Re: Raw vs. tap (was: Re: [Qemu-devel] Re: Release plan for 0.12.0)

[Mark McLoughlin <markmc@redhat.com>]

On Wed, 2009-10-14 at 17:53 -0500, Anthony Liguori wrote:

> So at this point, I think it's a mistake to include raw socket support.  
> If the goal is to improve networking usability such that it just works 
> as a root user, let's incorporate a default network script that creates 
> a bridge or something like that.  There are better ways to achieve that 
> goal.

FWIW, I haven't really played with the raw backend yet, but my initial
thought was also "what exactly does this gain us apart from yet more
confusion for users?".

So, I tend to agree, but I'm not so hung up on the "user confusion"
aspect - the users that I worry about confusing (e.g. virt-manager
users) would never even know the backend exists, even if qemu did
support it.

The one hope I had for raw is that it might allow us to get closer to
the NIC, get more details on the NIC tx queue and have more intelligent
tx mitigation. This is probably better explored in the context of
vhost-net, though.

Wrt. to configuring bridges, libvirt comes with a good default setup - a
bridge without any physical NICs connected, but NAT set up for access to
the outside world.

For bridging to a physical NIC, our plan continues to be that
NetworkManager will eventually make this trivial for users, but that's
still in progress. In the meantime, the config isn't all that complex:

  http://wiki.libvirt.org/page/Networking#Fedora.2FRHEL_Bridging

Cheers,
Mark.