1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) B.A.T.M.A.N. contributors:
3  *
4  * Antonio Quartulli
5  */
6 
7 #include "distributed-arp-table.h"
8 #include "main.h"
9 
10 #include <asm/unaligned.h>
11 #include <linux/atomic.h>
12 #include <linux/bitops.h>
13 #include <linux/byteorder/generic.h>
14 #include <linux/container_of.h>
15 #include <linux/errno.h>
16 #include <linux/etherdevice.h>
17 #include <linux/gfp.h>
18 #include <linux/if_arp.h>
19 #include <linux/if_ether.h>
20 #include <linux/if_vlan.h>
21 #include <linux/in.h>
22 #include <linux/ip.h>
23 #include <linux/jiffies.h>
24 #include <linux/kref.h>
25 #include <linux/list.h>
26 #include <linux/netlink.h>
27 #include <linux/rculist.h>
28 #include <linux/rcupdate.h>
29 #include <linux/skbuff.h>
30 #include <linux/slab.h>
31 #include <linux/spinlock.h>
32 #include <linux/stddef.h>
33 #include <linux/string.h>
34 #include <linux/udp.h>
35 #include <linux/workqueue.h>
36 #include <net/arp.h>
37 #include <net/genetlink.h>
38 #include <net/netlink.h>
39 #include <net/sock.h>
40 #include <uapi/linux/batman_adv.h>
41 
42 #include "bridge_loop_avoidance.h"
43 #include "hard-interface.h"
44 #include "hash.h"
45 #include "log.h"
46 #include "netlink.h"
47 #include "originator.h"
48 #include "send.h"
49 #include "soft-interface.h"
50 #include "translation-table.h"
51 #include "tvlv.h"
52 
53 enum batadv_bootpop {
54 	BATADV_BOOTREPLY	= 2,
55 };
56 
57 enum batadv_boothtype {
58 	BATADV_HTYPE_ETHERNET	= 1,
59 };
60 
61 enum batadv_dhcpoptioncode {
62 	BATADV_DHCP_OPT_PAD		= 0,
63 	BATADV_DHCP_OPT_MSG_TYPE	= 53,
64 	BATADV_DHCP_OPT_END		= 255,
65 };
66 
67 enum batadv_dhcptype {
68 	BATADV_DHCPACK		= 5,
69 };
70 
71 /* { 99, 130, 83, 99 } */
72 #define BATADV_DHCP_MAGIC 1669485411
73 
74 struct batadv_dhcp_packet {
75 	__u8 op;
76 	__u8 htype;
77 	__u8 hlen;
78 	__u8 hops;
79 	__be32 xid;
80 	__be16 secs;
81 	__be16 flags;
82 	__be32 ciaddr;
83 	__be32 yiaddr;
84 	__be32 siaddr;
85 	__be32 giaddr;
86 	__u8 chaddr[16];
87 	__u8 sname[64];
88 	__u8 file[128];
89 	__be32 magic;
90 	/* __u8 options[]; */
91 };
92 
93 #define BATADV_DHCP_YIADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->yiaddr)
94 #define BATADV_DHCP_CHADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->chaddr)
95 
96 static void batadv_dat_purge(struct work_struct *work);
97 
98 /**
99  * batadv_dat_start_timer() - initialise the DAT periodic worker
100  * @bat_priv: the bat priv with all the soft interface information
101  */
102 static void batadv_dat_start_timer(struct batadv_priv *bat_priv)
103 {
104 	INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
105 	queue_delayed_work(batadv_event_workqueue, &bat_priv->dat.work,
106 			   msecs_to_jiffies(10000));
107 }
108 
109 /**
110  * batadv_dat_entry_release() - release dat_entry from lists and queue for free
111  *  after rcu grace period
112  * @ref: kref pointer of the dat_entry
113  */
114 static void batadv_dat_entry_release(struct kref *ref)
115 {
116 	struct batadv_dat_entry *dat_entry;
117 
118 	dat_entry = container_of(ref, struct batadv_dat_entry, refcount);
119 
120 	kfree_rcu(dat_entry, rcu);
121 }
122 
123 /**
124  * batadv_dat_entry_put() - decrement the dat_entry refcounter and possibly
125  *  release it
126  * @dat_entry: dat_entry to be free'd
127  */
128 static void batadv_dat_entry_put(struct batadv_dat_entry *dat_entry)
129 {
130 	if (!dat_entry)
131 		return;
132 
133 	kref_put(&dat_entry->refcount, batadv_dat_entry_release);
134 }
135 
136 /**
137  * batadv_dat_to_purge() - check whether a dat_entry has to be purged or not
138  * @dat_entry: the entry to check
139  *
140  * Return: true if the entry has to be purged now, false otherwise.
141  */
142 static bool batadv_dat_to_purge(struct batadv_dat_entry *dat_entry)
143 {
144 	return batadv_has_timed_out(dat_entry->last_update,
145 				    BATADV_DAT_ENTRY_TIMEOUT);
146 }
147 
148 /**
149  * __batadv_dat_purge() - delete entries from the DAT local storage
150  * @bat_priv: the bat priv with all the soft interface information
151  * @to_purge: function in charge to decide whether an entry has to be purged or
152  *	      not. This function takes the dat_entry as argument and has to
153  *	      returns a boolean value: true is the entry has to be deleted,
154  *	      false otherwise
155  *
156  * Loops over each entry in the DAT local storage and deletes it if and only if
157  * the to_purge function passed as argument returns true.
158  */
159 static void __batadv_dat_purge(struct batadv_priv *bat_priv,
160 			       bool (*to_purge)(struct batadv_dat_entry *))
161 {
162 	spinlock_t *list_lock; /* protects write access to the hash lists */
163 	struct batadv_dat_entry *dat_entry;
164 	struct hlist_node *node_tmp;
165 	struct hlist_head *head;
166 	u32 i;
167 
168 	if (!bat_priv->dat.hash)
169 		return;
170 
171 	for (i = 0; i < bat_priv->dat.hash->size; i++) {
172 		head = &bat_priv->dat.hash->table[i];
173 		list_lock = &bat_priv->dat.hash->list_locks[i];
174 
175 		spin_lock_bh(list_lock);
176 		hlist_for_each_entry_safe(dat_entry, node_tmp, head,
177 					  hash_entry) {
178 			/* if a helper function has been passed as parameter,
179 			 * ask it if the entry has to be purged or not
180 			 */
181 			if (to_purge && !to_purge(dat_entry))
182 				continue;
183 
184 			hlist_del_rcu(&dat_entry->hash_entry);
185 			batadv_dat_entry_put(dat_entry);
186 		}
187 		spin_unlock_bh(list_lock);
188 	}
189 }
190 
191 /**
192  * batadv_dat_purge() - periodic task that deletes old entries from the local
193  *  DAT hash table
194  * @work: kernel work struct
195  */
196 static void batadv_dat_purge(struct work_struct *work)
197 {
198 	struct delayed_work *delayed_work;
199 	struct batadv_priv_dat *priv_dat;
200 	struct batadv_priv *bat_priv;
201 
202 	delayed_work = to_delayed_work(work);
203 	priv_dat = container_of(delayed_work, struct batadv_priv_dat, work);
204 	bat_priv = container_of(priv_dat, struct batadv_priv, dat);
205 
206 	__batadv_dat_purge(bat_priv, batadv_dat_to_purge);
207 	batadv_dat_start_timer(bat_priv);
208 }
209 
210 /**
211  * batadv_compare_dat() - comparing function used in the local DAT hash table
212  * @node: node in the local table
213  * @data2: second object to compare the node to
214  *
215  * Return: true if the two entries are the same, false otherwise.
216  */
217 static bool batadv_compare_dat(const struct hlist_node *node, const void *data2)
218 {
219 	const void *data1 = container_of(node, struct batadv_dat_entry,
220 					 hash_entry);
221 
222 	return memcmp(data1, data2, sizeof(__be32)) == 0;
223 }
224 
225 /**
226  * batadv_arp_hw_src() - extract the hw_src field from an ARP packet
227  * @skb: ARP packet
228  * @hdr_size: size of the possible header before the ARP packet
229  *
230  * Return: the value of the hw_src field in the ARP packet.
231  */
232 static u8 *batadv_arp_hw_src(struct sk_buff *skb, int hdr_size)
233 {
234 	u8 *addr;
235 
236 	addr = (u8 *)(skb->data + hdr_size);
237 	addr += ETH_HLEN + sizeof(struct arphdr);
238 
239 	return addr;
240 }
241 
242 /**
243  * batadv_arp_ip_src() - extract the ip_src field from an ARP packet
244  * @skb: ARP packet
245  * @hdr_size: size of the possible header before the ARP packet
246  *
247  * Return: the value of the ip_src field in the ARP packet.
