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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 | |
904dcaf9 | 106 | dns_server_unref_stream(s); |
98767d75 | 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 | ||
904dcaf9 LP |
161 | /* No need to keep a default stream around anymore */ |
162 | dns_server_unref_stream(s); | |
163 | ||
0eac4623 | 164 | dns_server_unref(s); |
91b14d6f TG |
165 | } |
166 | ||
0b58db65 LP |
167 | void dns_server_move_back_and_unmark(DnsServer *s) { |
168 | DnsServer *tail; | |
169 | ||
170 | assert(s); | |
171 | ||
172 | if (!s->marked) | |
173 | return; | |
174 | ||
175 | s->marked = false; | |
176 | ||
177 | if (!s->linked || !s->servers_next) | |
178 | return; | |
179 | ||
180 | /* Move us to the end of the list, so that the order is | |
181 | * strictly kept, if we are not at the end anyway. */ | |
182 | ||
183 | switch (s->type) { | |
184 | ||
185 | case DNS_SERVER_LINK: | |
186 | assert(s->link); | |
187 | LIST_FIND_TAIL(servers, s, tail); | |
188 | LIST_REMOVE(servers, s->link->dns_servers, s); | |
189 | LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s); | |
190 | break; | |
191 | ||
192 | case DNS_SERVER_SYSTEM: | |
193 | LIST_FIND_TAIL(servers, s, tail); | |
194 | LIST_REMOVE(servers, s->manager->dns_servers, s); | |
195 | LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s); | |
196 | break; | |
197 | ||
198 | case DNS_SERVER_FALLBACK: | |
199 | LIST_FIND_TAIL(servers, s, tail); | |
200 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); | |
201 | LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s); | |
202 | break; | |
203 | ||
204 | default: | |
205 | assert_not_reached("Unknown server type"); | |
206 | } | |
207 | } | |
208 | ||
6bb2c085 | 209 | static void dns_server_verified(DnsServer *s, DnsServerFeatureLevel level) { |
9df3ba6c TG |
210 | assert(s); |
211 | ||
6bb2c085 LP |
212 | if (s->verified_feature_level > level) |
213 | return; | |
b652d4a2 | 214 | |
6bb2c085 | 215 | if (s->verified_feature_level != level) { |
de54e62b LP |
216 | log_debug("Verified we get a response at feature level %s from DNS server %s.", |
217 | dns_server_feature_level_to_string(level), | |
218 | dns_server_string(s)); | |
f4461e56 | 219 | s->verified_feature_level = level; |
be808ea0 TG |
220 | } |
221 | ||
6bb2c085 LP |
222 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0); |
223 | } | |
224 | ||
d001e0a3 LP |
225 | static void dns_server_reset_counters(DnsServer *s) { |
226 | assert(s); | |
227 | ||
228 | s->n_failed_udp = 0; | |
229 | s->n_failed_tcp = 0; | |
5d67a7ae | 230 | s->n_failed_tls = 0; |
d001e0a3 LP |
231 | s->packet_truncated = false; |
232 | s->verified_usec = 0; | |
233 | ||
234 | /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the | |
235 | * grace period ends, but not when lowering the possible feature level, as a lower level feature level should | |
236 | * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's | |
237 | * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that | |
238 | * either. | |
239 | * | |
240 | * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A), | |
241 | * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not | |
242 | * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be | |
243 | * incomplete. */ | |
244 | } | |
245 | ||
dbc4661a | 246 | void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, size_t size) { |
6bb2c085 LP |
247 | assert(s); |
248 | ||
249 | if (protocol == IPPROTO_UDP) { | |
250 | if (s->possible_feature_level == level) | |
251 | s->n_failed_udp = 0; | |
6bb2c085 | 252 | } else if (protocol == IPPROTO_TCP) { |
5d67a7ae IT |
