MAX_HEADER
skb = alloc_skb(len + MAX_HEADER, GFP_ATOMIC);
skb_reserve(skb, MAX_HEADER);
#define GRO_MAX_HEAD (MAX_HEADER + 128)
#define LAPB_HEADER_LEN MAX_HEADER /* LAPB over Ethernet + a bit more */
#define LIBETH_MAX_HEAD roundup_pow_of_two(max(MAX_HEADER, 256))
#define MAX_PHONET_HEADER (8 + MAX_HEADER)
#define MAX_TCP_HEADER L1_CACHE_ALIGN(128 + MAX_HEADER)
len = min_t(int, skb->len, MAX_HEADER + 128);
nskb = alloc_skb(pkt_size + MAX_HEADER, gfp);
skb_reserve(nskb, packet->overhead + MAX_HEADER);
MAX_HEADER, gfp);
skb_reserve(head, packet->overhead + MAX_HEADER);
xprt->max_payload = (1U << 16) - (MAX_HEADER << 3);