net/batman-adv/gateway_client.c

   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
  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
  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
  63 struct orig_node *batadv_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
  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
 106 void batadv_gw_deselect(struct bat_priv *bat_priv)
 107 {
 108         atomic_set(&bat_priv->gw_reselect, 1);
 109 }
 110
 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         struct orig_node *orig_node;
 120
 121         rcu_read_lock();
 122         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
 123                 if (gw_node->deleted)
 124                         continue;
 125
 126                 orig_node = gw_node->orig_node;
 127                 router = batadv_orig_node_get_router(orig_node);
 128                 if (!router)
 129                         continue;
 130
 131                 if (!atomic_inc_not_zero(&gw_node->refcount))
 132                         goto next;
 133
 134                 switch (atomic_read(&bat_priv->gw_sel_class)) {
 135                 case 1: /* fast connection */
 136                         batadv_gw_bandwidth_to_kbit(orig_node->gw_flags,
 137                                                     &down, &up);
 138
 139                         tmp_gw_factor = (router->tq_avg * router->tq_avg *
 140                                          down * 100 * 100) /
 141                                          (TQ_LOCAL_WINDOW_SIZE *
 142                                          TQ_LOCAL_WINDOW_SIZE * 64);
 143
 144                         if ((tmp_gw_factor > max_gw_factor) ||
 145                             ((tmp_gw_factor == max_gw_factor) &&
 146                              (router->tq_avg > max_tq))) {
 147                                 if (curr_gw)
 148                                         gw_node_free_ref(curr_gw);
 149                                 curr_gw = gw_node;
 150                                 atomic_inc(&curr_gw->refcount);
 151                         }
 152                         break;
 153
 154                 default: /**
 155                           * 2:  stable connection (use best statistic)
 156                           * 3:  fast-switch (use best statistic but change as
 157                           *     soon as a better gateway appears)
 158                           * XX: late-switch (use best statistic but change as
 159                           *     soon as a better gateway appears which has
 160                           *     $routing_class more tq points)
 161                           **/
 162                         if (router->tq_avg > max_tq) {
 163                                 if (curr_gw)
 164                                         gw_node_free_ref(curr_gw);
 165                                 curr_gw = gw_node;
 166                                 atomic_inc(&curr_gw->refcount);
 167                         }
 168                         break;
 169                 }
 170
 171                 if (router->tq_avg > max_tq)
 172                         max_tq = router->tq_avg;
 173
 174                 if (tmp_gw_factor > max_gw_factor)
 175                         max_gw_factor = tmp_gw_factor;
 176
 177                 gw_node_free_ref(gw_node);
 178
 179 next:
 180                 batadv_neigh_node_free_ref(router);
 181         }
 182         rcu_read_unlock();
 183
 184         return curr_gw;
 185 }
 186
 187 void batadv_gw_election(struct bat_priv *bat_priv)
 188 {
 189         struct gw_node *curr_gw = NULL, *next_gw = NULL;
 190         struct neigh_node *router = NULL;
 191         char gw_addr[18] = { '\0' };
 192
 193         /**
 194          * The batman daemon checks here if we already passed a full originator
 195          * cycle in order to make sure we don't choose the first gateway we
 196          * hear about. This check is based on the daemon's uptime which we
 197          * don't have.
