code: def __intermediate_dns_search(self, uci, address):
          
          # allow override
          if 'dns_search' in uci:
              return uci['dns_search']
          # ignore if "proto" is none
          if address['proto'] == 'none':
              return None
          dns_search = self.netjson.get('dns_search', None)
          if dns_search:
              return ' '.join(dns_search)
docs: determines UCI interface "dns_search" option