1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) B.A.T.M.A.N. contributors:
3  *
4  * Marek Lindner
5  */
6 
7 #include "gateway_client.h"
8 #include "main.h"
9 
10 #include <linux/atomic.h>
11 #include <linux/byteorder/generic.h>
12 #include <linux/container_of.h>
13 #include <linux/errno.h>
14 #include <linux/etherdevice.h>
15 #include <linux/gfp.h>
16 #include <linux/if_ether.h>
17 #include <linux/if_vlan.h>
18 #include <linux/in.h>
19 #include <linux/ip.h>
20 #include <linux/ipv6.h>
21 #include <linux/kernel.h>
22 #include <linux/kref.h>
23 #include <linux/list.h>
24 #include <linux/lockdep.h>
25 #include <linux/netdevice.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/udp.h>
34 #include <net/sock.h>
35 #include <uapi/linux/batadv_packet.h>
36 #include <uapi/linux/batman_adv.h>
37 
38 #include "hard-interface.h"
39 #include "log.h"
40 #include "netlink.h"
41 #include "originator.h"
42 #include "routing.h"
43 #include "soft-interface.h"
44 #include "translation-table.h"
45 
46 /* These are the offsets of the "hw type" and "hw address length" in the dhcp
47  * packet starting at the beginning of the dhcp header
48  */
49 #define BATADV_DHCP_HTYPE_OFFSET	1
50 #define BATADV_DHCP_HLEN_OFFSET		2
51 /* Value of htype representing Ethernet */
52 #define BATADV_DHCP_HTYPE_ETHERNET	0x01
53 /* This is the offset of the "chaddr" field in the dhcp packet starting at the
54  * beginning of the dhcp header
55  */
56 #define BATADV_DHCP_CHADDR_OFFSET	28
57 
58 /**
59  * batadv_gw_node_release() - release gw_node from lists and queue for free
60  *  after rcu grace period
61  * @ref: kref pointer of the gw_node
62  */
63 void batadv_gw_node_release(struct kref *ref)
64 {
65 	struct batadv_gw_node *gw_node;
66 
67 	gw_node = container_of(ref, struct batadv_gw_node, refcount);
68 
69 	batadv_orig_node_put(gw_node->orig_node);
70 	kfree_rcu(gw_node, rcu);
71 }
72 
73 /**
74  * batadv_gw_get_selected_gw_node() - Get currently selected gateway
75  * @bat_priv: the bat priv with all the soft interface information
76  *
77  * Return: selected gateway (with increased refcnt), NULL on errors
78  */
79 struct batadv_gw_node *
80 batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv)
81 {
82 	struct batadv_gw_node *gw_node;
83 
84 	rcu_read_lock();
85 	gw_node = rcu_dereference(bat_priv->gw.curr_gw);
86 	if (!gw_node)
87 		goto out;
88 
89 	if (!kref_get_unless_zero(&gw_node->refcount))
90 		gw_node = NULL;
91 
92 out:
93 	rcu_read_unlock();
94 	return gw_node;
95 }
96 
97 /**
98  * batadv_gw_get_selected_orig() - Get originator of currently selected gateway
99  * @bat_priv: the bat priv with all the soft interface information
100  *
101  * Return: orig_node of selected gateway (with increased refcnt), NULL on errors
102  */
103 struct batadv_orig_node *
104 batadv_gw_get_selected_orig(struct batadv_priv *bat_priv)
105 {
106 	struct batadv_gw_node *gw_node;
107 	struct batadv_orig_node *orig_node = NULL;
108 
109 	gw_node = batadv_gw_get_selected_gw_node(bat_priv);
110 	if (!gw_node)
111 		goto out;
112 
113 	rcu_read_lock();
114 	orig_node = gw_node->orig_node;
115 	if (!orig_node)
116 		goto unlock;
117 
118 	if (!kref_get_unless_zero(&orig_node->refcount))
119 		orig_node = NULL;
120 
121 unlock:
122 	rcu_read_unlock();
123 out:
124 	batadv_gw_node_put(gw_node);
125 	return orig_node;
126 }
127 
128 static void batadv_gw_select(struct batadv_priv *bat_priv,
129 			     struct batadv_gw_node *new_gw_node)
130 {
131 	struct batadv_gw_node *curr_gw_node;
132 
133 	spin_lock_bh(&bat_priv->gw.list_lock);
134 
135 	if (new_gw_node)
136 		kref_get(&new_gw_node->refcount);
137 
138 	curr_gw_node = rcu_replace_pointer(bat_priv->gw.curr_gw, new_gw_node,
139 					   true);
140 
141 	batadv_gw_node_put(curr_gw_node);
142 
143 	spin_unlock_bh(&bat_priv->gw.list_lock);
144 }
145 
146 /**
147  * batadv_gw_reselect() - force a gateway reselection
148  * @bat_priv: the bat priv with all the soft interface information
149  *
150  * Set a flag to remind the GW component to perform a new gateway reselection.
