batman-adv: B.A.T.M.A.N. V - implement GW selection logic

Since the GW selection logic has been made routing protocol specific
it is now possible for B.A.T.M.A.N V to have its own mechanism by
providing the API implementation.

Implement the GW specific API in the B.A.T.M.A.N. V protocol in
order to provide a working GW selection mechanism.

Signed-off-by: Antonio Quartulli <a@unstable.cc>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

3 files changed, 226 insertions, 4 deletions

diff --git a/net/batman-adv/bat_v.c b/net/batman-adv/bat_v.c
index 90fd5ee877d1..1d777b171366 100644
--- a/net/batman-adv/bat_v.c
+++ b/net/batman-adv/bat_v.c
@@ -25,6 +25,7 @@
 #include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
+#include <linux/kref.h>
 #include <linux/netdevice.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
@@ -40,6 +41,7 @@
 #include "gateway_common.h"
 #include "hard-interface.h"
 #include "hash.h"
+#include "log.h"
 #include "originator.h"
 #include "packet.h"
 
@@ -350,6 +352,213 @@ static ssize_t batadv_v_show_sel_class(struct batadv_priv *bat_priv, char *buff)
         return sprintf(buff, "%u.%u MBit\n", class / 10, class % 10);
 }
 
+/**
+ * batadv_v_gw_throughput_get - retrieve the GW-bandwidth for a given GW
+ * @gw_node: the GW to retrieve the metric for
+ * @bw: the pointer where the metric will be stored. The metric is computed as
+ *  the minimum between the GW advertised throughput and the path throughput to
+ *  it in the mesh
+ *
+ * Return: 0 on success, -1 on failure
+ */
+static int batadv_v_gw_throughput_get(struct batadv_gw_node *gw_node, u32 *bw)
+{
+        struct batadv_neigh_ifinfo *router_ifinfo = NULL;
+        struct batadv_orig_node *orig_node;
+        struct batadv_neigh_node *router;
+        int ret = -1;
+
+        orig_node = gw_node->orig_node;
+        router = batadv_orig_router_get(orig_node, BATADV_IF_DEFAULT);
+        if (!router)
+                goto out;
+
+        router_ifinfo = batadv_neigh_ifinfo_get(router, BATADV_IF_DEFAULT);
+        if (!router_ifinfo)
+                goto out;
+
+        /* the GW metric is computed as the minimum between the path throughput
+         * to reach the GW itself and the advertised bandwidth.
+         * This gives us an approximation of the effective throughput that the
+         * client can expect via this particular GW node
+         */
+        *bw = router_ifinfo->bat_v.throughput;
+        *bw = min_t(u32, *bw, gw_node->bandwidth_down);
+
+        ret = 0;
+out:
+        if (router)
+                batadv_neigh_node_put(router);
+        if (router_ifinfo)
+                batadv_neigh_ifinfo_put(router_ifinfo);
+
+        return ret;
+}
+
+/**
+ * batadv_v_gw_get_best_gw_node - retrieve the best GW node
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Return: the GW node having the best GW-metric, NULL if no GW is known
+ */
+static struct batadv_gw_node *
+batadv_v_gw_get_best_gw_node(struct batadv_priv *bat_priv)
+{
+        struct batadv_gw_node *gw_node, *curr_gw = NULL;
+        u32 max_bw = 0, bw;
+
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(gw_node, &bat_priv->gw.list, list) {
+                if (!kref_get_unless_zero(&gw_node->refcount))
+                        continue;
+
+                if (batadv_v_gw_throughput_get(gw_node, &bw) < 0)
+                        goto next;
+
+                if (curr_gw && (bw <= max_bw))
+                        goto next;
+
+                if (curr_gw)
+                        batadv_gw_node_put(curr_gw);
+
+                curr_gw = gw_node;
+                kref_get(&curr_gw->refcount);
+                max_bw = bw;
+
+next:
+                batadv_gw_node_put(gw_node);
+        }
+        rcu_read_unlock();
+
+        return curr_gw;
+}
+
+/**
+ * batadv_v_gw_is_eligible - check if a originator would be selected as GW
+ * @bat_priv: the bat priv with all the soft interface information
+ * @curr_gw_orig: originator representing the currently selected GW
+ * @orig_node: the originator representing the new candidate
+ *
+ * Return: true if orig_node can be selected as current GW, false otherwise
+ */
+static bool batadv_v_gw_is_eligible(struct batadv_priv *bat_priv,
+                                    struct batadv_orig_node *curr_gw_orig,
+                                    struct batadv_orig_node *orig_node)
+{
+        struct batadv_gw_node *curr_gw = NULL, *orig_gw = NULL;
+        u32 gw_throughput, orig_throughput, threshold;
+        bool ret = false;
+
+        threshold = atomic_read(&bat_priv->gw.sel_class);
+
+        curr_gw = batadv_gw_node_get(bat_priv, curr_gw_orig);
+        if (!curr_gw) {
+                ret = true;
+                goto out;
+        }
+
+        if (batadv_v_gw_throughput_get(curr_gw, &gw_throughput) < 0) {
+                ret = true;
+                goto out;
+        }
+
+        orig_gw = batadv_gw_node_get(bat_priv, orig_node);
+        if (!orig_node)
+                goto out;
+
+        if (batadv_v_gw_throughput_get(orig_gw, &orig_throughput) < 0)
+                goto out;
+
+        if (orig_throughput < gw_throughput)
+                goto out;
+
+        if ((orig_throughput - gw_throughput) < threshold)
+                goto out;
+
+        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+                   "Restarting gateway selection: better gateway found (throughput curr: %u, throughput new: %u)\n",
+                   gw_throughput, orig_throughput);
+
+        ret = true;
+out:
+        if (curr_gw)
+                batadv_gw_node_put(curr_gw);
+        if (orig_gw)
+                batadv_gw_node_put(orig_gw);
+
+        return ret;
+}
+
+/* fails if orig_node has no router */
+static int batadv_v_gw_write_buffer_text(struct batadv_priv *bat_priv,
+                                         struct seq_file *seq,
+                                         const struct batadv_gw_node *gw_node)
+{
+        struct batadv_gw_node *curr_gw;
+        struct batadv_neigh_node *router;
+        struct batadv_neigh_ifinfo *router_ifinfo = NULL;
+        int ret = -1;
+
+        router = batadv_orig_router_get(gw_node->orig_node, BATADV_IF_DEFAULT);
+        if (!router)
+                goto out;
+
+        router_ifinfo = batadv_neigh_ifinfo_get(router, BATADV_IF_DEFAULT);
+        if (!router_ifinfo)
+                goto out;
+
+        curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
+
+        seq_printf(seq, "%s %pM (%9u.%1u) %pM [%10s]: %u.%u/%u.%u MBit\n",
+                   (curr_gw == gw_node ? "=>" : "  "),
+                   gw_node->orig_node->orig,
+                   router_ifinfo->bat_v.throughput / 10,
+                   router_ifinfo->bat_v.throughput % 10, router->addr,
+                   router->if_incoming->net_dev->name,
+                   gw_node->bandwidth_down / 10,
+                   gw_node->bandwidth_down % 10,
+                   gw_node->bandwidth_up / 10,
+                   gw_node->bandwidth_up % 10);
+        ret = seq_has_overflowed(seq) ? -1 : 0;
+
+        if (curr_gw)
+                batadv_gw_node_put(curr_gw);
+out:
+        if (router_ifinfo)
+                batadv_neigh_ifinfo_put(router_ifinfo);
+        if (router)
+                batadv_neigh_node_put(router);
+        return ret;
+}
+
+/**
+ * batadv_v_gw_print - print the gateway list
+ * @bat_priv: the bat priv with all the soft interface information
+ * @seq: gateway table seq_file struct
+ */
+static void batadv_v_gw_print(struct batadv_priv *bat_priv,
+                              struct seq_file *seq)
+{
+        struct batadv_gw_node *gw_node;
+        int gw_count = 0;
+
+        seq_puts(seq,
+                 "      Gateway        ( throughput)           Nexthop [outgoingIF]: advertised uplink bandwidth\n");
+
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(gw_node, &bat_priv->gw.list, list) {
+                /* fails if orig_node has no router */
+                if (batadv_v_gw_write_buffer_text(bat_priv, seq, gw_node) < 0)
+                        continue;
+
+                gw_count++;
+        }
+        rcu_read_unlock();
+
+        if (gw_count == 0)
+                seq_puts(seq, "No gateways in range ...\n");
+}
+
 static struct batadv_algo_ops batadv_batman_v __read_mostly = {
         .name = "BATMAN_V",
         .iface = {
@@ -371,6 +580,9 @@ static struct batadv_algo_ops batadv_batman_v __read_mostly = {
         .gw = {
                 .store_sel_class = batadv_v_store_sel_class,
                 .show_sel_class = batadv_v_show_sel_class,
+                .get_best_gw_node = batadv_v_gw_get_best_gw_node,
+                .is_eligible = batadv_v_gw_is_eligible,
+                .print = batadv_v_gw_print,
         },
 };
 
