code: function _dns_error (connection, next, err, host, plugin, nxdomain, dnserror) {
      switch (err.code) {
          case dns.NXDOMAIN:
          case dns.NOTFOUND:
          case dns.NOTDATA:
              connection.loginfo(plugin, 'could not find a address for ' + host +
                  '. Disconnecting.');
              next(DENYDISCONNECT, 'Sorry we could not find address for ' +
                  host + '. ' + nxdomain);
              break;
  
          default:
              connection.loginfo(plugin, 'encountered an error when looking up ' +
                  host + '. Disconnecting.');
              next(DENYDISCONNECT, 'Sorry we encountered an error when ' +
                  'looking up ' + host + '. ' + dnserror);
              break;
      }
  }
docs: _dns_error handles err from node.dns callbacks.  It will always call next() with a DENYDISCONNECT for this plugin.