video_rtp_session: allow socket transmissions for response packets

Bitrate adjustment (REMB) packets in video calls are sent back on the
same socket pair as the video itself.
Video being enabled or disabled should thusly not stop communication
on these sockets fully as they could still be needed for these packets.

Change-Id: I3789aae44884ad5acfe5e1b014767ff2bf84ba33

src/media/video/video_rtp_session.cpp

@@ -218,6 +218,9 @@ VideoRtpSession::startSender()
             rtcpCheckerThread_.start();
         else if (not autoQuality and rtcpCheckerThread_.isRunning())
             rtcpCheckerThread_.join();
+        // Block reads to received feedback packets
+        if(socketPair_)
+            socketPair_->setReadBlockingMode(true);
     }
 }
 
@@ -239,7 +242,7 @@ VideoRtpSession::restartSender()
 }
 
 void
-VideoRtpSession::stopSender()
+VideoRtpSession::stopSender(bool forceStopSocket)
 {
     // Concurrency protection must be done by caller.
 
@@ -256,8 +259,13 @@ VideoRtpSession::stopSender()
         sender_.reset();
     }
 
-    if (socketPair_)
+    if (socketPair_) {
+        bool const isReceivingVideo = receive_.enabled && !receive_.onHold;
+        if(forceStopSocket || !isReceivingVideo) {
             socketPair_->stopSendOp();
+            socketPair_->setReadBlockingMode(false);
+        }
+    }
 }
 
 void
@@ -316,7 +324,7 @@ VideoRtpSession::startReceiver()
 }
 
 void
-VideoRtpSession::stopReceiver()
+VideoRtpSession::stopReceiver(bool forceStopSocket)
 {
     // Concurrency protection must be done by caller.
 
@@ -338,8 +346,13 @@ VideoRtpSession::stopReceiver()
     // We need to disable the read operation, otherwise the
     // receiver thread will block since the peer stopped sending
     // RTP packets.
-    if (socketPair_)
+    bool const isSendingVideo = send_.enabled && !send_.onHold;
+    if (socketPair_) {
+        if (forceStopSocket || !isSendingVideo) {
             socketPair_->setReadBlockingMode(false);
+            socketPair_->stopSendOp();
+        }
+    }
 
     auto ms = receiveThread_->getInfo();
     if (auto ob = recorder_->getStream(ms.name)) {
@@ -347,6 +360,7 @@ VideoRtpSession::stopReceiver()
         recorder_->removeStream(ms);
     }
 
+    if(forceStopSocket || !isSendingVideo)
         receiveThread_->stopLoop();
     receiveThread_->stopSink();
 }
@@ -413,8 +427,8 @@ VideoRtpSession::stop()
 {
     std::lock_guard<std::recursive_mutex> lock(mutex_);
 
-    stopSender();
-    stopReceiver();
+    stopSender(true);
+    stopReceiver(true);
 
     if (socketPair_)
         socketPair_->interrupt();

src/media/video/video_rtp_session.h

@@ -117,9 +117,9 @@ private:
     void setupConferenceVideoPipeline(Conference& conference, Direction dir);
     void setupVideoPipeline();
     void startSender();
-    void stopSender();
+    void stopSender(bool forceStopSocket = false);
     void startReceiver();
-    void stopReceiver();
+    void stopReceiver(bool forceStopSocket = false);
     using clock = std::chrono::steady_clock;
     using time_point = clock::time_point;