Skip fib test on topology t1-isolated-d32u1s2

[echuawu]

Description of PR

Skip fib test on topology t1-isolated-d32u1s2
Due to there is only one nexthop in topology t1-isolated-d32u1s2 which could not meet the hash requirement

Summary:
Fixes # (issue)

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• New Test case
  • Skipped for non-supported platforms
• Test case improvement

Back port request

• 202311
• 202405
• 202411
• 202505
• 202511
• 202512
• 202605

Approach

What is the motivation for this PR?

Fib test could not run pass on topology t1-isolated-d32u1s2

How did you do it?

Skip fib test on topology t1-isolated-d32u1s2

How did you verify/test it?

Run it locally

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[mssonicbld]

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This PR has backport request for branch(es): 202511,202605.

Request label(s) for branch(es) 202511 already exists.
Added label(s) for branch(es) 202605.

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[anders-nexthop]

@echuawu thanks for this - one correctness issue to flag before it merges, because I don't think the skip takes effect as written.

The fib/test_fib.py skip block has two conditions but no conditions_logical_operator, so it defaults to AND (the list is combined with all()). The two conditions are:

• topo_name in ['t1-isolated-d128', 't1-isolated-d32', 't1-isolated-d32u1s2']
• https://github.com/sonic-net/sonic-mgmt/issues/17930 and topo_name in ['t1-isolated-d28u1']

A single topo_name can't be in both sets at once, so the AND is never satisfied and the skip never fires - adding t1-isolated-d32u1s2 to the first list won't cause the test to skip there. The same reason the original t1-isolated-d128/d32 skip has been inactive since #21733 added the second (issue-17930 / d28u1) condition without switching the block to OR. The reason string already says "...topos or due to github issue...", so OR was the intent.

The one-line fix makes all the intended skips work at once:

fib/test_fib.py:
  skip:
    reason: 'Skip on t1-isolated-d32/128 topos or due to github issue https://github.com/sonic-net/sonic-mgmt/issues/17930'
    conditions_logical_operator: or
    conditions:
      - "topo_name in ['t1-isolated-d128', 't1-isolated-d32', 't1-isolated-d32u1s2']"
      - "https://github.com/sonic-net/sonic-mgmt/issues/17930 and topo_name in ['t1-isolated-d28u1']"

conditions_logical_operator: or is the standard idiom here (~195 other blocks in this file use it for multi-reason skips). Worth confirming on a t1-isolated-d32u1s2 testbed that the test is collected-and-skipped after the change.

— anders-bot (AI-assisted, on behalf of @anders-nexthop)