[Libguestfs] Should umask takes effect when we create device file via mknod?

Hi all, Currently, umask takes effect when we create device file via mknod, as bellow commands show: brwxr----- 1 root root 8, 1 Apr 15 11:10 /sysroot/dev/sdf But I wonder whether it is reasonable? For mknod(1), when we use option -m mode, we set file permission bits to MODE, not a=rw - umask. Should this also be applicable to mknod in guestfish, thus when we create device file with mode set, umask doesn't take effect?