MAINTAINERS: CHINESE MAINTAINERS mailing list is subscribers only

[linux-2.6/libata-dev.git] / net / batman-adv / routing.c

/* Copyright (C) 2007-2012 B.A.T.M.A.N. contributors:
 *
 * Marek Lindner, Simon Wunderlich
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA
 */

#include "main.h"
#include "routing.h"
#include "send.h"
#include "soft-interface.h"
#include "hard-interface.h"
#include "icmp_socket.h"
#include "translation-table.h"
#include "originator.h"
#include "vis.h"
#include "unicast.h"
#include "bridge_loop_avoidance.h"
#include "distributed-arp-table.h"

static int batadv_route_unicast_packet(struct sk_buff *skb,
                                       struct batadv_hard_iface *recv_if);

void batadv_slide_own_bcast_window(struct batadv_hard_iface *hard_iface)
{
        struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
        struct batadv_hashtable *hash = bat_priv->orig_hash;
        struct hlist_node *node;
        struct hlist_head *head;
        struct batadv_orig_node *orig_node;
        unsigned long *word;
        uint32_t i;
        size_t word_index;
        uint8_t *w;

        for (i = 0; i < hash->size; i++) {
                head = &hash->table[i];

                rcu_read_lock();
                hlist_for_each_entry_rcu(orig_node, node, head, hash_entry) {
                        spin_lock_bh(&orig_node->ogm_cnt_lock);
                        word_index = hard_iface->if_num * BATADV_NUM_WORDS;
                        word = &(orig_node->bcast_own[word_index]);

                        batadv_bit_get_packet(bat_priv, word, 1, 0);
                        w = &orig_node->bcast_own_sum[hard_iface->if_num];
                        *w = bitmap_weight(word, BATADV_TQ_LOCAL_WINDOW_SIZE);
                        spin_unlock_bh(&orig_node->ogm_cnt_lock);
                }
                rcu_read_unlock();
        }
}

static void _batadv_update_route(struct batadv_priv *bat_priv,
                                 struct batadv_orig_node *orig_node,
                                 struct batadv_neigh_node *neigh_node)
{
        struct batadv_neigh_node *curr_router;

        curr_router = batadv_orig_node_get_router(orig_node);

        /* route deleted */
        if ((curr_router) && (!neigh_node)) {
                batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
                           "Deleting route towards: %pM\n", orig_node->orig);
                batadv_tt_global_del_orig(bat_priv, orig_node,
                                          "Deleted route towards originator");

        /* route added */
        } else if ((!curr_router) && (neigh_node)) {

                batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
                           "Adding route towards: %pM (via %pM)\n",
                           orig_node->orig, neigh_node->addr);
        /* route changed */
        } else if (neigh_node && curr_router) {
                batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
                           "Changing route towards: %pM (now via %pM - was via %pM)\n",
                           orig_node->orig, neigh_node->addr,
                           curr_router->addr);
        }

        if (curr_router)
                batadv_neigh_node_free_ref(curr_router);

        /* increase refcount of new best neighbor */
        if (neigh_node && !atomic_inc_not_zero(&neigh_node->refcount))
                neigh_node = NULL;

        spin_lock_bh(&orig_node->neigh_list_lock);
        rcu_assign_pointer(orig_node->router, neigh_node);
        spin_unlock_bh(&orig_node->neigh_list_lock);