248  */
249 static __be32 batadv_arp_ip_src(struct sk_buff *skb, int hdr_size)
250 {
251 	return *(__force __be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN);
252 }
253 
254 /**
255  * batadv_arp_hw_dst() - extract the hw_dst field from an ARP packet
256  * @skb: ARP packet
257  * @hdr_size: size of the possible header before the ARP packet
258  *
259  * Return: the value of the hw_dst field in the ARP packet.
260  */
261 static u8 *batadv_arp_hw_dst(struct sk_buff *skb, int hdr_size)
262 {
263 	return batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN + 4;
264 }
265 
266 /**
267  * batadv_arp_ip_dst() - extract the ip_dst field from an ARP packet
268  * @skb: ARP packet
269  * @hdr_size: size of the possible header before the ARP packet
270  *
271  * Return: the value of the ip_dst field in the ARP packet.
272  */
273 static __be32 batadv_arp_ip_dst(struct sk_buff *skb, int hdr_size)
274 {
275 	u8 *dst = batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN * 2 + 4;
276 
277 	return *(__force __be32 *)dst;
278 }
279 
280 /**
281  * batadv_hash_dat() - compute the hash value for an IP address
282  * @data: data to hash
283  * @size: size of the hash table
284  *
285  * Return: the selected index in the hash table for the given data.
286  */
287 static u32 batadv_hash_dat(const void *data, u32 size)
288 {
289 	u32 hash = 0;
290 	const struct batadv_dat_entry *dat = data;
291 	const unsigned char *key;
292 	__be16 vid;
293 	u32 i;
294 
295 	key = (__force const unsigned char *)&dat->ip;
296 	for (i = 0; i < sizeof(dat->ip); i++) {
297 		hash += key[i];
298 		hash += (hash << 10);
299 		hash ^= (hash >> 6);
300 	}
301 
302 	vid = htons(dat->vid);
303 	key = (__force const unsigned char *)&vid;
304 	for (i = 0; i < sizeof(dat->vid); i++) {
305 		hash += key[i];
306 		hash += (hash << 10);
307 		hash ^= (hash >> 6);
308 	}
309 
310 	hash += (hash << 3);
311 	hash ^= (hash >> 11);
312 	hash += (hash << 15);
313 
314 	return hash % size;
315 }
316 
317 /**
318  * batadv_dat_entry_hash_find() - look for a given dat_entry in the local hash
319  * table
320  * @bat_priv: the bat priv with all the soft interface information
321  * @ip: search key
322  * @vid: VLAN identifier
323  *
324  * Return: the dat_entry if found, NULL otherwise.
325  */
326 static struct batadv_dat_entry *
327 batadv_dat_entry_hash_find(struct batadv_priv *bat_priv, __be32 ip,
328 			   unsigned short vid)
329 {
330 	struct hlist_head *head;
331 	struct batadv_dat_entry to_find, *dat_entry, *dat_entry_tmp = NULL;
332 	struct batadv_hashtable *hash = bat_priv->dat.hash;
333 	u32 index;
334 
335 	if (!hash)
336 		return NULL;
337 
338 	to_find.ip = ip;
339 	to_find.vid = vid;
340 
341 	index = batadv_hash_dat(&to_find, hash->size);
342 	head = &hash->table[index];
343 
344 	rcu_read_lock();
345 	hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {
346 		if (dat_entry->ip != ip)
347 			continue;
348 
349 		if (!kref_get_unless_zero(&dat_entry->refcount))
350 			continue;
351 
352 		dat_entry_tmp = dat_entry;
353 		break;
354 	}
355 	rcu_read_unlock();
356 
357 	return dat_entry_tmp;
358 }
359 
360 /**
361  * batadv_dat_entry_add() - add a new dat entry or update it if already exists
362  * @bat_priv: the bat priv with all the soft interface information
363  * @ip: ipv4 to add/edit
364  * @mac_addr: mac address to assign to the given ipv4
365  * @vid: VLAN identifier
366  */
367 static void batadv_dat_entry_add(struct batadv_priv *bat_priv, __be32 ip,
368 				 u8 *mac_addr, unsigned short vid)
369 {
370 	struct batadv_dat_entry *dat_entry;
371 	int hash_added;
372 
373 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip, vid);
374 	/* if this entry is already known, just update it */
375 	if (dat_entry) {
376 		if (!batadv_compare_eth(dat_entry->mac_addr, mac_addr))
377 			ether_addr_copy(dat_entry->mac_addr, mac_addr);
378 		dat_entry->last_update = jiffies;
379 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
380 			   "Entry updated: %pI4 %pM (vid: %d)\n",
381 			   &dat_entry->ip, dat_entry->mac_addr,
382 			   batadv_print_vid(vid));
383 		goto out;
384 	}
385 
386 	dat_entry = kmalloc(sizeof(*dat_entry), GFP_ATOMIC);
387 	if (!dat_entry)
388 		goto out;
389 
390 	dat_entry->ip = ip;
391 	dat_entry->vid = vid;
392 	ether_addr_copy(dat_entry->mac_addr, mac_addr);
393 	dat_entry->last_update = jiffies;
394 	kref_init(&dat_entry->refcount);
395 
396 	kref_get(&dat_entry->refcount);
397 	hash_added = batadv_hash_add(bat_priv->dat.hash, batadv_compare_dat,
398 				     batadv_hash_dat, dat_entry,
399 				     &dat_entry->hash_entry);
400 
401 	if (unlikely(hash_added != 0)) {
402 		/* remove the reference for the hash */
403 		batadv_dat_entry_put(dat_entry);
404 		goto out;
405 	}
406 
407 	batadv_dbg(BATADV_DBG_DAT, bat_priv, "New entry added: %pI4 %pM (vid: %d)\n",
408 		   &dat_entry->ip, dat_entry->mac_addr, batadv_print_vid(vid));
409 
410 out:
411 	batadv_dat_entry_put(dat_entry);
412 }
413 
414 #ifdef CONFIG_BATMAN_ADV_DEBUG
415 
416 /**
417  * batadv_dbg_arp() - print a debug message containing all the ARP packet
418  *  details
419  * @bat_priv: the bat priv with all the soft interface information
420  * @skb: ARP packet
421  * @hdr_size: size of the possible header before the ARP packet
422  * @msg: message to print together with the debugging information
423  */
424 static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,
425 			   int hdr_size, char *msg)
426 {
427 	struct batadv_unicast_4addr_packet *unicast_4addr_packet;
428 	struct batadv_bcast_packet *bcast_pkt;
429 	u8 *orig_addr;
430 	__be32 ip_src, ip_dst;
431 
432 	if (msg)
433 		batadv_dbg(BATADV_DBG_DAT, bat_priv, "%s\n", msg);
434 
435 	ip_src = batadv_arp_ip_src(skb, hdr_size);
436 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
437 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
438 		   "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
439 		   batadv_arp_hw_src(skb, hdr_size), &ip_src,
440 		   batadv_arp_hw_dst(skb, hdr_size), &ip_dst);
441 
442 	if (hdr_size < sizeof(struct batadv_unicast_packet))
443 		return;
444 
445 	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
446 
447 	switch (unicast_4addr_packet->u.packet_type) {
448 	case BATADV_UNICAST:
449 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
450 			   "* encapsulated within a UNICAST packet\n");
451 		break;
452 	case BATADV_UNICAST_4ADDR:
453 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
454 			   "* encapsulated within a UNICAST_4ADDR packet (src: %pM)\n",
455 			   unicast_4addr_packet->src);
456 		switch (unicast_4addr_packet->subtype) {
457 		case BATADV_P_DAT_DHT_PUT:
458 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_PUT\n");
459 			break;
460 		case BATADV_P_DAT_DHT_GET:
461 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_GET\n");
462 			break;
463 		case BATADV_P_DAT_CACHE_REPLY:
464 			batadv_dbg(BATADV_DBG_DAT, bat_priv,
465 				   "* type: DAT_CACHE_REPLY\n");
466 			break;
467 		case BATADV_P_DATA:
468 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DATA\n");
469 			break;
470 		default:
471 			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: Unknown (%u)!\n",
472 				   unicast_4addr_packet->u.packet_type);
473 		}
474 		break;
475 	case BATADV_BCAST:
476 		bcast_pkt = (struct batadv_bcast_packet *)unicast_4addr_packet;
477 		orig_addr = bcast_pkt->orig;
478 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
479 			   "* encapsulated within a BCAST packet (src: %pM)\n",
480 			   orig_addr);
481 		break;
482 	default:
483 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
484 			   "* encapsulated within an unknown packet type (0x%x)\n",
485 			   unicast_4addr_packet->u.packet_type);
486 	}
487 }
488 
489 #else
490 
491 static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,
492 			   int hdr_size, char *msg)
493 {
494 }
495 
496 #endif /* CONFIG_BATMAN_ADV_DEBUG */
497 
498 /**
499  * batadv_is_orig_node_eligible() - check whether a node can be a DHT candidate
500  * @res: the array with the already selected candidates
501  * @select: number of already selected candidates
502  * @tmp_max: address of the currently evaluated node
503  * @max: current round max address
504  * @last_max: address of the last selected candidate
505  * @candidate: orig_node under evaluation
506  * @max_orig_node: last selected candidate
507  *
508  * Return: true if the node has been elected as next candidate or false
509  * otherwise.
