netdev - Re: [PATCH net-next 06/33] net: XDP-generic determining XDP frame size

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Date:   Fri, 24 Apr 2020 16:03:23 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, sameehj@...zon.com
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, zorik@...zon.com, akiyano@...zon.com,
        gtzalik@...zon.com, Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        David Ahern <dsahern@...il.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        steffen.klassert@...unet.com
Subject: Re: [PATCH net-next 06/33] net: XDP-generic determining XDP frame size

Jesper Dangaard Brouer <brouer@...hat.com> writes:

> The SKB "head" pointer points to the data area that contains
> skb_shared_info, that can be found via skb_end_pointer(). Given
> xdp->data_hard_start have been established (basically pointing to
> skb->head), frame size is between skb_end_pointer() and data_hard_start,
> plus the size reserved to skb_shared_info.
>
> Change the bpf_xdp_adjust_tail offset adjust of skb->len, to be a positive
> offset number on grow, and negative number on shrink.  As this seems more
> natural when reading the code.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>

Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>