+#define IFEF_CLAT46 0x00001000 /* CLAT46 RFC 6877 */
+
+#define IS_INTF_CLAT46(ifp) ((ifp) != NULL && ((ifp)->if_eflags & IFEF_CLAT46))
+#define INTF_ADJUST_MTU_FOR_CLAT46(intf) \
+ (IS_INTF_CLAT46((intf)) || \
+ IS_INTF_CLAT46((intf)->if_delegated.ifp)) \
+