Repair the CWND reduction caused by spurious RTO's in QUIC's congestion

net/quic/quic_connection_test.cc

 // Copyright (c) 2012 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 "net/quic/quic_connection.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/stl_util.h"
 #include "net/base/net_errors.h"
@@ skipping 1971 matching lines @@
   writer_->set_is_write_blocked_data_buffered(true);
   // Simulate the retransmission alarm firing.
   EXPECT_CALL(*send_algorithm_, OnRetransmissionTimeout(_));
   clock_.AdvanceTime(DefaultRetransmissionTime());
   connection_.GetRetransmissionAlarm()->Fire();
 
   // Ack the sent packet before the callback returns, which happens in
   // rare circumstances with write blocked sockets.
   QuicAckFrame ack = InitAckFrame(1, 0);
   EXPECT_CALL(*send_algorithm_, OnCongestionEvent(true, _, _, _));
+  EXPECT_CALL(*send_algorithm_, RevertRetransmissionTimeout());
   ProcessAckPacket(&ack);
 
   connection_.OnPacketSent(WriteResult(WRITE_STATUS_OK, 0));
   // There is now a pending packet, but with no retransmittable frames.
   EXPECT_TRUE(connection_.GetRetransmissionAlarm()->IsSet());
   EXPECT_FALSE(connection_.sent_packet_manager().HasRetransmittableFrames(2));
 }
 
 TEST_P(QuicConnectionTest, AlarmsWhenWriteBlocked) {
   // Block the connection.
@@ skipping 1547 matching lines @@
   NackPacket(3, &nack_three);
   NackPacket(1, &nack_three);
   SequenceNumberSet lost_packets;
   lost_packets.insert(1);
   lost_packets.insert(3);
   EXPECT_CALL(*loss_algorithm_, DetectLostPackets(_, _, _, _))
       .WillOnce(Return(lost_packets));
   EXPECT_CALL(*send_algorithm_, OnCongestionEvent(true, _, _, _));
   EXPECT_CALL(visitor_, OnCanWrite()).Times(2);
   EXPECT_CALL(visitor_, OnSuccessfulVersionNegotiation(_));
+  EXPECT_CALL(*send_algorithm_, RevertRetransmissionTimeout());
   ProcessAckPacket(&nack_three);
 
   EXPECT_CALL(*send_algorithm_, BandwidthEstimate()).WillOnce(
       Return(QuicBandwidth::Zero()));
 
   const QuicConnectionStats& stats = connection_.GetStats();
   EXPECT_EQ(3 * first_packet_size + 2 * second_packet_size - kQuicVersionSize,
             stats.bytes_sent);
   EXPECT_EQ(5u, stats.packets_sent);
   EXPECT_EQ(2 * first_packet_size + second_packet_size - kQuicVersionSize,
@@ skipping 231 matching lines @@
             connection_.GetRetransmissionAlarm()->deadline());
   // Simulate the retransmission alarm firing.
   clock_.AdvanceTime(DefaultRetransmissionTime());
   EXPECT_CALL(*send_algorithm_, OnRetransmissionTimeout(true));
   EXPECT_CALL(*send_algorithm_, OnPacketSent(_, _, 2u, _, _));
   connection_.GetRetransmissionAlarm()->Fire();
   EXPECT_EQ(2u, writer_->header().packet_sequence_number);
   // We do not raise the high water mark yet.
   EXPECT_EQ(1u, outgoing_ack()->sent_info.least_unacked);
 
-  // Ack the original packet.
+  // Ack the original packet, which will revert the RTO.
   EXPECT_CALL(visitor_, OnSuccessfulVersionNegotiation(_));
   EXPECT_CALL(*delegate, OnAckNotification(1, _, 1, _, _));
+  EXPECT_CALL(*send_algorithm_, RevertRetransmissionTimeout());
   EXPECT_CALL(*send_algorithm_, OnCongestionEvent(true, _, _, _));
   QuicAckFrame ack_frame = InitAckFrame(1, 0);
   ProcessAckPacket(&ack_frame);
 
   // Delegate is not notified again when the retransmit is acked.
   EXPECT_CALL(*send_algorithm_, OnCongestionEvent(true, _, _, _));
   QuicAckFrame second_ack_frame = InitAckFrame(2, 0);
   ProcessAckPacket(&second_ack_frame);
 }
 
@@ skipping 203 matching lines @@
   QuicBlockedFrame blocked;
   blocked.stream_id = 3;
   EXPECT_CALL(visitor_, OnBlockedFrames(_));
   ProcessFramePacket(QuicFrame(&blocked));
   EXPECT_TRUE(ack_alarm->IsSet());
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace net