uottun: add udp over tcp local server support

uottun.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"io/ioutil"
+	"net"
+)
+
+// UoTTun udp over tcp tunnel
+type UoTTun struct {
+	*Forwarder
+	sDialer Dialer
+
+	raddr string
+}
+
+// NewUoTTun returns a UoTTun proxy.
+func NewUoTTun(addr, raddr string, sDialer Dialer) (*UoTTun, error) {
+	s := &UoTTun{
+		Forwarder: NewForwarder(addr, nil),
+		sDialer:   sDialer,
+		raddr:     raddr,
+	}
+
+	return s, nil
+}
+
+// ListenAndServe redirected requests as a server.
+func (s *UoTTun) ListenAndServe() {
+
+	c, err := net.ListenPacket("udp", s.addr)
+	if err != nil {
+		logf("proxy-uottun failed to listen on %s: %v", s.addr, err)
+		return
+	}
+	defer c.Close()
+
+	logf("proxy-uottun listening UDP on %s", s.addr)
+
+	buf := make([]byte, udpBufSize)
+
+	for {
+		n, clientAddr, err := c.ReadFrom(buf)
+		if err != nil {
+			logf("proxy-uottun read error: %v", err)
+			continue
+		}
+
+		// NOTE: acturally udp over tcp
+		rc, err := s.sDialer.Dial("udp", s.raddr)
+		if err != nil {
+			logf("failed to connect to server %v: %v", s.raddr, err)
+			continue
+		}
+
+		rc.Write(buf[:n])
+
+		resp, err := ioutil.ReadAll(rc)
+		if err != nil {
+			logf("error in ioutil.ReadAll: %s\n", err)
+			return
+		}
+		rc.Close()
+
+		c.WriteTo(resp, clientAddr)
+
+		logf("proxy-uottun %s <-> %s", clientAddr, s.raddr)
+	}
+}