Re: Bridge interface and IP address

[David Young <dyoung%pobox.com@localhost>]

On Mon, Aug 30, 2010 at 10:47:55AM -0400, der Mouse wrote:
> >> I ask because it always seemed backwards to me - the bridge ouught
> >> to be the "higher level" interface,
> 
> Actually, I would say the bridge ought not to be an interface at all.
> It's an in-host implementation of what would be done externally with a
> switch, and they aren't interfaces.  (Some (real-hardware) switches can
> reasonably be said to have addresses, but it's not the switch itself
> that has the address; it's the management computer housed in the same
> box that has the address.)
> 
> I'm not sure why bridges were implemented as interfaces in NetBSD.
> Convenience of some sort, I suppose.

der Mouse is right, bridges should never have been an interface at all.
Each bridge should be a routing domain, and IEEE-802 interfaces should
be bridged together by adding them to the same domain.

Adding IP addresses to bridges is a step in the wrong direction.

The way that protocols and pseudo-interfaces like IP, AppleTalk, agr(4),
bridge(4), pppoe(4), and vlan(4) hook (more like hijack) ether_input()
and ether_output() leads to bugs and awkward workarounds, and it defeats
modularity.  We should decompose ethernet (pseudo-)interfaces into a few
layers with well-defined APIs in between.

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 278-3933