Add a QUIC connection option to use a more conservative handshake retransmission timer. Protected …

net/quic/core/quic_sent_packet_manager.cc

Index: net/quic/core/quic_sent_packet_manager.cc
diff --git a/net/quic/core/quic_sent_packet_manager.cc b/net/quic/core/quic_sent_packet_manager.cc
index 7738e34381d960a0033f8bb186034d746ee93a45..89a1dc5ffa23bff721d4264aed7cb9ed18a9b8b5 100644
--- a/net/quic/core/quic_sent_packet_manager.cc
+++ b/net/quic/core/quic_sent_packet_manager.cc
@@ -38,6 +38,9 @@ const size_t kMinTimeoutsBeforePathDegrading = 2;
 // This limits the tenth retransmitted packet to 10s after the initial CHLO.
 static const int64_t kMinHandshakeTimeoutMs = 10;
 
+// Ensure the handshake timer isnt't faster than 25ms.
+static const int64_t kConservativeMinHandshakeTimeoutMs = kMaxDelayedAckTimeMs;
+
 // 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;
@@ -85,6 +88,7 @@ QuicSentPacketManager::QuicSentPacketManager(
       using_pacing_(false),
       use_new_rto_(false),
       undo_pending_retransmits_(false),
+      conservative_handshake_retransmits_(false),
       largest_newly_acked_(0),
       largest_mtu_acked_(0),
       handshake_confirmed_(false) {
@@ -151,6 +155,10 @@ void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) {
   if (config.HasClientSentConnectionOption(kUNDO, perspective_)) {
     undo_pending_retransmits_ = true;
   }
+  if (FLAGS_quic_conservative_handshake_retransmits &&
+      config.HasClientSentConnectionOption(kCONH, perspective_)) {
+    conservative_handshake_retransmits_ = true;
+  }
   send_algorithm_->SetFromConfig(config, perspective_);
 
   if (network_change_visitor_ != nullptr) {
@@ -816,11 +824,17 @@ const QuicTime::Delta QuicSentPacketManager::GetCryptoRetransmissionDelay()
   // This is equivalent to the TailLossProbeDelay, but slightly more aggressive
   // because crypto handshake messages don't incur a delayed ack time.
   QuicTime::Delta srtt = rtt_stats_.smoothed_rtt();
+  int64_t delay_ms;
   if (srtt.IsZero()) {
     srtt = QuicTime::Delta::FromMicroseconds(rtt_stats_.initial_rtt_us());
   }
-  int64_t delay_ms = max(kMinHandshakeTimeoutMs,
-                         static_cast<int64_t>(1.5 * srtt.ToMilliseconds()));
+  if (conservative_handshake_retransmits_) {
+    delay_ms = max(kConservativeMinHandshakeTimeoutMs,
+                   static_cast<int64_t>(2 * srtt.ToMilliseconds()));
+  } else {
+    delay_ms = max(kMinHandshakeTimeoutMs,
+                   static_cast<int64_t>(1.5 * srtt.ToMilliseconds()));
+  }
   return QuicTime::Delta::FromMilliseconds(
       delay_ms << consecutive_crypto_retransmission_count_);
 }