def modify_iface_xml(br_name, nwfilter, vm_name):
"""
Modify interface xml with the new bridge and the nwfilter
:param br_name: bridge name
:param nwfilter: nwfilter name
:param vm_name: vm name
"""
vmxml = vm_xml.VMXML.new_from_dumpxml(vm_name)
iface_xml = vmxml.get_devices('interface')[0]
vmxml.del_device(iface_xml)
iface_xml = Interface(type_name='bridge')
iface_xml.source = {'bridge': br_name}
iface_xml.model = 'virtio'
iface_xml.filterref = iface_xml.new_filterref(name=nwfilter)
logging.debug("new interface xml is: %s" % iface_xml)
vmxml.add_device(iface_xml)
vmxml.sync()
