/* Copyright (C) 2012-2017  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, see <http://www.gnu.org/licenses/>.

   */

  #include "network-coding.h"
  #include "main.h"
  
  #include <linux/atomic.h>

  #include <linux/bitops.h>

  #include <linux/byteorder/generic.h>
  #include <linux/compiler.h>

  #include <linux/debugfs.h>

  #include <linux/errno.h>
  #include <linux/etherdevice.h>
  #include <linux/fs.h>
  #include <linux/if_ether.h>
  #include <linux/if_packet.h>
  #include <linux/init.h>
  #include <linux/jhash.h>
  #include <linux/jiffies.h>
  #include <linux/kernel.h>

  #include <linux/kref.h>

  #include <linux/list.h>
  #include <linux/lockdep.h>
  #include <linux/netdevice.h>
  #include <linux/printk.h>
  #include <linux/random.h>
  #include <linux/rculist.h>
  #include <linux/rcupdate.h>
  #include <linux/seq_file.h>
  #include <linux/skbuff.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>

  #include <linux/stddef.h>
  #include <linux/string.h>
  #include <linux/workqueue.h>

  #include "hard-interface.h"

  #include "hash.h"

  #include "log.h"

  #include "originator.h"

  #include "packet.h"

  #include "routing.h"

  #include "send.h"

  #include "tvlv.h"

  static struct lock_class_key batadv_nc_coding_hash_lock_class_key;

  static struct lock_class_key batadv_nc_decoding_hash_lock_class_key;

  static void batadv_nc_worker(struct work_struct *work);

  static int batadv_nc_recv_coded_packet(struct sk_buff *skb,
  				       struct batadv_hard_iface *recv_if);

  
  /**

   * batadv_nc_init - one-time initialization for network coding

   *
   * Return: 0 on success or negative error number in case of failure

   */
  int __init batadv_nc_init(void)
  {
  	int ret;
  
  	/* Register our packet type */
  	ret = batadv_recv_handler_register(BATADV_CODED,
  					   batadv_nc_recv_coded_packet);
  
  	return ret;
  }
  
  /**

   * 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_tvlv_container_update - update the network coding tvlv container
   *  after network coding setting change
   * @bat_priv: the bat priv with all the soft interface information
   */
  static void batadv_nc_tvlv_container_update(struct batadv_priv *bat_priv)
  {
  	char nc_mode;
  
  	nc_mode = atomic_read(&bat_priv->network_coding);
  
  	switch (nc_mode) {
  	case 0:
  		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_NC, 1);
  		break;
  	case 1:
  		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_NC, 1,
  					       NULL, 0);
  		break;
  	}
  }
  
  /**
   * batadv_nc_status_update - update the network coding tvlv container after
   *  network coding setting change
   * @net_dev: the soft interface net device
   */
  void batadv_nc_status_update(struct net_device *net_dev)
  {
  	struct batadv_priv *bat_priv = netdev_priv(net_dev);

  	batadv_nc_tvlv_container_update(bat_priv);
  }
  
  /**
   * batadv_nc_tvlv_ogm_handler_v1 - process incoming nc tvlv container
   * @bat_priv: the bat priv with all the soft interface information
   * @orig: the orig_node of the ogm
   * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
   * @tvlv_value: tvlv buffer containing the gateway data
   * @tvlv_value_len: tvlv buffer length
   */
  static void batadv_nc_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
  					  struct batadv_orig_node *orig,

  					  u8 flags,
  					  void *tvlv_value, u16 tvlv_value_len)

  {
  	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)

  		clear_bit(BATADV_ORIG_CAPA_HAS_NC, &orig->capabilities);

  	else

  		set_bit(BATADV_ORIG_CAPA_HAS_NC, &orig->capabilities);

  }
  
  /**

   * batadv_nc_mesh_init - initialise coding hash table and start house keeping

   * @bat_priv: the bat priv with all the soft interface information

   *
   * Return: 0 on success or negative error number in case of failure

   */

  int batadv_nc_mesh_init(struct batadv_priv *bat_priv)

  {

  	bat_priv->nc.timestamp_fwd_flush = jiffies;

  	bat_priv->nc.timestamp_sniffed_purge = jiffies;

  	if (bat_priv->nc.coding_hash || bat_priv->nc.decoding_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);

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

  	batadv_hash_set_lock_class(bat_priv->nc.decoding_hash,

  				   &batadv_nc_decoding_hash_lock_class_key);

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

  	batadv_tvlv_handler_register(bat_priv, batadv_nc_tvlv_ogm_handler_v1,
  				     NULL, BATADV_TVLV_NC, 1,
  				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
  	batadv_nc_tvlv_container_update(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, 0);

  	bat_priv->nc.min_tq = 200;

  	bat_priv->nc.max_fwd_delay = 10;

  	bat_priv->nc.max_buffer_time = 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_release - release nc_node from lists and queue for free after
   *  rcu grace period

   * @ref: kref pointer of the nc_node

   */

  static void batadv_nc_node_release(struct kref *ref)

  {

  	struct batadv_nc_node *nc_node;
  
  	nc_node = container_of(ref, struct batadv_nc_node, refcount);

  	batadv_orig_node_put(nc_node->orig_node);

  	kfree_rcu(nc_node, rcu);

  }
  
  /**

   * batadv_nc_node_put - decrement the nc_node refcounter and possibly

   *  release it

   * @nc_node: nc_node to be free'd

   */

  static void batadv_nc_node_put(struct batadv_nc_node *nc_node)

  {

  	kref_put(&nc_node->refcount, batadv_nc_node_release);

