Most of the performance of TCP stacks has more to do with the order that comparisons are made for incoming packets (sometimes called fast path -- check for and handle normal packets first), locking of data structures, and congestion strategies (including retransmit behavior, SACK, etc). Macros or typing is less likely to make that faster.
For a new stack, though, correctness and readability are more important than performance.
For a new stack, though, correctness and readability are more important than performance.