Make client keep track of originalDestinationConnectionId

Summary:
When I tested against picoquic, I found that an exception was thrown here: https://fburl.com/diffusion/qsnzingx.

The reason is that we modify `conn.initialDestinationConnectionId` in the event of a retry, so it's no longer the original destination connection id. By separately keeping track of the original destination connection id, we can solve this issue.

Reviewed By: mjoras

Differential Revision: D23722127

fbshipit-source-id: 94be08812e675feaf46f5af86e7304af84c1910c

quic/client/QuicClientTransport.cpp

@@ -55,6 +55,8 @@ QuicClientTransport::QuicClientTransport(
   conn_->selfConnectionIds.emplace_back(srcConnId, kInitialSequenceNumber);
   clientConn_->initialDestinationConnectionId =
       ConnectionId::createRandom(kMinInitialDestinationConnIdLength);
+  clientConn_->originalDestinationConnectionId =
+      clientConn_->initialDestinationConnectionId;
   conn_->clientChosenDestConnectionId =
       clientConn_->initialDestinationConnectionId;
   VLOG(4) << "initial dcid: "
@@ -159,7 +161,7 @@ void QuicClientTransport::processPacketData(
     }
 
     const ConnectionId* originalDstConnId =
-        &(*clientConn_->initialDestinationConnectionId);
+        &(*clientConn_->originalDestinationConnectionId);
 
     if (!clientConn_->clientHandshakeLayer->verifyRetryIntegrityTag(
             *originalDstConnId, *retryPacket)) {

quic/client/state/ClientStateMachine.cpp

@@ -30,6 +30,8 @@ std::unique_ptr<QuicClientConnectionState> undoAllClientStateForRetry(
   newConn->clientConnectionId = conn->clientConnectionId;
   newConn->initialDestinationConnectionId =
       conn->initialDestinationConnectionId;
+  newConn->originalDestinationConnectionId =
+      conn->originalDestinationConnectionId;
   // TODO: don't carry server connection id over to the new connection.
   newConn->serverConnectionId = conn->serverConnectionId;
   newConn->ackStates.initialAckState.nextPacketNum =
@@ -100,7 +102,7 @@ void processServerInitialParams(
         initialSourceConnId.value() !=
             conn.readCodec->getServerConnectionId() ||
         originalDestinationConnId.value() !=
-            conn.initialDestinationConnectionId) {
+            conn.originalDestinationConnectionId) {
       throw QuicTransportException(
           "Initial CID does not match.",
           TransportErrorCode::TRANSPORT_PARAMETER_ERROR);

quic/client/state/ClientStateMachine.h

@@ -30,9 +30,16 @@ struct QuicClientConnectionState : public QuicConnectionStateBase {
   // The retry token sent by the server.
   std::string retryToken;
 
-  // Initial destination connection id.
+  // This is the destination connection id that will be sent in the outgoing
+  // client initial packet. It is modified in the event of a retry.
   folly::Optional<ConnectionId> initialDestinationConnectionId;
 
+  // This is the original destination connection id. It is the same as the
+  // initialDestinationConnectionId when there is no retry involved. When
+  // there is retry involved, this is the value of the destination connection
+  // id sent in the very first initial packet.
+  folly::Optional<ConnectionId> originalDestinationConnectionId;
+
   std::shared_ptr<ClientHandshakeFactory> handshakeFactory;
   ClientHandshake* clientHandshakeLayer;
 

quic/fizz/client/test/QuicClientTransportTest.cpp

@@ -4449,6 +4449,7 @@ TEST_F(QuicClientTransportVersionAndRetryTest, RetryPacket) {
   client->getNonConstConn().qLogger = qLogger;
   client->getNonConstConn().readCodec->setClientConnectionId(clientConnId);
   client->getNonConstConn().initialDestinationConnectionId = initialDstConnId;
+  client->getNonConstConn().originalDestinationConnectionId = initialDstConnId;
 
   StreamId streamId = *client->createBidirectionalStream();
   auto write = IOBuf::copyBuffer("ice cream");