netdev - Re: [patch net-next] net: call notifiers for mtu change even if iface is not up

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Message-ID: <20121203152250.GB21816@hmsreliant.think-freely.org>
Date:	Mon, 3 Dec 2012 10:22:50 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	bhutchings@...arflare.com, psimerda@...hat.com
Subject: Re: [patch net-next] net: call notifiers for mtu change even if
 iface is not up

On Mon, Dec 03, 2012 at 03:22:29PM +0100, Jiri Pirko wrote:
> Mon, Dec 03, 2012 at 03:18:23PM CET, nhorman@...driver.com wrote:
> >On Mon, Dec 03, 2012 at 12:16:32PM +0100, Jiri Pirko wrote:
> >> Do the same thing as in set mac. Call notifiers every time.
> >> 
> >> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
> >> ---
> >>  net/core/dev.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >> 
> >> diff --git a/net/core/dev.c b/net/core/dev.c
> >> index 2f94df2..0685a72 100644
> >> --- a/net/core/dev.c
> >> +++ b/net/core/dev.c
> >> @@ -4971,7 +4971,7 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
> >>  	else
> >>  		dev->mtu = new_mtu;
> >>  
> >> -	if (!err && dev->flags & IFF_UP)
> >> +	if (!err)
> >>  		call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
> >>  	return err;
> >>  }
> >
> >I'm not opposed to this change, but is there something that it expressly fixes?
> 
> This is about a consistency. To have the same behaviour as set_mac
> for example.
> 
> >While it doesn't hurt to send around mtu change events, one would presume that
> >listeners would pick up mtu changes when the NETDEV_UP event went' around.
> >
> >Neil
> >
I figured, I just wanted to be sure that there wasn't a bug fix that needed
documenting in the changelog, or that listeners for this event didn't expect the
interface to already be up.  It looks pretty clean, with the exception of the
TIPC protocol.  It appears that it might require enable_bearer to be called
prior to any netdevice CHANGEMTU events, so that the eth_bearers array gets
filled out, and it looks like that has to get triggered either by user space, or
the receipt of a message over the network.  Let me know what you think

Neil

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