RE: [RFC PATCH net-next 1/1] net: Support for switch port configuration

[Arad, Ronen]

The proposed patch introduces a way for supporting device specific switch port attributes.
Can we expect user-space tools such as iproute2 to be aware of such attributes from every device?
A generic tool like iproute2 can't be aware of all the specific attributes of all the devices that will use the newly proposed ndo.
Do we need a generic mechanism for a device to expose to user-space the set of device specific attributes it supports?
Exported information should include:
- Attribute keyword - will be used by iproute2 to parse user input and display in device specific help
- Attribute type - the numeric value for the 'attr' argument of ndo_switch_port_set_cfg().
- Attribute value range - range of supported values for the attribute
- Attribute help
  Note: A generic ndo patch as suggested by Roopa requires going beyond simple range to make it useable by generic user-space tool like iproute2.

With such mechanism in place iproute2 could provide end-user friendly experience in a generic way.

-Ronen

> -----Original Message-----
> From: netdev-owner@xxxxxxxxxxxxxxx [mailto:netdev-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Varlese, Marco
> Sent: Monday, December 15, 2014 1:40 AM
> To: Roopa Prabhu
> Cc: Jiri Pirko; John Fastabend; netdev@xxxxxxxxxxxxxxx;
> stephen@xxxxxxxxxxxxxxxxxx; Fastabend, John R; sfeldma@xxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [RFC PATCH net-next 1/1] net: Support for switch port
> configuration
> 
> > -----Original Message-----
> > From: Roopa Prabhu [mailto:roopa@xxxxxxxxxxxxxxxxxxx]
> > Sent: Saturday, December 13, 2014 7:06 AM
> > To: Varlese, Marco
> > Cc: Jiri Pirko; John Fastabend; netdev@xxxxxxxxxxxxxxx;
> > stephen@xxxxxxxxxxxxxxxxxx; Fastabend, John R; sfeldma@xxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [RFC PATCH net-next 1/1] net: Support for switch port
> > configuration
> >
> > On 12/12/14, 1:19 AM, Varlese, Marco wrote:
> > >> -----Original Message-----
> > >> From: Roopa Prabhu [mailto:roopa@xxxxxxxxxxxxxxxxxxx]
> > >> Sent: Thursday, December 11, 2014 5:41 PM
> > >> To: Jiri Pirko
> > >> Cc: Varlese, Marco; John Fastabend; netdev@xxxxxxxxxxxxxxx;
> > >> stephen@xxxxxxxxxxxxxxxxxx; Fastabend, John R;
> sfeldma@xxxxxxxxx;
> > >> linux-kernel@xxxxxxxxxxxxxxx
> > >> Subject: Re: [RFC PATCH net-next 1/1] net: Support for switch port
> > >> configuration
> > >>
> > >> On 12/11/14, 8:56 AM, Jiri Pirko wrote:
> > >>> Thu, Dec 11, 2014 at 05:37:46PM CET, roopa@xxxxxxxxxxxxxxxxxxx
> > wrote:
> > >>>> On 12/11/14, 3:01 AM, Jiri Pirko wrote:
> > >>>>> Thu, Dec 11, 2014 at 10:59:42AM CET, marco.varlese@xxxxxxxxx
> wrote:
> > >>>>>>> -----Original Message-----
> > >>>>>>> From: John Fastabend [mailto:john.fastabend@xxxxxxxxx]
> > >>>>>>> Sent: Wednesday, December 10, 2014 5:04 PM
> > >>>>>>> To: Jiri Pirko
> > >>>>>>> Cc: Varlese, Marco; netdev@xxxxxxxxxxxxxxx;
> > >>>>>>> stephen@xxxxxxxxxxxxxxxxxx; Fastabend, John R;
> > >>>>>>> roopa@xxxxxxxxxxxxxxxxxxx; sfeldma@xxxxxxxxx; linux-
> > >>>>>>> kernel@xxxxxxxxxxxxxxx
> > >>>>>>> Subject: Re: [RFC PATCH net-next 1/1] net: Support for switch
> > >>>>>>> port configuration
> > >>>>>>>
> > >>>>>>> On 12/10/2014 08:50 AM, Jiri Pirko wrote:
> > >>>>>>>> Wed, Dec 10, 2014 at 05:23:40PM CET, marco.varlese@xxxxxxxxx
> > >> wrote:
> > >>>>>>>>> From: Marco Varlese <marco.varlese@xxxxxxxxx>
> > >>>>>>>>>
> > >>>>>>>>> Switch hardware offers a list of attributes that are
> > >>>>>>>>> configurable on a per port basis.
> > >>>>>>>>> This patch provides a mechanism to configure switch ports by
> > >>>>>>>>> adding an NDO for setting specific values to specific attributes.
> > >>>>>>>>> There will be a separate patch that extends iproute2 to call
> > >>>>>>>>> the new NDO.
> > >>>>>>>> What are these attributes? Can you give some examples. I'm
> > >>>>>>>> asking because there is a plan to pass generic attributes to
> > >>>>>>>> switch ports replacing current specific
> > >>>>>>>> ndo_switch_port_stp_update. In this case, bridge is setting
> > >>>>>>>> that
> > attribute.
> > >>>>>>>>
> > >>>>>>>> Is there need to set something directly from userspace or
> > >>>>>>>> does it make rather sense to use involved bridge/ovs/bond ? I
> > >>>>>>>> think that both will be needed.
> > >>>>>>> +1
> > >>>>>>>
> > >>>>>>> I think for many attributes it would be best to have both. The
> > >>>>>>> in kernel callers and netlink userspace can use the same
> > >>>>>>> driver
> > ndo_ops.
> > >>>>>>>
> > >>>>>>> But then we don't _require_ any specific bridge/ovs/etc module.
> > >>>>>>> And we may have some attributes that are not specific to any
> > >>>>>>> existing software module. I'm guessing Marco has some examples
> > >>>>>>> of
> > >> these.
> > >>>>>>> [...]
> > >>>>>>>
> > >>>>>>>
> > >>>>>>> --
> > >>>>>>> John Fastabend         Intel Corporation
> > >>>>>> We do have a need to configure the attributes directly from
> > >>>>>> user-space
> > >> and I have identified the tool to do that in iproute2.
> > >>>>>> An example of attributes are:
> > >>>>>> * enabling/disabling of learning of source addresses on a given
> > >>>>>> port (you can imagine the attribute called LEARNING for
> > >>>>>> example);
> > >>>>>> * internal loopback control (i.e. LOOPBACK) which will control
> > >>>>>> how the flow of traffic behaves from the switch fabric towards
> > >>>>>> an egress port;
> > >>>>>> * flooding for broadcast/multicast/unicast type of packets (i.e.
> > >>>>>> BFLOODING, MFLOODING, UFLOODING);
> > >>>>>>
> > >>>>>> Some attributes would be of the type enabled/disabled while
> > >>>>>> other will
> > >> allow specific values to allow the user to configure different
> > >> behaviours of that feature on that particular port on that platform.
> > >>>>>> One thing to mention - as John stated as well - there might be
> > >>>>>> some
> > >> attributes that are not specific to any software module but rather
> > >> have to do with the actual hardware/platform to configure.
> > >>>>>> I hope this clarifies some points.
> > >>>>> It does. Makes sense. We need to expose this attr set/get for
> > >>>>> both in-kernel and userspace use cases.
> > >>>>>
> > >>>>> Please adjust you patch for this. Also, as a second patch, it
> > >>>>> would be great if you can convert ndo_switch_port_stp_update to
> > >>>>> this new
> > >> ndo.
> > >>>> Why are we exposing generic switch attribute get/set from
> > >>>> userspace ?. We already have specific attributes for
> > >>>> learning/flooding which can be extended further.
> > >>> Yes, but that is for PF_BRIDGE and bridge specific attributes.
> > >>> There might be another generic attrs, no?
> > >> I cant think of any. And plus, the whole point of switchdev l2
> > >> offloads was to map these to existing bridge attributes. And we
> > >> already have a match for some of the attributes that marco wants.
> > >>
> > >> If there is a need for such attributes, i don't see why it is
> > >> needed for switch devices only.
> > >> It is needed for any hw (nics etc). And, a precedence to this is to
> > >> do it via ethtool.
> > >>
> > >> Having said that, am sure we will find a need for this in the future.
> > >> And having a netlink attribute always helps.
> > >>
> > >> Today, it seems like these can be mapped to existing attributes
> > >> that are settable via ndo_bridge_setlink/getlink.
> > >>
> > >>>> And for in kernel api....i had a sample patch in my RFC series
> > >>>> (Which i was going to resubmit, until it was decided that we will
> > >>>> use existing api around
> > >>>> ndo_bridge_setlink/ndo_bridge_getlink):
> > >>>> http://www.spinics.net/lists/netdev/msg305473.html
> > >>> Yes, this might become handy for other generic non-bridge attrs.
> > >>>
> > >>>> Thanks,
> > >>>> Roopa
> > >>>>
> > >>>>
> > >>>>
> > > The list I provided is only a subset of the attributes we will need
> > > to be
> > exposed. I do have more and I'm sure that more will come in the
> > future. As I mentioned in few posts earlier, some attributes are
> > generic and some are not.
> > >
> > > I did not consider ethtool for few reasons but the main one is that
> > > I was
> > under the impression that netlink was preferred in many circumstances
> > over the ethotool_ops.
> > That is correct. I don't think anybody hinted that you should extend
> ethtool.
> > >   Plus, all the cases I have identified so far are going to nicely
> > > fit into the
> > setlink set of operations.
> > >
> >
> > Would be better if you submitted your iproute2 patch with this patch.
> >
> > I do plan to resubmit my generic ndo patch soon.
> >
> > Thanks,
> > Roopa
> 
> I honestly do not understand what extra "help" the iproute2 would have
> brought to this RFC: that patch simply adds a new section for the iproute2
> help and a new args parser for the input. From an infrastructure perspective
> is leveraging what netlink messages are using RTM_SETLINK hence hooking
> up eventually in the do_setlink(). Sure, obviously contains all the attributes I
> have in mind but from an infrastructure patch perspective I don't think that
> you would have gained much in seeing it.
> 
> Anyway, good to know you're reworking you generic patch. I'll keep an eye
> out for your new NDO.
> 
> 
> Thanks,
> Marco
> 
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