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TOMOYO Linux Cross Reference
Linux/net/batman-adv/gateway_client.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /* Copyright (C) 2009-2018  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, see <http://www.gnu.org/licenses/>.
 17  */
 18 
 19 #include "gateway_client.h"
 20 #include "main.h"
 21 
 22 #include <linux/atomic.h>
 23 #include <linux/byteorder/generic.h>
 24 #include <linux/errno.h>
 25 #include <linux/etherdevice.h>
 26 #include <linux/gfp.h>
 27 #include <linux/if_ether.h>
 28 #include <linux/if_vlan.h>
 29 #include <linux/in.h>
 30 #include <linux/ip.h>
 31 #include <linux/ipv6.h>
 32 #include <linux/kernel.h>
 33 #include <linux/kref.h>
 34 #include <linux/list.h>
 35 #include <linux/lockdep.h>
 36 #include <linux/netdevice.h>
 37 #include <linux/netlink.h>
 38 #include <linux/rculist.h>
 39 #include <linux/rcupdate.h>
 40 #include <linux/seq_file.h>
 41 #include <linux/skbuff.h>
 42 #include <linux/slab.h>
 43 #include <linux/spinlock.h>
 44 #include <linux/stddef.h>
 45 #include <linux/udp.h>
 46 #include <net/sock.h>
 47 #include <uapi/linux/batadv_packet.h>
 48 #include <uapi/linux/batman_adv.h>
 49 
 50 #include "gateway_common.h"
 51 #include "hard-interface.h"
 52 #include "log.h"
 53 #include "netlink.h"
 54 #include "originator.h"
 55 #include "routing.h"
 56 #include "soft-interface.h"
 57 #include "sysfs.h"
 58 #include "translation-table.h"
 59 
 60 /* These are the offsets of the "hw type" and "hw address length" in the dhcp
 61  * packet starting at the beginning of the dhcp header
 62  */
 63 #define BATADV_DHCP_HTYPE_OFFSET        1
 64 #define BATADV_DHCP_HLEN_OFFSET         2
 65 /* Value of htype representing Ethernet */
 66 #define BATADV_DHCP_HTYPE_ETHERNET      0x01
 67 /* This is the offset of the "chaddr" field in the dhcp packet starting at the
 68  * beginning of the dhcp header
 69  */
 70 #define BATADV_DHCP_CHADDR_OFFSET       28
 71 
 72 /**
 73  * batadv_gw_node_release() - release gw_node from lists and queue for free
 74  *  after rcu grace period
 75  * @ref: kref pointer of the gw_node
 76  */
 77 static void batadv_gw_node_release(struct kref *ref)
 78 {
 79         struct batadv_gw_node *gw_node;
 80 
 81         gw_node = container_of(ref, struct batadv_gw_node, refcount);
 82 
 83         batadv_orig_node_put(gw_node->orig_node);
 84         kfree_rcu(gw_node, rcu);
 85 }
 86 
 87 /**
 88  * batadv_gw_node_put() - decrement the gw_node refcounter and possibly release
 89  *  it
 90  * @gw_node: gateway node to free
 91  */
 92 void batadv_gw_node_put(struct batadv_gw_node *gw_node)
 93 {
 94         kref_put(&gw_node->refcount, batadv_gw_node_release);
 95 }
 96 
 97 /**
 98  * batadv_gw_get_selected_gw_node() - Get currently selected gateway
 99  * @bat_priv: the bat priv with all the soft interface information
100  *
101  * Return: selected gateway (with increased refcnt), NULL on errors
102  */
103 struct batadv_gw_node *
104 batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv)
105 {
106         struct batadv_gw_node *gw_node;
107 
108         rcu_read_lock();
109         gw_node = rcu_dereference(bat_priv->gw.curr_gw);
110         if (!gw_node)
111                 goto out;
112 
113         if (!kref_get_unless_zero(&gw_node->refcount))
114                 gw_node = NULL;
115 
116 out:
117         rcu_read_unlock();
118         return gw_node;
119 }
120 
121 /**
122  * batadv_gw_get_selected_orig() - Get originator of currently selected gateway
123  * @bat_priv: the bat priv with all the soft interface information
124  *
125  * Return: orig_node of selected gateway (with increased refcnt), NULL on errors
126  */
127 struct batadv_orig_node *
128 batadv_gw_get_selected_orig(struct batadv_priv *bat_priv)
129 {
130         struct batadv_gw_node *gw_node;
131         struct batadv_orig_node *orig_node = NULL;
132 
133         gw_node = batadv_gw_get_selected_gw_node(bat_priv);
134         if (!gw_node)
135                 goto out;
136 
137         rcu_read_lock();
138         orig_node = gw_node->orig_node;
139         if (!orig_node)
140                 goto unlock;
141 
142         if (!kref_get_unless_zero(&orig_node->refcount))
