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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 | |
56ddbf10 | 85 | #if ENABLE_DNS_OVER_TLS |
6016fcb0 | 86 | dnstls_server_init(s); |
5d67a7ae IT |
87 | #endif |
88 | ||
4e945a6f LP |
89 | /* A new DNS server that isn't fallback is added and the one |
90 | * we used so far was a fallback one? Then let's try to pick | |
91 | * the new one */ | |
92 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
93 | m->current_dns_server && |
94 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
95 | manager_set_dns_server(m, NULL); | |
4e945a6f | 96 | |
74b2466e LP |
97 | if (ret) |
98 | *ret = s; | |
99 | ||
100 | return 0; | |
101 | } | |
102 | ||
8301aa0b YW |
103 | static DnsServer* dns_server_free(DnsServer *s) { |
104 | assert(s); | |
74b2466e | 105 | |
98767d75 IT |
106 | dns_stream_unref(s->stream); |
107 | ||
56ddbf10 | 108 | #if ENABLE_DNS_OVER_TLS |
6016fcb0 | 109 | dnstls_server_free(s); |
5d67a7ae IT |
110 | #endif |
111 | ||
6cb08a89 | 112 | free(s->server_string); |
6b430fdb | 113 | return mfree(s); |
74b2466e | 114 | } |
87f5a193 | 115 | |
8301aa0b YW |
116 | DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsServer, dns_server, dns_server_free); |
117 | ||
0eac4623 LP |
118 | void dns_server_unlink(DnsServer *s) { |
119 | assert(s); | |
120 | assert(s->manager); | |
91b14d6f | 121 | |
0eac4623 LP |
122 | /* This removes the specified server from the linked list of |
123 | * servers, but any server might still stay around if it has | |
124 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 125 | |
0eac4623 LP |
126 | if (!s->linked) |
127 | return; | |
91b14d6f | 128 | |
0eac4623 LP |
129 | switch (s->type) { |
130 | ||
131 | case DNS_SERVER_LINK: | |
132 | assert(s->link); | |
eed857b7 | 133 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 134 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 135 | s->link->n_dns_servers--; |
0eac4623 LP |
136 | break; |
137 | ||
138 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 139 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 140 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 141 | s->manager->n_dns_servers--; |
0eac4623 LP |
142 | break; |
143 | ||
144 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 145 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 146 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 147 | s->manager->n_dns_servers--; |
0eac4623 | 148 | break; |
df0fbad0 YW |
149 | default: |
150 | assert_not_reached("Unknown server type"); | |
0eac4623 LP |
151 | } |
152 | ||
153 | s->linked = false; | |
154 | ||
155 | if (s->link && s->link->current_dns_server == s) | |
156 | link_set_dns_server(s->link, NULL); | |
157 | ||
158 | if (s->manager->current_dns_server == s) | |
159 | manager_set_dns_server(s->manager, NULL); | |
160 | ||
161 | dns_server_unref(s); | |
91b14d6f TG |
162 | } |
163 | ||
0b58db65 LP |
164 | void dns_server_move_back_and_unmark(DnsServer *s) { |
165 | DnsServer *tail; | |
166 | ||
167 | assert(s); | |
168 | ||
169 | if (!s->marked) | |
170 | return; | |
171 | ||
172 | s->marked = false; | |
173 | ||
174 | if (!s->linked || !s->servers_next) | |
175 | return; | |
176 | ||
177 | /* Move us to the end of the list, so that the order is | |
178 | * strictly kept, if we are not at the end anyway. */ | |
179 | ||
180 | switch (s->type) { | |
181 | ||
182 | case DNS_SERVER_LINK: | |
183 | assert(s->link); | |
184 | LIST_FIND_TAIL(servers, s, tail); | |
185 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
186 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
187 | break; | |
188 | ||
189 | case DNS_SERVER_SYSTEM: | |
190 | LIST_FIND_TAIL(servers, s, tail); | |
191 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
192 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
193 | break; | |
194 | ||
195 | case DNS_SERVER_FALLBACK: | |
196 | LIST_FIND_TAIL(servers, s, tail); | |
197 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
198 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
199 | break; | |
200 | ||
201 | default: | |
202 | assert_not_reached("Unknown server type"); | |
