1 /* SPDX-License-Identifier: LGPL-2.1+ */
5 This file is part of systemd.
7 Copyright 2014 Lennart Poettering
9 systemd is free software; you can redistribute it and/or modify it
10 under the terms of the GNU Lesser General Public License as published by
11 the Free Software Foundation; either version 2.1 of the License, or
12 (at your option) any later version.
14 systemd is distributed in the hope that it will be useful, but
15 WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 Lesser General Public License for more details.
19 You should have received a copy of the GNU Lesser General Public License
20 along with systemd; If not, see <http://www.gnu.org/licenses/>.
23 #include <netinet/ip.h>
24 #include <netinet/udp.h>
27 #include "in-addr-util.h"
29 #include "sparse-endian.h"
31 typedef struct DnsPacketHeader DnsPacketHeader
;
32 typedef struct DnsPacket DnsPacket
;
34 #include "resolved-def.h"
35 #include "resolved-dns-answer.h"
36 #include "resolved-dns-question.h"
37 #include "resolved-dns-rr.h"
39 typedef enum DnsProtocol
{
44 _DNS_PROTOCOL_INVALID
= -1
47 struct DnsPacketHeader
{
56 #define DNS_PACKET_HEADER_SIZE sizeof(DnsPacketHeader)
57 #define UDP_PACKET_HEADER_SIZE (sizeof(struct iphdr) + sizeof(struct udphdr))
59 /* The various DNS protocols deviate in how large a packet can grow,
60 * but the TCP transport has a 16bit size field, hence that appears to
61 * be the absolute maximum. */
62 #define DNS_PACKET_SIZE_MAX 0xFFFFu
64 /* The default size to use for allocation when we don't know how large
65 * the packet will turn out to be. */
66 #define DNS_PACKET_SIZE_START 512u
68 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
69 #define DNS_PACKET_UNICAST_SIZE_MAX 512u
71 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
72 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
77 size_t size
, allocated
, rindex
, max_size
;
78 void *_data
; /* don't access directly, use DNS_PACKET_DATA()! */
79 Hashmap
*names
; /* For name compression */
80 size_t opt_start
, opt_size
;
83 DnsQuestion
*question
;
85 DnsResourceRecord
*opt
;
87 /* Packet reception metadata */
90 union in_addr_union sender
, destination
;
91 uint16_t sender_port
, destination_port
;
94 /* For support of truncated packets */
99 bool refuse_compression
:1;
100 bool canonical_form
:1;
103 static inline uint8_t* DNS_PACKET_DATA(DnsPacket
*p
) {
110 return ((uint8_t*) p
) + ALIGN(sizeof(DnsPacket
));
113 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
114 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
115 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
116 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
117 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
118 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
119 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
120 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
121 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
122 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
124 #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
126 static inline uint16_t DNS_PACKET_RCODE(DnsPacket
*p
) {
130 rcode
= (uint16_t) (p
->opt
->ttl
>> 24);
134 return rcode
| (be16toh(DNS_PACKET_HEADER(p
)->flags
) & 0xF);
137 static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket
*p
) {
139 /* Returns the advertised maximum datagram size for replies, or the DNS default if there's nothing defined. */
142 return MAX(DNS_PACKET_UNICAST_SIZE_MAX
, p
->opt
->key
