Beispiel #1
0
func startWalker(dir string, res chan<- fileInfo, abort <-chan struct{}) {
	walker := func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		rn, _ := filepath.Rel(dir, path)
		if rn == "." || rn == ".stfolder" {
			return nil
		}

		var f fileInfo
		if ok, err := symlinks.IsSymlink(path); err == nil && ok {
			f = fileInfo{
				name: rn,
				mode: os.ModeSymlink,
			}

			tgt, _, err := symlinks.Read(path)
			if err != nil {
				return err
			}
			h := md5.New()
			h.Write([]byte(tgt))
			hash := h.Sum(nil)

			copy(f.hash[:], hash)
		} else if info.IsDir() {
			f = fileInfo{
				name: rn,
				mode: info.Mode(),
				// hash and modtime zero for directories
			}
		} else {
			f = fileInfo{
				name: rn,
				mode: info.Mode(),
				mod:  info.ModTime().Unix(),
			}
			sum, err := md5file(path)
			if err != nil {
				return err
			}
			f.hash = sum
		}

		select {
		case res <- f:
			return nil
		case <-abort:
			return errors.New("abort")
		}
	}
	go func() {
		filepath.Walk(dir, walker)
		close(res)
	}()
}
Beispiel #2
0
// Request returns the specified data segment by reading it from local disk.
// Implements the protocol.Model interface.
func (m *Model) Request(deviceID protocol.DeviceID, folder, name string, offset int64, size int) ([]byte, error) {
	// Verify that the requested file exists in the local model.
	m.fmut.RLock()
	r, ok := m.folderFiles[folder]
	m.fmut.RUnlock()

	if !ok {
		l.Warnf("Request from %s for file %s in nonexistent folder %q", deviceID, name, folder)
		return nil, ErrNoSuchFile
	}

	lf := r.Get(protocol.LocalDeviceID, name)
	if lf.IsInvalid() || lf.IsDeleted() {
		if debug {
			l.Debugf("%v REQ(in): %s: %q / %q o=%d s=%d; invalid: %v", m, deviceID, folder, name, offset, size, lf)
		}
		return nil, ErrInvalid
	}

	if offset > lf.Size() {
		if debug {
			l.Debugf("%v REQ(in; nonexistent): %s: %q o=%d s=%d", m, deviceID, name, offset, size)
		}
		return nil, ErrNoSuchFile
	}

	if debug && deviceID != protocol.LocalDeviceID {
		l.Debugf("%v REQ(in): %s: %q / %q o=%d s=%d", m, deviceID, folder, name, offset, size)
	}
	m.fmut.RLock()
	fn := filepath.Join(m.folderCfgs[folder].Path, name)
	m.fmut.RUnlock()

	var reader io.ReaderAt
	var err error
	if lf.IsSymlink() {
		target, _, err := symlinks.Read(fn)
		if err != nil {
			return nil, err
		}
		reader = strings.NewReader(target)
	} else {
		reader, err = os.Open(fn) // XXX: Inefficient, should cache fd?
		if err != nil {
			return nil, err
		}

		defer reader.(*os.File).Close()
	}

	buf := make([]byte, size)
	_, err = reader.ReadAt(buf, offset)
	if err != nil {
		return nil, err
	}

	return buf, nil
}
Beispiel #3
0
// Request returns the specified data segment by reading it from local disk.
// Implements the protocol.Model interface.
func (m *Model) Request(deviceID protocol.DeviceID, folder, name string, offset int64, size int, hash []byte, flags uint32, options []protocol.Option) ([]byte, error) {
	if offset < 0 || size < 0 {
		return nil, protocol.ErrNoSuchFile
	}

	if !m.folderSharedWith(folder, deviceID) {
		l.Warnf("Request from %s for file %s in unshared folder %q", deviceID, name, folder)
		return nil, protocol.ErrNoSuchFile
	}

	if flags != 0 {
		// We don't currently support or expect any flags.
		return nil, fmt.Errorf("protocol error: unknown flags 0x%x in Request message", flags)
	}

	// Verify that the requested file exists in the local model. We only need
	// to validate this file if we haven't done so recently, so we keep a
	// cache of successfull results. "Recently" can be quite a long time, as
	// we remove validation cache entries when we detect local changes. If
	// we're out of sync here and the file actually doesn't exist any more, or
	// has shrunk or something, then we'll anyway get a read error that we
	// pass on to the other side.

