netdev - Re: [patch net-next v2 8/9] switchdev: introduce Netlink API

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Date:	Sat, 20 Sep 2014 07:32:30 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Thomas Graf <tgraf@...g.ch>
CC:	Jiri Pirko <jiri@...nulli.us>,
	John Fastabend <john.r.fastabend@...el.com>,
	netdev@...r.kernel.org, davem@...emloft.net, nhorman@...driver.com,
	andy@...yhouse.net, dborkman@...hat.com, ogerlitz@...lanox.com,
	jesse@...ira.com, pshelar@...ira.com, azhou@...ira.com,
	ben@...adent.org.uk, stephen@...workplumber.org,
	jeffrey.t.kirsher@...el.com, vyasevic@...hat.com,
	xiyou.wangcong@...il.com, edumazet@...gle.com,
	sfeldma@...ulusnetworks.com, f.fainelli@...il.com,
	roopa@...ulusnetworks.com, linville@...driver.com,
	dev@...nvswitch.org, jasowang@...hat.com, ebiederm@...ssion.com,
	nicolas.dichtel@...nd.com, ryazanov.s.a@...il.com,
	buytenh@...tstofly.org, aviadr@...lanox.com, nbd@...nwrt.org,
	alexei.starovoitov@...il.com, Neil.Jerram@...aswitch.com,
	ronye@...lanox.com, simon.horman@...ronome.com,
	alexander.h.duyck@...el.com
Subject: Re: [patch net-next v2 8/9] switchdev: introduce Netlink API

On 09/20/14 07:01, Thomas Graf wrote:

> Nothing speaks against having such a tc classifier. In fact, having
> the interface consist of only an embedded Netlink attribute structure
> would allow for such a classifier in a very straight forward way.
>
> That doesn't mean everybody should be forced to use the stateful
> tc interface.
>


Agreed. The response was to Jiri's strange statement that now that
he cant use OVS, there is no such api. I point to tc as very capable of
such usage.

> No need for false accusations here. Nobody ever mentioned vendor SDKs.
>

I am sorry to have tied the two together. Maybe not OVS but the approach
described is heaven for vendor SDKs.

> The statement was that the requirement of deriving hardware flows from
> software flows *in the kernel* is not flexible enough for the future
> for reasons such as:
>
> 1) The OVS software data path might be based on eBPF in the future and
>     it is unclear how we could derive hardware flows from that
>     transparently.
>

Who says you cant put BPF in hardware?
And why is OVS defining how BPF should evolve or how it should be used?

> 2) Depending on hardware capabilities. Hardware flows might need to be
>     assisted by software flow counterparts and it is believed that it
>     is the wrong approach to push all the necessary context for the
>     decision down into the kernel. This can be argued about and I don't
>     feel strongly either way.
>

Pointing to the current FDB offload: You can select to bypass
and not use s/ware.

cheers,
jamal
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