Theoretically speaking....
It is possible to craft a packets header files to make it seem like it is being sent from a different IP Address. Unfortunately, you will not receive the reply (it will be sent to the other IP) and will not be able to complete a three way handshake.
My question is, without a MITM (man in the middle) attack, is it in any way possible to complete a three way handshake using a spoofed IP address? To visualize this, Pretend you are Computer A, Your trying to spoof Computer B's IP and you are targetting computer C.
So Computer A will tell Computer C, Hi I'm Computer B, but please send your response to Computer A.
Any help or Ideas would be greatly appreciated.