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* Copyright 2012 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 <deque>
#include <memory>
#include <set>
#include <string>
#include "api/data_channel_interface.h"
#include "api/proxy.h"
#include "api/scoped_refptr.h"
#include "media/base/media_channel.h"
#include "pc/channel.h"
#include "rtc_base/async_invoker.h"
#include "rtc_base/third_party/sigslot/sigslot.h"
namespace webrtc {
class DataChannel;
// TODO(deadbeef): Once RTP data channels go away, get rid of this and have
// DataChannel depend on SctpTransportInternal (pure virtual SctpTransport
// interface) instead.
class DataChannelProviderInterface {
// Sends the data to the transport.
virtual bool SendData(const cricket::SendDataParams& params,
const rtc::CopyOnWriteBuffer& payload,
cricket::SendDataResult* result) = 0;
// Connects to the transport signals.
virtual bool ConnectDataChannel(DataChannel* data_channel) = 0;
// Disconnects from the transport signals.
virtual void DisconnectDataChannel(DataChannel* data_channel) = 0;
// Adds the data channel SID to the transport for SCTP.
virtual void AddSctpDataStream(int sid) = 0;
// Begins the closing procedure by sending an outgoing stream reset. Still
// need to wait for callbacks to tell when this completes.
virtual void RemoveSctpDataStream(int sid) = 0;
// Returns true if the transport channel is ready to send data.
virtual bool ReadyToSendData() const = 0;
virtual ~DataChannelProviderInterface() {}
struct InternalDataChannelInit : public DataChannelInit {
enum OpenHandshakeRole { kOpener, kAcker, kNone };
// The default role is kOpener because the default |negotiated| is false.
InternalDataChannelInit() : open_handshake_role(kOpener) {}
explicit InternalDataChannelInit(const DataChannelInit& base);
OpenHandshakeRole open_handshake_role;
// Helper class to allocate unique IDs for SCTP DataChannels
class SctpSidAllocator {
// Gets the first unused odd/even id based on the DTLS role. If |role| is
// SSL_CLIENT, the allocated id starts from 0 and takes even numbers;
// otherwise, the id starts from 1 and takes odd numbers.
// Returns false if no ID can be allocated.
bool AllocateSid(rtc::SSLRole role, int* sid);
// Attempts to reserve a specific sid. Returns false if it's unavailable.
bool ReserveSid(int sid);
// Indicates that |sid| isn't in use any more, and is thus available again.
void ReleaseSid(int sid);
// Checks if |sid| is available to be assigned to a new SCTP data channel.
bool IsSidAvailable(int sid) const;
std::set<int> used_sids_;
// DataChannel is a an implementation of the DataChannelInterface based on
// libjingle's data engine. It provides an implementation of unreliable or
// reliabledata channels. Currently this class is specifically designed to use
// both RtpDataChannel and SctpTransport.
// DataChannel states:
// kConnecting: The channel has been created the transport might not yet be
// ready.
// kOpen: The channel have a local SSRC set by a call to UpdateSendSsrc
// and a remote SSRC set by call to UpdateReceiveSsrc and the transport
// has been writable once.
// kClosing: DataChannelInterface::Close has been called or UpdateReceiveSsrc
// has been called with SSRC==0
// kClosed: Both UpdateReceiveSsrc and UpdateSendSsrc has been called with
// SSRC==0.
// How the closing procedure works for SCTP:
// 1. Alice calls Close(), state changes to kClosing.
// 2. Alice finishes sending any queued data.
// 3. Alice calls RemoveSctpDataStream, sends outgoing stream reset.
// 4. Bob receives incoming stream reset; OnClosingProcedureStartedRemotely
// called.
// 5. Bob sends outgoing stream reset. 6. Alice receives incoming reset,
// Bob receives acknowledgement. Both receive OnClosingProcedureComplete
// callback and transition to kClosed.
class DataChannel : public DataChannelInterface, public sigslot::has_slots<> {
static rtc::scoped_refptr<DataChannel> Create(
DataChannelProviderInterface* provider,
cricket::DataChannelType dct,
const std::string& label,
const InternalDataChannelInit& config);
static bool IsSctpLike(cricket::DataChannelType type);
virtual void RegisterObserver(DataChannelObserver* observer);
virtual void UnregisterObserver();
virtual std::string label() const { return label_; }
virtual bool reliable() const;
virtual bool ordered() const { return config_.ordered; }
// Backwards compatible accessors
virtual uint16_t maxRetransmitTime() const {
return config_.maxRetransmitTime ? *config_.maxRetransmitTime
: static_cast<uint16_t>(-1);
virtual uint16_t maxRetransmits() const {
return config_.maxRetransmits ? *config_.maxRetransmits
: static_cast<uint16_t>(-1);
virtual absl::optional<int> maxPacketLifeTime() const {
return config_.maxRetransmitTime;
virtual absl::optional<int> maxRetransmitsOpt() const {
return config_.maxRetransmits;
virtual std::string protocol() const { return config_.protocol; }
virtual bool negotiated() const { return config_.negotiated; }
virtual int id() const { return; }
virtual uint64_t buffered_amount() const;
virtual void Close();
virtual DataState state() const { return state_; }
virtual uint32_t messages_sent() const { return messages_sent_; }
virtual uint64_t bytes_sent() const { return bytes_sent_; }
virtual uint32_t messages_received() const { return messages_received_; }
virtual uint64_t bytes_received() const { return bytes_received_; }
virtual bool Send(const DataBuffer& buffer);
// Close immediately, ignoring any queued data or closing procedure.
// This is called for RTP data channels when SDP indicates a channel should
// be removed, or SCTP data channels when the underlying SctpTransport is
// being destroyed.
// It is also called by the PeerConnection if SCTP ID assignment fails.
void CloseAbruptly();
// Called when the channel's ready to use. That can happen when the
// underlying DataMediaChannel becomes ready, or when this channel is a new
// stream on an existing DataMediaChannel, and we've finished negotiation.
void OnChannelReady(bool writable);
// Slots for provider to connect signals to.
void OnDataReceived(const cricket::ReceiveDataParams& params,
const rtc::CopyOnWriteBuffer& payload);
* The following methods are for SCTP only. *
// Sets the SCTP sid and adds to transport layer if not set yet. Should only
// be called once.
void SetSctpSid(int sid);
// The remote side started the closing procedure by resetting its outgoing
// stream (our incoming stream). Sets state to kClosing.
void OnClosingProcedureStartedRemotely(int sid);
// The closing procedure is complete; both incoming and outgoing stream
// resets are done and the channel can transition to kClosed. Called
// asynchronously after RemoveSctpDataStream.
void OnClosingProcedureComplete(int sid);
// Called when the transport channel is created.
// Only needs to be called for SCTP data channels.
void OnTransportChannelCreated();
// Called when the transport channel is destroyed.
// This method makes sure the DataChannel is disconnected and changes state
// to kClosed.
void OnTransportChannelDestroyed();
* The following methods are for RTP only. *
// The remote peer requested that this channel should be closed.
void RemotePeerRequestClose();
// Set the SSRC this channel should use to send data on the
// underlying data engine. |send_ssrc| == 0 means that the channel is no
// longer part of the session negotiation.
void SetSendSsrc(uint32_t send_ssrc);
// Set the SSRC this channel should use to receive data from the
// underlying data engine.
void SetReceiveSsrc(uint32_t receive_ssrc);
cricket::DataChannelType data_channel_type() const {
return data_channel_type_;
// Emitted when state transitions to kOpen.
sigslot::signal1<DataChannel*> SignalOpened;
// Emitted when state transitions to kClosed.
// In the case of SCTP channels, this signal can be used to tell when the
// channel's sid is free.
sigslot::signal1<DataChannel*> SignalClosed;
DataChannel(DataChannelProviderInterface* client,
cricket::DataChannelType dct,
const std::string& label);
virtual ~DataChannel();
// A packet queue which tracks the total queued bytes. Queued packets are
// owned by this class.
class PacketQueue final {
size_t byte_count() const { return byte_count_; }
bool Empty() const;
std::unique_ptr<DataBuffer> PopFront();
void PushFront(std::unique_ptr<DataBuffer> packet);
void PushBack(std::unique_ptr<DataBuffer> packet);
void Clear();
void Swap(PacketQueue* other);
std::deque<std::unique_ptr<DataBuffer>> packets_;
size_t byte_count_ = 0;
// The OPEN(_ACK) signaling state.
enum HandshakeState {
bool Init(const InternalDataChannelInit& config);
void UpdateState();
void SetState(DataState state);
void DisconnectFromProvider();
void DeliverQueuedReceivedData();
void SendQueuedDataMessages();
bool SendDataMessage(const DataBuffer& buffer, bool queue_if_blocked);
bool QueueSendDataMessage(const DataBuffer& buffer);
void SendQueuedControlMessages();
void QueueControlMessage(const rtc::CopyOnWriteBuffer& buffer);
bool SendControlMessage(const rtc::CopyOnWriteBuffer& buffer);
std::string label_;
InternalDataChannelInit config_;
DataChannelObserver* observer_;
DataState state_;
uint32_t messages_sent_;
uint64_t bytes_sent_;
uint32_t messages_received_;
uint64_t bytes_received_;
// Number of bytes of data that have been queued using Send(). Increased
// before each transport send and decreased after each successful send.
uint64_t buffered_amount_;
cricket::DataChannelType data_channel_type_;
DataChannelProviderInterface* provider_;
HandshakeState handshake_state_;
bool connected_to_provider_;
bool send_ssrc_set_;
bool receive_ssrc_set_;
bool writable_;
// Did we already start the graceful SCTP closing procedure?
bool started_closing_procedure_ = false;
uint32_t send_ssrc_;
uint32_t receive_ssrc_;
// Control messages that always have to get sent out before any queued
// data.
PacketQueue queued_control_data_;
PacketQueue queued_received_data_;
PacketQueue queued_send_data_;
rtc::AsyncInvoker invoker_;
// Define proxy for DataChannelInterface.
PROXY_METHOD1(void, RegisterObserver, DataChannelObserver*)
PROXY_METHOD0(void, UnregisterObserver)
PROXY_CONSTMETHOD0(std::string, label)
PROXY_CONSTMETHOD0(bool, reliable)
PROXY_CONSTMETHOD0(bool, ordered)
PROXY_CONSTMETHOD0(uint16_t, maxRetransmitTime)
PROXY_CONSTMETHOD0(uint16_t, maxRetransmits)
PROXY_CONSTMETHOD0(absl::optional<int>, maxRetransmitsOpt)
PROXY_CONSTMETHOD0(absl::optional<int>, maxPacketLifeTime)
PROXY_CONSTMETHOD0(std::string, protocol)
PROXY_CONSTMETHOD0(bool, negotiated)
PROXY_CONSTMETHOD0(DataState, state)
PROXY_CONSTMETHOD0(uint32_t, messages_sent)
PROXY_CONSTMETHOD0(uint64_t, bytes_sent)
PROXY_CONSTMETHOD0(uint32_t, messages_received)
PROXY_CONSTMETHOD0(uint64_t, bytes_received)
PROXY_CONSTMETHOD0(uint64_t, buffered_amount)
PROXY_METHOD0(void, Close)
PROXY_METHOD1(bool, Send, const DataBuffer&)
} // namespace webrtc
#endif // PC_DATA_CHANNEL_H_