iptables rule and/or proxy server help request

[Edward]

Mike Burger wrote:
> I've got a pretty good iptables firewall in place which, at present, 
> allows fairly broad access to the net from the machines behind the 
> firewall.
> 
> What I'd like to do, now, is have the firewall forward outbound packets 
> for port 80 (to any address) to port 8080 on my server, which will then 
> proxy (DansGuardian+Squid or Privoxy).
> 
> I've tried this (keeping in mind that I'm trying it for one system, first, 
> before implementing it network-wide):
> 
> $IPTABLES -t nat -A PREROUTING -s 192.168.0.4 -p tcp --dport 80 -j DNAT 
> --to 192.168.0.1:8080
> $IPTABLES -A FORWARD -i eth1 -p tcp --dport 80 -m state --state NEW -d 
> 192.168.0.1 -j ACCEPT
> 
> I've tried using a "REDIRECT", but then connections go absolutely 
> nowhere...it seems that REDIRECT only works on the local system, not 
> across the network.
> 
> But then the proxies don't actually grab any info and present it back to 
> the browser.
> 
> If I set up direct proxy connections in the browsers, though, to the proxy 
> server at 8080, it works just fine.
> 
> Maybe it's not an iptables setting, but a proxy server setting I want?  
> I'm at a loss.

Hey Mike.

I know you've been around a fair while, and probably have already done 
this, but have you checked this document?

http://www.tldp.org/HOWTO/TransparentProxy.html

Chapter 5 has iptables examples.

May do the trick?

You're probably miles ahead of this suggestion anyway, so just ignore me 
if I'm talking from where the sun don't shine.

Regards,
Ed.