510  */
511 static bool batadv_is_orig_node_eligible(struct batadv_dat_candidate *res,
512 					 int select, batadv_dat_addr_t tmp_max,
513 					 batadv_dat_addr_t max,
514 					 batadv_dat_addr_t last_max,
515 					 struct batadv_orig_node *candidate,
516 					 struct batadv_orig_node *max_orig_node)
517 {
518 	bool ret = false;
519 	int j;
520 
521 	/* check if orig node candidate is running DAT */
522 	if (!test_bit(BATADV_ORIG_CAPA_HAS_DAT, &candidate->capabilities))
523 		goto out;
524 
525 	/* Check if this node has already been selected... */
526 	for (j = 0; j < select; j++)
527 		if (res[j].orig_node == candidate)
528 			break;
529 	/* ..and possibly skip it */
530 	if (j < select)
531 		goto out;
532 	/* sanity check: has it already been selected? This should not happen */
533 	if (tmp_max > last_max)
534 		goto out;
535 	/* check if during this iteration an originator with a closer dht
536 	 * address has already been found
537 	 */
538 	if (tmp_max < max)
539 		goto out;
540 	/* this is an hash collision with the temporary selected node. Choose
541 	 * the one with the lowest address
542 	 */
543 	if (tmp_max == max && max_orig_node &&
544 	    batadv_compare_eth(candidate->orig, max_orig_node->orig))
545 		goto out;
546 
547 	ret = true;
548 out:
549 	return ret;
550 }
551 
552 /**
553  * batadv_choose_next_candidate() - select the next DHT candidate
554  * @bat_priv: the bat priv with all the soft interface information
555  * @cands: candidates array
556  * @select: number of candidates already present in the array
557  * @ip_key: key to look up in the DHT
558  * @last_max: pointer where the address of the selected candidate will be saved
559  */
560 static void batadv_choose_next_candidate(struct batadv_priv *bat_priv,
561 					 struct batadv_dat_candidate *cands,
562 					 int select, batadv_dat_addr_t ip_key,
563 					 batadv_dat_addr_t *last_max)
564 {
565 	batadv_dat_addr_t max = 0;
566 	batadv_dat_addr_t tmp_max = 0;
567 	struct batadv_orig_node *orig_node, *max_orig_node = NULL;
568 	struct batadv_hashtable *hash = bat_priv->orig_hash;
569 	struct hlist_head *head;
570 	int i;
571 
572 	/* if no node is eligible as candidate, leave the candidate type as
573 	 * NOT_FOUND
574 	 */
575 	cands[select].type = BATADV_DAT_CANDIDATE_NOT_FOUND;
576 
577 	/* iterate over the originator list and find the node with the closest
578 	 * dat_address which has not been selected yet
579 	 */
580 	for (i = 0; i < hash->size; i++) {
581 		head = &hash->table[i];
582 
583 		rcu_read_lock();
584 		hlist_for_each_entry_rcu(orig_node, head, hash_entry) {
585 			/* the dht space is a ring using unsigned addresses */
586 			tmp_max = BATADV_DAT_ADDR_MAX - orig_node->dat_addr +
587 				  ip_key;
588 
589 			if (!batadv_is_orig_node_eligible(cands, select,
590 							  tmp_max, max,
591 							  *last_max, orig_node,
592 							  max_orig_node))
593 				continue;
594 
595 			if (!kref_get_unless_zero(&orig_node->refcount))
596 				continue;
597 
598 			max = tmp_max;
599 			batadv_orig_node_put(max_orig_node);
600 			max_orig_node = orig_node;
601 		}
602 		rcu_read_unlock();
603 	}
604 	if (max_orig_node) {
605 		cands[select].type = BATADV_DAT_CANDIDATE_ORIG;
606 		cands[select].orig_node = max_orig_node;
607 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
608 			   "dat_select_candidates() %d: selected %pM addr=%u dist=%u\n",
609 			   select, max_orig_node->orig, max_orig_node->dat_addr,
610 			   max);
611 	}
612 	*last_max = max;
613 }
614 
615 /**
616  * batadv_dat_select_candidates() - select the nodes which the DHT message has
617  *  to be sent to
618  * @bat_priv: the bat priv with all the soft interface information
619  * @ip_dst: ipv4 to look up in the DHT
620  * @vid: VLAN identifier
621  *
622  * An originator O is selected if and only if its DHT_ID value is one of three
623  * closest values (from the LEFT, with wrap around if needed) then the hash
624  * value of the key. ip_dst is the key.
625  *
626  * Return: the candidate array of size BATADV_DAT_CANDIDATE_NUM.
627  */
628 static struct batadv_dat_candidate *
629 batadv_dat_select_candidates(struct batadv_priv *bat_priv, __be32 ip_dst,
630 			     unsigned short vid)
631 {
632 	int select;
633 	batadv_dat_addr_t last_max = BATADV_DAT_ADDR_MAX, ip_key;
634 	struct batadv_dat_candidate *res;
635 	struct batadv_dat_entry dat;
636 
637 	if (!bat_priv->orig_hash)
638 		return NULL;
639 
640 	res = kmalloc_array(BATADV_DAT_CANDIDATES_NUM, sizeof(*res),
641 			    GFP_ATOMIC);
642 	if (!res)
643 		return NULL;
644 
645 	dat.ip = ip_dst;
646 	dat.vid = vid;
647 	ip_key = (batadv_dat_addr_t)batadv_hash_dat(&dat,
648 						    BATADV_DAT_ADDR_MAX);
649 
650 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
651 		   "%s(): IP=%pI4 hash(IP)=%u\n", __func__, &ip_dst,
652 		   ip_key);
653 
654 	for (select = 0; select < BATADV_DAT_CANDIDATES_NUM; select++)
655 		batadv_choose_next_candidate(bat_priv, res, select, ip_key,
656 					     &last_max);
657 
658 	return res;
659 }
660 
661 /**
662  * batadv_dat_forward_data() - copy and send payload to the selected candidates
663  * @bat_priv: the bat priv with all the soft interface information
664  * @skb: payload to send
665  * @ip: the DHT key
666  * @vid: VLAN identifier
667  * @packet_subtype: unicast4addr packet subtype to use
668  *
669  * This function copies the skb with pskb_copy() and is sent as a unicast packet
670  * to each of the selected candidates.
671  *
672  * Return: true if the packet is sent to at least one candidate, false
673  * otherwise.