	m.rvmut.RLock()
	validated := m.reqValidationCache[folder+"/"+name]
	m.rvmut.RUnlock()

	if time.Since(validated) > reqValidationTime {
		m.fmut.RLock()
		folderFiles, ok := m.folderFiles[folder]
		m.fmut.RUnlock()

		if !ok {
			l.Warnf("Request from %s for file %s in nonexistent folder %q", deviceID, name, folder)
			return nil, protocol.ErrNoSuchFile
		}

		// This call is really expensive for large files, as we load the full
		// block list which may be megabytes and megabytes of data to allocate
		// space for, read, and deserialize.
		lf, ok := folderFiles.Get(protocol.LocalDeviceID, name)
		if !ok {
			return nil, protocol.ErrNoSuchFile
		}

		if lf.IsInvalid() || lf.IsDeleted() {
			if debug {
				l.Debugf("%v REQ(in): %s: %q / %q o=%d s=%d; invalid: %v", m, deviceID, folder, name, offset, size, lf)
			}
			return nil, protocol.ErrInvalid
		}

		if offset > lf.Size() {
			if debug {
				l.Debugf("%v REQ(in; nonexistent): %s: %q o=%d s=%d", m, deviceID, name, offset, size)
			}
			return nil, protocol.ErrNoSuchFile
		}

		m.rvmut.Lock()
		m.reqValidationCache[folder+"/"+name] = time.Now()
		if len(m.reqValidationCache) > reqValidationCacheSize {
			// Don't let the cache grow infinitely
			for name, validated := range m.reqValidationCache {
				if time.Since(validated) > time.Minute {
					delete(m.reqValidationCache, name)
				}
			}
		}
		m.rvmut.Unlock()
	}

	if debug && deviceID != protocol.LocalDeviceID {
		l.Debugf("%v REQ(in): %s: %q / %q o=%d s=%d", m, deviceID, folder, name, offset, size)
	}
	m.fmut.RLock()
	fn := filepath.Join(m.folderCfgs[folder].Path(), name)
	m.fmut.RUnlock()

	var reader io.ReaderAt
	var err error
	if info, err := os.Lstat(fn); err == nil && info.Mode()&os.ModeSymlink != 0 {
		target, _, err := symlinks.Read(fn)
		if err != nil {
			return nil, err
		}
		reader = strings.NewReader(target)
	} else {
		// Cannot easily cache fd's because we might need to delete the file
		// at any moment.
		reader, err = os.Open(fn)
		if err != nil {
			return nil, err
		}

		defer reader.(*os.File).Close()
	}

	buf := make([]byte, size)
	_, err = reader.ReadAt(buf, offset)
	if err != nil {
		return nil, err
	}

	return buf, nil
}
Beispiel #4
0
func (w *Walker) walkAndHashFiles(fchan chan protocol.FileInfo) filepath.WalkFunc {
	now := time.Now()
	return func(p string, info os.FileInfo, err error) error {
		// Return value used when we are returning early and don't want to
		// process the item. For directories, this means do-not-descend.
		var skip error // nil
		// info nil when error is not nil
		if info != nil && info.IsDir() {
			skip = filepath.SkipDir
		}

		if err != nil {
			if debug {
				l.Debugln("error:", p, info, err)
			}
			return skip
		}

		rn, err := filepath.Rel(w.Dir, p)
		if err != nil {
			if debug {
				l.Debugln("rel error:", p, err)
			}
			return skip
		}

		if rn == "." {
			return nil
		}

		mtime := info.ModTime()
		if w.MtimeRepo != nil {
			mtime = w.MtimeRepo.GetMtime(rn, mtime)
		}

		if w.TempNamer != nil && w.TempNamer.IsTemporary(rn) {
			// A temporary file
			if debug {
				l.Debugln("temporary:", rn)
			}
			if info.Mode().IsRegular() && mtime.Add(w.TempLifetime).Before(now) {
				os.Remove(p)
				if debug {
					l.Debugln("removing temporary:", rn, mtime)
				}
			}
			return nil
		}

		if sn := filepath.Base(rn); sn == ".stignore" || sn == ".stfolder" ||
			strings.HasPrefix(rn, ".stversions") || w.Matcher.Match(rn) {
			// An ignored file
			if debug {
				l.Debugln("ignored:", rn)
			}
			return skip
		}

		if !utf8.ValidString(rn) {
			l.Warnf("File name %q is not in UTF8 encoding; skipping.", rn)
			return skip
		}

		var normalizedRn string
		if runtime.GOOS == "darwin" {
			// Mac OS X file names should always be NFD normalized.
			normalizedRn = norm.NFD.String(rn)
		} else {
			// Every other OS in the known universe uses NFC or just plain
			// doesn't bother to define an encoding. In our case *we* do care,
			// so we enforce NFC regardless.
			normalizedRn = norm.NFC.String(rn)
		}

		if rn != normalizedRn {
			// The file name was not normalized.

			if !w.AutoNormalize {
				// We're not authorized to do anything about it, so complain and skip.

				l.Warnf("File name %q is not in the correct UTF8 normalization form; skipping.", rn)
				return skip
			}

			// We will attempt to normalize it.
			normalizedPath := filepath.Join(w.Dir, normalizedRn)
			if _, err := osutil.Lstat(normalizedPath); os.IsNotExist(err) {
				// Nothing exists with the normalized filename. Good.
				if err = os.Rename(p, normalizedPath); err != nil {
					l.Infof(`Error normalizing UTF8 encoding of file "%s": %v`, rn, err)
					return skip
				}
				l.Infof(`Normalized UTF8 encoding of file name "%s".`, rn)
			} else {
				// There is something already in the way at the normalized
				// file name.
				l.Infof(`File "%s" has UTF8 encoding conflict with another file; ignoring.`, rn)
				return skip
			}

			rn = normalizedRn
		}

		var cf protocol.FileInfo
		var ok bool

		// Index wise symlinks are always files, regardless of what the target
		// is, because symlinks carry their target path as their content.
		if info.Mode()&os.ModeSymlink == os.ModeSymlink {
			// If the target is a directory, do NOT descend down there. This
			// will cause files to get tracked, and removing the symlink will
			// as a result remove files in their real location.
			if !symlinks.Supported {
				return skip
			}

			// We always rehash symlinks as they have no modtime or
			// permissions. We check if they point to the old target by
			// checking that their existing blocks match with the blocks in
			// the index.

			target, flags, err := symlinks.Read(p)
			flags = flags & protocol.SymlinkTypeMask
			if err != nil {
				if debug {
					l.Debugln("readlink error:", p, err)
				}
				return skip
			}

			blocks, err := Blocks(strings.NewReader(target), w.BlockSize, 0)
			if err != nil {
				if debug {
					l.Debugln("hash link error:", p, err)
				}
				return skip
			}

			if w.CurrentFiler != nil {
				// A symlink is "unchanged", if
				//  - it exists
				//  - it wasn't deleted (because it isn't now)
				//  - it was a symlink
				//  - it wasn't invalid
				//  - the symlink type (file/dir) was the same
				//  - the block list (i.e. hash of target) was the same
				cf, ok = w.CurrentFiler.CurrentFile(rn)
				if ok && !cf.IsDeleted() && cf.IsSymlink() && !cf.IsInvalid() && SymlinkTypeEqual(flags, cf.Flags) && BlocksEqual(cf.Blocks, blocks) {
					return skip
				}
			}

			f := protocol.FileInfo{
				Name:     rn,
				Version:  cf.Version.Update(w.ShortID),
				Flags:    protocol.FlagSymlink | flags | protocol.FlagNoPermBits | 0666,
				Modified: 0,
				Blocks:   blocks,
			}

			if debug {
				l.Debugln("symlink to hash:", p, f)
			}

			fchan <- f

			return skip
		}

		if info.Mode().IsDir() {
			if w.CurrentFiler != nil {
				// A directory is "unchanged", if it
				//  - exists
				//  - has the same permissions as previously, unless we are ignoring permissions
				//  - was not marked deleted (since it apparently exists now)
				//  - was a directory previously (not a file or something else)
				//  - was not a symlink (since it's a directory now)
				//  - was not invalid (since it looks valid now)
				cf, ok = w.CurrentFiler.CurrentFile(rn)
				permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
				if ok && permUnchanged && !cf.IsDeleted() && cf.IsDirectory() && !cf.IsSymlink() && !cf.IsInvalid() {
					return nil
				}
			}

