[RTNL]: Introduce the rtnl_kill_links helper.

This one is responsible for calling ->dellink on each net
device found in net to help with vlan net_exit hook in the
nearest future.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Acked-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/rtnetlink.h

@@ -74,6 +74,7 @@ struct rtnl_link_ops {
 
 extern int	__rtnl_link_register(struct rtnl_link_ops *ops);
 extern void	__rtnl_link_unregister(struct rtnl_link_ops *ops);
+extern void	rtnl_kill_links(struct net *net, struct rtnl_link_ops *ops);
 
 extern int	rtnl_link_register(struct rtnl_link_ops *ops);
 extern void	rtnl_link_unregister(struct rtnl_link_ops *ops);

net/core/rtnetlink.c

@@ -269,6 +269,26 @@ int rtnl_link_register(struct rtnl_link_ops *ops)
 
 EXPORT_SYMBOL_GPL(rtnl_link_register);
 
+static void __rtnl_kill_links(struct net *net, struct rtnl_link_ops *ops)
+{
+	struct net_device *dev;
+restart:
+	for_each_netdev(net, dev) {
+		if (dev->rtnl_link_ops == ops) {
+			ops->dellink(dev);
+			goto restart;
+		}
+	}
+}
+
+void rtnl_kill_links(struct net *net, struct rtnl_link_ops *ops)
+{
+	rtnl_lock();
+	__rtnl_kill_links(net, ops);
+	rtnl_unlock();
+}
+EXPORT_SYMBOL_GPL(rtnl_kill_links);
+
 /**
  * __rtnl_link_unregister - Unregister rtnl_link_ops from rtnetlink.
  * @ops: struct rtnl_link_ops * to unregister
@@ -277,17 +297,10 @@ EXPORT_SYMBOL_GPL(rtnl_link_register);
  */
 void __rtnl_link_unregister(struct rtnl_link_ops *ops)
 {
-	struct net_device *dev;
 	struct net *net;
 
 	for_each_net(net) {
-restart:
-		for_each_netdev(net, dev) {
-			if (dev->rtnl_link_ops == ops) {
-				ops->dellink(dev);
-				goto restart;
-			}
-		}
+		__rtnl_kill_links(net, ops);
 	}
 	list_del(&ops->list);
 }