Implemented support for DSCP

include/rtc/message.hpp

@@ -42,7 +42,8 @@ struct RTC_CPP_EXPORT Message : binary {
 	Message(binary &&data, Type type_ = Binary) : binary(std::move(data)), type(type_) {}
 
 	Type type;
-	unsigned int stream = 0;
+	unsigned int stream = 0; // Stream id (SCTP stream or SSRC)
+	int dscp = 0;            // Differentiated Services Code Point
 	std::shared_ptr<Reliability> reliability;
 };
 

src/dtlssrtptransport.cpp

@@ -141,6 +141,8 @@ bool DtlsSrtpTransport::sendMedia(message_ptr message) {
 	}
 
 	message->resize(size);
+
+	// DSCP is set by Track according to the type
 	return outgoing(message);
 }
 

src/dtlstransport.cpp

@@ -53,7 +53,7 @@ DtlsTransport::DtlsTransport(shared_ptr<IceTransport> lower, certificate_ptr cer
                              verifier_callback verifierCallback, state_callback stateChangeCallback)
     : Transport(lower, std::move(stateChangeCallback)), mCertificate(certificate),
       mVerifierCallback(std::move(verifierCallback)),
-      mIsClient(lower->role() == Description::Role::Active) {
+      mIsClient(lower->role() == Description::Role::Active), mCurrentDscp(0) {
 
 	PLOG_DEBUG << "Initializing DTLS transport (GnuTLS)";
 
@@ -122,6 +122,7 @@ bool DtlsTransport::send(message_ptr message) {
 
 	PLOG_VERBOSE << "Send size=" << message->size();
 
+	mCurrentDscp = message->dscp;
 	ssize_t ret;
 	do {
 		ret = gnutls_record_send(mSession, message->data(), message->size());
@@ -143,6 +144,11 @@ void DtlsTransport::incoming(message_ptr message) {
 	mIncomingQueue.push(message);
 }
 
+bool DtlsTransport::outgoing(message_ptr message) {
+	message->dscp = mCurrentDscp;
+	return Transport::outgoing(std::move(message));
+}
+
 void DtlsTransport::postHandshake() {
 	// Dummy
 }
@@ -309,7 +315,7 @@ DtlsTransport::DtlsTransport(shared_ptr<IceTransport> lower, shared_ptr<Certific
                              verifier_callback verifierCallback, state_callback stateChangeCallback)
     : Transport(lower, std::move(stateChangeCallback)), mCertificate(certificate),
       mVerifierCallback(std::move(verifierCallback)),
-      mIsClient(lower->role() == Description::Role::Active) {
+      mIsClient(lower->role() == Description::Role::Active), mCurrentDscp(0) {
 	PLOG_DEBUG << "Initializing DTLS transport (OpenSSL)";
 
 	try {
@@ -405,6 +411,7 @@ bool DtlsTransport::send(message_ptr message) {
 
 	PLOG_VERBOSE << "Send size=" << message->size();
 
+	mCurrentDscp = message->dscp;
 	int ret = SSL_write(mSsl, message->data(), int(message->size()));
 	return openssl::check(mSsl, ret);
 }
@@ -419,6 +426,11 @@ void DtlsTransport::incoming(message_ptr message) {
 	mIncomingQueue.push(message);
 }
 
+bool DtlsTransport::outgoing(message_ptr message) {
+	message->dscp = mCurrentDscp;
+	return Transport::outgoing(std::move(message));
+}
+
 void DtlsTransport::postHandshake() {
 	// Dummy
 }

src/dtlstransport.hpp

@@ -53,6 +53,7 @@ public:
 
 protected:
 	virtual void incoming(message_ptr message) override;
+	virtual bool outgoing(message_ptr message) override;
 	virtual void postHandshake();
 	void runRecvLoop();
 
@@ -62,6 +63,7 @@ protected:
 
 	Queue<message_ptr> mIncomingQueue;
 	std::thread mRecvThread;
+	std::atomic<int> mCurrentDscp;
 
