TCP_METRIC_RTTVAR
val |= 1 << TCP_METRIC_RTTVAR;
tcp_metric_set(tm, TCP_METRIC_RTTVAR, msval * USEC_PER_MSEC);
if (!tcp_metric_locked(tm, TCP_METRIC_RTTVAR)) {
var = tcp_metric_get(tm, TCP_METRIC_RTTVAR);
tcp_metric_set(tm, TCP_METRIC_RTTVAR, var);
if (i == TCP_METRIC_RTTVAR) {