@@ -397,7 +609,16 @@ void batadv_v_hardif_init(struct batadv_hard_iface *hard_iface)
  */
 int batadv_v_mesh_init(struct batadv_priv *bat_priv)
 {
-        return batadv_v_ogm_init(bat_priv);
+        int ret = 0;
+
+        ret = batadv_v_ogm_init(bat_priv);
+        if (ret < 0)
+                return ret;
+
+        /* set default throughput difference threshold to 5Mbps */
+        atomic_set(&bat_priv->gw.sel_class, 50);
+
+        return 0;
 }
 
 /**
diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index ec363f39b6a9..a77a17939f1e 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -360,9 +360,8 @@ static void batadv_gw_node_add(struct batadv_priv *bat_priv,
  *
  * Return: gateway node if found or NULL otherwise.
  */
-static struct batadv_gw_node *
-batadv_gw_node_get(struct batadv_priv *bat_priv,
-                   struct batadv_orig_node *orig_node)
+struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
+                                          struct batadv_orig_node *orig_node)
 {
         struct batadv_gw_node *gw_node_tmp, *gw_node = NULL;
 
diff --git a/net/batman-adv/gateway_client.h b/net/batman-adv/gateway_client.h
index 4c9edde48914..6b40432aa1ed 100644
--- a/net/batman-adv/gateway_client.h
+++ b/net/batman-adv/gateway_client.h
@@ -47,5 +47,7 @@ bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, struct sk_buff *skb);
 enum batadv_dhcp_recipient
 batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
                              u8 *chaddr);
+struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
+                                          struct batadv_orig_node *orig_node);
 
 #endif /* _NET_BATMAN_ADV_GATEWAY_CLIENT_H_ */