calculate the median offset from all servers we sync to and call

adjtime() when necessary to keep the local clock in sync
yes, that means ntpd syncs the local clock now.

src/usr.sbin/ntpd/ntp.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.9 2004/06/22 07:59:48 alexander Exp $ */
+/*	$OpenBSD: ntp.c,v 1.10 2004/07/05 07:46:16 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -38,6 +38,7 @@ struct l_fixedpt	 ref_ts;
 void	ntp_sighdlr(int);
 int	ntp_dispatch_imsg(void);
 int	ntp_dispatch(int fd);
+void	ntp_adjtime(struct ntpd_conf *);
 
 void
 ntp_sighdlr(int sig)
@@ -63,7 +64,7 @@ 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;
+	time_t			 nextaction, next_adjtime;
 	void			*newp;
 
 	switch (pid = fork()) {
@@ -114,6 +115,8 @@ 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) {
@@ -146,11 +149,9 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 
 		bzero(pfd, sizeof(struct pollfd) * pfd_elms);
 		bzero(idx2peer, sizeof(struct ntp_peer) * idx2peer_elms);
-		nextaction = time(NULL) + 240;
+		nextaction = next_adjtime;
 		pfd[PFD_PIPE_MAIN].fd = ibuf_main.fd;
 		pfd[PFD_PIPE_MAIN].events = POLLIN;
-		if (ibuf_main.w.queued > 0)
-			pfd[PFD_PIPE_MAIN].events |= POLLOUT;
 
 		i = 1;
 		TAILQ_FOREACH(la, &conf->listen_addrs, entry) {
@@ -159,7 +160,6 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 			i++;
 		}
 
-
 		idx_peers = i;
 		TAILQ_FOREACH(p, &conf->ntp_peers, entry) {
 			if (p->next > 0 && p->next < nextaction)
@@ -176,6 +176,14 @@ 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;
+
 		timeout = nextaction - time(NULL);
 		if (timeout < 0)
 			timeout = 0;
@@ -185,6 +193,7 @@ ntp_main(int pipe_prnt[2], struct ntpd_conf *conf)
 				log_warn("poll error");
 				ntp_quit = 1;
 			}
+
 		if (nfds > 0 && (pfd[PFD_PIPE_MAIN].revents & POLLOUT))
 			if (msgbuf_write(&ibuf_main.w) < 0) {
 				log_warn("pipe write error (to parent)");
@@ -269,3 +278,28 @@ ntp_dispatch(int fd)
 
 	return (0);
 }
+
+void
+ntp_adjtime(struct ntpd_conf *conf)
+{
+	struct ntp_peer	*p;
+	double		 offset_median = 0;
+	int		 offset_cnt = 0;
+
+	TAILQ_FOREACH(p, &conf->ntp_peers, entry) {
+		if (p->state == STATE_NONE)
+			continue;
+
+		offset_median += p->offset;
+		offset_cnt++;
+	}
+
+	offset_median /= offset_cnt;
+
+	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.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.c,v 1.5 2004/06/17 19:17:48 henning Exp $ */
+/*	$OpenBSD: ntpd.c,v 1.6 2004/07/05 07:46:16 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -40,6 +40,7 @@ int	main(int, char *[]);
 int	check_child(pid_t, const char *);
 int	reconfigure(char *);
 int	dispatch_imsg(void);
+void	ntpd_adjtime(double);
 
 int			rfd = -1;
 volatile sig_atomic_t	quit = 0;
@@ -227,6 +228,7 @@ dispatch_imsg(void)
 {
 	struct imsg		 imsg;
 	int			 n;
+	double			 d;
 
 	if ((n = imsg_read(&ibuf)) == -1)
 		return (-1);
@@ -244,6 +246,11 @@ dispatch_imsg(void)
 			break;
 
 		switch (imsg.hdr.type) {
+		case IMSG_ADJTIME:
+			if (imsg.hdr.len != IMSG_HEADER_SIZE + sizeof(d))
+				fatal("invalid IMSG_ADJTIME received");
+			memcpy(&d, imsg.data, sizeof(d));
+			ntpd_adjtime(d);
 		default:
 			break;
 		}
@@ -251,3 +258,14 @@ dispatch_imsg(void)
 	}
 	return (0);
 }
+
+void
+ntpd_adjtime(double d)
+{
+	struct timeval	tv;
+
+	d_to_tv(d, &tv);
+	log_debug("calling adjtime, offset=%fs", d);
+	if (adjtime(&tv, NULL) == -1)
+		log_warn("adjtime failed");
+}

src/usr.sbin/ntpd/ntpd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.9 2004/07/04 22:24:20 henning Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.10 2004/07/05 07:46:16 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -36,6 +36,7 @@
 #define	NTPD_OPT_VERBOSE	0x0001
 #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 */
 
@@ -101,7 +102,8 @@ struct imsgbuf {
 };
 
 enum imsg_type {
-	IMSG_NONE
+	IMSG_NONE,
+	IMSG_ADJTIME
 };
 
 struct imsg_hdr {
@@ -176,5 +178,6 @@ int	client_dispatch(struct ntp_peer *);
 
 /* util.c */
 double	gettime(void);
+void	d_to_tv(double, struct timeval *);
 double	lfp_to_d(struct l_fixedpt);
 struct	l_fixedpt d_to_lfp(double);

src/usr.sbin/ntpd/util.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: util.c,v 1.2 2004/07/04 18:07:15 henning Exp $ */
+/*	$OpenBSD: util.c,v 1.3 2004/07/05 07:46:16 henning Exp $ */
 
 /*
  * Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
@@ -31,6 +31,14 @@ gettime(void)
 	return (tv.tv_sec + JAN_1970 + 1.0e-6 * tv.tv_usec);
 }
 
+
+void
+d_to_tv(double d, struct timeval *tv)
+{
+	tv->tv_sec = (long)d;
+	tv->tv_usec = (d - tv->tv_sec) * 1000;
+}
+
 double
 lfp_to_d(struct l_fixedpt lfp)
 {