]>
Commit | Line | Data |
---|---|---|
53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
74b2466e LP |
2 | /*** |
3 | This file is part of systemd. | |
4 | ||
5 | Copyright 2014 Lennart Poettering | |
74b2466e LP |
6 | ***/ |
7 | ||
62cc1c55 | 8 | #include "sd-messages.h" |
1e02e182 | 9 | |
b5efdb8a | 10 | #include "alloc-util.h" |
74b2466e | 11 | #include "resolved-dns-server.h" |
b30bf55d | 12 | #include "resolved-dns-stub.h" |
f2f1dbe5 | 13 | #include "resolved-resolv-conf.h" |
b5efdb8a | 14 | #include "siphash24.h" |
be808ea0 | 15 | #include "string-table.h" |
f2f1dbe5 | 16 | #include "string-util.h" |
74b2466e | 17 | |
9df3ba6c | 18 | /* After how much time to repeat classic DNS requests */ |
74a3ed74 | 19 | #define DNS_TIMEOUT_MIN_USEC (750 * USEC_PER_MSEC) |
4cbfd62b | 20 | #define DNS_TIMEOUT_MAX_USEC (SD_RESOLVED_QUERY_TIMEOUT_USEC / DNS_TRANSACTION_ATTEMPTS_MAX) |
9df3ba6c | 21 | |
be808ea0 TG |
22 | /* The amount of time to wait before retrying with a full feature set */ |
23 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
24 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
25 | ||
26 | /* The number of times we will attempt a certain feature set before degrading */ | |
27 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
28 | ||
74b2466e LP |
29 | int dns_server_new( |
30 | Manager *m, | |
31 | DnsServer **ret, | |
4e945a6f | 32 | DnsServerType type, |
74b2466e | 33 | Link *l, |
0dd25fb9 | 34 | int family, |
2817157b LP |
35 | const union in_addr_union *in_addr, |
36 | int ifindex) { | |
74b2466e | 37 | |
eed857b7 | 38 | DnsServer *s; |
74b2466e LP |
39 | |
40 | assert(m); | |
4e945a6f | 41 | assert((type == DNS_SERVER_LINK) == !!l); |
74b2466e | 42 | assert(in_addr); |
74b2466e | 43 | |
eed857b7 LP |
44 | if (!IN_SET(family, AF_INET, AF_INET6)) |
45 | return -EAFNOSUPPORT; | |
46 | ||
47 | if (l) { | |
48 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
49 | return -E2BIG; | |
50 | } else { | |
51 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
52 | return -E2BIG; | |
53 | } | |
54 | ||
74b2466e LP |
55 | s = new0(DnsServer, 1); |
56 | if (!s) | |
57 | return -ENOMEM; | |
58 | ||
91b14d6f | 59 | s->n_ref = 1; |
0b58db65 | 60 | s->manager = m; |
4e945a6f | 61 | s->type = type; |
74b2466e LP |
62 | s->family = family; |
63 | s->address = *in_addr; | |
2817157b | 64 | s->ifindex = ifindex; |
59c0fd0e LP |
65 | |
66 | dns_server_reset_features(s); | |
74b2466e | 67 | |
0b58db65 LP |
68 | switch (type) { |
69 | ||
70 | case DNS_SERVER_LINK: | |
71 | s->link = l; | |
eed857b7 LP |
72 | LIST_APPEND(servers, l->dns_servers, s); |
73 | l->n_dns_servers++; | |
0b58db65 LP |
74 | break; |
75 | ||
76 | case DNS_SERVER_SYSTEM: | |
eed857b7 LP |
77 | LIST_APPEND(servers, m->dns_servers, s); |
78 | m->n_dns_servers++; | |
0b58db65 LP |
79 | break; |
80 | ||
81 | case DNS_SERVER_FALLBACK: | |
eed857b7 LP |
82 | LIST_APPEND(servers, m->fallback_dns_servers, s); |
83 | m->n_dns_servers++; | |
0b58db65 LP |
84 | break; |
85 | ||
86 | default: | |
4e945a6f | 87 | assert_not_reached("Unknown server type"); |
0b58db65 | 88 | } |
74b2466e | 89 | |
0eac4623 | 90 | s->linked = true; |
74b2466e | 91 | |
4e945a6f LP |
92 | /* A new DNS server that isn't fallback is added and the one |
93 | * we used so far was a fallback one? Then let's try to pick | |
94 | * the new one */ | |
95 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
96 | m->current_dns_server && |
97 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
98 | manager_set_dns_server(m, NULL); | |
4e945a6f | 99 | |
74b2466e LP |
100 | if (ret) |
101 | *ret = s; | |
102 | ||
103 | return 0; | |
104 | } | |
105 | ||
91b14d6f | 106 | DnsServer* dns_server_ref(DnsServer *s) { |
74b2466e LP |
107 | if (!s) |
108 | return NULL; | |
109 | ||
91b14d6f | 110 | assert(s->n_ref > 0); |
313cefa1 | 111 | s->n_ref++; |
cab5b059 | 112 | |
91b14d6f TG |
113 | return s; |
114 | } | |
