, fs_locations_info, or fs_status, then if attributes fs_locations, fs_locations_info, or fs_status, then if
the rdattr_error attribute is requested, each directory entry for the rdattr_error attribute is requested, each directory entry for
the root of an absent file system, will report NFS4ERR_MOVED as the root of an absent file system will report NFS4ERR_MOVED as the
the value of the rdattr_error attribute. value of the rdattr_error attribute.
o If the attribute set requested does not include any of the o If the attribute set requested does not include any of the
attributes fs_locations, fs_locations_info, fs_status, or attributes fs_locations, fs_locations_info, fs_status, or
rdattr_error then the occurrence of the root of an absent file rdattr_error, then the occurrence of the root of an absent file
system within the directory will result in the READDIR failing system within the directory will result in the READDIR failing
with an NFS4ERR_MOVED error. with an NFS4ERR_MOVED error.
o The unavailability of an attribute because of a file system's o The unavailability of an attribute because of a file system's
absence, even one that is ordinarily REQUIRED, does not result in absence, even one that is ordinarily REQUIRED, does not result in
any error indication. The set of attributes returned for the root any error indication. The set of attributes returned for the root
directory of the absent file system in that case is simply directory of the absent file system in that case is simply
restricted to those actually available. restricted to those actually available.
11.4. Uses of Location Information 11.4. Uses of Location Information
The location-bearing attributes (fs_locations and fs_locations_info), The location-bearing attributes (fs_locations and fs_locations_info),
provide, together with the possibility of absent file systems, a together with the possibility of absent file systems, provide a
number of important facilities in providing reliable, manageable, and number of important facilities in providing reliable, manageable, and
scalable data access. scalable data access.
When a file system is present, these attributes can provide When a file system is present, these attributes can provide
alternative locations, to be used to access the same data, in the alternative locations, to be used to access the same data, in the
event of server failures, communications problems, or other event of server failures, communications problems, or other
difficulties that make continued access to the current file system difficulties that make continued access to the current file system
impossible or otherwise impractical. Under some circumstances impossible or otherwise impractical. Under some circumstances,
multiple alternative locations may be used simultaneously to provide multiple alternative locations may be used simultaneously to provide
higher performance access to the file system in question. Provision higher-performance access to the file system in question. Provision
of such alternate locations is referred to as "replication" although of such alternate locations is referred to as "replication" although
there are cases in which replicated sets of data are not in fact there are cases in which replicated sets of data are not in fact
present, and the replicas are instead different paths to the same present, and the replicas are instead different paths to the same
data. data.
When a file system is present and becomes absent, clients can be When a file system is present and becomes absent, clients can be
given the opportunity to have continued access to their data, at an given the opportunity to have continued access to their data, at an
alternate location. In this case, a continued attempt to use the alternate location. In this case, a continued attempt to use the
data in the now-absent file system will result in an NFS4ERR_MOVED data in the now-absent file system will result in an NFS4ERR_MOVED
error and at that point the successor locations (typically only one error and, at that point, the successor locations (typically only one
but multiple choices are possible) can be fetched and used to although multiple choices are possible) can be fetched and used to
continue access. Transfer of the file system contents to the new continue access. Transfer of the file system contents to the new
location is referred to as "migration", but it should be kept in mind location is referred to as "migration", but it should be kept in mind
that there are cases in which this term can be used, like that there are cases in which this term can be used, like
"replication", when there is no actual data migration per se. "replication", when there is no actual data migration per se.
Where a file system was not previously present, specification of file Where a file system was not previously present, specification of file
system location provides a means by which file systems located on one system location provides a means by which file systems located on one
server can be associated with a namespace defined by another server, server can be associated with a namespace defined by another server,
thus allowing a general multi-server namespace facility. A thus allowing a general multi-server namespace facility. A
designation of such a location, in place of an absent file system, is designation of such a location, in place of an absent file system, is
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The alternate locations may be physical replicas of the (typically The alternate locations may be physical replicas of the (typically
read-only) file system data, or they may reflect alternate paths to read-only) file system data, or they may reflect alternate paths to
the same server or provide for the use of various forms of server the same server or provide for the use of various forms of server
clustering in which multiple servers provide alternate ways of clustering in which multiple servers provide alternate ways of
accessing the same physical file system. How these different modes accessing the same physical file system. How these different modes
of file system transition are represented within the fs_locations and of file system transition are represented within the fs_locations and
fs_locations_info attributes and how the client deals with file fs_locations_info attributes and how the client deals with file
system transition issues will be discussed in detail below. system transition issues will be discussed in detail below.
Multiple server addresses, whether they are derived from a single Multiple server addresses, whether they are derived from a single
entry with a DNS name representing a set of IP addresses, or from entry with a DNS name representing a set of IP addresses or from
multiple entries each with its own server address may correspond to multiple entries each with its own server address, may correspond to
the same actual server. The fact that two addresses correspond to the same actual server. The fact that two addresses correspond to
the same server is shown by a common so_major_id field within the the same server is shown by a common so_major_id field within the
eir_server_owner field returned by EXCHANGE_ID (see Section 18.35.3). eir_server_owner field returned by EXCHANGE_ID (see Section 18.35.3).
For a detailed discussion of how server address targets interact with For a detailed discussion of how server address targets interact with
the determination of server identity specified by the server owner the determination of server identity specified by the server owner
field, see Section 11.5. field, see Section 11.5.
11.4.2. File System Migration 11.4.2. File System Migration
When a file system is present and becomes absent, clients can be When a file system is present and becomes absent, clients can be
given the opportunity to have continued access to their data, at an given the opportunity to have continued access to their data, at an
alternate location, as specified by the fs_locations or alternate location, as specified by the fs_locations or
fs_locations_info attribute. Typically, a client will be accessing fs_locations_info attribute. Typically, a client will be accessing
the file system in question, get an NFS4ERR_MOVED error, and then use the file system in question, get an NFS4ERR_MOVED error, and then use
the fs_locations or fs_locations_info attribute to determine the new the fs_locations or fs_locations_info attribute to determine the new
location of the data. When fs_locations_info is used, additional location of the data. When fs_locations_info is used, additional
information will be available which will define the nature of the information will be available that will define the nature of the
client's handling of the transition to a new server. client's handling of the transition to a new server.
Such migration can be helpful in providing load balancing or general Such migration can be helpful in providing load balancing or general
resource reallocation. The protocol does not specify how the file resource reallocation. The protocol does not specify how the file
system will be moved between servers. It is anticipated that a system will be moved between servers. It is anticipated that a
number of different server-to-server transfer mechanisms might be number of different server-to-server transfer mechanisms might be
used with the choice left to the server implementer. The NFSv4.1 used with the choice left to the server implementor. The NFSv4.1
protocol specifies the method used to communicate the migration event protocol specifies the method used to communicate the migration event
between client and server. between client and server.
The new location may be an alternate communication path to the same The new location may be an alternate communication path to the same
server, or, in the case of various forms of server clustering, server or, in the case of various forms of server clustering, another
another server providing access to the same physical file system. server providing access to the same physical file system. The
client's responsibilities in dealing with this transition depend on
The client's responsibilities in dealing with this transition depend the specific nature of the new access path as well as how and whether
on the specific nature of the new access path and how and whether
data was in fact migrated. These issues will be discussed in detail data was in fact migrated. These issues will be discussed in detail
below. below.
When multiple server addresses correspond to the same actual server, When multiple server addresses correspond to the same actual server,
as shown by a common value for the so_major_id field of the as shown by a common value for the so_major_id field of the
eir_server_owner field returned by EXCHANGE_ID, the location or eir_server_owner field returned by EXCHANGE_ID, the location or
locations may designate alternate server addresses in the form of locations may designate alternate server addresses in the form of
specific server network addresses. These can be used to access the specific server network addresses. These can be used to access the
file system in question at those addresses and when it is no longer file system in question at those addresses and when it is no longer
accessible at the original address. accessible at the original address.
Although a single successor location is typical, multiple locations Although a single successor location is typical, multiple locations
may be provided, together with information that allows priority among may be provided, together with information that allows priority among
the choices to be indicated, via information in the fs_locations_info the choices to be indicated, via information in the fs_locations_info
attribute. Where suitable clustering mechanisms make it possible to attribute. Where suitable, clustering mechanisms make it possible to
provide multiple identical file systems or paths to them, this allows provide multiple identical file systems or paths to them; this allows
the client the opportunity to deal with any resource or the client the opportunity to deal with any resource or
communications issues that might limit data availability. communications issues that might limit data availability.
When an alternate location is designated as the target for migration, When an alternate location is designated as the target for migration,
it must designate the same data (with metadata being the same to the it must designate the same data (with metadata being the same to the
degree indicated by the fs_locations_info attribute). Where file degree indicated by the fs_locations_info attribute). Where file
systems are writable, a change made on the original file system must systems are writable, a change made on the original file system must
be visible on all migration targets. Where a file system is not be visible on all migration targets. Where a file system is not
writable but represents a read-only copy (possibly periodically writable but represents a read-only copy (possibly periodically
updated) of a writable file system, similar requirements apply to the updated) of a writable file system, similar requirements apply to the
propagation of updates. Any change visible in the original file propagation of updates. Any change visible in the original file
system must already be effected on all migration targets, to avoid system must already be effected on all migration targets, to avoid
any possibility, that a client in effecting a transition to the any possibility that a client, in effecting a transition to the
migration target will see any reversion in file system state. migration target, will see any reversion in file system state.
11.4.3. Referrals 11.4.3. Referrals
Referrals provide a way of placing a file system in a location within Referrals provide a way of placing a file system in a location within
the namespace essentially without respect to its physical location on the namespace essentially without respect to its physical location on
a given server. This allows a single server or a set of servers to a given server. This allows a single server or a set of servers to
present a multi-server namespace that encompasses file systems present a multi-server namespace that encompasses file systems
located on multiple servers. Some likely uses of this include located on multiple servers. Some likely uses of this include
establishment of site-wide or organization-wide namespaces, or even establishment of site-wide or organization-wide namespaces, or even
knitting such together into a truly global namespace. knitting such together into a truly global namespace.
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Referrals occur when a client determines, upon first referencing a Referrals occur when a client determines, upon first referencing a
position in the current namespace, that it is part of a new file position in the current namespace, that it is part of a new file
system and that the file system is absent. When this occurs, system and that the file system is absent. When this occurs,
typically by receiving the error NFS4ERR_MOVED, the actual location typically by receiving the error NFS4ERR_MOVED, the actual location
or locations of the file system can be determined by fetching the or locations of the file system can be determined by fetching the
fs_locations or fs_locations_info attribute. fs_locations or fs_locations_info attribute.
The locations-related attribute may designate a single file system The locations-related attribute may designate a single file system
location or multiple file system locations, to be selected based on location or multiple file system locations, to be selected based on
the needs of the client. The server, in the fs_locations_info the needs of the client. The server, in the fs_locations_info
attribute may specify priorities to be associated with various file attribute, may specify priorities to be associated with various file
system location choices. The server may assign different priorities system location choices. The server may assign different priorities
to different locations as reported to individual clients, in order to to different locations as reported to individual clients, in order to
adapt to client physical location or to effect load balancing. When adapt to client physical location or to effect load balancing. When
both read-only and read-write file systems are present, some of the both read-only and read-write file systems are present, some of the
read-only locations may not be absolutely up-to-date (as they would read-only locations might not be absolutely up-to-date (as they would
have to be in the case of replication and migration). Servers may have to be in the case of replication and migration). Servers may
also specify file system locations that include client-substituted also specify file system locations that include client-substituted
variables so that different clients are referred to different file variables so that different clients are referred to different file
systems (with different data contents) based on client attributes systems (with different data contents) based on client attributes
such as CPU architecture. such as CPU architecture.
When the fs_locations_info attribute indicates that there are When the fs_locations_info attribute indicates that there are
multiple possible targets listed, the relationships among them may be multiple possible targets listed, the relationships among them may be
important to the client in selecting the one to use. The same rules important to the client in selecting which one to use. The same
specified in Section 11.4.1 defining the appropriate standards for rules specified in Section 11.4.1 defining the appropriate standards
the data propagation, apply to these multiple replicas as well. For for the data propagation apply to these multiple replicas as well.
example, the client might prefer a writable target on a server that For example, the client might prefer a writable target on a server
has additional writable replicas to which it subsequently might that has additional writable replicas to which it subsequently might
switch. Note that, as distinguished from the case of replication, switch. Note that, as distinguished from the case of replication,
there is no need to deal with the case of propagation of updates made there is no need to deal with the case of propagation of updates made
by the current client, since the current client has not accessed the by the current client, since the current client has not accessed the
file system in question. file system in question.
Use of multi-server namespaces is enabled by NFSv4.1 but is not Use of multi-server namespaces is enabled by NFSv4.1 but is not
required. The use of multi-server namespaces and their scope will required. The use of multi-server namespaces and their scope will
depend on the applications used, and system administration depend on the applications used and system administration
preferences. preferences.
Multi-server namespaces can be established by a single server Multi-server namespaces can be established by a single server
providing a large set of referrals to all of the included file providing a large set of referrals to all of the included file
systems. Alternatively, a single multi-server namespace may be systems. Alternatively, a single multi-server namespace may be
administratively segmented with separate referral file systems (on administratively segmented with separate referral file systems (on
separate servers) for each separately-administered portion of the separate servers) for each separately administered portion of the
namespace. Any segment or the top-level referral file system may use namespace. The top-level referral file system or any segment may use
replicated referral file systems for higher availability. replicated referral file systems for higher availability.
Generally, multi-server namespaces are for the most part uniform, in Generally, multi-server namespaces are for the most part uniform, in
that the same data made available to one client at a given location that the same data made available to one client at a given location
in the namespace is made available to all clients at that location. in the namespace is made available to all clients at that location.
There are however facilities provided which allow different clients However, there are facilities provided that allow different clients
to be directed to different sets of data, so as to adapt to such to be directed to different sets of data, so as to adapt to such
client characteristics as CPU architecture. client characteristics as CPU architecture.
11.5. Location Entries and Server Identity 11.5. Location Entries and Server Identity
As mentioned above, a single location entry may have a server address As mentioned above, a single location entry may have a server address
target in the form of a DNS name which may represent multiple IP target in the form of a DNS name that may represent multiple IP
addresses, while multiple location entries may have their own server addresses, while multiple location entries may have their own server
address targets, that reference the same server. Whether two IP address targets that reference the same server. Whether two IP
addresses designate the same server is indicated by the existence of addresses designate the same server is indicated by the existence of
a common so_major_id field within the eir_server_owner field returned a common so_major_id field within the eir_server_owner field returned
by EXCHANGE_ID (see Section 18.35.3), subject to further by EXCHANGE_ID (see Section 18.35.3), subject to further verification
verification, for details of which see Section 2.10.5. (for details see Section 2.10.5).
When multiple addresses for the same server exist, the client may When multiple addresses for the same server exist, the client may
assume that for each file system in the namespace of a given server assume that for each file system in the namespace of a given server
network address, there exist file systems at corresponding namespace network address, there exist file systems at corresponding namespace
locations for each of the other server network addresses. It may do locations for each of the other server network addresses. It may do
this even in the absence of explicit listing in fs_locations and this even in the absence of explicit listing in fs_locations and
fs_locations_info. Such corresponding file system locations can be fs_locations_info. Such corresponding file system locations can be
used as alternate locations, just as those explicitly specified via used as alternate locations, just as those explicitly specified via
the fs_locations and fs_locations_info attributes. Where these the fs_locations and fs_locations_info attributes. Where these
specific addresses are explicitly designated in the fs_locations_info specific addresses are explicitly designated in the fs_locations_info
attribute, the conditions of use specified in this attribute (e.g. attribute, the conditions of use specified in this attribute (e.g.,
priorities, specification of simultaneous use) may limit the client's priorities, specification of simultaneous use) may limit the client's
use of these alternate locations. use of these alternate locations.
If a single location entry designates multiple server IP addresses, If a single location entry designates multiple server IP addresses,
the client cannot assume that these addresses are multiple paths to the client cannot assume that these addresses are multiple paths to
the same server. In most case they will be, but the client MUST the same server. In most cases, they will be, but the client MUST
verify that before acting on that assumption. When two server verify that before acting on that assumption. When two server
addresses are designated by a single location entry and they addresses are designated by a single location entry and they
correspond to different servers, this normally indicates some sort of correspond to different servers, this normally indicates some sort of
misconfiguration, and so the client should avoid using such location misconfiguration, and so the client should avoid using such location
entries when alternatives are available. When they are not, clients entries when alternatives are available. When they are not, clients
should pick one of IP addresses and use it, without using others that should pick one of IP addresses and use it, without using others that
are not directed to the same server. are not directed to the same server.
11.6. Additional Client-side Considerations 11.6. Additional Client-Side Considerations
When clients make use of servers that implement referrals, When clients make use of servers that implement referrals,
replication, and migration, care should be taken so that a user who replication, and migration, care should be taken that a user who
mounts a given file system that includes a referral or a relocated mounts a given file system that includes a referral or a relocated
file system continues to see a coherent picture of that user-side file system continues to see a coherent picture of that user-side
file system despite the fact that it contains a number of server-side file system despite the fact that it contains a number of server-side
file systems which may be on different servers. file systems that may be on different servers.
One important issue is upward navigation from the root of a server- One important issue is upward navigation from the root of a server-
side file system to its parent (specified as ".." in UNIX), in the side file system to its parent (specified as ".." in UNIX), in the
case in which it transitions to that file system as a result of case in which it transitions to that file system as a result of
referral, migration, or a transition as a result of replication. referral, migration, or a transition as a result of replication.
When the client is at such a point, and it needs to ascend to the When the client is at such a point, and it needs to ascend to the
parent, it must go back to the parent as seen within the multi-server parent, it must go back to the parent as seen within the multi-server
namespace rather than sending a LOOKUPP operation to the server, namespace rather than sending a LOOKUPP operation to the server,
which would result in the parent within that server's single-server which would result in the parent within that server's single-server
namespace. In order to do this, the client needs to remember the namespace. In order to do this, the client needs to remember the
filehandles that represent such file system roots, and use these filehandles that represent such file system roots and use these
instead of sending a LOOKUPP operation to the current server. This instead of sending a LOOKUPP operation to the current server. This
will allow the client to present to applications a consistent will allow the client to present to applications a consistent
namespace, where upward navigation and downward navigation are namespace, where upward navigation and downward navigation are
consistent. consistent.
Another issue concerns refresh of referral locations. When referrals Another issue concerns refresh of referral locations. When referrals
are used extensively, they may change as server configurations are used extensively, they may change as server configurations
change. It is expected that clients will cache information related change. It is expected that clients will cache information related
to traversing referrals so that future client side requests are to traversing referrals so that future client-side requests are
resolved locally without server communication. This is usually resolved locally without server communication. This is usually
rooted in client-side name lookup caching. Clients should rooted in client-side name lookup caching. Clients should
periodically purge this data for referral points in order to detect periodically purge this data for referral points in order to detect
changes in location information. When the change_policy attribute changes in location information. When the change_policy attribute
changes for directories that hold referral entries or for the changes for directories that hold referral entries or for the
referral entries themselves, clients should consider any associated referral entries themselves, clients should consider any associated
cached referral information to be out of date. cached referral information to be out of date.
11.7. Effecting File System Transitions 11.7. Effecting File System Transitions
Transitions between file system instances, whether due to switching Transitions between file system instances, whether due to switching
between replicas upon server unavailability, or in response to between replicas upon server unavailability or to server-initiated
server-initiated migration events are best dealt with together. This migration events, are best dealt with together. This is so even
is so even though for the server, pragmatic considerations will though, for the server, pragmatic considerations will normally force
normally force different implementation strategies for planned and different implementation strategies for planned and unplanned
unplanned transitions. Even though the prototypical use cases of transitions. Even though the prototypical use cases of replication
replication and migration contain distinctive sets of features, when and migration contain distinctive sets of features, when all
all possibilities for these operations are considered, there is an possibilities for these operations are considered, there is an
underlying unity of these operations, from the client's point of underlying unity of these operations, from the client's point of
view, that makes treating them together desirable. view, that makes treating them together desirable.
A number of methods are possible for servers to replicate data and to A number of methods are possible for servers to replicate data and to
track client state in order to allow clients to transition between track client state in order to allow clients to transition between
file system instances with a minimum of disruption. Such methods file system instances with a minimum of disruption. Such methods
vary between those that use inter-server clustering techniques to vary between those that use inter-server clustering techniques to
limit the changes seen by the client, to those that are less limit the changes seen by the client, to those that are less
aggressive, use more standard methods of replicating data, and impose aggressive, use more standard methods of replicating data, and impose
a greater burden on the client to adapt to the transition. a greater burden on the client to adapt to the transition.
The NFSv4.1 protocol does not impose choices on clients and servers The NFSv4.1 protocol does not impose choices on clients and servers
with regard to that spectrum of transition methods. In fact, there with regard to that spectrum of transition methods. In fact, there
are many valid choices, depending on client and application are many valid choices, depending on client and application
requirements and their interaction with server implementation requirements and their interaction with server implementation
choices. The NFSv4.1 protocol does define the specific choices that choices. The NFSv4.1 protocol does define the specific choices that
can be made, how these choices are communicated to the client and how can be made, how these choices are communicated to the client, and
the client is to deal with any discontinuities. how the client is to deal with any discontinuities.
In the sections below, references will be made to various possible In the sections below, references will be made to various possible
server implementation choices as a way of illustrating the transition server implementation choices as a way of illustrating the transition
scenarios that clients may deal with. The intent here is not to scenarios that clients may deal with. The intent here is not to
define or limit server implementations but rather to illustrate the define or limit server implementations but rather to illustrate the
range of issues that clients may face. range of issues that clients may face.
In the discussion below, references will be made to a file system In the discussion below, references will be made to a file system
having a particular property or of two file systems (typically the having a particular property or to two file systems (typically the
source and destination) belonging to a common class of any of several source and destination) belonging to a common class of any of several
types. Two file systems that belong to such a class share some types. Two file systems that belong to such a class share some
important aspect of file system behavior that clients may depend upon important aspects of file system behavior that clients may depend
when present, to easily effect a seamless transition between file upon when present, to easily effect a seamless transition between
system instances. Conversely, where the file systems do not belong file system instances. Conversely, where the file systems do not
to such a common class, the client has to deal with various sorts of belong to such a common class, the client has to deal with various
implementation discontinuities which may cause performance or other sorts of implementation discontinuities that may cause performance or
issues in effecting a transition. other issues in effecting a transition.
Where the fs_locations_info attribute is available, such file system Where the fs_locations_info attribute is available, such file system
classification data will be made directly available to the client classification data will be made directly available to the client
(see Section 11.10 for details). When only fs_locations is (see Section 11.10 for details). When only fs_locations is
available, default assumptions with regard to such classifications available, default assumptions with regard to such classifications
have to be inferred (see Section 11.9 for details). have to be inferred (see Section 11.9 for details).
In cases in which one server is expected to accept opaque values from In cases in which one server is expected to accept opaque values from
the client that originated from another server, the servers SHOULD the client that originated from another server, the servers SHOULD
encode the "opaque" values in big endian byte order. If this is encode the "opaque" values in big-endian byte order. If this is
done, servers acting as replicas or immigrating file systems will be done, servers acting as replicas or immigrating file systems will be
able to parse values like stateids, directory cookies, filehandles, able to parse values like stateids, directory cookies, filehandles,
etc. even if their native byte order is different from that of other etc., even if their native byte order is different from that of other
servers cooperating in the replication and migration of the file servers cooperating in the replication and migration of the file
system. system.
11.7.1. File System Transitions and Simultaneous Access 11.7.1. File System Transitions and Simultaneous Access
When a single file system may be accessed at multiple locations, When a single file system may be accessed at multiple locations,
whether this is because of an indication of file system identity as either because of an indication of file system identity as reported
reported by the fs_locations or fs_locations_info attributes or by the fs_locations or fs_locations_info attributes or because two
because two file system instances have corresponding locations on file system instances have corresponding locations on server
server addresses which connect to the same server (as indicated by a addresses that connect to the same server (as indicated by a common
common so_major_id field in the eir_server_owner field returned by so_major_id field in the eir_server_owner field returned by
EXCHANGE_ID), the client will, depending on specific circumstances as EXCHANGE_ID), the client will, depending on specific circumstances as
discussed below, either: discussed below, either:
o The client accesses multiple instances simultaneously, as o Access multiple instances simultaneously, each of which represents
representing alternate paths to the same data and metadata. an alternate path to the same data and metadata.
o The client accesses one instance (or set of instances) and then o Access one instance (or set of instances) and then transition to
transitions to an alternative instance (or set of instances) as a an alternative instance (or set of instances) as a result of
result of network issues, server unresponsiveness, or server- network issues, server unresponsiveness, or server-directed
directed migration. The transition may involve changes in migration. The transition may involve changes in filehandles,
filehandles, fileids, the change attribute, and/or locking state, fileids, the change attribute, and/or locking state, depending on
depending on the attributes of the source and destination file the attributes of the source and destination file system
system instances, as specified in the fs_locations_info attribute. instances, as specified in the fs_locations_info attribute.
Which of these choices is possible, and how a transition is effected, Which of these choices is possible, and how a transition is effected,
is governed by equivalence classes of file system instances as is governed by equivalence classes of file system instances as
reported by the fs_locations_info attribute, and, for file system reported by the fs_locations_info attribute, and for file system
instances in the same location within a multiple single-server instances in the same location within a multi-homed single-server
namespace as indicated by the so_major_id field in the namespace, as indicated by the value of the so_major_id field of the
eir_server_owner field returned by EXCHANGE_ID. eir_server_owner field returned by EXCHANGE_ID.
11.7.2. Simultaneous Use and Transparent Transitions 11.7.2. Simultaneous Use and Transparent Transitions
When two file system instances have the same location within their When two file system instances have the same location within their
respective single-server namespaces and those two server network respective single-server namespaces and those two server network
addresses designate the same server (as indicated by the same addresses designate the same server (as indicated by the same value
so_major_id value in the eir_server_owner value returned in response of the so_major_id field of the eir_server_owner field returned in
to EXCHANGE_ID), those file systems instances can be treated as the response to EXCHANGE_ID), those file system instances can be treated
same, and either used together simultaneously or serially with no as the same, and either used together simultaneously or serially with
transition activity required on the part of the client. In this case no transition activity required on the part of the client. In this
we refer to the transition as "transparent" and the client in case, we refer to the transition as "transparent", and the client in
transferring access from to the other is acting as it would in the transferring access from one to the other is acting as it would in
event that communication is interrupted, with a new connection and the event that communication is interrupted, with a new connection
possibly a new session being established to continue access to the and possibly a new session being established to continue access to
same file system. the same file system.
Whether simultaneous use of the two file system instances is valid is Whether simultaneous use of the two file system instances is valid is
controlled by whether the fs_locations_info attribute shows the two controlled by whether the fs_locations_info attribute shows the two
instances as having the same _simultaneous-use_ class. See instances as having the same simultaneous-use class. See
Section 11.10.1 for information about the definition of the various Section 11.10.1 for information about the definition of the various
use classes, including the _simultaneous-use_ class. use classes, including the simultaneous-use class.
Note that for two such file systems, any information within the Note that for two such file systems, any information within the
fs_locations_info attribute that indicates the need for special fs_locations_info attribute that indicates the need for special
transition activity, i.e. the appearance of the two file system transition activity, i.e., the appearance of the two file system
instances with different _handle_, _fileid_, _write-verifier_, instances with different handle, fileid, write-verifier, change, and
_change_, _readdir_ classes, indicates a serious problem and the readdir classes, indicates a serious problem. The client, if it
client, if it allows transition to the file system instance at all, allows transition to the file system instance at all, must not treat
must not treat this as a transparent transition. The server SHOULD this as a transparent transition. The server SHOULD NOT indicate
NOT indicate that these instances belong to different _handle_, that these instances belong to different handle, fileid, write-
_fileid_, _write-verifier_, _change_, _readdir_ classes, whether the verifier, change, and readdir classes, whether or not the two
two instances are shown belonging to the same _simultaneous-use_ instances are shown belonging to the same simultaneous-use class.
class or not.
Where these conditions do not apply, a non-transparent file system Where these conditions do not apply, a non-transparent file system
instance transition is required with the details depending on the instance transition is required with the details depending on the
respective _handle_, _fileid_, _write-verifier_, _change_, _readdir_ respective handle, fileid, write-verifier, change, and readdir
classes of the two file system instances and whether the two servers classes of the two file system instances, and whether the two
address in question have the same eir_server_scope value as reported servers' addresses in question have the same eir_server_scope value
by EXCHANGE_ID. as reported by EXCHANGE_ID.
11.7.2.1. Simultaneous Use of File System Instances 11.7.2.1. Simultaneous Use of File System Instances
When the conditions in Section 11.7.2 hold, in either of the When the conditions in Section 11.7.2 hold, in either of the
following two cases, the client may use the two file system instances following two cases, the client may use the two file system instances
simultaneously. simultaneously.
o The fs_locations_info attribute does not contain separate per- o The fs_locations_info attribute does not contain separate per-
network-address entries for file systems instances at the distinct network-address entries for file system instances at the distinct
network addresses. This includes the case in which the network addresses. This includes the case in which the
fs_locations_info attribute is unavailable. In this case, the fs_locations_info attribute is unavailable. In this case, the
fact that the two server addresses connect to the same server (as fact that the two server addresses connect to the same server (as
indicated by the two addresses sharing the same the so_major_id indicated by the two addresses sharing the same the so_major_id
value and subsequently confirmed as described in Section 2.10.5) value and subsequently confirmed as described in Section 2.10.5)
justifies simultaneous use and there is no fs_locations_info justifies simultaneous use, and there is no fs_locations_info
attribute information contradicting that. attribute information contradicting that.
o The fs_locations_info attribute indicates that two file system o The fs_locations_info attribute indicates that two file system
instances belong to the same _simultaneous-use_ class. instances belong to the same simultaneous-use class.
In this case, the client may use both file system instances In this case, the client may use both file system instances
simultaneously, as representations of the same file system, whether simultaneously, as representations of the same file system, whether
that happens because the two network addresses connect to the same that happens because the two network addresses connect to the same
physical server or because different servers connect to clustered physical server or because different servers connect to clustered
file systems and export their data in common. When simultaneous use file systems and export their data in common. When simultaneous use
is in effect, any change made to one file system instance must be is in effect, any change made to one file system instance must be
immediately reflected in the other file system instance(s). Locks immediately reflected in the other file system instance(s). Locks
are treated as part of a common lease, associated with a common are treated as part of a common lease, associated with a common
client ID. Depending on the details of the eir_server_owner returned client ID. Depending on the details of the eir_server_owner returned
by EXCHANGE_ID, the two server instances may be accessed by different by EXCHANGE_ID, the two server instances may be accessed by different
sessions or a single session in common. sessions or a single session in common.
11.7.2.2. Transparent File System Transitions 11.7.2.2. Transparent File System Transitions
When the conditions in Section 11.7.2.1 hold and the When the conditions in Section 11.7.2.1 hold and the
fs_locations_info attribute explicitly shows the file system fs_locations_info attribute explicitly shows the file system
instances for these distinct network addresses as belonging to instances for these distinct network addresses as belonging to
different _simultaneous-use_ classes, the file system instances different simultaneous-use classes, the file system instances should
should not be used by the client simultaneously, but rather serially not be used by the client simultaneously. Rather, they should be
with one being used unless and until communication difficulties, lack used serially with one being used unless and until communication
of responsiveness, or an explicit migration event causes another file difficulties, lack of responsiveness, or an explicit migration event
system instance (or set of file system instances sharing a common causes another file system instance (or set of file system instances
_simultaneous-use_ class) to be used. sharing a common simultaneous-use class) to be used.
When a change of file system instance is to be done, the client will When a change of file system instance is to be done, the client will
use the same client ID already in effect. If it already has use the same client ID already in effect. If the client already has
connections to the new server address, these will be used. Otherwise connections to the new server address, these will be used.
new connections to existing sessions or new sessions associated with Otherwise, new connections to existing sessions or new sessions
the existing client ID are established as indicated by the associated with the existing client ID are established as indicated
eir_server_owner returned by EXCHANGE_ID. by the eir_server_owner returned by EXCHANGE_ID.
In all such transparent transition cases, the following apply: In all such transparent transition cases, the following apply:
o If filehandles are persistent they stay the same. If filehandles o If filehandles are persistent, they stay the same. If filehandles
are volatile, they either stay the same, or if they expire, the are volatile, they either stay the same or expire, but the reason
reason for expiration is not due to the file system transition. for expiration is not due to the file system transition.
o Fileid values do not change across the transition. o Fileid values do not change across the transition.
o The file system will have the same fsid in both the old and new o The file system will have the same fsid in both the old and new
locations. locations.
o Change attribute values are consistent across the transition and o Change attribute values are consistent across the transition and
do not have to be refetched. When change attributes indicate that do not have to be refetched. When change attributes indicate that
a cached object is still valid, it can remain cached. a cached object is still valid, it can remain cached.
o Client and state identifiers retain their validity across the o Client and state identifiers retain their validity across the
transition, except where their staleness is recognized and transition, except where their staleness is recognized and
reported by the new server. Except where such staleness requires reported by the new server. Except where such staleness requires
it, no lock reclamation is needed. Any such staleness is an it, no lock reclamation is needed. Any such staleness is an
indication that the server should be considered to have restarted indication that the server should be considered to have restarted
and is reported as discussed in Section 8.4.2. and is reported as discussed in Section 8.4.2.
o Write verifiers are presumed to retain their validity and can be o Write verifiers are presumed to retain their validity and can be
used to compare with verifiers returned by COMMIT on the new used to compare with verifiers returned by COMMIT on the new
server, with the expectation that if COMMIT on the new server server. If COMMIT on the new server returns an identical
returns an identical verifier, then that server has all of the verifier, then it is expected that the new server has all of the
data unstably written to the original server and has committed it data that was written unstably to the original server and has
to stable storage as requested. committed that data to stable storage as requested.
o Readdir cookies are presumed to retain their validity and can be o Readdir cookies are presumed to retain their validity and can be
presented to subsequent READDIR requests together with the readdir presented to subsequent READDIR requests together with the readdir
verifier with which they are associated. When the verifier is verifier with which they are associated. When the verifier is
accepted as valid, the cookie will continue the READDIR operation accepted as valid, the cookie will continue the READDIR operation
so that the entire directory can be obtained by the client. so that the entire directory can be obtained by the client.
11.7.3. Filehandles and File System Transitions 11.7.3. Filehandles and File System Transitions
There are a number of ways in which filehandles can be handled across There are a number of ways in which filehandles can be handled across
a file system transition. These can be divided into two broad a file system transition. These can be divided into two broad
classes depending upon whether the two file systems across which the classes depending upon whether the two file systems across which the
transition happens share sufficient state to effect some sort of transition happens share sufficient state to effect some sort of
continuity of file system handling. continuity of file system handling.
When there is no such co-operation in filehandle assignment, the two When there is no such cooperation in filehandle assignment, the two
file systems are reported as being in different _handle_ classes. In file systems are reported as being in different handle classes. In
this case, all filehandles are assumed to expire as part of the file this case, all filehandles are assumed to expire as part of the file
system transition. Note that this behavior does not depend on system transition. Note that this behavior does not depend on the
fh_expire_type attribute and supersedes the specification of fh_expire_type attribute and supersedes the specification of the
FH4_VOL_MIGRATION bit, which only affects behavior when FH4_VOL_MIGRATION bit, which only affects behavior when
fs_locations_info is not available. fs_locations_info is not available.
When there is co-operation in filehandle assignment, the two file When there is cooperation in filehandle assignment, the two file
systems are reported as being in the same _handle_ classes. In this systems are reported as being in the same handle classes. In this
case, persistent filehandles remain valid after the file system case, persistent filehandles remain valid after the file system
transition, while volatile filehandles (excluding those that are only transition, while volatile filehandles (excluding those that are only
volatile due to the FH4_VOL_MIGRATION bit) are subject to expiration volatile due to the FH4_VOL_MIGRATION bit) are subject to expiration
on the target server. on the target server.
11.7.4. Fileids and File System Transitions 11.7.4. Fileids and File System Transitions
In NFSv4.0, the issue of continuity of fileids in the event of a file In NFSv4.0, the issue of continuity of fileids in the event of a file
system transition was not addressed. The general expectation had system transition was not addressed. The general expectation had
been that in situations in which the two file system instances are been that in situations in which the two file system instances are
created by a single vendor using some sort of file system image copy, created by a single vendor using some sort of file system image copy,
fileids will be consistent across the transition while in the fileids will be consistent across the transition, while in the
analogous multi-vendor transitions they will not. This poses analogous multi-vendor transitions they will not. This poses
difficulties, especially for the client without special knowledge of difficulties, especially for the client without special knowledge of
the transition mechanisms adopted by the server. Note that although the transition mechanisms adopted by the server. Note that although
fileid is not a REQUIRED attribute, many servers support fileids and fileid is not a REQUIRED attribute, many servers support fileids and
many clients provide API's that depend on fileids. many clients provide APIs that depend on fileids.
It is important to note that while clients themselves may have no It is important to note that while clients themselves may have no
trouble with a fileid changing as a result of a file system trouble with a fileid changing as a result of a file system
transition event, applications do typically have access to the fileid transition event, applications do typically have access to the fileid
(e.g. via stat), and the result of this is that an application may (e.g., via stat). The result is that an application may work
work perfectly well if there is no file system instance transition or perfectly well if there is no file system instance transition or if
if any such transition is among instances created by a single vendor, any such transition is among instances created by a single vendor,
yet be unable to deal with the situation in which a multi-vendor yet be unable to deal with the situation in which a multi-vendor
transition occurs, at the wrong time. transition occurs at the wrong time.
Providing the same fileids in a multi-vendor (multiple server Providing the same fileids in a multi-vendor (multiple server
vendors) environment has generally been held to be quite difficult. vendors) environment has generally been held to be quite difficult.
While there is work to be done, it needs to be pointed out that this While there is work to be done, it needs to be pointed out that this
difficulty is partly self-imposed. Servers have typically identified difficulty is partly self-imposed. Servers have typically identified
fileid with inode number, i.e. with a quantity used to find the file fileid with inode number, i.e. with a quantity used to find the file
in question. This identification poses special difficulties for in question. This identification poses special difficulties for
migration of a file system between vendors where assigning the same migration of a file system between vendors where assigning the same
index to a given file may not be possible. Note here that a fileid index to a given file may not be possible. Note here that a fileid
is not required to be useful to find the file in question, only that is not required to be useful to find the file in question, only that
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accept a fileid as a single piece of metadata and store it apart from accept a fileid as a single piece of metadata and store it apart from
the value used to index the file information can relatively easily the value used to index the file information can relatively easily
maintain a fileid value across a migration event, allowing a truly maintain a fileid value across a migration event, allowing a truly
transparent migration event. transparent migration event.
In any case, where servers can provide continuity of fileids, they In any case, where servers can provide continuity of fileids, they
should, and the client should be able to find out that such should, and the client should be able to find out that such
continuity is available and take appropriate action. Information continuity is available and take appropriate action. Information
about the continuity (or lack thereof) of fileids across a file about the continuity (or lack thereof) of fileids across a file
system transition is represented by specifying whether the file system transition is represented by specifying whether the file
systems in question are of the same _fileid_ class. systems in question are of the same fileid class.
Note that when consistent fileids do not exist across a transition Note that when consistent fileids do not exist across a transition
(either because there is no continuity of fileids or because fileid (either because there is no continuity of fileids or because fileid
is not a supported attribute on one of instances involved), and there is not a supported attribute on one of instances involved), and there
are no reliable filehandles across a transition event (either because are no reliable filehandles across a transition event (either because
there is no filehandle continuity or because the filehandles are there is no filehandle continuity or because the filehandles are
volatile), the client is in a position where it cannot verify that volatile), the client is in a position where it cannot verify that
files it was accessing before the transition are the same objects. files it was accessing before the transition are the same objects.
It is forced to assume that no object has been renamed, and, unless It is forced to assume that no object has been renamed, and, unless
there are guarantees that provide this (e.g. the file system is read- there are guarantees that provide this (e.g., the file system is
only), problems for applications may occur. Therefore, use of such read-only), problems for applications may occur. Therefore, use of
configurations should be limited to situations where the problems such configurations should be limited to situations where the
that this may cause can be tolerated. problems that this may cause can be tolerated.
11.7.5. Fsids and File System Transitions 11.7.5. Fsids and File System Transitions
Since fsids are generally only unique within a per-server basis, it Since fsids are generally only unique within a per-server basis, it
is likely that they will change during a file system transition. One is likely that they will change during a file system transition. One
exception is the case of transparent transitions, but in that case we exception is the case of transparent transitions, but in that case we
have multiple network addresses that are defined as the same server have multiple network addresses that are defined as the same server
(as specified by a common value of the so_major_id field of (as specified by a common value of the so_major_id field of
eir_server_owner). Clients should not make the fsids received from eir_server_owner). Clients should not make the fsids received from
the server visible to applications since they may not be globally the server visible to applications since they may not be globally
unique, and because they may change during a file system transition unique, and because they may change during a file system transition
event. Applications are best served if they are isolated from such event. Applications are best served if they are isolated from such
transitions to the extent possible. transitions to the extent possible.
Although normally, a single source file system will transition to a Although normally a single source file system will transition to a
single target file system, there is a provision for splitting a single target file system, there is a provision for splitting a
single source file system into multiple target file systems, by single source file system into multiple target file systems, by
specifying the FSLI4F_MULTI_FS flag. specifying the FSLI4F_MULTI_FS flag.
11.7.5.1. File System Splitting 11.7.5.1. File System Splitting
When a file system transition is made and the fs_locations_info When a file system transition is made and the fs_locations_info
indicates that the file system in question may be split into multiple indicates that the file system in question may be split into multiple
file systems (via the FSLI4F_MULTI_FS flag), the client SHOULD do file systems (via the FSLI4F_MULTI_FS flag), the client SHOULD do
GETATTRs to determine the fsid attribute on all known objects within GETATTRs to determine the fsid attribute on all known objects within
the file system undergoing transition to determine the new file the file system undergoing transition to determine the new file
system boundaries. system boundaries.
Clients may maintain the fsids passed to existing applications by Clients may maintain the fsids passed to existing applications by
mapping all of the fsids for the descendant file systems to the mapping all of the fsids for the descendant file systems to the
common fsid used for the original file system. common fsid used for the original file system.
Splitting a file system may be done on a transition between file Splitting a file system may be done on a transition between file
systems of the same _fileid_ class, since the fact that fileids are systems of the same fileid class, since the fact that fileids are
unique within the source file system ensure they will be unique in unique within the source file system ensure they will be unique in
each of the target file systems. each of the target file systems.
11.7.6. The Change Attribute and File System Transitions 11.7.6. The Change Attribute and File System Transitions
Since the change attribute is defined as a server-specific one, Since the change attribute is defined as a server-specific one,
change attributes fetched from one server are normally presumed to be change attributes fetched from one server are normally presumed to be
invalid on another server. Such a presumption is troublesome since invalid on another server. Such a presumption is troublesome since
it would invalidate all cached change attributes, requiring it would invalidate all cached change attributes, requiring
refetching. Even more disruptive, the absence of any assured refetching. Even more disruptive, the absence of any assured
continuity for the change attribute means that even if the same value continuity for the change attribute means that even if the same value
is retrieved on refetch no conclusions can drawn as to whether the is retrieved on refetch, no conclusions can be drawn as to whether
object in question has changed. The identical change attribute could the object in question has changed. The identical change attribute
be merely an artifact of a modified file with a different change could be merely an artifact of a modified file with a different
attribute construction algorithm, with that new algorithm just change attribute construction algorithm, with that new algorithm just
happening to result in an identical change value. happening to result in an identical change value.
When the two file systems have consistent change attribute formats, When the two file systems have consistent change attribute formats,
and this fact is communicated to the client by reporting as in the and this fact is communicated to the client by reporting in the same
same _change_ class, the client may assume a continuity of change change class, the client may assume a continuity of change attribute
attribute construction and handle this situation just as it would be construction and handle this situation just as it would be handled
handled without any file system transition. without any file system transition.
11.7.7. Lock State and File System Transitions 11.7.7. Lock State and File System Transitions
In a file system transition, the client needs to handle cases in In a file system transition, the client needs to handle cases in
which the two servers have cooperated in state management and in which the two servers have cooperated in state management and in
which they have not. Cooperation by two servers in state management which they have not. Cooperation by two servers in state management
requires coordination of client IDs. Before the client attempts to requires coordination of client IDs. Before the client attempts to
use a client ID associated with one server in a request to the server use a client ID associated with one server in a request to the server
of the other file system, it must eliminate the possibility that two of the other file system, it must eliminate the possibility that two
non-cooperating servers have assigned the same client ID by accident. non-cooperating servers have assigned the same client ID by accident.
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not cooperated in state management. If the scope values match, then not cooperated in state management. If the scope values match, then
this indicates the servers have cooperated in assigning client IDs to this indicates the servers have cooperated in assigning client IDs to
the point that they will reject client IDs that refer to state they the point that they will reject client IDs that refer to state they
do not know about. See Section 2.10.4 for more information about the do not know about. See Section 2.10.4 for more information about the
use of server scope. use of server scope.
In the case of migration, the servers involved in the migration of a In the case of migration, the servers involved in the migration of a
file system SHOULD transfer all server state from the original to the file system SHOULD transfer all server state from the original to the
new server. When this is done, it must be done in a way that is new server. When this is done, it must be done in a way that is
transparent to the client. With replication, such a degree of common transparent to the client. With replication, such a degree of common
state is typically not the case. Clients, however should use the state is typically not the case. Clients, however, should use the
information provided by the eir_server_scope returned by EXCHANGE_ID information provided by the eir_server_scope returned by EXCHANGE_ID
(as modified by the validation procedures described in (as modified by the validation procedures described in
Section 2.10.4) to determine whether such sharing may be in effect, Section 2.10.4) to determine whether such sharing may be in effect,
rather than making assumptions based on the reason for the rather than making assumptions based on the reason for the
transition. transition.
This state transfer will reduce disruption to the client when a file This state transfer will reduce disruption to the client when a file
system transition occurs. If the servers are successful in system transition occurs. If the servers are successful in
transferring all state, the client can attempt to establish sessions transferring all state, the client can attempt to establish sessions
associated with the client ID used for the source file system associated with the client ID used for the source file system
instance. If the server accepts that as a valid client ID, then the instance. If the server accepts that as a valid client ID, then the
client may use the existing stateids associated with that client ID client may use the existing stateids associated with that client ID
for the old file system instance in connection with that same client for the old file system instance in connection with that same client
ID in connection with the transitioned file system instance. If the ID in connection with the transitioned file system instance. If the
client in question already had a client ID on the target system, it client in question already had a client ID on the target system, it
may interrogate the stateid values from the source system under that may interrogate the stateid values from the source system under that
new client ID, with the assurance that if they are accepted as valid, new client ID, with the assurance that if they are accepted as valid,
then they represent validly transferred lock state for the source then they represent validly transferred lock state for the source
file system, transferred to the target server. file system, which has been transferred to the target server.
When the two servers belong to the same server scope, it does not When the two servers belong to the same server scope, it does not
mean that when dealing with the transition, the client will not have mean that when dealing with the transition, the client will not have
to reclaim state. However it does mean that the client may proceed to reclaim state. However, it does mean that the client may proceed
using its current client ID when establishing communication with the using its current client ID when establishing communication with the
new server and the new server will either recognize the client ID as new server, and the new server will either recognize the client ID as
valid, or reject it, in which case locks must be reclaimed by the valid or reject it, in which case locks must be reclaimed by the
client. client.
File systems co-operating in state management may actually share File systems cooperating in state management may actually share state
state or simply divide the identifier space so as to recognize (and or simply divide the identifier space so as to recognize (and reject
reject as stale) each other's stateids and client IDs. Servers which as stale) each other's stateids and client IDs. Servers that do
do share state may not do so under all conditions or at all times. share state may not do so under all conditions or at all times. If
The requirement for the server is that if it cannot be sure in the server cannot be sure when accepting a client ID that it reflects
accepting a client ID that it reflects the locks the client was the locks the client was given, the server must treat all associated
given, it must treat all associated state as stale and report it as state as stale and report it as such to the client.
such to the client.
When the two file system instances are on servers that do not share a When the two file system instances are on servers that do not share a
server scope value, the client must establish a new client ID on the server scope value, the client must establish a new client ID on the
destination, if it does not have one already, and reclaim locks if destination, if it does not have one already, and reclaim locks if
allowed by the server. In this case, old stateids and client IDs allowed by the server. In this case, old stateids and client IDs
should not be presented to the new server since there is no assurance should not be presented to the new server since there is no assurance
that they will not conflict with IDs valid on that server. Note that that they will not conflict with IDs valid on that server. Note that
in this case lock reclaim may be attempted even when the servers in this case, lock reclaim may be attempted even when the servers
involved in the transfer have different server scope values (see involved in the transfer have different server scope values (see
Section 8.4.2.1 for the contrary case of reclaim after server reboot. Section 8.4.2.1 for the contrary case of reclaim after server
Servers with different server scope values may co-operate to allow reboot). Servers with different server scope values may cooperate to
reclaim for locks associated with the transfer of a filesystem even allow reclaim for locks associated with the transfer of a file system
if they do not co-operate sufficiently to share a server scope. even if they do not cooperate sufficiently to share a server scope.
In either case, when actual locks are not known to be maintained, the In either case, when actual locks are not known to be maintained, the
destination server may establish a grace period specific to the given destination server may establish a grace period specific to the given
file system, with non-reclaim locks being rejected for that file file system, with non-reclaim locks being rejected for that file
system, even though normal locks are being granted for other file system, even though normal locks are being granted for other file
systems. Clients should not infer the absence of a grace period for systems. Clients should not infer the absence of a grace period for
file systems being transitioned to a server from responses to file systems being transitioned to a server from responses to
requests for other file systems. requests for other file systems.
In the case of lock reclamation for a given file system after a file In the case of lock reclamation for a given file system after a file
system transition, edge conditions can arise similar to those for system transition, edge conditions can arise similar to those for
reclaim after server restart (although in the case of the planned reclaim after server restart (although in the case of the planned
state transfer associated with migration, these can be avoided by state transfer associated with migration, these can be avoided by
securely recording lock state as part of state migration). Unless securely recording lock state as part of state migration). Unless
the destination server can guarantee that locks will not be the destination server can guarantee that locks will not be
incorrectly granted, the destination server should not allow lock incorrectly granted, the destination server should not allow lock
reclaims and avoid establishing a grace period. reclaims and should avoid establishing a grace period.
Once all locks have been reclaimed, or there were no locks to Once all locks have been reclaimed, or there were no locks to
reclaim, the client indicates that there are no more reclaims to be reclaim, the client indicates that there are no more reclaims to be
done for the file system in question by sending a RECLAIM_COMPLETE done for the file system in question by sending a RECLAIM_COMPLETE
operation with the rca_one_fs parameter set to true. Once this has operation with the rca_one_fs parameter set to true. Once this has
been done, non-reclaim locking operations may be done, and any been done, non-reclaim locking operations may be done, and any
subsequent request to do reclaims will be rejected with the error subsequent request to do reclaims will be rejected with the error
NFS4ERR_NO_GRACE. NFS4ERR_NO_GRACE.
Information about client identity may be propagated between servers Information about client identity may be propagated between servers
in the form of client_owner4 and associated verifiers, under the in the form of client_owner4 and associated verifiers, under the
assumption that the client presents the same values to all the assumption that the client presents the same values to all the
servers with which it deals. servers with which it deals.
Servers are encouraged to provide facilities to allow locks to be Servers are encouraged to provide facilities to allow locks to be
reclaimed on the new server after a file system transition. Often, reclaimed on the new server after a file system transition. Often,
however, in cases in which the two servers do not share a server however, in cases in which the two servers do not share a server
scope value, such facilities may not be available and client should scope value, such facilities may not be available and the client
be prepared to re-obtain locks, even though it is possible that the should be prepared to re-obtain locks, even though it is possible
client may have its LOCK or OPEN request denied due to a conflicting that the client may have its LOCK or OPEN request denied due to a
lock. conflicting lock.
The consequences of having no facilities available to reclaim locks The consequences of having no facilities available to reclaim locks
on the new server will depend on the type of environment. In some on the new server will depend on the type of environment. In some
environments, such as the transition between read-only file systems, environments, such as the transition between read-only file systems,
such denial of locks should not pose large difficulties in practice. such denial of locks should not pose large difficulties in practice.
When an attempt to re-establish a lock on a new server is denied, the When an attempt to re-establish a lock on a new server is denied, the
client should treat the situation as if its original lock had been client should treat the situation as if its original lock had been
revoked. Note that when the lock is granted, the client cannot revoked. Note that when the lock is granted, the client cannot
assume that no conflicting lock could have been granted in the assume that no conflicting lock could have been granted in the
interim. Where change attribute continuity is present, the client interim. Where change attribute continuity is present, the client
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11.7.7.1. Leases and File System Transitions 11.7.7.1. Leases and File System Transitions
In the case of lease renewal, the client may not be submitting In the case of lease renewal, the client may not be submitting
requests for a file system that has been transferred to another requests for a file system that has been transferred to another
server. This can occur because of the lease renewal mechanism. The server. This can occur because of the lease renewal mechanism. The
client renews the lease associated with all file systems when client renews the lease associated with all file systems when
submitting a request on an associated session, regardless of the submitting a request on an associated session, regardless of the
specific file system being referenced. specific file system being referenced.
In order for the client to schedule renewal of leases where there is In order for the client to schedule renewal of its lease where there
locking state that may have been relocated to the new server, the is locking state that may have been relocated to the new server, the
client must find out about lease relocation before those leases client must find out about lease relocation before that lease expire.
expire. To accomplish this, the SEQUENCE operation will return the To accomplish this, the SEQUENCE operation will return the status bit
status bit SEQ4_STATUS_LEASE_MOVED, if responsibility for any of the SEQ4_STATUS_LEASE_MOVED if responsibility for any of the renewed
locking state renewed has been transferred to a new server. This locking state has been transferred to a new server. This will
will continue until the client receives an NFS4ERR_MOVED error for continue until the client receives an NFS4ERR_MOVED error for each of
each of the file systems for which there has been locking state the file systems for which there has been locking state relocation.
relocation.
When a client receives an SEQ4_STATUS_LEASE_MOVED indication, it When a client receives an SEQ4_STATUS_LEASE_MOVED indication from a
should perform an operation on each file system associated with the server, for each file system of the server for which the client has
server where there is locking state for the current client associated locking state, the client should perform an operation. For
with the file system in question. The client may choose to reference simplicity, the client may choose to reference all file systems, but
all file systems in the interests of simplicity but what is important what is important is that it must reference all file systems for
is that it must reference all file systems for which there was which there was locking state where that state has moved. Once the
locking state where that state moved. Once the client receives an client receives an NFS4ERR_MOVED error for each such file system, the
NFS4ERR_MOVED error for each file system, the SEQ4_STATUS_LEASE_MOVED server will clear the SEQ4_STATUS_LEASE_MOVED indication. The client
indication is cleared. The client can terminate the process of can terminate the process of checking file systems once this
checking file systems once this indication is cleared (but only if indication is cleared (but only if the client has received a reply
the client has received a reply for all outstanding SEQUENCE requests for all outstanding SEQUENCE requests on all sessions it has with the
on all sessions it has with the server), since there are no others server), since there are no others for which locking state has moved.
for which locking state has moved.
A client may use GETATTR of the fs_status (or fs_locations_info) A client may use GETATTR of the fs_status (or fs_locations_info)
attribute on all of the file systems to get absence indications in a attribute on all of the file systems to get absence indications in a
single (or a few) request(s), since absent file systems will not single (or a few) request(s), since absent file systems will not
cause an error in this context. However, it still must do an cause an error in this context. However, it still must do an
operation which receives NFS4ERR_MOVED on each file system, in order operation that receives NFS4ERR_MOVED on each file system, in order
to clear the SEQ4_STATUS_LEASE_MOVED indication is cleared. to clear the SEQ4_STATUS_LEASE_MOVED indication.
Once the set of file systems with transferred locking state has been Once the set of file systems with transferred locking state has been
determined, the client can follow the normal process to obtain the determined, the client can follow the normal process to obtain the
new server information (through the fs_locations and new server information (through the fs_locations and
fs_locations_info attributes) and perform renewal of those leases on fs_locations_info attributes) and perform renewal of that lease on
the new server, unless information in fs_locations_info attribute the new server, unless information in the fs_locations_info attribute
shows that no state could have been transferred. If the server has shows that no state could have been transferred. If the server has
not had state transferred to it transparently, the client will not had state transferred to it transparently, the client will
receive NFS4ERR_STALE_CLIENTID from the new server, as described receive NFS4ERR_STALE_CLIENTID from the new server, as described
above, and the client can then reclaim locks as is done in the event above, and the client can then reclaim locks as is done in the event
of server failure. of server failure.
11.7.7.2. Transitions and the Lease_time Attribute 11.7.7.2. Transitions and the Lease_time Attribute
In order that the client may appropriately manage its leases in the In order that the client may appropriately manage its lease in the
case of a file system transition, the destination server must case of a file system transition, the destination server must
establish proper values for the lease_time attribute. establish proper values for the lease_time attribute.
When state is transferred transparently, that state should include When state is transferred transparently, that state should include
the correct value of the lease_time attribute. The lease_time the correct value of the lease_time attribute. The lease_time
attribute on the destination server must never be less than that on attribute on the destination server must never be less than that on
the source since this would result in premature expiration of leases the source, since this would result in premature expiration of a
granted by the source server. Upon transitions in which state is lease granted by the source server. Upon transitions in which state
transferred transparently, the client is under no obligation to re- is transferred transparently, the client is under no obligation to
fetch the lease_time attribute and may continue to use the value refetch the lease_time attribute and may continue to use the value
previously fetched (on the source server). previously fetched (on the source server).
If state has not been transferred transparently, either because the If state has not been transferred transparently, either because the
associated servers are shown as having different eir_server_scope associated servers are shown as having different eir_server_scope
strings or because the client ID is rejected when presented to the strings or because the client ID is rejected when presented to the
new server, the client should fetch the value of lease_time on the new server, the client should fetch the value of lease_time on the
new (i.e. destination) server, and use it for subsequent locking new (i.e., destination) server, and use it for subsequent locking
requests. However the server must respect a grace period at least as requests. However, the server must respect a grace period of at
long as the lease_time on the source server, in order to ensure that least as long as the lease_time on the source server, in order to
clients have ample time to reclaim their lock before potentially ensure that clients have ample time to reclaim their lock before
conflicting non-reclaimed locks are granted. potentially conflicting non-reclaimed locks are granted.
11.7.8. Write Verifiers and File System Transitions 11.7.8. Write Verifiers and File System Transitions
In a file system transition, the two file systems may be clustered in In a file system transition, the two file systems may be clustered in
the handling of unstably written data. When this is the case, and the handling of unstably written data. When this is the case, and
the two file systems belong to the same _write-verifier_ class, write the two file systems belong to the same write-verifier class, write
verifiers returned from one system may be compared to those returned verifiers returned from one system may be compared to those returned
by the other and superfluous writes avoided. by the other and superfluous writes avoided.
When two file systems belong to different _write-verifier_ classes, When two file systems belong to different write-verifier classes, any
any verifier generated by one must not be compared to one provided by verifier generated by one must not be compared to one provided by the
the other. Instead, it should be treated as not equal even when the other. Instead, it should be treated as not equal even when the
values are identical. values are identical.
11.7.9. Readdir Cookies and Verifiers and File System Transitions 11.7.9. Readdir Cookies and Verifiers and File System Transitions
In a file system transition, the two file systems may be consistent In a file system transition, the two file systems may be consistent
in their handling of READDIR cookies and verifiers. When this is the in their handling of READDIR cookies and verifiers. When this is the
case, and the two file systems belong to the same _readdir_ class, case, and the two file systems belong to the same readdir class,
READDIR cookies and verifiers from one system may be recognized by READDIR cookies and verifiers from one system may be recognized by
the other and READDIR operations started on one server may be validly the other and READDIR operations started on one server may be validly
continued on the other, simply by presenting the cookie and verifier continued on the other, simply by presenting the cookie and verifier
returned by a READDIR operation done on the first file system to the returned by a READDIR operation done on the first file system to the
second. second.
When two file systems belong to different _readdir_ classes, any When two file systems belong to different readdir classes, any
READDIR cookie and verifier generated by one is not valid on the READDIR cookie and verifier generated by one is not valid on the
second, and must not be presented to that server by the client. The second, and must not be presented to that server by the client. The
client should act as if the verifier was rejected. client should act as if the verifier was rejected.
11.7.10. File System Data and File System Transitions 11.7.10. File System Data and File System Transitions
When multiple replicas exist and are used simultaneously or in When multiple replicas exist and are used simultaneously or in
succession by a client, applications using them will normally expect succession by a client, applications using them will normally expect
that they contain data the same data or data which is consistent with that they contain either the same data or data that is consistent
the normal sorts of changes that are made by other clients updating with the normal sorts of changes that are made by other clients
the data of the file system. (with metadata being the same to the updating the data of the file system (with metadata being the same to
degree indicated by the fs_locations_info attribute). However, when the degree indicated by the fs_locations_info attribute). However,
multiple file systems are presented as replicas of one another, the when multiple file systems are presented as replicas of one another,
precise relationship between the data of one and the data of another the precise relationship between the data of one and the data of
is not, as a general matter, specified by the NFSv4.1 protocol. It another is not, as a general matter, specified by the NFSv4.1
is quite possible to present as replicas file systems where the data protocol. It is quite possible to present as replicas file systems
of those file systems is sufficiently different that some where the data of those file systems is sufficiently different that
applications have problems dealing with the transition between some applications have problems dealing with the transition between
replicas. The namespace will typically be constructed so that replicas. The namespace will typically be constructed so that
applications can choose an appropriate level of support, so that in applications can choose an appropriate level of support, so that in
one position in the namespace a varied set of replicas will be listed one position in the namespace a varied set of replicas will be
while in another only those that are up-to-date may be considered listed, while in another only those that are up-to-date may be
replicas. The protocol does define three special cases of the considered replicas. The protocol does define four special cases of
relationship among replicas to be specified by the server and relied the relationship among replicas to be specified by the server and
upon by clients: relied upon by clients:
o When multiple server addresses correspond to the same actual o When multiple server addresses correspond to the same actual
server, as indicated by a common so_major_id field within the server, as indicated by a common so_major_id field within the
eir_server_owner field returned by EXCHANGE_ID, the client may eir_server_owner field returned by EXCHANGE_ID, the client may
depend on the fact that changes to data, metadata, or locks made depend on the fact that changes to data, metadata, or locks made
on one file system are immediately reflected on others. on one file system are immediately reflected on others.
o When multiple replicas exist and are used simultaneously by a o When multiple replicas exist and are used simultaneously by a
client (see the FSLIB4_CLSIMUL definition within client (see the FSLIB4_CLSIMUL definition within
fs_locations_info), they must designate the same data. Where file fs_locations_info), they must designate the same data. Where file
systems are writable, a change made on one instance must be systems are writable, a change made on one instance must be
visible on all instances, immediately upon the earlier of the visible on all instances, immediately upon the earlier of the
return of the modifying requester or the visibility of that change return of the modifying requester or the visibility of that change
on any of the associated replicas. This allows a client to use on any of the associated replicas. This allows a client to use
these replicas simultaneously without any special adaptation to these replicas simultaneously without any special adaptation to
the fact that there are multiple replicas. In this case, locks, the fact that there are multiple replicas. In this case, locks
whether shared or byte-range, and delegations obtained one replica (whether share reservations or byte-range locks) and delegations
are immediately reflected on all replicas, even though these locks obtained on one replica are immediately reflected on all replicas,
will be managed under a set of client IDs. even though these locks will be managed under a set of client IDs.
o When one replica is designated as the successor instance to o When one replica is designated as the successor instance to
another existing instance after return NFS4ERR_MOVED (i.e. the another existing instance after return NFS4ERR_MOVED (i.e., the
case of migration), the client may depend on the fact that all case of migration), the client may depend on the fact that all
changes securely made to data (uncommitted writes are dealt with changes written to stable storage on the original instance are
in Section 11.7.8) on the original instance are made to the written to stable storage of the successor (uncommitted writes are
successor image. dealt with in Section 11.7.8).
o Where a file system is not writable but represents a read-only o Where a file system is not writable but represents a read-only
copy (possibly periodically updated) of a writable file system, copy (possibly periodically updated) of a writable file system,
clients have similar requirements with regard to the propagation clients have similar requirements with regard to the propagation
of updates. They may need a guarantee that any change visible on of updates. They may need a guarantee that any change visible on
the original file system instance must be immediately visible on the original file system instance must be immediately visible on
any replica before the client transitions access to that replica, any replica before the client transitions access to that replica,
in order to avoid any possibility that a client, in effecting a in order to avoid any possibility that a client, in effecting a
transition to a replica, will see any reversion in file system transition to a replica, will see any reversion in file system
state. The specific means by which this will be prevented varies state. The specific means of this guarantee varies based on the
based on fs4_status_type reported as part of the fs_status value of the fss_type field that is reported as part of the
attribute (see Section 11.11). Since these file systems are fs_status attribute (see Section 11.11). Since these file systems
presumed not to be suitable for simultaneous use, there is no are presumed to be unsuitable for simultaneous use, there is no
specification of how locking is handled and it generally will be specification of how locking is handled; in general, locks
the case that locks obtained one file system will be separate from obtained on one file system will be separate from those on others.
those on others. Since these are going to be read-only file
systems, this is not expected to pose an issue for clients or Since these are going to be read-only file systems, this is not
applications. expected to pose an issue for clients or applications.
11.8. Effecting File System Referrals 11.8. Effecting File System Referrals
Referrals are effected when an absent file system is encountered, and Referrals are effected when an absent file system is encountered and
one or more alternate locations are made available by the one or more alternate locations are made available by the
fs_locations or fs_locations_info attributes. The client will fs_locations or fs_locations_info attributes. The client will
typically get an NFS4ERR_MOVED error, fetch the appropriate location typically get an NFS4ERR_MOVED error, fetch the appropriate location
information and proceed to access the file system on a different information, and proceed to access the file system on a different
server, even though it retains its logical position within the server, even though it retains its logical position within the
original namespace. Referrals differ from migration events in that original namespace. Referrals differ from migration events in that
they happen only when the client has not previously referenced the they happen only when the client has not previously referenced the
file system in question (so there is nothing to transition). file system in question (so there is nothing to transition).
Referrals can only come into effect when an absent file system is Referrals can only come into effect when an absent file system is
encountered at its root. encountered at its root.
The examples given in the sections below are somewhat artificial in The examples given in the sections below are somewhat artificial in
that an actual client will not typically do a multi-component lookup, that an actual client will not typically do a multi-component look
but will have cached information regarding the upper levels of the up, but will have cached information regarding the upper levels of
name hierarchy. However, these example are chosen to make the the name hierarchy. However, these example are chosen to make the
required behavior clear and easy to put within the scope of a small required behavior clear and easy to put within the scope of a small
number of requests, without getting unduly into details of how number of requests, without getting unduly into details of how
specific clients might choose to cache things. specific clients might choose to cache things.
11.8.1. Referral Example (LOOKUP) 11.8.1. Referral Example (LOOKUP)
Let us suppose that the following COMPOUND is sent in an environment Let us suppose that the following COMPOUND is sent in an environment
in which /this/is/the/path is absent from the target server. This in which /this/is/the/path is absent from the target server. This
may be for a number of reasons. It may be the case that the file may be for a number of reasons. It may be that the file system has
system has moved, or, it may be the case that the target server is moved, or it may be that the target server is functioning mainly, or
functioning mainly, or solely, to refer clients to the servers on solely, to refer clients to the servers on which various file systems
which various file systems are located. are located.
o PUTROOTFH o PUTROOTFH
o LOOKUP "this" o LOOKUP "this"
o LOOKUP "is" o LOOKUP "is"
o LOOKUP "the" o LOOKUP "the"
o LOOKUP "path" o LOOKUP "path"
o GETFH o GETFH
o GETATTR fsid,fileid,size,time_modify o GETATTR (fsid, fileid, size, time_modify)
Under the given circumstances, the following will be the result. Under the given circumstances, the following will be the result.
o PUTROOTFH --> NFS_OK. The current fh is now the root of the o PUTROOTFH --> NFS_OK. The current fh is now the root of the
pseudo-fs. pseudo-fs.
o LOOKUP "this" --> NFS_OK. The current fh is for /this and is o LOOKUP "this" --> NFS_OK. The current fh is for /this and is
within the pseudo-fs. within the pseudo-fs.
o LOOKUP "is" --> NFS_OK. The current fh is for /this/is and is o LOOKUP "is" --> NFS_OK. The current fh is for /this/is and is
within the pseudo-fs. within the pseudo-fs.
o LOOKUP "the" --> NFS_OK. The current fh is for /this/is/the and o LOOKUP "the" --> NFS_OK. The current fh is for /this/is/the and
is within the pseudo-fs. is within the pseudo-fs.
o LOOKUP "path" --> NFS_OK. The current fh is for /this/is/the/path o LOOKUP "path" --> NFS_OK. The current fh is for /this/is/the/path
and is within a new, absent file system, but ... the client will and is within a new, absent file system, but ... the client will
never see the value of that fh. never see the value of that fh.
o GETFH --> NFS4ERR_MOVED. Fails because current fh is in an absent o GETFH --> NFS4ERR_MOVED. Fails because current fh is in an absent
file system at the start of the operation and the spec makes no file system at the start of the operation, and the specification
exception for GETFH. makes no exception for GETFH.
o GETATTR fsid,fileid,size,time_modify. Not executed because the o GETATTR (fsid, fileid, size, time_modify). Not executed because
failure of the GETFH stops processing of the COMPOUND. the failure of the GETFH stops processing of the COMPOUND.
Given the failure of the GETFH, the client has the job of determining Given the failure of the GETFH, the client has the job of determining
the root of the absent file system and where to find that file the root of the absent file system and where to find that file
system, i.e. the server and path relative to that server's root fh. system, i.e., the server and path relative to that server's root fh.
Note here that in this example, the client did not obtain filehandles Note that in this example, the client did not obtain filehandles and
and attribute information (e.g. fsid) for the intermediate attribute information (e.g., fsid) for the intermediate directories,
directories, so that it would not be sure where the absent file so that it would not be sure where the absent file system starts. It
system starts. It could be the case, for example, that /this/is/the could be the case, for example, that /this/is/the is the root of the
is the root of the moved file system and that the reason that the moved file system and that the reason that the look up of "path"
lookup of "path" succeeded is that the file system was not absent on succeeded is that the file system was not absent on that operation
that operation but was moved between the last LOOKUP and the GETFH but was moved between the last LOOKUP and the GETFH (since COMPOUND
(since COMPOUND is not atomic). Even if we had the fsids for all of is not atomic). Even if we had the fsids for all of the intermediate
the intermediate directories, we could have no way of knowing that directories, we could have no way of knowing that /this/is/the/path
/this/is/the/path was the root of a new file system, since we don't was the root of a new file system, since we don't yet have its fsid.
yet have its fsid.
In order to get the necessary information, let us re-send the chain In order to get the necessary information, let us re-send the chain
of LOOKUPs with GETFHs and GETATTRs to at least get the fsids so we of LOOKUPs with GETFHs and GETATTRs to at least get the fsids so we
can be sure where the appropriate file system boundaries are. The can be sure where the appropriate file system boundaries are. The
client could choose to get fs_locations_info at the same time but in client could choose to get fs_locations_info at the same time but in
most cases the client will have a good guess as to where file system most cases the client will have a good guess as to where file system
boundaries are (because of where and where not NFS4ERR_MOVED was boundaries are (because of where NFS4ERR_MOVED was, and was not,
received) making fetching of fs_locations_info unnecessary. received) making fetching of fs_locations_info unnecessary.
OP01: PUTROOTFH --> NFS_OK OP01: PUTROOTFH --> NFS_OK
- Current fh is root of pseudo-fs. - Current fh is root of pseudo-fs.
OP02: GETATTR(fsid) --> NFS_OK OP02: GETATTR(fsid) --> NFS_OK
- Just for completeness. Normally, clients will know the fsid of - Just for completeness. Normally, clients will know the fsid of
the pseudo-fs as soon as they establish communication with a the pseudo-fs as soon as they establish communication with a
skipping to change at page 254, line 14 skipping to change at page 254, line 14
OP11: GETFH --> NFS_OK OP11: GETFH --> NFS_OK
- Current fh is for /this/is/the and is within pseudo-fs. - Current fh is for /this/is/the and is within pseudo-fs.
OP12: LOOKUP "path" --> NFS_OK OP12: LOOKUP "path" --> NFS_OK
- Current fh is for /this/is/the/path and is within a new, absent - Current fh is for /this/is/the/path and is within a new, absent
file system, but ... file system, but ...
- The client will never see the value of that fh - The client will never see the value of that fh.
OP13: GETATTR(fsid, fs_locations_info) --> NFS_OK OP13: GETATTR(fsid, fs_locations_info) --> NFS_OK
- We are getting the fsid to know where the file system boundaries - We are getting the fsid to know where the file system boundaries
are. In this operation the fsid will be different than that of are. In this operation, the fsid will be different than that of
the parent directory (which in turn was retrieved in OP10). Note the parent directory (which in turn was retrieved in OP10). Note
that the fsid we are given will not necessarily be preserved at that the fsid we are given will not necessarily be preserved at
the new location. That fsid might be different and in fact the the new location. That fsid might be different, and in fact the
fsid we have for this file system might be a valid fsid of a fsid we have for this file system might be a valid fsid of a
different file system on that new server. different file system on that new server.
- In this particular case, we are pretty sure anyway that what has - In this particular case, we are pretty sure anyway that what has
moved is /this/is/the/path rather than /this/is/the since we have moved is /this/is/the/path rather than /this/is/the since we have
the fsid of the latter and it is that of the pseudo-fs, which the fsid of the latter and it is that of the pseudo-fs, which
presumably cannot move. However, in other examples, we might not presumably cannot move. However, in other examples, we might not
have this kind of information to rely on (e.g. /this/is/the might have this kind of information to rely on (e.g., /this/is/the might
be a non-pseudo file system separate from /this/is/the/path), so be a non-pseudo file system separate from /this/is/the/path), so
we need to have another reliable source information on the we need to have other reliable source information on the boundary
boundary of the file system which is moved. If, for example, the of the file system that is moved. If, for example, the file
file system "/this/is" had moved we would have a case of migration system /this/is had moved, we would have a case of migration
rather than referral and once the boundaries of the migrated file rather than referral, and once the boundaries of the migrated file
system was clear we could fetch fs_locations_info. system was clear we could fetch fs_locations_info.
- We are fetching fs_locations_info because the fact that we got an - We are fetching fs_locations_info because the fact that we got an
NFS4ERR_MOVED at this point means that it most likely that this is NFS4ERR_MOVED at this point means that it is most likely that this
a referral and we need the destination. Even if it is the case is a referral and we need the destination. Even if it is the case
that "/this/is/the" is a file system which has migrated, we will that /this/is/the is a file system that has migrated, we will
still need the location information for that file system. still need the location information for that file system.
OP14: GETFH --> NFS4ERR_MOVED OP14: GETFH --> NFS4ERR_MOVED
- Fails because current fh is in an absent file system at the start - Fails because current fh is in an absent file system at the start
of the operation and the spec makes no exception for GETFH. Note of the operation, and the specification makes no exception for
that this means the server will never send the client a filehandle GETFH. Note that this means the server will never send the client
from within an absent file system. a filehandle from within an absent file system.
Given the above, the client knows where the root of the absent file Given the above, the client knows where the root of the absent file
system is (/this/is/the/path), by noting where the change of fsid system is (/this/is/the/path) by noting where the change of fsid
occurred (between "the" and "path"). The fs_locations_info attribute occurred (between "the" and "path"). The fs_locations_info attribute
also gives the client the actual location of the absent file system, also gives the client the actual location of the absent file system,
so that the referral can proceed. The server gives the client the so that the referral can proceed. The server gives the client the
bare minimum of information about the absent file system so that bare minimum of information about the absent file system so that
there will be very little scope for problems of conflict between there will be very little scope for problems of conflict between
information sent by the referring server and information of the file information sent by the referring server and information of the file
system's home. No filehandles and very few attributes are present on system's home. No filehandles and very few attributes are present on
the referring server and the client can treat those it receives as the referring server, and the client can treat those it receives as
basically transient information with the function of enabling the transient information with the function of enabling the referral.
referral.
11.8.2. Referral Example (READDIR) 11.8.2. Referral Example (READDIR)
Another context in which a client may encounter referrals is when it Another context in which a client may encounter referrals is when it
does a READDIR on directory in which some of the sub-directories are does a READDIR on a directory in which some of the sub-directories
the roots of absent file systems. are the roots of absent file systems.
Suppose such a directory is read as follows: Suppose such a directory is read as follows:
o PUTROOTFH o PUTROOTFH
o LOOKUP "this" o LOOKUP "this"
o LOOKUP "is" o LOOKUP "is"
o LOOKUP "the" o LOOKUP "the"
o READDIR (fsid, size, time_modify, mounted_on_fileid) o READDIR (fsid, size, time_modify, mounted_on_fileid)
In this case, because rdattr_error is not requested, In this case, because rdattr_error is not requested,
fs_locations_info is not requested, and some of attributes cannot be fs_locations_info is not requested, and some of the attributes cannot
provided, the result will be an NFS4ERR_MOVED error on the READDIR, be provided, the result will be an NFS4ERR_MOVED error on the
with the detailed results as follows: READDIR, with the detailed results as follows:
o PUTROOTFH --> NFS_OK. The current fh is at the root of the o PUTROOTFH --> NFS_OK. The current fh is at the root of the
pseudo-fs. pseudo-fs.
o LOOKUP "this" --> NFS_OK. The current fh is for /this and is o LOOKUP "this" --> NFS_OK. The current fh is for /this and is
within the pseudo-fs. within the pseudo-fs.
o LOOKUP "is" --> NFS_OK. The current fh is for /this/is and is o LOOKUP "is" --> NFS_OK. The current fh is for /this/is and is
within the pseudo-fs. within the pseudo-fs.
o LOOKUP "the" --> NFS_OK. The current fh is for /this/is/the and o LOOKUP "the" --> NFS_OK. The current fh is for /this/is/the and
is within the pseudo-fs. is within the pseudo-fs.
o READDIR (fsid, size, time_modify, mounted_on_fileid) --> o READDIR (fsid, size, time_modify, mounted_on_fileid) -->
NFS4ERR_MOVED. Note that the same error would have been returned NFS4ERR_MOVED. Note that the same error would have been returned
if /this/is/the had migrated, when in fact it is because the if /this/is/the had migrated, but it is returned because the
directory contains the root of an absent file system. directory contains the root of an absent file system.
So now suppose that we re-send with rdattr_error: So now suppose that we re-send with rdattr_error:
o PUTROOTFH o PUTROOTFH
o LOOKUP "this" o LOOKUP "this"
o LOOKUP "is" o LOOKUP "is"
skipping to change at page 257, line 23 skipping to change at page 257, line 23
within the pseudo-fs. within the pseudo-fs.
o LOOKUP "the" --> NFS_OK. The current fh is for /this/is/the and o LOOKUP "the" --> NFS_OK. The current fh is for /this/is/the and
is within the pseudo-fs. is within the pseudo-fs.
o READDIR (rdattr_error, fs_locations_info, mounted_on_fileid, fsid, o READDIR (rdattr_error, fs_locations_info, mounted_on_fileid, fsid,
size, time_modify) --> NFS_OK. The attributes will be as shown size, time_modify) --> NFS_OK. The attributes will be as shown
below. below.
The attributes for the directory entry with the component named The attributes for the directory entry with the component named
"path" will only contain "path" will only contain:
o rdattr_error (value: NFS_OK) o rdattr_error (value: NFS_OK)
o fs_locations_info o fs_locations_info
o mounted_on_fileid (value: unique fileid within referring file o mounted_on_fileid (value: unique fileid within referring file
system) system)
o fsid (value: unique value within referring server) o fsid (value: unique value within referring server)
skipping to change at page 258, line 12 skipping to change at page 258, line 12
pathname4 fs_root; pathname4 fs_root;
fs_location4 locations<>; fs_location4 locations<>;
}; };
The fs_location4 data type is used to represent the location of a The fs_location4 data type is used to represent the location of a
file system by providing a server name and the path to the root of file system by providing a server name and the path to the root of
the file system within that server's namespace. When a set of the file system within that server's namespace. When a set of
servers have corresponding file systems at the same path within their servers have corresponding file systems at the same path within their
namespaces, an array of server names may be provided. An entry in namespaces, an array of server names may be provided. An entry in
the server array is a UTF-8 string and represents one of a the server array is a UTF-8 string and represents one of a
traditional DNS host name, IPv4 address, or IPv6 address, or a zero- traditional DNS host name, IPv4 address, IPv6 address, or a zero-
length string. An IPv4 or IPv6 address is represented as a universal length string. An IPv4 or IPv6 address is represented as a universal
address (see Section 3.3.9 and [15]), minus the netid, and either address (see Section 3.3.9 and [15]), minus the netid, and either
with or without the trailing ".p1.p2" suffix that represents the port with or without the trailing ".p1.p2" suffix that represents the port
number. If the suffix is omitted, then the default port, 2049, number. If the suffix is omitted, then the default port, 2049,
SHOULD be assumed. A zero-length string SHOULD be used to indicate SHOULD be assumed. A zero-length string SHOULD be used to indicate
the current address being used for the RPC call. It is not a the current address being used for the RPC call. It is not a
requirement that all servers that share the same rootpath be listed requirement that all servers that share the same rootpath be listed
in one fs_location4 instance. The array of server names is provided in one fs_location4 instance. The array of server names is provided
for convenience. Servers that share the same rootpath may also be for convenience. Servers that share the same rootpath may also be
listed in separate fs_location4 entries in the fs_locations listed in separate fs_location4 entries in the fs_locations
attribute. attribute.
The fs_locations4 data type and fs_locations attribute contain an The fs_locations4 data type and fs_locations attribute contain an
array of such locations. Since the namespace of each server may be array of such locations. Since the namespace of each server may be
constructed differently, the "fs_root" field is provided. The path constructed differently, the "fs_root" field is provided. The path
represented by fs_root represents the location of the file system in represented by fs_root represents the location of the file system in
the current server's namespace, i.e. that of the server from which the current server's namespace, i.e., that of the server from which
the fs_locations attribute was obtained. The fs_root path is meant the fs_locations attribute was obtained. The fs_root path is meant
to aid the client by clearly referencing the root of the file system to aid the client by clearly referencing the root of the file system
whose locations are being reported, no matter what object within the whose locations are being reported, no matter what object within the
current file system the current filehandle designates. The fs_root current file system the current filehandle designates. The fs_root
is simply the pathname the client used to reach the object on the is simply the pathname the client used to reach the object on the
current server, the object being that the fs_locations attribute current server (i.e., the object to which the fs_locations attribute
applies to. applies).
When the fs_locations attribute is interrogated and there are no When the fs_locations attribute is interrogated and there are no
alternate file system locations, the server SHOULD return a zero- alternate file system locations, the server SHOULD return a zero-
length array of fs_location4 structures, together with a valid length array of fs_location4 structures, together with a valid
fs_root. fs_root.
As an example, suppose there is a replicated file system located at As an example, suppose there is a replicated file system located at
two servers (servA and servB). At servA, the file system is located two servers (servA and servB). At servA, the file system is located
at path "/a/b/c". At, servB the file system is located at path at path /a/b/c. At, servB the file system is located at path /x/y/z.
"/x/y/z". If the client were to obtain the fs_locations value for If the client were to obtain the fs_locations value for the directory
the directory at "/a/b/c/d", it might not necessarily know that the at /a/b/c/d, it might not necessarily know that the file system's
file system's root is located in servA's namespace at "/a/b/c". When root is located in servA's namespace at /a/b/c. When the client
the client switches to servB, it will need to determine that the switches to servB, it will need to determine that the directory it
directory it first referenced at servA is now represented by the path first referenced at servA is now represented by the path /x/y/z/d on
"/x/y/z/d" on servB. To facilitate this, the fs_locations attribute servB. To facilitate this, the fs_locations attribute provided by
provided by servA would have a fs_root value of "/a/b/c" and two servA would have an fs_root value of /a/b/c and two entries in
entries in fs_locations. One entry in fs_locations will be for fs_locations. One entry in fs_locations will be for itself (servA)
itself (servA) and the other will be for servB with a path of and the other will be for servB with a path of /x/y/z. With this
"/x/y/z". With this information, the client is able to substitute information, the client is able to substitute /x/y/z for the /a/b/c
"/x/y/z" for the "/a/b/c" at the beginning of its access path and at the beginning of its access path and construct /x/y/z/d to use for
construct "/x/y/z/d" to use for the new server. the new server.
Note that: there is no requirement that the number of components in Note that there is no requirement that the number of components in
each rootpath be the same; there is no relation between the number of each rootpath be the same; there is no relation between the number of
components in rootpath or fs_root; and the none of the components in components in rootpath or fs_root, and none of the components in a
each rootpath and fs_root have to be the same. In the above example, rootpath and fs_root have to be the same. In the above example, we
we could have had a third element in the locations array, with server could have had a third element in the locations array, with server
equal to "servC", and rootpath equal to "/I/II", and a fourth element equal to "servC" and rootpath equal to "/I/II", and a fourth element
in locations with server equal to "servD", and rootpath equal to in locations with server equal to "servD" and rootpath equal to
"/aleph/beth/gimel/daleth/he". "/aleph/beth/gimel/daleth/he".
The relationship between fs_root to a rootpath is that the client The relationship between fs_root to a rootpath is that the client
replaces the pathname indicated in fs_root for the current server for replaces the pathname indicated in fs_root for the current server for
the substitute indicated in rootpath for the new server. the substitute indicated in rootpath for the new server.
For an example for a referred or migrated file system, suppose there For an example of a referred or migrated file system, suppose there
is a file system located at serv1. At serv1, the file system is is a file system located at serv1. At serv1, the file system is
located at "/az/buky/vedi/glagoli". The client finds that object at located at /az/buky/vedi/glagoli. The client finds that object at
"glagoli" has migrated (or is a referral). The client gets the glagoli has migrated (or is a referral). The client gets the
fs_locations attribute, which contains an fs_root of "/az/buky/vedi/ fs_locations attribute, which contains an fs_root of /az/buky/vedi/
glagoli", and one element in the locations array, with server equal glagoli, and one element in the locations array, with server equal to
to "serv2", and rootpath equal to "/izhitsa/fita". The client serv2, and rootpath equal to /izhitsa/fita. The client replaces /az/
replaces "/az/buky/vedi/glagoli" with "/izhitsa/fita", and uses the buky/vedi/glagoli with /izhitsa/fita, and uses the latter pathname on
latter pathname on "serv2". serv2.
Thus, the server MUST return an fs_root that is equal to the path the Thus, the server MUST return an fs_root that is equal to the path the
client used to reach the object the fs_locations attribute applies client used to reach the object to which the fs_locations attribute
to. Otherwise the client cannot determine the new path to use on the applies. Otherwise, the client cannot determine the new path to use
new server. on the new server.
Since the fs_locations attribute lacks information defining various Since the fs_locations attribute lacks information defining various
attributes of the various file system choices presented, it SHOULD attributes of the various file system choices presented, it SHOULD
only be interrogated and used when fs_locations_info is not only be interrogated and used when fs_locations_info is not
available. When fs_locations is used, information about the specific available. When fs_locations is used, information about the specific
locations should be assumed based on the following rules. locations should be assumed based on the following rules.
The following rules are general and apply irrespective of the The following rules are general and apply irrespective of the
context. context.
o All listed file system instances should be considered as of the o All listed file system instances should be considered as of the
same _handle_ class, if and only if, the current fh_expire_type same handle class, if and only if, the current fh_expire_type
attribute does not include the FH4_VOL_MIGRATION bit. Note that attribute does not include the FH4_VOL_MIGRATION bit. Note that
in the case of referral, filehandle issues do not apply since in the case of referral, filehandle issues do not apply since
there can be no filehandles known within the current file system there can be no filehandles known within the current file system,
nor is there any access to the fh_expire_type attribute on the nor is there any access to the fh_expire_type attribute on the
referring (absent) file system. referring (absent) file system.
o All listed file system instances should be considered as of the o All listed file system instances should be considered as of the
same _fileid_ class, if and only if, the fh_expire_type attribute same fileid class if and only if the fh_expire_type attribute
indicates persistent filehandles and does not include the indicates persistent filehandles and does not include the
FH4_VOL_MIGRATION bit. Note that in the case of referral, fileid FH4_VOL_MIGRATION bit. Note that in the case of referral, fileid
issues do not apply since there can be no fileids known within the issues do not apply since there can be no fileids known within the
referring (absent) file system nor is there any access to the referring (absent) file system, nor is there any access to the
fh_expire_type attribute. fh_expire_type attribute.
o All file system instances servers should be considered as of o All file system instances servers should be considered as of
different _change_ classes. different change classes.
For other class assignments, handling of file system transitions For other class assignments, handling of file system transitions
depends on the reasons for the transition: depends on the reasons for the transition:
o When the transition is due to migration, that is the client was o When the transition is due to migration, that is, the client was
directed to new file system after receiving an NFS4ERR_MOVED directed to a new file system after receiving an NFS4ERR_MOVED
error, the target should be treated as being of the same _write- error, the target should be treated as being of the same write-
verifier_ class as the source. verifier class as the source.
o When the transition is due to failover to another replica, that o When the transition is due to failover to another replica, that
is, the client selected another replica without receiving and is, the client selected another replica without receiving an
NFS4ERR_MOVED error, the target should be treated as being of a NFS4ERR_MOVED error, the target should be treated as being of a
different _write-verifier_ class from the source. different write-verifier class from the source.
The specific choices reflect typical implementation patterns for The specific choices reflect typical implementation patterns for
failover and controlled migration respectively. Since other choices failover and controlled migration, respectively. Since other choices
are possible and useful, this information is better obtained by using are possible and useful, this information is better obtained by using
fs_locations_info. When a server implementation needs to communicate fs_locations_info. When a server implementation needs to communicate
other choices, it MUST support the fs_locations_info attribute. other choices, it MUST support the fs_locations_info attribute.
See Section 21 for a discussion on the recommendations for the See Section 21 for a discussion on the recommendations for the
security flavor to be used by any GETATTR operation that requests the security flavor to be used by any GETATTR operation that requests the
"fs_locations" attribute. "fs_locations" attribute.
11.10. The Attribute fs_locations_info 11.10. The Attribute fs_locations_info
The fs_locations_info attribute is intended as a more functional The fs_locations_info attribute is intended as a more functional
replacement for fs_locations which will continue to exist and be replacement for fs_locations that will continue to exist and be
supported. Clients can use it to get a more complete set of supported. Clients can use it to get a more complete set of
information about alternative file system locations. When the server information about alternative file system locations. When the server
does not support fs_locations_info, fs_locations can be used to get a does not support fs_locations_info, fs_locations can be used to get a
subset of the information. A server which supports fs_locations_info subset of the information. A server that supports fs_locations_info
MUST support fs_locations as well. MUST support fs_locations as well.
There is additional information present in fs_locations_info, that is There is additional information present in fs_locations_info, that is
not available in fs_locations: not available in fs_locations:
o Attribute continuity information to allow a client to select a o Attribute continuity information. This information will allow a
location which meets the transparency requirements of the client to select a location that meets the transparency
applications accessing the data and to take advantage of requirements of the applications accessing the data and to
optimizations that server guarantees as to attribute continuity leverage optimizations due to the server guarantees of attribute
may provide (e.g. change attribute). continuity (e.g., if between multiple server locations the change
attribute of a file of the file system is continuous, the client
does not have to invalidate the file's cache if the change
attribute is the same among all locations).
o File System identity information which indicates when multiple o File system identity information that indicates when multiple
replicas, from the client's point of view, correspond to the same replicas, from the client's point of view, correspond to the same
target file system, allowing them to be used interchangeably, target file system, allowing them to be used interchangeably,
without disruption, as multiple paths to the same thing. without disruption, as multiple paths to the same thing.
o Information which will bear on the suitability of various o Information that will bear on the suitability of various replicas,
replicas, depending on the use that the client intends. For depending on the use that the client intends. For example, many
example, many applications need an absolutely up-to-date copy applications need an absolutely up-to-date copy (e.g., those that
(e.g. those that write), while others may only need access to the write), while others may only need access to the most up-to-date
most up-to-date copy reasonably available. copy reasonably available.
o Server-derived preference information for replicas, which can be o Server-derived preference information for replicas, which can be
used to implement load-balancing while giving the client the used to implement load-balancing while giving the client the
entire file system list to be used in case the primary fails. entire file system list to be used in case the primary fails.
The fs_locations_info attribute is structured similarly to the The fs_locations_info attribute is structured similarly to the
fs_locations attribute. A top-level structure (fs_locations_info4) fs_locations attribute. A top-level structure (fs_locations_info4)
contains the entire attribute including the root pathname of the file contains the entire attribute including the root pathname of the file
system and an array of lower-level structures that define replicas system and an array of lower-level structures that define replicas
that share a common root path on their respective servers. The that share a common rootpath on their respective servers. The lower-
lower-level structure in turn (fs_locations_item4) contains a level structure in turn (fs_locations_item4) contains a specific
specific pathname and information on one or more individual server pathname and information on one or more individual server replicas.
replicas. For that last lowest-level fs_locations_info has a For that last lowest-level, fs_locations_info has an
fs_locations_server4 structure that contains per-server-replica fs_locations_server4 structure that contains per-server-replica
information in addition to the server name. This per-server-replica information in addition to the server name. This per-server-replica
information includes a nominally opaque array, fls_info, in which information includes a nominally opaque array, fls_info, in which
specific pieces of information are located at the specific indices specific pieces of information are located at the specific indices
listed below. listed below.
The attribute will always contains at least a single The attribute will always contain at least a single
fs_locations_server entry. Typically, this will be an entry with the fs_locations_server entry. Typically, this will be an entry with the
FS4LIGF_CUR_REQ flag set, although in the case of a referral there FS4LIGF_CUR_REQ flag set, although in the case of a referral there
will be no entry with that flag set. will be no entry with that flag set.
It should be noted that fs_locations_info attributes returned by It should be noted that fs_locations_info attributes returned by
servers for various replicas may differ for various reasons. One servers for various replicas may differ for various reasons. One
server may know about a set of replicas that are not know to other server may know about a set of replicas that are not known to other
servers. Further, compatibility attributes may differ. Filehandles servers. Further, compatibility attributes may differ. Filehandles
might be of the same class going from replica A to replica B but not might be of the same class going from replica A to replica B but not
going in the reverse direction. This might happen because the going in the reverse direction. This might happen because the
filehandles are the same but replica B's server implementation might filehandles are the same, but replica B's server implementation might
not have provision to note and report that equivalence. not have provision to note and report that equivalence.
The fs_locations_info attribute consists of a root pathname The fs_locations_info attribute consists of a root pathname
(fli_fs_root, just like fs_root in the fs_locations attribute), (fli_fs_root, just like fs_root in the fs_locations attribute),
together with an array of fs_location_item4 structures. The together with an array of fs_location_item4 structures. The
fs_location_item4 structures in turn consist of a root pathname fs_location_item4 structures in turn consist of a root pathname
(fli_rootpath) together with an array (fli_entries) of elements of (fli_rootpath) together with an array (fli_entries) of elements of
data type fs_locations_server4, all defined as follows. data type fs_locations_server4, all defined as follows.
/* /*
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/* /*
* Flag bits in fli_flags. * Flag bits in fli_flags.
*/ */
const FSLI4IF_VAR_SUB = 0x00000001; const FSLI4IF_VAR_SUB = 0x00000001;
typedef fs_locations_info4 fattr4_fs_locations_info; typedef fs_locations_info4 fattr4_fs_locations_info;
As noted above, the fs_locations_info attribute, when supported, may As noted above, the fs_locations_info attribute, when supported, may
be requested of absent file systems without causing NFS4ERR_MOVED to be requested of absent file systems without causing NFS4ERR_MOVED to
be returned and it is generally expected that it will be available be returned. It is generally expected that it will be available for
for both present and absent file systems even if only a single both present and absent file systems even if only a single
fs_locations_server4 entry is present, designating the current fs_locations_server4 entry is present, designating the current
(present) file system, or two fs_locations_server4 entries (present) file system, or two fs_locations_server4 entries
designating the previous location of an absent file system (the one designating the previous location of an absent file system (the one
just referenced) and its successor location. Servers are strongly just referenced) and its successor location. Servers are strongly
urged to support this attribute on all file systems if they support urged to support this attribute on all file systems if they support
it on any file system. it on any file system.
The data presented in the fs_locations_info attribute may be obtained The data presented in the fs_locations_info attribute may be obtained
by the server in any number of ways, including specification by the by the server in any number of ways, including specification by the
administrator or by current protocols for transferring data among administrator or by current protocols for transferring data among
replicas and protocols not yet developed. NFSv4.1 only defines how replicas and protocols not yet developed. NFSv4.1 only defines how
this information is presented by the server to the client. this information is presented by the server to the client.
11.10.1. The fs_locations_server4 Structure 11.10.1. The fs_locations_server4 Structure
The fs_locations_server4 structure consists of the following items: The fs_locations_server4 structure consists of the following items:
o An indication of file system up-to-date-ness (fls_currency) in o An indication of how up-to-date the file system is (fls_currency)
seconds. This value is relative to the master copy. A negative in seconds. This value is relative to the master copy. A
value indicates that the server is unable to give any reasonably negative value indicates that the server is unable to give any
useful value here. A zero indicates that file system is the reasonably useful value here. A value of zero indicates that the
actual writable data or a reliably coherent and fully up-to-date file system is the actual writable data or a reliably coherent and
copy. Positive values indicate how out-of-date this copy can fully up-to-date copy. Positive values indicate how out-of-date
normally be before it is considered for update. Such a value is this copy can normally be before it is considered for update.
not a guarantee that such updates will always be performed on the Such a value is not a guarantee that such updates will always be
required schedule but instead serves as a hint about how far the performed on the required schedule but instead serves as a hint
copy of the data would be expected to be behind the most up-to- about how far the copy of the data would be expected to be behind
date copy. the most up-to-date copy.
o A counted array of one-byte values (fls_info) containing o A counted array of one-byte values (fls_info) containing
information about the particular file system instance. This data information about the particular file system instance. This data
includes general flags, transport capability flags, file system includes general flags, transport capability flags, file system
equivalence class information, and selection priority information. equivalence class information, and selection priority information.
The encoding will be discussed below. The encoding will be discussed below.
o The server string (fls_server). For the case of the replica o The server string (fls_server). For the case of the replica
currently being accessed (via GETATTR), a zero-length string MAY currently being accessed (via GETATTR), a zero-length string MAY
be used to indicate the current address being used for the RPC be used to indicate the current address being used for the RPC
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formatted the same way as an IPv4 or IPv6 address in the "server" formatted the same way as an IPv4 or IPv6 address in the "server"
field of the fs_location4 data type (see Section 11.9). field of the fs_location4 data type (see Section 11.9).
Data within the fls_info array is in the form of 8-bit data items Data within the fls_info array is in the form of 8-bit data items
with constants giving the offsets within the array of various values with constants giving the offsets within the array of various values
describing this particular file system instance. This style of describing this particular file system instance. This style of
definition was chosen, in preference to explicit XDR structure definition was chosen, in preference to explicit XDR structure
definitions for these values, for a number of reasons. definitions for these values, for a number of reasons.
o The kinds of data in the fls_info array, representing flags, file o The kinds of data in the fls_info array, representing flags, file
system classes and priorities among set of file systems system classes, and priorities among sets of file systems
representing the same data, are such that eight bits provides a representing the same data, are such that 8 bits provide a quite
quite acceptable range of values. Even where there might be more acceptable range of values. Even where there might be more than
than 256 such file system instances, having more than 256 distinct 256 such file system instances, having more than 256 distinct
classes or priorities is unlikely. classes or priorities is unlikely.
o Explicit definition of the various specific data items within XDR o Explicit definition of the various specific data items within XDR
would limit expandability in that any extension within a would limit expandability in that any extension within a
subsequent minor version would require yet another attribute, subsequent minor version would require yet another attribute,
leading to specification and implementation clumsiness. leading to specification and implementation clumsiness.
o Such explicit definitions would also make it impossible to propose o Such explicit definitions would also make it impossible to propose
standards-track extensions apart from a full minor version. Standards Track extensions apart from a full minor version.
This encoding scheme can be adapted to the specification of multi- This encoding scheme can be adapted to the specification of multi-
byte numeric values, even though none are currently defined. If byte numeric values, even though none are currently defined. If
extensions are made via standards-track RFC's, multi-byte quantities extensions are made via Standards Track RFCs, multi-byte quantities
will be encoded as a range of bytes with a range of indices with the will be encoded as a range of bytes with a range of indices, with the
byte interpreted in big endian byte order. Further any such index byte interpreted in big-endian byte order. Further, any such index
assignments are constrained so that the relevant quantities will not assignments are constrained so that the relevant quantities will not
cross XDR word boundaries. cross XDR word boundaries.
The set of fls_info data is subject to expansion in a future minor The set of fls_info data is subject to expansion in a future minor
version, or in a standard-track RFC, within the context of a single version, or in a Standards Track RFC, within the context of a single
minor version. The server SHOULD NOT send and the client MUST NOT minor version. The server SHOULD NOT send and the client MUST NOT
use indices within the fls_info array that are not defined in use indices within the fls_info array that are not defined in
standards-track RFC's. Standards Track RFCs.
The fls_info array contains within it: The fls_info array contains:
o Two 8-bit flag fields, one devoted to general file-system o Two 8-bit flag fields, one devoted to general file-system
characteristics and a second reserved for transport-related characteristics and a second reserved for transport-related
capabilities. capabilities.
o Six 8-bit class values which define various file system o Six 8-bit class values that define various file system equivalence
equivalence classes as explained below. classes as explained below.
o Four 8-bit priority values which govern file system selection as o Four 8-bit priority values that govern file system selection as
explained below. explained below.
The general file system characteristics flag (at byte index The general file system characteristics flag (at byte index
FSLI4BX_GFLAGS) has the following bits defined within it: FSLI4BX_GFLAGS) has the following bits defined within it:
o FSLI4GF_WRITABLE indicates that this file system target is o FSLI4GF_WRITABLE indicates that this file system target is
writable, allowing it to be selected by clients which may need to writable, allowing it to be selected by clients that may need to
write on this file system. When the current file system instance write on this file system. When the current file system instance
is writable, and is defined as of the same simultaneous use class is writable and is defined as of the same simultaneous use class
(as specified by the value at index FSLI4BX_CLSIMUL) to which the (as specified by the value at index FSLI4BX_CLSIMUL) to which the
client was previously writing, then it must incorporate within its client was previously writing, then it must incorporate within its
data any committed write made on the source file system instance. data any committed write made on the source file system instance.
See Section 11.7.8 which discusses the write-verifier class. See Section 11.7.8, which discusses the write-verifier class.
While there is no harm in not setting this flag for a file system While there is no harm in not setting this flag for a file system
that turns out to be writable, turning the flag on for read-only that turns out to be writable, turning the flag on for a read-only
file system can cause problems for clients which select a file system can cause problems for clients that select a migration
migration or replication target based on it and then find or replication target based on the flag and then find themselves
themselves unable to write. unable to write.
o FSLI4GF_CUR_REQ indicates that this replica is the one on which o FSLI4GF_CUR_REQ indicates that this replica is the one on which
the request is being made. Only a single server entry may have the request is being made. Only a single server entry may have
this flag set and in the case of a referral, no entry will have this flag set and, in the case of a referral, no entry will have
it. it.
o FSLI4GF_ABSENT indicates that this entry corresponds an absent o FSLI4GF_ABSENT indicates that this entry corresponds to an absent
file system replica. It can only be set if FSLI4GF_CUR_REQ is file system replica. It can only be set if FSLI4GF_CUR_REQ is
set. When both such bits are set it indicates that a file system set. When both such bits are set, it indicates that a file system
instance is not usable but that the information in the entry can instance is not usable but that the information in the entry can
be used to determine the sorts of continuity available when be used to determine the sorts of continuity available when
switching from this replica to other possible replicas. Since switching from this replica to other possible replicas. Since
this bit can only be true if FSLI4GF_CUR_REQ is true, the value this bit can only be true if FSLI4GF_CUR_REQ is true, the value
could be determined using the fs_status attribute but the could be determined using the fs_status attribute, but the
information is also made available here for the convenience of the information is also made available here for the convenience of the
client. An entry with this bit, since it represents a true file client. An entry with this bit, since it represents a true file
system (albeit absent), does not appear in the event of a system (albeit absent), does not appear in the event of a
referral, but only where a file system has been accessed at this referral, but only when a file system has been accessed at this
location and has subsequently been migrated. location and has subsequently been migrated.
o FSLI4GF_GOING indicates that a replica, while still available, o FSLI4GF_GOING indicates that a replica, while still available,
should not be used further. The client, if using it, should make should not be used further. The client, if using it, should make
an orderly transfer to another file system instance as an orderly transfer to another file system instance as
expeditiously as possible. It is expected that file systems going expeditiously as possible. It is expected that file systems going
out of service will be announced as FSLI4GF_GOING some time before out of service will be announced as FSLI4GF_GOING some time before
the actual loss of service and that the valid_for value will be the actual loss of service. It is also expected that the
sufficiently small to allow clients to detect and act on scheduled fli_valid_for value will be sufficiently small to allow clients to
events while large enough that the cost of the requests to fetch detect and act on scheduled events, while large enough that the
the fs_locations_info values will not be excessive. Values on the cost of the requests to fetch the fs_locations_info values will
order of ten minutes seem reasonable. not be excessive. Values on the order of ten minutes seem
reasonable.
When this flag is seen as part of a transition into a new file When this flag is seen as part of a transition into a new file
system, a client might choose to transfer immediately to another system, a client might choose to transfer immediately to another
replica, or it may reference the current file system and only replica, or it may reference the current file system and only
transition when a migration event occurs. Similarly, when this transition when a migration event occurs. Similarly, when this
flag appears as a replica in the referral, clients would likely to flag appears as a replica in the referral, clients would likely
avoid being referred to this instance whenever there is another avoid being referred to this instance whenever there is another
choice. choice.
o FSLI4GF_SPLIT indicates that when a transition occurs from the o FSLI4GF_SPLIT indicates that when a transition occurs from the
current file system instance to this one, the replacement may current file system instance to this one, the replacement may
consist of multiple file systems. In this case, the client has to consist of multiple file systems. In this case, the client has to
be prepared for the possibility that objects on the same file be prepared for the possibility that objects on the same file
system before migration will be on different ones after. Note system before migration will be on different ones after. Note
that FSLI4GF_SPLIT is not incompatible with the file systems that FSLI4GF_SPLIT is not incompatible with the file systems
belonging to the same _fileid_ class since, if one has a set of belonging to the same fileid class since, if one has a set of
fileids that are unique within a file system, each subset assigned fileids that are unique within a file system, each subset assigned
to a smaller file system after migration would not have any to a smaller file system after migration would not have any
conflicts internal to that file system. conflicts internal to that file system.
A client, in the case of a split file system, will interrogate A client, in the case of a split file system, will interrogate
existing files with which it has continuing connection (it is free existing files with which it has continuing connection (it is free
simply forget cached filehandles). If the client remembers the to simply forget cached filehandles). If the client remembers the
directory filehandle associated with each open file, it may directory filehandle associated with each open file, it may
proceed upward using LOOKUPP to find the new file system proceed upward using LOOKUPP to find the new file system
boundaries. Note that in the event of a referral, there will not boundaries. Note that in the event of a referral, there will not
be any such files and so these action will not be performed. be any such files and so these actions will not be performed.
Instead, a reference to a portion of the original file system now Instead, a reference to a portion of the original file system now
split off into other file systems will encounter an fsid change split off into other file systems will encounter an fsid change
and possibly a further referral. and possibly a further referral.
Once the client recognizes that one file system has been split Once the client recognizes that one file system has been split
into two, it can prevent the disruption of running applications by into two, it can prevent the disruption of running applications by
presenting the two file systems as a single one until a convenient presenting the two file systems as a single one until a convenient
point to recognize the transition, such as a restart. This would point to recognize the transition, such as a restart. This would
require a mapping from the server's fsids to fsids as seen by the require a mapping from the server's fsids to fsids as seen by the
client but this is already necessary for other reasons. As noted client, but this is already necessary for other reasons. As noted
above, existing fileids within the two descendant file systems above, existing fileids within the two descendant file systems
will not conflict. Providing non-conflicting fileids for newly- will not conflict. Providing non-conflicting fileids for newly
created files on the split file systems is the responsibility of created files on the split file systems is the responsibility of
the server (or servers working in concert). The server can encode the server (or servers working in concert). The server can encode
filehandles such that filehandles generated before the split event filehandles such that filehandles generated before the split event
can be discerned from those generated after the split, allowing can be discerned from those generated after the split, allowing
the server to determine when the need for emulating two file the server to determine when the need for emulating two file
systems as one is over. systems as one is over.
Although it is possible for this flag to be present in the event Although it is possible for this flag to be present in the event
of referral, it would generally be of little interest to the of referral, it would generally be of little interest to the
client, since the client is not expected to have information client, since the client is not expected to have information
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o FSLI4TF_RDMA indicates that this file system provides NFSv4.1 file o FSLI4TF_RDMA indicates that this file system provides NFSv4.1 file
system access using an RDMA-capable transport. system access using an RDMA-capable transport.
Attribute continuity and file system identity information are Attribute continuity and file system identity information are
expressed by defining equivalence relations on the sets of file expressed by defining equivalence relations on the sets of file
systems presented to the client. Each such relation is expressed as systems presented to the client. Each such relation is expressed as
a set of file system equivalence classes. For each relation, a file a set of file system equivalence classes. For each relation, a file
system has an 8-bit class number. Two file systems belong to the system has an 8-bit class number. Two file systems belong to the
same class if both have identical non-zero class numbers. Zero is same class if both have identical non-zero class numbers. Zero is
treated as non-matching. Most often, the relevant question for the treated as non-matching. Most often, the relevant question for the
client will be whether a given replica is identical-to/ client will be whether a given replica is identical to / continuous
continuous-with the current one in a given respect but the with the current one in a given respect, but the information should
information should be available also as to whether two other replicas be available also as to whether two other replicas match in that
match in that respect as well. respect as well.
The following fields specify the file system's class numbers for the The following fields specify the file system's class numbers for the
equivalence relations used in determining the nature of file system equivalence relations used in determining the nature of file system
transitions. See Section 11.7 and its various subsections for transitions. See Section 11.7 and its various subsections for
details about how this information is to be used. Servers may assign details about how this information is to be used. Servers may assign
these values as they wish, so long as file system instances that these values as they wish, so long as file system instances that
share the same value have the specified relationship to one another, share the same value have the specified relationship to one another;
conversely file systems which have the specified relationship to one conversely, file systems that have the specified relationship to one
another share a common class value. As each instance entry is added, another share a common class value. As each instance entry is added,
the relationships of this instance to previously entered instances the relationships of this instance to previously entered instances
can be consulted and if one is found that bears the specified can be consulted, and if one is found that bears the specified
relationship, that entry's class value can be copied to the new relationship, that entry's class value can be copied to the new
entry. When no such previous entry exists, a new value for that byte entry. When no such previous entry exists, a new value for that byte
index, not previously used can be selected, most likely by index (not previously used) can be selected, most likely by
incrementing the value of the last class value assigned for that incrementing the value of the last class value assigned for that
index. index.
o The field with byte index FSLI4BX_CLSIMUL defines the o The field with byte index FSLI4BX_CLSIMUL defines the
simultaneous-use class for the file system. simultaneous-use class for the file system.
o The field with byte index FSLI4BX_CLHANDLE defines the handle o The field with byte index FSLI4BX_CLHANDLE defines the handle
class for the file system. class for the file system.
o The field with byte index FSLI4BX_CLFILEID defines the fileid o The field with byte index FSLI4BX_CLFILEID defines the fileid
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class for the file system. class for the file system.
Server-specified preference information is also provided via 8-bit Server-specified preference information is also provided via 8-bit
values within the fls_info array. The values provide a rank and an values within the fls_info array. The values provide a rank and an
order (see below) to be used with separate values specifiable for the order (see below) to be used with separate values specifiable for the
cases of read-only and writable file systems. These values are cases of read-only and writable file systems. These values are
compared for different file systems to establish the server-specified compared for different file systems to establish the server-specified
preference, with lower values indicating "more preferred". preference, with lower values indicating "more preferred".
Rank is used to express a strict server-imposed ordering on clients, Rank is used to express a strict server-imposed ordering on clients,
with lower values indicating "more preferred." Clients should with lower values indicating "more preferred". Clients should
attempt to use all replicas with a given rank before they use one attempt to use all replicas with a given rank before they use one
with a higher rank. Only if all of those file systems are with a higher rank. Only if all of those file systems are
unavailable should the client proceed to those of a higher rank. unavailable should the client proceed to those of a higher rank.
Because specifying a rank will override client preferences, servers Because specifying a rank will override client preferences, servers
should be conservative about using this mechanism, particularly when should be conservative about using this mechanism, particularly when
the environment is one in client communication characteristics are the environment is one in which client communication characteristics
not tightly controlled and visible to the server. are neither tightly controlled nor visible to the server.
Within a rank, the order value is used to specify the server's Within a rank, the order value is used to specify the server's
preference to guide the client's selection when the client's own preference to guide the client's selection when the client's own
preferences are not controlling, with lower values of order preferences are not controlling, with lower values of order
indicating "more preferred." If replicas are approximately equal in indicating "more preferred". If replicas are approximately equal in
all respects, clients should defer to the order specified by the all respects, clients should defer to the order specified by the
server. When clients look at server latency as part of their server. When clients look at server latency as part of their
selection, they are free to use this criterion but it is suggested selection, they are free to use this criterion but it is suggested
that when latency differences are not significant, the server- that when latency differences are not significant, the server-
specified order should guide selection. specified order should guide selection.
o The field at byte index FSLI4BX_READRANK gives the rank value to o The field at byte index FSLI4BX_READRANK gives the rank value to
be used for read-only access. be used for read-only access.
o The field at byte index FSLI4BX_READORDER gives the order value to o The field at byte index FSLI4BX_READORDER gives the order value to
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one of the pairs of rank and order values is used. The read rank and one of the pairs of rank and order values is used. The read rank and
order should only be used if the client knows that only reading will order should only be used if the client knows that only reading will
ever be done or if it is prepared to switch to a different replica in ever be done or if it is prepared to switch to a different replica in
the event that any write access capability is required in the future. the event that any write access capability is required in the future.
11.10.2. The fs_locations_info4 Structure 11.10.2. The fs_locations_info4 Structure
The fs_locations_info4 structure, encoding the fs_locations_info The fs_locations_info4 structure, encoding the fs_locations_info
attribute, contains the following: attribute, contains the following:
o The fli_flags field which contains general flags that affect the o The fli_flags field, which contains general flags that affect the
interpretation of this fs_locations_info4 structure and all interpretation of this fs_locations_info4 structure and all
fs_locations_item4 structures within it. The only flag currently fs_locations_item4 structures within it. The only flag currently
defined is FSLI4IF_VAR_SUB. All bits in the fli_flags field which defined is FSLI4IF_VAR_SUB. All bits in the fli_flags field that
are not defined should always be returned as zero. are not defined should always be returned as zero.
o The fli_fs_root field which contains the pathname of the root of o The fli_fs_root field, which contains the pathname of the root of
the current file system on the current server, just as it does in the current file system on the current server, just as it does in
the fs_locations4 structure. the fs_locations4 structure.
o An array called fli_items of fs_locations4_item structures, which o An array called fli_items of fs_locations4_item structures, which
contain information about replicas of the current file system. contain information about replicas of the current file system.
Where the current file system is actually present, or has been Where the current file system is actually present, or has been
present, i.e. this is not a referral situation, one of the present, i.e., this is not a referral situation, one of the
fs_locations_item4 structures will contain an fs_locations_server4 fs_locations_item4 structures will contain an fs_locations_server4
for the current server. This structure will have FSLI4GF_ABSENT for the current server. This structure will have FSLI4GF_ABSENT
set if the current file system is absent, i.e. normal access to it set if the current file system is absent, i.e., normal access to
will return NFS4ERR_MOVED. it will return NFS4ERR_MOVED.
o The fli_valid_for field specifies a time in seconds for which it o The fli_valid_for field specifies a time in seconds for which it
is reasonable for a client to use the fs_locations_info attribute is reasonable for a client to use the fs_locations_info attribute
without refetch. The fli_valid_for value does not provide a without refetch. The fli_valid_for value does not provide a
guarantee of validity since servers can unexpectedly go out of guarantee of validity since servers can unexpectedly go out of
service or become inaccessible for any number of reasons. Clients service or become inaccessible for any number of reasons. Clients
are well-advised to refetch this information for actively accessed are well-advised to refetch this information for an actively
file system at every fli_valid_for seconds. This is particularly accessed file system at every fli_valid_for seconds. This is
important when file system replicas may go out of service in a particularly important when file system replicas may go out of
controlled way using the FSLI4GF_GOING flag to communicate an service in a controlled way using the FSLI4GF_GOING flag to
ongoing change. The server should set fli_valid_for to a value communicate an ongoing change. The server should set
which allows well-behaved clients to notice the FSLI4GF_GOING flag fli_valid_for to a value that allows well-behaved clients to
and make an orderly switch before the loss of service becomes notice the FSLI4GF_GOING flag and make an orderly switch before
effective. If this value is zero, then no refetch interval is the loss of service becomes effective. If this value is zero,
appropriate and the client need not refetch this data on any then no refetch interval is appropriate and the client need not
particular schedule. In the event of a transition to a new file refetch this data on any particular schedule. In the event of a
system instance, a new value of the fs_locations_info attribute transition to a new file system instance, a new value of the
will be fetched at the destination and it is to be expected that fs_locations_info attribute will be fetched at the destination.
this may have a different valid_for value, which the client should It is to be expected that this may have a different fli_valid_for
then use, in the same fashion as the previous value. value, which the client should then use in the same fashion as the
previous value.
