1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) B.A.T.M.A.N. contributors:
3  *
4  * Martin Hundebøll, Jeppe Ledet-Pedersen
5  */
6 
7 #include "network-coding.h"
8 #include "main.h"
9 
10 #include <linux/atomic.h>
11 #include <linux/bitops.h>
12 #include <linux/byteorder/generic.h>
13 #include <linux/compiler.h>
14 #include <linux/errno.h>
15 #include <linux/etherdevice.h>
16 #include <linux/gfp.h>
17 #include <linux/if_ether.h>
18 #include <linux/if_packet.h>
19 #include <linux/init.h>
20 #include <linux/jhash.h>
21 #include <linux/jiffies.h>
22 #include <linux/kernel.h>
23 #include <linux/kref.h>
24 #include <linux/list.h>
25 #include <linux/lockdep.h>
26 #include <linux/net.h>
27 #include <linux/netdevice.h>
28 #include <linux/prandom.h>
29 #include <linux/printk.h>
30 #include <linux/rculist.h>
31 #include <linux/rcupdate.h>
32 #include <linux/skbuff.h>
33 #include <linux/slab.h>
34 #include <linux/spinlock.h>
35 #include <linux/stddef.h>
36 #include <linux/string.h>
37 #include <linux/workqueue.h>
38 #include <uapi/linux/batadv_packet.h>
39 
40 #include "hash.h"
41 #include "log.h"
42 #include "originator.h"
43 #include "routing.h"
44 #include "send.h"
45 #include "tvlv.h"
46 
47 static struct lock_class_key batadv_nc_coding_hash_lock_class_key;
48 static struct lock_class_key batadv_nc_decoding_hash_lock_class_key;
49 
50 static void batadv_nc_worker(struct work_struct *work);
51 static int batadv_nc_recv_coded_packet(struct sk_buff *skb,
52 				       struct batadv_hard_iface *recv_if);
53 
54 /**
55  * batadv_nc_init() - one-time initialization for network coding
56  *
57  * Return: 0 on success or negative error number in case of failure
58  */
59 int __init batadv_nc_init(void)
60 {
61 	/* Register our packet type */
62 	return batadv_recv_handler_register(BATADV_CODED,
63 					    batadv_nc_recv_coded_packet);
64 }
65 
66 /**
67  * batadv_nc_start_timer() - initialise the nc periodic worker
68  * @bat_priv: the bat priv with all the soft interface information
69  */
70 static void batadv_nc_start_timer(struct batadv_priv *bat_priv)
71 {
72 	queue_delayed_work(batadv_event_workqueue, &bat_priv->nc.work,
73 			   msecs_to_jiffies(10));
74 }
75 
76 /**
77  * batadv_nc_tvlv_container_update() - update the network coding tvlv container
78  *  after network coding setting change
79  * @bat_priv: the bat priv with all the soft interface information
80  */
81 static void batadv_nc_tvlv_container_update(struct batadv_priv *bat_priv)
82 {
83 	char nc_mode;
84 
85 	nc_mode = atomic_read(&bat_priv->network_coding);
86 
87 	switch (nc_mode) {
88 	case 0:
89 		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_NC, 1);
90 		break;
91 	case 1:
92 		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_NC, 1,
93 					       NULL, 0);
94 		break;
95 	}
96 }
97 
98 /**
99  * batadv_nc_status_update() - update the network coding tvlv container after
100  *  network coding setting change
101  * @net_dev: the soft interface net device
102  */
103 void batadv_nc_status_update(struct net_device *net_dev)
104 {
105 	struct batadv_priv *bat_priv = netdev_priv(net_dev);
106 
107 	batadv_nc_tvlv_container_update(bat_priv);
108 }
109 
110 /**
111  * batadv_nc_tvlv_ogm_handler_v1() - process incoming nc tvlv container
112  * @bat_priv: the bat priv with all the soft interface information
113  * @orig: the orig_node of the ogm
114  * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
115  * @tvlv_value: tvlv buffer containing the gateway data
116  * @tvlv_value_len: tvlv buffer length
117  */
118 static void batadv_nc_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
119 					  struct batadv_orig_node *orig,
120 					  u8 flags,
121 					  void *tvlv_value, u16 tvlv_value_len)
122 {
123 	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)
124 		clear_bit(BATADV_ORIG_CAPA_HAS_NC, &orig->capabilities);
125 	else
126 		set_bit(BATADV_ORIG_CAPA_HAS_NC, &orig->capabilities);
127 }
128 
129 /**
130  * batadv_nc_mesh_init() - initialise coding hash table and start housekeeping
131  * @bat_priv: the bat priv with all the soft interface information
132  *
133  * Return: 0 on success or negative error number in case of failure
134  */
135 int batadv_nc_mesh_init(struct batadv_priv *bat_priv)
136 {
137 	bat_priv->nc.timestamp_fwd_flush = jiffies;
138 	bat_priv->nc.timestamp_sniffed_purge = jiffies;
139 
140 	if (bat_priv->nc.coding_hash || bat_priv->nc.decoding_hash)
141 		return 0;
142 
143 	bat_priv->nc.coding_hash = batadv_hash_new(128);
144 	if (!bat_priv->nc.coding_hash)
145 		goto err;
146 
147 	batadv_hash_set_lock_class(bat_priv->nc.coding_hash,
148 				   &batadv_nc_coding_hash_lock_class_key);
149 
150 	bat_priv->nc.decoding_hash = batadv_hash_new(128);
151 	if (!bat_priv->nc.decoding_hash) {
152 		batadv_hash_destroy(bat_priv->nc.coding_hash);
153 		goto err;
154 	}
155 
156 	batadv_hash_set_lock_class(bat_priv->nc.decoding_hash,
157 				   &batadv_nc_decoding_hash_lock_class_key);
158 
159 	INIT_DELAYED_WORK(&bat_priv->nc.work, batadv_nc_worker);
160 	batadv_nc_start_timer(bat_priv);
161 
162 	batadv_tvlv_handler_register(bat_priv, batadv_nc_tvlv_ogm_handler_v1,
163 				     NULL, BATADV_TVLV_NC, 1,
164 				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
165 	batadv_nc_tvlv_container_update(bat_priv);
166 	return 0;
167 
168 err:
169 	return -ENOMEM;
170 }
171 
172 /**
173  * batadv_nc_init_bat_priv() - initialise the nc specific bat_priv variables
174  * @bat_priv: the bat priv with all the soft interface information
175  */
176 void batadv_nc_init_bat_priv(struct batadv_priv *bat_priv)
177 {
178 	atomic_set(&bat_priv->network_coding, 0);
179 	bat_priv->nc.min_tq = 200;
180 	bat_priv->nc.max_fwd_delay = 10;
181 	bat_priv->nc.max_buffer_time = 200;
182 }
183 
184 /**
185  * batadv_nc_init_orig() - initialise the nc fields of an orig_node
186  * @orig_node: the orig_node which is going to be initialised
187  */
188 void batadv_nc_init_orig(struct batadv_orig_node *orig_node)
189 {
190 	INIT_LIST_HEAD(&orig_node->in_coding_list);
191 	INIT_LIST_HEAD(&orig_node->out_coding_list);
192 	spin_lock_init(&orig_node->in_coding_list_lock);
193 	spin_lock_init(&orig_node->out_coding_list_lock);
194 }
195 
196 /**
197  * batadv_nc_node_release() - release nc_node from lists and queue for free
198  *  after rcu grace period
199  * @ref: kref pointer of the nc_node
200  */
201 static void batadv_nc_node_release(struct kref *ref)
202 {
203 	struct batadv_nc_node *nc_node;
204 
205 	nc_node = container_of(ref, struct batadv_nc_node, refcount);
206 
207 	batadv_orig_node_put(nc_node->orig_node);
208 	kfree_rcu(nc_node, rcu);
209 }
210 
211 /**
212  * batadv_nc_node_put() - decrement the nc_node refcounter and possibly
213  *  release it
214  * @nc_node: nc_node to be free'd
215  */
216 static void batadv_nc_node_put(struct batadv_nc_node *nc_node)
217 {
218 	if (!nc_node)
219 		return;
220 
221 	kref_put(&nc_node->refcount, batadv_nc_node_release);
222 }
223 
224 /**
225  * batadv_nc_path_release() - release nc_path from lists and queue for free
226  *  after rcu grace period
227  * @ref: kref pointer of the nc_path
228  */
229 static void batadv_nc_path_release(struct kref *ref)
230 {
231 	struct batadv_nc_path *nc_path;
232 
233 	nc_path = container_of(ref, struct batadv_nc_path, refcount);
234 
235 	kfree_rcu(nc_path, rcu);
236 }
237 
238 /**
239  * batadv_nc_path_put() - decrement the nc_path refcounter and possibly
240  *  release it
241  * @nc_path: nc_path to be free'd
242  */
243 static void batadv_nc_path_put(struct batadv_nc_path *nc_path)
244 {
245 	if (!nc_path)
246 		return;
247 
248 	kref_put(&nc_path->refcount, batadv_nc_path_release);
249 }
250 
251 /**
252  * batadv_nc_packet_free() - frees nc packet
253  * @nc_packet: the nc packet to free
254  * @dropped: whether the packet is freed because is dropped
255  */
256 static void batadv_nc_packet_free(struct batadv_nc_packet *nc_packet,
257 				  bool dropped)
258 {
259 	if (dropped)
260 		kfree_skb(nc_packet->skb);
261 	else
262 		consume_skb(nc_packet->skb);
263 
264 	batadv_nc_path_put(nc_packet->nc_path);
265 	kfree(nc_packet);
266 }
267 
268 /**
