Delay a QUIC server's use of the FORWARD_SECURE encrypter until the

net/quic/quic_connection_test.cc

Index: net/quic/quic_connection_test.cc
diff --git a/net/quic/quic_connection_test.cc b/net/quic/quic_connection_test.cc
index 4dbbe13a578da3b0612750abc6ca28f6f1200e61..f76444fa674c1d3f5f0e595c5ff909205a1f15ce 100644
--- a/net/quic/quic_connection_test.cc
+++ b/net/quic/quic_connection_test.cc
@@ -2447,6 +2447,63 @@ TEST_P(QuicConnectionTest, RetransmitPacketsWithInitialEncryption) {
   connection_.RetransmitUnackedPackets(ALL_INITIAL_RETRANSMISSION);
 }
 
+TEST_P(QuicConnectionTest, DelayForwardSecureEncryptionUntilClientIsReady) {
+  ValueRestore<bool> old_flag(&FLAGS_enable_quic_delay_forward_security, true);
+
+  // A TaggingEncrypter puts kTagSize copies of the given byte (0x02 here) at
+  // the end of the packet. We can test this to check which encrypter was used.
+  use_tagging_decrypter();
+  connection_.SetEncrypter(ENCRYPTION_INITIAL, new TaggingEncrypter(0x02));
+  connection_.SetDefaultEncryptionLevel(ENCRYPTION_INITIAL);
+  SendAckPacketToPeer();
+  EXPECT_EQ(0x02020202u, writer_->final_bytes_of_last_packet());
+
+  // Set a forward-secure encrypter but do not make it the default, and verify
+  // that it is not yet used.
+  connection_.SetEncrypter(ENCRYPTION_FORWARD_SECURE,
+                           new TaggingEncrypter(0x03));
+  SendAckPacketToPeer();
+  EXPECT_EQ(0x02020202u, writer_->final_bytes_of_last_packet());
+
+  // Now simulate receipt of a forward-secure packet and verify that the
+  // forward-secure encrypter is now used.
+  connection_.OnDecryptedPacket(ENCRYPTION_FORWARD_SECURE);
+  SendAckPacketToPeer();
+  EXPECT_EQ(0x03030303u, writer_->final_bytes_of_last_packet());
+}
+
+TEST_P(QuicConnectionTest, DelayForwardSecureEncryptionUntilManyPacketSent) {
+  ValueRestore<bool> old_flag(&FLAGS_enable_quic_delay_forward_security, true);
+
+  // Set a congestion window of 10 packets.
+  QuicPacketCount congestion_window = 10;
+  EXPECT_CALL(*send_algorithm_, GetCongestionWindow()).WillRepeatedly(
+      Return(congestion_window * kDefaultMaxPacketSize));
+
+  // A TaggingEncrypter puts kTagSize copies of the given byte (0x02 here) at
+  // the end of the packet. We can test this to check which encrypter was used.
+  use_tagging_decrypter();
+  connection_.SetEncrypter(ENCRYPTION_INITIAL, new TaggingEncrypter(0x02));
+  connection_.SetDefaultEncryptionLevel(ENCRYPTION_INITIAL);
+  SendAckPacketToPeer();
+  EXPECT_EQ(0x02020202u, writer_->final_bytes_of_last_packet());
+
+  // Set a forward-secure encrypter but do not make it the default, and
+  // verify that it is not yet used.
+  connection_.SetEncrypter(ENCRYPTION_FORWARD_SECURE,
+                           new TaggingEncrypter(0x03));
+  SendAckPacketToPeer();
+  EXPECT_EQ(0x02020202u, writer_->final_bytes_of_last_packet());
+
+  // Now send a packet "Far enough" after the encrypter was set and verify that
+  // the forward-secure encrypter is now used.
+  for (uint64 i = 0; i < 3 * congestion_window - 1; ++i) {
+    EXPECT_EQ(0x02020202u, writer_->final_bytes_of_last_packet());
+    SendAckPacketToPeer();
+  }
+  EXPECT_EQ(0x03030303u, writer_->final_bytes_of_last_packet());
+}
+
 TEST_P(QuicConnectionTest, BufferNonDecryptablePackets) {
   // SetFromConfig is always called after construction from InitializeSession.
   EXPECT_CALL(*send_algorithm_, SetFromConfig(_, _));