linux/net/batman-adv/gateway_client.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/* Copyright (C) B.A.T.M.A.N. contributors:
   3 *
   4 * Marek Lindner
   5 */
   6
   7#include "gateway_client.h"
   8#include "main.h"
   9
  10#include <linux/atomic.h>
  11#include <linux/byteorder/generic.h>
  12#include <linux/errno.h>
  13#include <linux/etherdevice.h>
  14#include <linux/gfp.h>
  15#include <linux/if_ether.h>
  16#include <linux/if_vlan.h>
  17#include <linux/in.h>
  18#include <linux/ip.h>
  19#include <linux/ipv6.h>
  20#include <linux/kernel.h>
  21#include <linux/kref.h>
  22#include <linux/list.h>
  23#include <linux/lockdep.h>
  24#include <linux/netdevice.h>
  25#include <linux/netlink.h>
  26#include <linux/rculist.h>
  27#include <linux/rcupdate.h>
  28#include <linux/skbuff.h>
  29#include <linux/slab.h>
  30#include <linux/spinlock.h>
  31#include <linux/stddef.h>
  32#include <linux/udp.h>
  33#include <net/sock.h>
  34#include <uapi/linux/batadv_packet.h>
  35#include <uapi/linux/batman_adv.h>
  36
  37#include "hard-interface.h"
  38#include "log.h"
  39#include "netlink.h"
  40#include "originator.h"
  41#include "routing.h"
  42#include "soft-interface.h"
  43#include "translation-table.h"
  44
  45/* These are the offsets of the "hw type" and "hw address length" in the dhcp
  46 * packet starting at the beginning of the dhcp header
  47 */
  48#define BATADV_DHCP_HTYPE_OFFSET        1
  49#define BATADV_DHCP_HLEN_OFFSET         2
  50/* Value of htype representing Ethernet */
  51#define BATADV_DHCP_HTYPE_ETHERNET      0x01
  52/* This is the offset of the "chaddr" field in the dhcp packet starting at the
  53 * beginning of the dhcp header
  54 */
  55#define BATADV_DHCP_CHADDR_OFFSET       28
  56
  57/**
  58 * batadv_gw_node_release() - release gw_node from lists and queue for free
  59 *  after rcu grace period
  60 * @ref: kref pointer of the gw_node
  61 */
  62static void batadv_gw_node_release(struct kref *ref)
  63{
  64        struct batadv_gw_node *gw_node;
  65
  66        gw_node = container_of(ref, struct batadv_gw_node, refcount);
  67
  68        batadv_orig_node_put(gw_node->orig_node);
  69        kfree_rcu(gw_node, rcu);
  70}
  71
  72/**
  73 * batadv_gw_node_put() - decrement the gw_node refcounter and possibly release
  74 *  it
  75 * @gw_node: gateway node to free
  76 */
  77void batadv_gw_node_put(struct batadv_gw_node *gw_node)
  78{
  79        kref_put(&gw_node->refcount, batadv_gw_node_release);
  80}
  81
  82/**
  83 * batadv_gw_get_selected_gw_node() - Get currently selected gateway
  84 * @bat_priv: the bat priv with all the soft interface information
  85 *
  86 * Return: selected gateway (with increased refcnt), NULL on errors
  87 */
  88struct batadv_gw_node *
  89batadv_gw_get_selected_gw_node(struct batadv_priv *bat_priv)
  90{
  91        struct batadv_gw_node *gw_node;
  92
  93        rcu_read_lock();
  94        gw_node = rcu_dereference(bat_priv->gw.curr_gw);
  95        if (!gw_node)
  96                goto out;
  97
  98        if (!kref_get_unless_zero(&gw_node->refcount))
  99                gw_node = NULL;
 100
 101out:
 102        rcu_read_unlock();
 103        return gw_node;
 104}
 105
 106/**
 107 * batadv_gw_get_selected_orig() - Get originator of currently selected gateway
 108 * @bat_priv: the bat priv with all the soft interface information
 109 *
 110 * Return: orig_node of selected gateway (with increased refcnt), NULL on errors
 111 */
 112struct batadv_orig_node *
 113batadv_gw_get_selected_orig(struct batadv_priv *bat_priv)
 114{
 115        struct batadv_gw_node *gw_node;
 116        struct batadv_orig_node *orig_node = NULL;
 117
 118        gw_node = batadv_gw_get_selected_gw_node(bat_priv);
 119        if (!gw_node)
 120                goto out;
 121
 122        rcu_read_lock();
 123        orig_node = gw_node->orig_node;
 124        if (!orig_node)
 125                goto unlock;
 126
 127        if (!kref_get_unless_zero(&orig_node->refcount))
 128                orig_node = NULL;
 129
 130unlock:
 131        rcu_read_unlock();
 132out:
 133        if (gw_node)
