1 /* Copyright (C) 2011-2017  B.A.T.M.A.N. contributors:
2  *
3  * Antonio Quartulli
4  *
5  * This program is free software; you can redistribute it and/or
6  * modify it under the terms of version 2 of the GNU General Public
7  * License as published by the Free Software Foundation.
8  *
9  * This program is distributed in the hope that it will be useful, but
10  * WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
16  */
17 
18 #include "distributed-arp-table.h"
19 #include "main.h"
20 
21 #include <linux/atomic.h>
22 #include <linux/bitops.h>
23 #include <linux/byteorder/generic.h>
24 #include <linux/errno.h>
25 #include <linux/etherdevice.h>
26 #include <linux/fs.h>
27 #include <linux/if_arp.h>
28 #include <linux/if_ether.h>
29 #include <linux/if_vlan.h>
30 #include <linux/in.h>
31 #include <linux/jiffies.h>
32 #include <linux/kernel.h>
33 #include <linux/kref.h>
34 #include <linux/list.h>
35 #include <linux/rculist.h>
36 #include <linux/rcupdate.h>
37 #include <linux/seq_file.h>
38 #include <linux/skbuff.h>
39 #include <linux/slab.h>
40 #include <linux/spinlock.h>
41 #include <linux/stddef.h>
42 #include <linux/string.h>
43 #include <linux/workqueue.h>
44 #include <net/arp.h>
45 
46 #include "bridge_loop_avoidance.h"
47 #include "hard-interface.h"
48 #include "hash.h"
49 #include "log.h"
50 #include "originator.h"
51 #include "send.h"
52 #include "translation-table.h"
53 #include "tvlv.h"
54 
55 static void batadv_dat_purge(struct work_struct *work);
56 
57 /**
58  * batadv_dat_start_timer - initialise the DAT periodic worker
59  * @bat_priv: the bat priv with all the soft interface information
60  */
61 static void batadv_dat_start_timer(struct batadv_priv *bat_priv)
62 {
63 	INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
64 	queue_delayed_work(batadv_event_workqueue, &bat_priv->dat.work,
65 			   msecs_to_jiffies(10000));
66 }
67 
68 /**
69  * batadv_dat_entry_release - release dat_entry from lists and queue for free
70  *  after rcu grace period
71  * @ref: kref pointer of the dat_entry
72  */
73 static void batadv_dat_entry_release(struct kref *ref)
74 {
75 	struct batadv_dat_entry *dat_entry;
76 
77 	dat_entry = container_of(ref, struct batadv_dat_entry, refcount);
78 
79 	kfree_rcu(dat_entry, rcu);
80 }
81 
82 /**
83  * batadv_dat_entry_put - decrement the dat_entry refcounter and possibly
84  *  release it
85  * @dat_entry: dat_entry to be free'd
86  */
87 static void batadv_dat_entry_put(struct batadv_dat_entry *dat_entry)
88 {
89 	kref_put(&dat_entry->refcount, batadv_dat_entry_release);
90 }
91 
92 /**
93  * batadv_dat_to_purge - check whether a dat_entry has to be purged or not
94  * @dat_entry: the entry to check
95  *
96  * Return: true if the entry has to be purged now, false otherwise.
97  */
98 static bool batadv_dat_to_purge(struct batadv_dat_entry *dat_entry)
99 {
100 	return batadv_has_timed_out(dat_entry->last_update,
101 				    BATADV_DAT_ENTRY_TIMEOUT);
102 }
103 
104 /**
105  * __batadv_dat_purge - delete entries from the DAT local storage
106  * @bat_priv: the bat priv with all the soft interface information
107  * @to_purge: function in charge to decide whether an entry has to be purged or
108  *	      not. This function takes the dat_entry as argument and has to
109  *	      returns a boolean value: true is the entry has to be deleted,
110  *	      false otherwise
111  *
112  * Loops over each entry in the DAT local storage and deletes it if and only if
113  * the to_purge function passed as argument returns true.
114  */
115 static void __batadv_dat_purge(struct batadv_priv *bat_priv,
116 			       bool (*to_purge)(struct batadv_dat_entry *))
117 {
118 	spinlock_t *list_lock; /* protects write access to the hash lists */
119 	struct batadv_dat_entry *dat_entry;
120 	struct hlist_node *node_tmp;
121 	struct hlist_head *head;
122 	u32 i;
123 
124 	if (!bat_priv->dat.hash)
125 		return;
126 
127 	for (i = 0; i < bat_priv->dat.hash->size; i++) {
128 		head = &bat_priv->dat.hash->table[i];
129 		list_lock = &bat_priv->dat.hash->list_locks[i];
130 
131 		spin_lock_bh(list_lock);
132 		hlist_for_each_entry_safe(dat_entry, node_tmp, head,
133 					  hash_entry) {
134 			/* if a helper function has been passed as parameter,
135 			 * ask it if the entry has to be purged or not
136 			 */
137 			if (to_purge && !to_purge(dat_entry))
138 				continue;
139 
140 			hlist_del_rcu(&dat_entry->hash_entry);
141 			batadv_dat_entry_put(dat_entry);
142 		}
143 		spin_unlock_bh(list_lock);
144 	}
145 }
146 
147 /**
148  * batadv_dat_purge - periodic task that deletes old entries from the local DAT
149  * hash table
150  * @work: kernel work struct
151  */
152 static void batadv_dat_purge(struct work_struct *work)
153 {
154 	struct delayed_work *delayed_work;
155 	struct batadv_priv_dat *priv_dat;
156 	struct batadv_priv *bat_priv;
157 
158 	delayed_work = to_delayed_work(work);
159 	priv_dat = container_of(delayed_work, struct batadv_priv_dat, work);
160 	bat_priv = container_of(priv_dat, struct batadv_priv, dat);
161 
162 	__batadv_dat_purge(bat_priv, batadv_dat_to_purge);
163 	batadv_dat_start_timer(bat_priv);
164 }
165 
166 /**
167  * batadv_compare_dat - comparing function used in the local DAT hash table
168  * @node: node in the local table
169  * @data2: second object to compare the node to
170  *
171  * Return: true if the two entries are the same, false otherwise.
