How to send and receive proxy protocol header in ipip?

Question

linux

Hello!
There is a task, a TCP proxy with support for proxy protocol v2 from which traffic is directed to a server on which an IPIP tunnel is raised to the next server. The question is, how can the last server on which the ipip tunnel is up see all traffic with headers through this tunnel?
I tried this:
Proxy v2 -> HAproxy (TCP Roundrobin) -> IPIP -> Destination server
In this case, headers are not transmitted, I used the keys in HAproxy "send proxy v2"
Please tell me where to dig