Fix Accept to not return error for sockets in accept queue.

Accept on gVisor will return an error if a socket in the accept queue was closed
before Accept() was called. Linux will return the new fd even if the returned
socket is already closed by the peer say due to a RST being sent by the peer.

This seems to be intentional in linux more details on the github issue.

Fixes #3780

PiperOrigin-RevId: 329828404

4 files changed, 73 insertions, 70 deletions

diff --git a/pkg/tcpip/transport/tcp/dual_stack_test.go b/pkg/tcpip/transport/tcp/dual_stack_test.go
index 6074cc24e..80e9dd465 100644
--- a/pkg/tcpip/transport/tcp/dual_stack_test.go
+++ b/pkg/tcpip/transport/tcp/dual_stack_test.go
@@ -371,12 +371,12 @@ func testV4Accept(t *testing.T, c *context.Context) {
 	c.WQ.EventRegister(&we, waiter.EventIn)
 	defer c.WQ.EventUnregister(&we)
 
-	nep, _, err := c.EP.Accept()
+	nep, _, err := c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			nep, _, err = c.EP.Accept()
+			nep, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %v", err)
 			}
@@ -510,13 +510,13 @@ func TestV6AcceptOnV6(t *testing.T) {
 	we, ch := waiter.NewChannelEntry(nil)
 	c.WQ.EventRegister(&we, waiter.EventIn)
 	defer c.WQ.EventUnregister(&we)
-
-	nep, _, err := c.EP.Accept()
+	var addr tcpip.FullAddress
+	nep, _, err := c.EP.Accept(&addr)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			nep, _, err = c.EP.Accept()
+			nep, _, err = c.EP.Accept(&addr)
 			if err != nil {
 				t.Fatalf("Accept failed: %v", err)
 			}
@@ -526,20 +526,14 @@ func TestV6AcceptOnV6(t *testing.T) {
 		}
 	}
 
+	if addr.Addr != context.TestV6Addr {
+		t.Errorf("Unexpected remote address: got %s, want %s", addr.Addr, context.TestV6Addr)
+	}
+
 	// Make sure we can still query the v6 only status of the new endpoint,
 	// that is, that it is in fact a v6 socket.
 	if _, err := nep.GetSockOptBool(tcpip.V6OnlyOption); err != nil {
-		t.Fatalf("GetSockOpt failed failed: %v", err)
-	}
-
-	// Check the peer address.
-	addr, err := nep.GetRemoteAddress()
-	if err != nil {
-		t.Fatalf("GetRemoteAddress failed failed: %v", err)
-	}
-
-	if addr.Addr != context.TestV6Addr {
-		t.Fatalf("Unexpected remote address: got %v, want %v", addr.Addr, context.TestV6Addr)
+		t.Errorf("GetSockOptBool(tcpip.V6OnlyOption) failed: %s", err)
 	}
 }
 
@@ -610,12 +604,12 @@ func testV4ListenClose(t *testing.T, c *context.Context) {
 	we, ch := waiter.NewChannelEntry(nil)
 	c.WQ.EventRegister(&we, waiter.EventIn)
 	defer c.WQ.EventUnregister(&we)
-	nep, _, err := c.EP.Accept()
+	nep, _, err := c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			nep, _, err = c.EP.Accept()
+			nep, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %v", err)
 			}
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 3f18efeef..4cf966b65 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -2453,7 +2453,9 @@ func (e *endpoint) startAcceptedLoop() {
 
 // Accept returns a new endpoint if a peer has established a connection
 // to an endpoint previously set to listen mode.
-func (e *endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
+//
+// addr if not-nil will contain the peer address of the returned endpoint.
+func (e *endpoint) Accept(peerAddr *tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
 	e.LockUser()
 	defer e.UnlockUser()
 
@@ -2475,6 +2477,9 @@ func (e *endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
 	default:
 		return nil, nil, tcpip.ErrWouldBlock
 	}
+	if peerAddr != nil {
+		*peerAddr = n.getRemoteAddress()
+	}
 	return n, n.waiterQueue, nil
 }
 
@@ -2577,11 +2582,15 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
 		return tcpip.FullAddress{}, tcpip.ErrNotConnected
 	}
 
