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From:   Song Liu <song@kernel.org>
Date:   Thu, 5 Nov 2020 09:57:30 -0800
Message-ID: <CAPhsuW45MMnHHSpAKXB9iOrHxujiO_DroBmqEsRYXq6sKVso8g@mail.gmail.com>
Subject: Re: [PATCH bpf] tools/bpftool: fix attaching flow dissector
To:     Lorenz Bauer <lmb@cloudflare.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        kernel-team@cloudflare.com, Jiri Benc <jbenc@redhat.com>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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On Thu, Nov 5, 2020 at 3:54 AM Lorenz Bauer <lmb@cloudflare.com> wrote:
>
> My earlier patch to reject non-zero arguments to flow dissector attach
> broke attaching via bpftool. Instead of 0 it uses -1 for target_fd.
> Fix this by passing a zero argument when attaching the flow dissector.
>
> Fixes: 1b514239e859 ("bpf: flow_dissector: Check value of unused flags to BPF_PROG_ATTACH")
> Reported-by: Jiri Benc <jbenc@redhat.com>
> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
>  tools/bpf/bpftool/prog.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index d942c1e3372c..acdb2c245f0a 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -940,7 +940,7 @@ static int parse_attach_detach_args(int argc, char **argv, int *progfd,
>         }
>
>         if (*attach_type == BPF_FLOW_DISSECTOR) {
> -               *mapfd = -1;
> +               *mapfd = 0;
>                 return 0;
>         }
>
> --
> 2.25.1
>