tcp_skb_shift
int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, int pcount,
if (!tcp_skb_shift(prev, skb, pcount, len))
if (tcp_skb_shift(prev, skb, pcount, len))
if (next_skb_size && !tcp_skb_shift(skb, next_skb, 1, next_skb_size))