[PATCH net-next 0/2 v2] xen-netback: Changes around carrier handling

This series starts using carrier off as a way to purge packets when the guest is
not able (or willing) to receive them. It is a much faster way to get rid of
packets waiting for an overwhelmed guest.
The first patch changes current netback code where it relies currently on
netif_carrier_ok.
The second turns off the carrier if the guest times out on a queue, and only
turn it on again if that queue (or queues) resurrects.

Signed-off-by: Zoltan Kiss <redacted>
Signed-off-by: David Vrabel <redacted>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org