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      1 /*
      2  * libjingle
      3  * Copyright 2012 Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #include "talk/app/webrtc/datachannel.h"
     29 
     30 #include <string>
     31 
     32 #include "talk/app/webrtc/mediastreamprovider.h"
     33 #include "talk/app/webrtc/sctputils.h"
     34 #include "talk/media/sctp/sctpdataengine.h"
     35 #include "webrtc/base/logging.h"
     36 #include "webrtc/base/refcount.h"
     37 
     38 namespace webrtc {
     39 
     40 static size_t kMaxQueuedReceivedDataBytes = 16 * 1024 * 1024;
     41 static size_t kMaxQueuedSendDataBytes = 16 * 1024 * 1024;
     42 
     43 enum {
     44   MSG_CHANNELREADY,
     45 };
     46 
     47 bool SctpSidAllocator::AllocateSid(rtc::SSLRole role, int* sid) {
     48   int potential_sid = (role == rtc::SSL_CLIENT) ? 0 : 1;
     49   while (!IsSidAvailable(potential_sid)) {
     50     potential_sid += 2;
     51     if (potential_sid > static_cast<int>(cricket::kMaxSctpSid)) {
     52       return false;
     53     }
     54   }
     55 
     56   *sid = potential_sid;
     57   used_sids_.insert(potential_sid);
     58   return true;
     59 }
     60 
     61 bool SctpSidAllocator::ReserveSid(int sid) {
     62   if (!IsSidAvailable(sid)) {
     63     return false;
     64   }
     65   used_sids_.insert(sid);
     66   return true;
     67 }
     68 
     69 void SctpSidAllocator::ReleaseSid(int sid) {
     70   auto it = used_sids_.find(sid);
     71   if (it != used_sids_.end()) {
     72     used_sids_.erase(it);
     73   }
     74 }
     75 
     76 bool SctpSidAllocator::IsSidAvailable(int sid) const {
     77   if (sid < 0 || sid > static_cast<int>(cricket::kMaxSctpSid)) {
     78     return false;
     79   }
     80   return used_sids_.find(sid) == used_sids_.end();
     81 }
     82 
     83 DataChannel::PacketQueue::PacketQueue() : byte_count_(0) {}
     84 
     85 DataChannel::PacketQueue::~PacketQueue() {
     86   Clear();
     87 }
     88 
     89 bool DataChannel::PacketQueue::Empty() const {
     90   return packets_.empty();
     91 }
     92 
     93 DataBuffer* DataChannel::PacketQueue::Front() {
     94   return packets_.front();
     95 }
     96 
     97 void DataChannel::PacketQueue::Pop() {
     98   if (packets_.empty()) {
     99     return;
    100   }
    101 
    102   byte_count_ -= packets_.front()->size();
    103   packets_.pop_front();
    104 }
    105 
    106 void DataChannel::PacketQueue::Push(DataBuffer* packet) {
    107   byte_count_ += packet->size();
    108   packets_.push_back(packet);
    109 }
    110 
    111 void DataChannel::PacketQueue::Clear() {
    112   while (!packets_.empty()) {
    113     delete packets_.front();
    114     packets_.pop_front();
    115   }
    116   byte_count_ = 0;
    117 }
    118 
    119 void DataChannel::PacketQueue::Swap(PacketQueue* other) {
    120   size_t other_byte_count = other->byte_count_;
    121   other->byte_count_ = byte_count_;
    122   byte_count_ = other_byte_count;
    123 
    124   other->packets_.swap(packets_);
    125 }
    126 
    127 rtc::scoped_refptr<DataChannel> DataChannel::Create(
    128     DataChannelProviderInterface* provider,
    129     cricket::DataChannelType dct,
    130     const std::string& label,
    131     const InternalDataChannelInit& config) {
    132   rtc::scoped_refptr<DataChannel> channel(
    133       new rtc::RefCountedObject<DataChannel>(provider, dct, label));
    134   if (!channel->Init(config)) {
    135     return NULL;
    136   }
    137   return channel;
    138 }
    139 
    140 DataChannel::DataChannel(
    141     DataChannelProviderInterface* provider,
    142     cricket::DataChannelType dct,
    143     const std::string& label)
    144     : label_(label),
    145       observer_(NULL),
    146       state_(kConnecting),
    147       data_channel_type_(dct),
    148       provider_(provider),
