Before we merge this PR, I would like to discuss this comment:
src/network/wire/lib.zig

    // I believe it's safe. No payload will be longer than u32.MAX
    const payload_len: u32 = @intCast(payload.len);

As stated in the bitcoin documentation, "The current maximum number of bytes (“MAX_SIZE”) allowed in the payload by Bitcoin Core is 32 MiB—messages with a payload size larger than this will be dropped or rejected."

So, I removed the "I believe" part, as 32 * 1024 * 1024 < u32::MAX

To actually enforce the limit, we could do something like this maybe:

const MAX_PAYLOAD_SIZE: u32 = 32 * 1024 * 1024

const payload_len: u32 = @intCast(payload.len);
if (payload_len > MAX_PAYLOAD_SIZE) {
    return someerror
}

Is it worth opening an issue for ?