Writing a virtual NIC
 

Hello everybody,
I want to create a virtual NIC to redirect outgoing packets to a server (basically I'm writing a VPN client).

What do you recommend me to read? What do I need to know? What do I need to learn?

Also, I want this to be a kernel module just for fun and practice.

Thanks ahead.

I'd recommend _Linux_Device_Drivers_, by Jonathan Corbet, Alessandro Rubini, & Greg Kroah-Hartman. I believe the 3rd Edition is the latest, and it is a bit old (2005), but still good. There are many other good books on Linux device drivers and kernel programming. Another great resource for something similar to a VPN client would be the documentation and source code for OpenVPN:
https://sourceforge.net/projects/openvpn/
https://forums.openvpn.net/
http://community.openvpn.net/openvpn