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>

Documentation/networking/batman-adv.txt

@@ -67,10 +67,11 @@ To deactivate an interface you have  to  write  "none"  into  its
 All  mesh  wide  settings  can be found in batman's own interface
 folder:
 
-#  ls  /sys/class/net/bat0/mesh/
-# aggregated_ogms   fragmentation gw_sel_class   vis_mode
-# ap_isolation      gw_bandwidth  hop_penalty
-# bonding           gw_mode       orig_interval
+# ls /sys/class/net/bat0/mesh/
+# aggregated_ogms        fragmentation          hop_penalty
+# ap_isolation           gw_bandwidth           log_level
+# bonding                gw_mode                orig_interval
+# bridge_loop_avoidance  gw_sel_class           vis_mode
 
 
 There is a special folder for debugging information:
@@ -202,12 +203,13 @@ abled  during run time. Following log_levels are defined:
 1 - Enable messages related to routing / flooding / broadcasting
 2 - Enable messages related to route added / changed / deleted
 4 - Enable messages related to translation table operations
-7 - Enable all messages
+8 - Enable messages related to bridge loop avoidance
+15 - enable all messages
 
 The debug output can be changed at runtime  using  the  file
 /sys/class/net/bat0/mesh/log_level. e.g.
 
-# echo 2 > /sys/class/net/bat0/mesh/log_level
+# echo 6 > /sys/class/net/bat0/mesh/log_level
 
 will enable debug messages for when routes change.
 

net/batman-adv/Kconfig

@@ -4,7 +4,7 @@
 
 config BATMAN_ADV
 	tristate "B.A.T.M.A.N. Advanced Meshing Protocol"
-	depends on NET
+	depends on NET && INET
 	select CRC16
         default n
 	help

net/batman-adv/Makefile

@@ -23,6 +23,7 @@ batman-adv-y += bat_debugfs.o
 batman-adv-y += bat_iv_ogm.o
 batman-adv-y += bat_sysfs.o
 batman-adv-y += bitarray.o
+batman-adv-y += bridge_loop_avoidance.o
 batman-adv-y += gateway_client.o
 batman-adv-y += gateway_common.o
 batman-adv-y += hard-interface.o

net/batman-adv/bat_sysfs.c

@@ -398,7 +398,7 @@ BAT_ATTR_UINT(gw_sel_class, S_IRUGO | S_IWUSR, 1, TQ_MAX_VALUE,
 static BAT_ATTR(gw_bandwidth, S_IRUGO | S_IWUSR, show_gw_bwidth,
 		store_gw_bwidth);
 #ifdef CONFIG_BATMAN_ADV_DEBUG
-BAT_ATTR_UINT(log_level, S_IRUGO | S_IWUSR, 0, 7, NULL);
+BAT_ATTR_UINT(log_level, S_IRUGO | S_IWUSR, 0, 15, NULL);
 #endif
 
 static struct bat_attribute *mesh_attrs[] = {

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_ */

net/batman-adv/hard-interface.c

@@ -28,6 +28,7 @@
 #include "bat_sysfs.h"
 #include "originator.h"
 #include "hash.h"
+#include "bridge_loop_avoidance.h"
 
 #include <linux/if_arp.h>
 
@@ -107,7 +108,8 @@ out:
 	return hard_iface;
 }
 
-static void primary_if_update_addr(struct bat_priv *bat_priv)
+static void primary_if_update_addr(struct bat_priv *bat_priv,
+				   struct hard_iface *oldif)
 {
 	struct vis_packet *vis_packet;
 	struct hard_iface *primary_if;
@@ -122,6 +124,7 @@ static void primary_if_update_addr(struct bat_priv *bat_priv)
 	memcpy(vis_packet->sender_orig,
 	       primary_if->net_dev->dev_addr, ETH_ALEN);
 
+	bla_update_orig_address(bat_priv, primary_if, oldif);
 out:
 	if (primary_if)
 		hardif_free_ref(primary_if);
@@ -140,14 +143,15 @@ static void primary_if_select(struct bat_priv *bat_priv,
 	curr_hard_iface = rcu_dereference_protected(bat_priv->primary_if, 1);
 	rcu_assign_pointer(bat_priv->primary_if, new_hard_iface);
 
