+ /*
+ * If we sent enough data to get some meaningful characteristics,
+ * save them in the routing entry. 'Enough' is arbitrarily
+ * defined as the sendpipesize (default 4K) * 16. This would
+ * give us 16 rtt samples assuming we only get one sample per
+ * window (the usual case on a long haul net). 16 samples is
+ * enough for the srtt filter to converge to within 5% of the correct
+ * value; fewer samples and we could save a very bogus rtt.
+ *
+ * Don't update the default route's characteristics and don't
+ * update anything that the user "locked".
+ */
+ if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) &&
+ (rt = inp->inp_route.ro_rt) &&
+ ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) {
+ register u_long i;
+
+ if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {
+ i = tp->t_srtt *
+ (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));
+ if (rt->rt_rmx.rmx_rtt && i)
+ /*
+ * filter this update to half the old & half
+ * the new values, converting scale.
+ * See route.h and tcp_var.h for a
+ * description of the scaling constants.
+ */
+ rt->rt_rmx.rmx_rtt =
+ (rt->rt_rmx.rmx_rtt + i) / 2;
+ else
+ rt->rt_rmx.rmx_rtt = i;
+ }
+ if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {
+ i = tp->t_rttvar *
+ (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE));
+ if (rt->rt_rmx.rmx_rttvar && i)
+ rt->rt_rmx.rmx_rttvar =
+ (rt->rt_rmx.rmx_rttvar + i) / 2;
+ else
+ rt->rt_rmx.rmx_rttvar = i;
+ }
+ /*
+ * update the pipelimit (ssthresh) if it has been updated
+ * already or if a pipesize was specified & the threshhold
+ * got below half the pipesize. I.e., wait for bad news
+ * before we start updating, then update on both good
+ * and bad news.
+ */
+ if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
+ (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh ||
+ i < (rt->rt_rmx.rmx_sendpipe / 2)) {
+ /*
+ * convert the limit from user data bytes to
+ * packets then to packet data bytes.
+ */
+ i = (i + tp->t_maxseg / 2) / tp->t_maxseg;
+ if (i < 2)
+ i = 2;
+ i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr));
+ if (rt->rt_rmx.rmx_ssthresh)
+ rt->rt_rmx.rmx_ssthresh =
+ (rt->rt_rmx.rmx_ssthresh + i) / 2;
+ else
+ rt->rt_rmx.rmx_ssthresh = i;
+ }
+ }
+#endif /* RTV_RTT */
+ /* free the reassembly queue, if any */