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

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Message-ID: <5489D739.9010303@cumulusnetworks.com>
Date:	Thu, 11 Dec 2014 09:41:13 -0800
From:	Roopa Prabhu <roopa@...ulusnetworks.com>
To:	Jiri Pirko <jiri@...nulli.us>
CC:	"Varlese, Marco" <marco.varlese@...el.com>,
	John Fastabend <john.fastabend@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	"Fastabend, John R" <john.r.fastabend@...el.com>,
	"sfeldma@...il.com" <sfeldma@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
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@...ulusnetworks.com wrote:
>> On 12/11/14, 3:01 AM, Jiri Pirko wrote:
>>> Thu, Dec 11, 2014 at 10:59:42AM CET, marco.varlese@...el.com wrote:
>>>>> -----Original Message-----
>>>>> From: John Fastabend [mailto:john.fastabend@...il.com]
>>>>> Sent: Wednesday, December 10, 2014 5:04 PM
>>>>> To: Jiri Pirko
>>>>> Cc: Varlese, Marco; netdev@...r.kernel.org;
>>>>> stephen@...workplumber.org; Fastabend, John R;
>>>>> roopa@...ulusnetworks.com; sfeldma@...il.com; linux-
>>>>> kernel@...r.kernel.org
>>>>> 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@...el.com wrote:
>>>>>>> From: Marco Varlese <marco.varlese@...el.com>
>>>>>>>
>>>>>>> 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
>>
>>
>>

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