// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "quiche/quic/core/quic_received_packet_manager.h"

#include <algorithm>
#include <cstddef>
#include <ostream>
#include <vector>

#include "quiche/quic/core/congestion_control/rtt_stats.h"
#include "quiche/quic/core/crypto/crypto_protocol.h"
#include "quiche/quic/core/quic_connection_stats.h"
#include "quiche/quic/core/quic_constants.h"
#include "quiche/quic/core/quic_types.h"
#include "quiche/quic/platform/api/quic_expect_bug.h"
#include "quiche/quic/platform/api/quic_flags.h"
#include "quiche/quic/platform/api/quic_test.h"
#include "quiche/quic/test_tools/mock_clock.h"

namespace quic {
namespace test {

class QuicReceivedPacketManagerPeer {
 public:
  static void SetOneImmediateAck(QuicReceivedPacketManager* manager,
                                 bool one_immediate_ack) {
    manager->one_immediate_ack_ = one_immediate_ack;
  }

  static void SetAckDecimationDelay(QuicReceivedPacketManager* manager,
                                    float ack_decimation_delay) {
    manager->ack_decimation_delay_ = ack_decimation_delay;
  }
};

namespace {

const bool kInstigateAck = true;
const QuicTime::Delta kMinRttMs = QuicTime::Delta::FromMilliseconds(40);
const QuicTime::Delta kDelayedAckTime =
    QuicTime::Delta::FromMilliseconds(GetDefaultDelayedAckTimeMs());

class QuicReceivedPacketManagerTest : public QuicTest {
 protected:
  QuicReceivedPacketManagerTest() : received_manager_(&stats_) {
    clock_.AdvanceTime(QuicTime::Delta::FromSeconds(1));
    rtt_stats_.UpdateRtt(kMinRttMs, QuicTime::Delta::Zero(), QuicTime::Zero());
    received_manager_.set_save_timestamps(true, false);
  }

  void RecordPacketReceipt(uint64_t packet_number) {
    RecordPacketReceipt(packet_number, QuicTime::Zero());
  }

  void RecordPacketReceipt(uint64_t packet_number, QuicTime receipt_time) {
    RecordPacketReceipt(packet_number, receipt_time, ECN_NOT_ECT);
  }

  void RecordPacketReceipt(uint64_t packet_number, QuicTime receipt_time,
                           QuicEcnCodepoint ecn_codepoint) {
    QuicPacketHeader header;
    header.packet_number = QuicPacketNumber(packet_number);
    received_manager_.RecordPacketReceived(header, receipt_time, ecn_codepoint);
  }

  bool HasPendingAck() {
    return received_manager_.ack_timeout().IsInitialized();
  }

  void MaybeUpdateAckTimeout(bool should_last_packet_instigate_acks,
                             uint64_t last_received_packet_number) {
    received_manager_.MaybeUpdateAckTimeout(
        should_last_packet_instigate_acks,
        QuicPacketNumber(last_received_packet_number),
        /*last_packet_receipt_time=*/clock_.ApproximateNow(),
        /*now=*/clock_.ApproximateNow(), &rtt_stats_);
  }

  void CheckAckTimeout(QuicTime time) {
    QUICHE_DCHECK(HasPendingAck());
    QUICHE_DCHECK_EQ(received_manager_.ack_timeout(), time);
    if (time <= clock_.ApproximateNow()) {
      // ACK timeout expires, send an ACK.
      received_manager_.ResetAckStates();
      QUICHE_DCHECK(!HasPendingAck());
    }
  }

  MockClock clock_;
  RttStats rtt_stats_;
  QuicConnectionStats stats_;
  QuicReceivedPacketManager received_manager_;
};

TEST_F(QuicReceivedPacketManagerTest, DontWaitForPacketsBefore) {
  QuicPacketHeader header;
  header.packet_number = QuicPacketNumber(2u);
  received_manager_.RecordPacketReceived(header, QuicTime::Zero(), ECN_NOT_ECT);
  header.packet_number = QuicPacketNumber(7u);
  received_manager_.RecordPacketReceived(header, QuicTime::Zero(), ECN_NOT_ECT);
  EXPECT_TRUE(received_manager_.IsAwaitingPacket(QuicPacketNumber(3u)));
  EXPECT_TRUE(received_manager_.IsAwaitingPacket(QuicPacketNumber(6u)));
  received_manager_.DontWaitForPacketsBefore(QuicPacketNumber(4));
  EXPECT_FALSE(received_manager_.IsAwaitingPacket(QuicPacketNumber(3u)));
  EXPECT_TRUE(received_manager_.IsAwaitingPacket(QuicPacketNumber(6u)));
}

TEST_F(QuicReceivedPacketManagerTest, GetUpdatedAckFrame) {
  QuicPacketHeader header;
  header.packet_number = QuicPacketNumber(2u);
  QuicTime two_ms = QuicTime::Zero() + QuicTime::Delta::FromMilliseconds(2);
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  received_manager_.RecordPacketReceived(header, two_ms, ECN_NOT_ECT);
  EXPECT_TRUE(received_manager_.ack_frame_updated());

  QuicFrame ack = received_manager_.GetUpdatedAckFrame(QuicTime::Zero());
  received_manager_.ResetAckStates();
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  // When UpdateReceivedPacketInfo with a time earlier than the time of the
  // largest observed packet, make sure that the delta is 0, not negative.
  EXPECT_EQ(QuicTime::Delta::Zero(), ack.ack_frame->ack_delay_time);
  EXPECT_EQ(1u, ack.ack_frame->received_packet_times.size());

  QuicTime four_ms = QuicTime::Zero() + QuicTime::Delta::FromMilliseconds(4);
  ack = received_manager_.GetUpdatedAckFrame(four_ms);
  received_manager_.ResetAckStates();
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  // When UpdateReceivedPacketInfo after not having received a new packet,
  // the delta should still be accurate.
  EXPECT_EQ(QuicTime::Delta::FromMilliseconds(2),
            ack.ack_frame->ack_delay_time);
  // And received packet times won't have change.
  EXPECT_EQ(1u, ack.ack_frame->received_packet_times.size());

  header.packet_number = QuicPacketNumber(999u);
  received_manager_.RecordPacketReceived(header, two_ms, ECN_NOT_ECT);
  header.packet_number = QuicPacketNumber(4u);
  received_manager_.RecordPacketReceived(header, two_ms, ECN_NOT_ECT);
  header.packet_number = QuicPacketNumber(1000u);
  received_manager_.RecordPacketReceived(header, two_ms, ECN_NOT_ECT);
  EXPECT_TRUE(received_manager_.ack_frame_updated());
  ack = received_manager_.GetUpdatedAckFrame(two_ms);
  received_manager_.ResetAckStates();
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  // UpdateReceivedPacketInfo should discard any times which can't be
  // expressed on the wire.
  EXPECT_EQ(2u, ack.ack_frame->received_packet_times.size());
}

TEST_F(QuicReceivedPacketManagerTest, UpdateReceivedConnectionStats) {
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  RecordPacketReceipt(1);
  EXPECT_TRUE(received_manager_.ack_frame_updated());
  RecordPacketReceipt(6);
  RecordPacketReceipt(2,
                      QuicTime::Zero() + QuicTime::Delta::FromMilliseconds(1));

  EXPECT_EQ(4u, stats_.max_sequence_reordering);
  EXPECT_EQ(1000, stats_.max_time_reordering_us);
  EXPECT_EQ(1u, stats_.packets_reordered);
}

TEST_F(QuicReceivedPacketManagerTest, LimitAckRanges) {
  received_manager_.set_max_ack_ranges(10);
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  for (int i = 0; i < 100; ++i) {
    RecordPacketReceipt(1 + 2 * i);
    EXPECT_TRUE(received_manager_.ack_frame_updated());
    received_manager_.GetUpdatedAckFrame(QuicTime::Zero());
    EXPECT_GE(10u, received_manager_.ack_frame().packets.NumIntervals());
    EXPECT_EQ(QuicPacketNumber(1u + 2 * i),
              received_manager_.ack_frame().packets.Max());
    for (int j = 0; j < std::min(10, i + 1); ++j) {
      ASSERT_GE(i, j);
      EXPECT_TRUE(received_manager_.ack_frame().packets.Contains(
          QuicPacketNumber(1 + (i - j) * 2)));
      if (i > j) {
        EXPECT_FALSE(received_manager_.ack_frame().packets.Contains(
            QuicPacketNumber((i - j) * 2)));
      }
    }
  }
}

