net/batman-adv/gateway_client.c

   1 /* Copyright (C) 2009-2012 B.A.T.M.A.N. contributors:
   2  *
   3  * Marek Lindner
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 2 of the GNU General Public
   7  * License as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA
  18  */
  19
  20 #include "main.h"
  21 #include "bat_sysfs.h"
  22 #include "gateway_client.h"
  23 #include "gateway_common.h"
  24 #include "hard-interface.h"
  25 #include "originator.h"
  26 #include "translation-table.h"
  27 #include "routing.h"
  28 #include <linux/ip.h>
  29 #include <linux/ipv6.h>
  30 #include <linux/udp.h>
  31 #include <linux/if_vlan.h>
  32
  33 /* This is the offset of the options field in a dhcp packet starting at
  34  * the beginning of the dhcp header
  35  */
  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 *batadv_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 batadv_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         struct orig_node *orig_node;
 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                 orig_node = gw_node->orig_node;
 126                 router = batadv_orig_node_get_router(orig_node);
 127                 if (!router)
 128                         continue;
 129
 130                 if (!atomic_inc_not_zero(&gw_node->refcount))
 131                         goto next;
 132
 133                 switch (atomic_read(&bat_priv->gw_sel_class)) {
 134                 case 1: /* fast connection */
 135                         batadv_gw_bandwidth_to_kbit(orig_node->gw_flags,
 136                                                     &down, &up);
 137
 138                         tmp_gw_factor = (router->tq_avg * router->tq_avg *
 139                                          down * 100 * 100) /
 140                                          (TQ_LOCAL_WINDOW_SIZE *
 141                                          TQ_LOCAL_WINDOW_SIZE * 64);
 142
 143                         if ((tmp_gw_factor > max_gw_factor) ||
 144                             ((tmp_gw_factor == max_gw_factor) &&
 145                              (router->tq_avg > max_tq))) {
 146                                 if (curr_gw)
 147                                         gw_node_free_ref(curr_gw);
 148                                 curr_gw = gw_node;
 149                                 atomic_inc(&curr_gw->refcount);
 150                         }
 151                         break;
 152
 153                 default: /* 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                 batadv_neigh_node_free_ref(router);
 179         }
 180         rcu_read_unlock();
 181
 182         return curr_gw;
 183 }
 184
 185 void batadv_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         /* 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 = batadv_orig_node_get_router(next_gw->orig_node);
 213                 if (!router) {
 214                         batadv_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                 batadv_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, next_gw->orig_node->gw_flags,
 227                         router->tq_avg);
 228                 batadv_throw_uevent(bat_priv, UEV_GW, UEV_ADD, gw_addr);
 229         } else {
 230                 bat_dbg(DBG_BATMAN, bat_priv,
 231                         "Changing route to gateway %pM (gw_flags: %i, tq: %i)\n",
 232                         next_gw->orig_node->orig, next_gw->orig_node->gw_flags,
 233                         router->tq_avg);
 234                 batadv_throw_uevent(bat_priv, UEV_GW, UEV_CHANGE, gw_addr);
 235         }
 236
 237         gw_select(bat_priv, next_gw);
 238
 239 out:
 240         if (curr_gw)
 241                 gw_node_free_ref(curr_gw);
 242         if (next_gw)
 243                 gw_node_free_ref(next_gw);
 244         if (router)
 245                 batadv_neigh_node_free_ref(router);
 246 }
 247
 248 void batadv_gw_check_election(struct bat_priv *bat_priv,
 249                               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 = batadv_gw_get_selected_orig(bat_priv);
