2 This file is part of systemd.
4 Copyright 2014 Lennart Poettering
6 systemd is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as published by
8 the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version.
11 systemd is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public License
17 along with systemd; If not, see <http://www.gnu.org/licenses/>.
20 #include "sd-messages.h"
22 #include "alloc-util.h"
23 #include "resolved-dns-server.h"
24 #include "resolved-dns-stub.h"
25 #include "resolved-resolv-conf.h"
26 #include "siphash24.h"
27 #include "string-table.h"
28 #include "string-util.h"
30 /* After how much time to repeat classic DNS requests */
31 #define DNS_TIMEOUT_MIN_USEC (750 * USEC_PER_MSEC)
32 #define DNS_TIMEOUT_MAX_USEC (5 * USEC_PER_SEC)
34 /* The amount of time to wait before retrying with a full feature set */
35 #define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR)
36 #define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE)
38 /* The number of times we will attempt a certain feature set before degrading */
39 #define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3
47 const union in_addr_union
*in_addr
,
53 assert((type
== DNS_SERVER_LINK
) == !!l
);
56 if (!IN_SET(family
, AF_INET
, AF_INET6
))
60 if (l
->n_dns_servers
>= LINK_DNS_SERVERS_MAX
)
63 if (m
->n_dns_servers
>= MANAGER_DNS_SERVERS_MAX
)
67 s
= new0(DnsServer
, 1);
73 s
->verified_feature_level
= _DNS_SERVER_FEATURE_LEVEL_INVALID
;
74 s
->possible_feature_level
= DNS_SERVER_FEATURE_LEVEL_BEST
;
75 s
->features_grace_period_usec
= DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC
;
76 s
->received_udp_packet_max
= DNS_PACKET_UNICAST_SIZE_MAX
;
79 s
->address
= *in_addr
;
81 s
->resend_timeout
= DNS_TIMEOUT_MIN_USEC
;
87 LIST_APPEND(servers
, l
->dns_servers
, s
);
91 case DNS_SERVER_SYSTEM
:
92 LIST_APPEND(servers
, m
->dns_servers
, s
);
96 case DNS_SERVER_FALLBACK
:
97 LIST_APPEND(servers
, m
->fallback_dns_servers
, s
);
102 assert_not_reached("Unknown server type");
107 /* A new DNS server that isn't fallback is added and the one
108 * we used so far was a fallback one? Then let's try to pick
110 if (type
!= DNS_SERVER_FALLBACK
&&
111 m
->current_dns_server
&&
112 m
->current_dns_server
->type
== DNS_SERVER_FALLBACK
)
113 manager_set_dns_server(m
, NULL
);
121 DnsServer
* dns_server_ref(DnsServer
*s
) {
125 assert(s
->n_ref
> 0);
131 DnsServer
* dns_server_unref(DnsServer
*s
) {
135 assert(s
->n_ref
> 0);
141 free(s
->server_string
);
145 void dns_server_unlink(DnsServer
*s
) {
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. */
158 case DNS_SERVER_LINK
:
160 assert(s
->link
->n_dns_servers
> 0);
161 LIST_REMOVE(servers
, s
->link
->dns_servers
, s
);
162 s
->link
->n_dns_servers
--;
165 case DNS_SERVER_SYSTEM
:
166 assert(s
->manager
->n_dns_servers
> 0);
167 LIST_REMOVE(servers
, s
->manager
->dns_servers
, s
);
168 s
->manager
->n_dns_servers
--;
171 case DNS_SERVER_FALLBACK
:
172 assert(s
->manager
->n_dns_servers
> 0);
173 LIST_REMOVE(servers
, s
->manager
->fallback_dns_servers
, s
);
174 s
->manager
->n_dns_servers
--;
180 if (s
->link
&& s
->link
->current_dns_server
== s
)
181 link_set_dns_server(s
->link
, NULL
);
183 if (s
->manager
->current_dns_server
== s
)
184 manager_set_dns_server(s
->manager
, NULL
);
189 void dns_server_move_back_and_unmark(DnsServer
*s
) {
199 if (!s
->linked
|| !s
->servers_next
)
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. */
207 case DNS_SERVER_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
);
