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Date:   Tue, 2 Oct 2018 13:12:15 +0200
From:   Jiri Pirko <jiri@resnulli.us>
To:     Chas Williams <3chas3@gmail.com>
Cc:     Stephen Hemminger <stephen@networkplumber.org>,
        Jan Blunck <jblunck@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>, netdev@vger.kernel.org
Subject: Re: [PATCH] team: set IFF_SLAVE on team ports
Message-ID: <20181002111215.GA2222@nanopsycho>
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Mon, Oct 01, 2018 at 04:06:16PM CEST, 3chas3@gmail.com wrote:
>
>
>On 09/30/18 05:34, Jiri Pirko wrote:
>> Sun, Sep 30, 2018 at 11:38:05AM CEST, stephen@networkplumber.org wrote:
>> > On Sun, 30 Sep 2018 09:14:14 +0200
>> > Jiri Pirko <jiri@resnulli.us> wrote:
>> > 
>> > > Thu, Sep 27, 2018 at 04:04:26PM CEST, 3chas3@gmail.com wrote:
>> > > > 
>> > > > 
>> > > > On 07/10/15 02:41, Jiri Pirko wrote:
>> > > > > Thu, Jul 09, 2015 at 05:36:55PM CEST, jblunck@infradead.org wrote:
>> > > > > > On Thu, Jul 9, 2015 at 12:07 PM, Jiri Pirko <jiri@resnulli.us> wrote:
>> > > > > > > Thu, Jul 09, 2015 at 11:58:34AM CEST, jblunck@infradead.org wrote:
>> > > > > > > > The code in net/ipv6/addrconf.c:addrconf_notify() tests for IFF_SLAVE to
>> > > > > > > > decide if it should start the address configuration. Since team ports
>> > > > > > > > shouldn't get link-local addresses assigned lets set IFF_SLAVE when linking
>> > > > > > > > a port to the team master.
>> > > > > > > 
>> > > > > > > I don't want to use IFF_SLAVE in team. Other master-slave devices are
>> > > > > > > not using that as well, for example bridge, ovs, etc.
>> > > > > > 
>> > > > > > Maybe they need to get fixed too. I've used that flag because it is
>> > > > > > documented as
>> > > > > > a "slave of a load balancer" which describes what a team port is.
>> > > > > > 
>> > > > > > > I think that this should be fixed in addrconf_notify. It should lookup
>> > > > > > > if there is a master on top and bail out in that case.
>> > > > > > 
>> > > > > > There are other virtual interfaces that have a master assigned and want to
>> > > > > > participate in IPv6 address configuration.
>> > > > > 
>> > > > > Can you give me an example?
>> > > > 
>> > > > I would like to revisit this patch (yes, I know it has been a while).  I
>> > > > believe the VRF implementation uses master to group the interfaces under
>> > > > a single interface.
>> > > > 
>> > > > I don't see a reason not to use IFF_SLAVE since team and bonding are fairly
>> > > > similar.
>> > > 
>> > > Again, why do you need team port to have IFF_SLAVE flag? What do you
>> > > want to achieve
>> > 
>> > Without setting this flag IPv6 will try and make a link specific address.

You are talking about addrconf_notify() right? Easy to fix to check
something more convenient. Like netif_is_lag_port() if you want to avoid
it for bond/team. netif_is_ovs_port(), netif_is_bridge_port() etc. Lot's
of helpers to cover this.


>> 
>> Why is it not an issue with bridge, ovs, and other master-slave devices?
>> 
>
>It very well might be an issue for bridge and ovs.  Other master-slave
>devices include the existing VRF implementation in the kernel and those slave
>interfaces will certainly want to use IPv6.
>
>However, IFF_SLAVE has a specific meaning:
>
>./include/uapi/linux/if.h: * @IFF_SLAVE: slave of a load balancer. Volatile.

I know that some userspace apps are using this flag to determine a
"bonding slave". I don't think that they care much about eql...


>
>The bonding driver is not the only user:
>
>./drivers/net/eql.c:#define eql_is_slave(dev)	((dev->flags & IFF_SLAVE) ==
>IFF_SLAVE)
>./drivers/net/eql.c:	slave->dev->flags &= ~IFF_SLAVE;
>./drivers/net/eql.c:		slave->dev->flags |= IFF_SLAVE;
>
>The team driver would like to use this same flag since it is a load balancer
>as well.  The side effect of not assigning IPv6 is a bonus. The fact that

No, please leave IFF_SLAVE as it is. Both kernel and userspace have
their clear indications right now about the master/slave relationships.


>bridges and ovs are also likely broken is a different issue.  Should there be
>a another flag that says "layer 2 only"?  Very possibly, but that is
>something all these interfaces should be using to include bonding, team, eql,
>obs, bridge etc.  That's not a reasonable objection to labeling the team
>slave as slaves since they are literally slaves of a load balancer.
>
>
>