172  */
173 static bool batadv_compare_dat(const struct hlist_node *node, const void *data2)
174 {
175 	const void *data1 = container_of(node, struct batadv_dat_entry,
176 					 hash_entry);
177 
178 	return memcmp(data1, data2, sizeof(__be32)) == 0;
179 }
180 
181 /**
182  * batadv_arp_hw_src - extract the hw_src field from an ARP packet
183  * @skb: ARP packet
184  * @hdr_size: size of the possible header before the ARP packet
185  *
186  * Return: the value of the hw_src field in the ARP packet.
187  */
188 static u8 *batadv_arp_hw_src(struct sk_buff *skb, int hdr_size)
189 {
190 	u8 *addr;
191 
192 	addr = (u8 *)(skb->data + hdr_size);
193 	addr += ETH_HLEN + sizeof(struct arphdr);
194 
195 	return addr;
196 }
197 
198 /**
199  * batadv_arp_ip_src - extract the ip_src field from an ARP packet
200  * @skb: ARP packet
201  * @hdr_size: size of the possible header before the ARP packet
202  *
203  * Return: the value of the ip_src field in the ARP packet.
204  */
205 static __be32 batadv_arp_ip_src(struct sk_buff *skb, int hdr_size)
206 {
207 	return *(__be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN);
208 }
209 
210 /**
211  * batadv_arp_hw_dst - extract the hw_dst field from an ARP packet
212  * @skb: ARP packet
213  * @hdr_size: size of the possible header before the ARP packet
214  *
215  * Return: the value of the hw_dst field in the ARP packet.
216  */
217 static u8 *batadv_arp_hw_dst(struct sk_buff *skb, int hdr_size)
218 {
219 	return batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN + 4;
220 }
221 
222 /**
223  * batadv_arp_ip_dst - extract the ip_dst field from an ARP packet
224  * @skb: ARP packet
225  * @hdr_size: size of the possible header before the ARP packet
226  *
227  * Return: the value of the ip_dst field in the ARP packet.
228  */
229 static __be32 batadv_arp_ip_dst(struct sk_buff *skb, int hdr_size)
230 {
231 	return *(__be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN * 2 + 4);
232 }
233 
234 /**
235  * batadv_hash_dat - compute the hash value for an IP address
236  * @data: data to hash
237  * @size: size of the hash table
238  *
239  * Return: the selected index in the hash table for the given data.
240  */
241 static u32 batadv_hash_dat(const void *data, u32 size)
242 {
243 	u32 hash = 0;
244 	const struct batadv_dat_entry *dat = data;
245 	const unsigned char *key;
246 	u32 i;
247 
248 	key = (const unsigned char *)&dat->ip;
249 	for (i = 0; i < sizeof(dat->ip); i++) {
250 		hash += key[i];
251 		hash += (hash << 10);
252 		hash ^= (hash >> 6);
253 	}
254 
255 	key = (const unsigned char *)&dat->vid;
256 	for (i = 0; i < sizeof(dat->vid); i++) {
257 		hash += key[i];
258 		hash += (hash << 10);
259 		hash ^= (hash >> 6);
260 	}
261 
262 	hash += (hash << 3);
263 	hash ^= (hash >> 11);
264 	hash += (hash << 15);
265 
266 	return hash % size;
267 }
268 
269 /**
270  * batadv_dat_entry_hash_find - look for a given dat_entry in the local hash
271  * table
272  * @bat_priv: the bat priv with all the soft interface information
273  * @ip: search key
274  * @vid: VLAN identifier
275  *
276  * Return: the dat_entry if found, NULL otherwise.
277  */
278 static struct batadv_dat_entry *
279 batadv_dat_entry_hash_find(struct batadv_priv *bat_priv, __be32 ip,
280 			   unsigned short vid)
281 {
282 	struct hlist_head *head;
283 	struct batadv_dat_entry to_find, *dat_entry, *dat_entry_tmp = NULL;
284 	struct batadv_hashtable *hash = bat_priv->dat.hash;
285 	u32 index;
286 
287 	if (!hash)
288 		return NULL;
289 
290 	to_find.ip = ip;
291 	to_find.vid = vid;
292 
293 	index = batadv_hash_dat(&to_find, hash->size);
294 	head = &hash->table[index];
295 
296 	rcu_read_lock();
297 	hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {
298 		if (dat_entry->ip != ip)
299 			continue;
300 
301 		if (!kref_get_unless_zero(&dat_entry->refcount))
302 			continue;
303 
304 		dat_entry_tmp = dat_entry;
305 		break;
306 	}
307 	rcu_read_unlock();
308 
309 	return dat_entry_tmp;
310 }
311 
312 /**
313  * batadv_dat_entry_add - add a new dat entry or update it if already exists
314  * @bat_priv: the bat priv with all the soft interface information
315  * @ip: ipv4 to add/edit
316  * @mac_addr: mac address to assign to the given ipv4
317  * @vid: VLAN identifier
318  */
319 static void batadv_dat_entry_add(struct batadv_priv *bat_priv, __be32 ip,
320 				 u8 *mac_addr, unsigned short vid)
321 {
322 	struct batadv_dat_entry *dat_entry;
323 	int hash_added;
324 
325 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip, vid);
326 	/* if this entry is already known, just update it */
327 	if (dat_entry) {
328 		if (!batadv_compare_eth(dat_entry->mac_addr, mac_addr))
329 			ether_addr_copy(dat_entry->mac_addr, mac_addr);
330 		dat_entry->last_update = jiffies;
331 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
332 			   "Entry updated: %pI4 %pM (vid: %d)\n",
333 			   &dat_entry->ip, dat_entry->mac_addr,
334 			   batadv_print_vid(vid));
335 		goto out;
