Server.Close held s.mu for the entire shutdown duration, including
netstack.Close (which waits for gVisor goroutines to exit) and
lb.Shutdown. gVisor callbacks like getTCPHandlerForFlow acquire s.mu via
listenerForDstAddr, so any in-flight gVisor goroutine attempting that
callback during stack shutdown would deadlock with Close.
Replace the mu-guarded closed bool with a sync.Once, and release s.mu
after closing listeners but before the heavy shutdown operations. Also
cancel shutdownCtx before netstack.Close so pending handlers observe
cancellation rather than contending on the lock.
Updates #18423
Signed-off-by: James Tucker <james@tailscale.com>
James TuckerandJames Tucker
fa13f83375