Date: Fri, 12 Oct 2001 18:47:41 -0700 From: "Crist J. Clark" <cristjc@earthlink.net> To: Henrik Holmstam <turbo@lamering.org> Cc: Kenneth Wayne Culver <culverk@wam.umd.edu>, Alfatrion <alfatrion@cybertron.tmfweb.nl>, "Maine LOA List Admin (Brent Bailey)" <brentb@loa.com>, "Hartmann, O." <ohartman@klima.physik.uni-mainz.de>, freebsd-stable@FreeBSD.ORG, freebsd-questions@FreeBSD.ORG Subject: Re: IPFW or IPFILTER? Message-ID: <20011012184741.D6274@blossom.cjclark.org> In-Reply-To: <20011012185458.K69352-100000@darkwing.turbo.net>; from turbo@lamering.org on Fri, Oct 12, 2001 at 06:56:48PM %2B0200 References: <Pine.GSO.4.21.0110121216390.27495-100000@sun10pg2.wam.umd.edu> <20011012185458.K69352-100000@darkwing.turbo.net>
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On Fri, Oct 12, 2001 at 06:56:48PM +0200, Henrik Holmstam wrote:
>
> Can IPFW keep state on UDP and ICMP as IPFilter can?
Yes and kinda.
"Keeping state" on UDP (a stateless protocol, BTW) is pretty easy. You
see a packet,
<src_ip>:<src_port> -> <dst_ip>:<dst_port>
So you then allow,
<dst_ip>:<dst_port> -> <src_ip>:<src_port>
To go through for a while. ipfw(8) dynamic rules will handle this just
fine.
ICMP is another issue. Doing something like,
pass icmp from any to any out via <external_if> keep-state
Will let you ping the rest of the word and even let Windows-style
traceroutes work, but that's because it works like this:
<src_ip>:<src_icmp_type.src_icmp_code> -> <dst_ip>
Creates a dynamic rule,
pass icmp from <dst_ip> to <src_ip>
That is, _any_ ICMP from <dst_ip> to <src_ip> is passed for the
dynamic's rule lifetime.
--
Crist J. Clark | cjclark@alum.mit.edu
| cjclark@jhu.edu
http://people.freebsd.org/~cjc/ | cjc@freebsd.org
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