On Fri, Dec 07, 2012 at 09:57:12AM -0500, Greg Troxel wrote:
>
> jnem...@victoria.tc.ca (John Nemeth) writes:
>
> > On Apr 27, 3:15am, David Laight wrote:
> > } One thing I discovered long ago, in an operating system far ... well
> > } not NetBSD is that dhcp's use of the bpf (equivalent) caused a data
> > } copy for every received ethernet frame - at considerable cost.
> > } I've NFI whether this happens withthe current code.
> >
> > Given that DHCP is very low traffic, I'm not sure that this really
> > matters.
>
> I don't think that's what he means. In most drivers, the idiom is
>
> if (there are bpf listeners) {
> m0 = cons up an mbuf chain that represents the packet
> bpf_mtap(m0, blah blah)
> }
>
> So the work to marshall the packet that might be tapped happens if there
> is a listener, not if the listener wants this packet.
You've also missed the fact that it wasn't NetBSD - try VxWorks.
All the filtering happened in the dhcp code.
David
--
David Laight: da...@l8s.co.uk
