1 /*
2  * Copyright (C) 2009-2012 B.A.T.M.A.N. contributors:
3  *
4  * Marek Lindner
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of version 2 of the GNU General Public
8  * License as published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful, but
11  * WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  * General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program; if not, write to the Free Software
17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18  * 02110-1301, USA
19  *
20  */
21 
22 #include "main.h"
23 #include "bat_sysfs.h"
24 #include "gateway_client.h"
25 #include "gateway_common.h"
26 #include "hard-interface.h"
27 #include "originator.h"
28 #include "translation-table.h"
29 #include "routing.h"
30 #include <linux/ip.h>
31 #include <linux/ipv6.h>
32 #include <linux/udp.h>
33 #include <linux/if_vlan.h>
34 
35 /* This is the offset of the options field in a dhcp packet starting at
36  * the beginning of the dhcp header */
37 #define DHCP_OPTIONS_OFFSET 240
38 #define DHCP_REQUEST 3
39 
gw_node_free_ref(struct gw_node * gw_node)40 static void gw_node_free_ref(struct gw_node *gw_node)
41 {
42 	if (atomic_dec_and_test(&gw_node->refcount))
43 		kfree_rcu(gw_node, rcu);
44 }
45 
gw_get_selected_gw_node(struct bat_priv * bat_priv)46 static struct gw_node *gw_get_selected_gw_node(struct bat_priv *bat_priv)
47 {
48 	struct gw_node *gw_node;
49 
50 	rcu_read_lock();
51 	gw_node = rcu_dereference(bat_priv->curr_gw);
52 	if (!gw_node)
53 		goto out;
54 
55 	if (!atomic_inc_not_zero(&gw_node->refcount))
56 		gw_node = NULL;
57 
58 out:
59 	rcu_read_unlock();
60 	return gw_node;
61 }
62 
gw_get_selected_orig(struct bat_priv * bat_priv)63 struct orig_node *gw_get_selected_orig(struct bat_priv *bat_priv)
64 {
65 	struct gw_node *gw_node;
66 	struct orig_node *orig_node = NULL;
67 
68 	gw_node = gw_get_selected_gw_node(bat_priv);
69 	if (!gw_node)
70 		goto out;
71 
72 	rcu_read_lock();
73 	orig_node = gw_node->orig_node;
74 	if (!orig_node)
75 		goto unlock;
76 
77 	if (!atomic_inc_not_zero(&orig_node->refcount))
78 		orig_node = NULL;
79 
80 unlock:
81 	rcu_read_unlock();
82 out:
83 	if (gw_node)
84 		gw_node_free_ref(gw_node);
85 	return orig_node;
86 }
87 
gw_select(struct bat_priv * bat_priv,struct gw_node * new_gw_node)88 static void gw_select(struct bat_priv *bat_priv, struct gw_node *new_gw_node)
89 {
90 	struct gw_node *curr_gw_node;
91 
92 	spin_lock_bh(&bat_priv->gw_list_lock);
93 
94 	if (new_gw_node && !atomic_inc_not_zero(&new_gw_node->refcount))
95 		new_gw_node = NULL;
96 
97 	curr_gw_node = rcu_dereference_protected(bat_priv->curr_gw, 1);
98 	rcu_assign_pointer(bat_priv->curr_gw, new_gw_node);
99 
100 	if (curr_gw_node)
101 		gw_node_free_ref(curr_gw_node);
102 
103 	spin_unlock_bh(&bat_priv->gw_list_lock);
104 }
105 
gw_deselect(struct bat_priv * bat_priv)106 void gw_deselect(struct bat_priv *bat_priv)
107 {
108 	atomic_set(&bat_priv->gw_reselect, 1);
109 }
110 
gw_get_best_gw_node(struct bat_priv * bat_priv)111 static struct gw_node *gw_get_best_gw_node(struct bat_priv *bat_priv)
112 {
113 	struct neigh_node *router;
114 	struct hlist_node *node;
115 	struct gw_node *gw_node, *curr_gw = NULL;
116 	uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
117 	uint8_t max_tq = 0;
118 	int down, up;
119 
120 	rcu_read_lock();
121 	hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
122 		if (gw_node->deleted)
