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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 | |
5d67a7ae IT |
92 | #if HAVE_GNUTLS |
93 | /* Do not verify cerificate */ | |
94 | gnutls_certificate_allocate_credentials(&s->tls_cert_cred); | |
95 | #endif | |
96 | ||
4e945a6f LP |
97 | /* A new DNS server that isn't fallback is added and the one |
98 | * we used so far was a fallback one? Then let's try to pick | |
99 | * the new one */ | |
100 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
101 | m->current_dns_server && |
102 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
103 | manager_set_dns_server(m, NULL); | |
4e945a6f | 104 | |
74b2466e LP |
105 | if (ret) |
106 | *ret = s; | |
107 | ||
108 | return 0; | |
109 | } | |
110 | ||
91b14d6f | 111 | DnsServer* dns_server_ref(DnsServer *s) { |
74b2466e LP |
112 | if (!s) |
113 | return NULL; | |
114 | ||
91b14d6f | 115 | assert(s->n_ref > 0); |
313cefa1 | 116 | s->n_ref++; |
cab5b059 | 117 | |
91b14d6f TG |
118 | return s; |
119 | } | |
120 | ||
0eac4623 | 121 | DnsServer* dns_server_unref(DnsServer *s) { |
91b14d6f TG |
122 | if (!s) |
123 | return NULL; | |
3e684349 | 124 | |
0eac4623 | 125 | assert(s->n_ref > 0); |
313cefa1 | 126 | s->n_ref--; |
91b14d6f | 127 | |
0eac4623 LP |
128 | if (s->n_ref > 0) |
129 | return NULL; | |
74b2466e | 130 | |
98767d75 IT |
131 | dns_stream_unref(s->stream); |
132 | ||
5d67a7ae IT |
133 | #if HAVE_GNUTLS |
134 | if (s->tls_cert_cred) | |
135 | gnutls_certificate_free_credentials(s->tls_cert_cred); | |
136 | ||
137 | if (s->tls_session_data.data) | |
138 | gnutls_free(s->tls_session_data.data); | |
139 | #endif | |
140 | ||
6cb08a89 | 141 | free(s->server_string); |
6b430fdb | 142 | return mfree(s); |
74b2466e | 143 | } |
87f5a193 | 144 | |
0eac4623 LP |
145 | void dns_server_unlink(DnsServer *s) { |
146 | assert(s); | |
147 | assert(s->manager); | |
91b14d6f | 148 | |
0eac4623 LP |
149 | /* This removes the specified server from the linked list of |
150 | * servers, but any server might still stay around if it has | |
151 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 152 | |
0eac4623 LP |
153 | if (!s->linked) |
154 | return; | |
91b14d6f | 155 | |
0eac4623 LP |
156 | switch (s->type) { |
157 | ||
158 | case DNS_SERVER_LINK: | |
159 | assert(s->link); | |
eed857b7 | 160 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 161 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 162 | s->link->n_dns_servers--; |
0eac4623 LP |
163 | break; |
164 | ||
165 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 166 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 167 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 168 | s->manager->n_dns_servers--; |
0eac4623 LP |
169 | break; |
170 | ||
171 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 172 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 173 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 174 | s->manager->n_dns_servers--; |
0eac4623 LP |
175 | break; |
176 | } | |
177 | ||
178 | s->linked = false; | |
179 | ||
180 | if (s->link && s->link->current_dns_server == s) | |
181 | link_set_dns_server(s->link, NULL); | |
182 | ||
183 | if (s->manager->current_dns_server == s) | |
184 | manager_set_dns_server(s->manager, NULL); | |
185 | ||
186 | dns_server_unref(s); | |
91b14d6f TG |
187 | } |
188 | ||
0b58db65 LP |
189 | void dns_server_move_back_and_unmark(DnsServer *s) { |
190 | DnsServer *tail; | |
191 | ||
192 | assert(s); | |
193 | ||
194 | if (!s->marked) | |
195 | return; | |
196 | ||
197 | s->marked = false; | |
198 | ||
199 | if (!s->linked || !s->servers_next) | |
200 | return; | |
201 | ||
202 | /* Move us to the end of the list, so that the order is | |
203 | * strictly kept, if we are not at the end anyway. */ | |
204 | ||
205 | switch (s->type) { | |
206 | ||
207 | case DNS_SERVER_LINK: | |
208 | assert(s->link); | |
209 | LIST_FIND_TAIL(servers, s, tail); | |
210 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
211 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
212 | break; | |
213 | ||
214 | case DNS_SERVER_SYSTEM: | |
215 | LIST_FIND_TAIL(servers, s, tail); | |
216 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
217 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
218 | break; | |
219 | ||
220 | case DNS_SERVER_FALLBACK: | |