269  * batadv_nc_to_purge_nc_node() - checks whether an nc node has to be purged
270  * @bat_priv: the bat priv with all the soft interface information
271  * @nc_node: the nc node to check
272  *
273  * Return: true if the entry has to be purged now, false otherwise
274  */
275 static bool batadv_nc_to_purge_nc_node(struct batadv_priv *bat_priv,
276 				       struct batadv_nc_node *nc_node)
277 {
278 	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
279 		return true;
280 
281 	return batadv_has_timed_out(nc_node->last_seen, BATADV_NC_NODE_TIMEOUT);
282 }
283 
284 /**
285  * batadv_nc_to_purge_nc_path_coding() - checks whether an nc path has timed out
286  * @bat_priv: the bat priv with all the soft interface information
287  * @nc_path: the nc path to check
288  *
289  * Return: true if the entry has to be purged now, false otherwise
290  */
291 static bool batadv_nc_to_purge_nc_path_coding(struct batadv_priv *bat_priv,
292 					      struct batadv_nc_path *nc_path)
293 {
294 	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
295 		return true;
296 
297 	/* purge the path when no packets has been added for 10 times the
298 	 * max_fwd_delay time
299 	 */
300 	return batadv_has_timed_out(nc_path->last_valid,
301 				    bat_priv->nc.max_fwd_delay * 10);
302 }
303 
304 /**
305  * batadv_nc_to_purge_nc_path_decoding() - checks whether an nc path has timed
306  *  out
307  * @bat_priv: the bat priv with all the soft interface information
308  * @nc_path: the nc path to check
309  *
310  * Return: true if the entry has to be purged now, false otherwise
311  */
312 static bool batadv_nc_to_purge_nc_path_decoding(struct batadv_priv *bat_priv,
313 						struct batadv_nc_path *nc_path)
314 {
315 	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
316 		return true;
317 
318 	/* purge the path when no packets has been added for 10 times the
319 	 * max_buffer time
320 	 */
321 	return batadv_has_timed_out(nc_path->last_valid,
322 				    bat_priv->nc.max_buffer_time * 10);
323 }
324 
325 /**
326  * batadv_nc_purge_orig_nc_nodes() - go through list of nc nodes and purge stale
327  *  entries
328  * @bat_priv: the bat priv with all the soft interface information
329  * @list: list of nc nodes
330  * @lock: nc node list lock
331  * @to_purge: function in charge to decide whether an entry has to be purged or
332  *	      not. This function takes the nc node as argument and has to return
333  *	      a boolean value: true if the entry has to be deleted, false
334  *	      otherwise
335  */
336 static void
337 batadv_nc_purge_orig_nc_nodes(struct batadv_priv *bat_priv,
338 			      struct list_head *list,
339 			      spinlock_t *lock,
340 			      bool (*to_purge)(struct batadv_priv *,
341 					       struct batadv_nc_node *))
342 {
343 	struct batadv_nc_node *nc_node, *nc_node_tmp;
344 
345 	/* For each nc_node in list */
346 	spin_lock_bh(lock);
347 	list_for_each_entry_safe(nc_node, nc_node_tmp, list, list) {
348 		/* if an helper function has been passed as parameter,
349 		 * ask it if the entry has to be purged or not
350 		 */
351 		if (to_purge && !to_purge(bat_priv, nc_node))
352 			continue;
353 
354 		batadv_dbg(BATADV_DBG_NC, bat_priv,
355 			   "Removing nc_node %pM -> %pM\n",
356 			   nc_node->addr, nc_node->orig_node->orig);
357 		list_del_rcu(&nc_node->list);
358 		batadv_nc_node_put(nc_node);
359 	}
360 	spin_unlock_bh(lock);
361 }
362 
363 /**
364  * batadv_nc_purge_orig() - purges all nc node data attached of the given
365  *  originator
366  * @bat_priv: the bat priv with all the soft interface information
367  * @orig_node: orig_node with the nc node entries to be purged
368  * @to_purge: function in charge to decide whether an entry has to be purged or
369  *	      not. This function takes the nc node as argument and has to return
370  *	      a boolean value: true is the entry has to be deleted, false
371  *	      otherwise
372  */
373 void batadv_nc_purge_orig(struct batadv_priv *bat_priv,
374 			  struct batadv_orig_node *orig_node,
375 			  bool (*to_purge)(struct batadv_priv *,
376 					   struct batadv_nc_node *))
377 {
378 	/* Check ingoing nc_node's of this orig_node */
379 	batadv_nc_purge_orig_nc_nodes(bat_priv, &orig_node->in_coding_list,
380 				      &orig_node->in_coding_list_lock,
381 				      to_purge);
382 
383 	/* Check outgoing nc_node's of this orig_node */
384 	batadv_nc_purge_orig_nc_nodes(bat_priv, &orig_node->out_coding_list,
385 				      &orig_node->out_coding_list_lock,
386 				      to_purge);
387 }
388 
389 /**
390  * batadv_nc_purge_orig_hash() - traverse entire originator hash to check if
391  *  they have timed out nc nodes
392  * @bat_priv: the bat priv with all the soft interface information
393  */
394 static void batadv_nc_purge_orig_hash(struct batadv_priv *bat_priv)
395 {
396 	struct batadv_hashtable *hash = bat_priv->orig_hash;
397 	struct hlist_head *head;
398 	struct batadv_orig_node *orig_node;
399 	u32 i;
400 
401 	if (!hash)
402 		return;
403 
404 	/* For each orig_node */
405 	for (i = 0; i < hash->size; i++) {
406 		head = &hash->table[i];
407 
408 		rcu_read_lock();
409 		hlist_for_each_entry_rcu(orig_node, head, hash_entry)
410 			batadv_nc_purge_orig(bat_priv, orig_node,
411 					     batadv_nc_to_purge_nc_node);
412 		rcu_read_unlock();
413 	}
414 }
415 
416 /**
417  * batadv_nc_purge_paths() - traverse all nc paths part of the hash and remove
418  *  unused ones
419  * @bat_priv: the bat priv with all the soft interface information
420  * @hash: hash table containing the nc paths to check
421  * @to_purge: function in charge to decide whether an entry has to be purged or
422  *	      not. This function takes the nc node as argument and has to return
423  *	      a boolean value: true is the entry has to be deleted, false
424  *	      otherwise
425  */
426 static void batadv_nc_purge_paths(struct batadv_priv *bat_priv,
427 				  struct batadv_hashtable *hash,
428 				  bool (*to_purge)(struct batadv_priv *,
429 						   struct batadv_nc_path *))
430 {
431 	struct hlist_head *head;
432 	struct hlist_node *node_tmp;
433 	struct batadv_nc_path *nc_path;
434 	spinlock_t *lock; /* Protects lists in hash */
435 	u32 i;
436 
437 	for (i = 0; i < hash->size; i++) {
438 		head = &hash->table[i];
439 		lock = &hash->list_locks[i];
440 
441 		/* For each nc_path in this bin */
442 		spin_lock_bh(lock);
443 		hlist_for_each_entry_safe(nc_path, node_tmp, head, hash_entry) {
444 			/* if an helper function has been passed as parameter,
445 			 * ask it if the entry has to be purged or not
446 			 */
447 			if (to_purge && !to_purge(bat_priv, nc_path))
448 				continue;
449 
450 			/* purging an non-empty nc_path should never happen, but
451 			 * is observed under high CPU load. Delay the purging
452 			 * until next iteration to allow the packet_list to be
453 			 * emptied first.
454 			 */
455 			if (!unlikely(list_empty(&nc_path->packet_list))) {
456 				net_ratelimited_function(printk,
457 							 KERN_WARNING
458 							 "Skipping free of non-empty nc_path (%pM -> %pM)!\n",
459 							 nc_path->prev_hop,
460 							 nc_path->next_hop);
461 				continue;
462 			}
463 
464 			/* nc_path is unused, so remove it */
465 			batadv_dbg(BATADV_DBG_NC, bat_priv,
466 				   "Remove nc_path %pM -> %pM\n",
467 				   nc_path->prev_hop, nc_path->next_hop);
468 			hlist_del_rcu(&nc_path->hash_entry);
469 			batadv_nc_path_put(nc_path);
470 		}
471 		spin_unlock_bh(lock);
472 	}
473 }
474 
475 /**
476  * batadv_nc_hash_key_gen() - computes the nc_path hash key
477  * @key: buffer to hold the final hash key
478  * @src: source ethernet mac address going into the hash key
479  * @dst: destination ethernet mac address going into the hash key
480  */
481 static void batadv_nc_hash_key_gen(struct batadv_nc_path *key, const char *src,
482 				   const char *dst)
483 {
484 	memcpy(key->prev_hop, src, sizeof(key->prev_hop));
485 	memcpy(key->next_hop, dst, sizeof(key->next_hop));
486 }
487 
488 /**
489  * batadv_nc_hash_choose() - compute the hash value for an nc path
490  * @data: data to hash
491  * @size: size of the hash table
492  *
493  * Return: the selected index in the hash table for the given data.