674  */
675 static bool batadv_dat_forward_data(struct batadv_priv *bat_priv,
676 				    struct sk_buff *skb, __be32 ip,
677 				    unsigned short vid, int packet_subtype)
678 {
679 	int i;
680 	bool ret = false;
681 	int send_status;
682 	struct batadv_neigh_node *neigh_node = NULL;
683 	struct sk_buff *tmp_skb;
684 	struct batadv_dat_candidate *cand;
685 
686 	cand = batadv_dat_select_candidates(bat_priv, ip, vid);
687 	if (!cand)
688 		goto out;
689 
690 	batadv_dbg(BATADV_DBG_DAT, bat_priv, "DHT_SEND for %pI4\n", &ip);
691 
692 	for (i = 0; i < BATADV_DAT_CANDIDATES_NUM; i++) {
693 		if (cand[i].type == BATADV_DAT_CANDIDATE_NOT_FOUND)
694 			continue;
695 
696 		neigh_node = batadv_orig_router_get(cand[i].orig_node,
697 						    BATADV_IF_DEFAULT);
698 		if (!neigh_node)
699 			goto free_orig;
700 
701 		tmp_skb = pskb_copy_for_clone(skb, GFP_ATOMIC);
702 		if (!batadv_send_skb_prepare_unicast_4addr(bat_priv, tmp_skb,
703 							   cand[i].orig_node,
704 							   packet_subtype)) {
705 			kfree_skb(tmp_skb);
706 			goto free_neigh;
707 		}
708 
709 		send_status = batadv_send_unicast_skb(tmp_skb, neigh_node);
710 		if (send_status == NET_XMIT_SUCCESS) {
711 			/* count the sent packet */
712 			switch (packet_subtype) {
713 			case BATADV_P_DAT_DHT_GET:
714 				batadv_inc_counter(bat_priv,
715 						   BATADV_CNT_DAT_GET_TX);
716 				break;
717 			case BATADV_P_DAT_DHT_PUT:
718 				batadv_inc_counter(bat_priv,
719 						   BATADV_CNT_DAT_PUT_TX);
720 				break;
721 			}
722 
723 			/* packet sent to a candidate: return true */
724 			ret = true;
725 		}
726 free_neigh:
727 		batadv_neigh_node_put(neigh_node);
728 free_orig:
729 		batadv_orig_node_put(cand[i].orig_node);
730 	}
731 
732 out:
733 	kfree(cand);
734 	return ret;
735 }
736 
737 /**
738  * batadv_dat_tvlv_container_update() - update the dat tvlv container after dat
739  *  setting change
740  * @bat_priv: the bat priv with all the soft interface information
741  */
742 static void batadv_dat_tvlv_container_update(struct batadv_priv *bat_priv)
743 {
744 	char dat_mode;
745 
746 	dat_mode = atomic_read(&bat_priv->distributed_arp_table);
747 
748 	switch (dat_mode) {
749 	case 0:
750 		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
751 		break;
752 	case 1:
753 		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_DAT, 1,
754 					       NULL, 0);
755 		break;
756 	}
757 }
758 
759 /**
760  * batadv_dat_status_update() - update the dat tvlv container after dat
761  *  setting change
762  * @net_dev: the soft interface net device
763  */
764 void batadv_dat_status_update(struct net_device *net_dev)
765 {
766 	struct batadv_priv *bat_priv = netdev_priv(net_dev);
767 
768 	batadv_dat_tvlv_container_update(bat_priv);
769 }
770 
771 /**
772  * batadv_dat_tvlv_ogm_handler_v1() - process incoming dat tvlv container
773  * @bat_priv: the bat priv with all the soft interface information
774  * @orig: the orig_node of the ogm
775  * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
776  * @tvlv_value: tvlv buffer containing the gateway data
777  * @tvlv_value_len: tvlv buffer length
778  */
779 static void batadv_dat_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
780 					   struct batadv_orig_node *orig,
781 					   u8 flags,
782 					   void *tvlv_value, u16 tvlv_value_len)
783 {
784 	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)
785 		clear_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);
786 	else
787 		set_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);
788 }
789 
790 /**
791  * batadv_dat_hash_free() - free the local DAT hash table
792  * @bat_priv: the bat priv with all the soft interface information
793  */
794 static void batadv_dat_hash_free(struct batadv_priv *bat_priv)
795 {
796 	if (!bat_priv->dat.hash)
797 		return;
798 
799 	__batadv_dat_purge(bat_priv, NULL);
800 
801 	batadv_hash_destroy(bat_priv->dat.hash);
802 
803 	bat_priv->dat.hash = NULL;
804 }
805 
806 /**
807  * batadv_dat_init() - initialise the DAT internals
808  * @bat_priv: the bat priv with all the soft interface information
809  *
810  * Return: 0 in case of success, a negative error code otherwise
811  */
812 int batadv_dat_init(struct batadv_priv *bat_priv)
813 {
814 	if (bat_priv->dat.hash)
815 		return 0;
816 
817 	bat_priv->dat.hash = batadv_hash_new(1024);
818 
819 	if (!bat_priv->dat.hash)
820 		return -ENOMEM;
821 
822 	batadv_dat_start_timer(bat_priv);
823 
824 	batadv_tvlv_handler_register(bat_priv, batadv_dat_tvlv_ogm_handler_v1,
825 				     NULL, BATADV_TVLV_DAT, 1,
826 				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
827 	batadv_dat_tvlv_container_update(bat_priv);
828 	return 0;
829 }
830 
831 /**
832  * batadv_dat_free() - free the DAT internals
833  * @bat_priv: the bat priv with all the soft interface information
834  */
835 void batadv_dat_free(struct batadv_priv *bat_priv)
836 {
837 	batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
838 	batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_DAT, 1);
839 
840 	cancel_delayed_work_sync(&bat_priv->dat.work);
841 
842 	batadv_dat_hash_free(bat_priv);
843 }
844 
845 /**
846  * batadv_dat_cache_dump_entry() - dump one entry of the DAT cache table to a
847  *  netlink socket
848  * @msg: buffer for the message
849  * @portid: netlink port
850  * @cb: Control block containing additional options
851  * @dat_entry: entry to dump
852  *
853  * Return: 0 or error code.
854  */
855 static int
856 batadv_dat_cache_dump_entry(struct sk_buff *msg, u32 portid,
857 			    struct netlink_callback *cb,
858 			    struct batadv_dat_entry *dat_entry)
859 {
860 	int msecs;
861 	void *hdr;
862 
863 	hdr = genlmsg_put(msg, portid, cb->nlh->nlmsg_seq,
864 			  &batadv_netlink_family, NLM_F_MULTI,
865 			  BATADV_CMD_GET_DAT_CACHE);
866 	if (!hdr)
867 		return -ENOBUFS;
868 
869 	genl_dump_check_consistent(cb, hdr);
870 
871 	msecs = jiffies_to_msecs(jiffies - dat_entry->last_update);
872 
873 	if (nla_put_in_addr(msg, BATADV_ATTR_DAT_CACHE_IP4ADDRESS,
874 			    dat_entry->ip) ||
875 	    nla_put(msg, BATADV_ATTR_DAT_CACHE_HWADDRESS, ETH_ALEN,
876 		    dat_entry->mac_addr) ||
877 	    nla_put_u16(msg, BATADV_ATTR_DAT_CACHE_VID, dat_entry->vid) ||
878 	    nla_put_u32(msg, BATADV_ATTR_LAST_SEEN_MSECS, msecs)) {
879 		genlmsg_cancel(msg, hdr);
880 		return -EMSGSIZE;
881 	}
882 
883 	genlmsg_end(msg, hdr);
884 	return 0;
885 }
886 
887 /**
888  * batadv_dat_cache_dump_bucket() - dump one bucket of the DAT cache table to
889  *  a netlink socket
890  * @msg: buffer for the message
891  * @portid: netlink port
892  * @cb: Control block containing additional options
893  * @hash: hash to dump
894  * @bucket: bucket index to dump
895  * @idx_skip: How many entries to skip
896  *
897  * Return: 0 or error code.
898  */
899 static int
900 batadv_dat_cache_dump_bucket(struct sk_buff *msg, u32 portid,
901 			     struct netlink_callback *cb,
902 			     struct batadv_hashtable *hash, unsigned int bucket,
903 			     int *idx_skip)
904 {
905 	struct batadv_dat_entry *dat_entry;
906 	int idx = 0;
907 
908 	spin_lock_bh(&hash->list_locks[bucket]);
909 	cb->seq = atomic_read(&hash->generation) << 1 | 1;
910 
911 	hlist_for_each_entry(dat_entry, &hash->table[bucket], hash_entry) {
912 		if (idx < *idx_skip)
913 			goto skip;
914 
915 		if (batadv_dat_cache_dump_entry(msg, portid, cb, dat_entry)) {
916 			spin_unlock_bh(&hash->list_locks[bucket]);
917 			*idx_skip = idx;
918 
919 			return -EMSGSIZE;
920 		}
921 
922 skip:
923 		idx++;
924 	}
925 	spin_unlock_bh(&hash->list_locks[bucket]);
926 
927 	return 0;
928 }
929 
930 /**
931  * batadv_dat_cache_dump() - dump DAT cache table to a netlink socket
932  * @msg: buffer for the message
933  * @cb: callback structure containing arguments
934  *
935  * Return: message length.