			flags := uint32(protocol.FlagDirectory)
			if w.IgnorePerms {
				flags |= protocol.FlagNoPermBits | 0777
			} else {
				flags |= uint32(info.Mode() & maskModePerm)
			}
			f := protocol.FileInfo{
				Name:     rn,
				Version:  cf.Version.Update(w.ShortID),
				Flags:    flags,
				Modified: mtime.Unix(),
			}
			if debug {
				l.Debugln("dir:", p, f)
			}
			fchan <- f
			return nil
		}

		if info.Mode().IsRegular() {
			curMode := uint32(info.Mode())
			if runtime.GOOS == "windows" && osutil.IsWindowsExecutable(rn) {
				curMode |= 0111
			}

			if w.CurrentFiler != nil {
				// A file is "unchanged", if it
				//  - exists
				//  - has the same permissions as previously, unless we are ignoring permissions
				//  - was not marked deleted (since it apparently exists now)
				//  - had the same modification time as it has now
				//  - was not a directory previously (since it's a file now)
				//  - was not a symlink (since it's a file now)
				//  - was not invalid (since it looks valid now)
				//  - has the same size as previously
				cf, ok = w.CurrentFiler.CurrentFile(rn)
				permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, curMode)
				if ok && permUnchanged && !cf.IsDeleted() && cf.Modified == mtime.Unix() && !cf.IsDirectory() &&
					!cf.IsSymlink() && !cf.IsInvalid() && cf.Size() == info.Size() {
					return nil
				}

				if debug {
					l.Debugln("rescan:", cf, mtime.Unix(), info.Mode()&os.ModePerm)
				}
			}

			var flags = curMode & uint32(maskModePerm)
			if w.IgnorePerms {
				flags = protocol.FlagNoPermBits | 0666
			}

			f := protocol.FileInfo{
				Name:     rn,
				Version:  cf.Version.Update(w.ShortID),
				Flags:    flags,
				Modified: mtime.Unix(),
			}
			if debug {
				l.Debugln("to hash:", p, f)
			}
			fchan <- f
		}

		return nil
	}
}
Beispiel #5
0
func (w *Walker) walkAndHashFiles(fchan chan protocol.FileInfo) filepath.WalkFunc {
	return func(p string, info os.FileInfo, err error) error {
		if err != nil {
			if debug {
				l.Debugln("error:", p, info, err)
			}
			return nil
		}

		rn, err := filepath.Rel(w.Dir, p)
		if err != nil {
			if debug {
				l.Debugln("rel error:", p, err)
			}
			return nil
		}

		if rn == "." {
			return nil
		}

		if w.TempNamer != nil && w.TempNamer.IsTemporary(rn) {
			// A temporary file
			if debug {
				l.Debugln("temporary:", rn)
			}
			return nil
		}

		if sn := filepath.Base(rn); sn == ".stignore" || sn == ".stfolder" ||
			strings.HasPrefix(rn, ".stversions") || (w.Matcher != nil && w.Matcher.Match(rn)) {
			// An ignored file
			if debug {
				l.Debugln("ignored:", rn)
			}
			if info.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}

		if (runtime.GOOS == "linux" || runtime.GOOS == "windows") && !norm.NFC.IsNormalString(rn) {
			l.Warnf("File %q contains non-NFC UTF-8 sequences and cannot be synced. Consider renaming.", rn)
			return nil
		}

		// We must perform this check, as symlinks on Windows are always
		// .IsRegular or .IsDir unlike on Unix.
		// Index wise symlinks are always files, regardless of what the target
		// is, because symlinks carry their target path as their content.
		isSymlink, _ := symlinks.IsSymlink(p)
		if isSymlink {
			var rval error
			// If the target is a directory, do NOT descend down there.
			// This will cause files to get tracked, and removing the symlink
			// will as a result remove files in their real location.
			// But do not SkipDir if the target is not a directory, as it will
			// stop scanning the current directory.
			if info.IsDir() {
				rval = filepath.SkipDir
			}

