Bumped version to 0.11.5

Fix path MTU

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.7)
 project(libdatachannel
-	VERSION 0.11.1
+	VERSION 0.11.5
 	LANGUAGES CXX)
 set(PROJECT_DESCRIPTION "WebRTC Data Channels Library")
 
@@ -67,13 +67,30 @@ set(LIBDATACHANNEL_SOURCES
 	${CMAKE_CURRENT_SOURCE_DIR}/src/processor.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/capi.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/rtppacketizationconfig.cpp
-	${CMAKE_CURRENT_SOURCE_DIR}/src/rtcpsenderreporter.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/rtcpsrreporter.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/rtppacketizer.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/opusrtppacketizer.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/opuspacketizationhandler.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/h264rtppacketizer.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/nalunit.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/src/h264packetizationhandler.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/mediachainablehandler.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/mediahandlerelement.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/mediahandlerrootelement.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/rtcpnackresponder.cpp
+)
+
+set(LIBDATACHANNEL_PRIVATE_HEADERS
+	${CMAKE_CURRENT_SOURCE_DIR}/src/certificate.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/dtlssrtptransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/dtlstransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/icetransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/logcounter.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/sctptransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/threadpool.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/tls.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/processor.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/transport.hpp
 )
 
 set(LIBDATACHANNEL_WEBSOCKET_SOURCES
@@ -85,6 +102,14 @@ set(LIBDATACHANNEL_WEBSOCKET_SOURCES
 	${CMAKE_CURRENT_SOURCE_DIR}/src/wstransport.cpp
 )
 
+set(LIBDATACHANNEL_WEBSOCKET_PRIVATE_HEADERS
+	${CMAKE_CURRENT_SOURCE_DIR}/src/base64.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/tcptransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/tlstransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/verifiedtlstransport.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/src/wstransport.hpp
+)
+
 set(LIBDATACHANNEL_HEADERS
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/candidate.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/channel.hpp
@@ -92,7 +117,7 @@ set(LIBDATACHANNEL_HEADERS
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/configuration.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/datachannel.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/description.hpp
-	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtcphandler.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/mediahandler.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtcpreceivingsession.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/include.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/init.hpp
@@ -107,13 +132,17 @@ set(LIBDATACHANNEL_HEADERS
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/track.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/websocket.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtppacketizationconfig.hpp
-	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtcpsenderreporter.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtcpsrreporter.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtppacketizer.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/opusrtppacketizer.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/opuspacketizationhandler.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/h264rtppacketizer.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/nalunit.hpp
 	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/h264packetizationhandler.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/mediachainablehandler.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/mediahandlerelement.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/mediahandlerrootelement.hpp
+	${CMAKE_CURRENT_SOURCE_DIR}/include/rtc/rtcpnackresponder.hpp
 )
 
 set(TESTS_SOURCES
@@ -165,18 +194,28 @@ add_library(Usrsctp::Usrsctp ALIAS usrsctp)
 
 if (NO_WEBSOCKET)
 	add_library(datachannel SHARED
-		${LIBDATACHANNEL_SOURCES})
+		${LIBDATACHANNEL_SOURCES}
+		${LIBDATACHANNEL_PRIVATE_HEADERS}
+		${LIBDATACHANNEL_HEADERS})
 	add_library(datachannel-static STATIC EXCLUDE_FROM_ALL
-		${LIBDATACHANNEL_SOURCES})
+		${LIBDATACHANNEL_SOURCES}
+		${LIBDATACHANNEL_PRIVATE_HEADERS}
+		${LIBDATACHANNEL_HEADERS})
 	target_compile_definitions(datachannel PUBLIC RTC_ENABLE_WEBSOCKET=0)
 	target_compile_definitions(datachannel-static PUBLIC RTC_ENABLE_WEBSOCKET=0)
 else()
 	add_library(datachannel SHARED
 		${LIBDATACHANNEL_SOURCES}
-		${LIBDATACHANNEL_WEBSOCKET_SOURCES})
+		${LIBDATACHANNEL_PRIVATE_HEADERS}
+		${LIBDATACHANNEL_WEBSOCKET_SOURCES}
+		${LIBDATACHANNEL_WEBSOCKET_PRIVATE_HEADERS}
+		${LIBDATACHANNEL_HEADERS})
 	add_library(datachannel-static STATIC EXCLUDE_FROM_ALL
 		${LIBDATACHANNEL_SOURCES}
-		${LIBDATACHANNEL_WEBSOCKET_SOURCES})
+		${LIBDATACHANNEL_PRIVATE_HEADERS}
+		${LIBDATACHANNEL_WEBSOCKET_SOURCES}
+		${LIBDATACHANNEL_WEBSOCKET_PRIVATE_HEADERS}
+		${LIBDATACHANNEL_HEADERS})
 	target_compile_definitions(datachannel PUBLIC RTC_ENABLE_WEBSOCKET=1)
 	target_compile_definitions(datachannel-static PUBLIC RTC_ENABLE_WEBSOCKET=1)
 endif()

examples/client/CMakeLists.txt

@@ -4,10 +4,10 @@ if(POLICY CMP0079)
 endif()
 
 if(WIN32)
-add_executable(datachannel-client main.cpp parse_cl.cpp parse_cl.h getopt.cpp getopt.h)
+	add_executable(datachannel-client main.cpp parse_cl.cpp parse_cl.h getopt.cpp getopt.h)
-target_compile_definitions(datachannel-client PUBLIC STATIC_GETOPT)
+	target_compile_definitions(datachannel-client PUBLIC STATIC_GETOPT)
 else()
-add_executable(datachannel-client main.cpp parse_cl.cpp parse_cl.h)
+	add_executable(datachannel-client main.cpp parse_cl.cpp parse_cl.h)
 endif()
 
 set_target_properties(datachannel-client PROPERTIES
@@ -15,3 +15,10 @@ set_target_properties(datachannel-client PROPERTIES
 	OUTPUT_NAME client)
 target_link_libraries(datachannel-client datachannel nlohmann_json)
 
+if(WIN32)
+	add_custom_command(TARGET datachannel-client POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-client>
+	)
+endif()

examples/copy-paste-capi/CMakeLists.txt

@@ -13,3 +13,15 @@ set_target_properties(datachannel-copy-paste-capi-answerer PROPERTIES
 	OUTPUT_NAME answerer)
 target_link_libraries(datachannel-copy-paste-capi-answerer datachannel)
 
+if(WIN32)
+	add_custom_command(TARGET datachannel-copy-paste-capi-offerer POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-copy-paste-capi-offerer>
+	)
+	add_custom_command(TARGET datachannel-copy-paste-capi-answerer POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-copy-paste-capi-answerer>
+	)
+endif()

examples/copy-paste/CMakeLists.txt

@@ -12,3 +12,15 @@ set_target_properties(datachannel-copy-paste-answerer PROPERTIES
 	OUTPUT_NAME answerer)
 target_link_libraries(datachannel-copy-paste-answerer datachannel)
 
+if(WIN32)
+	add_custom_command(TARGET datachannel-copy-paste-offerer POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-copy-paste-offerer>
+	)
+	add_custom_command(TARGET datachannel-copy-paste-answerer POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-copy-paste-answerer>
+	)
+endif()

examples/media/CMakeLists.txt

@@ -6,3 +6,10 @@ set_target_properties(datachannel-media PROPERTIES
         OUTPUT_NAME media)
 target_link_libraries(datachannel-media datachannel nlohmann_json)
 
+if(WIN32)
+	add_custom_command(TARGET datachannel-media POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-media>
+	)
+endif()

examples/sfu-media/CMakeLists.txt

@@ -6,3 +6,10 @@ set_target_properties(datachannel-sfu-media PROPERTIES
 		OUTPUT_NAME sfu-media)
 target_link_libraries(datachannel-sfu-media datachannel nlohmann_json)
 
+if(WIN32)
+	add_custom_command(TARGET datachannel-sfu-media POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:datachannel-sfu-media>
+	)
+endif()

examples/streamer/CMakeLists.txt

@@ -3,17 +3,38 @@ if(POLICY CMP0079)
 	cmake_policy(SET CMP0079 NEW)
 endif()
 
+add_executable(streamer
+	main.cpp
+	dispatchqueue.cpp
+	dispatchqueue.hpp
+	h264fileparser.cpp
+	h264fileparser.hpp
+	helpers.cpp
+	helpers.hpp
+	opusfileparser.cpp
+	opusfileparser.hpp
+	fileparser.cpp
+	fileparser.hpp
+	stream.cpp
+	stream.hpp
+	ArgParser.cpp
+	ArgParser.hpp
+)
+
 if(WIN32)
-add_executable(streamer main.cpp dispatchqueue.cpp dispatchqueue.hpp h264fileparser.cpp h264fileparser.hpp helpers.cpp helpers.hpp opusfileparser.cpp opusfileparser.hpp fileparser.cpp fileparser.hpp stream.cpp stream.hpp ArgParser.hpp ArgParser.cpp)
+	target_compile_definitions(streamer PUBLIC STATIC_GETOPT)
-target_compile_definitions(streamer PUBLIC STATIC_GETOPT)
-else()
-add_executable(streamer main.cpp dispatchqueue.cpp dispatchqueue.hpp h264fileparser.cpp h264fileparser.hpp helpers.cpp helpers.hpp opusfileparser.cpp opusfileparser.hpp fileparser.cpp fileparser.hpp stream.cpp stream.hpp ArgParser.hpp ArgParser.cpp)
 endif()
+
 set_target_properties(streamer PROPERTIES
 	CXX_STANDARD 17
 	OUTPUT_NAME streamer)
 
-target_link_libraries(streamer datachannel)
-
 target_link_libraries(streamer datachannel nlohmann_json)
 
+if(WIN32)
+	add_custom_command(TARGET streamer POST_BUILD
+		COMMAND ${CMAKE_COMMAND} -E copy_if_different
+		"$<TARGET_FILE_DIR:datachannel>/datachannel.dll"
+		$<TARGET_FILE_DIR:streamer>
+	)
+endif()

examples/streamer/client.js

@@ -54,12 +54,10 @@ function createPeerConnection() {
 
     // connect audio / video
     pc.addEventListener('track', function (evt) {
-        if (evt.track.kind == 'video') {
+        document.getElementById('media').style.display = 'block';
-            document.getElementById('media').style.display = 'block';
+        const videoTag = document.getElementById('video');
-            document.getElementById('video').srcObject = evt.streams[0];
+        videoTag.srcObject = evt.streams[0];
-        } else {
+        videoTag.play();
-            document.getElementById('audio').srcObject = evt.streams[0];
-        }
     });
 
     let time_start = null;

examples/streamer/helpers.cpp

@@ -60,7 +60,7 @@ int gettimeofday(struct timeval *tv, struct timezone *tz)
 using namespace std;
 using namespace rtc;
 
-ClientTrackData::ClientTrackData(shared_ptr<Track> track, shared_ptr<RtcpSenderReporter> sender) {
+ClientTrackData::ClientTrackData(shared_ptr<Track> track, shared_ptr<RtcpSrReporter> sender) {
     this->track = track;
     this->sender = sender;
 }

examples/streamer/helpers.hpp

@@ -23,9 +23,9 @@
 
 struct ClientTrackData {
     std::shared_ptr<rtc::Track> track;
-    std::shared_ptr<rtc::RtcpSenderReporter> sender;
+	std::shared_ptr<rtc::RtcpSrReporter> sender;
 
-    ClientTrackData(std::shared_ptr<rtc::Track> track, std::shared_ptr<rtc::RtcpSenderReporter> sender);
+	ClientTrackData(std::shared_ptr<rtc::Track> track, std::shared_ptr<rtc::RtcpSrReporter> sender);
 };
 
 struct Client {

examples/streamer/index.html

@@ -52,7 +52,6 @@
 
 <div id="media" style="display: none">
     <h2>Media</h2>
-    <audio id="audio" autoplay></audio>
     <video id="video" autoplay playsinline></video>
 </div>
 

examples/streamer/main.cpp

@@ -214,36 +214,48 @@ int main(int argc, char **argv) try {
 shared_ptr<ClientTrackData> addVideo(const shared_ptr<PeerConnection> pc, const uint8_t payloadType, const uint32_t ssrc, const string cname, const string msid, const function<void (void)> onOpen) {
     auto video = Description::Video(cname);
     video.addH264Codec(payloadType);
-    video.addSSRC(ssrc, cname, msid);
+    video.addSSRC(ssrc, cname, msid, cname);
     auto track = pc->addTrack(video);
     // create RTP configuration
     auto rtpConfig = shared_ptr<RtpPacketizationConfig>(new RtpPacketizationConfig(ssrc, cname, payloadType, H264RtpPacketizer::defaultClockRate));
     // create packetizer
-    auto packetizer = shared_ptr<H264RtpPacketizer>(new H264RtpPacketizer(rtpConfig));
+	auto packetizer = shared_ptr<H264RtpPacketizer>(new H264RtpPacketizer(H264RtpPacketizer::Separator::Length, rtpConfig));
-    // create H264 and RTCP SP handler
+	// create H264 handler
-    shared_ptr<H264PacketizationHandler> h264Handler(new H264PacketizationHandler(H264PacketizationHandler::Separator::Length, packetizer));
+	shared_ptr<H264PacketizationHandler> h264Handler(new H264PacketizationHandler(packetizer));
+	// add RTCP SR handler
+	auto srReporter = make_shared<RtcpSrReporter>(rtpConfig);
+	h264Handler->addToChain(srReporter);
+	// add RTCP NACK handler
+	auto nackResponder = make_shared<RtcpNackResponder>();
+	h264Handler->addToChain(nackResponder);
     // set handler
     track->setRtcpHandler(h264Handler);
     track->onOpen(onOpen);
-    auto trackData = make_shared<ClientTrackData>(track, h264Handler);
+    auto trackData = make_shared<ClientTrackData>(track, srReporter);
     return trackData;
 }
 
 shared_ptr<ClientTrackData> addAudio(const shared_ptr<PeerConnection> pc, const uint8_t payloadType, const uint32_t ssrc, const string cname, const string msid, const function<void (void)> onOpen) {
     auto audio = Description::Audio(cname);
     audio.addOpusCodec(payloadType);
-    audio.addSSRC(ssrc, cname, msid);
+    audio.addSSRC(ssrc, cname, msid, cname);
     auto track = pc->addTrack(audio);
     // create RTP configuration
     auto rtpConfig = shared_ptr<RtpPacketizationConfig>(new RtpPacketizationConfig(ssrc, cname, payloadType, OpusRtpPacketizer::defaultClockRate));
     // create packetizer
     auto packetizer = make_shared<OpusRtpPacketizer>(rtpConfig);
-    // create opus and RTCP SP handler
+	// create opus handler
     auto opusHandler = make_shared<OpusPacketizationHandler>(packetizer);
+	// add RTCP SR handler
+	auto srReporter = make_shared<RtcpSrReporter>(rtpConfig);
+	opusHandler->addToChain(srReporter);
+	// add RTCP NACK handler
+	auto nackResponder = make_shared<RtcpNackResponder>();
+	opusHandler->addToChain(nackResponder);
     // set handler
     track->setRtcpHandler(opusHandler);
     track->onOpen(onOpen);
-    auto trackData = make_shared<ClientTrackData>(track, opusHandler);
+    auto trackData = make_shared<ClientTrackData>(track, srReporter);
     return trackData;
 }
 

include/rtc/configuration.hpp

@@ -70,6 +70,7 @@ struct RTC_CPP_EXPORT Configuration {
 	bool enableIceTcp = false;
 	uint16_t portRangeBegin = 1024;
 	uint16_t portRangeEnd = 65535;
+	std::optional<size_t> mtu;
 };
 
 } // namespace rtc

include/rtc/datachannel.hpp

@@ -30,6 +30,7 @@
 #include <functional>
 #include <type_traits>
 #include <variant>
+#include <shared_mutex>
 
 namespace rtc {
 
@@ -79,6 +80,8 @@ protected:
 	string mProtocol;
 	std::shared_ptr<Reliability> mReliability;
 
+	mutable std::shared_mutex mMutex;
+
 	std::atomic<bool> mIsOpen = false;
 	std::atomic<bool> mIsClosed = false;
 
@@ -88,13 +91,13 @@ private:
 	friend class PeerConnection;
 };
 
-class RTC_CPP_EXPORT NegociatedDataChannel final : public DataChannel {
+class RTC_CPP_EXPORT NegotiatedDataChannel final : public DataChannel {
 public:
-	NegociatedDataChannel(std::weak_ptr<PeerConnection> pc, uint16_t stream, string label,
+	NegotiatedDataChannel(std::weak_ptr<PeerConnection> pc, uint16_t stream, string label,
 	                      string protocol, Reliability reliability);
-	NegociatedDataChannel(std::weak_ptr<PeerConnection> pc, std::weak_ptr<SctpTransport> transport,
+	NegotiatedDataChannel(std::weak_ptr<PeerConnection> pc, std::weak_ptr<SctpTransport> transport,
 	                      uint16_t stream);
-	~NegociatedDataChannel();
+	~NegotiatedDataChannel();
 
 private:
 	void open(std::shared_ptr<SctpTransport> transport) override;

include/rtc/description.hpp

@@ -141,9 +141,9 @@ public:
 		void removeFormat(const string &fmt);
 
 		void addSSRC(uint32_t ssrc, std::optional<string> name,
-		             std::optional<string> msid = nullopt);
+					 std::optional<string> msid = nullopt, std::optional<string> trackID = nullopt);
 		void replaceSSRC(uint32_t oldSSRC, uint32_t ssrc, std::optional<string> name,
-		                 std::optional<string> msid = nullopt);
+						 std::optional<string> msid = nullopt, std::optional<string> trackID = nullopt);
 		bool hasSSRC(uint32_t ssrc);
 		std::vector<uint32_t> getSSRCs();
 

include/rtc/h264packetizationhandler.hpp

@@ -23,50 +23,16 @@
 
 #include "h264rtppacketizer.hpp"
 #include "nalunit.hpp"
-#include "rtcphandler.hpp"
+#include "mediachainablehandler.hpp"
-#include "rtcpsenderreporter.hpp"
 
 namespace rtc {
 
 /// Handler for H264 packetization
-class RTC_CPP_EXPORT H264PacketizationHandler : public RtcpHandler, public RtcpSenderReporter {
+class RTC_CPP_EXPORT H264PacketizationHandler : public MediaChainableHandler {
-	/// RTP packetizer for H264
-	const std::shared_ptr<H264RtpPacketizer> packetizer;
-
-	const uint16_t maximumFragmentSize;
-
-	std::shared_ptr<NalUnits> splitMessage(message_ptr message);
-
 public:
-	/// Nalunit separator
-	enum class Separator {
-		LongStartSequence,  // 0x00, 0x00, 0x00, 0x01
-		ShortStartSequence, // 0x00, 0x00, 0x01
-		StartSequence,      // LongStartSequence or ShortStartSequence
-		Length              // first 4 bytes is nal unit length
-	};
-
 	/// Construct handler for H264 packetization.
-	/// @param separator Nal units separator
 	/// @param packetizer RTP packetizer for h264
-	H264PacketizationHandler(Separator separator, std::shared_ptr<H264RtpPacketizer> packetizer,
+	H264PacketizationHandler(std::shared_ptr<H264RtpPacketizer> packetizer);
-	                         uint16_t maximumFragmentSize = NalUnits::defaultMaximumFragmentSize);
-
-	/// Returns message unchanged
-	/// @param ptr message
-	message_ptr incoming(message_ptr ptr) override;
-
-	/// Returns packetized message if message type is binary
-	/// @note NAL units in `ptr` message must be separated by `separator` given in constructor
-	/// @note If message generates multiple rtp packets, all but last are send using
-	/// `outgoingCallback`. It is your responsibility to send last packet.
-	/// @param ptr message containing all NAL units for current timestamp (one sample)
-	/// @return last packet
-	message_ptr outgoing(message_ptr ptr) override;
-
-private:
-	/// Separator
-	const Separator separator;
 };
 