253 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) { |
254 | if (s->possible_feature_level == level) | |
255 | s->n_failed_tls = 0; | |
256 | } else { | |
257 | if (s->possible_feature_level == level) | |
258 | s->n_failed_tcp = 0; | |
259 | ||
260 | /* Successful TCP connections are only useful to verify the TCP feature level. */ | |
261 | level = DNS_SERVER_FEATURE_LEVEL_TCP; | |
262 | } | |
263 | } | |
6bb2c085 | 264 | |
5d67a7ae IT |
265 | /* If the RRSIG data is missing, then we can only validate EDNS0 at max */ |
266 | if (s->packet_rrsig_missing && level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
267 | level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; | |
6bb2c085 | 268 | |
5d67a7ae IT |
269 | /* If the OPT RR got lost, then we can only validate UDP at max */ |
270 | if (s->packet_bad_opt && level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
271 | level = DNS_SERVER_FEATURE_LEVEL_EDNS0 - 1; | |
272 | ||
273 | /* Even if we successfully receive a reply to a request announcing support for large packets, | |
274 | that does not mean we can necessarily receive large packets. */ | |
275 | if (level == DNS_SERVER_FEATURE_LEVEL_LARGE) | |
276 | level = DNS_SERVER_FEATURE_LEVEL_LARGE - 1; | |
84129d46 | 277 | |
b6451358 LP |
278 | dns_server_verified(s, level); |
279 | ||
d74fb368 TG |
280 | /* Remember the size of the largest UDP packet we received from a server, |
281 | we know that we can always announce support for packets with at least | |
282 | this size. */ | |
6bb2c085 | 283 | if (protocol == IPPROTO_UDP && s->received_udp_packet_max < size) |
d74fb368 | 284 | s->received_udp_packet_max = size; |
9df3ba6c TG |
285 | } |
286 | ||
3da3cdd5 | 287 | void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level) { |
9df3ba6c | 288 | assert(s); |
be808ea0 TG |
289 | assert(s->manager); |
290 | ||
6bb2c085 LP |
291 | if (s->possible_feature_level == level) { |
292 | if (protocol == IPPROTO_UDP) | |
313cefa1 | 293 | s->n_failed_udp++; |
5d67a7ae IT |
294 | else if (protocol == IPPROTO_TCP) { |
295 | if (DNS_SERVER_FEATURE_LEVEL_IS_TLS(level)) | |
296 | s->n_failed_tls++; | |
297 | else | |
298 | s->n_failed_tcp++; | |
299 | } | |
6bb2c085 | 300 | } |
9df3ba6c TG |
301 | } |
302 | ||
6bb2c085 LP |
303 | void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level) { |
304 | assert(s); | |
571370c1 | 305 | |
6bb2c085 LP |
306 | /* Invoked whenever we get a packet with TC bit set. */ |
307 | ||
308 | if (s->possible_feature_level != level) | |
571370c1 LP |
309 | return; |
310 | ||
6bb2c085 | 311 | s->packet_truncated = true; |
4e0b8b17 TG |
312 | } |
313 | ||
de54e62b LP |
314 | void dns_server_packet_rrsig_missing(DnsServer *s, DnsServerFeatureLevel level) { |
315 | assert(s); | |
316 | ||
317 | if (level < DNS_SERVER_FEATURE_LEVEL_DO) | |
318 | return; | |
319 | ||
b6451358 LP |
320 | /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */ |
321 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) | |
5d67a7ae | 322 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_IS_TLS(level) ? DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN : DNS_SERVER_FEATURE_LEVEL_EDNS0; |
b6451358 | 323 | |
de54e62b LP |
324 | s->packet_rrsig_missing = true; |
325 | } | |
326 | ||
327 | void dns_server_packet_bad_opt(DnsServer *s, DnsServerFeatureLevel level) { | |
b652d4a2 | 328 | assert(s); |
b652d4a2 | 329 | |
de54e62b LP |
330 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) |
331 | return; | |
b652d4a2 | 332 | |
b6451358 LP |
333 | /* If the OPT RR got lost, we have to downgrade what we previously verified */ |
