netdev - Re: [PATCH bpf-next v3 1/3] tools: bpftool: clean up function to dump map entry

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Message-ID: <CAEf4BzZZce3evrwkjQ1EbiHo5b_QKWn1kvCkZ=04X594Ee9RjA@mail.gmail.com>
Date:   Thu, 10 Sep 2020 09:41:54 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Quentin Monnet <quentin@...valent.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 1/3] tools: bpftool: clean up function to dump
 map entry

On Thu, Sep 10, 2020 at 3:27 AM Quentin Monnet <quentin@...valent.com> wrote:
>
> The function used to dump a map entry in bpftool is a bit difficult to
> follow, as a consequence to earlier refactorings. There is a variable
> ("num_elems") which does not appear to be necessary, and the error
> handling would look cleaner if moved to its own function. Let's clean it
> up. No functional change.
>
> v2:
> - v1 was erroneously removing the check on fd maps in an attempt to get
>   support for outer map dumps. This is already working. Instead, v2
>   focuses on cleaning up the dump_map_elem() function, to avoid
>   similar confusion in the future.
>
> Signed-off-by: Quentin Monnet <quentin@...valent.com>
> ---
>  tools/bpf/bpftool/map.c | 101 +++++++++++++++++++++-------------------
>  1 file changed, 52 insertions(+), 49 deletions(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index bc0071228f88..c8159cb4fb1e 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -213,8 +213,9 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
>         jsonw_end_object(json_wtr);
>  }
>
> -static void print_entry_error(struct bpf_map_info *info, unsigned char *key,
> -                             const char *error_msg)
> +static void
> +print_entry_error_msg(struct bpf_map_info *info, unsigned char *key,
> +                     const char *error_msg)
>  {
>         int msg_size = strlen(error_msg);
>         bool single_line, break_names;
> @@ -232,6 +233,40 @@ static void print_entry_error(struct bpf_map_info *info, unsigned char *key,
>         printf("\n");
>  }
>
> +static void
> +print_entry_error(struct bpf_map_info *map_info, void *key, int lookup_errno)
> +{
> +       /* For prog_array maps or arrays of maps, failure to lookup the value
> +        * means there is no entry for that key. Do not print an error message
> +        * in that case.
> +        */
> +       if (map_is_map_of_maps(map_info->type) ||
> +           map_is_map_of_progs(map_info->type))

&& lookup_errno == ENOENT

?


> +               return;
> +

[...]