In short, the caller places a x-opaque line in SDP for each m= section that
uses datagram transport. If the answerer supports datagram transport, it will
parse this line and create a datagram transport. It will then echo the x-opaque
line into the answer (to indicate that it accepted use of datagram transport).
If the offer and answer contain exactly the same x-opaque line, both peers will
use datagram transport. If the x-opaque line is omitted from the answer (or is
different in the answer) they will fall back to RTP.
Note that a different x-opaque line in the answer means the answerer did not
understand something in the negotiation proto. Since WebRTC cannot know what
was misunderstood, or whether it's still possible to use the datagram transport,
it must fall back to RTP. This may change in the future, possibly by passing
the answer to the datagram transport, but it's good enough for now.
Negotiation consists of four parts:
1. DatagramTransport exposes transport parameters for both client and server
perspectives. The client just echoes what it received from the server (modulo
any fields it might not have understood).
2. SDP adds a x-opaque line for opaque transport parameters. Identical to
x-mt, but this is specific to datagram transport and goes in each m= section,
and appears in the answer as well as the offer.
- This is propagated to Jsep as part of the TransportDescription.
- SDP files: transport_description.h,cc, transport_description_factory.h,cc,
media_session.cc, webrtc_sdp.cc
3. JsepTransport/Controller:
- Exposes opaque parameters for each mid (m= section). On offerer, this means
pre-allocating a datagram transport and getting its parameters. On the
answerer, this means echoing the offerer's parameters.
- Uses a composite RTP transport to receive from either default RTP or
datagram transport until both offer and answer arrive.
- If a provisional answer arrives, sets the composite to send on the
provisionally selected transport.
- Once both offer and answer are set, deletes the unneeded transports and
keeps whichever transport is selected.
4. PeerConnection pulls transport parameters out of Jsep and adds them to SDP.
Bug: webrtc:9719
Change-Id: Ifcc428c8d76fb77dcc8abaa79507c620bcfb31b9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/140920
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Bjorn Mellem <mellem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28198}
194 lines
6.8 KiB
C++
194 lines
6.8 KiB
C++
/*
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* Copyright 2018 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef API_TEST_FAKE_MEDIA_TRANSPORT_H_
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#define API_TEST_FAKE_MEDIA_TRANSPORT_H_
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#include <memory>
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#include <string>
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#include <utility>
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#include <vector>
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#include "absl/algorithm/container.h"
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#include "absl/memory/memory.h"
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#include "api/media_transport_interface.h"
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#include "api/test/fake_datagram_transport.h"
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namespace webrtc {
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// TODO(sukhanov): For now fake media transport does nothing and is used only
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// in jsepcontroller unittests. In the future we should implement fake media
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// transport, which forwards frames to another fake media transport, so we
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// could unit test audio / video integration.
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class FakeMediaTransport : public MediaTransportInterface {
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public:
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explicit FakeMediaTransport(
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const MediaTransportSettings& settings,
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const absl::optional<std::string>& transport_offer = "",
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const absl::optional<std::string>& remote_transport_parameters = "")
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: settings_(settings),
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transport_offer_(transport_offer),
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remote_transport_parameters_(remote_transport_parameters) {}
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~FakeMediaTransport() = default;
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RTCError SendAudioFrame(uint64_t channel_id,
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MediaTransportEncodedAudioFrame frame) override {
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return RTCError::OK();
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}
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RTCError SendVideoFrame(
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uint64_t channel_id,
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const MediaTransportEncodedVideoFrame& frame) override {
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return RTCError::OK();
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}
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RTCError RequestKeyFrame(uint64_t channel_id) override {
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return RTCError::OK();
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}
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void SetReceiveAudioSink(MediaTransportAudioSinkInterface* sink) override {}
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void SetReceiveVideoSink(MediaTransportVideoSinkInterface* sink) override {}
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// Returns true if fake media transport was created as a caller.
