Re: [PATCH] team: set IFF_SLAVE on team ports

[Chas Williams]

On 09/30/18 05:34, Jiri Pirko wrote:
> Sun, Sep 30, 2018 at 11:38:05AM CEST, stephen@xxxxxxxxxxxxxxxxxx wrote:
> > On Sun, 30 Sep 2018 09:14:14 +0200
> > Jiri Pirko <jiri@xxxxxxxxxxx> wrote:
> >
> > > Thu, Sep 27, 2018 at 04:04:26PM CEST, 3chas3@xxxxxxxxx wrote:
> > > > On 07/10/15 02:41, Jiri Pirko wrote:
> > > > > Thu, Jul 09, 2015 at 05:36:55PM CEST, jblunck@xxxxxxxxxxxxx wrote:
> > > > > > On Thu, Jul 9, 2015 at 12:07 PM, Jiri Pirko <jiri@xxxxxxxxxxx> wrote:
> > > > > > > Thu, Jul 09, 2015 at 11:58:34AM CEST, jblunck@xxxxxxxxxxxxx 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.
>
> 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.

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 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.