From 8c57d477dbc7515adabbdbe5bc77dbb0b9a18ca5 Mon Sep 17 00:00:00 2001
From: Martin Regen <mregen@microsoft.com>
Date: Mon, 9 Oct 2017 15:27:22 +0200
Subject: [PATCH] fix a race condition during connect, when both addresses
 return quickly with an error condition TaskCompletionSource could be signaled
 twice, causing an exception.

Fix: Advance connection counters before connecting
---
 Stack/Opc.Ua.Core/Stack/Tcp/TcpMessageSocket.cs | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/Stack/Opc.Ua.Core/Stack/Tcp/TcpMessageSocket.cs b/Stack/Opc.Ua.Core/Stack/Tcp/TcpMessageSocket.cs
index b52273af5c..fe7ac68258 100644
--- a/Stack/Opc.Ua.Core/Stack/Tcp/TcpMessageSocket.cs
+++ b/Stack/Opc.Ua.Core/Stack/Tcp/TcpMessageSocket.cs
@@ -361,6 +361,17 @@ namespace Opc.Ua.Bindings
             do
             {
                 error = SocketError.NotInitialized;
+
+                lock (m_socketLock)
+                {
+                    if (addressesV6.Length > arrayV6Index)
+                        m_socketResponses++;
+                    if (addressesV4.Length > arrayV4Index)
+                        m_socketResponses++;
+                    if (m_tcs.Task.IsCompleted)
+                        m_tcs = new TaskCompletionSource<SocketError>();
+                }
+
                 if (addressesV6.Length > arrayV6Index && m_socket == null)
                 {
                     if (BeginConnect(addressesV6[arrayV6Index], AddressFamily.InterNetworkV6, port, doCallback) == SocketError.Success)
@@ -394,7 +405,6 @@ namespace Opc.Ua.Bindings
                         case SocketError.Success:
                             return true;
                         case SocketError.ConnectionRefused:
-                            m_tcs = new TaskCompletionSource<SocketError>();
                             break;
                         default:
                             goto ErrorExit;
@@ -699,10 +709,6 @@ namespace Opc.Ua.Bindings
                 RemoteEndPoint = new IPEndPoint(address, port),
             };
             args.Completed += new EventHandler<SocketAsyncEventArgs>(OnSocketConnected);
-            lock (m_socketLock)
-            {
-                m_socketResponses++;
-            }
             if (!socket.ConnectAsync(args))
             {
                 // I/O completed synchronously