segmentation fault due to byte tag

[Suraj Kota]

HI,

Am using onoffapplication with tcpsocket factory. and inserting a byte tag in packet in onoffapplication's send function.
void OnOffApplication::SendPacket (){

...

Ptr<Packet> packet = Create<Packet> (m_pktSize+2);

m_pktSize+=2;

MyFlowTag1 tag;

tag.SetSimpleValue ((uint16_t)22);

packet->AddByteTag (tag);

...

}
When am inserting following code in ipv4-nix-vetor-routing route output function :

Ptr<Ipv4Route> 

Ipv4NixVectorRouting::RouteOutput (Ptr<Packet> p, const Ipv4Header &header, Ptr<NetDevice> oif, Socket::SocketErrno &sockerr){

...

MyFlowTag1 tagCopy;

bool found = p->FindFirstMatchingByteTag (tagCopy);

if (found)

  std::cout << (int)tagCopy.GetSimpleValue () << "hho"<<std::endl;

else

 std::cout << "tag not found" << std::endl;

...}  

For udpsocketfactoy the code runs for some time and then it aborts and for tcpsocket factory in gives segmentation fault error in the beginng itself.

I have attached gdb's backtrace output.
Can you get an idea what is the problem ?

[Tommaso Pecorella]

In RouteOutput you should check if the packet is there.

I.e.:

MyFlowTag1 tagCopy;
if (p)
{

  bool found = p->FindFirstMatchingByteTag (tagCopy);
  if (found)
    std::cout << (int)tagCopy.GetSimpleValue () << "hho"<<std::endl;
  else
   std::cout << "tag not found" << std::endl;
}

As a side note, your packets are growing in size. They'll reach the point to be cut, discarded or worse.

m_pktSize+=2;

Are you sure that this is your intended behaviour ?

T.

[Suraj K]

Hie Sir,

+=2 I was doing to see what is the outcome :P

(1) I have put many debug lines in the onoffhelper,cc and onoffapllication.cc but am not able to get the program flow, Can you give an idea about how it reaches send () in onoffapplication.cc and when is Onoffapplication's object created ?
InstallPriv installs a application then how is send() function called after that

like for example ,

OnOffHelper oo = OnOffHelper("ns3::TcpSocketFactory",Address(InetSocketAddress(Ipv4Address(add), port))); // ip address of server

               oo.SetAttribute("OnTime", StringValue("ns3::ConstantRandomVariable[Constant=1]"));

                oo.SetAttribute("OffTime", StringValue("ns3::ConstantRandomVariable[Constant=0]"));

                oo.SetAttribute("PacketSize",UintegerValue (packetSize));

                oo.SetAttribute("DataRate",StringValue (dataRate_OnOff));      

                oo.SetAttribute("MaxBytes",StringValue (maxBytes));

rand1=1;

rand2=0;

rand3=0;

                while (rand1== podRand && swRand == rand2 && (rand3+2) == hostRand){

                        rand1 = rand() % num_pod + 0;

                        rand2 = rand() % num_edge + 0;

                        rand3 = rand() % num_host + 0;

                } // to make sure that client and server are different

        // Install On/Off Application to the client

                NodeContainer onoff;

                onoff.Add(host[rand1][rand2].Get(rand3));

                app[i] = oo.Install (onoff);

How to insert a tag when tcp acknowledge comes back ? and make client work on my desired port no. ?

(2) I have made a traffic generator which will give a TCP traffic (plz see attachment), But I want to create client socket on my desired port no. Can this be done ?

and also, How to insert a tag when tcp acknowledge comes back ?

Am still trying to create a flow classifier only.

K SURAJ

Information Technology

NIT Raipur

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