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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
74b2466e | 2 | |
62cc1c55 | 3 | #include "sd-messages.h" |
1e02e182 | 4 | |
b5efdb8a | 5 | #include "alloc-util.h" |
74b2466e | 6 | #include "resolved-dns-server.h" |
b30bf55d | 7 | #include "resolved-dns-stub.h" |
f2f1dbe5 | 8 | #include "resolved-resolv-conf.h" |
b5efdb8a | 9 | #include "siphash24.h" |
be808ea0 | 10 | #include "string-table.h" |
f2f1dbe5 | 11 | #include "string-util.h" |
74b2466e | 12 | |
be808ea0 TG |
13 | /* The amount of time to wait before retrying with a full feature set */ |
14 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
15 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
16 | ||
17 | /* The number of times we will attempt a certain feature set before degrading */ | |
18 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
19 | ||
74b2466e LP |
20 | int dns_server_new( |
21 | Manager *m, | |
22 | DnsServer **ret, | |
4e945a6f | 23 | DnsServerType type, |
74b2466e | 24 | Link *l, |
0dd25fb9 | 25 | int family, |
2817157b LP |
26 | const union in_addr_union *in_addr, |
27 | int ifindex) { | |
74b2466e | 28 | |
eed857b7 | 29 | DnsServer *s; |
74b2466e LP |
30 | |
31 | assert(m); | |
4e945a6f | 32 | assert((type == DNS_SERVER_LINK) == !!l); |
74b2466e | 33 | assert(in_addr); |
74b2466e | 34 | |
eed857b7 LP |
35 | if (!IN_SET(family, AF_INET, AF_INET6)) |
36 | return -EAFNOSUPPORT; | |
37 | ||
38 | if (l) { | |
39 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
40 | return -E2BIG; | |
41 | } else { | |
42 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
43 | return -E2BIG; | |
44 | } | |
45 | ||
65b0179a | 46 | s = new(DnsServer, 1); |
74b2466e LP |
47 | if (!s) |
48 | return -ENOMEM; | |
49 | ||
65b0179a LP |
50 | *s = (DnsServer) { |
51 | .n_ref = 1, | |
52 | .manager = m, | |
53 | .type = type, | |
54 | .family = family, | |
55 | .address = *in_addr, | |
56 | .ifindex = ifindex, | |
57 | }; | |
59c0fd0e LP |
58 | |
59 | dns_server_reset_features(s); | |
74b2466e | 60 | |
0b58db65 LP |
61 | switch (type) { |
62 | ||
63 | case DNS_SERVER_LINK: | |
64 | s->link = l; | |
eed857b7 LP |
65 | LIST_APPEND(servers, l->dns_servers, s); |
66 | l->n_dns_servers++; | |
0b58db65 LP |
67 | break; |
68 | ||
69 | case DNS_SERVER_SYSTEM: | |
eed857b7 LP |
70 | LIST_APPEND(servers, m->dns_servers, s); |
71 | m->n_dns_servers++; | |
0b58db65 LP |
72 | break; |
73 | ||
74 | case DNS_SERVER_FALLBACK: | |
eed857b7 LP |
75 | LIST_APPEND(servers, m->fallback_dns_servers, s); |
76 | m->n_dns_servers++; | |
0b58db65 LP |
77 | break; |
78 | ||
79 | default: | |
4e945a6f | 80 | assert_not_reached("Unknown server type"); |
0b58db65 | 81 | } |
74b2466e | 82 | |
0eac4623 | 83 | s->linked = true; |
74b2466e | 84 | |
4e945a6f LP |
85 | /* A new DNS server that isn't fallback is added and the one |
86 | * we used so far was a fallback one? Then let's try to pick | |
87 | * the new one */ | |
88 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
89 | m->current_dns_server && |
90 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
91 | manager_set_dns_server(m, NULL); | |
4e945a6f | 92 | |
74b2466e LP |
93 | if (ret) |
94 | *ret = s; | |
95 | ||
96 | return 0; | |
97 | } | |
98 | ||
8301aa0b YW |
99 | static DnsServer* dns_server_free(DnsServer *s) { |
100 | assert(s); | |
74b2466e | 101 | |
904dcaf9 | 102 | dns_server_unref_stream(s); |
98767d75 | 103 | |
56ddbf10 | 104 | #if ENABLE_DNS_OVER_TLS |
6016fcb0 | 105 | dnstls_server_free(s); |
5d67a7ae IT |
106 | #endif |
107 | ||
6cb08a89 | 108 | free(s->server_string); |
6b430fdb | 109 | return mfree(s); |
74b2466e | 110 | } |
87f5a193 | 111 | |
8301aa0b YW |
112 | DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsServer, dns_server, dns_server_free); |
113 | ||
0eac4623 LP |
114 | void dns_server_unlink(DnsServer *s) { |
115 | assert(s); | |
116 | assert(s->manager); | |
91b14d6f | 117 | |
0eac4623 LP |
118 | /* This removes the specified server from the linked list of |
119 | * servers, but any server might still stay around if it has | |
120 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 121 | |
0eac4623 LP |
122 | if (!s->linked) |
123 | return; | |
91b14d6f | 124 | |
0eac4623 LP |
125 | switch (s->type) { |
126 | ||
127 | case DNS_SERVER_LINK: | |
128 | assert(s->link); | |
eed857b7 | 129 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 130 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 131 | s->link->n_dns_servers--; |
0eac4623 LP |
132 | break; |
133 | ||
134 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 135 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 136 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 137 | s->manager->n_dns_servers--; |
0eac4623 LP |
138 | break; |
139 | ||
140 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 141 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 142 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 143 | s->manager->n_dns_servers--; |
0eac4623 | 144 | break; |
df0fbad0 YW |
145 | default: |
146 | assert_not_reached("Unknown server type"); | |
0eac4623 LP |
147 | } |
148 | ||
149 | s->linked = false; | |
150 | ||
151 | if (s->link && s->link->current_dns_server == s) | |
152 | link_set_dns_server(s->link, NULL); | |
153 | ||
154 | if (s->manager->current_dns_server == s) | |
155 | manager_set_dns_server(s->manager, NULL); | |
156 | ||
904dcaf9 LP |
157 | /* No need to keep a default stream around anymore */ |
158 | dns_server_unref_stream(s); | |
159 | ||
0eac4623 | 160 | dns_server_unref(s); |
91b14d6f TG |
161 | } |
162 | ||
0b58db65 LP |
163 | void dns_server_move_back_and_unmark(DnsServer *s) { |
164 | DnsServer *tail; | |
165 | ||
166 | assert(s); | |
167 | ||
168 | if (!s->marked) | |
169 | return; | |
170 | ||
171 | s->marked = false; | |
172 | ||
173 | if (!s->linked || !s->servers_next) | |
174 | return; | |
175 | ||
176 | /* Move us to the end of the list, so that the order is | |
177 | * strictly kept, if we are not at the end anyway. */ | |
178 | ||
179 | switch (s->type) { | |
180 | ||
181 | case DNS_SERVER_LINK: | |
182 | assert(s->link); | |
183 | LIST_FIND_TAIL(servers, s, tail); | |
184 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
185 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
186 | break; | |
187 | ||
188 | case DNS_SERVER_SYSTEM: | |
189 | LIST_FIND_TAIL(servers, s, tail); | |
190 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
191 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
192 | break; | |
193 | ||
194 | case DNS_SERVER_FALLBACK: | |
195 | LIST_FIND_TAIL(servers, s, tail); | |
196 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
197 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
198 | break; | |
199 | ||
200 | default: | |
201 | assert_not_reached("Unknown server type"); | |
202 | } | |
203 | } | |
204 | ||
6bb2c085 | 205 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
206 | assert(s); |
207 | ||
6bb2c085 LP |
208 | if (s->verified_feature_level > level) |
209 | return; | |
b652d4a2 | 210 | |
6bb2c085 | 211 | if (s->verified_feature_level != level) { |
de54e62b LP |
212 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
213 | dns_server_feature_level_to_string(level), | |
214 | dns_server_string(s)); | |
f4461e56 | 215 | s->verified_feature_level = level; |
be808ea0 TG |
216 | } |
217 | ||
6bb2c085 LP |
218 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
219 | } | |
220 | ||
d001e0a3 LP |
221 | static void dns_server_reset_counters(DnsServer *s) { |
222 | assert(s); | |
223 | ||
224 | s->n_failed_udp = 0; | |
225 | s->n_failed_tcp = 0; | |
5d67a7ae | 226 | s->n_failed_tls = 0; |
d001e0a3 LP |
227 | s->packet_truncated = false; |
228 | s->verified_usec = 0; | |
229 | ||
230 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
231 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
232 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
233 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
234 | * either. | |
235 | * | |
236 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
237 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
5238e957 | 238 | * re-enable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be |
d001e0a3 LP |
239 | * incomplete. */ |
240 | } | |
241 | ||
dbc4661a | 242 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, size_t size) { |
6bb2c085 LP |
243 | assert(s); |
244 | ||
245 | if (protocol == IPPROTO_UDP) { | |
246 | if (s->possible_feature_level == level) | |
247 | s->n_failed_udp = 0; | |
6bb2c085 | 248 | } else if (protocol == IPPROTO_TCP) { |
5d67a7ae IT |
249 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { |
250 | if (s->possible_feature_level == level) | |
251 | s->n_failed_tls = 0; | |
252 | } else { | |
253 | if (s->possible_feature_level == level) | |
254 | s->n_failed_tcp = 0; | |
255 | ||
256 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
