[libvirt] nwfilter - limit VM traffic to specific mac address

[Stefan Berger]

On 11/07/2011 04:25 AM, Shahar Havivi wrote:
> Hi,
>
> I want to limit VM traffic to a specific MAC address, ie VMs cannot
> traffic each other other then a specific gateway.
>
> I am using custom nwfilter name: isolatedprivatevlan-vdsm.xml
> located in /etc/libvirt/nwfilter/:
>
> <filter name='isolatedprivatevlan-vdsm' chain='root'>
>      <filterref filter='clean-traffic'/>
>      <rule action='drop' direction='out' priority='500'>
>          <mac match='no' dstmacaddr='$GATEWAY_MAC'/>
>      </rule>
> </filter>
>
Try this one -- it works in 'my' subnet:

<filter name='isolatedprivatevlan-vdsm' chain='ipv4'>
     <filterref filter='clean-traffic'/>
     <rule action='drop' direction='out' priority='10'>
         <mac match='no' dstmacaddr='$GATEWAY_MAC'/>
     </rule>
</filter>


> VM1 domian xml portion:
> <interface type="bridge">
>      <mac address="00:1a:4a:16:01:53"/>
>      <model type="virtio"/>
>      <source bridge="red"/>
>      <filterref filter="isolatedprivatevlan-vdsm">
>          <parameter name="GATEWAY_MAC" value="00:00:0c:07:ac:00"/>
>      </filterref>
> </interface>
>
>
> VM2 domian xml portion:
> <interface type="bridge">
>      <mac address="00:1a:4a:16:01:52"/>
>      <model type="virtio"/>
>      <source bridge="red"/>
>      <filterref filter="isolatedprivatevlan-vdsm">
>          <parameter name="GATEWAY_MAC" value="00:00:0c:07:ac:00"/>
>      </filterref>
> </interface>
>
>
> in each VM (Fedora 15 LiveCD) I assign ip:
> # ifconfig eth0 10.35.1.240 netmask 255.255.254.0
> # route add default gw 10.35.1.1
>
> vm2:
> # ifconfig eth0 10.35.1.241 netmask 255.255.254.0
> # route add default gw 10.35.1.1
>
> but the filter is not working,
> I can ping the VMs from each other,
>
> Am I missing something?
Try the above filter that puts the check into a different 'chain' into 
different order. I'll be introducing a 'mac' chain where this can then 
be put into rather than into the 'ipv4' chain.
The challenging part about the filtering rules is their order and the 
XML can unfortunately not abstract this 'away'.

    Stefan


> Thanks,
> Shahar Havivi.
>
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