rumpuser_iovwrite
error = rumpuser_iovwrite(sc->sc_ugenfd[endpt], &iov, 1,
error = rumpuser_iovwrite(pap->comfd, &iov, 1,
int rumpuser_iovwrite(int, const struct rumpuser_iovec *, size_t,
if ((error = rumpuser_iovwrite(rn->rn_writefd, &iov, 1,
rumpuser_iovwrite(sc->sc_memfd, &iov, 1, IFMEM_WAKEUP, &n);