initial commit

handler/redirect/handler_linux.go

@@ -0,0 +1,40 @@
+package redirect
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"syscall"
+)
+
+func (h *redirectHandler) getOriginalDstAddr(conn net.Conn) (addr net.Addr, c net.Conn, err error) {
+	defer conn.Close()
+
+	tc, ok := conn.(*net.TCPConn)
+	if !ok {
+		err = errors.New("wrong connection type, must be TCP")
+		return
+	}
+
+	fc, err := tc.File()
+	if err != nil {
+		return
+	}
+	defer fc.Close()
+
+	mreq, err := syscall.GetsockoptIPv6Mreq(int(fc.Fd()), syscall.IPPROTO_IP, 80)
+	if err != nil {
+		return
+	}
+
+	// only ipv4 support
+	ip := net.IPv4(mreq.Multiaddr[4], mreq.Multiaddr[5], mreq.Multiaddr[6], mreq.Multiaddr[7])
+	port := uint16(mreq.Multiaddr[2])<<8 + uint16(mreq.Multiaddr[3])
+	addr, err = net.ResolveTCPAddr("tcp4", fmt.Sprintf("%s:%d", ip.String(), port))
+	if err != nil {
+		return
+	}
+
+	c, err = net.FileConn(fc)
+	return
+}