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, 54 insertions, 5 deletions

diff --git a/net/batman-adv/packet.h b/net/batman-adv/packet.h
index 6ddbfd830784..407dd2e84aff 100644
--- a/net/batman-adv/packet.h
+++ b/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)
@@ -112,7 +133,7 @@ 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;
 
@@ -120,7 +141,7 @@ 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_ */