[test-only][DO NOT MERGE] Pin sonic-sairedis to the MPLS VPP branch to build a test image

[augusdn]

Description of PR

This is a throwaway test-only PR. It must never be merged, and I will close it once the image has been built.

It pins src/sonic-sairedis to the branch behind sonic-net/sonic-sairedis#2008 (commit 16005ff) so the pipeline produces a real sonic-vs/vpp image containing the VPP SAI MPLS backend.

That image is needed to validate sonic-net/sonic-mgmt#26619 end to end before either PR merges. Without it the newly enabled tests/mpls cases have no backend to talk to, so kvmtest-t1-lag-vpp on that PR cannot pass no matter how correct the test code is.

Thanks to @lolyu for suggesting this approach (same mechanism as #27555).

Type of change

• Test only / not for merge

Approach

What is the motivation for this PR?

sonic-buildimage#25782 asks for MPLS data-plane support on sonic-vpp. The work is split across two PRs:

• [vpp] Add MPLS data-plane support (INSEG + IP-route push) sonic-sairedis#2008 — the VPP SAI MPLS backend (INSEG + IP-route push)
• [mpls][sonic-vpp] Enable MPLS data-plane tests on the VPP t1-lag testbed sonic-mgmt#26619 — enabling tests/mpls on the t1-lag-vpp testbed

They are mutually dependent for validation: the tests need the backend in the image, and the backend has no automated coverage without the tests. This PR breaks that cycle by building an image from the unmerged backend.

How did you do it?

Two changes only:

• .gitmodules — point the sonic-sairedis submodule at augusdn/sonic-sairedis, branch augusdn/vpp-mpls-inseg-25782
• src/sonic-sairedis — bump the submodule pointer to 16005ff1e744c4aa85964be6d3702e2635341d58

How did you verify/test it?

The backend has already been validated on a local KVM testbed with the library installed into syncd:

mpls/test_mpls.py::TestBasicMpls::test_pop_label        PASSED
mpls/test_mpls.py::TestBasicMpls::test_swap_label       PASSED
mpls/test_mpls.py::TestBasicMpls::test_push_label       SKIPPED
mpls/test_mpls.py::TestBasicMpls::test_swap_labelstack  PASSED

and the full surrounding framework run on the same testbed was 17 passed, 5 skipped, 0 failed. sonic-sairedis#2008's own CI is green across all nine build jobs plus ASAN, CodeQL and Semgrep.

This PR exists purely to produce the image artifact so the same result can be reproduced on Elastictest against a properly built image rather than a hot-swapped library.

Documentation

No documentation change — test-only, not for merge.

[mssonicbld]

/azp run Azure.sonic-buildimage

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[Copilot]

🟡 Not ready to approve

The submodule is repointed to a personal fork/branch, which is not acceptable for a mergeable change due to supply-chain and long-term reproducibility risk.

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Pull request overview

Pins the sonic-sairedis git submodule configuration to a non-upstream repository/branch to enable CI to build a sonic-vs/VPP test image that includes the MPLS-capable VPP SAI backend for end-to-end validation with sonic-mgmt MPLS tests.

Changes:

• Repoints the src/sonic-sairedis submodule URL from sonic-net/sonic-sairedis to augusdn/sonic-sairedis.
• Adds a branch = augusdn/vpp-mpls-inseg-25782 tracking hint for that submodule.

File summaries

File	Description
.gitmodules	Repoints the sonic-sairedis submodule source (and adds a branch hint) to build a test image from an unmerged backend branch.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

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