 } // namespace rtc

include/rtc/h264rtppacketizer.hpp

@@ -21,22 +21,43 @@
 
 #if RTC_ENABLE_MEDIA
 
+#include "nalunit.hpp"
 #include "rtppacketizer.hpp"
+#include "mediahandlerrootelement.hpp"
 
 namespace rtc {
 
 /// RTP packetization of h264 payload
-class RTC_CPP_EXPORT H264RtpPacketizer : public RtpPacketizer {
+class RTC_CPP_EXPORT H264RtpPacketizer : public RtpPacketizer, public MediaHandlerRootElement {
+	std::shared_ptr<NalUnits> splitMessage(binary_ptr message);
+	const uint16_t maximumFragmentSize;
 
 public:
 	/// Default clock rate for H264 in RTP
 	static const auto defaultClockRate = 90 * 1000;
 
+	/// Nalunit separator
+	enum class Separator {
+		LongStartSequence,  // 0x00, 0x00, 0x00, 0x01
+		ShortStartSequence, // 0x00, 0x00, 0x01
+		StartSequence,      // LongStartSequence or ShortStartSequence
+		Length              // first 4 bytes is nal unit length
+	};
+
+	H264RtpPacketizer(H264RtpPacketizer::Separator separator, std::shared_ptr<RtpPacketizationConfig> rtpConfig,
+					  uint16_t maximumFragmentSize = NalUnits::defaultMaximumFragmentSize);
+
 	/// Constructs h264 payload packetizer with given RTP configuration.
 	/// @note RTP configuration is used in packetization process which may change some configuration
 	/// properties such as sequence number.
 	/// @param rtpConfig  RTP configuration
-	H264RtpPacketizer(std::shared_ptr<RtpPacketizationConfig> rtpConfig);
+	/// @param maximumFragmentSize maximum size of one NALU fragment
+	H264RtpPacketizer(std::shared_ptr<RtpPacketizationConfig> rtpConfig,
+					  uint16_t maximumFragmentSize = NalUnits::defaultMaximumFragmentSize);
+
+	ChainedOutgoingProduct processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) override;
+private:
+	const Separator separator;
 };
 
 } // namespace rtc

include/rtc/include.hpp

@@ -56,6 +56,7 @@ using std::byte;
 using std::string;
 using std::string_view;
 using binary = std::vector<byte>;
+using binary_ptr = std::shared_ptr<binary>;
 
 using std::nullopt;
 
@@ -76,6 +77,8 @@ const size_t RECV_QUEUE_LIMIT = 1024 * 1024; // Max per-channel queue size
 
 const int THREADPOOL_SIZE = 4; // Number of threads in the global thread pool
 
+const size_t DEFAULT_IPV4_MTU = 1200; // IPv4 safe MTU value recommended by RFC 8261
+
 // overloaded helper
 template <class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
 template <class... Ts> overloaded(Ts...) -> overloaded<Ts...>;

include/rtc/mediachainablehandler.hpp

@@ -0,0 +1,55 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef RTC_MEDIA_CHAINABLE_HANDLER_H
+#define RTC_MEDIA_CHAINABLE_HANDLER_H
+
+#if RTC_ENABLE_MEDIA
+
+#include "mediahandler.hpp"
+#include "mediahandlerrootelement.hpp"
+
+namespace rtc {
+
+class RTC_CPP_EXPORT MediaChainableHandler : public MediaHandler {
+	const std::shared_ptr<MediaHandlerRootElement> root;
+	std::shared_ptr<MediaHandlerElement> leaf;
+	std::mutex inoutMutex;
+
+	message_ptr handleIncomingBinary(message_ptr);
+	message_ptr handleIncomingControl(message_ptr);
+	message_ptr handleOutgoingBinary(message_ptr);
+	message_ptr handleOutgoingControl(message_ptr);
+	bool sendProduct(ChainedOutgoingProduct product);
+public:
+	MediaChainableHandler(std::shared_ptr<MediaHandlerRootElement> root);
+	~MediaChainableHandler();
+	message_ptr incoming(message_ptr ptr) override;
+	message_ptr outgoing(message_ptr ptr) override;
+
+	bool send(message_ptr msg);
+
+	/// Adds element to chain
+	/// @param chainable Chainable element
+    void addToChain(std::shared_ptr<MediaHandlerElement> chainable);
+};
+
+} // namespace rtc
+
+#endif // RTC_ENABLE_MEDIA
+
+#endif // RTC_MEDIA_CHAINABLE_HANDLER_H

include/rtc/mediahandler.hpp

@@ -17,15 +17,15 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#ifndef RTC_RTCP_HANDLER_H
+#ifndef RTC_MEDIA_HANDLER_H
-#define RTC_RTCP_HANDLER_H
+#define RTC_MEDIA_HANDLER_H
 
 #include "include.hpp"
 #include "message.hpp"
 
 namespace rtc {
 
-class RTC_CPP_EXPORT RtcpHandler {
+class RTC_CPP_EXPORT MediaHandler {
 protected:
 	// Use this callback when trying to send custom data (such as RTCP) to the client.
 	synchronized_callback<message_ptr> outgoingCallback;
@@ -47,4 +47,4 @@ public:
 
 } // namespace rtc
 
-#endif // RTC_RTCP_HANDLER_H
+#endif // RTC_MEDIA_HANDLER_H

include/rtc/mediahandlerelement.hpp

@@ -0,0 +1,111 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef RTC_MEDIA_HANDLER_ELEMENT_H
+#define RTC_MEDIA_HANDLER_ELEMENT_H
+
+#if RTC_ENABLE_MEDIA
+
+#include "include.hpp"
+#include "message.hpp"
+#include "rtp.hpp"
+
+namespace rtc {
+
+using ChainedMessagesProduct = std::shared_ptr<std::vector<binary_ptr>>;
+
+RTC_CPP_EXPORT ChainedMessagesProduct make_chained_messages_product();
+RTC_CPP_EXPORT ChainedMessagesProduct make_chained_messages_product(message_ptr msg);
+
+/// Ougoing messages
+struct RTC_CPP_EXPORT ChainedOutgoingProduct {
+	ChainedOutgoingProduct(ChainedMessagesProduct messages = nullptr, message_ptr control = nullptr);
+	const ChainedMessagesProduct messages;
+	const message_ptr control;
+};
+
+/// Incoming messages with response
+struct RTC_CPP_EXPORT ChainedIncomingProduct {
+	ChainedIncomingProduct(ChainedMessagesProduct incoming = nullptr, ChainedMessagesProduct outgoing = nullptr);
+	const ChainedMessagesProduct incoming;
+	const ChainedOutgoingProduct outgoing;
+};
+
+/// Incoming control messages with response
+struct RTC_CPP_EXPORT ChainedIncomingControlProduct {
+	ChainedIncomingControlProduct(message_ptr incoming, std::optional<ChainedOutgoingProduct> outgoing = nullopt);
+	const message_ptr incoming;
+	const std::optional<ChainedOutgoingProduct> outgoing;
+};
+
+/// Chainable handler
+class RTC_CPP_EXPORT MediaHandlerElement: public std::enable_shared_from_this<MediaHandlerElement> {
+	std::shared_ptr<MediaHandlerElement> upstream = nullptr;
+	std::shared_ptr<MediaHandlerElement> downstream = nullptr;
+
+	void prepareAndSendResponse(std::optional<ChainedOutgoingProduct> outgoing, std::function<bool (ChainedOutgoingProduct)> send);
+
+	void removeFromChain();
+public:
+	MediaHandlerElement();
+
+	/// Creates response to incoming message
+	/// @param messages Current repsonse
+	/// @returns New response
+	std::optional<ChainedOutgoingProduct> processOutgoingResponse(ChainedOutgoingProduct messages);
+
+	// Process incoming and ougoing messages
+	message_ptr formIncomingControlMessage(message_ptr message, std::function<bool (ChainedOutgoingProduct)> send);
+	ChainedMessagesProduct formIncomingBinaryMessage(ChainedMessagesProduct messages, std::function<bool (ChainedOutgoingProduct)> send);
+	message_ptr formOutgoingControlMessage(message_ptr message);
+	std::optional<ChainedOutgoingProduct> formOutgoingBinaryMessage(ChainedOutgoingProduct product);
+
+	/// Process current control message
+	/// @param messages current message
+	/// @returns Modified message and response
+	virtual ChainedIncomingControlProduct processIncomingControlMessage(message_ptr messages);
+
+	/// Process current control message
+	/// @param messages current message
+	/// @returns Modified message
+	virtual message_ptr processOutgoingControlMessage(message_ptr messages);
+
+	/// Process current binary message
+	/// @param messages current message
+	/// @returns Modified message and response
+	virtual ChainedIncomingProduct processIncomingBinaryMessage(ChainedMessagesProduct messages);
+
+	/// Process current binary message
+	/// @param messages current message
+	/// @param control current control message
+	/// @returns Modified binary message and control message
+	virtual ChainedOutgoingProduct processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control);
+
+	/// Set given element as upstream to this
+	/// @param upstream Upstream element
+	/// @returns Upstream element
+	std::shared_ptr<MediaHandlerElement> chainWith(std::shared_ptr<MediaHandlerElement> upstream);
+
+	/// Remove all downstream elements from chain
+	void recursiveRemoveChain();
+};
+
+} // namespace rtc
+
+#endif // RTC_ENABLE_MEDIA
+
+#endif // RTC_MEDIA_HANDLER_ELEMENT_H

include/rtc/mediahandlerrootelement.hpp

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef RTCP_MEDIA_HANDLER_ROOT_ELEMENT_H
+#define RTCP_MEDIA_HANDLER_ROOT_ELEMENT_H
+
+#if RTC_ENABLE_MEDIA
+
+#include "mediahandlerelement.hpp"
+
+namespace rtc {
+
+/// Chainable message handler
+class RTC_CPP_EXPORT MediaHandlerRootElement : public MediaHandlerElement {
+public:
+	MediaHandlerRootElement() { }
+
+	/// Reduce multiple messages into one message
+	/// @param messages Messages to reduce
+	virtual message_ptr reduce(ChainedMessagesProduct messages);
+
+	/// Splits message into multiple messages
+	/// @param message Message to split
+	virtual ChainedMessagesProduct split(message_ptr message);
+};
+
+} // namespace rtc
+
+#endif // RTC_ENABLE_MEDIA
+
+#endif // RTCP_MEDIA_HANDLER_ROOT_ELEMENT_H

include/rtc/nalunit.hpp

@@ -101,9 +101,9 @@ struct RTC_CPP_EXPORT NalUnitFragmentA : NalUnit {
 	enum class FragmentType { Start, Middle, End };
 
 	NalUnitFragmentA(FragmentType type, bool forbiddenBit, uint8_t nri, uint8_t unitType,
-	                 binary data);
+					 binary data);
 
-	static std::vector<NalUnitFragmentA> fragmentsFrom(NalUnit nalu, uint16_t maximumFragmentSize);
+	static std::vector<std::shared_ptr<NalUnitFragmentA>> fragmentsFrom(std::shared_ptr<NalUnit> nalu, uint16_t maximumFragmentSize);
 
 	uint8_t unitType() { return fragmentHeader()->unitType(); }
 
@@ -142,11 +142,10 @@ protected:
 	const uint8_t nal_type_fu_A = 28;
 };
 
-class RTC_CPP_EXPORT NalUnits : public std::vector<NalUnit> {
+class RTC_CPP_EXPORT NalUnits : public std::vector<std::shared_ptr<NalUnit>> {
 public:
 	static const uint16_t defaultMaximumFragmentSize = 1400;
-	std::vector<binary>
+	std::vector<std::shared_ptr<binary>> generateFragments(uint16_t maximumFragmentSize);
-	generateFragments(uint16_t maximumFragmentSize = NalUnits::defaultMaximumFragmentSize);
 };
 
 } // namespace rtc

include/rtc/opuspacketizationhandler.hpp

@@ -22,27 +22,17 @@
 #if RTC_ENABLE_MEDIA
 
 #include "opusrtppacketizer.hpp"
-#include "rtcphandler.hpp"
+#include "mediachainablehandler.hpp"
-#include "rtcpsenderreporter.hpp"
 
 namespace rtc {
 
 /// Handler for opus packetization
-class RTC_CPP_EXPORT OpusPacketizationHandler : public RtcpHandler, public RtcpSenderReporter {
+class RTC_CPP_EXPORT OpusPacketizationHandler : public MediaChainableHandler {
-	/// RTP packetizer for opus
-	const std::shared_ptr<OpusRtpPacketizer> packetizer;
 
 public:
 	/// Construct handler for opus packetization.
 	/// @param packetizer RTP packetizer for opus
 	OpusPacketizationHandler(std::shared_ptr<OpusRtpPacketizer> packetizer);
-
-	/// Returns message unchanged
-	/// @param ptr message
-	message_ptr incoming(message_ptr ptr) override;
-	/// Returns packetized message if message type is binary
-	/// @param ptr message
-	message_ptr outgoing(message_ptr ptr) override;
 };
 
 } // namespace rtc

include/rtc/opusrtppacketizer.hpp

@@ -22,12 +22,12 @@
 #if RTC_ENABLE_MEDIA
 
 #include "rtppacketizer.hpp"
+#include "mediahandlerrootelement.hpp"
 
 namespace rtc {
 
 /// RTP packetizer for opus
-class RTC_CPP_EXPORT OpusRtpPacketizer : public RtpPacketizer {
+class RTC_CPP_EXPORT OpusRtpPacketizer : public RtpPacketizer, public MediaHandlerRootElement {
-
 public:
 	/// default clock rate used in opus RTP communication
 	static const uint32_t defaultClockRate = 48 * 1000;
@@ -42,7 +42,13 @@ public:
 	/// @note This function increase sequence number after packetization.
 	/// @param payload RTP payload
 	/// @param setMark This needs to be `false` for all RTP packets with opus payload
-	message_ptr packetize(binary payload, bool setMark) override;
+	binary_ptr packetize(binary_ptr payload, bool setMark) override;
+
+	/// Creates RTP packet for given samples (all samples share same RTP timesamp)
+	/// @param messages opus samples
+	/// @param control RTCP
+	/// @returns RTP packets and unchanged `control`
+	ChainedOutgoingProduct processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) override;
 };
 
 } // namespace rtc

include/rtc/rtc.h

@@ -41,6 +41,7 @@ extern "C" {
 
 #if RTC_ENABLE_MEDIA
 #define RTC_DEFAULT_MAXIMUM_FRAGMENT_SIZE ((uint16_t)1400)
+#define RTC_DEFAULT_MAXIMUM_PACKET_COUNT_FOR_NACK_CACHE ((unsigned)512)
 #endif
 
 #include <stdbool.h>
@@ -85,20 +86,20 @@ typedef enum { // Don't change, it must match plog severity
 
 typedef enum {
     // video
-    RTC_CODEC_H264,
+    RTC_CODEC_H264 = 0,
-    RTC_CODEC_VP8,
+    RTC_CODEC_VP8 = 1,
-    RTC_CODEC_VP9,
+    RTC_CODEC_VP9 = 2,
 
     // audio
-    RTC_CODEC_OPUS
+    RTC_CODEC_OPUS = 128
 } rtcCodec;
 
 typedef enum {
-    RTC_DIRECTION_UNKNOWN,
+    RTC_DIRECTION_UNKNOWN = 0,
-    RTC_DIRECTION_SENDONLY,
+    RTC_DIRECTION_SENDONLY = 1,
-    RTC_DIRECTION_RECVONLY,
+    RTC_DIRECTION_RECVONLY = 2,
-    RTC_DIRECTION_SENDRECV,
+    RTC_DIRECTION_SENDRECV = 3,
-    RTC_DIRECTION_INACTIVE
+    RTC_DIRECTION_INACTIVE = 4
 } rtcDirection;
 
 #endif // RTC_ENABLE_MEDIA
@@ -174,6 +175,9 @@ RTC_EXPORT int rtcAddRemoteCandidate(int pc, const char *cand, const char *mid);
 RTC_EXPORT int rtcGetLocalDescription(int pc, char *buffer, int size);
 RTC_EXPORT int rtcGetRemoteDescription(int pc, char *buffer, int size);
 
+RTC_EXPORT int rtcGetLocalDescriptionType(int pc, char *buffer, int size);
+RTC_EXPORT int rtcGetRemoteDescriptionType(int pc, char *buffer, int size);
+
 RTC_EXPORT int rtcGetLocalAddress(int pc, char *buffer, int size);
 RTC_EXPORT int rtcGetRemoteAddress(int pc, char *buffer, int size);
 
@@ -215,8 +219,9 @@ RTC_EXPORT int rtcGetTrackDescription(int tr, char *buffer, int size);
 /// @param _direction Direction
 /// @param _name Name (optional)
 /// @param _msid MSID (optional)
+/// @param _trackID Track ID used in MSID (optional)
 /// @returns Track id
-RTC_EXPORT int rtcAddTrackEx(int pc, rtcCodec codec, int payloadType, uint32_t ssrc, const char *_mid, rtcDirection direction, const char *_name, const char *_msid);
+RTC_EXPORT int rtcAddTrackEx(int pc, rtcCodec codec, int payloadType, uint32_t ssrc, const char *_mid, rtcDirection direction, const char *_name, const char *_msid, const char *_trackID);
 
 /// Set H264PacketizationHandler for track
 /// @param tr Track id
@@ -239,6 +244,15 @@ RTC_EXPORT int rtcSetH264PacketizationHandler(int tr, uint32_t ssrc, const char
 /// @param _timestamp Timestamp
 RTC_EXPORT int rtcSetOpusPacketizationHandler(int tr, uint32_t ssrc, const char * cname, uint8_t payloadType, uint32_t clockRate, uint16_t _sequenceNumber, uint32_t _timestamp);
 
+/// Chain RtcpSrReporter to handler chain for given track
+/// @param tr Track id
+int rtcChainRtcpSrReporter(int tr);
+
+/// Chain RtcpNackResponder to handler chain for given track
+/// @param tr Track id
+/// @param maxStoredPacketsCount Maximum stored packet count
+int rtcChainRtcpNackResponder(int tr, unsigned maxStoredPacketsCount);
+
 /// Set start time for RTP stream
 /// @param startTime_s Start time in seconds
 /// @param timeIntervalSince1970 Set true if `startTime_s` is time interval since 1970, false if `startTime_s` is time interval since 1900
@@ -249,7 +263,6 @@ int rtcSetRtpConfigurationStartTime(int id, double startTime_s, bool timeInterva
 /// @param id Track identifier
 int rtcStartRtcpSenderReporterRecording(int id);
 
-
 /// Transform seconds to timestamp using track's clock rate
 /// @param id Track id
 /// @param seconds Seconds
@@ -282,9 +295,9 @@ int rtcSetTrackRTPTimestamp(int id, uint32_t timestamp);
 /// @param timestamp Pointer for result
 int rtcGetPreviousTrackSenderReportTimestamp(int id, uint32_t * timestamp);
 
-/// Set `NeedsToReport` flag in RtcpSenderReporter handler identified by given track id
+/// Set `NeedsToReport` flag in RtcpSrReporter handler identified by given track id
 /// @param id Track id
-int rtcSetNeedsToSendRTCPSR(int id);
+int rtcSetNeedsToSendRtcpSr(int id);
 
 #endif // RTC_ENABLE_MEDIA
 

include/rtc/rtc.hpp

@@ -27,8 +27,11 @@
 
 #if RTC_ENABLE_MEDIA
 
-// RTCP handling
+// Media handling
 #include "rtcpreceivingsession.hpp"
+#include "mediachainablehandler.hpp"
+#include "rtcpsrreporter.hpp"
+#include "rtcpnackresponder.hpp"
 
