batman-adv: gateway election code refactoring

The gateway election mechanism has been a little revised. Now the
gw_election is trigered by an atomic_t flag (gw_reselect) which is set
to 1 in case of election needed, avoding to set curr_gw to NULL.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

3 files changed, 82 insertions, 56 deletions

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 7248de2e66dc..0350c0cd690e 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -20,6 +20,7 @@
  */
 
 #include "main.h"
+#include "bat_sysfs.h"
 #include "gateway_client.h"
 #include "gateway_common.h"
 #include "hard-interface.h"
@@ -97,40 +98,19 @@ static void gw_select(struct bat_priv *bat_priv, struct gw_node *new_gw_node)
 
 void gw_deselect(struct bat_priv *bat_priv)
 {
-        gw_select(bat_priv, NULL);
+        atomic_set(&bat_priv->gw_reselect, 1);
 }
 
-void gw_election(struct bat_priv *bat_priv)
+static struct gw_node *gw_get_best_gw_node(struct bat_priv *bat_priv)
 {
-        struct hlist_node *node;
-        struct gw_node *gw_node, *curr_gw = NULL, *curr_gw_tmp = NULL;
         struct neigh_node *router;
-        uint8_t max_tq = 0;
+        struct hlist_node *node;
+        struct gw_node *gw_node, *curr_gw = NULL;
         uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
+        uint8_t max_tq = 0;
         int down, up;
 
-        /**
-         * The batman daemon checks here if we already passed a full originator
-         * cycle in order to make sure we don't choose the first gateway we
-         * hear about. This check is based on the daemon's uptime which we
-         * don't have.
-         **/
-        if (atomic_read(&bat_priv->gw_mode) != GW_MODE_CLIENT)
-                return;
-
-        curr_gw = gw_get_selected_gw_node(bat_priv);
-        if (curr_gw)
-                goto out;
-
         rcu_read_lock();
-        if (hlist_empty(&bat_priv->gw_list)) {
-                bat_dbg(DBG_BATMAN, bat_priv,
-                        "Removing selected gateway - "
-                        "no gateway in range\n");
-                gw_deselect(bat_priv);
-                goto unlock;
-        }
-
         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
                 if (gw_node->deleted)
                         continue;
@@ -139,6 +119,9 @@ void gw_election(struct bat_priv *bat_priv)
                 if (!router)
                         continue;
 
+                if (!atomic_inc_not_zero(&gw_node->refcount))
+                        goto next;
+
                 switch (atomic_read(&bat_priv->gw_sel_class)) {
                 case 1: /* fast connection */
                         gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags,
@@ -151,8 +134,12 @@ void gw_election(struct bat_priv *bat_priv)
 
                         if ((tmp_gw_factor > max_gw_factor) ||
                             ((tmp_gw_factor == max_gw_factor) &&
-                             (router->tq_avg > max_tq)))
-                                curr_gw_tmp = gw_node;
+                             (router->tq_avg > max_tq))) {
+                                if (curr_gw)
+                                        gw_node_free_ref(curr_gw);
+                                curr_gw = gw_node;
+                                atomic_inc(&curr_gw->refcount);
+                        }
                         break;
 
                 default: /**
@@ -163,8 +150,12 @@ void gw_election(struct bat_priv *bat_priv)
                           *     soon as a better gateway appears which has
                           *     $routing_class more tq points)
                           **/
-                        if (router->tq_avg > max_tq)
-                                curr_gw_tmp = gw_node;
+                        if (router->tq_avg > max_tq) {
+                                if (curr_gw)
+                                        gw_node_free_ref(curr_gw);
+                                curr_gw = gw_node;
+                                atomic_inc(&curr_gw->refcount);
+                        }
                         break;
                 }
 
@@ -174,42 +165,75 @@ void gw_election(struct bat_priv *bat_priv)
                 if (tmp_gw_factor > max_gw_factor)
                         max_gw_factor = tmp_gw_factor;
 
+                gw_node_free_ref(gw_node);
+
+next:
                 neigh_node_free_ref(router);
         }
+        rcu_read_unlock();
 
