HH_DATA_OFF
h = (struct fwnet_header *)((u8 *)hh->hh_data + HH_DATA_OFF(sizeof(*h)));
memcpy((u8 *)hh->hh_data + HH_DATA_OFF(FWNET_HLEN), haddr, net->addr_len);
HH_DATA_OFF(sizeof(*eth)));
#define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
(((u8 *) hh->hh_data) + (HH_DATA_OFF(sizeof(*eth))));
memcpy(((u8 *) hh->hh_data) + HH_DATA_OFF(sizeof(struct ethhdr)),