pc/data_channel_controller.cc - src - Git at Google

 /*
  *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "pc/data_channel_controller.h"

 #include <utility>

 #include "absl/algorithm/container.h"
 #include "api/peer_connection_interface.h"
 #include "api/rtc_error.h"
 #include "pc/peer_connection_internal.h"
 #include "pc/sctp_utils.h"
 #include "rtc_base/logging.h"

 namespace webrtc {

 DataChannelController::~DataChannelController() {
 #if RTC_DCHECK_IS_ON
   // `sctp_data_channels_n_` might be empty while `sctp_data_channels_` is
   // not. An example of that is when the `DataChannelController` goes out of
   // scope with outstanding channels that have been properly terminated on the
   // network thread but not yet cleared from `sctp_data_channels_`. However,
   // if `sctp_data_channels_n_` is not empty, then `sctp_data_channels_n_` and
   // sctp_data_channels_ should hold the same contents.
   if (!sctp_data_channels_n_.empty()) {
     RTC_DCHECK_EQ(sctp_data_channels_n_.size(), sctp_data_channels_.size());
   }
 #endif
 }

 bool DataChannelController::HasDataChannelsForTest() const {
   RTC_DCHECK_RUN_ON(signaling_thread());
   return !sctp_data_channels_.empty();
 }

 bool DataChannelController::HasUsedDataChannels() const {
   RTC_DCHECK_RUN_ON(signaling_thread());
   return has_used_data_channels_;
 }

 RTCError DataChannelController::SendData(
     StreamId sid,
     const SendDataParams& params,
     const rtc::CopyOnWriteBuffer& payload) {
   if (data_channel_transport())
     return DataChannelSendData(sid, params, payload);
   RTC_LOG(LS_ERROR) << "SendData called before transport is ready";
   return RTCError(RTCErrorType::INVALID_STATE);
 }

 void DataChannelController::AddSctpDataStream(StreamId sid) {
   RTC_DCHECK_RUN_ON(network_thread());
   RTC_DCHECK(sid.HasValue());
   if (data_channel_transport()) {
     data_channel_transport()->OpenChannel(sid.stream_id_int());
   }
 }

 void DataChannelController::RemoveSctpDataStream(StreamId sid) {
   RTC_DCHECK_RUN_ON(network_thread());
   if (data_channel_transport()) {
     data_channel_transport()->CloseChannel(sid.stream_id_int());
   }
 }

 void DataChannelController::OnChannelStateChanged(
     SctpDataChannel* channel,
     DataChannelInterface::DataState state) {
   RTC_DCHECK_RUN_ON(signaling_thread());
   if (state == DataChannelInterface::DataState::kClosed)
     OnSctpDataChannelClosed(channel);

   pc_->OnSctpDataChannelStateChanged(channel->internal_id(), state);
 }

 void DataChannelController::OnDataReceived(
     int channel_id,
     DataMessageType type,
     const rtc::CopyOnWriteBuffer& buffer) {
   RTC_DCHECK_RUN_ON(network_thread());

   if (HandleOpenMessage_n(channel_id, type, buffer))
     return;

   signaling_thread()->PostTask(
       SafeTask(signaling_safety_.flag(), [this, channel_id, type, buffer] {
         RTC_DCHECK_RUN_ON(signaling_thread());
         // TODO(bugs.webrtc.org/11547): The data being received should be
         // delivered on the network thread.
         auto it = FindChannel(StreamId(channel_id));
         if (it != sctp_data_channels_.end())
           (*it)->OnDataReceived(type, buffer);
       }));
 }

 void DataChannelController::OnChannelClosing(int channel_id) {
   RTC_DCHECK_RUN_ON(network_thread());
   signaling_thread()->PostTask(
       SafeTask(signaling_safety_.flag(), [this, channel_id] {
         RTC_DCHECK_RUN_ON(signaling_thread());
         // TODO(bugs.webrtc.org/11547): Should run on the network thread.
         auto it = FindChannel(StreamId(channel_id));
         if (it != sctp_data_channels_.end())
           (*it)->OnClosingProcedureStartedRemotely();
       }));
 }

 void DataChannelController::OnChannelClosed(int channel_id) {
   RTC_DCHECK_RUN_ON(network_thread());
   StreamId sid(channel_id);
   sid_allocator_.ReleaseSid(sid);
   auto it = absl::c_find_if(sctp_data_channels_n_,
                             [&](const auto& c) { return c->sid_n() == sid; });

   if (it != sctp_data_channels_n_.end())
     sctp_data_channels_n_.erase(it);

   signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this, sid] {
     RTC_DCHECK_RUN_ON(signaling_thread());
     auto it = FindChannel(sid);
     // Remove the channel from our list, close it and free up resources.
     if (it != sctp_data_channels_.end()) {
       rtc::scoped_refptr<SctpDataChannel> channel = std::move(*it);
       // Note: this causes OnSctpDataChannelClosed() to not do anything
       // when called from within `OnClosingProcedureComplete`.
       sctp_data_channels_.erase(it);

       channel->OnClosingProcedureComplete();
     }
   }));
 }

 void DataChannelController::OnReadyToSend() {
   RTC_DCHECK_RUN_ON(network_thread());
   signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this] {
     RTC_DCHECK_RUN_ON(signaling_thread());
     auto copy = sctp_data_channels_;
     for (const auto& channel : copy)
       channel->OnTransportReady();
   }));
 }

 void DataChannelController::OnTransportClosed(RTCError error) {
   RTC_DCHECK_RUN_ON(network_thread());
   signaling_thread()->PostTask(
       SafeTask(signaling_safety_.flag(), [this, error] {
         RTC_DCHECK_RUN_ON(signaling_thread());
         OnTransportChannelClosed(error);
       }));
 }

 void DataChannelController::SetupDataChannelTransport_n() {
   RTC_DCHECK_RUN_ON(network_thread());

   // There's a new data channel transport.  This needs to be signaled to the
   // `sctp_data_channels_` so that they can reopen and reconnect.  This is
   // necessary when bundling is applied.
   NotifyDataChannelsOfTransportCreated();
 }

 void DataChannelController::TeardownDataChannelTransport_n() {
   RTC_DCHECK_RUN_ON(network_thread());
   if (data_channel_transport()) {
     data_channel_transport()->SetDataSink(nullptr);
   }
   set_data_channel_transport(nullptr);
   sctp_data_channels_n_.clear();
 }

 void DataChannelController::OnTransportChanged(
     DataChannelTransportInterface* new_data_channel_transport) {
   RTC_DCHECK_RUN_ON(network_thread());
   if (data_channel_transport() &&
       data_channel_transport() != new_data_channel_transport) {
     // Changed which data channel transport is used for `sctp_mid_` (eg. now
     // it's bundled).
     data_channel_transport()->SetDataSink(nullptr);
     set_data_channel_transport(new_data_channel_transport);
     if (new_data_channel_transport) {
       new_data_channel_transport->SetDataSink(this);

       // There's a new data channel transport.  This needs to be signaled to the
       // `sctp_data_channels_` so that they can reopen and reconnect.  This is
       // necessary when bundling is applied.
       NotifyDataChannelsOfTransportCreated();
     }
   }
 }

 std::vector<DataChannelStats> DataChannelController::GetDataChannelStats()
     const {
   RTC_DCHECK_RUN_ON(signaling_thread());
   std::vector<DataChannelStats> stats;
   stats.reserve(sctp_data_channels_.size());
   for (const auto& channel : sctp_data_channels_)
     stats.push_back(channel->GetStats());
   return stats;
 }

 bool DataChannelController::HandleOpenMessage_n(
     int channel_id,
     DataMessageType type,
     const rtc::CopyOnWriteBuffer& buffer) {
   if (type != DataMessageType::kControl || !IsOpenMessage(buffer))
     return false;

   // Received OPEN message; parse and signal that a new data channel should
   // be created.
   std::string label;
   InternalDataChannelInit config;
   config.id = channel_id;
   if (!ParseDataChannelOpenMessage(buffer, &label, &config)) {
     RTC_LOG(LS_WARNING) << "Failed to parse the OPEN message for sid "
                         << channel_id;
   } else {
     config.open_handshake_role = InternalDataChannelInit::kAcker;
     signaling_thread()->PostTask(
         SafeTask(signaling_safety_.flag(),
                  [this, label = std::move(label), config = std::move(config)] {
                    RTC_DCHECK_RUN_ON(signaling_thread());
                    OnDataChannelOpenMessage(label, config);
                  }));
   }
   return true;
 }

 void DataChannelController::OnDataChannelOpenMessage(
     const std::string& label,
     const InternalDataChannelInit& config) {
   auto channel_or_error = InternalCreateDataChannelWithProxy(label, config);
   if (!channel_or_error.ok()) {
     RTC_LOG(LS_ERROR) << "Failed to create DataChannel from the OPEN message."
                       << ToString(channel_or_error.error().type());
     return;
   }

   pc_->Observer()->OnDataChannel(channel_or_error.MoveValue());
   pc_->NoteDataAddedEvent();
 }

