[tproxy] Fw: Tproxy4, fwmark and netfilter route_me_harder

Ming-Ching Tiew mingching.tiew at redtone.com
Mon Jan 21 02:21:31 CET 2008

Forwarded here just in case some of you are not in netfilter-devel list.

----- Original Message ----- 
From: "Patrick McHardy" <kaber at trash.net>
To: "Ming-Ching Tiew" <mingching.tiew at redtone.com>
Cc: <netfilter-devel at vger.kernel.org>; <tproxy at lists.balabit.hu>
Sent: Sunday, January 20, 2008 11:31 PM
Subject: Re: Tproxy4, fwmark and netfilter route_me_harder

> Ming-Ching Tiew wrote:
> > I  sort of just forward this to netfilter-devel.
> >  
> > For those who in netfilter-devel but not in tproxy mail list, a little 
> > background here :-
> >  
> > I discovered after applying the tproxy4 patch which allows one to spoof 
> > originating traffic with a foreign IP address ( for the purpose of doing 
> > transparent proxy ) that after doing it, traffics with foreign IP will 
> > not leave the system if there is a FWMARK in the mangle table OUTPUT 
> > chain. Any MARK will screw up the routing.
> >  
> > And the patch above seems to be able to get the packets out of the machine
> > again.
> > 
> > So the motivation here perhaps someone here could throw some light as to 
> > how this situation is best handled.
> IIRC the current TPROXY patches use a flag in the dst_entry
> to indicate that the source address is non-local. So
> ip_route_me_harder should probably check that flag and
> use routing for foreign addresses for that case.
> -

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