494  */
495 static u32 batadv_nc_hash_choose(const void *data, u32 size)
496 {
497 	const struct batadv_nc_path *nc_path = data;
498 	u32 hash = 0;
499 
500 	hash = jhash(&nc_path->prev_hop, sizeof(nc_path->prev_hop), hash);
501 	hash = jhash(&nc_path->next_hop, sizeof(nc_path->next_hop), hash);
502 
503 	return hash % size;
504 }
505 
506 /**
507  * batadv_nc_hash_compare() - comparing function used in the network coding hash
508  *  tables
509  * @node: node in the local table
510  * @data2: second object to compare the node to
511  *
512  * Return: true if the two entry are the same, false otherwise
513  */
514 static bool batadv_nc_hash_compare(const struct hlist_node *node,
515 				   const void *data2)
516 {
517 	const struct batadv_nc_path *nc_path1, *nc_path2;
518 
519 	nc_path1 = container_of(node, struct batadv_nc_path, hash_entry);
520 	nc_path2 = data2;
521 
522 	/* Return 1 if the two keys are identical */
523 	if (!batadv_compare_eth(nc_path1->prev_hop, nc_path2->prev_hop))
524 		return false;
525 
526 	if (!batadv_compare_eth(nc_path1->next_hop, nc_path2->next_hop))
527 		return false;
528 
529 	return true;
530 }
531 
532 /**
533  * batadv_nc_hash_find() - search for an existing nc path and return it
534  * @hash: hash table containing the nc path
535  * @data: search key
536  *
537  * Return: the nc_path if found, NULL otherwise.
538  */
539 static struct batadv_nc_path *
540 batadv_nc_hash_find(struct batadv_hashtable *hash,
541 		    void *data)
542 {
543 	struct hlist_head *head;
544 	struct batadv_nc_path *nc_path, *nc_path_tmp = NULL;
545 	int index;
546 
547 	if (!hash)
548 		return NULL;
549 
550 	index = batadv_nc_hash_choose(data, hash->size);
551 	head = &hash->table[index];
552 
553 	rcu_read_lock();
554 	hlist_for_each_entry_rcu(nc_path, head, hash_entry) {
555 		if (!batadv_nc_hash_compare(&nc_path->hash_entry, data))
556 			continue;
557 
558 		if (!kref_get_unless_zero(&nc_path->refcount))
559 			continue;
560 
561 		nc_path_tmp = nc_path;
562 		break;
563 	}
564 	rcu_read_unlock();
565 
566 	return nc_path_tmp;
567 }
568 
569 /**
570  * batadv_nc_send_packet() - send non-coded packet and free nc_packet struct
571  * @nc_packet: the nc packet to send
572  */
573 static void batadv_nc_send_packet(struct batadv_nc_packet *nc_packet)
574 {
575 	batadv_send_unicast_skb(nc_packet->skb, nc_packet->neigh_node);
576 	nc_packet->skb = NULL;
577 	batadv_nc_packet_free(nc_packet, false);
578 }
579 
580 /**
581  * batadv_nc_sniffed_purge() - Checks timestamp of given sniffed nc_packet.
582  * @bat_priv: the bat priv with all the soft interface information
583  * @nc_path: the nc path the packet belongs to
584  * @nc_packet: the nc packet to be checked
585  *
586  * Checks whether the given sniffed (overheard) nc_packet has hit its buffering
587  * timeout. If so, the packet is no longer kept and the entry deleted from the
588  * queue. Has to be called with the appropriate locks.
589  *
590  * Return: false as soon as the entry in the fifo queue has not been timed out
591  * yet and true otherwise.
592  */
593 static bool batadv_nc_sniffed_purge(struct batadv_priv *bat_priv,
594 				    struct batadv_nc_path *nc_path,
595 				    struct batadv_nc_packet *nc_packet)
596 {
597 	unsigned long timeout = bat_priv->nc.max_buffer_time;
598 	bool res = false;
599 
600 	lockdep_assert_held(&nc_path->packet_list_lock);
601 
602 	/* Packets are added to tail, so the remaining packets did not time
603 	 * out and we can stop processing the current queue
604 	 */
605 	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_ACTIVE &&
606 	    !batadv_has_timed_out(nc_packet->timestamp, timeout))
607 		goto out;
608 
609 	/* purge nc packet */
610 	list_del(&nc_packet->list);
611 	batadv_nc_packet_free(nc_packet, true);
612 
613 	res = true;
614 
615 out:
616 	return res;
617 }
618 
619 /**
620  * batadv_nc_fwd_flush() - Checks the timestamp of the given nc packet.
621  * @bat_priv: the bat priv with all the soft interface information
622  * @nc_path: the nc path the packet belongs to
623  * @nc_packet: the nc packet to be checked
624  *
625  * Checks whether the given nc packet has hit its forward timeout. If so, the
626  * packet is no longer delayed, immediately sent and the entry deleted from the
627  * queue. Has to be called with the appropriate locks.
628  *
629  * Return: false as soon as the entry in the fifo queue has not been timed out
630  * yet and true otherwise.
631  */
632 static bool batadv_nc_fwd_flush(struct batadv_priv *bat_priv,
633 				struct batadv_nc_path *nc_path,
634 				struct batadv_nc_packet *nc_packet)
635 {
636 	unsigned long timeout = bat_priv->nc.max_fwd_delay;
637 
638 	lockdep_assert_held(&nc_path->packet_list_lock);
639 
640 	/* Packets are added to tail, so the remaining packets did not time
641 	 * out and we can stop processing the current queue
642 	 */
643 	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_ACTIVE &&
644 	    !batadv_has_timed_out(nc_packet->timestamp, timeout))
645 		return false;
646 
647 	/* Send packet */
648 	batadv_inc_counter(bat_priv, BATADV_CNT_FORWARD);
649 	batadv_add_counter(bat_priv, BATADV_CNT_FORWARD_BYTES,
650 			   nc_packet->skb->len + ETH_HLEN);
651 	list_del(&nc_packet->list);
652 	batadv_nc_send_packet(nc_packet);
653 
654 	return true;
655 }
656 
657 /**
658  * batadv_nc_process_nc_paths() - traverse given nc packet pool and free timed
659  *  out nc packets
660  * @bat_priv: the bat priv with all the soft interface information
661  * @hash: to be processed hash table
662  * @process_fn: Function called to process given nc packet. Should return true
663  *	        to encourage this function to proceed with the next packet.
664  *	        Otherwise the rest of the current queue is skipped.
665  */
666 static void
667 batadv_nc_process_nc_paths(struct batadv_priv *bat_priv,
668 			   struct batadv_hashtable *hash,
669 			   bool (*process_fn)(struct batadv_priv *,
670 					      struct batadv_nc_path *,
671 					      struct batadv_nc_packet *))
672 {
673 	struct hlist_head *head;
674 	struct batadv_nc_packet *nc_packet, *nc_packet_tmp;
675 	struct batadv_nc_path *nc_path;
676 	bool ret;
677 	int i;
678 
679 	if (!hash)
680 		return;
681 
682 	/* Loop hash table bins */
683 	for (i = 0; i < hash->size; i++) {
684 		head = &hash->table[i];
685 
686 		/* Loop coding paths */
687 		rcu_read_lock();
688 		hlist_for_each_entry_rcu(nc_path, head, hash_entry) {
689 			/* Loop packets */
690 			spin_lock_bh(&nc_path->packet_list_lock);
691 			list_for_each_entry_safe(nc_packet, nc_packet_tmp,
692 						 &nc_path->packet_list, list) {
693 				ret = process_fn(bat_priv, nc_path, nc_packet);
694 				if (!ret)
695 					break;
696 			}
697 			spin_unlock_bh(&nc_path->packet_list_lock);
698 		}
699 		rcu_read_unlock();
700 	}
701 }
702 
703 /**
704  * batadv_nc_worker() - periodic task for housekeeping related to network
705  *  coding
706  * @work: kernel work struct
707  */
708 static void batadv_nc_worker(struct work_struct *work)
709 {
710 	struct delayed_work *delayed_work;
711 	struct batadv_priv_nc *priv_nc;
712 	struct batadv_priv *bat_priv;
713 	unsigned long timeout;
714 
715 	delayed_work = to_delayed_work(work);
716 	priv_nc = container_of(delayed_work, struct batadv_priv_nc, work);
717 	bat_priv = container_of(priv_nc, struct batadv_priv, nc);
718 
719 	batadv_nc_purge_orig_hash(bat_priv);
720 	batadv_nc_purge_paths(bat_priv, bat_priv->nc.coding_hash,
721 			      batadv_nc_to_purge_nc_path_coding);
722 	batadv_nc_purge_paths(bat_priv, bat_priv->nc.decoding_hash,
723 			      batadv_nc_to_purge_nc_path_decoding);
724 
725 	timeout = bat_priv->nc.max_fwd_delay;
726 
727 	if (batadv_has_timed_out(bat_priv->nc.timestamp_fwd_flush, timeout)) {
728 		batadv_nc_process_nc_paths(bat_priv, bat_priv->nc.coding_hash,
729 					   batadv_nc_fwd_flush);
730 		bat_priv->nc.timestamp_fwd_flush = jiffies;
731 	}
732 
733 	if (batadv_has_timed_out(bat_priv->nc.timestamp_sniffed_purge,
734 				 bat_priv->nc.max_buffer_time)) {
735 		batadv_nc_process_nc_paths(bat_priv, bat_priv->nc.decoding_hash,
736 					   batadv_nc_sniffed_purge);
737 		bat_priv->nc.timestamp_sniffed_purge = jiffies;
738 	}
739 
740 	/* Schedule a new check */
741 	batadv_nc_start_timer(bat_priv);
742 }
743 
744 /**
745  * batadv_can_nc_with_orig() - checks whether the given orig node is suitable
746  *  for coding or not
747  * @bat_priv: the bat priv with all the soft interface information
748  * @orig_node: neighboring orig node which may be used as nc candidate
749  * @ogm_packet: incoming ogm packet also used for the checks
750  *
751  * Return: true if:
752  *  1) The OGM must have the most recent sequence number.
753  *  2) The TTL must be decremented by one and only one.
754  *  3) The OGM must be received from the first hop from orig_node.
755  *  4) The TQ value of the OGM must be above bat_priv->nc.min_tq.