TEST_F(QuicReceivedPacketManagerTest, TrimAckRangesEarly) {
  const size_t kMaxAckRanges = 10;
  received_manager_.set_max_ack_ranges(kMaxAckRanges);
  for (size_t i = 0; i < kMaxAckRanges + 10; ++i) {
    RecordPacketReceipt(1 + 2 * i);
    if (i < kMaxAckRanges) {
      EXPECT_EQ(i + 1, received_manager_.ack_frame().packets.NumIntervals());
    } else {
      EXPECT_EQ(kMaxAckRanges,
                received_manager_.ack_frame().packets.NumIntervals());
    }
  }
}

TEST_F(QuicReceivedPacketManagerTest, IgnoreOutOfOrderTimestamps) {
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  RecordPacketReceipt(1, QuicTime::Zero());
  EXPECT_TRUE(received_manager_.ack_frame_updated());
  EXPECT_EQ(1u, received_manager_.ack_frame().received_packet_times.size());
  RecordPacketReceipt(2,
                      QuicTime::Zero() + QuicTime::Delta::FromMilliseconds(1));
  EXPECT_EQ(2u, received_manager_.ack_frame().received_packet_times.size());
  RecordPacketReceipt(3, QuicTime::Zero());
  EXPECT_EQ(2u, received_manager_.ack_frame().received_packet_times.size());
}

TEST_F(QuicReceivedPacketManagerTest, IgnoreOutOfOrderPackets) {
  received_manager_.set_save_timestamps(true, true);
  EXPECT_FALSE(received_manager_.ack_frame_updated());
  RecordPacketReceipt(1, QuicTime::Zero());
  EXPECT_TRUE(received_manager_.ack_frame_updated());
  EXPECT_EQ(1u, received_manager_.ack_frame().received_packet_times.size());
  RecordPacketReceipt(4,
                      QuicTime::Zero() + QuicTime::Delta::FromMilliseconds(1));
  EXPECT_EQ(2u, received_manager_.ack_frame().received_packet_times.size());

  RecordPacketReceipt(3,
                      QuicTime::Zero() + QuicTime::Delta::FromMilliseconds(3));
  EXPECT_EQ(2u, received_manager_.ack_frame().received_packet_times.size());
}

TEST_F(QuicReceivedPacketManagerTest, HasMissingPackets) {
  EXPECT_QUIC_BUG(received_manager_.PeerFirstSendingPacketNumber(),
                  "No packets have been received yet");
  RecordPacketReceipt(4, QuicTime::Zero());
  EXPECT_EQ(QuicPacketNumber(4),
            received_manager_.PeerFirstSendingPacketNumber());
  EXPECT_FALSE(received_manager_.HasMissingPackets());
  RecordPacketReceipt(3, QuicTime::Zero());
  EXPECT_FALSE(received_manager_.HasMissingPackets());
  EXPECT_EQ(QuicPacketNumber(3),
            received_manager_.PeerFirstSendingPacketNumber());
  RecordPacketReceipt(1, QuicTime::Zero());
  EXPECT_EQ(QuicPacketNumber(1),
            received_manager_.PeerFirstSendingPacketNumber());
  EXPECT_TRUE(received_manager_.HasMissingPackets());
  RecordPacketReceipt(2, QuicTime::Zero());
  EXPECT_EQ(QuicPacketNumber(1),
            received_manager_.PeerFirstSendingPacketNumber());
  EXPECT_FALSE(received_manager_.HasMissingPackets());
}

TEST_F(QuicReceivedPacketManagerTest, OutOfOrderReceiptCausesAckSent) {
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(3, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 3);
  // Delayed ack is scheduled.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);

  RecordPacketReceipt(5, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 5);
  // Immediate ack is sent.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(6, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 6);
  // Immediate ack is scheduled, because 4 is still missing.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(2, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 2);
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(1, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 1);
  // Should ack immediately, since this fills the last hole.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(7, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 7);
  // Immediate ack is scheduled, because 4 is still missing.
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest, OutOfOrderReceiptCausesAckSent1Ack) {
  QuicReceivedPacketManagerPeer::SetOneImmediateAck(&received_manager_, true);
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(3, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 3);
  // Delayed ack is scheduled.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);

  RecordPacketReceipt(5, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 5);
  // Immediate ack is sent.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(6, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 6);
  // Delayed ack is scheduled.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);

  RecordPacketReceipt(2, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 2);
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(1, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 1);
  // Should ack immediately, since this fills the last hole.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(7, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 7);
  // Delayed ack is scheduled, even though 4 is still missing.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
}