203 | } | |
204 | } | |
205 | ||
6bb2c085 | 206 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
207 | assert(s); |
208 | ||
6bb2c085 LP |
209 | if (s->verified_feature_level > level) |
210 | return; | |
b652d4a2 | 211 | |
6bb2c085 | 212 | if (s->verified_feature_level != level) { |
de54e62b LP |
213 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
214 | dns_server_feature_level_to_string(level), | |
215 | dns_server_string(s)); | |
f4461e56 | 216 | s->verified_feature_level = level; |
be808ea0 TG |
217 | } |
218 | ||
6bb2c085 LP |
219 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
220 | } | |
221 | ||
d001e0a3 LP |
222 | static void dns_server_reset_counters(DnsServer *s) { |
223 | assert(s); | |
224 | ||
225 | s->n_failed_udp = 0; | |
226 | s->n_failed_tcp = 0; | |
5d67a7ae | 227 | s->n_failed_tls = 0; |
d001e0a3 LP |
228 | s->packet_truncated = false; |
229 | s->verified_usec = 0; | |
230 | ||
231 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
232 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
233 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
234 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
235 | * either. | |
236 | * | |
237 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
238 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
239 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
240 | * incomplete. */ | |
241 | } | |
242 | ||
dbc4661a | 243 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, size_t size) { |
6bb2c085 LP |
244 | assert(s); |
245 | ||
246 | if (protocol == IPPROTO_UDP) { | |
247 | if (s->possible_feature_level == level) | |
248 | s->n_failed_udp = 0; | |
6bb2c085 | 249 | } else if (protocol == IPPROTO_TCP) { |
5d67a7ae IT |
250 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { |
251 | if (s->possible_feature_level == level) | |
252 | s->n_failed_tls = 0; | |
253 | } else { | |
254 | if (s->possible_feature_level == level) | |
255 | s->n_failed_tcp = 0; | |
256 | ||
257 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
258 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
259 | } | |
260 | } | |
6bb2c085 | 261 | |
5d67a7ae IT |
262 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
263 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
264 | level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
6bb2c085 | 265 | |
5d67a7ae IT |
266 | /* If the OPT RR got lost, then we can only validate UDP at max */ |
267 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
268 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
269 | ||
270 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
271 | that does not mean we can necessarily receive large packets. */ | |
272 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
273 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
84129d46 | 274 | |
b6451358 LP |
275 | dns_server_verified(s, level); |
276 | ||
d74fb368 TG |
277 | /* Remember the size of the largest UDP packet we received from a server, |
278 | we know that we can always announce support for packets with at least | |
279 | this size. */ | |
6bb2c085 | 280 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 | 281 | s->received_udp_packet_max = size; |
9df3ba6c TG |
282 | } |
283 | ||
3da3cdd5 | 284 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level) { |
9df3ba6c | 285 | assert(s); |
be808ea0 TG |
286 | assert(s->manager); |
287 | ||
6bb2c085 LP |
288 | if (s->possible_feature_level == level) { |
289 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 290 | s->n_failed_udp++; |
5d67a7ae IT |
291 | else if (protocol == IPPROTO_TCP) { |
292 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
293 | s->n_failed_tls++; | |
294 | else | |
295 | s->n_failed_tcp++; | |
296 | } | |
6bb2c085 | 297 | } |
9df3ba6c TG |
298 | } |
299 | ||
6bb2c085 LP |
300 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
301 | assert(s); | |
571370c1 | 302 | |
6bb2c085 LP |
303 | /* Invoked whenever we get a packet with TC bit set. */ |
304 | ||
305 | if (s->possible_feature_level != level) | |
571370c1 LP |
306 | return; |
307 | ||
6bb2c085 | 308 | s->packet_truncated = true; |
