I'd not have the slightest clue, attempt to get in contact with your hosting provider and ask them to filter the attack or just change your IPV4 address.
Also give VNC or vKVM or what ever it is a shot.
If you still have access to your VPS, give D-Guard a try (
You must be registered for see links
)
If you cannot access your VPS due to the flood affecting remote connection, contact your hosting provider and tell them that your VPS is under attack and it needs to be filtered and brought back up.
After the issue getting resolved, try #1 again (if you did #2).