->class);
144 return DNS_PACKET_UNICAST_SIZE_MAX
;
147 static inline bool DNS_PACKET_DO(DnsPacket
*p
) {
151 return !!(p
->opt
->ttl
& (1U << 15));
154 static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket
*p
) {
155 /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
156 * of any newer versions */
161 return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p
->opt
);
164 /* LLMNR defines some bits differently */
165 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
166 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
168 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
169 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
170 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
171 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
173 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
174 (((uint16_t) !!(qr) << 15) | \
175 ((uint16_t) ((opcode) & 15) << 11) | \
176 ((uint16_t) !!(aa) << 10) | /* on LLMNR: c */ \
177 ((uint16_t) !!(tc) << 9) | \
178 ((uint16_t) !!(rd) << 8) | /* on LLMNR: t */ \
179 ((uint16_t) !!(ra) << 7) | \
180 ((uint16_t) !!(ad) << 5) | \
181 ((uint16_t) !!(cd) << 4) | \
182 ((uint16_t) ((rcode) & 15)))
184 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket
*p
) {
186 (unsigned) DNS_PACKET_ANCOUNT(p
) +
187 (unsigned) DNS_PACKET_NSCOUNT(p
) +
188 (unsigned) DNS_PACKET_ARCOUNT(p
);
191 int dns_packet_new(DnsPacket
**p
, DnsProtocol protocol
, size_t min_alloc_dsize
, size_t max_size
);
192 int dns_packet_new_query(DnsPacket
**p
, DnsProtocol protocol
, size_t min_alloc_dsize
, bool dnssec_checking_disabled
);
194 void dns_packet_set_flags(DnsPacket
*p
, bool dnssec_checking_disabled
, bool truncated
);
196 DnsPacket
*dns_packet_ref(DnsPacket
*p
);
197 DnsPacket
*dns_packet_unref(DnsPacket
*p
);
199 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket
*, dns_packet_unref
);
201 int dns_packet_validate(DnsPacket
*p
);
202 int dns_packet_validate_reply(DnsPacket
*p
);
203 int dns_packet_validate_query(DnsPacket
*p
);
205 int dns_packet_is_reply_for(DnsPacket
*p
, const DnsResourceKey
*key
);
207 int dns_packet_append_blob(DnsPacket
*p
, const void *d
, size_t sz
, size_t *start
);
208 int dns_packet_append_uint8(DnsPacket
*p
, uint8_t v
, size_t *start
);
209 int dns_packet_append_uint16(DnsPacket
*p
, uint16_t v
, size_t *start
);
210 int dns_packet_append_uint32(DnsPacket
*p
, uint32_t v
, size_t *start
);
211 int dns_packet_append_string(DnsPacket
*p
, const char *s
, size_t *start
);
212 int dns_packet_append_raw_string(DnsPacket
*p
, const void *s
, size_t size
, size_t *start
);
213 int dns_packet_append_label(DnsPacket
*p
, const char *s
, size_t l
, bool canonical_candidate
, size_t *start
);
214 int dns_packet_append_name(DnsPacket
*p
, const char *name
, bool allow_compression
, bool canonical_candidate
, size_t *start
);
215 int dns_packet_append_key(DnsPacket
*p
, const DnsResourceKey
*key
, const DnsAnswerFlags flags
, size_t *start
);
216 int dns_packet_append_rr(DnsPacket
*p
, const DnsResourceRecord
*rr
, const DnsAnswerFlags flags
, size_t *start
, size_t *rdata_start
);
217 int dns_packet_append_opt(DnsPacket
*p
, uint16_t max_udp_size
, bool edns0_do
, int rcode
, size_t *start
);
218 int dns_packet_append_question(DnsPacket
*p
, DnsQuestion
*q
);
219 int dns_packet_append_answer(DnsPacket
*p
, DnsAnswer
*a
);
221 void dns_packet_truncate(DnsPacket
*p
, size_t sz
);
222 int dns_packet_truncate_opt(DnsPacket
*p
);
224 int dns_packet_read(DnsPacket