 198          **/
 199         if (atomic_read(&bat_priv->gw_mode) != GW_MODE_CLIENT)
 200                 goto out;
 201
 202         if (!atomic_dec_not_zero(&bat_priv->gw_reselect))
 203                 goto out;
 204
 205         curr_gw = gw_get_selected_gw_node(bat_priv);
 206
 207         next_gw = gw_get_best_gw_node(bat_priv);
 208
 209         if (curr_gw == next_gw)
 210                 goto out;
 211
 212         if (next_gw) {
 213                 sprintf(gw_addr, "%pM", next_gw->orig_node->orig);
 214
 215                 router = batadv_orig_node_get_router(next_gw->orig_node);
 216                 if (!router) {
 217                         batadv_gw_deselect(bat_priv);
 218                         goto out;
 219                 }
 220         }
 221
 222         if ((curr_gw) && (!next_gw)) {
 223                 bat_dbg(DBG_BATMAN, bat_priv,
 224                         "Removing selected gateway - no gateway in range\n");
 225                 batadv_throw_uevent(bat_priv, UEV_GW, UEV_DEL, NULL);
 226         } else if ((!curr_gw) && (next_gw)) {
 227                 bat_dbg(DBG_BATMAN, bat_priv,
 228                         "Adding route to gateway %pM (gw_flags: %i, tq: %i)\n",
 229                         next_gw->orig_node->orig, next_gw->orig_node->gw_flags,
 230                         router->tq_avg);
 231                 batadv_throw_uevent(bat_priv, UEV_GW, UEV_ADD, gw_addr);
 232         } else {
 233                 bat_dbg(DBG_BATMAN, bat_priv,
 234                         "Changing route to gateway %pM (gw_flags: %i, tq: %i)\n",
 235                         next_gw->orig_node->orig, next_gw->orig_node->gw_flags,
 236                         router->tq_avg);
 237                 batadv_throw_uevent(bat_priv, UEV_GW, UEV_CHANGE, gw_addr);
 238         }
 239
 240         gw_select(bat_priv, next_gw);
 241
 242 out:
 243         if (curr_gw)
 244                 gw_node_free_ref(curr_gw);
 245         if (next_gw)
 246                 gw_node_free_ref(next_gw);
 247         if (router)
 248                 batadv_neigh_node_free_ref(router);
 249 }
 250
 251 void batadv_gw_check_election(struct bat_priv *bat_priv,
 252                               struct orig_node *orig_node)
 253 {
 254         struct orig_node *curr_gw_orig;
 255         struct neigh_node *router_gw = NULL, *router_orig = NULL;
 256         uint8_t gw_tq_avg, orig_tq_avg;
 257
 258         curr_gw_orig = batadv_gw_get_selected_orig(bat_priv);
 259         if (!curr_gw_orig)
 260                 goto deselect;
 261
 262         router_gw = batadv_orig_node_get_router(curr_gw_orig);
 263         if (!router_gw)
 264                 goto deselect;
 265
 266         /* this node already is the gateway */
 267         if (curr_gw_orig == orig_node)
 268                 goto out;
 269
 270         router_orig = batadv_orig_node_get_router(orig_node);
 271         if (!router_orig)
 272                 goto out;
 273
 274         gw_tq_avg = router_gw->tq_avg;
 275         orig_tq_avg = router_orig->tq_avg;
 276
 277         /* the TQ value has to be better */
 278         if (orig_tq_avg < gw_tq_avg)
 279                 goto out;
 280
 281         /**
 282          * if the routing class is greater than 3 the value tells us how much
 283          * greater the TQ value of the new gateway must be
 284          **/
 285         if ((atomic_read(&bat_priv->gw_sel_class) > 3) &&
 286             (orig_tq_avg - gw_tq_avg < atomic_read(&bat_priv->gw_sel_class)))
 287                 goto out;
 288
 289         bat_dbg(DBG_BATMAN, bat_priv,
 290                 "Restarting gateway selection: better gateway found (tq curr: %i, tq new: %i)\n",
 291                 gw_tq_avg, orig_tq_avg);
 292
 293 deselect:
 294         batadv_gw_deselect(bat_priv);
 295 out:
 296         if (curr_gw_orig)
 297                 batadv_orig_node_free_ref(curr_gw_orig);
 298         if (router_gw)
 299                 batadv_neigh_node_free_ref(router_gw);
 300         if (router_orig)
 301                 batadv_neigh_node_free_ref(router_orig);
 302
 303         return;
 304 }
 305
 306 static void gw_node_add(struct bat_priv *bat_priv,
 307                         struct orig_node *orig_node, uint8_t new_gwflags)
 308 {
 309         struct gw_node *gw_node;
 310         int down, up;
 311
 312         gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
 313         if (!gw_node)
 314                 return;
 315
 316         INIT_HLIST_NODE(&gw_node->list);
 317         gw_node->orig_node = orig_node;
 318         atomic_set(&gw_node->refcount, 1);
 319
 320         spin_lock_bh(&bat_priv->gw_list_lock);
 321         hlist_add_head_rcu(&gw_node->list, &bat_priv->gw_list);
 322         spin_unlock_bh(&bat_priv->gw_list_lock);
 323
 324         batadv_gw_bandwidth_to_kbit(new_gwflags, &down, &up);
 325         bat_dbg(DBG_BATMAN, bat_priv,
 326                 "Found new gateway %pM -> gw_class: %i - %i%s/%i%s\n",
 327                 orig_node->orig, new_gwflags,
 328                 (down > 2048 ? down / 1024 : down),
 329                 (down > 2048 ? "MBit" : "KBit"),
 330                 (up > 2048 ? up / 1024 : up),
 331                 (up > 2048 ? "MBit" : "KBit"));
 332 }
 333
 334 void batadv_gw_node_update(struct bat_priv *bat_priv,
 335                            struct orig_node *orig_node, uint8_t new_gwflags)
 336 {
 337         struct hlist_node *node;
 338         struct gw_node *gw_node, *curr_gw;
 339
 340         /**
 341          * Note: We don't need a NULL check here, since curr_gw never gets
 342          * dereferenced. If curr_gw is NULL we also should not exit as we may
 343          * have this gateway in our list (duplication check!) even though we
 344          * have no currently selected gateway.