 // RTC_RUN_ON(network_thread())
 RTCError DataChannelController::ReserveOrAllocateSid(
     StreamId& sid,
     absl::optional<rtc::SSLRole> fallback_ssl_role) {
   if (sid.HasValue()) {
     return sid_allocator_.ReserveSid(sid)
                ? RTCError::OK()
                : RTCError(RTCErrorType::INVALID_RANGE,
                           "StreamId out of range or reserved.");
   }

   // Attempt to allocate an ID based on the negotiated role.
   absl::optional<rtc::SSLRole> role = pc_->GetSctpSslRole_n();
   if (!role)
     role = fallback_ssl_role;
   if (role) {
     sid = sid_allocator_.AllocateSid(*role);
     if (!sid.HasValue())
       return RTCError(RTCErrorType::RESOURCE_EXHAUSTED);
   }
   // When we get here, we may still not have an ID, but that's a supported case
   // whereby an id will be assigned later.
   RTC_DCHECK(sid.HasValue() || !role);
   return RTCError::OK();
 }

 RTCErrorOr<rtc::scoped_refptr<DataChannelInterface>>
 DataChannelController::InternalCreateDataChannelWithProxy(
     const std::string& label,
     const InternalDataChannelInit& config) {
   RTC_DCHECK_RUN_ON(signaling_thread());
   RTC_DCHECK(!pc_->IsClosed());
   if (!config.IsValid()) {
     LOG_AND_RETURN_ERROR(RTCErrorType::INVALID_PARAMETER,
                          "Invalid DataChannelInit");
   }

   bool ready_to_send = false;
   InternalDataChannelInit new_config = config;
   StreamId sid(new_config.id);
   auto weak_ptr = weak_factory_.GetWeakPtr();
   RTC_DCHECK(weak_ptr);  // Associate with current thread.
   auto ret = network_thread()->BlockingCall(
       [&]() -> RTCErrorOr<rtc::scoped_refptr<SctpDataChannel>> {
         RTC_DCHECK_RUN_ON(network_thread());
         RTCError err = ReserveOrAllocateSid(sid, new_config.fallback_ssl_role);
         if (!err.ok())
           return err;

         // In case `sid` has changed. Update `new_config` accordingly.
         new_config.id = sid.stream_id_int();
         ready_to_send =
             data_channel_transport_ && data_channel_transport_->IsReadyToSend();

         rtc::scoped_refptr<SctpDataChannel> channel(SctpDataChannel::Create(
             std::move(weak_ptr), label, data_channel_transport_ != nullptr,
             new_config, signaling_thread(), network_thread()));
         RTC_DCHECK(channel);
         sctp_data_channels_n_.push_back(channel);

         // If we have an id already, notify the transport.
         if (sid.HasValue())
           AddSctpDataStream(sid);

         return channel;
       });

   if (!ret.ok())
     return ret.MoveError();

   if (ready_to_send) {
     // Checks if the transport is ready to send because the initial channel
     // ready signal may have been sent before the DataChannel creation.
     // This has to be done async because the upper layer objects (e.g.
     // Chrome glue and WebKit) are not wired up properly until after this
     // function returns.
     signaling_thread()->PostTask(
         SafeTask(signaling_safety_.flag(), [channel = ret.value()] {
           if (channel->state() != DataChannelInterface::DataState::kClosed)
             channel->OnTransportReady();
         }));
   }

   sctp_data_channels_.push_back(ret.value());
   has_used_data_channels_ = true;
   return SctpDataChannel::CreateProxy(ret.MoveValue());
 }

 void DataChannelController::AllocateSctpSids(rtc::SSLRole role) {
   RTC_DCHECK_RUN_ON(signaling_thread());

   std::vector<std::pair<SctpDataChannel*, StreamId>> channels_to_update;
   std::vector<rtc::scoped_refptr<SctpDataChannel>> channels_to_close;

   network_thread()->BlockingCall([&] {
     RTC_DCHECK_RUN_ON(network_thread());
     for (auto it = sctp_data_channels_n_.begin();
          it != sctp_data_channels_n_.end();) {
       if (!(*it)->sid_n().HasValue()) {
         StreamId sid = sid_allocator_.AllocateSid(role);
         if (sid.HasValue()) {
           (*it)->SetSctpSid_n(sid);
           AddSctpDataStream(sid);
           channels_to_update.push_back(std::make_pair((*it).get(), sid));
         } else {
           channels_to_close.push_back(std::move(*it));
           it = sctp_data_channels_n_.erase(it);
           continue;
         }
       }
       ++it;
     }
   });