*p
, size_t sz
, const void **ret
, size_t *start
);
225 int dns_packet_read_blob(DnsPacket
*p
, void *d
, size_t sz
, size_t *start
);
226 int dns_packet_read_uint8(DnsPacket
*p
, uint8_t *ret
, size_t *start
);
227 int dns_packet_read_uint16(DnsPacket
*p
, uint16_t *ret
, size_t *start
);
228 int dns_packet_read_uint32(DnsPacket
*p
, uint32_t *ret
, size_t *start
);
229 int dns_packet_read_string(DnsPacket
*p
, char **ret
, size_t *start
);
230 int dns_packet_read_raw_string(DnsPacket
*p
, const void **ret
, size_t *size
, size_t *start
);
231 int dns_packet_read_name(DnsPacket
*p
, char **ret
, bool allow_compression
, size_t *start
);
232 int dns_packet_read_key(DnsPacket
*p
, DnsResourceKey
**ret
, bool *ret_cache_flush
, size_t *start
);
233 int dns_packet_read_rr(DnsPacket
*p
, DnsResourceRecord
**ret
, bool *ret_cache_flush
, size_t *start
);
235 void dns_packet_rewind(DnsPacket
*p
, size_t idx
);
237 int dns_packet_skip_question(DnsPacket
*p
);
238 int dns_packet_extract(DnsPacket
*p
);
240 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket
*p
) {
241 /* Never cache data originating from localhost, under the
242 * assumption, that it's coming from a locally DNS forwarder
243 * or server, that is caching on its own. */
245 return in_addr_is_localhost(p
->family
, &p
->sender
) == 0;
248 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
250 DNS_RCODE_SUCCESS
= 0,
251 DNS_RCODE_FORMERR
= 1,
252 DNS_RCODE_SERVFAIL
= 2,
253 DNS_RCODE_NXDOMAIN
= 3,
254 DNS_RCODE_NOTIMP
= 4,
255 DNS_RCODE_REFUSED
= 5,
256 DNS_RCODE_YXDOMAIN
= 6,
257 DNS_RCODE_YXRRSET
= 7,
258 DNS_RCODE_NXRRSET
= 8,
259 DNS_RCODE_NOTAUTH
= 9,
260 DNS_RCODE_NOTZONE
= 10,
261 DNS_RCODE_BADVERS
= 16,
262 DNS_RCODE_BADSIG
= 16, /* duplicate value! */
263 DNS_RCODE_BADKEY
= 17,
264 DNS_RCODE_BADTIME
= 18,
265 DNS_RCODE_BADMODE
= 19,
266 DNS_RCODE_BADNAME
= 20,
267 DNS_RCODE_BADALG
= 21,
268 DNS_RCODE_BADTRUNC
= 22,
269 DNS_RCODE_BADCOOKIE
= 23,
270 _DNS_RCODE_MAX_DEFINED
,
271 _DNS_RCODE_MAX
= 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
274 const char* dns_rcode_to_string(int i
) _const_
;
275 int dns_rcode_from_string(const char *s
) _pure_
;
277 const char* dns_protocol_to_string(DnsProtocol p
) _const_
;
278 DnsProtocol
dns_protocol_from_string(const char *s
) _pure_
;
280 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
281 #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 } })
283 #define MDNS_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
284 #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 } })
286 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol
, int family
, bool authenticated
) {
289 /* Converts a protocol + family into a flags field as used in queries and responses */
291 f
= authenticated
? SD_RESOLVED_AUTHENTICATED
: 0;
294 case DNS_PROTOCOL_DNS
:
295 return f
|SD_RESOLVED_DNS
;
297 case DNS_PROTOCOL_LLMNR
:
298 return f
|(family
== AF_INET6
? SD_RESOLVED_LLMNR_IPV6
: SD_RESOLVED_LLMNR_IPV4
);
300 case DNS_PROTOCOL_MDNS
:
301 return f
|(family
== AF_INET6
? SD_RESOLVED_MDNS_IPV6
: SD_RESOLVED_MDNS_IPV4
);
308 static inline size_t dns_packet_size_max(DnsPacket
*p
) {
311 /* Why not insist on a fully initialized max_size during DnsPacket construction? Well, this way it's easy to
312 * allocate a transient, throw-away DnsPacket on the stack by simple zero initialization, without having to
313 * deal with explicit field initialization. */
315 return p
->max_size
!= 0 ? p
->max_size
: DNS_PACKET_SIZE_MAX
;