221 | LIST_FIND_TAIL(servers, s, tail); | |
222 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
223 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
224 | break; | |
225 | ||
226 | default: | |
227 | assert_not_reached("Unknown server type"); | |
228 | } | |
229 | } | |
230 | ||
6bb2c085 | 231 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
232 | assert(s); |
233 | ||
6bb2c085 LP |
234 | if (s->verified_feature_level > level) |
235 | return; | |
b652d4a2 | 236 | |
6bb2c085 | 237 | if (s->verified_feature_level != level) { |
de54e62b LP |
238 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
239 | dns_server_feature_level_to_string(level), | |
240 | dns_server_string(s)); | |
f4461e56 | 241 | s->verified_feature_level = level; |
be808ea0 TG |
242 | } |
243 | ||
6bb2c085 LP |
244 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
245 | } | |
246 | ||
d001e0a3 LP |
247 | static void dns_server_reset_counters(DnsServer *s) { |
248 | assert(s); | |
249 | ||
250 | s->n_failed_udp = 0; | |
251 | s->n_failed_tcp = 0; | |
5d67a7ae | 252 | s->n_failed_tls = 0; |
d001e0a3 LP |
253 | s->packet_truncated = false; |
254 | s->verified_usec = 0; | |
255 | ||
256 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
257 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
258 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
259 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
260 | * either. | |
261 | * | |
262 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
263 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
264 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
265 | * incomplete. */ | |
266 | } | |
267 | ||
6bb2c085 LP |
268 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size) { |
269 | assert(s); | |
270 | ||
271 | if (protocol == IPPROTO_UDP) { | |
272 | if (s->possible_feature_level == level) | |
273 | s->n_failed_udp = 0; | |
6bb2c085 | 274 | } else if (protocol == IPPROTO_TCP) { |
5d67a7ae IT |
275 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { |
276 | if (s->possible_feature_level == level) | |
277 | s->n_failed_tls = 0; | |
278 | } else { | |
279 | if (s->possible_feature_level == level) | |
280 | s->n_failed_tcp = 0; | |
281 | ||
282 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
283 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
284 | } | |
285 | } | |
6bb2c085 | 286 | |
5d67a7ae IT |
287 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
288 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
289 | level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
6bb2c085 | 290 | |
5d67a7ae IT |
291 | /* If the OPT RR got lost, then we can only validate UDP at max */ |
292 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
293 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
294 | ||
295 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
296 | that does not mean we can necessarily receive large packets. */ | |
297 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
298 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
84129d46 | 299 | |
b6451358 LP |
300 | dns_server_verified(s, level); |
301 | ||
d74fb368 TG |
302 | /* Remember the size of the largest UDP packet we received from a server, |
303 | we know that we can always announce support for packets with at least | |
304 | this size. */ | |
6bb2c085 | 305 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 TG |
306 | s->received_udp_packet_max = size; |
307 | ||
be808ea0 TG |
308 | if (s->max_rtt < rtt) { |
309 | s->max_rtt = rtt; | |
efd46a69 | 310 | s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); |
496ae8c8 KK |
311 | } else if (s->resend_timeout > rtt) |
312 | /* If we received the packet faster than the resend_timeout, bias | |
313 | * the resend_timeout back to the rtt. */ | |
314 | s->resend_timeout = CLAMP((2 * s->resend_timeout + rtt) / 3, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
315 | } |
316 | ||
6bb2c085 | 317 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { |
9df3ba6c | 318 | assert(s); |
be808ea0 TG |
319 | assert(s->manager); |
320 | ||
6bb2c085 LP |
321 | if (s->possible_feature_level == level) { |
322 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 323 | s->n_failed_udp++; |
5d67a7ae IT |
324 | else if (protocol == IPPROTO_TCP) { |