   // Since closing modifies the list of channels, we have to do the actual
   // closing outside the loop.
   for (const auto& channel : channels_to_close) {
     channel->CloseAbruptlyWithDataChannelFailure("Failed to allocate SCTP SID");
     // The channel should now have been removed from sctp_data_channels_.
     RTC_DCHECK(absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
                  return c.get() == channel.get();
                }) == sctp_data_channels_.end());
   }

   for (auto& pair : channels_to_update) {
     auto it = absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
       return c.get() == pair.first;
     });
     RTC_DCHECK(it != sctp_data_channels_.end());
     (*it)->SetSctpSid_s(pair.second);
   }
 }

 void DataChannelController::OnSctpDataChannelClosed(SctpDataChannel* channel) {
   RTC_DCHECK_RUN_ON(signaling_thread());

   network_thread()->BlockingCall([&] {
     RTC_DCHECK_RUN_ON(network_thread());
     // After the closing procedure is done, it's safe to use this ID for
     // another data channel.
     if (channel->sid_n().HasValue()) {
       sid_allocator_.ReleaseSid(channel->sid_n());
     }

     auto it = absl::c_find_if(sctp_data_channels_n_, [&](const auto& c) {
       return c.get() == channel;
     });

     if (it != sctp_data_channels_n_.end())
       sctp_data_channels_n_.erase(it);
   });

   for (auto it = sctp_data_channels_.begin(); it != sctp_data_channels_.end();
        ++it) {
     if (it->get() == channel) {
       // Since this method is triggered by a signal from the DataChannel,
       // we can't free it directly here; we need to free it asynchronously.
       rtc::scoped_refptr<SctpDataChannel> release = std::move(*it);
       sctp_data_channels_.erase(it);
       signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(),
                                             [release = std::move(release)] {}));
       return;
     }
   }
 }

 void DataChannelController::OnTransportChannelClosed(RTCError error) {
   RTC_DCHECK_RUN_ON(signaling_thread());
   // Use a temporary copy of the SCTP DataChannel list because the
   // DataChannel may callback to us and try to modify the list.
   // TODO(tommi): `OnTransportChannelClosed` is called from
   // `SdpOfferAnswerHandler::DestroyDataChannelTransport` just before
   // `TeardownDataChannelTransport_n` is called (but on the network thread) from
   // the same function. Once `sctp_data_channels_` moves to the network thread,
   // we can get rid of this function (OnTransportChannelClosed) and run this
   // loop from within the TeardownDataChannelTransport_n callback.
   std::vector<rtc::scoped_refptr<SctpDataChannel>> temp_sctp_dcs;
   temp_sctp_dcs.swap(sctp_data_channels_);
   for (const auto& channel : temp_sctp_dcs) {
     channel->OnTransportChannelClosed(error);
   }
 }

 DataChannelTransportInterface* DataChannelController::data_channel_transport()
     const {
   // TODO(bugs.webrtc.org/11547): Only allow this accessor to be called on the
   // network thread.
   // RTC_DCHECK_RUN_ON(network_thread());
   return data_channel_transport_;
 }

 void DataChannelController::set_data_channel_transport(
     DataChannelTransportInterface* transport) {
   RTC_DCHECK_RUN_ON(network_thread());
   data_channel_transport_ = transport;
 }

 RTCError DataChannelController::DataChannelSendData(
     StreamId sid,
     const SendDataParams& params,
     const rtc::CopyOnWriteBuffer& payload) {
   // TODO(bugs.webrtc.org/11547): Expect method to be called on the network
   // thread instead. Remove the BlockingCall() below and move associated state
   // to the network thread.
   RTC_DCHECK_RUN_ON(signaling_thread());
   RTC_DCHECK(data_channel_transport());

   return network_thread()->BlockingCall([this, sid, params, payload] {
     return data_channel_transport()->SendData(sid.stream_id_int(), params,
                                               payload);
   });
 }

 void DataChannelController::NotifyDataChannelsOfTransportCreated() {
   RTC_DCHECK_RUN_ON(network_thread());
   RTC_DCHECK(data_channel_transport());

   for (const auto& channel : sctp_data_channels_n_) {
     if (channel->sid_n().HasValue())
       AddSctpDataStream(channel->sid_n());
   }

   signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this] {
     RTC_DCHECK_RUN_ON(signaling_thread());
     for (const auto& channel : sctp_data_channels_) {
       channel->OnTransportChannelCreated();
     }
   }));
 }

 std::vector<rtc::scoped_refptr<SctpDataChannel>>::iterator
 DataChannelController::FindChannel(StreamId stream_id) {
   RTC_DCHECK_RUN_ON(signaling_thread());
   return absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
     return c->sid_s() == stream_id;
   });
 }

 rtc::Thread* DataChannelController::network_thread() const {
   return pc_->network_thread();
 }
 rtc::Thread* DataChannelController::signaling_thread() const {
   return pc_->signaling_thread();
 }

