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1 | /* SPDX-License-Identifier: LGPL-2.1+ */ | |
2 | ||
3 | #include "sd-messages.h" | |
4 | ||
5 | #include "alloc-util.h" | |
6 | #include "resolved-dns-server.h" | |
7 | #include "resolved-dns-stub.h" | |
8 | #include "resolved-resolv-conf.h" | |
9 | #include "siphash24.h" | |
10 | #include "string-table.h" | |
11 | #include "string-util.h" | |
12 | ||
13 | /* The amount of time to wait before retrying with a full feature set */ | |
14 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
15 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
16 | ||
17 | /* The number of times we will attempt a certain feature set before degrading */ | |
18 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
19 | ||
20 | int dns_server_new( | |
21 | Manager *m, | |
22 | DnsServer **ret, | |
23 | DnsServerType type, | |
24 | Link *l, | |
25 | int family, | |
26 | const union in_addr_union *in_addr, | |
27 | int ifindex) { | |
28 | ||
29 | DnsServer *s; | |
30 | ||
31 | assert(m); | |
32 | assert((type == DNS_SERVER_LINK) == !!l); | |
33 | assert(in_addr); | |
34 | ||
35 | if (!IN_SET(family, AF_INET, AF_INET6)) | |
36 | return -EAFNOSUPPORT; | |
37 | ||
38 | if (l) { | |
39 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
40 | return -E2BIG; | |
41 | } else { | |
42 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
43 | return -E2BIG; | |
44 | } | |
45 | ||
46 | s = new0(DnsServer, 1); | |
47 | if (!s) | |
48 | return -ENOMEM; | |
49 | ||
50 | s->n_ref = 1; | |
51 | s->manager = m; | |
52 | s->type = type; | |
53 | s->family = family; | |
54 | s->address = *in_addr; | |
55 | s->ifindex = ifindex; | |
56 | ||
57 | dns_server_reset_features(s); | |
58 | ||
59 | switch (type) { | |
60 | ||
61 | case DNS_SERVER_LINK: | |
62 | s->link = l; | |
63 | LIST_APPEND(servers, l->dns_servers, s); | |
64 | l->n_dns_servers++; | |
65 | break; | |
66 | ||
67 | case DNS_SERVER_SYSTEM: | |
68 | LIST_APPEND(servers, m->dns_servers, s); | |
69 | m->n_dns_servers++; | |
70 | break; | |
71 | ||
72 | case DNS_SERVER_FALLBACK: | |
73 | LIST_APPEND(servers, m->fallback_dns_servers, s); | |
74 | m->n_dns_servers++; | |
75 | break; | |
76 | ||
77 | default: | |
78 | assert_not_reached("Unknown server type"); | |
79 | } | |
80 | ||
81 | s->linked = true; | |
82 | ||
83 | #if ENABLE_DNS_OVER_TLS | |
84 | dnstls_server_init(s); | |
85 | #endif | |
86 | ||
87 | /* A new DNS server that isn't fallback is added and the one | |
88 | * we used so far was a fallback one? Then let's try to pick | |
89 | * the new one */ | |
90 | if (type != DNS_SERVER_FALLBACK && | |
91 | m->current_dns_server && | |
92 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
93 | manager_set_dns_server(m, NULL); | |
94 | ||
95 | if (ret) | |
96 | *ret = s; | |
97 | ||
98 | return 0; | |
99 | } | |
100 | ||
101 | static DnsServer* dns_server_free(DnsServer *s) { | |
102 | assert(s); | |
103 | ||
104 | dns_stream_unref(s->stream); | |
105 | ||
106 | #if ENABLE_DNS_OVER_TLS | |
107 | dnstls_server_free(s); | |
108 | #endif | |
109 | ||
110 | free(s->server_string); | |
111 | return mfree(s); | |
112 | } | |
113 | ||
114 | DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsServer, dns_server, dns_server_free); | |
115 | ||
116 | void dns_server_unlink(DnsServer *s) { | |
117 | assert(s); | |
118 | assert(s->manager); | |
119 | ||
120 | /* This removes the specified server from the linked list of | |
121 | * servers, but any server might still stay around if it has | |
122 | * refs, for example from an ongoing transaction. */ | |
123 | ||
124 | if (!s->linked) | |
125 | return; | |
126 | ||
127 | switch (s->type) { | |
128 | ||
129 | case DNS_SERVER_LINK: | |
130 | assert(s->link); | |
131 | assert(s->link->n_dns_servers > 0); | |
132 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
133 | s->link->n_dns_servers--; | |
134 | break; | |
135 | ||
136 | case DNS_SERVER_SYSTEM: | |
137 | assert(s->manager->n_dns_servers > 0); | |
138 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
139 | s->manager->n_dns_servers--; | |
140 | break; | |
141 | ||
142 | case DNS_SERVER_FALLBACK: | |
143 | assert(s->manager->n_dns_servers > 0); | |
144 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
145 | s->manager->n_dns_servers--; | |
146 | break; | |
147 | default: | |
148 | assert_not_reached("Unknown server type"); | |
149 | } | |
150 | ||
151 | s->linked = false; | |
152 | ||
153 | if (s->link && s->link->current_dns_server == s) | |
154 | link_set_dns_server(s->link, NULL); | |
155 | ||
156 | if (s->manager->current_dns_server == s) | |
157 | manager_set_dns_server(s->manager, NULL); | |
158 | ||
159 | dns_server_unref(s); | |
160 | } | |
161 | ||
162 | void dns_server_move_back_and_unmark(DnsServer *s) { | |
163 | DnsServer *tail; | |
164 | ||
165 | assert(s); | |
166 | ||
167 | if (!s->marked) | |
168 | return; | |
169 | ||
170 | s->marked = false; | |
171 | ||
172 | if (!s->linked || !s->servers_next) | |
173 | return; | |
174 | ||
175 | /* Move us to the end of the list, so that the order is | |
176 | * strictly kept, if we are not at the end anyway. */ | |
177 | ||
178 | switch (s->type) { | |
179 | ||
180 | case DNS_SERVER_LINK: | |
181 | assert(s->link); | |
182 | LIST_FIND_TAIL(servers, s, tail); | |
183 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
184 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
185 | break; | |
186 | ||
187 | case DNS_SERVER_SYSTEM: | |
188 | LIST_FIND_TAIL(servers, s, tail); | |
189 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
190 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
191 | break; | |
192 | ||
193 | case DNS_SERVER_FALLBACK: | |
194 | LIST_FIND_TAIL(servers, s, tail); | |
195 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
196 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
197 | break; | |
198 | ||
199 | default: | |
200 | assert_not_reached("Unknown server type"); | |
201 | } | |
202 | } | |
203 | ||
204 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { | |
205 | assert(s); | |
206 | ||
207 | if (s->verified_feature_level > level) | |
208 | return; | |
209 | ||
210 | if (s->verified_feature_level != level) { | |
211 | log_debug("Verified we get a response at feature level %s from DNS server %s.", | |
212 | dns_server_feature_level_to_string(level), | |
213 | dns_server_string(s)); | |
214 | s->verified_feature_level = level; | |
215 | } | |
216 | ||
217 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); | |
218 | } | |
219 | ||
220 | static void dns_server_reset_counters(DnsServer *s) { | |
221 | assert(s); | |
222 | ||
223 | s->n_failed_udp = 0; | |
224 | s->n_failed_tcp = 0; | |
225 | s->n_failed_tls = 0; | |
226 | s->packet_truncated = false; | |
227 | s->verified_usec = 0; | |
228 | ||
229 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
230 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
231 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
232 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
233 | * either. | |
234 | * | |
235 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
236 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
237 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
238 | * incomplete. */ | |
239 | } | |
240 | ||
241 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, size_t size) { | |
242 | assert(s); | |
243 | ||
244 | if (protocol == IPPROTO_UDP) { | |
245 | if (s->possible_feature_level == level) | |
246 | s->n_failed_udp = 0; | |
247 | } else if (protocol == IPPROTO_TCP) { | |
248 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { | |
249 | if (s->possible_feature_level == level) | |
250 | s->n_failed_tls = 0; | |
251 | } else { | |
252 | if (s->possible_feature_level == level) | |
253 | s->n_failed_tcp = 0; | |
254 | ||
255 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
256 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
257 | } | |
258 | } | |
259 | ||
260 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ | |
261 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
262 | level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
263 | ||
264 | /* If the OPT RR got lost, then we can only validate UDP at max */ | |
265 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
266 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
267 | ||
