<filter name='no-mac-spoofing' chain='mac' priority='-800'>
  <uuid>7edd722f-2e93-4a81-aae1-963ab8217a51</uuid>
  <rule action='return' direction='out' priority='500'>
    <mac srcmacaddr='$MAC'/>
  </rule>
  <rule action='drop' direction='out' priority='500'>
    <mac/>
  </rule>
</filter>