  }
  
  /**

   * batadv_nc_path_release - release nc_path from lists and queue for free after
   *  rcu grace period
   * @ref: kref pointer of the nc_path
   */
  static void batadv_nc_path_release(struct kref *ref)
  {
  	struct batadv_nc_path *nc_path;
  
  	nc_path = container_of(ref, struct batadv_nc_path, refcount);
  
  	kfree_rcu(nc_path, rcu);
  }
  
  /**

   * batadv_nc_path_put - decrement the nc_path refcounter and possibly

   *  release it
   * @nc_path: nc_path to be free'd

   */

  static void batadv_nc_path_put(struct batadv_nc_path *nc_path)

  {

  	kref_put(&nc_path->refcount, batadv_nc_path_release);

  }
  
  /**
   * batadv_nc_packet_free - frees nc packet
   * @nc_packet: the nc packet to free

   * @dropped: whether the packet is freed because is is dropped

   */

  static void batadv_nc_packet_free(struct batadv_nc_packet *nc_packet,
  				  bool dropped)

  {

  	if (dropped)
  		kfree_skb(nc_packet->skb);
  	else
  		consume_skb(nc_packet->skb);

  	batadv_nc_path_put(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
   *

   * Return: 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
   *

   * Return: 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_to_purge_nc_path_decoding - 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
   *

   * Return: true if the entry has to be purged now, false otherwise

   */
  static bool batadv_nc_to_purge_nc_path_decoding(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_buffer time
  	 */
  	return batadv_has_timed_out(nc_path->last_valid,

  				    bat_priv->nc.max_buffer_time * 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
  ",
  			   nc_node->addr, nc_node->orig_node->orig);
  		list_del_rcu(&nc_node->list);

  		batadv_nc_node_put(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;

  	u32 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 */

  	u32 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)!
  ",
  							 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
  ",
  				   nc_path->prev_hop, nc_path->next_hop);
  			hlist_del_rcu(&nc_path->hash_entry);

  			batadv_nc_path_put(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
   *

   * Return: the selected index in the hash table for the given data.

   */

  static u32 batadv_nc_hash_choose(const void *data, u32 size)

  {
  	const struct batadv_nc_path *nc_path = data;

  	u32 hash = 0;

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

  
  	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
   *

   * Return: true if the two entry are the same, false otherwise

   */

  static bool 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 (!batadv_compare_eth(nc_path1->prev_hop, nc_path2->prev_hop))

  		return false;

  	if (!batadv_compare_eth(nc_path1->next_hop, nc_path2->next_hop))

  		return false;

  	return true;

  }
  
  /**
   * batadv_nc_hash_find - search for an existing nc path and return it
   * @hash: hash table containing the nc path
   * @data: search key
   *

   * Return: 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 (!kref_get_unless_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_unicast_skb(nc_packet->skb, nc_packet->neigh_node);

  	nc_packet->skb = NULL;

  	batadv_nc_packet_free(nc_packet, false);

  }
  
  /**

   * batadv_nc_sniffed_purge - Checks timestamp of given sniffed 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 sniffed (overheard) nc_packet has hit its buffering
   * timeout. If so, the packet is no longer kept and the entry deleted from the
   * queue. Has to be called with the appropriate locks.
   *

   * Return: false as soon as the entry in the fifo queue has not been timed out

   * yet and true otherwise.
   */
  static bool batadv_nc_sniffed_purge(struct batadv_priv *bat_priv,
  				    struct batadv_nc_path *nc_path,
  				    struct batadv_nc_packet *nc_packet)
  {
  	unsigned long timeout = bat_priv->nc.max_buffer_time;
  	bool res = false;

  	lockdep_assert_held(&nc_path->packet_list_lock);

  	/* 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))
  		goto out;
  
  	/* purge nc packet */
  	list_del(&nc_packet->list);

  	batadv_nc_packet_free(nc_packet, true);

  
  	res = true;
  
  out:
  	return res;
  }
  
  /**

   * 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.
   *

   * Return: 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;

  	lockdep_assert_held(&nc_path->packet_list_lock);

  	/* 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 = to_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);

  	batadv_nc_purge_paths(bat_priv, bat_priv->nc.decoding_hash,
  			      batadv_nc_to_purge_nc_path_decoding);

  
  	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;
  	}

  	if (batadv_has_timed_out(bat_priv->nc.timestamp_sniffed_purge,
  				 bat_priv->nc.max_buffer_time)) {
  		batadv_nc_process_nc_paths(bat_priv, bat_priv->nc.decoding_hash,
  					   batadv_nc_sniffed_purge);
  		bat_priv->nc.timestamp_sniffed_purge = 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
   *

   * Return: 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)
  {

  	struct batadv_orig_ifinfo *orig_ifinfo;

  	u32 last_real_seqno;
  	u8 last_ttl;

  
  	orig_ifinfo = batadv_orig_ifinfo_get(orig_node, BATADV_IF_DEFAULT);
  	if (!orig_ifinfo)

  		return false;

  
  	last_ttl = orig_ifinfo->last_ttl;
  	last_real_seqno = orig_ifinfo->last_real_seqno;

  	batadv_orig_ifinfo_put(orig_ifinfo);

  
  	if (last_real_seqno != ntohl(ogm_packet->seqno))
  		return false;
  	if (last_ttl != ogm_packet->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
   *

   * Return: 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 (!kref_get_unless_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
   *

   * Return: 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;

  	/* 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;
  	}
  
  	spin_lock_bh(lock);

  	/* 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)

  		goto unlock;

  
  	nc_node = kzalloc(sizeof(*nc_node), GFP_ATOMIC);
  	if (!nc_node)

  		goto unlock;