143                 orig_node = NULL;
144 
145 unlock:
146         rcu_read_unlock();
147 out:
148         if (gw_node)
149                 batadv_gw_node_put(gw_node);
150         return orig_node;
151 }
152 
153 static void batadv_gw_select(struct batadv_priv *bat_priv,
154                              struct batadv_gw_node *new_gw_node)
155 {
156         struct batadv_gw_node *curr_gw_node;
157 
158         spin_lock_bh(&bat_priv->gw.list_lock);
159 
160         if (new_gw_node)
161                 kref_get(&new_gw_node->refcount);
162 
163         curr_gw_node = rcu_dereference_protected(bat_priv->gw.curr_gw, 1);
164         rcu_assign_pointer(bat_priv->gw.curr_gw, new_gw_node);
165 
166         if (curr_gw_node)
167                 batadv_gw_node_put(curr_gw_node);
168 
169         spin_unlock_bh(&bat_priv->gw.list_lock);
170 }
171 
172 /**
173  * batadv_gw_reselect() - force a gateway reselection
174  * @bat_priv: the bat priv with all the soft interface information
175  *
176  * Set a flag to remind the GW component to perform a new gateway reselection.
177  * However this function does not ensure that the current gateway is going to be
178  * deselected. The reselection mechanism may elect the same gateway once again.
179  *
180  * This means that invoking batadv_gw_reselect() does not guarantee a gateway
181  * change and therefore a uevent is not necessarily expected.
182  */
183 void batadv_gw_reselect(struct batadv_priv *bat_priv)
184 {
185         atomic_set(&bat_priv->gw.reselect, 1);
186 }
187 
188 /**
189  * batadv_gw_check_client_stop() - check if client mode has been switched off
190  * @bat_priv: the bat priv with all the soft interface information
191  *
192  * This function assumes the caller has checked that the gw state *is actually
193  * changing*. This function is not supposed to be called when there is no state
194  * change.
195  */
196 void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
197 {
198         struct batadv_gw_node *curr_gw;
199 
200         if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
201                 return;
202 
203         curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
204         if (!curr_gw)
205                 return;
206 
207         /* deselect the current gateway so that next time that client mode is
208          * enabled a proper GW_ADD event can be sent
209          */
210         batadv_gw_select(bat_priv, NULL);
211 
212         /* if batman-adv is switching the gw client mode off and a gateway was
213          * already selected, send a DEL uevent
214          */
215         batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL, NULL);
216 
217         batadv_gw_node_put(curr_gw);
218 }
219 
220 /**
221  * batadv_gw_election() - Elect the best gateway
222  * @bat_priv: the bat priv with all the soft interface information
223  */
224 void batadv_gw_election(struct batadv_priv *bat_priv)
225 {
226         struct batadv_gw_node *curr_gw = NULL;
227         struct batadv_gw_node *next_gw = NULL;
228         struct batadv_neigh_node *router = NULL;
229         struct batadv_neigh_ifinfo *router_ifinfo = NULL;
230         char gw_addr[18] = { '\0' };
231 
232         if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
233                 goto out;
234 
235         if (!bat_priv->algo_ops->gw.get_best_gw_node)
236                 goto out;
237 
238         curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
239 
240         if (!batadv_atomic_dec_not_zero(&bat_priv->gw.reselect) && curr_gw)
241                 goto out;
242 
243         /* if gw.reselect is set to 1 it means that a previous call to
244          * gw.is_eligible() said that we have a new best GW, therefore it can
245          * now be picked from the list and selected
246          */
247         next_gw = bat_priv->algo_ops->gw.get_best_gw_node(bat_priv);
248 
249         if (curr_gw == next_gw)
250                 goto out;
251 
252         if (next_gw) {
253                 sprintf(gw_addr, "%pM", next_gw->orig_node->orig);
254 
255                 router = batadv_orig_router_get(next_gw->orig_node,
256                                                 BATADV_IF_DEFAULT);
