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Date:      Thu, 15 Jul 1999 13:02:22 +0100
From:      Karl Pielorz <kpielorz@tdx.co.uk>
To:        questions@freebsd.org
Subject:   Strange goins on with IPFW ?
Message-ID:  <378DCDCE.B6053096@tdx.co.uk>

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Hi All,

A faultless machine we've been using for a firewall failed today, in a very
unusual way... It decided to 'silently' drop any packets coming to / from port
25 for our hosts...

Checking the /var/log/messages for 'denied' packets showed nothing... Running
tcpdump on the interface would show packets coming in fxp0 for the host, going
out of fxp1 to that host. On the flipside, the replies would go into fxp1 on
the host, and just 'not appear' on fxp0 (destined for the Internet).

Yet, internal hosts trying to connect to external machines on port 80, would
work fine - as would anything connecting inbound on port 80.

Has anyone seen anything like this before? - The machine had been up for 207
days before this problem happened...

It was almost like the firewall had a rule saying "deny from any to any 25" -
which it definitely didn't have!

Looking through the logs, I did find some interesting messages, such as:

"
Jul 14 20:15:01 spider /kernel: ipfw: 10800 Deny UDP 194.134.135.28:31790 195.
Jul 14 20:15:01 spider /kernel: 188.211.199:31789 in via fxp0
"

(Why did this line get split across two syslog entries?)

And,

"
Jul 13 19:22:56 spider /kernel: rm_class: bogus time values
"

(Anyone know what this means?)

The machines a P200, w/16Mb RAM and running FreeBSD 2.2.7-RELEASE. It's got no
services running on it, and normally sits there with about 8 processes
running, and a load-average of 0.00

Rebooting the machine (which runs the same firewall config as it comes up -
it's not been changed in months) fixed the problem...

-Kp


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