On Sat, 10 Nov 2001, Bryan D. Payne wrote:

> > You don't need to put the card in AP mode to transmit raw 802.11 frames. I
>
> Really? How else could I do it? I thought that, if the card wasn't in ap
> mode, it would simply take 802.3 frames and convert the link layer to
> 802.11 "on the fly" and then send out the packet. Thus, you wouldn't be
> able to control the 802.11 link layer. Am I missing something?

If you change TXCTL_802_3 to TXCTL_802_11 in the "txControl = ..." line
the driver will take raw 802.11 frames instead of 802.3 frames (and you
will break all protocol stacks :-)

> > haven't implemented that functionality because the upper layers doesn't
> > know how to handle an 802.11 device and I haven't figured out how
> > to keep the card looking as an standard 802.3 device for some applications
> > and as an 802.11 device for others. I need to find out how to do that
> > without rewriting the whole API :-)
>
> Hmmm...good point. Though this may not be a problem for the application
> that I have in mind (see below).
>
> > OTOH, I haven't seen an application for that feature. It may be useful for
> > implementing the AP functionality, but I don't have enough equipment for
> > doing (testing) that development.
>
> I'm working in a wireless security research group at Univ of Maryland at
> College Park. So we have a fair ammount of equipment to test with and
> such...
>
> What we would like to do with this functionality is to write a libnet API
> that could write aribrary 802.11 frames for us. Then, using this library,
> we could essentially build an access point. This would be a little
> different than using a prism II card as an AP, because with those cards
> you wouldn't have fine grained control over things like beacon frequency
> and such (which would be nice for research purposes).

That should be great, but the problem is that, while doing that, the
standard connectivity should be maintained, so the problem is being able
to open a raw (802.11) socket to the interface while maintaining the rest
of the system (the protocol stack and other sockets) transmitting in 802.3
mode. For an internal application disabling that function shouldn't be a
problem, but there's something that needs to be fixed in a general purpose
driver.

OTOH, switching the card to AP mode activates a limited AP functionality
within the firmware, so I think there isn't a need of implementing the
full AP functionality in an user space app. The problem I have with that
is that there is no documentation about all this and I cannot test it due
to the lack of equipment. If you feel you can work on this, I can help
with it. Keep in mind that being able to transmit 802.11 frames without
switching to AP mode won't allow you to implement an AP as the card will
still be trying to associate to an AP.

Javier Achirica

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