fix race condition

client.go

@@ -112,13 +112,15 @@ type client struct {
 	streamSdpParsed *sdp.Message // filled only if publisher
 	streamProtocol  streamProtocol
 	streamTracks    []*track
+	chanWrite       chan *gortsplib.InterleavedFrame
 }
 
 func newClient(p *program, nconn net.Conn) *client {
 	c := &client{
-		p:     p,
-		conn:  gortsplib.NewConnServer(nconn),
-		state: _CLIENT_STATE_STARTING,
+		p:         p,
+		conn:      gortsplib.NewConnServer(nconn),
+		state:     _CLIENT_STATE_STARTING,
+		chanWrite: make(chan *gortsplib.InterleavedFrame),
 	}
 
 	c.p.mutex.Lock()
@@ -136,6 +138,7 @@ func (c *client) close() error {
 
 	delete(c.p.clients, c)
 	c.conn.NetConn().Close()
+	close(c.chanWrite)
 
 	if c.path != "" {
 		if pub, ok := c.p.publishers[c.path]; ok && pub == c {
@@ -251,7 +254,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 			StatusCode: 200,
 			Status:     "OK",
 			Header: gortsplib.Header{
-				"CSeq": cseq,
+				"CSeq": []string{cseq[0]},
 				"Public": []string{strings.Join([]string{
 					"DESCRIBE",
 					"ANNOUNCE",
@@ -411,7 +414,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 						StatusCode: 461,
 						Status:     "Unsupported Transport",
 						Header: gortsplib.Header{
-							"CSeq": cseq,
+							"CSeq": []string{cseq[0]},
 						},
 					})
 					return false
@@ -484,7 +487,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 						StatusCode: 461,
 						Status:     "Unsupported Transport",
 						Header: gortsplib.Header{
-							"CSeq": cseq,
+							"CSeq": []string{cseq[0]},
 						},
 					})
 					return false
@@ -579,7 +582,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 						StatusCode: 461,
 						Status:     "Unsupported Transport",
 						Header: gortsplib.Header{
-							"CSeq": cseq,
+							"CSeq": []string{cseq[0]},
 						},
 					})
 					return false
@@ -641,7 +644,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 						StatusCode: 461,
 						Status:     "Unsupported Transport",
 						Header: gortsplib.Header{
-							"CSeq": cseq,
+							"CSeq": []string{cseq[0]},
 						},
 					})
 					return false
@@ -763,9 +766,19 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 		c.state = _CLIENT_STATE_PLAY
 		c.p.mutex.Unlock()
 
+		//c.conn.NetConn().SetWriteDeadline(time.Now().Add(_WRITE_TIMEOUT))
+
 		// when protocol is TCP, the RTSP connection becomes a RTP connection
-		// receive RTP feedback, do not parse it, wait until connection closes
 		if c.streamProtocol == _STREAM_PROTOCOL_TCP {
+			// write RTP frames sequentially
+			go func() {
+				for frame := range c.chanWrite {
+					c.conn.NetConn().SetWriteDeadline(time.Now().Add(_WRITE_TIMEOUT))
+					c.conn.WriteInterleavedFrame(frame)
+				}
+			}()
+
+			// receive RTP feedback, do not parse it, wait until connection closes
 			buf := make([]byte, 2048)
 			for {
 				_, err := c.conn.NetConn().Read(buf)

go.mod

@@ -5,7 +5,7 @@ go 1.13
 require (
 	github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 // indirect
 	github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d // indirect
-	github.com/aler9/gortsplib v0.0.0-20200126151926-9e5868a1b8a3
+	github.com/aler9/gortsplib v0.0.0-20200126152308-13da0e672306
 	gopkg.in/alecthomas/kingpin.v2 v2.2.6
 	gortc.io/sdp v0.17.0
 )

go.sum

@@ -2,8 +2,8 @@ github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 h1:JYp7IbQjafo
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d h1:UQZhZ2O0vMHr2cI+DC1Mbh0TJxzA3RcLoMsFw+aXw7E=
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d/go.mod h1:rBZYJk541a8SKzHPHnH3zbiI+7dagKZ0cgpgrD7Fyho=
-github.com/aler9/gortsplib v0.0.0-20200126151926-9e5868a1b8a3 h1:CK8JKsFz82I2mPrB5oBnu0HYZm4q4UW/1xzr58/ZzU4=
-github.com/aler9/gortsplib v0.0.0-20200126151926-9e5868a1b8a3/go.mod h1:YiIgmmv0ELkWUy11Jj2h5AgfqLCpy8sIX/l9MmS8+uw=
+github.com/aler9/gortsplib v0.0.0-20200126152308-13da0e672306 h1:mSGMii9I9cEyw2cgyujnlaYwml9MwUkC2Ko8R0vKS6w=
+github.com/aler9/gortsplib v0.0.0-20200126152308-13da0e672306/go.mod h1:YiIgmmv0ELkWUy11Jj2h5AgfqLCpy8sIX/l9MmS8+uw=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=

