[v8,1/5] batman-adv: prevent multiple ARP replies sent by gateways if dat enabled

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 7332d284..546e66ec 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -2449,3 +2449,52 @@  int batadv_bla_backbone_dump(struct sk_buff *msg, struct netlink_callback *cb)
 
 	return ret;
 }
+
+#ifdef CONFIG_BATMAN_ADV_DAT
+/**
+ * batadv_bla_check_claim - check if address is claimed
+ *
+ * @bat_priv: the bat priv with all the soft interface information
+ * @addr: mac address of which the claim status is checked
+ * @vid: the VLAN ID
+ *
+ * addr is checked if this address is claimed by the local device itself.
+ *
+ * Return: true if bla is disabled or the mac is claimed by the device,
+ * false if the device addr is already claimed by another gateway
+ */
+bool batadv_bla_check_claim(struct batadv_priv *bat_priv,
+			    u8 *addr, unsigned short vid)
+{
+	struct batadv_bla_claim search_claim;
+	struct batadv_bla_claim *claim = NULL;
+	struct batadv_hard_iface *primary_if = NULL;
+	bool ret = true;
+
+	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+		return ret;
+
+	primary_if = batadv_primary_if_get_selected(bat_priv);
+	if (!primary_if)
+		return ret;
+
+	/* First look if the mac address is claimed */
+	ether_addr_copy(search_claim.addr, addr);
+	search_claim.vid = vid;
+
+	claim = batadv_claim_hash_find(bat_priv, &search_claim);
+
+	/* If there is a claim and we are not owner of the claim,
+	 * return false.
+	 */
+	if (claim) {
+		if (!batadv_compare_eth(claim->backbone_gw->orig,
+					primary_if->net_dev->dev_addr))
+			ret = false;
+		batadv_claim_put(claim);
+	}
+
+	batadv_hardif_put(primary_if);
+	return ret;
+}
+#endif
diff --git a/net/batman-adv/bridge_loop_avoidance.h b/net/batman-adv/bridge_loop_avoidance.h
index e157986b..23477574 100644
--- a/net/batman-adv/bridge_loop_avoidance.h
+++ b/net/batman-adv/bridge_loop_avoidance.h
@@ -69,6 +69,10 @@  void batadv_bla_status_update(struct net_device *net_dev);
 int batadv_bla_init(struct batadv_priv *bat_priv);
 void batadv_bla_free(struct batadv_priv *bat_priv);
 int batadv_bla_claim_dump(struct sk_buff *msg, struct netlink_callback *cb);
+#ifdef CONFIG_BATMAN_ADV_DAT
+bool batadv_bla_check_claim(struct batadv_priv *bat_priv, u8 *addr,
+			    unsigned short vid);
+#endif
 #define BATADV_BLA_CRC_INIT	0
 #else /* ifdef CONFIG_BATMAN_ADV_BLA */
 
@@ -145,6 +149,13 @@  static inline int batadv_bla_backbone_dump(struct sk_buff *msg,
 	return -EOPNOTSUPP;
 }
 
+static inline
+bool batadv_bla_check_claim(struct batadv_priv *bat_priv, u8 *addr,
+			    unsigned short vid)
+{
+	return true;
+}
+
 #endif /* ifdef CONFIG_BATMAN_ADV_BLA */
 
 #endif /* ifndef _NET_BATMAN_ADV_BLA_H_ */
diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 4f643fdb..28cfa538 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -43,6 +43,7 @@ 
 #include <linux/workqueue.h>
 #include <net/arp.h>
 
+#include "bridge_loop_avoidance.h"
 #include "hard-interface.h"
 #include "hash.h"
 #include "log.h"
@@ -1040,6 +1041,20 @@  bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
 			goto out;
 		}
 
+		/* If BLA is enabled, only send ARP replies if we have claimed
+		 * the destination for the ARP request or if no one else of
+		 * the backbone gws belonging to our backbone has claimed the
+		 * destination.
+		 */
+		if (!batadv_bla_check_claim(bat_priv,
+					    dat_entry->mac_addr, vid)) {
+			batadv_dbg(BATADV_DBG_DAT, bat_priv,
+				   "Device %pM claimed by another backbone gw. Don't send ARP reply!",
+				   dat_entry->mac_addr);
+			ret = true;
+			goto out;
+		}
+
 		skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
 						      dat_entry->mac_addr,
 						      hw_src, vid);