How to esteblish NOT static L2TPv3 socket connection over IP between two machines

I did not found any examples how to implement L2TPv3 over IP

I found only a couple of open source implementations of L2TP which are:

• openL2TP: https://github.com/breed/openl2tp which does not support L2TPv3 and use UDP
• tunneldigger: https://github.com/wlanslovenija/tunneldigger supports L2TPv3 but uses UDP also

L2TPv3 rfc says nothing how it is implemented in linux which is obvious

kernel documentation: https://github.com/torvalds/linux/blob/master/Documentation/networking/l2tp.txt says we must use netlink + standard sockets which tells us something. But I do not understand why we must use netlink along with standard sockets?

kernel header file: https://github.com/torvalds/linux/blob/master/include/uapi/linux/l2tp.h it has tons of enums and commands for netlink + l2tpip structure for . I am confused of how to use them properly.

And final part of L2TPv3 control exchange establishment (SCCRQ, SCCRP, SCCCN). Having read kernel documentation I have only own understanding which might not be right but here it is.

server side:

1. Prepare tunnel 0 socket
2. Create genl socket for l2tp
3. Create standard socket filling l2tpip structure (socket create + bind) where tunnel_id is 0
4. Using genl socket create tunnel 0

5. Wait for SCCRQ (As I understand header will have controll connection id equls zero)

6. On received SCCRQ on tunnel 0 socket

7. From received SCCRQ grab AVL's Assigned Conntrol Connection ID which is received_tunnel_id on other side
8. Generate local_tunnel_id for oure side
9. Create standard socket filling l2tpip structure (socket create + bind) where tunnel_id is local_tunnel_id
10. Using genl socket create tunnel with local_tunnel_id
11. Send SCCRP wich has header's Controll Connaction ID equal to received_tunnel_id and AVL Assigned Conntrol Connection ID equal to local_tunnel_id
12. Wait for SCCN on that socket

client side

1. I do not know how it is done on that side

As I understand further communication will be over second standard socket and tunnel id zero is receiving ONLY SCCRQ

It would be great to get clarification on these details