-void format_odp_action(struct ds *, const union odp_action *);
-void format_odp_actions(struct ds *, const union odp_action *actions,
- size_t n_actions);
-void format_odp_flow_stats(struct ds *, const struct odp_flow_stats *);
-void format_odp_flow(struct ds *, const struct odp_flow *);
+int odp_action_len(uint16_t type);
+void format_odp_action(struct ds *, const struct nlattr *);
+void format_odp_actions(struct ds *, const struct nlattr *odp_actions,
+ size_t actions_len);
+
+/* By my calculations currently the longest valid nlattr-formatted flow key is
+ * 80 bytes long, so this leaves some safety margin.
+ *
+ * We allocate temporary on-stack buffers for flow keys as arrays of uint32_t
+ * to ensure proper 32-bit alignment for Netlink attributes. (An array of
+ * "struct nlattr" might not, in theory, be sufficiently aligned because it
+ * only contains 16-bit types.) */
+#define ODPUTIL_FLOW_KEY_BYTES 96
+#define ODPUTIL_FLOW_KEY_U32S DIV_ROUND_UP(ODPUTIL_FLOW_KEY_BYTES, 4)
+
+void odp_flow_key_format(const struct nlattr *, size_t, struct ds *);
+
+void odp_flow_key_from_flow(struct ofpbuf *, const struct flow *);
+int odp_flow_key_to_flow(const struct nlattr *, size_t, struct flow *);