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[tor-commits] [snowflake/master] Golang implementation of standalone snowflake proxy
commit 4b5794c93580d9a48d7a52c9e8f7e50db73836a7
Author: yinghuocho <yinghuocho@xxxxxxxxx>
Date: Mon Apr 24 16:16:02 2017 -0700
Golang implementation of standalone snowflake proxy
---
proxy-go/snowflake.go | 326 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 326 insertions(+)
diff --git a/proxy-go/snowflake.go b/proxy-go/snowflake.go
new file mode 100644
index 0000000..c7ee24a
--- /dev/null
+++ b/proxy-go/snowflake.go
@@ -0,0 +1,326 @@
+package main
+
+import (
+ "bytes"
+ "encoding/base64"
+ "flag"
+ "fmt"
+ "io"
+ "io/ioutil"
+ "log"
+ "math/rand"
+ "net"
+ "net/http"
+ "net/url"
+ "strings"
+ "sync"
+ "time"
+
+ "github.com/keroserene/go-webrtc"
+ "golang.org/x/net/websocket"
+)
+
+type snowflakeOptions struct {
+ capacity int
+ broker string
+ brokerURL *url.URL
+ stun string
+ stunURL *url.URL
+ relay string
+ relayURL *url.URL
+}
+
+const (
+ sessionIDLength = 16
+)
+
+var (
+ tokens chan bool
+ opt *snowflakeOptions
+ config *webrtc.Configuration
+ client http.Client
+)
+
+type webRTCConn struct {
+ dc *webrtc.DataChannel
+ pc *webrtc.PeerConnection
+ pr *io.PipeReader
+}
+
+func (c *webRTCConn) Read(b []byte) (int, error) {
+ return c.pr.Read(b)
+}
+
+func (c *webRTCConn) Write(b []byte) (int, error) {
+ // log.Printf("webrtc Write %d %+q", len(b), string(b))
+ log.Printf("Write %d bytes --> WebRTC", len(b))
+ c.dc.Send(b)
+ return len(b), nil
+}
+
+func (c *webRTCConn) Close() error {
+ return c.pc.Close()
+}
+
+func (c *webRTCConn) LocalAddr() net.Addr {
+ return nil
+}
+
+func (c *webRTCConn) RemoteAddr() net.Addr {
+ return nil
+}
+
+func (c *webRTCConn) SetDeadline(t time.Time) error {
+ return fmt.Errorf("SetDeadline not implemented")
+}
+
+func (c *webRTCConn) SetReadDeadline(t time.Time) error {
+ return fmt.Errorf("SetReadDeadline not implemented")
+}
+
+func (c *webRTCConn) SetWriteDeadline(t time.Time) error {
+ return fmt.Errorf("SetWriteDeadline not implemented")
+}
+
+func getToken() {
+ <-tokens
+}
+
+func retToken() {
+ tokens <- true
+}
+
+func genSessionID() string {
+ buf := make([]byte, sessionIDLength)
+ _, err := rand.Read(buf)
+ if err != nil {
+ panic(err.Error())
+ }
+ return strings.TrimRight(base64.StdEncoding.EncodeToString(buf), "=")
+}
+
+func pollOffer(sid string, broker *url.URL) *webrtc.SessionDescription {
+ broker.Path = "/proxy"
+ for {
+ req, _ := http.NewRequest("POST", broker.String(), bytes.NewBuffer([]byte(sid)))
+ req.Header.Set("X-Session-ID", sid)
+ resp, err := client.Do(req)
+ if err != nil {
+ log.Printf("error to poll broker: %s", err)
+ } else {
+ defer resp.Body.Close()
+ if resp.StatusCode != http.StatusOK {
+ log.Printf("broker returns: %d", resp.StatusCode)
+ } else {
+ body, err := ioutil.ReadAll(resp.Body)
+ if err != nil {
+ log.Printf("error to read broker responses: %s", err)
+ } else {
+ return webrtc.DeserializeSessionDescription(string(body))
+ }
+ }
+ }
+ }
+}
+
+func sendAnswer(sid string, broker *url.URL, pc *webrtc.PeerConnection) error {
+ broker.Path = "/answer"
+ body := bytes.NewBuffer([]byte(pc.LocalDescription().Serialize()))
+ req, _ := http.NewRequest("POST", broker.String(), body)
+ req.Header.Set("X-Session-ID", sid)
+ resp, err := client.Do(req)
+ if err != nil {
+ return err
+ }
+ if resp.StatusCode != http.StatusOK {
+ return fmt.Errorf("broker returned %d", resp.StatusCode)
+ }
+ return nil
+}
+
+type timeoutConn struct {
+ c net.Conn
+ t time.Duration
+}
+
+func (tc timeoutConn) Read(buf []byte) (int, error) {
+ tc.c.SetDeadline(time.Now().Add(tc.t))
+ return tc.c.Read(buf)
+}
+
+func (tc timeoutConn) Write(buf []byte) (int, error) {
+ tc.c.SetDeadline(time.Now().Add(tc.t))
+ return tc.c.Write(buf)
+}
+
+func (tc timeoutConn) Close() error {
+ return tc.c.Close()
+}
+
+func CopyLoopTimeout(c1 net.Conn, c2 net.Conn, timeout time.Duration) {
+ tc1 := timeoutConn{c: c1, t: timeout}
+ tc2 := timeoutConn{c: c2, t: timeout}
+ var wg sync.WaitGroup
+ copyer := func(dst io.ReadWriteCloser, src io.ReadWriteCloser) {
+ defer wg.Done()
+ io.Copy(dst, src)
+ dst.Close()
+ src.Close()
+ }
+ wg.Add(2)
+ go copyer(tc1, tc2)
+ go copyer(tc2, tc1)
+ wg.Wait()
+}
+
+func datachannelHandler(conn *webRTCConn) {
+ defer conn.Close()
+ defer retToken()
+
+ wsConn, err := websocket.Dial(opt.relay, "", opt.relay)
+ if err != nil {
+ log.Printf("error to dial relay: %s", err)
+ return
+ }
+ log.Printf("connected to relay")
+ defer wsConn.Close()
+ wsConn.PayloadType = websocket.BinaryFrame
+ CopyLoopTimeout(conn, wsConn, time.Minute)
+ log.Printf("datachannelHandler ends")
+}
+
+// Create a PeerConnection from an SDP offer. Blocks until the gathering of ICE
+// candidates is complete and the answer is available in LocalDescription.
