netdev - Re: [PATCH net-next,v6 00/12] add flow

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Message-ID: <20181219162653.2aeeb15a@cakuba.netronome.com>
Date:   Wed, 19 Dec 2018 16:26:53 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        thomas.lendacky@....com, f.fainelli@...il.com,
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Subject: Re: [PATCH net-next,v6 00/12] add flow_rule infrastructure

On Thu, 20 Dec 2018 01:03:13 +0100, Pablo Neira Ayuso wrote:
> On Wed, Dec 19, 2018 at 11:57:03AM -0800, Jakub Kicinski wrote:
> > > Anyway, the problem that this patchset addresses _already exists_ with
> > > ethtool_rxnfc and cls_flower in place, it would be good to fix it now.  
> > 
> > That's not the point of contention.  
> 
> What is your alternative plan to unify driver codebase for
> ethtool_rx_flow_spec and tc/cls_flower to offload ACL from the ingress
> path?

The point of contention for me is the "reuse of ndo_setup_tc" :)  
I haven't played with your IR, but it looks fairly close to the flower
dissector based thing, so it's probably fine

> > Did you consider things like tunnels and bonds?  There are a lot of
> > problems which have been solved for TC offloads, if you create a
> > separate subsystem offload you'll have to repeat all that work.  
> 
> Did I repeat any work to unify ethtool_rx_flow_spec and tc/cls_flower?
> No :-). I spinned over the existing work and delivered an incremental
> update.

Ethtool exists, so you don't have to teach the driver about it.  nft
offload does not, yet, exist in upstream drivers AFAIK.  Besides, if
ethtool n-tuples were rich and supported complex use cases we wouldn't
have TC flower offloads, so it's not apples to apples ;)

> > I'm not suggesting we replace netfilter with TC.  I'm suggesting we
> > replace nf_flow_offload table with something that fits into TC.
> > 
> > You're not going to offload entire netfilter.  You want to offload
> > simplistic flows through the nf_flow_table.  What I'm saying, is add a
> > equivalent of that table into TC.  Make user space "link" netfilter to
> > that.  
> 
> This patchset is not related to nf_flow_table infrastructure.

Let's not let the elephant back into the room, please :)

> From what I'm reading, you assume we can use nf_flow_table everywhere,
> which is probably true if you assume people use your NICs. However,
> there is a class of hardware where CPU is extremely smallish to cope
> with flows in software, where dataplane is almost entirely offloaded
> to hardware. In that scenario, nf_flow_table cannot be used.

I'm confused, could you rephrase?  How does you work help such devices?
How is tc not suitable for them?