756  */
757 static bool batadv_can_nc_with_orig(struct batadv_priv *bat_priv,
758 				    struct batadv_orig_node *orig_node,
759 				    struct batadv_ogm_packet *ogm_packet)
760 {
761 	struct batadv_orig_ifinfo *orig_ifinfo;
762 	u32 last_real_seqno;
763 	u8 last_ttl;
764 
765 	orig_ifinfo = batadv_orig_ifinfo_get(orig_node, BATADV_IF_DEFAULT);
766 	if (!orig_ifinfo)
767 		return false;
768 
769 	last_ttl = orig_ifinfo->last_ttl;
770 	last_real_seqno = orig_ifinfo->last_real_seqno;
771 	batadv_orig_ifinfo_put(orig_ifinfo);
772 
773 	if (last_real_seqno != ntohl(ogm_packet->seqno))
774 		return false;
775 	if (last_ttl != ogm_packet->ttl + 1)
776 		return false;
777 	if (!batadv_compare_eth(ogm_packet->orig, ogm_packet->prev_sender))
778 		return false;
779 	if (ogm_packet->tq < bat_priv->nc.min_tq)
780 		return false;
781 
782 	return true;
783 }
784 
785 /**
786  * batadv_nc_find_nc_node() - search for an existing nc node and return it
787  * @orig_node: orig node originating the ogm packet
788  * @orig_neigh_node: neighboring orig node from which we received the ogm packet
789  *  (can be equal to orig_node)
790  * @in_coding: traverse incoming or outgoing network coding list
791  *
792  * Return: the nc_node if found, NULL otherwise.
793  */
794 static struct batadv_nc_node *
795 batadv_nc_find_nc_node(struct batadv_orig_node *orig_node,
796 		       struct batadv_orig_node *orig_neigh_node,
797 		       bool in_coding)
798 {
799 	struct batadv_nc_node *nc_node, *nc_node_out = NULL;
800 	struct list_head *list;
801 
802 	if (in_coding)
803 		list = &orig_neigh_node->in_coding_list;
804 	else
805 		list = &orig_neigh_node->out_coding_list;
806 
807 	/* Traverse list of nc_nodes to orig_node */
808 	rcu_read_lock();
809 	list_for_each_entry_rcu(nc_node, list, list) {
810 		if (!batadv_compare_eth(nc_node->addr, orig_node->orig))
811 			continue;
812 
813 		if (!kref_get_unless_zero(&nc_node->refcount))
814 			continue;
815 
816 		/* Found a match */
817 		nc_node_out = nc_node;
818 		break;
819 	}
820 	rcu_read_unlock();
821 
822 	return nc_node_out;
823 }
824 
825 /**
826  * batadv_nc_get_nc_node() - retrieves an nc node or creates the entry if it was
827  *  not found
828  * @bat_priv: the bat priv with all the soft interface information
829  * @orig_node: orig node originating the ogm packet
830  * @orig_neigh_node: neighboring orig node from which we received the ogm packet
831  *  (can be equal to orig_node)
832  * @in_coding: traverse incoming or outgoing network coding list
833  *
834  * Return: the nc_node if found or created, NULL in case of an error.
835  */
836 static struct batadv_nc_node *
837 batadv_nc_get_nc_node(struct batadv_priv *bat_priv,
838 		      struct batadv_orig_node *orig_node,
839 		      struct batadv_orig_node *orig_neigh_node,
840 		      bool in_coding)
841 {
842 	struct batadv_nc_node *nc_node;
843 	spinlock_t *lock; /* Used to lock list selected by "int in_coding" */
844 	struct list_head *list;
845 
846 	/* Select ingoing or outgoing coding node */
847 	if (in_coding) {
848 		lock = &orig_neigh_node->in_coding_list_lock;
849 		list = &orig_neigh_node->in_coding_list;
850 	} else {
851 		lock = &orig_neigh_node->out_coding_list_lock;
852 		list = &orig_neigh_node->out_coding_list;
853 	}
854 
855 	spin_lock_bh(lock);
856 
857 	/* Check if nc_node is already added */
858 	nc_node = batadv_nc_find_nc_node(orig_node, orig_neigh_node, in_coding);
859 
860 	/* Node found */
861 	if (nc_node)
862 		goto unlock;
863 
864 	nc_node = kzalloc(sizeof(*nc_node), GFP_ATOMIC);
865 	if (!nc_node)
866 		goto unlock;
867 
868 	/* Initialize nc_node */
869 	INIT_LIST_HEAD(&nc_node->list);
870 	kref_init(&nc_node->refcount);
871 	ether_addr_copy(nc_node->addr, orig_node->orig);
872 	kref_get(&orig_neigh_node->refcount);
873 	nc_node->orig_node = orig_neigh_node;
874 
875 	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_node %pM -> %pM\n",
876 		   nc_node->addr, nc_node->orig_node->orig);
877 
878 	/* Add nc_node to orig_node */
879 	kref_get(&nc_node->refcount);
880 	list_add_tail_rcu(&nc_node->list, list);
881 
882 unlock:
883 	spin_unlock_bh(lock);
884 
885 	return nc_node;
886 }
887 
888 /**
889  * batadv_nc_update_nc_node() - updates stored incoming and outgoing nc node
890  *  structs (best called on incoming OGMs)
891  * @bat_priv: the bat priv with all the soft interface information
892  * @orig_node: orig node originating the ogm packet
893  * @orig_neigh_node: neighboring orig node from which we received the ogm packet
894  *  (can be equal to orig_node)
895  * @ogm_packet: incoming ogm packet
896  * @is_single_hop_neigh: orig_node is a single hop neighbor
897  */
898 void batadv_nc_update_nc_node(struct batadv_priv *bat_priv,
899 			      struct batadv_orig_node *orig_node,
900 			      struct batadv_orig_node *orig_neigh_node,
901 			      struct batadv_ogm_packet *ogm_packet,
902 			      int is_single_hop_neigh)
903 {
904 	struct batadv_nc_node *in_nc_node = NULL;
905 	struct batadv_nc_node *out_nc_node = NULL;
906 
907 	/* Check if network coding is enabled */
908 	if (!atomic_read(&bat_priv->network_coding))
909 		goto out;
910 
911 	/* check if orig node is network coding enabled */
912 	if (!test_bit(BATADV_ORIG_CAPA_HAS_NC, &orig_node->capabilities))
913 		goto out;
914 
915 	/* accept ogms from 'good' neighbors and single hop neighbors */
916 	if (!batadv_can_nc_with_orig(bat_priv, orig_node, ogm_packet) &&
917 	    !is_single_hop_neigh)
918 		goto out;
919 
920 	/* Add orig_node as in_nc_node on hop */
921 	in_nc_node = batadv_nc_get_nc_node(bat_priv, orig_node,
922 					   orig_neigh_node, true);
923 	if (!in_nc_node)
924 		goto out;
925 
926 	in_nc_node->last_seen = jiffies;
927 
928 	/* Add hop as out_nc_node on orig_node */
929 	out_nc_node = batadv_nc_get_nc_node(bat_priv, orig_neigh_node,
930 					    orig_node, false);
931 	if (!out_nc_node)
932 		goto out;
933 
934 	out_nc_node->last_seen = jiffies;
935 
936 out:
937 	batadv_nc_node_put(in_nc_node);
938 	batadv_nc_node_put(out_nc_node);
939 }
940 
941 /**
942  * batadv_nc_get_path() - get existing nc_path or allocate a new one
943  * @bat_priv: the bat priv with all the soft interface information
944  * @hash: hash table containing the nc path
945  * @src: ethernet source address - first half of the nc path search key
946  * @dst: ethernet destination address - second half of the nc path search key
947  *
948  * Return: pointer to nc_path if the path was found or created, returns NULL
949  * on error.
950  */
951 static struct batadv_nc_path *batadv_nc_get_path(struct batadv_priv *bat_priv,
952 						 struct batadv_hashtable *hash,
953 						 u8 *src,
954 						 u8 *dst)
955 {
956 	int hash_added;
957 	struct batadv_nc_path *nc_path, nc_path_key;
958 
959 	batadv_nc_hash_key_gen(&nc_path_key, src, dst);
960 
961 	/* Search for existing nc_path */
962 	nc_path = batadv_nc_hash_find(hash, (void *)&nc_path_key);
963 
964 	if (nc_path) {
965 		/* Set timestamp to delay removal of nc_path */
966 		nc_path->last_valid = jiffies;
967 		return nc_path;
968 	}
969 
970 	/* No existing nc_path was found; create a new */
971 	nc_path = kzalloc(sizeof(*nc_path), GFP_ATOMIC);
972 
973 	if (!nc_path)
974 		return NULL;
975 
976 	/* Initialize nc_path */
977 	INIT_LIST_HEAD(&nc_path->packet_list);
978 	spin_lock_init(&nc_path->packet_list_lock);
979 	kref_init(&nc_path->refcount);
980 	nc_path->last_valid = jiffies;
981 	ether_addr_copy(nc_path->next_hop, dst);
982 	ether_addr_copy(nc_path->prev_hop, src);
983 
984 	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_path %pM -> %pM\n",
985 		   nc_path->prev_hop,
986 		   nc_path->next_hop);
987 
988 	/* Add nc_path to hash table */
989 	kref_get(&nc_path->refcount);
990 	hash_added = batadv_hash_add(hash, batadv_nc_hash_compare,
991 				     batadv_nc_hash_choose, &nc_path_key,
992 				     &nc_path->hash_entry);
993 
994 	if (hash_added < 0) {
995 		kfree(nc_path);
996 		return NULL;
997 	}
998 
999 	return nc_path;
1000 }
1001 
1002 /**
1003  * batadv_nc_random_weight_tq() - scale the receivers TQ-value to avoid unfair
1004  *  selection of a receiver with slightly lower TQ than the other
1005  * @tq: to be weighted tq value
1006  *
1007  * Return: scaled tq value
1008  */
1009 static u8 batadv_nc_random_weight_tq(u8 tq)
1010 {
1011 	/* randomize the estimated packet loss (max TQ - estimated TQ) */
1012 	u8 rand_tq = prandom_u32_max(BATADV_TQ_MAX_VALUE + 1 - tq);
1013 
1014 	/* convert to (randomized) estimated tq again */
1015 	return BATADV_TQ_MAX_VALUE - rand_tq;
1016 }
1017 
1018 /**
1019  * batadv_nc_memxor() - XOR destination with source
1020  * @dst: byte array to XOR into
1021  * @src: byte array to XOR from
1022  * @len: length of destination array
1023  */
1024 static void batadv_nc_memxor(char *dst, const char *src, unsigned int len)
1025 {
1026 	unsigned int i;
1027 
1028 	for (i = 0; i < len; ++i)
1029 		dst[i] ^= src[i];
1030 }
1031 
1032 /**
1033  * batadv_nc_code_packets() - code a received unicast_packet with an nc packet
1034  *  into a coded_packet and send it
1035  * @bat_priv: the bat priv with all the soft interface information
1036  * @skb: data skb to forward
1037  * @ethhdr: pointer to the ethernet header inside the skb
1038  * @nc_packet: structure containing the packet to the skb can be coded with
1039  * @neigh_node: next hop to forward packet to
1040  *
1041  * Return: true if both packets are consumed, false otherwise.