123 			continue;
124 
125 		router = orig_node_get_router(gw_node->orig_node);
126 		if (!router)
127 			continue;
128 
129 		if (!atomic_inc_not_zero(&gw_node->refcount))
130 			goto next;
131 
132 		switch (atomic_read(&bat_priv->gw_sel_class)) {
133 		case 1: /* fast connection */
134 			gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags,
135 					     &down, &up);
136 
137 			tmp_gw_factor = (router->tq_avg * router->tq_avg *
138 					 down * 100 * 100) /
139 					 (TQ_LOCAL_WINDOW_SIZE *
140 					 TQ_LOCAL_WINDOW_SIZE * 64);
141 
142 			if ((tmp_gw_factor > max_gw_factor) ||
143 			    ((tmp_gw_factor == max_gw_factor) &&
144 			     (router->tq_avg > max_tq))) {
145 				if (curr_gw)
146 					gw_node_free_ref(curr_gw);
147 				curr_gw = gw_node;
148 				atomic_inc(&curr_gw->refcount);
149 			}
150 			break;
151 
152 		default: /**
153 			  * 2:  stable connection (use best statistic)
154 			  * 3:  fast-switch (use best statistic but change as
155 			  *     soon as a better gateway appears)
156 			  * XX: late-switch (use best statistic but change as
157 			  *     soon as a better gateway appears which has
158 			  *     $routing_class more tq points)
159 			  **/
160 			if (router->tq_avg > max_tq) {
161 				if (curr_gw)
162 					gw_node_free_ref(curr_gw);
163 				curr_gw = gw_node;
164 				atomic_inc(&curr_gw->refcount);
165 			}
166 			break;
167 		}
168 
169 		if (router->tq_avg > max_tq)
170 			max_tq = router->tq_avg;
171 
172 		if (tmp_gw_factor > max_gw_factor)
173 			max_gw_factor = tmp_gw_factor;
174 
175 		gw_node_free_ref(gw_node);
176 
177 next:
178 		neigh_node_free_ref(router);
179 	}
180 	rcu_read_unlock();
181 
182 	return curr_gw;
183 }
184 
gw_election(struct bat_priv * bat_priv)185 void gw_election(struct bat_priv *bat_priv)
186 {
187 	struct gw_node *curr_gw = NULL, *next_gw = NULL;
188 	struct neigh_node *router = NULL;
189 	char gw_addr[18] = { '\0' };
190 
191 	/**
192 	 * The batman daemon checks here if we already passed a full originator
193 	 * cycle in order to make sure we don't choose the first gateway we
194 	 * hear about. This check is based on the daemon's uptime which we
195 	 * don't have.
196 	 **/
197 	if (atomic_read(&bat_priv->gw_mode) != GW_MODE_CLIENT)
198 		goto out;
199 
200 	if (!atomic_dec_not_zero(&bat_priv->gw_reselect))
201 		goto out;
202 
203 	curr_gw = gw_get_selected_gw_node(bat_priv);
204 
205 	next_gw = gw_get_best_gw_node(bat_priv);
206 
207 	if (curr_gw == next_gw)
208 		goto out;
209 
210 	if (next_gw) {
211 		sprintf(gw_addr, "%pM", next_gw->orig_node->orig);
212 
213 		router = orig_node_get_router(next_gw->orig_node);
214 		if (!router) {
215 			gw_deselect(bat_priv);
216 			goto out;
217 		}
218 	}
219 
220 	if ((curr_gw) && (!next_gw)) {
221 		bat_dbg(DBG_BATMAN, bat_priv,
222 			"Removing selected gateway - no gateway in range\n");
223 		throw_uevent(bat_priv, UEV_GW, UEV_DEL, NULL);
224 	} else if ((!curr_gw) && (next_gw)) {
225 		bat_dbg(DBG_BATMAN, bat_priv,
226 			"Adding route to gateway %pM (gw_flags: %i, tq: %i)\n",
227 			next_gw->orig_node->orig, next_gw->orig_node->gw_flags,
228 			router->tq_avg);
229 		throw_uevent(bat_priv, UEV_GW, UEV_ADD, gw_addr);
230 	} else {
231 		bat_dbg(DBG_BATMAN, bat_priv,
232 			"Changing route to gateway %pM (gw_flags: %i, tq: %i)\n",
233 			next_gw->orig_node->orig, next_gw->orig_node->gw_flags,
234 			router->tq_avg);
