How to generate openflow pcaps?

[Kam]

Hi,

I am a NS3 newbie. I am trying to understand the Openflow example script(openflow-switch.cc)

I enabled pcap tracing in the example but do not see any Openflow messages in the pcap(using wireshark and tcpdump):

  //

  // Also configure some tcpdump traces; each interface will be traced.

  // The output files will be named:

  //     openflow-switch-<nodeId>-<interfaceId>.pcap

  // and can be read by the "tcpdump -r" command (use "-tt" option to

  // display timestamps correctly)

  //

  csma.EnablePcapAll ("openflow-switch", false);

Am I doing something wrong?  Is Pcap tracing not supported for Openflow messages in NS3?

Please help!