pru_sense
(void)pru_sense(so, ub);
.pru_sense = uipc_sense,
.pru_sense = uipc_sense,
.pru_sense = tcp_sense,
.pru_sense = tcp_sense,
if (so->so_proto->pr_usrreqs->pru_sense)
return (*so->so_proto->pr_usrreqs->pru_sense)(so, ub);
int (*pru_sense)(struct socket *, struct stat *);