268 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
269 | that does not mean we can necessarily receive large packets. */ | |
270 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
271 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
272 | ||
273 | dns_server_verified(s, level); | |
274 | ||
275 | /* Remember the size of the largest UDP packet we received from a server, | |
276 | we know that we can always announce support for packets with at least | |
277 | this size. */ | |
278 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) | |
279 | s->received_udp_packet_max = size; | |
280 | } | |
281 | ||
282 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level) { | |
283 | assert(s); | |
284 | assert(s->manager); | |
285 | ||
286 | if (s->possible_feature_level == level) { | |
287 | if (protocol == IPPROTO_UDP) | |
288 | s->n_failed_udp++; | |
289 | else if (protocol == IPPROTO_TCP) { | |
290 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
291 | s->n_failed_tls++; | |
292 | else | |
293 | s->n_failed_tcp++; | |
294 | } | |
295 | } | |
296 | } | |
297 | ||
298 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { | |
299 | assert(s); | |
300 | ||
301 | /* Invoked whenever we get a packet with TC bit set. */ | |
302 | ||
303 | if (s->possible_feature_level != level) | |
304 | return; | |
305 | ||
306 | s->packet_truncated = true; | |
307 | } | |
308 | ||
309 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { | |
310 | assert(s); | |
311 | ||
312 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
313 | return; | |
314 | ||
315 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ | |
316 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
317 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
318 | ||
319 | s->packet_rrsig_missing = true; | |
320 | } | |
321 | ||
322 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
323 | assert(s); | |
324 | ||
325 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
326 | return; | |
327 | ||
328 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ | |
329 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
330 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
331 | ||
332 | s->packet_bad_opt = true; | |
333 | } | |
334 | ||
335 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { | |
336 | assert(s); | |
337 | ||
338 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
339 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
340 | * things work. */ | |
341 | ||
342 | if (s->verified_feature_level > level) | |
343 | s->verified_feature_level = level; | |
344 | ||
345 | if (s->possible_feature_level > level) { | |
346 | s->possible_feature_level = level; | |
347 | dns_server_reset_counters(s); | |
348 | } | |
349 | ||
350 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
351 | } | |
352 | ||
353 | static bool dns_server_grace_period_expired(DnsServer *s) { | |
354 | usec_t ts; | |
355 | ||
356 | assert(s); | |
357 | assert(s->manager); | |
358 | ||
359 | if (s->verified_usec == 0) | |
360 | return false; | |
361 | ||
362 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
363 | ||
364 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
365 | return false; | |
366 | ||
367 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
368 | ||
369 | return true; | |
370 | } | |
371 | ||
372 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { | |
373 | DnsServerFeatureLevel best; | |
374 | ||
375 | assert(s); | |
376 | ||
377 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything | |
378 | * better than EDNS0, hence don't even try. */ | |
379 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) | |
380 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? | |
381 | DNS_SERVER_FEATURE_LEVEL_LARGE : | |
382 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
383 | else | |
384 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? | |
385 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : | |
386 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
387 | ||
388 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
389 | * time, hence let's downgrade if we are still at a higher level. */ | |
390 | if (s->possible_feature_level > best) | |
