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Diffstat (limited to 'src/resolve/resolved-dns-transaction.c')
-rw-r--r--src/resolve/resolved-dns-transaction.c75
1 files changed, 58 insertions, 17 deletions
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 06e7145422..d455b6b1fa 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -214,6 +214,7 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key)
t->answer_nsec_ttl = (uint32_t) -1;
t->key = dns_resource_key_ref(key);
t->current_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID;
+ t->clamp_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID;
t->id = pick_new_id(s->manager);
@@ -378,22 +379,38 @@ static int dns_transaction_pick_server(DnsTransaction *t) {
assert(t);
assert(t->scope->protocol == DNS_PROTOCOL_DNS);
+ /* Pick a DNS server and a feature level for it. */
+
server = dns_scope_get_dns_server(t->scope);
if (!server)
return -ESRCH;
+ /* If we changed the server invalidate the feature level clamping, as the new server might have completely
+ * different properties. */
+ if (server != t->server)
+ t->clamp_feature_level = _DNS_SERVER_FEATURE_LEVEL_INVALID;
+
t->current_feature_level = dns_server_possible_feature_level(server);
+ /* Clamp the feature level if that is requested. */
+ if (t->clamp_feature_level != _DNS_SERVER_FEATURE_LEVEL_INVALID &&
+ t->current_feature_level > t->clamp_feature_level)
+ t->current_feature_level = t->clamp_feature_level;
+
+ log_debug("Using feature level %s for transaction %u.", dns_server_feature_level_to_string(t->current_feature_level), t->id);
+
if (server == t->server)
return 0;
dns_server_unref(t->server);
t->server = dns_server_ref(server);
+ log_debug("Using DNS server %s for transaction %u.", dns_server_string(t->server), t->id);
+
return 1;
}
-static void dns_transaction_retry(DnsTransaction *t) {
+static void dns_transaction_retry(DnsTransaction *t, bool next_server) {
int r;
assert(t);
@@ -401,7 +418,8 @@ static void dns_transaction_retry(DnsTransaction *t) {
log_debug("Retrying transaction %" PRIu16 ".", t->id);
/* Before we try again, switch to a new server. */
- dns_scope_next_dns_server(t->scope);
+ if (next_server)
+ dns_scope_next_dns_server(t->scope);
r = dns_transaction_go(t);
if (r < 0) {
@@ -467,7 +485,7 @@ static int on_stream_complete(DnsStream *s, int error) {
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &usec) >= 0);
dns_server_packet_lost(t->server, IPPROTO_TCP, t->current_feature_level, usec - t->start_usec);
- dns_transaction_retry(t);
+ dns_transaction_retry(t, true);
return 0;
}
if (error != 0) {
@@ -645,14 +663,15 @@ static int dns_transaction_dnssec_ready(DnsTransaction *t) {
return 0;
case DNS_TRANSACTION_RCODE_FAILURE:
- if (dt->answer_rcode != DNS_RCODE_NXDOMAIN) {
+ if (!IN_SET(dt->answer_rcode, DNS_RCODE_NXDOMAIN, DNS_RCODE_SERVFAIL)) {
log_debug("Auxiliary DNSSEC RR query failed with rcode=%s.", dns_rcode_to_string(dt->answer_rcode));
goto fail;
}
- /* Fall-through: NXDOMAIN is good enough for us. This is because some DNS servers erronously
- * return NXDOMAIN for empty non-terminals (Akamai...), and we need to handle that nicely, when
- * asking for parent SOA or similar RRs to make unsigned proofs. */
+ /* Fall-through: NXDOMAIN/SERVFAIL is good enough for us. This is because some DNS servers
+ * erronously return NXDOMAIN/SERVFAIL for empty non-terminals (Akamai...) or missing DS
+ * records (Facebook), and we need to handle that nicely, when asking for parent SOA or similar
+ * RRs to make unsigned proofs. */
case DNS_TRANSACTION_SUCCESS:
/* All good. */
@@ -889,10 +908,22 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
if (IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_FORMERR, DNS_RCODE_SERVFAIL, DNS_RCODE_NOTIMP)) {
/* Request failed, immediately try again with reduced features */
- log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p)));
- dns_server_packet_failed(t->server, t->current_feature_level);
- dns_transaction_retry(t);
+ if (t->current_feature_level <= DNS_SERVER_FEATURE_LEVEL_WORST) {
+ /* This was already at the lowest possible feature level? If so, we can't downgrade
+ * this transaction anymore, hence let's process the response, and accept the rcode. */
+ log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p)));
+ break;
+ }
+
+ /* Reduce this feature level by one and try again. */
+ t->clamp_feature_level = t->current_feature_level - 1;
+
+ log_debug("Server returned error %s, retrying transaction with reduced feature level %s.",
+ dns_rcode_to_string(DNS_PACKET_RCODE(p)),
+ dns_server_feature_level_to_string(t->clamp_feature_level));
+
+ dns_transaction_retry(t, false /* use the same server */);
return;
} else if (DNS_PACKET_TC(p))
dns_server_packet_truncated(t->server, t->current_feature_level);
@@ -937,7 +968,7 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
goto fail;
/* On DNS, couldn't send? Try immediately again, with a new server */
- dns_transaction_retry(t);
+ dns_transaction_retry(t, true);
}
return;
@@ -950,11 +981,19 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
return;
}
- /* Report that the OPT RR was missing */
if (t->server) {
+ /* Report that we successfully received a valid packet with a good rcode after we initially got a bad
+ * rcode and subsequently downgraded the protocol */
+
+ if (IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN) &&
+ t->clamp_feature_level != _DNS_SERVER_FEATURE_LEVEL_INVALID)
+ dns_server_packet_rcode_downgrade(t->server, t->clamp_feature_level);
+
+ /* Report that the OPT RR was missing */
if (!p->opt)
dns_server_packet_bad_opt(t->server, t->current_feature_level);
+ /* Report that we successfully received a packet */
dns_server_packet_received(t->server, p->ipproto, t->current_feature_level, ts - t->start_usec, p->size);
}
@@ -1041,7 +1080,7 @@ static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *use
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &usec) >= 0);
dns_server_packet_lost(t->server, IPPROTO_UDP, t->current_feature_level, usec - t->start_usec);
- dns_transaction_retry(t);
+ dns_transaction_retry(t, true);
return 0;
}
if (r < 0) {
@@ -1150,7 +1189,7 @@ static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdat
log_debug("Timeout reached on transaction %" PRIu16 ".", t->id);
- dns_transaction_retry(t);
+ dns_transaction_retry(t, true);
return 0;
}
@@ -1781,8 +1820,10 @@ static bool dns_transaction_dnssec_supported(DnsTransaction *t) {
if (!t->server)
return true;
- if (t->current_feature_level < DNS_SERVER_FEATURE_LEVEL_DO)
- return false;
+ /* Note that we do not check the feature level actually used for the transaction but instead the feature level
+ * the server is known to support currently, as the transaction feature level might be lower than what the
+ * server actually supports, since we might have downgraded this transaction's feature level because we got a
+ * SERVFAIL earlier and wanted to check whether downgrading fixes it. */
return dns_server_dnssec_supported(t->server);
}
@@ -2874,7 +2915,7 @@ int dns_transaction_validate_dnssec(DnsTransaction *t) {
if (!dns_transaction_dnssec_supported_full(t)) {
/* The server does not support DNSSEC, or doesn't augment responses with RRSIGs. */
t->answer_dnssec_result = DNSSEC_INCOMPATIBLE_SERVER;
- log_debug("Not validating response for %" PRIu16 ", server lacks DNSSEC support.", t->id);
+ log_debug("Not validating response for %" PRIu16 ", used server feature level does not support DNSSEC.", t->id);
return 0;
}
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-29 23:27:07 +0000