336 	}
337 
338 	dat_entry = kmalloc(sizeof(*dat_entry), GFP_ATOMIC);
339 	if (!dat_entry)
340 		goto out;
341 
342 	dat_entry->ip = ip;
343 	dat_entry->vid = vid;
344 	ether_addr_copy(dat_entry->mac_addr, mac_addr);
345 	dat_entry->last_update = jiffies;
346 	kref_init(&dat_entry->refcount);
347 
348 	kref_get(&dat_entry->refcount);
349 	hash_added = batadv_hash_add(bat_priv->dat.hash, batadv_compare_dat,
350 				     batadv_hash_dat, dat_entry,
351 				     &dat_entry->hash_entry);
352 
353 	if (unlikely(hash_added != 0)) {
354 		/* remove the reference for the hash */
355 		batadv_dat_entry_put(dat_entry);
356 		goto out;
357 	}
358 
359 	batadv_dbg(BATADV_DBG_DAT, bat_priv, "New entry added: %pI4 %pM (vid: %d)\n",
360 		   &dat_entry->ip, dat_entry->mac_addr, batadv_print_vid(vid));
361 
362 out:
363 	if (dat_entry)
364 		batadv_dat_entry_put(dat_entry);
365 }
366 
367 #ifdef CONFIG_BATMAN_ADV_DEBUG
368 
369 /**
370  * batadv_dbg_arp - print a debug message containing all the ARP packet details
371  * @bat_priv: the bat priv with all the soft interface information
372  * @skb: ARP packet
373  * @hdr_size: size of the possible header before the ARP packet
374  * @msg: message to print together with the debugging information
375  */
376 static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,
377 			   int hdr_size, char *msg)
378 {
379 	struct batadv_unicast_4addr_packet *unicast_4addr_packet;
380 	struct batadv_bcast_packet *bcast_pkt;
381 	u8 *orig_addr;
382 	__be32 ip_src, ip_dst;
383 
384 	if (msg)
385 		batadv_dbg(BATADV_DBG_DAT, bat_priv, "%s\n", msg);
386 
387 	ip_src = batadv_arp_ip_src(skb, hdr_size);
388 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
389 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
390 		   "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
391 		   batadv_arp_hw_src(skb, hdr_size), &ip_src,
392 		   batadv_arp_hw_dst(skb, hdr_size), &ip_dst);
393 
394 	if (hdr_size == 0)
395 		return;
396 
397 	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
398 
399 	switch (unicast_4addr_packet->u.packet_type) {
400 	case BATADV_UNICAST:
401 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
402 			   "* encapsulated within a UNICAST packet\n");
403 		break;
404 	case BATADV_UNICAST_4ADDR:
405 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
406 			   "* encapsulated within a UNICAST_4ADDR packet (src: %pM)\n",
407 			   unicast_4addr_packet->src);
408 		switch (unicast_4addr_packet->subtype) {
409 		case BATADV_P_DAT_DHT_PUT:
410 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_PUT\n");
411 			break;
412 		case BATADV_P_DAT_DHT_GET:
413 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_GET\n");
414 			break;
415 		case BATADV_P_DAT_CACHE_REPLY:
416 			batadv_dbg(BATADV_DBG_DAT, bat_priv,
417 				   "* type: DAT_CACHE_REPLY\n");
418 			break;
419 		case BATADV_P_DATA:
420 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DATA\n");
421 			break;
422 		default:
423 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: Unknown (%u)!\n",
424 				   unicast_4addr_packet->u.packet_type);
425 		}
426 		break;
427 	case BATADV_BCAST:
428 		bcast_pkt = (struct batadv_bcast_packet *)unicast_4addr_packet;
429 		orig_addr = bcast_pkt->orig;
430 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
431 			   "* encapsulated within a BCAST packet (src: %pM)\n",
432 			   orig_addr);
433 		break;
434 	default:
435 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
436 			   "* encapsulated within an unknown packet type (0x%x)\n",
437 			   unicast_4addr_packet->u.packet_type);
438 	}
439 }
440 
441 #else
442 
443 static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,
444 			   int hdr_size, char *msg)
445 {
446 }
447 
448 #endif /* CONFIG_BATMAN_ADV_DEBUG */
449 
450 /**
451  * batadv_is_orig_node_eligible - check whether a node can be a DHT candidate
452  * @res: the array with the already selected candidates
453  * @select: number of already selected candidates
454  * @tmp_max: address of the currently evaluated node
455  * @max: current round max address
456  * @last_max: address of the last selected candidate
457  * @candidate: orig_node under evaluation
458  * @max_orig_node: last selected candidate
459  *
460  * Return: true if the node has been elected as next candidate or false
461  * otherwise.
462  */
463 static bool batadv_is_orig_node_eligible(struct batadv_dat_candidate *res,
464 					 int select, batadv_dat_addr_t tmp_max,
465 					 batadv_dat_addr_t max,
466 					 batadv_dat_addr_t last_max,
467 					 struct batadv_orig_node *candidate,
468 					 struct batadv_orig_node *max_orig_node)
469 {
470 	bool ret = false;
471 	int j;
472 
473 	/* check if orig node candidate is running DAT */
474 	if (!test_bit(BATADV_ORIG_CAPA_HAS_DAT, &candidate->capabilities))
475 		goto out;
476 
477 	/* Check if this node has already been selected... */
478 	for (j = 0; j < select; j++)
479 		if (res[j].orig_node == candidate)
480 			break;
481 	/* ..and possibly skip it */
482 	if (j < select)
483 		goto out;
484 	/* sanity check: has it already been selected? This should not happen */
485 	if (tmp_max > last_max)
486 		goto out;
487 	/* check if during this iteration an originator with a closer dht
488 	 * address has already been found
489 	 */
490 	if (tmp_max < max)
491 		goto out;
492 	/* this is an hash collision with the temporary selected node. Choose
493 	 * the one with the lowest address
494 	 */
495 	if ((tmp_max == max) && max_orig_node &&
496 	    (batadv_compare_eth(candidate->orig, max_orig_node->orig) > 0))
497 		goto out;
498 
499 	ret = true;
500 out:
501 	return ret;
502 }
503 
504 /**
505  * batadv_choose_next_candidate - select the next DHT candidate
506  * @bat_priv: the bat priv with all the soft interface information
507  * @cands: candidates array
508  * @select: number of candidates already present in the array
509  * @ip_key: key to look up in the DHT
510  * @last_max: pointer where the address of the selected candidate will be saved
511  */
512 static void batadv_choose_next_candidate(struct batadv_priv *bat_priv,
513 					 struct batadv_dat_candidate *cands,
514 					 int select, batadv_dat_addr_t ip_key,
515 					 batadv_dat_addr_t *last_max)
516 {
517 	batadv_dat_addr_t max = 0;
518 	batadv_dat_addr_t tmp_max = 0;
519 	struct batadv_orig_node *orig_node, *max_orig_node = NULL;
520 	struct batadv_hashtable *hash = bat_priv->orig_hash;
521 	struct hlist_head *head;
522 	int i;
523 
524 	/* if no node is eligible as candidate, leave the candidate type as
525 	 * NOT_FOUND
526 	 */
527 	cands[select].type = BATADV_DAT_CANDIDATE_NOT_FOUND;
528 
529 	/* iterate over the originator list and find the node with the closest
530 	 * dat_address which has not been selected yet
531 	 */
532 	for (i = 0; i < hash->size; i++) {
533 		head = &hash->table[i];
534 
535 		rcu_read_lock();
536 		hlist_for_each_entry_rcu(orig_node, head, hash_entry) {
537 			/* the dht space is a ring using unsigned addresses */
538 			tmp_max = BATADV_DAT_ADDR_MAX - orig_node->dat_addr +
539 				  ip_key;
540 
541 			if (!batadv_is_orig_node_eligible(cands, select,
542 							  tmp_max, max,
543 							  *last_max, orig_node,
544 							  max_orig_node))
545 				continue;
546 
547 			if (!kref_get_unless_zero(&orig_node->refcount))
548 				continue;
549 
550 			max = tmp_max;
551 			if (max_orig_node)
552 				batadv_orig_node_put(max_orig_node);
553 			max_orig_node = orig_node;
554 		}
555 		rcu_read_unlock();
556 	}
557 	if (max_orig_node) {
558 		cands[select].type = BATADV_DAT_CANDIDATE_ORIG;
559 		cands[select].orig_node = max_orig_node;
560 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
561 			   "dat_select_candidates() %d: selected %pM addr=%u dist=%u\n",
562 			   select, max_orig_node->orig, max_orig_node->dat_addr,
563 			   max);
564 	}
565 	*last_max = max;
566 }
567 
568 /**
569  * batadv_dat_select_candidates - select the nodes which the DHT message has to
570  * be sent to
571  * @bat_priv: the bat priv with all the soft interface information
572  * @ip_dst: ipv4 to look up in the DHT
573  * @vid: VLAN identifier
574  *
575  * An originator O is selected if and only if its DHT_ID value is one of three
576  * closest values (from the LEFT, with wrap around if needed) then the hash
577  * value of the key. ip_dst is the key.
578  *
579  * Return: the candidate array of size BATADV_DAT_CANDIDATE_NUM.
580  */
581 static struct batadv_dat_candidate *
582 batadv_dat_select_candidates(struct batadv_priv *bat_priv, __be32 ip_dst,
583 			     unsigned short vid)
584 {
585 	int select;
586 	batadv_dat_addr_t last_max = BATADV_DAT_ADDR_MAX, ip_key;
587 	struct batadv_dat_candidate *res;
588 	struct batadv_dat_entry dat;
589 
590 	if (!bat_priv->orig_hash)
591 		return NULL;
592 
593 	res = kmalloc_array(BATADV_DAT_CANDIDATES_NUM, sizeof(*res),
594 			    GFP_ATOMIC);
595 	if (!res)
596 		return NULL;
597 
598 	dat.ip = ip_dst;
599 	dat.vid = vid;
600 	ip_key = (batadv_dat_addr_t)batadv_hash_dat(&dat,
601 						    BATADV_DAT_ADDR_MAX);
602 
603 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
604 		   "%s(): IP=%pI4 hash(IP)=%u\n", __func__, &ip_dst,
605 		   ip_key);
606 
607 	for (select = 0; select < BATADV_DAT_CANDIDATES_NUM; select++)
608 		batadv_choose_next_candidate(bat_priv, res, select, ip_key,
609 					     &last_max);
610 
611 	return res;
612 }
613 
614 /**
615  * batadv_dat_send_data - send a payload to the selected candidates
616  * @bat_priv: the bat priv with all the soft interface information
617  * @skb: payload to send
618  * @ip: the DHT key
619  * @vid: VLAN identifier
620  * @packet_subtype: unicast4addr packet subtype to use
621  *
622  * This function copies the skb with pskb_copy() and is sent as unicast packet
623  * to each of the selected candidates.
624  *
625  * Return: true if the packet is sent to at least one candidate, false
626  * otherwise.
