Cache the negotiated config for ACKs once the transport parameters are received

Summary: Cache the negotiated config for what ACK type to write and which fields to use once the peer transport parameters are available. This avoids computing the config with every ack frame being written.

Reviewed By: sharmafb

Differential Revision: D70004436

fbshipit-source-id: 79354f5137c77353c3a97d4c41782a700622e986

quic/api/QuicTransportFunctions.cpp

@@ -2131,4 +2131,35 @@ void maybeScheduleAckForCongestionFeedback(
   }
 }
 
+void updateNegotiatedAckFeatures(QuicConnectionStateBase& conn) {
+  bool isAckReceiveTimestampsSupported =
+      conn.transportSettings.maybeAckReceiveTimestampsConfigSentToPeer &&
+      conn.maybePeerAckReceiveTimestampsConfig;
+
+  uint64_t peerRequestedTimestampsCount =
+      conn.maybePeerAckReceiveTimestampsConfig.has_value()
+      ? conn.maybePeerAckReceiveTimestampsConfig.value()
+            .maxReceiveTimestampsPerAck
+      : 0;
+
+  conn.negotiatedAckReceiveTimestampSupport =
+      isAckReceiveTimestampsSupported && (peerRequestedTimestampsCount > 0);
+
+  conn.negotiatedExtendedAckFeatures = conn.peerAdvertisedExtendedAckFeatures &
+      conn.transportSettings.enableExtendedAckFeatures;
+  // Disable the ECN fields if we are not reading them
+  if (!conn.transportSettings.readEcnOnIngress) {
+    conn.negotiatedExtendedAckFeatures &=
+        ~static_cast<ExtendedAckFeatureMaskType>(
+            ExtendedAckFeatureMask::ECN_COUNTS);
+  }
+  // Disable the receive timestamps fields if we have not regoatiated receive
+  // timestamps support
+  if (!conn.negotiatedAckReceiveTimestampSupport) {
+    conn.negotiatedExtendedAckFeatures &=
+        ~static_cast<ExtendedAckFeatureMaskType>(
+            ExtendedAckFeatureMask::RECEIVE_TIMESTAMPS);
+  }
+}
+
 } // namespace quic