        /* decrease refcount of previous best neighbor */
        if (curr_router)
                batadv_neigh_node_free_ref(curr_router);
}

void batadv_update_route(struct batadv_priv *bat_priv,
                         struct batadv_orig_node *orig_node,
                         struct batadv_neigh_node *neigh_node)
{
        struct batadv_neigh_node *router = NULL;

        if (!orig_node)
                goto out;

        router = batadv_orig_node_get_router(orig_node);

        if (router != neigh_node)
                _batadv_update_route(bat_priv, orig_node, neigh_node);

out:
        if (router)
                batadv_neigh_node_free_ref(router);
}

/* caller must hold the neigh_list_lock */
void batadv_bonding_candidate_del(struct batadv_orig_node *orig_node,
                                  struct batadv_neigh_node *neigh_node)
{
        /* this neighbor is not part of our candidate list */
        if (list_empty(&neigh_node->bonding_list))
                goto out;

        list_del_rcu(&neigh_node->bonding_list);
        INIT_LIST_HEAD(&neigh_node->bonding_list);
        batadv_neigh_node_free_ref(neigh_node);
        atomic_dec(&orig_node->bond_candidates);

out:
        return;
}

void batadv_bonding_candidate_add(struct batadv_orig_node *orig_node,
                                  struct batadv_neigh_node *neigh_node)
{
        struct hlist_node *node;
        struct batadv_neigh_node *tmp_neigh_node, *router = NULL;
        uint8_t interference_candidate = 0;

        spin_lock_bh(&orig_node->neigh_list_lock);

        /* only consider if it has the same primary address ...  */
        if (!batadv_compare_eth(orig_node->orig,
                                neigh_node->orig_node->primary_addr))
                goto candidate_del;

        router = batadv_orig_node_get_router(orig_node);
        if (!router)
                goto candidate_del;

        /* ... and is good enough to be considered */
        if (neigh_node->tq_avg < router->tq_avg - BATADV_BONDING_TQ_THRESHOLD)
                goto candidate_del;

        /* check if we have another candidate with the same mac address or
         * interface. If we do, we won't select this candidate because of
         * possible interference.
         */
        hlist_for_each_entry_rcu(tmp_neigh_node, node,
                                 &orig_node->neigh_list, list) {

                if (tmp_neigh_node == neigh_node)
                        continue;

                /* we only care if the other candidate is even
                 * considered as candidate.
                 */
                if (list_empty(&tmp_neigh_node->bonding_list))
                        continue;

                if ((neigh_node->if_incoming == tmp_neigh_node->if_incoming) ||
                    (batadv_compare_eth(neigh_node->addr,
                                        tmp_neigh_node->addr))) {
                        interference_candidate = 1;
                        break;
                }
        }

        /* don't care further if it is an interference candidate */
        if (interference_candidate)
                goto candidate_del;

        /* this neighbor already is part of our candidate list */
        if (!list_empty(&neigh_node->bonding_list))
                goto out;

        if (!atomic_inc_not_zero(&neigh_node->refcount))
                goto out;

        list_add_rcu(&neigh_node->bonding_list, &orig_node->bond_list);
        atomic_inc(&orig_node->bond_candidates);
        goto out;

candidate_del:
        batadv_bonding_candidate_del(orig_node, neigh_node);

out:
        spin_unlock_bh(&orig_node->neigh_list_lock);

        if (router)
                batadv_neigh_node_free_ref(router);
}

/* copy primary address for bonding */
void
batadv_bonding_save_primary(const struct batadv_orig_node *orig_node,
                            struct batadv_orig_node *orig_neigh_node,
                            const struct batadv_ogm_packet *batman_ogm_packet)
{
        if (!(batman_ogm_packet->flags & BATADV_PRIMARIES_FIRST_HOP))
                return;

        memcpy(orig_neigh_node->primary_addr, orig_node->orig, ETH_ALEN);
}

/* checks whether the host restarted and is in the protection time.
 * returns:
 *  0 if the packet is to be accepted
 *  1 if the packet is to be ignored.
 */
int batadv_window_protected(struct batadv_priv *bat_priv, int32_t seq_num_diff,
                            unsigned long *last_reset)
{
        if (seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE ||
            seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE) {
                if (!batadv_has_timed_out(*last_reset,
                                          BATADV_RESET_PROTECTION_MS))
                        return 1;

