/* dnsmasq is Copyright (c) 2000-2026 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 . string
is 253 characters. Reasoning: the wire format representation of a
label is one byte length followed by up to length characters so each of
these labels except the last takes the same space since the length is
replaced by the '.' seperator.
The last label doesn't have the "." so it takes one less character
and the terminating zero-length label takes no character either.
When we introduce the dnsmasq escaped format, the maximum length
of this representation is when there are the minimum number of labels,
since that gives us the maximum number of characters that may need
escaping. The minimum number of labels is four, so the overhead
is five bytes (four non-zero lengths plus the zero length terminator)
leaving a total of 250 characters in labels. If every one of these
is escaped and becomes two characters, that gives 500 characters,
plus the three '.' seperators between the four labels, for a total of
503 characters.
*/
#define MAXDNAME 255 /* Maximum size of a domain name in wire format */
#define MAXDNAMESTR 503 /* Maximum size of dnsmasq c-string representaion of a domain name. */
#define PACKETSZ 512 /* maximum packet size */
#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_EDE 15 /* IANA - RFC 8914 */
#define EDNS0_OPTION_NOMDEVICEID 65073 /* Nominum temporary assignment */
#define EDNS0_OPTION_NOMCPEID 65074 /* Nominum temporary assignment */
#define EDNS0_OPTION_UMBRELLA 20292 /* Cisco Umbrella temporary assignment */
/* RFC-8914 extended errors, negative values are our definitions */
#define EDE_US_SERVFAIL -2 /* SERVFAIL from usptream */
#define EDE_UNSET -1 /* No extended DNS error available */
#define EDE_OTHER 0 /* Other */
#define EDE_USUPDNSKEY 1 /* Unsupported DNSKEY algo */
#define EDE_USUPDS 2 /* Unsupported DS Digest */
#define EDE_STALE 3 /* Stale answer */
#define EDE_FORGED 4 /* Forged answer */
#define EDE_DNSSEC_IND 5 /* DNSSEC Indeterminate */
#define EDE_DNSSEC_BOGUS 6 /* DNSSEC Bogus */
#define EDE_SIG_EXP 7 /* Signature Expired */
#define EDE_SIG_NYV 8 /* Signature Not Yet Valid */
#define EDE_NO_DNSKEY 9 /* DNSKEY missing */
#define EDE_NO_RRSIG 10 /* RRSIGs missing */
#define EDE_NO_ZONEKEY 11 /* No Zone Key Bit Set */
#define EDE_NO_NSEC 12 /* NSEC Missing */
#define EDE_CACHED_ERR 13 /* Cached Error */
#define EDE_NOT_READY 14 /* Not Ready */
#define EDE_BLOCKED 15 /* Blocked */
#define EDE_CENSORED 16 /* Censored */
#define EDE_FILTERED 17 /* Filtered */
#define EDE_PROHIBITED 18 /* Prohibited */
#define EDE_STALE_NXD 19 /* Stale NXDOMAIN */
#define EDE_NOT_AUTH 20 /* Not Authoritative */
#define EDE_NOT_SUP 21 /* Not Supported */
#define EDE_NO_AUTH 22 /* No Reachable Authority */
#define EDE_NETERR 23 /* Network error */
#define EDE_INVALID_DATA 24 /* Invalid Data */
#define EDE_SIG_E_B_V 25 /* Signature Expired before Valid */
#define EDE_TOO_EARLY 26 /* To Early */
#define EDE_UNS_NS3_ITER 27 /* Unsupported NSEC3 Iterations Value */
#define EDE_UNABLE_POLICY 28 /* Unable to conform to policy */
#define EDE_SYNTHESIZED 29 /* Synthesized */
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) do { \
unsigned char *t_cp = (unsigned char *)(cp); \
(s) = ((u16)t_cp[0] << 8) \
| ((u16)t_cp[1]) \
; \
(cp) += 2; \
} while(0)
#define GETLONG(l, cp) do { \
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; \
} while (0)
#define PUTSHORT(s, cp) do { \
u16 t_s = (u16)(s); \
unsigned char *t_cp = (unsigned char *)(cp); \
*t_cp++ = t_s >> 8; \
*t_cp = t_s; \
(cp) += 2; \
} while(0)
#define PUTLONG(l, cp) do { \
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; \
} while (0)
#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 internal c-string format for names.
Cannot be '.' or /000 and must be !isprint().
Note that escaped chars are stored as
to ensure that the escaped form of /000 doesn't include /000
*/
#define NAME_ESCAPE 1
#define IS_NAME_ESCAPE(x) ((x) == 0 || (x) == '.' || (x) == NAME_ESCAPE)