recvit
error = recvit(td, s, &msg, fromlenaddr);
return (recvit(td, uap->s, &msg, NULL));
error = recvit(td, uap->s, &msg, &uap->msg->msg_namelen);
error = recvit(td, uap->s, &msg, NULL);
static int recvit(struct thread *td, int s, struct msghdr *mp, void *namelenp);