 256         if (!curr_gw_orig)
 257                 goto deselect;
 258
 259         router_gw = batadv_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 = batadv_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         /* if the routing class is greater than 3 the value tells us how much
 279          * greater the TQ value of the new gateway must be
 280          */
 281         if ((atomic_read(&bat_priv->gw_sel_class) > 3) &&
 282             (orig_tq_avg - gw_tq_avg < atomic_read(&bat_priv->gw_sel_class)))
 283                 goto out;
 284
 285         bat_dbg(DBG_BATMAN, bat_priv,
 286                 "Restarting gateway selection: better gateway found (tq curr: %i, tq new: %i)\n",
 287                 gw_tq_avg, orig_tq_avg);
 288
 289 deselect:
 290         batadv_gw_deselect(bat_priv);
 291 out:
 292         if (curr_gw_orig)
 293                 batadv_orig_node_free_ref(curr_gw_orig);
 294         if (router_gw)
 295                 batadv_neigh_node_free_ref(router_gw);
 296         if (router_orig)
 297                 batadv_neigh_node_free_ref(router_orig);
 298
 299         return;
 300 }
 301
 302 static void gw_node_add(struct bat_priv *bat_priv,
 303                         struct orig_node *orig_node, uint8_t new_gwflags)
 304 {
 305         struct gw_node *gw_node;
 306         int down, up;
 307
 308         gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
 309         if (!gw_node)
 310                 return;
 311
 312         INIT_HLIST_NODE(&gw_node->list);
 313         gw_node->orig_node = orig_node;
 314         atomic_set(&gw_node->refcount, 1);
 315
 316         spin_lock_bh(&bat_priv->gw_list_lock);
 317         hlist_add_head_rcu(&gw_node->list, &bat_priv->gw_list);
 318         spin_unlock_bh(&bat_priv->gw_list_lock);
 319
 320         batadv_gw_bandwidth_to_kbit(new_gwflags, &down, &up);
 321         bat_dbg(DBG_BATMAN, bat_priv,
 322                 "Found new gateway %pM -> gw_class: %i - %i%s/%i%s\n",
 323                 orig_node->orig, new_gwflags,
 324                 (down > 2048 ? down / 1024 : down),
 325                 (down > 2048 ? "MBit" : "KBit"),
 326                 (up > 2048 ? up / 1024 : up),
 327                 (up > 2048 ? "MBit" : "KBit"));
 328 }
 329
 330 void batadv_gw_node_update(struct bat_priv *bat_priv,
 331                            struct orig_node *orig_node, uint8_t new_gwflags)
 332 {
 333         struct hlist_node *node;
 334         struct gw_node *gw_node, *curr_gw;
 335
 336         /* Note: We don't need a NULL check here, since curr_gw never gets
 337          * dereferenced. If curr_gw is NULL we also should not exit as we may
 338          * have this gateway in our list (duplication check!) even though we
 339          * have no currently selected gateway.
 340          */
 341         curr_gw = gw_get_selected_gw_node(bat_priv);
 342
 343         rcu_read_lock();
 344         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
 345                 if (gw_node->orig_node != orig_node)
 346                         continue;
 347
 348                 bat_dbg(DBG_BATMAN, bat_priv,
 349                         "Gateway class of originator %pM changed from %i to %i\n",
 350                         orig_node->orig, gw_node->orig_node->gw_flags,
 351                         new_gwflags);
 352
 353                 gw_node->deleted = 0;
 354
 355                 if (new_gwflags == NO_FLAGS) {
 356                         gw_node->deleted = jiffies;
 357                         bat_dbg(DBG_BATMAN, bat_priv,
 358                                 "Gateway %pM removed from gateway list\n",
 359                                 orig_node->orig);
 360
 361                         if (gw_node == curr_gw)
 362                                 goto deselect;
 363                 }
 364
 365                 goto unlock;
 366         }
 367
 368         if (new_gwflags == NO_FLAGS)
 369                 goto unlock;
 370
 371         gw_node_add(bat_priv, orig_node, new_gwflags);
 372         goto unlock;
 373
 374 deselect:
 375         batadv_gw_deselect(bat_priv);
 376 unlock:
