[PATCH bpf-next] bpftool: use only nftw for file tree parsing

[Tony Ambardar <tony.ambardar@gmail.com>]

The bpftool sources include code to walk file trees, but use multiple
frameworks to do so: nftw and fts. While nftw conforms to POSIX/SUSv3 and
is widely available, fts is not conformant and less common, especially on
non-glibc systems. The inconsistent framework usage hampers maintenance
and portability of bpftool, in particular for embedded systems.

Standardize usage by rewriting one fts-based function to use nftw. This
change allows building bpftool against musl for OpenWrt.

Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
---
 tools/bpf/bpftool/common.c | 102 ++++++++++++++++++++-----------------
 1 file changed, 54 insertions(+), 48 deletions(-)

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index 29f4e7611ae8..765de99770fb 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -4,7 +4,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
-#include <fts.h>
+#include <ftw.h>
 #include <libgen.h>
 #include <mntent.h>
 #include <stdbool.h>
@@ -367,68 +367,74 @@ void print_hex_data_json(uint8_t *data, size_t len)
 	jsonw_end_array(json_wtr);
 }
 
-int build_pinned_obj_table(struct pinned_obj_table *tab,
-			   enum bpf_obj_type type)
+static struct pinned_obj_table *build_fn_table; /* params for nftw cb*/
+static enum bpf_obj_type build_fn_type;
+
+static int do_build_table_cb(const char *fpath, const struct stat *sb,
+			    int typeflag, struct FTW *ftwbuf)
 {
 	struct bpf_prog_info pinned_info = {};
 	struct pinned_obj *obj_node = NULL;
 	__u32 len = sizeof(pinned_info);
-	struct mntent *mntent = NULL;
 	enum bpf_obj_type objtype;
+	int fd, err = 0;
+
+	if (typeflag != FTW_F)
+		goto out_ret;
+	fd = open_obj_pinned(fpath, true);
+	if (fd < 0)
+		goto out_ret;
+
+	objtype = get_fd_type(fd);
+	if (objtype != build_fn_type)
+		goto out_close;
+
+	memset(&pinned_info, 0, sizeof(pinned_info));
+	if (bpf_obj_get_info_by_fd(fd, &pinned_info, &len)) {
+		p_err("can't get obj info: %s", strerror(errno));
+		goto out_close;
+	}
+
+	obj_node = malloc(sizeof(*obj_node));
+	if (!obj_node) {
+		p_err("mem alloc failed");
+		err = -1;
+		goto out_close;
+	}
+
+	memset(obj_node, 0, sizeof(*obj_node));
+	obj_node->id = pinned_info.id;
+	obj_node->path = strdup(fpath);
+	hash_add(build_fn_table->table, &obj_node->hash, obj_node->id);
+
+out_close:
+	close(fd);
+out_ret:
+	return err;
+}
+
+int build_pinned_obj_table(struct pinned_obj_table *tab,
+			   enum bpf_obj_type type)
+{
+	struct mntent *mntent = NULL;
 	FILE *mntfile = NULL;
-	FTSENT *ftse = NULL;
-	FTS *fts = NULL;
-	int fd, err;
+	int flags = FTW_PHYS;
+	int nopenfd = 16;
 
 	mntfile = setmntent("/proc/mounts", "r");
 	if (!mntfile)
 		return -1;
 
+	build_fn_table = tab;
+	build_fn_type = type;
+
 	while ((mntent = getmntent(mntfile))) {
-		char *path[] = { mntent->mnt_dir, NULL };
+		char *path = mntent->mnt_dir;
 
 		if (strncmp(mntent->mnt_type, "bpf", 3) != 0)
 			continue;
-
-		fts = fts_open(path, 0, NULL);
-		if (!fts)
-			continue;
-
-		while ((ftse = fts_read(fts))) {
-			if (!(ftse->fts_info & FTS_F))
-				continue;
-			fd = open_obj_pinned(ftse->fts_path, true);
-			if (fd < 0)
-				continue;
-
-			objtype = get_fd_type(fd);
-			if (objtype != type) {
-				close(fd);
-				continue;
-			}
-			memset(&pinned_info, 0, sizeof(pinned_info));
-			err = bpf_obj_get_info_by_fd(fd, &pinned_info, &len);
-			if (err) {
-				close(fd);
-				continue;
-			}
-
-			obj_node = malloc(sizeof(*obj_node));
-			if (!obj_node) {
-				close(fd);
-				fts_close(fts);
-				fclose(mntfile);
-				return -1;
-			}
-
-			memset(obj_node, 0, sizeof(*obj_node));
-			obj_node->id = pinned_info.id;
-			obj_node->path = strdup(ftse->fts_path);
-			hash_add(tab->table, &obj_node->hash, obj_node->id);
-
-			close(fd);
-		}
-		fts_close(fts);
+		if (nftw(path, do_build_table_cb, nopenfd, flags) == -1)
+			break;
 	}
 	fclose(mntfile);
 	return 0;
-- 
2.17.1