936  */
937 int batadv_dat_cache_dump(struct sk_buff *msg, struct netlink_callback *cb)
938 {
939 	struct batadv_hard_iface *primary_if = NULL;
940 	int portid = NETLINK_CB(cb->skb).portid;
941 	struct net *net = sock_net(cb->skb->sk);
942 	struct net_device *soft_iface;
943 	struct batadv_hashtable *hash;
944 	struct batadv_priv *bat_priv;
945 	int bucket = cb->args[0];
946 	int idx = cb->args[1];
947 	int ifindex;
948 	int ret = 0;
949 
950 	ifindex = batadv_netlink_get_ifindex(cb->nlh,
951 					     BATADV_ATTR_MESH_IFINDEX);
952 	if (!ifindex)
953 		return -EINVAL;
954 
955 	soft_iface = dev_get_by_index(net, ifindex);
956 	if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
957 		ret = -ENODEV;
958 		goto out;
959 	}
960 
961 	bat_priv = netdev_priv(soft_iface);
962 	hash = bat_priv->dat.hash;
963 
964 	primary_if = batadv_primary_if_get_selected(bat_priv);
965 	if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
966 		ret = -ENOENT;
967 		goto out;
968 	}
969 
970 	while (bucket < hash->size) {
971 		if (batadv_dat_cache_dump_bucket(msg, portid, cb, hash, bucket,
972 						 &idx))
973 			break;
974 
975 		bucket++;
976 		idx = 0;
977 	}
978 
979 	cb->args[0] = bucket;
980 	cb->args[1] = idx;
981 
982 	ret = msg->len;
983 
984 out:
985 	batadv_hardif_put(primary_if);
986 
987 	dev_put(soft_iface);
988 
989 	return ret;
990 }
991 
992 /**
993  * batadv_arp_get_type() - parse an ARP packet and gets the type
994  * @bat_priv: the bat priv with all the soft interface information
995  * @skb: packet to analyse
996  * @hdr_size: size of the possible header before the ARP packet in the skb
997  *
998  * Return: the ARP type if the skb contains a valid ARP packet, 0 otherwise.
999  */
1000 static u16 batadv_arp_get_type(struct batadv_priv *bat_priv,
1001 			       struct sk_buff *skb, int hdr_size)
1002 {
1003 	struct arphdr *arphdr;
1004 	struct ethhdr *ethhdr;
1005 	__be32 ip_src, ip_dst;
1006 	u8 *hw_src, *hw_dst;
1007 	u16 type = 0;
1008 
1009 	/* pull the ethernet header */
1010 	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
1011 		goto out;
1012 
1013 	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
1014 
1015 	if (ethhdr->h_proto != htons(ETH_P_ARP))
1016 		goto out;
1017 
1018 	/* pull the ARP payload */
1019 	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN +
1020 				    arp_hdr_len(skb->dev))))
1021 		goto out;
1022 
1023 	arphdr = (struct arphdr *)(skb->data + hdr_size + ETH_HLEN);
1024 
1025 	/* check whether the ARP packet carries a valid IP information */
1026 	if (arphdr->ar_hrd != htons(ARPHRD_ETHER))
1027 		goto out;
1028 
1029 	if (arphdr->ar_pro != htons(ETH_P_IP))
1030 		goto out;
1031 
1032 	if (arphdr->ar_hln != ETH_ALEN)
1033 		goto out;
1034 
1035 	if (arphdr->ar_pln != 4)
1036 		goto out;
1037 
1038 	/* Check for bad reply/request. If the ARP message is not sane, DAT
1039 	 * will simply ignore it
1040 	 */
1041 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1042 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1043 	if (ipv4_is_loopback(ip_src) || ipv4_is_multicast(ip_src) ||
1044 	    ipv4_is_loopback(ip_dst) || ipv4_is_multicast(ip_dst) ||
1045 	    ipv4_is_zeronet(ip_src) || ipv4_is_lbcast(ip_src) ||
1046 	    ipv4_is_zeronet(ip_dst) || ipv4_is_lbcast(ip_dst))
1047 		goto out;
1048 
1049 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1050 	if (is_zero_ether_addr(hw_src) || is_multicast_ether_addr(hw_src))
1051 		goto out;
1052 
1053 	/* don't care about the destination MAC address in ARP requests */
1054 	if (arphdr->ar_op != htons(ARPOP_REQUEST)) {
1055 		hw_dst = batadv_arp_hw_dst(skb, hdr_size);
1056 		if (is_zero_ether_addr(hw_dst) ||
1057 		    is_multicast_ether_addr(hw_dst))
1058 			goto out;
1059 	}
1060 
1061 	type = ntohs(arphdr->ar_op);
1062 out:
1063 	return type;
1064 }
1065 
1066 /**
1067  * batadv_dat_get_vid() - extract the VLAN identifier from skb if any
1068  * @skb: the buffer containing the packet to extract the VID from
1069  * @hdr_size: the size of the batman-adv header encapsulating the packet
1070  *
1071  * Return: If the packet embedded in the skb is vlan tagged this function
1072  * returns the VID with the BATADV_VLAN_HAS_TAG flag. Otherwise BATADV_NO_FLAGS
1073  * is returned.
1074  */
1075 static unsigned short batadv_dat_get_vid(struct sk_buff *skb, int *hdr_size)
1076 {
1077 	unsigned short vid;
1078 
1079 	vid = batadv_get_vid(skb, *hdr_size);
1080 
1081 	/* ARP parsing functions jump forward of hdr_size + ETH_HLEN.
1082 	 * If the header contained in the packet is a VLAN one (which is longer)
1083 	 * hdr_size is updated so that the functions will still skip the
1084 	 * correct amount of bytes.
1085 	 */
1086 	if (vid & BATADV_VLAN_HAS_TAG)
1087 		*hdr_size += VLAN_HLEN;
1088 
1089 	return vid;
1090 }
1091 
1092 /**
1093  * batadv_dat_arp_create_reply() - create an ARP Reply
1094  * @bat_priv: the bat priv with all the soft interface information
1095  * @ip_src: ARP sender IP
1096  * @ip_dst: ARP target IP
1097  * @hw_src: Ethernet source and ARP sender MAC
1098  * @hw_dst: Ethernet destination and ARP target MAC
1099  * @vid: VLAN identifier (optional, set to zero otherwise)
1100  *
1101  * Creates an ARP Reply from the given values, optionally encapsulated in a
1102  * VLAN header.
1103  *
1104  * Return: An skb containing an ARP Reply.
1105  */
1106 static struct sk_buff *
1107 batadv_dat_arp_create_reply(struct batadv_priv *bat_priv, __be32 ip_src,
1108 			    __be32 ip_dst, u8 *hw_src, u8 *hw_dst,
1109 			    unsigned short vid)
1110 {
1111 	struct sk_buff *skb;
1112 
1113 	skb = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_dst, bat_priv->soft_iface,
1114 			 ip_src, hw_dst, hw_src, hw_dst);
1115 	if (!skb)
1116 		return NULL;
1117 
1118 	skb_reset_mac_header(skb);
1119 
1120 	if (vid & BATADV_VLAN_HAS_TAG)
1121 		skb = vlan_insert_tag(skb, htons(ETH_P_8021Q),
1122 				      vid & VLAN_VID_MASK);
1123 
1124 	return skb;
1125 }
1126 
1127 /**
1128  * batadv_dat_snoop_outgoing_arp_request() - snoop the ARP request and try to
1129  * answer using DAT
1130  * @bat_priv: the bat priv with all the soft interface information
1131  * @skb: packet to check
1132  *
1133  * Return: true if the message has been sent to the dht candidates, false
1134  * otherwise. In case of a positive return value the message has to be enqueued
1135  * to permit the fallback.
1136  */
1137 bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
1138 					   struct sk_buff *skb)
1139 {
1140 	u16 type = 0;
1141 	__be32 ip_dst, ip_src;
1142 	u8 *hw_src;
1143 	bool ret = false;
1144 	struct batadv_dat_entry *dat_entry = NULL;
1145 	struct sk_buff *skb_new;
1146 	struct net_device *soft_iface = bat_priv->soft_iface;
1147 	int hdr_size = 0;
1148 	unsigned short vid;
1149 
1150 	if (!atomic_read(&bat_priv->distributed_arp_table))
1151 		goto out;
1152 
1153 	vid = batadv_dat_get_vid(skb, &hdr_size);
1154 
1155 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1156 	/* If the node gets an ARP_REQUEST it has to send a DHT_GET unicast
1157 	 * message to the selected DHT candidates
1158 	 */
1159 	if (type != ARPOP_REQUEST)
1160 		goto out;
1161 
1162 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REQUEST");
1163 
1164 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1165 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1166 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1167 
1168 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1169 
1170 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
1171 	if (dat_entry) {
1172 		/* If the ARP request is destined for a local client the local
1173 		 * client will answer itself. DAT would only generate a
1174 		 * duplicate packet.
1175 		 *
1176 		 * Moreover, if the soft-interface is enslaved into a bridge, an
1177 		 * additional DAT answer may trigger kernel warnings about
1178 		 * a packet coming from the wrong port.
1179 		 */
1180 		if (batadv_is_my_client(bat_priv, dat_entry->mac_addr, vid)) {
1181 			ret = true;
1182 			goto out;
1183 		}
1184 
1185 		/* If BLA is enabled, only send ARP replies if we have claimed
1186 		 * the destination for the ARP request or if no one else of
1187 		 * the backbone gws belonging to our backbone has claimed the
1188 		 * destination.
1189 		 */
1190 		if (!batadv_bla_check_claim(bat_priv,
1191 					    dat_entry->mac_addr, vid)) {
1192 			batadv_dbg(BATADV_DBG_DAT, bat_priv,
1193 				   "Device %pM claimed by another backbone gw. Don't send ARP reply!",
1194 				   dat_entry->mac_addr);
1195 			ret = true;
1196 			goto out;
1197 		}
1198 
1199 		skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
1200 						      dat_entry->mac_addr,
1201 						      hw_src, vid);
1202 		if (!skb_new)
1203 			goto out;
1204 
1205 		skb_new->protocol = eth_type_trans(skb_new, soft_iface);
1206 
1207 		batadv_inc_counter(bat_priv, BATADV_CNT_RX);
1208 		batadv_add_counter(bat_priv, BATADV_CNT_RX_BYTES,
1209 				   skb->len + ETH_HLEN + hdr_size);
1210 
1211 		netif_rx(skb_new);
1212 		batadv_dbg(BATADV_DBG_DAT, bat_priv, "ARP request replied locally\n");
1213 		ret = true;
1214 	} else {
1215 		/* Send the request to the DHT */
1216 		ret = batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
1217 					      BATADV_P_DAT_DHT_GET);
1218 	}
1219 out:
1220 	batadv_dat_entry_put(dat_entry);
1221 	return ret;
1222 }
1223 
1224 /**
1225  * batadv_dat_snoop_incoming_arp_request() - snoop the ARP request and try to
1226  * answer using the local DAT storage
1227  * @bat_priv: the bat priv with all the soft interface information
1228  * @skb: packet to check
1229  * @hdr_size: size of the encapsulation header
1230  *
1231  * Return: true if the request has been answered, false otherwise.
1232  */
1233 bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
1234 					   struct sk_buff *skb, int hdr_size)
1235 {
1236 	u16 type;
1237 	__be32 ip_src, ip_dst;
1238 	u8 *hw_src;
1239 	struct sk_buff *skb_new;
1240 	struct batadv_dat_entry *dat_entry = NULL;
1241 	bool ret = false;
1242 	unsigned short vid;
1243 	int err;
1244 
1245 	if (!atomic_read(&bat_priv->distributed_arp_table))
1246 		goto out;
1247 
1248 	vid = batadv_dat_get_vid(skb, &hdr_size);
1249 
1250 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1251 	if (type != ARPOP_REQUEST)
1252 		goto out;
1253 
1254 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1255 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1256 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1257 
1258 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REQUEST");
1259 
1260 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1261 
1262 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
1263 	if (!dat_entry)
1264 		goto out;
1265 
1266 	skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
1267 					      dat_entry->mac_addr, hw_src, vid);
1268 	if (!skb_new)
1269 		goto out;
1270 
1271 	/* To preserve backwards compatibility, the node has choose the outgoing
1272 	 * format based on the incoming request packet type. The assumption is
1273 	 * that a node not using the 4addr packet format doesn't support it.
1274 	 */
1275 	if (hdr_size == sizeof(struct batadv_unicast_4addr_packet))
1276 		err = batadv_send_skb_via_tt_4addr(bat_priv, skb_new,
1277 						   BATADV_P_DAT_CACHE_REPLY,
1278 						   NULL, vid);
1279 	else
1280 		err = batadv_send_skb_via_tt(bat_priv, skb_new, NULL, vid);
1281 
1282 	if (err != NET_XMIT_DROP) {
1283 		batadv_inc_counter(bat_priv, BATADV_CNT_DAT_CACHED_REPLY_TX);
1284 		ret = true;
1285 	}
1286 out:
1287 	batadv_dat_entry_put(dat_entry);
1288 	if (ret)
1289 		kfree_skb(skb);
1290 	return ret;
1291 }
1292 
1293 /**
1294  * batadv_dat_snoop_outgoing_arp_reply() - snoop the ARP reply and fill the DHT
1295  * @bat_priv: the bat priv with all the soft interface information
1296  * @skb: packet to check
1297  */
1298 void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
1299 					 struct sk_buff *skb)
1300 {
1301 	u16 type;
1302 	__be32 ip_src, ip_dst;
1303 	u8 *hw_src, *hw_dst;
1304 	int hdr_size = 0;
1305 	unsigned short vid;
1306 
1307 	if (!atomic_read(&bat_priv->distributed_arp_table))
1308 		return;
1309 
1310 	vid = batadv_dat_get_vid(skb, &hdr_size);
1311 
1312 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1313 	if (type != ARPOP_REPLY)
1314 		return;
1315 
1316 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REPLY");
1317 
1318 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1319 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1320 	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
1321 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1322 
1323 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1324 	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);
1325 
1326 	/* Send the ARP reply to the candidates for both the IP addresses that
1327 	 * the node obtained from the ARP reply
1328 	 */
1329 	batadv_dat_forward_data(bat_priv, skb, ip_src, vid,
1330 				BATADV_P_DAT_DHT_PUT);
1331 	batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
1332 				BATADV_P_DAT_DHT_PUT);
1333 }
1334 
1335 /**
1336  * batadv_dat_snoop_incoming_arp_reply() - snoop the ARP reply and fill the
1337  *  local DAT storage only
1338  * @bat_priv: the bat priv with all the soft interface information
1339  * @skb: packet to check
1340  * @hdr_size: size of the encapsulation header
1341  *
1342  * Return: true if the packet was snooped and consumed by DAT. False if the
1343  * packet has to be delivered to the interface
1344  */
1345 bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
1346 					 struct sk_buff *skb, int hdr_size)
1347 {
1348 	struct batadv_dat_entry *dat_entry = NULL;
1349 	u16 type;
1350 	__be32 ip_src, ip_dst;
1351 	u8 *hw_src, *hw_dst;
1352 	bool dropped = false;
1353 	unsigned short vid;
1354 
1355 	if (!atomic_read(&bat_priv->distributed_arp_table))
1356 		goto out;
1357 
1358 	vid = batadv_dat_get_vid(skb, &hdr_size);
1359 
1360 	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
1361 	if (type != ARPOP_REPLY)
1362 		goto out;
1363 
1364 	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REPLY");
1365 
1366 	hw_src = batadv_arp_hw_src(skb, hdr_size);
1367 	ip_src = batadv_arp_ip_src(skb, hdr_size);
1368 	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
1369 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
1370 
1371 	/* If ip_dst is already in cache and has the right mac address,
1372 	 * drop this frame if this ARP reply is destined for us because it's
1373 	 * most probably an ARP reply generated by another node of the DHT.
1374 	 * We have most probably received already a reply earlier. Delivering
1375 	 * this frame would lead to doubled receive of an ARP reply.
1376 	 */
1377 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_src, vid);
1378 	if (dat_entry && batadv_compare_eth(hw_src, dat_entry->mac_addr)) {
1379 		batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP reply removed: ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; dat_entry: %pM-%pI4\n",
1380 			   hw_src, &ip_src, hw_dst, &ip_dst,
1381 			   dat_entry->mac_addr,	&dat_entry->ip);
1382 		dropped = true;
1383 	}
1384 
1385 	/* Update our internal cache with both the IP addresses the node got
1386 	 * within the ARP reply
1387 	 */
1388 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1389 	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);
1390 
1391 	if (dropped)
1392 		goto out;
1393 
1394 	/* If BLA is enabled, only forward ARP replies if we have claimed the
1395 	 * source of the ARP reply or if no one else of the same backbone has
1396 	 * already claimed that client. This prevents that different gateways
1397 	 * to the same backbone all forward the ARP reply leading to multiple
1398 	 * replies in the backbone.
