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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
74b2466e | 2 | |
62cc1c55 | 3 | #include "sd-messages.h" |
1e02e182 | 4 | |
b5efdb8a | 5 | #include "alloc-util.h" |
4a6f996c | 6 | #include "resolved-bus.h" |
74b2466e | 7 | #include "resolved-dns-server.h" |
b30bf55d | 8 | #include "resolved-dns-stub.h" |
be28f72d | 9 | #include "resolved-manager.h" |
f2f1dbe5 | 10 | #include "resolved-resolv-conf.h" |
b5efdb8a | 11 | #include "siphash24.h" |
be808ea0 | 12 | #include "string-table.h" |
f2f1dbe5 | 13 | #include "string-util.h" |
74b2466e | 14 | |
be808ea0 TG |
15 | /* The amount of time to wait before retrying with a full feature set */ |
16 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
17 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
18 | ||
19 | /* The number of times we will attempt a certain feature set before degrading */ | |
20 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
21 | ||
74b2466e LP |
22 | int dns_server_new( |
23 | Manager *m, | |
24 | DnsServer **ret, | |
4e945a6f | 25 | DnsServerType type, |
74b2466e | 26 | Link *l, |
0dd25fb9 | 27 | int family, |
2817157b | 28 | const union in_addr_union *in_addr, |
da9de738 | 29 | uint16_t port, |
2e22a54f GL |
30 | int ifindex, |
31 | const char *server_name) { | |
74b2466e | 32 | |
2e22a54f | 33 | _cleanup_free_ char *name = NULL; |
eed857b7 | 34 | DnsServer *s; |
74b2466e LP |
35 | |
36 | assert(m); | |
4e945a6f | 37 | assert((type == DNS_SERVER_LINK) == !!l); |
74b2466e | 38 | assert(in_addr); |
74b2466e | 39 | |
eed857b7 LP |
40 | if (!IN_SET(family, AF_INET, AF_INET6)) |
41 | return -EAFNOSUPPORT; | |
42 | ||
43 | if (l) { | |
44 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
45 | return -E2BIG; | |
46 | } else { | |
47 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
48 | return -E2BIG; | |
49 | } | |
50 | ||
395aa340 | 51 | if (!isempty(server_name)) { |
2e22a54f GL |
52 | name = strdup(server_name); |
53 | if (!name) | |
54 | return -ENOMEM; | |
55 | } | |
56 | ||
65b0179a | 57 | s = new(DnsServer, 1); |
74b2466e LP |
58 | if (!s) |
59 | return -ENOMEM; | |
60 | ||
65b0179a LP |
61 | *s = (DnsServer) { |
62 | .n_ref = 1, | |
63 | .manager = m, | |
64 | .type = type, | |
65 | .family = family, | |
66 | .address = *in_addr, | |
da9de738 | 67 | .port = port, |
65b0179a | 68 | .ifindex = ifindex, |
2e22a54f | 69 | .server_name = TAKE_PTR(name), |
65b0179a | 70 | }; |
59c0fd0e LP |
71 | |
72 | dns_server_reset_features(s); | |
74b2466e | 73 | |
0b58db65 LP |
74 | switch (type) { |
75 | ||
76 | case DNS_SERVER_LINK: | |
77 | s->link = l; | |
eed857b7 LP |
78 | LIST_APPEND(servers, l->dns_servers, s); |
79 | l->n_dns_servers++; | |
0b58db65 LP |
80 | break; |
81 | ||
82 | case DNS_SERVER_SYSTEM: | |
eed857b7 LP |
83 | LIST_APPEND(servers, m->dns_servers, s); |
84 | m->n_dns_servers++; | |
0b58db65 LP |
85 | break; |
86 | ||
87 | case DNS_SERVER_FALLBACK: | |
eed857b7 LP |
88 | LIST_APPEND(servers, m->fallback_dns_servers, s); |
89 | m->n_dns_servers++; | |
0b58db65 LP |
90 | break; |
91 | ||
92 | default: | |
4e945a6f | 93 | assert_not_reached("Unknown server type"); |
0b58db65 | 94 | } |
74b2466e | 95 | |
0eac4623 | 96 | s->linked = true; |
74b2466e | 97 | |
4e945a6f LP |
98 | /* A new DNS server that isn't fallback is added and the one |
99 | * we used so far was a fallback one? Then let's try to pick | |
100 | * the new one */ | |
101 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
102 | m->current_dns_server && |
103 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
104 | manager_set_dns_server(m, NULL); | |
4e945a6f | 105 | |
74b2466e LP |
106 | if (ret) |
107 | *ret = s; | |
108 | ||
109 | return 0; | |
110 | } | |
111 | ||
8301aa0b YW |
112 | static DnsServer* dns_server_free(DnsServer *s) { |
113 | assert(s); | |
74b2466e | 114 | |
904dcaf9 | 115 | dns_server_unref_stream(s); |
98767d75 | 116 | |
56ddbf10 | 117 | #if ENABLE_DNS_OVER_TLS |
6016fcb0 | 118 | dnstls_server_free(s); |
5d67a7ae IT |
119 | #endif |
120 | ||
6cb08a89 | 121 | free(s->server_string); |
8aa5afd2 | 122 | free(s->server_string_full); |
2e22a54f | 123 | free(s->server_name); |
6b430fdb | 124 | return mfree(s); |
74b2466e | 125 | } |
87f5a193 | 126 | |
8301aa0b YW |
