How to change the package creation process in Linux Ubuntu?

Question

linux

There is a Mininet network emulator ( mininet.org , written in python) in which you can create an SDN network. I need packets to be processed in a slightly different way when sent / received from hosts (for example, so that when sending, some encrypted information can be embedded in the header). How can I do that? I heard that you can somehow change the TUN / TAP driver, but I did not succeed.

Answer 1

In the title of what? TCP? IP? Ethernet? OSI7 i.e. user application? Different methods are used depending on the place of modification.