How to IP-Forwarding for Man In the Middle Attack (In Qt Code)

[MohammadReza]

I`m working on a project about Man In The Middle Attack by ARP poisoning method.

In this project I need to work like as a router. For example suppose In My Lan there is two other device (a modem & a laptop). I says to laptop that I`m the modem to fraud it. whenever the laptop wants to send a packet to outside of the LAN, sends the packet to me! All thing I need is I want to send the received packet to the modem & sends the response to victim laptop.

How can I do it programmatically?
Do you Have any idea or solution in Qt code?

Thanks a lot. Ya Ali.