Fix a race between delUpConn and addLocal.

We could call addLocal after the remote was closed, which
would cause the local connection to remain forever.

Thanks to Ludovic Rateau.

rtpconn/rtpconn.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"log"
 	"math/bits"
+	"os"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -461,6 +462,7 @@ type rtpUpConnection struct {
 	iceCandidates []*webrtc.ICECandidateInit
 
 	mu      sync.Mutex
+	closed  bool
 	pushed  bool
 	replace string
 	tracks  []*rtpUpTrack
@@ -500,6 +502,11 @@ func (up *rtpUpConnection) User() (string, string) {
 func (up *rtpUpConnection) AddLocal(local conn.Down) error {
 	up.mu.Lock()
 	defer up.mu.Unlock()
+	// the connection may have been closed in the meantime, in which
+	// case we'd never get rid of the down connection
+	if up.closed {
+		return os.ErrClosed
+	}
 	for _, t := range up.local {
 		if t == local {
 			return nil

rtpconn/webclient.go

@@ -231,6 +231,10 @@ func delUpConn(c *webClient, id string, userId string, push bool) error {
 	g := c.group
 	c.mu.Unlock()
 
+	conn.mu.Lock()
+	conn.closed = true
+	conn.mu.Unlock()
+
 	conn.pc.Close()
 
 	if push && g != nil {
@@ -616,7 +620,10 @@ func gotAnswer(c *webClient, id string, sdp string) error {
 	add := func() {
 		down.pc.OnConnectionStateChange(nil)
 		for _, t := range down.tracks {
-			t.remote.AddLocal(t)
+			err := t.remote.AddLocal(t)
+			if err != nil && err != os.ErrClosed {
+				log.Printf("Add track: %v", err)
+			}
 		}
 	}
 	down.pc.OnConnectionStateChange(func(state webrtc.PeerConnectionState) {
@@ -981,6 +988,9 @@ func handleAction(c *webClient, a interface{}) error {
 
 		down, _, err := addDownConn(c, a.conn)
 		if err != nil {
+			if err == os.ErrClosed {
+				return nil
+			}
 			return err
 		}
 		done, err := replaceTracks(down, tracks, a.conn)