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 static inline uint16_t DNS_PACKET_RCODE(DnsPacket
*p
) {
125 rcode
= (uint16_t) (p
->opt
->ttl
>> 24);
129 return rcode
| (be16toh(DNS_PACKET_HEADER(p
)->flags
) & 15);
132 /* LLMNR defines some bits differently */
133 #define DNS_PACKET_LLMNR_C(p) DNS_PACKET_AA(p)
134 #define DNS_PACKET_LLMNR_T(p) DNS_PACKET_RD(p)
136 #define DNS_PACKET_QDCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->qdcount)
137 #define DNS_PACKET_ANCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->ancount)
138 #define DNS_PACKET_NSCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->nscount)
139 #define DNS_PACKET_ARCOUNT(p) be16toh(DNS_PACKET_HEADER(p)->arcount)
141 #define DNS_PACKET_MAKE_FLAGS(qr, opcode, aa, tc, rd, ra, ad, cd, rcode) \
142 (((uint16_t) !!(qr) << 15) | \
143 ((uint16_t) ((opcode) & 15) << 11) | \
144 ((uint16_t) !!(aa) << 10) | /* on LLMNR: c */ \
145 ((uint16_t) !!(tc) << 9) | \
146 ((uint16_t) !!(rd) << 8) | /* on LLMNR: t */ \
147 ((uint16_t) !!(ra) << 7) | \
148 ((uint16_t) !!(ad) << 5) | \
149 ((uint16_t) !!(cd) << 4) | \
150 ((uint16_t) ((rcode) & 15)))
152 static inline unsigned DNS_PACKET_RRCOUNT(DnsPacket
*p
) {
154 (unsigned) DNS_PACKET_ANCOUNT(p
) +
155 (unsigned) DNS_PACKET_NSCOUNT(p
) +
156 (unsigned) DNS_PACKET_ARCOUNT(p
);
159 int dns_packet_new(DnsPacket
**p
, DnsProtocol protocol
, size_t mtu
);
160 int dns_packet_new_query(DnsPacket
**p
, DnsProtocol protocol
, size_t mtu
, bool dnssec_checking_disabled
);
162 void dns_packet_set_flags(DnsPacket
*p
, bool dnssec_checking_disabled
, bool truncated
);
164 DnsPacket
*dns_packet_ref(DnsPacket
*p
);
165 DnsPacket
*dns_packet_unref(DnsPacket
*p
);
167 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsPacket
*, dns_packet_unref
);
169 int dns_packet_validate(DnsPacket
*p
);
170 int dns_packet_validate_reply(DnsPacket
*p
);
171 int dns_packet_validate_query(DnsPacket
*p
);
173 int dns_packet_is_reply_for(DnsPacket
*p
, const DnsResourceKey
*key
);
175 int dns_packet_append_blob(DnsPacket
*p
, const void *d
, size_t sz
, size_t *start
);
176 int dns_packet_append_uint8(DnsPacket
*p
, uint8_t v
, size_t *start
);
177 int dns_packet_append_uint16(DnsPacket
*p
, uint16_t v
, size_t *start
);
178 int dns_packet_append_uint32(DnsPacket
*p
, uint32_t v
, size_t *start
);
179 int dns_packet_append_string(DnsPacket
*p
, const char *s
, size_t *start
);
180 int dns_packet_append_raw_string(DnsPacket
*p
, const void *s
, size_t size
, size_t *start
);
181 int dns_packet_append_label(DnsPacket
*p
, const char *s
, size_t l
, bool canonical_candidate
, size_t *start
);
182 int dns_packet_append_name(DnsPacket
*p
, const char *name
, bool allow_compression
, bool canonical_candidate
, size_t *start
);
183 int dns_packet_append_key(DnsPacket
*p
, const DnsResourceKey
*key
, size_t *start
);
184 int dns_packet_append_rr(DnsPacket
*p
, const DnsResourceRecord
*rr
, size_t *start
, size_t *rdata_start
);
185 int dns_packet_append_opt(DnsPacket
*p
, uint16_t max_udp_size
, bool edns0_do
, size_t *start
);
187 void dns_packet_truncate(DnsPacket
*p
, size_t sz
);
