



NMOP                                                        A. Elhassany
Internet-Draft                                                   T. Graf
Intended status: Standards Track                                Swisscom
Expires: 4 January 2026                                      3 July 2025


               Validating anydata in YANG Library context
              draft-netana-nmop-yang-anydata-validation-00

Abstract

   This document describes a method to use YANG RFC 8525 and standard
   YANG validation rules in RFC 7950 to validate YANG data nodes that
   are children of an "anydata" data node.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 4 January 2026.

Copyright Notice

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   document authors.  All rights reserved.

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   provided without warranty as described in the Revised BSD License.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Instantiated data node schema lookup  . . . . . . . . . . . .   3
   4.  Validating "anydata" Data Tree  . . . . . . . . . . . . . . .   4
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Section 7.10 of [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, Section 7.10 of [RFC7950]
   left the verification of the "anydata" tree open to become known
   through protocol signaling or other means.  Several IETF models,
   e.g., [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 data type of these data nodes against a YANG
   schema.  This creates a real problem for any YANG data consumer when
   validating YANG data against YANG data tree.  For instance, a YANG
   Message Broker Consumer described in Section 4.6 of
   [I-D.ietf-nmop-yang-message-broker-integration] is not able to fully
   validate the received messages published by the network nodes.

   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 [RFC8641].  A current proposed
   approach, 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.

   This document propeses using the [RFC8525] to define the context in
   which anydata trees are validated.  This would require the YANG
   tooling to implement additional flags that enables 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

   This document uses the terminology defined in YANG [RFC7950] for
   schema node and schema tree but refines 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.  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 [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.  Instantiated data node schema lookup

   This document builds on the fact that when a YANG validator examines
   a node in an instantiated data tree, it can find the corresponding
   data node in a YANG schema.  For the existing YANG encodings, the
   following rules are defined to encode instantiated data nodes:

   *  In YANG XML encoding [RFC7950], The element's local name is the
      data node identifier, and its namespace is the module's XML
      namespace.

   *  In JSON encoding [RFC7951], each object member must be identical
      to the corresponding YANG data node identifier or namespace-
      qualified - the data node identifier is prefixed with the name of
      the module in which the data node is defined, separated from the
      data node identifier by the colon character (":").






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   *  In CBOR [RFC9254] encoding, node should include information that
      would allow each node to be - identified in a stateless way, for
      instance, the SID number associated with the node, the SID delta
      from another SID in the application payload, the namespace-
      qualified name, or the instance-identifier.

   Given the encoding rules that maintain complete information to
   identify the corresponding data node for each instantiated data node,
   the YANG validator can easily find the schema for the data node in
   the YANG Library.

4.  Validating "anydata" Data Tree

   This document introduces two new YANG validation options: anydata-
   complete and anydata-candidate.  These two options align with
   Section 8.3.3 of [RFC7950], such that the complete validation
   validates the contents of the anydata subtree, which MUST obey all
   validation rules defined in the corresponding schema in the YANG
   Library.  The candidate does not apply the constraint checks.

5.  Implementation Status

   Note to the RFC-Editor: Please remove this section before publishing.

   anydata-candidate validation is implemented for libyang and avaiable
   at https://github.com/ahassany/libyang/tree/anydata-strict-parsing

6.  IANA Considerations

   This memo includes no request to IANA.

7.  Security Considerations

   TBD

8.  References

8.1.  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>.

   [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>.




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   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [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>.

   [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", RFC 8525,
              DOI 10.17487/RFC8525, March 2019,
              <https://www.rfc-editor.org/info/rfc8525>.

   [RFC9254]  Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
              C., and M. Richardson, "Encoding of Data Modeled with YANG
              in the Concise Binary Object Representation (CBOR)",
              RFC 9254, DOI 10.17487/RFC9254, July 2022,
              <https://www.rfc-editor.org/info/rfc9254>.

8.2.  Informative References

   [I-D.ietf-nmop-yang-message-broker-integration]
              Graf, T. and A. Elhassany, "An Architecture for YANG-Push
              to Message Broker Integration", Work in Progress,
              Internet-Draft, draft-ietf-nmop-yang-message-broker-
              integration-07, 3 March 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-nmop-
              yang-message-broker-integration-07>.

   [I-D.jouqui-netmod-yang-full-include]
              Quilbeuf, J., Claise, B., and T. Joubert, "YANG Full
              Embed", Work in Progress, Internet-Draft, draft-jouqui-
              netmod-yang-full-include-02, 5 July 2024,
              <https://datatracker.ietf.org/doc/html/draft-jouqui-
              netmod-yang-full-include-02>.

   [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>.






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   [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, Benoit Claise, and
   Alex Huang Feng for their review and valuable comments.

Authors' Addresses

   Ahmed Elhassany
   Swisscom
   Binzring 17
   CH- Zurich 8045
   Switzerland
   Email: ahmed.elhassany@swisscom.com


   Thomas Graf
   Swisscom
   Binzring 17
   CH-8045 Zurich
   Switzerland
   Email: thomas.graf@swisscom.com












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