tcp_respond
tcp_respond(NULL, ip6, (struct tcphdr *)(ip6 + 1),
tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
tcp_respond(NULL, m, m, th,
tcp_respond(tp, t_template->tt_ipgen,
void tcp_respond (struct tcpcb *, void *,