batman-adv: substitute tt_poss_change with a per-tt_entry flag

tt_poss_change is a node-wide flag which tells whether the node is in a roaming
state (a client recently moved to/away from it) in order to let it apply special
re-routing rules. However this flag does not give a clear idea of the current
state because it is not possible to understand *which client* is actually
involved in the roaming. For this reason a better approach has been chosen:
instead of using a node-wide variable, the roaming state is now given by a
per-tt_entry ROAM flag which, in case of packet coming through the node, tells
the node whether the real destination is in roaming state or not.

With this flag change, batadv_check_unicast_ttvn() has also been rearranged in
order to better fit the new re-routing logic and to be much more readable.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>

1 files changed, 122 insertions, 51 deletions

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 32aa4d460e1f..78d657264cbf 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -711,12 +711,6 @@ int batadv_recv_roam_adv(struct sk_buff *skb, struct batadv_hard_iface *recv_if)
                              BATADV_TT_CLIENT_ROAM,
                              atomic_read(&orig_node->last_ttvn) + 1);
 
-        /* Roaming phase starts: I have new information but the ttvn has not
-         * been incremented yet. This flag will make me check all the incoming
-         * packets for the correct destination.
-         */
-        bat_priv->tt.poss_change = true;
-
         batadv_orig_node_free_ref(orig_node);
 out:
         /* returning NET_RX_DROP will make the caller function kfree the skb */
@@ -899,14 +893,67 @@ out:
         return ret;
 }
 
+/**
+ * batadv_reroute_unicast_packet - update the unicast header for re-routing
+ * @bat_priv: the bat priv with all the soft interface information
+ * @unicast_packet: the unicast header to be updated
+ * @dst_addr: the payload destination
+ *
+ * Search the translation table for dst_addr and update the unicast header with
+ * the new corresponding information (originator address where the destination
+ * client currently is and its known TTVN)
+ *
+ * Returns true if the packet header has been updated, false otherwise
+ */
+static bool
+batadv_reroute_unicast_packet(struct batadv_priv *bat_priv,
+                              struct batadv_unicast_packet *unicast_packet,
+                              uint8_t *dst_addr)
+{
+        struct batadv_orig_node *orig_node = NULL;
+        struct batadv_hard_iface *primary_if = NULL;
+        bool ret = false;
+        uint8_t *orig_addr, orig_ttvn;
+
+        if (batadv_is_my_client(bat_priv, dst_addr)) {
+                primary_if = batadv_primary_if_get_selected(bat_priv);
+                if (!primary_if)
+                        goto out;
+                orig_addr = primary_if->net_dev->dev_addr;
+                orig_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
+        } else {
+                orig_node = batadv_transtable_search(bat_priv, NULL, dst_addr);
+                if (!orig_node)
+                        goto out;
+
+                if (batadv_compare_eth(orig_node->orig, unicast_packet->dest))
+                        goto out;
+
+                orig_addr = orig_node->orig;
+                orig_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
+        }
+
+        /* update the packet header */
+        memcpy(unicast_packet->dest, orig_addr, ETH_ALEN);
+        unicast_packet->ttvn = orig_ttvn;
+
+        ret = true;
+out:
+        if (primary_if)
+                batadv_hardif_free_ref(primary_if);
+        if (orig_node)
+                batadv_orig_node_free_ref(orig_node);
+
+        return ret;
+}
+
 static int batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
                                      struct sk_buff *skb) {
-        uint8_t curr_ttvn;
+        uint8_t curr_ttvn, old_ttvn;
         struct batadv_orig_node *orig_node;
         struct ethhdr *ethhdr;
         struct batadv_hard_iface *primary_if;
         struct batadv_unicast_packet *unicast_packet;
-        bool tt_poss_change;
         int is_old_ttvn;
 
         /* check if there is enough data before accessing it */
@@ -918,65 +965,89 @@ static int batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
                 return 0;
 
         unicast_packet = (struct batadv_unicast_packet *)skb->data;
+        ethhdr = (struct ethhdr *)(skb->data + sizeof(*unicast_packet));
 
-        if (batadv_is_my_mac(unicast_packet->dest)) {
-                tt_poss_change = bat_priv->tt.poss_change;
-                curr_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
-        } else {
+        /* check if the destination client was served by this node and it is now
+         * roaming. In this case, it means that the node has got a ROAM_ADV
+         * message and that it knows the new destination in the mesh to re-route
+         * the packet to
+         */
+        if (batadv_tt_local_client_is_roaming(bat_priv, ethhdr->h_dest)) {
+                if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
+                                                  ethhdr->h_dest))
+                        net_ratelimited_function(batadv_dbg, BATADV_DBG_TT,
+                                                 bat_priv,
+                                                 "Rerouting unicast packet to %pM (dst=%pM): Local Roaming\n",
+                                                 unicast_packet->dest,
+                                                 ethhdr->h_dest);
+                /* at this point the mesh destination should have been
+                 * substituted with the originator address found in the global
+                 * table. If not, let the packet go untouched anyway because
+                 * there is nothing the node can do
+                 */
+                return 1;
+        }
+
+        /* retrieve the TTVN known by this node for the packet destination. This
+         * value is used later to check if the node which sent (or re-routed
+         * last time) the packet had an updated information or not
+         */
+        curr_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
+        if (!batadv_is_my_mac(unicast_packet->dest)) {
                 orig_node = batadv_orig_hash_find(bat_priv,
                                                   unicast_packet->dest);
-
+                /* if it is not possible to find the orig_node representing the
+                 * destination, the packet can immediately be dropped as it will
+                 * not be possible to deliver it
+                 */
                 if (!orig_node)
                         return 0;
 
                 curr_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
-                tt_poss_change = orig_node->tt_poss_change;
                 batadv_orig_node_free_ref(orig_node);
         }
 
-        /* Check whether I have to reroute the packet */
+        /* check if the TTVN contained in the packet is fresher than what the
+         * node knows
+         */
         is_old_ttvn = batadv_seq_before(unicast_packet->ttvn, curr_ttvn);
-        if (is_old_ttvn || tt_poss_change) {
-                /* check if there is enough data before accessing it */
-                if (pskb_may_pull(skb, sizeof(struct batadv_unicast_packet) +
-                                  ETH_HLEN) < 0)
-                        return 0;
+        if (!is_old_ttvn)
+                return 1;
 
-                ethhdr = (struct ethhdr *)(skb->data + sizeof(*unicast_packet));
+        old_ttvn = unicast_packet->ttvn;
+        /* the packet was forged based on outdated network information. Its
+         * destination can possibly be updated and forwarded towards the new
+         * target host
+         */
+        if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
+                                          ethhdr->h_dest)) {
+                net_ratelimited_function(batadv_dbg, BATADV_DBG_TT, bat_priv,
+                                         "Rerouting unicast packet to %pM (dst=%pM): TTVN mismatch old_ttvn=%u new_ttvn=%u\n",
+                                         unicast_packet->dest, ethhdr->h_dest,
+                                         old_ttvn, curr_ttvn);
+                return 1;
+        }
 
-                /* we don't have an updated route for this client, so we should
-                 * not try to reroute the packet!!
-                 */
-                if (batadv_tt_global_client_is_roaming(bat_priv,
-                                                       ethhdr->h_dest))
-                        return 1;
+        /* the packet has not been re-routed: either the destination is
+         * currently served by this node or there is no destination at all and
+         * it is possible to drop the packet
+         */
+        if (!batadv_is_my_client(bat_priv, ethhdr->h_dest))
+                return 0;
 
-                orig_node = batadv_transtable_search(bat_priv, NULL,
-                                                     ethhdr->h_dest);
-
-                if (!orig_node) {
-                        if (!batadv_is_my_client(bat_priv, ethhdr->h_dest))
-                                return 0;
-                        primary_if = batadv_primary_if_get_selected(bat_priv);
-                        if (!primary_if)
-                                return 0;
-                        memcpy(unicast_packet->dest,
-                               primary_if->net_dev->dev_addr, ETH_ALEN);
-                        batadv_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);
-                        batadv_orig_node_free_ref(orig_node);
-                }
+        /* update the header in order to let the packet be delivered to this
+         * node's soft interface
+         */
+        primary_if = batadv_primary_if_get_selected(bat_priv);
+        if (!primary_if)
+                return 0;
 
-                net_ratelimited_function(batadv_dbg, BATADV_DBG_TT, 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);
+        memcpy(unicast_packet->dest, primary_if->net_dev->dev_addr, ETH_ALEN);
+
+        batadv_hardif_free_ref(primary_if);
+
+        unicast_packet->ttvn = curr_ttvn;
 
-                unicast_packet->ttvn = curr_ttvn;
-        }
         return 1;
 }