115 | ||
0eac4623 | 116 | DnsServer* dns_server_unref(DnsServer *s) { |
91b14d6f TG |
117 | if (!s) |
118 | return NULL; | |
3e684349 | 119 | |
0eac4623 | 120 | assert(s->n_ref > 0); |
313cefa1 | 121 | s->n_ref--; |
91b14d6f | 122 | |
0eac4623 LP |
123 | if (s->n_ref > 0) |
124 | return NULL; | |
74b2466e | 125 | |
6cb08a89 | 126 | free(s->server_string); |
6b430fdb | 127 | return mfree(s); |
74b2466e | 128 | } |
87f5a193 | 129 | |
0eac4623 LP |
130 | void dns_server_unlink(DnsServer *s) { |
131 | assert(s); | |
132 | assert(s->manager); | |
91b14d6f | 133 | |
0eac4623 LP |
134 | /* This removes the specified server from the linked list of |
135 | * servers, but any server might still stay around if it has | |
136 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 137 | |
0eac4623 LP |
138 | if (!s->linked) |
139 | return; | |
91b14d6f | 140 | |
0eac4623 LP |
141 | switch (s->type) { |
142 | ||
143 | case DNS_SERVER_LINK: | |
144 | assert(s->link); | |
eed857b7 | 145 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 146 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 147 | s->link->n_dns_servers--; |
0eac4623 LP |
148 | break; |
149 | ||
150 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 151 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 152 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 153 | s->manager->n_dns_servers--; |
0eac4623 LP |
154 | break; |
155 | ||
156 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 157 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 158 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 159 | s->manager->n_dns_servers--; |
0eac4623 LP |
160 | break; |
161 | } | |
162 | ||
163 | s->linked = false; | |
164 | ||
165 | if (s->link && s->link->current_dns_server == s) | |
166 | link_set_dns_server(s->link, NULL); | |
167 | ||
168 | if (s->manager->current_dns_server == s) | |
169 | manager_set_dns_server(s->manager, NULL); | |
170 | ||
171 | dns_server_unref(s); | |
91b14d6f TG |
172 | } |
173 | ||
0b58db65 LP |
174 | void dns_server_move_back_and_unmark(DnsServer *s) { |
175 | DnsServer *tail; | |
176 | ||
177 | assert(s); | |
178 | ||
179 | if (!s->marked) | |
180 | return; | |
181 | ||
182 | s->marked = false; | |
183 | ||
184 | if (!s->linked || !s->servers_next) | |
185 | return; | |
186 | ||
187 | /* Move us to the end of the list, so that the order is | |
188 | * strictly kept, if we are not at the end anyway. */ | |
189 | ||
190 | switch (s->type) { | |
191 | ||
192 | case DNS_SERVER_LINK: | |
193 | assert(s->link); | |
194 | LIST_FIND_TAIL(servers, s, tail); | |
195 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
196 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
197 | break; | |
198 | ||
199 | case DNS_SERVER_SYSTEM: | |
200 | LIST_FIND_TAIL(servers, s, tail); | |
201 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
202 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
203 | break; | |
204 | ||
205 | case DNS_SERVER_FALLBACK: | |
206 | LIST_FIND_TAIL(servers, s, tail); | |
207 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
208 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
209 | break; | |
210 | ||
211 | default: | |
212 | assert_not_reached("Unknown server type"); | |
213 | } | |
214 | } | |
215 | ||
6bb2c085 | 216 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
217 | assert(s); |
218 | ||
6bb2c085 LP |
219 | if (s->verified_feature_level > level) |
220 | return; | |
b652d4a2 | 221 | |
6bb2c085 | 222 | if (s->verified_feature_level != level) { |
de54e62b LP |
223 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
224 | dns_server_feature_level_to_string(level), | |
225 | dns_server_string(s)); | |
f4461e56 | 226 | s->verified_feature_level = level; |
be808ea0 TG |
227 | } |
228 | ||
6bb2c085 LP |
229 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
230 | } | |
231 | ||
d001e0a3 LP |
232 | static void dns_server_reset_counters(DnsServer *s) { |
