net/tstun: add logging to aid developers missing Start calls

Since 5297bd2cff, tstun.Wrapper has required its Start method to be called for it to function. Failure to do so just results in weird hangs and I've wasted too much time multiple times now debugging. Hopefully this prevents more lost time. Updates tailscale/corp#24454 Change-Id: I87f4539f7be7dc154627f8835a37a8db88c31be0 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2025-01-16 16:04:35 -08:00 · 2025-01-16 16:04:35 -08:00 · d912a49be6
commit d912a49be6
parent de5683f7c6
1 changed files with 15 additions and 1 deletions
--- a/net/tstun/wrap.go
+++ b/net/tstun/wrap.go
@ -904,9 +904,23 @@ func (t *Wrapper) IdleDuration() time.Duration {
 	return mono.Since(t.lastActivityAtomic.LoadAtomic())
 }

+func (t *Wrapper) awaitStart() {
+	for {
+		select {
+		case <-t.startCh:
+			return
+		case <-time.After(1 * time.Second):
+			// Multiple times while remixing tailscaled I (Brad) have forgotten
+			// to call Start and then wasted far too much time debugging.
+			// I do not wish that debugging on anyone else. Hopefully this'll help:
+			t.logf("tstun: awaiting Wrapper.Start call")
+		}
+	}
+}
+
 func (t *Wrapper) Read(buffs [][]byte, sizes []int, offset int) (int, error) {
 	if !t.started.Load() {
-		<-t.startCh
+		t.awaitStart()
 	}
 	// packet from OS read and sent to WG
 	res, ok := <-t.vectorOutbound