]>
Commit | Line | Data |
---|---|---|
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 | ||
248 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size) { | |
249 | assert(s); | |
250 | ||
251 | if (protocol == IPPROTO_UDP) { | |
252 | if (s->possible_feature_level == level) | |
253 | s->n_failed_udp = 0; | |
254 | ||
b6451358 LP |
255 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
256 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
257 | level = DNS_SERVER_FEATURE_LEVEL_DO - 1; | |
258 | ||
259 | /* If the OPT RR got lost, then we can only validate UDP at max */ | |
260 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
261 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
262 | ||
263 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
264 | that does not mean we can necessarily receive large packets. */ | |
6bb2c085 | 265 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) |
b6451358 | 266 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; |
6bb2c085 LP |
267 | |
268 | } else if (protocol == IPPROTO_TCP) { | |
269 | ||
270 | if (s->possible_feature_level == level) | |
271 | s->n_failed_tcp = 0; | |
272 | ||
273 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
b6451358 | 274 | level = DNS_SERVER_FEATURE_LEVEL_TCP; |
6bb2c085 | 275 | } |
84129d46 | 276 | |
b6451358 LP |
277 | dns_server_verified(s, level); |
278 | ||
d74fb368 TG |
279 | /* Remember the size of the largest UDP packet we received from a server, |
280 | we know that we can always announce support for packets with at least | |
281 | this size. */ | |
6bb2c085 | 282 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 TG |
283 | s->received_udp_packet_max = size; |
284 | ||
be808ea0 TG |
285 | if (s->max_rtt < rtt) { |
286 | s->max_rtt = rtt; | |
efd46a69 | 287 | s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); |
be808ea0 | 288 | } |
9df3ba6c TG |
289 | } |
290 | ||
6bb2c085 | 291 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { |
9df3ba6c | 292 | assert(s); |
be808ea0 TG |
293 | assert(s->manager); |
294 | ||
6bb2c085 LP |
295 | if (s->possible_feature_level == level) { |
296 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 297 | s->n_failed_udp++; |
6bb2c085 | 298 | else if (protocol == IPPROTO_TCP) |
313cefa1 | 299 | s->n_failed_tcp++; |
6bb2c085 | 300 | } |
9df3ba6c | 301 | |
84129d46 LP |
302 | if (s->resend_timeout > usec) |
303 | return; | |
304 | ||
305 | s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
306 | } |
307 | ||
f4461e56 | 308 | void dns_server_packet_failed(DnsServer *s, DnsServerFeatureLevel level) { |
4e0b8b17 | 309 | assert(s); |
4e0b8b17 | 310 | |
6bb2c085 LP |
311 | /* Invoked whenever we get a FORMERR, SERVFAIL or NOTIMP rcode from a server. */ |
312 | ||
f4461e56 | 313 | if (s->possible_feature_level != level) |
4e0b8b17 TG |
314 | return; |
315 | ||
6bb2c085 LP |
316 | s->packet_failed = true; |
317 | } | |
318 | ||
319 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { | |
320 | assert(s); | |
571370c1 | 321 | |
6bb2c085 LP |
322 | /* Invoked whenever we get a packet with TC bit set. */ |
323 | ||
324 | if (s->possible_feature_level != level) | |
571370c1 LP |
325 | return; |
326 | ||
6bb2c085 | 327 | s->packet_truncated = true; |
4e0b8b17 TG |
328 | } |
329 | ||
de54e62b LP |
330 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
331 | assert(s); | |
332 | ||
333 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
334 | return; | |
335 | ||
b6451358 LP |
336 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
337 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
338 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_DO-1; | |
339 | ||
de54e62b LP |
340 | s->packet_rrsig_missing = true; |
341 | } | |
342 | ||
343 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 344 | assert(s); |
b652d4a2 | 345 | |
de54e62b LP |
346 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
347 | return; | |
b652d4a2 | 348 | |
b6451358 LP |
349 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
350 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
351 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
352 | ||
de54e62b | 353 | s->packet_bad_opt = true; |
b652d4a2 LP |
354 | } |
355 | ||
be808ea0 TG |
356 | static bool dns_server_grace_period_expired(DnsServer *s) { |
357 | usec_t ts; | |
358 | ||
359 | assert(s); | |
360 | assert(s->manager); | |
361 | ||
362 | if (s->verified_usec == 0) | |
363 | return false; | |
364 | ||
365 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
366 | ||
367 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
368 | return false; | |
369 | ||
370 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
371 | ||
372 | return true; | |
373 | } | |
374 | ||
01184277 LP |
375 | static void dns_server_reset_counters(DnsServer *s) { |
