1// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)
2
3package org.xbill.DNS;
4
5/**
6 * Constants and functions relating to flags in the DNS header.
7 *
8 * @author Brian Wellington
9 */
10
11public final class Flags {
12
13private static Mnemonic flags = new Mnemonic("DNS Header Flag",
14					     Mnemonic.CASE_LOWER);
15
16/** query/response */
17public static final byte QR		= 0;
18
19/** authoritative answer */
20public static final byte AA		= 5;
21
22/** truncated */
23public static final byte TC		= 6;
24
25/** recursion desired */
26public static final byte RD		= 7;
27
28/** recursion available */
29public static final byte RA		= 8;
30
31/** authenticated data */
32public static final byte AD		= 10;
33
34/** (security) checking disabled */
35public static final byte CD		= 11;
36
37/** dnssec ok (extended) */
38public static final int DO		= ExtendedFlags.DO;
39
40static {
41	flags.setMaximum(0xF);
42	flags.setPrefix("FLAG");
43	flags.setNumericAllowed(true);
44
45	flags.add(QR, "qr");
46	flags.add(AA, "aa");
47	flags.add(TC, "tc");
48	flags.add(RD, "rd");
49	flags.add(RA, "ra");
50	flags.add(AD, "ad");
51	flags.add(CD, "cd");
52}
53
54private
55Flags() {}
56
57/** Converts a numeric Flag into a String */
58public static String
59string(int i) {
60	return flags.getText(i);
61}
62
63/** Converts a String representation of an Flag into its numeric value */
64public static int
65value(String s) {
66	return flags.getValue(s);
67}
68
69/**
70 * Indicates if a bit in the flags field is a flag or not.  If it's part of
71 * the rcode or opcode, it's not.
72 */
73public static boolean
74isFlag(int index) {
75	flags.check(index);
76	if ((index >= 1 && index <= 4) || (index >= 12))
77		return false;
78	return true;
79}
80
81}
82