commit 9929cc4d7163250d637bccb24a1f9ca05c3e68e0
author QUICHE team <quiche-dev@google.com> Wed Mar 13 08:17:43 2019 -0700
committer Copybara-Service <copybara-worker@google.com> Wed Mar 13 08:18:28 2019 -0700
tree fd6700e7ccb943ee033005231d76d02693a62c64
parent 73e63a7a037c2c50f81ec91749569102b9173b10

gfe-relnote: In QUIC, do not close connection if received an in-order ACK with decreased largest_acked. Protected by gfe2_reloadable_flag_quic_tolerate_reneging.

By dremel, this connection close occurs rarely in prod: https://screenshot.googleplex.com/jZpfvdY4nzk

Largest_acked can decrease currently in IETF QUIC, though that may change: https://github.com/quicwg/base-drafts/issues/2205

PiperOrigin-RevId: 238228491
Change-Id: If7586fb8da192dea4436a5572c76bb7aeb1a3227

quic/core/quic_sent_packet_manager.cc

diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index 93909b7..e078f5f 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -111,7 +111,11 @@
       delayed_ack_time_(
           QuicTime::Delta::FromMilliseconds(kDefaultDelayedAckTimeMs)),
       rtt_updated_(false),
-      acked_packets_iter_(last_ack_frame_.packets.rbegin()) {
+      acked_packets_iter_(last_ack_frame_.packets.rbegin()),
+      tolerate_reneging_(GetQuicReloadableFlag(quic_tolerate_reneging)) {
+  if (tolerate_reneging_) {
+    QUIC_RELOADABLE_FLAG_COUNT(quic_tolerate_reneging);
+  }
   SetSendAlgorithm(congestion_control_type);
 }
 
@@ -1063,7 +1067,8 @@
   rtt_updated_ =
       MaybeUpdateRTT(largest_acked, ack_delay_time, ack_receive_time);
   DCHECK(!unacked_packets_.largest_acked().IsInitialized() ||
-         largest_acked >= unacked_packets_.largest_acked());
+         largest_acked >= unacked_packets_.largest_acked() ||
+         tolerate_reneging_);
   last_ack_frame_.ack_delay_time = ack_delay_time;
   acked_packets_iter_ = last_ack_frame_.packets.rbegin();
 }