OSCL-LXR linux-6.0.1/​net/​batman-adv/​network-coding.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (C) B.A.T.M.A.N. contributors:
  *
  * Martin Hundebøll, Jeppe Ledet-Pedersen
  */
 
 #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/container_of.h>
 #include <linux/errno.h>
 #include <linux/etherdevice.h>
 #include <linux/gfp.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/kref.h>
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/net.h>
 #include <linux/netdevice.h>
 #include <linux/prandom.h>
 #include <linux/printk.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.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 <uapi/linux/batadv_packet.h>
 
 #include "hash.h"
 #include "log.h"
 #include "originator.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)
 {
     /* Register our packet type */
     return batadv_recv_handler_register(BATADV_CODED,
                         batadv_nc_recv_coded_packet);
 }
 
 /**
  * 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 housekeeping
  * @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) {
         batadv_hash_destroy(bat_priv->nc.coding_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)
 {
     if (!nc_node)
         return;
 
     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)
 {
     if (!nc_path)
         return;
 
     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 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\n",
                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)!\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_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 housekeeping 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\n",
            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:
     batadv_nc_node_put(in_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\n",
            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)
 {
     /* randomize the estimated packet loss (max TQ - estimated TQ) */
     u8 rand_tq = prandom_u32_max(BATADV_TQ_MAX_VALUE + 1 - tq);
 
     /* 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:
     batadv_neigh_node_put(router_neigh);
     batadv_neigh_node_put(router_coding);
     batadv_neigh_ifinfo_put(router_neigh_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 neighboring 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 the 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\n", 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);
 }

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