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
);
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
);
227 assert_not_reached("Unknown server type");
231 static void dns_server_verified(DnsServer
*s
, DnsServerFeatureLevel level
) {
234 if (s
->verified_feature_level
> level
)
237 if (s
->verified_feature_level
!= level
) {
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
));
241 s
->verified_feature_level
= level
;
244 assert_se(sd_event_now(s
->manager
->event
, clock_boottime_or_monotonic(), &s
->verified_usec
) >= 0);
247 static void dns_server_reset_counters(DnsServer
*s
) {
252 s
->packet_truncated
= false;
253 s
->verified_usec
= 0;
255 /* Note that we do not reset s->packet_bad_opt and s->packet_rrsig_missing here. We reset them only when the
256 * grace period ends, but not when lowering the possible feature level, as a lower level feature level should
257 * not make RRSIGs appear or OPT appear, but rather make them disappear. If the reappear anyway, then that's
258 * indication for a differently broken OPT/RRSIG implementation, and we really don't want to support that
261 * This is particularly important to deal with certain Belkin routers which break OPT for certain lookups (A),
262 * but pass traffic through for others (AAAA). If we detect the broken behaviour on one lookup we should not
263 * reenable it for another, because we cannot validate things anyway, given that the RRSIG/OPT data will be
267 void dns_server_packet_received(DnsServer
*s
, int protocol
, DnsServerFeatureLevel level
, usec_t rtt
, size_t size
) {
270 if (protocol
== IPPROTO_UDP
) {
271 if (s
->possible_feature_level
== level
)
274 /* If the RRSIG data is missing, then we can only validate EDNS0 at max */
275 if (s
->packet_rrsig_missing
&& level
>= DNS_SERVER_FEATURE_LEVEL_DO
)
276 level
= DNS_SERVER_FEATURE_LEVEL_DO
- 1;
278 /* If the OPT RR got lost, then we can only validate UDP at max */
279 if (s
->packet_bad_opt
&& level
>= DNS_SERVER_FEATURE_LEVEL_EDNS0
)
280 level
= DNS_SERVER_FEATURE_LEVEL_EDNS0
- 1;
282 /* Even if we successfully receive a reply to a request announcing support for large packets,
283 that does not mean we can necessarily receive large packets. */
284 if (level
== DNS_SERVER_FEATURE_LEVEL_LARGE
)
285 level
= DNS_SERVER_FEATURE_LEVEL_LARGE
- 1;
287 } else if (protocol
== IPPROTO_TCP
) {
289 if (s
->possible_feature_level
== level
)
292 /* Successful TCP connections are only useful to verify the TCP feature level. */
293 level
= DNS_SERVER_FEATURE_LEVEL_TCP
;
296 dns_server_verified(s
, level
);
298 /* Remember the size of the largest UDP packet we received from a server,
299 we know that we can always announce support for packets with at least
301 if (protocol
== IPPROTO_UDP
&& s
->received_udp_packet_max
< size
)
302 s
->received_udp_packet_max
= size
;
304 if (s
->max_rtt
< rtt
) {
306 s
->resend_timeout
= CLAMP(s
->max_rtt
* 2, DNS_TIMEOUT_MIN_USEC
, DNS_TIMEOUT_MAX_USEC
);
307 } else if (s
->resend_timeout
> rtt
)
308 /* If we received the packet faster than the resend_timeout, bias
309 * the resend_timeout back to the rtt. */
310 s
->resend_timeout
= CLAMP((2 * s
->resend_timeout
+ rtt
) / 3, DNS_TIMEOUT_MIN_USEC
, DNS_TIMEOUT_MAX_USEC
);
313 void dns_server_packet_lost(DnsServer
*s
, int protocol
, DnsServerFeatureLevel level
, usec_t usec
) {
317 if (s
->possible_feature_level
== level
) {
318 if (protocol
== IPPROTO_UDP
)
320 else if (protocol
== IPPROTO_TCP
)
324 if (s
->resend_timeout
> usec
)
327 s
->resend_timeout
= MIN(s
->resend_timeout
* 2, DNS_TIMEOUT_MAX_USEC
);
330 void dns_server_packet_truncated(DnsServer
*s
, DnsServerFeatureLevel level
) {
333 /* Invoked whenever we get a packet with TC bit set. */
335 if (s
->possible_feature_level
!= level
)
338 s
->packet_truncated
= true;
341 void dns_server_packet_rrsig_missing(DnsServer
*s
, DnsServerFeatureLevel level
) {
344 if (level
< DNS_SERVER_FEATURE_LEVEL_DO
)
347 /* If the RRSIG RRs are missing, we have to downgrade what we previously verified */
348 if (s
->verified_feature_level
>= DNS_SERVER_FEATURE_LEVEL_DO
)
349 s
->verified_feature_level
= DNS_SERVER_FEATURE_LEVEL_DO
-1;
351 s
->packet_rrsig_missing
= true;
354 void dns_server_packet_bad_opt(DnsServer
*s
, DnsServerFeatureLevel level
) {
357 if (level
< DNS_SERVER_FEATURE_LEVEL_EDNS0
)
360 /* If the OPT RR got lost, we have to downgrade what we previously verified */
361 if (s
->verified_feature_level
>= DNS_SERVER_FEATURE_LEVEL_EDNS0
)
362 s
->verified_feature_level
= DNS_SERVER_FEATURE_LEVEL_EDNS0
-1;
364 s
->packet_bad_opt
= true;
367 void dns_server_packet_rcode_downgrade(DnsServer
*s
, DnsServerFeatureLevel level
) {
370 /* Invoked whenever we got a FORMERR, SERVFAIL or NOTIMP rcode from a server and downgrading the feature level
371 * for the transaction made it go away. In this case we immediately downgrade to the feature level that made
374 if (s
->verified_feature_level
> level
)
375 s
->verified_feature_level
= level
;
377 if (s
->possible_feature_level
> level
) {
378 s
->possible_feature_level
= level
;
379 dns_server_reset_counters(s
);
382 log_debug("Downgrading transaction feature level fixed an RCODE error, downgrading server %s too.", dns_server_string(s
));
385 static bool dns_server_grace_period_expired(DnsServer
*s
) {
391 if (s
->verified_usec
== 0)
394 assert_se(sd_event_now(s
->manager
->event
, clock_boottime_or_monotonic(), &ts
) >= 0);
396 if (s
->verified_usec
+ s
->features_grace_period_usec
> ts
)
399 s
->features_grace_period_usec
= MIN(s
->features_grace_period_usec
* 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC
);
404 DnsServerFeatureLevel
dns_server_possible_feature_level(DnsServer
*s
) {
405 DnsServerFeatureLevel best
;
409 /* Determine the best feature level we care about. If DNSSEC mode is off there's no point in using anything
410 * better than EDNS0, hence don't even try. */
411 best
= dns_server_get_dnssec_mode(s
) == DNSSEC_NO
?
412 DNS_SERVER_FEATURE_LEVEL_EDNS0
:
413 DNS_SERVER_FEATURE_LEVEL_BEST
;
415 /* Clamp the feature level the highest level we care about. The DNSSEC mode might have changed since the last
416 * time, hence let's downgrade if we are still at a higher level. */
417 if (s
->possible_feature_level
> best
)
418 s
->possible_feature_level
= best
;
420 if (s
->possible_feature_level
< best
&& dns_server_grace_period_expired(s
)) {
422 s
->possible_feature_level
= best
;
424 dns_server_reset_counters(s
);
426 s
->packet_bad_opt
= false;
427 s
->packet_rrsig_missing
= false;
429 log_info("Grace period over, resuming full feature set (%s) for DNS server %s.",
430 dns_server_feature_level_to_string(s
->possible_feature_level
),
431 dns_server_string(s
));
433 dns_server_flush_cache(s
);
435 } else if (s
->possible_feature_level
<= s
->verified_feature_level
)
436 s
->possible_feature_level
= s
->verified_feature_level
;
438 DnsServerFeatureLevel p
= s
->possible_feature_level
;
440 if (s
->n_failed_tcp
>= DNS_SERVER_FEATURE_RETRY_ATTEMPTS
&&
441 s
->possible_feature_level
== DNS_SERVER_FEATURE_LEVEL_TCP
) {
443 /* We are at the TCP (lowest) level, and we tried a couple of TCP connections, and it didn't
444 * work. Upgrade back to UDP again. */
445 log_debug("Reached maximum number of failed TCP connection attempts, trying UDP again...");
446 s
->possible_feature_level
= DNS_SERVER_FEATURE_LEVEL_UDP
;
448 } else if (s
->packet_bad_opt
&&
449 s
->possible_feature_level
>= DNS_SERVER_FEATURE_LEVEL_EDNS0
) {
451 /* A reply to one of our EDNS0 queries didn't carry a valid OPT RR, then downgrade to below
452 * EDNS0 levels. After all, some records generate different responses with and without OPT RR
453 * in the request. Example:
454 * https://open.nlnetlabs.nl/pipermail/dnssec-trigger/2014-November/000376.html */
456 log_debug("Server doesn't support EDNS(0) properly, downgrading feature level...");
457 s
->possible_feature_level
= DNS_SERVER_FEATURE_LEVEL_UDP
;
459 } else if (s
->packet_rrsig_missing
&&
460 s
->possible_feature_level
>= DNS_SERVER_FEATURE_LEVEL_DO
) {
462 /* RRSIG data was missing on a EDNS0 packet with DO bit set. This means the server doesn't
463 * augment responses with DNSSEC RRs. If so, let's better not ask the server for it anymore,
464 * after all some servers generate different replies depending if an OPT RR is in the query or
467 log_debug("Detected server responses lack RRSIG records, downgrading feature level...");
468 s
->possible_feature_level
= DNS_SERVER_FEATURE_LEVEL_EDNS0
;
470 } else if (s
->n_failed_udp
>= DNS_SERVER_FEATURE_RETRY_ATTEMPTS
&&
471 s
->possible_feature_level
>= (dns_server_get_dnssec_mode(s
) == DNSSEC_YES
? DNS_SERVER_FEATURE_LEVEL_LARGE
: DNS_SERVER_FEATURE_LEVEL_UDP
)) {
473 /* We lost too many UDP packets in a row, and are on a feature level of UDP or higher. If the
474 * packets are lost, maybe the server cannot parse them, hence downgrading sounds like a good
475 * idea. We might downgrade all the way down to TCP this way.
477 * If strict DNSSEC mode is used we won't downgrade below DO level however, as packet loss
478 * might have many reasons, a broken DNSSEC implementation being only one reason. And if the
479 * user is strict on DNSSEC, then let's assume that DNSSEC is not the fault here. */
481 log_debug("Lost too many UDP packets, downgrading feature level...");
482 s
->possible_feature_level
--;
484 } else if (s
->n_failed_tcp
>= DNS_SERVER_FEATURE_RETRY_ATTEMPTS
&&
485 s
->packet_truncated
&&
486 s
->possible_feature_level
> (dns_server_get_dnssec_mode(s
) == DNSSEC_YES
? DNS_SERVER_FEATURE_LEVEL_LARGE
: DNS_SERVER_FEATURE_LEVEL_UDP
)) {
488 /* We got too many TCP connection failures in a row, we had at least one truncated packet, and
489 * are on a feature level above UDP. By downgrading things and getting rid of DNSSEC or EDNS0
490 * data we hope to make the packet smaller, so that it still works via UDP given that TCP
491 * appears not to be a fallback. Note that if we are already at the lowest UDP level, we don't
492 * go further down, since that's TCP, and TCP failed too often after all. */
494 log_debug("Got too many failed TCP connection failures and truncated UDP packets, downgrading feature level...");
495 s
->possible_feature_level
--;
498 if (p
!= s
->possible_feature_level
) {
500 /* We changed the feature level, reset the counting */
501 dns_server_reset_counters(s
);
503 log_warning("Using degraded feature set (%s) for DNS server %s.",
504 dns_server_feature_level_to_string(s
->possible_feature_level
),
505 dns_server_string(s
));
509 return s
->possible_feature_level
;
512 int dns_server_adjust_opt(DnsServer
*server
, DnsPacket
*packet
, DnsServerFeatureLevel level
) {
519 assert(packet
->protocol
== DNS_PROTOCOL_DNS
);
521 /* Fix the OPT field in the packet to match our current feature level. */
523 r
= dns_packet_truncate_opt(packet
);
527 if (level
< DNS_SERVER_FEATURE_LEVEL_EDNS0
)
530 edns_do
= level
>= DNS_SERVER_FEATURE_LEVEL_DO
;
532 if (level
>= DNS_SERVER_FEATURE_LEVEL_LARGE
)
533 packet_size
= DNS_PACKET_UNICAST_SIZE_LARGE_MAX
;
535 packet_size
= server
->received_udp_packet_max
;
537 return dns_packet_append_opt(packet
, packet_size
, edns_do
, 0, NULL
);
540 int dns_server_ifindex(const DnsServer
*s
) {
543 /* The link ifindex always takes precedence */
545 return s
->link
->ifindex
;
553 const char *dns_server_string(DnsServer
*server
) {
556 if (!server
->server_string
)
557 (void) in_addr_ifindex_to_string(server
->family
, &server
->address
, dns_server_ifindex(server
), &server
->server_string
);
559 return strna(server
->server_string
);
562 bool dns_server_dnssec_supported(DnsServer
*server
) {
565 /* Returns whether the server supports DNSSEC according to what we know about it */
567 if (server
->possible_feature_level
< DNS_SERVER_FEATURE_LEVEL_DO
)
570 if (server
->packet_bad_opt
)
573 if (server
->packet_rrsig_missing
)
576 /* DNSSEC servers need to support TCP properly (see RFC5966), if they don't, we assume DNSSEC is borked too */
577 if (server
->n_failed_tcp
>= DNS_SERVER_FEATURE_RETRY_ATTEMPTS
)
583 void dns_server_warn_downgrade(DnsServer
*server
) {
586 if (server
->warned_downgrade
)
589 log_struct(LOG_NOTICE
,
590 "MESSAGE_ID=" SD_MESSAGE_DNSSEC_DOWNGRADE_STR
,
591 LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server
)),
592 "DNS_SERVER=%s", dns_server_string(server
),
593 "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server
->possible_feature_level
),
596 server
->warned_downgrade
= true;
599 bool dns_server_limited_domains(DnsServer
*server
) {
600 DnsSearchDomain
*domain
;
601 bool domain_restricted
= false;
603 /* Check if the server has route-only domains without ~., i. e. whether
604 * it should only be used for particular domains */
608 LIST_FOREACH(domains
, domain
, server
->link
->search_domains
)
609 if (domain
->route_only
) {
610 domain_restricted
= true;
611 /* ~. means "any domain", thus it is a global server */
612 if (dns_name_is_root(DNS_SEARCH_DOMAIN_NAME(domain
)))
616 return domain_restricted
;
619 static void dns_server_hash_func(const void *p
, struct siphash
*state
) {
620 const DnsServer
*s
= p
;
624 siphash24_compress(&s
->family
, sizeof(s
->family
), state
);
625 siphash24_compress(&s
->address
, FAMILY_ADDRESS_SIZE(s
->family
), state
);
626 siphash24_compress(&s
->ifindex
, sizeof(s
->ifindex
), state
);
629 static int dns_server_compare_func(const void *a
, const void *b
) {
630 const DnsServer
*x
= a
, *y
= b
;
633 if (x
->family
< y
->family
)
635 if (x
->family
> y
->family
)
638 r
= memcmp(&x
->address
, &y
->address
, FAMILY_ADDRESS_SIZE(x
->family
));
642 if (x
->ifindex
< y
->ifindex
)
644 if (x
->ifindex
> y
->ifindex
)
650 const struct hash_ops dns_server_hash_ops
= {
651 .hash
= dns_server_hash_func
,
652 .compare
= dns_server_compare_func
655 void dns_server_unlink_all(DnsServer
*first
) {
661 next
= first
->servers_next
;
662 dns_server_unlink(first
);
664 dns_server_unlink_all(next
);
667 void dns_server_unlink_marked(DnsServer
*first
) {
673 next
= first
->servers_next
;
676 dns_server_unlink(first
);
678 dns_server_unlink_marked(next
);
681 void dns_server_mark_all(DnsServer
*first
) {
685 first
->marked
= true;
686 dns_server_mark_all(first
->servers_next
);
689 DnsServer
*dns_server_find(DnsServer
*first
, int family
, const union in_addr_union
*in_addr
, int ifindex
) {
692 LIST_FOREACH(servers
, s
, first
)
693 if (s
->family
== family
&& in_addr_equal(family
, &s
->address
, in_addr
) > 0 && s
->ifindex
== ifindex
)
699 DnsServer
*manager_get_first_dns_server(Manager
*m
, DnsServerType t
) {
704 case DNS_SERVER_SYSTEM
:
705 return m
->dns_servers
;
707 case DNS_SERVER_FALLBACK
:
708 return m
->fallback_dns_servers
;
715 DnsServer
*manager_set_dns_server(Manager
*m
, DnsServer
*s
) {
718 if (m
->current_dns_server
== s
)
722 log_info("Switching to %s DNS server %s.",
723 dns_server_type_to_string(s
->type
),
724 dns_server_string(s
));
726 dns_server_unref(m
->current_dns_server
);
727 m
->current_dns_server
= dns_server_ref(s
);
729 if (m
->unicast_scope
)
730 dns_cache_flush(&m
->unicast_scope
->cache
);
735 DnsServer
*manager_get_dns_server(Manager
*m
) {
739 /* Try to read updates resolv.conf */
740 manager_read_resolv_conf(m
);
742 /* If no DNS server was chosen so far, pick the first one */
743 if (!m
->current_dns_server
)
744 manager_set_dns_server(m
, m
->dns_servers
);
746 if (!m
->current_dns_server
) {
750 /* No DNS servers configured, let's see if there are
751 * any on any links. If not, we use the fallback
754 HASHMAP_FOREACH(l
, m
->links
, i
)
755 if (l
->dns_servers
) {
761 manager_set_dns_server(m
, m
->fallback_dns_servers
);
764 return m
->current_dns_server
;
767 void manager_next_dns_server(Manager
*m
) {
770 /* If there's currently no DNS server set, then the next
771 * manager_get_dns_server() will find one */
772 if (!m
->current_dns_server
)
775 /* Change to the next one, but make sure to follow the linked
776 * list only if the server is still linked. */
777 if (m
->current_dns_server
->linked
&& m
->current_dns_server
->servers_next
) {
778 manager_set_dns_server(m
, m
->current_dns_server
->servers_next
);
782 /* If there was no next one, then start from the beginning of
784 if (m
->current_dns_server
->type
== DNS_SERVER_FALLBACK
)
785 manager_set_dns_server(m
, m
->fallback_dns_servers
);
787 manager_set_dns_server(m
, m
->dns_servers
);
790 bool dns_server_address_valid(int family
, const union in_addr_union
*sa
) {
792 /* Refuses the 0 IP addresses as well as 127.0.0.53 (which is our own DNS stub) */
794 if (in_addr_is_null(family
, sa
))
797 if (family
== AF_INET
&& sa
->in
.s_addr
== htobe32(INADDR_DNS_STUB
))
803 DnssecMode
dns_server_get_dnssec_mode(DnsServer
*s
) {
807 return link_get_dnssec_mode(s
->link
);
809 return manager_get_dnssec_mode(s
->manager
);
812 void dns_server_flush_cache(DnsServer
*s
) {
818 /* Flush the cache of the scope this server belongs to */
820 current
= s
->link
? s
->link
->current_dns_server
: s
->manager
->current_dns_server
;
824 scope
= s
->link
? s
->link
->unicast_scope
: s
->manager
->unicast_scope
;
828 dns_cache_flush(&scope
->cache
);
831 static const char* const dns_server_type_table
[_DNS_SERVER_TYPE_MAX
] = {
832 [DNS_SERVER_SYSTEM
] = "system",
833 [DNS_SERVER_FALLBACK
] = "fallback",
834 [DNS_SERVER_LINK
] = "link",
836 DEFINE_STRING_TABLE_LOOKUP(dns_server_type
, DnsServerType
);
838 static const char* const dns_server_feature_level_table
[_DNS_SERVER_FEATURE_LEVEL_MAX
] = {
839 [DNS_SERVER_FEATURE_LEVEL_TCP
] = "TCP",
840 [DNS_SERVER_FEATURE_LEVEL_UDP
] = "UDP",
841 [DNS_SERVER_FEATURE_LEVEL_EDNS0
] = "UDP+EDNS0",
842 [DNS_SERVER_FEATURE_LEVEL_DO
] = "UDP+EDNS0+DO",
843 [DNS_SERVER_FEATURE_LEVEL_LARGE
] = "UDP+EDNS0+DO+LARGE",
845 DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level
, DnsServerFeatureLevel
);