 }  // namespace webrtc
	/*
	* Copyright 2019 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "pc/data_channel_controller.h"

	#include <utility>

	#include "absl/algorithm/container.h"
	#include "api/peer_connection_interface.h"
	#include "api/rtc_error.h"
	#include "pc/peer_connection_internal.h"
	#include "pc/sctp_utils.h"
	#include "rtc_base/logging.h"

	namespace webrtc {

	DataChannelController::~DataChannelController() {
	#if RTC_DCHECK_IS_ON
	// `sctp_data_channels_n_` might be empty while `sctp_data_channels_` is
	// not. An example of that is when the `DataChannelController` goes out of
	// scope with outstanding channels that have been properly terminated on the
	// network thread but not yet cleared from `sctp_data_channels_`. However,
	// if `sctp_data_channels_n_` is not empty, then `sctp_data_channels_n_` and
	// sctp_data_channels_ should hold the same contents.
	if (!sctp_data_channels_n_.empty()) {
	RTC_DCHECK_EQ(sctp_data_channels_n_.size(), sctp_data_channels_.size());
	}
	#endif
	}

	bool DataChannelController::HasDataChannelsForTest() const {
	RTC_DCHECK_RUN_ON(signaling_thread());
	return !sctp_data_channels_.empty();
	}

	bool DataChannelController::HasUsedDataChannels() const {
	RTC_DCHECK_RUN_ON(signaling_thread());
	return has_used_data_channels_;
	}

	RTCError DataChannelController::SendData(
	StreamId sid,
	const SendDataParams& params,
	const rtc::CopyOnWriteBuffer& payload) {
	if (data_channel_transport())
	return DataChannelSendData(sid, params, payload);
	RTC_LOG(LS_ERROR) << "SendData called before transport is ready";
	return RTCError(RTCErrorType::INVALID_STATE);
	}

	void DataChannelController::AddSctpDataStream(StreamId sid) {
	RTC_DCHECK_RUN_ON(network_thread());
	RTC_DCHECK(sid.HasValue());
	if (data_channel_transport()) {
	data_channel_transport()->OpenChannel(sid.stream_id_int());
	}
	}

	void DataChannelController::RemoveSctpDataStream(StreamId sid) {
	RTC_DCHECK_RUN_ON(network_thread());
	if (data_channel_transport()) {
	data_channel_transport()->CloseChannel(sid.stream_id_int());
	}
	}

	void DataChannelController::OnChannelStateChanged(
	SctpDataChannel* channel,
	DataChannelInterface::DataState state) {
	RTC_DCHECK_RUN_ON(signaling_thread());
	if (state == DataChannelInterface::DataState::kClosed)
	OnSctpDataChannelClosed(channel);

	pc_->OnSctpDataChannelStateChanged(channel->internal_id(), state);
	}

	void DataChannelController::OnDataReceived(
	int channel_id,
	DataMessageType type,
	const rtc::CopyOnWriteBuffer& buffer) {
	RTC_DCHECK_RUN_ON(network_thread());

	if (HandleOpenMessage_n(channel_id, type, buffer))
	return;

	signaling_thread()->PostTask(
	SafeTask(signaling_safety_.flag(), [this, channel_id, type, buffer] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	// TODO(bugs.webrtc.org/11547): The data being received should be
	// delivered on the network thread.
	auto it = FindChannel(StreamId(channel_id));
	if (it != sctp_data_channels_.end())
	(*it)->OnDataReceived(type, buffer);
	}));
	}

	void DataChannelController::OnChannelClosing(int channel_id) {
	RTC_DCHECK_RUN_ON(network_thread());
	signaling_thread()->PostTask(
	SafeTask(signaling_safety_.flag(), [this, channel_id] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	// TODO(bugs.webrtc.org/11547): Should run on the network thread.
	auto it = FindChannel(StreamId(channel_id));
	if (it != sctp_data_channels_.end())
	(*it)->OnClosingProcedureStartedRemotely();
	}));
	}

	void DataChannelController::OnChannelClosed(int channel_id) {
	RTC_DCHECK_RUN_ON(network_thread());
	StreamId sid(channel_id);
	sid_allocator_.ReleaseSid(sid);
	auto it = absl::c_find_if(sctp_data_channels_n_,
	[&](const auto& c) { return c->sid_n() == sid; });

	if (it != sctp_data_channels_n_.end())
	sctp_data_channels_n_.erase(it);

	signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this, sid] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	auto it = FindChannel(sid);
	// Remove the channel from our list, close it and free up resources.
	if (it != sctp_data_channels_.end()) {
	rtc::scoped_refptr<SctpDataChannel> channel = std::move(*it);
	// Note: this causes OnSctpDataChannelClosed() to not do anything
	// when called from within `OnClosingProcedureComplete`.
	sctp_data_channels_.erase(it);

	channel->OnClosingProcedureComplete();
	}
	}));
	}

	void DataChannelController::OnReadyToSend() {
	RTC_DCHECK_RUN_ON(network_thread());
	signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	auto copy = sctp_data_channels_;
	for (const auto& channel : copy)
	channel->OnTransportReady();
	}));
	}

	void DataChannelController::OnTransportClosed(RTCError error) {
	RTC_DCHECK_RUN_ON(network_thread());
	signaling_thread()->PostTask(
	SafeTask(signaling_safety_.flag(), [this, error] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	OnTransportChannelClosed(error);
	}));
	}

	void DataChannelController::SetupDataChannelTransport_n() {
	RTC_DCHECK_RUN_ON(network_thread());

	// There's a new data channel transport. This needs to be signaled to the
	// `sctp_data_channels_` so that they can reopen and reconnect. This is
	// necessary when bundling is applied.
	NotifyDataChannelsOfTransportCreated();
	}

	void DataChannelController::TeardownDataChannelTransport_n() {
	RTC_DCHECK_RUN_ON(network_thread());
	if (data_channel_transport()) {
	data_channel_transport()->SetDataSink(nullptr);
	}
	set_data_channel_transport(nullptr);
	sctp_data_channels_n_.clear();
	}

	void DataChannelController::OnTransportChanged(
	DataChannelTransportInterface* new_data_channel_transport) {
	RTC_DCHECK_RUN_ON(network_thread());
	if (data_channel_transport() &&
	data_channel_transport() != new_data_channel_transport) {
	// Changed which data channel transport is used for `sctp_mid_` (eg. now
	// it's bundled).
	data_channel_transport()->SetDataSink(nullptr);
	set_data_channel_transport(new_data_channel_transport);
	if (new_data_channel_transport) {
	new_data_channel_transport->SetDataSink(this);

	// There's a new data channel transport. This needs to be signaled to the
	// `sctp_data_channels_` so that they can reopen and reconnect. This is
	// necessary when bundling is applied.
	NotifyDataChannelsOfTransportCreated();
	}
	}
	}

	std::vector<DataChannelStats> DataChannelController::GetDataChannelStats()
	const {
	RTC_DCHECK_RUN_ON(signaling_thread());
	std::vector<DataChannelStats> stats;
	stats.reserve(sctp_data_channels_.size());
	for (const auto& channel : sctp_data_channels_)
	stats.push_back(channel->GetStats());
	return stats;
	}

	bool DataChannelController::HandleOpenMessage_n(
	int channel_id,
	DataMessageType type,
	const rtc::CopyOnWriteBuffer& buffer) {
	if (type != DataMessageType::kControl \|\| !IsOpenMessage(buffer))
	return false;

	// Received OPEN message; parse and signal that a new data channel should
	// be created.
	std::string label;
	InternalDataChannelInit config;
	config.id = channel_id;
	if (!ParseDataChannelOpenMessage(buffer, &label, &config)) {
	RTC_LOG(LS_WARNING) << "Failed to parse the OPEN message for sid "
	<< channel_id;
	} else {
	config.open_handshake_role = InternalDataChannelInit::kAcker;
	signaling_thread()->PostTask(
	SafeTask(signaling_safety_.flag(),
	[this, label = std::move(label), config = std::move(config)] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	OnDataChannelOpenMessage(label, config);
	}));
	}
	return true;
	}

	void DataChannelController::OnDataChannelOpenMessage(
	const std::string& label,
	const InternalDataChannelInit& config) {
	auto channel_or_error = InternalCreateDataChannelWithProxy(label, config);
	if (!channel_or_error.ok()) {
	RTC_LOG(LS_ERROR) << "Failed to create DataChannel from the OPEN message."
	<< ToString(channel_or_error.error().type());
	return;
	}

	pc_->Observer()->OnDataChannel(channel_or_error.MoveValue());
	pc_->NoteDataAddedEvent();
	}

	// RTC_RUN_ON(network_thread())
	RTCError DataChannelController::ReserveOrAllocateSid(
	StreamId& sid,
	absl::optional<rtc::SSLRole> fallback_ssl_role) {
	if (sid.HasValue()) {
	return sid_allocator_.ReserveSid(sid)
	? RTCError::OK()
	: RTCError(RTCErrorType::INVALID_RANGE,
	"StreamId out of range or reserved.");
	}