-	if (curr_hard_iface)
-		hardif_free_ref(curr_hard_iface);
-
 	if (!new_hard_iface)
-		return;
+		goto out;
 
 	bat_priv->bat_algo_ops->bat_ogm_init_primary(new_hard_iface);
-	primary_if_update_addr(bat_priv);
+	primary_if_update_addr(bat_priv, curr_hard_iface);
+
+out:
+	if (curr_hard_iface)
+		hardif_free_ref(curr_hard_iface);
 }
 
 static bool hardif_is_iface_up(const struct hard_iface *hard_iface)
@@ -531,7 +535,7 @@ static int hard_if_event(struct notifier_block *this,
 			goto hardif_put;
 
 		if (hard_iface == primary_if)
-			primary_if_update_addr(bat_priv);
+			primary_if_update_addr(bat_priv, NULL);
 		break;
 	default:
 		break;

net/batman-adv/main.c

@@ -30,6 +30,7 @@
 #include "translation-table.h"
 #include "hard-interface.h"
 #include "gateway_client.h"
+#include "bridge_loop_avoidance.h"
 #include "vis.h"
 #include "hash.h"
 #include "bat_algo.h"
@@ -115,6 +116,9 @@ int mesh_init(struct net_device *soft_iface)
 	if (vis_init(bat_priv) < 1)
 		goto err;
 
+	if (bla_init(bat_priv) < 1)
+		goto err;
+
 	atomic_set(&bat_priv->gw_reselect, 0);
 	atomic_set(&bat_priv->mesh_state, MESH_ACTIVE);
 	goto end;
@@ -142,6 +146,8 @@ void mesh_free(struct net_device *soft_iface)
 
 	tt_free(bat_priv);
 
+	bla_free(bat_priv);
+
 	atomic_set(&bat_priv->mesh_state, MESH_INACTIVE);
 }
 

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 */

net/batman-adv/originator.c

@@ -28,6 +28,7 @@
 #include "hard-interface.h"
 #include "unicast.h"
 #include "soft-interface.h"
+#include "bridge_loop_avoidance.h"
 
 static void purge_orig(struct work_struct *work);
 

net/batman-adv/packet.h

@@ -90,6 +90,23 @@ enum tt_client_flags {
 	TT_CLIENT_PENDING = 1 << 10
 };
 
+/* claim frame types for the bridge loop avoidance */
+enum bla_claimframe {
+	CLAIM_TYPE_ADD		= 0x00,
+	CLAIM_TYPE_DEL		= 0x01,
+	CLAIM_TYPE_ANNOUNCE	= 0x02,
+	CLAIM_TYPE_REQUEST	= 0x03
+};
+
+/* the destination hardware field in the ARP frame is used to
+ * transport the claim type and the group id
+ */
+struct bla_claim_dst {
+	uint8_t magic[3];	/* FF:43:05 */
+	uint8_t type;		/* bla_claimframe */
+	uint16_t group;		/* group id */
+} __packed;
+
 struct batman_header {
 	uint8_t  packet_type;
 	uint8_t  version;  /* batman version field */

net/batman-adv/routing.c

@@ -29,6 +29,7 @@
 #include "originator.h"
 #include "vis.h"
 #include "unicast.h"
+#include "bridge_loop_avoidance.h"
 
 static int route_unicast_packet(struct sk_buff *skb,
 				struct hard_iface *recv_if);
@@ -1071,6 +1072,12 @@ int recv_bcast_packet(struct sk_buff *skb, struct hard_iface *recv_if)
 	/* rebroadcast packet */
 	add_bcast_packet_to_list(bat_priv, skb, 1);
 
+	/* don't hand the broadcast up if it is from an originator
+	 * from the same backbone.
+	 */
+	if (bla_is_backbone_gw(skb, orig_node, hdr_size))
+		goto out;
+
 	/* broadcast for me */
 	interface_rx(recv_if->soft_iface, skb, recv_if, hdr_size);
 	ret = NET_RX_SUCCESS;

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;

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;