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Wireshark-dev: Re: [Wireshark-dev] Modbus/TCP hookup for subdissector

From: Anders Broman <anders.broman@xxxxxxxxxxxx>
Date: Fri, 25 Mar 2011 17:17:44 +0100
 

-----Original Message-----
From: wireshark-dev-bounces@xxxxxxxxxxxxx [mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] On Behalf Of Roland Knall
Sent: den 25 mars 2011 17:10
To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] Modbus/TCP hookup for subdissector

Am 25.03.2011 um 17:06 schrieb Chris Maynard <chris.maynard@xxxxxxxxx>:

> Roland Knall <rknall@...> writes:
>
>> 1. Is there a way to provide additional information to the 
>> subdissector? Someone could use private_data, but that field I need 
>> somewhere else, therefore can not be used here.
>
> I haven't looked at the patch or anything, but I just wanted to 
> comment on this part.  If you want/need to use the private data, you 
> can do what several dissectors do and save a pointer to the current 
> private_data before replacing the pinfo->private_data with your own, then restore the original afterwards.
> One example is packet-http.c, but there are others.  (search for
> "save_private_data")

I thought of that. But the main argument against the use of the private data would be, that the subdissector isn't expecting the data in that place.

Anyway, I do not need the functionality anyway, just thought that there should be a way of dealing with such cases.

kind regards,
Roland

What type of information does the subdisector need? Glancing at the patch it looks like you might as well
Call the subdisector via a handle as it will allways be called(if present)
If it's using the function code you could use a uint table registering for the function code(s)

Regards
Anders
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