 // Opus/h264 streaming
 #include "h264packetizationhandler.hpp"

include/rtc/rtcpnackresponder.hpp

@@ -0,0 +1,94 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef RTC_RTCP_NACK_RESPONDER_H
+#define RTC_RTCP_NACK_RESPONDER_H
+
+#if RTC_ENABLE_MEDIA
+
+#include "mediahandlerelement.hpp"
+
+#include <unordered_map>
+#include <queue>
+
+namespace rtc {
+
+class RTC_CPP_EXPORT RtcpNackResponder: public MediaHandlerElement {
+
+	/// Packet storage
+	class RTC_CPP_EXPORT Storage {
+		
+		/// Packet storage element
+		struct RTC_CPP_EXPORT Element {
+			Element(binary_ptr packet, uint16_t sequenceNumber, std::shared_ptr<Element> next = nullptr);
+			const binary_ptr packet;
+			const uint16_t sequenceNumber;
+			/// Pointer to newer element
+			std::shared_ptr<Element> next = nullptr;
+		};
+
+	private:
+		/// Oldest packet in storage
+		std::shared_ptr<Element> oldest = nullptr;
+		/// Newest packet in storage
+		std::shared_ptr<Element> newest = nullptr;
+
+		/// Inner storage
+		std::unordered_map<uint16_t, std::shared_ptr<Element>> storage{};
+
+		/// Maximum storage size
+		const unsigned maximumSize;
+
+		/// Returnst current size
+		unsigned size();
+
+	public:
+		static const unsigned defaultMaximumSize = 512;
+
+		Storage(unsigned _maximumSize);
+
+		/// Returns packet with given sequence number
+		std::optional<binary_ptr> get(uint16_t sequenceNumber);
+
+		/// Stores packet
+		/// @param packet Packet
+		void store(binary_ptr packet);
+	};
+
+	const std::shared_ptr<Storage> storage;
+	std::mutex reportMutex;
+
+public:
+	RtcpNackResponder(unsigned maxStoredPacketCount = Storage::defaultMaximumSize);
+
+	/// Checks for RTCP NACK and handles it,
+	/// @param message RTCP message
+	/// @returns unchanged RTCP message and requested RTP packets
+	ChainedIncomingControlProduct processIncomingControlMessage(message_ptr message) override;
+
+	/// Stores RTP packets in internal storage
+	/// @param messages RTP packets
+	/// @param control RTCP
+	/// @returns Unchanged RTP and RTCP
+	ChainedOutgoingProduct processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) override;
+};
+
+} // namespace rtc
+
+#endif /* RTC_ENABLE_MEDIA */
+
+#endif /* RTC_RTCP_NACK_RESPONDER_H */

include/rtc/rtcpreceivingsession.hpp

@@ -23,14 +23,14 @@
 #if RTC_ENABLE_MEDIA
 
 #include "include.hpp"
-#include "rtcphandler.hpp"
+#include "mediahandler.hpp"
 #include "message.hpp"
 #include "rtp.hpp"
 
 namespace rtc {
 
 // An RtcpSession can be plugged into a Track to handle the whole RTCP session
-class RTC_CPP_EXPORT RtcpReceivingSession : public RtcpHandler {
+class RTC_CPP_EXPORT RtcpReceivingSession : public MediaHandler {
 public:
 	message_ptr incoming(message_ptr ptr) override;
 	message_ptr outgoing(message_ptr ptr) override;

include/rtc/rtcpsrreporter.hpp

@@ -1,5 +1,4 @@
-/*
+/**
- * libdatachannel streamer example
  * Copyright (c) 2020 Filip Klembara (in2core)
  *
  * This program is free software; you can redistribute it and/or
@@ -23,11 +22,12 @@
 
 #include "message.hpp"
 #include "rtppacketizationconfig.hpp"
+#include "mediahandlerelement.hpp"
 
 namespace rtc {
 
-/// Class for sending RTCP SR
+class RTC_CPP_EXPORT RtcpSrReporter: public MediaHandlerElement {
-class RTC_CPP_EXPORT RtcpSenderReporter {
+
 	bool needsToReport = false;
 
 	uint32_t packetCount = 0;
@@ -39,10 +39,6 @@ class RTC_CPP_EXPORT RtcpSenderReporter {
 	void addToReport(RTP *rtp, uint32_t rtpSize);
 	message_ptr getSenderReport(uint32_t timestamp);
 
-protected:
-	/// Outgoing callback for sender reports
-	synchronized_callback<message_ptr> senderReportOutgoingCallback;
-
 public:
 	static uint64_t secondsToNTP(double seconds);
 
@@ -52,7 +48,9 @@ public:
 	/// RTP configuration
 	const std::shared_ptr<RtpPacketizationConfig> rtpConfig;
 
-	RtcpSenderReporter(std::shared_ptr<RtpPacketizationConfig> rtpConfig);
+	RtcpSrReporter(std::shared_ptr<RtpPacketizationConfig> rtpConfig);
+
+	ChainedOutgoingProduct processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) override;
 
 	/// Set `needsToReport` flag. Sender report will be sent before next RTP packet with same
 	/// timestamp.
@@ -63,27 +61,6 @@ public:
 	/// @note `time_offset = rtpConfig->startTime_s -
 	/// rtpConfig->timestampToSeconds(rtpConfig->timestamp)`
 	void startRecording();
-
-	/// Send RTCP SR with given timestamp
-	/// @param timestamp timestamp of the RTCP SR
-	void sendReport(uint32_t timestamp);
-
-protected:
-	/// Calls given block with function for statistics. Sends RTCP SR packet with current timestamp
-	/// before `block` call if `needs_to_report` flag is true.
-	/// @param block Block of code to run. This block has function for rtp stats recording.
-	template <typename T>
-	T withStatsRecording(std::function<T(std::function<void(message_ptr)>)> block) {
-		if (needsToReport) {
-			sendReport(rtpConfig->timestamp);
-			needsToReport = false;
-		}
-		auto result = block([this](message_ptr _rtp) {
-			auto rtp = reinterpret_cast<RTP *>(_rtp->data());
-			this->addToReport(rtp, _rtp->size());
-		});
-		return result;
-	}
 };
 
 } // namespace rtc

include/rtc/rtp.hpp

@@ -298,13 +298,16 @@ public:
 
 private:
 	uint8_t _length;
-	char _text;
+	char _text[1];
 
 public:
-	inline std::string text() const { return std::string(&_text, _length); }
+	inline std::string text() const { return std::string(_text, _length); }
 	inline void setText(std::string text) {
-		_length = text.length();
+		if(text.size() > 0xFF)
-		memcpy(&_text, text.data(), _length);
+			throw std::invalid_argument("text is too long");
+
+		_length = uint8_t(text.size());
+		memcpy(_text, text.data(), text.size());
 	}
 
 	inline uint8_t length() { return _length; }
@@ -334,12 +337,12 @@ public:
 		return reinterpret_cast<RTCP_SDES_ITEM *>(base);
 	}
 
-	long safelyCountChunkSize(unsigned int maxChunkSize) {
+	long safelyCountChunkSize(size_t maxChunkSize) {
 		if (maxChunkSize < RTCP_SDES_CHUNK::size({})) {
 			// chunk is truncated
 			return -1;
 		} else {
-			unsigned int size = sizeof(SSRC);
+			size_t size = sizeof(SSRC);
 			unsigned int i = 0;
 			// We can always access first 4 bytes of first item (in case of no items there will be 4
 			// null bytes)
@@ -407,7 +410,7 @@ public:
 			auto chunk = getChunk(i);
 			chunkSize += chunk->getSize();
 		}
-		uint16_t length = (sizeof(header) + chunkSize) / 4 - 1;
+		uint16_t length = uint16_t((sizeof(header) + chunkSize) / 4 - 1);
 		header.prepareHeader(202, chunkCount, length);
 	}
 
@@ -617,8 +620,31 @@ struct RTCP_FIR {
 };
 
 struct RTCP_NACK_PART {
-	uint16_t pid;
+	uint16_t _pid;
-	uint16_t blp;
+	uint16_t _blp;
+
+	uint16_t getPID() { return ntohs(_pid); }
+	uint16_t getBLP() { return ntohs(_blp); }
+
+	void setPID(uint16_t pid) { _pid = htons(pid); }
+	void setBLP(uint16_t blp) { _blp = htons(blp); }
+
+	std::vector<uint16_t> getSequenceNumbers() {
+		std::vector<uint16_t> result{};
+		result.reserve(17);
+		uint16_t pid = getPID();
+		result.push_back(pid);
+		uint16_t bitmask = getBLP();
+		uint16_t i = pid + 1;
+		while (bitmask > 0) {
+			if (bitmask & 0x1) {
+				result.push_back(i);
+			}
+			i += 1;
+			bitmask >>= 1;
+		}
+		return result;
+	}
 };
 
 class RTCP_NACK {
@@ -644,16 +670,16 @@ public:
 	 */
 	bool addMissingPacket(unsigned int *fciCount, uint16_t *fciPID, uint16_t missingPacket) {
 		if (*fciCount == 0 || missingPacket < *fciPID || missingPacket > (*fciPID + 16)) {
-			parts[*fciCount].pid = htons(missingPacket);
+			parts[*fciCount].setPID(missingPacket);
-			parts[*fciCount].blp = 0;
+			parts[*fciCount].setBLP(0);
 			*fciPID = missingPacket;
 			(*fciCount)++;
 			return true;
 		} else {
-			// TODO SPEEED!
+			// TODO SPEED!
-			auto blp = ntohs(parts[(*fciCount) - 1].blp);
+			uint16_t blp = parts[(*fciCount) - 1].getBLP();
-			auto newBit = 1u << (unsigned int)(missingPacket - (1 + *fciPID));
+			uint16_t newBit = uint16_t(1u << (missingPacket - (1 + *fciPID)));
-			parts[(*fciCount) - 1].blp = htons(blp | newBit);
+			parts[(*fciCount) - 1].setBLP(blp | newBit);
 			return false;
 		}
 	}

include/rtc/rtppacketizer.hpp

@@ -44,7 +44,7 @@ public:
 	/// @note This function increase sequence number after packetization.
 	/// @param payload RTP payload
 	/// @param setMark Set marker flag in RTP packet if true
-	virtual message_ptr packetize(binary payload, bool setMark);
+	virtual std::shared_ptr<binary> packetize(std::shared_ptr<binary> payload, bool setMark);
 };
 
 } // namespace rtc

include/rtc/track.hpp

@@ -24,7 +24,7 @@
 #include "include.hpp"
 #include "message.hpp"
 #include "queue.hpp"
-#include "rtcphandler.hpp"
+#include "mediahandler.hpp"
 
 #include <atomic>
 #include <variant>
@@ -43,6 +43,7 @@ public:
 
 	string mid() const;
 	Description::Media description() const;
+	Description::Direction direction() const;
 
 	void setDescription(Description::Media description);
 
@@ -62,8 +63,8 @@ public:
 	bool requestKeyframe();
 
 	// RTCP handler
-	void setRtcpHandler(std::shared_ptr<RtcpHandler> handler);
+	void setRtcpHandler(std::shared_ptr<MediaHandler> handler);
-	std::shared_ptr<RtcpHandler> getRtcpHandler();
+	std::shared_ptr<MediaHandler> getRtcpHandler();
 
 private:
 #if RTC_ENABLE_MEDIA
@@ -75,13 +76,14 @@ private:
 	bool outgoing(message_ptr message);
 
 	Description::Media mMediaDescription;
+	std::shared_ptr<MediaHandler> mRtcpHandler;
+
+	mutable std::shared_mutex mMutex;
+
 	std::atomic<bool> mIsClosed = false;
 
 	Queue<message_ptr> mRecvQueue;
 
-	std::shared_mutex mRtcpHandlerMutex;
-	std::shared_ptr<RtcpHandler> mRtcpHandler;
-
 	friend class PeerConnection;
 };
 

src/capi.cpp

@@ -53,7 +53,8 @@ std::unordered_map<int, shared_ptr<PeerConnection>> peerConnectionMap;
 std::unordered_map<int, shared_ptr<DataChannel>> dataChannelMap;
 std::unordered_map<int, shared_ptr<Track>> trackMap;
 #if RTC_ENABLE_MEDIA
-std::unordered_map<int, shared_ptr<RtcpSenderReporter>> rtcpSenderMap;
+std::unordered_map<int, shared_ptr<MediaChainableHandler>> rtcpChainableHandlerMap;
+std::unordered_map<int, shared_ptr<RtcpSrReporter>> rtcpSrReporterMap;
 std::unordered_map<int, shared_ptr<RtpPacketizationConfig>> rtpConfigMap;
 #endif
 #if RTC_ENABLE_WEBSOCKET
@@ -141,7 +142,8 @@ void eraseTrack(int tr) {
 	if (trackMap.erase(tr) == 0)
 		throw std::invalid_argument("Track ID does not exist");
 #if RTC_ENABLE_MEDIA
-	rtcpSenderMap.erase(tr);
+	rtcpSrReporterMap.erase(tr);
+	rtcpChainableHandlerMap.erase(tr);
 	rtpConfigMap.erase(tr);
 #endif
 	userPointerMap.erase(tr);
@@ -149,25 +151,41 @@ void eraseTrack(int tr) {
 
 #if RTC_ENABLE_MEDIA
 
-shared_ptr<RtcpSenderReporter> getRTCPSender(int id) {
+shared_ptr<RtcpSrReporter> getRtcpSrReporter(int id) {
 	std::lock_guard lock(mutex);
-	if (auto it = rtcpSenderMap.find(id); it != rtcpSenderMap.end())
+	if (auto it = rtcpSrReporterMap.find(id); it != rtcpSrReporterMap.end()) {
 		return it->second;
-	else
+	} else {
-		throw std::invalid_argument("RtcpSenderReporter ID does not exist");
+		throw std::invalid_argument("RtcpSRReporter ID does not exist");
+	}
 }
 
-void emplaceRTCPSender(shared_ptr<RtcpSenderReporter> ptr, int tr) {
+void emplaceRtcpSrReporter(shared_ptr<RtcpSrReporter> ptr, int tr) {
 	std::lock_guard lock(mutex);
-	rtcpSenderMap.emplace(std::make_pair(tr, ptr));
+	rtcpSrReporterMap.emplace(std::make_pair(tr, ptr));
+}
+
+shared_ptr<MediaChainableHandler> getMediaChainableHandler(int id) {
+	std::lock_guard lock(mutex);
+	if (auto it = rtcpChainableHandlerMap.find(id); it != rtcpChainableHandlerMap.end()) {
+		return it->second;
+	} else {
+		throw std::invalid_argument("RtcpChainableHandler ID does not exist");
+	}
+}
+
+void emplaceMediaChainableHandler(shared_ptr<MediaChainableHandler> ptr, int tr) {
+	std::lock_guard lock(mutex);
+	rtcpChainableHandlerMap.emplace(std::make_pair(tr, ptr));
 }
 
 shared_ptr<RtpPacketizationConfig> getRTPConfig(int id) {
 	std::lock_guard lock(mutex);
-	if (auto it = rtpConfigMap.find(id); it != rtpConfigMap.end())
+	if (auto it = rtpConfigMap.find(id); it != rtpConfigMap.end()) {
 		return it->second;
-	else
+	} else {
 		throw std::invalid_argument("RTPConfiguration ID does not exist");
+	}
 }
 
 void emplaceRTPConfig(shared_ptr<RtpPacketizationConfig> ptr, int tr) {
@@ -254,12 +272,6 @@ template <typename F> int wrap(F func) {
 	}
 }
 
-#define WRAP(statement)                                                                            \
-	wrap([&]() {                                                                                   \
-		statement;                                                                                 \
-		return RTC_ERR_SUCCESS;                                                                    \
-	})
-
 int copyAndReturn(string s, char *buffer, int size) {
 	if (!buffer)
 		return int(s.size() + 1);
@@ -344,7 +356,7 @@ void rtcSetUserPointer(int i, void *ptr) { setUserPointer(i, ptr); }
 void *rtcGetUserPointer(int i) { return getUserPointer(i).value_or(nullptr); }
 
 int rtcCreatePeerConnection(const rtcConfiguration *config) {
-	return WRAP({
+	return wrap([config] {
 		Configuration c;
 		for (int i = 0; i < config->iceServersCount; ++i)
 			c.iceServers.emplace_back(string(config->iceServers[i]));
@@ -360,7 +372,7 @@ int rtcCreatePeerConnection(const rtcConfiguration *config) {
 }
 
 int rtcDeletePeerConnection(int pc) {
-	return WRAP({
+	return wrap([pc] {
 		auto peerConnection = getPeerConnection(pc);
 		peerConnection->onDataChannel(nullptr);
 		peerConnection->onTrack(nullptr);
@@ -370,13 +382,14 @@ int rtcDeletePeerConnection(int pc) {
 		peerConnection->onGatheringStateChange(nullptr);
 
 		erasePeerConnection(pc);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcAddDataChannel(int pc, const char *label) { return rtcAddDataChannelEx(pc, label, nullptr); }
 
 int rtcAddDataChannelEx(int pc, const char *label, const rtcDataChannelInit *init) {
-	return WRAP({
+	return wrap([&] {
 		DataChannelInit dci = {};
 		if (init) {
 			auto *reliability = &init->reliability;
@@ -420,7 +433,7 @@ int rtcCreateDataChannelEx(int pc, const char *label, const rtcDataChannelInit *
 }
 
 int rtcDeleteDataChannel(int dc) {
-	return WRAP({
+	return wrap([dc] {
 		auto dataChannel = getDataChannel(dc);
 		dataChannel->onOpen(nullptr);
 		dataChannel->onClosed(nullptr);
@@ -430,12 +443,13 @@ int rtcDeleteDataChannel(int dc) {
 		dataChannel->onAvailable(nullptr);
 
 		eraseDataChannel(dc);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 #if RTC_ENABLE_MEDIA
 
-void setSSRC(Description::Media *description, uint32_t ssrc, const char *_name, const char *_msid) {
+void setSSRC(Description::Media *description, uint32_t ssrc, const char *_name, const char *_msid, const char *_trackID) {
 
 	optional<string> name = nullopt;
 	if (_name) {
@@ -447,12 +461,17 @@ void setSSRC(Description::Media *description, uint32_t ssrc, const char *_name,
 		msid = string(_msid);
 	}
 