1042  */
1043 static bool batadv_nc_code_packets(struct batadv_priv *bat_priv,
1044 				   struct sk_buff *skb,
1045 				   struct ethhdr *ethhdr,
1046 				   struct batadv_nc_packet *nc_packet,
1047 				   struct batadv_neigh_node *neigh_node)
1048 {
1049 	u8 tq_weighted_neigh, tq_weighted_coding, tq_tmp;
1050 	struct sk_buff *skb_dest, *skb_src;
1051 	struct batadv_unicast_packet *packet1;
1052 	struct batadv_unicast_packet *packet2;
1053 	struct batadv_coded_packet *coded_packet;
1054 	struct batadv_neigh_node *neigh_tmp, *router_neigh, *first_dest;
1055 	struct batadv_neigh_node *router_coding = NULL, *second_dest;
1056 	struct batadv_neigh_ifinfo *router_neigh_ifinfo = NULL;
1057 	struct batadv_neigh_ifinfo *router_coding_ifinfo = NULL;
1058 	u8 *first_source, *second_source;
1059 	__be32 packet_id1, packet_id2;
1060 	size_t count;
1061 	bool res = false;
1062 	int coding_len;
1063 	int unicast_size = sizeof(*packet1);
1064 	int coded_size = sizeof(*coded_packet);
1065 	int header_add = coded_size - unicast_size;
1066 
1067 	/* TODO: do we need to consider the outgoing interface for
1068 	 * coded packets?
1069 	 */
1070 	router_neigh = batadv_orig_router_get(neigh_node->orig_node,
1071 					      BATADV_IF_DEFAULT);
1072 	if (!router_neigh)
1073 		goto out;
1074 
1075 	router_neigh_ifinfo = batadv_neigh_ifinfo_get(router_neigh,
1076 						      BATADV_IF_DEFAULT);
1077 	if (!router_neigh_ifinfo)
1078 		goto out;
1079 
1080 	neigh_tmp = nc_packet->neigh_node;
1081 	router_coding = batadv_orig_router_get(neigh_tmp->orig_node,
1082 					       BATADV_IF_DEFAULT);
1083 	if (!router_coding)
1084 		goto out;
1085 
1086 	router_coding_ifinfo = batadv_neigh_ifinfo_get(router_coding,
1087 						       BATADV_IF_DEFAULT);
1088 	if (!router_coding_ifinfo)
1089 		goto out;
1090 
1091 	tq_tmp = router_neigh_ifinfo->bat_iv.tq_avg;
1092 	tq_weighted_neigh = batadv_nc_random_weight_tq(tq_tmp);
1093 	tq_tmp = router_coding_ifinfo->bat_iv.tq_avg;
1094 	tq_weighted_coding = batadv_nc_random_weight_tq(tq_tmp);
1095 
1096 	/* Select one destination for the MAC-header dst-field based on
1097 	 * weighted TQ-values.
1098 	 */
1099 	if (tq_weighted_neigh >= tq_weighted_coding) {
1100 		/* Destination from nc_packet is selected for MAC-header */
1101 		first_dest = nc_packet->neigh_node;
1102 		first_source = nc_packet->nc_path->prev_hop;
1103 		second_dest = neigh_node;
1104 		second_source = ethhdr->h_source;
1105 		packet1 = (struct batadv_unicast_packet *)nc_packet->skb->data;
1106 		packet2 = (struct batadv_unicast_packet *)skb->data;
1107 		packet_id1 = nc_packet->packet_id;
1108 		packet_id2 = batadv_skb_crc32(skb,
1109 					      skb->data + sizeof(*packet2));
1110 	} else {
1111 		/* Destination for skb is selected for MAC-header */
1112 		first_dest = neigh_node;
1113 		first_source = ethhdr->h_source;
1114 		second_dest = nc_packet->neigh_node;
1115 		second_source = nc_packet->nc_path->prev_hop;
1116 		packet1 = (struct batadv_unicast_packet *)skb->data;
1117 		packet2 = (struct batadv_unicast_packet *)nc_packet->skb->data;
1118 		packet_id1 = batadv_skb_crc32(skb,
1119 					      skb->data + sizeof(*packet1));
1120 		packet_id2 = nc_packet->packet_id;
1121 	}
1122 
1123 	/* Instead of zero padding the smallest data buffer, we
1124 	 * code into the largest.
1125 	 */
1126 	if (skb->len <= nc_packet->skb->len) {
1127 		skb_dest = nc_packet->skb;
1128 		skb_src = skb;
1129 	} else {
1130 		skb_dest = skb;
1131 		skb_src = nc_packet->skb;
1132 	}
1133 
1134 	/* coding_len is used when decoding the packet shorter packet */
1135 	coding_len = skb_src->len - unicast_size;
1136 
1137 	if (skb_linearize(skb_dest) < 0 || skb_linearize(skb_src) < 0)
1138 		goto out;
1139 
1140 	skb_push(skb_dest, header_add);
1141 
1142 	coded_packet = (struct batadv_coded_packet *)skb_dest->data;
1143 	skb_reset_mac_header(skb_dest);
1144 
1145 	coded_packet->packet_type = BATADV_CODED;
1146 	coded_packet->version = BATADV_COMPAT_VERSION;
1147 	coded_packet->ttl = packet1->ttl;
1148 
1149 	/* Info about first unicast packet */
1150 	ether_addr_copy(coded_packet->first_source, first_source);
1151 	ether_addr_copy(coded_packet->first_orig_dest, packet1->dest);
1152 	coded_packet->first_crc = packet_id1;
1153 	coded_packet->first_ttvn = packet1->ttvn;
1154 
1155 	/* Info about second unicast packet */
1156 	ether_addr_copy(coded_packet->second_dest, second_dest->addr);
1157 	ether_addr_copy(coded_packet->second_source, second_source);
1158 	ether_addr_copy(coded_packet->second_orig_dest, packet2->dest);
1159 	coded_packet->second_crc = packet_id2;
1160 	coded_packet->second_ttl = packet2->ttl;
1161 	coded_packet->second_ttvn = packet2->ttvn;
1162 	coded_packet->coded_len = htons(coding_len);
1163 
1164 	/* This is where the magic happens: Code skb_src into skb_dest */
1165 	batadv_nc_memxor(skb_dest->data + coded_size,
1166 			 skb_src->data + unicast_size, coding_len);
1167 
1168 	/* Update counters accordingly */
1169 	if (BATADV_SKB_CB(skb_src)->decoded &&
1170 	    BATADV_SKB_CB(skb_dest)->decoded) {
1171 		/* Both packets are recoded */
1172 		count = skb_src->len + ETH_HLEN;
1173 		count += skb_dest->len + ETH_HLEN;
1174 		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE, 2);
1175 		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE_BYTES, count);
1176 	} else if (!BATADV_SKB_CB(skb_src)->decoded &&
1177 		   !BATADV_SKB_CB(skb_dest)->decoded) {
1178 		/* Both packets are newly coded */
1179 		count = skb_src->len + ETH_HLEN;
1180 		count += skb_dest->len + ETH_HLEN;
1181 		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE, 2);
1182 		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE_BYTES, count);
1183 	} else if (BATADV_SKB_CB(skb_src)->decoded &&
1184 		   !BATADV_SKB_CB(skb_dest)->decoded) {
1185 		/* skb_src recoded and skb_dest is newly coded */
1186 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_RECODE);
1187 		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE_BYTES,
1188 				   skb_src->len + ETH_HLEN);
1189 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_CODE);
1190 		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE_BYTES,
1191 				   skb_dest->len + ETH_HLEN);
1192 	} else if (!BATADV_SKB_CB(skb_src)->decoded &&
1193 		   BATADV_SKB_CB(skb_dest)->decoded) {
1194 		/* skb_src is newly coded and skb_dest is recoded */
1195 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_CODE);
1196 		batadv_add_counter(bat_priv, BATADV_CNT_NC_CODE_BYTES,
1197 				   skb_src->len + ETH_HLEN);
1198 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_RECODE);
1199 		batadv_add_counter(bat_priv, BATADV_CNT_NC_RECODE_BYTES,
1200 				   skb_dest->len + ETH_HLEN);
1201 	}
1202 
1203 	/* skb_src is now coded into skb_dest, so free it */
1204 	consume_skb(skb_src);
1205 
1206 	/* avoid duplicate free of skb from nc_packet */
1207 	nc_packet->skb = NULL;
1208 	batadv_nc_packet_free(nc_packet, false);
1209 
1210 	/* Send the coded packet and return true */
1211 	batadv_send_unicast_skb(skb_dest, first_dest);
1212 	res = true;
1213 out:
1214 	batadv_neigh_node_put(router_neigh);
1215 	batadv_neigh_node_put(router_coding);
1216 	batadv_neigh_ifinfo_put(router_neigh_ifinfo);
1217 	batadv_neigh_ifinfo_put(router_coding_ifinfo);
1218 	return res;
1219 }
1220 
1221 /**
1222  * batadv_nc_skb_coding_possible() - true if a decoded skb is available at dst.
