tcp: (fixes #2285) Loss of ack of SYN can cause improper setup

RELEASE_NOTES

@@ -42,6 +42,7 @@ Bugs fixed
 - Bug 2248 - tcp: TCP SACK added after reviews
 - Bug 2256 - tcp: bytes in flight now updated in TcpTxBuffer
 - Bug 2263 - Support processing of multiple TCP options
+- Bug 2285 - tcp: Loss of ack of SYN can cause improper connection setup
 - Bug 2367 - BlockAckManager does not remove iterators to freed items
 - Bug 2450 - LogDistancePropagationLossModel is not continuous
 - Bug 2463 - create trace source to trace the TXOP time that is actually used

src/internet/model/tcp-socket-base.cc

@@ -1996,8 +1996,8 @@ TcpSocketBase::ProcessSynRcvd (Ptr<Packet> packet, const TcpHeader& tcpHeader,
       // Always respond to first data packet to speed up the connection.
       // Remove to get the behaviour of old NS-3 code.
       m_delAckCount = m_delAckMaxCount;
-      ReceivedAck (packet, tcpHeader);
       NotifyNewConnectionCreated (this, fromAddress);
+      ReceivedAck (packet, tcpHeader);
       // As this connection is established, the socket is available to send data now
       if (GetTxAvailable () > 0)
         {
@@ -2027,6 +2027,7 @@ TcpSocketBase::ProcessSynRcvd (Ptr<Packet> packet, const TcpHeader& tcpHeader,
               m_endPoint6->SetPeer (Inet6SocketAddress::ConvertFrom (fromAddress).GetIpv6 (),
                                     Inet6SocketAddress::ConvertFrom (fromAddress).GetPort ());
             }
+          NotifyNewConnectionCreated (this, fromAddress);
           PeerClose (packet, tcpHeader);
         }
     }