Wireshark-users: Re: [Wireshark-users] transparent GTP-'detunneling' in wireshark

From: Guy Harris <guy@xxxxxxxxxxxx>
Date: Sun, 19 Oct 2008 10:55:13 -0700

On Oct 19, 2008, at 2:55 AM, Ariel Burbaickij wrote:

Now, I want to get only SMTP traffic from my monitoring interface that flows inside GTP tunnel -- do you say that something like gtp&&smtp should work
towards this end?

It will work to the extent that, if the traffic weren't tunneled inside GTP, just "smtp" would have worked.

For example, if an SMTP request or reply is split over multiple TCP segments, and reassembly is being done, I'm not sure it'd work in either case, as all but the last TCP segment would probably be dissected only as TCP, not as SMTP, and would not be matched by the filter "smtp". That's not a tunneling issue, however.