151  * However this function does not ensure that the current gateway is going to be
152  * deselected. The reselection mechanism may elect the same gateway once again.
153  *
154  * This means that invoking batadv_gw_reselect() does not guarantee a gateway
155  * change and therefore a uevent is not necessarily expected.
156  */
157 void batadv_gw_reselect(struct batadv_priv *bat_priv)
158 {
159 	atomic_set(&bat_priv->gw.reselect, 1);
160 }
161 
162 /**
163  * batadv_gw_check_client_stop() - check if client mode has been switched off
164  * @bat_priv: the bat priv with all the soft interface information
165  *
166  * This function assumes the caller has checked that the gw state *is actually
167  * changing*. This function is not supposed to be called when there is no state
168  * change.
169  */
170 void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
171 {
172 	struct batadv_gw_node *curr_gw;
173 
174 	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
175 		return;
176 
177 	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
178 	if (!curr_gw)
179 		return;
180 
181 	/* deselect the current gateway so that next time that client mode is
182 	 * enabled a proper GW_ADD event can be sent
183 	 */
184 	batadv_gw_select(bat_priv, NULL);
185 
186 	/* if batman-adv is switching the gw client mode off and a gateway was
187 	 * already selected, send a DEL uevent
188 	 */
189 	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL, NULL);
190 
191 	batadv_gw_node_put(curr_gw);
192 }
193 
194 /**
195  * batadv_gw_election() - Elect the best gateway
196  * @bat_priv: the bat priv with all the soft interface information
197  */
198 void batadv_gw_election(struct batadv_priv *bat_priv)
199 {
200 	struct batadv_gw_node *curr_gw = NULL;
201 	struct batadv_gw_node *next_gw = NULL;
202 	struct batadv_neigh_node *router = NULL;
203 	struct batadv_neigh_ifinfo *router_ifinfo = NULL;
204 	char gw_addr[18] = { '\0' };
205 
206 	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
207 		goto out;
208 
209 	if (!bat_priv->algo_ops->gw.get_best_gw_node)
210 		goto out;
211 
212 	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
213 
214 	if (!batadv_atomic_dec_not_zero(&bat_priv->gw.reselect) && curr_gw)
215 		goto out;
216 
217 	/* if gw.reselect is set to 1 it means that a previous call to
218 	 * gw.is_eligible() said that we have a new best GW, therefore it can
219 	 * now be picked from the list and selected
220 	 */
221 	next_gw = bat_priv->algo_ops->gw.get_best_gw_node(bat_priv);
222 
223 	if (curr_gw == next_gw)
224 		goto out;
225 
226 	if (next_gw) {
227 		sprintf(gw_addr, "%pM", next_gw->orig_node->orig);
228 
229 		router = batadv_orig_router_get(next_gw->orig_node,
230 						BATADV_IF_DEFAULT);
231 		if (!router) {
232 			batadv_gw_reselect(bat_priv);
233 			goto out;
234 		}
235 
236 		router_ifinfo = batadv_neigh_ifinfo_get(router,
237 							BATADV_IF_DEFAULT);
238 		if (!router_ifinfo) {
239 			batadv_gw_reselect(bat_priv);
240 			goto out;
241 		}
242 	}
243 
244 	if (curr_gw && !next_gw) {
245 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
246 			   "Removing selected gateway - no gateway in range\n");
247 		batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL,
248 				    NULL);
249 	} else if (!curr_gw && next_gw) {
250 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
251 			   "Adding route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
252 			   next_gw->orig_node->orig,
253 			   next_gw->bandwidth_down / 10,
254 			   next_gw->bandwidth_down % 10,
255 			   next_gw->bandwidth_up / 10,
256 			   next_gw->bandwidth_up % 10,
257 			   router_ifinfo->bat_iv.tq_avg);