391 | s->possible_feature_level = best; | |
392 | ||
393 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
394 | ||
395 | s->possible_feature_level = best; | |
396 | ||
397 | dns_server_reset_counters(s); | |
398 | ||
399 | s->packet_bad_opt = false; | |
400 | s->packet_rrsig_missing = false; | |
401 | ||
402 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", | |
403 | dns_server_feature_level_to_string(s->possible_feature_level), | |
404 | dns_server_string(s)); | |
405 | ||
406 | dns_server_flush_cache(s); | |
407 | ||
408 | } else if (s->possible_feature_level <= s->verified_feature_level) | |
409 | s->possible_feature_level = s->verified_feature_level; | |
410 | else { | |
411 | DnsServerFeatureLevel p = s->possible_feature_level; | |
412 | ||
413 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
414 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { | |
415 | ||
416 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't | |
417 | * work. Upgrade back to UDP again. */ | |
418 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); | |
419 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
420 | } else if (s->n_failed_tls > 0 && | |
421 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level)) { | |
422 | ||
423 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
424 | * if we don't require DNS-over-TLS */ | |
425 | ||
426 | log_debug("Server doesn't support DNS-over-TLS, downgrading protocol..."); | |
427 | s->possible_feature_level--; | |
428 | } else if (s->packet_bad_opt && | |
429 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
430 | ||
431 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
432 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
433 | * in the request. Example: | |
434 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
435 | ||
436 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
437 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
438 | ||
439 | } else if (s->packet_rrsig_missing && | |
440 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
441 | ||
442 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't | |
443 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
444 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
445 | * not. */ | |
446 | ||
447 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
448 | 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; | |
449 | ||
450 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
451 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { | |
452 | ||
453 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
454 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
455 | * idea. We might downgrade all the way down to TCP this way. | |
456 | * | |
457 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
458 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
459 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
460 | ||
461 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
462 | s->possible_feature_level--; | |
463 | ||
464 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
465 | s->packet_truncated && | |
466 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { | |
467 | ||
468 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
469 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
470 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
471 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
472 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
473 | ||
474 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
475 | s->possible_feature_level--; | |
476 | } | |
477 | ||
478 | if (p != s->possible_feature_level) { | |
479 | ||
480 | /* We changed the feature level, reset the counting */ | |
481 | dns_server_reset_counters(s); | |
482 | ||
483 | log_warning("Using degraded feature set (%s) for DNS server %s.", | |
484 | dns_server_feature_level_to_string(s->possible_feature_level), | |
485 | dns_server_string(s)); | |
486 | } | |
487 | } | |
488 | ||
489 | return s->possible_feature_level; | |
490 | } | |
491 | ||
492 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { | |
493 | size_t packet_size; | |
494 | bool edns_do; | |