1223  * @skb: data skb to forward
1224  * @dst: destination mac address of the other skb to code with
1225  * @src: source mac address of skb
1226  *
1227  * Whenever we network code a packet we have to check whether we received it in
1228  * a network coded form. If so, we may not be able to use it for coding because
1229  * some neighbors may also have received (overheard) the packet in the network
1230  * coded form without being able to decode it. It is hard to know which of the
1231  * neighboring nodes was able to decode the packet, therefore we can only
1232  * re-code the packet if the source of the previous encoded packet is involved.
1233  * Since the source encoded the packet we can be certain it has all necessary
1234  * decode information.
1235  *
1236  * Return: true if coding of a decoded packet is allowed.
1237  */
1238 static bool batadv_nc_skb_coding_possible(struct sk_buff *skb, u8 *dst, u8 *src)
1239 {
1240 	if (BATADV_SKB_CB(skb)->decoded && !batadv_compare_eth(dst, src))
1241 		return false;
1242 	return true;
1243 }
1244 
1245 /**
1246  * batadv_nc_path_search() - Find the coding path matching in_nc_node and
1247  *  out_nc_node to retrieve a buffered packet that can be used for coding.
1248  * @bat_priv: the bat priv with all the soft interface information
1249  * @in_nc_node: pointer to skb next hop's neighbor nc node
1250  * @out_nc_node: pointer to skb source's neighbor nc node
1251  * @skb: data skb to forward
1252  * @eth_dst: next hop mac address of skb
1253  *
1254  * Return: true if coding of a decoded skb is allowed.
1255  */
1256 static struct batadv_nc_packet *
1257 batadv_nc_path_search(struct batadv_priv *bat_priv,
1258 		      struct batadv_nc_node *in_nc_node,
1259 		      struct batadv_nc_node *out_nc_node,
1260 		      struct sk_buff *skb,
1261 		      u8 *eth_dst)
1262 {
1263 	struct batadv_nc_path *nc_path, nc_path_key;
1264 	struct batadv_nc_packet *nc_packet_out = NULL;
1265 	struct batadv_nc_packet *nc_packet, *nc_packet_tmp;
1266 	struct batadv_hashtable *hash = bat_priv->nc.coding_hash;
1267 	int idx;
1268 
1269 	if (!hash)
1270 		return NULL;
1271 
1272 	/* Create almost path key */
1273 	batadv_nc_hash_key_gen(&nc_path_key, in_nc_node->addr,
1274 			       out_nc_node->addr);
1275 	idx = batadv_nc_hash_choose(&nc_path_key, hash->size);
1276 
1277 	/* Check for coding opportunities in this nc_path */
1278 	rcu_read_lock();
1279 	hlist_for_each_entry_rcu(nc_path, &hash->table[idx], hash_entry) {
1280 		if (!batadv_compare_eth(nc_path->prev_hop, in_nc_node->addr))
1281 			continue;
1282 
1283 		if (!batadv_compare_eth(nc_path->next_hop, out_nc_node->addr))
1284 			continue;
1285 
1286 		spin_lock_bh(&nc_path->packet_list_lock);
1287 		if (list_empty(&nc_path->packet_list)) {
1288 			spin_unlock_bh(&nc_path->packet_list_lock);
1289 			continue;
1290 		}
1291 
1292 		list_for_each_entry_safe(nc_packet, nc_packet_tmp,
1293 					 &nc_path->packet_list, list) {
1294 			if (!batadv_nc_skb_coding_possible(nc_packet->skb,
1295 							   eth_dst,
1296 							   in_nc_node->addr))
1297 				continue;
1298 
1299 			/* Coding opportunity is found! */
1300 			list_del(&nc_packet->list);
1301 			nc_packet_out = nc_packet;
1302 			break;
1303 		}
1304 
1305 		spin_unlock_bh(&nc_path->packet_list_lock);
1306 		break;
1307 	}
1308 	rcu_read_unlock();
1309 
1310 	return nc_packet_out;
1311 }
1312 
1313 /**
1314  * batadv_nc_skb_src_search() - Loops through the list of neighboring nodes of
1315  *  the skb's sender (may be equal to the originator).
1316  * @bat_priv: the bat priv with all the soft interface information
1317  * @skb: data skb to forward
1318  * @eth_dst: next hop mac address of skb
1319  * @eth_src: source mac address of skb
1320  * @in_nc_node: pointer to skb next hop's neighbor nc node
1321  *
1322  * Return: an nc packet if a suitable coding packet was found, NULL otherwise.
1323  */
1324 static struct batadv_nc_packet *
1325 batadv_nc_skb_src_search(struct batadv_priv *bat_priv,
1326 			 struct sk_buff *skb,
1327 			 u8 *eth_dst,
1328 			 u8 *eth_src,
1329 			 struct batadv_nc_node *in_nc_node)
1330 {
1331 	struct batadv_orig_node *orig_node;
1332 	struct batadv_nc_node *out_nc_node;
1333 	struct batadv_nc_packet *nc_packet = NULL;
1334 
1335 	orig_node = batadv_orig_hash_find(bat_priv, eth_src);
1336 	if (!orig_node)
1337 		return NULL;
1338 
1339 	rcu_read_lock();
1340 	list_for_each_entry_rcu(out_nc_node,
1341 				&orig_node->out_coding_list, list) {
1342 		/* Check if the skb is decoded and if recoding is possible */
1343 		if (!batadv_nc_skb_coding_possible(skb,
1344 						   out_nc_node->addr, eth_src))
1345 			continue;
1346 
1347 		/* Search for an opportunity in this nc_path */
1348 		nc_packet = batadv_nc_path_search(bat_priv, in_nc_node,
1349 						  out_nc_node, skb, eth_dst);
1350 		if (nc_packet)
1351 			break;
1352 	}
1353 	rcu_read_unlock();
1354 
1355 	batadv_orig_node_put(orig_node);
1356 	return nc_packet;
1357 }
1358 
1359 /**
1360  * batadv_nc_skb_store_before_coding() - set the ethernet src and dst of the
1361  *  unicast skb before it is stored for use in later decoding
1362  * @bat_priv: the bat priv with all the soft interface information
1363  * @skb: data skb to store
1364  * @eth_dst_new: new destination mac address of skb
1365  */
1366 static void batadv_nc_skb_store_before_coding(struct batadv_priv *bat_priv,
1367 					      struct sk_buff *skb,
1368 					      u8 *eth_dst_new)
1369 {
1370 	struct ethhdr *ethhdr;
1371 
1372 	/* Copy skb header to change the mac header */
1373 	skb = pskb_copy_for_clone(skb, GFP_ATOMIC);
1374 	if (!skb)
1375 		return;
1376 
1377 	/* Set the mac header as if we actually sent the packet uncoded */
1378 	ethhdr = eth_hdr(skb);
1379 	ether_addr_copy(ethhdr->h_source, ethhdr->h_dest);
1380 	ether_addr_copy(ethhdr->h_dest, eth_dst_new);
1381 
1382 	/* Set data pointer to MAC header to mimic packets from our tx path */
1383 	skb_push(skb, ETH_HLEN);
1384 
1385 	/* Add the packet to the decoding packet pool */
1386 	batadv_nc_skb_store_for_decoding(bat_priv, skb);
1387 
1388 	/* batadv_nc_skb_store_for_decoding() clones the skb, so we must free
1389 	 * our ref
1390 	 */
1391 	consume_skb(skb);
1392 }
1393 
1394 /**
1395  * batadv_nc_skb_dst_search() - Loops through list of neighboring nodes to dst.
1396  * @skb: data skb to forward
1397  * @neigh_node: next hop to forward packet to
1398  * @ethhdr: pointer to the ethernet header inside the skb
1399  *
1400  * Loops through the list of neighboring nodes the next hop has a good
1401  * connection to (receives OGMs with a sufficient quality). We need to find a
1402  * neighbor of our next hop that potentially sent a packet which our next hop
1403  * also received (overheard) and has stored for later decoding.
