-/** Outer IP checksum of TX packet, computed by NIC for tunneling packet.
- * The tunnel type must also be specified, ex: PKT_TX_UDP_TUNNEL_PKT. */
+/**
+ * Offload the IP checksum of an external header in the hardware. The
+ * flag PKT_TX_OUTER_IPV4 should also be set by the application, alto ugh
+ * a PMD will only check PKT_TX_IP_CKSUM. The IP checksum field in the
+ * packet must be set to 0.
+ * - set the outer IP checksum field in the packet to 0
+ * - fill the mbuf offload information: outer_l2_len, outer_l3_len
+ */