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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 | |
be808ea0 TG |
18 | /* The amount of time to wait before retrying with a full feature set */ |
19 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
20 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
21 | ||
22 | /* The number of times we will attempt a certain feature set before degrading */ | |
23 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
24 | ||
74b2466e LP |
25 | int dns_server_new( |
26 | Manager *m, | |
27 | DnsServer **ret, | |
4e945a6f | 28 | DnsServerType type, |
74b2466e | 29 | Link *l, |
0dd25fb9 | 30 | int family, |
2817157b LP |
31 | const union in_addr_union *in_addr, |
32 | int ifindex) { | |
74b2466e | 33 | |
eed857b7 | 34 | DnsServer *s; |
74b2466e LP |
35 | |
36 | assert(m); | |
4e945a6f | 37 | assert((type == DNS_SERVER_LINK) == !!l); |
74b2466e | 38 | assert(in_addr); |
74b2466e | 39 | |
eed857b7 LP |
40 | if (!IN_SET(family, AF_INET, AF_INET6)) |
41 | return -EAFNOSUPPORT; | |
42 | ||
43 | if (l) { | |
44 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
45 | return -E2BIG; | |
46 | } else { | |
47 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
48 | return -E2BIG; | |
49 | } | |
50 | ||
74b2466e LP |
51 | s = new0(DnsServer, 1); |
52 | if (!s) | |
53 | return -ENOMEM; | |
54 | ||
91b14d6f | 55 | s->n_ref = 1; |
0b58db65 | 56 | s->manager = m; |
4e945a6f | 57 | s->type = type; |
74b2466e LP |
58 | s->family = family; |
59 | s->address = *in_addr; | |
2817157b | 60 | s->ifindex = ifindex; |
59c0fd0e LP |
61 | |
62 | dns_server_reset_features(s); | |
74b2466e | 63 | |
0b58db65 LP |
64 | switch (type) { |
65 | ||
66 | case DNS_SERVER_LINK: | |
67 | s->link = l; | |
eed857b7 LP |
68 | LIST_APPEND(servers, l->dns_servers, s); |
69 | l->n_dns_servers++; | |
0b58db65 LP |
70 | break; |
71 | ||
72 | case DNS_SERVER_SYSTEM: | |
eed857b7 LP |
73 | LIST_APPEND(servers, m->dns_servers, s); |
74 | m->n_dns_servers++; | |
0b58db65 LP |
75 | break; |
76 | ||
77 | case DNS_SERVER_FALLBACK: | |
eed857b7 LP |
78 | LIST_APPEND(servers, m->fallback_dns_servers, s); |
79 | m->n_dns_servers++; | |
0b58db65 LP |
80 | break; |
81 | ||
82 | default: | |
4e945a6f | 83 | assert_not_reached("Unknown server type"); |
0b58db65 | 84 | } |
74b2466e | 85 | |
0eac4623 | 86 | s->linked = true; |
74b2466e | 87 | |
5d67a7ae IT |
88 | #if HAVE_GNUTLS |
89 | /* Do not verify cerificate */ | |
90 | gnutls_certificate_allocate_credentials(&s->tls_cert_cred); | |
91 | #endif | |
92 | ||
4e945a6f LP |
93 | /* A new DNS server that isn't fallback is added and the one |
94 | * we used so far was a fallback one? Then let's try to pick | |
95 | * the new one */ | |
96 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
97 | m->current_dns_server && |
98 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
99 | manager_set_dns_server(m, NULL); | |
4e945a6f | 100 | |
74b2466e LP |
101 | if (ret) |
102 | *ret = s; | |
103 | ||
104 | return 0; | |
105 | } | |
106 | ||
91b14d6f | 107 | DnsServer* dns_server_ref(DnsServer *s) { |
74b2466e LP |
108 | if (!s) |
109 | return NULL; | |
110 | ||
91b14d6f | 111 | assert(s->n_ref > 0); |
313cefa1 | 112 | s->n_ref++; |
cab5b059 | 113 | |
91b14d6f TG |
114 | return s; |
115 | } | |
116 | ||
0eac4623 | 117 | DnsServer* dns_server_unref(DnsServer *s) { |
91b14d6f TG |
118 | if (!s) |
119 | return NULL; | |
3e684349 | 120 | |
0eac4623 | 121 | assert(s->n_ref > 0); |
313cefa1 | 122 | s->n_ref--; |
91b14d6f | 123 | |
0eac4623 LP |
124 | if (s->n_ref > 0) |
125 | return NULL; | |
74b2466e | 126 | |
98767d75 IT |
127 | dns_stream_unref(s->stream); |
128 | ||
5d67a7ae IT |
129 | #if HAVE_GNUTLS |
130 | if (s->tls_cert_cred) | |
131 | gnutls_certificate_free_credentials(s->tls_cert_cred); | |
132 | ||
133 | if (s->tls_session_data.data) | |
134 | gnutls_free(s->tls_session_data.data); | |
135 | #endif | |
136 | ||
6cb08a89 | 137 | free(s->server_string); |