  	/* Initialize nc_node */
  	INIT_LIST_HEAD(&nc_node->list);

  	kref_init(&nc_node->refcount);

  	ether_addr_copy(nc_node->addr, orig_node->orig);
  	kref_get(&orig_neigh_node->refcount);
  	nc_node->orig_node = orig_neigh_node;

  	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_node %pM -> %pM
  ",
  		   nc_node->addr, nc_node->orig_node->orig);
  
  	/* Add nc_node to orig_node */

  	kref_get(&nc_node->refcount);

  	list_add_tail_rcu(&nc_node->list, list);

  
  unlock:

  	spin_unlock_bh(lock);
  
  	return nc_node;

  }
  
  /**

   * 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;
  	struct batadv_nc_node *out_nc_node = NULL;

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

  	/* check if orig node is network coding enabled */

  	if (!test_bit(BATADV_ORIG_CAPA_HAS_NC, &orig_node->capabilities))

  		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_put(in_nc_node);

  	if (out_nc_node)

  		batadv_nc_node_put(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
   *

   * Return: 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,

  						 u8 *src,
  						 u8 *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);

  	kref_init(&nc_path->refcount);

  	nc_path->last_valid = jiffies;

  	ether_addr_copy(nc_path->next_hop, dst);
  	ether_addr_copy(nc_path->prev_hop, src);

  
  	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_path %pM -> %pM
  ",
  		   nc_path->prev_hop,
  		   nc_path->next_hop);
  
  	/* Add nc_path to hash table */

  	kref_get(&nc_path->refcount);

  	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_random_weight_tq - scale the receivers TQ-value to avoid unfair
   *  selection of a receiver with slightly lower TQ than the other
   * @tq: to be weighted tq value

   *
   * Return: scaled tq value

   */

  static u8 batadv_nc_random_weight_tq(u8 tq)

  {

  	u8 rand_val, rand_tq;

  
  	get_random_bytes(&rand_val, sizeof(rand_val));
  
  	/* randomize the estimated packet loss (max TQ - estimated TQ) */
  	rand_tq = rand_val * (BATADV_TQ_MAX_VALUE - tq);
  
  	/* normalize the randomized packet loss */
  	rand_tq /= BATADV_TQ_MAX_VALUE;
  
  	/* convert to (randomized) estimated tq again */
  	return BATADV_TQ_MAX_VALUE - rand_tq;
  }
  
  /**
   * batadv_nc_memxor - XOR destination with source
   * @dst: byte array to XOR into
   * @src: byte array to XOR from
   * @len: length of destination array
   */
  static void batadv_nc_memxor(char *dst, const char *src, unsigned int len)
  {
  	unsigned int i;
  
  	for (i = 0; i < len; ++i)
  		dst[i] ^= src[i];
  }
  
  /**
   * batadv_nc_code_packets - code a received unicast_packet with an nc packet
   *  into a coded_packet and send it
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: data skb to forward
   * @ethhdr: pointer to the ethernet header inside the skb
   * @nc_packet: structure containing the packet to the skb can be coded with
   * @neigh_node: next hop to forward packet to
   *

   * Return: true if both packets are consumed, false otherwise.

   */
  static bool batadv_nc_code_packets(struct batadv_priv *bat_priv,
  				   struct sk_buff *skb,
  				   struct ethhdr *ethhdr,
  				   struct batadv_nc_packet *nc_packet,
  				   struct batadv_neigh_node *neigh_node)
  {

  	u8 tq_weighted_neigh, tq_weighted_coding, tq_tmp;

  	struct sk_buff *skb_dest, *skb_src;
  	struct batadv_unicast_packet *packet1;
  	struct batadv_unicast_packet *packet2;
  	struct batadv_coded_packet *coded_packet;

  	struct batadv_neigh_node *neigh_tmp, *router_neigh, *first_dest;
  	struct batadv_neigh_node *router_coding = NULL, *second_dest;

  	struct batadv_neigh_ifinfo *router_neigh_ifinfo = NULL;
  	struct batadv_neigh_ifinfo *router_coding_ifinfo = NULL;

  	u8 *first_source, *second_source;

  	__be32 packet_id1, packet_id2;
  	size_t count;
  	bool res = false;
  	int coding_len;
  	int unicast_size = sizeof(*packet1);
  	int coded_size = sizeof(*coded_packet);
  	int header_add = coded_size - unicast_size;

  	/* TODO: do we need to consider the outgoing interface for
  	 * coded packets?
  	 */
  	router_neigh = batadv_orig_router_get(neigh_node->orig_node,
  					      BATADV_IF_DEFAULT);

  	if (!router_neigh)
  		goto out;

  	router_neigh_ifinfo = batadv_neigh_ifinfo_get(router_neigh,
  						      BATADV_IF_DEFAULT);
  	if (!router_neigh_ifinfo)
  		goto out;

  	neigh_tmp = nc_packet->neigh_node;

  	router_coding = batadv_orig_router_get(neigh_tmp->orig_node,
  					       BATADV_IF_DEFAULT);

  	if (!router_coding)
  		goto out;

  	router_coding_ifinfo = batadv_neigh_ifinfo_get(router_coding,
  						       BATADV_IF_DEFAULT);
  	if (!router_coding_ifinfo)
  		goto out;
  
  	tq_tmp = router_neigh_ifinfo->bat_iv.tq_avg;
  	tq_weighted_neigh = batadv_nc_random_weight_tq(tq_tmp);
  	tq_tmp = router_coding_ifinfo->bat_iv.tq_avg;
  	tq_weighted_coding = batadv_nc_random_weight_tq(tq_tmp);

  
  	/* Select one destination for the MAC-header dst-field based on
  	 * weighted TQ-values.
  	 */
  	if (tq_weighted_neigh >= tq_weighted_coding) {
  		/* Destination from nc_packet is selected for MAC-header */

  		first_dest = nc_packet->neigh_node;

  		first_source = nc_packet->nc_path->prev_hop;

  		second_dest = neigh_node;

  		second_source = ethhdr->h_source;
  		packet1 = (struct batadv_unicast_packet *)nc_packet->skb->data;
  		packet2 = (struct batadv_unicast_packet *)skb->data;
  		packet_id1 = nc_packet->packet_id;
  		packet_id2 = batadv_skb_crc32(skb,
  					      skb->data + sizeof(*packet2));
  	} else {
  		/* Destination for skb is selected for MAC-header */

  		first_dest = neigh_node;

  		first_source = ethhdr->h_source;

  		second_dest = nc_packet->neigh_node;

  		second_source = nc_packet->nc_path->prev_hop;
  		packet1 = (struct batadv_unicast_packet *)skb->data;
  		packet2 = (struct batadv_unicast_packet *)nc_packet->skb->data;
  		packet_id1 = batadv_skb_crc32(skb,
  					      skb->data + sizeof(*packet1));
  		packet_id2 = nc_packet->packet_id;
  	}
  
  	/* Instead of zero padding the smallest data buffer, we
  	 * code into the largest.
  	 */
  	if (skb->len <= nc_packet->skb->len) {
  		skb_dest = nc_packet->skb;
  		skb_src = skb;
  	} else {
  		skb_dest = skb;
  		skb_src = nc_packet->skb;
  	}
  
  	/* coding_len is used when decoding the packet shorter packet */
  	coding_len = skb_src->len - unicast_size;
  
  	if (skb_linearize(skb_dest) < 0 || skb_linearize(skb_src) < 0)
  		goto out;
  
  	skb_push(skb_dest, header_add);
  
  	coded_packet = (struct batadv_coded_packet *)skb_dest->data;
  	skb_reset_mac_header(skb_dest);

  	coded_packet->packet_type = BATADV_CODED;
  	coded_packet->version = BATADV_COMPAT_VERSION;
  	coded_packet->ttl = packet1->ttl;

  
  	/* Info about first unicast packet */

  	ether_addr_copy(coded_packet->first_source, first_source);
  	ether_addr_copy(coded_packet->first_orig_dest, packet1->dest);

  	coded_packet->first_crc = packet_id1;
  	coded_packet->first_ttvn = packet1->ttvn;
  
  	/* Info about second unicast packet */

  	ether_addr_copy(coded_packet->second_dest, second_dest->addr);

  	ether_addr_copy(coded_packet->second_source, second_source);
  	ether_addr_copy(coded_packet->second_orig_dest, packet2->dest);

  	coded_packet->second_crc = packet_id2;

  	coded_packet->second_ttl = packet2->ttl;

  	coded_packet->second_ttvn = packet2->ttvn;
  	coded_packet->coded_len = htons(coding_len);
  
  	/* This is where the magic happens: Code skb_src into skb_dest */
  	batadv_nc_memxor(skb_dest->data + coded_size,
  			 skb_src->data + unicast_size, coding_len);
  
  	/* Update counters accordingly */
  	if (BATADV_SKB_CB(skb_src)->decoded &&
  	    BATADV_SKB_CB(skb_dest)->decoded) {
  		/* Both packets are recoded */
  		count = skb_src->len + ETH_HLEN;
  		count += skb_dest->len + ETH_HLEN;
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE, 2);
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE_BYTES, count);
  	} else if (!BATADV_SKB_CB(skb_src)->decoded &&
  		   !BATADV_SKB_CB(skb_dest)->decoded) {
  		/* Both packets are newly coded */
  		count = skb_src->len + ETH_HLEN;
  		count += skb_dest->len + ETH_HLEN;
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE, 2);
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE_BYTES, count);
  	} else if (BATADV_SKB_CB(skb_src)->decoded &&
  		   !BATADV_SKB_CB(skb_dest)->decoded) {
  		/* skb_src recoded and skb_dest is newly coded */
  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_RECODE);
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE_BYTES,
  				   skb_src->len + ETH_HLEN);
  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_CODE);
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE_BYTES,
  				   skb_dest->len + ETH_HLEN);
  	} else if (!BATADV_SKB_CB(skb_src)->decoded &&
  		   BATADV_SKB_CB(skb_dest)->decoded) {
  		/* skb_src is newly coded and skb_dest is recoded */
  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_CODE);
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE_BYTES,
  				   skb_src->len + ETH_HLEN);
  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_RECODE);
  		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE_BYTES,
  				   skb_dest->len + ETH_HLEN);
  	}
  
  	/* skb_src is now coded into skb_dest, so free it */

  	consume_skb(skb_src);

  
  	/* avoid duplicate free of skb from nc_packet */
  	nc_packet->skb = NULL;

  	batadv_nc_packet_free(nc_packet, false);

  
  	/* Send the coded packet and return true */

  	batadv_send_unicast_skb(skb_dest, first_dest);

  	res = true;
  out:
  	if (router_neigh)

  		batadv_neigh_node_put(router_neigh);

  	if (router_coding)

  		batadv_neigh_node_put(router_coding);

  	if (router_neigh_ifinfo)

  		batadv_neigh_ifinfo_put(router_neigh_ifinfo);

  	if (router_coding_ifinfo)

  		batadv_neigh_ifinfo_put(router_coding_ifinfo);

  	return res;
  }
  
  /**
   * batadv_nc_skb_coding_possible - true if a decoded skb is available at dst.
   * @skb: data skb to forward
   * @dst: destination mac address of the other skb to code with
   * @src: source mac address of skb
   *
   * Whenever we network code a packet we have to check whether we received it in
   * a network coded form. If so, we may not be able to use it for coding because
   * some neighbors may also have received (overheard) the packet in the network
   * coded form without being able to decode it. It is hard to know which of the
   * neighboring nodes was able to decode the packet, therefore we can only
   * re-code the packet if the source of the previous encoded packet is involved.
   * Since the source encoded the packet we can be certain it has all necessary
   * decode information.
   *

   * Return: true if coding of a decoded packet is allowed.

   */

  static bool batadv_nc_skb_coding_possible(struct sk_buff *skb, u8 *dst, u8 *src)

  {
  	if (BATADV_SKB_CB(skb)->decoded && !batadv_compare_eth(dst, src))
  		return false;

  	return true;

  }
  
  /**
   * batadv_nc_path_search - Find the coding path matching in_nc_node and
   *  out_nc_node to retrieve a buffered packet that can be used for coding.
   * @bat_priv: the bat priv with all the soft interface information
   * @in_nc_node: pointer to skb next hop's neighbor nc node
   * @out_nc_node: pointer to skb source's neighbor nc node
   * @skb: data skb to forward
   * @eth_dst: next hop mac address of skb
   *

   * Return: true if coding of a decoded skb is allowed.

   */
  static struct batadv_nc_packet *
  batadv_nc_path_search(struct batadv_priv *bat_priv,
  		      struct batadv_nc_node *in_nc_node,
  		      struct batadv_nc_node *out_nc_node,
  		      struct sk_buff *skb,

  		      u8 *eth_dst)

  {
  	struct batadv_nc_path *nc_path, nc_path_key;
  	struct batadv_nc_packet *nc_packet_out = NULL;
  	struct batadv_nc_packet *nc_packet, *nc_packet_tmp;
  	struct batadv_hashtable *hash = bat_priv->nc.coding_hash;
  	int idx;
  
  	if (!hash)
  		return NULL;
  
  	/* Create almost path key */
  	batadv_nc_hash_key_gen(&nc_path_key, in_nc_node->addr,
  			       out_nc_node->addr);
  	idx = batadv_nc_hash_choose(&nc_path_key, hash->size);
  
  	/* Check for coding opportunities in this nc_path */
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(nc_path, &hash->table[idx], hash_entry) {
  		if (!batadv_compare_eth(nc_path->prev_hop, in_nc_node->addr))
  			continue;
  
  		if (!batadv_compare_eth(nc_path->next_hop, out_nc_node->addr))
  			continue;
  
  		spin_lock_bh(&nc_path->packet_list_lock);
  		if (list_empty(&nc_path->packet_list)) {
  			spin_unlock_bh(&nc_path->packet_list_lock);
  			continue;
  		}
  
  		list_for_each_entry_safe(nc_packet, nc_packet_tmp,
  					 &nc_path->packet_list, list) {
  			if (!batadv_nc_skb_coding_possible(nc_packet->skb,
  							   eth_dst,
  							   in_nc_node->addr))
  				continue;
  
  			/* Coding opportunity is found! */
  			list_del(&nc_packet->list);
  			nc_packet_out = nc_packet;
  			break;
  		}
  
  		spin_unlock_bh(&nc_path->packet_list_lock);
  		break;
  	}
  	rcu_read_unlock();
  
  	return nc_packet_out;
  }
  
  /**
   * batadv_nc_skb_src_search - Loops through the list of neighoring nodes of the
   *  skb's sender (may be equal to the originator).
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: data skb to forward
   * @eth_dst: next hop mac address of skb
   * @eth_src: source mac address of skb
   * @in_nc_node: pointer to skb next hop's neighbor nc node
   *

   * Return: an nc packet if a suitable coding packet was found, NULL otherwise.

   */
  static struct batadv_nc_packet *
  batadv_nc_skb_src_search(struct batadv_priv *bat_priv,
  			 struct sk_buff *skb,

  			 u8 *eth_dst,
  			 u8 *eth_src,

  			 struct batadv_nc_node *in_nc_node)
  {
  	struct batadv_orig_node *orig_node;
  	struct batadv_nc_node *out_nc_node;
  	struct batadv_nc_packet *nc_packet = NULL;
  
  	orig_node = batadv_orig_hash_find(bat_priv, eth_src);
  	if (!orig_node)
  		return NULL;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(out_nc_node,
  				&orig_node->out_coding_list, list) {
  		/* Check if the skb is decoded and if recoding is possible */
  		if (!batadv_nc_skb_coding_possible(skb,
  						   out_nc_node->addr, eth_src))
  			continue;
  
  		/* Search for an opportunity in this nc_path */
  		nc_packet = batadv_nc_path_search(bat_priv, in_nc_node,
  						  out_nc_node, skb, eth_dst);
  		if (nc_packet)
  			break;
  	}
  	rcu_read_unlock();

  	batadv_orig_node_put(orig_node);

  	return nc_packet;
  }
  
  /**

   * batadv_nc_skb_store_before_coding - set the ethernet src and dst of the
   *  unicast skb before it is stored for use in later decoding
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: data skb to store
   * @eth_dst_new: new destination mac address of skb
   */
  static void batadv_nc_skb_store_before_coding(struct batadv_priv *bat_priv,
  					      struct sk_buff *skb,

  					      u8 *eth_dst_new)

  {
  	struct ethhdr *ethhdr;
  
  	/* Copy skb header to change the mac header */

  	skb = pskb_copy_for_clone(skb, GFP_ATOMIC);

  	if (!skb)
  		return;
  
  	/* Set the mac header as if we actually sent the packet uncoded */

  	ethhdr = eth_hdr(skb);

  	ether_addr_copy(ethhdr->h_source, ethhdr->h_dest);
  	ether_addr_copy(ethhdr->h_dest, eth_dst_new);

  
  	/* Set data pointer to MAC header to mimic packets from our tx path */
  	skb_push(skb, ETH_HLEN);
  
  	/* Add the packet to the decoding packet pool */
  	batadv_nc_skb_store_for_decoding(bat_priv, skb);
  
  	/* batadv_nc_skb_store_for_decoding() clones the skb, so we must free
  	 * our ref
  	 */

  	consume_skb(skb);

  }
  
  /**

   * batadv_nc_skb_dst_search - Loops through list of neighboring nodes to dst.
   * @skb: data skb to forward
   * @neigh_node: next hop to forward packet to
   * @ethhdr: pointer to the ethernet header inside the skb
   *
   * Loops through list of neighboring nodes the next hop has a good connection to
   * (receives OGMs with a sufficient quality). We need to find a neighbor of our
   * next hop that potentially sent a packet which our next hop also received
   * (overheard) and has stored for later decoding.
   *

   * Return: true if the skb was consumed (encoded packet sent) or false otherwise

   */
  static bool batadv_nc_skb_dst_search(struct sk_buff *skb,
  				     struct batadv_neigh_node *neigh_node,
  				     struct ethhdr *ethhdr)
  {
  	struct net_device *netdev = neigh_node->if_incoming->soft_iface;
  	struct batadv_priv *bat_priv = netdev_priv(netdev);
  	struct batadv_orig_node *orig_node = neigh_node->orig_node;
  	struct batadv_nc_node *nc_node;
  	struct batadv_nc_packet *nc_packet = NULL;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(nc_node, &orig_node->in_coding_list, list) {
  		/* Search for coding opportunity with this in_nc_node */
  		nc_packet = batadv_nc_skb_src_search(bat_priv, skb,
  						     neigh_node->addr,
  						     ethhdr->h_source, nc_node);
  
  		/* Opportunity was found, so stop searching */
  		if (nc_packet)
  			break;
  	}
  	rcu_read_unlock();
  
  	if (!nc_packet)
  		return false;

  	/* Save packets for later decoding */
  	batadv_nc_skb_store_before_coding(bat_priv, skb,
  					  neigh_node->addr);
  	batadv_nc_skb_store_before_coding(bat_priv, nc_packet->skb,
  					  nc_packet->neigh_node->addr);

  	/* Code and send packets */
  	if (batadv_nc_code_packets(bat_priv, skb, ethhdr, nc_packet,
  				   neigh_node))
  		return true;
  
  	/* out of mem ? Coding failed - we have to free the buffered packet
  	 * to avoid memleaks. The skb passed as argument will be dealt with
  	 * by the calling function.
  	 */
  	batadv_nc_send_packet(nc_packet);
  	return false;
  }
  
  /**

   * 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
   *

   * Return: 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

   *

   * Return: 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)

  {
  	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;

  	struct ethhdr *ethhdr = eth_hdr(skb);

  	__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->packet_type != BATADV_UNICAST)

  		goto out;

  	/* Try to find a coding opportunity and send the skb if one is found */
  	if (batadv_nc_skb_dst_search(skb, neigh_node, ethhdr))
  		return true;

  	/* 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_put(nc_path);

  out:
  	/* Packet is not consumed */
  	return false;
  }
  
  /**

   * batadv_nc_skb_store_for_decoding - save a clone of the skb which can be used
   *  when decoding coded packets
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: data skb to store
   */
  void batadv_nc_skb_store_for_decoding(struct batadv_priv *bat_priv,
  				      struct sk_buff *skb)
  {
  	struct batadv_unicast_packet *packet;
  	struct batadv_nc_path *nc_path;

  	struct ethhdr *ethhdr = eth_hdr(skb);

  	__be32 packet_id;
  	u8 *payload;
  
  	/* Check if network coding is enabled */
  	if (!atomic_read(&bat_priv->network_coding))
  		goto out;
  
  	/* Check for supported packet type */
  	payload = skb_network_header(skb);
  	packet = (struct batadv_unicast_packet *)payload;

  	if (packet->packet_type != BATADV_UNICAST)

  		goto out;
  
  	/* Find existing nc_path or create a new */
  	nc_path = batadv_nc_get_path(bat_priv,
  				     bat_priv->nc.decoding_hash,
  				     ethhdr->h_source,
  				     ethhdr->h_dest);
  
  	if (!nc_path)
  		goto out;
  
  	/* Clone skb and adjust skb->data to point at batman header */
  	skb = skb_clone(skb, GFP_ATOMIC);
  	if (unlikely(!skb))
  		goto free_nc_path;
  
  	if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
  		goto free_skb;
  
  	if (unlikely(!skb_pull_rcsum(skb, ETH_HLEN)))
  		goto free_skb;
  
  	/* Add skb to nc_path */
  	packet_id = batadv_skb_crc32(skb, payload + sizeof(*packet));
  	if (!batadv_nc_skb_add_to_path(skb, nc_path, NULL, packet_id))
  		goto free_skb;
  
  	batadv_inc_counter(bat_priv, BATADV_CNT_NC_BUFFER);
  	return;
  
  free_skb:
  	kfree_skb(skb);
  free_nc_path:

  	batadv_nc_path_put(nc_path);

  out:
  	return;
  }
  
  /**
   * batadv_nc_skb_store_sniffed_unicast - check if a received unicast packet
   *  should be saved in the decoding buffer and, if so, store it there
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: unicast skb to store
   */
  void batadv_nc_skb_store_sniffed_unicast(struct batadv_priv *bat_priv,
  					 struct sk_buff *skb)
  {

  	struct ethhdr *ethhdr = eth_hdr(skb);

  	if (batadv_is_my_mac(bat_priv, ethhdr->h_dest))

  		return;
  