 345          */
 346         curr_gw = gw_get_selected_gw_node(bat_priv);
 347
 348         rcu_read_lock();
 349         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
 350                 if (gw_node->orig_node != orig_node)
 351                         continue;
 352
 353                 bat_dbg(DBG_BATMAN, bat_priv,
 354                         "Gateway class of originator %pM changed from %i to %i\n",
 355                         orig_node->orig, gw_node->orig_node->gw_flags,
 356                         new_gwflags);
 357
 358                 gw_node->deleted = 0;
 359
 360                 if (new_gwflags == NO_FLAGS) {
 361                         gw_node->deleted = jiffies;
 362                         bat_dbg(DBG_BATMAN, bat_priv,
 363                                 "Gateway %pM removed from gateway list\n",
 364                                 orig_node->orig);
 365
 366                         if (gw_node == curr_gw)
 367                                 goto deselect;
 368                 }
 369
 370                 goto unlock;
 371         }
 372
 373         if (new_gwflags == NO_FLAGS)
 374                 goto unlock;
 375
 376         gw_node_add(bat_priv, orig_node, new_gwflags);
 377         goto unlock;
 378
 379 deselect:
 380         batadv_gw_deselect(bat_priv);
 381 unlock:
 382         rcu_read_unlock();
 383
 384         if (curr_gw)
 385                 gw_node_free_ref(curr_gw);
 386 }
 387
 388 void batadv_gw_node_delete(struct bat_priv *bat_priv,
 389                            struct orig_node *orig_node)
 390 {
 391         batadv_gw_node_update(bat_priv, orig_node, 0);
 392 }
 393
 394 void batadv_gw_node_purge(struct bat_priv *bat_priv)
 395 {
 396         struct gw_node *gw_node, *curr_gw;
 397         struct hlist_node *node, *node_tmp;
 398         unsigned long timeout = msecs_to_jiffies(2 * PURGE_TIMEOUT);
 399         int do_deselect = 0;
 400
 401         curr_gw = gw_get_selected_gw_node(bat_priv);
 402
 403         spin_lock_bh(&bat_priv->gw_list_lock);
 404
 405         hlist_for_each_entry_safe(gw_node, node, node_tmp,
 406                                   &bat_priv->gw_list, list) {
 407                 if (((!gw_node->deleted) ||
 408                      (time_before(jiffies, gw_node->deleted + timeout))) &&
 409                     atomic_read(&bat_priv->mesh_state) == MESH_ACTIVE)
 410                         continue;
 411
 412                 if (curr_gw == gw_node)
 413                         do_deselect = 1;
 414
 415                 hlist_del_rcu(&gw_node->list);
 416                 gw_node_free_ref(gw_node);
 417         }
 418
 419         spin_unlock_bh(&bat_priv->gw_list_lock);
 420
 421         /* gw_deselect() needs to acquire the gw_list_lock */
 422         if (do_deselect)
 423                 batadv_gw_deselect(bat_priv);
 424
 425         if (curr_gw)
 426                 gw_node_free_ref(curr_gw);
 427 }
 428
 429 /**
 430  * fails if orig_node has no router
 431  */
 432 static int _write_buffer_text(struct bat_priv *bat_priv, struct seq_file *seq,
 433                               const struct gw_node *gw_node)
 434 {
 435         struct gw_node *curr_gw;
 436         struct neigh_node *router;
 437         int down, up, ret = -1;
 438
 439         batadv_gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags, &down, &up);
 440
 441         router = batadv_orig_node_get_router(gw_node->orig_node);
 442         if (!router)
 443                 goto out;
 444
 445         curr_gw = gw_get_selected_gw_node(bat_priv);
 446
 447         ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %3i - %i%s/%i%s\n",
 448                          (curr_gw == gw_node ? "=>" : "  "),
