[Jachu]

I have found a solution:
1. Send raw ping after receiving incoming connection packet from client.
2. Wait for response from ip that requested slot.
3. When u get response from that ip then it's not fake, so pass incoming connection packet for further processing.

Works like a charm for me. It filters all fake IPs and does not reserve slot for, but this solution involves a little bit hacking server memory, so I won't post plugin I made on this forum, sorry.

EDIT:

And "ping" is not ICMP ping, but rather built in network engine raw udp ping that should result "pong" from client/server.