325 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
326 | s->n_failed_tls++; | |
327 | else | |
328 | s->n_failed_tcp++; | |
329 | } | |
6bb2c085 | 330 | } |
9df3ba6c | 331 | |
84129d46 LP |
332 | if (s->resend_timeout > usec) |
333 | return; | |
334 | ||
335 | s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC); | |
9df3ba6c TG |
336 | } |
337 | ||
6bb2c085 LP |
338 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
339 | assert(s); | |
571370c1 | 340 | |
6bb2c085 LP |
341 | /* Invoked whenever we get a packet with TC bit set. */ |
342 | ||
343 | if (s->possible_feature_level != level) | |
571370c1 LP |
344 | return; |
345 | ||
6bb2c085 | 346 | s->packet_truncated = true; |
4e0b8b17 TG |
347 | } |
348 | ||
de54e62b LP |
349 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
350 | assert(s); | |
351 | ||
352 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
353 | return; | |
354 | ||
b6451358 LP |
355 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
356 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
5d67a7ae | 357 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
b6451358 | 358 | |
de54e62b LP |
359 | s->packet_rrsig_missing = true; |
360 | } | |
361 | ||
362 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 363 | assert(s); |
b652d4a2 | 364 | |
de54e62b LP |
365 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
366 | return; | |
b652d4a2 | 367 | |
b6451358 LP |
368 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
369 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
370 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
371 | ||
de54e62b | 372 | s->packet_bad_opt = true; |
b652d4a2 LP |
373 | } |
374 | ||
d001e0a3 LP |
375 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
376 | assert(s); | |
377 | ||
378 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
379 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
380 | * things work. */ | |
381 | ||
382 | if (s->verified_feature_level > level) | |
383 | s->verified_feature_level = level; | |
384 | ||
385 | if (s->possible_feature_level > level) { | |
386 | s->possible_feature_level = level; | |
387 | dns_server_reset_counters(s); | |
388 | } | |
389 | ||
390 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
391 | } | |
392 | ||
be808ea0 TG |
393 | static bool dns_server_grace_period_expired(DnsServer *s) { |
394 | usec_t ts; | |
395 | ||
396 | assert(s); | |
397 | assert(s->manager); | |
398 | ||
399 | if (s->verified_usec == 0) | |
400 | return false; | |
401 | ||
402 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
403 | ||
404 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
405 | return false; | |
406 | ||
407 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
408 | ||
409 | return true; | |
410 | } | |
411 | ||
f4461e56 | 412 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
413 | DnsServerFeatureLevel best; |
414 | ||
be808ea0 TG |
415 | assert(s); |
416 | ||
97277567 LP |
417 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
418 | * better than EDNS0, hence don't even try. */ | |
5d67a7ae IT |
419 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) |
420 | best = dns_server_get_private_dns_mode(s) == PRIVATE_DNS_NO ? | |
421 | DNS_SERVER_FEATURE_LEVEL_LARGE : | |
422 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
423 | else | |
424 | best = dns_server_get_private_dns_mode(s) == PRIVATE_DNS_NO ? | |
425 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : | |
426 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
97277567 LP |
427 | |
428 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
429 | * time, hence let's downgrade if we are still at a higher level. */ | |
430 | if (s->possible_feature_level > best) | |
431 | s->possible_feature_level = best; | |
432 | ||
433 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 434 | |
97277567 | 435 | s->possible_feature_level = best; |
cc450722 | 436 | |
01184277 LP |
437 | dns_server_reset_counters(s); |
438 | ||
cc450722 LP |
439 | s->packet_bad_opt = false; |
440 | s->packet_rrsig_missing = false; | |
441 | ||
de54e62b | 442 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
443 | dns_server_feature_level_to_string(s->possible_feature_level), |
444 | dns_server_string(s)); | |
6bb2c085 | 445 | |
ce7c8b20 LP |
446 | dns_server_flush_cache(s); |
447 | ||
f4461e56 LP |