233 | assert(s); | |
234 | ||
235 | s->n_failed_udp = 0; | |
236 | s->n_failed_tcp = 0; | |
237 | s->packet_truncated = false; | |
238 | s->verified_usec = 0; | |
239 | ||
240 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
241 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
242 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
243 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
244 | * either. | |
245 | * | |
246 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
247 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
248 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
249 | * incomplete. */ | |
250 | } | |
251 | ||
6bb2c085 LP |
252 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size) { |
253 | assert(s); | |
254 | ||
255 | if (protocol == IPPROTO_UDP) { | |
256 | if (s->possible_feature_level == level) | |
257 | s->n_failed_udp = 0; | |
258 | ||
b6451358 LP |
259 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
260 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
261 | level = DNS_SERVER_FEATURE_LEVEL_DO - 1; | |
262 | ||
263 | /* If the OPT RR got lost, then we can only validate UDP at max */ | |
264 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
265 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
266 | ||
267 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
268 | that does not mean we can necessarily receive large packets. */ | |
6bb2c085 | 269 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) |
b6451358 | 270 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; |
6bb2c085 LP |
271 | |
272 | } else if (protocol == IPPROTO_TCP) { | |
273 | ||
274 | if (s->possible_feature_level == level) | |
275 | s->n_failed_tcp = 0; | |
276 | ||
277 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
b6451358 | 278 | level = DNS_SERVER_FEATURE_LEVEL_TCP; |
6bb2c085 | 279 | } |
84129d46 | 280 | |
b6451358 LP |
281 | dns_server_verified(s, level); |
282 | ||
d74fb368 TG |
283 | /* Remember the size of the largest UDP packet we received from a server, |
284 | we know that we can always announce support for packets with at least | |
285 | this size. */ | |
6bb2c085 | 286 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 TG |
287 | s->received_udp_packet_max = size; |
288 | ||
be808ea0 TG |
289 | if (s->max_rtt < rtt) { |
290 | s->max_rtt = rtt; | |
efd46a69 | 291 | s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); |
496ae8c8 KK |
292 | } else if (s->resend_timeout > rtt) |
293 | /* If we received the packet faster than the resend_timeout, bias | |
294 | * the resend_timeout back to the rtt. */ | |
295 | s->resend_timeout = CLAMP((2 * s->resend_timeout + rtt) / 3, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
296 | } |
297 | ||
6bb2c085 | 298 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { |
9df3ba6c | 299 | assert(s); |
be808ea0 TG |
300 | assert(s->manager); |
301 | ||
6bb2c085 LP |
302 | if (s->possible_feature_level == level) { |
303 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 304 | s->n_failed_udp++; |
6bb2c085 | 305 | else if (protocol == IPPROTO_TCP) |
313cefa1 | 306 | s->n_failed_tcp++; |
6bb2c085 | 307 | } |
9df3ba6c | 308 | |
84129d46 LP |
309 | if (s->resend_timeout > usec) |
310 | return; | |
311 | ||
312 | s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
313 | } |
314 | ||
6bb2c085 LP |
315 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
316 | assert(s); | |
571370c1 | 317 | |
6bb2c085 LP |
318 | /* Invoked whenever we get a packet with TC bit set. */ |
319 | ||
320 | if (s->possible_feature_level != level) | |
571370c1 LP |
321 | return; |
322 | ||
6bb2c085 | 323 | s->packet_truncated = true; |
4e0b8b17 TG |
324 | } |
325 | ||
de54e62b LP |
326 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
327 | assert(s); | |
328 | ||
329 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
330 | return; | |
331 | ||
