netdev - [PATCH iproute2 master v2 2/2] bpf: fix mnt path when from env

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Date:   Sun, 23 Jul 2017 01:22:19 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     stephen@...workplumber.org
Cc:     ast@...com, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH iproute2 master v2 2/2] bpf: fix mnt path when from env

When bpf fs mount path is from env, behavior is currently broken as
we continue to search in default paths, thus fix this up.

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
 lib/bpf.c | 55 +++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 45 insertions(+), 10 deletions(-)

diff --git a/lib/bpf.c b/lib/bpf.c
index 5d9f0a5..e7a4d12 100644
--- a/lib/bpf.c
+++ b/lib/bpf.c
@@ -459,6 +459,24 @@ static int bpf_mnt_fs(const char *target)
 	return 0;
 }
 
+static int bpf_mnt_check_target(const char *target)
+{
+	struct stat sb = {};
+	int ret;
+
+	ret = stat(target, &sb);
+	if (ret) {
+		ret = mkdir(target, S_IRWXU);
+		if (ret) {
+			fprintf(stderr, "mkdir %s failed: %s\n", target,
+				strerror(errno));
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
 static int bpf_valid_mntpt(const char *mnt, unsigned long magic)
 {
 	struct statfs st_fs;
@@ -471,6 +489,21 @@ static int bpf_valid_mntpt(const char *mnt, unsigned long magic)
 	return 0;
 }
 
+static const char *bpf_find_mntpt_single(unsigned long magic, char *mnt,
+					 int len, const char *mntpt)
+{
+	int ret;
+
+	ret = bpf_valid_mntpt(mntpt, magic);
+	if (!ret) {
+		strncpy(mnt, mntpt, len - 1);
+		mnt[len - 1] = 0;
+		return mnt;
+	}
+
+	return NULL;
+}
+
 static const char *bpf_find_mntpt(const char *fstype, unsigned long magic,
 				  char *mnt, int len,
 				  const char * const *known_mnts)
@@ -482,11 +515,8 @@ static const char *bpf_find_mntpt(const char *fstype, unsigned long magic,
 	if (known_mnts) {
 		ptr = known_mnts;
 		while (*ptr) {
-			if (bpf_valid_mntpt(*ptr, magic) == 0) {
-				strncpy(mnt, *ptr, len - 1);
-				mnt[len - 1] = 0;
+			if (bpf_find_mntpt_single(magic, mnt, len, *ptr))
 				return mnt;
-			}
 			ptr++;
 		}
 	}
@@ -664,6 +694,7 @@ static const char *bpf_get_work_dir(enum bpf_prog_type type)
 	static char bpf_wrk_dir[PATH_MAX];
 	static const char *mnt;
 	static bool bpf_mnt_cached;
+	const char *mnt_env = getenv(BPF_ENV_MNT);
 	static const char * const bpf_known_mnts[] = {
 		BPF_DIR_MNT,
 		"/bpf",
@@ -682,13 +713,17 @@ static const char *bpf_get_work_dir(enum bpf_prog_type type)
 		return out;
 	}
 
-	mnt = bpf_find_mntpt("bpf", BPF_FS_MAGIC, bpf_tmp, sizeof(bpf_tmp),
-			     bpf_known_mnts);
+	if (mnt_env)
+		mnt = bpf_find_mntpt_single(BPF_FS_MAGIC, bpf_tmp,
+					    sizeof(bpf_tmp), mnt_env);
+	else
+		mnt = bpf_find_mntpt("bpf", BPF_FS_MAGIC, bpf_tmp,
+				     sizeof(bpf_tmp), bpf_known_mnts);
 	if (!mnt) {
-		mnt = getenv(BPF_ENV_MNT);
-		if (!mnt)
-			mnt = BPF_DIR_MNT;
-		ret = bpf_mnt_fs(mnt);
+		mnt = mnt_env ? : BPF_DIR_MNT;
+		ret = bpf_mnt_check_target(mnt);
+		if (!ret)
+			ret = bpf_mnt_fs(mnt);
 		if (ret) {
 			mnt = NULL;
 			goto out;
-- 
2.9.3