tar-util: add support for extracting OCI compatible whiteouts, and turn them into overlayfs whiteouts
This commit is contained in:
Lennart Poettering
+136
-20
@@ -147,8 +147,8 @@ static int open_inode_finalize(OpenInode *of) {
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/* We adjust the UID/GID right before the mode, since doing this might affect the mode (drops
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* suid/sgid bits).
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*
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* We adjust the mode only when leaving a dir, because if we are unpriv we might lose the
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* ability to enter it once we do this. */
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* We adjust the mode only when leaving a dir, because if we are unprivileged we might lose
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* the ability to enter it once we do this. */
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if (uid_is_valid(of->uid) || gid_is_valid(of->gid) || of->mode != MODE_INVALID) {
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k = fchmod_and_chown_with_fallback(of->fd, /* path= */ NULL, of->mode, of->uid, of->gid);
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@@ -277,6 +277,91 @@ static int archive_unpack_regular(
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return TAKE_FD(fd);
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}
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static int overlayfs_fsetfattr(
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const char *path, /* purely decorative, for log purposes */
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int fd,
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const char *name, /* xattr key name */
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const char *value /* xattr value */) {
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int r;
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assert(fd >= 0);
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assert(path);
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assert(name);
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assert(value);
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/* overlayfs knows magic {user|trusted}.overlay.* xattrs for whiteouts and opaque directories. The
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* 'user.overlay.*' ones are only checked if overlayfs is mounted with "userxattr". We only set that
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* one because we want to operate unprivileged. Ideally, we'd set both here, to maximize the chance
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* that things work both in privileged and unprivileged scenarios, but unfortunately this has the
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* effect that the privileged ones are ignored (and visible in the overlayfs mount). */
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_cleanup_free_ char *n = strjoin("user.overlay.", name);
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if (!n)
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return log_oom();
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r = xsetxattr(fd, /* path= */ NULL, AT_EMPTY_PATH, n, value);
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if (r < 0)
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return log_error_errno(r, "Failed to set '%s' xattr on file '%s': %m", n, path);
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return 0;
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}
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static int archive_unpack_whiteout(
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struct archive *a,
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struct archive_entry *entry,
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int parent_fd,
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const char *parent_path, /* Full path of 'parent_fd', purely decorative for log purposes */
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const char *filename, /* Just the filename we are supposed to whiteout */
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const char *path /* Full path of the whiteout file, purely decorative for log purposes */) {
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int r;
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assert(a);
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assert(entry);
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assert(parent_fd >= 0);
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assert(parent_path);
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assert(filename);
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assert(path);
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_cleanup_free_ char *tmp = NULL;
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_cleanup_close_ int fd = open_tmpfile_linkable_at(parent_fd, filename, O_CLOEXEC|O_WRONLY, &tmp);
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if (fd < 0)
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return log_error_errno(fd, "Failed to create whiteout file for '%s': %m", path);
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CLEANUP_TMPFILE_AT(parent_fd, tmp);
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r = overlayfs_fsetfattr(path, fd, "whiteout", "y");
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if (r < 0)
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return r;
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/* As per https://docs.kernel.org/filesystems/overlayfs.html also mark the parent */
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r = overlayfs_fsetfattr(parent_path, parent_fd, "opaque", "x");
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if (r < 0)
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return r;
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r = link_tmpfile_at(fd, parent_fd, tmp, filename, LINK_TMPFILE_REPLACE);
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if (r < 0)
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return log_error_errno(r, "Failed to install regular file '%s': %m", path);
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tmp = mfree(tmp); /* disarm CLEANUP_TMPFILE_AT */
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return 0; /* we do not return an fd here, because this kills an inode, and doesn't synthesize one */
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}
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static int archive_unpack_opaque(
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struct archive *a,
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struct archive_entry *entry,
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int parent_fd,
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const char *parent_path) {
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assert(a);
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assert(entry);
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assert(parent_fd >= 0);
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assert(parent_path);
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/* we do not return an fd here either */
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return overlayfs_fsetfattr(parent_path, parent_fd, "opaque", "y");
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}
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static int archive_unpack_directory(
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struct archive *a,
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struct archive_entry *entry,
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@@ -908,15 +993,45 @@ int tar_x(int input_fd, int tree_fd, TarFlags flags) {
