process_ftp_ctl_v6(struct conntrack *ct,
                   struct dp_packet *pkt,
                   const struct conn *conn_for_expectation,
                   long long now,
                   struct ct_addr *v6_addr_rep,
                   char **ftp_data_start,
                   size_t *addr_offset_from_ftp_data_start,
                   size_t *addr_size, enum ct_alg_mode *mode)
{
    struct tcp_header *th = dp_packet_l4(pkt);
    size_t tcp_hdr_len = TCP_OFFSET(th->tcp_ctl) * 4;
    char *tcp_hdr = (char *) th;
    char ftp_msg[LARGEST_FTP_MSG_OF_INTEREST + 1] = {0};

    get_ftp_ctl_msg(pkt, ftp_msg);
    *ftp_data_start = tcp_hdr + tcp_hdr_len;

    char *ftp = ftp_msg;
    struct in6_addr ip6_addr;
    if (!strncasecmp(ftp_msg, FTP_EPRT_CMD, strlen(FTP_EPRT_CMD))) {
        ftp = ftp_msg + strlen(FTP_EPRT_CMD);
        ftp = skip_non_digits(ftp);
        if (*ftp != FTP_AF_V6 || isdigit(ftp[1])) {
            return CT_FTP_CTL_INVALID;
        }
        /* Jump over delimiter. */
        ftp += 2;

        char *ip_addr_start = ftp;
        memset(&ip6_addr, 0, sizeof ip6_addr);
        *addr_offset_from_ftp_data_start = ip_addr_start - ftp_msg;
        ftp = skip_ipv6_digits(ftp);
        *ftp = 0;
        *addr_size = ftp - ip_addr_start;
        int rc2 = inet_pton(AF_INET6, ip_addr_start, &ip6_addr);
        if (rc2 != 1) {
            return CT_FTP_CTL_INVALID;
        }
        ftp++;
        *mode = CT_FTP_MODE_ACTIVE;
    } else {
        ftp = ftp_msg + strcspn(ftp_msg, "(");
        ftp = skip_non_digits(ftp);
        if (!isdigit(*ftp)) {
            return CT_FTP_CTL_INVALID;
        }

        /* Not used for passive mode. */
        *addr_offset_from_ftp_data_start = 0;
        *addr_size = 0;

        *mode = CT_FTP_MODE_PASSIVE;
    }

    char *save_ftp = ftp;
    ftp = terminate_number_str(ftp, MAX_EXT_FTP_PORT_DGTS);
    if (!ftp) {
        return CT_FTP_CTL_INVALID;
    }
    int value;
    if (!str_to_int(save_ftp, 10, &value)) {
        return CT_FTP_CTL_INVALID;
    }
    if (value > CT_MAX_L4_PORT) {
        return CT_FTP_CTL_INVALID;
    }

    uint16_t port_hs = value;
    ovs_be16 port = htons(port_hs);

    switch (*mode) {
    case CT_FTP_MODE_ACTIVE:
        *v6_addr_rep = conn_for_expectation->rev_key.dst.addr;
        /* Although most servers will block this exploit, there may be some
         * less well managed. */
        if (memcmp(&ip6_addr, &v6_addr_rep->ipv6_aligned, sizeof ip6_addr) &&
            memcmp(&ip6_addr, &conn_for_expectation->key.src.addr.ipv6_aligned,
                   sizeof ip6_addr)) {
            return CT_FTP_CTL_INVALID;
        }
        break;
    case CT_FTP_MODE_PASSIVE:
        *v6_addr_rep = conn_for_expectation->key.dst.addr;
        break;
    case CT_TFTP_MODE:
    default:
        OVS_NOT_REACHED();
    }

    expectation_create(ct, port, now, *mode, conn_for_expectation);
    return CT_FTP_CTL_INTEREST;
}
process_ftp_ctl_v6(struct conntrack *ct,
                   struct dp_packet *pkt,
                   const struct conn *conn_for_expectation,
                   long long now,
                   struct ct_addr *v6_addr_rep,
                   char **ftp_data_start,
                   size_t *addr_offset_from_ftp_data_start,
                   size_t *addr_size, enum ct_alg_mode *mode)
{
    struct tcp_header *th = dp_packet_l4(pkt);
    size_t tcp_hdr_len = TCP_OFFSET(th->tcp_ctl) * 4;
    char *tcp_hdr = (char *) th;
    char ftp_msg[LARGEST_FTP_MSG_OF_INTEREST + 1] = {0};

    get_ftp_ctl_msg(pkt, ftp_msg);
    *ftp_data_start = tcp_hdr + tcp_hdr_len;

    char *ftp = ftp_msg;
    struct in6_addr ip6_addr;
    if (!strncasecmp(ftp_msg, FTP_EPRT_CMD, strlen(FTP_EPRT_CMD))) {
        ftp = ftp_msg + strlen(FTP_EPRT_CMD);
        ftp = skip_non_digits(ftp);
        if (*ftp != FTP_AF_V6 || isdigit(ftp[1])) {
            return CT_FTP_CTL_INVALID;
        }
         
        ftp += 2;

        char *ip_addr_start = ftp;
        memset(&ip6_addr, 0, sizeof ip6_addr);
        *addr_offset_from_ftp_data_start = ip_addr_start - ftp_msg;
        ftp = skip_ipv6_digits(ftp);
        *ftp = 0;
        *addr_size = ftp - ip_addr_start;
        int rc2 = inet_pton(AF_INET6, ip_addr_start, &ip6_addr);
        if (rc2 != 1) {
            return CT_FTP_CTL_INVALID;
        }
        ftp++;
        *mode = CT_FTP_MODE_ACTIVE;
    } else {
        ftp = ftp_msg + strcspn(ftp_msg, "(");
        ftp = skip_non_digits(ftp);
        if (!isdigit(*ftp)) {
            return CT_FTP_CTL_INVALID;
        }

         
        *addr_offset_from_ftp_data_start = 0;
        *addr_size = 0;

        *mode = CT_FTP_MODE_PASSIVE;
    }

    char *save_ftp = ftp;
    ftp = terminate_number_str(ftp, MAX_EXT_FTP_PORT_DGTS);
    if (!ftp) {
        return CT_FTP_CTL_INVALID;
    }
    int value;
    if (!str_to_int(save_ftp, 10, &value)) {
        return CT_FTP_CTL_INVALID;
    }
    if (value > CT_MAX_L4_PORT) {
        return CT_FTP_CTL_INVALID;
    }

    uint16_t port_hs = value;
    ovs_be16 port = htons(port_hs);

    switch (*mode) {
    case CT_FTP_MODE_ACTIVE:
        *v6_addr_rep = conn_for_expectation->rev_key.dst.addr;
         
        if (memcmp(&ip6_addr, &v6_addr_rep->ipv6_aligned, sizeof ip6_addr) &&
            memcmp(&ip6_addr, &conn_for_expectation->key.src.addr.ipv6_aligned,
                   sizeof ip6_addr)) {
            return CT_FTP_CTL_INVALID;
        }
        break;
    case CT_FTP_MODE_PASSIVE:
        *v6_addr_rep = conn_for_expectation->key.dst.addr;
        break;
    case CT_TFTP_MODE:
    default:
        OVS_NOT_REACHED();
    }

    expectation_create(ct, port, now, *mode, conn_for_expectation);
    return CT_FTP_CTL_INTEREST;
}