257                 if (!router) {
258                         batadv_gw_reselect(bat_priv);
259                         goto out;
260                 }
261 
262                 router_ifinfo = batadv_neigh_ifinfo_get(router,
263                                                         BATADV_IF_DEFAULT);
264                 if (!router_ifinfo) {
265                         batadv_gw_reselect(bat_priv);
266                         goto out;
267                 }
268         }
269 
270         if (curr_gw && !next_gw) {
271                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
272                            "Removing selected gateway - no gateway in range\n");
273                 batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL,
274                                     NULL);
275         } else if (!curr_gw && next_gw) {
276                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
277                            "Adding route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
278                            next_gw->orig_node->orig,
279                            next_gw->bandwidth_down / 10,
280                            next_gw->bandwidth_down % 10,
281                            next_gw->bandwidth_up / 10,
282                            next_gw->bandwidth_up % 10,
283                            router_ifinfo->bat_iv.tq_avg);
284                 batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_ADD,
285                                     gw_addr);
286         } else {
287                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
288                            "Changing route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
289                            next_gw->orig_node->orig,
290                            next_gw->bandwidth_down / 10,
291                            next_gw->bandwidth_down % 10,
292                            next_gw->bandwidth_up / 10,
293                            next_gw->bandwidth_up % 10,
294                            router_ifinfo->bat_iv.tq_avg);
295                 batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_CHANGE,
296                                     gw_addr);
297         }
298 
299         batadv_gw_select(bat_priv, next_gw);
300 
301 out:
302         if (curr_gw)
303                 batadv_gw_node_put(curr_gw);
304         if (next_gw)
305                 batadv_gw_node_put(next_gw);
306         if (router)
307                 batadv_neigh_node_put(router);
308         if (router_ifinfo)
309                 batadv_neigh_ifinfo_put(router_ifinfo);
310 }
311 
312 /**
313  * batadv_gw_check_election() - Elect orig node as best gateway when eligible
314  * @bat_priv: the bat priv with all the soft interface information
315  * @orig_node: orig node which is to be checked
316  */
317 void batadv_gw_check_election(struct batadv_priv *bat_priv,
318                               struct batadv_orig_node *orig_node)
319 {
320         struct batadv_orig_node *curr_gw_orig;
321 
322         /* abort immediately if the routing algorithm does not support gateway
323          * election
324          */
325         if (!bat_priv->algo_ops->gw.is_eligible)
326                 return;
327 
328         curr_gw_orig = batadv_gw_get_selected_orig(bat_priv);
329         if (!curr_gw_orig)
330                 goto reselect;
331 
332         /* this node already is the gateway */
333         if (curr_gw_orig == orig_node)
334                 goto out;
335 
336         if (!bat_priv->algo_ops->gw.is_eligible(bat_priv, curr_gw_orig,
337                                                 orig_node))
338                 goto out;
339 
340 reselect:
341         batadv_gw_reselect(bat_priv);
342 out:
343         if (curr_gw_orig)
344                 batadv_orig_node_put(curr_gw_orig);
345 }
346 
347 /**
348  * batadv_gw_node_add() - add gateway node to list of available gateways
349  * @bat_priv: the bat priv with all the soft interface information
350  * @orig_node: originator announcing gateway capabilities
351  * @gateway: announced bandwidth information
352  *
353  * Has to be called with the appropriate locks being acquired
354  * (gw.list_lock).
355  */
356 static void batadv_gw_node_add(struct batadv_priv *bat_priv,
357                                struct batadv_orig_node *orig_node,
358                                struct batadv_tvlv_gateway_data *gateway)
359 {
360         struct batadv_gw_node *gw_node;
361 
362         lockdep_assert_held(&bat_priv->gw.list_lock);
363 
364         if (gateway->bandwidth_down == 0)
365                 return;
366 
367         gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
368         if (!gw_node)
369                 return;
370 
371         kref_init(&gw_node->refcount);
372         INIT_HLIST_NODE(&gw_node->list);
373         kref_get(&orig_node->refcount);
374         gw_node->orig_node = orig_node;
375         gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
376         gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
377 
378         kref_get(&gw_node->refcount);
379         hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list);
380 
381         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
382                    "Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n",
383                    orig_node->orig,
384                    ntohl(gateway->bandwidth_down) / 10,
385                    ntohl(gateway->bandwidth_down) % 10,
386                    ntohl(gateway->bandwidth_up) / 10,
387                    ntohl(gateway->bandwidth_up) % 10);
388 
389         /* don't return reference to new gw_node */
390         batadv_gw_node_put(gw_node);
391 }
392 
393 /**
394  * batadv_gw_node_get() - retrieve gateway node from list of available gateways
395  * @bat_priv: the bat priv with all the soft interface information
396  * @orig_node: originator announcing gateway capabilities
397  *
398  * Return: gateway node if found or NULL otherwise.
399  */
400 struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
401                                           struct batadv_orig_node *orig_node)
402 {
403         struct batadv_gw_node *gw_node_tmp, *gw_node = NULL;
404 
405         rcu_read_lock();
406         hlist_for_each_entry_rcu(gw_node_tmp, &bat_priv->gw.gateway_list,
407                                  list) {
408                 if (gw_node_tmp->orig_node != orig_node)
409                         continue;
410 
411                 if (!kref_get_unless_zero(&gw_node_tmp->refcount))
412                         continue;
413 
414                 gw_node = gw_node_tmp;
415                 break;
416         }
417         rcu_read_unlock();
418 
419         return gw_node;
420 }
421 
422 /**
423  * batadv_gw_node_update() - update list of available gateways with changed
424  *  bandwidth information
425  * @bat_priv: the bat priv with all the soft interface information
426  * @orig_node: originator announcing gateway capabilities
427  * @gateway: announced bandwidth information
428  */
429 void batadv_gw_node_update(struct batadv_priv *bat_priv,
430                            struct batadv_orig_node *orig_node,
431                            struct batadv_tvlv_gateway_data *gateway)
432 {
433         struct batadv_gw_node *gw_node, *curr_gw = NULL;
434 
435         spin_lock_bh(&bat_priv->gw.list_lock);
436         gw_node = batadv_gw_node_get(bat_priv, orig_node);
437         if (!gw_node) {
438                 batadv_gw_node_add(bat_priv, orig_node, gateway);
439                 spin_unlock_bh(&bat_priv->gw.list_lock);
440                 goto out;
441         }
442         spin_unlock_bh(&bat_priv->gw.list_lock);
443 
444         if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) &&
445             gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))
446                 goto out;
447 
448         batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
449                    "Gateway bandwidth of originator %pM changed from %u.%u/%u.%u MBit to %u.%u/%u.%u MBit\n",
450                    orig_node->orig,
451                    gw_node->bandwidth_down / 10,
452                    gw_node->bandwidth_down % 10,
453                    gw_node->bandwidth_up / 10,
454                    gw_node->bandwidth_up % 10,
455                    ntohl(gateway->bandwidth_down) / 10,
456                    ntohl(gateway->bandwidth_down) % 10,
457                    ntohl(gateway->bandwidth_up) / 10,
458                    ntohl(gateway->bandwidth_up) % 10);
459 
460         gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
461         gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
462 
463         if (ntohl(gateway->bandwidth_down) == 0) {
464                 batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
465                            "Gateway %pM removed from gateway list\n",
466                            orig_node->orig);
467 
468                 /* Note: We don't need a NULL check here, since curr_gw never
469                  * gets dereferenced.
