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, 204 insertions, 48 deletions

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index eb6fb7d2d368..8b0f8330b06d 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -64,27 +64,56 @@ void slide_own_bcast_window(struct hard_iface *hard_iface)
         }
 }
 
-static void update_TT(struct bat_priv *bat_priv, struct orig_node *orig_node,
-                      const unsigned char *tt_buff, int tt_buff_len)
+static void update_transtable(struct bat_priv *bat_priv,
+                              struct orig_node *orig_node,
+                              const unsigned char *tt_buff,
+                              uint8_t tt_num_changes, uint8_t ttvn,
+                              uint16_t tt_crc)
 {
-        if ((tt_buff_len != orig_node->tt_buff_len) ||
-            ((tt_buff_len > 0) &&
-             (orig_node->tt_buff_len > 0) &&
-             (memcmp(orig_node->tt_buff, tt_buff, tt_buff_len) != 0))) {
-
-                if (orig_node->tt_buff_len > 0)
-                        tt_global_del_orig(bat_priv, orig_node,
-                                            "originator changed tt");
-
-                if ((tt_buff_len > 0) && (tt_buff))
-                        tt_global_add_orig(bat_priv, orig_node,
-                                            tt_buff, tt_buff_len);
+        uint8_t orig_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
+        bool full_table = true;
+
+        /* the ttvn increased by one -> we can apply the attached changes */
+        if (ttvn - orig_ttvn == 1) {
+                /* the OGM could not contain the changes because they were too
+                 * many to fit in one frame or because they have already been
+                 * sent TT_OGM_APPEND_MAX times. In this case send a tt
+                 * request */
+                if (!tt_num_changes) {
+                        full_table = false;
+                        goto request_table;
+                }
+
+                tt_update_changes(bat_priv, orig_node, tt_num_changes, ttvn,
+                                  (struct tt_change *)tt_buff);
+
+                /* Even if we received the crc into the OGM, we prefer
+                 * to recompute it to spot any possible inconsistency
+                 * in the global table */
+                spin_lock_bh(&bat_priv->tt_ghash_lock);
+                orig_node->tt_crc = tt_global_crc(bat_priv, orig_node);
+                spin_unlock_bh(&bat_priv->tt_ghash_lock);
+        } else {
+                /* if we missed more than one change or our tables are not
+                 * in sync anymore -> request fresh tt data */
+                if (ttvn != orig_ttvn || orig_node->tt_crc != tt_crc) {
+request_table:
+                        bat_dbg(DBG_TT, bat_priv, "TT inconsistency for %pM. "
+                                "Need to retrieve the correct information "
+                                "(ttvn: %u last_ttvn: %u crc: %u last_crc: "
+                                "%u num_changes: %u)\n", orig_node->orig, ttvn,
+                                orig_ttvn, tt_crc, orig_node->tt_crc,
+                                tt_num_changes);
+                        send_tt_request(bat_priv, orig_node, ttvn, tt_crc,
+                                        full_table);
+                        return;
+                }
         }
 }
 
-static void update_route(struct bat_priv *bat_priv, struct orig_node *orig_node,
-                         struct neigh_node *neigh_node,
-                         const unsigned char *tt_buff, int tt_buff_len)
+static void update_route(struct bat_priv *bat_priv,
+                         struct orig_node *orig_node,
+                         struct neigh_node *neigh_node)
 {
         struct neigh_node *curr_router;
 
@@ -92,11 +121,10 @@ static void update_route(struct bat_priv *bat_priv, struct orig_node *orig_node,
 
         /* route deleted */
         if ((curr_router) && (!neigh_node)) {
-
                 bat_dbg(DBG_ROUTES, bat_priv, "Deleting route towards: %pM\n",
                         orig_node->orig);
                 tt_global_del_orig(bat_priv, orig_node,
-                                    "originator timed out");
+                                    "Deleted route towards originator");
 
