batman-adv: improved client announcement mechanism

The client announcement mechanism informs every mesh node in the network
of any connected non-mesh client, in order to find the path towards that
client from any given point in the mesh.

The old implementation was based on the simple idea of appending a data
buffer to each OGM containing all the client MAC addresses the node is
serving. All other nodes can populate their global translation tables
(table which links client MAC addresses to node addresses) using this
MAC address buffer and linking it to the node's address contained in the
OGM. A node that wants to contact a client has to lookup the node the
client is connected to and its address in the global translation table.

It is easy to understand that this implementation suffers from several
issues:
 - big overhead (each and every OGM contains the entire list of
   connected clients)
 - high latencies for client route updates due to long OGM trip time and
   OGM losses

The new implementation addresses these issues by appending client
changes (new client joined or a client left) to the OGM instead of
filling it with all the client addresses each time. In this way nodes
can modify their global tables by means of "updates", thus reducing the
overhead within the OGMs.

To keep the entire network in sync each node maintains a translation
table version number (ttvn) and a translation table checksum. These
values are spread with the OGM to allow all the network participants to
determine whether or not they need to update their translation table
information.

When a translation table lookup is performed in order to send a packet
to a client attached to another node, the destination's ttvn is added to
the payload packet. Forwarding nodes can compare the packet's ttvn with
their destination's ttvn (this node could have a fresher information
than the source) and re-route the packet if necessary. This greatly
reduces the packet loss of clients roaming from one AP to the next.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

Author: Antonio Quartulli

net/batman-adv/Kconfig

@@ -5,6 +5,7 @@
 config BATMAN_ADV
 	tristate "B.A.T.M.A.N. Advanced Meshing Protocol"
 	depends on NET
+	select CRC16
         default n
 	---help---
 

net/batman-adv/aggregation.c

@@ -20,17 +20,12 @@
  */
 
 #include "main.h"
+#include "translation-table.h"
 #include "aggregation.h"
 #include "send.h"
 #include "routing.h"
 #include "hard-interface.h"
 
-/* calculate the size of the tt information for a given packet */
-static int tt_len(const struct batman_packet *batman_packet)
-{
-	return batman_packet->num_tt * ETH_ALEN;
-}
-
 /* return true if new_packet can be aggregated with forw_packet */
 static bool can_aggregate_with(const struct batman_packet *new_batman_packet,
 			       int packet_len,
@@ -264,18 +259,20 @@ void receive_aggr_bat_packet(const struct ethhdr *ethhdr,
 	batman_packet = (struct batman_packet *)packet_buff;
 
 	do {
-		/* network to host order for our 32bit seqno, and the
-		   orig_interval. */
+		/* network to host order for our 32bit seqno and the
+		   orig_interval */
 		batman_packet->seqno = ntohl(batman_packet->seqno);
+		batman_packet->tt_crc = ntohs(batman_packet->tt_crc);
 
 		tt_buff = packet_buff + buff_pos + BAT_PACKET_LEN;
-		receive_bat_packet(ethhdr, batman_packet,
-				   tt_buff, tt_len(batman_packet),
-				   if_incoming);
 
-		buff_pos += BAT_PACKET_LEN + tt_len(batman_packet);
+		receive_bat_packet(ethhdr, batman_packet, tt_buff, if_incoming);
+
+		buff_pos += BAT_PACKET_LEN +
+			tt_len(batman_packet->tt_num_changes);
+
 		batman_packet = (struct batman_packet *)
 			(packet_buff + buff_pos);
 	} while (aggregated_packet(buff_pos, packet_len,
-				   batman_packet->num_tt));
+				   batman_packet->tt_num_changes));
 }

net/batman-adv/aggregation.h

@@ -25,9 +25,11 @@
 #include "main.h"
 
 /* is there another aggregated packet here? */
-static inline int aggregated_packet(int buff_pos, int packet_len, int num_tt)
+static inline int aggregated_packet(int buff_pos, int packet_len,
+				    int tt_num_changes)
 {
-	int next_buff_pos = buff_pos + BAT_PACKET_LEN + (num_tt * ETH_ALEN);
+	int next_buff_pos = buff_pos + BAT_PACKET_LEN + (tt_num_changes *
+						sizeof(struct tt_change));
 
 	return (next_buff_pos <= packet_len) &&
 		(next_buff_pos <= MAX_AGGREGATION_BYTES);

net/batman-adv/bat_sysfs.c

@@ -375,7 +375,7 @@ 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, 3, NULL);
+BAT_ATTR_UINT(log_level, S_IRUGO | S_IWUSR, 0, 7, NULL);
 #endif
 
 static struct bat_attribute *mesh_attrs[] = {

net/batman-adv/hard-interface.c

@@ -152,12 +152,6 @@ static void primary_if_select(struct bat_priv *bat_priv,
 	batman_packet->ttl = TTL;
 
 	primary_if_update_addr(bat_priv);
-
-	/***
-	 * hacky trick to make sure that we send the TT information via
-	 * our new primary interface
-	 */
-	atomic_set(&bat_priv->tt_local_changed, 1);
 }
 