                *last_reset = jiffies;
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "old packet received, start protection\n");
        }

        return 0;
}

bool batadv_check_management_packet(struct sk_buff *skb,
                                    struct batadv_hard_iface *hard_iface,
                                    int header_len)
{
        struct ethhdr *ethhdr;

        /* drop packet if it has not necessary minimum size */
        if (unlikely(!pskb_may_pull(skb, header_len)))
                return false;

        ethhdr = (struct ethhdr *)skb_mac_header(skb);

        /* packet with broadcast indication but unicast recipient */
        if (!is_broadcast_ether_addr(ethhdr->h_dest))
                return false;

        /* packet with broadcast sender address */
        if (is_broadcast_ether_addr(ethhdr->h_source))
                return false;

        /* create a copy of the skb, if needed, to modify it. */
        if (skb_cow(skb, 0) < 0)
                return false;

        /* keep skb linear */
        if (skb_linearize(skb) < 0)
                return false;

        return true;
}

static int batadv_recv_my_icmp_packet(struct batadv_priv *bat_priv,
                                      struct sk_buff *skb, size_t icmp_len)
{
        struct batadv_hard_iface *primary_if = NULL;
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_icmp_packet_rr *icmp_packet;
        int ret = NET_RX_DROP;

        icmp_packet = (struct batadv_icmp_packet_rr *)skb->data;

        /* add data to device queue */
        if (icmp_packet->msg_type != BATADV_ECHO_REQUEST) {
                batadv_socket_receive_packet(icmp_packet, icmp_len);
                goto out;
        }

        primary_if = batadv_primary_if_get_selected(bat_priv);
        if (!primary_if)
                goto out;

        /* answer echo request (ping) */
        /* get routing information */
        orig_node = batadv_orig_hash_find(bat_priv, icmp_packet->orig);
        if (!orig_node)
                goto out;

        /* create a copy of the skb, if needed, to modify it. */
        if (skb_cow(skb, ETH_HLEN) < 0)
                goto out;

        icmp_packet = (struct batadv_icmp_packet_rr *)skb->data;

        memcpy(icmp_packet->dst, icmp_packet->orig, ETH_ALEN);
        memcpy(icmp_packet->orig, primary_if->net_dev->dev_addr, ETH_ALEN);
        icmp_packet->msg_type = BATADV_ECHO_REPLY;
        icmp_packet->header.ttl = BATADV_TTL;

        if (batadv_send_skb_to_orig(skb, orig_node, NULL))
                ret = NET_RX_SUCCESS;

out:
        if (primary_if)
                batadv_hardif_free_ref(primary_if);
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}

static int batadv_recv_icmp_ttl_exceeded(struct batadv_priv *bat_priv,
                                         struct sk_buff *skb)
{
        struct batadv_hard_iface *primary_if = NULL;
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_icmp_packet *icmp_packet;
        int ret = NET_RX_DROP;

        icmp_packet = (struct batadv_icmp_packet *)skb->data;

        /* send TTL exceeded if packet is an echo request (traceroute) */
        if (icmp_packet->msg_type != BATADV_ECHO_REQUEST) {
                pr_debug("Warning - can't forward icmp packet from %pM to %pM: ttl exceeded\n",
                         icmp_packet->orig, icmp_packet->dst);
                goto out;
        }

        primary_if = batadv_primary_if_get_selected(bat_priv);
        if (!primary_if)
                goto out;

        /* get routing information */
        orig_node = batadv_orig_hash_find(bat_priv, icmp_packet->orig);
        if (!orig_node)
                goto out;