448 | } else if (s->possible_feature_level <= s->verified_feature_level) |
449 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
450 | else { |
451 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 452 | |
6bb2c085 | 453 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 454 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 455 | |
6bb2c085 LP |
456 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
457 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
458 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
459 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
5d67a7ae IT |
460 | } else if (s->n_failed_tls > 0 && |
461 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level)) { | |
462 | ||
463 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
464 | * if we don't require DNS-over-TLS */ | |
de54e62b | 465 | |
5d67a7ae IT |
466 | log_debug("Server doesn't support seem to support DNS-over-TLS, downgrading protocol..."); |
467 | s->possible_feature_level--; | |
de54e62b LP |
468 | } else if (s->packet_bad_opt && |
469 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
470 | ||
471 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
472 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
473 | * in the request. Example: | |
474 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
475 | ||
476 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 477 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 478 | |
de54e62b LP |
479 | } else if (s->packet_rrsig_missing && |
480 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 481 | |
de54e62b LP |
482 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
483 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
484 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
485 | * not. */ | |
486 | ||
487 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
5d67a7ae | 488 | 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 |
489 | |
490 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 491 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
492 | |
493 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
494 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
495 | * idea. We might downgrade all the way down to TCP this way. |
496 | * | |
497 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
498 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
499 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
500 | |
501 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
502 | s->possible_feature_level--; | |
503 | ||
de54e62b LP |
504 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
505 | s->packet_truncated && | |
12bf2331 | 506 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
507 | |
508 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
509 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
510 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
511 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
512 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
513 | ||
514 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
515 | s->possible_feature_level--; | |
516 | } | |
517 | ||
6bb2c085 | 518 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
519 | |
520 | /* We changed the feature level, reset the counting */ | |
01184277 | 521 | dns_server_reset_counters(s); |
6bb2c085 | 522 | |
de54e62b | 523 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
524 | dns_server_feature_level_to_string(s->possible_feature_level), |
525 | dns_server_string(s)); | |
6bb2c085 | 526 | } |
be808ea0 TG |
527 | } |
528 | ||
f4461e56 | 529 | return s->possible_feature_level; |
be808ea0 TG |
530 | } |
531 | ||
519ef046 LP |
532 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
533 | size_t packet_size; | |
534 | bool edns_do; | |
535 | int r; | |
536 | ||
537 | assert(server); | |
538 | assert(packet); | |
539 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
540 | ||
541 | /* Fix the OPT field in the packet to match our current feature level. */ | |
542 | ||
543 | r = dns_packet_truncate_opt(packet); | |
544 | if (r < 0) | |
545 | return r; | |
546 | ||
547 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
548 | return 0; | |
549 | ||
550 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
551 | ||
552 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
