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74b2466e LP |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2014 Lennart Poettering | |
5 | ||
6 | systemd is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | systemd is distributed in the hope that it will be useful, but | |
12 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public License | |
17 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
18 | ***/ | |
19 | ||
1e02e182 LP |
20 | #include <sd-messages.h> |
21 | ||
b5efdb8a | 22 | #include "alloc-util.h" |
74b2466e | 23 | #include "resolved-dns-server.h" |
b30bf55d | 24 | #include "resolved-dns-stub.h" |
f2f1dbe5 | 25 | #include "resolved-resolv-conf.h" |
b5efdb8a | 26 | #include "siphash24.h" |
be808ea0 | 27 | #include "string-table.h" |
f2f1dbe5 | 28 | #include "string-util.h" |
74b2466e | 29 | |
9df3ba6c TG |
30 | /* After how much time to repeat classic DNS requests */ |
31 | #define DNS_TIMEOUT_MIN_USEC (500 * USEC_PER_MSEC) | |
32 | #define DNS_TIMEOUT_MAX_USEC (5 * USEC_PER_SEC) | |
33 | ||
be808ea0 TG |
34 | /* The amount of time to wait before retrying with a full feature set */ |
35 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
36 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
37 | ||
38 | /* The number of times we will attempt a certain feature set before degrading */ | |
39 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
40 | ||
74b2466e LP |
41 | int dns_server_new( |
42 | Manager *m, | |
43 | DnsServer **ret, | |
4e945a6f | 44 | DnsServerType type, |
74b2466e | 45 | Link *l, |
0dd25fb9 | 46 | int family, |
2817157b LP |
47 | const union in_addr_union *in_addr, |
48 | int ifindex) { | |
74b2466e | 49 | |
eed857b7 | 50 | DnsServer *s; |
74b2466e LP |
51 | |
52 | assert(m); | |
4e945a6f | 53 | assert((type == DNS_SERVER_LINK) == !!l); |
74b2466e | 54 | assert(in_addr); |
74b2466e | 55 | |
eed857b7 LP |
56 | if (!IN_SET(family, AF_INET, AF_INET6)) |
57 | return -EAFNOSUPPORT; | |
58 | ||
59 | if (l) { | |
60 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
61 | return -E2BIG; | |
62 | } else { | |
63 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
64 | return -E2BIG; | |
65 | } | |
66 | ||
74b2466e LP |
67 | s = new0(DnsServer, 1); |
68 | if (!s) | |
69 | return -ENOMEM; | |
70 | ||
91b14d6f | 71 | s->n_ref = 1; |
0b58db65 | 72 | s->manager = m; |
f4461e56 LP |
73 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
74 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
be808ea0 | 75 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; |
d74fb368 | 76 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; |
4e945a6f | 77 | s->type = type; |
74b2466e LP |
78 | s->family = family; |
79 | s->address = *in_addr; | |
2817157b | 80 | s->ifindex = ifindex; |
9df3ba6c | 81 | s->resend_timeout = DNS_TIMEOUT_MIN_USEC; |
74b2466e | 82 | |
0b58db65 LP |
83 | switch (type) { |
84 | ||
85 | case DNS_SERVER_LINK: | |
86 | s->link = l; | |
eed857b7 LP |
87 | LIST_APPEND(servers, l->dns_servers, s); |
88 | l->n_dns_servers++; | |
0b58db65 LP |
89 | break; |
90 | ||
91 | case DNS_SERVER_SYSTEM: | |
eed857b7 LP |
92 | LIST_APPEND(servers, m->dns_servers, s); |
93 | m->n_dns_servers++; | |
0b58db65 LP |
94 | break; |
95 | ||
96 | case DNS_SERVER_FALLBACK: | |
eed857b7 LP |
97 | LIST_APPEND(servers, m->fallback_dns_servers, s); |
98 | m->n_dns_servers++; | |
0b58db65 LP |
99 | break; |
100 | ||
101 | default: | |
4e945a6f | 102 | assert_not_reached("Unknown server type"); |
0b58db65 | 103 | } |
74b2466e | 104 | |
0eac4623 | 105 | s->linked = true; |
74b2466e | 106 | |
4e945a6f LP |
107 | /* A new DNS server that isn't fallback is added and the one |
108 | * we used so far was a fallback one? Then let's try to pick | |
109 | * the new one */ | |
110 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
111 | m->current_dns_server && |
112 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
