Re: [PATCH net-net 0/4] Increase the limit of tuntap queues

From: Pankaj Gupta
Date: Mon Nov 24 2014 - 09:28:50 EST



> On Sun, Nov 23, 2014 at 08:23:21PM -0500, David Miller wrote:
> > From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> > 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.

I will drop patch2 to add sysctl entry and and will send a v2 with other
patches.

Thanks,
Pankaj

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