libbpf: Add a helper for retrieving a map fd for a given name

XDP samples are mostly cooperating with eBPF maps through their file
descriptors. In case of a eBPF program that contains multiple maps it
might be tiresome to iterate through them and call bpf_map__fd for each
one. Add a helper mostly based on bpf_object__find_map_by_name, but
instead of returning the struct bpf_map pointer, return map fd.

Suggested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

3 files changed, 10 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2ccde17957e6..03bc01ca2577 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2884,6 +2884,12 @@ bpf_object__find_map_by_name(struct bpf_object *obj, const char *name)
         return NULL;
 }
 
+int
+bpf_object__find_map_fd_by_name(struct bpf_object *obj, const char *name)
+{
+        return bpf_map__fd(bpf_object__find_map_by_name(obj, name));
+}
+
 struct bpf_map *
 bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)
 {
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 62ae6cb93da1..931be6f3408c 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -264,6 +264,9 @@ struct bpf_map;
 LIBBPF_API struct bpf_map *
 bpf_object__find_map_by_name(struct bpf_object *obj, const char *name);
 
+LIBBPF_API int
+bpf_object__find_map_fd_by_name(struct bpf_object *obj, const char *name);
+
 /*
  * Get bpf_map through the offset of corresponding struct bpf_map_def
  * in the BPF object file.
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index f6f96fc38c50..43ba9bb8d24b 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -131,4 +131,5 @@ LIBBPF_0.0.2 {
                 bpf_probe_map_type;
                 bpf_probe_prog_type;
                 bpf_map_lookup_elem_flags;
+                bpf_object__find_map_fd_by_name;
 } LIBBPF_0.0.1;