-	description->addSSRC(ssrc, name, msid);
+	optional<string> trackID = nullopt;
+	if (_trackID) {
+		trackID = string(_trackID);
+	}
+
+	description->addSSRC(ssrc, name, msid, trackID);
 }
 
 int rtcAddTrackEx(int pc, rtcCodec codec, int payloadType, uint32_t ssrc, const char *_mid,
-                  rtcDirection _direction, const char *_name, const char *_msid) {
+				  rtcDirection _direction, const char *_name, const char *_msid, const char *_trackID) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		auto direction = rtcDirectionToDirection(_direction);
@@ -516,7 +535,7 @@ int rtcAddTrackEx(int pc, rtcCodec codec, int payloadType, uint32_t ssrc, const
 			throw std::invalid_argument("Unexpected codec");
 		} else {
 			auto description = optDescription.value();
-			setSSRC(&description, ssrc, _name, _msid);
+			setSSRC(&description, ssrc, _name, _msid, _trackID);
 
 			int tr = emplaceTrack(peerConnection->addTrack(std::move(description)));
 			if (auto ptr = getUserPointer(pc)) {
@@ -530,114 +549,144 @@ int rtcAddTrackEx(int pc, rtcCodec codec, int payloadType, uint32_t ssrc, const
 int rtcSetH264PacketizationHandler(int tr, uint32_t ssrc, const char *cname, uint8_t payloadType,
                                    uint32_t clockRate, uint16_t maxFragmentSize, uint16_t sequenceNumber,
                                    uint32_t timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto track = getTrack(tr);
 		// create RTP configuration
 		auto rtpConfig = getNewRtpPacketizationConfig(ssrc, cname, payloadType, clockRate,
-		                                              sequenceNumber, timestamp);
+													  sequenceNumber, timestamp);
 		// create packetizer
-		auto packetizer = shared_ptr<H264RtpPacketizer>(new H264RtpPacketizer(rtpConfig));
+		auto packetizer = std::make_shared<H264RtpPacketizer>(rtpConfig, maxFragmentSize);
-		// create H264 and RTCP SP handler
+		// create H264 handler
-		shared_ptr<H264PacketizationHandler> h264Handler(
+		auto h264Handler = std::make_shared<H264PacketizationHandler>(packetizer);
-		    new H264PacketizationHandler(H264PacketizationHandler::Separator::Length, packetizer, maxFragmentSize));
+		emplaceMediaChainableHandler(h264Handler, tr);
-		emplaceRTCPSender(h264Handler, tr);
 		emplaceRTPConfig(rtpConfig, tr);
 		// set handler
 		track->setRtcpHandler(h264Handler);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetOpusPacketizationHandler(int tr, uint32_t ssrc, const char *cname, uint8_t payloadType,
                                    uint32_t clockRate, uint16_t sequenceNumber,
                                    uint32_t timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto track = getTrack(tr);
 		// create RTP configuration
 		auto rtpConfig = getNewRtpPacketizationConfig(ssrc, cname, payloadType, clockRate,
 		                                              sequenceNumber, timestamp);
 		// create packetizer
-		auto packetizer = shared_ptr<OpusRtpPacketizer>(new OpusRtpPacketizer(rtpConfig));
+		auto packetizer = std::make_shared<OpusRtpPacketizer>(rtpConfig);
-		// create Opus and RTCP SP handler
+		// create Opus handler
-		shared_ptr<OpusPacketizationHandler> opusHandler(new OpusPacketizationHandler(packetizer));
+		auto opusHandler = std::make_shared<OpusPacketizationHandler>(packetizer);
-		emplaceRTCPSender(opusHandler, tr);
+        emplaceMediaChainableHandler(opusHandler, tr);
 		emplaceRTPConfig(rtpConfig, tr);
 		// set handler
 		track->setRtcpHandler(opusHandler);
+		return RTC_ERR_SUCCESS;
+	});
+}
+
+int rtcChainRtcpSrReporter(int tr) {
+	return wrap([tr] {
+		auto config = getRTPConfig(tr);
+		auto reporter = std::make_shared<RtcpSrReporter>(config);
+		emplaceRtcpSrReporter(reporter, tr);
+		auto chainableHandler = getMediaChainableHandler(tr);
+		chainableHandler->addToChain(reporter);
+		return RTC_ERR_SUCCESS;
+	});
+}
+
+int rtcChainRtcpNackResponder(int tr, unsigned maxStoredPacketsCount) {
+	return wrap([tr, maxStoredPacketsCount] {
+		auto responder = std::make_shared<RtcpNackResponder>(maxStoredPacketsCount);
+		auto chainableHandler = getMediaChainableHandler(tr);
+		chainableHandler->addToChain(responder);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetRtpConfigurationStartTime(int id, double startTime_s, bool timeIntervalSince1970,
                                     uint32_t timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto config = getRTPConfig(id);
 		auto epoch = RtpPacketizationConfig::EpochStart::T1900;
 		if (timeIntervalSince1970) {
 			epoch = RtpPacketizationConfig::EpochStart::T1970;
 		}
 		config->setStartTime(startTime_s, epoch, timestamp);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcStartRtcpSenderReporterRecording(int id) {
-	return WRAP({
+	return wrap([id] {
-		auto sender = getRTCPSender(id);
+		auto sender = getRtcpSrReporter(id);
 		sender->startRecording();
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcTransformSecondsToTimestamp(int id, double seconds, uint32_t *timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto config = getRTPConfig(id);
 		*timestamp = config->secondsToTimestamp(seconds);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcTransformTimestampToSeconds(int id, uint32_t timestamp, double *seconds) {
-	return WRAP({
+	return wrap([&] {
 		auto config = getRTPConfig(id);
 		*seconds = config->timestampToSeconds(timestamp);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcGetCurrentTrackTimestamp(int id, uint32_t *timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto config = getRTPConfig(id);
 		*timestamp = config->timestamp;
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcGetTrackStartTimestamp(int id, uint32_t *timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto config = getRTPConfig(id);
 		*timestamp = config->startTimestamp;
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetTrackRTPTimestamp(int id, uint32_t timestamp) {
-	return WRAP({
+	return wrap([&] {
 		auto config = getRTPConfig(id);
 		config->timestamp = timestamp;
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcGetPreviousTrackSenderReportTimestamp(int id, uint32_t *timestamp) {
-	return WRAP({
+	return wrap([&] {
-		auto sender = getRTCPSender(id);
+		auto sender = getRtcpSrReporter(id);
 		*timestamp = sender->previousReportedTimestamp;
+		return RTC_ERR_SUCCESS;
 	});
 }
 
-int rtcSetNeedsToSendRTCPSR(int id) {
+int rtcSetNeedsToSendRtcpSr(int id) {
-	return WRAP({
+	return wrap([id]{
-		auto sender = getRTCPSender(id);
+		auto sender = getRtcpSrReporter(id);
 		sender->setNeedsToReport();
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 #endif // RTC_ENABLE_MEDIA
 
 int rtcAddTrack(int pc, const char *mediaDescriptionSdp) {
-	return WRAP({
+	return wrap([&] {
 		if (!mediaDescriptionSdp)
 			throw std::invalid_argument("Unexpected null pointer for track media description");
 
@@ -652,7 +701,7 @@ int rtcAddTrack(int pc, const char *mediaDescriptionSdp) {
 }
 
 int rtcDeleteTrack(int tr) {
-	return WRAP({
+	return wrap([&] {
 		auto track = getTrack(tr);
 		track->onOpen(nullptr);
 		track->onClosed(nullptr);
@@ -662,11 +711,12 @@ int rtcDeleteTrack(int tr) {
 		track->onAvailable(nullptr);
 
 		eraseTrack(tr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcGetTrackDescription(int tr, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto track = getTrack(tr);
 		return copyAndReturn(track->description(), buffer, size);
 	});
@@ -674,7 +724,7 @@ int rtcGetTrackDescription(int tr, char *buffer, int size) {
 
 #if RTC_ENABLE_WEBSOCKET
 int rtcCreateWebSocket(const char *url) {
-	return WRAP({
+	return wrap([&] {
 		auto ws = std::make_shared<WebSocket>();
 		ws->open(url);
 		return emplaceWebSocket(ws);
@@ -682,7 +732,7 @@ int rtcCreateWebSocket(const char *url) {
 }
 
 int rtcCreateWebSocketEx(const char *url, const rtcWsConfiguration *config) {
-	return WRAP({
+	return wrap([&] {
 		WebSocket::Configuration c;
 		c.disableTlsVerification = config->disableTlsVerification;
 		auto ws = std::make_shared<WebSocket>(c);
@@ -692,7 +742,7 @@ int rtcCreateWebSocketEx(const char *url, const rtcWsConfiguration *config) {
 }
 
 int rtcDeleteWebsocket(int ws) {
-	return WRAP({
+	return wrap([&] {
 		auto webSocket = getWebSocket(ws);
 		webSocket->onOpen(nullptr);
 		webSocket->onClosed(nullptr);
@@ -702,12 +752,13 @@ int rtcDeleteWebsocket(int ws) {
 		webSocket->onAvailable(nullptr);
 
 		eraseWebSocket(ws);
+		return RTC_ERR_SUCCESS;
 	});
 }
 #endif
 
 int rtcSetLocalDescriptionCallback(int pc, rtcDescriptionCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onLocalDescription([pc, cb](Description desc) {
@@ -716,11 +767,12 @@ int rtcSetLocalDescriptionCallback(int pc, rtcDescriptionCallbackFunc cb) {
 			});
 		else
 			peerConnection->onLocalDescription(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetLocalCandidateCallback(int pc, rtcCandidateCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onLocalCandidate([pc, cb](Candidate cand) {
@@ -729,11 +781,12 @@ int rtcSetLocalCandidateCallback(int pc, rtcCandidateCallbackFunc cb) {
 			});
 		else
 			peerConnection->onLocalCandidate(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetStateChangeCallback(int pc, rtcStateChangeCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onStateChange([pc, cb](PeerConnection::State state) {
@@ -742,11 +795,12 @@ int rtcSetStateChangeCallback(int pc, rtcStateChangeCallbackFunc cb) {
 			});
 		else
 			peerConnection->onStateChange(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetGatheringStateChangeCallback(int pc, rtcGatheringStateCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onGatheringStateChange([pc, cb](PeerConnection::GatheringState state) {
@@ -755,11 +809,12 @@ int rtcSetGatheringStateChangeCallback(int pc, rtcGatheringStateCallbackFunc cb)
 			});
 		else
 			peerConnection->onGatheringStateChange(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetSignalingStateChangeCallback(int pc, rtcSignalingStateCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onSignalingStateChange([pc, cb](PeerConnection::SignalingState state) {
@@ -768,11 +823,12 @@ int rtcSetSignalingStateChangeCallback(int pc, rtcSignalingStateCallbackFunc cb)
 			});
 		else
 			peerConnection->onGatheringStateChange(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetDataChannelCallback(int pc, rtcDataChannelCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onDataChannel([pc, cb](std::shared_ptr<DataChannel> dataChannel) {
@@ -784,11 +840,12 @@ int rtcSetDataChannelCallback(int pc, rtcDataChannelCallbackFunc cb) {
 			});
 		else
 			peerConnection->onDataChannel(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetTrackCallback(int pc, rtcTrackCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		if (cb)
 			peerConnection->onTrack([pc, cb](std::shared_ptr<Track> track) {
@@ -800,41 +857,45 @@ int rtcSetTrackCallback(int pc, rtcTrackCallbackFunc cb) {
 			});
 		else
 			peerConnection->onTrack(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetLocalDescription(int pc, const char *type) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 		peerConnection->setLocalDescription(type ? Description::stringToType(type)
 		                                         : Description::Type::Unspec);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetRemoteDescription(int pc, const char *sdp, const char *type) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		if (!sdp)
 			throw std::invalid_argument("Unexpected null pointer for remote description");
 
 		peerConnection->setRemoteDescription({string(sdp), type ? string(type) : ""});
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcAddRemoteCandidate(int pc, const char *cand, const char *mid) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		if (!cand)
 			throw std::invalid_argument("Unexpected null pointer for remote candidate");
 
 		peerConnection->addRemoteCandidate({string(cand), mid ? string(mid) : ""});
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcGetLocalDescription(int pc, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		if (auto desc = peerConnection->localDescription())
@@ -845,7 +906,7 @@ int rtcGetLocalDescription(int pc, char *buffer, int size) {
 }
 
 int rtcGetRemoteDescription(int pc, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		if (auto desc = peerConnection->remoteDescription())
@@ -855,8 +916,30 @@ int rtcGetRemoteDescription(int pc, char *buffer, int size) {
 	});
 }
 
+int rtcGetLocalDescriptionType(int pc, char *buffer, int size) {
+	return wrap([&] {
+		auto peerConnection = getPeerConnection(pc);
+
+		if (auto desc = peerConnection->localDescription())
+			return copyAndReturn(desc->typeString(), buffer, size);
+		else
+			return RTC_ERR_NOT_AVAIL;
+	});
+}
+
+int rtcGetRemoteDescriptionType(int pc, char *buffer, int size) {
+	return wrap([&] {
+		auto peerConnection = getPeerConnection(pc);
+
+		if (auto desc = peerConnection->remoteDescription())
+			return copyAndReturn(desc->typeString(), buffer, size);
+		else
+			return RTC_ERR_NOT_AVAIL;
+	});
+}
+
 int rtcGetLocalAddress(int pc, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		if (auto addr = peerConnection->localAddress())
@@ -867,7 +950,7 @@ int rtcGetLocalAddress(int pc, char *buffer, int size) {
 }
 
 int rtcGetRemoteAddress(int pc, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		if (auto addr = peerConnection->remoteAddress())
@@ -878,7 +961,7 @@ int rtcGetRemoteAddress(int pc, char *buffer, int size) {
 }
 
 int rtcGetSelectedCandidatePair(int pc, char *local, int localSize, char *remote, int remoteSize) {
-	return WRAP({
+	return wrap([&] {
 		auto peerConnection = getPeerConnection(pc);
 
 		Candidate localCand;
@@ -899,28 +982,28 @@ int rtcGetSelectedCandidatePair(int pc, char *local, int localSize, char *remote
 }
 
 int rtcGetDataChannelStream(int dc) {
-	return WRAP({
+	return wrap([dc] {
 		auto dataChannel = getDataChannel(dc);
 		return int(dataChannel->id());
 	});
 }
 
 int rtcGetDataChannelLabel(int dc, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto dataChannel = getDataChannel(dc);
 		return copyAndReturn(dataChannel->label(), buffer, size);
 	});
 }
 
 int rtcGetDataChannelProtocol(int dc, char *buffer, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto dataChannel = getDataChannel(dc);
 		return copyAndReturn(dataChannel->protocol(), buffer, size);
 	});
 }
 
 int rtcGetDataChannelReliability(int dc, rtcReliability *reliability) {
-	return WRAP({
+	return wrap([&] {
 		auto dataChannel = getDataChannel(dc);
 
 		if (!reliability)
@@ -943,7 +1026,7 @@ int rtcGetDataChannelReliability(int dc, rtcReliability *reliability) {
 }
 
 int rtcSetOpenCallback(int id, rtcOpenCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		if (cb)
 			channel->onOpen([id, cb]() {
@@ -952,11 +1035,12 @@ int rtcSetOpenCallback(int id, rtcOpenCallbackFunc cb) {
 			});
 		else
 			channel->onOpen(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetClosedCallback(int id, rtcClosedCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		if (cb)
 			channel->onClosed([id, cb]() {
@@ -965,11 +1049,12 @@ int rtcSetClosedCallback(int id, rtcClosedCallbackFunc cb) {
 			});
 		else
 			channel->onClosed(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetErrorCallback(int id, rtcErrorCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		if (cb)
 			channel->onError([id, cb](string error) {
@@ -978,11 +1063,12 @@ int rtcSetErrorCallback(int id, rtcErrorCallbackFunc cb) {
 			});
 		else
 			channel->onError(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetMessageCallback(int id, rtcMessageCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		if (cb)
 			channel->onMessage(
@@ -996,11 +1082,12 @@ int rtcSetMessageCallback(int id, rtcMessageCallbackFunc cb) {
 			    });
 		else
 			channel->onMessage(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSendMessage(int id, const char *data, int size) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 
 		if (!data && size != 0)
@@ -1020,21 +1107,22 @@ int rtcSendMessage(int id, const char *data, int size) {
 }
 
 int rtcGetBufferedAmount(int id) {
-	return WRAP({
+	return wrap([id] {
 		auto channel = getChannel(id);
 		return int(channel->bufferedAmount());
 	});
 }
 
 int rtcSetBufferedAmountLowThreshold(int id, int amount) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		channel->setBufferedAmountLowThreshold(size_t(amount));
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcSetBufferedAmountLowCallback(int id, rtcBufferedAmountLowCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		if (cb)
 			channel->onBufferedAmountLow([id, cb]() {
@@ -1043,15 +1131,16 @@ int rtcSetBufferedAmountLowCallback(int id, rtcBufferedAmountLowCallbackFunc cb)
 			});
 		else
 			channel->onBufferedAmountLow(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcGetAvailableAmount(int id) {
-	return WRAP({ return int(getChannel(id)->availableAmount()); });
+	return wrap([id] { return int(getChannel(id)->availableAmount()); });
 }
 
 int rtcSetAvailableCallback(int id, rtcAvailableCallbackFunc cb) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 		if (cb)
 			channel->onAvailable([id, cb]() {
@@ -1060,11 +1149,12 @@ int rtcSetAvailableCallback(int id, rtcAvailableCallbackFunc cb) {
 			});
 		else
 			channel->onAvailable(nullptr);
+		return RTC_ERR_SUCCESS;
 	});
 }
 
 int rtcReceiveMessage(int id, char *buffer, int *size) {
-	return WRAP({
+	return wrap([&] {
 		auto channel = getChannel(id);
 
 		if (!size)

src/datachannel.cpp

@@ -87,21 +87,34 @@ DataChannel::~DataChannel() { close(); }
 
 uint16_t DataChannel::stream() const { return mStream; }
 
-uint16_t DataChannel::id() const { return uint16_t(mStream); }
+uint16_t DataChannel::id() const { return mStream; }
 
-string DataChannel::label() const { return mLabel; }
+string DataChannel::label() const {
+	std::shared_lock lock(mMutex);
+	return mLabel;
+}
 
-string DataChannel::protocol() const { return mProtocol; }
+string DataChannel::protocol() const {
+	std::shared_lock lock(mMutex);
+	return mProtocol;
+}
 
-Reliability DataChannel::reliability() const { return *mReliability; }
+Reliability DataChannel::reliability() const {
+	std::shared_lock lock(mMutex);
+	return *mReliability;
+}
 
 void DataChannel::close() {
-	mIsClosed = true;
+	std::shared_ptr<SctpTransport> transport;
-	if (mIsOpen.exchange(false))
+	{
-		if (auto transport = mSctpTransport.lock())
+		std::shared_lock lock(mMutex);
-			transport->closeStream(mStream);
+		transport = mSctpTransport.lock();
+	}
+
+	mIsClosed = true;
+	if (mIsOpen.exchange(false) && transport)
+		transport->closeStream(mStream);
 
-	mSctpTransport.reset();
 	resetCallbacks();
 }
 
@@ -110,7 +123,6 @@ void DataChannel::remoteClose() {
 		triggerClosed();
 
 	mIsOpen = false;
-	mSctpTransport.reset();
 }
 
 bool DataChannel::send(message_variant data) { return outgoing(make_message(std::move(data))); }
@@ -167,7 +179,10 @@ size_t DataChannel::maxMessageSize() const {
 size_t DataChannel::availableAmount() const { return mRecvQueue.amount(); }
 
 void DataChannel::open(shared_ptr<SctpTransport> transport) {
-	mSctpTransport = transport;
+	{
+		std::unique_lock lock(mMutex);
+		mSctpTransport = transport;
+	}
 
 	if (!mIsOpen.exchange(true))
 		triggerOpen();
@@ -179,19 +194,22 @@ void DataChannel::processOpenMessage(message_ptr) {
 }
 
 bool DataChannel::outgoing(message_ptr message) {
-	if (mIsClosed)
+	std::shared_ptr<SctpTransport> transport;
-		throw std::runtime_error("DataChannel is closed");
+	{
+		std::shared_lock lock(mMutex);
+		transport = mSctpTransport.lock();
 
-	if (message->size() > maxMessageSize())
+		if (!transport || mIsClosed)
-		throw std::runtime_error("Message size exceeds limit");
+			throw std::runtime_error("DataChannel is closed");
 
-	auto transport = mSctpTransport.lock();
+		if (message->size() > maxMessageSize())
-	if (!transport)
+			throw std::runtime_error("Message size exceeds limit");
-		throw std::runtime_error("DataChannel transport is not open");
+
+		// Before the ACK has been received on a DataChannel, all messages must be sent ordered
+		message->reliability = mIsOpen ? mReliability : nullptr;
+		message->stream = mStream;
+	}
 
-	// Before the ACK has been received on a DataChannel, all messages must be sent ordered
-	message->reliability = mIsOpen ? mReliability : nullptr;
-	message->stream = mStream;
 	return transport->send(message);
 }
 
@@ -235,20 +253,21 @@ void DataChannel::incoming(message_ptr message) {
 	}
 }
 
-NegociatedDataChannel::NegociatedDataChannel(std::weak_ptr<PeerConnection> pc, uint16_t stream,
+NegotiatedDataChannel::NegotiatedDataChannel(std::weak_ptr<PeerConnection> pc, uint16_t stream,
                                              string label, string protocol, Reliability reliability)
     : DataChannel(pc, stream, std::move(label), std::move(protocol), std::move(reliability)) {}
 