334 | if (s->verified_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
335 | s->verified_feature_level = DNS_SERVER_FEATURE_LEVEL_EDNS0-1; | |
336 | ||
de54e62b | 337 | s->packet_bad_opt = true; |
b652d4a2 LP |
338 | } |
339 | ||
d001e0a3 LP |
340 | void dns_server_packet_rcode_downgrade(DnsServer *s, DnsServerFeatureLevel level) { |
341 | assert(s); | |
342 | ||
343 | /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level | |
344 | * for the transaction made it go away. In this case we immediately downgrade to the feature level that made | |
345 | * things work. */ | |
346 | ||
347 | if (s->verified_feature_level > level) | |
348 | s->verified_feature_level = level; | |
349 | ||
350 | if (s->possible_feature_level > level) { | |
351 | s->possible_feature_level = level; | |
352 | dns_server_reset_counters(s); | |
353 | } | |
354 | ||
355 | log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s)); | |
356 | } | |
357 | ||
be808ea0 TG |
358 | static bool dns_server_grace_period_expired(DnsServer *s) { |
359 | usec_t ts; | |
360 | ||
361 | assert(s); | |
362 | assert(s->manager); | |
363 | ||
364 | if (s->verified_usec == 0) | |
365 | return false; | |
366 | ||
367 | assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
368 | ||
369 | if (s->verified_usec + s->features_grace_period_usec > ts) | |
370 | return false; | |
371 | ||
372 | s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC); | |
373 | ||
374 | return true; | |
375 | } | |
376 | ||
f4461e56 | 377 | DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s) { |
97277567 LP |
378 | DnsServerFeatureLevel best; |
379 | ||
be808ea0 TG |
380 | assert(s); |
381 | ||
97277567 LP |
382 | /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything |
383 | * better than EDNS0, hence don't even try. */ | |
5d67a7ae | 384 | if (dns_server_get_dnssec_mode(s) != DNSSEC_NO) |
c9299be2 | 385 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
386 | DNS_SERVER_FEATURE_LEVEL_LARGE : |
387 | DNS_SERVER_FEATURE_LEVEL_TLS_DO; | |
388 | else | |
c9299be2 | 389 | best = dns_server_get_dns_over_tls_mode(s) == DNS_OVER_TLS_NO ? |
5d67a7ae IT |
390 | DNS_SERVER_FEATURE_LEVEL_EDNS0 : |
391 | DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN; | |
97277567 LP |
392 | |
393 | /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last | |
394 | * time, hence let's downgrade if we are still at a higher level. */ | |
395 | if (s->possible_feature_level > best) | |
396 | s->possible_feature_level = best; | |
397 | ||
398 | if (s->possible_feature_level < best && dns_server_grace_period_expired(s)) { | |
be808ea0 | 399 | |
97277567 | 400 | s->possible_feature_level = best; |
cc450722 | 401 | |
01184277 LP |
402 | dns_server_reset_counters(s); |
403 | ||
cc450722 LP |
404 | s->packet_bad_opt = false; |
405 | s->packet_rrsig_missing = false; | |
406 | ||
de54e62b | 407 | log_info("Grace period over, resuming full feature set (%s) for DNS server %s.", |
6cb08a89 LP |
408 | dns_server_feature_level_to_string(s->possible_feature_level), |
409 | dns_server_string(s)); | |
6bb2c085 | 410 | |
ce7c8b20 LP |
411 | dns_server_flush_cache(s); |
412 | ||
f4461e56 LP |
413 | } else if (s->possible_feature_level <= s->verified_feature_level) |
414 | s->possible_feature_level = s->verified_feature_level; | |
6bb2c085 LP |
415 | else { |
416 | DnsServerFeatureLevel p = s->possible_feature_level; | |
be808ea0 | 417 | |
6bb2c085 | 418 | if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
de54e62b | 419 | s->possible_feature_level == DNS_SERVER_FEATURE_LEVEL_TCP) { |
6a1a5eec | 420 | |
6bb2c085 LP |
421 | /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't |
422 | * work. Upgrade back to UDP again. */ | |
de54e62b LP |
423 | log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again..."); |
424 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; | |
5d67a7ae IT |
425 | } else if (s->n_failed_tls > 0 && |
426 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level)) { | |
427 | ||
428 | /* We tried to connect using DNS-over-TLS, and it didn't work. Downgrade to plaintext UDP | |
429 | * if we don't require DNS-over-TLS */ | |
de54e62b | 430 | |
3c0dcbcf | 431 | log_debug("Server doesn't support DNS-over-TLS, downgrading protocol..."); |
5d67a7ae | 432 | s->possible_feature_level--; |
de54e62b LP |
433 | } else if (s->packet_bad_opt && |
434 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_EDNS0) { | |
435 | ||
436 | /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below | |
437 | * EDNS0 levels. After all, some records generate different responses with and without OPT RR | |
438 | * in the request. Example: | |
439 | * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */ | |
440 | ||
441 | log_debug("Server doesn't support EDNS(0) properly, downgrading feature level..."); | |
6a1a5eec | 442 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_UDP; |
be808ea0 | 443 | |
de54e62b LP |
444 | } else if (s->packet_rrsig_missing && |
445 | s->possible_feature_level >= DNS_SERVER_FEATURE_LEVEL_DO) { | |
6bb2c085 | 446 | |
de54e62b LP |
447 | /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't |
448 | * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore, | |
449 | * after all some servers generate different replies depending if an OPT RR is in the query or | |
450 | * not. */ | |
451 | ||
452 | log_debug("Detected server responses lack RRSIG records, downgrading feature level..."); | |
5d67a7ae | 453 | 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 |
454 | |
455 | } else if (s->n_failed_udp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && | |
12bf2331 | 456 | s->possible_feature_level >= (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
457 | |
458 | /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the | |
459 | * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good | |
12bf2331 LP |
460 | * idea. We might downgrade all the way down to TCP this way. |
461 | * | |
462 | * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss | |
463 | * might have many reasons, a broken DNSSEC implementation being only one reason. And if the | |
464 | * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */ | |
de54e62b LP |
465 | |
466 | log_debug("Lost too many UDP packets, downgrading feature level..."); | |
467 | s->possible_feature_level--; | |
468 | ||
de54e62b LP |
469 | } else if (s->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS && |
470 | s->packet_truncated && | |
12bf2331 | 471 | s->possible_feature_level > (dns_server_get_dnssec_mode(s) == DNSSEC_YES ? DNS_SERVER_FEATURE_LEVEL_LARGE : DNS_SERVER_FEATURE_LEVEL_UDP)) { |
de54e62b LP |
472 | |
473 | /* We got too many TCP connection failures in a row, we had at least one truncated packet, and | |
474 | * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0 | |
475 | * data we hope to make the packet smaller, so that it still works via UDP given that TCP | |
476 | * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't | |
477 | * go further down, since that's TCP, and TCP failed too often after all. */ | |
478 | ||
479 | log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level..."); | |
480 | s->possible_feature_level--; | |
481 | } | |
482 | ||
6bb2c085 | 483 | if (p != s->possible_feature_level) { |
6bb2c085 LP |
484 | |
485 | /* We changed the feature level, reset the counting */ | |
01184277 | 486 | dns_server_reset_counters(s); |
6bb2c085 | 487 | |
de54e62b | 488 | log_warning("Using degraded feature set (%s) for DNS server %s.", |
6cb08a89 LP |
489 | dns_server_feature_level_to_string(s->possible_feature_level), |
490 | dns_server_string(s)); | |
6bb2c085 | 491 | } |
be808ea0 TG |
492 | } |
493 | ||
f4461e56 | 494 | return s->possible_feature_level; |
be808ea0 TG |
495 | } |
496 | ||
519ef046 LP |
497 | int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level) { |
498 | size_t packet_size; | |
499 | bool edns_do; | |
500 | int r; | |
501 | ||
502 | assert(server); | |
503 | assert(packet); | |
504 | assert(packet->protocol == DNS_PROTOCOL_DNS); | |
505 | ||
506 | /* Fix the OPT field in the packet to match our current feature level. */ | |
507 | ||
508 | r = dns_packet_truncate_opt(packet); | |
509 | if (r < 0) | |
510 | return r; | |
511 | ||
512 | if (level < DNS_SERVER_FEATURE_LEVEL_EDNS0) | |
513 | return 0; | |
514 | ||
515 | edns_do = level >= DNS_SERVER_FEATURE_LEVEL_DO; | |
516 | ||
517 | if (level >= DNS_SERVER_FEATURE_LEVEL_LARGE) | |
518 | packet_size = DNS_PACKET_UNICAST_SIZE_LARGE_MAX; | |
519 | else | |
520 | packet_size = server->received_udp_packet_max; | |
521 | ||
f2ed4c69 | 522 | return dns_packet_append_opt(packet, packet_size, edns_do, 0, NULL); |
519ef046 LP |
523 | } |
524 | ||
2817157b LP |
525 | int dns_server_ifindex(const DnsServer *s) { |
526 | assert(s); | |
527 | ||
528 | /* The link ifindex always takes precedence */ | |
529 | if (s->link) | |
530 | return s->link->ifindex; | |
531 | ||
532 | if (s->ifindex > 0) | |
533 | return s->ifindex; | |
534 | ||
535 | return 0; | |
536 | } | |
537 | ||
6cb08a89 LP |
538 | const char *dns_server_string(DnsServer *server) { |
539 | assert(server); | |
540 | ||
541 | if (!server->server_string) | |
2817157b | 542 | (void) in_addr_ifindex_to_string(server->family, &server->address, dns_server_ifindex(server), &server->server_string); |
6cb08a89 LP |
543 | |
544 | return strna(server->server_string); | |
545 | } | |
546 | ||
92ec902a LP |
547 | bool dns_server_dnssec_supported(DnsServer *server) { |
548 | assert(server); | |
549 | ||
550 | /* Returns whether the server supports DNSSEC according to what we know about it */ | |
551 | ||
552 | if (server->possible_feature_level < DNS_SERVER_FEATURE_LEVEL_DO) | |
553 | return false; | |
554 | ||
de54e62b LP |
555 | if (server->packet_bad_opt) |
556 | return false; | |
557 | ||
558 | if (server->packet_rrsig_missing) | |
92ec902a LP |
559 | return false; |
560 | ||
561 | /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */ | |
562 | if (server->n_failed_tcp >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS) | |
563 | return false; | |
564 | ||
565 | return true; | |
566 | } | |
567 | ||
1e02e182 LP |
568 | void dns_server_warn_downgrade(DnsServer *server) { |
569 | assert(server); | |
570 | ||
571 | if (server->warned_downgrade) | |
572 | return; | |
573 | ||
574 | log_struct(LOG_NOTICE, | |
2b044526 | 575 | "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR, |
1e02e182 LP |
576 | LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)), |
577 | "DNS_SERVER=%s", dns_server_string(server), | |
f4cf1d66 | 578 | "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level)); |
1e02e182 LP |
579 | |
580 | server->warned_downgrade = true; | |
581 | } | |
582 | ||
7a08d314 | 583 | static void dns_server_hash_func(const DnsServer *s, struct siphash *state) { |
b826ab58 | 584 | assert(s); |
87f5a193 | 585 | |
b826ab58 TG |
586 | siphash24_compress(&s->family, sizeof(s->family), state); |
