resolved: log recognizably about DNSSEC downgrades

If we downgrade from DNSSEC to non-DNSSEC mode, let's log about this in a recognizable way (i.e. with a message ID),
after all, this is of major importance.

3 files changed, 29 insertions, 1 deletions

diff --git a/src/resolve/resolved-dns-server.c b/src/resolve/resolved-dns-server.c
index 5a86661807..e1d2025863 100644
--- a/src/resolve/resolved-dns-server.c
+++ b/src/resolve/resolved-dns-server.c
@@ -19,6 +19,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <sd-messages.h>
+
 #include "alloc-util.h"
 #include "resolved-dns-server.h"
 #include "resolved-resolv-conf.h"
@@ -547,6 +549,22 @@ bool dns_server_dnssec_supported(DnsServer *server) {
         return true;
 }
 
+void dns_server_warn_downgrade(DnsServer *server) {
+        assert(server);
+
+        if (server->warned_downgrade)
+                return;
+
+        log_struct(LOG_NOTICE,
+                   LOG_MESSAGE_ID(SD_MESSAGE_DNSSEC_DOWNGRADE),
+                   LOG_MESSAGE("Server %s does not support DNSSEC, downgrading to non-DNSSEC mode.", dns_server_string(server)),
+                   "DNS_SERVER=%s", dns_server_string(server),
+                   "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(server->possible_feature_level),
+                   NULL);
+
+        server->warned_downgrade = true;
+}
+
 static void dns_server_hash_func(const void *p, struct siphash *state) {
         const DnsServer *s = p;
 
diff --git a/src/resolve/resolved-dns-server.h b/src/resolve/resolved-dns-server.h
index 02bd3463a7..2a3c921678 100644
--- a/src/resolve/resolved-dns-server.h
+++ b/src/resolve/resolved-dns-server.h
@@ -82,6 +82,9 @@ struct DnsServer {
         usec_t verified_usec;
         usec_t features_grace_period_usec;
 
+        /* Whether we already warned about downgrading to non-DNSSEC mode for this server */
+        bool warned_downgrade:1;
+
         /* Used when GC'ing old DNS servers when configuration changes. */
         bool marked:1;
 
@@ -119,6 +122,8 @@ const char *dns_server_string(DnsServer *server);
 
 bool dns_server_dnssec_supported(DnsServer *server);
 
+void dns_server_warn_downgrade(DnsServer *server);
+
 DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr);
 
 void dns_server_unlink_all(DnsServer *first);
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 43ee783ba9..02269498c9 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -296,6 +296,8 @@ void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {
                            "DNS_TRANSACTION=%" PRIu16, t->id,
                            "DNS_QUESTION=%s", dns_transaction_key_string(t),
                            "DNSSEC_RESULT=%s", dnssec_result_to_string(t->answer_dnssec_result),
+                           "DNS_SERVER=%s", dns_server_string(t->server),
+                           "DNS_SERVER_FEATURE_LEVEL=%s", dns_server_feature_level_to_string(t->server->possible_feature_level),
                            NULL);
 
         /* Note that this call might invalidate the query. Callers
@@ -708,6 +710,9 @@ static void dns_transaction_process_dnssec(DnsTransaction *t) {
                 return;
         }
 
+        if (t->answer_dnssec_result == DNSSEC_INCOMPATIBLE_SERVER)
+                dns_server_warn_downgrade(t->server);
+
         dns_transaction_cache_answer(t);
 
         if (t->answer_rcode == DNS_RCODE_SUCCESS)
@@ -2568,7 +2573,7 @@ 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, server lacks DNSSEC support.");
+                log_debug("Not validating response for %" PRIu16 ", server lacks DNSSEC support.", t->id);
                 return 0;
         }