static int StreamTcpValidateTimestamp (TcpSession *ssn, Packet *p)
{
    SCEnter();

    TcpStream *sender_stream;
    TcpStream *receiver_stream;
    uint8_t ret = 1;
    uint8_t check_ts = 1;

    if (PKT_IS_TOSERVER(p)) {
        sender_stream = &ssn->client;
        receiver_stream = &ssn->server;
    } else {
        sender_stream = &ssn->server;
        receiver_stream = &ssn->client;
    }

    /* Set up the os_policy to be used in validating the timestamps based on
       the target system */
    if (receiver_stream->os_policy == 0) {
        StreamTcpSetOSPolicy(receiver_stream, p);
    }

    if (TCP_HAS_TS(p)) {
        uint32_t ts = TCP_GET_TSVAL(p);
        uint32_t last_pkt_ts = sender_stream->last_pkt_ts;
        uint32_t last_ts = sender_stream->last_ts;

        if (sender_stream->flags & STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP) {
            /* The 3whs used the timestamp with 0 value. */
            switch (receiver_stream->os_policy) {
                case OS_POLICY_LINUX:
                case OS_POLICY_WINDOWS2K3:
                    /* Linux and windows 2003 does not allow the use of 0 as
                     * timestamp in the 3whs. */
                    check_ts = 0;
                    break;

                case OS_POLICY_OLD_LINUX:
                case OS_POLICY_WINDOWS:
                case OS_POLICY_VISTA:
                    if (SEQ_EQ(sender_stream->next_seq, TCP_GET_SEQ(p))) {
                        last_ts = ts;
                        check_ts = 0; /*next packet will be checked for validity
                                        and stream TS has been updated with this
                                        one.*/
                    }
                    break;
            }
        }

        if (receiver_stream->os_policy == OS_POLICY_HPUX11) {
            /* HPUX11 igoners the timestamp of out of order packets */
            if (!SEQ_EQ(sender_stream->next_seq, TCP_GET_SEQ(p)))
                check_ts = 0;
        }

        if (ts == 0) {
            switch (receiver_stream->os_policy) {
                case OS_POLICY_OLD_LINUX:
                case OS_POLICY_WINDOWS:
                case OS_POLICY_WINDOWS2K3:
                case OS_POLICY_VISTA:
                case OS_POLICY_SOLARIS:
                    /* Old Linux and windows allowed packet with 0 timestamp. */
                    break;
                default:
                    /* other OS simply drop the pakcet with 0 timestamp, when
                     * 3whs has valid timestamp*/
                    goto invalid;
            }
        }

        if (check_ts) {
            int32_t result = 0;

            SCLogDebug("ts %"PRIu32", last_ts %"PRIu32"", ts, last_ts);

            if (receiver_stream->os_policy == OS_POLICY_LINUX) {
                /* Linux accepts TS which are off by one.*/
                result = (int32_t) ((ts - last_ts) + 1);
            } else {
                result = (int32_t) (ts - last_ts);
            }

            SCLogDebug("result %"PRIi32", p->ts.tv_sec %"PRIuMAX"", result, (uintmax_t)p->ts.tv_sec);

            if (last_pkt_ts == 0 &&
                    (ssn->flags & STREAMTCP_FLAG_MIDSTREAM))
            {
                last_pkt_ts = p->ts.tv_sec;
            }

            if (result < 0) {
                SCLogDebug("timestamp is not valid last_ts "
                           "%" PRIu32 " p->tcpvars->ts %" PRIu32 " result "
                           "%" PRId32 "", last_ts, ts, result);
                /* candidate for rejection */
                ret = 0;
            } else if ((sender_stream->last_ts != 0) &&
                        (((uint32_t) p->ts.tv_sec) >
                            last_pkt_ts + PAWS_24DAYS))
            {
                SCLogDebug("packet is not valid last_pkt_ts "
                           "%" PRIu32 " p->ts.tv_sec %" PRIu32 "",
                            last_pkt_ts, (uint32_t) p->ts.tv_sec);
                /* candidate for rejection */
                ret = 0;
            }

            if (ret == 0) {
                /* if the timestamp of packet is not valid then, check if the
                 * current stream timestamp is not so old. if so then we need to
                 * accept the packet and update the stream->last_ts (RFC 1323)*/
                if ((SEQ_EQ(sender_stream->next_seq, TCP_GET_SEQ(p))) &&
                        (((uint32_t) p->ts.tv_sec > (last_pkt_ts + PAWS_24DAYS))))
                {
                    SCLogDebug("timestamp considered valid anyway");
                } else {
                    goto invalid;
                }
            }
        }
    }