257 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
258 | } | |
259 | } | |
6bb2c085 | 260 | |
5d67a7ae IT |
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_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
6bb2c085 | 264 | |
5d67a7ae IT |
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. */ | |
271 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
272 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
84129d46 | 273 | |
b6451358 LP |
274 | dns_server_verified(s, level); |
275 | ||
d74fb368 TG |
276 | /* Remember the size of the largest UDP packet we received from a server, |
277 | we know that we can always announce support for packets with at least | |
278 | this size. */ | |
6bb2c085 | 279 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 | 280 | s->received_udp_packet_max = size; |
9df3ba6c TG |
281 | } |
282 | ||
3da3cdd5 | 283 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level) { |
9df3ba6c | 284 | assert(s); |
be808ea0 TG |
285 | assert(s->manager); |
286 | ||
6bb2c085 LP |
287 | if (s->possible_feature_level == level) { |
288 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 289 | s->n_failed_udp++; |
5d67a7ae IT |
290 | else if (protocol == IPPROTO_TCP) { |
291 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
292 | s->n_failed_tls++; | |
293 | else | |
294 | s->n_failed_tcp++; | |
295 | } | |
6bb2c085 | 296 | } |
9df3ba6c TG |
297 | } |
298 | ||
6bb2c085 LP |
299 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
300 | assert(s); | |
571370c1 | 301 | |
6bb2c085 LP |
302 | /* Invoked whenever we get a packet with TC bit set. */ |
303 | ||
304 | if (s->possible_feature_level != level) | |
571370c1 LP |
305 | return; |
306 | ||
6bb2c085 | 307 | s->packet_truncated = true; |
4e0b8b17 TG |
308 | } |
309 | ||
de54e62b LP |
310 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
311 | assert(s); | |
312 | ||
313 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
314 | return; | |
315 | ||
b6451358 LP |
316 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
317 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
5d67a7ae | 318 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
b6451358 | 319 | |
de54e62b LP |
320 | s->packet_rrsig_missing = true; |
321 | } | |
322 | ||
323 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 324 | assert(s); |
b652d4a2 | 325 | |
de54e62b LP |
326 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
327 | return; | |
b652d4a2 | 328 | |
b6451358 LP |
329 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
330 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
331 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
332 | ||
de54e62b | 333 | s->packet_bad_opt = true; |
b652d4a2 LP |
334 | } |
335 | ||
d001e0a3 LP |
336 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
337 | assert(s); | |
338 | ||
339 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
340 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
341 | * things work. */ | |
342 | ||
343 | if (s->verified_feature_level > level) | |
344 | s->verified_feature_level = level; | |
345 | ||
346 | if (s->possible_feature_level > level) { | |
347 | s->possible_feature_level = level; | |
348 | dns_server_reset_counters(s); | |
349 | } | |
350 | ||
351 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
352 | } | |
353 | ||
be808ea0 TG |
354 | static bool dns_server_grace_period_expired(DnsServer *s) { |
355 | usec_t ts; | |
356 | ||
357 | assert(s); | |
358 | assert(s->manager); | |
359 | ||
360 | if (s->verified_usec == 0) | |
361 | return false; | |
362 | ||
363 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
364 | ||
365 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
366 | return false; | |
367 | ||
368 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
369 | ||
370 | return true; | |
371 | } | |
372 | ||
f4461e56 | 373 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
374 | DnsServerFeatureLevel best; |
375 | ||
be808ea0 TG |
376 | assert(s); |
377 | ||
97277567 LP |
378 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
379 | * better than EDNS0, hence don't even try. */ | |
5d67a7ae | 380 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) |
c9299be2 | 381 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
382 | DNS_SERVER_FEATURE_LEVEL_LARGE : |
383 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
384 | else | |
c9299be2 | 385 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
