NAF_BUSY
hwna->na_flags &= ~NAF_BUSY;
na->na_flags |= NAF_BUSY;
na->na_flags &= ~NAF_BUSY;
hostna->na_flags = NAF_BUSY; /* prevent NIOCREGIF */
hwna->na_flags |= NAF_BUSY;
#define NETMAP_OWNED_BY_KERN(na) ((na)->na_flags & NAF_BUSY)