netdev - Re: sysctls below net.ipv[46].conf.all not working as expected

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Message-ID: <20101230204319.GE14221@pengutronix.de>
Date:	Thu, 30 Dec 2010 21:43:19 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: sysctls below net.ipv[46].conf.all not working as expected

Hello David,

On Thu, Dec 30, 2010 at 12:30:23PM -0800, David Miller wrote:
> From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Date: Wed, 29 Dec 2010 17:06:07 +0100
> 
> > I did the following:
> > 
> > 	cassiopeia:~# sysctl net.ipv6.conf.all.use_tempaddr
> > 	net.ipv6.conf.all.use_tempaddr = 0
> > 
> > 	cassiopeia:~# sysctl net.ipv6.conf.eth0.use_tempaddr
> > 	net.ipv6.conf.eth0.use_tempaddr = 0
> > 
> > 	cassiopeia:~# sysctl -w net.ipv6.conf.all.use_tempaddr=1
> > 	net.ipv6.conf.all.use_tempaddr = 1
> > 
> > 	cassiopeia:~# sysctl net.ipv6.conf.all.use_tempaddr
> > 	net.ipv6.conf.all.use_tempaddr = 1
> > 
> > 	cassiopeia:~# sysctl net.ipv6.conf.eth0.use_tempaddr
> > 	net.ipv6.conf.eth0.use_tempaddr = 0
> > 
> > Here I would have expected that eth0's use_tempaddr is 1, too.  The
> > problem is not that this entry isn't writeable:
> 
> The "all" value is propagated at the first moment that the ipv6 device
> private is created, usually that is when the device is first brought up
> which means it can happen as early as the exact moment the device is
> registered.
> 
> Therefore, if you want "all" to apply to "eth0", you must make sure
> the sysctl is set properly before the device is registered.
I thought this is what "default" was used for?!
If you are really right, the documentation is (IMHO) misleading.  e.g.
Documentation/networking/ip-sysctl.txt tells:

	conf/default/*:
		Change the interface-specific default settings.

	conf/all/*:
		Change all the interface-specific settings.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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