376 | assert(s); | |
377 | ||
378 | s->n_failed_udp = 0; | |
379 | s->n_failed_tcp = 0; | |
380 | s->packet_failed = false; | |
381 | s->packet_truncated = false; | |
382 | s->verified_usec = 0; | |
cc450722 LP |
383 | |
384 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
385 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
386 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
387 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
388 | * either. | |
389 | * | |
390 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
391 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
392 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
393 | * incomplete. */ | |
01184277 LP |
394 | } |
395 | ||
f4461e56 | 396 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
be808ea0 TG |
397 | assert(s); |
398 | ||
f4461e56 | 399 | if (s->possible_feature_level != DNS_SERVER_FEATURE_LEVEL_BEST && |
be808ea0 | 400 | dns_server_grace_period_expired(s)) { |
be808ea0 | 401 | |
f4461e56 | 402 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; |
cc450722 | 403 | |
01184277 LP |
404 | dns_server_reset_counters(s); |
405 | ||
cc450722 LP |
406 | s->packet_bad_opt = false; |
407 | s->packet_rrsig_missing = false; | |
408 | ||
de54e62b | 409 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
410 | dns_server_feature_level_to_string(s->possible_feature_level), |
411 | dns_server_string(s)); | |
6bb2c085 | 412 | |
f4461e56 LP |
413 | } else if (s->possible_feature_level <= s->verified_feature_level) |
414 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
415 | else { |
416 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 417 | |
6bb2c085 | 418 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 419 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 420 | |
6bb2c085 LP |
421 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
422 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
423 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
424 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
425 | ||
426 | } else if (s->packet_bad_opt && | |
427 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
428 | ||
429 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
430 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
431 | * in the request. Example: | |
432 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
433 | ||
434 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 435 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 436 | |
de54e62b LP |
437 | } else if (s->packet_rrsig_missing && |
438 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 439 | |
de54e62b LP |
440 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
441 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
442 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
443 | * not. */ | |
444 | ||
445 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
446 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
447 | ||
448 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
449 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_UDP) { | |
450 | ||
451 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
452 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
453 | * idea. We might downgrade all the way down to TCP this way. */ | |
454 | ||
455 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
456 | s->possible_feature_level--; | |
457 | ||
458 | } else if (s->packet_failed && | |
459 | s->possible_feature_level > DNS_SERVER_FEATURE_LEVEL_UDP) { | |
460 | ||
461 | /* We got a failure packet, and are at a feature level above UDP. Note that in this case we | |
462 | * downgrade no further than UDP, under the assumption that a failure packet indicates an | |
463 | * incompatible packet contents, but not a problem with the transport. */ | |
464 | ||
465 | log_debug("Got server failure, downgrading feature level..."); | |
6bb2c085 LP |
466 | s->possible_feature_level--; |
467 | ||
de54e62b LP |
468 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
469 | s->packet_truncated && | |
470 | s->possible_feature_level > DNS_SERVER_FEATURE_LEVEL_UDP) { | |
471 | ||
472 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
473 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
474 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
475 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
476 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
477 | ||
478 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
479 | s->possible_feature_level--; | |
480 | } | |
481 | ||
6bb2c085 | 482 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
483 | |
484 | /* We changed the feature level, reset the counting */ | |
01184277 | 485 | dns_server_reset_counters(s); |
