fix: Lock when obtaining a peer connection answer<->offer (#24)

* fix: Lock when obtaining a peer connection answer<->offer

This fixes a race in the peerbroker package where ICE candidates could be added before the connection was negotiated. This would result in the connection failing.

* Remove unnecessary log

peer/conn.go

@@ -116,6 +116,7 @@ type Conn struct {
 	localCandidateChannel           chan webrtc.ICECandidateInit
 	localSessionDescriptionChannel  chan webrtc.SessionDescription
 	remoteSessionDescriptionChannel chan webrtc.SessionDescription
+	remoteSessionDescriptionMutex   sync.Mutex
 
 	pingChannelID     uint16
 	pingEchoChannelID uint16
@@ -228,6 +229,11 @@ func (c *Conn) negotiate() {
 	c.opts.Logger.Debug(context.Background(), "negotiating")
 	flushCandidates := c.proxyICECandidates()
 
+	// Locks while the negotiation for a remote session
+	// description is taking place.
+	c.remoteSessionDescriptionMutex.Lock()
+	defer c.remoteSessionDescriptionMutex.Unlock()
+
 	if c.offerrer {
 		offer, err := c.rtc.CreateOffer(&webrtc.OfferOptions{})
 		if err != nil {
@@ -328,6 +334,9 @@ func (c *Conn) LocalCandidate() <-chan webrtc.ICECandidateInit {
 
 // AddRemoteCandidate adds a remote candidate to the RTC connection.
 func (c *Conn) AddRemoteCandidate(i webrtc.ICECandidateInit) error {
+	// Prevents candidates from being added before an offer<->answer has occurred.
+	c.remoteSessionDescriptionMutex.Lock()
+	defer c.remoteSessionDescriptionMutex.Unlock()
 	return c.rtc.AddICECandidate(i)
 }
 

peerbroker/dial.go

@@ -84,7 +84,7 @@ func Dial(stream proto.DRPCPeerBroker_NegotiateConnectionClient, iceServers []we
 		for {
 			serverToClientMessage, err := stream.Recv()
 			if err != nil {
-				_ = peerConn.CloseWithError(err)
+				_ = peerConn.CloseWithError(xerrors.Errorf("recv: %w", err))
 				return
 			}
 

peerbroker/dial_test.go

@@ -18,7 +18,10 @@ func TestMain(m *testing.M) {
 }
 
 func TestDial(t *testing.T) {
+	t.Parallel()
+
 	t.Run("Connect", func(t *testing.T) {
+		t.Parallel()
 		ctx := context.Background()
 		client, server := provisionersdk.TransportPipe()
 		defer client.Close()