        /* create a copy of the skb, if needed, to modify it. */
        if (skb_cow(skb, ETH_HLEN) < 0)
                goto out;

        icmp_packet = (struct batadv_icmp_packet *)skb->data;

        memcpy(icmp_packet->dst, icmp_packet->orig, ETH_ALEN);
        memcpy(icmp_packet->orig, primary_if->net_dev->dev_addr, ETH_ALEN);
        icmp_packet->msg_type = BATADV_TTL_EXCEEDED;
        icmp_packet->header.ttl = BATADV_TTL;

        if (batadv_send_skb_to_orig(skb, orig_node, NULL))
                ret = NET_RX_SUCCESS;

out:
        if (primary_if)
                batadv_hardif_free_ref(primary_if);
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}


int batadv_recv_icmp_packet(struct sk_buff *skb,
                            struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_icmp_packet_rr *icmp_packet;
        struct ethhdr *ethhdr;
        struct batadv_orig_node *orig_node = NULL;
        int hdr_size = sizeof(struct batadv_icmp_packet);
        int ret = NET_RX_DROP;

        /* we truncate all incoming icmp packets if they don't match our size */
        if (skb->len >= sizeof(struct batadv_icmp_packet_rr))
                hdr_size = sizeof(struct batadv_icmp_packet_rr);

        /* drop packet if it has not necessary minimum size */
        if (unlikely(!pskb_may_pull(skb, hdr_size)))
                goto out;

        ethhdr = (struct ethhdr *)skb_mac_header(skb);

        /* packet with unicast indication but broadcast recipient */
        if (is_broadcast_ether_addr(ethhdr->h_dest))
                goto out;

        /* packet with broadcast sender address */
        if (is_broadcast_ether_addr(ethhdr->h_source))
                goto out;

        /* not for me */
        if (!batadv_is_my_mac(ethhdr->h_dest))
                goto out;

        icmp_packet = (struct batadv_icmp_packet_rr *)skb->data;

        /* add record route information if not full */
        if ((hdr_size == sizeof(struct batadv_icmp_packet_rr)) &&
            (icmp_packet->rr_cur < BATADV_RR_LEN)) {
                memcpy(&(icmp_packet->rr[icmp_packet->rr_cur]),
                       ethhdr->h_dest, ETH_ALEN);
                icmp_packet->rr_cur++;
        }

        /* packet for me */
        if (batadv_is_my_mac(icmp_packet->dst))
                return batadv_recv_my_icmp_packet(bat_priv, skb, hdr_size);

        /* TTL exceeded */
        if (icmp_packet->header.ttl < 2)
                return batadv_recv_icmp_ttl_exceeded(bat_priv, skb);

        /* get routing information */
        orig_node = batadv_orig_hash_find(bat_priv, icmp_packet->dst);
        if (!orig_node)
                goto out;

        /* create a copy of the skb, if needed, to modify it. */
        if (skb_cow(skb, ETH_HLEN) < 0)
                goto out;

        icmp_packet = (struct batadv_icmp_packet_rr *)skb->data;

        /* decrement ttl */
        icmp_packet->header.ttl--;

        /* route it */
        if (batadv_send_skb_to_orig(skb, orig_node, recv_if))
                ret = NET_RX_SUCCESS;

out:
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}

/* In the bonding case, send the packets in a round
 * robin fashion over the remaining interfaces.
 *
 * This method rotates the bonding list and increases the
 * returned router's refcount.
 */
static struct batadv_neigh_node *
batadv_find_bond_router(struct batadv_orig_node *primary_orig,
                        const struct batadv_hard_iface *recv_if)
{
        struct batadv_neigh_node *tmp_neigh_node;
        struct batadv_neigh_node *router = NULL, *first_candidate = NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(tmp_neigh_node, &primary_orig->bond_list,
                                bonding_list) {
                if (!first_candidate)
                        first_candidate = tmp_neigh_node;

                /* recv_if == NULL on the first node. */
                if (tmp_neigh_node->if_incoming == recv_if)
                        continue;

                if (!atomic_inc_not_zero(&tmp_neigh_node->refcount))
                        continue;

                router = tmp_neigh_node;
                break;
        }

        /* use the first candidate if nothing was found. */
        if (!router && first_candidate &&
            atomic_inc_not_zero(&first_candidate->refcount))
                router = first_candidate;

        if (!router)
                goto out;

        /* selected should point to the next element
         * after the current router
         */
        spin_lock_bh(&primary_orig->neigh_list_lock);
        /* this is a list_move(), which unfortunately
         * does not exist as rcu version
         */
        list_del_rcu(&primary_orig->bond_list);
        list_add_rcu(&primary_orig->bond_list,
                     &router->bonding_list);
        spin_unlock_bh(&primary_orig->neigh_list_lock);

out:
        rcu_read_unlock();
        return router;
}

/* Interface Alternating: Use the best of the
 * remaining candidates which are not using
 * this interface.
 *
 * Increases the returned router's refcount
 */
static struct batadv_neigh_node *
batadv_find_ifalter_router(struct batadv_orig_node *primary_orig,
                           const struct batadv_hard_iface *recv_if)
{
        struct batadv_neigh_node *tmp_neigh_node;
        struct batadv_neigh_node *router = NULL, *first_candidate = NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(tmp_neigh_node, &primary_orig->bond_list,
                                bonding_list) {
                if (!first_candidate)
                        first_candidate = tmp_neigh_node;

                /* recv_if == NULL on the first node. */
                if (tmp_neigh_node->if_incoming == recv_if)
                        continue;

                if (router && tmp_neigh_node->tq_avg <= router->tq_avg)
                        continue;

                if (!atomic_inc_not_zero(&tmp_neigh_node->refcount))
                        continue;

                /* decrement refcount of previously selected router */
                if (router)
                        batadv_neigh_node_free_ref(router);

                /* we found a better router (or at least one valid router) */
                router = tmp_neigh_node;
        }

        /* use the first candidate if nothing was found. */
        if (!router && first_candidate &&
            atomic_inc_not_zero(&first_candidate->refcount))
                router = first_candidate;

        rcu_read_unlock();
        return router;
}

static int batadv_check_unicast_packet(struct sk_buff *skb, int hdr_size)
{
        struct ethhdr *ethhdr;

        /* drop packet if it has not necessary minimum size */
        if (unlikely(!pskb_may_pull(skb, hdr_size)))
                return -1;

        ethhdr = (struct ethhdr *)skb_mac_header(skb);

        /* packet with unicast indication but broadcast recipient */
        if (is_broadcast_ether_addr(ethhdr->h_dest))
                return -1;

        /* packet with broadcast sender address */
        if (is_broadcast_ether_addr(ethhdr->h_source))
                return -1;

        /* not for me */
        if (!batadv_is_my_mac(ethhdr->h_dest))
                return -1;

        return 0;
}

int batadv_recv_tt_query(struct sk_buff *skb, struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_tt_query_packet *tt_query;
        uint16_t tt_size;
        int hdr_size = sizeof(*tt_query);
        char tt_flag;
        size_t packet_size;

        if (batadv_check_unicast_packet(skb, hdr_size) < 0)
                return NET_RX_DROP;

        /* I could need to modify it */
        if (skb_cow(skb, sizeof(struct batadv_tt_query_packet)) < 0)
                goto out;

        tt_query = (struct batadv_tt_query_packet *)skb->data;

        switch (tt_query->flags & BATADV_TT_QUERY_TYPE_MASK) {
        case BATADV_TT_REQUEST:
                batadv_inc_counter(bat_priv, BATADV_CNT_TT_REQUEST_RX);

                /* If we cannot provide an answer the tt_request is
                 * forwarded
                 */
                if (!batadv_send_tt_response(bat_priv, tt_query)) {
                        if (tt_query->flags & BATADV_TT_FULL_TABLE)
                                tt_flag = 'F';
                        else
                                tt_flag = '.';

