Add QUIC connection options for testing:
- CHP1: Add 1-packet padding to CHLO.
- CHP2: Add 2-packet padding to CHLO.

PiperOrigin-RevId: 681031206

quiche/quic/core/crypto/crypto_protocol.h

diff --git a/quiche/quic/core/crypto/crypto_protocol.h b/quiche/quic/core/crypto/crypto_protocol.h
index d76547d..48e98d5 100644
--- a/quiche/quic/core/crypto/crypto_protocol.h
+++ b/quiche/quic/core/crypto/crypto_protocol.h
@@ -472,6 +472,10 @@
 // Universal tags
 const QuicTag kPAD  = TAG('P', 'A', 'D', '\0');  // Padding
 
+// Client Hello Padding tags, for experiments.
+const QuicTag kCHP1 = TAG('C', 'H', 'P', '1');   // 1-packet padding to CHLO.
+const QuicTag kCHP2 = TAG('C', 'H', 'P', '2');   // 2-packet padding to CHLO.
+
 // Stats collection tags
 const QuicTag kEPID = TAG('E', 'P', 'I', 'D');  // Endpoint identifier.
 

quiche/quic/core/http/end_to_end_test.cc

diff --git a/quiche/quic/core/http/end_to_end_test.cc b/quiche/quic/core/http/end_to_end_test.cc
index 452586c..8732d4b 100644
--- a/quiche/quic/core/http/end_to_end_test.cc
+++ b/quiche/quic/core/http/end_to_end_test.cc
@@ -1211,8 +1211,7 @@
 TEST_P(EndToEndTest, TestDispatcherAckWithTwoPacketCHLO) {
   SetQuicFlag(quic_allow_chlo_buffering, true);
   SetQuicFlag(quic_dispatcher_max_ack_sent_per_connection, 1);
-  std::string google_handshake_message(kEthernetMTU, 'a');
-  client_config_.SetGoogleHandshakeMessageToSend(google_handshake_message);
+  client_extra_copts_.push_back(kCHP1);
   ASSERT_TRUE(Initialize());
   if (!version_.HasIetfQuicFrames()) {
     return;
@@ -1359,8 +1358,7 @@
 TEST_P(EndToEndTest, TestDispatcherAckWithThreePacketCHLO) {
   SetQuicFlag(quic_allow_chlo_buffering, true);
   SetQuicFlag(quic_dispatcher_max_ack_sent_per_connection, 2);
-  std::string google_handshake_message(2 * kEthernetMTU, 'a');
-  client_config_.SetGoogleHandshakeMessageToSend(google_handshake_message);
+  client_extra_copts_.push_back(kCHP2);
   ASSERT_TRUE(Initialize());
   if (!version_.HasIetfQuicFrames()) {
     return;

quiche/quic/core/quic_session.cc

diff --git a/quiche/quic/core/quic_session.cc b/quiche/quic/core/quic_session.cc
index 66d8935..afdb44b 100644
--- a/quiche/quic/core/quic_session.cc
+++ b/quiche/quic/core/quic_session.cc
@@ -172,6 +172,15 @@
   connection_->SetSessionNotifier(this);
   connection_->SetDataProducer(this);
   connection_->SetUnackedMapInitialCapacity();
+  if (perspective_ == Perspective::IS_CLIENT) {
+    if (config_.HasClientSentConnectionOption(kCHP1, perspective_)) {
+      config_.SetGoogleHandshakeMessageToSend(
+          std::string(kDefaultMaxPacketSize, '0'));
+    } else if (config_.HasClientSentConnectionOption(kCHP2, perspective_)) {
+      config_.SetGoogleHandshakeMessageToSend(
+          std::string(kDefaultMaxPacketSize * 2, '0'));
+    }
+  }
   connection_->SetFromConfig(config_);
   if (perspective_ == Perspective::IS_CLIENT) {
     if (config_.HasClientRequestedIndependentOption(kAFFE, perspective_) &&
@@ -1862,6 +1871,11 @@
       MaybeSendAddressToken();
     }
   }
+  if (perspective_ == Perspective::IS_CLIENT &&
+      (config_.HasClientSentConnectionOption(kCHP1, perspective_) ||
+       config_.HasClientSentConnectionOption(kCHP2, perspective_))) {
+    config_.ClearGoogleHandshakeMessage();
+  }
 }
 
 bool QuicSession::MaybeSendAddressToken() {