470                  */
471                 spin_lock_bh(&bat_priv->gw.list_lock);
472                 if (!hlist_unhashed(&gw_node->list)) {
473                         hlist_del_init_rcu(&gw_node->list);
474                         batadv_gw_node_put(gw_node);
475                 }
476                 spin_unlock_bh(&bat_priv->gw.list_lock);
477 
478                 curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
479                 if (gw_node == curr_gw)
480                         batadv_gw_reselect(bat_priv);
481 
482                 if (curr_gw)
483                         batadv_gw_node_put(curr_gw);
484         }
485 
486 out:
487         if (gw_node)
488                 batadv_gw_node_put(gw_node);
489 }
490 
491 /**
492  * batadv_gw_node_delete() - Remove orig_node from gateway list
493  * @bat_priv: the bat priv with all the soft interface information
494  * @orig_node: orig node which is currently in process of being removed
495  */
496 void batadv_gw_node_delete(struct batadv_priv *bat_priv,
497                            struct batadv_orig_node *orig_node)
498 {
499         struct batadv_tvlv_gateway_data gateway;
500 
501         gateway.bandwidth_down = 0;
502         gateway.bandwidth_up = 0;
503 
504         batadv_gw_node_update(bat_priv, orig_node, &gateway);
505 }
506 
507 /**
508  * batadv_gw_node_free() - Free gateway information from soft interface
509  * @bat_priv: the bat priv with all the soft interface information
510  */
511 void batadv_gw_node_free(struct batadv_priv *bat_priv)
512 {
513         struct batadv_gw_node *gw_node;
514         struct hlist_node *node_tmp;
515 
516         spin_lock_bh(&bat_priv->gw.list_lock);
517         hlist_for_each_entry_safe(gw_node, node_tmp,
518                                   &bat_priv->gw.gateway_list, list) {
519                 hlist_del_init_rcu(&gw_node->list);
520                 batadv_gw_node_put(gw_node);
521         }
522         spin_unlock_bh(&bat_priv->gw.list_lock);
523 }
524 
525 #ifdef CONFIG_BATMAN_ADV_DEBUGFS
526 
527 /**
528  * batadv_gw_client_seq_print_text() - Print the gateway table in a seq file
529  * @seq: seq file to print on
530  * @offset: not used
531  *
532  * Return: always 0
533  */
534 int batadv_gw_client_seq_print_text(struct seq_file *seq, void *offset)
535 {
536         struct net_device *net_dev = (struct net_device *)seq->private;
537         struct batadv_priv *bat_priv = netdev_priv(net_dev);
538         struct batadv_hard_iface *primary_if;
539 
540         primary_if = batadv_seq_print_text_primary_if_get(seq);
541         if (!primary_if)
542                 return 0;
543 
544         seq_printf(seq, "[B.A.T.M.A.N. adv %s, MainIF/MAC: %s/%pM (%s %s)]\n",
545                    BATADV_SOURCE_VERSION, primary_if->net_dev->name,
546                    primary_if->net_dev->dev_addr, net_dev->name,
547                    bat_priv->algo_ops->name);
548 
549         batadv_hardif_put(primary_if);
550 
551         if (!bat_priv->algo_ops->gw.print) {
552                 seq_puts(seq,
553                          "No printing function for this routing protocol\n");
554                 return 0;
555         }
556 
557         bat_priv->algo_ops->gw.print(bat_priv, seq);
558 
559         return 0;
560 }
561 #endif
562 
563 /**
564  * batadv_gw_dump() - Dump gateways into a message
565  * @msg: Netlink message to dump into
566  * @cb: Control block containing additional options
567  *
568  * Return: Error code, or length of message
569  */
570 int batadv_gw_dump(struct sk_buff *msg, struct netlink_callback *cb)
571 {
572         struct batadv_hard_iface *primary_if = NULL;
573         struct net *net = sock_net(cb->skb->sk);
574         struct net_device *soft_iface;
575         struct batadv_priv *bat_priv;
576         int ifindex;
577         int ret;
578 
579         ifindex = batadv_netlink_get_ifindex(cb->nlh,
580                                              BATADV_ATTR_MESH_IFINDEX);
581         if (!ifindex)
582                 return -EINVAL;
583 
584         soft_iface = dev_get_by_index(net, ifindex);
585         if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
586                 ret = -ENODEV;
587                 goto out;
588         }
589 
590         bat_priv = netdev_priv(soft_iface);
591 
592         primary_if = batadv_primary_if_get_selected(bat_priv);
593         if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
594                 ret = -ENOENT;
595                 goto out;
596         }
597 
598         if (!bat_priv->algo_ops->gw.dump) {
599                 ret = -EOPNOTSUPP;
600                 goto out;
601         }
602 
603         bat_priv->algo_ops->gw.dump(msg, cb, bat_priv);
604 
605         ret = msg->len;
606 
607 out:
608         if (primary_if)
609                 batadv_hardif_put(primary_if);
610         if (soft_iface)
611                 dev_put(soft_iface);
612 
613         return ret;
614 }
615 
616 /**
617  * batadv_gw_dhcp_recipient_get() - check if a packet is a DHCP message
618  * @skb: the packet to check
619  * @header_len: a pointer to the batman-adv header size
620  * @chaddr: buffer where the client address will be stored. Valid
621  *  only if the function returns BATADV_DHCP_TO_CLIENT
622  *
623  * This function may re-allocate the data buffer of the skb passed as argument.