587 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 588 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
589 | } |
590 | ||
7a08d314 | 591 | static int dns_server_compare_func(const DnsServer *x, const DnsServer *y) { |
2817157b | 592 | int r; |
87f5a193 | 593 | |
a0edd02e FB |
594 | r = CMP(x->family, y->family); |
595 | if (r != 0) | |
596 | return r; | |
87f5a193 | 597 | |
2817157b LP |
598 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
599 | if (r != 0) | |
600 | return r; | |
601 | ||
a0edd02e FB |
602 | r = CMP(x->ifindex, y->ifindex); |
603 | if (r != 0) | |
604 | return r; | |
2817157b LP |
605 | |
606 | return 0; | |
87f5a193 | 607 | } |
d5099efc | 608 | |
7a08d314 | 609 | DEFINE_HASH_OPS(dns_server_hash_ops, DnsServer, dns_server_hash_func, dns_server_compare_func); |
636e813d | 610 | |
4b95f179 LP |
611 | void dns_server_unlink_all(DnsServer *first) { |
612 | DnsServer *next; | |
0eac4623 | 613 | |
4b95f179 LP |
614 | if (!first) |
615 | return; | |
0eac4623 | 616 | |
4b95f179 LP |
617 | next = first->servers_next; |
618 | dns_server_unlink(first); | |
636e813d | 619 | |
4b95f179 | 620 | dns_server_unlink_all(next); |
0eac4623 LP |
621 | } |
622 | ||
4b95f179 LP |
623 | void dns_server_unlink_marked(DnsServer *first) { |
624 | DnsServer *next; | |
636e813d | 625 | |
4b95f179 LP |
626 | if (!first) |
627 | return; | |
636e813d | 628 | |
4b95f179 | 629 | next = first->servers_next; |
636e813d | 630 | |
4b95f179 | 631 | if (first->marked) |
0eac4623 | 632 | dns_server_unlink(first); |
636e813d | 633 | |
4b95f179 LP |
634 | dns_server_unlink_marked(next); |
635 | } | |
636e813d | 636 | |
4b95f179 LP |
637 | void dns_server_mark_all(DnsServer *first) { |
638 | if (!first) | |
639 | return; | |
636e813d | 640 | |
4b95f179 LP |
641 | first->marked = true; |
642 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
643 | } |
644 | ||
2817157b | 645 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 646 | DnsServer *s; |
636e813d | 647 | |
636e813d | 648 | LIST_FOREACH(servers, s, first) |
2817157b | 649 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 650 | return s; |
f2f1dbe5 | 651 | |
4b95f179 LP |
652 | return NULL; |
653 | } | |
f2f1dbe5 | 654 | |
4b95f179 | 655 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 656 | assert(m); |
f2f1dbe5 | 657 | |
4b95f179 | 658 | switch (t) { |
f2f1dbe5 | 659 | |
4b95f179 LP |
660 | case DNS_SERVER_SYSTEM: |
661 | return m->dns_servers; | |
f2f1dbe5 | 662 | |
4b95f179 LP |
663 | case DNS_SERVER_FALLBACK: |
664 | return m->fallback_dns_servers; | |
665 | ||
666 | default: | |
667 | return NULL; | |
668 | } | |
f2f1dbe5 LP |
669 | } |
670 | ||
671 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
672 | assert(m); | |
673 | ||
674 | if (m->current_dns_server == s) | |
675 | return s; | |
676 | ||
6cb08a89 | 677 | if (s) |
db8e1324 LP |
678 | log_debug("Switching to %s DNS server %s.", |
679 | dns_server_type_to_string(s->type), | |
680 | dns_server_string(s)); | |
f2f1dbe5 | 681 | |
0eac4623 LP |
682 | dns_server_unref(m->current_dns_server); |
683 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
684 | |
685 | if (m->unicast_scope) | |
686 | dns_cache_flush(&m->unicast_scope->cache); | |
687 | ||
688 | return s; | |
689 | } | |
690 | ||
691 | DnsServer *manager_get_dns_server(Manager *m) { | |
692 | Link *l; | |
693 | assert(m); | |
694 | ||
695 | /* Try to read updates resolv.conf */ | |
696 | manager_read_resolv_conf(m); | |
697 | ||
e3309036 | 698 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
699 | if (!m->current_dns_server) |
700 | manager_set_dns_server(m, m->dns_servers); | |
701 | ||
702 | if (!m->current_dns_server) { | |
703 | bool found = false; | |
704 | Iterator i; | |
705 | ||
706 | /* No DNS servers configured, let's see if there are | |
707 | * any on any links. If not, we use the fallback | |
708 | * servers */ | |
709 | ||
710 | HASHMAP_FOREACH(l, m->links, i) | |
711 | if (l->dns_servers) { | |
712 | found = true; | |
713 | break; | |
714 | } | |
715 | ||
716 | if (!found) | |
717 | manager_set_dns_server(m, m->fallback_dns_servers); | |
718 | } | |
719 | ||
720 | return m->current_dns_server; | |
721 | } | |
722 | ||
723 | void manager_next_dns_server(Manager *m) { | |
724 | assert(m); | |
725 | ||
726 | /* If there's currently no DNS server set, then the next | |
727 | * manager_get_dns_server() will find one */ | |
728 | if (!m->current_dns_server) | |
729 | return; | |
730 | ||
0eac4623 LP |
731 | /* Change to the next one, but make sure to follow the linked |
732 | * list only if the server is still linked. */ | |
733 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
734 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
735 | return; | |
736 | } | |
737 | ||
738 | /* If there was no next one, then start from the beginning of | |
739 | * the list */ | |
740 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
741 | manager_set_dns_server(m, m->fallback_dns_servers); | |
742 | else | |
743 | manager_set_dns_server(m, m->dns_servers); | |
744 | } | |
be808ea0 | 745 | |
b30bf55d LP |
746 | bool dns_server_address_valid(int family, const union in_addr_union *sa) { |
747 | ||
748 | /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */ | |
749 | ||
750 | if (in_addr_is_null(family, sa)) | |
751 | return false; | |
752 | ||
753 | if (family == AF_INET && sa->in.s_addr == htobe32(INADDR_DNS_STUB)) | |
754 | return false; | |
755 | ||
756 | return true; | |
757 | } | |
758 | ||
12bf2331 LP |
759 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
760 | assert(s); | |
761 | ||
762 | if (s->link) | |
763 | return link_get_dnssec_mode(s->link); | |
764 | ||
765 | return manager_get_dnssec_mode(s->manager); | |
766 | } | |
767 | ||
c9299be2 | 768 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { |
5d67a7ae IT |
769 | assert(s); |
770 | ||
d050561a | 771 | if (s->link) |
c9299be2 | 772 | return link_get_dns_over_tls_mode(s->link); |
d050561a | 773 | |
c9299be2 | 774 | return manager_get_dns_over_tls_mode(s->manager); |
5d67a7ae IT |
775 | } |
776 | ||
ce7c8b20 LP |
777 | void dns_server_flush_cache(DnsServer *s) { |
778 | DnsServer *current; | |
779 | DnsScope *scope; | |
780 | ||
781 | assert(s); | |
782 | ||
783 | /* Flush the cache of the scope this server belongs to */ | |
784 | ||
785 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
786 | if (current != s) | |
787 | return; | |
788 | ||
789 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
790 | if (!scope) | |
791 | return; | |
792 | ||
793 | dns_cache_flush(&scope->cache); | |
794 | } | |
795 | ||
59c0fd0e LP |
796 | void dns_server_reset_features(DnsServer *s) { |
797 | assert(s); | |
798 | ||
59c0fd0e LP |
799 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
800 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
801 | ||
802 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
803 | ||
804 | s->packet_bad_opt = false; | |
805 | s->packet_rrsig_missing = false; | |
806 | ||
807 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
808 | ||
809 | s->warned_downgrade = false; | |
810 | ||
811 | dns_server_reset_counters(s); | |
904dcaf9 LP |
812 | |
813 | /* Let's close the default stream, so that we reprobe with the new features */ | |
814 | dns_server_unref_stream(s); | |
59c0fd0e LP |
815 | } |
816 | ||
817 | void dns_server_reset_features_all(DnsServer *s) { | |
818 | DnsServer *i; | |
819 | ||
820 | LIST_FOREACH(servers, i, s) | |
821 | dns_server_reset_features(i); | |
822 | } | |
823 | ||
cf84484a LP |
824 | void dns_server_dump(DnsServer *s, FILE *f) { |
825 | assert(s); | |
826 | ||
827 | if (!f) | |
828 | f = stdout; | |
829 | ||
830 | fputs("[Server ", f); | |
831 | fputs(dns_server_string(s), f); | |
832 | fputs(" type=", f); | |
833 | fputs(dns_server_type_to_string(s->type), f); | |
834 | ||
835 | if (s->type == DNS_SERVER_LINK) { | |
836 | assert(s->link); | |
837 | ||
838 | fputs(" interface=", f); | |
6ff79f76 | 839 | fputs(s->link->ifname, f); |
cf84484a LP |
840 | } |
841 | ||
842 | fputs("]\n", f); | |
843 | ||
844 | fputs("\tVerified feature level: ", f); | |
845 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
846 | fputc('\n', f); | |
847 | ||
848 | fputs("\tPossible feature level: ", f); | |
849 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
850 | fputc('\n', f); | |
851 | ||
852 | fputs("\tDNSSEC Mode: ", f); | |
853 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
854 | fputc('\n', f); | |
855 | ||
856 | fputs("\tCan do DNSSEC: ", f); | |
857 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
858 | fputc('\n', f); | |
859 | ||
860 | fprintf(f, | |
861 | "\tMaximum UDP packet size received: %zu\n" | |
862 | "\tFailed UDP attempts: %u\n" | |
863 | "\tFailed TCP attempts: %u\n" | |
864 | "\tSeen truncated packet: %s\n" | |
865 | "\tSeen OPT RR getting lost: %s\n" | |
866 | "\tSeen RRSIG RR missing: %s\n", | |
867 | s->received_udp_packet_max, | |
868 | s->n_failed_udp, | |
869 | s->n_failed_tcp, | |
870 | yes_no(s->packet_truncated), | |
871 | yes_no(s->packet_bad_opt), | |
872 | yes_no(s->packet_rrsig_missing)); | |
873 | } | |
874 | ||
904dcaf9 LP |
875 | void dns_server_unref_stream(DnsServer *s) { |
876 | DnsStream *ref; | |
877 | ||
878 | assert(s); | |
879 | ||
880 | /* Detaches the default stream of this server. Some special care needs to be taken here, as that stream and | |
881 | * this server reference each other. First, take the stream out of the server. It's destructor will check if it | |
882 | * is registered with us, hence let's invalidate this separatly, so that it is already unregistered. */ | |
883 | ref = TAKE_PTR(s->stream); | |
884 | ||
885 | /* And then, unref it */ | |
886 | dns_stream_unref(ref); | |
887 | } | |
888 | ||
f76fa088 LP |
889 | DnsScope *dns_server_scope(DnsServer *s) { |
890 | assert(s); | |
891 | assert((s->type == DNS_SERVER_LINK) == !!s->link); | |
892 | ||
893 | if (s->link) | |
894 | return s->link->unicast_scope; | |
895 | ||
896 | return s->manager->unicast_scope; | |
897 | } | |
898 | ||
e3309036 ZJS |
899 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
900 | [DNS_SERVER_SYSTEM] = "system", | |
901 | [DNS_SERVER_FALLBACK] = "fallback", | |
902 | [DNS_SERVER_LINK] = "link", | |
903 | }; | |
904 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
905 | ||
be808ea0 TG |
906 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
907 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
908 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 909 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
5d67a7ae | 910 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 911 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 912 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 913 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
914 | }; |
915 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |