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/*
* Copyright 2018 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 CALL_SIMULATED_NETWORK_H_
#define CALL_SIMULATED_NETWORK_H_
#include <stdint.h>
#include <deque>
#include <queue>
#include <vector>
#include "absl/types/optional.h"
#include "api/test/simulated_network.h"
#include "api/units/data_size.h"
#include "api/units/timestamp.h"
#include "rtc_base/critical_section.h"
#include "rtc_base/race_checker.h"
#include "rtc_base/random.h"
#include "rtc_base/thread_annotations.h"
#include "rtc_base/thread_checker.h"
namespace webrtc {
// Implementation of the CoDel active queue management algorithm. Loosely based
// on CoDel pseudocode from ACMQueue. CoDel keeps queuing delays low by dropping
// packets when delay is high. For each packet ready for dequeue, call
// DropDequeuePacket with the packet parameters to update the CoDel state.
class CoDelSimulation {
public:
CoDelSimulation();
~CoDelSimulation();
// Returns true if packet should be dropped.
bool DropDequeuedPacket(Timestamp now,
Timestamp enqueing_time,
DataSize packet_size,
DataSize queue_size);
private:
enum State { kNormal, kPending, kDropping };
Timestamp enter_drop_state_at_ = Timestamp::PlusInfinity();
Timestamp last_drop_at_ = Timestamp::MinusInfinity();
int drop_count_ = 0;
int previous_drop_count_ = 0;
State state_ = State::kNormal;
};
// Class simulating a network link. This is a simple and naive solution just
// faking capacity and adding an extra transport delay in addition to the
// capacity introduced delay.
class SimulatedNetwork : public SimulatedNetworkInterface {
public:
using Config = BuiltInNetworkBehaviorConfig;
explicit SimulatedNetwork(Config config, uint64_t random_seed = 1);
~SimulatedNetwork() override;
// Sets a new configuration. This won't affect packets already in the pipe.
void SetConfig(const Config& config) override;
void UpdateConfig(std::function<void(BuiltInNetworkBehaviorConfig*)>
config_modifier) override;
void PauseTransmissionUntil(int64_t until_us) override;
// NetworkBehaviorInterface
bool EnqueuePacket(PacketInFlightInfo packet) override;
std::vector<PacketDeliveryInfo> DequeueDeliverablePackets(
int64_t receive_time_us) override;
absl::optional<int64_t> NextDeliveryTimeUs() const override;
private:
struct PacketInfo {
PacketInFlightInfo packet;
int64_t arrival_time_us;
};
// Contains current configuration state.
struct ConfigState {
// Static link configuration.
Config config;
// The probability to drop the packet if we are currently dropping a
// burst of packet
double prob_loss_bursting;
// The probability to drop a burst of packets.
double prob_start_bursting;
// Used for temporary delay spikes.
int64_t pause_transmission_until_us = 0;
};
// Moves packets from capacity- to delay link.
void UpdateCapacityQueue(ConfigState state, int64_t time_now_us)
RTC_RUN_ON(&process_checker_);
ConfigState GetConfigState() const;
rtc::CriticalSection config_lock_;
// |process_checker_| guards the data structures involved in delay and loss
// processes, such as the packet queues.
rtc::RaceChecker process_checker_;
CoDelSimulation codel_controller_ RTC_GUARDED_BY(process_checker_);
std::queue<PacketInfo> capacity_link_ RTC_GUARDED_BY(process_checker_);
Random random_;
std::deque<PacketInfo> delay_link_ RTC_GUARDED_BY(process_checker_);
ConfigState config_state_ RTC_GUARDED_BY(config_lock_);
// Are we currently dropping a burst of packets?
bool bursting_;
int64_t queue_size_bytes_ RTC_GUARDED_BY(process_checker_) = 0;
int64_t pending_drain_bits_ RTC_GUARDED_BY(process_checker_) = 0;
absl::optional<int64_t> last_capacity_link_visit_us_
RTC_GUARDED_BY(process_checker_);
absl::optional<int64_t> next_process_time_us_
RTC_GUARDED_BY(process_checker_);
};
} // namespace webrtc
#endif // CALL_SIMULATED_NETWORK_H_
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