    149       handshake_state_(kHandshakeInit),
    150       connected_to_provider_(false),
    151       send_ssrc_set_(false),
    152       receive_ssrc_set_(false),
    153       writable_(false),
    154       send_ssrc_(0),
    155       receive_ssrc_(0) {
    156 }
    157 
    158 bool DataChannel::Init(const InternalDataChannelInit& config) {
    159   if (data_channel_type_ == cricket::DCT_RTP) {
    160     if (config.reliable ||
    161         config.id != -1 ||
    162         config.maxRetransmits != -1 ||
    163         config.maxRetransmitTime != -1) {
    164       LOG(LS_ERROR) << "Failed to initialize the RTP data channel due to "
    165                     << "invalid DataChannelInit.";
    166       return false;
    167     }
    168     handshake_state_ = kHandshakeReady;
    169   } else if (data_channel_type_ == cricket::DCT_SCTP) {
    170     if (config.id < -1 ||
    171         config.maxRetransmits < -1 ||
    172         config.maxRetransmitTime < -1) {
    173       LOG(LS_ERROR) << "Failed to initialize the SCTP data channel due to "
    174                     << "invalid DataChannelInit.";
    175       return false;
    176     }
    177     if (config.maxRetransmits != -1 && config.maxRetransmitTime != -1) {
    178       LOG(LS_ERROR) <<
    179           "maxRetransmits and maxRetransmitTime should not be both set.";
    180       return false;
    181     }
    182     config_ = config;
    183 
    184     switch (config_.open_handshake_role) {
    185     case webrtc::InternalDataChannelInit::kNone:  // pre-negotiated
    186       handshake_state_ = kHandshakeReady;
    187       break;
    188     case webrtc::InternalDataChannelInit::kOpener:
    189       handshake_state_ = kHandshakeShouldSendOpen;
    190       break;
    191     case webrtc::InternalDataChannelInit::kAcker:
    192       handshake_state_ = kHandshakeShouldSendAck;
    193       break;
    194     };
    195 
    196     // Try to connect to the transport in case the transport channel already
    197     // exists.
    198     OnTransportChannelCreated();
    199 
    200     // Checks if the transport is ready to send because the initial channel
    201     // ready signal may have been sent before the DataChannel creation.
    202     // This has to be done async because the upper layer objects (e.g.
    203     // Chrome glue and WebKit) are not wired up properly until after this
    204     // function returns.
    205     if (provider_->ReadyToSendData()) {
    206       rtc::Thread::Current()->Post(this, MSG_CHANNELREADY, NULL);
    207     }
    208   }
    209 
    210   return true;
    211 }
    212 
    213 DataChannel::~DataChannel() {}
    214 
    215 void DataChannel::RegisterObserver(DataChannelObserver* observer) {
    216   observer_ = observer;
    217   DeliverQueuedReceivedData();
    218 }
    219 
    220 void DataChannel::UnregisterObserver() {
    221   observer_ = NULL;
    222 }
    223 
    224 bool DataChannel::reliable() const {
    225   if (data_channel_type_ == cricket::DCT_RTP) {
    226     return false;
    227   } else {
    228     return config_.maxRetransmits == -1 &&
    229            config_.maxRetransmitTime == -1;
    230   }
    231 }
    232 
    233 uint64_t DataChannel::buffered_amount() const {
    234   return queued_send_data_.byte_count();
    235 }
    236 
    237 void DataChannel::Close() {
    238   if (state_ == kClosed)
    239     return;
    240   send_ssrc_ = 0;
    241   send_ssrc_set_ = false;
    242   SetState(kClosing);
    243   UpdateState();
    244 }
    245 
    246 bool DataChannel::Send(const DataBuffer& buffer) {
    247   if (state_ != kOpen) {
    248     return false;
    249   }
    250 
    251   // TODO(jiayl): the spec is unclear about if the remote side should get the
    252   // onmessage event. We need to figure out the expected behavior and change the
    253   // code accordingly.