495 | int r; | |
496 | ||
497 | assert(server); | |
498 | assert(packet); | |
499 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
500 | ||
501 | /* Fix the OPT field in the packet to match our current feature level. */ | |
502 | ||
503 | r = dns_packet_truncate_opt(packet); | |
504 | if (r < 0) | |
505 | return r; | |
506 | ||
507 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
508 | return 0; | |
509 | ||
510 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
511 | ||
512 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
513 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
514 | else | |
515 | packet_size = server->received_udp_packet_max; | |
516 | ||
517 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); | |
518 | } | |
519 | ||
520 | int dns_server_ifindex(const DnsServer *s) { | |
521 | assert(s); | |
522 | ||
523 | /* The link ifindex always takes precedence */ | |
524 | if (s->link) | |
525 | return s->link->ifindex; | |
526 | ||
527 | if (s->ifindex > 0) | |
528 | return s->ifindex; | |
529 | ||
530 | return 0; | |
531 | } | |
532 | ||
533 | const char *dns_server_string(DnsServer *server) { | |
534 | assert(server); | |
535 | ||
536 | if (!server->server_string) | |
537 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); | |
538 | ||
539 | return strna(server->server_string); | |
540 | } | |
541 | ||
542 | bool dns_server_dnssec_supported(DnsServer *server) { | |
543 | assert(server); | |
544 | ||
545 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
546 | ||
547 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
548 | return false; | |
549 | ||
550 | if (server->packet_bad_opt) | |
551 | return false; | |
552 | ||
553 | if (server->packet_rrsig_missing) | |
554 | return false; | |
555 | ||
556 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
557 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
558 | return false; | |
559 | ||
560 | return true; | |
561 | } | |
562 | ||
563 | void dns_server_warn_downgrade(DnsServer *server) { | |
564 | assert(server); | |
565 | ||
566 | if (server->warned_downgrade) | |
567 | return; | |
568 | ||
569 | log_struct(LOG_NOTICE, | |
570 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, | |
571 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), | |
572 | "DNS_SERVER=%s", dns_server_string(server), | |
573 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); | |
574 | ||
575 | server->warned_downgrade = true; | |
576 | } | |
577 | ||
578 | bool dns_server_limited_domains(DnsServer *server) { | |
579 | DnsSearchDomain *domain; | |
580 | bool domain_restricted = false; | |
581 | ||
582 | /* Check if the server has route-only domains without ~., i. e. whether | |
583 | * it should only be used for particular domains */ | |
584 | if (!server->link) | |
585 | return false; | |
586 | ||
587 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
588 | if (domain->route_only) { | |
589 | domain_restricted = true; | |
590 | /* ~. means "any domain", thus it is a global server */ | |
591 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) | |
592 | return false; | |
593 | } | |
594 | ||
595 | return domain_restricted; | |
596 | } | |
597 | ||
598 | static void dns_server_hash_func(const void *p, struct siphash *state) { | |
599 | const DnsServer *s = p; | |
600 | ||
601 | assert(s); | |
602 | ||
603 | siphash24_compress(&s->family, sizeof(s->family), state); | |
604 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
605 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); | |
606 | } | |
607 | ||
608 | static int dns_server_compare_func(const void *a, const void *b) { | |
609 | const DnsServer *x = a, *y = b; | |
610 | int r; | |
611 | ||
612 | r = CMP(x->family, y->family); | |
613 | if (r != 0) | |
614 | return r; | |
615 | ||
616 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); | |
617 | if (r != 0) | |
618 | return r; | |
619 | ||
620 | r = CMP(x->ifindex, y->ifindex); | |
621 | if (r != 0) | |
622 | return r; | |
623 | ||
624 | return 0; | |
625 | } | |
626 | ||
627 | const struct hash_ops dns_server_hash_ops = { | |
628 | .hash = dns_server_hash_func, | |
629 | .compare = dns_server_compare_func | |