 449                          gw_node->orig_node->orig,
 450                          router->tq_avg, router->addr,
 451                          router->if_incoming->net_dev->name,
 452                          gw_node->orig_node->gw_flags,
 453                          (down > 2048 ? down / 1024 : down),
 454                          (down > 2048 ? "MBit" : "KBit"),
 455                          (up > 2048 ? up / 1024 : up),
 456                          (up > 2048 ? "MBit" : "KBit"));
 457
 458         batadv_neigh_node_free_ref(router);
 459         if (curr_gw)
 460                 gw_node_free_ref(curr_gw);
 461 out:
 462         return ret;
 463 }
 464
 465 int batadv_gw_client_seq_print_text(struct seq_file *seq, void *offset)
 466 {
 467         struct net_device *net_dev = (struct net_device *)seq->private;
 468         struct bat_priv *bat_priv = netdev_priv(net_dev);
 469         struct hard_iface *primary_if;
 470         struct gw_node *gw_node;
 471         struct hlist_node *node;
 472         int gw_count = 0, ret = 0;
 473
 474         primary_if = primary_if_get_selected(bat_priv);
 475         if (!primary_if) {
 476                 ret = seq_printf(seq,
 477                                  "BATMAN mesh %s disabled - please specify interfaces to enable it\n",
 478                                  net_dev->name);
 479                 goto out;
 480         }
 481
 482         if (primary_if->if_status != IF_ACTIVE) {
 483                 ret = seq_printf(seq,
 484                                  "BATMAN mesh %s disabled - primary interface not active\n",
 485                                  net_dev->name);
 486                 goto out;
 487         }
 488
 489         seq_printf(seq,
 490                    "      %-12s (%s/%i) %17s [%10s]: gw_class ... [B.A.T.M.A.N. adv %s, MainIF/MAC: %s/%pM (%s)]\n",
 491                    "Gateway", "#", TQ_MAX_VALUE, "Nexthop", "outgoingIF",
 492                    SOURCE_VERSION, primary_if->net_dev->name,
 493                    primary_if->net_dev->dev_addr, net_dev->name);
 494
 495         rcu_read_lock();
 496         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
 497                 if (gw_node->deleted)
 498                         continue;
 499
 500                 /* fails if orig_node has no router */
 501                 if (_write_buffer_text(bat_priv, seq, gw_node) < 0)
 502                         continue;
 503
 504                 gw_count++;
 505         }
 506         rcu_read_unlock();
 507
 508         if (gw_count == 0)
 509                 seq_printf(seq, "No gateways in range ...\n");
 510
 511 out:
 512         if (primary_if)
 513                 hardif_free_ref(primary_if);
 514         return ret;
 515 }
 516
 517 static bool is_type_dhcprequest(struct sk_buff *skb, int header_len)
 518 {
 519         int ret = false;
 520         unsigned char *p;
 521         int pkt_len;
 522
 523         if (skb_linearize(skb) < 0)
 524                 goto out;
 525
 526         pkt_len = skb_headlen(skb);
 527
 528         if (pkt_len < header_len + DHCP_OPTIONS_OFFSET + 1)
 529                 goto out;
 530
 531         p = skb->data + header_len + DHCP_OPTIONS_OFFSET;
 532         pkt_len -= header_len + DHCP_OPTIONS_OFFSET + 1;
 533
 534         /* Access the dhcp option lists. Each entry is made up by:
 535          * - octet 1: option type
 536          * - octet 2: option data len (only if type != 255 and 0)
 537          * - octet 3: option data */
 538         while (*p != 255 && !ret) {
 539                 /* p now points to the first octet: option type */
 540                 if (*p == 53) {
 541                         /* type 53 is the message type option.