1399 	 */
1400 	if (!batadv_bla_check_claim(bat_priv, hw_src, vid)) {
1401 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
1402 			   "Device %pM claimed by another backbone gw. Drop ARP reply.\n",
1403 			   hw_src);
1404 		dropped = true;
1405 		goto out;
1406 	}
1407 
1408 	/* if this REPLY is directed to a client of mine, let's deliver the
1409 	 * packet to the interface
1410 	 */
1411 	dropped = !batadv_is_my_client(bat_priv, hw_dst, vid);
1412 
1413 	/* if this REPLY is sent on behalf of a client of mine, let's drop the
1414 	 * packet because the client will reply by itself
1415 	 */
1416 	dropped |= batadv_is_my_client(bat_priv, hw_src, vid);
1417 out:
1418 	if (dropped)
1419 		kfree_skb(skb);
1420 	batadv_dat_entry_put(dat_entry);
1421 	/* if dropped == false -> deliver to the interface */
1422 	return dropped;
1423 }
1424 
1425 /**
1426  * batadv_dat_check_dhcp_ipudp() - check skb for IP+UDP headers valid for DHCP
1427  * @skb: the packet to check
1428  * @ip_src: a buffer to store the IPv4 source address in
1429  *
1430  * Checks whether the given skb has an IP and UDP header valid for a DHCP
1431  * message from a DHCP server. And if so, stores the IPv4 source address in
1432  * the provided buffer.
1433  *
1434  * Return: True if valid, false otherwise.
1435  */
1436 static bool
1437 batadv_dat_check_dhcp_ipudp(struct sk_buff *skb, __be32 *ip_src)
1438 {
1439 	unsigned int offset = skb_network_offset(skb);
1440 	struct udphdr *udphdr, _udphdr;
1441 	struct iphdr *iphdr, _iphdr;
1442 
1443 	iphdr = skb_header_pointer(skb, offset, sizeof(_iphdr), &_iphdr);
1444 	if (!iphdr || iphdr->version != 4 || iphdr->ihl * 4 < sizeof(_iphdr))
1445 		return false;
1446 
1447 	if (iphdr->protocol != IPPROTO_UDP)
1448 		return false;
1449 
1450 	offset += iphdr->ihl * 4;
1451 	skb_set_transport_header(skb, offset);
1452 
1453 	udphdr = skb_header_pointer(skb, offset, sizeof(_udphdr), &_udphdr);
1454 	if (!udphdr || udphdr->source != htons(67))
1455 		return false;
1456 
1457 	*ip_src = get_unaligned(&iphdr->saddr);
1458 
1459 	return true;
1460 }
1461 
1462 /**
1463  * batadv_dat_check_dhcp() - examine packet for valid DHCP message
1464  * @skb: the packet to check
1465  * @proto: ethernet protocol hint (behind a potential vlan)
1466  * @ip_src: a buffer to store the IPv4 source address in
1467  *
1468  * Checks whether the given skb is a valid DHCP packet. And if so, stores the
1469  * IPv4 source address in the provided buffer.
1470  *
1471  * Caller needs to ensure that the skb network header is set correctly.
1472  *
1473  * Return: If skb is a valid DHCP packet, then returns its op code
1474  * (e.g. BOOTREPLY vs. BOOTREQUEST). Otherwise returns -EINVAL.
1475  */
1476 static int
1477 batadv_dat_check_dhcp(struct sk_buff *skb, __be16 proto, __be32 *ip_src)
1478 {
1479 	__be32 *magic, _magic;
1480 	unsigned int offset;
1481 	struct {
1482 		__u8 op;
1483 		__u8 htype;
1484 		__u8 hlen;
1485 		__u8 hops;
1486 	} *dhcp_h, _dhcp_h;
1487 
1488 	if (proto != htons(ETH_P_IP))
1489 		return -EINVAL;
1490 
1491 	if (!batadv_dat_check_dhcp_ipudp(skb, ip_src))
1492 		return -EINVAL;
1493 
1494 	offset = skb_transport_offset(skb) + sizeof(struct udphdr);
1495 	if (skb->len < offset + sizeof(struct batadv_dhcp_packet))
1496 		return -EINVAL;
1497 
1498 	dhcp_h = skb_header_pointer(skb, offset, sizeof(_dhcp_h), &_dhcp_h);
1499 	if (!dhcp_h || dhcp_h->htype != BATADV_HTYPE_ETHERNET ||
1500 	    dhcp_h->hlen != ETH_ALEN)
1501 		return -EINVAL;
1502 
1503 	offset += offsetof(struct batadv_dhcp_packet, magic);
1504 
1505 	magic = skb_header_pointer(skb, offset, sizeof(_magic), &_magic);
1506 	if (!magic || get_unaligned(magic) != htonl(BATADV_DHCP_MAGIC))
1507 		return -EINVAL;
1508 
1509 	return dhcp_h->op;
1510 }
1511 
1512 /**
1513  * batadv_dat_get_dhcp_message_type() - get message type of a DHCP packet
1514  * @skb: the DHCP packet to parse
1515  *
1516  * Iterates over the DHCP options of the given DHCP packet to find a
1517  * DHCP Message Type option and parse it.
1518  *
1519  * Caller needs to ensure that the given skb is a valid DHCP packet and
1520  * that the skb transport header is set correctly.
1521  *
1522  * Return: The found DHCP message type value, if found. -EINVAL otherwise.
1523  */
1524 static int batadv_dat_get_dhcp_message_type(struct sk_buff *skb)
1525 {
1526 	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
1527 	u8 *type, _type;
1528 	struct {
1529 		u8 type;
1530 		u8 len;
1531 	} *tl, _tl;
1532 
1533 	offset += sizeof(struct batadv_dhcp_packet);
1534 
1535 	while ((tl = skb_header_pointer(skb, offset, sizeof(_tl), &_tl))) {
1536 		if (tl->type == BATADV_DHCP_OPT_MSG_TYPE)
1537 			break;
1538 
1539 		if (tl->type == BATADV_DHCP_OPT_END)
1540 			break;
1541 
1542 		if (tl->type == BATADV_DHCP_OPT_PAD)
1543 			offset++;
1544 		else
1545 			offset += tl->len + sizeof(_tl);
1546 	}
1547 
1548 	/* Option Overload Code not supported */
1549 	if (!tl || tl->type != BATADV_DHCP_OPT_MSG_TYPE ||
1550 	    tl->len != sizeof(_type))
1551 		return -EINVAL;
1552 
1553 	offset += sizeof(_tl);
1554 
1555 	type = skb_header_pointer(skb, offset, sizeof(_type), &_type);
1556 	if (!type)
1557 		return -EINVAL;
1558 
1559 	return *type;
1560 }
1561 
1562 /**
1563  * batadv_dat_dhcp_get_yiaddr() - get yiaddr from a DHCP packet
1564  * @skb: the DHCP packet to parse
1565  * @buf: a buffer to store the yiaddr in
1566  *
1567  * Caller needs to ensure that the given skb is a valid DHCP packet and
1568  * that the skb transport header is set correctly.
1569  *
1570  * Return: True on success, false otherwise.
1571  */
1572 static bool batadv_dat_dhcp_get_yiaddr(struct sk_buff *skb, __be32 *buf)
1573 {
1574 	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
1575 	__be32 *yiaddr;
1576 
1577 	offset += offsetof(struct batadv_dhcp_packet, yiaddr);
1578 	yiaddr = skb_header_pointer(skb, offset, BATADV_DHCP_YIADDR_LEN, buf);
1579 
1580 	if (!yiaddr)
1581 		return false;
1582 
1583 	if (yiaddr != buf)
1584 		*buf = get_unaligned(yiaddr);
1585 
1586 	return true;
1587 }
1588 
1589 /**
1590  * batadv_dat_get_dhcp_chaddr() - get chaddr from a DHCP packet
1591  * @skb: the DHCP packet to parse
1592  * @buf: a buffer to store the chaddr in
1593  *
1594  * Caller needs to ensure that the given skb is a valid DHCP packet and
1595  * that the skb transport header is set correctly.
1596  *
1597  * Return: True on success, false otherwise
1598  */
1599 static bool batadv_dat_get_dhcp_chaddr(struct sk_buff *skb, u8 *buf)
1600 {
1601 	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
1602 	u8 *chaddr;
1603 
1604 	offset += offsetof(struct batadv_dhcp_packet, chaddr);
1605 	chaddr = skb_header_pointer(skb, offset, BATADV_DHCP_CHADDR_LEN, buf);
1606 
1607 	if (!chaddr)
1608 		return false;
1609 
1610 	if (chaddr != buf)
1611 		memcpy(buf, chaddr, BATADV_DHCP_CHADDR_LEN);
1612 
1613 	return true;
1614 }
1615 
1616 /**
1617  * batadv_dat_put_dhcp() - puts addresses from a DHCP packet into the DHT and
1618  *  DAT cache
1619  * @bat_priv: the bat priv with all the soft interface information
1620  * @chaddr: the DHCP client MAC address
1621  * @yiaddr: the DHCP client IP address
1622  * @hw_dst: the DHCP server MAC address
1623  * @ip_dst: the DHCP server IP address
1624  * @vid: VLAN identifier
1625  *
1626  * Adds given MAC/IP pairs to the local DAT cache and propagates them further
1627  * into the DHT.
