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-rw-r--r--src/resolve/resolved-dns-scope.c5
-rw-r--r--src/resolve/resolved-dns-server.c90
-rw-r--r--src/resolve/resolved-dns-server.h26
-rw-r--r--src/resolve/resolved-dns-transaction.c34
-rw-r--r--src/resolve/resolved-dns-transaction.h3
5 files changed, 140 insertions, 18 deletions
diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index fc4ae57ce0..a8c0ae1569 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -243,6 +243,11 @@ static int dns_scope_socket(DnsScope *s, int type, int family, const union in_ad
if (!srv)
return -ESRCH;
+ srv->possible_features = dns_server_possible_features(srv);
+
+ if (type == SOCK_DGRAM && srv->possible_features < DNS_SERVER_FEATURE_LEVEL_UDP)
+ return -EAGAIN;
+
sa.sa.sa_family = srv->family;
if (srv->family == AF_INET) {
sa.in.sin_port = htobe16(port);
diff --git a/src/resolve/resolved-dns-server.c b/src/resolve/resolved-dns-server.c
index 0ebd22fe22..5fc7c3187f 100644
--- a/src/resolve/resolved-dns-server.c
+++ b/src/resolve/resolved-dns-server.c
@@ -23,12 +23,20 @@
#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,
@@ -60,6 +68,9 @@ int dns_server_new(
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->type = type;
s->family = family;
s->address = *in_addr;
@@ -212,18 +223,29 @@ void dns_server_move_back_and_unmark(DnsServer *s) {
}
}
-void dns_server_packet_received(DnsServer *s, usec_t rtt) {
+void dns_server_packet_received(DnsServer *s, DnsServerFeatureLevel features, usec_t rtt) {
assert(s);
- if (rtt <= s->max_rtt)
- return;
+ 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;
- s->max_rtt = rtt;
- s->resend_timeout = MIN(MAX(DNS_TIMEOUT_MIN_USEC, s->max_rtt * 2), DNS_TIMEOUT_MAX_USEC);
+ 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;
@@ -231,6 +253,56 @@ void dns_server_packet_lost(DnsServer *s, usec_t usec) {
s->resend_timeout = MIN(s->resend_timeout * 2, DNS_TIMEOUT_MAX_USEC);
}
+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;
@@ -392,3 +464,9 @@ void manager_next_dns_server(Manager *m) {
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",
+};
+DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel);
diff --git a/src/resolve/resolved-dns-server.h b/src/resolve/resolved-dns-server.h
index 3a78d4a3b5..f82b14e8fb 100644
--- a/src/resolve/resolved-dns-server.h
+++ b/src/resolve/resolved-dns-server.h
@@ -31,8 +31,21 @@ typedef enum DnsServerType {
DNS_SERVER_LINK,
} DnsServerType;
-#include "resolved-manager.h"
+typedef enum DnsServerFeatureLevel {
+ DNS_SERVER_FEATURE_LEVEL_TCP,
+ DNS_SERVER_FEATURE_LEVEL_UDP,
+ _DNS_SERVER_FEATURE_LEVEL_MAX,
+ _DNS_SERVER_FEATURE_LEVEL_INVALID = -1
+} DnsServerFeatureLevel;
+
+#define DNS_SERVER_FEATURE_LEVEL_WORST 0
+#define DNS_SERVER_FEATURE_LEVEL_BEST (_DNS_SERVER_FEATURE_LEVEL_MAX - 1)
+
+const char* dns_server_feature_level_to_string(int i) _const_;
+int dns_server_feature_level_from_string(const char *s) _pure_;
+
#include "resolved-link.h"
+#include "resolved-manager.h"
struct DnsServer {
Manager *manager;
@@ -49,6 +62,11 @@ struct DnsServer {
usec_t max_rtt;
bool marked:1;
+ DnsServerFeatureLevel verified_features;
+ DnsServerFeatureLevel possible_features;
+ unsigned n_failed_attempts;
+ usec_t verified_usec;
+ usec_t features_grace_period_usec;
/* If linked is set, then this server appears in the servers linked list */
bool linked:1;
@@ -69,8 +87,8 @@ DnsServer* dns_server_unref(DnsServer *s);
void dns_server_unlink(DnsServer *s);
void dns_server_move_back_and_unmark(DnsServer *s);
-void dns_server_packet_received(DnsServer *s, usec_t rtt);
-void dns_server_packet_lost(DnsServer *s, usec_t usec);
+void dns_server_packet_received(DnsServer *s, DnsServerFeatureLevel features, usec_t rtt);
+void dns_server_packet_lost(DnsServer *s, DnsServerFeatureLevel features, usec_t usec);
DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr);
@@ -86,4 +104,6 @@ void manager_next_dns_server(Manager *m);
DEFINE_TRIVIAL_CLEANUP_FUNC(DnsServer*, dns_server_unref);
+DnsServerFeatureLevel dns_server_possible_features(DnsServer *s);
+
extern const struct hash_ops dns_server_hash_ops;
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 8c4f23a4da..0e09a339aa 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -418,7 +418,7 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
case DNS_PROTOCOL_DNS:
assert(t->server);
- dns_server_packet_received(t->server, ts - t->start_usec);
+ dns_server_packet_received(t->server, t->current_features, ts - t->start_usec);
break;
case DNS_PROTOCOL_LLMNR:
@@ -534,6 +534,9 @@ static int dns_transaction_emit(DnsTransaction *t) {
if (r < 0)
return r;
+ if (t->server)
+ t->current_features = t->server->possible_features;
+
return 0;
}
@@ -544,15 +547,26 @@ static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdat
assert(s);
assert(t);
- /* Timeout reached? Try again, with a new server */
- dns_transaction_next_dns_server(t);
+ /* Timeout reached? Increase the timeout for the server used */
+ switch (t->scope->protocol) {
+ case DNS_PROTOCOL_DNS:
+ assert(t->server);
- /* ... and possibly increased timeout */
- if (t->server)
- dns_server_packet_lost(t->server, usec - t->start_usec);
- else
+ dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
+
+ break;
+ case DNS_PROTOCOL_LLMNR:
+ case DNS_PROTOCOL_MDNS:
dns_scope_packet_lost(t->scope, usec - t->start_usec);
+ break;
+ default:
+ assert_not_reached("Invalid DNS protocol.");
+ }
+
+ /* ...and try again with a new server */
+ dns_transaction_next_dns_server(t);
+
r = dns_transaction_go(t);
if (r < 0)
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
@@ -734,11 +748,13 @@ int dns_transaction_go(DnsTransaction *t) {
* always be made via TCP on LLMNR */
r = dns_transaction_open_tcp(t);
} else {
- /* Try via UDP, and if that fails due to large size try via TCP */
+ /* Try via UDP, and if that fails due to large size or lack of
+ * support try via TCP */
r = dns_transaction_emit(t);
- if (r == -EMSGSIZE)
+ if (r == -EMSGSIZE || r == -EAGAIN)
r = dns_transaction_open_tcp(t);
}
+
if (r == -ESRCH) {
/* No servers to send this to? */
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index ee80dcf5a9..5778913cc8 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -79,6 +79,9 @@ struct DnsTransaction {
/* The active server */
DnsServer *server;
+ /* the features of the DNS server at time of transaction start */
+ DnsServerFeatureLevel current_features;
+
/* TCP connection logic, if we need it */
DnsStream *stream;
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-12-28 02:57:43 +0000