/etc/libvirt/nwfilter/no-other-l2-traffic.xml is in libvirt-bin 1.3.1-1ubuntu10.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | <filter name='no-other-l2-traffic'>
<!-- drop all other l2 traffic than for which rules have been
written for; i.e., drop all other than arp and ipv4 traffic -->
<rule action='drop' direction='inout' priority='1000'/>
</filter>
|