 377         rcu_read_unlock();
 378
 379         if (curr_gw)
 380                 gw_node_free_ref(curr_gw);
 381 }
 382
 383 void batadv_gw_node_delete(struct bat_priv *bat_priv,
 384                            struct orig_node *orig_node)
 385 {
 386         batadv_gw_node_update(bat_priv, orig_node, 0);
 387 }
 388
 389 void batadv_gw_node_purge(struct bat_priv *bat_priv)
 390 {
 391         struct gw_node *gw_node, *curr_gw;
 392         struct hlist_node *node, *node_tmp;
 393         unsigned long timeout = msecs_to_jiffies(2 * PURGE_TIMEOUT);
 394         int do_deselect = 0;
 395
 396         curr_gw = gw_get_selected_gw_node(bat_priv);
 397
 398         spin_lock_bh(&bat_priv->gw_list_lock);
 399
 400         hlist_for_each_entry_safe(gw_node, node, node_tmp,
 401                                   &bat_priv->gw_list, list) {
 402                 if (((!gw_node->deleted) ||
 403                      (time_before(jiffies, gw_node->deleted + timeout))) &&
 404                     atomic_read(&bat_priv->mesh_state) == MESH_ACTIVE)
 405                         continue;
 406
 407                 if (curr_gw == gw_node)
 408                         do_deselect = 1;
 409
 410                 hlist_del_rcu(&gw_node->list);
 411                 gw_node_free_ref(gw_node);
 412         }
 413
 414         spin_unlock_bh(&bat_priv->gw_list_lock);
 415
 416         /* gw_deselect() needs to acquire the gw_list_lock */
 417         if (do_deselect)
 418                 batadv_gw_deselect(bat_priv);
 419
 420         if (curr_gw)
 421                 gw_node_free_ref(curr_gw);
 422 }
 423
 424 /* fails if orig_node has no router */
 425 static int _write_buffer_text(struct bat_priv *bat_priv, struct seq_file *seq,
 426                               const struct gw_node *gw_node)
 427 {
 428         struct gw_node *curr_gw;
 429         struct neigh_node *router;
 430         int down, up, ret = -1;
 431
 432         batadv_gw_bandwidth_to_kbit(gw_node->orig_node->gw_flags, &down, &up);
 433
 434         router = batadv_orig_node_get_router(gw_node->orig_node);
 435         if (!router)
 436                 goto out;
 437
 438         curr_gw = gw_get_selected_gw_node(bat_priv);
 439
 440         ret = seq_printf(seq, "%s %pM (%3i) %pM [%10s]: %3i - %i%s/%i%s\n",
 441                          (curr_gw == gw_node ? "=>" : "  "),
 442                          gw_node->orig_node->orig,
 443                          router->tq_avg, router->addr,
 444                          router->if_incoming->net_dev->name,
 445                          gw_node->orig_node->gw_flags,
 446                          (down > 2048 ? down / 1024 : down),
 447                          (down > 2048 ? "MBit" : "KBit"),
 448                          (up > 2048 ? up / 1024 : up),
 449                          (up > 2048 ? "MBit" : "KBit"));
 450
 451         batadv_neigh_node_free_ref(router);
 452         if (curr_gw)
 453                 gw_node_free_ref(curr_gw);
 454 out:
 455         return ret;
 456 }
 457
 458 int batadv_gw_client_seq_print_text(struct seq_file *seq, void *offset)
 459 {
 460         struct net_device *net_dev = (struct net_device *)seq->private;
 461         struct bat_priv *bat_priv = netdev_priv(net_dev);
 462         struct hard_iface *primary_if;
 463         struct gw_node *gw_node;
 464         struct hlist_node *node;
 465         int gw_count = 0, ret = 0;
 466
 467         primary_if = batadv_primary_if_get_selected(bat_priv);
 468         if (!primary_if) {
 469                 ret = seq_printf(seq,
 470                                  "BATMAN mesh %s disabled - please specify interfaces to enable it\n",
 471                                  net_dev->name);
 472                 goto out;
 473         }
 474
 475         if (primary_if->if_status != IF_ACTIVE) {
 476                 ret = seq_printf(seq,
 477                                  "BATMAN mesh %s disabled - primary interface not active\n",
 478                                  net_dev->name);
 479                 goto out;
 480         }
 481
 482         seq_printf(seq,
 483                    "      %-12s (%s/%i) %17s [%10s]: gw_class ... [B.A.T.M.A.N. adv %s, MainIF/MAC: %s/%pM (%s)]\n",
 484                    "Gateway", "#", TQ_MAX_VALUE, "Nexthop", "outgoingIF",
 485                    SOURCE_VERSION, primary_if->net_dev->name,
 486                    primary_if->net_dev->dev_addr, net_dev->name);
 487
 488         rcu_read_lock();
 489         hlist_for_each_entry_rcu(gw_node, node, &bat_priv->gw_list, list) {
 490                 if (gw_node->deleted)
 491                         continue;
 492
 493                 /* fails if orig_node has no router */
 494                 if (_write_buffer_text(bat_priv, seq, gw_node) < 0)
 495                         continue;
 496
 497                 gw_count++;
 498         }
 499         rcu_read_unlock();
 500
 501         if (gw_count == 0)
 502                 seq_printf(seq, "No gateways in range ...\n");
 503
 504 out:
 505         if (primary_if)
 506                 batadv_hardif_free_ref(primary_if);
 507         return ret;
 508 }
 509
 510 static bool is_type_dhcprequest(struct sk_buff *skb, int header_len)
 511 {
 512         int ret = false;
 513         unsigned char *p;
 514         int pkt_len;
 515
 516         if (skb_linearize(skb) < 0)
 517                 goto out;
 518
 519         pkt_len = skb_headlen(skb);
 520
 521         if (pkt_len < header_len + DHCP_OPTIONS_OFFSET + 1)
 522                 goto out;
 523
 524         p = skb->data + header_len + DHCP_OPTIONS_OFFSET;
 525         pkt_len -= header_len + DHCP_OPTIONS_OFFSET + 1;
 526
 527         /* Access the dhcp option lists. Each entry is made up by:
 528          * - octet 1: option type
 529          * - octet 2: option data len (only if type != 255 and 0)
 530          * - octet 3: option data
 531          */
 532         while (*p != 255 && !ret) {
 533                 /* p now points to the first octet: option type */
 534                 if (*p == 53) {
 535                         /* type 53 is the message type option.
 536                          * Jump the len octet and go to the data octet
 537                          */
 538                         if (pkt_len < 2)
 539                                 goto out;
 540                         p += 2;
 541
 542                         /* check if the message type is what we need */
 543                         if (*p == DHCP_REQUEST)
 544                                 ret = true;
 545                         break;
 546                 } else if (*p == 0) {
 547                         /* option type 0 (padding), just go forward */
 548                         if (pkt_len < 1)
 549                                 goto out;
 550                         pkt_len--;
 551                         p++;
 552                 } else {
 553                         /* This is any other option. So we get the length... */
 554                         if (pkt_len < 1)
 555                                 goto out;
 556                         pkt_len--;
 557                         p++;
 558
 559                         /* ...and then we jump over the data */
 560                         if (pkt_len < 1 + (*p))
 561                                 goto out;
 562                         pkt_len -= 1 + (*p);
 563                         p += 1 + (*p);
 564                 }
 565         }
 566 out:
 567         return ret;
 568 }
 569
 570 bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len)
 571 {
 572         struct ethhdr *ethhdr;
 573         struct iphdr *iphdr;
 574         struct ipv6hdr *ipv6hdr;
 575         struct udphdr *udphdr;
 576
 577         /* check for ethernet header */
 578         if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
 579                 return false;
 580         ethhdr = (struct ethhdr *)skb->data;
 581         *header_len += ETH_HLEN;
 582
 583         /* check for initial vlan header */
 584         if (ntohs(ethhdr->h_proto) == ETH_P_8021Q) {
 585                 if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
 586                         return false;
 587                 ethhdr = (struct ethhdr *)(skb->data + VLAN_HLEN);
