is_ftp_ctl(const struct dp_packet *pkt)
{
    uint8_t ip_proto = get_ip_proto(pkt);
    struct tcp_header *th = dp_packet_l4(pkt);

    /* CT_IPPORT_FTP is used because IPPORT_FTP in not defined in OSX,
     * at least in in.h. Since this value will never change, just remove
     * the external dependency. */
#define CT_IPPORT_FTP 21

    return (ip_proto == IPPROTO_TCP &&
            (th->tcp_src == htons(CT_IPPORT_FTP) ||
             th->tcp_dst == htons(CT_IPPORT_FTP)));

}
is_ftp_ctl(const struct dp_packet *pkt)
{
    uint8_t ip_proto = get_ip_proto(pkt);
    struct tcp_header *th = dp_packet_l4(pkt);

     
#define CT_IPPORT_FTP 21

    return (ip_proto == IPPROTO_TCP &&
            (th->tcp_src == htons(CT_IPPORT_FTP) ||
             th->tcp_dst == htons(CT_IPPORT_FTP)));

}