transparent proxy -- two userspace processes problem

eugene@xxxxxxxxxxxx (Eugene Portnoy) · Thu, 17 Jul 2003 23:29:42 -0700

I'm trying to combine two userspace applications on a single 2.4 kernel
machine. One of the applications is actually well known squid, another one
is not-so-well-known TCP proxy. I need the wan output of squid to be picked
up by this second proxy which is implemented using TUN/TAP driver.

By itself, both of the proxies work. Squid by usual "REDIRECT -- to-ports
3128" clause and the other using FMARK, corresponding ip rules and virtual
interfaces.

So, it looks like this

TCP
(LAN) eth0 <--> tun0 <--> TCP proxy <--> tun1 <-->eth1 (WAN)

or

HTTP
(LAN) eth0 <--> Squid <-->eth1 (WAN)

I'd imagine something like this

HTTP eth0 <--> Squid
                           /\
                            |
                           V
TCP   eth0 <--> tun0 <--> TCP proxy <--> tun1 <-->eth1

I'm trying to do this without modifying the code of any of the applications,
but rather using iptables/iproute2. It it possible?

If something is not clear, please do not hesitate to ask.

Thanks in advance,
Eugene.