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

[Daniel Borkmann]

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 <dan...@iogearbox.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