netdev - Re: [RFC bpf-next 3/5] libbpf: Pass prog_ifindex via bpf_object_open

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Message-ID: <CAEf4BzbgjOaxVFAfnrRyPP0_1Rh-gC3er4tKLkfr=OPb_x-ueA@mail.gmail.com>
Date:   Thu, 27 Oct 2022 13:05:36 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        haoluo@...gle.com, jolsa@...nel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org
Subject: Re: [RFC bpf-next 3/5] libbpf: Pass prog_ifindex via bpf_object_open_opts

On Thu, Oct 27, 2022 at 1:00 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> Allow passing prog_ifindex to BPF_PROG_LOAD. This patch is
> not XDP metadata specific but it's here because we (ab)use
> prog_ifindex as "target metadata" device during loading.
> We can figure out proper UAPI story if we decide to go forward
> with the kfunc approach.
>
> Cc: Martin KaFai Lau <martin.lau@...ux.dev>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Cc: Jesper Dangaard Brouer <brouer@...hat.com>
> Cc: Anatoly Burakov <anatoly.burakov@...el.com>
> Cc: Alexander Lobakin <alexandr.lobakin@...el.com>
> Cc: Magnus Karlsson <magnus.karlsson@...il.com>
> Cc: Maryam Tahhan <mtahhan@...hat.com>
> Cc: xdp-hints@...-project.net
> Cc: netdev@...r.kernel.org
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  tools/lib/bpf/libbpf.c | 1 +
>  tools/lib/bpf/libbpf.h | 6 +++++-
>  2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 5d7819edf074..61bc37006fe4 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -7190,6 +7190,7 @@ static int bpf_object_init_progs(struct bpf_object *obj, const struct bpf_object
>
>                 prog->type = prog->sec_def->prog_type;
>                 prog->expected_attach_type = prog->sec_def->expected_attach_type;
> +               prog->prog_ifindex = opts->prog_ifindex;
>
>                 /* sec_def can have custom callback which should be called
>                  * after bpf_program is initialized to adjust its properties
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index eee883f007f9..4a40b7623099 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -170,9 +170,13 @@ struct bpf_object_open_opts {
>          */
>         __u32 kernel_log_level;
>
> +       /* Optional ifindex of netdev for offload purposes.
> +        */
> +       int prog_ifindex;
> +

nope, don't do that, open_opts are for entire object, while this is
per-program thing

So bpf_program__set_ifindex() setter would be more appropriate


>         size_t :0;
>  };
> -#define bpf_object_open_opts__last_field kernel_log_level
> +#define bpf_object_open_opts__last_field prog_ifindex
>
>  LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
>
> --
> 2.38.1.273.g43a17bfeac-goog
>