syncthing/internal/scanner/walk.go

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// Copyright (C) 2014 The Syncthing Authors.
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//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along
// with this program. If not, see <http://www.gnu.org/licenses/>.
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package scanner
import (
"errors"
"os"
"path/filepath"
"runtime"
"strings"
"time"
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"github.com/syncthing/syncthing/internal/ignore"
"github.com/syncthing/syncthing/internal/lamport"
"github.com/syncthing/syncthing/internal/protocol"
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"github.com/syncthing/syncthing/internal/symlinks"
"golang.org/x/text/unicode/norm"
)
type Walker struct {
// Dir is the base directory for the walk
Dir string
// Limit walking to this path within Dir, or no limit if Sub is blank
Sub string
// BlockSize controls the size of the block used when hashing.
BlockSize int
// If Matcher is not nil, it is used to identify files to ignore which were specified by the user.
Matcher *ignore.Matcher
// If TempNamer is not nil, it is used to ignore tempory files when walking.
TempNamer TempNamer
// Number of hours to keep temporary files for
TempLifetime time.Duration
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// If CurrentFiler is not nil, it is queried for the current file before rescanning.
CurrentFiler CurrentFiler
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// If IgnorePerms is true, changes to permission bits will not be
// detected. Scanned files will get zero permission bits and the
// NoPermissionBits flag set.
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IgnorePerms bool
}
type TempNamer interface {
// Temporary returns a temporary name for the filed referred to by filepath.
TempName(path string) string
// IsTemporary returns true if path refers to the name of temporary file.
IsTemporary(path string) bool
}
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type CurrentFiler interface {
// CurrentFile returns the file as seen at last scan.
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CurrentFile(name string) protocol.FileInfo
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}
// Walk returns the list of files found in the local folder by scanning the
// file system. Files are blockwise hashed.
func (w *Walker) Walk() (chan protocol.FileInfo, error) {
if debug {
l.Debugln("Walk", w.Dir, w.Sub, w.BlockSize, w.Matcher)
}
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err := checkDir(w.Dir)
if err != nil {
return nil, err
}
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files := make(chan protocol.FileInfo)
hashedFiles := make(chan protocol.FileInfo)
newParallelHasher(w.Dir, w.BlockSize, runtime.NumCPU(), hashedFiles, files)
go func() {
hashFiles := w.walkAndHashFiles(files)
filepath.Walk(filepath.Join(w.Dir, w.Sub), hashFiles)
close(files)
}()
return hashedFiles, nil
}
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 {
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l.Debugln("error:", p, info, err)
}
return nil
}
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rn, err := filepath.Rel(w.Dir, p)
if err != nil {
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if debug {
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l.Debugln("rel error:", p, err)
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}
return nil
}
if rn == "." {
return nil
}
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if w.TempNamer != nil && w.TempNamer.IsTemporary(rn) {
// A temporary file
if debug {
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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 {
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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
}
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// 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 {
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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.
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if info.IsDir() {
rval = filepath.SkipDir
}
// If we don't support symlinks, skip.
if !symlinks.Supported {
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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.
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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 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 := w.CurrentFiler.CurrentFile(rn)
if !cf.IsDeleted() && cf.IsSymlink() && !cf.IsInvalid() && SymlinkTypeEqual(flags, cf.Flags) && BlocksEqual(cf.Blocks, blocks) {
return rval
}
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}
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
// - 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 := w.CurrentFiler.CurrentFile(rn)
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permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
if permUnchanged && !cf.IsDeleted() && cf.IsDirectory() && !cf.IsSymlink() && !cf.IsInvalid() {
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return nil
}
}
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flags := uint32(protocol.FlagDirectory)
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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 {
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l.Debugln("dir:", p, f)
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}
fchan <- f
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return nil
}
if info.Mode().IsRegular() {
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if w.CurrentFiler != nil {
// A file is "unchanged", if it
// - 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)
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cf := w.CurrentFiler.CurrentFile(rn)
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permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Flags, uint32(info.Mode()))
if permUnchanged && !cf.IsDeleted() && cf.Modified == info.ModTime().Unix() && !cf.IsDirectory() && !cf.IsSymlink() && !cf.IsInvalid() {
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return nil
}
if debug {
l.Debugln("rescan:", cf, info.ModTime().Unix(), info.Mode()&os.ModePerm)
}
}
var flags = uint32(info.Mode() & os.ModePerm)
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if w.IgnorePerms {
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flags = protocol.FlagNoPermBits | 0666
}
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f := protocol.FileInfo{
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Name: rn,
Version: lamport.Default.Tick(0),
Flags: flags,
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Modified: info.ModTime().Unix(),
}
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if debug {
l.Debugln("to hash:", p, f)
}
fchan <- f
}
return nil
}
}
func checkDir(dir string) error {
if info, err := os.Lstat(dir); err != nil {
return err
} else if !info.IsDir() {
return errors.New(dir + ": not a directory")
} else if debug {
l.Debugln("checkDir", dir, info)
}
return nil
}
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func PermsEqual(a, b uint32) bool {
switch runtime.GOOS {
case "windows":
// There is only writeable and read only, represented for user, group
// and other equally. We only compare against user.
return a&0600 == b&0600
default:
// All bits count
return a&0777 == b&0777
}
}
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// If the target is missing, Unix never knows what type of symlink it is
// and Windows always knows even if there is no target.
// Which means that without this special check a Unix node would be fighting
// with a Windows node about whether or not the target is known.
// Basically, if you don't know and someone else knows, just accept it.
// The fact that you don't know means you are on Unix, and on Unix you don't
// really care what the target type is. The moment you do know, and if something
// doesn't match, that will propogate throught the cluster.
func SymlinkTypeEqual(disk, index uint32) bool {
if disk&protocol.FlagSymlinkMissingTarget != 0 && index&protocol.FlagSymlinkMissingTarget == 0 {
return true
}
return disk&protocol.SymlinkTypeMask == index&protocol.SymlinkTypeMask
}