235 		throw_uevent(bat_priv, UEV_GW, UEV_CHANGE, gw_addr);
236 	}
237 
238 	gw_select(bat_priv, next_gw);
239 
240 out:
241 	if (curr_gw)
242 		gw_node_free_ref(curr_gw);
243 	if (next_gw)
244 		gw_node_free_ref(next_gw);
245 	if (router)
246 		neigh_node_free_ref(router);
247 }
248 
gw_check_election(struct bat_priv * bat_priv,struct orig_node * orig_node)249 void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
250 {
251 	struct orig_node *curr_gw_orig;
252 	struct neigh_node *router_gw = NULL, *router_orig = NULL;
253 	uint8_t gw_tq_avg, orig_tq_avg;
254 
255 	curr_gw_orig = gw_get_selected_orig(bat_priv);
256 	if (!curr_gw_orig)
257 		goto deselect;
258 
259 	router_gw = orig_node_get_router(curr_gw_orig);
260 	if (!router_gw)
261 		goto deselect;
262 
263 	/* this node already is the gateway */
264 	if (curr_gw_orig == orig_node)
265 		goto out;
266 
267 	router_orig = orig_node_get_router(orig_node);
268 	if (!router_orig)
269 		goto out;
270 
271 	gw_tq_avg = router_gw->tq_avg;
272 	orig_tq_avg = router_orig->tq_avg;
273 
274 	/* the TQ value has to be better */
275 	if (orig_tq_avg < gw_tq_avg)
276 		goto out;
277 
278 	/**
279 	 * if the routing class is greater than 3 the value tells us how much
280 	 * greater the TQ value of the new gateway must be
281 	 **/
282 	if ((atomic_read(&bat_priv->gw_sel_class) > 3) &&
283 	    (orig_tq_avg - gw_tq_avg < atomic_read(&bat_priv->gw_sel_class)))
284 		goto out;
285 
286 	bat_dbg(DBG_BATMAN, bat_priv,
287 		"Restarting gateway selection: better gateway found (tq curr: %i, tq new: %i)\n",
288 		gw_tq_avg, orig_tq_avg);
289 
290 deselect:
291 	gw_deselect(bat_priv);
292 out:
293 	if (curr_gw_orig)
294 		orig_node_free_ref(curr_gw_orig);
295 	if (router_gw)
296 		neigh_node_free_ref(router_gw);
297 	if (router_orig)
298 		neigh_node_free_ref(router_orig);
299 
300 	return;
301 }
302 
gw_node_add(struct bat_priv * bat_priv,struct orig_node * orig_node,uint8_t new_gwflags)303 static void gw_node_add(struct bat_priv *bat_priv,
304 			struct orig_node *orig_node, uint8_t new_gwflags)
305 {
306 	struct gw_node *gw_node;
307 	int down, up;
308 
309 	gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
310 	if (!gw_node)
311 		return;
312 
313 	INIT_HLIST_NODE(&gw_node->list);
314 	gw_node->orig_node = orig_node;
315 	atomic_set(&gw_node->refcount, 1);
316 
317 	spin_lock_bh(&bat_priv->gw_list_lock);
318 	hlist_add_head_rcu(&gw_node->list, &bat_priv->gw_list);
319 	spin_unlock_bh(&bat_priv->gw_list_lock);
320 
321 	gw_bandwidth_to_kbit(new_gwflags, &down, &up);
322 	bat_dbg(DBG_BATMAN, bat_priv,
323 		"Found new gateway %pM -> gw_class: %i - %i%s/%i%s\n",
324 		orig_node->orig, new_gwflags,
325 		(down > 2048 ? down / 1024 : down),
326 		(down > 2048 ? "MBit" : "KBit"),
327 		(up > 2048 ? up / 1024 : up),
328 		(up > 2048 ? "MBit" : "KBit"));
329 }
330 
gw_node_update(struct bat_priv * bat_priv,struct orig_node * orig_node,uint8_t new_gwflags)331 void gw_node_update(struct bat_priv *bat_priv,
332 		    struct orig_node *orig_node, uint8_t new_gwflags)
333 {
334 	struct hlist_node *node;
335 	struct gw_node *gw_node, *curr_gw;
336 
337 	/**
338 	 * Note: We don't need a NULL check here, since curr_gw never gets
339 	 * dereferenced. If curr_gw is NULL we also should not exit as we may
340 	 * have this gateway in our list (duplication check!) even though we
341 	 * have no currently selected gateway.
