virtio_net: Make virtio_net support carrier detection

Impact: Make NetworkManager work with virtio_net

For now the semantics are simple: There is always carrier.

This allows a seamless experience with e.g., qemu/kvm
where NetworkManager just configures and sets up
everything automagically.

If/when a generally agreed-upon way to control
carrier on/off in the emulator/hypervisor level
emerges, it will be trivial to extend the driver
to support that too, but for now even this 2-liner
makes user experience that much better.

Signed-off-by: Pantelis Koukousoulas <pktoss@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -612,6 +612,7 @@ static struct ethtool_ops virtnet_ethtool_ops = {
 	.set_tx_csum = virtnet_set_tx_csum,
 	.set_sg = ethtool_op_set_sg,
 	.set_tso = ethtool_op_set_tso,
+	.get_link = ethtool_op_get_link,
 };
 
 #define MIN_MTU 68
@@ -739,6 +740,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 		goto unregister;
 	}
 
+	netif_carrier_on(dev);
+
 	pr_debug("virtnet: registered device %s\n", dev->name);
 	return 0;