Subject: Re: bpf, net80211 and FCS
To: David Young <dyoung@pobox.com>
From: Eric Auge <eau@phear.org>
List: tech-net
Date: 06/03/2005 09:35:10
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David Young wrote:
> Eric,
> 
> The FCS is ordinarily stripped before BPF-tapping because apps do not
> expect for it to be present.  For your app, consider using radiotap
> (DLT_IEEE802_11_RADIO).  The radiotap header may contain a flag,
> IEEE80211_RADIOTAP_F_FCS, that tells whether there is an FCS in the last
> four bytes of a tapped frame.

hmm ok i missed something then...thanks for information.

> 
> All 802.11 NICs check the FCS.  Most NICs will indicate to the driver
> whether the FCS was correct or not.  The radiotap header was designed
> to carry that kind of "meta-information" about frames.  If you were
> so inclined, you could modify the drivers to set a "FCS (in)correct"
> flag in the radiotap header, and submit a patch. :-)

right, I first wanted to ask if I was not missing something obvious,
and to get an idea of a clean patch, which you gave.

I'll do one and submit here for review, or should I send-pr ?

Thanks for your help,
Regards,
Eric.
> 
> Dave
> 

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