-NegociatedDataChannel::NegociatedDataChannel(std::weak_ptr<PeerConnection> pc,
+NegotiatedDataChannel::NegotiatedDataChannel(std::weak_ptr<PeerConnection> pc,
                                              std::weak_ptr<SctpTransport> transport,
                                              uint16_t stream)
     : DataChannel(pc, stream, "", "", {}) {
 	mSctpTransport = transport;
 }
 
-NegociatedDataChannel::~NegociatedDataChannel() {}
+NegotiatedDataChannel::~NegotiatedDataChannel() {}
 
-void NegociatedDataChannel::open(shared_ptr<SctpTransport> transport) {
+void NegotiatedDataChannel::open(shared_ptr<SctpTransport> transport) {
+	std::unique_lock lock(mMutex);
 	mSctpTransport = transport;
 
 	uint8_t channelType;
@@ -287,10 +306,13 @@ void NegociatedDataChannel::open(shared_ptr<SctpTransport> transport) {
 	std::copy(mLabel.begin(), mLabel.end(), end);
 	std::copy(mProtocol.begin(), mProtocol.end(), end + mLabel.size());
 
+	lock.unlock();
+
 	transport->send(make_message(buffer.begin(), buffer.end(), Message::Control, mStream));
 }
 
-void NegociatedDataChannel::processOpenMessage(message_ptr message) {
+void NegotiatedDataChannel::processOpenMessage(message_ptr message) {
+	std::unique_lock lock(mMutex);
 	auto transport = mSctpTransport.lock();
 	if (!transport)
 		throw std::runtime_error("DataChannel has no transport");
@@ -326,6 +348,8 @@ void NegociatedDataChannel::processOpenMessage(message_ptr message) {
 		mReliability->rexmit = int(0);
 	}
 
+	lock.unlock();
+
 	binary buffer(sizeof(AckMessage), byte(0));
 	auto &ack = *reinterpret_cast<AckMessage *>(buffer.data());
 	ack.type = MESSAGE_ACK;

src/description.cpp

@@ -525,20 +525,20 @@ Description::Entry::removeAttribute(std::vector<string>::iterator it) {
 }
 
 void Description::Media::addSSRC(uint32_t ssrc, std::optional<string> name,
-                                 std::optional<string> msid) {
+								 std::optional<string> msid, std::optional<string> trackID) {
 	if (name)
 		mAttributes.emplace_back("ssrc:" + std::to_string(ssrc) + " cname:" + *name);
 	else
 		mAttributes.emplace_back("ssrc:" + std::to_string(ssrc));
 
 	if (msid)
-		mAttributes.emplace_back("ssrc:" + std::to_string(ssrc) + " msid:" + *msid + " " + *msid);
+		mAttributes.emplace_back("ssrc:" + std::to_string(ssrc) + " msid:" + *msid + " " + trackID.value_or(*msid));
 
 	mSsrcs.emplace_back(ssrc);
 }
 
 void Description::Media::replaceSSRC(uint32_t oldSSRC, uint32_t ssrc, std::optional<string> name,
-                                     std::optional<string> msid) {
+									 std::optional<string> msid, std::optional<string> trackID) {
 	auto it = mAttributes.begin();
 	while (it != mAttributes.end()) {
 		if (it->find("ssrc:" + std::to_string(oldSSRC)) == 0) {
@@ -546,7 +546,7 @@ void Description::Media::replaceSSRC(uint32_t oldSSRC, uint32_t ssrc, std::optio
 		} else
 			it++;
 	}
-	addSSRC(ssrc, std::move(name), std::move(msid));
+	addSSRC(ssrc, std::move(name), std::move(msid), std::move(trackID));
 }
 
 void Description::Media::removeSSRC(uint32_t oldSSRC) {

src/dtlssrtptransport.cpp

@@ -58,10 +58,11 @@ void DtlsSrtpTransport::Cleanup() { srtp_shutdown(); }
 
 DtlsSrtpTransport::DtlsSrtpTransport(std::shared_ptr<IceTransport> lower,
                                      shared_ptr<Certificate> certificate,
+                                     std::optional<size_t> mtu,
                                      verifier_callback verifierCallback,
                                      message_callback srtpRecvCallback,
                                      state_callback stateChangeCallback)
-    : DtlsTransport(lower, certificate, std::move(verifierCallback),
+    : DtlsTransport(lower, certificate, mtu, std::move(verifierCallback),
                     std::move(stateChangeCallback)),
       mSrtpRecvCallback(std::move(srtpRecvCallback)) { // distinct from Transport recv callback
 

src/dtlssrtptransport.hpp

@@ -39,9 +39,9 @@ public:
 	static void Init();
 	static void Cleanup();
 
-	DtlsSrtpTransport(std::shared_ptr<IceTransport> lower, std::shared_ptr<Certificate> certificate,
+	DtlsSrtpTransport(std::shared_ptr<IceTransport> lower, certificate_ptr certificate,
-	                  verifier_callback verifierCallback, message_callback srtpRecvCallback,
+	                  std::optional<size_t> mtu, verifier_callback verifierCallback,
-	                  state_callback stateChangeCallback);
+	                  message_callback srtpRecvCallback, state_callback stateChangeCallback);
 	~DtlsSrtpTransport();
 
 	bool sendMedia(message_ptr message);

src/dtlstransport.cpp

@@ -50,8 +50,9 @@ void DtlsTransport::Init() {
 void DtlsTransport::Cleanup() { gnutls_global_deinit(); }
 
 DtlsTransport::DtlsTransport(shared_ptr<IceTransport> lower, certificate_ptr certificate,
-                             verifier_callback verifierCallback, state_callback stateChangeCallback)
+                             std::optional<size_t> mtu, verifier_callback verifierCallback,
-    : Transport(lower, std::move(stateChangeCallback)), mCertificate(certificate),
+                             state_callback stateChangeCallback)
+    : Transport(lower, std::move(stateChangeCallback)), mMtu(mtu), mCertificate(certificate),
       mVerifierCallback(std::move(verifierCallback)),
       mIsClient(lower->role() == Description::Role::Active), mCurrentDscp(0) {
 
@@ -156,11 +157,15 @@ void DtlsTransport::postHandshake() {
 }
 
 void DtlsTransport::runRecvLoop() {
-	const size_t maxMtu = 4096;
+	const size_t bufferSize = 4096;
+
 	// Handshake loop
 	try {
 		changeState(State::Connecting);
-		gnutls_dtls_set_mtu(mSession, 1280 - 40 - 8); // min MTU over UDP/IPv6
+
+		size_t mtu = mMtu.value_or(DEFAULT_IPV4_MTU + 20) - 8 - 40; // UDP/IPv6
+		gnutls_dtls_set_mtu(mSession, static_cast<unsigned int>(mtu));
+		PLOG_VERBOSE << "SSL MTU set to " << mtu;
 
 		int ret;
 		do {
@@ -174,7 +179,7 @@ void DtlsTransport::runRecvLoop() {
 
 		// RFC 8261: DTLS MUST support sending messages larger than the current path MTU
 		// See https://tools.ietf.org/html/rfc8261#section-5
-		gnutls_dtls_set_mtu(mSession, maxMtu + 1);
+		gnutls_dtls_set_mtu(mSession, bufferSize + 1);
 
 	} catch (const std::exception &e) {
 		PLOG_ERROR << "DTLS handshake: " << e.what();
@@ -188,7 +193,6 @@ void DtlsTransport::runRecvLoop() {
 		postHandshake();
 		changeState(State::Connected);
 
-		const size_t bufferSize = maxMtu;
 		char buffer[bufferSize];
 
 		while (true) {
@@ -314,8 +318,9 @@ void DtlsTransport::Cleanup() {
 }
 
 DtlsTransport::DtlsTransport(shared_ptr<IceTransport> lower, shared_ptr<Certificate> certificate,
-                             verifier_callback verifierCallback, state_callback stateChangeCallback)
+                             std::optional<size_t> mtu, verifier_callback verifierCallback,
-    : Transport(lower, std::move(stateChangeCallback)), mCertificate(certificate),
+                             state_callback stateChangeCallback)
+    : Transport(lower, std::move(stateChangeCallback)), mMtu(mtu), mCertificate(certificate),
       mVerifierCallback(std::move(verifierCallback)),
       mIsClient(lower->role() == Description::Role::Active), mCurrentDscp(0) {
 	PLOG_DEBUG << "Initializing DTLS transport (OpenSSL)";
@@ -440,16 +445,18 @@ void DtlsTransport::postHandshake() {
 }
 
 void DtlsTransport::runRecvLoop() {
-	const size_t maxMtu = 4096;
+	const size_t bufferSize = 4096;
 	try {
 		changeState(State::Connecting);
-		SSL_set_mtu(mSsl, 1280 - 40 - 8); // min MTU over UDP/IPv6
+
+		size_t mtu = mMtu.value_or(DEFAULT_IPV4_MTU + 20) - 8 - 40; // UDP/IPv6
+		SSL_set_mtu(mSsl, static_cast<unsigned int>(mtu));
+		PLOG_VERBOSE << "SSL MTU set to " << mtu;
 
 		// Initiate the handshake
 		int ret = SSL_do_handshake(mSsl);
 		openssl::check(mSsl, ret, "Handshake failed");
 
-		const size_t bufferSize = maxMtu;
 		byte buffer[bufferSize];
 		while (mIncomingQueue.running()) {
 			// Process pending messages
@@ -466,7 +473,7 @@ void DtlsTransport::runRecvLoop() {
 					if (SSL_is_init_finished(mSsl)) {
 						// RFC 8261: DTLS MUST support sending messages larger than the current path
 						// MTU See https://tools.ietf.org/html/rfc8261#section-5
-						SSL_set_mtu(mSsl, maxMtu + 1);
+						SSL_set_mtu(mSsl, bufferSize + 1);
 
 						PLOG_INFO << "DTLS handshake finished";
 						postHandshake();

src/dtlstransport.hpp

@@ -44,7 +44,8 @@ public:
 	using verifier_callback = std::function<bool(const std::string &fingerprint)>;
 
 	DtlsTransport(std::shared_ptr<IceTransport> lower, certificate_ptr certificate,
-	              verifier_callback verifierCallback, state_callback stateChangeCallback);
+	              std::optional<size_t> mtu, verifier_callback verifierCallback,
+	              state_callback stateChangeCallback);
 	~DtlsTransport();
 
 	virtual void start() override;
@@ -57,6 +58,7 @@ protected:
 	virtual void postHandshake();
 	void runRecvLoop();
 
+	const std::optional<size_t> mMtu;
 	const certificate_ptr mCertificate;
 	const verifier_callback mVerifierCallback;
 	const bool mIsClient;

src/h264packetizationhandler.cpp

@@ -22,146 +22,7 @@
 
 namespace rtc {
 
-using std::function;
+H264PacketizationHandler::H264PacketizationHandler(std::shared_ptr<H264RtpPacketizer> packetizer): MediaChainableHandler(packetizer) { }
-using std::make_shared;
-using std::shared_ptr;
-
-typedef enum {
-	NUSM_noMatch,
-	NUSM_firstZero,
-	NUSM_secondZero,
-	NUSM_thirdZero,
-	NUSM_shortMatch,
-	NUSM_longMatch
-} NalUnitStartSequenceMatch;
-
-NalUnitStartSequenceMatch StartSequenceMatchSucc(NalUnitStartSequenceMatch match, byte _byte,
-                                                 H264PacketizationHandler::Separator separator) {
-	assert(separator != H264PacketizationHandler::Separator::Length);
-	auto byte = (uint8_t)_byte;
-	auto detectShort = separator == H264PacketizationHandler::Separator::ShortStartSequence ||
-	                   separator == H264PacketizationHandler::Separator::StartSequence;
-	auto detectLong = separator == H264PacketizationHandler::Separator::LongStartSequence ||
-	                  separator == H264PacketizationHandler::Separator::StartSequence;
-	switch (match) {
-	case NUSM_noMatch:
-		if (byte == 0x00) {
-			return NUSM_firstZero;
-		}
-		break;
-	case NUSM_firstZero:
-		if (byte == 0x00) {
-			return NUSM_secondZero;
-		}
-		break;
-	case NUSM_secondZero:
-		if (byte == 0x00 && detectLong) {
-			return NUSM_thirdZero;
-		} else if (byte == 0x01 && detectShort) {
-			return NUSM_shortMatch;
-		}
-		break;
-	case NUSM_thirdZero:
-		if (byte == 0x01 && detectLong) {
-			return NUSM_longMatch;
-		}
-		break;
-	case NUSM_shortMatch:
-		return NUSM_shortMatch;
-	case NUSM_longMatch:
-		return NUSM_longMatch;
-	}
-	return NUSM_noMatch;
-}
-
-message_ptr H264PacketizationHandler::incoming(message_ptr ptr) { return ptr; }
-
-shared_ptr<NalUnits> H264PacketizationHandler::splitMessage(message_ptr message) {
-	auto nalus = make_shared<NalUnits>();
-	if (separator == Separator::Length) {
-		unsigned long long index = 0;
-		while (index < message->size()) {
-			assert(index + 4 < message->size());
-			if (index + 4 >= message->size()) {
-				LOG_WARNING << "Invalid NAL Unit data (incomplete length), ignoring!";
-				break;
-			}
-			auto lengthPtr = (uint32_t *)(message->data() + index);
-			uint32_t length = ntohl(*lengthPtr);
-			auto naluStartIndex = index + 4;
-			auto naluEndIndex = naluStartIndex + length;
-
-			assert(naluEndIndex <= message->size());
-			if (naluEndIndex > message->size()) {
-				LOG_WARNING << "Invalid NAL Unit data (incomplete unit), ignoring!";
-				break;
-			}
-			nalus->push_back(
-			    NalUnit(message->begin() + naluStartIndex, message->begin() + naluEndIndex));
-			index = naluEndIndex;
-		}
-	} else {
-		NalUnitStartSequenceMatch match = NUSM_noMatch;
-		unsigned long long index = 0;
-		while (index < message->size()) {
-			match = StartSequenceMatchSucc(match, (*message)[index++], separator);
-			if (match == NUSM_longMatch || match == NUSM_shortMatch) {
-				match = NUSM_noMatch;
-				break;
-			}
-		}
-		index++;
-		unsigned long long naluStartIndex = index;
-
-		while (index < message->size()) {
-			match = StartSequenceMatchSucc(match, (*message)[index], separator);
-			if (match == NUSM_longMatch || match == NUSM_shortMatch) {
-				auto sequenceLength = match == NUSM_longMatch ? 4 : 3;
-				unsigned long long naluEndIndex = index - sequenceLength;
-				match = NUSM_noMatch;
-				nalus->push_back(NalUnit(message->begin() + naluStartIndex,
-				                         message->begin() + naluEndIndex + 1));
-				naluStartIndex = index + 1;
-			}
-			index++;
-		}
-		nalus->push_back(NalUnit(message->begin() + naluStartIndex, message->end()));
-	}
-	return nalus;
-}
-
-message_ptr H264PacketizationHandler::outgoing(message_ptr ptr) {
-	if (ptr->type == Message::Binary) {
-		auto nalus = splitMessage(ptr);
-		auto fragments = nalus->generateFragments(maximumFragmentSize);
-
-		auto lastPacket = withStatsRecording<message_ptr>(
-		    [fragments, this](function<void(message_ptr)> addToReport) {
-			    for (unsigned long long index = 0; index < fragments.size() - 1; index++) {
-				    auto packet = packetizer->packetize(fragments[index], false);
-
-				    addToReport(packet);
-
-				    outgoingCallback(std::move(packet));
-			    }
-			    // packet is last, marker must be set
-			    auto lastPacket = packetizer->packetize(fragments[fragments.size() - 1], true);
-			    addToReport(lastPacket);
-			    return lastPacket;
-		    });
-		return lastPacket;
-	}
-	return ptr;
-}
-
-H264PacketizationHandler::H264PacketizationHandler(Separator separator,
-                                                   std::shared_ptr<H264RtpPacketizer> packetizer,
-                                                   uint16_t maximumFragmentSize)
-    : RtcpHandler(), RtcpSenderReporter(packetizer->rtpConfig), packetizer(packetizer),
-      maximumFragmentSize(maximumFragmentSize), separator(separator) {
-
-	senderReportOutgoingCallback = [this](message_ptr msg) { outgoingCallback(msg); };
-}
 
 } // namespace rtc
 

src/h264rtppacketizer.cpp

@@ -22,8 +22,139 @@
 
 namespace rtc {
 
-H264RtpPacketizer::H264RtpPacketizer(std::shared_ptr<RtpPacketizationConfig> rtpConfig)
+using std::make_shared;
-    : RtpPacketizer(rtpConfig) {}
+using std::shared_ptr;
+
+typedef enum {
+	NUSM_noMatch,
+	NUSM_firstZero,
+	NUSM_secondZero,
+	NUSM_thirdZero,
+	NUSM_shortMatch,
+	NUSM_longMatch
+} NalUnitStartSequenceMatch;
+
+NalUnitStartSequenceMatch StartSequenceMatchSucc(NalUnitStartSequenceMatch match, byte _byte,
+												 H264RtpPacketizer::Separator separator) {
+	assert(separator != H264RtpPacketizer::Separator::Length);
+	auto byte = (uint8_t)_byte;
+	auto detectShort = separator == H264RtpPacketizer::Separator::ShortStartSequence ||
+	separator == H264RtpPacketizer::Separator::StartSequence;
+	auto detectLong = separator == H264RtpPacketizer::Separator::LongStartSequence ||
+	separator == H264RtpPacketizer::Separator::StartSequence;
+	switch (match) {
+		case NUSM_noMatch:
+			if (byte == 0x00) {
+				return NUSM_firstZero;
+			}
+			break;
+		case NUSM_firstZero:
+			if (byte == 0x00) {
+				return NUSM_secondZero;
+			}
+			break;
+		case NUSM_secondZero:
+			if (byte == 0x00 && detectLong) {
+				return NUSM_thirdZero;
+			} else if (byte == 0x01 && detectShort) {
+				return NUSM_shortMatch;
+			}
+			break;
+		case NUSM_thirdZero:
+			if (byte == 0x01 && detectLong) {
+				return NUSM_longMatch;
+			}
+			break;
+		case NUSM_shortMatch:
+			return NUSM_shortMatch;
+		case NUSM_longMatch:
+			return NUSM_longMatch;
+	}
+	return NUSM_noMatch;
+}
+
+shared_ptr<NalUnits> H264RtpPacketizer::splitMessage(binary_ptr message) {
+	auto nalus = make_shared<NalUnits>();
+	if (separator == Separator::Length) {
+		unsigned long long index = 0;
+		while (index < message->size()) {
+			assert(index + 4 < message->size());
+			if (index + 4 >= message->size()) {
+				LOG_WARNING << "Invalid NAL Unit data (incomplete length), ignoring!";
+				break;
+			}
+			auto lengthPtr = (uint32_t *)(message->data() + index);
+			uint32_t length = ntohl(*lengthPtr);
+			auto naluStartIndex = index + 4;
+			auto naluEndIndex = naluStartIndex + length;
+
+			assert(naluEndIndex <= message->size());
+			if (naluEndIndex > message->size()) {
+				LOG_WARNING << "Invalid NAL Unit data (incomplete unit), ignoring!";
+				break;
+			}
+			auto begin = message->begin() + naluStartIndex;
+			auto end = message->begin() + naluEndIndex;
+			nalus->push_back(std::make_shared<NalUnit>(begin, end));
+			index = naluEndIndex;
+		}
+	} else {
+		NalUnitStartSequenceMatch match = NUSM_noMatch;
+		unsigned long long index = 0;
+		while (index < message->size()) {
+			match = StartSequenceMatchSucc(match, (*message)[index++], separator);
+			if (match == NUSM_longMatch || match == NUSM_shortMatch) {
+				match = NUSM_noMatch;
+				break;
+			}
+		}
+
+		unsigned long long naluStartIndex = index;
+
+		while (index < message->size()) {
+			match = StartSequenceMatchSucc(match, (*message)[index], separator);
+			if (match == NUSM_longMatch || match == NUSM_shortMatch) {
+				auto sequenceLength = match == NUSM_longMatch ? 4 : 3;
+				unsigned long long naluEndIndex = index - sequenceLength;
+				match = NUSM_noMatch;
+				auto begin = message->begin() + naluStartIndex;
+				auto end = message->begin() + naluEndIndex + 1;
+				nalus->push_back(std::make_shared<NalUnit>(begin, end));
+				naluStartIndex = index + 1;
+			}
+			index++;
+		}
+		auto begin = message->begin() + naluStartIndex;
+		auto end = message->end();
+		nalus->push_back(std::make_shared<NalUnit>(begin, end));
+	}
+	return nalus;
+}
+
+H264RtpPacketizer::H264RtpPacketizer(std::shared_ptr<RtpPacketizationConfig> rtpConfig,
+									 uint16_t maximumFragmentSize)
+: RtpPacketizer(rtpConfig), MediaHandlerRootElement(), maximumFragmentSize(maximumFragmentSize), separator(Separator::Length) {}
+
+H264RtpPacketizer::H264RtpPacketizer(H264RtpPacketizer::Separator separator, std::shared_ptr<RtpPacketizationConfig> rtpConfig,
+									 uint16_t maximumFragmentSize)
+: RtpPacketizer(rtpConfig), MediaHandlerRootElement(), maximumFragmentSize(maximumFragmentSize), separator(separator) {}
+
+ChainedOutgoingProduct H264RtpPacketizer::processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) {
+	ChainedMessagesProduct packets = std::make_shared<std::vector<binary_ptr>>();
+	for (auto message: *messages) {
+		auto nalus = splitMessage(message);
+		auto fragments = nalus->generateFragments(maximumFragmentSize);
+		if (fragments.size() == 0) {
+			return ChainedOutgoingProduct();
+		}
+		unsigned i = 0;
+		for (; i < fragments.size() - 1; i++) {
+			packets->push_back(packetize(fragments[i], false));
+		}
+		packets->push_back(packetize(fragments[i], true));
+	}
+	return {packets, control};
+}
 
