[plug] Squid / Transparent Proxying / iptables

[Arkem]

Hi Everyone

Recently I decided to dedicate some of my ample /var/ partition free 
space to a nice large web cache also to help those on the same lan 
using my computer as a gateway I made it transparent (changed the 
recommended settings in squid) by forwarding all port 80 traffic not 
coming in through the external interface to the proxy server using 
the command:

/sbin/iptables -t nat -A PREROUTING -p tcp -i !ppp0 --dport 80 \
-j DNAT --to 192.168.0.10:8080

This works great but now I seem to be getting some slowdowns when web 
surfing (I haven't really investigated the cause much but since it 
just acts unresponsive... speed is still there just the response time 
is shocked) I've decided that I'd like to make my redirection a 
little more specific to make locally bound web traffic not be passed 
to the proxy. I tried a couple of things but it didn't seem to work 
the attempt that I had the most hope in was:

/sbin/iptables -t nat -N cache_check
/sbin/iptables -t nat -A PREROUTING -p tcp -i !ppp0 --dport 80 \
-j cache_check
/sbin/iptables -t nat -A cache_check -p tcp -d 192.168.0.0/16 \
-j ACCEPT
/sbin/iptables -t nat -A cache_check -p tcp -d 127.0.0.1/32 -j ACCEPT
/sbin/iptables -t nat -A cache_check -p tcp --dport 80 -j DNAT \
--to 192.168.0.10:8080

Though unfortunately this still seem to route all web traffic through 
squid even the local traffic. Can anyone see a problem with this or 
make any suggestions (about the redirection problem or about the 
squid problem) They'd be very appreciated.

Regards, Paul Chamberlain