::getServerTransportParams signature change

Summary:
change signature of both `ClientHandshake::getServerTransportParams` & `ClientTransportParametersExtension::getServerTransportParams`

from:
```
folly::Optional<ServerTransportParameters> getServerTransportParams()
```
to:
```
const folly::Optional<ServerTransportParameters>& getServerTransportParams()
```

previously this would `std::move(serverTransportParameters_)` after reading it, effectively making it possible to only read the value once.

Reviewed By: kvtsoy

Differential Revision: D48356933

fbshipit-source-id: deddd9101979c1ef30d540b67216dc9611ced713

quic/client/QuicClientTransport.cpp

@@ -684,7 +684,7 @@ void QuicClientTransport::processPacketData(
     // was rejected, or we have derived 1-rtt keys and 0-rtt was never
     // attempted.
     if (oneRttKeyDerivationTriggered) {
-      auto serverParams = handshakeLayer->getServerTransportParams();
+      const auto& serverParams = handshakeLayer->getServerTransportParams();
       if (!serverParams) {
         throw QuicTransportException(
             "No server transport params",
@@ -711,7 +711,7 @@ void QuicClientTransport::processPacketData(
             TransportParameterId::initial_max_streams_uni,
             serverParams->parameters);
         processServerInitialParams(
-            *clientConn_, std::move(*serverParams), packetNum);
+            *clientConn_, serverParams.value(), packetNum);
 
         cacheServerInitialParams(
             *clientConn_,

quic/client/handshake/ClientHandshake.cpp

@@ -109,7 +109,7 @@ ClientHandshake::Phase ClientHandshake::getPhase() const {
   return phase_;
 }
 
-folly::Optional<ServerTransportParameters>
+const folly::Optional<ServerTransportParameters>&
 ClientHandshake::getServerTransportParams() {
   return transportParams_->getServerTransportParams();
 }

quic/client/handshake/ClientHandshake.h

@@ -87,7 +87,8 @@ class ClientHandshake : public Handshake {
   /**
    * Returns the negotiated transport parameters chosen by the server
    */
-  virtual folly::Optional<ServerTransportParameters> getServerTransportParams();
+  virtual const folly::Optional<ServerTransportParameters>&
+  getServerTransportParams();
 
   ~ClientHandshake() override = default;
 

quic/client/handshake/ClientTransportParametersExtension.h

@@ -41,8 +41,8 @@ struct ClientTransportParametersExtension {
         initialSourceCid_(initialSourceCid),
         customTransportParameters_(std::move(customTransportParameters)) {}
 
-  folly::Optional<ServerTransportParameters> getServerTransportParams() {
+  const folly::Optional<ServerTransportParameters>& getServerTransportParams() {
-    return std::move(serverTransportParameters_);
+    return serverTransportParameters_;
   }
 
   QuicVersion encodingVersion_;

quic/client/state/ClientStateMachine.cpp

@@ -101,7 +101,7 @@ std::unique_ptr<QuicClientConnectionState> undoAllClientStateForRetry(
 
 void processServerInitialParams(
     QuicClientConnectionState& conn,
-    ServerTransportParameters serverParams,
+    const ServerTransportParameters& serverParams,
     PacketNum packetNum) {
   auto maxData = getIntegerParameter(
       TransportParameterId::initial_max_data, serverParams.parameters);

quic/client/state/ClientStateMachine.h

@@ -144,7 +144,7 @@ std::unique_ptr<QuicClientConnectionState> undoAllClientStateForRetry(
 
 void processServerInitialParams(
     QuicClientConnectionState& conn,
-    ServerTransportParameters serverParams,
+    const ServerTransportParameters& serverParams,
     PacketNum packetNum);
 
 void cacheServerInitialParams(

quic/client/test/Mocks.h

@@ -56,7 +56,7 @@ class MockClientHandshake : public ClientHandshake {
   MOCK_METHOD(bool, isTLSResumed, (), (const));
   MOCK_METHOD(folly::Optional<bool>, getZeroRttRejected, ());
   MOCK_METHOD(
-      folly::Optional<ServerTransportParameters>,
+      const folly::Optional<ServerTransportParameters>&,
       getServerTransportParams,
       ());
   MOCK_METHOD(void, destroy, ());

quic/fizz/client/test/QuicClientTransportTestUtil.h

@@ -316,7 +316,7 @@ class FakeOneRttHandshakeLayer : public FizzClientHandshake {
     return connected_;
   }
 
-  folly::Optional<ServerTransportParameters> getServerTransportParams()
+  const folly::Optional<ServerTransportParameters>& getServerTransportParams()
       override {
     return params_;
   }