netdev - Re: [PATCH bpf-next v2 1/2] net: xdp: refactor XDP_QUERY_PROG{,

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Date:   Mon, 3 Jun 2019 11:04:18 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        "toke@...hat.com" <toke@...hat.com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "ast@...nel.org" <ast@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "magnus.karlsson@...el.com" <magnus.karlsson@...el.com>,
        "bjorn.topel@...el.com" <bjorn.topel@...el.com>,
        "brouer@...hat.com" <brouer@...hat.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 1/2] net: xdp: refactor XDP_QUERY_PROG{,_HW}
 to netdev

On Sat, 1 Jun 2019 at 21:42, Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
>
> On Fri, 31 May 2019 19:18:17 +0000, Saeed Mahameed wrote:
> > On Fri, 2019-05-31 at 11:42 +0200, Björn Töpel wrote:
> > > From: Björn Töpel <bjorn.topel@...el.com>
> > >
> > > All XDP capable drivers need to implement the XDP_QUERY_PROG{,_HW}
> > > command of ndo_bpf. The query code is fairly generic. This commit
> > > refactors the query code up from the drivers to the netdev level.
> > >
> > > The struct net_device has gained two new members: xdp_prog_hw and
> > > xdp_flags. The former is the offloaded XDP program, if any, and the
> > > latter tracks the flags that the supplied when attaching the XDP
> > > program. The flags only apply to SKB_MODE or DRV_MODE, not HW_MODE.
> > >
> > > The xdp_prog member, previously only used for SKB_MODE, is shared
> > > with
> > > DRV_MODE. This is OK, due to the fact that SKB_MODE and DRV_MODE are
> > > mutually exclusive. To differentiate between the two modes, a new
> > > internal flag is introduced as well.
> >
> > Just thinking out loud, why can't we allow any combination of
> > HW/DRV/SKB modes? they are totally different attach points in a totally
> > different checkpoints in a frame life cycle.
>
> FWIW see Message-ID: <20190201080236.446d84d4@...hat.com>
>

I've always seen the SKB-mode as something that will eventually be removed.

Clickable link:
https://lore.kernel.org/netdev/20190201080236.446d84d4@redhat.com/ :-P

> > Down the road i think we will utilize this fact and start introducing
> > SKB helpers for SKB mode and driver helpers for DRV mode..
>
> Any reason why we would want the extra complexity?  There is cls_bpf
> if someone wants skb features after all..