grab earliest possible receive time in socket

libraries/networking/src/udt/BasePacket.h

@@ -18,6 +18,8 @@
 
 #include <QtCore/QIODevice>
 
+#include <PortableHighResolutionClock.h>
+
 #include "../HifiSockAddr.h"
 #include "Constants.h"
 
@@ -80,6 +82,9 @@ public:
 
     qint64 writeString(const QString& string);
     QString readString();
+
+    void setReceiveTime(p_high_resolution_clock::time_point receiveTime) { _receiveTime = receiveTime; }
+    p_high_resolution_clock::time_point getReceiveTime() const { return _receiveTime; }
    
     template<typename T> qint64 peekPrimitive(T* data);
     template<typename T> qint64 readPrimitive(T* data);
@@ -108,6 +113,8 @@ protected:
     qint64 _payloadSize = 0;          // How much of the payload is actually used
     
     HifiSockAddr _senderSockAddr;  // sender address for packet (only used on receiving end)
+
+    p_high_resolution_clock::time_point _receiveTime; // captures the time the packet received (only used on receiving end)
 };
 
 template<typename T> qint64 BasePacket::peekPrimitive(T* data) {

libraries/networking/src/udt/CongestionControl.cpp

@@ -49,7 +49,7 @@ DefaultCC::DefaultCC() :
     setPacketSendPeriod(1.0);
 }
 
-bool DefaultCC::onACK(SequenceNumber ackNum) {
+bool DefaultCC::onACK(SequenceNumber ackNum, p_high_resolution_clock::time_point receiveTime) {
     double increase = 0;
     
     // Note from UDT original code:

libraries/networking/src/udt/CongestionControl.h

@@ -40,7 +40,7 @@ public:
     void setMaxBandwidth(int maxBandwidth);
 
     virtual void init() {}
-    virtual bool onACK(SequenceNumber ackNum) { return false; }
+    virtual bool onACK(SequenceNumber ackNum, p_high_resolution_clock::time_point receiveTime) { return false; }
     virtual void onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {}
     virtual void onTimeout() {}
 
@@ -107,7 +107,7 @@ public:
     DefaultCC();
     
 public:
-    virtual bool onACK(SequenceNumber ackNum) override;
+    virtual bool onACK(SequenceNumber ackNum, p_high_resolution_clock::time_point receiveTime) override;
     virtual void onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) override;
     virtual void onTimeout() override;
 

libraries/networking/src/udt/Connection.cpp

@@ -690,8 +690,8 @@ void Connection::processACK(ControlPacketPointer controlPacket) {
     }
     
     // give this ACK to the congestion control and update the send queue parameters
-    updateCongestionControlAndSendQueue([this, ack](){
-        if (_congestionControl->onACK(ack)) {
+    updateCongestionControlAndSendQueue([this, ack, &controlPacket](){
+        if (_congestionControl->onACK(ack, controlPacket->getReceiveTime())) {
             // the congestion control has told us it needs a fast re-transmit of ack + 1, add that now
             _sendQueue->fastRetransmit(ack + 1);
         }

libraries/networking/src/udt/SendQueue.cpp

@@ -258,7 +258,7 @@ bool SendQueue::sendNewPacketAndAddToSentList(std::unique_ptr<Packet> newPacket,
     auto payloadSize = newPacket->getPayloadSize();
     
     auto bytesWritten = sendPacket(*newPacket);
-    
+
     emit packetSent(packetSize, payloadSize, sequenceNumber, p_high_resolution_clock::now());
 
     {

libraries/networking/src/udt/Socket.cpp

@@ -305,12 +305,16 @@ void Socket::readPendingDatagrams() {
             continue;
         }
 
+        // grab a time point we can mark as the receive time of this packet
+        auto receiveTime = p_high_resolution_clock::now();
+
         auto it = _unfilteredHandlers.find(senderSockAddr);
 
         if (it != _unfilteredHandlers.end()) {
             // we have a registered unfiltered handler for this HifiSockAddr - call that and return
             if (it->second) {
                 auto basePacket = BasePacket::fromReceivedPacket(std::move(buffer), packetSizeWithHeader, senderSockAddr);
+                basePacket->setReceiveTime(receiveTime);
                 it->second(std::move(basePacket));
             }
 
@@ -323,6 +327,7 @@ void Socket::readPendingDatagrams() {
         if (isControlPacket) {
             // setup a control packet from the data we just read
             auto controlPacket = ControlPacket::fromReceivedPacket(std::move(buffer), packetSizeWithHeader, senderSockAddr);
+            controlPacket->setReceiveTime(receiveTime);
 
             // move this control packet to the matching connection, if there is one
             auto connection = findOrCreateConnection(senderSockAddr);
@@ -334,6 +339,7 @@ void Socket::readPendingDatagrams() {
         } else {
             // setup a Packet from the data we just read
             auto packet = Packet::fromReceivedPacket(std::move(buffer), packetSizeWithHeader, senderSockAddr);
+            packet->setReceiveTime(receiveTime);
 
             // call our verification operator to see if this packet is verified
             if (!_packetFilterOperator || _packetFilterOperator(*packet)) {

libraries/networking/src/udt/TCPVegasCC.cpp

@@ -24,14 +24,13 @@ TCPVegasCC::TCPVegasCC() {
     setAckInterval(1); // TCP sends an ACK for every packet received
 }
 
-bool TCPVegasCC::onACK(SequenceNumber ack) {
+bool TCPVegasCC::onACK(SequenceNumber ack, p_high_resolution_clock::time_point receiveTime) {
     auto it = _sentPacketTimes.find(ack);
 
     if (it != _sentPacketTimes.end()) {
 
-        // calculate the RTT (time now - time ACK sent)
-        auto now = p_high_resolution_clock::now();
-        int lastRTT = duration_cast<microseconds>(now - it->second.first).count();
+        // calculate the RTT (receive time - time ACK sent)
+        int lastRTT = duration_cast<microseconds>(receiveTime - it->second.first).count();
 
         if (lastRTT < 0) {
             Q_ASSERT_X(false, "TCPVegasCC::onACK", "calculated an RTT that is not > 0");
@@ -61,7 +60,7 @@ bool TCPVegasCC::onACK(SequenceNumber ack) {
         // find the min RTT during the last RTT
         _currentMinRTT = std::min(_currentMinRTT, lastRTT);
 
-        auto sinceLastAdjustment = duration_cast<microseconds>(now - _lastAdjustmentTime).count();
+        auto sinceLastAdjustment = duration_cast<microseconds>(p_high_resolution_clock::now() - _lastAdjustmentTime).count();
         if (sinceLastAdjustment >= _ewmaRTT) {
             performCongestionAvoidance(ack);
         }

libraries/networking/src/udt/TCPVegasCC.h

@@ -27,7 +27,7 @@ public:
     TCPVegasCC();
 
 public:
-    virtual bool onACK(SequenceNumber ackNum) override;
+    virtual bool onACK(SequenceNumber ackNum, p_high_resolution_clock::time_point receiveTime) override;
     virtual void onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) override {};
     virtual void onTimeout() override {};