net/batman-adv/network-coding.c

/* Copyright (C) 2012-2013 B.A.T.M.A.N. contributors:
 *
 * Martin Hundebøll, Jeppe Ledet-Pedersen
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#include <linux/debugfs.h>

#include "main.h"
#include "hash.h"
#include "network-coding.h"
#include "send.h"
#include "originator.h"
#include "hard-interface.h"

static struct lock_class_key batadv_nc_coding_hash_lock_class_key;

static void batadv_nc_worker(struct work_struct *work);

/**
 * batadv_nc_start_timer - initialise the nc periodic worker
 * @bat_priv: the bat priv with all the soft interface information
 */
static void batadv_nc_start_timer(struct batadv_priv *bat_priv)
{
	queue_delayed_work(batadv_event_workqueue, &bat_priv->nc.work,
			   msecs_to_jiffies(10));
}

/**
 * batadv_nc_init - initialise coding hash table and start house keeping
 * @bat_priv: the bat priv with all the soft interface information
 */
int batadv_nc_init(struct batadv_priv *bat_priv)
{
	bat_priv->nc.timestamp_fwd_flush = jiffies;

	if (bat_priv->nc.coding_hash)
		return 0;

	bat_priv->nc.coding_hash = batadv_hash_new(128);
	if (!bat_priv->nc.coding_hash)
		goto err;

	batadv_hash_set_lock_class(bat_priv->nc.coding_hash,
				   &batadv_nc_coding_hash_lock_class_key);

	INIT_DELAYED_WORK(&bat_priv->nc.work, batadv_nc_worker);
	batadv_nc_start_timer(bat_priv);

	return 0;

err:
	return -ENOMEM;
}

/**
 * batadv_nc_init_bat_priv - initialise the nc specific bat_priv variables
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_nc_init_bat_priv(struct batadv_priv *bat_priv)
{
	atomic_set(&bat_priv->network_coding, 1);
	bat_priv->nc.min_tq = 200;
	bat_priv->nc.max_fwd_delay = 10;
}

/**
 * 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_path_free_ref - decrements the nc path refcounter and possibly
 * frees it
 * @nc_path: the nc node to free
 */
static void batadv_nc_path_free_ref(struct batadv_nc_path *nc_path)
{
	if (atomic_dec_and_test(&nc_path->refcount))
		kfree_rcu(nc_path, rcu);
}

/**
 * batadv_nc_packet_free - frees nc packet
 * @nc_packet: the nc packet to free
 */
static void batadv_nc_packet_free(struct batadv_nc_packet *nc_packet)
{
	if (nc_packet->skb)
		kfree_skb(nc_packet->skb);

	batadv_nc_path_free_ref(nc_packet->nc_path);
	kfree(nc_packet);
}

/**
 * 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_to_purge_nc_path_coding - checks whether an nc path has timed out
 * @bat_priv: the bat priv with all the soft interface information
 * @nc_path: the nc path to check
 *
 * Returns true if the entry has to be purged now, false otherwise
 */
static bool batadv_nc_to_purge_nc_path_coding(struct batadv_priv *bat_priv,
					      struct batadv_nc_path *nc_path)
{
	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
		return true;

	/* purge the path when no packets has been added for 10 times the
	 * max_fwd_delay time
	 */
	return batadv_has_timed_out(nc_path->last_valid,
				    bat_priv->nc.max_fwd_delay * 10);
}

/**
 * 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();
	}
}

/**
 * batadv_nc_purge_paths - traverse all nc paths part of the hash and remove
 *  unused ones
 * @bat_priv: the bat priv with all the soft interface information
 * @hash: hash table containing the nc paths to check
 * @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
 */
static void batadv_nc_purge_paths(struct batadv_priv *bat_priv,
				  struct batadv_hashtable *hash,
				  bool (*to_purge)(struct batadv_priv *,
						   struct batadv_nc_path *))
{
	struct hlist_head *head;
	struct hlist_node *node_tmp;
	struct batadv_nc_path *nc_path;
	spinlock_t *lock; /* Protects lists in hash */
	uint32_t i;

	for (i = 0; i < hash->size; i++) {
		head = &hash->table[i];
		lock = &hash->list_locks[i];

		/* For each nc_path in this bin */
		spin_lock_bh(lock);
		hlist_for_each_entry_safe(nc_path, 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(bat_priv, nc_path))
				continue;

			/* purging an non-empty nc_path should never happen, but
			 * is observed under high CPU load. Delay the purging
			 * until next iteration to allow the packet_list to be
			 * emptied first.
			 */
			if (!unlikely(list_empty(&nc_path->packet_list))) {
				net_ratelimited_function(printk,
							 KERN_WARNING
							 "Skipping free of non-empty nc_path (%pM -> %pM)!\n",
							 nc_path->prev_hop,
							 nc_path->next_hop);
				continue;
			}

			/* nc_path is unused, so remove it */
			batadv_dbg(BATADV_DBG_NC, bat_priv,
				   "Remove nc_path %pM -> %pM\n",
				   nc_path->prev_hop, nc_path->next_hop);
			hlist_del_rcu(&nc_path->hash_entry);
			batadv_nc_path_free_ref(nc_path);
		}
		spin_unlock_bh(lock);
	}
}

/**
 * batadv_nc_hash_key_gen - computes the nc_path hash key
 * @key: buffer to hold the final hash key
 * @src: source ethernet mac address going into the hash key
 * @dst: destination ethernet mac address going into the hash key
 */
static void batadv_nc_hash_key_gen(struct batadv_nc_path *key, const char *src,
				   const char *dst)
{
	memcpy(key->prev_hop, src, sizeof(key->prev_hop));
	memcpy(key->next_hop, dst, sizeof(key->next_hop));
}

/**
 * batadv_nc_hash_choose - compute the hash value for an nc path
 * @data: data to hash
 * @size: size of the hash table
 *
 * Returns the selected index in the hash table for the given data.
 */
static uint32_t batadv_nc_hash_choose(const void *data, uint32_t size)
{
	const struct batadv_nc_path *nc_path = data;
	uint32_t hash = 0;

	hash = batadv_hash_bytes(hash, &nc_path->prev_hop,
				 sizeof(nc_path->prev_hop));
	hash = batadv_hash_bytes(hash, &nc_path->next_hop,
				 sizeof(nc_path->next_hop));

	hash += (hash << 3);
	hash ^= (hash >> 11);
	hash += (hash << 15);

	return hash % size;
}

/**
 * batadv_nc_hash_compare - comparing function used in the network coding hash
 *  tables
 * @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_nc_hash_compare(const struct hlist_node *node,
				  const void *data2)
{
	const struct batadv_nc_path *nc_path1, *nc_path2;

	nc_path1 = container_of(node, struct batadv_nc_path, hash_entry);
	nc_path2 = data2;

	/* Return 1 if the two keys are identical */
	if (memcmp(nc_path1->prev_hop, nc_path2->prev_hop,
		   sizeof(nc_path1->prev_hop)) != 0)
		return 0;

	if (memcmp(nc_path1->next_hop, nc_path2->next_hop,
		   sizeof(nc_path1->next_hop)) != 0)
		return 0;

	return 1;
}

/**
 * batadv_nc_hash_find - search for an existing nc path and return it
 * @hash: hash table containing the nc path
 * @data: search key
 *
 * Returns the nc_path if found, NULL otherwise.
 */
static struct batadv_nc_path *
batadv_nc_hash_find(struct batadv_hashtable *hash,
		    void *data)
{
	struct hlist_head *head;
	struct batadv_nc_path *nc_path, *nc_path_tmp = NULL;
	int index;

	if (!hash)
		return NULL;

	index = batadv_nc_hash_choose(data, hash->size);
	head = &hash->table[index];

	rcu_read_lock();
	hlist_for_each_entry_rcu(nc_path, head, hash_entry) {
		if (!batadv_nc_hash_compare(&nc_path->hash_entry, data))
			continue;

		if (!atomic_inc_not_zero(&nc_path->refcount))
			continue;

		nc_path_tmp = nc_path;
		break;
	}
	rcu_read_unlock();

	return nc_path_tmp;
}

/**
 * batadv_nc_send_packet - send non-coded packet and free nc_packet struct
 * @nc_packet: the nc packet to send
 */
static void batadv_nc_send_packet(struct batadv_nc_packet *nc_packet)
{
	batadv_send_skb_packet(nc_packet->skb,
			       nc_packet->neigh_node->if_incoming,
			       nc_packet->nc_path->next_hop);
	nc_packet->skb = NULL;
	batadv_nc_packet_free(nc_packet);
}

/**
 * batadv_nc_fwd_flush - Checks the timestamp of the given nc packet.
 * @bat_priv: the bat priv with all the soft interface information
 * @nc_path: the nc path the packet belongs to
 * @nc_packet: the nc packet to be checked
 *
 * Checks whether the given nc packet has hit its forward timeout. If so, the
 * packet is no longer delayed, immediately sent and the entry deleted from the
 * queue. Has to be called with the appropriate locks.
 *
 * Returns false as soon as the entry in the fifo queue has not been timed out
 * yet and true otherwise.
 */
static bool batadv_nc_fwd_flush(struct batadv_priv *bat_priv,
				struct batadv_nc_path *nc_path,
				struct batadv_nc_packet *nc_packet)
{
	unsigned long timeout = bat_priv->nc.max_fwd_delay;

