From 1b322c8d015fd59a657e71c4aa88b4949c5df0f1 Mon Sep 17 00:00:00 2001
From: Stephen Birarda <commit@birarda.com>
Date: Wed, 23 Mar 2016 18:07:28 -0700
Subject: [PATCH] don't oversend because of packet pairs

---
 libraries/networking/src/udt/SendQueue.cpp | 21 ++++++++++++++-------
 libraries/networking/src/udt/SendQueue.h   |  2 +-
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/libraries/networking/src/udt/SendQueue.cpp b/libraries/networking/src/udt/SendQueue.cpp
index 2c3303537c..30c9f2f491 100644
--- a/libraries/networking/src/udt/SendQueue.cpp
+++ b/libraries/networking/src/udt/SendQueue.cpp
@@ -306,8 +306,10 @@ void SendQueue::run() {
         
         // if we didn't find a packet to re-send AND we think we can fit a new packet on the wire
         // (this is according to the current flow window size) then we send out a new packet
+        auto newPacketCount = 0;
         if (!attemptedToSendPacket) {
-            attemptedToSendPacket = maybeSendNewPacket();
+            newPacketCount = maybeSendNewPacket();
+            attemptedToSendPacket = (newPacketCount > 0);
         }
         
         // since we're a while loop, give the thread a chance to process events
@@ -322,7 +324,8 @@ void SendQueue::run() {
         }
 
         // push the next packet timestamp forwards by the current packet send period
-        nextPacketTimestamp += std::chrono::microseconds(_packetSendPeriod);
+        auto nextPacketDelta = (newPacketCount == 2 ? 2 : 1) * _packetSendPeriod;
+        nextPacketTimestamp += std::chrono::microseconds(nextPacketDelta);
 
         // sleep as long as we need until next packet send, if we can
         const auto timeToSleep = duration_cast<microseconds>(nextPacketTimestamp - p_high_resolution_clock::now());
@@ -331,7 +334,7 @@ void SendQueue::run() {
     }
 }
 
-bool SendQueue::maybeSendNewPacket() {
+int SendQueue::maybeSendNewPacket() {
     if (!isFlowWindowFull()) {
         // we didn't re-send a packet, so time to send a new one
         
@@ -366,14 +369,18 @@ bool SendQueue::maybeSendNewPacket() {
                     static auto pairTailPacket = ControlPacket::create(ControlPacket::ProbeTail);
                     _socket->writeBasePacket(*pairTailPacket, _destination);
                 }
-            }
 
-            // We attempted to send packet(s), return here
-            return true;
+                // we attempted to send two packets, return 2
+                return 2;
+            } else {
+                // we attempted to send a single packet, return 1
+                return 1;
+            }
         }
     }
+    
     // No packets were sent
-    return false;
+    return 0;
 }
 
 bool SendQueue::maybeResendPacket() {
diff --git a/libraries/networking/src/udt/SendQueue.h b/libraries/networking/src/udt/SendQueue.h
index dc151e9f4d..77c7f3e85e 100644
--- a/libraries/networking/src/udt/SendQueue.h
+++ b/libraries/networking/src/udt/SendQueue.h
@@ -95,7 +95,7 @@ private:
     int sendPacket(const Packet& packet);
     bool sendNewPacketAndAddToSentList(std::unique_ptr<Packet> newPacket, SequenceNumber sequenceNumber);
     
-    bool maybeSendNewPacket(); // Figures out what packet to send next
+    int maybeSendNewPacket(); // Figures out what packet to send next
     bool maybeResendPacket(); // Determines whether to resend a packet and which one
     
     bool isInactive(bool attemptedToSendPacket);