+/* Converts abstract ofputil_packet_in 'pin' into an OFPT_PACKET_IN message
+ * and returns the message.
+ *
+ * If 'rw_packet' is NULL, the caller takes ownership of the newly allocated
+ * returned ofpbuf.
+ *
+ * If 'rw_packet' is nonnull, then it must contain the same data as
+ * pin->packet. 'rw_packet' is allowed to be the same ofpbuf as pin->packet.
+ * It is modified in-place into an OFPT_PACKET_IN message according to 'pin',
+ * and then ofputil_encode_packet_in() returns 'rw_packet'. If 'rw_packet' has
+ * enough headroom to insert a "struct ofp_packet_in", this is more efficient
+ * than ofputil_encode_packet_in() because it does not copy the packet
+ * payload. */
+struct ofpbuf *
+ofputil_encode_packet_in(const struct ofputil_packet_in *pin,
+ struct ofpbuf *rw_packet)
+{
+ int total_len = pin->packet->size;
+ struct ofp_packet_in *opi;
+
+ if (rw_packet) {
+ if (pin->send_len < rw_packet->size) {
+ rw_packet->size = pin->send_len;
+ }
+ } else {
+ rw_packet = ofpbuf_clone_data_with_headroom(
+ pin->packet->data, MIN(pin->send_len, pin->packet->size),
+ offsetof(struct ofp_packet_in, data));
+ }
+
+ /* Add OFPT_PACKET_IN. */
+ opi = ofpbuf_push_zeros(rw_packet, offsetof(struct ofp_packet_in, data));
+ opi->header.version = OFP_VERSION;
+ opi->header.type = OFPT_PACKET_IN;
+ opi->total_len = htons(total_len);
+ opi->in_port = htons(pin->in_port);
+ opi->reason = pin->reason;
+ opi->buffer_id = htonl(pin->buffer_id);
+ update_openflow_length(rw_packet);
+
+ return rw_packet;
+}
+