Re: Broadcast traffic on vlans leaks into the parent interface on NetBSD-5.1

[David Laight <david%l8s.co.uk@localhost>]

On Fri, Dec 07, 2012 at 09:57:12AM -0500, Greg Troxel wrote:
> 
> jnemeth%victoria.tc.ca@localhost (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: david%l8s.co.uk@localhost