ip traffic redirection.

[Matthew Seaman]

On Wed, Jul 28, 2004 at 10:23:28AM +0200, fred at bsdhost.net wrote:

> This is maybe the wrong list for this question but anyway...

No -- this is the right list for questions.

> For a proof of concept I need to setup a gateway to divert certain kind 
> of ip traffic to a special program who do some counting and 
> modification on these packets and then re-inject them back. This has to 
> be a gateway and not a router.

Yes, that's doable.  It sounds very much like transparent proxying.
So long as you can select the traffic you want to process solely by
examining the IP headers it should be easy.  Of course, the process
you feed the selected packets to can do whatever it wants with them
and can be programmed to decode packet payloads as required.
 
> Does someone know if there is a package un the FreeBSD ports who can 
> help me do that? Can I do that using ipfw and in that case can someone 
> send me a pointer to some docs or examples ?

What you want to do sounds very much like transparent proxying.  That
can be implemented fairly simply under FreeBSD using, for example
ipfw(8)'s 'fwd' mechanism.

There's a nics discussion in the Squid FAQ which you should be able to
mine for clues:

    http://www.squid-cache.org/Doc/FAQ/FAQ-17.html

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP: http://www.infracaninophile.co.uk/pgpkey         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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