 static bool hardif_is_iface_up(const struct hard_iface *hard_iface)
@@ -340,7 +334,8 @@ int hardif_enable_interface(struct hard_iface *hard_iface,
 	batman_packet->flags = NO_FLAGS;
 	batman_packet->ttl = 2;
 	batman_packet->tq = TQ_MAX_VALUE;
-	batman_packet->num_tt = 0;
+	batman_packet->tt_num_changes = 0;
+	batman_packet->ttvn = 0;
 
 	hard_iface->if_num = bat_priv->num_ifaces;
 	bat_priv->num_ifaces++;
@@ -659,6 +654,10 @@ static int batman_skb_recv(struct sk_buff *skb, struct net_device *dev,
 	case BAT_VIS:
 		ret = recv_vis_packet(skb, hard_iface);
 		break;
+		/* Translation table query (request or response) */
+	case BAT_TT_QUERY:
+		ret = recv_tt_query(skb, hard_iface);
+		break;
 	default:
 		ret = NET_RX_DROP;
 	}

net/batman-adv/main.c

@@ -86,6 +86,9 @@ int mesh_init(struct net_device *soft_iface)
 	spin_lock_init(&bat_priv->forw_bcast_list_lock);
 	spin_lock_init(&bat_priv->tt_lhash_lock);
 	spin_lock_init(&bat_priv->tt_ghash_lock);
+	spin_lock_init(&bat_priv->tt_changes_list_lock);
+	spin_lock_init(&bat_priv->tt_req_list_lock);
+	spin_lock_init(&bat_priv->tt_buff_lock);
 	spin_lock_init(&bat_priv->gw_list_lock);
 	spin_lock_init(&bat_priv->vis_hash_lock);
 	spin_lock_init(&bat_priv->vis_list_lock);
@@ -96,14 +99,13 @@ int mesh_init(struct net_device *soft_iface)
 	INIT_HLIST_HEAD(&bat_priv->forw_bcast_list);
 	INIT_HLIST_HEAD(&bat_priv->gw_list);
 	INIT_HLIST_HEAD(&bat_priv->softif_neigh_vids);
+	INIT_LIST_HEAD(&bat_priv->tt_changes_list);
+	INIT_LIST_HEAD(&bat_priv->tt_req_list);
 
 	if (originator_init(bat_priv) < 1)
 		goto err;
 
-	if (tt_local_init(bat_priv) < 1)
-		goto err;
-
-	if (tt_global_init(bat_priv) < 1)
+	if (tt_init(bat_priv) < 1)
 		goto err;
 
 	tt_local_add(soft_iface, soft_iface->dev_addr);
@@ -137,8 +139,7 @@ void mesh_free(struct net_device *soft_iface)
 	gw_node_purge(bat_priv);
 	originator_free(bat_priv);
 
-	tt_local_free(bat_priv);
-	tt_global_free(bat_priv);
+	tt_free(bat_priv);
 
 	softif_neigh_purge(bat_priv);
 

net/batman-adv/main.h

@@ -46,11 +46,15 @@
 /* sliding packet range of received originator messages in squence numbers
  * (should be a multiple of our word size) */
 #define TQ_LOCAL_WINDOW_SIZE 64
+#define TT_REQUEST_TIMEOUT 3 /* seconds we have to keep pending tt_req */
+
 #define TQ_GLOBAL_WINDOW_SIZE 5
 #define TQ_LOCAL_BIDRECT_SEND_MINIMUM 1
 #define TQ_LOCAL_BIDRECT_RECV_MINIMUM 1
 #define TQ_TOTAL_BIDRECT_LIMIT 1
 
+#define TT_OGM_APPEND_MAX 3 /* number of OGMs sent with the last tt diff */
+
 #define NO_FLAGS 0
 
 #define NUM_WORDS (TQ_LOCAL_WINDOW_SIZE / WORD_BIT_SIZE)
@@ -96,7 +100,8 @@ enum mesh_state {
 enum dbg_level {
 	DBG_BATMAN = 1 << 0,
 	DBG_ROUTES = 1 << 1, /* route added / changed / deleted */
-	DBG_ALL    = 3
+	DBG_TT	   = 1 << 2, /* translation table operations */
+	DBG_ALL    = 7
 };
 
 

net/batman-adv/originator.c

@@ -145,6 +145,7 @@ static void orig_node_free_rcu(struct rcu_head *rcu)
 	tt_global_del_orig(orig_node->bat_priv, orig_node,
 			    "originator timed out");
 
+	kfree(orig_node->tt_buff);
 	kfree(orig_node->bcast_own);
 	kfree(orig_node->bcast_own_sum);
 	kfree(orig_node);
@@ -213,6 +214,7 @@ struct orig_node *get_orig_node(struct bat_priv *bat_priv, const uint8_t *addr)
 	spin_lock_init(&orig_node->ogm_cnt_lock);
 	spin_lock_init(&orig_node->bcast_seqno_lock);
 	spin_lock_init(&orig_node->neigh_list_lock);
+	spin_lock_init(&orig_node->tt_buff_lock);
 