553 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
554 | else | |
555 | packet_size = server->received_udp_packet_max; | |
556 | ||
f2ed4c69 | 557 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
558 | } |
559 | ||
2817157b LP |
560 | int dns_server_ifindex(const DnsServer *s) { |
561 | assert(s); | |
562 | ||
563 | /* The link ifindex always takes precedence */ | |
564 | if (s->link) | |
565 | return s->link->ifindex; | |
566 | ||
567 | if (s->ifindex > 0) | |
568 | return s->ifindex; | |
569 | ||
570 | return 0; | |
571 | } | |
572 | ||
6cb08a89 LP |
573 | const char *dns_server_string(DnsServer *server) { |
574 | assert(server); | |
575 | ||
576 | if (!server->server_string) | |
2817157b | 577 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
578 | |
579 | return strna(server->server_string); | |
580 | } | |
581 | ||
92ec902a LP |
582 | bool dns_server_dnssec_supported(DnsServer *server) { |
583 | assert(server); | |
584 | ||
585 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
586 | ||
587 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
588 | return false; | |
589 | ||
de54e62b LP |
590 | if (server->packet_bad_opt) |
591 | return false; | |
592 | ||
593 | if (server->packet_rrsig_missing) | |
92ec902a LP |
594 | return false; |
595 | ||
596 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
597 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
598 | return false; | |
599 | ||
600 | return true; | |
601 | } | |
602 | ||
1e02e182 LP |
603 | void dns_server_warn_downgrade(DnsServer *server) { |
604 | assert(server); | |
605 | ||
606 | if (server->warned_downgrade) | |
607 | return; | |
608 | ||
609 | log_struct(LOG_NOTICE, | |
2b044526 | 610 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
611 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
612 | "DNS_SERVER=%s", dns_server_string(server), | |
f4cf1d66 | 613 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
614 | |
615 | server->warned_downgrade = true; | |
616 | } | |
617 | ||
413b05cc | 618 | bool dns_server_limited_domains(DnsServer *server) { |
b9fe94ca MP |
619 | DnsSearchDomain *domain; |
620 | bool domain_restricted = false; | |
621 | ||
622 | /* Check if the server has route-only domains without ~., i. e. whether | |
623 | * it should only be used for particular domains */ | |
624 | if (!server->link) | |
625 | return false; | |
626 | ||
627 | LIST_FOREACH(domains, domain, server->link->search_domains) | |
628 | if (domain->route_only) { | |
629 | domain_restricted = true; | |
630 | /* ~. means "any domain", thus it is a global server */ | |
413b05cc | 631 | if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain))) |
b9fe94ca MP |
632 | return false; |
633 | } | |
634 | ||
635 | return domain_restricted; | |
636 | } | |
637 | ||
b826ab58 | 638 | static void dns_server_hash_func(const void *p, struct siphash *state) { |
87f5a193 | 639 | const DnsServer *s = p; |
87f5a193 | 640 | |
b826ab58 | 641 | assert(s); |
87f5a193 | 642 | |
b826ab58 TG |
643 | siphash24_compress(&s->family, sizeof(s->family), state); |
644 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 645 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
646 | } |
647 | ||
d5099efc | 648 | static int dns_server_compare_func(const void *a, const void *b) { |
87f5a193 | 649 | const DnsServer *x = a, *y = b; |
2817157b | 650 | int r; |
87f5a193 LP |
651 | |
652 | if (x->family < y->family) | |
653 | return -1; | |
654 | if (x->family > y->family) | |
655 | return 1; | |
656 | ||
2817157b LP |
657 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
658 | if (r != 0) | |
659 | return r; | |
660 | ||
661 | if (x->ifindex < y->ifindex) | |
662 | return -1; | |
663 | if (x->ifindex > y->ifindex) | |
664 | return 1; | |
665 | ||
666 | return 0; | |
87f5a193 | 667 | } |
d5099efc MS |
668 | |
669 | const struct hash_ops dns_server_hash_ops = { | |
670 | .hash = dns_server_hash_func, | |
671 | .compare = dns_server_compare_func | |
672 | }; | |
636e813d | 673 | |
4b95f179 LP |
674 | void dns_server_unlink_all(DnsServer *first) { |
675 | DnsServer *next; | |
0eac4623 | 676 | |
4b95f179 LP |
677 | if (!first) |
678 | return; | |
0eac4623 | 679 | |
4b95f179 LP |
680 | next = first->servers_next; |
681 | dns_server_unlink(first); | |
636e813d | 682 | |
4b95f179 | 683 | dns_server_unlink_all(next); |
0eac4623 LP |
684 | } |
685 | ||
4b95f179 LP |
686 | void dns_server_unlink_marked(DnsServer *first) { |
687 | DnsServer *next; | |
636e813d | 688 | |
4b95f179 LP |
689 | if (!first) |
690 | return; | |
636e813d | 691 | |
4b95f179 | 692 | next = first->servers_next; |
636e813d | 693 | |
4b95f179 | 694 | if (first->marked) |
0eac4623 | 695 | dns_server_unlink(first); |
636e813d | 696 | |
4b95f179 LP |
697 | dns_server_unlink_marked(next); |
698 | } | |
636e813d | 699 | |
4b95f179 LP |
700 | void dns_server_mark_all(DnsServer *first) { |
701 | if (!first) | |
702 | return; | |
636e813d | 703 | |
4b95f179 LP |
704 | first->marked = true; |
705 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
706 | } |
707 | ||
2817157b | 708 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 709 | DnsServer *s; |
636e813d | 710 | |
636e813d | 711 | LIST_FOREACH(servers, s, first) |
2817157b | 712 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 713 | return s; |
f2f1dbe5 | 714 | |
4b95f179 LP |
715 | return NULL; |
716 | } | |
f2f1dbe5 | 717 | |
4b95f179 | 718 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 719 | assert(m); |
f2f1dbe5 | 720 | |
4b95f179 | 721 | switch (t) { |
f2f1dbe5 | 722 | |
4b95f179 LP |
723 | case DNS_SERVER_SYSTEM: |
724 | return m->dns_servers; | |
f2f1dbe5 | 725 | |
4b95f179 LP |
726 | case DNS_SERVER_FALLBACK: |
727 | return m->fallback_dns_servers; | |
728 | ||
729 | default: | |
730 | return NULL; | |
731 | } | |
f2f1dbe5 LP |
732 | } |
733 | ||
734 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
735 | assert(m); | |
736 | ||
737 | if (m->current_dns_server == s) | |
738 | return s; | |
739 | ||
6cb08a89 | 740 | if (s) |
db8e1324 LP |
741 | log_debug("Switching to %s DNS server %s.", |
742 | dns_server_type_to_string(s->type), | |
743 | dns_server_string(s)); | |
f2f1dbe5 | 744 | |
0eac4623 LP |
745 | dns_server_unref(m->current_dns_server); |
746 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
747 | |
748 | if (m->unicast_scope) | |
749 | dns_cache_flush(&m->unicast_scope->cache); | |
750 | ||
751 | return s; | |
752 | } | |
753 | ||
754 | DnsServer *manager_get_dns_server(Manager *m) { | |
755 | Link *l; | |
756 | assert(m); | |
757 | ||
758 | /* Try to read updates resolv.conf */ | |
759 | manager_read_resolv_conf(m); | |
760 | ||
e3309036 | 761 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
762 | if (!m->current_dns_server) |
763 | manager_set_dns_server(m, m->dns_servers); | |
764 | ||
765 | if (!m->current_dns_server) { | |
766 | bool found = false; | |
767 | Iterator i; | |
768 | ||
769 | /* No DNS servers configured, let's see if there are | |
770 | * any on any links. If not, we use the fallback | |
771 | * servers */ | |
772 | ||
773 | HASHMAP_FOREACH(l, m->links, i) | |
774 | if (l->dns_servers) { | |
775 | found = true; | |
776 | break; | |
777 | } | |
778 | ||
779 | if (!found) | |
780 | manager_set_dns_server(m, m->fallback_dns_servers); | |
781 | } | |
782 | ||
783 | return m->current_dns_server; | |
784 | } | |
785 | ||
786 | void manager_next_dns_server(Manager *m) { | |
787 | assert(m); | |
788 | ||
789 | /* If there's currently no DNS server set, then the next | |
790 | * manager_get_dns_server() will find one */ | |
791 | if (!m->current_dns_server) | |
792 | return; | |
793 | ||
0eac4623 LP |
794 | /* Change to the next one, but make sure to follow the linked |
795 | * list only if the server is still linked. */ | |
796 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
797 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
798 | return; | |
799 | } | |
800 | ||
801 | /* If there was no next one, then start from the beginning of | |
802 | * the list */ | |
803 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
804 | manager_set_dns_server(m, m->fallback_dns_servers); | |
805 | else | |
806 | manager_set_dns_server(m, m->dns_servers); | |
807 | } | |
be808ea0 | 808 | |
b30bf55d LP |
809 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
810 | ||
811 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
812 | ||
813 | if (in_addr_is_null(family, sa)) | |
814 | return false; | |
815 | ||
816 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
817 | return false; | |
818 | ||
819 | return true; | |
820 | } | |
821 | ||
12bf2331 LP |