 588                 *header_len += VLAN_HLEN;
 589         }
 590
 591         /* check for ip header */
 592         switch (ntohs(ethhdr->h_proto)) {
 593         case ETH_P_IP:
 594                 if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
 595                         return false;
 596                 iphdr = (struct iphdr *)(skb->data + *header_len);
 597                 *header_len += iphdr->ihl * 4;
 598
 599                 /* check for udp header */
 600                 if (iphdr->protocol != IPPROTO_UDP)
 601                         return false;
 602
 603                 break;
 604         case ETH_P_IPV6:
 605                 if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
 606                         return false;
 607                 ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
 608                 *header_len += sizeof(*ipv6hdr);
 609
 610                 /* check for udp header */
 611                 if (ipv6hdr->nexthdr != IPPROTO_UDP)
 612                         return false;
 613
 614                 break;
 615         default:
 616                 return false;
 617         }
 618
 619         if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
 620                 return false;
 621         udphdr = (struct udphdr *)(skb->data + *header_len);
 622         *header_len += sizeof(*udphdr);
 623
 624         /* check for bootp port */
 625         if ((ntohs(ethhdr->h_proto) == ETH_P_IP) &&
 626             (ntohs(udphdr->dest) != 67))
 627                 return false;
 628
 629         if ((ntohs(ethhdr->h_proto) == ETH_P_IPV6) &&
 630             (ntohs(udphdr->dest) != 547))
 631                 return false;
 632
 633         return true;
 634 }
 635
 636 bool batadv_gw_out_of_range(struct bat_priv *bat_priv,
 637                             struct sk_buff *skb, struct ethhdr *ethhdr)
 638 {
 639         struct neigh_node *neigh_curr = NULL, *neigh_old = NULL;
 640         struct orig_node *orig_dst_node = NULL;
 641         struct gw_node *curr_gw = NULL;
 642         bool ret, out_of_range = false;
 643         unsigned int header_len = 0;
 644         uint8_t curr_tq_avg;
 645
 646         ret = batadv_gw_is_dhcp_target(skb, &header_len);
 647         if (!ret)
 648                 goto out;
 649
 650         orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
 651                                                  ethhdr->h_dest);
 652         if (!orig_dst_node)
 653                 goto out;
 654
 655         if (!orig_dst_node->gw_flags)
 656                 goto out;
 657
 658         ret = is_type_dhcprequest(skb, header_len);
 659         if (!ret)
 660                 goto out;
 661
 662         switch (atomic_read(&bat_priv->gw_mode)) {
 663         case GW_MODE_SERVER:
 664                 /* If we are a GW then we are our best GW. We can artificially
 665                  * set the tq towards ourself as the maximum value
 666                  */
 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                  */
 682                 neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
 683                                                 NULL);
 684                 if (!neigh_curr)
 685                         goto out;
 686
 687                 curr_tq_avg = neigh_curr->tq_avg;
 688                 break;
 689         case GW_MODE_OFF:
 690         default:
 691                 goto out;
 692         }
 693
 694         neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
 695         if (!neigh_old)
 696                 goto out;
 697
 698         if (curr_tq_avg - neigh_old->tq_avg > GW_THRESHOLD)
 699                 out_of_range = true;
 700
 701 out:
 702         if (orig_dst_node)
 703                 batadv_orig_node_free_ref(orig_dst_node);
 704         if (curr_gw)
 705                 gw_node_free_ref(curr_gw);
 706         if (neigh_old)
 707                 batadv_neigh_node_free_ref(neigh_old);
 708         if (neigh_curr)
 709                 batadv_neigh_node_free_ref(neigh_curr);
 710         return out_of_range;
 711 }