 #if USE_GNUTLS
 	gnutls_session_t mSession;

src/icetransport.cpp

@@ -222,8 +222,10 @@ bool IceTransport::send(message_ptr message) {
 }
 
 bool IceTransport::outgoing(message_ptr message) {
-	return juice_send(mAgent.get(), reinterpret_cast<const char *>(message->data()),
-	                  message->size()) >= 0;
+	// Explicit Congestion Notification takes the least-significant 2 bits of the DS field
+	int ds = message->dscp << 2;
+	return juice_send_diffserv(mAgent.get(), reinterpret_cast<const char *>(message->data()),
+	                           message->size(), ds) >= 0;
 }
 
 void IceTransport::changeGatheringState(GatheringState state) {
@@ -330,7 +332,7 @@ IceTransport::IceTransport(const Configuration &config, candidate_callback candi
       mMid("0"), mGatheringState(GatheringState::New),
       mCandidateCallback(std::move(candidateCallback)),
       mGatheringStateChangeCallback(std::move(gatheringStateChangeCallback)),
-      mNiceAgent(nullptr, nullptr), mMainLoop(nullptr, nullptr) {
+      mNiceAgent(nullptr, nullptr), mMainLoop(nullptr, nullptr), mOutgoingDscp(0) {
 
 	PLOG_DEBUG << "Initializing ICE transport (libnice)";
 
@@ -617,6 +619,13 @@ bool IceTransport::send(message_ptr message) {
 }
 
 bool IceTransport::outgoing(message_ptr message) {
+	std::lock_guard lock(mOutgoingMutex);
+	if (mOutgoingDscp != message->dscp) {
+		mOutgoingDscp = message->dscp;
+		// Explicit Congestion Notification takes the least-significant 2 bits of the DS field
+		int ds = message->dscp << 2;
+		nice_agent_set_stream_tos(mNiceAgent.get(), mStreamId, ds); // ToS is the legacy name for DS
+	}
 	return nice_agent_send(mNiceAgent.get(), mStreamId, 1, message->size(),
 	                       reinterpret_cast<const char *>(message->data())) >= 0;
 }

src/icetransport.hpp

@@ -35,6 +35,7 @@
 #include <atomic>
 #include <chrono>
 #include <thread>
+#include <mutex>
 
 namespace rtc {
 
@@ -99,6 +100,8 @@ private:
 	std::unique_ptr<GMainLoop, void (*)(GMainLoop *)> mMainLoop;
 	std::thread mMainLoopThread;
 	guint mTimeoutId = 0;
+	std::mutex mOutgoingMutex;
+	int mOutgoingDscp;
 
 	static string AddressToString(const NiceAddress &addr);
 

src/sctptransport.cpp

@@ -325,6 +325,13 @@ void SctpTransport::incoming(message_ptr message) {
 	usrsctp_conninput(this, message->data(), message->size(), 0);
 }
 
+bool SctpTransport::outgoing(message_ptr message) {
+	// Set recommended medium-priority DSCP value
+	// See https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18
+	message->dscp = 10; // AF11: Assured Forwarding class 1, low drop probability
+	return Transport::outgoing(std::move(message));
+}
+
 void SctpTransport::doRecv() {
 	std::lock_guard lock(mRecvMutex);
 	--mPendingRecvCount;
@@ -554,6 +561,7 @@ int SctpTransport::handleWrite(byte *data, size_t len, uint8_t /*tos*/, uint8_t
 		std::unique_lock lock(mWriteMutex);
 		PLOG_VERBOSE << "Handle write, len=" << len;
 
+		auto message = make_message(data, data + len);
 		if (!outgoing(make_message(data, data + len)))
 			return -1;
 

src/sctptransport.hpp

@@ -77,6 +77,7 @@ private:
 	void shutdown();
 	void close();
 	void incoming(message_ptr message) override;
+	bool outgoing(message_ptr message) override;
 
 	void doRecv();
 	bool trySendQueue();

src/track.cpp

@@ -107,14 +107,18 @@ bool Track::outgoing(message_ptr message) {
 	if (mIsClosed)
 		throw std::runtime_error("Track is closed");
 
-	if (message->size() > maxMessageSize())
-		throw std::runtime_error("Message size exceeds limit");
-
 #if RTC_ENABLE_MEDIA
 	auto transport = mDtlsSrtpTransport.lock();
 	if (!transport)
 		throw std::runtime_error("Track transport is not open");
 
+	// Set recommended medium-priority DSCP value
+	// See https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18
+	if (mMediaDescription.type() == "audio")
+		message->dscp = 46; // EF: Expedited Forwarding
+	else
+		message->dscp = 36; // AF42: Assured Forwarding class 4, medium drop probability
+
 	return transport->sendMedia(message);
 #else
 	PLOG_WARNING << "Ignoring track send (not compiled with SRTP support)";