4e0b8b17 TG |
309 | } |
310 | ||
de54e62b LP |
311 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
312 | assert(s); | |
313 | ||
314 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
315 | return; | |
316 | ||
b6451358 LP |
317 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
318 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
5d67a7ae | 319 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
b6451358 | 320 | |
de54e62b LP |
321 | s->packet_rrsig_missing = true; |
322 | } | |
323 | ||
324 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 325 | assert(s); |
b652d4a2 | 326 | |
de54e62b LP |
327 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
328 | return; | |
b652d4a2 | 329 | |
b6451358 LP |
330 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
331 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
332 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
333 | ||
de54e62b | 334 | s->packet_bad_opt = true; |
b652d4a2 LP |
335 | } |
336 | ||
d001e0a3 LP |
337 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
338 | assert(s); | |
339 | ||
340 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
341 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
342 | * things work. */ | |
343 | ||
344 | if (s->verified_feature_level > level) | |
345 | s->verified_feature_level = level; | |
346 | ||
347 | if (s->possible_feature_level > level) { | |
348 | s->possible_feature_level = level; | |
349 | dns_server_reset_counters(s); | |
350 | } | |
351 | ||
352 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
353 | } | |
354 | ||
be808ea0 TG |
355 | static bool dns_server_grace_period_expired(DnsServer *s) { |
356 | usec_t ts; | |
357 | ||
358 | assert(s); | |
359 | assert(s->manager); | |
360 | ||
361 | if (s->verified_usec == 0) | |
362 | return false; | |
363 | ||
364 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
365 | ||
366 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
367 | return false; | |
368 | ||
369 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
370 | ||
371 | return true; | |
372 | } | |
373 | ||
f4461e56 | 374 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
375 | DnsServerFeatureLevel best; |
376 | ||
be808ea0 TG |
377 | assert(s); |
378 | ||
97277567 LP |
379 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
380 | * better than EDNS0, hence don't even try. */ | |
5d67a7ae | 381 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) |
c9299be2 | 382 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
383 | DNS_SERVER_FEATURE_LEVEL_LARGE : |
384 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
385 | else | |
c9299be2 | 386 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
387 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : |
388 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
97277567 LP |
389 | |
390 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
391 | * time, hence let's downgrade if we are still at a higher level. */ | |
392 | if (s->possible_feature_level > best) | |
393 | s->possible_feature_level = best; | |
394 | ||
395 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 396 | |
97277567 | 397 | s->possible_feature_level = best; |
cc450722 | 398 | |
01184277 LP |
399 | dns_server_reset_counters(s); |
400 | ||
cc450722 LP |
401 | s->packet_bad_opt = false; |
402 | s->packet_rrsig_missing = false; | |
403 | ||
de54e62b | 404 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
405 | dns_server_feature_level_to_string(s->possible_feature_level), |
406 | dns_server_string(s)); | |
6bb2c085 | 407 | |
ce7c8b20 LP |
408 | dns_server_flush_cache(s); |
409 | ||
f4461e56 LP |
410 | } else if (s->possible_feature_level <= s->verified_feature_level) |
411 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
412 | else { |
413 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 414 | |
6bb2c085 | 415 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 416 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 417 | |
6bb2c085 LP |
418 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
419 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
