Use LeastUnacked to calculate the packet number length instead of GetLeastPacketAwaitedByPeer.

net/quic/core/quic_connection.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/core/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 
 #include <algorithm>
@@ skipping 1669 matching lines @@
   }
   SetPingAlarm();
   MaybeSetMtuAlarm();
   DVLOG(1) << ENDPOINT << "time we began writing last sent packet: "
            << packet_send_time.ToDebuggingValue();
 
   if (!FLAGS_quic_simple_packet_number_length) {
     // TODO(ianswett): Change the packet number length and other packet creator
     // options by a more explicit API than setting a struct value directly,
     // perhaps via the NetworkChangeVisitor.
-    packet_generator_.UpdateSequenceNumberLength(
-        sent_packet_manager_->GetLeastPacketAwaitedByPeer(packet->path_id),
-        sent_packet_manager_->EstimateMaxPacketsInFlight(max_packet_length()));
+    if (FLAGS_quic_least_unacked_packet_number_length) {
+      packet_generator_.UpdateSequenceNumberLength(
+          sent_packet_manager_->GetLeastUnacked(packet->path_id),
+          sent_packet_manager_->EstimateMaxPacketsInFlight(
+              max_packet_length()));
+    } else {
+      packet_generator_.UpdateSequenceNumberLength(
+          sent_packet_manager_->GetLeastPacketAwaitedByPeer(packet->path_id),
+          sent_packet_manager_->EstimateMaxPacketsInFlight(
+              max_packet_length()));
+    }
   }
 
   bool reset_retransmission_alarm = sent_packet_manager_->OnPacketSent(
       packet, packet->original_path_id, packet->original_packet_number,
       packet_send_time, packet->transmission_type, IsRetransmittable(*packet));
 
   if (reset_retransmission_alarm || !retransmission_alarm_->IsSet()) {
     SetRetransmissionAlarm();
   }
 
   if (FLAGS_quic_simple_packet_number_length) {
     // The packet number length must be updated after OnPacketSent, because it
     // may change the packet number length in packet.
-    packet_generator_.UpdateSequenceNumberLength(
-        sent_packet_manager_->GetLeastPacketAwaitedByPeer(packet->path_id),
-        sent_packet_manager_->EstimateMaxPacketsInFlight(max_packet_length()));
+    if (FLAGS_quic_least_unacked_packet_number_length) {
+      packet_generator_.UpdateSequenceNumberLength(
+          sent_packet_manager_->GetLeastUnacked(packet->path_id),
+          sent_packet_manager_->EstimateMaxPacketsInFlight(
+              max_packet_length()));
+    } else {
+      packet_generator_.UpdateSequenceNumberLength(
+          sent_packet_manager_->GetLeastPacketAwaitedByPeer(packet->path_id),
+          sent_packet_manager_->EstimateMaxPacketsInFlight(
+              max_packet_length()));
+    }
   }
 
   stats_.bytes_sent += result.bytes_written;
   ++stats_.packets_sent;
   if (packet->transmission_type != NOT_RETRANSMISSION) {
     stats_.bytes_retransmitted += result.bytes_written;
     ++stats_.packets_retransmitted;
   }
 
   if (result.status == WRITE_STATUS_ERROR) {
@@ skipping 790 matching lines @@
 // the sender and a signaling mechanism -- if the sender uses a
 // different MinRTO, we may get spurious retransmissions. May not have
 // any benefits, but if the delayed ack becomes a significant source
 // of (likely, tail) latency, then consider such a mechanism.
 const QuicTime::Delta QuicConnection::DelayedAckTime() {
   return QuicTime::Delta::FromMilliseconds(
       min(kMaxDelayedAckTimeMs, kMinRetransmissionTimeMs / 2));
 }
 
 }  // namespace net