commit 4b5794c93580d9a48d7a52c9e8f7e50db73836a7 Author: yinghuocho yinghuocho@gmail.com 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) + } +}