netdev - Re: Fwd: Linux bridge for route

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Message-ID: <52D992F4.8070500@pandora.be>
Date:	Fri, 17 Jan 2014 21:30:44 +0100
From:	Bart De Schuymer <bdschuym@...dora.be>
To:	tingwei liu <tingw.liu@...il.com>, netfilter-devel@...r.kernel.org,
	netfilter@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: Fwd: Linux bridge for route

tingwei liu schreef op 17/01/2014 10:14:
> Dear all,
>
>         There is  a question has puzzled me for a long time.
>         You can find the topology from attachment.
>
>         Normal traffic is:
>
>                 PC(192.168.1.8)--->Bridge(eth0)--->Bridget(eth1)--->NAT
> server-->switch--->Server(192.168.5.3)
>
>         Now I want the ssh traffic like this:
>                PC(182.168.1.8)--->Bridge(eth0)--->eth2--->NAT
> server--->switch--->Server(192.168.5.3)
>
>
>        What I have done on LINUX Server:
>                #net.bridge.bridge-nf-call-iptables = 1
>                #iptables -t nat -A POSTROUTING -s 192.168.1.8 -p tcp
> --dport 22 -j SNAT --to-source 192.168.5.2
>
>        I have find the rule matched through command "iptables -t nat
> -nvL", but the packets doesn't sent to 192.168.5.3.
>        and "tcpdump -i eth2 tcp port 22" can not capture any packet!

You are trying to make a brouter. You don't need to set 
net.bridge.bridge-nf-call-iptables to 1, instead you need to add an 
ebtables rule in the BROUTING chain, see:
http://ebtables.sourceforge.net/examples/basic.html#ex_brouter

Something like this (in combination with your existing iptables rules):
ebtables -t broute -A BROUTING -p ipv4 --ip-source 192.168.1.8 \
--ip-protocol tcp --ip-destination-port 22 \
-j redirect --redirect-target DROP

cheers,
Bart

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