iptables -N IPP2P
iptables -A FORWARD -m ipp2p --{x,y,z} -j IPP2P
iptables -A IPP2P -s your.ip -j RETURN
iptables -A IPP2P -d your.ip -j RETURN
iptables -A IPP2P -s some.ip -j RETURN
iptables -A IPP2P -d some.ip -j RETURN
iptables -A IPP2P -j DROP