The FSLI4IF_VAR_SUB flag within fli_flags controls whether variable The FSLI4IF_VAR_SUB flag within fli_flags controls whether variable
substitution is to be enabled. See Section 11.10.3 for an substitution is to be enabled. See Section 11.10.3 for an
explanation of variable substitution. explanation of variable substitution.
11.10.3. The fs_locations_item4 Structure 11.10.3. The fs_locations_item4 Structure
The fs_locations_item4 structure contains a pathname (in the field The fs_locations_item4 structure contains a pathname (in the field
fli_rootpath) which encodes the path of the target file system fli_rootpath) that encodes the path of the target file system
replicas on the set of servers designated by the included replicas on the set of servers designated by the included
fs_locations_server4 entries. The precise manner in which this fs_locations_server4 entries. The precise manner in which this
target location is specified depends on the value of the target location is specified depends on the value of the
FSLI4IF_VAR_SUB flag within the associated fs_locations_info4 FSLI4IF_VAR_SUB flag within the associated fs_locations_info4
structure. structure.
If this flag is not set, then fli_rootpath simply designates the If this flag is not set, then fli_rootpath simply designates the
location of the target file system within each server's single-server location of the target file system within each server's single-server
namespace just as it does for the rootpath within the fs_location4 namespace just as it does for the rootpath within the fs_location4
structure. When this bit is set, however, component entries of a structure. When this bit is set, however, component entries of a
certain form are subject to client-specific variable substitution so certain form are subject to client-specific variable substitution so
as to allow a degree of namespace non-uniformity in order to as to allow a degree of namespace non-uniformity in order to
accommodate the selection of client-specific file system targets to accommodate the selection of client-specific file system targets to
adapt to different client architectures or other characteristics. adapt to different client architectures or other characteristics.
When such substitution is in effect a variable beginning with the When such substitution is in effect, a variable beginning with the
string "${" and ending with the string "}" and containing a colon is string "${" and ending with the string "}" and containing a colon is
to be replaced by the client-specific value associated with that to be replaced by the client-specific value associated with that
variable. The string "unknown" should be used by the client when it variable. The string "unknown" should be used by the client when it
has no value for such a variable. The pathname resulting from such has no value for such a variable. The pathname resulting from such
substitutions is used to designate the target file system, so that substitutions is used to designate the target file system, so that
different clients may have different file systems, corresponding to different clients may have different file systems, corresponding to
that location in the multi-server namespace. that location in the multi-server namespace.
As mentioned above, such substituted pathname variables contain a As mentioned above, such substituted pathname variables contain a
colon. The part before the colon is to be a DNS domain name with the colon. The part before the colon is to be a DNS domain name, and the
part after being a case-insensitive alphanumeric string. part after is to be a case-insensitive alphanumeric string.
Where the domain is "ietf.org", only variable names defined in this Where the domain is "ietf.org", only variable names defined in this
document or subsequent standards-track RFC's are subject to such document or subsequent Standards Track RFCs are subject to such
substitution. Organizations are free to use their domain names to substitution. Organizations are free to use their domain names to
create their own sets of client-specific variables, to be subject to create their own sets of client-specific variables, to be subject to
such substitution. In case where such variables are intended to be such substitution. In cases where such variables are intended to be
used more broadly than a single organization, publication of an used more broadly than a single organization, publication of an
informational RFC defining such variables is RECOMMENDED. Informational RFC defining such variables is RECOMMENDED.
The variable ${ietf.org:CPU_ARCH} is used to denote the CPU The variable ${ietf.org:CPU_ARCH} is used to denote that the CPU
architecture object files are compiled. This specification does not architecture object files are compiled. This specification does not
limit the acceptable values (except that they must be valid UTF-8 limit the acceptable values (except that they must be valid UTF-8
strings) but such values as "x86", "x86_64" and "sparc" would be strings), but such values as "x86", "x86_64", and "sparc" would be
expected to be used in line with industry practice. expected to be used in line with industry practice.
The variable ${ietf.org:OS_TYPE} is used to denote the operating The variable ${ietf.org:OS_TYPE} is used to denote the operating
system and thus the kernel and library API's for which code might be system, and thus the kernel and library APIs, for which code might be
compiled. This specification does not limit the acceptable values compiled. This specification does not limit the acceptable values
(except that they must be valid UTF-8 strings) but such values as (except that they must be valid UTF-8 strings), but such values as
"linux" and "freebsd" would be expected to be used in line with "linux" and "freebsd" would be expected to be used in line with
industry practice. industry practice.
The variable ${ietf.org:OS_VERSION} is used to denote the operating The variable ${ietf.org:OS_VERSION} is used to denote the operating
system version and thus the specific details of versioned interfaces system version, and thus the specific details of versioned
for which code might be compiled. This specification does not limit interfaces, for which code might be compiled. This specification
the acceptable values (except that they must be valid UTF-8 strings). does not limit the acceptable values (except that they must be valid
However, combinations of numbers and letters with interspersed dots UTF-8 strings). However, combinations of numbers and letters with
would be expected to be used in line with industry practice, with the interspersed dots would be expected to be used in line with industry
details of the version format depending on the specific value of the practice, with the details of the version format depending on the
variable ${ietf.org:OS_TYPE} with which it is used. specific value of the variable ${ietf.org:OS_TYPE} with which it is
used.
Use of these variable could result in direction of different clients Use of these variables could result in the direction of different
to different file systems on the same server, as appropriate to clients to different file systems on the same server, as appropriate
particular clients. In cases in which the target file systems are to particular clients. In cases in which the target file systems are
located on different servers, a single server could serve as a located on different servers, a single server could serve as a
referral point so that each valid combination of variable values referral point so that each valid combination of variable values
would designate a referral hosted on a single server, with the would designate a referral hosted on a single server, with the
targets of those referrals on a number of different servers. targets of those referrals on a number of different servers.
Because namespace administration is affected by the values selected Because namespace administration is affected by the values selected
to substitute for various variables, clients should provide to substitute for various variables, clients should provide
convenient means of determining what variable substitutions a client convenient means of determining what variable substitutions a client
will implement, as well as, where appropriate, providing means to will implement, as well as, where appropriate, providing means to
control the substitutions to be used. The exact means by which this control the substitutions to be used. The exact means by which this
will be done is outside the scope of this specification. will be done is outside the scope of this specification.
Although variable substitution is most suitable for use in the Although variable substitution is most suitable for use in the
context of referrals, if may be used in the context of replication context of referrals, it may be used in the context of replication
and migration. If it is used in these contexts, the server must and migration. If it is used in these contexts, the server must
ensure that no matter what values the client presents for the ensure that no matter what values the client presents for the
substituted variables, the result is always a valid successor file substituted variables, the result is always a valid successor file
system instance to that from which a transition is occurring, i.e. system instance to that from which a transition is occurring, i.e.,
that the data is identical or represents a later image of a writable that the data is identical or represents a later image of a writable
file system. file system.
Note that when fli_rootpath is a null pathname (that is, one with Note that when fli_rootpath is a null pathname (that is, one with
zero components), the file system designated is at the root of the zero components), the file system designated is at the root of the
specified server, whether the FSLI4IF_VAR_SUB flag within the specified server, whether or not the FSLI4IF_VAR_SUB flag within the
associated fs_locations_info4 structure is set or not. associated fs_locations_info4 structure is set.
11.11. The Attribute fs_status 11.11. The Attribute fs_status
In an environment in which multiple copies of the same basic set of In an environment in which multiple copies of the same basic set of
data are available, information regarding the particular source of data are available, information regarding the particular source of
such data and the relationships among different copies can be very such data and the relationships among different copies can be very
helpful in providing consistent data to applications. helpful in providing consistent data to applications.
enum fs4_status_type { enum fs4_status_type {
STATUS4_FIXED = 1, STATUS4_FIXED = 1,
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the fs4_status reflects that last valid when the file system was the fs4_status reflects that last valid when the file system was
present. present.
The fss_type field indicates the kind of file system image The fss_type field indicates the kind of file system image
represented. This is of particular importance when using the version represented. This is of particular importance when using the version
values to determine appropriate succession of file system images. values to determine appropriate succession of file system images.
When fss_absent is set, and the file system was previously present, When fss_absent is set, and the file system was previously present,
the value of fss_type reflected is that when the file was last the value of fss_type reflected is that when the file was last
present. Five values are distinguished: present. Five values are distinguished:
o STATUS4_FIXED which indicates a read-only image in the sense that o STATUS4_FIXED, which indicates a read-only image in the sense that
it will never change. The possibility is allowed that, as a it will never change. The possibility is allowed that, as a
result of migration or switch to a different image, changed data result of migration or switch to a different image, changed data
can be accessed, but within the confines of this instance, no can be accessed, but within the confines of this instance, no
change is allowed. The client can use this fact to cache change is allowed. The client can use this fact to cache
aggressively. aggressively.
o STATUS4_VERSIONED which indicates that the image, like the o STATUS4_VERSIONED, which indicates that the image, like the
STATUS4_UPDATED case, is updated externally, but it provides a STATUS4_UPDATED case, is updated externally, but it provides a
guarantee that the server will carefully update an associated guarantee that the server will carefully update an associated
version value so that the client can protect itself from a version value so that the client can protect itself from a
situation in which it reads data from one version of the file situation in which it reads data from one version of the file
system, and then later reads data from an earlier version of the system and then later reads data from an earlier version of the
same file system. See below for a discussion of how this can be same file system. See below for a discussion of how this can be
done. done.
o STATUS4_UPDATED which indicates an image that cannot be updated by o STATUS4_UPDATED, which indicates an image that cannot be updated
the user writing to it but may be changed externally, typically by the user writing to it but that may be changed externally,
because it is a periodically updated copy of another writable file typically because it is a periodically updated copy of another
system somewhere else. In this case, version information is not writable file system somewhere else. In this case, version
provided and the client does not have the responsibility of making information is not provided, and the client does not have the
sure that this version only advances upon a file system instance responsibility of making sure that this version only advances upon
transition. In this case, it is the responsibility of the server a file system instance transition. In this case, it is the
to make sure that the data presented after a file system instance responsibility of the server to make sure that the data presented
transition is a proper successor image and includes all changes after a file system instance transition is a proper successor
seen by the client and any change made before all such changes. image and includes all changes seen by the client and any change
made before all such changes.
o STATUS4_WRITABLE which indicates that the file system is an actual o STATUS4_WRITABLE, which indicates that the file system is an
writable one. The client need not, of course, actually write to actual writable one. The client need not, of course, actually
the file system, but once it does, it should not accept a write to the file system, but once it does, it should not accept a
transition to anything other than a writable instance of that same transition to anything other than a writable instance of that same
file system. file system.
o STATUS4_REFERRAL which indicates that the file system is question o STATUS4_REFERRAL, which indicates that the file system in question
is absent and has never been present on this server. is absent and has never been present on this server.
Note that in the STATUS4_UPDATED and STATUS4_VERSIONED cases, the Note that in the STATUS4_UPDATED and STATUS4_VERSIONED cases, the
server is responsible for the appropriate handling of locks that are server is responsible for the appropriate handling of locks that are
inconsistent with external changes to delegations. If a server gives inconsistent with external changes to delegations. If a server gives
out delegations, they SHOULD be recalled before an inconsistent out delegations, they SHOULD be recalled before an inconsistent
change made to data, and MUST be revoked if this is not possible. change is made to the data, and MUST be revoked if this is not
Similarly, if an open is inconsistent with data that is changed (the possible. Similarly, if an OPEN is inconsistent with data that is
open denies WRITE and the data is changed), that lock SHOULD be changed (the OPEN has OPEN4_SHARE_DENY_WRITE/OPEN4_SHARE_DENY_BOTH
considered administratively revoked. and the data is changed), that OPEN SHOULD be considered
administratively revoked.
The opaque strings fss_source and fss_current provide a way of The opaque strings fss_source and fss_current provide a way of
presenting information about the source of the file system image presenting information about the source of the file system image
being present. It is not intended that client do anything with this being present. It is not intended that the client do anything with
information other than make it available to administrative tools. It this information other than make it available to administrative
is intended that this information be helpful when researching tools. It is intended that this information be helpful when
possible problems with a file system image that might arise when it researching possible problems with a file system image that might
is unclear if the correct image is being accessed and if not, how arise when it is unclear if the correct image is being accessed and,
that image came to be made. This kind of diagnostic information will if not, how that image came to be made. This kind of diagnostic
be helpful, if, as seems likely, copies of file systems are made in information will be helpful, if, as seems likely, copies of file
many different ways (e.g. simple user-level copies, file system-level systems are made in many different ways (e.g., simple user-level
point-in-time copies, clones of the underlying storage), under a copies, file-system-level point-in-time copies, clones of the
variety of administrative arrangements. In such environments, underlying storage), under a variety of administrative arrangements.
determining how a given set of data was constructed can be very In such environments, determining how a given set of data was
helpful in resolving problems. constructed can be very helpful in resolving problems.
The opaque string fss_source is used to indicate the source of a The opaque string fss_source is used to indicate the source of a
given file system with the expectation that tools capable of creating given file system with the expectation that tools capable of creating
a file system image propagate this information, when that is a file system image propagate this information, when possible. It is
possible. It is understood that this may not always be possible understood that this may not always be possible since a user-level
since a user-level copy may be thought of as creating a new data set copy may be thought of as creating a new data set and the tools used
and the tools used may have no mechanism to propagate this data. may have no mechanism to propagate this data. When a file system is
When a file system is initially created, it is desirable to associate initially created, it is desirable to associate with it data
with it data regarding how the file system was created, where it was regarding how the file system was created, where it was created, who
created, by whom, etc. Making this information available in this created it, etc. Making this information available in this attribute
attribute in a human-readable string form will be helpful for in a human-readable string will be helpful for applications and
applications and system administrators and also serves to make it system administrators and will also serve to make it available when
available when the original file system is used to make subsequent the original file system is used to make subsequent copies.
copies.
The opaque string fss_current should provide whatever information is The opaque string fss_current should provide whatever information is
available about the source of the current copy. Such information as available about the source of the current copy. Such information
the tool creating it, any relevant parameters to that tool, the time includes the tool creating it, any relevant parameters to that tool,
at which the copy was done, the user making the change, the server on the time at which the copy was done, the user making the change, the
which the change was made, etc. All information should be in a server on which the change was made, etc. All information should be
human-readable string form. in a human-readable string.
The field fss_age provides an indication of how out-of-date the file The field fss_age provides an indication of how out-of-date the file
system currently is with respect to its ultimate data source (in case system currently is with respect to its ultimate data source (in case
of cascading data updates). This complements the fls_currency field of cascading data updates). This complements the fls_currency field
of fs_locations_server4 (see Section 11.10) in the following way: the of fs_locations_server4 (see Section 11.10) in the following way: the
information in fls_currency gives a bound for how out of date the information in fls_currency gives a bound for how out of date the
data in a file system might typically get, while the value in fss_age data in a file system might typically get, while the value in fss_age
gives a bound on how out of date that data actually is. Negative gives a bound on how out-of-date that data actually is. Negative
values imply that no information is available. A zero means that values imply that no information is available. A zero means that
this data is known to be current. A positive value means that this this data is known to be current. A positive value means that this
data is known to be no older than that number of seconds with respect data is known to be no older than that number of seconds with respect
to the ultimate data source. Using this value, the client may be to the ultimate data source. Using this value, the client may be
able to decide that a data copy is too old, so that it may search for able to decide that a data copy is too old, so that it may search for
a newer version to use. a newer version to use.
The fss_version field provides a version identification, in the form The fss_version field provides a version identification, in the form
of a time value, such that successive versions always have later time of a time value, such that successive versions always have later time
values. When the fs_type is anything other than STATUS4_VERSIONED, values. When the fs_type is anything other than STATUS4_VERSIONED,
the server may provide such a value but there is no guarantee as to the server may provide such a value, but there is no guarantee as to
its validity and clients will not use it except to provide additional its validity and clients will not use it except to provide additional
information to add to fss_source and fss_current. information to add to fss_source and fss_current.
When fss_type is STATUS4_VERSIONED, servers SHOULD provide a value of When fss_type is STATUS4_VERSIONED, servers SHOULD provide a value of
version which progresses monotonically whenever any new version of fss_version that progresses monotonically whenever any new version of
the data is established. This allows the client, if reliable image the data is established. This allows the client, if reliable image
progression is important to it, to fetch this attribute as part of progression is important to it, to fetch this attribute as part of
each COMPOUND where data or metadata from the file system is used. each COMPOUND where data or metadata from the file system is used.
When it is important to the client to make sure that only valid When it is important to the client to make sure that only valid
successor images are accepted, it must make sure that it does not successor images are accepted, it must make sure that it does not
read data or metadata from the file system without updating its sense read data or metadata from the file system without updating its sense
of the current state of the image, to avoid the possibility that the of the current state of the image. This is to avoid the possibility
fs_status which the client holds will be one for an earlier image, that the fs_status that the client holds will be one for an earlier
and so accept a new file system instance which is later than that but image, which would cause the client to accept a new file system
still earlier than updated data read by the client. instance that is later than that but still earlier than the updated
data read by the client.
In order to do this reliably, it must do a GETATTR of the fs_status In order to accept valid images reliably, the client must do a
attribute that follows any interrogation of data or metadata within GETATTR of the fs_status attribute that follows any interrogation of
the file system in question. Often this is most conveniently done by data or metadata within the file system in question. Often this is
appending such a GETATTR after all other operations that reference a most conveniently done by appending such a GETATTR after all other
given file system. When errors occur between reading file system operations that reference a given file system. When errors occur
data and performing such a GETATTR, care must be exercised to make between reading file system data and performing such a GETATTR, care
sure that the data in question is not used before obtaining the must be exercised to make sure that the data in question is not used
proper fs_status value. In this connection, when an OPEN is done before obtaining the proper fs_status value. In this connection,
within such a versioned file system and the associated GETATTR of when an OPEN is done within such a versioned file system and the
fs_status is not successfully completed, the open file in question associated GETATTR of fs_status is not successfully completed, the
must not be accessed until that fs_status is fetched. open file in question must not be accessed until that fs_status is
fetched.
The procedure above will ensure that before using any data from the The procedure above will ensure that before using any data from the
file system the client has in hand a newly-fetched current version of file system the client has in hand a newly-fetched current version of
the file system image. Multiple values for multiple requests in the file system image. Multiple values for multiple requests in
flight can be resolved by assembling them into the required partial flight can be resolved by assembling them into the required partial
order (and the elements should form a total order within it) and order (and the elements should form a total order within the partial
using the last. The client may then, when switching among file order) and using the last. The client may then, when switching among
system instances, decline to use an instance which does not have an file system instances, decline to use an instance that does not have
fss_type of STATUS4_VERSIONED or whose fss_version field is earlier an fss_type of STATUS4_VERSIONED or whose fss_version field is
than the last one obtained from the predecessor file system instance. earlier than the last one obtained from the predecessor file system
instance.
12. Parallel NFS (pNFS) 12. Parallel NFS (pNFS)
12.1. Introduction 12.1. Introduction
pNFS is an OPTIONAL feature within NFSv4.1; the pNFS feature set pNFS is an OPTIONAL feature within NFSv4.1; the pNFS feature set
allows direct client access to the storage devices containing file allows direct client access to the storage devices containing file
data. When file data for a single NFSv4 server is stored on multiple data. When file data for a single NFSv4 server is stored on multiple
and/or higher throughput storage devices (by comparison to the and/or higher-throughput storage devices (by comparison to the
server's throughput capability), the result can be significantly server's throughput capability), the result can be significantly
better file access performance. The relationship among multiple better file access performance. The relationship among multiple
clients, a single server, and multiple storage devices for pNFS clients, a single server, and multiple storage devices for pNFS
(server and clients have access to all storage devices) is shown in (server and clients have access to all storage devices) is shown in
Figure 1. Figure 1.
+-----------+ +-----------+
|+-----------+ +-----------+ |+-----------+ +-----------+
||+-----------+ | | ||+-----------+ | |
||| | NFSv4.1 + pNFS | | ||| | NFSv4.1 + pNFS | |
skipping to change at page 277, line 27 skipping to change at page 277, line 27
||+----------------||+-----------+ Control | ||+----------------||+-----------+ Control |
|+-----------------||| | Protocol| |+-----------------||| | Protocol|
+------------------+|| Storage |------------+ +------------------+|| Storage |------------+
+| Devices | +| Devices |
+-----------+ +-----------+
Figure 1 Figure 1
In this model, the clients, server, and storage devices are In this model, the clients, server, and storage devices are
responsible for managing file access. This is in contrast to NFSv4 responsible for managing file access. This is in contrast to NFSv4
without pNFS where it is primarily the server's responsibility; some without pNFS, where it is primarily the server's responsibility; some
of this responsibility may be delegated to the client under strictly of this responsibility may be delegated to the client under strictly
specified conditions. See Section 12.2.6 for a discussion of the specified conditions. See Section 12.2.5 for a discussion of the
Control Protocol. See Section 12.2.5 for a discussion of the Storage Storage Protocol. See Section 12.2.6 for a discussion of the Control
Protocol. Protocol.
pNFS takes the form of OPTIONAL operations that manage protocol pNFS takes the form of OPTIONAL operations that manage protocol
objects called 'layouts' (Section 12.2.7) which contain a byte-range objects called 'layouts' (Section 12.2.7) that contain a byte-range
and storage location information. The layout is managed in a similar and storage location information. The layout is managed in a similar
fashion as NFSv4.1 data delegations. For example, the layout is fashion as NFSv4.1 data delegations. For example, the layout is
leased, recallable and revocable. However, layouts are distinct leased, recallable, and revocable. However, layouts are distinct
abstractions and are manipulated with new operations. When a client abstractions and are manipulated with new operations. When a client
holds a layout, it is granted the ability to directly access the holds a layout, it is granted the ability to directly access the
byte-range at the storage location specified in the layout. byte-range at the storage location specified in the layout.
There are interactions between layouts and other NFSv4.1 abstractions There are interactions between layouts and other NFSv4.1 abstractions
such as data delegations and byte-range locking. Delegation issues such as data delegations and byte-range locking. Delegation issues
are discussed in Section 12.5.5. Byte range locking issues are are discussed in Section 12.5.5. Byte-range locking issues are
discussed in Section 12.2.9 and Section 12.5.1. discussed in Sections 12.2.9 and 12.5.1.
12.2. pNFS Definitions 12.2. pNFS Definitions
NFSv4.1's pNFS feature provides parallel data access to a file system NFSv4.1's pNFS feature provides parallel data access to a file system
that stripes its content across multiple storage servers. The first that stripes its content across multiple storage servers. The first
instantiation of pNFS, as part of NFSv4.1, separates the file system instantiation of pNFS, as part of NFSv4.1, separates the file system
protocol processing into two parts: metadata processing and data protocol processing into two parts: metadata processing and data
processing. Data consist of the contents of regular files which are processing. Data consist of the contents of regular files that are
striped across storage servers. Data striping occurs in at least two striped across storage servers. Data striping occurs in at least two
ways: on a file-by-file basis, and within sufficiently large files, ways: on a file-by-file basis and, within sufficiently large files,
on a block-by-block basis. In contrast, striped access to metadata on a block-by-block basis. In contrast, striped access to metadata
by pNFS clients is not provided in NFSv4.1, even though the file by pNFS clients is not provided in NFSv4.1, even though the file
system back end of a pNFS server might stripe metadata. Metadata system back end of a pNFS server might stripe metadata. Metadata
consist of everything else, including the contents of non-regular consist of everything else, including the contents of non-regular
files (e.g. directories); see Section 12.2.1. The metadata files (e.g., directories); see Section 12.2.1. The metadata
functionality is implemented by an NFSv4.1 server that supports pNFS functionality is implemented by an NFSv4.1 server that supports pNFS
and the operations described in (Section 18); such a server is called and the operations described in Section 18; such a server is called a
a metadata server (Section 12.2.2). metadata server (Section 12.2.2).
The data functionality is implemented by one or more storage devices, The data functionality is implemented by one or more storage devices,
each of which are accessed by the client via a storage protocol. A each of which are accessed by the client via a storage protocol. A
subset (defined in Section 13.6) of NFSv4.1 is one such storage subset (defined in Section 13.6) of NFSv4.1 is one such storage
protocol. New terms are introduced to the NFSv4.1 nomenclature and protocol. New terms are introduced to the NFSv4.1 nomenclature and
existing terms are clarified to allow for the description of the pNFS existing terms are clarified to allow for the description of the pNFS
feature. feature.
12.2.1. Metadata 12.2.1. Metadata
Information about a file system object, such as its name, location Information about a file system object, such as its name, location
within the namespace, owner, ACL and other attributes. Metadata may within the namespace, owner, ACL, and other attributes. Metadata may
also include storage location information and this will vary based on also include storage location information, and this will vary based
the underlying storage mechanism that is used. on the underlying storage mechanism that is used.
12.2.2. Metadata Server 12.2.2. Metadata Server
An NFSv4.1 server which supports the pNFS feature. A variety of An NFSv4.1 server that supports the pNFS feature. A variety of
architectural choices exists for the metadata server and its use of architectural choices exist for the metadata server and its use of
file system information held at the server. Some servers may contain file system information held at the server. Some servers may contain
metadata only for file objects residing at the metadata server while metadata only for file objects residing at the metadata server, while
the file data resides on associated storage devices. Other metadata the file data resides on associated storage devices. Other metadata
servers may hold both metadata and a varying degree of file data. servers may hold both metadata and a varying degree of file data.
12.2.3. pNFS Client 12.2.3. pNFS Client
An NFSv4.1 client that supports pNFS operations and supports at least An NFSv4.1 client that supports pNFS operations and supports at least
one storage protocol for performing I/O to storage devices. one storage protocol for performing I/O to storage devices.
12.2.4. Storage Device 12.2.4. Storage Device
A storage device stores a regular file's data, but leaves metadata A storage device stores a regular file's data, but leaves metadata
management to the metadata server. A storage device could be another management to the metadata server. A storage device could be another
NFSv4.1 server, an object storage device (OSD), a block device NFSv4.1 server, an object-based storage device (OSD), a block device
accessed over a SAN (e.g., either FiberChannel or iSCSI SAN), or some accessed over a System Area Network (SAN, e.g., either FiberChannel
other entity. or iSCSI SAN), or some other entity.
12.2.5. Storage Protocol 12.2.5. Storage Protocol
As noted in the Figure 1, the storage protocol is the method used by As noted in Figure 1, the storage protocol is the method used by the
the client to store and retrieve data directly from the storage client to store and retrieve data directly from the storage devices.
devices.
The NFSv4.1 pNFS feature has been structured to allow for a variety The NFSv4.1 pNFS feature has been structured to allow for a variety
of storage protocols to be defined and used. One example storage of storage protocols to be defined and used. One example storage
protocol is NFSv4.1 itself (as documented in Section 13). Other protocol is NFSv4.1 itself (as documented in Section 13). Other
options for the storage protocol are described elsewhere and include: options for the storage protocol are described elsewhere and include:
o Block/volume protocols such as iSCSI ([48]), and FCP ([49]). The o Block/volume protocols such as Internet SCSI (iSCSI) [48] and FCP
block/volume protocol support can be independent of the addressing [49]. The block/volume protocol support can be independent of the
structure of the block/volume protocol used, allowing more than addressing structure of the block/volume protocol used, allowing
one protocol to access the same file data and enabling more than one protocol to access the same file data and enabling
extensibility to other block/volume protocols. See [41] for a extensibility to other block/volume protocols. See [41] for a
layout specification that allows pNFS to use block/volume storage layout specification that allows pNFS to use block/volume storage
protocols. protocols.
o Object protocols such as OSD over iSCSI or Fibre Channel [50]. o Object protocols such as OSD over iSCSI or Fibre Channel [50].
See [40] for a layout specification that allows pNFS to use object See [40] for a layout specification that allows pNFS to use object
storage protocols. storage protocols.
It is possible that various storage protocols are available to both It is possible that various storage protocols are available to both
client and server and it may be possible that a client and server do client and server and it may be possible that a client and server do
not have a matching storage protocol available to them. Because of not have a matching storage protocol available to them. Because of
this, the pNFS server MUST support normal NFSv4.1 access to any file this, the pNFS server MUST support normal NFSv4.1 access to any file
accessible by the pNFS feature; this will allow for continued accessible by the pNFS feature; this will allow for continued
interoperability between an NFSv4.1 client and server. interoperability between an NFSv4.1 client and server.
12.2.6. Control Protocol 12.2.6. Control Protocol
As noted in the Figure 1, the control protocol is used by the As noted in Figure 1, the control protocol is used by the exported
exported file system between the metadata server and storage devices. file system between the metadata server and storage devices.
Specification of such protocols is outside the scope of the NFSv4.1 Specification of such protocols is outside the scope of the NFSv4.1
protocol. Such control protocols would be used to control activities protocol. Such control protocols would be used to control activities
such as the allocation and deallocation of storage, the management of such as the allocation and deallocation of storage, the management of
state required by the storage devices to perform client access state required by the storage devices to perform client access
control, and, depending on the storage protocol, the enforcement of control, and, depending on the storage protocol, the enforcement of
authentication and authorization so that restrictions that would be authentication and authorization so that restrictions that would be
enforced by the metadata server are also enforced by the storage enforced by the metadata server are also enforced by the storage
device. device.
A particular control protocol is not REQUIRED by NFSv4.1 but A particular control protocol is not REQUIRED by NFSv4.1 but
requirements are placed on the control protocol for maintaining requirements are placed on the control protocol for maintaining
attributes like modify time, the change attribute, and the end-of- attributes like modify time, the change attribute, and the end-of-
file (EOF) position. Note that if pNFS is layered over a clustered, file (EOF) position. Note that if pNFS is layered over a clustered,
parallel file system (e.g. PVFS [51]), the mechanisms that enable parallel file system (e.g., PVFS [51]), the mechanisms that enable
clustering and parallelism in that file system can be considered the clustering and parallelism in that file system can be considered the
control protocol. control protocol.
12.2.7. Layout Types 12.2.7. Layout Types
A layout describes the mapping of a file's data to the storage A layout describes the mapping of a file's data to the storage
devices that hold the data. A layout is said to belong to a specific devices that hold the data. A layout is said to belong to a specific
layout type (data type layouttype4, see Section 3.3.13). The layout layout type (data type layouttype4, see Section 3.3.13). The layout
type allows for variants to handle different storage protocols, such type allows for variants to handle different storage protocols, such
as those associated with block/volume [41], object [40], and file as those associated with block/volume [41], object [40], and file
(Section 13) layout types. A metadata server, along with its control (Section 13) layout types. A metadata server, along with its control
protocol, MUST support at least one layout type. A private sub-range protocol, MUST support at least one layout type. A private sub-range
of the layout type name space is also defined. Values from the of the layout type name space is also defined. Values from the
private layout type range MAY be used for internal testing or private layout type range MAY be used for internal testing or
experimentation (see Section 3.3.13). experimentation (see Section 3.3.13).
As an example, the organization of the file layout type could be an As an example, the organization of the file layout type could be an
array of tuples (e.g., device ID, filehandle), along with a array of tuples (e.g., device ID, filehandle), along with a
definition of how the data is stored across the devices (e.g., definition of how the data is stored across the devices (e.g.,
striping). A block/volume layout might be an array of tuples that striping). A block/volume layout might be an array of tuples that
store <device ID, block_number, block count> along with information store <device ID, block number, block count> along with information
about block size and the associated file offset of the block number. about block size and the associated file offset of the block number.
An object layout might be an array of tuples <device ID, object ID> An object layout might be an array of tuples <device ID, object ID>
and an additional structure (i.e., the aggregation map) that defines and an additional structure (i.e., the aggregation map) that defines
how the logical byte sequence of the file data is serialized into the how the logical byte sequence of the file data is serialized into the
different objects. Note that the actual layouts are typically more different objects. Note that the actual layouts are typically more
complex than these simple expository examples. complex than these simple expository examples.
Requests for pNFS-related operations will often specify a layout Requests for pNFS-related operations will often specify a layout
type. Examples of such operations are GETDEVICEINFO and LAYOUTGET. type. Examples of such operations are GETDEVICEINFO and LAYOUTGET.
The response for these operations will include structures such a The response for these operations will include structures such as a
device_addr4 or a layout4, each of which includes a layout type device_addr4 or a layout4, each of which includes a layout type
within it. The layout type sent by the server MUST always be the within it. The layout type sent by the server MUST always be the
same one requested by the client. When a server sends a response same one requested by the client. When a server sends a response
that includes a different layout type, the client SHOULD ignore the that includes a different layout type, the client SHOULD ignore the
response and behave as if the server had returned an error response. response and behave as if the server had returned an error response.
12.2.8. Layout 12.2.8. Layout
A layout defines how a file's data is organized on one or more A layout defines how a file's data is organized on one or more
storage devices. There are many potential layout types; each of the storage devices. There are many potential layout types; each of the
layout types are differentiated by the storage protocol used to layout types are differentiated by the storage protocol used to
access data and in the aggregation scheme that lays out the file data access data and by the aggregation scheme that lays out the file data
on the underlying storage devices. A layout is precisely identified on the underlying storage devices. A layout is precisely identified
by the following tuple: <client ID, filehandle, layout type, iomode, by the tuple <client ID, filehandle, layout type, iomode, range>,
range>; where filehandle refers to the filehandle of the file on the where filehandle refers to the filehandle of the file on the metadata
metadata server. server.
It is important to define when layouts overlap and/or conflict with It is important to define when layouts overlap and/or conflict with
each other. For two layouts with overlapping byte ranges to actually each other. For two layouts with overlapping byte-ranges to actually
overlap each other, both layouts must be of the same layout type, overlap each other, both layouts must be of the same layout type,
correspond to the same filehandle, and have the same iomode. Layouts correspond to the same filehandle, and have the same iomode. Layouts
conflict when they overlap and differ in the content of the layout conflict when they overlap and differ in the content of the layout
(i.e., the storage device/file mapping parameters differ). Note that (i.e., the storage device/file mapping parameters differ). Note that
differing iomodes do not lead to conflicting layouts. It is differing iomodes do not lead to conflicting layouts. It is
permissible for layouts with different iomodes, pertaining to the permissible for layouts with different iomodes, pertaining to the
same byte range, to be held by the same client. An example of this same byte-range, to be held by the same client. An example of this
would be copy-on-write functionality for a block/volume layout type. would be copy-on-write functionality for a block/volume layout type.
12.2.9. Layout Iomode 12.2.9. Layout Iomode
The layout iomode (data type layoutiomode4, see Section 3.3.20) The layout iomode (data type layoutiomode4, see Section 3.3.20)
indicates to the metadata server the client's intent to perform indicates to the metadata server the client's intent to perform
either just read operations or a mixture of I/O possibly containing either just READ operations or a mixture containing READ and WRITE
read and write operations. For certain layout types, it is useful operations. For certain layout types, it is useful for a client to
for a client to specify this intent at the time it sends LAYOUTGET specify this intent at the time it sends LAYOUTGET (Section 18.43).
(Section 18.43). For example, block/volume based protocols, block For example, for block/volume-based protocols, block allocation could
allocation could occur when a READ/WRITE iomode is specified. A occur when a LAYOUTIOMODE4_RW iomode is specified. A special
special LAYOUTIOMODE4_ANY iomode is defined and can only be used for LAYOUTIOMODE4_ANY iomode is defined and can only be used for
LAYOUTRETURN and CB_LAYOUTRECALL, not for LAYOUTGET. It specifies LAYOUTRETURN and CB_LAYOUTRECALL, not for LAYOUTGET. It specifies
that layouts pertaining to both READ and READ/WRITE iomodes are being that layouts pertaining to both LAYOUTIOMODE4_READ and
returned or recalled, respectively. LAYOUTIOMODE4_RW iomodes are being returned or recalled,
respectively.
A storage device may validate I/O with regard to the iomode; this is A storage device may validate I/O with regard to the iomode; this is
dependent upon storage device implementation and layout type. Thus, dependent upon storage device implementation and layout type. Thus,
if the client's layout iomode is inconsistent with the I/O being if the client's layout iomode is inconsistent with the I/O being
performed, the storage device may reject the client's I/O with an performed, the storage device may reject the client's I/O with an
error indicating a new layout with the correct iomode should be error indicating that a new layout with the correct iomode should be
obtained via LAYOUTGET. For example, if a client gets a layout with obtained via LAYOUTGET. For example, if a client gets a layout with
a READ iomode and performs a WRITE to a storage device, the storage a LAYOUTIOMODE4_READ iomode and performs a WRITE to a storage device,
device is allowed to reject that WRITE. the storage device is allowed to reject that WRITE.
The use of the layout iomode does not conflict with OPEN share modes The use of the layout iomode does not conflict with OPEN share modes
or byte-range lock requests; open mode and lock conflicts are or byte-range LOCK operations; open share mode and byte-range lock
enforced as they are without the use of pNFS, and are logically conflicts are enforced as they are without the use of pNFS and are
separate from the pNFS layout level. Open modes and locks are the logically separate from the pNFS layout level. Open share modes and
preferred method for restricting user access to data files. For byte-range locks are the preferred method for restricting user access
example, an OPEN of read, deny-write does not conflict with a to data files. For example, an OPEN of OPEN4_SHARE_ACCESS_WRITE does
LAYOUTGET containing an iomode of READ/WRITE performed by another not conflict with a LAYOUTGET containing an iomode of
client. Applications that depend on writing into the same file LAYOUTIOMODE4_RW performed by another client. Applications that
concurrently may use byte-range locking to serialize their accesses. depend on writing into the same file concurrently may use byte-range
locking to serialize their accesses.
12.2.10. Device IDs 12.2.10. Device IDs
The device ID (data type deviceid4, see Section 3.3.14) identifies a The device ID (data type deviceid4, see Section 3.3.14) identifies a
group of storage devices. The scope of a device ID is the pair group of storage devices. The scope of a device ID is the pair
<client ID, layout type>. In practice, a significant amount of <client ID, layout type>. In practice, a significant amount of
information may be required to fully address a storage device. information may be required to fully address a storage device.
Rather than embedding all such information in a layout, layouts embed Rather than embedding all such information in a layout, layouts embed
device IDs. The NFSv4.1 operation GETDEVICEINFO (Section 18.40) is device IDs. The NFSv4.1 operation GETDEVICEINFO (Section 18.40) is
used to retrieve the complete address information (including all used to retrieve the complete address information (including all
device addresses for the device ID) regarding the storage device device addresses for the device ID) regarding the storage device
according to its layout type and device ID. For example, the address according to its layout type and device ID. For example, the address
of an NFSv4.1 data server or of an object storage device could be an of an NFSv4.1 data server or of an object-based storage device could
IP address and port. The address of a block storage device could be be an IP address and port. The address of a block storage device
a volume label. could be a volume label.
Clients cannot expect the mapping between a device ID and its storage Clients cannot expect the mapping between a device ID and its storage
device address(es) to persist across metadata server restart. See device address(es) to persist across metadata server restart. See
Section 12.7.4 for a description of how recovery works in that Section 12.7.4 for a description of how recovery works in that
situation. situation.
A device ID lives as long as there is a layout referring to the A device ID lives as long as there is a layout referring to the
device ID. If there are no layouts referring to the device ID, the device ID. If there are no layouts referring to the device ID, the
server is free to delete the device ID any time. Once a device ID is server is free to delete the device ID any time. Once a device ID is
deleted by the server, the server MUST NOT reuse the device ID for deleted by the server, the server MUST NOT reuse the device ID for
the same layout type and client ID again. This requirement is the same layout type and client ID again. This requirement is
feasible because the device ID is 16 bytes long, leaving sufficient feasible because the device ID is 16 bytes long, leaving sufficient
room to store a generation number if server's implementation requires room to store a generation number if the server's implementation
most of the rest of the device ID's content to be reused. This requires most of the rest of the device ID's content to be reused.
requirement is necessary because otherwise the race conditions This requirement is necessary because otherwise the race conditions
between asynchronous notification of device ID addition and deletion between asynchronous notification of device ID addition and deletion
would be too difficult to sort out. would be too difficult to sort out.
Device ID to device address mappings are not leased, and can be Device ID to device address mappings are not leased, and can be
changed at any time. (Note that while device ID to device address changed at any time. (Note that while device ID to device address
mappings are likely to change after the metadata server restarts, the mappings are likely to change after the metadata server restarts, the
server is not required to change the mappings.) A server has two server is not required to change the mappings.) A server has two
choices for changing mappings. It can recall all layouts referring choices for changing mappings. It can recall all layouts referring
to the device ID or it can use a notification mechanism. to the device ID or it can use a notification mechanism.
The NFSv4.1 protocol has no optimal way to recall all layouts that The NFSv4.1 protocol has no optimal way to recall all layouts that
referred to a particular device ID (unless the server associates a referred to a particular device ID (unless the server associates a
single device ID with a single fsid or a single client ID; in which single device ID with a single fsid or a single client ID; in which
case, CB_LAYOUTRECALL has options for recalling all layouts case, CB_LAYOUTRECALL has options for recalling all layouts
associated with the fsid, client ID pair or just the client ID). associated with the fsid, client ID pair, or just the client ID).
Via a notification mechanism (see Section 20.12), device ID to device Via a notification mechanism (see Section 20.12), device ID to device
address mappings can change over the duration of server operation address mappings can change over the duration of server operation
without recalling or revoking the layouts that refer to device ID. without recalling or revoking the layouts that refer to device ID.
The notification mechanism can also delete a device ID, but only if The notification mechanism can also delete a device ID, but only if
the client has no layouts referring to the device ID. A notification the client has no layouts referring to the device ID. A notification
of a change to a device ID to device address mapping will immediately of a change to a device ID to device address mapping will immediately
or eventually invalidate some or all of the device ID's mappings. or eventually invalidate some or all of the device ID's mappings.
The server MUST support notifications and the client must request The server MUST support notifications and the client must request
them before they can be used. For further information about the them before they can be used. For further information about the
notification types Section 20.12. notification types Section 20.12.
12.3. pNFS Operations 12.3. pNFS Operations
NFSv4.1 has several operations that are needed for pNFS servers, NFSv4.1 has several operations that are needed for pNFS servers,
regardless of layout type or storage protocol. These operations are regardless of layout type or storage protocol. These operations are
all sent to a metadata server and summarized here. While pNFS is an all sent to a metadata server and summarized here. While pNFS is an
OPTIONAL feature, if pNFS is implemented, some operations are OPTIONAL feature, if pNFS is implemented, some operations are
skipping to change at page 283, line 19 skipping to change at page 283, line 23
12.3. pNFS Operations 12.3. pNFS Operations
NFSv4.1 has several operations that are needed for pNFS servers, NFSv4.1 has several operations that are needed for pNFS servers,
regardless of layout type or storage protocol. These operations are regardless of layout type or storage protocol. These operations are
all sent to a metadata server and summarized here. While pNFS is an all sent to a metadata server and summarized here. While pNFS is an
OPTIONAL feature, if pNFS is implemented, some operations are OPTIONAL feature, if pNFS is implemented, some operations are
REQUIRED in order to comply with pNFS. See Section 17. REQUIRED in order to comply with pNFS. See Section 17.
These are the fore channel pNFS operations: These are the fore channel pNFS operations:
GETDEVICEINFO. As noted previously (Section 12.2.10), GETDEVICEINFO GETDEVICEINFO (Section 18.40), as noted previously
(Section 18.40) returns the mapping of device ID to storage device (Section 12.2.10), returns the mapping of device ID to storage
address. device address.
GETDEVICELIST (Section 18.41), allows clients to fetch all device GETDEVICELIST (Section 18.41) allows clients to fetch all device IDs
IDs for a specific file system. for a specific file system.
LAYOUTGET (Section 18.43) is used by a client to get a layout for a LAYOUTGET (Section 18.43) is used by a client to get a layout for a
file. file.
LAYOUTCOMMIT (Section 18.42) is used to inform the metadata server LAYOUTCOMMIT (Section 18.42) is used to inform the metadata server
of the client's intent to commit data which has been written to of the client's intent to commit data that has been written to the
the storage device; the storage device as originally indicated in storage device (the storage device as originally indicated in the
the return value of LAYOUTGET. return value of LAYOUTGET).
LAYOUTRETURN (Section 18.44) is used to return layouts for a file, LAYOUTRETURN (Section 18.44) is used to return layouts for a file, a
an FSID and for client ID. file system ID (FSID), or a client ID.
These are the backchannel pNFS operations: These are the backchannel pNFS operations:
CB_LAYOUTRECALL (Section 20.3) recalls a layout or all layouts CB_LAYOUTRECALL (Section 20.3) recalls a layout, all layouts
belonging to a file system, or all layouts belonging to a client belonging to a file system, or all layouts belonging to a client
ID. ID.
CB_RECALL_ANY (Section 20.6), tells a client that it needs to return CB_RECALL_ANY (Section 20.6) tells a client that it needs to return
some number of recallable objects, including layouts, to the some number of recallable objects, including layouts, to the
metadata server. metadata server.
CB_RECALLABLE_OBJ_AVAIL (Section 20.7) tells a client that a CB_RECALLABLE_OBJ_AVAIL (Section 20.7) tells a client that a
recallable object that it was denied (in case of pNFS, a layout, recallable object that it was denied (in case of pNFS, a layout
denied by LAYOUTGET) due to resource exhaustion, is now available. denied by LAYOUTGET) due to resource exhaustion is now available.
CB_NOTIFY_DEVICEID (Section 20.12) Notifies the client of changes to CB_NOTIFY_DEVICEID (Section 20.12) notifies the client of changes to
device IDs. device IDs.
12.4. pNFS Attributes 12.4. pNFS Attributes
A number of attributes specific to pNFS are listed and described in A number of attributes specific to pNFS are listed and described in
Section 5.12 Section 5.12.
12.5. Layout Semantics 12.5. Layout Semantics
12.5.1. Guarantees Provided by Layouts 12.5.1. Guarantees Provided by Layouts
Layouts grant to the client the ability to access data located at a Layouts grant to the client the ability to access data located at a
storage device with the appropriate storage protocol. The client is storage device with the appropriate storage protocol. The client is
guaranteed the layout will be recalled when one of two things occur; guaranteed the layout will be recalled when one of two things occur:
either a conflicting layout is requested or the state encapsulated by either a conflicting layout is requested or the state encapsulated by
the layout becomes invalid and this can happen when an event directly the layout becomes invalid (this can happen when an event directly or
or indirectly modifies the layout. When a layout is recalled and indirectly modifies the layout). When a layout is recalled and
returned by the client, the client continues with the ability to returned by the client, the client continues with the ability to
access file data with normal NFSv4.1 operations through the metadata access file data with normal NFSv4.1 operations through the metadata
server. Only the ability to access the storage devices is affected. server. Only the ability to access the storage devices is affected.
The requirement of NFSv4.1, that all user access rights MUST be The requirement of NFSv4.1 that all user access rights MUST be
obtained through the appropriate open, lock, and access operations, obtained through the appropriate OPEN, LOCK, and ACCESS operations is
is not modified with the existence of layouts. Layouts are provided not modified with the existence of layouts. Layouts are provided to
to NFSv4.1 clients and user access still follows the rules of the NFSv4.1 clients, and user access still follows the rules of the
protocol as if they did not exist. It is a requirement that for a protocol as if they did not exist. It is a requirement that for a
client to access a storage device, a layout must be held by the client to access a storage device, a layout must be held by the
client. If a storage device receives an I/O for a byte range for client. If a storage device receives an I/O request for a byte-range
which the client does not hold a layout, the storage device SHOULD for which the client does not hold a layout, the storage device
reject that I/O request. Note that the act of modifying a file for SHOULD reject that I/O request. Note that the act of modifying a
which a layout is held, does not necessarily conflict with the file for which a layout is held does not necessarily conflict with
holding of the layout that describes the file being modified. the holding of the layout that describes the file being modified.
Therefore, it is the requirement of the storage protocol or layout Therefore, it is the requirement of the storage protocol or layout
type that determines the necessary behavior. For example, block/ type that determines the necessary behavior. For example, block/
volume layout types require that the layout's iomode agree with the volume layout types require that the layout's iomode agree with the
type of I/O being performed. type of I/O being performed.
Depending upon the layout type and storage protocol in use, storage Depending upon the layout type and storage protocol in use, storage
device access permissions may be granted by LAYOUTGET and may be device access permissions may be granted by LAYOUTGET and may be
encoded within the type-specific layout. For an example of storage encoded within the type-specific layout. For an example of storage
device access permissions, see an object based protocol such as [50]. device access permissions, see an object-based protocol such as [50].
If access permissions are encoded within the layout, the metadata If access permissions are encoded within the layout, the metadata
server SHOULD recall the layout when those permissions become invalid server SHOULD recall the layout when those permissions become invalid
for any reason; for example when a file becomes unwritable or for any reason -- for example, when a file becomes unwritable or
inaccessible to a client. Note, clients are still required to inaccessible to a client. Note, clients are still required to
perform the appropriate access operations with open, lock and access perform the appropriate OPEN, LOCK, and ACCESS operations as
as described above. The degree to which it is possible for the described above. The degree to which it is possible for the client
client to circumvent these access operations and the consequences of to circumvent these operations and the consequences of doing so must
doing so must be clearly specified by the individual layout type be clearly specified by the individual layout type specifications.
specifications. In addition, these specifications must be clear In addition, these specifications must be clear about the
about the requirements and non-requirements for the checking requirements and non-requirements for the checking performed by the
performed by the server. server.
In the presence of pNFS functionality, mandatory file locks MUST In the presence of pNFS functionality, mandatory byte-range locks
behave as they would without pNFS. Therefore, if mandatory file MUST behave as they would without pNFS. Therefore, if mandatory file
locks and layouts are provided simultaneously, the storage device locks and layouts are provided simultaneously, the storage device
MUST be able to enforce the mandatory file locks. For example, if MUST be able to enforce the mandatory byte-range locks. For example,
one client obtains a mandatory lock and a second client accesses the if one client obtains a mandatory byte-range lock and a second client
storage device, the storage device MUST appropriately restrict I/O accesses the storage device, the storage device MUST appropriately
for the byte range of the mandatory file lock. If the storage device restrict I/O for the range of the mandatory byte-range lock. If the
is incapable of providing this check in the presence of mandatory storage device is incapable of providing this check in the presence
file locks, the metadata server then MUST NOT grant layouts and of mandatory byte-range locks, then the metadata server MUST NOT
mandatory file locks simultaneously. grant layouts and mandatory byte-range locks simultaneously.
12.5.2. Getting a Layout 12.5.2. Getting a Layout
A client obtains a layout with the LAYOUTGET operation. The metadata A client obtains a layout with the LAYOUTGET operation. The metadata
server will grant layouts of a particular type (e.g., block/volume, server will grant layouts of a particular type (e.g., block/volume,
object, or file). The client selects an appropriate layout type that object, or file). The client selects an appropriate layout type that
the server supports and the client is prepared to use. The layout the server supports and the client is prepared to use. The layout
returned to the client might not exactly match the requested byte returned to the client might not exactly match the requested byte-
range as described in Section 18.43.3. As needed a client may make range as described in Section 18.43.3. As needed a client may send
multiple LAYOUTGET requests; these might result in multiple multiple LAYOUTGET operations; these might result in multiple
overlapping, non-conflicting layouts (see Section 12.2.8). overlapping, non-conflicting layouts (see Section 12.2.8).
In order to get a layout, the client must first have opened the file In order to get a layout, the client must first have opened the file
via the OPEN operation. When a client has no layout on a file, it via the OPEN operation. When a client has no layout on a file, it
MUST present a stateid as returned by OPEN, a delegation stateid, or MUST present an open stateid, a delegation stateid, or a byte-range
a byte-range lock stateid in the loga_stateid argument. A successful lock stateid in the loga_stateid argument. A successful LAYOUTGET
LAYOUTGET result includes a layout stateid. The first successful result includes a layout stateid. The first successful LAYOUTGET
LAYOUTGET processed by the server using a non-layout stateid as an processed by the server using a non-layout stateid as an argument
argument MUST have the "seqid" field of the layout stateid in the MUST have the "seqid" field of the layout stateid in the response set
response set to one. Thereafter, the client MUST use a layout to one. Thereafter, the client MUST use a layout stateid (see
stateid (see Section 12.5.3) on future invocations of LAYOUTGET on Section 12.5.3) on future invocations of LAYOUTGET on the file, and
the file, and the "seqid" MUST NOT be set to zero. Once the layout the "seqid" MUST NOT be set to zero. Once the layout has been
has been retrieved, it can be held across multiple OPEN and CLOSE retrieved, it can be held across multiple OPEN and CLOSE sequences.
sequences. Therefore, a client may hold a layout for a file that is Therefore, a client may hold a layout for a file that is not
not currently open by any user on the client. This allows for the currently open by any user on the client. This allows for the
caching of layouts beyond CLOSE. caching of layouts beyond CLOSE.
The storage protocol used by the client to access the data on the The storage protocol used by the client to access the data on the
storage device is determined by the layout's type. The client is storage device is determined by the layout's type. The client is
responsible for matching the layout type with an available method to responsible for matching the layout type with an available method to
interpret and use the layout. The method for this layout type interpret and use the layout. The method for this layout type
selection is outside the scope of the pNFS functionality. selection is outside the scope of the pNFS functionality.
Although the metadata server is in control of the layout for a file, Although the metadata server is in control of the layout for a file,
the pNFS client can provide hints to the server when a file is opened the pNFS client can provide hints to the server when a file is opened
or created about the preferred layout type and aggregation schemes. or created about the preferred layout type and aggregation schemes.
pNFS introduces a layout_hint (Section 5.12.4) attribute that the pNFS introduces a layout_hint attribute (Section 5.12.4) that the
client can set at file creation time to provide a hint to the server client can set at file creation time to provide a hint to the server
for new files. Setting this attribute separately, after the file has for new files. Setting this attribute separately, after the file has
been created might make it difficult, or impossible, for the server been created might make it difficult, or impossible, for the server
implementation to comply. implementation to comply.
Because the EXCLUSIVE4 createmode4 does not allow the setting of Because the EXCLUSIVE4 createmode4 does not allow the setting of
attributes at file creation time, NFSv4.1 introduces the EXCLUSIVE4_1 attributes at file creation time, NFSv4.1 introduces the EXCLUSIVE4_1
createmode4, which does allow attributes to be set at file creation createmode4, which does allow attributes to be set at file creation
time. In addition, if the session is created with persistent reply time. In addition, if the session is created with persistent reply
caches, EXCLUSIVE4_1 is neither necessary nor allowed. Instead, caches, EXCLUSIVE4_1 is neither necessary nor allowed. Instead,
GUARDED4 both works better and is prescribed. Table 10 in GUARDED4 both works better and is prescribed. Table 10 in
Section 18.16.3, summarizes how a client is allowed to send an Section 18.16.3 summarizes how a client is allowed to send an
exclusive create. exclusive create.
12.5.3. Layout Stateid 12.5.3. Layout Stateid
As with all other stateids, the layout stateid consists of a "seqid" As with all other stateids, the layout stateid consists of a "seqid"
and "other" field. Once a layout stateid is changed, the "other" and "other" field. Once a layout stateid is changed, the "other"
field will stay constant unless the stateid is revoked, or the client field will stay constant unless the stateid is revoked or the client
returns all layouts on the file and the server disposes of the returns all layouts on the file and the server disposes of the
stateid. The "seqid" field is initially set to one, and is never stateid. The "seqid" field is initially set to one, and is never
zero on any NFSv4.1 operation that uses layout stateids, whether it zero on any NFSv4.1 operation that uses layout stateids, whether it
is a fore channel or backchannel operation. After the layout stateid is a fore channel or backchannel operation. After the layout stateid
is established, the server increments by one the value of the "seqid" is established, the server increments by one the value of the "seqid"
in each subsequent LAYOUTGET and LAYOUTRETURN response, and in each in each subsequent LAYOUTGET and LAYOUTRETURN response, and in each
CB_LAYOUTRECALL request. CB_LAYOUTRECALL request.
Given the design goal of pNFS to provide parallelism, the layout Given the design goal of pNFS to provide parallelism, the layout
stateid differs from other stateid types in that the client is stateid differs from other stateid types in that the client is
expected to send LAYOUTGET and LAYOUTRETURN operations in parallel. expected to send LAYOUTGET and LAYOUTRETURN operations in parallel.
The "seqid" value is used by the client to properly sort responses to The "seqid" value is used by the client to properly sort responses to
LAYOUTGET and LAYOUTRETURN. The "seqid" is also used to prevent race LAYOUTGET and LAYOUTRETURN. The "seqid" is also used to prevent race
conditions between LAYOUTGET and CB_LAYOUTRECALL. Given the conditions between LAYOUTGET and CB_LAYOUTRECALL. Given that the
processing rules differ from layout stateids and other stateid types, processing rules differ from layout stateids and other stateid types,
only the pNFS sections of this document should be considered to only the pNFS sections of this document should be considered to
determine proper layout stateid handling. determine proper layout stateid handling.
Once the client receives a layout stateid, it MUST use the correct Once the client receives a layout stateid, it MUST use the correct
"seqid" for subsequent LAYOUTGET or LAYOUTRETURN operations. The "seqid" for subsequent LAYOUTGET or LAYOUTRETURN operations. The
correct "seqid" is defined as the highest "seqid" value from correct "seqid" is defined as the highest "seqid" value from
responses of fully processed LAYOUTGET or LAYOUTRETURN operations or responses of fully processed LAYOUTGET or LAYOUTRETURN operations or
arguments of a fully processed CB_LAYOUTRECALL operation. Since the arguments of a fully processed CB_LAYOUTRECALL operation. Since the
server is incrementing the "seqid" value on each layout operation, server is incrementing the "seqid" value on each layout operation,
skipping to change at page 287, line 30 skipping to change at page 287, line 35
seqid. For CB_LAYOUTRECALL arguments, the client MUST send a seqid. For CB_LAYOUTRECALL arguments, the client MUST send a
response to the recall before using the seqid. The fundamental response to the recall before using the seqid. The fundamental
requirement in client processing is that the "seqid" is used to requirement in client processing is that the "seqid" is used to
provide the order of processing. LAYOUTGET results may be processed provide the order of processing. LAYOUTGET results may be processed
in parallel. LAYOUTRETURN results may be processed in parallel. in parallel. LAYOUTRETURN results may be processed in parallel.
LAYOUTGET and LAYOUTRETURN responses may be processed in parallel as LAYOUTGET and LAYOUTRETURN responses may be processed in parallel as
long as the ranges do not overlap. CB_LAYOUTRECALL request long as the ranges do not overlap. CB_LAYOUTRECALL request
processing MUST be processed in "seqid" order at all times. processing MUST be processed in "seqid" order at all times.
Once a client has no more layouts on a file, the layout stateid is no Once a client has no more layouts on a file, the layout stateid is no
longer valid, and MUST NOT be used. Any attempt to use such a layout longer valid and MUST NOT be used. Any attempt to use such a layout
stateid will result in NFS4ERR_BAD_STATEID. stateid will result in NFS4ERR_BAD_STATEID.
12.5.4. Committing a Layout 12.5.4. Committing a Layout
Allowing for varying storage protocols capabilities, the pNFS Allowing for varying storage protocol capabilities, the pNFS protocol
protocol does not require the metadata server and storage devices to does not require the metadata server and storage devices to have a
have a consistent view of file attributes and data location mappings. consistent view of file attributes and data location mappings. Data
Data location mapping refers to aspects such as which offsets store location mapping refers to aspects such as which offsets store data
data as opposed to storing holes (see Section 13.4.4 for a as opposed to storing holes (see Section 13.4.4 for a discussion).
discussion). Related issues arise for storage protocols where a Related issues arise for storage protocols where a layout may hold
layout may hold provisionally allocated blocks where the allocation provisionally allocated blocks where the allocation of those blocks
of those blocks does not survive a complete restart of both the does not survive a complete restart of both the client and server.
client and server. Because of this inconsistency, it is necessary to Because of this inconsistency, it is necessary to resynchronize the
re-synchronize the client with the metadata server and its storage client with the metadata server and its storage devices and make any
devices and make any potential changes available to other clients. potential changes available to other clients. This is accomplished
This is accomplished by use of the LAYOUTCOMMIT operation. by use of the LAYOUTCOMMIT operation.
The LAYOUTCOMMIT operation is responsible for committing a modified The LAYOUTCOMMIT operation is responsible for committing a modified
layout to the metadata server. The data should be written and layout to the metadata server. The data should be written and
committed to the appropriate storage devices before the LAYOUTCOMMIT committed to the appropriate storage devices before the LAYOUTCOMMIT
occurs. The scope of the LAYOUTCOMMIT operation depends on the occurs. The scope of the LAYOUTCOMMIT operation depends on the
storage protocol in use. It is important to note that the level of storage protocol in use. It is important to note that the level of
synchronization is from the point of view of the client which sent synchronization is from the point of view of the client that sent the
the LAYOUTCOMMIT. The updated state on the metadata server need only LAYOUTCOMMIT. The updated state on the metadata server need only
reflect the state as of the client's last operation previous to the reflect the state as of the client's last operation previous to the
LAYOUTCOMMIT. It is not REQUIRED to maintain a global view that LAYOUTCOMMIT. The metadata server is not REQUIRED to maintain a
accounts for other clients' I/O that may have occurred within the global view that accounts for other clients' I/O that may have
same time frame. occurred within the same time frame.
For block/volume-based layouts, LAYOUTCOMMIT may require updating the For block/volume-based layouts, LAYOUTCOMMIT may require updating the
block list that comprises the file and committing this layout to block list that comprises the file and committing this layout to
stable storage. For file-based layouts synchronization of attributes stable storage. For file-based layouts, synchronization of
between the metadata and storage devices (primarily the size attributes between the metadata and storage devices, primarily the
attribute) is required. size attribute, is required.
The control protocol is free to synchronize the attributes before it The control protocol is free to synchronize the attributes before it
receives a LAYOUTCOMMIT, however upon successful completion of a receives a LAYOUTCOMMIT; however, upon successful completion of a
LAYOUTCOMMIT, state that exists on the metadata server that describes LAYOUTCOMMIT, state that exists on the metadata server that describes
the file MUST be synchronized with the state existing on the storage the file MUST be synchronized with the state that exists on the
devices that comprise that file as of the time of the client's last storage devices that comprise that file as of the client's last sent
sent operation. Thus, a client that queries the size of a file operation. Thus, a client that queries the size of a file between a
between a WRITE to a storage device and the LAYOUTCOMMIT might WRITE to a storage device and the LAYOUTCOMMIT might observe a size
observe a size that does not reflect the actual data written. that does not reflect the actual data written.
The client MUST have a layout in order to send a LAYOUTCOMMIT The client MUST have a layout in order to send a LAYOUTCOMMIT
operation. operation.
12.5.4.1. LAYOUTCOMMIT and change/time_modify 12.5.4.1. LAYOUTCOMMIT and change/time_modify
The change and time_modify attributes may be updated by the server The change and time_modify attributes may be updated by the server
when the LAYOUTCOMMIT operation is processed. The reason for this is when the LAYOUTCOMMIT operation is processed. The reason for this is
that some layout types do not support the update of these attributes that some layout types do not support the update of these attributes
when the storage devices process I/O operations. If client has a when the storage devices process I/O operations. If a client has a
layout with the LAYOUTIOMODE4_RW iomode on the file, the client MAY layout with the LAYOUTIOMODE4_RW iomode on the file, the client MAY
provide a suggested value to the server for time_modify within the provide a suggested value to the server for time_modify within the
arguments to LAYOUTCOMMIT. Based on the layout type, the provided arguments to LAYOUTCOMMIT. Based on the layout type, the provided
value may or may not be used. The server should sanity check the value may or may not be used. The server should sanity-check the
client provided values before they are used. For example, the server client-provided values before they are used. For example, the server
should ensure that time does not flow backwards. The client always should ensure that time does not flow backwards. The client always
has the option to set time_modify through an explicit SETATTR has the option to set time_modify through an explicit SETATTR
operation. operation.
For some layout protocols, the storage device is able to notify the For some layout protocols, the storage device is able to notify the
metadata server of the occurrence of an I/O and as a result the metadata server of the occurrence of an I/O; as a result, the change
change and time_modify attributes may be updated at the metadata and time_modify attributes may be updated at the metadata server.
server. For a metadata server that is capable of monitoring updates
to the change and time_modify attributes, LAYOUTCOMMIT processing is For a metadata server that is capable of monitoring updates to the
not required to update the change attribute; in this case the change and time_modify attributes, LAYOUTCOMMIT processing is not
metadata server must ensure that no further update to the data has required to update the change attribute. In this case, the metadata
occurred since the last update of the attributes; file-based server must ensure that no further update to the data has occurred
protocols may have enough information to make this determination or since the last update of the attributes; file-based protocols may
may update the change attribute upon each file modification. This have enough information to make this determination or may update the
also applies for the time_modify attribute. If the server change attribute upon each file modification. This also applies for
implementation is able to determine that the file has not been the time_modify attribute. If the server implementation is able to
modified since the last time_modify update, the server need not determine that the file has not been modified since the last
update time_modify at LAYOUTCOMMIT. At LAYOUTCOMMIT completion, the time_modify update, the server need not update time_modify at
updated attributes should be visible if that file was modified since LAYOUTCOMMIT. At LAYOUTCOMMIT completion, the updated attributes
the latest previous LAYOUTCOMMIT or LAYOUTGET. should be visible if that file was modified since the latest previous
LAYOUTCOMMIT or LAYOUTGET.
12.5.4.2. LAYOUTCOMMIT and size 12.5.4.2. LAYOUTCOMMIT and size
The size of a file may be updated when the LAYOUTCOMMIT operation is The size of a file may be updated when the LAYOUTCOMMIT operation is
used by the client. One of the fields in the argument to used by the client. One of the fields in the argument to
LAYOUTCOMMIT is loca_last_write_offset; this field indicates the LAYOUTCOMMIT is loca_last_write_offset; this field indicates the
highest byte offset written but not yet committed with the highest byte offset written but not yet committed with the
LAYOUTCOMMIT operation. The data type of loca_last_write_offset is LAYOUTCOMMIT operation. The data type of loca_last_write_offset is
newoffset4 and is switched on a boolean value, no_newoffset, that newoffset4 and is switched on a boolean value, no_newoffset, that
indicates if a previous write occurred or not. If no_newoffset is indicates if a previous write occurred or not. If no_newoffset is
FALSE, an offset is not given. If the client has a layout with FALSE, an offset is not given. If the client has a layout with
LAYOUTIOMODE4_RW iomode on the file, with an lo_offset and lo_length LAYOUTIOMODE4_RW iomode on the file, with a byte-range (denoted by
that overlaps loca_last_write_offset, then the client MAY set the values of lo_offset and lo_length) that overlaps
no_newoffset to TRUE and provide an offset that will update the file loca_last_write_offset, then the client MAY set no_newoffset to TRUE
size. Keep in mind that offset is not the same as length, though and provide an offset that will update the file size. Keep in mind
they are related. For example, a loca_last_write_offset value of that offset is not the same as length, though they are related. For
zero means that one byte was written at offset zero, and so the example, a loca_last_write_offset value of zero means that one byte
length of the file is at least one byte. was written at offset zero, and so the length of the file is at least
one byte.
The metadata server may do one of the following: The metadata server may do one of the following:
1. Update the file's size using the last write offset provided by 1. Update the file's size using the last write offset provided by
the client as either the true file size or as a hint of the file the client as either the true file size or as a hint of the file
size. If the metadata server has a method available, any new size. If the metadata server has a method available, any new
value for file size should be sanity checked. For example, the value for file size should be sanity-checked. For example, the
file must not be truncated if the client presents a last write file must not be truncated if the client presents a last write
offset less than the file's current size. offset less than the file's current size.
2. Ignore the client provided last write offset; the metadata server 2. Ignore the client-provided last write offset; the metadata server
must have sufficient knowledge from other sources to determine must have sufficient knowledge from other sources to determine
the file's size. For example, the metadata server queries the the file's size. For example, the metadata server queries the
storage devices with the control protocol. storage devices with the control protocol.
The method chosen to update the file's size will depend on the The method chosen to update the file's size will depend on the
storage device's and/or the control protocol's capabilities. For storage device's and/or the control protocol's capabilities. For
example, if the storage devices are block devices with no knowledge example, if the storage devices are block devices with no knowledge
of file size, the metadata server must rely on the client to set the of file size, the metadata server must rely on the client to set the
last write offset appropriately. last write offset appropriately.
The results of LAYOUTCOMMIT contain a new size value in the form of a The results of LAYOUTCOMMIT contain a new size value in the form of a
newsize4 union data type. If the file's size is set as a result of newsize4 union data type. If the file's size is set as a result of
LAYOUTCOMMIT, the metadata server must reply with the new size; LAYOUTCOMMIT, the metadata server must reply with the new size;
otherwise the new size is not provided. If the file size is updated, otherwise, the new size is not provided. If the file size is
the metadata server SHOULD update the storage devices such that the updated, the metadata server SHOULD update the storage devices such
new file size is reflected when LAYOUTCOMMIT processing is complete. that the new file size is reflected when LAYOUTCOMMIT processing is
For example, the client should be able to READ up to the new file complete. For example, the client should be able to read up to the
size. new file size.
The client can extend the length of a file or truncate a file by The client can extend the length of a file or truncate a file by
sending a SETATTR operation to the metadata server with the size sending a SETATTR operation to the metadata server with the size
attribute specified. If the size specified is larger than the attribute specified. If the size specified is larger than the
current size of the file, the file is "zero extended", i.e., zeroes current size of the file, the file is "zero extended", i.e., zeros
are implicitly added between the file's previous EOF and the new EOF. are implicitly added between the file's previous EOF and the new EOF.
(In many implementations the zero extended region of the file (In many implementations, the zero-extended byte-range of the file
consists of unallocated holes in the file.) When the client writes consists of unallocated holes in the file.) When the client writes
past EOF via WRITE, the SETATTR operation does not need to be used. past EOF via WRITE, the SETATTR operation does not need to be used.
12.5.4.3. LAYOUTCOMMIT and layoutupdate 12.5.4.3. LAYOUTCOMMIT and layoutupdate
The LAYOUTCOMMIT argument contains a loca_layoutupdate field The LAYOUTCOMMIT argument contains a loca_layoutupdate field
(Section 18.42.1) of data type layoutupdate4 (Section 3.3.18). This (Section 18.42.1) of data type layoutupdate4 (Section 3.3.18). This
argument is a layout type-specific structure. The structure can be argument is a layout-type-specific structure. The structure can be
used to pass arbitrary layout type-specific information from the used to pass arbitrary layout-type-specific information from the
client to the metadata server at LAYOUTCOMMIT time. For example, if client to the metadata server at LAYOUTCOMMIT time. For example, if
using a block/volume layout, the client can indicate to the metadata using a block/volume layout, the client can indicate to the metadata
server which reserved or allocated blocks the client used or did not server which reserved or allocated blocks the client used or did not
use. The content of loca_layoutupdate (field lou_body) need not be use. The content of loca_layoutupdate (field lou_body) need not be
the same layout type-specific content returned by LAYOUTGET the same layout-type-specific content returned by LAYOUTGET
(Section 18.43.2) in the loc_body field of the lo_content field, of (Section 18.43.2) in the loc_body field of the lo_content field of
the logr_layout field. The content of loca_layoutupdate is defined the logr_layout field. The content of loca_layoutupdate is defined
by the layout type specification and is opaque to LAYOUTCOMMIT. by the layout type specification and is opaque to LAYOUTCOMMIT.
12.5.5. Recalling a Layout 12.5.5. Recalling a Layout
Since a layout protects a client's access to a file via a direct Since a layout protects a client's access to a file via a direct
client-storage-device path, a layout need only be recalled when it is client-storage-device path, a layout need only be recalled when it is
semantically unable to serve this function. Typically, this occurs semantically unable to serve this function. Typically, this occurs
when the layout no longer encapsulates the true location of the file when the layout no longer encapsulates the true location of the file
over the byte range it represents. Any operation or action, such as over the byte-range it represents. Any operation or action, such as
server driven restriping or load balancing, that changes the layout server-driven restriping or load balancing, that changes the layout
will result in a recall of the layout. A layout is recalled by the will result in a recall of the layout. A layout is recalled by the
CB_LAYOUTRECALL callback operation (see Section 20.3) and returned CB_LAYOUTRECALL callback operation (see Section 20.3) and returned
with LAYOUTRETURN Section 18.44. The CB_LAYOUTRECALL operation may with LAYOUTRETURN (see Section 18.44). The CB_LAYOUTRECALL operation
recall a layout identified by a byte range, all the layouts may recall a layout identified by a byte-range, all layouts
associated with a file system (FSID), or all layouts associated with associated with a file system ID (FSID), or all layouts associated
a client ID. Section 12.5.5.2 discusses sequencing issues with a client ID. Section 12.5.5.2 discusses sequencing issues
surrounding the getting, returning, and recalling of layouts. surrounding the getting, returning, and recalling of layouts.
An iomode is also specified when recalling a layout. Generally, the An iomode is also specified when recalling a layout. Generally, the
iomode in the recall request must match the layout being returned; iomode in the recall request must match the layout being returned;
for example, a recall with an iomode of LAYOUTIOMODE4_RW should cause for example, a recall with an iomode of LAYOUTIOMODE4_RW should cause
the client to only return LAYOUTIOMODE4_RW layouts and not the client to only return LAYOUTIOMODE4_RW layouts and not
LAYOUTIOMODE4_READ layouts. However, a special LAYOUTIOMODE4_ANY LAYOUTIOMODE4_READ layouts. However, a special LAYOUTIOMODE4_ANY
enumeration is defined to enable recalling a layout of any iomode; in enumeration is defined to enable recalling a layout of any iomode; in
other words, the client must return both read-only and read/write other words, the client must return both LAYOUTIOMODE4_READ and
layouts. LAYOUTIOMODE4_RW layouts.
A REMOVE operation SHOULD cause the metadata server to recall the A REMOVE operation SHOULD cause the metadata server to recall the
layout to prevent the client from accessing a non-existent file and layout to prevent the client from accessing a non-existent file and
to reclaim state stored on the client. Since a REMOVE may be delayed to reclaim state stored on the client. Since a REMOVE may be delayed
until the last close of the file has occurred, the recall may also be until the last close of the file has occurred, the recall may also be
delayed until this time. After the last reference on the file has delayed until this time. After the last reference on the file has
been released and the file has been removed, the client should no been released and the file has been removed, the client should no
longer be able to perform I/O using the layout. In the case of a longer be able to perform I/O using the layout. In the case of a
files based layout, the data server SHOULD return NFS4ERR_STALE in file-based layout, the data server SHOULD return NFS4ERR_STALE in
response to any operation on the removed file. response to any operation on the removed file.
Once a layout has been returned, the client MUST NOT send I/Os to the Once a layout has been returned, the client MUST NOT send I/Os to the
storage devices for the file, byte range, and iomode represented by storage devices for the file, byte-range, and iomode represented by
the returned layout. If a client does send an I/O to a storage the returned layout. If a client does send an I/O to a storage
device for which it does not hold a layout, the storage device SHOULD device for which it does not hold a layout, the storage device SHOULD
reject the I/O. reject the I/O.
Although pNFS does not alter the file data caching capabilities of Although pNFS does not alter the file data caching capabilities of
clients, or their semantics, it recognizes that some clients may clients, or their semantics, it recognizes that some clients may
perform more aggressive write-behind caching to optimize the benefits perform more aggressive write-behind caching to optimize the benefits
provided by pNFS. However, write-behind caching may negatively provided by pNFS. However, write-behind caching may negatively
affect the latency in returning a layout in response to a affect the latency in returning a layout in response to a
CB_LAYOUTRECALL; this is similar to file delegations and the impact CB_LAYOUTRECALL; this is similar to file delegations and the impact
that file data caching has on DELEGRETURN. Client implementations that file data caching has on DELEGRETURN. Client implementations
SHOULD limit the amount of unwritten data they have outstanding at SHOULD limit the amount of unwritten data they have outstanding at
any one time in order to prevent excessively long responses to any one time in order to prevent excessively long responses to
CB_LAYOUTRECALL. Once a layout is recalled, a server MUST wait one CB_LAYOUTRECALL. Once a layout is recalled, a server MUST wait one
lease period before taking further action. As soon as a lease period lease period before taking further action. As soon as a lease period
has past, the server may choose to fence the client's access to the has passed, the server may choose to fence the client's access to the
storage devices if the server perceives the client has taken too long storage devices if the server perceives the client has taken too long
to return a layout. However, just as in the case of data delegation to return a layout. However, just as in the case of data delegation
and DELEGRETURN, the server may choose to wait given that the client and DELEGRETURN, the server may choose to wait, given that the client
is showing forward progress on its way to returning the layout. This is showing forward progress on its way to returning the layout. This
forward progress can take the form of successful interaction with the forward progress can take the form of successful interaction with the
storage devices or sub-portions of the layout being returned by the storage devices or of sub-portions of the layout being returned by
client. The server can also limit exposure to these problems by the client. The server can also limit exposure to these problems by
limiting the byte ranges initially provided in the layouts and thus limiting the byte-ranges initially provided in the layouts and thus
the amount of outstanding modified data. the amount of outstanding modified data.
12.5.5.1. Layout Recall Callback Robustness 12.5.5.1. Layout Recall Callback Robustness
It has been assumed thus far that pNFS client state for a file It has been assumed thus far that pNFS client state (layout ranges
exactly matches the pNFS server state for that file and client and iomode) for a file exactly matches that of the pNFS server for
regarding layout ranges and iomode. This assumption leads to the that file. This assumption leads to the implication that any
implication that any callback results in a LAYOUTRETURN or set of callback results in a LAYOUTRETURN or set of LAYOUTRETURNs that
LAYOUTRETURNs that exactly match the range in the callback, since exactly match the range in the callback, since both client and server
both client and server agree about the state being maintained. agree about the state being maintained. However, it can be useful if
However, it can be useful if this assumption does not always hold. this assumption does not always hold. For example:
For example:
o If conflicts that require callbacks are very rare, and a server o If conflicts that require callbacks are very rare, and a server
can use a multi-file callback to recover per-client resources can use a multi-file callback to recover per-client resources
(e.g., via a FSID recall, or a multi-file recall within a single (e.g., via an FSID recall or a multi-file recall within a single
compound), the result may be significantly less client-server pNFS CB_COMPOUND), the result may be significantly less client-server
traffic. pNFS traffic.
o It may be useful for servers to maintain information about what o It may be useful for servers to maintain information about what
ranges are held by a client on a coarse-grained basis, leading to ranges are held by a client on a coarse-grained basis, leading to
the server's layout ranges being beyond those actually held by the the server's layout ranges being beyond those actually held by the
client. In the extreme, a server could manage conflicts on a per- client. In the extreme, a server could manage conflicts on a per-
file basis, only sending whole-file callbacks even though clients file basis, only sending whole-file callbacks even though clients
may request and be granted sub-file ranges. may request and be granted sub-file ranges.
o It may be useful for clients to "forget" details about what o It may be useful for clients to "forget" details about what
layouts and ranges the client actually has, leading to the layouts and ranges the client actually has, leading to the
server's layout ranges being beyond those what the client "thinks" server's layout ranges being beyond those that the client "thinks"
it has. As long as the client does not assume it has layouts that it has. As long as the client does not assume it has layouts that
are beyond what the server has granted, this is a safe practice. are beyond what the server has granted, this is a safe practice.
When a client forgets what ranges and layouts it has, and it When a client forgets what ranges and layouts it has, and it
receives a CB_LAYOUTRECALL operation, the client MUST follow up receives a CB_LAYOUTRECALL operation, the client MUST follow up
with a LAYOUTRETURN for what the server recalled, or alternatively with a LAYOUTRETURN for what the server recalled, or alternatively
return the NFS4ERR_NOMATCHING_LAYOUT error if it has no layout to return the NFS4ERR_NOMATCHING_LAYOUT error if it has no layout to
return in the recalled range. return in the recalled range.
o In order to avoid errors, it is vital that a client not assign o In order to avoid errors, it is vital that a client not assign
itself layout permissions beyond what the server has granted and itself layout permissions beyond what the server has granted, and
that the server not forget layout permissions that have been that the server not forget layout permissions that have been
granted. On the other hand, if a server believes that a client granted. On the other hand, if a server believes that a client
holds a layout that the client does not know about, it is useful holds a layout that the client does not know about, it is useful
for the client to cleanly indicate completion of the requested for the client to cleanly indicate completion of the requested
recall either by sending a LAYOUTRETURN operation for the entire recall either by sending a LAYOUTRETURN operation for the entire
requested range or by returning an NFS4ERR_NOMATCHING_LAYOUT error requested range or by returning an NFS4ERR_NOMATCHING_LAYOUT error
to the CB_LAYOUTRECALL. to the CB_LAYOUTRECALL.
Thus, in light of the above, it is useful for a server to be able to Thus, in light of the above, it is useful for a server to be able to
send callbacks for layout ranges it has not granted to a client, and send callbacks for layout ranges it has not granted to a client, and
for a client to return ranges it does not hold. A pNFS client MUST for a client to return ranges it does not hold. A pNFS client MUST
always return layouts that comprise the full range specified by the always return layouts that comprise the full range specified by the
recall. Note, the full recalled layout range need not be returned as recall. Note, the full recalled layout range need not be returned as
part of a single operation, but may be returned in portions. This part of a single operation, but may be returned in portions. This
allows the client to stage the flushing of dirty data, layout allows the client to stage the flushing of dirty data and commits and
commits, and returns. Also, it indicates to the metadata server that returns of layouts. Also, it indicates to the metadata server that
the client is making progress. the client is making progress.
When a layout is returned, the client MUST NOT have any outstanding When a layout is returned, the client MUST NOT have any outstanding
I/O requests to the storage devices involved in the layout. I/O requests to the storage devices involved in the layout.
Rephrasing, the client MUST NOT return the layout while it has Rephrasing, the client MUST NOT return the layout while it has
outstanding I/O requests to the storage device. outstanding I/O requests to the storage device.
Even with this requirement for the client, it is possible that I/O Even with this requirement for the client, it is possible that I/O
requests may be presented to a storage device no longer allowed to requests may be presented to a storage device no longer allowed to
perform them. Since the server has no strict control as to when the perform them. Since the server has no strict control as to when the
client will return the layout, the server may later decide to client will return the layout, the server may later decide to
unilaterally revoke the client's access to the storage devices as unilaterally revoke the client's access to the storage devices as
provided by the layout. In choosing to revoke access, the server provided by the layout. In choosing to revoke access, the server
must deal with the possibility of lingering I/O request; those must deal with the possibility of lingering I/O requests, i.e., I/O
outstanding I/O requests are still in flight to storage devices requests that are still in flight to storage devices identified by
identified by the revoked layout. All layout type specifications the revoked layout. All layout type specifications MUST define
MUST define whether unilateral layout revocation by the metadata whether unilateral layout revocation by the metadata server is
server is supported; if it is, the specification must also describe supported; if it is, the specification must also describe how
how lingering writes are processed. For example, storage devices lingering writes are processed. For example, storage devices
identified by the revoked layout could be fenced off from the client identified by the revoked layout could be fenced off from the client
that held the layout. that held the layout.
In order to ensure client/server convergence with regard to layout In order to ensure client/server convergence with regard to layout
state, the final LAYOUTRETURN operation in a sequence of LAYOUTRETURN state, the final LAYOUTRETURN operation in a sequence of LAYOUTRETURN
operations for a particular recall, MUST specify the entire range operations for a particular recall MUST specify the entire range
being recalled, echoing the recalled layout type, iomode, recall/ being recalled, echoing the recalled layout type, iomode, recall/
return type (FILE, FSID, or ALL), and byte range; even if layouts return type (FILE, FSID, or ALL), and byte-range, even if layouts
pertaining to partial ranges were previously returned. In addition, pertaining to partial ranges were previously returned. In addition,
if the client holds no layouts that overlaps the range being if the client holds no layouts that overlap the range being recalled,
recalled, the client should return the NFS4ERR_NOMATCHING_LAYOUT the client should return the NFS4ERR_NOMATCHING_LAYOUT error code to
error code to CB_LAYOUTRECALL. This allows the server to update its CB_LAYOUTRECALL. This allows the server to update its view of the
view of the client's layout state. client's layout state.
12.5.5.2. Sequencing of Layout Operations 12.5.5.2. Sequencing of Layout Operations
As with other stateful operations, pNFS requires the correct As with other stateful operations, pNFS requires the correct
sequencing of layout operations. pNFS uses the "seqid" in the layout sequencing of layout operations. pNFS uses the "seqid" in the layout
stateid to provide the correct sequencing between regular operations stateid to provide the correct sequencing between regular operations
and callbacks. It is the server's responsibility to avoid and callbacks. It is the server's responsibility to avoid
inconsistencies regarding the layouts provided and the client's inconsistencies regarding the layouts provided and the client's
responsibility to properly serialize its layout requests and layout responsibility to properly serialize its layout requests and layout
returns. returns.
12.5.5.2.1. Layout Recall and Return Sequencing 12.5.5.2.1. Layout Recall and Return Sequencing
One critical issue with regard to layout operations sequencing One critical issue with regard to layout operations sequencing
concerns callbacks. The protocol must defend against races between concerns callbacks. The protocol must defend against races between
the reply to a LAYOUTGET or LAYOUTRETURN operation and a subsequent the reply to a LAYOUTGET or LAYOUTRETURN operation and a subsequent
CB_LAYOUTRECALL. A client MUST NOT process a CB_LAYOUTRECALL that CB_LAYOUTRECALL. A client MUST NOT process a CB_LAYOUTRECALL that
implies one or more outstanding LAYOUTGET or LAYOUTRETURN operations implies one or more outstanding LAYOUTGET or LAYOUTRETURN operations
to which the client has not yet received a reply. The client detects to which the client has not yet received a reply. The client detects
such a CB_LAYOUTRECALL by examining the "seqid" field of the recall's such a CB_LAYOUTRECALL by examining the "seqid" field of the recall's
layout stateid. If the "seqid" is not one higher than what the layout stateid. If the "seqid" is not exactly one higher than what
client currently has recorded, and the client has at least one the client currently has recorded, and the client has at least one
LAYOUTGET and/or LAYOUTRETURN operation outstanding, the client knows LAYOUTGET and/or LAYOUTRETURN operation outstanding, the client knows
the server sent the CB_LAYOUTRECALL after sending a response to an the server sent the CB_LAYOUTRECALL after sending a response to an
outstanding LAYOUTGET or LAYOUTRETURN. The client MUST wait before outstanding LAYOUTGET or LAYOUTRETURN. The client MUST wait before
processing such a CB_LAYOUTRECALL until it processes all replies for processing such a CB_LAYOUTRECALL until it processes all replies for
outstanding LAYOUTGET and LAYOUTRETURN operations for the outstanding LAYOUTGET and LAYOUTRETURN operations for the
corresponding file with seqid less than the seqid given by corresponding file with seqid less than the seqid given by
CB_LAYOUTRECALL (lor_stateid, see Section 20.3.) CB_LAYOUTRECALL (lor_stateid; see Section 20.3.)
In addition to the seqid-based mechanism, Section 2.10.6.3 describes In addition to the seqid-based mechanism, Section 2.10.6.3 describes
the sessions mechanism for allowing the client to detect callback the sessions mechanism for allowing the client to detect callback
race conditions and delay processing such a CB_LAYOUTRECALL. The race conditions and delay processing such a CB_LAYOUTRECALL. The
server MAY reference conflicting operations in the CB_SEQUENCE that server MAY reference conflicting operations in the CB_SEQUENCE that
precedes the CB_LAYOUTRECALL. Because the server has already sent precedes the CB_LAYOUTRECALL. Because the server has already sent
replies for these operations before sending the callback, the replies replies for these operations before sending the callback, the replies
may race with the CB_LAYOUTRECALL. The client MUST wait for all the may race with the CB_LAYOUTRECALL. The client MUST wait for all the
referenced calls to complete and update its view of the layout state referenced calls to complete and update its view of the layout state
before processing the CB_LAYOUTRECALL. before processing the CB_LAYOUTRECALL.
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which they were created. However, through the use of the "seqid" which they were created. However, through the use of the "seqid"
field in the layout stateid, the client can determine the order in field in the layout stateid, the client can determine the order in
which parallel outstanding operations were processed by the server. which parallel outstanding operations were processed by the server.
Thus, when a layout retrieved by an outstanding LAYOUTGET operation Thus, when a layout retrieved by an outstanding LAYOUTGET operation
intersects with a layout returned by an outstanding LAYOUTRETURN on intersects with a layout returned by an outstanding LAYOUTRETURN on
the same file, the order in which the two conflicting operations are the same file, the order in which the two conflicting operations are
processed determines the final state of the overlapping layout. The processed determines the final state of the overlapping layout. The
order is determined by the "seqid" returned in each operation: the order is determined by the "seqid" returned in each operation: the
operation with the higher seqid was executed later. operation with the higher seqid was executed later.
It is permissible for the client to send in parallel multiple It is permissible for the client to send multiple parallel LAYOUTGET
LAYOUTGET operations for the same file or multiple LAYOUTRETURN operations for the same file or multiple parallel LAYOUTRETURN
operations for the same file, and a mix of both. operations for the same file or a mix of both.
It is permissible for the client to use the current stateid (see It is permissible for the client to use the current stateid (see
Section 16.2.3.1.2) for LAYOUTGET operations for example when Section 16.2.3.1.2) for LAYOUTGET operations, for example, when
compounding LAYOUTGETs or compounding OPEN and LAYOUTGETs. It is compounding LAYOUTGETs or compounding OPEN and LAYOUTGETs. It is
also permissible to use the current stateid when compounding also permissible to use the current stateid when compounding
LAYOUTRETURNs. LAYOUTRETURNs.
It is permissible for the client to use the current stateid when It is permissible for the client to use the current stateid when
combining LAYOUTRETURN and LAYOUTGET operations for the same file in combining LAYOUTRETURN and LAYOUTGET operations for the same file in
the same COMPOUND request since the server MUST process these in the same COMPOUND request since the server MUST process these in
order. However, if a client does send such COMPOUND requests, it order. However, if a client does send such COMPOUND requests, it
MUST NOT have more than one outstanding for the same file at the same MUST NOT have more than one outstanding for the same file at the same
time and MUST NOT have other LAYOUTGET or LAYOUTRETURN operations time, and it MUST NOT have other LAYOUTGET or LAYOUTRETURN operations
outstanding at the same time for that same file. outstanding at the same time for that same file.
12.5.5.2.1.2. Client Considerations 12.5.5.2.1.2. Client Considerations
Consider a pNFS client that has sent a LAYOUTGET and before it Consider a pNFS client that has sent a LAYOUTGET, and before it
receives the reply to LAYOUTGET, it receives a CB_LAYOUTRECALL for receives the reply to LAYOUTGET, it receives a CB_LAYOUTRECALL for
the same file with an overlapping range. There are two the same file with an overlapping range. There are two
possibilities, which the client can distinguish via the layout possibilities, which the client can distinguish via the layout
stateid in the recall. stateid in the recall.
1. The server processed the LAYOUTGET before sending the recall, so 1. The server processed the LAYOUTGET before sending the recall, so
the LAYOUTGET must be waited for because it may be carrying the LAYOUTGET must be waited for because it may be carrying
layout information that will need to be returned to deal with the layout information that will need to be returned to deal with the
CB_LAYOUTRECALL. CB_LAYOUTRECALL.
2. The server sent the callback before receiving the LAYOUTGET. The 2. The server sent the callback before receiving the LAYOUTGET. The
server will not respond to the LAYOUTGET until the server will not respond to the LAYOUTGET until the
CB_LAYOUTRECALL is processed. CB_LAYOUTRECALL is processed.
If these possibilities cannot be distinguished, a deadlock could If these possibilities cannot be distinguished, a deadlock could
result, as the client must wait for the LAYOUTGET response before result, as the client must wait for the LAYOUTGET response before
processing the recall in the first case, but that response will not processing the recall in the first case, but that response will not
arrive until after the recall is processed in the second case. Note arrive until after the recall is processed in the second case. Note
that in the first case, the "seqid" in the layout stateid of the that in the first case, the "seqid" in the layout stateid of the
recall is two greater than what the client has recorded and in the recall is two greater than what the client has recorded; in the
second case, the "seqid" is one greater than what the client has second case, the "seqid" is one greater than what the client has
recorded. This allows the client to disambiguate between the two recorded. This allows the client to disambiguate between the two
cases. The client thus knows precisely which possibility applies. cases. The client thus knows precisely which possibility applies.
In case 1 the client knows it needs to wait for the LAYOUTGET In case 1, the client knows it needs to wait for the LAYOUTGET
response before processing the recall (or the client can return response before processing the recall (or the client can return
NFS4ERR_DELAY). NFS4ERR_DELAY).
In case 2 the client will not wait for the LAYOUTGET response before In case 2, the client will not wait for the LAYOUTGET response before
processing the recall, because waiting would cause deadlock. processing the recall because waiting would cause deadlock.
Therefore, the action at the client will only require waiting in the Therefore, the action at the client will only require waiting in the
case that the client has not yet seen the server's earlier responses case that the client has not yet seen the server's earlier responses
to the LAYOUTGET operation(s). to the LAYOUTGET operation(s).
The recall process can be considered completed when the final The recall process can be considered completed when the final
LAYOUTRETURN operation for the recalled range is completed. The LAYOUTRETURN operation for the recalled range is completed. The
LAYOUTRETURN uses the layout stateid (with seqid) specified in LAYOUTRETURN uses the layout stateid (with seqid) specified in
CB_LAYOUTRECALL. If the client uses multiple LAYOUTRETURNs in CB_LAYOUTRECALL. If the client uses multiple LAYOUTRETURNs in
processing the recall, the first LAYOUTRETURN will use the layout processing the recall, the first LAYOUTRETURN will use the layout
stateid as specified in CB_LAYOUTRECALL. Subsequent LAYOUTRETURNs stateid as specified in CB_LAYOUTRECALL. Subsequent LAYOUTRETURNs
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2. The client sent the LAYOUTGET after processing the 2. The client sent the LAYOUTGET after processing the
CB_LAYOUTRECALL, but the LAYOUTGET arrived before the CB_LAYOUTRECALL, but the LAYOUTGET arrived before the
LAYOUTRETURN and the response to CB_LAYOUTRECALL that completed LAYOUTRETURN and the response to CB_LAYOUTRECALL that completed
that processing. The "seqid" in the layout stateid of LAYOUTGET that processing. The "seqid" in the layout stateid of LAYOUTGET
is equal to or greater than that of the "seqid" in is equal to or greater than that of the "seqid" in
CB_LAYOUTRECALL. The server has not received a response to the CB_LAYOUTRECALL. The server has not received a response to the
CB_LAYOUTRECALL, so it returns NFS4ERR_RECALLCONFLICT. CB_LAYOUTRECALL, so it returns NFS4ERR_RECALLCONFLICT.
3. The client sent the LAYOUTGET after processing the 3. The client sent the LAYOUTGET after processing the
CB_LAYOUTRECALL, the server received the CB_LAYOUTRECALL CB_LAYOUTRECALL; the server received the CB_LAYOUTRECALL
response, but the LAYOUTGET arrived before the LAYOUTRETURN that response, but the LAYOUTGET arrived before the LAYOUTRETURN that
completed that processing. The "seqid" in the layout stateid of completed that processing. The "seqid" in the layout stateid of
LAYOUTGET is equal to that of the "seqid" in CB_LAYOUTRECALL. LAYOUTGET is equal to that of the "seqid" in CB_LAYOUTRECALL.
The server has received a response to the CB_LAYOUTRECALL, so it The server has received a response to the CB_LAYOUTRECALL, so it
returns NFS4ERR_RETURNCONFLICT. returns NFS4ERR_RETURNCONFLICT.
12.5.5.2.1.4. Wraparound and Validation of Seqid 12.5.5.2.1.4. Wraparound and Validation of Seqid
The rules for layout stateid processing differ from other stateids in The rules for layout stateid processing differ from other stateids in
the protocol because the "seqid" value cannot be zero and the the protocol because the "seqid" value cannot be zero and the
stateid's "seqid" value changes in a CB_LAYOUTRECALL operation. The stateid's "seqid" value changes in a CB_LAYOUTRECALL operation. The
non-zero requirement combined with the inherent parallelism of layout non-zero requirement combined with the inherent parallelism of layout
operations means that a set of LAYOUTGET and LAYOUTRETURN operations operations means that a set of LAYOUTGET and LAYOUTRETURN operations
may contain the same value for "seqid". The server uses a slightly may contain the same value for "seqid". The server uses a slightly
modified version of the modulo arithmetic as described in modified version of the modulo arithmetic as described in
Section 2.10.6.1 when incrementing the layout stateid's "seqid". The Section 2.10.6.1 when incrementing the layout stateid's "seqid". The
modification to that modulo arithmetic description is to not use difference is that zero is not a valid value for "seqid"; when the
zero. The modulo arithmetic is also used for the comparisons of the value of a "seqid" is 0xFFFFFFFF, the next valid value will be
"seqid" values in the processing of CB_LAYOUTRECALL events as 0x00000001. The modulo arithmetic is also used for the comparisons
of "seqid" values in the processing of CB_LAYOUTRECALL events as
described above in Section 12.5.5.2.1.3. described above in Section 12.5.5.2.1.3.
Just as the server validates the "seqid" in the event of Just as the server validates the "seqid" in the event of
CB_LAYOUTRECALL usage, as described in Section 12.5.5.2.1.3, the CB_LAYOUTRECALL usage, as described in Section 12.5.5.2.1.3, the
server also validates the "seqid" value to ensure that it is within server also validates the "seqid" value to ensure that it is within
an appropriate range. This range represents the degree of an appropriate range. This range represents the degree of
parallelism the server supports for layout stateids. If the client parallelism the server supports for layout stateids. If the client
is sending multiple layout operations to the server in parallel, by is sending multiple layout operations to the server in parallel, by
definition, the "seqid" value in the supplied stateid will not be the definition, the "seqid" value in the supplied stateid will not be the
current "seqid" as held by the server. The range of parallelism current "seqid" as held by the server. The range of parallelism
spans from the highest or current "seqid" to a "seqid" value in the spans from the highest or current "seqid" to a "seqid" value in the
past. To assist in the discussion, the server's current "seqid" past. To assist in the discussion, the server's current "seqid"
value for a layout stateid is defined as: SERVER_CURRENT_SEQID. The value for a layout stateid is defined as SERVER_CURRENT_SEQID. The
lowest "seqid" value that is acceptable to the server is represented lowest "seqid" value that is acceptable to the server is represented
by PAST_SEQID. And the value for the range of valid "seqid"s or by PAST_SEQID. And the value for the range of valid "seqid"s or
range of parallelism is VALID_SEQID_RANGE. Therefore, the following range of parallelism is VALID_SEQID_RANGE. Therefore, the following
holds: VALID_SEQID_RANGE = SERVER_CURRENT_SEQID - PAST_SEQID. In the holds: VALID_SEQID_RANGE = SERVER_CURRENT_SEQID - PAST_SEQID. In the
following, all arithmetic is the modulo arithmetic as described following, all arithmetic is the modulo arithmetic as described
above. above.
The server MUST support a minimum VALID_SEQID_RANGE. The minimum is The server MUST support a minimum VALID_SEQID_RANGE. The minimum is
defined as: VALID_SEQID_RANGE = summation of 1..N of defined as: VALID_SEQID_RANGE = summation of 1..N of
(ca_maxoperations(i) - 1) where N is the number of session fore (ca_maxoperations(i) - 1), where N is the number of session fore
channels and ca_maxoperations(i) is the value of the ca_maxoperations channels and ca_maxoperations(i) is the value of the ca_maxoperations
returned from CREATE_SESSION of the i'th session. The reason for returned from CREATE_SESSION of the i'th session. The reason for "-
minus 1 is to allow for the required SEQUENCE operation. The server 1" is to allow for the required SEQUENCE operation. The server MAY
MAY support a VALID_SEQID_RANGE value larger than the minimum. The support a VALID_SEQID_RANGE value larger than the minimum. The
maximum VALID_SEQID_RANGE is (2 ^ 32 - 2) (accounts for 0 not being a maximum VALID_SEQID_RANGE is (2 ^ 32 - 2) (accounts for zero not
valid "seqid" value). being a valid "seqid" value).
If the server finds the "seqid" is zero, the NFS4ERR_BAD_STATEID If the server finds the "seqid" is zero, the NFS4ERR_BAD_STATEID
error is returned to the client. The server further validates the error is returned to the client. The server further validates the
"seqid" to ensure it is within the range of parallelism, "seqid" to ensure it is within the range of parallelism,
VALID_SEQID_RANGE. If the "seqid" value is outside of that range, VALID_SEQID_RANGE. If the "seqid" value is outside of that range,
the error NFS4ERR_OLD_STATEID is returned to the client. Upon the error NFS4ERR_OLD_STATEID is returned to the client. Upon
receipt of NFS4ERR_OLD_STATEID, the client updates the stateid in the receipt of NFS4ERR_OLD_STATEID, the client updates the stateid in the
layout request based on processing of other layout requests and re- layout request based on processing of other layout requests and re-
sends the operation to the server. sends the operation to the server.
12.5.5.2.1.5. Bulk Recall and Return 12.5.5.2.1.5. Bulk Recall and Return
pNFS supports recalling and returning all layouts that are for files pNFS supports recalling and returning all layouts that are for files
belonging to a particular fsid (LAYOUTRECALL4_FSID, belonging to a particular fsid (LAYOUTRECALL4_FSID,
LAYOUTRETURN4_FSID) or client ID (LAYOUTRECALL4_ALL, LAYOUTRETURN4_FSID) or client ID (LAYOUTRECALL4_ALL,
LAYOUTRETURN4_ALL). There are no "bulk" stateids, so detection of LAYOUTRETURN4_ALL). There are no "bulk" stateids, so detection of
races via the seqid is not possible. The server MUST NOT initiate races via the seqid is not possible. The server MUST NOT initiate
bulk recall while another recall is in progress, or the corresponding bulk recall while another recall is in progress, or the corresponding
LAYOUTRETURN is in progress or pending. In the event the server LAYOUTRETURN is in progress or pending. In the event the server
sends a bulk recall while the client has pending or in progress sends a bulk recall while the client has a pending or in-progress
LAYOUTRETURN, CB_LAYOUTRECALL, or LAYOUTGET, the client returns LAYOUTRETURN, CB_LAYOUTRECALL, or LAYOUTGET, the client returns
NFS4ERR_DELAY. In the event the client sends a LAYOUTGET or NFS4ERR_DELAY. In the event the client sends a LAYOUTGET or
LAYOUTRETURN while a bulk recall is in progress, the server returns LAYOUTRETURN while a bulk recall is in progress, the server returns
NFS4ERR_RECALLCONFLICT. If the client sends a LAYOUTGET or NFS4ERR_RECALLCONFLICT. If the client sends a LAYOUTGET or
LAYOUTRETURN after the server receives NFS4ERR_DELAY from a bulk LAYOUTRETURN after the server receives NFS4ERR_DELAY from a bulk
recall, then to ensure forward progress, the server MAY return recall, then to ensure forward progress, the server MAY return
NFS4ERR_RECALLCONFLICT. NFS4ERR_RECALLCONFLICT.
Once a CB_LAYOUTRECALL of LAYOUTRECALL4_ALL is sent, the server MUST Once a CB_LAYOUTRECALL of LAYOUTRECALL4_ALL is sent, the server MUST
NOT allow the client to use any layout stateid except for NOT allow the client to use any layout stateid except for
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client MUST NOT use the layout stateids again. It MUST use LAYOUTGET client MUST NOT use the layout stateids again. It MUST use LAYOUTGET
to obtain new layout stateids. to obtain new layout stateids.
Once a CB_LAYOUTRECALL of LAYOUTRECALL4_FSID is sent, the server MUST Once a CB_LAYOUTRECALL of LAYOUTRECALL4_FSID is sent, the server MUST
NOT allow the client to use any layout stateid that refers to a file NOT allow the client to use any layout stateid that refers to a file
with the specified fsid except for LAYOUTCOMMIT operations. Once the with the specified fsid except for LAYOUTCOMMIT operations. Once the
client receives a CB_LAYOUTRECALL of LAYOUTRECALL4_ALL, it MUST NOT client receives a CB_LAYOUTRECALL of LAYOUTRECALL4_ALL, it MUST NOT
use any layout stateid that refers to a file with the specified fsid use any layout stateid that refers to a file with the specified fsid
except for LAYOUTCOMMIT operations. Once a LAYOUTRETURN of except for LAYOUTCOMMIT operations. Once a LAYOUTRETURN of
LAYOUTRETURN4_FSID is sent, all layout stateids granted to the LAYOUTRETURN4_FSID is sent, all layout stateids granted to the
referenced fsid are freed. The client MUST NOT use the layout referenced fsid are freed. The client MUST NOT use those freed
stateids for files with the referenced fsid again. It MUST use layout stateids for files with the referenced fsid again.
LAYOUTGET to obtain new layout stateids files with the referenced Subsequently, for any file with the referenced fsid, to use a layout,
fsid. the client MUST first send a LAYOUTGET operation in order to obtain a
new layout stateid for that file.
If the server has sent a bulk CB_LAYOUTRECALL, and receives a If the server has sent a bulk CB_LAYOUTRECALL and receives a
LAYOUTGET, or a LAYOUTRETURN with a stateid, the server MUST return LAYOUTGET, or a LAYOUTRETURN with a stateid, the server MUST return
NFS4ERR_RECALLCONFLICT. If the server has sent a bulk NFS4ERR_RECALLCONFLICT. If the server has sent a bulk
CB_LAYOUTRECALL, and receives a LAYOUTRETURN with an lr_returntype CB_LAYOUTRECALL and receives a LAYOUTRETURN with an lr_returntype
that is not equal to the lor_recalltype of the CB_LAYOUTRECALL, the that is not equal to the lor_recalltype of the CB_LAYOUTRECALL, the
server MUST return NFS4ERR_RECALLCONFLICT. server MUST return NFS4ERR_RECALLCONFLICT.
12.5.6. Revoking Layouts 12.5.6. Revoking Layouts
Parallel NFS permits servers to revoke layouts from clients that fail Parallel NFS permits servers to revoke layouts from clients that fail
to response to recalls and/or fail to renew their lease in time. to respond to recalls and/or fail to renew their lease in time.
Whether the server revokes the layout or not depends on the layout Depending on the layout type, the server might revoke the layout and
type, and what actions are taken with respect to the client's I/O to might take certain actions with respect to the client's I/O to data
data servers is also layout type specific. servers.
12.5.7. Metadata Server Write Propagation 12.5.7. Metadata Server Write Propagation
Asynchronous writes written through the metadata server may be Asynchronous writes written through the metadata server may be
propagated lazily to the storage devices. For data written propagated lazily to the storage devices. For data written
asynchronously through the metadata server, a client performing a asynchronously through the metadata server, a client performing a
read at the appropriate storage device is not guaranteed to see the read at the appropriate storage device is not guaranteed to see the
newly written data until a COMMIT occurs at the metadata server. newly written data until a COMMIT occurs at the metadata server.
While the write is pending, reads to the storage device may give out While the write is pending, reads to the storage device may give out
either the old data, the new data, or a mixture of new and old. Upon either the old data, the new data, or a mixture of new and old. Upon
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what the fs_layout_type attribute said, the server does not support what the fs_layout_type attribute said, the server does not support
pNFS, and the client will not be able use pNFS to that server; in pNFS, and the client will not be able use pNFS to that server; in
this case, the server MUST return NFS4ERR_NOTSUPP in response to any this case, the server MUST return NFS4ERR_NOTSUPP in response to any
pNFS operation. pNFS operation.
The client then creates a session, requesting a persistent session, The client then creates a session, requesting a persistent session,
so that exclusive creates can be done with single round trip via the so that exclusive creates can be done with single round trip via the
createmode4 of GUARDED4. If the session ends up not being createmode4 of GUARDED4. If the session ends up not being
persistent, the client will use EXCLUSIVE4_1 for exclusive creates. persistent, the client will use EXCLUSIVE4_1 for exclusive creates.
If a file is to be created on a pNFS enabled file system, the client If a file is to be created on a pNFS-enabled file system, the client
uses the OPEN operation. With the normal set of attributes that may uses the OPEN operation. With the normal set of attributes that may
be provided upon OPEN used for creation, there is an OPTIONAL be provided upon OPEN used for creation, there is an OPTIONAL
layout_hint attribute. The client's use of layout_hint allows the layout_hint attribute. The client's use of layout_hint allows the
client to express its preference for a layout type and its associated client to express its preference for a layout type and its associated
layout details. The use of a createmode4 of UNCHECKED4, GUARDED4, or layout details. The use of a createmode4 of UNCHECKED4, GUARDED4, or
EXCLUSIVE4_1 will allow the client to provide the layout_hint EXCLUSIVE4_1 will allow the client to provide the layout_hint
attribute at create time. The client MUST NOT use EXCLUSIVE4 (see attribute at create time. The client MUST NOT use EXCLUSIVE4 (see
Table 10). The client is RECOMMENDED to combine a GETATTR operation Table 10). The client is RECOMMENDED to combine a GETATTR operation
after the OPEN within the same COMPOUND. The GETATTR may then after the OPEN within the same COMPOUND. The GETATTR may then
retrieve the layout_type attribute for the newly created file. The retrieve the layout_type attribute for the newly created file. The
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Assuming the client supports the layout type returned by GETATTR and Assuming the client supports the layout type returned by GETATTR and
it chooses to use pNFS for data access, it then sends LAYOUTGET using it chooses to use pNFS for data access, it then sends LAYOUTGET using
the filehandle and stateid returned by OPEN, specifying the range it the filehandle and stateid returned by OPEN, specifying the range it
wants to do I/O on. The response is a layout, which may be a subset wants to do I/O on. The response is a layout, which may be a subset
of the range for which the client asked. It also includes device IDs of the range for which the client asked. It also includes device IDs
and a description of how data is organized (or in the case of and a description of how data is organized (or in the case of
writing, how data is to be organized) across the devices. The device writing, how data is to be organized) across the devices. The device
IDs and data description are encoded in a format that is specific to IDs and data description are encoded in a format that is specific to
the layout type, but the client is expected to understand. the layout type, but the client is expected to understand.
When the client wants to send an I/O, it determines which device ID When the client wants to send an I/O, it determines to which device
it needs to send the I/O command to by examining the data description ID it needs to send the I/O command by examining the data description
in the layout. It then sends a GETDEVICEINFO to find the device in the layout. It then sends a GETDEVICEINFO to find the device
address(es) of the device ID. The client then sends the I/O request address(es) of the device ID. The client then sends the I/O request
one of device ID's device addresses, using the storage protocol one of device ID's device addresses, using the storage protocol
defined for the layout type. Note that if a client has multiple I/Os defined for the layout type. Note that if a client has multiple I/Os
to send, these I/O requests may be done in parallel. to send, these I/O requests may be done in parallel.
If the I/O was a WRITE, then at some point the client may want to use If the I/O was a WRITE, then at some point the client may want to use
LAYOUTCOMMIT to commit the modification time and the new size of the LAYOUTCOMMIT to commit the modification time and the new size of the
file (if it believes it extended the file size) to the metadata file (if it believes it extended the file size) to the metadata
server and the modified data to the file system. server and the modified data to the file system.
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Recovery is complicated by the distributed nature of the pNFS Recovery is complicated by the distributed nature of the pNFS
protocol. In general, crash recovery for layouts is similar to crash protocol. In general, crash recovery for layouts is similar to crash
recovery for delegations in the base NFSv4.1 protocol. However, the recovery for delegations in the base NFSv4.1 protocol. However, the
client's ability to perform I/O without contacting the metadata client's ability to perform I/O without contacting the metadata
server introduces subtleties that must be handled correctly if the server introduces subtleties that must be handled correctly if the
possibility of file system corruption is to be avoided. possibility of file system corruption is to be avoided.
12.7.1. Recovery from Client Restart 12.7.1. Recovery from Client Restart
Client recovery for layouts is similar to client recovery for other Client recovery for layouts is similar to client recovery for other
lock and delegation state. When an pNFS client restarts, it will lock and delegation state. When a pNFS client restarts, it will lose
lose all information about the layouts that it previously owned. all information about the layouts that it previously owned. There
There are two methods by which the server can reclaim these resources are two methods by which the server can reclaim these resources and
and allow otherwise conflicting layouts to be provided to other allow otherwise conflicting layouts to be provided to other clients.
clients.
The first is through the expiry of the client's lease. If the client The first is through the expiry of the client's lease. If the client
recovery time is longer than the lease period, the client's lease recovery time is longer than the lease period, the client's lease
will expire and the server will know that state may be released. For will expire and the server will know that state may be released. For
layouts the server may release the state immediately upon lease layouts, the server may release the state immediately upon lease
expiry or it may allow the layout to persist awaiting possible lease expiry or it may allow the layout to persist, awaiting possible lease
revival, as long as no other layout conflicts. revival, as long as no other layout conflicts.
The second is through the client restarting in less time than it The second is through the client restarting in less time than it
takes for the lease period to expire. In such a case, the client takes for the lease period to expire. In such a case, the client
will contact the server through the standard EXCHANGE_ID protocol. will contact the server through the standard EXCHANGE_ID protocol.
The server will find that the client's co_ownerid matches the The server will find that the client's co_ownerid matches the
co_ownerid of the previous client invocation, but that the verifier co_ownerid of the previous client invocation, but that the verifier
is different. The server uses this as a signal to release all layout is different. The server uses this as a signal to release all layout
state associated with the client's previous invocation. In this state associated with the client's previous invocation. In this
scenario, the data written by the client but not covered by a scenario, the data written by the client but not covered by a
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If a client believes its lease has expired, it MUST NOT send I/O to If a client believes its lease has expired, it MUST NOT send I/O to
the storage device until it has validated its lease. The client can the storage device until it has validated its lease. The client can
send a SEQUENCE operation to the metadata server. If the SEQUENCE send a SEQUENCE operation to the metadata server. If the SEQUENCE
operation is successful, but sr_status_flag has operation is successful, but sr_status_flag has
SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED, SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED,
SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED, or SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED, or
SEQ4_STATUS_ADMIN_STATE_REVOKED set, the client MUST NOT use SEQ4_STATUS_ADMIN_STATE_REVOKED set, the client MUST NOT use
currently held layouts. The client has two choices to recover from currently held layouts. The client has two choices to recover from
the lease expiration. First, for all modified but uncommitted data, the lease expiration. First, for all modified but uncommitted data,
write it to the metadata server using the FILE_SYNC4 flag for the the client writes it to the metadata server using the FILE_SYNC4 flag
WRITEs or WRITE and COMMIT. Second, the client reestablishes a for the WRITEs, or WRITE and COMMIT. Second, the client re-
client ID and session with the server and obtain new layouts and establishes a client ID and session with the server and obtains new
device ID to device address mappings for the modified data ranges and layouts and device-ID-to-device-address mappings for the modified
then write the data to the storage devices with the newly obtained data ranges and then writes the data to the storage devices with the
layouts. newly obtained layouts.
If sr_status_flags from the metadata server has If sr_status_flags from the metadata server has
SEQ4_STATUS_RESTART_RECLAIM_NEEDED set (or SEQUENCE returns SEQ4_STATUS_RESTART_RECLAIM_NEEDED set (or SEQUENCE returns
NFS4ERR_BAD_SESSION and CREATE_SESSION returns NFS4ERR_BAD_SESSION and CREATE_SESSION returns
NFS4ERR_STALE_CLIENTID) then the metadata server has restarted, and NFS4ERR_STALE_CLIENTID), then the metadata server has restarted, and
the client SHOULD recover using the methods described in the client SHOULD recover using the methods described in
Section 12.7.4. Section 12.7.4.
If sr_status_flags from the metadata server has If sr_status_flags from the metadata server has
SEQ4_STATUS_LEASE_MOVED set, then the client recovers by following SEQ4_STATUS_LEASE_MOVED set, then the client recovers by following
the procedure described in Section 11.7.7.1. After that, the client the procedure described in Section 11.7.7.1. After that, the client
may get an indication that the layout state was not moved with the may get an indication that the layout state was not moved with the
file system. The client recovers as in the other applicable file system. The client recovers as in the other applicable
situations discussed in Paragraph 1 or Paragraph 2 of this section. situations discussed in the first two paragraphs of this section.
If sr_status_flags reports no loss of state, then the lease for the If sr_status_flags reports no loss of state, then the lease for the
layouts the client has are valid and renewed, and the client can once layouts that the client has are valid and renewed, and the client can
again send I/O requests to the storage devices. once again send I/O requests to the storage devices.
While clients SHOULD NOT send I/Os to storage devices that may extend While clients SHOULD NOT send I/Os to storage devices that may extend
past the lease expiration time period, this is not always possible; past the lease expiration time period, this is not always possible,
for example, an extended network partition that starts after the I/O for example, an extended network partition that starts after the I/O
is sent and does not heal until the I/O request is received by the is sent and does not heal until the I/O request is received by the
storage device. Thus the metadata server and/or storage devices are storage device. Thus, the metadata server and/or storage devices are
responsible for protecting themselves from I/Os that are sent before responsible for protecting themselves from I/Os that are both sent
the lease expires, but arrive after the lease expires. See before the lease expires and arrive after the lease expires. See
Section 12.7.3. Section 12.7.3.
12.7.3. Dealing with Loss of Layout State on the Metadata Server 12.7.3. Dealing with Loss of Layout State on the Metadata Server
This is a description of the case where all of the following are This is a description of the case where all of the following are
true: true:
o the metadata server has not restarted o the metadata server has not restarted
o a pNFS client's layouts have been discarded (usually because the o a pNFS client's layouts have been discarded (usually because the
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12.7.3. Dealing with Loss of Layout State on the Metadata Server 12.7.3. Dealing with Loss of Layout State on the Metadata Server
This is a description of the case where all of the following are This is a description of the case where all of the following are
true: true:
o the metadata server has not restarted o the metadata server has not restarted
o a pNFS client's layouts have been discarded (usually because the o a pNFS client's layouts have been discarded (usually because the
client's lease expired) and are invalid client's lease expired) and are invalid
o an I/O from the pNFS client arrives at the storage device o an I/O from the pNFS client arrives at the storage device
The metadata server and its storage devices MUST solve this by The metadata server and its storage devices MUST solve this by
fencing the client. In other words, prevent the execution of I/O fencing the client. In other words, they MUST solve this by
operations from the client to the storage devices after layout state preventing the execution of I/O operations from the client to the
loss. The details of how fencing is done are specific to the layout storage devices after layout state loss. The details of how fencing
type. The solution for NFSv4.1 file-based layouts is described in is done are specific to the layout type. The solution for NFSv4.1
(Section 13.11), and for other layout types in their respective file-based layouts is described in (Section 13.11), and solutions for
external specification documents. other layout types are in their respective external specification
documents.
