Disable Ack Receive Timestamps based on hostname

Summary:
Added the capability to disable Ack receive timestamps based on hostname.
We want to disable timestamps on dynamic content (graph.facebook.com, i.instagram.com etc) to reduce network and resource overhead (thereby saving uplink BW). The hostnames can be specified via a MC. Timestamps should still be enabled for hostnames serving static content (like video, fbcdn...)

We have observed upto 40% more duplicate timestamps being sent on ACKs and ACK packet size has increased by more than 30% on average for such cases. This is a first step in reducing ACK wastage.

(Note: this ignores all push blocking failures!)

Reviewed By: jbeshay

Differential Revision: D48812624

fbshipit-source-id: aa72ec2dcc41ebe9d982364d8d45739e062daddb

quic/api/QuicTransportBase.cpp

@@ -2833,6 +2833,13 @@ void QuicTransportBase::setSupportedVersions(
   conn_->supportedVersions = versions;
 }
 
+void QuicTransportBase::setAckRxTimestampsDisabled(
+    bool disableAckRxTimestamps) {
+  if (disableAckRxTimestamps) {
+    conn_->transportSettings.maybeAckReceiveTimestampsConfigSentToPeer.clear();
+  }
+}
+
 void QuicTransportBase::setConnectionSetupCallback(
     ConnectionSetupCallback* callback) {
   connSetupCallback_ = callback;

quic/api/QuicTransportBase.h

@@ -238,6 +238,8 @@ class QuicTransportBase : public QuicSocket, QuicStreamPrioritiesObserver {
 
   virtual void setSupportedVersions(const std::vector<QuicVersion>& versions);
 
+  virtual void setAckRxTimestampsDisabled(bool disableAckRxTimestamps);
+
   void setConnectionSetupCallback(ConnectionSetupCallback* callback) final;
 
   void setConnectionCallback(ConnectionCallback* callback) final;