	// Attempt to allocate an ID based on the negotiated role.
	absl::optional<rtc::SSLRole> role = pc_->GetSctpSslRole_n();
	if (!role)
	role = fallback_ssl_role;
	if (role) {
	sid = sid_allocator_.AllocateSid(*role);
	if (!sid.HasValue())
	return RTCError(RTCErrorType::RESOURCE_EXHAUSTED);
	}
	// When we get here, we may still not have an ID, but that's a supported case
	// whereby an id will be assigned later.
	RTC_DCHECK(sid.HasValue() \|\| !role);
	return RTCError::OK();
	}

	RTCErrorOr<rtc::scoped_refptr<DataChannelInterface>>
	DataChannelController::InternalCreateDataChannelWithProxy(
	const std::string& label,
	const InternalDataChannelInit& config) {
	RTC_DCHECK_RUN_ON(signaling_thread());
	RTC_DCHECK(!pc_->IsClosed());
	if (!config.IsValid()) {
	LOG_AND_RETURN_ERROR(RTCErrorType::INVALID_PARAMETER,
	"Invalid DataChannelInit");
	}

	bool ready_to_send = false;
	InternalDataChannelInit new_config = config;
	StreamId sid(new_config.id);
	auto weak_ptr = weak_factory_.GetWeakPtr();
	RTC_DCHECK(weak_ptr); // Associate with current thread.
	auto ret = network_thread()->BlockingCall(
	[&]() -> RTCErrorOr<rtc::scoped_refptr<SctpDataChannel>> {
	RTC_DCHECK_RUN_ON(network_thread());
	RTCError err = ReserveOrAllocateSid(sid, new_config.fallback_ssl_role);
	if (!err.ok())
	return err;

	// In case `sid` has changed. Update `new_config` accordingly.
	new_config.id = sid.stream_id_int();
	ready_to_send =
	data_channel_transport_ && data_channel_transport_->IsReadyToSend();

	rtc::scoped_refptr<SctpDataChannel> channel(SctpDataChannel::Create(
	std::move(weak_ptr), label, data_channel_transport_ != nullptr,
	new_config, signaling_thread(), network_thread()));
	RTC_DCHECK(channel);
	sctp_data_channels_n_.push_back(channel);

	// If we have an id already, notify the transport.
	if (sid.HasValue())
	AddSctpDataStream(sid);

	return channel;
	});

	if (!ret.ok())
	return ret.MoveError();

	if (ready_to_send) {
	// Checks if the transport is ready to send because the initial channel
	// ready signal may have been sent before the DataChannel creation.
	// This has to be done async because the upper layer objects (e.g.
	// Chrome glue and WebKit) are not wired up properly until after this
	// function returns.
	signaling_thread()->PostTask(
	SafeTask(signaling_safety_.flag(), [channel = ret.value()] {
	if (channel->state() != DataChannelInterface::DataState::kClosed)
	channel->OnTransportReady();
	}));
	}

	sctp_data_channels_.push_back(ret.value());
	has_used_data_channels_ = true;
	return SctpDataChannel::CreateProxy(ret.MoveValue());
	}

	void DataChannelController::AllocateSctpSids(rtc::SSLRole role) {
	RTC_DCHECK_RUN_ON(signaling_thread());

	std::vector<std::pair<SctpDataChannel*, StreamId>> channels_to_update;
	std::vector<rtc::scoped_refptr<SctpDataChannel>> channels_to_close;

	network_thread()->BlockingCall([&] {
	RTC_DCHECK_RUN_ON(network_thread());
	for (auto it = sctp_data_channels_n_.begin();
	it != sctp_data_channels_n_.end();) {
	if (!(*it)->sid_n().HasValue()) {
	StreamId sid = sid_allocator_.AllocateSid(role);
	if (sid.HasValue()) {
	(*it)->SetSctpSid_n(sid);
	AddSctpDataStream(sid);
	channels_to_update.push_back(std::make_pair((*it).get(), sid));
	} else {
	channels_to_close.push_back(std::move(*it));
	it = sctp_data_channels_n_.erase(it);
	continue;
	}
	}
	++it;
	}
	});

