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

3 files changed, 130 insertions, 4 deletions

diff --git a/src/connman.h b/src/connman.h
index 734213d8..7f998ebc 100644
--- a/src/connman.h
+++ b/src/connman.h
@@ -147,6 +147,9 @@ typedef void (*__connman_inet_rs_cb_t) (struct nd_router_advert *reply,
 
 int __connman_inet_ipv6_send_rs(int index, int timeout,
 			__connman_inet_rs_cb_t callback, void *user_data);
+
+int __connman_refresh_rs_ipv6(struct connman_network *network, int index);
+
 GSList *__connman_inet_ipv6_get_prefixes(struct nd_router_advert *hdr,
 					unsigned int length);
 
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;
diff --git a/src/resolver.c b/src/resolver.c
index 421b12f0..4780ac12 100644
--- a/src/resolver.c
+++ b/src/resolver.c
@@ -36,11 +36,18 @@
 
 #define RESOLVER_FLAG_PUBLIC (1 << 0)
 
+/*
+ * Threshold for RDNSS lifetime. Will be used to trigger RS
+ * before RDNSS entries actually expire
+ */
+#define RESOLVER_LIFETIME_REFRESH_THRESHOLD 0.8
+
 struct entry_data {
 	char *interface;
 	char *domain;
 	char *server;
 	unsigned int flags;
+	unsigned int lifetime;
 	guint timeout;
 };
 
@@ -253,11 +260,47 @@ static gboolean resolver_expire_cb(gpointer user_data)
 	return FALSE;
 }
 
+static gboolean resolver_refresh_cb(gpointer user_data)
+{
+	struct entry_data *entry = user_data;
+	int index;
+	unsigned int interval;
+	struct connman_service *service = NULL;
+
+	/* Round up what we have left from lifetime */
+	interval = entry->lifetime *
+		(1 - RESOLVER_LIFETIME_REFRESH_THRESHOLD) + 1.0;
+
+	DBG("RDNSS start interface %s domain %s "
+			"server %s remaining lifetime %d",
+			entry->interface, entry->domain,
+			entry->server, interval);
+
+	entry->timeout = g_timeout_add_seconds(interval,
+			resolver_expire_cb, entry);
+
+	index = connman_inet_ifindex(entry->interface);
+	if (index >= 0) {
+		service = __connman_service_lookup_from_index(index);
+		if (service != NULL) {
+			/*
+			 * Send Router Solicitation to refresh RDNSS entries
+			 * before their lifetime expires
+			 */
+			__connman_refresh_rs_ipv6(
+					__connman_service_get_network(service),
+					index);
+		}
+	}
+	return FALSE;
+}
+
 static int append_resolver(const char *interface, const char *domain,
 				const char *server, unsigned int lifetime,
 							unsigned int flags)
 {
 	struct entry_data *entry;
+	unsigned int interval;
 
 	DBG("interface %s domain %s server %s lifetime %d flags %d",
 				interface, domain, server, lifetime, flags);
@@ -273,10 +316,17 @@ static int append_resolver(const char *interface, const char *domain,
 	entry->domain = g_strdup(domain);
 	entry->server = g_strdup(server);
 	entry->flags = flags;
+	entry->lifetime = lifetime;
 	if (lifetime) {
 		int index;
-		entry->timeout = g_timeout_add_seconds(lifetime,
-						resolver_expire_cb, entry);
+		interval = lifetime * RESOLVER_LIFETIME_REFRESH_THRESHOLD;
+
+		DBG("RDNSS start interface %s domain %s "
+				"server %s lifetime threshold %d",
+				interface, domain, server, interval);
+
+		entry->timeout = g_timeout_add_seconds(interval,
+				resolver_refresh_cb, entry);
 
 		/*
 		 * We update the service only for those nameservers
@@ -350,6 +400,7 @@ int connman_resolver_append_lifetime(const char *interface, const char *domain,
 				const char *server, unsigned int lifetime)
 {
 	GSList *list;
+	unsigned int interval;
 
 	DBG("interface %s domain %s server %s lifetime %d",
 				interface, domain, server, lifetime);
@@ -373,8 +424,14 @@ int connman_resolver_append_lifetime(const char *interface, const char *domain,
 			return 0;
 		}
 
-		entry->timeout = g_timeout_add_seconds(lifetime,
-						resolver_expire_cb, entry);
+		interval = lifetime * RESOLVER_LIFETIME_REFRESH_THRESHOLD;
+
+		DBG("RDNSS start interface %s domain %s "
+				"server %s lifetime threshold %d",
+				interface, domain, server, interval);
+
+		entry->timeout = g_timeout_add_seconds(interval,
+				resolver_refresh_cb, entry);
 		return 0;
 	}