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

[Chas Williams]

On 10/03/18 06:44, Jiri Pirko wrote:
> Tue, Oct 02, 2018 at 11:20:25PM CEST, 3chas3@xxxxxxxxx wrote:
> > On 10/02/18 07:12, Jiri Pirko wrote:
> > > Mon, Oct 01, 2018 at 04:06:16PM CEST, 3chas3@xxxxxxxxx wrote:
> > > > 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.
> > >
> > > 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.
> >
> > OK, IPv6 should probably be using 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.
> >
> > The team driver does create a master/slave relationship.  The team slaves are
> > literally slaves of the master device.  It's not clear to me
> > why you we can't mark the slaves of the team master as actually being
> > slave interfaces?
>
> So? IFF_SLAVE flag serves a different purpose. That's it. Team does not
> need it, bridge does not need it, macvlan does not need it, etc.

I agree.  But team *is* a load balancer.  Why can't team mark its slave 
interfaces as IFF_SLAVE?  They are literally slaves of a load balancer 
which is the exact meaning of the IFF_SLAVE flag.

> > > > 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.