627  */
628 static bool batadv_dat_send_data(struct batadv_priv *bat_priv,
629 				 struct sk_buff *skb, __be32 ip,
630 				 unsigned short vid, int packet_subtype)
631 {
632 	int i;
633 	bool ret = false;
634 	int send_status;
635 	struct batadv_neigh_node *neigh_node = NULL;
636 	struct sk_buff *tmp_skb;
637 	struct batadv_dat_candidate *cand;
638 
639 	cand = batadv_dat_select_candidates(bat_priv, ip, vid);
640 	if (!cand)
641 		goto out;
642 
643 	batadv_dbg(BATADV_DBG_DAT, bat_priv, "DHT_SEND for %pI4\n", &ip);
644 
645 	for (i = 0; i < BATADV_DAT_CANDIDATES_NUM; i++) {
646 		if (cand[i].type == BATADV_DAT_CANDIDATE_NOT_FOUND)
647 			continue;
648 
649 		neigh_node = batadv_orig_router_get(cand[i].orig_node,
650 						    BATADV_IF_DEFAULT);
651 		if (!neigh_node)
652 			goto free_orig;
653 
654 		tmp_skb = pskb_copy_for_clone(skb, GFP_ATOMIC);
655 		if (!batadv_send_skb_prepare_unicast_4addr(bat_priv, tmp_skb,
656 							   cand[i].orig_node,
657 							   packet_subtype)) {
658 			kfree_skb(tmp_skb);
659 			goto free_neigh;
660 		}
661 
662 		send_status = batadv_send_unicast_skb(tmp_skb, neigh_node);
663 		if (send_status == NET_XMIT_SUCCESS) {
664 			/* count the sent packet */
665 			switch (packet_subtype) {
666 			case BATADV_P_DAT_DHT_GET:
667 				batadv_inc_counter(bat_priv,
668 						   BATADV_CNT_DAT_GET_TX);
669 				break;
670 			case BATADV_P_DAT_DHT_PUT:
671 				batadv_inc_counter(bat_priv,
672 						   BATADV_CNT_DAT_PUT_TX);
673 				break;
674 			}
675 
676 			/* packet sent to a candidate: return true */
677 			ret = true;
678 		}
679 free_neigh:
680 		batadv_neigh_node_put(neigh_node);
681 free_orig:
682 		batadv_orig_node_put(cand[i].orig_node);
683 	}
684 
685 out:
686 	kfree(cand);
687 	return ret;
688 }
689 
690 /**
691  * batadv_dat_tvlv_container_update - update the dat tvlv container after dat
692  *  setting change
693  * @bat_priv: the bat priv with all the soft interface information
694  */
695 static void batadv_dat_tvlv_container_update(struct batadv_priv *bat_priv)
696 {
697 	char dat_mode;
698 
699 	dat_mode = atomic_read(&bat_priv->distributed_arp_table);
700 
701 	switch (dat_mode) {
702 	case 0:
703 		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
704 		break;
705 	case 1:
706 		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_DAT, 1,
707 					       NULL, 0);
708 		break;
709 	}
710 }
711 
712 /**
713  * batadv_dat_status_update - update the dat tvlv container after dat
714  *  setting change
715  * @net_dev: the soft interface net device
716  */
717 void batadv_dat_status_update(struct net_device *net_dev)
718 {
719 	struct batadv_priv *bat_priv = netdev_priv(net_dev);
720 
721 	batadv_dat_tvlv_container_update(bat_priv);
722 }
723 
724 /**
725  * batadv_dat_tvlv_ogm_handler_v1 - process incoming dat tvlv container
726  * @bat_priv: the bat priv with all the soft interface information
727  * @orig: the orig_node of the ogm
728  * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
729  * @tvlv_value: tvlv buffer containing the gateway data
730  * @tvlv_value_len: tvlv buffer length
731  */
732 static void batadv_dat_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
733 					   struct batadv_orig_node *orig,
734 					   u8 flags,
735 					   void *tvlv_value, u16 tvlv_value_len)
736 {
737 	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)
738 		clear_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);
739 	else
740 		set_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);
741 }
742 
743 /**
744  * batadv_dat_hash_free - free the local DAT hash table
745  * @bat_priv: the bat priv with all the soft interface information
746  */
747 static void batadv_dat_hash_free(struct batadv_priv *bat_priv)
748 {
749 	if (!bat_priv->dat.hash)
750 		return;
751 
752 	__batadv_dat_purge(bat_priv, NULL);
753 
754 	batadv_hash_destroy(bat_priv->dat.hash);
755 
756 	bat_priv->dat.hash = NULL;
757 }
758 
759 /**
760  * batadv_dat_init - initialise the DAT internals
761  * @bat_priv: the bat priv with all the soft interface information
762  *
763  * Return: 0 in case of success, a negative error code otherwise
764  */
765 int batadv_dat_init(struct batadv_priv *bat_priv)
766 {
767 	if (bat_priv->dat.hash)
768 		return 0;
769 
770 	bat_priv->dat.hash = batadv_hash_new(1024);
771 
772 	if (!bat_priv->dat.hash)
773 		return -ENOMEM;
774 
775 	batadv_dat_start_timer(bat_priv);
776 
777 	batadv_tvlv_handler_register(bat_priv, batadv_dat_tvlv_ogm_handler_v1,
778 				     NULL, BATADV_TVLV_DAT, 1,
779 				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
780 	batadv_dat_tvlv_container_update(bat_priv);
781 	return 0;
782 }
783 
784 /**
785  * batadv_dat_free - free the DAT internals
786  * @bat_priv: the bat priv with all the soft interface information
787  */
788 void batadv_dat_free(struct batadv_priv *bat_priv)
789 {
790 	batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
791 	batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_DAT, 1);
792 
793 	cancel_delayed_work_sync(&bat_priv->dat.work);
794 
795 	batadv_dat_hash_free(bat_priv);
796 }
797 
798 #ifdef CONFIG_BATMAN_ADV_DEBUGFS
799 /**
800  * batadv_dat_cache_seq_print_text - print the local DAT hash table
801  * @seq: seq file to print on
802  * @offset: not used
803  *
804  * Return: always 0
805  */
806 int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset)
807 {
808 	struct net_device *net_dev = (struct net_device *)seq->private;
809 	struct batadv_priv *bat_priv = netdev_priv(net_dev);
810 	struct batadv_hashtable *hash = bat_priv->dat.hash;
811 	struct batadv_dat_entry *dat_entry;
812 	struct batadv_hard_iface *primary_if;
813 	struct hlist_head *head;
814 	unsigned long last_seen_jiffies;
815 	int last_seen_msecs, last_seen_secs, last_seen_mins;
816 	u32 i;
817 
818 	primary_if = batadv_seq_print_text_primary_if_get(seq);
819 	if (!primary_if)
820 		goto out;
821 
822 	seq_printf(seq, "Distributed ARP Table (%s):\n", net_dev->name);
823 	seq_puts(seq,
824 		 "          IPv4             MAC        VID   last-seen\n");
825 
826 	for (i = 0; i < hash->size; i++) {
827 		head = &hash->table[i];
828 
829 		rcu_read_lock();
830 		hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {
831 			last_seen_jiffies = jiffies - dat_entry->last_update;
832 			last_seen_msecs = jiffies_to_msecs(last_seen_jiffies);
833 			last_seen_mins = last_seen_msecs / 60000;
834 			last_seen_msecs = last_seen_msecs % 60000;
835 			last_seen_secs = last_seen_msecs / 1000;
836 
837 			seq_printf(seq, " * %15pI4 %pM %4i %6i:%02i\n",
838 				   &dat_entry->ip, dat_entry->mac_addr,
839 				   batadv_print_vid(dat_entry->vid),
840 				   last_seen_mins, last_seen_secs);
841 		}
842 		rcu_read_unlock();
843 	}
844 
845 out:
846 	if (primary_if)
847 		batadv_hardif_put(primary_if);
848 	return 0;
849 }
850 #endif
851 
852 /**
853  * batadv_arp_get_type - parse an ARP packet and gets the type
854  * @bat_priv: the bat priv with all the soft interface information
855  * @skb: packet to analyse
856  * @hdr_size: size of the possible header before the ARP packet in the skb
857  *
858  * Return: the ARP type if the skb contains a valid ARP packet, 0 otherwise.
