Heya wise monks!

I breaking my head over this problem for a few days now, and I can't seem to find an answer. What I'm trying to accomplish is the following: 
--------     ----------     -----------
|      |     |  PC II  |    |         |
| PC I | --> | (PROXY) | -> | GATEWAY |
|      |     |         |    |         |
--------     ----------     -----------

[download]
The simple code running on PC II: 
#!/usr/bin/perl -w

use HTTP::Proxy;
use HTTP::Proxy::BodyFilter::tags;
use HTTP::Proxy::BodyFilter::simple;

system("echo 1 > /proc/sys/net/ipv4/ip_forward");

my $proxy = HTTP::Proxy->new( port => 8080, host => 'localhost' );

$proxy->push_filter(
    mime     => 'text/html',
    response => HTTP::Proxy::BodyFilter::tags->new(),
    response => HTTP::Proxy::BodyFilter::simple->new(

sub { ${ $_[1] } =~ s!src=.+(.jpg|.gif|.bmp|.png)!src=\"http://files.m
+yopera.com/Idonotlikebroccoli/albums/3758/thumbs/noob.jpg_thumb.jpg\"
+!ig;
print "Filter ran!\n"; }
    )
);

$proxy->start;

[download]
And with this iptables rules to forward all the HTTP traffic to the proxy: 
iptables -F
iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports
+ 8080

[download]
What this does is replace the <img> on HTML pages tag with an alternate picture. When I change the default gateway of PC I to the IP of PC II everything works just fine (by propagating an other default gateway by the DHCP server), but what I want to accomplish is that I can just "man in the middle" PC I so that all the traffic reroutes trough PC II, without changing anything to the DHCP server.

But when I do this, I only get the message "this connection had been reinitialized" on my browser, and it doesn't load any further.

Does anyone have an idea where to look? I'm getting really desperate.. ;)

Also a second question: My script is spawning a separate process for every page and keep that one open. After 10 pages or so, the resources are depleted on PC II, and the script crashes. How can I overcome this?

Thanks in advance for your wisdom!

Greetz, p0c!

In reply to Transparent proxy / Intercepting proxy by p0c

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