netdev - Re: [PATCH] net: Fix userspace RTM

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Message-Id: <1260756336.4041.3.camel@localhost.localdomain>
Date:	Mon, 14 Dec 2009 03:05:36 +0100
From:	Marcel Holtmann <marcel@...tmann.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	stable@...nel.org
Subject: Re: [PATCH] net: Fix userspace RTM_NEWLINK notifications.

Hi Eric,

> I received some bug reports about userspace programs having problems
> because after RTM_NEWLINK was received they could not immediate access
> files under /proc/sys/net/ because they had not been registered yet.
> 
> The original problem was trivially fixed by moving the userspace
> notification from rtnetlink_event() to the end of
> register_netdevice().
> 
> When testing that change I discovered I was still getting RTM_NEWLINK
> events before I could access proc and I was also getting RTM_NEWLINK
> events after I was seeing RTM_DELLINK.  Things practically guaranteed
> to confuse userspace.
> 
> After a little more investigation these extra notifications proved to
> be from the new notifiers NETDEV_POST_INIT and NETDEV_UNREGISTER_BATCH
> hitting the default case in rtnetlink_event, and triggering
> unnecessary RTM_NEWLINK messages.
> 
> rtnetlink_event now explicitly handles NETDEV_UNREGISTER_BATCH and
> NETDEV_POST_INIT to avoid sending the incorrect userspace
> notifications.

the POST_INIT and UNREGISTER_BATCH are not 2.6.32 features. They are
2.6.33 features and thus you need to create a separate patch for -stable
if you wanna fix the /proc access issue.

Regards

Marcel


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