    254   if (buffer.size() == 0) {
    255     return true;
    256   }
    257 
    258   // If the queue is non-empty, we're waiting for SignalReadyToSend,
    259   // so just add to the end of the queue and keep waiting.
    260   if (!queued_send_data_.Empty()) {
    261     // Only SCTP DataChannel queues the outgoing data when the transport is
    262     // blocked.
    263     ASSERT(data_channel_type_ == cricket::DCT_SCTP);
    264     if (!QueueSendDataMessage(buffer)) {
    265       Close();
    266     }
    267     return true;
    268   }
    269 
    270   bool success = SendDataMessage(buffer, true);
    271   if (data_channel_type_ == cricket::DCT_RTP) {
    272     return success;
    273   }
    274 
    275   // Always return true for SCTP DataChannel per the spec.
    276   return true;
    277 }
    278 
    279 void DataChannel::SetReceiveSsrc(uint32_t receive_ssrc) {
    280   ASSERT(data_channel_type_ == cricket::DCT_RTP);
    281 
    282   if (receive_ssrc_set_) {
    283     return;
    284   }
    285   receive_ssrc_ = receive_ssrc;
    286   receive_ssrc_set_ = true;
    287   UpdateState();
    288 }
    289 
    290 // The remote peer request that this channel shall be closed.
    291 void DataChannel::RemotePeerRequestClose() {
    292   DoClose();
    293 }
    294 
    295 void DataChannel::SetSctpSid(int sid) {
    296   ASSERT(config_.id < 0 && sid >= 0 && data_channel_type_ == cricket::DCT_SCTP);
    297   if (config_.id == sid) {
    298     return;
    299   }
    300 
    301   config_.id = sid;
    302   provider_->AddSctpDataStream(sid);
    303 }
    304 
    305 void DataChannel::OnTransportChannelCreated() {
    306   ASSERT(data_channel_type_ == cricket::DCT_SCTP);
    307   if (!connected_to_provider_) {
    308     connected_to_provider_ = provider_->ConnectDataChannel(this);
    309   }
    310   // The sid may have been unassigned when provider_->ConnectDataChannel was
    311   // done. So always add the streams even if connected_to_provider_ is true.
    312   if (config_.id >= 0) {
    313     provider_->AddSctpDataStream(config_.id);
    314   }
    315 }
    316 
    317 // The underlying transport channel was destroyed.
    318 // This function makes sure the DataChannel is disconnected and changes state to
    319 // kClosed.
    320 void DataChannel::OnTransportChannelDestroyed() {
    321   DoClose();
    322 }
    323 
    324 void DataChannel::SetSendSsrc(uint32_t send_ssrc) {
    325   ASSERT(data_channel_type_ == cricket::DCT_RTP);
    326   if (send_ssrc_set_) {
    327     return;
    328   }
    329   send_ssrc_ = send_ssrc;
    330   send_ssrc_set_ = true;
    331   UpdateState();
    332 }
    333 
    334 void DataChannel::OnMessage(rtc::Message* msg) {
    335   switch (msg->message_id) {
    336     case MSG_CHANNELREADY:
    337       OnChannelReady(true);
    338       break;
    339   }
    340 }
    341 
    342 void DataChannel::OnDataReceived(cricket::DataChannel* channel,
    343                                  const cricket::ReceiveDataParams& params,
    344                                  const rtc::Buffer& payload) {
    345   uint32_t expected_ssrc =
    346       (data_channel_type_ == cricket::DCT_RTP) ? receive_ssrc_ : config_.id;
    347   if (params.ssrc != expected_ssrc) {
    348     return;
    349   }
    350 
    351   if (params.type == cricket::DMT_CONTROL) {
    352     ASSERT(data_channel_type_ == cricket::DCT_SCTP);
    353     if (handshake_state_ != kHandshakeWaitingForAck) {
    354       // Ignore it if we are not expecting an ACK message.