         /* route added */
         } else if ((!curr_router) && (neigh_node)) {
@@ -104,9 +132,6 @@ static void update_route(struct bat_priv *bat_priv, struct orig_node *orig_node,
                 bat_dbg(DBG_ROUTES, bat_priv,
                         "Adding route towards: %pM (via %pM)\n",
                         orig_node->orig, neigh_node->addr);
-                tt_global_add_orig(bat_priv, orig_node,
-                                    tt_buff, tt_buff_len);
-
         /* route changed */
         } else if (neigh_node && curr_router) {
                 bat_dbg(DBG_ROUTES, bat_priv,
@@ -133,8 +158,7 @@ static void update_route(struct bat_priv *bat_priv, struct orig_node *orig_node,
 }
 
 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)
 {
         struct neigh_node *router = NULL;
 
@@ -144,11 +168,7 @@ void update_routes(struct bat_priv *bat_priv, struct orig_node *orig_node,
         router = orig_node_get_router(orig_node);
 
         if (router != neigh_node)
-                update_route(bat_priv, orig_node, neigh_node,
-                             tt_buff, tt_buff_len);
-        /* may be just TT changed */
-        else
-                update_TT(bat_priv, orig_node, tt_buff, tt_buff_len);
+                update_route(bat_priv, orig_node, neigh_node);
 
 out:
         if (router)
@@ -360,14 +380,12 @@ static void update_orig(struct bat_priv *bat_priv, struct orig_node *orig_node,
                         const struct ethhdr *ethhdr,
                         const struct batman_packet *batman_packet,
                         struct hard_iface *if_incoming,
-                        const unsigned char *tt_buff, int tt_buff_len,
-                        int is_duplicate)
+                        const unsigned char *tt_buff, int is_duplicate)
 {
         struct neigh_node *neigh_node = NULL, *tmp_neigh_node = NULL;
         struct neigh_node *router = NULL;
         struct orig_node *orig_node_tmp;
         struct hlist_node *node;
-        int tmp_tt_buff_len;
         uint8_t bcast_own_sum_orig, bcast_own_sum_neigh;
 
         bat_dbg(DBG_BATMAN, bat_priv, "update_originator(): "
@@ -432,9 +450,6 @@ static void update_orig(struct bat_priv *bat_priv, struct orig_node *orig_node,
 
         bonding_candidate_add(orig_node, neigh_node);
 
-        tmp_tt_buff_len = (tt_buff_len > batman_packet->num_tt * ETH_ALEN ?
-                            batman_packet->num_tt * ETH_ALEN : tt_buff_len);
-
         /* if this neighbor already is our next hop there is nothing
          * to change */
         router = orig_node_get_router(orig_node);
@@ -464,15 +479,19 @@ static void update_orig(struct bat_priv *bat_priv, struct orig_node *orig_node,
                         goto update_tt;
         }
 
-        update_routes(bat_priv, orig_node, neigh_node,
-                      tt_buff, tmp_tt_buff_len);
-        goto update_gw;
+        update_routes(bat_priv, orig_node, neigh_node);
 
 update_tt:
-        update_routes(bat_priv, orig_node, router,
-                      tt_buff, tmp_tt_buff_len);
+        /* I have to check for transtable changes only if the OGM has been
+         * sent through a primary interface */
+        if (((batman_packet->orig != ethhdr->h_source) &&
+                                (batman_packet->ttl > 2)) ||
+                                (batman_packet->flags & PRIMARIES_FIRST_HOP))
+                update_transtable(bat_priv, orig_node, tt_buff,
+                                  batman_packet->tt_num_changes,
+                                  batman_packet->ttvn,
+                                  batman_packet->tt_crc);
 
-update_gw:
         if (orig_node->gw_flags != batman_packet->gw_flags)
                 gw_node_update(bat_priv, orig_node, batman_packet->gw_flags);
 
@@ -594,7 +613,7 @@ out:
 
 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)
 {
         struct bat_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
@@ -633,12 +652,14 @@ void receive_bat_packet(const struct ethhdr *ethhdr,
 
         bat_dbg(DBG_BATMAN, bat_priv,
                 "Received BATMAN packet via NB: %pM, IF: %s [%pM] "
-                "(from OG: %pM, via prev OG: %pM, seqno %d, tq %d, "
-                "TTL %d, V %d, IDF %d)\n",
+                "(from OG: %pM, via prev OG: %pM, seqno %d, ttvn %u, "
+                "crc %u, changes %u, td %d, TTL %d, V %d, IDF %d)\n",
                 ethhdr->h_source, if_incoming->net_dev->name,
                 if_incoming->net_dev->dev_addr, batman_packet->orig,
                 batman_packet->prev_sender, batman_packet->seqno,
-                batman_packet->tq, batman_packet->ttl, batman_packet->version,
+                batman_packet->ttvn, batman_packet->tt_crc,
+                batman_packet->tt_num_changes, batman_packet->tq,
+                batman_packet->ttl, batman_packet->version,
                 has_directlink_flag);
 
         rcu_read_lock();
@@ -790,14 +811,14 @@ void receive_bat_packet(const struct ethhdr *ethhdr,
              ((orig_node->last_real_seqno == batman_packet->seqno) &&
               (orig_node->last_ttl - 3 <= batman_packet->ttl))))
                 update_orig(bat_priv, orig_node, ethhdr, batman_packet,
-                            if_incoming, tt_buff, tt_buff_len, is_duplicate);
+                            if_incoming, tt_buff, is_duplicate);
 
         /* is single hop (direct) neighbor */
         if (is_single_hop_neigh) {
 
                 /* mark direct link on incoming interface */
                 schedule_forward_packet(orig_node, ethhdr, batman_packet,
-                                        1, tt_buff_len, if_incoming);
+                                        1, if_incoming);
 
                 bat_dbg(DBG_BATMAN, bat_priv, "Forwarding packet: "
                         "rebroadcast neighbor packet with direct link flag\n");
@@ -820,7 +841,7 @@ void receive_bat_packet(const struct ethhdr *ethhdr,
         bat_dbg(DBG_BATMAN, bat_priv,
                 "Forwarding packet: rebroadcast originator packet\n");
         schedule_forward_packet(orig_node, ethhdr, batman_packet,
-                                0, tt_buff_len, if_incoming);
+                                0, if_incoming);
 
 out_neigh:
         if ((orig_neigh_node) && (!is_single_hop_neigh))
@@ -1167,6 +1188,70 @@ static struct neigh_node *find_ifalter_router(struct orig_node *primary_orig,
         return router;
 }
 
+int recv_tt_query(struct sk_buff *skb, struct hard_iface *recv_if)
+{
+        struct bat_priv *bat_priv = netdev_priv(recv_if->soft_iface);
+        struct tt_query_packet *tt_query;
+        struct ethhdr *ethhdr;
+
+        /* drop packet if it has not necessary minimum size */
+        if (unlikely(!pskb_may_pull(skb, sizeof(struct tt_query_packet))))
+                goto out;
+
+        /* I could need to modify it */
+        if (skb_cow(skb, sizeof(struct tt_query_packet)) < 0)
+                goto out;
+
+        ethhdr = (struct ethhdr *)skb_mac_header(skb);
+
+        /* packet with unicast indication but broadcast recipient */
+        if (is_broadcast_ether_addr(ethhdr->h_dest))
+                goto out;
+
+        /* packet with broadcast sender address */
+        if (is_broadcast_ether_addr(ethhdr->h_source))
+                goto out;
+
+        tt_query = (struct tt_query_packet *)skb->data;
+
+        tt_query->tt_data = ntohs(tt_query->tt_data);
+
+        switch (tt_query->flags & TT_QUERY_TYPE_MASK) {
+        case TT_REQUEST:
+                /* If we cannot provide an answer the tt_request is
+                 * forwarded */
+                if (!send_tt_response(bat_priv, tt_query)) {
+                        bat_dbg(DBG_TT, bat_priv,
+                                "Routing TT_REQUEST to %pM [%c]\n",
+                                tt_query->dst,
+                                (tt_query->flags & TT_FULL_TABLE ? 'F' : '.'));
+                        tt_query->tt_data = htons(tt_query->tt_data);
+                        return route_unicast_packet(skb, recv_if);
+                }
+                break;
+        case TT_RESPONSE:
+                /* packet needs to be linearised to access the TT changes */
+                if (skb_linearize(skb) < 0)
+                        goto out;
+
+                if (is_my_mac(tt_query->dst))
+                        handle_tt_response(bat_priv, tt_query);
+                else {
+                        bat_dbg(DBG_TT, bat_priv,
+                                "Routing TT_RESPONSE to %pM [%c]\n",
+                                tt_query->dst,
+                                (tt_query->flags & TT_FULL_TABLE ? 'F' : '.'));
+                        tt_query->tt_data = htons(tt_query->tt_data);
+                        return route_unicast_packet(skb, recv_if);
+                }
+                break;
+        }
+
+out:
+        /* returning NET_RX_DROP will make the caller function kfree the skb */
+        return NET_RX_DROP;
+}
+
 /* find a suitable router for this originator, and use
  * bonding if possible. increases the found neighbors
  * refcount.*/
@@ -1353,14 +1438,82 @@ out:
         return ret;
 }
 