 134                batadv_gw_node_put(gw_node);
 135        return orig_node;
 136}
 137
 138static void batadv_gw_select(struct batadv_priv *bat_priv,
 139                             struct batadv_gw_node *new_gw_node)
 140{
 141        struct batadv_gw_node *curr_gw_node;
 142
 143        spin_lock_bh(&bat_priv->gw.list_lock);
 144
 145        if (new_gw_node)
 146                kref_get(&new_gw_node->refcount);
 147
 148        curr_gw_node = rcu_replace_pointer(bat_priv->gw.curr_gw, new_gw_node,
 149                                           true);
 150
 151        if (curr_gw_node)
 152                batadv_gw_node_put(curr_gw_node);
 153
 154        spin_unlock_bh(&bat_priv->gw.list_lock);
 155}
 156
 157/**
 158 * batadv_gw_reselect() - force a gateway reselection
 159 * @bat_priv: the bat priv with all the soft interface information
 160 *
 161 * Set a flag to remind the GW component to perform a new gateway reselection.
 162 * However this function does not ensure that the current gateway is going to be
 163 * deselected. The reselection mechanism may elect the same gateway once again.
 164 *
 165 * This means that invoking batadv_gw_reselect() does not guarantee a gateway
 166 * change and therefore a uevent is not necessarily expected.
 167 */
 168void batadv_gw_reselect(struct batadv_priv *bat_priv)
 169{
 170        atomic_set(&bat_priv->gw.reselect, 1);
 171}
 172
 173/**
 174 * batadv_gw_check_client_stop() - check if client mode has been switched off
 175 * @bat_priv: the bat priv with all the soft interface information
 176 *
 177 * This function assumes the caller has checked that the gw state *is actually
 178 * changing*. This function is not supposed to be called when there is no state
 179 * change.
 180 */
 181void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
 182{
 183        struct batadv_gw_node *curr_gw;
 184
 185        if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
 186                return;
 187
 188        curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 189        if (!curr_gw)
 190                return;
 191
 192        /* deselect the current gateway so that next time that client mode is
 193         * enabled a proper GW_ADD event can be sent
 194         */
 195        batadv_gw_select(bat_priv, NULL);
 196
 197        /* if batman-adv is switching the gw client mode off and a gateway was
 198         * already selected, send a DEL uevent
 199         */
 200        batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL, NULL);
 201
 202        batadv_gw_node_put(curr_gw);
 203}
 204
 205/**
 206 * batadv_gw_election() - Elect the best gateway
 207 * @bat_priv: the bat priv with all the soft interface information
 208 */
 209void batadv_gw_election(struct batadv_priv *bat_priv)
 210{
 211        struct batadv_gw_node *curr_gw = NULL;
 212        struct batadv_gw_node *next_gw = NULL;
 213        struct batadv_neigh_node *router = NULL;
 214        struct batadv_neigh_ifinfo *router_ifinfo = NULL;
 215        char gw_addr[18] = { '\0' };
 216
 217        if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
 218                goto out;
 219
 220        if (!bat_priv->algo_ops->gw.get_best_gw_node)
 221                goto out;
 222
 223        curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 224
 225        if (!batadv_atomic_dec_not_zero(&bat_priv->gw.reselect) && curr_gw)
 226                goto out;
 227
 228        /* if gw.reselect is set to 1 it means that a previous call to
 229         * gw.is_eligible() said that we have a new best GW, therefore it can
 230         * now be picked from the list and selected
 231         */
 232        next_gw = bat_priv->algo_ops->gw.get_best_gw_node(bat_priv);
 233
 234        if (curr_gw == next_gw)
 235                goto out;
 236
 237        if (next_gw) {
 238                sprintf(gw_addr, "%pM", next_gw->orig_node->orig);
 239
 240                router = batadv_orig_router_get(next_gw->orig_node,
 241                                                BATADV_IF_DEFAULT);
 242                if (!router) {
 243                        batadv_gw_reselect(bat_priv);
