batman-adv: Distributed ARP Table - implement local storage

Since batman-adv cannot inter-operate with the host ARP table, this patch
introduces a batman-adv private storage for ARP entries exchanged within DAT.
This storage will represent the node local cache in the DAT protocol.

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

net/batman-adv/distributed-arp-table.c

@@ -28,6 +28,119 @@
 #include "types.h"
 #include "unicast.h"
 
+static void batadv_dat_purge(struct work_struct *work);
+
+/**
+ * batadv_dat_start_timer - initialise the DAT periodic worker
+ * @bat_priv: the bat priv with all the soft interface information
+ */
+static void batadv_dat_start_timer(struct batadv_priv *bat_priv)
+{
+	INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
+	queue_delayed_work(batadv_event_workqueue, &bat_priv->dat.work,
+			   msecs_to_jiffies(10000));
+}
+
+/**
+ * batadv_dat_entry_free_ref - decrements the dat_entry refcounter and possibly
+ * free it
+ * @dat_entry: the oentry to free
+ */
+static void batadv_dat_entry_free_ref(struct batadv_dat_entry *dat_entry)
+{
+	if (atomic_dec_and_test(&dat_entry->refcount))
+		kfree_rcu(dat_entry, rcu);
+}
+
+/**
+ * batadv_dat_to_purge - checks whether a dat_entry has to be purged or not
+ * @dat_entry: the entry to check
+ *
+ * Returns true if the entry has to be purged now, false otherwise
+ */
+static bool batadv_dat_to_purge(struct batadv_dat_entry *dat_entry)
+{
+	return batadv_has_timed_out(dat_entry->last_update,
+				    BATADV_DAT_ENTRY_TIMEOUT);
+}
+
+/**
+ * __batadv_dat_purge - delete entries from the DAT local storage
+ * @bat_priv: the bat priv with all the soft interface information
+ * @to_purge: function in charge to decide whether an entry has to be purged or
+ *	      not. This function takes the dat_entry as argument and has to
+ *	      returns a boolean value: true is the entry has to be deleted,
+ *	      false otherwise
+ *
+ * Loops over each entry in the DAT local storage and delete it if and only if
+ * the to_purge function passed as argument returns true
+ */
+static void __batadv_dat_purge(struct batadv_priv *bat_priv,
+			       bool (*to_purge)(struct batadv_dat_entry *))
+{
+	spinlock_t *list_lock; /* protects write access to the hash lists */
+	struct batadv_dat_entry *dat_entry;
+	struct hlist_node *node, *node_tmp;
+	struct hlist_head *head;
+	uint32_t i;
+
+	if (!bat_priv->dat.hash)
+		return;
+
+	for (i = 0; i < bat_priv->dat.hash->size; i++) {
+		head = &bat_priv->dat.hash->table[i];
+		list_lock = &bat_priv->dat.hash->list_locks[i];
+
+		spin_lock_bh(list_lock);
+		hlist_for_each_entry_safe(dat_entry, node, node_tmp, head,
+					  hash_entry) {
+			/* if an helper function has been passed as parameter,
+			 * ask it if the entry has to be purged or not
+			 */
+			if (to_purge && !to_purge(dat_entry))
+				continue;
+
+			hlist_del_rcu(node);
+			batadv_dat_entry_free_ref(dat_entry);
+		}
+		spin_unlock_bh(list_lock);
+	}
+}
+
+/**
+ * batadv_dat_purge - periodic task that deletes old entries from the local DAT
+ * hash table
+ * @work: kernel work struct
+ */
+static void batadv_dat_purge(struct work_struct *work)
+{
+	struct delayed_work *delayed_work;
+	struct batadv_priv_dat *priv_dat;
+	struct batadv_priv *bat_priv;
+
+	delayed_work = container_of(work, struct delayed_work, work);
+	priv_dat = container_of(delayed_work, struct batadv_priv_dat, work);
+	bat_priv = container_of(priv_dat, struct batadv_priv, dat);
+
+	__batadv_dat_purge(bat_priv, batadv_dat_to_purge);
+	batadv_dat_start_timer(bat_priv);
+}
+
+/**
+ * batadv_compare_dat - comparing function used in the local DAT hash table
+ * @node: node in the local table
+ * @data2: second object to compare the node to
+ *
+ * Returns 1 if the two entry are the same, 0 otherwise
+ */
+static int batadv_compare_dat(const struct hlist_node *node, const void *data2)
+{
+	const void *data1 = container_of(node, struct batadv_dat_entry,
+					 hash_entry);
+
+	return (memcmp(data1, data2, sizeof(__be32)) == 0 ? 1 : 0);
+}
+
 /**
  * batadv_hash_dat - compute the hash value for an IP address
  * @data: data to hash
@@ -54,6 +167,96 @@ static uint32_t batadv_hash_dat(const void *data, uint32_t size)
 	return hash % size;
 }
 
