* at device setup time.
* NETIF_F_HW_CSUM - it is clever device, it is able to checksum
* everything.
- * NETIF_F_NO_CSUM - loopback or reliable single hop media.
* NETIF_F_IP_CSUM - device is dumb. It is able to csum only
* TCP/UDP over IPv4. Sigh. Vendors like this
* way by an unknown reason. Though, see comment above