386 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : |
387 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
97277567 LP |
388 | |
389 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
390 | * time, hence let's downgrade if we are still at a higher level. */ | |
391 | if (s->possible_feature_level > best) | |
392 | s->possible_feature_level = best; | |
393 | ||
394 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 395 | |
97277567 | 396 | s->possible_feature_level = best; |
cc450722 | 397 | |
01184277 LP |
398 | dns_server_reset_counters(s); |
399 | ||
cc450722 LP |
400 | s->packet_bad_opt = false; |
401 | s->packet_rrsig_missing = false; | |
402 | ||
de54e62b | 403 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
404 | dns_server_feature_level_to_string(s->possible_feature_level), |
405 | dns_server_string(s)); | |
6bb2c085 | 406 | |
ce7c8b20 LP |
407 | dns_server_flush_cache(s); |
408 | ||
f4461e56 LP |
409 | } else if (s->possible_feature_level <= s->verified_feature_level) |
410 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
411 | else { |
412 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 413 | |
6bb2c085 | 414 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 415 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 416 | |
6bb2c085 LP |
417 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
418 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
419 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
420 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
5d67a7ae IT |
421 | } else if (s->n_failed_tls > 0 && |
422 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level)) { | |
423 | ||
424 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
425 | * if we don't require DNS-over-TLS */ | |
de54e62b | 426 | |
3c0dcbcf | 427 | log_debug("Server doesn't support DNS-over-TLS, downgrading protocol..."); |
5d67a7ae | 428 | s->possible_feature_level--; |
de54e62b LP |
429 | } else if (s->packet_bad_opt && |
430 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
431 | ||
432 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
433 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
434 | * in the request. Example: | |
435 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
436 | ||
437 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 438 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 439 | |
de54e62b LP |
440 | } else if (s->packet_rrsig_missing && |
441 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 442 | |
de54e62b LP |
443 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
444 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
445 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
446 | * not. */ | |
447 | ||
448 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
5d67a7ae | 449 | 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 |
450 | |
451 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 452 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
453 | |
454 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
455 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
456 | * idea. We might downgrade all the way down to TCP this way. |
457 | * | |
458 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
459 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
460 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
461 | |
462 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
463 | s->possible_feature_level--; | |
464 | ||
de54e62b LP |
465 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
466 | s->packet_truncated && | |
12bf2331 | 467 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
468 | |
469 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
470 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
471 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
472 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
473 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
474 | ||
475 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
476 | s->possible_feature_level--; | |
477 | } | |
478 | ||
6bb2c085 | 479 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
480 | |
481 | /* We changed the feature level, reset the counting */ | |
01184277 | 482 | dns_server_reset_counters(s); |
6bb2c085 | 483 | |
de54e62b | 484 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
485 | dns_server_feature_level_to_string(s->possible_feature_level), |
486 | dns_server_string(s)); | |
6bb2c085 | 487 | } |