main.go

@@ -152,25 +152,28 @@ func (p *program) forwardTrack(path string, id int, flow trackFlow, frame []byte
 		if c.path == path && c.state == _CLIENT_STATE_PLAY {
 			if c.streamProtocol == _STREAM_PROTOCOL_UDP {
 				if flow == _TRACK_FLOW_RTP {
-					p.rtpl.nconn.SetWriteDeadline(time.Now().Add(_WRITE_TIMEOUT))
-					p.rtpl.nconn.WriteTo(frame, &net.UDPAddr{
-						IP:   c.ip,
-						Port: c.streamTracks[id].rtpPort,
-					})
+					p.rtpl.chanWrite <- &udpWrite{
+						addr: &net.UDPAddr{
+							IP:   c.ip,
+							Port: c.streamTracks[id].rtpPort,
+						},
+						buf: frame,
+					}
 				} else {
-					p.rtcpl.nconn.SetWriteDeadline(time.Now().Add(_WRITE_TIMEOUT))
-					p.rtcpl.nconn.WriteTo(frame, &net.UDPAddr{
-						IP:   c.ip,
-						Port: c.streamTracks[id].rtcpPort,
-					})
+					p.rtcpl.chanWrite <- &udpWrite{
+						addr: &net.UDPAddr{
+							IP:   c.ip,
+							Port: c.streamTracks[id].rtcpPort,
+						},
+						buf: frame,
+					}
 				}
 
 			} else {
-				c.conn.NetConn().SetWriteDeadline(time.Now().Add(_WRITE_TIMEOUT))
-				c.conn.WriteInterleavedFrame(&gortsplib.InterleavedFrame{
+				c.chanWrite <- &gortsplib.InterleavedFrame{
 					Channel: trackToInterleavedChannel(id, flow),
 					Content: frame,
-				})
+				}
 			}
 		}
 	}

server_udpl.go

@@ -3,12 +3,19 @@ package main
 import (
 	"log"
 	"net"
+	"time"
 )
 
+type udpWrite struct {
+	addr *net.UDPAddr
+	buf  []byte
+}
+
 type serverUdpListener struct {
-	p     *program
-	nconn *net.UDPConn
-	flow  trackFlow
+	p         *program
+	nconn     *net.UDPConn
+	flow      trackFlow
+	chanWrite chan *udpWrite
 }
 
 func newServerUdpListener(p *program, port int, flow trackFlow) (*serverUdpListener, error) {
@@ -20,9 +27,10 @@ func newServerUdpListener(p *program, port int, flow trackFlow) (*serverUdpListe
 	}
 
 	l := &serverUdpListener{
-		p:     p,
-		nconn: nconn,
-		flow:  flow,
+		p:         p,
+		nconn:     nconn,
+		flow:      flow,
+		chanWrite: make(chan *udpWrite),
 	}
 
 	l.log("opened on :%d", port)
@@ -40,45 +48,57 @@ func (l *serverUdpListener) log(format string, args ...interface{}) {
 }
 
 func (l *serverUdpListener) run() {
-	buf := make([]byte, 2048) // UDP MTU is 1400
-
-	for {
-		n, addr, err := l.nconn.ReadFromUDP(buf)
-		if err != nil {
-			l.log("ERR: %s", err)
-			break
-		}
-
-		func() {
-			l.p.mutex.RLock()
-			defer l.p.mutex.RUnlock()
+	go func() {
+		for {
+			// create a buffer for each read.
+			// this is necessary since the buffer is propagated with channels
+			// so it must be unique.
+			buf := make([]byte, 2048) // UDP MTU is 1400
+			n, addr, err := l.nconn.ReadFromUDP(buf)
+			if err != nil {
+				l.log("ERR: %s", err)
+				break
+			}
 
-			// find path and track id from ip and port
-			path, trackId := func() (string, int) {
-				for _, pub := range l.p.publishers {
-					for i, t := range pub.streamTracks {
-						if !pub.ip.Equal(addr.IP) {
-							continue
-						}
+			func() {
+				l.p.mutex.RLock()
+				defer l.p.mutex.RUnlock()
 
-						if l.flow == _TRACK_FLOW_RTP {
-							if t.rtpPort == addr.Port {
-								return pub.path, i
+				// find path and track id from ip and port
+				path, trackId := func() (string, int) {
+					for _, pub := range l.p.publishers {
+						for i, t := range pub.streamTracks {
+							if !pub.ip.Equal(addr.IP) {
+								continue
 							}
-						} else {
-							if t.rtcpPort == addr.Port {
-								return pub.path, i
+
+							if l.flow == _TRACK_FLOW_RTP {
+								if t.rtpPort == addr.Port {
+									return pub.path, i
+								}
+							} else {
+								if t.rtcpPort == addr.Port {
+									return pub.path, i
+								}
 							}
 						}
 					}
+					return "", -1
+				}()
+				if path == "" {
+					return
 				}
-				return "", -1
+
+				l.p.forwardTrack(path, trackId, l.flow, buf[:n])
 			}()
-			if path == "" {
-				return
-			}
+		}
+	}()
 
-			l.p.forwardTrack(path, trackId, l.flow, buf[:n])
-		}()
-	}
+	go func() {
+		for {
+			w := <-l.chanWrite
+			l.nconn.SetWriteDeadline(time.Now().Add(_WRITE_TIMEOUT))
+			l.nconn.WriteTo(w.buf, w.addr)
+		}
+	}()
 }