'Gets the dvr routers on vmport subnets.'

def get_dvr_routers_by_subnet_ids(self, context, subnet_ids):

    if (not subnet_ids):
        return set()
    router_ids = set()
    filter_sub = {'fixed_ips': {'subnet_id': subnet_ids}, 'device_owner': [n_const.DEVICE_OWNER_DVR_INTERFACE]}
    subnet_ports = self._core_plugin.get_ports(context, filters=filter_sub)
    for subnet_port in subnet_ports:
        router_ids.add(subnet_port['device_id'])
    return router_ids
