From 0398ae2bf7418f729f8b0d22fb08c26557242cb4 Mon Sep 17 00:00:00 2001
From: ache <ache@FreeBSD.org>
Date: Wed, 25 Feb 1998 09:40:21 +0000
Subject: Minimize clock drift between getting and setting time Submitted by:
 bde

---
 sbin/adjkerntz/adjkerntz.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

(limited to 'sbin/adjkerntz')

diff --git a/sbin/adjkerntz/adjkerntz.c b/sbin/adjkerntz/adjkerntz.c
index f92ea56..e7ad4a7 100644
--- a/sbin/adjkerntz/adjkerntz.c
+++ b/sbin/adjkerntz/adjkerntz.c
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *		$Id$
+ *		$Id: adjkerntz.c,v 1.20 1997/06/10 11:01:13 charnier Exp $
  */
 
 #ifndef lint
@@ -257,8 +257,10 @@ recalculate:
 #ifdef DEBUG
 			fprintf(stderr, "Final diff: %ld secs\n", diff);
 #endif
-			tv.tv_sec += diff;
-			tv.tv_usec = 0;       /* we are restarting here... */
+			/*
+			 * stv is abused as a flag.  The important value
+			 * is in `diff'.
+			 */
 			stv = &tv;
 		}
 	}
@@ -293,13 +295,28 @@ recalculate:
 		}
 	}
 
-	if (   (   (init && (stv != NULL || stz != NULL))
-		|| (stz != NULL && stv == NULL)
-	       )
-	    && settimeofday(stv, stz)
+	if (   (init && (stv != NULL || stz != NULL))
+	    || (stz != NULL && stv == NULL)
 	   ) {
-		syslog(LOG_ERR, "settimeofday: %m");
-		return 1;
+		if (stv != NULL) {
+			/*
+			 * Get the time again, as close as possible to
+			 * adjusting it, to minimise drift.
+			 * XXX we'd better not fail between here and
+			 * restoring disrtcset, since we don't clean up
+			 * anything.
+			 */
+			if (gettimeofday(&tv, (struct timezone *)NULL)) {
+				syslog(LOG_ERR, "gettimeofday: %m");
+				return 1;
+			}
+			tv.tv_sec += diff;
+			stv = &tv;
+		}
+		if (settimeofday(stv, stz)) {
+			syslog(LOG_ERR, "settimeofday: %m");
+			return 1;
+		}
 	}
 
 	/* setting CPU_ADJKERNTZ have a side effect: resettodr(), which */
-- 
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