127 | DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsServer, dns_server, dns_server_free); |
128 | ||
0eac4623 LP |
129 | void dns_server_unlink(DnsServer *s) { |
130 | assert(s); | |
131 | assert(s->manager); | |
91b14d6f | 132 | |
0eac4623 LP |
133 | /* This removes the specified server from the linked list of |
134 | * servers, but any server might still stay around if it has | |
135 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 136 | |
0eac4623 LP |
137 | if (!s->linked) |
138 | return; | |
91b14d6f | 139 | |
0eac4623 LP |
140 | switch (s->type) { |
141 | ||
142 | case DNS_SERVER_LINK: | |
143 | assert(s->link); | |
eed857b7 | 144 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 145 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 146 | s->link->n_dns_servers--; |
0eac4623 LP |
147 | break; |
148 | ||
149 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 150 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 151 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 152 | s->manager->n_dns_servers--; |
0eac4623 LP |
153 | break; |
154 | ||
155 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 156 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 157 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 158 | s->manager->n_dns_servers--; |
0eac4623 | 159 | break; |
df0fbad0 YW |
160 | default: |
161 | assert_not_reached("Unknown server type"); | |
0eac4623 LP |
162 | } |
163 | ||
164 | s->linked = false; | |
165 | ||
166 | if (s->link && s->link->current_dns_server == s) | |
167 | link_set_dns_server(s->link, NULL); | |
168 | ||
169 | if (s->manager->current_dns_server == s) | |
170 | manager_set_dns_server(s->manager, NULL); | |
171 | ||
904dcaf9 LP |
172 | /* No need to keep a default stream around anymore */ |
173 | dns_server_unref_stream(s); | |
174 | ||
0eac4623 | 175 | dns_server_unref(s); |
91b14d6f TG |
176 | } |
177 | ||
0b58db65 LP |
178 | void dns_server_move_back_and_unmark(DnsServer *s) { |
179 | DnsServer *tail; | |
180 | ||
181 | assert(s); | |
182 | ||
183 | if (!s->marked) | |
184 | return; | |
185 | ||
186 | s->marked = false; | |
187 | ||
188 | if (!s->linked || !s->servers_next) | |
189 | return; | |
190 | ||
191 | /* Move us to the end of the list, so that the order is | |
192 | * strictly kept, if we are not at the end anyway. */ | |
193 | ||
194 | switch (s->type) { | |
195 | ||
196 | case DNS_SERVER_LINK: | |
197 | assert(s->link); | |
198 | LIST_FIND_TAIL(servers, s, tail); | |
199 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
200 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
201 | break; | |
202 | ||
203 | case DNS_SERVER_SYSTEM: | |
204 | LIST_FIND_TAIL(servers, s, tail); | |
205 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
206 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
207 | break; | |
208 | ||
209 | case DNS_SERVER_FALLBACK: | |
210 | LIST_FIND_TAIL(servers, s, tail); | |
211 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
212 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
213 | break; | |
214 | ||
215 | default: | |
216 | assert_not_reached("Unknown server type"); | |
217 | } | |
218 | } | |
219 | ||
6bb2c085 | 220 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
221 | assert(s); |
222 | ||
6bb2c085 LP |
223 | if (s->verified_feature_level > level) |
224 | return; | |
b652d4a2 | 225 | |
6bb2c085 | 226 | if (s->verified_feature_level != level) { |
de54e62b LP |
227 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
228 | dns_server_feature_level_to_string(level), | |
8aa5afd2 | 229 | strna(dns_server_string_full(s))); |
f4461e56 | 230 | s->verified_feature_level = level; |
be808ea0 TG |
231 | } |
232 | ||
6bb2c085 LP |
233 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
234 | } | |
235 | ||
d001e0a3 LP |
236 | static void dns_server_reset_counters(DnsServer *s) { |
237 | assert(s); | |
238 | ||
239 | s->n_failed_udp = 0; | |
240 | s->n_failed_tcp = 0; | |
5d67a7ae | 241 | s->n_failed_tls = 0; |
d001e0a3 LP |
242 | s->packet_truncated = false; |
243 | s->verified_usec = 0; | |
244 | ||
245 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
246 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
247 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
248 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
