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From:   KP Singh <kpsingh@chromium.org>
Date:   Thu, 19 Nov 2020 22:51:12 +0100
Message-ID: <CACYkzJ79eOai+k1=YfwvP_DNdxX1G+yJ-1vyhgoCqxWyJZGAGQ@mail.gmail.com>
Subject: Re: [PATCH v2 2/5] bpf: Add a bpf_sock_from_file helper
To:     Florent Revest <revest@chromium.org>
Cc:     bpf <bpf@vger.kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Florent Revest <revest@google.com>,
        open list <linux-kernel@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>
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On Thu, Nov 19, 2020 at 5:27 PM Florent Revest <revest@chromium.org> wrote:
>
> From: Florent Revest <revest@google.com>
>
> While eBPF programs can check whether a file is a socket by file->f_op
> == &socket_file_ops, they cannot convert the void private_data pointer
> to a struct socket BTF pointer. In order to do this a new helper
> wrapping sock_from_file is added.
>
> This is useful to tracing programs but also other program types
> inheriting this set of helpers such as iterators or LSM programs.
>
> Signed-off-by: Florent Revest <revest@google.com>

Acked-by: KP Singh <kpsingh@google.com>

Some minor comments.

> ---
>  include/uapi/linux/bpf.h       |  7 +++++++
>  kernel/trace/bpf_trace.c       | 20 ++++++++++++++++++++
>  scripts/bpf_helpers_doc.py     |  4 ++++
>  tools/include/uapi/linux/bpf.h |  7 +++++++
>  4 files changed, 38 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 162999b12790..7d598f161dc0 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3787,6 +3787,12 @@ union bpf_attr {
>   *             *ARG_PTR_TO_BTF_ID* of type *task_struct*.
>   *     Return
>   *             Pointer to the current task.
> + *
> + * struct socket *bpf_sock_from_file(struct file *file)
> + *     Description
> + *             If the given file contains a socket, returns the associated socket.

"If the given file is a socket" or "represents a socket" would fit better here.

> + *     Return
> + *             A pointer to a struct socket on success or NULL on failure.

NULL if the file is not a socket.