ikev2: set unidirection transaction flag

rust/src/ikev2/ikev2.rs

@@ -710,7 +710,7 @@ pub unsafe extern "C" fn rs_register_ikev2_parser() {
         get_tx_iterator    : None,
         get_tx_data        : rs_ikev2_get_tx_data,
         apply_tx_config    : None,
-        flags              : 0,
+        flags              : APP_LAYER_PARSER_OPT_UNIDIR_TXS,
         truncate           : None,
     };