+/**
+ * batadv_dat_entry_hash_find - looks for a given dat_entry in the local hash
+ * table
+ * @bat_priv: the bat priv with all the soft interface information
+ * @ip: search key
+ *
+ * Returns the dat_entry if found, NULL otherwise
+ */
+static struct batadv_dat_entry *
+batadv_dat_entry_hash_find(struct batadv_priv *bat_priv, __be32 ip)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct batadv_dat_entry *dat_entry, *dat_entry_tmp = NULL;
+	struct batadv_hashtable *hash = bat_priv->dat.hash;
+	uint32_t index;
+
+	if (!hash)
+		return NULL;
+
+	index = batadv_hash_dat(&ip, hash->size);
+	head = &hash->table[index];
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(dat_entry, node, head, hash_entry) {
+		if (dat_entry->ip != ip)
+			continue;
+
+		if (!atomic_inc_not_zero(&dat_entry->refcount))
+			continue;
+
+		dat_entry_tmp = dat_entry;
+		break;
+	}
+	rcu_read_unlock();
+
+	return dat_entry_tmp;
+}
+
+/**
+ * batadv_dat_entry_add - add a new dat entry or update it if already exists
+ * @bat_priv: the bat priv with all the soft interface information
+ * @ip: ipv4 to add/edit
+ * @mac_addr: mac address to assign to the given ipv4
+ */
+static void batadv_dat_entry_add(struct batadv_priv *bat_priv, __be32 ip,
+				 uint8_t *mac_addr)
+{
+	struct batadv_dat_entry *dat_entry;
+	int hash_added;
+
+	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip);
+	/* if this entry is already known, just update it */
+	if (dat_entry) {
+		if (!batadv_compare_eth(dat_entry->mac_addr, mac_addr))
+			memcpy(dat_entry->mac_addr, mac_addr, ETH_ALEN);
+		dat_entry->last_update = jiffies;
+		batadv_dbg(BATADV_DBG_DAT, bat_priv,
+			   "Entry updated: %pI4 %pM\n", &dat_entry->ip,
+			   dat_entry->mac_addr);
+		goto out;
+	}
+
+	dat_entry = kmalloc(sizeof(*dat_entry), GFP_ATOMIC);
+	if (!dat_entry)
+		goto out;
+
+	dat_entry->ip = ip;
+	memcpy(dat_entry->mac_addr, mac_addr, ETH_ALEN);
+	dat_entry->last_update = jiffies;
+	atomic_set(&dat_entry->refcount, 2);
+
+	hash_added = batadv_hash_add(bat_priv->dat.hash, batadv_compare_dat,
+				     batadv_hash_dat, &dat_entry->ip,
+				     &dat_entry->hash_entry);
+
+	if (unlikely(hash_added != 0)) {
+		/* remove the reference for the hash */
+		batadv_dat_entry_free_ref(dat_entry);
+		goto out;
+	}
+
+	batadv_dbg(BATADV_DBG_DAT, bat_priv, "New entry added: %pI4 %pM\n",
+		   &dat_entry->ip, dat_entry->mac_addr);
+
+out:
+	if (dat_entry)
+		batadv_dat_entry_free_ref(dat_entry);
+}
+
 /**
  * batadv_is_orig_node_eligible - check whether a node can be a DHT candidate
  * @res: the array with the already selected candidates
@@ -268,3 +471,96 @@ out:
 	kfree(cand);
 	return ret;
 }
+
+/**
+ * batadv_dat_hash_free - free the local DAT hash table
+ * @bat_priv: the bat priv with all the soft interface information
+ */
+static void batadv_dat_hash_free(struct batadv_priv *bat_priv)
+{
+	__batadv_dat_purge(bat_priv, NULL);
+
+	batadv_hash_destroy(bat_priv->dat.hash);
+
+	bat_priv->dat.hash = NULL;
+}
+
+/**
+ * batadv_dat_init - initialise the DAT internals
+ * @bat_priv: the bat priv with all the soft interface information
+ */
+int batadv_dat_init(struct batadv_priv *bat_priv)
+{
+	if (bat_priv->dat.hash)
+		return 0;
+
+	bat_priv->dat.hash = batadv_hash_new(1024);
+
+	if (!bat_priv->dat.hash)
+		return -ENOMEM;
+
+	batadv_dat_start_timer(bat_priv);
+
+	return 0;
+}
+
+/**
+ * batadv_dat_free - free the DAT internals
+ * @bat_priv: the bat priv with all the soft interface information
+ */
+void batadv_dat_free(struct batadv_priv *bat_priv)
+{
+	cancel_delayed_work_sync(&bat_priv->dat.work);
+
+	batadv_dat_hash_free(bat_priv);
+}
+
+/**
+ * batadv_dat_cache_seq_print_text - print the local DAT hash table
+ * @seq: seq file to print on
+ * @offset: not used
+ */
+int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset)
+{
+	struct net_device *net_dev = (struct net_device *)seq->private;
+	struct batadv_priv *bat_priv = netdev_priv(net_dev);
+	struct batadv_hashtable *hash = bat_priv->dat.hash;
+	struct batadv_dat_entry *dat_entry;
+	struct batadv_hard_iface *primary_if;
+	struct hlist_node *node;
+	struct hlist_head *head;
+	unsigned long last_seen_jiffies;
+	int last_seen_msecs, last_seen_secs, last_seen_mins;
+	uint32_t i;
+
+	primary_if = batadv_seq_print_text_primary_if_get(seq);
+	if (!primary_if)
+		goto out;
+
+	seq_printf(seq, "Distributed ARP Table (%s):\n", net_dev->name);
+	seq_printf(seq, "          %-7s          %-13s %5s\n", "IPv4", "MAC",
+		   "last-seen");
+
+	for (i = 0; i < hash->size; i++) {
+		head = &hash->table[i];
+
+		rcu_read_lock();
+		hlist_for_each_entry_rcu(dat_entry, node, head, hash_entry) {
+			last_seen_jiffies = jiffies - dat_entry->last_update;
+			last_seen_msecs = jiffies_to_msecs(last_seen_jiffies);
+			last_seen_mins = last_seen_msecs / 60000;
+			last_seen_msecs = last_seen_msecs % 60000;
+			last_seen_secs = last_seen_msecs / 1000;
+
+			seq_printf(seq, " * %15pI4 %14pM %6i:%02i\n",
+				   &dat_entry->ip, dat_entry->mac_addr,
+				   last_seen_mins, last_seen_secs);
+		}
+		rcu_read_unlock();
+	}
+
+out:
+	if (primary_if)
+		batadv_hardif_free_ref(primary_if);
+	return 0;
+}