// SPDX-License-Identifier: BSD-3-Clause

// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)

package org.xbill.DNS;

/**

* Constants and functions relating to flags in the DNS header.

*

* @author Brian Wellington

*/

public final class Flags {

private static final Mnemonic HEADER_FLAGS = new Mnemonic("DNS Header Flag", Mnemonic.CASE_LOWER);

/** query/response */

public static final byte QR = 0;

/** authoritative answer */

public static final byte AA = 5;

/** truncated */

public static final byte TC = 6;

/** recursion desired */

public static final byte RD = 7;

/** recursion available */

public static final byte RA = 8;

/** authenticated data */

public static final byte AD = 10;

/** (security) checking disabled */

public static final byte CD = 11;

/** dnssec ok (extended) */

public static final int DO = ExtendedFlags.DO;

static {

HEADER_FLAGS.setMaximum(0xF);

HEADER_FLAGS.setPrefix("FLAG");

HEADER_FLAGS.setNumericAllowed(true);

HEADER_FLAGS.add(QR, "qr");

HEADER_FLAGS.add(AA, "aa");

HEADER_FLAGS.add(TC, "tc");

HEADER_FLAGS.add(RD, "rd");

HEADER_FLAGS.add(RA, "ra");

HEADER_FLAGS.add(AD, "ad");

HEADER_FLAGS.add(CD, "cd");

}

private Flags() {}

/** Converts a numeric Flag into a String */

public static String string(int i) {

return HEADER_FLAGS.getText(i);

}

/** Converts a String representation of an Flag into its numeric value */

public static int value(String s) {

return HEADER_FLAGS.getValue(s);

}

/**

* Indicates if a bit in the flags field is a flag or not. If it's part of the rcode or opcode,

* it's not.

*/

public static boolean isFlag(int index) {

HEADER_FLAGS.check(index);

return (index < 1 || index > 4) && (index < 12);

}

}