[PATCH bpf-next v2 1/3] bpftool: Add libbpf's version number to "bpftool version" output

[Quentin Monnet <quentin@xxxxxxxxxxxxx>]

To help users check what version of libbpf is being used with bpftool,
print the number along with bpftool's own version number.

Output:

    $ ./bpftool version
    ./bpftool v5.16.0
    using libbpf v0.7
    features: libbfd, libbpf_strict, skeletons

    $ ./bpftool version --json --pretty
    {
        "version": "5.16.0",
        "libbpf_version": "0.7",
        "features": {
            "libbfd": true,
            "libbpf_strict": true,
            "skeletons": true
        }
    }

Note that libbpf_version_string() does note return the patch number.

Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
---
 tools/bpf/bpftool/Documentation/common_options.rst | 13 +++++++------
 tools/bpf/bpftool/main.c                           |  4 ++++
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/common_options.rst b/tools/bpf/bpftool/Documentation/common_options.rst
index 908487b9c2ad..c88e4c6a06d2 100644
--- a/tools/bpf/bpftool/Documentation/common_options.rst
+++ b/tools/bpf/bpftool/Documentation/common_options.rst
@@ -4,12 +4,13 @@
 	  Print short help message (similar to **bpftool help**).
 
 -V, --version
-	  Print version number (similar to **bpftool version**), and optional
-	  features that were included when bpftool was compiled. Optional
-	  features include linking against libbfd to provide the disassembler
-	  for JIT-ted programs (**bpftool prog dump jited**) and usage of BPF
-	  skeletons (some features like **bpftool prog profile** or showing
-	  pids associated to BPF objects may rely on it).
+	  Print bpftool's version number (similar to **bpftool version**), the
+	  number of the version of libbpf in use, and optional features that
+	  were included when bpftool was compiled. Optional features include
+	  linking against libbfd to provide the disassembler for JIT-ted
+	  programs (**bpftool prog dump jited**) and usage of BPF skeletons
+	  (some features like **bpftool prog profile** or showing pids
+	  associated to BPF objects may rely on it).
 
 -j, --json
 	  Generate JSON output. For commands that cannot produce JSON, this
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 490f7bd54e4c..6265ac5bcf4e 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -89,6 +89,9 @@ static int do_version(int argc, char **argv)
 
 		jsonw_name(json_wtr, "version");
 		jsonw_printf(json_wtr, "\"%s\"", BPFTOOL_VERSION);
+		jsonw_name(json_wtr, "libbpf_version");
+		/* Offset by one to skip the "v" prefix */
+		jsonw_printf(json_wtr, "\"%s\"", libbpf_version_string() + 1);
 
 		jsonw_name(json_wtr, "features");
 		jsonw_start_object(json_wtr);	/* features */
@@ -102,6 +105,7 @@ static int do_version(int argc, char **argv)
 		unsigned int nb_features = 0;
 
 		printf("%s v%s\n", bin_name, BPFTOOL_VERSION);
+		printf("using libbpf %s\n", libbpf_version_string());
 		printf("features:");
 		if (has_libbfd) {
 			printf(" libbfd");
-- 
2.32.0