			// We always rehash symlinks as they have no modtime or
			// permissions.
			// We check if they point to the old target by checking that
			// their existing blocks match with the blocks in the index.
			// If we don't have a filer or don't support symlinks, skip.
			if w.CurrentFiler == nil || !symlinks.Supported {
				return rval
			}

			target, flags, err := symlinks.Read(p)
			flags = flags & protocol.SymlinkTypeMask
			if err != nil {
				if debug {
					l.Debugln("readlink error:", p, err)
				}
				return rval
			}

			blocks, err := Blocks(strings.NewReader(target), w.BlockSize, 0)
			if err != nil {
				if debug {
					l.Debugln("hash link error:", p, err)
				}
				return rval
			}

			cf := w.CurrentFiler.CurrentFile(rn)
			if !cf.IsDeleted() && cf.IsSymlink() && SymlinkTypeEqual(flags, cf.Flags) && BlocksEqual(cf.Blocks, blocks) {
				return rval
			}

			f := protocol.FileInfo{
				Name:     rn,
				Version:  lamport.Default.Tick(0),
				Flags:    protocol.FlagSymlink | flags | protocol.FlagNoPermBits | 0666,
				Modified: 0,
				Blocks:   blocks,
			}

			if debug {
				l.Debugln("symlink to hash:", p, f)
			}

			fchan <- f

			return rval
		}

		if info.Mode().IsDir() {
			if w.CurrentFiler != nil {
				cf := w.CurrentFiler.CurrentFile(rn)
				permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
				if !cf.IsDeleted() && cf.IsDirectory() && permUnchanged {
					return nil
				}
			}

			var flags uint32 = protocol.FlagDirectory
			if w.IgnorePerms {
				flags |= protocol.FlagNoPermBits | 0777
			} else {
				flags |= uint32(info.Mode() & os.ModePerm)
			}
			f := protocol.FileInfo{
				Name:     rn,
				Version:  lamport.Default.Tick(0),
				Flags:    flags,
				Modified: info.ModTime().Unix(),
			}
			if debug {
				l.Debugln("dir:", p, f)
			}
			fchan <- f
			return nil
		}

		if info.Mode().IsRegular() {
			if w.CurrentFiler != nil {
				cf := w.CurrentFiler.CurrentFile(rn)
				permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
				if !cf.IsDeleted() && cf.Modified == info.ModTime().Unix() && permUnchanged {
					return nil
				}

				if debug {
					l.Debugln("rescan:", cf, info.ModTime().Unix(), info.Mode()&os.ModePerm)
				}
			}

			var flags = uint32(info.Mode() & os.ModePerm)
			if w.IgnorePerms {
				flags = protocol.FlagNoPermBits | 0666
			}

			f := protocol.FileInfo{
				Name:     rn,
				Version:  lamport.Default.Tick(0),
				Flags:    flags,
				Modified: info.ModTime().Unix(),
			}
			if debug {
				l.Debugln("to hash:", p, f)
			}
			fchan <- f
		}

		return nil
	}
}
Beispiel #6
0
func (w *Walker) walkAndHashFiles(fchan chan protocol.FileInfo) filepath.WalkFunc {
	now := time.Now()
	return func(p string, info os.FileInfo, err error) error {
		if err != nil {
			if debug {
				l.Debugln("error:", p, info, err)
			}
			return nil
		}

		rn, err := filepath.Rel(w.Dir, p)
		if err != nil {
			if debug {
				l.Debugln("rel error:", p, err)
			}
			return nil
		}

		if rn == "." {
			return nil
		}

		if w.TempNamer != nil && w.TempNamer.IsTemporary(rn) {
			// A temporary file
			if debug {
				l.Debugln("temporary:", rn)
			}
			if info.Mode().IsRegular() && info.ModTime().Add(w.TempLifetime).Before(now) {
				os.Remove(p)
				if debug {
					l.Debugln("removing temporary:", rn, info.ModTime())
				}
			}
			return nil
		}

		if sn := filepath.Base(rn); sn == ".stignore" || sn == ".stfolder" ||
			strings.HasPrefix(rn, ".stversions") || (w.Matcher != nil && w.Matcher.Match(rn)) {
			// An ignored file
			if debug {
				l.Debugln("ignored:", rn)
			}
			if info.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}

		if (runtime.GOOS == "linux" || runtime.GOOS == "windows") && !norm.NFC.IsNormalString(rn) {
			l.Warnf("File %q contains non-NFC UTF-8 sequences and cannot be synced. Consider renaming.", rn)
			return nil
		}

		// Index wise symlinks are always files, regardless of what the target
		// is, because symlinks carry their target path as their content.
		if info.Mode()&os.ModeSymlink == os.ModeSymlink {
			var rval error
			// If the target is a directory, do NOT descend down there. This
			// will cause files to get tracked, and removing the symlink will
			// as a result remove files in their real location. But do not
			// SkipDir if the target is not a directory, as it will stop
			// scanning the current directory.
			if info.IsDir() {
				rval = filepath.SkipDir
			}