342 	 */
343 	curr_gw = gw_get_selected_gw_node(bat_priv);
344 
345 	rcu_read_lock();
346 	hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
347 		if (gw_node->orig_node != orig_node)
348 			continue;
349 
350 		bat_dbg(DBG_BATMAN, bat_priv,
351 			"Gateway class of originator %pM changed from %i to %i\n",
352 			orig_node->orig, gw_node->orig_node->gw_flags,
353 			new_gwflags);
354 
355 		gw_node->deleted = 0;
356 
357 		if (new_gwflags == NO_FLAGS) {
358 			gw_node->deleted = jiffies;
359 			bat_dbg(DBG_BATMAN, bat_priv,
360 				"Gateway %pM removed from gateway list\n",
361 				orig_node->orig);
362 
363 			if (gw_node == curr_gw)
364 				goto deselect;
365 		}
366 
367 		goto unlock;
368 	}
369 
370 	if (new_gwflags == NO_FLAGS)
371 		goto unlock;
372 
373 	gw_node_add(bat_priv, orig_node, new_gwflags);
374 	goto unlock;
375 
376 deselect:
377 	gw_deselect(bat_priv);
378 unlock:
379 	rcu_read_unlock();
380 
381 	if (curr_gw)
382 		gw_node_free_ref(curr_gw);
383 }
384 
gw_node_delete(struct bat_priv * bat_priv,struct orig_node * orig_node)385 void gw_node_delete(struct bat_priv *bat_priv, struct orig_node *orig_node)
386 {
387 	gw_node_update(bat_priv, orig_node, 0);
388 }
389 
gw_node_purge(struct bat_priv * bat_priv)390 void gw_node_purge(struct bat_priv *bat_priv)
391 {
392 	struct gw_node *gw_node, *curr_gw;
393 	struct hlist_node *node, *node_tmp;
394 	unsigned long timeout = msecs_to_jiffies(2 * PURGE_TIMEOUT);
395 	int do_deselect = 0;
396 
397 	curr_gw = gw_get_selected_gw_node(bat_priv);
398 
399 	spin_lock_bh(&bat_priv->gw_list_lock);
400 
401 	hlist_for_each_entry_safe(gw_node, node, node_tmp,
402 				  &bat_priv->gw_list, list) {
403 		if (((!gw_node->deleted) ||
404 		     (time_before(jiffies, gw_node->deleted + timeout))) &&
405 		    atomic_read(&bat_priv->mesh_state) == MESH_ACTIVE)
406 			continue;
407 
408 		if (curr_gw == gw_node)
409 			do_deselect = 1;
410 
411 		hlist_del_rcu(&gw_node->list);
412 		gw_node_free_ref(gw_node);
413 	}
414 
415 	spin_unlock_bh(&bat_priv->gw_list_lock);
416 
417 	/* gw_deselect() needs to acquire the gw_list_lock */
418 	if (do_deselect)
419 		gw_deselect(bat_priv);
420 
421 	if (curr_gw)
422 		gw_node_free_ref(curr_gw);
423 }
424 
425 /**
426  * fails if orig_node has no router
427  */
_write_buffer_text(struct bat_priv * bat_priv,struct seq_file * seq,const struct gw_node * gw_node)428 static int _write_buffer_text(struct bat_priv *bat_priv, struct seq_file *seq,
429 			      const struct gw_node *gw_node)
430 {
431 	struct gw_node *curr_gw;
432 	struct neigh_node *router;
433 	int down, up, ret = -1;
434 
435 	gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags, &down, &up);
436 
437 	router = orig_node_get_router(gw_node->orig_node);
438 	if (!router)
439 		goto out;
440 
441 	curr_gw = gw_get_selected_gw_node(bat_priv);
442 
443 	ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %3i - %i%s/%i%s\n",
444 			 (curr_gw == gw_node ? "=>" : "  "),
445 			 gw_node->orig_node->orig,
446 			 router->tq_avg, router->addr,
447 			 router->if_incoming->net_dev->name,
448 			 gw_node->orig_node->gw_flags,
449 			 (down > 2048 ? down / 1024 : down),
450 			 (down > 2048 ? "MBit" : "KBit"),
451 			 (up > 2048 ? up / 1024 : up),
452 			 (up > 2048 ? "MBit" : "KBit"));
453 
454 	neigh_node_free_ref(router);
455 	if (curr_gw)
456 		gw_node_free_ref(curr_gw);
457 out:
458 	return ret;
459 }
460 
gw_client_seq_print_text(struct seq_file * seq,void * offset)461 int gw_client_seq_print_text(struct seq_file *seq, void *offset)
462 {
