[NET]: Avoid duplicate netlink notification when changing link state

[NET]: Avoid duplicate netlink notification when changing link state

[Thomas Graf]

When changing the link state from userspace not affecting any other
flags. Two duplicate notification are being sent, once as action
in the NETDEV_UP/NETDEV_DOWN notification chain and a second time
when comparing old and new device flags after the change has been
completed. Although harmless, the duplicates should be avoided.

Signed-off-by: Thomas Graf <tgraf@suug.ch>

Index: net-2.6/net/core/dev.c
===================================================================
--- net-2.6.orig/net/core/dev.c	2007-06-05 17:50:13.000000000 +0200
+++ net-2.6/net/core/dev.c	2007-06-06 00:48:53.000000000 +0200
@@ -2577,7 +2577,7 @@ unsigned dev_get_flags(const struct net_
 
 int dev_change_flags(struct net_device *dev, unsigned flags)
 {
-	int ret;
+	int ret, changes;
 	int old_flags = dev->flags;
 
 	/*
@@ -2632,8 +2632,10 @@ int dev_change_flags(struct net_device *
 		dev_set_allmulti(dev, inc);
 	}
 
-	if (old_flags ^ dev->flags)
-		rtmsg_ifinfo(RTM_NEWLINK, dev, old_flags ^ dev->flags);
+	/* Exclude state transition flags, already notified */
+	changes = (old_flags ^ dev->flags) & ~(IFF_UP | IFF_RUNNING);
+	if (changes)
+		rtmsg_ifinfo(RTM_NEWLINK, dev, changes);
 
 	return ret;
 }

Re: [NET]: Avoid duplicate netlink notification when changing link state

[David Miller]

From: Thomas Graf <tgraf@suug.ch>
Date: Wed, 6 Jun 2007 00:54:53 +0200

> When changing the link state from userspace not affecting any other
> flags. Two duplicate notification are being sent, once as action
> in the NETDEV_UP/NETDEV_DOWN notification chain and a second time
> when comparing old and new device flags after the change has been
> completed. Although harmless, the duplicates should be avoided.
> 
> Signed-off-by: Thomas Graf <tgraf@suug.ch>

Thanks for fixing this, patch applied.