 } // namespace rtc
 

src/mediachainablehandler.cpp

@@ -0,0 +1,167 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if RTC_ENABLE_MEDIA
+
+#include "mediachainablehandler.hpp"
+
+namespace rtc {
+
+MediaChainableHandler::MediaChainableHandler(std::shared_ptr<MediaHandlerRootElement> root): MediaHandler(), root(root), leaf(root) { }
+
+MediaChainableHandler::~MediaChainableHandler() {
+	leaf->recursiveRemoveChain();
+}
+
+bool MediaChainableHandler::sendProduct(ChainedOutgoingProduct product) {
+	bool result = true;
+	if (product.control) {
+		assert(product.control->type == Message::Control);
+		auto sendResult = send(product.control);
+		if(!sendResult) {
+			LOG_DEBUG << "Failed to send control message";
+		}
+		result = result && sendResult;
+	}
+	if (product.messages) {
+		auto messages = product.messages;
+		for (unsigned i = 0; i < messages->size(); i++) {
+			auto message = messages->at(i);
+			if (!message) {
+				LOG_DEBUG << "Invalid message to send " << i + 1 << "/" << messages->size();
+			}
+			auto sendResult = send(make_message(*message));
+			if(!sendResult) {
+				LOG_DEBUG << "Failed to send message " << i + 1 << "/" << messages->size();
+			}
+			result = result && sendResult;
+		}
+	}
+	return result;
+}
+
+message_ptr MediaChainableHandler::handleIncomingBinary(message_ptr msg) {
+	assert(msg->type == Message::Binary);
+	auto messages = root->split(msg);
+	auto incoming = leaf->formIncomingBinaryMessage(messages, [this](ChainedOutgoingProduct outgoing) {
+		return sendProduct(outgoing);
+	});
+	if (incoming) {
+		return root->reduce(incoming);
+	} else {
+		return nullptr;
+	}
+}
+
+message_ptr MediaChainableHandler::handleIncomingControl(message_ptr msg) {
+	assert(msg->type == Message::Control);
+	auto incoming = leaf->formIncomingControlMessage(msg, [this](ChainedOutgoingProduct outgoing) {
+		return sendProduct(outgoing);
+	});
+	assert(!incoming || incoming->type == Message::Control);
+	return incoming;
+}
+
+message_ptr MediaChainableHandler::handleOutgoingBinary(message_ptr msg) {
+	assert(msg->type == Message::Binary);
+	auto messages = make_chained_messages_product(msg);
+	auto optOutgoing = root->formOutgoingBinaryMessage(ChainedOutgoingProduct(messages));
+	if (!optOutgoing.has_value()) {
+		LOG_ERROR << "Generating outgoing message failed";
+		return nullptr;
+	}
+	auto outgoing = optOutgoing.value();
+	if (outgoing.control) {
+		if(!send(outgoing.control)) {
+			LOG_DEBUG << "Failed to send control message";
+		}
+	}
+	auto lastMessage = outgoing.messages->back();
+	if (!lastMessage) {
+		LOG_DEBUG << "Invalid message to send";
+		return nullptr;
+	}
+	for (unsigned i = 0; i < outgoing.messages->size() - 1; i++) {
+		auto message = outgoing.messages->at(i);
+		if (!message) {
+			LOG_DEBUG << "Invalid message to send " << i + 1 << "/" << outgoing.messages->size();
+		}
+		if(!send(make_message(*message))) {
+			LOG_DEBUG << "Failed to send message " << i + 1 << "/" << outgoing.messages->size();
+		}
+	}
+	return make_message(*lastMessage);
+}
+
+message_ptr MediaChainableHandler::handleOutgoingControl(message_ptr msg) {
+	assert(msg->type == Message::Control);
+	auto outgoing = root->formOutgoingControlMessage(msg);
+	assert(!outgoing || outgoing->type == Message::Control);
+	if (!outgoing) {
+		LOG_ERROR << "Generating outgoing control message failed";
+		return nullptr;
+	}
+	return outgoing;
+}
+
+message_ptr MediaChainableHandler::outgoing(message_ptr ptr) {
+	assert(ptr);
+	if (!ptr) {
+		LOG_ERROR << "Outgoing message is nullptr, ignoring";
+		return nullptr;
+	}
+	std::lock_guard<std::mutex> guard(inoutMutex);
+	if (ptr->type == Message::Binary) {
+		return handleOutgoingBinary(ptr);
+	} else if (ptr->type == Message::Control) {
+		return handleOutgoingControl(ptr);
+	}
+	return ptr;
+}
+
+message_ptr MediaChainableHandler::incoming(message_ptr ptr) {
+	if (!ptr) {
+		LOG_ERROR << "Incoming message is nullptr, ignoring";
+		return nullptr;
+	}
+	std::lock_guard<std::mutex> guard(inoutMutex);
+	if (ptr->type == Message::Binary) {
+		return handleIncomingBinary(ptr);
+	} else if (ptr->type == Message::Control) {
+		return handleIncomingControl(ptr);
+	}
+	return ptr;
+}
+
+bool MediaChainableHandler::send(message_ptr msg) {
+	try {
+		outgoingCallback(std::move(msg));
+		return true;
+	} catch (const std::exception &e) {
+		LOG_DEBUG << "Send in RTCP chain handler failed: " << e.what();
+	}
+	return false;
+}
+
+void MediaChainableHandler::addToChain(std::shared_ptr<MediaHandlerElement> chainable) {
+	assert(leaf);
+	leaf = leaf->chainWith(chainable);
+}
+
+} // namespace rtc
+
+#endif /* RTC_ENABLE_MEDIA */

src/mediahandlerelement.cpp

@@ -0,0 +1,201 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if RTC_ENABLE_MEDIA
+
+#include "mediahandlerelement.hpp"
+
+namespace rtc {
+
+ChainedMessagesProduct make_chained_messages_product() {
+	return std::make_shared<std::vector<binary_ptr>>();
+}
+
+ChainedMessagesProduct make_chained_messages_product(message_ptr msg) {
+	std::vector<binary_ptr> msgs = {msg};
+	return std::make_shared<std::vector<binary_ptr>>(msgs);
+}
+
+ChainedOutgoingProduct::ChainedOutgoingProduct(ChainedMessagesProduct messages, message_ptr control)
+: messages(messages), control(control) { }
+
+ChainedIncomingProduct::ChainedIncomingProduct(ChainedMessagesProduct incoming, ChainedMessagesProduct outgoing)
+: incoming(incoming), outgoing(outgoing) { }
+
+ChainedIncomingControlProduct::ChainedIncomingControlProduct(message_ptr incoming, std::optional<ChainedOutgoingProduct> outgoing)
+: incoming(incoming), outgoing(outgoing) { }
+
+MediaHandlerElement::MediaHandlerElement() { }
+
+void MediaHandlerElement::removeFromChain() {
+	if (upstream) {
+		upstream->downstream = downstream;
+	}
+	if (downstream) {
+		downstream->upstream = upstream;
+	}
+	upstream = nullptr;
+	downstream = nullptr;
+}
+
+void MediaHandlerElement::recursiveRemoveChain() {
+	if (downstream) {
+		// `recursiveRemoveChain` removes last strong reference to downstream element
+		// we need to keep strong reference to prevent deallocation of downstream element
+		// during `recursiveRemoveChain`
+		auto strongDownstreamPtr = downstream;
+		downstream->recursiveRemoveChain();
+	}
+	removeFromChain();
+}
+
+std::optional<ChainedOutgoingProduct> MediaHandlerElement::processOutgoingResponse(ChainedOutgoingProduct messages) {
+	if (messages.messages) {
+		if (upstream) {
+			auto msgs = upstream->formOutgoingBinaryMessage(ChainedOutgoingProduct(messages.messages, messages.control));
+			if (msgs.has_value()) {
+				return msgs.value();
+			} else {
+				LOG_ERROR << "Generating outgoing message failed";
+				return nullopt;
+			}
+		} else {
+			return messages;
+		}
+	} else if (messages.control) {
+		if (upstream) {
+			auto control = upstream->formOutgoingControlMessage(messages.control);
+			if (control) {
+				return ChainedOutgoingProduct(nullptr, control);
+			} else {
+				LOG_ERROR << "Generating outgoing control message failed";
+				return nullopt;
+			}
+		} else {
+			return messages;
+		}
+	} else {
+		return ChainedOutgoingProduct();
+	}
+}
+
+void MediaHandlerElement::prepareAndSendResponse(std::optional<ChainedOutgoingProduct> outgoing, std::function<bool (ChainedOutgoingProduct)> send) {
+	if (outgoing.has_value()) {
+		auto message = outgoing.value();
+		auto response = processOutgoingResponse(message);
+		if (response.has_value()) {
+			if(!send(response.value())) {
+				LOG_DEBUG << "Send failed";
+			}
+		} else {
+			LOG_DEBUG << "No response to send";
+		}
+	}
+}
+
+message_ptr MediaHandlerElement::formIncomingControlMessage(message_ptr message, std::function<bool (ChainedOutgoingProduct)> send) {
+	assert(message);
+	auto product = processIncomingControlMessage(message);
+	prepareAndSendResponse(product.outgoing, send);
+	if (product.incoming) {
+		if (downstream) {
+			return downstream->formIncomingControlMessage(product.incoming, send);
+		} else {
+			return product.incoming;
+		}
+	} else {
+		return nullptr;
+	}
+}
+
+ChainedMessagesProduct MediaHandlerElement::formIncomingBinaryMessage(ChainedMessagesProduct messages, std::function<bool (ChainedOutgoingProduct)> send) {
+	assert(messages && !messages->empty());
+	auto product = processIncomingBinaryMessage(messages);
+	prepareAndSendResponse(product.outgoing, send);
+	if (product.incoming) {
+		if (downstream) {
+			return downstream->formIncomingBinaryMessage(product.incoming, send);
+		} else {
+			return product.incoming;
+		}
+	} else {
+		return nullptr;
+	}
+}
+
+message_ptr MediaHandlerElement::formOutgoingControlMessage(message_ptr message) {
+	assert(message);
+	auto newMessage = processOutgoingControlMessage(message);
+	assert(newMessage);
+	if(!newMessage) {
+		LOG_ERROR << "Failed to generate outgoing message";
+		return nullptr;
+	}
+	if (upstream) {
+		return upstream->formOutgoingControlMessage(newMessage);
+	} else {
+		return newMessage;
+	}
+}
+
+std::optional<ChainedOutgoingProduct> MediaHandlerElement::formOutgoingBinaryMessage(ChainedOutgoingProduct product) {
+	assert(product.messages && !product.messages->empty());
+	auto newProduct = processOutgoingBinaryMessage(product.messages, product.control);
+	assert(!product.control || newProduct.control);
+	assert(newProduct.messages && !newProduct.messages->empty());
+	if (product.control && !newProduct.control) {
+		LOG_ERROR << "Outgoing message must not remove control message";
+		return nullopt;
+	}
+	if (!newProduct.messages || newProduct.messages->empty()) {
+		LOG_ERROR << "Failed to generate message";
+		return nullopt;
+	}
+	if (upstream) {
+		return upstream->formOutgoingBinaryMessage(newProduct);
+	} else {
+		return newProduct;
+	}
+}
+
+ChainedIncomingControlProduct MediaHandlerElement::processIncomingControlMessage(message_ptr messages) {
+	return {messages};
+}
+
+message_ptr MediaHandlerElement::processOutgoingControlMessage(message_ptr messages) {
+	return messages;
+}
+
+ChainedIncomingProduct MediaHandlerElement::processIncomingBinaryMessage(ChainedMessagesProduct messages) {
+	return {messages};
+}
+
+ChainedOutgoingProduct MediaHandlerElement::processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) {
+	return {messages, control};
+}
+
+std::shared_ptr<MediaHandlerElement> MediaHandlerElement::chainWith(std::shared_ptr<MediaHandlerElement> upstream) {
+	assert(this->upstream == nullptr);
+	assert(upstream->downstream == nullptr);
+	this->upstream = upstream;
+	upstream->downstream = shared_from_this();
+	return upstream;
+}
+
+} // namespace rtc
+
+#endif /* RTC_ENABLE_MEDIA */

src/mediahandlerrootelement.cpp

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) 2020 Filip Klembara (in2core)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if RTC_ENABLE_MEDIA
+
+#include "mediahandlerrootelement.hpp"
+
+namespace rtc {
+
+message_ptr MediaHandlerRootElement::reduce(ChainedMessagesProduct messages) {
+	if (messages && !messages->empty()) {
+		auto msg_ptr = messages->front();
+		if (msg_ptr) {
+			return make_message(*msg_ptr);
+		} else {
+			return nullptr;
+		}
+	} else {
+		return nullptr;
+	}
+}
+
+ChainedMessagesProduct MediaHandlerRootElement::split(message_ptr message) {
+	return make_chained_messages_product(message);
+}
+
+} // namespace rtc
+
+#endif /* RTC_ENABLE_MEDIA */

src/nalunit.cpp

@@ -24,8 +24,8 @@
 namespace rtc {
 
 NalUnitFragmentA::NalUnitFragmentA(FragmentType type, bool forbiddenBit, uint8_t nri,
-                                   uint8_t unitType, binary data)
+								   uint8_t unitType, binary data)
-    : NalUnit(data.size() + 2) {
+: NalUnit(data.size() + 2) {
 	setForbiddenBit(forbiddenBit);
 	setNRI(nri);
 	fragmentIndicator()->setUnitType(NalUnitFragmentA::nal_type_fu_A);
@@ -34,23 +34,23 @@ NalUnitFragmentA::NalUnitFragmentA(FragmentType type, bool forbiddenBit, uint8_t
 	copy(data.begin(), data.end(), begin() + 2);
 }
 
-std::vector<NalUnitFragmentA> NalUnitFragmentA::fragmentsFrom(NalUnit nalu,
+std::vector<std::shared_ptr<NalUnitFragmentA>> NalUnitFragmentA::fragmentsFrom(std::shared_ptr<NalUnit> nalu,
-                                                              uint16_t maximumFragmentSize) {
+																			   uint16_t maximumFragmentSize) {
-	assert(nalu.size() > maximumFragmentSize);
+	assert(nalu->size() > maximumFragmentSize);
-	if (nalu.size() <= maximumFragmentSize) {
+	if (nalu->size() <= maximumFragmentSize) {
 		// we need to change `maximum_fragment_size` to have at least two fragments
-		maximumFragmentSize = nalu.size() / 2;
+		maximumFragmentSize = nalu->size() / 2;
 	}
-	auto fragments_count = ceil(double(nalu.size()) / maximumFragmentSize);
+	auto fragments_count = ceil(double(nalu->size()) / maximumFragmentSize);
-	maximumFragmentSize = ceil(nalu.size() / fragments_count);
+	maximumFragmentSize = ceil(nalu->size() / fragments_count);
 
 	// 2 bytes for FU indicator and FU header
 	maximumFragmentSize -= 2;
-	auto f = nalu.forbiddenBit();
+	auto f = nalu->forbiddenBit();
-	uint8_t nri = nalu.nri() & 0x03;
+	uint8_t nri = nalu->nri() & 0x03;
-	uint8_t naluType = nalu.unitType() & 0x1F;
+	uint8_t naluType = nalu->unitType() & 0x1F;
-	auto payload = nalu.payload();
+	auto payload = nalu->payload();
-	vector<NalUnitFragmentA> result{};
+	vector<std::shared_ptr<NalUnitFragmentA>> result{};
 	uint64_t offset = 0;
 	while (offset < payload.size()) {
 		vector<byte> fragmentData;
@@ -66,7 +66,7 @@ std::vector<NalUnitFragmentA> NalUnitFragmentA::fragmentsFrom(NalUnit nalu,
 			fragmentType = FragmentType::End;
 		}
 		fragmentData = {payload.begin() + offset, payload.begin() + offset + maximumFragmentSize};
-		NalUnitFragmentA fragment{fragmentType, f, nri, naluType, fragmentData};
+		auto fragment = std::make_shared<NalUnitFragmentA>(fragmentType, f, nri, naluType, fragmentData);
 		result.push_back(fragment);
 		offset += maximumFragmentSize;
 	}
@@ -76,26 +76,26 @@ std::vector<NalUnitFragmentA> NalUnitFragmentA::fragmentsFrom(NalUnit nalu,
 void NalUnitFragmentA::setFragmentType(FragmentType type) {
 	fragmentHeader()->setReservedBit6(false);
 	switch (type) {
-	case FragmentType::Start:
+		case FragmentType::Start:
-		fragmentHeader()->setStart(true);
+			fragmentHeader()->setStart(true);
-		fragmentHeader()->setEnd(false);
+			fragmentHeader()->setEnd(false);
-		break;
+			break;
-	case FragmentType::End:
+		case FragmentType::End:
-		fragmentHeader()->setStart(false);
+			fragmentHeader()->setStart(false);
-		fragmentHeader()->setEnd(true);
+			fragmentHeader()->setEnd(true);
-		break;
+			break;
-	default:
+		default:
-		fragmentHeader()->setStart(false);
+			fragmentHeader()->setStart(false);
-		fragmentHeader()->setEnd(false);
+			fragmentHeader()->setEnd(false);
 	}
 }
 
