if_setnetmapadapter
if_setnetmapadapter(ifp, na); \
#define NM_RESTORE_NA(ifp, na) if_setnetmapadapter(ifp, na);
#define NM_DETACH_NA(ifp) do { if_setnetmapadapter(ifp, NULL); } while (0)
void if_setnetmapadapter(if_t ifp, struct netmap_adapter *na);