You could write some iptables rules to do this: personally I prefer to install Firestarter, which is a nice, simple gui front-end to iptables firewalls and makes life soooo much simpler. (As long as you're not configuring a router with 3 NICs, or something complicated, which it seems you're not).
Hostname/IP restrictions are all there, and it's got a good log for firewall violations as well, which I like.
Hope this helps, from a fellow oracle dba!!