Wireshark-dev: [Wireshark-dev] what parameters for dissector_add() for a non-nested protocol
Date: Mon, 16 Jul 2007 10:02:37 -0400
I've scoured the READMEs and dissectors for details on the parameters
for disector_add().  It seems as though all the cases are different
than my (simple) case, so I'm at a loss as to how to register my
sub-protocol, so it gets called properly.

I have a private WTAP type for which I have written a simple dissector.
(so far so good)  In that dissector it looks at some data in
'pinfo->psuedo_header->acn.proto' that I use to figure out what
dissector to call next... Ie.  call_dissector(ipars_handle, tvb, pinfo,
tree);
For example:

if (pinfo->psuedo_header->acn.proto == 0x5) {
  call_dissector(ipars_handle, tvb, pinfo, tree);
}

But when wireshark tries to call my (sub)dissector I get the error:

  Err  file packet.c: line 1710 (call_dissector): assertion failed: (handle
!= NULL)

Thats because right now I'm missing the dissector_add() in my
(sub)dissector
... because I don't know what to code in my case.



The normal approach is to have (for a frame level dissector):

  dissector_add("wtap_encap", WTAP_ENCAP_MYTYPE, mytype_handle);

OR something like this for a nested dissector (where its based
on data in the super-frame (I think)):

  dissector_add("ip.proto", SOME_INDICATOR, mytype_handle);


But I in my case, my (sub)dissector protocol isn't a WTAP type,
nor is it (really) sub-protocol of a super-frame type (in my
first scenario).  Yes, it can also be found in all sorts of
other encapsulations (that I'm not going to disect right now)
but this is the primary case.

What I think I want to is something like:

  dissector_add("", NULL, mytype_handle);

just to make it aribitrarily available for that explicit call.

When I code later dissector, I'll probably have more dissector_add()
entries that _are_ based on super-frame data, but not right now.

Either my approach is wrong, or I'm just missing something...
Any ideas ?

TIA
Fulko



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