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bool is_caller() const { return settings_.is_caller; }
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absl::optional<std::string> pre_shared_key() const {
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return settings_.pre_shared_key;
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}
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RTCError OpenChannel(int channel_id) override { return RTCError::OK(); }
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RTCError SendData(int channel_id,
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const SendDataParams& params,
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const rtc::CopyOnWriteBuffer& buffer) override {
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return RTCError::OK();
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}
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RTCError CloseChannel(int channel_id) override { return RTCError::OK(); }
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void SetDataSink(DataChannelSink* sink) override {}
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void SetMediaTransportStateCallback(
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MediaTransportStateCallback* callback) override {
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state_callback_ = callback;
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}
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void SetState(webrtc::MediaTransportState state) {
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if (state_callback_) {
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state_callback_->OnStateChanged(state);
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}
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}
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void AddTargetTransferRateObserver(
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webrtc::TargetTransferRateObserver* observer) override {
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RTC_CHECK(!absl::c_linear_search(target_rate_observers_, observer));
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target_rate_observers_.push_back(observer);
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}
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void RemoveTargetTransferRateObserver(
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webrtc::TargetTransferRateObserver* observer) override {
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auto it = absl::c_find(target_rate_observers_, observer);
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if (it != target_rate_observers_.end()) {
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target_rate_observers_.erase(it);
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}
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}
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void SetAllocatedBitrateLimits(
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const MediaTransportAllocatedBitrateLimits& limits) override {}
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void SetTargetBitrateLimits(const MediaTransportTargetRateConstraints&
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target_rate_constraints) override {
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target_rate_constraints_in_order_.push_back(target_rate_constraints);
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}
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const std::vector<MediaTransportTargetRateConstraints>&
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target_rate_constraints_in_order() {
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return target_rate_constraints_in_order_;
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}
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int target_rate_observers_size() { return target_rate_observers_.size(); }
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// Settings that were passed down to fake media transport.
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const MediaTransportSettings& settings() { return settings_; }
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absl::optional<std::string> GetTransportParametersOffer() const override {
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// At least right now, we intend to use GetTransportParametersOffer before
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// the transport is connected. This may change in the future.
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RTC_CHECK(!is_connected_);
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return transport_offer_;
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}
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const absl::optional<std::string>& remote_transport_parameters() {
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return remote_transport_parameters_;
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}
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void Connect(rtc::PacketTransportInternal* packet_transport) {
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RTC_CHECK(!is_connected_) << "::Connect was called twice";
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is_connected_ = true;
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}
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bool is_connected() { return is_connected_; }
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private:
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const MediaTransportSettings settings_;
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MediaTransportStateCallback* state_callback_ = nullptr;
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std::vector<webrtc::TargetTransferRateObserver*> target_rate_observers_;
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const absl::optional<std::string> transport_offer_;
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const absl::optional<std::string> remote_transport_parameters_;
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bool is_connected_ = false;
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std::vector<MediaTransportTargetRateConstraints>
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target_rate_constraints_in_order_;
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};
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// Fake media transport factory creates fake media transport.
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// Also creates fake datagram transport, since both media and datagram
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// transports are created by |MediaTransportFactory|.
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class FakeMediaTransportFactory : public MediaTransportFactory {
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public:
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explicit FakeMediaTransportFactory(
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const absl::optional<std::string>& transport_offer = "")
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: transport_offer_(transport_offer) {}
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~FakeMediaTransportFactory() = default;
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std::string GetTransportName() const override { return "fake"; }
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RTCErrorOr<std::unique_ptr<MediaTransportInterface>> CreateMediaTransport(
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rtc::PacketTransportInternal* packet_transport,
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rtc::Thread* network_thread,
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const MediaTransportSettings& settings) override {
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std::unique_ptr<MediaTransportInterface> media_transport =
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absl::make_unique<FakeMediaTransport>(settings, transport_offer_);
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media_transport->Connect(packet_transport);
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return std::move(media_transport);
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}
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RTCErrorOr<std::unique_ptr<MediaTransportInterface>> CreateMediaTransport(
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rtc::Thread* network_thread,
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const MediaTransportSettings& settings) override {
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std::unique_ptr<MediaTransportInterface> media_transport =
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absl::make_unique<FakeMediaTransport>(
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settings, transport_offer_, settings.remote_transport_parameters);
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return std::move(media_transport);
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}
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RTCErrorOr<std::unique_ptr<DatagramTransportInterface>>
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CreateDatagramTransport(rtc::Thread* network_thread,
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const MediaTransportSettings& settings) override {
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return std::unique_ptr<DatagramTransportInterface>(
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new FakeDatagramTransport(settings, transport_offer_.value_or("")));
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}
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private:
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const absl::optional<std::string> transport_offer_;
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};
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} // namespace webrtc
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#endif // API_TEST_FAKE_MEDIA_TRANSPORT_H_
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