 244                        goto out;
 245                }
 246
 247                router_ifinfo = batadv_neigh_ifinfo_get(router,
 248                                                        BATADV_IF_DEFAULT);
 249                if (!router_ifinfo) {
 250                        batadv_gw_reselect(bat_priv);
 251                        goto out;
 252                }
 253        }
 254
 255        if (curr_gw && !next_gw) {
 256                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 257                           "Removing selected gateway - no gateway in range\n");
 258                batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL,
 259                                    NULL);
 260        } else if (!curr_gw && next_gw) {
 261                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 262                           "Adding route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
 263                           next_gw->orig_node->orig,
 264                           next_gw->bandwidth_down / 10,
 265                           next_gw->bandwidth_down % 10,
 266                           next_gw->bandwidth_up / 10,
 267                           next_gw->bandwidth_up % 10,
 268                           router_ifinfo->bat_iv.tq_avg);
 269                batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_ADD,
 270                                    gw_addr);
 271        } else {
 272                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 273                           "Changing route to gateway %pM (bandwidth: %u.%u/%u.%u MBit, tq: %i)\n",
 274                           next_gw->orig_node->orig,
 275                           next_gw->bandwidth_down / 10,
 276                           next_gw->bandwidth_down % 10,
 277                           next_gw->bandwidth_up / 10,
 278                           next_gw->bandwidth_up % 10,
 279                           router_ifinfo->bat_iv.tq_avg);
 280                batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_CHANGE,
 281                                    gw_addr);
 282        }
 283
 284        batadv_gw_select(bat_priv, next_gw);
 285
 286out:
 287        if (curr_gw)
 288                batadv_gw_node_put(curr_gw);
 289        if (next_gw)
 290                batadv_gw_node_put(next_gw);
 291        if (router)
 292                batadv_neigh_node_put(router);
 293        if (router_ifinfo)
 294                batadv_neigh_ifinfo_put(router_ifinfo);
 295}
 296
 297/**
 298 * batadv_gw_check_election() - Elect orig node as best gateway when eligible
 299 * @bat_priv: the bat priv with all the soft interface information
 300 * @orig_node: orig node which is to be checked
 301 */
 302void batadv_gw_check_election(struct batadv_priv *bat_priv,
 303                              struct batadv_orig_node *orig_node)
 304{
 305        struct batadv_orig_node *curr_gw_orig;
 306
 307        /* abort immediately if the routing algorithm does not support gateway
 308         * election
 309         */
 310        if (!bat_priv->algo_ops->gw.is_eligible)
 311                return;
 312
 313        curr_gw_orig = batadv_gw_get_selected_orig(bat_priv);
 314        if (!curr_gw_orig)
 315                goto reselect;
 316
 317        /* this node already is the gateway */
 318        if (curr_gw_orig == orig_node)
 319                goto out;
 320
 321        if (!bat_priv->algo_ops->gw.is_eligible(bat_priv, curr_gw_orig,
 322                                                orig_node))
 323                goto out;
 324
 325reselect:
 326        batadv_gw_reselect(bat_priv);
 327out:
 328        if (curr_gw_orig)
 329                batadv_orig_node_put(curr_gw_orig);
 330}
 331
 332/**
 333 * batadv_gw_node_add() - add gateway node to list of available gateways
 334 * @bat_priv: the bat priv with all the soft interface information
 335 * @orig_node: originator announcing gateway capabilities
 336 * @gateway: announced bandwidth information
 337 *
 338 * Has to be called with the appropriate locks being acquired
 339 * (gw.list_lock).
