stat-util: introduce {stat,fd}_verify_linked()

src/basic/stat-util.c

@@ -260,6 +260,26 @@ int path_is_network_fs(const char *path) {
         return is_network_fs(&s);
 }
 
+int stat_verify_linked(const struct stat *st) {
+        assert(st);
+
+        if (st->st_nlink <= 0)
+                return -EIDRM; /* recognizable error. */
+
+        return 0;
+}
+
+int fd_verify_linked(int fd) {
+        struct stat st;
+
+        assert(fd >= 0);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        return stat_verify_linked(&st);
+}
+
 int stat_verify_regular(const struct stat *st) {
         assert(st);
 

src/basic/stat-util.h

@@ -72,6 +72,9 @@ int path_is_network_fs(const char *path);
  */
 #define F_TYPE_EQUAL(a, b) (a == (typeof(a)) b)
 
+int stat_verify_linked(const struct stat *st);
+int fd_verify_linked(int fd);
+
 int stat_verify_regular(const struct stat *st);
 int fd_verify_regular(int fd);
 int verify_regular_at(int dir_fd, const char *path, bool follow);