b6451358 LP |
332 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
333 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
334 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_DO-1; | |
335 | ||
de54e62b LP |
336 | s->packet_rrsig_missing = true; |
337 | } | |
338 | ||
339 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 340 | assert(s); |
b652d4a2 | 341 | |
de54e62b LP |
342 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
343 | return; | |
b652d4a2 | 344 | |
b6451358 LP |
345 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
346 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
347 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
348 | ||
de54e62b | 349 | s->packet_bad_opt = true; |
b652d4a2 LP |
350 | } |
351 | ||
d001e0a3 LP |
352 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
353 | assert(s); | |
354 | ||
355 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
356 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
357 | * things work. */ | |
358 | ||
359 | if (s->verified_feature_level > level) | |
360 | s->verified_feature_level = level; | |
361 | ||
362 | if (s->possible_feature_level > level) { | |
363 | s->possible_feature_level = level; | |
364 | dns_server_reset_counters(s); | |
365 | } | |
366 | ||
367 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
368 | } | |
369 | ||
be808ea0 TG |
370 | static bool dns_server_grace_period_expired(DnsServer *s) { |
371 | usec_t ts; | |
372 | ||
373 | assert(s); | |
374 | assert(s->manager); | |
375 | ||
376 | if (s->verified_usec == 0) | |
377 | return false; | |
378 | ||
379 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
380 | ||
381 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
382 | return false; | |
383 | ||
384 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
385 | ||
386 | return true; | |
387 | } | |
388 | ||
f4461e56 | 389 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
390 | DnsServerFeatureLevel best; |
391 | ||
be808ea0 TG |
392 | assert(s); |
393 | ||
97277567 LP |
394 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
395 | * better than EDNS0, hence don't even try. */ | |
396 | best = dns_server_get_dnssec_mode(s) == DNSSEC_NO ? | |
397 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : | |
398 | DNS_SERVER_FEATURE_LEVEL_BEST; | |
399 | ||
400 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
401 | * time, hence let's downgrade if we are still at a higher level. */ | |
402 | if (s->possible_feature_level > best) | |
403 | s->possible_feature_level = best; | |
404 | ||
405 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 406 | |
97277567 | 407 | s->possible_feature_level = best; |
cc450722 | 408 | |
01184277 LP |
409 | dns_server_reset_counters(s); |
410 | ||
cc450722 LP |
411 | s->packet_bad_opt = false; |
412 | s->packet_rrsig_missing = false; | |
413 | ||
de54e62b | 414 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
415 | dns_server_feature_level_to_string(s->possible_feature_level), |
416 | dns_server_string(s)); | |
6bb2c085 | 417 | |
ce7c8b20 LP |
418 | dns_server_flush_cache(s); |
419 | ||
f4461e56 LP |
420 | } else if (s->possible_feature_level <= s->verified_feature_level) |
421 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
422 | else { |
423 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 424 | |
6bb2c085 | 425 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 426 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 427 | |
6bb2c085 LP |
428 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
429 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
430 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
431 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
432 | ||
433 | } else if (s->packet_bad_opt && | |
434 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
435 | ||
436 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
