Subject: Re: access point list from Lucent wireless cards
To: Andrew Brown <>
From: Bill Studenmund <>
List: current-users
Date: 09/20/2001 12:28:03
On Fri, 21 Sep 2001, Andrew Brown wrote:

> >The concensus I'd heard when I asked the right way to do this was that
> >we'd need to teach bpf about 802.11 frames, i.e. DLT_IEEE80211. I'm not
> >sure how a bpf user would say it wanted to get one or the other.
> off the top of my head, i'd suggest that the default action be to
> receive ethernet frames from the bpf, but provide an ioctl to switch
> to the 802.11 format if you want it.  that ought to provide for total
> backwards compatibility very easily.  imagine, if you will, a
> companion ioctl to BIOCGDLT called BIOCSDLT that can set a bpf
> attached to an 802.11 interface into DLT_IEEE80211?

That would be a good userland way to do it. The other half of my question
is how do we do this in the kernel? Will the bpf system deal with
different kinds of packets coming up to it? Also, since the only consumer
(other than the driver) of 802.11 frames at the moment would be bpf, it'd
be nice to know when we should and shouldn't generate 802.11 frames.

> the more fun project with be the one that allows you to switch from
> regular packets to raw, unencrypted, 802.11 frames (with the caveat,
> of course, that while you are doing this you can't use the interface
> for anything else).


Take care,