tcp_get_seg_mp
snxt_mp = tcp_get_seg_mp(tcp, begin, &off);
static mblk_t *tcp_get_seg_mp(tcp_t *, uint32_t, int32_t *);
snxt_mp = tcp_get_seg_mp(tcp, snxt, &off);
snxt_mp = tcp_get_seg_mp(tcp, begin, &off);
snxt_mp = tcp_get_seg_mp(tcp, snxt, &off);
xmit_tail = tcp_get_seg_mp(tcp, snxt, &offset);
static mblk_t *tcp_get_seg_mp(tcp_t *, uint32_t, int32_t *);