Fix tcp retransmit/persist timers, provos@ OK.

Adapted from NetBSD:
    Fix a retransmission bug introduced by the Brakmo and Peterson
    RTO estimation changes.  Under some circumstances it would
    return a value of 0, while the old Van Jacobson RTO code would
    return a minimum of 3.  This would result in 12 retransmissions,
    each 1 second apart.  This takes care of those instances, and
    ensures that t_rttmin is used everywhere as a lower bound.

3 files changed, 24 insertions, 10 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 142452d0849..e2a6b6136d3 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcp_input.c,v 1.50 1999/11/04 11:24:23 ho Exp $	*/
+/*	$OpenBSD: tcp_input.c,v 1.51 1999/11/15 05:50:59 hugh Exp $	*/
 /*	$NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $	*/
 
 /*
@@ -2551,6 +2551,7 @@ tcp_xmit_timer(tp, rtt)
 	short rtt;
 {
 	register short delta;
+	short rttmin;
 
 	tcpstat.tcps_rttupdated++;
 	--rtt;
@@ -2603,8 +2604,11 @@ tcp_xmit_timer(tp, rtt)
 	 * statistical, we have to test that we don't drop below
 	 * the minimum feasible timer (which is 2 ticks).
 	 */
-	TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
-	    rtt + 2, TCPTV_REXMTMAX);
+	if (tp->t_rttmin > rtt + 2)
+		rttmin = tp->t_rttmin;
+	else
+		rttmin = rtt + 2;
+	TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, TCPTV_REXMTMAX);
 	
 	/*
 	 * We received an ack for a packet that wasn't retransmitted;
@@ -2704,7 +2708,9 @@ tcp_mss(tp, offer)
 		 * is also a minimum value; this is subject to time.
 		 */
 		if (rt->rt_rmx.rmx_locks & RTV_RTT)
-			tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ);
+			TCPT_RANGESET(tp->t_rttmin,
+			    rtt / (RTM_RTTUNIT / PR_SLOWHZ),
+			    TCPTV_MIN, TCPTV_REXMTMAX);
 		tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));
 		if (rt->rt_rmx.rmx_rttvar)
 			tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 5324d78f931..b204dfe9b50 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcp_output.c,v 1.22 1999/11/04 11:24:24 ho Exp $	*/
+/*	$OpenBSD: tcp_output.c,v 1.23 1999/11/15 05:50:59 hugh Exp $	*/
 /*	$NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $	*/
 
 /*
@@ -1077,6 +1077,8 @@ tcp_setpersist(tp)
 	/*
 	 * Start/restart persistance timer.
 	 */
+	if (t < tp->t_rttmin)
+		t = tp->t_rttmin;
 	TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
 	    t * tcp_backoff[tp->t_rxtshift],
 	    TCPTV_PERSMIN, TCPTV_PERSMAX);
diff --git a/sys/netinet/tcp_timer.c b/sys/netinet/tcp_timer.c
index 79d318637b9..591dc18d7d1 100644
--- a/sys/netinet/tcp_timer.c
+++ b/sys/netinet/tcp_timer.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcp_timer.c,v 1.14 1999/09/01 21:38:21 provos Exp $	*/
+/*	$OpenBSD: tcp_timer.c,v 1.15 1999/11/15 05:50:59 hugh Exp $	*/
 /*	$NetBSD: tcp_timer.c,v 1.14 1996/02/13 23:44:09 christos Exp $	*/
 
 /*
@@ -177,7 +177,7 @@ tcp_timers(tp, timer)
 	register struct tcpcb *tp;
 	int timer;
 {
-	register int rexmt;
+	short rto;
 #ifdef TCP_SACK
 	struct sackhole *p, *q;
 	/*
@@ -229,8 +229,11 @@ tcp_timers(tp, timer)
 			break;
 		}
 		tcpstat.tcps_rexmttimeo++;
-		rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
-		TCPT_RANGESET((long) tp->t_rxtcur, rexmt,
+		rto = TCP_REXMTVAL(tp);
+		if (rto < tp->t_rttmin)
+			rto = tp->t_rttmin;
+		TCPT_RANGESET((long) tp->t_rxtcur,
+		    rto * tcp_backoff[tp->t_rxtshift],
 		    tp->t_rttmin, TCPTV_REXMTMAX);
 		tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
 		/*
@@ -306,9 +309,12 @@ tcp_timers(tp, timer)
 		 * (no responses to probes) reaches the maximum
 		 * backoff that we would use if retransmitting.
 		 */
+		rto = TCP_REXMTVAL(tp);
+		if (rto < tp->t_rttmin)
+			rto = tp->t_rttmin;
 		if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
 		    (tp->t_idle >= tcp_maxpersistidle ||
-		     tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
+		     tp->t_idle >= rto * tcp_totbackoff)) {
 			tcpstat.tcps_persistdrop++;
 			tp = tcp_drop(tp, ETIMEDOUT);
 			break;