822 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
823 | assert(s); | |
824 | ||
825 | if (s->link) | |
826 | return link_get_dnssec_mode(s->link); | |
827 | ||
828 | return manager_get_dnssec_mode(s->manager); | |
829 | } | |
830 | ||
5d67a7ae IT |
831 | PrivateDnsMode dns_server_get_private_dns_mode(DnsServer *s) { |
832 | assert(s); | |
833 | ||
d050561a IT |
834 | if (s->link) |
835 | return link_get_private_dns_mode(s->link); | |
836 | ||
5d67a7ae IT |
837 | return manager_get_private_dns_mode(s->manager); |
838 | } | |
839 | ||
ce7c8b20 LP |
840 | void dns_server_flush_cache(DnsServer *s) { |
841 | DnsServer *current; | |
842 | DnsScope *scope; | |
843 | ||
844 | assert(s); | |
845 | ||
846 | /* Flush the cache of the scope this server belongs to */ | |
847 | ||
848 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
849 | if (current != s) | |
850 | return; | |
851 | ||
852 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
853 | if (!scope) | |
854 | return; | |
855 | ||
856 | dns_cache_flush(&scope->cache); | |
857 | } | |
858 | ||
59c0fd0e LP |
859 | void dns_server_reset_features(DnsServer *s) { |
860 | assert(s); | |
861 | ||
862 | s->max_rtt = 0; | |
863 | s->resend_timeout = DNS_TIMEOUT_MIN_USEC; | |
864 | ||
865 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; | |
866 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
867 | ||
868 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
869 | ||
870 | s->packet_bad_opt = false; | |
871 | s->packet_rrsig_missing = false; | |
872 | ||
873 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
874 | ||
875 | s->warned_downgrade = false; | |
876 | ||
877 | dns_server_reset_counters(s); | |
878 | } | |
879 | ||
880 | void dns_server_reset_features_all(DnsServer *s) { | |
881 | DnsServer *i; | |
882 | ||
883 | LIST_FOREACH(servers, i, s) | |
884 | dns_server_reset_features(i); | |
885 | } | |
886 | ||
cf84484a LP |
887 | void dns_server_dump(DnsServer *s, FILE *f) { |
888 | assert(s); | |
889 | ||
890 | if (!f) | |
891 | f = stdout; | |
892 | ||
893 | fputs("[Server ", f); | |
894 | fputs(dns_server_string(s), f); | |
895 | fputs(" type=", f); | |
896 | fputs(dns_server_type_to_string(s->type), f); | |
897 | ||
898 | if (s->type == DNS_SERVER_LINK) { | |
899 | assert(s->link); | |
900 | ||
901 | fputs(" interface=", f); | |
902 | fputs(s->link->name, f); | |
903 | } | |
904 | ||
905 | fputs("]\n", f); | |
906 | ||
907 | fputs("\tVerified feature level: ", f); | |
908 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
909 | fputc('\n', f); | |
910 | ||
911 | fputs("\tPossible feature level: ", f); | |
912 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
913 | fputc('\n', f); | |
914 | ||
915 | fputs("\tDNSSEC Mode: ", f); | |
916 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
917 | fputc('\n', f); | |
918 | ||
919 | fputs("\tCan do DNSSEC: ", f); | |
920 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
921 | fputc('\n', f); | |
922 | ||
923 | fprintf(f, | |
924 | "\tMaximum UDP packet size received: %zu\n" | |
925 | "\tFailed UDP attempts: %u\n" | |
926 | "\tFailed TCP attempts: %u\n" | |
927 | "\tSeen truncated packet: %s\n" | |
928 | "\tSeen OPT RR getting lost: %s\n" | |
929 | "\tSeen RRSIG RR missing: %s\n", | |
930 | s->received_udp_packet_max, | |
931 | s->n_failed_udp, | |
932 | s->n_failed_tcp, | |
933 | yes_no(s->packet_truncated), | |
934 | yes_no(s->packet_bad_opt), | |
935 | yes_no(s->packet_rrsig_missing)); | |
936 | } | |
937 | ||
e3309036 ZJS |
938 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
939 | [DNS_SERVER_SYSTEM] = "system", | |
940 | [DNS_SERVER_FALLBACK] = "fallback", | |
941 | [DNS_SERVER_LINK] = "link", | |
942 | }; | |
943 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
944 | ||
be808ea0 TG |
945 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
946 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
947 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 948 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
5d67a7ae | 949 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 950 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 951 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 952 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
953 | }; |
954 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |