sctp_data_channel.h

/*

 *  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.

*/

#ifndef PC_SCTP_DATA_CHANNEL_H_

#define PC_SCTP_DATA_CHANNEL_H_

#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/sequence_checker.h"

#include "api/task_queue/pending_task_safety_flag.h"

#include "api/transport/data_channel_transport_interface.h"

#include "pc/data_channel_utils.h"

#include "pc/sctp_utils.h"

#include "rtc_base/containers/flat_set.h"

#include "rtc_base/copy_on_write_buffer.h"

#include "rtc_base/ssl_stream_adapter.h"  // For SSLRole

#include "rtc_base/system/no_unique_address.h"

#include "rtc_base/thread.h"

#include "rtc_base/thread_annotations.h"

#include "rtc_base/weak_ptr.h"

namespace webrtc {

class SctpDataChannel;

// Interface that acts as a bridge from the data channel to the transport.

// All methods in this interface need to be invoked on the network thread.

class SctpDataChannelControllerInterface {

 public:

  // Sends the data to the transport.

  virtual RTCError SendData(StreamId sid,

                            const SendDataParams& params,

                            const rtc::CopyOnWriteBuffer& payload) = 0;

  // Adds the data channel SID to the transport for SCTP.

  virtual void AddSctpDataStream(StreamId sid, PriorityValue priority) = 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(StreamId sid) = 0;

  // Notifies the controller of state changes.

  virtual void OnChannelStateChanged(SctpDataChannel* data_channel,

                                     DataChannelInterface::DataState state) = 0;

  virtual size_t buffered_amount(StreamId sid) const = 0;

  virtual size_t buffered_amount_low_threshold(StreamId sid) const = 0;

  virtual void SetBufferedAmountLowThreshold(StreamId sid, size_t bytes) = 0;

 protected:

  virtual ~SctpDataChannelControllerInterface() {}

};

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);

  // Does basic validation to determine if a data channel instance can be

  // constructed using the configuration.

  bool IsValid() const;

  OpenHandshakeRole open_handshake_role;

  // Optional fallback or backup flag from PC that's used for non-prenegotiated

  // stream ids in situations where we cannot determine the SSL role from the

  // transport for purposes of generating a stream ID.

  // See: https://www.rfc-editor.org/rfc/rfc8832.html#name-protocol-overview

  absl::optional<rtc::SSLRole> fallback_ssl_role;

};

// Helper class to allocate unique IDs for SCTP DataChannels.

class SctpSidAllocator {

 public:

  SctpSidAllocator() = default;

  // 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.

  // If a `StreamId` cannot be allocated, `absl::nullopt` is returned.

  absl::optional<StreamId> AllocateSid(rtc::SSLRole role);

  // Attempts to reserve a specific sid. Returns false if it's unavailable.

  bool ReserveSid(StreamId sid);

  // Indicates that `sid` isn't in use any more, and is thus available again.

  void ReleaseSid(StreamId sid);

 private:

  flat_set<StreamId> used_sids_ RTC_GUARDED_BY(&sequence_checker_);

  RTC_NO_UNIQUE_ADDRESS SequenceChecker sequence_checker_{

      SequenceChecker::kDetached};

};

// SctpDataChannel is an implementation of the DataChannelInterface based on

// SctpTransport. It provides an implementation of unreliable or

// reliable data 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:

  static rtc::scoped_refptr<SctpDataChannel> Create(

      rtc::WeakPtr<SctpDataChannelControllerInterface> controller,

      const std::string& label,

      bool connected_to_transport,

      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.

  // The `signaling_safety` flag is used for the ObserverAdapter callback proxy

  // which delivers callbacks on the signaling thread but must not deliver such

  // callbacks after the peerconnection has been closed. The data controller

  // will update the flag when closed, which will cancel any pending event

  // notifications.

  static rtc::scoped_refptr<DataChannelInterface> CreateProxy(

      rtc::scoped_refptr<SctpDataChannel> channel,

      rtc::scoped_refptr<PendingTaskSafetyFlag> signaling_safety);

  void RegisterObserver(DataChannelObserver* observer) override;

  void UnregisterObserver() override;

  std::string label() const override;

  bool reliable() const override;

  bool ordered() const override;

  // Backwards compatible accessors

  uint16_t maxRetransmitTime() const override;

  uint16_t maxRetransmits() const override;

  absl::optional<int> maxPacketLifeTime() const override;

  absl::optional<int> maxRetransmitsOpt() const override;

  std::string protocol() const override;

  bool negotiated() const override;

  int id() const override;

  PriorityValue priority() const override;

  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;

  void SendAsync(DataBuffer buffer,

                 absl::AnyInvocable<void(RTCError) &&> on_complete) 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);

  // 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();

  void OnDataReceived(DataMessageType type,

                      const rtc::CopyOnWriteBuffer& payload);

  // Sets the SCTP sid and adds to transport layer if not set yet. Should only

  // be called once.

  void SetSctpSid_n(StreamId sid);

  // The remote side started the closing procedure by resetting its outgoing

  // stream (our incoming stream). Sets state to kClosing.

  void OnClosingProcedureStartedRemotely();

  // 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();

  // Called when the transport channel is created.

  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);

  // Called when the amount of data buffered to be sent falls to or below the

  // threshold set when calling `SetBufferedAmountLowThreshold`.

  void OnBufferedAmountLow();

  DataChannelStats GetStats() const;

  // Returns a unique identifier that's guaranteed to always be available,

  // doesn't change throughout SctpDataChannel's lifetime and is used for

  // stats purposes (see also `GetStats()`).

  int internal_id() const { return internal_id_; }

  absl::optional<StreamId> sid_n() const {

    RTC_DCHECK_RUN_ON(network_thread_);

    return id_n_;

  // 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);

 protected:

  SctpDataChannel(const InternalDataChannelInit& config,

                  rtc::WeakPtr<SctpDataChannelControllerInterface> controller,

                  const std::string& label,

                  bool connected_to_transport,

                  rtc::Thread* signaling_thread,

                  rtc::Thread* network_thread);

  ~SctpDataChannel() override;

 private:

  class ObserverAdapter;

  // The OPEN(_ACK) signaling state.

  enum HandshakeState {

    kHandshakeInit,

    kHandshakeShouldSendOpen,

    kHandshakeShouldSendAck,

    kHandshakeWaitingForAck,

    kHandshakeReady

};

  RTCError SendImpl(DataBuffer buffer) RTC_RUN_ON(network_thread_);

  void UpdateState() RTC_RUN_ON(network_thread_);

  void SetState(DataState state) RTC_RUN_ON(network_thread_);

  void DeliverQueuedReceivedData() RTC_RUN_ON(network_thread_);

  RTCError SendDataMessage(const DataBuffer& buffer, bool queue_if_blocked)

      RTC_RUN_ON(network_thread_);

  bool SendControlMessage(const rtc::CopyOnWriteBuffer& buffer)

      RTC_RUN_ON(network_thread_);

  bool connected_to_transport() const RTC_RUN_ON(network_thread_) {

    return network_safety_->alive();

  void MaybeSendOnBufferedAmountChanged() RTC_RUN_ON(network_thread_);

  rtc::Thread* const signaling_thread_;

  rtc::Thread* const network_thread_;

  absl::optional<StreamId> id_n_ RTC_GUARDED_BY(network_thread_) =

      absl::nullopt;

  const int internal_id_;

  const std::string label_;

  const std::string protocol_;

  const absl::optional<int> max_retransmit_time_;

  const absl::optional<int> max_retransmits_;

  const absl::optional<PriorityValue> priority_;

  const bool negotiated_;

  const bool ordered_;

  // See the body of `MaybeSendOnBufferedAmountChanged`.

  size_t expected_buffer_amount_ = 0;

  DataChannelObserver* observer_ RTC_GUARDED_BY(network_thread_) = nullptr;

  std::unique_ptr<ObserverAdapter> observer_adapter_;

  DataState state_ RTC_GUARDED_BY(network_thread_) = kConnecting;

  RTCError error_ RTC_GUARDED_BY(network_thread_);

  uint32_t messages_sent_ RTC_GUARDED_BY(network_thread_) = 0;

  uint64_t bytes_sent_ RTC_GUARDED_BY(network_thread_) = 0;

  uint32_t messages_received_ RTC_GUARDED_BY(network_thread_) = 0;

  uint64_t bytes_received_ RTC_GUARDED_BY(network_thread_) = 0;

  rtc::WeakPtr<SctpDataChannelControllerInterface> controller_

      RTC_GUARDED_BY(network_thread_);

  HandshakeState handshake_state_ RTC_GUARDED_BY(network_thread_) =

      kHandshakeInit;

  // Did we already start the graceful SCTP closing procedure?

  bool started_closing_procedure_ RTC_GUARDED_BY(network_thread_) = false;

  PacketQueue queued_received_data_ RTC_GUARDED_BY(network_thread_);

  rtc::scoped_refptr<PendingTaskSafetyFlag> network_safety_ =

      PendingTaskSafetyFlag::CreateDetachedInactive();

};

}  // namespace webrtc

#endif  // PC_SCTP_DATA_CHANNEL_H_

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