                        batadv_dbg(BATADV_DBG_TT, bat_priv,
                                   "Routing TT_REQUEST to %pM [%c]\n",
                                   tt_query->dst,
                                   tt_flag);
                        return batadv_route_unicast_packet(skb, recv_if);
                }
                break;
        case BATADV_TT_RESPONSE:
                batadv_inc_counter(bat_priv, BATADV_CNT_TT_RESPONSE_RX);

                if (batadv_is_my_mac(tt_query->dst)) {
                        /* packet needs to be linearized to access the TT
                         * changes
                         */
                        if (skb_linearize(skb) < 0)
                                goto out;
                        /* skb_linearize() possibly changed skb->data */
                        tt_query = (struct batadv_tt_query_packet *)skb->data;

                        tt_size = batadv_tt_len(ntohs(tt_query->tt_data));

                        /* Ensure we have all the claimed data */
                        packet_size = sizeof(struct batadv_tt_query_packet);
                        packet_size += tt_size;
                        if (unlikely(skb_headlen(skb) < packet_size))
                                goto out;

                        batadv_handle_tt_response(bat_priv, tt_query);
                } else {
                        if (tt_query->flags & BATADV_TT_FULL_TABLE)
                                tt_flag =  'F';
                        else
                                tt_flag = '.';
                        batadv_dbg(BATADV_DBG_TT, bat_priv,
                                   "Routing TT_RESPONSE to %pM [%c]\n",
                                   tt_query->dst,
                                   tt_flag);
                        return batadv_route_unicast_packet(skb, recv_if);
                }
                break;
        }

out:
        /* returning NET_RX_DROP will make the caller function kfree the skb */
        return NET_RX_DROP;
}

int batadv_recv_roam_adv(struct sk_buff *skb, struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_roam_adv_packet *roam_adv_packet;
        struct batadv_orig_node *orig_node;

        if (batadv_check_unicast_packet(skb, sizeof(*roam_adv_packet)) < 0)
                goto out;

        batadv_inc_counter(bat_priv, BATADV_CNT_TT_ROAM_ADV_RX);

        roam_adv_packet = (struct batadv_roam_adv_packet *)skb->data;

        if (!batadv_is_my_mac(roam_adv_packet->dst))
                return batadv_route_unicast_packet(skb, recv_if);

        /* check if it is a backbone gateway. we don't accept
         * roaming advertisement from it, as it has the same
         * entries as we have.
         */
        if (batadv_bla_is_backbone_gw_orig(bat_priv, roam_adv_packet->src))
                goto out;

        orig_node = batadv_orig_hash_find(bat_priv, roam_adv_packet->src);
        if (!orig_node)
                goto out;

        batadv_dbg(BATADV_DBG_TT, bat_priv,
                   "Received ROAMING_ADV from %pM (client %pM)\n",
                   roam_adv_packet->src, roam_adv_packet->client);

        batadv_tt_global_add(bat_priv, orig_node, roam_adv_packet->client,
                             BATADV_TT_CLIENT_ROAM,
                             atomic_read(&orig_node->last_ttvn) + 1);

        batadv_orig_node_free_ref(orig_node);
out:
        /* returning NET_RX_DROP will make the caller function kfree the skb */
        return NET_RX_DROP;
}

/* find a suitable router for this originator, and use
 * bonding if possible. increases the found neighbors
 * refcount.
 */
struct batadv_neigh_node *
batadv_find_router(struct batadv_priv *bat_priv,
                   struct batadv_orig_node *orig_node,
                   const struct batadv_hard_iface *recv_if)
{
        struct batadv_orig_node *primary_orig_node;
        struct batadv_orig_node *router_orig;
        struct batadv_neigh_node *router;
        static uint8_t zero_mac[ETH_ALEN] = {0, 0, 0, 0, 0, 0};
        int bonding_enabled;
        uint8_t *primary_addr;

        if (!orig_node)
                return NULL;

        router = batadv_orig_node_get_router(orig_node);
        if (!router)
                goto err;

        /* without bonding, the first node should
         * always choose the default router.
         */
        bonding_enabled = atomic_read(&bat_priv->bonding);

        rcu_read_lock();
        /* select default router to output */
        router_orig = router->orig_node;
        if (!router_orig)
                goto err_unlock;

        if ((!recv_if) && (!bonding_enabled))
                goto return_router;

        primary_addr = router_orig->primary_addr;

