src/dns-protocol.h

/* dnsmasq is Copyright (c) 2000-2020 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 MIN_PORT        1024           /* first non-reserved port */
#define MAX_PORT        65535u

#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_HESIOD        4               /* hesiod */
#define C_ANY           255             /* wildcard match */

#define T_A		1
#define T_NS            2
#define T_MD            3
#define T_MF            4             
#define T_CNAME		5
#define T_SOA		6
#define T_MB            7
#define T_MG            8
#define T_MR            9
#define T_PTR		12
#define T_MINFO         14
#define T_MX		15
#define T_TXT		16
#define T_RP            17
#define T_AFSDB         18
#define T_RT            21
#define T_SIG		24
#define T_PX            26
#define T_AAAA		28
#define T_NXT           30
#define T_SRV		33
#define T_NAPTR		35
#define T_KX            36
#define T_DNAME         39
#define T_OPT		41
#define T_DS            43
#define T_RRSIG         46
#define T_NSEC          47
#define T_DNSKEY        48
#define T_NSEC3         50
#define	T_TKEY		249		
#define	T_TSIG		250
#define T_AXFR          252
#define T_MAILB		253	
#define T_ANY		255
#define T_CAA           257

#define EDNS0_OPTION_MAC            65001 /* dyndns.org temporary assignment */
#define EDNS0_OPTION_CLIENT_SUBNET  8     /* IANA */
#define EDNS0_OPTION_NOMDEVICEID    65073 /* Nominum temporary assignment */
#define EDNS0_OPTION_NOMCPEID       65074 /* Nominum temporary assignment */

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

#define HB3_QR       0x80 /* Query */
#define HB3_OPCODE   0x78
#define HB3_AA       0x04 /* Authoritative Answer */
#define HB3_TC       0x02 /* TrunCated */
#define HB3_RD       0x01 /* Recursion Desired */

#define HB4_RA       0x80 /* Recursion Available */
#define HB4_AD       0x20 /* Authenticated Data */
#define HB4_CD       0x10 /* Checking Disabled */
#define HB4_RCODE    0x0f

#define OPCODE(x)          (((x)->hb3 & HB3_OPCODE) >> 3)
#define SET_OPCODE(x, code) (x)->hb3 = ((x)->hb3 & ~HB3_OPCODE) | code

#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; \
}

#define CHECK_LEN(header, pp, plen, len) \
    ((size_t)((pp) - (unsigned char *)(header) + (len)) <= (plen))

#define ADD_RDLEN(header, pp, plen, len) \
  (!CHECK_LEN(header, pp, plen, len) ? 0 : (((pp) += (len)), 1))

/* Escape character in our presentation format for names.
   Cannot be '.' or /000 and must be !isprint().
   Note that escaped chars are stored as
   <NAME_ESCAPE> <orig-char+1>
   to ensure that the escaped form of /000 doesn't include /000
*/
#define NAME_ESCAPE 1