249 | * either. | |
250 | * | |
251 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
252 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
5238e957 | 253 | * re-enable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be |
d001e0a3 LP |
254 | * incomplete. */ |
255 | } | |
256 | ||
dbc4661a | 257 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, size_t size) { |
6bb2c085 LP |
258 | assert(s); |
259 | ||
260 | if (protocol == IPPROTO_UDP) { | |
261 | if (s->possible_feature_level == level) | |
262 | s->n_failed_udp = 0; | |
6bb2c085 | 263 | } else if (protocol == IPPROTO_TCP) { |
5d67a7ae IT |
264 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { |
265 | if (s->possible_feature_level == level) | |
266 | s->n_failed_tls = 0; | |
267 | } else { | |
268 | if (s->possible_feature_level == level) | |
269 | s->n_failed_tcp = 0; | |
270 | ||
271 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
272 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
273 | } | |
274 | } | |
6bb2c085 | 275 | |
5d67a7ae IT |
276 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
277 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
278 | level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
6bb2c085 | 279 | |
5d67a7ae IT |
280 | /* If the OPT RR got lost, then we can only validate UDP at max */ |
281 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
282 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
283 | ||
284 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
285 | that does not mean we can necessarily receive large packets. */ | |
286 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
287 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
84129d46 | 288 | |
b6451358 LP |
289 | dns_server_verified(s, level); |
290 | ||
d74fb368 TG |
291 | /* Remember the size of the largest UDP packet we received from a server, |
292 | we know that we can always announce support for packets with at least | |
293 | this size. */ | |
6bb2c085 | 294 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 | 295 | s->received_udp_packet_max = size; |
9df3ba6c TG |
296 | } |
297 | ||
3da3cdd5 | 298 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level) { |
9df3ba6c | 299 | assert(s); |
be808ea0 TG |
300 | assert(s->manager); |
301 | ||
6bb2c085 LP |
302 | if (s->possible_feature_level == level) { |
303 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 304 | s->n_failed_udp++; |
5d67a7ae IT |
305 | else if (protocol == IPPROTO_TCP) { |
306 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
307 | s->n_failed_tls++; | |
308 | else | |
309 | s->n_failed_tcp++; | |
310 | } | |
6bb2c085 | 311 | } |
9df3ba6c TG |
312 | } |
313 | ||
6bb2c085 LP |
314 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
315 | assert(s); | |
571370c1 | 316 | |
6bb2c085 LP |
317 | /* Invoked whenever we get a packet with TC bit set. */ |
318 | ||
319 | if (s->possible_feature_level != level) | |
571370c1 LP |
320 | return; |
321 | ||
6bb2c085 | 322 | s->packet_truncated = true; |
4e0b8b17 TG |
323 | } |
324 | ||
de54e62b LP |
325 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
326 | assert(s); | |
327 | ||
328 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
329 | return; | |
330 | ||
b6451358 LP |
331 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
332 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
5d67a7ae | 333 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
b6451358 | 334 | |
de54e62b LP |
335 | s->packet_rrsig_missing = true; |
336 | } | |
337 | ||
338 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 339 | assert(s); |
b652d4a2 | 340 | |
de54e62b LP |
341 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
342 | return; | |
b652d4a2 | 343 | |
b6451358 LP |
344 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
345 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
346 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
347 | ||
de54e62b | 348 | s->packet_bad_opt = true; |
b652d4a2 LP |
349 | } |
350 | ||
d001e0a3 LP |
351 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
352 | assert(s); | |
353 | ||
354 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
355 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
356 | * things work. */ | |
357 | ||
