Forwarding traffic from host machine to vm?

Question

Virtualization

Hello.
1. There is a dedicated server with VMmanager KVM installed with a network that does not have DDoS protection. In addition to personal projects that are not related to the question, there are two virtual machines with Windows installed (allocated to friends for the game server). For a couple of days schoolchildren - players - have been pouring ddos.
2. There is a vps rented from ovh with ddos ​​protection.
The task is the following, through GRE or IPIP to create a tunnel to dedicated in order to filter traffic. I did this without any problems, but my knowledge was not enough to solve the question of how to wrap virtual machine traffic so that requests to them pass through the Dedicated network.
Of course, the best option is to create a NAT on a dedicated with the assignment of local ip virtualkam. Unfortunately, the VMmanager documentation does not contain any explanations regarding traffic forwarding.
I really ask for your help.
(options for renting a server with protection or protection are not financially suitable)