437 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
438 | * in the request. Example: | |
439 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
440 | ||
441 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 442 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 443 | |
de54e62b LP |
444 | } else if (s->packet_rrsig_missing && |
445 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 446 | |
de54e62b LP |
447 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
448 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
449 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
450 | * not. */ | |
451 | ||
452 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
453 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
454 | ||
455 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 456 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
457 | |
458 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
459 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
460 | * idea. We might downgrade all the way down to TCP this way. |
461 | * | |
462 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
463 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
464 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
465 | |
466 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
467 | s->possible_feature_level--; | |
468 | ||
de54e62b LP |
469 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
470 | s->packet_truncated && | |
12bf2331 | 471 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
472 | |
473 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
474 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
475 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
476 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
477 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
478 | ||
479 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
480 | s->possible_feature_level--; | |
481 | } | |
482 | ||
6bb2c085 | 483 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
484 | |
485 | /* We changed the feature level, reset the counting */ | |
01184277 | 486 | dns_server_reset_counters(s); |
6bb2c085 | 487 | |
de54e62b | 488 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
489 | dns_server_feature_level_to_string(s->possible_feature_level), |
490 | dns_server_string(s)); | |
6bb2c085 | 491 | } |
be808ea0 TG |
492 | } |
493 | ||
f4461e56 | 494 | return s->possible_feature_level; |
be808ea0 TG |
495 | } |
496 | ||
519ef046 LP |
497 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
498 | size_t packet_size; | |
499 | bool edns_do; | |
500 | int r; | |
501 | ||
502 | assert(server); | |
503 | assert(packet); | |
504 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
505 | ||
506 | /* Fix the OPT field in the packet to match our current feature level. */ | |
507 | ||
508 | r = dns_packet_truncate_opt(packet); | |
509 | if (r < 0) | |
510 | return r; | |
511 | ||
512 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
513 | return 0; | |
514 | ||
515 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
516 | ||
517 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
518 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
519 | else | |
520 | packet_size = server->received_udp_packet_max; | |
521 | ||
f2ed4c69 | 522 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
523 | } |
524 | ||
2817157b LP |
525 | int dns_server_ifindex(const DnsServer *s) { |
526 | assert(s); | |
527 | ||
528 | /* The link ifindex always takes precedence */ | |
529 | if (s->link) | |
530 | return s->link->ifindex; | |
531 | ||
532 | if (s->ifindex > 0) | |
533 | return s->ifindex; | |
534 | ||
535 | return 0; | |
536 | } | |
537 | ||
6cb08a89 LP |
538 | const char *dns_server_string(DnsServer *server) { |
539 | assert(server); | |
540 | ||
541 | if (!server->server_string) | |
2817157b | 542 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
543 | |
