Trouble with if_bridge and wlan nic in infrastructure mode

[Fabian Keil]

I have a problem with if_bridge if one of the members
is a wlan nic in infrastructure mode.

Bridges between the following device combinations work:

em0 and tap0;
em0 and wi0 in hostap mode;
em0 and ath0 in hostap mode;
rl0 and re0 (different system);

Bridges between the following don't:

em0 and ndis0 in infrastructure mode;
em0 and wi0 in infrastructure mode;
em0 and ath0 infrastructure mode;
tap0 and ndis0 in infrastructure mode; 

My bridge is a ThinkPad R51 running
FreeBSD 6.1-PRERELEASE #11: Fri Mar 10 13:05:07 CET 2006.

PF is disabled and all net.link.bridge sysctls are set to 0.

I tested two Access Points for the infrastructure mode,
a Netgear WGT624 and another Laptop running Anonym.OS.

The ThinkPad can ping the AP and the system behind em0
(or tap0), but the system behind em0 (or tap0) can't reach
the AP and can't be reached by the AP either. Both systems
between the bridge can ping the bridge itself. 

If I run tcpdump on the members of the bridge I can see
arp requests (who has IP foo tell bar) on both members,
but answers coming in on em0 don't appear on the wlan nic
in infrastructure mode and the wlan nic doesn't get any
answers which could be bridged to em0 at all. 

I'm under the impression that even the arp requests
coming in on em0 and shown on the wlan nic in infrastructure
mode aren't send out. At least I can't see them on the AP
running Anonym.OS.

Arp requests made my the AP are bridged and answered by
the system behind em0, but the answers itself aren't bridged.

man if_bridge's wi0 example assumes "the 802.11 interface is in
ad-hoc mode" but it doesn't say wlan bridging would be limited
to ad-hoc and hostap mode.

I worked around the problem by using NAT, but I'm still interested
if anybody is using an if_bridge member in infrastructure mode or
if there's a reason why it shouldn't work. 

Fabian
-- 
http://www.fabiankeil.de/
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