[PATCH bpf-next v3 7/8] libbpf: add bpf_map__inner_map API

[Yauheni Kaliuta <yauheni.kaliuta@redhat.com>]

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>

The API gives access to inner map for map in map types (array or
hash of map). It will be used to dynamically set max_entries in it.

Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
---
 tools/lib/bpf/libbpf.c   | 10 ++++++++++
 tools/lib/bpf/libbpf.h   |  1 +
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 12 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7aad78dbb4b4..b48dc380059d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2194,6 +2194,7 @@ static int parse_btf_map_def(struct bpf_object *obj,
 			map->inner_map = calloc(1, sizeof(*map->inner_map));
 			if (!map->inner_map)
 				return -ENOMEM;
+			map->inner_map->fd = -1;
 			map->inner_map->sec_idx = obj->efile.btf_maps_shndx;
 			map->inner_map->name = malloc(strlen(map->name) +
 						      sizeof(".inner") + 1);
@@ -3845,6 +3846,14 @@ __u32 bpf_map__max_entries(const struct bpf_map *map)
 	return map->def.max_entries;
 }
 
+struct bpf_map *bpf_map__inner_map(struct bpf_map *map)
+{
+    if (!bpf_map_type__is_map_in_map(map->def.type))
+        return NULL;
+
+    return map->inner_map;
+}
+
 int bpf_map__set_max_entries(struct bpf_map *map, __u32 max_entries)
 {
 	if (map->fd >= 0)
@@ -9476,6 +9485,7 @@ int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd)
 		pr_warn("error: inner_map_fd already specified\n");
 		return -EINVAL;
 	}
+	zfree(&map->inner_map);
 	map->inner_map_fd = fd;
 	return 0;
 }
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index f500621d28e5..bec4e6a6e31d 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -480,6 +480,7 @@ LIBBPF_API int bpf_map__pin(struct bpf_map *map, const char *path);
 LIBBPF_API int bpf_map__unpin(struct bpf_map *map, const char *path);
 
 LIBBPF_API int bpf_map__set_inner_map_fd(struct bpf_map *map, int fd);
+LIBBPF_API struct bpf_map *bpf_map__inner_map(struct bpf_map *map);
 
 LIBBPF_API long libbpf_get_error(const void *ptr);
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index f5990f7208ce..eeb6d5ebd1cc 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -360,4 +360,5 @@ LIBBPF_0.4.0 {
 		bpf_linker__free;
 		bpf_linker__new;
 		bpf_object__set_kversion;
+		bpf_map__inner_map;
 } LIBBPF_0.3.0;
-- 
2.31.1