net/batman-adv/gateway_client.c

   1 /*
   2  * Copyright (C) 2009-2011 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 "routing.h"
  29 #include <linux/ip.h>
  30 #include <linux/ipv6.h>
  31 #include <linux/udp.h>
  32 #include <linux/if_vlan.h>
  33
  34 /* This is the offset of the options field in a dhcp packet starting at
  35  * the beginning of the dhcp header */
  36 #define DHCP_OPTIONS_OFFSET 240
  37 #define DHCP_REQUEST 3
  38
  39 static void gw_node_free_ref(struct gw_node *gw_node)
  40 {
  41         if (atomic_dec_and_test(&gw_node->refcount))
  42                 kfree_rcu(gw_node, rcu);
  43 }
  44
  45 static struct gw_node *gw_get_selected_gw_node(struct bat_priv *bat_priv)
  46 {
  47         struct gw_node *gw_node;
  48
  49         rcu_read_lock();
  50         gw_node = rcu_dereference(bat_priv->curr_gw);
  51         if (!gw_node)
  52                 goto out;
  53
  54         if (!atomic_inc_not_zero(&gw_node->refcount))
  55                 gw_node = NULL;
  56
  57 out:
  58         rcu_read_unlock();
  59         return gw_node;
  60 }
  61
  62 struct orig_node *gw_get_selected_orig(struct bat_priv *bat_priv)
  63 {
  64         struct gw_node *gw_node;
  65         struct orig_node *orig_node = NULL;
  66
  67         gw_node = gw_get_selected_gw_node(bat_priv);
  68         if (!gw_node)
  69                 goto out;
  70
  71         rcu_read_lock();
  72         orig_node = gw_node->orig_node;
  73         if (!orig_node)
  74                 goto unlock;
  75
  76         if (!atomic_inc_not_zero(&orig_node->refcount))
  77                 orig_node = NULL;
  78
  79 unlock:
  80         rcu_read_unlock();
  81 out:
  82         if (gw_node)
  83                 gw_node_free_ref(gw_node);
  84         return orig_node;
  85 }
  86
  87 static void gw_select(struct bat_priv *bat_priv, struct gw_node *new_gw_node)
  88 {
  89         struct gw_node *curr_gw_node;
  90
  91         spin_lock_bh(&bat_priv->gw_list_lock);
  92
  93         if (new_gw_node && !atomic_inc_not_zero(&new_gw_node->refcount))
  94                 new_gw_node = NULL;
  95
  96         curr_gw_node = rcu_dereference_protected(bat_priv->curr_gw, 1);
  97         rcu_assign_pointer(bat_priv->curr_gw, new_gw_node);
  98
  99         if (curr_gw_node)
 100                 gw_node_free_ref(curr_gw_node);
 101
 102         spin_unlock_bh(&bat_priv->gw_list_lock);
 103 }
 104
 105 void gw_deselect(struct bat_priv *bat_priv)
 106 {
 107         atomic_set(&bat_priv->gw_reselect, 1);
 108 }
 109
 110 static struct gw_node *gw_get_best_gw_node(struct bat_priv *bat_priv)
 111 {
 112         struct neigh_node *router;
 113         struct hlist_node *node;
 114         struct gw_node *gw_node, *curr_gw = NULL;
 115         uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
 116         uint8_t max_tq = 0;
 117         int down, up;
 118
 119         rcu_read_lock();
 120         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
 121                 if (gw_node->deleted)
 122                         continue;
 123
 124                 router = orig_node_get_router(gw_node->orig_node);
 125                 if (!router)
 126                         continue;
 127
 128                 if (!atomic_inc_not_zero(&gw_node->refcount))
 129                         goto next;
 130
 131                 switch (atomic_read(&bat_priv->gw_sel_class)) {
 132                 case 1: /* fast connection */
 133                         gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags,
 134                                              &down, &up);
 135
 136                         tmp_gw_factor = (router->tq_avg * router->tq_avg *
 137                                          down * 100 * 100) /
 138                                          (TQ_LOCAL_WINDOW_SIZE *
 139                                          TQ_LOCAL_WINDOW_SIZE * 64);
 140
 141                         if ((tmp_gw_factor > max_gw_factor) ||
 142                             ((tmp_gw_factor == max_gw_factor) &&
 143                              (router->tq_avg > max_tq))) {
 144                                 if (curr_gw)
 145                                         gw_node_free_ref(curr_gw);