6b430fdb | 138 | return mfree(s); |
74b2466e | 139 | } |
87f5a193 | 140 | |
0eac4623 LP |
141 | void dns_server_unlink(DnsServer *s) { |
142 | assert(s); | |
143 | assert(s->manager); | |
91b14d6f | 144 | |
0eac4623 LP |
145 | /* This removes the specified server from the linked list of |
146 | * servers, but any server might still stay around if it has | |
147 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 148 | |
0eac4623 LP |
149 | if (!s->linked) |
150 | return; | |
91b14d6f | 151 | |
0eac4623 LP |
152 | switch (s->type) { |
153 | ||
154 | case DNS_SERVER_LINK: | |
155 | assert(s->link); | |
eed857b7 | 156 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 157 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 158 | s->link->n_dns_servers--; |
0eac4623 LP |
159 | break; |
160 | ||
161 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 162 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 163 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 164 | s->manager->n_dns_servers--; |
0eac4623 LP |
165 | break; |
166 | ||
167 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 168 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 169 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 170 | s->manager->n_dns_servers--; |
0eac4623 LP |
171 | break; |
172 | } | |
173 | ||
174 | s->linked = false; | |
175 | ||
176 | if (s->link && s->link->current_dns_server == s) | |
177 | link_set_dns_server(s->link, NULL); | |
178 | ||
179 | if (s->manager->current_dns_server == s) | |
180 | manager_set_dns_server(s->manager, NULL); | |
181 | ||
182 | dns_server_unref(s); | |
91b14d6f TG |
183 | } |
184 | ||
0b58db65 LP |
185 | void dns_server_move_back_and_unmark(DnsServer *s) { |
186 | DnsServer *tail; | |
187 | ||
188 | assert(s); | |
189 | ||
190 | if (!s->marked) | |
191 | return; | |
192 | ||
193 | s->marked = false; | |
194 | ||
195 | if (!s->linked || !s->servers_next) | |
196 | return; | |
197 | ||
198 | /* Move us to the end of the list, so that the order is | |
199 | * strictly kept, if we are not at the end anyway. */ | |
200 | ||
201 | switch (s->type) { | |
202 | ||
203 | case DNS_SERVER_LINK: | |
204 | assert(s->link); | |
205 | LIST_FIND_TAIL(servers, s, tail); | |
206 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
207 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
208 | break; | |
209 | ||
210 | case DNS_SERVER_SYSTEM: | |
211 | LIST_FIND_TAIL(servers, s, tail); | |
212 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
213 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
214 | break; | |
215 | ||
216 | case DNS_SERVER_FALLBACK: | |
217 | LIST_FIND_TAIL(servers, s, tail); | |
218 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
219 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
220 | break; | |
221 | ||
222 | default: | |
223 | assert_not_reached("Unknown server type"); | |
224 | } | |
225 | } | |
226 | ||
6bb2c085 | 227 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
228 | assert(s); |
229 | ||
6bb2c085 LP |
230 | if (s->verified_feature_level > level) |
231 | return; | |
b652d4a2 | 232 | |
6bb2c085 | 233 | if (s->verified_feature_level != level) { |
de54e62b LP |
234 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
235 | dns_server_feature_level_to_string(level), | |
236 | dns_server_string(s)); | |
f4461e56 | 237 | s->verified_feature_level = level; |
be808ea0 TG |
238 | } |
239 | ||
6bb2c085 LP |
240 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
241 | } | |
242 | ||
d001e0a3 LP |
243 | static void dns_server_reset_counters(DnsServer *s) { |
244 | assert(s); | |
245 | ||
246 | s->n_failed_udp = 0; | |
247 | s->n_failed_tcp = 0; | |
5d67a7ae | 248 | s->n_failed_tls = 0; |
d001e0a3 LP |
249 | s->packet_truncated = false; |
250 | s->verified_usec = 0; | |
251 | ||
252 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
253 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
254 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
