__tcp_v4_send_check
void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
__tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
__tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
__tcp_v4_send_check(skb, iph->saddr, iph->daddr);