I have a requirement to implement an experimental TCP stack on Linux. In essence, I need to override any flow control, congestion control, window size adjustments, etc. I have a layer that sits on top of TCP that adds data to the SYN, SYN|ACK, ACK packets in the handshake. I also need to provide my own packet scheduling for transmission.
Without writing/rewriting an entire stack, what are some other alternatives to achieving this?