 542                          * Jump the len octet and go to the data octet */
 543                         if (pkt_len < 2)
 544                                 goto out;
 545                         p += 2;
 546
 547                         /* check if the message type is what we need */
 548                         if (*p == DHCP_REQUEST)
 549                                 ret = true;
 550                         break;
 551                 } else if (*p == 0) {
 552                         /* option type 0 (padding), just go forward */
 553                         if (pkt_len < 1)
 554                                 goto out;
 555                         pkt_len--;
 556                         p++;
 557                 } else {
 558                         /* This is any other option. So we get the length... */
 559                         if (pkt_len < 1)
 560                                 goto out;
 561                         pkt_len--;
 562                         p++;
 563
 564                         /* ...and then we jump over the data */
 565                         if (pkt_len < 1 + (*p))
 566                                 goto out;
 567                         pkt_len -= 1 + (*p);
 568                         p += 1 + (*p);
 569                 }
 570         }
 571 out:
 572         return ret;
 573 }
 574
 575 bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len)
 576 {
 577         struct ethhdr *ethhdr;
 578         struct iphdr *iphdr;
 579         struct ipv6hdr *ipv6hdr;
 580         struct udphdr *udphdr;
 581
 582         /* check for ethernet header */
 583         if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
 584                 return false;
 585         ethhdr = (struct ethhdr *)skb->data;
 586         *header_len += ETH_HLEN;
 587
 588         /* check for initial vlan header */
 589         if (ntohs(ethhdr->h_proto) == ETH_P_8021Q) {
 590                 if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
 591                         return false;
 592                 ethhdr = (struct ethhdr *)(skb->data + VLAN_HLEN);
 593                 *header_len += VLAN_HLEN;
 594         }
 595
 596         /* check for ip header */
 597         switch (ntohs(ethhdr->h_proto)) {
 598         case ETH_P_IP:
 599                 if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
 600                         return false;
 601                 iphdr = (struct iphdr *)(skb->data + *header_len);
 602                 *header_len += iphdr->ihl * 4;
 603
 604                 /* check for udp header */
 605                 if (iphdr->protocol != IPPROTO_UDP)
 606                         return false;
 607
 608                 break;
 609         case ETH_P_IPV6:
 610                 if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
 611                         return false;
 612                 ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
 613                 *header_len += sizeof(*ipv6hdr);
 614
 615                 /* check for udp header */
 616                 if (ipv6hdr->nexthdr != IPPROTO_UDP)
 617                         return false;
 618
 619                 break;
 620         default:
 621                 return false;
 622         }
 623
 624         if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
 625                 return false;
 626         udphdr = (struct udphdr *)(skb->data + *header_len);
 627         *header_len += sizeof(*udphdr);
 628
 629         /* check for bootp port */
 630         if ((ntohs(ethhdr->h_proto) == ETH_P_IP) &&
 631             (ntohs(udphdr->dest) != 67))
 632                 return false;
 633
 634         if ((ntohs(ethhdr->h_proto) == ETH_P_IPV6) &&
 635             (ntohs(udphdr->dest) != 547))
 636                 return false;
 637
 638         return true;
 639 }
 640
 641 bool batadv_gw_out_of_range(struct bat_priv *bat_priv,
 642                             struct sk_buff *skb, struct ethhdr *ethhdr)
 643 {
 644         struct neigh_node *neigh_curr = NULL, *neigh_old = NULL;
 645         struct orig_node *orig_dst_node = NULL;
 646         struct gw_node *curr_gw = NULL;
 647         bool ret, out_of_range = false;
 648         unsigned int header_len = 0;
 649         uint8_t curr_tq_avg;
 650
 651         ret = batadv_gw_is_dhcp_target(skb, &header_len);
 652         if (!ret)
 653                 goto out;
 654
 655         orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
 656                                                  ethhdr->h_dest);
 657         if (!orig_dst_node)
 658                 goto out;
 659
 660         if (!orig_dst_node->gw_flags)
 661                 goto out;
 662
 663         ret = is_type_dhcprequest(skb, header_len);
 664         if (!ret)
 665                 goto out;
 666
 667         switch (atomic_read(&bat_priv->gw_mode)) {
 668         case GW_MODE_SERVER:
 669                 /* If we are a GW then we are our best GW. We can artificially
 670                  * set the tq towards ourself as the maximum value */
 671                 curr_tq_avg = TQ_MAX_VALUE;
 672                 break;
 673         case GW_MODE_CLIENT:
 674                 curr_gw = gw_get_selected_gw_node(bat_priv);
 675                 if (!curr_gw)
 676                         goto out;
 677
 678                 /* packet is going to our gateway */
 679                 if (curr_gw->orig_node == orig_dst_node)
 680                         goto out;
 681
 682                 /* If the dhcp packet has been sent to a different gw,
 683                  * we have to evaluate whether the old gw is still
 684                  * reliable enough */
 685                 neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
 686                                                 NULL);
 687                 if (!neigh_curr)
 688                         goto out;
 689
 690                 curr_tq_avg = neigh_curr->tq_avg;
 691                 break;
 692         case GW_MODE_OFF:
 693         default:
 694                 goto out;
 695         }
 696
 697         neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
 698         if (!neigh_old)
 699                 goto out;
 700
 701         if (curr_tq_avg - neigh_old->tq_avg > GW_THRESHOLD)
 702                 out_of_range = true;
 703
 704 out:
 705         if (orig_dst_node)
 706                 batadv_orig_node_free_ref(orig_dst_node);
 707         if (curr_gw)
 708                 gw_node_free_ref(curr_gw);
 709         if (neigh_old)
 710                 batadv_neigh_node_free_ref(neigh_old);
 711         if (neigh_curr)
 712                 batadv_neigh_node_free_ref(neigh_curr);
 713         return out_of_range;
 714 }