Hi John, John Lauro wrote, On 01/18/2015 01:59 AM:

I have done used it with single interface on the box running tproxy and the server on the same subnet also with a single interface. (Technically they have extra interfaces with policy based routing for handling outgoing connections differently, but probably not strictly required unless you are doing ANYCAST).

yes, my current working solution is similar, but now I need to run both the server app and the proxy app on the same box.

I would think that at a minimum, if you run on the same box and want to reuse the client's ip on the application, you will have to use a secondary IP on the same interface, or possibly a loopback interface. You might have to setup policy based routing from that secondary IP so it stays local, just a guess. Is it ok to bind the app to listen on 127.0.0.1 or some other secondary IP?

Have you in practice used such a single-box solution? If yes, I would very much appreciate if you could post the relevant steps (iptables, ip route etc.). As said. I already tried this by binding the server app to a secondary IP, but I guess my other stuff (iptables, rules, routes) wasn't right.

Easier would be if you could loose the client IP info on the app (track or tag it with the proxy) and just recreate a new session... but I assume that is not an option...

Hmm. I try to avoid this in favour of keeping the tproxying independent of the capabilities of the server app(s). Thx Uenal

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From: "U.Mutlu" <for-forums@mutluit.com> To: tproxy@lists.balabit.hu Sent: Saturday, January 17, 2015 6:56:57 PM Subject: [tproxy] proxy app and server app on the same host

Hello,

TPROXY works fine if the server application is on a different host, and if that host has the proxy host defined as its gateway.

I have this special tproxy requirement: A transparent proxy program needs to sit between client and server program, ie. like a MITM, and both (proxy pgm and server pgm) must be on the same host. The host has only one physical interface (eth0).

So, I have to move the server app to the proxy host. But then TPROXYing no more functions. I'm sure it's a routing problem, but I couldn't find a solution yet. I know some advanced routing (policy routing), ie. using different routine tables and assigning rules for them etc., but if everything is on the same host then somewhere it hangs; the SYN-ACK of the server app doesn't receive the proxy pgm, it seems to go out to the internet.

I also tried with alias IPs, virtual subnets, and also with tap devices, unfortunately the results so far are negative :-(

The author of haproxy writes at their web site http://blog.loadbalancer.org/configure-haproxy-with-tproxy-kernel-for-full-t... "We also need to ensure that we have the correct architecture for the TPROXY trick to work. Using the normal HAProxy you can have real servers anywhere on the internet because the source address always points back at the HAProxy units IP address. However if the clients source IP address is going to be used then the HAProxy server MUST BE IN THE PATH of the return traffic. The easiest way to do this is to put the backend servers in a different subnet to the front end clients and make sure that the default gateway points back at the HAProxy load balancer. NB. With clever routing this should be possible on the same subnet but I haven’t tried that yet! "

So, I'm looking for the above said "clever routing" solution.

Could someone help me please?

My environment: recent Linux kernel (3.16), Debian 8, x86_64

Thx U.Mutlu