Sean Doran wrote:
> [this is only marginally related to the problems i was having
> last weekend; we tried a test setup in CPH on an alpha -current,
> with tlp(4) onboard, and a wi(4).  unfortunately, this didn't
> work as a way of reproducing the data corruption problem...]
> 
> bridge(4) says:
> 
>      A bridge can be used to provide several services, such as a simple
>      802.11-to-Ethernet bridge for wireless hosts
> 
> while this may be true, i was told that the reason it isn't
> working in practise with wi(4) lucent/orinoco
> gold/silver cards because the firmware does not allow for changing
> MAC addresses on the wireless media.
> 
The linux bridging FAQ says:

# Has anyone found a way to get around wavelan not allowing anything but 
its own mac address?
(answer by Michael Renzmann (mrenzmann at compulan.de))

Well, for 99% of computer users there will never be a way to get rid of 
this. For this function a special firmware is needed. This firmware can 
be loaded into the RAM of any WaveLAN card, so it could do its job with 
bridging. But there is no documentation on the interface available to 
the public. The only way to achieve this is to have a full version of 
the hcf library which controls every function of the card and also 
allows accessing the cardīs RAM. To get this full version Lucent wants 
to know that it will be a financial win for them, also you have to sign 
an NDA. So be sure that you wonīt most probably get access to this peace 
of software until Lucent does not change its mind in this (which I doubt 
never will happen).

If you urgently need to have a wireless lan card which is able to 
bridge, you should use one of those having the prism chipset onboard 
(manufactured by Harris Intersil). There are drivers for those cards 
available at www.linux-wlan.com (which is the website from Absoval), and 
I found a mail that says that there is the necessary firmware and an 
upload tool available for Linux to the public. If you need additional 
features of an access point you should also talk to Absoval.

# I still don't understand!!
(answer by Mark S. Mathews (mark at absoval.com))

Bridging ethernet (v2 or 802.3) is predicated on the ability of a 
station to transmit frames with a source address (SA) other than its 
own. This is possible because ethernet uses a 'transmit and 
forget'/stateless transmission model.

This isn't possible with 'normal' 802.11 station cards and software 
because 802.11 station mode doesn't allow the transmission of frames 
with 'someone else's source address. The primary reason is that 802.11 
is an acknowledged protocol. If you transmit a frame with someone lses 
source address, the ACK will nver come back to you. The ACK will be sent 
to the station whose source address you used.

There are ways to make it work (that's how I earn a living ;-), but it 
is not always straightforward and you probably won't get it right 
without a pretty solid understanding of 802.11, it's modes, and the 
frame header format.