netdev - Re: [PATCH nf-next 0/8] netfilter: make nf_flowtable lifetime differ from container struct

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Date: Fri, 24 Nov 2023 10:55:12 +0100
From: Florian Westphal <fw@...len.de>
To: Pablo Neira Ayuso <pablo@...filter.org>
Cc: Florian Westphal <fw@...len.de>, netfilter-devel@...r.kernel.org,
	lorenzo@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH nf-next 0/8] netfilter: make nf_flowtable lifetime differ
 from container struct

Pablo Neira Ayuso <pablo@...filter.org> wrote:
> > Next, a new nftables flowtable flag is introduced to mark a flowtable
> > for explicit XDP-based offload.
> 
> If XDP uses the hardware offload infrastructure, then I don't see how
> would it be possible to combine a software dataplane with hardware
> offload, ie. assuming XDP for software acceleration and hardware
> offload, because it takes a while for the flowtable hw offload
> workqueue to set up things and meanwhile that happens, the software
> path is exercised.

Lorenzo adds a kfunc that gets called from the xdp program
to do a lookup in the flowtable.

This patchset prepares for the kfunc by adding a function that
returns the flowtable based on net_device pointer.

The work queue for hw offload (or ndo ops) are not used.

> > The XDP kfunc will be added in a followup patch.
> 
> What is the plan to support for stackable device? eg. VLAN, or even
> tunneling drivers such as VxLAN. I have (incomplete) patches to use
> dev_fill_forward_path() to discover the path then configure the
> flowtable datapath forwarding.

If the xdp program can't handle it packet will be pushed up the stack,
i.e. nf ingress hook will handle it next.

> My understand is that XDP is all about programmibility, if user
> decides to go for XDP then simply fully implement the fast path is the
> XDP framework? I know of software already does so and they are
> perfectly fine with this approach.

I don't understand, you mean no integration at all?