624  *
625  * Return:
626  * - BATADV_DHCP_NO if the packet is not a dhcp message or if there was an error
627  *   while parsing it
628  * - BATADV_DHCP_TO_SERVER if this is a message going to the DHCP server
629  * - BATADV_DHCP_TO_CLIENT if this is a message going to a DHCP client
630  */
631 enum batadv_dhcp_recipient
632 batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
633                              u8 *chaddr)
634 {
635         enum batadv_dhcp_recipient ret = BATADV_DHCP_NO;
636         struct ethhdr *ethhdr;
637         struct iphdr *iphdr;
638         struct ipv6hdr *ipv6hdr;
639         struct udphdr *udphdr;
640         struct vlan_ethhdr *vhdr;
641         int chaddr_offset;
642         __be16 proto;
643         u8 *p;
644 
645         /* check for ethernet header */
646         if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
647                 return BATADV_DHCP_NO;
648 
649         ethhdr = eth_hdr(skb);
650         proto = ethhdr->h_proto;
651         *header_len += ETH_HLEN;
652 
653         /* check for initial vlan header */
654         if (proto == htons(ETH_P_8021Q)) {
655                 if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
656                         return BATADV_DHCP_NO;
657 
658                 vhdr = vlan_eth_hdr(skb);
659                 proto = vhdr->h_vlan_encapsulated_proto;
660                 *header_len += VLAN_HLEN;
661         }
662 
663         /* check for ip header */
664         switch (proto) {
665         case htons(ETH_P_IP):
666                 if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
667                         return BATADV_DHCP_NO;
668 
669                 iphdr = (struct iphdr *)(skb->data + *header_len);
670                 *header_len += iphdr->ihl * 4;
671 
672                 /* check for udp header */
673                 if (iphdr->protocol != IPPROTO_UDP)
674                         return BATADV_DHCP_NO;
675 
676                 break;
677         case htons(ETH_P_IPV6):
678                 if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
679                         return BATADV_DHCP_NO;
680 
681                 ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
682                 *header_len += sizeof(*ipv6hdr);
683 
684                 /* check for udp header */
685                 if (ipv6hdr->nexthdr != IPPROTO_UDP)
686                         return BATADV_DHCP_NO;
687 
688                 break;
689         default:
690                 return BATADV_DHCP_NO;
691         }
692 
693         if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
694                 return BATADV_DHCP_NO;
695 
696         udphdr = (struct udphdr *)(skb->data + *header_len);
697         *header_len += sizeof(*udphdr);
698 
699         /* check for bootp port */
700         switch (proto) {
701         case htons(ETH_P_IP):
702                 if (udphdr->dest == htons(67))
703                         ret = BATADV_DHCP_TO_SERVER;
704                 else if (udphdr->source == htons(67))
705                         ret = BATADV_DHCP_TO_CLIENT;
706                 break;
707         case htons(ETH_P_IPV6):
708                 if (udphdr->dest == htons(547))
709                         ret = BATADV_DHCP_TO_SERVER;
710                 else if (udphdr->source == htons(547))
711                         ret = BATADV_DHCP_TO_CLIENT;
712                 break;
713         }
714 
715         chaddr_offset = *header_len + BATADV_DHCP_CHADDR_OFFSET;
716         /* store the client address if the message is going to a client */
717         if (ret == BATADV_DHCP_TO_CLIENT &&
718             pskb_may_pull(skb, chaddr_offset + ETH_ALEN)) {
719                 /* check if the DHCP packet carries an Ethernet DHCP */
720                 p = skb->data + *header_len + BATADV_DHCP_HTYPE_OFFSET;
721                 if (*p != BATADV_DHCP_HTYPE_ETHERNET)
722                         return BATADV_DHCP_NO;
723 
724                 /* check if the DHCP packet carries a valid Ethernet address */
725                 p = skb->data + *header_len + BATADV_DHCP_HLEN_OFFSET;
726                 if (*p != ETH_ALEN)
727                         return BATADV_DHCP_NO;
728 
729                 ether_addr_copy(chaddr, skb->data + chaddr_offset);
730         }
731 
732         return ret;
733 }
734 
735 /**
736  * batadv_gw_out_of_range() - check if the dhcp request destination is the best
737  *  gateway
738  * @bat_priv: the bat priv with all the soft interface information
739  * @skb: the outgoing packet
740  *
741  * Check if the skb is a DHCP request and if it is sent to the current best GW
742  * server. Due to topology changes it may be the case that the GW server
743  * previously selected is not the best one anymore.