463 	struct net_device *net_dev = (struct net_device *)seq->private;
464 	struct bat_priv *bat_priv = netdev_priv(net_dev);
465 	struct hard_iface *primary_if;
466 	struct gw_node *gw_node;
467 	struct hlist_node *node;
468 	int gw_count = 0, ret = 0;
469 
470 	primary_if = primary_if_get_selected(bat_priv);
471 	if (!primary_if) {
472 		ret = seq_printf(seq,
473 				 "BATMAN mesh %s disabled - please specify interfaces to enable it\n",
474 				 net_dev->name);
475 		goto out;
476 	}
477 
478 	if (primary_if->if_status != IF_ACTIVE) {
479 		ret = seq_printf(seq,
480 				 "BATMAN mesh %s disabled - primary interface not active\n",
481 				 net_dev->name);
482 		goto out;
483 	}
484 
485 	seq_printf(seq,
486 		   "      %-12s (%s/%i) %17s [%10s]: gw_class ... [B.A.T.M.A.N. adv %s, MainIF/MAC: %s/%pM (%s)]\n",
487 		   "Gateway", "#", TQ_MAX_VALUE, "Nexthop", "outgoingIF",
488 		   SOURCE_VERSION, primary_if->net_dev->name,
489 		   primary_if->net_dev->dev_addr, net_dev->name);
490 
491 	rcu_read_lock();
492 	hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
493 		if (gw_node->deleted)
494 			continue;
495 
496 		/* fails if orig_node has no router */
497 		if (_write_buffer_text(bat_priv, seq, gw_node) < 0)
498 			continue;
499 
500 		gw_count++;
501 	}
502 	rcu_read_unlock();
503 
504 	if (gw_count == 0)
505 		seq_printf(seq, "No gateways in range ...\n");
506 
507 out:
508 	if (primary_if)
509 		hardif_free_ref(primary_if);
510 	return ret;
511 }
512 
is_type_dhcprequest(struct sk_buff * skb,int header_len)513 static bool is_type_dhcprequest(struct sk_buff *skb, int header_len)
514 {
515 	int ret = false;
516 	unsigned char *p;
517 	int pkt_len;
518 
519 	if (skb_linearize(skb) < 0)
520 		goto out;
521 
522 	pkt_len = skb_headlen(skb);
523 
524 	if (pkt_len < header_len + DHCP_OPTIONS_OFFSET + 1)
525 		goto out;
526 
527 	p = skb->data + header_len + DHCP_OPTIONS_OFFSET;
528 	pkt_len -= header_len + DHCP_OPTIONS_OFFSET + 1;
529 
530 	/* Access the dhcp option lists. Each entry is made up by:
531 	 * - octet 1: option type
532 	 * - octet 2: option data len (only if type != 255 and 0)
533 	 * - octet 3: option data */
534 	while (*p != 255 && !ret) {
535 		/* p now points to the first octet: option type */
536 		if (*p == 53) {
537 			/* type 53 is the message type option.
538 			 * Jump the len octet and go to the data octet */
539 			if (pkt_len < 2)
540 				goto out;
541 			p += 2;
542 
543 			/* check if the message type is what we need */
544 			if (*p == DHCP_REQUEST)
545 				ret = true;
546 			break;
547 		} else if (*p == 0) {
548 			/* option type 0 (padding), just go forward */
549 			if (pkt_len < 1)
550 				goto out;
551 			pkt_len--;
552 			p++;
553 		} else {
554 			/* This is any other option. So we get the length... */
555 			if (pkt_len < 1)
556 				goto out;
557 			pkt_len--;
558 			p++;
559 
560 			/* ...and then we jump over the data */
561 			if (pkt_len < *p)
562 				goto out;
563 			pkt_len -= *p;
564 			p += (*p);
565 		}
566 	}
567 out:
568 	return ret;
569 }
570 
gw_is_dhcp_target(struct sk_buff * skb,unsigned int * header_len)571 bool gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len)
572 {
573 	struct ethhdr *ethhdr;
574 	struct iphdr *iphdr;
575 	struct ipv6hdr *ipv6hdr;
576 	struct udphdr *udphdr;
577 
578 	/* check for ethernet header */
579 	if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
580 		return false;
581 	ethhdr = (struct ethhdr *)skb->data;
582 	*header_len += ETH_HLEN;
583 
584 	/* check for initial vlan header */
585 	if (ntohs(ethhdr->h_proto) == ETH_P_8021Q) {