630 | }; | |
631 | ||
632 | void dns_server_unlink_all(DnsServer *first) { | |
633 | DnsServer *next; | |
634 | ||
635 | if (!first) | |
636 | return; | |
637 | ||
638 | next = first->servers_next; | |
639 | dns_server_unlink(first); | |
640 | ||
641 | dns_server_unlink_all(next); | |
642 | } | |
643 | ||
644 | void dns_server_unlink_marked(DnsServer *first) { | |
645 | DnsServer *next; | |
646 | ||
647 | if (!first) | |
648 | return; | |
649 | ||
650 | next = first->servers_next; | |
651 | ||
652 | if (first->marked) | |
653 | dns_server_unlink(first); | |
654 | ||
655 | dns_server_unlink_marked(next); | |
656 | } | |
657 | ||
658 | void dns_server_mark_all(DnsServer *first) { | |
659 | if (!first) | |
660 | return; | |
661 | ||
662 | first->marked = true; | |
663 | dns_server_mark_all(first->servers_next); | |
664 | } | |
665 | ||
666 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { | |
667 | DnsServer *s; | |
668 | ||
669 | LIST_FOREACH(servers, s, first) | |
670 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) | |
671 | return s; | |
672 | ||
673 | return NULL; | |
674 | } | |
675 | ||
676 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { | |
677 | assert(m); | |
678 | ||
679 | switch (t) { | |
680 | ||
681 | case DNS_SERVER_SYSTEM: | |
682 | return m->dns_servers; | |
683 | ||
684 | case DNS_SERVER_FALLBACK: | |
685 | return m->fallback_dns_servers; | |
686 | ||
687 | default: | |
688 | return NULL; | |
689 | } | |
690 | } | |
691 | ||
692 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
693 | assert(m); | |
694 | ||
695 | if (m->current_dns_server == s) | |
696 | return s; | |
697 | ||
698 | if (s) | |
699 | log_debug("Switching to %s DNS server %s.", | |
700 | dns_server_type_to_string(s->type), | |
701 | dns_server_string(s)); | |
702 | ||
703 | dns_server_unref(m->current_dns_server); | |
704 | m->current_dns_server = dns_server_ref(s); | |
705 | ||
706 | if (m->unicast_scope) | |
707 | dns_cache_flush(&m->unicast_scope->cache); | |
708 | ||
709 | return s; | |
710 | } | |
711 | ||
712 | DnsServer *manager_get_dns_server(Manager *m) { | |
713 | Link *l; | |
714 | assert(m); | |
715 | ||
716 | /* Try to read updates resolv.conf */ | |
717 | manager_read_resolv_conf(m); | |
718 | ||
719 | /* If no DNS server was chosen so far, pick the first one */ | |
720 | if (!m->current_dns_server) | |
721 | manager_set_dns_server(m, m->dns_servers); | |
722 | ||
723 | if (!m->current_dns_server) { | |
724 | bool found = false; | |
725 | Iterator i; | |
726 | ||
727 | /* No DNS servers configured, let's see if there are | |
728 | * any on any links. If not, we use the fallback | |
729 | * servers */ | |
730 | ||
731 | HASHMAP_FOREACH(l, m->links, i) | |
732 | if (l->dns_servers) { | |
733 | found = true; | |
734 | break; | |
735 | } | |
736 | ||
737 | if (!found) | |
738 | manager_set_dns_server(m, m->fallback_dns_servers); | |
739 | } | |
740 | ||
741 | return m->current_dns_server; | |
742 | } | |
743 | ||
744 | void manager_next_dns_server(Manager *m) { | |
745 | assert(m); | |
746 | ||
747 | /* If there's currently no DNS server set, then the next | |
748 | * manager_get_dns_server() will find one */ | |
749 | if (!m->current_dns_server) | |
750 | return; | |
751 | ||
752 | /* Change to the next one, but make sure to follow the linked | |
753 | * list only if the server is still linked. */ | |
754 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
755 | manager_set_dns_server(m, m->current_dns_server->servers_next); | |
756 | return; | |
757 | } | |
758 | ||
759 | /* If there was no next one, then start from the beginning of | |
760 | * the list */ | |
761 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
762 | manager_set_dns_server(m, m->fallback_dns_servers); | |
763 | else | |
764 | manager_set_dns_server(m, m->dns_servers); | |
765 | } | |
766 | ||
767 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { | |
768 | ||
769 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
770 | ||
771 | if (in_addr_is_null(family, sa)) | |
772 | return false; | |
773 | ||
774 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
775 | return false; | |
776 | ||
777 | return true; | |
778 | } | |
