diff options
| -rw-r--r-- | src/resolve/resolved-dns-scope.c | 5 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-server.c | 90 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-server.h | 26 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-transaction.c | 34 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-transaction.h | 3 |
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; |