| Internet-Draft | anydata validation | July 2025 |
| Elhassany & Graf | Expires 4 January 2026 | [Page] |
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.¶
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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months 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."¶
This Internet-Draft will expire on 4 January 2026.¶
Copyright (c) 2025 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
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.¶
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.¶
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.¶
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:¶
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.¶
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.¶
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¶
This memo includes no request to IANA.¶
The authors would like to thank Jean Quilbeuf, Benoit Claise, and Alex Huang Feng for their review and valuable comments.¶