Re: [netmod] question about unprefixed path in leafref

Hi all,

This immediately made me worried about all such xxx-ref constructs in YANG that I've seen in a few modules.

But looking at IETF interfaces https://datatracker.ietf.org/doc/html/rfc8343 I see that this error is avoided because interface-ref is fully qualified right ?

     typedef interface-ref {
       type leafref {
         path "/if:interfaces/if:interface/if:name";
       }
       description
         "This type is used by data models that need to reference
          interfaces.";
     }

Jason

From: netmod <netmod-bounces@ietf.org> On Behalf Of Jernej Tuljak
Sent: Wednesday, February 9, 2022 3:47 AM
To: Fengchong (frank) <frank.fengchong=40huawei.com@dmarc.ietf.org>; netmod@ietf.org
Subject: Re: [netmod] question about unprefixed path in leafref

On 08/02/2022 03:40, Fengchong (frank) wrote:
Hi all,

In RFC7950 sec6.4.1 says:

o  Names without a namespace prefix belong to the same namespace as

      the identifier of the current node.  Inside a grouping, that

      namespace is affected by where the grouping is used (see

      Section 7.13<https://datatracker.ietf.org/doc/html/rfc7950#section-7.13>).  Inside a typedef, that namespace is affected by

      where the typedef is referenced.  If a typedef is defined and

      referenced within a grouping, the namespace is affected by where

      the grouping is used (see Section 7.13<https://datatracker.ietf.org/doc/html/rfc7950#section-7.13>).

But in module openconfig-aft-network-instance:

  augment "/oc-ni:network-instances/oc-ni:network-instance/" +
          "oc-ni:afts/oc-ni:next-hops/oc-ni:next-hop/oc-ni:state" {

    description
      "Add leaves that require referencing of a network instance to the
      operational state parameters of a next-hop within the AFT for IPv4
      unicast.";

    uses aft-nexthop-ni-state;
  }

  grouping aft-nexthop-ni-state {
    description
      "Operational state parameters relating to a next-hop which reference a
      network instance.";

    leaf network-instance {
      type oc-ni:network-instance-ref;
      description
        "The network-instance within which the next-hop should be resolved.
         When this leaf is unspecified, the next-hop is resolved within
         the local instance.";
    }
  }

The typedef network-instance-ref is defined in module openconfig-network-instance:

  typedef network-instance-ref {
    type leafref {
      path "/network-instances/network-instance/config/name";
    }
    description
      "A re-usable type that can be referenced within other
       modules that references a network instance.";
  }

The leafref’s path is a unprefixed path.

So, according RFC7950, the typedef network-instance-ref is referenced in leaf network-instance, and the leaf is inside grouping aft-nexthop-ni-state, and this grouping is used in augment "/oc-ni:network-instances/oc-ni:network-instance/" +
          "oc-ni:afts/oc-ni:next-hops/oc-ni:next-hop/oc-ni:state"
So the path "/network-instances/network-instance/config/name" ‘s namespace is module openconfig-aft-network-instance’s namespace. But in fact, there is no node called network-instances with namespace: http://openconfig.net/yang/aft/ni.

Is it incorrect?

I try to use pyang to compile it, and no error is reported.

These modules are written in YANG 1.0, therefore RFC6020 applies, not RFC7950. This was one of the cases where RFC6020 was unclear, hence new text you quote from RFC7950. If you change openconfig-network-instance to YANG 1.1, pyang should report an error for that "path" when the "typedef" gets used in openconfig-aft-network-instance.

Jernej

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