iptables dnat to loopback

Hello listers.

I know this is probably not the proper place to ask a support question, but after a long googling session and asking in my regular lists i was unable to get an answer for what i think is a rather tough situation..

So, flame me if you must, but here it is =oP

I have a rather busy server box hosting several web sites in separate independent installation directories, which means several apache, mysql and tomcat installations running simultaneously, with each mysql instance binding a port in the loopback interface.

Now, for a very specific reason, i need to provide someone with remote access to one of these mysql instances.

It would be a real hassle to change mysql's config (and the webapps' working with it) so i just decided to use DNAT to redirect incoming tcp connections to the loopback interface.... but for some reason you hopefully already know about, it doesn't seem to work.

So, while this iptables rule does work for port forwarding to another host:

iptables -t nat -A PREROUTING -p tcp -i eth0 -m multiport \
        --dports mysql -j DNAT --to some.other.host

changing "some.other.host" to 127.0.0.1 doesn't work as expected, and packets seem to be dropped altogether. Using tcpdump i can see packets reaching eth0, but never reaching loopback.

Is there any way to make iptables do what i'm looking for? Any help will be greatly appreciated.

Thanks much.

Damian Gatabria <[email protected]>

----- Original Message -----
From: "Damian Gatabria" <[email protected]>
To: "Lista Netfilter" <[email protected]>
Sent: Friday, August 06, 2004 1:38 PM
Subject: iptables dnat to loopback

Is your FORWARD chain set to DROP? Is so, do you have the rule in the FORWARD chain that allows traffic from eth0 to localhost?

Example:

iptables -t nat -A PREROUTING -p tcp -i eth0 -m multiport \
        --dports mysql -j DNAT --to some.other.host

iptables -A FORWARD -p tcp -d some.other.host --dport some.port -j ACCEPT

Correct me if I'm wrong.

Greets,
Klemen Kecman