netdev - Re: [patch net-next] bonding: create netlink event when bonding option is changed

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Date:	Wed, 20 Aug 2014 10:00:51 -0400
From:	Andy Gospodarek <gospo@...ulusnetworks.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, j.vosburgh@...il.com,
	vfalico@...il.com, andy@...yhouse.net, nikolay@...hat.com,
	dingtianhong@...wei.com, sfeldma@...ulusnetworks.com
Subject: Re: [patch net-next] bonding: create netlink event when bonding
 option is changed

On Wed, Aug 20, 2014 at 08:44:58AM +0200, Jiri Pirko wrote:
> Tue, Aug 19, 2014 at 10:46:34PM CEST, gospo@...ulusnetworks.com wrote:
> >On Tue, Aug 19, 2014 at 10:37:48PM +0200, Jiri Pirko wrote:
> >> Tue, Aug 19, 2014 at 10:34:01PM CEST, gospo@...ulusnetworks.com wrote:
> >> >On Tue, Aug 19, 2014 at 04:02:12PM +0200, Jiri Pirko wrote:
> >> >> Userspace needs to be notified if one changes some option.
> >> >> 
> >> >> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
> >> >> ---
> >> >>  drivers/net/bonding/bond_options.c | 2 ++
> >> >>  include/linux/netdevice.h          | 1 +
> >> >>  2 files changed, 3 insertions(+)
> >> >> 
> >> >> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
> >> >> index dc73463..d8dc17f 100644
> >> >> --- a/drivers/net/bonding/bond_options.c
> >> >> +++ b/drivers/net/bonding/bond_options.c
> >> >> @@ -625,6 +625,8 @@ int __bond_opt_set(struct bonding *bond,
> >> >>  out:
> >> >>  	if (ret)
> >> >>  		bond_opt_error_interpret(bond, opt, ret, val);
> >> >> +	else
> >> >> +		call_netdevice_notifiers(NETDEV_CHANGEINFODATA, bond->dev);
> >> >Is this valuable where the configuration change to the bonding driver
> >> >came from netlink.  Do you have a good example why this useful in the
> >> >netlink path as well as when using sysfs?  It would seem more logical to
> >> >add call_netdevice_notifiers to bonding_sysfs_store_option so anything
> >> >listening to netlink messages or the netlink cache can know to check for
> >> >changes.
> >> 
> >> But this is called for sysfs as well.
> >Sorry for the confusion.  I was suggesting that this call is *only* used
> >for sysfs changes not for changes from sysfs and netlink as it would
> >with your patch.
> >
> >> Example of use is that application can monitor rtnetlink to see if for
> >> example active slave changed, or whatever other option changed.
> >Any application monitoring netlink messages will already know about the
> >configuration change if it came down via netlink.  There would not be a
> >need for an extra message.
> >
> >My question was:  Is there a need for 2 netlink messages to indicate
> >that a bonding configuration change was needed when the config came over
> >netlink.  I did not see the need for 2 netlink messages in this case and
> >was asking for clarification from you.
> 
> Imagine 2 applications. One is just monitoring netlink events ("ip
> mon"), the second is setting up bond via netlink. Now, the second sends
> a message to kernel, that is unicast to kernel. The first application
> does not see that message. Therefore there is need to generate the event
> message in kernel and send it back to userspace via multicast.
> That message the first application will see. And that is exactly what
> my patch is doing.

Agreed.  Thanks for having the discussion on this.

Acked-by: Andy Gospodarek <gospo@...ulusnetworks.com>

> 
> >
> >> 
> >> >
> >> >>  
> >> >>  	return ret;
> >> >>  }
> >> >> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> >> >> index 967ddcc..44bc4bd 100644
> >> >> --- a/include/linux/netdevice.h
> >> >> +++ b/include/linux/netdevice.h
> >> >> @@ -2017,6 +2017,7 @@ struct pcpu_sw_netstats {
> >> >>  #define NETDEV_CHANGEUPPER	0x0015
> >> >>  #define NETDEV_RESEND_IGMP	0x0016
> >> >>  #define NETDEV_PRECHANGEMTU	0x0017 /* notify before mtu change happened */
> >> >> +#define NETDEV_CHANGEINFODATA	0x0018
> >> >>  
> >> >>  int register_netdevice_notifier(struct notifier_block *nb);
> >> >>  int unregister_netdevice_notifier(struct notifier_block *nb);
> >> >> -- 
> >> >> 1.9.3
> >> >> 
> >> >> --
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