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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 | |
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 | |
98767d75 IT |
126 | dns_stream_unref(s->stream); |
127 | ||
6cb08a89 | 128 | free(s->server_string); |
6b430fdb | 129 | return mfree(s); |
74b2466e | 130 | } |
87f5a193 | 131 | |
0eac4623 LP |
132 | void dns_server_unlink(DnsServer *s) { |
133 | assert(s); | |
134 | assert(s->manager); | |
91b14d6f | 135 | |
0eac4623 LP |
136 | /* This removes the specified server from the linked list of |
137 | * servers, but any server might still stay around if it has | |
138 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 139 | |
0eac4623 LP |
140 | if (!s->linked) |
141 | return; | |
91b14d6f | 142 | |
0eac4623 LP |
143 | switch (s->type) { |
144 | ||
145 | case DNS_SERVER_LINK: | |
146 | assert(s->link); | |
eed857b7 | 147 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 148 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 149 | s->link->n_dns_servers--; |
0eac4623 LP |
150 | break; |
151 | ||
152 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 153 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 154 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 155 | s->manager->n_dns_servers--; |
0eac4623 LP |
156 | break; |
157 | ||
158 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 159 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 160 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 161 | s->manager->n_dns_servers--; |
0eac4623 LP |
162 | break; |
163 | } | |
164 | ||
165 | s->linked = false; | |
166 | ||
167 | if (s->link && s->link->current_dns_server == s) | |
168 | link_set_dns_server(s->link, NULL); | |
169 | ||
170 | if (s->manager->current_dns_server == s) | |
171 | manager_set_dns_server(s->manager, NULL); | |
172 | ||
173 | dns_server_unref(s); | |
91b14d6f TG |
174 | } |
175 | ||
0b58db65 LP |
176 | void dns_server_move_back_and_unmark(DnsServer *s) { |
177 | DnsServer *tail; | |
178 | ||
179 | assert(s); | |
180 | ||
181 | if (!s->marked) | |
182 | return; | |
183 | ||
184 | s->marked = false; | |
185 | ||
186 | if (!s->linked || !s->servers_next) | |
187 | return; | |
188 | ||
189 | /* Move us to the end of the list, so that the order is | |
190 | * strictly kept, if we are not at the end anyway. */ | |
191 | ||
192 | switch (s->type) { | |
193 | ||
194 | case DNS_SERVER_LINK: | |
195 | assert(s->link); | |
196 | LIST_FIND_TAIL(servers, s, tail); | |
197 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
198 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
199 | break; | |
200 | ||
201 | case DNS_SERVER_SYSTEM: | |
202 | LIST_FIND_TAIL(servers, s, tail); | |
203 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
204 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
205 | break; | |
206 | ||
207 | case DNS_SERVER_FALLBACK: | |
208 | LIST_FIND_TAIL(servers, s, tail); | |
209 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
210 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
211 | break; | |
212 | ||
213 | default: | |
214 | assert_not_reached("Unknown server type"); | |
215 | } | |
216 | } | |
217 | ||
6bb2c085 | 218 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
219 | assert(s); |
220 | ||
6bb2c085 LP |
221 | if (s->verified_feature_level > level) |
222 | return; | |
b652d4a2 | 223 | |
6bb2c085 | 224 | if (s->verified_feature_level != level) { |
de54e62b LP |
225 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
226 | dns_server_feature_level_to_string(level), | |
227 | dns_server_string(s)); | |
f4461e56 | 228 | s->verified_feature_level = level; |
be808ea0 TG |
229 | } |
230 | ||
6bb2c085 LP |
231 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
232 | } | |
233 | ||
d001e0a3 LP |
234 | static void dns_server_reset_counters(DnsServer *s) { |
235 | assert(s); | |
236 | ||
237 | s->n_failed_udp = 0; | |
238 | s->n_failed_tcp = 0; | |
239 | s->packet_truncated = false; | |
240 | s->verified_usec = 0; | |
241 | ||
242 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
243 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
244 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
245 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
246 | * either. | |
247 | * | |
248 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
249 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
250 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
251 | * incomplete. */ | |
252 | } | |
253 | ||
6bb2c085 LP |
