Handle Shutdown on connecting tcp socket

Fixes #6495

PiperOrigin-RevId: 398121921

4 files changed, 95 insertions, 5 deletions

diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 5d8e18484..80cd07218 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -30,6 +30,10 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// InitialRTO is the initial retransmission timeout.
+// https://github.com/torvalds/linux/blob/7c636d4d20f/include/net/tcp.h#L142
+const InitialRTO = time.Second
+
 // maxSegmentsPerWake is the maximum number of segments to process in the main
 // protocol goroutine per wake-up. Yielding [after this number of segments are
 // processed] allows other events to be processed as well (e.g., timeouts,
@@ -532,7 +536,7 @@ func (h *handshake) complete() tcpip.Error {
 	defer s.Done()
 
 	// Initialize the resend timer.
-	timer, err := newBackoffTimer(h.ep.stack.Clock(), time.Second, MaxRTO, resendWaker.Assert)
+	timer, err := newBackoffTimer(h.ep.stack.Clock(), InitialRTO, MaxRTO, resendWaker.Assert)
 	if err != nil {
 		return err
 	}
@@ -578,6 +582,9 @@ func (h *handshake) complete() tcpip.Error {
 			if (n&notifyClose)|(n&notifyAbort) != 0 {
 				return &tcpip.ErrAborted{}
 			}
+			if n&notifyShutdown != 0 {
+				return &tcpip.ErrConnectionReset{}
+			}
 			if n&notifyDrain != 0 {
 				for !h.ep.segmentQueue.empty() {
 					s := h.ep.segmentQueue.dequeue()
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 83c51e855..a3002abf3 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -187,6 +187,8 @@ const (
 	// say TIME_WAIT.
 	notifyTickleWorker
 	notifyError
+	// notifyShutdown means that a connecting socket was shutdown.
+	notifyShutdown
 )
 
 // SACKInfo holds TCP SACK related information for a given endpoint.
@@ -2384,6 +2386,18 @@ func (*endpoint) ConnectEndpoint(tcpip.Endpoint) tcpip.Error {
 func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) tcpip.Error {
 	e.LockUser()
 	defer e.UnlockUser()
+
+	if e.EndpointState().connecting() {
+		// When calling shutdown(2) on a connecting socket, the endpoint must
+		// enter the error state. But this logic cannot belong to the shutdownLocked
+		// method because that method is called during a close(2) (and closing a
+		// connecting socket is not an error).
+		e.resetConnectionLocked(&tcpip.ErrConnectionReset{})
+		e.notifyProtocolGoroutine(notifyShutdown)
+		e.waiterQueue.Notify(waiter.WritableEvents | waiter.EventHUp | waiter.EventErr)
+		return nil
+	}
+
 	return e.shutdownLocked(flags)
 }
 
diff --git a/pkg/tcpip/transport/tcp/segment_test.go b/pkg/tcpip/transport/tcp/segment_test.go
index 2e6ea06f5..2d5fdda19 100644
--- a/pkg/tcpip/transport/tcp/segment_test.go
+++ b/pkg/tcpip/transport/tcp/segment_test.go
@@ -34,7 +34,7 @@ func checkSegmentSize(t *testing.T, name string, seg *segment, want segmentSizeW
 		DataSize:   seg.data.Size(),
 		SegMemSize: seg.segMemSize(),
 	}
-	if diff := cmp.Diff(got, want); diff != "" {
+	if diff := cmp.Diff(want, got); diff != "" {
 		t.Errorf("%s differs (-want +got):\n%s", name, diff)
 	}
 }
diff --git a/pkg/tcpip/transport/tcp/tcp_test.go b/pkg/tcpip/transport/tcp/tcp_test.go
index 58817371e..6f1ee3816 100644
--- a/pkg/tcpip/transport/tcp/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/tcp_test.go
@@ -1656,6 +1656,71 @@ func TestConnectBindToDevice(t *testing.T) {
 	}
 }
 