-        if (curr_gw != curr_gw_tmp) {
-                router = orig_node_get_router(curr_gw_tmp->orig_node);
-                if (!router)
-                        goto unlock;
+        return curr_gw;
+}
 
-                if ((curr_gw) && (!curr_gw_tmp))
-                        bat_dbg(DBG_BATMAN, bat_priv,
-                                "Removing selected gateway - "
-                                "no gateway in range\n");
-                else if ((!curr_gw) && (curr_gw_tmp))
-                        bat_dbg(DBG_BATMAN, bat_priv,
-                                "Adding route to gateway %pM "
-                                "(gw_flags: %i, tq: %i)\n",
-                                curr_gw_tmp->orig_node->orig,
-                                curr_gw_tmp->orig_node->gw_flags,
-                                router->tq_avg);
-                else
-                        bat_dbg(DBG_BATMAN, bat_priv,
-                                "Changing route to gateway %pM "
-                                "(gw_flags: %i, tq: %i)\n",
-                                curr_gw_tmp->orig_node->orig,
-                                curr_gw_tmp->orig_node->gw_flags,
-                                router->tq_avg);
+void gw_election(struct bat_priv *bat_priv)
+{
+        struct gw_node *curr_gw = NULL, *next_gw = NULL;
+        struct neigh_node *router = NULL;
 
-                neigh_node_free_ref(router);
-                gw_select(bat_priv, curr_gw_tmp);
+        /**
+         * The batman daemon checks here if we already passed a full originator
+         * cycle in order to make sure we don't choose the first gateway we
+         * hear about. This check is based on the daemon's uptime which we
+         * don't have.
+         **/
+        if (atomic_read(&bat_priv->gw_mode) != GW_MODE_CLIENT)
+                goto out;
+
+        if (!atomic_dec_not_zero(&bat_priv->gw_reselect))
+                goto out;
+
+        curr_gw = gw_get_selected_gw_node(bat_priv);
+
+        next_gw = gw_get_best_gw_node(bat_priv);
+
+        if (curr_gw == next_gw)
+                goto out;
+
+        if (next_gw) {
+                router = orig_node_get_router(next_gw->orig_node);
+                if (!router) {
+                        gw_deselect(bat_priv);
+                        goto out;
+                }
         }
 
-unlock:
-        rcu_read_unlock();
+        if ((curr_gw) && (!next_gw)) {
+                bat_dbg(DBG_BATMAN, bat_priv,
+                        "Removing selected gateway - no gateway in range\n");
+        } else if ((!curr_gw) && (next_gw)) {
+                bat_dbg(DBG_BATMAN, bat_priv,
+                        "Adding route to gateway %pM (gw_flags: %i, tq: %i)\n",
+                        next_gw->orig_node->orig,
+                        next_gw->orig_node->gw_flags,
+                        router->tq_avg);
+        } else {
+                bat_dbg(DBG_BATMAN, bat_priv,
+                        "Changing route to gateway %pM "
+                        "(gw_flags: %i, tq: %i)\n",
+                        next_gw->orig_node->orig,
+                        next_gw->orig_node->gw_flags,
+                        router->tq_avg);
+        }
+
+        gw_select(bat_priv, next_gw);
+
 out:
         if (curr_gw)
                 gw_node_free_ref(curr_gw);
+        if (next_gw)
+                gw_node_free_ref(next_gw);
+        if (router)
+                neigh_node_free_ref(router);
 }
 
 void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index c2b06b71d574..e367e690a9f6 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -113,6 +113,7 @@ int mesh_init(struct net_device *soft_iface)
         if (vis_init(bat_priv) < 1)
                 goto err;
 
+        atomic_set(&bat_priv->gw_reselect, 0);
         atomic_set(&bat_priv->mesh_state, MESH_ACTIVE);
         goto end;
 
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 11e8569a8ca7..85cf1224881e 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -201,6 +201,7 @@ struct bat_priv {
         struct delayed_work orig_work;
         struct delayed_work vis_work;
         struct gw_node __rcu *curr_gw;  /* rcu protected pointer */
+        atomic_t gw_reselect;
         struct hard_iface __rcu *primary_if;  /* rcu protected pointer */
         struct vis_info *my_vis_info;
 };