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Wireshark-dev: Re: [Wireshark-dev] clarification on 802.11 dissector

From: Richard Sharpe <realrichardsharpe@xxxxxxxxx>
Date: Wed, 5 Dec 2018 07:04:25 -0800
On Wed, Dec 5, 2018 at 6:47 AM francisco javier sanchez-roselly
<franciscojavier.sanchezroselly@xxxxxxxx> wrote:
>
> hi All, i am checking some 802.11 frames and i have two doubts taking into account 802.11-2016 standard.
>
> the first one has to do with To DS and From DS bits. the dissector groups these bits as a ‘DS status’ field not defined in the standard. the meaning is clear, but in my opinion, this association breaks the endianness criterion for the rest of the frame fields.

The code dealing with those two fields was likely written well before
IEEE80211-2016 or even IEEE80211-2012 were written. The standard may
have changed in that area.

> my other suggestion refers to FCS field, as standard says the general convention is not followed for this field, and the highest order term is transmited first.

I think you have misunderstood and perhaps you are looking at the way
we write the fields in a frame from left to right. The lowest order
bit of each field is first on the wire, and the frames will generally
be laid out in memory with the left most fields in the lowest
addresses. On little endian systems the lowest order bytes will be in
the lower addresses as well.

> please ask you to guide me if i am missing something. otherwise, i will be glad to contribute with any change in the code.
>
> thanks, regards.
>
> francisco javier sanchez-roselly
>
>
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-- 
Regards,
Richard Sharpe
(何以解憂?唯有杜康。--曹操)(传说杜康是酒的发明者)