netdev - Re: [PATCH net-next 6/6] netdevsim: Add simple FIB resource controller via devlink

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Message-ID: <c85f2b41-6100-fe12-b30a-8f12f63e8aab@cumulusnetworks.com>
Date:   Fri, 6 Apr 2018 15:22:29 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        roopa@...ulusnetworks.com, shm@...ulusnetworks.com,
        jiri@...lanox.com, idosch@...lanox.com,
        jakub.kicinski@...ronome.com, andy.roulin@...il.com
Subject: Re: [PATCH net-next 6/6] netdevsim: Add simple FIB resource
 controller via devlink

On 4/5/18 11:52 PM, Jiri Pirko wrote:
> Thu, Apr 05, 2018 at 11:06:41PM CEST, dsa@...ulusnetworks.com wrote:
>> On 4/5/18 2:10 PM, David Ahern wrote:
>>>
>>> The ASIC here is the kernel tables in a namespace. It does not make
>>> sense to have 2 devlink instances for a single namespace.
>>
>> I put this example controller in netdevsim per a suggestion from Ido.
>> The netdevsim seemed like a good idea given that modules intention --
>> testing network facilities. Perhaps I should have done this as a
>> completely standalone module ...
>>
>> The intention is to treat the kernel's tables *per namespace* as a
>> standalone entity that can be managed very similar to ASIC resources.
> 
> So you say you want to treat a namespace as an ASIC? That sounds very
> odd to me :/

Why? The kernel has forwarding tables, acl's, etc just like the ASIC,
and each namespace is a separate set of tables.

If you think about it, userspace "programs" the kernel just like mlxsw
and userspace SDKs "program" an asic.


>> Given that I can add a resource controller module
>> (drivers/net/kern_res_mgr.c?) that creates a 'struct device' per network
>> namespace with a devlink instance. In this case the device would very
>> much be tied to the namespace 1:1.
> 
> That sounds more reasonable and accurate, yet still odd. You would not
> have any netdevices there? Any ports?
> 

Sure, what ever ports are assigned to or created in the namespace.

Nothing about the devlink API says it has to be a real h/w device.
Nothing about the devlink API says it can only be used for real h/w that
has ports represented by netdevices that the devlink instance some how
has "control" over.

As the netdevsim demo shows, I can build an L3 resource controller for
the kernel tables using just the devlink API and the in-kernel notifiers.