be808ea0 TG |
488 | } |
489 | ||
f4461e56 | 490 | return s->possible_feature_level; |
be808ea0 TG |
491 | } |
492 | ||
519ef046 LP |
493 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
494 | size_t packet_size; | |
495 | bool edns_do; | |
496 | int r; | |
497 | ||
498 | assert(server); | |
499 | assert(packet); | |
500 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
501 | ||
502 | /* Fix the OPT field in the packet to match our current feature level. */ | |
503 | ||
504 | r = dns_packet_truncate_opt(packet); | |
505 | if (r < 0) | |
506 | return r; | |
507 | ||
508 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
509 | return 0; | |
510 | ||
511 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
512 | ||
513 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
514 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
515 | else | |
516 | packet_size = server->received_udp_packet_max; | |
517 | ||
f2ed4c69 | 518 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
519 | } |
520 | ||
2817157b LP |
521 | int dns_server_ifindex(const DnsServer *s) { |
522 | assert(s); | |
523 | ||
524 | /* The link ifindex always takes precedence */ | |
525 | if (s->link) | |
526 | return s->link->ifindex; | |
527 | ||
528 | if (s->ifindex > 0) | |
529 | return s->ifindex; | |
530 | ||
531 | return 0; | |
532 | } | |
533 | ||
6cb08a89 LP |
534 | const char *dns_server_string(DnsServer *server) { |
535 | assert(server); | |
536 | ||
537 | if (!server->server_string) | |
2817157b | 538 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
539 | |
540 | return strna(server->server_string); | |
541 | } | |
542 | ||
92ec902a LP |
543 | bool dns_server_dnssec_supported(DnsServer *server) { |
544 | assert(server); | |
545 | ||
546 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
547 | ||
548 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
549 | return false; | |
550 | ||
de54e62b LP |
551 | if (server->packet_bad_opt) |
552 | return false; | |
553 | ||
554 | if (server->packet_rrsig_missing) | |
92ec902a LP |
555 | return false; |
556 | ||
557 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
558 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
559 | return false; | |
560 | ||
561 | return true; | |
562 | } | |
563 | ||
1e02e182 LP |
564 | void dns_server_warn_downgrade(DnsServer *server) { |
565 | assert(server); | |
566 | ||
567 | if (server->warned_downgrade) | |
568 | return; | |
569 | ||
570 | log_struct(LOG_NOTICE, | |
2b044526 | 571 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
572 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
573 | "DNS_SERVER=%s", dns_server_string(server), | |
f4cf1d66 | 574 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
575 | |
576 | server->warned_downgrade = true; | |
577 | } | |
578 | ||
7a08d314 | 579 | static void dns_server_hash_func(const DnsServer *s, struct siphash *state) { |
b826ab58 | 580 | assert(s); |
87f5a193 | 581 | |
b826ab58 TG |
582 | siphash24_compress(&s->family, sizeof(s->family), state); |
583 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 584 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
585 | } |
586 | ||
7a08d314 | 587 | static int dns_server_compare_func(const DnsServer *x, const DnsServer *y) { |
2817157b | 588 | int r; |
87f5a193 | 589 | |
a0edd02e FB |
590 | r = CMP(x->family, y->family); |
591 | if (r != 0) | |
592 | return r; | |
87f5a193 | 593 | |
2817157b LP |
594 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
595 | if (r != 0) | |
596 | return r; | |
597 | ||
a0edd02e FB |
598 | r = CMP(x->ifindex, y->ifindex); |
599 | if (r != 0) | |
600 | return r; | |
2817157b LP |
601 | |
602 | return 0; | |
87f5a193 | 603 | } |
d5099efc | 604 | |
7a08d314 | 605 | DEFINE_HASH_OPS(dns_server_hash_ops, DnsServer, dns_server_hash_func, dns_server_compare_func); |
636e813d | 606 | |
4b95f179 LP |
607 | void dns_server_unlink_all(DnsServer *first) { |
608 | DnsServer *next; | |
0eac4623 | 609 | |
4b95f179 LP |
610 | if (!first) |
611 | return; | |
0eac4623 | 612 | |
4b95f179 LP |
613 | next = first->servers_next; |
614 | dns_server_unlink(first); | |
636e813d | 615 | |
4b95f179 | 616 | dns_server_unlink_all(next); |
0eac4623 LP |
617 | } |
618 | ||
4b95f179 LP |
619 | void dns_server_unlink_marked(DnsServer *first) { |
620 | DnsServer *next; | |
636e813d | 621 | |
4b95f179 LP |
622 | if (!first) |
623 | return; | |
636e813d | 624 | |
4b95f179 | 625 | next = first->servers_next; |
