MAX_PHONET_HEADER
#define MAX_PNPIPE_HEADER (MAX_PHONET_HEADER + 4)
struct sk_buff *skb = alloc_skb(MAX_PHONET_HEADER + len, GFP_ATOMIC);
skb_reserve(skb, MAX_PHONET_HEADER);
skb = sock_alloc_send_skb(sk, MAX_PHONET_HEADER + len,
skb_reserve(skb, MAX_PHONET_HEADER);
skb_reserve(skb, MAX_PHONET_HEADER + 3 + pn->aligned);
skb_reserve(rskb, MAX_PHONET_HEADER + 3);