usr/src/sys/netinet/tcpip.h

/*      tcpip.h 4.1     81/11/29        */

/*
 * Tcp+ip header, after ip options removed.
 */
struct tcpiphdr {
        struct  ipovly ti_i;            /* overlaid ip structure */
        struct  tcphdr ti_t;            /* tcp header */
};
#define ti_next         ti_i.ih_next
#define ti_prev         ti_i.ih_prev
#define ti_x1           ti_i.ih_x1
#define ti_pr           ti_i.ih_pr
#define ti_len          ti_i.ih_len
#define ti_src          ti_i.ih_src
#define ti_dst          ti_i.ih_dst
#define ti_sport        ti_t.th_sport
#define ti_dport        ti_t.th_dport
#define ti_seq          ti_t.th_seq
#define ti_ack          ti_t.th_ack
#define ti_x2           ti_t.th_x2
#define ti_off          ti_t.th_off
#define ti_flags        ti_t.th_flags
#define ti_win          ti_t.th_win
#define ti_sum          ti_t.th_sum
#define ti_urp          ti_t.th_urp