4 files changed, 76 insertions, 32 deletions
diff --git a/internal/syscallcompat/getdents_linux.go b/internal/syscallcompat/getdents_linux.go
index 55bffff..49f9233 100644
--- a/internal/syscallcompat/getdents_linux.go
+++ b/internal/syscallcompat/getdents_linux.go
@@ -12,26 +12,17 @@ import (
 	"syscall"
 	"unsafe"
 
+	"golang.org/x/sys/unix"
+
 	"github.com/hanwen/go-fuse/fuse"
 
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
-// HaveGetdents is true if we have a working implementation of Getdents
-const HaveGetdents = true
-
 const sizeofDirent = int(unsafe.Sizeof(syscall.Dirent{}))
 
-// Getdents wraps syscall.Getdents and converts the result to []fuse.DirEntry.
-// The function takes a path instead of an fd because we need to be able to
-// call Lstat on files. Fstatat is not yet available in Go as of v1.9:
-// https://github.com/golang/go/issues/14216
-func Getdents(dir string) ([]fuse.DirEntry, error) {
-	fd, err := syscall.Open(dir, syscall.O_RDONLY, 0)
-	if err != nil {
-		return nil, err
-	}
-	defer syscall.Close(fd)
+// getdents wraps syscall.Getdents and converts the result to []fuse.DirEntry.
+func getdents(fd int) ([]fuse.DirEntry, error) {
 	// Collect syscall result in smartBuf.
 	// "bytes.Buffer" is smart about expanding the capacity and avoids the
 	// exponential runtime of simple append().
@@ -84,7 +75,7 @@ func Getdents(dir string) ([]fuse.DirEntry, error) {
 			// os.File.Readdir() drops "." and "..". Let's be compatible.
 			continue
 		}
-		mode, err := convertDType(s.Type, dir+"/"+name)
+		mode, err := convertDType(fd, name, s.Type)
 		if err != nil {
 			// The file may have been deleted in the meantime. Just skip it
 			// and go on.
@@ -125,17 +116,17 @@ func getdentsName(s syscall.Dirent) (string, error) {
 var dtUnknownWarnOnce sync.Once
 
 // convertDType converts a Dirent.Type to at Stat_t.Mode value.
-func convertDType(dtype uint8, file string) (uint32, error) {
+func convertDType(dirfd int, name string, dtype uint8) (uint32, error) {
 	if dtype != syscall.DT_UNKNOWN {
 		// Shift up by four octal digits = 12 bits
 		return uint32(dtype) << 12, nil
 	}
-	// DT_UNKNOWN: we have to call Lstat()
+	// DT_UNKNOWN: we have to call stat()
 	dtUnknownWarnOnce.Do(func() {
-		tlog.Warn.Printf("Getdents: convertDType: received DT_UNKNOWN, falling back to Lstat")
+		tlog.Warn.Printf("Getdents: convertDType: received DT_UNKNOWN, falling back to stat")
 	})
-	var st syscall.Stat_t
-	err := syscall.Lstat(file, &st)
+	var st unix.Stat_t
+	err := Fstatat(dirfd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
 	if err != nil {
 		return 0, err
 	}
diff --git a/internal/syscallcompat/getdents_other.go b/internal/syscallcompat/getdents_other.go
index 4ef5b8f..6d08a9b 100644
--- a/internal/syscallcompat/getdents_other.go
+++ b/internal/syscallcompat/getdents_other.go
@@ -1,17 +1,49 @@
-// +build !linux
-
 package syscallcompat
 
 import (
-	"log"
+	"os"
+	"syscall"
+
+	"golang.org/x/sys/unix"
 
 	"github.com/hanwen/go-fuse/fuse"
 )
 
-// HaveGetdents is true if we have a working implementation of Getdents
-const HaveGetdents = false
-
-func Getdents(dir string) ([]fuse.DirEntry, error) {
-	log.Panic("only implemented on Linux")
-	return nil, nil
+// emulateGetdents reads all directory entries from the open directory "fd"
+// and returns them in a fuse.DirEntry slice.
+func emulateGetdents(fd int) (out []fuse.DirEntry, err error) {
+	// os.File closes the fd in its finalizer. Duplicate the fd to not affect
+	// the original fd.
+	newFd, err := syscall.Dup(fd)
+	if err != nil {
+		return nil, err
+	}
+	f := os.NewFile(uintptr(newFd), "")
+	defer f.Close()
+	// Get all file names in the directory
+	names, err := f.Readdirnames(0)
+	if err != nil {
+		return nil, err
+	}
+	// Stat all of them and convert to fuse.DirEntry
+	out = make([]fuse.DirEntry, 0, len(names))
+	for _, name := range names {
+		var st unix.Stat_t
+		err = Fstatat(fd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
+		if err == syscall.ENOENT {
+			// File disappeared between readdir and stat. Pretend we did not
+			// see it.
+			continue
+		}
+		if err != nil {
+			return nil, err
+		}
+		newEntry := fuse.DirEntry{
+			Name: name,
+			Mode: uint32(st.Mode) & syscall.S_IFMT,
+			Ino:  st.Ino,
+		}
+		out = append(out, newEntry)
+	}
+	return out, nil
 }
diff --git a/internal/syscallcompat/getdents_test.go b/internal/syscallcompat/getdents_test.go
index 8f2bd09..131ffee 100644
--- a/internal/syscallcompat/getdents_test.go
+++ b/internal/syscallcompat/getdents_test.go
@@ -12,9 +12,19 @@ import (
 	"github.com/hanwen/go-fuse/fuse"
 )
 
+var getdentsUnderTest = getdents
+
 func TestGetdents(t *testing.T) {
+	t.Logf("testing native getdents")
+	testGetdents(t)
+	t.Logf("testing emulateGetdents")
+	getdentsUnderTest = emulateGetdents
+	testGetdents(t)
+}
+
+func testGetdents(t *testing.T) {
 	// Fill a directory with filenames of length 1 ... 255
-	testDir, err := ioutil.TempDir("", "TestGetdents")
+	testDir, err := ioutil.TempDir(tmpDir, "TestGetdents")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -35,17 +45,21 @@ func TestGetdents(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
+		defer fd.Close()
 		readdirEntries, err := fd.Readdir(0)
 		if err != nil {
 			t.Fatal(err)
 		}
-		fd.Close()
 		readdirMap := make(map[string]*syscall.Stat_t)
 		for _, v := range readdirEntries {
 			readdirMap[v.Name()] = fuse.ToStatT(v)
 		}
-		// Read using our Getdents()
-		getdentsEntries, err := Getdents(dir)
+		// Read using our Getdents() implementation
+		_, err = fd.Seek(0, 0) // Rewind directory
+		if err != nil {
+			t.Fatal(err)
+		}
+		getdentsEntries, err := getdentsUnderTest(int(fd.Fd()))
 		if err != nil {
 			t.Fatal(err)
 		}
diff --git a/internal/syscallcompat/sys_linux.go b/internal/syscallcompat/sys_linux.go
index fb8d8b3..b5b949e 100644
--- a/internal/syscallcompat/sys_linux.go
+++ b/internal/syscallcompat/sys_linux.go
@@ -7,6 +7,8 @@ import (
 
 	"golang.org/x/sys/unix"
 
+	"github.com/hanwen/go-fuse/fuse"
+
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
@@ -115,3 +117,8 @@ func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
 	}
 	return unix.Fstatat(dirfd, path, stat, flags)
 }
+
+// Getdents syscall.
+func Getdents(fd int) ([]fuse.DirEntry, error) {
+	return getdents(fd)
+}