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

[Rosen, Rami]

Hi, all,

Regarding preferring using netlink sockets versus ethtool IOCTLs for setting kernel network attributes from userspace, I fully agree with Marco. The netlink API is much more structured and
much more geared towards this type of operation, than the IOCTL-based ethtool. 

Regards,
Rami Rosen
Software Engineer, Intel

-----Original Message-----
From: netdev-owner@xxxxxxxxxxxxxxx [mailto:netdev-owner@xxxxxxxxxxxxxxx] On Behalf Of Varlese, Marco
Sent: Friday, December 12, 2014 11:20
To: Roopa Prabhu; Jiri Pirko
Cc: 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: 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. Plus, all the cases I have identified so far are going to nicely fit into the setlink set of operations.

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