From 54167035198230e65aea2a4054d29ac67a7c8d60 Mon Sep 17 00:00:00 2001
From: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Date: Wed, 14 Mar 2012 17:28:59 +0200
Subject: [PATCH] connection: Try to avoid having two default gateways

It is possible that because the rtnl messages arrive
asynchronously, we might end up having two default gateways
that are both active at the same time. If that happens, we try
to downgrade the one that is not yet active.
---
 src/connection.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 131 insertions(+), 13 deletions(-)

diff --git a/src/connection.c b/src/connection.c
index c4c8643..daaea42 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -49,6 +49,7 @@ struct gateway_data {
 	unsigned int order;
 	struct gateway_config *ipv4_gateway;
 	struct gateway_config *ipv6_gateway;
+	connman_bool_t default_checked;
 };
 
 static GHashTable *gateway_hash = NULL;
@@ -80,6 +81,31 @@ static struct gateway_config *find_gateway(int index, const char *gateway)
 	return NULL;
 }
 
+static struct gateway_data *lookup_gateway_data(struct gateway_config *config)
+{
+	GHashTableIter iter;
+	gpointer value, key;
+
+	if (config == NULL)
+		return NULL;
+
+	g_hash_table_iter_init(&iter, gateway_hash);
+
+	while (g_hash_table_iter_next(&iter, &key, &value) == TRUE) {
+		struct gateway_data *data = value;
+
+		if (data->ipv4_gateway != NULL &&
+				data->ipv4_gateway == config)
+			return data;
+
+		if (data->ipv6_gateway != NULL &&
+				data->ipv6_gateway == config)
+			return data;
+	}
+
+	return NULL;
+}
+
 /*
  * Find the gateway that is serving the VPN link
  */
@@ -313,19 +339,6 @@ static struct gateway_data *add_gateway(struct connman_service *service,
 	return data;
 }
 
-static void connection_newgateway(int index, const char *gateway)
-{
-	struct gateway_config *config;
-
-	DBG("index %d gateway %s", index, gateway);
-
-	config = find_gateway(index, gateway);
-	if (config == NULL)
-		return;
-
-	config->active = TRUE;
-}
-
 static void set_default_gateway(struct gateway_data *data,
 				enum connman_ipconfig_type type)
 {
@@ -504,6 +517,111 @@ static struct gateway_data *find_default_gateway(void)
 	return found;
 }
 
+static gboolean choose_default_gateway(struct gateway_data *data,
+					struct gateway_data *candidate)
+{
+	gboolean downgraded = FALSE;
+
+	/*
+	 * If the current default is not active, then we mark
+	 * this one as default. If the other one is already active
+	 * we mark this one as non default.
+	 */
+	if (data->ipv4_gateway != NULL) {
+		if (candidate->ipv4_gateway != NULL &&
+				candidate->ipv4_gateway->active == FALSE) {
+			DBG("ipv4 downgrading %p", candidate);
+			unset_default_gateway(candidate,
+						CONNMAN_IPCONFIG_TYPE_IPV4);
+		}
+		if (candidate->ipv4_gateway != NULL &&
+				candidate->ipv4_gateway->active == TRUE &&
+				candidate->order > data->order) {
+			DBG("ipv4 downgrading this %p", data);
+			unset_default_gateway(data,
+						CONNMAN_IPCONFIG_TYPE_IPV4);
+			downgraded = TRUE;
+		}
+	}
+
+	if (data->ipv6_gateway != NULL) {
+		if (candidate->ipv6_gateway != NULL &&
+				candidate->ipv6_gateway->active == FALSE) {
+			DBG("ipv6 downgrading %p", candidate);
+			unset_default_gateway(candidate,
+						CONNMAN_IPCONFIG_TYPE_IPV6);
+		}
+
+		if (candidate->ipv6_gateway != NULL &&
+				candidate->ipv6_gateway->active == TRUE &&
+				candidate->order > data->order) {
+			DBG("ipv6 downgrading this %p", data);
+			unset_default_gateway(data,
+						CONNMAN_IPCONFIG_TYPE_IPV6);
+			downgraded = TRUE;
+		}
+	}
+
+	return downgraded;
+}
+
+static void connection_newgateway(int index, const char *gateway)
+{
+	struct gateway_config *config;
+	struct gateway_data *data;
+	GHashTableIter iter;
+	gpointer value, key;
+	gboolean found = FALSE;
+
+	DBG("index %d gateway %s", index, gateway);
+
+	config = find_gateway(index, gateway);
+	if (config == NULL)
+		return;
+
+	config->active = TRUE;
+
+	/*
+	 * It is possible that we have two default routes atm
+	 * if there are two gateways waiting rtnl activation at the
+	 * same time.
+	 */
+	data = lookup_gateway_data(config);
+	if (data == NULL)
+		return;
+
+	if (data->default_checked == TRUE)
+		return;
+
+	/*
+	 * The next checks are only done once, otherwise setting
+	 * the default gateway could lead into rtnl forever loop.
+	 */
+
+	g_hash_table_iter_init(&iter, gateway_hash);
+
+	while (g_hash_table_iter_next(&iter, &key, &value) == TRUE) {
+		struct gateway_data *candidate = value;
+
+		if (candidate == data)
+			continue;
+
+		found = choose_default_gateway(data, candidate);
+		if (found == TRUE)
+			break;
+	}
+
+	if (found == FALSE) {
+		if (data->ipv4_gateway != NULL)
+			set_default_gateway(data, CONNMAN_IPCONFIG_TYPE_IPV4);
+
+		if (data->ipv6_gateway != NULL)
+			set_default_gateway(data, CONNMAN_IPCONFIG_TYPE_IPV6);
+	}
+
+	data->default_checked = TRUE;
+}
+
 static void remove_gateway(gpointer user_data)
 {
 	struct gateway_data *data = user_data;
-- 
2.7.4