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dnsmasq

/* dnsmasq is Copyright (c) 2000-2013 Simon Kelley

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 dated June, 1991, or
   (at your option) version 3 dated 29 June, 2007.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
     
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#define NAMESERVER_PORT 53
#define TFTP_PORT       69

#define IN6ADDRSZ       16
#define INADDRSZ        4

#define PACKETSZ	512		/* maximum packet size */
#define MAXDNAME	1025		/* maximum presentation domain name */
#define RRFIXEDSZ	10		/* #/bytes of fixed data in r record */
#define MAXLABEL        63              /* maximum length of domain label */

#define NOERROR		0		/* no error */
#define FORMERR		1		/* format error */
#define SERVFAIL	2		/* server failure */
#define NXDOMAIN	3		/* non existent domain */
#define NOTIMP		4		/* not implemented */
#define REFUSED		5		/* query refused */

#define QUERY           0               /* opcode */

#define C_IN            1               /* the arpa internet */
#define C_CHAOS         3               /* for chaos net (MIT) */
#define C_ANY           255             /* wildcard match */

#define T_A		1
#define T_NS            2               
#define T_CNAME		5
#define T_SOA		6
#define T_PTR		12
#define T_MX		15
#define T_TXT		16
#define T_SIG		24
#define T_AAAA		28
#define T_SRV		33
#define T_NAPTR		35
#define T_OPT		41
#define	T_TKEY		249		
#define	T_TSIG		250
#define T_AXFR          252
#define T_MAILB		253	
#define T_ANY		255

struct dns_header {
  u16 id;
  u8  hb3,hb4;
  u16 qdcount,ancount,nscount,arcount;
};

#define HB3_QR       0x80
#define HB3_OPCODE   0x78
#define HB3_AA       0x04
#define HB3_TC       0x02
#define HB3_RD       0x01

#define HB4_RA       0x80
#define HB4_AD       0x20
#define HB4_CD       0x10
#define HB4_RCODE    0x0f

#define OPCODE(x)          (((x)->hb3 & HB3_OPCODE) >> 3)
#define RCODE(x)           ((x)->hb4 & HB4_RCODE)
#define SET_RCODE(x, code) (x)->hb4 = ((x)->hb4 & ~HB4_RCODE) | code
  
#define GETSHORT(s, cp) { \
	unsigned char *t_cp = (unsigned char *)(cp); \
	(s) = ((u16)t_cp[0] << 8) \
	    | ((u16)t_cp[1]) \
	    ; \
	(cp) += 2; \
}

#define GETLONG(l, cp) { \
	unsigned char *t_cp = (unsigned char *)(cp); \
	(l) = ((u32)t_cp[0] << 24) \
	    | ((u32)t_cp[1] << 16) \
	    | ((u32)t_cp[2] << 8) \
	    | ((u32)t_cp[3]) \
	    ; \
	(cp) += 4; \
}

#define PUTSHORT(s, cp) { \
	u16 t_s = (u16)(s); \
	unsigned char *t_cp = (unsigned char *)(cp); \
	*t_cp++ = t_s >> 8; \
	*t_cp   = t_s; \
	(cp) += 2; \
}

#define PUTLONG(l, cp) { \
	u32 t_l = (u32)(l); \
	unsigned char *t_cp = (unsigned char *)(cp); \
	*t_cp++ = t_l >> 24; \
	*t_cp++ = t_l >> 16; \
	*t_cp++ = t_l >> 8; \
	*t_cp   = t_l; \
	(cp) += 4; \
}