 340 */
 341static void batadv_gw_node_add(struct batadv_priv *bat_priv,
 342                               struct batadv_orig_node *orig_node,
 343                               struct batadv_tvlv_gateway_data *gateway)
 344{
 345        struct batadv_gw_node *gw_node;
 346
 347        lockdep_assert_held(&bat_priv->gw.list_lock);
 348
 349        if (gateway->bandwidth_down == 0)
 350                return;
 351
 352        gw_node = kzalloc(sizeof(*gw_node), GFP_ATOMIC);
 353        if (!gw_node)
 354                return;
 355
 356        kref_init(&gw_node->refcount);
 357        INIT_HLIST_NODE(&gw_node->list);
 358        kref_get(&orig_node->refcount);
 359        gw_node->orig_node = orig_node;
 360        gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
 361        gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
 362
 363        kref_get(&gw_node->refcount);
 364        hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list);
 365        bat_priv->gw.generation++;
 366
 367        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 368                   "Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n",
 369                   orig_node->orig,
 370                   ntohl(gateway->bandwidth_down) / 10,
 371                   ntohl(gateway->bandwidth_down) % 10,
 372                   ntohl(gateway->bandwidth_up) / 10,
 373                   ntohl(gateway->bandwidth_up) % 10);
 374
 375        /* don't return reference to new gw_node */
 376        batadv_gw_node_put(gw_node);
 377}
 378
 379/**
 380 * batadv_gw_node_get() - retrieve gateway node from list of available gateways
 381 * @bat_priv: the bat priv with all the soft interface information
 382 * @orig_node: originator announcing gateway capabilities
 383 *
 384 * Return: gateway node if found or NULL otherwise.
 385 */
 386struct batadv_gw_node *batadv_gw_node_get(struct batadv_priv *bat_priv,
 387                                          struct batadv_orig_node *orig_node)
 388{
 389        struct batadv_gw_node *gw_node_tmp, *gw_node = NULL;
 390
 391        rcu_read_lock();
 392        hlist_for_each_entry_rcu(gw_node_tmp, &bat_priv->gw.gateway_list,
 393                                 list) {
 394                if (gw_node_tmp->orig_node != orig_node)
 395                        continue;
 396
 397                if (!kref_get_unless_zero(&gw_node_tmp->refcount))
 398                        continue;
 399
 400                gw_node = gw_node_tmp;
 401                break;
 402        }
 403        rcu_read_unlock();
 404
 405        return gw_node;
 406}
 407
 408/**
 409 * batadv_gw_node_update() - update list of available gateways with changed
 410 *  bandwidth information
 411 * @bat_priv: the bat priv with all the soft interface information
 412 * @orig_node: originator announcing gateway capabilities
 413 * @gateway: announced bandwidth information
 414 */
 415void batadv_gw_node_update(struct batadv_priv *bat_priv,
 416                           struct batadv_orig_node *orig_node,
 417                           struct batadv_tvlv_gateway_data *gateway)
 418{
 419        struct batadv_gw_node *gw_node, *curr_gw = NULL;
 420
 421        spin_lock_bh(&bat_priv->gw.list_lock);
 422        gw_node = batadv_gw_node_get(bat_priv, orig_node);
 423        if (!gw_node) {
 424                batadv_gw_node_add(bat_priv, orig_node, gateway);
 425                spin_unlock_bh(&bat_priv->gw.list_lock);
 426                goto out;
 427        }
 428        spin_unlock_bh(&bat_priv->gw.list_lock);
 429
 430        if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) &&
 431            gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))
 432                goto out;
 433
 434        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 435                   "Gateway bandwidth of originator %pM changed from %u.%u/%u.%u MBit to %u.%u/%u.%u MBit\n",
 436                   orig_node->orig,
 437                   gw_node->bandwidth_down / 10,
 438                   gw_node->bandwidth_down % 10,
 439                   gw_node->bandwidth_up / 10,
 440                   gw_node->bandwidth_up % 10,
 441                   ntohl(gateway->bandwidth_down) / 10,
 442                   ntohl(gateway->bandwidth_down) % 10,
 443                   ntohl(gateway->bandwidth_up) / 10,
 444                   ntohl(gateway->bandwidth_up) % 10);
 445
 446        gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
 447        gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
 448
 449        if (ntohl(gateway->bandwidth_down) == 0) {
 450                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 451                           "Gateway %pM removed from gateway list\n",
 452                           orig_node->orig);
 453
 454                /* Note: We don't need a NULL check here, since curr_gw never
 455                 * gets dereferenced.