188 int dns_packet_truncate_opt(DnsPacket
*p
);
190 int dns_packet_read(DnsPacket
*p
, size_t sz
, const void **ret
, size_t *start
);
191 int dns_packet_read_blob(DnsPacket
*p
, void *d
, size_t sz
, size_t *start
);
192 int dns_packet_read_uint8(DnsPacket
*p
, uint8_t *ret
, size_t *start
);
193 int dns_packet_read_uint16(DnsPacket
*p
, uint16_t *ret
, size_t *start
);
194 int dns_packet_read_uint32(DnsPacket
*p
, uint32_t *ret
, size_t *start
);
195 int dns_packet_read_string(DnsPacket
*p
, char **ret
, size_t *start
);
196 int dns_packet_read_raw_string(DnsPacket
*p
, const void **ret
, size_t *size
, size_t *start
);
197 int dns_packet_read_name(DnsPacket
*p
, char **ret
, bool allow_compression
, size_t *start
);
198 int dns_packet_read_key(DnsPacket
*p
, DnsResourceKey
**ret
, bool *ret_cache_flush
, size_t *start
);
199 int dns_packet_read_rr(DnsPacket
*p
, DnsResourceRecord
**ret
, bool *ret_cache_flush
, size_t *start
);
201 void dns_packet_rewind(DnsPacket
*p
, size_t idx
);
203 int dns_packet_skip_question(DnsPacket
*p
);
204 int dns_packet_extract(DnsPacket
*p
);
206 static inline bool DNS_PACKET_SHALL_CACHE(DnsPacket
*p
) {
207 /* Never cache data originating from localhost, under the
208 * assumption, that it's coming from a locally DNS forwarder
209 * or server, that is caching on its own. */
211 return in_addr_is_localhost(p
->family
, &p
->sender
) == 0;
214 /* https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-6 */
216 DNS_RCODE_SUCCESS
= 0,
217 DNS_RCODE_FORMERR
= 1,
218 DNS_RCODE_SERVFAIL
= 2,
219 DNS_RCODE_NXDOMAIN
= 3,
220 DNS_RCODE_NOTIMP
= 4,
221 DNS_RCODE_REFUSED
= 5,
222 DNS_RCODE_YXDOMAIN
= 6,
223 DNS_RCODE_YXRRSET
= 7,
224 DNS_RCODE_NXRRSET
= 8,
225 DNS_RCODE_NOTAUTH
= 9,
226 DNS_RCODE_NOTZONE
= 10,
227 DNS_RCODE_BADVERS
= 16,
228 DNS_RCODE_BADSIG
= 16, /* duplicate value! */
229 DNS_RCODE_BADKEY
= 17,
230 DNS_RCODE_BADTIME
= 18,
231 DNS_RCODE_BADMODE
= 19,
232 DNS_RCODE_BADNAME
= 20,
233 DNS_RCODE_BADALG
= 21,
234 DNS_RCODE_BADTRUNC
= 22,
235 _DNS_RCODE_MAX_DEFINED
238 const char* dns_rcode_to_string(int i
) _const_
;
239 int dns_rcode_from_string(const char *s
) _pure_
;
241 const char* dns_protocol_to_string(DnsProtocol p
) _const_
;
242 DnsProtocol
dns_protocol_from_string(const char *s
) _pure_
;
244 #define LLMNR_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 252U) })
245 #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 } })
247 #define MDNS_MULTICAST_IPV4_ADDRESS ((struct in_addr) { .s_addr = htobe32(224U << 24 | 251U) })
248 #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 } })
250 static inline uint64_t SD_RESOLVED_FLAGS_MAKE(DnsProtocol protocol
, int family
, bool authenticated
) {
253 /* Converts a protocol + family into a flags field as used in queries and responses */
255 f
= authenticated
? SD_RESOLVED_AUTHENTICATED
: 0;
258 case DNS_PROTOCOL_DNS
:
259 return f
|SD_RESOLVED_DNS
;
261 case DNS_PROTOCOL_LLMNR
:
262 return f
|(family
== AF_INET6
? SD_RESOLVED_LLMNR_IPV6
: SD_RESOLVED_LLMNR_IPV4
);
264 case DNS_PROTOCOL_MDNS
:
265 return f
|(family
== AF_INET6
? SD_RESOLVED_MDNS_IPV6
: SD_RESOLVED_MDNS_IPV4
);