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 0xFFFFu
63 /* The default size to use for allocation when we don't know how large
64 * the packet will turn out to be. */
65 #define DNS_PACKET_SIZE_START 512u
67 /* RFC 1035 say 512 is the maximum, for classic unicast DNS */
68 #define DNS_PACKET_UNICAST_SIZE_MAX 512u
70 /* With EDNS0 we can use larger packets, default to 4096, which is what is commonly used */
71 #define DNS_PACKET_UNICAST_SIZE_LARGE_MAX 4096u
76 size_t size
, allocated
, rindex
;
77 void *_data
; /* don't access directly, use DNS_PACKET_DATA()! */
78 Hashmap
*names
; /* For name compression */
79 size_t opt_start
, opt_size
;
82 DnsQuestion
*question
;
84 DnsResourceRecord
*opt
;
86 /* Packet reception metadata */
89 union in_addr_union sender
, destination
;
90 uint16_t sender_port
, destination_port
;
93 /* For support of truncated packets */
98 bool refuse_compression
:1;
99 bool canonical_form
:1;
102 static inline uint8_t* DNS_PACKET_DATA(DnsPacket
*p
) {
109 return ((uint8_t*) p
) + ALIGN(sizeof(DnsPacket
));
112 #define DNS_PACKET_HEADER(p) ((DnsPacketHeader*) DNS_PACKET_DATA(p))
113 #define DNS_PACKET_ID(p) DNS_PACKET_HEADER(p)->id
114 #define DNS_PACKET_QR(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 15) & 1)
115 #define DNS_PACKET_OPCODE(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 11) & 15)
116 #define DNS_PACKET_AA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 10) & 1)
117 #define DNS_PACKET_TC(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 9) & 1)
118 #define DNS_PACKET_RD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 8) & 1)
119 #define DNS_PACKET_RA(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 7) & 1)
120 #define DNS_PACKET_AD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 5) & 1)
121 #define DNS_PACKET_CD(p) ((be16toh(DNS_PACKET_HEADER(p)->flags) >> 4) & 1)
123 #define DNS_PACKET_FLAG_TC (UINT16_C(1) << 9)
125 static inline uint16_t DNS_PACKET_RCODE(DnsPacket
*p
) {
129 rcode
= (uint16_t) (p
->opt
->ttl
>> 24);
133 return rcode
| (be16toh(DNS_PACKET_HEADER(p
)->flags
) & 0xF);
136 static inline uint16_t DNS_PACKET_PAYLOAD_SIZE_MAX(DnsPacket
*p
) {
138 /* Returns the advertised maximum datagram size for replies, or the DNS default if there's nothing defined. */
141 return MAX(DNS_PACKET_UNICAST_SIZE_MAX
, p
->opt
->key
->class);
143 return DNS_PACKET_UNICAST_SIZE_MAX
;
146 static inline bool DNS_PACKET_DO(DnsPacket
*p
) {
150 return !!(p
->opt
->ttl
& (1U << 15));
153 static inline bool DNS_PACKET_VERSION_SUPPORTED(DnsPacket
*p
) {
154 /* Returns true if this packet is in a version we support. Which means either non-EDNS or EDNS(0), but not EDNS
155 * of any newer versions */
160 return DNS_RESOURCE_RECORD_OPT_VERSION_SUPPORTED(p
->opt
);
163 /* LLMNR defines some bits differently */
164 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
165 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
167 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
168 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
169 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
170 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
172 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
173 (((uint16_t) !!(qr) << 15) | \
174 ((uint16_t) ((opcode) & 15) << 11) | \
175 ((uint16_t) !!(aa) << 10) | /* on LLMNR: c */ \
176 ((uint16_t) !!(tc) << 9) | \
177 ((uint16_t) !!(rd) << 8) | /* on LLMNR: t */ \
178 ((uint16_t) !!(ra) << 7) | \
179 ((uint16_t) !!(ad) << 5) | \
180 ((uint16_t) !!(cd) << 4) | \
181 ((uint16_t) ((rcode) & 15)))
183 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket
*p
) {
185 (unsigned) DNS_PACKET_ANCOUNT(p
) +
186 (unsigned) DNS_PACKET_NSCOUNT(p
) +
187 (unsigned) DNS_PACKET_ARCOUNT(p
);
190 int dns_packet_new(DnsPacket
**p
, DnsProtocol protocol
, size_t min_alloc_dsize
);
191 int dns_packet_new_query(DnsPacket
**p
, DnsProtocol protocol
, size_t min_alloc_dsize
, bool dnssec_checking_disabled
);
193 void dns_packet_set_flags(DnsPacket
*p
, bool dnssec_checking_disabled
, bool truncated
);
195 DnsPacket
*dns_packet_ref(DnsPacket
*p
);
196 DnsPacket
*dns_packet_unref(DnsPacket
*p
);
198 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket
*, dns_packet_unref
);
200 int dns_packet_validate(DnsPacket
*p
);
201 int dns_packet_validate_reply(DnsPacket
*p
);
202 int dns_packet_validate_query(DnsPacket
*p
);
204 int dns_packet_is_reply_for(DnsPacket
*p
, const DnsResourceKey
*key
);
