-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);
+
+/* Upper bound on the length of a nlattr-formatted flow key. The longest
+ * nlattr-formatted flow key would be:
+ *
+ * struct pad nl hdr total
+ * ------ --- ------ -----
+ * ODP_KEY_ATTR_TUN_ID 8 -- 4 12
+ * ODP_KEY_ATTR_IN_PORT 4 -- 4 8
+ * ODP_KEY_ATTR_ETHERNET 12 -- 4 16
+ * ODP_KEY_ATTR_8021Q 4 -- 4 8
+ * ODP_KEY_ATTR_ETHERTYPE 2 2 4 8
+ * ODP_KEY_ATTR_IPV6 34 2 4 40
+ * ODP_KEY_ATTR_ICMPV6 2 2 4 8
+ * ODP_KEY_ATTR_ND 28 -- 4 32
+ * -------------------------------------------------
+ * total 132
+ */
+#define ODPUTIL_FLOW_KEY_BYTES 132
+
+/* This is an imperfect sanity-check that ODPUTIL_FLOW_KEY_BYTES doesn't
+ * need to be updated, but will at least raise awareness when new ODP
+ * key types are added. */
+BUILD_ASSERT_DECL(__ODP_KEY_ATTR_MAX == 14);
+
+/* A buffer with sufficient size and alignment to hold an nlattr-formatted flow
+ * key. An array of "struct nlattr" might not, in theory, be sufficiently
+ * aligned because it only contains 16-bit types. */
+struct odputil_keybuf {
+ uint32_t keybuf[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 *);