TEST_F(QuicReceivedPacketManagerTest, OutOfOrderAckReceiptCausesNoAck) {
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(2, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(!kInstigateAck, 2);
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(1, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(!kInstigateAck, 1);
  EXPECT_FALSE(HasPendingAck());
}

TEST_F(QuicReceivedPacketManagerTest, AckReceiptCausesAckSend) {
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(1, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(!kInstigateAck, 1);
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(2, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(!kInstigateAck, 2);
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(3, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 3);
  // Delayed ack is scheduled.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
  clock_.AdvanceTime(kDelayedAckTime);
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(4, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(!kInstigateAck, 4);
  EXPECT_FALSE(HasPendingAck());

  RecordPacketReceipt(5, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(!kInstigateAck, 5);
  EXPECT_FALSE(HasPendingAck());
}

TEST_F(QuicReceivedPacketManagerTest, AckSentEveryNthPacket) {
  EXPECT_FALSE(HasPendingAck());
  received_manager_.set_ack_frequency(3);

  // Receives packets 1 - 39.
  for (size_t i = 1; i <= 39; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % 3 == 0) {
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
    }
  }
}

TEST_F(QuicReceivedPacketManagerTest, AckDecimationReducesAcks) {
  EXPECT_FALSE(HasPendingAck());

  // Start ack decimation from 10th packet.
  received_manager_.set_min_received_before_ack_decimation(10);

  // Receives packets 1 - 29.
  for (size_t i = 1; i <= 29; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i <= 10) {
      // For packets 1-10, ack every 2 packets.
      if (i % 2 == 0) {
        CheckAckTimeout(clock_.ApproximateNow());
      } else {
        CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
      }
      continue;
    }
    // ack at 20.
    if (i == 20) {
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + kMinRttMs * 0.25);
    }
  }

  // We now receive the 30th packet, and so we send an ack.
  RecordPacketReceipt(30, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 30);
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest, SendDelayedAckDecimation) {
  EXPECT_FALSE(HasPendingAck());
  // The ack time should be based on min_rtt * 1/4, since it's less than the
  // default delayed ack time.
  QuicTime ack_time = clock_.ApproximateNow() + kMinRttMs * 0.25;

  // Process all the packets in order so there aren't missing packets.
  uint64_t kFirstDecimatedPacket = 101;
  for (uint64_t i = 1; i < kFirstDecimatedPacket; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % 2 == 0) {
      // Ack every 2 packets by default.
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
    }
  }

  RecordPacketReceipt(kFirstDecimatedPacket, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket);
  CheckAckTimeout(ack_time);

  // The 10th received packet causes an ack to be sent.
  for (uint64_t i = 1; i < 10; ++i) {
    RecordPacketReceipt(kFirstDecimatedPacket + i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket + i);
  }
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest, SendDelayedAckDecimationMin1ms) {
  EXPECT_FALSE(HasPendingAck());
  // Seed the min_rtt with a kAlarmGranularity signal.
  rtt_stats_.UpdateRtt(kAlarmGranularity, QuicTime::Delta::Zero(),
                       clock_.ApproximateNow());
  // The ack time should be based on kAlarmGranularity, since the RTT is 1ms.
  QuicTime ack_time = clock_.ApproximateNow() + kAlarmGranularity;

  // Process all the packets in order so there aren't missing packets.
  uint64_t kFirstDecimatedPacket = 101;
  for (uint64_t i = 1; i < kFirstDecimatedPacket; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % 2 == 0) {
      // Ack every 2 packets by default.
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
    }
  }

  RecordPacketReceipt(kFirstDecimatedPacket, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket);
  CheckAckTimeout(ack_time);

  // The 10th received packet causes an ack to be sent.
  for (uint64_t i = 1; i < 10; ++i) {
    RecordPacketReceipt(kFirstDecimatedPacket + i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket + i);
  }
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest,
       SendDelayedAckDecimationUnlimitedAggregation) {
  EXPECT_FALSE(HasPendingAck());
  QuicConfig config;
  QuicTagVector connection_options;
  // No limit on the number of packets received before sending an ack.
  connection_options.push_back(kAKDU);
  config.SetConnectionOptionsToSend(connection_options);
  received_manager_.SetFromConfig(config, Perspective::IS_CLIENT);

