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, 5 insertions, 1 deletions

diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index 7a6a25f22fc2..82723b5dce61 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -80,6 +80,9 @@
 #define MAX_AGGREGATION_BYTES 512
 #define MAX_AGGREGATION_MS 100
 
+#define BLA_PERIOD_LENGTH       10000   /* 10 seconds */
+#define BLA_BACKBONE_TIMEOUT    (BLA_PERIOD_LENGTH * 3)
+#define BLA_CLAIM_TIMEOUT       (BLA_PERIOD_LENGTH * 10)
 /* don't reset again within 30 seconds */
 #define RESET_PROTECTION_MS 30000
 #define EXPECTED_SEQNO_RANGE    65536
@@ -117,7 +120,8 @@ enum dbg_level {
         DBG_BATMAN = 1 << 0,
         DBG_ROUTES = 1 << 1, /* route added / changed / deleted */
         DBG_TT     = 1 << 2, /* translation table operations */
-        DBG_ALL    = 7
+        DBG_BLA    = 1 << 3, /* bridge loop avoidance */
+        DBG_ALL    = 15
 };
 
 /* Kernel headers */