fix DNS update on IPv6-triggered WAN switch

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[j-sallyjin]

PR Review Summary

✅ What looks good

• Adds _applyActiveGlobalDefaultRoutingAndNotify() to centralize WAN-switch notification behavior.
• Keeps IPv6-triggered route re-application publishing EVENT_WAN_SWITCHED only when the active WAN set/order changes.
• Uses ordered active WAN names for comparison, which is better than only checking count or truthiness.
• PR metadata was accessible; title is fix DNS update on IPv6-triggered WAN switch. No linked issue found in title/body/comments.

⚠️ Issues found

• No linked issue found.

• Medium — notification may be missed when _wanStatus is updated before comparison.
  In the apply() path, this._wanStatus = wanStatus happens before _applyActiveGlobalDefaultRoutingAndNotify(false) is called. Since _applyActiveGlobalDefaultRouting() captures activeWANsBefore from this._wanStatus, the “before” snapshot may already contain the new active WAN state, making wanSwitched false even when the active WAN changed. If this path is expected to emit EVENT_WAN_SWITCHED, capture the old active WANs before assigning this._wanStatus, or pass the previous active WAN list into the helper.

💡 Suggestions

• Add regression coverage for:
  • IPv6 route recalculation changes active WAN → emits EVENT_WAN_SWITCHED
  • regular apply() changes active WAN → emits EVENT_WAN_SWITCHED
  • route recalculation without active WAN change → does not emit
• Consider logging active WAN arrays with JSON.stringify() to avoid ambiguous comma-joined output.

Verdict

REQUEST_CHANGES

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Repo: firewalla/firerouter
PR: #1855
Head SHA: a5776a86362759f1ddf408ed8a07356c92b8a914
Checked at: 2026-05-12 11:16:56 CST