 	/* extra reference for return */
 	atomic_set(&orig_node->refcount, 2);
@@ -221,6 +223,8 @@ struct orig_node *get_orig_node(struct bat_priv *bat_priv, const uint8_t *addr)
 	memcpy(orig_node->orig, addr, ETH_ALEN);
 	orig_node->router = NULL;
 	orig_node->tt_buff = NULL;
+	orig_node->tt_buff_len = 0;
+	atomic_set(&orig_node->tt_size, 0);
 	orig_node->bcast_seqno_reset = jiffies - 1
 					- msecs_to_jiffies(RESET_PROTECTION_MS);
 	orig_node->batman_seqno_reset = jiffies - 1
@@ -330,9 +334,7 @@ static bool purge_orig_node(struct bat_priv *bat_priv,
 		if (purge_orig_neighbors(bat_priv, orig_node,
 							&best_neigh_node)) {
 			update_routes(bat_priv, orig_node,
-				      best_neigh_node,
-				      orig_node->tt_buff,
-				      orig_node->tt_buff_len);
+				      best_neigh_node);
 		}
 	}
 

net/batman-adv/packet.h

@@ -30,7 +30,8 @@ enum bat_packettype {
 	BAT_UNICAST      = 0x03,
 	BAT_BCAST        = 0x04,
 	BAT_VIS          = 0x05,
-	BAT_UNICAST_FRAG = 0x06
+	BAT_UNICAST_FRAG = 0x06,
+	BAT_TT_QUERY     = 0x07
 };
 
 /* this file is included by batctl which needs these defines */
@@ -63,6 +64,25 @@ enum unicast_frag_flags {
 	UNI_FRAG_LARGETAIL = 1 << 1
 };
 
+/* TT_QUERY subtypes */
+#define TT_QUERY_TYPE_MASK 0x3
+
+enum tt_query_packettype {
+	TT_REQUEST    = 0,
+	TT_RESPONSE   = 1
+};
+
+/* TT_QUERY flags */
+enum tt_query_flags {
+	TT_FULL_TABLE = 1 << 2
+};
+
+/* TT_CHANGE flags */
+enum tt_change_flags {
+	TT_CHANGE_DEL  = 0x01,
+	TT_CLIENT_ROAM = 0x02
+};
+
 struct batman_packet {
 	uint8_t  packet_type;
 	uint8_t  version;  /* batman version field */
@@ -73,8 +93,9 @@ struct batman_packet {
 	uint8_t  prev_sender[6];
 	uint8_t  gw_flags;  /* flags related to gateway class */
 	uint8_t  tq;
-	uint8_t  num_tt;
-	uint8_t  reserved;
+	uint8_t  tt_num_changes;
+	uint8_t  ttvn; /* translation table version number */
+	uint16_t tt_crc;
 } __packed;
 
 #define BAT_PACKET_LEN sizeof(struct batman_packet)
@@ -112,15 +133,15 @@ struct unicast_packet {
 	uint8_t  packet_type;
 	uint8_t  version;  /* batman version field */
 	uint8_t  ttl;
-	uint8_t  reserved;
+	uint8_t  ttvn; /* destination translation table version number */
 	uint8_t  dest[6];
 } __packed;
 
 struct unicast_frag_packet {
 	uint8_t  packet_type;
 	uint8_t  version;  /* batman version field */
 	uint8_t  ttl;
-	uint8_t  reserved;
+	uint8_t  ttvn; /* destination translation table version number */
 	uint8_t  dest[6];
 	uint8_t  flags;
 	uint8_t  align;
@@ -150,4 +171,32 @@ struct vis_packet {
 	uint8_t  sender_orig[6]; /* who sent or rebroadcasted this packet */
 } __packed;
 
+struct tt_query_packet {
+	uint8_t  packet_type;
+	uint8_t  version;  /* batman version field */
+	uint8_t  ttl;
+	/* the flag field is a combination of:
+	 * - TT_REQUEST or TT_RESPONSE
+	 * - TT_FULL_TABLE */
+	uint8_t  flags;
+	uint8_t  dst[ETH_ALEN];
+	uint8_t  src[ETH_ALEN];
+	/* the ttvn field is:
+	 * if TT_REQUEST: ttvn that triggered the
+	 *		  request
+	 * if TT_RESPONSE: new ttvn for the src
+	 *		   orig_node */
+	uint8_t  ttvn;
+	/* tt_data field is:
+	 * if TT_REQUEST: crc associated with the
+	 *		  ttvn
+	 * if TT_RESPONSE: table_size */
+	uint16_t tt_data;
+} __packed;
+
+struct tt_change {
+	uint8_t flags;
+	uint8_t addr[ETH_ALEN];
+} __packed;
+
 #endif /* _NET_BATMAN_ADV_PACKET_H_ */