358 | if (s->verified_feature_level > level) | |
359 | s->verified_feature_level = level; | |
360 | ||
361 | if (s->possible_feature_level > level) { | |
362 | s->possible_feature_level = level; | |
363 | dns_server_reset_counters(s); | |
364 | } | |
365 | ||
8aa5afd2 | 366 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", strna(dns_server_string_full(s))); |
d001e0a3 LP |
367 | } |
368 | ||
be808ea0 TG |
369 | static bool dns_server_grace_period_expired(DnsServer *s) { |
370 | usec_t ts; | |
371 | ||
372 | assert(s); | |
373 | assert(s->manager); | |
374 | ||
375 | if (s->verified_usec == 0) | |
376 | return false; | |
377 | ||
378 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
379 | ||
380 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
381 | return false; | |
382 | ||
383 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
384 | ||
385 | return true; | |
386 | } | |
387 | ||
f4461e56 | 388 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
389 | DnsServerFeatureLevel best; |
390 | ||
be808ea0 TG |
391 | assert(s); |
392 | ||
97277567 LP |
393 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
394 | * better than EDNS0, hence don't even try. */ | |
5d67a7ae | 395 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) |
c9299be2 | 396 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
397 | DNS_SERVER_FEATURE_LEVEL_LARGE : |
398 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
399 | else | |
c9299be2 | 400 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
401 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : |
402 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
97277567 LP |
403 | |
404 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
405 | * time, hence let's downgrade if we are still at a higher level. */ | |
406 | if (s->possible_feature_level > best) | |
407 | s->possible_feature_level = best; | |
408 | ||
409 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 410 | |
97277567 | 411 | s->possible_feature_level = best; |
cc450722 | 412 | |
01184277 LP |
413 | dns_server_reset_counters(s); |
414 | ||
cc450722 LP |
415 | s->packet_bad_opt = false; |
416 | s->packet_rrsig_missing = false; | |
417 | ||
de54e62b | 418 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 | 419 | dns_server_feature_level_to_string(s->possible_feature_level), |
8aa5afd2 | 420 | strna(dns_server_string_full(s))); |
6bb2c085 | 421 | |
ce7c8b20 LP |
422 | dns_server_flush_cache(s); |
423 | ||
f4461e56 LP |
424 | } else if (s->possible_feature_level <= s->verified_feature_level) |
425 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
426 | else { |
427 | DnsServerFeatureLevel p = s->possible_feature_level; | |
e034886b | 428 | int log_level = LOG_WARNING; |
be808ea0 | 429 | |
6bb2c085 | 430 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 431 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 432 | |
6bb2c085 LP |
433 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
434 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
435 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
436 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
5d67a7ae | 437 | } else if (s->n_failed_tls > 0 && |
4310bfc2 | 438 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level) && dns_server_get_dns_over_tls_mode(s) != DNS_OVER_TLS_YES) { |
5d67a7ae IT |
439 | |
440 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
441 | * if we don't require DNS-over-TLS */ | |
de54e62b | 442 | |
3c0dcbcf | 443 | log_debug("Server doesn't support DNS-over-TLS, downgrading protocol..."); |
5d67a7ae | 444 | s->possible_feature_level--; |
de54e62b LP |
445 | } else if (s->packet_bad_opt && |
446 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
447 | ||
448 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
449 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
450 | * in the request. Example: | |
451 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
452 | ||
453 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 454 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 455 | |
e034886b DDM |
456 | /* Users often don't control the DNS server they use so let's not complain too loudly |
457 | * when we can't use EDNS because the DNS server doesn't support it. */ | |
458 | log_level = LOG_NOTICE; | |
