From f5d1075cd49c7a7ab6545aae22ed9875a69778a3 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Thu, 11 Dec 2025 08:46:53 -0800
Subject: [PATCH] ipn/ipnlocal: avoid ResetAndStop panic

Updates #18187

Change-Id: If7375efb7df0452a5e85b742fc4c4eecbbd62717
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
(cherry picked from commit 0df463130889799588b95e63c0040be3501ec8b4)
---
 ipn/ipnlocal/local.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/ipn/ipnlocal/local.go b/ipn/ipnlocal/local.go
index 998c10196..a95b7b921 100644
--- a/ipn/ipnlocal/local.go
+++ b/ipn/ipnlocal/local.go
@@ -5768,7 +5768,14 @@ func (b *LocalBackend) stateMachineLocked() {
 // b.mu must be held.
 func (b *LocalBackend) stopEngineAndWaitLocked() {
 	b.logf("stopEngineAndWait...")
-	st, _ := b.e.ResetAndStop() // TODO: what should we do if this returns an error?
+	st, err := b.e.ResetAndStop()
+	if err != nil {
+		// TODO(braditz): our caller, popBrowserAuthNowLocked, probably
+		// should handle this somehow. For now, just log it.
+		// See tailscale/tailscale#18187
+		b.logf("stopEngineAndWait: ResetAndStop error: %v", err)
+		return
+	}
 	b.setWgengineStatusLocked(st)
 	b.logf("stopEngineAndWait: done.")
 }