#include "resolved-dns-server.h"
#include "resolved-resolv-conf.h"
#include "siphash24.h"
+#include "string-table.h"
#include "string-util.h"
/* After how much time to repeat classic DNS requests */
#define DNS_TIMEOUT_MIN_USEC (500 * USEC_PER_MSEC)
#define DNS_TIMEOUT_MAX_USEC (5 * USEC_PER_SEC)
+/* The amount of time to wait before retrying with a full feature set */
+#define DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC (6 * USEC_PER_HOUR)
+#define DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC (5 * USEC_PER_MINUTE)
+
+/* The number of times we will attempt a certain feature set before degrading */
+#define DNS_SERVER_FEATURE_RETRY_ATTEMPTS 3
+
int dns_server_new(
Manager *m,
DnsServer **ret,
int family,
const union in_addr_union *in_addr) {
- DnsServer *s, *tail;
+ DnsServer *s;
assert(m);
assert((type == DNS_SERVER_LINK) == !!l);
assert(in_addr);
+ if (!IN_SET(family, AF_INET, AF_INET6))
+ return -EAFNOSUPPORT;
+
+ if (l) {
+ if (l->n_dns_servers >= LINK_DNS_SERVERS_MAX)
+ return -E2BIG;
+ } else {
+ if (m->n_dns_servers >= MANAGER_DNS_SERVERS_MAX)
+ return -E2BIG;
+ }
+
s = new0(DnsServer, 1);
if (!s)
return -ENOMEM;
s->n_ref = 1;
+ s->manager = m;
+ s->verified_features = _DNS_SERVER_FEATURE_LEVEL_INVALID;
+ s->possible_features = DNS_SERVER_FEATURE_LEVEL_BEST;
+ s->features_grace_period_usec = DNS_SERVER_FEATURE_GRACE_PERIOD_MIN_USEC;
+ s->received_udp_packet_max = DNS_PACKET_UNICAST_SIZE_MAX;
s->type = type;
s->family = family;
s->address = *in_addr;
s->resend_timeout = DNS_TIMEOUT_MIN_USEC;
- if (type == DNS_SERVER_LINK) {
- LIST_FIND_TAIL(servers, l->dns_servers, tail);
- LIST_INSERT_AFTER(servers, l->dns_servers, tail, s);
+ switch (type) {
+
+ case DNS_SERVER_LINK:
s->link = l;
- } else if (type == DNS_SERVER_SYSTEM) {
- LIST_FIND_TAIL(servers, m->dns_servers, tail);
- LIST_INSERT_AFTER(servers, m->dns_servers, tail, s);
- } else if (type == DNS_SERVER_FALLBACK) {
- LIST_FIND_TAIL(servers, m->fallback_dns_servers, tail);
- LIST_INSERT_AFTER(servers, m->fallback_dns_servers, tail, s);
- } else
+ LIST_APPEND(servers, l->dns_servers, s);
+ l->n_dns_servers++;
+ break;
+
+ case DNS_SERVER_SYSTEM:
+ LIST_APPEND(servers, m->dns_servers, s);
+ m->n_dns_servers++;
+ break;
+
+ case DNS_SERVER_FALLBACK:
+ LIST_APPEND(servers, m->fallback_dns_servers, s);
+ m->n_dns_servers++;
+ break;
+
+ default:
assert_not_reached("Unknown server type");
+ }
- s->manager = m;
+ s->linked = true;
/* A new DNS server that isn't fallback is added and the one
* we used so far was a fallback one? Then let's try to pick
return NULL;
assert(s->n_ref > 0);
-
s->n_ref ++;
return s;
}
-static DnsServer* dns_server_free(DnsServer *s) {
+DnsServer* dns_server_unref(DnsServer *s) {
if (!s)
return NULL;
- if (s->link && s->link->current_dns_server == s)
- link_set_dns_server(s->link, NULL);
+ assert(s->n_ref > 0);
+ s->n_ref --;
- if (s->manager && s->manager->current_dns_server == s)
- manager_set_dns_server(s->manager, NULL);
+ if (s->n_ref > 0)
+ return NULL;
free(s);
-
return NULL;
}
-DnsServer* dns_server_unref(DnsServer *s) {
- if (!s)
- return NULL;
+void dns_server_unlink(DnsServer *s) {
+ assert(s);
+ assert(s->manager);
- assert(s->n_ref > 0);
+ /* This removes the specified server from the linked list of
+ * servers, but any server might still stay around if it has
+ * refs, for example from an ongoing transaction. */
- if (s->n_ref == 1)
- dns_server_free(s);
- else
- s->n_ref --;
+ if (!s->linked)
+ return;
- return NULL;
+ switch (s->type) {
+
+ case DNS_SERVER_LINK:
+ assert(s->link);
+ assert(s->link->n_dns_servers > 0);
+ LIST_REMOVE(servers, s->link->dns_servers, s);
+ break;
+
+ case DNS_SERVER_SYSTEM:
+ assert(s->manager->n_dns_servers > 0);
+ LIST_REMOVE(servers, s->manager->dns_servers, s);
+ s->manager->n_dns_servers--;
+ break;
+
+ case DNS_SERVER_FALLBACK:
+ assert(s->manager->n_dns_servers > 0);
+ LIST_REMOVE(servers, s->manager->fallback_dns_servers, s);
+ s->manager->n_dns_servers--;
+ break;
+ }
+
+ s->linked = false;
+
+ if (s->link && s->link->current_dns_server == s)
+ link_set_dns_server(s->link, NULL);
+
+ if (s->manager->current_dns_server == s)
+ manager_set_dns_server(s->manager, NULL);
+
+ dns_server_unref(s);
}
-void dns_server_packet_received(DnsServer *s, usec_t rtt) {
+void dns_server_move_back_and_unmark(DnsServer *s) {
+ DnsServer *tail;
+
assert(s);
- if (rtt <= s->max_rtt)
+ if (!s->marked)
+ return;
+
+ s->marked = false;
+
+ if (!s->linked || !s->servers_next)
return;
- s->max_rtt = rtt;
- s->resend_timeout = MIN(MAX(DNS_TIMEOUT_MIN_USEC, s->max_rtt * 2), DNS_TIMEOUT_MAX_USEC);
+ /* Move us to the end of the list, so that the order is
+ * strictly kept, if we are not at the end anyway. */
+
+ switch (s->type) {
+
+ case DNS_SERVER_LINK:
+ assert(s->link);
+ LIST_FIND_TAIL(servers, s, tail);
+ LIST_REMOVE(servers, s->link->dns_servers, s);
+ LIST_INSERT_AFTER(servers, s->link->dns_servers, tail, s);
+ break;
+
+ case DNS_SERVER_SYSTEM:
+ LIST_FIND_TAIL(servers, s, tail);
+ LIST_REMOVE(servers, s->manager->dns_servers, s);
+ LIST_INSERT_AFTER(servers, s->manager->dns_servers, tail, s);
+ break;
+
+ case DNS_SERVER_FALLBACK:
+ LIST_FIND_TAIL(servers, s, tail);
+ LIST_REMOVE(servers, s->manager->fallback_dns_servers, s);
+ LIST_INSERT_AFTER(servers, s->manager->fallback_dns_servers, tail, s);
+ break;
+
+ default:
+ assert_not_reached("Unknown server type");
+ }
+}
+
+void dns_server_packet_received(DnsServer *s, DnsServerFeatureLevel features, usec_t rtt, size_t size) {
+ assert(s);
+
+ if (features == DNS_SERVER_FEATURE_LEVEL_LARGE) {
+ /* even if we successfully receive a reply to a request announcing
+ support for large packets, that does not mean we can necessarily
+ receive large packets. */
+ if (s->verified_features < DNS_SERVER_FEATURE_LEVEL_LARGE - 1) {
+ s->verified_features = DNS_SERVER_FEATURE_LEVEL_LARGE - 1;
+ assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0);
+ }
+ } else if (s->verified_features < features) {
+ s->verified_features = features;
+ assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &s->verified_usec) >= 0);
+ }
+
+ if (s->possible_features == features)
+ s->n_failed_attempts = 0;
+
+ /* Remember the size of the largest UDP packet we received from a server,
+ we know that we can always announce support for packets with at least
+ this size. */
+ if (s->received_udp_packet_max < size)
+ s->received_udp_packet_max = size;
+
+ if (s->max_rtt < rtt) {
+ s->max_rtt = rtt;
+ s->resend_timeout = MIN(MAX(DNS_TIMEOUT_MIN_USEC, s->max_rtt * 2), DNS_TIMEOUT_MAX_USEC);
+ }
}
-void dns_server_packet_lost(DnsServer *s, usec_t usec) {
+void dns_server_packet_lost(DnsServer *s, DnsServerFeatureLevel features, usec_t usec) {
assert(s);
+ assert(s->manager);
+
+ if (s->possible_features == features)
+ s->n_failed_attempts ++;
if (s->resend_timeout > usec)
return;
s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC);
}
+void dns_server_packet_failed(DnsServer *s, DnsServerFeatureLevel features) {
+ assert(s);
+ assert(s->manager);
+
+ if (s->possible_features != features)
+ return;
+
+ s->n_failed_attempts = (unsigned) -1;
+}
+
+static bool dns_server_grace_period_expired(DnsServer *s) {
+ usec_t ts;
+
+ assert(s);
+ assert(s->manager);
+
+ if (s->verified_usec == 0)
+ return false;
+
+ assert_se(sd_event_now(s->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
+
+ if (s->verified_usec + s->features_grace_period_usec > ts)
+ return false;
+
+ s->features_grace_period_usec = MIN(s->features_grace_period_usec * 2, DNS_SERVER_FEATURE_GRACE_PERIOD_MAX_USEC);
+
+ return true;
+}
+
+DnsServerFeatureLevel dns_server_possible_features(DnsServer *s) {
+ assert(s);
+
+ if (s->possible_features != DNS_SERVER_FEATURE_LEVEL_BEST &&
+ dns_server_grace_period_expired(s)) {
+ _cleanup_free_ char *ip = NULL;
+
+ s->possible_features = DNS_SERVER_FEATURE_LEVEL_BEST;
+ s->n_failed_attempts = 0;
+ s->verified_usec = 0;
+
+ in_addr_to_string(s->family, &s->address, &ip);
+ log_info("Grace period over, resuming full feature set for DNS server %s", strna(ip));
+ } else if (s->possible_features <= s->verified_features)
+ s->possible_features = s->verified_features;
+ else if (s->n_failed_attempts >= DNS_SERVER_FEATURE_RETRY_ATTEMPTS &&
+ s->possible_features > DNS_SERVER_FEATURE_LEVEL_WORST) {
+ _cleanup_free_ char *ip = NULL;
+
+ s->possible_features --;
+ s->n_failed_attempts = 0;
+ s->verified_usec = 0;
+
+ in_addr_to_string(s->family, &s->address, &ip);
+ log_warning("Using degraded feature set (%s) for DNS server %s",
+ dns_server_feature_level_to_string(s->possible_features), strna(ip));
+ }
+
+ return s->possible_features;
+}
+
static void dns_server_hash_func(const void *p, struct siphash *state) {
const DnsServer *s = p;
.compare = dns_server_compare_func
};
-void manager_flush_dns_servers(Manager *m, DnsServerType type) {
- DnsServer **first, *s;
+void dns_server_unlink_all(DnsServer *first) {
+ DnsServer *next;
- assert(m);
-
- first = type == DNS_SERVER_FALLBACK ? &m->fallback_dns_servers : &m->dns_servers;
+ if (!first)
+ return;
- while (*first) {
- s = *first;
+ next = first->servers_next;
+ dns_server_unlink(first);
- LIST_REMOVE(servers, *first, s);
- dns_server_unref(s);
- }
+ dns_server_unlink_all(next);
}
-void manager_flush_marked_dns_servers(Manager *m, DnsServerType type) {
- DnsServer **first, *s, *next;
+void dns_server_unlink_marked(DnsServer *first) {
+ DnsServer *next;
- assert(m);
+ if (!first)
+ return;
- first = type == DNS_SERVER_FALLBACK ? &m->fallback_dns_servers : &m->dns_servers;
+ next = first->servers_next;
- LIST_FOREACH_SAFE(servers, s, next, *first) {
- if (!s->marked)
- continue;
+ if (first->marked)
+ dns_server_unlink(first);
- LIST_REMOVE(servers, *first, s);
- dns_server_unref(s);
- }
+ dns_server_unlink_marked(next);
}
-void manager_mark_dns_servers(Manager *m, DnsServerType type) {
- DnsServer *first, *s;
+void dns_server_mark_all(DnsServer *first) {
+ if (!first)
+ return;
- assert(m);
+ first->marked = true;
+ dns_server_mark_all(first->servers_next);
+}
- first = type == DNS_SERVER_FALLBACK ? m->fallback_dns_servers : m->dns_servers;
+DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr) {
+ DnsServer *s;
LIST_FOREACH(servers, s, first)
- s->marked = true;
-}
+ if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0)
+ return s;
-DnsServer* manager_find_dns_server(Manager *m, int family, const union in_addr_union *in_addr) {
- DnsServer *s;
+ return NULL;
+}
+DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t) {
assert(m);
- assert(in_addr);
- LIST_FOREACH(servers, s, m->dns_servers)
- if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0)
- return s;
+ switch (t) {
- LIST_FOREACH(servers, s, m->fallback_dns_servers)
- if (s->family == family && in_addr_equal(family, &s->address, in_addr) > 0)
- return s;
+ case DNS_SERVER_SYSTEM:
+ return m->dns_servers;
- return NULL;
+ case DNS_SERVER_FALLBACK:
+ return m->fallback_dns_servers;
+
+ default:
+ return NULL;
+ }
}
DnsServer *manager_set_dns_server(Manager *m, DnsServer *s) {
log_info("Switching to system DNS server %s.", strna(ip));
}
- m->current_dns_server = s;
+ dns_server_unref(m->current_dns_server);
+ m->current_dns_server = dns_server_ref(s);
if (m->unicast_scope)
dns_cache_flush(&m->unicast_scope->cache);
if (!m->current_dns_server)
return;
- /* Change to the next one */
- if (m->current_dns_server->servers_next) {
+ /* Change to the next one, but make sure to follow the linked
+ * list only if the server is still linked. */
+ if (m->current_dns_server->linked && m->current_dns_server->servers_next) {
manager_set_dns_server(m, m->current_dns_server->servers_next);
return;
}
else
manager_set_dns_server(m, m->dns_servers);
}
+
+static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVEL_MAX] = {
+ [DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP",
+ [DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP",
+ [DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0",
+ [DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO",
+ [DNS_SERVER_FEATURE_LEVEL_LARGE] = "UDP+EDNS0+DO+LARGE",
+};
+DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel);
projects / thirdparty / systemd.git / blobdiff