459 | ||
de54e62b LP |
460 | } else if (s->packet_rrsig_missing && |
461 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 462 | |
de54e62b LP |
463 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
464 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
465 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
466 | * not. */ | |
467 | ||
468 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
5d67a7ae | 469 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
de54e62b LP |
470 | |
471 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 472 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
473 | |
474 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
475 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
476 | * idea. We might downgrade all the way down to TCP this way. |
477 | * | |
478 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
479 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
480 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
481 | |
482 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
483 | s->possible_feature_level--; | |
484 | ||
de54e62b LP |
485 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
486 | s->packet_truncated && | |
12bf2331 | 487 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
488 | |
489 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
490 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
491 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
492 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
493 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
494 | ||
495 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
496 | s->possible_feature_level--; | |
497 | } | |
498 | ||
6bb2c085 | 499 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
500 | |
501 | /* We changed the feature level, reset the counting */ | |
01184277 | 502 | dns_server_reset_counters(s); |
6bb2c085 | 503 | |
4f571b40 | 504 | log_full(log_level, "Using degraded feature set %s instead of %s for DNS server %s.", |
e034886b | 505 | dns_server_feature_level_to_string(s->possible_feature_level), |
8aa5afd2 | 506 | dns_server_feature_level_to_string(p), strna(dns_server_string_full(s))); |
6bb2c085 | 507 | } |
be808ea0 TG |
508 | } |
509 | ||
f4461e56 | 510 | return s->possible_feature_level; |
be808ea0 TG |
511 | } |
512 | ||
519ef046 LP |
513 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
514 | size_t packet_size; | |
515 | bool edns_do; | |
516 | int r; | |
517 | ||
518 | assert(server); | |
519 | assert(packet); | |
520 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
521 | ||
522 | /* Fix the OPT field in the packet to match our current feature level. */ | |
523 | ||
524 | r = dns_packet_truncate_opt(packet); | |
525 | if (r < 0) | |
526 | return r; | |
527 | ||
528 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
529 | return 0; | |
530 | ||
531 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
532 | ||
533 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
534 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
535 | else | |
536 | packet_size = server->received_udp_packet_max; | |
537 | ||
f2ed4c69 | 538 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
539 | } |
540 | ||
2817157b LP |
541 | int dns_server_ifindex(const DnsServer *s) { |
542 | assert(s); | |
543 | ||
544 | /* The link ifindex always takes precedence */ | |
545 | if (s->link) | |
546 | return s->link->ifindex; | |
547 | ||
548 | if (s->ifindex > 0) | |
549 | return s->ifindex; | |
550 | ||
551 | return 0; | |
552 | } | |
553 | ||
da9de738 YW |
554 | uint16_t dns_server_port(const DnsServer *s) { |
555 | assert(s); | |
556 | ||
557 | if (s->port > 0) | |
558 | return s->port; | |
559 | ||
560 | return 53; | |
561 | } | |
562 | ||
6cb08a89 LP |
563 | const char *dns_server_string(DnsServer *server) { |
564 | assert(server); | |
565 | ||
566 | if (!server->server_string) | |
2817157b | 567 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 | 568 | |
8aa5afd2 YW |
569 | return server->server_string; |
570 | } | |
571 | ||
572 | const char *dns_server_string_full(DnsServer *server) { | |
573 | assert(server); | |
574 | ||
575 | if (!server->server_string_full) | |
576 | (void) in_addr_port_ifindex_name_to_string( | |
577 | server->family, | |
