IEEE 802.11 Proxy ARP using netfilter?

[Kyeyoon Park]

Hi guys,

I am trying to use netfilter infrastructure to implement Proxy ARP in
IEEE 802.11. This is different from proxy_arp that can be enabled via
/proc/sys/net/ipv4/conf/<iface>/proxy_arp.

I initially tried to implement this feature entirely in the mac80211
stack, but was asked to look at alternative designs (i.e. netfilter).
The relevant discussion can be found at:

http://comments.gmane.org/gmane.linux.kernel.wireless.general/123342

In a nutshell, I am trying to keep track of MAC <-> IP address mapping
for only the associated stations for the access point (AP). Of course,
as the stations associate and disassociate from the AP, I will need to
update whether to keep track of a particular MAC address or not. When an
entity asks for the IP address of one of the associated stations, the AP
will reply on behalf of the station and drop the broadcast ARP request
that would go out to the wireless-medium.

I was thinking about implementing this using the target extension for
ebtables (i.e. a target extension module for "ebtable_filter" something
that would look similar to "ebt_arpreply.c").

Then I saw that I cannot dynamically change the data that is being used
by my own target extension module. So when a new station associates or
when an associated station disassociates, I cannot dynamically alter
database within my own target extension module; the dynamic data being
the database of the MAC addresses to keep track of.

I COULD rewrite the whole table every time, but this is obviously not
scalable (i.e. imagine rewriting the table of 100 MAC addresses from the
userspace on every association/disassociation).

What do you think is the best way to approach this? I don't even have to
use the target extension necessarily. I just thought it was the most
suitable solution on a first glance.

Your comment on this would be greatly appreciated.

Best Regards,
Kyeyoon
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