 456                 */
 457                spin_lock_bh(&bat_priv->gw.list_lock);
 458                if (!hlist_unhashed(&gw_node->list)) {
 459                        hlist_del_init_rcu(&gw_node->list);
 460                        batadv_gw_node_put(gw_node);
 461                        bat_priv->gw.generation++;
 462                }
 463                spin_unlock_bh(&bat_priv->gw.list_lock);
 464
 465                curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 466                if (gw_node == curr_gw)
 467                        batadv_gw_reselect(bat_priv);
 468
 469                if (curr_gw)
 470                        batadv_gw_node_put(curr_gw);
 471        }
 472
 473out:
 474        if (gw_node)
 475                batadv_gw_node_put(gw_node);
 476}
 477
 478/**
 479 * batadv_gw_node_delete() - Remove orig_node from gateway list
 480 * @bat_priv: the bat priv with all the soft interface information
 481 * @orig_node: orig node which is currently in process of being removed
 482 */
 483void batadv_gw_node_delete(struct batadv_priv *bat_priv,
 484                           struct batadv_orig_node *orig_node)
 485{
 486        struct batadv_tvlv_gateway_data gateway;
 487
 488        gateway.bandwidth_down = 0;
 489        gateway.bandwidth_up = 0;
 490
 491        batadv_gw_node_update(bat_priv, orig_node, &gateway);
 492}
 493
 494/**
 495 * batadv_gw_node_free() - Free gateway information from soft interface
 496 * @bat_priv: the bat priv with all the soft interface information
 497 */
 498void batadv_gw_node_free(struct batadv_priv *bat_priv)
 499{
 500        struct batadv_gw_node *gw_node;
 501        struct hlist_node *node_tmp;
 502
 503        spin_lock_bh(&bat_priv->gw.list_lock);
 504        hlist_for_each_entry_safe(gw_node, node_tmp,
 505                                  &bat_priv->gw.gateway_list, list) {
 506                hlist_del_init_rcu(&gw_node->list);
 507                batadv_gw_node_put(gw_node);
 508                bat_priv->gw.generation++;
 509        }
 510        spin_unlock_bh(&bat_priv->gw.list_lock);
 511}
 512
 513/**
 514 * batadv_gw_dump() - Dump gateways into a message
 515 * @msg: Netlink message to dump into
 516 * @cb: Control block containing additional options
 517 *
 518 * Return: Error code, or length of message
 519 */
 520int batadv_gw_dump(struct sk_buff *msg, struct netlink_callback *cb)
 521{
 522        struct batadv_hard_iface *primary_if = NULL;
 523        struct net *net = sock_net(cb->skb->sk);
 524        struct net_device *soft_iface;
 525        struct batadv_priv *bat_priv;
 526        int ifindex;
 527        int ret;
 528
 529        ifindex = batadv_netlink_get_ifindex(cb->nlh,
 530                                             BATADV_ATTR_MESH_IFINDEX);
 531        if (!ifindex)
 532                return -EINVAL;
 533
 534        soft_iface = dev_get_by_index(net, ifindex);
 535        if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
 536                ret = -ENODEV;
 537                goto out;
 538        }
 539
 540        bat_priv = netdev_priv(soft_iface);
 541
 542        primary_if = batadv_primary_if_get_selected(bat_priv);
 543        if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
 544                ret = -ENOENT;
 545                goto out;
 546        }
 547
 548        if (!bat_priv->algo_ops->gw.dump) {
 549                ret = -EOPNOTSUPP;
 550                goto out;
 551        }
 552
 553        bat_priv->algo_ops->gw.dump(msg, cb, bat_priv);
 554
 555        ret = msg->len;
 556
 557out:
 558        if (primary_if)
 559                batadv_hardif_put(primary_if);
 560        if (soft_iface)
 561                dev_put(soft_iface);
 562
 563        return ret;
 564}
 565
 566/**
 567 * batadv_gw_dhcp_recipient_get() - check if a packet is a DHCP message
 568 * @skb: the packet to check
 569 * @header_len: a pointer to the batman-adv header size
 570 * @chaddr: buffer where the client address will be stored. Valid
 571 *  only if the function returns BATADV_DHCP_TO_CLIENT
 572 *
 573 * This function may re-allocate the data buffer of the skb passed as argument.
