libdatachannel/src/track.cpp

/**
 * Copyright (c) 2020 Paul-Louis Ageneau
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "track.hpp"
#include "dtlssrtptransport.hpp"
#include "include.hpp"

namespace rtc {

using std::shared_ptr;
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(); }

Description::Media Track::description() const { return mMediaDescription; }

void Track::setDescription(Description::Media description) {
	if (description.mid() != mMediaDescription.mid())
		throw std::logic_error("Media description mid does not match track mid");

	mMediaDescription = std::move(description);
}

void Track::close() {
	mIsClosed = true;
	resetCallbacks();
	setRtcpHandler(nullptr);
}

bool Track::send(message_variant data) { return outgoing(make_message(std::move(data))); }

bool Track::send(const byte *data, size_t size) {
	return outgoing(std::make_shared<Message>(data, data + size, Message::Binary));
}

std::optional<message_variant> Track::receive() {
	if (auto next = mRecvQueue.tryPop())
		return to_variant(std::move(**next));

	return nullopt;
}

std::optional<message_variant> Track::peek() {
	if (auto next = mRecvQueue.peek())
		return to_variant(std::move(**next));

	return nullopt;
}

bool Track::isOpen(void) const {
#if RTC_ENABLE_MEDIA
	return !mIsClosed && mDtlsSrtpTransport.lock();
#else
	return !mIsClosed;
#endif
}

bool Track::isClosed(void) const { return mIsClosed; }

size_t Track::maxMessageSize() const {
	return 65535 - 12 - 4; // SRTP/UDP
}

size_t Track::availableAmount() const { return mRecvQueue.amount(); }

#if RTC_ENABLE_MEDIA
void Track::open(shared_ptr<DtlsSrtpTransport> transport) {
	mDtlsSrtpTransport = transport;
	triggerOpen();
}
#endif

bool Track::outgoing(message_ptr message) {

	if (mRtcpHandler) {
		message = mRtcpHandler->outgoing(message);
		if (!message)
			return false;
	}

	auto direction = mMediaDescription.direction();
	if ((direction == Description::Direction::RecvOnly ||
	     direction == Description::Direction::Inactive) &&
	    message->type != Message::Control) {
		PLOG_WARNING << "Track media direction does not allow transmission, dropping";
		return false;
	}

	if (mIsClosed)
		throw std::runtime_error("Track is closed");

#if RTC_ENABLE_MEDIA
	auto transport = mDtlsSrtpTransport.lock();
	if (!transport)
		throw std::runtime_error("Track transport is not open");

	// Set recommended medium-priority DSCP value
	// See https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18
	if (mMediaDescription.type() == "audio")
		message->dscp = 46; // EF: Expedited Forwarding
	else
		message->dscp = 36; // AF42: Assured Forwarding class 4, medium drop probability

	return transport->sendMedia(message);
#else
	PLOG_WARNING << "Ignoring track send (not compiled with SRTP support)";
	return false;
#endif
}

void Track::incoming(message_ptr message) {
	if (!message)
		return;

	if (mRtcpHandler) {
		message = mRtcpHandler->incoming(message);
		if (!message)
			return;
	}

	auto direction = mMediaDescription.direction();
	if ((direction == Description::Direction::SendOnly ||
	     direction == Description::Direction::Inactive) &&
	    message->type != Message::Control) {
		PLOG_WARNING << "Track media direction does not allow reception, dropping";
		return;
	}

	// Tail drop if queue is full
	if (mRecvQueue.full())
		return;

	mRecvQueue.push(message);
	triggerAvailable(mRecvQueue.size());
}

void Track::setRtcpHandler(std::shared_ptr<RtcpHandler> handler) {
	mRtcpHandler = std::move(handler);
	if (mRtcpHandler) {
		mRtcpHandler->onOutgoing([&]([[maybe_unused]] const rtc::message_ptr &message) {
#if RTC_ENABLE_MEDIA
			auto transport = mDtlsSrtpTransport.lock();
			if (!transport)
				throw std::runtime_error("Track transport is not open");

			return transport->sendMedia(message);
#else
			PLOG_WARNING << "Ignoring track send (not compiled with SRTP support)";
			return false;
#endif
		});
	}
}

bool Track::requestKeyframe() {
	if (mRtcpHandler)
		return mRtcpHandler->requestKeyframe();
	return false;
}

std::shared_ptr<RtcpHandler> Track::getRtcpHandler() { return mRtcpHandler; }

} // namespace rtc