From: Martin Burnicki <burnicki@ntp.org>
Date: Wed, 23 Jan 2013 16:50:49 +0000 (+0100)
Subject: [Bug 2328] Don't apply small time adjustments on Windows versions which don't support... 
X-Git-Tag: NTP_4_2_7P351~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=68941c6e2c140ad3c238d97cd82f24bc6b5d38e8;p=thirdparty%2Fntp.git

[Bug 2328] Don't apply small time adjustments on Windows versions which don't support this.

bk: 510014e9LVCWTJg3lZDt5DQ6p_dc0Q
---

diff --git a/ChangeLog b/ChangeLog
index 881455049..0244abbfb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,5 @@
+* [Bug 2328] Don't apply small time adjustments on Windows versions
+  which don't support this.
 (4.2.7p350) 2013/01/21 Released by Harlan Stenn <stenn@ntp.org>
 * Added sntp/loc/netbsd based on info from Christos Zoulas.
 (4.2.7p349) 2013/01/20 Released by Harlan Stenn <stenn@ntp.org>
diff --git a/ports/winnt/ntpd/nt_clockstuff.c b/ports/winnt/ntpd/nt_clockstuff.c
index 53c5415ae..aaf21b887 100644
--- a/ports/winnt/ntpd/nt_clockstuff.c
+++ b/ports/winnt/ntpd/nt_clockstuff.c
@@ -129,6 +129,14 @@ static LONGLONG		baseline_times[BASELINES_TOT] = {0};
 static ULONGLONG	clock_backward_max = CLOCK_BACK_THRESHOLD;
 static int		clock_backward_count;
 
+/**
+ * A flag set on Windows versions which ignore small time adjustments.
+ *
+ * Windows Vista and Windows 7 ignore TimeAdjustment less than 16.
+ * @note Has to be checked for Windows Server 2008/2012 and Windows 8.
+ * Ref: http://support.microsoft.com/kb/2537623, bug #2328
+ */
+static BOOL os_ignores_small_adjustment;
 
 /*
  * clockperiod is the period used for SetSystemTimeAdjustment 
@@ -268,6 +276,42 @@ perf_ctr(void)
 }
 
 
+/*
+ * init_small_adjustment
+ *
+ * Set variable os_ignores_small_adjustment
+ *
+ */
+static void init_small_adjustment(void)
+{
+	OSVERSIONINFO vi;
+	memset(&vi, 0, sizeof(vi));
+	vi.dwOSVersionInfoSize = sizeof(vi);
+
+	if (!GetVersionEx(&vi)) {
+		msyslog(LOG_WARNING, "GetVersionEx failed with error code %d.", GetLastError());
+		os_ignores_small_adjustment = FALSE;
+		return;
+	}
+
+	if (vi.dwMajorVersion == 6 && vi.dwMinorVersion == 1) {
+		// Windows 7 and Windows Server 2008 R2
+		//
+		// Windows 7 is documented as affected.
+		// Windows Server 2008 R2 is assumed affected.
+		os_ignores_small_adjustment = TRUE;
+	} else if (vi.dwMajorVersion == 6 && vi.dwMinorVersion == 0) {
+		// Windows Vista and Windows Server 2008
+		//
+		// Windows Vista is documented as affected.
+		// Windows Server 2008 is assumed affected.
+		os_ignores_small_adjustment = TRUE;
+	} else {
+		os_ignores_small_adjustment = FALSE;
+	}
+}
+
+
 /*
  * choose_interp_counter - select between QueryPerformanceCounter and
  *			   the x86 processor cycle counter (TSC).
@@ -468,6 +512,18 @@ adj_systime(
 				((isneg)
 				     ? -0.5
 				     : 0.5));
+
+	if (os_ignores_small_adjustment) {
+		/*
+		 * As the OS ignores adjustments smaller than 16, we need to
+		 * leave these small adjustments in sys_residual, causing
+		 * the small values to be averaged over time.
+		 */
+		if (TimeAdjustment > -16 && TimeAdjustment < 16) {
+			TimeAdjustment = 0;
+		}
+	}
+
 	dtemp -= TimeAdjustment * ppm_per_adjust_unit;	
 
 
@@ -639,6 +695,8 @@ init_winnt_time(void)
 
 #pragma warning(pop)
 
+	init_small_adjustment();
+
 	/*
 	 * Get privileges needed for fiddling with the clock
 	 */