254 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size) { |
255 | assert(s); | |
256 | ||
257 | if (protocol == IPPROTO_UDP) { | |
258 | if (s->possible_feature_level == level) | |
259 | s->n_failed_udp = 0; | |
260 | ||
b6451358 LP |
261 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
262 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
263 | level = DNS_SERVER_FEATURE_LEVEL_DO - 1; | |
264 | ||
265 | /* If the OPT RR got lost, then we can only validate UDP at max */ | |
266 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
267 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
268 | ||
269 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
270 | that does not mean we can necessarily receive large packets. */ | |
6bb2c085 | 271 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) |
b6451358 | 272 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; |
6bb2c085 LP |
273 | |
274 | } else if (protocol == IPPROTO_TCP) { | |
275 | ||
276 | if (s->possible_feature_level == level) | |
277 | s->n_failed_tcp = 0; | |
278 | ||
279 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
b6451358 | 280 | level = DNS_SERVER_FEATURE_LEVEL_TCP; |
6bb2c085 | 281 | } |
84129d46 | 282 | |
b6451358 LP |
283 | dns_server_verified(s, level); |
284 | ||
d74fb368 TG |
285 | /* Remember the size of the largest UDP packet we received from a server, |
286 | we know that we can always announce support for packets with at least | |
287 | this size. */ | |
6bb2c085 | 288 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 TG |
289 | s->received_udp_packet_max = size; |
290 | ||
be808ea0 TG |
291 | if (s->max_rtt < rtt) { |
292 | s->max_rtt = rtt; | |
efd46a69 | 293 | s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); |
496ae8c8 KK |
294 | } else if (s->resend_timeout > rtt) |
295 | /* If we received the packet faster than the resend_timeout, bias | |
296 | * the resend_timeout back to the rtt. */ | |
297 | s->resend_timeout = CLAMP((2 * s->resend_timeout + rtt) / 3, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
298 | } |
299 | ||
6bb2c085 | 300 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { |
9df3ba6c | 301 | assert(s); |
be808ea0 TG |
302 | assert(s->manager); |
303 | ||
6bb2c085 LP |
304 | if (s->possible_feature_level == level) { |
305 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 306 | s->n_failed_udp++; |
6bb2c085 | 307 | else if (protocol == IPPROTO_TCP) |
313cefa1 | 308 | s->n_failed_tcp++; |
6bb2c085 | 309 | } |
9df3ba6c | 310 | |
84129d46 LP |
311 | if (s->resend_timeout > usec) |
312 | return; | |
313 | ||
314 | s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
315 | } |
316 | ||
6bb2c085 LP |
317 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
318 | assert(s); | |
571370c1 | 319 | |
6bb2c085 LP |
320 | /* Invoked whenever we get a packet with TC bit set. */ |
321 | ||
322 | if (s->possible_feature_level != level) | |
571370c1 LP |
323 | return; |
324 | ||
6bb2c085 | 325 | s->packet_truncated = true; |
4e0b8b17 TG |
326 | } |
327 | ||
de54e62b LP |
328 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
329 | assert(s); | |
330 | ||
331 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
332 | return; | |
333 | ||
b6451358 LP |
334 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
335 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
336 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_DO-1; | |
337 | ||
de54e62b LP |
338 | s->packet_rrsig_missing = true; |
339 | } | |
340 | ||
341 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 342 | assert(s); |
b652d4a2 | 343 | |
de54e62b LP |
344 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
345 | return; | |
b652d4a2 | 346 | |
b6451358 LP |
347 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
348 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
349 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
350 | ||
de54e62b | 351 | s->packet_bad_opt = true; |
b652d4a2 LP |
352 | } |
353 | ||
d001e0a3 LP |
354 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
355 | assert(s); | |
356 | ||
357 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
358 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
359 | * things work. */ | |
360 | ||
361 | if (s->verified_feature_level > level) | |
362 | s->verified_feature_level = level; | |
363 | ||
364 | if (s->possible_feature_level > level) { | |
365 | s->possible_feature_level = level; | |
366 | dns_server_reset_counters(s); | |
367 | } | |
368 | ||
369 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
370 | } | |
371 | ||