  // The ack time should be based on min_rtt/4, since it's less than the
  // default delayed ack time.
  QuicTime ack_time = clock_.ApproximateNow() + kMinRttMs * 0.25;

  // Process all the initial packets in order so there aren't missing packets.
  uint64_t kFirstDecimatedPacket = 101;
  for (uint64_t i = 1; i < kFirstDecimatedPacket; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % 2 == 0) {
      // Ack every 2 packets by default.
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
    }
  }

  RecordPacketReceipt(kFirstDecimatedPacket, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket);
  CheckAckTimeout(ack_time);

  // 18 packets will not cause an ack to be sent.  19 will because when
  // stop waiting frames are in use, we ack every 20 packets no matter what.
  for (int i = 1; i <= 18; ++i) {
    RecordPacketReceipt(kFirstDecimatedPacket + i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket + i);
  }
  CheckAckTimeout(ack_time);
}

TEST_F(QuicReceivedPacketManagerTest, SendDelayedAckDecimationEighthRtt) {
  EXPECT_FALSE(HasPendingAck());
  QuicReceivedPacketManagerPeer::SetAckDecimationDelay(&received_manager_,
                                                       0.125);

  // The ack time should be based on min_rtt/8, since it's less than the
  // default delayed ack time.
  QuicTime ack_time = clock_.ApproximateNow() + kMinRttMs * 0.125;

  // Process all the packets in order so there aren't missing packets.
  uint64_t kFirstDecimatedPacket = 101;
  for (uint64_t i = 1; i < kFirstDecimatedPacket; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % 2 == 0) {
      // Ack every 2 packets by default.
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
    }
  }

  RecordPacketReceipt(kFirstDecimatedPacket, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket);
  CheckAckTimeout(ack_time);

  // The 10th received packet causes an ack to be sent.
  for (uint64_t i = 1; i < 10; ++i) {
    RecordPacketReceipt(kFirstDecimatedPacket + i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, kFirstDecimatedPacket + i);
  }
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest,
       UpdateMaxAckDelayAndAckFrequencyFromAckFrequencyFrame) {
  EXPECT_FALSE(HasPendingAck());

  QuicAckFrequencyFrame frame;
  frame.max_ack_delay = QuicTime::Delta::FromMilliseconds(10);
  frame.packet_tolerance = 5;
  received_manager_.OnAckFrequencyFrame(frame);

  for (int i = 1; i <= 50; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % frame.packet_tolerance == 0) {
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      CheckAckTimeout(clock_.ApproximateNow() + frame.max_ack_delay);
    }
  }
}

TEST_F(QuicReceivedPacketManagerTest,
       DisableOutOfOrderAckByIgnoreOrderFromAckFrequencyFrame) {
  EXPECT_FALSE(HasPendingAck());

  QuicAckFrequencyFrame frame;
  frame.max_ack_delay = kDelayedAckTime;
  frame.packet_tolerance = 2;
  frame.ignore_order = true;
  received_manager_.OnAckFrequencyFrame(frame);

  RecordPacketReceipt(4, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 4);
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
  RecordPacketReceipt(5, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 5);
  // Immediate ack is sent as this is the 2nd packet of every two packets.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(3, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 3);
  // Don't ack as ignore_order is set by AckFrequencyFrame.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);

  RecordPacketReceipt(2, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 2);
  // Immediate ack is sent as this is the 2nd packet of every two packets.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(1, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 1);
  // Don't ack as ignore_order is set by AckFrequencyFrame.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
}

TEST_F(QuicReceivedPacketManagerTest,
       DisableMissingPaketsAckByIgnoreOrderFromAckFrequencyFrame) {
  EXPECT_FALSE(HasPendingAck());
  QuicConfig config;
  config.SetConnectionOptionsToSend({kAFFE});
  received_manager_.SetFromConfig(config, Perspective::IS_CLIENT);

  QuicAckFrequencyFrame frame;
  frame.max_ack_delay = kDelayedAckTime;
  frame.packet_tolerance = 2;
  frame.ignore_order = true;
  received_manager_.OnAckFrequencyFrame(frame);

  RecordPacketReceipt(1, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 1);
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
  RecordPacketReceipt(2, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 2);
  // Immediate ack is sent as this is the 2nd packet of every two packets.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(4, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 4);
  // Don't ack even if packet 3 is newly missing as ignore_order is set by
  // AckFrequencyFrame.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);

  RecordPacketReceipt(5, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 5);
  // Immediate ack is sent as this is the 2nd packet of every two packets.
  CheckAckTimeout(clock_.ApproximateNow());

  RecordPacketReceipt(7, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 7);
  // Don't ack even if packet 6 is newly missing as ignore_order is set by
  // AckFrequencyFrame.
  CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
}

TEST_F(QuicReceivedPacketManagerTest,
       AckDecimationDisabledWhenAckFrequencyFrameIsReceived) {
  EXPECT_FALSE(HasPendingAck());

  QuicAckFrequencyFrame frame;
  frame.max_ack_delay = kDelayedAckTime;
  frame.packet_tolerance = 3;
  frame.ignore_order = true;
  received_manager_.OnAckFrequencyFrame(frame);

  // Process all the packets in order so there aren't missing packets.
  uint64_t kFirstDecimatedPacket = 101;
  uint64_t FiftyPacketsAfterAckDecimation = kFirstDecimatedPacket + 50;
  for (uint64_t i = 1; i < FiftyPacketsAfterAckDecimation; ++i) {
    RecordPacketReceipt(i, clock_.ApproximateNow());
    MaybeUpdateAckTimeout(kInstigateAck, i);
    if (i % 3 == 0) {
      // Ack every 3 packets as decimation is disabled.
      CheckAckTimeout(clock_.ApproximateNow());
    } else {
      // Ack at default delay as decimation is disabled.
      CheckAckTimeout(clock_.ApproximateNow() + kDelayedAckTime);
    }
  }
}

TEST_F(QuicReceivedPacketManagerTest, UpdateAckTimeoutOnPacketReceiptTime) {
  EXPECT_FALSE(HasPendingAck());

  // Received packets 3 and 4.
  QuicTime packet_receipt_time3 = clock_.ApproximateNow();
  // Packet 3 gets processed after 10ms.
  clock_.AdvanceTime(QuicTime::Delta::FromMilliseconds(10));
  RecordPacketReceipt(3, packet_receipt_time3);
  received_manager_.MaybeUpdateAckTimeout(
      kInstigateAck, QuicPacketNumber(3),
      /*last_packet_receipt_time=*/packet_receipt_time3,
      clock_.ApproximateNow(), &rtt_stats_);
  // Make sure ACK timeout is based on receipt time.
  CheckAckTimeout(packet_receipt_time3 + kDelayedAckTime);

  RecordPacketReceipt(4, clock_.ApproximateNow());
  MaybeUpdateAckTimeout(kInstigateAck, 4);
  // Immediate ack is sent.
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest,
       UpdateAckTimeoutOnPacketReceiptTimeLongerQueuingTime) {
  EXPECT_FALSE(HasPendingAck());

  // Received packets 3 and 4.
  QuicTime packet_receipt_time3 = clock_.ApproximateNow();
  // Packet 3 gets processed after 100ms.
  clock_.AdvanceTime(QuicTime::Delta::FromMilliseconds(100));
  RecordPacketReceipt(3, packet_receipt_time3);
  received_manager_.MaybeUpdateAckTimeout(
      kInstigateAck, QuicPacketNumber(3),
      /*last_packet_receipt_time=*/packet_receipt_time3,
      clock_.ApproximateNow(), &rtt_stats_);
  // Given 100ms > ack delay, verify immediate ACK.
  CheckAckTimeout(clock_.ApproximateNow());
}

TEST_F(QuicReceivedPacketManagerTest, CountEcnPackets) {
  EXPECT_FALSE(HasPendingAck());
  RecordPacketReceipt(3, QuicTime::Zero(), ECN_NOT_ECT);
  RecordPacketReceipt(4, QuicTime::Zero(), ECN_ECT0);
  RecordPacketReceipt(5, QuicTime::Zero(), ECN_ECT1);
  RecordPacketReceipt(6, QuicTime::Zero(), ECN_CE);
  QuicFrame ack = received_manager_.GetUpdatedAckFrame(QuicTime::Zero());
  EXPECT_TRUE(ack.ack_frame->ecn_counters.has_value());
  EXPECT_EQ(ack.ack_frame->ecn_counters->ect0, 1);
  EXPECT_EQ(ack.ack_frame->ecn_counters->ect1, 1);
  EXPECT_EQ(ack.ack_frame->ecn_counters->ce, 1);
}

}  // namespace
}  // namespace test
}  // namespace quic