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Date:      Sat, 16 Feb 2002 00:47:21 -0800
From:      "Crist J. Clark" <cjc@FreeBSD.ORG>
To:        "Michael R. Wayne" <wayne@staff.msen.com>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: Odd ipfw behaviour
Message-ID:  <20020216004721.B36782@blossom.cjclark.org>
In-Reply-To: <200202152309.SAA00831@manor.msen.com>; from wayne@staff.msen.com on Fri, Feb 15, 2002 at 06:09:51PM -0500
References:  <200202152309.SAA00831@manor.msen.com>

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On Fri, Feb 15, 2002 at 06:09:51PM -0500, Michael R. Wayne wrote:
[snip]

> Using this ipfw rule on ProxyFirewall:
>    fwd $(squid-box) log tcp from $(windows-box) to any 80 
> and checking the logs on ProxyFirewall, I see this horrible mess:
> 
> ipfw: 11005 Forward to SQUIDbox TCP BROWSERbox:1631 216.136.204.21:80 in via fxp1
> ipfw: 11005 Forward to SQUIDbox TCP BROWSERbox:1631 216.136.204.21:80 out via fxp0	<---!!!
> ipfw: 11005 Forward to SQUIDbox TCP BROWSERbox:1631 216.136.204.21:80 in via fxp1
> ipfw: 11005 Forward to SQUIDbox TCP BROWSERbox:1631 216.136.204.21:80 out via fxp1
> ipfw: 60000 Deny ICMP:5.1 ProxyFirewall BROWSERbox out via fxp1
> ipfw: 60000 Deny ICMP:5.1 ProxyFirewall SQUIDbox out via fxp1
> last message repeated 31 times
> 
> This, of course, causes terrible performance as the packets destined
> for the local net bounce out the default interface.  It can be
> corrected by specifying an interface in the fwd rule:
>    fwd $(squid-box) log tcp from $(windows-box) to any 80 via fxp1
> 
> Is it expected behaviour for ipfw to disregard routing and put
> packets out on interfaces where they have no chance of being properly
> delivered (which would be odd) or is this a bug?

I believe you are misinterpretting the logs. Each of those log entries
is saying,

  "At rule 11005 I am forwarding this packet to SQUIDbox. The packet
that triggered this rule was TCP BROWSERbox:1631 216.136.204.21:80
that came (out of|into) to the firewall via interface (fxp0|fxp1)"

That is, the 'via fxp?' at the end is telling you about the packet
that _triggered_ the rule, not where the packet was actually forwared
to. If you sniffed the connection, I expect that you would have seen
four packets go from the firewall to SQUIDbox.
-- 
Crist J. Clark                     |     cjclark@alum.mit.edu
                                   |     cjclark@jhu.edu
http://people.freebsd.org/~cjc/    |     cjc@freebsd.org

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