From: Dave Hart <hart@ntp.org>
Date: Sat, 26 Nov 2011 12:50:07 +0000 (+0000)
Subject: Restore 4.2.6 clock_combine() weighting to ntp-dev, reverting
X-Git-Tag: NTP_4_2_7P237~8
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e20a412409c26fdce0513d06dc5d156e28ad5204;p=thirdparty%2Fntp.git

Restore 4.2.6 clock_combine() weighting to ntp-dev, reverting
 to pre-4.2.7p70 logic and avoiding divide-by-zero (from Dave Mills).

bk: 4ed0e07fUNqauJbuVlO9UQV-UCZK2w
---

diff --git a/ChangeLog b/ChangeLog
index c84c915fa..3cbbe26f1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,7 +7,9 @@
 * [Bug 2069] from 4.2.6p5-RC2: broadcastclient, multicastclient spin up
   duplicate ephemeral associations without broadcastdelay.
 * from 4.2.6p5-RC2: Exclude not-yet-determined sys_refid from use in
-  loopback TEST12 (from David Mills).  
+  loopback TEST12 (from Dave Mills).
+* Restore 4.2.6 clock_combine() weighting to ntp-dev, reverting to pre-
+  4.2.7p70 logic and avoiding divide-by-zero (from Dave Mills).
 (4.2.7p236) 2011/11/16 Released by Harlan Stenn <stenn@ntp.org>
 * Documentation updates from Dave Mills.
 (4.2.7p235) 2011/11/16 Released by Harlan Stenn <stenn@ntp.org>
diff --git a/ntpd/ntp_proto.c b/ntpd/ntp_proto.c
index 8c77650a6..be6d78a00 100644
--- a/ntpd/ntp_proto.c
+++ b/ntpd/ntp_proto.c
@@ -2903,9 +2903,6 @@ clock_select(void)
 }
 
 
-/*
- * clock_combine - compute system offset and jitter from selected peers
- */
 static void
 clock_combine(
 	struct peer **peers,	/* survivor list */
@@ -2913,11 +2910,14 @@ clock_combine(
 	)
 {
 	int	i;
-	double	x, y, z, w;
+	double	d, x, y, z, w;
 
 	y = z = w = 0;
 	for (i = 0; i < npeers; i++) {
-		x = max(sys_maxdist - root_distance(peers[i]), sys_mindisp);
+		d = root_distance(peers[i]);
+		if (0. == d)
+			d = 1e-6;	/* hart avoid div by 0 */
+		x = 1. / d;
 		y += x;
 		z += peers[i]->offset * x;
 		w += SQUARE(peers[i]->offset - peers[0]->offset) * x;