Converting Openflow packet into Ptr<Packet>

[Kam]

Hello ns3 community,

I am working on a project, where I am trying to study GTPU processing in an Openflow controller.

I have a topology where LTE EPC traffic would go through an Openflow switch.

I am trying to modify the following function in openflow/model/openflow-interface.cc

LearningController::ReceiveFromSwitch (Ptr<OpenFlowSwitchNetDevice> swtch, ofpbuf* buffer) {

     ofp_packet_in * opi = (ofp_packet_in*)ofpbuf_try_pull (buffer, offsetof (ofp_packet_in, data));

     Ptr<Packet> pkt = Create<Packet>(opi->data, opi->header.length); 

     // extract the GTPU header and print it

     int removed = pkt->RemoveHeader (gtpu);

     printf ("GTPU Header length: %d\n", removed);

     gtpu.Print(std::cout << "GTPU Header Info: \n");  

}

Now after extracting the GTPU header, when I print it, I get all garbage data:

GTPU Header Info:  version=0 [], messageType=0, length=0, teid=65536, sequenceNumber=0, nPduNumber=0, nextExtensionType=8

I instrumented epc-enb-application.cc, which is generating this packet(in Uplink) and this is the kind of GTPU header that I should be getting:

Epc Enb Application GTPU Header Info:   version=1 [ PT  S  PN ], messageType=255, length=1056, teid=1, sequenceNumber=1, nPduNumber=0, nextExtensionType=0

Questions:

- How to cast ofp_packet_in into Ptr<Packet> ??? Is the Packet initialization im doing incorrect?

- Does the data portion of ofp_packet_in (ofp_packet_in->data) start at the GTPU header as I am expecting?

Please any help from the community would be greatly appreciated as I am completely stumped :(

Kind Regards,
Kam