timeserver: refresh the nameservers before each lookup

There is a possibility where the UDP channel connections in the resolv
instance are being closed because of how the external DNS service might
respond, and are never opened again.  The DNS resolve will keep failing,
and there is no automatic recovery from this.

Similar to the behavior of the WISPR module, refresh the nameservers in
the resolv instance before each DNS request.

1 files changed, 46 insertions, 41 deletions

diff --git a/src/timeserver.c b/src/timeserver.c
index feef8e83..92d0d6bc 100644
--- a/src/timeserver.c
+++ b/src/timeserver.c
@@ -47,6 +47,7 @@ static GResolv *resolv = NULL;
 static int resolv_id = 0;
 
 static void sync_next(void);
+static void ts_set_nameservers(struct connman_service *service);
 
 static void resolv_debug(const char *str, void *data)
 {
@@ -183,6 +184,7 @@ static void sync_next(void)
 	}
 
 	__connman_ntp_stop();
+	ts_set_nameservers(ts_service);
 
 	while (ts_list) {
 		ts_current = ts_list->data;
@@ -347,24 +349,34 @@ static void ts_recheck_enable(void)
 			NULL);
 }
 
-static void ts_reset(struct connman_service *service)
+static int ts_setup_resolv(struct connman_service *service)
 {
-	char **nameservers;
 	int i;
 
+	i = __connman_service_get_index(service);
+	if (i < 0)
+		return -EINVAL;
+
+	if (resolv) {
+		g_resolv_unref(resolv);
+		resolv = NULL;
+	}
+
+	resolv = g_resolv_new(i);
 	if (!resolv)
-		return;
+		return -ENOMEM;
 
-	__connman_timeserver_set_synced(false);
+	if (getenv("CONNMAN_RESOLV_DEBUG"))
+		g_resolv_set_debug(resolv, resolv_debug, "RESOLV");
 
-	/*
-	 * Before we start creating the new timeserver list we must stop
-	 * any ongoing ntp query and server resolution.
-	 */
+	return 0;
+}
 
-	__connman_ntp_stop();
 
-	ts_recheck_disable();
+static void ts_set_nameservers(struct connman_service *service)
+{
+	char **nameservers;
+	int i;
 
 	if (resolv_id > 0)
 		g_resolv_cancel_lookup(resolv, resolv_id);
@@ -378,6 +390,25 @@ static void ts_reset(struct connman_service *service)
 
 		g_strfreev(nameservers);
 	}
+}
+
+static void ts_reset(struct connman_service *service)
+{
+	if (!resolv)
+		return;
+
+	__connman_timeserver_set_synced(false);
+
+	/*
+	 * Before we start creating the new timeserver list we must stop
+	 * any ongoing ntp query and server resolution.
+	 */
+
+	__connman_ntp_stop();
+
+	ts_recheck_disable();
+
+	ts_set_nameservers(service);
 
 	g_slist_free_full(timeservers_list, g_free);
 
@@ -434,42 +465,16 @@ void __connman_timeserver_set_synced(bool status)
 
 static int timeserver_start(struct connman_service *service)
 {
-	char **nameservers;
-	int i;
+	int rv;
 
 	DBG("service %p", service);
 
-	i = __connman_service_get_index(service);
-	if (i < 0)
-		return -EINVAL;
-
-	nameservers = connman_service_get_nameservers(service);
-
-	/* Stop an already ongoing resolution, if there is one */
-	if (resolv && resolv_id > 0)
-		g_resolv_cancel_lookup(resolv, resolv_id);
-
 	/* get rid of the old resolver */
-	if (resolv) {
-		g_resolv_unref(resolv);
-		resolv = NULL;
-	}
-
-	resolv = g_resolv_new(i);
-	if (!resolv) {
-		g_strfreev(nameservers);
-		return -ENOMEM;
-	}
+	rv = ts_setup_resolv(service);
+	if (rv)
+		return rv;
 
-	if (getenv("CONNMAN_RESOLV_DEBUG"))
-		g_resolv_set_debug(resolv, resolv_debug, "RESOLV");
-
-	if (nameservers) {
-		for (i = 0; nameservers[i]; i++)
-			g_resolv_add_nameserver(resolv, nameservers[i], 53, 0);
-
-		g_strfreev(nameservers);
-	}
+	ts_set_nameservers(service);
 
 	__connman_timeserver_sync(service);