859  */
860 static u16 batadv_arp_get_type(struct batadv_priv *bat_priv,
861 			       struct sk_buff *skb, int hdr_size)
862 {
863 	struct arphdr *arphdr;
864 	struct ethhdr *ethhdr;
865 	__be32 ip_src, ip_dst;
866 	u8 *hw_src, *hw_dst;
867 	u16 type = 0;
868 
869 	/* pull the ethernet header */
870 	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
871 		goto out;
872 
873 	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
874 
875 	if (ethhdr->h_proto != htons(ETH_P_ARP))
876 		goto out;
877 
878 	/* pull the ARP payload */
879 	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN +
880 				    arp_hdr_len(skb->dev))))
881 		goto out;
882 
883 	arphdr = (struct arphdr *)(skb->data + hdr_size + ETH_HLEN);
884 
885 	/* check whether the ARP packet carries a valid IP information */
886 	if (arphdr->ar_hrd != htons(ARPHRD_ETHER))
887 		goto out;
888 
889 	if (arphdr->ar_pro != htons(ETH_P_IP))
890 		goto out;
891 
892 	if (arphdr->ar_hln != ETH_ALEN)
893 		goto out;
894 
895 	if (arphdr->ar_pln != 4)
896 		goto out;
897 
898 	/* Check for bad reply/request. If the ARP message is not sane, DAT
899 	 * will simply ignore it
900 	 */
901 	ip_src = batadv_arp_ip_src(skb, hdr_size);
902 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
903 	if (ipv4_is_loopback(ip_src) || ipv4_is_multicast(ip_src) ||
904 	    ipv4_is_loopback(ip_dst) || ipv4_is_multicast(ip_dst) ||
905 	    ipv4_is_zeronet(ip_src) || ipv4_is_lbcast(ip_src) ||
906 	    ipv4_is_zeronet(ip_dst) || ipv4_is_lbcast(ip_dst))
907 		goto out;
908 
909 	hw_src = batadv_arp_hw_src(skb, hdr_size);
910 	if (is_zero_ether_addr(hw_src) || is_multicast_ether_addr(hw_src))
911 		goto out;
912 
913 	/* don't care about the destination MAC address in ARP requests */
914 	if (arphdr->ar_op != htons(ARPOP_REQUEST)) {
915 		hw_dst = batadv_arp_hw_dst(skb, hdr_size);
916 		if (is_zero_ether_addr(hw_dst) ||
917 		    is_multicast_ether_addr(hw_dst))
918 			goto out;
919 	}
920 
921 	type = ntohs(arphdr->ar_op);
922 out:
923 	return type;
924 }
925 
926 /**
927  * batadv_dat_get_vid - extract the VLAN identifier from skb if any
928  * @skb: the buffer containing the packet to extract the VID from
929  * @hdr_size: the size of the batman-adv header encapsulating the packet
930  *
931  * Return: If the packet embedded in the skb is vlan tagged this function
932  * returns the VID with the BATADV_VLAN_HAS_TAG flag. Otherwise BATADV_NO_FLAGS
933  * is returned.
934  */
935 static unsigned short batadv_dat_get_vid(struct sk_buff *skb, int *hdr_size)
936 {
937 	unsigned short vid;
938 
939 	vid = batadv_get_vid(skb, *hdr_size);
940 
941 	/* ARP parsing functions jump forward of hdr_size + ETH_HLEN.
942 	 * If the header contained in the packet is a VLAN one (which is longer)
943 	 * hdr_size is updated so that the functions will still skip the
944 	 * correct amount of bytes.
945 	 */
946 	if (vid & BATADV_VLAN_HAS_TAG)
947 		*hdr_size += VLAN_HLEN;
948 
949 	return vid;
950 }
951 
952 /**
953  * batadv_dat_arp_create_reply - create an ARP Reply
954  * @bat_priv: the bat priv with all the soft interface information
955  * @ip_src: ARP sender IP
956  * @ip_dst: ARP target IP
957  * @hw_src: Ethernet source and ARP sender MAC
958  * @hw_dst: Ethernet destination and ARP target MAC
959  * @vid: VLAN identifier (optional, set to zero otherwise)
960  *
961  * Creates an ARP Reply from the given values, optionally encapsulated in a
962  * VLAN header.
963  *
964  * Return: An skb containing an ARP Reply.
965  */
966 static struct sk_buff *
967 batadv_dat_arp_create_reply(struct batadv_priv *bat_priv, __be32 ip_src,
968 			    __be32 ip_dst, u8 *hw_src, u8 *hw_dst,
969 			    unsigned short vid)
970 {
971 	struct sk_buff *skb;
972 
973 	skb = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_dst, bat_priv->soft_iface,
974 			 ip_src, hw_dst, hw_src, hw_dst);
975 	if (!skb)
976 		return NULL;
977 
978 	skb_reset_mac_header(skb);
979 
980 	if (vid & BATADV_VLAN_HAS_TAG)
981 		skb = vlan_insert_tag(skb, htons(ETH_P_8021Q),
982 				      vid & VLAN_VID_MASK);
983 
984 	return skb;
985 }
986 
987 /**
988  * batadv_dat_snoop_outgoing_arp_request - snoop the ARP request and try to
989  * answer using DAT
990  * @bat_priv: the bat priv with all the soft interface information
991  * @skb: packet to check
992  *
993  * Return: true if the message has been sent to the dht candidates, false
994  * otherwise. In case of a positive return value the message has to be enqueued
995  * to permit the fallback.
