Add a knob to compensate for a refclock that is early or late. Based on a

src/usr.sbin/ntpd/ntpd.conf.5

@@ -1,4 +1,4 @@
-.\" $OpenBSD: ntpd.conf.5,v 1.16 2007/05/31 19:20:26 jmc Exp $
+.\" $OpenBSD: ntpd.conf.5,v 1.17 2007/09/12 21:08:45 ckuethe Exp $
 .\"
 .\" Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 .\" OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: May 31 2007 $
+.Dd $Mdocdate: September 12 2007 $
 .Dt NTPD.CONF 5
 .Os
 .Sh NAME
@@ -71,6 +71,7 @@ listen on 127.0.0.1
 listen on ::1
 .Ed
 .It Xo Ic sensor Ar device
+.Op Ic correction Ar microseconds
 .Op Ic weight Ar weight-value
 .Xc
 Specify a timedelta sensor device
@@ -92,6 +93,15 @@ For example:
 sensor *
 sensor udcf0
 .Ed
+.Pp
+An optional correction in microseconds can be given to compensate
+for the sensor's offset.
+The maximum correction is 127 seconds.
+For example, if your DCF77 receiver is lagging 15 ms behind
+actual time:
+.Bd -literal -offset indent
+sensor udcf0 correction 15000
+.Ed
 .It Xo Ic server Ar address
 .Op Ic weight Ar weight-value
 .Xc

src/usr.sbin/ntpd/ntpd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.85 2007/08/04 02:58:02 ckuethe Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.86 2007/09/12 21:08:46 ckuethe Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -141,6 +141,7 @@ struct ntp_sensor {
 	time_t				 last;
 	char				*device;
 	int				 sensordevid;
+	int				 correction;
 	u_int8_t			 weight;
 	u_int8_t			 shift;
 };
@@ -148,6 +149,7 @@ struct ntp_sensor {
 struct ntp_conf_sensor {
 	TAILQ_ENTRY(ntp_conf_sensor)		 entry;
 	char					*device;
+	int					 correction;
 	u_int8_t				 weight;
 };
 

src/usr.sbin/ntpd/parse.y

@@ -1,4 +1,4 @@
-/*	$OpenBSD: parse.y,v 1.32 2007/09/12 18:32:54 deraadt Exp $ */
+/*	$OpenBSD: parse.y,v 1.33 2007/09/12 21:08:46 ckuethe Exp $ */
 
 /*
  * Copyright (c) 2002, 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -53,6 +53,7 @@ int	 yylex(void);
 
 struct opts {
 	int		weight;
+	int		correction;
 } opts;
 
 typedef struct {
@@ -68,13 +69,14 @@ typedef struct {
 %}
 
 %token	LISTEN ON
-%token	SERVER SERVERS SENSOR WEIGHT
+%token	SERVER SERVERS SENSOR CORRECTION WEIGHT
 %token	ERROR
 %token	<v.string>		STRING
 %token	<v.number>		NUMBER
 %type	<v.addr>		address
 %type	<v.opts>		server_opts server_opts_l server_opt
 %type	<v.opts>		sensor_opts sensor_opts_l sensor_opt
+%type	<v.opts>		correction
 %type	<v.opts>		weight
 %%
 
@@ -193,6 +195,7 @@ conf_main	: LISTEN ON address	{
 
 			s = new_sensor($2);
 			s->weight = $3.weight;
+			s->correction = $3.correction;
 			free($2);
 			TAILQ_INSERT_TAIL(&conf->ntp_conf_sensors, s, entry);
 		}
@@ -232,7 +235,18 @@ sensor_opts	:	{ bzero(&opts, sizeof opts); opts.weight = 1; }
 sensor_opts_l	: sensor_opts_l sensor_opt
 		| sensor_opt
 		;
-sensor_opt	: weight
+sensor_opt	: correction
+		| weight
+		;
+
+correction	: CORRECTION NUMBER {
+			if ($2 < -127000000 || $2 > 127000000) {
+				yyerror("correction must be between "
+				    "-127000000 and 127000000 microseconds");
+				YYERROR;
+			}
+			opts.correction = $2;
+		}
 		;
 
 weight		: WEIGHT NUMBER	{
@@ -278,6 +292,7 @@ lookup(char *s)
 {
 	/* this has to be sorted always */
 	static const struct keywords keywords[] = {
+		{ "correction",		CORRECTION},
 		{ "listen",		LISTEN},
 		{ "on",			ON},
 		{ "sensor",		SENSOR},

src/usr.sbin/ntpd/sensors.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: sensors.c,v 1.33 2007/08/04 02:58:02 ckuethe Exp $ */
+/*	$OpenBSD: sensors.c,v 1.34 2007/09/12 21:08:46 ckuethe Exp $ */
 
 /*
  * Copyright (c) 2006 Henning Brauer <henning@openbsd.org>
@@ -121,13 +121,15 @@ sensor_add(int sensordev, char *dxname)
 
 	s->next = getmonotime();
 	s->weight = cs->weight;
+	s->correction = cs->correction;
 	if ((s->device = strdup(dxname)) == NULL)
 		fatal("sensor_add strdup");
 	s->sensordevid = sensordev;
 
 	TAILQ_INSERT_TAIL(&conf->ntp_sensors, s, entry);
 
-	log_debug("sensor %s added", s->device);
+	log_debug("sensor %s added (weight %d, correction %.6f)",
+	    s->device, s->weight, s->correction / 1e6);
 }
 
 void
@@ -176,7 +178,8 @@ sensor_query(struct ntp_sensor *s)
 	 * sensor.value = TS - TD in ns
 	 * if value is positive, system time is ahead
 	 */
-	s->offsets[s->shift].offset = (sensor.value / -1e9) - getoffset();
+	s->offsets[s->shift].offset = (sensor.value / -1e9) - getoffset() +
+	    (s->correction / 1e6);
 	s->offsets[s->shift].rcvd = sensor.tv.tv_sec;
 	s->offsets[s->shift].good = 1;