be808ea0 TG |
372 | static bool dns_server_grace_period_expired(DnsServer *s) { |
373 | usec_t ts; | |
374 | ||
375 | assert(s); | |
376 | assert(s->manager); | |
377 | ||
378 | if (s->verified_usec == 0) | |
379 | return false; | |
380 | ||
381 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
382 | ||
383 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
384 | return false; | |
385 | ||
386 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
387 | ||
388 | return true; | |
389 | } | |
390 | ||
f4461e56 | 391 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
392 | DnsServerFeatureLevel best; |
393 | ||
be808ea0 TG |
394 | assert(s); |
395 | ||
97277567 LP |
396 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
397 | * better than EDNS0, hence don't even try. */ | |
398 | best = dns_server_get_dnssec_mode(s) == DNSSEC_NO ? | |
399 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : | |
400 | DNS_SERVER_FEATURE_LEVEL_BEST; | |
401 | ||
402 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
403 | * time, hence let's downgrade if we are still at a higher level. */ | |
404 | if (s->possible_feature_level > best) | |
405 | s->possible_feature_level = best; | |
406 | ||
407 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 408 | |
97277567 | 409 | s->possible_feature_level = best; |
cc450722 | 410 | |
01184277 LP |
411 | dns_server_reset_counters(s); |
412 | ||
cc450722 LP |
413 | s->packet_bad_opt = false; |
414 | s->packet_rrsig_missing = false; | |
415 | ||
de54e62b | 416 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
417 | dns_server_feature_level_to_string(s->possible_feature_level), |
418 | dns_server_string(s)); | |
6bb2c085 | 419 | |
ce7c8b20 LP |
420 | dns_server_flush_cache(s); |
421 | ||
f4461e56 LP |
422 | } else if (s->possible_feature_level <= s->verified_feature_level) |
423 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
424 | else { |
425 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 426 | |
6bb2c085 | 427 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 428 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 429 | |
6bb2c085 LP |
430 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
431 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
432 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
433 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
434 | ||
435 | } else if (s->packet_bad_opt && | |
436 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
437 | ||
438 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
439 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
440 | * in the request. Example: | |
441 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
442 | ||
443 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 444 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 445 | |
de54e62b LP |
446 | } else if (s->packet_rrsig_missing && |
447 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 448 | |
de54e62b LP |
449 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
450 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
451 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
452 | * not. */ | |
453 | ||
454 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
455 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
456 | ||
457 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 458 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
459 | |
460 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
461 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
462 | * idea. We might downgrade all the way down to TCP this way. |
463 | * | |
464 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
465 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
466 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
467 | |
468 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
469 | s->possible_feature_level--; | |
470 | ||
de54e62b LP |
471 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
472 | s->packet_truncated && | |
12bf2331 | 473 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
474 | |
475 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
476 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
477 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
478 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
479 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
480 | ||
481 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
482 | s->possible_feature_level--; | |
483 | } | |
484 | ||
6bb2c085 | 485 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
