static __inline__ void tcp_ww_re_calc(struct sock* sk,
                                      struct tcp_opt* tp,
                                      __u32 ack_seq,
                                      ww_time_t ack_time)
{
        __u32 re_sample = 0;
        __u32 scale;
        __u32 T;
        __u32 acked;
        static u_int re_shift = TCP_WW_BE_SHIFT;
        static __u32 re_alpha = 3; /* 0.75 << 2 */

        if ( tcp_ww_time_is_zero(tp->ww.re_ack_time) ) {
                /* This is the first packet in the RTT cycle */
                tp->ww.re_ack_time = ack_time;
                tp->ww.re_ack_seq = ack_seq;
                tp->ww.srtt = tp->srtt;
                return;
        }

        /* We only want to proceed with the RE calculation if
         * we can distinguish the arrival time of the two packets.
         */

        if ( !tcp_ww_time_diff(ack_time, tp->ww.re_ack_time))
                return;

        /* Cumulative time of ACKs in an RTT cycle
         * Cumulative bytes acked so far
         */
        T = tcp_ww_get_time_diff(tp->ww.re_ack_time, ack_time, &scale);

        /* Assumption: We will never run the kernel with 1 usec tick :) */
        if (T >= ((tp->ww.srtt>>3)*(1000000/HZ))) {
                /*
                 * Proceed RE Calculation
                 */
                acked = ack_seq - tp->ww.re_ack_seq;

                if ( acked == 0 )
                        /* No data */
                        return;

                /* Following adjustments are need to maintain accuracy */
                re_sample = (scale*acked)/T);

                if ( ! tp->ww.re_est )
                                /* First sample */
                                tp->ww.re_est = re_sample;
                else {
                                tp->ww.re_est = re_alpha*tp->ww.re_est
                                        + ((1<<re_shift) - re_alpha)*re_sample;
                                tp->ww.re_est >>= re_shift;
                }

#ifdef TCP_WW_DEBUG
                printk("TCPWW-%x-%lu: RE: acked=%lu T=%lu re_sample=%lu re_est=%lu ww_srtt=%lu\n",
                       (u_int)sk, jiffies, (u_long)acked,
                       (u_long)T, (u_long)re_sample,
                       (u_long)tp->ww.re_est, (u_long)tp->ww.srtt);
#endif

                tp->ww.re_ack_seq = 0;
                tcp_ww_time_set_zero(&(tp->ww.re_ack_time));
                tp->ww.srtt = tp->srtt;

        }
}