Cache Ack Rx timestamps transport settings in PSK cache for 0-rtt

Summary:
Ack Rx timestamps are currently disabled on 0-rtt connections, which is enabled on mvfst for all non-video connections.

This is because the timestamp config is negotiated with transport settings during handshake which doesn't happen on a new 0-rtt connection (resumption).

Solution:
Store the peer's rx timestamp config in PSKCache on the client. On 0-rtt resumption of the connection, this peer config is restored and used to send Rx timestamps (if enabled).

Note that if the server had changed its timestamp config during this period (through configerator) then the server needs to reject this 0-rtt connection and start anew. Server code changes to support this will be in a followup diff. With this client diff though,  server will drop the Rx timestamps if its own config is suddenly disabled (this is a waste of network resource).

Reviewed By: jbeshay

Differential Revision: D58572572

fbshipit-source-id: d95720c177ac4bc8dcbe40362f19b279b3f8e708

Author: Ilango Purushothaman

proxygen/lib/transport/PersistentQuicPskCache.cpp

@@ -68,6 +68,14 @@ folly::Optional<quic::QuicCachedPsk> PersistentQuicPskCache::getPsk(
     uint8_t knobFrameSupport;
     fizz::detail::read(knobFrameSupport, cursor);
     quicCachedPsk.transportParams.knobFrameSupport = knobFrameSupport > 0;
+    uint8_t ackReceiveTimestampsEnabled;
+    fizz::detail::read(ackReceiveTimestampsEnabled, cursor);
+    quicCachedPsk.transportParams.ackReceiveTimestampsEnabled =
+        ackReceiveTimestampsEnabled > 0;
+    fizz::detail::read(quicCachedPsk.transportParams.maxReceiveTimestampsPerAck,
+                       cursor);
+    fizz::detail::read(quicCachedPsk.transportParams.receiveTimestampsExponent,
+                       cursor);
 
     std::unique_ptr<folly::IOBuf> appParams;
     fizz::detail::readBuf<uint16_t>(appParams, cursor);
@@ -110,6 +118,13 @@ void PersistentQuicPskCache::putPsk(const std::string& identity,
                       appender);
   uint8_t knobSupport = quicCachedPsk.transportParams.knobFrameSupport ? 1 : 0;
   fizz::detail::write(knobSupport, appender);
+  uint8_t ackReceiveTimestampsEnabled =
+      quicCachedPsk.transportParams.ackReceiveTimestampsEnabled ? 1 : 0;
+  fizz::detail::write(ackReceiveTimestampsEnabled, appender);
+  fizz::detail::write(quicCachedPsk.transportParams.maxReceiveTimestampsPerAck,
+                      appender);
+  fizz::detail::write(quicCachedPsk.transportParams.receiveTimestampsExponent,
+                      appender);
 
   fizz::detail::writeBuf<uint16_t>(
       folly::IOBuf::wrapBuffer(folly::StringPiece(quicCachedPsk.appParams)),

proxygen/lib/transport/test/PersistentQuicPskCacheTest.cpp

@@ -57,6 +57,9 @@ class PersistentQuicPskCacheTest : public Test {
     quicPsk1_.transportParams.initialMaxStreamsBidi = 234;
     quicPsk1_.transportParams.initialMaxStreamsUni = 123;
     quicPsk1_.transportParams.knobFrameSupport = true;
+    quicPsk1_.transportParams.ackReceiveTimestampsEnabled = true;
+    quicPsk1_.transportParams.maxReceiveTimestampsPerAck = 30;
+    quicPsk1_.transportParams.receiveTimestampsExponent = 0;
     quicPsk1_.appParams = "QPACK param";
 
     auto& fizzPsk2 = quicPsk2_.cachedPsk;
@@ -85,6 +88,9 @@ class PersistentQuicPskCacheTest : public Test {
     quicPsk2_.transportParams.initialMaxStreamsBidi = 2345;
     quicPsk2_.transportParams.initialMaxStreamsUni = 1233;
     quicPsk2_.transportParams.knobFrameSupport = false;
+    quicPsk1_.transportParams.ackReceiveTimestampsEnabled = false;
+    quicPsk1_.transportParams.maxReceiveTimestampsPerAck = 10;
+    quicPsk1_.transportParams.receiveTimestampsExponent = 0;
   }
 
   void TearDown() override {
@@ -142,6 +148,12 @@ static void expectMatch(const QuicCachedPsk& a, const QuicCachedPsk& b) {
   EXPECT_EQ(paramsA.initialMaxStreamsBidi, paramsB.initialMaxStreamsBidi);
   EXPECT_EQ(paramsA.initialMaxStreamsUni, paramsB.initialMaxStreamsUni);
   EXPECT_EQ(paramsA.knobFrameSupport, paramsB.knobFrameSupport);
+  EXPECT_EQ(paramsA.ackReceiveTimestampsEnabled,
+            paramsB.ackReceiveTimestampsEnabled);
+  EXPECT_EQ(paramsA.maxReceiveTimestampsPerAck,
+            paramsB.maxReceiveTimestampsPerAck);
+  EXPECT_EQ(paramsA.receiveTimestampsExponent,
+            paramsB.receiveTimestampsExponent);
 
   EXPECT_EQ(a.appParams, b.appParams);
 }