12.7.4. Recovery from Metadata Server Restart 12.7.4. Recovery from Metadata Server Restart
The pNFS client will discover that the metadata server has restarted The pNFS client will discover that the metadata server has restarted
via the methods described in Section 8.4.2 and discussed in a pNFS- via the methods described in Section 8.4.2 and discussed in a pNFS-
specific context in Paragraph 2, of Section 12.7.2. The client MUST specific context in Paragraph 2, of Section 12.7.2. The client MUST
stop using layouts and delete the device ID to device address stop using layouts and delete the device ID to device address
mappings it previously received from the metadata server. Having mappings it previously received from the metadata server. Having
done that, if the client wrote data to the storage device without done that, if the client wrote data to the storage device without
committing the layouts via LAYOUTCOMMIT, then the client has committing the layouts via LAYOUTCOMMIT, then the client has
additional work to do in order to have the client, metadata server additional work to do in order to have the client, metadata server,
and storage device(s) all synchronized on the state of the data. and storage device(s) all synchronized on the state of the data.
o If the client has data still modified and unwritten in the o If the client has data still modified and unwritten in the
client's memory, the client has only two choices. client's memory, the client has only two choices.
1. The client can obtain a layout via LAYOUTGET after the 1. The client can obtain a layout via LAYOUTGET after the
server's grace period and write the data to the storage server's grace period and write the data to the storage
devices. devices.
2. The client can write that data through the metadata server 2. The client can WRITE that data through the metadata server
using the WRITE (Section 18.32) operation, and then obtain using the WRITE (Section 18.32) operation, and then obtain
layouts as desired. layouts as desired.
o Even if the client synchronously wrote data to the storage device, o If the client asynchronously wrote data to the storage device, but
if it still has a copy of the data in its memory, then it has still has a copy of the data in its memory, then it has available
available to it the recovery options listed above in the previous to it the recovery options listed above in the previous bullet
bullet point. If the metadata server is also in its grace period, point. If the metadata server is also in its grace period, the
the client has available to it the options below in the next client has available to it the options below in the next bullet
bullet item. point.
o The client does not have a copy of the data in its memory and the o The client does not have a copy of the data in its memory and the
metadata server is still in its grace period. The client cannot metadata server is still in its grace period. The client cannot
use LAYOUTGET (within or outside the grace period) to reclaim a use LAYOUTGET (within or outside the grace period) to reclaim a
layout because the contents of the response from LAYOUTGET may not layout because the contents of the response from LAYOUTGET may not
match what it had previously. The range might be different or it match what it had previously. The range might be different or the
might get the same range but the content of the layout might be client might get the same range but the content of the layout
different. Even if the content of the layout appears to be the might be different. Even if the content of the layout appears to
same, the device IDs may map to different device addresses, and be the same, the device IDs may map to different device addresses,
even if the device addresses are the same, the device addresses and even if the device addresses are the same, the device
could have been assigned to a different storage device. The addresses could have been assigned to a different storage device.
option of retrieving the data from the storage device and writing The option of retrieving the data from the storage device and
it to the metadata server per the recovery scenario described writing it to the metadata server per the recovery scenario
above is not available because, again, the mappings of range to described above is not available because, again, the mappings of
device ID, device ID to device address, device address to physical range to device ID, device ID to device address, and device
device are stale and new mappings via new LAYOUTGET do not solve address to physical device are stale, and new mappings via new
the problem. LAYOUTGET do not solve the problem.
The only recovery option for this scenario is to send a The only recovery option for this scenario is to send a
LAYOUTCOMMIT in reclaim mode, which the metadata server will LAYOUTCOMMIT in reclaim mode, which the metadata server will
accept as long as it is in its grace period. The use of accept as long as it is in its grace period. The use of
LAYOUTCOMMIT in reclaim mode informs the metadata server that the LAYOUTCOMMIT in reclaim mode informs the metadata server that the
layout has changed. It is critical the metadata server receive layout has changed. It is critical that the metadata server
this information before its grace period ends, and thus before it receive this information before its grace period ends, and thus
starts allowing updates to the file system. before it starts allowing updates to the file system.
To send LAYOUTCOMMIT in reclaim mode, the client sets the To send LAYOUTCOMMIT in reclaim mode, the client sets the
loca_reclaim field of the operation's arguments (Section 18.42.1) loca_reclaim field of the operation's arguments (Section 18.42.1)
to TRUE. During the metadata server's recovery grace period (and to TRUE. During the metadata server's recovery grace period (and
only during the recovery grace period) the metadata server is only during the recovery grace period) the metadata server is
prepared to accept LAYOUTCOMMIT requests with the loca_reclaim prepared to accept LAYOUTCOMMIT requests with the loca_reclaim
field set to TRUE. field set to TRUE.
When loca_reclaim is TRUE, the client is attempting to commit When loca_reclaim is TRUE, the client is attempting to commit
changes to the layout that occurred prior to the restart of the changes to the layout that occurred prior to the restart of the
metadata server. The metadata server applies some consistency metadata server. The metadata server applies some consistency
checks on the loca_layoutupdate field of the arguments to checks on the loca_layoutupdate field of the arguments to
determine whether the client can commit the data written to the determine whether the client can commit the data written to the
storage device to the file system. The loca_layoutupdate field is storage device to the file system. The loca_layoutupdate field is
of data type layoutupdate4, and contains layout type-specific of data type layoutupdate4 and contains layout-type-specific
content (in the lou_body field of loca_layoutupdate). The layout content (in the lou_body field of loca_layoutupdate). The layout-
type-specific information that loca_layoutupdate might have is type-specific information that loca_layoutupdate might have is
discussed in Section 12.5.4.3. If the metadata server's discussed in Section 12.5.4.3. If the metadata server's
consistency checks on loca_layoutupdate succeed, then the metadata consistency checks on loca_layoutupdate succeed, then the metadata
server MUST commit the data (as described by the loca_offset, server MUST commit the data (as described by the loca_offset,
loca_length, and loca_layoutupdate fields of the arguments) that loca_length, and loca_layoutupdate fields of the arguments) that
was written to storage device. If the metadata server's was written to the storage device. If the metadata server's
consistency checks on loca_layoutupdate fail, the metadata server consistency checks on loca_layoutupdate fail, the metadata server
rejects the LAYOUTCOMMIT operation, and makes no changes to the rejects the LAYOUTCOMMIT operation and makes no changes to the
file system. However, any time LAYOUTCOMMIT with loca_reclaim file system. However, any time LAYOUTCOMMIT with loca_reclaim
TRUE fails, the pNFS client has lost all the data in the range TRUE fails, the pNFS client has lost all the data in the range
defined by <loca_offset, loca_length>. A client can defend defined by <loca_offset, loca_length>. A client can defend
against this risk by caching all data, whether written against this risk by caching all data, whether written
synchronously or asynchronously in its memory and not release the synchronously or asynchronously in its memory, and by not
cached data until a successful LAYOUTCOMMIT. This condition does releasing the cached data until a successful LAYOUTCOMMIT. This
not hold true for all layout types; for example, files-based condition does not hold true for all layout types; for example,
storage devices need not suffer from this limitation. file-based storage devices need not suffer from this limitation.
o The client does not have a copy of the data in its memory and the o The client does not have a copy of the data in its memory and the
metadata server is no longer in its grace period; i.e. the metadata server is no longer in its grace period; i.e., the
metadata server returns NFS4ERR_NO_GRACE. As with the scenario in metadata server returns NFS4ERR_NO_GRACE. As with the scenario in
the above bullet item, the failure of LAYOUTCOMMIT means the data the above bullet point, the failure of LAYOUTCOMMIT means the data
in the range <loca_offset, loca_length> lost. The defense against in the range <loca_offset, loca_length> lost. The defense against
the risk is the same; cache all written data on the client until a the risk is the same -- cache all written data on the client until
successful LAYOUTCOMMIT. a successful LAYOUTCOMMIT.
12.7.5. Operations During Metadata Server Grace Period 12.7.5. Operations during Metadata Server Grace Period
Some of the recovery scenarios thus far noted that some operations, Some of the recovery scenarios thus far noted that some operations
namely WRITE and LAYOUTGET might be permitted during the metadata (namely, WRITE and LAYOUTGET) might be permitted during the metadata
server's grace period. The metadata server may allow these server's grace period. The metadata server may allow these
operations during its grace period. For LAYOUTGET, the metadata operations during its grace period. For LAYOUTGET, the metadata
server must reliably determine that servicing such a request will not server must reliably determine that servicing such a request will not
conflict with an impending LAYOUTCOMMIT reclaim request. For WRITE, conflict with an impending LAYOUTCOMMIT reclaim request. For WRITE,
it must reliably determine that it will not conflict with an the metadata server must reliably determine that servicing the
impending OPEN; or a LOCK where the file has mandatory file locking request will not conflict with an impending OPEN or with a LOCK where
enabled. the file has mandatory byte-range locking enabled.
As mentioned previously, some operations, namely WRITE and LAYOUTGET As mentioned previously, for expediency, the metadata server might
may be rejected during the metadata server's grace period, because to reject some operations (namely, WRITE and LAYOUTGET) during its grace
provide simple, valid handling during the grace period, the easiest period, because the simplest correct approach is to reject all non-
method is to simply reject all non-reclaim pNFS requests and WRITE reclaim pNFS requests and WRITE operations by returning the
operations by returning the NFS4ERR_GRACE error. However, depending NFS4ERR_GRACE error. However, depending on the storage protocol
on the storage protocol (which is specific to the layout type) and (which is specific to the layout type) and metadata server
metadata server implementation, the metadata server may be able to implementation, the metadata server may be able to determine that a
determine that a particular request is safe. For example, a metadata particular request is safe. For example, a metadata server may save
server may save provisional allocation mappings for each file to provisional allocation mappings for each file to stable storage, as
stable storage, as well as information about potentially conflicting well as information about potentially conflicting OPEN share modes
OPEN share modes and mandatory byte-range locks that might have been and mandatory byte-range locks that might have been in effect at the
in effect at the time of restart, and use this information during the time of restart, and the metadata server may use this information
recovery grace period to determine that a WRITE request is safe. during the recovery grace period to determine that a WRITE request is
safe.
12.7.6. Storage Device Recovery 12.7.6. Storage Device Recovery
Recovery from storage device restart is mostly dependent upon the Recovery from storage device restart is mostly dependent upon the
layout type in use. However, there are a few general techniques a layout type in use. However, there are a few general techniques a
client can use if it discovers a storage device has crashed while client can use if it discovers a storage device has crashed while
holding modified, uncommitted data that was asynchronously written. holding modified, uncommitted data that was asynchronously written.
First and foremost, it is important to realize that the client is the First and foremost, it is important to realize that the client is the
only one which has the information necessary to recover non-committed only one that has the information necessary to recover non-committed
data; since, it holds the modified data and probably nothing else data since it holds the modified data and probably nothing else does.
does. Second, the best solution is for the client to err on the side Second, the best solution is for the client to err on the side of
of caution and attempt to re-write the modified data through another caution and attempt to rewrite the modified data through another
path. path.
The client SHOULD immediately write the data to the metadata server, The client SHOULD immediately WRITE the data to the metadata server,
with the stable field in the WRITE4args set to FILE_SYNC4. Once it with the stable field in the WRITE4args set to FILE_SYNC4. Once it
does this, there is no need to wait for the original storage device. does this, there is no need to wait for the original storage device.
12.8. Metadata and Storage Device Roles 12.8. Metadata and Storage Device Roles
If the same physical hardware is used to implement both a metadata If the same physical hardware is used to implement both a metadata
server and storage device, then the same hardware entity is to be server and storage device, then the same hardware entity is to be
understood to be implementing two distinct roles and it is important understood to be implementing two distinct roles and it is important
that it be clearly understood on behalf of which role the hardware is that it be clearly understood on behalf of which role the hardware is
executing at any given time. executing at any given time.
Two sub-cases can be distinguished. Two sub-cases can be distinguished.
1. The storage device uses NFSv4.1 as the storage protocol, i.e. 1. The storage device uses NFSv4.1 as the storage protocol, i.e.,
same physical hardware is used to implement both a metadata and the same physical hardware is used to implement both a metadata
data server. See Section 13.1 for a description how multiple and data server. See Section 13.1 for a description of how
roles are handled. multiple roles are handled.
2. The storage device does not use NFSv4.1 as the storage protocol, 2. The storage device does not use NFSv4.1 as the storage protocol,
and the same physical hardware is used to implement both a and the same physical hardware is used to implement both a
metadata and storage device. Whether distinct network addresses metadata and storage device. Whether distinct network addresses
are used to access metadata server and storage device is are used to access the metadata server and storage device is
immaterial, because, it is always clear to the pNFS client and immaterial. This is because it is always clear to the pNFS
server, from upper layer protocol being used (NFSv4.1 or non- client and server, from the upper-layer protocol being used
NFSv4.1) what role the request to the common server network (NFSv4.1 or non-NFSv4.1), to which role the request to the common
address is directed to. server network address is directed.
12.9. Security Considerations for pNFS 12.9. Security Considerations for pNFS
pNFS separates file system metadata and data and provides access to pNFS separates file system metadata and data and provides access to
both. There are pNFS-specific operations (listed in Section 12.3) both. There are pNFS-specific operations (listed in Section 12.3)
that provide access to the metadata; all existing NFSv4.1 that provide access to the metadata; all existing NFSv4.1
conventional (non-pNFS) security mechanisms and features apply to conventional (non-pNFS) security mechanisms and features apply to
accessing the metadata. The combination of components in a pNFS accessing the metadata. The combination of components in a pNFS
system (see Figure 1) is required to preserve the security properties system (see Figure 1) is required to preserve the security properties
of NFSv4.1 with respect to an entity accessing storage device from a of NFSv4.1 with respect to an entity that is accessing a storage
client, including security countermeasures to defend against threats device from a client, including security countermeasures to defend
that NFSv4.1 provides defenses for in environments where these against threats for which NFSv4.1 provides defenses in environments
threats are considered significant. where these threats are considered significant.
In some cases, the security countermeasures for connections to In some cases, the security countermeasures for connections to
storage devices may take the form of physical isolation or a storage devices may take the form of physical isolation or a
recommendation not to use pNFS in an environment. For example, it recommendation to avoid the use of pNFS in an environment. For
may be impractical to provide confidentiality protection for some example, it may be impractical to provide confidentiality protection
storage protocols to protect against eavesdropping; in environments for some storage protocols to protect against eavesdropping. In
where eavesdropping on such protocols is of sufficient concern to environments where eavesdropping on such protocols is of sufficient
require countermeasures, physical isolation of the communication concern to require countermeasures, physical isolation of the
channel (e.g., via direct connection from client(s) to storage communication channel (e.g., via direct connection from client(s) to
device(s)) and/or a decision to forgo use of pNFS (e.g., and fall storage device(s)) and/or a decision to forgo use of pNFS (e.g., and
back to conventional NFSv4.1) may be appropriate courses of action. fall back to conventional NFSv4.1) may be appropriate courses of
action.
Where communication with storage devices is subject to the same Where communication with storage devices is subject to the same
threats as client to metadata server communication, the protocols threats as client-to-metadata server communication, the protocols
used for that communication need to provide security mechanisms as used for that communication need to provide security mechanisms as
strong as or no weaker than those available via RPCSEC_GSS for strong as or no weaker than those available via RPCSEC_GSS for
NFSv4.1. Except for the storage protocol used for the NFSv4.1. Except for the storage protocol used for the
LAYOUT4_NFSV4_1_FILES layout (see Section 13), i.e. except for LAYOUT4_NFSV4_1_FILES layout (see Section 13), i.e., except for
NFSv4.1, it is beyond the scope of this document to specify the NFSv4.1, it is beyond the scope of this document to specify the
security mechanisms for storage access protocols. security mechanisms for storage access protocols.
pNFS implementations MUST NOT remove NFSv4.1's access controls. The pNFS implementations MUST NOT remove NFSv4.1's access controls. The
combination of clients, storage devices, and the metadata server are combination of clients, storage devices, and the metadata server are
responsible for ensuring that all client to storage device file data responsible for ensuring that all client-to-storage-device file data
access respects NFSv4.1's ACLs and file open modes. This entails access respects NFSv4.1's ACLs and file open modes. This entails
performing both of these checks on every access in the client, the performing both of these checks on every access in the client, the
storage device, or both (as applicable; when the storage device is an storage device, or both (as applicable; when the storage device is an
NFSv4.1 server, the storage device is ultimately responsible for NFSv4.1 server, the storage device is ultimately responsible for
controlling access as described in Section 13.9.2). If a pNFS controlling access as described in Section 13.9.2). If a pNFS
configuration performs these checks only in the client, the risk of a configuration performs these checks only in the client, the risk of a
misbehaving client obtaining unauthorized access is an important misbehaving client obtaining unauthorized access is an important
consideration in determining when it is appropriate to use such a consideration in determining when it is appropriate to use such a
pNFS configuration. Such layout types SHOULD NOT be used when pNFS configuration. Such layout types SHOULD NOT be used when
client-only access checks do not provide sufficient assurance that client-only access checks do not provide sufficient assurance that
NFSv4.1 access control is being applied correctly. (This is not a NFSv4.1 access control is being applied correctly. (This is not a
problem for the file layout type described in Section 13 because the problem for the file layout type described in Section 13 because the
storage access protocol for LAYOUT4_NFSV4_1_FILES is NFSv4.1, and storage access protocol for LAYOUT4_NFSV4_1_FILES is NFSv4.1, and
thus the security model for storage device access via thus the security model for storage device access via
LAYOUT4_NFSv4_1_FILES is the sames as that of the metadata server.) LAYOUT4_NFSv4_1_FILES is the same as that of the metadata server.)
For handling of access control specific to a layout, the reader For handling of access control specific to a layout, the reader
should examine the layout specification, such as the NFSv4.1/ should examine the layout specification, such as the NFSv4.1/
files-based layout (Section 13) of this document, the blocks layout file-based layout (Section 13) of this document, the blocks layout
[41], and objects layout [40]. [41], and objects layout [40].
13. NFSv4.1 as a Storage Protocol in pNFS: the File Layout Type 13. NFSv4.1 as a Storage Protocol in pNFS: the File Layout Type
This section describes the semantics and format of NFSv4.1 file-based This section describes the semantics and format of NFSv4.1 file-based
layouts for pNFS. NFSv4.1 file-based layouts uses the layouts for pNFS. NFSv4.1 file-based layouts use the
LAYOUT4_NFSV4_1_FILES layout type. The LAYOUT4_NFSV4_1_FILES type LAYOUT4_NFSV4_1_FILES layout type. The LAYOUT4_NFSV4_1_FILES type
defines striping data across multiple NFSv4.1 data servers. defines striping data across multiple NFSv4.1 data servers.
13.1. Client ID and Session Considerations 13.1. Client ID and Session Considerations
Sessions are a REQUIRED feature of NFSv4.1, and this extends to both Sessions are a REQUIRED feature of NFSv4.1, and this extends to both
the metadata server and file-based (NFSv4.1-based) data servers. the metadata server and file-based (NFSv4.1-based) data servers.
The role a server plays in pNFS is determined by the result it The role a server plays in pNFS is determined by the result it
returns from EXCHANGE_ID. The roles are: returns from EXCHANGE_ID. The roles are:
o metadata server (EXCHGID4_FLAG_USE_PNFS_MDS is set in the result o Metadata server (EXCHGID4_FLAG_USE_PNFS_MDS is set in the result
eir_flags), eir_flags).
o data server (EXCHGID4_FLAG_USE_PNFS_DS) o Data server (EXCHGID4_FLAG_USE_PNFS_DS).
o non-metadata server (EXCHGID4_FLAG_USE_NON_PNFS). This is an o Non-metadata server (EXCHGID4_FLAG_USE_NON_PNFS). This is an
NFSv4.1 server that does not support operations (e.g. LAYOUTGET) NFSv4.1 server that does not support operations (e.g., LAYOUTGET)
or attributes that pertain to pNFS. or attributes that pertain to pNFS.
The client MAY request zero or more of EXCHGID4_FLAG_USE_NON_PNFS, The client MAY request zero or more of EXCHGID4_FLAG_USE_NON_PNFS,
EXCHGID4_FLAG_USE_PNFS_DS, or EXCHGID4_FLAG_USE_PNFS_MDS, even though EXCHGID4_FLAG_USE_PNFS_DS, or EXCHGID4_FLAG_USE_PNFS_MDS, even though
some combinations (e.g. EXCHGID4_FLAG_USE_NON_PNFS | some combinations (e.g., EXCHGID4_FLAG_USE_NON_PNFS |
EXCHGID4_FLAG_USE_PNFS_MDS) are contradictory. The server however EXCHGID4_FLAG_USE_PNFS_MDS) are contradictory. However, the server
MUST only return the following acceptable combinations: MUST only return the following acceptable combinations:
+--------------------------------------------------------+ +--------------------------------------------------------+
| Acceptable Results from EXCHANGE_ID | | Acceptable Results from EXCHANGE_ID |
+--------------------------------------------------------+ +--------------------------------------------------------+
| EXCHGID4_FLAG_USE_PNFS_MDS | | EXCHGID4_FLAG_USE_PNFS_MDS |
| EXCHGID4_FLAG_USE_PNFS_MDS | EXCHGID4_FLAG_USE_PNFS_DS | | EXCHGID4_FLAG_USE_PNFS_MDS | EXCHGID4_FLAG_USE_PNFS_DS |
| EXCHGID4_FLAG_USE_PNFS_DS | | EXCHGID4_FLAG_USE_PNFS_DS |
| EXCHGID4_FLAG_USE_NON_PNFS | | EXCHGID4_FLAG_USE_NON_PNFS |
| EXCHGID4_FLAG_USE_PNFS_DS | EXCHGID4_FLAG_USE_NON_PNFS | | EXCHGID4_FLAG_USE_PNFS_DS | EXCHGID4_FLAG_USE_NON_PNFS |
+--------------------------------------------------------+ +--------------------------------------------------------+
As the above table implies, a server can have one or two roles. A As the above table implies, a server can have one or two roles. A
server can be both a metadata server and a data server or it can be server can be both a metadata server and a data server, or it can be
both a data server and non-metadata server. In addition to returning both a data server and non-metadata server. In addition to returning
two roles in EXCHANGE_ID's results, and thus serving both roles via a two roles in the EXCHANGE_ID's results, and thus serving both roles
common client ID, a server can serve two roles by returning a unique via a common client ID, a server can serve two roles by returning a
client ID and server owner for each role in each of two EXCHANGE_ID unique client ID and server owner for each role in each of two
results, with each result indicating each role. EXCHANGE_ID results, with each result indicating each role.
In the case of a server with concurrent pNFS roles that are served by In the case of a server with concurrent pNFS roles that are served by
a common client ID, if the EXCHANGE_ID request from the client has a common client ID, if the EXCHANGE_ID request from the client has
zero or a combination of the bits set in eia_flags, the server result zero or a combination of the bits set in eia_flags, the server result
should set bits which represent the higher of the acceptable should set bits that represent the higher of the acceptable
combination of the server roles, with a preference to match the roles combination of the server roles, with a preference to match the roles
requested by the client. Thus if a client request has requested by the client. Thus, if a client request has
(EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS | (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS |
EXCHGID4_FLAG_USE_PNFS_DS) flags set, and the server is both a EXCHGID4_FLAG_USE_PNFS_DS) flags set, and the server is both a
metadata server and a data server, serving both the roles by a common metadata server and a data server, serving both the roles by a common
client ID, the server SHOULD return with (EXCHGID4_FLAG_USE_PNFS_MDS client ID, the server SHOULD return with (EXCHGID4_FLAG_USE_PNFS_MDS
| EXCHGID4_FLAG_USE_PNFS_DS) set. | EXCHGID4_FLAG_USE_PNFS_DS) set.
In the case of a server that has multiple concurrent pNFS roles, each In the case of a server that has multiple concurrent pNFS roles, each
role served by a unique client ID, if the client specifies zero or a role served by a unique client ID, if the client specifies zero or a
combination of roles in the request, the server results SHOULD return combination of roles in the request, the server results SHOULD return
only one of the roles from the combination specified by the client only one of the roles from the combination specified by the client
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data server, it needs a client ID on that data server. If it does data server, it needs a client ID on that data server. If it does
not yet have a client ID from the server that had the not yet have a client ID from the server that had the
EXCHGID4_FLAG_USE_PNFS_DS flag set in the EXCHANGE_ID results, then EXCHGID4_FLAG_USE_PNFS_DS flag set in the EXCHANGE_ID results, then
the client needs to send an EXCHANGE_ID to the data server, using the the client needs to send an EXCHANGE_ID to the data server, using the
same co_ownerid as it sent to the metadata server, with the same co_ownerid as it sent to the metadata server, with the
EXCHGID4_FLAG_USE_PNFS_DS flag set in the arguments. If the server's EXCHGID4_FLAG_USE_PNFS_DS flag set in the arguments. If the server's
EXCHANGE_ID results have EXCHGID4_FLAG_USE_PNFS_DS set, then the EXCHANGE_ID results have EXCHGID4_FLAG_USE_PNFS_DS set, then the
client may use the client ID to create sessions that will exchange client may use the client ID to create sessions that will exchange
pNFS data operations. The client ID returned by the data server has pNFS data operations. The client ID returned by the data server has
no relationship with the client ID returned by a metadata server no relationship with the client ID returned by a metadata server
unless the client IDs are equal and the server owners and server unless the client IDs are equal, and the server owners and server
scopes of the data server and metadata server are equal. scopes of the data server and metadata server are equal.
In NFSv4.1, the session ID in the SEQUENCE operation implies the In NFSv4.1, the session ID in the SEQUENCE operation implies the
client ID, which in turn might be used by the server to map the client ID, which in turn might be used by the server to map the
stateid to the right client/server pair. However, when a data server stateid to the right client/server pair. However, when a data server
is presented with a READ or WRITE operation with a stateid, because is presented with a READ or WRITE operation with a stateid, because
the stateid is associated with client ID on a metadata server, and the stateid is associated with a client ID on a metadata server, and
because the session ID in the preceding SEQUENCE operation is tied to because the session ID in the preceding SEQUENCE operation is tied to
the client ID of the data server, the data server has no obvious way the client ID of the data server, the data server has no obvious way
to determine the metadata server from the COMPOUND procedure, and to determine the metadata server from the COMPOUND procedure, and
thus has no way to validate the stateid. One RECOMMENDED approach is thus has no way to validate the stateid. One RECOMMENDED approach is
for pNFS servers to encode metadata server routing and/or identity for pNFS servers to encode metadata server routing and/or identity
information in the data server filehandles as returned in the layout. information in the data server filehandles as returned in the layout.
If metadata server routing and/or identity information is encoded in If metadata server routing and/or identity information is encoded in
data server filehandles, when the metadata server identity or data server filehandles, when the metadata server identity or
location changes, the data server filehandles it gave out will become location changes, the data server filehandles it gave out will become
invalid (stale), and so the metadata server MUST first recall the invalid (stale), and so the metadata server MUST first recall the
layouts. Invalidating a data server filehandle does not render the layouts. Invalidating a data server filehandle does not render the
NFS client's data cache invalid. The client's cache should map a NFS client's data cache invalid. The client's cache should map a
data server filehandle to a metadata server filehandle, and a data server filehandle to a metadata server filehandle, and a
metadata server filehandle to cached data. metadata server filehandle to cached data.
If a server is both a metadata server and a data server, the server If a server is both a metadata server and a data server, the server
might need to distinguish operations on files that are directed to might need to distinguish operations on files that are directed to
the metadata server from those that are directed to the data server. the metadata server from those that are directed to the data server.
It is RECOMMENDED that the values of the filehandles returned by the It is RECOMMENDED that the values of the filehandles returned by the
LAYOUTGET operation to be different than the value of the filehandle LAYOUTGET operation be different than the value of the filehandle
returned by the OPEN of the same file. returned by the OPEN of the same file.
Another scenario is for the metadata server and the storage device to Another scenario is for the metadata server and the storage device to
be distinct from one client's point of view, and the roles reversed be distinct from one client's point of view, and the roles reversed
from another client's point of view. For example, in the cluster from another client's point of view. For example, in the cluster
file system model, a metadata server to one client might be a data file system model, a metadata server to one client might be a data
server to another client. If NFSv4.1 is being used as the storage server to another client. If NFSv4.1 is being used as the storage
protocol, then pNFS servers need to encode the values of filehandles protocol, then pNFS servers need to encode the values of filehandles
according to their specific roles. according to their specific roles.
13.1.1. Sessions Considerations for Data Servers 13.1.1. Sessions Considerations for Data Servers
Section 2.10.11.2 states that a client has to keep its lease renewed Section 2.10.11.2 states that a client has to keep its lease renewed
in order to prevent a session from being deleted by the server. If in order to prevent a session from being deleted by the server. If
the reply to EXCHANGE_ID has just the EXCHGID4_FLAG_USE_PNFS_DS role the reply to EXCHANGE_ID has just the EXCHGID4_FLAG_USE_PNFS_DS role
set, then as noted in Section 13.6 the client will not be able to set, then (as noted in Section 13.6) the client will not be able to
determine the data server's lease_time attribute, because GETATTR determine the data server's lease_time attribute because GETATTR will
will not be permitted. Instead, the rule is that any time a client not be permitted. Instead, the rule is that any time a client
receives a layout referring it to a data server that returns just the receives a layout referring it to a data server that returns just the
EXCHGID4_FLAG_USE_PNFS_DS role, the client MAY assume that the EXCHGID4_FLAG_USE_PNFS_DS role, the client MAY assume that the
lease_time attribute from the metadata server that returned the lease_time attribute from the metadata server that returned the
layout applies to the data server. Thus the data server MUST be layout applies to the data server. Thus, the data server MUST be
aware of the values of all lease_time attributes of all metadata aware of the values of all lease_time attributes of all metadata
servers it is providing I/O for, and MUST use the maximum of all such servers for which it is providing I/O, and it MUST use the maximum of
lease_time values as the lease interval for all client IDs and all such lease_time values as the lease interval for all client IDs
sessions established on it. and sessions established on it.
For example, if one metadata server has a lease_time attribute of 20 For example, if one metadata server has a lease_time attribute of 20
seconds, and a second metadata server has a lease_time attribute of seconds, and a second metadata server has a lease_time attribute of
10 seconds, then if both servers return layouts that refer to an 10 seconds, then if both servers return layouts that refer to an
EXCHGID4_FLAG_USE_PNFS_DS-only data server, the data server MUST EXCHGID4_FLAG_USE_PNFS_DS-only data server, the data server MUST
renew a client's lease if the interval between two SEQUENCE renew a client's lease if the interval between two SEQUENCE
operations on different COMPOUND requests is less than 20 seconds. operations on different COMPOUND requests is less than 20 seconds.
13.2. File Layout Definitions 13.2. File Layout Definitions
The following definitions apply to the LAYOUT4_NFSV4_1_FILES layout The following definitions apply to the LAYOUT4_NFSV4_1_FILES layout
type, and may be applicable to other layout types. type and may be applicable to other layout types.
Unit. A unit is a fixed size quantity of data written to a data Unit. A unit is a fixed-size quantity of data written to a data
server. server.
Pattern. A pattern is a method of distributing one or more equal Pattern. A pattern is a method of distributing one or more equal
sized units across a set of data servers. A pattern is iterated sized units across a set of data servers. A pattern is iterated
one or more times. one or more times.
Stripe. An stripe is a set of data distributed across a set of data Stripe. A stripe is a set of data distributed across a set of data
servers in a pattern before that pattern repeats. servers in a pattern before that pattern repeats.
Stripe Count. A stripe count is the number of units in a pattern. Stripe Count. A stripe count is the number of units in a pattern.
Stripe Width. A stripe width is the size of stripe in bytes. The Stripe Width. A stripe width is the size of a stripe in bytes. The
stripe width = the stripe count * the size of the stripe unit. stripe width = the stripe count * the size of the stripe unit.
Hereafter, this document will refer to a unit that is a written in a Hereafter, this document will refer to a unit that is a written in a
pattern as a "stripe unit". pattern as a "stripe unit".
A pattern may have more stripe units than data servers. If so, some A pattern may have more stripe units than data servers. If so, some
data servers will have more than one stripe unit per stripe. A data data servers will have more than one stripe unit per stripe. A data
server that has multiple stripe units per stripe MAY store each unit server that has multiple stripe units per stripe MAY store each unit
in a different data file (and depending on the implementation, will in a different data file (and depending on the implementation, will
possibly assign a unique data filehandle to each data file). possibly assign a unique data filehandle to each data file).
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struct nfsv4_1_file_layouthint4 { struct nfsv4_1_file_layouthint4 {
uint32_t nflh_care; uint32_t nflh_care;
nfl_util4 nflh_util; nfl_util4 nflh_util;
count4 nflh_stripe_count; count4 nflh_stripe_count;
}; };
The generic layout hint structure is described in Section 3.3.19. The generic layout hint structure is described in Section 3.3.19.
The client uses the layout hint in the layout_hint (Section 5.12.4) The client uses the layout hint in the layout_hint (Section 5.12.4)
attribute to indicate the preferred type of layout to be used for a attribute to indicate the preferred type of layout to be used for a
newly created file. The LAYOUT4_NFSV4_1_FILES layout type-specific newly created file. The LAYOUT4_NFSV4_1_FILES layout-type-specific
content for the layout hint is composed of three fields. The first content for the layout hint is composed of three fields. The first
field, nflh_care, is a set of flags indicating which values of the field, nflh_care, is a set of flags indicating which values of the
hint the client cares about. If the NFLH4_CARE_DENSE flag is set, hint the client cares about. If the NFLH4_CARE_DENSE flag is set,
then the client indicates in the second field, nflh_util, a then the client indicates in the second field, nflh_util, a
preference for how the data file is packed (Section 13.4.4), which is preference for how the data file is packed (Section 13.4.4), which is
controlled by the value of nflh_util & NFL4_UFLG_DENSE. If the controlled by the value of the expression nflh_util & NFL4_UFLG_DENSE
("&" represents the bitwise AND operator). If the
NFLH4_CARE_COMMIT_THRU_MDS flag is set, then the client indicates a NFLH4_CARE_COMMIT_THRU_MDS flag is set, then the client indicates a
preference for whether the client should send COMMIT operations to preference for whether the client should send COMMIT operations to
the metadata server or data server (Section 13.7), which is the metadata server or data server (Section 13.7), which is
controlled by the value of nflh_util & NFL4_UFLG_COMMIT_THRU_MDS. If controlled by the value of nflh_util & NFL4_UFLG_COMMIT_THRU_MDS. If
the NFLH4_CARE_STRIPE_UNIT_SIZE flag is set, the client indicates its the NFLH4_CARE_STRIPE_UNIT_SIZE flag is set, the client indicates its
preferred stripe unit size, which is indicated in nflh_util & preferred stripe unit size, which is indicated in nflh_util &
NFL4_UFLG_STRIPE_UNIT_SIZE_MASK (thus the stripe unit size MUST be a NFL4_UFLG_STRIPE_UNIT_SIZE_MASK (thus, the stripe unit size MUST be a
multiple of 64 bytes). The minimum stripe unit size is 64 bytes. If multiple of 64 bytes). The minimum stripe unit size is 64 bytes. If
the NFLH4_CARE_STRIPE_COUNT flag is set, the client indicates in the the NFLH4_CARE_STRIPE_COUNT flag is set, the client indicates in the
third field, nflh_stripe_count, the stripe count. The stripe count third field, nflh_stripe_count, the stripe count. The stripe count
multiplied by the stripe unit size is the stripe width. multiplied by the stripe unit size is the stripe width.
When LAYOUTGET returns a LAYOUT4_NFSV4_1_FILES layout (indicated in When LAYOUTGET returns a LAYOUT4_NFSV4_1_FILES layout (indicated in
the loc_type field of the lo_content field), the loc_body field of the loc_type field of the lo_content field), the loc_body field of
the lo_content field contains a value of data type the lo_content field contains a value of data type
nfsv4_1_file_layout4. Among other content, nfsv4_1_file_layout4 has nfsv4_1_file_layout4. Among other content, nfsv4_1_file_layout4 has
a storage device ID (field nfl_deviceid) of data type deviceid4. The a storage device ID (field nfl_deviceid) of data type deviceid4. The
skipping to change at page 313, line 25 skipping to change at page 313, line 26
struct nfsv4_1_file_layout_ds_addr4 { struct nfsv4_1_file_layout_ds_addr4 {
uint32_t nflda_stripe_indices<>; uint32_t nflda_stripe_indices<>;
multipath_list4 nflda_multipath_ds_list<>; multipath_list4 nflda_multipath_ds_list<>;
}; };
The nfsv4_1_file_layout_ds_addr4 data type represents the device The nfsv4_1_file_layout_ds_addr4 data type represents the device
address. It is composed of two fields: address. It is composed of two fields:
1. nflda_multipath_ds_list: An array of lists of data servers, where 1. nflda_multipath_ds_list: An array of lists of data servers, where
each list can be one or more elements, and each element each list can be one or more elements, and each element
represents a (see Section 13.5) data server address which may represents a data server address that may serve equally as the
serve equally as the target of IO operations. The length of this target of I/O operations (see Section 13.5). The length of this
array might be different than the stripe count. array might be different than the stripe count.
2. nflda_stripe_indices: An array of indices used to index into 2. nflda_stripe_indices: An array of indices used to index into
nflda_multipath_ds_list. The value of each element of nflda_multipath_ds_list. The value of each element of
nflda_stripe_indices MUST be less than the number of elements in nflda_stripe_indices MUST be less than the number of elements in
nflda_multipath_ds_list. Each element of nflda_multipath_ds_list nflda_multipath_ds_list. Each element of nflda_multipath_ds_list
SHOULD be referred to by one or more elements of SHOULD be referred to by one or more elements of
nflda_stripe_indices. The number of elements in nflda_stripe_indices. The number of elements in
nflda_stripe_indices is always equal to the stripe count. nflda_stripe_indices is always equal to the stripe count.
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struct nfsv4_1_file_layout4 { struct nfsv4_1_file_layout4 {
deviceid4 nfl_deviceid; deviceid4 nfl_deviceid;
nfl_util4 nfl_util; nfl_util4 nfl_util;
uint32_t nfl_first_stripe_index; uint32_t nfl_first_stripe_index;
offset4 nfl_pattern_offset; offset4 nfl_pattern_offset;
nfs_fh4 nfl_fh_list<>; nfs_fh4 nfl_fh_list<>;
}; };
The nfsv4_1_file_layout4 data type represents the layout. It is The nfsv4_1_file_layout4 data type represents the layout. It is
composed of the following fields: composed of the following fields:
1. nfl_deviceid: The device ID which maps to a value of type 1. nfl_deviceid: The device ID that maps to a value of type
nfsv4_1_file_layout_ds_addr4. nfsv4_1_file_layout_ds_addr4.
2. nfl_util: Like the nflh_util field of data type 2. nfl_util: Like the nflh_util field of data type
nfsv4_1_file_layouthint4, a compact representation of how the nfsv4_1_file_layouthint4, a compact representation of how the
data on a file on each data server is packed, whether the client data on a file on each data server is packed, whether the client
should send COMMIT operations to the metadata server or data should send COMMIT operations to the metadata server or data
server, and the stripe unit size. If a server returns two or server, and the stripe unit size. If a server returns two or
more overlapping layouts, each stripe unit size in each more overlapping layouts, each stripe unit size in each
overlapping layout MUST be the same. overlapping layout MUST be the same.
3. nfl_first_stripe_index: The index into the first element of the 3. nfl_first_stripe_index: The index into the first element of the
nflda_stripe_indices array to use. nflda_stripe_indices array to use.
4. nfl_pattern_offset: This field is the logical offset into the 4. nfl_pattern_offset: This field is the logical offset into the
file where the striping pattern starts. It is required for file where the striping pattern starts. It is required for
converting the client's logical I/O offset (e.g. the current converting the client's logical I/O offset (e.g., the current
offset in a POSIX file descriptor before the read() or write() offset in a POSIX file descriptor before the read() or write()
system call is sent) into the stripe unit number (see system call is sent) into the stripe unit number (see
Section 13.4.1). Section 13.4.1).
If dense packing is used, then nfl_pattern_offset is also needed If dense packing is used, then nfl_pattern_offset is also needed
to convert the client's logical I/O offset to an offset on the to convert the client's logical I/O offset to an offset on the
file on the data server corresponding to the stripe unit number file on the data server corresponding to the stripe unit number
(see Section 13.4.4). (see Section 13.4.4).
Note that nfl_pattern_offset is not always the same as lo_offset. Note that nfl_pattern_offset is not always the same as lo_offset.
For example, via the LAYOUTGET operation, a client might request For example, via the LAYOUTGET operation, a client might request
a layout starting at offset 1000 of a file that has its striping a layout starting at offset 1000 of a file that has its striping
pattern start at offset 0. pattern start at offset zero.
5. nfl_fh_list: An array of data server filehandles for each list of 5. nfl_fh_list: An array of data server filehandles for each list of
data servers in each element of the nflda_multipath_ds_list data servers in each element of the nflda_multipath_ds_list
array. The number of elements in nfl_fh_list depends on whether array. The number of elements in nfl_fh_list depends on whether
sparse or dense packing is being used. sparse or dense packing is being used.
* If sparse packing is being used, the number of elements in * If sparse packing is being used, the number of elements in
nfl_fh_list MUST be one of three values: nfl_fh_list MUST be one of three values:
+ Zero. This means that filehandles used for each data + Zero. This means that filehandles used for each data
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+ One. This means that every data server uses the same + One. This means that every data server uses the same
filehandle: what is specified in nfl_fh_list[0]. filehandle: what is specified in nfl_fh_list[0].
+ The same number of elements in nflda_multipath_ds_list. + The same number of elements in nflda_multipath_ds_list.
Thus, in this case, when sending an I/O operation to any Thus, in this case, when sending an I/O operation to any
data server in nflda_multipath_ds_list[X], the filehandle data server in nflda_multipath_ds_list[X], the filehandle
in nfl_fh_list[X] MUST be used. in nfl_fh_list[X] MUST be used.
See the discussion on sparse packing in Section 13.4.4. See the discussion on sparse packing in Section 13.4.4.
* If dense packing is being used, number of elements in * If dense packing is being used, the number of elements in
nfl_fh_list MUST be the same as the number of elements in nfl_fh_list MUST be the same as the number of elements in
nflda_stripe_indices. Thus when sending an I/O operation to nflda_stripe_indices. Thus, when sending an I/O operation to
any data server in any data server in
nflda_multipath_ds_list[nflda_stripe_indices[Y]], the nflda_multipath_ds_list[nflda_stripe_indices[Y]], the
filehandle in nfl_fh_list[Y] MUST be used. In addition, any filehandle in nfl_fh_list[Y] MUST be used. In addition, any
time there exists i, and j, (i != j) such that the time there exists i and j, (i != j), such that the
intersection of intersection of
nflda_multipath_ds_list[nflda_stripe_indices[i]] and nflda_multipath_ds_list[nflda_stripe_indices[i]] and
nflda_multipath_ds_list[nflda_stripe_indices[j]] is not empty, nflda_multipath_ds_list[nflda_stripe_indices[j]] is not empty,
then nfl_fh_list[i] MUST NOT equal nfl_fh_list[j]. In other then nfl_fh_list[i] MUST NOT equal nfl_fh_list[j]. In other
words, when dense packing is being used, if a data server words, when dense packing is being used, if a data server
appears in two or more units of a striping pattern, each appears in two or more units of a striping pattern, each
reference to the data server MUST use a different filehandle. reference to the data server MUST use a different filehandle.
Indeed, if there are multiple striping patterns, as indicated Indeed, if there are multiple striping patterns, as indicated
by the presence of multiple objects of data type layout4 by the presence of multiple objects of data type layout4
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To find the stripe unit number that corresponds to the client's To find the stripe unit number that corresponds to the client's
logical file offset, the pattern offset will also be used. The i'th logical file offset, the pattern offset will also be used. The i'th
stripe unit (SUi) is: stripe unit (SUi) is:
relative_offset = file_offset - nfl_pattern_offset; relative_offset = file_offset - nfl_pattern_offset;
SUi = floor(relative_offset / stripe_unit_size); SUi = floor(relative_offset / stripe_unit_size);
13.4.2. Interpreting the File Layout Using Sparse Packing 13.4.2. Interpreting the File Layout Using Sparse Packing
When sparse packing is used, the algorithm for determining the When sparse packing is used, the algorithm for determining the
filehandle and set of data server network addresses to write stripe filehandle and set of data-server network addresses to write stripe
unit i (SUi) to is: unit i (SUi) to is:
stripe_count = number of elements in nflda_stripe_indices; stripe_count = number of elements in nflda_stripe_indices;
j = (SUi + nfl_first_stripe_index) % stripe_count; j = (SUi + nfl_first_stripe_index) % stripe_count;
idx = nflda_stripe_indices[j]; idx = nflda_stripe_indices[j];
fh_count = number of elements in nfl_fh_list; fh_count = number of elements in nfl_fh_list;
ds_count = number of elements in nflda_multipath_ds_list; ds_count = number of elements in nflda_multipath_ds_list;
skipping to change at page 316, line 50 skipping to change at page 316, line 50
The client would then select a data server from address_list, and The client would then select a data server from address_list, and
send a READ or WRITE operation using the filehandle specified in fh. send a READ or WRITE operation using the filehandle specified in fh.
Consider the following example: Consider the following example:
Suppose we have a device address consisting of seven data servers, Suppose we have a device address consisting of seven data servers,
arranged in three equivalence (Section 13.5) classes: arranged in three equivalence (Section 13.5) classes:
{ A, B, C, D }, { E }, { F, G } { A, B, C, D }, { E }, { F, G }
Where A through G are network addresses. where A through G are network addresses.
Then Then
nflda_multipath_ds_list<> = { A, B, C, D }, { E }, { F, G } nflda_multipath_ds_list<> = { A, B, C, D }, { E }, { F, G }
i.e. i.e.,
nflda_multipath_ds_list[0] = { A, B, C, D } nflda_multipath_ds_list[0] = { A, B, C, D }
nflda_multipath_ds_list[1] = { E } nflda_multipath_ds_list[1] = { E }
nflda_multipath_ds_list[2] = { F, G } nflda_multipath_ds_list[2] = { F, G }
Suppose the striping index array is: Suppose the striping index array is:
nflda_stripe_indices<> = { 2, 0, 1, 0 } nflda_stripe_indices<> = { 2, 0, 1, 0 }
Now suppose the client gets a layout which has a device ID that maps Now suppose the client gets a layout that has a device ID that maps
to the above device address. The initial index, to the above device address. The initial index contains
nfl_first_stripe_index = 2, nfl_first_stripe_index = 2,
and and the filehandle list is
nfl_fh_list = { 0x36, 0x87, 0x67 }. nfl_fh_list = { 0x36, 0x87, 0x67 }.
If the client wants to write to SU0, the set of valid { network If the client wants to write to SU0, the set of valid { network
address, filehandle } combinations for SUi are determined by: address, filehandle } combinations for SUi are determined by:
nfl_first_stripe_index = 2 nfl_first_stripe_index = 2
So So
skipping to change at page 317, line 51 skipping to change at page 317, line 51
= 1 = 1
So So
nflda_multipath_ds_list[1] = { E } nflda_multipath_ds_list[1] = { E }
and and
nfl_fh_list[1] = { 0x87 } nfl_fh_list[1] = { 0x87 }
The client can thus write SU0 to { 0x87, { E }, }. The client can thus write SU0 to { 0x87, { E } }.
The destinations of the first thirteen storage units are: The destinations of the first 13 storage units are:
+-----+------------+--------------+ +-----+------------+--------------+
| SUi | filehandle | data servers | | SUi | filehandle | data servers |
+-----+------------+--------------+ +-----+------------+--------------+
| 0 | 87 | E | | 0 | 87 | E |
| 1 | 36 | A,B,C,D | | 1 | 36 | A,B,C,D |
| 2 | 67 | F,G | | 2 | 67 | F,G |
| 3 | 36 | A,B,C,D | | 3 | 36 | A,B,C,D |
| 4 | 87 | E | | 4 | 87 | E |
| 5 | 36 | A,B,C,D | | 5 | 36 | A,B,C,D |
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send a READ or WRITE operation using the filehandle specified in fh. send a READ or WRITE operation using the filehandle specified in fh.
Consider the following example (which is the same as the sparse Consider the following example (which is the same as the sparse
packing example, except for the filehandle list): packing example, except for the filehandle list):
Suppose we have a device address consisting of seven data servers, Suppose we have a device address consisting of seven data servers,
arranged in three equivalence (Section 13.5) classes: arranged in three equivalence (Section 13.5) classes:
{ A, B, C, D }, { E }, { F, G } { A, B, C, D }, { E }, { F, G }
Where A through G are network addresses. where A through G are network addresses.
Then Then
nflda_multipath_ds_list<> = { A, B, C, D }, { E }, { F, G } nflda_multipath_ds_list<> = { A, B, C, D }, { E }, { F, G }
i.e. i.e.,
nflda_multipath_ds_list[0] = { A, B, C, D } nflda_multipath_ds_list[0] = { A, B, C, D }
nflda_multipath_ds_list[1] = { E } nflda_multipath_ds_list[1] = { E }
nflda_multipath_ds_list[2] = { F, G } nflda_multipath_ds_list[2] = { F, G }
Suppose the striping index array is: Suppose the striping index array is:
nflda_stripe_indices<> = { 2, 0, 1, 0 } nflda_stripe_indices<> = { 2, 0, 1, 0 }
Now suppose the client gets a layout which has a device ID that maps Now suppose the client gets a layout that has a device ID that maps
to the above device address. The initial index, to the above device address. The initial index contains
nfl_first_stripe_index = 2, nfl_first_stripe_index = 2,
and and
nfl_fh_list = { 0x67, 0x37, 0x87, 0x36 }. nfl_fh_list = { 0x67, 0x37, 0x87, 0x36 }.
The interesting examples for dense packing are SU1 and SU3, because The interesting examples for dense packing are SU1 and SU3 because
each stripe unit refers to the same data server list, yet MUST use a each stripe unit refers to the same data server list, yet each stripe
different filehandle. If the client wants to write to SU1, the set unit MUST use a different filehandle. If the client wants to write
of valid { network address, filehandle } combinations for SUi are to SU1, the set of valid { network address, filehandle } combinations
determined by: for SUi are determined by:
nfl_first_stripe_index = 2 nfl_first_stripe_index = 2
So So
j = (1 + 2) % 4 = 3 j = (1 + 2) % 4 = 3
idx = nflda_stripe_indices[j] idx = nflda_stripe_indices[j]
= nflda_stripe_indices[3] = nflda_stripe_indices[3]
= 0 = 0
So So
nflda_multipath_ds_list[0] = { A, B, C, D } nflda_multipath_ds_list[0] = { A, B, C, D }
and and
nfl_fh_list[3] = { 0x36 } nfl_fh_list[3] = { 0x36 }
The client can thus write SU1 to { 0x36, { A, B, C, D }, }. The client can thus write SU1 to { 0x36, { A, B, C, D } }.
For SU3, j = (3 + 2) % 4 = 1, and nflda_stripe_indices[1] = 0. Then For SU3, j = (3 + 2) % 4 = 1, and nflda_stripe_indices[1] = 0. Then
nflda_multipath_ds_list[0] = { A, B, C, D }, and nfl_fh_list[1] = nflda_multipath_ds_list[0] = { A, B, C, D }, and nfl_fh_list[1] =
0x37. The client can thus write SU3 to { 0x37, { A, B, C, D } }. 0x37. The client can thus write SU3 to { 0x37, { A, B, C, D } }.
The destinations of the first thirteen storage units are: The destinations of the first 13 storage units are:
+-----+------------+--------------+ +-----+------------+--------------+
| SUi | filehandle | data servers | | SUi | filehandle | data servers |
+-----+------------+--------------+ +-----+------------+--------------+
| 0 | 87 | E | | 0 | 87 | E |
| 1 | 36 | A,B,C,D | | 1 | 36 | A,B,C,D |
| 2 | 67 | F,G | | 2 | 67 | F,G |
| 3 | 37 | A,B,C,D | | 3 | 37 | A,B,C,D |
| 4 | 87 | E | | 4 | 87 | E |
| 5 | 36 | A,B,C,D | | 5 | 36 | A,B,C,D |
skipping to change at page 321, line 5 skipping to change at page 321, line 5
| 12 | 87 | E | | 12 | 87 | E |
+-----+------------+--------------+ +-----+------------+--------------+
13.4.4. Sparse and Dense Stripe Unit Packing 13.4.4. Sparse and Dense Stripe Unit Packing
The flag NFL4_UFLG_DENSE of the nfl_util4 data type (field nflh_util The flag NFL4_UFLG_DENSE of the nfl_util4 data type (field nflh_util
of the data type nfsv4_1_file_layouthint4 and field nfl_util of data of the data type nfsv4_1_file_layouthint4 and field nfl_util of data
type nfsv4_1_file_layout_ds_addr4) specifies how the data is packed type nfsv4_1_file_layout_ds_addr4) specifies how the data is packed
within the data file on a data server. It allows for two different within the data file on a data server. It allows for two different
data packings: sparse and dense. The packing type determines the data packings: sparse and dense. The packing type determines the
calculation that will be made to map the client visible file offset calculation that will be made to map the client-visible file offset
to the offset within the data file located on the data server. to the offset within the data file located on the data server.
If nfl_util & NFL4_UFLG_DENSE is zero, this means that sparse packing If nfl_util & NFL4_UFLG_DENSE is zero, this means that sparse packing
is being used. Hence the logical offsets of the file as viewed by a is being used. Hence, the logical offsets of the file as viewed by a
client sending READs and WRITEs directly to the metadata server are client sending READs and WRITEs directly to the metadata server are
the same offsets each data server uses when storing a stripe unit. the same offsets each data server uses when storing a stripe unit.
The effect then, for striping patterns consisting of at least two The effect then, for striping patterns consisting of at least two
stripe units, is for each data server file to be sparse or holey. So stripe units, is for each data server file to be sparse or "holey".
for example, suppose there is a pattern with three stripe units, the So for example, suppose there is a pattern with three stripe units,
stripe unit size is a 4096 bytes, and there are three data servers in the stripe unit size is 4096 bytes, and there are three data servers
the pattern, then the file in data server 1 will have stripe units 0, in the pattern. Then, the file in data server 1 will have stripe
3, 6, 9, ... filled, data server 2's file will have stripe units 1, units 0, 3, 6, 9, ... filled; data server 2's file will have stripe
4, 7, 10, ... filled, and data server 3's file will have stripe units units 1, 4, 7, 10, ... filled; and data server 3's file will have
2, 5, 8, 11, ... filled. The unfilled stripe units of each file will stripe units 2, 5, 8, 11, ... filled. The unfilled stripe units of
be holes, hence the files in each data server are sparse. each file will be holes; hence, the files in each data server are
sparse.
If sparse packing is being used and a client attempts I/O to one of If sparse packing is being used and a client attempts I/O to one of
the holes, then an error MUST be returned by the data server. Using the holes, then an error MUST be returned by the data server. Using
the above example, if data server 3 received a READ or WRITE request the above example, if data server 3 received a READ or WRITE
for block 4, the data server would return NFS4ERR_PNFS_IO_HOLE. Thus operation for block 4, the data server would return
data servers need to understand the striping pattern in order to NFS4ERR_PNFS_IO_HOLE. Thus, data servers need to understand the
support sparse packing. striping pattern in order to support sparse packing.
If nfl_util & NFL4_UFLG_DENSE is one, this means that dense packing If nfl_util & NFL4_UFLG_DENSE is one, this means that dense packing
is being used and the data server files have no holes. Dense packing is being used, and the data server files have no holes. Dense
might be selected because the data server does not (efficiently) packing might be selected because the data server does not
support holey files, or because the data server cannot recognize (efficiently) support holey files or because the data server cannot
read-ahead unless there are no holes. If dense packing is indicated recognize read-ahead unless there are no holes. If dense packing is
in the layout, the data files will be packed. Using the example indicated in the layout, the data files will be packed. Using the
striping pattern and stripe unit size that was used for the sparse same striping pattern and stripe unit size that were used for the
packing example, the corresponding dense packing would have all sparse packing example, the corresponding dense packing example would
stripe units of all data files filled. Logical stripe units 0, 3, 6, have all stripe units of all data files filled as follows:
... of the file would live on stripe units 0, 1, 2, ... of the file
of data server 1, logical stripe units 1, 4, 7, ... of the file would o Logical stripe units 0, 3, 6, ... of the file would live on stripe
live on stripe units 0, 1, 2, ... of the file of data server 2, and units 0, 1, 2, ... of the file of data server 1.
logical stripe units 2, 5, 8, ... of the file would live on stripe
o Logical stripe units 1, 4, 7, ... of the file would live on stripe
units 0, 1, 2, ... of the file of data server 2.
o Logical stripe units 2, 5, 8, ... of the file would live on stripe
units 0, 1, 2, ... of the file of data server 3. units 0, 1, 2, ... of the file of data server 3.
Because dense packing does not leave holes on the data servers, the Because dense packing does not leave holes on the data servers, the
pNFS client is allowed to write to any offset of any data file of any pNFS client is allowed to write to any offset of any data file of any
data server in the stripe. Thus the data servers need not know the data server in the stripe. Thus, the data servers need not know the
file's striping pattern. file's striping pattern.
The calculation to determine the byte offset within the data file for The calculation to determine the byte offset within the data file for
dense data server layouts is: dense data server layouts is:
stripe_width = stripe_unit_size * N; stripe_width = stripe_unit_size * N;
where N = number of elements in nflda_stripe_indices. where N = number of elements in nflda_stripe_indices.
relative_offset = file_offset - nfl_pattern_offset; relative_offset = file_offset - nfl_pattern_offset;
data_file_offset = floor(relative_offset / stripe_width) data_file_offset = floor(relative_offset / stripe_width)
* stripe_unit_size * stripe_unit_size
+ relative_offset % stripe_unit_size + relative_offset % stripe_unit_size
If dense packing is being used, and a data server appears more than If dense packing is being used, and a data server appears more than
once in a striping pattern, then to distinguish one stripe unit from once in a striping pattern, then to distinguish one stripe unit from
another, the data server MUST use a different filehandle. Let's another, the data server MUST use a different filehandle. Let's
suppose there are two data servers. Logical stripe units 0, 3, 6 are suppose there are two data servers. Logical stripe units 0, 3, 6 are
served by data server 1, logical stripe units 1, 4, 7 are served by served by data server 1; logical stripe units 1, 4, 7 are served by
data server 2, and logical stripe units 2, 5, 8 are also served by data server 2; and logical stripe units 2, 5, 8 are also served by
data server 2. Unless data server 2 has two filehandles (each data server 2. Unless data server 2 has two filehandles (each
referring to a different data file), then, for example, a write to referring to a different data file), then, for example, a write to
logical stripe unit 1 overwrites the write to logical stripe unit 2, logical stripe unit 1 overwrites the write to logical stripe unit 2
because both logical stripe units are located in the same stripe unit because both logical stripe units are located in the same stripe unit
(0) of data server 2. (0) of data server 2.
13.5. Data Server Multipathing 13.5. Data Server Multipathing
The NFSv4.1 file layout supports multipathing to multiple data server The NFSv4.1 file layout supports multipathing to multiple data server
addresses. Data server-level multipathing is used for bandwidth addresses. Data-server-level multipathing is used for bandwidth
scaling via trunking (Section 2.10.5) and for higher availability of scaling via trunking (Section 2.10.5) and for higher availability of
use in the case of a data server failure. Multipathing allows the use in the case of a data-server failure. Multipathing allows the
client to switch to another data server address which may that of client to switch to another data server address which may be that of
another data server that is exporting the same data stripe unit, another data server that is exporting the same data stripe unit,
without having to contact the metadata server for a new layout. without having to contact the metadata server for a new layout.
To support data server multipathing, each element of the To support data server multipathing, each element of the
nflda_multipath_ds_list contains an array of one more data server nflda_multipath_ds_list contains an array of one more data server
network addresses. This array (data type multipath_list4) represents network addresses. This array (data type multipath_list4) represents
a list of data servers (each identified by a network address), with a list of data servers (each identified by a network address), with
it being possible that some data servers will appear in the list the possibility that some data servers will appear in the list
multiple times. multiple times.
The client is free to use any of the network addresses as a The client is free to use any of the network addresses as a
destination to send data server requests. If some network addresses destination to send data server requests. If some network addresses
are less optimal paths to the data than others, then the MDS SHOULD are less optimal paths to the data than others, then the MDS SHOULD
NOT include those network addresses in an element of NOT include those network addresses in an element of
nflda_multipath_ds_list. If less optimal network addresses exist to nflda_multipath_ds_list. If less optimal network addresses exist to
provide fail over, the RECOMMENDED method to offer the addresses is provide failover, the RECOMMENDED method to offer the addresses is to
to provide them in a replacement device ID to device address mapping, provide them in a replacement device-ID-to-device-address mapping, or
or a replacement device ID. When a client finds that no data server a replacement device ID. When a client finds that no data server in
in an element of nflda_multipath_ds_list responds, it SHOULD send a an element of nflda_multipath_ds_list responds, it SHOULD send a
GETDEVICEINFO to attempt to replace the existing device ID to device GETDEVICEINFO to attempt to replace the existing device-ID-to-device-
address mappings. If the MDS detects that all data servers address mappings. If the MDS detects that all data servers
represented by an element of nflda_multipath_ds_list are unavailable, represented by an element of nflda_multipath_ds_list are unavailable,
the MDS SHOULD send a CB_NOTIFY_DEVICEID (if the client has indicated the MDS SHOULD send a CB_NOTIFY_DEVICEID (if the client has indicated
it wants device ID notifications for changed device IDs) to change it wants device ID notifications for changed device IDs) to change
the device ID to device address mappings to the available data the device-ID-to-device-address mappings to the available data
servers. If the device ID itself will be replaced, the MDS SHOULD servers. If the device ID itself will be replaced, the MDS SHOULD
recall all layouts with the device ID, and thus force the client to recall all layouts with the device ID, and thus force the client to
get new layouts and device ID mappings via LAYOUTGET and get new layouts and device ID mappings via LAYOUTGET and
GETDEVICEINFO. GETDEVICEINFO.
Generally if two network addresses appear in an element of Generally, if two network addresses appear in an element of
nflda_multipath_ds_list they will designate the same data server and nflda_multipath_ds_list, they will designate the same data server,
the two data server addresses will support the implementation client and the two data server addresses will support the implementation of
ID or session trunking (the latter is RECOMMENDED) as defined in client ID or session trunking (the latter is RECOMMENDED) as defined
Section 2.10.5, and the two data server addresses will share the same in Section 2.10.5. The two data server addresses will share the same
server owner, or major ID of the server owner. It is not always server owner or major ID of the server owner. It is not always
necessary for the two data server addresses to designate the same necessary for the two data server addresses to designate the same
server with trunking being used. For example the data could be read- server with trunking being used. For example, the data could be
only, and the data consist of exact replicas. read-only, and the data consist of exact replicas.
13.6. Operations Sent to NFSv4.1 Data Servers 13.6. Operations Sent to NFSv4.1 Data Servers
Clients accessing data on an NFSv4.1 data server MUST send only the Clients accessing data on an NFSv4.1 data server MUST send only the
NULL procedure and COMPOUND procedures whose operations are taken NULL procedure and COMPOUND procedures whose operations are taken
only from two restricted subsets of the operations defined as valid only from two restricted subsets of the operations defined as valid
NFSv4.1 operations. Clients MUST use the filehandle specified by the NFSv4.1 operations. Clients MUST use the filehandle specified by the
layout when accessing data on NFSv4.1 data servers. layout when accessing data on NFSv4.1 data servers.
The first of these operation subsets consist of management The first of these operation subsets consists of management
operations. This subset consists of the BACKCHANNEL_CTL, operations. This subset consists of the BACKCHANNEL_CTL,
BIND_CONN_TO_SESSION, CREATE_SESSION, DESTROY_CLIENTID, BIND_CONN_TO_SESSION, CREATE_SESSION, DESTROY_CLIENTID,
DESTROY_SESSION, EXCHANGE_ID, SECINFO_NO_NAME, SET_SSV, and SEQUENCE DESTROY_SESSION, EXCHANGE_ID, SECINFO_NO_NAME, SET_SSV, and SEQUENCE
operations. The client may use these operations in order to set up operations. The client may use these operations in order to set up
and maintain the appropriate client IDs, sessions, and security and maintain the appropriate client IDs, sessions, and security
contexts involved in communication with the data server. Henceforth contexts involved in communication with the data server. Henceforth,
these will be referred to as data-server housekeeping operations. these will be referred to as data-server housekeeping operations.
The second subset consists of COMMIT, READ, WRITE, and PUTFH, These The second subset consists of COMMIT, READ, WRITE, and PUTFH. These
operations MUST be used with a current filehandle specified by the operations MUST be used with a current filehandle specified by the
layout. In the case of PUTFH, the new current filehandle MUST be one layout. In the case of PUTFH, the new current filehandle MUST be one
taken from the layout. Henceforth, these will be referred to as taken from the layout. Henceforth, these will be referred to as
data-server I/O operations. As described in Section 12.5.1, a client data-server I/O operations. As described in Section 12.5.1, a client
MUST NOT send an I/O to a data server for which it does not hold a MUST NOT send an I/O to a data server for which it does not hold a
valid layout; the data server MUST reject such an I/O. valid layout; the data server MUST reject such an I/O.
Unless the server has a concurrent non-data-server personality, i.e. Unless the server has a concurrent non-data-server personality --
EXCHANGE_ID results returned (EXCHGID4_FLAG_USE_PNFS_DS | i.e., EXCHANGE_ID results returned (EXCHGID4_FLAG_USE_PNFS_DS |
EXCHGID4_FLAG_USE_PNFS_MDS) or (EXCHGID4_FLAG_USE_PNFS_DS | EXCHGID4_FLAG_USE_PNFS_MDS) or (EXCHGID4_FLAG_USE_PNFS_DS |
EXCHGID4_FLAG_USE_NON_PNFS), see Section 13.1, any attempted use of EXCHGID4_FLAG_USE_NON_PNFS) see Section 13.1 -- any attempted use of
operations against a data server other than those specified in the operations against a data server other than those specified in the
two subsets above MUST return NFS4ERR_NOTSUPP to the client. two subsets above MUST return NFS4ERR_NOTSUPP to the client.
When the server has concurrent data server and non-data-server When the server has concurrent data-server and non-data-server
personalities, each COMPOUND sent by the client MUST be constructed personalities, each COMPOUND sent by the client MUST be constructed
so that it is appropriate to one of the two personalities, and MUST so that it is appropriate to one of the two personalities, and it
NOT contain operations directed to a mix of those personalities. The MUST NOT contain operations directed to a mix of those personalities.
server MUST enforce this. To understand the constraints, operations The server MUST enforce this. To understand the constraints,
within a COMPOUND are divided into the following three classes: operations within a COMPOUND are divided into the following three
classes:
1. An operation which is ambiguous regarding its personality 1. An operation that is ambiguous regarding its personality
assignment. These include all of the data-server housekeeping assignment. This includes all of the data-server housekeeping
operations. Additionally, if the server has assigned filehandles operations. Additionally, if the server has assigned filehandles
so that the ones defined by the layout are the same as those used so that the ones defined by the layout are the same as those used
by the metadata server, all operations using such filehandles are by the metadata server, all operations using such filehandles are
within this class, with the following exception. The exception within this class, with the following exception. The exception
is that if the operation uses a stateid that is incompatible with is that if the operation uses a stateid that is incompatible with
a data-server personality (e.g. a special stateid or the stateid a data-server personality (e.g., a special stateid or the stateid
has a non-zero seqid field, see Section 13.9.1); if so, the has a non-zero "seqid" field, see Section 13.9.1), the operation
operation is in class 3, as described below. A COMPOUND is in class 3, as described below. A COMPOUND containing
containing multiple class 1 operations (and operations of no multiple class 1 operations (and operations of no other class)
other class) MAY be sent to a server with multiple concurrent MAY be sent to a server with multiple concurrent data server and
data server and non-data-server personalities. non-data-server personalities.
2. An operation which is unambiguously referable to the data server 2. An operation that is unambiguously referable to the data-server
personality. These are data-server I/O operations where the personality. This includes data-server I/O operations where the
filehandle is one that can only be validly directed to the data- filehandle is one that can only be validly directed to the data-
server personality. server personality.
3. An operation which is unambiguously referable to the non-data- 3. An operation that is unambiguously referable to the non-data-
server personality. These include all COMPOUND operations that server personality. This includes all COMPOUND operations that
are neither data-server housekeeping nor data-server I/O are neither data-server housekeeping nor data-server I/O
operations plus data-server I/O operations where the current fh operations, plus data-server I/O operations where the current fh
(or the one to be made the current fh in the case of PUTFH) is (or the one to be made the current fh in the case of PUTFH) is
one that is only valid on the metadata server or where a stateid only valid on the metadata server or where a stateid is used that
is used that is incompatible with the data server, i.e. is a is incompatible with the data server, i.e., is a special stateid
special stateid or has a non-zero seqid value. or has a non-zero seqid value.
When a COMPOUND first executes an operation from class 3 above, it When a COMPOUND first executes an operation from class 3 above, it
acts as a normal COMPOUND on any other server and the data server acts as a normal COMPOUND on any other server, and the data-server
personality ceases to be relevant. There are no special restrictions personality ceases to be relevant. There are no special restrictions
on the operations in the COMPOUND to limit them to those for a data on the operations in the COMPOUND to limit them to those for a data
server. When a PUTFH is done, filehandles derived from the layout server. When a PUTFH is done, filehandles derived from the layout
are not valid. If their format is not normally acceptable, then are not valid. If their format is not normally acceptable, then
NFS4ERR_BADHANDLE MUST result. Similarly, current filehandles for NFS4ERR_BADHANDLE MUST result. Similarly, current filehandles for
other operations do not accept filehandles derived from layouts and other operations do not accept filehandles derived from layouts and
are not normally usable on the metadata server. Using these will are not normally usable on the metadata server. Using these will
result in NFS4ERR_STALE. result in NFS4ERR_STALE.
When a COMPOUND first executes an operation from class 2, which would When a COMPOUND first executes an operation from class 2, which would
be PUTFH where the filehandle is one from a layout, the COMPOUND be PUTFH where the filehandle is one from a layout, the COMPOUND
henceforth is interpreted with respect to the data server henceforth is interpreted with respect to the data-server
personality. Operations outside the two classes discussed above MUST personality. Operations outside the two classes discussed above MUST
result in NFS4ERR_NOTSUPP. Filehandles are validated using the rules result in NFS4ERR_NOTSUPP. Filehandles are validated using the rules
of the data server, resulting in NFS4ERR_BADHANDLE and/or of the data server, resulting in NFS4ERR_BADHANDLE and/or
NFS4ERR_STALE even when they would not normally do so when addressed NFS4ERR_STALE even when they would not normally do so when addressed
to the non-data-server personality. Stateids must obey the rules of to the non-data-server personality. Stateids must obey the rules of
the data server in that any use of special stateids or stateids with the data server in that any use of special stateids or stateids with
non-zero seqid values must result in NFS4ERR_BAD_STATEID. non-zero seqid values must result in NFS4ERR_BAD_STATEID.
Until the server first executes an operation from class 2 or class 3, Until the server first executes an operation from class 2 or class 3,
the client MUST NOT depend on the operation being executed by either the client MUST NOT depend on the operation being executed by either
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RECOMMENDED that where the same server can have both personalities, RECOMMENDED that where the same server can have both personalities,
the server assign separate unique filehandles to both personalities. the server assign separate unique filehandles to both personalities.
This makes it unambiguous for which server a given request is This makes it unambiguous for which server a given request is
intended. intended.
GETATTR and SETATTR MUST be directed to the metadata server. In the GETATTR and SETATTR MUST be directed to the metadata server. In the
case of a SETATTR of the size attribute, the control protocol is case of a SETATTR of the size attribute, the control protocol is
responsible for propagating size updates/truncations to the data responsible for propagating size updates/truncations to the data
servers. In the case of extending WRITEs to the data servers, the servers. In the case of extending WRITEs to the data servers, the
new size must be visible on the metadata server once a LAYOUTCOMMIT new size must be visible on the metadata server once a LAYOUTCOMMIT
has completed (see Section 12.5.4.2). Section 13.10, describes the has completed (see Section 12.5.4.2). Section 13.10 describes the
mechanism by which the client is to handle data server files that do mechanism by which the client is to handle data-server files that do
not reflect the metadata server's size. not reflect the metadata server's size.
13.7. COMMIT Through Metadata Server 13.7. COMMIT through Metadata Server
The file layout provides two alternate means of providing for the The file layout provides two alternate means of providing for the
commit of data written through data servers. The flag commit of data written through data servers. The flag
NFL4_UFLG_COMMIT_THRU_MDS in the field nfl_util of the file layout NFL4_UFLG_COMMIT_THRU_MDS in the field nfl_util of the file layout
(data type nfsv4_1_file_layout4) is an indication from the metadata (data type nfsv4_1_file_layout4) is an indication from the metadata
server to the client of the REQUIRED way of performing COMMIT, either server to the client of the REQUIRED way of performing COMMIT, either
by sending the COMMIT to the data server or the metadata server. by sending the COMMIT to the data server or the metadata server.
These two methods of dealing with the issue correspond to broad These two methods of dealing with the issue correspond to broad
styles of implementation for a pNFS server supporting the files styles of implementation for a pNFS server supporting the file layout
layout type. type.
o When the flag is FALSE, COMMIT operations MUST to be sent to the o When the flag is FALSE, COMMIT operations MUST to be sent to the
data server to which the corresponding WRITE operations were sent. data server to which the corresponding WRITE operations were sent.
This approach is most useful when striping of files is implemented This approach is sometimes useful when file striping is
as part of pNFS server, with the individual data servers each implemented within the pNFS server (instead of the file system),
implementing their own file systems. with the individual data servers each implementing their own file
systems.
o When the flag is TRUE, COMMIT operations MUST be sent to the o When the flag is TRUE, COMMIT operations MUST be sent to the
metadata server, rather than to the individual data servers. This metadata server, rather than to the individual data servers. This
approach is most useful when the pNFS server is implemented on top approach is sometimes useful when file striping is implemented
of a clustered file system. In such an implementation, sending within the clustered file system that is the backend to the pNFS
COMMIT's to multiple data servers may result in repeated writes of server. In such an implementation, each COMMIT to each data
metadata blocks as each individual COMMIT is executed, to the server might result in repeated writes of metadata blocks to the
detriment of write performance. Sending a single COMMIT to the detriment of write performance. Sending a single COMMIT to the
metadata server can provide more efficiency when there exists a metadata server can be more efficient when there exists a
clustered file system capable of implementing such a co-ordinated clustered file system capable of implementing such a coordinated
COMMIT. COMMIT.
If nfl_util & NFL4_UFLG_COMMIT_THRU_MDS is TRUE, then in order to If nfl_util & NFL4_UFLG_COMMIT_THRU_MDS is TRUE, then in order to
maintain the current NFSv4.1 commit and recovery model, the data maintain the current NFSv4.1 commit and recovery model, the data
servers MUST return a common writeverf verifier in all WRITE servers MUST return a common writeverf verifier in all WRITE
responses for a given file layout, and the metadata server's responses for a given file layout, and the metadata server's
COMMIT implementation must return the same writeverf. The value COMMIT implementation must return the same writeverf. The value
of the writeverf verifier MUST be changed at the metadata server of the writeverf verifier MUST be changed at the metadata server
or any data server that is referenced in the layout, whenever or any data server that is referenced in the layout, whenever
there is a server event that can possibly lead to loss of there is a server event that can possibly lead to loss of
uncommitted data. The scope of the verifier can be for a file or uncommitted data. The scope of the verifier can be for a file or
for the entire pNFS server. It might be more difficult for the for the entire pNFS server. It might be more difficult for the
server to maintain the verifier at the file level but the benefit server to maintain the verifier at the file level, but the benefit
is that only events that impact a given file will require recovery is that only events that impact a given file will require recovery
action. action.
Note that if the layout specified dense packing, then the offset used Note that if the layout specified dense packing, then the offset used
to a COMMIT to the MDS may differ than that of an offset used to a to a COMMIT to the MDS may differ than that of an offset used to a
COMMIT to the data server. COMMIT to the data server.
The single COMMIT to the metadata server will return a verifier and The single COMMIT to the metadata server will return a verifier, and
the client should compare it to all the verifiers from the WRITEs and the client should compare it to all the verifiers from the WRITEs and
fail the COMMIT if there is any mismatched verifiers. If COMMIT to fail the COMMIT if there are any mismatched verifiers. If COMMIT to
the metadata server fails, the client should re-send WRITEs for all the metadata server fails, the client should re-send WRITEs for all
the modified data in the file. The client should treat modified data the modified data in the file. The client should treat modified data
with a mismatched verifier as a WRITE failure and try to recover by with a mismatched verifier as a WRITE failure and try to recover by
resending the WRITEs to the original data server or using another resending the WRITEs to the original data server or using another
path to that data if the layout has not been recalled. Another path to that data if the layout has not been recalled.
option the client has is getting a new layout or just rewrite the Alternatively, the client can obtain a new layout or it could rewrite
data through the metadata server. If nfl_util & the data directly to the metadata server. If nfl_util &
NFL4_UFLG_COMMIT_THRU_MDS is FALSE, sending a COMMIT to the metadata NFL4_UFLG_COMMIT_THRU_MDS is FALSE, sending a COMMIT to the metadata
server might have no effect. If nfl_util & NFL4_UFLG_COMMIT_THRU_MDS server might have no effect. If nfl_util & NFL4_UFLG_COMMIT_THRU_MDS
is FALSE, a COMMIT sent to the metadata server should be used only to is FALSE, a COMMIT sent to the metadata server should be used only to
commit data that was written to the metadata server. See commit data that was written to the metadata server. See
Section 12.7.6 for recovery options. Section 12.7.6 for recovery options.
13.8. The Layout Iomode 13.8. The Layout Iomode
The layout iomode need not be used by the metadata server when The layout iomode need not be used by the metadata server when
servicing NFSv4.1 file-based layouts, although in some circumstances servicing NFSv4.1 file-based layouts, although in some circumstances
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client holds a valid layout and return an error if the client does client holds a valid layout and return an error if the client does
not. not.
13.9. Metadata and Data Server State Coordination 13.9. Metadata and Data Server State Coordination
13.9.1. Global Stateid Requirements 13.9.1. Global Stateid Requirements
When the client sends I/O to a data server, the stateid used MUST NOT When the client sends I/O to a data server, the stateid used MUST NOT
be a layout stateid as returned by LAYOUTGET or sent by be a layout stateid as returned by LAYOUTGET or sent by
CB_LAYOUTRECALL. Permitted stateids are based on one of the CB_LAYOUTRECALL. Permitted stateids are based on one of the
following: an open stateid (the stateid field of data type OPEN4resok following: an OPEN stateid (the stateid field of data type OPEN4resok
as returned by OPEN), a delegation stateid (the stateid field of data as returned by OPEN), a delegation stateid (the stateid field of data
types open_read_delegation4 and open_write_delegation4 as returned by types open_read_delegation4 and open_write_delegation4 as returned by
OPEN or WANT_DELEGATION, or as sent by CB_PUSH_DELEG), or a stateid OPEN or WANT_DELEGATION, or as sent by CB_PUSH_DELEG), or a stateid
returned by the LOCK or LOCKU operations. The stateid sent to the returned by the LOCK or LOCKU operations. The stateid sent to the
data server MUST be sent with the seqid set to zero, indicating the data server MUST be sent with the seqid set to zero, indicating the
most current version of that stateid, rather than indicating a most current version of that stateid, rather than indicating a
specific non-zero seqid value. In no case is the use of special specific non-zero seqid value. In no case is the use of special
stateid values allowed. stateid values allowed.
The stateid used for I/O MUST have the same effect and be subject to The stateid used for I/O MUST have the same effect and be subject to
the same validation on a data server as it would if the I/O was being the same validation on a data server as it would if the I/O was being
performed on the metadata server itself in the absence of pNFS. This performed on the metadata server itself in the absence of pNFS. This
has the implication that stateids are globally valid on both the has the implication that stateids are globally valid on both the
metadata and data servers. This requires the metadata server to metadata and data servers. This requires the metadata server to
propagate changes in lock and open state to the data servers, so that propagate changes in LOCK and OPEN state to the data servers, so that
the data servers can validate I/O accesses. This is discussed the data servers can validate I/O accesses. This is discussed
further in Section 13.9.2. Depending on when stateids are further in Section 13.9.2. Depending on when stateids are
propagated, the existence of a valid stateid on the data server may propagated, the existence of a valid stateid on the data server may
act as proof of a valid layout. act as proof of a valid layout.
Clients performing I/O operations need to select an appropriate Clients performing I/O operations need to select an appropriate
stateid based on the locks (including opens and delegations) held by stateid based on the locks (including opens and delegations) held by
the client and the various types of state-owners sending the I/O the client and the various types of state-owners sending the I/O
requests. The rules for doing so when referencing data servers are requests. The rules for doing so when referencing data servers are
somewhat different from those discussed in Section 8.2.5 which apply somewhat different from those discussed in Section 8.2.5, which apply
when accessing metadata servers. when accessing metadata servers.
The following rules, applied in order of decreasing priority, govern The following rules, applied in order of decreasing priority, govern
the selection of the appropriate stateid: the selection of the appropriate stateid:
o If the client holds a delegation for the file in question, the o If the client holds a delegation for the file in question, the
delegation stateid should be used. delegation stateid should be used.
o Otherwise, there must be an open stateid for the current open- o Otherwise, there must be an OPEN stateid for the current open-
owner, and that open stateid for the open file in question is owner, and that OPEN stateid for the open file in question is
used, unless mandatory locking, prevents that. See below. used, unless mandatory locking prevents that. See below.
o If the data server had previously responded with NFS4ERR_LOCKED to o If the data server had previously responded with NFS4ERR_LOCKED to
use of the open stateid, then the client should use the lock use of the OPEN stateid, then the client should use the byte-range
stateid whenever one exists for that open file with the current lock stateid whenever one exists for that open file with the
lock-owner. current lock-owner.
o Special stateids should never be used and if used the data server o Special stateids should never be used. If they are used, the data
MUST reject the I/O with an NFS4ERR_BAD_STATEID error. server MUST reject the I/O with an NFS4ERR_BAD_STATEID error.
13.9.2. Data Server State Propagation 13.9.2. Data Server State Propagation
Since the metadata server, which handles lock and open-mode state Since the metadata server, which handles byte-range lock and open-
changes, as well as ACLs, might not be co-located with the data mode state changes as well as ACLs, might not be co-located with the
servers where I/O access are validated, the server implementation data servers where I/O accesses are validated, the server
MUST take care of propagating changes of this state to the data implementation MUST take care of propagating changes of this state to
servers. Once the propagation to the data servers is complete, the the data servers. Once the propagation to the data servers is
full effect of those changes MUST be in effect at the data servers. complete, the full effect of those changes MUST be in effect at the
However, some state changes need not be propagated immediately, data servers. However, some state changes need not be propagated
although all changes SHOULD be propagated promptly. These state immediately, although all changes SHOULD be propagated promptly.
propagations have an impact on the design of the control protocol, These state propagations have an impact on the design of the control
even though the control protocol is outside of the scope of this protocol, even though the control protocol is outside of the scope of
specification. Immediate propagation refers to the synchronous this specification. Immediate propagation refers to the synchronous
propagation of state from the metadata server to the data server(s); propagation of state from the metadata server to the data server(s);
the propagation must be complete before returning to the client. the propagation must be complete before returning to the client.
13.9.2.1. Lock State Propagation 13.9.2.1. Lock State Propagation
If the pNFS server supports mandatory locking, any mandatory locks on If the pNFS server supports mandatory byte-range locking, any
a file MUST be made effective at the data servers before the request mandatory byte-range locks on a file MUST be made effective at the
that establishes them returns to the caller. The effect MUST be the data servers before the request that establishes them returns to the
same as if the mandatory lock state were synchronously propagated to caller. The effect MUST be the same as if the mandatory byte-range
the data servers, even though the details of the control protocol may lock state were synchronously propagated to the data servers, even
avoid actual transfer of the state under certain circumstances. though the details of the control protocol may avoid actual transfer
of the state under certain circumstances.
On the other hand, since advisory lock state is not used for checking On the other hand, since advisory byte-range lock state is not used
I/O accesses at the data servers, there is no semantic reason for for checking I/O accesses at the data servers, there is no semantic
propagating advisory lock state to the data servers. Since updates reason for propagating advisory byte-range lock state to the data
to advisory locks neither confer nor remove privileges, these changes servers. Since updates to advisory locks neither confer nor remove
need not be propagated immediately, and may not need to be propagated privileges, these changes need not be propagated immediately, and may
promptly. The updates to advisory locks need only be propagated when not need to be propagated promptly. The updates to advisory locks
the data server needs to resolve a question about a stateid. In need only be propagated when the data server needs to resolve a
fact, if byte-range locking is not mandatory (i.e., is advisory) the question about a stateid. In fact, if byte-range locking is not
clients are advised not to use the lock-based stateids for I/O at mandatory (i.e., is advisory) the clients are advised to avoid using
all. The stateids returned by open are sufficient and eliminate the byte-range lock-based stateids for I/O. The stateids returned by
overhead for this kind of state propagation. OPEN are sufficient and eliminate overhead for this kind of state
propagation.
If a client gets back an NFS4ERR_LOCKED error from a data server, If a client gets back an NFS4ERR_LOCKED error from a data server,
this is an indication that mandatory byte-range locking is in force. this is an indication that mandatory byte-range locking is in force.
The client recovers from this by getting a byte-range lock that The client recovers from this by getting a byte-range lock that
covers the affected range and re-sends the I/O with the stateid of covers the affected range and re-sends the I/O with the stateid of
the byte-range lock. the byte-range lock.
13.9.2.2. Open and Deny Mode Validation 13.9.2.2. Open and Deny Mode Validation
Open and deny mode validation MUST be performed against the open and Open and deny mode validation MUST be performed against the open and
deny mode(s) held by the data servers. When access is reduced or a deny mode(s) held by the data servers. When access is reduced or a
deny mode made more restrictive (because of CLOSE or DOWNGRADE) the deny mode made more restrictive (because of CLOSE or OPEN_DOWNGRADE),
data server MUST prevent any I/Os that would be denied if performed the data server MUST prevent any I/Os that would be denied if
on the metadata server. When access is expanded, the data server performed on the metadata server. When access is expanded, the data
MUST make sure that no requests are subsequently rejected because of server MUST make sure that no requests are subsequently rejected
open or deny issues that no longer apply, given the previous because of open or deny issues that no longer apply, given the
relaxation. previous relaxation.
13.9.2.3. File Attributes 13.9.2.3. File Attributes
Since the SETATTR operation has the ability to modify state that is Since the SETATTR operation has the ability to modify state that is
visible on both the metadata and data servers (e.g., the size), care visible on both the metadata and data servers (e.g., the size), care
must be taken to ensure that the resultant state across the set of must be taken to ensure that the resultant state across the set of
data servers is consistent; especially when truncating or growing the data servers is consistent, especially when truncating or growing the
file. file.
As described earlier, the LAYOUTCOMMIT operation is used to ensure As described earlier, the LAYOUTCOMMIT operation is used to ensure
that the metadata is synchronized with changes made to the data that the metadata is synchronized with changes made to the data
servers. For the NFSv4.1-based data storage protocol, it is servers. For the NFSv4.1-based data storage protocol, it is
necessary to re-synchronize state such as the size attribute, and the necessary to re-synchronize state such as the size attribute, and the
setting of mtime/change/atime. See Section 12.5.4 for a full setting of mtime/change/atime. See Section 12.5.4 for a full
description of the semantics regarding LAYOUTCOMMIT and attribute description of the semantics regarding LAYOUTCOMMIT and attribute
synchronization. It should be noted, that by using an NFSv4.1-based synchronization. It should be noted that by using an NFSv4.1-based
layout type, it is possible to synchronize this state before layout type, it is possible to synchronize this state before
LAYOUTCOMMIT occurs. For example, the control protocol can be used LAYOUTCOMMIT occurs. For example, the control protocol can be used
to query the attributes present on the data servers. to query the attributes present on the data servers.
Any changes to file attributes that control authorization or access Any changes to file attributes that control authorization or access
as reflected by ACCESS calls or READs and WRITEs on the metadata as reflected by ACCESS calls or READs and WRITEs on the metadata
server, MUST be propagated to the data servers for enforcement on server, MUST be propagated to the data servers for enforcement on
READ and WRITE I/O calls. If the changes made on the metadata server READ and WRITE I/O calls. If the changes made on the metadata server
result in more restrictive access permissions for any user, those result in more restrictive access permissions for any user, those
changes MUST be propagated to the data servers synchronously. changes MUST be propagated to the data servers synchronously.
The OPEN operation (Section 18.16.4) does not impose any requirement The OPEN operation (Section 18.16.4) does not impose any requirement
that I/O operations on an open file have the same credentials as the that I/O operations on an open file have the same credentials as the
OPEN itself (unless EXCHGID4_FLAG_BIND_PRINC_STATEID is set when OPEN itself (unless EXCHGID4_FLAG_BIND_PRINC_STATEID is set when
EXCHANGE_ID creates the client ID) and so requires the server's READ EXCHANGE_ID creates the client ID), and so it requires the server's
and WRITE operations to perform appropriate access checking. Changes READ and WRITE operations to perform appropriate access checking.
to ACLs also require new access checking by READ and WRITE on the Changes to ACLs also require new access checking by READ and WRITE on
server. The propagation of access right changes due to changes in the server. The propagation of access-right changes due to changes
ACLs may be asynchronous only if the server implementation is able to in ACLs may be asynchronous only if the server implementation is able
determine that the updated ACL is not more restrictive for any user to determine that the updated ACL is not more restrictive for any
specified in the old ACL. Due to the relative infrequency of ACL user specified in the old ACL. Due to the relative infrequency of
updates, it is suggested that all changes be propagated ACL updates, it is suggested that all changes be propagated
synchronously. synchronously.
13.10. Data Server Component File Size 13.10. Data Server Component File Size
A potential problem exists when a component data file on a particular A potential problem exists when a component data file on a particular
data server is grown past EOF; the problem exists for both dense and data server has grown past EOF; the problem exists for both dense and
sparse layouts. Imagine the following scenario: a client creates a sparse layouts. Imagine the following scenario: a client creates a
new file (size == 0) and writes to byte 131072; the client then seeks new file (size == 0) and writes to byte 131072; the client then seeks
to the beginning of the file and reads byte 100. The client should to the beginning of the file and reads byte 100. The client should
receive 0s back as a result of the READ. However, if the READ falls receive zeroes back as a result of the READ. However, if the
on a data server other than the one that received client's original striping pattern directs the client to send the READ to a data server
WRITE, the data server servicing the READ may still believe that the other than the one that received the client's original WRITE, the
file's size is at 0 and return no data with the EOF flag set. The data server servicing the READ may believe that the file's size is
data server can only return 0s if it knows that the file's size has still 0 bytes. In that event, the data server's READ response will
been extended. This would require the immediate propagation of the contain zero bytes and an indication of EOF. The data server can
file's size to all data servers, which is potentially very costly. only return zeroes if it knows that the file's size has been
extended. This would require the immediate propagation of the file's
size to all data servers, which is potentially very costly.
Therefore, the client that has initiated the extension of the file's Therefore, the client that has initiated the extension of the file's
size MUST be prepared to deal with these EOF conditions; the EOF'ed size MUST be prepared to deal with these EOF conditions. When the
or short READs will be treated as a hole in the file and the NFS offset in the arguments to READ is less than the client's view of the
client will substitute 0s for the data when the offset is less than file size, if the READ response indicates EOF and/or contains fewer
the client's view of the file size. bytes than requested, the client will interpret such a response as a
hole in the file, and the NFS client will substitute zeroes for the
data.
The NFSv4.1 protocol only provides close to open file data cache The NFSv4.1 protocol only provides close-to-open file data cache
semantics; meaning that when the file is closed all modified data is semantics; meaning that when the file is closed, all modified data is
written to the server. When a subsequent OPEN of the file is done, written to the server. When a subsequent OPEN of the file is done,
the change attribute is inspected for a difference from a cached the change attribute is inspected for a difference from a cached
value for the change attribute. For the case above, this means that value for the change attribute. For the case above, this means that
a LAYOUTCOMMIT will be done at close (along with the data WRITEs) and a LAYOUTCOMMIT will be done at close (along with the data WRITEs) and
will update the file's size and change attribute. Access from will update the file's size and change attribute. Access from
another client after that point will result in the appropriate size another client after that point will result in the appropriate size
being returned. being returned.
13.11. Layout Revocation and Fencing 13.11. Layout Revocation and Fencing
As described in Section 12.7, the layout type-specific storage As described in Section 12.7, the layout-type-specific storage
protocol is responsible for handling the effects of I/Os started protocol is responsible for handling the effects of I/Os that started
before lease expiration, extending through lease expiration. The before lease expiration and extend through lease expiration. The
LAYOUT4_NFSV4_1_FILES layout type can prevent all I/Os to data LAYOUT4_NFSV4_1_FILES layout type can prevent all I/Os to data
servers from being executed after lease expiration, without relying servers from being executed after lease expiration (this prevention
on a precise client lease timer and without requiring data servers to is called "fencing"), without relying on a precise client lease timer
maintain lease timers. However, while LAYOUT4_NFSV4_1_FILES pNFS and without requiring data servers to maintain lease timers. The
server is free to deny the client all access to the data servers, LAYOUT4_NFSV4_1_FILES pNFS server has the flexibility to revoke
because it supports revocation of layouts, it is also free to perform individual layouts, and thus fence I/O on a per-file basis.
a denial on a per file basis only when revoking a layout.
In addition to lease expiration, the reasons a layout can be revoked In addition to lease expiration, the reasons a layout can be revoked
include: client fails to respond to a CB_LAYOUTRECALL, the metadata include: client fails to respond to a CB_LAYOUTRECALL, the metadata
server restarts, or administrative intervention. Regardless of the server restarts, or administrative intervention. Regardless of the
reason, once a client's layout has been revoked, the pNFS server MUST reason, once a client's layout has been revoked, the pNFS server MUST
prevent the client from sending I/O for the affected file from and to prevent the client from sending I/O for the affected file from and to
all data servers, in other words, it MUST fence the client from the all data servers; in other words, it MUST fence the client from the
affected file on the data servers. affected file on the data servers.
Fencing works as follows. As described in Section 13.1, in COMPOUND Fencing works as follows. As described in Section 13.1, in COMPOUND
procedure requests to the data server, the data filehandle provided procedure requests to the data server, the data filehandle provided
by the PUTFH operation and the stateid in the READ or WRITE operation by the PUTFH operation and the stateid in the READ or WRITE operation
are used to validate that the client has a valid layout for the I/O are used to ensure that the client has a valid layout for the I/O
being performed, if it does not, the I/O is rejected with being performed; if it does not, the I/O is rejected with
NFS4ERR_PNFS_NO_LAYOUT. The server can simply check the stateid, and NFS4ERR_PNFS_NO_LAYOUT. The server can simply check the stateid and,
additionally, make the data filehandle stale if the layout specified additionally, make the data filehandle stale if the layout specified
a data filehandle that is different from the metadata server's a data filehandle that is different from the metadata server's
filehandle for the file (see the nfl_fh_list description in filehandle for the file (see the nfl_fh_list description in
Section 13.3). Section 13.3).
Before the metadata server takes any action to invalidate layout Before the metadata server takes any action to revoke layout state
state given out by a previous instance, it must make sure that all given out by a previous instance, it must make sure that all layout
layout state from that previous instance are invalidated at the data state from that previous instance are invalidated at the data
servers. This means that a metadata server may not restripe a file servers. This has the following implications.
until it has contacted all of the data servers to invalidate the
layouts from the previous instance nor may it give out mandatory o The metadata server must not restripe a file until it has
locks that conflict with layouts from the previous instance without contacted all of the data servers to invalidate the layouts from
either doing a specific invalidation (as it would have to do anyway) the previous instance.
or doing a global data server invalidation.
o The metadata server must not give out mandatory locks that
conflict with layouts from the previous instance without either
doing a specific layout invalidation (as it would have to do
anyway) or doing a global data server invalidation.
13.12. Security Considerations for the File Layout Type 13.12. Security Considerations for the File Layout Type
The NFSv4.1 file layout type MUST adhere to the security The NFSv4.1 file layout type MUST adhere to the security
considerations outlined in Section 12.9. NFSv4.1 data servers MUST considerations outlined in Section 12.9. NFSv4.1 data servers MUST
make all of the required access checks on each READ or WRITE I/O as make all of the required access checks on each READ or WRITE I/O as
determined by the NFSv4.1 protocol. If the metadata server would determined by the NFSv4.1 protocol. If the metadata server would
deny READ or WRITE operation on a given file due its ACL, mode deny a READ or WRITE operation on a file due to its ACL, mode
attribute, open mode, open deny mode, mandatory lock state, or any attribute, open access mode, open deny mode, mandatory byte-range
other attributes and state, the data server MUST also deny the READ lock state, or any other attributes and state, the data server MUST
or WRITE operation. This impacts the control protocol and the also deny the READ or WRITE operation. This impacts the control
propagation of state from the metadata server to the data servers; protocol and the propagation of state from the metadata server to the
see Section 13.9.2 for more details. data servers; see Section 13.9.2 for more details.
The methods for authentication, integrity, and privacy for file The methods for authentication, integrity, and privacy for data
layout-based data servers are the same as those used by metadata servers based on the LAYOUT4_NFSV4_1_FILES layout type are the same
servers. Metadata and data servers use ONC RPC security flavors to as those used by metadata servers. Metadata and data servers use ONC
authenticate, and SECINFO and SECINFO_NO_NAME to negotiate the RPC security flavors to authenticate, and SECINFO and SECINFO_NO_NAME
security mechanism and services to be used. Thus when using the to negotiate the security mechanism and services to be used. Thus,
LAYOUT4_NFSV4_1_FILES layout type, the impact on the RPC-based when using the LAYOUT4_NFSV4_1_FILES layout type, the impact on the
security model due to pNFS (as alluded to in Section 1.6.1 and RPC-based security model due to pNFS (as alluded to in Sections 1.7.1
Section 1.6.2.2) is zero. and 1.7.2.2) is zero.
For a given file object, a metadata server MAY require different For a given file object, a metadata server MAY require different
security parameters (secinfo4 value) than the data server. For a security parameters (secinfo4 value) than the data server. For a
given file object with multiple data servers, the secinfo4 value given file object with multiple data servers, the secinfo4 value
SHOULD be the same across all data servers. If the secinfo4 values SHOULD be the same across all data servers. If the secinfo4 values
across a metadata server and its data servers differ for a specific across a metadata server and its data servers differ for a specific
file, the mapping of the principal to the server's internal user file, the mapping of the principal to the server's internal user
identifier MUST be the same in order for the access control checks identifier MUST be the same in order for the access-control checks
based on ACL, mode, open and deny mode, and mandatory locking to be based on ACL, mode, open and deny mode, and mandatory locking to be
consistent across on the pNFS server. consistent across on the pNFS server.
If an NFSv4.1 implementation supports pNFS and supports NFSv4.1 file If an NFSv4.1 implementation supports pNFS and supports NFSv4.1 file
layouts, then the implementation MUST support the SECINFO_NO_NAME layouts, then the implementation MUST support the SECINFO_NO_NAME
operation, on both the metadata and data servers. operation on both the metadata and data servers.
14. Internationalization 14. Internationalization
The primary issue in which NFSv4.1 needs to deal with The primary issue in which NFSv4.1 needs to deal with
internationalization, or I18N, is with respect to file names and internationalization, or I18N, is with respect to file names and
other strings as used within the protocol. The choice of string other strings as used within the protocol. The choice of string
representation must allow reasonable name/string access to clients representation must allow reasonable name/string access to clients
which use various languages. The UTF-8 encoding of the UCS as that use various languages. The UTF-8 encoding of the UCS (Universal
defined by ISO10646 [21] allows for this type of access and follows Multiple-Octet Coded Character Set) as defined by ISO10646 [21]
the policy described in "IETF Policy on Character Sets and allows for this type of access and follows the policy described in
Languages", RFC2277 [22]. "IETF Policy on Character Sets and Languages", RFC 2277 [22].
RFC3454 [19], otherwise know as "stringprep", documents a framework RFC3454 [19], otherwise know as "stringprep", documents a framework
for using Unicode/UTF-8 in networking protocols, so as "to increase for using Unicode/UTF-8 in networking protocols so as "to increase
the likelihood that string input and string comparison work in ways the likelihood that string input and string comparison work in ways
that make sense for typical users throughout the world." A protocol that make sense for typical users throughout the world". A protocol
must define a profile of stringprep "in order to fully specify the must define a profile of stringprep "in order to fully specify the
processing options." The remainder of this Internationalization processing options". The remainder of this section defines the
section defines the NFSv4.1 stringprep profiles. Much of terminology NFSv4.1 stringprep profiles. Much of the terminology used for the
used for the remainder of this section comes from stringprep. remainder of this section comes from stringprep.
There are three UTF-8 string types defined for NFSv4.1: utf8str_cs, There are three UTF-8 string types defined for NFSv4.1: utf8str_cs,
utf8str_cis, and utf8str_mixed. Separate profiles are defined for utf8str_cis, and utf8str_mixed. Separate profiles are defined for
each. Each profile defines the following, as required by stringprep: each. Each profile defines the following, as required by stringprep:
o The intended applicability of the profile o The intended applicability of the profile.
o The character repertoire that is the input and output to o The character repertoire that is the input and output to
stringprep (which is Unicode 3.2 for referenced version of stringprep (which is Unicode 3.2 for the referenced version of
stringprep). However, NFSv4.1 implementations are not limited to stringprep). However, NFSv4.1 implementations are not limited to
3.2. 3.2.
o The mapping tables from stringprep used (as described in section 3 o The mapping tables from stringprep used (as described in Section 3
of stringprep) of stringprep).
o Any additional mapping tables specific to the profile o Any additional mapping tables specific to the profile.
o The Unicode normalization used, if any (as described in section 4 o The Unicode normalization used, if any (as described in Section 4
of stringprep) of stringprep).
o The tables from stringprep listing of characters that are o The tables from the stringprep listing of characters that are
prohibited as output (as described in section 5 of stringprep) prohibited as output (as described in Section 5 of stringprep).
o The bidirectional string testing used, if any (as described in o The bidirectional string testing used, if any (as described in
section 6 of stringprep) Section 6 of stringprep).
o Any additional characters that are prohibited as output specific o Any additional characters that are prohibited as output specific
to the profile to the profile.
Stringprep discusses Unicode characters, whereas NFSv4.1 renders Stringprep discusses Unicode characters, whereas NFSv4.1 renders
UTF-8 characters. Since there is a one-to-one mapping from UTF-8 to UTF-8 characters. Since there is a one-to-one mapping from UTF-8 to
Unicode, when the remainder of this document refers to Unicode, the Unicode, when the remainder of this document refers to Unicode, the
reader should assume UTF-8. reader should assume UTF-8.
Much of the text for the profiles comes from RFC3491 [23]. Much of the text for the profiles comes from RFC3491 [23].
14.1. Stringprep profile for the utf8str_cs type 14.1. Stringprep Profile for the utf8str_cs Type
Every use of the utf8str_cs type definition in the NFSv4 protocol Every use of the utf8str_cs type definition in the NFSv4 protocol
specification follows the profile named nfs4_cs_prep. specification follows the profile named nfs4_cs_prep.
14.1.1. Intended applicability of the nfs4_cs_prep profile 14.1.1. Intended Applicability of the nfs4_cs_prep Profile
The utf8str_cs type is a case sensitive string of UTF-8 characters. The utf8str_cs type is a case-sensitive string of UTF-8 characters.
Its primary use in NFSv4.1 is for naming components and pathnames. Its primary use in NFSv4.1 is for naming components and pathnames.
Components and pathnames are stored on the server's file system. Two Components and pathnames are stored on the server's file system. Two
valid distinct UTF-8 strings might be the same after processing via valid distinct UTF-8 strings might be the same after processing via
the utf8str_cs profile. If the strings are two names inside a the utf8str_cs profile. If the strings are two names inside a
directory, the NFSv4.1 server will need to either: directory, the NFSv4.1 server will need to either:
o disallow the creation of a second name if its post processed form o disallow the creation of a second name if its post-processed form
collides with that of an existing name, or collides with that of an existing name, or
o allow the creation of the second name, but arrange so that after o allow the creation of the second name, but arrange so that after
post processing, the second name is different than the post post-processing, the second name is different than the post-
processed form of the first name. processed form of the first name.
14.1.2. Character repertoire of nfs4_cs_prep 14.1.2. Character Repertoire of nfs4_cs_prep
The nfs4_cs_prep profile uses Unicode 3.2, as defined in stringprep's The nfs4_cs_prep profile uses Unicode 3.2, as defined in stringprep's
Appendix A.1. However, NFSv4.1 implementations are not limited to Appendix A.1. However, NFSv4.1 implementations are not limited to
3.2. 3.2.
14.1.3. Mapping used by nfs4_cs_prep 14.1.3. Mapping Used by nfs4_cs_prep
The nfs4_cs_prep profile specifies mapping using the following tables The nfs4_cs_prep profile specifies mapping using the following tables
from stringprep: from stringprep:
Table B.1 Table B.1
Table B.2 is normally not part of the nfs4_cs_prep profile as it is Table B.2 is normally not part of the nfs4_cs_prep profile as it is
primarily for dealing with case-insensitive comparisons. However, if primarily for dealing with case-insensitive comparisons. However, if
the NFSv4.1 file server supports the case_insensitive file system the NFSv4.1 file server supports the case_insensitive file system
attribute, and if case_insensitive is TRUE, the NFSv4.1 server MUST attribute, and if case_insensitive is TRUE, the NFSv4.1 server MUST
use Table B.2 (in addition to Table B1) when processing utf8str_cs use Table B.2 (in addition to Table B1) when processing utf8str_cs
strings, and the NFSv4.1 client MUST assume Table B.2 (in addition to strings, and the NFSv4.1 client MUST assume Table B.2 (in addition to
Table B.1) are being used. Table B.1) is being used.
If the case_preserving attribute is present and set to FALSE, then If the case_preserving attribute is present and set to FALSE, then
the NFSv4.1 server MUST use table B.2 to map case when processing the NFSv4.1 server MUST use Table B.2 to map case when processing
utf8str_cs strings. Whether the server maps from lower to upper case utf8str_cs strings. Whether the server maps from lower to upper case
or the upper to lower case is an implementation dependency. or from upper to lower case is an implementation dependency.
14.1.4. Normalization used by nfs4_cs_prep 14.1.4. Normalization used by nfs4_cs_prep
The nfs4_cs_prep profile does not specify a normalization form. A The nfs4_cs_prep profile does not specify a normalization form. A
later revision of this specification may specify a particular later revision of this specification may specify a particular
normalization form. Therefore, the server and client can expect that normalization form. Therefore, the server and client can expect that
they may receive unnormalized characters within protocol requests and they may receive unnormalized characters within protocol requests and
responses. If the operating environment requires normalization, then responses. If the operating environment requires normalization, then
the implementation must normalize utf8str_cs strings within the the implementation must normalize utf8str_cs strings within the
protocol before presenting the information to an application (at the protocol before presenting the information to an application (at the
client) or local file system (at the server). client) or local file system (at the server).
14.1.5. Prohibited output for nfs4_cs_prep 14.1.5. Prohibited Output for nfs4_cs_prep
The nfs4_cs_prep profile RECOMMENDS prohibiting the use of the The nfs4_cs_prep profile RECOMMENDS prohibiting the use of the
following tables from stringprep: following tables from stringprep:
Table C.5 Table C.5
Table C.6 Table C.6
14.1.6. Bidirectional output for nfs4_cs_prep 14.1.6. Bidirectional Output for nfs4_cs_prep
The nfs4_cs_prep profile does not specify any checking of The nfs4_cs_prep profile does not specify any checking of
bidirectional strings. bidirectional strings.
14.2. Stringprep profile for the utf8str_cis type 14.2. Stringprep Profile for the utf8str_cis Type
Every use of the utf8str_cis type definition in the NFSv4.1 protocol Every use of the utf8str_cis type definition in the NFSv4.1 protocol
specification follows the profile named nfs4_cis_prep. specification follows the profile named nfs4_cis_prep.
14.2.1. Intended applicability of the nfs4_cis_prep profile 14.2.1. Intended Applicability of the nfs4_cis_prep Profile
The utf8str_cis type is a case insensitive string of UTF-8 The utf8str_cis type is a case-insensitive string of UTF-8
characters. Its primary use in NFSv4.1 is for naming NFS servers. characters. Its primary use in NFSv4.1 is for naming NFS servers.
14.2.2. Character repertoire of nfs4_cis_prep 14.2.2. Character Repertoire of nfs4_cis_prep
The nfs4_cis_prep profile uses Unicode 3.2, as defined in The nfs4_cis_prep profile uses Unicode 3.2, as defined in
stringprep's Appendix A.1. However, NFSv4.1 implementations are not stringprep's Appendix A.1. However, NFSv4.1 implementations are not
limited to 3.2. limited to 3.2.
14.2.3. Mapping used by nfs4_cis_prep 14.2.3. Mapping Used by nfs4_cis_prep
The nfs4_cis_prep profile specifies mapping using the following The nfs4_cis_prep profile specifies mapping using the following
tables from stringprep: tables from stringprep:
Table B.1 Table B.1
Table B.2 Table B.2
14.2.4. Normalization used by nfs4_cis_prep 14.2.4. Normalization Used by nfs4_cis_prep
The nfs4_cis_prep profile specifies using Unicode normalization form The nfs4_cis_prep profile specifies using Unicode normalization form
KC, as described in stringprep. KC, as described in stringprep.
14.2.5. Prohibited output for nfs4_cis_prep 14.2.5. Prohibited Output for nfs4_cis_prep
The nfs4_cis_prep profile specifies prohibiting using the following The nfs4_cis_prep profile specifies prohibiting using the following
tables from stringprep: tables from stringprep:
Table C.1.2 Table C.1.2
Table C.2.2 Table C.2.2
Table C.3 Table C.3
skipping to change at page 336, line 23 skipping to change at page 336, line 43
Table C.5 Table C.5
Table C.6 Table C.6
Table C.7 Table C.7
Table C.8 Table C.8
Table C.9 Table C.9
14.2.6. Bidirectional output for nfs4_cis_prep 14.2.6. Bidirectional Output for nfs4_cis_prep
The nfs4_cis_prep profile specifies checking bidirectional strings as The nfs4_cis_prep profile specifies checking bidirectional strings as
described in stringprep's section 6. described in stringprep's Section 6.
14.3. Stringprep profile for the utf8str_mixed type 14.3. Stringprep Profile for the utf8str_mixed Type
Every use of the utf8str_mixed type definition in the NFSv4.1 Every use of the utf8str_mixed type definition in the NFSv4.1
protocol specification follows the profile named nfs4_mixed_prep. protocol specification follows the profile named nfs4_mixed_prep.
14.3.1. Intended applicability of the nfs4_mixed_prep profile 14.3.1. Intended Applicability of the nfs4_mixed_prep Profile
The utf8str_mixed type is a string of UTF-8 characters, with a prefix The utf8str_mixed type is a string of UTF-8 characters, with a prefix
that is case sensitive, a separator equal to '@', and a suffix that that is case sensitive, a separator equal to '@', and a suffix that
is fully qualified domain name. Its primary use in NFSv4.1 is for is a fully qualified domain name. Its primary use in NFSv4.1 is for
naming principals identified in an Access Control Entry. naming principals identified in an Access Control Entry.
14.3.2. Character repertoire of nfs4_mixed_prep 14.3.2. Character Repertoire of nfs4_mixed_prep
The nfs4_mixed_prep profile uses Unicode 3.2, as defined in The nfs4_mixed_prep profile uses Unicode 3.2, as defined in
stringprep's Appendix A.1. However, NFSv4.1 implementations are not stringprep's Appendix A.1. However, NFSv4.1 implementations are not
limited to 3.2. limited to 3.2.
14.3.3. Mapping used by nfs4_cis_prep 14.3.3. Mapping Used by nfs4_cis_prep
For the prefix and the separator of a utf8str_mixed string, the For the prefix and the separator of a utf8str_mixed string, the
nfs4_mixed_prep profile specifies mapping using the following table nfs4_mixed_prep profile specifies mapping using the following table
from stringprep: from stringprep:
Table B.1 Table B.1
For the suffix of a utf8str_mixed string, the nfs4_mixed_prep profile For the suffix of a utf8str_mixed string, the nfs4_mixed_prep profile
specifies mapping using the following tables from stringprep: specifies mapping using the following tables from stringprep:
Table B.1 Table B.1
Table B.2 Table B.2
14.3.4. Normalization used by nfs4_mixed_prep 14.3.4. Normalization Used by nfs4_mixed_prep
The nfs4_mixed_prep profile specifies using Unicode normalization The nfs4_mixed_prep profile specifies using Unicode normalization
form KC, as described in stringprep. form KC, as described in stringprep.
14.3.5. Prohibited output for nfs4_mixed_prep 14.3.5. Prohibited Output for nfs4_mixed_prep
The nfs4_mixed_prep profile specifies prohibiting using the following The nfs4_mixed_prep profile specifies prohibiting using the following
tables from stringprep: tables from stringprep:
Table C.1.2 Table C.1.2
Table C.2.2 Table C.2.2
Table C.3 Table C.3
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Table C.1.2 Table C.1.2
Table C.2.2 Table C.2.2
Table C.3 Table C.3
Table C.4 Table C.4
Table C.5 Table C.5
Table C.6 Table C.6
Table C.7 Table C.7
Table C.8 Table C.8
Table C.9 Table C.9
14.3.6. Bidirectional output for nfs4_mixed_prep 14.3.6. Bidirectional Output for nfs4_mixed_prep
The nfs4_mixed_prep profile specifies checking bidirectional strings The nfs4_mixed_prep profile specifies checking bidirectional strings
as described in stringprep's section 6. as described in stringprep's Section 6.
14.4. UTF-8 Capabilities 14.4. UTF-8 Capabilities
const FSCHARSET_CAP4_CONTAINS_NON_UTF8 = 0x1; const FSCHARSET_CAP4_CONTAINS_NON_UTF8 = 0x1;
const FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 = 0x2; const FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 = 0x2;
typedef uint32_t fs_charset_cap4; typedef uint32_t fs_charset_cap4;
Because some operating environments and file systems do not enforce Because some operating environments and file systems do not enforce
character set encodings, NFSv4.1 supports the fs_charset_cap character set encodings, NFSv4.1 supports the fs_charset_cap
attribute (Section 5.8.2.11) that indicates to the client a file attribute (Section 5.8.2.11) that indicates to the client a file
system's UTF-8 capabilities. The attribute is an integer containing system's UTF-8 capabilities. The attribute is an integer containing
a pair of flags. The first flag is FSCHARSET_CAP4_CONTAINS_NON_UTF8, a pair of flags. The first flag is FSCHARSET_CAP4_CONTAINS_NON_UTF8,
which, if set to one tells the client the file system contains non- which, if set to one, tells the client that the file system contains
UTF-8 characters, and the server will not convert non-UTF characters non-UTF-8 characters, and the server will not convert non-UTF
to UTF-8 if the client reads a symlink or directory, nor will characters to UTF-8 if the client reads a symlink or directory,
operations with component names or pathnames in the arguments convert neither will operations with component names or pathnames in the
the strings to UTF-8. The second flag is arguments convert the strings to UTF-8. The second flag is
FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 which if set to one, indicates that FSCHARSET_CAP4_ALLOWS_ONLY_UTF8, which, if set to one, indicates that
the server will accept (and generate) only UTF-8 characters on the the server will accept (and generate) only UTF-8 characters on the
file system. If FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 is set to one, file system. If FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 is set to one,
FSCHARSET_CAP4_CONTAINS_NON_UTF8 MUST be set to zero. FSCHARSET_CAP4_CONTAINS_NON_UTF8 MUST be set to zero.
FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 SHOULD always be set to one. FSCHARSET_CAP4_ALLOWS_ONLY_UTF8 SHOULD always be set to one.
14.5. UTF-8 Related Errors 14.5. UTF-8 Related Errors
Where the client sends an invalid UTF-8 string, the server should Where the client sends an invalid UTF-8 string, the server should
return NFS4ERR_INVAL (see Table 5). This includes cases in which return NFS4ERR_INVAL (see Table 5). This includes cases in which
inappropriate prefixes are detected and where the count includes inappropriate prefixes are detected and where the count includes
trailing bytes that do not constitute a full UCS character. trailing bytes that do not constitute a full UCS character.
Where the client supplied string is valid UTF-8 but contains Where the client-supplied string is valid UTF-8 but contains
characters that are not supported by the server as a value for that characters that are not supported by the server as a value for that
string (e.g. names containing characters outside of Unicode plane 0 string (e.g., names containing characters outside of Unicode plane 0
on filesystems that fail to support such characters despite their on filesystems that fail to support such characters despite their
presence in the Unicode standard), the server should return presence in the Unicode standard), the server should return
NFS4ERR_BADCHAR. NFS4ERR_BADCHAR.
Where a UTF-8 string is used as a file name, and the file system, Where a UTF-8 string is used as a file name, and the file system
while supporting all of the characters within the name, does not (while supporting all of the characters within the name) does not
allow that particular name to be used, the server should return the allow that particular name to be used, the server should return the
error NFS4ERR_BADNAME (Table 5). This includes situations in which error NFS4ERR_BADNAME (Table 5). This includes situations in which
the server file system imposes a normalization constraint on name the server file system imposes a normalization constraint on name
strings, but will also include such situations as file system strings, but will also include such situations as file system
prohibitions of "." and ".." as file names for certain operations, prohibitions of "." and ".." as file names for certain operations,
and other such constraints. and other such constraints.
15. Error Values 15. Error Values
NFS error numbers are assigned to failed operations within a Compound NFS error numbers are assigned to failed operations within a Compound
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This section deals with errors that are applicable to a broad set of This section deals with errors that are applicable to a broad set of
different purposes. different purposes.
