Subject: Re: pf for NetBSD
To: None <tech-net@netbsd.org>
From: Wolfgang Rupprecht <wolfgang+gnus20021106T082313@wsrcc.com>
List: tech-net
Date: 11/06/2002 08:32:08
> > How does pf handle state from an outgoing connection that is closing?
> > Under ipf the state for an outgoing TCP connection appeared to be
> > torn down as soon as the local side closed the connection. [...] If
> > pf handled that state better and kept the TCP-filter state around for
> > 2xMSL that would be a vast improvement.
>
> But still not very good. There is no reason why a TCP connection
> cannot be closed in one direction and still keep streaming data in the
> other more or less indefinitely. If ipf - or any such firewalling
> package - tears down its state as soon as one direction closes, I would
> call that a priority-1 bug.
I never explicitly tested ipf with half-closed connections, but I did
observe lots of problems at closing time when both sides attempted to
do a 3-way close (fin / fin-ack / ack). I'd often see extra acks or
tcp-rst's hitting the firewall instead of making it to the TCP stack
machinery. Essentially a day of running all outgoing TCP connections
with a state-based filter filled up /var/log/messages with pages of
gripes. Some of the remote systems were remarkably persistent in
trying to get their last few packets to me.
-wolfgang
--
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