  	/* Set data pointer to MAC header to mimic packets from our tx path */
  	skb_push(skb, ETH_HLEN);
  
  	batadv_nc_skb_store_for_decoding(bat_priv, skb);
  }
  
  /**

   * batadv_nc_skb_decode_packet - decode given skb using the decode data stored
   *  in nc_packet

   * @bat_priv: the bat priv with all the soft interface information

   * @skb: unicast skb to decode
   * @nc_packet: decode data needed to decode the skb
   *

   * Return: pointer to decoded unicast packet if the packet was decoded or NULL

   * in case of an error.
   */
  static struct batadv_unicast_packet *

  batadv_nc_skb_decode_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,

  			    struct batadv_nc_packet *nc_packet)
  {
  	const int h_size = sizeof(struct batadv_unicast_packet);
  	const int h_diff = sizeof(struct batadv_coded_packet) - h_size;
  	struct batadv_unicast_packet *unicast_packet;
  	struct batadv_coded_packet coded_packet_tmp;
  	struct ethhdr *ethhdr, ethhdr_tmp;

  	u8 *orig_dest, ttl, ttvn;

  	unsigned int coding_len;

  	int err;

  
  	/* Save headers temporarily */
  	memcpy(&coded_packet_tmp, skb->data, sizeof(coded_packet_tmp));
  	memcpy(&ethhdr_tmp, skb_mac_header(skb), sizeof(ethhdr_tmp));
  
  	if (skb_cow(skb, 0) < 0)
  		return NULL;
  
  	if (unlikely(!skb_pull_rcsum(skb, h_diff)))
  		return NULL;
  
  	/* Data points to batman header, so set mac header 14 bytes before
  	 * and network to data
  	 */
  	skb_set_mac_header(skb, -ETH_HLEN);
  	skb_reset_network_header(skb);
  
  	/* Reconstruct original mac header */

  	ethhdr = eth_hdr(skb);

  	*ethhdr = ethhdr_tmp;

  
  	/* Select the correct unicast header information based on the location
  	 * of our mac address in the coded_packet header
  	 */

  	if (batadv_is_my_mac(bat_priv, coded_packet_tmp.second_dest)) {

  		/* If we are the second destination the packet was overheard,
  		 * so the Ethernet address must be copied to h_dest and
  		 * pkt_type changed from PACKET_OTHERHOST to PACKET_HOST
  		 */

  		ether_addr_copy(ethhdr->h_dest, coded_packet_tmp.second_dest);

  		skb->pkt_type = PACKET_HOST;
  
  		orig_dest = coded_packet_tmp.second_orig_dest;
  		ttl = coded_packet_tmp.second_ttl;
  		ttvn = coded_packet_tmp.second_ttvn;
  	} else {
  		orig_dest = coded_packet_tmp.first_orig_dest;

  		ttl = coded_packet_tmp.ttl;

  		ttvn = coded_packet_tmp.first_ttvn;
  	}
  
  	coding_len = ntohs(coded_packet_tmp.coded_len);
  
  	if (coding_len > skb->len)
  		return NULL;
  
  	/* Here the magic is reversed:
  	 *   extract the missing packet from the received coded packet
  	 */
  	batadv_nc_memxor(skb->data + h_size,
  			 nc_packet->skb->data + h_size,
  			 coding_len);
  
  	/* Resize decoded skb if decoded with larger packet */

  	if (nc_packet->skb->len > coding_len + h_size) {
  		err = pskb_trim_rcsum(skb, coding_len + h_size);
  		if (err)
  			return NULL;
  	}

  
  	/* Create decoded unicast packet */
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;

  	unicast_packet->packet_type = BATADV_UNICAST;
  	unicast_packet->version = BATADV_COMPAT_VERSION;
  	unicast_packet->ttl = ttl;

  	ether_addr_copy(unicast_packet->dest, orig_dest);

  	unicast_packet->ttvn = ttvn;

  	batadv_nc_packet_free(nc_packet, false);

  	return unicast_packet;
  }
  
  /**
   * batadv_nc_find_decoding_packet - search through buffered decoding data to
   *  find the data needed to decode the coded packet
   * @bat_priv: the bat priv with all the soft interface information
   * @ethhdr: pointer to the ethernet header inside the coded packet
   * @coded: coded packet we try to find decode data for
   *

   * Return: pointer to nc packet if the needed data was found or NULL otherwise.

   */
  static struct batadv_nc_packet *
  batadv_nc_find_decoding_packet(struct batadv_priv *bat_priv,
  			       struct ethhdr *ethhdr,
  			       struct batadv_coded_packet *coded)
  {
  	struct batadv_hashtable *hash = bat_priv->nc.decoding_hash;
  	struct batadv_nc_packet *tmp_nc_packet, *nc_packet = NULL;
  	struct batadv_nc_path *nc_path, nc_path_key;

  	u8 *dest, *source;

  	__be32 packet_id;
  	int index;
  
  	if (!hash)
  		return NULL;
  
  	/* Select the correct packet id based on the location of our mac-addr */
  	dest = ethhdr->h_source;

  	if (!batadv_is_my_mac(bat_priv, coded->second_dest)) {

  		source = coded->second_source;
  		packet_id = coded->second_crc;
  	} else {
  		source = coded->first_source;
  		packet_id = coded->first_crc;
  	}
  
  	batadv_nc_hash_key_gen(&nc_path_key, source, dest);
  	index = batadv_nc_hash_choose(&nc_path_key, hash->size);
  
