keep last 8 offset,delay pairs - we'll need them for the clock filters later.

for now, average over those to adjust the local clock.

src/usr.sbin/ntpd/client.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: client.c,v 1.6 2004/07/05 20:41:34 henning Exp $ */
+/*	$OpenBSD: client.c,v 1.7 2004/07/05 22:12:53 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -135,14 +135,20 @@ client_dispatch(struct ntp_peer *p)
 	T2 = lfp_to_d(msg.rectime);
 	T3 = lfp_to_d(msg.xmttime);
 
-	p->offset = ((T2 - T1) + (T3 - T4)) / 2;
-	p->delay = (T2 - T1) - (T3 - T4);
+	p->offset[p->shift] = ((T2 - T1) + (T3 - T4)) / 2;
+	p->delay[p->shift] = (T2 - T1) - (T3 - T4);
 
 	p->state = STATE_REPLY_RECEIVED;
 	p->next = time(NULL) + INTERVAL_QUERY;
 	p->deadline = 0;
 
-	log_debug("reply received: offset %f delay %f", p->offset, p->delay);
+	log_debug("reply received: offset %f delay %f", p->offset[p->shift],
+	    p->delay[p->shift]);
+
+	if (++p->shift >= OFFSET_ARRAY_SIZE) {
+		p->shift = 0;
+		p->valid = 1;
+	}
 
 	return (0);
 }

src/usr.sbin/ntpd/ntp.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.10 2004/07/05 07:46:16 henning Exp $ */
+/*	$OpenBSD: ntp.c,v 1.11 2004/07/05 22:12:53 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -285,21 +285,21 @@ ntp_adjtime(struct ntpd_conf *conf)
 	struct ntp_peer	*p;
 	double		 offset_median = 0;
 	int		 offset_cnt = 0;
+	u_int8_t	 idx;
 
 	TAILQ_FOREACH(p, &conf->ntp_peers, entry) {
-		if (p->state == STATE_NONE)
+		if (!p->valid)
 			continue;
 
-		offset_median += p->offset;
-		offset_cnt++;
+		for (idx = 0; idx < OFFSET_ARRAY_SIZE; idx++) {
+			offset_median += p->offset[idx];
+			offset_cnt++;
+		}
 	}
 
 	offset_median /= offset_cnt;
 
-	if (offset_median >= 0.001 || offset_median <= 0.001) {
+	if (offset_median >= 0.001 || offset_median <= 0.001)
 		imsg_compose(&ibuf_main, IMSG_ADJTIME, 0,
 			    &offset_median, sizeof(offset_median));
-		TAILQ_FOREACH(p, &conf->ntp_peers, entry)
-			p->offset = 0;
-	}
 }

src/usr.sbin/ntpd/ntpd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.11 2004/07/05 20:41:35 henning Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.12 2004/07/05 22:12:53 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -37,8 +37,9 @@
 #define	NTPD_OPT_VERBOSE2	0x0002
 
 #define	INTERVAL_ADJTIME	120	/* call adjtime every n seconds */
-#define	INTERVAL_QUERY		60	/* sync with peers every n seconds */
-#define	QUERYTIME_MAX		30	/* single query might take n secs max */
+#define	INTERVAL_QUERY		30	/* sync with peers every n seconds */
+#define	QUERYTIME_MAX		15	/* single query might take n secs max */
+#define	OFFSET_ARRAY_SIZE	8
 
 enum client_state {
 	STATE_NONE,
@@ -59,8 +60,10 @@ struct ntp_peer {
 	enum client_state		 state;
 	time_t				 next;
 	time_t				 deadline;
-	double				 offset;
-	double				 delay;
+	double				 offset[OFFSET_ARRAY_SIZE];
+	double				 delay[OFFSET_ARRAY_SIZE];
+	u_int8_t			 shift;
+	u_int8_t			 valid;
 };
 
 struct ntpd_conf {