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1 | /* SPDX-License-Identifier: LGPL-2.1+ */ | |
2 | /*** | |
3 | This file is part of systemd. | |
4 | ||
5 | Copyright 2014 Lennart Poettering | |
6 | ||
7 | systemd is free software; you can redistribute it and/or modify it | |
8 | under the terms of the GNU Lesser General Public License as published by | |
9 | the Free Software Foundation; either version 2.1 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | systemd is distributed in the hope that it will be useful, but | |
13 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Lesser General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Lesser General Public License | |
18 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
19 | ***/ | |
20 | ||
21 | #include "sd-messages.h" | |
22 | ||
23 | #include "alloc-util.h" | |
24 | #include "resolved-dns-server.h" | |
25 | #include "resolved-dns-stub.h" | |
26 | #include "resolved-resolv-conf.h" | |
27 | #include "siphash24.h" | |
28 | #include "string-table.h" | |
29 | #include "string-util.h" | |
30 | ||
31 | /* After how much time to repeat classic DNS requests */ | |
32 | #define DNS_TIMEOUT_MIN_USEC (750 * USEC_PER_MSEC) | |
33 | #define DNS_TIMEOUT_MAX_USEC (5 * USEC_PER_SEC) | |
34 | ||
35 | /* The amount of time to wait before retrying with a full feature set */ | |
36 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
37 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
38 | ||
39 | /* The number of times we will attempt a certain feature set before degrading */ | |
40 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
41 | ||
42 | int dns_server_new( | |
43 | Manager *m, | |
44 | DnsServer **ret, | |
45 | DnsServerType type, | |
46 | Link *l, | |
47 | int family, | |
48 | const union in_addr_union *in_addr, | |
49 | int ifindex) { | |
50 | ||
51 | DnsServer *s; | |
52 | ||
53 | assert(m); | |
54 | assert((type == DNS_SERVER_LINK) == !!l); | |
55 | assert(in_addr); | |
56 | ||
57 | if (!IN_SET(family, AF_INET, AF_INET6)) | |
58 | return -EAFNOSUPPORT; | |
59 | ||
60 | if (l) { | |
61 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
62 | return -E2BIG; | |
63 | } else { | |
64 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
65 | return -E2BIG; | |
66 | } | |
67 | ||
68 | s = new0(DnsServer, 1); | |
69 | if (!s) | |
70 | return -ENOMEM; | |
71 | ||
72 | s->n_ref = 1; | |
73 | s->manager = m; | |
74 | s->type = type; | |
75 | s->family = family; | |
76 | s->address = *in_addr; | |
77 | s->ifindex = ifindex; | |
78 | ||
79 | dns_server_reset_features(s); | |
80 | ||
81 | switch (type) { | |
82 | ||
83 | case DNS_SERVER_LINK: | |
84 | s->link = l; | |
85 | LIST_APPEND(servers, l->dns_servers, s); | |
86 | l->n_dns_servers++; | |
87 | break; | |
88 | ||
89 | case DNS_SERVER_SYSTEM: | |
90 | LIST_APPEND(servers, m->dns_servers, s); | |
91 | m->n_dns_servers++; | |
92 | break; | |
93 | ||
94 | case DNS_SERVER_FALLBACK: | |
95 | LIST_APPEND(servers, m->fallback_dns_servers, s); | |
96 | m->n_dns_servers++; | |
97 | break; | |
98 | ||
99 | default: | |
100 | assert_not_reached("Unknown server type"); | |
101 | } | |
102 | ||
103 | s->linked = true; | |
104 | ||
105 | /* A new DNS server that isn't fallback is added and the one | |
106 | * we used so far was a fallback one? Then let's try to pick | |
107 | * the new one */ | |
108 | if (type != DNS_SERVER_FALLBACK && | |
109 | m->current_dns_server && | |
110 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
111 | manager_set_dns_server(m, NULL); | |
112 | ||
113 | if (ret) | |
114 | *ret = s; | |
115 | ||
116 | return 0; | |
117 | } | |
118 | ||
119 | DnsServer* dns_server_ref(DnsServer *s) { | |
120 | if (!s) | |
121 | return NULL; | |
122 | ||
123 | assert(s->n_ref > 0); | |
124 | s->n_ref++; | |
125 | ||
126 | return s; | |
127 | } | |
128 | ||
129 | DnsServer* dns_server_unref(DnsServer *s) { | |
130 | if (!s) | |
131 | return NULL; | |
132 | ||
133 | assert(s->n_ref > 0); | |
134 | s->n_ref--; | |
135 | ||
136 | if (s->n_ref > 0) | |
137 | return NULL; | |
138 | ||
139 | free(s->server_string); | |
140 | return mfree(s); | |
141 | } | |
142 | ||
143 | void dns_server_unlink(DnsServer *s) { | |
