conf: use static buffer instead of dynamic memory for catalog name

src/knot/conf/conf.c

@@ -204,8 +204,8 @@ conf_val_t conf_zone_get_txn(
 
 	// Check if this is a catalog member zone.
 	if (conf->catalog != NULL) {
-		knot_dname_t *catalog = NULL;
-		int ret = catalog_get_zone_threadsafe(conf->catalog, dname, &catalog);
+		knot_dname_storage_t catalog;
+		int ret = catalog_get_zone_threadsafe(conf->catalog, dname, catalog);
 		if (ret == KNOT_EOK) {
 			conf_db_get(conf, txn, C_ZONE, C_CATALOG_TPL, catalog,
 			            knot_dname_size(catalog), &val);
@@ -215,7 +215,6 @@ conf_val_t conf_zone_get_txn(
 				              knot_strerror(val.code));
 				return val;
 			}
-			knot_dname_free(catalog, NULL);
 			conf_val(&val);
 			conf_db_get(conf, txn, C_TPL, key1_name, val.data, val.len, &val);
 			goto got_template;

src/knot/zone/catalog.c

@@ -260,7 +260,7 @@ int catalog_get_zone(catalog_t *cat, const knot_dname_t *member,
 }
 
 int catalog_get_zone_threadsafe(catalog_t *cat, const knot_dname_t *member,
-                                knot_dname_t **catzone)
+                                knot_dname_storage_t catzone)
 {
 	if (cat->ro_txn == NULL) {
 		return KNOT_ENOENT;
@@ -273,9 +273,8 @@ int catalog_get_zone_threadsafe(catalog_t *cat, const knot_dname_t *member,
 		uint8_t zero, shift;
 		const knot_dname_t *ow = NULL;
 		knot_lmdb_unmake_key(val.mv_data, val.mv_size, "BBN", &zero, &shift, &ow);
-		*catzone = knot_dname_copy(ow + shift, NULL);
-		if (*catzone == NULL) {
-			ret = KNOT_ENOMEM;
+		if (knot_dname_store(catzone, ow + shift) == 0) {
+			ret = KNOT_EINVAL;
 		}
 		free(val.mv_data);
 	}

src/knot/zone/catalog.h

@@ -179,7 +179,7 @@ int catalog_get_zone(catalog_t *cat, const knot_dname_t *member,
  * \return KNOT_E*
  */
 int catalog_get_zone_threadsafe(catalog_t *cat, const knot_dname_t *member,
-                                knot_dname_t **catzone);
+                                knot_dname_storage_t catzone);
 
 /*!
  * \brief Find specific member record in catalog database.