Report inode number for the root node

Now that https://github.com/hanwen/go-fuse/issues/399 has
landed we can report an inode number for the root node.

Fixes https://github.com/rfjakob/gocryptfs/issues/580

5 files changed, 53 insertions, 4 deletions

diff --git a/internal/fusefrontend/root_node.go b/internal/fusefrontend/root_node.go
index 39cdef7..ac814ad 100644
--- a/internal/fusefrontend/root_node.go
+++ b/internal/fusefrontend/root_node.go
@@ -59,13 +59,16 @@ type RootNode struct {
 	// quirks is a bitmap that enables workaround for quirks in the filesystem
 	// backing the cipherdir
 	quirks uint64
+	// rootIno is the inode number that we report for the root node on mount
+	rootIno uint64
 }
 
 func NewRootNode(args Args, c *contentenc.ContentEnc, n *nametransform.NameTransform) *RootNode {
 	var rootDev uint64
 	var st syscall.Stat_t
-	if err := syscall.Stat(args.Cipherdir, &st); err != nil {
-		tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, err)
+	var statErr error
+	if statErr = syscall.Stat(args.Cipherdir, &st); statErr != nil {
+		tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, statErr)
 	} else {
 		rootDev = uint64(st.Dev)
 	}
@@ -87,6 +90,10 @@ func NewRootNode(args Args, c *contentenc.ContentEnc, n *nametransform.NameTrans
 		dirCache:      dirCache{ivLen: ivLen},
 		quirks:        syscallcompat.DetectQuirks(args.Cipherdir),
 	}
+	if statErr == nil {
+		rn.inoMap.TranslateStat(&st)
+		rn.rootIno = st.Ino
+	}
 	return rn
 }
 
@@ -288,3 +295,7 @@ func (rn *RootNode) decryptXattrName(cAttr string) (attr string, err error) {
 	}
 	return attr, nil
 }
+
+func (rn *RootNode) RootIno() uint64 {
+	return rn.rootIno
+}
diff --git a/internal/fusefrontend_reverse/root_node.go b/internal/fusefrontend_reverse/root_node.go
index 9de81b5..cb04151 100644
--- a/internal/fusefrontend_reverse/root_node.go
+++ b/internal/fusefrontend_reverse/root_node.go
@@ -51,6 +51,8 @@ type RootNode struct {
 	// bizarre problems when inode numbers are reused behind our back,
 	// like this one: https://github.com/rfjakob/gocryptfs/issues/802
 	gen uint64
+	// rootIno is the inode number that we report for the root node on mount
+	rootIno uint64
 }
 
 // NewRootNode returns an encrypted FUSE overlay filesystem.
@@ -59,9 +61,10 @@ type RootNode struct {
 func NewRootNode(args fusefrontend.Args, c *contentenc.ContentEnc, n *nametransform.NameTransform) *RootNode {
 	var rootDev uint64
 	var st syscall.Stat_t
+	var statErr error
 	var shortNameMax int
-	if err := syscall.Stat(args.Cipherdir, &st); err != nil {
-		tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, err)
+	if statErr = syscall.Stat(args.Cipherdir, &st); statErr != nil {
+		tlog.Warn.Printf("Could not stat backing directory %q: %v", args.Cipherdir, statErr)
 		if args.OneFileSystem {
 			tlog.Fatal.Printf("This is a fatal error in combination with -one-file-system")
 			os.Exit(exitcodes.CipherDir)
@@ -81,6 +84,10 @@ func NewRootNode(args fusefrontend.Args, c *contentenc.ContentEnc, n *nametransf
 		rootDev:       rootDev,
 		shortNameMax:  shortNameMax,
 	}
+	if statErr == nil {
+		rn.inoMap.TranslateStat(&st)
+		rn.rootIno = st.Ino
+	}
 	if len(args.Exclude) > 0 || len(args.ExcludeWildcard) > 0 || len(args.ExcludeFrom) > 0 {
 		rn.excluder = prepareExcluder(args)
 	}
@@ -171,3 +178,7 @@ func (rn *RootNode) uniqueStableAttr(mode uint32, ino uint64) fs.StableAttr {
 		Gen: atomic.AddUint64(&rn.gen, 1),
 	}
 }
+
+func (rn *RootNode) RootIno() uint64 {
+	return rn.rootIno
+}
diff --git a/mount.go b/mount.go
index 61079a9..0eaa3dd 100644
--- a/mount.go
+++ b/mount.go
@@ -351,6 +351,10 @@ func initFuseFrontend(args *argContainer) (rootNode fs.InodeEmbedder, wipeKeys f
 	return rootNode, func() { cCore.Wipe() }
 }
 
+type RootInoer interface {
+	RootIno() uint64
+}
+
 // initGoFuse calls into go-fuse to mount `rootNode` on `args.mountpoint`.
 // The mountpoint is ready to use when the functions returns.
 // On error, it calls os.Exit and does not return.
@@ -375,6 +379,9 @@ func initGoFuse(rootNode fs.InodeEmbedder, args *argContainer) *fuse.Server {
 		}
 	}
 	fuseOpts.NullPermissions = true
+	// The inode number for the root node must be manually set on mount
+	// https://github.com/hanwen/go-fuse/issues/399
+	fuseOpts.RootStableAttr = &fs.StableAttr{Ino: rootNode.(RootInoer).RootIno()}
 	// Enable go-fuse warnings
 	fuseOpts.Logger = log.New(os.Stderr, "go-fuse: ", log.Lmicroseconds)
 	fuseOpts.MountOptions = fuse.MountOptions{
diff --git a/tests/matrix/matrix_test.go b/tests/matrix/matrix_test.go
index 0d9c22c..417e126 100644
--- a/tests/matrix/matrix_test.go
+++ b/tests/matrix/matrix_test.go
@@ -972,3 +972,13 @@ func TestPwd(t *testing.T) {
 		os.Mkdir(dir, 0700)
 	}
 }
+
+// TestRootIno checks that inode number of the root dir is set
+// https://github.com/hanwen/go-fuse/issues/399
+func TestRootIno(t *testing.T) {
+	var st syscall.Stat_t
+	syscall.Stat(test_helpers.DefaultPlainDir, &st)
+	if st.Ino == 0 {
+		t.Errorf("inode number of root dir is zero")
+	}
+}
diff --git a/tests/plaintextnames/plaintextnames_test.go b/tests/plaintextnames/plaintextnames_test.go
index 8892c39..4de0730 100644
--- a/tests/plaintextnames/plaintextnames_test.go
+++ b/tests/plaintextnames/plaintextnames_test.go
@@ -125,3 +125,13 @@ func TestInoReuseEvil(t *testing.T) {
 		t.Logf("file ino = %d", st.Ino)
 	}
 }
+
+// TestRootIno checks that inode number of the root dir is set
+// https://github.com/hanwen/go-fuse/issues/399
+func TestRootIno(t *testing.T) {
+	var st syscall.Stat_t
+	syscall.Stat(cDir, &st)
+	if st.Ino == 0 {
+		t.Errorf("inode number of root dir is zero")
+	}
+}