144 | assert(s); | |
145 | assert(s->manager); | |
146 | ||
147 | /* This removes the specified server from the linked list of | |
148 | * servers, but any server might still stay around if it has | |
149 | * refs, for example from an ongoing transaction. */ | |
150 | ||
151 | if (!s->linked) | |
152 | return; | |
153 | ||
154 | switch (s->type) { | |
155 | ||
156 | case DNS_SERVER_LINK: | |
157 | assert(s->link); | |
158 | assert(s->link->n_dns_servers > 0); | |
159 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
160 | s->link->n_dns_servers--; | |
161 | break; | |
162 | ||
163 | case DNS_SERVER_SYSTEM: | |
164 | assert(s->manager->n_dns_servers > 0); | |
165 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
166 | s->manager->n_dns_servers--; | |
167 | break; | |
168 | ||
169 | case DNS_SERVER_FALLBACK: | |
170 | assert(s->manager->n_dns_servers > 0); | |
171 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
172 | s->manager->n_dns_servers--; | |
173 | break; | |
174 | } | |
175 | ||
176 | s->linked = false; | |
177 | ||
178 | if (s->link && s->link->current_dns_server == s) | |
179 | link_set_dns_server(s->link, NULL); | |
180 | ||
181 | if (s->manager->current_dns_server == s) | |
182 | manager_set_dns_server(s->manager, NULL); | |
183 | ||
184 | dns_server_unref(s); | |
185 | } | |
186 | ||
187 | void dns_server_move_back_and_unmark(DnsServer *s) { | |
188 | DnsServer *tail; | |
189 | ||
190 | assert(s); | |
191 | ||
192 | if (!s->marked) | |
193 | return; | |
194 | ||
195 | s->marked = false; | |
196 | ||
197 | if (!s->linked || !s->servers_next) | |
198 | return; | |
199 | ||
200 | /* Move us to the end of the list, so that the order is | |
201 | * strictly kept, if we are not at the end anyway. */ | |
202 | ||
203 | switch (s->type) { | |
204 | ||
205 | case DNS_SERVER_LINK: | |
206 | assert(s->link); | |
207 | LIST_FIND_TAIL(servers, s, tail); | |
208 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
209 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
210 | break; | |
211 | ||
212 | case DNS_SERVER_SYSTEM: | |
213 | LIST_FIND_TAIL(servers, s, tail); | |
214 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
215 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
216 | break; | |
217 | ||
218 | case DNS_SERVER_FALLBACK: | |
219 | LIST_FIND_TAIL(servers, s, tail); | |
220 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
221 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
222 | break; | |
223 | ||
224 | default: | |
225 | assert_not_reached("Unknown server type"); | |
226 | } | |
227 | } | |
228 | ||
229 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { | |
230 | assert(s); | |
231 | ||
232 | if (s->verified_feature_level > level) | |
233 | return; | |
234 | ||
235 | if (s->verified_feature_level != level) { | |
236 | log_debug("Verified we get a response at feature level %s from DNS server %s.", | |
237 | dns_server_feature_level_to_string(level), | |
238 | dns_server_string(s)); | |
239 | s->verified_feature_level = level; | |
240 | } | |
241 | ||
242 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); | |
243 | } | |
244 | ||
245 | static void dns_server_reset_counters(DnsServer *s) { | |
246 | assert(s); | |
247 | ||
248 | s->n_failed_udp = 0; | |
249 | s->n_failed_tcp = 0; | |
250 | s->packet_truncated = false; | |
251 | s->verified_usec = 0; | |
252 | ||
253 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
254 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
255 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
256 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
257 | * either. | |
258 | * | |
259 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
260 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
261 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
262 | * incomplete. */ | |
263 | } | |
264 | ||
265 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size) { | |
266 | assert(s); | |
267 | ||
268 | if (protocol == IPPROTO_UDP) { | |
269 | if (s->possible_feature_level == level) | |
270 | s->n_failed_udp = 0; | |
271 | ||
272 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ | |
273 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
274 | level = DNS_SERVER_FEATURE_LEVEL_DO - 1; | |
275 | ||
276 | /* If the OPT RR got lost, then we can only validate UDP at max */ | |
277 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
278 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
279 | ||
280 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
281 | that does not mean we can necessarily receive large packets. */ | |
282 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
283 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
284 | ||
285 | } else if (protocol == IPPROTO_TCP) { | |
286 | ||
287 | if (s->possible_feature_level == level) | |
288 | s->n_failed_tcp = 0; | |
289 | ||
290 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
291 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
292 | } | |
293 | ||
294 | dns_server_verified(s, level); | |
295 | ||
296 | /* Remember the size of the largest UDP packet we received from a server, | |
297 | we know that we can always announce support for packets with at least | |
298 | this size. */ | |
299 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) | |
300 | s->received_udp_packet_max = size; | |
301 | ||
302 | if (s->max_rtt < rtt) { | |
303 | s->max_rtt = rtt; | |
304 | s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); | |
305 | } else if (s->resend_timeout > rtt) | |
306 | /* If we received the packet faster than the resend_timeout, bias | |
307 | * the resend_timeout back to the rtt. */ | |
308 | s->resend_timeout = CLAMP((2 * s->resend_timeout + rtt) / 3, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); | |
309 | } | |
310 | ||
311 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { | |
312 | assert(s); | |
313 | assert(s->manager); | |
314 | ||
315 | if (s->possible_feature_level == level) { | |
316 | if (protocol == IPPROTO_UDP) | |
317 | s->n_failed_udp++; | |
318 | else if (protocol == IPPROTO_TCP) | |
319 | s->n_failed_tcp++; | |
320 | } | |
321 | ||
322 | if (s->resend_timeout > usec) | |
323 | return; | |
324 | ||
325 | s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC); | |
326 | } | |
327 | ||
328 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { | |
329 | assert(s); | |
330 | ||
331 | /* Invoked whenever we get a packet with TC bit set. */ | |
332 | ||
333 | if (s->possible_feature_level != level) | |
334 | return; | |
335 | ||
336 | s->packet_truncated = true; | |
337 | } | |
338 | ||
339 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { | |
340 | assert(s); | |
341 | ||
342 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
343 | return; | |
344 | ||
345 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ | |
346 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
347 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_DO-1; | |
348 | ||
349 | s->packet_rrsig_missing = true; | |
350 | } | |
351 | ||
352 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
353 | assert(s); | |
354 | ||
355 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
356 | return; | |
357 | ||
358 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ | |
359 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
360 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
361 | ||
362 | s->packet_bad_opt = true; | |
363 | } | |
364 | ||
365 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { | |
366 | assert(s); | |
367 | ||
368 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
369 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
370 | * things work. */ | |
371 | ||
372 | if (s->verified_feature_level > level) | |
373 | s->verified_feature_level = level; | |
374 | ||
375 | if (s->possible_feature_level > level) { | |
376 | s->possible_feature_level = level; | |
377 | dns_server_reset_counters(s); | |
378 | } | |
379 | ||
380 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
381 | } | |
382 | ||
383 | static bool dns_server_grace_period_expired(DnsServer *s) { | |
384 | usec_t ts; | |
385 | ||
386 | assert(s); | |
387 | assert(s->manager); | |
388 | ||
389 | if (s->verified_usec == 0) | |
390 | return false; | |
391 | ||
392 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
393 | ||
394 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
395 | return false; | |
396 | ||
397 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
398 | ||
399 | return true; | |
400 | } | |
401 | ||
402 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { | |
403 | DnsServerFeatureLevel best; | |
404 | ||
405 | assert(s); | |
406 | ||
407 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything | |
408 | * better than EDNS0, hence don't even try. */ | |
409 | best = dns_server_get_dnssec_mode(s) == DNSSEC_NO ? | |
410 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : | |
411 | DNS_SERVER_FEATURE_LEVEL_BEST; | |
412 | ||
413 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
414 | * time, hence let's downgrade if we are still at a higher level. */ | |
415 | if (s->possible_feature_level > best) | |
416 | s->possible_feature_level = best; | |
417 | ||
418 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
419 | ||
420 | s->possible_feature_level = best; | |
421 | ||
422 | dns_server_reset_counters(s); | |
423 | ||
424 | s->packet_bad_opt = false; | |
425 | s->packet_rrsig_missing = false; | |
426 | ||
427 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", | |
428 | dns_server_feature_level_to_string(s->possible_feature_level), | |
429 | dns_server_string(s)); | |
430 | ||
431 | dns_server_flush_cache(s); | |
432 | ||
433 | } else if (s->possible_feature_level <= s->verified_feature_level) | |
434 | s->possible_feature_level = s->verified_feature_level; | |
435 | else { | |
436 | DnsServerFeatureLevel p = s->possible_feature_level; | |
437 | ||
438 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
439 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { | |
440 | ||
441 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't | |
442 | * work. Upgrade back to UDP again. */ | |
443 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); | |
444 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
445 | ||
446 | } else if (s->packet_bad_opt && | |
447 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
448 | ||
449 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
450 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
451 | * in the request. Example: | |
452 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
453 | ||
454 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
455 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
456 | ||
457 | } else if (s->packet_rrsig_missing && | |
458 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
459 | ||
460 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't | |
461 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
462 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
463 | * not. */ | |
464 | ||
465 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
466 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
467 | ||
468 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
469 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { | |
470 | ||
471 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
472 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
473 | * idea. We might downgrade all the way down to TCP this way. | |
474 | * | |
475 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
476 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
477 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
478 | ||
479 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
480 | s->possible_feature_level--; | |
481 | ||
482 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
483 | s->packet_truncated && | |
484 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { | |
485 | ||
486 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
487 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
488 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
489 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
490 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
491 | ||
492 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
493 | s->possible_feature_level--; | |
494 | } | |
495 | ||
496 | if (p != s->possible_feature_level) { | |
497 | ||
498 | /* We changed the feature level, reset the counting */ | |
499 | dns_server_reset_counters(s); | |
500 | ||
501 | log_warning("Using degraded feature set (%s) for DNS server %s.", | |
502 | dns_server_feature_level_to_string(s->possible_feature_level), | |
503 | dns_server_string(s)); | |
504 | } | |
505 | } | |
506 | ||
507 | return s->possible_feature_level; | |
508 | } | |
509 | ||
510 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { | |
511 | size_t packet_size; | |
512 | bool edns_do; | |
513 | int r; | |
514 | ||
515 | assert(server); | |
516 | assert(packet); | |
517 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
518 | ||
519 | /* Fix the OPT field in the packet to match our current feature level. */ | |
520 | ||
521 | r = dns_packet_truncate_opt(packet); | |
522 | if (r < 0) | |
523 | return r; | |
524 | ||
525 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
526 | return 0; | |
527 | ||
528 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
529 | ||
530 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
531 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
532 | else | |
533 | packet_size = server->received_udp_packet_max; | |
534 | ||
535 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); | |
536 | } | |
537 | ||
538 | int dns_server_ifindex(const DnsServer *s) { | |
539 | assert(s); | |
540 | ||
541 | /* The link ifindex always takes precedence */ | |
542 | if (s->link) | |
543 | return s->link->ifindex; | |
544 | ||
545 | if (s->ifindex > 0) | |
546 | return s->ifindex; | |
547 | ||
548 | return 0; | |
549 | } | |
550 | ||
551 | const char *dns_server_string(DnsServer *server) { | |
552 | assert(server); | |
553 | ||
554 | if (!server->server_string) | |
555 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); | |
556 | ||
557 | return strna(server->server_string); | |
558 | } | |
559 | ||
560 | bool dns_server_dnssec_supported(DnsServer *server) { | |
561 | assert(server); | |
562 | ||
563 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
564 | ||
565 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
566 | return false; | |
567 | ||
568 | if (server->packet_bad_opt) | |
569 | return false; | |
570 | ||
571 | if (server->packet_rrsig_missing) | |
572 | return false; | |
573 | ||
574 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
575 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
576 | return false; | |
577 | ||
578 | return true; | |
579 | } | |
580 | ||
581 | void dns_server_warn_downgrade(DnsServer *server) { | |
582 | assert(server); | |
583 | ||
584 | if (server->warned_downgrade) | |
585 | return; | |
586 | ||
587 | log_struct(LOG_NOTICE, | |
588 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, | |
589 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), | |
590 | "DNS_SERVER=%s", dns_server_string(server), | |
591 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level), | |
592 | NULL); | |
593 | ||
594 | server->warned_downgrade = true; | |
595 | } | |
596 | ||
597 | bool dns_server_limited_domains(DnsServer *server) { | |
598 | DnsSearchDomain *domain; | |
599 | bool domain_restricted = false; | |
600 | ||
601 | /* Check if the server has route-only domains without ~., i. e. whether | |
602 | * it should only be used for particular domains */ | |
603 | if (!server->link) | |
604 | return false; | |
605 | ||
606 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
607 | if (domain->route_only) { | |
608 | domain_restricted = true; | |
609 | /* ~. means "any domain", thus it is a global server */ | |
610 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) | |
611 | return false; | |
612 | } | |
613 | ||
614 | return domain_restricted; | |
615 | } | |
616 | ||
617 | static void dns_server_hash_func(const void *p, struct siphash *state) { | |
618 | const DnsServer *s = p; | |
619 | ||
620 | assert(s); | |
621 | ||
622 | siphash24_compress(&s->family, sizeof(s->family), state); | |
623 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
624 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); | |
625 | } | |
626 | ||
627 | static int dns_server_compare_func(const void *a, const void *b) { | |
628 | const DnsServer *x = a, *y = b; | |
629 | int r; | |
630 | ||
631 | if (x->family < y->family) | |
632 | return -1; | |
633 | if (x->family > y->family) | |
634 | return 1; | |
635 | ||
636 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); | |
637 | if (r != 0) | |
638 | return r; | |
639 | ||
640 | if (x->ifindex < y->ifindex) | |
641 | return -1; | |
642 | if (x->ifindex > y->ifindex) | |
643 | return 1; | |
644 | ||
645 | return 0; | |
646 | } | |
647 | ||
648 | const struct hash_ops dns_server_hash_ops = { | |
649 | .hash = dns_server_hash_func, | |
650 | .compare = dns_server_compare_func | |
651 | }; | |
652 | ||
653 | void dns_server_unlink_all(DnsServer *first) { | |
654 | DnsServer *next; | |
655 | ||
656 | if (!first) | |
657 | return; | |
658 | ||
659 | next = first->servers_next; | |
660 | dns_server_unlink(first); | |
661 | ||
662 | dns_server_unlink_all(next); | |
663 | } | |
664 | ||
665 | void dns_server_unlink_marked(DnsServer *first) { | |
666 | DnsServer *next; | |
667 | ||
668 | if (!first) | |
669 | return; | |
670 | ||
671 | next = first->servers_next; | |
672 | ||
673 | if (first->marked) | |
674 | dns_server_unlink(first); | |
675 | ||
676 | dns_server_unlink_marked(next); | |
677 | } | |
678 | ||
679 | void dns_server_mark_all(DnsServer *first) { | |
680 | if (!first) | |
681 | return; | |
682 | ||
683 | first->marked = true; | |
684 | dns_server_mark_all(first->servers_next); | |
685 | } | |
686 | ||
687 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { | |
688 | DnsServer *s; | |
689 | ||
690 | LIST_FOREACH(servers, s, first) | |
691 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) | |
692 | return s; | |
693 | ||
694 | return NULL; | |
695 | } | |
696 | ||
697 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { | |
698 | assert(m); | |
699 | ||
700 | switch (t) { | |
701 | ||
702 | case DNS_SERVER_SYSTEM: | |
703 | return m->dns_servers; | |
704 | ||
705 | case DNS_SERVER_FALLBACK: | |
706 | return m->fallback_dns_servers; | |
707 | ||
708 | default: | |
709 | return NULL; | |
710 | } | |
711 | } | |
712 | ||
713 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
714 | assert(m); | |
715 | ||
716 | if (m->current_dns_server == s) | |
717 | return s; | |
718 | ||
719 | if (s) | |
720 | log_debug("Switching to %s DNS server %s.", | |
721 | dns_server_type_to_string(s->type), | |
722 | dns_server_string(s)); | |
723 | ||
724 | dns_server_unref(m->current_dns_server); | |
725 | m->current_dns_server = dns_server_ref(s); | |
726 | ||
727 | if (m->unicast_scope) | |
728 | dns_cache_flush(&m->unicast_scope->cache); | |
729 | ||
730 | return s; | |
731 | } | |
732 | ||
733 | DnsServer *manager_get_dns_server(Manager *m) { | |
734 | Link *l; | |
735 | assert(m); | |
736 | ||
737 | /* Try to read updates resolv.conf */ | |
738 | manager_read_resolv_conf(m); | |
739 | ||
740 | /* If no DNS server was chosen so far, pick the first one */ | |
741 | if (!m->current_dns_server) | |
742 | manager_set_dns_server(m, m->dns_servers); | |
743 | ||
744 | if (!m->current_dns_server) { | |
745 | bool found = false; | |
746 | Iterator i; | |
747 | ||
748 | /* No DNS servers configured, let's see if there are | |
749 | * any on any links. If not, we use the fallback | |
750 | * servers */ | |
751 | ||
752 | HASHMAP_FOREACH(l, m->links, i) | |
753 | if (l->dns_servers) { | |
754 | found = true; | |
755 | break; | |
756 | } | |
757 | ||
758 | if (!found) | |
759 | manager_set_dns_server(m, m->fallback_dns_servers); | |
760 | } | |
761 | ||
762 | return m->current_dns_server; | |
763 | } | |
764 | ||
765 | void manager_next_dns_server(Manager *m) { | |
766 | assert(m); | |
767 | ||
768 | /* If there's currently no DNS server set, then the next | |
769 | * manager_get_dns_server() will find one */ | |
770 | if (!m->current_dns_server) | |
771 | return; | |
772 | ||
773 | /* Change to the next one, but make sure to follow the linked | |
774 | * list only if the server is still linked. */ | |
775 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
776 | manager_set_dns_server(m, m->current_dns_server->servers_next); | |
777 | return; | |
778 | } | |
779 | ||
780 | /* If there was no next one, then start from the beginning of | |
781 | * the list */ | |
782 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
783 | manager_set_dns_server(m, m->fallback_dns_servers); | |
784 | else | |
785 | manager_set_dns_server(m, m->dns_servers); | |
786 | } | |
787 | ||
788 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { | |
789 | ||
790 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
791 | ||
792 | if (in_addr_is_null(family, sa)) | |
793 | return false; | |
794 | ||
795 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
796 | return false; | |
797 | ||
798 | return true; | |
799 | } | |
800 | ||
801 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { | |
802 | assert(s); | |
803 | ||
804 | if (s->link) | |
805 | return link_get_dnssec_mode(s->link); | |
806 | ||
807 | return manager_get_dnssec_mode(s->manager); | |
808 | } | |
809 | ||
810 | void dns_server_flush_cache(DnsServer *s) { | |
811 | DnsServer *current; | |
812 | DnsScope *scope; | |
813 | ||
814 | assert(s); | |
815 | ||
816 | /* Flush the cache of the scope this server belongs to */ | |
817 | ||
818 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
819 | if (current != s) | |
820 | return; | |
821 | ||
822 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
823 | if (!scope) | |
824 | return; | |
825 | ||
826 | dns_cache_flush(&scope->cache); | |
827 | } | |
828 | ||
829 | void dns_server_reset_features(DnsServer *s) { | |
830 | assert(s); | |
831 | ||
832 | s->max_rtt = 0; | |
833 | s->resend_timeout = DNS_TIMEOUT_MIN_USEC; | |
834 | ||
835 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; | |
836 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
837 | ||
838 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
839 | ||
840 | s->packet_bad_opt = false; | |
841 | s->packet_rrsig_missing = false; | |
842 | ||
843 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
844 | ||
845 | s->warned_downgrade = false; | |
846 | ||
847 | dns_server_reset_counters(s); | |
848 | } | |
849 | ||
850 | void dns_server_reset_features_all(DnsServer *s) { | |
851 | DnsServer *i; | |
852 | ||
853 | LIST_FOREACH(servers, i, s) | |
854 | dns_server_reset_features(i); | |
855 | } | |
856 | ||
857 | void dns_server_dump(DnsServer *s, FILE *f) { | |
858 | assert(s); | |
859 | ||
860 | if (!f) | |
861 | f = stdout; | |
862 | ||
863 | fputs("[Server ", f); | |
864 | fputs(dns_server_string(s), f); | |
865 | fputs(" type=", f); | |
866 | fputs(dns_server_type_to_string(s->type), f); | |
867 | ||
868 | if (s->type == DNS_SERVER_LINK) { | |
869 | assert(s->link); | |
870 | ||
871 | fputs(" interface=", f); | |
872 | fputs(s->link->name, f); | |
873 | } | |
874 | ||
875 | fputs("]\n", f); | |
876 | ||
877 | fputs("\tVerified feature level: ", f); | |
878 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
879 | fputc('\n', f); | |
880 | ||
881 | fputs("\tPossible feature level: ", f); | |
882 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
883 | fputc('\n', f); | |
884 | ||
885 | fputs("\tDNSSEC Mode: ", f); | |
886 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
887 | fputc('\n', f); | |
888 | ||
889 | fputs("\tCan do DNSSEC: ", f); | |
890 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
891 | fputc('\n', f); | |
892 | ||
893 | fprintf(f, | |
894 | "\tMaximum UDP packet size received: %zu\n" | |
895 | "\tFailed UDP attempts: %u\n" | |
896 | "\tFailed TCP attempts: %u\n" | |
897 | "\tSeen truncated packet: %s\n" | |
898 | "\tSeen OPT RR getting lost: %s\n" | |
899 | "\tSeen RRSIG RR missing: %s\n", | |
900 | s->received_udp_packet_max, | |
901 | s->n_failed_udp, | |
902 | s->n_failed_tcp, | |
903 | yes_no(s->packet_truncated), | |
904 | yes_no(s->packet_bad_opt), | |
905 | yes_no(s->packet_rrsig_missing)); | |
906 | } | |
907 | ||
908 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { | |
909 | [DNS_SERVER_SYSTEM] = "system", | |
910 | [DNS_SERVER_FALLBACK] = "fallback", | |
911 | [DNS_SERVER_LINK] = "link", | |
912 | }; | |
913 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
914 | ||
915 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { | |
916 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
917 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
918 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", | |
919 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", | |
920 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", | |
921 | }; | |
922 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |