TCP_RTTVAR_SHIFT
delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1);
((RTM_RTTUNIT / PR_SLOWHZ) >> (TCP_RTTVAR_SHIFT + 2));
(TCP_RTTVAR_SHIFT + 2));
tp->t_srtt >> (TCP_RTT_SHIFT - TCP_RTTVAR_SHIFT);
tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << TCP_RTTVAR_SHIFT;
>> (TCP_RTTVAR_SHIFT + 2);