@@ -4,6 +4,7 @@ import (

 	"encoding/binary"

 	"errors"

 	"fmt"

+	"io"

 	"log"

 	"net"

 	"os/exec"

@@ -221,10 +222,55 @@ func (mapper *PortMapper) Map(port int, dest net.TCPAddr) error {

 	if err := mapper.iptablesForward("-A", port, dest); err != nil {

 		return err

 	}

+

 	mapper.mapping[port] = dest

+	listener, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", port))

+	if err != nil {

+		mapper.Unmap(port)

+		return err

+	}

+	// FIXME: store the listener so we can close it at Unmap

+	go proxy(listener, "tcp", dest.String())

 	return nil

 }

+// proxy listens for socket connections on `listener`, and forwards them unmodified

+// to `proto:address`

+func proxy(listener net.Listener, proto, address string) error {

+	Debugf("proxying to %s:%s", proto, address)

+	defer Debugf("Done proxying to %s:%s", proto, address)

+	for {

+		Debugf("Listening on %s", listener)

+		src, err := listener.Accept()

+		if err != nil {

+			return err

+		}

+		Debugf("Connecting to %s:%s", proto, address)

+		dst, err := net.Dial(proto, address)

+		if err != nil {

+			log.Printf("Error connecting to %s:%s: %s", proto, address, err)

+			src.Close()

+			continue

+		}

+		Debugf("Connected to backend, splicing")

+		splice(src, dst)

+	}

+	return nil

+}

+

+func halfSplice(dst, src net.Conn) error {

+	_, err := io.Copy(dst, src)

+	// FIXME: on EOF from a tcp connection, pass WriteClose()

+	dst.Close()

+	src.Close()

+	return err

+}

+

+func splice(a, b net.Conn) {

+	go halfSplice(a, b)

+	go halfSplice(b, a)

+}

+

 func (mapper *PortMapper) Unmap(port int) error {

 	dest, ok := mapper.mapping[port]

 	if !ok {