1628  *
1629  * For the DHT propagation, client MAC + IP will appear as the ARP Reply
1630  * transmitter (and hw_dst/ip_dst as the target).
1631  */
1632 static void batadv_dat_put_dhcp(struct batadv_priv *bat_priv, u8 *chaddr,
1633 				__be32 yiaddr, u8 *hw_dst, __be32 ip_dst,
1634 				unsigned short vid)
1635 {
1636 	struct sk_buff *skb;
1637 
1638 	skb = batadv_dat_arp_create_reply(bat_priv, yiaddr, ip_dst, chaddr,
1639 					  hw_dst, vid);
1640 	if (!skb)
1641 		return;
1642 
1643 	skb_set_network_header(skb, ETH_HLEN);
1644 
1645 	batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid);
1646 	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);
1647 
1648 	batadv_dat_forward_data(bat_priv, skb, yiaddr, vid,
1649 				BATADV_P_DAT_DHT_PUT);
1650 	batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
1651 				BATADV_P_DAT_DHT_PUT);
1652 
1653 	consume_skb(skb);
1654 
1655 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
1656 		   "Snooped from outgoing DHCPACK (server address): %pI4, %pM (vid: %i)\n",
1657 		   &ip_dst, hw_dst, batadv_print_vid(vid));
1658 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
1659 		   "Snooped from outgoing DHCPACK (client address): %pI4, %pM (vid: %i)\n",
1660 		   &yiaddr, chaddr, batadv_print_vid(vid));
1661 }
1662 
1663 /**
1664  * batadv_dat_check_dhcp_ack() - examine packet for valid DHCP message
1665  * @skb: the packet to check
1666  * @proto: ethernet protocol hint (behind a potential vlan)
1667  * @ip_src: a buffer to store the IPv4 source address in
1668  * @chaddr: a buffer to store the DHCP Client Hardware Address in
1669  * @yiaddr: a buffer to store the DHCP Your IP Address in
1670  *
1671  * Checks whether the given skb is a valid DHCPACK. And if so, stores the
1672  * IPv4 server source address (ip_src), client MAC address (chaddr) and client
1673  * IPv4 address (yiaddr) in the provided buffers.
1674  *
1675  * Caller needs to ensure that the skb network header is set correctly.
1676  *
1677  * Return: True if the skb is a valid DHCPACK. False otherwise.
1678  */
1679 static bool
1680 batadv_dat_check_dhcp_ack(struct sk_buff *skb, __be16 proto, __be32 *ip_src,
1681 			  u8 *chaddr, __be32 *yiaddr)
1682 {
1683 	int type;
1684 
1685 	type = batadv_dat_check_dhcp(skb, proto, ip_src);
1686 	if (type != BATADV_BOOTREPLY)
1687 		return false;
1688 
1689 	type = batadv_dat_get_dhcp_message_type(skb);
1690 	if (type != BATADV_DHCPACK)
1691 		return false;
1692 
1693 	if (!batadv_dat_dhcp_get_yiaddr(skb, yiaddr))
1694 		return false;
1695 
1696 	if (!batadv_dat_get_dhcp_chaddr(skb, chaddr))
1697 		return false;
1698 
1699 	return true;
1700 }
1701 
1702 /**
1703  * batadv_dat_snoop_outgoing_dhcp_ack() - snoop DHCPACK and fill DAT with it
1704  * @bat_priv: the bat priv with all the soft interface information
1705  * @skb: the packet to snoop
1706  * @proto: ethernet protocol hint (behind a potential vlan)
1707  * @vid: VLAN identifier
1708  *
1709  * This function first checks whether the given skb is a valid DHCPACK. If
1710  * so then its source MAC and IP as well as its DHCP Client Hardware Address
1711  * field and DHCP Your IP Address field are added to the local DAT cache and
1712  * propagated into the DHT.
1713  *
1714  * Caller needs to ensure that the skb mac and network headers are set
1715  * correctly.
1716  */
1717 void batadv_dat_snoop_outgoing_dhcp_ack(struct batadv_priv *bat_priv,
1718 					struct sk_buff *skb,
1719 					__be16 proto,
1720 					unsigned short vid)
1721 {
1722 	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
1723 	__be32 ip_src, yiaddr;
1724 
1725 	if (!atomic_read(&bat_priv->distributed_arp_table))
1726 		return;
1727 
1728 	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
1729 		return;
1730 
1731 	batadv_dat_put_dhcp(bat_priv, chaddr, yiaddr, eth_hdr(skb)->h_source,
1732 			    ip_src, vid);
1733 }
1734 
1735 /**
1736  * batadv_dat_snoop_incoming_dhcp_ack() - snoop DHCPACK and fill DAT cache
1737  * @bat_priv: the bat priv with all the soft interface information
1738  * @skb: the packet to snoop
1739  * @hdr_size: header size, up to the tail of the batman-adv header
1740  *
1741  * This function first checks whether the given skb is a valid DHCPACK. If
1742  * so then its source MAC and IP as well as its DHCP Client Hardware Address
1743  * field and DHCP Your IP Address field are added to the local DAT cache.
1744  */
1745 void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv,
1746 					struct sk_buff *skb, int hdr_size)
1747 {
1748 	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
1749 	struct ethhdr *ethhdr;
1750 	__be32 ip_src, yiaddr;
1751 	unsigned short vid;
1752 	__be16 proto;
1753 	u8 *hw_src;
1754 
1755 	if (!atomic_read(&bat_priv->distributed_arp_table))
1756 		return;
1757 
1758 	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
1759 		return;
1760 
1761 	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
1762 	skb_set_network_header(skb, hdr_size + ETH_HLEN);
1763 	proto = ethhdr->h_proto;
1764 
1765 	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
1766 		return;
1767 
1768 	hw_src = ethhdr->h_source;
1769 	vid = batadv_dat_get_vid(skb, &hdr_size);
1770 
1771 	batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid);
1772 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
1773 
1774 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
1775 		   "Snooped from incoming DHCPACK (server address): %pI4, %pM (vid: %i)\n",
1776 		   &ip_src, hw_src, batadv_print_vid(vid));
1777 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
1778 		   "Snooped from incoming DHCPACK (client address): %pI4, %pM (vid: %i)\n",
1779 		   &yiaddr, chaddr, batadv_print_vid(vid));
1780 }
1781 
1782 /**
1783  * batadv_dat_drop_broadcast_packet() - check if an ARP request has to be
1784  *  dropped (because the node has already obtained the reply via DAT) or not
1785  * @bat_priv: the bat priv with all the soft interface information
1786  * @forw_packet: the broadcast packet
1787  *
1788  * Return: true if the node can drop the packet, false otherwise.
1789  */
1790 bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
1791 				      struct batadv_forw_packet *forw_packet)
1792 {
1793 	u16 type;
1794 	__be32 ip_dst;
1795 	struct batadv_dat_entry *dat_entry = NULL;
1796 	bool ret = false;
1797 	int hdr_size = sizeof(struct batadv_bcast_packet);
1798 	unsigned short vid;
1799 
1800 	if (!atomic_read(&bat_priv->distributed_arp_table))
1801 		goto out;
1802 
1803 	/* If this packet is an ARP_REQUEST and the node already has the
1804 	 * information that it is going to ask, then the packet can be dropped
1805 	 */
1806 	if (batadv_forw_packet_is_rebroadcast(forw_packet))
1807 		goto out;
1808 
1809 	vid = batadv_dat_get_vid(forw_packet->skb, &hdr_size);
1810 
1811 	type = batadv_arp_get_type(bat_priv, forw_packet->skb, hdr_size);
1812 	if (type != ARPOP_REQUEST)
1813 		goto out;
1814 
1815 	ip_dst = batadv_arp_ip_dst(forw_packet->skb, hdr_size);
1816 	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);
1817 	/* check if the node already got this entry */
1818 	if (!dat_entry) {
1819 		batadv_dbg(BATADV_DBG_DAT, bat_priv,
1820 			   "ARP Request for %pI4: fallback\n", &ip_dst);
1821 		goto out;
1822 	}
1823 
1824 	batadv_dbg(BATADV_DBG_DAT, bat_priv,
1825 		   "ARP Request for %pI4: fallback prevented\n", &ip_dst);
1826 	ret = true;
1827 
1828 out:
1829 	batadv_dat_entry_put(dat_entry);
1830 	return ret;
1831 }
1832