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

[Jamie Lokier <jamie@shareable.org>]

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.

Even Anthony's helper program only makes it easier to do dynamic taps
attaching to br0; it won't work on a vanilla Linux system.  A vanilla
Linux system still needs to be modified to have br0 before the helper
can work, and while that modification would be easy for distros to do
for most home systems, which run NetworkManager and are limited to
exactly one active interface, it's not a pretty change for anything
else and cannot be fully automated.

(Even on home systems, sometimes you'd want vMs bridged to your mobile
phone internet connection, and sometimes you wouldn't.  There are
still policy issues).

Unnamed bridges would simplify the problem on systems which aren't
running something like NetworkManager, by keeping eth0's IP
configuration on eth0, and Anthony's helper would just attach tap0 to
eth0 (or whatever interface you prefer).  All you specify is which
real network you want the VM's virtual NIC to appear on.

It'd behave like VMware etc., but cleaner :-)

-- Jamie