4 This file is part of systemd.
6 Copyright 2014 Lennart Poettering
8 systemd is free software; you can redistribute it and/or modify it
9 under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 2.1 of the License, or
11 (at your option) any later version.
13 systemd is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 Lesser General Public License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with systemd; If not, see <http://www.gnu.org/licenses/>.
22 #include <netinet/ip.h>
23 #include <netinet/udp.h>
26 #include "in-addr-util.h"
28 #include "sparse-endian.h"
30 typedef struct DnsPacketHeader DnsPacketHeader
;
31 typedef struct DnsPacket DnsPacket
;
33 #include "resolved-def.h"
34 #include "resolved-dns-answer.h"
35 #include "resolved-dns-question.h"
36 #include "resolved-dns-rr.h"
38 typedef enum DnsProtocol
{
43 _DNS_PROTOCOL_INVALID
= -1
46 struct DnsPacketHeader
{
55 #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
56 #define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
58 /* The various DNS protocols deviate in how large a packet can grow,
59 but the TCP transport has a 16bit size field, hence that appears to
60 be the absolute maximum. */
61 #define DNS_PACKET_SIZE_MAX 0xFFFF
63 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
64 #define DNS_PACKET_UNICAST_SIZE_MAX 512
66 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
67 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096
69 #define DNS_PACKET_SIZE_START 512
74 size_t size
, allocated
, rindex
;
75 void *_data
; /* don't access directly, use DNS_PACKET_DATA()! */
76 Hashmap
*names
; /* For name compression */
77 size_t opt_start
, opt_size
;
80 DnsQuestion
*question
;
82 DnsResourceRecord
*opt
;
84 /* Packet reception metadata */
87 union in_addr_union sender
, destination
;
88 uint16_t sender_port
, destination_port
;
91 /* For support of truncated packets */
96 bool refuse_compression
:1;
97 bool canonical_form
:1;
100 static inline uint8_t* DNS_PACKET_DATA(DnsPacket
*p
) {
107 return ((uint8_t*) p
) + ALIGN(sizeof(DnsPacket
));
110 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
111 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
112 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
113 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
114 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
115 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
116 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
117 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
118 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
119 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
121 #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
123 static inline uint16_t DNS_PACKET_RCODE(DnsPacket
*p
) {
127 rcode
= (uint16_t) (p
->opt
->ttl
>> 24);
131 return rcode
| (be16toh(DNS_PACKET_HEADER(p
)->flags
) & 0xF);
134 static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket
*p
) {
136 /* Returns the advertised maximum datagram size for replies, or the DNS default if there's nothing defined. */
139 return MAX(DNS_PACKET_UNICAST_SIZE_MAX
, p
->opt
->key
->class);
141 return DNS_PACKET_UNICAST_SIZE_MAX
;
144 static inline bool DNS_PACKET_DO(DnsPacket
*p
) {
148 return !!(p
->opt
->ttl
& (1U << 15));
151 static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket
*p
) {
152 /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
153 * of any newer versions */
158 return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p
->opt
);
161 /* LLMNR defines some bits differently */
162 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
163 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
165 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
166 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
167 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
168 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
170 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
171 (((uint16_t) !!(qr) << 15) | \
172 ((uint16_t) ((opcode) & 15) << 11) | \
173 ((uint16_t) !!(aa) << 10) | /* on LLMNR: c */ \
174 ((uint16_t) !!(tc) << 9) | \
175 ((uint16_t) !!(rd) << 8) | /* on LLMNR: t */ \
176 ((uint16_t) !!(ra) << 7) | \
177 ((uint16_t) !!(ad) << 5) | \
178 ((uint16_t) !!(cd) << 4) | \
179 ((uint16_t) ((rcode) & 15)))
181 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket
*p
) {
183 (unsigned) DNS_PACKET_ANCOUNT(p
) +
184 (unsigned) DNS_PACKET_NSCOUNT(p
) +
185 (unsigned) DNS_PACKET_ARCOUNT(p
);
188 int dns_packet_new(DnsPacket
**p
, DnsProtocol protocol
, size_t mtu
);
189 int dns_packet_new_query(DnsPacket
**p
, DnsProtocol protocol
, size_t mtu
, bool dnssec_checking_disabled
);
191 void dns_packet_set_flags(DnsPacket
*p
, bool dnssec_checking_disabled
, bool truncated
);
193 DnsPacket
*dns_packet_ref(DnsPacket
*p
);
194 DnsPacket