258 		batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_ADD,
259 				    gw_addr);
260 	} else {
261 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
262 			   "Changing route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
263 			   next_gw->orig_node->orig,
264 			   next_gw->bandwidth_down / 10,
265 			   next_gw->bandwidth_down % 10,
266 			   next_gw->bandwidth_up / 10,
267 			   next_gw->bandwidth_up % 10,
268 			   router_ifinfo->bat_iv.tq_avg);
269 		batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_CHANGE,
270 				    gw_addr);
271 	}
272 
273 	batadv_gw_select(bat_priv, next_gw);
274 
275 out:
276 	batadv_gw_node_put(curr_gw);
277 	batadv_gw_node_put(next_gw);
278 	batadv_neigh_node_put(router);
279 	batadv_neigh_ifinfo_put(router_ifinfo);
280 }
281 
282 /**
283  * batadv_gw_check_election() - Elect orig node as best gateway when eligible
284  * @bat_priv: the bat priv with all the soft interface information
285  * @orig_node: orig node which is to be checked
286  */
287 void batadv_gw_check_election(struct batadv_priv *bat_priv,
288 			      struct batadv_orig_node *orig_node)
289 {
290 	struct batadv_orig_node *curr_gw_orig;
291 
292 	/* abort immediately if the routing algorithm does not support gateway
293 	 * election
294 	 */
295 	if (!bat_priv->algo_ops->gw.is_eligible)
296 		return;
297 
298 	curr_gw_orig = batadv_gw_get_selected_orig(bat_priv);
299 	if (!curr_gw_orig)
300 		goto reselect;
301 
302 	/* this node already is the gateway */
303 	if (curr_gw_orig == orig_node)
304 		goto out;
305 
306 	if (!bat_priv->algo_ops->gw.is_eligible(bat_priv, curr_gw_orig,
307 						orig_node))
308 		goto out;
309 
310 reselect:
311 	batadv_gw_reselect(bat_priv);
312 out:
313 	batadv_orig_node_put(curr_gw_orig);
314 }
315 
316 /**
317  * batadv_gw_node_add() - add gateway node to list of available gateways
318  * @bat_priv: the bat priv with all the soft interface information
319  * @orig_node: originator announcing gateway capabilities
320  * @gateway: announced bandwidth information
321  *
322  * Has to be called with the appropriate locks being acquired
323  * (gw.list_lock).
324  */
325 static void batadv_gw_node_add(struct batadv_priv *bat_priv,
326 			       struct batadv_orig_node *orig_node,
327 			       struct batadv_tvlv_gateway_data *gateway)
328 {
329 	struct batadv_gw_node *gw_node;
330 
331 	lockdep_assert_held(&bat_priv->gw.list_lock);
332 
333 	if (gateway->bandwidth_down == 0)
334 		return;
335 
336 	gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
337 	if (!gw_node)
338 		return;
339 
340 	kref_init(&gw_node->refcount);
341 	INIT_HLIST_NODE(&gw_node->list);
342 	kref_get(&orig_node->refcount);
343 	gw_node->orig_node = orig_node;
344 	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
345 	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
346 
347 	kref_get(&gw_node->refcount);
348 	hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list);
349 	bat_priv->gw.generation++;
350 
351 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
352 		   "Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n",
353 		   orig_node->orig,
354 		   ntohl(gateway->bandwidth_down) / 10,
355 		   ntohl(gateway->bandwidth_down) % 10,
356 		   ntohl(gateway->bandwidth_up) / 10,
357 		   ntohl(gateway->bandwidth_up) % 10);
358 
359 	/* don't return reference to new gw_node */
360 	batadv_gw_node_put(gw_node);
361 }
362 
363 /**
364  * batadv_gw_node_get() - retrieve gateway node from list of available gateways
365  * @bat_priv: the bat priv with all the soft interface information
366  * @orig_node: originator announcing gateway capabilities
367  *
368  * Return: gateway node if found or NULL otherwise.
