Hi All,

I need to forward all the traffic sent to "lo:127.0.0.1:2255" to "eth1:10.10.2.1:2255". The application, which is accessing localhost:2255 must not see the difference (of course, it runs locally). It should be fully confident it is talking to localhost and localhost is responding to it (which would be the altered packets from 10.10.2.1). The logic is a little more then just this, so it needs to be done on the kernel level.

iptables did not seem to help here. As a simpliest alternative, I started to take 2.4.30 kernel apart. "netif_receive_skb" and "dev_queue_xmit" seemed to be the place to mangle incoming/outgoing packets. But I cannot manage it for the local communication.

I did it the following way. When packet appeared in "netif_receive_skb", if it goes to "lo:127.0.0.1:2255", I clone the packet, change skb->dev (to "eth1"), skb->type, ip addresses, mac addresses and checksum and call dev_queue_xmit(cloned packet); then kfree_skb(old one). In case of "lo", the last call fails causing kernel BUG(): "kfree_skb passed an skb still on a list."

When I try to alter packets coming from e.g. "eth0" the same way, the whole idea works.

Anyway, I'm stuck and have no idea how to continue.

Any ideas how to do it so it works? Or, even better, how to do it right?

Thanks!

I'm not sure exactly what you are doing, but if you just need to forward all the tcp traffic from a local port to a remote port, would this program work for you? http://aspn.activestate.com/ASPN/Coo.../Recipe/114642