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Date:      Fri, 11 Jan 2002 23:36:23 +0100
From:      Rene de Vries <rene@canyon.xs4all.nl>
To:        hackers@freebsd.org
Subject:   Filtering packets received through an ipsec tunnel 
Message-ID:  <A3F0121C-06E3-11D6-A736-00039357FA7A@canyon.xs4all.nl>

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Hello,

By experimenting with ipsec and looking at the source of "ip_input.c" a 
co-worker and I found the following out.

When a ipsec tunnel packet is received this (protocol 50/51) packet is 
passed through ip-filter (& co). After filtering and when it has been 
determent that the current host is the destination (tunnel end-point), 
this packet is decrypted/verified. The decrypted packet is then pushed 
back into the queue that leads to ip_input(...). So far so good....

But once in ip_input(...) the filtering code is skipped and we were 
wondering why.

I know that ipsec has some handles to be able to filter on address, 
protocol and/or port. But for more complex situations this is not 
enough. In these situations it would be nice to be able to use 
ip-filter (& co) on traffic from the tunnel (and also for traffic going 
into the tunnel).

I was wondering why this is implemented the way it is. Maybe someone on 
this list could shed a light on this?

Rene
--
Rene de Vries <rene@tcja.nl>


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