Add UDP Like transport mode to snowflake

client/lib/packetIDConnClient.go

@@ -0,0 +1,109 @@
+package snowflake_client
+
+import (
+	"io"
+	"log"
+	"net"
+	"time"
+
+	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/turbotunnel"
+)
+
+const (
+	packetClientIDConn_StateNew = iota
+	packetClientIDConn_StateConnectionIDAcknowledged
+)
+
+type ClientID = turbotunnel.ClientID
+
+func newPacketClientIDConn(ClientID ClientID, transport io.ReadWriter) *packetClientIDConn {
+	return &packetClientIDConn{
+		state:     packetClientIDConn_StateNew,
+		ConnID:    ClientID,
+		transport: transport,
+	}
+}
+
+type packetClientIDConn struct {
+	state     int
+	ConnID    ClientID
+	transport io.ReadWriter
+}
+
+func (c *packetClientIDConn) Write(p []byte) (int, error) {
+	switch c.state {
+	case packetClientIDConn_StateConnectionIDAcknowledged:
+		packet := make([]byte, len(p)+1)
+		packet[0] = 0xff
+		copy(packet[1:], p)
+		_, err := c.transport.Write(packet)
+		if err != nil {
+			return 0, err
+		}
+		return len(p), nil
+	case packetClientIDConn_StateNew:
+		packet := make([]byte, len(p)+1+len(c.ConnID))
+		packet[0] = 0xfe
+		copy(packet[1:], c.ConnID[:])
+		copy(packet[1+len(c.ConnID):], p)
+		_, err := c.transport.Write(packet)
+		if err != nil {
+			return 0, err
+		}
+		return len(p), nil
+	default:
+		panic("invalid state")
+	}
+}
+
+func (c *packetClientIDConn) Read(p []byte) (int, error) {
+	n, err := c.transport.Read(p)
+	if err != nil {
+		return 0, err
+	}
+	if p[0] == 0xff {
+		c.state = packetClientIDConn_StateConnectionIDAcknowledged
+		return copy(p, p[1:n]), nil
+	} else {
+		log.Println("discarded unknown packet")
+	}
+	return 0, nil
+}
+
+type packetConnWrapper struct {
+	io.ReadWriter
+	remoteAddr net.Addr
+	localAddr  net.Addr
+}
+
+func (pcw *packetConnWrapper) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
+	n, err = pcw.Read(p)
+	if err != nil {
+		return 0, nil, err
+	}
+	return n, pcw.remoteAddr, nil
+}
+
+func (pcw *packetConnWrapper) WriteTo(p []byte, addr net.Addr) (n int, err error) {
+	return pcw.Write(p)
+}
+
+func (pcw *packetConnWrapper) Close() error {
+	return nil
+}
+
+func (pcw *packetConnWrapper) LocalAddr() net.Addr {
+	return pcw.localAddr
+}
+
+func (pcw *packetConnWrapper) SetDeadline(t time.Time) error {
+	return nil
+}
+
+func (pcw *packetConnWrapper) SetReadDeadline(t time.Time) error {
+	return nil
+}
+
+func (pcw *packetConnWrapper) SetWriteDeadline(t time.Time) error {
+	return nil
+}