Add gonet.DialContextTCP.

Allows cancellation and timeouts.

PiperOrigin-RevId: 247090428
Change-Id: I91907f12e218677dcd0e0b6d72819deedbd9f20c

pkg/tcpip/adapters/gonet/gonet.go

@@ -16,6 +16,7 @@
 package gonet
 
 import (
+	"context"
 	"errors"
 	"io"
 	"net"
@@ -495,6 +496,12 @@ func fullToUDPAddr(addr tcpip.FullAddress) *net.UDPAddr {
 
 // DialTCP creates a new TCP Conn connected to the specified address.
 func DialTCP(s *stack.Stack, addr tcpip.FullAddress, network tcpip.NetworkProtocolNumber) (*Conn, error) {
+	return DialContextTCP(context.Background(), s, addr, network)
+}
+
+// DialContextTCP creates a new TCP Conn connected to the specified address
+// with the option of adding cancellation and timeouts.
+func DialContextTCP(ctx context.Context, s *stack.Stack, addr tcpip.FullAddress, network tcpip.NetworkProtocolNumber) (*Conn, error) {
 	// Create TCP endpoint, then connect.
 	var wq waiter.Queue
 	ep, err := s.NewEndpoint(tcp.ProtocolNumber, network, &wq)
@@ -509,9 +516,21 @@ func DialTCP(s *stack.Stack, addr tcpip.FullAddress, network tcpip.NetworkProtoc
 	wq.EventRegister(&waitEntry, waiter.EventOut)
 	defer wq.EventUnregister(&waitEntry)
 
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
 	err = ep.Connect(addr)
 	if err == tcpip.ErrConnectStarted {
-		<-notifyCh
+		select {
+		case <-ctx.Done():
+			ep.Close()
+			return nil, ctx.Err()
+		case <-notifyCh:
+		}
+
 		err = ep.GetSockOpt(tcpip.ErrorOption{})
 	}
 	if err != nil {

pkg/tcpip/adapters/gonet/gonet_test.go

@@ -15,6 +15,7 @@
 package gonet
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"net"
@@ -595,6 +596,48 @@ func TestTCPDialError(t *testing.T) {
 	}
 }
 
+func TestDialContextTCPCanceled(t *testing.T) {
+	s, err := newLoopbackStack()
+	if err != nil {
+		t.Fatalf("newLoopbackStack() = %v", err)
+	}
+
+	addr := tcpip.FullAddress{NICID, tcpip.Address(net.IPv4(169, 254, 10, 1).To4()), 11211}
+	s.AddAddress(NICID, ipv4.ProtocolNumber, addr.Addr)
+
+	ctx := context.Background()
+	ctx, cancel := context.WithCancel(ctx)
+	cancel()
+
+	if _, err := DialContextTCP(ctx, s, addr, ipv4.ProtocolNumber); err != context.Canceled {
+		t.Errorf("got DialContextTCP(...) = %v, want = %v", err, context.Canceled)
+	}
+}
+
+func TestDialContextTCPTimeout(t *testing.T) {
+	s, err := newLoopbackStack()
+	if err != nil {
+		t.Fatalf("newLoopbackStack() = %v", err)
+	}
+
+	addr := tcpip.FullAddress{NICID, tcpip.Address(net.IPv4(169, 254, 10, 1).To4()), 11211}
+	s.AddAddress(NICID, ipv4.ProtocolNumber, addr.Addr)
+
+	fwd := tcp.NewForwarder(s, 30000, 10, func(r *tcp.ForwarderRequest) {
+		time.Sleep(time.Second)
+		r.Complete(true)
+	})
+	s.SetTransportProtocolHandler(tcp.ProtocolNumber, fwd.HandlePacket)
+
+	ctx := context.Background()
+	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(100*time.Millisecond))
+	defer cancel()
+
+	if _, err := DialContextTCP(ctx, s, addr, ipv4.ProtocolNumber); err != context.DeadlineExceeded {
+		t.Errorf("got DialContextTCP(...) = %v, want = %v", err, context.DeadlineExceeded)
+	}
+}
+
 func TestNetTest(t *testing.T) {
 	nettest.TestConn(t, makePipe)
 }