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From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [Qemu-devel] Re: Network bridging without adding bridge with
	brctl, possible?
Date: Sun, 20 Feb 2011 22:28:55 +0100
References: <alpine.LFD.2.02.1102192024040.22181@bbs.intern>
	<4D60E26D.3060202@web.de>
	<alpine.LFD.2.02.1102201058010.31275@bbs.intern>
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To: Gerhard Wiesinger <lists@wiesinger.com>
Cc: Jan Kiszka <jan.kiszka@web.de>, qemu-devel@nongnu.org

On Sunday 20 February 2011, Gerhard Wiesinger wrote:
> >
> > Not sure if this is by design or due to internals of the networking
> > stack, but it looks unintuitive from user perspective. Maybe Arnd can
> > shed a light on this.

The lower device cannot be in bridge mode, because that would make the
logic in the kernel awfully complex. I agree that it's a bit unfortunate,
but it simplified the design a lot.

> 
> > Of course, you could also simply offload all that setup to libvirt.
> 
> http://wiki.libvirt.org/page/Networking
> But that still needs a bridge on ethernet level and break up the existing 
> interface, right?

No. macvtap is a tap that sits on an external interface, you don't
need a bridge if you use it.
 
> BTW: From: http://virt.kernelnewbies.org/MacVTap
> As of QEMU 0.12:
> qemu -net nic,model=virtio,addr=1a:46:0b:ca:bc:7b -net tap,fd=3 3<>/dev/tap11
> Is there a newer Syntax with tap interfaces possible (QEMU GIT) without 
> bash redirects?

I made some suggestions how to integrate it with qemu, but they never got in.
Libvirt makes it a lot easier, though. We discussed that it should be cleaned
up when the networking helper scripts make it into qemu. Not sure if that
ever happened.

	Arnd