369  */
370 struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
371 					  struct batadv_orig_node *orig_node)
372 {
373 	struct batadv_gw_node *gw_node_tmp, *gw_node = NULL;
374 
375 	rcu_read_lock();
376 	hlist_for_each_entry_rcu(gw_node_tmp, &bat_priv->gw.gateway_list,
377 				 list) {
378 		if (gw_node_tmp->orig_node != orig_node)
379 			continue;
380 
381 		if (!kref_get_unless_zero(&gw_node_tmp->refcount))
382 			continue;
383 
384 		gw_node = gw_node_tmp;
385 		break;
386 	}
387 	rcu_read_unlock();
388 
389 	return gw_node;
390 }
391 
392 /**
393  * batadv_gw_node_update() - update list of available gateways with changed
394  *  bandwidth information
395  * @bat_priv: the bat priv with all the soft interface information
396  * @orig_node: originator announcing gateway capabilities
397  * @gateway: announced bandwidth information
398  */
399 void batadv_gw_node_update(struct batadv_priv *bat_priv,
400 			   struct batadv_orig_node *orig_node,
401 			   struct batadv_tvlv_gateway_data *gateway)
402 {
403 	struct batadv_gw_node *gw_node, *curr_gw = NULL;
404 
405 	spin_lock_bh(&bat_priv->gw.list_lock);
406 	gw_node = batadv_gw_node_get(bat_priv, orig_node);
407 	if (!gw_node) {
408 		batadv_gw_node_add(bat_priv, orig_node, gateway);
409 		spin_unlock_bh(&bat_priv->gw.list_lock);
410 		goto out;
411 	}
412 	spin_unlock_bh(&bat_priv->gw.list_lock);
413 
414 	if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) &&
415 	    gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))
416 		goto out;
417 
418 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
419 		   "Gateway bandwidth of originator %pM changed from %u.%u/%u.%u MBit to %u.%u/%u.%u MBit\n",
420 		   orig_node->orig,
421 		   gw_node->bandwidth_down / 10,
422 		   gw_node->bandwidth_down % 10,
423 		   gw_node->bandwidth_up / 10,
424 		   gw_node->bandwidth_up % 10,
425 		   ntohl(gateway->bandwidth_down) / 10,
426 		   ntohl(gateway->bandwidth_down) % 10,
427 		   ntohl(gateway->bandwidth_up) / 10,
428 		   ntohl(gateway->bandwidth_up) % 10);
429 
430 	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
431 	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
432 
433 	if (ntohl(gateway->bandwidth_down) == 0) {
434 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
435 			   "Gateway %pM removed from gateway list\n",
436 			   orig_node->orig);
437 
438 		/* Note: We don't need a NULL check here, since curr_gw never
439 		 * gets dereferenced.