+// Installs an OnDataChannel callback that creates a webRTCConn and passes it to
+// datachannelHandler.
+func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription, config *webrtc.Configuration) (*webrtc.PeerConnection, error) {
+ errChan := make(chan error)
+ answerChan := make(chan struct{})
+
+ pc, err := webrtc.NewPeerConnection(config)
+ if err != nil {
+ return nil, fmt.Errorf("accept: NewPeerConnection: %s", err)
+ }
+ pc.OnNegotiationNeeded = func() {
+ panic("OnNegotiationNeeded")
+ }
+ pc.OnIceComplete = func() {
+ answerChan <- struct{}{}
+ }
+ pc.OnDataChannel = func(dc *webrtc.DataChannel) {
+ log.Println("OnDataChannel")
+
+ pr, pw := io.Pipe()
+
+ dc.OnOpen = func() {
+ log.Println("OnOpen channel")
+ }
+ dc.OnClose = func() {
+ log.Println("OnClose channel")
+ pw.Close()
+ }
+ dc.OnMessage = func(msg []byte) {
+ log.Printf("OnMessage <--- %d bytes", len(msg))
+ n, err := pw.Write(msg)
+ if err != nil {
+ pw.CloseWithError(err)
+ }
+ if n != len(msg) {
+ panic("short write")
+ }
+ }
+ conn := &webRTCConn{pc: pc, dc: dc, pr: pr}
+ go datachannelHandler(conn)
+ }
+
+ err = pc.SetRemoteDescription(sdp)
+ if err != nil {
+ pc.Close()
+ return nil, fmt.Errorf("accept: SetRemoteDescription: %s", err)
+ }
+ log.Println("sdp offer successfully received.")
+
+ go func() {
+ log.Println("Generating answer...")
+ answer, err := pc.CreateAnswer() // blocking
+ if err != nil {
+ errChan <- err
+ return
+ }
+ err = pc.SetLocalDescription(answer)
+ if err != nil {
+ errChan <- err
+ return
+ }
+ }()
+
+ // Wait until answer is ready.
+ select {
+ case err = <-errChan:
+ pc.Close()
+ return nil, err
+ case _, ok := <-answerChan:
+ if !ok {
+ pc.Close()
+ return nil, fmt.Errorf("Failed gathering ICE candidates.")
+ }
+ }
+ return pc, nil
+}
+
+func runSession(sid string) {
+ offer := pollOffer(sid, opt.brokerURL)
+ if offer == nil {
+ log.Printf("bad offer from broker")
+ retToken()
+ return
+ }
+ pc, err := makePeerConnectionFromOffer(offer, config)
+ if err != nil {
+ log.Printf("error to make WebRTC connection: %s", err)
+ retToken()
+ return
+ }
+ err = sendAnswer(sid, opt.brokerURL, pc)
+ if err != nil {
+ log.Printf("error to send answer to client through broker: %s", err)
+ pc.Close()
+ retToken()
+ return
+ }
+}
+
+func main() {
+ opt = new(snowflakeOptions)
+ flag.IntVar(&opt.capacity, "capacity", 10, "maximum concurrent clients")
+ flag.StringVar(&opt.broker, "broker", "https://snowflake-reg.appspot.com/";, "broker URL")
+ flag.StringVar(&opt.relay, "relay", "wss://snowflake.bamsoftware.com/", "websocket relay URL")
+ flag.StringVar(&opt.stun, "stun", "stun:stun.l.google.com:19302", "stun URL")
+ flag.Parse()
+
+ var err error
+ opt.brokerURL, err = url.Parse(opt.broker)
+ if err != nil {
+ log.Fatalf("invalid broker url: %s", err)
+ }
+ opt.stunURL, err = url.Parse(opt.stun)
+ if err != nil {
+ log.Fatalf("invalid stun url: %s", err)
+ }
+ opt.relayURL, err = url.Parse(opt.relay)
+ if err != nil {
+ log.Fatalf("invalid relay url: %s", err)
+ }
+
+ config = webrtc.NewConfiguration(webrtc.OptionIceServer(opt.stun))
+ tokens = make(chan bool, opt.capacity)
+ for i := 0; i < opt.capacity; i++ {
+ tokens <- true
+ }
+
+ for {
+ getToken()
+ sessionID := genSessionID()
+ runSession(sessionID)
+ }
+}
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