batman-adv: Distributed ARP Table - add snooping functions for ARP messages

In case of an ARP message going in or out the soft_iface, it is intercepted and
a special action is performed. In particular the DHT helper functions previously
implemented are used to store all the ARP entries belonging to the network in
order to provide a fast and unicast lookup instead of the classic broadcast
flooding mechanism.
Each node stores the entries it is responsible for (following the DHT rules) in
its soft_iface ARP table. This makes it possible to reuse the kernel data
structures and functions for ARP management.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/send.c b/net/batman-adv/send.c
index 570a8bc..660d9bf 100644
--- a/net/batman-adv/send.c
+++ b/net/batman-adv/send.c
@@ -18,6 +18,7 @@
  */
 
 #include "main.h"
+#include "distributed-arp-table.h"
 #include "send.h"
 #include "routing.h"
 #include "translation-table.h"
@@ -209,6 +210,9 @@
 	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING)
 		goto out;
 
+	if (batadv_dat_drop_broadcast_packet(bat_priv, forw_packet))
+		goto out;
+
 	/* rebroadcast packet */
 	rcu_read_lock();
 	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {