[PR #6224] [MERGED] [client] Fix nil channel panic in external chain monitor stop #29182

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saavagebueno · 2026-08-05T08:07:37-04:00

saavagebueno commented

2026-08-05 08:07:37 -04:00

📋 Pull Request Information

Original PR: https://github.com/netbirdio/netbird/pull/6224
Author: @lixmal
Created: 5/20/2026
Status: ✅ Merged
Merged: 5/20/2026
Merged by: @mlsmaycon

Base: main ← Head: fix-external-chain-monitor-panic

📝 Commits (1)

ce5a694 Fix nil channel panic in external chain monitor stop

📊 Changes

1 file changed (+5 additions, -4 deletions)

View changed files

📝 client/firewall/nftables/external_chain_monitor_linux.go (+5 -4)

📄 Description

Describe your changes

externalChainMonitor.stop() nilled m.done before the monitor goroutine's defer close(m.done) ran, causing panic: close of nil channel when the engine shut down while the monitor was still active (e.g. after a failed wireguard interface bring-up).

Pass the done channel as a goroutine parameter so the run goroutine holds its own reference and can't race with stop() nilling the field

Issue ticket number and link

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Checklist

Is it a bug fix
Is a typo/documentation fix
Is a feature enhancement
It is a refactor
Created tests that fail without the change (if possible)
This change does not modify the public API, gRPC protocols, functionality behavior, CLI / service flags, or introduce a new feature — OR I have discussed it with the NetBird team beforehand (link the issue / Slack thread in the description). See CONTRIBUTING.md.

By submitting this pull request, you confirm that you have read and agree to the terms of the Contributor License Agreement.

Documentation

Select exactly one:

I added/updated documentation for this change
Documentation is not needed for this change (explain why)

Internal bug fix, no user-facing surface.

Docs PR URL (required if "docs added" is checked)

Paste the PR link from https://github.com/netbirdio/docs here:

https://github.com/netbirdio/docs/pull/__

Summary by CodeRabbit

Refactor
- Improved internal lifecycle management for the firewall chain monitor to enhance code reliability and maintainability.

_{🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.}

## 📋 Pull Request Information **Original PR:** https://github.com/netbirdio/netbird/pull/6224 **Author:** [@lixmal](https://github.com/lixmal) **Created:** 5/20/2026 **Status:** ✅ Merged **Merged:** 5/20/2026 **Merged by:** [@mlsmaycon](https://github.com/mlsmaycon) **Base:** `main` ← **Head:** `fix-external-chain-monitor-panic` --- ### 📝 Commits (1) - [`ce5a694`](https://github.com/netbirdio/netbird/commit/ce5a694d0f6c2a555a67706155de11d523ed7e3b) Fix nil channel panic in external chain monitor stop ### 📊 Changes **1 file changed** (+5 additions, -4 deletions) <details> <summary>View changed files</summary> 📝 `client/firewall/nftables/external_chain_monitor_linux.go` (+5 -4) </details> ### 📄 Description ## Describe your changes `externalChainMonitor.stop()` nilled `m.done` before the monitor goroutine's `defer close(m.done)` ran, causing `panic: close of nil channel` when the engine shut down while the monitor was still active (e.g. after a failed wireguard interface bring-up). - Pass the done channel as a goroutine parameter so the run goroutine holds its own reference and can't race with `stop()` nilling the field ## Issue ticket number and link ## Stack  ### Checklist - [x] Is it a bug fix - [ ] Is a typo/documentation fix - [ ] Is a feature enhancement - [ ] It is a refactor - [ ] Created tests that fail without the change (if possible) - [x] This change does **not** modify the public API, gRPC protocols, functionality behavior, CLI / service flags, or introduce a new feature — **OR** I have discussed it with the NetBird team beforehand (link the issue / Slack thread in the description). See [CONTRIBUTING.md](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTING.md#discuss-changes-with-the-netbird-team-first). > By submitting this pull request, you confirm that you have read and agree to the terms of the [Contributor License Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md). ## Documentation Select exactly one: - [ ] I added/updated documentation for this change - [x] Documentation is **not needed** for this change (explain why) Internal bug fix, no user-facing surface. ### Docs PR URL (required if "docs added" is checked) Paste the PR link from https://github.com/netbirdio/docs here: https://github.com/netbirdio/docs/pull/__  ## Summary by CodeRabbit * **Refactor** * Improved internal lifecycle management for the firewall chain monitor to enhance code reliability and maintainability.  [![Review Change Stack](https://storage.googleapis.com/coderabbit_public_assets/review-stack-in-coderabbit-ui.svg)](https://app.coderabbit.ai/change-stack/netbirdio/netbird/pull/6224?utm_source=github_walkthrough&utm_medium=github&utm_campaign=change_stack)   --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>

saavagebueno added the pull-request label 2026-08-05 08:07:37 -04:00

saavagebueno closed this issue

2026-08-05 08:07:37 -04:00

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Reference: DYNR/netbird#29182