Skip `EventHUp` notify in `FIN_WAIT2` on a socket close.

This Notify was added as part of cl/279106406; but notifying `EventHUp`
in `FIN_WAIT2` is incorrect, as we want to only notify later on
`TIME_WAIT` or a reset. However, we do need to notify any blocked
waiters of an activity on the endpoint with `EventIn`|`EventOut`.

PiperOrigin-RevId: 341490913

3 files changed, 9 insertions, 7 deletions

diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 2facbebec..6e9015be1 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -1451,7 +1451,6 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 						// The socket has been closed and we are in FIN_WAIT2
 						// so start the FIN_WAIT2 timer.
 						closeTimer = time.AfterFunc(e.tcpLingerTimeout, closeWaker.Assert)
-						e.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
 					}
 				}
 
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 258f9f1bb..23b9de8c5 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1069,9 +1069,7 @@ func (e *endpoint) Close() {
 	e.closeNoShutdownLocked()
 }
 
-// closeNoShutdown closes the endpoint without doing a full shutdown. This is
-// used when a connection needs to be aborted with a RST and we want to skip
-// a full 4 way TCP shutdown.
+// closeNoShutdown closes the endpoint without doing a full shutdown.
 func (e *endpoint) closeNoShutdownLocked() {
 	// For listening sockets, we always release ports inline so that they
 	// are immediately available for reuse after Close() is called. If also
@@ -1098,6 +1096,7 @@ func (e *endpoint) closeNoShutdownLocked() {
 		return
 	}
 
+	eventMask := waiter.EventIn | waiter.EventOut
 	// Either perform the local cleanup or kick the worker to make sure it
 	// knows it needs to cleanup.
 	if e.workerRunning {
@@ -1109,8 +1108,12 @@ func (e *endpoint) closeNoShutdownLocked() {
 	} else {
 		e.transitionToStateCloseLocked()
 		// Notify that the endpoint is closed.
-		e.waiterQueue.Notify(waiter.EventHUp)
+		eventMask |= waiter.EventHUp
 	}
+
+	// The TCP closing state-machine would eventually notify EventHUp, but we
+	// notify EventIn|EventOut immediately to unblock any blocked waiters.
+	e.waiterQueue.Notify(eventMask)
 }
 
 // closePendingAcceptableConnections closes all connections that have completed
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 5f05608e2..fcc3c5000 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -63,7 +63,7 @@ func TestGiveUpConnect(t *testing.T) {
 
 	// Register for notification, then start connection attempt.
 	waitEntry, notifyCh := waiter.NewChannelEntry(nil)
-	wq.EventRegister(&waitEntry, waiter.EventOut)
+	wq.EventRegister(&waitEntry, waiter.EventHUp)
 	defer wq.EventUnregister(&waitEntry)
 
 	if err := ep.Connect(tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}); err != tcpip.ErrConnectStarted {
@@ -1448,7 +1448,7 @@ func TestSynSent(t *testing.T) {
 
 			// Start connection attempt.
 			waitEntry, ch := waiter.NewChannelEntry(nil)
-			c.WQ.EventRegister(&waitEntry, waiter.EventOut)
+			c.WQ.EventRegister(&waitEntry, waiter.EventHUp)
 			defer c.WQ.EventUnregister(&waitEntry)
 
 			addr := tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}