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>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/batman-adv/routing.h b/net/batman-adv/routing.h
index 0ce0392..e77d464 100644
--- a/net/batman-adv/routing.h
+++ b/net/batman-adv/routing.h
@@ -25,11 +25,10 @@
 void slide_own_bcast_window(struct hard_iface *hard_iface);
 void receive_bat_packet(const struct ethhdr *ethhdr,
 			struct batman_packet *batman_packet,
-			const unsigned char *tt_buff, int tt_buff_len,
+			const unsigned char *tt_buff,
 			struct hard_iface *if_incoming);
 void update_routes(struct bat_priv *bat_priv, struct orig_node *orig_node,
-		   struct neigh_node *neigh_node, const unsigned char *tt_buff,
-		   int tt_buff_len);
+		   struct neigh_node *neigh_node);
 int route_unicast_packet(struct sk_buff *skb, struct hard_iface *recv_if);
 int recv_icmp_packet(struct sk_buff *skb, struct hard_iface *recv_if);
 int recv_unicast_packet(struct sk_buff *skb, struct hard_iface *recv_if);
@@ -37,6 +36,7 @@ int recv_ucast_frag_packet(struct sk_buff *skb, struct hard_iface *recv_if);
 int recv_bcast_packet(struct sk_buff *skb, struct hard_iface *recv_if);
 int recv_vis_packet(struct sk_buff *skb, struct hard_iface *recv_if);
 int recv_bat_packet(struct sk_buff *skb, struct hard_iface *recv_if);
+int recv_tt_query(struct sk_buff *skb, struct hard_iface *recv_if);
 struct neigh_node *find_router(struct bat_priv *bat_priv,
 			       struct orig_node *orig_node,
 			       const struct hard_iface *recv_if);