6bb2c085 | 486 | |
de54e62b | 487 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
488 | dns_server_feature_level_to_string(s->possible_feature_level), |
489 | dns_server_string(s)); | |
6bb2c085 | 490 | } |
be808ea0 TG |
491 | } |
492 | ||
f4461e56 | 493 | return s->possible_feature_level; |
be808ea0 TG |
494 | } |
495 | ||
519ef046 LP |
496 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
497 | size_t packet_size; | |
498 | bool edns_do; | |
499 | int r; | |
500 | ||
501 | assert(server); | |
502 | assert(packet); | |
503 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
504 | ||
505 | /* Fix the OPT field in the packet to match our current feature level. */ | |
506 | ||
507 | r = dns_packet_truncate_opt(packet); | |
508 | if (r < 0) | |
509 | return r; | |
510 | ||
511 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
512 | return 0; | |
513 | ||
514 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
515 | ||
516 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
517 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
518 | else | |
519 | packet_size = server->received_udp_packet_max; | |
520 | ||
f2ed4c69 | 521 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
522 | } |
523 | ||
2817157b LP |
524 | int dns_server_ifindex(const DnsServer *s) { |
525 | assert(s); | |
526 | ||
527 | /* The link ifindex always takes precedence */ | |
528 | if (s->link) | |
529 | return s->link->ifindex; | |
530 | ||
531 | if (s->ifindex > 0) | |
532 | return s->ifindex; | |
533 | ||
534 | return 0; | |
535 | } | |
536 | ||
6cb08a89 LP |
537 | const char *dns_server_string(DnsServer *server) { |
538 | assert(server); | |
539 | ||
540 | if (!server->server_string) | |
2817157b | 541 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
542 | |
543 | return strna(server->server_string); | |
544 | } | |
545 | ||
92ec902a LP |
546 | bool dns_server_dnssec_supported(DnsServer *server) { |
547 | assert(server); | |
548 | ||
549 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
550 | ||
551 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
552 | return false; | |
553 | ||
de54e62b LP |
554 | if (server->packet_bad_opt) |
555 | return false; | |
556 | ||
557 | if (server->packet_rrsig_missing) | |
92ec902a LP |
558 | return false; |
559 | ||
560 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
561 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
562 | return false; | |
563 | ||
564 | return true; | |
565 | } | |
566 | ||
1e02e182 LP |
567 | void dns_server_warn_downgrade(DnsServer *server) { |
568 | assert(server); | |
569 | ||
570 | if (server->warned_downgrade) | |
571 | return; | |
572 | ||
573 | log_struct(LOG_NOTICE, | |
574 | LOG_MESSAGE_ID(SD_MESSAGE_DNSSEC_DOWNGRADE), | |
575 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), | |
576 | "DNS_SERVER=%s", dns_server_string(server), | |
577 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level), | |
578 | NULL); | |
579 | ||
580 | server->warned_downgrade = true; | |
581 | } | |
582 | ||
b826ab58 | 583 | static void dns_server_hash_func(const void *p, struct siphash *state) { |
87f5a193 | 584 | const DnsServer *s = p; |
87f5a193 | 585 | |
b826ab58 | 586 | assert(s); |
87f5a193 | 587 | |
b826ab58 TG |
588 | siphash24_compress(&s->family, sizeof(s->family), state); |
589 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 590 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
591 | } |
592 | ||
d5099efc | 593 | static int dns_server_compare_func(const void *a, const void *b) { |
87f5a193 | 594 | const DnsServer *x = a, *y = b; |
2817157b | 595 | int r; |
87f5a193 LP |
596 | |
597 | if (x->family < y->family) | |
598 | return -1; | |
599 | if (x->family > y->family) | |
600 | return 1; | |
601 | ||
2817157b LP |
602 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
603 | if (r != 0) | |
604 | return r; | |
605 | ||
606 | if (x->ifindex < y->ifindex) | |
607 | return -1; | |
608 | if (x->ifindex > y->ifindex) | |
609 | return 1; | |
610 | ||
611 | return 0; | |
87f5a193 | 612 | } |
d5099efc MS |
613 | |
614 | const struct hash_ops dns_server_hash_ops = { | |
615 | .hash = dns_server_hash_func, | |
616 | .compare = dns_server_compare_func | |
617 | }; | |
636e813d | 618 | |
4b95f179 LP |
619 | void dns_server_unlink_all(DnsServer *first) { |
620 | DnsServer *next; | |
0eac4623 | 621 | |
4b95f179 LP |
622 | if (!first) |
623 | return; | |
0eac4623 | 624 | |
4b95f179 LP |
625 | next = first->servers_next; |
626 | dns_server_unlink(first); | |
636e813d | 627 | |
4b95f179 | 628 | dns_server_unlink_all(next); |
0eac4623 LP |
629 | } |
630 | ||
4b95f179 LP |
631 | void dns_server_unlink_marked(DnsServer *first) { |
632 | DnsServer *next; | |
636e813d | 633 | |
4b95f179 LP |
634 | if (!first) |
635 | return; | |
636e813d | 636 | |