578 | &server->address, | |
579 | server->port, | |
580 | dns_server_ifindex(server), | |
581 | server->server_name, | |
582 | &server->server_string_full); | |
583 | ||
584 | return server->server_string_full; | |
6cb08a89 LP |
585 | } |
586 | ||
92ec902a LP |
587 | bool dns_server_dnssec_supported(DnsServer *server) { |
588 | assert(server); | |
589 | ||
590 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
591 | ||
592 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
593 | return false; | |
594 | ||
de54e62b LP |
595 | if (server->packet_bad_opt) |
596 | return false; | |
597 | ||
598 | if (server->packet_rrsig_missing) | |
92ec902a LP |
599 | return false; |
600 | ||
601 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
602 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
603 | return false; | |
604 | ||
605 | return true; | |
606 | } | |
607 | ||
1e02e182 LP |
608 | void dns_server_warn_downgrade(DnsServer *server) { |
609 | assert(server); | |
610 | ||
611 | if (server->warned_downgrade) | |
612 | return; | |
613 | ||
614 | log_struct(LOG_NOTICE, | |
2b044526 | 615 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
8aa5afd2 YW |
616 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", strna(dns_server_string_full(server))), |
617 | "DNS_SERVER=%s", strna(dns_server_string_full(server)), | |
f4cf1d66 | 618 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
619 | |
620 | server->warned_downgrade = true; | |
621 | } | |
622 | ||
7a08d314 | 623 | static void dns_server_hash_func(const DnsServer *s, struct siphash *state) { |
b826ab58 | 624 | assert(s); |
87f5a193 | 625 | |
b826ab58 TG |
626 | siphash24_compress(&s->family, sizeof(s->family), state); |
627 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
b6af2824 | 628 | siphash24_compress(&s->port, sizeof(s->port), state); |
2817157b | 629 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
f281fc1e | 630 | siphash24_compress_string(s->server_name, state); |
87f5a193 LP |
631 | } |
632 | ||
7a08d314 | 633 | static int dns_server_compare_func(const DnsServer *x, const DnsServer *y) { |
2817157b | 634 | int r; |
87f5a193 | 635 | |
a0edd02e FB |
636 | r = CMP(x->family, y->family); |
637 | if (r != 0) | |
638 | return r; | |
87f5a193 | 639 | |
2817157b LP |
640 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
641 | if (r != 0) | |
642 | return r; | |
643 | ||
b6af2824 YW |
644 | r = CMP(x->port, y->port); |
645 | if (r != 0) | |
646 | return r; | |
647 | ||
a0edd02e FB |
648 | r = CMP(x->ifindex, y->ifindex); |
649 | if (r != 0) | |
650 | return r; | |
2817157b | 651 | |
b6af2824 | 652 | return streq_ptr(x->server_name, y->server_name); |
87f5a193 | 653 | } |
d5099efc | 654 | |
7a08d314 | 655 | DEFINE_HASH_OPS(dns_server_hash_ops, DnsServer, dns_server_hash_func, dns_server_compare_func); |
636e813d | 656 | |
4b95f179 LP |
657 | void dns_server_unlink_all(DnsServer *first) { |
658 | DnsServer *next; | |
0eac4623 | 659 | |
4b95f179 LP |
660 | if (!first) |
661 | return; | |
0eac4623 | 662 | |
4b95f179 LP |
663 | next = first->servers_next; |
664 | dns_server_unlink(first); | |
636e813d | 665 | |
4b95f179 | 666 | dns_server_unlink_all(next); |
0eac4623 LP |
667 | } |
668 | ||
4b95f179 LP |
669 | void dns_server_unlink_marked(DnsServer *first) { |
670 | DnsServer *next; | |
636e813d | 671 | |
4b95f179 LP |
672 | if (!first) |
673 | return; | |
636e813d | 674 | |
4b95f179 | 675 | next = first->servers_next; |
636e813d | 676 | |
4b95f179 | 677 | if (first->marked) |
0eac4623 | 678 | dns_server_unlink(first); |
636e813d | 679 | |
4b95f179 LP |
680 | dns_server_unlink_marked(next); |
681 | } | |
636e813d | 682 | |
4b95f179 LP |
683 | void dns_server_mark_all(DnsServer *first) { |
684 | if (!first) | |
685 | return; | |
636e813d | 686 | |
4b95f179 LP |
687 | first->marked = true; |
688 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
689 | } |
690 | ||
1b860092 | 691 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, uint16_t port, int ifindex, const char *name) { |
4b95f179 | 692 | DnsServer *s; |
636e813d | 693 | |
636e813d | 694 | LIST_FOREACH(servers, s, first) |
1b860092 YW |
695 | if (s->family == family && |
696 | in_addr_equal(family, &s->address, in_addr) > 0 && | |
697 | s->port == port && | |
698 | s->ifindex == ifindex && | |