440 		 */
441 		spin_lock_bh(&bat_priv->gw.list_lock);
442 		if (!hlist_unhashed(&gw_node->list)) {
443 			hlist_del_init_rcu(&gw_node->list);
444 			batadv_gw_node_put(gw_node);
445 			bat_priv->gw.generation++;
446 		}
447 		spin_unlock_bh(&bat_priv->gw.list_lock);
448 
449 		curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
450 		if (gw_node == curr_gw)
451 			batadv_gw_reselect(bat_priv);
452 
453 		batadv_gw_node_put(curr_gw);
454 	}
455 
456 out:
457 	batadv_gw_node_put(gw_node);
458 }
459 
460 /**
461  * batadv_gw_node_delete() - Remove orig_node from gateway list
462  * @bat_priv: the bat priv with all the soft interface information
463  * @orig_node: orig node which is currently in process of being removed
464  */
465 void batadv_gw_node_delete(struct batadv_priv *bat_priv,
466 			   struct batadv_orig_node *orig_node)
467 {
468 	struct batadv_tvlv_gateway_data gateway;
469 
470 	gateway.bandwidth_down = 0;
471 	gateway.bandwidth_up = 0;
472 
473 	batadv_gw_node_update(bat_priv, orig_node, &gateway);
474 }
475 
476 /**
477  * batadv_gw_node_free() - Free gateway information from soft interface
478  * @bat_priv: the bat priv with all the soft interface information
479  */
480 void batadv_gw_node_free(struct batadv_priv *bat_priv)
481 {
482 	struct batadv_gw_node *gw_node;
483 	struct hlist_node *node_tmp;
484 
485 	spin_lock_bh(&bat_priv->gw.list_lock);
486 	hlist_for_each_entry_safe(gw_node, node_tmp,
487 				  &bat_priv->gw.gateway_list, list) {
488 		hlist_del_init_rcu(&gw_node->list);
489 		batadv_gw_node_put(gw_node);
490 		bat_priv->gw.generation++;
491 	}
492 	spin_unlock_bh(&bat_priv->gw.list_lock);
493 }
494 
495 /**
496  * batadv_gw_dump() - Dump gateways into a message
497  * @msg: Netlink message to dump into
498  * @cb: Control block containing additional options
499  *
500  * Return: Error code, or length of message
501  */
502 int batadv_gw_dump(struct sk_buff *msg, struct netlink_callback *cb)
503 {
504 	struct batadv_hard_iface *primary_if = NULL;
505 	struct net *net = sock_net(cb->skb->sk);
506 	struct net_device *soft_iface;
507 	struct batadv_priv *bat_priv;
508 	int ifindex;
509 	int ret;
510 
511 	ifindex = batadv_netlink_get_ifindex(cb->nlh,
512 					     BATADV_ATTR_MESH_IFINDEX);
513 	if (!ifindex)
514 		return -EINVAL;
515 
516 	soft_iface = dev_get_by_index(net, ifindex);
517 	if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
518 		ret = -ENODEV;
519 		goto out;
520 	}
521 
522 	bat_priv = netdev_priv(soft_iface);
523 
524 	primary_if = batadv_primary_if_get_selected(bat_priv);
525 	if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
526 		ret = -ENOENT;
527 		goto out;
528 	}
529 
530 	if (!bat_priv->algo_ops->gw.dump) {
531 		ret = -EOPNOTSUPP;
532 		goto out;
533 	}
534 
535 	bat_priv->algo_ops->gw.dump(msg, cb, bat_priv);
536 
537 	ret = msg->len;
538 
539 out:
540 	batadv_hardif_put(primary_if);
541 	dev_put(soft_iface);
542 
543 	return ret;
544 }
545 
546 /**
547  * batadv_gw_dhcp_recipient_get() - check if a packet is a DHCP message
548  * @skb: the packet to check
549  * @header_len: a pointer to the batman-adv header size
550  * @chaddr: buffer where the client address will be stored. Valid
551  *  only if the function returns BATADV_DHCP_TO_CLIENT
552  *
553  * This function may re-allocate the data buffer of the skb passed as argument.
554  *
555  * Return:
556  * - BATADV_DHCP_NO if the packet is not a dhcp message or if there was an error
557  *   while parsing it
558  * - BATADV_DHCP_TO_SERVER if this is a message going to the DHCP server
559  * - BATADV_DHCP_TO_CLIENT if this is a message going to a DHCP client
560  */
561 enum batadv_dhcp_recipient
562 batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
563 			     u8 *chaddr)
564 {
565 	enum batadv_dhcp_recipient ret = BATADV_DHCP_NO;
566 	struct ethhdr *ethhdr;
567 	struct iphdr *iphdr;
568 	struct ipv6hdr *ipv6hdr;
569 	struct udphdr *udphdr;
570 	struct vlan_ethhdr *vhdr;
571 	int chaddr_offset;
572 	__be16 proto;
573 	u8 *p;
574 
575 	/* check for ethernet header */
576 	if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
577 		return BATADV_DHCP_NO;
578 
579 	ethhdr = eth_hdr(skb);
580 	proto = ethhdr->h_proto;
581 	*header_len += ETH_HLEN;
582 
583 	/* check for initial vlan header */
584 	if (proto == htons(ETH_P_8021Q)) {
585 		if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
586 			return BATADV_DHCP_NO;
587 
588 		vhdr = vlan_eth_hdr(skb);
589 		proto = vhdr->h_vlan_encapsulated_proto;
590 		*header_len += VLAN_HLEN;
591 	}
592 
593 	/* check for ip header */
594 	switch (proto) {
595 	case htons(ETH_P_IP):
596 		if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
597 			return BATADV_DHCP_NO;
598 
599 		iphdr = (struct iphdr *)(skb->data + *header_len);
600 		*header_len += iphdr->ihl * 4;
601 
602 		/* check for udp header */
603 		if (iphdr->protocol != IPPROTO_UDP)
604 			return BATADV_DHCP_NO;
605 
606 		break;
607 	case htons(ETH_P_IPV6):
608 		if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
609 			return BATADV_DHCP_NO;
610 
611 		ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
612 		*header_len += sizeof(*ipv6hdr);
613 
614 		/* check for udp header */
615 		if (ipv6hdr->nexthdr != IPPROTO_UDP)
616 			return BATADV_DHCP_NO;
617 
618 		break;
619 	default:
620 		return BATADV_DHCP_NO;
621 	}
622 
623 	if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
624 		return BATADV_DHCP_NO;
625 
626 	udphdr = (struct udphdr *)(skb->data + *header_len);
627 	*header_len += sizeof(*udphdr);
628 
629 	/* check for bootp port */
630 	switch (proto) {
631 	case htons(ETH_P_IP):
632 		if (udphdr->dest == htons(67))
633 			ret = BATADV_DHCP_TO_SERVER;
634 		else if (udphdr->source == htons(67))
635 			ret = BATADV_DHCP_TO_CLIENT;
636 		break;
637 	case htons(ETH_P_IPV6):
638 		if (udphdr->dest == htons(547))
639 			ret = BATADV_DHCP_TO_SERVER;
640 		else if (udphdr->source == htons(547))
641 			ret = BATADV_DHCP_TO_CLIENT;
642 		break;
643 	}
644 
645 	chaddr_offset = *header_len + BATADV_DHCP_CHADDR_OFFSET;
646 	/* store the client address if the message is going to a client */
647 	if (ret == BATADV_DHCP_TO_CLIENT) {
648 		if (!pskb_may_pull(skb, chaddr_offset + ETH_ALEN))
649 			return BATADV_DHCP_NO;
650 
651 		/* check if the DHCP packet carries an Ethernet DHCP */
652 		p = skb->data + *header_len + BATADV_DHCP_HTYPE_OFFSET;
653 		if (*p != BATADV_DHCP_HTYPE_ETHERNET)
654 			return BATADV_DHCP_NO;
655 
656 		/* check if the DHCP packet carries a valid Ethernet address */
657 		p = skb->data + *header_len + BATADV_DHCP_HLEN_OFFSET;
658 		if (*p != ETH_ALEN)
659 			return BATADV_DHCP_NO;
660 
661 		ether_addr_copy(chaddr, skb->data + chaddr_offset);
662 	}
663 
664 	return ret;
665 }
666 
667 /**
668  * batadv_gw_out_of_range() - check if the dhcp request destination is the best
669  *  gateway
670  * @bat_priv: the bat priv with all the soft interface information
671  * @skb: the outgoing packet
672  *
673  * Check if the skb is a DHCP request and if it is sent to the current best GW
674  * server. Due to topology changes it may be the case that the GW server
675  * previously selected is not the best one anymore.
