tcpiphdr
struct tcpiphdr *ti;
ti = (struct tcpiphdr *)headers;
bzero(&td->td_ti, sizeof(struct tcpiphdr));
struct tcpiphdr td_ti;
struct tcpiphdr tcpip;
void tcp_trace(short, short, struct tcpcb *, struct tcpiphdr *,
struct tcpiphdr *ti, struct tcpipv6hdr *ti6, int req)