420 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
421 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
5d67a7ae IT |
422 | } else if (s->n_failed_tls > 0 && |
423 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level)) { | |
424 | ||
425 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
426 | * if we don't require DNS-over-TLS */ | |
de54e62b | 427 | |
3c0dcbcf | 428 | log_debug("Server doesn't support DNS-over-TLS, downgrading protocol..."); |
5d67a7ae | 429 | s->possible_feature_level--; |
de54e62b LP |
430 | } else if (s->packet_bad_opt && |
431 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
432 | ||
433 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
434 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
435 | * in the request. Example: | |
436 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
437 | ||
438 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 439 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 440 | |
de54e62b LP |
441 | } else if (s->packet_rrsig_missing && |
442 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 443 | |
de54e62b LP |
444 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
445 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
446 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
447 | * not. */ | |
448 | ||
449 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
5d67a7ae | 450 | 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 |
451 | |
452 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 453 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
454 | |
455 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
456 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
457 | * idea. We might downgrade all the way down to TCP this way. |
458 | * | |
459 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
460 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
461 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
462 | |
463 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
464 | s->possible_feature_level--; | |
465 | ||
de54e62b LP |
466 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
467 | s->packet_truncated && | |
12bf2331 | 468 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
469 | |
470 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
471 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
472 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
473 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
474 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
475 | ||
476 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
477 | s->possible_feature_level--; | |
478 | } | |
479 | ||
6bb2c085 | 480 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
481 | |
482 | /* We changed the feature level, reset the counting */ | |
01184277 | 483 | dns_server_reset_counters(s); |
6bb2c085 | 484 | |
de54e62b | 485 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
486 | dns_server_feature_level_to_string(s->possible_feature_level), |
487 | dns_server_string(s)); | |
6bb2c085 | 488 | } |
be808ea0 TG |
489 | } |
490 | ||
f4461e56 | 491 | return s->possible_feature_level; |
be808ea0 TG |
492 | } |
493 | ||
519ef046 LP |
494 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
495 | size_t packet_size; | |
496 | bool edns_do; | |
497 | int r; | |
498 | ||
499 | assert(server); | |
500 | assert(packet); | |
501 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
502 | ||
503 | /* Fix the OPT field in the packet to match our current feature level. */ | |
504 | ||
505 | r = dns_packet_truncate_opt(packet); | |
506 | if (r < 0) | |
507 | return r; | |
508 | ||
509 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
510 | return 0; | |
511 | ||
512 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
513 | ||
514 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
515 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
516 | else | |
517 | packet_size = server->received_udp_packet_max; | |
518 | ||
f2ed4c69 | 519 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
520 | } |
521 | ||
2817157b LP |
522 | int dns_server_ifindex(const DnsServer *s) { |
