batman-adv: fix TT VLAN inconsistency on VLAN re-add

When a VLAN interface (on top of batX) is removed and
re-added within a short timeframe TT does not have enough
time to properly cleanup. This creates an internal TT state
mismatch as the newly created softif_vlan will be
initialized from scratch with a TT client count of zero
(even if TT entries for this VLAN still exist). The
resulting TT messages are bogus due to the counter / tt
client listing mismatch, thus creating inconsistencies on
every node in the network

To fix this issue destroy_vlan() has to not free the VLAN
object immediately but it has to be kept alive until all the
TT entries for this VLAN have been removed. destroy_vlan()
still removes the sysfs folder so that the user has the
feeling that everything went fine.

If the same VLAN is re-added before the old object is free'd,
then the latter is resurrected and re-used.

Implement such behaviour by increasing the reference counter
of a softif_vlan object every time a new local TT entry for
such VLAN is created and remove the object from the list
only when all the TT entries have been destroyed.

Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>

3 files changed, 74 insertions, 14 deletions

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index e7ee65dc20bf..cbd677f48c00 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -448,10 +448,15 @@ out:
  *  possibly free it
  * @softif_vlan: the vlan object to release
  */
-void batadv_softif_vlan_free_ref(struct batadv_softif_vlan *softif_vlan)
+void batadv_softif_vlan_free_ref(struct batadv_softif_vlan *vlan)
 {
-        if (atomic_dec_and_test(&softif_vlan->refcount))
-                kfree_rcu(softif_vlan, rcu);
+        if (atomic_dec_and_test(&vlan->refcount)) {
+                spin_lock_bh(&vlan->bat_priv->softif_vlan_list_lock);
+                hlist_del_rcu(&vlan->list);
+                spin_unlock_bh(&vlan->bat_priv->softif_vlan_list_lock);
+
+                kfree_rcu(vlan, rcu);
+        }
 }
 
 /**
@@ -505,6 +510,7 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
         if (!vlan)
                 return -ENOMEM;
 
+        vlan->bat_priv = bat_priv;
         vlan->vid = vid;
         atomic_set(&vlan->refcount, 1);
 
@@ -516,6 +522,10 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
                 return err;
         }
 
+        spin_lock_bh(&bat_priv->softif_vlan_list_lock);
+        hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
+        spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
+
         /* add a new TT local entry. This one will be marked with the NOPURGE
          * flag
          */
@@ -523,10 +533,6 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
                             bat_priv->soft_iface->dev_addr, vid,
                             BATADV_NULL_IFINDEX, BATADV_NO_MARK);
 
-        spin_lock_bh(&bat_priv->softif_vlan_list_lock);
-        hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
-        spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
-
         return 0;
 }
 
@@ -538,18 +544,13 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 static void batadv_softif_destroy_vlan(struct batadv_priv *bat_priv,
                                        struct batadv_softif_vlan *vlan)
 {
-        spin_lock_bh(&bat_priv->softif_vlan_list_lock);
-        hlist_del_rcu(&vlan->list);
-        spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
-
-        batadv_sysfs_del_vlan(bat_priv, vlan);
-
         /* explicitly remove the associated TT local entry because it is marked
          * with the NOPURGE flag
          */
         batadv_tt_local_remove(bat_priv, bat_priv->soft_iface->dev_addr,
                                vlan->vid, "vlan interface destroyed", false);
 
+        batadv_sysfs_del_vlan(bat_priv, vlan);
         batadv_softif_vlan_free_ref(vlan);
 }
 
@@ -567,6 +568,8 @@ static int batadv_interface_add_vid(struct net_device *dev, __be16 proto,
                                     unsigned short vid)
 {
         struct batadv_priv *bat_priv = netdev_priv(dev);
+        struct batadv_softif_vlan *vlan;
+        int ret;
 
         /* only 802.1Q vlans are supported.
          * batman-adv does not know how to handle other types
@@ -576,7 +579,36 @@ static int batadv_interface_add_vid(struct net_device *dev, __be16 proto,
 
         vid |= BATADV_VLAN_HAS_TAG;
 
-        return batadv_softif_create_vlan(bat_priv, vid);
+        /* if a new vlan is getting created and it already exists, it means that
+         * it was not deleted yet. batadv_softif_vlan_get() increases the
+         * refcount in order to revive the object.
+         *
+         * if it does not exist then create it.
+         */
+        vlan = batadv_softif_vlan_get(bat_priv, vid);
+        if (!vlan)
+                return batadv_softif_create_vlan(bat_priv, vid);
+
+        /* recreate the sysfs object if it was already destroyed (and it should
+         * be since we received a kill_vid() for this vlan
+         */
+        if (!vlan->kobj) {
+                ret = batadv_sysfs_add_vlan(bat_priv->soft_iface, vlan);
+                if (ret) {
+                        batadv_softif_vlan_free_ref(vlan);
+                        return ret;
+                }
+        }
+
+        /* add a new TT local entry. This one will be marked with the NOPURGE
+         * flag. This must be added again, even if the vlan object already
+         * exists, because the entry was deleted by kill_vid()
+         */
+        batadv_tt_local_add(bat_priv->soft_iface,
+                            bat_priv->soft_iface->dev_addr, vid,
+                            BATADV_NULL_IFINDEX, BATADV_NO_MARK);
+
+        return 0;
 }
 
