Multiple local fix

[donaldsharp]

See first commit, but explicilty fix the problem where when receiving multiple link up events FRR is creating multpile local routes when it should not be.

[mjstapp]

I like this fix - let's see how CI goes

[greptile-apps]

Greptile Overview

Greptile Summary

This PR fixes a bug where multiple interface link-up events caused duplicate local routes in the RIB. The fix extends the route comparison logic in rib_compare_routes to treat ZEBRA_ROUTE_LOCAL routes the same way as ZEBRA_ROUTE_CONNECT routes - allowing multiple routes on the same interface to be considered equivalent.

Key changes:

• Modified zebra/zebra_rib.c line 1650 to include ZEBRA_ROUTE_LOCAL in the condition that prevents duplicate routes on the same interface
• Added test test_zebra_mtu_single_local_route_per_address that triggers interface events via MTU change and verifies only one local route exists per address
• Test also includes minor formatting fixes (spacing/indentation)

The fix is minimal, targeted, and consistent with the existing pattern at line 1654 where both route types are already handled together.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The change is a single-line fix that follows an established pattern in the codebase (line 1654), addresses a clear bug with well-documented behavior, and includes a comprehensive test to prevent regression
• No files require special attention

Important Files Changed

Filename	Overview
zebra/zebra_rib.c	Added ZEBRA_ROUTE_LOCAL to route comparison logic to prevent duplicate local routes on interface events - consistent with existing pattern at line 1654
tests/topotests/zebra_multiple_connected/test_zebra_multiple_connected.py	Added comprehensive test to verify exactly one local route per address after MTU changes trigger interface events - validates the fix

[donaldsharp]

@Mergifyio backport dev/10.6 stable/10.5 stable/10.4 stable/10.3 stable/10.2 stable/10.1 stable/10.0

[mergify]

backport dev/10.6 stable/10.5 stable/10.4 stable/10.3 stable/10.2 stable/10.1 stable/10.0

✅ Backports have been created

Details

• #20815 Multiple local fix (backport #20798) has been created for branch dev/10.6
• #20816 Multiple local fix (backport #20798) has been created for branch stable/10.5
• #20817 Multiple local fix (backport #20798) has been created for branch stable/10.4
• #20818 Multiple local fix (backport #20798) has been created for branch stable/10.3
• #20819 Multiple local fix (backport #20798) has been created for branch stable/10.2 but encountered conflicts

Cherry-pick of 23261aa has failed:

On branch mergify/bp/stable/10.2/pr-20798
Your branch is ahead of 'origin/stable/10.2' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 23261aa5b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   tests/topotests/zebra_multiple_connected/r1/frr.conf
	deleted:    tests/topotests/zebra_multiple_connected/r1/zebra.conf
	new file:   tests/topotests/zebra_multiple_connected/r2/frr.conf
	new file:   tests/topotests/zebra_multiple_connected/r3/frr.conf

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   tests/topotests/zebra_multiple_connected/test_zebra_multiple_connected.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

• #20820 Multiple local fix (backport #20798) has been created for branch stable/10.1 but encountered conflicts

Cherry-pick of bf1312b has failed:

On branch mergify/bp/stable/10.1/pr-20798
Your branch is up to date with 'origin/stable/10.1'.

You are currently cherry-picking commit bf1312b8e.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   zebra/zebra_rib.c

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of 23261aa has failed:

On branch mergify/bp/stable/10.1/pr-20798
Your branch is ahead of 'origin/stable/10.1' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 23261aa5b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   tests/topotests/zebra_multiple_connected/r1/frr.conf
	deleted:    tests/topotests/zebra_multiple_connected/r1/zebra.conf
	new file:   tests/topotests/zebra_multiple_connected/r2/frr.conf
	new file:   tests/topotests/zebra_multiple_connected/r3/frr.conf

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   tests/topotests/zebra_multiple_connected/test_zebra_multiple_connected.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

• #20821 Multiple local fix (backport #20798) has been created for branch stable/10.0 but encountered conflicts

Cherry-pick of bf1312b has failed:

On branch mergify/bp/stable/10.0/pr-20798
Your branch is up to date with 'origin/stable/10.0'.

You are currently cherry-picking commit bf1312b8e.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   zebra/zebra_rib.c

no changes added to commit (use "git add" and/or "git commit -a")

Cherry-pick of 23261aa has failed:

On branch mergify/bp/stable/10.0/pr-20798
Your branch is ahead of 'origin/stable/10.0' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit 23261aa5b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   tests/topotests/zebra_multiple_connected/r1/frr.conf
	deleted:    tests/topotests/zebra_multiple_connected/r1/zebra.conf
	new file:   tests/topotests/zebra_multiple_connected/r2/frr.conf
	new file:   tests/topotests/zebra_multiple_connected/r3/frr.conf

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   tests/topotests/zebra_multiple_connected/test_zebra_multiple_connected.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally