rumpuser_iovread
error = rumpuser_iovread(sc->sc_ugenfd[endpt], &iov, 1,
error = rumpuser_iovread(pap->comfd, &iov, 1,
int rumpuser_iovread(int, struct rumpuser_iovec *, size_t, int64_t, size_t *);
if ((error = rumpuser_iovread(rn->rn_readfd, &iov, 1,