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, 27 insertions, 0 deletions

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index feac2f4030c8..089dd44a29b1 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -148,6 +148,7 @@ struct bat_priv {
 	atomic_t bonding;		/* boolean */
 	atomic_t fragmentation;		/* boolean */
 	atomic_t ap_isolation;		/* boolean */
+	atomic_t bridge_loop_avoidance;	/* boolean */
 	atomic_t vis_mode;		/* VIS_TYPE_* */
 	atomic_t gw_mode;		/* GW_MODE_* */
 	atomic_t gw_sel_class;		/* uint */
@@ -161,6 +162,7 @@ struct bat_priv {
 	atomic_t ttvn; /* translation table version number */
 	atomic_t tt_ogm_append_cnt;
 	atomic_t tt_local_changes; /* changes registered in a OGM interval */
+	atomic_t bla_num_requests; /* number of bla requests in flight */
 	/* The tt_poss_change flag is used to detect an ongoing roaming phase.
 	 * If true, then I received a Roaming_adv and I have to inspect every
 	 * packet directed to me to check whether I am still the true
@@ -179,6 +181,8 @@ struct bat_priv {
 	struct hashtable_t *orig_hash;
 	struct hashtable_t *tt_local_hash;
 	struct hashtable_t *tt_global_hash;
+	struct hashtable_t *claim_hash;
+	struct hashtable_t *backbone_hash;
 	struct list_head tt_req_list; /* list of pending tt_requests */
 	struct list_head tt_roam_list;
 	struct hashtable_t *vis_hash;
@@ -199,6 +203,7 @@ struct bat_priv {
 	struct delayed_work tt_work;
 	struct delayed_work orig_work;
 	struct delayed_work vis_work;
+	struct delayed_work bla_work;
 	struct gw_node __rcu *curr_gw;  /* rcu protected pointer */
 	atomic_t gw_reselect;
 	struct hard_iface __rcu *primary_if;  /* rcu protected pointer */
@@ -241,6 +246,28 @@ struct tt_global_entry {
 	unsigned long roam_at; /* time at which TT_GLOBAL_ROAM was set */
 };
 
+struct backbone_gw {
+	uint8_t orig[ETH_ALEN];
+	short vid;		/* used VLAN ID */
+	struct hlist_node hash_entry;
+	struct bat_priv *bat_priv;
+	unsigned long lasttime;	/* last time we heard of this backbone gw */
+	atomic_t request_sent;
+	atomic_t refcount;
+	struct rcu_head rcu;
+	uint16_t crc;		/* crc checksum over all claims */
+};
+
+struct claim {
+	uint8_t addr[ETH_ALEN];
+	short vid;
+	struct backbone_gw *backbone_gw;
+	unsigned long lasttime;	/* last time we heard of claim (locals only) */
+	struct rcu_head rcu;
+	atomic_t refcount;
+	struct hlist_node hash_entry;
+};
+
 struct tt_change_node {
 	struct list_head list;
 	struct tt_change change;