batman-adv: add basic bridge loop avoidance code

This second version of the bridge loop avoidance for batman-adv
avoids loops between the mesh and a backbone (usually a LAN).

By connecting multiple batman-adv mesh nodes to the same ethernet
segment a loop can be created when the soft-interface is bridged
into that ethernet segment. A simple visualization of the loop
involving the most common case - a LAN as ethernet segment:

node1  <-- LAN  -->  node2
  |                   |
wifi   <-- mesh -->  wifi

Packets from the LAN (e.g. ARP broadcasts) will circle forever from
node1 or node2 over the mesh back into the LAN.

With this patch, batman recognizes backbone gateways, nodes which are
part of the mesh and backbone/LAN at the same time. Each backbone
gateway "claims" clients from within the mesh to handle them
exclusively. By restricting that only responsible backbone gateways
may handle their claimed clients traffic, loops are effectively
avoided.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

1 files changed, 11 insertions, 7 deletions

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 377897701a8..8c4b790b98b 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -28,6 +28,7 @@
 #include "bat_sysfs.h"
 #include "originator.h"
 #include "hash.h"
+#include "bridge_loop_avoidance.h"
 
 #include <linux/if_arp.h>
 
@@ -107,7 +108,8 @@ out:
 	return hard_iface;
 }
 
-static void primary_if_update_addr(struct bat_priv *bat_priv)
+static void primary_if_update_addr(struct bat_priv *bat_priv,
+				   struct hard_iface *oldif)
 {
 	struct vis_packet *vis_packet;
 	struct hard_iface *primary_if;
@@ -122,6 +124,7 @@ static void primary_if_update_addr(struct bat_priv *bat_priv)
 	memcpy(vis_packet->sender_orig,
 	       primary_if->net_dev->dev_addr, ETH_ALEN);
 
+	bla_update_orig_address(bat_priv, primary_if, oldif);
 out:
 	if (primary_if)
 		hardif_free_ref(primary_if);
@@ -140,14 +143,15 @@ static void primary_if_select(struct bat_priv *bat_priv,
 	curr_hard_iface = rcu_dereference_protected(bat_priv->primary_if, 1);
 	rcu_assign_pointer(bat_priv->primary_if, new_hard_iface);
 
-	if (curr_hard_iface)
-		hardif_free_ref(curr_hard_iface);
-
 	if (!new_hard_iface)
-		return;
+		goto out;
 
 	bat_priv->bat_algo_ops->bat_ogm_init_primary(new_hard_iface);
-	primary_if_update_addr(bat_priv);
+	primary_if_update_addr(bat_priv, curr_hard_iface);
+
+out:
+	if (curr_hard_iface)
+		hardif_free_ref(curr_hard_iface);
 }
 
 static bool hardif_is_iface_up(const struct hard_iface *hard_iface)
@@ -531,7 +535,7 @@ static int hard_if_event(struct notifier_block *this,
 			goto hardif_put;
 
 		if (hard_iface == primary_if)
-			primary_if_update_addr(bat_priv);
+			primary_if_update_addr(bat_priv, NULL);
 		break;
 	default:
 		break;