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

net/quic/quic_sent_packet_manager.h

 // 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.
 
 #ifndef NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_
 #define NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_
 
 #include <deque>
 #include <list>
 #include <map>
@@ skipping 273 matching lines @@
   AckNotifierManager ack_notifier_manager_;
 
   const QuicClock* clock_;
   QuicConnectionStats* stats_;
   DebugDelegate* debug_delegate_;
   RttStats rtt_stats_;
   scoped_ptr<SendAlgorithmInterface> send_algorithm_;
   scoped_ptr<LossDetectionInterface> loss_algorithm_;
 
   QuicPacketSequenceNumber largest_observed_;  // From the most recent ACK.
+  // Tracks the first RTO packet.  If any packet before that packet gets acked,
+  // it indicates the RTO was spurious and should be reversed(F-RTO).
+  QuicPacketSequenceNumber first_rto_transmission_;
   // Number of times the RTO timer has fired in a row without receiving an ack.
   size_t consecutive_rto_count_;
   // Number of times the tail loss probe has been sent.
   size_t consecutive_tlp_count_;
   // Number of times the crypto handshake has been retransmitted.
   size_t consecutive_crypto_retransmission_count_;
   // Whether a tlp packet can be sent even if the send algorithm says not to.
   bool pending_tlp_transmission_;
   // Maximum number of tail loss probes to send before firing an RTO.
   size_t max_tail_loss_probes_;
   bool using_pacing_;
 
   // Sets of packets acked and lost as a result of the last congestion event.
   SendAlgorithmInterface::CongestionMap packets_acked_;
   SendAlgorithmInterface::CongestionMap packets_lost_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicSentPacketManager);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_SENT_PACKET_MANAGER_H_