Merge pull request #17821 from poettering/local-address-fix

fix ipv4/ipv6 NXDOMAIN/NODATA confusion for synthesized local addresses

src/resolve/resolved-dns-synthesize.c

@@ -322,8 +322,24 @@ static int synthesize_gateway_rr(Manager *m, const DnsResourceKey *key, int ifin
         af = dns_type_to_af(key->type);
         if (af >= 0) {
                 n = local_gateways(m->rtnl, ifindex, af, &addresses);
-                if (n <= 0)
-                        return n;  /* < 0 means: error; == 0 means we have no gateway */
+                if (n < 0) /* < 0 means: error */
+                        return n;
+
+                if (n == 0) { /* == 0 means we have no gateway */
+                        /* See if there's a gateway on the other protocol */
+                        if (af == AF_INET)
+                                n = local_gateways(m->rtnl, ifindex, AF_INET6, NULL);
+                        else {
+                                assert(af == AF_INET6);
+                                n = local_gateways(m->rtnl, ifindex, AF_INET, NULL);
+                        }
+                        if (n <= 0) /* error (if < 0) or really no gateway at all (if == 0) */
+                                return n;
+
+                        /* We have a gateway on the other protocol. Let's return > 0 without adding any RR to
+                         * the answer, i.e. synthesize NODATA (and not NXDOMAIN!) */
+                        return 1;
+                }
         }
 
         r = answer_add_addresses_rr(answer, dns_resource_key_name(key), addresses, n);

src/resolve/resolved-dns-transaction.c

@@ -1712,7 +1712,7 @@ int dns_transaction_go(DnsTransaction *t) {
                 if (r == -EMSGSIZE)
                         log_debug("Sending query via TCP since it is too large.");
                 else if (r == -EAGAIN)
-                        log_debug("Sending query via TCP since UDP isn't supported.");
+                        log_debug("Sending query via TCP since UDP isn't supported or DNS-over-TLS is selected.");
                 if (IN_SET(r, -EMSGSIZE, -EAGAIN))
                         r = dns_transaction_emit_tcp(t);
         }

src/shared/local-addresses.c

@@ -41,8 +41,6 @@ int local_addresses(sd_netlink *context, int ifindex, int af, struct local_addre
         sd_netlink_message *m;
         int r;
 
-        assert(ret);
-
         if (context)
                 rtnl = sd_netlink_ref(context);
         else {
@@ -135,9 +133,10 @@ int local_addresses(sd_netlink *context, int ifindex, int af, struct local_addre
                 n_list++;
         };
 
-        typesafe_qsort(list, n_list, address_compare);
-
-        *ret = TAKE_PTR(list);
+        if (ret) {
+                typesafe_qsort(list, n_list, address_compare);
+                *ret = TAKE_PTR(list);
+        }
 
         return (int) n_list;
 }
@@ -179,8 +178,6 @@ int local_gateways(sd_netlink *context, int ifindex, int af, struct local_addres
         size_t n_list = 0, n_allocated = 0;
         int r;
 
-        assert(ret);
-
         if (context)
                 rtnl = sd_netlink_ref(context);
         else {
@@ -309,9 +306,10 @@ int local_gateways(sd_netlink *context, int ifindex, int af, struct local_addres
                 }
         }
 
-        typesafe_qsort(list, n_list, address_compare);
-
-        *ret = TAKE_PTR(list);
+        if (ret) {
+                typesafe_qsort(list, n_list, address_compare);
+                *ret = TAKE_PTR(list);
+        }
 
         return (int) n_list;
 }