batman-adv: add detection for complex bridge loops

There are network setups where the current bridge loop avoidance can't
detect bridge loops. The minimal setup affected would consist of two
LANs and two separate meshes, connected in a ring like that:

   A...(mesh1)...B
   |             |
 (LAN1)        (LAN2)
   |             |
   C...(mesh2)...D

Since both the meshes and backbones are separate, the bridge loop
avoidance has not enough information to detect and avoid the loop
in this case. Even if these scenarios can't be fixed easily,
these kind of loops can be detected.

This patch implements a periodic check (running every 60 seconds for
now) which sends a broadcast frame with a random MAC address on
each backbone VLAN. If a broadcast frame with the same MAC address
is received shortly after on the mesh, we know that there must be a
loop and report that incident as well as throw an uevent to let others
handle that problem.

Signed-off-by: Simon Wunderlich <simon.wunderlich@open-mesh.com>
[sven@narfation.org: fix conflicts with current version]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>

1 files changed, 8 insertions, 0 deletions

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 1e47fbe8bb7b..6a577f4f8ba7 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -657,6 +657,9 @@ struct batadv_priv_tt {
  * @num_requests: number of bla requests in flight
  * @claim_hash: hash table containing mesh nodes this host has claimed
  * @backbone_hash: hash table containing all detected backbone gateways
+ * @loopdetect_addr: MAC address used for own loopdetection frames
+ * @loopdetect_lasttime: time when the loopdetection frames were sent
+ * @loopdetect_next: how many periods to wait for the next loopdetect process
  * @bcast_duplist: recently received broadcast packets array (for broadcast
  *  duplicate suppression)
  * @bcast_duplist_curr: index of last broadcast packet added to bcast_duplist
@@ -668,6 +671,9 @@ struct batadv_priv_bla {
 	atomic_t num_requests;
 	struct batadv_hashtable *claim_hash;
 	struct batadv_hashtable *backbone_hash;
+	u8 loopdetect_addr[ETH_ALEN];
+	unsigned long loopdetect_lasttime;
+	atomic_t loopdetect_next;
 	struct batadv_bcast_duplist_entry bcast_duplist[BATADV_DUPLIST_SIZE];
 	int bcast_duplist_curr;
 	/* protects bcast_duplist & bcast_duplist_curr */
@@ -1012,6 +1018,7 @@ struct batadv_socket_packet {
  *  resolved
  * @crc: crc16 checksum over all claims
  * @crc_lock: lock protecting crc
+ * @report_work: work struct for reporting detected loops
  * @refcount: number of contexts the object is used
  * @rcu: struct used for freeing in an RCU-safe manner
  */
@@ -1025,6 +1032,7 @@ struct batadv_bla_backbone_gw {
 	atomic_t request_sent;
 	u16 crc;
 	spinlock_t crc_lock; /* protects crc */
+	struct work_struct report_work;
 	struct kref refcount;
 	struct rcu_head rcu;
 };