523 | assert(s); | |
524 | ||
525 | /* The link ifindex always takes precedence */ | |
526 | if (s->link) | |
527 | return s->link->ifindex; | |
528 | ||
529 | if (s->ifindex > 0) | |
530 | return s->ifindex; | |
531 | ||
532 | return 0; | |
533 | } | |
534 | ||
6cb08a89 LP |
535 | const char *dns_server_string(DnsServer *server) { |
536 | assert(server); | |
537 | ||
538 | if (!server->server_string) | |
2817157b | 539 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
540 | |
541 | return strna(server->server_string); | |
542 | } | |
543 | ||
92ec902a LP |
544 | bool dns_server_dnssec_supported(DnsServer *server) { |
545 | assert(server); | |
546 | ||
547 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
548 | ||
549 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
550 | return false; | |
551 | ||
de54e62b LP |
552 | if (server->packet_bad_opt) |
553 | return false; | |
554 | ||
555 | if (server->packet_rrsig_missing) | |
92ec902a LP |
556 | return false; |
557 | ||
558 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
559 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
560 | return false; | |
561 | ||
562 | return true; | |
563 | } | |
564 | ||
1e02e182 LP |
565 | void dns_server_warn_downgrade(DnsServer *server) { |
566 | assert(server); | |
567 | ||
568 | if (server->warned_downgrade) | |
569 | return; | |
570 | ||
571 | log_struct(LOG_NOTICE, | |
2b044526 | 572 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
573 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
574 | "DNS_SERVER=%s", dns_server_string(server), | |
f4cf1d66 | 575 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
576 | |
577 | server->warned_downgrade = true; | |
578 | } | |
579 | ||
413b05cc | 580 | bool dns_server_limited_domains(DnsServer *server) { |
b9fe94ca MP |
581 | DnsSearchDomain *domain; |
582 | bool domain_restricted = false; | |
583 | ||
584 | /* Check if the server has route-only domains without ~., i. e. whether | |
585 | * it should only be used for particular domains */ | |
586 | if (!server->link) | |
587 | return false; | |
588 | ||
589 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
590 | if (domain->route_only) { | |
591 | domain_restricted = true; | |
592 | /* ~. means "any domain", thus it is a global server */ | |
413b05cc | 593 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) |
b9fe94ca MP |
594 | return false; |
595 | } | |
596 | ||
597 | return domain_restricted; | |
598 | } | |
599 | ||
7a08d314 | 600 | static void dns_server_hash_func(const DnsServer *s, struct siphash *state) { |
b826ab58 | 601 | assert(s); |
87f5a193 | 602 | |
b826ab58 TG |
603 | siphash24_compress(&s->family, sizeof(s->family), state); |
604 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 605 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
606 | } |
607 | ||
7a08d314 | 608 | static int dns_server_compare_func(const DnsServer *x, const DnsServer *y) { |
2817157b | 609 | int r; |
87f5a193 | 610 | |
a0edd02e FB |
611 | r = CMP(x->family, y->family); |
612 | if (r != 0) | |
613 | return r; | |
87f5a193 | 614 | |
2817157b LP |
615 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
616 | if (r != 0) | |
617 | return r; | |
618 | ||
a0edd02e FB |
619 | r = CMP(x->ifindex, y->ifindex); |
620 | if (r != 0) | |
621 | return r; | |
2817157b LP |
622 | |
623 | return 0; | |
87f5a193 | 624 | } |
d5099efc | 625 | |
7a08d314 | 626 | DEFINE_HASH_OPS(dns_server_hash_ops, DnsServer, dns_server_hash_func, dns_server_compare_func); |
636e813d | 627 | |
4b95f179 LP |
628 | void dns_server_unlink_all(DnsServer *first) { |
629 | DnsServer *next; | |
0eac4623 | 630 | |
4b95f179 LP |
631 | if (!first) |
632 | return; | |
0eac4623 | 633 | |
4b95f179 LP |
634 | next = first->servers_next; |
635 | dns_server_unlink(first); | |
636e813d | 636 | |
4b95f179 | 637 | dns_server_unlink_all(next); |
0eac4623 LP |
638 | } |
639 | ||
4b95f179 LP |
640 | void dns_server_unlink_marked(DnsServer *first) { |
641 | DnsServer *next; | |
636e813d | 642 | |
4b95f179 LP |
643 | if (!first) |
644 | return; | |
636e813d | 645 | |
4b95f179 | 646 | next = first->servers_next; |
636e813d | 647 | |
