How can I whitelist P2P connections?
I used to have something called Netlimiter. Basically it allows you to rate limit, disconnect, reconnect, any connection incoming on your PC. If your friends were to give you their IPs, you could practically kick any player that joins the session, by disconnecting their IPs. I'm sure there's a way for you to whitelist connections also, and Netlimiter will deny access of any other connections incoming through GTA 5.