544 | return strna(server->server_string); | |
545 | } | |
546 | ||
92ec902a LP |
547 | bool dns_server_dnssec_supported(DnsServer *server) { |
548 | assert(server); | |
549 | ||
550 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
551 | ||
552 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
553 | return false; | |
554 | ||
de54e62b LP |
555 | if (server->packet_bad_opt) |
556 | return false; | |
557 | ||
558 | if (server->packet_rrsig_missing) | |
92ec902a LP |
559 | return false; |
560 | ||
561 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
562 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
563 | return false; | |
564 | ||
565 | return true; | |
566 | } | |
567 | ||
1e02e182 LP |
568 | void dns_server_warn_downgrade(DnsServer *server) { |
569 | assert(server); | |
570 | ||
571 | if (server->warned_downgrade) | |
572 | return; | |
573 | ||
574 | log_struct(LOG_NOTICE, | |
2b044526 | 575 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
576 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
577 | "DNS_SERVER=%s", dns_server_string(server), | |
578 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level), | |
579 | NULL); | |
580 | ||
581 | server->warned_downgrade = true; | |
582 | } | |
583 | ||
413b05cc | 584 | bool dns_server_limited_domains(DnsServer *server) { |
b9fe94ca MP |
585 | DnsSearchDomain *domain; |
586 | bool domain_restricted = false; | |
587 | ||
588 | /* Check if the server has route-only domains without ~., i. e. whether | |
589 | * it should only be used for particular domains */ | |
590 | if (!server->link) | |
591 | return false; | |
592 | ||
593 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
594 | if (domain->route_only) { | |
595 | domain_restricted = true; | |
596 | /* ~. means "any domain", thus it is a global server */ | |
413b05cc | 597 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) |
b9fe94ca MP |
598 | return false; |
599 | } | |
600 | ||
601 | return domain_restricted; | |
602 | } | |
603 | ||
b826ab58 | 604 | static void dns_server_hash_func(const void *p, struct siphash *state) { |
87f5a193 | 605 | const DnsServer *s = p; |
87f5a193 | 606 | |
b826ab58 | 607 | assert(s); |
87f5a193 | 608 | |
b826ab58 TG |
609 | siphash24_compress(&s->family, sizeof(s->family), state); |
610 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 611 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
612 | } |
613 | ||
d5099efc | 614 | static int dns_server_compare_func(const void *a, const void *b) { |
87f5a193 | 615 | const DnsServer *x = a, *y = b; |
2817157b | 616 | int r; |
87f5a193 LP |
617 | |
618 | if (x->family < y->family) | |
619 | return -1; | |
620 | if (x->family > y->family) | |
621 | return 1; | |
622 | ||
2817157b LP |
623 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
624 | if (r != 0) | |
625 | return r; | |
626 | ||
627 | if (x->ifindex < y->ifindex) | |
628 | return -1; | |
629 | if (x->ifindex > y->ifindex) | |
630 | return 1; | |
631 | ||
632 | return 0; | |
87f5a193 | 633 | } |
d5099efc MS |
634 | |
635 | const struct hash_ops dns_server_hash_ops = { | |
636 | .hash = dns_server_hash_func, | |
637 | .compare = dns_server_compare_func | |
638 | }; | |
636e813d | 639 | |
4b95f179 LP |
640 | void dns_server_unlink_all(DnsServer *first) { |
641 | DnsServer *next; | |
0eac4623 | 642 | |
4b95f179 LP |
643 | if (!first) |
644 | return; | |
0eac4623 | 645 | |
4b95f179 LP |
646 | next = first->servers_next; |
647 | dns_server_unlink(first); | |
636e813d | 648 | |
4b95f179 | 649 | dns_server_unlink_all(next); |
0eac4623 LP |
650 | } |
651 | ||
4b95f179 LP |
652 | void dns_server_unlink_marked(DnsServer *first) { |
653 | DnsServer *next; | |
636e813d | 654 | |
4b95f179 LP |
655 | if (!first) |
656 | return; | |
636e813d | 657 | |
4b95f179 | 658 | next = first->servers_next; |
636e813d | 659 | |
4b95f179 | 660 | if (first->marked) |
0eac4623 | 661 | dns_server_unlink(first); |
