netdev - Re: [PATCH v4] netdev attribute to control xdpgeneric skb linearization

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Date:   Tue, 3 Mar 2020 22:04:55 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Luigi Rizzo <lrizzo@...gle.com>,
        Network Development <netdev@...r.kernel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        David Miller <davem@...emloft.net>, hawk@...nel.org,
        "Jubran, Samih" <sameehj@...zon.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, ast@...nel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v4] netdev attribute to control xdpgeneric skb
 linearization

On 3/3/20 9:50 PM, Jakub Kicinski wrote:
> On Tue, 3 Mar 2020 20:46:55 +0100 Daniel Borkmann wrote:
>> Thus, when the data/data_end test fails in generic XDP, the user can
>> call e.g. bpf_xdp_pull_data(xdp, 64) to make sure we pull in as much as
>> is needed w/o full linearization and once done the data/data_end can be
>> repeated to proceed. Native XDP will leave xdp->rxq->skb as NULL, but
>> later we could perhaps reuse the same bpf_xdp_pull_data() helper for
>> native with skb-less backing. Thoughts?
> 
> I'm curious why we consider a xdpgeneric-only addition. Is attaching
> a cls_bpf program noticeably slower than xdpgeneric?

Yeah, agree, I'm curious about that part as well.

Thanks,
Daniel