/*
                 * SYN-COOKIE LOGIC
                 *  Figure out the source IP/port, and the SYN cookie
                 */
                if (src.ipv4_mask > 1 || src.port_mask > 1) {
                    uint64_t ck = syn_cookie_ipv4((unsigned)(i+repeats),
                                            (unsigned)((i+repeats)>>32),
                                            (unsigned)xXx, (unsigned)(xXx>>32),
                                            entropy);
                    port_me = src.port + (ck & src.port_mask);
                    ip_me = src.ipv4 + ((ck>>16) & src.ipv4_mask);
                } else {
                    ip_me = src.ipv4;
                    port_me = src.port;
                }

    src->ipv4_mask = ifsrc->ipv4.last - ifsrc->ipv4.first;