996  */
997 bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
998 					   struct sk_buff *skb)
999 {
1000 	u16 type = 0;
1001 	__be32 ip_dst, ip_src;
1002 	u8 *hw_src;
1003 	bool ret = false;
1004 	struct batadv_dat_entry *dat_entry = NULL;
1005 	struct sk_buff *skb_new;
1006 	struct net_device *soft_iface = bat_priv->soft_iface;
1007 	int hdr_size = 0;
1008 	unsigned short vid;
1009 
1010 	if (!atomic_read(&bat_priv->distributed_arp_table))
1011 		goto out;
1012 
1013 	vid = batadv_dat_get_vid(skb, &hdr_size);
1014 
1015 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1016 	/* If the node gets an ARP_REQUEST it has to send a DHT_GET unicast
1017 	 * message to the selected DHT candidates
1018 	 */
1019 	if (type != ARPOP_REQUEST)
1020 		goto out;
1021 
1022 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REQUEST");
1023 
1024 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1025 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1026 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1027 
1028 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1029 
1030 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
1031 	if (dat_entry) {
1032 		/* If the ARP request is destined for a local client the local
1033 		 * client will answer itself. DAT would only generate a
1034 		 * duplicate packet.
1035 		 *
1036 		 * Moreover, if the soft-interface is enslaved into a bridge, an
1037 		 * additional DAT answer may trigger kernel warnings about
1038 		 * a packet coming from the wrong port.
1039 		 */
1040 		if (batadv_is_my_client(bat_priv, dat_entry->mac_addr, vid)) {
1041 			ret = true;
1042 			goto out;
1043 		}
1044 
1045 		/* If BLA is enabled, only send ARP replies if we have claimed
1046 		 * the destination for the ARP request or if no one else of
1047 		 * the backbone gws belonging to our backbone has claimed the
1048 		 * destination.
1049 		 */
1050 		if (!batadv_bla_check_claim(bat_priv,
1051 					    dat_entry->mac_addr, vid)) {
1052 			batadv_dbg(BATADV_DBG_DAT, bat_priv,
1053 				   "Device %pM claimed by another backbone gw. Don't send ARP reply!",
1054 				   dat_entry->mac_addr);
1055 			ret = true;
1056 			goto out;
1057 		}
1058 
1059 		skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
1060 						      dat_entry->mac_addr,
1061 						      hw_src, vid);
1062 		if (!skb_new)
1063 			goto out;
1064 
1065 		skb_new->protocol = eth_type_trans(skb_new, soft_iface);
1066 
1067 		batadv_inc_counter(bat_priv, BATADV_CNT_RX);
1068 		batadv_add_counter(bat_priv, BATADV_CNT_RX_BYTES,
1069 				   skb->len + ETH_HLEN + hdr_size);
1070 
1071 		netif_rx(skb_new);
1072 		batadv_dbg(BATADV_DBG_DAT, bat_priv, "ARP request replied locally\n");
1073 		ret = true;
1074 	} else {
1075 		/* Send the request to the DHT */
1076 		ret = batadv_dat_send_data(bat_priv, skb, ip_dst, vid,
1077 					   BATADV_P_DAT_DHT_GET);
1078 	}
1079 out:
1080 	if (dat_entry)
1081 		batadv_dat_entry_put(dat_entry);
1082 	return ret;
1083 }
1084 
1085 /**
1086  * batadv_dat_snoop_incoming_arp_request - snoop the ARP request and try to
1087  * answer using the local DAT storage
1088  * @bat_priv: the bat priv with all the soft interface information
1089  * @skb: packet to check
1090  * @hdr_size: size of the encapsulation header
1091  *
1092  * Return: true if the request has been answered, false otherwise.
1093  */
1094 bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
1095 					   struct sk_buff *skb, int hdr_size)
1096 {
1097 	u16 type;
1098 	__be32 ip_src, ip_dst;
1099 	u8 *hw_src;
1100 	struct sk_buff *skb_new;
1101 	struct batadv_dat_entry *dat_entry = NULL;
1102 	bool ret = false;
1103 	unsigned short vid;
1104 	int err;
1105 
1106 	if (!atomic_read(&bat_priv->distributed_arp_table))
1107 		goto out;
1108 
1109 	vid = batadv_dat_get_vid(skb, &hdr_size);
1110 
1111 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1112 	if (type != ARPOP_REQUEST)
1113 		goto out;
1114 
1115 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1116 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1117 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1118 
1119 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REQUEST");
1120 
1121 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1122 
1123 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
1124 	if (!dat_entry)
1125 		goto out;
1126 
1127 	skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
1128 					      dat_entry->mac_addr, hw_src, vid);
1129 	if (!skb_new)
1130 		goto out;
1131 
1132 	/* To preserve backwards compatibility, the node has choose the outgoing
1133 	 * format based on the incoming request packet type. The assumption is
1134 	 * that a node not using the 4addr packet format doesn't support it.