15.1.1.1. NFS4ERR_BADXDR (Error Code 10036) 15.1.1.1. NFS4ERR_BADXDR (Error Code 10036)
The arguments for this operation do not match those specified in the The arguments for this operation do not match those specified in the
XDR definition. This includes situations in which the request ends XDR definition. This includes situations in which the request ends
before all the arguments have been seen. Note that this error before all the arguments have been seen. Note that this error
applies when fixed enumerations (these include booleans) have a value applies when fixed enumerations (these include booleans) have a value
within the input stream which is not valid for the enum. A replier within the input stream that is not valid for the enum. A replier
may pre-parse all operations for a Compound procedure before doing may pre-parse all operations for a Compound procedure before doing
any operation execution and return RPC-level XDR errors in that case. any operation execution and return RPC-level XDR errors in that case.
15.1.1.2. NFS4ERR_BAD_COOKIE (Error Code 10003) 15.1.1.2. NFS4ERR_BAD_COOKIE (Error Code 10003)
Used for operations that provide a set of information indexed by some Used for operations that provide a set of information indexed by some
quantity provided by the client or cookie sent by the server for an quantity provided by the client or cookie sent by the server for an
earlier invocation. Where the value cannot be used for its intended earlier invocation. Where the value cannot be used for its intended
purpose, this error results. purpose, this error results.
15.1.1.3. NFS4ERR_DELAY (Error Code 10008) 15.1.1.3. NFS4ERR_DELAY (Error Code 10008)
For any of a number of reasons, the replier could not process this For any of a number of reasons, the replier could not process this
operation in what was deemed a reasonable time. The client should operation in what was deemed a reasonable time. The client should
wait and then try the request with a new slot and sequence value. wait and then try the request with a new slot and sequence value.
Some example of situations that might lead to this situation: Some examples of scenarios that might lead to this situation:
o A server that supports hierarchical storage receives a request to o A server that supports hierarchical storage receives a request to
process a file that had been migrated. process a file that had been migrated.
o An operation requires a delegation recall to proceed and waiting o An operation requires a delegation recall to proceed, and waiting
for this delegation recall makes processing this request in a for this delegation recall makes processing this request in a
timely fashion impossible. timely fashion impossible.
In such cases, the error NFS4ERR_DELAY allows these preparatory In such cases, the error NFS4ERR_DELAY allows these preparatory
operations to proceed without holding up client resources such as a operations to proceed without holding up client resources such as a
session slot. After delaying for period of time, the client can then session slot. After delaying for period of time, the client can then
re-send the operation in question (but not with the same slot ID and re-send the operation in question (but not with the same slot ID and
sequence ID; one or both MUST be different on the re-send). sequence ID; one or both MUST be different on the re-send).
Note that without the ability to return NFS4ERR_DELAY and the Note that without the ability to return NFS4ERR_DELAY and the
client's willingness to re-send when receiving it, deadlock might client's willingness to re-send when receiving it, deadlock might
well result. E.g., if a recall is done, and if the delegation return result. For example, if a recall is done, and if the delegation
or operations preparatory to delegation return are held up by other return or operations preparatory to delegation return are held up by
operations that need the delegation to be returned, session slots other operations that need the delegation to be returned, session
might not be available. The result could be deadlock. slots might not be available. The result could be deadlock.
15.1.1.4. NFS4ERR_INVAL (Error Code 22) 15.1.1.4. NFS4ERR_INVAL (Error Code 22)
The arguments for this operation are not valid for some reason, even The arguments for this operation are not valid for some reason, even
though they do match those specified in the XDR definition for the though they do match those specified in the XDR definition for the
request. request.
15.1.1.5. NFS4ERR_NOTSUPP (Error Code 10004) 15.1.1.5. NFS4ERR_NOTSUPP (Error Code 10004)
Operation not supported, either because the operation is an OPTIONAL Operation not supported, either because the operation is an OPTIONAL
one and is not supported by this server or because the operation MUST one and is not supported by this server or because the operation MUST
NOT be implemented in the current minor version. NOT be implemented in the current minor version.
15.1.1.6. NFS4ERR_SERVERFAULT (Error Code 10006) 15.1.1.6. NFS4ERR_SERVERFAULT (Error Code 10006)
An error occurred on the server which does not map to any of the An error occurred on the server that does not map to any of the
specific legal NFSv4.1 protocol error values. The client should specific legal NFSv4.1 protocol error values. The client should
translate this into an appropriate error. UNIX clients may choose to translate this into an appropriate error. UNIX clients may choose to
translate this to EIO. translate this to EIO.
15.1.1.7. NFS4ERR_TOOSMALL (Error Code 10005) 15.1.1.7. NFS4ERR_TOOSMALL (Error Code 10005)
Used where an operation returns a variable amount of data, with a Used where an operation returns a variable amount of data, with a
limit specified by the client. Where the data returned cannot be fit limit specified by the client. Where the data returned cannot be fit
within the limit specified by the client, this error results. within the limit specified by the client, this error results.
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15.1.2.1. NFS4ERR_BADHANDLE (Error Code 10001) 15.1.2.1. NFS4ERR_BADHANDLE (Error Code 10001)
Illegal NFS filehandle for the current server. The current file Illegal NFS filehandle for the current server. The current file
handle failed internal consistency checks. Once accepted as valid handle failed internal consistency checks. Once accepted as valid
(by PUTFH), no subsequent status change can cause the filehandle to (by PUTFH), no subsequent status change can cause the filehandle to
generate this error. generate this error.
15.1.2.2. NFS4ERR_FHEXPIRED (Error Code 10014) 15.1.2.2. NFS4ERR_FHEXPIRED (Error Code 10014)
A current or saved filehandle which is an argument to the current A current or saved filehandle that is an argument to the current
operation is volatile and has expired at the server. operation is volatile and has expired at the server.
15.1.2.3. NFS4ERR_ISDIR (Error Code 21) 15.1.2.3. NFS4ERR_ISDIR (Error Code 21)
The current or saved filehandle designates a directory when the The current or saved filehandle designates a directory when the
current operation does not allow a directory to be accepted as the current operation does not allow a directory to be accepted as the
target of this operation. target of this operation.
15.1.2.4. NFS4ERR_MOVED (Error Code 10019) 15.1.2.4. NFS4ERR_MOVED (Error Code 10019)
The file system which contains the current filehandle object is not The file system that contains the current filehandle object is not
present at the server. It may have been relocated, migrated to present at the server. It may have been relocated or migrated to
another server or may have never been present. The client may obtain another server, or it may have never been present. The client may
the new file system location by obtaining the "fs_locations" or obtain the new file system location by obtaining the "fs_locations"
"fs_locations_info" attribute for the current filehandle. For or "fs_locations_info" attribute for the current filehandle. For
further discussion, refer to Section 11.2 further discussion, refer to Section 11.2.
15.1.2.5. NFS4ERR_NOFILEHANDLE (Error Code 10020) 15.1.2.5. NFS4ERR_NOFILEHANDLE (Error Code 10020)
The logical current or saved filehandle value is required by the The logical current or saved filehandle value is required by the
current operation and is not set. This may be a result of a current operation and is not set. This may be a result of a
malformed COMPOUND operation (i.e. no PUTFH or PUTROOTFH before an malformed COMPOUND operation (i.e., no PUTFH or PUTROOTFH before an
operation that requires the current filehandle be set). operation that requires the current filehandle be set).
15.1.2.6. NFS4ERR_NOTDIR (Error Code 20) 15.1.2.6. NFS4ERR_NOTDIR (Error Code 20)
The current (or saved) filehandle designates an object which is not a The current (or saved) filehandle designates an object that is not a
directory for an operation in which a directory is required. directory for an operation in which a directory is required.
15.1.2.7. NFS4ERR_STALE (Error Code 70) 15.1.2.7. NFS4ERR_STALE (Error Code 70)
The current or saved filehandle value designating an argument to the The current or saved filehandle value designating an argument to the
current operation is invalid The file referred to by that filehandle current operation is invalid. The file referred to by that
no longer exists or access to it has been revoked. filehandle no longer exists or access to it has been revoked.
15.1.2.8. NFS4ERR_SYMLINK (Error Code 10029) 15.1.2.8. NFS4ERR_SYMLINK (Error Code 10029)
The current filehandle designates a symbolic link when the current The current filehandle designates a symbolic link when the current
operation does not allow a symbolic link as the target. operation does not allow a symbolic link as the target.
15.1.2.9. NFS4ERR_WRONG_TYPE (Error Code 10083) 15.1.2.9. NFS4ERR_WRONG_TYPE (Error Code 10083)
The current (or saved) filehandle designates an object which is of an The current (or saved) filehandle designates an object that is of an
invalid type for the current operation and there is no more specific invalid type for the current operation, and there is no more specific
error (such as NFS4ERR_ISDIR or NFS4ERR_SYMLINK) that applies. Note error (such as NFS4ERR_ISDIR or NFS4ERR_SYMLINK) that applies. Note
that in NFSv4.0, such situations generally resulted in the less that in NFSv4.0, such situations generally resulted in the less-
specific error NFS4ERR_INVAL. specific error NFS4ERR_INVAL.
15.1.3. Compound Structure Errors 15.1.3. Compound Structure Errors
This section deals with errors that relate to overall structure of a This section deals with errors that relate to the overall structure
Compound request (by which we mean to include both COMPOUND and of a Compound request (by which we mean to include both COMPOUND and
CB_COMPOUND), rather than to particular operations. CB_COMPOUND), rather than to particular operations.
There are a number of basic constraints on the operations that may There are a number of basic constraints on the operations that may
appear in a Compound request. Sessions adds to these basic appear in a Compound request. Sessions add to these basic
constraints by requiring a Sequence operation (either SEQUENCE or constraints by requiring a Sequence operation (either SEQUENCE or
CB_SEQUENCE) at the start of the Compound. CB_SEQUENCE) at the start of the Compound.
15.1.3.1. NFS_OK (Error code 0) 15.1.3.1. NFS_OK (Error code 0)
Indicates the operation completed successfully, in that all of the Indicates the operation completed successfully, in that all of the
constituent operations completed without error. constituent operations completed without error.
15.1.3.2. NFS4ERR_MINOR_VERS_MISMATCH (Error code 10021) 15.1.3.2. NFS4ERR_MINOR_VERS_MISMATCH (Error code 10021)
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Compound does not start with a Sequence operation. This error Compound does not start with a Sequence operation. This error
results when that constraint is not met. results when that constraint is not met.
15.1.3.4. NFS4ERR_OP_ILLEGAL (Error Code 10044) 15.1.3.4. NFS4ERR_OP_ILLEGAL (Error Code 10044)
The operation code is not a valid one for the current Compound The operation code is not a valid one for the current Compound
procedure. The opcode in the result stream matched with this error procedure. The opcode in the result stream matched with this error
is the ILLEGAL value, although the value that appears in the request is the ILLEGAL value, although the value that appears in the request
stream may be different. Where an illegal value appears and the stream may be different. Where an illegal value appears and the
replier pre-parses all operations for a Compound procedure before replier pre-parses all operations for a Compound procedure before
doing any operation execution, an RPC-level XDR error may be returned doing any operation execution, an RPC-level XDR error may be
in this case. returned.
15.1.3.5. NFS4ERR_OP_NOT_IN_SESSION (Error Code 10071) 15.1.3.5. NFS4ERR_OP_NOT_IN_SESSION (Error Code 10071)
Most forward operations and all callback operations are only valid Most forward operations and all callback operations are only valid
within the context of a session, so that the Compound request in within the context of a session, so that the Compound request in
question MUST begin with a Sequence operation. If an attempt is made question MUST begin with a Sequence operation. If an attempt is made
to execute these operations outside the context of session, this to execute these operations outside the context of session, this
error results. error results.
15.1.3.6. NFS4ERR_REP_TOO_BIG (Error Code 10066) 15.1.3.6. NFS4ERR_REP_TOO_BIG (Error Code 10066)
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size for replies cached in the reply cache when the Sequence for the size for replies cached in the reply cache when the Sequence for the
current request specifies that this request is to be cached. current request specifies that this request is to be cached.
15.1.3.8. NFS4ERR_REQ_TOO_BIG (Error Code 10065) 15.1.3.8. NFS4ERR_REQ_TOO_BIG (Error Code 10065)
The Compound request exceeds the channel's negotiated maximum size The Compound request exceeds the channel's negotiated maximum size
for requests. for requests.
15.1.3.9. NFS4ERR_RETRY_UNCACHED_REP (Error Code 10068) 15.1.3.9. NFS4ERR_RETRY_UNCACHED_REP (Error Code 10068)
The requester has attempted a retry of a Compound which it previously The requester has attempted a retry of a Compound that it previously
requested not be placed in the reply cache. requested not be placed in the reply cache.
15.1.3.10. NFS4ERR_SEQUENCE_POS (Error Code 10064) 15.1.3.10. NFS4ERR_SEQUENCE_POS (Error Code 10064)
A Sequence operation appeared in a position other than the first A Sequence operation appeared in a position other than the first
operation of a Compound request. operation of a Compound request.
15.1.3.11. NFS4ERR_TOO_MANY_OPS (Error Code 10070) 15.1.3.11. NFS4ERR_TOO_MANY_OPS (Error Code 10070)
The Compound request has too many operations, exceeding the count The Compound request has too many operations, exceeding the count
negotiated when the session was created. negotiated when the session was created.
15.1.3.12. NFS4ERR_UNSAFE_COMPOUND (Error Code 10068) 15.1.3.12. NFS4ERR_UNSAFE_COMPOUND (Error Code 10068)
The client has sent a COMPOUND request with an unsafe mix of The client has sent a COMPOUND request with an unsafe mix of
operations, specifically with a non-idempotent operation changing the operations -- specifically, with a non-idempotent operation that
current filehandle which is not followed by a GETFH. changes the current filehandle and that is not followed by a GETFH.
15.1.4. File System Errors 15.1.4. File System Errors
These errors describe situations which occurred in the underlying These errors describe situations that occurred in the underlying file
file system implementation rather than in the protocol or any NFSv4.x system implementation rather than in the protocol or any NFSv4.x
feature. feature.
15.1.4.1. NFS4ERR_BADTYPE (Error Code 10007) 15.1.4.1. NFS4ERR_BADTYPE (Error Code 10007)
An attempt was made to create an object with an inappropriate type An attempt was made to create an object with an inappropriate type
specified to CREATE. This may be because the type is undefined, specified to CREATE. This may be because the type is undefined,
because it is a type not supported by the server, or because it is a because the type is not supported by the server, or because the type
type for which create is not intended such as a regular file or named is not intended to be created by CREATE (such as a regular file or
attribute, for which OPEN is used to do the file creation. named attribute, for which OPEN is used to do the file creation).
15.1.4.2. NFS4ERR_DQUOT (Error Code 19) 15.1.4.2. NFS4ERR_DQUOT (Error Code 19)
Resource (quota) hard limit exceeded. The user's resource limit on Resource (quota) hard limit exceeded. The user's resource limit on
the server has been exceeded. the server has been exceeded.
15.1.4.3. NFS4ERR_EXIST (Error Code 17) 15.1.4.3. NFS4ERR_EXIST (Error Code 17)
A file of the specified target name (when creating, renaming or A file of the specified target name (when creating, renaming, or
linking) already exists. linking) already exists.
15.1.4.4. NFS4ERR_FBIG (Error Code 27) 15.1.4.4. NFS4ERR_FBIG (Error Code 27)
File too large. The operation would have caused a file to grow The file is too large. The operation would have caused the file to
beyond the server's limit. grow beyond the server's limit.
15.1.4.5. NFS4ERR_FILE_OPEN (Error Code 10046) 15.1.4.5. NFS4ERR_FILE_OPEN (Error Code 10046)
The operation is not allowed because a file involved in the operation The operation is not allowed because a file involved in the operation
is currently open. Servers may, but are not required to disallow is currently open. Servers may, but are not required to, disallow
linking-to, removing, or renaming open files. linking-to, removing, or renaming open files.
15.1.4.6. NFS4ERR_IO (Error Code 5) 15.1.4.6. NFS4ERR_IO (Error Code 5)
Indicates that an I/O error occurred for which the file system was Indicates that an I/O error occurred for which the file system was
unable to provide recovery. unable to provide recovery.
15.1.4.7. NFS4ERR_MLINK (Error Code 31) 15.1.4.7. NFS4ERR_MLINK (Error Code 31)
The request would have caused the server's limit for the number of The request would have caused the server's limit for the number of
hard links a file may have to be exceeded. hard links a file may have to be exceeded.
15.1.4.8. NFS4ERR_NOENT (Error Code 2) 15.1.4.8. NFS4ERR_NOENT (Error Code 2)
Indicates no such file or directory. The file or directory name Indicates no such file or directory. The file or directory name
specified does not exist. specified does not exist.
15.1.4.9. NFS4ERR_NOSPC (Error Code 28) 15.1.4.9. NFS4ERR_NOSPC (Error Code 28)
Indicates no space left on device. The operation would have caused Indicates there is no space left on the device. The operation would
the server's file system to exceed its limit. have caused the server's file system to exceed its limit.
15.1.4.10. NFS4ERR_NOTEMPTY (Error Code 66) 15.1.4.10. NFS4ERR_NOTEMPTY (Error Code 66)
An attempt was made to remove a directory that was not empty. An attempt was made to remove a directory that was not empty.
15.1.4.11. NFS4ERR_ROFS (Error Code 30) 15.1.4.11. NFS4ERR_ROFS (Error Code 30)
Indicates a read-only file system. A modifying operation was Indicates a read-only file system. A modifying operation was
attempted on a read-only file system. attempted on a read-only file system.
15.1.4.12. NFS4ERR_XDEV (Error Code 18) 15.1.4.12. NFS4ERR_XDEV (Error Code 18)
Indicates an attempt to do an operation, such as linking, that Indicates an attempt to do an operation, such as linking, that
inappropriately crosses a boundary. This may be due to such inappropriately crosses a boundary. This may be due to such
boundaries as: boundaries as:
o That between file systems (where the fsids are different). o that between file systems (where the fsids are different).
o That between different named attribute directories or between a o that between different named attribute directories or between a
named attribute directory and an ordinary directory. named attribute directory and an ordinary directory.
o That between regions of a file system that the file system o that between byte-ranges of a file system that the file system
implementation treats as separate (for example for space implementation treats as separate (for example, for space
accounting purposes), and where cross-connection between the accounting purposes), and where cross-connection between the byte-
regions are not allowed. ranges are not allowed.
15.1.5. State Management Errors 15.1.5. State Management Errors
These errors indicate problems with the stateid (or one of the These errors indicate problems with the stateid (or one of the
stateids) passed to a given operation. This includes situations in stateids) passed to a given operation. This includes situations in
which the stateid is invalid as well as situations in which the which the stateid is invalid as well as situations in which the
stateid is valid but designates revoked locking state. Depending on stateid is valid but designates locking state that has been revoked.
the operation, the stateid when valid may designate opens, byte-range Depending on the operation, the stateid when valid may designate
locks, file or directory delegations, layouts, or device maps. opens, byte-range locks, file or directory delegations, layouts, or
device maps.
15.1.5.1. NFS4ERR_ADMIN_REVOKED (Error Code 10047) 15.1.5.1. NFS4ERR_ADMIN_REVOKED (Error Code 10047)
A stateid designates locking state of any type that has been revoked A stateid designates locking state of any type that has been revoked
due to administrative interaction, possibly while the lease is valid. due to administrative interaction, possibly while the lease is valid.
15.1.5.2. NFS4ERR_BAD_STATEID (Error Code 10026) 15.1.5.2. NFS4ERR_BAD_STATEID (Error Code 10026)
A stateid does not properly designate any valid state. See A stateid does not properly designate any valid state. See Sections
Section 8.2.4 and Section 8.2.3 for a discussion of how stateids are 8.2.4 and 8.2.3 for a discussion of how stateids are validated.
validated.
15.1.5.3. NFS4ERR_DELEG_REVOKED (Error Code 10087) 15.1.5.3. NFS4ERR_DELEG_REVOKED (Error Code 10087)
A stateid designates recallable locking state of any type (delegation A stateid designates recallable locking state of any type (delegation
or layout) that has been revoked due to the failure of the client to or layout) that has been revoked due to the failure of the client to
return the lock when it was recalled. return the lock when it was recalled.
15.1.5.4. NFS4ERR_EXPIRED (Error Code 10011) 15.1.5.4. NFS4ERR_EXPIRED (Error Code 10011)
A stateid designates locking state of any type that has been revoked A stateid designates locking state of any type that has been revoked
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15.1.6. Security Errors 15.1.6. Security Errors
These are the various permission-related errors in NFSv4.1. These are the various permission-related errors in NFSv4.1.
15.1.6.1. NFS4ERR_ACCESS (Error Code 13) 15.1.6.1. NFS4ERR_ACCESS (Error Code 13)
Indicates permission denied. The caller does not have the correct Indicates permission denied. The caller does not have the correct
permission to perform the requested operation. Contrast this with permission to perform the requested operation. Contrast this with
NFS4ERR_PERM (Section 15.1.6.2), which restricts itself to owner or NFS4ERR_PERM (Section 15.1.6.2), which restricts itself to owner or
privileged user permission failures, and NFS4ERR_WRONG_CRED privileged-user permission failures, and NFS4ERR_WRONG_CRED
(Section 15.1.6.4) which deals with appropriate permission to delete (Section 15.1.6.4), which deals with appropriate permission to delete
or modify transient objects, based on the credentials of the user or modify transient objects based on the credentials of the user that
that created them. created them.
15.1.6.2. NFS4ERR_PERM (Error Code 1) 15.1.6.2. NFS4ERR_PERM (Error Code 1)
Indicates requester is not the owner. The operation was not allowed Indicates requester is not the owner. The operation was not allowed
because the caller is neither a privileged user (root) nor the owner because the caller is neither a privileged user (root) nor the owner
of the target of the operation. of the target of the operation.
15.1.6.3. NFS4ERR_WRONGSEC (Error Code 10016) 15.1.6.3. NFS4ERR_WRONGSEC (Error Code 10016)
Indicates that the security mechanism being used by the client for Indicates that the security mechanism being used by the client for
the operation does not match the server's security policy. The the operation does not match the server's security policy. The
client should change the security mechanism being used and re-send client should change the security mechanism being used and re-send
the operation (but not with the same slot ID and sequence ID; one or the operation (but not with the same slot ID and sequence ID; one or
both MUST be different on the re-send). SECINFO and SECINFO_NO_NAME both MUST be different on the re-send). SECINFO and SECINFO_NO_NAME
can be used to determine the appropriate mechanism. can be used to determine the appropriate mechanism.
15.1.6.4. NFS4ERR_WRONG_CRED (Error Code 10082) 15.1.6.4. NFS4ERR_WRONG_CRED (Error Code 10082)
An operation manipulating state was attempted by a principal that was An operation that manipulates state was attempted by a principal that
not allowed to modify that piece of state. was not allowed to modify that piece of state.
15.1.7. Name Errors 15.1.7. Name Errors
Names in NFSv4 are UTF-8 strings. When the strings are not valid Names in NFSv4 are UTF-8 strings. When the strings are not valid
UTF-8 or are of length zero, the error NFS4ERR_INVAL results. UTF-8 or are of length zero, the error NFS4ERR_INVAL results.
Besides this, there are a number of other errors to indicate specific Besides this, there are a number of other errors to indicate specific
problems with names. problems with names.
15.1.7.1. NFS4ERR_BADCHAR (Error Code 10040) 15.1.7.1. NFS4ERR_BADCHAR (Error Code 10040)
A UTF-8 string contains a character which is not supported by the A UTF-8 string contains a character that is not supported by the
server in the context in which it being used. server in the context in which it being used.
15.1.7.2. NFS4ERR_BADNAME (Error Code 10041) 15.1.7.2. NFS4ERR_BADNAME (Error Code 10041)
A name string in a request consisted of valid UTF-8 characters A name string in a request consisted of valid UTF-8 characters
supported by the server but the name is not supported by the server supported by the server, but the name is not supported by the server
as a valid name for current operation. An example might be creating as a valid name for the current operation. An example might be
a file or directory named ".." on a server whose file system uses creating a file or directory named ".." on a server whose file system
that name for links to parent directories. uses that name for links to parent directories.
15.1.7.3. NFS4ERR_NAMETOOLONG (Error Code 63) 15.1.7.3. NFS4ERR_NAMETOOLONG (Error Code 63)
Returned when the filename in an operation exceeds the server's Returned when the filename in an operation exceeds the server's
implementation limit. implementation limit.
15.1.8. Locking Errors 15.1.8. Locking Errors
This section deal with errors related to locking, both as to share This section deals with errors related to locking, both as to share
reservations and byte-range locking. It does not deal with errors reservations and byte-range locking. It does not deal with errors
specific to the process of reclaiming locks. Those are dealt with in specific to the process of reclaiming locks. Those are dealt with in
the next section. Section 15.1.9.
15.1.8.1. NFS4ERR_BAD_RANGE (Error Code 10042) 15.1.8.1. NFS4ERR_BAD_RANGE (Error Code 10042)
The range for a LOCK, LOCKT, or LOCKU operation is not appropriate to The byte-range of a LOCK, LOCKT, or LOCKU operation is not allowed by
the allowable range of offsets for the server. E.g., this error the server. For example, this error results when a server that only
results when a server which only supports 32-bit ranges receives a supports 32-bit ranges receives a range that cannot be handled by
range that cannot be handled by that server. (See Section 18.10.3). that server. (See Section 18.10.3.)
15.1.8.2. NFS4ERR_DEADLOCK (Error Code 10045) 15.1.8.2. NFS4ERR_DEADLOCK (Error Code 10045)
The server has been able to determine a file locking deadlock The server has been able to determine a byte-range locking deadlock
condition for a blocking lock request. condition for a READW_LT or WRITEW_LT LOCK operation.
15.1.8.3. NFS4ERR_DENIED (Error Code 10010) 15.1.8.3. NFS4ERR_DENIED (Error Code 10010)
An attempt to lock a file is denied. Since this may be a temporary An attempt to lock a file is denied. Since this may be a temporary
condition, the client is encouraged to re-send the lock request (but condition, the client is encouraged to re-send the lock request (but
not with the same slot ID and sequence ID; one or both MUST be not with the same slot ID and sequence ID; one or both MUST be
different on the re-send) until the lock is accepted. See different on the re-send) until the lock is accepted. See
Section 9.6 for a discussion of the re-send. Section 9.6 for a discussion of the re-send.
15.1.8.4. NFS4ERR_LOCKED (Error Code 10012) 15.1.8.4. NFS4ERR_LOCKED (Error Code 10012)
A read or write operation was attempted on a file where there was a A READ or WRITE operation was attempted on a file where there was a
conflict between the I/O and an existing lock: conflict between the I/O and an existing lock:
o There is a share reservation inconsistent with the I/O being done. o There is a share reservation inconsistent with the I/O being done.
o The range to be read or written intersects an existing mandatory o The range to be read or written intersects an existing mandatory
byte range lock. byte-range lock.
15.1.8.5. NFS4ERR_LOCKS_HELD (Error Code 10037) 15.1.8.5. NFS4ERR_LOCKS_HELD (Error Code 10037)
An operation was prevented by the unexpected presence of locks. An operation was prevented by the unexpected presence of locks.
15.1.8.6. NFS4ERR_LOCK_NOTSUPP (Error Code 10043) 15.1.8.6. NFS4ERR_LOCK_NOTSUPP (Error Code 10043)
A locking request was attempted which would require the upgrade or A LOCK operation was attempted that would require the upgrade or
downgrade of a lock range already held by the owner when the server downgrade of a byte-range lock range already held by the owner, and
does not support atomic upgrade or downgrade of locks. the server does not support atomic upgrade or downgrade of locks.
15.1.8.7. NFS4ERR_LOCK_RANGE (Error Code 10028) 15.1.8.7. NFS4ERR_LOCK_RANGE (Error Code 10028)
A lock request is operating on a range that overlaps in part a A LOCK operation is operating on a range that overlaps in part a
currently held lock for the current lock-owner and does not precisely currently held byte-range lock for the current lock-owner and does
match a single such lock where the server does not support this type not precisely match a single such byte-range lock where the server
of request, and thus does not implement POSIX locking semantics [24]. does not support this type of request, and thus does not implement
See Section 18.10.4, Section 18.11.4, and Section 18.12.4 for a POSIX locking semantics [24]. See Sections 18.10.4, 18.11.4, and
discussion of how this applies to LOCK, LOCKT, and LOCKU 18.12.4 for a discussion of how this applies to LOCK, LOCKT, and
respectively. LOCKU respectively.
15.1.8.8. NFS4ERR_OPENMODE (Error Code 10038) 15.1.8.8. NFS4ERR_OPENMODE (Error Code 10038)
The client attempted a READ, WRITE, LOCK or other operation not The client attempted a READ, WRITE, LOCK, or other operation not
sanctioned by the stateid passed (e.g. writing to a file opened only sanctioned by the stateid passed (e.g., writing to a file opened for
for read). read-only access).
15.1.8.9. NFS4ERR_SHARE_DENIED (Error Code 10015) 15.1.8.9. NFS4ERR_SHARE_DENIED (Error Code 10015)
An attempt to OPEN a file with a share reservation has failed because An attempt to OPEN a file with a share reservation has failed because
of a share conflict. of a share conflict.
15.1.9. Reclaim Errors 15.1.9. Reclaim Errors
These errors relate to the process of reclaiming locks after a server These errors relate to the process of reclaiming locks after a server
restart. restart.
15.1.9.1. NFS4ERR_COMPLETE_ALREADY (Error Code 10054) 15.1.9.1. NFS4ERR_COMPLETE_ALREADY (Error Code 10054)
The client previously sent a successful RECLAIM_COMPLETE operation. The client previously sent a successful RECLAIM_COMPLETE operation.
An additional RECLAIM_COMPLETE operation is not necessary and results An additional RECLAIM_COMPLETE operation is not necessary and results
in this error. in this error.
15.1.9.2. NFS4ERR_GRACE (Error Code 10013) 15.1.9.2. NFS4ERR_GRACE (Error Code 10013)
The server is in its recovery or grace period which should at least The server was in its recovery or grace period. The locking request
match the lease period of the server. A locking request other than a was not a reclaim request and so could not be granted during that
reclaim could not be granted during that period. period.
15.1.9.3. NFS4ERR_NO_GRACE (Error Code 10033) 15.1.9.3. NFS4ERR_NO_GRACE (Error Code 10033)
A reclaim of client state was attempted in circumstances in which the A reclaim of client state was attempted in circumstances in which the
server cannot guarantee that conflicting state has not been provided server cannot guarantee that conflicting state has not been provided
to another client. This can occur because the reclaim has been done to another client. This can occur because the reclaim has been done
outside of the grace period of the server, after the client has done outside of the grace period of the server, after the client has done
a RECLAIM_COMPLETE operation, or because previous operations have a RECLAIM_COMPLETE operation, or because previous operations have
created a situation in which the server is not able to determine that created a situation in which the server is not able to determine that
a reclaim-interfering edge condition does not exist. a reclaim-interfering edge condition does not exist.
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lock with which this client conflicted. See also Section 15.1.9.4 lock with which this client conflicted. See also Section 15.1.9.4
for the related error, NFS4ERR_RECLAIM_BAD. for the related error, NFS4ERR_RECLAIM_BAD.
15.1.10. pNFS Errors 15.1.10. pNFS Errors
This section deals with pNFS-related errors including those that are This section deals with pNFS-related errors including those that are
associated with using NFSv4.1 to communicate with a data server. associated with using NFSv4.1 to communicate with a data server.
15.1.10.1. NFS4ERR_BADIOMODE (Error Code 10049) 15.1.10.1. NFS4ERR_BADIOMODE (Error Code 10049)
An invalid or inappropriate layout iomode was specified. An invalid or inappropriate layout iomode was specified. For example
an inappropriate layout iomode, suppose a client's LAYOUTGET
operation specified an iomode of LAYOUTIOMODE4_RW, and the server is
neither able nor willing to let the client send write requests to
data servers; the server can reply with NFS4ERR_BADIOMODE. The
client would then send another LAYOUTGET with an iomode of
LAYOUTIOMODE4_READ.
15.1.10.2. NFS4ERR_BADLAYOUT (Error Code 10050) 15.1.10.2. NFS4ERR_BADLAYOUT (Error Code 10050)
The layout specified is invalid in some way. For LAYOUTCOMMIT, this The layout specified is invalid in some way. For LAYOUTCOMMIT, this
indicates that the specified layout is not held by the client or is indicates that the specified layout is not held by the client or is
not of mode LAYOUTIOMODE4_RW. For LAYOUTGET, it indicates that a not of mode LAYOUTIOMODE4_RW. For LAYOUTGET, it indicates that a
layout matching the client's specification as to minimum length layout matching the client's specification as to minimum length
cannot be granted. cannot be granted.
15.1.10.3. NFS4ERR_LAYOUTTRYLATER (Error Code 10058) 15.1.10.3. NFS4ERR_LAYOUTTRYLATER (Error Code 10058)
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not allow a WRITE. not allow a WRITE.
15.1.10.8. NFS4ERR_RETURNCONFLICT (Error Code 10086) 15.1.10.8. NFS4ERR_RETURNCONFLICT (Error Code 10086)
A layout is unavailable due to an attempt to perform the LAYOUTGET A layout is unavailable due to an attempt to perform the LAYOUTGET
before a pending LAYOUTRETURN on the file has been received. See before a pending LAYOUTRETURN on the file has been received. See
Section 12.5.5.2.1.3. Section 12.5.5.2.1.3.
15.1.10.9. NFS4ERR_UNKNOWN_LAYOUTTYPE (Error Code 10062) 15.1.10.9. NFS4ERR_UNKNOWN_LAYOUTTYPE (Error Code 10062)
The client has specified a layout type which is not supported by the The client has specified a layout type that is not supported by the
server. server.
15.1.11. Session Use Errors 15.1.11. Session Use Errors
This section deals with errors encountered in using sessions, that This section deals with errors encountered when using sessions, that
is, in sending requests over sessions using Sequence (i.e. either is, errors encountered when a request uses a Sequence (i.e., either
SEQUENCE or CB_SEQUENCE) operations. SEQUENCE or CB_SEQUENCE) operation.
15.1.11.1. NFS4ERR_BADSESSION (Error Code 10052) 15.1.11.1. NFS4ERR_BADSESSION (Error Code 10052)
The specified session ID is unknown to the server to which the The specified session ID is unknown to the server to which the
operation is addressed. operation is addressed.
15.1.11.2. NFS4ERR_BADSLOT (Error Code 10053) 15.1.11.2. NFS4ERR_BADSLOT (Error Code 10053)
The requester sent a Sequence operation that attempted to use a slot The requester sent a Sequence operation that attempted to use a slot
the replier does not have in its slot table. It is possible the slot the replier does not have in its slot table. It is possible the slot
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15.1.11.4. NFS4ERR_CB_PATH_DOWN (Error Code 10048) 15.1.11.4. NFS4ERR_CB_PATH_DOWN (Error Code 10048)
There is a problem contacting the client via the callback path. The There is a problem contacting the client via the callback path. The
function of this error has been mostly superseded by the use of function of this error has been mostly superseded by the use of
status flags in the reply to the SEQUENCE operation (see status flags in the reply to the SEQUENCE operation (see
Section 18.46). Section 18.46).
15.1.11.5. NFS4ERR_DEADSESSION (Error Code 10078) 15.1.11.5. NFS4ERR_DEADSESSION (Error Code 10078)
The specified session is a persistent session which is dead and does The specified session is a persistent session that is dead and does
not accept new requests or perform new operations on existing not accept new requests or perform new operations on existing
requests (in the case in which a request was partially executed requests (in the case in which a request was partially executed
before server restart). before server restart).
15.1.11.6. NFS4ERR_CONN_NOT_BOUND_TO_SESSION (Error Code 10055) 15.1.11.6. NFS4ERR_CONN_NOT_BOUND_TO_SESSION (Error Code 10055)
A Sequence operation was sent on a connection that has not been A Sequence operation was sent on a connection that has not been
associated with the specified session, where the client specified associated with the specified session, where the client specified
that connection association was to be enforced with SP4_MACH_CRED or that connection association was to be enforced with SP4_MACH_CRED or
SP4_SSV state protection. SP4_SSV state protection.
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An attempt was made to destroy a session when the session cannot be An attempt was made to destroy a session when the session cannot be
destroyed because the server has callback requests outstanding. destroyed because the server has callback requests outstanding.
15.1.12.2. NFS4ERR_BAD_SESSION_DIGEST (Error Code 10051) 15.1.12.2. NFS4ERR_BAD_SESSION_DIGEST (Error Code 10051)
The digest used in a SET_SSV request is not valid. The digest used in a SET_SSV request is not valid.
15.1.13. Client Management Errors 15.1.13. Client Management Errors
This sections deals with errors associated with requests used to This section deals with errors associated with requests used to
create and manage client IDs. create and manage client IDs.
15.1.13.1. NFS4ERR_CLIENTID_BUSY (Error Code 10074) 15.1.13.1. NFS4ERR_CLIENTID_BUSY (Error Code 10074)
The DESTROY_CLIENTID operation has found there are sessions and/or The DESTROY_CLIENTID operation has found there are sessions and/or
unexpired state associated with the client ID to be destroyed. unexpired state associated with the client ID to be destroyed.
15.1.13.2. NFS4ERR_CLID_INUSE (Error Code 10017) 15.1.13.2. NFS4ERR_CLID_INUSE (Error Code 10017)
While processing an EXCHANGE_ID operation, the server was presented While processing an EXCHANGE_ID operation, the server was presented
with a co_ownerid field matches an existing client with valid leased with a co_ownerid field that matches an existing client with valid
state but the principal sending the EXCHANGE_ID operation is leased state, but the principal sending the EXCHANGE_ID operation
different than that establishing the existing client. This indicates differs from the principal that established the existing client.
a (most likely due to chance) collision between clients. The client This indicates a collision (most likely due to chance) between
should recover by changing the co_ownerid and re-sending EXCHANGE_ID clients. The client should recover by changing the co_ownerid and
(but not with the same slot ID and sequence ID; one or both MUST be re-sending EXCHANGE_ID (but not with the same slot ID and sequence
different on the re-send). ID; one or both MUST be different on the re-send).
15.1.13.3. NFS4ERR_ENCR_ALG_UNSUPP (Error Code 10079) 15.1.13.3. NFS4ERR_ENCR_ALG_UNSUPP (Error Code 10079)
An EXCHANGE_ID was sent which specified state protection via SSV, and An EXCHANGE_ID was sent that specified state protection via SSV, and
where the set of encryption algorithms presented by the client did where the set of encryption algorithms presented by the client did
not include any supported by the server. not include any supported by the server.
15.1.13.4. NFS4ERR_HASH_ALG_UNSUPP (Error Code 10072) 15.1.13.4. NFS4ERR_HASH_ALG_UNSUPP (Error Code 10072)
An EXCHANGE_ID was sent which specified state protection via SSV, and An EXCHANGE_ID was sent that specified state protection via SSV, and
where the set of hashing algorithms presented by the client did not where the set of hashing algorithms presented by the client did not
include any supported by the server. include any supported by the server.
15.1.13.5. NFS4ERR_STALE_CLIENTID (Error Code 10022) 15.1.13.5. NFS4ERR_STALE_CLIENTID (Error Code 10022)
A client ID not recognized by the server was passed to an operation. A client ID not recognized by the server was passed to an operation.
Note that unlike the case of NFSv4.0, client IDs are not passed Note that unlike the case of NFSv4.0, client IDs are not passed
explicitly to the server in ordinary locking operations and cannot explicitly to the server in ordinary locking operations and cannot
result in this error. Instead, when there is a server restart, it is result in this error. Instead, when there is a server restart, it is
first manifested through an error on the associated session and the first manifested through an error on the associated session, and the
staleness of the client ID is detected when trying to associate a staleness of the client ID is detected when trying to associate a
client ID with a new session. client ID with a new session.
15.1.14. Delegation Errors 15.1.14. Delegation Errors
This section deals with errors associated with requesting and This section deals with errors associated with requesting and
returning delegations. returning delegations.
15.1.14.1. NFS4ERR_DELEG_ALREADY_WANTED (Error Code 10056) 15.1.14.1. NFS4ERR_DELEG_ALREADY_WANTED (Error Code 10056)
The client has requested a delegation when it had already registered The client has requested a delegation when it had already registered
that it wants that same delegation. that it wants that same delegation.
15.1.14.2. NFS4ERR_DIRDELEG_UNAVAIL (Error Code 10084) 15.1.14.2. NFS4ERR_DIRDELEG_UNAVAIL (Error Code 10084)
This error is returned when the server is unable or unwilling to This error is returned when the server is unable or unwilling to
provide a requested directory delegation. provide a requested directory delegation.
15.1.14.3. NFS4ERR_RECALLCONFLICT (Error Code 10061) 15.1.14.3. NFS4ERR_RECALLCONFLICT (Error Code 10061)
A recallable object (i.e. a layout or delegation) is unavailable due A recallable object (i.e., a layout or delegation) is unavailable due
to a conflicting recall operation for that object that is currently to a conflicting recall operation that is currently in progress for
in progress. that object.
15.1.14.4. NFS4ERR_REJECT_DELEG (Error Code 10085) 15.1.14.4. NFS4ERR_REJECT_DELEG (Error Code 10085)
The callback operation invoked to deal with a new delegation has The callback operation invoked to deal with a new delegation has
rejected it. rejected it.
15.1.15. Attribute Handling Errors 15.1.15. Attribute Handling Errors
This section deals with errors specific to attribute handling within This section deals with errors specific to attribute handling within
NFSv4. NFSv4.
15.1.15.1. NFS4ERR_ATTRNOTSUPP (Error Code 10032) 15.1.15.1. NFS4ERR_ATTRNOTSUPP (Error Code 10032)
An attribute specified is not supported by the server. This error An attribute specified is not supported by the server. This error
MUST NOT be returned by the GETATTR operation. MUST NOT be returned by the GETATTR operation.
15.1.15.2. NFS4ERR_BADOWNER (Error Code 10039) 15.1.15.2. NFS4ERR_BADOWNER (Error Code 10039)
Returned when an owner or owner_group attribute value or the who This error is returned when an owner or owner_group attribute value
field of an ace within an ACL attribute value cannot be translated to or the who field of an ACE within an ACL attribute value cannot be
a local representation. translated to a local representation.
15.1.15.3. NFS4ERR_NOT_SAME (Error Code 10027) 15.1.15.3. NFS4ERR_NOT_SAME (Error Code 10027)
This error is returned by the VERIFY operation to signify that the This error is returned by the VERIFY operation to signify that the
attributes compared were not the same as those provided in the attributes compared were not the same as those provided in the
client's request. client's request.
15.1.15.4. NFS4ERR_SAME (Error Code 10009) 15.1.15.4. NFS4ERR_SAME (Error Code 10009)
This error is returned by the NVERIFY operation to signify that the This error is returned by the NVERIFY operation to signify that the
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These errors MUST NOT be generated by any NFSv4.1 operation. This These errors MUST NOT be generated by any NFSv4.1 operation. This
can be for a number of reasons. can be for a number of reasons.
o The function provided by the error has been superseded by one of o The function provided by the error has been superseded by one of
the status bits returned by the SEQUENCE operation. the status bits returned by the SEQUENCE operation.
o The new session structure and associated change in locking have o The new session structure and associated change in locking have
made the error unnecessary. made the error unnecessary.
o There has been a restructuring of some errors for NFSv4.1 which o There has been a restructuring of some errors for NFSv4.1 that
resulted in the elimination of certain of the errors. resulted in the elimination of certain errors.
15.1.16.1. NFS4ERR_BAD_SEQID (Error Code 10026) 15.1.16.1. NFS4ERR_BAD_SEQID (Error Code 10026)
The sequence number (seqid) in a locking request is neither the next The sequence number (seqid) in a locking request is neither the next
expected number or the last number processed. These seqids are expected number or the last number processed. These seqids are
ignored in NFSv4.1. ignored in NFSv4.1.
15.1.16.2. NFS4ERR_LEASE_MOVED (Error Code 10031) 15.1.16.2. NFS4ERR_LEASE_MOVED (Error Code 10031)
A lease being renewed is associated with a file system that has been A lease being renewed is associated with a file system that has been
migrated to a new server. The error has been superseded by the migrated to a new server. The error has been superseded by the
SEQ4_STATUS_LEASE_MOVED status bit (see Section 18.46). SEQ4_STATUS_LEASE_MOVED status bit (see Section 18.46).
15.1.16.3. NFS4ERR_NXIO (Error Code 5) 15.1.16.3. NFS4ERR_NXIO (Error Code 5)
I/O error. No such device or address. This error is for errors I/O error. No such device or address. This error is for errors
involving block and character device access, but NFSv4.1 is not a involving block and character device access, but because NFSv4.1 is
device access protocol. not a device-access protocol, this error is not applicable.
15.1.16.4. NFS4ERR_RESTOREFH (Error Code 10030) 15.1.16.4. NFS4ERR_RESTOREFH (Error Code 10030)
The RESTOREFH operation does not have a saved filehandle (identified The RESTOREFH operation does not have a saved filehandle (identified
by SAVEFH) to operate upon. In NFSv4.1, this error has been by SAVEFH) to operate upon. In NFSv4.1, this error has been
superseded by NFS4ERR_NOFILEHANDLE. superseded by NFS4ERR_NOFILEHANDLE.
15.1.16.5. NFS4ERR_STALE_STATEID (Error Code 10023) 15.1.16.5. NFS4ERR_STALE_STATEID (Error Code 10023)
A stateid generated by an earlier server instance was used. This A stateid generated by an earlier server instance was used. This
error is moot in NFSv4.1 because all operations that take a stateid error is moot in NFSv4.1 because all operations that take a stateid
MUST be preceded by the SEQUENCE operation, and the earlier server MUST be preceded by the SEQUENCE operation, and the earlier server
instance is detected by the session infrastructure that supports instance is detected by the session infrastructure that supports
SEQUENCE. SEQUENCE.
15.2. Operations and their valid errors 15.2. Operations and Their Valid Errors
This section contains a table which gives the valid error returns for This section contains a table that gives the valid error returns for
each protocol operation. The error code NFS4_OK (indicating no each protocol operation. The error code NFS4_OK (indicating no
error) is not listed but should be understood to be returnable by all error) is not listed but should be understood to be returnable by all
operations with two important exceptions: operations with two important exceptions:
o The operations which MUST NOT be implemented: OPEN_CONFIRM, o The operations that MUST NOT be implemented: OPEN_CONFIRM,
RELEASE_LOCKOWNER, RENEW, SETCLIENTID, and SETCLIENTID_CONFIRM. RELEASE_LOCKOWNER, RENEW, SETCLIENTID, and SETCLIENTID_CONFIRM.
o The invalid operation: ILLEGAL. o The invalid operation: ILLEGAL.
Valid error returns for each protocol operation Valid Error Returns for Each Protocol Operation
+----------------------+--------------------------------------------+ +----------------------+--------------------------------------------+
| Operation | Errors | | Operation | Errors |
+----------------------+--------------------------------------------+ +----------------------+--------------------------------------------+
| ACCESS | NFS4ERR_ACCESS, NFS4ERR_BADXDR, | | ACCESS | NFS4ERR_ACCESS, NFS4ERR_BADXDR, |
| | NFS4ERR_DEADSESSION, NFS4ERR_DELAY, | | | NFS4ERR_DEADSESSION, NFS4ERR_DELAY, |
| | NFS4ERR_FHEXPIRED, NFS4ERR_INVAL, | | | NFS4ERR_FHEXPIRED, NFS4ERR_INVAL, |
| | NFS4ERR_IO, NFS4ERR_MOVED, | | | NFS4ERR_IO, NFS4ERR_MOVED, |
| | NFS4ERR_NOFILEHANDLE, | | | NFS4ERR_NOFILEHANDLE, |
| | NFS4ERR_OP_NOT_IN_SESSION, | | | NFS4ERR_OP_NOT_IN_SESSION, |
skipping to change at page 375, line 28 skipping to change at page 375, line 45
| | NFS4ERR_REP_TOO_BIG_TO_CACHE, | | | NFS4ERR_REP_TOO_BIG_TO_CACHE, |
| | NFS4ERR_REQ_TOO_BIG, | | | NFS4ERR_REQ_TOO_BIG, |
| | NFS4ERR_RETRY_UNCACHED_REP, NFS4ERR_ROFS, | | | NFS4ERR_RETRY_UNCACHED_REP, NFS4ERR_ROFS, |
| | NFS4ERR_SERVERFAULT, NFS4ERR_STALE, | | | NFS4ERR_SERVERFAULT, NFS4ERR_STALE, |
| | NFS4ERR_SYMLINK, NFS4ERR_TOO_MANY_OPS, | | | NFS4ERR_SYMLINK, NFS4ERR_TOO_MANY_OPS, |
| | NFS4ERR_WRONG_TYPE | | | NFS4ERR_WRONG_TYPE |
+----------------------+--------------------------------------------+ +----------------------+--------------------------------------------+
Table 6 Table 6
15.3. Callback operations and their valid errors 15.3. Callback Operations and Their Valid Errors
This section contains a table which gives the valid error returns for This section contains a table that gives the valid error returns for
each callback operation. The error code NFS4_OK (indicating no each callback operation. The error code NFS4_OK (indicating no
error) is not listed but should be understood to be returnable by all error) is not listed but should be understood to be returnable by all
callback operations with the exception of CB_ILLEGAL. callback operations with the exception of CB_ILLEGAL.
Valid error returns for each protocol callback operation Valid Error Returns for Each Protocol Callback Operation
+-------------------------+-----------------------------------------+ +-------------------------+-----------------------------------------+
| Callback Operation | Errors | | Callback Operation | Errors |
+-------------------------+-----------------------------------------+ +-------------------------+-----------------------------------------+
| CB_GETATTR | NFS4ERR_BADHANDLE, NFS4ERR_BADXDR, | | CB_GETATTR | NFS4ERR_BADHANDLE, NFS4ERR_BADXDR, |
| | NFS4ERR_DELAY, NFS4ERR_INVAL, | | | NFS4ERR_DELAY, NFS4ERR_INVAL, |
| | NFS4ERR_OP_NOT_IN_SESSION, | | | NFS4ERR_OP_NOT_IN_SESSION, |
| | NFS4ERR_REP_TOO_BIG, | | | NFS4ERR_REP_TOO_BIG, |
| | NFS4ERR_REP_TOO_BIG_TO_CACHE, | | | NFS4ERR_REP_TOO_BIG_TO_CACHE, |
| | NFS4ERR_REQ_TOO_BIG, | | | NFS4ERR_REQ_TOO_BIG, |
skipping to change at page 378, line 36 skipping to change at page 378, line 36
| | NFS4ERR_REP_TOO_BIG, | | | NFS4ERR_REP_TOO_BIG, |
| | NFS4ERR_REP_TOO_BIG_TO_CACHE, | | | NFS4ERR_REP_TOO_BIG_TO_CACHE, |
| | NFS4ERR_REQ_TOO_BIG, | | | NFS4ERR_REQ_TOO_BIG, |
| | NFS4ERR_RETRY_UNCACHED_REP, | | | NFS4ERR_RETRY_UNCACHED_REP, |
| | NFS4ERR_SERVERFAULT, | | | NFS4ERR_SERVERFAULT, |
| | NFS4ERR_TOO_MANY_OPS | | | NFS4ERR_TOO_MANY_OPS |
+-------------------------+-----------------------------------------+ +-------------------------+-----------------------------------------+
Table 7 Table 7
15.4. Errors and the operations that use them 15.4. Errors and the Operations That Use Them
+-----------------------------------+-------------------------------+ +-----------------------------------+-------------------------------+
| Error | Operations | | Error | Operations |
+-----------------------------------+-------------------------------+ +-----------------------------------+-------------------------------+
| NFS4ERR_ACCESS | ACCESS, COMMIT, CREATE, | | NFS4ERR_ACCESS | ACCESS, COMMIT, CREATE, |
| | GETATTR, GET_DIR_DELEGATION, | | | GETATTR, GET_DIR_DELEGATION, |
| | LAYOUTCOMMIT, LAYOUTGET, | | | LAYOUTCOMMIT, LAYOUTGET, |
| | LINK, LOCK, LOCKT, LOCKU, | | | LINK, LOCK, LOCKT, LOCKU, |
| | LOOKUP, LOOKUPP, NVERIFY, | | | LOOKUP, LOOKUPP, NVERIFY, |
| | OPEN, OPENATTR, READ, | | | OPEN, OPENATTR, READ, |
skipping to change at page 394, line 44 skipping to change at page 394, line 44
void; void;
16.1.2. RESULTS 16.1.2. RESULTS
void; void;
16.1.3. DESCRIPTION 16.1.3. DESCRIPTION
This is the standard NULL procedure with the standard void argument This is the standard NULL procedure with the standard void argument
and void response. This procedure has no functionality associated and void response. This procedure has no functionality associated
with it. Because of this it is sometimes used to measure the with it. Because of this, it is sometimes used to measure the
overhead of processing a service request. Therefore, the server overhead of processing a service request. Therefore, the server
SHOULD ensure that no unnecessary work is done in servicing this SHOULD ensure that no unnecessary work is done in servicing this
procedure. procedure.
16.1.4. ERRORS 16.1.4. ERRORS
None. None.
16.2. Procedure 1: COMPOUND - Compound Operations 16.2. Procedure 1: COMPOUND - Compound Operations
skipping to change at page 401, line 24 skipping to change at page 401, line 24
}; };
struct COMPOUND4res { struct COMPOUND4res {
nfsstat4 status; nfsstat4 status;
utf8str_cs tag; utf8str_cs tag;
nfs_resop4 resarray<>; nfs_resop4 resarray<>;
}; };
16.2.3. DESCRIPTION 16.2.3. DESCRIPTION
The COMPOUND procedure is used to combine one or more of the NFS The COMPOUND procedure is used to combine one or more NFSv4
operations into a single RPC request. The NFS RPC program has two operations into a single RPC request. The server interprets each of
main procedures: NULL and COMPOUND. All other operations use the the operations in turn. If an operation is executed by the server
COMPOUND procedure as a wrapper. and the status of that operation is NFS4_OK, then the next operation
in the COMPOUND procedure is executed. The server continues this
The COMPOUND procedure is used to combine individual operations into process until there are no more operations to be executed or until
a single RPC request. The server interprets each of the operations one of the operations has a status value other than NFS4_OK.
in turn. If an operation is executed by the server and the status of
that operation is NFS4_OK, then the next operation in the COMPOUND
procedure is executed. The server continues this process until there
are no more operations to be executed or one of the operations has a
status value other than NFS4_OK.
In the processing of the COMPOUND procedure, the server may find that In the processing of the COMPOUND procedure, the server may find that
it does not have the available resources to execute any or all of the it does not have the available resources to execute any or all of the
operations within the COMPOUND sequence. See Section 2.10.6.4 for a operations within the COMPOUND sequence. See Section 2.10.6.4 for a
more detailed discussion. more detailed discussion.
The server will generally choose between two methods of decoding the The server will generally choose between two methods of decoding the
client's request. The first would be the traditional one pass XDR client's request. The first would be the traditional one-pass XDR
decode. If there is an XDR decoding error in this case, the RPC XDR decode. If there is an XDR decoding error in this case, the RPC XDR
decode error would be returned. The second method would be to make decode error would be returned. The second method would be to make
an initial pass to decode the basic COMPOUND request and then to XDR an initial pass to decode the basic COMPOUND request and then to XDR
decode the individual operations; the most interesting is the decode decode the individual operations; the most interesting is the decode
of attributes. In this case, the server may encounter an XDR decode of attributes. In this case, the server may encounter an XDR decode
error during the second pass. In this case, the server would return error during the second pass. If it does, the server would return
the error NFS4ERR_BADXDR to signify the decode error. the error NFS4ERR_BADXDR to signify the decode error.
The COMPOUND arguments contain a "minorversion" field. For NFSv4.1, The COMPOUND arguments contain a "minorversion" field. For NFSv4.1,
the value for this field is 1. If the server receives a COMPOUND the value for this field is 1. If the server receives a COMPOUND
procedure with a minorversion field value that it does not support, procedure with a minorversion field value that it does not support,
the server MUST return an error of NFS4ERR_MINOR_VERS_MISMATCH and a the server MUST return an error of NFS4ERR_MINOR_VERS_MISMATCH and a
zero length resultdata array. zero-length resultdata array.
Contained within the COMPOUND results is a "status" field. If the Contained within the COMPOUND results is a "status" field. If the
results array length is non-zero, this status must be equivalent to results array length is non-zero, this status must be equivalent to
the status of the last operation that was executed within the the status of the last operation that was executed within the
COMPOUND procedure. Therefore, if an operation incurred an error COMPOUND procedure. Therefore, if an operation incurred an error
then the "status" value will be the same error value as is being then the "status" value will be the same error value as is being
returned for the operation that failed. returned for the operation that failed.
Note that operations, 0 (zero) and 1 (one) are not defined for the Note that operations zero and one are not defined for the COMPOUND
COMPOUND procedure. Operation 2 is not defined and is reserved for procedure. Operation 2 is not defined and is reserved for future
future definition and use with minor versioning. If the server definition and use with minor versioning. If the server receives an
receives a operation array that contains operation 2 and the operation array that contains operation 2 and the minorversion field
minorversion field has a value of 0 (zero), an error of has a value of zero, an error of NFS4ERR_OP_ILLEGAL, as described in
NFS4ERR_OP_ILLEGAL, as described in the next paragraph, is returned the next paragraph, is returned to the client. If an operation array
to the client. If an operation array contains an operation 2 and the contains an operation 2 and the minorversion field is non-zero and
minorversion field is non-zero and the server does not support the the server does not support the minor version, the server returns an
minor version, the server returns an error of error of NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the
NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the
NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other
errors. errors.
It is possible that the server receives a request that contains an It is possible that the server receives a request that contains an
operation that is less than the first legal operation (OP_ACCESS) or operation that is less than the first legal operation (OP_ACCESS) or
greater than the last legal operation (OP_RELEASE_LOCKOWNER). In greater than the last legal operation (OP_RELEASE_LOCKOWNER). In
this case, the server's response will encode the opcode OP_ILLEGAL this case, the server's response will encode the opcode OP_ILLEGAL
rather than the illegal opcode of the request. The status field in rather than the illegal opcode of the request. The status field in
the ILLEGAL return results will set to NFS4ERR_OP_ILLEGAL. The the ILLEGAL return results will be set to NFS4ERR_OP_ILLEGAL. The
COMPOUND procedure's return results will also be NFS4ERR_OP_ILLEGAL. COMPOUND procedure's return results will also be NFS4ERR_OP_ILLEGAL.
The definition of the "tag" in the request is left to the The definition of the "tag" in the request is left to the
implementor. It may be used to summarize the content of the compound implementor. It may be used to summarize the content of the Compound
request for the benefit of packet sniffers and engineers debugging request for the benefit of packet-sniffers and engineers debugging
implementations. However, the value of "tag" in the response SHOULD implementations. However, the value of "tag" in the response SHOULD
be the same value as provided in the request. This applies to the be the same value as provided in the request. This applies to the
tag field of the CB_COMPOUND procedure as well. tag field of the CB_COMPOUND procedure as well.
16.2.3.1. Current Filehandle and Stateid 16.2.3.1. Current Filehandle and Stateid
The COMPOUND procedure offers a simple environment for the execution The COMPOUND procedure offers a simple environment for the execution
of the operations specified by the client. The first two relate to of the operations specified by the client. The first two relate to
the filehandle while the second two relate to the current stateid. the filehandle while the second two relate to the current stateid.
16.2.3.1.1. Current Filehandle 16.2.3.1.1. Current Filehandle
The current and saved filehandle are used throughout the protocol. The current and saved filehandles are used throughout the protocol.
Most operations implicitly use the current filehandle as a argument Most operations implicitly use the current filehandle as an argument,
and many set the current filehandle as part of the results. The and many set the current filehandle as part of the results. The
combination of client specified sequences of operations and current combination of client-specified sequences of operations and current
and saved filehandle arguments and results allows for greater and saved filehandle arguments and results allows for greater
protocol flexibility. The best or easiest example of current protocol flexibility. The best or easiest example of current
filehandle usage is a sequence like the following: filehandle usage is a sequence like the following:
PUTFH fh1 {fh1} PUTFH fh1 {fh1}
LOOKUP "compA" {fh2} LOOKUP "compA" {fh2}
GETATTR {fh2} GETATTR {fh2}
LOOKUP "compB" {fh3} LOOKUP "compB" {fh3}
GETATTR {fh3} GETATTR {fh3}
LOOKUP "compC" {fh4} LOOKUP "compC" {fh4}
skipping to change at page 403, line 41 skipping to change at page 403, line 32
The PUTROOTFH (Section 18.21) and PUTPUBFH (Section 18.20) operations The PUTROOTFH (Section 18.21) and PUTPUBFH (Section 18.20) operations
also set the current filehandle. The above example would replace also set the current filehandle. The above example would replace
"PUTFH fh1" with PUTROOTFH or PUTPUBFH with no filehandle argument in "PUTFH fh1" with PUTROOTFH or PUTPUBFH with no filehandle argument in
order to achieve the same effect (on the assumption that "compA" is order to achieve the same effect (on the assumption that "compA" is
directly below the root of the namespace). directly below the root of the namespace).
Along with the current filehandle, there is a saved filehandle. Along with the current filehandle, there is a saved filehandle.
While the current filehandle is set as the result of operations like While the current filehandle is set as the result of operations like
LOOKUP, the saved filehandle must be set directly with the use of the LOOKUP, the saved filehandle must be set directly with the use of the
SAVEFH operation. The SAVEFH operations copies the current SAVEFH operation. The SAVEFH operation copies the current filehandle
filehandle value to the saved value. The saved filehandle value is value to the saved value. The saved filehandle value is used in
used in combination with the current filehandle value for the LINK combination with the current filehandle value for the LINK and RENAME
and RENAME operations. The RESTOREFH operation will copy the saved operations. The RESTOREFH operation will copy the saved filehandle
filehandle value to the current filehandle value; as a result, the value to the current filehandle value; as a result, the saved
saved filehandle value may be used a sort of "scratch" area for the filehandle value may be used a sort of "scratch" area for the
client's series of operations. client's series of operations.
16.2.3.1.2. Current Stateid 16.2.3.1.2. Current Stateid
With NFSv4.1, additions of a current stateid and a saved stateid have With NFSv4.1, additions of a current stateid and a saved stateid have
been made to the COMPOUND processing environment; this allows for the been made to the COMPOUND processing environment; this allows for the
passing of stateids between operations. There are no changes to the passing of stateids between operations. There are no changes to the
syntax of the protocol, only changes to the semantics of a few syntax of the protocol, only changes to the semantics of a few
operations. operations.
A "current stateid" is the stateid that is associated with the A "current stateid" is the stateid that is associated with the
current filehandle. The current stateid may only be changed by an current filehandle. The current stateid may only be changed by an
operation that modifies the current filehandle or returns a stateid. operation that modifies the current filehandle or returns a stateid.
If an operation returns a stateid it MUST set the current stateid to
If an operation returns a stateid, it MUST set the current stateid to
the returned value. If an operation sets the current filehandle but the returned value. If an operation sets the current filehandle but
does not return a stateid, the current stateid MUST be set to the does not return a stateid, the current stateid MUST be set to the
all-zeros special stateid, i.e. (seqid, other) = (0, 0). If an all-zeros special stateid, i.e., (seqid, other) = (0, 0). If an
operation uses a stateid as an argument but does not return a operation uses a stateid as an argument but does not return a
stateid, the current stateid MUST NOT be changed. E.g., PUTFH, stateid, the current stateid MUST NOT be changed. For example,
PUTROOTFH, and PUTPUBFH will change the current server state from PUTFH, PUTROOTFH, and PUTPUBFH will change the current server state
{ocfh, (osid)} to {cfh, (0, 0)} while LOCK will change the current from {ocfh, (osid)} to {cfh, (0, 0)}, while LOCK will change the
state from {cfh, (osid} to {cfh, (nsid)}. Operations like LOOKUP current state from {cfh, (osid} to {cfh, (nsid)}. Operations like
that transform a current filehandle and component name into a new LOOKUP that transform a current filehandle and component name into a
current filehandle will also change the current stateid to {0, 0}. new current filehandle will also change the current state to {0, 0}.
The SAVEFH and RESTOREFH operations will save and restore both the The SAVEFH and RESTOREFH operations will save and restore both the
current filehandle and the current stateid as a set. current filehandle and the current stateid as a set.
The following example is the common case of a simple READ operation The following example is the common case of a simple READ operation
with a supplied stateid showing that the PUTFH initializes the with a normal stateid showing that the PUTFH initializes the current
current stateid to (0, 0). The subsequent READ with stateid (sid1) stateid to (0, 0). The subsequent READ with stateid (sid1) leaves
leaves the current stateid unchanged, but does evaluate the the current stateid unchanged.
operation.
PUTFH fh1 - -> {fh1, (0, 0)} PUTFH fh1 - -> {fh1, (0, 0)}
READ (sid1), 0, 1024 {fh1, (0, 0)} -> {fh1, (0, 0)} READ (sid1), 0, 1024 {fh1, (0, 0)} -> {fh1, (0, 0)}
Figure 3 Figure 3
This next example performs an OPEN with the root filehandle and as a This next example performs an OPEN with the root filehandle and, as a
result generates stateid (sid1). The next operation specifies the result, generates stateid (sid1). The next operation specifies the
READ with the argument stateid set such that (seqid, other) are equal READ with the argument stateid set such that (seqid, other) are equal
to (1, 0), but the current stateid set by the previous operation is to (1, 0), but the current stateid set by the previous operation is
actually used when the operation is evaluated. This allows correct actually used when the operation is evaluated. This allows correct
interaction with any existing, potentially conflicting, locks. interaction with any existing, potentially conflicting, locks.
PUTROOTFH - -> {fh1, (0, 0)} PUTROOTFH - -> {fh1, (0, 0)}
OPEN "compA" {fh1, (0, 0)} -> {fh2, (sid1)} OPEN "compA" {fh1, (0, 0)} -> {fh2, (sid1)}
READ (1, 0), 0, 1024 {fh2, (sid1)} -> {fh2, (sid1)} READ (1, 0), 0, 1024 {fh2, (sid1)} -> {fh2, (sid1)}
CLOSE (1, 0) {fh2, (sid1)} -> {fh2, (sid2)} CLOSE (1, 0) {fh2, (sid1)} -> {fh2, (sid2)}
Figure 4 Figure 4
This next example is similar to the second in how it passes the This next example is similar to the second in how it passes the
stateid sid2 generated by the LOCK operation to the next READ stateid sid2 generated by the LOCK operation to the next READ
operation. This allows the client to explicitly surround a single operation. This allows the client to explicitly surround a single
I/O operation with a lock and its appropriate stateid to guarantee I/O operation with a lock and its appropriate stateid to guarantee
correctness with other client locks. The example also shows how correctness with other client locks. The example also shows how
SAVEFH and RESTOREFH can save and later re-use a filehandle and SAVEFH and RESTOREFH can save and later reuse a filehandle and
stateid, passing them as the current filehandle and stateid to a READ stateid, passing them as the current filehandle and stateid to a READ
operation. operation.
PUTFH fh1 - -> {fh1, (0, 0)} PUTFH fh1 - -> {fh1, (0, 0)}
LOCK 0, 1024, (sid1) {fh1, (sid1)} -> {fh1, (sid2)} LOCK 0, 1024, (sid1) {fh1, (sid1)} -> {fh1, (sid2)}
READ (1, 0), 0, 1024 {fh1, (sid2)} -> {fh1, (sid2)} READ (1, 0), 0, 1024 {fh1, (sid2)} -> {fh1, (sid2)}
LOCKU 0, 1024, (1, 0) {fh1, (sid2)} -> {fh1, (sid3)} LOCKU 0, 1024, (1, 0) {fh1, (sid2)} -> {fh1, (sid3)}
SAVEFH {fh1, (sid3)} -> {fh1, (sid3)} SAVEFH {fh1, (sid3)} -> {fh1, (sid3)}
PUTFH fh2 {fh1, (sid3)} -> {fh2, (0, 0)} PUTFH fh2 {fh1, (sid3)} -> {fh2, (0, 0)}
WRITE (1, 0), 0, 1024 {fh2, (0, 0)} -> {fh2, (0, 0)} WRITE (1, 0), 0, 1024 {fh2, (0, 0)} -> {fh2, (0, 0)}
RESTOREFH {fh2, (0, 0)} -> {fh1, (sid3)} RESTOREFH {fh2, (0, 0)} -> {fh1, (sid3)}
READ (1, 0), 1024, 1024 {fh1, (sid3)} -> {fh1, (sid3)} READ (1, 0), 1024, 1024 {fh1, (sid3)} -> {fh1, (sid3)}
Figure 5 Figure 5
The final example shows a disallowed use of the current stateid. The The final example shows a disallowed use of the current stateid. The
client is attempting to implicitly pass anonymous special stateid, client is attempting to implicitly pass an anonymous special stateid,
(0,0) to the READ operation. The server MUST return (0,0), to the READ operation. The server MUST return
NFS4ERR_BAD_STATEID in the reply to the READ operation. NFS4ERR_BAD_STATEID in the reply to the READ operation.
PUTFH fh1 - -> {fh1, (0, 0)} PUTFH fh1 - -> {fh1, (0, 0)}
READ (1, 0), 0, 1024 {fh1, (0, 0)} -> NFS4ERR_BAD_STATEID READ (1, 0), 0, 1024 {fh1, (0, 0)} -> NFS4ERR_BAD_STATEID
Figure 6 Figure 6
16.2.4. ERRORS 16.2.4. ERRORS
COMPOUND will of course return every error that each operation on the COMPOUND will of course return every error that each operation on the
fore channel can return (see Table 6). However if COMPOUND returns fore channel can return (see Table 6). However, if COMPOUND returns
zero operations, obviously the error returned by COMPOUND has nothing zero operations, obviously the error returned by COMPOUND has nothing
to do with an error returned by an operation. The list of errors to do with an error returned by an operation. The list of errors
COMPOUND will return if it processes zero operations include: COMPOUND will return if it processes zero operations include:
COMPOUND error returns COMPOUND Error Returns
+------------------------------+------------------------------------+ +------------------------------+------------------------------------+
| Error | Notes | | Error | Notes |
+------------------------------+------------------------------------+ +------------------------------+------------------------------------+
| NFS4ERR_BADCHAR | The tag argument has a character | | NFS4ERR_BADCHAR | The tag argument has a character |
| | the replier does not support. | | | the replier does not support. |
| NFS4ERR_BADXDR | | | NFS4ERR_BADXDR | |
| NFS4ERR_DELAY | | | NFS4ERR_DELAY | |
| NFS4ERR_INVAL | The tag argument is not in UTF-8 | | NFS4ERR_INVAL | The tag argument is not in UTF-8 |
| | encoding. | | | encoding. |
skipping to change at page 406, line 29 skipping to change at page 406, line 29
| NFS4ERR_REP_TOO_BIG | | | NFS4ERR_REP_TOO_BIG | |
| NFS4ERR_REP_TOO_BIG_TO_CACHE | | | NFS4ERR_REP_TOO_BIG_TO_CACHE | |
| NFS4ERR_REQ_TOO_BIG | | | NFS4ERR_REQ_TOO_BIG | |
+------------------------------+------------------------------------+ +------------------------------+------------------------------------+
Table 9 Table 9
17. Operations: REQUIRED, RECOMMENDED, or OPTIONAL 17. Operations: REQUIRED, RECOMMENDED, or OPTIONAL
The following tables summarize the operations of the NFSv4.1 protocol The following tables summarize the operations of the NFSv4.1 protocol
and the corresponding designation of REQUIRED, RECOMMENDED, OPTIONAL and the corresponding designation of REQUIRED, RECOMMENDED, and
to implement or MUST NOT implement. The designation of MUST NOT OPTIONAL to implement or MUST NOT implement. The designation of MUST
implement is reserved for those operations that were defined in NOT implement is reserved for those operations that were defined in
NFSv4.0 and MUST NOT be implemented in NFSv4.1. NFSv4.0 and MUST NOT be implemented in NFSv4.1.
For the most part, the REQUIRED, RECOMMENDED, or OPTIONAL designation For the most part, the REQUIRED, RECOMMENDED, or OPTIONAL designation
for operations sent by the client is for the server implementation. for operations sent by the client is for the server implementation.
The client is generally required to implement the operations needed The client is generally required to implement the operations needed
for the operating environment for which it serves. For example, a for the operating environment for which it serves. For example, a
read-only NFSv4.1 client would have no need to implement the WRITE read-only NFSv4.1 client would have no need to implement the WRITE
operation and is not required to do so. operation and is not required to do so.
The REQUIRED or OPTIONAL designation for callback operations sent by The REQUIRED or OPTIONAL designation for callback operations sent by
skipping to change at page 407, line 19 skipping to change at page 407, line 18
REQ REQUIRED to implement REQ REQUIRED to implement
REC RECOMMEND to implement REC RECOMMEND to implement
OPT OPTIONAL to implement OPT OPTIONAL to implement
MNI MUST NOT implement MNI MUST NOT implement
For the NFSv4.1 features that are OPTIONAL, the operations that For the NFSv4.1 features that are OPTIONAL, the operations that
support those features are OPTIONAL and the server would return support those features are OPTIONAL, and the server would return
NFS4ERR_NOTSUPP in response to the client's use of those operations. NFS4ERR_NOTSUPP in response to the client's use of those operations.
If an OPTIONAL feature is supported, it is possible that a set of If an OPTIONAL feature is supported, it is possible that a set of
operations related to the feature become REQUIRED to implement. The operations related to the feature become REQUIRED to implement. The
third column of the table designates the feature(s) and if the third column of the table designates the feature(s) and if the
operation is REQUIRED or OPTIONAL in the presence of support for the operation is REQUIRED or OPTIONAL in the presence of support for the
feature. feature.
The OPTIONAL features identified and their abbreviations are as The OPTIONAL features identified and their abbreviations are as
follows: follows:
skipping to change at page 408, line 44 skipping to change at page 408, line 44
| READDIR | REQ | | Section 18.23 | | READDIR | REQ | | Section 18.23 |
| READLINK | OPT | | Section 18.24 | | READLINK | OPT | | Section 18.24 |
| RECLAIM_COMPLETE | REQ | | Section 18.51 | | RECLAIM_COMPLETE | REQ | | Section 18.51 |
| RELEASE_LOCKOWNER | MNI | | N/A | | RELEASE_LOCKOWNER | MNI | | N/A |
| REMOVE | REQ | | Section 18.25 | | REMOVE | REQ | | Section 18.25 |
| RENAME | REQ | | Section 18.26 | | RENAME | REQ | | Section 18.26 |
| RENEW | MNI | | N/A | | RENEW | MNI | | N/A |
| RESTOREFH | REQ | | Section 18.27 | | RESTOREFH | REQ | | Section 18.27 |
| SAVEFH | REQ | | Section 18.28 | | SAVEFH | REQ | | Section 18.28 |
| SECINFO | REQ | | Section 18.29 | | SECINFO | REQ | | Section 18.29 |
| SECINFO_NO_NAME | REC | pNFS files | Section 18.45, | | SECINFO_NO_NAME | REC | pNFS file | Section 18.45, |
| | | layout (REQ) | Section 13.12 | | | | layout (REQ) | Section 13.12 |
| SEQUENCE | REQ | | Section 18.46 | | SEQUENCE | REQ | | Section 18.46 |
| SETATTR | REQ | | Section 18.30 | | SETATTR | REQ | | Section 18.30 |
| SETCLIENTID | MNI | | N/A | | SETCLIENTID | MNI | | N/A |
| SETCLIENTID_CONFIRM | MNI | | N/A | | SETCLIENTID_CONFIRM | MNI | | N/A |
| SET_SSV | REQ | | Section 18.47 | | SET_SSV | REQ | | Section 18.47 |
| TEST_STATEID | REQ | | Section 18.48 | | TEST_STATEID | REQ | | Section 18.48 |
| VERIFY | REQ | | Section 18.31 | | VERIFY | REQ | | Section 18.31 |
| WANT_DELEGATION | OPT | FDELG (OPT) | Section 18.49 | | WANT_DELEGATION | OPT | FDELG (OPT) | Section 18.49 |
| WRITE | REQ | | Section 18.32 | | WRITE | REQ | | Section 18.32 |
+----------------------+------------+--------------+----------------+ +----------------------+------------+--------------+----------------+
Callback Operations:
Callback Operations Callback Operations
+-------------------------+-----------+-------------+---------------+ +-------------------------+-----------+-------------+---------------+
| Operation | REQ, REC, | Feature | Definition | | Operation | REQ, REC, | Feature | Definition |
| | OPT, or | (REQ, REC, | | | | OPT, or | (REQ, REC, | |
| | MNI | or OPT) | | | | MNI | or OPT) | |
+-------------------------+-----------+-------------+---------------+ +-------------------------+-----------+-------------+---------------+
| CB_GETATTR | OPT | FDELG (REQ) | Section 20.1 | | CB_GETATTR | OPT | FDELG (REQ) | Section 20.1 |
| CB_LAYOUTRECALL | OPT | pNFS (REQ) | Section 20.3 | | CB_LAYOUTRECALL | OPT | pNFS (REQ) | Section 20.3 |
| CB_NOTIFY | OPT | DDELG (REQ) | Section 20.4 | | CB_NOTIFY | OPT | DDELG (REQ) | Section 20.4 |
skipping to change at page 411, line 12 skipping to change at page 411, line 12
example, if the client sends an ACCESS operation with just the example, if the client sends an ACCESS operation with just the
ACCESS4_READ value set and the server supports this value, the server ACCESS4_READ value set and the server supports this value, the server
MUST NOT set more than ACCESS4_READ in the supported field even if it MUST NOT set more than ACCESS4_READ in the supported field even if it
could have reliably checked other values. could have reliably checked other values.
The reply's access field MUST NOT contain more values than the The reply's access field MUST NOT contain more values than the
supported field. supported field.
The results of this operation are necessarily advisory in nature. A The results of this operation are necessarily advisory in nature. A
return status of NFS4_OK and the appropriate bit set in the bit mask return status of NFS4_OK and the appropriate bit set in the bit mask
does not imply that such access will be allowed to the file system do not imply that such access will be allowed to the file system
object in the future. This is because access rights can be revoked object in the future. This is because access rights can be revoked
by the server at any time. by the server at any time.
The following access permissions may be requested: The following access permissions may be requested:
ACCESS4_READ Read data from file or read a directory. ACCESS4_READ Read data from file or read a directory.
ACCESS4_LOOKUP Look up a name in a directory (no meaning for non- ACCESS4_LOOKUP Look up a name in a directory (no meaning for non-
directory objects). directory objects).
skipping to change at page 411, line 38 skipping to change at page 411, line 38
ACCESS4_DELETE Delete an existing directory entry. ACCESS4_DELETE Delete an existing directory entry.
ACCESS4_EXECUTE Execute a regular file (no meaning for a directory). ACCESS4_EXECUTE Execute a regular file (no meaning for a directory).
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
ACCESS4_EXECUTE is a challenging semantic to implement because NFS ACCESS4_EXECUTE is a challenging semantic to implement because NFS
provides remote file access, not remote execution. This leads to the provides remote file access, not remote execution. This leads to the
following: following:
o Whether a regular file is executable or not ought to be the o Whether or not a regular file is executable ought to be the
responsibility of the NFS client and not the server. And yet the responsibility of the NFS client and not the server. And yet the
ACCESS operation is specified to seemingly require a server to own ACCESS operation is specified to seemingly require a server to own
that responsibility. that responsibility.
o When a client executes a regular file, it has to read the file o When a client executes a regular file, it has to read the file
from the server. Strictly speaking, the server should not allow from the server. Strictly speaking, the server should not allow
the client to read a file being executed unless the user has read the client to read a file being executed unless the user has read
permissions on the file. Requiring users and administers to set permissions on the file. Requiring explicit read permissions on
read permissions on executable files in order to access them over executable files in order to access them over NFS is not going to
NFS is not going to be acceptable to some people. Historically, be acceptable to some users and storage administrators.
NFS servers have allowed a user to READ a file if the user has Historically, NFS servers have allowed a user to READ a file if
execute access to the file. the user has execute access to the file.
As a practical example, the UNIX specification [52] states that an As a practical example, the UNIX specification [52] states that an
implementation claiming conformance to UNIX may indicate in the implementation claiming conformance to UNIX may indicate in the
access() programming interface's result that a privileged user has access() programming interface's result that a privileged user has
execute rights, even if no execute permission bits are set on the execute rights, even if no execute permission bits are set on the
regular file's attributes. It is possible to claim conformance to regular file's attributes. It is possible to claim conformance to
the UNIX specification and instead not indicate execute rights in the UNIX specification and instead not indicate execute rights in
that situation, which is true for some operating environments. that situation, which is true for some operating environments.
Suppose the operating environments of the client and server are Suppose the operating environments of the client and server are
implementing the access() semantics for privileged users differently, implementing the access() semantics for privileged users differently,
skipping to change at page 412, line 36 skipping to change at page 412, line 36
the user is privileged, and no execute permission bits are set on the user is privileged, and no execute permission bits are set on
the regular file's attribute, and the server's access() interface the regular file's attribute, and the server's access() interface
does return X_OK in that situation. Then: does return X_OK in that situation. Then:
* The client will be able to execute files stored on the NFS * The client will be able to execute files stored on the NFS
server that could be executed if stored on a non-NFS file server that could be executed if stored on a non-NFS file
system, unless the client's execution subsystem also checks for system, unless the client's execution subsystem also checks for
execute permission bits. execute permission bits.
* Even if the execution subsystem is checking for execute * Even if the execution subsystem is checking for execute
permission bits, there are more potential issues. E.g. suppose permission bits, there are more potential issues. For example,
the client is invoking access() to build a "path search table" suppose the client is invoking access() to build a "path search
of all executable files in the user's "search path", where the table" of all executable files in the user's "search path",
path is a list of directories each containing executable files. where the path is a list of directories each containing
Suppose there are two files each in separate directories of the executable files. Suppose there are two files each in separate
search path, such that files have the same component name. In directories of the search path, such that files have the same
the first directory the file has no execute permission bits component name. In the first directory the file has no execute
set, and in the second directory the file has execute bits set. permission bits set, and in the second directory the file has
The path search table will indicate that the first directory execute bits set. The path search table will indicate that the
has the executable file, but the execute subsystem will fail to first directory has the executable file, but the execute
execute it. The command shell might fail to try the second subsystem will fail to execute it. The command shell might
file in the second directory. And even if it did, this is a fail to try the second file in the second directory. And even
potential performance issue. Clearly the desired outcome for if it did, this is a potential performance issue. Clearly, the
the client is for the path search table to not contain the desired outcome for the client is for the path search table to
first file. not contain the first file.
To deal the problems described above, the smart client, stupid server To deal with the problems described above, the "smart client, stupid
principle is used. The client owns overall responsibility for server" principle is used. The client owns overall responsibility
determining execute access and relies on the server to parse the for determining execute access and relies on the server to parse the
execution permissions within the file's mode, acl, and dacl execution permissions within the file's mode, acl, and dacl
attributes. The rules for the client and server follow: attributes. The rules for the client and server follow:
o If the client is sending ACCESS in order to determine if the user o If the client is sending ACCESS in order to determine if the user
can read the file, the client SHOULD set ACCESS4_READ in the can read the file, the client SHOULD set ACCESS4_READ in the
request's access field. request's access field.
o If the client's operating environment only grants execution to the o If the client's operating environment only grants execution to the
user if the user has execute access according to the execute user if the user has execute access according to the execute
permissions in the mode, acl, and dacl attributes, then if the permissions in the mode, acl, and dacl attributes, then if the
skipping to change at page 413, line 33 skipping to change at page 413, line 33
the client wants to determine execute access, it SHOULD send an the client wants to determine execute access, it SHOULD send an
ACCESS request with both the ACCESS4_EXECUTE and ACCESS4_READ bits ACCESS request with both the ACCESS4_EXECUTE and ACCESS4_READ bits
set in the request's access field. This way, if any read or set in the request's access field. This way, if any read or
execute permission grants the user read or execute access (or if execute permission grants the user read or execute access (or if
the server interprets the user as privileged), as indicated by the the server interprets the user as privileged), as indicated by the
presence of ACCESS4_EXECUTE and/or ACCESS4_READ in the reply's presence of ACCESS4_EXECUTE and/or ACCESS4_READ in the reply's
access field, the client will be able to grant the user execute access field, the client will be able to grant the user execute
access to the file. access to the file.
o If the server supports execute permission bits, or some other o If the server supports execute permission bits, or some other
method for denoting executability (e.g. the suffix of the name of method for denoting executability (e.g., the suffix of the name of
the file might indicate execute), it MUST check only execute the file might indicate execute), it MUST check only execute
permissions, not read permissions, when determining whether the permissions, not read permissions, when determining whether or not
reply will have ACCESS4_EXECUTE set in the access field or not. the reply will have ACCESS4_EXECUTE set in the access field. The
The server MUST NOT also examine read permission bits when server MUST NOT also examine read permission bits when determining
determining whether the reply will have ACCESS4_EXECUTE set in the whether or not the reply will have ACCESS4_EXECUTE set in the
access field or not. Even if the server's operating environment access field. Even if the server's operating environment would
would grant execute access to the user (e.g., the user is grant execute access to the user (e.g., the user is privileged),
privileged), the server MUST NOT reply with ACCESS4_EXECUTE set in the server MUST NOT reply with ACCESS4_EXECUTE set in reply's
reply's access field, unless there is at least one execute access field unless there is at least one execute permission bit
permission bit set in the mode, acl, or dacl attributes. In the set in the mode, acl, or dacl attributes. In the case of acl and
case of acl and dacl, the "one execute permission bit" MUST be an dacl, the "one execute permission bit" MUST be an ACE4_EXECUTE bit
ACE4_EXECUTE bit set in an ALLOW ACE. set in an ALLOW ACE.
o If the server does not support execute permission bits or some o If the server does not support execute permission bits or some
other method for denoting executability, it MUST NOT set other method for denoting executability, it MUST NOT set
ACCESS4_EXECUTE in the reply's supported and access fields. If ACCESS4_EXECUTE in the reply's supported and access fields. If
the client set ACCESS4_EXECUTE in the ACCESS request's access the client set ACCESS4_EXECUTE in the ACCESS request's access
field, and ACCESS4_EXECUTE is not set in the reply's supported field, and ACCESS4_EXECUTE is not set in the reply's supported
field, then the client will have to send an ACCESS request with field, then the client will have to send an ACCESS request with
the ACCESS4_READ bit set in the request's access field. the ACCESS4_READ bit set in the request's access field.
o If the server supports read permission bits, it MUST only check o If the server supports read permission bits, it MUST only check
for read permissions in the mode, acl, and dacl attributes when it for read permissions in the mode, acl, and dacl attributes when it
receives an ACCESS request with ACCESS4_READ set the access field. receives an ACCESS request with ACCESS4_READ set in the access
The server MUST NOT also examine execute permission bits when field. The server MUST NOT also examine execute permission bits
determining whether the reply will have ACCESS4_READ set in the when determining whether the reply will have ACCESS4_READ set in
access field or not. the access field or not.
Note that if the ACCESS reply has ACCESS4_READ or ACCESS_EXECUTE set, Note that if the ACCESS reply has ACCESS4_READ or ACCESS_EXECUTE set,
then the user also has permissions to OPEN (Section 18.16) or READ then the user also has permissions to OPEN (Section 18.16) or READ
(Section 18.22) the file. I.e., if client sends an ACCESS request (Section 18.22) the file. In other words, if the client sends an
with the ACCESS4_READ and ACCESS_EXECUTE set in the access field (or ACCESS request with the ACCESS4_READ and ACCESS_EXECUTE set in the
two separate requests, one with ACCESS4_READ set, and the other with access field (or two separate requests, one with ACCESS4_READ set and
ACCESS4_EXECUTE set), and the reply has just ACCESS4_EXECUTE set in the other with ACCESS4_EXECUTE set), and the reply has just
the access field (or just one reply has ACCESS4_EXECUTE set), then ACCESS4_EXECUTE set in the access field (or just one reply has
the user has authorization to OPEN or READ the file. ACCESS4_EXECUTE set), then the user has authorization to OPEN or READ
the file.
18.1.4. IMPLEMENTATION 18.1.4. IMPLEMENTATION
In general, it is not sufficient for the client to attempt to deduce In general, it is not sufficient for the client to attempt to deduce
access permissions by inspecting the uid, gid, and mode fields in the access permissions by inspecting the uid, gid, and mode fields in the
file attributes or by attempting to interpret the contents of the ACL file attributes or by attempting to interpret the contents of the ACL
attribute. This is because the server may perform uid or gid mapping attribute. This is because the server may perform uid or gid mapping
or enforce additional access control restrictions. It is also or enforce additional access-control restrictions. It is also
possible that the server may not be in the same ID space as the possible that the server may not be in the same ID space as the
client. In these cases (and perhaps others), the client can not client. In these cases (and perhaps others), the client can not
reliably perform an access check with only current file attributes. reliably perform an access check with only current file attributes.
In the NFSv2 protocol, the only reliable way to determine whether an In the NFSv2 protocol, the only reliable way to determine whether an
operation was allowed was to try it and see if it succeeded or operation was allowed was to try it and see if it succeeded or
failed. Using the ACCESS operation in the NFSv4.1 protocol, the failed. Using the ACCESS operation in the NFSv4.1 protocol, the
client can ask the server to indicate whether or not one or more client can ask the server to indicate whether or not one or more
classes of operations are permitted. The ACCESS operation is classes of operations are permitted. The ACCESS operation is
provided to allow clients to check before doing a series of provided to allow clients to check before doing a series of
operations which will result in an access failure. The OPEN operations that will result in an access failure. The OPEN operation
operation provides a point where the server can verify access to the provides a point where the server can verify access to the file
file object and method to return that information to the client. The object and a method to return that information to the client. The
ACCESS operation is still useful for directory operations or for use ACCESS operation is still useful for directory operations or for use
in the case the UNIX interface access() is used on the client. in the case that the UNIX interface access() is used on the client.
The information returned by the server in response to an ACCESS call The information returned by the server in response to an ACCESS call
is not permanent. It was correct at the exact time that the server is not permanent. It was correct at the exact time that the server
performed the checks, but not necessarily afterwards. The server can performed the checks, but not necessarily afterwards. The server can
revoke access permission at any time. revoke access permission at any time.
The client should use the effective credentials of the user to build The client should use the effective credentials of the user to build
the authentication information in the ACCESS request used to the authentication information in the ACCESS request used to
determine access rights. It is the effective user and group determine access rights. It is the effective user and group
credentials that are used in subsequent read and write operations. credentials that are used in subsequent READ and WRITE operations.
Many implementations do not directly support the ACCESS4_DELETE Many implementations do not directly support the ACCESS4_DELETE
permission. Operating systems like UNIX will ignore the permission. Operating systems like UNIX will ignore the
ACCESS4_DELETE bit if set on an access request on a non-directory ACCESS4_DELETE bit if set on an access request on a non-directory
object. In these systems, delete permission on a file is determined object. In these systems, delete permission on a file is determined
by the access permissions on the directory in which the file resides, by the access permissions on the directory in which the file resides,
instead of being determined by the permissions of the file itself. instead of being determined by the permissions of the file itself.
Therefore, the mask returned enumerating which access rights can be Therefore, the mask returned enumerating which access rights can be
determined will have the ACCESS4_DELETE value set to 0. This determined will have the ACCESS4_DELETE value set to 0. This
indicates to the client that the server was unable to check that indicates to the client that the server was unable to check that
skipping to change at page 415, line 44 skipping to change at page 415, line 46
stateid4 open_stateid; stateid4 open_stateid;
default: default:
void; void;
}; };
18.2.3. DESCRIPTION 18.2.3. DESCRIPTION
The CLOSE operation releases share reservations for the regular or The CLOSE operation releases share reservations for the regular or
named attribute file as specified by the current filehandle. The named attribute file as specified by the current filehandle. The
share reservations and other state information released at the server share reservations and other state information released at the server
as a result of this CLOSE is only that associated with the supplied as a result of this CLOSE are only those associated with the supplied
stateid. State associated with other OPENs is not affected. stateid. State associated with other OPENs is not affected.
If byte-range locks are held, the client SHOULD release all locks If byte-range locks are held, the client SHOULD release all locks
before sending a CLOSE. The server MAY free all outstanding locks on before sending a CLOSE. The server MAY free all outstanding locks on
CLOSE but some servers may not support the CLOSE of a file that still CLOSE, but some servers may not support the CLOSE of a file that
has byte-range locks held. The server MUST return failure if any still has byte-range locks held. The server MUST return failure if
locks would exist after the CLOSE. any locks would exist after the CLOSE.
The argument seqid MAY have any value and the server MUST ignore The argument seqid MAY have any value, and the server MUST ignore
seqid. seqid.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
The server MAY require that the principal, security flavor, and The server MAY require that the combination of principal, security
applicable, the GSS mechanism, combination that sent the OPEN request flavor, and, if applicable, GSS mechanism that sent the OPEN request
also be the one to CLOSE the file. This might not be possible if also be the one to CLOSE the file. This might not be possible if
credentials for the principal are no longer available. The server credentials for the principal are no longer available. The server
MAY allow the machine credential or SSV credential (see MAY allow the machine credential or SSV credential (see
Section 18.35) to send CLOSE. Section 18.35) to send CLOSE.
18.2.4. IMPLEMENTATION 18.2.4. IMPLEMENTATION
Even though CLOSE returns a stateid, this stateid is not useful to Even though CLOSE returns a stateid, this stateid is not useful to
the client and should be treated as deprecated. CLOSE "shuts down" the client and should be treated as deprecated. CLOSE "shuts down"
the state associated with all OPENs for the file by a single open- the state associated with all OPENs for the file by a single open-
owner. As noted above, CLOSE will either release all file locking owner. As noted above, CLOSE will either release all file-locking
state or return an error. Therefore, the stateid returned by CLOSE state or return an error. Therefore, the stateid returned by CLOSE
is not useful for operations that follow. To help find any uses of is not useful for operations that follow. To help find any uses of
this stateid by clients, the server SHOULD return the invalid special this stateid by clients, the server SHOULD return the invalid special
stated (the "other" value is zero and the "seqid" field is stateid (the "other" value is zero and the "seqid" field is
NFS4_UINT32_MAX, see Section 8.2.3). NFS4_UINT32_MAX, see Section 8.2.3).
A CLOSE operation may make delegations grantable where they were not A CLOSE operation may make delegations grantable where they were not
previously. Servers may choose to respond immediately if there are previously. Servers may choose to respond immediately if there are
pending delegation want requests or may respond to the situation at a pending delegation want requests or may respond to the situation at a
later time. later time.
18.3. Operation 5: COMMIT - Commit Cached Data 18.3. Operation 5: COMMIT - Commit Cached Data
18.3.1. ARGUMENTS 18.3.1. ARGUMENTS
skipping to change at page 417, line 22 skipping to change at page 417, line 22
case NFS4_OK: case NFS4_OK:
COMMIT4resok resok4; COMMIT4resok resok4;
default: default:
void; void;
}; };
18.3.3. DESCRIPTION 18.3.3. DESCRIPTION
The COMMIT operation forces or flushes uncommitted, modified data to The COMMIT operation forces or flushes uncommitted, modified data to
stable storage for the file specified by the current filehandle. The stable storage for the file specified by the current filehandle. The
flushed data is that which was previously written with a WRITE flushed data is that which was previously written with one or more
operation which had the stable field set to UNSTABLE4. WRITE operations that had the "committed" field of their results
field set to UNSTABLE4.
The offset specifies the position within the file where the flush is The offset specifies the position within the file where the flush is
to begin. An offset value of 0 (zero) means to flush data starting to begin. An offset value of zero means to flush data starting at
at the beginning of the file. The count specifies the number of the beginning of the file. The count specifies the number of bytes
bytes of data to flush. If count is 0 (zero), a flush from offset to of data to flush. If the count is zero, a flush from the offset to
the end of the file is done. the end of the file is done.
The server returns a write verifier upon successful completion of the The server returns a write verifier upon successful completion of the
COMMIT. The write verifier is used by the client to determine if the COMMIT. The write verifier is used by the client to determine if the
server has restarted between the initial WRITE(s) and the COMMIT. server has restarted between the initial WRITE operations and the
The client does this by comparing the write verifier returned from COMMIT. The client does this by comparing the write verifier
the initial writes and the verifier returned by the COMMIT operation. returned from the initial WRITE operations and the verifier returned
The server must vary the value of the write verifier at each server by the COMMIT operation. The server must vary the value of the write
event or instantiation that may lead to a loss of uncommitted data. verifier at each server event or instantiation that may lead to a
Most commonly this occurs when the server is restarted; however, loss of uncommitted data. Most commonly this occurs when the server
other events at the server may result in uncommitted data loss as is restarted; however, other events at the server may result in
well. uncommitted data loss as well.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.3.4. IMPLEMENTATION 18.3.4. IMPLEMENTATION
The COMMIT operation is similar in operation and semantics to the The COMMIT operation is similar in operation and semantics to the
POSIX fsync() [25] system interface that synchronizes a file's state POSIX fsync() [25] system interface that synchronizes a file's state
with the disk (file data and metadata is flushed to disk or stable with the disk (file data and metadata is flushed to disk or stable
storage). COMMIT performs the same operation for a client, flushing storage). COMMIT performs the same operation for a client, flushing
any unsynchronized data and metadata on the server to the server's any unsynchronized data and metadata on the server to the server's
disk or stable storage for the specified file. Like fsync(2), it may disk or stable storage for the specified file. Like fsync(), it may
be that there is some modified data or no modified data to be that there is some modified data or no modified data to
synchronize. The data may have been synchronized by the server's synchronize. The data may have been synchronized by the server's
normal periodic buffer synchronization activity. COMMIT should normal periodic buffer synchronization activity. COMMIT should
return NFS4_OK, unless there has been an unexpected error. return NFS4_OK, unless there has been an unexpected error.
COMMIT differs from fsync(2) in that it is possible for the client to COMMIT differs from fsync() in that it is possible for the client to
flush a range of the file (most likely triggered by a buffer- flush a range of the file (most likely triggered by a buffer-
reclamation scheme on the client before file has been completely reclamation scheme on the client before the file has been completely
written). written).
The server implementation of COMMIT is reasonably simple. If the The server implementation of COMMIT is reasonably simple. If the
server receives a full file COMMIT request, that is starting at server receives a full file COMMIT request, that is, starting at
offset 0 and count 0, it should do the equivalent of fsync()'ing the offset zero and count zero, it should do the equivalent of applying
file. Otherwise, it should arrange to have the modified data in the fsync() to the entire file. Otherwise, it should arrange to have the
range specified by offset and count to be flushed to stable storage. modified data in the range specified by offset and count to be
In both cases, any metadata associated with the file must be flushed flushed to stable storage. In both cases, any metadata associated
to stable storage before returning. It is not an error for there to with the file must be flushed to stable storage before returning. It
be nothing to flush on the server. This means that the data and is not an error for there to be nothing to flush on the server. This
metadata that needed to be flushed have already been flushed or lost means that the data and metadata that needed to be flushed have
during the last server failure. already been flushed or lost during the last server failure.
The client implementation of COMMIT is a little more complex. There The client implementation of COMMIT is a little more complex. There
are two reasons for wanting to commit a client buffer to stable are two reasons for wanting to commit a client buffer to stable
storage. The first is that the client wants to reuse a buffer. In storage. The first is that the client wants to reuse a buffer. In
this case, the offset and count of the buffer are sent to the server this case, the offset and count of the buffer are sent to the server
in the COMMIT request. The server then flushes any modified data in the COMMIT request. The server then flushes any modified data
based on the offset and count, and flushes any modified metadata based on the offset and count, and flushes any modified metadata
associated with the file. It then returns the status of the flush associated with the file. It then returns the status of the flush
and the write verifier. The other reason for the client to generate and the write verifier. The second reason for the client to generate
a COMMIT is for a full file flush, such as may be done at close. In a COMMIT is for a full file flush, such as may be done at close. In
this case, the client would gather all of the buffers for this file this case, the client would gather all of the buffers for this file
that contain uncommitted data, do the COMMIT operation with an offset that contain uncommitted data, do the COMMIT operation with an offset
of 0 and count of 0, and then free all of those buffers. Any other of zero and count of zero, and then free all of those buffers. Any
dirty buffers would be sent to the server in the normal fashion. other dirty buffers would be sent to the server in the normal
fashion.
After a buffer is written by the client with the stable parameter set After a buffer is written (via the WRITE operation) by the client
to UNSTABLE4, the buffer must be considered as modified by the client with the "committed" field in the result of WRITE set to UNSTABLE4,
until the buffer has either been flushed via a COMMIT operation or the buffer must be considered as modified by the client until the
written via a WRITE operation with stable parameter set to FILE_SYNC4 buffer has either been flushed via a COMMIT operation or written via
or DATA_SYNC4. This is done to prevent the buffer from being freed a WRITE operation with the "committed" field in the result set to
and reused before the data can be flushed to stable storage on the FILE_SYNC4 or DATA_SYNC4. This is done to prevent the buffer from
server. being freed and reused before the data can be flushed to stable
storage on the server.
When a response is returned from either a WRITE or a COMMIT operation When a response is returned from either a WRITE or a COMMIT operation
and it contains a write verifier that is different than previously and it contains a write verifier that differs from that previously
returned by the server, the client will need to retransmit all of the returned by the server, the client will need to retransmit all of the
buffers containing uncommitted data to the server. How this is to be buffers containing uncommitted data to the server. How this is to be
done is up to the implementor. If there is only one buffer of done is up to the implementor. If there is only one buffer of
interest, then it should sent in a WRITE request with the FILE_SYNC4 interest, then it should be sent in a WRITE request with the
stable parameter. If there is more than one buffer, it might be FILE_SYNC4 stable parameter. If there is more than one buffer, it
worthwhile retransmitting all of the buffers in WRITE requests with might be worthwhile retransmitting all of the buffers in WRITE
the stable parameter set to UNSTABLE4 and then retransmitting the operations with the stable parameter set to UNSTABLE4 and then
COMMIT operation to flush all of the data on the server to stable retransmitting the COMMIT operation to flush all of the data on the
storage. However, if the server repeatably returns from COMMIT a server to stable storage. However, if the server repeatably returns
verifier that differs from that returned by WRITE, the only way to from COMMIT a verifier that differs from that returned by WRITE, the
ensure progress is to retransmit all of the buffers with WRITE only way to ensure progress is to retransmit all of the buffers with
requests with the FILE_SYNC4 stable parameter. WRITE requests with the FILE_SYNC4 stable parameter.
The above description applies to page-cache-based systems as well as The above description applies to page-cache-based systems as well as
buffer-cache-based systems. In those systems, the virtual memory buffer-cache-based systems. In the former systems, the virtual
system will need to be modified instead of the buffer cache. memory system will need to be modified instead of the buffer cache.
18.4. Operation 6: CREATE - Create a Non-Regular File Object 18.4. Operation 6: CREATE - Create a Non-Regular File Object
18.4.1. ARGUMENTS 18.4.1. ARGUMENTS
union createtype4 switch (nfs_ftype4 type) { union createtype4 switch (nfs_ftype4 type) {
case NF4LNK: case NF4LNK:
linktext4 linkdata; linktext4 linkdata;
case NF4BLK: case NF4BLK:
case NF4CHR: case NF4CHR:
skipping to change at page 420, line 47 skipping to change at page 420, line 47
If an object of the same name already exists in the directory, the If an object of the same name already exists in the directory, the
server will return the error NFS4ERR_EXIST. server will return the error NFS4ERR_EXIST.
For the directory where the new file object was created, the server For the directory where the new file object was created, the server
returns change_info4 information in cinfo. With the atomic field of returns change_info4 information in cinfo. With the atomic field of
the change_info4 data type, the server will indicate if the before the change_info4 data type, the server will indicate if the before
and after change attributes were obtained atomically with respect to and after change attributes were obtained atomically with respect to
the file object creation. the file object creation.
If the objname has a length of 0 (zero), or if objname does not obey If the objname has a length of zero, or if objname does not obey the
the UTF-8 definition, the error NFS4ERR_INVAL will be returned. UTF-8 definition, the error NFS4ERR_INVAL will be returned.
The current filehandle is replaced by that of the new object. The current filehandle is replaced by that of the new object.
The createattrs specifies the initial set of attributes for the The createattrs specifies the initial set of attributes for the
object. The set of attributes may include any writable attribute object. The set of attributes may include any writable attribute
valid for the object type. When the operation is successful, the valid for the object type. When the operation is successful, the
server will return to the client an attribute mask signifying which server will return to the client an attribute mask signifying which
attributes were successfully set for the object. attributes were successfully set for the object.
If createattrs includes neither the owner attribute nor an ACL with If createattrs includes neither the owner attribute nor an ACL with
an ACE for the owner, and if the server's file system both supports an ACE for the owner, and if the server's file system both supports
and requires an owner attribute (or an owner ACE) then the server and requires an owner attribute (or an owner ACE), then the server
MUST derive the owner (or the owner ACE). This would typically be MUST derive the owner (or the owner ACE). This would typically be
from the principal indicated in the RPC credentials of the call, but from the principal indicated in the RPC credentials of the call, but
the server's operating environment or file system semantics may the server's operating environment or file system semantics may
dictate other methods of derivation. Similarly, if createattrs dictate other methods of derivation. Similarly, if createattrs
includes neither the group attribute nor a group ACE, and if the includes neither the group attribute nor a group ACE, and if the
server's file system both supports and requires the notion of a group server's file system both supports and requires the notion of a group
attribute (or group ACE), the server MUST derive the group attribute attribute (or group ACE), the server MUST derive the group attribute
(or the corresponding owner ACE) for the file. This could be from (or the corresponding owner ACE) for the file. This could be from
the RPC call's credentials, such as the group principal if the the RPC call's credentials, such as the group principal if the
credentials include it (such as with AUTH_SYS), from the group credentials include it (such as with AUTH_SYS), from the group
identifier associated with the principal in the credentials (e.g., identifier associated with the principal in the credentials (e.g.,
POSIX systems have a user database [26] that has a group identifier POSIX systems have a user database [26] that has a group identifier
for every user identifier), inherited from directory the object is for every user identifier), inherited from the directory in which the
created in, or whatever else the server's operating environment or object is created, or whatever else the server's operating
file system semantics dictate. This applies to the OPEN operation environment or file system semantics dictate. This applies to the
too. OPEN operation too.
Conversely, it is possible the client will specify in createattrs an Conversely, it is possible that the client will specify in
owner attribute, group attribute, or ACL that the principal indicated createattrs an owner attribute, group attribute, or ACL that the
the RPC call's credentials does not have permissions to create files principal indicated the RPC call's credentials does not have
for. The error to be returned in this instance is NFS4ERR_PERM. permissions to create files for. The error to be returned in this
This applies to the OPEN operation too. instance is NFS4ERR_PERM. This applies to the OPEN operation too.
If the current filehandle designates a directory for which another If the current filehandle designates a directory for which another
client holds a directory delegation, then, unless the delegation is client holds a directory delegation, then, unless the delegation is
such that the situation can be resolved by sending a notification, such that the situation can be resolved by sending a notification,
the delegation MUST be recalled, and the CREATE operation MUST NOT the delegation MUST be recalled, and the CREATE operation MUST NOT
proceed until the delegation is returned or revoked. Except where proceed until the delegation is returned or revoked. Except where
this happens very quickly, one or more NFS4ERR_DELAY errors will be this happens very quickly, one or more NFS4ERR_DELAY errors will be
returned to requests made while delegation remains outstanding. returned to requests made while delegation remains outstanding.
When the current filehandle designates a directory for which one or When the current filehandle designates a directory for which one or
skipping to change at page 422, line 27 skipping to change at page 422, line 27
}; };
18.5.2. RESULTS 18.5.2. RESULTS
struct DELEGPURGE4res { struct DELEGPURGE4res {
nfsstat4 status; nfsstat4 status;
}; };
18.5.3. DESCRIPTION 18.5.3. DESCRIPTION
Purges all of the delegations awaiting recovery for a given client. This operation purges all of the delegations awaiting recovery for a
This is useful for clients which do not commit delegation information given client. This is useful for clients that do not commit
to stable storage to indicate that conflicting requests need not be delegation information to stable storage to indicate that conflicting
delayed by the server awaiting recovery of delegation information. requests need not be delayed by the server awaiting recovery of
delegation information.
The client is NOT specified by the clientid field of the request. The client is NOT specified by the clientid field of the request.
The client SHOULD set the client field to zero and the server MUST The client SHOULD set the client field to zero, and the server MUST
ignore the clientid field. Instead the server MUST derive the client ignore the clientid field. Instead, the server MUST derive the
ID from the value of the session ID in the arguments of the SEQUENCE client ID from the value of the session ID in the arguments of the
operation that precedes DELEGPURGE in the COMPOUND request. SEQUENCE operation that precedes DELEGPURGE in the COMPOUND request.
This operation should be used by clients that record delegation The DELEGPURGE operation should be used by clients that record
information on stable storage on the client. In this case, delegation information on stable storage on the client. In this
DELEGPURGE should be sent immediately after doing delegation recovery case, after the client recovers all delegations it knows of, it
on all delegations known to the client. Doing so will notify the should immediately send a DELEGPURGE operation. Doing so will notify
server that no additional delegations for the client will be the server that no additional delegations for the client will be
recovered allowing it to free resources, and avoid delaying other recovered allowing it to free resources, and avoid delaying other
clients which make requests that conflict with the unrecovered clients which make requests that conflict with the unrecovered
delegations. The set of delegations known to the server and the delegations. The set of delegations known to the server and the
client may be different. The reason for this is that a client may client might be different. The reason for this is that after sending
fail after making a request which resulted in delegation but before a request that resulted in a delegation, the client might experience
it received the results and committed them to the client's stable a failure before it both received the delegation and committed the
storage. delegation to the client's stable storage.
The server MAY support DELEGPURGE, but if it does not, it MUST NOT The server MAY support DELEGPURGE, but if it does not, it MUST NOT
support CLAIM_DELEGATE_PREV. support CLAIM_DELEGATE_PREV and MUST NOT support CLAIM_DELEG_PREV_FH.
18.6. Operation 8: DELEGRETURN - Return Delegation 18.6. Operation 8: DELEGRETURN - Return Delegation
18.6.1. ARGUMENTS 18.6.1. ARGUMENTS
struct DELEGRETURN4args { struct DELEGRETURN4args {
/* CURRENT_FH: delegated object */ /* CURRENT_FH: delegated object */
stateid4 deleg_stateid; stateid4 deleg_stateid;
}; };
18.6.2. RESULTS 18.6.2. RESULTS
struct DELEGRETURN4res { struct DELEGRETURN4res {
nfsstat4 status; nfsstat4 status;
}; };
18.6.3. DESCRIPTION 18.6.3. DESCRIPTION
Returns the delegation represented by the current filehandle and The DELEGRETURN operation returns the delegation represented by the
stateid. current filehandle and stateid.
Delegations may be returned when recalled or voluntarily (i.e. before Delegations may be returned voluntarily (i.e., before the server has
the server has recalled them). In either case the client must recalled them) or when recalled. In either case, the client must
properly propagate state changed under the context of the delegation properly propagate state changed under the context of the delegation
to the server before returning the delegation. to the server before returning the delegation.
The server MAY require that the principal, security flavor, and if The server MAY require that the principal, security flavor, and if
applicable, the GSS mechanism, combination that acquired the applicable, the GSS mechanism, combination that acquired the
delegation also be the one to send DELEGRETURN on the file. This delegation also be the one to send DELEGRETURN on the file. This
might not be possible if credentials for the principal are no longer might not be possible if credentials for the principal are no longer
available. The server MAY allow the machine credential or SSV available. The server MAY allow the machine credential or SSV
credential (see Section 18.35) to send DELEGRETURN. credential (see Section 18.35) to send DELEGRETURN.
skipping to change at page 424, line 24 skipping to change at page 424, line 24
default: default:
void; void;
}; };
18.7.3. DESCRIPTION 18.7.3. DESCRIPTION
The GETATTR operation will obtain attributes for the file system The GETATTR operation will obtain attributes for the file system
object specified by the current filehandle. The client sets a bit in object specified by the current filehandle. The client sets a bit in
the bitmap argument for each attribute value that it would like the the bitmap argument for each attribute value that it would like the
server to return. The server returns an attribute bitmap that server to return. The server returns an attribute bitmap that
indicates the attribute values which it was able to return, which indicates the attribute values that it was able to return, which will
will include all attributes requested by the client which are include all attributes requested by the client that are attributes
attributes supported by the server for the target file system. This supported by the server for the target file system. This bitmap is
bitmap is followed by the attribute values ordered lowest attribute followed by the attribute values ordered lowest attribute number
number first. first.
The server MUST return a value for each attribute that the client The server MUST return a value for each attribute that the client
requests if the attribute is supported by the server for the target requests if the attribute is supported by the server for the target
file system. If the server does not support a particular attribute file system. If the server does not support a particular attribute
on the target file system then it MUST NOT return the attribute value on the target file system, then it MUST NOT return the attribute
and MUST NOT set the attribute bit in the result bitmap. The server value and MUST NOT set the attribute bit in the result bitmap. The
MUST return an error if it supports an attribute on the target but server MUST return an error if it supports an attribute on the target
cannot obtain its value. In that case, no attribute values will be but cannot obtain its value. In that case, no attribute values will
returned. be returned.
File systems which are absent should be treated as having support for File systems that are absent should be treated as having support for
a very small set of attributes as described in Section 11.3.1, even a very small set of attributes as described in Section 11.3.1, even
if previously, when the file system was present, more attributes were if previously, when the file system was present, more attributes were
supported. supported.
All servers MUST support the REQUIRED attributes as specified in All servers MUST support the REQUIRED attributes as specified in
Section 5.6, for all file systems, with the exception of absent file Section 5.6, for all file systems, with the exception of absent file
systems. systems.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.7.4. IMPLEMENTATION 18.7.4. IMPLEMENTATION
Suppose there is a write delegation held by another client for file Suppose there is an OPEN_DELEGATE_WRITE delegation held by another
in question and size and/or change are among the set of attributes client for the file in question and size and/or change are among the
being interrogated. The server has two choices. First, the server set of attributes being interrogated. The server has two choices.
can obtain the actual current value of these attributes from the First, the server can obtain the actual current value of these
client holding the delegation by using the CB_GETATTR callback. attributes from the client holding the delegation by using the
Second, the server, particularly when the delegated client is CB_GETATTR callback. Second, the server, particularly when the
unresponsive, can recall the delegation in question. The GETATTR delegated client is unresponsive, can recall the delegation in
MUST NOT proceed until one of the following occurs: question. The GETATTR MUST NOT proceed until one of the following
occurs:
o The requested attribute values are returned in the response to o The requested attribute values are returned in the response to
CB_GETATTR. CB_GETATTR.
o The write delegation is returned. o The OPEN_DELEGATE_WRITE delegation is returned.
o The write delegation is revoked. o The OPEN_DELEGATE_WRITE delegation is revoked.
Unless one of the above happens very quickly, one or more Unless one of the above happens very quickly, one or more
NFS4ERR_DELAY errors will be returned if while a delegation is NFS4ERR_DELAY errors will be returned while a delegation is
outstanding. outstanding.
18.8. Operation 10: GETFH - Get Current Filehandle 18.8. Operation 10: GETFH - Get Current Filehandle
18.8.1. ARGUMENTS 18.8.1. ARGUMENTS
/* CURRENT_FH: */ /* CURRENT_FH: */
void; void;
18.8.2. RESULTS 18.8.2. RESULTS
skipping to change at page 426, line 7 skipping to change at page 426, line 13
}; };
18.8.3. DESCRIPTION 18.8.3. DESCRIPTION
This operation returns the current filehandle value. This operation returns the current filehandle value.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
As described in Section 2.10.6.4, GETFH is REQUIRED or RECOMMENDED to As described in Section 2.10.6.4, GETFH is REQUIRED or RECOMMENDED to
immediately follow certain operations, and servers are free to reject immediately follow certain operations, and servers are free to reject
such operations the client fails to insert GETFH in the request as such operations if the client fails to insert GETFH in the request as
REQUIRED or RECOMMENDED. Section 18.16.4.1 provides additional REQUIRED or RECOMMENDED. Section 18.16.4.1 provides additional
justification for why GETFH MUST follow OPEN. justification for why GETFH MUST follow OPEN.
18.8.4. IMPLEMENTATION 18.8.4. IMPLEMENTATION
Operations that change the current filehandle like LOOKUP or CREATE Operations that change the current filehandle like LOOKUP or CREATE
do not automatically return the new filehandle as a result. For do not automatically return the new filehandle as a result. For
instance, if a client needs to lookup a directory entry and obtain instance, if a client needs to lookup a directory entry and obtain
its filehandle then the following request is needed. its filehandle, then the following request is needed.
PUTFH (directory filehandle) PUTFH (directory filehandle)
LOOKUP (entry name) LOOKUP (entry name)
GETFH GETFH
18.9. Operation 11: LINK - Create Link to a File 18.9. Operation 11: LINK - Create Link to a File
18.9.1. ARGUMENTS 18.9.1. ARGUMENTS
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file and the target directory must reside within the same file system file and the target directory must reside within the same file system
on the server. On success, the current filehandle will continue to on the server. On success, the current filehandle will continue to
be the target directory. If an object exists in the target directory be the target directory. If an object exists in the target directory
with the same name as newname, the server must return NFS4ERR_EXIST. with the same name as newname, the server must return NFS4ERR_EXIST.
For the target directory, the server returns change_info4 information For the target directory, the server returns change_info4 information
in cinfo. With the atomic field of the change_info4 data type, the in cinfo. With the atomic field of the change_info4 data type, the
server will indicate if the before and after change attributes were server will indicate if the before and after change attributes were
obtained atomically with respect to the link creation. obtained atomically with respect to the link creation.
If the newname has a length of 0 (zero), or if newname does not obey If the newname has a length of zero, or if newname does not obey the
the UTF-8 definition, the error NFS4ERR_INVAL will be returned. UTF-8 definition, the error NFS4ERR_INVAL will be returned.