699 | streq_ptr(s->server_name, name)) | |
4b95f179 | 700 | return s; |
f2f1dbe5 | 701 | |
4b95f179 LP |
702 | return NULL; |
703 | } | |
f2f1dbe5 | 704 | |
4b95f179 | 705 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 706 | assert(m); |
f2f1dbe5 | 707 | |
4b95f179 | 708 | switch (t) { |
f2f1dbe5 | 709 | |
4b95f179 LP |
710 | case DNS_SERVER_SYSTEM: |
711 | return m->dns_servers; | |
f2f1dbe5 | 712 | |
4b95f179 LP |
713 | case DNS_SERVER_FALLBACK: |
714 | return m->fallback_dns_servers; | |
715 | ||
716 | default: | |
717 | return NULL; | |
718 | } | |
f2f1dbe5 LP |
719 | } |
720 | ||
721 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
722 | assert(m); | |
723 | ||
724 | if (m->current_dns_server == s) | |
725 | return s; | |
726 | ||
6cb08a89 | 727 | if (s) |
db8e1324 LP |
728 | log_debug("Switching to %s DNS server %s.", |
729 | dns_server_type_to_string(s->type), | |
8aa5afd2 | 730 | strna(dns_server_string_full(s))); |
f2f1dbe5 | 731 | |
0eac4623 LP |
732 | dns_server_unref(m->current_dns_server); |
733 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
734 | |
735 | if (m->unicast_scope) | |
736 | dns_cache_flush(&m->unicast_scope->cache); | |
737 | ||
4a6f996c ZJS |
738 | (void) manager_send_changed(m, "CurrentDNSServer"); |
739 | ||
f2f1dbe5 LP |
740 | return s; |
741 | } | |
742 | ||
743 | DnsServer *manager_get_dns_server(Manager *m) { | |
744 | Link *l; | |
745 | assert(m); | |
746 | ||
747 | /* Try to read updates resolv.conf */ | |
748 | manager_read_resolv_conf(m); | |
749 | ||
e3309036 | 750 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
751 | if (!m->current_dns_server) |
752 | manager_set_dns_server(m, m->dns_servers); | |
753 | ||
754 | if (!m->current_dns_server) { | |
755 | bool found = false; | |
f2f1dbe5 LP |
756 | |
757 | /* No DNS servers configured, let's see if there are | |
758 | * any on any links. If not, we use the fallback | |
759 | * servers */ | |
760 | ||
90e74a66 | 761 | HASHMAP_FOREACH(l, m->links) |
f2f1dbe5 LP |
762 | if (l->dns_servers) { |
763 | found = true; | |
764 | break; | |
765 | } | |
766 | ||
767 | if (!found) | |
768 | manager_set_dns_server(m, m->fallback_dns_servers); | |
769 | } | |
770 | ||
771 | return m->current_dns_server; | |
772 | } | |
773 | ||
774 | void manager_next_dns_server(Manager *m) { | |
775 | assert(m); | |
776 | ||
777 | /* If there's currently no DNS server set, then the next | |
778 | * manager_get_dns_server() will find one */ | |
779 | if (!m->current_dns_server) | |
780 | return; | |
781 | ||
0eac4623 LP |
782 | /* Change to the next one, but make sure to follow the linked |
783 | * list only if the server is still linked. */ | |
784 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
785 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
786 | return; | |
787 | } | |
788 | ||
789 | /* If there was no next one, then start from the beginning of | |
790 | * the list */ | |
791 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
792 | manager_set_dns_server(m, m->fallback_dns_servers); | |
793 | else | |
794 | manager_set_dns_server(m, m->dns_servers); | |
795 | } | |
be808ea0 | 796 | |
12bf2331 LP |
797 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
798 | assert(s); | |
799 | ||
800 | if (s->link) | |
801 | return link_get_dnssec_mode(s->link); | |
802 | ||
803 | return manager_get_dnssec_mode(s->manager); | |
804 | } | |
805 | ||
c9299be2 | 806 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { |
5d67a7ae IT |
807 | assert(s); |
808 | ||
d050561a | 809 | if (s->link) |
c9299be2 | 810 | return link_get_dns_over_tls_mode(s->link); |
d050561a | 811 | |
c9299be2 | 812 | return manager_get_dns_over_tls_mode(s->manager); |
5d67a7ae IT |
813 | } |
814 | ||
ce7c8b20 LP |
815 | void dns_server_flush_cache(DnsServer *s) { |
816 | DnsServer *current; | |
817 | DnsScope *scope; | |
818 | ||
819 | assert(s); | |
820 | ||
821 | /* Flush the cache of the scope this server belongs to */ | |
822 | ||
823 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
824 | if (current != s) | |
825 | return; | |
826 | ||
827 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
828 | if (!scope) | |
829 | return; | |
830 | ||
831 | dns_cache_flush(&scope->cache); | |
832 | } | |
833 | ||
59c0fd0e LP |
834 | void dns_server_reset_features(DnsServer *s) { |