486 | |
487 | /* We changed the feature level, reset the counting */ | |
01184277 | 488 | dns_server_reset_counters(s); |
6bb2c085 | 489 | |
de54e62b | 490 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
491 | dns_server_feature_level_to_string(s->possible_feature_level), |
492 | dns_server_string(s)); | |
6bb2c085 | 493 | } |
be808ea0 TG |
494 | } |
495 | ||
f4461e56 | 496 | return s->possible_feature_level; |
be808ea0 TG |
497 | } |
498 | ||
519ef046 LP |
499 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
500 | size_t packet_size; | |
501 | bool edns_do; | |
502 | int r; | |
503 | ||
504 | assert(server); | |
505 | assert(packet); | |
506 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
507 | ||
508 | /* Fix the OPT field in the packet to match our current feature level. */ | |
509 | ||
510 | r = dns_packet_truncate_opt(packet); | |
511 | if (r < 0) | |
512 | return r; | |
513 | ||
514 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
515 | return 0; | |
516 | ||
517 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
518 | ||
519 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
520 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
521 | else | |
522 | packet_size = server->received_udp_packet_max; | |
523 | ||
f2ed4c69 | 524 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
525 | } |
526 | ||
2817157b LP |
527 | int dns_server_ifindex(const DnsServer *s) { |
528 | assert(s); | |
529 | ||
530 | /* The link ifindex always takes precedence */ | |
531 | if (s->link) | |
532 | return s->link->ifindex; | |
533 | ||
534 | if (s->ifindex > 0) | |
535 | return s->ifindex; | |
536 | ||
537 | return 0; | |
538 | } | |
539 | ||
6cb08a89 LP |
540 | const char *dns_server_string(DnsServer *server) { |
541 | assert(server); | |
542 | ||
543 | if (!server->server_string) | |
2817157b | 544 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
545 | |
546 | return strna(server->server_string); | |
547 | } | |
548 | ||
92ec902a LP |
549 | bool dns_server_dnssec_supported(DnsServer *server) { |
550 | assert(server); | |
551 | ||
552 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
553 | ||
554 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
555 | return false; | |
556 | ||
de54e62b LP |
557 | if (server->packet_bad_opt) |
558 | return false; | |
559 | ||
560 | if (server->packet_rrsig_missing) | |
92ec902a LP |
561 | return false; |
562 | ||
563 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
564 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
565 | return false; | |
566 | ||
567 | return true; | |
568 | } | |
569 | ||
1e02e182 LP |
570 | void dns_server_warn_downgrade(DnsServer *server) { |
571 | assert(server); | |
572 | ||
573 | if (server->warned_downgrade) | |
574 | return; | |
575 | ||
576 | log_struct(LOG_NOTICE, | |
2b044526 | 577 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
578 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
579 | "DNS_SERVER=%s", dns_server_string(server), | |
f4cf1d66 | 580 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
581 | |
582 | server->warned_downgrade = true; | |
583 | } | |
584 | ||
413b05cc | 585 | bool dns_server_limited_domains(DnsServer *server) { |
b9fe94ca MP |
586 | DnsSearchDomain *domain; |
587 | bool domain_restricted = false; | |
588 | ||
589 | /* Check if the server has route-only domains without ~., i. e. whether | |
590 | * it should only be used for particular domains */ | |
591 | if (!server->link) | |
592 | return false; | |
593 | ||
594 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
595 | if (domain->route_only) { | |
596 | domain_restricted = true; | |
597 | /* ~. means "any domain", thus it is a global server */ | |
413b05cc | 598 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) |
b9fe94ca MP |
599 | return false; |
600 | } | |
601 | ||
602 | return domain_restricted; | |
603 | } | |
604 | ||
b826ab58 | 605 | static void dns_server_hash_func(const void *p, struct siphash *state) { |
87f5a193 | 606 | const DnsServer *s = p; |
87f5a193 | 607 | |
b826ab58 | 608 | assert(s); |
87f5a193 | 609 | |
b826ab58 TG |
610 | siphash24_compress(&s->family, sizeof(s->family), state); |
611 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 612 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
613 | } |
614 | ||
d5099efc | 615 | static int dns_server_compare_func(const void *a, const void *b) { |
87f5a193 | 616 | const DnsServer *x = a, *y = b; |
2817157b | 617 | int r; |
87f5a193 LP |
618 | |
619 | if (x->family < y->family) | |
620 | return -1; | |
