Request for Comments: 8072
Category: Standards Track
ISSN: 2070-1721
YumaWorks
M. Bjorklund
Tail-f Systems
K. Watsen
Juniper Networks
February 2017
YANG Patch Media Type
Abstract
-
This document describes a method for applying patches to configuration datastores using data defined with the YANG data modeling language.
Status of This Memo
-
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc8072.
Copyright Notice
-
Copyright © 2017 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
Table of Contents
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1. Introduction ....................................................3 1.1. Terminology ................................................3 1.1.1. NETCONF .............................................3 1.1.2. HTTP ................................................4 1.1.3. YANG ................................................4 1.1.4. RESTCONF ............................................4 1.1.5. YANG Patch ..........................................5 1.1.6. Examples ............................................5 1.1.7. Tree Diagram Notations ..............................6 2. YANG Patch ......................................................6 2.1. Target Resource ............................................7 2.2. yang-patch Request .........................................8 2.3. yang-patch-status Response .................................9 2.4. Target Data Node ..........................................10 2.5. Edit Operations ...........................................11 2.6. Successful Edit Response Handling .........................11 2.7. Error Handling ............................................12 2.8. ":yang-patch" RESTCONF Capability .........................12 3. YANG Module ....................................................13 4. IANA Considerations ............................................22 4.1. Registrations for New URI and YANG Module .................22 4.2. Media Types ...............................................23 4.2.1. Media Type "application/yang-patch+xml" ............23 4.2.2. Media Type "application/yang-patch+json" ...........24 4.3. RESTCONF Capability URNs ..................................25 5. Security Considerations ........................................25 6. References .....................................................26 6.1. Normative References ......................................26 6.2. Informative References ....................................27 Appendix A. Example YANG Module ...................................28 A.1. YANG Patch Examples ........................................29 A.1.1. Add Resources: Error ...................................29 A.1.2. Add Resources: Success .................................33 A.1.3. Insert List Entry ......................................35 A.1.4. Move List Entry ........................................36 A.1.5. Edit Datastore Resource ................................37 Acknowledgements ..................................................39 Authors' Addresses ................................................39
1. Introduction
-
There is a need for standard mechanisms to patch datastores defined in [RFC6241], which contain conceptual data that conforms to schema specified with YANG [RFC7950]. An "ordered 'edit' list" approach is needed to provide RESTCONF client developers with more precise RESTCONF client control of the edit procedure than the "plain patch" mechanism found in [RFC8040].
This document defines a media type for a YANG-based editing mechanism that can be used with the HTTP PATCH method [RFC5789]. YANG Patch is designed to support the RESTCONF protocol, defined in [RFC8040]. This document only specifies the use of the YANG Patch media type with the RESTCONF protocol.
It may be possible to use YANG Patch with other protocols besides RESTCONF. This is outside the scope of this document. For any protocol that supports the YANG Patch media type, if the entire patch document cannot be successfully applied, then the server MUST NOT apply any of the changes. It may be possible to use YANG Patch with datastore types other than a configuration datastore. This is outside the scope of this document.
1.1. Terminology
-
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 [RFC2119].
1.1.1. NETCONF
-
The following terms are defined in [RFC6241]:
- configuration data
- datastore
- configuration datastore
- protocol operation
- running configuration datastore
- state data
- user
1.1.2. HTTP
-
The following terms are defined in [RFC7230]:
- header field
- message-body
- query
- request URI
The following terms are defined in [RFC7231]:
- method
- request
- resource
1.1.3. YANG
-
The following terms are defined in [RFC7950]:
- container
- data node
- leaf
- leaf-list
- list
1.1.4. RESTCONF
-
The following terms are defined in [RFC8040]:
- application/yang-data+xml
- application/yang-data+json
- data resource
- datastore resource
- patch
- RESTCONF capability
- target resource
- YANG data template
1.1.5. YANG Patch
-
The following terms are used within this document:
- RESTCONF client: a client that implements the RESTCONF protocol.
- RESTCONF server: a server that implements the RESTCONF protocol.
- YANG Patch: a conceptual edit request using the "yang-patch" YANG Patch template, defined in Section 3. In HTTP, refers to a PATCH method where a representation uses either the media type "application/yang-patch+xml" or "application/yang-patch+json".
- YANG Patch Status: a conceptual edit status response using the YANG "yang-patch-status" YANG data template, defined in Section 3. In HTTP, refers to a response message for a PATCH method, where it has a representation with either the media type "application/yang-data+xml" or "application/yang-data+json".
- YANG Patch template: similar to a YANG data template, except that it has a representation with the media type "application/yang-patch+xml" or "application/yang-patch+json".
1.1.6. Examples
-
Some protocol message lines within examples throughout this document are split into multiple lines for display purposes only. When a line ends with a backslash ("\") as the last character, the line is wrapped for display purposes. It is to be considered to be joined to the next line by deleting the backslash, the following line break, and the leading whitespace of the next line.
1.1.7. Tree Diagram Notations
-
A simplified graphical representation of the data model is used in this document. The meanings of the symbols in these diagrams are as follows:
- Brackets "[" and "]" enclose list keys.
- Abbreviations before data node names: "rw" means configuration data (read-write), "ro" means state data (read-only), and "x" means operation resource (executable).
- Symbols after data node names: "?" means an optional node, and "*" denotes a "list" and "leaf-list".
- Parentheses enclose choice and case nodes, and case nodes are also marked with a colon (":").
- Ellipsis ("...") stands for contents of subtrees that are not shown.
2. YANG Patch
-
A "YANG Patch" is an ordered list of edits that are applied to the target datastore by the RESTCONF server. The specific fields are defined in the YANG module in Section 3.
The YANG Patch operation is invoked by the RESTCONF client by sending a PATCH method request with a representation using either the media type "application/yang-patch+xml" or "application/yang-patch+json". This message-body representing the YANG Patch input parameters MUST be present.
YANG Patch has some features that are not possible with the "plain-patch" mechanism defined in RESTCONF [RFC8040]:
- YANG Patch allows multiple sub-resources to be edited within the same PATCH method.
- YANG Patch allows a more precise edit operation than the "plain patch" mechanism found in [RFC8040]. There are seven operations supported ("create", "delete", "insert", "merge", "move", "replace", and "remove").
- YANG Patch uses an "edit" list with an explicit processing order. The edits are processed in client-specified order, and error processing can be precise even when multiple errors occur in the same YANG Patch request.
The YANG Patch "patch-id" may be useful for debugging and SHOULD be present in any audit logging records generated by the RESTCONF server for a patch.
The RESTCONF server MUST return the "Accept-Patch" header field in an OPTIONS response, as specified in [RFC5789], which includes the media type for YANG Patch. This is needed by a client to determine the message-encoding formats supported by the server (e.g., XML, JSON, or both). The following is an example of an "Accept-Patch" header:
Accept-Patch: application/yang-patch+xml,application/yang-patch+json
Note that YANG Patch can only edit data resources. The PATCH method cannot be used to replace the datastore resource. Although the "ietf-yang-patch" YANG module is written using YANG version 1.1 [RFC7950], an implementation of YANG Patch can be used with content defined in YANG version 1 [RFC6020] as well.
A YANG Patch can be encoded in XML format according to [W3C.REC-xml-20081126]. It can also be encoded in JSON according to "JSON Encoding of Data Modeled with YANG" [RFC7951]. If any metadata needs to be sent in a JSON message, it is encoded according to "Defining and Using Metadata with YANG" [RFC7952].
2.1. Target Resource
-
The YANG Patch operation uses the RESTCONF target resource URI to identify the resource that will be patched. This can be the datastore resource itself, i.e., "{+restconf}/data", to edit top-level configuration data resources, or it can be a configuration data resource within the datastore resource, e.g., "{+restconf}/data/ietf-interfaces:interfaces", to edit sub-resources within a top-level configuration data resource.
The target resource MUST identify exactly one resource instance. If more than one resource instance is identified, then the request MUST NOT be processed and a "400 Bad Request" error response MUST be sent by the server. If the target resource does not identify any existing resource instance, then the request MUST NOT be processed and a "404 Not Found" error response MUST be sent by the server.
Each edit with a YANG Patch identifies a target data node for the associated edit. This is described in Section 2.4.
2.2. yang-patch Request
-
A YANG Patch is identified by a unique "patch-id", and it may have an optional comment. A patch is an ordered collection of edits. Each edit is identified by an "edit-id", and it has an edit operation ("create", "delete", "insert", "merge", "move", "replace", or "remove") that is applied to the target resource. Each edit can be applied to a sub-resource "target" within the target resource. If the operation is "insert" or "move", then the "where" parameter indicates how the node is inserted or moved. For values "before" and "after", the "point" parameter specifies the data node insertion point.
The "merge", "replace", "create", "delete", and "remove" edit operations have exactly the same meanings as those defined for the "operation" attribute described in Section 7.2 of [RFC6241].
Each edit within a YANG Patch MUST identify exactly one data resource instance. If an edit represents more than one resource instance, then the request MUST NOT be processed and a "400 Bad Request" error response MUST be sent by the server. If the edit does not identify any existing resource instance and the operation for the edit is not "create", then the request MUST NOT be processed and a "404 Not Found" error response MUST be sent by the server. A "yang-patch-status" response MUST be sent by the server identifying the edit or edits that are not valid.
YANG Patch does not provide any access to specific datastores. How a server processes an edit if it is co-located with a Network Configuration Protocol (NETCONF) server that does provide access to individual datastores is left up to the implementation. A complete datastore cannot be replaced in the same manner as that provided by the <copy-config> operation defined in Section 7.3 of [RFC6241]. Only the specified nodes in a YANG Patch are affected.
A message-body representing the YANG Patch is sent by the RESTCONF client to specify the edit operation request. When used with the HTTP PATCH method, this data is identified by the YANG Patch media type.
YANG tree diagram for "yang-patch" container:
+---- yang-patch +---- patch-id string +---- comment? string +---- edit* [edit-id] +---- edit-id string +---- operation enumeration +---- target target-resource-offset +---- point? target-resource-offset +---- where? enumeration +---- value?
2.3. yang-patch-status Response
-
A message-body representing the YANG Patch Status is returned to the RESTCONF client to report the detailed status of the edit operation. When used with the HTTP PATCH method, this data is identified by the YANG Patch Status media type; the syntax specification is defined in Section 3.
YANG tree diagram for "yang-patch-status" container:
+---- yang-patch-status +---- patch-id string +---- (global-status)? | +--:(global-errors) | | +---- errors | | +---- error* | | +---- error-type enumeration | | +---- error-tag string | | +---- error-app-tag? string | | +---- error-path? instance-identifier | | +---- error-message? string | | +---- error-info? | +--:(ok) | +---- ok? empty +---- edit-status +---- edit* [edit-id] +---- edit-id string +---- (edit-status-choice)? +--:(ok) | +---- ok? empty +--:(errors) +---- errors +---- error* +---- error-type enumeration +---- error-tag string +---- error-app-tag? string +---- error-path? instance-identifier +---- error-message? string +---- error-info?
2.4. Target Data Node
-
The target data node for each edit operation is determined by the value of the target resource in the request and the "target" leaf within each "edit" entry.
If the target resource specified in the request URI identifies a datastore resource, then the path string in the "target" leaf is treated as an absolute path expression identifying the target data node for the corresponding edit. The first node specified in the "target" leaf is a top-level data node defined within a YANG module. The "target" leaf MUST NOT contain a single forward slash ("/"), since this would identify the datastore resource, not a data resource.
If the target resource specified in the request URI identifies a configuration data resource, then the path string in the "target" leaf is treated as a relative path expression. The first node specified in the "target" leaf is a child configuration data node of the data node associated with the target resource. If the "target" leaf contains a single forward slash ("/"), then the target data node is the target resource data node.
2.5. Edit Operations
-
Each YANG Patch edit specifies one edit operation on the target data node. The set of operations is aligned with the NETCONF edit operations but also includes some new operations.
+-----------+-------------------------------------------------------+ | Operation | Description | +-----------+-------------------------------------------------------+ | create | create a new data resource if it does not already | | | exist; if it already exists, return an error | | | | | delete | delete a data resource if it already exists; if it | | | does not exist, return an error | | | | | insert | insert a new user-ordered data resource | | | | | merge | merge the edit value with the target data resource; | | | create if it does not already exist | | | | | move | reorder the target data resource | | | | | replace | replace the target data resource with the edit value | | | | | remove | remove a data resource if it already exists | +-----------+-------------------------------------------------------+
YANG Patch Edit Operations
2.6. Successful Edit Response Handling
-
If a YANG Patch is completed without errors, the RESTCONF server MUST return a "yang-patch-status" message with a "global-status" choice set to "ok".
Refer to Appendix A.1.2 for an example of a successful YANG Patch response.
2.7. Error Handling
-
If a well-formed, schema-valid YANG Patch message is received, then the RESTCONF server will process the supplied edits in ascending order. The following error modes apply to the processing of this "edit" list:
If a YANG Patch is completed with errors, the RESTCONF server SHOULD return a "yang-patch-status" message. It is possible (e.g., within a distributed implementation) that an invalid request will be rejected before the YANG Patch edits are processed. In this case, the server MUST send the appropriate HTTP error response instead.
Refer to Appendix A.1.1 for an example of an error YANG Patch response.
2.8. ":yang-patch" RESTCONF Capability
-
A URI is defined to identify the YANG Patch extension to the base RESTCONF protocol. If the RESTCONF server supports the YANG Patch media type, then the ":yang-patch" RESTCONF capability defined in Section 4.3 MUST be present in the "capability" leaf-list in the "ietf-restconf-monitoring" module defined in [RFC8040].
3. YANG Module
-
The "ietf-yang-patch" module defines conceptual definitions with the "yang-data" extension statements, which are not meant to be implemented as datastore contents by a RESTCONF server.
The "ietf-restconf" module from [RFC8040] is used by this module for the "yang-data" extension definition.