636e813d | 662 | |
4b95f179 LP |
663 | dns_server_unlink_marked(next); |
664 | } | |
636e813d | 665 | |
4b95f179 LP |
666 | void dns_server_mark_all(DnsServer *first) { |
667 | if (!first) | |
668 | return; | |
636e813d | 669 | |
4b95f179 LP |
670 | first->marked = true; |
671 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
672 | } |
673 | ||
2817157b | 674 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 675 | DnsServer *s; |
636e813d | 676 | |
636e813d | 677 | LIST_FOREACH(servers, s, first) |
2817157b | 678 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 679 | return s; |
f2f1dbe5 | 680 | |
4b95f179 LP |
681 | return NULL; |
682 | } | |
f2f1dbe5 | 683 | |
4b95f179 | 684 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 685 | assert(m); |
f2f1dbe5 | 686 | |
4b95f179 | 687 | switch (t) { |
f2f1dbe5 | 688 | |
4b95f179 LP |
689 | case DNS_SERVER_SYSTEM: |
690 | return m->dns_servers; | |
f2f1dbe5 | 691 | |
4b95f179 LP |
692 | case DNS_SERVER_FALLBACK: |
693 | return m->fallback_dns_servers; | |
694 | ||
695 | default: | |
696 | return NULL; | |
697 | } | |
f2f1dbe5 LP |
698 | } |
699 | ||
700 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
701 | assert(m); | |
702 | ||
703 | if (m->current_dns_server == s) | |
704 | return s; | |
705 | ||
6cb08a89 | 706 | if (s) |
db8e1324 LP |
707 | log_debug("Switching to %s DNS server %s.", |
708 | dns_server_type_to_string(s->type), | |
709 | dns_server_string(s)); | |
f2f1dbe5 | 710 | |
0eac4623 LP |
711 | dns_server_unref(m->current_dns_server); |
712 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
713 | |
714 | if (m->unicast_scope) | |
715 | dns_cache_flush(&m->unicast_scope->cache); | |
716 | ||
717 | return s; | |
718 | } | |
719 | ||
720 | DnsServer *manager_get_dns_server(Manager *m) { | |
721 | Link *l; | |
722 | assert(m); | |
723 | ||
724 | /* Try to read updates resolv.conf */ | |
725 | manager_read_resolv_conf(m); | |
726 | ||
e3309036 | 727 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
728 | if (!m->current_dns_server) |
729 | manager_set_dns_server(m, m->dns_servers); | |
730 | ||
731 | if (!m->current_dns_server) { | |
732 | bool found = false; | |
733 | Iterator i; | |
734 | ||
735 | /* No DNS servers configured, let's see if there are | |
736 | * any on any links. If not, we use the fallback | |
737 | * servers */ | |
738 | ||
739 | HASHMAP_FOREACH(l, m->links, i) | |
740 | if (l->dns_servers) { | |
741 | found = true; | |
742 | break; | |
743 | } | |
744 | ||
745 | if (!found) | |
746 | manager_set_dns_server(m, m->fallback_dns_servers); | |
747 | } | |
748 | ||
749 | return m->current_dns_server; | |
750 | } | |
751 | ||
752 | void manager_next_dns_server(Manager *m) { | |
753 | assert(m); | |
754 | ||
755 | /* If there's currently no DNS server set, then the next | |
756 | * manager_get_dns_server() will find one */ | |
757 | if (!m->current_dns_server) | |
758 | return; | |
759 | ||
0eac4623 LP |
760 | /* Change to the next one, but make sure to follow the linked |
761 | * list only if the server is still linked. */ | |
762 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
763 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
764 | return; | |
765 | } | |
766 | ||
767 | /* If there was no next one, then start from the beginning of | |
768 | * the list */ | |
769 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
770 | manager_set_dns_server(m, m->fallback_dns_servers); | |
771 | else | |
772 | manager_set_dns_server(m, m->dns_servers); | |
773 | } | |
be808ea0 | 774 | |
b30bf55d LP |
775 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
776 | ||
777 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
778 | ||
779 | if (in_addr_is_null(family, sa)) | |
780 | return false; | |
781 | ||
782 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
783 | return false; | |
784 | ||
785 | return true; | |
786 | } | |
787 | ||
12bf2331 LP |
