From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pablo Neira Ayuso <pablo@netfilter.org>
Subject: Re: Natted packets
Date: Tue, 09 Jan 2007 11:13:51 +0100
Message-ID: <45A36ADF.1090506@netfilter.org>
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To: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: netfilter@lists.netfilter.org

Jan Engelhardt wrote:
>> Is it possible to know if a packet passing through my router is (s)natted?
> 
> I think `-m conntrack --ctstate SNAT` should do that.
> 
>> And the original (s)natted IP?
> 
> For userspace there's a getsockopt() call that you can use to find out.

That getsockopt() interface is deprecated. If you're in userspace,
better use the libnetfilter_conntrack library. It has a function to
check if a conntrack has been snatted.

-- 
The dawn of the fourth age of Linux firewalling is coming; a time of
great struggle and heroic deeds -- J.Kadlecsik got inspired by J.Morris