 574 *
 575 * Return:
 576 * - BATADV_DHCP_NO if the packet is not a dhcp message or if there was an error
 577 *   while parsing it
 578 * - BATADV_DHCP_TO_SERVER if this is a message going to the DHCP server
 579 * - BATADV_DHCP_TO_CLIENT if this is a message going to a DHCP client
 580 */
 581enum batadv_dhcp_recipient
 582batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len,
 583                             u8 *chaddr)
 584{
 585        enum batadv_dhcp_recipient ret = BATADV_DHCP_NO;
 586        struct ethhdr *ethhdr;
 587        struct iphdr *iphdr;
 588        struct ipv6hdr *ipv6hdr;
 589        struct udphdr *udphdr;
 590        struct vlan_ethhdr *vhdr;
 591        int chaddr_offset;
 592        __be16 proto;
 593        u8 *p;
 594
 595        /* check for ethernet header */
 596        if (!pskb_may_pull(skb, *header_len + ETH_HLEN))
 597                return BATADV_DHCP_NO;
 598
 599        ethhdr = eth_hdr(skb);
 600        proto = ethhdr->h_proto;
 601        *header_len += ETH_HLEN;
 602
 603        /* check for initial vlan header */
 604        if (proto == htons(ETH_P_8021Q)) {
 605                if (!pskb_may_pull(skb, *header_len + VLAN_HLEN))
 606                        return BATADV_DHCP_NO;
 607
 608                vhdr = vlan_eth_hdr(skb);
 609                proto = vhdr->h_vlan_encapsulated_proto;
 610                *header_len += VLAN_HLEN;
 611        }
 612
 613        /* check for ip header */
 614        switch (proto) {
 615        case htons(ETH_P_IP):
 616                if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr)))
 617                        return BATADV_DHCP_NO;
 618
 619                iphdr = (struct iphdr *)(skb->data + *header_len);
 620                *header_len += iphdr->ihl * 4;
 621
 622                /* check for udp header */
 623                if (iphdr->protocol != IPPROTO_UDP)
 624                        return BATADV_DHCP_NO;
 625
 626                break;
 627        case htons(ETH_P_IPV6):
 628                if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr)))
 629                        return BATADV_DHCP_NO;
 630
 631                ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len);
 632                *header_len += sizeof(*ipv6hdr);
 633
 634                /* check for udp header */
 635                if (ipv6hdr->nexthdr != IPPROTO_UDP)
 636                        return BATADV_DHCP_NO;
 637
 638                break;
 639        default:
 640                return BATADV_DHCP_NO;
 641        }
 642
 643        if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr)))
 644                return BATADV_DHCP_NO;
 645
 646        udphdr = (struct udphdr *)(skb->data + *header_len);
 647        *header_len += sizeof(*udphdr);
 648
 649        /* check for bootp port */
 650        switch (proto) {
 651        case htons(ETH_P_IP):
 652                if (udphdr->dest == htons(67))
 653                        ret = BATADV_DHCP_TO_SERVER;
 654                else if (udphdr->source == htons(67))
 655                        ret = BATADV_DHCP_TO_CLIENT;
 656                break;
 657        case htons(ETH_P_IPV6):
 658                if (udphdr->dest == htons(547))
 659                        ret = BATADV_DHCP_TO_SERVER;
 660                else if (udphdr->source == htons(547))
 661                        ret = BATADV_DHCP_TO_CLIENT;
 662                break;
 663        }
 664
 665        chaddr_offset = *header_len + BATADV_DHCP_CHADDR_OFFSET;
 666        /* store the client address if the message is going to a client */
 667        if (ret == BATADV_DHCP_TO_CLIENT) {
 668                if (!pskb_may_pull(skb, chaddr_offset + ETH_ALEN))
 669                        return BATADV_DHCP_NO;
 670
 671                /* check if the DHCP packet carries an Ethernet DHCP */
 672                p = skb->data + *header_len + BATADV_DHCP_HTYPE_OFFSET;
 673                if (*p != BATADV_DHCP_HTYPE_ETHERNET)
 674                        return BATADV_DHCP_NO;
 675
 676                /* check if the DHCP packet carries a valid Ethernet address */
 677                p = skb->data + *header_len + BATADV_DHCP_HLEN_OFFSET;
 678                if (*p != ETH_ALEN)
 679                        return BATADV_DHCP_NO;
 680
 681                ether_addr_copy(chaddr, skb->data + chaddr_offset);
 682        }
 683
 684        return ret;
 685}
 686
 687/**
 688 * batadv_gw_out_of_range() - check if the dhcp request destination is the best
 689 *  gateway
 690 * @bat_priv: the bat priv with all the soft interface information
 691 * @skb: the outgoing packet
 692 *
 693 * Check if the skb is a DHCP request and if it is sent to the current best GW
 694 * server. Due to topology changes it may be the case that the GW server
 695 * previously selected is not the best one anymore.
 696 *
 697 * This call might reallocate skb data.
 698 * Must be invoked only when the DHCP packet is going TO a DHCP SERVER.
 699 *
 700 * Return: true if the packet destination is unicast and it is not the best gw,
 701 * false otherwise.
 702 */
 703bool batadv_gw_out_of_range(struct batadv_priv *bat_priv,
 704                            struct sk_buff *skb)
 705{
 706        struct batadv_neigh_node *neigh_curr = NULL;
 707        struct batadv_neigh_node *neigh_old = NULL;
 708        struct batadv_orig_node *orig_dst_node = NULL;
 709        struct batadv_gw_node *gw_node = NULL;
 710        struct batadv_gw_node *curr_gw = NULL;
 711        struct batadv_neigh_ifinfo *curr_ifinfo, *old_ifinfo;
 712        struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
 713        bool out_of_range = false;
 714        u8 curr_tq_avg;
 715        unsigned short vid;
 716
 717        vid = batadv_get_vid(skb, 0);
 718
 719        if (is_multicast_ether_addr(ethhdr->h_dest))
 720                goto out;
 721
 722        orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source,
 723                                                 ethhdr->h_dest, vid);
 724        if (!orig_dst_node)
 725                goto out;
 726
 727        gw_node = batadv_gw_node_get(bat_priv, orig_dst_node);
 728        if (!gw_node)
 729                goto out;
 730
 731        switch (atomic_read(&bat_priv->gw.mode)) {
 732        case BATADV_GW_MODE_SERVER:
 733                /* If we are a GW then we are our best GW. We can artificially
 734                 * set the tq towards ourself as the maximum value
 735                 */
 736                curr_tq_avg = BATADV_TQ_MAX_VALUE;
 737                break;
 738        case BATADV_GW_MODE_CLIENT:
 739                curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
 740                if (!curr_gw)
 741                        goto out;
 742
 743                /* packet is going to our gateway */
 744                if (curr_gw->orig_node == orig_dst_node)
 745                        goto out;
 746
 747                /* If the dhcp packet has been sent to a different gw,
 748                 * we have to evaluate whether the old gw is still
 749                 * reliable enough
 750                 */
 751                neigh_curr = batadv_find_router(bat_priv, curr_gw->orig_node,
 752                                                NULL);
 753                if (!neigh_curr)
 754                        goto out;
 755
 756                curr_ifinfo = batadv_neigh_ifinfo_get(neigh_curr,
 757                                                      BATADV_IF_DEFAULT);
 758                if (!curr_ifinfo)
 759                        goto out;
 760
 761                curr_tq_avg = curr_ifinfo->bat_iv.tq_avg;
 762                batadv_neigh_ifinfo_put(curr_ifinfo);
 763
 764                break;
 765        case BATADV_GW_MODE_OFF:
 766        default:
 767                goto out;
 768        }
 769
 770        neigh_old = batadv_find_router(bat_priv, orig_dst_node, NULL);
 771        if (!neigh_old)
 772                goto out;
 773
 774        old_ifinfo = batadv_neigh_ifinfo_get(neigh_old, BATADV_IF_DEFAULT);
 775        if (!old_ifinfo)
 776                goto out;
 777
 778        if ((curr_tq_avg - old_ifinfo->bat_iv.tq_avg) > BATADV_GW_THRESHOLD)
 779                out_of_range = true;
 780        batadv_neigh_ifinfo_put(old_ifinfo);
 781
 782out:
 783        if (orig_dst_node)
 784                batadv_orig_node_put(orig_dst_node);
 785        if (curr_gw)
 786                batadv_gw_node_put(curr_gw);
 787        if (gw_node)
 788                batadv_gw_node_put(gw_node);
 789        if (neigh_old)
 790                batadv_neigh_node_put(neigh_old);
 791        if (neigh_curr)
 792                batadv_neigh_node_put(neigh_curr);
 793        return out_of_range;
 794}
 795