Add an IncreaseLargestObserved to QuicUnackedPacketMap to remove the rtt

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 108 matching lines @@
                                          new_sequence_number);
 }
 
 void QuicSentPacketManager::OnIncomingAck(
     const ReceivedPacketInfo& received_info,
     QuicTime ack_receive_time) {
   QuicByteCount bytes_in_flight = unacked_packets_.bytes_in_flight();
 
   // We rely on delta_time_largest_observed to compute an RTT estimate, so
   // we only update rtt when the largest observed gets acked.
-  largest_observed_ = received_info.largest_observed;
   bool largest_observed_acked = MaybeUpdateRTT(received_info, ack_receive_time);
+  if (largest_observed_ < received_info.largest_observed) {
+    largest_observed_ = received_info.largest_observed;
+    unacked_packets_.IncreaseLargestObserved(largest_observed_);
+  }
   HandleAckForSentPackets(received_info);
   InvokeLossDetection(ack_receive_time);
   MaybeInvokeCongestionEvent(largest_observed_acked, bytes_in_flight);
 
   // If we have received a truncated ack, then we need to clear out some
   // previous transmissions to allow the peer to actually ACK new packets.
   if (received_info.is_truncated) {
     unacked_packets_.ClearPreviousRetransmissions(
         received_info.missing_packets.size() / 2);
   }
@@ skipping 27 matching lines @@
       received_info.delta_time_largest_observed;
   QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
   while (it != unacked_packets_.end()) {
     QuicPacketSequenceNumber sequence_number = it->first;
     if (sequence_number > received_info.largest_observed) {
       // These packets are still in flight.
       break;
     }
 
     if (IsAwaitingPacket(received_info, sequence_number)) {
-      // Remove any rtt only packets less than or equal to the largest observed,
-      // since they will not produce an RTT measurement.
-      if (QuicUnackedPacketMap::IsForRttOnly(it->second)) {
-        ++it;
-        unacked_packets_.RemoveRttOnlyPacket(sequence_number);
-      } else {
-        // Consider it multiple nacks when there is a gap between the missing
-        // packet and the largest observed, since the purpose of a nack
-        // threshold is to tolerate re-ordering.  This handles both StretchAcks
-        // and Forward Acks.
-        // The nack count only increases when the largest observed increases.
-        size_t min_nacks = received_info.largest_observed - sequence_number;
-        // Truncated acks can nack the largest observed, so use a min of 1.
-        if (min_nacks == 0) {
-          min_nacks = 1;
-        }
-        unacked_packets_.NackPacket(sequence_number, min_nacks);
-        ++it;
+      // Consider it multiple nacks when there is a gap between the missing
+      // packet and the largest observed, since the purpose of a nack
+      // threshold is to tolerate re-ordering.  This handles both StretchAcks
+      // and Forward Acks.
+      // The nack count only increases when the largest observed increases.
+      size_t min_nacks = received_info.largest_observed - sequence_number;
+      // Truncated acks can nack the largest observed, so use a min of 1.
+      if (min_nacks == 0) {
+        min_nacks = 1;
       }
+      unacked_packets_.NackPacket(sequence_number, min_nacks);
+      ++it;
       continue;
     }
-
     // Packet was acked, so remove it from our unacked packet list.
     DVLOG(1) << ENDPOINT << "Got an ack for packet " << sequence_number;
     // If data is associated with the most recent transmission of this
     // packet, then inform the caller.
     if (it->second.pending) {
       packets_acked_[sequence_number] = it->second;
     }
     it = MarkPacketHandled(it, delta_largest_observed);
   }
 
@@ skipping 21 matching lines @@
     // numbers with no connection to the previous ones.
     if (frames != NULL && (retransmission_type == ALL_PACKETS ||
                            frames->encryption_level() == ENCRYPTION_INITIAL)) {
       MarkForRetransmission(unacked_it->first, ALL_UNACKED_RETRANSMISSION);
     }
     ++unacked_it;
   }
 }
 
 void QuicSentPacketManager::NeuterUnencryptedPackets() {
-  for (QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
-       it != unacked_packets_.end(); ++it) {
+  QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
+  while (it != unacked_packets_.end()) {
     const RetransmittableFrames* frames =
         it->second.retransmittable_frames;
+    QuicPacketSequenceNumber sequence_number = it->first;
+    ++it;
     if (frames != NULL && frames->encryption_level() == ENCRYPTION_NONE) {
       // Once you're forward secure, no unencrypted packets will be sent, crypto
       // or otherwise. Unencrypted packets are neutered and abandoned, to ensure
       // they are not retransmitted or considered lost from a congestion control
       // perspective.
-      pending_retransmissions_.erase(it->first);
-      unacked_packets_.RemoveRetransmittability(it->first, largest_observed_);
-      unacked_packets_.SetNotPending(it->first);
+      pending_retransmissions_.erase(sequence_number);
+      unacked_packets_.SetNotPending(sequence_number);
+      // RemoveRetransmittibility is safe because only the newest sequence
+      // number can have frames.
+      unacked_packets_.RemoveRetransmittability(sequence_number);
     }
   }
 }
 
 void QuicSentPacketManager::MarkForRetransmission(
     QuicPacketSequenceNumber sequence_number,
     TransmissionType transmission_type) {
   const TransmissionInfo& transmission_info =
       unacked_packets_.GetTransmissionInfo(sequence_number);
   LOG_IF(DFATAL, transmission_info.retransmittable_frames == NULL);
@@ skipping 58 matching lines @@
   // retransmit it, do not retransmit it anymore.
   pending_retransmissions_.erase(newest_transmission);
 
   // The AckNotifierManager needs to be notified for revived packets,
   // since it indicates the packet arrived from the appliction's perspective.
   if (transmission_info.retransmittable_frames) {
     ack_notifier_manager_.OnPacketAcked(
         newest_transmission, delta_largest_observed);
   }
 
-  unacked_packets_.RemoveRetransmittability(sequence_number, largest_observed_);
+  unacked_packets_.RemoveRetransmittability(sequence_number);
 }
 
 QuicUnackedPacketMap::const_iterator QuicSentPacketManager::MarkPacketHandled(
     QuicUnackedPacketMap::const_iterator it,
     QuicTime::Delta delta_largest_observed) {
   LOG_IF(DFATAL, it == unacked_packets_.end())
       << "MarkPacketHandled must be passed a valid iterator entry.";
   const QuicPacketSequenceNumber sequence_number = it->first;
   const TransmissionInfo& transmission_info = it->second;
 
@@ skipping 18 matching lines @@
 
   // If it's a crypto handshake packet, discard it and all retransmissions,
   // since they won't be acked now that one has been processed.
   // TODO(ianswett): Instead of handling all crypto packets in a special way,
   // only handle NULL encrypted packets in a special way.
   if (HasCryptoHandshake(
           unacked_packets_.GetTransmissionInfo(newest_transmission))) {
     unacked_packets_.SetNotPending(newest_transmission);
   }
   unacked_packets_.SetNotPending(sequence_number);
-  unacked_packets_.RemoveRetransmittability(sequence_number, largest_observed_);
+  unacked_packets_.RemoveRetransmittability(sequence_number);
 
   QuicUnackedPacketMap::const_iterator next_unacked = unacked_packets_.begin();
   while (next_unacked != unacked_packets_.end() &&
          next_unacked->first <= sequence_number) {
     ++next_unacked;
   }
   return next_unacked;
 }
 
 bool QuicSentPacketManager::IsUnacked(
@@ skipping 123 matching lines @@
   // retransmission delay.
 
   DVLOG(1) << "OnRetransmissionTimeout() fired with "
            << unacked_packets_.GetNumUnackedPackets() << " unacked packets.";
 
   // Request retransmission of all retransmittable packets when the RTO
   // fires, and let the congestion manager decide how many to send
   // immediately and the remaining packets will be queued.
   // Abandon any non-retransmittable packets that are sufficiently old.
   bool packets_retransmitted = false;
-  for (QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
-       it != unacked_packets_.end(); ++it) {
-    if (it->second.retransmittable_frames != NULL) {
+  QuicUnackedPacketMap::const_iterator it = unacked_packets_.begin();
+  while (it != unacked_packets_.end()) {
+    const RetransmittableFrames* frames =
+        it->second.retransmittable_frames;
+    QuicPacketSequenceNumber sequence_number = it->first;
+    ++it;
+    if (frames != NULL) {
       packets_retransmitted = true;
-      MarkForRetransmission(it->first, RTO_RETRANSMISSION);
+      MarkForRetransmission(sequence_number, RTO_RETRANSMISSION);
     } else {
-      unacked_packets_.SetNotPending(it->first);
+      unacked_packets_.SetNotPending(sequence_number);
     }
   }
 
   send_algorithm_->OnRetransmissionTimeout(packets_retransmitted);
   if (packets_retransmitted) {
     ++consecutive_rto_count_;
   }
 }
 
 QuicSentPacketManager::RetransmissionTimeoutMode
@@ skipping 39 matching lines @@
     DVLOG(1) << ENDPOINT << "Lost packet " << sequence_number;
 
     if (transmission_info.retransmittable_frames != NULL) {
       MarkForRetransmission(sequence_number, LOSS_RETRANSMISSION);
     } else {
       // Since we will not retransmit this, we need to remove it from
       // unacked_packets_.   This is either the current transmission of
       // a packet whose previous transmission has been acked, a packet that has
       // been TLP retransmitted, or an FEC packet.
       unacked_packets_.SetNotPending(sequence_number);
-      if (QuicUnackedPacketMap::IsForRttOnly(transmission_info)) {
-        unacked_packets_.RemoveRttOnlyPacket(sequence_number);
-      }
     }
   }
 }
 
 bool QuicSentPacketManager::MaybeUpdateRTT(
     const ReceivedPacketInfo& received_info,
     const QuicTime& ack_receive_time) {
   if (!unacked_packets_.IsUnacked(received_info.largest_observed)) {
     return false;
   }
@@ skipping 141 matching lines @@
     return;
   }
 
   using_pacing_ = true;
   send_algorithm_.reset(
       new PacingSender(send_algorithm_.release(),
                        QuicTime::Delta::FromMicroseconds(1)));
 }
 
 }  // namespace net