586 		if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
587 			return false;
588 		ethhdr = (struct ethhdr *)(skb->data + VLAN_HLEN);
589 		*header_len += VLAN_HLEN;
590 	}
591 
592 	/* check for ip header */
593 	switch (ntohs(ethhdr->h_proto)) {
594 	case ETH_P_IP:
595 		if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
596 			return false;
597 		iphdr = (struct iphdr *)(skb->data + *header_len);
598 		*header_len += iphdr->ihl * 4;
599 
600 		/* check for udp header */
601 		if (iphdr->protocol != IPPROTO_UDP)
602 			return false;
603 
604 		break;
605 	case ETH_P_IPV6:
606 		if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
607 			return false;
608 		ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
609 		*header_len += sizeof(*ipv6hdr);
610 
611 		/* check for udp header */
612 		if (ipv6hdr->nexthdr != IPPROTO_UDP)
613 			return false;
614 
615 		break;
616 	default:
617 		return false;
618 	}
619 
620 	if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
621 		return false;
622 	udphdr = (struct udphdr *)(skb->data + *header_len);
623 	*header_len += sizeof(*udphdr);
624 
625 	/* check for bootp port */
626 	if ((ntohs(ethhdr->h_proto) == ETH_P_IP) &&
627 	    (ntohs(udphdr->dest) != 67))
628 		return false;
629 
630 	if ((ntohs(ethhdr->h_proto) == ETH_P_IPV6) &&
631 	    (ntohs(udphdr->dest) != 547))
632 		return false;
633 
634 	return true;
635 }
636 
gw_out_of_range(struct bat_priv * bat_priv,struct sk_buff * skb,struct ethhdr * ethhdr)637 bool gw_out_of_range(struct bat_priv *bat_priv,
638 		     struct sk_buff *skb, struct ethhdr *ethhdr)
639 {
640 	struct neigh_node *neigh_curr = NULL, *neigh_old = NULL;
641 	struct orig_node *orig_dst_node = NULL;
642 	struct gw_node *curr_gw = NULL;
643 	bool ret, out_of_range = false;
644 	unsigned int header_len = 0;
645 	uint8_t curr_tq_avg;
646 
647 	ret = gw_is_dhcp_target(skb, &header_len);
648 	if (!ret)
649 		goto out;
650 
651 	orig_dst_node = transtable_search(bat_priv, ethhdr->h_source,
652 					  ethhdr->h_dest);
653 	if (!orig_dst_node)
654 		goto out;
655 
656 	if (!orig_dst_node->gw_flags)
657 		goto out;
658 
659 	ret = is_type_dhcprequest(skb, header_len);
660 	if (!ret)
661 		goto out;
662 
663 	switch (atomic_read(&bat_priv->gw_mode)) {
664 	case GW_MODE_SERVER:
665 		/* If we are a GW then we are our best GW. We can artificially
666 		 * set the tq towards ourself as the maximum value */
667 		curr_tq_avg = TQ_MAX_VALUE;
668 		break;
669 	case GW_MODE_CLIENT:
670 		curr_gw = gw_get_selected_gw_node(bat_priv);
671 		if (!curr_gw)
672 			goto out;
673 
674 		/* packet is going to our gateway */
675 		if (curr_gw->orig_node == orig_dst_node)
676 			goto out;
677 
678 		/* If the dhcp packet has been sent to a different gw,
679 		 * we have to evaluate whether the old gw is still
680 		 * reliable enough */
681 		neigh_curr = find_router(bat_priv, curr_gw->orig_node, NULL);
682 		if (!neigh_curr)
683 			goto out;
684 
685 		curr_tq_avg = neigh_curr->tq_avg;
686 		break;
687 	case GW_MODE_OFF:
688 	default:
689 		goto out;
690 	}
691 
692 	neigh_old = find_router(bat_priv, orig_dst_node, NULL);
693 	if (!neigh_old)
694 		goto out;
695 
696 	if (curr_tq_avg - neigh_old->tq_avg > GW_THRESHOLD)
697 		out_of_range = true;
698 
699 out:
700 	if (orig_dst_node)
701 		orig_node_free_ref(orig_dst_node);
702 	if (curr_gw)
703 		gw_node_free_ref(curr_gw);
704 	if (neigh_old)
705 		neigh_node_free_ref(neigh_old);
706 	if (neigh_curr)
707 		neigh_node_free_ref(neigh_curr);
708 	return out_of_range;
709 }
710