Re: [RFC PATCH net-next v2 1/1] net: Support for switch port configuration

From: Roopa Prabhu
Date: Thu Dec 18 2014 - 18:48:39 EST


On 12/18/14, 3:26 PM, Samudrala, Sridhar wrote:

On 12/18/2014 3:07 PM, Roopa Prabhu wrote:
On 12/18/14, 11:21 AM, John Fastabend wrote:
On 12/18/2014 10:14 AM, Roopa Prabhu wrote:
On 12/18/14, 10:02 AM, Varlese, Marco wrote:
Removed unnecessary content for ease of reading...

+/* Switch Port Attributes section */
+
+enum {
+ IFLA_ATTR_UNSPEC,
+ IFLA_ATTR_LEARNING,
Any reason you want learning here ?. This is covered as part of
the bridge setlink attributes.

Yes, because the user may _not_ want to go through a bridge
interface
necessarily.
But, the bridge setlink/getlink interface was changed to accommodate
'self'
for exactly such cases.
I kind of understand your case for the other attributes (these are
per port settings that switch asics provide).

However, i don't understand the reason to pull in bridge attributes here.

Maybe, I am missing something so you might help. The learning attribute -
in my case - it is like all other attributes: a port attribute (as you said, port
settings that the switch provides per port).
So, what I was saying is "why the user shall go through a bridge to configure
the learning attribute"? From my perspective, it is as any other attribute and
as such configurable on the port.

Thinking about this some more, i don't see why any of these attributes
(except loopback. I dont understand the loopback attribute) cant be part of
the birdge port attributes.

With this we will end up adding l2 attributes in two places: the general link
attributes and bridge attributes.

And since we have gone down the path of using ndo_bridge_setlink/getlink
with 'self'....we should stick to that for all l2 attributes.

The idea of overloading ndo_bridge_set/getlink, was to have the same set of
attributes but support both cases where the user wants to go through the
bridge driver or directly to the switch port driver. So, you are not really going
through the bridge driver if you use 'self' and ndo_bridge_setlink/getlink.

Roopa, one of the comments I got from Thomas Graf on my v1 patch
was that your patch and mine were supplementary ("I think Roopa's
patches are supplementary. Not all switchdev users will be backed
with a Linux Bridge. I therefore welcome your patches very
much")... I also understood by others that the patch made sense for
the same reason. I simply do not understand why these attributes
(and maybe others in the future) could not be configured directly
on a standard port but have to go through a bridge.

ok, i am very confused in that case. The whole moving of bridge
attributes from the bridge driver to rtnetlink.c was to make the
bridge attributes accessible to any driver who wants to set l2/bridge
attributes on their switch ports. So, its unclear to me why we are
doing this parallel thing again. This move to rtnetlink.c was done
during the recent rocker support. so, maybe scott/jiri can elaborate
more.

Not sure if this will add to the confusion or help. But you do not
need to have the bridge.ko loaded or netdev's attached to a bridge
to use the setlink/getlink ndo ops and netlink messages.

This was intentionally done. Its already used with NIC devices to
configure embedded bridge settings such as VEB/VEPA.

that helps my case, thanks.

So the user interface to set/get the per-port attributes will be via 'bridge', not 'ip'

bridge link set dev sw0p1 port_attr bcast_flooding 1 self
bridge link get dev sw0p1 port_attr bcast_flooding self

yes, l2 attributes.

We also need an interface to set per-switch attributes. Can this work?
bridge link set dev sw0 sw_attr bcast_flooding 1 master
where sw0 is a bridge representing the hardware switch.

Not today. We discussed this @ LPC, and one way to do this would be to have a device
representing the switch asic. This is in the works.

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