batman-adv: network coding - detect coding nodes and remove these after timeout

To use network coding efficiently, a relay must know when neighbor nodes
are likely to have enough information to be able to decode a network
coded packet. This is detected by using OGMs from batman-adv to discover
when one neighbor is in range of another neighbor. The relay check the
TLL to detect when an OGM is forwarded from one neighbor by another
neighbor, and thereby knows that the two neighbors are in range and thus
overhear packets sent by each other.

This information is saved in the orig_node struct to be used when
searching for coding opportunities. Two lists are added to the
orig_node struct: One for neighbors that can hear the orig_node
(outgoing nc_nodes) and one for neighbors that the orig_node can hear
(incoming nc_nodes).

Information about nc_nodes is kept for 10 seconds and is available
through debugfs in batman_adv/nc_nodes to use when debugging network
coding.

Signed-off-by: Martin Hundebøll <martin@hundeboll.net>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

1 files changed, 414 insertions, 0 deletions

diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index 9c2d54bdd2ce..ff4985d84726 100644
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -17,8 +17,12 @@
  * 02110-1301, USA
  */
 
+#include <linux/debugfs.h>
+
 #include "main.h"
 #include "network-coding.h"
+#include "originator.h"
+#include "hard-interface.h"
 
 static void batadv_nc_worker(struct work_struct *work);
 
@@ -51,6 +55,151 @@ int batadv_nc_init(struct batadv_priv *bat_priv)
 void batadv_nc_init_bat_priv(struct batadv_priv *bat_priv)
 {
 	atomic_set(&bat_priv->network_coding, 1);
+	bat_priv->nc.min_tq = 200;
+}
+
+/**
+ * batadv_nc_init_orig - initialise the nc fields of an orig_node
+ * @orig_node: the orig_node which is going to be initialised
+ */
+void batadv_nc_init_orig(struct batadv_orig_node *orig_node)
+{
+	INIT_LIST_HEAD(&orig_node->in_coding_list);
+	INIT_LIST_HEAD(&orig_node->out_coding_list);
+	spin_lock_init(&orig_node->in_coding_list_lock);
+	spin_lock_init(&orig_node->out_coding_list_lock);
+}
+
+/**
+ * batadv_nc_node_free_rcu - rcu callback to free an nc node and remove
+ *  its refcount on the orig_node
+ * @rcu: rcu pointer of the nc node
+ */
+static void batadv_nc_node_free_rcu(struct rcu_head *rcu)
+{
+	struct batadv_nc_node *nc_node;
+
+	nc_node = container_of(rcu, struct batadv_nc_node, rcu);
+	batadv_orig_node_free_ref(nc_node->orig_node);
+	kfree(nc_node);
+}
+
+/**
+ * batadv_nc_node_free_ref - decrements the nc node refcounter and possibly
+ * frees it
+ * @nc_node: the nc node to free
+ */
+static void batadv_nc_node_free_ref(struct batadv_nc_node *nc_node)
+{
+	if (atomic_dec_and_test(&nc_node->refcount))
+		call_rcu(&nc_node->rcu, batadv_nc_node_free_rcu);
+}
+
+/**
+ * batadv_nc_to_purge_nc_node - checks whether an nc node has to be purged
+ * @bat_priv: the bat priv with all the soft interface information
+ * @nc_node: the nc node to check
+ *
+ * Returns true if the entry has to be purged now, false otherwise
+ */
+static bool batadv_nc_to_purge_nc_node(struct batadv_priv *bat_priv,
+				       struct batadv_nc_node *nc_node)
+{
+	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
+		return true;
+
+	return batadv_has_timed_out(nc_node->last_seen, BATADV_NC_NODE_TIMEOUT);
+}
+
+/**
+ * batadv_nc_purge_orig_nc_nodes - go through list of nc nodes and purge stale
+ *  entries
+ * @bat_priv: the bat priv with all the soft interface information
+ * @list: list of nc nodes
+ * @lock: nc node list lock
+ * @to_purge: function in charge to decide whether an entry has to be purged or
+ *	      not. This function takes the nc node as argument and has to return
+ *	      a boolean value: true if the entry has to be deleted, false
+ *	      otherwise
+ */
+static void
+batadv_nc_purge_orig_nc_nodes(struct batadv_priv *bat_priv,
+			      struct list_head *list,
+			      spinlock_t *lock,
+			      bool (*to_purge)(struct batadv_priv *,
+					       struct batadv_nc_node *))
+{
+	struct batadv_nc_node *nc_node, *nc_node_tmp;
+
+	/* For each nc_node in list */
+	spin_lock_bh(lock);
+	list_for_each_entry_safe(nc_node, nc_node_tmp, list, list) {
+		/* 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(bat_priv, nc_node))
+			continue;
+
+		batadv_dbg(BATADV_DBG_NC, bat_priv,
+			   "Removing nc_node %pM -> %pM\n",
+			   nc_node->addr, nc_node->orig_node->orig);
+		list_del_rcu(&nc_node->list);
+		batadv_nc_node_free_ref(nc_node);
+	}
+	spin_unlock_bh(lock);
+}
+
+/**
+ * batadv_nc_purge_orig - purges all nc node data attached of the given
+ *  originator
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig_node: orig_node with the nc node entries to be purged
+ * @to_purge: function in charge to decide whether an entry has to be purged or
+ *	      not. This function takes the nc node as argument and has to return
+ *	      a boolean value: true is the entry has to be deleted, false
+ *	      otherwise
+ */
+void batadv_nc_purge_orig(struct batadv_priv *bat_priv,
+			  struct batadv_orig_node *orig_node,
+			  bool (*to_purge)(struct batadv_priv *,
+					   struct batadv_nc_node *))
+{
+	/* Check ingoing nc_node's of this orig_node */
+	batadv_nc_purge_orig_nc_nodes(bat_priv, &orig_node->in_coding_list,
+				      &orig_node->in_coding_list_lock,
+				      to_purge);
+
+	/* Check outgoing nc_node's of this orig_node */
+	batadv_nc_purge_orig_nc_nodes(bat_priv, &orig_node->out_coding_list,
+				      &orig_node->out_coding_list_lock,
+				      to_purge);
+}
+
+/**
+ * batadv_nc_purge_orig_hash - traverse entire originator hash to check if they
+ *  have timed out nc nodes
+ * @bat_priv: the bat priv with all the soft interface information
+ */
+static void batadv_nc_purge_orig_hash(struct batadv_priv *bat_priv)
+{
+	struct batadv_hashtable *hash = bat_priv->orig_hash;
+	struct hlist_head *head;
+	struct batadv_orig_node *orig_node;
+	uint32_t i;
+
+	if (!hash)
+		return;
+
+	/* For each orig_node */
+	for (i = 0; i < hash->size; i++) {
+		head = &hash->table[i];
+
+		rcu_read_lock();
+		hlist_for_each_entry_rcu(orig_node, head, hash_entry)
+			batadv_nc_purge_orig(bat_priv, orig_node,
+					     batadv_nc_to_purge_nc_node);
+		rcu_read_unlock();
+	}
 }
 
 /**
@@ -67,11 +216,197 @@ static void batadv_nc_worker(struct work_struct *work)
 	priv_nc = container_of(delayed_work, struct batadv_priv_nc, work);
 	bat_priv = container_of(priv_nc, struct batadv_priv, nc);
 
+	batadv_nc_purge_orig_hash(bat_priv);
+
 	/* Schedule a new check */
 	batadv_nc_start_timer(bat_priv);
 }
 
 /**
+ * batadv_can_nc_with_orig - checks whether the given orig node is suitable for
+ *  coding or not
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig_node: neighboring orig node which may be used as nc candidate
+ * @ogm_packet: incoming ogm packet also used for the checks
+ *
+ * Returns true if:
+ *  1) The OGM must have the most recent sequence number.
+ *  2) The TTL must be decremented by one and only one.
+ *  3) The OGM must be received from the first hop from orig_node.
+ *  4) The TQ value of the OGM must be above bat_priv->nc.min_tq.
+ */
+static bool batadv_can_nc_with_orig(struct batadv_priv *bat_priv,
+				    struct batadv_orig_node *orig_node,
+				    struct batadv_ogm_packet *ogm_packet)
+{
+	if (orig_node->last_real_seqno != ogm_packet->seqno)
+		return false;
+	if (orig_node->last_ttl != ogm_packet->header.ttl + 1)
+		return false;
+	if (!batadv_compare_eth(ogm_packet->orig, ogm_packet->prev_sender))
+		return false;
+	if (ogm_packet->tq < bat_priv->nc.min_tq)
+		return false;
+
+	return true;
+}
+
+/**
+ * batadv_nc_find_nc_node - search for an existing nc node and return it
+ * @orig_node: orig node originating the ogm packet
+ * @orig_neigh_node: neighboring orig node from which we received the ogm packet
+ *  (can be equal to orig_node)
+ * @in_coding: traverse incoming or outgoing network coding list
+ *
+ * Returns the nc_node if found, NULL otherwise.
+ */
+static struct batadv_nc_node
+*batadv_nc_find_nc_node(struct batadv_orig_node *orig_node,
+			struct batadv_orig_node *orig_neigh_node,
+			bool in_coding)
+{
+	struct batadv_nc_node *nc_node, *nc_node_out = NULL;
+	struct list_head *list;
+
+	if (in_coding)
+		list = &orig_neigh_node->in_coding_list;
+	else
+		list = &orig_neigh_node->out_coding_list;
+
+	/* Traverse list of nc_nodes to orig_node */
+	rcu_read_lock();
+	list_for_each_entry_rcu(nc_node, list, list) {
+		if (!batadv_compare_eth(nc_node->addr, orig_node->orig))
+			continue;
+
+		if (!atomic_inc_not_zero(&nc_node->refcount))
+			continue;
+
+		/* Found a match */
+		nc_node_out = nc_node;
+		break;
+	}
+	rcu_read_unlock();
+
+	return nc_node_out;
+}
+
+/**
+ * batadv_nc_get_nc_node - retrieves an nc node or creates the entry if it was
+ *  not found
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig_node: orig node originating the ogm packet
+ * @orig_neigh_node: neighboring orig node from which we received the ogm packet
+ *  (can be equal to orig_node)
+ * @in_coding: traverse incoming or outgoing network coding list
+ *
+ * Returns the nc_node if found or created, NULL in case of an error.
+ */
+static struct batadv_nc_node
+*batadv_nc_get_nc_node(struct batadv_priv *bat_priv,
+		       struct batadv_orig_node *orig_node,
+		       struct batadv_orig_node *orig_neigh_node,
+		       bool in_coding)
+{
+	struct batadv_nc_node *nc_node;
+	spinlock_t *lock; /* Used to lock list selected by "int in_coding" */
+	struct list_head *list;
+
+	/* Check if nc_node is already added */
+	nc_node = batadv_nc_find_nc_node(orig_node, orig_neigh_node, in_coding);
+
+	/* Node found */
+	if (nc_node)
+		return nc_node;
+
+	nc_node = kzalloc(sizeof(*nc_node), GFP_ATOMIC);
+	if (!nc_node)
+		return NULL;
+
+	if (!atomic_inc_not_zero(&orig_neigh_node->refcount))
+		goto free;
+
+	/* Initialize nc_node */
+	INIT_LIST_HEAD(&nc_node->list);
+	memcpy(nc_node->addr, orig_node->orig, ETH_ALEN);
+	nc_node->orig_node = orig_neigh_node;
+	atomic_set(&nc_node->refcount, 2);
+
+	/* Select ingoing or outgoing coding node */
+	if (in_coding) {
+		lock = &orig_neigh_node->in_coding_list_lock;
+		list = &orig_neigh_node->in_coding_list;
+	} else {
+		lock = &orig_neigh_node->out_coding_list_lock;