	/* Packets are added to tail, so the remaining packets did not time
	 * out and we can stop processing the current queue
	 */
	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_ACTIVE &&
	    !batadv_has_timed_out(nc_packet->timestamp, timeout))
		return false;

	/* Send packet */
	batadv_inc_counter(bat_priv, BATADV_CNT_FORWARD);
	batadv_add_counter(bat_priv, BATADV_CNT_FORWARD_BYTES,
			   nc_packet->skb->len + ETH_HLEN);
	list_del(&nc_packet->list);
	batadv_nc_send_packet(nc_packet);

	return true;
}

/**
 * batadv_nc_process_nc_paths - traverse given nc packet pool and free timed out
 *  nc packets
 * @bat_priv: the bat priv with all the soft interface information
 * @hash: to be processed hash table
 * @process_fn: Function called to process given nc packet. Should return true
 *	        to encourage this function to proceed with the next packet.
 *	        Otherwise the rest of the current queue is skipped.
 */
static void
batadv_nc_process_nc_paths(struct batadv_priv *bat_priv,
			   struct batadv_hashtable *hash,
			   bool (*process_fn)(struct batadv_priv *,
					      struct batadv_nc_path *,
					      struct batadv_nc_packet *))
{
	struct hlist_head *head;
	struct batadv_nc_packet *nc_packet, *nc_packet_tmp;
	struct batadv_nc_path *nc_path;
	bool ret;
	int i;

	if (!hash)
		return;

	/* Loop hash table bins */
	for (i = 0; i < hash->size; i++) {
		head = &hash->table[i];

		/* Loop coding paths */
		rcu_read_lock();
		hlist_for_each_entry_rcu(nc_path, head, hash_entry) {
			/* Loop packets */
			spin_lock_bh(&nc_path->packet_list_lock);
			list_for_each_entry_safe(nc_packet, nc_packet_tmp,
						 &nc_path->packet_list, list) {
				ret = process_fn(bat_priv, nc_path, nc_packet);
				if (!ret)
					break;
			}
			spin_unlock_bh(&nc_path->packet_list_lock);
		}
		rcu_read_unlock();
	}
}

/**
 * batadv_nc_worker - periodic task for house keeping related to network coding
 * @work: kernel work struct
 */
static void batadv_nc_worker(struct work_struct *work)
{
	struct delayed_work *delayed_work;
	struct batadv_priv_nc *priv_nc;
	struct batadv_priv *bat_priv;
	unsigned long timeout;

	delayed_work = container_of(work, struct delayed_work, 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);
	batadv_nc_purge_paths(bat_priv, bat_priv->nc.coding_hash,
			      batadv_nc_to_purge_nc_path_coding);

	timeout = bat_priv->nc.max_fwd_delay;

	if (batadv_has_timed_out(bat_priv->nc.timestamp_fwd_flush, timeout)) {
		batadv_nc_process_nc_paths(bat_priv, bat_priv->nc.coding_hash,
					   batadv_nc_fwd_flush);
		bat_priv->nc.timestamp_fwd_flush = jiffies;
	}

	/* 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_get_path - get existing nc_path or allocate a new one
 * @bat_priv: the bat priv with all the soft interface information
 * @hash: hash table containing the nc path
 * @src: ethernet source address - first half of the nc path search key
 * @dst: ethernet destination address - second half of the nc path search key
 *
 * Returns pointer to nc_path if the path was found or created, returns NULL
 * on error.
 */
static struct batadv_nc_path *batadv_nc_get_path(struct batadv_priv *bat_priv,
						 struct batadv_hashtable *hash,
						 uint8_t *src,
						 uint8_t *dst)
{
	int hash_added;
	struct batadv_nc_path *nc_path, nc_path_key;

	batadv_nc_hash_key_gen(&nc_path_key, src, dst);

	/* Search for existing nc_path */
	nc_path = batadv_nc_hash_find(hash, (void *)&nc_path_key);

	if (nc_path) {
		/* Set timestamp to delay removal of nc_path */
		nc_path->last_valid = jiffies;
		return nc_path;
	}

	/* No existing nc_path was found; create a new */
	nc_path = kzalloc(sizeof(*nc_path), GFP_ATOMIC);

	if (!nc_path)
		return NULL;

