Problems with Linux Firewall

["A. Clausen" <techlists@alberni.net>]

We've been running a Linux 2.4.19 firewall for about a year and a half
now, using Netfilter and proxyarp so that devices on both side of the
firewall can be on the same subnet.  We run a wireless network, using
wireless bridges, so these should be largely invisible to the Linux
box.

Within the last four months we have suspected there is a slow down.
I've upgraded to 2.4.21 and upgraded netfilter/iptables to 1.2.8, to
no effect.  Just to test things out, I grabbed an old 10mbit hub so
that I could see performance locally, and not just through the
wireless network.

Everything seemed to be going fine (around 1050kbs on an FTP
transfer), but I discovered that while that download was going on, no
other traffic, including 32 byte pings, would go through.

Now I realize that hubs are only half-duplex, but I don't ever recall
this situation, and it seems to indicate a problem with the Linux
firewall.  One bad thing is that I'm running some Realtek cards (I
know I shouldn't but they've worked for over a year).

Does anybody have any ideas or suggestions?

-- 
Aaron Clausen

techlists@alberni.net