-std::vector<binary> NalUnits::generateFragments(uint16_t maximumFragmentSize) {
+std::vector<std::shared_ptr<binary>> NalUnits::generateFragments(uint16_t maximumFragmentSize) {
-	vector<binary> result{};
+	vector<std::shared_ptr<binary>> result{};
 	for (auto nalu : *this) {
-		if (nalu.size() > maximumFragmentSize) {
+		if (nalu->size() > maximumFragmentSize) {
-			std::vector<NalUnitFragmentA> fragments =
+			std::vector<std::shared_ptr<NalUnitFragmentA>> fragments =
-			    NalUnitFragmentA::fragmentsFrom(nalu, maximumFragmentSize);
+			NalUnitFragmentA::fragmentsFrom(nalu, maximumFragmentSize);
 			result.insert(result.end(), fragments.begin(), fragments.end());
 		} else {
 			result.push_back(nalu);

src/opuspacketizationhandler.cpp

@@ -23,23 +23,7 @@
 namespace rtc {
 
 OpusPacketizationHandler::OpusPacketizationHandler(std::shared_ptr<OpusRtpPacketizer> packetizer)
-    : RtcpHandler(), RtcpSenderReporter(packetizer->rtpConfig), packetizer(packetizer) {
+: MediaChainableHandler(packetizer) { }
-	senderReportOutgoingCallback = [this](message_ptr msg) { outgoingCallback(msg); };
-}
-
-message_ptr OpusPacketizationHandler::incoming(message_ptr ptr) { return ptr; }
-
-message_ptr OpusPacketizationHandler::outgoing(message_ptr ptr) {
-	if (ptr->type == Message::Binary) {
-		return withStatsRecording<message_ptr>(
-		    [this, ptr](std::function<void(message_ptr)> addToReport) {
-			    auto rtp = packetizer->packetize(*ptr, false);
-			    addToReport(rtp);
-			    return rtp;
-		    });
-	}
-	return ptr;
-}
 
 } // namespace rtc
 

src/opusrtppacketizer.cpp

@@ -23,13 +23,22 @@
 namespace rtc {
 
 OpusRtpPacketizer::OpusRtpPacketizer(std::shared_ptr<RtpPacketizationConfig> rtpConfig)
-    : RtpPacketizer(rtpConfig) {}
+: RtpPacketizer(rtpConfig), MediaHandlerRootElement() {}
 
-message_ptr OpusRtpPacketizer::packetize(binary payload, bool setMark) {
+binary_ptr OpusRtpPacketizer::packetize(binary_ptr payload, [[maybe_unused]] bool setMark) {
 	assert(!setMark);
 	return RtpPacketizer::packetize(payload, false);
 }
 
+ChainedOutgoingProduct OpusRtpPacketizer::processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) {
+	ChainedMessagesProduct packets = make_chained_messages_product();
+	packets->reserve(messages->size());
+	for (auto message: *messages) {
+		packets->push_back(packetize(message, false));
+	}
+	return {packets, control};
+}
+
 } // namespace rtc
 
 #endif /* RTC_ENABLE_MEDIA */

src/peerconnection.cpp

@@ -22,8 +22,8 @@
 #include "include.hpp"
 #include "logcounter.hpp"
 #include "processor.hpp"
-#include "threadpool.hpp"
 #include "rtp.hpp"
+#include "threadpool.hpp"
 
 #include "dtlstransport.hpp"
 #include "icetransport.hpp"
@@ -75,6 +75,17 @@ PeerConnection::PeerConnection(const Configuration &config)
 
 	if (config.portRangeEnd && config.portRangeBegin > config.portRangeEnd)
 		throw std::invalid_argument("Invalid port range");
+
+	if (config.mtu) {
+		if (*config.mtu < 576) // Min MTU for IPv4
+			throw std::invalid_argument("Invalid MTU value");
+
+		if (*config.mtu > 1500) { // Standard Ethernet
+			PLOG_WARNING << "MTU set to " << *config.mtu;
+		} else {
+			PLOG_VERBOSE << "MTU set to " << *config.mtu;
+		}
+	}
 }
 
 PeerConnection::~PeerConnection() {
@@ -515,7 +526,7 @@ shared_ptr<DtlsTransport> PeerConnection::initDtlsTransport() {
 
 			// DTLS-SRTP
 			transport = std::make_shared<DtlsSrtpTransport>(
-			    lower, certificate, verifierCallback,
+			    lower, certificate, mConfig.mtu, verifierCallback,
 			    weak_bind(&PeerConnection::forwardMedia, this, _1), stateChangeCallback);
 #else
 			PLOG_WARNING << "Ignoring media support (not compiled with media support)";
@@ -524,8 +535,8 @@ shared_ptr<DtlsTransport> PeerConnection::initDtlsTransport() {
 
 		if (!transport) {
 			// DTLS only
-			transport = std::make_shared<DtlsTransport>(lower, certificate, verifierCallback,
+			transport = std::make_shared<DtlsTransport>(lower, certificate, mConfig.mtu,
-			                                            stateChangeCallback);
+			                                            verifierCallback, stateChangeCallback);
 		}
 
 		std::atomic_store(&mDtlsTransport, transport);
@@ -557,7 +568,7 @@ shared_ptr<SctpTransport> PeerConnection::initSctpTransport() {
 		uint16_t sctpPort = remote->application()->sctpPort().value_or(DEFAULT_SCTP_PORT);
 		auto lower = std::atomic_load(&mDtlsTransport);
 		auto transport = std::make_shared<SctpTransport>(
-		    lower, sctpPort, weak_bind(&PeerConnection::forwardMessage, this, _1),
+		    lower, sctpPort, mConfig.mtu, weak_bind(&PeerConnection::forwardMessage, this, _1),
 		    weak_bind(&PeerConnection::forwardBufferedAmount, this, _1, _2),
 		    [this, weak_this = weak_from_this()](SctpTransport::State state) {
 			    auto shared_this = weak_this.lock();
@@ -663,10 +674,12 @@ void PeerConnection::forwardMessage(message_ptr message) {
 		if (message->type == Message::Control && *message->data() == dataChannelOpenMessage &&
 		    stream % 2 == remoteParity) {
 
-			channel = std::make_shared<NegociatedDataChannel>(shared_from_this(), sctpTransport,
+			channel =
-			                                                  stream);
+			    std::make_shared<NegotiatedDataChannel>(shared_from_this(), sctpTransport, stream);
 			channel->onOpen(weak_bind(&PeerConnection::triggerDataChannel, this,
 			                          weak_ptr<DataChannel>{channel}));
+
+			std::unique_lock lock(mDataChannelsMutex); // we are going to emplace
 			mDataChannels.emplace(stream, channel);
 		} else {
 			// Invalid, close the DataChannel
@@ -833,7 +846,7 @@ shared_ptr<DataChannel> PeerConnection::emplaceDataChannel(Description::Role rol
 	    init.negotiated
 	        ? std::make_shared<DataChannel>(shared_from_this(), stream, std::move(label),
 	                                        std::move(init.protocol), std::move(init.reliability))
-	        : std::make_shared<NegociatedDataChannel>(shared_from_this(), stream, std::move(label),
+	        : std::make_shared<NegotiatedDataChannel>(shared_from_this(), stream, std::move(label),
 	                                                  std::move(init.protocol),
 	                                                  std::move(init.reliability));
 	mDataChannels.emplace(std::make_pair(stream, channel));

src/processor.cpp

@@ -25,39 +25,18 @@ Processor::Processor(size_t limit) : mTasks(limit) {}
 Processor::~Processor() { join(); }
 
 void Processor::join() {
-	// We need to detect situations where the thread pool does not execute a pending task at exit
+	std::unique_lock lock(mMutex);
-	std::optional<unsigned int> counter;
+	mCondition.wait(lock, [this]() { return !mPending && mTasks.empty(); });
-	while (true) {
-		std::shared_future<void> pending;
-		{
-			std::unique_lock lock(mMutex);
-			if (!mPending                               // no pending task
-			    || (counter && *counter == mCounter)) { // or no scheduled task after the last one
-
-				// Processing is stopped, clear everything and return
-				mPending.reset();
-				while (!mTasks.empty())
-					mTasks.pop();
-
-				return;
-			}
-
-			pending = *mPending;
-			counter = mCounter;
-		}
-
-		// Wait for the pending task
-		pending.wait();
-	}
 }
 
 void Processor::schedule() {
 	std::unique_lock lock(mMutex);
 	if (auto next = mTasks.tryPop()) {
-		mPending = ThreadPool::Instance().enqueue(std::move(*next)).share();
+		ThreadPool::Instance().enqueue(std::move(*next));
-		++mCounter;
 	} else {
-		mPending.reset(); // No more tasks
+		// No more tasks
+		mPending = false;
+		mCondition.notify_all();
 	}
 }
 

src/processor.hpp

@@ -54,10 +54,10 @@ protected:
 	const init_token mInitToken = Init::Token();
 
 	Queue<std::function<void()>> mTasks;
-	std::optional<std::shared_future<void>> mPending; // future of the pending task
+	bool mPending = false; // true iff a task is pending in the thread pool
-	unsigned int mCounter = 0; // Number of scheduled tasks
 
 	mutable std::mutex mMutex;
+	std::condition_variable mCondition;
 };
 
 template <class F, class... Args> void Processor::enqueue(F &&f, Args &&...args) {
@@ -65,12 +65,12 @@ template <class F, class... Args> void Processor::enqueue(F &&f, Args &&...args)
 	auto bound = std::bind(std::forward<F>(f), std::forward<Args>(args)...);
 	auto task = [this, bound = std::move(bound)]() mutable {
 		scope_guard guard(std::bind(&Processor::schedule, this)); // chain the next task
-		bound();
+		return bound();
 	};
 
 	if (!mPending) {
-		mPending = ThreadPool::Instance().enqueue(std::move(task)).share();
+		ThreadPool::Instance().enqueue(std::move(task));
-		++mCounter;
+		mPending = true;
 	} else {
 		mTasks.push(std::move(task));
 	}

src/rtcpnackresponder.cpp

@@ -0,0 +1,118 @@
+/**
+ * libdatachannel streamer example
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if RTC_ENABLE_MEDIA
+
+#include "rtcpnackresponder.hpp"
+
+namespace rtc {
+
+RtcpNackResponder::Storage::Element::Element(binary_ptr packet, uint16_t sequenceNumber, std::shared_ptr<Element> next)
+: packet(packet), sequenceNumber(sequenceNumber), next(next) { }
+
+unsigned RtcpNackResponder::Storage::size() { return storage.size(); }
+
+RtcpNackResponder::Storage::Storage(unsigned _maximumSize): maximumSize(_maximumSize) {
+	assert(maximumSize > 0);
+	storage.reserve(maximumSize);
+}
+
+std::optional<binary_ptr> RtcpNackResponder::Storage::get(uint16_t sequenceNumber) {
+	auto position = storage.find(sequenceNumber);
+	return position != storage.end() ? std::make_optional(storage.at(sequenceNumber)->packet) : nullopt;
+}
+
+void RtcpNackResponder::Storage::store(binary_ptr packet) {
+	if (!packet || packet->size() < 12) {
+		return;
+	}
+	auto rtp = reinterpret_cast<RTP *>(packet->data());
+	auto sequenceNumber = rtp->seqNumber();
+
+	assert((storage.empty() && !oldest && !newest) || (!storage.empty() && oldest && newest));
+
+	if (size() == 0) {
+		newest = std::make_shared<Element>(packet, sequenceNumber);
+		oldest = newest;
+	} else {
+		auto current = std::make_shared<Element>(packet, sequenceNumber);
+		newest->next = current;
+		newest = current;
+	}
+
+	storage.emplace(sequenceNumber, newest);
+
+	if (size() > maximumSize) {
+		assert(oldest);
+		if (oldest) {
+			storage.erase(oldest->sequenceNumber);
+			oldest = oldest->next;
+		}
+	}
+}
+
+RtcpNackResponder::RtcpNackResponder(unsigned maxStoredPacketCount)
+: MediaHandlerElement(), storage(std::make_shared<Storage>(maxStoredPacketCount)) { }
+
+ChainedIncomingControlProduct RtcpNackResponder::processIncomingControlMessage(message_ptr message) {
+	std::optional<ChainedOutgoingProduct> optPackets = ChainedOutgoingProduct(nullptr);
+	auto packets = make_chained_messages_product();
+
+	unsigned int i = 0;
+	while (i < message->size()) {
+		auto nack = reinterpret_cast<RTCP_NACK *>(message->data() + i);
+		i += nack->header.header.lengthInBytes();
+		// check if rtcp is nack
+		if (nack->header.header.payloadType() != 205 || nack->header.header.reportCount() != 1) {
+			continue;
+		}
+		
+		auto fieldsCount = nack->getSeqNoCount();
+
+		std::vector<uint16_t> missingSequenceNumbers{};
+		for(unsigned int i = 0; i < fieldsCount; i++) {
+			auto field = nack->parts[i];
+			auto newMissingSeqenceNumbers = field.getSequenceNumbers();
+			missingSequenceNumbers.insert(missingSequenceNumbers.end(), newMissingSeqenceNumbers.begin(), newMissingSeqenceNumbers.end());
+		}
+		packets->reserve(packets->size() + missingSequenceNumbers.size());
+		for (auto sequenceNumber: missingSequenceNumbers) {
+			auto optPacket = storage->get(sequenceNumber);
+			if (optPacket.has_value()) {
+				auto packet = optPacket.value();
+				packets->push_back(packet);
+			}
+		}
+	}
+
+	if (!packets->empty()) {
+		return {message, ChainedOutgoingProduct(packets)};
+	} else {
+		return {message, nullopt};
+	}
+}
+
+ChainedOutgoingProduct RtcpNackResponder::processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) {
+	for (auto message: *messages) {
+		storage->store(message);
+	}
+	return {messages, control};
+}
+
+} // namespace rtc
+
+#endif /* RTC_ENABLE_MEDIA */

src/rtcpsrreporter.cpp

@@ -1,5 +1,4 @@
-/*
+/**
- * libdatachannel streamer example
  * Copyright (c) 2020 Filip Klembara (in2core)
  *
  * This program is free software; you can redistribute it and/or
@@ -18,40 +17,52 @@
 
 #if RTC_ENABLE_MEDIA
 
-#include "rtcpsenderreporter.hpp"
+#include "rtcpsrreporter.hpp"
 
 namespace rtc {
 
-void RtcpSenderReporter::startRecording() {
+ChainedOutgoingProduct RtcpSrReporter::processOutgoingBinaryMessage(ChainedMessagesProduct messages, message_ptr control) {
+	if (needsToReport) {
+		auto timestamp = rtpConfig->timestamp;
+		auto sr = getSenderReport(timestamp);
+		if (control) {
+			control->insert(control->end(), sr->begin(), sr->end());
+		} else {
+			control = sr;
+		}
+		needsToReport = false;
+	}
+	for (auto message: *messages) {
+		auto rtp = reinterpret_cast<RTP *>(message->data());
+		addToReport(rtp, message->size());
+	}
+	return {messages, control};
+}
+
+void RtcpSrReporter::startRecording() {
 	_previousReportedTimestamp = rtpConfig->timestamp;
 	timeOffset = rtpConfig->startTime_s - rtpConfig->timestampToSeconds(rtpConfig->timestamp);
 }
 
-void RtcpSenderReporter::sendReport(uint32_t timestamp) {
+void RtcpSrReporter::addToReport(RTP *rtp, uint32_t rtpSize) {
-	auto sr = getSenderReport(timestamp);
-	_previousReportedTimestamp = timestamp;
-	senderReportOutgoingCallback(move(sr));
-}
-
-void RtcpSenderReporter::addToReport(RTP *rtp, uint32_t rtpSize) {
 	packetCount += 1;
 	assert(!rtp->padding());
 	payloadOctets += rtpSize - rtp->getSize();
 }
 
-RtcpSenderReporter::RtcpSenderReporter(std::shared_ptr<RtpPacketizationConfig> rtpConfig)
+RtcpSrReporter::RtcpSrReporter(std::shared_ptr<RtpPacketizationConfig> rtpConfig)
-    : rtpConfig(rtpConfig) {}
+: MediaHandlerElement(), rtpConfig(rtpConfig) {}
 
-uint64_t RtcpSenderReporter::secondsToNTP(double seconds) {
+uint64_t RtcpSrReporter::secondsToNTP(double seconds) {
 	return std::round(seconds * double(uint64_t(1) << 32));
 }
 
-void RtcpSenderReporter::setNeedsToReport() { needsToReport = true; }
+void RtcpSrReporter::setNeedsToReport() { needsToReport = true; }
 
-message_ptr RtcpSenderReporter::getSenderReport(uint32_t timestamp) {
+message_ptr RtcpSrReporter::getSenderReport(uint32_t timestamp) {
 	auto srSize = RTCP_SR::size(0);
 	auto msg = make_message(srSize + RTCP_SDES::size({{uint8_t(rtpConfig->cname.size())}}),
-	                        Message::Type::Control);
+							Message::Type::Control);
 	auto sr = reinterpret_cast<RTCP_SR *>(msg->data());
 	auto timestamp_s = rtpConfig->timestampToSeconds(timestamp);
 	auto currentTime = timeOffset + timestamp_s;
@@ -68,6 +79,9 @@ message_ptr RtcpSenderReporter::getSenderReport(uint32_t timestamp) {
 	item->type = 1;
 	item->setText(rtpConfig->cname);
 	sdes->preparePacket(1);
+
+	_previousReportedTimestamp = timestamp;
+
 	return msg;
 }
 

src/rtppacketizer.cpp

@@ -25,8 +25,8 @@ namespace rtc {
 RtpPacketizer::RtpPacketizer(std::shared_ptr<RtpPacketizationConfig> rtpConfig)
     : rtpConfig(rtpConfig) {}
 
-message_ptr RtpPacketizer::packetize(binary payload, bool setMark) {
+binary_ptr RtpPacketizer::packetize(std::shared_ptr<binary> payload, bool setMark) {
-	auto msg = make_message(rtpHeaderSize + payload.size());
+	auto msg = std::make_shared<binary>(rtpHeaderSize + payload->size());
 	auto *rtp = (RTP *)msg->data();
 	rtp->setPayloadType(rtpConfig->payloadType);
 	// increase sequence number
@@ -37,7 +37,7 @@ message_ptr RtpPacketizer::packetize(binary payload, bool setMark) {
 		rtp->setMarker(true);
 	}
 	rtp->preparePacket();
-	copy(payload.begin(), payload.end(), msg->begin() + rtpHeaderSize);
+	memcpy(msg->data() + rtpHeaderSize, payload->data(), payload->size());
 	return msg;
 }
 

src/sctptransport.cpp

@@ -17,6 +17,7 @@
  */
 
 #include "sctptransport.hpp"
+#include "dtlstransport.hpp"
 #include "logcounter.hpp"
 
 #include <chrono>
@@ -27,8 +28,7 @@
 
 // The IETF draft says:
 // SCTP MUST support performing Path MTU discovery without relying on ICMP or ICMPv6 as specified in
-// [RFC4821] using probing messages specified in [RFC4820]. The initial Path MTU at the IP layer
+// [RFC4821] using probing messages specified in [RFC4820].
-// SHOULD NOT exceed 1200 bytes for IPv4 and 1280 for IPv6.
 // See https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-13#section-5
 //
 // However, usrsctp does not implement Path MTU discovery, so we need to disable it for now.
@@ -54,8 +54,6 @@
 using namespace std::chrono_literals;
 using namespace std::chrono;
 
-using std::shared_ptr;
-
 namespace rtc {
 
 static LogCounter COUNTER_UNKNOWN_PPID(plog::warning,
@@ -102,7 +100,8 @@ void SctpTransport::Cleanup() {
 }
 
