Squid +iptables + apache

Squid +iptables + apache

[Enrique Augusto Tobis]

Hi!

I've been looking for a solution to this problem, but I haven't been able to 
find one. Any ideas?

I have a small home network. I recently set up an old pc as out gateway. I 
have

192.168.0.3 connecting to the internet, running squid, and acting as the 
firewall/gateway (using nat).
192.168.0.1 running apache.

I want to use squid in 192.168.0.3 as a transparent proxy. So far, that works. 
That is, traffic from the 192.168.0.0 network is processed transparently 
by .0.3 

I also forwarded connections to port 80 on .0.3 to .0.1, which is running the 
web server. I can successfully access that web server from outside the 
network.

To sum it up, almost everything is working as it should. But, if I try to 
access 192.168.0.3 from INSIDE the network, I get an error from squid...

I activate the transparent proxy with
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 
8080   

and forward the port 80 connections with 
iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to 192.168.0.1:80     

in that order.

Any ideas?
Thanks!
Enrique

Re: Squid +iptables + apache

[Edmundo Carmona]

what is the error squid reports?

On 9/20/05, Enrique Augusto Tobis <etobis@dc.uba.ar> wrote:
> Hi!
> 
> I've been looking for a solution to this problem, but I haven't been able to
> find one. Any ideas?
> 
> I have a small home network. I recently set up an old pc as out gateway. I
> have
> 
> 192.168.0.3 connecting to the internet, running squid, and acting as the
> firewall/gateway (using nat).
> 192.168.0.1 running apache.
> 
> I want to use squid in 192.168.0.3 as a transparent proxy. So far, that works.
> That is, traffic from the 192.168.0.0 network is processed transparently
> by .0.3
> 
> I also forwarded connections to port 80 on .0.3 to .0.1, which is running the
> web server. I can successfully access that web server from outside the
> network.
> 
> To sum it up, almost everything is working as it should. But, if I try to
> access 192.168.0.3 from INSIDE the network, I get an error from squid...
> 
> I activate the transparent proxy with
> iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port
> 8080
> 
> and forward the port 80 connections with
> iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to 192.168.0.1:80
> 
> in that order.
> 
> Any ideas?
> Thanks!
> Enrique
> 
>

Re: Squid +iptables + apache

[/dev/rob0]

On Monday 19 September 2005 23:57, Enrique Augusto Tobis wrote:
> To sum it up, almost everything is working as it should. But, if I
> try to access 192.168.0.3 from INSIDE the network, I get an error
> from squid...
>
> I activate the transparent proxy with
> iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT
> --to-port 8080
>
> and forward the port 80 connections with
> iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to
> 192.168.0.1:80

iptables -vt nat -I PREROUTING -i eth0 -d 192.168.0.3 -p tcp \
    --dport 80 -j ACCEPT

*Might* do it. My guess is that this router is seeing the packets to 
192.168.0.3 for some reason. My rule (-I to insert at top) will bypass 
your REDIRECT rule.

Edmundo's question is valid. Normally a host would not go through your 
firewall to reach another host on the same physical segment. So my 
guess might be wrong.
-- 
    mail to this address is discarded unless "/dev/rob0"
    or "not-spam" is in Subject: header

Squid + iptables + apache

[Enrique A. Tobis]

I managed to solve my problem, but, for future reference, I answer
Edmundo's question. The error I was getting from squid was

"
ERROR
The requested URL could not be retrieved

While trying to retrieve the URL: http://something.dyndns.org/

The following error was encountered:

    * Connection Failed

The system returned:

    (111) Connection refused

The remote host or network may be down. Please try the request again.
"

support@ilgtravel.com suggested enabling the option
X-forwarded-something on squid. I tried that, and it didn't work.

Now, /dev/rob0's solution doesn't work either. Firefox just cannot
connect to the host.

However, as you might have seen from the squid message, I was trying
to access 192.168.0.3, as a host, but using the dyndns name it has. Of
course, that name is associated with the ppp0 interface. Adding an
appropriate rule in ip-up did the trick.

/usr/sbin/iptables -t nat -I PREROUTING 1 -i eth0 -p tcp -d $4 --dport
80 -j DNAT --to 192.168.0.1:80

Even so, I tried /dev/rob0's solution, and I tried to acces the host
as 192.168.0.3, and it still doesn't work.

Thank you all for your suggestions.
Enrique

On Monday 19 September 2005 23:57, Enrique Augusto Tobis wrote:
> To sum it up, almost everything is working as it should. But, if I
> try to access 192.168.0.3 from INSIDE the network, I get an error
> from squid...
>
> I activate the transparent proxy with
> iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT
> --to-port 8080
>
> and forward the port 80 connections with
> iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to
> 192.168.0.1:80

iptables -vt nat -I PREROUTING -i eth0 -d 192.168.0.3 -p tcp \
    --dport 80 -j ACCEPT

*Might* do it. My guess is that this router is seeing the packets to
192.168.0.3 for some reason. My rule (-I to insert at top) will bypass
your REDIRECT rule.

Edmundo's question is valid. Normally a host would not go through your
firewall to reach another host on the same physical segment. So my
guess might be wrong.