636e813d | 626 | |
4b95f179 | 627 | if (first->marked) |
0eac4623 | 628 | dns_server_unlink(first); |
636e813d | 629 | |
4b95f179 LP |
630 | dns_server_unlink_marked(next); |
631 | } | |
636e813d | 632 | |
4b95f179 LP |
633 | void dns_server_mark_all(DnsServer *first) { |
634 | if (!first) | |
635 | return; | |
636e813d | 636 | |
4b95f179 LP |
637 | first->marked = true; |
638 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
639 | } |
640 | ||
2817157b | 641 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 642 | DnsServer *s; |
636e813d | 643 | |
636e813d | 644 | LIST_FOREACH(servers, s, first) |
2817157b | 645 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 646 | return s; |
f2f1dbe5 | 647 | |
4b95f179 LP |
648 | return NULL; |
649 | } | |
f2f1dbe5 | 650 | |
4b95f179 | 651 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 652 | assert(m); |
f2f1dbe5 | 653 | |
4b95f179 | 654 | switch (t) { |
f2f1dbe5 | 655 | |
4b95f179 LP |
656 | case DNS_SERVER_SYSTEM: |
657 | return m->dns_servers; | |
f2f1dbe5 | 658 | |
4b95f179 LP |
659 | case DNS_SERVER_FALLBACK: |
660 | return m->fallback_dns_servers; | |
661 | ||
662 | default: | |
663 | return NULL; | |
664 | } | |
f2f1dbe5 LP |
665 | } |
666 | ||
667 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
668 | assert(m); | |
669 | ||
670 | if (m->current_dns_server == s) | |
671 | return s; | |
672 | ||
6cb08a89 | 673 | if (s) |
db8e1324 LP |
674 | log_debug("Switching to %s DNS server %s.", |
675 | dns_server_type_to_string(s->type), | |
676 | dns_server_string(s)); | |
f2f1dbe5 | 677 | |
0eac4623 LP |
678 | dns_server_unref(m->current_dns_server); |
679 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
680 | |
681 | if (m->unicast_scope) | |
682 | dns_cache_flush(&m->unicast_scope->cache); | |
683 | ||
684 | return s; | |
685 | } | |
686 | ||
687 | DnsServer *manager_get_dns_server(Manager *m) { | |
688 | Link *l; | |
689 | assert(m); | |
690 | ||
691 | /* Try to read updates resolv.conf */ | |
692 | manager_read_resolv_conf(m); | |
693 | ||
e3309036 | 694 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
695 | if (!m->current_dns_server) |
696 | manager_set_dns_server(m, m->dns_servers); | |
697 | ||
698 | if (!m->current_dns_server) { | |
699 | bool found = false; | |
700 | Iterator i; | |
701 | ||
702 | /* No DNS servers configured, let's see if there are | |
703 | * any on any links. If not, we use the fallback | |
704 | * servers */ | |
705 | ||
706 | HASHMAP_FOREACH(l, m->links, i) | |
707 | if (l->dns_servers) { | |
708 | found = true; | |
709 | break; | |
710 | } | |
711 | ||
712 | if (!found) | |
713 | manager_set_dns_server(m, m->fallback_dns_servers); | |
714 | } | |
715 | ||
716 | return m->current_dns_server; | |
717 | } | |
718 | ||
719 | void manager_next_dns_server(Manager *m) { | |
720 | assert(m); | |
721 | ||
722 | /* If there's currently no DNS server set, then the next | |
723 | * manager_get_dns_server() will find one */ | |
724 | if (!m->current_dns_server) | |
725 | return; | |
726 | ||
0eac4623 LP |
727 | /* Change to the next one, but make sure to follow the linked |
728 | * list only if the server is still linked. */ | |
729 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
730 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
731 | return; | |
732 | } | |
733 | ||
734 | /* If there was no next one, then start from the beginning of | |
735 | * the list */ | |
736 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
737 | manager_set_dns_server(m, m->fallback_dns_servers); | |
738 | else | |
739 | manager_set_dns_server(m, m->dns_servers); | |
740 | } | |
be808ea0 | 741 | |
b30bf55d LP |
742 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
743 | ||
744 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
745 | ||
746 | if (in_addr_is_null(family, sa)) | |
747 | return false; | |
748 | ||
749 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
750 | return false; | |
751 | ||
752 | return true; | |
753 | } | |
754 | ||
12bf2331 LP |
755 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
756 | assert(s); | |
757 | ||
758 | if (s->link) | |
759 | return link_get_dnssec_mode(s->link); | |
760 | ||
761 | return manager_get_dnssec_mode(s->manager); | |
762 | } | |
763 | ||
c9299be2 | 764 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { |
5d67a7ae IT |
765 | assert(s); |
766 | ||
d050561a | 767 | if (s->link) |
c9299be2 | 768 | return link_get_dns_over_tls_mode(s->link); |
