netdev - Re: Allow group ownership of TUN/TAP devices.

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Message-Id: <20090202.233521.87347951.davem@davemloft.net>
Date:	Mon, 02 Feb 2009 23:35:21 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	mjt@....msk.ru
Cc:	netdev@...r.kernel.org, agx@...xcpu.org
Subject: Re: Allow group ownership of TUN/TAP devices.

From: Michael Tokarev <mjt@....msk.ru>
Date: Mon, 02 Feb 2009 17:44:34 +0300

> Michael Tokarev wrote:
> []
> > 2, and this is the main one: How about supplementary groups?
> > 
> > Here I have a valid usage case: a group of testers running various
> > versions of windows using KVM (kernel virtual machine), 1 at a time,
> > to test some software.  kvm is set up to use bridge with a tap device
> > (there should be a way to connect to the machine).  Anyone on that group
> > has to be able to start/stop the virtual machines.
> > 
> > My first attempt - pretty obvious when I saw -g option of tunctl - is
> > to add group ownership for the tun device and add a supplementary group
> > to each user (their primary group should be different).  But that fails,
> > since kernel only checks for egid, not any other group ids.
> > 
> > What's the reasoning to not allow supplementary groups and to only check
> > for egid?
> 
> Like this.
> 
> Signed-off-by: Michael Tokarev <mjt@....msk.ru>

Seems reasonable, applied, thanks.
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