Fix data race on the socket disconnect handler

[jlucaso1]

FrameSocket.OnDisconnect was read and written without shared synchronization.

Close reads the handler while holding fs.lock, but newNoiseSocket installed it with a plain assignment and NoiseSocket.Stop cleared it with a plain assignment. When a remote close landed at the same time as socket setup or teardown, those accesses raced. The read pump calls Close(0) when the peer goes away, so this was reachable in normal operation, not just in tests.

This change adds FrameSocket.SetOnDisconnect, which replaces the handler under fs.lock, and switches both writers to use it. The read in Close already holds the lock, so every access is now serialized. The callback itself still runs in its own goroutine after the lock is released, so the locking behavior of Close is unchanged. A comment on the field points at the setter.

Also adds socket/noisesocket_test.go with concurrent close/setup/teardown tests plus table coverage of Stop with and without disconnect callbacks.

Verified:

• go build ./... passes.
• go test -race -count=1 ./socket/ passes.
• The new concurrent tests fail with race detected against the pre-fix files and pass with the fix applied.

Drive-by CI fix (no relation to the race): the Build (old) job installs goimports@latest, which now resolves to x/tools v0.50.0 and needs go >= 1.26, while the job pins go 1.25.14 with GOTOOLCHAIN=local. The same failure hits main. This PR pins the install to x/tools v0.49.0, the newest release that still builds on go 1.25.

Summary by CodeRabbit

• Bug Fixes

  • Improved socket shutdown handling during concurrent close and stop operations.
  • Disconnect callbacks now behave more consistently for local and remote disconnects, including repeated shutdown attempts.
  • Prevented stale disconnect handlers from remaining active after a socket is stopped.

• New Features

  • Added a supported way to safely update a socket’s disconnect handler while the socket is in use.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-09T21:10:07.332622Z	7668f7a	PR opened

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

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Run ID: 4a4bcd1e-ef1a-4752-83f3-002e791f6e19

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Reviewing files that changed from the base of the PR and between a682fb7 and 9c9a065.

📒 Files selected for processing (1)

• socket/noisesocket_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• socket/noisesocket_test.go

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📝 Walkthrough

Walkthrough

FrameSocket now provides synchronized disconnect-handler replacement. NoiseSocket uses this API during setup and shutdown. WebSocket-backed tests cover concurrent closure, construction races, callback behavior, and remote disconnect cleanup. The Go workflow pins goimports to v0.49.0.

Changes

Disconnect handler safety

Layer / File(s)	Summary
FrameSocket handler API socket/framesocket.go	Adds SetOnDisconnect, which replaces the handler while holding the socket lock.
NoiseSocket handler wiring socket/noisesocket.go	Registers and clears the disconnect handler through SetOnDisconnect.
Shutdown race validation socket/noisesocket_test.go	Adds tests for concurrent shutdown, construction during closure, local and remote disconnects, callback behavior, and cleanup.

Workflow toolchain pinning

Layer / File(s)	Summary
Workflow toolchain pinning .github/workflows/go.yml	Pins goimports to v0.49.0 for the Go 1.25 job.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 9c9a0

This change synchronizes disconnect-handler updates during socket setup and shutdown, with concurrent socket lifecycle coverage. No current merge-blocking risk remains.

🚥 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly and concisely describes the primary change: fixing the data race on the socket disconnect handler.
Description check	✅ Passed	The description clearly explains the race, the synchronization fix, the tests, verification results, and the related CI fix. It does not include the template checklist, but the main required change in…

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

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Inline comments:
In `@socket/noisesocket_test.go`:
- Line 28: Update the deferred conn.CloseNow call in the test to assign its
error result to the blank identifier, satisfying errcheck without changing the
cleanup behavior.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 930f02e5-bbbf-4490-ba4d-b6b86de66ee6

📥 Commits

Reviewing files that changed from the base of the PR and between 07d103b and 7668f7a.

📒 Files selected for processing (3)

• socket/framesocket.go
• socket/noisesocket.go
• socket/noisesocket_test.go

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[chatgpt-codex-connector]

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Reviewed commit: 7668f7aeba

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