v2api: implement Opendir

internal/fusefrontend/node_api_check.go

@@ -14,3 +14,4 @@ var _ = (fs.NodeRmdirer)((*Node)(nil))
 var _ = (fs.NodeUnlinker)((*Node)(nil))
 var _ = (fs.NodeReadlinker)((*Node)(nil))
 var _ = (fs.NodeOpener)((*Node)(nil))
+var _ = (fs.NodeOpendirer)((*Node)(nil))

internal/fusefrontend/node_dir_ops.go

@@ -348,3 +348,20 @@ retry:
 	}
 	return 0
 }
+
+// Opendir is a FUSE call to check if the directory can be opened.
+func (n *Node) Opendir(ctx context.Context) (errno syscall.Errno) {
+	dirfd, cName, errno := n.prepareAtSyscall("")
+	if errno != 0 {
+		return
+	}
+	defer syscall.Close(dirfd)
+
+	// Open backing directory
+	fd, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
+	if err != nil {
+		return fs.ToErrno(err)
+	}
+	syscall.Close(fd)
+	return 0
+}