I recently implimented a transparent proxy running Fedora Core 5 and Dansguardian for web filtering purposes.
Not knowing much about iptables, through a mix of resources and EE advice, I used the following for Internet traffic to be allowed through, and for traffic to be redirected to the Dansguardian filter:
iptables --table nat --flush
iptables --table nat --delete-chain
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE (where eth1 is the NIC connected to the wireless router)
iptables -A FORWARD -i eth0 -j ACCEPT (where eth0 is the nic connected to your LAN i.e. your laptop)
iptables -t nat -A PREROUTING -m tcp -p tcp --dport 80 -j REDIRECT --to-port 8080
It works just fine.
I have one user on the simple network having problems with Yahoo Mail. When they login with this network the colors are gone, the text jumbled everywhere, and much of the functionality not working. In effect their email is unusable in this network. -Works fine elsewhere.
It was recommended that maybe Yahoo was using a port I didn't have open, BUT I believe the above iptable command allows all outbound ports. I want to fix that too but first things first.
I can't find a reference to Yahoo using a special port. All other web-based and POP3 mail works perfectly fine.
mail.yahoo.com is whitelisted with regard to the filter.
If someone thinks I need to make iptables changes please provide commands, as I haven't figured that aspect out yet.
Explanations and step by step directions are appreciated.