113 | manager_set_dns_server(m, NULL); | |
4e945a6f | 114 | |
74b2466e LP |
115 | if (ret) |
116 | *ret = s; | |
117 | ||
118 | return 0; | |
119 | } | |
120 | ||
91b14d6f | 121 | DnsServer* dns_server_ref(DnsServer *s) { |
74b2466e LP |
122 | if (!s) |
123 | return NULL; | |
124 | ||
91b14d6f | 125 | assert(s->n_ref > 0); |
313cefa1 | 126 | s->n_ref++; |
cab5b059 | 127 | |
91b14d6f TG |
128 | return s; |
129 | } | |
130 | ||
0eac4623 | 131 | DnsServer* dns_server_unref(DnsServer *s) { |
91b14d6f TG |
132 | if (!s) |
133 | return NULL; | |
3e684349 | 134 | |
0eac4623 | 135 | assert(s->n_ref > 0); |
313cefa1 | 136 | s->n_ref--; |
91b14d6f | 137 | |
0eac4623 LP |
138 | if (s->n_ref > 0) |
139 | return NULL; | |
74b2466e | 140 | |
6cb08a89 | 141 | free(s->server_string); |
74b2466e | 142 | free(s); |
74b2466e LP |
143 | return NULL; |
144 | } | |
87f5a193 | 145 | |
0eac4623 LP |
146 | void dns_server_unlink(DnsServer *s) { |
147 | assert(s); | |
148 | assert(s->manager); | |
91b14d6f | 149 | |
0eac4623 LP |
150 | /* This removes the specified server from the linked list of |
151 | * servers, but any server might still stay around if it has | |
152 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 153 | |
0eac4623 LP |
154 | if (!s->linked) |
155 | return; | |
91b14d6f | 156 | |
0eac4623 LP |
157 | switch (s->type) { |
158 | ||
159 | case DNS_SERVER_LINK: | |
160 | assert(s->link); | |
eed857b7 | 161 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 162 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 163 | s->link->n_dns_servers--; |
0eac4623 LP |
164 | break; |
165 | ||
166 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 167 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 168 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 169 | s->manager->n_dns_servers--; |
0eac4623 LP |
170 | break; |
171 | ||
172 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 173 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 174 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 175 | s->manager->n_dns_servers--; |
0eac4623 LP |
176 | break; |
177 | } | |
178 | ||
179 | s->linked = false; | |
180 | ||
181 | if (s->link && s->link->current_dns_server == s) | |
182 | link_set_dns_server(s->link, NULL); | |
183 | ||
184 | if (s->manager->current_dns_server == s) | |
185 | manager_set_dns_server(s->manager, NULL); | |
186 | ||
187 | dns_server_unref(s); | |
91b14d6f TG |
188 | } |
189 | ||
0b58db65 LP |
190 | void dns_server_move_back_and_unmark(DnsServer *s) { |
191 | DnsServer *tail; | |
192 | ||
193 | assert(s); | |
194 | ||
195 | if (!s->marked) | |
196 | return; | |
197 | ||
198 | s->marked = false; | |
199 | ||
200 | if (!s->linked || !s->servers_next) | |
201 | return; | |
202 | ||
203 | /* Move us to the end of the list, so that the order is | |
204 | * strictly kept, if we are not at the end anyway. */ | |
205 | ||
206 | switch (s->type) { | |
207 | ||
208 | case DNS_SERVER_LINK: | |
209 | assert(s->link); | |
210 | LIST_FIND_TAIL(servers, s, tail); | |
211 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
212 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
213 | break; | |
214 | ||
215 | case DNS_SERVER_SYSTEM: | |
216 | LIST_FIND_TAIL(servers, s, tail); | |
217 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
218 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
219 | break; | |
220 | ||
221 | case DNS_SERVER_FALLBACK: | |
222 | LIST_FIND_TAIL(servers, s, tail); | |
223 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
224 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
225 | break; | |
226 | ||
227 | default: | |
228 | assert_not_reached("Unknown server type"); | |
229 | } | |
230 | } | |
231 | ||
6bb2c085 | 232 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
233 | assert(s); |
234 | ||
6bb2c085 LP |
235 | if (s->verified_feature_level > level) |
236 | return; | |
b652d4a2 | 237 | |
6bb2c085 | 238 | if (s->verified_feature_level != level) { |
de54e62b LP |
239 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
240 | dns_server_feature_level_to_string(level), | |
241 | dns_server_string(s)); | |
f4461e56 | 242 | s->verified_feature_level = level; |
be808ea0 TG |
243 | } |
244 | ||
6bb2c085 LP |
245 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
246 | } | |
247 | ||
d001e0a3 LP |
248 | static void dns_server_reset_counters(DnsServer *s) { |
249 | assert(s); | |
250 | ||
251 | s->n_failed_udp = 0; | |
252 | s->n_failed_tcp = 0; | |
253 | s->packet_truncated = false; | |
254 | s->verified_usec = 0; | |
255 | ||
256 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
257 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
258 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
259 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
260 | * either. | |
261 | * | |
262 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
263 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
264 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
265 | * incomplete. */ | |
266 | } | |
267 | ||
6bb2c085 LP |
268 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size) { |
269 | assert(s); | |
270 | ||
271 | if (protocol == IPPROTO_UDP) { | |
272 | if (s->possible_feature_level == level) | |
273 | s->n_failed_udp = 0; | |
274 | ||
b6451358 LP |
275 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
276 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
277 | level = DNS_SERVER_FEATURE_LEVEL_DO - 1; | |
278 | ||
279 | /* If the OPT RR got lost, then we can only validate UDP at max */ | |
280 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
281 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
282 | ||
283 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
284 | that does not mean we can necessarily receive large packets. */ | |
6bb2c085 | 285 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) |
b6451358 | 286 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; |
6bb2c085 LP |
287 | |
288 | } else if (protocol == IPPROTO_TCP) { | |
289 | ||
290 | if (s->possible_feature_level == level) | |
291 | s->n_failed_tcp = 0; | |
292 | ||
293 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
b6451358 | 294 | level = DNS_SERVER_FEATURE_LEVEL_TCP; |
6bb2c085 | 295 | } |
84129d46 | 296 | |
b6451358 LP |
297 | dns_server_verified(s, level); |
298 | ||
d74fb368 TG |
299 | /* Remember the size of the largest UDP packet we received from a server, |
300 | we know that we can always announce support for packets with at least | |
301 | this size. */ | |
6bb2c085 | 302 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 TG |
303 | s->received_udp_packet_max = size; |
304 | ||
be808ea0 TG |
305 | if (s->max_rtt < rtt) { |
306 | s->max_rtt = rtt; | |
efd46a69 | 307 | s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); |
be808ea0 | 308 | } |
9df3ba6c TG |
309 | } |
310 | ||
6bb2c085 | 311 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { |
9df3ba6c | 312 | assert(s); |
be808ea0 TG |
313 | assert(s->manager); |
314 | ||
6bb2c085 LP |
315 | if (s->possible_feature_level == level) { |
316 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 317 | s->n_failed_udp++; |
6bb2c085 | 318 | else if (protocol == IPPROTO_TCP) |
313cefa1 | 319 | s->n_failed_tcp++; |
6bb2c085 | 320 | } |
9df3ba6c | 321 | |
84129d46 LP |
322 | if (s->resend_timeout > usec) |
323 | return; | |
324 | ||
325 | s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
326 | } |
327 | ||
6bb2c085 LP |
328 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
329 | assert(s); | |
571370c1 | 330 | |
6bb2c085 LP |
331 | /* Invoked whenever we get a packet with TC bit set. */ |
332 | ||
333 | if (s->possible_feature_level != level) | |
571370c1 LP |
334 | return; |
335 | ||
6bb2c085 | 336 | s->packet_truncated = true; |
4e0b8b17 TG |
337 | } |
338 | ||
de54e62b LP |
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 | ||
b6451358 LP |
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 | ||
de54e62b LP |
349 | s->packet_rrsig_missing = true; |
350 | } | |
351 | ||
352 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 353 | assert(s); |
b652d4a2 | 354 | |
de54e62b LP |
355 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
356 | return; | |
b652d4a2 | 357 | |
b6451358 LP |
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 | ||
de54e62b | 362 | s->packet_bad_opt = true; |
b652d4a2 LP |
363 | } |
364 | ||
d001e0a3 LP |
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 | ||
be808ea0 TG |
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 | ||
f4461e56 | 402 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
be808ea0 TG |
403 | assert(s); |
404 | ||
f4461e56 | 405 | if (s->possible_feature_level != DNS_SERVER_FEATURE_LEVEL_BEST && |
be808ea0 | 406 | dns_server_grace_period_expired(s)) { |
be808ea0 | 407 | |
f4461e56 | 408 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; |
cc450722 | 409 | |
01184277 LP |
410 | dns_server_reset_counters(s); |
411 | ||
cc450722 LP |
412 | s->packet_bad_opt = false; |
413 | s->packet_rrsig_missing = false; | |
414 | ||
de54e62b | 415 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
416 | dns_server_feature_level_to_string(s->possible_feature_level), |
417 | dns_server_string(s)); | |
6bb2c085 | 418 | |
f4461e56 LP |
419 | } else if (s->possible_feature_level <= s->verified_feature_level) |
420 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
421 | else { |
422 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 423 | |
6bb2c085 | 424 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 425 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 426 | |
6bb2c085 LP |
427 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
428 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
429 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
430 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
431 | ||
432 | } else if (s->packet_bad_opt && | |
433 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
434 | ||
435 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
436 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
437 | * in the request. Example: | |
438 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
439 | ||
440 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 441 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 442 | |
de54e62b LP |
443 | } else if (s->packet_rrsig_missing && |
444 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 445 | |
de54e62b LP |
446 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
447 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
448 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
449 | * not. */ | |
450 | ||
451 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
452 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
453 | ||
454 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
455 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_UDP) { | |
456 | ||
457 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
458 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
459 | * idea. We might downgrade all the way down to TCP this way. */ | |
460 | ||
461 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
462 | s->possible_feature_level--; | |
463 | ||
de54e62b LP |
464 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
465 | s->packet_truncated && | |
466 | s->possible_feature_level > 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 | ||
6bb2c085 | 478 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
479 | |
480 | /* We changed the feature level, reset the counting */ | |
01184277 | 481 | dns_server_reset_counters(s); |
6bb2c085 | 482 | |
de54e62b | 483 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
484 | dns_server_feature_level_to_string(s->possible_feature_level), |
485 | dns_server_string(s)); | |
6bb2c085 | 486 | } |
be808ea0 TG |
487 | } |
488 | ||
f4461e56 | 489 | return s->possible_feature_level; |
be808ea0 TG |
490 | } |
491 | ||
519ef046 LP |
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 | ||
f2ed4c69 | 517 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
518 | } |
519 | ||
2817157b LP |
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 | ||
6cb08a89 LP |
533 | const char *dns_server_string(DnsServer *server) { |
534 | assert(server); | |
535 | ||
536 | if (!server->server_string) | |
2817157b | 537 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
538 | |
539 | return strna(server->server_string); | |
540 | } | |
541 | ||
92ec902a LP |
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 | ||
de54e62b LP |
550 | if (server->packet_bad_opt) |
551 | return false; | |
552 | ||
553 | if (server->packet_rrsig_missing) | |
92ec902a LP |
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 | ||
1e02e182 LP |
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 | LOG_MESSAGE_ID(SD_MESSAGE_DNSSEC_DOWNGRADE), | |
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 | NULL); | |
575 | ||
576 | server->warned_downgrade = true; | |
577 | } | |
578 | ||
b826ab58 | 579 | static void dns_server_hash_func(const void *p, struct siphash *state) { |
87f5a193 | 580 | const DnsServer *s = p; |
87f5a193 | 581 | |
b826ab58 | 582 | assert(s); |
87f5a193 | 583 | |
b826ab58 TG |
584 | siphash24_compress(&s->family, sizeof(s->family), state); |
585 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 586 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
587 | } |
588 | ||
d5099efc | 589 | static int dns_server_compare_func(const void *a, const void *b) { |
87f5a193 | 590 | const DnsServer *x = a, *y = b; |
2817157b | 591 | int r; |
87f5a193 LP |
592 | |
593 | if (x->family < y->family) | |
594 | return -1; | |
595 | if (x->family > y->family) | |
596 | return 1; | |
597 | ||
2817157b LP |
598 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
599 | if (r != 0) | |
600 | return r; | |
601 | ||
602 | if (x->ifindex < y->ifindex) | |
603 | return -1; | |
604 | if (x->ifindex > y->ifindex) | |
605 | return 1; | |
606 | ||
607 | return 0; | |
87f5a193 | 608 | } |
d5099efc MS |
609 | |
610 | const struct hash_ops dns_server_hash_ops = { | |
611 | .hash = dns_server_hash_func, | |
612 | .compare = dns_server_compare_func | |
613 | }; | |
636e813d | 614 | |
4b95f179 LP |
615 | void dns_server_unlink_all(DnsServer *first) { |
616 | DnsServer *next; | |
0eac4623 | 617 | |
4b95f179 LP |
618 | if (!first) |
619 | return; | |
0eac4623 | 620 | |
4b95f179 LP |
621 | next = first->servers_next; |
622 | dns_server_unlink(first); | |
636e813d | 623 | |
4b95f179 | 624 | dns_server_unlink_all(next); |
0eac4623 LP |
625 | } |
626 | ||
4b95f179 LP |
627 | void dns_server_unlink_marked(DnsServer *first) { |
628 | DnsServer *next; | |
636e813d | 629 | |
4b95f179 LP |
630 | if (!first) |
631 | return; | |
636e813d | 632 | |
4b95f179 | 633 | next = first->servers_next; |
636e813d | 634 | |
4b95f179 | 635 | if (first->marked) |
0eac4623 | 636 | dns_server_unlink(first); |
636e813d | 637 | |
4b95f179 LP |
638 | dns_server_unlink_marked(next); |
639 | } | |
636e813d | 640 | |
4b95f179 LP |
641 | void dns_server_mark_all(DnsServer *first) { |
642 | if (!first) | |
643 | return; | |
636e813d | 644 | |
4b95f179 LP |
645 | first->marked = true; |
646 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
647 | } |
648 | ||
2817157b | 649 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 650 | DnsServer *s; |
636e813d | 651 | |
636e813d | 652 | LIST_FOREACH(servers, s, first) |
2817157b | 653 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 654 | return s; |
f2f1dbe5 | 655 | |
4b95f179 LP |
656 | return NULL; |
657 | } | |
f2f1dbe5 | 658 | |
4b95f179 | 659 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 660 | assert(m); |
f2f1dbe5 | 661 | |
4b95f179 | 662 | switch (t) { |
f2f1dbe5 | 663 | |
4b95f179 LP |
664 | case DNS_SERVER_SYSTEM: |
665 | return m->dns_servers; | |
f2f1dbe5 | 666 | |
4b95f179 LP |
667 | case DNS_SERVER_FALLBACK: |
668 | return m->fallback_dns_servers; | |
669 | ||
670 | default: | |
671 | return NULL; | |
672 | } | |
f2f1dbe5 LP |
673 | } |
674 | ||
675 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
676 | assert(m); | |
677 | ||
678 | if (m->current_dns_server == s) | |
679 | return s; | |
680 | ||
6cb08a89 | 681 | if (s) |
e3309036 ZJS |
682 | log_info("Switching to %s DNS server %s.", |
683 | dns_server_type_to_string(s->type), | |
684 | dns_server_string(s)); | |
f2f1dbe5 | 685 | |
0eac4623 LP |
686 | dns_server_unref(m->current_dns_server); |
687 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
688 | |
689 | if (m->unicast_scope) | |
690 | dns_cache_flush(&m->unicast_scope->cache); | |
691 | ||
692 | return s; | |
693 | } | |
694 | ||
695 | DnsServer *manager_get_dns_server(Manager *m) { | |
696 | Link *l; | |
697 | assert(m); | |
698 | ||
699 | /* Try to read updates resolv.conf */ | |
700 | manager_read_resolv_conf(m); | |
701 | ||
e3309036 | 702 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
703 | if (!m->current_dns_server) |
704 | manager_set_dns_server(m, m->dns_servers); | |
705 | ||
706 | if (!m->current_dns_server) { | |
707 | bool found = false; | |
708 | Iterator i; | |
709 | ||
710 | /* No DNS servers configured, let's see if there are | |
711 | * any on any links. If not, we use the fallback | |
712 | * servers */ | |
713 | ||
714 | HASHMAP_FOREACH(l, m->links, i) | |
715 | if (l->dns_servers) { | |
716 | found = true; | |
717 | break; | |
718 | } | |
719 | ||
720 | if (!found) | |
721 | manager_set_dns_server(m, m->fallback_dns_servers); | |
722 | } | |
723 | ||
724 | return m->current_dns_server; | |
725 | } | |
726 | ||
727 | void manager_next_dns_server(Manager *m) { | |
728 | assert(m); | |
729 | ||
730 | /* If there's currently no DNS server set, then the next | |
731 | * manager_get_dns_server() will find one */ | |
732 | if (!m->current_dns_server) | |
733 | return; | |
734 | ||
0eac4623 LP |
735 | /* Change to the next one, but make sure to follow the linked |
736 | * list only if the server is still linked. */ | |
737 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
738 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
739 | return; | |
740 | } | |
741 | ||
742 | /* If there was no next one, then start from the beginning of | |
743 | * the list */ | |
744 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
745 | manager_set_dns_server(m, m->fallback_dns_servers); | |
746 | else | |
747 | manager_set_dns_server(m, m->dns_servers); | |
748 | } | |
be808ea0 | 749 | |
b30bf55d LP |
750 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
751 | ||
752 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
753 | ||
754 | if (in_addr_is_null(family, sa)) | |
755 | return false; | |
756 | ||
757 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
758 | return false; | |
759 | ||
760 | return true; | |
761 | } | |
762 | ||
e3309036 ZJS |
763 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
764 | [DNS_SERVER_SYSTEM] = "system", | |
765 | [DNS_SERVER_FALLBACK] = "fallback", | |
766 | [DNS_SERVER_LINK] = "link", | |
767 | }; | |
768 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
769 | ||
be808ea0 TG |
770 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
771 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
772 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 773 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
7586f4d1 | 774 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 775 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
be808ea0 TG |
776 | }; |
777 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |