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* Copyright 2020 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 <stdint.h>
#include <memory>
#include <set>
#include <string>
#include "absl/types/optional.h"
#include "api/data_channel_interface.h"
#include "api/priority.h"
#include "api/rtc_error.h"
#include "api/scoped_refptr.h"
#include "api/transport/data_channel_transport_interface.h"
#include "media/base/media_channel.h"
#include "pc/data_channel_utils.h"
#include "rtc_base/copy_on_write_buffer.h"
#include "rtc_base/ssl_stream_adapter.h" // For SSLRole
#include "rtc_base/third_party/sigslot/sigslot.h"
#include "rtc_base/thread.h"
#include "rtc_base/thread_annotations.h"
namespace webrtc {
class SctpDataChannel;
// TODO(deadbeef): Get rid of this and have SctpDataChannel depend on
// SctpTransportInternal (pure virtual SctpTransport interface) instead.
class SctpDataChannelProviderInterface {
// Sends the data to the transport.
virtual bool SendData(int sid,
const SendDataParams& params,
const rtc::CopyOnWriteBuffer& payload,
cricket::SendDataResult* result) = 0;
// Connects to the transport signals.
virtual bool ConnectDataChannel(SctpDataChannel* data_channel) = 0;
// Disconnects from the transport signals.
virtual void DisconnectDataChannel(SctpDataChannel* 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 ~SctpDataChannelProviderInterface() {}
// TODO(tommi): Change to not inherit from DataChannelInit but to have it as
// a const member. Block access to the 'id' member since it cannot be const.
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_;
// SctpDataChannel is an implementation of the DataChannelInterface based on
// SctpTransport. It provides an implementation of unreliable or
// reliabledata channels.
// DataChannel states:
// kConnecting: The channel has been created the transport might not yet be
// ready.
// kOpen: The open handshake has been performed (if relevant) and the data
// channel is able to send messages.
// kClosing: DataChannelInterface::Close has been called, or the remote side
// initiated the closing procedure, but the closing procedure has not
// yet finished.
// kClosed: The closing handshake is finished (possibly initiated from this,
// side, possibly from the peer).
// 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 SctpDataChannel : public DataChannelInterface,
public sigslot::has_slots<> {
static rtc::scoped_refptr<SctpDataChannel> Create(
SctpDataChannelProviderInterface* provider,
const std::string& label,
const InternalDataChannelInit& config,
rtc::Thread* signaling_thread,
rtc::Thread* network_thread);
// Instantiates an API proxy for a SctpDataChannel instance that will be
// handed out to external callers.
static rtc::scoped_refptr<DataChannelInterface> CreateProxy(
rtc::scoped_refptr<SctpDataChannel> channel);
void RegisterObserver(DataChannelObserver* observer) override;
void UnregisterObserver() override;
std::string label() const override { return label_; }
bool reliable() const override;
bool ordered() const override { return config_.ordered; }
// Backwards compatible accessors
uint16_t maxRetransmitTime() const override {
return config_.maxRetransmitTime ? *config_.maxRetransmitTime
: static_cast<uint16_t>(-1);
uint16_t maxRetransmits() const override {
return config_.maxRetransmits ? *config_.maxRetransmits
: static_cast<uint16_t>(-1);
absl::optional<int> maxPacketLifeTime() const override {
return config_.maxRetransmitTime;
absl::optional<int> maxRetransmitsOpt() const override {
return config_.maxRetransmits;
std::string protocol() const override { return config_.protocol; }
bool negotiated() const override { return config_.negotiated; }
int id() const override { return; }
Priority priority() const override {
return config_.priority ? *config_.priority : Priority::kLow;
virtual int internal_id() const { return internal_id_; }
uint64_t buffered_amount() const override;
void Close() override;
DataState state() const override;
RTCError error() const override;
uint32_t messages_sent() const override;
uint64_t bytes_sent() const override;
uint32_t messages_received() const override;
uint64_t bytes_received() const override;
bool Send(const DataBuffer& buffer) override;
// Close immediately, ignoring any queued data or closing procedure.
// This is called when the underlying SctpTransport is being destroyed.
// It is also called by the PeerConnection if SCTP ID assignment fails.
void CloseAbruptlyWithError(RTCError error);
// Specializations of CloseAbruptlyWithError
void CloseAbruptlyWithDataChannelFailure(const std::string& message);
// Slots for provider to connect signals to.
// TODO(deadbeef): Make these private once we're hooking up signals ourselves,
// instead of relying on SctpDataChannelProviderInterface.
// Called when the SctpTransport's ready to use. That can happen when we've
// finished negotiation, or if the channel was created after negotiation has
// already finished.
void OnTransportReady(bool writable);
void OnDataReceived(const cricket::ReceiveDataParams& params,
const rtc::CopyOnWriteBuffer& payload);
// 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 unusable.
// This method makes sure the DataChannel is disconnected and changes state
// to kClosed.
void OnTransportChannelClosed(RTCError error);
DataChannelStats GetStats() const;
// Emitted when state transitions to kOpen.
sigslot::signal1<DataChannelInterface*> SignalOpened;
// Emitted when state transitions to kClosed.
// This signal can be used to tell when the channel's sid is free.
sigslot::signal1<DataChannelInterface*> SignalClosed;
// Reset the allocator for internal ID values for testing, so that
// the internal IDs generated are predictable. Test only.
static void ResetInternalIdAllocatorForTesting(int new_value);
SctpDataChannel(const InternalDataChannelInit& config,
SctpDataChannelProviderInterface* client,
const std::string& label,
rtc::Thread* signaling_thread,
rtc::Thread* network_thread);
~SctpDataChannel() override;
// The OPEN(_ACK) signaling state.
enum HandshakeState {
bool Init();
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);
rtc::Thread* const signaling_thread_;
rtc::Thread* const network_thread_;
const int internal_id_;
const std::string label_;
const InternalDataChannelInit config_;
DataChannelObserver* observer_ RTC_GUARDED_BY(signaling_thread_) = nullptr;
DataState state_ RTC_GUARDED_BY(signaling_thread_) = kConnecting;
RTCError error_ RTC_GUARDED_BY(signaling_thread_);
uint32_t messages_sent_ RTC_GUARDED_BY(signaling_thread_) = 0;
uint64_t bytes_sent_ RTC_GUARDED_BY(signaling_thread_) = 0;
uint32_t messages_received_ RTC_GUARDED_BY(signaling_thread_) = 0;
uint64_t bytes_received_ RTC_GUARDED_BY(signaling_thread_) = 0;
// 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_ RTC_GUARDED_BY(signaling_thread_) = 0;
SctpDataChannelProviderInterface* const provider_
HandshakeState handshake_state_ RTC_GUARDED_BY(signaling_thread_) =
bool connected_to_provider_ RTC_GUARDED_BY(signaling_thread_) = false;
bool writable_ RTC_GUARDED_BY(signaling_thread_) = false;
// Did we already start the graceful SCTP closing procedure?
bool started_closing_procedure_ RTC_GUARDED_BY(signaling_thread_) = false;
// Control messages that always have to get sent out before any queued
// data.
PacketQueue queued_control_data_ RTC_GUARDED_BY(signaling_thread_);
PacketQueue queued_received_data_ RTC_GUARDED_BY(signaling_thread_);
PacketQueue queued_send_data_ RTC_GUARDED_BY(signaling_thread_);
} // namespace webrtc