Part 1 - Using raw sockets, do you have to calculate the checksum for the IP header if you create the Ethernet frame (as opposed to letting the kernel do it for you)?

Part 2 - Why do you need root privilege to run the programs that use raw sockets? Where does the program fail if you execute it without root?

Part 3 - Can you set the IP packet length field to a value different than the actual packet size? If so, are there any limitations on what size you set it to?