    355       LOG(LS_WARNING) << "DataChannel received unexpected CONTROL message, "
    356                       << "sid = " << params.ssrc;
    357       return;
    358     }
    359     if (ParseDataChannelOpenAckMessage(payload)) {
    360       // We can send unordered as soon as we receive the ACK message.
    361       handshake_state_ = kHandshakeReady;
    362       LOG(LS_INFO) << "DataChannel received OPEN_ACK message, sid = "
    363                    << params.ssrc;
    364     } else {
    365       LOG(LS_WARNING) << "DataChannel failed to parse OPEN_ACK message, sid = "
    366                       << params.ssrc;
    367     }
    368     return;
    369   }
    370 
    371   ASSERT(params.type == cricket::DMT_BINARY ||
    372          params.type == cricket::DMT_TEXT);
    373 
    374   LOG(LS_VERBOSE) << "DataChannel received DATA message, sid = " << params.ssrc;
    375   // We can send unordered as soon as we receive any DATA message since the
    376   // remote side must have received the OPEN (and old clients do not send
    377   // OPEN_ACK).
    378   if (handshake_state_ == kHandshakeWaitingForAck) {
    379     handshake_state_ = kHandshakeReady;
    380   }
    381 
    382   bool binary = (params.type == cricket::DMT_BINARY);
    383   rtc::scoped_ptr<DataBuffer> buffer(new DataBuffer(payload, binary));
    384   if (state_ == kOpen && observer_) {
    385     observer_->OnMessage(*buffer.get());
    386   } else {
    387     if (queued_received_data_.byte_count() + payload.size() >
    388         kMaxQueuedReceivedDataBytes) {
    389       LOG(LS_ERROR) << "Queued received data exceeds the max buffer size.";
    390 
    391       queued_received_data_.Clear();
    392       if (data_channel_type_ != cricket::DCT_RTP) {
    393         Close();
    394       }
    395 
    396       return;
    397     }
    398     queued_received_data_.Push(buffer.release());
    399   }
    400 }
    401 
    402 void DataChannel::OnStreamClosedRemotely(uint32_t sid) {
    403   if (data_channel_type_ == cricket::DCT_SCTP && sid == config_.id) {
    404     Close();
    405   }
    406 }
    407 
    408 void DataChannel::OnChannelReady(bool writable) {
    409   writable_ = writable;
    410   if (!writable) {
    411     return;
    412   }
    413 
    414   SendQueuedControlMessages();
    415   SendQueuedDataMessages();
    416   UpdateState();
    417 }
    418 
    419 void DataChannel::DoClose() {
    420   if (state_ == kClosed)
    421     return;
    422 
    423   receive_ssrc_set_ = false;
    424   send_ssrc_set_ = false;
    425   SetState(kClosing);
    426   UpdateState();
    427 }
    428 
    429 void DataChannel::UpdateState() {
    430   // UpdateState determines what to do from a few state variables.  Include
    431   // all conditions required for each state transition here for
    432   // clarity. OnChannelReady(true) will send any queued data and then invoke
    433   // UpdateState().
    434   switch (state_) {
    435     case kConnecting: {
    436       if (send_ssrc_set_ == receive_ssrc_set_) {
    437         if (data_channel_type_ == cricket::DCT_RTP && !connected_to_provider_) {
    438           connected_to_provider_ = provider_->ConnectDataChannel(this);
    439         }
    440         if (connected_to_provider_) {
    441           if (handshake_state_ == kHandshakeShouldSendOpen) {
    442             rtc::Buffer payload;
    443             WriteDataChannelOpenMessage(label_, config_, &payload);
    444             SendControlMessage(payload);
    445           } else if (handshake_state_ == kHandshakeShouldSendAck) {
    446             rtc::Buffer payload;
    447             WriteDataChannelOpenAckMessage(&payload);
    448             SendControlMessage(payload);
    449           }
    450           if (writable_ &&
    451               (handshake_state_ == kHandshakeReady ||
    452                handshake_state_ == kHandshakeWaitingForAck)) {
    453             SetState(kOpen);
    454             // If we have received buffers before the channel got writable.
    455             // Deliver them now.
    456             DeliverQueuedReceivedData();
    457           }
    458         }
    459       }
    460       break;
    461     }
    462     case kOpen: {
    463       break;
    464     }
    465     case kClosing: {
    466       if (queued_send_data_.Empty() && queued_control_data_.Empty()) {
    467         if (connected_to_provider_) {
    468           DisconnectFromProvider();
    469         }
    470 
    471         if (!connected_to_provider_ && !send_ssrc_set_ && !receive_ssrc_set_) {
    472           SetState(kClosed);
    473         }
    474       }
    475       break;
    476     }
    477     case kClosed:
    478       break;
    479   }
    480 }
    481 
    482 void DataChannel::SetState(DataState state) {
    483   if (state_ == state) {
    484     return;
    485   }
    486 
    487   state_ = state;
    488   if (observer_) {
    489     observer_->OnStateChange();
    490   }
    491   if (state_ == kClosed) {
    492     SignalClosed(this);
    493   }
    494 }
    495 
    496 void DataChannel::DisconnectFromProvider() {
    497   if (!connected_to_provider_)
    498     return;
    499 
    500   provider_->DisconnectDataChannel(this);
    501   connected_to_provider_ = false;
    502 
    503   if (data_channel_type_ == cricket::DCT_SCTP && config_.id >= 0) {
    504     provider_->RemoveSctpDataStream(config_.id);
    505   }
    506 }
    507 
    508 void DataChannel::DeliverQueuedReceivedData() {
    509   if (!observer_) {
    510     return;
    511   }
    512 
    513   while (!queued_received_data_.Empty()) {
    514     rtc::scoped_ptr<DataBuffer> buffer(queued_received_data_.Front());
    515     observer_->OnMessage(*buffer);
    516     queued_received_data_.Pop();
    517   }
    518 }
    519 
    520 void DataChannel::SendQueuedDataMessages() {
    521   if (queued_send_data_.Empty()) {
    522     return;
    523   }
    524 
    525   ASSERT(state_ == kOpen || state_ == kClosing);
    526 
    527   uint64_t start_buffered_amount = buffered_amount();
    528   while (!queued_send_data_.Empty()) {
    529     DataBuffer* buffer = queued_send_data_.Front();
    530     if (!SendDataMessage(*buffer, false)) {
    531       // Leave the message in the queue if sending is aborted.
    532       break;
    533     }
    534     queued_send_data_.Pop();
    535     delete buffer;
    536   }
    537 
    538   if (observer_ && buffered_amount() < start_buffered_amount) {
    539     observer_->OnBufferedAmountChange(start_buffered_amount);
    540   }
    541 }
    542 
    543 bool DataChannel::SendDataMessage(const DataBuffer& buffer,
    544                                   bool queue_if_blocked) {
    545   cricket::SendDataParams send_params;
    546 
    547   if (data_channel_type_ == cricket::DCT_SCTP) {
    548     send_params.ordered = config_.ordered;
    549     // Send as ordered if it is still going through OPEN/ACK signaling.