  	/* Search for matching coding path */
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(nc_path, &hash->table[index], hash_entry) {
  		/* Find matching nc_packet */
  		spin_lock_bh(&nc_path->packet_list_lock);
  		list_for_each_entry(tmp_nc_packet,
  				    &nc_path->packet_list, list) {
  			if (packet_id == tmp_nc_packet->packet_id) {
  				list_del(&tmp_nc_packet->list);
  
  				nc_packet = tmp_nc_packet;
  				break;
  			}
  		}
  		spin_unlock_bh(&nc_path->packet_list_lock);
  
  		if (nc_packet)
  			break;
  	}
  	rcu_read_unlock();
  
  	if (!nc_packet)
  		batadv_dbg(BATADV_DBG_NC, bat_priv,
  			   "No decoding packet found for %u
  ", packet_id);
  
  	return nc_packet;
  }
  
  /**
   * batadv_nc_recv_coded_packet - try to decode coded packet and enqueue the
   *  resulting unicast packet
   * @skb: incoming coded packet
   * @recv_if: pointer to interface this packet was received on

   *
   * Return: NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
   * otherwise.

   */
  static int batadv_nc_recv_coded_packet(struct sk_buff *skb,
  				       struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_unicast_packet *unicast_packet;
  	struct batadv_coded_packet *coded_packet;
  	struct batadv_nc_packet *nc_packet;
  	struct ethhdr *ethhdr;
  	int hdr_size = sizeof(*coded_packet);
  
  	/* Check if network coding is enabled */
  	if (!atomic_read(&bat_priv->network_coding))

  		goto free_skb;

  
  	/* Make sure we can access (and remove) header */
  	if (unlikely(!pskb_may_pull(skb, hdr_size)))

  		goto free_skb;

  
  	coded_packet = (struct batadv_coded_packet *)skb->data;

  	ethhdr = eth_hdr(skb);

  
  	/* Verify frame is destined for us */

  	if (!batadv_is_my_mac(bat_priv, ethhdr->h_dest) &&
  	    !batadv_is_my_mac(bat_priv, coded_packet->second_dest))

  		goto free_skb;

  
  	/* Update stat counter */

  	if (batadv_is_my_mac(bat_priv, coded_packet->second_dest))

  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_SNIFFED);
  
  	nc_packet = batadv_nc_find_decoding_packet(bat_priv, ethhdr,
  						   coded_packet);
  	if (!nc_packet) {
  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_DECODE_FAILED);

  		goto free_skb;

  	}
  
  	/* Make skb's linear, because decoding accesses the entire buffer */
  	if (skb_linearize(skb) < 0)
  		goto free_nc_packet;
  
  	if (skb_linearize(nc_packet->skb) < 0)
  		goto free_nc_packet;
  
  	/* Decode the packet */

  	unicast_packet = batadv_nc_skb_decode_packet(bat_priv, skb, nc_packet);

  	if (!unicast_packet) {
  		batadv_inc_counter(bat_priv, BATADV_CNT_NC_DECODE_FAILED);
  		goto free_nc_packet;
  	}
  
  	/* Mark packet as decoded to do correct recoding when forwarding */
  	BATADV_SKB_CB(skb)->decoded = true;
  	batadv_inc_counter(bat_priv, BATADV_CNT_NC_DECODE);
  	batadv_add_counter(bat_priv, BATADV_CNT_NC_DECODE_BYTES,
  			   skb->len + ETH_HLEN);
  	return batadv_recv_unicast_packet(skb, recv_if);
  
  free_nc_packet:

  	batadv_nc_packet_free(nc_packet, true);

  free_skb:
  	kfree_skb(skb);

  	return NET_RX_DROP;
  }
  
  /**

   * batadv_nc_mesh_free - clean up network coding memory

   * @bat_priv: the bat priv with all the soft interface information
   */

  void batadv_nc_mesh_free(struct batadv_priv *bat_priv)

  {

  	batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_NC, 1);
  	batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_NC, 1);

  	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_purge_paths(bat_priv, bat_priv->nc.decoding_hash, NULL);
  	batadv_hash_destroy(bat_priv->nc.decoding_hash);

  }

  #ifdef CONFIG_BATMAN_ADV_DEBUGFS

  /**
   * batadv_nc_nodes_seq_print_text - print the nc node information
   * @seq: seq file to print on
   * @offset: not used

   *
   * Return: always 0

   */
  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) {

  			/* no need to print the orig node if it does not have
  			 * network coding neighbors
  			 */
  			if (list_empty(&orig_node->in_coding_list) &&
  			    list_empty(&orig_node->out_coding_list))
  				continue;

  			seq_printf(seq, "Node:      %pM
  ", orig_node->orig);

  			seq_puts(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_puts(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_puts(seq, "
  
  ");

  		}
  		rcu_read_unlock();
  	}
  
  out:
  	if (primary_if)

  		batadv_hardif_put(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

   *
   * Return: 0 on success or negative error number in case of failure

   */
  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", 0644, nc_dir, &bat_priv->nc.min_tq);

  	if (!file)
  		goto out;

  	file = debugfs_create_u32("max_fwd_delay", 0644, nc_dir,

  				  &bat_priv->nc.max_fwd_delay);
  	if (!file)
  		goto out;

  	file = debugfs_create_u32("max_buffer_time", 0644, nc_dir,

  				  &bat_priv->nc.max_buffer_time);
  	if (!file)
  		goto out;

  	return 0;
  
  out:
  	return -ENOMEM;
  }

  #endif