netdev - Re: [PATCH bpf] libbpf: fix XDP program load regression for old kernels

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Message-ID: <CAADnVQLtxtMOsuBvt0U_UTLVuX-X__AWuih8t-CuGu67GbZJ_w@mail.gmail.com>
Date:   Thu, 24 Sep 2020 10:34:33 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Kernel Team <kernel-team@...com>,
        Nikita Shirokov <tehnerd@...nerd.com>,
        Udip Pant <udippant@...com>
Subject: Re: [PATCH bpf] libbpf: fix XDP program load regression for old kernels

On Thu, Sep 24, 2020 at 10:18 AM Andrii Nakryiko <andriin@...com> wrote:
>
> Fix regression in libbpf, introduced by XDP link change, which causes XDP
> programs to fail to be loaded into kernel due to specified BPF_XDP
> expected_attach_type. While kernel doesn't enforce expected_attach_type for
> BPF_PROG_TYPE_XDP, some old kernels already support XDP program, but they
> don't yet recognize expected_attach_type field in bpf_attr, so setting it to
> non-zero value causes program load to fail.
>
> Luckily, libbpf already has a mechanism to deal with such cases, so just make
> expected_attach_type optional for XDP programs.
>
> Reported-by: Nikita Shirokov <tehnerd@...nerd.com>
> Reported-by: Udip Pant <udippant@...com>
> Fixes: dc8698cac7aa ("libbpf: Add support for BPF XDP link")
> Signed-off-by: Andrii Nakryiko <andriin@...com>

Applied. Thanks

Looks like libbpf CI needs to add a few old kernels.