788 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
789 | assert(s); | |
790 | ||
791 | if (s->link) | |
792 | return link_get_dnssec_mode(s->link); | |
793 | ||
794 | return manager_get_dnssec_mode(s->manager); | |
795 | } | |
796 | ||
ce7c8b20 LP |
797 | void dns_server_flush_cache(DnsServer *s) { |
798 | DnsServer *current; | |
799 | DnsScope *scope; | |
800 | ||
801 | assert(s); | |
802 | ||
803 | /* Flush the cache of the scope this server belongs to */ | |
804 | ||
805 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
806 | if (current != s) | |
807 | return; | |
808 | ||
809 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
810 | if (!scope) | |
811 | return; | |
812 | ||
813 | dns_cache_flush(&scope->cache); | |
814 | } | |
815 | ||
59c0fd0e LP |
816 | void dns_server_reset_features(DnsServer *s) { |
817 | assert(s); | |
818 | ||
819 | s->max_rtt = 0; | |
820 | s->resend_timeout = DNS_TIMEOUT_MIN_USEC; | |
821 | ||
822 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; | |
823 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
824 | ||
825 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
826 | ||
827 | s->packet_bad_opt = false; | |
828 | s->packet_rrsig_missing = false; | |
829 | ||
830 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
831 | ||
832 | s->warned_downgrade = false; | |
833 | ||
834 | dns_server_reset_counters(s); | |
835 | } | |
836 | ||
837 | void dns_server_reset_features_all(DnsServer *s) { | |
838 | DnsServer *i; | |
839 | ||
840 | LIST_FOREACH(servers, i, s) | |
841 | dns_server_reset_features(i); | |
842 | } | |
843 | ||
cf84484a LP |
844 | void dns_server_dump(DnsServer *s, FILE *f) { |
845 | assert(s); | |
846 | ||
847 | if (!f) | |
848 | f = stdout; | |
849 | ||
850 | fputs("[Server ", f); | |
851 | fputs(dns_server_string(s), f); | |
852 | fputs(" type=", f); | |
853 | fputs(dns_server_type_to_string(s->type), f); | |
854 | ||
855 | if (s->type == DNS_SERVER_LINK) { | |
856 | assert(s->link); | |
857 | ||
858 | fputs(" interface=", f); | |
859 | fputs(s->link->name, f); | |
860 | } | |
861 | ||
862 | fputs("]\n", f); | |
863 | ||
864 | fputs("\tVerified feature level: ", f); | |
865 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
866 | fputc('\n', f); | |
867 | ||
868 | fputs("\tPossible feature level: ", f); | |
869 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
870 | fputc('\n', f); | |
871 | ||
872 | fputs("\tDNSSEC Mode: ", f); | |
873 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
874 | fputc('\n', f); | |
875 | ||
876 | fputs("\tCan do DNSSEC: ", f); | |
877 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
878 | fputc('\n', f); | |
879 | ||
880 | fprintf(f, | |
881 | "\tMaximum UDP packet size received: %zu\n" | |
882 | "\tFailed UDP attempts: %u\n" | |
883 | "\tFailed TCP attempts: %u\n" | |
884 | "\tSeen truncated packet: %s\n" | |
885 | "\tSeen OPT RR getting lost: %s\n" | |
886 | "\tSeen RRSIG RR missing: %s\n", | |
887 | s->received_udp_packet_max, | |
888 | s->n_failed_udp, | |
889 | s->n_failed_tcp, | |
890 | yes_no(s->packet_truncated), | |
891 | yes_no(s->packet_bad_opt), | |
892 | yes_no(s->packet_rrsig_missing)); | |
893 | } | |
894 | ||
e3309036 ZJS |
895 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
896 | [DNS_SERVER_SYSTEM] = "system", | |
897 | [DNS_SERVER_FALLBACK] = "fallback", | |
898 | [DNS_SERVER_LINK] = "link", | |
899 | }; | |
900 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
901 | ||
be808ea0 TG |
902 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
903 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
904 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 905 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
7586f4d1 | 906 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 907 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
be808ea0 TG |
908 | }; |
909 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |