package archive import ( "bytes" "fmt" "io" "os" "path/filepath" "strings" "syscall" "time" "github.com/docker/docker/vendor/src/code.google.com/p/go/src/pkg/archive/tar" "github.com/docker/docker/pkg/log" "github.com/docker/docker/pkg/pools" "github.com/docker/docker/pkg/system" ) type ChangeType int const ( ChangeModify = iota ChangeAdd ChangeDelete ) type Change struct { Path string Kind ChangeType } func (change *Change) String() string { var kind string switch change.Kind { case ChangeModify: kind = "C" case ChangeAdd: kind = "A" case ChangeDelete: kind = "D" } return fmt.Sprintf("%s %s", kind, change.Path) } // Gnu tar and the go tar writer don't have sub-second mtime // precision, which is problematic when we apply changes via tar // files, we handle this by comparing for exact times, *or* same // second count and either a or b having exactly 0 nanoseconds func sameFsTime(a, b time.Time) bool { return a == b || (a.Unix() == b.Unix() && (a.Nanosecond() == 0 || b.Nanosecond() == 0)) } func sameFsTimeSpec(a, b syscall.Timespec) bool { return a.Sec == b.Sec && (a.Nsec == b.Nsec || a.Nsec == 0 || b.Nsec == 0) } // Changes walks the path rw and determines changes for the files in the path, // with respect to the parent layers func Changes(layers []string, rw string) ([]Change, error) { var changes []Change err := filepath.Walk(rw, func(path string, f os.FileInfo, err error) error { if err != nil { return err } // Rebase path path, err = filepath.Rel(rw, path) if err != nil { return err } path = filepath.Join("/", path) // Skip root if path == "/" { return nil } // Skip AUFS metadata if matched, err := filepath.Match("/.wh..wh.*", path); err != nil || matched { return err } change := Change{ Path: path, } // Find out what kind of modification happened file := filepath.Base(path) // If there is a whiteout, then the file was removed if strings.HasPrefix(file, ".wh.") { originalFile := file[len(".wh."):] change.Path = filepath.Join(filepath.Dir(path), originalFile) change.Kind = ChangeDelete } else { // Otherwise, the file was added change.Kind = ChangeAdd // ...Unless it already existed in a top layer, in which case, it's a modification for _, layer := range layers { stat, err := os.Stat(filepath.Join(layer, path)) if err != nil && !os.IsNotExist(err) { return err } if err == nil { // The file existed in the top layer, so that's a modification // However, if it's a directory, maybe it wasn't actually modified. // If you modify /foo/bar/baz, then /foo will be part of the changed files only because it's the parent of bar if stat.IsDir() && f.IsDir() { if f.Size() == stat.Size() && f.Mode() == stat.Mode() && sameFsTime(f.ModTime(), stat.ModTime()) { // Both directories are the same, don't record the change return nil } } change.Kind = ChangeModify break } } } // Record change changes = append(changes, change) return nil }) if err != nil && !os.IsNotExist(err) { return nil, err } return changes, nil } type FileInfo struct { parent *FileInfo name string stat syscall.Stat_t children map[string]*FileInfo capability []byte added bool } func (root *FileInfo) LookUp(path string) *FileInfo { parent := root if path == "/" { return root } pathElements := strings.Split(path, "/") for _, elem := range pathElements { if elem != "" { child := parent.children[elem] if child == nil { return nil } parent = child } } return parent } func (info *FileInfo) path() string { if info.parent == nil { return "/" } return filepath.Join(info.parent.path(), info.name) } func (info *FileInfo) isDir() bool { return info.parent == nil || info.stat.Mode&syscall.S_IFDIR == syscall.S_IFDIR } func (info *FileInfo) addChanges(oldInfo *FileInfo, changes *[]Change) { sizeAtEntry := len(*changes) if oldInfo == nil { // add change := Change{ Path: info.path(), Kind: ChangeAdd, } *changes = append(*changes, change) info.added = true } // We make a copy so we can modify it to detect additions // also, we only recurse on the old dir if the new info is a directory // otherwise any previous delete/change is considered recursive oldChildren := make(map[string]*FileInfo) if oldInfo != nil && info.isDir() { for k, v := range oldInfo.children { oldChildren[k] = v } } for name, newChild := range info.children { oldChild, _ := oldChildren[name] if oldChild != nil { // change? oldStat := &oldChild.stat newStat := &newChild.stat // Note: We can't compare inode or ctime or blocksize here, because these change // when copying a file into a container. However, that is not generally a problem // because any content change will change mtime, and any status change should // be visible when actually comparing the stat fields. The only time this // breaks down is if some code intentionally hides a change by setting // back mtime if oldStat.Mode != newStat.Mode || oldStat.Uid != newStat.Uid || oldStat.Gid != newStat.Gid || oldStat.Rdev != newStat.Rdev || // Don't look at size for dirs, its not a good measure of change (oldStat.Size != newStat.Size && oldStat.Mode&syscall.S_IFDIR != syscall.S_IFDIR) || !sameFsTimeSpec(system.GetLastModification(oldStat), system.GetLastModification(newStat)) || bytes.Compare(oldChild.capability, newChild.capability) != 0 { change := Change{ Path: newChild.path(), Kind: ChangeModify, } *changes = append(*changes, change) newChild.added = true } // Remove from copy so we can detect deletions delete(oldChildren, name) } newChild.addChanges(oldChild, changes) } for _, oldChild := range oldChildren { // delete change := Change{ Path: oldChild.path(), Kind: ChangeDelete, } *changes = append(*changes, change) } // If there were changes inside this directory, we need to add it, even if the directory // itself wasn't changed. This is needed to properly save and restore filesystem permissions. if len(*changes) > sizeAtEntry && info.isDir() && !info.added && info.path() != "/" { change := Change{ Path: info.path(), Kind: ChangeModify, } // Let's insert the directory entry before the recently added entries located inside this dir *changes = append(*changes, change) // just to resize the slice, will be overwritten copy((*changes)[sizeAtEntry+1:], (*changes)[sizeAtEntry:]) (*changes)[sizeAtEntry] = change } } func (info *FileInfo) Changes(oldInfo *FileInfo) []Change { var changes []Change info.addChanges(oldInfo, &changes) return changes } func newRootFileInfo() *FileInfo { root := &FileInfo{ name: "/", children: make(map[string]*FileInfo), } return root } func collectFileInfo(sourceDir string) (*FileInfo, error) { root := newRootFileInfo() err := filepath.Walk(sourceDir, func(path string, f os.FileInfo, err error) error { if err != nil { return err } // Rebase path relPath, err := filepath.Rel(sourceDir, path) if err != nil { return err } relPath = filepath.Join("/", relPath) if relPath == "/" { return nil } parent := root.LookUp(filepath.Dir(relPath)) if parent == nil { return fmt.Errorf("collectFileInfo: Unexpectedly no parent for %s", relPath) } info := &FileInfo{ name: filepath.Base(relPath), children: make(map[string]*FileInfo), parent: parent, } if err := syscall.Lstat(path, &info.stat); err != nil { return err } info.capability, _ = system.Lgetxattr(path, "security.capability") parent.children[info.name] = info return nil }) if err != nil { return nil, err } return root, nil } // ChangesDirs compares two directories and generates an array of Change objects describing the changes. // If oldDir is "", then all files in newDir will be Add-Changes. func ChangesDirs(newDir, oldDir string) ([]Change, error) { var ( oldRoot, newRoot *FileInfo err1, err2 error errs = make(chan error, 2) ) go func() { if oldDir != "" { oldRoot, err1 = collectFileInfo(oldDir) } errs <- err1 }() go func() { newRoot, err2 = collectFileInfo(newDir) errs <- err2 }() for i := 0; i < 2; i++ { if err := <-errs; err != nil { return nil, err } } return newRoot.Changes(oldRoot), nil } // ChangesSize calculates the size in bytes of the provided changes, based on newDir. func ChangesSize(newDir string, changes []Change) int64 { var size int64 for _, change := range changes { if change.Kind == ChangeModify || change.Kind == ChangeAdd { file := filepath.Join(newDir, change.Path) fileInfo, _ := os.Lstat(file) if fileInfo != nil && !fileInfo.IsDir() { size += fileInfo.Size() } } } return size } func major(device uint64) uint64 { return (device >> 8) & 0xfff } func minor(device uint64) uint64 { return (device & 0xff) | ((device >> 12) & 0xfff00) } // ExportChanges produces an Archive from the provided changes, relative to dir. func ExportChanges(dir string, changes []Change) (Archive, error) { reader, writer := io.Pipe() tw := tar.NewWriter(writer) go func() { twBuf := pools.BufioWriter32KPool.Get(nil) defer pools.BufioWriter32KPool.Put(twBuf) // In general we log errors here but ignore them because // during e.g. a diff operation the container can continue // mutating the filesystem and we can see transient errors // from this for _, change := range changes { if change.Kind == ChangeDelete { whiteOutDir := filepath.Dir(change.Path) whiteOutBase := filepath.Base(change.Path) whiteOut := filepath.Join(whiteOutDir, ".wh."+whiteOutBase) timestamp := time.Now() hdr := &tar.Header{ Name: whiteOut[1:], Size: 0, ModTime: timestamp, AccessTime: timestamp, ChangeTime: timestamp, } if err := tw.WriteHeader(hdr); err != nil { log.Debugf("Can't write whiteout header: %s", err) } } else { path := filepath.Join(dir, change.Path) if err := addTarFile(path, change.Path[1:], tw, twBuf); err != nil { log.Debugf("Can't add file %s to tar: %s", path, err) } } } // Make sure to check the error on Close. if err := tw.Close(); err != nil { log.Debugf("Can't close layer: %s", err) } writer.Close() }() return reader, nil }