835 | assert(s); | |
836 | ||
59c0fd0e LP |
837 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
838 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
839 | ||
840 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
841 | ||
842 | s->packet_bad_opt = false; | |
843 | s->packet_rrsig_missing = false; | |
844 | ||
845 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
846 | ||
847 | s->warned_downgrade = false; | |
848 | ||
849 | dns_server_reset_counters(s); | |
904dcaf9 LP |
850 | |
851 | /* Let's close the default stream, so that we reprobe with the new features */ | |
852 | dns_server_unref_stream(s); | |
59c0fd0e LP |
853 | } |
854 | ||
855 | void dns_server_reset_features_all(DnsServer *s) { | |
856 | DnsServer *i; | |
857 | ||
858 | LIST_FOREACH(servers, i, s) | |
859 | dns_server_reset_features(i); | |
860 | } | |
861 | ||
cf84484a LP |
862 | void dns_server_dump(DnsServer *s, FILE *f) { |
863 | assert(s); | |
864 | ||
865 | if (!f) | |
866 | f = stdout; | |
867 | ||
868 | fputs("[Server ", f); | |
8aa5afd2 | 869 | fputs(strna(dns_server_string_full(s)), f); |
cf84484a LP |
870 | fputs(" type=", f); |
871 | fputs(dns_server_type_to_string(s->type), f); | |
872 | ||
873 | if (s->type == DNS_SERVER_LINK) { | |
874 | assert(s->link); | |
875 | ||
876 | fputs(" interface=", f); | |
6ff79f76 | 877 | fputs(s->link->ifname, f); |
cf84484a LP |
878 | } |
879 | ||
880 | fputs("]\n", f); | |
881 | ||
882 | fputs("\tVerified feature level: ", f); | |
883 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
884 | fputc('\n', f); | |
885 | ||
886 | fputs("\tPossible feature level: ", f); | |
887 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
888 | fputc('\n', f); | |
889 | ||
890 | fputs("\tDNSSEC Mode: ", f); | |
891 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
892 | fputc('\n', f); | |
893 | ||
894 | fputs("\tCan do DNSSEC: ", f); | |
895 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
896 | fputc('\n', f); | |
897 | ||
898 | fprintf(f, | |
899 | "\tMaximum UDP packet size received: %zu\n" | |
900 | "\tFailed UDP attempts: %u\n" | |
901 | "\tFailed TCP attempts: %u\n" | |
902 | "\tSeen truncated packet: %s\n" | |
903 | "\tSeen OPT RR getting lost: %s\n" | |
904 | "\tSeen RRSIG RR missing: %s\n", | |
905 | s->received_udp_packet_max, | |
906 | s->n_failed_udp, | |
907 | s->n_failed_tcp, | |
908 | yes_no(s->packet_truncated), | |
909 | yes_no(s->packet_bad_opt), | |
910 | yes_no(s->packet_rrsig_missing)); | |
911 | } | |
912 | ||
904dcaf9 LP |
913 | void dns_server_unref_stream(DnsServer *s) { |
914 | DnsStream *ref; | |
915 | ||
916 | assert(s); | |
917 | ||
918 | /* Detaches the default stream of this server. Some special care needs to be taken here, as that stream and | |
919 | * this server reference each other. First, take the stream out of the server. It's destructor will check if it | |
5238e957 | 920 | * is registered with us, hence let's invalidate this separately, so that it is already unregistered. */ |
904dcaf9 LP |
921 | ref = TAKE_PTR(s->stream); |
922 | ||
923 | /* And then, unref it */ | |
924 | dns_stream_unref(ref); | |
925 | } | |
926 | ||
f76fa088 LP |
927 | DnsScope *dns_server_scope(DnsServer *s) { |
928 | assert(s); | |
929 | assert((s->type == DNS_SERVER_LINK) == !!s->link); | |
930 | ||
931 | if (s->link) | |
932 | return s->link->unicast_scope; | |
933 | ||
934 | return s->manager->unicast_scope; | |
935 | } | |
936 | ||
e3309036 ZJS |
937 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
938 | [DNS_SERVER_SYSTEM] = "system", | |
939 | [DNS_SERVER_FALLBACK] = "fallback", | |
940 | [DNS_SERVER_LINK] = "link", | |
941 | }; | |
942 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
943 | ||
be808ea0 TG |
944 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
945 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
946 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 947 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
5d67a7ae | 948 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 949 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 950 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 951 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
952 | }; |
953 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |