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

[Dustin Kirkland <kirkland@canonical.com>]

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On Tue, 2009-11-03 at 18:28 -0600, Anthony Liguori wrote:
> This series solves a problem that I've been struggling with for a few years now.
> One of the best things about qemu is that it's possible to run guests as an
> unprivileged user to improve security.  However, if you want to have your guests
> communicate with the outside world, you're pretty much forced to run qemu as
> root.
> 
> At least with KVM support, this is probably the most common use case which means
> that most of our users are running qemu as root.  That's terrible.

Ack.

> We address this problem by introducing a new network backend: -net bridge.  This
> backend is less flexible than -net tap because it relies on a helper with
> elevated privileges to do the heavy lifting of allocating and attaching a tap
> device to a bridge.  We use a special purpose helper because we don't want
> to elevate the privileges of more generic tools like brctl.
> 
> From a user perspective, to use bridged networking with a guest, you simply use:
> 
>   qemu -hda linux.img -net bridge -net nic

I know that this patch is less than a day old and untested, but would it
be reasonable to make this the "default" network configuration at some
point in the future?  This certainly seems to be what I want 99% of the
time when I launch qemu or kvm by hand from the command line.

> And assuming a bridge is defined named qemubr0 and the administrator has setup
> permissions accordingly, it will Just Work.  My hope is that distributions will
> do this work as part of the qemu packaging process such that for most users,
> the out-of-the-box experience will also Just Work.

Also, ack.  I'll handle the Ubuntu packaging to enable this support in
Lucid by the time qemu-0.12-rc1 is available.  As Alexander mentions,
there's a bit more complexity we'll need to account for (wifi, network
manager, multiple nic's).

:-Dustin

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