Re: [PATCH net-next v2] tap: report IFF_DETACH_QUEUE in TUNGETIFF

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Umang Pokhriyal wrote:
> Willem de Bruijn wrote:
> > I suppose we want tap to expose this state through TUNGETIFF, like tun,
> > because applications already use that?
> 
> Yes. CRIU reads IFF_DETACH_QUEUE from TUNGETIFF when it dumps a tun
> file, and Cloud Hypervisor did the same until it found that macvtap
> reports every queue as attached. Code written for tun's queue API gets
> the wrong answer on macvtap, even though macvtap accepts the same
> TUNSETQUEUE.
> 
> > Else cleaner than working around bits would be a whole new TUNGETQUEUE
> > call to match TUNSETQUEUE. Rather than to squish this into TUNGETIFF,
> > while that has no equivalent in TUNSETIFF.
> >
> > But, that approach does not help existing applications.
> 
> Right, those applications would have to be changed to use a new
> TUNGETQUEUE.
> 
> Thanks for taking another look.

Thanks for verifying.

Reviewed-by: Willem de Bruijn <willemb@google.com>