netdev - Re: [PATCH bpf-next v4 0/3] Add skb + xdp dynptrs

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Date:   Tue, 23 Aug 2022 04:31:49 +0200
From:   Kumar Kartikeya Dwivedi <memxor@...il.com>
To:     Joanne Koong <joannelkoong@...il.com>
Cc:     bpf@...r.kernel.org, andrii@...nel.org, daniel@...earbox.net,
        ast@...nel.org, kafai@...com, kuba@...nel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v4 0/3] Add skb + xdp dynptrs

On Tue, 23 Aug 2022 at 02:06, Joanne Koong <joannelkoong@...il.com> wrote:
>
> This patchset is the 2nd in the dynptr series. The 1st can be found here [0].
>
> This patchset adds skb and xdp type dynptrs, which have two main benefits for
> packet parsing:
>     * allowing operations on sizes that are not statically known at
>       compile-time (eg variable-sized accesses).
>     * more ergonomic and less brittle iteration through data (eg does not need
>       manual if checking for being within bounds of data_end)
>

Just curious: so would you be adding a dynptr interface for obtaining
data_meta slices as well in the future? Since the same manual bounds
checking is needed for data_meta vs data. How would that look in the
generic dynptr interface of data/read/write this set is trying to fit
things in?



> When comparing the differences in runtime for packet parsing without dynptrs
> vs. with dynptrs for the more simple cases, there is no noticeable difference.
> For the more complex cases where lengths are non-statically known at compile
> time, there can be a significant speed-up when using dynptrs (eg a 2x speed up
> for cls redirection). Patch 3 contains more details as well as examples of how
> to use skb and xdp dynptrs.
>
> [0] https://lore.kernel.org/bpf/20220523210712.3641569-1-joannelkoong@gmail.com/
>
> --