From 55555cf13e10579b800a7e26f1849ae9659b843c Mon Sep 17 00:00:00 2001
From: Stephen Birarda <commit@birarda.com>
Date: Wed, 29 Jul 2015 15:28:20 -0700
Subject: [PATCH] setup default for RTT, RTT variance, _synInterval

---
 libraries/networking/src/udt/CongestionControl.cpp | 2 +-
 libraries/networking/src/udt/Connection.cpp        | 8 +++++++-
 libraries/networking/src/udt/Connection.h          | 5 +++--
 libraries/networking/src/udt/Constants.h           | 4 +++-
 4 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/libraries/networking/src/udt/CongestionControl.cpp b/libraries/networking/src/udt/CongestionControl.cpp
index 06b63ec60e..1450e60930 100644
--- a/libraries/networking/src/udt/CongestionControl.cpp
+++ b/libraries/networking/src/udt/CongestionControl.cpp
@@ -20,7 +20,7 @@ static const double USECS_PER_SECOND = 1000000.0;
 void DefaultCC::init() {
     _lastRCTime = high_resolution_clock::now();
     
-    _mss = udt::MAX_PACKET_SIZE;
+    _mss = udt::MAX_PACKET_SIZE_WITH_UDP_HEADER;
     
     _slowStartLastAck = _sendCurrSeqNum;
     _lastDecreaseMaxSeq = SequenceNumber { SequenceNumber::MAX };
diff --git a/libraries/networking/src/udt/Connection.cpp b/libraries/networking/src/udt/Connection.cpp
index 146714df10..39e4254895 100644
--- a/libraries/networking/src/udt/Connection.cpp
+++ b/libraries/networking/src/udt/Connection.cpp
@@ -30,6 +30,10 @@ Connection::Connection(Socket* parentSocket, HifiSockAddr destination, unique_pt
     _destination(destination),
     _congestionControl(move(congestionControl))
 {
+    // setup default SYN, RTT and RTT Variance based on the SYN interval in CongestionControl object
+    _synInterval = _congestionControl->synInterval();
+    _rtt = _synInterval * 10;
+    _rttVariance = _rtt / 2;
 }
 
 Connection::~Connection() {
@@ -126,7 +130,9 @@ void Connection::sendACK(bool wasCausedBySyncTimeout) {
     // pack in the RTT and variance
     ackPacket->writePrimitive(_rtt);
     
-    // pack the available buffer size - must be a minimum of 2
+    // pack the available buffer size, in packets
+    // in our implementation we have no hard limit on receive buffer size, send the default value
+    ackPacket->writePrimitive((int32_t) udt::CONNECTION_RECEIVE_BUFFER_SIZE_PACKETS);
     
     if (wasCausedBySyncTimeout) {
         // pack in the receive speed and estimatedBandwidth
diff --git a/libraries/networking/src/udt/Connection.h b/libraries/networking/src/udt/Connection.h
index b42ef0d8ea..d957339b9f 100644
--- a/libraries/networking/src/udt/Connection.h
+++ b/libraries/networking/src/udt/Connection.h
@@ -15,6 +15,7 @@
 #include <chrono>
 #include <memory>
 
+#include "Constants.h"
 #include "LossList.h"
 #include "PacketTimeWindow.h"
 #include "SendQueue.h"
@@ -61,7 +62,7 @@ private:
     
     int estimatedTimeout() const;
     
-    int _synInterval; // Periodical Rate Control Interval, in microseconds, defaults to 10ms
+    int _synInterval; // Periodical Rate Control Interval, in microseconds
     
     int _nakInterval; // NAK timeout interval, in microseconds
     int _minNAKInterval { 100000 }; // NAK timeout interval lower bound, default of 100ms
@@ -79,7 +80,7 @@ private:
     
     int32_t _rtt; // RTT, in microseconds
     int32_t _rttVariance; // RTT variance
-    int _flowWindowSize; // Flow control window size
+    int _flowWindowSize { udt::MAX_PACKETS_IN_FLIGHT }; // Flow control window size
     
     int _bandwidth { 1 }; // Exponential moving average for estimated bandwidth, in packets per second
     int _deliveryRate { 16 }; // Exponential moving average for receiver's receive rate, in packets per second
diff --git a/libraries/networking/src/udt/Constants.h b/libraries/networking/src/udt/Constants.h
index 5c5ba392a1..e8a7658bf9 100644
--- a/libraries/networking/src/udt/Constants.h
+++ b/libraries/networking/src/udt/Constants.h
@@ -15,12 +15,14 @@
 #define hifi_udt_Constants_h
 
 namespace udt {
-    static const int MAX_PACKET_SIZE = 1450;
+    static const int MAX_PACKET_SIZE_WITH_UDP_HEADER = 1500;
+    static const int MAX_PACKET_SIZE = MAX_PACKET_SIZE_WITH_UDP_HEADER - 28;
     static const int MAX_PACKETS_IN_FLIGHT = 25600;
     static const int CONNECTION_RECEIVE_BUFFER_SIZE_PACKETS = 8192;
     static const int CONNECTION_SEND_BUFFER_SIZE_PACKETS = 8192;
     static const int UDP_SEND_BUFFER_SIZE_BYTES = 1048576;
     static const int UDP_RECEIVE_BUFFER_SIZE_BYTES = 1048576;
+    static const int DEFAULT_SYN_INTERVAL_USECS = 10 * 1000;
 }
 
 #endif // hifi_udt_Constants_h