*dns_packet_unref(DnsPacket
*p
);
196 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket
*, dns_packet_unref
);
198 int dns_packet_validate(DnsPacket
*p
);
199 int dns_packet_validate_reply(DnsPacket
*p
);
200 int dns_packet_validate_query(DnsPacket
*p
);
202 int dns_packet_is_reply_for(DnsPacket
*p
, const DnsResourceKey
*key
);
204 int dns_packet_append_blob(DnsPacket
*p
, const void *d
, size_t sz
, size_t *start
);
205 int dns_packet_append_uint8(DnsPacket
*p
, uint8_t v
, size_t *start
);
206 int dns_packet_append_uint16(DnsPacket
*p
, uint16_t v
, size_t *start
);
207 int dns_packet_append_uint32(DnsPacket
*p
, uint32_t v
, size_t *start
);
208 int dns_packet_append_string(DnsPacket
*p
, const char *s
, size_t *start
);
209 int dns_packet_append_raw_string(DnsPacket
*p
, const void *s
, size_t size
, size_t *start
);
210 int dns_packet_append_label(DnsPacket
*p
, const char *s
, size_t l
, bool canonical_candidate
, size_t *start
);
211 int dns_packet_append_name(DnsPacket
*p
, const char *name
, bool allow_compression
, bool canonical_candidate
, size_t *start
);
212 int dns_packet_append_key(DnsPacket
*p
, const DnsResourceKey
*key
, size_t *start
);
213 int dns_packet_append_rr(DnsPacket
*p
, const DnsResourceRecord
*rr
, size_t *start
, size_t *rdata_start
);
214 int dns_packet_append_opt(DnsPacket
*p
, uint16_t max_udp_size
, bool edns0_do
, int rcode
, size_t *start
);
215 int dns_packet_append_question(DnsPacket
*p
, DnsQuestion
*q
);
216 int dns_packet_append_answer(DnsPacket
*p
, DnsAnswer
*a
);
218 void dns_packet_truncate(DnsPacket
*p
, size_t sz
);
219 int dns_packet_truncate_opt(DnsPacket
*p
);
221 int dns_packet_read(DnsPacket
*p
, size_t sz
, const void **ret
, size_t *start
);
222 int dns_packet_read_blob(DnsPacket
*p
, void *d
, size_t sz
, size_t *start
);
223 int dns_packet_read_uint8(DnsPacket
*p
, uint8_t *ret
, size_t *start
);
224 int dns_packet_read_uint16(DnsPacket
*p
, uint16_t *ret
, size_t *start
);
225 int dns_packet_read_uint32(DnsPacket
*p
, uint32_t *ret
, size_t *start
);
226 int dns_packet_read_string(DnsPacket
*p
, char **ret
, size_t *start
);
227 int dns_packet_read_raw_string(DnsPacket
*p
, const void **ret
, size_t *size
, size_t *start
);
228 int dns_packet_read_name(DnsPacket
*p
, char **ret
, bool allow_compression
, size_t *start
);
229 int dns_packet_read_key(DnsPacket
*p
, DnsResourceKey
**ret
, bool *ret_cache_flush
, size_t *start
);
230 int dns_packet_read_rr(DnsPacket
*p
, DnsResourceRecord
**ret
, bool *ret_cache_flush
, size_t *start
);
232 void dns_packet_rewind(DnsPacket
*p
, size_t idx
);
234 int dns_packet_skip_question(DnsPacket
*p
);
235 int dns_packet_extract(DnsPacket
*p
);
237 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket
*p
) {
238 /* Never cache data originating from localhost, under the
239 * assumption, that it's coming from a locally DNS forwarder
240 * or server, that is caching on its own. */
242 return in_addr_is_localhost(p
->family
, &p
->sender
) == 0;
245 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
247 DNS_RCODE_SUCCESS
= 0,
248 DNS_RCODE_FORMERR
= 1,
249 DNS_RCODE_SERVFAIL
= 2,
250 DNS_RCODE_NXDOMAIN
= 3,
251 DNS_RCODE_NOTIMP
= 4,
252 DNS_RCODE_REFUSED
= 5,
253 DNS_RCODE_YXDOMAIN
= 6,
254 DNS_RCODE_YXRRSET
= 7,
255 DNS_RCODE_NXRRSET
= 8,
256 DNS_RCODE_NOTAUTH
= 9,
257 DNS_RCODE_NOTZONE
= 10,
258 DNS_RCODE_BADVERS
= 16,
259 DNS_RCODE_BADSIG
= 16, /* duplicate value! */
260 DNS_RCODE_BADKEY
= 17,
261 DNS_RCODE_BADTIME
= 18,
262 DNS_RCODE_BADMODE
= 19,
263 DNS_RCODE_BADNAME
= 20,
264 DNS_RCODE_BADALG
= 21,
265 DNS_RCODE_BADTRUNC
= 22,
266 DNS_RCODE_BADCOOKIE
= 23,
267 _DNS_RCODE_MAX_DEFINED
,
268 _DNS_RCODE_MAX
= 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
271 const char* dns_rcode_to_string(int i
) _const_
;
272 int dns_rcode_from_string(const char *s
) _pure_
;
274 const char* dns_protocol_to_string(DnsProtocol p
) _const_
;
275 DnsProtocol
dns_protocol_from_string(const char *s
) _pure_
;
277 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
278 #define LLMNR_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x03 } })
280 #define MDNS_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
281 #define MDNS_MULTICAST_IPV6_ADDRESS ((struct in6_addr) { .s6_addr = { 0xFF, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfb } })
283 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol
, int family
, bool authenticated
) {
286 /* Converts a protocol + family into a flags field as used in queries and responses */
288 f
= authenticated
? SD_RESOLVED_AUTHENTICATED
: 0;
291 case DNS_PROTOCOL_DNS
:
292 return f
|SD_RESOLVED_DNS
;
294 case DNS_PROTOCOL_LLMNR
:
295 return f
|(family
== AF_INET6
? SD_RESOLVED_LLMNR_IPV6
: SD_RESOLVED_LLMNR_IPV4
);
297 case DNS_PROTOCOL_MDNS
:
298 return f
|(family
== AF_INET6
? SD_RESOLVED_MDNS_IPV6
: SD_RESOLVED_MDNS_IPV4
);