621 | if (x->family > y->family) | |
622 | return 1; | |
623 | ||
2817157b LP |
624 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
625 | if (r != 0) | |
626 | return r; | |
627 | ||
628 | if (x->ifindex < y->ifindex) | |
629 | return -1; | |
630 | if (x->ifindex > y->ifindex) | |
631 | return 1; | |
632 | ||
633 | return 0; | |
87f5a193 | 634 | } |
d5099efc MS |
635 | |
636 | const struct hash_ops dns_server_hash_ops = { | |
637 | .hash = dns_server_hash_func, | |
638 | .compare = dns_server_compare_func | |
639 | }; | |
636e813d | 640 | |
4b95f179 LP |
641 | void dns_server_unlink_all(DnsServer *first) { |
642 | DnsServer *next; | |
0eac4623 | 643 | |
4b95f179 LP |
644 | if (!first) |
645 | return; | |
0eac4623 | 646 | |
4b95f179 LP |
647 | next = first->servers_next; |
648 | dns_server_unlink(first); | |
636e813d | 649 | |
4b95f179 | 650 | dns_server_unlink_all(next); |
0eac4623 LP |
651 | } |
652 | ||
4b95f179 LP |
653 | void dns_server_unlink_marked(DnsServer *first) { |
654 | DnsServer *next; | |
636e813d | 655 | |
4b95f179 LP |
656 | if (!first) |
657 | return; | |
636e813d | 658 | |
4b95f179 | 659 | next = first->servers_next; |
636e813d | 660 | |
4b95f179 | 661 | if (first->marked) |
0eac4623 | 662 | dns_server_unlink(first); |
636e813d | 663 | |
4b95f179 LP |
664 | dns_server_unlink_marked(next); |
665 | } | |
636e813d | 666 | |
4b95f179 LP |
667 | void dns_server_mark_all(DnsServer *first) { |
668 | if (!first) | |
669 | return; | |
636e813d | 670 | |
4b95f179 LP |
671 | first->marked = true; |
672 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
673 | } |
674 | ||
2817157b | 675 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 676 | DnsServer *s; |
636e813d | 677 | |
636e813d | 678 | LIST_FOREACH(servers, s, first) |
2817157b | 679 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 680 | return s; |
f2f1dbe5 | 681 | |
4b95f179 LP |
682 | return NULL; |
683 | } | |
f2f1dbe5 | 684 | |
4b95f179 | 685 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 686 | assert(m); |
f2f1dbe5 | 687 | |
4b95f179 | 688 | switch (t) { |
f2f1dbe5 | 689 | |
4b95f179 LP |
690 | case DNS_SERVER_SYSTEM: |
691 | return m->dns_servers; | |
f2f1dbe5 | 692 | |
4b95f179 LP |
693 | case DNS_SERVER_FALLBACK: |
694 | return m->fallback_dns_servers; | |
695 | ||
696 | default: | |
697 | return NULL; | |
698 | } | |
f2f1dbe5 LP |
699 | } |
700 | ||
701 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
702 | assert(m); | |
703 | ||
704 | if (m->current_dns_server == s) | |
705 | return s; | |
706 | ||
6cb08a89 | 707 | if (s) |
db8e1324 LP |
708 | log_debug("Switching to %s DNS server %s.", |
709 | dns_server_type_to_string(s->type), | |
710 | dns_server_string(s)); | |
f2f1dbe5 | 711 | |
0eac4623 LP |
712 | dns_server_unref(m->current_dns_server); |
713 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
714 | |
715 | if (m->unicast_scope) | |
716 | dns_cache_flush(&m->unicast_scope->cache); | |
717 | ||
718 | return s; | |
719 | } | |
720 | ||
721 | DnsServer *manager_get_dns_server(Manager *m) { | |
722 | Link *l; | |
723 | assert(m); | |
724 | ||
725 | /* Try to read updates resolv.conf */ | |
726 | manager_read_resolv_conf(m); | |
727 | ||
e3309036 | 728 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
729 | if (!m->current_dns_server) |
730 | manager_set_dns_server(m, m->dns_servers); | |
731 | ||
732 | if (!m->current_dns_server) { | |
733 | bool found = false; | |
734 | Iterator i; | |
735 | ||
736 | /* No DNS servers configured, let's see if there are | |
737 | * any on any links. If not, we use the fallback | |
738 | * servers */ | |
739 | ||
740 | HASHMAP_FOREACH(l, m->links, i) | |
741 | if (l->dns_servers) { | |
742 | found = true; | |
743 | break; | |
744 | } | |
745 | ||
746 | if (!found) | |
747 | manager_set_dns_server(m, m->fallback_dns_servers); | |
748 | } | |
749 | ||
750 | return m->current_dns_server; | |
751 | } | |
752 | ||
753 | void manager_next_dns_server(Manager *m) { | |
754 | assert(m); | |
755 | ||
756 | /* If there's currently no DNS server set, then the next | |
757 | * manager_get_dns_server() will find one */ | |
758 | if (!m->current_dns_server) | |
759 | return; | |
760 | ||
0eac4623 LP |
761 | /* Change to the next one, but make sure to follow the linked |
762 | * list only if the server is still linked. */ | |
763 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
764 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
765 | return; | |
766 | } | |
767 | ||
768 | /* If there was no next one, then start from the beginning of | |
769 | * the list */ | |
770 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
771 | manager_set_dns_server(m, m->fallback_dns_servers); | |
772 | else | |
773 | manager_set_dns_server(m, m->dns_servers); | |
774 | } | |
be808ea0 | 775 | |
b30bf55d LP |
776 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
777 | ||
778 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
779 | ||
780 | if (in_addr_is_null(family, sa)) | |
781 | return false; | |
782 | ||
783 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
784 | return false; | |
785 | ||
786 | return true; | |
787 | } | |
788 | ||
12bf2331 LP |
789 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
790 | assert(s); | |
791 | ||
792 | if (s->link) | |
793 | return link_get_dnssec_mode(s->link); | |
794 | ||
795 | return manager_get_dnssec_mode(s->manager); | |
796 | } | |
797 | ||
ce7c8b20 LP |
798 | void dns_server_flush_cache(DnsServer *s) { |
799 | DnsServer *current; | |
800 | DnsScope *scope; | |
801 | ||
802 | assert(s); | |
803 | ||
804 | /* Flush the cache of the scope this server belongs to */ | |
805 | ||
806 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
807 | if (current != s) | |
808 | return; | |
809 | ||
810 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
811 | if (!scope) | |
812 | return; | |
813 | ||
814 | dns_cache_flush(&scope->cache); | |
815 | } | |
816 | ||
59c0fd0e LP |
817 | void dns_server_reset_features(DnsServer *s) { |
818 | assert(s); | |
819 | ||
820 | s->max_rtt = 0; | |
821 | s->resend_timeout = DNS_TIMEOUT_MIN_USEC; | |
822 | ||
823 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; | |
824 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
825 | ||
826 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
827 | ||
828 | s->packet_bad_opt = false; | |
829 | s->packet_rrsig_missing = false; | |
830 | ||
831 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
832 | ||
833 | s->warned_downgrade = false; | |
834 | ||
835 | dns_server_reset_counters(s); | |
836 | } | |
837 | ||
838 | void dns_server_reset_features_all(DnsServer *s) { | |
839 | DnsServer *i; | |
840 | ||
841 | LIST_FOREACH(servers, i, s) | |
842 | dns_server_reset_features(i); | |
843 | } | |
844 | ||
cf84484a LP |
845 | void dns_server_dump(DnsServer *s, FILE *f) { |
846 | assert(s); | |
847 | ||
848 | if (!f) | |
849 | f = stdout; | |
850 | ||
851 | fputs("[Server ", f); | |
852 | fputs(dns_server_string(s), f); | |
853 | fputs(" type=", f); | |
854 | fputs(dns_server_type_to_string(s->type), f); | |
855 | ||
856 | if (s->type == DNS_SERVER_LINK) { | |
857 | assert(s->link); | |
858 | ||
859 | fputs(" interface=", f); | |
860 | fputs(s->link->name, f); | |
861 | } | |
862 | ||
863 | fputs("]\n", f); | |
864 | ||
865 | fputs("\tVerified feature level: ", f); | |
866 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
867 | fputc('\n', f); | |
868 | ||
869 | fputs("\tPossible feature level: ", f); | |
870 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
871 | fputc('\n', f); | |
872 | ||
873 | fputs("\tDNSSEC Mode: ", f); | |
874 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
875 | fputc('\n', f); | |
876 | ||
877 | fputs("\tCan do DNSSEC: ", f); | |
878 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
879 | fputc('\n', f); | |
880 | ||
881 | fprintf(f, | |
882 | "\tMaximum UDP packet size received: %zu\n" | |
883 | "\tFailed UDP attempts: %u\n" | |
884 | "\tFailed TCP attempts: %u\n" | |
885 | "\tSeen truncated packet: %s\n" | |
886 | "\tSeen OPT RR getting lost: %s\n" | |
887 | "\tSeen RRSIG RR missing: %s\n", | |
888 | s->received_udp_packet_max, | |
889 | s->n_failed_udp, | |
890 | s->n_failed_tcp, | |
891 | yes_no(s->packet_truncated), | |
892 | yes_no(s->packet_bad_opt), | |
893 | yes_no(s->packet_rrsig_missing)); | |
894 | } | |
895 | ||
e3309036 ZJS |
896 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
897 | [DNS_SERVER_SYSTEM] = "system", | |
898 | [DNS_SERVER_FALLBACK] = "fallback", | |
899 | [DNS_SERVER_LINK] = "link", | |
900 | }; | |
901 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
902 | ||
be808ea0 TG |
903 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
904 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
905 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 906 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
7586f4d1 | 907 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 908 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
be808ea0 TG |
909 | }; |
910 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |