resolver: Send RS before RDNSS lifetime expires

Implemented feature from RFC 6106 section
'5.1. Recursive DNS Server Option':
	"Lifetime      32-bit unsigned integer.
	...
	Hosts MAY send a Router Solicitation to ensure
	the RDNSS information is fresh before the interval expires."

Host will send RS when a certain threshold of RDNSS lifetime is reached.
Values which can be adjusted:
- lifetime threshold - set to 80% from lifetime
- number of retries in case RA is not received - set to 0
- time between retries, in case RA is not received - set to 3 seconds

1 files changed, 66 insertions, 0 deletions

diff --git a/src/network.c b/src/network.c
index 10f1bf32..6fe1d9c5 100644
--- a/src/network.c
+++ b/src/network.c
@@ -28,6 +28,19 @@
 
 #include "connman.h"
 
+/*
+ * How many times to send RS with the purpose of
+ * refreshing RDNSS entries before they actually expire.
+ * With a value of 1, one RS will be sent, with no retries.
+ */
+#define RS_REFRESH_COUNT	1
+
+/*
+ * Value in seconds to wait for RA after RS was sent.
+ * After this time elapsed, we can send another RS.
+ */
+#define RS_REFRESH_TIMEOUT	3
+
 static GSList *network_list = NULL;
 static GSList *driver_list = NULL;
 
@@ -46,6 +59,7 @@ struct connman_network {
 	char *path;
 	int index;
 	int router_solicit_count;
+	int router_solicit_refresh_count;
 
 	struct connman_network_driver *driver;
 	void *driver_data;
@@ -1113,6 +1127,58 @@ static void check_dhcpv6(struct nd_router_advert *reply,
 	connman_network_unref(network);
 }
 
+static void receive_refresh_rs_reply(struct nd_router_advert *reply,
+		unsigned int length, void *user_data)
+{
+	struct connman_network *network = user_data;
+
+	DBG("reply %p", reply);
+
+	if (reply == NULL) {
+		/*
+		 * Router solicitation message seem to get lost easily so
+		 * try to send it again.
+		 */
+		if (network->router_solicit_refresh_count > 1) {
+			network->router_solicit_refresh_count--;
+			DBG("re-send router solicitation %d",
+					network->router_solicit_refresh_count);
+			__connman_inet_ipv6_send_rs(network->index,
+					RS_REFRESH_TIMEOUT,
+					receive_refresh_rs_reply,
+					network);
+			return;
+		}
+	}
+
+	/* RS refresh not in progress anymore */
+	network->router_solicit_refresh_count = 0;
+
+	connman_network_unref(network);
+	return;
+}
+
+int __connman_refresh_rs_ipv6(struct connman_network *network, int index)
+{
+	int ret = 0;
+
+	DBG("network %p index %d", network, index);
+
+	/* Send only one RS for all RDNSS entries which are about to expire */
+	if (network->router_solicit_refresh_count > 0) {
+		DBG("RS refresh already started");
+		return 0;
+	}
+
+	network->router_solicit_refresh_count = RS_REFRESH_COUNT;
+
+	connman_network_ref(network);
+
+	ret = __connman_inet_ipv6_send_rs(index, RS_REFRESH_TIMEOUT,
+			receive_refresh_rs_reply, network);
+	return ret;
+}
+
 static void autoconf_ipv6_set(struct connman_network *network)
 {
 	struct connman_service *service;