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switch (filetype) {
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case S_IFREG:
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if (FLAGS_SET(flags, TAR_OCI_WHITEOUTS)) {
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if (streq(e, ".wh..wh..opq")) {
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r = archive_unpack_opaque(a, entry, parent_fd, empty_to_root(parent_path));
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if (r < 0)
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return r;
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/* NB: this does not create an inode! */
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break;
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}
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const char *w = startswith(e, ".wh.");
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if (w) {
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if (!filename_is_valid(w))
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return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Invalid whiteout file entry '%s', refusing.", e);
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r = archive_unpack_whiteout(a, entry, parent_fd, empty_to_root(parent_path), w, j);
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if (r < 0)
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return r;
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/* NB: this does not create an inode! */
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break;
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}
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}
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fd = archive_unpack_regular(a, entry, parent_fd, e, j, fflags);
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if (fd < 0)
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return fd;
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break;
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case S_IFDIR:
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fd = archive_unpack_directory(a, entry, parent_fd, e, j, fflags);
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if (fd < 0)
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return fd;
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break;
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case S_IFLNK:
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fd = archive_unpack_symlink(a, entry, parent_fd, e, j);
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if (fd < 0)
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return fd;
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break;
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case S_IFCHR:
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@@ -924,6 +1039,8 @@ int tar_x(int input_fd, int tree_fd, TarFlags flags) {
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case S_IFIFO:
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case S_IFSOCK:
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fd = archive_unpack_special_inode(a, entry, parent_fd, e, j, filetype);
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if (fd < 0)
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return fd;
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break;
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default:
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@@ -931,9 +1048,6 @@ int tar_x(int input_fd, int tree_fd, TarFlags flags) {
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SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Unexpected file type %i of '%s', refusing.", (int) filetype, j);
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}
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if (fd < 0)
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return fd;
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} else {
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/* This is some intermediary node in the path that we haven't opened yet. Create it with default attributes */
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fd = open_mkdir_at(parent_fd, e, O_CLOEXEC, 0700);
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@@ -949,22 +1063,24 @@ int tar_x(int input_fd, int tree_fd, TarFlags flags) {
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* fully done with the inode (i.e. after creating further inodes inside of dir inodes
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* for example), due to permission problems this might create or that the mtime
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* changes we do might still be affected by our changes. */
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open_inodes[n_open_inodes++] = (OpenInode) {
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.fd = TAKE_FD(fd),
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.path = TAKE_PTR(j),
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.filetype = filetype,
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.mode = mode,
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.mtime = mtime,
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.uid = uid,
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.gid = gid,
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.fflags = fflags,
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.acl_access = TAKE_PTR(acl_access),
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.acl_default = TAKE_PTR(acl_default),
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.xattr = TAKE_PTR(xa),
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.n_xattr = n_xa,
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};
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if (fd >= 0) {
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open_inodes[n_open_inodes++] = (OpenInode) {
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.fd = TAKE_FD(fd),
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.path = TAKE_PTR(j),
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.filetype = filetype,
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.mode = mode,
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.mtime = mtime,
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.uid = uid,
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.gid = gid,
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.fflags = fflags,
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.acl_access = TAKE_PTR(acl_access),
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.acl_default = TAKE_PTR(acl_default),
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.xattr = TAKE_PTR(xa),
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.n_xattr = n_xa,
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};
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n_xa = 0;
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n_xa = 0;
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}
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}
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}
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@@ -4,6 +4,7 @@
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typedef enum TarFlags {
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TAR_SELINUX = 1 << 0, /* Include SELinux xattr in tarball, or unpack it */
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TAR_SQUASH_UIDS_ABOVE_64K = 1 << 1, /* Squash UIDs/GIDs above 64K when packing/unpacking to the nobody user */
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TAR_OCI_WHITEOUTS = 1 << 2, /* Turn OCI/aufs whiteout inodes into overlayfs whiteouts */
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} TarFlags;
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int tar_x(int input_fd, int tree_fd, TarFlags flags);
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