Wireshark-users: Re: [Wireshark-users] Display filter for TCP reserved field

From: Marco S. Zuppone <msz@xxxxxx>
Date: Wed, 29 Sep 2010 22:41:53 +0100
Hello,

thanks a lot for your reply! A curiosity:
have you, in your professional experience, ever found a traffic where the reserved field was not 0000 ??
I noticed that in WireShark 1.4 is possible to write a dissector with LUA...is this working well? Seems a great feature to me!
 Thanks a lot!! 
Regards,
Marco S. Zuppone
On 29 Sep 2010, at 17:37, Stephen Fisher wrote:

> On Wed, Sep 29, 2010 at 05:17:50PM +0100, Marco Simone Zuppone wrote:
> 
>> I was wondering how is the best way (if any) to create a filter about 
>> the reserved ( 4 bits between bit 100 and 104 ) field of the TCP 
>> packet. The expression as tcp[n:y] == are interesting but n and y are 
>> expressed in byte and not in bit.
> 
> I recently changed the TCP dissector to show the nonce flag and the 
> three reserved bits as separate filterable fields.  That change is only 
> in the development 1.5.x branch from SVN though.  If you want, you can 
> download the lastest automated release from 
> http://www.wireshark.org/download/automated/ and use the "tcp.flags.res" 
> field.
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