+	return e.getRemoteAddress(), nil
+}
+
+func (e *endpoint) getRemoteAddress() tcpip.FullAddress {
 	return tcpip.FullAddress{
 		Addr: e.ID.RemoteAddress,
 		Port: e.ID.RemotePort,
 		NIC:  e.boundNICID,
-	}, nil
+	}
 }
 
 func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) {
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index adb32e428..3d09d6def 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -291,12 +291,12 @@ func TestTCPResetSentForACKWhenNotUsingSynCookies(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -2203,12 +2203,12 @@ func TestScaledWindowAccept(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -2277,12 +2277,12 @@ func TestNonScaledWindowAccept(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -2840,12 +2840,12 @@ func TestPassiveSendMSSLessThanMTU(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -2895,12 +2895,12 @@ func TestSynCookiePassiveSendMSSLessThanMTU(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5135,12 +5135,12 @@ func TestListenBacklogFull(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	for i := 0; i < listenBacklog; i++ {
-		_, _, err = c.EP.Accept()
+		_, _, err = c.EP.Accept(nil)
 		if err == tcpip.ErrWouldBlock {
 			// Wait for connection to be established.
 			select {
 			case <-ch:
-				_, _, err = c.EP.Accept()
+				_, _, err = c.EP.Accept(nil)
 				if err != nil {
 					t.Fatalf("Accept failed: %s", err)
 				}
@@ -5152,7 +5152,7 @@ func TestListenBacklogFull(t *testing.T) {
 	}
 
 	// Now verify that there are no more connections that can be accepted.
-	_, _, err = c.EP.Accept()
+	_, _, err = c.EP.Accept(nil)
 	if err != tcpip.ErrWouldBlock {
 		select {
 		case <-ch:
@@ -5164,12 +5164,12 @@ func TestListenBacklogFull(t *testing.T) {
 	// Now a new handshake must succeed.
 	executeHandshake(t, c, context.TestPort+2, false /*synCookieInUse */)
 
-	newEP, _, err := c.EP.Accept()
+	newEP, _, err := c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			newEP, _, err = c.EP.Accept()
+			newEP, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5476,12 +5476,12 @@ func TestListenSynRcvdQueueFull(t *testing.T) {
 	c.WQ.EventRegister(&we, waiter.EventIn)
 	defer c.WQ.EventUnregister(&we)
 
-	newEP, _, err := c.EP.Accept()
+	newEP, _, err := c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			newEP, _, err = c.EP.Accept()
+			newEP, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5552,12 +5552,12 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
 	c.WQ.EventRegister(&we, waiter.EventIn)
 	defer c.WQ.EventUnregister(&we)
 
-	_, _, err = c.EP.Accept()
+	_, _, err = c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			_, _, err = c.EP.Accept()
+			_, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5568,7 +5568,7 @@ func TestListenBacklogFullSynCookieInUse(t *testing.T) {
 	}
 
 	// Now verify that there are no more connections that can be accepted.
-	_, _, err = c.EP.Accept()
+	_, _, err = c.EP.Accept(nil)
 	if err != tcpip.ErrWouldBlock {
 		select {
 		case <-ch:
@@ -5657,7 +5657,7 @@ func TestSynRcvdBadSeqNumber(t *testing.T) {
 		RcvWnd:  30000,
 	})
 
-	newEP, _, err := c.EP.Accept()
+	newEP, _, err := c.EP.Accept(nil)
 
 	if err != nil && err != tcpip.ErrWouldBlock {
 		t.Fatalf("Accept failed: %s", err)
@@ -5672,7 +5672,7 @@ func TestSynRcvdBadSeqNumber(t *testing.T) {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			newEP, _, err = c.EP.Accept()
+			newEP, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5730,12 +5730,12 @@ func TestPassiveConnectionAttemptIncrement(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	// Verify that there is only one acceptable connection at this point.
-	_, _, err = c.EP.Accept()
+	_, _, err = c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			_, _, err = c.EP.Accept()
+			_, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5800,12 +5800,12 @@ func TestPassiveFailedConnectionAttemptIncrement(t *testing.T) {
 	defer c.WQ.EventUnregister(&we)
 
