From bc8554fd9045c6d816492071079276754b3190aa Mon Sep 17 00:00:00 2001
From: Atlante45 <clement.brisset@gmail.com>
Date: Wed, 19 Oct 2016 13:31:00 -0700
Subject: [PATCH] Fix sequence number race condition

---
 libraries/networking/src/udt/Socket.cpp | 8 +++++++-
 libraries/networking/src/udt/Socket.h   | 9 ++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/libraries/networking/src/udt/Socket.cpp b/libraries/networking/src/udt/Socket.cpp
index 16a1bd1639..6dddf50e0a 100644
--- a/libraries/networking/src/udt/Socket.cpp
+++ b/libraries/networking/src/udt/Socket.cpp
@@ -118,8 +118,14 @@ qint64 Socket::writeBasePacket(const udt::BasePacket& packet, const HifiSockAddr
 qint64 Socket::writePacket(const Packet& packet, const HifiSockAddr& sockAddr) {
     Q_ASSERT_X(!packet.isReliable(), "Socket::writePacket", "Cannot send a reliable packet unreliably");
 
+    SequenceNumber sequenceNumber;
+    {
+        Lock lock(_unreliableSequenceNumbersMutex);
+        sequenceNumber = ++_unreliableSequenceNumbers[sockAddr];
+    }
+
     // write the correct sequence number to the Packet here
-    packet.writeSequenceNumber(++_unreliableSequenceNumbers[sockAddr]);
+    packet.writeSequenceNumber(sequenceNumber);
 
     return writeDatagram(packet.getData(), packet.getDataSize(), sockAddr);
 }
diff --git a/libraries/networking/src/udt/Socket.h b/libraries/networking/src/udt/Socket.h
index cced0c53df..2a6d119b64 100644
--- a/libraries/networking/src/udt/Socket.h
+++ b/libraries/networking/src/udt/Socket.h
@@ -16,6 +16,7 @@
 
 #include <functional>
 #include <unordered_map>
+#include <mutex>
 
 #include <QtCore/QObject>
 #include <QtCore/QTimer>
@@ -46,6 +47,10 @@ using MessageFailureHandler = std::function<void(HifiSockAddr, udt::Packet::Mess
 
 class Socket : public QObject {
     Q_OBJECT
+
+    using Mutex = std::mutex;
+    using Lock = std::unique_lock<Mutex>;
+
 public:
     using StatsVector = std::vector<std::pair<HifiSockAddr, ConnectionStats::Stats>>;
     
@@ -121,7 +126,9 @@ private:
     MessageHandler _messageHandler;
     MessageFailureHandler _messageFailureHandler;
     ConnectionCreationFilterOperator _connectionCreationFilterOperator;
-    
+
+    Mutex _unreliableSequenceNumbersMutex;
+
     std::unordered_map<HifiSockAddr, BasePacketHandler> _unfilteredHandlers;
     std::unordered_map<HifiSockAddr, SequenceNumber> _unreliableSequenceNumbers;
     std::unordered_map<HifiSockAddr, std::unique_ptr<Connection>> _connectionsHash;