+
+size_t nl_msg_start_nested(struct ofpbuf *, uint16_t type);
+void nl_msg_end_nested(struct ofpbuf *, size_t offset);
+void nl_msg_put_nested(struct ofpbuf *, uint16_t type,
+ const void *data, size_t size);
+
+/* Prepending attributes. */
+void *nl_msg_push_unspec_uninit(struct ofpbuf *, uint16_t type, size_t);
+void nl_msg_push_unspec(struct ofpbuf *, uint16_t type, const void *, size_t);
+void nl_msg_push_flag(struct ofpbuf *, uint16_t type);
+void nl_msg_push_u8(struct ofpbuf *, uint16_t type, uint8_t value);
+void nl_msg_push_u16(struct ofpbuf *, uint16_t type, uint16_t value);
+void nl_msg_push_u32(struct ofpbuf *, uint16_t type, uint32_t value);
+void nl_msg_push_u64(struct ofpbuf *, uint16_t type, uint64_t value);
+void nl_msg_push_be16(struct ofpbuf *, uint16_t type, ovs_be16 value);
+void nl_msg_push_be32(struct ofpbuf *, uint16_t type, ovs_be32 value);
+void nl_msg_push_be64(struct ofpbuf *, uint16_t type, ovs_be64 value);
+void nl_msg_push_string(struct ofpbuf *, uint16_t type, const char *value);
+
+/* Separating buffers into individual messages. */
+struct nlmsghdr *nl_msg_next(struct ofpbuf *buffer, struct ofpbuf *msg);
+
+/* Sizes of various attribute types, in bytes, including the attribute header
+ * and padding. */
+#define NL_ATTR_SIZE(PAYLOAD_SIZE) (NLA_HDRLEN + NLA_ALIGN(PAYLOAD_SIZE))
+#define NL_A_U8_SIZE NL_ATTR_SIZE(sizeof(uint8_t))
+#define NL_A_U16_SIZE NL_ATTR_SIZE(sizeof(uint16_t))
+#define NL_A_U32_SIZE NL_ATTR_SIZE(sizeof(uint32_t))
+#define NL_A_U64_SIZE NL_ATTR_SIZE(sizeof(uint64_t))
+#define NL_A_BE16_SIZE NL_ATTR_SIZE(sizeof(ovs_be16))
+#define NL_A_BE32_SIZE NL_ATTR_SIZE(sizeof(ovs_be32))
+#define NL_A_BE64_SIZE NL_ATTR_SIZE(sizeof(ovs_be64))
+#define NL_A_FLAG_SIZE NL_ATTR_SIZE(0)
+
+bool nl_attr_oversized(size_t payload_size);