<CODE BEGINS> file "ietf-yang-patch@2017-02-22.yang"
module ietf-yang-patch {
yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-patch"; prefix "ypatch"; import ietf-restconf { prefix rc; }-
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org> Author: Andy Bierman <mailto:andy@yumaworks.com> Author: Martin Bjorklund <mailto:mbj@tail-f.com> Author: Kent Watsen <mailto:kwatsen@juniper.net>";-
description
"This module contains conceptual YANG specifications
for the YANG Patch and YANG Patch Status data structures.
-
-
Note that the YANG definitions within this module do not represent configuration data of any kind.
The YANG grouping statements provide a normative syntax for XML and JSON message-encoding purposes.Copyright © 2017 IETF Trust and the persons identified as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 8072; see the RFC itself for full legal notices.";
revision 2017-02-22 { description "Initial revision."; reference "RFC 8072: YANG Patch Media Type."; }-
typedef target-resource-offset {
type string;
description-
"Contains a data resource identifier string representing
a sub-resource within the target resource.
The document root for this expression is the target resource that is specified in the protocol operation (e.g., the URI for the PATCH request).
This string is encoded according to the same rules as those for a data resource identifier in a RESTCONF request URI."; reference "RFC 8040, Section 3.5.3."; } rc:yang-data "yang-patch" { uses yang-patch; } rc:yang-data "yang-patch-status" { uses yang-patch-status; } grouping yang-patch {-
description
-
"A grouping that contains a YANG container representing the
syntax and semantics of a YANG Patch edit request message.";
container yang-patch {
-
description
"Represents a conceptual sequence of datastore edits,
called a patch. Each patch is given a client-assigned patch identifier. Each edit MUST be applied in ascending order, and all edits MUST be applied. If any errors occur, then the target datastore MUST NOT be changed by the YANG Patch operation.
It is possible for a datastore constraint violation to occur due to any node in the datastore, including nodes not included in the 'edit' list. Any validation errors MUST be reported in the reply message.";
reference
"RFC 7950, Section 8.3.";
leaf patch-id { type string; mandatory true; description "An arbitrary string provided by the client to identify the entire patch. Error messages returned by the server that pertain to this patch will be identified by this 'patch-id' value. A client SHOULD attempt to generate unique 'patch-id' values to distinguish between transactions from multiple clients in any audit logs maintained by the server."; } leaf comment { type string; description "An arbitrary string provided by the client to describe the entire patch. This value SHOULD be present in any audit logging records generated by the server for the patch."; }-
-
list edit {
-
key edit-id; ordered-by user;-
-
description
-
"Represents one edit within the YANG Patch request message.
The 'edit' list is applied in the following manner:
-
- The first edit is conceptually applied to a copy of the existing target datastore, e.g., the running configuration datastore. - Each ascending edit is conceptually applied to the result of the previous edit(s). - After all edits have been successfully processed, the result is validated according to YANG constraints. - If successful, the server will attempt to apply the result to the target datastore."; leaf edit-id { type string; description "Arbitrary string index for the edit. Error messages returned by the server that pertain to a specific edit will be identified by this value."; }-
-
leaf operation {
-
type enumeration {
-
enum create { description "The target data node is created using the supplied value, only if it does not already exist. The 'target' leaf identifies the data node to be created, not the parent data node."; } enum delete { description "Delete the target node, only if the data resource currently exists; otherwise, return an error."; } enum insert { description "Insert the supplied value into a user-ordered list or leaf-list entry. The target node must represent a new data resource. If the 'where' parameter is set to 'before' or 'after', then the 'point' parameter identifies the insertion point for the target node."; } enum merge { description "The supplied value is merged with the target data node."; } enum move { description "Move the target node. Reorder a user-ordered list or leaf-list. The target node must represent an existing data resource. If the 'where' parameter is set to 'before' or 'after', then the 'point' parameter identifies the insertion point to move the target node."; } enum replace { description "The supplied value is used to replace the target data node."; } enum remove { description "Delete the target node if it currently exists."; } } mandatory true; description "The datastore operation requested for the associated 'edit' entry."; } leaf target { type target-resource-offset; mandatory true; description "Identifies the target data node for the edit operation. If the target has the value '/', then the target data node is the target resource. The target node MUST identify a data resource, not the datastore resource."; } leaf point { when "(../operation = 'insert' or ../operation = 'move')" + "and (../where = 'before' or ../where = 'after')" { description "This leaf only applies for 'insert' or 'move' operations, before or after an existing entry."; } type target-resource-offset; description "The absolute URL path for the data node that is being used as the insertion point or move point for the target of this 'edit' entry."; }-
-
leaf where {
-
when "../operation = 'insert' or ../operation = 'move'" { description "This leaf only applies for 'insert' or 'move' operations."; } type enumeration { enum before { description "Insert or move a data node before the data resource identified by the 'point' parameter."; } enum after { description "Insert or move a data node after the data resource identified by the 'point' parameter."; } enum first { description "Insert or move a data node so it becomes ordered as the first entry."; } enum last { description "Insert or move a data node so it becomes ordered as the last entry."; } } default last; description "Identifies where a data resource will be inserted or moved. YANG only allows these operations for list and leaf-list data nodes that are 'ordered-by user'."; }-
-
anydata value {
-
when "../operation = 'create' " + "or ../operation = 'merge' " + "or ../operation = 'replace' " + "or ../operation = 'insert'" { description "The anydata 'value' is only used for 'create', 'merge', 'replace', and 'insert' operations."; } description "Value used for this edit operation. The anydata 'value' contains the target resource associated with the 'target' leaf.-
-
-
For example, suppose the target node is a YANG container named foo:
-
-
container foo { leaf a { type string; } leaf b { type int32; } }-
-
-
The 'value' node contains one instance of foo:
-
-
<value> <foo xmlns='example-foo-namespace'> <a>some value</a> <b>42</b> </foo> </value> "; } } } } // grouping yang-patch grouping yang-patch-status {-
description
-
"A grouping that contains a YANG container representing the
syntax and semantics of a YANG Patch Status response message.";
container yang-patch-status {
-
description
"A container representing the response message sent by the
server after a YANG Patch edit request message has been processed.";
leaf patch-id { type string; mandatory true; description "The 'patch-id' value used in the request."; }-
-
choice global-status {
description
-
-
"Report global errors or complete success.
If there is no case selected, then errors
are reported in the 'edit-status' container.";
-
case global-errors { uses rc:errors; description "This container will be present if global errors that are unrelated to a specific edit occurred."; } leaf ok { type empty; description "This leaf will be present if the request succeeded and there are no errors reported in the 'edit-status' container."; } }-
-
container edit-status {
description
-
"This container will be present if there are
edit-specific status responses to report.
If all edits succeeded and the 'global-status' returned is 'ok', then a server MAY omit this container.";
list edit {
-
key edit-id;
-
-
-
description
"Represents a list of status responses,
corresponding to edits in the YANG Patch request message. If an 'edit' entry was
skipped or not reached by the server,
then this list will not contain a corresponding entry for that edit.";
-
-
leaf edit-id { type string; description "Response status is for the 'edit' list entry with this 'edit-id' value."; } choice edit-status-choice { description "A choice between different types of status responses for each 'edit' entry."; leaf ok { type empty; description "This 'edit' entry was invoked without any errors detected by the server associated with this edit."; } case errors { uses rc:errors; description "The server detected errors associated with the edit identified by the same 'edit-id' value."; } } } } } } // grouping yang-patch-status } <CODE ENDS> -
4. IANA Considerations
4.1. Registrations for New URI and YANG Module
-
This document registers one URI as a namespace in the "IETF XML Registry" [RFC3688]. It follows the format in RFC 3688.
URI: urn:ietf:params:xml:ns:yang:ietf-yang-patch Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace.This document registers one YANG module in the "YANG Module Names" registry [RFC6020].
name: ietf-yang-patch namespace: urn:ietf:params:xml:ns:yang:ietf-yang-patch prefix: ypatch reference: RFC 8072
4.2. Media Types
4.2.1. Media Type "application/yang-patch+xml"
-
Type name: application Subtype name: yang-patch+xml Required parameters: None Optional parameters: None
Encoding considerations: 8-bit
-
The "utf-8" charset is always used for this type. Each conceptual YANG data node is encoded according to the XML Encoding Rules and Canonical Format for the specific YANG data node type defined in [RFC7950].
In addition, the "yang-patch" YANG Patch template found in RFC 8072 defines the structure of a YANG Patch request.
Security considerations: Security considerations related
-
to the generation and consumption of RESTCONF messages are discussed in Section 5 of RFC 8072.
Additional security considerations are specific to the semantics of particular YANG data models. Each YANG module is expected to specify security considerations for the YANG data defined in that module.
Interoperability considerations: RFC 8072 specifies the format
-
of conforming messages and the interpretation thereof.
Published specification: RFC 8072
Applications that use this media type: Instance document
-
data parsers used within a protocol or automation tool that utilize the YANG Patch data structure.
Fragment identifier considerations: The syntax and semantics
-
of fragment identifiers are the same as the syntax and semantics specified for the "application/xml" media type.
Additional information:
Deprecated alias names for this type: N/A Magic number(s): N/A File extension(s): None Macintosh file type code(s): "TEXT"Person & email address to contact for further information: See
-
the Authors' Addresses section of RFC 8072.
Intended usage: COMMON
Restrictions on usage: N/A
Author:
See the Authors' Addresses section of RFC 8072.
-
Change controller: Internet Engineering Task Force
-
(mailto:iesg@ietf.org).
Provisional registration? (standards tree only): no
4.2.2. Media Type "application/yang-patch+json"
-
Type name: application Subtype name: yang-patch+json Required parameters: None Optional parameters: None
Encoding considerations: 8-bit
-
The "utf-8" charset is always used for this type. Each conceptual YANG data node is encoded according to RFC 7951. A metadata annotation is encoded according to RFC 7952. In addition, the "yang-patch" YANG Patch template found in RFC 8072 defines the structure of a YANG Patch request.
Security considerations: Security considerations related
-
to the generation and consumption of RESTCONF messages are discussed in Section 5 of RFC 8072.
Additional security considerations are specific to the semantics of particular YANG data models. Each YANG module is expected to specify security considerations for the YANG data defined in that module.
Interoperability considerations: RFC 8072 specifies the format
-
of conforming messages and the interpretation thereof.
Published specification: RFC 8072
Applications that use this media type: Instance document
-
data parsers used within a protocol or automation tool that utilize the YANG Patch data structure.
Fragment identifier considerations: The syntax and semantics
-
of fragment identifiers are the same as the syntax and semantics specified for the "application/json" media type.
Additional information:
Deprecated alias names for this type: N/A Magic number(s): N/A File extension(s): None Macintosh file type code(s): "TEXT"Person & email address to contact for further information: See
-
the Authors' Addresses section of RFC 8072.
Intended usage: COMMON
Restrictions on usage: N/A
Author:
See the Authors' Addresses section of RFC 8072.
-
Change controller: Internet Engineering Task Force
-
(mailto:iesg@ietf.org).
Provisional registration? (standards tree only): no
4.3. RESTCONF Capability URNs
-
This document registers one capability identifier in the "RESTCONF Capability URNs" registry [RFC8040]. The review policy for this registry is "IETF Review" [RFC5226].
Index Capability Identifier ------------------------------------------------------------------ :yang-patch urn:ietf:params:restconf:capability:yang-patch:1.0
5. Security Considerations
-
The YANG Patch media type does not introduce any significant new security threats, beyond what is described in [RFC8040]. This document defines edit processing instructions for a variant of the PATCH method, as used within the RESTCONF protocol. Message integrity is provided by the RESTCONF protocol. There is no additional capability to validate that a patch has not been altered.
It may be possible to use YANG Patch with other protocols besides RESTCONF; this topic is outside the scope of this document.
For RESTCONF, both the client and server MUST be authenticated according to Section 2 of [RFC8040]. It is important for RESTCONF server implementations to carefully validate all the edit request parameters in some manner. If the entire YANG Patch request cannot be completed, then no configuration changes to the system are done. A PATCH request MUST be applied atomically, as specified in Section 2 of [RFC5789].
A RESTCONF server implementation SHOULD attempt to prevent system disruption due to incremental processing of the YANG Patch "edit" list. It may be possible to construct an attack on such a RESTCONF server, which relies on the edit processing order mandated by YANG Patch. A server SHOULD apply only the fully validated configuration to the underlying system. For example, an "edit" list that deleted an interface and then recreated it could cause system disruption if the "edit" list was incrementally applied.
A RESTCONF server implementation SHOULD attempt to prevent system disruption due to excessive resource consumption required to fulfill YANG Patch edit requests. On such an implementation, it may be possible to construct an attack that attempts to consume all available memory or other resource types.
6. References
6.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, <http://www.rfc-editor.org/info/rfc3688>. [RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP", RFC 5789, DOI 10.17487/RFC5789, March 2010, <http://www.rfc-editor.org/info/rfc5789>. [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, <http://www.rfc-editor.org/info/rfc6020>. [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, <http://www.rfc-editor.org/info/rfc6241>. [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014, <http://www.rfc-editor.org/info/rfc7159>. [RFC7230] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014, <http://www.rfc-editor.org/info/rfc7230>. [RFC7231] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, <http://www.rfc-editor.org/info/rfc7231>. [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, <http://www.rfc-editor.org/info/rfc7950>. [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016, <http://www.rfc-editor.org/info/rfc7951>. [RFC7952] Lhotka, L., "Defining and Using Metadata with YANG", RFC 7952, DOI 10.17487/RFC7952, August 2016, <http://www.rfc-editor.org/info/rfc7952>. [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, <http://www.rfc-editor.org/info/rfc8040>.
[W3C.REC-xml-20081126]
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth Edition)", World Wide Web Consortium Recommendation REC-xml-20081126, November 2008, <http://www.w3.org/TR/2008/REC-xml-20081126>.
6.2. Informative References
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[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, <http://www.rfc-editor.org/info/rfc5226>.
Appendix A. Example YANG Module
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The example YANG module used in this document represents a simple media jukebox interface. The "example-jukebox" YANG module is defined in [RFC8040].
YANG tree diagram for the "example-jukebox" module:
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+--rw jukebox!
+--rw library | +--rw artist* [name] | | +--rw name string | | +--rw album* [name] | | +--rw name string | | +--rw genre? identityref | | +--rw year? uint16 | | +--rw admin | | | +--rw label? string | | | +--rw catalogue-number? string | | +--rw song* [name] | | +--rw name string | | +--rw location string | | +--rw format? string | | +--rw length? uint32 | +--ro artist-count? uint32 | +--ro album-count? uint32 | +--ro song-count? uint32 +--rw playlist* [name] | +--rw name string | +--rw description? string | +--rw song* [index] | +--rw index uint32 | +--rw id instance-identifier +--rw player +--rw gap? decimal64-
rpcs:
+---x play +--ro input +--ro playlist string +--ro song-number uint32 -
A.1. YANG Patch Examples
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This section includes RESTCONF examples. Most examples are shown in JSON encoding [RFC7159], and some are shown in XML encoding [W3C.REC-xml-20081126].
A.1.1. Add Resources: Error
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The following example shows several songs being added to an existing album. Each edit contains one song. The first song already exists, so an error will be reported for that edit. The rest of the edits were not attempted, since the first edit failed. XML encoding is used in this example.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\ library/artist=Foo%20Fighters/album=Wasting%20Light HTTP/1.1 Host: example.com Accept: application/yang-data+xml Content-Type: application/yang-patch+xml-
<yang-patch xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch">
<patch-id>add-songs-patch</patch-id> <edit> <edit-id>edit1</edit-id> <operation>create</operation> <target>/song=Bridge%20Burning</target> <value> <song xmlns="http://example.com/ns/example-jukebox"> <name>Bridge Burning</name> <location>/media/bridge_burning.mp3</location> <format>MP3</format> <length>288</length> </song> </value> </edit> <edit> <edit-id>edit2</edit-id> <operation>create</operation> <target>/song=Rope</target> <value> <song xmlns="http://example.com/ns/example-jukebox"> <name>Rope</name> <location>/media/rope.mp3</location> <format>MP3</format> <length>259</length> </song> </value> </edit> <edit> <edit-id>edit3</edit-id> <operation>create</operation> <target>/song=Dear%20Rosemary</target> <value> <song xmlns="http://example.com/ns/example-jukebox"> <name>Dear Rosemary</name> <location>/media/dear_rosemary.mp3</location> <format>MP3</format> <length>269</length> </song> </value> </edit> </yang-patch>XML response from the RESTCONF server:
HTTP/1.1 409 Conflict Date: Thu, 26 Jan 2017 20:56:30 GMT Server: example-server Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT Content-Type: application/yang-data+xml <yang-patch-status xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch"> <patch-id>add-songs-patch</patch-id> <edit-status> <edit> <edit-id>edit1</edit-id> <errors> <error> <error-type>application</error-type> <error-tag>data-exists</error-tag> <error-path xmlns:jb="http://example.com/ns/example-jukebox"> /jb:jukebox/jb:library /jb:artist[jb:name='Foo Fighters'] /jb:album[jb:name='Wasting Light'] /jb:song[jb:name='Bridge Burning'] </error-path> <error-message> Data already exists; cannot be created </error-message> </error> </errors> </edit> </edit-status> </yang-patch-status>JSON response from the RESTCONF server:
The following response is shown in JSON format to highlight the difference in the "error-path" object encoding. For JSON, the instance-identifier encoding specified in [RFC7951] is used.
HTTP/1.1 409 Conflict Date: Thu, 26 Jan 2017 20:56:30 GMT Server: example-server Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT Content-Type: application/yang-data+json { "ietf-yang-patch:yang-patch-status" : { "patch-id" : "add-songs-patch", "edit-status" : { "edit" : [ { "edit-id" : "edit1", "errors" : { "error" : [ { "error-type": "application", "error-tag": "data-exists", "error-path": "/example-jukebox:jukebox/library\ /artist[name='Foo Fighters']\ /album[name='Wasting Light']\ /song[name='Bridge Burning']", "error-message": "Data already exists; cannot be created" } ] } } ] } } } -
A.1.2. Add Resources: Success
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The following example shows several songs being added to an existing album.
- Each of two edits contains one song.
- Both edits succeed, and new sub-resources are created.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\ library/artist=Foo%20Fighters/album=Wasting%20Light \ HTTP/1.1 Host: example.com Accept: application/yang-data+json Content-Type: application/yang-patch+json-
{
"ietf-yang-patch:yang-patch" : {
"patch-id" : "add-songs-patch-2", "edit" : [ { "edit-id" : "edit1", "operation" : "create", "target" : "/song=Rope", "value" : { "song" : [ { "name" : "Rope", "location" : "/media/rope.mp3", "format" : "MP3", "length" : 259 } ] } }, { "edit-id" : "edit2", "operation" : "create", "target" : "/song=Dear%20Rosemary", "value" : { "song" : [ { "name" : "Dear Rosemary", "location" : "/media/dear_rosemary.mp3", "format" : "MP3", "length" : 269 } ] } } ] } }Response from the RESTCONF server:
HTTP/1.1 200 OK Date: Thu, 26 Jan 2017 20:56:30 GMT Server: example-server Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT Content-Type: application/yang-data+json { "ietf-yang-patch:yang-patch-status" : { "patch-id" : "add-songs-patch-2", "ok" : [null] } }
A.1.3. Insert List Entry
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The following example shows a song being inserted within an existing playlist. Song "6" in playlist "Foo-One" is being inserted after song "5" in the playlist. The operation succeeds, so a non-error reply can be provided.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\ playlist=Foo-One HTTP/1.1 Host: example.com Accept: application/yang-data+json Content-Type: application/yang-patch+json-
{
"ietf-yang-patch:yang-patch" : { "patch-id" : "insert-song-patch", "comment" : "Insert song 6 after song 5", "edit" : [ { "edit-id" : "edit1", "operation" : "insert", "target" : "/song=6", "point" : "/song=5", "where" : "after", "value" : { "example-jukebox:song" : [ { "index" : 6, "id" : "/example-jukebox:jukebox/library\ /artist[name='Foo Fighters']\ /album[name='Wasting Light']\ /song[name='Bridge Burning']" } ] } } ] }Response from the RESTCONF server:
HTTP/1.1 200 OK Date: Thu, 26 Jan 2017 20:56:30 GMT Server: example-server Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT Content-Type: application/yang-data+json { "ietf-yang-patch:yang-patch-status" : { "patch-id" : "insert-song-patch", "ok" : [null] } } -
A.1.4. Move List Entry
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The following example shows a song being moved within an existing playlist. Song "1" in playlist "Foo-One" is being moved after song "3" in the playlist. Note that no "value" parameter is needed for a "move" operation. The operation succeeds, so a non-error reply can be provided.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\ playlist=Foo-One HTTP/1.1 Host: example.com Accept: application/yang-data+json Content-Type: application/yang-patch+json { "ietf-yang-patch:yang-patch" : { "patch-id" : "move-song-patch", "comment" : "Move song 1 after song 3", "edit" : [ { "edit-id" : "edit1", "operation" : "move", "target" : "/song=1", "point" : "/song=3", "where" : "after" } ] } }Response from the RESTCONF server:
HTTP/1.1 200 OK Date: Thu, 26 Jan 2017 20:56:30 GMT Server: example-server Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT Content-Type: application/yang-data+json { "ietf-restconf:yang-patch-status" : { "patch-id" : "move-song-patch", "ok" : [null] } }
A.1.5. Edit Datastore Resource
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The following example shows how three top-level data nodes from different modules can be edited at the same time.
Example module "foo" defines leaf X. Example module "bar" defines container Y, with child leafs A and B. Example module "baz" defines list Z, with key C and child leafs D and E.
Request from the RESTCONF client:
PATCH /restconf/data HTTP/1.1 Host: example.com Accept: application/yang-data+json Content-Type: application/yang-patch+json-
{
"ietf-yang-patch:yang-patch" : {
"patch-id" : "datastore-patch-1", "comment" : "Edit 3 top-level data nodes at once", "edit" : [ { "edit-id" : "edit1", "operation" : "create", "target" : "/foo:X", "value" : { "foo:X" : 42 } }, { "edit-id" : "edit2", "operation" : "merge", "target" : "/bar:Y", "value" : { "bar:Y" : { "A" : "test1", "B" : 99 } } }, { "edit-id" : "edit3", "operation" : "replace", "target" : "/baz:Z=2", "value" : { "baz:Z" : [ { "C" : 2, "D" : 100, "E" : false } ] } } ] } }Response from the RESTCONF server:
HTTP/1.1 200 OK Date: Thu, 26 Jan 2017 20:56:30 GMT Server: example-server Last-Modified: Thu, 26 Jan 2017 20:55:30 GMT Content-Type: application/yang-data+json { "ietf-yang-patch:yang-patch-status" : { "patch-id" : "datastore-patch-1", "ok" : [null] } } -
Acknowledgements
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The authors would like to thank Rex Fernando for his contributions to this document.
Contributions to this material by Andy Bierman are based upon work supported by the United States Army, Space & Terrestrial Communications Directorate (S&TCD) under Contract No. W15P7T-13-C-A616. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the S&TCD.
Authors' Addresses
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Andy Bierman
YumaWorksEmail:
andy@yumaworks.com
Martin Bjorklund
Tail-f SystemsEmail: mbj@tail-f.com
Kent Watsen
Juniper NetworksEmail:
kwatsen@juniper.net