Fix Android internet blackhole caused by stale route re-injection on TUN rebuild

[pappz]

Problem

After upgrading to v0.4.0, Android users lose all internet connectivity while the VPN is active.

• Internal NetBird mesh traffic continues to work
• External traffic (e.g., ping duckduckgo.com) results in 100% packet loss
• Downgrading to v0.3.2 resolves the issue
• Bump Netbird submodule version to v0.68.2

Fixes #158

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Root Cause

The netbird submodule was bumped from v0.64.1 → v0.68.0, which included [netbirdio/netbird#5739].

That change introduced extraInitialRoutes() to preserve the fake IP block route (240.0.0.0/8) across Android TUN rebuilds. Without it, DNS resolution via fake IPs breaks after the first route update.

However, the implementation has an unintended side effect:

• extraInitialRoutes() diffs all initial routes against current routes and re-injects missing ones
• The initial route set includes:
  • All client routes from the first management sync
  • Exit node routes (e.g., 0.0.0.0/0)

When FilterSelectedExitNodes removes an unselected exit node:

• extraInitialRoutes() re-injects 0.0.0.0/0 during TUN rebuild
• This causes Android VPN to:
  • Capture all traffic
  • Have no exit node to route it through

➡️ Result: routing black hole (total internet loss)

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Fix

Instead of diffing and re-injecting the entire initial route set:

• Store the fake IP route (240.0.0.0/8) explicitly on the notifier
• Append only this route in notify()

Summary by CodeRabbit

• Chores
  • Updated an internal dependency to a newer upstream revision to incorporate recent fixes and maintenance. No public API changes or user-facing differences expected. Low review effort; minimal changes overall.

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request updates the netbird git submodule reference from commit 332c624c55a486c0ab7b981a26cf8e00a6fa0774 to commit 4eed459f27bd7e90faa7fe99e1edf4a59dc71265.

Changes

Cohort / File(s)	Summary
Submodule Update netbird	Bumped the netbird git submodule reference to a newer commit (332c624c... → 4eed459f...). No other source changes in this diff.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• Update submodule to v0.61.0 #124: Also updates the netbird submodule pointer (different target commit).
• Bump the Netbird submodule to v0.68.0 #156: Previously updated the netbird submodule pointer to commit 332c624c..., which this PR advances further.

Suggested reviewers

• doromaraujo
• lixmal

Poem

🐰 I hopped through hashes, quick and light,
Swapped one little tag in the pale moonlight.
A tiny leap, a silent cheer,
New commit found — the path is clear.
✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly describes the main fix: preventing stale route re-injection on TUN rebuild that caused Android internet loss, matching the PR's core objective.
Linked Issues check	✅ Passed	The PR addresses issue #158 by fixing the stale route re-injection problem during TUN rebuilds, restoring external internet connectivity for Android clients.
Out of Scope Changes check	✅ Passed	The change is limited to updating the netbird submodule reference to a patched version addressing the specific routing issue, remaining in scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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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 fix/android-route-blackhole-on-tun-rebuild

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