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Date:      Sun, 30 Jul 2000 18:00:01 -0500
From:      stephen@math.missouri.edu
To:        Bill Fumerola <billf@chimesnet.com>
Cc:        "Jonathan M. Bresler" <jmb@hub.freebsd.org>, freebsd-security@FreeBSD.ORG
Subject:   Re: log with dynamic firewall rules
Message-ID:  <3984B371.A5BF509E@math.missouri.edu>
References:  <20000730194202.447F937B6C1@hub.freebsd.org> <3984AB32.53B8D793@math.missouri.edu> <20000730185309.W5021@jade.chc-chimes.com>

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Bill Fumerola wrote:
> 
> I fear the dynamic rule code, or I'd attempt to figure it all out
> and come up with something better, but:
> 
> > Now wait five minutes and the dynamic rule times out, and it stops
> > working.  Well, that is OK I suppose - you shouldn't have left it so long.
> 
> [boa.internal-billf 18:52:25]
> < /home/billf > sysctl -a |grep dyn
> net.inet.ip.fw.dyn_buckets: 256
> net.inet.ip.fw.curr_dyn_buckets: 256
> net.inet.ip.fw.dyn_count: 0
> net.inet.ip.fw.dyn_max: 1000
> net.inet.ip.fw.dyn_ack_lifetime: 300
> net.inet.ip.fw.dyn_syn_lifetime: 20
> net.inet.ip.fw.dyn_fin_lifetime: 20
> net.inet.ip.fw.dyn_rst_lifetime: 5
> 
> ... it is a controllable behavior.

Yes, I knew that.  (I alluded to it at the end of my message.)
Although it is not controllable unless you are
root.  There must have been some thought given to these default
values, and why they are right.  Make net.inet.ip.fw.dyn_ack_lifetime
too big, and you begin to defeat its purpose.  Make it too small,
and you have the problem I describe.

-- 
Stephen Montgomery-Smith
Department of Mathematics, University of Missouri, Columbia, MO 65211
Phone 573-882-4540, fax 573-882-1869
http://www.math.missouri.edu/~stephen  stephen@math.missouri.edu


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