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Date:      Sun, 16 Dec 2001 19:04:39 -0800
From:      "Crist J . Clark" <cjc@FreeBSD.ORG>
To:        =?iso-8859-1?Q?Boris_K=F6ster_?= <koester@x-itec.de>
Cc:        freebsd-net@FreeBSD.ORG
Subject:   Re: nat / ipdivert problem - if possible please help
Message-ID:  <20011216190439.B15624@blossom.cjclark.org>
In-Reply-To: <3C1D1186.26005.1F1D48@localhost>; from koester@x-itec.de on Sun, Dec 16, 2001 at 09:26:30PM %2B0100
References:  <3C1D1186.26005.1F1D48@localhost>

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On Sun, Dec 16, 2001 at 09:26:30PM +0100, Boris Köster  wrote:
> I have a problem.
> 
> hope# uname -a
> FreeBSD hope.hope 4.4-STABLE FreeBSD 4.4-STABLE #2: Fri Dec 14 14:59:52 CET 
> 2006 (???)
> 
> I have a BSD laptop on 192.168.0.3
> 
> I have a BSD server 192.168.0.99
> 
> I have a win2k server at 192.168.0.1
> 
> I want to route telnet service on .99 to .3 
> that means if you telnet from .1 to .99 the laptop answers on 3
> 
> This feature requires ipfw/natd and I have made a kernel for this (IPFIREWALL, 
> IPDIVERT)
> 
> I don´t know how to continue, i tried this on the bsd server:
> 
> /sbin/ipfw -f flush
> /sbin/ipfw add divert natd all from any to any via ed0
> /sbin/ipfw add pass all from any to any
> natd -interface ed0 -redirect_port tcp 192.168.0.3:telnet 192.168.0.99:telnet
> 
> But without success.

The problem I see is this,

  1) The Win2k machine tries to initiate a connection to the BSD
     server,

	192.168.0.1	->	192.168.0.99	SYN

  2) The BSD server rewrites the packet and sends its on its way,

	192.168.0.1	->	192.168.0.3	SYN

  3) The BSD laptop gets the packet and sends back a response,

	192.168.0.3	->	192.168.0.1	SYN-ACK

  4) The Win2k machine receives the packet, but since it hasn't tried
     to initiate a connection to 192.168.0.3,

	192.168.0.1	->	192.168.0.3	RST

See the problem now?
-- 
"It's always funny until someone gets hurt. Then it's hilarious."

Crist J. Clark                     |     cjclark@alum.mit.edu
                                   |     cjclark@jhu.edu
http://people.freebsd.org/~cjc/    |     cjc@freebsd.org

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