netdev - Re: [PATCH v2 net-next] virtio-net: Fix operstate for virtio when no VIRTIO_NET_F

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Message-Id: <20180323.121704.2141481482842731916.davem@davemloft.net>
Date:   Fri, 23 Mar 2018 12:17:04 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     jay.vosburgh@...onical.com
Cc:     netdev@...r.kernel.org, mst@...hat.com, jasowang@...hat.com,
        ben@...adent.org.uk
Subject: Re: [PATCH v2 net-next] virtio-net: Fix operstate for virtio when
 no VIRTIO_NET_F_STATUS

From: Jay Vosburgh <jay.vosburgh@...onical.com>
Date: Thu, 22 Mar 2018 14:42:41 +0000

> 	The operstate update logic will leave an interface in the
> default UNKNOWN operstate if the interface carrier state never changes
> from the default carrier up state set at creation.  This includes the
> case of an explicit call to netif_carrier_on, as the carrier on to on
> transition has no effect on operstate.
> 
> 	This affects virtio-net for the case that the virtio peer does
> not support VIRTIO_NET_F_STATUS (the feature that provides carrier state
> updates).  Without this feature, the virtio specification states that
> "the link should be assumed active," so, logically, the operstate should
> be UP instead of UNKNOWN.  This has impact on user space applications
> that use the operstate to make availability decisions for the interface.
> 
> 	Resolve this by changing the virtio probe logic slightly to call
> netif_carrier_off for both the "with" and "without" VIRTIO_NET_F_STATUS
> cases, and then the existing call to netif_carrier_on for the "without"
> case will cause an operstate transition.
> 
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: Ben Hutchings <ben@...adent.org.uk>
> Signed-off-by: Jay Vosburgh <jay.vosburgh@...onical.com>

Applied, thank you.