1404  *
1405  * Return: true if the skb was consumed (encoded packet sent) or false otherwise
1406  */
1407 static bool batadv_nc_skb_dst_search(struct sk_buff *skb,
1408 				     struct batadv_neigh_node *neigh_node,
1409 				     struct ethhdr *ethhdr)
1410 {
1411 	struct net_device *netdev = neigh_node->if_incoming->soft_iface;
1412 	struct batadv_priv *bat_priv = netdev_priv(netdev);
1413 	struct batadv_orig_node *orig_node = neigh_node->orig_node;
1414 	struct batadv_nc_node *nc_node;
1415 	struct batadv_nc_packet *nc_packet = NULL;
1416 
1417 	rcu_read_lock();
1418 	list_for_each_entry_rcu(nc_node, &orig_node->in_coding_list, list) {
1419 		/* Search for coding opportunity with this in_nc_node */
1420 		nc_packet = batadv_nc_skb_src_search(bat_priv, skb,
1421 						     neigh_node->addr,
1422 						     ethhdr->h_source, nc_node);
1423 
1424 		/* Opportunity was found, so stop searching */
1425 		if (nc_packet)
1426 			break;
1427 	}
1428 	rcu_read_unlock();
1429 
1430 	if (!nc_packet)
1431 		return false;
1432 
1433 	/* Save packets for later decoding */
1434 	batadv_nc_skb_store_before_coding(bat_priv, skb,
1435 					  neigh_node->addr);
1436 	batadv_nc_skb_store_before_coding(bat_priv, nc_packet->skb,
1437 					  nc_packet->neigh_node->addr);
1438 
1439 	/* Code and send packets */
1440 	if (batadv_nc_code_packets(bat_priv, skb, ethhdr, nc_packet,
1441 				   neigh_node))
1442 		return true;
1443 
1444 	/* out of mem ? Coding failed - we have to free the buffered packet
1445 	 * to avoid memleaks. The skb passed as argument will be dealt with
1446 	 * by the calling function.
1447 	 */
1448 	batadv_nc_send_packet(nc_packet);
1449 	return false;
1450 }
1451 
1452 /**
1453  * batadv_nc_skb_add_to_path() - buffer skb for later encoding / decoding
1454  * @skb: skb to add to path
1455  * @nc_path: path to add skb to
1456  * @neigh_node: next hop to forward packet to
1457  * @packet_id: checksum to identify packet
1458  *
1459  * Return: true if the packet was buffered or false in case of an error.
1460  */
1461 static bool batadv_nc_skb_add_to_path(struct sk_buff *skb,
1462 				      struct batadv_nc_path *nc_path,
1463 				      struct batadv_neigh_node *neigh_node,
1464 				      __be32 packet_id)
1465 {
1466 	struct batadv_nc_packet *nc_packet;
1467 
1468 	nc_packet = kzalloc(sizeof(*nc_packet), GFP_ATOMIC);
1469 	if (!nc_packet)
1470 		return false;
1471 
1472 	/* Initialize nc_packet */
1473 	nc_packet->timestamp = jiffies;
1474 	nc_packet->packet_id = packet_id;
1475 	nc_packet->skb = skb;
1476 	nc_packet->neigh_node = neigh_node;
1477 	nc_packet->nc_path = nc_path;
1478 
1479 	/* Add coding packet to list */
1480 	spin_lock_bh(&nc_path->packet_list_lock);
1481 	list_add_tail(&nc_packet->list, &nc_path->packet_list);
1482 	spin_unlock_bh(&nc_path->packet_list_lock);
1483 
1484 	return true;
1485 }
1486 
1487 /**
1488  * batadv_nc_skb_forward() - try to code a packet or add it to the coding packet
1489  *  buffer
1490  * @skb: data skb to forward
1491  * @neigh_node: next hop to forward packet to
1492  *
1493  * Return: true if the skb was consumed (encoded packet sent) or false otherwise
1494  */
1495 bool batadv_nc_skb_forward(struct sk_buff *skb,
1496 			   struct batadv_neigh_node *neigh_node)
1497 {
1498 	const struct net_device *netdev = neigh_node->if_incoming->soft_iface;
1499 	struct batadv_priv *bat_priv = netdev_priv(netdev);
1500 	struct batadv_unicast_packet *packet;
1501 	struct batadv_nc_path *nc_path;
1502 	struct ethhdr *ethhdr = eth_hdr(skb);
1503 	__be32 packet_id;
1504 	u8 *payload;
1505 
1506 	/* Check if network coding is enabled */
1507 	if (!atomic_read(&bat_priv->network_coding))
1508 		goto out;
1509 
1510 	/* We only handle unicast packets */
1511 	payload = skb_network_header(skb);
1512 	packet = (struct batadv_unicast_packet *)payload;
1513 	if (packet->packet_type != BATADV_UNICAST)
1514 		goto out;
1515 
1516 	/* Try to find a coding opportunity and send the skb if one is found */
1517 	if (batadv_nc_skb_dst_search(skb, neigh_node, ethhdr))
1518 		return true;
1519 
1520 	/* Find or create a nc_path for this src-dst pair */
1521 	nc_path = batadv_nc_get_path(bat_priv,
1522 				     bat_priv->nc.coding_hash,
1523 				     ethhdr->h_source,
1524 				     neigh_node->addr);
1525 
1526 	if (!nc_path)
1527 		goto out;
1528 
1529 	/* Add skb to nc_path */
1530 	packet_id = batadv_skb_crc32(skb, payload + sizeof(*packet));
1531 	if (!batadv_nc_skb_add_to_path(skb, nc_path, neigh_node, packet_id))
1532 		goto free_nc_path;
1533 
1534 	/* Packet is consumed */
1535 	return true;
1536 
1537 free_nc_path:
1538 	batadv_nc_path_put(nc_path);
1539 out:
1540 	/* Packet is not consumed */
1541 	return false;
1542 }
1543 
1544 /**
1545  * batadv_nc_skb_store_for_decoding() - save a clone of the skb which can be
1546  *  used when decoding coded packets
1547  * @bat_priv: the bat priv with all the soft interface information
1548  * @skb: data skb to store
1549  */
1550 void batadv_nc_skb_store_for_decoding(struct batadv_priv *bat_priv,
1551 				      struct sk_buff *skb)
1552 {
1553 	struct batadv_unicast_packet *packet;
1554 	struct batadv_nc_path *nc_path;
1555 	struct ethhdr *ethhdr = eth_hdr(skb);
1556 	__be32 packet_id;
1557 	u8 *payload;
1558 
1559 	/* Check if network coding is enabled */
1560 	if (!atomic_read(&bat_priv->network_coding))
1561 		goto out;
1562 
1563 	/* Check for supported packet type */
1564 	payload = skb_network_header(skb);
1565 	packet = (struct batadv_unicast_packet *)payload;
1566 	if (packet->packet_type != BATADV_UNICAST)
1567 		goto out;
1568 
1569 	/* Find existing nc_path or create a new */
1570 	nc_path = batadv_nc_get_path(bat_priv,
1571 				     bat_priv->nc.decoding_hash,
1572 				     ethhdr->h_source,
1573 				     ethhdr->h_dest);
1574 
1575 	if (!nc_path)
1576 		goto out;
1577 
1578 	/* Clone skb and adjust skb->data to point at batman header */
1579 	skb = skb_clone(skb, GFP_ATOMIC);
1580 	if (unlikely(!skb))
1581 		goto free_nc_path;
1582 
1583 	if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
1584 		goto free_skb;
1585 
1586 	if (unlikely(!skb_pull_rcsum(skb, ETH_HLEN)))
1587 		goto free_skb;
1588 
1589 	/* Add skb to nc_path */
1590 	packet_id = batadv_skb_crc32(skb, payload + sizeof(*packet));
1591 	if (!batadv_nc_skb_add_to_path(skb, nc_path, NULL, packet_id))
1592 		goto free_skb;
1593 
1594 	batadv_inc_counter(bat_priv, BATADV_CNT_NC_BUFFER);
1595 	return;
1596 
1597 free_skb:
1598 	kfree_skb(skb);
1599 free_nc_path:
1600 	batadv_nc_path_put(nc_path);
1601 out:
1602 	return;
1603 }
1604 
1605 /**
1606  * batadv_nc_skb_store_sniffed_unicast() - check if a received unicast packet
1607  *  should be saved in the decoding buffer and, if so, store it there
1608  * @bat_priv: the bat priv with all the soft interface information
1609  * @skb: unicast skb to store
1610  */
1611 void batadv_nc_skb_store_sniffed_unicast(struct batadv_priv *bat_priv,
1612 					 struct sk_buff *skb)
1613 {
1614 	struct ethhdr *ethhdr = eth_hdr(skb);
1615 
1616 	if (batadv_is_my_mac(bat_priv, ethhdr->h_dest))
1617 		return;
1618 
1619 	/* Set data pointer to MAC header to mimic packets from our tx path */
1620 	skb_push(skb, ETH_HLEN);
1621 
1622 	batadv_nc_skb_store_for_decoding(bat_priv, skb);
1623 }
1624 
1625 /**
1626  * batadv_nc_skb_decode_packet() - decode given skb using the decode data stored
1627  *  in nc_packet
1628  * @bat_priv: the bat priv with all the soft interface information
1629  * @skb: unicast skb to decode
1630  * @nc_packet: decode data needed to decode the skb
1631  *
1632  * Return: pointer to decoded unicast packet if the packet was decoded or NULL
1633  * in case of an error.