206 int dns_packet_append_blob(DnsPacket
*p
, const void *d
, size_t sz
, size_t *start
);
207 int dns_packet_append_uint8(DnsPacket
*p
, uint8_t v
, size_t *start
);
208 int dns_packet_append_uint16(DnsPacket
*p
, uint16_t v
, size_t *start
);
209 int dns_packet_append_uint32(DnsPacket
*p
, uint32_t v
, size_t *start
);
210 int dns_packet_append_string(DnsPacket
*p
, const char *s
, size_t *start
);
211 int dns_packet_append_raw_string(DnsPacket
*p
, const void *s
, size_t size
, size_t *start
);
212 int dns_packet_append_label(DnsPacket
*p
, const char *s
, size_t l
, bool canonical_candidate
, size_t *start
);
213 int dns_packet_append_name(DnsPacket
*p
, const char *name
, bool allow_compression
, bool canonical_candidate
, size_t *start
);
214 int dns_packet_append_key(DnsPacket
*p
, const DnsResourceKey
*key
, const DnsAnswerFlags flags
, size_t *start
);
215 int dns_packet_append_rr(DnsPacket
*p
, const DnsResourceRecord
*rr
, const DnsAnswerFlags flags
, size_t *start
, size_t *rdata_start
);
216 int dns_packet_append_opt(DnsPacket
*p
, uint16_t max_udp_size
, bool edns0_do
, int rcode
, size_t *start
);
217 int dns_packet_append_question(DnsPacket
*p
, DnsQuestion
*q
);
218 int dns_packet_append_answer(DnsPacket
*p
, DnsAnswer
*a
);
220 void dns_packet_truncate(DnsPacket
*p
, size_t sz
);
221 int dns_packet_truncate_opt(DnsPacket
*p
);
223 int dns_packet_read(DnsPacket
*p
, size_t sz
, const void **ret
, size_t *start
);
224 int dns_packet_read_blob(DnsPacket
*p
, void *d
, size_t sz
, size_t *start
);
225 int dns_packet_read_uint8(DnsPacket
*p
, uint8_t *ret
, size_t *start
);
226 int dns_packet_read_uint16(DnsPacket
*p
, uint16_t *ret
, size_t *start
);
227 int dns_packet_read_uint32(DnsPacket
*p
, uint32_t *ret
, size_t *start
);
228 int dns_packet_read_string(DnsPacket
*p
, char **ret
, size_t *start
);
229 int dns_packet_read_raw_string(DnsPacket
*p
, const void **ret
, size_t *size
, size_t *start
);
230 int dns_packet_read_name(DnsPacket
*p
, char **ret
, bool allow_compression
, size_t *start
);
231 int dns_packet_read_key(DnsPacket
*p
, DnsResourceKey
**ret
, bool *ret_cache_flush
, size_t *start
);
232 int dns_packet_read_rr(DnsPacket
*p
, DnsResourceRecord
**ret
, bool *ret_cache_flush
, size_t *start
);
234 void dns_packet_rewind(DnsPacket
*p
, size_t idx
);
236 int dns_packet_skip_question(DnsPacket
*p
);
237 int dns_packet_extract(DnsPacket
*p
);
239 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket
*p
) {
240 /* Never cache data originating from localhost, under the
241 * assumption, that it's coming from a locally DNS forwarder
242 * or server, that is caching on its own. */
244 return in_addr_is_localhost(p
->family
, &p
->sender
) == 0;
247 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
249 DNS_RCODE_SUCCESS
= 0,
250 DNS_RCODE_FORMERR
= 1,
251 DNS_RCODE_SERVFAIL
= 2,
252 DNS_RCODE_NXDOMAIN
= 3,
253 DNS_RCODE_NOTIMP
= 4,
254 DNS_RCODE_REFUSED
= 5,
255 DNS_RCODE_YXDOMAIN
= 6,
256 DNS_RCODE_YXRRSET
= 7,
257 DNS_RCODE_NXRRSET
= 8,
258 DNS_RCODE_NOTAUTH
= 9,
259 DNS_RCODE_NOTZONE
= 10,
260 DNS_RCODE_BADVERS
= 16,
261 DNS_RCODE_BADSIG
= 16, /* duplicate value! */
262 DNS_RCODE_BADKEY
= 17,
263 DNS_RCODE_BADTIME
= 18,
264 DNS_RCODE_BADMODE
= 19,
265 DNS_RCODE_BADNAME
= 20,
266 DNS_RCODE_BADALG
= 21,
267 DNS_RCODE_BADTRUNC
= 22,
268 DNS_RCODE_BADCOOKIE
= 23,
269 _DNS_RCODE_MAX_DEFINED
,
270 _DNS_RCODE_MAX
= 4095 /* 4 bit rcode in the header plus 8 bit rcode in OPT, makes 12 bit */
273 const char* dns_rcode_to_string(int i
) _const_
;
274 int dns_rcode_from_string(const char *s
) _pure_
;
276 const char* dns_protocol_to_string(DnsProtocol p
) _const_
;
277 DnsProtocol
dns_protocol_from_string(const char *s
) _pure_
;
279 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
280 #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 } })
282 #define MDNS_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
283 #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 } })
285 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol
, int family
, bool authenticated
) {
288 /* Converts a protocol + family into a flags field as used in queries and responses */
290 f
= authenticated
? SD_RESOLVED_AUTHENTICATED
: 0;
293 case DNS_PROTOCOL_DNS
:
294 return f
|SD_RESOLVED_DNS
;
296 case DNS_PROTOCOL_LLMNR
:
297 return f
|(family
== AF_INET6
? SD_RESOLVED_LLMNR_IPV6
: SD_RESOLVED_LLMNR_IPV4
);
299 case DNS_PROTOCOL_MDNS
:
300 return f
|(family
== AF_INET6
? SD_RESOLVED_MDNS_IPV6
: SD_RESOLVED_MDNS_IPV4
);