4b95f179 | 648 | if (first->marked) |
0eac4623 | 649 | dns_server_unlink(first); |
636e813d | 650 | |
4b95f179 LP |
651 | dns_server_unlink_marked(next); |
652 | } | |
636e813d | 653 | |
4b95f179 LP |
654 | void dns_server_mark_all(DnsServer *first) { |
655 | if (!first) | |
656 | return; | |
636e813d | 657 | |
4b95f179 LP |
658 | first->marked = true; |
659 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
660 | } |
661 | ||
2817157b | 662 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 663 | DnsServer *s; |
636e813d | 664 | |
636e813d | 665 | LIST_FOREACH(servers, s, first) |
2817157b | 666 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 667 | return s; |
f2f1dbe5 | 668 | |
4b95f179 LP |
669 | return NULL; |
670 | } | |
f2f1dbe5 | 671 | |
4b95f179 | 672 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 673 | assert(m); |
f2f1dbe5 | 674 | |
4b95f179 | 675 | switch (t) { |
f2f1dbe5 | 676 | |
4b95f179 LP |
677 | case DNS_SERVER_SYSTEM: |
678 | return m->dns_servers; | |
f2f1dbe5 | 679 | |
4b95f179 LP |
680 | case DNS_SERVER_FALLBACK: |
681 | return m->fallback_dns_servers; | |
682 | ||
683 | default: | |
684 | return NULL; | |
685 | } | |
f2f1dbe5 LP |
686 | } |
687 | ||
688 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
689 | assert(m); | |
690 | ||
691 | if (m->current_dns_server == s) | |
692 | return s; | |
693 | ||
6cb08a89 | 694 | if (s) |
db8e1324 LP |
695 | log_debug("Switching to %s DNS server %s.", |
696 | dns_server_type_to_string(s->type), | |
697 | dns_server_string(s)); | |
f2f1dbe5 | 698 | |
0eac4623 LP |
699 | dns_server_unref(m->current_dns_server); |
700 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
701 | |
702 | if (m->unicast_scope) | |
703 | dns_cache_flush(&m->unicast_scope->cache); | |
704 | ||
705 | return s; | |
706 | } | |
707 | ||
708 | DnsServer *manager_get_dns_server(Manager *m) { | |
709 | Link *l; | |
710 | assert(m); | |
711 | ||
712 | /* Try to read updates resolv.conf */ | |
713 | manager_read_resolv_conf(m); | |
714 | ||
e3309036 | 715 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
716 | if (!m->current_dns_server) |
717 | manager_set_dns_server(m, m->dns_servers); | |
718 | ||
719 | if (!m->current_dns_server) { | |
720 | bool found = false; | |
721 | Iterator i; | |
722 | ||
723 | /* No DNS servers configured, let's see if there are | |
724 | * any on any links. If not, we use the fallback | |
725 | * servers */ | |
726 | ||
727 | HASHMAP_FOREACH(l, m->links, i) | |
728 | if (l->dns_servers) { | |
729 | found = true; | |
730 | break; | |
731 | } | |
732 | ||
733 | if (!found) | |
734 | manager_set_dns_server(m, m->fallback_dns_servers); | |
735 | } | |
736 | ||
737 | return m->current_dns_server; | |
738 | } | |
739 | ||
740 | void manager_next_dns_server(Manager *m) { | |
741 | assert(m); | |
742 | ||
743 | /* If there's currently no DNS server set, then the next | |
744 | * manager_get_dns_server() will find one */ | |
745 | if (!m->current_dns_server) | |
746 | return; | |
747 | ||
0eac4623 LP |
748 | /* Change to the next one, but make sure to follow the linked |
749 | * list only if the server is still linked. */ | |
750 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
751 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
752 | return; | |
753 | } | |
754 | ||
755 | /* If there was no next one, then start from the beginning of | |
756 | * the list */ | |
757 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
758 | manager_set_dns_server(m, m->fallback_dns_servers); | |
759 | else | |
760 | manager_set_dns_server(m, m->dns_servers); | |
761 | } | |
be808ea0 | 762 | |
b30bf55d LP |
763 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
764 | ||
765 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
766 | ||
767 | if (in_addr_is_null(family, sa)) | |
768 | return false; | |
769 | ||
770 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
771 | return false; | |
772 | ||
773 | return true; | |
774 | } | |
775 | ||
12bf2331 LP |
776 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
777 | assert(s); | |
778 | ||
779 | if (s->link) | |
780 | return link_get_dnssec_mode(s->link); | |
