code: def subintf_real_ip_check_gw_port(self, gw_port, ip_addr, netmask):
          
          if gw_port is not None:
              found = False
              for i in range(len(gw_port['fixed_ips'])):
                  target_ip = gw_port['fixed_ips'][i]['ip_address']
                  if ip_addr == target_ip:
                      found = True
                      break
              if found is False:
                  LOG.info("Subintf real IP is incorrect, deleting")
                  return False
              subnet_id = gw_port['fixed_ips'][i]['subnet_id']
              subnet = next(
                  sn for sn in gw_port['subnets'] if sn['id'] == subnet_id)
              target_net = netaddr.IPNetwork(subnet['cidr'])
              if netmask != str(target_net.netmask):
                  LOG.info("Subintf has incorrect netmask, deleting")
                  return False
  
              return True
  
          return False
docs: checks running-cfg derived ip_addr and netmask against neutron-db
          gw_port