def nova_dhcp_filter(self):

        return '''<filter name='nova-allow-dhcp-server' chain='ipv4'>
                    <uuid>891e4787-e5c0-d59b-cbd6-41bc3c6b36fc</uuid>
                    <rule action='accept' direction='out'
                          priority='100'>
                      <udp srcipaddr='0.0.0.0'
                           dstipaddr='255.255.255.255'
                           srcportstart='68'
                           dstportstart='67'/>
                    </rule>
                    <rule action='accept' direction='in'
                          priority='100'>
                      <udp srcipaddr='$DHCPSERVER'
                           srcportstart='67'
                           dstportstart='68'/>
                    </rule>
                  </filter>'''
The standard allow-dhcp-server filter is an <ip> one, so it uses
dataset/ETHPy150Open nii-cloud/dodai-compute/nova/virt/libvirt/firewall.py/NWFilterFirewall.nova_dhcp_filter