	/* Initialize nc_path */
	INIT_LIST_HEAD(&nc_path->packet_list);
	spin_lock_init(&nc_path->packet_list_lock);
	atomic_set(&nc_path->refcount, 2);
	nc_path->last_valid = jiffies;
	memcpy(nc_path->next_hop, dst, ETH_ALEN);
	memcpy(nc_path->prev_hop, src, ETH_ALEN);

	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_path %pM -> %pM\n",
		   nc_path->prev_hop,
		   nc_path->next_hop);

	/* Add nc_path to hash table */
	hash_added = batadv_hash_add(hash, batadv_nc_hash_compare,
				     batadv_nc_hash_choose, &nc_path_key,
				     &nc_path->hash_entry);

	if (hash_added < 0) {
		kfree(nc_path);
		return NULL;
	}

	return nc_path;
}

/**
 * batadv_nc_skb_add_to_path - buffer skb for later encoding / decoding
 * @skb: skb to add to path
 * @nc_path: path to add skb to
 * @neigh_node: next hop to forward packet to
 * @packet_id: checksum to identify packet
 *
 * Returns true if the packet was buffered or false in case of an error.
 */
static bool batadv_nc_skb_add_to_path(struct sk_buff *skb,
				      struct batadv_nc_path *nc_path,
				      struct batadv_neigh_node *neigh_node,
				      __be32 packet_id)
{
	struct batadv_nc_packet *nc_packet;

	nc_packet = kzalloc(sizeof(*nc_packet), GFP_ATOMIC);
	if (!nc_packet)
		return false;

	/* Initialize nc_packet */
	nc_packet->timestamp = jiffies;
	nc_packet->packet_id = packet_id;
	nc_packet->skb = skb;
	nc_packet->neigh_node = neigh_node;
	nc_packet->nc_path = nc_path;

	/* Add coding packet to list */
	spin_lock_bh(&nc_path->packet_list_lock);
	list_add_tail(&nc_packet->list, &nc_path->packet_list);
	spin_unlock_bh(&nc_path->packet_list_lock);

	return true;
}

/**
 * batadv_nc_skb_forward - try to code a packet or add it to the coding packet
 *  buffer
 * @skb: data skb to forward
 * @neigh_node: next hop to forward packet to
 * @ethhdr: pointer to the ethernet header inside the skb
 *
 * Returns true if the skb was consumed (encoded packet sent) or false otherwise
 */
bool batadv_nc_skb_forward(struct sk_buff *skb,
			   struct batadv_neigh_node *neigh_node,
			   struct ethhdr *ethhdr)
{
	const struct net_device *netdev = neigh_node->if_incoming->soft_iface;
	struct batadv_priv *bat_priv = netdev_priv(netdev);
	struct batadv_unicast_packet *packet;
	struct batadv_nc_path *nc_path;
	__be32 packet_id;
	u8 *payload;

	/* Check if network coding is enabled */
	if (!atomic_read(&bat_priv->network_coding))
		goto out;

	/* We only handle unicast packets */
	payload = skb_network_header(skb);
	packet = (struct batadv_unicast_packet *)payload;
	if (packet->header.packet_type != BATADV_UNICAST)
		goto out;

	/* Find or create a nc_path for this src-dst pair */
	nc_path = batadv_nc_get_path(bat_priv,
				     bat_priv->nc.coding_hash,
				     ethhdr->h_source,
				     neigh_node->addr);

	if (!nc_path)
		goto out;

	/* Add skb to nc_path */
	packet_id = batadv_skb_crc32(skb, payload + sizeof(*packet));
	if (!batadv_nc_skb_add_to_path(skb, nc_path, neigh_node, packet_id))
		goto free_nc_path;

	/* Packet is consumed */
	return true;

free_nc_path:
	batadv_nc_path_free_ref(nc_path);
out:
	/* Packet is not consumed */
	return false;
}

/**
 * batadv_nc_free - clean up network coding memory
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_nc_free(struct batadv_priv *bat_priv)
{
	cancel_delayed_work_sync(&bat_priv->nc.work);
	batadv_nc_purge_paths(bat_priv, bat_priv->nc.coding_hash, NULL);
	batadv_hash_destroy(bat_priv->nc.coding_hash);
}

/**
 * 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;

	file = debugfs_create_u32("max_fwd_delay", S_IRUGO | S_IWUSR, nc_dir,
				  &bat_priv->nc.max_fwd_delay);
	if (!file)
		goto out;

	return 0;

out:
	return -ENOMEM;
}