1135 	 */
1136 	if (hdr_size == sizeof(struct batadv_unicast_4addr_packet))
1137 		err = batadv_send_skb_via_tt_4addr(bat_priv, skb_new,
1138 						   BATADV_P_DAT_CACHE_REPLY,
1139 						   NULL, vid);
1140 	else
1141 		err = batadv_send_skb_via_tt(bat_priv, skb_new, NULL, vid);
1142 
1143 	if (err != NET_XMIT_DROP) {
1144 		batadv_inc_counter(bat_priv, BATADV_CNT_DAT_CACHED_REPLY_TX);
1145 		ret = true;
1146 	}
1147 out:
1148 	if (dat_entry)
1149 		batadv_dat_entry_put(dat_entry);
1150 	if (ret)
1151 		kfree_skb(skb);
1152 	return ret;
1153 }
1154 
1155 /**
1156  * batadv_dat_snoop_outgoing_arp_reply - snoop the ARP reply and fill the DHT
1157  * @bat_priv: the bat priv with all the soft interface information
1158  * @skb: packet to check
1159  */
1160 void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
1161 					 struct sk_buff *skb)
1162 {
1163 	u16 type;
1164 	__be32 ip_src, ip_dst;
1165 	u8 *hw_src, *hw_dst;
1166 	int hdr_size = 0;
1167 	unsigned short vid;
1168 
1169 	if (!atomic_read(&bat_priv->distributed_arp_table))
1170 		return;
1171 
1172 	vid = batadv_dat_get_vid(skb, &hdr_size);
1173 
1174 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1175 	if (type != ARPOP_REPLY)
1176 		return;
1177 
1178 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REPLY");
1179 
1180 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1181 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1182 	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
1183 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1184 
1185 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1186 	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);
1187 
1188 	/* Send the ARP reply to the candidates for both the IP addresses that
1189 	 * the node obtained from the ARP reply
1190 	 */
1191 	batadv_dat_send_data(bat_priv, skb, ip_src, vid, BATADV_P_DAT_DHT_PUT);
1192 	batadv_dat_send_data(bat_priv, skb, ip_dst, vid, BATADV_P_DAT_DHT_PUT);
1193 }
1194 
1195 /**
1196  * batadv_dat_snoop_incoming_arp_reply - snoop the ARP reply and fill the local
1197  * DAT storage only
1198  * @bat_priv: the bat priv with all the soft interface information
1199  * @skb: packet to check
1200  * @hdr_size: size of the encapsulation header
1201  *
1202  * Return: true if the packet was snooped and consumed by DAT. False if the
1203  * packet has to be delivered to the interface
1204  */
1205 bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
1206 					 struct sk_buff *skb, int hdr_size)
1207 {
1208 	struct batadv_dat_entry *dat_entry = NULL;
1209 	u16 type;
1210 	__be32 ip_src, ip_dst;
1211 	u8 *hw_src, *hw_dst;
1212 	bool dropped = false;
1213 	unsigned short vid;
1214 
1215 	if (!atomic_read(&bat_priv->distributed_arp_table))
1216 		goto out;
1217 
1218 	vid = batadv_dat_get_vid(skb, &hdr_size);
1219 
1220 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1221 	if (type != ARPOP_REPLY)
1222 		goto out;
1223 
1224 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REPLY");
1225 
1226 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1227 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1228 	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
1229 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1230 
1231 	/* If ip_dst is already in cache and has the right mac address,
1232 	 * drop this frame if this ARP reply is destined for us because it's
1233 	 * most probably an ARP reply generated by another node of the DHT.
1234 	 * We have most probably received already a reply earlier. Delivering
1235 	 * this frame would lead to doubled receive of an ARP reply.
1236 	 */
1237 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_src, vid);
1238 	if (dat_entry && batadv_compare_eth(hw_src, dat_entry->mac_addr)) {
1239 		batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP reply removed: ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; dat_entry: %pM-%pI4\n",
1240 			   hw_src, &ip_src, hw_dst, &ip_dst,
1241 			   dat_entry->mac_addr,	&dat_entry->ip);
1242 		dropped = true;
1243 		goto out;
1244 	}
1245 
1246 	/* Update our internal cache with both the IP addresses the node got
1247 	 * within the ARP reply
1248 	 */
1249 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1250 	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);
1251 
1252 	/* If BLA is enabled, only forward ARP replies if we have claimed the
1253 	 * source of the ARP reply or if no one else of the same backbone has
1254 	 * already claimed that client. This prevents that different gateways
1255 	 * to the same backbone all forward the ARP reply leading to multiple
1256 	 * replies in the backbone.
1257 	 */
1258 	if (!batadv_bla_check_claim(bat_priv, hw_src, vid)) {
1259 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
1260 			   "Device %pM claimed by another backbone gw. Drop ARP reply.\n",
1261 			   hw_src);
1262 		dropped = true;
1263 		goto out;
1264 	}
1265 
1266 	/* if this REPLY is directed to a client of mine, let's deliver the
1267 	 * packet to the interface
1268 	 */
1269 	dropped = !batadv_is_my_client(bat_priv, hw_dst, vid);
1270 
1271 	/* if this REPLY is sent on behalf of a client of mine, let's drop the
1272 	 * packet because the client will reply by itself
1273 	 */
1274 	dropped |= batadv_is_my_client(bat_priv, hw_src, vid);
1275 out:
1276 	if (dropped)
1277 		kfree_skb(skb);
1278 	if (dat_entry)
1279 		batadv_dat_entry_put(dat_entry);
1280 	/* if dropped == false -> deliver to the interface */
1281 	return dropped;
1282 }
1283 
1284 /**
1285  * batadv_dat_drop_broadcast_packet - check if an ARP request has to be dropped
1286  * (because the node has already obtained the reply via DAT) or not
1287  * @bat_priv: the bat priv with all the soft interface information
1288  * @forw_packet: the broadcast packet
1289  *
1290  * Return: true if the node can drop the packet, false otherwise.
1291  */
1292 bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
1293 				      struct batadv_forw_packet *forw_packet)
1294 {
1295 	u16 type;
1296 	__be32 ip_dst;
1297 	struct batadv_dat_entry *dat_entry = NULL;
1298 	bool ret = false;
1299 	int hdr_size = sizeof(struct batadv_bcast_packet);
1300 	unsigned short vid;
1301 
1302 	if (!atomic_read(&bat_priv->distributed_arp_table))
1303 		goto out;
1304 
1305 	/* If this packet is an ARP_REQUEST and the node already has the
1306 	 * information that it is going to ask, then the packet can be dropped
1307 	 */
1308 	if (batadv_forw_packet_is_rebroadcast(forw_packet))
1309 		goto out;
1310 
1311 	vid = batadv_dat_get_vid(forw_packet->skb, &hdr_size);
1312 
1313 	type = batadv_arp_get_type(bat_priv, forw_packet->skb, hdr_size);
1314 	if (type != ARPOP_REQUEST)
1315 		goto out;
1316 
1317 	ip_dst = batadv_arp_ip_dst(forw_packet->skb, hdr_size);
1318 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
1319 	/* check if the node already got this entry */
1320 	if (!dat_entry) {
1321 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
1322 			   "ARP Request for %pI4: fallback\n", &ip_dst);
1323 		goto out;
1324 	}
1325 
1326 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
1327 		   "ARP Request for %pI4: fallback prevented\n", &ip_dst);
1328 	ret = true;
1329 
1330 out:
1331 	if (dat_entry)
1332 		batadv_dat_entry_put(dat_entry);
1333 	return ret;
1334 }
1335