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, 12 insertions, 0 deletions

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index e56cb88ef2b..4d639b303bd 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -36,6 +36,7 @@
 #include <linux/etherdevice.h>
 #include <linux/if_vlan.h>
 #include "unicast.h"
+#include "bridge_loop_avoidance.h"
 
 
 static int bat_get_settings(struct net_device *dev, struct ethtool_cmd *cmd);
@@ -152,6 +153,9 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
 		goto dropped;
 	}
 
+	if (bla_tx(bat_priv, skb, vid))
+		goto dropped;
+
 	/* Register the client MAC in the transtable */
 	tt_local_add(soft_iface, ethhdr->h_source, skb->skb_iif);
 
@@ -287,6 +291,12 @@ void interface_rx(struct net_device *soft_iface,
 	if (is_ap_isolated(bat_priv, ethhdr->h_source, ethhdr->h_dest))
 		goto dropped;
 
+	/* Let the bridge loop avoidance check the packet. If will
+	 * not handle it, we can safely push it up.
+	 */
+	if (bla_rx(bat_priv, skb, vid))
+		goto out;
+
 	netif_rx(skb);
 	goto out;
 
@@ -354,6 +364,7 @@ struct net_device *softif_create(const char *name)
 
 	atomic_set(&bat_priv->aggregated_ogms, 1);
 	atomic_set(&bat_priv->bonding, 0);
+	atomic_set(&bat_priv->bridge_loop_avoidance, 0);
 	atomic_set(&bat_priv->ap_isolation, 0);
 	atomic_set(&bat_priv->vis_mode, VIS_TYPE_CLIENT_UPDATE);
 	atomic_set(&bat_priv->gw_mode, GW_MODE_OFF);
@@ -371,6 +382,7 @@ struct net_device *softif_create(const char *name)
 	atomic_set(&bat_priv->ttvn, 0);
 	atomic_set(&bat_priv->tt_local_changes, 0);
 	atomic_set(&bat_priv->tt_ogm_append_cnt, 0);
+	atomic_set(&bat_priv->bla_num_requests, 0);
 
 	bat_priv->tt_buff = NULL;
 	bat_priv->tt_buff_len = 0;