+func TestShutdownConnectingSocket(t *testing.T) {
+	for _, test := range []struct {
+		name         string
+		shutdownMode tcpip.ShutdownFlags
+	}{
+		{"ShutdownRead", tcpip.ShutdownRead},
+		{"ShutdownWrite", tcpip.ShutdownWrite},
+		{"ShutdownReadWrite", tcpip.ShutdownRead | tcpip.ShutdownWrite},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			c := context.New(t, defaultMTU)
+			defer c.Cleanup()
+
+			// Create an endpoint, don't handshake because we want to interfere with
+			// the handshake process.
+			c.Create(-1)
+
+			waitEntry, ch := waiter.NewChannelEntry(nil)
+			c.WQ.EventRegister(&waitEntry, waiter.EventHUp)
+			defer c.WQ.EventUnregister(&waitEntry)
+
+			// Start connection attempt.
+			addr := tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}
+			if d := cmp.Diff(&tcpip.ErrConnectStarted{}, c.EP.Connect(addr)); d != "" {
+				t.Fatalf("Connect(...) mismatch (-want +got):\n%s", d)
+			}
+
+			// Check the SYN packet.
+			b := c.GetPacket()
+			checker.IPv4(t, b,
+				checker.TCP(
+					checker.DstPort(context.TestPort),
+					checker.TCPFlags(header.TCPFlagSyn),
+				),
+			)
+
+			if got, want := tcp.EndpointState(c.EP.State()), tcp.StateSynSent; got != want {
+				t.Fatalf("got State() = %s, want %s", got, want)
+			}
+
+			if err := c.EP.Shutdown(test.shutdownMode); err != nil {
+				t.Fatalf("Shutdown failed: %s", err)
+			}
+
+			// The endpoint internal state is updated immediately.
+			if got, want := tcp.EndpointState(c.EP.State()), tcp.StateError; got != want {
+				t.Fatalf("got State() = %s, want %s", got, want)
+			}
+
+			select {
+			case <-ch:
+			default:
+				t.Fatal("endpoint was not notified")
+			}
+
+			ept := endpointTester{c.EP}
+			ept.CheckReadError(t, &tcpip.ErrConnectionReset{})
+
+			// If the endpoint is not properly shutdown, it'll re-attempt to connect
+			// by sending another ACK packet.
+			c.CheckNoPacketTimeout("got an unexpected packet", tcp.InitialRTO+(500*time.Millisecond))
+		})
+	}
+}
+
 func TestSynSent(t *testing.T) {
 	for _, test := range []struct {
 		name  string
@@ -1679,7 +1744,7 @@ func TestSynSent(t *testing.T) {
 
 			addr := tcpip.FullAddress{Addr: context.TestAddr, Port: context.TestPort}
 			err := c.EP.Connect(addr)
-			if d := cmp.Diff(err, &tcpip.ErrConnectStarted{}); d != "" {
+			if d := cmp.Diff(&tcpip.ErrConnectStarted{}, err); d != "" {
 				t.Fatalf("Connect(...) mismatch (-want +got):\n%s", d)
 			}
 
@@ -1995,7 +2060,9 @@ func TestRstOnCloseWithUnreadDataFinConvertRst(t *testing.T) {
 	)
 
 	// Cause a FIN to be generated.
-	c.EP.Shutdown(tcpip.ShutdownWrite)
+	if err := c.EP.Shutdown(tcpip.ShutdownWrite); err != nil {
+		t.Fatalf("Shutdown failed: %s", err)
+	}
 
 	// Make sure we get the FIN but DON't ACK IT.
 	checker.IPv4(t, c.GetPacket(),
@@ -2011,7 +2078,9 @@ func TestRstOnCloseWithUnreadDataFinConvertRst(t *testing.T) {
 
 	// Cause a RST to be generated by closing the read end now since we have
 	// unread data.
-	c.EP.Shutdown(tcpip.ShutdownRead)
+	if err := c.EP.Shutdown(tcpip.ShutdownRead); err != nil {
+		t.Fatalf("Shutdown failed: %s", err)
+	}
 
 	// Make sure we get the RST
 	checker.IPv4(t, c.GetPacket(),