+		list = &orig_neigh_node->out_coding_list;
+	}
+
+	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_node %pM -> %pM\n",
+		   nc_node->addr, nc_node->orig_node->orig);
+
+	/* Add nc_node to orig_node */
+	spin_lock_bh(lock);
+	list_add_tail_rcu(&nc_node->list, list);
+	spin_unlock_bh(lock);
+
+	return nc_node;
+
+free:
+	kfree(nc_node);
+	return NULL;
+}
+
+/**
+ * batadv_nc_update_nc_node - updates stored incoming and outgoing nc node structs
+ *  (best called on incoming OGMs)
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig_node: orig node originating the ogm packet
+ * @orig_neigh_node: neighboring orig node from which we received the ogm packet
+ *  (can be equal to orig_node)
+ * @ogm_packet: incoming ogm packet
+ * @is_single_hop_neigh: orig_node is a single hop neighbor
+ */
+void batadv_nc_update_nc_node(struct batadv_priv *bat_priv,
+			      struct batadv_orig_node *orig_node,
+			      struct batadv_orig_node *orig_neigh_node,
+			      struct batadv_ogm_packet *ogm_packet,
+			      int is_single_hop_neigh)
+{
+	struct batadv_nc_node *in_nc_node = NULL, *out_nc_node = NULL;
+
+	/* Check if network coding is enabled */
+	if (!atomic_read(&bat_priv->network_coding))
+		goto out;
+
+	/* accept ogms from 'good' neighbors and single hop neighbors */
+	if (!batadv_can_nc_with_orig(bat_priv, orig_node, ogm_packet) &&
+	    !is_single_hop_neigh)
+		goto out;
+
+	/* Add orig_node as in_nc_node on hop */
+	in_nc_node = batadv_nc_get_nc_node(bat_priv, orig_node,
+					   orig_neigh_node, true);
+	if (!in_nc_node)
+		goto out;
+
+	in_nc_node->last_seen = jiffies;
+
+	/* Add hop as out_nc_node on orig_node */
+	out_nc_node = batadv_nc_get_nc_node(bat_priv, orig_neigh_node,
+					    orig_node, false);
+	if (!out_nc_node)
+		goto out;
+
+	out_nc_node->last_seen = jiffies;
+
+out:
+	if (in_nc_node)
+		batadv_nc_node_free_ref(in_nc_node);
+	if (out_nc_node)
+		batadv_nc_node_free_ref(out_nc_node);
+}
+
+/**
  * batadv_nc_free - clean up network coding memory
  * @bat_priv: the bat priv with all the soft interface information
  */
@@ -79,3 +414,82 @@ void batadv_nc_free(struct batadv_priv *bat_priv)
 {
 	cancel_delayed_work_sync(&bat_priv->nc.work);
 }
+
+/**
+ * batadv_nc_nodes_seq_print_text - print the nc node information
+ * @seq: seq file to print on
+ * @offset: not used
+ */
+int batadv_nc_nodes_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->orig_hash;
+	struct batadv_hard_iface *primary_if;
+	struct hlist_head *head;
+	struct batadv_orig_node *orig_node;
+	struct batadv_nc_node *nc_node;
+	int i;
+
+	primary_if = batadv_seq_print_text_primary_if_get(seq);
+	if (!primary_if)
+		goto out;
+
+	/* Traverse list of originators */
+	for (i = 0; i < hash->size; i++) {
+		head = &hash->table[i];
+
+		/* For each orig_node in this bin */
+		rcu_read_lock();
+		hlist_for_each_entry_rcu(orig_node, head, hash_entry) {
+			seq_printf(seq, "Node:      %pM\n", orig_node->orig);
+
+			seq_printf(seq, " Ingoing:  ");
+			/* For each in_nc_node to this orig_node */
+			list_for_each_entry_rcu(nc_node,
+						&orig_node->in_coding_list,
+						list)
+				seq_printf(seq, "%pM ",
+					   nc_node->addr);
+			seq_printf(seq, "\n");
+
+			seq_printf(seq, " Outgoing: ");
+			/* For out_nc_node to this orig_node */
+			list_for_each_entry_rcu(nc_node,
+						&orig_node->out_coding_list,
+						list)
+				seq_printf(seq, "%pM ",
+					   nc_node->addr);
+			seq_printf(seq, "\n\n");
+		}
+		rcu_read_unlock();
+	}
+
+out:
+	if (primary_if)
+		batadv_hardif_free_ref(primary_if);
+	return 0;
+}
+
+/**
+ * batadv_nc_init_debugfs - create nc folder and related files in debugfs
+ * @bat_priv: the bat priv with all the soft interface information
+ */
+int batadv_nc_init_debugfs(struct batadv_priv *bat_priv)
+{
+	struct dentry *nc_dir, *file;
+
+	nc_dir = debugfs_create_dir("nc", bat_priv->debug_dir);
+	if (!nc_dir)
+		goto out;
+
+	file = debugfs_create_u8("min_tq", S_IRUGO | S_IWUSR, nc_dir,
+				 &bat_priv->nc.min_tq);
+	if (!file)
+		goto out;
+
+	return 0;
+
+out:
+	return -ENOMEM;
+}