781 | ||
782 | return manager_get_dnssec_mode(s->manager); | |
783 | } | |
784 | ||
c9299be2 | 785 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { |
5d67a7ae IT |
786 | assert(s); |
787 | ||
d050561a | 788 | if (s->link) |
c9299be2 | 789 | return link_get_dns_over_tls_mode(s->link); |
d050561a | 790 | |
c9299be2 | 791 | return manager_get_dns_over_tls_mode(s->manager); |
5d67a7ae IT |
792 | } |
793 | ||
ce7c8b20 LP |
794 | void dns_server_flush_cache(DnsServer *s) { |
795 | DnsServer *current; | |
796 | DnsScope *scope; | |
797 | ||
798 | assert(s); | |
799 | ||
800 | /* Flush the cache of the scope this server belongs to */ | |
801 | ||
802 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
803 | if (current != s) | |
804 | return; | |
805 | ||
806 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
807 | if (!scope) | |
808 | return; | |
809 | ||
810 | dns_cache_flush(&scope->cache); | |
811 | } | |
812 | ||
59c0fd0e LP |
813 | void dns_server_reset_features(DnsServer *s) { |
814 | assert(s); | |
815 | ||
59c0fd0e LP |
816 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
817 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
818 | ||
819 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
820 | ||
821 | s->packet_bad_opt = false; | |
822 | s->packet_rrsig_missing = false; | |
823 | ||
824 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
825 | ||
826 | s->warned_downgrade = false; | |
827 | ||
828 | dns_server_reset_counters(s); | |
829 | } | |
830 | ||
831 | void dns_server_reset_features_all(DnsServer *s) { | |
832 | DnsServer *i; | |
833 | ||
834 | LIST_FOREACH(servers, i, s) | |
835 | dns_server_reset_features(i); | |
836 | } | |
837 | ||
cf84484a LP |
838 | void dns_server_dump(DnsServer *s, FILE *f) { |
839 | assert(s); | |
840 | ||
841 | if (!f) | |
842 | f = stdout; | |
843 | ||
844 | fputs("[Server ", f); | |
845 | fputs(dns_server_string(s), f); | |
846 | fputs(" type=", f); | |
847 | fputs(dns_server_type_to_string(s->type), f); | |
848 | ||
849 | if (s->type == DNS_SERVER_LINK) { | |
850 | assert(s->link); | |
851 | ||
852 | fputs(" interface=", f); | |
853 | fputs(s->link->name, f); | |
854 | } | |
855 | ||
856 | fputs("]\n", f); | |
857 | ||
858 | fputs("\tVerified feature level: ", f); | |
859 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
860 | fputc('\n', f); | |
861 | ||
862 | fputs("\tPossible feature level: ", f); | |
863 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
864 | fputc('\n', f); | |
865 | ||
866 | fputs("\tDNSSEC Mode: ", f); | |
867 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
868 | fputc('\n', f); | |
869 | ||
870 | fputs("\tCan do DNSSEC: ", f); | |
871 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
872 | fputc('\n', f); | |
873 | ||
874 | fprintf(f, | |
875 | "\tMaximum UDP packet size received: %zu\n" | |
876 | "\tFailed UDP attempts: %u\n" | |
877 | "\tFailed TCP attempts: %u\n" | |
878 | "\tSeen truncated packet: %s\n" | |
879 | "\tSeen OPT RR getting lost: %s\n" | |
880 | "\tSeen RRSIG RR missing: %s\n", | |
881 | s->received_udp_packet_max, | |
882 | s->n_failed_udp, | |
883 | s->n_failed_tcp, | |
884 | yes_no(s->packet_truncated), | |
885 | yes_no(s->packet_bad_opt), | |
886 | yes_no(s->packet_rrsig_missing)); | |
887 | } | |
888 | ||
e3309036 ZJS |
889 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
890 | [DNS_SERVER_SYSTEM] = "system", | |
891 | [DNS_SERVER_FALLBACK] = "fallback", | |
892 | [DNS_SERVER_LINK] = "link", | |
893 | }; | |
894 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
895 | ||
be808ea0 TG |
896 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
897 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
898 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 899 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
5d67a7ae | 900 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 901 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 902 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 903 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
904 | }; |
905 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |