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Date:	Mon, 24 Nov 2014 10:02:43 +0200
From:	"Michael S. Tsirkin" <>
To:	David Miller <>
Subject: Re: [PATCH net-net 0/4] Increase the limit of tuntap queues

On Sun, Nov 23, 2014 at 08:23:21PM -0500, David Miller wrote:
> From: "Michael S. Tsirkin" <>
> Date: Sun, 23 Nov 2014 22:30:32 +0200
> > qemu runs in the host, but it's unpriveledged: it gets
> > passed tun FDs by a priveledged daemon, and it only
> > has the rights to some operations,
> > in particular to attach and detach queues.
> > 
> > The assumption always was that this operation is safe
> > and can't make kernel run out of resources.
> This creates a rather rediculous situation in my opinion.
> Configuring a network device is a privileged operation, the daemon
> should be setting this thing up.
> In no other context would we have to worry about something like this.

Right.  Jason corrected me.  I got it wrong:
what qemu does is TUNSETQUEUE and that needs to get a queue
that's already initialized by the daemon.

To create new queues daemon calls TUNSETIFF,
and that already can be used to create new devices,
so it's a priveledged operation.

This means it's safe to just drop the restriction,
exactly as you suggested originally.
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