On Mon, Apr 30, 2001 at 09:57:26PM +0200, Martin Husemann wrote:

 > which would return 0 if there are no listeners attached to the struct bpf_if
 > (that hides behind "arg"); i.e. would do something like this:
 > 
 > int bpf_haslisteners(caddr_t arg)
 > {
 > 	struct bpf_if *bp = (struct bpf_if *)arg;
 > 	return (bp->bif_dlist != NULL);
 > }
 > 
 > This would be usefull for interface where the bpf_mtap call needs some
 > special, maybe expensive work.

I don't think you need to do this.  Checking ifp->if_bpf != NULL should
be sufficient.

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>