+
+int same_fd(int a, int b) {
+ struct stat sta, stb;
+ pid_t pid;
+ int r, fa, fb;
+
+ assert(a >= 0);
+ assert(b >= 0);
+
+ /* Compares two file descriptors. Note that semantics are
+ * quite different depending on whether we have kcmp() or we
+ * don't. If we have kcmp() this will only return true for
+ * dup()ed file descriptors, but not otherwise. If we don't
+ * have kcmp() this will also return true for two fds of the same
+ * file, created by separate open() calls. Since we use this
+ * call mostly for filtering out duplicates in the fd store
+ * this difference hopefully doesn't matter too much. */
+
+ if (a == b)
+ return true;
+
+ /* Try to use kcmp() if we have it. */
+ pid = getpid();
+ r = kcmp(pid, pid, KCMP_FILE, a, b);
+ if (r == 0)
+ return true;
+ if (r > 0)
+ return false;
+ if (errno != ENOSYS)
+ return -errno;
+
+ /* We don't have kcmp(), use fstat() instead. */
+ if (fstat(a, &sta) < 0)
+ return -errno;
+
+ if (fstat(b, &stb) < 0)
+ return -errno;
+
+ if ((sta.st_mode & S_IFMT) != (stb.st_mode & S_IFMT))
+ return false;
+
+ /* We consider all device fds different, since two device fds
+ * might refer to quite different device contexts even though
+ * they share the same inode and backing dev_t. */
+
+ if (S_ISCHR(sta.st_mode) || S_ISBLK(sta.st_mode))
+ return false;
+
+ if (sta.st_dev != stb.st_dev || sta.st_ino != stb.st_ino)
+ return false;
+
+ /* The fds refer to the same inode on disk, let's also check
+ * if they have the same fd flags. This is useful to
+ * distuingish the read and write side of a pipe created with
+ * pipe(). */
+ fa = fcntl(a, F_GETFL);
+ if (fa < 0)
+ return -errno;
+
+ fb = fcntl(b, F_GETFL);
+ if (fb < 0)
+ return -errno;
+
+ return fa == fb;
+}
+
+int chattr_fd(int fd, bool b, int mask) {
+ int old_attr, new_attr;
+
+ assert(fd >= 0);
+
+ if (ioctl(fd, FS_IOC_GETFLAGS, &old_attr) < 0)
+ return -errno;
+
+ if (b)
+ new_attr = old_attr | mask;
+ else
+ new_attr = old_attr & ~mask;
+
+ if (new_attr == old_attr)
+ return 0;
+
+ if (ioctl(fd, FS_IOC_SETFLAGS, &new_attr) < 0)
+ return -errno;
+
+ return 0;
+}
+
+int chattr_path(const char *p, bool b, int mask) {
+ _cleanup_close_ int fd = -1;
+
+ fd = open(p, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+ if (fd < 0)
+ return -errno;
+
+ return chattr_fd(fd, b, mask);
+}