Log selected ICE candidate pair (#865)

* Log selected ICE candidate pair

* simplify

pkg/rtc/participant.go

@@ -1283,8 +1283,38 @@ func (p *ParticipantImpl) handleDataMessage(kind livekit.DataPacket_Kind, data [
 	}
 }
 
+func (p *ParticipantImpl) logSelectedCandidatePair(isPrimary bool) {
+	pcTransport := p.publisher
+	if (isPrimary && p.SubscriberAsPrimary()) || (!isPrimary && !p.SubscriberAsPrimary()) {
+		pcTransport = p.subscriber
+	}
+
+	sctp := pcTransport.pc.SCTP()
+	if sctp == nil {
+		return
+	}
+
+	transport := sctp.Transport()
+	if transport == nil {
+		return
+	}
+
+	iceTransport := transport.ICETransport()
+	if iceTransport == nil {
+		return
+	}
+
+	selectedCandidatePair, err := iceTransport.GetSelectedCandidatePair()
+	if err != nil {
+		pcTransport.Logger().Errorw("error getting selected ICE candidate pair", err)
+	} else {
+		pcTransport.Logger().Infow("selected ICE candidate pair", "pair", selectedCandidatePair)
+	}
+}
+
 func (p *ParticipantImpl) handlePrimaryStateChange(state webrtc.PeerConnectionState) {
 	if state == webrtc.PeerConnectionStateConnected {
+		p.logSelectedCandidatePair(true)
 		if !p.firstConnected.Swap(true) {
 			p.setDowntracksConnected()
 		}
@@ -1302,9 +1332,11 @@ func (p *ParticipantImpl) handlePrimaryStateChange(state webrtc.PeerConnectionSt
 			p.lock.Lock()
 			if p.disconnectTimer != nil {
 				p.disconnectTimer.Stop()
+				p.disconnectTimer = nil
 			}
 			p.disconnectTimer = time.AfterFunc(disconnectCleanupDuration, func() {
 				p.lock.Lock()
+				p.disconnectTimer.Stop()
 				p.disconnectTimer = nil
 				p.lock.Unlock()
 
@@ -1329,7 +1361,9 @@ func (p *ParticipantImpl) handlePrimaryStateChange(state webrtc.PeerConnectionSt
 // for the secondary peer connection, we still need to handle when they become disconnected
 // instead of allowing them to silently fail.
 func (p *ParticipantImpl) handleSecondaryStateChange(state webrtc.PeerConnectionState) {
-	if state == webrtc.PeerConnectionStateFailed {
+	if state == webrtc.PeerConnectionStateConnected {
+		p.logSelectedCandidatePair(false)
+	} else if state == webrtc.PeerConnectionStateFailed {
 		// clients support resuming of connections when websocket becomes disconnected
 		p.closeSignalConnection()
 	}

pkg/rtc/transport.go

@@ -212,6 +212,10 @@ func NewPCTransport(params TransportParams) (*PCTransport, error) {
 	return t, nil
 }
 
+func (t *PCTransport) Logger() logger.Logger {
+	return t.params.Logger
+}
+
 func (t *PCTransport) createPeerConnection() error {
 	var bwe cc.BandwidthEstimator
 	pc, me, err := newPeerConnection(t.params, func(estimator cc.BandwidthEstimator) {