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Index: head/sys/netinet/tcp_input.c
===================================================================
--- head/sys/netinet/tcp_input.c
+++ head/sys/netinet/tcp_input.c
@@ -3494,7 +3494,7 @@
TCPSTAT_INC(tcps_rttupdated);
tp->t_rttupdated++;
- if (tp->t_srtt != 0) {
+ if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) {
/*
* srtt is stored as fixed point with 5 bits after the
* binary point (i.e., scaled by 8). The following magic
Index: head/sys/netinet/tcp_timer.h
===================================================================
--- head/sys/netinet/tcp_timer.h
+++ head/sys/netinet/tcp_timer.h
@@ -119,6 +119,13 @@
#define TCPTV_DELACK ( hz/10 ) /* 100ms timeout */
+/*
+ * If we exceed this number of retransmits for a single segment, we'll consider
+ * the current srtt measurement no longer valid and will recalculate from
+ * scratch starting with the next ACK.
+ */
+#define TCP_RTT_INVALIDATE (TCP_MAXRXTSHIFT / 4)
+
#ifdef TCPTIMERS
static const char *tcptimers[] =
{ "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" };
Index: head/sys/netinet/tcp_timer.c
===================================================================
--- head/sys/netinet/tcp_timer.c
+++ head/sys/netinet/tcp_timer.c
@@ -845,20 +845,16 @@
(tp->t_rxtshift == 3))
tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
/*
- * If we backed off this far, our srtt estimate is probably bogus.
- * Clobber it so we'll take the next rtt measurement as our srtt;
- * move the current srtt into rttvar to keep the current
- * retransmit times until then.
+ * If we backed off this far, notify the L3 protocol that we're having
+ * connection problems.
*/
- if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
+ if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
#ifdef INET6
if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
in6_losing(tp->t_inpcb);
else
#endif
in_losing(tp->t_inpcb);
- tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
- tp->t_srtt = 0;
}
tp->snd_nxt = tp->snd_una;
tp->snd_recover = tp->snd_max;

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