255 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
256 | * either. | |
257 | * | |
258 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
259 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
260 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
261 | * incomplete. */ | |
262 | } | |
263 | ||
dbc4661a | 264 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, size_t size) { |
6bb2c085 LP |
265 | assert(s); |
266 | ||
267 | if (protocol == IPPROTO_UDP) { | |
268 | if (s->possible_feature_level == level) | |
269 | s->n_failed_udp = 0; | |
6bb2c085 | 270 | } else if (protocol == IPPROTO_TCP) { |
5d67a7ae IT |
271 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { |
272 | if (s->possible_feature_level == level) | |
273 | s->n_failed_tls = 0; | |
274 | } else { | |
275 | if (s->possible_feature_level == level) | |
276 | s->n_failed_tcp = 0; | |
277 | ||
278 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
279 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
280 | } | |
281 | } | |
6bb2c085 | 282 | |
5d67a7ae IT |
283 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
284 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
285 | level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
6bb2c085 | 286 | |
5d67a7ae IT |
287 | /* If the OPT RR got lost, then we can only validate UDP at max */ |
288 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
289 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
290 | ||
291 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
292 | that does not mean we can necessarily receive large packets. */ | |
293 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
294 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
84129d46 | 295 | |
b6451358 LP |
296 | dns_server_verified(s, level); |
297 | ||
d74fb368 TG |
298 | /* Remember the size of the largest UDP packet we received from a server, |
299 | we know that we can always announce support for packets with at least | |
300 | this size. */ | |
6bb2c085 | 301 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 | 302 | s->received_udp_packet_max = size; |
9df3ba6c TG |
303 | } |
304 | ||
3da3cdd5 | 305 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level) { |
9df3ba6c | 306 | assert(s); |
be808ea0 TG |
307 | assert(s->manager); |
308 | ||
6bb2c085 LP |
309 | if (s->possible_feature_level == level) { |
310 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 311 | s->n_failed_udp++; |
5d67a7ae IT |
312 | else if (protocol == IPPROTO_TCP) { |
313 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
314 | s->n_failed_tls++; | |
315 | else | |
316 | s->n_failed_tcp++; | |
317 | } | |
6bb2c085 | 318 | } |
9df3ba6c TG |
319 | } |
320 | ||
6bb2c085 LP |
321 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
322 | assert(s); | |
571370c1 | 323 | |
6bb2c085 LP |
324 | /* Invoked whenever we get a packet with TC bit set. */ |
325 | ||
326 | if (s->possible_feature_level != level) | |
571370c1 LP |
327 | return; |
328 | ||
6bb2c085 | 329 | s->packet_truncated = true; |
4e0b8b17 TG |
330 | } |
331 | ||
de54e62b LP |
332 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
333 | assert(s); | |
334 | ||
335 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
336 | return; | |
337 | ||
b6451358 LP |
338 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
339 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
5d67a7ae | 340 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
b6451358 | 341 | |
de54e62b LP |
342 | s->packet_rrsig_missing = true; |
343 | } | |
344 | ||
345 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 346 | assert(s); |
b652d4a2 | 347 | |
de54e62b LP |
348 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
349 | return; | |
b652d4a2 | 350 | |
b6451358 LP |
351 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
352 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
353 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
354 | ||
de54e62b | 355 | s->packet_bad_opt = true; |
