DialerProxy: Fix SplitHTTP H3 dialerProxy (#3570)

* wip

* wip

* formatting

* cnc connection no longer needs to be a Packetconn

* dialerProxy: do not cancel connection when Dial context is cancelled

transport/internet/dialer.go

@@ -123,10 +123,16 @@ func redirect(ctx context.Context, dst net.Destination, obt string) net.Conn {
 		ur, uw := pipe.New(pipe.OptionsFromContext(ctx)...)
 		dr, dw := pipe.New(pipe.OptionsFromContext(ctx)...)
 
-		go h.Dispatch(ctx, &transport.Link{Reader: ur, Writer: dw})
+		go h.Dispatch(context.WithoutCancel(ctx), &transport.Link{Reader: ur, Writer: dw})
+		var readerOpt cnc.ConnectionOption
+		if dst.Network == net.Network_TCP {
+			readerOpt = cnc.ConnectionOutputMulti(dr)
+		} else {
+			readerOpt = cnc.ConnectionOutputMultiUDP(dr)
+		}
 		nc := cnc.NewConnection(
 			cnc.ConnectionInputMulti(uw),
-			cnc.ConnectionOutputMulti(dr),
+			readerOpt,
 			cnc.ConnectionOnClose(common.ChainedClosable{uw, dw}),
 		)
 		return nc

transport/internet/splithttp/dialer.go

@@ -118,7 +118,7 @@ func getHTTPClient(ctx context.Context, dest net.Destination, streamSettings *in
 					return nil, err
 				}
 
-				var udpConn *net.UDPConn
+				var udpConn net.PacketConn
 				var udpAddr *net.UDPAddr
 
 				switch c := conn.(type) {
@@ -139,7 +139,11 @@ func getHTTPClient(ctx context.Context, dest net.Destination, streamSettings *in
 						return nil, err
 					}
 				default:
-					return nil, errors.New("unsupported connection type: %T", conn)
+					udpConn = &internet.FakePacketConn{c}
+					udpAddr, err = net.ResolveUDPAddr("udp", c.RemoteAddr().String())
+					if err != nil {
+						return nil, err
+					}
 				}
 
 				return quic.DialEarly(ctx, udpConn, udpAddr, tlsCfg, cfg)

transport/internet/system_dialer.go

@@ -2,6 +2,7 @@ package internet
 
 import (
 	"context"
+	"math/rand"
 	"syscall"
 	"time"
 
@@ -221,3 +222,29 @@ func RegisterDialerController(ctl control.Func) error {
 	dialer.controllers = append(dialer.controllers, ctl)
 	return nil
 }
+
+type FakePacketConn struct {
+	net.Conn
+}
+
+func (c *FakePacketConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
+	n, err = c.Read(p)
+	return n, c.RemoteAddr(), err
+}
+
+func (c *FakePacketConn) WriteTo(p []byte, _ net.Addr) (n int, err error) {
+	return c.Write(p)
+}
+
+func (c *FakePacketConn) LocalAddr() net.Addr {
+	return &net.TCPAddr{
+		IP:   net.IP{byte(rand.Intn(256)), byte(rand.Intn(256)), byte(rand.Intn(256)), byte(rand.Intn(256))},
+		Port: rand.Intn(65536),
+	}
+}
+
+func (c *FakePacketConn) SetReadBuffer(bytes int) error {
+	// do nothing, this function is only there to suppress quic-go printing
+	// random warnings about UDP buffers to stdout
+	return nil
+}