code: public int
  getRcode() {
  	int rcode = header.getRcode();
  	OPTRecord opt = getOPT();
  	if (opt != null)
  		rcode += (opt.getExtendedRcode() << 4);
  	return rcode;
  }
docs: Returns the message's rcode (error code).  This incorporates the EDNS
  extended rcode.