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@@ -47,6 +47,9 @@ type (
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GIDMaps []idtools.IDMap
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ChownOpts *TarChownOptions
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IncludeSourceDir bool
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+ // When unpacking convert whiteouts and opaque dirs from aufs format to overlayfs format
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+ // When packing convert whiteouts and opaque dirs from overlayfs format to aufs format
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+ OverlayFormat bool
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// When unpacking, specifies whether overwriting a directory with a
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// non-directory is allowed and vice versa.
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NoOverwriteDirNonDir bool
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@@ -236,6 +239,11 @@ type tarAppender struct {
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SeenFiles map[uint64]string
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UIDMaps []idtools.IDMap
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GIDMaps []idtools.IDMap
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+
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+ // `overlayFormat` controls whether to interpret character devices with numbers 0,0
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+ // and directories with the attribute `trusted.overlay.opaque` using their overlayfs
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+ // meanings and remap them to AUFS format
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+ OverlayFormat bool
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}
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// canonicalTarName provides a platform-independent and consistent posix-style
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@@ -253,6 +261,7 @@ func canonicalTarName(name string, isDir bool) (string, error) {
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return name, nil
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}
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+// addTarFile adds to the tar archive a file from `path` as `name`
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func (ta *tarAppender) addTarFile(path, name string) error {
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fi, err := os.Lstat(path)
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if err != nil {
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@@ -323,6 +332,16 @@ func (ta *tarAppender) addTarFile(path, name string) error {
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hdr.Gid = xGID
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}
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+ if ta.OverlayFormat {
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+ // convert whiteouts to AUFS format
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+ if fi.Mode()&os.ModeCharDevice != 0 && hdr.Devmajor == 0 && hdr.Devminor == 0 {
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+ // we just rename the file and make it normal
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+ hdr.Name = WhiteoutPrefix + hdr.Name
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+ hdr.Mode = 0600
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+ hdr.Typeflag = tar.TypeReg
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+ }
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+ }
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+
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if err := ta.TarWriter.WriteHeader(hdr); err != nil {
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return err
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}
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@@ -346,6 +365,30 @@ func (ta *tarAppender) addTarFile(path, name string) error {
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}
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}
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+ if ta.OverlayFormat {
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+ // convert opaque dirs to AUFS format by writing an empty file with the prefix
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+ opaque, _ := system.Lgetxattr(path, "trusted.overlay.opaque")
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+ if opaque != nil && len(opaque) == 1 && opaque[0] == 'y' {
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+ // create a header for the whiteout file
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+ // it should inherit some properties from the parent, but be a regular file
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+ whHdr := &tar.Header{
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+ Typeflag: tar.TypeReg,
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+ Mode: hdr.Mode & int64(os.ModePerm),
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+ Name: filepath.Join(name, WhiteoutOpaqueDir),
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+ Size: 0,
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+ Uid: hdr.Uid,
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+ Uname: hdr.Uname,
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+ Gid: hdr.Gid,
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+ Gname: hdr.Gname,
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+ AccessTime: hdr.AccessTime,
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+ ChangeTime: hdr.ChangeTime,
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+ }
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+ if err := ta.TarWriter.WriteHeader(whHdr); err != nil {
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+ return err
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+ }
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+ }
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+ }
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+
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return nil
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}
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@@ -501,11 +544,12 @@ func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error)
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go func() {
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ta := &tarAppender{
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- TarWriter: tar.NewWriter(compressWriter),
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- Buffer: pools.BufioWriter32KPool.Get(nil),
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- SeenFiles: make(map[uint64]string),
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- UIDMaps: options.UIDMaps,
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- GIDMaps: options.GIDMaps,
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+ TarWriter: tar.NewWriter(compressWriter),
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+ Buffer: pools.BufioWriter32KPool.Get(nil),
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+ SeenFiles: make(map[uint64]string),
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+ UIDMaps: options.UIDMaps,
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+ GIDMaps: options.GIDMaps,
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+ OverlayFormat: options.OverlayFormat,
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}
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defer func() {
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@@ -766,6 +810,37 @@ loop:
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hdr.Gid = xGID
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}
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+ base := filepath.Base(path)
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+ dir := filepath.Dir(path)
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+
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+ if options.OverlayFormat {
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+ // if a directory is marked as opaque by the AUFS special file, we need to translate that to overlay
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+ if base == WhiteoutOpaqueDir {
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+ if err := syscall.Setxattr(dir, "trusted.overlay.opaque", []byte{'y'}, 0); err != nil {
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+ return err
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+ }
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+
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+ // don't write the file itself
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+ continue
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+ }
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+
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+ // if a file was deleted and we are using overlay, we need to create a character device
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+ if strings.HasPrefix(base, WhiteoutPrefix) {
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+ originalBase := base[len(WhiteoutPrefix):]
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+ originalPath := filepath.Join(dir, originalBase)
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+
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+ if err := syscall.Mknod(originalPath, syscall.S_IFCHR, 0); err != nil {
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+ return err
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+ }
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+ if err := os.Chown(originalPath, hdr.Uid, hdr.Gid); err != nil {
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+ return err
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+ }
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+
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+ // don't write the file itself
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+ continue
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+ }
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+ }
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+
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if err := createTarFile(path, dest, hdr, trBuf, !options.NoLchown, options.ChownOpts); err != nil {
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return err
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}
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