netdev - Re: [PATCH bpf-next v2 0/3] Add XDP support for bpf_load_hdr

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Message-ID: <87h7dsnbh5.fsf@toke.dk>
Date:   Thu, 07 Oct 2021 16:41:42 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Joanne Koong <joannekoong@...com>, bpf@...r.kernel.org
Cc:     kafai@...com, netdev@...r.kernel.org, Kernel-team@...com
Subject: Re: [PATCH bpf-next v2 0/3] Add XDP support for bpf_load_hdr_opt

Joanne Koong <joannekoong@...com> writes:

> Currently, bpf_sockops programs have been using bpf_load_hdr_opt() to
> parse the tcp header option. It will be useful to allow other bpf prog
> types to have a similar way of handling tcp hdr options.
>
> This series adds XDP support for bpf_load_hdr_opt(). At a high level,
> these patches are:

Why is this needed? Why not just parse the header directly in XDP? Seems
a bit arbitrary to add a helper for this particular type of packet
payload parsing to this particular program type. I.e., what about other
headers (IP options?)? Are we going to have a whole bunch of
special-purpose parsing helpers to pick out protocol data from packets?

Also, why only enable this for XDP (and not, say the TC hook as well)?

-Toke