[libvirt-users] nwfilter example for security

hi, libvirt folks, I'm trying to use libvirt's nwfilter to achieve two goals: 1, by default all ports are closed, means that the virtual machine is isolated. 2, only some selected ports are opened, for example, tcp 22 for ssh, tcp 80 for http web, udp 67 and 68 for dhcp. Can somebody drop me a simple example how to do this in libvirt? I'm using libvirt 0.10.1, the latest version. thanks.