779 | ||
780 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { | |
781 | assert(s); | |
782 | ||
783 | if (s->link) | |
784 | return link_get_dnssec_mode(s->link); | |
785 | ||
786 | return manager_get_dnssec_mode(s->manager); | |
787 | } | |
788 | ||
789 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { | |
790 | assert(s); | |
791 | ||
792 | if (s->link) | |
793 | return link_get_dns_over_tls_mode(s->link); | |
794 | ||
795 | return manager_get_dns_over_tls_mode(s->manager); | |
796 | } | |
797 | ||
798 | void dns_server_flush_cache(DnsServer *s) { | |
799 | DnsServer *current; | |
800 | DnsScope *scope; | |
801 | ||
802 | assert(s); | |
803 | ||
804 | /* Flush the cache of the scope this server belongs to */ | |
805 | ||
806 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
807 | if (current != s) | |
808 | return; | |
809 | ||
810 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
811 | if (!scope) | |
812 | return; | |
813 | ||
814 | dns_cache_flush(&scope->cache); | |
815 | } | |
816 | ||
817 | void dns_server_reset_features(DnsServer *s) { | |
818 | assert(s); | |
819 | ||
820 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; | |
821 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
822 | ||
823 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
824 | ||
825 | s->packet_bad_opt = false; | |
826 | s->packet_rrsig_missing = false; | |
827 | ||
828 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
829 | ||
830 | s->warned_downgrade = false; | |
831 | ||
832 | dns_server_reset_counters(s); | |
833 | } | |
834 | ||
835 | void dns_server_reset_features_all(DnsServer *s) { | |
836 | DnsServer *i; | |
837 | ||
838 | LIST_FOREACH(servers, i, s) | |
839 | dns_server_reset_features(i); | |
840 | } | |
841 | ||
842 | void dns_server_dump(DnsServer *s, FILE *f) { | |
843 | assert(s); | |
844 | ||
845 | if (!f) | |
846 | f = stdout; | |
847 | ||
848 | fputs("[Server ", f); | |
849 | fputs(dns_server_string(s), f); | |
850 | fputs(" type=", f); | |
851 | fputs(dns_server_type_to_string(s->type), f); | |
852 | ||
853 | if (s->type == DNS_SERVER_LINK) { | |
854 | assert(s->link); | |
855 | ||
856 | fputs(" interface=", f); | |
857 | fputs(s->link->name, f); | |
858 | } | |
859 | ||
860 | fputs("]\n", f); | |
861 | ||
862 | fputs("\tVerified feature level: ", f); | |
863 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
864 | fputc('\n', f); | |
865 | ||
866 | fputs("\tPossible feature level: ", f); | |
867 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
868 | fputc('\n', f); | |
869 | ||
870 | fputs("\tDNSSEC Mode: ", f); | |
871 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
872 | fputc('\n', f); | |
873 | ||
874 | fputs("\tCan do DNSSEC: ", f); | |
875 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
876 | fputc('\n', f); | |
877 | ||
878 | fprintf(f, | |
879 | "\tMaximum UDP packet size received: %zu\n" | |
880 | "\tFailed UDP attempts: %u\n" | |
881 | "\tFailed TCP attempts: %u\n" | |
882 | "\tSeen truncated packet: %s\n" | |
883 | "\tSeen OPT RR getting lost: %s\n" | |
884 | "\tSeen RRSIG RR missing: %s\n", | |
885 | s->received_udp_packet_max, | |
886 | s->n_failed_udp, | |
887 | s->n_failed_tcp, | |
888 | yes_no(s->packet_truncated), | |
889 | yes_no(s->packet_bad_opt), | |
890 | yes_no(s->packet_rrsig_missing)); | |
891 | } | |
892 | ||
893 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { | |
894 | [DNS_SERVER_SYSTEM] = "system", | |
895 | [DNS_SERVER_FALLBACK] = "fallback", | |
896 | [DNS_SERVER_LINK] = "link", | |
897 | }; | |
898 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
899 | ||
900 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { | |
901 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
902 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
903 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", | |
904 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", | |
905 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", | |
906 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", | |
907 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", | |
908 | }; | |
909 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |