netdev - Re: [PATCH v9 bpf-next 01/14] net: skbuff: add data_len field to skb_shared

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Message-ID: <CAKgT0UcwYHXosz-XuQximak63=ugb9thEc=dkUUZzDpoPCH+Qg@mail.gmail.com>
Date:   Mon, 28 Jun 2021 12:58:33 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf <bpf@...r.kernel.org>, Netdev <netdev@...r.kernel.org>,
        lorenzo.bianconi@...hat.com, David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, shayagr@...zon.com,
        "Jubran, Samih" <sameehj@...zon.com>,
        John Fastabend <john.fastabend@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Saeed Mahameed <saeed@...nel.org>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Tirthendu <tirthendu.sarkar@...el.com>
Subject: Re: [PATCH v9 bpf-next 01/14] net: skbuff: add data_len field to skb_shared_info

On Mon, Jun 14, 2021 at 5:50 AM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
>
> data_len field will be used for paged frame len for xdp_buff/xdp_frame.
> This is a preliminary patch to properly support xdp-multibuff
>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>  include/linux/skbuff.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index dbf820a50a39..332ec56c200d 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -522,7 +522,10 @@ struct skb_shared_info {
>         struct sk_buff  *frag_list;
>         struct skb_shared_hwtstamps hwtstamps;
>         unsigned int    gso_type;
> -       u32             tskey;
> +       union {
> +               u32     tskey;
> +               u32     data_len;
> +       };
>

Rather than use the tskey field why not repurpose the gso_size field?
I would think in the XDP paths that the gso fields would be unused
since LRO and HW_GRO would be incompatible with XDP anyway.