744  *
745  * This call might reallocate skb data.
746  * Must be invoked only when the DHCP packet is going TO a DHCP SERVER.
747  *
748  * Return: true if the packet destination is unicast and it is not the best gw,
749  * false otherwise.
750  */
751 bool batadv_gw_out_of_range(struct batadv_priv *bat_priv,
752                             struct sk_buff *skb)
753 {
754         struct batadv_neigh_node *neigh_curr = NULL;
755         struct batadv_neigh_node *neigh_old = NULL;
756         struct batadv_orig_node *orig_dst_node = NULL;
757         struct batadv_gw_node *gw_node = NULL;
758         struct batadv_gw_node *curr_gw = NULL;
759         struct batadv_neigh_ifinfo *curr_ifinfo, *old_ifinfo;
760         struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
761         bool out_of_range = false;
762         u8 curr_tq_avg;
763         unsigned short vid;
764 
765         vid = batadv_get_vid(skb, 0);
766 
767         if (is_multicast_ether_addr(ethhdr->h_dest))
768                 goto out;
769 
770         orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
771                                                  ethhdr->h_dest, vid);
772         if (!orig_dst_node)
773                 goto out;
774 
775         gw_node = batadv_gw_node_get(bat_priv, orig_dst_node);
776         if (!gw_node)
777                 goto out;
778 
779         switch (atomic_read(&bat_priv->gw.mode)) {
780         case BATADV_GW_MODE_SERVER:
781                 /* If we are a GW then we are our best GW. We can artificially
782                  * set the tq towards ourself as the maximum value
783                  */
784                 curr_tq_avg = BATADV_TQ_MAX_VALUE;
785                 break;
786         case BATADV_GW_MODE_CLIENT:
787                 curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
788                 if (!curr_gw)
789                         goto out;
790 
791                 /* packet is going to our gateway */
792                 if (curr_gw->orig_node == orig_dst_node)
793                         goto out;
794 
795                 /* If the dhcp packet has been sent to a different gw,
796                  * we have to evaluate whether the old gw is still
797                  * reliable enough
798                  */
799                 neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
800                                                 NULL);
801                 if (!neigh_curr)
802                         goto out;
803 
804                 curr_ifinfo = batadv_neigh_ifinfo_get(neigh_curr,
805                                                       BATADV_IF_DEFAULT);
806                 if (!curr_ifinfo)
807                         goto out;
808 
809                 curr_tq_avg = curr_ifinfo->bat_iv.tq_avg;
810                 batadv_neigh_ifinfo_put(curr_ifinfo);
811 
812                 break;
813         case BATADV_GW_MODE_OFF:
814         default:
815                 goto out;
816         }
817 
818         neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
819         if (!neigh_old)
820                 goto out;
821 
822         old_ifinfo = batadv_neigh_ifinfo_get(neigh_old, BATADV_IF_DEFAULT);
823         if (!old_ifinfo)
824                 goto out;
825 
826         if ((curr_tq_avg - old_ifinfo->bat_iv.tq_avg) > BATADV_GW_THRESHOLD)
827                 out_of_range = true;
828         batadv_neigh_ifinfo_put(old_ifinfo);
829 
830 out:
831         if (orig_dst_node)
832                 batadv_orig_node_put(orig_dst_node);
833         if (curr_gw)
834                 batadv_gw_node_put(curr_gw);
835         if (gw_node)
836                 batadv_gw_node_put(gw_node);
837         if (neigh_old)
838                 batadv_neigh_node_put(neigh_old);
839         if (neigh_curr)
840                 batadv_neigh_node_put(neigh_curr);
841         return out_of_range;
842 }
843 

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