Finalize ietf-interfaces.yang: last-change, higher-layer-if, lower-layer-if

[troglobit]

Description

Completes #514 with the remaining ietf-interfaces.yang status leaves. Both CLI and WebUI support.

• higher-layer-if and lower-layer-if come from the kernel's
  upper_/lower_ links in sysfs, covering bridge ports, LAG
  members, VLAN parents and any other netdev adjacency.
• last-change is tracked by statd over rtnetlink in an in-memory
  map keyed by interface name. Interfaces whose state predates
  statd have no last-change, per RFC 8343.
• show interface <name> prints last change and the layer lists.

Note

As per RFC8343, the last-change node is not shown (included) "If the current state was entered prior to the last re-initialization of the local network management subsystem". I.e., on startup.

Checklist

Tick relevant boxes, this PR is-a or has-a:

• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
• Refactoring (please detail in commit messages)
• Build related changes
• Documentation content changes
  • ChangeLog updated (for major changes)
• Other (please describe):

[jovatn]

@troglobit Great enhancement!!

Some comments:

• I do not see any update to yang among the changed files. I suppose I look at the wrong place?!
• I also note that there are no updates to doc except for changelog, and it's because we do not have any show interface br0or show interface veth0a examples. Should we add that? (separate issue)
• How is it with link aggregates, does "lower-layer" status apply to that? (suppose not, but I am unsure)

[troglobit]

@troglobit Great enhancement!!

thx 😎

Some comments:

• I do not see any update to yang among the changed files. I suppose I look at the wrong place?!

These nodes were never deviated, just missing backend code.

• I also note that there are no updates to doc except for changelog, and it's because we do not have any show interface br0or show interface veth0a examples. Should we add that? (separate issue)

It's honestly such a minor thing, I think we can skip it for now. There's a lot of bridge changes coming, and possibly even veth if we do the podman swap, so the docs will be updated over time anyway.

• How is it with link aggregates, does "lower-layer" status apply to that? (suppose not, but I am unsure)

It does, the data comes from the kernel's netdev adjacency, and the bonding driver registers exactly that link when a port joins a LAG, the same call the bridge uses for its ports. So a LAG member shows the LAG under higher-layer-if, and the LAG lists its members under lower-layer-if.