From: Juergen Perlinger <perlinger@ntp.org>
Date: Sun, 1 Sep 2013 08:34:32 +0000 (+0200)
Subject: [Bug 2473] NTPD exits after clock is stepped backwards externally
X-Git-Tag: NTP_4_2_7P388~1^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3c48479dbffd2807ac1a8e54ce2c8629d4a19d67;p=thirdparty%2Fntp.git

[Bug 2473] NTPD exits after clock is stepped backwards externally

bk: 5222fc18X8S_S2T9c7ZtYpRxFeJk3g
---

diff --git a/ChangeLog b/ChangeLog
index 9ebb9dc05..4b7399f18 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,4 @@
+* [Bug 2473] NTPD exits after clock is stepped backwards externally
 (4.2.7p385) 2013/08/19 Released by Harlan Stenn <stenn@ntp.org>
 * CID 975596: Copy/paste error: vallen should be siglen.
 * CID 1009579: Check return status of X509_add_ext().
diff --git a/libntp/systime.c b/libntp/systime.c
index 5264b9e12..e8583c543 100644
--- a/libntp/systime.c
+++ b/libntp/systime.c
@@ -158,6 +158,7 @@ get_systime(
 	l_fp *now		/* system time */
 	)
 {
+        static struct timespec  ts_last;        /* last sampled os time */
 	static struct timespec	ts_prev;	/* prior os time */
 	static l_fp		lfp_prev;	/* prior result */
 	static double		dfuzz_prev;	/* prior fuzz */
@@ -175,6 +176,15 @@ get_systime(
 	DEBUG_REQUIRE(systime_init_done);
 	ENTER_GET_SYSTIME_CRITSEC();
 
+        /* First check if here was a Lamport violation, that is, two
+         * successive calls to 'get_ostime()' resulted in negative
+         * time difference. Use a few milliseconds of permissible
+         * tolerance -- being too sharp can hurt here.
+         */
+        if (cmp_tspec(ts, sub_tspec_ns(ts_last, 50000000)) < 0)
+                lamport_violated = 1;
+        ts_last = ts;
+
 	/*
 	 * After default_get_precision() has set a nonzero sys_fuzz,
 	 * ensure every reading of the OS clock advances by at least