netdev - Re: [PATCH bpf-next v2] bpftool: add current libbpf

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Date:   Mon, 15 Nov 2021 23:34:11 +0000
From:   Quentin Monnet <quentin@...valent.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH bpf-next v2] bpftool: add current libbpf_strict mode to
 version output

On Mon, 15 Nov 2021 at 19:31, Stanislav Fomichev <sdf@...gle.com> wrote:
>
> + bpftool --legacy --version
> bpftool v5.15.0
> features: libbfd, skeletons
> + bpftool --version
> bpftool v5.15.0
> features: libbfd, libbpf_strict, skeletons
>
> + bpftool --legacy --help
> Usage: bpftool [OPTIONS] OBJECT { COMMAND | help }
>        bpftool batch file FILE
>        bpftool version
>
>        OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter }
>        OPTIONS := { {-j|--json} [{-p|--pretty}] | {-d|--debug} | {-l|--legacy} |
>                     {-V|--version} }
> + bpftool --help
> Usage: bpftool [OPTIONS] OBJECT { COMMAND | help }
>        bpftool batch file FILE
>        bpftool version
>
>        OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter }
>        OPTIONS := { {-j|--json} [{-p|--pretty}] | {-d|--debug} | {-l|--legacy} |
>                     {-V|--version} }
>
> + bpftool --legacy
> Usage: bpftool [OPTIONS] OBJECT { COMMAND | help }
>        bpftool batch file FILE
>        bpftool version
>
>        OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter }
>        OPTIONS := { {-j|--json} [{-p|--pretty}] | {-d|--debug} | {-l|--legacy} |
>                     {-V|--version} }
> + bpftool
> Usage: bpftool [OPTIONS] OBJECT { COMMAND | help }
>        bpftool batch file FILE
>        bpftool version
>
>        OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter }
>        OPTIONS := { {-j|--json} [{-p|--pretty}] | {-d|--debug} | {-l|--legacy} |
>                     {-V|--version} }
>
> + bpftool --legacy version
> bpftool v5.15.0
> features: libbfd, skeletons
> + bpftool version
> bpftool v5.15.0
> features: libbfd, libbpf_strict, skeletons
>
> + bpftool --json --legacy version
> {"version":"5.15.0","features":{"libbfd":true,"libbpf_strict":false,"skeletons":true}}
> + bpftool --json version
> {"version":"5.15.0","features":{"libbfd":true,"libbpf_strict":true,"skeletons":true}}
>
> v2:
> - fixes for -h and -V (Quentin Monnet)
>
> Suggested-by: Quentin Monnet <quentin@...valent.com>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>

The behaviour will change in a few cases where both the help and
version commands and/or options are provided, e.g. "bpftool -h
version" used to print the help and will do the version instead,
"bpftool -V help" changes in an opposite fashion. Given that there's
no practical interest in having both commands/options, and that the
behaviour was not really consistent so far, I consider that this is
not an issue.

However, we now have "bpftool --version" returning -1 (instead of 0).
Any chance we can fix that? Maybe simply something like the change
below instead?

------
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 473791e87f7d..b2e67b0f02cf 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -400,6 +400,7 @@ int main(int argc, char **argv)
         { "legacy",    no_argument,    NULL,    'l' },
         { 0 }
     };
+    bool version_requested = false;
     int opt, ret;

     last_do_help = do_help;
@@ -414,7 +415,8 @@ int main(int argc, char **argv)
                   options, NULL)) >= 0) {
         switch (opt) {
         case 'V':
-            return do_version(argc, argv);
+            version_requested = true;
+            break;
         case 'h':
             return do_help(argc, argv);
         case 'p':
@@ -479,6 +481,9 @@ int main(int argc, char **argv)
     if (argc < 0)
         usage();

+    if (version_requested)
+        return do_version(argc, argv);
+
     ret = cmd_select(cmds, argc, argv, do_help);

     if (json_output)