676  *
677  * This call might reallocate skb data.
678  * Must be invoked only when the DHCP packet is going TO a DHCP SERVER.
679  *
680  * Return: true if the packet destination is unicast and it is not the best gw,
681  * false otherwise.
682  */
683 bool batadv_gw_out_of_range(struct batadv_priv *bat_priv,
684 			    struct sk_buff *skb)
685 {
686 	struct batadv_neigh_node *neigh_curr = NULL;
687 	struct batadv_neigh_node *neigh_old = NULL;
688 	struct batadv_orig_node *orig_dst_node = NULL;
689 	struct batadv_gw_node *gw_node = NULL;
690 	struct batadv_gw_node *curr_gw = NULL;
691 	struct batadv_neigh_ifinfo *curr_ifinfo, *old_ifinfo;
692 	struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
693 	bool out_of_range = false;
694 	u8 curr_tq_avg;
695 	unsigned short vid;
696 
697 	vid = batadv_get_vid(skb, 0);
698 
699 	if (is_multicast_ether_addr(ethhdr->h_dest))
700 		goto out;
701 
702 	orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
703 						 ethhdr->h_dest, vid);
704 	if (!orig_dst_node)
705 		goto out;
706 
707 	gw_node = batadv_gw_node_get(bat_priv, orig_dst_node);
708 	if (!gw_node)
709 		goto out;
710 
711 	switch (atomic_read(&bat_priv->gw.mode)) {
712 	case BATADV_GW_MODE_SERVER:
713 		/* If we are a GW then we are our best GW. We can artificially
714 		 * set the tq towards ourself as the maximum value
715 		 */
716 		curr_tq_avg = BATADV_TQ_MAX_VALUE;
717 		break;
718 	case BATADV_GW_MODE_CLIENT:
719 		curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
720 		if (!curr_gw)
721 			goto out;
722 
723 		/* packet is going to our gateway */
724 		if (curr_gw->orig_node == orig_dst_node)
725 			goto out;
726 
727 		/* If the dhcp packet has been sent to a different gw,
728 		 * we have to evaluate whether the old gw is still
729 		 * reliable enough
730 		 */
731 		neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
732 						NULL);
733 		if (!neigh_curr)
734 			goto out;
735 
736 		curr_ifinfo = batadv_neigh_ifinfo_get(neigh_curr,
737 						      BATADV_IF_DEFAULT);
738 		if (!curr_ifinfo)
739 			goto out;
740 
741 		curr_tq_avg = curr_ifinfo->bat_iv.tq_avg;
742 		batadv_neigh_ifinfo_put(curr_ifinfo);
743 
744 		break;
745 	case BATADV_GW_MODE_OFF:
746 	default:
747 		goto out;
748 	}
749 
750 	neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
751 	if (!neigh_old)
752 		goto out;
753 
754 	old_ifinfo = batadv_neigh_ifinfo_get(neigh_old, BATADV_IF_DEFAULT);
755 	if (!old_ifinfo)
756 		goto out;
757 
758 	if ((curr_tq_avg - old_ifinfo->bat_iv.tq_avg) > BATADV_GW_THRESHOLD)
759 		out_of_range = true;
760 	batadv_neigh_ifinfo_put(old_ifinfo);
761 
762 out:
763 	batadv_orig_node_put(orig_dst_node);
764 	batadv_gw_node_put(curr_gw);
765 	batadv_gw_node_put(gw_node);
766 	batadv_neigh_node_put(neigh_old);
767 	batadv_neigh_node_put(neigh_curr);
768 	return out_of_range;
769 }
770