b652d4a2 LP |
356 | } |
357 | ||
d001e0a3 LP |
358 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
359 | assert(s); | |
360 | ||
361 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
362 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
363 | * things work. */ | |
364 | ||
365 | if (s->verified_feature_level > level) | |
366 | s->verified_feature_level = level; | |
367 | ||
368 | if (s->possible_feature_level > level) { | |
369 | s->possible_feature_level = level; | |
370 | dns_server_reset_counters(s); | |
371 | } | |
372 | ||
373 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
374 | } | |
375 | ||
be808ea0 TG |
376 | static bool dns_server_grace_period_expired(DnsServer *s) { |
377 | usec_t ts; | |
378 | ||
379 | assert(s); | |
380 | assert(s->manager); | |
381 | ||
382 | if (s->verified_usec == 0) | |
383 | return false; | |
384 | ||
385 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
386 | ||
387 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
388 | return false; | |
389 | ||
390 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
391 | ||
392 | return true; | |
393 | } | |
394 | ||
f4461e56 | 395 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
396 | DnsServerFeatureLevel best; |
397 | ||
be808ea0 TG |
398 | assert(s); |
399 | ||
97277567 LP |
400 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
401 | * better than EDNS0, hence don't even try. */ | |
5d67a7ae | 402 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) |
c9299be2 | 403 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
404 | DNS_SERVER_FEATURE_LEVEL_LARGE : |
405 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
406 | else | |
c9299be2 | 407 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
408 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : |
409 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
97277567 LP |
410 | |
411 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
412 | * time, hence let's downgrade if we are still at a higher level. */ | |
413 | if (s->possible_feature_level > best) | |
414 | s->possible_feature_level = best; | |
415 | ||
416 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 417 | |
97277567 | 418 | s->possible_feature_level = best; |
cc450722 | 419 | |
01184277 LP |
420 | dns_server_reset_counters(s); |
421 | ||
cc450722 LP |
422 | s->packet_bad_opt = false; |
423 | s->packet_rrsig_missing = false; | |
424 | ||
de54e62b | 425 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
426 | dns_server_feature_level_to_string(s->possible_feature_level), |
427 | dns_server_string(s)); | |
6bb2c085 | 428 | |
ce7c8b20 LP |
429 | dns_server_flush_cache(s); |
430 | ||
f4461e56 LP |
431 | } else if (s->possible_feature_level <= s->verified_feature_level) |
432 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
433 | else { |
434 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 435 | |
6bb2c085 | 436 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 437 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 438 | |
6bb2c085 LP |
439 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
440 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
441 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
442 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
5d67a7ae IT |
443 | } else if (s->n_failed_tls > 0 && |
444 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level)) { | |
445 | ||
446 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
447 | * if we don't require DNS-over-TLS */ | |
de54e62b | 448 | |
3c0dcbcf | 449 | log_debug("Server doesn't support DNS-over-TLS, downgrading protocol..."); |
5d67a7ae | 450 | s->possible_feature_level--; |
de54e62b LP |
451 | } else if (s->packet_bad_opt && |
452 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
453 | ||
454 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
455 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
456 | * in the request. Example: | |
457 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
458 | ||
459 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 460 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 461 | |
de54e62b LP |
462 | } else if (s->packet_rrsig_missing && |
463 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 464 | |
de54e62b LP |
465 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
466 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
467 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
468 | * not. */ | |
469 | ||
470 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
5d67a7ae | 471 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
de54e62b LP |
472 | |
473 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 474 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
475 | |
476 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
477 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
478 | * idea. We might downgrade all the way down to TCP this way. |
479 | * | |
480 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
481 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
482 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
483 | |
484 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
485 | s->possible_feature_level--; | |
486 | ||
de54e62b LP |
487 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
488 | s->packet_truncated && | |
12bf2331 | 489 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
490 | |
491 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
492 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
493 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
494 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
495 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
496 | ||
497 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
498 | s->possible_feature_level--; | |
499 | } | |
500 | ||
6bb2c085 | 501 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
502 | |
503 | /* We changed the feature level, reset the counting */ | |
01184277 | 504 | dns_server_reset_counters(s); |
6bb2c085 | 505 | |
de54e62b | 506 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
507 | dns_server_feature_level_to_string(s->possible_feature_level), |
508 | dns_server_string(s)); | |
6bb2c085 | 509 | } |
be808ea0 TG |
510 | } |
511 | ||
f4461e56 | 512 | return s->possible_feature_level; |
be808ea0 TG |
513 | } |
514 | ||
519ef046 LP |
515 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
516 | size_t packet_size; | |
517 | bool edns_do; | |
518 | int r; | |
519 | ||
520 | assert(server); | |
521 | assert(packet); | |
522 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
523 | ||
524 | /* Fix the OPT field in the packet to match our current feature level. */ | |
525 | ||
526 | r = dns_packet_truncate_opt(packet); | |
527 | if (r < 0) | |
528 | return r; | |
529 | ||
530 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
531 | return 0; | |
532 | ||
533 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
534 | ||
535 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
536 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
537 | else | |
538 | packet_size = server->received_udp_packet_max; | |
539 | ||
f2ed4c69 | 540 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
541 | } |
542 | ||
2817157b LP |
543 | int dns_server_ifindex(const DnsServer *s) { |
544 | assert(s); | |
545 | ||
546 | /* The link ifindex always takes precedence */ | |
547 | if (s->link) | |
548 | return s->link->ifindex; | |
549 | ||
550 | if (s->ifindex > 0) | |
551 | return s->ifindex; | |
552 | ||
553 | return 0; | |
554 | } | |
555 | ||
6cb08a89 LP |
556 | const char *dns_server_string(DnsServer *server) { |
557 | assert(server); | |
558 | ||
559 | if (!server->server_string) | |
2817157b | 560 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
561 | |
562 | return strna(server->server_string); | |
563 | } | |
564 | ||
92ec902a LP |
565 | bool dns_server_dnssec_supported(DnsServer *server) { |