 146                                 curr_gw = gw_node;
 147                                 atomic_inc(&curr_gw->refcount);
 148                         }
 149                         break;
 150
 151                 default: /**
 152                           * 2:  stable connection (use best statistic)
 153                           * 3:  fast-switch (use best statistic but change as
 154                           *     soon as a better gateway appears)
 155                           * XX: late-switch (use best statistic but change as
 156                           *     soon as a better gateway appears which has
 157                           *     $routing_class more tq points)
 158                           **/
 159                         if (router->tq_avg > max_tq) {
 160                                 if (curr_gw)
 161                                         gw_node_free_ref(curr_gw);
 162                                 curr_gw = gw_node;
 163                                 atomic_inc(&curr_gw->refcount);
 164                         }
 165                         break;
 166                 }
 167
 168                 if (router->tq_avg > max_tq)
 169                         max_tq = router->tq_avg;
 170
 171                 if (tmp_gw_factor > max_gw_factor)
 172                         max_gw_factor = tmp_gw_factor;
 173
 174                 gw_node_free_ref(gw_node);
 175
 176 next:
 177                 neigh_node_free_ref(router);
 178         }
 179         rcu_read_unlock();
 180
 181         return curr_gw;
 182 }
 183
 184 void gw_election(struct bat_priv *bat_priv)
 185 {
 186         struct gw_node *curr_gw = NULL, *next_gw = NULL;
 187         struct neigh_node *router = NULL;
 188         char gw_addr[18] = { '\0' };
 189
 190         /**
 191          * The batman daemon checks here if we already passed a full originator
 192          * cycle in order to make sure we don't choose the first gateway we
 193          * hear about. This check is based on the daemon's uptime which we
 194          * don't have.
 195          **/
 196         if (atomic_read(&bat_priv->gw_mode) != GW_MODE_CLIENT)
 197                 goto out;
 198
 199         if (!atomic_dec_not_zero(&bat_priv->gw_reselect))
 200                 goto out;
 201
 202         curr_gw = gw_get_selected_gw_node(bat_priv);
 203
 204         next_gw = gw_get_best_gw_node(bat_priv);
 205
 206         if (curr_gw == next_gw)
 207                 goto out;
 208
 209         if (next_gw) {
 210                 sprintf(gw_addr, "%pM", next_gw->orig_node->orig);
 211
 212                 router = orig_node_get_router(next_gw->orig_node);
 213                 if (!router) {
 214                         gw_deselect(bat_priv);
 215                         goto out;
 216                 }
 217         }
 218
 219         if ((curr_gw) && (!next_gw)) {
 220                 bat_dbg(DBG_BATMAN, bat_priv,
 221                         "Removing selected gateway - no gateway in range\n");
 222                 throw_uevent(bat_priv, UEV_GW, UEV_DEL, NULL);
 223         } else if ((!curr_gw) && (next_gw)) {
 224                 bat_dbg(DBG_BATMAN, bat_priv,
 225                         "Adding route to gateway %pM (gw_flags: %i, tq: %i)\n",
 226                         next_gw->orig_node->orig,
 227                         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 "
 233                         "(gw_flags: %i, tq: %i)\n",
 234                         next_gw->orig_node->orig,
 235                         next_gw->orig_node->gw_flags,
 236                         router->tq_avg);
 237                 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                 neigh_node_free_ref(router);
 249 }
 250
 251 void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
 252 {
 253         struct orig_node *curr_gw_orig;
 254         struct neigh_node *router_gw = NULL, *router_orig = NULL;
 255         uint8_t gw_tq_avg, orig_tq_avg;
 256
 257         curr_gw_orig = gw_get_selected_orig(bat_priv);
 258         if (!curr_gw_orig)
 259                 goto deselect;
 260
 261         router_gw = orig_node_get_router(curr_gw_orig);
 262         if (!router_gw)
 263                 goto deselect;
 264
 265         /* this node already is the gateway */
 266         if (curr_gw_orig == orig_node)
 267                 goto out;
 268
 269         router_orig = orig_node_get_router(orig_node);
 270         if (!router_orig)
 271                 goto out;
 272
 273         gw_tq_avg = router_gw->tq_avg;
 274         orig_tq_avg = router_orig->tq_avg;
 275
 276         /* the TQ value has to be better */
 277         if (orig_tq_avg < gw_tq_avg)
 278                 goto out;
 279
 280         /**
 281          * if the routing class is greater than 3 the value tells us how much
 282          * greater the TQ value of the new gateway must be
 283          **/
 284         if ((atomic_read(&bat_priv->gw_sel_class) > 3) &&
 285             (orig_tq_avg - gw_tq_avg < atomic_read(&bat_priv->gw_sel_class)))
 286                 goto out;
 287
 288         bat_dbg(DBG_BATMAN, bat_priv,
 289                 "Restarting gateway selection: better gateway found (tq curr: "
 290                 "%i, tq new: %i)\n",
 291                 gw_tq_avg, orig_tq_avg);
 292
 293 deselect:
 294         gw_deselect(bat_priv);
 295 out:
 296         if (curr_gw_orig)
 297                 orig_node_free_ref(curr_gw_orig);
 298         if (router_gw)
 299                 neigh_node_free_ref(router_gw);
 300         if (router_orig)
 301                 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         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 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 "
 355                         "%i to %i\n",
 356                         orig_node->orig, gw_node->orig_node->gw_flags,
 357                         new_gwflags);
 358
 359                 gw_node->deleted = 0;
 360
 361                 if (new_gwflags == NO_FLAGS) {
 362                         gw_node->deleted = jiffies;
 363                         bat_dbg(DBG_BATMAN, bat_priv,
 364                                 "Gateway %pM removed from gateway list\n",
 365                                 orig_node->orig);
 366
 367                         if (gw_node == curr_gw)
 368                                 goto deselect;
 369                 }
 370
 371                 goto unlock;
 372         }
 373
 374         if (new_gwflags == NO_FLAGS)
 375                 goto unlock;
 376
 377         gw_node_add(bat_priv, orig_node, new_gwflags);
 378         goto unlock;
 379
 380 deselect:
 381         gw_deselect(bat_priv);
 382 unlock:
 383         rcu_read_unlock();
 384
 385         if (curr_gw)
 386                 gw_node_free_ref(curr_gw);
 387 }
 388
 389 void gw_node_delete(struct bat_priv *bat_priv, struct orig_node *orig_node)
 390 {
 391         gw_node_update(bat_priv, orig_node, 0);
 392 }
 393
 394 void 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 = 2 * PURGE_TIMEOUT * HZ;
 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                 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         gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags, &down, &up);
 440
 441         router = 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         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 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, "BATMAN mesh %s disabled - please "
 477                                  "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, "BATMAN mesh %s disabled - "
 484                                  "primary interface not active\n",
 485                                  net_dev->name);
 486                 goto out;
 487         }
 488
 489         seq_printf(seq, "      %-12s (%s/%i) %17s [%10s]: gw_class ... "
 490                    "[B.A.T.M.A.N. adv %s, MainIF/MAC: %s/%pM (%s)]\n",
 491                    "Gateway", "#", TQ_MAX_VALUE, "Nexthop",
 492                    "outgoingIF", 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 < *p)
 566                                 goto out;
 567                         pkt_len -= *p;
 568                         p += (*p);
 569                 }
 570         }
 571 out:
 572         return ret;
 573 }
 574
 575 int gw_is_target(struct bat_priv *bat_priv, struct sk_buff *skb,
 576                  struct orig_node *old_gw)
 577 {
 578         struct ethhdr *ethhdr;
 579         struct iphdr *iphdr;
 580         struct ipv6hdr *ipv6hdr;
 581         struct udphdr *udphdr;
 582         struct gw_node *curr_gw;
 583         struct neigh_node *neigh_curr = NULL, *neigh_old = NULL;
 584         unsigned int header_len = 0;
 585         int ret = 1;
 586
 587         if (atomic_read(&bat_priv->gw_mode) == GW_MODE_OFF)
 588                 return 0;
 589
 590         /* check for ethernet header */
 591         if (!pskb_may_pull(skb, header_len + ETH_HLEN))
 592                 return 0;
 593         ethhdr = (struct ethhdr *)skb->data;
 594         header_len += ETH_HLEN;
 595
 596         /* check for initial vlan header */
 597         if (ntohs(ethhdr->h_proto) == ETH_P_8021Q) {
 598                 if (!pskb_may_pull(skb, header_len + VLAN_HLEN))
 599                         return 0;
 600                 ethhdr = (struct ethhdr *)(skb->data + VLAN_HLEN);
 601                 header_len += VLAN_HLEN;
 602         }
 603
 604         /* check for ip header */
 605         switch (ntohs(ethhdr->h_proto)) {
 606         case ETH_P_IP:
 607                 if (!pskb_may_pull(skb, header_len + sizeof(*iphdr)))
 608                         return 0;
 609                 iphdr = (struct iphdr *)(skb->data + header_len);
 610                 header_len += iphdr->ihl * 4;
 611
 612                 /* check for udp header */
 613                 if (iphdr->protocol != IPPROTO_UDP)
 614                         return 0;
 615
 616                 break;
 617         case ETH_P_IPV6:
 618                 if (!pskb_may_pull(skb, header_len + sizeof(*ipv6hdr)))
 619                         return 0;
 620                 ipv6hdr = (struct ipv6hdr *)(skb->data + header_len);
 621                 header_len += sizeof(*ipv6hdr);
 622
 623                 /* check for udp header */
 624                 if (ipv6hdr->nexthdr != IPPROTO_UDP)
 625                         return 0;
 626
 627                 break;
 628         default:
 629                 return 0;
 630         }
 631
 632         if (!pskb_may_pull(skb, header_len + sizeof(*udphdr)))
 633                 return 0;
 634         udphdr = (struct udphdr *)(skb->data + header_len);
 635         header_len += sizeof(*udphdr);
 636
 637         /* check for bootp port */
 638         if ((ntohs(ethhdr->h_proto) == ETH_P_IP) &&
 639              (ntohs(udphdr->dest) != 67))
 640                 return 0;
 641
 642         if ((ntohs(ethhdr->h_proto) == ETH_P_IPV6) &&
 643             (ntohs(udphdr->dest) != 547))
 644                 return 0;
 645
 646         if (atomic_read(&bat_priv->gw_mode) == GW_MODE_SERVER)
 647                 return -1;
 648
 649         curr_gw = gw_get_selected_gw_node(bat_priv);
 650         if (!curr_gw)
 651                 return 0;
 652
 653         /* If old_gw != NULL then this packet is unicast.
 654          * So, at this point we have to check the message type: if it is a
 655          * DHCPREQUEST we have to decide whether to drop it or not */
 656         if (old_gw && curr_gw->orig_node != old_gw) {
 657                 if (is_type_dhcprequest(skb, header_len)) {
 658                         /* If the dhcp packet has been sent to a different gw,
 659                          * we have to evaluate whether the old gw is still
 660                          * reliable enough */
 661                         neigh_curr = find_router(bat_priv, curr_gw->orig_node,
 662                                                  NULL);
 663                         neigh_old = find_router(bat_priv, old_gw, NULL);
 664                         if (!neigh_curr || !neigh_old)
 665                                 goto free_neigh;
 666                         if (neigh_curr->tq_avg - neigh_old->tq_avg <
 667                                                                 GW_THRESHOLD)
 668                                 ret = -1;
 669                 }
 670         }
 671 free_neigh:
 672         if (neigh_old)
 673                 neigh_node_free_ref(neigh_old);
 674         if (neigh_curr)
 675                 neigh_node_free_ref(neigh_curr);
 676         if (curr_gw)
 677                 gw_node_free_ref(curr_gw);
 678         return ret;
 679 }