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Re: [libvirt] nwfilter: limit VM traffic to specific MAC



Shahar Havivi <shaharh redhat com> wrote on 06/20/2011 07:39:35 AM:

> From: Shahar Havivi <shaharh redhat com>

> To: libvirt-list redhat com
> Cc: Stefan Berger/Watson/IBM IBMUS
> Date: 06/20/2011 07:42 AM
> Subject: nwfilter: limit VM traffic to specific MAC
>
> Hi,
> I am trying to add custom filter to block VM traffic to other VMs by limiting
> the traffic only to the gateways MAC address.
> The filter XML:
>
> <filter name='rhev' chain='root'>
>     <uuid>cd4e5890-ccc9-1b0f-303f-e7fe7123646d</uuid>
>     <filterref filter='allow-dhcp'/>
>     <rule action='' direction='out' priority='500'>
>         <mac match='no' dstmacaddr='$MAC'/>
>     </rule>
> </filter>


>
> The MAC is not the interface MAC address it's the gateways MAC that pass as a
> parameter (I use the gateway address hardcoded as well).
>
> The VM is getting DHCP ip but cannot get any traffic,
> I notice that when I edit (comment and uncomment) the drop rule, thefilter is
> working fine, ie no traffic other then the gateway.
>
> 1. Am I doing something wrong?

Try to put the concret MAC address of the gateway into the dstmacaddr field. $MAC is going to be translated to the MAC address of the interface. Once it works, try using $GATEWAY_MAC and have that defined via <parameter name='GATEWAY_MAC' value='a.b.c.d'/> from wherever you are referencing the 'rhev' filter.

The DHCP server must be running on the gateway.

> 1. What is the table name that libvirt use for ebtables?

It's the 'nat' table : 'ebtables -t nat -L' shows you the resulting rules.

   Stefan

>
> Shahar.

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