map_in_map_fd 32 samples/bpf/test_map_in_map_user.c static void check_map_id(int inner_map_fd, int map_in_map_fd, uint32_t key) map_in_map_fd 41 samples/bpf/test_map_in_map_user.c ret = bpf_map_lookup_elem(map_in_map_fd, &key, &id);