    550     if (handshake_state_ != kHandshakeReady && !config_.ordered) {
    551       send_params.ordered = true;
    552       LOG(LS_VERBOSE) << "Sending data as ordered for unordered DataChannel "
    553                       << "because the OPEN_ACK message has not been received.";
    554     }
    555 
    556     send_params.max_rtx_count = config_.maxRetransmits;
    557     send_params.max_rtx_ms = config_.maxRetransmitTime;
    558     send_params.ssrc = config_.id;
    559   } else {
    560     send_params.ssrc = send_ssrc_;
    561   }
    562   send_params.type = buffer.binary ? cricket::DMT_BINARY : cricket::DMT_TEXT;
    563 
    564   cricket::SendDataResult send_result = cricket::SDR_SUCCESS;
    565   bool success = provider_->SendData(send_params, buffer.data, &send_result);
    566 
    567   if (success) {
    568     return true;
    569   }
    570 
    571   if (data_channel_type_ != cricket::DCT_SCTP) {
    572     return false;
    573   }
    574 
    575   if (send_result == cricket::SDR_BLOCK) {
    576     if (!queue_if_blocked || QueueSendDataMessage(buffer)) {
    577       return false;
    578     }
    579   }
    580   // Close the channel if the error is not SDR_BLOCK, or if queuing the
    581   // message failed.
    582   LOG(LS_ERROR) << "Closing the DataChannel due to a failure to send data, "
    583                 << "send_result = " << send_result;
    584   Close();
    585 
    586   return false;
    587 }
    588 
    589 bool DataChannel::QueueSendDataMessage(const DataBuffer& buffer) {
    590   size_t start_buffered_amount = buffered_amount();
    591   if (start_buffered_amount >= kMaxQueuedSendDataBytes) {
    592     LOG(LS_ERROR) << "Can't buffer any more data for the data channel.";
    593     return false;
    594   }
    595   queued_send_data_.Push(new DataBuffer(buffer));
    596 
    597   // The buffer can have length zero, in which case there is no change.
    598   if (observer_ && buffered_amount() > start_buffered_amount) {
    599     observer_->OnBufferedAmountChange(start_buffered_amount);
    600   }
    601   return true;
    602 }
    603 
    604 void DataChannel::SendQueuedControlMessages() {
    605   PacketQueue control_packets;
    606   control_packets.Swap(&queued_control_data_);
    607 
    608   while (!control_packets.Empty()) {
    609     rtc::scoped_ptr<DataBuffer> buf(control_packets.Front());
    610     SendControlMessage(buf->data);
    611     control_packets.Pop();
    612   }
    613 }
    614 
    615 void DataChannel::QueueControlMessage(const rtc::Buffer& buffer) {
    616   queued_control_data_.Push(new DataBuffer(buffer, true));
    617 }
    618 
    619 bool DataChannel::SendControlMessage(const rtc::Buffer& buffer) {
    620   bool is_open_message = handshake_state_ == kHandshakeShouldSendOpen;
    621 
    622   ASSERT(data_channel_type_ == cricket::DCT_SCTP &&
    623          writable_ &&
    624          config_.id >= 0 &&
    625          (!is_open_message || !config_.negotiated));
    626 
    627   cricket::SendDataParams send_params;
    628   send_params.ssrc = config_.id;
    629   // Send data as ordered before we receive any message from the remote peer to
    630   // make sure the remote peer will not receive any data before it receives the
    631   // OPEN message.
    632   send_params.ordered = config_.ordered || is_open_message;
    633   send_params.type = cricket::DMT_CONTROL;
    634 
    635   cricket::SendDataResult send_result = cricket::SDR_SUCCESS;
    636   bool retval = provider_->SendData(send_params, buffer, &send_result);
    637   if (retval) {
    638     LOG(LS_INFO) << "Sent CONTROL message on channel " << config_.id;
    639 
    640     if (handshake_state_ == kHandshakeShouldSendAck) {
    641       handshake_state_ = kHandshakeReady;
    642     } else if (handshake_state_ == kHandshakeShouldSendOpen) {
    643       handshake_state_ = kHandshakeWaitingForAck;
    644     }
    645   } else if (send_result == cricket::SDR_BLOCK) {
    646     QueueControlMessage(buffer);
    647   } else {
    648     LOG(LS_ERROR) << "Closing the DataChannel due to a failure to send"
    649                   << " the CONTROL message, send_result = " << send_result;
    650     Close();
    651   }
    652   return retval;
    653 }
    654 
    655 }  // namespace webrtc
    656