From 8c32d79bb0a10832ec59e075a47a4d3316deb252 Mon Sep 17 00:00:00 2001
From: Avery Pennarun <apenwarr@gmail.com>
Date: Wed, 17 Oct 2012 20:34:19 -0400
Subject: [PATCH 5/6] Don't call ntpd_write_synced() if we didn't actually set
 the time.

If we have >= 1 resolved DNS name of a time server, but that server responds
with an error (in the case we experienced, connect() gives "network
unreachable"), ntpd calls priv_settime(0).  I'm not sure that itself is
actually well-advised (why is failing to look up a DNS name a completely
different failure path than looking it up but being unable to reach it?),
but at the very least, when that happens, we don't want to call
ntpd_write_synced() because we definitely have not *actually* synced the
clock.

Also add an error message when connect() fails, similar to the recvfrom()
case for receiving from a time server.  Presumably the kernel ntpd was
tested on doesn't normally have connect() return errors for UDP sockets, but
our Linux kernel does.
---
 client.c |    1 +
 ntpd.c   |   11 +++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/client.c b/client.c
index 208672b..da6aa43 100644
--- a/client.c
+++ b/client.c
@@ -134,6 +134,7 @@ client_query(struct ntp_peer *p)
 		if (connect(p->query->fd, sa, SA_LEN(sa)) == -1) {
 			if (errno == ECONNREFUSED || errno == ENETUNREACH ||
 			    errno == EHOSTUNREACH) {
+				client_log_error(p, "connect", errno);
 				client_nextaddr(p);
 				set_next(p, error_interval());
 				return (-1);
diff --git a/ntpd.c b/ntpd.c
index 3439f3f..7cb72c9 100644
--- a/ntpd.c
+++ b/ntpd.c
@@ -299,7 +299,7 @@ dispatch_imsg(struct ntpd_conf *conf)
 				fatalx("invalid IMSG_ADJTIME received");
 			memcpy(&d, imsg.data, sizeof(d));
 			n = ntpd_adjtime(d);
-			ntpd_write_synced(conf->synced_file);
+			if (n) ntpd_write_synced(conf->synced_file);
 			imsg_compose(ibuf, IMSG_ADJTIME, 0, 0, &n, sizeof(n));
 			break;
 		case IMSG_SETTIME:
@@ -310,12 +310,13 @@ dispatch_imsg(struct ntpd_conf *conf)
 			log_init(conf->debug);
 			memcpy(&d, imsg.data, sizeof(d));
 			ntpd_settime(d);
-			ntpd_write_synced(conf->synced_file);
+			/* d==0 is a special case in ntp.c */
+			if (d) ntpd_write_synced(conf->synced_file);
 			/* daemonize now */
 			if (!conf->debug)
 				if (daemon(1, 0))
 					fatal("daemon");
-			conf->settime = 0;
+			if (d) conf->settime = 0;
 			break;
 		case IMSG_HOST_DNS:
 			name = imsg.data;
@@ -375,8 +376,10 @@ ntpd_settime(double d)
 	time_t		tval;
 
 	/* if the offset is small, don't call settimeofday */
-	if (d < SETTIME_MIN_OFFSET && d > -SETTIME_MIN_OFFSET)
+	if (d < SETTIME_MIN_OFFSET && d > -SETTIME_MIN_OFFSET) {
+		log_debug("ntpd_settime: offset %fs is small, ignoring", d);
 		return;
+	}
 
 	if (gettimeofday(&curtime, NULL) == -1) {
 		log_warn("gettimeofday");
-- 
1.7.7.3