batman-adv: Distributed ARP Table - add ARP parsing functions

ARP messages are now parsed to make it possible to trigger special actions
depending on their types (snooping).

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/distributed-arp-table.h b/net/batman-adv/distributed-arp-table.h
index 1b88303..f4e282a 100644
--- a/net/batman-adv/distributed-arp-table.h
+++ b/net/batman-adv/distributed-arp-table.h
@@ -23,6 +23,8 @@
 #include "types.h"
 #include "originator.h"
 
+#include <linux/if_arp.h>
+
 #define BATADV_DAT_ADDR_MAX ((batadv_dat_addr_t)~(batadv_dat_addr_t)0)
 
 /**