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, 37 insertions, 0 deletions

diff --git a/net/batman-adv/bridge_loop_avoidance.h b/net/batman-adv/bridge_loop_avoidance.h
new file mode 100644
index 000000000000..488d77895d01
--- /dev/null
+++ b/net/batman-adv/bridge_loop_avoidance.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2011 B.A.T.M.A.N. contributors:
+ *
+ * Simon Wunderlich
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA
+ *
+ */
+
+#ifndef _NET_BATMAN_ADV_BLA_H_
+#define _NET_BATMAN_ADV_BLA_H_
+
+int bla_rx(struct bat_priv *bat_priv, struct sk_buff *skb, short vid);
+int bla_tx(struct bat_priv *bat_priv, struct sk_buff *skb, short vid);
+int bla_is_backbone_gw(struct sk_buff *skb,
+		       struct orig_node *orig_node, int hdr_size);
+void bla_update_orig_address(struct bat_priv *bat_priv,
+			     struct hard_iface *primary_if,
+			     struct hard_iface *oldif);
+int bla_init(struct bat_priv *bat_priv);
+void bla_free(struct bat_priv *bat_priv);
+
+#define BLA_CRC_INIT	0
+
+#endif /* ifndef _NET_BATMAN_ADV_BLA_H_ */