	// Since closing modifies the list of channels, we have to do the actual
	// closing outside the loop.
	for (const auto& channel : channels_to_close) {
	channel->CloseAbruptlyWithDataChannelFailure("Failed to allocate SCTP SID");
	// The channel should now have been removed from sctp_data_channels_.
	RTC_DCHECK(absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
	return c.get() == channel.get();
	}) == sctp_data_channels_.end());
	}

	for (auto& pair : channels_to_update) {
	auto it = absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
	return c.get() == pair.first;
	});
	RTC_DCHECK(it != sctp_data_channels_.end());
	(*it)->SetSctpSid_s(pair.second);
	}
	}

	void DataChannelController::OnSctpDataChannelClosed(SctpDataChannel* channel) {
	RTC_DCHECK_RUN_ON(signaling_thread());

	network_thread()->BlockingCall([&] {
	RTC_DCHECK_RUN_ON(network_thread());
	// After the closing procedure is done, it's safe to use this ID for
	// another data channel.
	if (channel->sid_n().HasValue()) {
	sid_allocator_.ReleaseSid(channel->sid_n());
	}

	auto it = absl::c_find_if(sctp_data_channels_n_, [&](const auto& c) {
	return c.get() == channel;
	});

	if (it != sctp_data_channels_n_.end())
	sctp_data_channels_n_.erase(it);
	});

	for (auto it = sctp_data_channels_.begin(); it != sctp_data_channels_.end();
	++it) {
	if (it->get() == channel) {
	// Since this method is triggered by a signal from the DataChannel,
	// we can't free it directly here; we need to free it asynchronously.
	rtc::scoped_refptr<SctpDataChannel> release = std::move(*it);
	sctp_data_channels_.erase(it);
	signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(),
	[release = std::move(release)] {}));
	return;
	}
	}
	}

	void DataChannelController::OnTransportChannelClosed(RTCError error) {
	RTC_DCHECK_RUN_ON(signaling_thread());
	// Use a temporary copy of the SCTP DataChannel list because the
	// DataChannel may callback to us and try to modify the list.
	// TODO(tommi): `OnTransportChannelClosed` is called from
	// `SdpOfferAnswerHandler::DestroyDataChannelTransport` just before
	// `TeardownDataChannelTransport_n` is called (but on the network thread) from
	// the same function. Once `sctp_data_channels_` moves to the network thread,
	// we can get rid of this function (OnTransportChannelClosed) and run this
	// loop from within the TeardownDataChannelTransport_n callback.
	std::vector<rtc::scoped_refptr<SctpDataChannel>> temp_sctp_dcs;
	temp_sctp_dcs.swap(sctp_data_channels_);
	for (const auto& channel : temp_sctp_dcs) {
	channel->OnTransportChannelClosed(error);
	}
	}

	DataChannelTransportInterface* DataChannelController::data_channel_transport()
	const {
	// TODO(bugs.webrtc.org/11547): Only allow this accessor to be called on the
	// network thread.
	// RTC_DCHECK_RUN_ON(network_thread());
	return data_channel_transport_;
	}

	void DataChannelController::set_data_channel_transport(
	DataChannelTransportInterface* transport) {
	RTC_DCHECK_RUN_ON(network_thread());
	data_channel_transport_ = transport;
	}

	RTCError DataChannelController::DataChannelSendData(
	StreamId sid,
	const SendDataParams& params,
	const rtc::CopyOnWriteBuffer& payload) {
	// TODO(bugs.webrtc.org/11547): Expect method to be called on the network
	// thread instead. Remove the BlockingCall() below and move associated state
	// to the network thread.
	RTC_DCHECK_RUN_ON(signaling_thread());
	RTC_DCHECK(data_channel_transport());

	return network_thread()->BlockingCall([this, sid, params, payload] {
	return data_channel_transport()->SendData(sid.stream_id_int(), params,
	payload);
	});
	}

	void DataChannelController::NotifyDataChannelsOfTransportCreated() {
	RTC_DCHECK_RUN_ON(network_thread());
	RTC_DCHECK(data_channel_transport());

	for (const auto& channel : sctp_data_channels_n_) {
	if (channel->sid_n().HasValue())
	AddSctpDataStream(channel->sid_n());
	}

	signaling_thread()->PostTask(SafeTask(signaling_safety_.flag(), [this] {
	RTC_DCHECK_RUN_ON(signaling_thread());
	for (const auto& channel : sctp_data_channels_) {
	channel->OnTransportChannelCreated();
	}
	}));
	}

	std::vector<rtc::scoped_refptr<SctpDataChannel>>::iterator
	DataChannelController::FindChannel(StreamId stream_id) {
	RTC_DCHECK_RUN_ON(signaling_thread());
	return absl::c_find_if(sctp_data_channels_, [&](const auto& c) {
	return c->sid_s() == stream_id;
	});
	}

	rtc::Thread* DataChannelController::network_thread() const {
	return pc_->network_thread();
	}
	rtc::Thread* DataChannelController::signaling_thread() const {
	return pc_->signaling_thread();
	}

	} // namespace webrtc