1634  */
1635 static struct batadv_unicast_packet *
1636 batadv_nc_skb_decode_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
1637 			    struct batadv_nc_packet *nc_packet)
1638 {
1639 	const int h_size = sizeof(struct batadv_unicast_packet);
1640 	const int h_diff = sizeof(struct batadv_coded_packet) - h_size;
1641 	struct batadv_unicast_packet *unicast_packet;
1642 	struct batadv_coded_packet coded_packet_tmp;
1643 	struct ethhdr *ethhdr, ethhdr_tmp;
1644 	u8 *orig_dest, ttl, ttvn;
1645 	unsigned int coding_len;
1646 	int err;
1647 
1648 	/* Save headers temporarily */
1649 	memcpy(&coded_packet_tmp, skb->data, sizeof(coded_packet_tmp));
1650 	memcpy(&ethhdr_tmp, skb_mac_header(skb), sizeof(ethhdr_tmp));
1651 
1652 	if (skb_cow(skb, 0) < 0)
1653 		return NULL;
1654 
1655 	if (unlikely(!skb_pull_rcsum(skb, h_diff)))
1656 		return NULL;
1657 
1658 	/* Data points to batman header, so set mac header 14 bytes before
1659 	 * and network to data
1660 	 */
1661 	skb_set_mac_header(skb, -ETH_HLEN);
1662 	skb_reset_network_header(skb);
1663 
1664 	/* Reconstruct original mac header */
1665 	ethhdr = eth_hdr(skb);
1666 	*ethhdr = ethhdr_tmp;
1667 
1668 	/* Select the correct unicast header information based on the location
1669 	 * of our mac address in the coded_packet header
1670 	 */
1671 	if (batadv_is_my_mac(bat_priv, coded_packet_tmp.second_dest)) {
1672 		/* If we are the second destination the packet was overheard,
1673 		 * so the Ethernet address must be copied to h_dest and
1674 		 * pkt_type changed from PACKET_OTHERHOST to PACKET_HOST
1675 		 */
1676 		ether_addr_copy(ethhdr->h_dest, coded_packet_tmp.second_dest);
1677 		skb->pkt_type = PACKET_HOST;
1678 
1679 		orig_dest = coded_packet_tmp.second_orig_dest;
1680 		ttl = coded_packet_tmp.second_ttl;
1681 		ttvn = coded_packet_tmp.second_ttvn;
1682 	} else {
1683 		orig_dest = coded_packet_tmp.first_orig_dest;
1684 		ttl = coded_packet_tmp.ttl;
1685 		ttvn = coded_packet_tmp.first_ttvn;
1686 	}
1687 
1688 	coding_len = ntohs(coded_packet_tmp.coded_len);
1689 
1690 	if (coding_len > skb->len)
1691 		return NULL;
1692 
1693 	/* Here the magic is reversed:
1694 	 *   extract the missing packet from the received coded packet
1695 	 */
1696 	batadv_nc_memxor(skb->data + h_size,
1697 			 nc_packet->skb->data + h_size,
1698 			 coding_len);
1699 
1700 	/* Resize decoded skb if decoded with larger packet */
1701 	if (nc_packet->skb->len > coding_len + h_size) {
1702 		err = pskb_trim_rcsum(skb, coding_len + h_size);
1703 		if (err)
1704 			return NULL;
1705 	}
1706 
1707 	/* Create decoded unicast packet */
1708 	unicast_packet = (struct batadv_unicast_packet *)skb->data;
1709 	unicast_packet->packet_type = BATADV_UNICAST;
1710 	unicast_packet->version = BATADV_COMPAT_VERSION;
1711 	unicast_packet->ttl = ttl;
1712 	ether_addr_copy(unicast_packet->dest, orig_dest);
1713 	unicast_packet->ttvn = ttvn;
1714 
1715 	batadv_nc_packet_free(nc_packet, false);
1716 	return unicast_packet;
1717 }
1718 
1719 /**
1720  * batadv_nc_find_decoding_packet() - search through buffered decoding data to
1721  *  find the data needed to decode the coded packet
1722  * @bat_priv: the bat priv with all the soft interface information
1723  * @ethhdr: pointer to the ethernet header inside the coded packet
1724  * @coded: coded packet we try to find decode data for
1725  *
1726  * Return: pointer to nc packet if the needed data was found or NULL otherwise.
1727  */
1728 static struct batadv_nc_packet *
1729 batadv_nc_find_decoding_packet(struct batadv_priv *bat_priv,
1730 			       struct ethhdr *ethhdr,
1731 			       struct batadv_coded_packet *coded)
1732 {
1733 	struct batadv_hashtable *hash = bat_priv->nc.decoding_hash;
1734 	struct batadv_nc_packet *tmp_nc_packet, *nc_packet = NULL;
1735 	struct batadv_nc_path *nc_path, nc_path_key;
1736 	u8 *dest, *source;
1737 	__be32 packet_id;
1738 	int index;
1739 
1740 	if (!hash)
1741 		return NULL;
1742 
1743 	/* Select the correct packet id based on the location of our mac-addr */
1744 	dest = ethhdr->h_source;
1745 	if (!batadv_is_my_mac(bat_priv, coded->second_dest)) {
1746 		source = coded->second_source;
1747 		packet_id = coded->second_crc;
1748 	} else {
1749 		source = coded->first_source;
1750 		packet_id = coded->first_crc;
1751 	}
1752 
1753 	batadv_nc_hash_key_gen(&nc_path_key, source, dest);
1754 	index = batadv_nc_hash_choose(&nc_path_key, hash->size);
1755 
1756 	/* Search for matching coding path */
1757 	rcu_read_lock();
1758 	hlist_for_each_entry_rcu(nc_path, &hash->table[index], hash_entry) {
1759 		/* Find matching nc_packet */
1760 		spin_lock_bh(&nc_path->packet_list_lock);
1761 		list_for_each_entry(tmp_nc_packet,
1762 				    &nc_path->packet_list, list) {
1763 			if (packet_id == tmp_nc_packet->packet_id) {
1764 				list_del(&tmp_nc_packet->list);
1765 
1766 				nc_packet = tmp_nc_packet;
1767 				break;
1768 			}
1769 		}
1770 		spin_unlock_bh(&nc_path->packet_list_lock);
1771 
1772 		if (nc_packet)
1773 			break;
1774 	}
1775 	rcu_read_unlock();
1776 
1777 	if (!nc_packet)
1778 		batadv_dbg(BATADV_DBG_NC, bat_priv,
1779 			   "No decoding packet found for %u\n", packet_id);
1780 
1781 	return nc_packet;
1782 }
1783 
1784 /**
1785  * batadv_nc_recv_coded_packet() - try to decode coded packet and enqueue the
1786  *  resulting unicast packet
1787  * @skb: incoming coded packet
1788  * @recv_if: pointer to interface this packet was received on
1789  *
1790  * Return: NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
1791  * otherwise.
1792  */
1793 static int batadv_nc_recv_coded_packet(struct sk_buff *skb,
1794 				       struct batadv_hard_iface *recv_if)
1795 {
1796 	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
1797 	struct batadv_unicast_packet *unicast_packet;
1798 	struct batadv_coded_packet *coded_packet;
1799 	struct batadv_nc_packet *nc_packet;
1800 	struct ethhdr *ethhdr;
1801 	int hdr_size = sizeof(*coded_packet);
1802 
1803 	/* Check if network coding is enabled */
1804 	if (!atomic_read(&bat_priv->network_coding))
1805 		goto free_skb;
1806 
1807 	/* Make sure we can access (and remove) header */
1808 	if (unlikely(!pskb_may_pull(skb, hdr_size)))
1809 		goto free_skb;
1810 
1811 	coded_packet = (struct batadv_coded_packet *)skb->data;
1812 	ethhdr = eth_hdr(skb);
1813 
1814 	/* Verify frame is destined for us */
1815 	if (!batadv_is_my_mac(bat_priv, ethhdr->h_dest) &&
1816 	    !batadv_is_my_mac(bat_priv, coded_packet->second_dest))
1817 		goto free_skb;
1818 
1819 	/* Update stat counter */
1820 	if (batadv_is_my_mac(bat_priv, coded_packet->second_dest))
1821 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_SNIFFED);
1822 
1823 	nc_packet = batadv_nc_find_decoding_packet(bat_priv, ethhdr,
1824 						   coded_packet);
1825 	if (!nc_packet) {
1826 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_DECODE_FAILED);
1827 		goto free_skb;
1828 	}
1829 
1830 	/* Make skb's linear, because decoding accesses the entire buffer */
1831 	if (skb_linearize(skb) < 0)
1832 		goto free_nc_packet;
1833 
1834 	if (skb_linearize(nc_packet->skb) < 0)
1835 		goto free_nc_packet;
1836 
1837 	/* Decode the packet */
1838 	unicast_packet = batadv_nc_skb_decode_packet(bat_priv, skb, nc_packet);
1839 	if (!unicast_packet) {
1840 		batadv_inc_counter(bat_priv, BATADV_CNT_NC_DECODE_FAILED);
1841 		goto free_nc_packet;
1842 	}
1843 
1844 	/* Mark packet as decoded to do correct recoding when forwarding */
1845 	BATADV_SKB_CB(skb)->decoded = true;
1846 	batadv_inc_counter(bat_priv, BATADV_CNT_NC_DECODE);
1847 	batadv_add_counter(bat_priv, BATADV_CNT_NC_DECODE_BYTES,
1848 			   skb->len + ETH_HLEN);
1849 	return batadv_recv_unicast_packet(skb, recv_if);
1850 
1851 free_nc_packet:
1852 	batadv_nc_packet_free(nc_packet, true);
1853 free_skb:
1854 	kfree_skb(skb);
1855 
1856 	return NET_RX_DROP;
1857 }
1858 
1859 /**
1860  * batadv_nc_mesh_free() - clean up network coding memory
1861  * @bat_priv: the bat priv with all the soft interface information
1862  */
1863 void batadv_nc_mesh_free(struct batadv_priv *bat_priv)
1864 {
1865 	batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_NC, 1);
1866 	batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_NC, 1);
1867 	cancel_delayed_work_sync(&bat_priv->nc.work);
1868 
1869 	batadv_nc_purge_paths(bat_priv, bat_priv->nc.coding_hash, NULL);
1870 	batadv_hash_destroy(bat_priv->nc.coding_hash);
1871 	batadv_nc_purge_paths(bat_priv, bat_priv->nc.decoding_hash, NULL);
1872 	batadv_hash_destroy(bat_priv->nc.decoding_hash);
1873 }
1874