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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" |
4a6f996c | 6 | #include "resolved-bus.h" |
74b2466e | 7 | #include "resolved-dns-server.h" |
b30bf55d | 8 | #include "resolved-dns-stub.h" |
f2f1dbe5 | 9 | #include "resolved-resolv-conf.h" |
b5efdb8a | 10 | #include "siphash24.h" |
be808ea0 | 11 | #include "string-table.h" |
f2f1dbe5 | 12 | #include "string-util.h" |
74b2466e | 13 | |
be808ea0 TG |
14 | /* The amount of time to wait before retrying with a full feature set */ |
15 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR) | |
16 | #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE) | |
17 | ||
18 | /* The number of times we will attempt a certain feature set before degrading */ | |
19 | #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3 | |
20 | ||
74b2466e LP |
21 | int dns_server_new( |
22 | Manager *m, | |
23 | DnsServer **ret, | |
4e945a6f | 24 | DnsServerType type, |
74b2466e | 25 | Link *l, |
0dd25fb9 | 26 | int family, |
2817157b LP |
27 | const union in_addr_union *in_addr, |
28 | int ifindex) { | |
74b2466e | 29 | |
eed857b7 | 30 | DnsServer *s; |
74b2466e LP |
31 | |
32 | assert(m); | |
4e945a6f | 33 | assert((type == DNS_SERVER_LINK) == !!l); |
74b2466e | 34 | assert(in_addr); |
74b2466e | 35 | |
eed857b7 LP |
36 | if (!IN_SET(family, AF_INET, AF_INET6)) |
37 | return -EAFNOSUPPORT; | |
38 | ||
39 | if (l) { | |
40 | if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX) | |
41 | return -E2BIG; | |
42 | } else { | |
43 | if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX) | |
44 | return -E2BIG; | |
45 | } | |
46 | ||
65b0179a | 47 | s = new(DnsServer, 1); |
74b2466e LP |
48 | if (!s) |
49 | return -ENOMEM; | |
50 | ||
65b0179a LP |
51 | *s = (DnsServer) { |
52 | .n_ref = 1, | |
53 | .manager = m, | |
54 | .type = type, | |
55 | .family = family, | |
56 | .address = *in_addr, | |
57 | .ifindex = ifindex, | |
58 | }; | |
59c0fd0e LP |
59 | |
60 | dns_server_reset_features(s); | |
74b2466e | 61 | |
0b58db65 LP |
62 | switch (type) { |
63 | ||
64 | case DNS_SERVER_LINK: | |
65 | s->link = l; | |
eed857b7 LP |
66 | LIST_APPEND(servers, l->dns_servers, s); |
67 | l->n_dns_servers++; | |
0b58db65 LP |
68 | break; |
69 | ||
70 | case DNS_SERVER_SYSTEM: | |
eed857b7 LP |
71 | LIST_APPEND(servers, m->dns_servers, s); |
72 | m->n_dns_servers++; | |
0b58db65 LP |
73 | break; |
74 | ||
75 | case DNS_SERVER_FALLBACK: | |
eed857b7 LP |
76 | LIST_APPEND(servers, m->fallback_dns_servers, s); |
77 | m->n_dns_servers++; | |
0b58db65 LP |
78 | break; |
79 | ||
80 | default: | |
4e945a6f | 81 | assert_not_reached("Unknown server type"); |
0b58db65 | 82 | } |
74b2466e | 83 | |
0eac4623 | 84 | s->linked = true; |
74b2466e | 85 | |
4e945a6f LP |
86 | /* A new DNS server that isn't fallback is added and the one |
87 | * we used so far was a fallback one? Then let's try to pick | |
88 | * the new one */ | |
89 | if (type != DNS_SERVER_FALLBACK && | |
3e684349 LP |
90 | m->current_dns_server && |
91 | m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
92 | manager_set_dns_server(m, NULL); | |
4e945a6f | 93 | |
74b2466e LP |
94 | if (ret) |
95 | *ret = s; | |
96 | ||
97 | return 0; | |
98 | } | |
99 | ||
8301aa0b YW |
100 | static DnsServer* dns_server_free(DnsServer *s) { |
101 | assert(s); | |
74b2466e | 102 | |
904dcaf9 | 103 | dns_server_unref_stream(s); |
98767d75 | 104 | |
56ddbf10 | 105 | #if ENABLE_DNS_OVER_TLS |
6016fcb0 | 106 | dnstls_server_free(s); |