 /**
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index d636bde72c9a..5f59e7f899a0 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -511,6 +511,7 @@ bool batadv_tt_local_add(struct net_device *soft_iface, const uint8_t *addr,
         struct batadv_priv *bat_priv = netdev_priv(soft_iface);
         struct batadv_tt_local_entry *tt_local;
         struct batadv_tt_global_entry *tt_global = NULL;
+        struct batadv_softif_vlan *vlan;
         struct net_device *in_dev = NULL;
         struct hlist_head *head;
         struct batadv_tt_orig_list_entry *orig_entry;
@@ -572,6 +573,9 @@ bool batadv_tt_local_add(struct net_device *soft_iface, const uint8_t *addr,
         if (!tt_local)
                 goto out;
 
+        /* increase the refcounter of the related vlan */
+        vlan = batadv_softif_vlan_get(bat_priv, vid);
+
         batadv_dbg(BATADV_DBG_TT, bat_priv,
                    "Creating new local tt entry: %pM (vid: %d, ttvn: %d)\n",
                    addr, BATADV_PRINT_VID(vid),
@@ -604,6 +608,7 @@ bool batadv_tt_local_add(struct net_device *soft_iface, const uint8_t *addr,
         if (unlikely(hash_added != 0)) {
                 /* remove the reference for the hash */
                 batadv_tt_local_entry_free_ref(tt_local);
+                batadv_softif_vlan_free_ref(vlan);
                 goto out;
         }
 
@@ -1009,6 +1014,7 @@ uint16_t batadv_tt_local_remove(struct batadv_priv *bat_priv,
 {
         struct batadv_tt_local_entry *tt_local_entry;
         uint16_t flags, curr_flags = BATADV_NO_FLAGS;
+        struct batadv_softif_vlan *vlan;
 
         tt_local_entry = batadv_tt_local_hash_find(bat_priv, addr, vid);
         if (!tt_local_entry)
@@ -1039,6 +1045,11 @@ uint16_t batadv_tt_local_remove(struct batadv_priv *bat_priv,
         hlist_del_rcu(&tt_local_entry->common.hash_entry);
         batadv_tt_local_entry_free_ref(tt_local_entry);
 
+        /* decrease the reference held for this vlan */
+        vlan = batadv_softif_vlan_get(bat_priv, vid);
+        batadv_softif_vlan_free_ref(vlan);
+        batadv_softif_vlan_free_ref(vlan);
+
 out:
         if (tt_local_entry)
                 batadv_tt_local_entry_free_ref(tt_local_entry);
@@ -1111,6 +1122,7 @@ static void batadv_tt_local_table_free(struct batadv_priv *bat_priv)
         spinlock_t *list_lock; /* protects write access to the hash lists */
         struct batadv_tt_common_entry *tt_common_entry;
         struct batadv_tt_local_entry *tt_local;
+        struct batadv_softif_vlan *vlan;
         struct hlist_node *node_tmp;
         struct hlist_head *head;
         uint32_t i;
@@ -1131,6 +1143,13 @@ static void batadv_tt_local_table_free(struct batadv_priv *bat_priv)
                         tt_local = container_of(tt_common_entry,
                                                 struct batadv_tt_local_entry,
                                                 common);
+
+                        /* decrease the reference held for this vlan */
+                        vlan = batadv_softif_vlan_get(bat_priv,
+                                                      tt_common_entry->vid);
+                        batadv_softif_vlan_free_ref(vlan);
+                        batadv_softif_vlan_free_ref(vlan);
+
                         batadv_tt_local_entry_free_ref(tt_local);
                 }
                 spin_unlock_bh(list_lock);
@@ -3139,6 +3158,7 @@ static void batadv_tt_local_purge_pending_clients(struct batadv_priv *bat_priv)
         struct batadv_hashtable *hash = bat_priv->tt.local_hash;
         struct batadv_tt_common_entry *tt_common;
         struct batadv_tt_local_entry *tt_local;
+        struct batadv_softif_vlan *vlan;
         struct hlist_node *node_tmp;
         struct hlist_head *head;
         spinlock_t *list_lock; /* protects write access to the hash lists */
@@ -3167,6 +3187,12 @@ static void batadv_tt_local_purge_pending_clients(struct batadv_priv *bat_priv)
                         tt_local = container_of(tt_common,
                                                 struct batadv_tt_local_entry,
                                                 common);
+
+                        /* decrease the reference held for this vlan */
+                        vlan = batadv_softif_vlan_get(bat_priv, tt_common->vid);
+                        batadv_softif_vlan_free_ref(vlan);
+                        batadv_softif_vlan_free_ref(vlan);
+
                         batadv_tt_local_entry_free_ref(tt_local);
                 }
                 spin_unlock_bh(list_lock);
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 34891a56773f..8854c05622a9 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -687,6 +687,7 @@ struct batadv_priv_nc {
 
 /**
  * struct batadv_softif_vlan - per VLAN attributes set
+ * @bat_priv: pointer to the mesh object
  * @vid: VLAN identifier
  * @kobj: kobject for sysfs vlan subdirectory
  * @ap_isolation: AP isolation state
@@ -696,6 +697,7 @@ struct batadv_priv_nc {
  * @rcu: struct used for freeing in a RCU-safe manner
  */
 struct batadv_softif_vlan {
+        struct batadv_priv *bat_priv;
         unsigned short vid;
         struct kobject *kobj;
         atomic_t ap_isolation;          /* boolean */