566 | assert(server); | |
567 | ||
568 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
569 | ||
570 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
571 | return false; | |
572 | ||
de54e62b LP |
573 | if (server->packet_bad_opt) |
574 | return false; | |
575 | ||
576 | if (server->packet_rrsig_missing) | |
92ec902a LP |
577 | return false; |
578 | ||
579 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
580 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
581 | return false; | |
582 | ||
583 | return true; | |
584 | } | |
585 | ||
1e02e182 LP |
586 | void dns_server_warn_downgrade(DnsServer *server) { |
587 | assert(server); | |
588 | ||
589 | if (server->warned_downgrade) | |
590 | return; | |
591 | ||
592 | log_struct(LOG_NOTICE, | |
2b044526 | 593 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
594 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
595 | "DNS_SERVER=%s", dns_server_string(server), | |
f4cf1d66 | 596 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
597 | |
598 | server->warned_downgrade = true; | |
599 | } | |
600 | ||
413b05cc | 601 | bool dns_server_limited_domains(DnsServer *server) { |
b9fe94ca MP |
602 | DnsSearchDomain *domain; |
603 | bool domain_restricted = false; | |
604 | ||
605 | /* Check if the server has route-only domains without ~., i. e. whether | |
606 | * it should only be used for particular domains */ | |
607 | if (!server->link) | |
608 | return false; | |
609 | ||
610 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
611 | if (domain->route_only) { | |
612 | domain_restricted = true; | |
613 | /* ~. means "any domain", thus it is a global server */ | |
413b05cc | 614 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) |
b9fe94ca MP |
615 | return false; |
616 | } | |
617 | ||
618 | return domain_restricted; | |
619 | } | |
620 | ||
b826ab58 | 621 | static void dns_server_hash_func(const void *p, struct siphash *state) { |
87f5a193 | 622 | const DnsServer *s = p; |
87f5a193 | 623 | |
b826ab58 | 624 | assert(s); |
87f5a193 | 625 | |
b826ab58 TG |
626 | siphash24_compress(&s->family, sizeof(s->family), state); |
627 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 628 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
629 | } |
630 | ||
d5099efc | 631 | static int dns_server_compare_func(const void *a, const void *b) { |
87f5a193 | 632 | const DnsServer *x = a, *y = b; |
2817157b | 633 | int r; |
87f5a193 LP |
634 | |
635 | if (x->family < y->family) | |
636 | return -1; | |
637 | if (x->family > y->family) | |
638 | return 1; | |
639 | ||
2817157b LP |
640 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
641 | if (r != 0) | |
642 | return r; | |
643 | ||
644 | if (x->ifindex < y->ifindex) | |
645 | return -1; | |
646 | if (x->ifindex > y->ifindex) | |
647 | return 1; | |
648 | ||
649 | return 0; | |
87f5a193 | 650 | } |
d5099efc MS |
651 | |
652 | const struct hash_ops dns_server_hash_ops = { | |
653 | .hash = dns_server_hash_func, | |
654 | .compare = dns_server_compare_func | |
655 | }; | |
636e813d | 656 | |
4b95f179 LP |
657 | void dns_server_unlink_all(DnsServer *first) { |
658 | DnsServer *next; | |
0eac4623 | 659 | |
4b95f179 LP |
660 | if (!first) |
661 | return; | |
0eac4623 | 662 | |
4b95f179 LP |
663 | next = first->servers_next; |
664 | dns_server_unlink(first); | |
636e813d | 665 | |
4b95f179 | 666 | dns_server_unlink_all(next); |
0eac4623 LP |
667 | } |
668 | ||
4b95f179 LP |
669 | void dns_server_unlink_marked(DnsServer *first) { |
670 | DnsServer *next; | |
636e813d | 671 | |
4b95f179 LP |
672 | if (!first) |
673 | return; | |
636e813d | 674 | |
4b95f179 | 675 | next = first->servers_next; |
636e813d | 676 | |
4b95f179 | 677 | if (first->marked) |
0eac4623 | 678 | dns_server_unlink(first); |
636e813d | 679 | |
4b95f179 LP |
680 | dns_server_unlink_marked(next); |
681 | } | |
636e813d | 682 | |
4b95f179 LP |
683 | void dns_server_mark_all(DnsServer *first) { |
684 | if (!first) | |
685 | return; | |
636e813d | 686 | |
4b95f179 LP |
687 | first->marked = true; |
688 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
689 | } |
690 | ||
2817157b | 691 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 692 | DnsServer *s; |
636e813d | 693 | |
636e813d | 694 | LIST_FOREACH(servers, s, first) |
2817157b | 695 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 696 | return s; |
f2f1dbe5 | 697 | |
4b95f179 LP |
698 | return NULL; |
699 | } | |
f2f1dbe5 | 700 | |
4b95f179 | 701 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 702 | assert(m); |
f2f1dbe5 | 703 | |
4b95f179 | 704 | switch (t) { |
f2f1dbe5 | 705 | |
4b95f179 LP |
706 | case DNS_SERVER_SYSTEM: |
707 | return m->dns_servers; | |
f2f1dbe5 | 708 | |
4b95f179 LP |
709 | case DNS_SERVER_FALLBACK: |
710 | return m->fallback_dns_servers; | |
711 | ||
712 | default: | |
713 | return NULL; | |
714 | } | |
f2f1dbe5 LP |
715 | } |
716 | ||
717 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
718 | assert(m); | |
719 | ||
720 | if (m->current_dns_server == s) | |
721 | return s; | |
722 | ||
6cb08a89 | 723 | if (s) |
db8e1324 LP |
724 | log_debug("Switching to %s DNS server %s.", |
725 | dns_server_type_to_string(s->type), | |
726 | dns_server_string(s)); | |
f2f1dbe5 | 727 | |
0eac4623 LP |
728 | dns_server_unref(m->current_dns_server); |
729 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
730 | |
731 | if (m->unicast_scope) | |
732 | dns_cache_flush(&m->unicast_scope->cache); | |
733 | ||
734 | return s; | |
735 | } | |
736 | ||
737 | DnsServer *manager_get_dns_server(Manager *m) { | |
738 | Link *l; | |
739 | assert(m); | |
740 | ||
741 | /* Try to read updates resolv.conf */ | |
742 | manager_read_resolv_conf(m); | |
743 | ||
e3309036 | 744 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
745 | if (!m->current_dns_server) |
746 | manager_set_dns_server(m, m->dns_servers); | |
747 | ||
748 | if (!m->current_dns_server) { | |
749 | bool found = false; | |
750 | Iterator i; | |
751 | ||
752 | /* No DNS servers configured, let's see if there are | |
753 | * any on any links. If not, we use the fallback | |
754 | * servers */ | |
755 | ||
756 | HASHMAP_FOREACH(l, m->links, i) | |
757 | if (l->dns_servers) { | |
758 | found = true; | |
759 | break; | |
760 | } | |
761 | ||
762 | if (!found) | |
763 | manager_set_dns_server(m, m->fallback_dns_servers); | |
764 | } | |
765 | ||
766 | return m->current_dns_server; | |
767 | } | |
768 | ||
769 | void manager_next_dns_server(Manager *m) { | |
770 | assert(m); | |
771 | ||
772 | /* If there's currently no DNS server set, then the next | |
773 | * manager_get_dns_server() will find one */ | |
774 | if (!m->current_dns_server) | |
775 | return; | |
776 | ||
0eac4623 LP |
777 | /* Change to the next one, but make sure to follow the linked |
778 | * list only if the server is still linked. */ | |
779 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
780 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
781 | return; | |
782 | } | |
783 | ||
784 | /* If there was no next one, then start from the beginning of | |
785 | * the list */ | |
786 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
787 | manager_set_dns_server(m, m->fallback_dns_servers); | |
788 | else | |
789 | manager_set_dns_server(m, m->dns_servers); | |
790 | } | |
be808ea0 | 791 | |
b30bf55d LP |
792 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
793 | ||
794 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
795 | ||
796 | if (in_addr_is_null(family, sa)) | |
797 | return false; | |
798 | ||
799 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
800 | return false; | |
801 | ||
802 | return true; | |
803 | } | |
804 | ||
12bf2331 LP |
805 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
806 | assert(s); | |
807 | ||
808 | if (s->link) | |
809 | return link_get_dnssec_mode(s->link); | |
810 | ||
811 | return manager_get_dnssec_mode(s->manager); | |
812 | } | |
813 | ||
c9299be2 | 814 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { |
5d67a7ae IT |
815 | assert(s); |
816 | ||
d050561a | 817 | if (s->link) |
c9299be2 | 818 | return link_get_dns_over_tls_mode(s->link); |
d050561a | 819 | |
c9299be2 | 820 | return manager_get_dns_over_tls_mode(s->manager); |
5d67a7ae IT |
821 | } |
822 | ||
ce7c8b20 LP |
823 | void dns_server_flush_cache(DnsServer *s) { |
824 | DnsServer *current; | |
825 | DnsScope *scope; | |
826 | ||
827 | assert(s); | |
828 | ||
829 | /* Flush the cache of the scope this server belongs to */ | |
830 | ||
831 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
832 | if (current != s) | |
833 | return; | |
834 | ||
835 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
836 | if (!scope) | |
837 | return; | |
838 | ||
839 | dns_cache_flush(&scope->cache); | |
840 | } | |
841 | ||
59c0fd0e LP |
842 | void dns_server_reset_features(DnsServer *s) { |
843 | assert(s); | |
844 | ||
59c0fd0e LP |
845 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
846 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
847 | ||
848 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
849 | ||
850 | s->packet_bad_opt = false; | |
851 | s->packet_rrsig_missing = false; | |
852 | ||
853 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
854 | ||
855 | s->warned_downgrade = false; | |
856 | ||
857 | dns_server_reset_counters(s); | |
858 | } | |
859 | ||
860 | void dns_server_reset_features_all(DnsServer *s) { | |
861 | DnsServer *i; | |
862 | ||
863 | LIST_FOREACH(servers, i, s) | |
864 | dns_server_reset_features(i); | |
865 | } | |
866 | ||
cf84484a LP |
867 | void dns_server_dump(DnsServer *s, FILE *f) { |
868 | assert(s); | |
869 | ||
870 | if (!f) | |
871 | f = stdout; | |
872 | ||
873 | fputs("[Server ", f); | |
874 | fputs(dns_server_string(s), f); | |
875 | fputs(" type=", f); | |
876 | fputs(dns_server_type_to_string(s->type), f); | |
877 | ||
878 | if (s->type == DNS_SERVER_LINK) { | |
879 | assert(s->link); | |
880 | ||
881 | fputs(" interface=", f); | |
882 | fputs(s->link->name, f); | |
883 | } | |
884 | ||
885 | fputs("]\n", f); | |
886 | ||
887 | fputs("\tVerified feature level: ", f); | |
888 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
889 | fputc('\n', f); | |
890 | ||
891 | fputs("\tPossible feature level: ", f); | |
892 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
893 | fputc('\n', f); | |
894 | ||
895 | fputs("\tDNSSEC Mode: ", f); | |
896 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
897 | fputc('\n', f); | |
898 | ||
899 | fputs("\tCan do DNSSEC: ", f); | |
900 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
901 | fputc('\n', f); | |
902 | ||
903 | fprintf(f, | |
904 | "\tMaximum UDP packet size received: %zu\n" | |
905 | "\tFailed UDP attempts: %u\n" | |
906 | "\tFailed TCP attempts: %u\n" | |
907 | "\tSeen truncated packet: %s\n" | |
908 | "\tSeen OPT RR getting lost: %s\n" | |
909 | "\tSeen RRSIG RR missing: %s\n", | |
910 | s->received_udp_packet_max, | |
911 | s->n_failed_udp, | |
912 | s->n_failed_tcp, | |
913 | yes_no(s->packet_truncated), | |
914 | yes_no(s->packet_bad_opt), | |
915 | yes_no(s->packet_rrsig_missing)); | |
916 | } | |
917 | ||
e3309036 ZJS |
918 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
919 | [DNS_SERVER_SYSTEM] = "system", | |
920 | [DNS_SERVER_FALLBACK] = "fallback", | |
921 | [DNS_SERVER_LINK] = "link", | |
922 | }; | |
923 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
924 | ||
be808ea0 TG |
925 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
926 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
927 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 928 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
5d67a7ae | 929 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 930 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 931 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 932 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
933 | }; |
934 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |