libbpf: Add low-level APIs for new bpf_link commands

Add low-level API calls for bpf_link_get_next_id() and
bpf_link_get_fd_by_id().
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-6-andriin@fb.com

tools/lib/bpf/bpf.c

@@ -721,6 +721,11 @@ int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id)
 	return bpf_obj_get_next_id(start_id, next_id, BPF_BTF_GET_NEXT_ID);
 }
 
+int bpf_link_get_next_id(__u32 start_id, __u32 *next_id)
+{
+	return bpf_obj_get_next_id(start_id, next_id, BPF_LINK_GET_NEXT_ID);
+}
+
 int bpf_prog_get_fd_by_id(__u32 id)
 {
 	union bpf_attr attr;
@@ -751,13 +756,23 @@ int bpf_btf_get_fd_by_id(__u32 id)
 	return sys_bpf(BPF_BTF_GET_FD_BY_ID, &attr, sizeof(attr));
 }
 
-int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len)
+int bpf_link_get_fd_by_id(__u32 id)
+{
+	union bpf_attr attr;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.link_id = id;
+
+	return sys_bpf(BPF_LINK_GET_FD_BY_ID, &attr, sizeof(attr));
+}
+
+int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len)
 {
 	union bpf_attr attr;
 	int err;
 
 	memset(&attr, 0, sizeof(attr));
-	attr.info.bpf_fd = prog_fd;
+	attr.info.bpf_fd = bpf_fd;
 	attr.info.info_len = *info_len;
 	attr.info.info = ptr_to_u64(info);
 

tools/lib/bpf/bpf.h

@@ -216,10 +216,12 @@ LIBBPF_API int bpf_prog_test_run(int prog_fd, int repeat, void *data,
 LIBBPF_API int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id);
 LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id);
 LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id);
+LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id);
 LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
-LIBBPF_API int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len);
+LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
+LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len);
 LIBBPF_API int bpf_prog_query(int target_fd, enum bpf_attach_type type,
 			      __u32 query_flags, __u32 *attach_flags,
 			      __u32 *prog_ids, __u32 *prog_cnt);

tools/lib/bpf/libbpf.map

@@ -254,3 +254,9 @@ LIBBPF_0.0.8 {
 		bpf_program__set_lsm;
 		bpf_set_link_xdp_fd_opts;
 } LIBBPF_0.0.7;
+
+LIBBPF_0.0.9 {
+	global:
+		bpf_link_get_fd_by_id;
+		bpf_link_get_next_id;
+} LIBBPF_0.0.8;