nfs_boot_ifupdown
nfs_boot_ifupdown(nd->nd_ifp, lwp, 0);
tsleep(nfs_boot_ifupdown, PZERO, "nfsbif", 3 * hz);
(void) nfs_boot_ifupdown(ifp, lwp, 0);
error = nfs_boot_ifupdown(ifp, lwp, 1);
(void) nfs_boot_ifupdown(ifp, lwp, 0);
int nfs_boot_ifupdown(struct ifnet *, struct lwp *, int);