cmount: ignore com.apple.* xattrs on the macOS FSKit backend

cmd/cmount/fs.go

@@ -536,27 +536,56 @@ func (fsys *FS) Fsyncdir(path string, datasync bool, fh uint64) (errc int) {
 	return 0
 }
 
+// #9908: simulate macFUSE behaviour (discard setxattr calls) - otherwise Finder cannot copy files onto the mount
+func shouldIgnoreAppleXattr(opt *mountlib.Options) bool {
+	if !opt.NoAppleXattr {
+		return false
+	}
+	if runtime.GOOS != "darwin" {
+		return false
+	}
+	// only flip the behaviour on FSKit
+	for _, o := range opt.ExtraOptions {
+		if strings.TrimSpace(o) == "backend=fskit" {
+			return true
+		}
+	}
+	return false
+}
+
 // Setxattr sets extended attributes.
 func (fsys *FS) Setxattr(path string, name string, value []byte, flags int) (errc int) {
 	defer log.Trace(path, "name=%q, value=%q, flags=%d", name, value, flags)("errc=%d", &errc)
+	if shouldIgnoreAppleXattr(fsys.opt) && strings.HasPrefix(name, "com.apple.") {
+		return 0
+	}
 	return -fuse.ENOSYS
 }
 
 // Getxattr gets extended attributes.
 func (fsys *FS) Getxattr(path string, name string) (errc int, value []byte) {
 	defer log.Trace(path, "name=%q", name)("errc=%d, value=%q", &errc, &value)
+	if shouldIgnoreAppleXattr(fsys.opt) && strings.HasPrefix(name, "com.apple.") {
+		return -fuse.ENOATTR, nil
+	}
 	return -fuse.ENOSYS, nil
 }
 
 // Removexattr removes extended attributes.
 func (fsys *FS) Removexattr(path string, name string) (errc int) {
 	defer log.Trace(path, "name=%q", name)("errc=%d", &errc)
+	if shouldIgnoreAppleXattr(fsys.opt) && strings.HasPrefix(name, "com.apple.") {
+		return 0
+	}
 	return -fuse.ENOSYS
 }
 
 // Listxattr lists extended attributes.
 func (fsys *FS) Listxattr(path string, fill func(name string) bool) (errc int) {
 	defer log.Trace(path, "fill=%p", fill)("errc=%d", &errc)
+	if shouldIgnoreAppleXattr(fsys.opt) {
+		return 0
+	}
 	return -fuse.ENOSYS
 }