netdev - Re: [patch net-next RFC 10/12] openvswitch: add support for datapath hardware offload

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Date:	Mon, 25 Aug 2014 09:53:25 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	John Fastabend <john.fastabend@...il.com>,
	Scott Feldman <sfeldma@...ulusnetworks.com>
CC:	Thomas Graf <tgraf@...g.ch>, Jiri Pirko <jiri@...nulli.us>,
	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Neil Horman <nhorman@...driver.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	dborkman <dborkman@...hat.com>, ogerlitz <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, john.r.fastabend@...el.com,
	edumazet@...gle.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
Subject: Re: [patch net-next RFC 10/12] openvswitch: add support for datapath
 hardware offload

On 08/24/14 22:42, John Fastabend wrote:

> In the L2 case we already have the fdb_add and fdb_del semantics that
> are being used today by NICs with embedded switches. And we have a DSA
> patch we could dig out of patchwork for those drivers.

Indeed. That is an excellent starting point of something that is proven
to work. I was hoping L3 would follow this path. For L2,
there is the mess of claiming unicast NIC addresses as part of
the fdb, but that can almost be ignored.
Caveat: fdb_XXX works well for NICs as well as different larger
ASICs - but some quark handling is going to be needed for the tinier
openwrt type devices.
For larger switches we are going to need more for L2:
Really, the bridge already covers everthing large switches
offer (Vlan filtering, bridge port setting etc). We just need
to offload that...

> So I think it makes more sense to use the explicit interface rather
> than put another shim layer in the kernel. Its simpler and more to the
> point IMO. I suspect the resulting code will be smaller and easier to
> read. I'm the squemish one in the audience here.
>

L2/3 should be left alone and go this path. My concern on excessive
NDOs was more on the flow view of the world.

cheers,
jamal

> .John
>
>

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