 	// Now check that there is one acceptable connections.
-	_, _, err = c.EP.Accept()
+	_, _, err = c.EP.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			_, _, err = c.EP.Accept()
+			_, _, err = c.EP.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -5853,12 +5853,12 @@ func TestEndpointBindListenAcceptState(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	aep, _, err := ep.Accept()
+	aep, _, err := ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			aep, _, err = ep.Accept()
+			aep, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -6293,12 +6293,12 @@ func TestTCPTimeWaitRSTIgnored(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -6412,12 +6412,12 @@ func TestTCPTimeWaitOutOfOrder(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -6519,12 +6519,12 @@ func TestTCPTimeWaitNewSyn(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -6602,12 +6602,12 @@ func TestTCPTimeWaitNewSyn(t *testing.T) {
 	c.SendPacket(nil, ackHeaders)
 
 	// Try to accept the connection.
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -6675,12 +6675,12 @@ func TestTCPTimeWaitDuplicateFINExtendsTimeWait(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -6824,12 +6824,12 @@ func TestTCPCloseWithData(t *testing.T) {
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				t.Fatalf("Accept failed: %s", err)
 			}
@@ -7271,8 +7271,8 @@ func TestTCPDeferAccept(t *testing.T) {
 
 	irs, iss := executeHandshake(t, c, context.TestPort, false /* synCookiesInUse */)
 
-	if _, _, err := c.EP.Accept(); err != tcpip.ErrWouldBlock {
-		t.Fatalf("c.EP.Accept() returned unexpected error got: %s, want: %s", err, tcpip.ErrWouldBlock)
+	if _, _, err := c.EP.Accept(nil); err != tcpip.ErrWouldBlock {
+		t.Fatalf("got c.EP.Accept(nil) = %s, want: %s", err, tcpip.ErrWouldBlock)
 	}
 
 	// Send data. This should result in an acceptable endpoint.
@@ -7293,9 +7293,9 @@ func TestTCPDeferAccept(t *testing.T) {
 
 	// Give a bit of time for the socket to be delivered to the accept queue.
 	time.Sleep(50 * time.Millisecond)
-	aep, _, err := c.EP.Accept()
+	aep, _, err := c.EP.Accept(nil)
 	if err != nil {
-		t.Fatalf("c.EP.Accept() returned unexpected error got: %s, want: nil", err)
+		t.Fatalf("got c.EP.Accept(nil) = %s, want: nil", err)
 	}
 
 	aep.Close()
@@ -7329,8 +7329,8 @@ func TestTCPDeferAcceptTimeout(t *testing.T) {
 
 	irs, iss := executeHandshake(t, c, context.TestPort, false /* synCookiesInUse */)
 
-	if _, _, err := c.EP.Accept(); err != tcpip.ErrWouldBlock {
-		t.Fatalf("c.EP.Accept() returned unexpected error got: %s, want: %s", err, tcpip.ErrWouldBlock)
+	if _, _, err := c.EP.Accept(nil); err != tcpip.ErrWouldBlock {
+		t.Fatalf("got c.EP.Accept(nil) = %s, want: %s", err, tcpip.ErrWouldBlock)
 	}
 
 	// Sleep for a little of the tcpDeferAccept timeout.
@@ -7362,9 +7362,9 @@ func TestTCPDeferAcceptTimeout(t *testing.T) {
 
 	// Give sometime for the endpoint to be delivered to the accept queue.
 	time.Sleep(50 * time.Millisecond)
-	aep, _, err := c.EP.Accept()
+	aep, _, err := c.EP.Accept(nil)
 	if err != nil {
-		t.Fatalf("c.EP.Accept() returned unexpected error got: %s, want: nil", err)
+		t.Fatalf("got c.EP.Accept(nil) = %s, want: nil", err)
 	}
 
 	aep.Close()
diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go
index 1f5340cd0..8bb5e5f6d 100644
--- a/pkg/tcpip/transport/tcp/testing/context/context.go
+++ b/pkg/tcpip/transport/tcp/testing/context/context.go
@@ -948,12 +948,12 @@ func (c *Context) AcceptWithOptions(wndScale int, synOptions header.TCPSynOption
 	wq.EventRegister(&we, waiter.EventIn)
 	defer wq.EventUnregister(&we)
 
-	c.EP, _, err = ep.Accept()
+	c.EP, _, err = ep.Accept(nil)
 	if err == tcpip.ErrWouldBlock {
 		// Wait for connection to be established.
 		select {
 		case <-ch:
-			c.EP, _, err = ep.Accept()
+			c.EP, _, err = ep.Accept(nil)
 			if err != nil {
 				c.t.Fatalf("Accept failed: %v", err)
 			}