Internet DRAFT - draft-aelhassany-anydata-validation
draft-aelhassany-anydata-validation
NETCONF A. Elhassany
Internet-Draft Swisscom
Intended status: Standards Track 1 March 2024
Expires: 2 September 2024
Validating anydata in YANG Library context
draft-aelhassany-anydata-validation-00
Abstract
This document describes a method to use yang-library to validate YANG
data nodes with type anydata.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 2 September 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Validating "anydata" Data Tree . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
YANG [RFC7950] defines the "anydata" statement to represent an
unknown set of YANG nodes for which the data model is not known at
module design time. However, YANG [RFC7950] left the verification of
the "anydata" tree open to be done using external means. Several
IETF models, e.g., [RFC7895], [RFC8526], [RFC9144], [RFC8639],
[RFC8641], and [RFC8040], use "anydata" in their definitions.
Current YANG implementations accept syntactically valid YANG data
nodes as children of an "anydata" node but do not check the semantics
of these data nodes against a YANG schema. This creates a real
problem for any consumer of these models when validating all leaves
of the YANG data tree.
YANG Schema Mount [RFC8528] allows mounting complete data models at
implementation and run time. While powerful, schema mount cannot
address use cases where the user selects an arbitrary subset of an
instantiated data tree, such as YANG PUSH [RFC8641]. A current
proposed approach, YANG Full Include YANG Full Include
[I-D.jouqui-netmod-yang-full-include], complements YANG Schema Mount
and applies at design time, yet cannot address dynamic filtering of
an instantiated YANG data tree.
In this document we propese using YANG Library [RFC7895] to define
the context in which anydata trees are validated. This would require
the YANG tooling to implement an optional flag that enables a a flag
for validating "anydata" subtrees in the context of a YANG library.
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Terminology
We use the terminology defined in YANG [RFC7950] for schema node and
schema tree but refine data node and data tree to be more precise.
* data node: A node in the schema tree that can be instantiated in a
data tree. One of container, leaf, leaf-list, list, anydata, and
anyxml. We do not discuss anyxml in this document, and this
document does not change how YANG handles anyxml data nodes.
* instantiated data node: an instantiated instance of a data node
that contains before fully qualified name (module namespace +
identifier) for the data node and the data modeled within YANG.
* instantiated data tree: is what YANG [RFC7950] defines as "data
tree". Adding the term "instantiated" precisely indicates that
this tree is an instance of specific data modeled with YANG.
* data tree: a tree of data nodes (with no values).
3. Validating "anydata" Data Tree
The current YANG encodings, XML, JSON, and CBOR, encode instantiated
data nodes with fully qualified name using the module's namespace and
a local name. The module's namespace can be either explicit or
assumed from a default namespace defined in the top data tree.
This document introduces a new YANG validation option: anydata-
subtree-validation. In this mode, a YANG data parser MUST accept a
YANG library as input along the YANG data file. When this option is
enabled, any instantiated data node (NodeB) that is a child of
anydata node (NodeA) is accepted to be valid only if (i) the
qualified name of the node NodeB is found in one of the data trees
defined by the YANG library AND (ii) the instantiated data tree
rooted by NodeB is valid incomplete instantiated data tree according
to the data node of NodeB.
The first condition ensures the completeness of the YANG library, and
no subtree can be included as a child of anydata node unless a schema
is defined for all the children of anydata subtree and specified in
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the YANG library. The second condition applies a regular YANG
validation against the subtree of anydata, considering that the
subtree of anydata could be generated using an XPath [RFC8641] or a
subtree filter [RFC6241]. Thus, the validator MUST consider this
subtree incomplete and ignore any missing leaves.
4. IANA Considerations
This memo includes no request to IANA.
5. Security Considerations
TBD
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7895] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
<https://www.rfc-editor.org/info/rfc7895>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
6.2. Informative References
[I-D.jouqui-netmod-yang-full-include]
Joubert, T., Quilbeuf, J., and B. Claise, "YANG Full
Include", Work in Progress, Internet-Draft, draft-jouqui-
netmod-yang-full-include-00, 6 November 2023,
<https://datatracker.ietf.org/doc/html/draft-jouqui-
netmod-yang-full-include-00>.
[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,
<https://www.rfc-editor.org/info/rfc6241>.
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[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "NETCONF Extensions to Support the Network
Management Datastore Architecture", RFC 8526,
DOI 10.17487/RFC8526, March 2019,
<https://www.rfc-editor.org/info/rfc8526>.
[RFC8528] Bjorklund, M. and L. Lhotka, "YANG Schema Mount",
RFC 8528, DOI 10.17487/RFC8528, March 2019,
<https://www.rfc-editor.org/info/rfc8528>.
[RFC8639] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
E., and A. Tripathy, "Subscription to YANG Notifications",
RFC 8639, DOI 10.17487/RFC8639, September 2019,
<https://www.rfc-editor.org/info/rfc8639>.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, <https://www.rfc-editor.org/info/rfc8641>.
[RFC9144] Clemm, A., Qu, Y., Tantsura, J., and A. Bierman,
"Comparison of Network Management Datastore Architecture
(NMDA) Datastores", RFC 9144, DOI 10.17487/RFC9144,
December 2021, <https://www.rfc-editor.org/info/rfc9144>.
Acknowledgements
The authors would like to thank Jean Quilbeuf and Thomas Graf for
their review and valuable comments.
Author's Address
Ahmed Elhassany
Swisscom
Binzring 17
CH- Zuerich 8045
Switzerland
Email: ahmed.elhassany@swisscom.com
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