ARP: Iterate over states safely as the cb could remove ours

[rsmarples]

Reported by NVIDIA Project Vanessa

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a4d444d2-0395-46a1-ba15-c025f3ca5f9f

📥 Commits

Reviewing files that changed from the base of the PR and between e636ba2 and 32604bd.

📒 Files selected for processing (1)

• src/arp.c

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Walkthrough

In src/arp.c, the arp_announce() function's loop over ARP states is changed from TAILQ_FOREACH to TAILQ_FOREACH_SAFE with an added temporary pointer an, preventing iterator invalidation if arp_announced() frees the current state during iteration.

Changes

Safe ARP state iteration in arp_announce()

Layer / File(s)	Summary
TAILQ_FOREACH_SAFE fix src/arp.c	Introduces the an pointer and switches to TAILQ_FOREACH_SAFE so the loop remains valid even when arp_announced(a2) triggers removal or freeing of the current ARP state entry.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: switching from unsafe TAILQ_FOREACH to TAILQ_FOREACH_SAFE iteration to prevent crashes when callbacks remove states during iteration.
Description check	✅ Passed	The description references the reporting source (NVIDIA Project Vanessa) which contextualizes the fix, relating it to the actual safety issue being addressed in the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch arp

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