Fix for panic in endpoint.Close().

When sending a RST on shutdown we need to double check the
state after acquiring the work mutex as the endpoint could
have transitioned out of a connected state from the time
we checked it and we acquired the workMutex.

I added two tests but sadly neither reproduce the panic. I am
going to leave the tests in as they are good to have anyway.

PiperOrigin-RevId: 292393800

1 files changed, 8 insertions, 2 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 8d52414b7..b5a8e15ee 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2047,8 +2047,14 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
 				// work mutex is available.
 				if e.workMu.TryLock() {
 					e.mu.Lock()
-					e.resetConnectionLocked(tcpip.ErrConnectionAborted)
-					e.notifyProtocolGoroutine(notifyTickleWorker)
+					// We need to double check here to make
+					// sure worker has not transitioned the
+					// endpoint out of a connected state
+					// before trying to send a reset.
+					if e.EndpointState().connected() {
+						e.resetConnectionLocked(tcpip.ErrConnectionAborted)
+						e.notifyProtocolGoroutine(notifyTickleWorker)
+					}
 					e.mu.Unlock()
 					e.workMu.Unlock()
 				} else {