Merge pull request #651 from v2ray/udpfollow

Added UDP TPROXY Transmit Support

proxy/dokodemo/dokodemo.go

@@ -7,6 +7,8 @@ import (
 	"runtime"
 	"time"
 
+	gonet "net"
+
 	"v2ray.com/core/app"
 	"v2ray.com/core/app/dispatcher"
 	"v2ray.com/core/app/log"
@@ -16,6 +18,7 @@ import (
 	"v2ray.com/core/common/signal"
 	"v2ray.com/core/proxy"
 	"v2ray.com/core/transport/internet"
+	"v2ray.com/core/transport/internet/udp"
 )
 
 type DokodemoDoor struct {
@@ -88,7 +91,18 @@ func (d *DokodemoDoor) Process(ctx context.Context, network net.Network, conn in
 		if network == net.Network_TCP {
 			writer = buf.NewWriter(conn)
 		} else {
-			writer = buf.NewSequentialWriter(conn)
+			//if we are in TPROXY mode, use linux's udp forging functionality
+			if !d.config.FollowRedirect {
+				writer = buf.NewSequentialWriter(conn)
+			} else {
+				srca := gonet.UDPAddr{IP: dest.Address.IP(), Port: int(dest.Port.Value())}
+				origsend, err := udp.TransmitSocket(&srca, conn.RemoteAddr())
+				if err != nil {
+					return err
+				}
+				writer = buf.NewSequentialWriter(origsend)
+			}
+
 		}
 
 		if err := buf.Copy(inboundRay.InboundOutput(), writer, buf.UpdateActivity(timer)); err != nil {