 SctpTransport::SctpTransport(std::shared_ptr<Transport> lower, uint16_t port,
-                             message_callback recvCallback, amount_callback bufferedAmountCallback,
+                             std::optional<size_t> mtu, message_callback recvCallback,
+                             amount_callback bufferedAmountCallback,
                              state_callback stateChangeCallback)
     : Transport(lower, std::move(stateChangeCallback)), mPort(port), mPendingRecvCount(0),
       mSendQueue(0, message_size_func), mBufferedAmountCallback(std::move(bufferedAmountCallback)) {
@@ -180,13 +179,24 @@ SctpTransport::SctpTransport(std::shared_ptr<Transport> lower, uint16_t port,
 	// 1200 bytes.
 	// See https://tools.ietf.org/html/rfc8261#section-5
 #if USE_PMTUD
-	// Enable SCTP path MTU discovery
+	if (!mtu.has_value()) {
-	spp.spp_flags |= SPP_PMTUD_ENABLE;
 #else
-	// Fall back to a safe MTU value.
+	if (false) {
-	spp.spp_flags |= SPP_PMTUD_DISABLE;
-	spp.spp_pathmtu = 1200;
 #endif
+		// Enable SCTP path MTU discovery
+		spp.spp_flags |= SPP_PMTUD_ENABLE;
+		PLOG_VERBOSE << "Path MTU discovery enabled";
+
+	} else {
+		// Fall back to a safe MTU value.
+		spp.spp_flags |= SPP_PMTUD_DISABLE;
+		// The MTU value provided specifies the space available for chunks in the
+		// packet, so we also subtract the SCTP header size.
+		size_t pmtu = mtu.value_or(DEFAULT_IPV4_MTU + 20) - 12 - 37 - 8 - 40; // SCTP/DTLS/UDP/IPv6
+		spp.spp_pathmtu = uint32_t(pmtu);
+		PLOG_VERBOSE << "Path MTU discovery disabled, SCTP MTU set to " << pmtu;
+	}
+
 	if (usrsctp_setsockopt(mSock, IPPROTO_SCTP, SCTP_PEER_ADDR_PARAMS, &spp, sizeof(spp)))
 		throw std::runtime_error("Could not set socket option SCTP_PEER_ADDR_PARAMS, errno=" +
 		                         std::to_string(errno));
@@ -349,6 +359,10 @@ void SctpTransport::incoming(message_ptr message) {
 	}
 
 	PLOG_VERBOSE << "Incoming size=" << message->size();
+
+	// TODO: There seems to be a possible data race between usrsctp_sendv() and usrsctp_conninput()
+	// As a mitigation, lock the send mutex before calling usrsctp_conninput()
+	std::lock_guard lock(mSendMutex);
 	usrsctp_conninput(this, message->data(), message->size(), 0);
 }
 

src/sctptransport.hpp

@@ -43,8 +43,9 @@ public:
 
 	using amount_callback = std::function<void(uint16_t streamId, size_t amount)>;
 
-	SctpTransport(std::shared_ptr<Transport> lower, uint16_t port, message_callback recvCallback,
+	SctpTransport(std::shared_ptr<Transport> lower, uint16_t port, std::optional<size_t> mtu,
-	              amount_callback bufferedAmountCallback, state_callback stateChangeCallback);
+	              message_callback recvCallback, amount_callback bufferedAmountCallback,
+	              state_callback stateChangeCallback);
 	~SctpTransport();
 
 	void start() override;

src/tcptransport.cpp

@@ -63,7 +63,7 @@ int SelectInterrupter::prepare(fd_set &readfds, [[maybe_unused]] fd_set &writefd
 	return SOCKET_TO_INT(mDummySock) + 1;
 #else
 	char dummy;
-	::read(mPipeIn, &dummy, 1);
+	(void)::read(mPipeIn, &dummy, 1);
 	FD_SET(mPipeIn, &readfds);
 	return mPipeIn + 1;
 #endif
@@ -78,7 +78,7 @@ void SelectInterrupter::interrupt() {
 	}
 #else
 	char dummy = 0;
-	::write(mPipeOut, &dummy, 1);
+	(void)::write(mPipeOut, &dummy, 1);
 #endif
 }
 

src/threadpool.cpp

@@ -21,10 +21,10 @@
 #include <cstdlib>
 
 namespace {
-	void joinThreadPoolInstance() {
+
-		rtc::ThreadPool::Instance().join();
+void joinThreadPoolInstance() { rtc::ThreadPool::Instance().join(); }
-	}
+
-}
+} // namespace
 
 namespace rtc {
 
@@ -33,9 +33,7 @@ ThreadPool &ThreadPool::Instance() {
 	return *instance;
 }
 
-ThreadPool::ThreadPool() {
+ThreadPool::ThreadPool() { std::atexit(joinThreadPoolInstance); }
-	std::atexit(joinThreadPoolInstance);
-}
 
 ThreadPool::~ThreadPool() {}
 
@@ -46,20 +44,25 @@ int ThreadPool::count() const {
 
 void ThreadPool::spawn(int count) {
 	std::unique_lock lock(mWorkersMutex);
-	mJoining = false;
 	while (count-- > 0)
 		mWorkers.emplace_back(std::bind(&ThreadPool::run, this));
 }
 
 void ThreadPool::join() {
-	std::unique_lock lock(mWorkersMutex);
+	{
-	mJoining = true;
+		std::unique_lock lock(mMutex);
-	mCondition.notify_all();
+		mWaitingCondition.wait(lock, [&]() { return mWaitingWorkers == int(mWorkers.size()); });
+		mJoining = true;
+		mTasksCondition.notify_all();
+	}
 
+	std::unique_lock lock(mWorkersMutex);
 	for (auto &w : mWorkers)
 		w.join();
 
 	mWorkers.clear();
+
+	mJoining = false;
 }
 
 void ThreadPool::run() {
@@ -77,7 +80,7 @@ bool ThreadPool::runOne() {
 
 std::function<void()> ThreadPool::dequeue() {
 	std::unique_lock lock(mMutex);
-	while (true) {
+	while (!mJoining) {
 		if (!mTasks.empty()) {
 			if (mTasks.top().time <= clock::now()) {
 				auto func = std::move(mTasks.top().func);
@@ -85,21 +88,18 @@ std::function<void()> ThreadPool::dequeue() {
 				return func;
 			}
 
-			if (mJoining)
+			++mWaitingWorkers;
-				break;
+			mWaitingCondition.notify_all();
+			mTasksCondition.wait_until(lock, mTasks.top().time);
 
-			mCondition.wait_until(lock, mTasks.top().time);
 		} else {
-			if (mJoining)
+			++mWaitingWorkers;
-				break;
+			mWaitingCondition.notify_all();
-
+			mTasksCondition.wait(lock);
-			mCondition.wait(lock);
 		}
+
+		--mWaitingWorkers;
 	}
-
-	while (!mTasks.empty())
-		mTasks.pop();
-
 	return nullptr;
 }
 

src/threadpool.hpp

@@ -72,6 +72,7 @@ protected:
 	std::function<void()> dequeue(); // returns null function if joining
 
 	std::vector<std::thread> mWorkers;
+	int mWaitingWorkers = 0;
 	std::atomic<bool> mJoining = false;
 
 	struct Task {
@@ -82,8 +83,8 @@ protected:
 	};
 	std::priority_queue<Task, std::deque<Task>, std::greater<Task>> mTasks;
 
+	std::condition_variable mTasksCondition, mWaitingCondition;
 	mutable std::mutex mMutex, mWorkersMutex;
-	std::condition_variable mCondition;
 };
 
 template <class F, class... Args>
@@ -100,16 +101,8 @@ auto ThreadPool::schedule(clock::duration delay, F &&f, Args &&...args)
 template <class F, class... Args>
 auto ThreadPool::schedule(clock::time_point time, F &&f, Args &&...args)
     -> invoke_future_t<F, Args...> {
-	using R = std::invoke_result_t<std::decay_t<F>, std::decay_t<Args>...>;
 	std::unique_lock lock(mMutex);
-	if (mJoining) {
+	using R = std::invoke_result_t<std::decay_t<F>, std::decay_t<Args>...>;
-		std::promise<R> promise;
-		std::future<R> result = promise.get_future();
-		promise.set_exception(std::make_exception_ptr(
-		    std::runtime_error("Scheduled a task while joining the thread pool")));
-		return result;
-	}
-
 	auto bound = std::bind(std::forward<F>(f), std::forward<Args>(args)...);
 	auto task = std::make_shared<std::packaged_task<R()>>([bound = std::move(bound)]() mutable {
 		try {
@@ -122,7 +115,7 @@ auto ThreadPool::schedule(clock::time_point time, F &&f, Args &&...args)
 	std::future<R> result = task->get_future();
 
 	mTasks.push({time, [task = std::move(task), token = Init::Token()]() { return (*task)(); }});
-	mCondition.notify_one();
+	mTasksCondition.notify_one();
 	return result;
 }
 

src/track.cpp

@@ -35,11 +35,23 @@ using std::weak_ptr;
 Track::Track(Description::Media description)
     : mMediaDescription(std::move(description)), mRecvQueue(RECV_QUEUE_LIMIT, message_size_func) {}
 
-string Track::mid() const { return mMediaDescription.mid(); }
+string Track::mid() const {
+	std::shared_lock lock(mMutex);
+	return mMediaDescription.mid();
+}
 
-Description::Media Track::description() const { return mMediaDescription; }
+Description::Media Track::description() const {
+	std::shared_lock lock(mMutex);
+	return mMediaDescription;
+}
+
+Description::Direction Track::direction() const {
+	std::shared_lock lock(mMutex);
+	return mMediaDescription.direction();
+}
 
 void Track::setDescription(Description::Media description) {
+	std::unique_lock lock(mMutex);
 	if (description.mid() != mMediaDescription.mid())
 		throw std::logic_error("Media description mid does not match track mid");
 
@@ -48,17 +60,17 @@ void Track::setDescription(Description::Media description) {
 
 void Track::close() {
 	mIsClosed = true;
-	resetCallbacks();
+
 	setRtcpHandler(nullptr);
+	resetCallbacks();
 }
 
 bool Track::send(message_variant data) {
 	if (mIsClosed)
 		throw std::runtime_error("Track is closed");
 
-	auto direction = mMediaDescription.direction();
+	auto dir = direction();
-	if ((direction == Description::Direction::RecvOnly ||
+	if ((dir == Description::Direction::RecvOnly || dir == Description::Direction::Inactive)) {
-	     direction == Description::Direction::Inactive)) {
 		COUNTER_MEDIA_BAD_DIRECTION++;
 		return false;
 	}
@@ -92,6 +104,7 @@ std::optional<message_variant> Track::peek() {
 
 bool Track::isOpen(void) const {
 #if RTC_ENABLE_MEDIA
+	std::shared_lock lock(mMutex);
 	return !mIsClosed && mDtlsSrtpTransport.lock();
 #else
 	return !mIsClosed;
@@ -108,7 +121,11 @@ size_t Track::availableAmount() const { return mRecvQueue.amount(); }
 
 #if RTC_ENABLE_MEDIA
 void Track::open(shared_ptr<DtlsSrtpTransport> transport) {
-	mDtlsSrtpTransport = transport;
+	{
+		std::lock_guard lock(mMutex);
+		mDtlsSrtpTransport = transport;
+	}
+
 	triggerOpen();
 }
 #endif
@@ -117,9 +134,8 @@ void Track::incoming(message_ptr message) {
 	if (!message)
 		return;
 
-	auto direction = mMediaDescription.direction();
+	auto dir = direction();
-	if ((direction == Description::Direction::SendOnly ||
+	if ((dir == Description::Direction::SendOnly || dir == Description::Direction::Inactive) &&
-	     direction == Description::Direction::Inactive) &&
 	    message->type != Message::Control) {
 		COUNTER_MEDIA_BAD_DIRECTION++;
 		return;
@@ -142,17 +158,21 @@ void Track::incoming(message_ptr message) {
 }
 
 bool Track::outgoing([[maybe_unused]] message_ptr message) {
-#if RTC_ENABLE_MEDIA
+#if RTC_ENABLfiE_MEDIA
-	auto transport = mDtlsSrtpTransport.lock();
+	std::shared_ptr<DtlsSrtpTransport> transport;
-	if (!transport)
+	{
-		throw std::runtime_error("Track transport is not open");
+		std::shared_lock lock(mMutex);
+		transport = mDtlsSrtpTransport.lock();
+		if (!transport)
+			throw std::runtime_error("Track is closed");
 
-	// Set recommended medium-priority DSCP value
+		// Set recommended medium-priority DSCP value
-	// See https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18
+		// See https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18
-	if (mMediaDescription.type() == "audio")
+		if (mMediaDescription.type() == "audio")
-		message->dscp = 46; // EF: Expedited Forwarding
+			message->dscp = 46; // EF: Expedited Forwarding
-	else
+		else
-		message->dscp = 36; // AF42: Assured Forwarding class 4, medium drop probability
+			message->dscp = 36; // AF42: Assured Forwarding class 4, medium drop probability
+	}
 
 	return transport->sendMedia(message);
 #else
@@ -161,25 +181,24 @@ bool Track::outgoing([[maybe_unused]] message_ptr message) {
 #endif
 }
 
-void Track::setRtcpHandler(std::shared_ptr<RtcpHandler> handler) {
+void Track::setRtcpHandler(std::shared_ptr<MediaHandler> handler) {
-	std::unique_lock lock(mRtcpHandlerMutex);
+	{
-	mRtcpHandler = std::move(handler);
+		std::unique_lock lock(mMutex);
-	if (mRtcpHandler) {
+		mRtcpHandler = handler;
-		auto copy = mRtcpHandler;
-		lock.unlock();
-		copy->onOutgoing(std::bind(&Track::outgoing, this, std::placeholders::_1));
 	}
+
+	handler->onOutgoing(std::bind(&Track::outgoing, this, std::placeholders::_1));
 }
 
 bool Track::requestKeyframe() {
-	if (auto handler = getRtcpHandler()) {
+	if (auto handler = getRtcpHandler())
 		return handler->requestKeyframe();
-	}
+
 	return false;
 }
 
-std::shared_ptr<RtcpHandler> Track::getRtcpHandler() {
+std::shared_ptr<MediaHandler> Track::getRtcpHandler() {
-	std::shared_lock lock(mRtcpHandlerMutex);
+	std::shared_lock lock(mMutex);
 	return mRtcpHandler;
 }
 

test/benchmark.cpp

@@ -40,11 +40,13 @@ size_t benchmark(milliseconds duration) {
 
 	Configuration config1;
 	// config1.iceServers.emplace_back("stun:stun.l.google.com:19302");
+	// config1.mtu = 1500;
 
 	auto pc1 = std::make_shared<PeerConnection>(config1);
 
 	Configuration config2;
 	// config2.iceServers.emplace_back("stun:stun.l.google.com:19302");
+	// config2.mtu = 1500;
 
 	auto pc2 = std::make_shared<PeerConnection>(config2);
 

test/capi_connectivity.cpp

@@ -235,35 +235,59 @@ int test_capi_connectivity_main() {
 	char buffer[BUFFER_SIZE];
 	char buffer2[BUFFER_SIZE];
 
+	if (rtcGetLocalDescriptionType(peer1->pc, buffer, BUFFER_SIZE) < 0) {
+		fprintf(stderr, "rtcGetLocalDescriptionType failed\n");
+		goto error;
+	}
+	printf("Local description type 1: %s\n", buffer);
+
 	if (rtcGetLocalDescription(peer1->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetLocalDescription failed\n");
 		goto error;
 	}
-	printf("Local description 1:  %s\n", buffer);
+	printf("Local description 1: %s\n", buffer);
+
+	if (rtcGetRemoteDescriptionType(peer1->pc, buffer, BUFFER_SIZE) < 0) {
+		fprintf(stderr, "rtcGetRemoteDescriptionType failed\n");
+		goto error;
+	}
+	printf("Remote description type 1: %s\n", buffer);
 
 	if (rtcGetRemoteDescription(peer1->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetRemoteDescription failed\n");
 		goto error;
 	}
-	printf("Remote description 1:  %s\n", buffer);
+	printf("Remote description 1: %s\n", buffer);
+
+	if (rtcGetLocalDescriptionType(peer2->pc, buffer, BUFFER_SIZE) < 0) {
+		fprintf(stderr, "rtcGetLocalDescriptionType failed\n");
+		goto error;
+	}
+	printf("Local description type 2: %s\n", buffer);
 
 	if (rtcGetLocalDescription(peer2->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetLocalDescription failed\n");
 		goto error;
 	}
-	printf("Local description 2:  %s\n", buffer);
+	printf("Local description 2: %s\n", buffer);
+
+	if (rtcGetRemoteDescriptionType(peer2->pc, buffer, BUFFER_SIZE) < 0) {
+		fprintf(stderr, "rtcGetRemoteDescriptionType failed\n");
+		goto error;
+	}
+	printf("Remote description type 2: %s\n", buffer);
 
 	if (rtcGetRemoteDescription(peer2->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetRemoteDescription failed\n");
 		goto error;
 	}
-	printf("Remote description 2:  %s\n", buffer);
+	printf("Remote description 2: %s\n", buffer);
 
 	if (rtcGetLocalAddress(peer1->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetLocalAddress failed\n");
 		goto error;
 	}
-	printf("Local address 1:  %s\n", buffer);
+	printf("Local address 1: %s\n", buffer);
 
 	if (rtcGetRemoteAddress(peer1->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetRemoteAddress failed\n");
@@ -275,7 +299,7 @@ int test_capi_connectivity_main() {
 		fprintf(stderr, "rtcGetLocalAddress failed\n");
 		goto error;
 	}
-	printf("Local address 2:  %s\n", buffer);
+	printf("Local address 2: %s\n", buffer);
 
 	if (rtcGetRemoteAddress(peer2->pc, buffer, BUFFER_SIZE) < 0) {
 		fprintf(stderr, "rtcGetRemoteAddress failed\n");

test/connectivity.cpp

@@ -36,6 +36,8 @@ void test_connectivity() {
 	// STUN server example (not necessary to connect locally)
 	// Please do not use outside of libdatachannel tests
 	config1.iceServers.emplace_back("stun:stun.ageneau.net:3478");
+	// Custom MTU example
+	config1.mtu = 1500;
 
 	auto pc1 = std::make_shared<PeerConnection>(config1);
 
@@ -43,6 +45,8 @@ void test_connectivity() {
 	// STUN server example (not necessary to connect locally)
 	// Please do not use outside of libdatachannel tests
 	config2.iceServers.emplace_back("stun:stun.ageneau.net:3478");
+	// Custom MTU example
+	config2.mtu = 1500;
 	// Port range example
 	config2.portRangeBegin = 5000;
 	config2.portRangeEnd = 6000;
@@ -221,7 +225,7 @@ void test_connectivity() {
 	auto negotiated2 = pc2->createDataChannel("negoctated", init);
 
 	if (!negotiated1->isOpen() || !negotiated2->isOpen())
-		throw runtime_error("Negociated DataChannel is not open");
+		throw runtime_error("Negotiated DataChannel is not open");
 
 	std::atomic<bool> received = false;
 	negotiated2->onMessage([&received](const variant<binary, string> &message) {
@@ -239,7 +243,7 @@ void test_connectivity() {
 		this_thread::sleep_for(1s);
 
 	if (!received)
-		throw runtime_error("Negociated DataChannel failed");
+		throw runtime_error("Negotiated DataChannel failed");
 
 	// Delay close of peer 2 to check closing works properly
 	pc1->close();

test/turn_connectivity.cpp

@@ -232,7 +232,7 @@ void test_turn_connectivity() {
 	auto negotiated2 = pc2->createDataChannel("negoctated", init);
 
 	if (!negotiated1->isOpen() || !negotiated2->isOpen())
-		throw runtime_error("Negociated DataChannel is not open");
+		throw runtime_error("Negotiated DataChannel is not open");
 
 	std::atomic<bool> received = false;
 	negotiated2->onMessage([&received](const variant<binary, string> &message) {
@@ -250,7 +250,7 @@ void test_turn_connectivity() {
 		this_thread::sleep_for(1s);
 
 	if (!received)
-		throw runtime_error("Negociated DataChannel failed");
+		throw runtime_error("Negotiated DataChannel failed");
 
 	// Delay close of peer 2 to check closing works properly
 	pc1->close();