+
+void dns_zone_item_conflict(DnsZoneItem *i) {
+ _cleanup_free_ char *pretty = NULL;
+
+ assert(i);
+
+ if (!IN_SET(i->state, DNS_ZONE_ITEM_PROBING, DNS_ZONE_ITEM_VERIFYING, DNS_ZONE_ITEM_ESTABLISHED))
+ return;
+
+ dns_resource_record_to_string(i->rr, &pretty);
+ log_info("Detected conflict on %s", strna(pretty));
+
+ dns_zone_item_probe_stop(i);
+
+ /* Withdraw the conflict item */
+ i->state = DNS_ZONE_ITEM_WITHDRAWN;
+
+ /* Maybe change the hostname */
+ if (dns_name_equal(i->scope->manager->hostname, DNS_RESOURCE_KEY_NAME(i->rr->key)) > 0)
+ manager_next_hostname(i->scope->manager);
+}
+
+void dns_zone_item_ready(DnsZoneItem *i) {
+ _cleanup_free_ char *pretty = NULL;
+
+ assert(i);
+ assert(i->probe_transaction);
+
+ if (i->block_ready > 0)
+ return;
+
+ if (IN_SET(i->probe_transaction->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING))
+ return;
+
+ if (i->probe_transaction->state == DNS_TRANSACTION_SUCCESS) {
+ bool we_lost = false;
+
+ /* The probe got a successful reply. If we so far
+ * weren't established we just give up. If we already
+ * were established, and the peer has the
+ * lexicographically larger IP address we continue
+ * and defend it. */
+
+ if (!IN_SET(i->state, DNS_ZONE_ITEM_ESTABLISHED, DNS_ZONE_ITEM_VERIFYING)) {
+ log_debug("Got a successful probe for not yet established RR, we lost.");
+ we_lost = true;
+ } else {
+ assert(i->probe_transaction->received);
+ we_lost = memcmp(&i->probe_transaction->received->sender, &i->probe_transaction->received->destination, FAMILY_ADDRESS_SIZE(i->probe_transaction->received->family)) < 0;
+ if (we_lost)
+ log_debug("Got a successful probe reply for an established RR, and we have a lexicographically larger IP address and thus lost.");
+ }
+
+ if (we_lost) {
+ dns_zone_item_conflict(i);
+ return;
+ }
+
+ log_debug("Got a successful probe reply, but peer has lexicographically lower IP address and thus lost.");
+ }
+
+ dns_resource_record_to_string(i->rr, &pretty);
+ log_debug("Record %s successfully probed.", strna(pretty));
+
+ dns_zone_item_probe_stop(i);
+ i->state = DNS_ZONE_ITEM_ESTABLISHED;
+}
+
+static int dns_zone_item_verify(DnsZoneItem *i) {
+ _cleanup_free_ char *pretty = NULL;
+ int r;
+
+ assert(i);
+
+ if (i->state != DNS_ZONE_ITEM_ESTABLISHED)
+ return 0;
+
+ dns_resource_record_to_string(i->rr, &pretty);
+ log_debug("Verifying RR %s", strna(pretty));
+
+ i->state = DNS_ZONE_ITEM_VERIFYING;
+ r = dns_zone_item_probe_start(i);
+ if (r < 0) {
+ log_error_errno(r, "Failed to start probing for verifying RR: %m");
+ i->state = DNS_ZONE_ITEM_ESTABLISHED;
+ return r;
+ }
+
+ return 0;
+}
+
+int dns_zone_check_conflicts(DnsZone *zone, DnsResourceRecord *rr) {
+ DnsZoneItem *i, *first;
+ int c = 0;
+
+ assert(zone);
+ assert(rr);
+
+ /* This checks whether a response RR we received from somebody
+ * else is one that we actually thought was uniquely ours. If
+ * so, we'll verify our RRs. */
+
+ /* No conflict if we don't have the name at all. */
+ first = hashmap_get(zone->by_name, DNS_RESOURCE_KEY_NAME(rr->key));
+ if (!first)
+ return 0;
+
+ /* No conflict if we have the exact same RR */
+ if (dns_zone_get(zone, rr))
+ return 0;
+
+ /* OK, somebody else has RRs for the same name. Yuck! Let's
+ * start probing again */
+
+ LIST_FOREACH(by_name, i, first) {
+ if (dns_resource_record_equal(i->rr, rr))
+ continue;
+
+ dns_zone_item_verify(i);
+ c++;
+ }
+
+ return c;
+}
+
+int dns_zone_verify_conflicts(DnsZone *zone, DnsResourceKey *key) {
+ DnsZoneItem *i, *first;
+ int c = 0;
+
+ assert(zone);
+
+ /* Somebody else notified us about a possible conflict. Let's
+ * verify if that's true. */
+
+ first = hashmap_get(zone->by_name, DNS_RESOURCE_KEY_NAME(key));
+ if (!first)
+ return 0;
+
+ LIST_FOREACH(by_name, i, first) {
+ dns_zone_item_verify(i);
+ c++;
+ }
+
+ return c;
+}
+
+void dns_zone_verify_all(DnsZone *zone) {
+ DnsZoneItem *i;
+ Iterator iterator;
+
+ assert(zone);
+
+ HASHMAP_FOREACH(i, zone->by_key, iterator) {
+ DnsZoneItem *j;
+
+ LIST_FOREACH(by_key, j, i)
+ dns_zone_item_verify(j);
+ }
+}