Re: [Qemu-devel] accidental mistyping of command line kills networking

[Gleb Natapov <gleb@redhat.com>]

On Wed, Oct 28, 2009 at 08:29:42AM +0200, Avi Kivity wrote:
> On 10/27/2009 11:44 PM, Anthony Liguori wrote:
> >
> >It's actually not okay.  You're creating a bridge with two tap
> >devices on the bridge that happen to be connected in qemu by a
> >vlan.  If one tap device receives a packet, qemu is going to
> >forward that packet to the other tap device, which will in turn
> >send the packet to the bridge which in turn sends it to the first
> >tap device.
> >
> >Resulting in an infinite networking loop.
> >
> 
> It shouldn't kill networking though.  If a guest has two nics
> connected to the same host bridge (a reasonable configuration), and
> then connects these two nics through its own bridge, it creates the
> same sort of loop.  If that kills networking, we have a
> guest-initiated DoS (not that the userspace-initiated DoS was much
> better).
> 
That's what STP is for.

--
			Gleb.