Adds plumbing for QUIC early connection migration. No behavior change.

net/quic/quic_sent_packet_manager.cc

 // 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 "net/quic/quic_sent_packet_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 19 matching lines @@
 static const int64_t kDefaultRetransmissionTimeMs = 500;
 // TCP RFC calls for 1 second RTO however Linux differs from this default and
 // define the minimum RTO to 200ms, we will use the same until we have data to
 // support a higher or lower value.
 static const int64_t kMinRetransmissionTimeMs = 200;
 static const int64_t kMaxRetransmissionTimeMs = 60000;
 // Maximum number of exponential backoffs used for RTO timeouts.
 static const size_t kMaxRetransmissions = 10;
 // Maximum number of packets retransmitted upon an RTO.
 static const size_t kMaxRetransmissionsOnTimeout = 2;
+// Minimum number of consecutive RTOs before path is considered to be degrading.
+const size_t kMinTimeoutsBeforePathDegrading = 2;
 
 // Ensure the handshake timer isnt't faster than 10ms.
 // This limits the tenth retransmitted packet to 10s after the initial CHLO.
 static const int64_t kMinHandshakeTimeoutMs = 10;
 
 // Sends up to two tail loss probes before firing an RTO,
 // per draft RFC draft-dukkipati-tcpm-tcp-loss-probe.
 static const size_t kDefaultMaxTailLossProbes = 2;
 static const int64_t kMinTailLossProbeTimeoutMs = 10;
 
@@ skipping 562 matching lines @@
       // packets, execute a conventional RTO to abandon old packets.
       ++stats_->tlp_count;
       ++consecutive_tlp_count_;
       pending_timer_transmission_count_ = 1;
       // TLPs prefer sending new data instead of retransmitting data, so
       // give the connection a chance to write before completing the TLP.
       return;
     case RTO_MODE:
       ++stats_->rto_count;
       RetransmitRtoPackets();
+      if (network_change_visitor_ != nullptr &&
+          consecutive_rto_count_ == kMinTimeoutsBeforePathDegrading) {
+        network_change_visitor_->OnPathDegrading();
+      }
       return;
   }
 }
 
 void QuicSentPacketManager::RetransmitCryptoPackets() {
   DCHECK_EQ(HANDSHAKE_MODE, GetRetransmissionMode());
   ++consecutive_crypto_retransmission_count_;
   bool packet_retransmitted = false;
   QuicPacketNumber packet_number = unacked_packets_.GetLeastUnacked();
   for (QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
@@ skipping 340 matching lines @@
 TransmissionInfo* QuicSentPacketManager::GetMutableTransmissionInfo(
     QuicPacketNumber packet_number) {
   return unacked_packets_.GetMutableTransmissionInfo(packet_number);
 }
 
 void QuicSentPacketManager::RemoveObsoletePackets() {
   unacked_packets_.RemoveObsoletePackets();
 }
 
 }  // namespace net