    SCReturnInt(1);

invalid:
    StreamTcpSetEvent(p, STREAM_PKT_INVALID_TIMESTAMP);
    SCReturnInt(0);
}
static int StreamTcpValidateTimestamp (TcpSession *ssn, Packet *p)
{
    SCEnter();

    TcpStream *sender_stream;
    TcpStream *receiver_stream;
    uint8_t ret = 1;
    uint8_t check_ts = 1;

    if (PKT_IS_TOSERVER(p)) {
        sender_stream = &ssn->client;
        receiver_stream = &ssn->server;
    } else {
        sender_stream = &ssn->server;
        receiver_stream = &ssn->client;
    }

     
    if (receiver_stream->os_policy == 0) {
        StreamTcpSetOSPolicy(receiver_stream, p);
    }

    if (TCP_HAS_TS(p)) {
        uint32_t ts = TCP_GET_TSVAL(p);
        uint32_t last_pkt_ts = sender_stream->last_pkt_ts;
        uint32_t last_ts = sender_stream->last_ts;

        if (sender_stream->flags & STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP) {
             
            switch (receiver_stream->os_policy) {
                case OS_POLICY_LINUX:
                case OS_POLICY_WINDOWS2K3:
                     
                    check_ts = 0;
                    break;

                case OS_POLICY_OLD_LINUX:
                case OS_POLICY_WINDOWS:
                case OS_POLICY_VISTA:
                    if (SEQ_EQ(sender_stream->next_seq, TCP_GET_SEQ(p))) {
                        last_ts = ts;
                        check_ts = 0;  
                    }
                    break;
            }
        }

        if (receiver_stream->os_policy == OS_POLICY_HPUX11) {
             
            if (!SEQ_EQ(sender_stream->next_seq, TCP_GET_SEQ(p)))
                check_ts = 0;
        }

        if (ts == 0) {
            switch (receiver_stream->os_policy) {
                case OS_POLICY_OLD_LINUX:
                case OS_POLICY_WINDOWS:
                case OS_POLICY_WINDOWS2K3:
                case OS_POLICY_VISTA:
                case OS_POLICY_SOLARIS:
                     
                    break;
                default:
                     
                    goto invalid;
            }
        }

        if (check_ts) {
            int32_t result = 0;

            SCLogDebug("ts %"PRIu32", last_ts %"PRIu32"", ts, last_ts);

            if (receiver_stream->os_policy == OS_POLICY_LINUX) {
                 
                result = (int32_t) ((ts - last_ts) + 1);
            } else {
                result = (int32_t) (ts - last_ts);
            }

            SCLogDebug("result %"PRIi32", p->ts.tv_sec %"PRIuMAX"", result, (uintmax_t)p->ts.tv_sec);

            if (last_pkt_ts == 0 &&
                    (ssn->flags & STREAMTCP_FLAG_MIDSTREAM))
            {
                last_pkt_ts = p->ts.tv_sec;
            }

            if (result < 0) {
                SCLogDebug("timestamp is not valid last_ts "
                           "%" PRIu32 " p->tcpvars->ts %" PRIu32 " result "
                           "%" PRId32 "", last_ts, ts, result);
                 
                ret = 0;
            } else if ((sender_stream->last_ts != 0) &&
                        (((uint32_t) p->ts.tv_sec) >
                            last_pkt_ts + PAWS_24DAYS))
            {
                SCLogDebug("packet is not valid last_pkt_ts "
                           "%" PRIu32 " p->ts.tv_sec %" PRIu32 "",
                            last_pkt_ts, (uint32_t) p->ts.tv_sec);
                 
                ret = 0;
            }

            if (ret == 0) {
                 
                if ((SEQ_EQ(sender_stream->next_seq, TCP_GET_SEQ(p))) &&
                        (((uint32_t) p->ts.tv_sec > (last_pkt_ts + PAWS_24DAYS))))
                {
                    SCLogDebug("timestamp considered valid anyway");
                } else {
                    goto invalid;
                }
            }
        }
    }

    SCReturnInt(1);

invalid:
    StreamTcpSetEvent(p, STREAM_PKT_INVALID_TIMESTAMP);
    SCReturnInt(0);
}