18.9.4. IMPLEMENTATION 18.9.4. IMPLEMENTATION
The server MAY impose restrictions on the LINK operation such that The server MAY impose restrictions on the LINK operation such that
LINK may not be done when the file is open or when that open is done LINK may not be done when the file is open or when that open is done
by particular protocols, or with particular options or access modes. by particular protocols, or with particular options or access modes.
When LINK is rejected because of such restrictions, the error When LINK is rejected because of such restrictions, the error
NFS4ERR_FILE_OPEN is returned. NFS4ERR_FILE_OPEN is returned.
If a server does implement such restrictions and those restrictions If a server does implement such restrictions and those restrictions
include cases of NFSv4 opens preventing successful execution of a include cases of NFSv4 opens preventing successful execution of a
link, the server needs to recall any delegations which could hide the link, the server needs to recall any delegations that could hide the
existence of opens relevant to that decision. The reason is that existence of opens relevant to that decision. The reason is that
when a client holds a delegation, the server might not have an when a client holds a delegation, the server might not have an
accurate account of the opens for that client, since the client may accurate account of the opens for that client, since the client may
execute OPENs and CLOSEs locally. The LINK operation must be delayed execute OPENs and CLOSEs locally. The LINK operation must be delayed
only until a definitive result can be obtained. E.g., suppose there only until a definitive result can be obtained. For example, suppose
are multiple delegations and one of them establishes an open whose there are multiple delegations and one of them establishes an open
presence would prevent the link. Given the server's semantics, whose presence would prevent the link. Given the server's semantics,
NFS4ERR_FILE_OPEN may be returned to the caller as soon as that NFS4ERR_FILE_OPEN may be returned to the caller as soon as that
delegation is returned without waiting for other delegations to be delegation is returned without waiting for other delegations to be
returned. Similarly, if such opens are not associated with returned. Similarly, if such opens are not associated with
delegations, NFS4ERR_FILE_OPEN can be returned immediately with no delegations, NFS4ERR_FILE_OPEN can be returned immediately with no
delegation recall being done. delegation recall being done.
If the current filehandle designates a directory for which another If the current filehandle designates a directory for which another
client holds a directory delegation, then, unless the delegation is client holds a directory delegation, then, unless the delegation is
such that the situation can be resolved by sending a notification, such that the situation can be resolved by sending a notification,
the delegation MUST be recalled, and the operation cannot be the delegation MUST be recalled, and the operation cannot be
performed successfully. until the delegation is returned or revoked. performed successfully until the delegation is returned or revoked.
Except where this happens very quickly, one or more NFS4ERR_DELAY Except where this happens very quickly, one or more NFS4ERR_DELAY
errors will be returned to requests made while delegation remains errors will be returned to requests made while delegation remains
outstanding. outstanding.
When the current filehandle designates a directory for which one or When the current filehandle designates a directory for which one or
more directory delegations exist, then, when those delegations more directory delegations exist, then, when those delegations
request such notifications, instead of a recall, NOTIFY4_ADD_ENTRY request such notifications, instead of a recall, NOTIFY4_ADD_ENTRY
will be generated as a result of the LINK operation. will be generated as a result of the LINK operation.
If the current file system supports the numlinks attribute, and other If the current file system supports the numlinks attribute, and other
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Changes to any property of the "hard" linked files are reflected in Changes to any property of the "hard" linked files are reflected in
all of the linked files. When a link is made to a file, the all of the linked files. When a link is made to a file, the
attributes for the file should have a value for numlinks that is one attributes for the file should have a value for numlinks that is one
greater than the value before the LINK operation. greater than the value before the LINK operation.
The statement "file and the target directory must reside within the The statement "file and the target directory must reside within the
same file system on the server" means that the fsid fields in the same file system on the server" means that the fsid fields in the
attributes for the objects are the same. If they reside on different attributes for the objects are the same. If they reside on different
file systems, the error NFS4ERR_XDEV is returned. This error may be file systems, the error NFS4ERR_XDEV is returned. This error may be
returned by some server when there is an internal partitioning of a returned by some servers when there is an internal partitioning of a
file system which the LINK operation would violate. file system that the LINK operation would violate.
On some servers, "." and ".." are illegal values for newname and the On some servers, "." and ".." are illegal values for newname and the
error NFS4ERR_BADNAME will be returned if they are specified. error NFS4ERR_BADNAME will be returned if they are specified.
When the current filehandle designates a named attribute directory When the current filehandle designates a named attribute directory
and the object to be linked (the saved filehandle) is not a named and the object to be linked (the saved filehandle) is not a named
attribute for the same object, the error NFS4ERR_XDEV MUST be attribute for the same object, the error NFS4ERR_XDEV MUST be
returned. When the saved filehandle designates a named attribute and returned. When the saved filehandle designates a named attribute and
the current filehandle is not the appropriate named attribute the current filehandle is not the appropriate named attribute
directory, the error NFS4ERR_XDEV MUST also be returned. directory, the error NFS4ERR_XDEV MUST also be returned.
skipping to change at page 430, line 29 skipping to change at page 431, line 29
case NFS4_OK: case NFS4_OK:
LOCK4resok resok4; LOCK4resok resok4;
case NFS4ERR_DENIED: case NFS4ERR_DENIED:
LOCK4denied denied; LOCK4denied denied;
default: default:
void; void;
}; };
18.10.3. DESCRIPTION 18.10.3. DESCRIPTION
The LOCK operation requests a byte-range lock for the byte range The LOCK operation requests a byte-range lock for the byte-range
specified by the offset and length parameters, and lock type specified by the offset and length parameters, and lock type
specified in the locktype parameter. If this is a reclaim request, specified in the locktype parameter. If this is a reclaim request,
the reclaim parameter will be TRUE. the reclaim parameter will be TRUE.
Bytes in a file may be locked even if those bytes are not currently Bytes in a file may be locked even if those bytes are not currently
allocated to the file. To lock the file from a specific offset allocated to the file. To lock the file from a specific offset
through the end-of-file (no matter how long the file actually is) use through the end-of-file (no matter how long the file actually is) use
a length field equal to NFS4_UINT64_MAX. The server MUST return a length field equal to NFS4_UINT64_MAX. The server MUST return
NFS4ERR_INVAL under the following combinations of length and offset: NFS4ERR_INVAL under the following combinations of length and offset:
o Length is equal to zero. o Length is equal to zero.
o Length is not equal to NFS4_UINT64_MAX, and the sum of length and o Length is not equal to NFS4_UINT64_MAX, and the sum of length and
offset exceeds NFS4_UINT64_MAX. offset exceeds NFS4_UINT64_MAX.
32-bit servers are servers that support locking for byte offsets that 32-bit servers are servers that support locking for byte offsets that
fit within 32 bits (i.e. less than or equal to NFS4_UINT32_MAX). If fit within 32 bits (i.e., less than or equal to NFS4_UINT32_MAX). If
the client specifies a range that overlaps one or more bytes beyond the client specifies a range that overlaps one or more bytes beyond
offset NFS4_UINT32_MAX, but does not end at offset NFS4_UINT64_MAX, offset NFS4_UINT32_MAX but does not end at offset NFS4_UINT64_MAX,
then such a 32-bit server MUST return the error NFS4ERR_BAD_RANGE. then such a 32-bit server MUST return the error NFS4ERR_BAD_RANGE.
If the server returns NFS4ERR_DENIED, owner, offset, and length of a If the server returns NFS4ERR_DENIED, the owner, offset, and length
conflicting lock are returned. of a conflicting lock are returned.
The locker argument specifies the lock-owner that is associated with The locker argument specifies the lock-owner that is associated with
the LOCK request. The locker4 structure is a switched union that the LOCK operation. The locker4 structure is a switched union that
indicates whether the client has already created byte-range locking indicates whether the client has already created byte-range locking
state associated with the current open file and lock-owner. In the state associated with the current open file and lock-owner. In the
case in which it has, the argument is just a stateid representing the case in which it has, the argument is just a stateid representing the
set of locks associated with that open file and lock-owner, together set of locks associated with that open file and lock-owner, together
with a lock_seqid value which MAY be any value and MUST be ignored by with a lock_seqid value that MAY be any value and MUST be ignored by
the server. In the case where no byte-range locking state has been the server. In the case where no byte-range locking state has been
established, or the client does not have the stateid available, the established, or the client does not have the stateid available, the
argument contains the stateid of the open file with which this lock argument contains the stateid of the open file with which this lock
is to be associated, together with the lock-owner with which the lock is to be associated, together with the lock-owner with which the lock
is to be associated. The open_to_lock_owner case covers the very is to be associated. The open_to_lock_owner case covers the very
first lock done by a lock-owner for a given open file and offers a first lock done by a lock-owner for a given open file and offers a
method to use the established state of the open_stateid to transition method to use the established state of the open_stateid to transition
to the use of a lock stateid. to the use of a lock stateid.
The following fields of the locker parameter MAY be set to any value The following fields of the locker parameter MAY be set to any value
skipping to change at page 431, line 39 skipping to change at page 432, line 39
COMPOUND request. COMPOUND request.
o The open_seqid and lock_seqid fields of the open_owner field o The open_seqid and lock_seqid fields of the open_owner field
(locker.open_owner.open_seqid and locker.open_owner.lock_seqid). (locker.open_owner.open_seqid and locker.open_owner.lock_seqid).
o The lock_seqid field of the lock_owner field o The lock_seqid field of the lock_owner field
(locker.lock_owner.lock_seqid). (locker.lock_owner.lock_seqid).
Note that the client ID appearing in a LOCK4denied structure is the Note that the client ID appearing in a LOCK4denied structure is the
actual client associated with the conflicting lock, whether this is actual client associated with the conflicting lock, whether this is
the client ID associated with the current session, or a different the client ID associated with the current session or a different one.
one. Thus if the server returns NFS4ERR_DENIED, it MUST set the Thus, if the server returns NFS4ERR_DENIED, it MUST set the clientid
clientid field of the owner field of the denied field. field of the owner field of the denied field.
If the current filehandle is not an ordinary file, an error will be If the current filehandle is not an ordinary file, an error will be
returned to the client. In the case that the current filehandle returned to the client. In the case that the current filehandle
represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. if represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. If
the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is
returned. In all other cases, NFS4ERR_WRONG_TYPE is returned. returned. In all other cases, NFS4ERR_WRONG_TYPE is returned.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.10.4. IMPLEMENTATION 18.10.4. IMPLEMENTATION
If the server is unable to determine the exact offset and length of If the server is unable to determine the exact offset and length of
the conflicting lock, the same offset and length that were provided the conflicting byte-range lock, the same offset and length that were
in the arguments should be returned in the denied results provided in the arguments should be returned in the denied results.
LOCK operations are subject to permission checks and to checks LOCK operations are subject to permission checks and to checks
against the access type of the associated file. However, the against the access type of the associated file. However, the
specific right and modes required for various type of locks, reflect specific right and modes required for various types of locks reflect
the semantics of the server-exported file system, and are not the semantics of the server-exported file system, and are not
specified by the protocol. For example, Windows 2000 allows a write specified by the protocol. For example, Windows 2000 allows a write
lock of a file open for READ, while a POSIX-compliant system does lock of a file open for read access, while a POSIX-compliant system
not. does not.
When the client makes a lock request that corresponds to a range that When the client sends a LOCK operation that corresponds to a range
the lock-owner has locked already (with the same or different lock that the lock-owner has locked already (with the same or different
type), or to a sub-region of such a range, or to a region which lock type), or to a sub-range of such a range, or to a byte-range
includes multiple locks already granted to that lock-owner, in whole that includes multiple locks already granted to that lock-owner, in
or in part, and the server does not support such locking operations whole or in part, and the server does not support such locking
(i.e. does not support POSIX locking semantics), the server will operations (i.e., does not support POSIX locking semantics), the
return the error NFS4ERR_LOCK_RANGE. In that case, the client may server will return the error NFS4ERR_LOCK_RANGE. In that case, the
return an error, or it may emulate the required operations, using client may return an error, or it may emulate the required
only LOCK for ranges that do not include any bytes already locked by operations, using only LOCK for ranges that do not include any bytes
that lock-owner and LOCKU of locks held by that lock-owner already locked by that lock-owner and LOCKU of locks held by that
(specifying an exactly-matching range and type). Similarly, when the lock-owner (specifying an exactly matching range and type).
client makes a lock request that amounts to upgrading (changing from Similarly, when the client sends a LOCK operation that amounts to
a read lock to a write lock) or downgrading (changing from write lock upgrading (changing from a READ_LT lock to a WRITE_LT lock) or
to a read lock) an existing byte-range lock, and the server does not downgrading (changing from WRITE_LT lock to a READ_LT lock) an
support such a lock, the server will return NFS4ERR_LOCK_NOTSUPP. existing byte-range lock, and the server does not support such a
Such operations may not perfectly reflect the required semantics in lock, the server will return NFS4ERR_LOCK_NOTSUPP. Such operations
the face of conflicting lock requests from other clients. may not perfectly reflect the required semantics in the face of
conflicting LOCK operations from other clients.
When a client holds a write delegation, the client holding that When a client holds an OPEN_DELEGATE_WRITE delegation, the client
delegation is assured that there are no opens by other clients. holding that delegation is assured that there are no opens by other
Thus, there can be no conflicting LOCK requests from such clients. clients. Thus, there can be no conflicting LOCK operations from such
Therefore, the client may be handling locking requests locally, clients. Therefore, the client may be handling locking requests
without doing LOCK operations on the server. If it does that, it locally, without doing LOCK operations on the server. If it does
must be prepared to update the lock status on the server, by doing that, it must be prepared to update the lock status on the server, by
appropriate LOCK and LOCKU requests before returning the delegation. sending appropriate LOCK and LOCKU operations before returning the
delegation.
When one or more clients hold read delegations, any LOCK request When one or more clients hold OPEN_DELEGATE_READ delegations, any
where the server is implementing mandatory locking semantics, MUST LOCK operation where the server is implementing mandatory locking
result in the recall of all such delegations. The LOCK request may semantics MUST result in the recall of all such delegations. The
not be granted until all such delegations are return or revoked. LOCK operation may not be granted until all such delegations are
Except where this happens very quickly, one or more NFS4ERR_DELAY returned or revoked. Except where this happens very quickly, one or
errors will be returned to requests made while the delegation remains more NFS4ERR_DELAY errors will be returned to requests made while the
outstanding. delegation remains outstanding.
18.11. Operation 13: LOCKT - Test For Lock 18.11. Operation 13: LOCKT - Test for Lock
18.11.1. ARGUMENTS 18.11.1. ARGUMENTS
struct LOCKT4args { struct LOCKT4args {
/* CURRENT_FH: file */ /* CURRENT_FH: file */
nfs_lock_type4 locktype; nfs_lock_type4 locktype;
offset4 offset; offset4 offset;
length4 length; length4 length;
lock_owner4 owner; lock_owner4 owner;
}; };
skipping to change at page 433, line 33 skipping to change at page 434, line 34
void; void;
default: default:
void; void;
}; };
18.11.3. DESCRIPTION 18.11.3. DESCRIPTION
The LOCKT operation tests the lock as specified in the arguments. If The LOCKT operation tests the lock as specified in the arguments. If
a conflicting lock exists, the owner, offset, length, and type of the a conflicting lock exists, the owner, offset, length, and type of the
conflicting lock are returned. The owner field in the results conflicting lock are returned. The owner field in the results
includes the client ID of the owner of conflicting lock, whether this includes the client ID of the owner of the conflicting lock, whether
is the client ID associated with the current session or a different this is the client ID associated with the current session or a
client ID. If no lock is held, nothing other than NFS4_OK is different client ID. If no lock is held, nothing other than NFS4_OK
returned. Lock types READ_LT and READW_LT are processed in the same is returned. Lock types READ_LT and READW_LT are processed in the
way in that a conflicting lock test is done without regard to same way in that a conflicting lock test is done without regard to
blocking or non-blocking. The same is true for WRITE_LT and blocking or non-blocking. The same is true for WRITE_LT and
WRITEW_LT. WRITEW_LT.
The ranges are specified as for LOCK. The NFS4ERR_INVAL and The ranges are specified as for LOCK. The NFS4ERR_INVAL and
NFS4ERR_BAD_RANGE errors are returned under the same circumstances as NFS4ERR_BAD_RANGE errors are returned under the same circumstances as
for LOCK. for LOCK.
The clientid field of the owner MAY be set to any value by the client The clientid field of the owner MAY be set to any value by the client
and MUST be ignored by the server. The reason the server MUST ignore and MUST be ignored by the server. The reason the server MUST ignore
the clientid field is that the server MUST derive the client ID from the clientid field is that the server MUST derive the client ID from
the session ID from the SEQUENCE operation of the COMPOUND request. the session ID from the SEQUENCE operation of the COMPOUND request.
If the current filehandle is not an ordinary file, an error will be If the current filehandle is not an ordinary file, an error will be
returned to the client. In the case that the current filehandle returned to the client. In the case that the current filehandle
represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. if represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. If
the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is
returned. In all other cases, NFS4ERR_WRONG_TYPE is returned. returned. In all other cases, NFS4ERR_WRONG_TYPE is returned.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.11.4. IMPLEMENTATION 18.11.4. IMPLEMENTATION
If the server is unable to determine the exact offset and length of If the server is unable to determine the exact offset and length of
the conflicting lock, the same offset and length that were provided the conflicting lock, the same offset and length that were provided
in the arguments should be returned in the denied results. in the arguments should be returned in the denied results.
LOCKT uses a lock_owner4 rather a stateid4, as is used in LOCK to LOCKT uses a lock_owner4 rather a stateid4, as is used in LOCK to
identify the owner. This is because the client does not have to open identify the owner. This is because the client does not have to open
the file to test for the existence of a lock, so a stateid might not the file to test for the existence of a lock, so a stateid might not
be available. be available.
As noted in Section 18.10.4, some servers may return As noted in Section 18.10.4, some servers may return
NFS4ERR_LOCK_RANGE to certain (otherwise non-conflicting) lock NFS4ERR_LOCK_RANGE to certain (otherwise non-conflicting) LOCK
requests that overlap ranges already granted to the current lock- operations that overlap ranges already granted to the current lock-
owner. owner.
The LOCKT operation's test for conflicting locks SHOULD exclude locks The LOCKT operation's test for conflicting locks SHOULD exclude locks
for the current lock-owner, and thus should return NFS4_OK in such for the current lock-owner, and thus should return NFS4_OK in such
cases. Note that this means that a server might return NFS4_OK to a cases. Note that this means that a server might return NFS4_OK to a
LOCKT request even though a LOCK request for the same range and lock- LOCKT request even though a LOCK operation for the same range and
owner would fail with NFS4ERR_LOCK_RANGE. lock-owner would fail with NFS4ERR_LOCK_RANGE.
When a client holds a write delegation, it may choose (see When a client holds an OPEN_DELEGATE_WRITE delegation, it may choose
Section 18.10.4) to handle LOCK requests locally. In such a case, (see Section 18.10.4) to handle LOCK requests locally. In such a
LOCKT requests will similarly be handled locally. case, LOCKT requests will similarly be handled locally.
18.12. Operation 14: LOCKU - Unlock File 18.12. Operation 14: LOCKU - Unlock File
18.12.1. ARGUMENTS 18.12.1. ARGUMENTS
struct LOCKU4args { struct LOCKU4args {
/* CURRENT_FH: file */ /* CURRENT_FH: file */
nfs_lock_type4 locktype; nfs_lock_type4 locktype;
seqid4 seqid; seqid4 seqid;
stateid4 lock_stateid; stateid4 lock_stateid;
skipping to change at page 435, line 30 skipping to change at page 436, line 30
has no effect on the success or failure of the LOCKU operation. has no effect on the success or failure of the LOCKU operation.
The ranges are specified as for LOCK. The NFS4ERR_INVAL and The ranges are specified as for LOCK. The NFS4ERR_INVAL and
NFS4ERR_BAD_RANGE errors are returned under the same circumstances as NFS4ERR_BAD_RANGE errors are returned under the same circumstances as
for LOCK. for LOCK.
The seqid parameter MAY be any value and the server MUST ignore it. The seqid parameter MAY be any value and the server MUST ignore it.
If the current filehandle is not an ordinary file, an error will be If the current filehandle is not an ordinary file, an error will be
returned to the client. In the case that the current filehandle returned to the client. In the case that the current filehandle
represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. if represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. If
the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is
returned. In all other cases, NFS4ERR_WRONG_TYPE is returned. returned. In all other cases, NFS4ERR_WRONG_TYPE is returned.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
The server MAY require that the principal, security flavor, and The server MAY require that the principal, security flavor, and if
applicable, the GSS mechanism, combination that sent a LOCK request applicable, the GSS mechanism, combination that sent a LOCK operation
also be the one to send LOCKU on the file. This might not be also be the one to send LOCKU on the file. This might not be
possible if credentials for the principal are no longer available. possible if credentials for the principal are no longer available.
The server MAY allow the machine credential or SSV credential (see The server MAY allow the machine credential or SSV credential (see
Section 18.35) to send LOCKU. Section 18.35) to send LOCKU.
18.12.4. IMPLEMENTATION 18.12.4. IMPLEMENTATION
If the area to be unlocked does not correspond exactly to a lock If the area to be unlocked does not correspond exactly to a lock
actually held by the lock-owner the server may return the error actually held by the lock-owner, the server may return the error
NFS4ERR_LOCK_RANGE. This includes the case in which the area is not NFS4ERR_LOCK_RANGE. This includes the case in which the area is not
locked, where the area is a sub-range of the area locked, where it locked, where the area is a sub-range of the area locked, where it
overlaps the area locked without matching exactly or the area overlaps the area locked without matching exactly, or the area
specified includes multiple locks held by the lock-owner. In all of specified includes multiple locks held by the lock-owner. In all of
these cases, allowed by POSIX locking [24] semantics, a client these cases, allowed by POSIX locking [24] semantics, a client
receiving this error, should if it desires support for such receiving this error should, if it desires support for such
operations, simulate the operation using LOCKU on ranges operations, simulate the operation using LOCKU on ranges
corresponding to locks it actually holds, possibly followed by LOCK corresponding to locks it actually holds, possibly followed by LOCK
requests for the sub-ranges not being unlocked. operations for the sub-ranges not being unlocked.
When a client holds a write delegation, it may choose (See When a client holds an OPEN_DELEGATE_WRITE delegation, it may choose
Section 18.10.4) to handle LOCK requests locally. In such a case, (see Section 18.10.4) to handle LOCK requests locally. In such a
LOCKU requests will similarly be handled locally. case, LOCKU operations will similarly be handled locally.
18.13. Operation 15: LOOKUP - Lookup Filename 18.13. Operation 15: LOOKUP - Lookup Filename
18.13.1. ARGUMENTS 18.13.1. ARGUMENTS
struct LOOKUP4args { struct LOOKUP4args {
/* CURRENT_FH: directory */ /* CURRENT_FH: directory */
component4 objname; component4 objname;
}; };
18.13.2. RESULTS 18.13.2. RESULTS
struct LOOKUP4res { struct LOOKUP4res {
/* New CURRENT_FH: object */ /* New CURRENT_FH: object */
nfsstat4 status; nfsstat4 status;
}; };
18.13.3. DESCRIPTION 18.13.3. DESCRIPTION
This operation LOOKUPs or finds a file system object using the The LOOKUP operation looks up or finds a file system object using the
directory specified by the current filehandle. LOOKUP evaluates the directory specified by the current filehandle. LOOKUP evaluates the
component and if the object exists the current filehandle is replaced component and if the object exists, the current filehandle is
with the component's filehandle. replaced with the component's filehandle.
If the component cannot be evaluated either because it does not exist If the component cannot be evaluated either because it does not exist
or because the client does not have permission to evaluate the or because the client does not have permission to evaluate the
component, then an error will be returned and the current filehandle component, then an error will be returned and the current filehandle
will be unchanged. will be unchanged.
If the component is a zero length string or if any component does not If the component is a zero-length string or if any component does not
obey the UTF-8 definition, the error NFS4ERR_INVAL will be returned. obey the UTF-8 definition, the error NFS4ERR_INVAL will be returned.
18.13.4. IMPLEMENTATION 18.13.4. IMPLEMENTATION
If the client wants to achieve the effect of a multi-component If the client wants to achieve the effect of a multi-component look
lookup, it may construct a COMPOUND request such as (and obtain each up, it may construct a COMPOUND request such as (and obtain each
filehandle): filehandle):
PUTFH (directory filehandle) PUTFH (directory filehandle)
LOOKUP "pub" LOOKUP "pub"
GETFH GETFH
LOOKUP "foo" LOOKUP "foo"
GETFH GETFH
LOOKUP "bar" LOOKUP "bar"
GETFH GETFH
Unlike NFSv3, NFSv4.1 allows LOOKUP requests to cross mountpoints on Unlike NFSv3, NFSv4.1 allows LOOKUP requests to cross mountpoints on
the server. The client can detect a mountpoint crossing by comparing the server. The client can detect a mountpoint crossing by comparing
the fsid attribute of the directory with the fsid attribute of the the fsid attribute of the directory with the fsid attribute of the
directory looked up. If the fsids are different then the new directory looked up. If the fsids are different, then the new
directory is a server mountpoint. UNIX clients that detect a directory is a server mountpoint. UNIX clients that detect a
mountpoint crossing will need to mount the server's file system. mountpoint crossing will need to mount the server's file system.
This needs to be done to maintain the file object identity checking This needs to be done to maintain the file object identity checking
mechanisms common to UNIX clients. mechanisms common to UNIX clients.
Servers that limit NFS access to "shares" or "exported" file systems Servers that limit NFS access to "shared" or "exported" file systems
should provide a pseudo file system into which the exported file should provide a pseudo file system into which the exported file
systems can be integrated, so that clients can browse the server's systems can be integrated, so that clients can browse the server's
name space. The clients view of a pseudo file system will be limited name space. The clients view of a pseudo file system will be limited
to paths that lead to exported file systems. to paths that lead to exported file systems.
Note: previous versions of the protocol assigned special semantics to Note: previous versions of the protocol assigned special semantics to
the names "." and "..". NFSv4.1 assigns no special semantics to the names "." and "..". NFSv4.1 assigns no special semantics to
these names. The LOOKUPP operator must be used to lookup a parent these names. The LOOKUPP operator must be used to lookup a parent
directory. directory.
Note that this operation does not follow symbolic links. The client Note that this operation does not follow symbolic links. The client
is responsible for all parsing of filenames including filenames that is responsible for all parsing of filenames including filenames that
are modified by symbolic links encountered during the lookup process. are modified by symbolic links encountered during the look up
process.
If the current filehandle supplied is not a directory but a symbolic If the current filehandle supplied is not a directory but a symbolic
link, the error NFS4ERR_SYMLINK is returned as the error. For all link, the error NFS4ERR_SYMLINK is returned as the error. For all
other non-directory file types, the error NFS4ERR_NOTDIR is returned. other non-directory file types, the error NFS4ERR_NOTDIR is returned.
18.14. Operation 16: LOOKUPP - Lookup Parent Directory 18.14. Operation 16: LOOKUPP - Lookup Parent Directory
18.14.1. ARGUMENTS 18.14.1. ARGUMENTS
/* CURRENT_FH: object */ /* CURRENT_FH: object */
skipping to change at page 438, line 17 skipping to change at page 439, line 17
struct LOOKUPP4res { struct LOOKUPP4res {
/* new CURRENT_FH: parent directory */ /* new CURRENT_FH: parent directory */
nfsstat4 status; nfsstat4 status;
}; };
18.14.3. DESCRIPTION 18.14.3. DESCRIPTION
The current filehandle is assumed to refer to a regular directory or The current filehandle is assumed to refer to a regular directory or
a named attribute directory. LOOKUPP assigns the filehandle for its a named attribute directory. LOOKUPP assigns the filehandle for its
parent directory to be the current filehandle. If there is no parent parent directory to be the current filehandle. If there is no parent
directory an NFS4ERR_NOENT error must be returned. Therefore, directory, an NFS4ERR_NOENT error must be returned. Therefore,
NFS4ERR_NOENT will be returned by the server when the current NFS4ERR_NOENT will be returned by the server when the current
filehandle is at the root or top of the server's file tree. filehandle is at the root or top of the server's file tree.
As is the case with LOOKUP, LOOKUPP will also cross mountpoints. As is the case with LOOKUP, LOOKUPP will also cross mountpoints.
If the current filehandle is not a directory or named attribute If the current filehandle is not a directory or named attribute
directory, the error NFS4ERR_NOTDIR is returned. directory, the error NFS4ERR_NOTDIR is returned.
If the requester's security flavor does not match that configured for If the requester's security flavor does not match that configured for
the parent directory, then the server SHOULD return NFS4ERR_WRONGSEC the parent directory, then the server SHOULD return NFS4ERR_WRONGSEC
(a future minor revision of NFSv4 may upgrade this to MUST) in the (a future minor revision of NFSv4 may upgrade this to MUST) in the
LOOKUPP response. However, if the server does so, it MUST support LOOKUPP response. However, if the server does so, it MUST support
the SECINFO_NO_NAME operation (Section 18.45), so that the client can the SECINFO_NO_NAME operation (Section 18.45), so that the client can
gracefully determine the correct security flavor. gracefully determine the correct security flavor.
If the current filehandle is a named attribute directory that is If the current filehandle is a named attribute directory that is
associated with a file system object via OPENATTR (i.e. not a sub- associated with a file system object via OPENATTR (i.e., not a sub-
directory of a named attribute directory) LOOKUPP SHOULD return the directory of a named attribute directory), LOOKUPP SHOULD return the
filehandle of the associated file system object. filehandle of the associated file system object.
18.14.4. IMPLEMENTATION 18.14.4. IMPLEMENTATION
An issue to note is upward navigation from named attribute An issue to note is upward navigation from named attribute
directories. The named attribute directories are essentially directories. The named attribute directories are essentially
detached from the namespace and this property should be safely detached from the namespace, and this property should be safely
represented in the client operating environment. LOOKUPP on a named represented in the client operating environment. LOOKUPP on a named
attribute directory may return the filehandle of the associated file attribute directory may return the filehandle of the associated file,
and conveying this to applications might be unsafe as many and conveying this to applications might be unsafe as many
applications expect the parent of an object to always be a directory. applications expect the parent of an object to always be a directory.
Therefore the client may want to hide the parent of named attribute Therefore, the client may want to hide the parent of named attribute
directories (represented as ".." in UNIX) or represent the named directories (represented as ".." in UNIX) or represent the named
attribute directory as its own parent (as typically done for the file attribute directory as its own parent (as is typically done for the
system root directory in UNIX). file system root directory in UNIX).
18.15. Operation 17: NVERIFY - Verify Difference in Attributes 18.15. Operation 17: NVERIFY - Verify Difference in Attributes
18.15.1. ARGUMENTS 18.15.1. ARGUMENTS
struct NVERIFY4args { struct NVERIFY4args {
/* CURRENT_FH: object */ /* CURRENT_FH: object */
fattr4 obj_attributes; fattr4 obj_attributes;
}; };
18.15.2. RESULTS 18.15.2. RESULTS
struct NVERIFY4res { struct NVERIFY4res {
nfsstat4 status; nfsstat4 status;
}; };
18.15.3. DESCRIPTION 18.15.3. DESCRIPTION
This operation is used to prefix a sequence of operations to be This operation is used to prefix a sequence of operations to be
performed if one or more attributes have changed on some file system performed if one or more attributes have changed on some file system
object. If all the attributes match then the error NFS4ERR_SAME MUST object. If all the attributes match, then the error NFS4ERR_SAME
be returned. MUST be returned.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.15.4. IMPLEMENTATION 18.15.4. IMPLEMENTATION
This operation is useful as a cache validation operator. If the This operation is useful as a cache validation operator. If the
object to which the attributes belong has changed then the following object to which the attributes belong has changed, then the following
operations may obtain new data associated with that object. For operations may obtain new data associated with that object, for
instance, to check if a file has been changed and obtain new data if instance, to check if a file has been changed and obtain new data if
it has: it has:
SEQUENCE SEQUENCE
PUTFH fh PUTFH fh
NVERIFY attrbits attrs NVERIFY attrbits attrs
READ 0 32767 READ 0 32767
Contrast this with NFSv3, which would first send a GETATTR in one Contrast this with NFSv3, which would first send a GETATTR in one
request/reply round trip, and then if attributes indicated that the request/reply round trip, and then if attributes indicated that the
client's cache was stale, then send a READ in another request/reply client's cache was stale, then send a READ in another request/reply
round trip. round trip.
In the case that a RECOMMENDED attribute is specified in the NVERIFY In the case that a RECOMMENDED attribute is specified in the NVERIFY
operation and the server does not support that attribute for the file operation and the server does not support that attribute for the file
system object, the error NFS4ERR_ATTRNOTSUPP is returned to the system object, the error NFS4ERR_ATTRNOTSUPP is returned to the
client. client.
When the attribute rdattr_error or any set-only attribute (e.g. When the attribute rdattr_error or any set-only attribute (e.g.,
time_modify_set) is specified, the error NFS4ERR_INVAL is returned to time_modify_set) is specified, the error NFS4ERR_INVAL is returned to
the client. the client.
18.16. Operation 18: OPEN - Open a Regular File 18.16. Operation 18: OPEN - Open a Regular File
18.16.1. ARGUMENTS 18.16.1. ARGUMENTS
/* /*
* Various definitions for OPEN * Various definitions for OPEN
*/ */
skipping to change at page 444, line 23 skipping to change at page 445, line 23
* a delegation granted by the server. * a delegation granted by the server.
* File is identified by filehandle. * File is identified by filehandle.
*/ */
case CLAIM_DELEG_CUR_FH: /* new to v4.1 */ case CLAIM_DELEG_CUR_FH: /* new to v4.1 */
/* CURRENT_FH: file being opened */ /* CURRENT_FH: file being opened */
stateid4 oc_delegate_stateid; stateid4 oc_delegate_stateid;
}; };
/* /*
* OPEN: Open a file, potentially receiving an open delegation * OPEN: Open a file, potentially receiving an OPEN delegation
*/ */
struct OPEN4args { struct OPEN4args {
seqid4 seqid; seqid4 seqid;
uint32_t share_access; uint32_t share_access;
uint32_t share_deny; uint32_t share_deny;
open_owner4 owner; open_owner4 owner;
openflag4 openhow; openflag4 openhow;
open_claim4 claim; open_claim4 claim;
}; };
skipping to change at page 446, line 46 skipping to change at page 447, line 46
OPEN4resok resok4; OPEN4resok resok4;
default: default:
void; void;
}; };
18.16.3. DESCRIPTION 18.16.3. DESCRIPTION
The OPEN operation opens a regular file in a directory with the The OPEN operation opens a regular file in a directory with the
provided name or filehandle. OPEN can also create a file if a name provided name or filehandle. OPEN can also create a file if a name
is provided, and the client specifies it wants to create a file. is provided, and the client specifies it wants to create a file.
Specification whether a file is be created or not, and the method of Specification of whether or not a file is to be created, and the
creation is via the openhow parameter. The openhow parameter method of creation is via the openhow parameter. The openhow
consists of a switched union (data type opengflag4), which switches parameter consists of a switched union (data type opengflag4), which
on the value of opentype (OPEN4_NOCREATE or OPEN4_CREATE). If switches on the value of opentype (OPEN4_NOCREATE or OPEN4_CREATE).
OPEN4_CREATE is specified, this leads to another switched union (data If OPEN4_CREATE is specified, this leads to another switched union
type createhow4) that supports four cases of creation methods: (data type createhow4) that supports four cases of creation methods:
UNCHECKED4, GUARDED4, EXCLUSIVE4, or EXCLUSIVE4_1. If opentype is UNCHECKED4, GUARDED4, EXCLUSIVE4, or EXCLUSIVE4_1. If opentype is
OPEN4_CREATE, then the claim field of the claim field (sic) MUST be OPEN4_CREATE, then the claim field of the claim field MUST be one of
one of CLAIM_NULL, CLAIM_DELEGATE_CUR, or CLAIM_DELEGATE_PREV, CLAIM_NULL, CLAIM_DELEGATE_CUR, or CLAIM_DELEGATE_PREV, because these
because these claim methods include a component of a file name. claim methods include a component of a file name.
Upon success (which might entail creation of a new file), the current Upon success (which might entail creation of a new file), the current
filehandle is replaced by that of the created or existing object. filehandle is replaced by that of the created or existing object.
If the current filehandle is a named attribute directory, OPEN will If the current filehandle is a named attribute directory, OPEN will
then create or open a named attribute file. Note that exclusive then create or open a named attribute file. Note that exclusive
create of a named attribute is not supported. If the createmode is create of a named attribute is not supported. If the createmode is
EXCLUSIVE4 or EXCLUSIVE4_1 and the current filehandle is a named EXCLUSIVE4 or EXCLUSIVE4_1 and the current filehandle is a named
attribute directory, the server will return EINVAL. attribute directory, the server will return EINVAL.
skipping to change at page 448, line 16 skipping to change at page 449, line 16
client MUST send a SETATTR to set attributes to a known state. client MUST send a SETATTR to set attributes to a known state.
In NFSv4.1, EXCLUSIVE4 has been deprecated in favor of EXCLUSIVE4_1. In NFSv4.1, EXCLUSIVE4 has been deprecated in favor of EXCLUSIVE4_1.
Unlike EXCLUSIVE4, attributes may be provided in the EXCLUSIVE4_1 Unlike EXCLUSIVE4, attributes may be provided in the EXCLUSIVE4_1
case, but because the server may use attributes of the target object case, but because the server may use attributes of the target object
to store the verifier, the set of allowable attributes may be fewer to store the verifier, the set of allowable attributes may be fewer
than the set of attributes SETATTR allows. The allowable attributes than the set of attributes SETATTR allows. The allowable attributes
for EXCLUSIVE4_1 are indicated in the suppattr_exclcreat for EXCLUSIVE4_1 are indicated in the suppattr_exclcreat
(Section 5.8.1.14) attribute. If the client attempts to set in (Section 5.8.1.14) attribute. If the client attempts to set in
cva_attrs an attribute that is not in suppattr_exclcreat, the server cva_attrs an attribute that is not in suppattr_exclcreat, the server
MUST return NFS4ERR_INVAL. The response field, attrset indicates MUST return NFS4ERR_INVAL. The response field, attrset, indicates
both which attributes the server set from cva_attrs, and which both which attributes the server set from cva_attrs and which
attributes the server used to store the verifier. As described in attributes the server used to store the verifier. As described in
Section 18.16.4, the client can compare cva_attrs.attrmask with Section 18.16.4, the client can compare cva_attrs.attrmask with
attrset to determine which attributes were used to store the attrset to determine which attributes were used to store the
verifier. verifier.
With the addition of persistent sessions and pNFS, under some With the addition of persistent sessions and pNFS, under some
conditions EXCLUSIVE4 MUST NOT be used by the client or supported by conditions EXCLUSIVE4 MUST NOT be used by the client or supported by
the server. The following table summarizes the appropriate and the server. The following table summarizes the appropriate and
mandated exclusive create methods for implementations of NFSv4.1: mandated exclusive create methods for implementations of NFSv4.1:
skipping to change at page 448, line 47 skipping to change at page 449, line 47
| | | EXCLUSIVE4 | EXCLUSIVE4 (SHOULD | | | | EXCLUSIVE4 | EXCLUSIVE4 (SHOULD |
| | | | NOT) | | | | | NOT) |
| no | yes | EXCLUSIVE4_1 | EXCLUSIVE4_1 | | no | yes | EXCLUSIVE4_1 | EXCLUSIVE4_1 |
| yes | no | GUARDED4 | GUARDED4 | | yes | no | GUARDED4 | GUARDED4 |
| yes | yes | GUARDED4 | GUARDED4 | | yes | yes | GUARDED4 | GUARDED4 |
+----------------+-----------+---------------+----------------------+ +----------------+-----------+---------------+----------------------+
Table 10 Table 10
If CREATE_SESSION4_FLAG_PERSIST is set in the results of If CREATE_SESSION4_FLAG_PERSIST is set in the results of
CREATE_SESSION the reply cache is persistent (see Section 18.36). If CREATE_SESSION, the reply cache is persistent (see Section 18.36).
the EXCHGID4_FLAG_USE_PNFS_MDS flag is set in the results from If the EXCHGID4_FLAG_USE_PNFS_MDS flag is set in the results from
EXCHANGE_ID, the server is a pNFS server (see Section 18.35). If the EXCHANGE_ID, the server is a pNFS server (see Section 18.35). If the
client attempts to use EXCLUSIVE4 on a persistent session, or a client attempts to use EXCLUSIVE4 on a persistent session, or a
session derived from a EXCHGID4_FLAG_USE_PNFS_MDS client ID, the session derived from an EXCHGID4_FLAG_USE_PNFS_MDS client ID, the
server MUST return NFS4ERR_INVAL. server MUST return NFS4ERR_INVAL.
With persistent sessions, exclusive create semantics are fully With persistent sessions, exclusive create semantics are fully
achievable via GUARDED4, and so EXCLUSIVE4 or EXCLUSIVE4_1 MUST NOT achievable via GUARDED4, and so EXCLUSIVE4 or EXCLUSIVE4_1 MUST NOT
be used. When pNFS is being used, the layout_hint attribute might be used. When pNFS is being used, the layout_hint attribute might
not be supported after the file is created. Only the EXCLUSIVE4_1 not be supported after the file is created. Only the EXCLUSIVE4_1
and GUARDED methods of exclusive file creation allow the atomic and GUARDED methods of exclusive file creation allow the atomic
setting of attributes. setting of attributes.
For the target directory, the server returns change_info4 information For the target directory, the server returns change_info4 information
in cinfo. With the atomic field of the change_info4 data type, the in cinfo. With the atomic field of the change_info4 data type, the
server will indicate if the before and after change attributes were server will indicate if the before and after change attributes were
obtained atomically with respect to the link creation. obtained atomically with respect to the link creation.
The OPEN operation provides for Windows share reservation capability The OPEN operation provides for Windows share reservation capability
with the use of the share_access and share_deny fields of the OPEN with the use of the share_access and share_deny fields of the OPEN
arguments. The client specifies at OPEN the required share_access arguments. The client specifies at OPEN the required share_access
and share_deny modes. For clients that do not directly support and share_deny modes. For clients that do not directly support
SHAREs (i.e. UNIX), the expected deny value is DENY_NONE. In the SHAREs (i.e., UNIX), the expected deny value is
case that there is a existing SHARE reservation that conflicts with OPEN4_SHARE_DENY_NONE. In the case that there is an existing SHARE
the OPEN request, the server returns the error NFS4ERR_SHARE_DENIED. reservation that conflicts with the OPEN request, the server returns
For additional discussion of SHARE semantics see Section 9.7. the error NFS4ERR_SHARE_DENIED. For additional discussion of SHARE
semantics, see Section 9.7.
For each OPEN, the client provides a value for the owner field of the For each OPEN, the client provides a value for the owner field of the
OPEN argument. The owner field is of data type open_owner4, and OPEN argument. The owner field is of data type open_owner4, and
contains a field called clientid and a field called owner. The contains a field called clientid and a field called owner. The
client can set the clientid field to any value and the server MUST client can set the clientid field to any value and the server MUST
ignore it. Instead the server MUST derive the client ID from the ignore it. Instead, the server MUST derive the client ID from the
session ID of the SEQUENCE operation of the COMPOUND request. session ID of the SEQUENCE operation of the COMPOUND request.
The seqid field of the request is not used in NFSv4.1, but it MAY be The "seqid" field of the request is not used in NFSv4.1, but it MAY
any value and the server MUST ignore it. be any value and the server MUST ignore it.
In the case that the client is recovering state from a server In the case that the client is recovering state from a server
failure, the claim field of the OPEN argument is used to signify that failure, the claim field of the OPEN argument is used to signify that
the request is meant to reclaim state previously held. the request is meant to reclaim state previously held.
The "claim" field of the OPEN argument is used to specify the file to The "claim" field of the OPEN argument is used to specify the file to
be opened and the state information which the client claims to be opened and the state information that the client claims to
possess. There are seven claim types as follows: possess. There are seven claim types as follows:
+----------------------+--------------------------------------------+ +----------------------+--------------------------------------------+
| open type | description | | open type | description |
+----------------------+--------------------------------------------+ +----------------------+--------------------------------------------+
| CLAIM_NULL, CLAIM_FH | For the client, this is a new OPEN request | | CLAIM_NULL, CLAIM_FH | For the client, this is a new OPEN request |
| | and there is no previous state associate | | | and there is no previous state associated |
| | with the file for the client. With | | | with the file for the client. With |
| | CLAIM_NULL the file is identified by the | | | CLAIM_NULL, the file is identified by the |
| | current filehandle and the specified | | | current filehandle and the specified |
| | component name. With CLAIM_FH (new to | | | component name. With CLAIM_FH (new to |
| | NFSv4.1) the file is identified by just | | | NFSv4.1), the file is identified by just |
| | the current filehandle. | | | the current filehandle. |
| CLAIM_PREVIOUS | The client is claiming basic OPEN state | | CLAIM_PREVIOUS | The client is claiming basic OPEN state |
| | for a file that was held previous to a | | | for a file that was held previous to a |
| | server restart. Generally used when a | | | server restart. Generally used when a |
| | server is returning persistent | | | server is returning persistent |
| | filehandles; the client may not have the | | | filehandles; the client may not have the |
| | file name to reclaim the OPEN. | | | file name to reclaim the OPEN. |
| CLAIM_DELEGATE_CUR, | The client is claiming a delegation for | | CLAIM_DELEGATE_CUR, | The client is claiming a delegation for |
| CLAIM_DELEG_CUR_FH | OPEN as granted by the server. Generally | | CLAIM_DELEG_CUR_FH | OPEN as granted by the server. Generally, |
| | this is done as part of recalling a | | | this is done as part of recalling a |
| | delegation. With CLAIM_DELEGATE_CUR, the | | | delegation. With CLAIM_DELEGATE_CUR, the |
| | file is identified by the current | | | file is identified by the current |
| | filehandle and the specified component | | | filehandle and the specified component |
| | name. With CLAIM_DELEG_CUR_FH (new to | | | name. With CLAIM_DELEG_CUR_FH (new to |
| | NFSv4.1), the file is identified by just | | | NFSv4.1), the file is identified by just |
| | the current filehandle. | | | the current filehandle. |
| CLAIM_DELEGATE_PREV, | The client is claiming a delegation | | CLAIM_DELEGATE_PREV, | The client is claiming a delegation |
| CLAIM_DELEG_PREV_FH | granted to a previous client instance; | | CLAIM_DELEG_PREV_FH | granted to a previous client instance; |
| | used after the client restarts. The server | | | used after the client restarts. The server |
| | MAY support CLAIM_DELEGATE_PREV or | | | MAY support CLAIM_DELEGATE_PREV and/or |
| | CLAIM_DELEG_PREV_FH (new to NFSv4.1). If | | | CLAIM_DELEG_PREV_FH (new to NFSv4.1). If |
| | it does support either open type, | | | it does support either claim type, |
| | CREATE_SESSION MUST NOT remove the | | | CREATE_SESSION MUST NOT remove the |
| | client's delegation state, and the server | | | client's delegation state, and the server |
| | MUST support the DELEGPURGE operation. | | | MUST support the DELEGPURGE operation. |
+----------------------+--------------------------------------------+ +----------------------+--------------------------------------------+
For OPEN requests that reach the server during the grace period, the For OPEN requests that reach the server during the grace period, the
server returns an error of NFS4ERR_GRACE. The following claim types server returns an error of NFS4ERR_GRACE. The following claim types
are exceptions: are exceptions:
o OPEN requests specifying the claim type CLAIM_PREVIOUS are devoted o OPEN requests specifying the claim type CLAIM_PREVIOUS are devoted
to reclaiming opens after a server restart and are typically only to reclaiming opens after a server restart and are typically only
valid during the grace period. valid during the grace period.
o OPEN requests specifying the claim types CLAIM_DELEGATE_CUR and o OPEN requests specifying the claim types CLAIM_DELEGATE_CUR and
CLAIM_DELEG_CUR_FH are valid both during and after the grace CLAIM_DELEG_CUR_FH are valid both during and after the grace
period. Since the granting of the delegation that they are period. Since the granting of the delegation that they are
subordinate to assures that there is no conflict with locks to be subordinate to assures that there is no conflict with locks to be
reclaimed by other clients, the server need not return reclaimed by other clients, the server need not return
NFS4ERR_GRACE when these are received during the grace period. NFS4ERR_GRACE when these are received during the grace period.
For any OPEN request, the server may return an open delegation, which For any OPEN request, the server may return an OPEN delegation, which
allows further opens and closes to be handled locally on the client allows further opens and closes to be handled locally on the client
as described in Section 10.4. Note that delegation is up to the as described in Section 10.4. Note that delegation is up to the
server to decide. The client should never assume that delegation server to decide. The client should never assume that delegation
will or will not be granted in a particular instance. It should will or will not be granted in a particular instance. It should
always be prepared for either case. A partial exception is the always be prepared for either case. A partial exception is the
reclaim (CLAIM_PREVIOUS) case, in which a delegation type is claimed. reclaim (CLAIM_PREVIOUS) case, in which a delegation type is claimed.
In this case, delegation will always be granted, although the server In this case, delegation will always be granted, although the server
may specify an immediate recall in the delegation structure. may specify an immediate recall in the delegation structure.
The rflags returned by a successful OPEN allow the server to return The rflags returned by a successful OPEN allow the server to return
information governing how the open file is to be handled. information governing how the open file is to be handled.
o OPEN4_RESULT_CONFIRM is deprecated and MUST NOT be returned by an o OPEN4_RESULT_CONFIRM is deprecated and MUST NOT be returned by an
NFSv4.1 server. NFSv4.1 server.
o OPEN4_RESULT_LOCKTYPE_POSIX indicates the server's file locking o OPEN4_RESULT_LOCKTYPE_POSIX indicates that the server's byte-range
behavior supports the complete set of POSIX locking techniques locking behavior supports the complete set of POSIX locking
[24]. From this the client can choose to manage file locking techniques [24]. From this, the client can choose to manage byte-
state in a way to handle a mis-match of file locking management. range locking state in a way to handle a mismatch of byte-range
locking management.
o OPEN4_RESULT_PRESERVE_UNLINKED indicates the server will preserve o OPEN4_RESULT_PRESERVE_UNLINKED indicates that the server will
the open file if the client (or any other client) removes the file preserve the open file if the client (or any other client) removes
as long as it is open. Furthermore, the server promises to the file as long as it is open. Furthermore, the server promises
preserve the file through the grace period after server restart, to preserve the file through the grace period after server
thereby giving the client the opportunity to reclaim its open. restart, thereby giving the client the opportunity to reclaim its
open.
o OPEN4_RESULT_MAY_NOTIFY_LOCK indicates that the server may attempt o OPEN4_RESULT_MAY_NOTIFY_LOCK indicates that the server may attempt
CB_NOTIFY_LOCK callbacks for locks on this file. This flag is a CB_NOTIFY_LOCK callbacks for locks on this file. This flag is a
hint only, and may be safely ignored by the client. hint only, and may be safely ignored by the client.
If the component is of zero length, NFS4ERR_INVAL will be returned. If the component is of zero length, NFS4ERR_INVAL will be returned.
The component is also subject to the normal UTF-8, character support, The component is also subject to the normal UTF-8, character support,
and name checks. See Section 14.5 for further discussion. and name checks. See Section 14.5 for further discussion.
When an OPEN is done and the specified open-owner already has the When an OPEN is done and the specified open-owner already has the
skipping to change at page 452, line 17 skipping to change at page 453, line 19
read-only mode and the OPEN request has specified ACCESS_WRITE or read-only mode and the OPEN request has specified ACCESS_WRITE or
ACCESS_BOTH, the server will return NFS4ERR_ROFS to indicate a read- ACCESS_BOTH, the server will return NFS4ERR_ROFS to indicate a read-
only file system. only file system.
As with the CREATE operation, the server MUST derive the owner, owner As with the CREATE operation, the server MUST derive the owner, owner
ACE, group, or group ACE if any of the four attributes are required ACE, group, or group ACE if any of the four attributes are required
and supported by the server's file system. For an OPEN with the and supported by the server's file system. For an OPEN with the
EXCLUSIVE4 createmode, the server has no choice, since such OPEN EXCLUSIVE4 createmode, the server has no choice, since such OPEN
calls do not include the createattrs field. Conversely, if calls do not include the createattrs field. Conversely, if
createattrs (UNCHECKED4 or GUARDED4) or cva_attrs (EXCLUSIVE4_1) is createattrs (UNCHECKED4 or GUARDED4) or cva_attrs (EXCLUSIVE4_1) is
specified, and includes an owner, or owner_group, or ACE that the specified, and includes an owner, owner_group, or ACE that the
principal in the RPC call's credentials does not have authorization principal in the RPC call's credentials does not have authorization
to create files for, then the server may return NFS4ERR_PERM. to create files for, then the server may return NFS4ERR_PERM.
In the case of an OPEN which specifies a size of zero (e.g. In the case of an OPEN that specifies a size of zero (e.g.,
truncation) and the file has named attributes, the named attributes truncation) and the file has named attributes, the named attributes
are left as is and are not removed. are left as is and are not removed.
NFSv4.1 gives more precise control to clients over acquisition of NFSv4.1 gives more precise control to clients over acquisition of
delegations via the following new flags for the share_access field of delegations via the following new flags for the share_access field of
OPEN4args: OPEN4args:
OPEN4_SHARE_ACCESS_WANT_READ_DELEG OPEN4_SHARE_ACCESS_WANT_READ_DELEG
OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG
skipping to change at page 452, line 47 skipping to change at page 454, line 4
OPEN4_SHARE_ACCESS_WANT_CANCEL OPEN4_SHARE_ACCESS_WANT_CANCEL
OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL
OPEN4_SHARE_ACCESS_WANT_PUSH_DELEG_WHEN_UNCONTENDED OPEN4_SHARE_ACCESS_WANT_PUSH_DELEG_WHEN_UNCONTENDED
If (share_access & OPEN4_SHARE_ACCESS_WANT_DELEG_MASK) is not zero, If (share_access & OPEN4_SHARE_ACCESS_WANT_DELEG_MASK) is not zero,
then the client will have specified one and only one of: then the client will have specified one and only one of:
OPEN4_SHARE_ACCESS_WANT_READ_DELEG OPEN4_SHARE_ACCESS_WANT_READ_DELEG
OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG
OPEN4_SHARE_ACCESS_WANT_ANY_DELEG OPEN4_SHARE_ACCESS_WANT_ANY_DELEG
OPEN4_SHARE_ACCESS_WANT_NO_DELEG OPEN4_SHARE_ACCESS_WANT_NO_DELEG
OPEN4_SHARE_ACCESS_WANT_CANCEL OPEN4_SHARE_ACCESS_WANT_CANCEL
Otherwise the client is indicating no desire for a delegation and the Otherwise, the client is neither indicating a desire nor a non-desire
server MAY or MAY not return a delegation in the OPEN response. for a delegation, and the server MAY or MAY not return a delegation
in the OPEN response.
If the server supports the new _WANT_ flags and the client sends one If the server supports the new _WANT_ flags and the client sends one
or more of the new flags, then in the event the server does not or more of the new flags, then in the event the server does not
return a delegation, it MUST return a delegation type of return a delegation, it MUST return a delegation type of
OPEN_DELEGATE_NONE_EXT. The field od_whynone in the reply indicates OPEN_DELEGATE_NONE_EXT. The field ond_why in the reply indicates why
why no delegation was returned and will be one of: no delegation was returned and will be one of:
WND4_NOT_WANTED The client specified WND4_NOT_WANTED The client specified
OPEN4_SHARE_ACCESS_WANT_NO_DELEG. OPEN4_SHARE_ACCESS_WANT_NO_DELEG.
WND4_CONTENTION There is a conflicting delegation or open on the WND4_CONTENTION There is a conflicting delegation or open on the
file. file.
WND4_RESOURCE Resource limitations prevent the server from granting WND4_RESOURCE Resource limitations prevent the server from granting
a delegation. a delegation.
WND4_NOT_SUPP_FTYPE The server does not support delegations on this WND4_NOT_SUPP_FTYPE The server does not support delegations on this
file type. file type.
WND4_WRITE_DELEG_NOT_SUPP_FTYPE The server does not support write WND4_WRITE_DELEG_NOT_SUPP_FTYPE The server does not support
delegations on this file type. OPEN_DELEGATE_WRITE delegations on this file type.
WND4_NOT_SUPP_UPGRADE The server does not support atomic upgrade of WND4_NOT_SUPP_UPGRADE The server does not support atomic upgrade of
a read delegation to a write delegation. an OPEN_DELEGATE_READ delegation to an OPEN_DELEGATE_WRITE
delegation.
WND4_NOT_SUPP_DOWNGRADE The server does not support atomic downgrade WND4_NOT_SUPP_DOWNGRADE The server does not support atomic downgrade
of a write delegation to a read delegation. of an OPEN_DELEGATE_WRITE delegation to an OPEN_DELEGATE_READ
delegation.
WND4_CANCELLED The client specified OPEN4_SHARE_ACCESS_WANT_CANCEL WND4_CANCELED The client specified OPEN4_SHARE_ACCESS_WANT_CANCEL
and now any "want" for this file object is cancelled. and now any "want" for this file object is cancelled.
WND4_IS_DIR The specified file object is a directory, and the WND4_IS_DIR The specified file object is a directory, and the
operation is OPEN or WANT_DELEGATION which do not support operation is OPEN or WANT_DELEGATION, which do not support
delegations on directories. delegations on directories.
OPEN4_SHARE_ACCESS_WANT_READ_DELEG, OPEN4_SHARE_ACCESS_WANT_READ_DELEG,
OPEN_SHARE_ACCESS_WANT_WRITE_DELEG, or OPEN_SHARE_ACCESS_WANT_WRITE_DELEG, or
OPEN_SHARE_ACCESS_WANT_ANY_DELEG mean, respectively, the client wants OPEN_SHARE_ACCESS_WANT_ANY_DELEG mean, respectively, the client wants
a read, write, or any delegation regardless which of an OPEN_DELEGATE_READ, OPEN_DELEGATE_WRITE, or any delegation
OPEN4_SHARE_ACCESS_READ, OPEN4_SHARE_ACCESS_WRITE, or regardless which of OPEN4_SHARE_ACCESS_READ,
OPEN4_SHARE_ACCESS_BOTH is set. If the client has a read delegation OPEN4_SHARE_ACCESS_WRITE, or OPEN4_SHARE_ACCESS_BOTH is set. If the
on a file, and requests a write delegation, then the client is client has an OPEN_DELEGATE_READ delegation on a file and requests an
requesting atomic upgrade of its read delegation to a write OPEN_DELEGATE_WRITE delegation, then the client is requesting atomic
delegation. If the client has a write delegation on a file, and upgrade of its OPEN_DELEGATE_READ delegation to an
requests a read delegation, then the client is requesting atomic OPEN_DELEGATE_WRITE delegation. If the client has an
downgrade to a read delegation. A server MAY support atomic upgrade OPEN_DELEGATE_WRITE delegation on a file and requests an
or downgrade. If it does, then the returned delegation_type of OPEN_DELEGATE_READ delegation, then the client is requesting atomic
OPEN_DELEGATE_READ or OPEN_DELEGATE_WRITE that is different than the downgrade to an OPEN_DELEGATE_READ delegation. A server MAY support
delegation type the client currently has, indicates successful atomic upgrade or downgrade. If it does, then the returned
upgrade or downgrade. If it does not support atomic delegation delegation_type of OPEN_DELEGATE_READ or OPEN_DELEGATE_WRITE that is
upgrade or downgrade, then od_whynone will be WND4_NOT_SUPP_UPGRADE different from the delegation type the client currently has,
or WND4_NOT_SUPP_DOWNGRADE. indicates successful upgrade or downgrade. If the server does not
support atomic delegation upgrade or downgrade, then ond_why will be
set to WND4_NOT_SUPP_UPGRADE or WND4_NOT_SUPP_DOWNGRADE.
OPEN4_SHARE_ACCESS_WANT_NO_DELEG means the client wants no OPEN4_SHARE_ACCESS_WANT_NO_DELEG means that the client wants no
delegation. delegation.
OPEN4_SHARE_ACCESS_WANT_CANCEL means the client wants no delegation OPEN4_SHARE_ACCESS_WANT_CANCEL means that the client wants no
and wants to cancel any previously registered "want" for a delegation and wants to cancel any previously registered "want" for a
delegation. delegation.
The client may set one or both of The client may set one or both of
OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL and OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL and
OPEN4_SHARE_ACCESS_WANT_PUSH_DELEG_WHEN_UNCONTENDED. However, they OPEN4_SHARE_ACCESS_WANT_PUSH_DELEG_WHEN_UNCONTENDED. However, they
will have no effect unless one of following are set: will have no effect unless one of following is set:
o OPEN4_SHARE_ACCESS_WANT_READ_DELEG o OPEN4_SHARE_ACCESS_WANT_READ_DELEG
o OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG o OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG
o OPEN4_SHARE_ACCESS_WANT_ANY_DELEG o OPEN4_SHARE_ACCESS_WANT_ANY_DELEG
If the client specifies If the client specifies
OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL, then it wishes OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL, then it wishes
to register a "want" for a delegation, in the event the OPEN results to register a "want" for a delegation, in the event the OPEN results
skipping to change at page 455, line 32 skipping to change at page 456, line 39
In absence of a persistent session, the client invokes exclusive In absence of a persistent session, the client invokes exclusive
create by setting the how parameter to EXCLUSIVE4 or EXCLUSIVE4_1. create by setting the how parameter to EXCLUSIVE4 or EXCLUSIVE4_1.
In these cases, the client provides a verifier that can reasonably be In these cases, the client provides a verifier that can reasonably be
expected to be unique. A combination of a client identifier, perhaps expected to be unique. A combination of a client identifier, perhaps
the client network address, and a unique number generated by the the client network address, and a unique number generated by the
client, perhaps the RPC transaction identifier, may be appropriate. client, perhaps the RPC transaction identifier, may be appropriate.
If the object does not exist, the server creates the object and If the object does not exist, the server creates the object and
stores the verifier in stable storage. For file systems that do not stores the verifier in stable storage. For file systems that do not
provide a mechanism for the storage of arbitrary file attributes, the provide a mechanism for the storage of arbitrary file attributes, the
server may use one or more elements of the object metadata to store server may use one or more elements of the object's metadata to store
the verifier. The verifier MUST be stored in stable storage to the verifier. The verifier MUST be stored in stable storage to
prevent erroneous failure on retransmission of the request. It is prevent erroneous failure on retransmission of the request. It is
assumed that an exclusive create is being performed because exclusive assumed that an exclusive create is being performed because exclusive
semantics are critical to the application. Because of the expected semantics are critical to the application. Because of the expected
usage, exclusive CREATE does not rely solely on the server's reply usage, exclusive CREATE does not rely solely on the server's reply
cache for storage of the verifier. A nonpersistent reply cache does cache for storage of the verifier. A nonpersistent reply cache does
not survive a crash and the session and reply cache may be deleted not survive a crash and the session and reply cache may be deleted
after a network partition that exceeds the lease time, thus opening after a network partition that exceeds the lease time, thus opening
failure windows. failure windows.
An NFSv4.1 server SHOULD NOT store the verifier in any of the file's An NFSv4.1 server SHOULD NOT store the verifier in any of the file's
RECOMMENDED or REQUIRED attributes. If it does, the server SHOULD RECOMMENDED or REQUIRED attributes. If it does, the server SHOULD
use time_modify_set or time_access_set to store the verifier. The use time_modify_set or time_access_set to store the verifier. The
server SHOULD NOT store the verifier in the following attributes: acl server SHOULD NOT store the verifier in the following attributes:
(it is desirable for access control to be established at creation),
dacl (ditto), mode (ditto), owner (ditto), owner_group (ditto), acl (it is desirable for access control to be established at
retentevt_set (it may be desired to establish retention at creation) creation),
retention_hold (ditto), retention_set (ditto), sacl (it is desirable
for auditing control to be established at creation), size (on some dacl (ditto),
servers, size may have a limited range of values), mode_set_masked
(as with mode), and time_creation (a meaningful file creation should mode (ditto),
be set when the file is created). Another alternative for the server
is to use a named attribute to store the verifier. owner (ditto),
owner_group (ditto),
retentevt_set (it may be desired to establish retention at
creation)
retention_hold (ditto),
retention_set (ditto),
sacl (it is desirable for auditing control to be established at
creation),
size (on some servers, size may have a limited range of values),
mode_set_masked (as with mode),
and
time_creation (a meaningful file creation should be set when the
file is created).
Another alternative for the server is to use a named attribute to
store the verifier.
Because the EXCLUSIVE4 create method does not specify initial Because the EXCLUSIVE4 create method does not specify initial
attributes, when processing an EXCLUSIVE4 create, the server attributes when processing an EXCLUSIVE4 create, the server
o SHOULD set the owner of the file to that corresponding to the o SHOULD set the owner of the file to that corresponding to the
credential of request's RPC header. credential of request's RPC header.
o SHOULD NOT leave the file's access control to anyone but the owner o SHOULD NOT leave the file's access control to anyone but the owner
of the file. of the file.
If the server cannot support exclusive create semantics, possibly If the server cannot support exclusive create semantics, possibly
because of the requirement to commit the verifier to stable storage, because of the requirement to commit the verifier to stable storage,
it should fail the OPEN request with the error, NFS4ERR_NOTSUPP. it should fail the OPEN request with the error NFS4ERR_NOTSUPP.
During an exclusive CREATE request, if the object already exists, the During an exclusive CREATE request, if the object already exists, the
server reconstructs the object's verifier and compares it with the server reconstructs the object's verifier and compares it with the
verifier in the request. If they match, the server treats the verifier in the request. If they match, the server treats the
request as a success. The request is presumed to be a duplicate of request as a success. The request is presumed to be a duplicate of
an earlier, successful request for which the reply was lost and that an earlier, successful request for which the reply was lost and that
the server duplicate request cache mechanism did not detect. If the the server duplicate request cache mechanism did not detect. If the
verifiers do not match, the request is rejected with the status, verifiers do not match, the request is rejected with the status
NFS4ERR_EXIST. NFS4ERR_EXIST.
After the client has performed a successful exclusive create, the After the client has performed a successful exclusive create, the
attrset response indicates which attributes were used to store the attrset response indicates which attributes were used to store the
verifier. If EXCLUSIVE4 was used, the attributes set in attrset were verifier. If EXCLUSIVE4 was used, the attributes set in attrset were
used for the verifier. If EXCLUSIVE4_1 was used, the client used for the verifier. If EXCLUSIVE4_1 was used, the client
determines the attributes used for the verifier by comparing attrset determines the attributes used for the verifier by comparing attrset
with cva_attrs.attrmask; any bits set in the former but not the with cva_attrs.attrmask; any bits set in the former but not the
latter identify the attributes used store the verifier. The client latter identify the attributes used to store the verifier. The
MUST immediately send a SETATTR to set attributes used to store the client MUST immediately send a SETATTR to set attributes used to
verifier. Until it does so, the attributes used to store the store the verifier. Until it does so, the attributes used to store
verifier cannot be relied upon. The subsequent SETATTR MUST NOT the verifier cannot be relied upon. The subsequent SETATTR MUST NOT
occur in the same COMPOUND request as the OPEN. occur in the same COMPOUND request as the OPEN.
Unless a persistent session is used, use of the GUARDED4 attribute Unless a persistent session is used, use of the GUARDED4 attribute
does not provide exactly-once semantics. In particular, if a reply does not provide exactly once semantics. In particular, if a reply
is lost and the server does not detect the retransmission of the is lost and the server does not detect the retransmission of the
request, the operation can fail with NFS4ERR_EXIST, even though the request, the operation can fail with NFS4ERR_EXIST, even though the
create was performed successfully. The client would use this create was performed successfully. The client would use this
behavior in the case that the application has not requested an behavior in the case that the application has not requested an
exclusive create but has asked to have the file truncated when the exclusive create but has asked to have the file truncated when the
file is opened. In the case of the client timing out and file is opened. In the case of the client timing out and
retransmitting the create request, the client can use GUARDED4 to retransmitting the create request, the client can use GUARDED4 to
prevent against a sequence like: create, write, create prevent against a sequence like create, write, create (retransmitted)
(retransmitted) from occurring. from occurring.
For SHARE reservations, the client MUST specify a value for For SHARE reservations, the value of the expression (share_access &
share_access that is one of READ, WRITE, or BOTH. For share_deny, ~OPEN4_SHARE_ACCESS_WANT_DELEG_MASK) MUST be one of
the client MUST specify one of NONE, READ, WRITE, or BOTH. If the OPEN4_SHARE_ACCESS_READ, OPEN4_SHARE_ACCESS_WRITE, or
client fails to do this, the server MUST return NFS4ERR_INVAL. OPEN4_SHARE_ACCESS_BOTH. If not, the server MUST return
NFS4ERR_INVAL. The value of share_deny MUST be one of
OPEN4_SHARE_DENY_NONE, OPEN4_SHARE_DENY_READ, OPEN4_SHARE_DENY_WRITE,
or OPEN4_SHARE_DENY_BOTH. If not, the server MUST return
NFS4ERR_INVAL.
Based on the share_access value (READ, WRITE, or BOTH) the client Based on the share_access value (OPEN4_SHARE_ACCESS_READ,
OPEN4_SHARE_ACCESS_WRITE, or OPEN4_SHARE_ACCESS_BOTH), the client
should check that the requester has the proper access rights to should check that the requester has the proper access rights to
perform the specified operation. This would generally be the results perform the specified operation. This would generally be the results
of applying the ACL access rules to the file for the current of applying the ACL access rules to the file for the current
requester. However, just as with the ACCESS operation, the client requester. However, just as with the ACCESS operation, the client
should not attempt to second-guess the server's decisions, as access should not attempt to second-guess the server's decisions, as access
rights may change and may be subject to server administrative rights may change and may be subject to server administrative
controls outside the ACL framework. If the requester is not controls outside the ACL framework. If the requester's READ or WRITE
authorized to READ or WRITE (depending on the share_access value), operation is not authorized (depending on the share_access value),
the server MUST return NFS4ERR_ACCESS. the server MUST return NFS4ERR_ACCESS.
Note that if the client ID was not created with Note that if the client ID was not created with the
EXCHGID4_FLAG_BIND_PRINC_STATEID set in the reply to EXCHANGE_ID, EXCHGID4_FLAG_BIND_PRINC_STATEID capability set in the reply to
then the server MUST NOT impose any requirement that READs and WRITEs EXCHANGE_ID, then the server MUST NOT impose any requirement that
sent for an open file have the same credentials as the OPEN itself, READs and WRITEs sent for an open file have the same credentials as
and the server is REQUIRED to perform access checking on the READs the OPEN itself, and the server is REQUIRED to perform access
and WRITEs themselves. Otherwise, if the reply to EXCHANGE_ID did checking on the READs and WRITEs themselves. Otherwise, if the reply
have EXCHGID4_FLAG_BIND_PRINC_STATEID set, then with one exception, to EXCHANGE_ID did have EXCHGID4_FLAG_BIND_PRINC_STATEID set, then
the credentials used in the OPEN request MUST match those used in the with one exception, the credentials used in the OPEN request MUST
READs and WRITEs, and the stateids in the READs and WRITEs MUST match those used in the READs and WRITEs, and the stateids in the
match, or be derived from the stateid from the reply to OPEN. The READs and WRITEs MUST match, or be derived from the stateid from the
exception is if SP4_SSV or SP4_MACH_CRED state protection is used, reply to OPEN. The exception is if SP4_SSV or SP4_MACH_CRED state
and the spo_must_allow result of EXCHANGE_ID includes the READ and/or protection is used, and the spo_must_allow result of EXCHANGE_ID
WRITE operations. In that case, the machine or SSV credential will includes the READ and/or WRITE operations. In that case, the machine
be allowed to send READ and/or WRITE. See Section 18.35. or SSV credential will be allowed to send READ and/or WRITE. See
Section 18.35.
If the component provided to OPEN is a symbolic link, the error If the component provided to OPEN is a symbolic link, the error
NFS4ERR_SYMLINK will be returned to the client, while if it is a NFS4ERR_SYMLINK will be returned to the client, while if it is a
directory the error NFS4ERR_ISDIR. If the component is neither of directory the error NFS4ERR_ISDIR will be returned. If the component
those but not an ordinary file, the error NFS4ERR_WRONG_TYPE is is neither of those but not an ordinary file, the error
returned. If the current filehandle is not a directory, the error NFS4ERR_WRONG_TYPE is returned. If the current filehandle is not a
NFS4ERR_NOTDIR will be returned. directory, the error NFS4ERR_NOTDIR will be returned.
The use of the OPEN4_RESULT_PRESERVE_UNLINKED result flag allows a The use of the OPEN4_RESULT_PRESERVE_UNLINKED result flag allows a
client avoid the common implementation practice of renaming an open client to avoid the common implementation practice of renaming an
file to ".nfs<unique value>" after it removes the file. After the open file to ".nfs<unique value>" after it removes the file. After
server returns OPEN4_RESULT_PRESERVE_UNLINKED, if a client sends a the server returns OPEN4_RESULT_PRESERVE_UNLINKED, if a client sends
REMOVE operation that would reduce the file's link count to zero, the a REMOVE operation that would reduce the file's link count to zero,
server SHOULD report a value of zero for the numlinks attribute on the server SHOULD report a value of zero for the numlinks attribute
the file. on the file.
If another client has a delegation of the file being opened that If another client has a delegation of the file being opened that
conflicts with open being done (sometimes depending of the conflicts with open being done (sometimes depending on the
share_access or share_deny value specified), the delegation(s) MUST share_access or share_deny value specified), the delegation(s) MUST
be recalled, and the operation cannot proceed until each such be recalled, and the operation cannot proceed until each such
delegation is returned or revoked. Except where this happens very delegation is returned or revoked. Except where this happens very
quickly, one or more NFS4ERR_DELAY errors will be returned to quickly, one or more NFS4ERR_DELAY errors will be returned to
requests made while delegation remains outstanding. In the case of a requests made while delegation remains outstanding. In the case of
write delegation, any open by a different client will conflict, while an OPEN_DELEGATE_WRITE delegation, any open by a different client
for a read delegation only opens with one of the following will conflict, while for an OPEN_DELEGATE_READ delegation, only opens
characteristics will be considered conflicting: with one of the following characteristics will be considered
conflicting:
o The value of share_access includes the bit o The value of share_access includes the bit
OPEN4_SHARE_ACCESS_WRITE. OPEN4_SHARE_ACCESS_WRITE.
o The value of share_deny specifies READ or BOTH. o The value of share_deny specifies OPEN4_SHARE_DENY_READ or
OPEN4_SHARE_DENY_BOTH.
o OPEN4_CREATE is specified together with UNCHECKED4, the size o OPEN4_CREATE is specified together with UNCHECKED4, the size
attribute is specified as zero (for truncation) and an existing attribute is specified as zero (for truncation), and an existing
file is truncated. file is truncated.
If OPEN4_CREATE is specified and the file does not exist and the If OPEN4_CREATE is specified and the file does not exist and the
current filehandle designates a directory for which another client current filehandle designates a directory for which another client
holds a directory delegation, then, unless the delegation is such holds a directory delegation, then, unless the delegation is such
that the situation can be resolved by sending a notification, the that the situation can be resolved by sending a notification, the
delegation MUST be recalled, and the operation cannot proceed until delegation MUST be recalled, and the operation cannot proceed until
the delegation is returned or revoked. Except where this happens the delegation is returned or revoked. Except where this happens
very quickly, one or more NFS4ERR_DELAY errors will be returned to very quickly, one or more NFS4ERR_DELAY errors will be returned to
requests made while delegation remains outstanding. requests made while delegation remains outstanding.
If OPEN4_CREATE is specified and the file does not exist and the If OPEN4_CREATE is specified and the file does not exist and the
current filehandle designates a directory for which one or more current filehandle designates a directory for which one or more
directory delegations exist, then, when those delegations request directory delegations exist, then, when those delegations request
such notifications, NOTIFY4_ADD_ENTRY will be generated as a result such notifications, NOTIFY4_ADD_ENTRY will be generated as a result
of this operation. of this operation.
18.16.4.1. WARNING TO CLIENT IMPLEMENTORS 18.16.4.1. Warning to Client Implementors
OPEN resembles LOOKUP in that it generates a filehandle for the OPEN resembles LOOKUP in that it generates a filehandle for the
client to use. Unlike LOOKUP though, OPEN creates server state on client to use. Unlike LOOKUP though, OPEN creates server state on
the filehandle. In normal circumstances, the client can only release the filehandle. In normal circumstances, the client can only release
this state with a CLOSE operation. CLOSE uses the current filehandle this state with a CLOSE operation. CLOSE uses the current filehandle
to determine which file to close. Therefore the client MUST follow to determine which file to close. Therefore, the client MUST follow
every OPEN operation with a GETFH operation in the same COMPOUND every OPEN operation with a GETFH operation in the same COMPOUND
procedure. This will supply the client with the filehandle such that procedure. This will supply the client with the filehandle such that
CLOSE can be used appropriately. CLOSE can be used appropriately.
Simply waiting for the lease on the file to expire is insufficient Simply waiting for the lease on the file to expire is insufficient
because the server may maintain the state indefinitely as long as because the server may maintain the state indefinitely as long as
another client does not attempt to make a conflicting access to the another client does not attempt to make a conflicting access to the
same file. same file.
See also Section 2.10.6.4. See also Section 2.10.6.4.
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18.18.3. DESCRIPTION 18.18.3. DESCRIPTION
This operation is used to adjust the access and deny states for a This operation is used to adjust the access and deny states for a
given open. This is necessary when a given open-owner opens the same given open. This is necessary when a given open-owner opens the same
file multiple times with different access and deny values. In this file multiple times with different access and deny values. In this
situation, a close of one of the opens may change the appropriate situation, a close of one of the opens may change the appropriate
share_access and share_deny flags to remove bits associated with share_access and share_deny flags to remove bits associated with
opens no longer in effect. opens no longer in effect.
Valid values for the share_access field are: OPEN4_SHARE_ACCESS_READ, Valid values for the expression (share_access &
~OPEN4_SHARE_ACCESS_WANT_DELEG_MASK) are OPEN4_SHARE_ACCESS_READ,
OPEN4_SHARE_ACCESS_WRITE, or OPEN4_SHARE_ACCESS_BOTH. If the client OPEN4_SHARE_ACCESS_WRITE, or OPEN4_SHARE_ACCESS_BOTH. If the client
specifies other values, the server MUST reply with NFS4ERR_INVAL. specifies other values, the server MUST reply with NFS4ERR_INVAL.
Valid values for the share_deny field are: OPEN4_SHARE_DENY_NONE, Valid values for the share_deny field are OPEN4_SHARE_DENY_NONE,
OPEN4_SHARE_DENY_READ, OPEN4_SHARE_DENY_WRITE, or OPEN4_SHARE_DENY_READ, OPEN4_SHARE_DENY_WRITE, or
OPEN4_SHARE_DENY_BOTH. If the client specifies other values, the OPEN4_SHARE_DENY_BOTH. If the client specifies other values, the
server MUST reply with NFS4ERR_INVAL. server MUST reply with NFS4ERR_INVAL.
After checking for valid values of share_access and share_deny, the After checking for valid values of share_access and share_deny, the
server replaces the current access and deny modes on the file with server replaces the current access and deny modes on the file with
share_access and share_deny subject to the following constraints: share_access and share_deny subject to the following constraints:
o The bits in share_access SHOULD equal the union of the o The bits in share_access SHOULD equal the union of the
share_access bits (not including OPEN4_SHARE_WANT_* bits) share_access bits (not including OPEN4_SHARE_WANT_* bits)
skipping to change at page 461, line 44 skipping to change at page 463, line 38
OPEN_DOWNGRADE request to be denied because of conflicting share OPEN_DOWNGRADE request to be denied because of conflicting share
reservations. reservations.
The seqid argument is not used in NFSv4.1, MAY be any value, and MUST The seqid argument is not used in NFSv4.1, MAY be any value, and MUST
be ignored by the server. be ignored by the server.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.18.4. IMPLEMENTATION 18.18.4. IMPLEMENTATION
An OPEN_DOWNGRADE operation may make read delegations grantable where An OPEN_DOWNGRADE operation may make OPEN_DELEGATE_READ delegations
they were not previously. Servers may choose to respond immediately grantable where they were not previously. Servers may choose to
if there are pending delegation want requests or may respond to the respond immediately if there are pending delegation want requests or
situation at a later time. may respond to the situation at a later time.
18.19. Operation 22: PUTFH - Set Current Filehandle 18.19. Operation 22: PUTFH - Set Current Filehandle
18.19.1. ARGUMENTS 18.19.1. ARGUMENTS
struct PUTFH4args { struct PUTFH4args {
nfs_fh4 object; nfs_fh4 object;
}; };
18.19.2. RESULTS 18.19.2. RESULTS
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struct PUTFH4res { struct PUTFH4res {
/* /*
* If status is NFS4_OK, * If status is NFS4_OK,
* new CURRENT_FH: argument to PUTFH * new CURRENT_FH: argument to PUTFH
*/ */
nfsstat4 status; nfsstat4 status;
}; };
18.19.3. DESCRIPTION 18.19.3. DESCRIPTION
Replaces the current filehandle with the filehandle provided as an This operation replaces the current filehandle with the filehandle
argument. Clears the current stateid. provided as an argument. It clears the current stateid.
If the security mechanism used by the requester does not meet the If the security mechanism used by the requester does not meet the
requirements of the filehandle provided to this operation, the server requirements of the filehandle provided to this operation, the server
MUST return NFS4ERR_WRONGSEC. MUST return NFS4ERR_WRONGSEC.
See Section 16.2.3.1.1 for more details on the current filehandle. See Section 16.2.3.1.1 for more details on the current filehandle.
See Section 16.2.3.1.2 for more details on the current stateid. See Section 16.2.3.1.2 for more details on the current stateid.
18.19.4. IMPLEMENTATION 18.19.4. IMPLEMENTATION
Commonly used as the second operator (after SEQUENCE) in a COMPOUND This operation is used in an NFS request to set the context for file
request to set the context for following operations. accessing operations that follow in the same COMPOUND request.
18.20. Operation 23: PUTPUBFH - Set Public Filehandle 18.20. Operation 23: PUTPUBFH - Set Public Filehandle
18.20.1. ARGUMENT 18.20.1. ARGUMENT
void; void;
18.20.2. RESULT 18.20.2. RESULT
struct PUTPUBFH4res { struct PUTPUBFH4res {
/* /*
* If status is NFS4_OK, * If status is NFS4_OK,
* new CURRENT_FH: public fh * new CURRENT_FH: public fh
*/ */
nfsstat4 status; nfsstat4 status;
}; };
18.20.3. DESCRIPTION 18.20.3. DESCRIPTION
Replaces the current filehandle with the filehandle that represents This operation replaces the current filehandle with the filehandle
the public filehandle of the server's name space. This filehandle that represents the public filehandle of the server's namespace.
may be different from the "root" filehandle which may be associated This filehandle may be different from the "root" filehandle that may
with some other directory on the server. be associated with some other directory on the server.
PUTPUBFH also clears the current stateid. PUTPUBFH also clears the current stateid.
The public filehandle represents the concepts embodied in RFC2054 The public filehandle represents the concepts embodied in RFC2054
[42], RFC2055 [43], and RFC2224 [53]. The intent for NFSv4.1 is that [42], RFC 2055 [43], and RFC 2224 [53]. The intent for NFSv4.1 is
the public filehandle (represented by the PUTPUBFH operation) be used that the public filehandle (represented by the PUTPUBFH operation) be
as a method of providing WebNFS server compatibility with NFSv3. used as a method of providing WebNFS server compatibility with NFSv3.
The public filehandle and the root filehandle (represented by the The public filehandle and the root filehandle (represented by the
PUTROOTFH operation) SHOULD be equivalent. If the public and root PUTROOTFH operation) SHOULD be equivalent. If the public and root
filehandles are not equivalent, then the directory corresponding to filehandles are not equivalent, then the directory corresponding to
the public filehandle MUST be a descendant of the directory the public filehandle MUST be a descendant of the directory
corresponding to the root filehandle. corresponding to the root filehandle.
See Section 16.2.3.1.1 for more details on the current filehandle. See Section 16.2.3.1.1 for more details on the current filehandle.
See Section 16.2.3.1.2 for more details on the current stateid. See Section 16.2.3.1.2 for more details on the current stateid.
18.20.4. IMPLEMENTATION 18.20.4. IMPLEMENTATION
Used as the second operator (after SEQUENCE) in an NFS request to set This operation is used in an NFS request to set the context for file
the context for file accessing operations that follow in the same accessing operations that follow in the same COMPOUND request.
COMPOUND request.
With the NFSv3 public filehandle, the client is able to specify With the NFSv3 public filehandle, the client is able to specify
whether the path name provided in the LOOKUP should be evaluated as whether the path name provided in the LOOKUP should be evaluated as
either an absolute path relative to the server's root or relative to either an absolute path relative to the server's root or relative to
the public filehandle. RFC2224 [53] contains further discussion of the public filehandle. RFC2224 [53] contains further discussion of
the functionality. With NFSv4.1, that type of specification is not the functionality. With NFSv4.1, that type of specification is not
directly available in the LOOKUP operation. The reason for this is directly available in the LOOKUP operation. The reason for this is
because the component separators needed to specify absolute vs. because the component separators needed to specify absolute vs.
relative are not allowed in NFSv4. Therefore, the client is relative are not allowed in NFSv4. Therefore, the client is
responsible for constructing its request such that the use of either responsible for constructing its request such that the use of either
PUTROOTFH or PUTPUBFH are used to signify absolute or relative PUTROOTFH or PUTPUBFH signifies absolute or relative evaluation of an
evaluation of an NFS URL respectively. NFS URL, respectively.
Note that there are warnings mentioned in RFC2224 [53] with respect Note that there are warnings mentioned in RFC2224 [53] with respect
to the use of absolute evaluation and the restrictions the server may to the use of absolute evaluation and the restrictions the server may
place on that evaluation with respect to how much of its namespace place on that evaluation with respect to how much of its namespace
has been made available. These same warnings apply to NFSv4.1. It has been made available. These same warnings apply to NFSv4.1. It
is likely, therefore that because of server implementation details, is likely, therefore, that because of server implementation details,
an NFSv3 absolute public filehandle lookup may behave differently an NFSv3 absolute public filehandle lookup may behave differently
than an NFSv4.1 absolute resolution. than an NFSv4.1 absolute resolution.
There is a form of security negotiation as described in RFC2755 [54] There is a form of security negotiation as described in RFC2755 [54]
that uses the public filehandle and an overloading of the pathname. that uses the public filehandle and an overloading of the pathname.
This method is not available with NFSv4.1 as filehandles are not This method is not available with NFSv4.1 as filehandles are not
overloaded with special meaning and therefore do not provide the same overloaded with special meaning and therefore do not provide the same
framework as NFSv3. Clients should therefore use the security framework as NFSv3. Clients should therefore use the security
negotiation mechanisms described in Section 2.6. negotiation mechanisms described in Section 2.6.
skipping to change at page 464, line 43 skipping to change at page 466, line 30
struct PUTROOTFH4res { struct PUTROOTFH4res {
/* /*
* If status is NFS4_OK, * If status is NFS4_OK,
* new CURRENT_FH: root fh * new CURRENT_FH: root fh
*/ */
nfsstat4 status; nfsstat4 status;
}; };
18.21.3. DESCRIPTION 18.21.3. DESCRIPTION
Replaces the current filehandle with the filehandle that represents This operation replaces the current filehandle with the filehandle
the root of the server's name space. From this filehandle a LOOKUP that represents the root of the server's namespace. From this
operation can locate any other filehandle on the server. This filehandle, a LOOKUP operation can locate any other filehandle on the
filehandle may be different from the "public" filehandle which may be server. This filehandle may be different from the "public"
associated with some other directory on the server. filehandle that may be associated with some other directory on the
server.
PUTROOTFH also clears the current stateid. PUTROOTFH also clears the current stateid.
See Section 16.2.3.1.1 for more details on the current filehandle. See Section 16.2.3.1.1 for more details on the current filehandle.
See Section 16.2.3.1.2 for more details on the current stateid. See Section 16.2.3.1.2 for more details on the current stateid.
18.21.4. IMPLEMENTATION 18.21.4. IMPLEMENTATION
Commonly used as the second operator (after SEQUENCE) in an NFS This operation is used in an NFS request to set the context for file
request to set the context for file accessing operations that follow accessing operations that follow in the same COMPOUND request.
in the same COMPOUND request.
18.22. Operation 25: READ - Read from File 18.22. Operation 25: READ - Read from File
18.22.1. ARGUMENTS 18.22.1. ARGUMENTS
struct READ4args { struct READ4args {
/* CURRENT_FH: file */ /* CURRENT_FH: file */
stateid4 stateid; stateid4 stateid;
offset4 offset; offset4 offset;
count4 count; count4 count;
skipping to change at page 465, line 44 skipping to change at page 467, line 34
default: default:
void; void;
}; };
18.22.3. DESCRIPTION 18.22.3. DESCRIPTION
The READ operation reads data from the regular file identified by the The READ operation reads data from the regular file identified by the
current filehandle. current filehandle.
The client provides an offset of where the READ is to start and a The client provides an offset of where the READ is to start and a
count of how many bytes are to be read. An offset of 0 (zero) means count of how many bytes are to be read. An offset of zero means to
to read data starting at the beginning of the file. If offset is read data starting at the beginning of the file. If offset is
greater than or equal to the size of the file, the status, NFS4_OK, greater than or equal to the size of the file, the status NFS4_OK is
is returned with a data length set to 0 (zero) and eof is set to returned with a data length set to zero and eof is set to TRUE. The
TRUE. The READ is subject to access permissions checking. READ is subject to access permissions checking.
If the client specifies a count value of 0 (zero), the READ succeeds If the client specifies a count value of zero, the READ succeeds and
and returns 0 (zero) bytes of data again subject to access returns zero bytes of data again subject to access permissions
permissions checking. The server may choose to return fewer bytes checking. The server may choose to return fewer bytes than specified
than specified by the client. The client needs to check for this by the client. The client needs to check for this condition and
condition and handle the condition appropriately. handle the condition appropriately.
Except when special stateids are used, the stateid value for a READ Except when special stateids are used, the stateid value for a READ
request represents a value returned from a previous byte-range lock request represents a value returned from a previous byte-range lock
or share reservation request or the stateid associated with a or share reservation request or the stateid associated with a
delegation. The stateid identifies the associated owners if any and delegation. The stateid identifies the associated owners if any and
is used by the server to verify that the associated locks are still is used by the server to verify that the associated locks are still
valid (e.g. have not been revoked). valid (e.g., have not been revoked).
If the read ended at the end-of-file (formally, in a correctly formed If the read ended at the end-of-file (formally, in a correctly formed
READ request, if offset + count is equal to the size of the file), or READ operation, if offset + count is equal to the size of the file),
the read request extends beyond the size of the file (if offset + or the READ operation extends beyond the size of the file (if offset
count is greater than the size of the file), eof is returned as TRUE; + count is greater than the size of the file), eof is returned as
otherwise it is FALSE. A successful READ of an empty file will TRUE; otherwise, it is FALSE. A successful READ of an empty file
always return eof as TRUE. will always return eof as TRUE.
If the current filehandle is not an ordinary file, an error will be If the current filehandle is not an ordinary file, an error will be
returned to the client. In the case that the current filehandle returned to the client. In the case that the current filehandle
represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. if represents an object of type NF4DIR, NFS4ERR_ISDIR is returned. If
the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is the current filehandle designates a symbolic link, NFS4ERR_SYMLINK is
returned. In all other cases, NFS4ERR_WRONG_TYPE is returned. returned. In all other cases, NFS4ERR_WRONG_TYPE is returned.
For a READ with a stateid value of all bits 0, the server MAY allow For a READ with a stateid value of all bits equal to zero, the server
the READ to be serviced subject to mandatory file locks or the MAY allow the READ to be serviced subject to mandatory byte-range
current share deny modes for the file. For a READ with a stateid locks or the current share deny modes for the file. For a READ with
value of all bits 1, the server MAY allow READ operations to bypass a stateid value of all bits equal to one, the server MAY allow READ
locking checks at the server. operations to bypass locking checks at the server.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.22.4. IMPLEMENTATION 18.22.4. IMPLEMENTATION
It is possible for the server to return fewer than count bytes of If the server returns a "short read" (i.e., fewer data than requested
data. If the server returns less than the count requested and eof is and eof is set to FALSE), the client should send another READ to get
set to FALSE, the client should send another READ to get the the remaining data. A server may return less data than requested
remaining data. A server may return less data than requested under under several circumstances. The file may have been truncated by
several circumstances. The file may have been truncated by another another client or perhaps on the server itself, changing the file
client or perhaps on the server itself, changing the file size from size from what the requesting client believes to be the case. This
what the requesting client believes to be the case. This would would reduce the actual amount of data available to the client. It
reduce the actual amount of data available to the client. It is is possible that the server reduce the transfer size and so return a
possible that the server may back off the transfer size and reduce short read result. Server resource exhaustion may also occur in a
the read request return. Server resource exhaustion may also occur short read.
necessitating a smaller read return.
If mandatory file locking is in effect for the file, and if the If mandatory byte-range locking is in effect for the file, and if the
region corresponding to the data to be read from file is write locked byte-range corresponding to the data to be read from the file is
by an owner not associated the stateid, the server will return the WRITE_LT locked by an owner not associated with the stateid, the
NFS4ERR_LOCKED error. The client should try to get the appropriate server will return the NFS4ERR_LOCKED error. The client should try
read byte-range lock via the LOCK operation before re-attempting the to get the appropriate READ_LT via the LOCK operation before re-
READ. When the READ completes, the client should release the byte- attempting the READ. When the READ completes, the client should
range lock via LOCKU. release the byte-range lock via LOCKU.
If another client has a write delegation for the file being read, the If another client has an OPEN_DELEGATE_WRITE delegation for the file
delegation must be recalled, and the operation cannot proceed until being read, the delegation must be recalled, and the operation cannot
that delegation is returned or revoked. Except where this happens proceed until that delegation is returned or revoked. Except where
very quickly, one or more NFS4ERR_DELAY errors will be returned to this happens very quickly, one or more NFS4ERR_DELAY errors will be
requests made while the delegation remains outstanding. Normally, returned to requests made while the delegation remains outstanding.
delegations will not be recalled as a result of a READ operation Normally, delegations will not be recalled as a result of a READ
since the recall will occur as a result of an earlier OPEN. However, operation since the recall will occur as a result of an earlier OPEN.
since it is possible for a READ to be done with a special stateid, However, since it is possible for a READ to be done with a special
the server needs to check for this case even though the client should stateid, the server needs to check for this case even though the
have done an OPEN previously. client should have done an OPEN previously.
18.23. Operation 26: READDIR - Read Directory 18.23. Operation 26: READDIR - Read Directory
18.23.1. ARGUMENTS 18.23.1. ARGUMENTS
struct READDIR4args { struct READDIR4args {
/* CURRENT_FH: directory */ /* CURRENT_FH: directory */
nfs_cookie4 cookie; nfs_cookie4 cookie;
verifier4 cookieverf; verifier4 cookieverf;
count4 dircount; count4 dircount;
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union READDIR4res switch (nfsstat4 status) { union READDIR4res switch (nfsstat4 status) {
case NFS4_OK: case NFS4_OK:
READDIR4resok resok4; READDIR4resok resok4;
default: default:
void; void;
}; };
18.23.3. DESCRIPTION 18.23.3. DESCRIPTION
The READDIR operation retrieves a variable number of entries from a The READDIR operation retrieves a variable number of entries from a
file system directory and returns client requested attributes for file system directory and returns client-requested attributes for
each entry along with information to allow the client to request each entry along with information to allow the client to request
additional directory entries in a subsequent READDIR. additional directory entries in a subsequent READDIR.
The arguments contain a cookie value that represents where the The arguments contain a cookie value that represents where the
READDIR should start within the directory. A value of 0 (zero) for READDIR should start within the directory. A value of zero for the
the cookie is used to start reading at the beginning of the cookie is used to start reading at the beginning of the directory.
directory. For subsequent READDIR requests, the client specifies a For subsequent READDIR requests, the client specifies a cookie value
cookie value that is provided by the server on a previous READDIR that is provided by the server on a previous READDIR request.
request.
The request's cookieverf field should be set to 0 (zero) when the The request's cookieverf field should be set to 0 zero) when the
request's cookie field is 0 (zero) (first directory read). On request's cookie field is zero (first read of the directory). On
subsequent requests, the cookieverf field must match the cookieverf subsequent requests, the cookieverf field must match the cookieverf
returned by the READDIR in which the cookie was acquired. If the returned by the READDIR in which the cookie was acquired. If the
server determines that the cookieverf is no longer valid for the server determines that the cookieverf is no longer valid for the
directory, the error NFS4ERR_NOT_SAME must be returned. directory, the error NFS4ERR_NOT_SAME must be returned.
The dircount field of the request is a hint of the maximum number of The dircount field of the request is a hint of the maximum number of
bytes of directory information that should be returned. This value bytes of directory information that should be returned. This value
represents the total length of the names of the directory entries and represents the total length of the names of the directory entries and
the cookie value for these entries. This length represents the XDR the cookie value for these entries. This length represents the XDR
encoding of the data (names and cookies) and not the length in the encoding of the data (names and cookies) and not the length in the
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the entire READDIR operation, the server can instead return the the entire READDIR operation, the server can instead return the
attribute rdattr_error (Section 5.8.1.12). With this, the server is attribute rdattr_error (Section 5.8.1.12). With this, the server is
able to communicate the failure to the client and not fail the entire able to communicate the failure to the client and not fail the entire
operation in the instance of what might be a transient failure. operation in the instance of what might be a transient failure.
Obviously, the client must request the fattr4_rdattr_error attribute Obviously, the client must request the fattr4_rdattr_error attribute
for this method to work properly. If the client does not request the for this method to work properly. If the client does not request the
attribute, the server has no choice but to return failure for the attribute, the server has no choice but to return failure for the
entire READDIR operation. entire READDIR operation.
For some file system environments, the directory entries "." and ".." For some file system environments, the directory entries "." and ".."
have special meaning and in other environments, they do not. If the have special meaning, and in other environments, they do not. If the
server supports these special entries within a directory, they SHOULD server supports these special entries within a directory, they SHOULD
NOT be returned to the client as part of the READDIR response. To NOT be returned to the client as part of the READDIR response. To
enable some client environments, the cookie values of 0, 1, and 2 are enable some client environments, the cookie values of zero, 1, and 2
to be considered reserved. Note that the UNIX client will use these are to be considered reserved. Note that the UNIX client will use
values when combining the server's response and local representations these values when combining the server's response and local
to enable a fully formed UNIX directory presentation to the representations to enable a fully formed UNIX directory presentation
application. to the application.
For READDIR arguments, cookie values of 1 and 2 SHOULD NOT be used For READDIR arguments, cookie values of one and two SHOULD NOT be
and for READDIR results cookie values of 0, 1, and 2 SHOULD NOT be used, and for READDIR results, cookie values of zero, one, and two
returned. SHOULD NOT be returned.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.23.4. IMPLEMENTATION 18.23.4. IMPLEMENTATION
The server's file system directory representations can differ The server's file system directory representations can differ
greatly. A client's programming interfaces may also be bound to the greatly. A client's programming interfaces may also be bound to the
local operating environment in a way that does not translate well local operating environment in a way that does not translate well
into the NFS protocol. Therefore the use of the dircount and into the NFS protocol. Therefore, the use of the dircount and
maxcount fields are provided to enable the client to provide hints to maxcount fields are provided to enable the client to provide hints to
the server. If the client is aggressive about attribute collection the server. If the client is aggressive about attribute collection
during a READDIR, the server has an idea of how to limit the encoded during a READDIR, the server has an idea of how to limit the encoded
response. response.
If dircount is zero, the server bounds the reply's size based on If dircount is zero, the server bounds the reply's size based on the
request's maxcount field. request's maxcount field.
The cookieverf may be used by the server to help manage cookie values The cookieverf may be used by the server to help manage cookie values
that may become stale. It should be a rare occurrence that a server that may become stale. It should be a rare occurrence that a server
is unable to continue properly reading a directory with the provided is unable to continue properly reading a directory with the provided
cookie/cookieverf pair. The server SHOULD make every effort to avoid cookie/cookieverf pair. The server SHOULD make every effort to avoid
this condition since the application at the client might be unable to this condition since the application at the client might be unable to
properly handle this type of failure. properly handle this type of failure.
The use of the cookieverf will also protect the client from using The use of the cookieverf will also protect the client from using
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If the entry in the directory was the last reference to the If the entry in the directory was the last reference to the
corresponding file system object, the object may be destroyed. The corresponding file system object, the object may be destroyed. The
directory may be either of type NF4DIR or NF4ATTRDIR. directory may be either of type NF4DIR or NF4ATTRDIR.
For the directory where the filename was removed, the server returns For the directory where the filename was removed, the server returns
change_info4 information in cinfo. With the atomic field of the change_info4 information in cinfo. With the atomic field of the
change_info4 data type, the server will indicate if the before and change_info4 data type, the server will indicate if the before and
after change attributes were obtained atomically with respect to the after change attributes were obtained atomically with respect to the
removal. removal.
If the target has a length of 0 (zero), or if target does not obey If the target has a length of zero, or if the target does not obey
the UTF-8 definition (and the server is enforcing UTF-8 encoding, see the UTF-8 definition (and the server is enforcing UTF-8 encoding; see
Section 14.4), the error NFS4ERR_INVAL will be returned. Section 14.4), the error NFS4ERR_INVAL will be returned.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.25.4. IMPLEMENTATION 18.25.4. IMPLEMENTATION
NFSv3 required a different operator RMDIR for directory removal and NFSv3 required a different operator RMDIR for directory removal and
REMOVE for non-directory removal. This allowed clients to skip REMOVE for non-directory removal. This allowed clients to skip
checking the file type when being passed a non-directory delete checking the file type when being passed a non-directory delete
system call (e.g. unlink() [27] in POSIX) to remove a directory, as system call (e.g., unlink() [27] in POSIX) to remove a directory, as
well as the converse (e.g. a rmdir() on a non-directory) because they well as the converse (e.g., a rmdir() on a non-directory) because
knew the server would check the file type. NFSv4.1 REMOVE can be they knew the server would check the file type. NFSv4.1 REMOVE can
used to delete any directory entry independent of its file type. The be used to delete any directory entry independent of its file type.
implementor of an NFSv4.1 client's entry points from the unlink() and The implementor of an NFSv4.1 client's entry points from the unlink()
rmdir() system calls should first check the file type against the and rmdir() system calls should first check the file type against the
types the system call is allowed to remove before sending a REMOVE types the system call is allowed to remove before sending a REMOVE
operation. Alternatively, the implementor can produce a COMPOUND operation. Alternatively, the implementor can produce a COMPOUND
call that includes a LOOKUP/VERIFY sequence of operations to verify call that includes a LOOKUP/VERIFY sequence of operations to verify
the file type before a REMOVE operation in the same COMPOUND call. the file type before a REMOVE operation in the same COMPOUND call.
The concept of last reference is server specific. However, if the The concept of last reference is server specific. However, if the
numlinks field in the previous attributes of the object had the value numlinks field in the previous attributes of the object had the value
1, the client should not rely on referring to the object via a 1, the client should not rely on referring to the object via a
filehandle. Likewise, the client should not rely on the resources filehandle. Likewise, the client should not rely on the resources
(disk space, directory entry, and so on) formerly associated with the (disk space, directory entry, and so on) formerly associated with the
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o The server MUST NOT delete the directory entry if the reply from o The server MUST NOT delete the directory entry if the reply from
OPEN had the flag OPEN4_RESULT_PRESERVE_UNLINKED set. OPEN had the flag OPEN4_RESULT_PRESERVE_UNLINKED set.
The server MAY implement its own restrictions on removal of a file The server MAY implement its own restrictions on removal of a file
while it is open. The server might disallow such a REMOVE (or a while it is open. The server might disallow such a REMOVE (or a
removal that occurs as part of RENAME). The conditions that removal that occurs as part of RENAME). The conditions that
influence the restrictions on removal of a file while it is still influence the restrictions on removal of a file while it is still
open include: open include:
o Whether certain access protocols (i.e. not just NFS) are holding o Whether certain access protocols (i.e., not just NFS) are holding
the file open. the file open.
o Whether particular options, access modes, or policies on the o Whether particular options, access modes, or policies on the
server are enabled. server are enabled.
In all cases in which a decision is made to not allow the file's If a file has an outstanding OPEN and this prevents the removal of
directory entry be removed because of an open, the error the file's directory entry, the error NFS4ERR_FILE_OPEN is returned.
NFS4ERR_FILE_OPEN is returned.
Where the determination above cannot be made definitively because Where the determination above cannot be made definitively because
delegations are being held, they MUST be recalled to allow processing delegations are being held, they MUST be recalled to allow processing
of the REMOVE to continue. When a delegation is held, the server's of the REMOVE to continue. When a delegation is held, the server has
knowledge of the status of opens for that client is not to be relied no reliable knowledge of the status of OPENs for that client, so
on, so that unless there are files opened with the particular deny unless there are files opened with the particular deny modes by
modes by clients without delegations, the determination cannot be clients without delegations, the determination cannot be made until
made until delegations are recalled, and the operation cannot proceed delegations are recalled, and the operation cannot proceed until each
until each sufficient delegations have been returned or revoked to sufficient delegation has been returned or revoked to allow the
allow the server to make a correct determination. server to make a correct determination.
In all cases in which delegations are recalled, the server is likely In all cases in which delegations are recalled, the server is likely
to return one or more NFS4ERR_DELAY errors while delegations remain to return one or more NFS4ERR_DELAY errors while delegations remain
outstanding. outstanding.
If the current filehandle designates a directory for which another If the current filehandle designates a directory for which another
client holds a directory delegation, then, unless the situation can client holds a directory delegation, then, unless the situation can
be resolved by sending a notification, the directory delegation MUST be resolved by sending a notification, the directory delegation MUST
be recalled, and the operation MUST NOT proceed until the delegation be recalled, and the operation MUST NOT proceed until the delegation
is returned or revoked. Except where this happens very quickly, one is returned or revoked. Except where this happens very quickly, one
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18.26.3. DESCRIPTION 18.26.3. DESCRIPTION
The RENAME operation renames the object identified by oldname in the The RENAME operation renames the object identified by oldname in the
source directory corresponding to the saved filehandle, as set by the source directory corresponding to the saved filehandle, as set by the
SAVEFH operation, to newname in the target directory corresponding to SAVEFH operation, to newname in the target directory corresponding to
the current filehandle. The operation is required to be atomic to the current filehandle. The operation is required to be atomic to
the client. Source and target directories MUST reside on the same the client. Source and target directories MUST reside on the same
file system on the server. On success, the current filehandle will file system on the server. On success, the current filehandle will
continue to be the target directory. continue to be the target directory.
If the target directory already contains an entry with the name, If the target directory already contains an entry with the name
newname, the source object MUST be compatible with the target: either newname, the source object MUST be compatible with the target: either
both are non-directories or both are directories and the target MUST both are non-directories or both are directories and the target MUST
be empty. If compatible, the existing target is removed before the be empty. If compatible, the existing target is removed before the
rename occurs or preferably as part of the rename and atomic with it. rename occurs or, preferably, the target is removed atomically as
See Section 18.25.4 for client and server actions whenever a target part of the rename. See Section 18.25.4 for client and server
is removed. Note however that when the removal is performed actions whenever a target is removed. Note however that when the
atomically with the rename, certain parts of the removal described removal is performed atomically with the rename, certain parts of the
there are integrated with the rename. For example, notification of removal described there are integrated with the rename. For example,
the removal will not be via a NOTIFY4_REMOVE_ENTRY but will be notification of the removal will not be via a NOTIFY4_REMOVE_ENTRY
indicated as part of the NOTIFY4_ADD_ENTRY or NOTIFY4_RENAME_ENTRY but will be indicated as part of the NOTIFY4_ADD_ENTRY or
generated by the rename. NOTIFY4_RENAME_ENTRY generated by the rename.
If the source object and the target are not compatible or if the If the source object and the target are not compatible or if the
target is a directory but not empty, the server will return the target is a directory but not empty, the server will return the error
error, NFS4ERR_EXIST. NFS4ERR_EXIST.
If oldname and newname both refer to the same file (e.g. they might If oldname and newname both refer to the same file (e.g., they might
be hard links of each other), then unless the file is open (see be hard links of each other), then unless the file is open (see
Section 18.26.4), RENAME MUST perform no action and return NFS4_OK. Section 18.26.4), RENAME MUST perform no action and return NFS4_OK.
For both directories involved in the RENAME, the server returns For both directories involved in the RENAME, the server returns
change_info4 information. With the atomic field of the change_info4 change_info4 information. With the atomic field of the change_info4
data type, the server will indicate if the before and after change data type, the server will indicate if the before and after change
attributes were obtained atomically with respect to the rename. attributes were obtained atomically with respect to the rename.
If oldname refers to a named attribute and the saved and current If oldname refers to a named attribute and the saved and current
filehandles refer to different file system objects, the server will filehandles refer to different file system objects, the server will
return NFS4ERR_XDEV just as if the saved and current filehandles return NFS4ERR_XDEV just as if the saved and current filehandles
represented directories on different file systems. represented directories on different file systems.
If oldname or newname have a length of 0 (zero), or if oldname or If oldname or newname has a length of zero, or if oldname or newname
newname do not obey the UTF-8 definition, the error NFS4ERR_INVAL does not obey the UTF-8 definition, the error NFS4ERR_INVAL will be
will be returned. returned.
18.26.4. IMPLEMENTATION 18.26.4. IMPLEMENTATION
The server MAY impose restrictions on the RENAME operation such that The server MAY impose restrictions on the RENAME operation such that
RENAME may not be done when the file being renamed is open or when RENAME may not be done when the file being renamed is open or when
that open is done by particular protocols, or with particular options that open is done by particular protocols, or with particular options
or access modes. Similar restrictions may be applied when a file or access modes. Similar restrictions may be applied when a file
exists with the target name and is open. When RENAME is rejected exists with the target name and is open. When RENAME is rejected
because of such restrictions, the error NFS4ERR_FILE_OPEN is because of such restrictions, the error NFS4ERR_FILE_OPEN is
returned. returned.
When oldname and rename refer to the same file and that file is open When oldname and rename refer to the same file and that file is open
in a fashion such that RENAME would normally be rejected with in a fashion such that RENAME would normally be rejected with
NFS4ERR_FILE_OPEN if oldname and newname were different files, then NFS4ERR_FILE_OPEN if oldname and newname were different files, then
RENAME SHOULD be rejected with NFS4ERR_FILE_OPEN. RENAME SHOULD be rejected with NFS4ERR_FILE_OPEN.
If a server does implement such restrictions and those restrictions If a server does implement such restrictions and those restrictions
include cases of NFSv4 opens preventing successful execution of a include cases of NFSv4 opens preventing successful execution of a
rename, the server needs to recall any delegations which could hide rename, the server needs to recall any delegations that could hide
the existence of opens relevant to that decision. This is because the existence of opens relevant to that decision. This is because
when a client holds a delegation, the server might not have an when a client holds a delegation, the server might not have an
accurate account of the opens for that client, since the client may accurate account of the opens for that client, since the client may
execute OPENs and CLOSEs locally. The RENAME operation need only be execute OPENs and CLOSEs locally. The RENAME operation need only be
delayed until a definitive result can be obtained. For example, if delayed until a definitive result can be obtained. For example, if
there are multiple delegations and one of them establishes an open there are multiple delegations and one of them establishes an open
whose presence would prevent the rename, given the server's whose presence would prevent the rename, given the server's
semantics, NFS4ERR_FILE_OPEN may be returned to the caller as soon as semantics, NFS4ERR_FILE_OPEN may be returned to the caller as soon as
that delegation is returned without waiting for other delegations to that delegation is returned without waiting for other delegations to
be returned. Similarly, if such opens are not associated with be returned. Similarly, if such opens are not associated with
delegations, NFS4ERR_FILE_OPEN can be returned immediately with no delegations, NFS4ERR_FILE_OPEN can be returned immediately with no
delegation recall being done. delegation recall being done.
If the current filehandle or the saved filehandle designate a If the current filehandle or the saved filehandle designates a
directory for which another client holds a directory delegation, directory for which another client holds a directory delegation,
then, unless the situation can be resolved by sending a notification, then, unless the situation can be resolved by sending a notification,
the delegation MUST be recalled, and the operation cannot proceed the delegation MUST be recalled, and the operation cannot proceed
until the delegation is returned or revoked. Except where this until the delegation is returned or revoked. Except where this
happens very quickly, one or more NFS4ERR_DELAY errors will be happens very quickly, one or more NFS4ERR_DELAY errors will be
returned to requests made while delegation remains outstanding. returned to requests made while delegation remains outstanding.
When the current and saved filehandles are the same and they When the current and saved filehandles are the same and they
designate a directory for which one or more directory delegations designate a directory for which one or more directory delegations
exist, then, when those delegations request such notifications, a exist, then, when those delegations request such notifications, a
notification of type NOTIFY4_RENAME_ENTRY will be generated as a notification of type NOTIFY4_RENAME_ENTRY will be generated as a
result of this operation. When oldname and rename refer to the same result of this operation. When oldname and rename refer to the same
file, no notification is generated (because as Section 18.26.3 file, no notification is generated (because, as Section 18.26.3
states, the server MUST take no action). When a file is removed states, the server MUST take no action). When a file is removed
because it has the same name as the target, if that removal is done because it has the same name as the target, if that removal is done
atomically with the rename, a NOTIFY4_REMOVE_ENTRY notification will atomically with the rename, a NOTIFY4_REMOVE_ENTRY notification will
not be generated. Instead, the deletion of the file will be reported not be generated. Instead, the deletion of the file will be reported
as part of the NOTIFY4_RENAME_ENTRY notification. as part of the NOTIFY4_RENAME_ENTRY notification.
When the current and saved filehandles are not the same: When the current and saved filehandles are not the same:
o If the current filehandle designates a directory for which one or o If the current filehandle designates a directory for which one or
more directory delegations exist, then, when those delegations more directory delegations exist, then, when those delegations
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request such notifications, NOTIFY4_REMOVE_ENTRY will be generated request such notifications, NOTIFY4_REMOVE_ENTRY will be generated
as a result of this operation. as a result of this operation.
If the object being renamed has file delegations held by clients If the object being renamed has file delegations held by clients
other than the one doing the RENAME, the delegations MUST be other than the one doing the RENAME, the delegations MUST be
recalled, and the operation cannot proceed until each such delegation recalled, and the operation cannot proceed until each such delegation
is returned or revoked. Note that in the case of multiply linked is returned or revoked. Note that in the case of multiply linked
files, the delegation recall requirement applies even if the files, the delegation recall requirement applies even if the
delegation was obtained through a different name than the one being delegation was obtained through a different name than the one being
renamed. In all cases in which delegations are recalled, the server renamed. In all cases in which delegations are recalled, the server
is likely to return one or more NFS4ERR_DELAY error while the is likely to return one or more NFS4ERR_DELAY errors while the
delegation(s) remains outstanding, although it may, if the returns delegation(s) remains outstanding, although it might not do that if
happen quickly, not do that. the delegations are returned quickly.
The RENAME operation must be atomic to the client. The statement The RENAME operation must be atomic to the client. The statement
"source and target directories MUST reside on the same file system on "source and target directories MUST reside on the same file system on
the server" means that the fsid fields in the attributes for the the server" means that the fsid fields in the attributes for the
directories are the same. If they reside on different file systems, directories are the same. If they reside on different file systems,
the error, NFS4ERR_XDEV, is returned. the error NFS4ERR_XDEV is returned.
Based on the value of the fh_expire_type attribute for the object, Based on the value of the fh_expire_type attribute for the object,
the filehandle may or may not expire on a RENAME. However, server the filehandle may or may not expire on a RENAME. However, server
implementors are strongly encouraged to attempt to keep filehandles implementors are strongly encouraged to attempt to keep filehandles
from expiring in this fashion. from expiring in this fashion.
On some servers, the file names "." and ".." are illegal as either On some servers, the file names "." and ".." are illegal as either
oldname or newname, and will result in the error NFS4ERR_BADNAME. In oldname or newname, and will result in the error NFS4ERR_BADNAME. In
addition, on many servers the case of oldname or newname being an addition, on many servers the case of oldname or newname being an
alias for the source directory will be checked for. Such servers alias for the source directory will be checked for. Such servers
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struct RESTOREFH4res { struct RESTOREFH4res {
/* /*
* If status is NFS4_OK, * If status is NFS4_OK,
* new CURRENT_FH: value of saved fh * new CURRENT_FH: value of saved fh
*/ */
nfsstat4 status; nfsstat4 status;
}; };
18.27.3. DESCRIPTION 18.27.3. DESCRIPTION
Set the current filehandle and stateid to the values in the saved The RESTOREFH operation sets the current filehandle and stateid to
filehandle and stateid. If there is no saved filehandle then the the values in the saved filehandle and stateid. If there is no saved
server will return the error NFS4ERR_NOFILEHANDLE. filehandle, then the server will return the error
NFS4ERR_NOFILEHANDLE.
See Section 16.2.3.1.1 for more details on the current filehandle. See Section 16.2.3.1.1 for more details on the current filehandle.
See Section 16.2.3.1.2 for more details on the current stateid. See Section 16.2.3.1.2 for more details on the current stateid.
18.27.4. IMPLEMENTATION 18.27.4. IMPLEMENTATION
Operations like OPEN and LOOKUP use the current filehandle to Operations like OPEN and LOOKUP use the current filehandle to
represent a directory and replace it with a new filehandle. Assuming represent a directory and replace it with a new filehandle. Assuming
the previous filehandle was saved with a SAVEFH operator, the that the previous filehandle was saved with a SAVEFH operator, the
previous filehandle can be restored as the current filehandle. This previous filehandle can be restored as the current filehandle. This
is commonly used to obtain post-operation attributes for the is commonly used to obtain post-operation attributes for the
directory, e.g. directory, e.g.,
PUTFH (directory filehandle) PUTFH (directory filehandle)
SAVEFH SAVEFH
GETATTR attrbits (pre-op dir attrs) GETATTR attrbits (pre-op dir attrs)
CREATE optbits "foo" attrs CREATE optbits "foo" attrs
GETATTR attrbits (file attributes) GETATTR attrbits (file attributes)
RESTOREFH RESTOREFH
GETATTR attrbits (post-op dir attrs) GETATTR attrbits (post-op dir attrs)
18.28. Operation 32: SAVEFH - Save Current Filehandle 18.28. Operation 32: SAVEFH - Save Current Filehandle
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struct SAVEFH4res { struct SAVEFH4res {
/* /*
* If status is NFS4_OK, * If status is NFS4_OK,
* new SAVED_FH: value of current fh * new SAVED_FH: value of current fh
*/ */
nfsstat4 status; nfsstat4 status;
}; };
18.28.3. DESCRIPTION 18.28.3. DESCRIPTION
Save the current filehandle and stateid. If a previous filehandle The SAVEFH operation saves the current filehandle and stateid. If a
was saved then it is no longer accessible. The saved filehandle can previous filehandle was saved, then it is no longer accessible. The
be restored as the current filehandle with the RESTOREFH operator. saved filehandle can be restored as the current filehandle with the
RESTOREFH operator.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
See Section 16.2.3.1.1 for more details on the current filehandle. See Section 16.2.3.1.1 for more details on the current filehandle.
See Section 16.2.3.1.2 for more details on the current stateid. See Section 16.2.3.1.2 for more details on the current stateid.
18.28.4. IMPLEMENTATION 18.28.4. IMPLEMENTATION
18.29. Operation 33: SECINFO - Obtain Available Security 18.29. Operation 33: SECINFO - Obtain Available Security
skipping to change at page 481, line 46 skipping to change at page 482, line 46
default: default:
void; void;
}; };
18.29.3. DESCRIPTION 18.29.3. DESCRIPTION
The SECINFO operation is used by the client to obtain a list of valid The SECINFO operation is used by the client to obtain a list of valid
RPC authentication flavors for a specific directory filehandle, file RPC authentication flavors for a specific directory filehandle, file
name pair. SECINFO should apply the same access methodology used for name pair. SECINFO should apply the same access methodology used for
LOOKUP when evaluating the name. Therefore, if the requester does LOOKUP when evaluating the name. Therefore, if the requester does
not have the appropriate access to LOOKUP the name then SECINFO MUST not have the appropriate access to LOOKUP the name, then SECINFO MUST
behave the same way and return NFS4ERR_ACCESS. behave the same way and return NFS4ERR_ACCESS.
The result will contain an array which represents the security The result will contain an array that represents the security
mechanisms available, with an order corresponding to the server's mechanisms available, with an order corresponding to the server's
preferences, the most preferred being first in the array. The client preferences, the most preferred being first in the array. The client
is free to pick whatever security mechanism it both desires and is free to pick whatever security mechanism it both desires and
supports, or to pick in the server's preference order the first one supports, or to pick in the server's preference order the first one
it supports. The array entries are represented by the secinfo4 it supports. The array entries are represented by the secinfo4
structure. The field 'flavor' will contain a value of AUTH_NONE, structure. The field 'flavor' will contain a value of AUTH_NONE,
AUTH_SYS (as defined in RFC1831 [3]), or RPCSEC_GSS (as defined in AUTH_SYS (as defined in RFC 5531 [3]), or RPCSEC_GSS (as defined in
RFC2203 [4]). The field flavor can also be any other security flavor RFC 2203 [4]). The field flavor can also be any other security
registered with IANA. flavor registered with IANA.
For the flavors AUTH_NONE and AUTH_SYS, no additional security For the flavors AUTH_NONE and AUTH_SYS, no additional security
information is returned. The same is true of many (if not most) information is returned. The same is true of many (if not most)
other security flavors, including AUTH_DH. For a return value of other security flavors, including AUTH_DH. For a return value of
RPCSEC_GSS, a security triple is returned that contains the mechanism RPCSEC_GSS, a security triple is returned that contains the mechanism
object identifier (OID, as defined in RFC2743 [7]), the quality of object identifier (OID, as defined in RFC2743 [7]), the quality of
protection (as defined in RFC2743 [7]) and the service type (as protection (as defined in RFC 2743 [7]), and the service type (as
defined in RFC2203 [4]). It is possible for SECINFO to return defined in RFC2203 [4]). It is possible for SECINFO to return
multiple entries with flavor equal to RPCSEC_GSS with different multiple entries with flavor equal to RPCSEC_GSS with different
security triple values. security triple values.
On success, the current filehandle is consumed (see On success, the current filehandle is consumed (see
Section 2.6.3.1.1.8), and if the next operation after SECINFO tries Section 2.6.3.1.1.8), and if the next operation after SECINFO tries
to use the current filehandle, that operation will fail with the to use the current filehandle, that operation will fail with the
status NFS4ERR_NOFILEHANDLE. status NFS4ERR_NOFILEHANDLE.
If the name has a length of 0 (zero), or if name does not obey the If the name has a length of zero, or if the name does not obey the
UTF-8 definition (assuming UTF-8 capabilities are enabled, see UTF-8 definition (assuming UTF-8 capabilities are enabled; see
Section 14.4), the error NFS4ERR_INVAL will be returned. Section 14.4), the error NFS4ERR_INVAL will be returned.
See Section 2.6 for additional information on the use of SECINFO. See Section 2.6 for additional information on the use of SECINFO.
18.29.4. IMPLEMENTATION 18.29.4. IMPLEMENTATION
The SECINFO operation is expected to be used by the NFS client when The SECINFO operation is expected to be used by the NFS client when
the error value of NFS4ERR_WRONGSEC is returned from another NFS the error value of NFS4ERR_WRONGSEC is returned from another NFS
operation. This signifies to the client that the server's security operation. This signifies to the client that the server's security
policy is different from what the client is currently using. At this policy is different from what the client is currently using. At this
point, the client is expected to obtain a list of possible security point, the client is expected to obtain a list of possible security
flavors and choose what best suits its policies. flavors and choose what best suits its policies.
As mentioned, the server's security policies will determine when a As mentioned, the server's security policies will determine when a
client request receives NFS4ERR_WRONGSEC. See Table 8 for a list client request receives NFS4ERR_WRONGSEC. See Table 8 for a list of
operations which can return NFS4ERR_WRONGSEC. In addition, when operations that can return NFS4ERR_WRONGSEC. In addition, when
READDIR returns attributes, the rdattr_error (Section 5.8.1.12) can READDIR returns attributes, the rdattr_error (Section 5.8.1.12) can
contain NFS4ERR_WRONGSEC. Note that CREATE and REMOVE MUST NOT contain NFS4ERR_WRONGSEC. Note that CREATE and REMOVE MUST NOT
return NFS4ERR_WRONGSEC. The rationale for CREATE is that unless the return NFS4ERR_WRONGSEC. The rationale for CREATE is that unless the
target name exists it cannot have a separate security policy from the target name exists, it cannot have a separate security policy from
parent directory, and the security policy of the parent was checked the parent directory, and the security policy of the parent was
when its filehandle was injected into the COMPOUND request's checked when its filehandle was injected into the COMPOUND request's
operations stream (for similar reasons, an OPEN operation that operations stream (for similar reasons, an OPEN operation that
creates the target MUST NOT return NFS4ERR_WRONGSEC). If the target creates the target MUST NOT return NFS4ERR_WRONGSEC). If the target
name exists, while it might have a separate security policy, that is name exists, while it might have a separate security policy, that is
irrelevant because CREATE MUST return NFS4ERR_EXIST. The rationale irrelevant because CREATE MUST return NFS4ERR_EXIST. The rationale
for REMOVE is that while that target might have separate security for REMOVE is that while that target might have a separate security
policy, the target is going to be removed, and so the security policy policy, the target is going to be removed, and so the security policy
of the parent trumps that of the object being removed. RENAME and of the parent trumps that of the object being removed. RENAME and
LINK MAY return NFS4ERR_WRONGSEC, but the NFS4ERR_WRONGSEC error LINK MAY return NFS4ERR_WRONGSEC, but the NFS4ERR_WRONGSEC error
applies only to the saved filehandle (see Section 2.6.3.1.2). Any applies only to the saved filehandle (see Section 2.6.3.1.2). Any
NFS4ERR_WRONGSEC error on the current filehandle used by LINK and NFS4ERR_WRONGSEC error on the current filehandle used by LINK and
RENAME MUST be returned by the PUTFH, PUTPUBFH, PUTROOTFH, or RENAME MUST be returned by the PUTFH, PUTPUBFH, PUTROOTFH, or
RESTOREFH operation that injected the current filehandle. RESTOREFH operation that injected the current filehandle.
With the exception of LINK and RENAME, the set of operations that can With the exception of LINK and RENAME, the set of operations that can
return NFS4ERR_WRONGSEC represent the point at which the client can return NFS4ERR_WRONGSEC represents the point at which the client can
inject a filehandle into the "current filehandle" at the server. The inject a filehandle into the "current filehandle" at the server. The
filehandle is either provided by the client (PUTFH, PUTPUBFH, filehandle is either provided by the client (PUTFH, PUTPUBFH,
PUTROOTFH), generated as a result of a name to filehandle translation PUTROOTFH), generated as a result of a name-to-filehandle translation
(LOOKUP and OPEN), or generated from the saved filehandle via (LOOKUP and OPEN), or generated from the saved filehandle via
RESTOREFH. As Section 2.6.3.1.1.1 states, a put filehandle operation RESTOREFH. As Section 2.6.3.1.1.1 states, a put filehandle operation
followed by SAVEFH MUST NOT return NFS4ERR_WRONGSEC. Thus the followed by SAVEFH MUST NOT return NFS4ERR_WRONGSEC. Thus, the
RESTOREFH operation, under certain conditions (see Section 2.6.3.1.1) RESTOREFH operation, under certain conditions (see
is permitted to return NFS4ERR_WRONGSEC so that security policies can Section 2.6.3.1.1), is permitted to return NFS4ERR_WRONGSEC so that
be honored. security policies can be honored.
The READDIR operation will not directly return the NFS4ERR_WRONGSEC The READDIR operation will not directly return the NFS4ERR_WRONGSEC
error. However, if the READDIR request included a request for error. However, if the READDIR request included a request for
attributes, it is possible that the READDIR request's security triple attributes, it is possible that the READDIR request's security triple
did not match that of a directory entry. If this is the case and the did not match that of a directory entry. If this is the case and the
client has requested the rdattr_error attribute, the server will client has requested the rdattr_error attribute, the server will
return the NFS4ERR_WRONGSEC error in rdattr_error for the entry. return the NFS4ERR_WRONGSEC error in rdattr_error for the entry.
To resolve an error return of NFS4ERR_WRONGSEC, the client does the To resolve an error return of NFS4ERR_WRONGSEC, the client does the
following: following:
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o For PUTFH, PUTROOTFH, PUTPUBFH, RESTOREFH, LINK, and RENAME, the o For PUTFH, PUTROOTFH, PUTPUBFH, RESTOREFH, LINK, and RENAME, the
client will use SECINFO_NO_NAME { style = client will use SECINFO_NO_NAME { style =
SECINFO_STYLE4_CURRENT_FH }. The client will prefix the SECINFO_STYLE4_CURRENT_FH }. The client will prefix the
SECINFO_NO_NAME operation with the appropriate PUTFH, PUTPUBFH, or SECINFO_NO_NAME operation with the appropriate PUTFH, PUTPUBFH, or
PUTROOTFH operation that provides the filehandle originally PUTROOTFH operation that provides the filehandle originally
provided by the PUTFH, PUTPUBFH, PUTROOTFH, or RESTOREFH provided by the PUTFH, PUTPUBFH, PUTROOTFH, or RESTOREFH
operation. operation.
NOTE: In NFSv4.0, the client was required to use SECINFO, and had NOTE: In NFSv4.0, the client was required to use SECINFO, and had
to reconstruct the parent of the original filehandle, and the to reconstruct the parent of the original filehandle and the
component name of the original filehandle. The introduction in component name of the original filehandle. The introduction in
NFSv4.1 of SECINFO_NO_NAME obviates the need for reconstruction. NFSv4.1 of SECINFO_NO_NAME obviates the need for reconstruction.
o For LOOKUPP, the client will use SECINFO_NO_NAME { style = o For LOOKUPP, the client will use SECINFO_NO_NAME { style =
SECINFO_STYLE4_PARENT } and provide the filehandle which equals SECINFO_STYLE4_PARENT } and provide the filehandle that equals the
the filehandle originally provided to LOOKUPP. filehandle originally provided to LOOKUPP.
See Section 21 for a discussion on the recommendations for the See Section 21 for a discussion on the recommendations for the
security flavor used by SECINFO and SECINFO_NO_NAME. security flavor used by SECINFO and SECINFO_NO_NAME.
18.30. Operation 34: SETATTR - Set Attributes 18.30. Operation 34: SETATTR - Set Attributes
18.30.1. ARGUMENTS 18.30.1. ARGUMENTS
struct SETATTR4args { struct SETATTR4args {
/* CURRENT_FH: target object */ /* CURRENT_FH: target object */
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nfsstat4 status; nfsstat4 status;
bitmap4 attrsset; bitmap4 attrsset;
}; };
18.30.3. DESCRIPTION 18.30.3. DESCRIPTION
The SETATTR operation changes one or more of the attributes of a file The SETATTR operation changes one or more of the attributes of a file
system object. The new attributes are specified with a bitmap and system object. The new attributes are specified with a bitmap and
the attributes that follow the bitmap in bit order. the attributes that follow the bitmap in bit order.
The stateid argument for SETATTR is used to provide file locking The stateid argument for SETATTR is used to provide byte-range
context that is necessary for SETATTR requests that set the size locking context that is necessary for SETATTR requests that set the
attribute. Since setting the size attribute modifies the file's size attribute. Since setting the size attribute modifies the file's
data, it has the same locking requirements as a corresponding WRITE. data, it has the same locking requirements as a corresponding WRITE.
Any SETATTR that sets the size attribute is incompatible with a share Any SETATTR that sets the size attribute is incompatible with a share
reservation that specifies DENY_WRITE. The area between the old end- reservation that specifies OPEN4_SHARE_DENY_WRITE. The area between
of-file and the new end-of-file is considered to be modified just as the old end-of-file and the new end-of-file is considered to be
would have been the case had the area in question been specified as modified just as would have been the case had the area in question
the target of WRITE, for the purpose of checking conflicts with byte- been specified as the target of WRITE, for the purpose of checking
range locks, for those cases in which a server is implementing conflicts with byte-range locks, for those cases in which a server is
mandatory byte-range locking behavior. A valid stateid SHOULD always implementing mandatory byte-range locking behavior. A valid stateid
be specified. When the file size attribute is not set, the special SHOULD always be specified. When the file size attribute is not set,
stateid consisting of all bits zero MAY be passed. the special stateid consisting of all bits equal to zero MAY be
passed.
On either success or failure of the operation, the server will return On either success or failure of the operation, the server will return
the attrsset bitmask to represent what (if any) attributes were the attrsset bitmask to represent what (if any) attributes were
successfully set. The attrsset in the response is a subset of the successfully set. The attrsset in the response is a subset of the
attrmask field of the obj_attributes field in the argument. attrmask field of the obj_attributes field in the argument.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.30.4. IMPLEMENTATION 18.30.4. IMPLEMENTATION
If the request specifies the owner attribute to be set, the server If the request specifies the owner attribute to be set, the server
SHOULD allow the operation to succeed if the current owner of the SHOULD allow the operation to succeed if the current owner of the
object matches the value specified in the request. Some servers may object matches the value specified in the request. Some servers may
be implemented in a way as to prohibit the setting of the owner be implemented in a way as to prohibit the setting of the owner
attribute unless the requester has privilege to do so. If the server attribute unless the requester has privilege to do so. If the server
is lenient in this one case of matching owner values, the client is lenient in this one case of matching owner values, the client
implementation may be simplified in cases of creation of an object implementation may be simplified in cases of creation of an object
(e.g. an exclusive create via OPEN) followed by a SETATTR. (e.g., an exclusive create via OPEN) followed by a SETATTR.
The file size attribute is used to request changes to the size of a The file size attribute is used to request changes to the size of a
file. A value of zero causes the file to be truncated, a value less file. A value of zero causes the file to be truncated, a value less
than the current size of the file causes data from new size to the than the current size of the file causes data from new size to the
end of the file to be discarded, and a size greater than the current end of the file to be discarded, and a size greater than the current
size of the file causes logically zeroed data bytes to be added to size of the file causes logically zeroed data bytes to be added to
the end of the file. Servers are free to implement this using the end of the file. Servers are free to implement this using
unallocated bytes (holes) or allocated data bytes set to zero. unallocated bytes (holes) or allocated data bytes set to zero.
Clients should not make any assumptions regarding a server's Clients should not make any assumptions regarding a server's
implementation of this feature, beyond that the bytes in affected implementation of this feature, beyond that the bytes in the affected
region returned by READ will be zeroed. Servers MUST support byte-range returned by READ will be zeroed. Servers MUST support
extending the file size via SETATTR. extending the file size via SETATTR.
SETATTR is not guaranteed to be atomic. A failed SETATTR may SETATTR is not guaranteed to be atomic. A failed SETATTR may
partially change a file's attributes, hence the reason why the reply partially change a file's attributes, hence the reason why the reply
always includes the status and the list of attributes that were set. always includes the status and the list of attributes that were set.
If the object whose attributes are being changed has a file If the object whose attributes are being changed has a file
delegation which is held by a client other than the one doing the delegation that is held by a client other than the one doing the
SETATTR, the delegation(s) must be recalled, and the operation cannot SETATTR, the delegation(s) must be recalled, and the operation cannot
proceed to actually change an attribute until each such delegation is proceed to actually change an attribute until each such delegation is
returned or revoked. In all cases in which delegations are recalled, returned or revoked. In all cases in which delegations are recalled,
the server is likely to return one or more NFS4ERR_DELAY error while the server is likely to return one or more NFS4ERR_DELAY errors while
the delegation(s) remains outstanding, although it may, if the the delegation(s) remains outstanding, although it might not do that
returns happen quickly, not do that. if the delegations are returned quickly.
If the object whose attributes are being set is a directory and If the object whose attributes are being set is a directory and
another client holds a directory delegation for that directory, then another client holds a directory delegation for that directory, then
if enabled, asynchronous notifications will be generated when the set if enabled, asynchronous notifications will be generated when the set
of attributes changed has a non-null intersection with the set of of attributes changed has a non-null intersection with the set of
attributes for which notification is requested. Notifications of attributes for which notification is requested. Notifications of
type NOTIFY4_CHANGE_DIR_ATTRS will be sent to the appropriate type NOTIFY4_CHANGE_DIR_ATTRS will be sent to the appropriate
client(s), but the SETATTR is not delayed by waiting for these client(s), but the SETATTR is not delayed by waiting for these
notifications to be sent. notifications to be sent.
If the object whose attributes are being set is a member of directory If the object whose attributes are being set is a member of the
for which another client holds a directory delegation, then directory for which another client holds a directory delegation, then
asynchronous notifications will be generated when the set of asynchronous notifications will be generated when the set of
attributes changed has a non-null intersection with the set of attributes changed has a non-null intersection with the set of
attributes for which notification is requested. Notifications of attributes for which notification is requested. Notifications of
type NOTIFY4_CHANGE_CHILD_ATTRS will be sent to the appropriate type NOTIFY4_CHANGE_CHILD_ATTRS will be sent to the appropriate
clients, but the SETATTR is not delayed by waiting for these clients, but the SETATTR is not delayed by waiting for these
notifications to be sent. notifications to be sent.
Changing the size of a file with SETATTR indirectly changes the Changing the size of a file with SETATTR indirectly changes the
time_modify and change attributes. A client must account for this as time_modify and change attributes. A client must account for this as
size changes can result in data deletion. size changes can result in data deletion.
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guard condition and the setting of the attributes have the potential guard condition and the setting of the attributes have the potential
to compromise this function, as would the corresponding delay in the to compromise this function, as would the corresponding delay in the
NFSv4 emulation. Therefore, NFSv4.1 servers SHOULD take care to NFSv4 emulation. Therefore, NFSv4.1 servers SHOULD take care to
avoid such delays, to the degree possible, when executing such a avoid such delays, to the degree possible, when executing such a
request. request.
If the server does not support an attribute as requested by the If the server does not support an attribute as requested by the
client, the server SHOULD return NFS4ERR_ATTRNOTSUPP. client, the server SHOULD return NFS4ERR_ATTRNOTSUPP.
A mask of the attributes actually set is returned by SETATTR in all A mask of the attributes actually set is returned by SETATTR in all
cases. That mask MUST NOT include attributes bits not requested to cases. That mask MUST NOT include attribute bits not requested to be
be set by the client. If the attribute masks in the request and set by the client. If the attribute masks in the request and reply
reply are equal, the status field in the reply MUST be NFS4_OK. are equal, the status field in the reply MUST be NFS4_OK.
18.31. Operation 37: VERIFY - Verify Same Attributes 18.31. Operation 37: VERIFY - Verify Same Attributes
18.31.1. ARGUMENTS 18.31.1. ARGUMENTS
struct VERIFY4args { struct VERIFY4args {
/* CURRENT_FH: object */ /* CURRENT_FH: object */
fattr4 obj_attributes; fattr4 obj_attributes;
}; };
18.31.2. RESULTS 18.31.2. RESULTS
struct VERIFY4res { struct VERIFY4res {
nfsstat4 status; nfsstat4 status;
}; };
18.31.3. DESCRIPTION 18.31.3. DESCRIPTION
The VERIFY operation is used to verify that attributes have the value The VERIFY operation is used to verify that attributes have the value
assumed by the client before proceeding with following operations in assumed by the client before proceeding with the following operations
the COMPOUND request. If any of the attributes do not match then the in the COMPOUND request. If any of the attributes do not match, then
error NFS4ERR_NOT_SAME must be returned. The current filehandle the error NFS4ERR_NOT_SAME must be returned. The current filehandle
retains its value after successful completion of the operation. retains its value after successful completion of the operation.
18.31.4. IMPLEMENTATION 18.31.4. IMPLEMENTATION
One possible use of the VERIFY operation is the following series of One possible use of the VERIFY operation is the following series of
operations. With this the client is attempting to verify that the operations. With this, the client is attempting to verify that the
file being removed will match what the client expects to be removed. file being removed will match what the client expects to be removed.
This series can help prevent the unintended deletion of a file. This series can help prevent the unintended deletion of a file.
PUTFH (directory filehandle) PUTFH (directory filehandle)
LOOKUP (file name) LOOKUP (file name)
VERIFY (filehandle == fh) VERIFY (filehandle == fh)
PUTFH (directory filehandle) PUTFH (directory filehandle)
REMOVE (file name) REMOVE (file name)
This series does not prevent a second client from removing and This series does not prevent a second client from removing and
creating a new file in the middle of this sequence but it does help creating a new file in the middle of this sequence, but it does help
avoid the unintended result. avoid the unintended result.
In the case that a RECOMMENDED attribute is specified in the VERIFY In the case that a RECOMMENDED attribute is specified in the VERIFY
operation and the server does not support that attribute for the file operation and the server does not support that attribute for the file
system object, the error NFS4ERR_ATTRNOTSUPP is returned to the system object, the error NFS4ERR_ATTRNOTSUPP is returned to the
client. client.
When the attribute rdattr_error or any set-only attribute (e.g. When the attribute rdattr_error or any set-only attribute (e.g.,
time_modify_set) is specified, the error NFS4ERR_INVAL is returned to time_modify_set) is specified, the error NFS4ERR_INVAL is returned to
the client. the client.
18.32. Operation 38: WRITE - Write to File 18.32. Operation 38: WRITE - Write to File
18.32.1. ARGUMENTS 18.32.1. ARGUMENTS
enum stable_how4 { enum stable_how4 {
UNSTABLE4 = 0, UNSTABLE4 = 0,
DATA_SYNC4 = 1, DATA_SYNC4 = 1,
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WRITE4resok resok4; WRITE4resok resok4;
default: default:
void; void;
}; };
18.32.3. DESCRIPTION 18.32.3. DESCRIPTION
The WRITE operation is used to write data to a regular file. The The WRITE operation is used to write data to a regular file. The
target file is specified by the current filehandle. The offset target file is specified by the current filehandle. The offset
specifies the offset where the data should be written. An offset of specifies the offset where the data should be written. An offset of
0 (zero) specifies that the write should start at the beginning of zero specifies that the write should start at the beginning of the
the file. The count, as encoded as part of the opaque data file. The count, as encoded as part of the opaque data parameter,
parameter, represents the number of bytes of data that are to be represents the number of bytes of data that are to be written. If
written. If the count is 0 (zero), the WRITE will succeed and return the count is zero, the WRITE will succeed and return a count of zero
a count of 0 (zero) subject to permissions checking. The server MAY subject to permissions checking. The server MAY write fewer bytes
write fewer bytes than requested by the client. than requested by the client.
The client specifies with the stable parameter the method of how the The client specifies with the stable parameter the method of how the
data is to be processed by the server. If stable is FILE_SYNC4, the data is to be processed by the server. If stable is FILE_SYNC4, the
server MUST commit the data written plus all file system metadata to server MUST commit the data written plus all file system metadata to
stable storage before returning results. This corresponds to the stable storage before returning results. This corresponds to the
NFSv2 protocol semantics. Any other behavior constitutes a protocol NFSv2 protocol semantics. Any other behavior constitutes a protocol
violation. If stable is DATA_SYNC4, then the server MUST commit all violation. If stable is DATA_SYNC4, then the server MUST commit all
of the data to stable storage and enough of the metadata to retrieve of the data to stable storage and enough of the metadata to retrieve
the data before returning. The server implementor is free to the data before returning. The server implementor is free to
implement DATA_SYNC4 in the same fashion as FILE_SYNC4, but with a implement DATA_SYNC4 in the same fashion as FILE_SYNC4, but with a
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will subsequently be committed to stable storage. The only will subsequently be committed to stable storage. The only
guarantees made by the server are that it will not destroy any data guarantees made by the server are that it will not destroy any data
without changing the value of writeverf and that it will not commit without changing the value of writeverf and that it will not commit
the data and metadata at a level less than that requested by the the data and metadata at a level less than that requested by the
client. client.
Except when special stateids are used, the stateid value for a WRITE Except when special stateids are used, the stateid value for a WRITE
request represents a value returned from a previous byte-range LOCK request represents a value returned from a previous byte-range LOCK
or OPEN request or the stateid associated with a delegation. The or OPEN request or the stateid associated with a delegation. The
stateid identifies the associated owners if any and is used by the stateid identifies the associated owners if any and is used by the
server to verify that the associated locks are still valid (e.g. have server to verify that the associated locks are still valid (e.g.,
not been revoked). have not been revoked).
Upon successful completion, the following results are returned. The Upon successful completion, the following results are returned. The
count result is the number of bytes of data written to the file. The count result is the number of bytes of data written to the file. The
server may write fewer bytes than requested. If so, the actual server may write fewer bytes than requested. If so, the actual
number of bytes written starting at location, offset, is returned. number of bytes written starting at location, offset, is returned.
The server also returns an indication of the level of commitment of The server also returns an indication of the level of commitment of
the data and metadata via committed. Per Table 11, the data and metadata via committed. Per Table 11,
o The server MAY commit the data at a stronger level than requested. o The server MAY commit the data at a stronger level than requested.
skipping to change at page 490, line 23 skipping to change at page 491, line 23
+------------+-----------------------------------+ +------------+-----------------------------------+
| UNSTABLE4 | FILE_SYNC4, DATA_SYNC4, UNSTABLE4 | | UNSTABLE4 | FILE_SYNC4, DATA_SYNC4, UNSTABLE4 |
| DATA_SYNC4 | FILE_SYNC4, DATA_SYNC4 | | DATA_SYNC4 | FILE_SYNC4, DATA_SYNC4 |
| FILE_SYNC4 | FILE_SYNC4 | | FILE_SYNC4 | FILE_SYNC4 |
+------------+-----------------------------------+ +------------+-----------------------------------+
Table 11 Table 11
The final portion of the result is the field writeverf. This field The final portion of the result is the field writeverf. This field
is the write verifier and is a cookie that the client can use to is the write verifier and is a cookie that the client can use to
determine whether a server has changed instance state (e.g. server determine whether a server has changed instance state (e.g., server
restart) between a call to WRITE and a subsequent call to either restart) between a call to WRITE and a subsequent call to either
WRITE or COMMIT. This cookie MUST be unchanged during a single WRITE or COMMIT. This cookie MUST be unchanged during a single
instance of the NFSv4.1 server and MUST be unique between instances instance of the NFSv4.1 server and MUST be unique between instances
of the NFSv4.1 server. If the cookie changes, then the client MUST of the NFSv4.1 server. If the cookie changes, then the client MUST
assume that any data written with an UNSTABLE4 value for committed assume that any data written with an UNSTABLE4 value for committed
and an old writeverf in the reply has been lost and will need to be and an old writeverf in the reply has been lost and will need to be
recovered. recovered.
If a client writes data to the server with the stable argument set to If a client writes data to the server with the stable argument set to
UNSTABLE4 and the reply yields a committed response of DATA_SYNC4 or UNSTABLE4 and the reply yields a committed response of DATA_SYNC4 or
UNSTABLE4, the client will follow up some time in the future with a UNSTABLE4, the client will follow up some time in the future with a
COMMIT operation to synchronize outstanding asynchronous data and COMMIT operation to synchronize outstanding asynchronous data and
metadata with the server's stable storage, barring client error. It metadata with the server's stable storage, barring client error. It
is possible that due to client crash or other error that a subsequent is possible that due to client crash or other error that a subsequent
COMMIT will not be received by the server. COMMIT will not be received by the server.
For a WRITE with a stateid value of all bits 0, the server MAY allow For a WRITE with a stateid value of all bits equal to zero, the
the WRITE to be serviced subject to mandatory file locks or the server MAY allow the WRITE to be serviced subject to mandatory byte-
current share deny modes for the file. For a WRITE with a stateid range locks or the current share deny modes for the file. For a
value of all bits 1, the server MUST NOT allow the WRITE operation to WRITE with a stateid value of all bits equal to 1, the server MUST
bypass locking checks at the server and otherwise is treated as if a NOT allow the WRITE operation to bypass locking checks at the server
stateid of all bits 0 were used. and otherwise is treated as if a stateid of all bits equal to zero
were used.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
18.32.4. IMPLEMENTATION 18.32.4. IMPLEMENTATION
It is possible for the server to write fewer bytes of data than It is possible for the server to write fewer bytes of data than
requested by the client. In this case, the server SHOULD NOT return requested by the client. In this case, the server SHOULD NOT return
an error unless no data was written at all. If the server writes an error unless no data was written at all. If the server writes
less than the number of bytes specified, the client will need to send less than the number of bytes specified, the client will need to send
another WRITE to write the remaining data. another WRITE to write the remaining data.
It is assumed that the act of writing data to a file will cause the It is assumed that the act of writing data to a file will cause the
time_modified and change attributes of the file to be updated. time_modified and change attributes of the file to be updated.
However, these attributes SHOULD NOT be changed unless the contents However, these attributes SHOULD NOT be changed unless the contents
of the file are changed. Thus, a WRITE request with count set to 0 of the file are changed. Thus, a WRITE request with count set to
SHOULD NOT cause the time_modified and change attributes of the file zero SHOULD NOT cause the time_modified and change attributes of the
to be updated. file to be updated.
Stable storage is persistent storage that survives: Stable storage is persistent storage that survives:
1. Repeated power failures. 1. Repeated power failures.
2. Hardware failures (of any board, power supply, etc.). 2. Hardware failures (of any board, power supply, etc.).
3. Repeated software crashes and restarts. 3. Repeated software crashes and restarts.
This definition does not address failure of the stable storage module This definition does not address failure of the stable storage module
itself. itself.
The verifier is defined to allow a client to detect different The verifier is defined to allow a client to detect different
instances of an NFSv4.1 protocol server over which cached, instances of an NFSv4.1 protocol server over which cached,
uncommitted data may be lost. In the most likely case, the verifier uncommitted data may be lost. In the most likely case, the verifier
allows the client to detect server restarts. This information is allows the client to detect server restarts. This information is
required so that the client can safely determine whether the server required so that the client can safely determine whether the server
could have lost cached data. If the server fails unexpectedly and could have lost cached data. If the server fails unexpectedly and
the client has uncommitted data from previous WRITE requests (done the client has uncommitted data from previous WRITE requests (done
with the stable argument set to UNSTABLE4 and in which the result with the stable argument set to UNSTABLE4 and in which the result
committed was returned as UNSTABLE4 as well) the server might not committed was returned as UNSTABLE4 as well), the server might not
have flushed cached data to stable storage. The burden of recovery have flushed cached data to stable storage. The burden of recovery
is on the client and the client will need to retransmit the data to is on the client, and the client will need to retransmit the data to
the server. the server.
A suggested verifier would be to use the time that the server was A suggested verifier would be to use the time that the server was
last started (if restarting the server results in lost buffers). last started (if restarting the server results in lost buffers).
The reply's committed field allows the client to do more effective The reply's committed field allows the client to do more effective
caching. If the server is committing all WRITE requests to stable caching. If the server is committing all WRITE requests to stable
storage, then it SHOULD return with committed set to FILE_SYNC4, storage, then it SHOULD return with committed set to FILE_SYNC4,
regardless of the value of the stable field in the arguments. A regardless of the value of the stable field in the arguments. A
server that uses an NVRAM accelerator may choose to implement this server that uses an NVRAM accelerator may choose to implement this
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Some implementations may return NFS4ERR_NOSPC instead of Some implementations may return NFS4ERR_NOSPC instead of
NFS4ERR_DQUOT when a user's quota is exceeded. NFS4ERR_DQUOT when a user's quota is exceeded.
In the case that the current filehandle is of type NF4DIR, the server In the case that the current filehandle is of type NF4DIR, the server
will return NFS4ERR_ISDIR. If the current file is a symbolic link, will return NFS4ERR_ISDIR. If the current file is a symbolic link,
the error NFS4ERR_SYMLINK will be returned. Otherwise, if the the error NFS4ERR_SYMLINK will be returned. Otherwise, if the
current filehandle does not designate an ordinary file, the server current filehandle does not designate an ordinary file, the server
will return NFS4ERR_WRONG_TYPE. will return NFS4ERR_WRONG_TYPE.
If mandatory file locking is in effect for the file, and the If mandatory byte-range locking is in effect for the file, and the
corresponding byte-range of the data to be written to the file is corresponding byte-range of the data to be written to the file is
read or write locked by an owner that is not associated with the READ_LT or WRITE_LT locked by an owner that is not associated with
stateid, the server MUST return NFS4ERR_LOCKED. If so, the client the stateid, the server MUST return NFS4ERR_LOCKED. If so, the
MUST check if the owner corresponding to the stateid used with the client MUST check if the owner corresponding to the stateid used with
WRITE operation has a conflicting read lock that overlaps with the the WRITE operation has a conflicting READ_LT lock that overlaps with
region that was to be written. If the stateid's owner has no the byte-range that was to be written. If the stateid's owner has no
conflicting read lock, then the client SHOULD try to get the conflicting READ_LT lock, then the client SHOULD try to get the
appropriate write byte-range lock via the LOCK operation before re- appropriate write byte-range lock via the LOCK operation before re-
attempting the WRITE. When the WRITE completes, the client SHOULD attempting the WRITE. When the WRITE completes, the client SHOULD
release the byte-range lock via LOCKU. release the byte-range lock via LOCKU.
If the stateid's owner had a conflicting read lock, then the client If the stateid's owner had a conflicting READ_LT lock, then the
has no choice but to return an error to the application that client has no choice but to return an error to the application that
attempted the WRITE. The reason is that since the stateid's owner attempted the WRITE. The reason is that since the stateid's owner
had a read lock, the server either attempted to temporarily had a READ_LT lock, either the server attempted to temporarily
effectively upgrade this read lock to a write lock, or the server has effectively upgrade this READ_LT lock to a WRITE_LT lock or the
no upgrade capability. If the server attempted to upgrade the read server has no upgrade capability. If the server attempted to upgrade
lock and failed, it is pointless for the client to re-attempt the the READ_LT lock and failed, it is pointless for the client to re-
upgrade via the LOCK operation, because there might be another client attempt the upgrade via the LOCK operation, because there might be
also trying to upgrade. If two clients are blocked trying upgrade another client also trying to upgrade. If two clients are blocked
the same lock, the clients deadlock. If the server has no upgrade trying to upgrade the same lock, the clients deadlock. If the server
capability, then it is pointless to try a LOCK operation to upgrade. has no upgrade capability, then it is pointless to try a LOCK
operation to upgrade.
If one or more other clients have delegations for the file being If one or more other clients have delegations for the file being
written, those delegations MUST be recalled, and the operation cannot written, those delegations MUST be recalled, and the operation cannot
proceed until those delegations are returned or revoked. Except proceed until those delegations are returned or revoked. Except
where this happens very quickly, one or more NFS4ERR_DELAY errors where this happens very quickly, one or more NFS4ERR_DELAY errors
will be returned to requests made while the delegation remains will be returned to requests made while the delegation remains
outstanding. Normally, delegations will not be recalled as a result outstanding. Normally, delegations will not be recalled as a result
of a WRITE operation since the recall will occur as a result of an of a WRITE operation since the recall will occur as a result of an
earlier OPEN. However, since it is possible for a WRITE to be done earlier OPEN. However, since it is possible for a WRITE to be done
with a special stateid, the server needs to check for this case even with a special stateid, the server needs to check for this case even
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If, when the client ID was created, the client opted for SP4_NONE If, when the client ID was created, the client opted for SP4_NONE
state protection, the client is not required to use state protection, the client is not required to use
BIND_CONN_TO_SESSION to associate the connection with the session, BIND_CONN_TO_SESSION to associate the connection with the session,
unless the client wishes to associate the connection with the unless the client wishes to associate the connection with the
backchannel. When SP4_NONE protection is used, simply sending a backchannel. When SP4_NONE protection is used, simply sending a
COMPOUND request with a SEQUENCE operation is sufficient to associate COMPOUND request with a SEQUENCE operation is sufficient to associate
the connection with the session specified in SEQUENCE. the connection with the session specified in SEQUENCE.
The field bctsa_dir indicates whether the client wants to associate The field bctsa_dir indicates whether the client wants to associate
the connection with the fore channel or the backchannel or both the connection with the fore channel or the backchannel or both
channels. The value CDFC4_FORE_OR_BOTH indicates the client wants to channels. The value CDFC4_FORE_OR_BOTH indicates that the client
associate the connection with both the fore channel and backchannel, wants to associate the connection with both the fore channel and
but will accept the connection being associated to just the fore backchannel, but will accept the connection being associated to just
channel. The value CDFC4_BACK_OR_BOTH indicates the client wants to the fore channel. The value CDFC4_BACK_OR_BOTH indicates that the
associate with both the fore and backchannel, but will accept the client wants to associate with both the fore channel and backchannel,
connection being associated with just the backchannel. The server but will accept the connection being associated with just the
replies in bctsr_dir which channel(s) the connection is associated backchannel. The server replies in bctsr_dir which channel(s) the
with. If the client specified CDFC4_FORE, the server MUST return connection is associated with. If the client specified CDFC4_FORE,
CDFS4_FORE. If the client specified CDFC4_BACK, the server MUST the server MUST return CDFS4_FORE. If the client specified
return CDFS4_BACK. If the client specified CDFC4_FORE_OR_BOTH, the CDFC4_BACK, the server MUST return CDFS4_BACK. If the client
server MUST return CDFS4_FORE or CDFS4_BOTH. If the client specified specified CDFC4_FORE_OR_BOTH, the server MUST return CDFS4_FORE or
CDFC4_BACK_OR_BOTH, the server MUST return CDFS4_BACK or CDFS4_BOTH. CDFS4_BOTH. If the client specified CDFC4_BACK_OR_BOTH, the server
MUST return CDFS4_BACK or CDFS4_BOTH.
See the CREATE_SESSION operation (Section 18.36), and the description See the CREATE_SESSION operation (Section 18.36), and the description
of the argument csa_use_conn_in_rdma_mode to understand of the argument csa_use_conn_in_rdma_mode to understand
bctsa_use_conn_in_rdma_mode, and the description of bctsa_use_conn_in_rdma_mode, and the description of
csr_use_conn_in_rdma_mode to understand bctsr_use_conn_in_rdma_mode. csr_use_conn_in_rdma_mode to understand bctsr_use_conn_in_rdma_mode.
Invoking BIND_CONN_TO_SESSION on a connection already associated with Invoking BIND_CONN_TO_SESSION on a connection already associated with
the specified session has no effect, and the server MUST respond with the specified session has no effect, and the server MUST respond with
NFS4_OK, unless the client is demanding changes to the set of NFS4_OK, unless the client is demanding changes to the set of
channels the connection is associated with. If so, the server MUST channels the connection is associated with. If so, the server MUST
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client, per the sessions model, MUST retry the SET_SSV. But it needs client, per the sessions model, MUST retry the SET_SSV. But it needs
a new connection to do so, and MUST associate that connection with a new connection to do so, and MUST associate that connection with
the session via a BIND_CONN_TO_SESSION authenticated with the SSV GSS the session via a BIND_CONN_TO_SESSION authenticated with the SSV GSS
mechanism. The problem is that the RPCSEC_GSS message integrity mechanism. The problem is that the RPCSEC_GSS message integrity
codes use a subkey derived from the SSV as the key and the SSV may codes use a subkey derived from the SSV as the key and the SSV may
have changed. While there are multiple recovery strategies, a have changed. While there are multiple recovery strategies, a
single, general strategy is described here. single, general strategy is described here.
o The client reconnects. o The client reconnects.
o The client assumes the SET_SSV was executed, and so sends o The client assumes that the SET_SSV was executed, and so sends
BIND_CONN_TO_SESSION with the subkey (derived from the new SSV, BIND_CONN_TO_SESSION with the subkey (derived from the new SSV,
i.e., what SET_SSV would have set the SSV to) used as the key for i.e., what SET_SSV would have set the SSV to) used as the key for
the RPCSEC_GSS credential message integrity codes. the RPCSEC_GSS credential message integrity codes.
o If the request succeeds, this means the original attempted SET_SSV o If the request succeeds, this means that the original attempted
did execute successfully. The client re-sends the original SET_SSV did execute successfully. The client re-sends the
SET_SSV, which the server will reply to via the reply cache. original SET_SSV, which the server will reply to via the reply
cache.
o If the server returns an RPC authentication error, this means the o If the server returns an RPC authentication error, this means that
server's current SSV was not changed, (and the SET_SSV was likely the server's current SSV was not changed (and the SET_SSV was
not executed). The client then tries BIND_CONN_TO_SESSION with likely not executed). The client then tries BIND_CONN_TO_SESSION
the subkey derived from the old SSV as the key for the RPCSEC_GSS with the subkey derived from the old SSV as the key for the
message integrity codes. RPCSEC_GSS message integrity codes.
o The attempted BIND_CONN_TO_SESSION with the old SSV should o The attempted BIND_CONN_TO_SESSION with the old SSV should
succeed. If so the client re-sends the original SET_SSV. If the succeed. If so, the client re-sends the original SET_SSV. If the
original SET_SSV was not executed, then the server executes it. original SET_SSV was not executed, then the server executes it.
If the original SET_SSV was executed, but failed, the server will If the original SET_SSV was executed but failed, the server will
return the SET_SSV from the reply cache. return the SET_SSV from the reply cache.
18.35. Operation 42: EXCHANGE_ID - Instantiate Client ID 18.35. Operation 42: EXCHANGE_ID - Instantiate Client ID
Exchange long hand client and server identifiers (owners), and create The EXCHANGE_ID exchanges long-hand client and server identifiers
a client ID (owners), and creates a client ID.
18.35.1. ARGUMENT 18.35.1. ARGUMENT
const EXCHGID4_FLAG_SUPP_MOVED_REFER = 0x00000001; const EXCHGID4_FLAG_SUPP_MOVED_REFER = 0x00000001;
const EXCHGID4_FLAG_SUPP_MOVED_MIGR = 0x00000002; const EXCHGID4_FLAG_SUPP_MOVED_MIGR = 0x00000002;
const EXCHGID4_FLAG_BIND_PRINC_STATEID = 0x00000100; const EXCHGID4_FLAG_BIND_PRINC_STATEID = 0x00000100;
const EXCHGID4_FLAG_USE_NON_PNFS = 0x00010000; const EXCHGID4_FLAG_USE_NON_PNFS = 0x00010000;
const EXCHGID4_FLAG_USE_PNFS_MDS = 0x00020000; const EXCHGID4_FLAG_USE_PNFS_MDS = 0x00020000;
const EXCHGID4_FLAG_USE_PNFS_DS = 0x00040000; const EXCHGID4_FLAG_USE_PNFS_DS = 0x00040000;
skipping to change at page 500, line 12 skipping to change at page 501, line 12
along with the returned eir_sequenceid, as arguments to along with the returned eir_sequenceid, as arguments to
CREATE_SESSION. If the flag EXCHGID4_FLAG_CONFIRMED_R is set in the CREATE_SESSION. If the flag EXCHGID4_FLAG_CONFIRMED_R is set in the
result, eir_flags, then eir_sequenceid MUST be ignored, as it has no result, eir_flags, then eir_sequenceid MUST be ignored, as it has no
relevancy. relevancy.
EXCHANGE_ID MAY be sent in a COMPOUND procedure that starts with EXCHANGE_ID MAY be sent in a COMPOUND procedure that starts with
SEQUENCE. However, when a client communicates with a server for the SEQUENCE. However, when a client communicates with a server for the
first time, it will not have a session, so using SEQUENCE will not be first time, it will not have a session, so using SEQUENCE will not be
possible. If EXCHANGE_ID is sent without a preceding SEQUENCE, then possible. If EXCHANGE_ID is sent without a preceding SEQUENCE, then
it MUST be the only operation in the COMPOUND procedure's request. it MUST be the only operation in the COMPOUND procedure's request.
If is not, the server MUST return NFS4ERR_NOT_ONLY_OP. If it is not, the server MUST return NFS4ERR_NOT_ONLY_OP.
The eia_clientowner field is composed of a co_verifier field and a The eia_clientowner field is composed of a co_verifier field and a
co_ownerid string. As noted in Section 2.4, the co_ownerid describes co_ownerid string. As noted in Section 2.4, the co_ownerid describes
the client, and the co_verifier is the incarnation of the client. An the client, and the co_verifier is the incarnation of the client. An
EXCHANGE_ID sent with a new incarnation of the client will lead to EXCHANGE_ID sent with a new incarnation of the client will lead to
the server removing lock state of the old incarnation. Whereas an the server removing lock state of the old incarnation. Whereas an
EXCHANGE_ID sent with the current incarnation and co_ownerid will EXCHANGE_ID sent with the current incarnation and co_ownerid will
result in an error or an update of the client ID's properties, result in an error or an update of the client ID's properties,
depending on the arguments to EXCHANGE_ID. depending on the arguments to EXCHANGE_ID.
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In addition to the client ID and sequence ID, the server returns a In addition to the client ID and sequence ID, the server returns a
server owner (eir_server_owner) and server scope (eir_server_scope). server owner (eir_server_owner) and server scope (eir_server_scope).
The former field is used for network trunking as described in The former field is used for network trunking as described in
Section 2.10.5. The latter field is used to allow clients to Section 2.10.5. The latter field is used to allow clients to
determine when client IDs sent by one server may be recognized by determine when client IDs sent by one server may be recognized by
another in the event of file system migration (see Section 11.7.7). another in the event of file system migration (see Section 11.7.7).
The client ID returned by EXCHANGE_ID is only unique relative to the The client ID returned by EXCHANGE_ID is only unique relative to the
combination of eir_server_owner.so_major_id and eir_server_scope. combination of eir_server_owner.so_major_id and eir_server_scope.
Thus if two servers return the same client ID, the onus is on the Thus, if two servers return the same client ID, the onus is on the
client to distinguish the client IDs on the basis of client to distinguish the client IDs on the basis of
eir_server_owner.so_major_id and eir_server_scope. In the event two eir_server_owner.so_major_id and eir_server_scope. In the event two
different server's claim matching server_owner.so_major_id and different servers claim matching server_owner.so_major_id and
eir_server_scope, the client can use the verification techniques eir_server_scope, the client can use the verification techniques
discussed in Section 2.10.5 to determine if the servers are distinct. discussed in Section 2.10.5 to determine if the servers are distinct.
If they are distinct, then the client will need to note the If they are distinct, then the client will need to note the
destination network addresses of the connections used with each destination network addresses of the connections used with each
server, and use the network address as the final discriminator. server, and use the network address as the final discriminator.
The server, as defined by the unique identity expressed in the The server, as defined by the unique identity expressed in the
so_major_id of the server owner and the server scope, needs to track so_major_id of the server owner and the server scope, needs to track
several properties of each client ID it hands out. The properties several properties of each client ID it hands out. The properties
apply to the client ID and all sessions associated with the client apply to the client ID and all sessions associated with the client
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on confirmed client IDs though the server MAY refuse to change on confirmed client IDs though the server MAY refuse to change
them. them.
o The state protection method used, one of SP4_NONE, SP4_MACH_CRED, o The state protection method used, one of SP4_NONE, SP4_MACH_CRED,
or SP4_SSV, as set by the spa_how field of the arguments to or SP4_SSV, as set by the spa_how field of the arguments to
EXCHANGE_ID. Once the client ID is confirmed, this property EXCHANGE_ID. Once the client ID is confirmed, this property
cannot be updated by subsequent EXCHANGE_ID requests. cannot be updated by subsequent EXCHANGE_ID requests.
o For SP4_MACH_CRED or SP4_SSV state protection: o For SP4_MACH_CRED or SP4_SSV state protection:
* The list of operations that MUST use the specified state * The list of operations (spo_must_enforce) that MUST use the
protection: spo_must_enforce, which come from the results of specified state protection. This list comes from the results
EXCHANGE_ID. of EXCHANGE_ID.
* The list of operations that MAY use the specified state * The list of operations (spo_must_allow) that MAY use the
protection: spo_must_allow, which come from the results of specified state protection. This list comes from the results
EXCHANGE_ID. of EXCHANGE_ID.
Once the client ID is confirmed, these properties cannot be Once the client ID is confirmed, these properties cannot be
updated by subsequent EXCHANGE_ID requests. updated by subsequent EXCHANGE_ID requests.
o For SP4_SSV protection: o For SP4_SSV protection:
* The OID of the hash algorithm. This property is represented by * The OID of the hash algorithm. This property is represented by
one of the algorithms in the ssp_hash_algs field of the one of the algorithms in the ssp_hash_algs field of the
EXCHANGE_ID arguments. Once the client ID is confirmed, this EXCHANGE_ID arguments. Once the client ID is confirmed, this
property cannot be updated by subsequent EXCHANGE_ID requests. property cannot be updated by subsequent EXCHANGE_ID requests.
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result of the above two invariants. result of the above two invariants.
+ key length SHOULD be >= hash length / 2. This is because + key length SHOULD be >= hash length / 2. This is because
the subkey derivation is via an HMAC and it is recommended the subkey derivation is via an HMAC and it is recommended
that if the HMAC has to be truncated, it should not be that if the HMAC has to be truncated, it should not be
truncated to less than half the hash length (see Section 4 truncated to less than half the hash length (see Section 4
of RFC2104 [11]). of RFC2104 [11]).
* Number of concurrent versions of the SSV the client and server * Number of concurrent versions of the SSV the client and server
will support (Section 2.10.9). This property is represented by will support (Section 2.10.9). This property is represented by
spi_window, in the EXCHANGE_ID results. The property may be spi_window in the EXCHANGE_ID results. The property may be
updated by subsequent EXCHANGE_ID requests. updated by subsequent EXCHANGE_ID requests.
o The client's implementation ID as represented by the o The client's implementation ID as represented by the
eia_client_impl_id field of the arguments. The property may be eia_client_impl_id field of the arguments. The property may be
updated by subsequent EXCHANGE_ID requests. updated by subsequent EXCHANGE_ID requests.
o The server's implementation ID as represented by the o The server's implementation ID as represented by the
eir_server_impl_id field of the reply. The property may be eir_server_impl_id field of the reply. The property may be
updated by replies to subsequent EXCHANGE_ID requests. updated by replies to subsequent EXCHANGE_ID requests.
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The EXCHGID4_FLAG_UPD_CONFIRMED_REC_A bit can only be set in The EXCHGID4_FLAG_UPD_CONFIRMED_REC_A bit can only be set in
eia_flags; it is always off in eir_flags. The eia_flags; it is always off in eir_flags. The
EXCHGID4_FLAG_CONFIRMED_R bit can only be set in eir_flags; it is EXCHGID4_FLAG_CONFIRMED_R bit can only be set in eir_flags; it is
always off in eia_flags. If the server recognizes the co_ownerid and always off in eia_flags. If the server recognizes the co_ownerid and
co_verifier as mapping to a confirmed client ID, it sets co_verifier as mapping to a confirmed client ID, it sets
EXCHGID4_FLAG_CONFIRMED_R in eir_flags. The EXCHGID4_FLAG_CONFIRMED_R in eir_flags. The
EXCHGID4_FLAG_CONFIRMED_R flag allows a client to tell if the client EXCHGID4_FLAG_CONFIRMED_R flag allows a client to tell if the client
ID it is trying to create already exists and is confirmed. ID it is trying to create already exists and is confirmed.
If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set in eia_flags, this means If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set in eia_flags, this means
the client is attempting to update properties of an existing that the client is attempting to update properties of an existing
confirmed client ID (if the client wants to update properties of an confirmed client ID (if the client wants to update properties of an
unconfirmed client ID, it MUST NOT set unconfirmed client ID, it MUST NOT set
EXCHGID4_FLAG_UPD_CONFIRMED_REC_A). If so, it is RECOMMENDED the EXCHGID4_FLAG_UPD_CONFIRMED_REC_A). If so, it is RECOMMENDED that
client send the update EXCHANGE_ID operation in the same COMPOUND as the client send the update EXCHANGE_ID operation in the same COMPOUND
a SEQUENCE so that the EXCHANGE_ID is executed exactly once. Whether as a SEQUENCE so that the EXCHANGE_ID is executed exactly once.
the client can update the properties of client ID depends on the Whether the client can update the properties of client ID depends on
state protection it selected when the client ID was created, and the the state protection it selected when the client ID was created, and
principal and security flavor it uses when sending the EXCHANGE_ID the principal and security flavor it uses when sending the
request. The situations described in Sub-Paragraph 6, Sub- EXCHANGE_ID request. The situations described in items 6, 7, 8, or 9
Paragraph 7, Sub-Paragraph 8, or Sub-Paragraph 9, of Paragraph 6 in of the second numbered list of Section 18.35.4 will apply. Note that
Section 18.35.4 will apply. Note that if the operation succeeds and if the operation succeeds and returns a client ID that is already
returns a client ID that is already confirmed, the server MUST set confirmed, the server MUST set the EXCHGID4_FLAG_CONFIRMED_R bit in
the EXCHGID4_FLAG_CONFIRMED_R bit in eir_flags. eir_flags.
If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is not set in eia_flags, this If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is not set in eia_flags, this
means the client is trying to establish a new client ID; it is means that the client is trying to establish a new client ID; it is
attempting to trunk data communication to the server attempting to trunk data communication to the server
(Section 2.10.5); or it is attempting to update properties of an (Section 2.10.5); or it is attempting to update properties of an
unconfirmed client ID. The situations described in Sub-Paragraph 1, unconfirmed client ID. The situations described in items 1, 2, 3, 4,
Sub-Paragraph 2, Sub-Paragraph 3, Sub-Paragraph 4, or Sub-Paragraph 5 or 5 of the second numbered list of Section 18.35.4 will apply. Note
of Paragraph 6 in Section 18.35.4 will apply. Note that if the that if the operation succeeds and returns a client ID that was
operation succeeds and returns a client ID that was previously previously confirmed, the server MUST set the
confirmed, the server MUST set the EXCHGID4_FLAG_CONFIRMED_R bit in EXCHGID4_FLAG_CONFIRMED_R bit in eir_flags.
eir_flags.
When the EXCHGID4_FLAG_SUPP_MOVED_REFER flag bit is set, the client When the EXCHGID4_FLAG_SUPP_MOVED_REFER flag bit is set, the client
indicates that it is capable of dealing with an NFS4ERR_MOVED error indicates that it is capable of dealing with an NFS4ERR_MOVED error
as part of a referral sequence. When this bit is not set, it is as part of a referral sequence. When this bit is not set, it is
still legal for the server to perform a referral sequence. However, still legal for the server to perform a referral sequence. However,
a server may use the fact that the client is incapable of correctly a server may use the fact that the client is incapable of correctly
responding to a referral, by avoiding it for that particular client. responding to a referral, by avoiding it for that particular client.
It may, for instance, act as a proxy for that particular file system, It may, for instance, act as a proxy for that particular file system,
at some cost in performance, although it is not obligated to do so. at some cost in performance, although it is not obligated to do so.
If the server will potentially perform a referral, it MUST set If the server will potentially perform a referral, it MUST set
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when this in fact happens. However, a server may use the fact that when this in fact happens. However, a server may use the fact that
the client is incapable of correctly responding to a migration in its the client is incapable of correctly responding to a migration in its
scheduling of file systems to migrate so as to avoid migration of scheduling of file systems to migrate so as to avoid migration of
file systems being actively used. It may also hide actual migrations file systems being actively used. It may also hide actual migrations
from clients unable to deal with them by acting as a proxy for a from clients unable to deal with them by acting as a proxy for a
migrated file system for particular clients, at some cost in migrated file system for particular clients, at some cost in
performance, although it is not obligated to do so. If the server performance, although it is not obligated to do so. If the server
will potentially perform a migration, it MUST set will potentially perform a migration, it MUST set
EXCHGID4_FLAG_SUPP_MOVED_MIGR in eir_flags. EXCHGID4_FLAG_SUPP_MOVED_MIGR in eir_flags.
When EXCHGID4_FLAG_BIND_PRINC_STATEID is set, the client indicates it When EXCHGID4_FLAG_BIND_PRINC_STATEID is set, the client indicates
wants the server to bind the stateid to the principal. This means that it wants the server to bind the stateid to the principal. This
that when a principal creates a stateid, it has to be the one to use means that when a principal creates a stateid, it has to be the one
the stateid. If the server will perform binding it will return to use the stateid. If the server will perform binding, it will
EXCHGID4_FLAG_BIND_PRINC_STATEID. The server MAY return return EXCHGID4_FLAG_BIND_PRINC_STATEID. The server MAY return
EXCHGID4_FLAG_BIND_PRINC_STATEID even if the client does not request EXCHGID4_FLAG_BIND_PRINC_STATEID even if the client does not request
it. If an update to the client ID changes the value of it. If an update to the client ID changes the value of
EXCHGID4_FLAG_BIND_PRINC_STATEID's client ID property, the effect EXCHGID4_FLAG_BIND_PRINC_STATEID's client ID property, the effect
applies only to new stateids. Existing stateids (and all stateids applies only to new stateids. Existing stateids (and all stateids
with the same "other" field) that were created with stateid to with the same "other" field) that were created with stateid to
principal binding in force will continue to have binding in force. principal binding in force will continue to have binding in force.
Existing stateids (and all stateids with same "other" field) that Existing stateids (and all stateids with the same "other" field) that
were created with stateid to principal not in force will continue to were created with stateid to principal not in force will continue to
have binding not in force. have binding not in force.
The EXCHGID4_FLAG_USE_NON_PNFS, EXCHGID4_FLAG_USE_PNFS_MDS, and The EXCHGID4_FLAG_USE_NON_PNFS, EXCHGID4_FLAG_USE_PNFS_MDS, and
EXCHGID4_FLAG_USE_PNFS_DS bits are described in Section 13.1 and EXCHGID4_FLAG_USE_PNFS_DS bits are described in Section 13.1 and
convey roles the client ID is to be used for in a pNFS environment. convey roles the client ID is to be used for in a pNFS environment.
The server MUST set one of the acceptable combinations of these bits The server MUST set one of the acceptable combinations of these bits
(roles) in eir_flags, as specified in Section 13.1. Note that the (roles) in eir_flags, as specified in Section 13.1. Note that the
same client owner/server owner pair can have multiple roles. same client owner/server owner pair can have multiple roles.
Multiple roles can be associated with the same client ID or with Multiple roles can be associated with the same client ID or with
different client IDs. Thus, if a client sends EXCHANGE_ID from the different client IDs. Thus, if a client sends EXCHANGE_ID from the
same client owner to the same server owner multiple times, but same client owner to the same server owner multiple times, but
specifies different pNFS roles each time, the server might return specifies different pNFS roles each time, the server might return
different client IDs. Given that different pNFS roles might have different client IDs. Given that different pNFS roles might have
different client IDs, the client may ask for different properties for different client IDs, the client may ask for different properties for
each role/client ID. each role/client ID.
The spa_how field of the eia_state_protect field specifies how the The spa_how field of the eia_state_protect field specifies how the
client wants to protect its client, locking and session state from client wants to protect its client, locking, and session states from
unauthorized changes (Section 2.10.8.3): unauthorized changes (Section 2.10.8.3):
o SP4_NONE. The client does not request the NFSv4.1 server to o SP4_NONE. The client does not request the NFSv4.1 server to
enforce state protection. The NFSv4.1 server MUST NOT enforce enforce state protection. The NFSv4.1 server MUST NOT enforce
state protection for the returned client ID. state protection for the returned client ID.
o SP4_MACH_CRED. If spa_how is SP4_MACH_CRED, then the client MUST o SP4_MACH_CRED. If spa_how is SP4_MACH_CRED, then the client MUST
send the EXCHANGE_ID request with RPCSEC_GSS as the security send the EXCHANGE_ID request with RPCSEC_GSS as the security
flavor, and with a service of RPC_GSS_SVC_INTEGRITY or flavor, and with a service of RPC_GSS_SVC_INTEGRITY or
RPC_GSS_SVC_PRIVACY. If SP4_MACH_CRED is specified, then the RPC_GSS_SVC_PRIVACY. If SP4_MACH_CRED is specified, then the
client wants to use an RPCSEC_GSS-based machine credential to client wants to use an RPCSEC_GSS-based machine credential to
protect its state. The server MUST note the principal the protect its state. The server MUST note the principal the
EXCHANGE_ID operation was sent with, and the GSS mechanism used. EXCHANGE_ID operation was sent with, and the GSS mechanism used.
These notes collectively comprise the machine credential. These notes collectively comprise the machine credential.
After the client ID is confirmed, as long as the lease associated After the client ID is confirmed, as long as the lease associated
with the client ID is unexpired, a subsequent EXCHANGE_ID with the client ID is unexpired, a subsequent EXCHANGE_ID
operation that uses the same eia_clientowner.co_owner as the first operation that uses the same eia_clientowner.co_owner as the first
EXCHANGE_ID, MUST also use the same machine credential as the EXCHANGE_ID MUST also use the same machine credential as the first
first EXCHANGE_ID. The server returns the same client ID for the EXCHANGE_ID. The server returns the same client ID for the
subsequent EXCHANGE_ID as that returned from the first subsequent EXCHANGE_ID as that returned from the first
EXCHANGE_ID. EXCHANGE_ID.
o SP4_SSV. If spa_how is SP4_SSV, then the client MUST send the o SP4_SSV. If spa_how is SP4_SSV, then the client MUST send the
EXCHANGE_ID request with RPCSEC_GSS as the security flavor, and EXCHANGE_ID request with RPCSEC_GSS as the security flavor, and
with a service of RPC_GSS_SVC_INTEGRITY or RPC_GSS_SVC_PRIVACY. with a service of RPC_GSS_SVC_INTEGRITY or RPC_GSS_SVC_PRIVACY.
If SP4_SSV is specified, then the client wants to use the SSV to If SP4_SSV is specified, then the client wants to use the SSV to
protect its state. The server records the credential used in the protect its state. The server records the credential used in the
request as the machine credential (as defined above) for the request as the machine credential (as defined above) for the
eia_clientowner.co_owner. The CREATE_SESSION operation that eia_clientowner.co_owner. The CREATE_SESSION operation that
confirms the client ID MUST use the same machine credential. confirms the client ID MUST use the same machine credential.
When a client specifies SP4_MACH_CRED or SP4_SSV, it also provides When a client specifies SP4_MACH_CRED or SP4_SSV, it also provides
two lists of operations (each expressed as a bit map). The first two lists of operations (each expressed as a bitmap). The first list
list is spo_must_enforce and consists of those operations the client is spo_must_enforce and consists of those operations the client MUST
MUST send (subject to the server confirming the list of operations in send (subject to the server confirming the list of operations in the
the result of EXCHANGE_ID) with the machine credential (if result of EXCHANGE_ID) with the machine credential (if SP4_MACH_CRED
SP4_MACH_CRED protection is specified) or the SSV-based credential protection is specified) or the SSV-based credential (if SP4_SSV
(if SP4_SSV protection is used). The client MUST send the operations protection is used). The client MUST send the operations with
with RPCSEC_GSS credentials that specify the RPC_GSS_SVC_INTEGRITY or RPCSEC_GSS credentials that specify the RPC_GSS_SVC_INTEGRITY or
RPC_GSS_SVC_PRIVACY security service. Typically the first list of RPC_GSS_SVC_PRIVACY security service. Typically, the first list of
operations includes EXCHANGE_ID, CREATE_SESSION, DELEGPURGE, operations includes EXCHANGE_ID, CREATE_SESSION, DELEGPURGE,
DESTROY_SESSION, BIND_CONN_TO_SESSION, and DESTROY_CLIENTID. The DESTROY_SESSION, BIND_CONN_TO_SESSION, and DESTROY_CLIENTID. The
client SHOULD NOT specify in this list any operations that require a client SHOULD NOT specify in this list any operations that require a
filehandle because the server's access policies MAY conflict with the filehandle because the server's access policies MAY conflict with the
client's choice, and thus the client would then be unable to access a client's choice, and thus the client would then be unable to access a
subset of the server's namespace. subset of the server's namespace.
Note that if SP4_SSV protection is specified, and the client Note that if SP4_SSV protection is specified, and the client
indicates that CREATE_SESSION must be protected with SP4_SSV, because indicates that CREATE_SESSION must be protected with SP4_SSV, because
the SSV cannot exist without a confirmed client ID, the first the SSV cannot exist without a confirmed client ID, the first
CREATE_SESSION MUST instead be sent using the machine credential, and CREATE_SESSION MUST instead be sent using the machine credential, and
the server MUST accept the machine credential. the server MUST accept the machine credential.
There is a corresponding result, also called spo_must_enforce, of the There is a corresponding result, also called spo_must_enforce, of the
operations the server will require SP4_MACH_CRED or SP4_SSV operations for which the server will require SP4_MACH_CRED or SP4_SSV
protection for. Normally the server's result equals the client's protection. Normally, the server's result equals the client's
argument, but the result MAY be different. If the client requests argument, but the result MAY be different. If the client requests
one or more operations in the set { EXCHANGE_ID, CREATE_SESSION, one or more operations in the set { EXCHANGE_ID, CREATE_SESSION,
DELEGPURGE, DESTROY_SESSION, BIND_CONN_TO_SESSION, DESTROY_CLIENTID DELEGPURGE, DESTROY_SESSION, BIND_CONN_TO_SESSION, DESTROY_CLIENTID
}, then the result spo_must_enforce MUST include the operations the }, then the result spo_must_enforce MUST include the operations the
client requested from that set. client requested from that set.
If spo_must_enforce in the results has BIND_CONN_TO_SESSION set, then If spo_must_enforce in the results has BIND_CONN_TO_SESSION set, then
connection binding enforcement is enabled, and the client MUST use connection binding enforcement is enabled, and the client MUST use
the machine (if SP4_MACH_CRED protection is used) or SSV (if SP4_SSV the machine (if SP4_MACH_CRED protection is used) or SSV (if SP4_SSV
protection is used) credential on calls to BIND_CONN_TO_SESSION. protection is used) credential on calls to BIND_CONN_TO_SESSION.
The second list is spo_must_allow and consists of those operations The second list is spo_must_allow and consists of those operations
the client wants to have the option of sending with the machine the client wants to have the option of sending with the machine
credential or the SSV-based credential, even if the object the credential or the SSV-based credential, even if the object the
operations are performed on is not owned by the machine or SSV operations are performed on is not owned by the machine or SSV
credential. credential.
The corresponding result, also called spo_must_allow, consists of the The corresponding result, also called spo_must_allow, consists of the
operations the server will allow the client to use SP4_SSV or operations the server will allow the client to use SP4_SSV or
SP4_MACH_CRED credentials with. Normally the server's result equals SP4_MACH_CRED credentials with. Normally, the server's result equals
the client's argument, but the result MAY be different. the client's argument, but the result MAY be different.
The purpose of spo_must_allow is to allow clients to solve the The purpose of spo_must_allow is to allow clients to solve the
following conundrum. Suppose the client ID is confirmed with following conundrum. Suppose the client ID is confirmed with
EXCHGID4_FLAG_BIND_PRINC_STATEID, and it calls OPEN with the EXCHGID4_FLAG_BIND_PRINC_STATEID, and it calls OPEN with the
RPCSEC_GSS credentials of a normal user. Now suppose the user's RPCSEC_GSS credentials of a normal user. Now suppose the user's
credentials expire, and cannot be renewed (e.g. a Kerberos ticket credentials expire, and cannot be renewed (e.g., a Kerberos ticket
granting ticket expires, and the user has logged off and will not be granting ticket expires, and the user has logged off and will not be
acquiring a new ticket granting ticket). The client will be unable acquiring a new ticket granting ticket). The client will be unable
to send CLOSE without the user's credentials, which is to say the to send CLOSE without the user's credentials, which is to say the
client has to either leave the state on the server, or it has to re- client has to either leave the state on the server or re-send
send EXCHANGE_ID with a new verifier to clear all state. That is, EXCHANGE_ID with a new verifier to clear all state, that is, unless
unless the client includes CLOSE on the list of operations in the client includes CLOSE on the list of operations in spo_must_allow
spo_must_allow and the server agrees. and the server agrees.
The SP4_SSV protection parameters also have: The SP4_SSV protection parameters also have:
ssp_hash_algs: ssp_hash_algs:
This is the set of algorithms the client supports for the purpose This is the set of algorithms the client supports for the purpose
of computing the digests needed for the internal SSV GSS mechanism of computing the digests needed for the internal SSV GSS mechanism
and for the SET_SSV operation. Each algorithm is specified as an and for the SET_SSV operation. Each algorithm is specified as an
object identifier (OID). The REQUIRED algorithms for a server are object identifier (OID). The REQUIRED algorithms for a server are
id-sha1, id-sha224, id-sha256, id-sha384, and id-sha512 [28]. The id-sha1, id-sha224, id-sha256, id-sha384, and id-sha512 [28]. The
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is empty, the server MUST return NFS4ERR_INVAL. Note that due to is empty, the server MUST return NFS4ERR_INVAL. Note that due to
previously stated requirements and recommendations on the previously stated requirements and recommendations on the
relationships between key length and hash length, some relationships between key length and hash length, some
combinations of RECOMMENDED and REQUIRED encryption algorithm and combinations of RECOMMENDED and REQUIRED encryption algorithm and
hash algorithm either SHOULD NOT or MUST NOT be used. Table 12 hash algorithm either SHOULD NOT or MUST NOT be used. Table 12
summarizes the illegal and discouraged combinations. summarizes the illegal and discouraged combinations.
ssp_window: ssp_window:
This is the number of SSV versions the client wants the server to This is the number of SSV versions the client wants the server to
maintain (i.e. each successful call to SET_SSV produces a new maintain (i.e., each successful call to SET_SSV produces a new
version of the SSV). If ssp_window is zero, the server MUST version of the SSV). If ssp_window is zero, the server MUST
return NFS4ERR_INVAL. The server responds with spi_window, which return NFS4ERR_INVAL. The server responds with spi_window, which
MUST NOT exceed ssp_window, and MUST be at least one (1). Any MUST NOT exceed ssp_window, and MUST be at least one. Any
requests on the backchannel or fore channel that are using a requests on the backchannel or fore channel that are using a
version of the SSV that is outside the window will fail with an version of the SSV that is outside the window will fail with an
ONC RPC authentication error, and the requester will have to retry ONC RPC authentication error, and the requester will have to retry
them with the same slot ID and sequence ID. them with the same slot ID and sequence ID.
ssp_num_gss_handles: ssp_num_gss_handles:
This is the number of RPCSEC_GSS handles the server should create This is the number of RPCSEC_GSS handles the server should create
that are based on the GSS SSV mechanism (Section 2.10.9). It is that are based on the GSS SSV mechanism (Section 2.10.9). It is
not the total number of RPCSEC_GSS handles for the client ID. not the total number of RPCSEC_GSS handles for the client ID.
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ID is confirmed, which could be immediately if EXCHANGE_ID returns ID is confirmed, which could be immediately if EXCHANGE_ID returns
EXCHGID4_FLAG_CONFIRMED_R, or upon successful confirmation from EXCHGID4_FLAG_CONFIRMED_R, or upon successful confirmation from
CREATE_SESSION. CREATE_SESSION.
While a client ID can span all the connections that are connected While a client ID can span all the connections that are connected
to a server sharing the same eir_server_owner.so_major_id, the to a server sharing the same eir_server_owner.so_major_id, the
RPCSEC_GSS handles returned in spi_handles can only be used on RPCSEC_GSS handles returned in spi_handles can only be used on
connections connected to a server that returns the same the connections connected to a server that returns the same the
eir_server_owner.so_major_id and eir_server_owner.so_minor_id on eir_server_owner.so_major_id and eir_server_owner.so_minor_id on
each connection. It is permissible for the client to set each connection. It is permissible for the client to set
ssp_num_gss_handles to zero (0); the client can create more ssp_num_gss_handles to zero; the client can create more handles
handles with another EXCHANGE_ID call. with another EXCHANGE_ID call.
Because each SSV RPCSEC_GSS handle shares a common SSV GSS Because each SSV RPCSEC_GSS handle shares a common SSV GSS
context, there are security considerations specific to this context, there are security considerations specific to this
situation discussed in Section 2.10.10. situation discussed in Section 2.10.10.
The seq_window (see Section 5.2.3.1 of RFC2203 [4]) of each The seq_window (see Section 5.2.3.1 of RFC2203 [4]) of each
RPCSEC_GSS handle in spi_handle MUST be the same as the seq_window RPCSEC_GSS handle in spi_handle MUST be the same as the seq_window
of the RPCSEC_GSS handle used for the credential of the RPC of the RPCSEC_GSS handle used for the credential of the RPC
request that the EXCHANGE_ID request was sent with. request that the EXCHANGE_ID request was sent with.
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| Algorithm | with | with | | Algorithm | with | with |
+-------------------+----------------------+------------------------+ +-------------------+----------------------+------------------------+
| id-aes128-CBC | | id-sha384, id-sha512 | | id-aes128-CBC | | id-sha384, id-sha512 |
| id-aes192-CBC | id-sha1 | id-sha512 | | id-aes192-CBC | id-sha1 | id-sha512 |
| id-aes256-CBC | id-sha1, id-sha224 | | | id-aes256-CBC | id-sha1, id-sha224 | |
+-------------------+----------------------+------------------------+ +-------------------+----------------------+------------------------+
Table 12 Table 12
The arguments include an array of up to one element in length called The arguments include an array of up to one element in length called
eia_client_impl_id. If eia_client_impl_id is present it contains the eia_client_impl_id. If eia_client_impl_id is present, it contains
information identifying the implementation of the client. Similarly, the information identifying the implementation of the client.
the results include an array of up to one element in length called Similarly, the results include an array of up to one element in
eir_server_impl_id that identifies the implementation of the server. length called eir_server_impl_id that identifies the implementation
of the server. Servers MUST accept a zero-length eia_client_impl_id
Servers MUST accept a zero length eia_client_impl_id array, and array, and clients MUST accept a zero-length eir_server_impl_id
clients MUST accept a zero length eir_server_impl_id array. array.
An example use for implementation identifiers would be diagnostic An example use for implementation identifiers would be diagnostic
software that extract this information in an attempt to identify software that extracts this information in an attempt to identify
interoperability problems, performance workload behaviors or general interoperability problems, performance workload behaviors, or general
usage statistics. Since the intent of having access to this usage statistics. Since the intent of having access to this
information is for planning or general diagnosis only, the client and information is for planning or general diagnosis only, the client and
server MUST NOT interpret this implementation identity information in server MUST NOT interpret this implementation identity information in
a way that affects interoperational behavior of the implementation. a way that affects interoperational behavior of the implementation.
The reason is that if clients and servers did such a thing, they The reason is that if clients and servers did such a thing, they
might use fewer capabilities of the protocol than the peer can might use fewer capabilities of the protocol than the peer can
support, or the client and server might refuse to interoperate. support, or the client and server might refuse to interoperate.
Because it is possible some implementations will violate the protocol Because it is possible that some implementations will violate the
specification and interpret the identity information, implementations protocol specification and interpret the identity information,
MUST allow the users of the NFSv4 client and server to set the implementations MUST allow the users of the NFSv4 client and server
contents of the sent nfs_impl_id structure to any value. to set the contents of the sent nfs_impl_id structure to any value.
18.35.4. IMPLEMENTATION 18.35.4. IMPLEMENTATION
A server's client record is a 5-tuple: A server's client record is a 5-tuple:
1. co_ownerid 1. co_ownerid
The client identifier string, from the eia_clientowner The client identifier string, from the eia_clientowner
structure of the EXCHANGE_ID4args structure structure of the EXCHANGE_ID4args structure.
2. co_verifier: 2. co_verifier:
A client-specific value used to indicate incarnations (where a A client-specific value used to indicate incarnations (where a
client restart represents a new incarnation), from the client restart represents a new incarnation), from the
eia_clientowner structure of the EXCHANGE_ID4args structure eia_clientowner structure of the EXCHANGE_ID4args structure.
3. principal: 3. principal:
The principal that was defined in the RPC header's credential The principal that was defined in the RPC header's credential
and/or verifier at the time the client record was established. and/or verifier at the time the client record was established.
4. client ID: 4. client ID:
The shorthand client identifier, generated by the server and The shorthand client identifier, generated by the server and
returned via the eir_clientid field in the EXCHANGE_ID4resok returned via the eir_clientid field in the EXCHANGE_ID4resok
structure structure.
5. confirmed: 5. confirmed:
A private field on the server indicating whether or not a A private field on the server indicating whether or not a
client record has been confirmed. A client record is client record has been confirmed. A client record is
confirmed if there has been a successful CREATE_SESSION confirmed if there has been a successful CREATE_SESSION
operation to confirm it. Otherwise it is unconfirmed. An operation to confirm it. Otherwise, it is unconfirmed. An
unconfirmed record is established by a EXCHANGE_ID call. Any unconfirmed record is established by an EXCHANGE_ID call. Any
unconfirmed record that is not confirmed within a lease period unconfirmed record that is not confirmed within a lease period
SHOULD be removed. SHOULD be removed.
The following identifiers represent special values for the fields in The following identifiers represent special values for the fields in
the records. the records.
ownerid_arg: ownerid_arg:
The value of the eia_clientowner.co_ownerid subfield of the The value of the eia_clientowner.co_ownerid subfield of the
EXCHANGE_ID4args structure of the current request. EXCHANGE_ID4args structure of the current request.
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The client ID has been confirmed. The client ID has been confirmed.
unconfirmed: unconfirmed:
The client ID has not been confirmed. The client ID has not been confirmed.
Since EXCHANGE_ID is a non-idempotent operation, we must consider the Since EXCHANGE_ID is a non-idempotent operation, we must consider the
possibility that retries occur as a result of a client restart, possibility that retries occur as a result of a client restart,
network partition, malfunctioning router, etc. Retries are network partition, malfunctioning router, etc. Retries are
identified by the value of the eia_clientowner field of identified by the value of the eia_clientowner field of
EXCHANGE_ID4args and the method for dealing with them is outlined in EXCHANGE_ID4args, and the method for dealing with them is outlined in
the scenarios below. the scenarios below.
The scenarios are described in terms of the client record(s) a server The scenarios are described in terms of the client record(s) a server
has for a given co_ownerid. Note if the client ID was created has for a given co_ownerid. Note that if the client ID was created
specifying SP4_SSV state protection and EXCHANGE_ID as the one of the specifying SP4_SSV state protection and EXCHANGE_ID as the one of the
operations in spo_must_allow, then server MUST authorize EXCHANGE_IDs operations in spo_must_allow, then the server MUST authorize
with the SSV principal in addition to the principal that created the EXCHANGE_IDs with the SSV principal in addition to the principal that
client ID. created the client ID.
1. New Owner ID 1. New Owner ID
If the server has no client records with If the server has no client records with
eia_clientowner.co_ownerid matching ownerid_arg, and eia_clientowner.co_ownerid matching ownerid_arg, and
EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is not set in the EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is not set in the
EXCHANGE_ID, then a new shorthand client ID (let us call it EXCHANGE_ID, then a new shorthand client ID (let us call it
clientid_ret) is generated, and the following unconfirmed clientid_ret) is generated, and the following unconfirmed
record is added to the server's state. record is added to the server's state.
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a new shorthand client ID is generated, and the following a new shorthand client ID is generated, and the following
unconfirmed record is added to the server's state. unconfirmed record is added to the server's state.
{ ownerid_arg, verifier_arg, principal_arg, clientid_ret, { ownerid_arg, verifier_arg, principal_arg, clientid_ret,
unconfirmed } unconfirmed }
Subsequently, the server returns clientid_ret. Subsequently, the server returns clientid_ret.
If old_clientid_ret has an unexpired lease with state, then no If old_clientid_ret has an unexpired lease with state, then no
state of old_clientid_ret is changed or deleted. The server state of old_clientid_ret is changed or deleted. The server
returns NFS4ERR_CLID_INUSE to indicate the client should retry returns NFS4ERR_CLID_INUSE to indicate that the client should
with a different value for the eia_clientowner.co_ownerid retry with a different value for the
subfield of EXCHANGE_ID4args. The client record is not eia_clientowner.co_ownerid subfield of EXCHANGE_ID4args. The
changed. client record is not changed.
4. Replacement of Unconfirmed Record 4. Replacement of Unconfirmed Record
If the EXCHGID4_FLAG_UPD_CONFIRMED_REC_A flag is not set, and If the EXCHGID4_FLAG_UPD_CONFIRMED_REC_A flag is not set, and
the server has the following unconfirmed record then the the server has the following unconfirmed record, then the
client is attempting EXCHANGE_ID again on an unconfirmed client is attempting EXCHANGE_ID again on an unconfirmed
client ID, perhaps due to a retry, or perhaps due to a client client ID, perhaps due to a retry, a client restart before
restart before client ID confirmation (i.e. before client ID confirmation (i.e., before CREATE_SESSION was
CREATE_SESSION was called), or some other reason. called), or some other reason.
{ ownerid_arg, *, *, old_clientid_ret, unconfirmed } { ownerid_arg, *, *, old_clientid_ret, unconfirmed }
It is possible the properties of old_clientid_ret are It is possible that the properties of old_clientid_ret are
different than those specified in the current EXCHANGE_ID. different than those specified in the current EXCHANGE_ID.
Whether the properties are being updated or not, to eliminate Whether or not the properties are being updated, to eliminate
ambiguity, the server deletes the unconfirmed record, ambiguity, the server deletes the unconfirmed record,
generates a new client ID (clientid_ret) and establishes the generates a new client ID (clientid_ret), and establishes the
following unconfirmed record: following unconfirmed record:
{ ownerid_arg, verifier_arg, principal_arg, clientid_ret, { ownerid_arg, verifier_arg, principal_arg, clientid_ret,
unconfirmed } unconfirmed }
5. Client Restart 5. Client Restart
If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is not set, and if the If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is not set, and if the
server has the following confirmed client record, then this server has the following confirmed client record, then this
request is likely from a previously confirmed client which has request is likely from a previously confirmed client that has
restarted. restarted.
{ ownerid_arg, old_verifier_arg, principal_arg, { ownerid_arg, old_verifier_arg, principal_arg,
old_clientid_ret, confirmed } old_clientid_ret, confirmed }
Since the previous incarnation of the same client will no Since the previous incarnation of the same client will no
longer be making requests, once the new client ID is confirmed longer be making requests, once the new client ID is confirmed
by CREATE_SESSION, lock and share reservations should be by CREATE_SESSION, byte-range locks and share reservations
released immediately rather than forcing the new incarnation should be released immediately rather than forcing the new
to wait for the lease time on the previous incarnation to incarnation to wait for the lease time on the previous
expire. Furthermore, session state should be removed since if incarnation to expire. Furthermore, session state should be
the client had maintained that information across restart, removed since if the client had maintained that information
this request would not have been sent. If the server does not across restart, this request would not have been sent. If the
support the CLAIM_DELEGATE_PREV claim type, associated server supports neither the CLAIM_DELEGATE_PREV nor
delegations should be purged as well; otherwise, delegations CLAIM_DELEG_PREV_FH claim types, associated delegations should
are retained and recovery proceeds according to be purged as well; otherwise, delegations are retained and
Section 10.2.1. recovery proceeds according to Section 10.2.1.
After processing, clientid_ret is returned to the client and After processing, clientid_ret is returned to the client and
this client record is added: this client record is added:
{ ownerid_arg, verifier_arg, principal_arg, clientid_ret, { ownerid_arg, verifier_arg, principal_arg, clientid_ret,
unconfirmed } unconfirmed }
The previously described confirmed record continues to exist, The previously described confirmed record continues to exist,
and thus the same ownerid_arg exists in both a confirmed and and thus the same ownerid_arg exists in both a confirmed and
unconfirmed state at the same time. The number of states can unconfirmed state at the same time. The number of states can
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If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set, and the server If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set, and the server
has no confirmed record corresponding ownerid_arg, then the has no confirmed record corresponding ownerid_arg, then the
server returns NFS4ERR_NOENT and leaves any unconfirmed record server returns NFS4ERR_NOENT and leaves any unconfirmed record
intact. intact.
8. Update but Wrong Verifier 8. Update but Wrong Verifier
If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set, and the server If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set, and the server
has the following confirmed record, then this request is an has the following confirmed record, then this request is an
illegal attempt at an update, perhaps because of a retry from illegal attempt at an update, perhaps because of a retry from
an previous client incarnation. a previous client incarnation.
{ ownerid_arg, old_verifier_arg, *, clientid_ret, confirmed } { ownerid_arg, old_verifier_arg, *, clientid_ret, confirmed }
The server returns NFS4ERR_NOT_SAME and leaves the client The server returns NFS4ERR_NOT_SAME and leaves the client
record intact. record intact.
9. Update but Wrong Principal 9. Update but Wrong Principal
If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set, and the server If EXCHGID4_FLAG_UPD_CONFIRMED_REC_A is set, and the server
has the following confirmed record, then this request is an has the following confirmed record, then this request is an
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This operation is used by the client to create new session objects on This operation is used by the client to create new session objects on
the server. the server.
CREATE_SESSION can be sent with or without a preceding SEQUENCE CREATE_SESSION can be sent with or without a preceding SEQUENCE
operation in the same COMPOUND procedure. If CREATE_SESSION is sent operation in the same COMPOUND procedure. If CREATE_SESSION is sent
with a preceding SEQUENCE operation, any session created by with a preceding SEQUENCE operation, any session created by
CREATE_SESSION has no direct relation to the session specified in the CREATE_SESSION has no direct relation to the session specified in the
SEQUENCE operation, although the two sessions might be associated SEQUENCE operation, although the two sessions might be associated
with the same client ID. If CREATE_SESSION is sent without a with the same client ID. If CREATE_SESSION is sent without a
preceding SEQUENCE, then it MUST be the only operation in the preceding SEQUENCE, then it MUST be the only operation in the
COMPOUND procedure's request. If is not, the server MUST return COMPOUND procedure's request. If it is not, the server MUST return
NFS4ERR_NOT_ONLY_OP. NFS4ERR_NOT_ONLY_OP.
In addition to creating a session, CREATE_SESSION has the following In addition to creating a session, CREATE_SESSION has the following
effects: effects:
o The first session created with a new client ID serves to confirm o The first session created with a new client ID serves to confirm
the creation of that client's state on the server. The server the creation of that client's state on the server. The server
returns the parameter values for the new session. returns the parameter values for the new session.
o The connection CREATE_SESSION is sent over is associated with the o The connection CREATE_SESSION that is sent over is associated with
session's fore channel. the session's fore channel.
The arguments and results of CREATE_SESSION are described as follows: The arguments and results of CREATE_SESSION are described as follows:
csa_clientid: csa_clientid:
This is the client ID the new session will be associated with. This is the client ID with which the new session will be
The corresponding result is csr_sessionid, the session ID of the associated. The corresponding result is csr_sessionid, the
new session. session ID of the new session.
csa_sequence: csa_sequence:
Each client ID serializes CREATE_SESSION via a per client ID Each client ID serializes CREATE_SESSION via a per-client ID
sequence number (see Section 18.36.4). The corresponding result sequence number (see Section 18.36.4). The corresponding result
is csr_sequence, which MUST be equal to csa_sequence. is csr_sequence, which MUST be equal to csa_sequence.
In the next three arguments, the client offers a value that is to be In the next three arguments, the client offers a value that is to be
a property of the session. Except where otherwise stated, it is a property of the session. Except where stated otherwise, it is
RECOMMENDED that the server accept the value, and if it is not RECOMMENDED that the server accept the value. If it is not
acceptable, the server MAY use a different value. Regardless, the acceptable, the server MAY use a different value. Regardless, the
value the server returns (which will be either what the client server MUST return the value the session will use (which will be
offered, or what the server is insisting on) will be the value the either what the client offered, or what the server is insisting on)
session uses. to the client.
csa_flags: csa_flags:
The csa_flags field contains a list of the following flag bits: The csa_flags field contains a list of the following flag bits:
CREATE_SESSION4_FLAG_PERSIST: CREATE_SESSION4_FLAG_PERSIST:
If CREATE_SESSION4_FLAG_PERSIST is set, the client wants the If CREATE_SESSION4_FLAG_PERSIST is set, the client wants the
server to provide a persistent reply cache. For sessions in server to provide a persistent reply cache. For sessions in
which only idempotent operations will be used (e.g. a read-only which only idempotent operations will be used (e.g., a read-
session), clients SHOULD NOT set CREATE_SESSION4_FLAG_PERSIST. only session), clients SHOULD NOT set
If the server does not or cannot provide a persistent reply CREATE_SESSION4_FLAG_PERSIST. If the server does not or cannot
cache, the server MUST NOT set CREATE_SESSION4_FLAG_PERSIST in provide a persistent reply cache, the server MUST NOT set
the field csr_flags. CREATE_SESSION4_FLAG_PERSIST in the field csr_flags.
If the server is a pNFS metadata server, for reasons described If the server is a pNFS metadata server, for reasons described
in Section 12.5.2 it SHOULD support in Section 12.5.2 it SHOULD support
CREATE_SESSION4_FLAG_PERSIST if it supports the layout_hint CREATE_SESSION4_FLAG_PERSIST if it supports the layout_hint
(Section 5.12.4) attribute. (Section 5.12.4) attribute.
CREATE_SESSION4_FLAG_CONN_BACK_CHAN: CREATE_SESSION4_FLAG_CONN_BACK_CHAN:
If CREATE_SESSION4_FLAG_CONN_BACK_CHAN is set in csa_flags, the If CREATE_SESSION4_FLAG_CONN_BACK_CHAN is set in csa_flags, the
client is requesting that the server use the connection client is requesting that the connection over which the
CREATE_SESSION is called over for the backchannel as well as CREATE_SESSION operation arrived be associated with the the
the fore channel. The server sets session's backchannel in addition to its fore channel. If the
CREATE_SESSION4_FLAG_CONN_BACK_CHAN in the result field server agrees, it sets CREATE_SESSION4_FLAG_CONN_BACK_CHAN in
csr_flags if it agrees. If CREATE_SESSION4_FLAG_CONN_BACK_CHAN the result field csr_flags. If
is not set in csa_flags, then CREATE_SESSION4_FLAG_CONN_BACK_CHAN is not set in csa_flags,
CREATE_SESSION4_FLAG_CONN_BACK_CHAN MUST NOT be set in then CREATE_SESSION4_FLAG_CONN_BACK_CHAN MUST NOT be set in
csr_flags. csr_flags.
CREATE_SESSION4_FLAG_CONN_RDMA: CREATE_SESSION4_FLAG_CONN_RDMA:
If CREATE_SESSION4_FLAG_CONN_RDMA is set in csa_flags, and if If CREATE_SESSION4_FLAG_CONN_RDMA is set in csa_flags, and if
the connection CREATE_SESSION is called over is currently in the connection over which the CREATE_SESSION operation arrived
non-RDMA mode, but has the capability to operate in RDMA mode, is currently in non-RDMA mode but has the capability to operate
then client is requesting the server agree to "step up" to RDMA in RDMA mode, then the client is requesting that the server
mode on the connection. The server sets "step up" to RDMA mode on the connection. If the server
CREATE_SESSION4_FLAG_CONN_RDMA in the result field csr_flags if agrees, it sets CREATE_SESSION4_FLAG_CONN_RDMA in the result
it agrees. If CREATE_SESSION4_FLAG_CONN_RDMA is not set in field csr_flags. If CREATE_SESSION4_FLAG_CONN_RDMA is not set
csa_flags, then CREATE_SESSION4_FLAG_CONN_RDMA MUST NOT be set in csa_flags, then CREATE_SESSION4_FLAG_CONN_RDMA MUST NOT be
in csr_flags. Note that once the server agrees to step up, it set in csr_flags. Note that once the server agrees to step up,
and the client MUST exchange all future traffic on the it and the client MUST exchange all future traffic on the
connection with RPC RDMA framing and not Record Marking ([8]). connection with RPC RDMA framing and not Record Marking ([8]).
csa_fore_chan_attrs, csa_fore_chan_attrs: csa_fore_chan_attrs, csa_fore_chan_attrs:
The csa_fore_chan_attrs and csa_back_chan_attrs fields apply to The csa_fore_chan_attrs and csa_back_chan_attrs fields apply to
attributes of the fore channel (which conveys requests originating attributes of the fore channel (which conveys requests originating
from the client to the server), and the backchannel (the channel from the client to the server), and the backchannel (the channel
that conveys callback requests originating from the server to the that conveys callback requests originating from the server to the
client), respectively. The results are in corresponding client), respectively. The results are in corresponding
structures called csr_fore_chan_attrs and csr_back_chan_attrs. structures called csr_fore_chan_attrs and csr_back_chan_attrs.
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reply. After the session is created, if a requester sends a reply. After the session is created, if a requester sends a
request for which the size of the reply would exceed this request for which the size of the reply would exceed this
value, the replier will return NFS4ERR_REP_TOO_BIG, per the value, the replier will return NFS4ERR_REP_TOO_BIG, per the
description in Section 2.10.6.4. description in Section 2.10.6.4.
ca_maxresponsesize_cached: ca_maxresponsesize_cached:
Like ca_maxresponsesize, but the maximum size of a reply that Like ca_maxresponsesize, but the maximum size of a reply that
will be stored in the reply cache (Section 2.10.6.1). For each will be stored in the reply cache (Section 2.10.6.1). For each
channel, the server MAY decrease this value, but MUST NOT channel, the server MAY decrease this value, but MUST NOT
increase it. If the reply to CREATE_SESSION has the value increase it. If, in the reply to CREATE_SESSION, the value of
ca_maxresponsesize_cached less than the value ca_maxresponsesize_cached of a channel is less than the value
ca_maxresponsesize, then this is an indication to the requester of ca_maxresponsesize of the same channel, then this is an
on the channel that it needs to be selective about which indication to the requester that it needs to be selective about
replies it directs the replier to cache; for example large which replies it directs the replier to cache; for example,
replies from nonidempotent operations (e.g. COMPOUND requests large replies from nonidempotent operations (e.g., COMPOUND
with a READ operation), should not be cached. The requester requests with a READ operation) should not be cached. The
decides which replies to cache via an argument to the SEQUENCE requester decides which replies to cache via an argument to the
(the sa_cachethis field, see Section 18.46) or CB_SEQUENCE (the SEQUENCE (the sa_cachethis field, see Section 18.46) or
csa_cachethis field, see Section 20.9) operations. After the CB_SEQUENCE (the csa_cachethis field, see Section 20.9)
session is created, if a requester sends a request for which operations. After the session is created, if a requester sends
the size of the reply would exceed this value, the replier will a request for which the size of the reply would exceed
return NFS4ERR_REP_TOO_BIG_TO_CACHE, per the description in ca_maxresponsesize_cached, the replier will return
NFS4ERR_REP_TOO_BIG_TO_CACHE, per the description in
Section 2.10.6.4. Section 2.10.6.4.
ca_maxoperations: ca_maxoperations:
The maximum number of operations the replier will accept in a The maximum number of operations the replier will accept in a
COMPOUND or CB_COMPOUND. For the backchannel, the server MUST COMPOUND or CB_COMPOUND. For the backchannel, the server MUST
NOT change the value the client offers. For the fore channel, NOT change the value the client offers. For the fore channel,
the server MAY change the requested value. After the session the server MAY change the requested value. After the session
is created, if a requester sends a COMPOUND or CB_COMPOUND with is created, if a requester sends a COMPOUND or CB_COMPOUND with
more operations than ca_maxoperations, the replier MUST return more operations than ca_maxoperations, the replier MUST return
NFS4ERR_TOO_MANY_OPS. NFS4ERR_TOO_MANY_OPS.
ca_maxrequests: ca_maxrequests:
The maximum number of concurrent COMPOUND or CB_COMPOUND The maximum number of concurrent COMPOUND or CB_COMPOUND
requests the requester will send on the session. Subsequent requests the requester will send on the session. Subsequent
requests will each be assigned a slot identifier by the requests will each be assigned a slot identifier by the
requester within the range 0 to ca_maxrequests - 1 inclusive. requester within the range zero to ca_maxrequests - 1
For the backchannel, the server MUST NOT change the value the inclusive. For the backchannel, the server MUST NOT change the
client offers. For the fore channel, the server MAY change the value the client offers. For the fore channel, the server MAY
requested value. change the requested value.
ca_rdma_ird: ca_rdma_ird:
This array has a maximum of one element. If this array has one This array has a maximum of one element. If this array has one
element, then the element contains the inbound RDMA read queue element, then the element contains the inbound RDMA read queue
depth (IRD). For each channel, the server MAY decrease this depth (IRD). For each channel, the server MAY decrease this
value, but MUST NOT increase it. value, but MUST NOT increase it.
csa_cb_program csa_cb_program
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specified, then the server is allowed to use the RPCSEC_GSS specified, then the server is allowed to use the RPCSEC_GSS
context specified in cbsp_gss_parms as the RPCSEC_GSS context in context specified in cbsp_gss_parms as the RPCSEC_GSS context in
the credential of the RPC header of callbacks to the client. the credential of the RPC header of callbacks to the client.
There is no corresponding result. There is no corresponding result.
The RPCSEC_GSS context for the backchannel is specified via a pair The RPCSEC_GSS context for the backchannel is specified via a pair
of values of data type gsshandle4_t. The data type gsshandle4_t of values of data type gsshandle4_t. The data type gsshandle4_t
represents an RPCSEC_GSS handle, and is precisely the same as the represents an RPCSEC_GSS handle, and is precisely the same as the
data type of the "handle" field of the rpc_gss_init_res data type data type of the "handle" field of the rpc_gss_init_res data type
defined in Section 5.2.3.1, "Context Creation Response - defined in Section 5.2.3.1, "Context Creation Response -
Successful Acceptance" of [4]. Successful Acceptance", of [4].
The first RPCSEC_GSS handle, gcbp_handle_from_server, is the fore The first RPCSEC_GSS handle, gcbp_handle_from_server, is the fore
handle the server returned to the client (either in the handle handle the server returned to the client (either in the handle
field of data type rpc_gss_init_res or one of the elements of the field of data type rpc_gss_init_res or as one of the elements of
spi_handles field returned in the reply to EXCHANGE_ID) when the the spi_handles field returned in the reply to EXCHANGE_ID) when
RPCSEC_GSS context was created on the server. The second handle, the RPCSEC_GSS context was created on the server. The second
gcbp_handle_from_client, is the back handle the client will map handle, gcbp_handle_from_client, is the back handle to which the
the RPCSEC_GSS context to. The server can immediately use the client will map the RPCSEC_GSS context. The server can
value of gcbp_handle_from_client in the RPCSEC_GSS credential in immediately use the value of gcbp_handle_from_client in the
callback RPCs. I.e., the value in gcbp_handle_from_client can be RPCSEC_GSS credential in callback RPCs. That is, the value in
used as the value of the field "handle" in data type gcbp_handle_from_client can be used as the value of the field
rpc_gss_cred_t (see Section 5, "Elements of the RPCSEC_GSS "handle" in data type rpc_gss_cred_t (see Section 5, "Elements of
Security Protocol" of [4]) in callback RPCs. The server MUST use the RPCSEC_GSS Security Protocol", of [4]) in callback RPCs. The
the RPCSEC_GSS security service specified in gcbp_service, i.e. it server MUST use the RPCSEC_GSS security service specified in
MUST set the "service" field of the rpc_gss_cred_t data type in gcbp_service, i.e., it MUST set the "service" field of the
RPCSEC_GSS credential to the value of gcbp_service (see Section rpc_gss_cred_t data type in RPCSEC_GSS credential to the value of
5.3.1, "RPC Request Header", of [4]). gcbp_service (see Section 5.3.1, "RPC Request Header", of [4]).
If the RPCSEC_GSS handle identified by gcbp_handle_from_server If the RPCSEC_GSS handle identified by gcbp_handle_from_server
does not exist on the server, the server will return does not exist on the server, the server will return
NFS4ERR_NOENT. NFS4ERR_NOENT.
Within each element of csa_sec_parms, the fore and back RPCSEC_GSS Within each element of csa_sec_parms, the fore and back RPCSEC_GSS
contexts MUST share the same GSS context and MUST have the same contexts MUST share the same GSS context and MUST have the same
seq_window (see Section 5.2.3.1 of RFC2203 [4]). The fore and seq_window (see Section 5.2.3.1 of RFC2203 [4]). The fore and
back RPCSEC_GSS context state are independent of each other as far back RPCSEC_GSS context state are independent of each other as far
as the RPCSEC_GSS sequence number (see the seq_num field in the as the RPCSEC_GSS sequence number (see the seq_num field in the
rpc_gss_cred_t data type of Section 5 and of Section 5.3.1, "RPC rpc_gss_cred_t data type of Sections 5 and 5.3.1 of [4]).
Request Header", of RFC2203).
If an RPCSEC_GSS handle is using the SSV context (see If an RPCSEC_GSS handle is using the SSV context (see
Section 2.10.9), then because each SSV RPCSEC_GSS handle shares a Section 2.10.9), then because each SSV RPCSEC_GSS handle shares a
common SSV GSS context, there are security considerations specific common SSV GSS context, there are security considerations specific
to this situation discussed in Section 2.10.10. to this situation discussed in Section 2.10.10.
Once the session is created, the first SEQUENCE or CB_SEQUENCE Once the session is created, the first SEQUENCE or CB_SEQUENCE
received on a slot MUST have a sequence ID equal to 1; if not the received on a slot MUST have a sequence ID equal to 1; if not, the
server MUST return NFS4ERR_SEQ_MISORDERED. replier MUST return NFS4ERR_SEQ_MISORDERED.
18.36.4. IMPLEMENTATION 18.36.4. IMPLEMENTATION
To describe a possible implementation, the same notation for client To describe a possible implementation, the same notation for client
records introduced in the description of EXCHANGE_ID is used with the records introduced in the description of EXCHANGE_ID is used with the
following addition: following addition:
clientid_arg: The value of the csa_clientid field of the clientid_arg: The value of the csa_clientid field of the
CREATE_SESSION4args structure of the current request. CREATE_SESSION4args structure of the current request.
Since CREATE_SESSION is a non-idempotent operation, we need to Since CREATE_SESSION is a non-idempotent operation, we need to
consider the possibility that retries may occur as a result of a consider the possibility that retries may occur as a result of a
client restart, network partition, malfunctioning router, etc. For client restart, network partition, malfunctioning router, etc. For
each client ID created by EXCHANGE_ID, the server maintains a each client ID created by EXCHANGE_ID, the server maintains a
separate reply cache (called the CREATE_SESSION reply cache) similar separate reply cache (called the CREATE_SESSION reply cache) similar
to the session reply cache used for SEQUENCE operations, with two to the session reply cache used for SEQUENCE operations, with two
distinctions. distinctions.
o First this is a reply cache just for detecting and processing o First, this is a reply cache just for detecting and processing
CREATE_SESSION requests for a given client ID. CREATE_SESSION requests for a given client ID.
o Second, the size of the client ID reply cache is of one slot (and o Second, the size of the client ID reply cache is of one slot (and
as a result, the CREATE_SESSION request does not carry a slot as a result, the CREATE_SESSION request does not carry a slot
number). This means that at most one CREATE_SESSION request for a number). This means that at most one CREATE_SESSION request for a
given client ID can be outstanding. given client ID can be outstanding.
As previously stated, CREATE_SESSION can be sent with or without a As previously stated, CREATE_SESSION can be sent with or without a
preceding SEQUENCE operation. Even if SEQUENCE precedes preceding SEQUENCE operation. Even if a SEQUENCE precedes
CREATE_SESSION, the server MUST maintain the CREATE_SESSION reply CREATE_SESSION, the server MUST maintain the CREATE_SESSION reply
cache, which is separate from the reply cache for the session cache, which is separate from the reply cache for the session
associated with SEQUENCE. If CREATE_SESSION was originally sent by associated with a SEQUENCE. If CREATE_SESSION was originally sent by
itself, the client MAY send a retry of the CREATE_SESSION operation itself, the client MAY send a retry of the CREATE_SESSION operation
within a COMPOUND preceded by SEQUENCE. If CREATE_SESSION was within a COMPOUND preceded by a SEQUENCE. If CREATE_SESSION was
originally sent in a COMPOUND that started with SEQUENCE, then the originally sent in a COMPOUND that started with a SEQUENCE, then the
client SHOULD send a retry in a COMPOUND that starts with SEQUENCE client SHOULD send a retry in a COMPOUND that starts with a SEQUENCE
that has the same session ID as the SEQUENCE of the original request. that has the same session ID as the SEQUENCE of the original request.
However, the client MAY send a retry in a COMPOUND that either has no However, the client MAY send a retry in a COMPOUND that either has no
preceding SEQUENCE, or has a preceding SEQUENCE that refers to a preceding SEQUENCE, or has a preceding SEQUENCE that refers to a
different session than the original CREATE_SESSION. This might be different session than the original CREATE_SESSION. This might be
necessary if the client sends a CREATE_SESSION in a COMPOUND preceded necessary if the client sends a CREATE_SESSION in a COMPOUND preceded
by a SEQUENCE with session ID X, and session X no longer exists. by a SEQUENCE with session ID X, and session X no longer exists.
Regardless, any retry of CREATE_SESSION, with or without a preceding Regardless, any retry of CREATE_SESSION, with or without a preceding
SEQUENCE, MUST use the same value of csa_sequence as the original. SEQUENCE, MUST use the same value of csa_sequence as the original.
When a client sends a successful EXCHANGE_ID and it is returned an After the client received a reply to an EXCHANGE_ID operation that
unconfirmed client ID, the client is also returned eir_sequenceid, contains a new, unconfirmed client ID, the server expects the client
and the client is expected to set the value of csa_sequenceid in the to follow with a CREATE_SESSION operation to confirm the client ID.
client ID-confirming-CREATE_SESSION it sends with that client ID to The server expects value of csa_sequenceid in the arguments to that
the value of eir_sequenceid. When EXCHANGE_ID returns a new, CREATE_SESSION to be to equal the value of the field eir_sequenceid
unconfirmed client ID, the server initializes the client ID slot to that was returned in results of the EXCHANGE_ID that returned the
be equal to eir_sequenceid - 1 (accounting for underflow), and unconfirmed client ID. Before the server replies to that EXCHANGE_ID
records a contrived CREATE_SESSION result with a "cached" result of operation, it initializes the client ID slot to be equal to
NFS4ERR_SEQ_MISORDERED. With the slot thus initialized, the eir_sequenceid - 1 (accounting for underflow), and records a
processing of the CREATE_SESSION operation is divided into four contrived CREATE_SESSION result with a "cached" result of
NFS4ERR_SEQ_MISORDERED. With the client ID slot thus initialized,
the processing of the CREATE_SESSION operation is divided into four
phases: phases:
1. Client record lookup. The server looks up the client ID in its 1. Client record lookup. The server looks up the client ID in its
client record table. If the server contains no records with client record table. If the server contains no records with
client ID equal to clientid_arg, then most likely the client's client ID equal to clientid_arg, then most likely the client's
state has been purged during a period of inactivity, possibly due state has been purged during a period of inactivity, possibly due
to a loss of connectivity. NFS4ERR_STALE_CLIENTID is returned, to a loss of connectivity. NFS4ERR_STALE_CLIENTID is returned,
and no changes are made to any client records on the server. and no changes are made to any client records on the server.
Otherwise, the server goes to phase 2. Otherwise, the server goes to phase 2.
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NFS4ERR_SEQ_MISORDERED, and does not change the slot. If NFS4ERR_SEQ_MISORDERED, and does not change the slot. If
csa_sequenceid is equal to the slot's sequence ID + 1 (accounting csa_sequenceid is equal to the slot's sequence ID + 1 (accounting
for wraparound), then the slot's sequence ID is set to for wraparound), then the slot's sequence ID is set to
csa_sequenceid, and the CREATE_SESSION processing goes to the csa_sequenceid, and the CREATE_SESSION processing goes to the
next phase. A subsequent new CREATE_SESSION call over the same next phase. A subsequent new CREATE_SESSION call over the same
client ID MUST use a csa_sequenceid that is one greater than the client ID MUST use a csa_sequenceid that is one greater than the
sequence ID in the slot. sequence ID in the slot.
3. Client ID confirmation. If this would be the first session for 3. Client ID confirmation. If this would be the first session for
the client ID, the CREATE_SESSION operation serves to confirm the the client ID, the CREATE_SESSION operation serves to confirm the
client ID. Otherwise the client ID confirmation phase is skipped client ID. Otherwise, the client ID confirmation phase is
and only the session creation phase occurs. Any case in which skipped and only the session creation phase occurs. Any case in
there is more than one record with identical values for client ID which there is more than one record with identical values for
represents a server implementation error. Operation in the client ID represents a server implementation error. Operation in
potential valid cases is summarized as follows. the potential valid cases is summarized as follows.
* Successful Confirmation * Successful Confirmation
If the server has the following unconfirmed record, then If the server has the following unconfirmed record, then
this is the expected confirmation of an unconfirmed record. this is the expected confirmation of an unconfirmed record.
{ ownerid, verifier, principal_arg, clientid_arg, { ownerid, verifier, principal_arg, clientid_arg,
unconfirmed } unconfirmed }
As noted in Section 18.35.4, the server might also have the As noted in Section 18.35.4, the server might also have the
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* Unsuccessful Confirmation * Unsuccessful Confirmation
If the server has the following record, then the client has If the server has the following record, then the client has
changed principals after the previous EXCHANGE_ID request, changed principals after the previous EXCHANGE_ID request,
or there has been a chance collision between shorthand or there has been a chance collision between shorthand
client identifiers. client identifiers.
{ *, *, old_principal_arg, clientid_arg, * } { *, *, old_principal_arg, clientid_arg, * }
Neither of these cases are permissible. Processing stops Neither of these cases is permissible. Processing stops
and NFS4ERR_CLID_INUSE is returned to the client. No and NFS4ERR_CLID_INUSE is returned to the client. No
changes are made to any client records on the server. changes are made to any client records on the server.
4. Session creation. The server confirmed the client ID, either in 4. Session creation. The server confirmed the client ID, either in
this CREATE_SESSION operation, or a previous CREATE_SESSION this CREATE_SESSION operation, or a previous CREATE_SESSION
operation. The server examines the remaining fields of the operation. The server examines the remaining fields of the
arguments. arguments.
The server creates the session by recording the parameter values The server creates the session by recording the parameter values
used (including whether the CREATE_SESSION4_FLAG_PERSIST flag is used (including whether the CREATE_SESSION4_FLAG_PERSIST flag is
set and has been accepted by the server) and allocating space for set and has been accepted by the server) and allocating space for
the session reply cache (if there is not enough space, the server the session reply cache (if there is not enough space, the server
returns NFS4ERR_NOSPC). For each slot in the reply cache, the returns NFS4ERR_NOSPC). For each slot in the reply cache, the
server sets the sequence ID to zero (0), and records an entry server sets the sequence ID to zero, and records an entry
containing a COMPOUND reply with zero operations and the error containing a COMPOUND reply with zero operations and the error
NFS4ERR_SEQ_MISORDERED. This way, if the first SEQUENCE request NFS4ERR_SEQ_MISORDERED. This way, if the first SEQUENCE request
sent has a sequence ID equal to zero, the server can simply sent has a sequence ID equal to zero, the server can simply
return what is in the reply cache: NFS4ERR_SEQ_MISORDERED. The return what is in the reply cache: NFS4ERR_SEQ_MISORDERED. The
client initializes its reply cache for receiving callbacks in the client initializes its reply cache for receiving callbacks in the
same way, and similarly, the first CB_SEQUENCE operation on a same way, and similarly, the first CB_SEQUENCE operation on a
slot after session creation MUST have a sequence ID of one. slot after session creation MUST have a sequence ID of one.
If the session state is created successfully, the server If the session state is created successfully, the server
associates the session with the client ID provided by the client. associates the session with the client ID provided by the client.
When a request that had CREATE_SESSION4_FLAG_CONN_RDMA set needs When a request that had CREATE_SESSION4_FLAG_CONN_RDMA set needs
to be retried, the retry MUST be done on a new connection that is to be retried, the retry MUST be done on a new connection that is
in non-RDMA mode. If properties of the new connection are in non-RDMA mode. If properties of the new connection are
different enough that the arguments to CREATE_SESSION need to different enough that the arguments to CREATE_SESSION need to
change, then a non-retry MUST be sent. The server will change, then a non-retry MUST be sent. The server will
eventually dispose of any session that was created on the eventually dispose of any session that was created on the
original connection. original connection.
On the backchannel, the client and server might wish to have many On the backchannel, the client and server might wish to have many
slots, in some cases perhaps more that the fore channel, in to deal slots, in some cases perhaps more that the fore channel, in order to
with the situations where the network link has high latency and is deal with the situations where the network link has high latency and
the primary bottleneck for response to recalls. If so, and if the is the primary bottleneck for response to recalls. If so, and if the
client provides too few slots to the backchannel, the server might client provides too few slots to the backchannel, the server might
limit the number of recallable objects it gives to the server. limit the number of recallable objects it gives to the server.
Implementing RPCSEC_GSS callback support requires the client and Implementing RPCSEC_GSS callback support requires changes to both the
server change their RPCSEC_GSS implementations. One possible set of client and server implementations of RPCSEC_GSS. One possible set of
changes includes: changes includes:
o Adding a data structure that wraps the GSS-API context with a o Adding a data structure that wraps the GSS-API context with a
reference count. reference count.
o New functions to increment and decrement the reference count. If o New functions to increment and decrement the reference count. If
the reference count is decremented to zero, the wrapper data the reference count is decremented to zero, the wrapper data
structure and the GSS-API context it refers to would be freed. structure and the GSS-API context it refers to would be freed.
o Change RPCSEC_GSS to create the wrapper data structure upon o Change RPCSEC_GSS to create the wrapper data structure upon
skipping to change at page 526, line 21 skipping to change at page 527, line 21
18.37.3. DESCRIPTION 18.37.3. DESCRIPTION
The DESTROY_SESSION operation closes the session and discards the The DESTROY_SESSION operation closes the session and discards the
session's reply cache, if any. Any remaining connections associated session's reply cache, if any. Any remaining connections associated
with the session are immediately disassociated. If the connection with the session are immediately disassociated. If the connection
has no remaining associated sessions, the connection MAY be closed by has no remaining associated sessions, the connection MAY be closed by
the server. Locks, delegations, layouts, wants, and the lease, which the server. Locks, delegations, layouts, wants, and the lease, which
are all tied to the client ID, are not affected by DESTROY_SESSION. are all tied to the client ID, are not affected by DESTROY_SESSION.
DESTROY_SESSION MUST be invoked on a connection that is associated DESTROY_SESSION MUST be invoked on a connection that is associated
with the session being destroyed. In addition if SP4_MACH_CRED state with the session being destroyed. In addition, if SP4_MACH_CRED
protection was specified when the client ID was created, the state protection was specified when the client ID was created, the
RPCSEC_GSS principal that created the session MUST be the one that RPCSEC_GSS principal that created the session MUST be the one that
destroys the session, using RPCSEC_GSS privacy or integrity. If destroys the session, using RPCSEC_GSS privacy or integrity. If
SP4_SSV state protection was specified when the client ID was SP4_SSV state protection was specified when the client ID was
created, RPCSEC_GSS using the SSV mechanism (Section 2.10.9) MUST be created, RPCSEC_GSS using the SSV mechanism (Section 2.10.9) MUST be
used, with integrity or privacy. used, with integrity or privacy.
If the COMPOUND request starts with SEQUENCE, and if the sessionids If the COMPOUND request starts with SEQUENCE, and if the sessionids
specified in SEQUENCE and DESTROY_SESSION are the same, then specified in SEQUENCE and DESTROY_SESSION are the same, then
o DESTROY_SESSION MUST be the final operation in the COMPOUND o DESTROY_SESSION MUST be the final operation in the COMPOUND
request. request.
o It is advisable to not place DESTROY_SESSION in a COMPOUND request o It is advisable to avoid placing DESTROY_SESSION in a COMPOUND
with other state-modifying operations, because the DESTROY_SESSION request with other state-modifying operations, because the
will destroy the reply cache. DESTROY_SESSION will destroy the reply cache.
o Because the session and its reply cache are destroyed, a client o Because the session and its reply cache are destroyed, a client
that retries the request may receive an error in reply to the that retries the request may receive an error in reply to the
retry, even though the original request was successful. retry, even though the original request was successful.
If the COMPOUND request starts with SEQUENCE, and if the sessionids If the COMPOUND request starts with SEQUENCE, and if the sessionids
specified in SEQUENCE and DESTROY_SESSION are the different, then specified in SEQUENCE and DESTROY_SESSION are different, then
DESTROY_SESSION can appear in any position of the COMPOUND request DESTROY_SESSION can appear in any position of the COMPOUND request
(except for the first position). The two sessionids can belong to (except for the first position). The two sessionids can belong to
different client IDs. different client IDs.
If the COMPOUND request does not start with SEQUENCE, and if If the COMPOUND request does not start with SEQUENCE, and if
DESTROY_SESSION is not the sole operation, then server MUST return DESTROY_SESSION is not the sole operation, then server MUST return
NFS4ERR_NOT_ONLY_OP. NFS4ERR_NOT_ONLY_OP.
If there is a backchannel on the session and the server has If there is a backchannel on the session and the server has
outstanding CB_COMPOUND operations for the session which have not outstanding CB_COMPOUND operations for the session which have not
been replied to, then the server MAY refuse to destroy the session been replied to, then the server MAY refuse to destroy the session
and return an error. If so, then in the event the backchannel is and return an error. If so, then in the event the backchannel is
down, the server SHOULD return NFS4ERR_CB_PATH_DOWN to inform the down, the server SHOULD return NFS4ERR_CB_PATH_DOWN to inform the
client that the backchannel needs to repaired before the server will client that the backchannel needs to be repaired before the server
allow the session to be destroyed. Otherwise, the error will allow the session to be destroyed. Otherwise, the error
CB_BACK_CHAN_BUSY SHOULD be returned to indicate that there are CB_BACK_CHAN_BUSY SHOULD be returned to indicate that there are
CB_COMPOUNDs that need to be replied to. The client SHOULD reply to CB_COMPOUNDs that need to be replied to. The client SHOULD reply to
all outstanding CB_COMPOUNDs before re-sending DESTROY_SESSION. all outstanding CB_COMPOUNDs before re-sending DESTROY_SESSION.
18.38. Operation 45: FREE_STATEID - Free Stateid with No Locks 18.38. Operation 45: FREE_STATEID - Free Stateid with No Locks
18.38.1. ARGUMENT 18.38.1. ARGUMENT
struct FREE_STATEID4args { struct FREE_STATEID4args {
stateid4 fsa_stateid; stateid4 fsa_stateid;
}; };
18.38.2. RESULT 18.38.2. RESULT
struct FREE_STATEID4res { struct FREE_STATEID4res {
nfsstat4 fsr_status; nfsstat4 fsr_status;
}; };
18.38.3. DESCRIPTION 18.38.3. DESCRIPTION
The FREE_STATEID operation is used to free a stateid which no longer The FREE_STATEID operation is used to free a stateid that no longer
has any associated locks (including opens, byte-range locks, has any associated locks (including opens, byte-range locks,
delegations, layouts). This may be because of client unlock delegations, and layouts). This may be because of client LOCKU
operations or because of server revocation. If there are valid locks operations or because of server revocation. If there are valid locks
(of any kind) associated with the stateid in question, the error (of any kind) associated with the stateid in question, the error
NFS4ERR_LOCKS_HELD will be returned, and the associated stateid will NFS4ERR_LOCKS_HELD will be returned, and the associated stateid will
not be freed. not be freed.
When a stateid is freed which had been associated with revoked locks, When a stateid is freed that had been associated with revoked locks,
the client, by doing the FREE_STATEID acknowledges the loss of those by sending the FREE_STATEID operation, the client acknowledges the
locks. This allows the server, once all such revoked state is loss of those locks. This allows the server, once all such revoked
acknowledged, to allow that client again to reclaim locks, without state is acknowledged, to allow that client again to reclaim locks,
encountering the edge conditions discussed in Section 8.4.2. without encountering the edge conditions discussed in Section 8.4.2.
Once a successful FREE_STATEID is done for a given stateid, any Once a successful FREE_STATEID is done for a given stateid, any
subsequent use of that stateid will result in an NFS4ERR_BAD_STATEID subsequent use of that stateid will result in an NFS4ERR_BAD_STATEID
error. error.
18.39. Operation 46: GET_DIR_DELEGATION - Get a directory delegation 18.39. Operation 46: GET_DIR_DELEGATION - Get a Directory Delegation
18.39.1. ARGUMENT 18.39.1. ARGUMENT
typedef nfstime4 attr_notice4; typedef nfstime4 attr_notice4;
struct GET_DIR_DELEGATION4args { struct GET_DIR_DELEGATION4args {
/* CURRENT_FH: delegated directory */ /* CURRENT_FH: delegated directory */
bool gdda_signal_deleg_avail; bool gdda_signal_deleg_avail;
bitmap4 gdda_notification_types; bitmap4 gdda_notification_types;
attr_notice4 gdda_child_attr_delay; attr_notice4 gdda_child_attr_delay;
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default: default:
void; void;
}; };
18.39.3. DESCRIPTION 18.39.3. DESCRIPTION
The GET_DIR_DELEGATION operation is used by a client to request a The GET_DIR_DELEGATION operation is used by a client to request a
directory delegation. The directory is represented by the current directory delegation. The directory is represented by the current
filehandle. The client also specifies whether it wants the server to filehandle. The client also specifies whether it wants the server to
notify it when the directory changes in certain ways by setting one notify it when the directory changes in certain ways by setting one
or more bits in a bitmap. The server may choose not to grant the or more bits in a bitmap. The server may refuse to grant the
delegation. In that case the server will return delegation. In that case, the server will return
NFS4ERR_DIRDELEG_UNAVAIL. If the server decides to hand out the NFS4ERR_DIRDELEG_UNAVAIL. If the server decides to hand out the
delegation, it will return a cookie verifier for that directory. If delegation, it will return a cookie verifier for that directory. If
the cookie verifier changes when the client is holding the the cookie verifier changes when the client is holding the
delegation, the delegation will be recalled unless the client has delegation, the delegation will be recalled unless the client has
asked for notification for this event. asked for notification for this event.
The server will also return a directory delegation stateid, The server will also return a directory delegation stateid,
gddr_stateid, as a result of the GET_DIR_DELEGATION operation. This gddr_stateid, as a result of the GET_DIR_DELEGATION operation. This
stateid will appear in callback messages related to the delegation, stateid will appear in callback messages related to the delegation,
such as notifications and delegation recalls. The client will use such as notifications and delegation recalls. The client will use
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client did not request. client did not request.
The GET_DIR_DELEGATION operation can be used for both normal and The GET_DIR_DELEGATION operation can be used for both normal and
named attribute directories. named attribute directories.
If client sets gdda_signal_deleg_avail to TRUE, then it is If client sets gdda_signal_deleg_avail to TRUE, then it is
registering with the client a "want" for a directory delegation. If registering with the client a "want" for a directory delegation. If
the delegation is not available, and the server supports and will the delegation is not available, and the server supports and will
honor the "want", the results will have honor the "want", the results will have
gddrnf_will_signal_deleg_avail set to TRUE and no error will be gddrnf_will_signal_deleg_avail set to TRUE and no error will be
indicated on return. If so the client should expect a future indicated on return. If so, the client should expect a future
CB_RECALLABLE_OBJ_AVAIL operation to indicate that a directory CB_RECALLABLE_OBJ_AVAIL operation to indicate that a directory
delegation is available. If the server does not wish to honor the delegation is available. If the server does not wish to honor the
"want" or is not able to do so, it returns the error "want" or is not able to do so, it returns the error
NFS4ERR_DIRDELEG_UNAVAIL. If the delegation is immediately NFS4ERR_DIRDELEG_UNAVAIL. If the delegation is immediately
available, the server SHOULD return it with the response to the available, the server SHOULD return it with the response to the
operation, rather than via a callback. operation, rather than via a callback.
When a client makes a request for a directory delegation while it When a client makes a request for a directory delegation while it
already holds a directory delegation for that directory (including already holds a directory delegation for that directory (including
the case where it has been recalled but not yet returned by the the case where it has been recalled but not yet returned by the
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or more bits in gdda_notification_types. The client can ask for or more bits in gdda_notification_types. The client can ask for
notifications on addition of entries to a directory (by setting the notifications on addition of entries to a directory (by setting the
NOTIFY4_ADD_ENTRY in gdda_notification_types), notifications on entry NOTIFY4_ADD_ENTRY in gdda_notification_types), notifications on entry
removal (NOTIFY4_REMOVE_ENTRY), renames (NOTIFY4_RENAME_ENTRY), removal (NOTIFY4_REMOVE_ENTRY), renames (NOTIFY4_RENAME_ENTRY),
directory attribute changes (NOTIFY4_CHANGE_DIR_ATTRIBUTES), and directory attribute changes (NOTIFY4_CHANGE_DIR_ATTRIBUTES), and
cookie verifier changes (NOTIFY4_CHANGE_COOKIE_VERIFIER) by setting cookie verifier changes (NOTIFY4_CHANGE_COOKIE_VERIFIER) by setting
one or more corresponding bits in the gdda_notification_types field. one or more corresponding bits in the gdda_notification_types field.
The client can also ask for notifications of changes to attributes of The client can also ask for notifications of changes to attributes of
directory entries (NOTIFY4_CHANGE_CHILD_ATTRIBUTES) in order to keep directory entries (NOTIFY4_CHANGE_CHILD_ATTRIBUTES) in order to keep
its attribute cache up to date. However any changes made to child its attribute cache up to date. However, any changes made to child
attributes do not cause the delegation to be recalled. If a client attributes do not cause the delegation to be recalled. If a client
is interested in directory entry caching, or negative name caching, is interested in directory entry caching or negative name caching, it
it can set the gdda_notification_types appropriately to its can set the gdda_notification_types appropriately to its particular
particular need and the server will notify it of all changes that need and the server will notify it of all changes that would
would otherwise invalidate its name cache. The kind of notification otherwise invalidate its name cache. The kind of notification a
a client asks for may depend on the directory size, its rate of client asks for may depend on the directory size, its rate of change,
change and the applications being used to access that directory. The and the applications being used to access that directory. The
enumeration of the conditions under which a client might ask for a enumeration of the conditions under which a client might ask for a
notification is out of the scope of this specification. notification is out of the scope of this specification.
For attribute notifications, the client will set bits in the For attribute notifications, the client will set bits in the
gdda_dir_attributes bitmap to indicate which attributes it wants to gdda_dir_attributes bitmap to indicate which attributes it wants to
be notified of. If the server does not support notifications for be notified of. If the server does not support notifications for
changes to a certain attribute, it SHOULD NOT set that attribute in changes to a certain attribute, it SHOULD NOT set that attribute in
the supported attribute bitmap specified in the reply the supported attribute bitmap specified in the reply
(gddr_dir_attributes). The client will also set in the (gddr_dir_attributes). The client will also set in the
gdda_child_attributes bitmap the attributes of directory entries it gdda_child_attributes bitmap the attributes of directory entries it
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gddr_child_attributes which attributes of directory entries it will gddr_child_attributes which attributes of directory entries it will
notify the client of. notify the client of.
The client will also let the server know if it wants to get the The client will also let the server know if it wants to get the
notification as soon as the attribute change occurs or after a notification as soon as the attribute change occurs or after a
certain delay by setting a delay factor; gdda_child_attr_delay is for certain delay by setting a delay factor; gdda_child_attr_delay is for
attribute changes to directory entries and gdda_dir_attr_delay is for attribute changes to directory entries and gdda_dir_attr_delay is for
attribute changes to the directory. If this delay factor is set to attribute changes to the directory. If this delay factor is set to
zero, that indicates to the server that the client wants to be zero, that indicates to the server that the client wants to be
notified of any attribute changes as soon as they occur. If the notified of any attribute changes as soon as they occur. If the
delay factor is set to N seconds, the server will make a best effort delay factor is set to N seconds, the server will make a best-effort
guarantee that attribute updates are synchronized within N seconds. guarantee that attribute updates are synchronized within N seconds.
If the client asks for a delay factor that the server does not If the client asks for a delay factor that the server does not
support or that may cause significant resource consumption on the support or that may cause significant resource consumption on the
server by causing the server to send a lot of notifications, the server by causing the server to send a lot of notifications, the
server should not commit to sending out notifications for attributes server should not commit to sending out notifications for attributes
and therefore must not set the appropriate bit in the and therefore must not set the appropriate bit in the
gddr_child_attributes and gddr_dir_attributes bitmaps in the gddr_child_attributes and gddr_dir_attributes bitmaps in the
response. response.
The client MUST use a security tuple (Section 2.6.1) that the The client MUST use a security tuple (Section 2.6.1) that the
skipping to change at page 533, line 7 skipping to change at page 534, line 7
case NFS4_OK: case NFS4_OK:
GETDEVICEINFO4resok gdir_resok4; GETDEVICEINFO4resok gdir_resok4;
case NFS4ERR_TOOSMALL: case NFS4ERR_TOOSMALL:
count4 gdir_mincount; count4 gdir_mincount;
default: default:
void; void;
}; };
18.40.3. DESCRIPTION 18.40.3. DESCRIPTION
Returns pNFS storage device address information for the specified The GETDEVICEINFO operation returns pNFS storage device address
device ID. The client identifies the device information to be information for the specified device ID. The client identifies the
returned by providing the gdia_device_id and gdia_layout_type that device information to be returned by providing the gdia_device_id and
uniquely identify the device. The client provides gdia_maxcount to gdia_layout_type that uniquely identify the device. The client
limit the number of bytes for the result. This maximum size provides gdia_maxcount to limit the number of bytes for the result.
represents all of the data being returned within the This maximum size represents all of the data being returned within
GETDEVICEINFO4resok structure and includes the XDR overhead. The the GETDEVICEINFO4resok structure and includes the XDR overhead. The
server may return less data. If the server is unable to return any server may return less data. If the server is unable to return any
information within the gdia_maxcount limit, the error information within the gdia_maxcount limit, the error
NFS4ERR_TOOSMALL will be returned. However, if gdia_maxcount is NFS4ERR_TOOSMALL will be returned. However, if gdia_maxcount is
zero, NFS4ERR_TOOSMALL MUST NOT be returned. zero, NFS4ERR_TOOSMALL MUST NOT be returned.
The da_layout_type field of the gdir_device_addr returned by the The da_layout_type field of the gdir_device_addr returned by the
server MUST be equal to the gdia_layout_type specified by the client. server MUST be equal to the gdia_layout_type specified by the client.
If it is not equal, the client SHOULD ignore the response as invalid If it is not equal, the client SHOULD ignore the response as invalid
and behave as if the server returned an error, even if the client and behave as if the server returned an error, even if the client
does have support for the layout type returned. does have support for the layout type returned.
The client also provides a notification bitmap, gdia_notify_types for The client also provides a notification bitmap, gdia_notify_types,
the device ID mapping notification for which it is interested in for the device ID mapping notification for which it is interested in
receiving; the server must support device ID notifications for the receiving; the server must support device ID notifications for the
notification request to have affect. The notification mask is notification request to have affect. The notification mask is
composed in the same manner as the bitmap for file attributes composed in the same manner as the bitmap for file attributes
(Section 3.3.7). The numbers of bit positions are listed in the (Section 3.3.7). The numbers of bit positions are listed in the
notify_device_type4 enumeration type (Section 20.12). Only two notify_device_type4 enumeration type (Section 20.12). Only two
enumerated values of notify_device_type4 currently apply to enumerated values of notify_device_type4 currently apply to
GETDEVICEINFO: NOTIFY_DEVICEID4_CHANGE and NOTIFY_DEVICEID4_DELETE GETDEVICEINFO: NOTIFY_DEVICEID4_CHANGE and NOTIFY_DEVICEID4_DELETE
(see Section 20.12). (see Section 20.12).
The notification bitmap applies only to the specified device ID. If The notification bitmap applies only to the specified device ID. If
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Aside from updating or turning off notifications, another use case Aside from updating or turning off notifications, another use case
for gdia_maxcount being set to zero is to validate a device ID. for gdia_maxcount being set to zero is to validate a device ID.
The client SHOULD request a notification for changes or deletion of a The client SHOULD request a notification for changes or deletion of a
device ID to device address mapping so that the server can allow the device ID to device address mapping so that the server can allow the
client gracefully use a new mapping, without having pending I/O fail client gracefully use a new mapping, without having pending I/O fail
abruptly, or force layouts using the device ID to be recalled or abruptly, or force layouts using the device ID to be recalled or
revoked. revoked.
It is possible that GETDEVICEINFO (and GETDEVICELIST) will race with It is possible that GETDEVICEINFO (and GETDEVICELIST) will race with
CB_NOTIFY_DEVICEID, i.e. CB_NOTIFY_DEVICEID arrives before the CB_NOTIFY_DEVICEID, i.e., CB_NOTIFY_DEVICEID arrives before the
client gets and processes the response to GETDEVICEINFO or client gets and processes the response to GETDEVICEINFO or
GETDEVICELIST. The analysis of the race leverages the fact that the GETDEVICELIST. The analysis of the race leverages the fact that the
server MUST NOT delete a device ID that is referred to by a layout server MUST NOT delete a device ID that is referred to by a layout
the client has. the client has.
o CB_NOTIFY_DEVICEID deletes a device ID. If the client believes it o CB_NOTIFY_DEVICEID deletes a device ID. If the client believes it
has layouts that refer to the device ID, then it is possible the has layouts that refer to the device ID, then it is possible that
layouts have been revoked. The client should send a TEST_STATEID layouts referring to the deleted device ID have been revoked. The
request using the stateid for each layout that might have been client should send a TEST_STATEID request using the stateid for
revoked. If TEST_STATEID indicates any layouts have been revoked, each layout that might have been revoked. If TEST_STATEID
the client must recover from layout revocation as described in indicates that any layouts have been revoked, the client must
Section 12.5.6. If TEST_STATEID indicates at least one layout has recover from layout revocation as described in Section 12.5.6. If
not been revoked, the client should send a GETDEVICEINFO on the TEST_STATEID indicates that at least one layout has not been
device ID to verify that the device ID has been deleted. If revoked, the client should send a GETDEVICEINFO operation on the
GETDEVICEINFO indicates the device ID does not exist, the client supposedly deleted device ID to verify that the device ID has been
then assumes the server is faulty, and recovers by sending an deleted.
EXCHANGE_ID operation. If the client does not have layouts that
refer to the device ID, no harm is done. The client should mark
the device ID as deleted, and when the GETDEVICEINFO or
GETDEVICELIST results are finally received for the device ID,
delete the device ID from client's cache.
o CB_NOTIFY_DEVICEID indicates a device ID's device addressing If GETDEVICEINFO indicates that the device ID does not exist, then
the client assumes the server is faulty and recovers by sending an
EXCHANGE_ID operation. If GETDEVICEINFO indicates that the device
ID does exist, then while the server is faulty for sending an
erroneous device ID deletion notification, the degree to which it
is faulty does not require the client to create a new client ID.
If the client does not have layouts that refer to the device ID,
no harm is done. The client should mark the device ID as deleted,
and when GETDEVICEINFO or GETDEVICELIST results are received that
indicate that the device ID has been in fact deleted, the device
ID should be removed from the client's cache.
o CB_NOTIFY_DEVICEID indicates that a device ID's device addressing
mappings have changed. The client should assume that the results mappings have changed. The client should assume that the results
from the in progress GETDEVICEINFO will be stale for the device ID from the in-progress GETDEVICEINFO will be stale for the device ID
once received, and so it should send another GETDEVICEINFO on the once received, and so it should send another GETDEVICEINFO on the
device ID. device ID.
18.41. Operation 48: GETDEVICELIST - Get All Device Mappings for a File 18.41. Operation 48: GETDEVICELIST - Get All Device Mappings for a File
System System
18.41.1. ARGUMENT 18.41.1. ARGUMENT
struct GETDEVICELIST4args { struct GETDEVICELIST4args {
/* CURRENT_FH: object belonging to the file system */ /* CURRENT_FH: object belonging to the file system */
skipping to change at page 535, line 40 skipping to change at page 536, line 46
union GETDEVICELIST4res switch (nfsstat4 gdlr_status) { union GETDEVICELIST4res switch (nfsstat4 gdlr_status) {
case NFS4_OK: case NFS4_OK:
GETDEVICELIST4resok gdlr_resok4; GETDEVICELIST4resok gdlr_resok4;
default: default:
void; void;
}; };
18.41.3. DESCRIPTION 18.41.3. DESCRIPTION
This operation is used by the client to enumerate all of the device This operation is used by the client to enumerate all of the device
IDs a server's file system uses. IDs that a server's file system uses.
The client provides a current filehandle of a file object that The client provides a current filehandle of a file object that
belongs to the file system (i.e. all file objects sharing the same belongs to the file system (i.e., all file objects sharing the same
fsid as that of the current filehandle), and the layout type in fsid as that of the current filehandle) and the layout type in
gdia_layout_type. Since this operation might require multiple calls gdia_layout_type. Since this operation might require multiple calls
to enumerate all the device IDs (and is thus similar to the READDIR to enumerate all the device IDs (and is thus similar to the READDIR
(Section 18.23) operation), the client also provides gdia_cookie and (Section 18.23) operation), the client also provides gdia_cookie and
gdia_cookieverf to specify the current cursor position in the list. gdia_cookieverf to specify the current cursor position in the list.
When the client wants to read from the beginning of the file system's When the client wants to read from the beginning of the file system's
device mappings, it sets gdla_cookie to zero. The field device mappings, it sets gdla_cookie to zero. The field
gdla_cookieverf MUST be ignored by the server when gdla_cookie is gdla_cookieverf MUST be ignored by the server when gdla_cookie is
zero. The client provides gdla_maxdevices to limit the number of zero. The client provides gdla_maxdevices to limit the number of
device IDs in the result. If gdla_maxdevices is zero, the server device IDs in the result. If gdla_maxdevices is zero, the server
MUST return NFS4ERR_INVAL. The server MAY return fewer device IDs. MUST return NFS4ERR_INVAL. The server MAY return fewer device IDs.
The successful response to the operation will contain the cookie, The successful response to the operation will contain the cookie,
gdlr_cookie, and cookie verifier, gdlr_cookieverf, to be used on the gdlr_cookie, and the cookie verifier, gdlr_cookieverf, to be used on
subsequent GETDEVICELIST. A gdlr_eof value of TRUE signifies that the subsequent GETDEVICELIST. A gdlr_eof value of TRUE signifies
there are no remaining entries in the server's device list. Each that there are no remaining entries in the server's device list.
element of gdlr_deviceid_list contains a device ID. Each element of gdlr_deviceid_list contains a device ID.
18.41.4. IMPLEMENTATION 18.41.4. IMPLEMENTATION
An example of the use of this operation is for pNFS clients and An example of the use of this operation is for pNFS clients and
servers that use LAYOUT4_BLOCK_VOLUME layouts. In these environments servers that use LAYOUT4_BLOCK_VOLUME layouts. In these environments
it may be helpful for a client to determine device accessibility upon it may be helpful for a client to determine device accessibility upon
first file system access. first file system access.
18.42. Operation 49: LAYOUTCOMMIT - Commit Writes Made Using a Layout 18.42. Operation 49: LAYOUTCOMMIT - Commit Writes Made Using a Layout
skipping to change at page 537, line 27 skipping to change at page 539, line 7
union LAYOUTCOMMIT4res switch (nfsstat4 locr_status) { union LAYOUTCOMMIT4res switch (nfsstat4 locr_status) {
case NFS4_OK: case NFS4_OK:
LAYOUTCOMMIT4resok locr_resok4; LAYOUTCOMMIT4resok locr_resok4;
default: default:
void; void;
}; };
18.42.3. DESCRIPTION 18.42.3. DESCRIPTION
Commits changes in the layout represented by the current filehandle, The LAYOUTCOMMIT operation commits changes in the layout represented
client ID (derived from the session ID in the preceding SEQUENCE by the current filehandle, client ID (derived from the session ID in
operation), byte range, and stateid. Since layouts are sub- the preceding SEQUENCE operation), byte-range, and stateid. Since
dividable, a smaller portion of a layout, retrieved via LAYOUTGET, layouts are sub-dividable, a smaller portion of a layout, retrieved
can be committed. The region being committed is specified through via LAYOUTGET, can be committed. The byte-range being committed is
the byte range (loca_offset and loca_length). This region MUST specified through the byte-range (loca_offset and loca_length). This
overlap with one or more existing layouts previously granted via byte-range MUST overlap with one or more existing layouts previously
LAYOUTGET (Section 18.43), each with an iomode of LAYOUTIOMODE4_RW. granted via LAYOUTGET (Section 18.43), each with an iomode of
In the case where the iomode of any held layout segment is not LAYOUTIOMODE4_RW. In the case where the iomode of any held layout
LAYOUTIOMODE4_RW, the server should return the error segment is not LAYOUTIOMODE4_RW, the server should return the error
NFS4ERR_BAD_IOMODE. For the case where the client does not hold NFS4ERR_BAD_IOMODE. For the case where the client does not hold
matching layout segment(s) for the defined region, the server should matching layout segment(s) for the defined byte-range, the server
return the error NFS4ERR_BAD_LAYOUT. should return the error NFS4ERR_BAD_LAYOUT.
The LAYOUTCOMMIT operation indicates that the client has completed The LAYOUTCOMMIT operation indicates that the client has completed
writes using a layout obtained by a previous LAYOUTGET. The client writes using a layout obtained by a previous LAYOUTGET. The client
may have only written a subset of the data range it previously may have only written a subset of the data range it previously
requested. LAYOUTCOMMIT allows it to commit or discard provisionally requested. LAYOUTCOMMIT allows it to commit or discard provisionally
allocated space and to update the server with a new end of file. The allocated space and to update the server with a new end-of-file. The
layout referenced by LAYOUTCOMMIT is still valid after the operation layout referenced by LAYOUTCOMMIT is still valid after the operation
completes and can be continued to be referenced by the client ID, completes and can be continued to be referenced by the client ID,
filehandle, byte range, layout type, and stateid. filehandle, byte-range, layout type, and stateid.
If the loca_reclaim field is set to TRUE, this indicates that the If the loca_reclaim field is set to TRUE, this indicates that the
client is attempting to commit changes to a layout after the restart client is attempting to commit changes to a layout after the restart
of the metadata server during the metadata server's recovery grace of the metadata server during the metadata server's recovery grace
period (see Section 12.7.4). This type of request may be necessary period (see Section 12.7.4). This type of request may be necessary
when the client has uncommitted writes to provisionally allocated when the client has uncommitted writes to provisionally allocated
regions of a file which were sent to the storage devices before the byte-ranges of a file that were sent to the storage devices before
restart of the metadata server. In this case the layout provided by the restart of the metadata server. In this case, the layout
the client MUST be a subset of a writable layout that the client held provided by the client MUST be a subset of a writable layout that the
immediately before the restart of the metadata server. The value of client held immediately before the restart of the metadata server.
the field loca_stateid MUST be a value the metadata server returned The value of the field loca_stateid MUST be a value that the metadata
before it restarted. The metadata server is free to accept or reject server returned before it restarted. The metadata server is free to
this request based on its own internal metadata consistency checks. accept or reject this request based on its own internal metadata
If the metadata server finds that the layout provided by the client consistency checks. If the metadata server finds that the layout
does not pass its consistency checks, it MUST reject the request with provided by the client does not pass its consistency checks, it MUST
the status NFS4ERR_RECLAIM_BAD. The successful completion of the reject the request with the status NFS4ERR_RECLAIM_BAD. The
LAYOUTCOMMIT request with loca_reclaim set to TRUE does NOT provide successful completion of the LAYOUTCOMMIT request with loca_reclaim
the client with a layout for the file. It simply commits the changes set to TRUE does NOT provide the client with a layout for the file.
to the layout specified in the loca_layoutupdate field. To obtain a It simply commits the changes to the layout specified in the
layout for the file the client must send a LAYOUTGET request to the loca_layoutupdate field. To obtain a layout for the file, the client
server after the server's grace period has expired. If the metadata must send a LAYOUTGET request to the server after the server's grace
server receives a LAYOUTCOMMIT request with loca_reclaim set to TRUE period has expired. If the metadata server receives a LAYOUTCOMMIT
when the metadata server is not in its recovery grace period, it MUST request with loca_reclaim set to TRUE when the metadata server is not
reject the request with the status NFS4ERR_NO_GRACE. in its recovery grace period, it MUST reject the request with the
status NFS4ERR_NO_GRACE.
Setting the loca_reclaim field to TRUE is required if and only if the Setting the loca_reclaim field to TRUE is required if and only if the
committed layout was acquired before the metadata server restart. If committed layout was acquired before the metadata server restart. If
the client is committing a layout that was acquired during the the client is committing a layout that was acquired during the
metadata server's grace period, it MUST set the "reclaim" field to metadata server's grace period, it MUST set the "reclaim" field to
FALSE. FALSE.
The loca_stateid is a layout stateid value as returned by previously The loca_stateid is a layout stateid value as returned by previously
successful layout operations (see Section 12.5.3). successful layout operations (see Section 12.5.3).
skipping to change at page 538, line 50 skipping to change at page 540, line 30
described by loca_offset and loca_length. The metadata server may described by loca_offset and loca_length. The metadata server may
use this information to determine whether the file's size needs to be use this information to determine whether the file's size needs to be
updated. If the metadata server updates the file's size as the updated. If the metadata server updates the file's size as the
result of the LAYOUTCOMMIT operation, it must return the new size result of the LAYOUTCOMMIT operation, it must return the new size
(locr_newsize.ns_size) as part of the results. (locr_newsize.ns_size) as part of the results.
The loca_time_modify field allows the client to suggest a The loca_time_modify field allows the client to suggest a
modification time it would like the metadata server to set. The modification time it would like the metadata server to set. The
metadata server may use the suggestion or it may use the time of the metadata server may use the suggestion or it may use the time of the
LAYOUTCOMMIT operation to set the modification time. If the metadata LAYOUTCOMMIT operation to set the modification time. If the metadata
server uses the client provided modification time, it should ensure server uses the client-provided modification time, it should ensure
time does not flow backwards. If the client wants to force the that time does not flow backwards. If the client wants to force the
metadata server to set an exact time, the client should use a SETATTR metadata server to set an exact time, the client should use a SETATTR
operation in a COMPOUND right after LAYOUTCOMMIT. See Section 12.5.4 operation in a COMPOUND right after LAYOUTCOMMIT. See Section 12.5.4
for more details. If the client desires the resultant modification for more details. If the client desires the resultant modification
time it should construct the COMPOUND so that a GETATTR follows the time, it should construct the COMPOUND so that a GETATTR follows the
LAYOUTCOMMIT. LAYOUTCOMMIT.
The loca_layoutupdate argument to LAYOUTCOMMIT provides a mechanism The loca_layoutupdate argument to LAYOUTCOMMIT provides a mechanism
for a client to provide layout specific updates to the metadata for a client to provide layout-specific updates to the metadata
server. For example, the layout update can describe what regions of server. For example, the layout update can describe what byte-ranges
the original layout have been used and what regions can be of the original layout have been used and what byte-ranges can be
deallocated. There is no NFSv4.1 file layout-specific layoutupdate4 deallocated. There is no NFSv4.1 file layout-specific layoutupdate4
structure. structure.
The layout information is more verbose for block devices than for The layout information is more verbose for block devices than for
objects and files because the latter two hide the details of block objects and files because the latter two hide the details of block
allocation behind their storage protocols. At the minimum, the allocation behind their storage protocols. At the minimum, the
client needs to communicate changes to the end of file location back client needs to communicate changes to the end-of-file location back
to the server, and, if desired, its view of the file's modification to the server, and, if desired, its view of the file's modification
time. For block/volume layouts, it needs to specify precisely which time. For block/volume layouts, it needs to specify precisely which
blocks have been used. blocks have been used.
If the layout identified in the arguments does not exist, the error If the layout identified in the arguments does not exist, the error
NFS4ERR_BADLAYOUT is returned. The layout being committed may also NFS4ERR_BADLAYOUT is returned. The layout being committed may also
be rejected if it does not correspond to an existing layout with an be rejected if it does not correspond to an existing layout with an
iomode of LAYOUTIOMODE4_RW. iomode of LAYOUTIOMODE4_RW.
On success, the current filehandle retains its value and the current On success, the current filehandle retains its value and the current
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18.42.4. IMPLEMENTATION 18.42.4. IMPLEMENTATION
The client MAY also use LAYOUTCOMMIT with the loca_reclaim field set The client MAY also use LAYOUTCOMMIT with the loca_reclaim field set
to TRUE to convey hints to modified file attributes or to report to TRUE to convey hints to modified file attributes or to report
layout-type specific information such as I/O errors for object-based layout-type specific information such as I/O errors for object-based
storage layouts, as normally done during normal operation. Doing so storage layouts, as normally done during normal operation. Doing so
may help the metadata server to recover files more efficiently after may help the metadata server to recover files more efficiently after
restart. For example, some file system implementations may require restart. For example, some file system implementations may require
expansive recovery of file system objects if the metadata server does expansive recovery of file system objects if the metadata server does
not get a positive indication from all clients holding a write layout not get a positive indication from all clients holding a
that they have successfully completed all their writes. Sending a LAYOUTIOMODE4_RW layout that they have successfully completed all
LAYOUTCOMMIT (if required) and then following with LAYOUTRETURN can their writes. Sending a LAYOUTCOMMIT (if required) and then
provide such an indication and allow for graceful and efficient following with LAYOUTRETURN can provide such an indication and allow
recovery. for graceful and efficient recovery.
If loca_reclaim is TRUE, the metadata server is free to either If loca_reclaim is TRUE, the metadata server is free to either
examine or ignore the value in the field loca_stateid. The metadata examine or ignore the value in the field loca_stateid. The metadata
server implementation might or might not encode in its layout stateid server implementation might or might not encode in its layout stateid
information that allows the metadate server to perform a consistency information that allows the metadate server to perform a consistency
check on the LAYOUTCOMMIT request. check on the LAYOUTCOMMIT request.
18.43. Operation 50: LAYOUTGET - Get Layout Information 18.43. Operation 50: LAYOUTGET - Get Layout Information
18.43.1. ARGUMENT 18.43.1. ARGUMENT
skipping to change at page 540, line 41 skipping to change at page 542, line 24
case NFS4_OK: case NFS4_OK:
LAYOUTGET4resok logr_resok4; LAYOUTGET4resok logr_resok4;
case NFS4ERR_LAYOUTTRYLATER: case NFS4ERR_LAYOUTTRYLATER:
bool logr_will_signal_layout_avail; bool logr_will_signal_layout_avail;
default: default:
void; void;
}; };
18.43.3. DESCRIPTION 18.43.3. DESCRIPTION
Requests a layout from the metadata server for reading or writing the The LAYOUTGET operation requests a layout from the metadata server
file given by the filehandle at the byte range specified by offset for reading or writing the file given by the filehandle at the byte-
and length. Layouts are identified by the client ID (derived from range specified by offset and length. Layouts are identified by the
the session ID in the preceding SEQUENCE operation), current client ID (derived from the session ID in the preceding SEQUENCE
filehandle, layout type (loga_layout_type), and the layout stateid operation), current filehandle, layout type (loga_layout_type), and
(loga_stateid). The use of the loga_iomode field depends upon the the layout stateid (loga_stateid). The use of the loga_iomode field
layout type, but should reflect the client's data access intent. depends upon the layout type, but should reflect the client's data
access intent.
If the metadata server is in a grace period, and does not persist If the metadata server is in a grace period, and does not persist
layouts and device ID to device address mappings, then it MUST return layouts and device ID to device address mappings, then it MUST return
NFS4ERR_GRACE (see Section 8.4.2.1). NFS4ERR_GRACE (see Section 8.4.2.1).
The LAYOUTGET operation returns layout information for the specified The LAYOUTGET operation returns layout information for the specified
byte range: a layout. The client actually specifies two ranges, both byte-range: a layout. The client actually specifies two ranges, both
starting at the offset in the loga_offset field. The first range is starting at the offset in the loga_offset field. The first range is
between loga_offset and loga_offset + loga_length - 1 inclusive. between loga_offset and loga_offset + loga_length - 1 inclusive.
This range indicates the desired range the client wants the layout to This range indicates the desired range the client wants the layout to
cover. The second range is between loga_offset and loga_offset + cover. The second range is between loga_offset and loga_offset +
loga_minlength - 1 inclusive. This range indicates the required loga_minlength - 1 inclusive. This range indicates the required
range the client needs the layout to cover. Thus, loga_minlength range the client needs the layout to cover. Thus, loga_minlength
MUST be less than or equal to loga_length. MUST be less than or equal to loga_length.
When a length field is set to NFS4_UINT64_MAX, this indicates a When a length field is set to NFS4_UINT64_MAX, this indicates a
desire (when loga_length is NFS4_UINT64_MAX) or requirement (when desire (when loga_length is NFS4_UINT64_MAX) or requirement (when
loga_minlength is NFS4_UINT64_MAX) to get a layout from loga_offset loga_minlength is NFS4_UINT64_MAX) to get a layout from loga_offset
through the end-of-file, regardless of the file's length. through the end-of-file, regardless of the file's length.
The following rules govern the relationships among, and the minima of The following rules govern the relationships among, and the minima
loga_length, loga_minlength, and loga_offset. of, loga_length, loga_minlength, and loga_offset.
o If loga_length is less than loga_minlength, the metadata server o If loga_length is less than loga_minlength, the metadata server
MUST return NFS4ERR_INVAL. MUST return NFS4ERR_INVAL.
o If loga_minlength is zero, this is an indication to the metadata o If loga_minlength is zero, this is an indication to the metadata
server that the client desires any layout at offset loga_offset or server that the client desires any layout at offset loga_offset or
less that the metadata server has "readily available". Readily is less that the metadata server has "readily available". Readily is
subjective, and depends on the layout type and the pNFS server subjective, and depends on the layout type and the pNFS server
implementation. For example, some metadata servers might have to implementation. For example, some metadata servers might have to
pre-allocate stable storage when they receive a request for a pre-allocate stable storage when they receive a request for a
range of a file that goes beyond the file's current length. If range of a file that goes beyond the file's current length. If
loga_minlength is zero and loga_length is greater than zero, this loga_minlength is zero and loga_length is greater than zero, this
tells the metadata server what range of the layout the client tells the metadata server what range of the layout the client
would prefer to have. If loga_length and loga_minlength are both would prefer to have. If loga_length and loga_minlength are both
zero, then the client is indicating it desires a layout of any zero, then the client is indicating that it desires a layout of
length with the ending offset of the range no less than specified any length with the ending offset of the range no less than the
loga_offset, and the starting offset at or below loga_offset. If value specified loga_offset, and the starting offset at or below
the metadata server does not have a layout that is readily loga_offset. If the metadata server does not have a layout that
available, then it MUST return NFS4ERR_LAYOUTTRYLATER. is readily available, then it MUST return NFS4ERR_LAYOUTTRYLATER.
o If the sum of loga_offset and loga_minlength exceeds o If the sum of loga_offset and loga_minlength exceeds
NFS4_UINT64_MAX, and loga_minlength is not NFS4_UINT64_MAX, the NFS4_UINT64_MAX, and loga_minlength is not NFS4_UINT64_MAX, the
error NFS4ERR_INVAL MUST result. error NFS4ERR_INVAL MUST result.
o If the sum of loga_offset and loga_length exceeds NFS4_UINT64_MAX, o If the sum of loga_offset and loga_length exceeds NFS4_UINT64_MAX,
and loga_length is not NFS4_UINT64_MAX, the error NFS4ERR_INVAL and loga_length is not NFS4_UINT64_MAX, the error NFS4ERR_INVAL
MUST result. MUST result.
After the metadata server has performed the above checks on After the metadata server has performed the above checks on
skipping to change at page 542, line 48 skipping to change at page 544, line 46
| | | _RW | <= a_off | | | | | _RW | <= a_off | |
+-----------+-----------+----------+----------+---------------------+ +-----------+-----------+----------+----------+---------------------+
Table 13 Table 13
If loga_minlength is not zero and the metadata server cannot return a If loga_minlength is not zero and the metadata server cannot return a
layout according to the rules in Table 13, then the metadata server layout according to the rules in Table 13, then the metadata server
MUST return the error NFS4ERR_BADLAYOUT. If loga_minlength is zero MUST return the error NFS4ERR_BADLAYOUT. If loga_minlength is zero
and the metadata server cannot or will not return a layout according and the metadata server cannot or will not return a layout according
to the rules in Table 13, then the metadata server MUST return the to the rules in Table 13, then the metadata server MUST return the
error NFS4ERR_LAYOUTTRYLATER. Assuming loga_length is greater than error NFS4ERR_LAYOUTTRYLATER. Assuming that loga_length is greater
loga_minlength or equal to zero, the metadata server SHOULD return a than loga_minlength or equal to zero, the metadata server SHOULD
layout according to the rules in Table 14. return a layout according to the rules in Table 14.
Desired layouts based on loga_length. The rules of Table 13 MUST be Desired layouts based on loga_length. The rules of Table 13 MUST be
applied first. Note: u64m = NFS4_UINT64_MAX; a_off = loga_offset; applied first. Note: u64m = NFS4_UINT64_MAX; a_off = loga_offset;
a_len = loga_length. a_len = loga_length.
+------------+------------+-----------+-----------+-----------------+ +------------+------------+-----------+-----------+-----------------+
| Layout | Layout | Layout | Layout | Layout length | | Layout | Layout | Layout | Layout | Layout length |
| iomode of | a_len of | iomode of | offset of | of reply | | iomode of | a_len of | iomode of | offset of | of reply |
| request | request | reply | reply | | | request | request | reply | reply | |
+------------+------------+-----------+-----------+-----------------+ +------------+------------+-----------+-----------+-----------------+
skipping to change at page 544, line 29 skipping to change at page 546, line 29
iomode iomode
The value of the returned layout iomode listed in Table 13 and The value of the returned layout iomode listed in Table 13 and
Table 14 is equal to the value of the lo_iomode field in each Table 14 is equal to the value of the lo_iomode field in each
element of logr_layout. As shown in Table 13 and Table 14, the element of logr_layout. As shown in Table 13 and Table 14, the
metadata server MAY return a layout with an lo_iomode different metadata server MAY return a layout with an lo_iomode different
from the requested iomode (field loga_iomode of the request). If from the requested iomode (field loga_iomode of the request). If
it does so, it MUST ensure that the lo_iomode is more permissive it does so, it MUST ensure that the lo_iomode is more permissive
than the loga_iomode requested. For example, this behavior allows than the loga_iomode requested. For example, this behavior allows
an implementation to upgrade read-only requests to read/write an implementation to upgrade LAYOUTIOMODE4_READ requests to
requests at its discretion, within the limits of the layout type LAYOUTIOMODE4_RW requests at its discretion, within the limits of
specific protocol. A lo_iomode of either LAYOUTIOMODE4_READ or the layout type specific protocol. A lo_iomode of either
LAYOUTIOMODE4_RW MUST be returned. LAYOUTIOMODE4_READ or LAYOUTIOMODE4_RW MUST be returned.
offset offset
The value of the returned layout offset listed in Table 13 and The value of the returned layout offset listed in Table 13 and
Table 14 is always equal to the lo_offset field of the first Table 14 is always equal to the lo_offset field of the first
element logr_layout. element logr_layout.
length length
When setting the value of the returned layout length, the When setting the value of the returned layout length, the
situation is complicated by the possibility that the special situation is complicated by the possibility that the special
layout length value NFS4_UINT64_MAX is involved. For a layout length value NFS4_UINT64_MAX is involved. For a
logr_layout array of N elements, the lo_length field in the first logr_layout array of N elements, the lo_length field in the first
N-1 elements MUST NOT be NFS4_UINT64_MAX. The lo_length field of N-1 elements MUST NOT be NFS4_UINT64_MAX. The lo_length field of
the last element of logr_layout can be NFS4_UINT64_MAX under some the last element of logr_layout can be NFS4_UINT64_MAX under some
conditions as described in the following list. conditions as described in the following list.
* If an applicable rule of Table 13 states the metadata server * If an applicable rule of Table 13 states that the metadata
MUST return a layout of length NFS4_UINT64_MAX, then lo_length server MUST return a layout of length NFS4_UINT64_MAX, then the
field of the last element of logr_layout MUST be lo_length field of the last element of logr_layout MUST be
NFS4_UINT64_MAX. NFS4_UINT64_MAX.
* If an applicable rule of Table 13 states the metadata server * If an applicable rule of Table 13 states that the metadata
MUST NOT return a layout of length NFS4_UINT64_MAX, then server MUST NOT return a layout of length NFS4_UINT64_MAX, then
lo_length field of the last element of logr_layout MUST NOT be the lo_length field of the last element of logr_layout MUST NOT
NFS4_UINT64_MAX. be NFS4_UINT64_MAX.
* If an applicable rule of Table 14 states the metadata server * If an applicable rule of Table 14 states that the metadata
SHOULD return a layout of length NFS4_UINT64_MAX, then server SHOULD return a layout of length NFS4_UINT64_MAX, then
lo_length field of the last element of logr_layout SHOULD be the lo_length field of the last element of logr_layout SHOULD
NFS4_UINT64_MAX. be NFS4_UINT64_MAX.
* When the value of the returned layout length of Table 13 and * When the value of the returned layout length of Table 13 and
Table 14 is not NFS4_UINT64_MAX, then the returned layout Table 14 is not NFS4_UINT64_MAX, then the returned layout
length is equal to the sum of the lo_length fields of each length is equal to the sum of the lo_length fields of each
element of logr_layout. element of logr_layout.
The logr_return_on_close result field is a directive to return the The logr_return_on_close result field is a directive to return the
layout before closing the file. When the metadata server sets this layout before closing the file. When the metadata server sets this
return value to TRUE, it MUST be prepared to recall the layout in the return value to TRUE, it MUST be prepared to recall the layout in the
case the client fails to return the layout before close. For the case in which the client fails to return the layout before close.
metadata server that knows a layout must be returned before a close For the metadata server that knows a layout must be returned before a
of the file, this return value can be used to communicate the desired close of the file, this return value can be used to communicate the
behavior to the client and thus remove one extra step from the desired behavior to the client and thus remove one extra step from
client's and metadata server's interaction. the client's and metadata server's interaction.
The logr_stateid stateid is returned to the client for use in The logr_stateid stateid is returned to the client for use in
subsequent layout related operations. See Section 8.2, subsequent layout related operations. See Sections 8.2, 12.5.3, and
Section 12.5.3, and Section 12.5.5.2 for a further discussion and 12.5.5.2 for a further discussion and requirements.
requirements.
The format of the returned layout (lo_content) is specific to the The format of the returned layout (lo_content) is specific to the
layout type. The value of the layout type (lo_content.loc_type) for layout type. The value of the layout type (lo_content.loc_type) for
each of the elements of the array of layouts returned by the metadata each of the elements of the array of layouts returned by the metadata
server (logr_layout) MUST be equal to the loga_layout_type specified server (logr_layout) MUST be equal to the loga_layout_type specified
by the client. If it is not equal, the client SHOULD ignore the by the client. If it is not equal, the client SHOULD ignore the
response as invalid and behave as if the metadata server returned an response as invalid and behave as if the metadata server returned an
error, even if the client does have support for the layout type error, even if the client does have support for the layout type
returned. returned.
If layouts are not supported for the requested file or its containing If neither the requested file nor its containing file system support
file system the metadata server MUST return layouts, the metadata server MUST return NFS4ERR_LAYOUTUNAVAILABLE.
NFS4ERR_LAYOUTUNAVAILABLE. If the layout type is not supported, the If the layout type is not supported, the metadata server MUST return
metadata server MUST return NFS4ERR_UNKNOWN_LAYOUTTYPE. If layouts NFS4ERR_UNKNOWN_LAYOUTTYPE. If layouts are supported but no layout
are supported but no layout matches the client provided layout matches the client provided layout identification, the metadata
identification, the metadata server MUST return NFS4ERR_BADLAYOUT. server MUST return NFS4ERR_BADLAYOUT. If an invalid loga_iomode is
If an invalid loga_iomode is specified, or a loga_iomode of specified, or a loga_iomode of LAYOUTIOMODE4_ANY is specified, the
LAYOUTIOMODE4_ANY is specified, the metadata server MUST return metadata server MUST return NFS4ERR_BADIOMODE.
NFS4ERR_BADIOMODE.
If the layout for the file is unavailable due to transient If the layout for the file is unavailable due to transient
conditions, e.g. file sharing prohibits layouts, the metadata server conditions, e.g., file sharing prohibits layouts, the metadata server
MUST return NFS4ERR_LAYOUTTRYLATER. MUST return NFS4ERR_LAYOUTTRYLATER.
If the layout request is rejected due to an overlapping layout If the layout request is rejected due to an overlapping layout
recall, the metadata server MUST return NFS4ERR_RECALLCONFLICT. See recall, the metadata server MUST return NFS4ERR_RECALLCONFLICT. See
Section 12.5.5.2 for details. Section 12.5.5.2 for details.
If the layout conflicts with a mandatory byte range lock held on the If the layout conflicts with a mandatory byte-range lock held on the
file, and if the storage devices have no method of enforcing file, and if the storage devices have no method of enforcing
mandatory locks, other than through the restriction of layouts, the mandatory locks, other than through the restriction of layouts, the
metadata server SHOULD return NFS4ERR_LOCKED. metadata server SHOULD return NFS4ERR_LOCKED.
If client sets loga_signal_layout_avail to TRUE, then it is If client sets loga_signal_layout_avail to TRUE, then it is
registering with the client a "want" for a layout in the event the registering with the client a "want" for a layout in the event the
layout cannot be obtained due to resource exhaustion. If the layout cannot be obtained due to resource exhaustion. If the
metadata server supports and will honor the "want", the results will metadata server supports and will honor the "want", the results will
have logr_will_signal_layout_avail set to TRUE. If so the client have logr_will_signal_layout_avail set to TRUE. If so, the client
should expect a CB_RECALLABLE_OBJ_AVAIL operation to indicate that a should expect a CB_RECALLABLE_OBJ_AVAIL operation to indicate that a
layout is available. layout is available.
On success, the current filehandle retains its value and the current On success, the current filehandle retains its value and the current
stateid is updated to match the value as returned in the results. stateid is updated to match the value as returned in the results.
18.43.4. IMPLEMENTATION 18.43.4. IMPLEMENTATION
Typically, LAYOUTGET will be called as part of a COMPOUND request Typically, LAYOUTGET will be called as part of a COMPOUND request
after an OPEN operation and results in the client having location after an OPEN operation and results in the client having location
information for the file; this requires that loga_stateid be set to information for the file. This requires that loga_stateid be set to
the special stateid that tells the metadata server to use the current the special stateid that tells the metadata server to use the current
stateid, which is set by OPEN (see Section 16.2.3.1.2) . A client stateid, which is set by OPEN (see Section 16.2.3.1.2). A client may
may also hold a layout across multiple OPENs. The client specifies a also hold a layout across multiple OPENs. The client specifies a
layout type that limits what kind of layout the metadata server will layout type that limits what kind of layout the metadata server will
return. This prevents metadata servers from granting layouts that return. This prevents metadata servers from granting layouts that
are unusable by the client. are unusable by the client.
As indicated by Table 13 and Table 14 the specification of LAYOUTGET As indicated by Table 13 and Table 14, the specification of LAYOUTGET
allows a pNFS client and server considerable flexibility. A pNFS allows a pNFS client and server considerable flexibility. A pNFS
client can take several strategies for sending LAYOUTGET. Some client can take several strategies for sending LAYOUTGET. Some
examples are as follows. examples are as follows.
o If LAYOUTGET is preceded by OPEN in the same COMPOUND request, and o If LAYOUTGET is preceded by OPEN in the same COMPOUND request and
the OPEN requests read access, the client might opt to request a the OPEN requests OPEN4_SHARE_ACCESS_READ access, the client might
_READ layout with loga_offset set to zero, loga_minlength set to opt to request a _READ layout with loga_offset set to zero,
zero, and loga_length set to NFS4_UINT64_MAX. If the file has loga_minlength set to zero, and loga_length set to
space allocated to it, that space is striped over one or more NFS4_UINT64_MAX. If the file has space allocated to it, that
storage devices, and there is either no conflicting layout, or the space is striped over one or more storage devices, and there is
concept of a conflicting layout does not apply to the pNFS either no conflicting layout or the concept of a conflicting
server's layout type or implementation, then the metadata server layout does not apply to the pNFS server's layout type or
might return a layout with a starting offset of zero, and a length implementation, then the metadata server might return a layout
equal to the length of the file, if not NFS4_UINT64_MAX. If the with a starting offset of zero, and a length equal to the length
length of the file is not a multiple of the pNFS server's stripe of the file, if not NFS4_UINT64_MAX. If the length of the file is
width (see Section 13.2 for a formal definition), the metadata not a multiple of the pNFS server's stripe width (see Section 13.2
server might round the returned layout's length up. for a formal definition), the metadata server might round up the
returned layout's length.
o If LAYOUTGET is preceded by OPEN in the same COMPOUND request, and o If LAYOUTGET is preceded by OPEN in the same COMPOUND request, and
the OPEN does not truncate the file, and requests write access, the OPEN requests OPEN4_SHARE_ACCESS_WRITE access and does not
the client might opt to request a _RW layout with loga_offset set truncate the file, the client might opt to request a _RW layout
to zero, loga_minlength set to zero, and loga_length set to the with loga_offset set to zero, loga_minlength set to zero, and
file's current length (if known), or NFS4_UINT64_MAX. As with the loga_length set to the file's current length (if known), or
previous case, under some conditions the metadata server might NFS4_UINT64_MAX. As with the previous case, under some conditions
return a layout that covers the entire length of the file or the metadata server might return a layout that covers the entire
beyond. length of the file or beyond.
o As above, but the OPEN truncates the file. In this case, client o This strategy is as above, but the OPEN truncates the file. In
might anticipate it will be writing to the file from offset zero, this case, the client might anticipate it will be writing to the
and so loga_offset and loga_minlength are set to zero, and file from offset zero, and so loga_offset and loga_minlength are
loga_length is set to the value of threshold4_write_iosize. The set to zero, and loga_length is set to the value of
metadata server might return a layout from offset zero with a threshold4_write_iosize. The metadata server might return a
length at least as long as as threshold4_write_iosize. layout from offset zero with a length at least as long as as
threshold4_write_iosize.
o A process on the client invokes a request to read from offset o A process on the client invokes a request to read from offset
10000 for length 50000. The client is using buffered I/O, and has 10000 for length 50000. The client is using buffered I/O, and has
buffer sizes of 4096 bytes. The client intends to map the request buffer sizes of 4096 bytes. The client intends to map the request
of the process into a series of READ requests starting at offset of the process into a series of READ requests starting at offset
8192. The end offset needs to be higher than 10000 + 50000 = 8192. The end offset needs to be higher than 10000 + 50000 =
60000, and the next offset that is a multiple of 4096 is 61440. 60000, and the next offset that is a multiple of 4096 is 61440.
The difference between 61440 and that starting offset of the The difference between 61440 and that starting offset of the
layout is 53248 (which is the product of 4096 and 15). The value layout is 53248 (which is the product of 4096 and 15). The value
of threshold4_read_iosize is less than 53248, so the client sends of threshold4_read_iosize is less than 53248, so the client sends
a LAYOUTGET request with loga_offset set to 8192, loga_minlength a LAYOUTGET request with loga_offset set to 8192, loga_minlength
set to 53248, and loga_length set to the file's length (if known) set to 53248, and loga_length set to the file's length (if known)
minus 8192 or NFS4_UINT64_MAX (if the file's length is not known). minus 8192 or NFS4_UINT64_MAX (if the file's length is not known).
Since this LAYOUTGET request exceeds the metadata server's Since this LAYOUTGET request exceeds the metadata server's
threshold, it grants the layout, possibly with an initial offset threshold, it grants the layout, possibly with an initial offset
of 0, with an end offset of at least 8192 + 53248 - 1 = 61439, but of zero, with an end offset of at least 8192 + 53248 - 1 = 61439,
preferably a layout with an offset aligned on the stripe width and but preferably a layout with an offset aligned on the stripe width
a length that is a multiple of the stripe width. and a length that is a multiple of the stripe width.
o As above, but the client is not using buffered I/O, and instead o This strategy is as above, but the client is not using buffered
all internal I/O requests are sent directly to the server. The I/O, and instead all internal I/O requests are sent directly to
LAYOUTGET request has loga_offset equal to 10000, and the server. The LAYOUTGET request has loga_offset equal to 10000
loga_minlength set to 50000. The value of loga_length is set to and loga_minlength set to 50000. The value of loga_length is set
the length of the file. The metadata server is free to return a to the length of the file. The metadata server is free to return
layout that fully overlaps the requested range, with a starting a layout that fully overlaps the requested range, with a starting
offset and length aligned on the stripe width. offset and length aligned on the stripe width.
o Again a process on the client invokes a request to read from o Again, a process on the client invokes a request to read from
offset 10000 for length 50000, and buffered I/O is in use. The offset 10000 for length 50000 (i.e. a range with a starting offset
client is expecting that the server might not be able to return of 10000 and an ending offset of 69999), and buffered I/O is in
the layout for the full I/O range, with loga_offset set to 8192 use. The client is expecting that the server might not be able to
and loga_minlength set to 53248. The client intends to map the return the layout for the full I/O range. The client intends to
request of the process into a series of READ requests starting at map the request of the process into a series of thirteen READ
offset 8192, each with length 4096, with a total length of 53248 requests starting at offset 8192, each with length 4096, with a
(which equals 13 * 4096). Because the value of total length of 53248 (which equals 13 * 4096), which fully
threshold4_read_iosize is equal to 4096, it is practical and contains the range that client's process wants to read. Because
reasonable for the client to use several LAYOUTGETs to complete the value of threshold4_read_iosize is equal to 4096, it is
the series of READs. The client sends a LAYOUTGET request with practical and reasonable for the client to use several LAYOUTGET
loga_offset set to 8192, loga_minlength set to 4096, and operations to complete the series of READs. The client sends a
loga_length set to 53248 or higher. The server will grant a LAYOUTGET request with loga_offset set to 8192, loga_minlength set
layout possibly with an initial offset of 0, with an end offset of to 4096, and loga_length set to 53248 or higher. The server will
at least 8192 + 4096 - 1 = 12287, but preferably a layout with an grant a layout possibly with an initial offset of zero, with an
offset aligned on the stripe width and a length that is a multiple end offset of at least 8192 + 4096 - 1 = 12287, but preferably a
of the stripe width. This will allow the client to make forward layout with an offset aligned on the stripe width and a length
progress, possibly having to send more LAYOUTGET operations for that is a multiple of the stripe width. This will allow the
the remainder of the range. client to make forward progress, possibly sending more LAYOUTGET
operations for the remainder of the range.
o An NFS client detects a sequential read pattern, and so sends a o An NFS client detects a sequential read pattern, and so sends a
LAYOUTGET operation that goes well beyond any current or pending LAYOUTGET operation that goes well beyond any current or pending
read requests to the server. The server might likewise detect read requests to the server. The server might likewise detect
this pattern, and grant the LAYOUTGET request. The client this pattern, and grant the LAYOUTGET request. Once the client
continues to send LAYOUTGET requests once it has read from an reads from an offset of the file that represents 50% of the way
offset of the file that represents 50% of the way through the through the range of the last layout it received, in order to
range of the last layout it received. avoid stalling I/O that would wait for a layout, the client sends
more operations from an offset of the file that represents 50% of
the way through the last layout it received. The client continues
to request layouts with byte-ranges that are well in advance of
the byte-ranges of recent and/or read requests of processes
running on the client.
o As above but the client fails to detect the pattern, but the o This strategy is as above, but the client fails to detect the
server does. The next time the metadata server gets a LAYOUTGET, pattern, but the server does. The next time the metadata server
it returns a layout with a length that is well beyond gets a LAYOUTGET, it returns a layout with a length that is well
loga_minlength. beyond loga_minlength.
o A client is using buffered I/O, and has a long queue of write o A client is using buffered I/O, and has a long queue of write-
behinds to process and also detects a sequential write pattern. behinds to process and also detects a sequential write pattern.
It sends a LAYOUTGET operation for a layout that spans the range It sends a LAYOUTGET for a layout that spans the range of the
of the queued write behinds and well beyond, including ranges queued write-behinds and well beyond, including ranges beyond the
beyond the filer's current length. The client continues to send filer's current length. The client continues to send LAYOUTGET
LAYOUTGET operations once the write behind queue reaches 50% of operations once the write-behind queue reaches 50% of the maximum
the maximum queue length. queue length.
Once the client has obtained a layout referring to a particular Once the client has obtained a layout referring to a particular
device ID, the metadata server MUST NOT delete the device ID until device ID, the metadata server MUST NOT delete the device ID until
the layout is returned or revoked. the layout is returned or revoked.
CB_NOTIFY_DEVICEID can race with LAYOUTGET. One race scenario is CB_NOTIFY_DEVICEID can race with LAYOUTGET. One race scenario is
that LAYOUTGET returns a device ID the client does not have device that LAYOUTGET returns a device ID for which the client does not have
address mappings for, and the metadata server sends a device address mappings, and the metadata server sends a
CB_NOTIFY_DEVICEID to add the device ID to the client's awareness and CB_NOTIFY_DEVICEID to add the device ID to the client's awareness and
meanwhile the client sends GETDEVICEINFO on the device ID. This meanwhile the client sends GETDEVICEINFO on the device ID. This
scenario is discussed in Section 18.40.4. Another scenario is that scenario is discussed in Section 18.40.4. Another scenario is that
the CB_NOTIFY_DEVICEID is processed by the client before it processes the CB_NOTIFY_DEVICEID is processed by the client before it processes
the results from LAYOUTGET. The client will send a GETDEVICEINFO on the results from LAYOUTGET. The client will send a GETDEVICEINFO on
the device ID. If the results from GETDEVICEINFO are received before the device ID. If the results from GETDEVICEINFO are received before
the client gets results from LAYOUTGET, then there is no longer a the client gets results from LAYOUTGET, then there is no longer a
race. If the results from LAYOUTGET are received before the results race. If the results from LAYOUTGET are received before the results
from GETDEVICEINFO, the client can either wait for results of from GETDEVICEINFO, the client can either wait for results of
GETDEVICEINFO, or send another one to get possibly more up to date GETDEVICEINFO or send another one to get possibly more up-to-date
device address mappings for the device ID. device address mappings for the device ID.
18.44. Operation 51: LAYOUTRETURN - Release Layout Information 18.44. Operation 51: LAYOUTRETURN - Release Layout Information
18.44.1. ARGUMENT 18.44.1. ARGUMENT
/* Constants used for LAYOUTRETURN and CB_LAYOUTRECALL */ /* Constants used for LAYOUTRETURN and CB_LAYOUTRECALL */
const LAYOUT4_RET_REC_FILE = 1; const LAYOUT4_RET_REC_FILE = 1;
const LAYOUT4_RET_REC_FSID = 2; const LAYOUT4_RET_REC_FSID = 2;
const LAYOUT4_RET_REC_ALL = 3; const LAYOUT4_RET_REC_ALL = 3;
skipping to change at page 550, line 36 skipping to change at page 553, line 29
}; };
18.44.3. DESCRIPTION 18.44.3. DESCRIPTION
This operation returns from the client to the server one or more This operation returns from the client to the server one or more
layouts represented by the client ID (derived from the session ID in layouts represented by the client ID (derived from the session ID in
the preceding SEQUENCE operation), lora_layout_type, and lora_iomode. the preceding SEQUENCE operation), lora_layout_type, and lora_iomode.
When lr_returntype is LAYOUTRETURN4_FILE, the returned layout is When lr_returntype is LAYOUTRETURN4_FILE, the returned layout is
further identified by the current filehandle, lrf_offset, lrf_length, further identified by the current filehandle, lrf_offset, lrf_length,
and lrf_stateid. If the lrf_length field is NFS4_UINT64_MAX, all and lrf_stateid. If the lrf_length field is NFS4_UINT64_MAX, all
bytes of the layout, starting at lrf_offset are returned. When bytes of the layout, starting at lrf_offset, are returned. When
lr_returntype is LAYOUTRETURN4_FSID, the current filehandle is used lr_returntype is LAYOUTRETURN4_FSID, the current filehandle is used
to identify the file system and all layouts matching the client ID, to identify the file system and all layouts matching the client ID,
the fsid of the file system, lora_layout_type, and lora_iomode are the fsid of the file system, lora_layout_type, and lora_iomode are
returned. When lr_returntype is LAYOUTRETURN4_ALL, all layouts returned. When lr_returntype is LAYOUTRETURN4_ALL, all layouts
matching the client ID, lora_layout_type, and lora_iomode are matching the client ID, lora_layout_type, and lora_iomode are
returned and the current filehandle is not used. After this call, returned and the current filehandle is not used. After this call,
the client MUST NOT use the returned layout(s) and the associated the client MUST NOT use the returned layout(s) and the associated
storage protocol to access the file data. storage protocol to access the file data.
If the set of layouts designated in the case of LAYOUTRETURN4_FSID or If the set of layouts designated in the case of LAYOUTRETURN4_FSID or
LAYOUTRETURN4_ALL is empty, then no error results. In the case of LAYOUTRETURN4_ALL is empty, then no error results. In the case of
LAYOUTRETURN4_FILE, the byte range specified is returned even if it LAYOUTRETURN4_FILE, the byte-range specified is returned even if it
is a subdivision of a layout previously obtained with LAYOUTGET, a is a subdivision of a layout previously obtained with LAYOUTGET, a
combination of multiple layouts previously obtained with LAYOUTGET, combination of multiple layouts previously obtained with LAYOUTGET,
or a combination including some layouts previously obtained with or a combination including some layouts previously obtained with
LAYOUTGET, and one or more subdivisions of such layouts. When the LAYOUTGET, and one or more subdivisions of such layouts. When the
byte range does not designate any bytes for which a layout is held byte-range does not designate any bytes for which a layout is held
for the specified file, client ID, layout type and mode, no error for the specified file, client ID, layout type and mode, no error
results. See Section 12.5.5.2.1.5 for considerations with "bulk" results. See Section 12.5.5.2.1.5 for considerations with "bulk"
return of layouts. return of layouts.
The layout being returned may be a subset or superset of a layout The layout being returned may be a subset or superset of a layout
specified by CB_LAYOUTRECALL. However, if it is a subset, the recall specified by CB_LAYOUTRECALL. However, if it is a subset, the recall
is not complete until the full recalled scope has been returned. is not complete until the full recalled scope has been returned.
Recalled scope refers to the byte range in the case of Recalled scope refers to the byte-range in the case of
LAYOUTRETURN4_FILE, use of LAYOUTRETURN4_FSID, or the use of LAYOUTRETURN4_FILE, the use of LAYOUTRETURN4_FSID, or the use of
LAYOUTRETURN4_ALL. There must be a LAYOUTRETURN with a matching LAYOUTRETURN4_ALL. There must be a LAYOUTRETURN with a matching
scope to complete the return even if all current layout ranges have scope to complete the return even if all current layout ranges have
been previously individually returned. been previously individually returned.
For all lr_returntype values, an iomode of LAYOUTIOMODE4_ANY For all lr_returntype values, an iomode of LAYOUTIOMODE4_ANY
specifies that all layouts that match the other arguments to specifies that all layouts that match the other arguments to
LAYOUTRETURN (i.e., client ID, lora_layout_type, and one of current LAYOUTRETURN (i.e., client ID, lora_layout_type, and one of current
filehandle and range; fsid derived from current filehandle; or filehandle and range; fsid derived from current filehandle; or
LAYOUTRETURN4_ALL) are being returned. LAYOUTRETURN4_ALL) are being returned.
In the case that lr_returntype is LAYOUTRETURN4_FILE, the lrf_stateid In the case that lr_returntype is LAYOUTRETURN4_FILE, the lrf_stateid
provided by the client is a layout stateid as returned from previous provided by the client is a layout stateid as returned from previous
layout operations. Note that the "seqid" field of lrf_stateid MUST layout operations. Note that the "seqid" field of lrf_stateid MUST
NOT be zero. See Section 8.2, Section 12.5.3, and Section 12.5.5.2 NOT be zero. See Sections 8.2, 12.5.3, and 12.5.5.2 for a further
for a further discussion and requirements. discussion and requirements.
Return of a layout or all layouts does not invalidate the mapping of Return of a layout or all layouts does not invalidate the mapping of
storage device ID to storage device address which remains in effect storage device ID to a storage device address. The mapping remains
until specifically changed or deleted via device ID notification in effect until specifically changed or deleted via device ID
callbacks. notification callbacks. Of course if there are no remaining layouts
that refer to a previously used device ID, the server is free to
delete a device ID without a notification callback, which will be the
case when notifications are not in effect.
If the lora_reclaim field is set to TRUE, the client is attempting to If the lora_reclaim field is set to TRUE, the client is attempting to
return a layout that was acquired before the restart of the metadata return a layout that was acquired before the restart of the metadata
server during the metadata server's grace period. When returning server during the metadata server's grace period. When returning
layouts that were acquired during the metadata server's grace period, layouts that were acquired during the metadata server's grace period,
the client MUST set the lora_reclaim field to FALSE. The the client MUST set the lora_reclaim field to FALSE. The
lora_reclaim field MUST be set to FALSE also when lr_layoutreturn is lora_reclaim field MUST be set to FALSE also when lr_layoutreturn is
LAYOUTRETURN4_FSID or LAYOUTRETURN4_ALL. See LAYOUTCOMMIT LAYOUTRETURN4_FSID or LAYOUTRETURN4_ALL. See LAYOUTCOMMIT
(Section 18.42) for more details. (Section 18.42) for more details.
Layouts may be returned when recalled or voluntarily (i.e., before Layouts may be returned when recalled or voluntarily (i.e., before
the server has recalled them). In either case the client must the server has recalled them). In either case, the client must
properly propagate state changed under the context of the layout to properly propagate state changed under the context of the layout to
the storage device(s) or to the metadata server before returning the the storage device(s) or to the metadata server before returning the
layout. layout.
If the client returns the layout in response to a CB_LAYOUTRECALL If the client returns the layout in response to a CB_LAYOUTRECALL
where the lor_recalltype field of the clora_recall field was where the lor_recalltype field of the clora_recall field was
LAYOUTRECALL4_FILE, the client should use the lor_stateid value from LAYOUTRECALL4_FILE, the client should use the lor_stateid value from
CB_LAYOUTRECALL as the value for lrf_stateid. Otherwise, it should CB_LAYOUTRECALL as the value for lrf_stateid. Otherwise, it should
use logr_stateid (from a previous LAYOUTGET result) or lorr_stateid use logr_stateid (from a previous LAYOUTGET result) or lorr_stateid
(from a previous LAYRETURN result). This is done to indicate the (from a previous LAYRETURN result). This is done to indicate the
point in time (in terms of layout stateid transitions) when the point in time (in terms of layout stateid transitions) when the
recall was sent. The client uses the precise lora_recallstateid recall was sent. The client uses the precise lora_recallstateid
value and MUST NOT set the stateid's seqid to zero; otherwise value and MUST NOT set the stateid's seqid to zero; otherwise,
NFS4ERR_BAD_STATEID MUST be returned. NFS4ERR_OLD_STATEID can be NFS4ERR_BAD_STATEID MUST be returned. NFS4ERR_OLD_STATEID can be
returned if the client is using an old seqid, and the server knows returned if the client is using an old seqid, and the server knows
the client should not be using the old seqid. E.g. the client uses the client should not be using the old seqid. For example, the
the seqid on slot 1 of the session, received the response with the client uses the seqid on slot 1 of the session, receives the response
new seqid, and uses the slot to send another request with the old with the new seqid, and uses the slot to send another request with
seqid. the old seqid.
If a client fails to return a layout in a timely manner, then the If a client fails to return a layout in a timely manner, then the
metadata server SHOULD use its control protocol with the storage metadata server SHOULD use its control protocol with the storage
devices to fence the client from accessing the data referenced by the devices to fence the client from accessing the data referenced by the
layout. See Section 12.5.5 for more details. layout. See Section 12.5.5 for more details.
If the LAYOUTRETURN request sets the lora_reclaim field to TRUE after If the LAYOUTRETURN request sets the lora_reclaim field to TRUE after
the metadata server's grace period, NFS4ERR_NO_GRACE is returned. the metadata server's grace period, NFS4ERR_NO_GRACE is returned.
If the LAYOUTRETURN request sets the lora_reclaim field to TRUE and If the LAYOUTRETURN request sets the lora_reclaim field to TRUE and
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NFS4ERR_INVAL is returned. NFS4ERR_INVAL is returned.
If the client sets the lr_returntype field to LAYOUTRETURN4_FILE, If the client sets the lr_returntype field to LAYOUTRETURN4_FILE,
then the lrs_stateid field will represent the layout stateid as then the lrs_stateid field will represent the layout stateid as
updated for this operation's processing; the current stateid will updated for this operation's processing; the current stateid will
also be updated to match the returned value. If the last byte of any also be updated to match the returned value. If the last byte of any
layout for the current file, client ID, and layout type is being layout for the current file, client ID, and layout type is being
returned and there are no remaining pending CB_LAYOUTRECALL returned and there are no remaining pending CB_LAYOUTRECALL
operations for which a LAYOUTRETURN operation must be done, operations for which a LAYOUTRETURN operation must be done,
lrs_present MUST be FALSE, and no stateid will be returned. In lrs_present MUST be FALSE, and no stateid will be returned. In
addition, the COMPOUND request's current stateid will be set to all- addition, the COMPOUND request's current stateid will be set to the
zeroes special stateid (see Section 16.2.3.1.2). The server MUST all-zeroes special stateid (see Section 16.2.3.1.2). The server MUST
reject with NFS4ERR_BAD_STATEID any further use of the current reject with NFS4ERR_BAD_STATEID any further use of the current
stateid in that COMPOUND until the current stateid is re-established stateid in that COMPOUND until the current stateid is re-established
by a later stateid-returning operation. by a later stateid-returning operation.
On success, the current filehandle retains its value. On success, the current filehandle retains its value.
If the EXCHGID4_FLAG_BIND_PRINC_STATEID capability is set on the If the EXCHGID4_FLAG_BIND_PRINC_STATEID capability is set on the
client ID (see Section 18.35), the server will require that the client ID (see Section 18.35), the server will require that the
principal, security flavor, and if applicable, the GSS mechanism, principal, security flavor, and if applicable, the GSS mechanism,
combination that acquired the layout also be the one to send combination that acquired the layout also be the one to send
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principal are no longer available. The server will allow the machine principal are no longer available. The server will allow the machine
credential or SSV credential (see Section 18.35) to send LAYOUTRETURN credential or SSV credential (see Section 18.35) to send LAYOUTRETURN
if LAYOUTRETURN's operation code was set in the spo_must_allow result if LAYOUTRETURN's operation code was set in the spo_must_allow result
of EXCHANGE_ID. of EXCHANGE_ID.
18.44.4. IMPLEMENTATION 18.44.4. IMPLEMENTATION
The final LAYOUTRETURN operation in response to a CB_LAYOUTRECALL The final LAYOUTRETURN operation in response to a CB_LAYOUTRECALL
callback MUST be serialized with any outstanding, intersecting callback MUST be serialized with any outstanding, intersecting
LAYOUTRETURN operations. Note that it is possible that while a LAYOUTRETURN operations. Note that it is possible that while a
client is returning the layout for some recalled range the server may client is returning the layout for some recalled range, the server
recall a superset of that range (e.g. LAYOUTRECALL4_ALL); the final may recall a superset of that range (e.g., LAYOUTRECALL4_ALL); the
return operation for the latter must block until the former layout final return operation for the latter must block until the former
recall is done. layout recall is done.
Returning all layouts in a file system using LAYOUTRETURN4_FSID is Returning all layouts in a file system using LAYOUTRETURN4_FSID is
typically done in response to a CB_LAYOUTRECALL for that file system typically done in response to a CB_LAYOUTRECALL for that file system
as the final return operation. Similarly, LAYOUTRETURN4_ALL is used as the final return operation. Similarly, LAYOUTRETURN4_ALL is used
in response to a recall callback for all layouts. It is possible in response to a recall callback for all layouts. It is possible
that the client already returned some outstanding layouts via that the client already returned some outstanding layouts via
individual LAYOUTRETURN calls and the call for LAYOUTRETURN4_FSID or individual LAYOUTRETURN calls and the call for LAYOUTRETURN4_FSID or
LAYOUTRETURN4_ALL marks the end of the LAYOUTRETURN sequence. See LAYOUTRETURN4_ALL marks the end of the LAYOUTRETURN sequence. See
Section 12.5.5.1 for more details. Section 12.5.5.1 for more details.
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There are two styles of SECINFO_NO_NAME, as determined by the value There are two styles of SECINFO_NO_NAME, as determined by the value
of the secinfo_style4 enumeration. If SECINFO_STYLE4_CURRENT_FH is of the secinfo_style4 enumeration. If SECINFO_STYLE4_CURRENT_FH is
passed, then SECINFO_NO_NAME is querying for the required security passed, then SECINFO_NO_NAME is querying for the required security
for the current filehandle. If SECINFO_STYLE4_PARENT is passed, then for the current filehandle. If SECINFO_STYLE4_PARENT is passed, then
SECINFO_NO_NAME is querying for the required security of the current SECINFO_NO_NAME is querying for the required security of the current
filehandle's parent. If the style selected is SECINFO_STYLE4_PARENT, filehandle's parent. If the style selected is SECINFO_STYLE4_PARENT,
then SECINFO should apply the same access methodology used for then SECINFO should apply the same access methodology used for
LOOKUPP when evaluating the traversal to the parent directory. LOOKUPP when evaluating the traversal to the parent directory.
Therefore, if the requester does not have the appropriate access to Therefore, if the requester does not have the appropriate access to
LOOKUPP the parent then SECINFO_NO_NAME must behave the same way and LOOKUPP the parent, then SECINFO_NO_NAME must behave the same way and
return NFS4ERR_ACCESS. return NFS4ERR_ACCESS.
If PUTFH, PUTPUBFH, PUTROOTFH, or RESTOREFH return NFS4ERR_WRONGSEC, If PUTFH, PUTPUBFH, PUTROOTFH, or RESTOREFH returns NFS4ERR_WRONGSEC,
then the client resolves the situation by sending a COMPOUND request then the client resolves the situation by sending a COMPOUND request
that consists of PUTFH, PUTPUBFH, or PUTROOTFH immediately followed that consists of PUTFH, PUTPUBFH, or PUTROOTFH immediately followed
by SECINFO_NO_NAME, style SECINFO_STYLE4_CURRENT_FH. See Section 2.6 by SECINFO_NO_NAME, style SECINFO_STYLE4_CURRENT_FH. See Section 2.6
for instructions on dealing with NFS4ERR_WRONGSEC error returns from for instructions on dealing with NFS4ERR_WRONGSEC error returns from
PUTFH, PUTROOTFH, PUTPUBFH, or RESTOREFH. PUTFH, PUTROOTFH, PUTPUBFH, or RESTOREFH.
If SECINFO_STYLE4_PARENT is specified and there is no parent If SECINFO_STYLE4_PARENT is specified and there is no parent
directory, SECINFO_NO_NAME MUST return NFS4ERR_NOENT. directory, SECINFO_NO_NAME MUST return NFS4ERR_NOENT.
On success, the current filehandle is consumed (see On success, the current filehandle is consumed (see
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SEQUENCE4resok sr_resok4; SEQUENCE4resok sr_resok4;
default: default:
void; void;
}; };
18.46.3. DESCRIPTION 18.46.3. DESCRIPTION
The SEQUENCE operation is used by the server to implement session The SEQUENCE operation is used by the server to implement session
request control and the reply cache semantics. request control and the reply cache semantics.
This operation MUST appear as the first operation of any COMPOUND in SEQUENCE MUST appear as the first operation of any COMPOUND in which
which it appears. The error NFS4ERR_SEQUENCE_POS will be returned it appears. The error NFS4ERR_SEQUENCE_POS will be returned when it
when it is found in any position in a COMPOUND beyond the first. is found in any position in a COMPOUND beyond the first. Operations
Operations other than SEQUENCE, BIND_CONN_TO_SESSION, EXCHANGE_ID, other than SEQUENCE, BIND_CONN_TO_SESSION, EXCHANGE_ID,
CREATE_SESSION, and DESTROY_SESSION, MUST NOT appear as the first CREATE_SESSION, and DESTROY_SESSION, MUST NOT appear as the first
operation in a COMPOUND. Such operations MUST yield the error operation in a COMPOUND. Such operations MUST yield the error
NFS4ERR_OP_NOT_IN_SESSION if they do appear at the start of a NFS4ERR_OP_NOT_IN_SESSION if they do appear at the start of a
COMPOUND. COMPOUND.
If SEQUENCE is received on a connection not associated with the If SEQUENCE is received on a connection not associated with the
session via CREATE_SESSION or BIND_CONN_TO_SESSION, and connection session via CREATE_SESSION or BIND_CONN_TO_SESSION, and connection
association enforcement is enabled (see Section 18.35), then the association enforcement is enabled (see Section 18.35), then the
server returns NFS4ERR_CONN_NOT_BOUND_TO_SESSION. server returns NFS4ERR_CONN_NOT_BOUND_TO_SESSION.
The sa_sessionid argument identifies the session this request applies The sa_sessionid argument identifies the session to which this
to. The sr_sessionid result MUST equal sa_sessionid. request applies. The sr_sessionid result MUST equal sa_sessionid.
The sa_slotid argument is the index in the reply cache for the The sa_slotid argument is the index in the reply cache for the
request. The sa_sequenceid field is the sequence number of the request. The sa_sequenceid field is the sequence number of the
request for the reply cache entry (slot). The sr_slotid result MUST request for the reply cache entry (slot). The sr_slotid result MUST
equal sa_slotid. The sr_sequenceid result MUST equal sa_sequenceid. equal sa_slotid. The sr_sequenceid result MUST equal sa_sequenceid.
The sa_highest_slotid argument is the highest slot ID the client has The sa_highest_slotid argument is the highest slot ID for which the
a request outstanding for; it could be equal to sa_slotid. The client has a request outstanding; it could be equal to sa_slotid.
server returns two "highest_slotid" values: sr_highest_slotid, and The server returns two "highest_slotid" values: sr_highest_slotid and
sr_target_highest_slotid. The former is the highest slot ID the sr_target_highest_slotid. The former is the highest slot ID the
server will accept in future SEQUENCE operation, and SHOULD NOT be server will accept in future SEQUENCE operation, and SHOULD NOT be
less than the value of sa_highest_slotid. (but see Section 2.10.6.1 less than the value of sa_highest_slotid (but see Section 2.10.6.1
for an exception). The latter is the highest slot ID the server for an exception). The latter is the highest slot ID the server
would prefer the client use on a future SEQUENCE operation. would prefer the client use on a future SEQUENCE operation.
If sa_cachethis is TRUE, then the client is requesting that the If sa_cachethis is TRUE, then the client is requesting that the
server cache the entire reply in the server's reply cache; therefore server cache the entire reply in the server's reply cache; therefore,
the server MUST cache the reply (see Section 2.10.6.1.3). The server the server MUST cache the reply (see Section 2.10.6.1.3). The server
MAY cache the reply if sa_cachethis is FALSE. If the server does not MAY cache the reply if sa_cachethis is FALSE. If the server does not
cache the entire reply, it MUST still record that it executed the cache the entire reply, it MUST still record that it executed the
request at the specified slot and sequence ID. request at the specified slot and sequence ID.
The response to the SEQUENCE operation contains a word of status The response to the SEQUENCE operation contains a word of status
flags (sr_status_flags) that can provide to the client information flags (sr_status_flags) that can provide to the client information
related to the status of the client's lock state and communications related to the status of the client's lock state and communications
paths. Note that any status bits relating to lock state MAY be reset paths. Note that any status bits relating to lock state MAY be reset
when lock state is lost due to a server restart (even if the session when lock state is lost due to a server restart (even if the session
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client ID until at least one backchannel is available on any client ID until at least one backchannel is available on any
session associated with the client ID. If the client fails to re- session associated with the client ID. If the client fails to re-
establish a backchannel for the client ID, it is subject to having establish a backchannel for the client ID, it is subject to having
recallable state revoked. recallable state revoked.
SEQ4_STATUS_CB_PATH_DOWN_SESSION SEQ4_STATUS_CB_PATH_DOWN_SESSION
When set, indicates that the session has no operational When set, indicates that the session has no operational
backchannel. There are two reasons why backchannel. There are two reasons why
SEQ4_STATUS_CB_PATH_DOWN_SESSION may be set and not SEQ4_STATUS_CB_PATH_DOWN_SESSION may be set and not
SEQ4_STATUS_CB_PATH_DOWN. First is that a callback operation that SEQ4_STATUS_CB_PATH_DOWN. First is that a callback operation that
applies specifically to the session (e.g. CB_RECALL_SLOT, see applies specifically to the session (e.g., CB_RECALL_SLOT, see
Section 20.8) needs to be sent. Second is that the server did Section 20.8) needs to be sent. Second is that the server did
send a callback operation, but the connection was lost before the send a callback operation, but the connection was lost before the
reply. The server cannot be sure whether the client received the reply. The server cannot be sure whether or not the client
callback operation or not, and so, per rules on request retry, the received the callback operation, and so, per rules on request
server MUST retry the callback operation over the same session. retry, the server MUST retry the callback operation over the same
The SEQ4_STATUS_CB_PATH_DOWN_SESSION bit is the indication to the session. The SEQ4_STATUS_CB_PATH_DOWN_SESSION bit is the
client that it needs to associate a connection to the session's indication to the client that it needs to associate a connection
backchannel. This bit remains set on all SEQUENCE responses on to the session's backchannel. This bit remains set on all
the session until a backchannel on the session the path is SEQUENCE responses of the session until a connection is associated
available. If the client fails to re-establish a backchannel for with the session's a backchannel. If the client fails to re-
the session, it is subject to having recallable state revoked. establish a backchannel for the session, it is subject to having
recallable state revoked.
SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRING SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRING
When set, indicates that all GSS contexts or RPCSEC_GSS handles When set, indicates that all GSS contexts or RPCSEC_GSS handles
assigned to the session's backchannel will expire within a period assigned to the session's backchannel will expire within a period
equal to the lease time. This bit remains set on all SEQUENCE equal to the lease time. This bit remains set on all SEQUENCE
replies until at least one of the following are true: replies until at least one of the following are true:
* All SSV RPCSEC_GSS handles on the session's backchannel have * All SSV RPCSEC_GSS handles on the session's backchannel have
been destroyed and all non-SSV GSS contexts have expired. been destroyed and all non-SSV GSS contexts have expired.
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When set, indicates that the lease has expired and as a result the When set, indicates that the lease has expired and as a result the
server released all of the client's locking state. This status server released all of the client's locking state. This status
bit remains set on all SEQUENCE replies until the loss of all such bit remains set on all SEQUENCE replies until the loss of all such
locks has been acknowledged by use of FREE_STATEID (see locks has been acknowledged by use of FREE_STATEID (see
Section 18.38), or by establishing a new client instance by Section 18.38), or by establishing a new client instance by
destroying all sessions (via DESTROY_SESSION), the client ID (via destroying all sessions (via DESTROY_SESSION), the client ID (via
DESTROY_CLIENTID), and then invoking EXCHANGE_ID and DESTROY_CLIENTID), and then invoking EXCHANGE_ID and
CREATE_SESSION to establish a new client ID. CREATE_SESSION to establish a new client ID.
SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED
When set indicates that some subset of the client's locks have When set, indicates that some subset of the client's locks have
been revoked due to expiration of the lease period followed by been revoked due to expiration of the lease period followed by
another client's conflicting lock request. This status bit another client's conflicting LOCK operation. This status bit
remains set on all SEQUENCE replies until the loss of all such remains set on all SEQUENCE replies until the loss of all such
locks has been acknowledged by use of FREE_STATEID. locks has been acknowledged by use of FREE_STATEID.
SEQ4_STATUS_ADMIN_STATE_REVOKED SEQ4_STATUS_ADMIN_STATE_REVOKED
When set indicates that one or more locks have been revoked When set, indicates that one or more locks have been revoked
without expiration of the lease period, due to administrative without expiration of the lease period, due to administrative
action. This status bit remains set on all SEQUENCE replies until action. This status bit remains set on all SEQUENCE replies until
the loss of all such locks has been acknowledged by use of the loss of all such locks has been acknowledged by use of
FREE_STATEID. FREE_STATEID.
SEQ4_STATUS_RECALLABLE_STATE_REVOKED SEQ4_STATUS_RECALLABLE_STATE_REVOKED
When set indicates that one or more recallable objects have been When set, indicates that one or more recallable objects have been
revoked without expiration of the lease period, due to the revoked without expiration of the lease period, due to the
client's failure to return them when recalled which may be a client's failure to return them when recalled, which may be a
consequence of there being no working backchannel and the client consequence of there being no working backchannel and the client
failing to reestablish a backchannel per the failing to re-establish a backchannel per the
SEQ4_STATUS_CB_PATH_DOWN, SEQ4_STATUS_CB_PATH_DOWN_SESSION, or SEQ4_STATUS_CB_PATH_DOWN, SEQ4_STATUS_CB_PATH_DOWN_SESSION, or
SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRED status flags. This status bit SEQ4_STATUS_CB_GSS_CONTEXTS_EXPIRED status flags. This status bit
remains set on all SEQUENCE replies until the loss of all such remains set on all SEQUENCE replies until the loss of all such
locks has been acknowledged by use of FREE_STATEID. locks has been acknowledged by use of FREE_STATEID.
SEQ4_STATUS_LEASE_MOVED SEQ4_STATUS_LEASE_MOVED
When set indicates that responsibility for lease renewal has been When set, indicates that responsibility for lease renewal has been
transferred to one or more new servers. This condition will transferred to one or more new servers. This condition will
continue until the client receives an NFS4ERR_MOVED error and the continue until the client receives an NFS4ERR_MOVED error and the
server receives the subsequent GETATTR for the fs_locations or server receives the subsequent GETATTR for the fs_locations or
fs_locations_info attribute for an access to each file system for fs_locations_info attribute for an access to each file system for
which a lease has been moved to a new server. See which a lease has been moved to a new server. See
Section 11.7.7.1. Section 11.7.7.1.
SEQ4_STATUS_RESTART_RECLAIM_NEEDED SEQ4_STATUS_RESTART_RECLAIM_NEEDED
When set indicates that due to server restart the client must When set, indicates that due to server restart, the client must
reclaim locking state. Until the client sends a global reclaim locking state. Until the client sends a global
RECLAIM_COMPLETE (Section 18.51), every SEQUENCE operation will RECLAIM_COMPLETE (Section 18.51), every SEQUENCE operation will
return SEQ4_STATUS_RESTART_RECLAIM_NEEDED. return SEQ4_STATUS_RESTART_RECLAIM_NEEDED.
SEQ4_STATUS_BACKCHANNEL_FAULT SEQ4_STATUS_BACKCHANNEL_FAULT
The server has encountered an unrecoverable fault with the The server has encountered an unrecoverable fault with the
backchannel (e.g. it has lost track of the sequence ID for a slot backchannel (e.g., it has lost track of the sequence ID for a slot
in the backchannel). The client MUST stop sending more requests in the backchannel). The client MUST stop sending more requests
on the session's fore channel, wait for all outstanding requests on the session's fore channel, wait for all outstanding requests
to complete on the fore and back channel, and then destroy the to complete on the fore and back channel, and then destroy the
session. session.
SEQ4_STATUS_DEVID_CHANGED SEQ4_STATUS_DEVID_CHANGED
The client is using device ID notifications and the server has The client is using device ID notifications and the server has
changed a device ID mapping held by the client. This flag will changed a device ID mapping held by the client. This flag will
stay present until the client has obtained the new mapping with stay present until the client has obtained the new mapping with
GETDEVICEINFO. GETDEVICEINFO.
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The value of the sa_sequenceid argument relative to the cached The value of the sa_sequenceid argument relative to the cached
sequence ID on the slot falls into one of three cases. sequence ID on the slot falls into one of three cases.
o If the difference between sa_sequenceid and the server's cached o If the difference between sa_sequenceid and the server's cached
sequence ID at the slot ID is two (2) or more, or if sa_sequenceid sequence ID at the slot ID is two (2) or more, or if sa_sequenceid
is less than the cached sequence ID (accounting for wraparound of is less than the cached sequence ID (accounting for wraparound of
the unsigned sequence ID value), then the server MUST return the unsigned sequence ID value), then the server MUST return
NFS4ERR_SEQ_MISORDERED. NFS4ERR_SEQ_MISORDERED.
o If sa_sequenceid and the cached sequence ID are the same, this is o If sa_sequenceid and the cached sequence ID are the same, this is
a retry, and the server replies with the COMPOUND reply that is a retry, and the server replies with what is recorded in the reply
stored the reply cache. The lease is possibly renewed as cache. The lease is possibly renewed as described below.
described below.
o If sa_sequenceid is one greater (accounting for wraparound) than o If sa_sequenceid is one greater (accounting for wraparound) than
the cached sequence ID, then this is a new request, and the slot's the cached sequence ID, then this is a new request, and the slot's
sequence ID is incremented. The operations subsequent to sequence ID is incremented. The operations subsequent to
SEQUENCE, if any, are processed. If there are no other SEQUENCE, if any, are processed. If there are no other
operations, the only other effects are to cache the SEQUENCE reply operations, the only other effects are to cache the SEQUENCE reply
in the slot, maintain the session's activity, and possibly renew in the slot, maintain the session's activity, and possibly renew
the lease. the lease.
If the client reuses a slot ID and sequence ID for a completely If the client reuses a slot ID and sequence ID for a completely
different request, the server MAY treat the request as if it is retry different request, the server MAY treat the request as if it is a
of what it has already executed. The server MAY however detect the retry of what it has already executed. The server MAY however detect
client's illegal reuse and return NFS4ERR_SEQ_FALSE_RETRY. the client's illegal reuse and return NFS4ERR_SEQ_FALSE_RETRY.
If SEQUENCE returns an error, then the state of the slot (sequence If SEQUENCE returns an error, then the state of the slot (sequence
ID, cached reply) MUST NOT change, and the associated lease MUST NOT ID, cached reply) MUST NOT change, and the associated lease MUST NOT
be renewed. be renewed.
If SEQUENCE returns NFS4_OK, then the associated lease MUST be If SEQUENCE returns NFS4_OK, then the associated lease MUST be
renewed (see Section 8.3), except if renewed (see Section 8.3), except if
SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED is returned in sr_status_flags. SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED is returned in sr_status_flags.
18.46.4. IMPLEMENTATION 18.46.4. IMPLEMENTATION
The server MUST maintain a mapping of session ID to client ID in The server MUST maintain a mapping of session ID to client ID in
order to validate any operations that follow SEQUENCE that take a order to validate any operations that follow SEQUENCE that take a
stateid as an argument and/or result. stateid as an argument and/or result.
If the client establishes a persistent session, then a SEQUENCE done If the client establishes a persistent session, then a SEQUENCE
after a server restart may encounter requests performed and recorded received after a server restart might encounter requests performed
in a persistent reply cache before the server restart. In this case, and recorded in a persistent reply cache before the server restart.
SEQUENCE will be processed successfully, while requests which were In this case, SEQUENCE will be processed successfully, while requests
not processed previously are rejected with NFS4ERR_DEADSESSION. that were not previously performed and recorded are rejected with
NFS4ERR_DEADSESSION.
Depending on which of the operations within the COMPOUND were Depending on which of the operations within the COMPOUND were
successfully performed before the server restart, these operations successfully performed before the server restart, these operations
will also have replies sent from the server reply cache. Note that will also have replies sent from the server reply cache. Note that
when these operations establish locking state it is locking state when these operations establish locking state, it is locking state
that applies to the previous server instance and to the previous that applies to the previous server instance and to the previous
client ID, even though the server restart, which logically happened client ID, even though the server restart, which logically happened
after these operations, eliminated that state. In the case of a after these operations, eliminated that state. In the case of a
partially executed COMPOUND, processing may reach an operation not partially executed COMPOUND, processing may reach an operation not
processed during the earlier server instance, making this operation a processed during the earlier server instance, making this operation a
new one and not performable on the existing session. In this case, new one and not performable on the existing session. In this case,
NFS4ERR_DEADSESSION will be returned from that operation. NFS4ERR_DEADSESSION will be returned from that operation.
18.47. Operation 54: SET_SSV - Update SSV for a Client ID 18.47. Operation 54: SET_SSV - Update SSV for a Client ID
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union SET_SSV4res switch (nfsstat4 ssr_status) { union SET_SSV4res switch (nfsstat4 ssr_status) {
case NFS4_OK: case NFS4_OK:
SET_SSV4resok ssr_resok4; SET_SSV4resok ssr_resok4;
default: default:
void; void;
}; };
18.47.3. DESCRIPTION 18.47.3. DESCRIPTION
This operation is used to update the SSV for a client ID. Before This operation is used to update the SSV for a client ID. Before
SET_SSV is called the first time on a client ID, the SSV is zero (0). SET_SSV is called the first time on a client ID, the SSV is zero.
The SSV is the key used for the SSV GSS mechanism (Section 2.10.9) The SSV is the key used for the SSV GSS mechanism (Section 2.10.9)
SET_SSV MUST be preceded by a SEQUENCE operation in the same SET_SSV MUST be preceded by a SEQUENCE operation in the same
COMPOUND. It MUST NOT be used if the client did not opt for SP4_SSV COMPOUND. It MUST NOT be used if the client did not opt for SP4_SSV
state protection when the client ID was created (see Section 18.35); state protection when the client ID was created (see Section 18.35);
the server returns NFS4ERR_INVAL in that case. the server returns NFS4ERR_INVAL in that case.
The field ssa_digest is computed as the output of the HMAC RFC2104 The field ssa_digest is computed as the output of the HMAC (RFC 2104
[11] using the subkey derived from the SSV4_SUBKEY_MIC_I2T and [11]) using the subkey derived from the SSV4_SUBKEY_MIC_I2T and
current SSV as the key (See Section 2.10.9 for a description of current SSV as the key (see Section 2.10.9 for a description of
subkeys), and an XDR encoded value of data type ssa_digest_input4. subkeys), and an XDR encoded value of data type ssa_digest_input4.
The field sdi_seqargs is equal to the arguments of the SEQUENCE The field sdi_seqargs is equal to the arguments of the SEQUENCE
operation for the COMPOUND procedure that SET_SSV is within. operation for the COMPOUND procedure that SET_SSV is within.
The argument ssa_ssv is XORed with the current SSV to produce the new The argument ssa_ssv is XORed with the current SSV to produce the new
SSV. The argument ssa_ssv SHOULD be generated randomly. SSV. The argument ssa_ssv SHOULD be generated randomly.
In the response, ssr_digest is the output of the HMAC using the In the response, ssr_digest is the output of the HMAC using the
subkey derived from SSV4_SUBKEY_MIC_T2I and new SSV as the key, and subkey derived from SSV4_SUBKEY_MIC_T2I and new SSV as the key, and
an XDR encoded value of data type ssr_digest_input4. The field an XDR encoded value of data type ssr_digest_input4. The field
sdi_seqres is equal to the results of the SEQUENCE operation for the sdi_seqres is equal to the results of the SEQUENCE operation for the
COMPOUND procedure that SET_SSV is within. COMPOUND procedure that SET_SSV is within.
As noted in Section 18.35, the client and server can maintain As noted in Section 18.35, the client and server can maintain
multiple concurrent versions of the SSV. The client and server each multiple concurrent versions of the SSV. The client and server each
MUST maintain an internal SSV version number, which is set to one (1) MUST maintain an internal SSV version number, which is set to one the
the first time SET_SSV executes on the server and the client receives first time SET_SSV executes on the server and the client receives the
the first SET_SSV reply. Each subsequent SET_SSV increases the first SET_SSV reply. Each subsequent SET_SSV increases the internal
internal SSV version number by one (1). The value of this version SSV version number by one. The value of this version number
number corresponds to the smpt_ssv_seq, smt_ssv_seq, sspt_ssv_seq, corresponds to the smpt_ssv_seq, smt_ssv_seq, sspt_ssv_seq, and
and ssct_ssv_seq fields of the SSV GSS mechanism tokens (see ssct_ssv_seq fields of the SSV GSS mechanism tokens (see
Section 2.10.9). Section 2.10.9).
18.47.4. IMPLEMENTATION 18.47.4. IMPLEMENTATION
When the server receives ssa_digest, it MUST verify the digest by When the server receives ssa_digest, it MUST verify the digest by
computing the digest the same way the client did and comparing it computing the digest the same way the client did and comparing it
with ssa_digest. If the server gets a different result, this is an with ssa_digest. If the server gets a different result, this is an
error, NFS4ERR_BAD_SESSION_DIGEST. This error might be the result of error, NFS4ERR_BAD_SESSION_DIGEST. This error might be the result of
another SET_SSV from the same client ID changing the SSV. If so, the another SET_SSV from the same client ID changing the SSV. If so, the
client recovers by sending a SET_SSV operation again with a client recovers by sending a SET_SSV operation again with a
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ssa_ssv, nor equal to a previous or current SSV (including an ssa_ssv ssa_ssv, nor equal to a previous or current SSV (including an ssa_ssv
equal to zero since the SSV is initialized to zero when the client ID equal to zero since the SSV is initialized to zero when the client ID
is created). is created).
Clients SHOULD send SET_SSV with RPCSEC_GSS privacy. Servers MUST Clients SHOULD send SET_SSV with RPCSEC_GSS privacy. Servers MUST
support RPCSEC_GSS with privacy for any COMPOUND that has { SEQUENCE, support RPCSEC_GSS with privacy for any COMPOUND that has { SEQUENCE,
SET_SSV }. SET_SSV }.
A client SHOULD NOT send SET_SSV with the SSV GSS mechanism's A client SHOULD NOT send SET_SSV with the SSV GSS mechanism's
credential because the purpose of SET_SSV is to seed the SSV from credential because the purpose of SET_SSV is to seed the SSV from
non-SSV credentials. Instead SET_SSV SHOULD be sent with the non-SSV credentials. Instead, SET_SSV SHOULD be sent with the
credential of a user that is accessing the client ID for the first credential of a user that is accessing the client ID for the first
time (Section 2.10.8.3). However if the client does send SET_SSV time (Section 2.10.8.3). However, if the client does send SET_SSV
with SSV credentials, the digest protecting the arguments uses the with SSV credentials, the digest protecting the arguments uses the
value of the SSV before ssa_ssv is XORed in, and the digest value of the SSV before ssa_ssv is XORed in, and the digest
protecting the results uses the value of the SSV after the ssa_ssv is protecting the results uses the value of the SSV after the ssa_ssv is
XORed in. XORed in.
18.48. Operation 55: TEST_STATEID - Test Stateids for Validity 18.48. Operation 55: TEST_STATEID - Test Stateids for Validity
18.48.1. ARGUMENT 18.48.1. ARGUMENT
struct TEST_STATEID4args { struct TEST_STATEID4args {
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union TEST_STATEID4res switch (nfsstat4 tsr_status) { union TEST_STATEID4res switch (nfsstat4 tsr_status) {
case NFS4_OK: case NFS4_OK:
TEST_STATEID4resok tsr_resok4; TEST_STATEID4resok tsr_resok4;
default: default:
void; void;
}; };
18.48.3. DESCRIPTION 18.48.3. DESCRIPTION
The TEST_STATEID operation is used to check the validity of a set of The TEST_STATEID operation is used to check the validity of a set of
stateids. It can be used at any time but the client should stateids. It can be used at any time, but the client should
definitely use it when it receives an indication that one or more of definitely use it when it receives an indication that one or more of
its stateids have been invalidated due to lock revocation. This its stateids have been invalidated due to lock revocation. This
occurs when the SEQUENCE operation returns with one of the following occurs when the SEQUENCE operation returns with one of the following
sr_status_flags set: sr_status_flags set:
o SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED o SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED
o SEQ4_STATUS_EXPIRED_ADMIN_STATE_REVOKED o SEQ4_STATUS_EXPIRED_ADMIN_STATE_REVOKED
o SEQ4_STATUS_EXPIRED_RECALLABLE_STATE_REVOKED o SEQ4_STATUS_EXPIRED_RECALLABLE_STATE_REVOKED
The client can use TEST_STATEID one or more times to test the The client can use TEST_STATEID one or more times to test the
validity of its stateids. Each use of TEST_STATEID allows a large validity of its stateids. Each use of TEST_STATEID allows a large
set of such stateids to be tested and allows problems with earlier set of such stateids to be tested and avoids problems with earlier
stateids not to interfere with checking of subsequent ones as would stateids in a COMPOUND request from interfering with the checking of
happen if individual stateids are tested by operation in a COMPOUND. subsequent stateids, as would happen if individual stateids were
tested by a series of corresponding by operations in a COMPOUND
request.
For each stateid, the server returns the status code that would be For each stateid, the server returns the status code that would be
returned if that stateid were to be used in normal operation. returned if that stateid were to be used in normal operation.
Returning such a status indication is not an error and does not cause Returning such a status indication is not an error and does not cause
compound processing to terminate. Checks for the validity of the COMPOUND processing to terminate. Checks for the validity of the
stateid proceed as they would for normal operations with a number of stateid proceed as they would for normal operations with a number of
exceptions: exceptions:
o There is no check for the type of stateid object, as would be the o There is no check for the type of stateid object, as would be the
case for normal use of a stateid. case for normal use of a stateid.
o There is no reference to the current filehandle. o There is no reference to the current filehandle.
o Special stateids are always considered invalid (they result in the o Special stateids are always considered invalid (they result in the
error code NFS4ERR_BAD_STATEID). error code NFS4ERR_BAD_STATEID).
All stateids are interpreted as being associated with the client for All stateids are interpreted as being associated with the client for
the current session. Any possible association with a previous the current session. Any possible association with a previous
instance of the client (as stale stateids) is not considered. instance of the client (as stale stateids) is not considered.
The errors which are validly returned within the status_code array The valid status values in the returned status_code array are
are: NFS4ERR_OK, NFS4ERR_BAD_STATEID, NFS4ERR_OLD_STATEID, NFS4ERR_OK, NFS4ERR_BAD_STATEID, NFS4ERR_OLD_STATEID,
NFS4ERR_EXPIRED, NFS4ERR_ADMIN_REVOKED, and NFS4ERR_DELEG_REVOKED. NFS4ERR_EXPIRED, NFS4ERR_ADMIN_REVOKED, and NFS4ERR_DELEG_REVOKED.
18.48.4. IMPLEMENTATION 18.48.4. IMPLEMENTATION
See Section 8.2.2 and Section 8.2.4 for a discussion of stateid See Sections 8.2.2 and 8.2.4 for a discussion of stateid structure,
structure, lifetime, and validation. lifetime, and validation.
18.49. Operation 56: WANT_DELEGATION - Request Delegation 18.49. Operation 56: WANT_DELEGATION - Request Delegation
18.49.1. ARGUMENT 18.49.1. ARGUMENT
union deleg_claim4 switch (open_claim_type4 dc_claim) { union deleg_claim4 switch (open_claim_type4 dc_claim) {
/* /*
* No special rights to object. Ordinary delegation * No special rights to object. Ordinary delegation
* request of the specified object. Object identified * request of the specified object. Object identified
* by filehandle. * by filehandle.
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for a specific condition, and where multiple conditions apply, the for a specific condition, and where multiple conditions apply, the
server MAY return any of the mandated error codes. server MAY return any of the mandated error codes.
This operation allows a client to: This operation allows a client to:
o Get a delegation on all types of files except directories. o Get a delegation on all types of files except directories.
o Register a "want" for a delegation for the specified file object, o Register a "want" for a delegation for the specified file object,
and be notified via a callback when the delegation is available. and be notified via a callback when the delegation is available.
The server MAY support notifications of availability via The server MAY support notifications of availability via
callbacks. If the server does not support registration of wants callbacks. If the server does not support registration of wants,
it MUST NOT return an error to indicate that, and instead MUST it MUST NOT return an error to indicate that, and instead MUST
return with ond_why set to WND4_CONTENTION or WND4_RESOURCE and return with ond_why set to WND4_CONTENTION or WND4_RESOURCE and
ond_server_will_push_deleg or ond_server_will_signal_avail set to ond_server_will_push_deleg or ond_server_will_signal_avail set to
FALSE. When the server indicates that it will notify the client FALSE. When the server indicates that it will notify the client
by means of a callback, it will either provide the delegation by means of a callback, it will either provide the delegation
using a CB_PUSH_DELEG operation, or cancel its promise by sending using a CB_PUSH_DELEG operation or cancel its promise by sending a
a CB_WANTS_CANCELLED operation. CB_WANTS_CANCELLED operation.
o Cancel a want for a delegation. o Cancel a want for a delegation.
The client SHOULD NOT set OPEN4_SHARE_ACCESS_READ and SHOULD NOT set The client SHOULD NOT set OPEN4_SHARE_ACCESS_READ and SHOULD NOT set
OPEN4_SHARE_ACCESS_WRITE in wda_want. If it does, the server MUST OPEN4_SHARE_ACCESS_WRITE in wda_want. If it does, the server MUST
ignore them. ignore them.
The meanings of the following flags in wda_want are the same as they The meanings of the following flags in wda_want are the same as they
are in OPEN: are in OPEN, except as noted below.
o OPEN4_SHARE_ACCESS_WANT_READ_DELEG o OPEN4_SHARE_ACCESS_WANT_READ_DELEG
o OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG o OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG
o OPEN4_SHARE_ACCESS_WANT_ANY_DELEG o OPEN4_SHARE_ACCESS_WANT_ANY_DELEG
o OPEN4_SHARE_ACCESS_WANT_NO_DELEG o OPEN4_SHARE_ACCESS_WANT_NO_DELEG. Unlike the OPEN operation, this
flag SHOULD NOT be set by the client in the arguments to
WANT_DELEGATION, and MUST be ignored by the server.
o OPEN4_SHARE_ACCESS_WANT_CANCEL o OPEN4_SHARE_ACCESS_WANT_CANCEL
o OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL o OPEN4_SHARE_ACCESS_WANT_SIGNAL_DELEG_WHEN_RESRC_AVAIL
o OPEN4_SHARE_ACCESS_WANT_PUSH_DELEG_WHEN_UNCONTENDED o OPEN4_SHARE_ACCESS_WANT_PUSH_DELEG_WHEN_UNCONTENDED
The handling of the above flags in WANT_DELEGATION is the same as in The handling of the above flags in WANT_DELEGATION is the same as in
OPEN. Information about the delegation and/or the promises the OPEN. Information about the delegation and/or the promises the
server is making regarding future callbacks are the same as those server is making regarding future callbacks are the same as those
described in the open_delegation4 structure. described in the open_delegation4 structure.
The successful results of WANT_DELEG are of type open_delegation4 The successful results of WANT_DELEGATION are of data type
which is the same type as the "delegation" field in the results of open_delegation4, which is the same data type as the "delegation"
the OPEN operation (see Section 18.16.3). The server constructs field in the results of the OPEN operation (see Section 18.16.3).
wdr_resok4 the same way it constructs OPEN's "delegation" with one The server constructs wdr_resok4 the same way it constructs OPEN's
difference: WANT_DELEGATION MUST NOT return a delegation type of "delegation" with one difference: WANT_DELEGATION MUST NOT return a
OPEN_DELEGATE_NONE. delegation type of OPEN_DELEGATE_NONE.
If (wda_want & OPEN4_SHARE_ACCESS_WANT_DELEG_MASK) is zero then the If ((wda_want & OPEN4_SHARE_ACCESS_WANT_DELEG_MASK) &
client is indicating no desire for a delegation and the server MUST ~OPEN4_SHARE_ACCESS_WANT_NO_DELEG) is zero, then the client is
return NFS4ERR_INVAL. indicating no explicit desire or non-desire for a delegation and the
server MUST return NFS4ERR_INVAL.
The client uses the OPEN4_SHARE_ACCESS_WANT_NO_DELEG flag in the The client uses the OPEN4_SHARE_ACCESS_WANT_CANCEL flag in the
WANT_DELEGATION operation to cancel a previously requested want for a WANT_DELEGATION operation to cancel a previously requested want for a
delegation. Note that if the server is in the process of sending the delegation. Note that if the server is in the process of sending the
delegation (via CB_PUSH_DELEG) at the time the client sends a delegation (via CB_PUSH_DELEG) at the time the client sends a
cancellation of the want, the delegation might still be pushed to the cancellation of the want, the delegation might still be pushed to the
client. client.
If WANT_DELEGATION fails to return a delegation, and the server If WANT_DELEGATION fails to return a delegation, and the server
returns NFS4_OK, the server MUST set the delegation type to returns NFS4_OK, the server MUST set the delegation type to
OPEN4_DELEGATE_NONE_EXT, and set od_whynone, as described in OPEN4_DELEGATE_NONE_EXT, and set od_whynone, as described in
Section 18.16. Write delegations are not available for file types Section 18.16. Write delegations are not available for file types
that are not writable. This includes file objects of types: NF4BLK, that are not writable. This includes file objects of types NF4BLK,
NF4CHR, NF4LNK, NF4SOCK, and NF4FIFO. If the client requests NF4CHR, NF4LNK, NF4SOCK, and NF4FIFO. If the client requests
OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG without OPEN4_SHARE_ACCESS_WANT_WRITE_DELEG without
OPEN4_SHARE_ACCESS_WANT_READ_DELEG on an object with one of the OPEN4_SHARE_ACCESS_WANT_READ_DELEG on an object with one of the
aforementioned file types, the server must set aforementioned file types, the server must set
WND4_WRITE_DELEG_NOT_SUPP_FTYPE. wdr_resok4.od_whynone.ond_why to WND4_WRITE_DELEG_NOT_SUPP_FTYPE.
18.49.4. IMPLEMENTATION 18.49.4. IMPLEMENTATION
A request for a conflicting delegation is not normally intended to A request for a conflicting delegation is not normally intended to
trigger the recall of the existing delegation. Servers may choose to trigger the recall of the existing delegation. Servers may choose to
treat some clients as having higher priority such that their wants treat some clients as having higher priority such that their wants
will trigger recall of an existing delegation, although that is will trigger recall of an existing delegation, although that is
expected to be an unusual situation. expected to be an unusual situation.
Servers will generally recall delegations assigned by WANT_DELEGATION Servers will generally recall delegations assigned by WANT_DELEGATION
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The DESTROY_CLIENTID operation destroys the client ID. If there are The DESTROY_CLIENTID operation destroys the client ID. If there are
sessions (both idle and non-idle), opens, locks, delegations, sessions (both idle and non-idle), opens, locks, delegations,
layouts, and/or wants (Section 18.49) associated with the unexpired layouts, and/or wants (Section 18.49) associated with the unexpired
lease of the client ID, the server MUST return NFS4ERR_CLIENTID_BUSY. lease of the client ID, the server MUST return NFS4ERR_CLIENTID_BUSY.
DESTROY_CLIENTID MAY be preceded with a SEQUENCE operation as long as DESTROY_CLIENTID MAY be preceded with a SEQUENCE operation as long as
the client ID derived from the session ID of SEQUENCE is not the same the client ID derived from the session ID of SEQUENCE is not the same
as the client ID to be destroyed. If the client IDs are the same, as the client ID to be destroyed. If the client IDs are the same,
then the server MUST return NFS4ERR_CLIENTID_BUSY. then the server MUST return NFS4ERR_CLIENTID_BUSY.
If DESTROY_CLIENTID is not prefixed by SEQUENCE, it MUST be the only If DESTROY_CLIENTID is not prefixed by SEQUENCE, it MUST be the only
operation in the COMPOUND request (otherwise the server MUST return operation in the COMPOUND request (otherwise, the server MUST return
NFS4ERR_NOT_ONLY_OP). If the operation is sent without a SEQUENCE NFS4ERR_NOT_ONLY_OP). If the operation is sent without a SEQUENCE
preceding it, a client that retransmits the request may receive an preceding it, a client that retransmits the request may receive an
error in response, because the original request might have been error in response, because the original request might have been
successfully executed. successfully executed.
18.50.4. IMPLEMENTATION 18.50.4. IMPLEMENTATION
DESTROY_CLIENTID allows a server to immediately reclaim the resources DESTROY_CLIENTID allows a server to immediately reclaim the resources
consumed by an unused client ID, and also to forget that it ever consumed by an unused client ID, and also to forget that it ever
generated the client ID. By forgetting it ever generated the client generated the client ID. By forgetting that it ever generated the
ID the server can safely reuse the client ID on a future EXCHANGE_ID client ID, the server can safely reuse the client ID on a future
operation. EXCHANGE_ID operation.
18.51. Operation 58: RECLAIM_COMPLETE - Indicates Reclaims Finished 18.51. Operation 58: RECLAIM_COMPLETE - Indicates Reclaims Finished
18.51.1. ARGUMENT 18.51.1. ARGUMENT
struct RECLAIM_COMPLETE4args { struct RECLAIM_COMPLETE4args {
/* /*
* If rca_one_fs TRUE, * If rca_one_fs TRUE,
* *
* CURRENT_FH: object in * CURRENT_FH: object in
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o When rca_one_fs is TRUE, a file system-specific RECLAIM_COMPLETE o When rca_one_fs is TRUE, a file system-specific RECLAIM_COMPLETE
is being done. This indicates that recovery of locks for a single is being done. This indicates that recovery of locks for a single
fs (the one designated by the current filehandle) due to a file fs (the one designated by the current filehandle) due to a file
system transition have been completed. Presence of a current system transition have been completed. Presence of a current
filehandle is only required when rca_one_fs is set to TRUE. filehandle is only required when rca_one_fs is set to TRUE.
Once a RECLAIM_COMPLETE is done, there can be no further reclaim Once a RECLAIM_COMPLETE is done, there can be no further reclaim
operations for locks whose scope is defined as having completed operations for locks whose scope is defined as having completed
recovery. Once the client sends RECLAIM_COMPLETE, the server will recovery. Once the client sends RECLAIM_COMPLETE, the server will
not allow the client to do subsequent reclaims of locking state for not allow the client to do subsequent reclaims of locking state for
that scope and if these are attempted, will return NFS4ERR_NO_GRACE. that scope and, if these are attempted, will return NFS4ERR_NO_GRACE.
Whenever a client establishes a new client ID and before it does the Whenever a client establishes a new client ID and before it does the
first non-reclaim operation that obtains a lock, it MUST send a first non-reclaim operation that obtains a lock, it MUST send a
RECLAIM_COMPLETE with rca_one_fs set to FALSE, even if there are no RECLAIM_COMPLETE with rca_one_fs set to FALSE, even if there are no
locks to reclaim. If non-reclaim locking operations are done before locks to reclaim. If non-reclaim locking operations are done before
the RECLAIM_COMPLETE, an NFS4ERR_GRACE error will be returned. the RECLAIM_COMPLETE, an NFS4ERR_GRACE error will be returned.
Similarly, when the client accesses a file system on a new server, Similarly, when the client accesses a file system on a new server,
before it sends the first non-reclaim operation that obtains a lock before it sends the first non-reclaim operation that obtains a lock
on this new server, it MUST send a RECLAIM_COMPLETE with rca_one_fs on this new server, it MUST send a RECLAIM_COMPLETE with rca_one_fs
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NFS4ERR_GRACE errors until the server is ready to terminate its grace NFS4ERR_GRACE errors until the server is ready to terminate its grace
period. period.
18.51.4. IMPLEMENTATION 18.51.4. IMPLEMENTATION
Servers will typically use the information as to when reclaim Servers will typically use the information as to when reclaim
activity is complete to reduce the length of the grace period. When activity is complete to reduce the length of the grace period. When
the server maintains in persistent storage a list of clients that the server maintains in persistent storage a list of clients that
might have had locks, it is in a position to use the fact that all might have had locks, it is in a position to use the fact that all
such clients have done a RECLAIM_COMPLETE to terminate the grace such clients have done a RECLAIM_COMPLETE to terminate the grace
period and begin normal operations (i.e. grant requests for new period and begin normal operations (i.e., grant requests for new
locks) sooner than it might otherwise. locks) sooner than it might otherwise.
Latency can be minimized by doing a RECLAIM_COMPLETE as part of the Latency can be minimized by doing a RECLAIM_COMPLETE as part of the
COMPOUND request in which the last lock-reclaiming operation is done. COMPOUND request in which the last lock-reclaiming operation is done.
When there are no reclaims to be done, RECLAIM_COMPLETE should be When there are no reclaims to be done, RECLAIM_COMPLETE should be
done immediately in order to allow the grace period to end as soon as done immediately in order to allow the grace period to end as soon as
possible. possible.
RECLAIM_COMPLETE should only be done once for each server instance, RECLAIM_COMPLETE should only be done once for each server instance or
or occasion of the transition of a file system. If it is done a occasion of the transition of a file system. If it is done a second
second time, the error NFS4ERR_COMPLETE_ALREADY will result. Note time, the error NFS4ERR_COMPLETE_ALREADY will result. Note that
that because of the session feature's retry protection, retries of because of the session feature's retry protection, retries of
COMPOUND requests containing RECLAIM_COMPLETE operation will not COMPOUND requests containing RECLAIM_COMPLETE operation will not
result in this error. result in this error.
When a RECLAIM_COMPLETE is done, the client effectively acknowledges When a RECLAIM_COMPLETE is sent, the client effectively acknowledges
any locks not yet reclaimed as lost. This allows the server to re- any locks not yet reclaimed as lost. This allows the server to re-
enable this client to subsequently recover locks. The server might enable the client to recover locks if the occurrence of edge
have disabled the client's ability to recover locks in order to conditions, as described in Section 8.4.3, had caused the server to
prevent the occurrence of the edge conditions described in disable the client from recovering locks. occurrence of edge
Section 8.4.3. conditions, as described in Section 8.4.3.
18.52. Operation 10044: ILLEGAL - Illegal operation 18.52. Operation 10044: ILLEGAL - Illegal Operation
18.52.1. ARGUMENTS 18.52.1. ARGUMENTS
void; void;
18.52.2. RESULTS 18.52.2. RESULTS
struct ILLEGAL4res { struct ILLEGAL4res {
nfsstat4 status; nfsstat4 status;
}; };
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callback procedures into a single RPC request. The main callback RPC callback procedures into a single RPC request. The main callback RPC
program has two main procedures: CB_NULL and CB_COMPOUND. All other program has two main procedures: CB_NULL and CB_COMPOUND. All other
operations use the CB_COMPOUND procedure as a wrapper. operations use the CB_COMPOUND procedure as a wrapper.
During the processing of the CB_COMPOUND procedure, the client may During the processing of the CB_COMPOUND procedure, the client may
find that it does not have the available resources to execute any or find that it does not have the available resources to execute any or
all of the operations within the CB_COMPOUND sequence. Refer to all of the operations within the CB_COMPOUND sequence. Refer to
Section 2.10.6.4 for details. Section 2.10.6.4 for details.
The minorversion field of the arguments MUST be the same as the The minorversion field of the arguments MUST be the same as the
minorversion of the COMPOUND procedure used to created the client ID minorversion of the COMPOUND procedure used to create the client ID
and session. For NFSv4.1, minorversion MUST be set to 1. and session. For NFSv4.1, minorversion MUST be set to 1.
Contained within the CB_COMPOUND results is a 'status' field. This Contained within the CB_COMPOUND results is a "status" field. This
status MUST be equal to the status of the last operation that was status MUST be equal to the status of the last operation that was
executed within the CB_COMPOUND procedure. Therefore, if an executed within the CB_COMPOUND procedure. Therefore, if an
operation incurred an error then the 'status' value will be the same operation incurred an error, then the "status" value will be the same
error value as is being returned for the operation that failed. error value as is being returned for the operation that failed.
The "tag" field is handled the same way as that of COMPOUND procedure The "tag" field is handled the same way as that of the COMPOUND
(see Section 16.2.3). procedure (see Section 16.2.3).
Illegal operation codes are handled in the same way as they are Illegal operation codes are handled in the same way as they are
handled for the COMPOUND procedure. handled for the COMPOUND procedure.
19.2.4. IMPLEMENTATION 19.2.4. IMPLEMENTATION
The CB_COMPOUND procedure is used to combine individual operations The CB_COMPOUND procedure is used to combine individual operations
into a single RPC request. The client interprets each of the into a single RPC request. The client interprets each of the
operations in turn. If an operation is executed by the client and operations in turn. If an operation is executed by the client and
the status of that operation is NFS4_OK, then the next operation in the status of that operation is NFS4_OK, then the next operation in
the CB_COMPOUND procedure is executed. The client continues this the CB_COMPOUND procedure is executed. The client continues this
process until there are no more operations to be executed or one of process until there are no more operations to be executed or one of
the operations has a status value other than NFS4_OK. the operations has a status value other than NFS4_OK.
19.2.5. ERRORS 19.2.5. ERRORS
CB_COMPOUND will of course return every error that each operation on CB_COMPOUND will of course return every error that each operation on
the backchannel can return (see Table 7). However if CB_COMPOUND the backchannel can return (see Table 7). However, if CB_COMPOUND
returns zero operations, obviously the error returned by COMPOUND has returns zero operations, obviously the error returned by COMPOUND has
nothing to do with an error returned by an operation. The list of nothing to do with an error returned by an operation. The list of
errors CB_COMPOUND will return if it processes zero operations errors CB_COMPOUND will return if it processes zero operations
include: includes:
CB_COMPOUND error returns CB_COMPOUND error returns
+------------------------------+------------------------------------+ +------------------------------+------------------------------------+
| Error | Notes | | Error | Notes |
+------------------------------+------------------------------------+ +------------------------------+------------------------------------+
| NFS4ERR_BADCHAR | The tag argument has a character | | NFS4ERR_BADCHAR | The tag argument has a character |
| | the replier does not support. | | | the replier does not support. |
| NFS4ERR_BADXDR | | | NFS4ERR_BADXDR | |
| NFS4ERR_DELAY | | | NFS4ERR_DELAY | |
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union CB_GETATTR4res switch (nfsstat4 status) { union CB_GETATTR4res switch (nfsstat4 status) {
case NFS4_OK: case NFS4_OK:
CB_GETATTR4resok resok4; CB_GETATTR4resok resok4;
default: default:
void; void;
}; };
20.1.3. DESCRIPTION 20.1.3. DESCRIPTION
The CB_GETATTR operation is used by the server to obtain the current The CB_GETATTR operation is used by the server to obtain the current
modified state of a file that has been write delegated. The modified state of a file that has been OPEN_DELEGATE_WRITE delegated.
attributes size and change are the only ones guaranteed to be The size and change attributes are the only ones guaranteed to be
serviced by the client. See Section 10.4.3 for a full description of serviced by the client. See Section 10.4.3 for a full description of
how the client and server are to interact with the use of CB_GETATTR. how the client and server are to interact with the use of CB_GETATTR.
If the filehandle specified is not one for which the client holds a If the filehandle specified is not one for which the client holds an
write delegation, an NFS4ERR_BADHANDLE error is returned. OPEN_DELEGATE_WRITE delegation, an NFS4ERR_BADHANDLE error is
returned.
20.1.4. IMPLEMENTATION 20.1.4. IMPLEMENTATION
The client returns attrmask bits and the associated attribute values The client returns attrmask bits and the associated attribute values
only for the change attribute, and attributes that it may change only for the change attribute, and attributes that it may change
(time_modify, and size). (time_modify, and size).
20.2. Operation 4: CB_RECALL - Recall a Delegation 20.2. Operation 4: CB_RECALL - Recall a Delegation
20.2.1. ARGUMENT 20.2.1. ARGUMENT
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struct CB_RECALL4res { struct CB_RECALL4res {
nfsstat4 status; nfsstat4 status;
}; };
20.2.3. DESCRIPTION 20.2.3. DESCRIPTION
The CB_RECALL operation is used to begin the process of recalling a The CB_RECALL operation is used to begin the process of recalling a
delegation and returning it to the server. delegation and returning it to the server.
The truncate flag is used to optimize recall for a file object which The truncate flag is used to optimize recall for a file object that
is a regular file and is about to be truncated to zero. When it is is a regular file and is about to be truncated to zero. When it is
TRUE, the client is freed of the obligation to propagate modified TRUE, the client is freed of the obligation to propagate modified
data for the file to the server, since this data is irrelevant. data for the file to the server, since this data is irrelevant.
If the handle specified is not one for which the client holds a If the handle specified is not one for which the client holds a
delegation, an NFS4ERR_BADHANDLE error is returned. delegation, an NFS4ERR_BADHANDLE error is returned.
If the stateid specified is not one corresponding to an open If the stateid specified is not one corresponding to an OPEN
delegation for the file specified by the filehandle, an delegation for the file specified by the filehandle, an
NFS4ERR_BAD_STATEID is returned. NFS4ERR_BAD_STATEID is returned.
20.2.4. IMPLEMENTATION 20.2.4. IMPLEMENTATION
The client SHOULD reply to the callback immediately. Replying does The client SHOULD reply to the callback immediately. Replying does
not complete the recall except when the value of the reply's status not complete the recall except when the value of the reply's status
field is neither NFS4ERR_DELAY nor NFS4_OK. The recall is not field is neither NFS4ERR_DELAY nor NFS4_OK. The recall is not
complete until the delegation is returned using a DELEGRETURN complete until the delegation is returned using a DELEGRETURN
operation. operation.
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struct CB_LAYOUTRECALL4res { struct CB_LAYOUTRECALL4res {
nfsstat4 clorr_status; nfsstat4 clorr_status;
}; };
20.3.3. DESCRIPTION 20.3.3. DESCRIPTION
The CB_LAYOUTRECALL operation is used by the server to recall layouts The CB_LAYOUTRECALL operation is used by the server to recall layouts
from the client; as a result, the client will begin the process of from the client; as a result, the client will begin the process of
returning layouts via LAYOUTRETURN. The CB_LAYOUTRECALL operation returning layouts via LAYOUTRETURN. The CB_LAYOUTRECALL operation
specifies one of three forms of recall processing with the value of specifies one of three forms of recall processing with the value of
layoutrecall_type4. The recall is either for a specific layout (by layoutrecall_type4. The recall is for one of the following: a
file), for an entire file system (FSID), or for all file systems specific layout of a specific file (LAYOUTRECALL4_FILE), an entire
(ALL). file system ID (LAYOUTRECALL4_FSID), or all file systems
(LAYOUTRECALL4_ALL).
The behavior of the operation varies based on the value of the The behavior of the operation varies based on the value of the
layoutrecall_type4. The value and behaviors are: layoutrecall_type4. The value and behaviors are:
LAYOUTRECALL4_FILE LAYOUTRECALL4_FILE
For a layout to match the recall request, the values of the For a layout to match the recall request, the values of the
following fields must match those of the layout: clora_type, following fields must match those of the layout: clora_type,
clora_iomode, lor_fh, and the byte range specified by lor_offset clora_iomode, lor_fh, and the byte-range specified by lor_offset
and lor_length. The clora_iomode field may have a special value and lor_length. The clora_iomode field may have a special value
of LAYOUTIOMODE4_ANY. The special value LAYOUTIOMODE4_ANY will of LAYOUTIOMODE4_ANY. The special value LAYOUTIOMODE4_ANY will
match any iomode originally returned in a layout; therefore it match any iomode originally returned in a layout; therefore, it
acts as a wild card. The other special value used is for acts as a wild card. The other special value used is for
lor_length. If lor_length has a value of NFS4_UINT64_MAX, the lor_length. If lor_length has a value of NFS4_UINT64_MAX, the
lor_length field means the maximum possible file size. If a lor_length field means the maximum possible file size. If a
matching layout is found, it MUST be returned using the matching layout is found, it MUST be returned using the
LAYOUTRETURN operation (see Section 18.44). An example of the LAYOUTRETURN operation (see Section 18.44). An example of the
field's special value use is if clora_iomode is LAYOUTIOMODE4_ANY, field's special value use is if clora_iomode is LAYOUTIOMODE4_ANY,
lor_offset is zero, and lor_length is NFS4_UINT64_MAX, then the lor_offset is zero, and lor_length is NFS4_UINT64_MAX, then the
entire layout is to be returned. entire layout is to be returned.
The NFS4ERR_NOMATCHING_LAYOUT error is only returned when the The NFS4ERR_NOMATCHING_LAYOUT error is only returned when the
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mappings. mappings.
In processing the layout recall request, the client also varies its In processing the layout recall request, the client also varies its
behavior based on the value of the clora_changed field. This field behavior based on the value of the clora_changed field. This field
is used by the server to provide additional context for the reason is used by the server to provide additional context for the reason
why the layout is being recalled. A FALSE value for clora_changed why the layout is being recalled. A FALSE value for clora_changed
indicates that no change in the layout is expected and the client may indicates that no change in the layout is expected and the client may
write modified data to the storage devices involved; this must be write modified data to the storage devices involved; this must be
done prior to returning the layout via LAYOUTRETURN. A TRUE value done prior to returning the layout via LAYOUTRETURN. A TRUE value
for clora_changed indicates that the server is changing the layout. for clora_changed indicates that the server is changing the layout.
Examples of layout changes and reasons for a TRUE indication are: the Examples of layout changes and reasons for a TRUE indication are the
metadata server is restriping the file or a permanent error has following: the metadata server is restriping the file or a permanent
occurred on a storage device and the metadata server would like to error has occurred on a storage device and the metadata server would
provide a new layout for the file. Therefore, a clora_changed value like to provide a new layout for the file. Therefore, a
of TRUE indicates some level of change for the layout and the client clora_changed value of TRUE indicates some level of change for the
SHOULD NOT write and commit modified data to the storage devices. In layout and the client SHOULD NOT write and commit modified data to
this case, the client writes and commits data through the metadata the storage devices. In this case, the client writes and commits
server. data through the metadata server.
See Section 12.5.3 for a description of how the lor_stateid field in See Section 12.5.3 for a description of how the lor_stateid field in
the arguments is to be constructed. Note that the "seqid" field of the arguments is to be constructed. Note that the "seqid" field of
lor_stateid MUST NOT be zero. See Section 8.2, Section 12.5.3, and lor_stateid MUST NOT be zero. See Sections 8.2, 12.5.3, and 12.5.5.2
Section 12.5.5.2 for a further discussion and requirements. for a further discussion and requirements.
20.3.4. IMPLEMENTATION 20.3.4. IMPLEMENTATION
The client's processing for CB_LAYOUTRECALL is similar to CB_RECALL The client's processing for CB_LAYOUTRECALL is similar to CB_RECALL
(recall of file delegations) in that the client responds to the (recall of file delegations) in that the client responds to the
request before actually returning layouts via the LAYOUTRETURN request before actually returning layouts via the LAYOUTRETURN
operation. While the client responds to the CB_LAYOUTRECALL operation. While the client responds to the CB_LAYOUTRECALL
immediately, the operation is not considered complete (i.e. immediately, the operation is not considered complete (i.e.,
considered pending) until all affected layouts are returned to the considered pending) until all affected layouts are returned to the
server via the LAYOUTRETURN operation. server via the LAYOUTRETURN operation.
Before returning the layout to the server via LAYOUTRETURN, the Before returning the layout to the server via LAYOUTRETURN, the
client should wait for the response from in-process or in-flight client should wait for the response from in-process or in-flight
READ, WRITE, or COMMIT operations that use the recalled layout. READ, WRITE, or COMMIT operations that use the recalled layout.
If the client is holding modified data which is affected by a If the client is holding modified data that is affected by a recalled
recalled layout, the client has various options for writing the data layout, the client has various options for writing the data to the
to the server. As always, the client may write the data through the server. As always, the client may write the data through the
metadata server. In fact, the client may not have a choice other metadata server. In fact, the client may not have a choice other
than writing to the metadata server when the clora_changed argument than writing to the metadata server when the clora_changed argument
is TRUE and a new layout is unavailable from the server. However, is TRUE and a new layout is unavailable from the server. However,
the client may be able to write the modified data to the storage the client may be able to write the modified data to the storage
device if the clora_changed argument is FALSE; this needs to be done device if the clora_changed argument is FALSE; this needs to be done
before returning the layout via LAYOUTRETURN. If the client were to before returning the layout via LAYOUTRETURN. If the client were to
obtain a new layout covering the modified data's range, then writing obtain a new layout covering the modified data's byte-range, then
to the storage devices is an available alternative. Note that before writing to the storage devices is an available alternative. Note
obtaining a new layout, the client must first return the original that before obtaining a new layout, the client must first return the
layout. original layout.
In the case of modified data being written while the layout is held, In the case of modified data being written while the layout is held,
the client must use LAYOUTCOMMIT operations at the appropriate time; the client must use LAYOUTCOMMIT operations at the appropriate time;
as required LAYOUTCOMMIT must be done before the LAYOUTRETURN. If a as required LAYOUTCOMMIT must be done before the LAYOUTRETURN. If a
large amount of modified data is outstanding, the client may send large amount of modified data is outstanding, the client may send
LAYOUTRETURNs for portions of the recalled layout; this allows the LAYOUTRETURNs for portions of the recalled layout; this allows the
server to monitor the client's progress and adherence to the original server to monitor the client's progress and adherence to the original
recall request. However, the last LAYOUTRETURN in a sequence of recall request. However, the last LAYOUTRETURN in a sequence of
returns, MUST specify the full range being recalled (see returns MUST specify the full range being recalled (see
Section 12.5.5.1 for details). Section 12.5.5.1 for details).
If a server needs to delete a device ID, and there are layouts If a server needs to delete a device ID and there are layouts
referring to the device ID, CB_LAYOUTRECALL MUST be invoked to cause referring to the device ID, CB_LAYOUTRECALL MUST be invoked to cause
the client to return all layouts referring to device ID before the the client to return all layouts referring to the device ID before
server can delete the device ID. If the client does not return the the server can delete the device ID. If the client does not return
affected layouts, the server MAY revoke the layouts. the affected layouts, the server MAY revoke the layouts.
20.4. Operation 6: CB_NOTIFY - Notify Client of Directory Changes 20.4. Operation 6: CB_NOTIFY - Notify Client of Directory Changes
20.4.1. ARGUMENT 20.4.1. ARGUMENT
/* /*
* Directory notification types. * Directory notification types.
*/ */
enum notify_type4 { enum notify_type4 {
NOTIFY4_CHANGE_CHILD_ATTRS = 0, NOTIFY4_CHANGE_CHILD_ATTRS = 0,
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over the backchannel. The notification is sent once the original over the backchannel. The notification is sent once the original
request has been processed on the server. The server will send an request has been processed on the server. The server will send an
array of notifications for changes that might have occurred in the array of notifications for changes that might have occurred in the
directory. The notifications are sent as list of pairs of bitmaps directory. The notifications are sent as list of pairs of bitmaps
and values. See Section 3.3.7 for a description of how NFSv4.1 and values. See Section 3.3.7 for a description of how NFSv4.1
bitmaps work. bitmaps work.
If the server has more notifications than can fit in the CB_COMPOUND If the server has more notifications than can fit in the CB_COMPOUND
request, it SHOULD send a sequence of serial CB_COMPOUND requests so request, it SHOULD send a sequence of serial CB_COMPOUND requests so
that the client's view of the directory does not become confused. that the client's view of the directory does not become confused.
E.g. If the server indicates a file named "foo" is added, and that For example, if the server indicates that a file named "foo" is added
the file "foo" is removed, the order in which the client receives and that the file "foo" is removed, the order in which the client
these notifications needs to be the same as the order in which receives these notifications needs to be the same as the order in
corresponding operations occurred on the server. which the corresponding operations occurred on the server.
If the client holding the delegation makes any changes in the If the client holding the delegation makes any changes in the
directory that cause files or sub directories to be added or removed, directory that cause files or sub-directories to be added or removed,
the server will notify that client of the resulting change(s). If the server will notify that client of the resulting change(s). If
the client holding the delegation is making attribute or cookie the client holding the delegation is making attribute or cookie
verifier changes only, the server does not need to send notifications verifier changes only, the server does not need to send notifications
to that client. The server will send the following information for to that client. The server will send the following information for
each operation: each operation:
NOTIFY4_ADD_ENTRY NOTIFY4_ADD_ENTRY
The server will send information about the new directory entry The server will send information about the new directory entry
being created along with the cookie for that entry. The entry being created along with the cookie for that entry. The entry
information (data type notify_add4) includes the component name of information (data type notify_add4) includes the component name of
the entry and attributes. The server will send this type of entry the entry and attributes. The server will send this type of entry
when a file is actually being created, when an entry is being when a file is actually being created, when an entry is being
added to a directory as a result of a rename across directories added to a directory as a result of a rename across directories
(see below), and when a hard link is being created to an existing (see below), and when a hard link is being created to an existing
file. If this entry is added to the end of the directory, the file. If this entry is added to the end of the directory, the
server will set the nad_last_entry flag to TRUE. If the file is server will set the nad_last_entry flag to TRUE. If the file is
added such that there is at least one entry before it, the server added such that there is at least one entry before it, the server
will also return the previous entry information (nad_prev_entry, a will also return the previous entry information (nad_prev_entry, a
variable length array of up to one element. If the array is of variable-length array of up to one element. If the array is of
zero length, there is no previous entry), along with its cookie. zero length, there is no previous entry), along with its cookie.
This is to help clients find the right location in their file name This is to help clients find the right location in their file name
caches and directory caches where this entry should be cached. If caches and directory caches where this entry should be cached. If
the new entry's cookie is available, it will be in the the new entry's cookie is available, it will be in the
nad_new_entry_cookie (another variable length array of up to one nad_new_entry_cookie (another variable-length array of up to one
element) field. If the addition of the entry causes another entry element) field. If the addition of the entry causes another entry
to be deleted (which can only happen in the rename case) to be deleted (which can only happen in the rename case)
atomically with the addition, then information on this entry is atomically with the addition, then information on this entry is
reported in nad_old_entry. reported in nad_old_entry.
NOTIFY4_REMOVE_ENTRY NOTIFY4_REMOVE_ENTRY
The server will send information about the directory entry being The server will send information about the directory entry being
deleted. The server will also send the cookie value for the deleted. The server will also send the cookie value for the
deleted entry so that clients can get to the cached information deleted entry so that clients can get to the cached information
for this entry. for this entry.
NOTIFY4_RENAME_ENTRY NOTIFY4_RENAME_ENTRY
The server will send information about both the old entry and the The server will send information about both the old entry and the
new entry. This includes name and attributes for each entry. In new entry. This includes the name and attributes for each entry.
addition, if the rename causes the deletion of an entry (i.e. the In addition, if the rename causes the deletion of an entry (i.e.,
case of a file renamed over) then this is reported in the case of a file renamed over), then this is reported in
nrn_new_new_entry.nad_old_entry. This notification is only sent nrn_new_new_entry.nad_old_entry. This notification is only sent
if both entries are in the same directory. If the rename is if both entries are in the same directory. If the rename is
across directories, the server will send a remove notification to across directories, the server will send a remove notification to
one directory and an add notification to the other directory, one directory and an add notification to the other directory,
assuming both have a directory delegation. assuming both have a directory delegation.
NOTIFY4_CHANGE_CHILD_ATTRS/NOTIFY4_CHANGE_DIR_ATTRS NOTIFY4_CHANGE_CHILD_ATTRS/NOTIFY4_CHANGE_DIR_ATTRS
The client will use the attribute mask to inform the server of The client will use the attribute mask to inform the server of
attributes for which it wants to receive notifications. This attributes for which it wants to receive notifications. This
change notification can be requested for both changes to the change notification can be requested for changes to the attributes
attributes of the directory as well as changes to any file's of the directory as well as changes to any file's attributes in
attributes in the directory by using two separate attribute masks. the directory by using two separate attribute masks. The client
The client cannot ask for change attribute notification for a cannot ask for change attribute notification for a specific file.
specific file. One attribute mask covers all the files in the One attribute mask covers all the files in the directory. Upon
directory. Upon any attribute change, the server will send back any attribute change, the server will send back the values of
the values of changed attributes. Notifications might not make changed attributes. Notifications might not make sense for some
sense for some file system wide attributes and it is up to the file system-wide attributes, and it is up to the server to decide
server to decide which subset it wants to support. The client can which subset it wants to support. The client can negotiate the
negotiate the frequency of attribute notifications by letting the frequency of attribute notifications by letting the server know
server know how often it wants to be notified of an attribute how often it wants to be notified of an attribute change. The
change. The server will return supported notification frequencies server will return supported notification frequencies or an
or an indication that no notification is permitted for directory indication that no notification is permitted for directory or
or child attributes by setting the dir_notif_delay and child attributes by setting the dir_notif_delay and
dir_entry_notif_delay attributes respectively. dir_entry_notif_delay attributes, respectively.
NOTIFY4_CHANGE_COOKIE_VERIFIER NOTIFY4_CHANGE_COOKIE_VERIFIER
If the cookie verifier changes while a client is holding a If the cookie verifier changes while a client is holding a
delegation, the server will notify the client so that it can delegation, the server will notify the client so that it can
invalidate its cookies and re-send a READDIR to get the new set of invalidate its cookies and re-send a READDIR to get the new set of
cookies. cookies.
20.5. Operation 7: CB_PUSH_DELEG - Offer Previously Requested 20.5. Operation 7: CB_PUSH_DELEG - Offer Previously Requested
Delegation to Client Delegation to Client
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}; };
20.5.2. RESULT 20.5.2. RESULT
struct CB_PUSH_DELEG4res { struct CB_PUSH_DELEG4res {
nfsstat4 cpdr_status; nfsstat4 cpdr_status;
}; };
20.5.3. DESCRIPTION 20.5.3. DESCRIPTION
CB_PUSH_DELEG is used by the server to both signal to the client that CB_PUSH_DELEG is used by the server both to signal to the client that
the delegation it wants (previously indicated via a want established the delegation it wants (previously indicated via a want established
from an OPEN or WANT_DELEGATION operation) is available and to from an OPEN or WANT_DELEGATION operation) is available and to
simultaneously offer the delegation to the client. The client has simultaneously offer the delegation to the client. The client has
the choice of accepting the delegation by returning NFS4_OK to the the choice of accepting the delegation by returning NFS4_OK to the
server, delaying the decision to accept the offered delegation by server, delaying the decision to accept the offered delegation by
returning NFS4ERR_DELAY or permanently rejecting the offer of the returning NFS4ERR_DELAY, or permanently rejecting the offer of the
delegation by returning NFS4ERR_REJECT_DELEG. When a delegation is delegation by returning NFS4ERR_REJECT_DELEG. When a delegation is
rejected in this fashion, the want previously established is rejected in this fashion, the want previously established is
permanently deleted and the delegation is subject to acquisition by permanently deleted and the delegation is subject to acquisition by
another client. another client.
20.5.4. IMPLEMENTATION 20.5.4. IMPLEMENTATION
If the client does return NFS4ERR_DELAY and there is a conflicting If the client does return NFS4ERR_DELAY and there is a conflicting
delegation request, the server MAY process it at the expense of the delegation request, the server MAY process it at the expense of the
client that returned NFS4ERR_DELAY. The client's want will not be client that returned NFS4ERR_DELAY. The client's want will not be
cancelled, but MAY processed behind other delegation requests or cancelled, but MAY be processed behind other delegation requests or
registered wants. registered wants.
When a client returns a status other than NFS4_OK, NFS4ERR_DELAY, or When a client returns a status other than NFS4_OK, NFS4ERR_DELAY, or
NFS4ERR_REJECT_DELAY, the want remains pending, although servers may NFS4ERR_REJECT_DELAY, the want remains pending, although servers may
decide to cancel the want by sending a CB_WANTS_CANCELLED. decide to cancel the want by sending a CB_WANTS_CANCELLED.
20.6. Operation 8: CB_RECALL_ANY - Keep Any N Recallable Objects 20.6. Operation 8: CB_RECALL_ANY - Keep Any N Recallable Objects
20.6.1. ARGUMENT 20.6.1. ARGUMENT
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20.6.2. RESULT 20.6.2. RESULT
struct CB_RECALL_ANY4res { struct CB_RECALL_ANY4res {
nfsstat4 crar_status; nfsstat4 crar_status;
}; };
20.6.3. DESCRIPTION 20.6.3. DESCRIPTION
The server may decide that it cannot hold all of the state for The server may decide that it cannot hold all of the state for
recallable objects, such as delegations and layouts, without running recallable objects, such as delegations and layouts, without running
out of resources. In such a case, it is free to recall individual out of resources. In such a case, while not optimal, the server is
objects to reduce the load but this would be far from optimal. free to recall individual objects to reduce the load.
Because the general purpose of such recallable objects as delegations Because the general purpose of such recallable objects as delegations
is to eliminate client interaction with the server, the server cannot is to eliminate client interaction with the server, the server cannot
interpret lack of recent use as indicating that the object is no interpret lack of recent use as indicating that the object is no
longer useful. The absence of visible use may be the result of a longer useful. The absence of visible use is consistent with a
large number of potential operations eliminated. In the case of delegation keeping potential operations from being sent to the
layouts, the layout will be used explicitly but the metadata server server. In the case of layouts, while it is true that the usefulness
does not have direct knowledge of such use. of a layout is indicated by the use of the layout when storage
devices receive I/O requests, because there is no mandate that a
storage device indicate to the metadata server any past or present
use of a layout, the metadata server is not likely to know which
layouts are good candidates to recall in response to low resources.
In order to implement an effective reclaim scheme for such objects, In order to implement an effective reclaim scheme for such objects,
the server's knowledge of available resources must be used to the server's knowledge of available resources must be used to
determine when objects must be recalled with the clients selecting determine when objects must be recalled with the clients selecting
the actual objects to be returned. the actual objects to be returned.
Server implementations may differ in their resource allocation Server implementations may differ in their resource allocation
requirements. For example, one server may share resources among all requirements. For example, one server may share resources among all
classes of recallable objects whereas another may use separate classes of recallable objects, whereas another may use separate
resource pools for layouts and for delegations, or further separate resource pools for layouts and for delegations, or further separate
resources by types of delegations. resources by types of delegations.
When a given resource pool is over-utilized, the server can send a When a given resource pool is over-utilized, the server can send a
CB_RECALL_ANY to clients holding recallable objects of the types CB_RECALL_ANY to clients holding recallable objects of the types
involved, allowing it to keep a certain number of such objects and involved, allowing it to keep a certain number of such objects and
return any excess. A mask specifies which types of objects are to be return any excess. A mask specifies which types of objects are to be
limited. The client chooses, based on its own knowledge of current limited. The client chooses, based on its own knowledge of current
usefulness, which of the objects in that class should be returned. usefulness, which of the objects in that class should be returned.
A number of bits are defined. For some of these, ranges are defined A number of bits are defined. For some of these, ranges are defined
and it is up to the definition of the storage protocol to specify how and it is up to the definition of the storage protocol to specify how
these are to be used. There are ranges reserved for object-based these are to be used. There are ranges reserved for object-based
storage protocols and for other experimental storage protocols. An storage protocols and for other experimental storage protocols. An
RFC defining such a storage protocol needs to specify how particular RFC defining such a storage protocol needs to specify how particular
bits within its range are to be used. For example, it may specify a bits within its range are to be used. For example, it may specify a
mapping between attributes of the layout (read vs. write, size of mapping between attributes of the layout (read vs. write, size of
area) and the bit to be used or it may define a field in the layout area) and the bit to be used, or it may define a field in the layout
where the associated bit position is made available by the server to where the associated bit position is made available by the server to
the client. the client.
RCA4_TYPE_MASK_RDATA_DLG RCA4_TYPE_MASK_RDATA_DLG
The client is to return read delegations on non-directory file The client is to return OPEN_DELEGATE_READ delegations on non-
objects. directory file objects.
RCA4_TYPE_MASK_WDATA_DLG RCA4_TYPE_MASK_WDATA_DLG
The client is to return write delegations on regular file objects. The client is to return OPEN_DELEGATE_WRITE delegations on regular
file objects.
RCA4_TYPE_MASK_DIR_DLG RCA4_TYPE_MASK_DIR_DLG
The client is to return directory delegations. The client is to return directory delegations.
RCA4_TYPE_MASK_FILE_LAYOUT RCA4_TYPE_MASK_FILE_LAYOUT
The client is to return layouts of type LAYOUT4_NFSV4_1_FILES. The client is to return layouts of type LAYOUT4_NFSV4_1_FILES.
RCA4_TYPE_MASK_BLK_LAYOUT RCA4_TYPE_MASK_BLK_LAYOUT
See [41] for a description. See [41] for a description.
RCA4_TYPE_MASK_OBJ_LAYOUT_MIN to RCA4_TYPE_MASK_OBJ_LAYOUT_MAX RCA4_TYPE_MASK_OBJ_LAYOUT_MIN to RCA4_TYPE_MASK_OBJ_LAYOUT_MAX
See [40] for a description. See [40] for a description.
RCA4_TYPE_MASK_OTHER_LAYOUT_MIN to RCA4_TYPE_MASK_OTHER_LAYOUT_MAX RCA4_TYPE_MASK_OTHER_LAYOUT_MIN to RCA4_TYPE_MASK_OTHER_LAYOUT_MAX
This range is reserved for telling the client to recall layouts of This range is reserved for telling the client to recall layouts of
experimental or site specific layout types (see Section 3.3.13). experimental or site-specific layout types (see Section 3.3.13).
When a bit is set in the type mask that corresponds to an undefined When a bit is set in the type mask that corresponds to an undefined
type of recallable object, NFS4ERR_INVAL MUST be returned. When a type of recallable object, NFS4ERR_INVAL MUST be returned. When a
bit is set that corresponds to a defined type of object, but the bit is set that corresponds to a defined type of object but the
client does not support an object of the type, NFS4ERR_INVAL MUST NOT client does not support an object of the type, NFS4ERR_INVAL MUST NOT
be returned. Future minor versions of NFSv4 may expand the set of be returned. Future minor versions of NFSv4 may expand the set of
valid type mask bits. valid type mask bits.
CB_RECALL_ANY specifies a count of objects that the client may keep CB_RECALL_ANY specifies a count of objects that the client may keep
as opposed to a count that the client must return. This is to avoid as opposed to a count that the client must return. This is to avoid
potential race between a CB_RECALL_ANY that had a count of objects to a potential race between a CB_RECALL_ANY that had a count of objects
free with a set of client-originated operations to return layouts or to free with a set of client-originated operations to return layouts
delegations. As a result of the race, the client and server would or delegations. As a result of the race, the client and server would
have differing ideas as to how many objects to return. Hence the have differing ideas as to how many objects to return. Hence, the
client could mistakenly free too many. client could mistakenly free too many.
If resource demands prompt it, the server may send another If resource demands prompt it, the server may send another
CB_RECALL_ANY with a lower count, even it has not yet received an CB_RECALL_ANY with a lower count, even if it has not yet received an
acknowledgement from the client for a previous CB_RECALL_ANY with the acknowledgment from the client for a previous CB_RECALL_ANY with the
same type mask. Although the possibility exists that these will be same type mask. Although the possibility exists that these will be
received by the client in a order different from the order in which received by the client in an order different from the order in which
they were sent, any such permutation of the callback stream is they were sent, any such permutation of the callback stream is
harmless. It is the job of the client to bring down the size of the harmless. It is the job of the client to bring down the size of the
recallable object set in line with each CB_RECALL_ANY received and recallable object set in line with each CB_RECALL_ANY received, and
until that obligation is met it cannot be cancelled or modified by until that obligation is met, it cannot be cancelled or modified by
any subsequent CB_RECALL_ANY for the same type mask. Thus if the any subsequent CB_RECALL_ANY for the same type mask. Thus, if the
server sends two CB_RECALL_ANY's, the effect will be the same as if server sends two CB_RECALL_ANYs, the effect will be the same as if
the lower count was sent, whatever the order of recall receipt. Note the lower count was sent, whatever the order of recall receipt. Note
that this means that a server may not cancel the effect of a that this means that a server may not cancel the effect of a
CB_RECALL_ANY by sending another recall with a higher count. When a CB_RECALL_ANY by sending another recall with a higher count. When a
CB_RECALL_ANY is received and the count is already within the limit CB_RECALL_ANY is received and the count is already within the limit
set or is above a limit that the client is working to get down to, set or is above a limit that the client is working to get down to,
that callback has no effect. that callback has no effect.
Servers are generally free not to give out recallable objects when Servers are generally free to deny recallable objects when
insufficient resources are available. Note that the effect of such a insufficient resources are available. Note that the effect of such a
policy is implicitly to give precedence to existing objects relative policy is implicitly to give precedence to existing objects relative
to requested ones, with the result that resources might not be to requested ones, with the result that resources might not be
optimally used. To prevent this, servers are well advised to make optimally used. To prevent this, servers are well advised to make
the point at which they start sending CB_RECALL_ANY callbacks the point at which they start sending CB_RECALL_ANY callbacks
somewhat below that at which they cease to give out new delegations somewhat below that at which they cease to give out new delegations
and layouts. This allows the client to purge its less-used objects and layouts. This allows the client to purge its less-used objects
whenever appropriate and so continue to have its subsequent requests whenever appropriate and so continue to have its subsequent requests
given new resources freed up by object returns. given new resources freed up by object returns.
20.6.4. IMPLEMENTATION 20.6.4. IMPLEMENTATION
The client can choose to return any type of object specified by the The client can choose to return any type of object specified by the
mask. If a server wishes to limit use of objects of a specific type, mask. If a server wishes to limit the use of objects of a specific
it should only specify that type in the mask sent. The client may type, it should only specify that type in the mask it sends. Should
not return requested objects and it is up to the server to handle the client fail to return requested objects, it is up to the server
this situation, typically by doing specific recalls to properly limit to handle this situation, typically by sending specific recalls
resource usage. The server should give the client enough time to (i.e., sending CB_RECALL operations) to properly limit resource
return objects before proceeding to specific recalls. This time usage. The server should give the client enough time to return
should not be less than the lease period. objects before proceeding to specific recalls. This time should not
be less than the lease period.
20.7. Operation 9: CB_RECALLABLE_OBJ_AVAIL - Signal Resources for 20.7. Operation 9: CB_RECALLABLE_OBJ_AVAIL - Signal Resources for
Recallable Objects Recallable Objects
20.7.1. ARGUMENT 20.7.1. ARGUMENT
typedef CB_RECALL_ANY4args CB_RECALLABLE_OBJ_AVAIL4args; typedef CB_RECALL_ANY4args CB_RECALLABLE_OBJ_AVAIL4args;
20.7.2. RESULT 20.7.2. RESULT
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can have runs the risk of having objects recalled. can have runs the risk of having objects recalled.
The server is not obligated to reserve the difference between the The server is not obligated to reserve the difference between the
number of the objects the client currently has and the value of number of the objects the client currently has and the value of
craa_objects_to_keep, nor does delaying the reply to craa_objects_to_keep, nor does delaying the reply to
CB_RECALLABLE_OBJ_AVAIL prevent the server from using the resources CB_RECALLABLE_OBJ_AVAIL prevent the server from using the resources
of the recallable objects for another purpose. Indeed, if a client of the recallable objects for another purpose. Indeed, if a client
responds slowly to CB_RECALLABLE_OBJ_AVAIL, the server might responds slowly to CB_RECALLABLE_OBJ_AVAIL, the server might
interpret the client as having reduced capability to manage interpret the client as having reduced capability to manage
recallable objects, and so cancel or reduce any reservation it is recallable objects, and so cancel or reduce any reservation it is
maintaining on behalf of the client. Thus if the client desires to maintaining on behalf of the client. Thus, if the client desires to
acquire more recallable objects, it needs to reply quickly to acquire more recallable objects, it needs to reply quickly to
CB_RECALLABLE_OBJ_AVAIL, and then send the appropriate operations to CB_RECALLABLE_OBJ_AVAIL, and then send the appropriate operations to
acquire recallable objects. acquire recallable objects.
20.8. Operation 10: CB_RECALL_SLOT - Change Flow Control Limits 20.8. Operation 10: CB_RECALL_SLOT - Change Flow Control Limits
20.8.1. ARGUMENT 20.8.1. ARGUMENT
struct CB_RECALL_SLOT4args { struct CB_RECALL_SLOT4args {
slotid4 rsa_target_highest_slotid; slotid4 rsa_target_highest_slotid;
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20.8.2. RESULT 20.8.2. RESULT
struct CB_RECALL_SLOT4res { struct CB_RECALL_SLOT4res {
nfsstat4 rsr_status; nfsstat4 rsr_status;
}; };
20.8.3. DESCRIPTION 20.8.3. DESCRIPTION
The CB_RECALL_SLOT operation requests the client to return session The CB_RECALL_SLOT operation requests the client to return session
slots, and if applicable, transport credits (e.g. RDMA credits for slots, and if applicable, transport credits (e.g., RDMA credits for
connections associated with the operations channel) of the session's connections associated with the operations channel) of the session's
fore channel. CB_RECALL_SLOT specifies rsa_target_highest_slotid, fore channel. CB_RECALL_SLOT specifies rsa_target_highest_slotid,
the value of the target highest slot ID the server wants for the the value of the target highest slot ID the server wants for the
session. The client MUST then progress toward reducing the session's session. The client MUST then progress toward reducing the session's
highest slot ID to the target value. highest slot ID to the target value.
If the session has only non-RDMA connections associated with its If the session has only non-RDMA connections associated with its
operations channel, then the client need only wait for all operations channel, then the client need only wait for all
outstanding requests with a slot ID > rsa_target_highest_slotid to outstanding requests with a slot ID > rsa_target_highest_slotid to
complete, then send a single COMPOUND consisting of a single SEQUENCE complete, then send a single COMPOUND consisting of a single SEQUENCE
operation, with the sa_highestslot field set to operation, with the sa_highestslot field set to
rsa_target_highest_slotid. If there are RDMA-based connections rsa_target_highest_slotid. If there are RDMA-based connections
associated with operation channel, then the client needs to also send associated with operation channel, then the client needs to also send
enough zero-length RDMA Sends to take the total RDMA credit count to enough zero-length "RDMA Send" messages to take the total RDMA credit
rsa_target_highest_slotid + 1 or below. count to rsa_target_highest_slotid + 1 or below.
20.8.4. IMPLEMENTATION 20.8.4. IMPLEMENTATION
If the client fails to reduce highest slot it has on the fore channel If the client fails to reduce highest slot it has on the fore channel
to what the server requests, the server can force the issue by to what the server requests, the server can force the issue by
asserting flow control on the receive side of all connections bound asserting flow control on the receive side of all connections bound
to the fore channel, and then finish servicing all outstanding to the fore channel, and then finish servicing all outstanding
requests that are in slots greater than rsa_target_highest_slotid. requests that are in slots greater than rsa_target_highest_slotid.
Once that is done, the server can then open the flow control, and any Once that is done, the server can then open the flow control, and any
time the client sends a new request on a slot greater than time the client sends a new request on a slot greater than
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void; void;
}; };
20.9.3. DESCRIPTION 20.9.3. DESCRIPTION
The CB_SEQUENCE operation is used to manage operational accounting The CB_SEQUENCE operation is used to manage operational accounting
for the backchannel of the session on which a request is sent. The for the backchannel of the session on which a request is sent. The
contents include the session ID to which this request belongs, the contents include the session ID to which this request belongs, the
slot ID and sequence ID used by the server to implement session slot ID and sequence ID used by the server to implement session
request control and exactly once semantics, and exchanged slot ID request control and exactly once semantics, and exchanged slot ID
maxima which are used to adjust the size of the reply cache. This maxima that are used to adjust the size of the reply cache. In each
operation will appear once as the first operation in each CB_COMPOUND CB_COMPOUND request, CB_SEQUENCE MUST appear once and MUST be the
request or a protocol error MUST result. See Section 18.46.3 for a first operation. The error NFS4ERR_SEQUENCE_POS MUST be returned
description of how slots are processed. when CB_SEQUENCE is found in any position in a CB_COMPOUND beyond the
first. If any other operation is in the first position of
CB_COMPOUND, NFS4ERR_OP_NOT_IN_SESSION MUST be returned.
See Section 18.46.3 for a description of how slots are processed.
If csa_cachethis is TRUE, then the server is requesting that the If csa_cachethis is TRUE, then the server is requesting that the
client cache the reply in the callback reply cache. The client MUST client cache the reply in the callback reply cache. The client MUST
cache the reply (see Section 2.10.6.1.3). cache the reply (see Section 2.10.6.1.3).
The csa_referring_call_lists array is the list of COMPOUND requests, The csa_referring_call_lists array is the list of COMPOUND requests,
identified by session ID, slot ID and sequence ID. These are identified by session ID, slot ID, and sequence ID. These are
requests that the client previously sent to the server. These requests that the client previously sent to the server. These
previous requests created state that some operation(s) in the same previous requests created state that some operation(s) in the same
CB_COMPOUND as the csa_referring_call_lists are identifying. A CB_COMPOUND as the csa_referring_call_lists are identifying. A
session ID is included because leased state is tied to a client ID, session ID is included because leased state is tied to a client ID,
and a client ID can have multiple sessions. See Section 2.10.6.3. and a client ID can have multiple sessions. See Section 2.10.6.3.
The value of the csa_sequenceid argument relative to the cached The value of the csa_sequenceid argument relative to the cached
sequence ID on the slot falls into one of three cases. sequence ID on the slot falls into one of three cases.
o If the difference between csa_sequenceid and the client's cached o If the difference between csa_sequenceid and the client's cached
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o If csa_sequenceid is one greater (accounting for wraparound) than o If csa_sequenceid is one greater (accounting for wraparound) than
the cached sequence ID, then this is a new request, and the slot's the cached sequence ID, then this is a new request, and the slot's
sequence ID is incremented. The operations subsequent to sequence ID is incremented. The operations subsequent to
CB_SEQUENCE, if any, are processed. If there are no other CB_SEQUENCE, if any, are processed. If there are no other
operations, the only other effects are to cache the CB_SEQUENCE operations, the only other effects are to cache the CB_SEQUENCE
reply in the slot, maintain the session's activity, and when the reply in the slot, maintain the session's activity, and when the
server receives the CB_SEQUENCE reply, renew the lease of state server receives the CB_SEQUENCE reply, renew the lease of state
related to the client ID. related to the client ID.
If the server reuses a slot ID and sequence ID for a completely If the server reuses a slot ID and sequence ID for a completely
different request, the client MAY treat the request as if it is retry different request, the client MAY treat the request as if it is a
of what it has already executed. The client MAY however detect the retry of what it has already executed. The client MAY however detect
server's illegal reuse and return NFS4ERR_SEQ_FALSE_RETRY. the server's illegal reuse and return NFS4ERR_SEQ_FALSE_RETRY.
If CB_SEQUENCE returns an error, then the state of the slot (sequence If CB_SEQUENCE returns an error, then the state of the slot (sequence
ID, cached reply) MUST NOT change. See Section 2.10.6.1.3 for the ID, cached reply) MUST NOT change. See Section 2.10.6.1.3 for the
conditions when the error NFS4ERR_RETRY_UNCACHED_REP might be conditions when the error NFS4ERR_RETRY_UNCACHED_REP might be
returned. returned.
The client returns two "highest_slotid" values: csr_highest_slotid, The client returns two "highest_slotid" values: csr_highest_slotid
and csr_target_highest_slotid. The former is the highest slot ID the and csr_target_highest_slotid. The former is the highest slot ID the
client will accept in a future CB_SEQUENCE operation, and SHOULD NOT client will accept in a future CB_SEQUENCE operation, and SHOULD NOT
be less than the value of csa_highest_slotid (but see be less than the value of csa_highest_slotid (but see
Section 2.10.6.1 for an exception). The latter is the highest slot Section 2.10.6.1 for an exception). The latter is the highest slot
ID the client would prefer the server use on a future CB_SEQUENCE ID the client would prefer the server use on a future CB_SEQUENCE
operation. operation.
20.10. Operation 12: CB_WANTS_CANCELLED - Cancel Pending Delegation 20.10. Operation 12: CB_WANTS_CANCELLED - Cancel Pending Delegation
Wants Wants
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20.10.2. RESULT 20.10.2. RESULT
struct CB_WANTS_CANCELLED4res { struct CB_WANTS_CANCELLED4res {
nfsstat4 cwcr_status; nfsstat4 cwcr_status;
}; };
20.10.3. DESCRIPTION 20.10.3. DESCRIPTION
The CB_WANTS_CANCELLED operation is used to notify the client that The CB_WANTS_CANCELLED operation is used to notify the client that
the some or all wants it registered for recallable delegations and some or all of the wants it registered for recallable delegations and
layouts have been cancelled. layouts have been cancelled.
If cwca_contended_wants_cancelled is TRUE, this indicates the server If cwca_contended_wants_cancelled is TRUE, this indicates that the
will not be pushing to the client any delegations that become server will not be pushing to the client any delegations that become
available after contention passes. available after contention passes.
If cwca_resourced_wants_cancelled is TRUE, this indicates the server If cwca_resourced_wants_cancelled is TRUE, this indicates that the
will not notify the client when there are resources on the server to server will not notify the client when there are resources on the
grant delegations or layouts. server to grant delegations or layouts.
After receiving a CB_WANTS_CANCELLED operation, the client is free to After receiving a CB_WANTS_CANCELLED operation, the client is free to
attempt to acquire the delegations or layouts it was waiting for, and attempt to acquire the delegations or layouts it was waiting for, and
possibly re-register wants. possibly re-register wants.
20.10.4. IMPLEMENTATION 20.10.4. IMPLEMENTATION
When a client has an OPEN, WANT_DELEGATION, or GET_DIR_DELEGATION When a client has an OPEN, WANT_DELEGATION, or GET_DIR_DELEGATION
request outstanding, when a CB_WANTS_CANCELLED is sent, the server request outstanding, when a CB_WANTS_CANCELLED is sent, the server
may need to make clear to the client whether a promise to signal may need to make clear to the client whether a promise to signal
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20.11.2. RESULT 20.11.2. RESULT
struct CB_NOTIFY_LOCK4res { struct CB_NOTIFY_LOCK4res {
nfsstat4 cnlr_status; nfsstat4 cnlr_status;
}; };
20.11.3. DESCRIPTION 20.11.3. DESCRIPTION
The server can use this operation to indicate that a byte-range lock The server can use this operation to indicate that a byte-range lock
for the given file and lock-owner, previously requested by the client for the given file and lock-owner, previously requested by the client
via an unsuccessful LOCK request, might be available. via an unsuccessful LOCK operation, might be available.
This callback is meant to be used by servers to help reduce the This callback is meant to be used by servers to help reduce the
latency of blocking locks in the case where they recognize that a latency of blocking locks in the case where they recognize that a
client which has been polling for a blocking lock may now be able to client that has been polling for a blocking byte-range lock may now
acquire the lock. If the server supports this callback for a given be able to acquire the lock. If the server supports this callback
file, it MUST set the OPEN4_RESULT_MAY_NOTIFY_LOCK flag when for a given file, it MUST set the OPEN4_RESULT_MAY_NOTIFY_LOCK flag
responding to successful opens for that file. This does not commit when responding to successful opens for that file. This does not
the server to the use of CB_NOTIFY_LOCK, but the client may use this commit the server to the use of CB_NOTIFY_LOCK, but the client may
as a hint to decide how frequently to poll for locks derived from use this as a hint to decide how frequently to poll for locks derived
that open. from that open.
If an OPEN operation results in an upgrade, in which the stateid If an OPEN operation results in an upgrade, in which the stateid
returned has an "other" value matching that of a stateid already returned has an "other" value matching that of a stateid already
allocated, with a new "seqid" indicating a change in the lock being allocated, with a new "seqid" indicating a change in the lock being
represented, then the value of the OPEN4_RESULT_MAY_NOTIFY_LOCK flag represented, then the value of the OPEN4_RESULT_MAY_NOTIFY_LOCK flag
when responding to that new OPEN controls handling from that point when responding to that new OPEN controls handling from that point
going forward. When parallel OPENs are done on the same file and going forward. When parallel OPENs are done on the same file and
open-owner, the ordering of the "seqid" field of the returned stateid open-owner, the ordering of the "seqid" fields of the returned
(subject to wraparound) are to be used to select the controlling stateids (subject to wraparound) are to be used to select the
value of the OPEN4_RESULT_MAY_NOTIFY_LOCK flag. controlling value of the OPEN4_RESULT_MAY_NOTIFY_LOCK flag.
20.11.4. IMPLEMENTATION 20.11.4. IMPLEMENTATION
The server MUST NOT grant the lock to the client unless and until it The server MUST NOT grant the byte-range lock to the client unless
receives an actual LOCK request from the client. Similarly, the and until it receives a LOCK operation from the client. Similarly,
client receiving this callback cannot assume that it now has the the client receiving this callback cannot assume that it now has the
lock, or that a subsequent LOCK request for the lock will be lock or that a subsequent LOCK operation for the lock will be
successful. successful.
The server is not required to implement this callback, and even if it The server is not required to implement this callback, and even if it
does, it is not required to use it in any particular case. Therefore does, it is not required to use it in any particular case.
the client must still rely on polling for blocking locks, as Therefore, the client must still rely on polling for blocking locks,
described in Section 9.6. as described in Section 9.6.
Similarly, the client is not required to implement this callback, and Similarly, the client is not required to implement this callback, and
even it does, is still free to ignore it. Therefore the server MUST even it does, is still free to ignore it. Therefore, the server MUST
NOT assume that the client will act based on the callback. NOT assume that the client will act based on the callback.
20.12. Operation 14: CB_NOTIFY_DEVICEID - Notify Client of Device ID 20.12. Operation 14: CB_NOTIFY_DEVICEID - Notify Client of Device ID
Changes Changes
20.12.1. ARGUMENT 20.12.1. ARGUMENT
/* /*
* Device notification types. * Device notification types.
*/ */
skipping to change at page 598, line 21 skipping to change at page 601, line 21
after being deleted (Section 12.2.10). after being deleted (Section 12.2.10).
All device ID notifications contain a device ID and a layout type. All device ID notifications contain a device ID and a layout type.
The layout type is necessary because two different layout types can The layout type is necessary because two different layout types can
share the same device ID, and the common device ID can have share the same device ID, and the common device ID can have
completely different mappings for each layout type. completely different mappings for each layout type.
The server will send the following notifications: The server will send the following notifications:
NOTIFY_DEVICEID4_CHANGE NOTIFY_DEVICEID4_CHANGE
A previously provided device ID to device address mapping has A previously provided device-ID-to-device-address mapping has
changed and the client uses GETDEVICEINFO to obtain the updated changed and the client uses GETDEVICEINFO to obtain the updated
mapping. The notification is encoded in a value of data type mapping. The notification is encoded in a value of data type
notify_deviceid_change4. This data type also contains a boolean notify_deviceid_change4. This data type also contains a boolean
field, ndc_immediate, which if TRUE indicates that the change will field, ndc_immediate, which if TRUE indicates that the change will
be enforced immediately, and so the client might not be able to be enforced immediately, and so the client might not be able to
complete any pending I/O to the device ID. If ndc_immediate is complete any pending I/O to the device ID. If ndc_immediate is
FALSE, then for an indefinite time, the client can complete FALSE, then for an indefinite time, the client can complete
pending I/O. After pending I/O is complete, the client SHOULD get pending I/O. After pending I/O is complete, the client SHOULD get
the new device ID to device address mappings before sending new the new device-ID-to-device-address mappings before sending new
I/O requests to the device ID. I/O requests to the storage devices addressed by the device ID.
NOTIFY4_DEVICEID_DELETE NOTIFY4_DEVICEID_DELETE
Deletes a device ID from the mappings. This notification MUST NOT Deletes a device ID from the mappings. This notification MUST NOT
be sent if the client has a layout that refers to the device ID. be sent if the client has a layout that refers to the device ID.
In other words if the server is sending a delete device ID In other words, if the server is sending a delete device ID
notification, one of the following is true for layouts associated notification, one of the following is true for layouts associated
with the layout type: with the layout type:
* The client never had a layout referring to that device ID. * The client never had a layout referring to that device ID.
* The client has returned all layouts referring to that device * The client has returned all layouts referring to that device
ID. ID.
* The server has revoked all layouts referring to that device ID. * The server has revoked all layouts referring to that device ID.
skipping to change at page 599, line 31 skipping to change at page 602, line 31
This operation is a placeholder for encoding a result to handle the This operation is a placeholder for encoding a result to handle the
case of the server sending an operation code within CB_COMPOUND that case of the server sending an operation code within CB_COMPOUND that
is not defined in the NFSv4.1 specification. See Section 19.2.3 for is not defined in the NFSv4.1 specification. See Section 19.2.3 for
more details. more details.
The status field of CB_ILLEGAL4res MUST be set to NFS4ERR_OP_ILLEGAL. The status field of CB_ILLEGAL4res MUST be set to NFS4ERR_OP_ILLEGAL.
20.13.4. IMPLEMENTATION 20.13.4. IMPLEMENTATION
A server will probably not send an operation with code OP_CB_ILLEGAL A server will probably not send an operation with code OP_CB_ILLEGAL,
but if it does, the response will be CB_ILLEGAL4res just as it would but if it does, the response will be CB_ILLEGAL4res just as it would
be with any other invalid operation code. Note that if the client be with any other invalid operation code. Note that if the client
gets an illegal operation code that is not OP_ILLEGAL, and if the gets an illegal operation code that is not OP_ILLEGAL, and if the
client checks for legal operation codes during the XDR decode phase, client checks for legal operation codes during the XDR decode phase,
then an instance of data type CB_ILLEGAL4res will not be returned. then an instance of data type CB_ILLEGAL4res will not be returned.
21. Security Considerations 21. Security Considerations
Historically the authentication of model of NFS had the entire Historically, the authentication model of NFS was based on the entire
machine being the NFS client, and the NFS server trusting the NFS machine being the NFS client, with the NFS server trusting the NFS
client to authenticate the end-user. The NFS server in turn shared client to authenticate the end-user. The NFS server in turn shared
its files only to specific clients, as identified by the client's its files only to specific clients, as identified by the client's
source network address. Given this model, the AUTH_SYS RPC security source network address. Given this model, the AUTH_SYS RPC security
flavor simply identified the end-user using the client to the NFS flavor simply identified the end-user using the client to the NFS
server. When processing NFS responses, the client ensured that the server. When processing NFS responses, the client ensured that the
responses came from the same network address and port number that the responses came from the same network address and port number to which
request was sent to. While such a model is easy to implement and the request was sent. While such a model is easy to implement and
simple to deploy and use, it is unsafe. Thus, NFSv4.1 simple to deploy and use, it is unsafe. Thus, NFSv4.1
implementations are REQUIRED to support a security model that uses implementations are REQUIRED to support a security model that uses
end to end authentication, where an end-user on a client mutually end-to-end authentication, where an end-user on a client mutually
authenticates (via cryptographic schemes that do not expose passwords authenticates (via cryptographic schemes that do not expose passwords
or keys in the clear on the network) to a principal on an NFS server. or keys in the clear on the network) to a principal on an NFS server.
Consideration is also be given to the integrity and privacy of NFS Consideration is also given to the integrity and privacy of NFS
requests and responses. The issues of end to end mutual requests and responses. The issues of end-to-end mutual
authentication, integrity, and privacy are discussed authentication, integrity, and privacy are discussed in
Section 2.2.1.1.1. There are specific considerations when using Section 2.2.1.1.1. There are specific considerations when using
Kerberos V5 as described in Section 2.2.1.1.1.2.1.1. Kerberos V5 as described in Section 2.2.1.1.1.2.1.1.
Note that being REQUIRED to implement does not mean REQUIRED to use; Note that being REQUIRED to implement does not mean REQUIRED to use;
AUTH_SYS can be used by NFSv4.1 clients and servers. However, AUTH_SYS can be used by NFSv4.1 clients and servers. However,
AUTH_SYS is merely an OPTIONAL security flavor in NFSv4.1, and so AUTH_SYS is merely an OPTIONAL security flavor in NFSv4.1, and so
interoperability via AUTH_SYS is not assured. interoperability via AUTH_SYS is not assured.
For reasons of reduced administration overhead, better performance For reasons of reduced administration overhead, better performance,
and/or reduction of CPU utilization, users of NFSv4.1 implementations and/or reduction of CPU utilization, users of NFSv4.1 implementations
may opt to not use security mechanisms that enable integrity might decline to use security mechanisms that enable integrity
protection on each remote procedure call and response. The use of protection on each remote procedure call and response. The use of
mechanisms without integrity leaves the user vulnerable to an mechanisms without integrity leaves the user vulnerable to a man-in-
attacker in the middle of the NFS client and server that modifies the the-middle of the NFS client and server that modifies the RPC request
RPC request and/or the response. While implementations are free to and/or the response. While implementations are free to provide the
provide the option to use weaker security mechanisms, there are three option to use weaker security mechanisms, there are three operations
operations in particular that warrant the implementation overriding in particular that warrant the implementation overriding user
user choices. choices.
o The first two such operations are SECINFO and SECINFO_NO_NAME. It o The first two such operations are SECINFO and SECINFO_NO_NAME. It
is RECOMMENDED that the client send both operations such that they is RECOMMENDED that the client send both operations such that they
are protected with a security flavor that has integrity are protected with a security flavor that has integrity
protection, such as RPCSEC_GSS with either the protection, such as RPCSEC_GSS with either the
rpc_gss_svc_integrity or rpc_gss_svc_privacy service. Without rpc_gss_svc_integrity or rpc_gss_svc_privacy service. Without
integrity protection encapsulating SECINFO and SECINFO_NO_NAME and integrity protection encapsulating SECINFO and SECINFO_NO_NAME and
their results, an attacker in the middle could modify results such their results, a man-in-the-middle could modify results such that
that the client might select a weaker algorithm in the set allowed the client might select a weaker algorithm in the set allowed by
by server, making the client and/or server vulnerable to further the server, making the client and/or server vulnerable to further
attacks. attacks.
o The third operation that SHOULD use integrity protection is any o The third operation that SHOULD use integrity protection is any
GETATTR for the fs_locations and fs_locations_info attributes, in GETATTR for the fs_locations and fs_locations_info attributes, in
order to mitigate the severity of a man in the middle attack. The order to mitigate the severity of a man-in-the-middle attack. The
attack has two steps. First the attacker modifies the unprotected attack has two steps. First the attacker modifies the unprotected
results of some operation to return NFS4ERR_MOVED. Second, when results of some operation to return NFS4ERR_MOVED. Second, when
the client follows up with a GETATTR for the fs_locations or the client follows up with a GETATTR for the fs_locations or
fs_locations_info attributes, the attacker modifies the results to fs_locations_info attributes, the attacker modifies the results to
cause the client migrate its traffic to a server controlled by the cause the client to migrate its traffic to a server controlled by
attacker. With integrity protection, this attack is mitigated. the attacker. With integrity protection, this attack is
mitigated.
Relative to previous NFS versions, NFSv4.1 has additional security Relative to previous NFS versions, NFSv4.1 has additional security
considerations for pNFS (see Section 12.9 and Section 13.12), locking considerations for pNFS (see Sections 12.9 and 13.12), locking and
and session state (see Section 2.10.8.3), and state recovery during session state (see Section 2.10.8.3), and state recovery during grace
grace period (see Section 8.4.2.1.1). With respect to locking and period (see Section 8.4.2.1.1). With respect to locking and session
session state, if SP4_SSV state protection is being used, state, if SP4_SSV state protection is being used, Section 2.10.10 has
Section 2.10.10 has specific security considerations for the NFSv4.1 specific security considerations for the NFSv4.1 client and server.
client and server.
22. IANA Considerations 22. IANA Considerations
This section uses terms that are defined in [55]. This section uses terms that are defined in [55].
22.1. Named Attribute Definitions 22.1. Named Attribute Definitions
IANA will create a registry called the "NFSv4 Named Attribute IANA created a registry called the "NFSv4 Named Attribute Definitions
Definitions Registry". Registry".
The NFSv4.1 protocol supports the association of a file with zero or The NFSv4.1 protocol supports the association of a file with zero or
more named attributes. The name space identifiers for these more named attributes. The name space identifiers for these
attributes are defined as string names. The protocol does not define attributes are defined as string names. The protocol does not define
the specific assignment of the name space for these file attributes. the specific assignment of the name space for these file attributes.
An IANA registry will promote interoperability where common interests The IANA registry promotes interoperability where common interests
exist. While application developers are allowed to define and use exist. While application developers are allowed to define and use
attributes as needed, they are encouraged to register the attributes attributes as needed, they are encouraged to register the attributes
with IANA. with IANA.
Such registered named attributes are presumed to apply to all minor Such registered named attributes are presumed to apply to all minor
versions of NFSv4, including those defined subsequently to the versions of NFSv4, including those defined subsequently to the
registration. Where the named attribute is intended to be limited registration. If the named attribute is intended to be limited to
with regard to the minor versions for which they are not be used, the specific minor versions, this will be clearly stated in the
assignment in registry will clearly state the applicable limits. registry's assignment.
All assignments to the registry are made on a First Come First Served All assignments to the registry are made on a First Come First Served
basis, per section 4.1 of [55]. The policy for each assignment is basis, per Section 4.1 of [55]. The policy for each assignment is
Specification Required, per section 4.1 of [55]. Specification Required, per Section 4.1 of [55].
Under the NFSv4.1 specification, the name of a named attribute can in Under the NFSv4.1 specification, the name of a named attribute can in
theory be up to 2^32 - 1 bytes in length, but in practice NFSv4.1 theory be up to 2^32 - 1 bytes in length, but in practice NFSv4.1
clients and servers will be unable to a handle string that long. clients and servers will be unable to handle a string that long.
IANA should reject any assignment request with a named attribute that IANA should reject any assignment request with a named attribute that
exceeds 128 UTF-8 characters. To give IESG the flexibility to set up exceeds 128 UTF-8 characters. To give the IESG the flexibility to
bases of assignment of Experimental Use and Standards Action, the set up bases of assignment of Experimental Use and Standards Action,
prefixes of "EXPE" and "STDS" are Reserved. The zero length named the prefixes of "EXPE" and "STDS" are Reserved. The named attribute
attribute name is Reserved. with a zero-length name is Reserved.
The prefix "PRIV" is allocated for Private Use. A site that wants to The prefix "PRIV" is designated for Private Use. A site that wants to
make use of unregistered named attributes without risk of conflicting make use of unregistered named attributes without risk of conflicting
with an assignment in IANA's registry should use the prefix "PRIV" in with an assignment in IANA's registry should use the prefix "PRIV" in
all of its named attributes. all of its named attributes.
Because some NFSv4.1 clients and servers have case insensitive Because some NFSv4.1 clients and servers have case-insensitive
semantics, the fifteen additional lower case and mixed case semantics, the fifteen additional lower case and mixed case
permutations of each of "EXPE", "PRIV", and "STDS", are Reserved permutations of each of "EXPE", "PRIV", and "STDS" are Reserved
(e.g. "expe", "expE", "exPe", etc. are Reserved). Similarly, IANA (e.g., "expe", "expE", "exPe", etc. are Reserved). Similarly, IANA
must not allow two assignments that would conflict if both named must not allow two assignments that would conflict if both named
attributes were converted to a common case. attributes were converted to a common case.
The registry of named attributes is a list of assignments, each The registry of named attributes is a list of assignments, each
containing three fields for each assignment. containing three fields for each assignment.
1. A US-ASCII string name that is the actual name of the attribute. 1. A US-ASCII string name that is the actual name of the attribute.
This name must be unique. This string name can be 1 to 128 UTF-8 This name must be unique. This string name can be 1 to 128 UTF-8
characters long. characters long.
skipping to change at page 602, line 32 skipping to change at page 605, line 30
3. The point of contact of the registrant. The point of contact can 3. The point of contact of the registrant. The point of contact can
consume up to 256 bytes (or more if IANA permits). consume up to 256 bytes (or more if IANA permits).
22.1.1. Initial Registry 22.1.1. Initial Registry
There is no initial registry. There is no initial registry.
22.1.2. Updating Registrations 22.1.2. Updating Registrations
The registrant is always permitted to update the point of contact The registrant is always permitted to update the point of contact
field. To make any other change will require Expert Review or IESG field. Any other change will require Expert Review or IESG Approval.
Approval.
22.2. Device ID Notifications 22.2. Device ID Notifications
IANA will create a registry called the "NFSv4.1 Device ID IANA created a registry called the "NFSv4 Device ID Notifications
Notifications Registry". Registry".
The potential exists for new notification types to be added to the The potential exists for new notification types to be added to the
CB_NOTIFY_DEVICEID operation Section 20.12. This can be done via CB_NOTIFY_DEVICEID operation (see Section 20.12). This can be done
changes to the operations that register notifications, or by adding via changes to the operations that register notifications, or by
new operations to NFSv4. This requires a new minor version of NFSv4, adding new operations to NFSv4. This requires a new minor version of
and requires a standards track document from IETF. Another way to NFSv4, and requires a Standards Track document from the IETF.
add a notification is to specify a new layout type (see Another way to add a notification is to specify a new layout type
Section 22.4). (see Section 22.4).
Hence all assignments to the registry are made on a Standards Action Hence, all assignments to the registry are made on a Standards Action
basis per section 4.1 of [55], with Expert Review required. basis per Section 4.1 of [55], with Expert Review required.
The registry is a list of assignments, each containing five fields The registry is a list of assignments, each containing five fields
per assignment. per assignment.
1. The name of the notification type. This name must have the 1. The name of the notification type. This name must have the
prefix: "NOTIFY_DEVICEID4_". This name must be unique. prefix "NOTIFY_DEVICEID4_". This name must be unique.
2. The value of the notification. IANA will assign this number, and 2. The value of the notification. IANA will assign this number, and
the request from the registrant will use TBD1 instead of an the request from the registrant will use TBD1 instead of an
actual value. IANA MUST use a whole number which can be no actual value. IANA MUST use a whole number that can be no higher
higher than 2^32-1, and should be the next available value. The than 2^32-1, and should be the next available value. The value
value assigned must be unique. A Designated Expert must be used assigned must be unique. A Designated Expert must be used to
to ensure that when the name of the notification type and its ensure that when the name of the notification type and its value
value are added to the NFSv4.1 notify_deviceid_type4 enumerated are added to the NFSv4.1 notify_deviceid_type4 enumerated data
data type in the NFSv4.1 XDR description ([13]), the result type in the NFSv4.1 XDR description ([13]), the result continues
continues to be a valid XDR description. to be a valid XDR description.
3. The Standards Track RFC(s) that describe the notification. If 3. The Standards Track RFC(s) that describe the notification. If
the RFC(s) have not yet been published, the registrant will use the RFC(s) have not yet been published, the registrant will use
RFCTBD2, RFCTBD3, etc. instead of an actual RFC number. RFCTBD2, RFCTBD3, etc. instead of an actual RFC number.
4. How the RFC introduces the notification. This is indicated by a 4. How the RFC introduces the notification. This is indicated by a
single US-ASCII value. If the value is N, it means a minor single US-ASCII value. If the value is N, it means a minor
revision to the NFSv4 protocol. If the value is L, it means a revision to the NFSv4 protocol. If the value is L, it means a
new pNFS layout type. Other values can be used with IESG new pNFS layout type. Other values can be used with IESG
Approval. Approval.
5. The minor versions of NFSv4 that are allowed to the use the 5. The minor versions of NFSv4 that are allowed to use the
notification. While these are numeric values, IANA will not notification. While these are numeric values, IANA will not
allocate and assign them; the author of the relevant RFCs with allocate and assign them; the author of the relevant RFCs with
IESG Approval assigns these numbers. Each time there is new IESG Approval assigns these numbers. Each time there is a new
minor version of NFSv4 approved, a Designated Expert should minor version of NFSv4 approved, a Designated Expert should
review the registry to make recommended updates as needed. review the registry to make recommended updates as needed.
22.2.1. Initial Registry 22.2.1. Initial Registry
The initial registry is in Table 16. Note that next available value The initial registry is in Table 16. Note that the next available
is zero. value is zero.
+-------------------------+-------+----------+-----+----------------+ +-------------------------+-------+---------+-----+----------------+
| Notification Name | Value | RFC | How | Minor Versions | | Notification Name | Value | RFC | How | Minor Versions |
+-------------------------+-------+----------+-----+----------------+ +-------------------------+-------+---------+-----+----------------+
| NOTIFY_DEVICEID4_CHANGE | 1 | RFCTBD10 | N | 1 | | NOTIFY_DEVICEID4_CHANGE | 1 | RFC5661 | N | 1 |
| NOTIFY_DEVICEID4_DELETE | 2 | RFCTBD10 | N | 1 | | NOTIFY_DEVICEID4_DELETE | 2 | RFC5661 | N | 1 |
+-------------------------+-------+----------+-----+----------------+ +-------------------------+-------+---------+-----+----------------+
Table 16: Initial Device ID Notification Assignments Table 16: Initial Device ID Notification Assignments
22.2.2. Updating Registrations 22.2.2. Updating Registrations
The update of a registration will require IESG Approval on the advice The update of a registration will require IESG Approval on the advice
of a Designated Expert. of a Designated Expert.
22.3. Object Recall Types 22.3. Object Recall Types
IANA will create a registry called the "NFSv4.1 Recallable Object IANA created a registry called the "NFSv4 Recallable Object Types
Types Registry". Registry".
The potential exists for new object types to be added to the The potential exists for new object types to be added to the
CB_RECALL_ANY operation (see Section 20.6). This can be done via CB_RECALL_ANY operation (see Section 20.6). This can be done via
changes to the operations that add recallable types, or by adding new changes to the operations that add recallable types, or by adding new
operations to NFSv4. This requires a new minor version of NFSv4, and operations to NFSv4. This requires a new minor version of NFSv4, and
requires a standards track document from IETF. Another way to add a requires a Standards Track document from IETF. Another way to add a
new recallable object is to specify a new layout type (see new recallable object is to specify a new layout type (see
Section 22.4). Section 22.4).
All assignments to the registry are made on a Standards Action basis All assignments to the registry are made on a Standards Action basis
per section 4.1 of [55], with Expert Review required. per Section 4.1 of [55], with Expert Review required.
Recallable object types are 32 bit unsigned numbers. There are no Recallable object types are 32-bit unsigned numbers. There are no
Reserved values. Values in the range 12 through 15, inclusive, are Reserved values. Values in the range 12 through 15, inclusive, are
for Private Use. designated for Private Use.
The registry is a list of assignments, each containing five fields The registry is a list of assignments, each containing five fields
per assignment. per assignment.
1. The name of the recallable object type. This name must have the 1. The name of the recallable object type. This name must have the
prefix: "RCA4_TYPE_MASK_". The name must be unique. prefix "RCA4_TYPE_MASK_". The name must be unique.
2. The value of the recallable object type. IANA will assign this 2. The value of the recallable object type. IANA will assign this
number, and the request from the registrant will use TBD1 instead number, and the request from the registrant will use TBD1 instead
of an actual value. IANA MUST use a whole number which can be no of an actual value. IANA MUST use a whole number that can be no
higher than 2^32-1, and should be the next available value. The higher than 2^32-1, and should be the next available value. The
value must be unique. A Designated Expert must be used to ensure value must be unique. A Designated Expert must be used to ensure
that when the name of the recallable type and its value are added that when the name of the recallable type and its value are added
to the NFSv4 XDR description [13], the result continues to be a to the NFSv4 XDR description [13], the result continues to be a
valid XDR description. valid XDR description.
3. The Standards Track RFC(s) that describe the recallable object 3. The Standards Track RFC(s) that describe the recallable object
type. If the RFC(s) have not yet been published, the registrant type. If the RFC(s) have not yet been published, the registrant
will use RFCTBD2, RFCTBD3, etc. instead of an actual RFC number. will use RFCTBD2, RFCTBD3, etc. instead of an actual RFC number.
4. How the RFC introduces the recallable object type. This is 4. How the RFC introduces the recallable object type. This is
indicated by a single US-ASCII value. If the value is N, it indicated by a single US-ASCII value. If the value is N, it
means a minor revision to the NFSv4 protocol. If the value is L, means a minor revision to the NFSv4 protocol. If the value is L,
it means a new pNFS layout type. Other values can be used with it means a new pNFS layout type. Other values can be used with
IESG Approval. IESG Approval.
5. The minor versions of NFSv4 that are allowed to the use the 5. The minor versions of NFSv4 that are allowed to use the
recallable object type. While these are numeric values, IANA recallable object type. While these are numeric values, IANA
will not allocate and assign them; the author of the relevant will not allocate and assign them; the author of the relevant
RFCs with IESG Approval assigns these numbers. Each time there RFCs with IESG Approval assigns these numbers. Each time there
is new minor version of NFSv4 approved, a Designated Expert is a new minor version of NFSv4 approved, a Designated Expert
should review the registry to make recommended updates as needed. should review the registry to make recommended updates as needed.
22.3.1. Initial Registry 22.3.1. Initial Registry
The initial registry is in Table 17. Note that next available value The initial registry is in Table 17. Note that the next available
is five. value is five.
+-------------------------------+-------+----------+-----+----------+ +-------------------------------+-------+--------+-----+------------+
| Recallable Object Type Name | Value | RFC | How | Minor | | Recallable Object Type Name | Value | RFC | How | Minor |
| | | | | Versions | | | | | | Versions |
+-------------------------------+-------+----------+-----+----------+ +-------------------------------+-------+--------+-----+------------+
| RCA4_TYPE_MASK_RDATA_DLG | 0 | RFCTBD10 | N | 1 | | RCA4_TYPE_MASK_RDATA_DLG | 0 | RFC | N | 1 |
| RCA4_TYPE_MASK_WDATA_DLG | 1 | RFCTBD10 | N | 1 | | | | 5661 | | |
| RCA4_TYPE_MASK_DIR_DLG | 2 | RFCTBD10 | N | 1 | | RCA4_TYPE_MASK_WDATA_DLG | 1 | RFC | N | 1 |
| RCA4_TYPE_MASK_FILE_LAYOUT | 3 | RFCTBD10 | N | 1 | | | | 5661 | | |
| RCA4_TYPE_MASK_BLK_LAYOUT | 4 | RFCTBD20 | L | 1 | | RCA4_TYPE_MASK_DIR_DLG | 2 | RFC | N | 1 |
| RCA4_TYPE_MASK_OBJ_LAYOUT_MIN | 8 | RFCTBD30 | L | 1 | | | | 5661 | | |
| RCA4_TYPE_MASK_OBJ_LAYOUT_MAX | 9 | RFCTBD30 | L | 1 | | RCA4_TYPE_MASK_FILE_LAYOUT | 3 | RFC | N | 1 |
| Private Use | 12-15 | RFCTBD10 | L | 1 | | | | 5661 | | |
+-------------------------------+-------+----------+-----+----------+ | RCA4_TYPE_MASK_BLK_LAYOUT | 4 | RFC | L | 1 |
| | | 5661 | | |
| RCA4_TYPE_MASK_OBJ_LAYOUT_MIN | 8 | RFC | L | 1 |
| | | 5661 | | |
| RCA4_TYPE_MASK_OBJ_LAYOUT_MAX | 9 | RFC | L | 1 |
| | | 5661 | | |
+-------------------------------+-------+--------+-----+------------+
Table 17: Initial Recallable Object Type Assignments Table 17: Initial Recallable Object Type Assignments
22.3.2. Updating Registrations 22.3.2. Updating Registrations
The update of a registration will require IESG Approval on the advice The update of a registration will require IESG Approval on the advice
of a Designated Expert. of a Designated Expert.
22.4. Layout Types 22.4. Layout Types
IANA will create a registry called the "pNFS Layout Types Registry". IANA created a registry called the "pNFS Layout Types Registry".
All assignments to the registry are made on a Standards Action basis, All assignments to the registry are made on a Standards Action basis,
with Expert Review required. with Expert Review required.
Layout types are 32 bit numbers. The value zero is Reserved. Values Layout types are 32-bit numbers. The value zero is Reserved. Values
in the range 0x80000000 to 0xFFFFFFFF inclusive are for Private Use. in the range 0x80000000 to 0xFFFFFFFF inclusive are designated for
IANA will assign numbers from the range 0x00000001 to 0x7FFFFFFF Private Use. IANA will assign numbers from the range 0x00000001 to
inclusive. 0x7FFFFFFF inclusive.
The registry is a list of assignments, each containing five fields. The registry is a list of assignments, each containing five fields.
1. The name of the layout type. This name must have the prefix: 1. The name of the layout type. This name must have the prefix
"LAYOUT4_". The name must be unique. "LAYOUT4_". The name must be unique.
2. The value of the layout type. IANA will assign this number, and 2. The value of the layout type. IANA will assign this number, and
the request from the registrant will use TBD1 instead of an the request from the registrant will use TBD1 instead of an
actual value. The value assigned must be unique. A Designated actual value. The value assigned must be unique. A Designated
Expert must be used to ensure that when the name of the layout Expert must be used to ensure that when the name of the layout
type and its value are added to the NFSv4.1 layouttype4 type and its value are added to the NFSv4.1 layouttype4
enumerated data type in the NFSv4.1 XDR description ([13]), the enumerated data type in the NFSv4.1 XDR description ([13]), the
result continues to be a valid XDR description. result continues to be a valid XDR description.
skipping to change at page 606, line 28 skipping to change at page 609, line 35
RFCTBD2, RFCTBD3, etc. instead of an actual RFC number. RFCTBD2, RFCTBD3, etc. instead of an actual RFC number.
Collectively, the RFC(s) must adhere to the guidelines listed in Collectively, the RFC(s) must adhere to the guidelines listed in
Section 22.4.3. Section 22.4.3.
4. How the RFC introduces the layout type. This is indicated by a 4. How the RFC introduces the layout type. This is indicated by a
single US-ASCII value. If the value is N, it means a minor single US-ASCII value. If the value is N, it means a minor
revision to the NFSv4 protocol. If the value is L, it means a revision to the NFSv4 protocol. If the value is L, it means a
new pNFS layout type. Other values can be used with IESG new pNFS layout type. Other values can be used with IESG
Approval. Approval.
5. The minor versions of NFSv4 that are allowed to the use the 5. The minor versions of NFSv4 that are allowed to use the
notification. While these are numeric values, IANA will not notification. While these are numeric values, IANA will not
allocate and assign them; the author of the relevant RFCs with allocate and assign them; the author of the relevant RFCs with
IESG Approval assigns these numbers. Each time there is new IESG Approval assigns these numbers. Each time there is a new
minor version of NFSv4 approved, a Designated Expert should minor version of NFSv4 approved, a Designated Expert should
review the registry to make recommended updates as needed. review the registry to make recommended updates as needed.
22.4.1. Initial Registry 22.4.1. Initial Registry
The initial registry is in Table 18. The initial registry is in Table 18.
+-----------------------+-------+----------+-----+----------------+ +-----------------------+-------+----------+-----+----------------+
| Layout Type Name | Value | RFC | How | Minor Versions | | Layout Type Name | Value | RFC | How | Minor Versions |
+-----------------------+-------+----------+-----+----------------+ +-----------------------+-------+----------+-----+----------------+
| LAYOUT4_NFSV4_1_FILES | 0x1 | RFCTBD10 | N | 1 | | LAYOUT4_NFSV4_1_FILES | 0x1 | RFC 5661 | N | 1 |
| LAYOUT4_OSD2_OBJECTS | 0x2 | RFCTBD30 | L | 1 | | LAYOUT4_OSD2_OBJECTS | 0x2 | RFC 5664 | L | 1 |
| LAYOUT4_BLOCK_VOLUME | 0x3 | RFCTBD20 | L | 1 | | LAYOUT4_BLOCK_VOLUME | 0x3 | RFC 5663 | L | 1 |
+-----------------------+-------+----------+-----+----------------+ +-----------------------+-------+----------+-----+----------------+
Table 18: Initial Layout Type Assignments Table 18: Initial Layout Type Assignments
22.4.2. Updating Registrations 22.4.2. Updating Registrations
The update of a registration will require IESG Approval on the advice The update of a registration will require IESG Approval on the advice
of a Designated Expert. of a Designated Expert.
22.4.3. Guidelines for Writing Layout Type Specifications 22.4.3. Guidelines for Writing Layout Type Specifications
skipping to change at page 607, line 46 skipping to change at page 611, line 8
* At a minimum, describe the methods of recovery from: * At a minimum, describe the methods of recovery from:
1. Failure and restart for client, server, storage device. 1. Failure and restart for client, server, storage device.
2. Lease expiration from perspective of the active client, 2. Lease expiration from perspective of the active client,
server, storage device. server, storage device.
3. Loss of layout state resulting in fencing of client access 3. Loss of layout state resulting in fencing of client access
to storage devices (for an example, see Section 12.7.3). to storage devices (for an example, see Section 12.7.3).
* Include an IANA considerations section, will in turn include: * Include an IANA considerations section, which will in turn
include:
+ A request to IANA for a new layout type per Section 22.4. + A request to IANA for a new layout type per Section 22.4.
+ A list of requests to IANA for any new recallable object + A list of requests to IANA for any new recallable object
types for CB_RECALL_ANY; each entry is to presented in the types for CB_RECALL_ANY; each entry is to be presented in
form described in Section 22.3. the form described in Section 22.3.
+ A list of requests to IANA for any new notification values + A list of requests to IANA for any new notification values
for CB_NOTIFY_DEVICEID; each entry is to presented in the for CB_NOTIFY_DEVICEID; each entry is to be presented in
form described in Section 22.2. the form described in Section 22.2.
* Include a security considerations section. This section MUST * Include a security considerations section. This section MUST
explain how the NFSv4.1 authentication, authorization, and explain how the NFSv4.1 authentication, authorization, and
access control models are preserved. I.e. if a metadata access-control models are preserved. That is, if a metadata
server would restrict a READ or WRITE operation, how would server would restrict a READ or WRITE operation, how would
pNFS via the layout similarly restrict a corresponding input pNFS via the layout similarly restrict a corresponding input
or output operation? or output operation?
3. The author documents the new layout specification as an Internet 3. The author documents the new layout specification as an Internet-
Draft. Draft.
4. The author submits the Internet Draft for review through the IETF 4. The author submits the Internet-Draft for review through the IETF
standards process as defined in "Internet Official Protocol standards process as defined in "The Internet Standards Process--
Standards" (STD 1). The new layout specification will be Revision 3" (BCP 9). The new layout specification will be
submitted for eventual publication as a standards track RFC. submitted for eventual publication as a Standards Track RFC.
5. The layout specification progresses through the IETF standards 5. The layout specification progresses through the IETF standards
process; the new option will be reviewed by the NFSv4 Working process.
Group (if that group still exists), or as an Internet Draft not
submitted by an IETF working group.
22.5. Path Variable Definitions 22.5. Path Variable Definitions
This section deals with the IANA considerations associated with the This section deals with the IANA considerations associated with the
variable substitution feature for location names as described in variable substitution feature for location names as described in
Section 11.10.3. As described there, variables subject to Section 11.10.3. As described there, variables subject to
substitution consist of a domain name and a specific name within that substitution consist of a domain name and a specific name within that
domain, with two separated by a colon. There are two sets of IANA domain, with the two separated by a colon. There are two sets of
considerations here: IANA considerations here:
1. The list of variable names. 1. The list of variable names.
2. For each variable name, the list of possible values. 2. For each variable name, the list of possible values.
Thus, there will be one registry for the list of variable names, and Thus, there will be one registry for the list of variable names, and
possibly one registry for listing the values of each variable name. possibly one registry for listing the values of each variable name.
22.5.1. Path Variables Registry 22.5.1. Path Variables Registry
IANA will create a registry called the "NFSv4 Path Variables IANA created a registry called the "NFSv4 Path Variables Registry".
Registry".
22.5.1.1. Path Variable Values 22.5.1.1. Path Variable Values
Variable names are of the form "${", followed by a domain name, Variable names are of the form "${", followed by a domain name,
followed by a colon (":"), followed by a domain-specific portion of followed by a colon (":"), followed by a domain-specific portion of
the variable name, followed by "}". When the domain name is the variable name, followed by "}". When the domain name is
"ietf.org" all variables names must be registered with IANA on a "ietf.org", all variables names must be registered with IANA on a
Standards Action basis, with Expert Review required. Path variables Standards Action basis, with Expert Review required. Path variables
with registered domain names neither part of nor equal to ietf.org with registered domain names neither part of nor equal to ietf.org
are assigned on a Hierarchical Allocation basis (delegating to the are assigned on a Hierarchical Allocation basis (delegating to the
domain owner) and thus of no concern to IANA, unless the domain owner domain owner) and thus of no concern to IANA, unless the domain owner
chooses to register a variable name from his domain. If the domain chooses to register a variable name from his domain. If the domain
owner chooses to do so, IANA will do so on a First Come First Serve owner chooses to do so, IANA will do so on a First Come First Serve
basis. To accommodate registrants who do not have their own domain, basis. To accommodate registrants who do not have their own domain,
IANA will accept requests to register variables with the prefix IANA will accept requests to register variables with the prefix
"${FCFS.ietf.org:" on a First Come First Served basis. Assignments "${FCFS.ietf.org:" on a First Come First Served basis. Assignments
on a First Come First Basis do not require Expert Review, unless the on a First Come First Basis do not require Expert Review, unless the
skipping to change at page 609, line 35 skipping to change at page 612, line 40
1. The name of the variable. The name of this variable must start 1. The name of the variable. The name of this variable must start
with a "${" followed by a registered domain name, followed by with a "${" followed by a registered domain name, followed by
":", or it must start with "${FCFS.ietf.org". The name must be ":", or it must start with "${FCFS.ietf.org". The name must be
no more than 64 UTF-8 characters long. The name must be unique. no more than 64 UTF-8 characters long. The name must be unique.
2. For assignments made on Standards Action basis, the Standards 2. For assignments made on Standards Action basis, the Standards
Track RFC(s) that describe the variable. If the RFC(s) have not Track RFC(s) that describe the variable. If the RFC(s) have not
yet been published, the registrant will use RFCTBD1, RFCTBD2, yet been published, the registrant will use RFCTBD1, RFCTBD2,
etc. instead of an actual RFC number. Note that the RFCs do not etc. instead of an actual RFC number. Note that the RFCs do not
have to be a part of a NFS minor version. For assignments made have to be a part of an NFS minor version. For assignments made
on a First Come First Serve basis, an explanation (consuming no on a First Come First Serve basis, an explanation (consuming no
more than 1024 bytes, or more if IANA permits) of the purpose of more than 1024 bytes, or more if IANA permits) of the purpose of
the variable. A reference to the explanation can be substituted. the variable. A reference to the explanation can be substituted.
3. The point of contact, including an email address. The point of 3. The point of contact, including an email address. The point of
contact can consume up to 256 bytes (or more if IANA permits). contact can consume up to 256 bytes (or more if IANA permits).
For assignments made on a Standards Action basis, the point of For assignments made on a Standards Action basis, the point of
contact is always IESG. contact is always IESG.
22.5.1.1.1. Initial Registry 22.5.1.1.1. Initial Registry
The initial registry is in Table 19. The initial registry is in Table 19.
+------------------------+----------+------------------+ +------------------------+----------+------------------+
| Variable Name | RFC | Point of Contact | | Variable Name | RFC | Point of Contact |
+------------------------+----------+------------------+ +------------------------+----------+------------------+
| ${ietf.org:CPU_ARCH} | RFCTBD10 | IESG | | ${ietf.org:CPU_ARCH} | RFC 5661 | IESG |
| ${ietf.org:OS_TYPE} | RFCTBD10 | IESG | | ${ietf.org:OS_TYPE} | RFC 5661 | IESG |
| ${ietf.org:OS_VERSION} | RFCTBD10 | IESG | | ${ietf.org:OS_VERSION} | RFC 5661 | IESG |
+------------------------+----------+------------------+ +------------------------+----------+------------------+
Table 19: Initial List of Path Variables Table 19: Initial List of Path Variables
IANA will need to create registries for the values of the variable IANA has created registries for the values of the variable names
names ${ietf.org:CPU_ARCH} and ${ietf.org:OS_TYPE}. See ${ietf.org:CPU_ARCH} and ${ietf.org:OS_TYPE}. See Sections 22.5.2
Section 22.5.2 and Section 22.5.3. and 22.5.3.
For the values of the variable ${ietf.org:OS_VERSION}, no registry is For the values of the variable ${ietf.org:OS_VERSION}, no registry is
needed as the specifics of the values of the variable will vary with needed as the specifics of the values of the variable will vary with
the value of ${ietf.org:OS_TYPE}. Thus values for ${ietf.org: the value of ${ietf.org:OS_TYPE}. Thus, values for ${ietf.org:
OS_VERSION} are on a Hierarchical Allocation basis and are of no OS_VERSION} are on a Hierarchical Allocation basis and are of no
concern to IANA. concern to IANA.
22.5.1.1.2. Updating Registrations 22.5.1.1.2. Updating Registrations
The update of an assignment made on a Standards Action basis will The update of an assignment made on a Standards Action basis will
require IESG Approval on the advice of a Designated Expert. require IESG Approval on the advice of a Designated Expert.
The registrant can always updated the point of contact of an The registrant can always update the point of contact of an
assignment made on a First Come First Serve basis. Any other update assignment made on a First Come First Serve basis. Any other update
will require Expert Review. will require Expert Review.
22.5.2. Values for the ${ietf.org:CPU_ARCH} Variable 22.5.2. Values for the ${ietf.org:CPU_ARCH} Variable
IANA will create a registry called the "NFSv4 ${ietf.org:CPU_ARCH} IANA created a registry called the "NFSv4 ${ietf.org:CPU_ARCH} Value
Value Registry". Registry".
Assignments to the registry are made on a First Come First Serve Assignments to the registry are made on a First Come First Serve
basis. The zero length value of ${ietf.org:CPU_ARCH} is Reserved. basis. The zero-length value of ${ietf.org:CPU_ARCH} is Reserved.
Values with a prefix of "PRIV" are Reserved for Private Use. Values with a prefix of "PRIV" are designated for Private Use.
The registry is a list of assignments, each containing three fields. The registry is a list of assignments, each containing three fields.
1. A value of the ${ietf.org:CPU_ARCH} variable. The value must be 1. A value of the ${ietf.org:CPU_ARCH} variable. The value must be
1 to 32 UTF-8 characters long. The value must be unique. 1 to 32 UTF-8 characters long. The value must be unique.
2. An explanation (consuming no more than 1024 bytes, or more if 2. An explanation (consuming no more than 1024 bytes, or more if
IANA permits) of what CPU architecture the value denotes. A IANA permits) of what CPU architecture the value denotes. A
reference to the explanation can be substituted. reference to the explanation can be substituted.
3. The point of contact, including an email address. The point of 3. The point of contact, including an email address. The point of
contact can consume up to 256 bytes (or more if IANA permits). contact can consume up to 256 bytes (or more if IANA permits).
22.5.2.1. Initial Registry 22.5.2.1. Initial Registry
There is no initial registry. There is no initial registry.
22.5.2.2. Updating Registrations 22.5.2.2. Updating Registrations
The registrant is free to update the assignment, i.e. change the The registrant is free to update the assignment, i.e., change the
explanation and/or point of contact fields. explanation and/or point-of-contact fields.
22.5.3. Values for the ${ietf.org:OS_TYPE} Variable 22.5.3. Values for the ${ietf.org:OS_TYPE} Variable
IANA will create a registry called the "NFSv4 ${ietf.org:OS_TYPE} IANA created a registry called the "NFSv4 ${ietf.org:OS_TYPE} Value
Value Registry". Registry".
Assignments to the registry are made on a First Come First Serve Assignments to the registry are made on a First Come First Serve
basis. The zero length value of ${ietf.org:OS_TYPE} is Reserved. basis. The zero-length value of ${ietf.org:OS_TYPE} is Reserved.
Values with a prefix of "PRIV" are Reserved for Private Use. Values with a prefix of "PRIV" are designated for Private Use.
The registry is a list of assignments, each containing three fields. The registry is a list of assignments, each containing three fields.
1. A value of the ${ietf.org:OS_TYPE} variable. The value must be 1 1. A value of the ${ietf.org:OS_TYPE} variable. The value must be 1
to 32 UTF-8 characters long. The value must be unique. to 32 UTF-8 characters long. The value must be unique.
2. An explanation (consuming no more than 1024 bytes, or more if 2. An explanation (consuming no more than 1024 bytes, or more if
IANA permits) of what CPU architecture the value denotes. A IANA permits) of what CPU architecture the value denotes. A
reference to the explanation can be substituted. reference to the explanation can be substituted.
3. The point of contact, including an email address. The point of 3. The point of contact, including an email address. The point of
contact can consume up to 256 bytes (or more if IANA permits). contact can consume up to 256 bytes (or more if IANA permits).
22.5.3.1. Initial Registry 22.5.3.1. Initial Registry
There is no initial registry. There is no initial registry.
22.5.3.2. Updating Registrations 22.5.3.2. Updating Registrations
The registrant is free to update the assignment, i.e. change the The registrant is free to update the assignment, i.e., change the
explanation and/or point of contact fields. explanation and/or point of contact fields.
23. References 23. References
23.1. Normative References 23.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Eisler, M., "XDR: External Data Representation Standard", [2] Eisler, M., Ed., "XDR: External Data Representation Standard",
STD 67, RFC 4506, May 2006. STD 67, RFC 4506, May 2006.
[3] Srinivasan, R., "RPC: Remote Procedure Call Protocol [3] Thurlow, R., "RPC: Remote Procedure Call Protocol Specification
Specification Version 2", RFC 1831, August 1995. Version 2", RFC 5531, May 2009.
[4] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol [4] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
Specification", RFC 2203, September 1997. Specification", RFC 2203, September 1997.
[5] Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos Version [5] Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos Version
5 Generic Security Service Application Program Interface (GSS- 5 Generic Security Service Application Program Interface (GSS-
API) Mechanism Version 2", RFC 4121, July 2005. API) Mechanism Version 2", RFC 4121, July 2005.
[6] The Open Group, "Section 3.191 of Chapter 3 of Base Definitions [6] The Open Group, "Section 3.191 of Chapter 3 of Base Definitions
of The Open Group Base Specifications Issue 6 IEEE Std 1003.1, of The Open Group Base Specifications Issue 6 IEEE Std 1003.1,
2004 Edition, HTML Version (www.opengroup.org), ISBN 2004 Edition, HTML Version (www.opengroup.org), ISBN
1931624232", 2004. 1931624232", 2004.
[7] Linn, J., "Generic Security Service Application Program [7] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000. Interface Version 2, Update 1", RFC 2743, January 2000.
[8] Talpey, T. and B. Callaghan, "Remote Direct Memory Access [8] Talpey, T. and B. Callaghan, "Remote Direct Memory Access
Transport for Remote Procedure Call", Transport for Remote Procedure Call", RFC 5666, October 2009.
draft-ietf-nfsv4-rpcrdma-09 (work in progress), December 2008.
[9] Talpey, T., Callaghan, B., and I. Property, "NFS Direct Data [9] Talpey, T. and B. Callaghan, "Network File System (NFS) Direct
Placement", draft-ietf-nfsv4-nfsdirect-08 (work in progress), Data Placement", RFC 5666, October 2009.
April 2008.
[10] Recio, P., Metzler, B., Culley, P., Hilland, J., and D. Garcia, [10] Recio, R., Metzler, B., Culley, P., Hilland, J., and D. Garcia,
"A Remote Direct Memory Access Protocol Specification", "A Remote Direct Memory Access Protocol Specification",
RFC 5040, October 2007. RFC 5040, October 2007.
[11] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing [11] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997. for Message Authentication", RFC 2104, February 1997.
[12] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February 2009. [12] Eisler, M., "RPCSEC_GSS Version 2", RFC 5403, February 2009.
[13] Shepler, S., Eisler, M., and D. Noveck, "NFSv4 Minor Version 1 [13] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed., "Network
XDR Description", draft-ietf-nfsv4-minorversion1-dot-x-12 (work File System (NFS) Version 4 Minor Version 1 External Data
in progress), Dec 2008. Representation Standard (XDR) Description", RFC 5662,
October 2009.
[14] The Open Group, "Section 3.372 of Chapter 3 of Base Definitions [14] The Open Group, "Section 3.372 of Chapter 3 of Base Definitions
of The Open Group Base Specifications Issue 6 IEEE Std 1003.1, of The Open Group Base Specifications Issue 6 IEEE Std 1003.1,
2004 Edition, HTML Version (www.opengroup.org), ISBN 2004 Edition, HTML Version (www.opengroup.org), ISBN
1931624232", 2004. 1931624232", 2004.
[15] Eisler, M., "IANA Considerations for RPC Net Identifiers and [15] Eisler, M., "IANA Considerations for Remote Procedure Call
Universal Address Formats", draft-ietf-nfsv4-rpc-netid-04 (work (RPC) Network Identifiers and Universal Address Formats",
in progress), December 2008. RFC 5665, October 2009.
[16] The Open Group, "Section 'read()' of System Interfaces of The [16] The Open Group, "Section 'read()' of System Interfaces of The
Open Group Base Specifications Issue 6 IEEE Std 1003.1, 2004 Open Group Base Specifications Issue 6 IEEE Std 1003.1, 2004
Edition, HTML Version (www.opengroup.org), ISBN 1931624232", Edition, HTML Version (www.opengroup.org), ISBN 1931624232",
2004. 2004.
[17] The Open Group, "Section 'readdir()' of System Interfaces of [17] The Open Group, "Section 'readdir()' of System Interfaces of
The Open Group Base Specifications Issue 6 IEEE Std 1003.1, The Open Group Base Specifications Issue 6 IEEE Std 1003.1,
2004 Edition, HTML Version (www.opengroup.org), ISBN 2004 Edition, HTML Version (www.opengroup.org), ISBN
1931624232", 2004. 1931624232", 2004.
skipping to change at page 614, line 49 skipping to change at page 617, line 47
[32] Eisler, M., "LIPKEY - A Low Infrastructure Public Key Mechanism [32] Eisler, M., "LIPKEY - A Low Infrastructure Public Key Mechanism
Using SPKM", RFC 2847, June 2000. Using SPKM", RFC 2847, June 2000.
[33] Eisler, M., "NFS Version 2 and Version 3 Security Issues and [33] Eisler, M., "NFS Version 2 and Version 3 Security Issues and
the NFS Protocol's Use of RPCSEC_GSS and Kerberos V5", the NFS Protocol's Use of RPCSEC_GSS and Kerberos V5",
RFC 2623, June 1999. RFC 2623, June 1999.
[34] Juszczak, C., "Improving the Performance and Correctness of an [34] Juszczak, C., "Improving the Performance and Correctness of an
NFS Server", USENIX Conference Proceedings , June 1990. NFS Server", USENIX Conference Proceedings , June 1990.
[35] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by an On- [35] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced by
line Database", RFC 3232, January 2002. an On-line Database", RFC 3232, January 2002.
[36] Srinivasan, R., "Binding Protocols for ONC RPC Version 2", [36] Srinivasan, R., "Binding Protocols for ONC RPC Version 2",
RFC 1833, August 1995. RFC 1833, August 1995.
[37] Werme, R., "RPC XID Issues", USENIX Conference Proceedings , [37] Werme, R., "RPC XID Issues", USENIX Conference Proceedings ,
February 1996. February 1996.
[38] Nowicki, B., "NFS: Network File System Protocol specification", [38] Nowicki, B., "NFS: Network File System Protocol specification",
RFC 1094, March 1989. RFC 1094, March 1989.
[39] Bhide, A., Elnozahy, E., and S. Morgan, "A Highly Available [39] Bhide, A., Elnozahy, E., and S. Morgan, "A Highly Available
Network Server", USENIX Conference Proceedings , January 1991. Network Server", USENIX Conference Proceedings , January 1991.
[40] Halevy, B., Welch, B., and J. Zelenka, "Object-based pNFS [40] Halevy, B., Welch, B., and J. Zelenka, "Object-Based Parallel
Operations", draft-ietf-nfsv4-pnfs-obj-11 (work in progress), NFS (pNFS) Operations", RFC 5664, October 2009.
December 2008.
[41] Black, D., Fridella, S., and J. Glasgow, "pNFS Block/Volume [41] Black, D., Glasgow, J., and S. Fridella, "Parallel NFS (pNFS)
Layout", draft-ietf-nfsv4-pnfs-block-11 (work in progress), Block/Volume Layout", RFC 5663, October 2009.
December 2008.
[42] Callaghan, B., "WebNFS Client Specification", RFC 2054, [42] Callaghan, B., "WebNFS Client Specification", RFC 2054,
October 1996. October 1996.
[43] Callaghan, B., "WebNFS Server Specification", RFC 2055, [43] Callaghan, B., "WebNFS Server Specification", RFC 2055,
October 1996. October 1996.
[44] IESG, "IESG Processing of RFC Errata for the IETF Stream", [44] IESG, "IESG Processing of RFC Errata for the IETF Stream",
July 2008. July 2008.
skipping to change at page 616, line 22 skipping to change at page 619, line 18
[53] Callaghan, B., "NFS URL Scheme", RFC 2224, October 1997. [53] Callaghan, B., "NFS URL Scheme", RFC 2224, October 1997.
[54] Chiu, A., Eisler, M., and B. Callaghan, "Security Negotiation [54] Chiu, A., Eisler, M., and B. Callaghan, "Security Negotiation
for WebNFS", RFC 2755, January 2000. for WebNFS", RFC 2755, January 2000.
[55] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [55] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
Appendix A. Acknowledgments Appendix A. Acknowledgments
The initial drafts for the SECINFO extensions were edited by Mike The initial text for the SECINFO extensions were edited by Mike
Eisler with contributions from Peng Dai, Sergey Klyushin, and Carl Eisler with contributions from Peng Dai, Sergey Klyushin, and Carl
Burnett. Burnett.
The initial drafts for the SESSIONS extensions were edited by Tom The initial text for the SESSIONS extensions were edited by Tom
Talpey, Spencer Shepler, Jon Bauman with contributions from Charles Talpey, Spencer Shepler, Jon Bauman with contributions from Charles
Antonelli, Brent Callaghan, Mike Eisler, John Howard, Chet Juszczak, Antonelli, Brent Callaghan, Mike Eisler, John Howard, Chet Juszczak,
Trond Myklebust, Dave Noveck, John Scott, Mike Stolarchuk and Mark Trond Myklebust, Dave Noveck, John Scott, Mike Stolarchuk, and Mark
Wittle. Wittle.
Initial drafts relating to multi-server namespace features, including Initial text relating to multi-server namespace features, including
the concept of referrals, were contributed by Dave Noveck, Carl the concept of referrals, were contributed by Dave Noveck, Carl
Burnett, and Charles Fan with contributions from Ted Anderson, Neil Burnett, and Charles Fan with contributions from Ted Anderson, Neil
Brown, and Jon Haswell. Brown, and Jon Haswell.
The initial drafts for the Directory Delegations support were The initial text for the Directory Delegations support were
contributed by Saadia Khan with input from Dave Noveck, Mike Eisler, contributed by Saadia Khan with input from Dave Noveck, Mike Eisler,
Carl Burnett, Ted Anderson and Tom Talpey. Carl Burnett, Ted Anderson, and Tom Talpey.
The initial drafts for the ACL explanations were contributed by Sam The initial text for the ACL explanations were contributed by Sam
Falkner and Lisa Week. Falkner and Lisa Week.
The pNFS work was inspired by the NASD and OSD work done by Garth The pNFS work was inspired by the NASD and OSD work done by Garth
Gibson. Gary Grider has also been a champion of high-performance Gibson. Gary Grider has also been a champion of high-performance
parallel I/O. Garth Gibson and Peter Corbett started the pNFS effort parallel I/O. Garth Gibson and Peter Corbett started the pNFS effort
with a problem statement document for IETF that formed the basis for with a problem statement document for the IETF that formed the basis
the pNFS work in NFSv4.1. for the pNFS work in NFSv4.1.
The initial drafts for the parallel NFS support were edited by Brent The initial text for the parallel NFS support was edited by Brent
Welch and Garth Goodson. Additional authors for those documents were Welch and Garth Goodson. Additional authors for those documents were
Benny Halevy, David Black, and Andy Adamson. Additional input came Benny Halevy, David Black, and Andy Adamson. Additional input came
from the informal group which contributed to the construction of the from the informal group that contributed to the construction of the
initial pNFS drafts; specific acknowledgement goes to Gary Grider, initial pNFS drafts; specific acknowledgment goes to Gary Grider,
Peter Corbett, Dave Noveck, Peter Honeyman, and Stephen Fridella. Peter Corbett, Dave Noveck, Peter Honeyman, and Stephen Fridella.
Fredric Isaman found several errors in draft versions of the ONC RPC Fredric Isaman found several errors in draft versions of the ONC RPC
XDR description of the NFSv4.1 protocol. XDR description of the NFSv4.1 protocol.
Audrey Van Belleghem provided, in numerous ways, essential co- Audrey Van Belleghem provided, in numerous ways, essential co-
ordination and management of the process of editing the specification ordination and management of the process of editing the specification
drafts. documents.
Richard Jernigan gave feedback on the file layout's striping pattern Richard Jernigan gave feedback on the file layout's striping pattern
design. design.
Several formal inspection teams were formed to review various areas Several formal inspection teams were formed to review various areas
of the protocol. All the inspections found significant errors and of the protocol. All the inspections found significant errors and
room for improvement. NFSv4.1's inspection teams were: room for improvement. NFSv4.1's inspection teams were:
o ACLs, with the following inspectors: Sam Falkner, Bruce Fields, o ACLs, with the following inspectors: Sam Falkner, Bruce Fields,
Rahul Iyer, Saadia Khan, Dave Noveck, Lisa Week, Mario Wurzl, and Rahul Iyer, Saadia Khan, Dave Noveck, Lisa Week, Mario Wurzl, and
skipping to change at page 617, line 38 skipping to change at page 620, line 34
Doeppner, Robert Gordon, Benny Halevy, Fredric Isaman, Rick Doeppner, Robert Gordon, Benny Halevy, Fredric Isaman, Rick
Macklem, Trond Myklebust, Dave Noveck, Karen Rochford, John Scott, Macklem, Trond Myklebust, Dave Noveck, Karen Rochford, John Scott,
and Peter Shah. and Peter Shah.
o Initial pNFS inspection, with the following inspectors: Andy o Initial pNFS inspection, with the following inspectors: Andy
Adamson, David Black, Mike Eisler, Marc Eshel, Sam Falkner, Garth Adamson, David Black, Mike Eisler, Marc Eshel, Sam Falkner, Garth
Goodson, Benny Halevy, Rahul Iyer, Trond Myklebust, Spencer Goodson, Benny Halevy, Rahul Iyer, Trond Myklebust, Spencer
Shepler, and Lisa Week. Shepler, and Lisa Week.
o Global namespace, with the following inspectors: Mike Eisler, Dan o Global namespace, with the following inspectors: Mike Eisler, Dan
Ellard, Craig Everhart, Fred Isaman, Trond Myklebust, Dave Noveck, Ellard, Craig Everhart, Fredric Isaman, Trond Myklebust, Dave
Theresa Raj, Spencer Shepler, Renu Tewari, and Robert Thurlow. Noveck, Theresa Raj, Spencer Shepler, Renu Tewari, and Robert
Thurlow.
o NFSv4.1 file layout type, with the following inspectors: Andy o NFSv4.1 file layout type, with the following inspectors: Andy
Adamson, Marc Eshel, Sam Falkner, Garth Goodson, Rahul Iyer, Trond Adamson, Marc Eshel, Sam Falkner, Garth Goodson, Rahul Iyer, Trond
Myklebust, and Lisa Week. Myklebust, and Lisa Week.
o NFSv4.1 locking and directory delegations, with the following o NFSv4.1 locking and directory delegations, with the following
inspectors: Mike Eisler, Pranoop Erasani, Robert Gordon, Saadia inspectors: Mike Eisler, Pranoop Erasani, Robert Gordon, Saadia
Khan, Eric Kustarz, Dave Noveck, Spencer Shepler, and Amy Weaver. Khan, Eric Kustarz, Dave Noveck, Spencer Shepler, and Amy Weaver.
o EXCHANGE_ID and DESTROY_CLIENTID, with the following inspectors: o EXCHANGE_ID and DESTROY_CLIENTID, with the following inspectors:
Mike Eisler, Pranoop Erasani, Robert Gordon, Benny Halevy, Fred Mike Eisler, Pranoop Erasani, Robert Gordon, Benny Halevy, Fredric
Isaman, Saadia Khan, Ricardo Labiaga, Rick Macklem, Trond Isaman, Saadia Khan, Ricardo Labiaga, Rick Macklem, Trond
Myklebust, Spencer Shepler, and Brent Welch. Myklebust, Spencer Shepler, and Brent Welch.
o Final pNFS inspection, with the following inspectors: Andy o Final pNFS inspection, with the following inspectors: Andy
Adamson, Mike Eisler, Mark Eshel, Sam Falkner, Jason Glasgow, Adamson, Mike Eisler, Mark Eshel, Sam Falkner, Jason Glasgow,
Garth Goodson, Robert Gordon, Benny Halevy, Dean Hildebrand, Rahul Garth Goodson, Robert Gordon, Benny Halevy, Dean Hildebrand, Rahul
Iyer, Suchit Kaura, Trond Myklebust, Anatoly Pinchuk, Spencer Iyer, Suchit Kaura, Trond Myklebust, Anatoly Pinchuk, Spencer
Shepler, Renu Tewari, Lisa Week, and Brent Welch. Shepler, Renu Tewari, Lisa Week, and Brent Welch.
A review team worked together to generate the tables of assignments A review team worked together to generate the tables of assignments
of error sets to operations and make sure that each such assignment of error sets to operations and make sure that each such assignment
had two or more people validating it. Participating in the process had two or more people validating it. Participating in the process
were: Andy Adamson, Mike Eisler, Sam Falkner, Garth Goodson, Robert were Andy Adamson, Mike Eisler, Sam Falkner, Garth Goodson, Robert
Gordon, Trond Myklebust, Dave Noveck, Spencer Shepler, Tom Talpey, Gordon, Trond Myklebust, Dave Noveck, Spencer Shepler, Tom Talpey,
Amy Weaver, and Lisa Week. Amy Weaver, and Lisa Week.
Jari Arkko, David Black, Scott Bradner, Lisa Dusseault, Lars Eggert, Jari Arkko, David Black, Scott Bradner, Lisa Dusseault, Lars Eggert,
Chris Newman, and Tim Polk provided valuable review and guidance. Chris Newman, and Tim Polk provided valuable review and guidance.
Olga Kornievskaia found several errors in the SSV specification. Olga Kornievskaia found several errors in the SSV specification.
Ricardo Labiaga found several places where the use of RPCSEC_GSS was Ricardo Labiaga found several places where the use of RPCSEC_GSS was
underspecified. underspecified.
Those who provided miscellaneous comments include: Andy Adamson, Those who provided miscellaneous comments include: Andy Adamson,
Sunil Bhargo, Alex Burlyga, Pranoop Erasani, Bruce Fields, Vadim Sunil Bhargo, Alex Burlyga, Pranoop Erasani, Bruce Fields, Vadim
Finkelstein, Jason Goldschmidt, Vijay K. Gurbani, Sergey Klyushin, Finkelstein, Jason Goldschmidt, Vijay K. Gurbani, Sergey Klyushin,
Ricardo Labiaga, James Lentini, Anshul Madan, Daniel Muntz, Daniel Ricardo Labiaga, James Lentini, Anshul Madan, Daniel Muntz, Daniel
Picken, Archana Ramani, Jim Rees, Mahesh Siddheshwar, Tom Talpey, and Picken, Archana Ramani, Jim Rees, Mahesh Siddheshwar, Tom Talpey, and
Peter Varga. Peter Varga.
Appendix B. RFC Editor Notes
[RFC Editor: please remove this section prior to publishing this
document as an RFC]
[RFC Editor: prior to publishing this document as an RFC, please
replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the
RFC number of this document]
[RFC Editor: prior to publishing this document as an RFC, please
replace all occurrences of RFCTBD20 with RFCyyyy where yyyy is the
RFC number of the document referenced in [41]]
[RFC Editor: prior to publishing this document as an RFC, please
replace all occurrences of RFCTBD30 with RFCzzzz where zzzz is the
RFC number of the document referenced in [40]]
[RFC Editor: prior to publishing this document as an RFC, please
ensure all section references to [15], including the reference from
Section 3.3.9 are accurate if document referenced by [15] has been
finalized for RFC publication. If not finalized for publication,
please remove section number references to [15].
Authors' Addresses Authors' Addresses
Spencer Shepler Spencer Shepler (editor)
Storspeed, Inc. Storspeed, Inc.
7808 Moonflower Drive 7808 Moonflower Drive
Austin, TX 78750 Austin, TX 78750
USA USA
Phone: +1-512-402-5811 ext 8530 Phone: +1-512-402-5811 ext 8530
Email: shepler@storspeed.com EMail: shepler@storspeed.com
Mike Eisler Mike Eisler (editor)
NetApp NetApp
5765 Chase Point Circle 5765 Chase Point Circle
Colorado Springs, CO 80919 Colorado Springs, CO 80919
USA USA
Phone: +1-719-599-9026 Phone: +1-719-599-9026
Email: mike@eisler.com EMail: mike@eisler.com
URI: http://www.eisler.com URI: http://www.eisler.com
David Noveck (editor)
David Noveck
NetApp NetApp
1601 Trapelo Road, Suite 16 1601 Trapelo Road, Suite 16
Waltham, MA 02451 Waltham, MA 02451
USA USA
Phone: +1-781-768-5347 Phone: +1-781-768-5347
Email: dnoveck@netapp.com EMail: dnoveck@netapp.com
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