d050561a | 769 | |
c9299be2 | 770 | return manager_get_dns_over_tls_mode(s->manager); |
5d67a7ae IT |
771 | } |
772 | ||
ce7c8b20 LP |
773 | void dns_server_flush_cache(DnsServer *s) { |
774 | DnsServer *current; | |
775 | DnsScope *scope; | |
776 | ||
777 | assert(s); | |
778 | ||
779 | /* Flush the cache of the scope this server belongs to */ | |
780 | ||
781 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
782 | if (current != s) | |
783 | return; | |
784 | ||
785 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
786 | if (!scope) | |
787 | return; | |
788 | ||
789 | dns_cache_flush(&scope->cache); | |
790 | } | |
791 | ||
59c0fd0e LP |
792 | void dns_server_reset_features(DnsServer *s) { |
793 | assert(s); | |
794 | ||
59c0fd0e LP |
795 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
796 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
797 | ||
798 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
799 | ||
800 | s->packet_bad_opt = false; | |
801 | s->packet_rrsig_missing = false; | |
802 | ||
803 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
804 | ||
805 | s->warned_downgrade = false; | |
806 | ||
807 | dns_server_reset_counters(s); | |
904dcaf9 LP |
808 | |
809 | /* Let's close the default stream, so that we reprobe with the new features */ | |
810 | dns_server_unref_stream(s); | |
59c0fd0e LP |
811 | } |
812 | ||
813 | void dns_server_reset_features_all(DnsServer *s) { | |
814 | DnsServer *i; | |
815 | ||
816 | LIST_FOREACH(servers, i, s) | |
817 | dns_server_reset_features(i); | |
818 | } | |
819 | ||
cf84484a LP |
820 | void dns_server_dump(DnsServer *s, FILE *f) { |
821 | assert(s); | |
822 | ||
823 | if (!f) | |
824 | f = stdout; | |
825 | ||
826 | fputs("[Server ", f); | |
827 | fputs(dns_server_string(s), f); | |
828 | fputs(" type=", f); | |
829 | fputs(dns_server_type_to_string(s->type), f); | |
830 | ||
831 | if (s->type == DNS_SERVER_LINK) { | |
832 | assert(s->link); | |
833 | ||
834 | fputs(" interface=", f); | |
6ff79f76 | 835 | fputs(s->link->ifname, f); |
cf84484a LP |
836 | } |
837 | ||
838 | fputs("]\n", f); | |
839 | ||
840 | fputs("\tVerified feature level: ", f); | |
841 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
842 | fputc('\n', f); | |
843 | ||
844 | fputs("\tPossible feature level: ", f); | |
845 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
846 | fputc('\n', f); | |
847 | ||
848 | fputs("\tDNSSEC Mode: ", f); | |
849 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
850 | fputc('\n', f); | |
851 | ||
852 | fputs("\tCan do DNSSEC: ", f); | |
853 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
854 | fputc('\n', f); | |
855 | ||
856 | fprintf(f, | |
857 | "\tMaximum UDP packet size received: %zu\n" | |
858 | "\tFailed UDP attempts: %u\n" | |
859 | "\tFailed TCP attempts: %u\n" | |
860 | "\tSeen truncated packet: %s\n" | |
861 | "\tSeen OPT RR getting lost: %s\n" | |
862 | "\tSeen RRSIG RR missing: %s\n", | |
863 | s->received_udp_packet_max, | |
864 | s->n_failed_udp, | |
865 | s->n_failed_tcp, | |
866 | yes_no(s->packet_truncated), | |
867 | yes_no(s->packet_bad_opt), | |
868 | yes_no(s->packet_rrsig_missing)); | |
869 | } | |
870 | ||
904dcaf9 LP |
871 | void dns_server_unref_stream(DnsServer *s) { |
872 | DnsStream *ref; | |
873 | ||
874 | assert(s); | |
875 | ||
876 | /* Detaches the default stream of this server. Some special care needs to be taken here, as that stream and | |
877 | * this server reference each other. First, take the stream out of the server. It's destructor will check if it | |
5238e957 | 878 | * is registered with us, hence let's invalidate this separately, so that it is already unregistered. */ |
904dcaf9 LP |
879 | ref = TAKE_PTR(s->stream); |
880 | ||
881 | /* And then, unref it */ | |
882 | dns_stream_unref(ref); | |
883 | } | |
884 | ||
f76fa088 LP |
885 | DnsScope *dns_server_scope(DnsServer *s) { |
886 | assert(s); | |
887 | assert((s->type == DNS_SERVER_LINK) == !!s->link); | |
888 | ||
889 | if (s->link) | |
890 | return s->link->unicast_scope; | |
891 | ||
892 | return s->manager->unicast_scope; | |
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", |
5d67a7ae | 906 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 907 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 908 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 909 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
910 | }; |
911 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |