query interval scaling, episode II

1) base the interval calculation on the offset from the last reply, not
from the last peer update.
Allows us to send more queries again faster when the local clock
diverges too much
2) every time we form a peer update (for which we need 8 replies)
check wether we have a ready peer update for all peers that are
currently trusted, and if so, calculate the total offset and call
adjtime().
that means that adjtime is no longer called in fixed intervals
but whenever we have enough data to reliably calculate the local
clock offset.
In practice, that means we call adjtime() less often, but with
probably better data.
3) invalidate peer updates after beeing used. no point in re-using them
- this resulted in calling adjtime() multiple times with the same
offset, which doesn't make sense
tested by many

src/usr.sbin/ntpd/client.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: client.c,v 1.25 2004/07/14 20:16:31 henning Exp $ */
+/*	$OpenBSD: client.c,v 1.26 2004/07/18 12:59:41 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -182,19 +182,19 @@ client_dispatch(struct ntp_peer *p)
 	else if (p->trustlevel < TRUSTLEVEL_AGRESSIVE)
 		interval = INTERVAL_QUERY_AGRESSIVE;
 	else {
-		if (p->update.offset < 0)
-			abs_offset = p->update.offset * -1;
+		if (p->reply[p->shift].offset < 0)
+			abs_offset = -p->reply[p->shift].offset;
 		else
-			abs_offset = p->update.offset;
+			abs_offset = p->reply[p->shift].offset;
 
-		if (!p->update.good)
-			interval = INTERVAL_QUERY_NORMAL;
-		else if (abs_offset > QSCALE_OFF_MAX)
+		if (abs_offset > QSCALE_OFF_MAX)
 			interval = INTERVAL_QUERY_NORMAL;
 		else if (abs_offset < QSCALE_OFF_MIN)
-			interval = INTERVAL_QUERY_NORMAL * (1 / QSCALE_OFF_MIN);
+			interval = INTERVAL_QUERY_NORMAL *
+			    (QSCALE_OFF_MAX / QSCALE_OFF_MIN);
 		else
-			interval = INTERVAL_QUERY_NORMAL * (1 / abs_offset);
+			interval = INTERVAL_QUERY_NORMAL *
+			    (QSCALE_OFF_MAX / abs_offset);
 	}
 
 	p->next = time(NULL) + interval;
@@ -240,22 +240,18 @@ client_update(struct ntp_peer *p)
 			best = i;
 		}
 
-	for (; i < OFFSET_ARRAY_SIZE; i++) {
-		if (p->reply[i].good &&
-		    p->reply[i].rcvd + REPLY_MAXAGE < time(NULL))
-			p->reply[i].good = 0;
-
+	for (; i < OFFSET_ARRAY_SIZE; i++)
 		if (p->reply[i].good) {
 			good++;
 			if (p->reply[i].delay < p->reply[best].delay)
 				best = i;
 		}
-	}
 
 	if (good < 8)
 		return (-1);
 
 	memcpy(&p->update, &p->reply[best], sizeof(p->update));
+	ntp_adjtime();
 
 	for (i = 0; i < OFFSET_ARRAY_SIZE; i++)
 		if (p->reply[i].rcvd <= p->reply[best].rcvd)

src/usr.sbin/ntpd/ntp.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.24 2004/07/14 20:16:31 henning Exp $ */
+/*	$OpenBSD: ntp.c,v 1.25 2004/07/18 12:59:41 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -34,10 +34,10 @@
 volatile sig_atomic_t	 ntp_quit = 0;
 struct imsgbuf		 ibuf_main;
 struct l_fixedpt	 ref_ts;
+struct ntpd_conf	*conf;
 
 void	ntp_sighdlr(int);
 int	ntp_dispatch_imsg(void);
-void	ntp_adjtime(struct ntpd_conf *);
 
 void
 ntp_sighdlr(int sig)
@@ -51,7 +51,7 @@ ntp_sighdlr(int sig)
 }
 
 pid_t
-ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
+ntp_main(int pipe_prnt[2], struct ntpd_conf *nconf)
 {
 	int			 nfds, i, j, idx_peers, timeout;
 	u_int			 pfd_elms = 0, idx2peer_elms = 0;
@@ -63,7 +63,7 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 	struct listen_addr	*la;
 	struct ntp_peer		*p;
 	struct ntp_peer		**idx2peer = NULL;
-	time_t			 nextaction, next_adjtime;
+	time_t			 nextaction;
 	void			*newp;
 
 	switch (pid = fork()) {
@@ -88,6 +88,7 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 
 	setproctitle("ntp engine");
 
+	conf = nconf;
 	setup_listeners(se, conf, &listener_cnt);
 
 	if (setgroups(1, &pw->pw_gid) ||
@@ -118,8 +119,6 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 	TAILQ_FOREACH(p, &conf->ntp_peers, entry)
 		peer_cnt++;
 
-	next_adjtime = time(NULL) + INTERVAL_ADJTIME;
-
 	while (ntp_quit == 0) {
 		if (peer_cnt > idx2peer_elms ||
 		    peer_cnt + IDX2PEER_RESERVE < idx2peer_elms) {
@@ -152,7 +151,7 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 
 		bzero(pfd, sizeof(struct pollfd) * pfd_elms);
 		bzero(idx2peer, sizeof(void *) * idx2peer_elms);
-		nextaction = next_adjtime;
+		nextaction = time(NULL) + 3600;
 		pfd[PFD_PIPE_MAIN].fd = ibuf_main.fd;
 		pfd[PFD_PIPE_MAIN].events = POLLIN;
 
@@ -193,11 +192,6 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 			}
 		}
 
-		if (next_adjtime <= time(NULL)) {
-			next_adjtime = time(NULL) + INTERVAL_ADJTIME;
-			ntp_adjtime(conf);
-		}
-
 		if (ibuf_main.w.queued > 0)
 			pfd[PFD_PIPE_MAIN].events |= POLLOUT;
 
@@ -277,24 +271,19 @@ ntp_dispatch_imsg(void)
 }
 
 void
-ntp_adjtime(struct ntpd_conf *conf)
+ntp_adjtime(void)
 {
 	struct ntp_peer	*p;
 	double		 offset_median = 0;
 	int		 offset_cnt = 0;
 
 	TAILQ_FOREACH(p, &conf->ntp_peers, entry) {
-		if (!p->update.good)
-			continue;
-
-		if (p->update.rcvd + REPLY_MAXAGE < time(NULL)) {
-			p->update.good = 0;
-			continue;
-		}
-
 		if (p->trustlevel < TRUSTLEVEL_BADPEER)
 			continue;
 
+		if (!p->update.good)
+			return;
+
 		offset_median += p->update.offset;
 		offset_cnt++;
 	}
@@ -307,4 +296,7 @@ ntp_adjtime(struct ntpd_conf *conf)
 		conf->status.reftime = gettime();
 		conf->status.leap = LI_NOWARNING;		/* XXX */
 	}
+
+	TAILQ_FOREACH(p, &conf->ntp_peers, entry)
+		p->update.good = 0;
 }

src/usr.sbin/ntpd/ntpd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.26 2004/07/14 20:16:31 henning Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.27 2004/07/18 12:59:41 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -37,7 +37,6 @@
 #define	NTPD_OPT_VERBOSE	0x0001
 #define	NTPD_OPT_VERBOSE2	0x0002
 
-#define	INTERVAL_ADJTIME		240	/* call adjtime every n secs */
 #define	INTERVAL_QUERY_NORMAL		30	/* sync to peers every n secs */
 #define	INTERVAL_QUERY_PATHETIC		60
 #define	INTERVAL_QUERY_AGRESSIVE	5
@@ -47,10 +46,9 @@
 #define	TRUSTLEVEL_AGRESSIVE		8
 
 #define	QSCALE_OFF_MIN			0.05
-#define	QSCALE_OFF_MAX			1
+#define	QSCALE_OFF_MAX			0.50
 
 #define	QUERYTIME_MAX		15	/* single query might take n secs max */
-#define	REPLY_MAXAGE		720
 #define	OFFSET_ARRAY_SIZE	8
 
 enum client_state {
@@ -195,6 +193,7 @@ void	 imsg_free(struct imsg *);
 
 /* ntp.c */
 pid_t	 ntp_main(int[2], struct ntpd_conf *);
+void	 ntp_adjtime(void);
 
 /* parse.y */
 int	 parse_config(char *, struct ntpd_conf *);