Re: [Qemu-devel] [PATCH 0/4] net-bridge: rootless bridge support for qemu

[Arnd Bergmann]

On Friday 06 November 2009, Jamie Lokier wrote:
> 
> Michael S. Tsirkin wrote:
> > On Thu, Nov 05, 2009 at 04:12:36AM +0000, Jamie Lokier wrote:
> > > I notice that if we eventually teach the kernel to have unnamed
> > > bridges (just attach interfaces to each other), only the helper
> > > commands will need changing to use it :-)
> > 
> > What do you mean by "attach interfaces to each other"?
> > Which interfaces do you want to attach to each other?
> 
> For example, attaching eth0 to tap0 without having to define br0,
> instead of the current method where you define br0 then attach eth0
> and tap0 to it, then transfer eth0's IP configuration to br0, then
> tell all the network management tools about it.

"Attaching" two network interfaces to each other does not work the
way you'd like it to. The tap device is on it's own unless you use
either a bridge or configure IP forwarding, which has another set
of problems.

I posted an experimental 'macvtap' driver a few some time ago that
would allow you to do something like that, i.e. add another logical
interface to an existing eth0 device, with a separate mac address,
and export that as a character device that is compatible with /dev/tun.

I probably need to start that one over from scratch, because I also
want to make it work with vhost-net, and to allow the guest and
the host to communicate with each other.
Note that this would be transparent to qemu, we'd only need a different
helper script to call.

        Arnd <><