net_bsp.c

uCOS-II V2.84 LM3S6965 TCPIP Demo

*********************************************************************************************************
*                                      NETWORK MODULE FUNCTIONS
*********************************************************************************************************
*********************************************************************************************************
*/

/*
*********************************************************************************************************
*                                          NetUtil_TS_Get()
*
* Description : Get current Internet Timestamp.
*
*               (1) "The Timestamp is a right-justified, 32-bit timestamp in milliseconds since midnight
*                    UT [Universal Time]" (RFC #791, Section 3.1 'Options : Internet Timestamp').
*
*               (2) The developer is responsible for providing a real-time clock with correct time-zone
*                   configuration to implement the Internet Timestamp.
*
*
* Argument(s) : none.
*
* Return(s)   : Internet Timestamp.
*
* Caller(s)   : various.
*
* Note(s)     : none.
*********************************************************************************************************
*/

NET_TS  NetUtil_TS_Get (void)
{
   NET_TS  ts;


   /* $$$$ Insert code to return Internet Timestamp (see Notes #1 & #2).   */

   ts = NET_TS_NONE;

   return (ts);
}


/*
*********************************************************************************************************
*********************************************************************************************************
*                            TRANSMISSION CONTROL PROTOCOL LAYER FUNCTIONS
*********************************************************************************************************
*********************************************************************************************************
*/

/*
*********************************************************************************************************
*                                        NetTCP_InitTxSeqNbr()
*
* Description : Initialize the TCP Transmit Initial Sequence Counter, 'NetTCP_TxSeqNbrCtr'.
*
*               (1) Possible initialization methods include :
*
*                   (a) Time-based initialization is one preferred method since it more appropriately
*                       provides a pseudo-random initial sequence number.
*                   (b) Hardware-generated random number initialization is NOT a preferred method since it
*                       tends to produce a discrete set of pseudo-random initial sequence numbers--often
*                       the same initial sequence number.
*                   (c) Hard-coded initial sequence number is NOT a preferred method since it is NOT random.
*
*                   See also 'net_tcp.h  MACRO'S  Note #2'.
*
*
* Argument(s) : none.
*
* Return(s)   : none.
*
* Caller(s)   : NetTCP_Init().
*
* Note(s)     : none.
*********************************************************************************************************
*/

#ifdef  NET_TCP_MODULE_PRESENT
void  NetTCP_InitTxSeqNbr (void)
{
   NetTCP_TxSeqNbrCtr = 5000;
}
#endif


/*
*********************************************************************************************************
*                                     NetTCP_TxRTT_GetTS()
*
* Description : Get a TCP Round-Trip Time (RTT) timestamp.
*
*               (1) (a) (1) Although RFC #2988, Section 4 states that "there is no requirement for the
*                           clock granularity G used for computing RTT measurements ... experience has
*                           shown that finer clock granularities (<= 100 msec) perform somewhat better
*                           than more coarse granularities".
*
*                       (2) (A) RFC #2988, Section 2.4 states that "whenever RTO is computed, if it is
*                               less than 1 second then the RTO SHOULD be rounded up to 1 second".
*
*                           (B) RFC #1122, Section 4.2.3.1 states that "the recommended ... RTO ... upper
*                               bound should be 2*MSL" where RFC #793, Section 3.3 'Sequence Numbers :
*                               Knowing When to Keep Quiet' states that "the Maximum Segment Lifetime
*                               (MSL) is ... to be 2 minutes".
*
*                               Therefore, the required upper bound is :
*
*                                   2 * MSL = 2 * 2 minutes = 4 minutes = 240 seconds
*
*                   (b) Therefore, the developer is responsible for providing a timestamp clock with
*                       adequate resolution to satisfy the clock granularity (see Note #1a1) & adequate
*                       range to satisfy the minimum/maximum RTO values (see Note #1a2).
*
*
* Argument(s) : none.
*
* Return(s)   : TCP RTT timestamp, in milliseconds.
*
* Caller(s)   : NetTCP_RxPktValidate(),
*               NetTCP_TxPktPrepareHdr().
*
* Note(s)     : (2) (a) To avoid timestamp calculation overflow, a maximum clock tick threshold value
*                       MUST be configured to truncate all clock tick values.
*
*                   (b) Also, since the clock tick integer will periodically overflow; the maximum
*                       threshold MUST be a multiple of the clock tick to avoid a discontinuity in
*                       the timestamp calculation when the clock tick integer overflows.
*********************************************************************************************************
*/

#ifdef  NET_TCP_MODULE_PRESENT
NET_TCP_TX_RTT_TS_MS  NetTCP_TxRTT_GetTS (void)
{
#if (CPU_CFG_CRITICAL_METHOD == CPU_CRITICAL_METHOD_STATUS_LOCAL)
    CPU_SR                cpu_sr;
#endif
    NET_TCP_TX_RTT_TS_MS  rtt_ts_ms;
    CPU_INT32U            clk_tick;
    CPU_INT32U            clk_tick_th;


    CPU_CRITICAL_ENTER();
    clk_tick = (CPU_INT32U)OSTime;
    CPU_CRITICAL_EXIT();

    if (OS_TICKS_PER_SEC > 0) {
        clk_tick_th  = (NET_TCP_TX_RTT_TS_MAX                       /* MUST cfg clk tick th ...                         */
                     /  DEF_TIME_NBR_mS_PER_SEC);                   /* ... as multiple of max ts (see Note #2b).        */
        clk_tick    %=  clk_tick_th;                                /* Truncate clk ticks to avoid ovf (see Note #2a).  */

        rtt_ts_ms    = (NET_TCP_TX_RTT_TS_MS)((clk_tick * DEF_TIME_NBR_mS_PER_SEC) / OS_TICKS_PER_SEC);

    } else {
        rtt_ts_ms    = (NET_TCP_TX_RTT_TS_MS)clk_tick;
    }


    return (rtt_ts_ms);
}
#endif


/*
*********************************************************************************************************
*                                     NetTCP_TxConnRTT_GetTS_ms()
*
* Description : Get a TCP Round-Trip Time (RTT) timestamp.
*
*               (1) (a) (1) Although RFC #2988, Section 4 states that "there is no requirement for the
*                           clock granularity G used for computing RTT measurements ... experience has
*                           shown that finer clock granularities (<= 100 msec) perform somewhat better
*                           than more coarse granularities".
*
*                       (2) (A) RFC #2988, Section 2.4 states that "whenever RTO is computed, if it is
*                               less than 1 second then the RTO SHOULD be rounded up to 1 second".
*
*                           (B) RFC #1122, Section 4.2.3.1 states that "the recommended ... RTO ... upper
*                               bound should be 2*MSL" where RFC #793, Section 3.3 'Sequence Numbers :
*                               Knowing When to Keep Quiet' states that "the Maximum Segment Lifetime
*                               (MSL) is ... to be 2 minutes".
*
*                               Therefore, the required upper bound is :
*
*                                   2 * MSL = 2 * 2 minutes = 4 minutes = 240 seconds
*
*                   (b) Therefore, the developer is responsible for providing a timestamp clock with
*                       adequate resolution to satisfy the clock granularity (see Note #1a1) & adequate
*                       range to satisfy the minimum/maximum RTO values (see Note #1a2).
*
*
* Argument(s) : none.
*
* Return(s)   : TCP RTT timestamp, in milliseconds.
*
* Caller(s)   : NetTCP_RxPktValidate(),
*               NetTCP_TxPktPrepareHdr().
*
* Note(s)     : none.
*********************************************************************************************************
*/

#ifdef  NET_TCP_MODULE_PRESENT
NET_TCP_TX_RTT_TS_MS  NetTCP_TxConnRTT_GetTS_ms (void)
{
    NET_TCP_TX_RTT_TS_MS  rtt_ts_ms;


    /* $$$$ Insert code to return TCP RTT timestamp (see Note #1).  */

    rtt_ts_ms = NET_TCP_TX_RTT_TS_NONE;

    return (rtt_ts_ms);
}
#endif