virtio-net: Fix operstate for virtio when no VIRTIO_NET_F_STATUS

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@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 23374603e4d900850afd3b667eb25cdd082743b5..7b187ec7411ec053d9825b3774fe4036ea4e59f8 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2857,8 +2857,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 
        /* Assume link up if device can't report link status,
           otherwise get link status from config. */
+       netif_carrier_off(dev);
        if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
-               netif_carrier_off(dev);
                schedule_work(&vi->config_work);
        } else {
                vi->status = VIRTIO_NET_S_LINK_UP;