From: Dave Hart <hart@ntp.org>
Date: Mon, 21 Nov 2011 09:35:28 +0000 (+0000)
Subject: [Bug 2050] Orphan mode stratum counting to infinity.
X-Git-Tag: NTP_4_2_6P5_RC2~7
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ae36303060b866a3f9a5ab359fe78233baa0d223;p=thirdparty%2Fntp.git

[Bug 2050] Orphan mode stratum counting to infinity.

bk: 4eca1b60hHB5nWd3Pp8_UEeji6tuKQ
---

diff --git a/ChangeLog b/ChangeLog
index b79cdd102..b81fa6d8d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+---
+
+* [Bug 2050] Orphan mode stratum counting to infinity.
+
 ---
 (4.2.6p5-RC1) 2011/10/18 Released by Harlan Stenn <stenn@ntp.org>
 
diff --git a/include/ntp_types.h b/include/ntp_types.h
index 9ace91fe9..cbc0c1c16 100644
--- a/include/ntp_types.h
+++ b/include/ntp_types.h
@@ -57,17 +57,23 @@ typedef unsigned int u_int;
 #if (SIZEOF_INT == 4)
 # ifndef int32
 #  define int32 int
+#  define INT32_MIN INT_MIN
+#  define INT32_MAX INT_MAX
 # endif
 # ifndef u_int32
 #  define u_int32 unsigned int
+#  define U_INT32_MAX UINT_MAX
 # endif
 #else /* not sizeof(int) == 4 */
 # if (SIZEOF_LONG == 4)
 #  ifndef int32
 #   define int32 long
+#   define INT32_MIN LONG_MIN
+#   define INT32_MAX LONG_MAX
 #  endif
 #  ifndef u_int32
 #   define u_int32 unsigned long
+#   define U_INT32_MAX ULONG_MAX
 #  endif
 # else /* not sizeof(long) == 4 */
 #  include "Bletch: what's 32 bits on this machine?"
diff --git a/ntpd/ntp_proto.c b/ntpd/ntp_proto.c
index 9651fc050..55177915d 100644
--- a/ntpd/ntp_proto.c
+++ b/ntpd/ntp_proto.c
@@ -2204,7 +2204,7 @@ clock_select(void)
 	double	high, low;
 	double	seljitter;
 	double	synch[NTP_MAXASSOC], error[NTP_MAXASSOC];
-	double	orphdist = 1e10;
+	double	orphmet = 2.0 * U_INT32_MAX; /* 2x is greater than */
 	struct peer *osys_peer = NULL;
 	struct peer *sys_prefer = NULL;	/* prefer peer */
 	struct peer *typesystem = NULL;
@@ -2279,20 +2279,43 @@ clock_select(void)
 				continue;
 
 			/*
-			 * If this is an orphan, choose the one with
-			 * the lowest metric defined as the IPv4 address
-			 * or the first 64 bits of the hashed IPv6 address.
+			 * If this peer is an orphan parent, elect the
+			 * one with the lowest metric defined as the
+			 * IPv4 address or the first 64 bits of the
+			 * hashed IPv6 address.  To ensure convergence
+			 * on the same selected orphan, consider as
+			 * well that this system may have the lowest
+			 * metric and be the orphan parent.  If this
+			 * system wins, sys_peer will be NULL to trigger
+			 * orphan mode in timer().
 			 */
 			if (peer->stratum == sys_orphan) {
-				double	ftemp;
+				u_int32	localmet;
+				u_int32 peermet;
 
-				ftemp = addr2refid(&peer->srcadr);
-				if (ftemp < orphdist) {
+				localmet = peer->dstadr->addr_refid;
+				peermet = addr2refid(&peer->srcadr);
+				if (peermet < localmet &&
+				    peermet < orphmet) {
 					typeorphan = peer;
-					orphdist = ftemp;
+					orphmet = peermet;
 				}
 				continue;
 			}
+
+			/*
+			 * If this peer could have the orphan parent
+			 * as a synchronization ancestor, exclude it
+			 * from selection to avoid forming a 
+			 * synchronization loop within the orphan mesh,
+			 * triggering stratum climb to infinity 
+			 * instability.  Peers at stratum higher than
+			 * the orphan stratum could have the orphan
+			 * parent in ancestry so are excluded.
+			 * See http://bugs.ntp.org/2050
+			 */
+			if (peer->stratum > sys_orphan)
+				continue;
 #ifdef REFCLOCK
 			/*
 			 * The following are special cases. We deal
diff --git a/ntpd/ntp_timer.c b/ntpd/ntp_timer.c
index d5a1206d0..3c2c832b1 100644
--- a/ntpd/ntp_timer.c
+++ b/ntpd/ntp_timer.c
@@ -302,8 +302,8 @@ timer(void)
 
 	/*
 	 * Orphan mode is active when enabled and when no servers less
-	 * than the orphan statum are available. A server with no other
-	 * synchronization source is an orphan It shows offset zero and
+	 * than the orphan stratum are available. A server with no other
+	 * synchronization source is an orphan. It shows offset zero and
 	 * reference ID the loopback address.
 	 */
 	if (sys_orphan < STRATUM_UNSPEC && sys_peer == NULL) {