+static int check_unicast_ttvn(struct bat_priv *bat_priv,
+                               struct sk_buff *skb) {
+        uint8_t curr_ttvn;
+        struct orig_node *orig_node;
+        struct ethhdr *ethhdr;
+        struct hard_iface *primary_if;
+        struct unicast_packet *unicast_packet;
+
+        /* I could need to modify it */
+        if (skb_cow(skb, sizeof(struct unicast_packet)) < 0)
+                return 0;
+
+        unicast_packet = (struct unicast_packet *)skb->data;
+
+        if (is_my_mac(unicast_packet->dest))
+                curr_ttvn = (uint8_t)atomic_read(&bat_priv->ttvn);
+        else {
+                orig_node = orig_hash_find(bat_priv, unicast_packet->dest);
+
+                if (!orig_node)
+                        return 0;
+
+                curr_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
+                orig_node_free_ref(orig_node);
+        }
+
+        /* Check whether I have to reroute the packet */
+        if (seq_before(unicast_packet->ttvn, curr_ttvn)) {
+                /* Linearize the skb before accessing it */
+                if (skb_linearize(skb) < 0)
+                        return 0;
+
+                ethhdr = (struct ethhdr *)(skb->data +
+                        sizeof(struct unicast_packet));
+
+                orig_node = transtable_search(bat_priv, ethhdr->h_dest);
+
+                if (!orig_node) {
+                        if (!is_my_client(bat_priv, ethhdr->h_dest))
+                                return 0;
+                        primary_if = primary_if_get_selected(bat_priv);
+                        if (!primary_if)
+                                return 0;
+                        memcpy(unicast_packet->dest,
+                               primary_if->net_dev->dev_addr, ETH_ALEN);
+                        hardif_free_ref(primary_if);
+                } else {
+                        memcpy(unicast_packet->dest, orig_node->orig,
+                               ETH_ALEN);
+                        curr_ttvn = (uint8_t)
+                                atomic_read(&orig_node->last_ttvn);
+                        orig_node_free_ref(orig_node);
+                }
+
+                bat_dbg(DBG_ROUTES, bat_priv, "TTVN mismatch (old_ttvn %u "
+                        "new_ttvn %u)! Rerouting unicast packet (for %pM) to "
+                        "%pM\n", unicast_packet->ttvn, curr_ttvn,
+                        ethhdr->h_dest, unicast_packet->dest);
+
+                unicast_packet->ttvn = curr_ttvn;
+        }
+        return 1;
+}
+
 int recv_unicast_packet(struct sk_buff *skb, struct hard_iface *recv_if)
 {
+        struct bat_priv *bat_priv = netdev_priv(recv_if->soft_iface);
         struct unicast_packet *unicast_packet;
         int hdr_size = sizeof(*unicast_packet);
 
         if (check_unicast_packet(skb, hdr_size) < 0)
                 return NET_RX_DROP;
 
+        if (!check_unicast_ttvn(bat_priv, skb))
+                return NET_RX_DROP;
+
         unicast_packet = (struct unicast_packet *)skb->data;
 
         /* packet for me */
@@ -1383,6 +1536,9 @@ int recv_ucast_frag_packet(struct sk_buff *skb, struct hard_iface *recv_if)
         if (check_unicast_packet(skb, hdr_size) < 0)
                 return NET_RX_DROP;
 
+        if (!check_unicast_ttvn(bat_priv, skb))
+                return NET_RX_DROP;
+
         unicast_packet = (struct unicast_frag_packet *)skb->data;
 
         /* packet for me */