veth: Fix carrier detect

The current implementation of carrier detect in veth is broken.
It reports the link is down until both sides of the veth pair
are administatively up and then forever after it reports link up.

So fix veth so that it only reports link up when both interfaces
of the pair are administratively up.

Signed-off-by: Eric Biederman <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/veth.c

···
 	return 0;
 }
 
+static int veth_close(struct net_device *dev)
+{
+	struct veth_priv *priv = netdev_priv(dev);
+
+	netif_carrier_off(dev);
+	netif_carrier_off(priv->peer);
+
+	return 0;
+}
+
 static int veth_dev_init(struct net_device *dev)
 {
 	struct veth_net_stats *stats;
···
 static const struct net_device_ops veth_netdev_ops = {
 	.ndo_init            = veth_dev_init,
 	.ndo_open            = veth_open,
+	.ndo_stop            = veth_close,
 	.ndo_start_xmit      = veth_xmit,
 	.ndo_get_stats       = veth_get_stats,
 	.ndo_set_mac_address = eth_mac_addr,
···
 	dev->features |= NETIF_F_LLTX;
 	dev->destructor = veth_dev_free;
 }
-
-static void veth_change_state(struct net_device *dev)
-{
-	struct net_device *peer;
-	struct veth_priv *priv;
-
-	priv = netdev_priv(dev);
-	peer = priv->peer;
-
-	if (netif_carrier_ok(peer)) {
-		if (!netif_carrier_ok(dev))
-			netif_carrier_on(dev);
-	} else {
-		if (netif_carrier_ok(dev))
-			netif_carrier_off(dev);
-	}
-}
-
-static int veth_device_event(struct notifier_block *unused,
-			     unsigned long event, void *ptr)
-{
-	struct net_device *dev = ptr;
-
-	if (dev->netdev_ops->ndo_open != veth_open)
-		goto out;
-
-	switch (event) {
-	case NETDEV_CHANGE:
-		veth_change_state(dev);
-		break;
-	}
-out:
-	return NOTIFY_DONE;
-}
-
-static struct notifier_block veth_notifier_block __read_mostly = {
-	.notifier_call	= veth_device_event,
-};
 
 /*
  * netlink interface
···
 
 static __init int veth_init(void)
 {
-	register_netdevice_notifier(&veth_notifier_block);
 	return rtnl_link_register(&veth_link_ops);
 }
 
 static __exit void veth_exit(void)
 {
 	rtnl_link_unregister(&veth_link_ops);
-	unregister_netdevice_notifier(&veth_notifier_block);
 }
 
 module_init(veth_init);