5d67a7ae IT |
107 | #endif |
108 | ||
6cb08a89 | 109 | free(s->server_string); |
6b430fdb | 110 | return mfree(s); |
74b2466e | 111 | } |
87f5a193 | 112 | |
8301aa0b YW |
113 | DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsServer, dns_server, dns_server_free); |
114 | ||
0eac4623 LP |
115 | void dns_server_unlink(DnsServer *s) { |
116 | assert(s); | |
117 | assert(s->manager); | |
91b14d6f | 118 | |
0eac4623 LP |
119 | /* This removes the specified server from the linked list of |
120 | * servers, but any server might still stay around if it has | |
121 | * refs, for example from an ongoing transaction. */ | |
91b14d6f | 122 | |
0eac4623 LP |
123 | if (!s->linked) |
124 | return; | |
91b14d6f | 125 | |
0eac4623 LP |
126 | switch (s->type) { |
127 | ||
128 | case DNS_SERVER_LINK: | |
129 | assert(s->link); | |
eed857b7 | 130 | assert(s->link->n_dns_servers > 0); |
0eac4623 | 131 | LIST_REMOVE(servers, s->link->dns_servers, s); |
0e3e1aef | 132 | s->link->n_dns_servers--; |
0eac4623 LP |
133 | break; |
134 | ||
135 | case DNS_SERVER_SYSTEM: | |
eed857b7 | 136 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 137 | LIST_REMOVE(servers, s->manager->dns_servers, s); |
eed857b7 | 138 | s->manager->n_dns_servers--; |
0eac4623 LP |
139 | break; |
140 | ||
141 | case DNS_SERVER_FALLBACK: | |
eed857b7 | 142 | assert(s->manager->n_dns_servers > 0); |
0eac4623 | 143 | LIST_REMOVE(servers, s->manager->fallback_dns_servers, s); |
eed857b7 | 144 | s->manager->n_dns_servers--; |
0eac4623 | 145 | break; |
df0fbad0 YW |
146 | default: |
147 | assert_not_reached("Unknown server type"); | |
0eac4623 LP |
148 | } |
149 | ||
150 | s->linked = false; | |
151 | ||
152 | if (s->link && s->link->current_dns_server == s) | |
153 | link_set_dns_server(s->link, NULL); | |
154 | ||
155 | if (s->manager->current_dns_server == s) | |
156 | manager_set_dns_server(s->manager, NULL); | |
157 | ||
904dcaf9 LP |
158 | /* No need to keep a default stream around anymore */ |
159 | dns_server_unref_stream(s); | |
160 | ||
0eac4623 | 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 | |
5238e957 | 239 | * re-enable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be |
d001e0a3 LP |
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 | 422 | } else if (s->n_failed_tls > 0 && |
4310bfc2 | 423 | DNS_SERVER_FEATURE_LEVEL_IS_TLS(s->possible_feature_level) && dns_server_get_dns_over_tls_mode(s) != DNS_OVER_TLS_YES) { |
5d67a7ae IT |
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 | ||
7a08d314 | 580 | static void dns_server_hash_func(const DnsServer *s, struct siphash *state) { |
b826ab58 | 581 | assert(s); |
87f5a193 | 582 | |
b826ab58 TG |
583 | siphash24_compress(&s->family, sizeof(s->family), state); |
584 | siphash24_compress(&s->address, FAMILY_ADDRESS_SIZE(s->family), state); | |
2817157b | 585 | siphash24_compress(&s->ifindex, sizeof(s->ifindex), state); |
87f5a193 LP |
586 | } |
587 | ||
7a08d314 | 588 | static int dns_server_compare_func(const DnsServer *x, const DnsServer *y) { |
2817157b | 589 | int r; |
87f5a193 | 590 | |
a0edd02e FB |
591 | r = CMP(x->family, y->family); |
592 | if (r != 0) | |
593 | return r; | |
87f5a193 | 594 | |
2817157b LP |
595 | r = memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family)); |
596 | if (r != 0) | |
597 | return r; | |
598 | ||
a0edd02e FB |
599 | r = CMP(x->ifindex, y->ifindex); |
600 | if (r != 0) | |
601 | return r; | |
2817157b LP |
602 | |
603 | return 0; | |
87f5a193 | 604 | } |
d5099efc | 605 | |
7a08d314 | 606 | DEFINE_HASH_OPS(dns_server_hash_ops, DnsServer, dns_server_hash_func, dns_server_compare_func); |
636e813d | 607 | |
4b95f179 LP |
608 | void dns_server_unlink_all(DnsServer *first) { |
609 | DnsServer *next; | |
0eac4623 | 610 | |
4b95f179 LP |
611 | if (!first) |
612 | return; | |
0eac4623 | 613 | |
4b95f179 LP |
614 | next = first->servers_next; |
615 | dns_server_unlink(first); | |
636e813d | 616 | |
4b95f179 | 617 | dns_server_unlink_all(next); |
0eac4623 LP |
618 | } |
619 | ||
4b95f179 LP |
620 | void dns_server_unlink_marked(DnsServer *first) { |
621 | DnsServer *next; | |
636e813d | 622 | |
4b95f179 LP |
623 | if (!first) |
624 | return; | |
636e813d | 625 | |
4b95f179 | 626 | next = first->servers_next; |
636e813d | 627 | |
4b95f179 | 628 | if (first->marked) |
0eac4623 | 629 | dns_server_unlink(first); |
636e813d | 630 | |
4b95f179 LP |
631 | dns_server_unlink_marked(next); |
632 | } | |
636e813d | 633 | |
4b95f179 LP |
634 | void dns_server_mark_all(DnsServer *first) { |
635 | if (!first) | |
636 | return; | |
636e813d | 637 | |
4b95f179 LP |
638 | first->marked = true; |
639 | dns_server_mark_all(first->servers_next); | |
636e813d LP |
640 | } |
641 | ||
2817157b | 642 | DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr, int ifindex) { |
4b95f179 | 643 | DnsServer *s; |
636e813d | 644 | |
636e813d | 645 | LIST_FOREACH(servers, s, first) |
2817157b | 646 | if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0 && s->ifindex == ifindex) |
4b95f179 | 647 | return s; |
f2f1dbe5 | 648 | |
4b95f179 LP |
649 | return NULL; |
650 | } | |
f2f1dbe5 | 651 | |
4b95f179 | 652 | DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) { |
f2f1dbe5 | 653 | assert(m); |
f2f1dbe5 | 654 | |
4b95f179 | 655 | switch (t) { |
f2f1dbe5 | 656 | |
4b95f179 LP |
657 | case DNS_SERVER_SYSTEM: |
658 | return m->dns_servers; | |
f2f1dbe5 | 659 | |
4b95f179 LP |
660 | case DNS_SERVER_FALLBACK: |
661 | return m->fallback_dns_servers; | |
662 | ||
663 | default: | |
664 | return NULL; | |
665 | } | |
f2f1dbe5 LP |
666 | } |
667 | ||
668 | DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) { | |
669 | assert(m); | |
670 | ||
671 | if (m->current_dns_server == s) | |
672 | return s; | |
673 | ||
6cb08a89 | 674 | if (s) |
db8e1324 LP |
675 | log_debug("Switching to %s DNS server %s.", |
676 | dns_server_type_to_string(s->type), | |
677 | dns_server_string(s)); | |
f2f1dbe5 | 678 | |
0eac4623 LP |
679 | dns_server_unref(m->current_dns_server); |
680 | m->current_dns_server = dns_server_ref(s); | |
f2f1dbe5 LP |
681 | |
682 | if (m->unicast_scope) | |
683 | dns_cache_flush(&m->unicast_scope->cache); | |
684 | ||
4a6f996c ZJS |
685 | (void) manager_send_changed(m, "CurrentDNSServer"); |
686 | ||
f2f1dbe5 LP |
687 | return s; |
688 | } | |
689 | ||
690 | DnsServer *manager_get_dns_server(Manager *m) { | |
691 | Link *l; | |
692 | assert(m); | |
693 | ||
694 | /* Try to read updates resolv.conf */ | |
695 | manager_read_resolv_conf(m); | |
696 | ||
e3309036 | 697 | /* If no DNS server was chosen so far, pick the first one */ |
f2f1dbe5 LP |
698 | if (!m->current_dns_server) |
699 | manager_set_dns_server(m, m->dns_servers); | |
700 | ||
701 | if (!m->current_dns_server) { | |
702 | bool found = false; | |
703 | Iterator i; | |
704 | ||
705 | /* No DNS servers configured, let's see if there are | |
706 | * any on any links. If not, we use the fallback | |
707 | * servers */ | |
708 | ||
709 | HASHMAP_FOREACH(l, m->links, i) | |
710 | if (l->dns_servers) { | |
711 | found = true; | |
712 | break; | |
713 | } | |
714 | ||
715 | if (!found) | |
716 | manager_set_dns_server(m, m->fallback_dns_servers); | |
717 | } | |
718 | ||
719 | return m->current_dns_server; | |
720 | } | |
721 | ||
722 | void manager_next_dns_server(Manager *m) { | |
723 | assert(m); | |
724 | ||
725 | /* If there's currently no DNS server set, then the next | |
726 | * manager_get_dns_server() will find one */ | |
727 | if (!m->current_dns_server) | |
728 | return; | |
729 | ||
0eac4623 LP |
730 | /* Change to the next one, but make sure to follow the linked |
731 | * list only if the server is still linked. */ | |
732 | if (m->current_dns_server->linked && m->current_dns_server->servers_next) { | |
f2f1dbe5 LP |
733 | manager_set_dns_server(m, m->current_dns_server->servers_next); |
734 | return; | |
735 | } | |
736 | ||
737 | /* If there was no next one, then start from the beginning of | |
738 | * the list */ | |
739 | if (m->current_dns_server->type == DNS_SERVER_FALLBACK) | |
740 | manager_set_dns_server(m, m->fallback_dns_servers); | |
741 | else | |
742 | manager_set_dns_server(m, m->dns_servers); | |
743 | } | |
be808ea0 | 744 | |
12bf2331 LP |
745 | DnssecMode dns_server_get_dnssec_mode(DnsServer *s) { |
746 | assert(s); | |
747 | ||
748 | if (s->link) | |
749 | return link_get_dnssec_mode(s->link); | |
750 | ||
751 | return manager_get_dnssec_mode(s->manager); | |
752 | } | |
753 | ||
c9299be2 | 754 | DnsOverTlsMode dns_server_get_dns_over_tls_mode(DnsServer *s) { |
5d67a7ae IT |
755 | assert(s); |
756 | ||
d050561a | 757 | if (s->link) |
c9299be2 | 758 | return link_get_dns_over_tls_mode(s->link); |
d050561a | 759 | |
c9299be2 | 760 | return manager_get_dns_over_tls_mode(s->manager); |
5d67a7ae IT |
761 | } |
762 | ||
ce7c8b20 LP |
763 | void dns_server_flush_cache(DnsServer *s) { |
764 | DnsServer *current; | |
765 | DnsScope *scope; | |
766 | ||
767 | assert(s); | |
768 | ||
769 | /* Flush the cache of the scope this server belongs to */ | |
770 | ||
771 | current = s->link ? s->link->current_dns_server : s->manager->current_dns_server; | |
772 | if (current != s) | |
773 | return; | |
774 | ||
775 | scope = s->link ? s->link->unicast_scope : s->manager->unicast_scope; | |
776 | if (!scope) | |
777 | return; | |
778 | ||
779 | dns_cache_flush(&scope->cache); | |
780 | } | |
781 | ||
59c0fd0e LP |
782 | void dns_server_reset_features(DnsServer *s) { |
783 | assert(s); | |
784 | ||
59c0fd0e LP |
785 | s->verified_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID; |
786 | s->possible_feature_level = DNS_SERVER_FEATURE_LEVEL_BEST; | |
787 | ||
788 | s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX; | |
789 | ||
790 | s->packet_bad_opt = false; | |
791 | s->packet_rrsig_missing = false; | |
792 | ||
793 | s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC; | |
794 | ||
795 | s->warned_downgrade = false; | |
796 | ||
797 | dns_server_reset_counters(s); | |
904dcaf9 LP |
798 | |
799 | /* Let's close the default stream, so that we reprobe with the new features */ | |
800 | dns_server_unref_stream(s); | |
59c0fd0e LP |
801 | } |
802 | ||
803 | void dns_server_reset_features_all(DnsServer *s) { | |
804 | DnsServer *i; | |
805 | ||
806 | LIST_FOREACH(servers, i, s) | |
807 | dns_server_reset_features(i); | |
808 | } | |
809 | ||
cf84484a LP |
810 | void dns_server_dump(DnsServer *s, FILE *f) { |
811 | assert(s); | |
812 | ||
813 | if (!f) | |
814 | f = stdout; | |
815 | ||
816 | fputs("[Server ", f); | |
817 | fputs(dns_server_string(s), f); | |
818 | fputs(" type=", f); | |
819 | fputs(dns_server_type_to_string(s->type), f); | |
820 | ||
821 | if (s->type == DNS_SERVER_LINK) { | |
822 | assert(s->link); | |
823 | ||
824 | fputs(" interface=", f); | |
6ff79f76 | 825 | fputs(s->link->ifname, f); |
cf84484a LP |
826 | } |
827 | ||
828 | fputs("]\n", f); | |
829 | ||
830 | fputs("\tVerified feature level: ", f); | |
831 | fputs(strna(dns_server_feature_level_to_string(s->verified_feature_level)), f); | |
832 | fputc('\n', f); | |
833 | ||
834 | fputs("\tPossible feature level: ", f); | |
835 | fputs(strna(dns_server_feature_level_to_string(s->possible_feature_level)), f); | |
836 | fputc('\n', f); | |
837 | ||
838 | fputs("\tDNSSEC Mode: ", f); | |
839 | fputs(strna(dnssec_mode_to_string(dns_server_get_dnssec_mode(s))), f); | |
840 | fputc('\n', f); | |
841 | ||
842 | fputs("\tCan do DNSSEC: ", f); | |
843 | fputs(yes_no(dns_server_dnssec_supported(s)), f); | |
844 | fputc('\n', f); | |
845 | ||
846 | fprintf(f, | |
847 | "\tMaximum UDP packet size received: %zu\n" | |
848 | "\tFailed UDP attempts: %u\n" | |
849 | "\tFailed TCP attempts: %u\n" | |
850 | "\tSeen truncated packet: %s\n" | |
851 | "\tSeen OPT RR getting lost: %s\n" | |
852 | "\tSeen RRSIG RR missing: %s\n", | |
853 | s->received_udp_packet_max, | |
854 | s->n_failed_udp, | |
855 | s->n_failed_tcp, | |
856 | yes_no(s->packet_truncated), | |
857 | yes_no(s->packet_bad_opt), | |
858 | yes_no(s->packet_rrsig_missing)); | |
859 | } | |
860 | ||
904dcaf9 LP |
861 | void dns_server_unref_stream(DnsServer *s) { |
862 | DnsStream *ref; | |
863 | ||
864 | assert(s); | |
865 | ||
866 | /* Detaches the default stream of this server. Some special care needs to be taken here, as that stream and | |
867 | * this server reference each other. First, take the stream out of the server. It's destructor will check if it | |
5238e957 | 868 | * is registered with us, hence let's invalidate this separately, so that it is already unregistered. */ |
904dcaf9 LP |
869 | ref = TAKE_PTR(s->stream); |
870 | ||
871 | /* And then, unref it */ | |
872 | dns_stream_unref(ref); | |
873 | } | |
874 | ||
f76fa088 LP |
875 | DnsScope *dns_server_scope(DnsServer *s) { |
876 | assert(s); | |
877 | assert((s->type == DNS_SERVER_LINK) == !!s->link); | |
878 | ||
879 | if (s->link) | |
880 | return s->link->unicast_scope; | |
881 | ||
882 | return s->manager->unicast_scope; | |
883 | } | |
884 | ||
e3309036 ZJS |
885 | static const char* const dns_server_type_table[_DNS_SERVER_TYPE_MAX] = { |
886 | [DNS_SERVER_SYSTEM] = "system", | |
887 | [DNS_SERVER_FALLBACK] = "fallback", | |
888 | [DNS_SERVER_LINK] = "link", | |
889 | }; | |
890 | DEFINE_STRING_TABLE_LOOKUP(dns_server_type, DnsServerType); | |
891 | ||
be808ea0 TG |
892 | static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = { |
893 | [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP", | |
894 | [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP", | |
9c5e12a4 | 895 | [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0", |
5d67a7ae | 896 | [DNS_SERVER_FEATURE_LEVEL_TLS_PLAIN] = "TLS+EDNS0", |
7586f4d1 | 897 | [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO", |
d74fb368 | 898 | [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE", |
5d67a7ae | 899 | [DNS_SERVER_FEATURE_LEVEL_TLS_DO] = "TLS+EDNS0+D0", |
be808ea0 TG |
900 | }; |
901 | DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel); |