4b95f179 | 637 | next = first->servers_next; |
636e813d | 638 | |
4b95f179 | 639 | if (first->marked) |
0eac4623 | 640 | dns_server_unlink(first); |
636e813d | 641 | |
4b95f179 LP |
642 | dns_server_unlink_marked(next); |
643 | } | |
636e813d | 644 | |
4b95f179 LP |
645 | void dns_server_mark_all(DnsServer *first) { |
646 | if (!first) | |
647 | return; | |
636e813d | 648 | |
4b95f179 LP |
649 | first->marked = true; |
650 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
651 | } |
652 | ||
2817157b | 653 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 654 | DnsServer *s; |
636e813d | 655 | |
636e813d | 656 | LIST_FOREACH(servers, s, first) |
2817157b | 657 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 658 | return s; |
f2f1dbe5 | 659 | |
4b95f179 LP |
660 | return NULL; |
661 | } | |
f2f1dbe5 | 662 | |
4b95f179 | 663 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 664 | assert(m); |
f2f1dbe5 | 665 | |
4b95f179 | 666 | switch (t) { |
f2f1dbe5 | 667 | |
4b95f179 LP |
668 | case DNS_SERVER_SYSTEM: |
669 | return m->dns_servers; | |
f2f1dbe5 | 670 | |
4b95f179 LP |
671 | case DNS_SERVER_FALLBACK: |
672 | return m->fallback_dns_servers; | |
673 | ||
674 | default: | |
675 | return NULL; | |
676 | } | |
f2f1dbe5 LP |
677 | } |
678 | ||
679 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
680 | assert(m); | |
681 | ||
682 | if (m->current_dns_server == s) | |
683 | return s; | |
684 | ||
6cb08a89 | 685 | if (s) |
e3309036 ZJS |
686 | log_info("Switching to %s DNS server %s.", |
687 | dns_server_type_to_string(s->type), | |
688 | dns_server_string(s)); | |
f2f1dbe5 | 689 | |
0eac4623 LP |
690 | dns_server_unref(m->current_dns_server); |
691 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
692 | |
693 | if (m->unicast_scope) | |
694 | dns_cache_flush(&m->unicast_scope->cache); | |
695 | ||
696 | return s; | |
697 | } | |
698 | ||
699 | DnsServer *manager_get_dns_server(Manager *m) { | |
700 | Link *l; | |
701 | assert(m); | |
702 | ||
703 | /* Try to read updates resolv.conf */ | |
704 | manager_read_resolv_conf(m); | |
705 | ||
e3309036 | 706 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
707 | if (!m->current_dns_server) |
708 | manager_set_dns_server(m, m->dns_servers); | |
709 | ||
710 | if (!m->current_dns_server) { | |
711 | bool found = false; | |
712 | Iterator i; | |
713 | ||
714 | /* No DNS servers configured, let's see if there are | |
715 | * any on any links. If not, we use the fallback | |
716 | * servers */ | |
717 | ||
718 | HASHMAP_FOREACH(l, m->links, i) | |
719 | if (l->dns_servers) { | |
720 | found = true; | |
721 | break; | |
722 | } | |
723 | ||
724 | if (!found) | |
725 | manager_set_dns_server(m, m->fallback_dns_servers); | |
726 | } | |
727 | ||
728 | return m->current_dns_server; | |
729 | } | |
730 | ||
731 | void manager_next_dns_server(Manager *m) { | |
732 | assert(m); | |
733 | ||
734 | /* If there's currently no DNS server set, then the next | |
735 | * manager_get_dns_server() will find one */ | |
736 | if (!m->current_dns_server) | |
737 | return; | |
738 | ||
0eac4623 LP |
739 | /* Change to the next one, but make sure to follow the linked |
740 | * list only if the server is still linked. */ | |
741 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
742 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
743 | return; | |
744 | } | |
745 | ||
746 | /* If there was no next one, then start from the beginning of | |
747 | * the list */ | |
748 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
749 | manager_set_dns_server(m, m->fallback_dns_servers); | |
750 | else | |
751 | manager_set_dns_server(m, m->dns_servers); | |
752 | } | |
be808ea0 | 753 | |
b30bf55d LP |
754 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
755 | ||
756 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
757 | ||
758 | if (in_addr_is_null(family, sa)) | |
759 | return false; | |
760 | ||
761 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
762 | return false; | |
763 | ||
764 | return true; | |
765 | } | |
766 | ||
e3309036 ZJS |
767 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
768 | [DNS_SERVER_SYSTEM] = "system", | |
769 | [DNS_SERVER_FALLBACK] = "fallback", | |
770 | [DNS_SERVER_LINK] = "link", | |
771 | }; | |
772 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
773 | ||
be808ea0 TG |
774 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
775 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
776 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 777 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
7586f4d1 | 778 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 779 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
be808ea0 TG |
780 | }; |
781 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |