void classifier_destroy(struct classifier *);
bool classifier_is_empty(const struct classifier *);
int classifier_count(const struct classifier *);
-struct cls_rule *classifier_insert(struct classifier *, struct cls_rule *);
+void classifier_insert(struct classifier *, struct cls_rule *);
+struct cls_rule *classifier_replace(struct classifier *, struct cls_rule *);
void classifier_remove(struct classifier *, struct cls_rule *);
struct cls_rule *classifier_lookup(const struct classifier *,
const struct flow *);