			// If we don't support symlinks, skip.
			if !symlinks.Supported {
				return rval
			}

			// We always rehash symlinks as they have no modtime or
			// permissions. We check if they point to the old target by
			// checking that their existing blocks match with the blocks in
			// the index.

			target, flags, err := symlinks.Read(p)
			flags = flags & protocol.SymlinkTypeMask
			if err != nil {
				if debug {
					l.Debugln("readlink error:", p, err)
				}
				return rval
			}

			blocks, err := Blocks(strings.NewReader(target), w.BlockSize, 0)
			if err != nil {
				if debug {
					l.Debugln("hash link error:", p, err)
				}
				return rval
			}

			if w.CurrentFiler != nil {
				// A symlink is "unchanged", if
				//  - it exists
				//  - it wasn't deleted (because it isn't now)
				//  - it was a symlink
				//  - it wasn't invalid
				//  - the symlink type (file/dir) was the same
				//  - the block list (i.e. hash of target) was the same
				cf, ok := w.CurrentFiler.CurrentFile(rn)
				if ok && !cf.IsDeleted() && cf.IsSymlink() && !cf.IsInvalid() && SymlinkTypeEqual(flags, cf.Flags) && BlocksEqual(cf.Blocks, blocks) {
					return rval
				}
			}

			f := protocol.FileInfo{
				Name:     rn,
				Version:  lamport.Default.Tick(0),
				Flags:    protocol.FlagSymlink | flags | protocol.FlagNoPermBits | 0666,
				Modified: 0,
				Blocks:   blocks,
			}

			if debug {
				l.Debugln("symlink to hash:", p, f)
			}

			fchan <- f

			return rval
		}

		if info.Mode().IsDir() {
			if w.CurrentFiler != nil {
				// A directory is "unchanged", if it
				//  - exists
				//  - has the same permissions as previously, unless we are ignoring permissions
				//  - was not marked deleted (since it apparently exists now)
				//  - was a directory previously (not a file or something else)
				//  - was not a symlink (since it's a directory now)
				//  - was not invalid (since it looks valid now)
				cf, ok := w.CurrentFiler.CurrentFile(rn)
				permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
				if ok && permUnchanged && !cf.IsDeleted() && cf.IsDirectory() && !cf.IsSymlink() && !cf.IsInvalid() {
					return nil
				}
			}

			flags := uint32(protocol.FlagDirectory)
			if w.IgnorePerms {
				flags |= protocol.FlagNoPermBits | 0777
			} else {
				flags |= uint32(info.Mode() & os.ModePerm)
			}
			f := protocol.FileInfo{
				Name:     rn,
				Version:  lamport.Default.Tick(0),
				Flags:    flags,
				Modified: info.ModTime().Unix(),
			}
			if debug {
				l.Debugln("dir:", p, f)
			}
			fchan <- f
			return nil
		}

		if info.Mode().IsRegular() {
			if w.CurrentFiler != nil {
				// A file is "unchanged", if it
				//  - exists
				//  - has the same permissions as previously, unless we are ignoring permissions
				//  - was not marked deleted (since it apparently exists now)
				//  - had the same modification time as it has now
				//  - was not a directory previously (since it's a file now)
				//  - was not a symlink (since it's a file now)
				//  - was not invalid (since it looks valid now)
				//  - has the same size as previously
				cf, ok := w.CurrentFiler.CurrentFile(rn)
				permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
				if ok && permUnchanged && !cf.IsDeleted() && cf.Modified == info.ModTime().Unix() && !cf.IsDirectory() &&
					!cf.IsSymlink() && !cf.IsInvalid() && cf.Size() == info.Size() {
					return nil
				}

				if debug {
					l.Debugln("rescan:", cf, info.ModTime().Unix(), info.Mode()&os.ModePerm)
				}
			}

			var flags = uint32(info.Mode() & os.ModePerm)
			if w.IgnorePerms {
				flags = protocol.FlagNoPermBits | 0666
			}

			f := protocol.FileInfo{
				Name:     rn,
				Version:  lamport.Default.Tick(0),
				Flags:    flags,
				Modified: info.ModTime().Unix(),
			}
			if debug {
				l.Debugln("to hash:", p, f)
			}
			fchan <- f
		}

		return nil
	}
}