Overlay2 support for rootless Docker

What does Tumbleweed need to support overlay2 for rootless Docker? Only podman supports fuse-overlayfs.

Restrictions
Only vfs graphdriver is supported. However, on Ubuntu and a few distros, overlay2 and overlay are also supported

Related? pkg/archive: support overlayfs in userns (Ubuntu kernel only) by AkihiroSuda · Pull Request #38038 · moby/moby · GitHub

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$ lsmod | grep overlay
    overlay               131072  0

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$ ll -a /home/user/test

drwxr-xr-x 3 user users 4,0K ../
drwxrwxrwx 2 user users 4,0K lower/
drwxrwxrwx 2 user users 4,0K merged/
drwxrwxrwx 2 user users 4,0K upper/
drwxrwxrwx 2 user users 4,0K work/

$ mkdir lower upper work merged
$ rootlesskit mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged

mount: /home/user/test/merged: permission denied.
[rootlesskit:child ] error: command [mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged] exited: exit status 32
[rootlesskit:parent] error: child exited: exit status 32

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$ nsenter -U --preserve-credentials -n -m -t $(cat $XDG_RUNTIME_DIR/docker.pid)

$ rootlesskit mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged

[rootlesskit:parent] error: failed to setup UID/GID map: newuidmap 24212 [0 0 1 1 200000 65536] failed: : exit status 1

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$ cat /etc/subgid $ cat /etc/subuid
dockremap:100000000:65537
user:100000:65536
root:200000:65536

Thanks

Is this it? Missing:

.fs_flags	= FS_USERNS_MOUNT,

https://kernel.ubuntu.com/git/ubuntu/ubuntu-artful.git/patch/fs/overlayfs?id=0a414bdc3d01f3b61ed86cfe3ce8b63a9240eba7

https://github.com/openSUSE/kernel/blob/master/fs/overlayfs/super.c#L1694-L1699