cc_feedback_generator.h

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/*

 *  Copyright (c) 2025 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 MODULES_CONGESTION_CONTROLLER_SCREAM_TEST_CC_FEEDBACK_GENERATOR_H_

#define MODULES_CONGESTION_CONTROLLER_SCREAM_TEST_CC_FEEDBACK_GENERATOR_H_

#include <cstdint>

#include <deque>

#include <memory>

#include <optional>

#include "api/test/network_emulation/network_queue.h"

#include "api/test/network_emulation/leaky_bucket_network_queue.h"

#include "api/test/simulated_network.h"

#include "api/transport/network_types.h"

#include "api/units/data_rate.h"

#include "api/units/data_size.h"

#include "api/units/time_delta.h"

#include "api/units/timestamp.h"

#include "system_wrappers/include/clock.h"

#include "test/network/simulated_network.h"

namespace webrtc {

// Simulates sending packets with a given send rate over a simulated network and

// generates TransportPacketsFeedback that is supposed to match

// TransportPacketsFeedback from rtcp::CongestionControlFeedback (RFC8888).

class CcFeedbackGenerator {

 public:

  struct Config {

    SimulatedNetwork::Config network_config;

    TimeDelta time_between_feedback = TimeDelta::Millis(25);

    bool send_as_ect1 = true;

    std::unique_ptr<NetworkQueue> queue =

        std::make_unique<LeakyBucketNetworkQueue>(

            LeakyBucketNetworkQueue::Config{

                .max_ect1_sojourn_time = TimeDelta::Millis(8),

                .target_ect1_sojourn_time = TimeDelta::Millis(4)});

    DataSize packet_size = DataSize::Bytes(1000);

};

  explicit CcFeedbackGenerator(Config config);

  // Processes the simulation until the next feedback message is received.

  // The function will send packets at the given send rate until the next

  // feedback message is generated.

  TransportPacketsFeedback ProcessUntilNextFeedback(

      DataRate send_rate, SimulatedClock& clock,

      TimeDelta max_time = TimeDelta::Seconds(1));

  static int CountCeMarks(const TransportPacketsFeedback& feedback);

 private:

  void MaybeSendPackets(Timestamp time, DataRate send_rate);

  void ProcessNetwork(Timestamp time);

  std::optional<TransportPacketsFeedback> MaybeSendFeedback(Timestamp time);

  const DataSize packet_size_;

  const TimeDelta time_between_feedback_;

  const TimeDelta one_way_delay_;

  const bool send_as_ect1_;

  SimulatedNetwork network_;

  int64_t next_packet_id_ = 0;

  std::deque<PacketInFlightInfo> packets_in_flight_;

  // `packets_received_` are packed that have been received by the remote, but

  // feedback has not yet been received by the sender. Feedback is delivered one

  // way delay later than when the packets were received.

  std::deque<PacketDeliveryInfo> packets_received_;

  Timestamp last_feedback_time_ = Timestamp::MinusInfinity();

  TimeDelta smoothed_rtt_ = TimeDelta::PlusInfinity();

  Timestamp last_send_budget_update = Timestamp::MinusInfinity();

  DataSize send_budget_;

};

}  // namespace webrtc

#endif  // MODULES_CONGESTION_CONTROLLER_SCREAM_TEST_CC_FEEDBACK_GENERATOR_H_