        /* if we have something in the primary_addr, we can search
         * for a potential bonding candidate.
         */
        if (batadv_compare_eth(primary_addr, zero_mac))
                goto return_router;

        /* find the orig_node which has the primary interface. might
         * even be the same as our router_orig in many cases
         */
        if (batadv_compare_eth(primary_addr, router_orig->orig)) {
                primary_orig_node = router_orig;
        } else {
                primary_orig_node = batadv_orig_hash_find(bat_priv,
                                                          primary_addr);
                if (!primary_orig_node)
                        goto return_router;

                batadv_orig_node_free_ref(primary_orig_node);
        }

        /* with less than 2 candidates, we can't do any
         * bonding and prefer the original router.
         */
        if (atomic_read(&primary_orig_node->bond_candidates) < 2)
                goto return_router;

        /* all nodes between should choose a candidate which
         * is is not on the interface where the packet came
         * in.
         */
        batadv_neigh_node_free_ref(router);

        if (bonding_enabled)
                router = batadv_find_bond_router(primary_orig_node, recv_if);
        else
                router = batadv_find_ifalter_router(primary_orig_node, recv_if);

return_router:
        if (router && router->if_incoming->if_status != BATADV_IF_ACTIVE)
                goto err_unlock;

        rcu_read_unlock();
        return router;
err_unlock:
        rcu_read_unlock();
err:
        if (router)
                batadv_neigh_node_free_ref(router);
        return NULL;
}

static int batadv_route_unicast_packet(struct sk_buff *skb,
                                       struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_neigh_node *neigh_node = NULL;
        struct batadv_unicast_packet *unicast_packet;
        struct ethhdr *ethhdr = (struct ethhdr *)skb_mac_header(skb);
        int ret = NET_RX_DROP;
        struct sk_buff *new_skb;

        unicast_packet = (struct batadv_unicast_packet *)skb->data;

        /* TTL exceeded */
        if (unicast_packet->header.ttl < 2) {
                pr_debug("Warning - can't forward unicast packet from %pM to %pM: ttl exceeded\n",
                         ethhdr->h_source, unicast_packet->dest);
                goto out;
        }

        /* get routing information */
        orig_node = batadv_orig_hash_find(bat_priv, unicast_packet->dest);

        if (!orig_node)
                goto out;

        /* find_router() increases neigh_nodes refcount if found. */
        neigh_node = batadv_find_router(bat_priv, orig_node, recv_if);

        if (!neigh_node)
                goto out;

        /* create a copy of the skb, if needed, to modify it. */
        if (skb_cow(skb, ETH_HLEN) < 0)
                goto out;

        unicast_packet = (struct batadv_unicast_packet *)skb->data;

        if (unicast_packet->header.packet_type == BATADV_UNICAST &&
            atomic_read(&bat_priv->fragmentation) &&
            skb->len > neigh_node->if_incoming->net_dev->mtu) {
                ret = batadv_frag_send_skb(skb, bat_priv,
                                           neigh_node->if_incoming,
                                           neigh_node->addr);
                goto out;
        }

        if (unicast_packet->header.packet_type == BATADV_UNICAST_FRAG &&
            batadv_frag_can_reassemble(skb,
                                       neigh_node->if_incoming->net_dev->mtu)) {

                ret = batadv_frag_reassemble_skb(skb, bat_priv, &new_skb);

                if (ret == NET_RX_DROP)
                        goto out;

                /* packet was buffered for late merge */
                if (!new_skb) {
                        ret = NET_RX_SUCCESS;
                        goto out;
                }

                skb = new_skb;
                unicast_packet = (struct batadv_unicast_packet *)skb->data;
        }

        /* decrement ttl */
        unicast_packet->header.ttl--;

        /* Update stats counter */
        batadv_inc_counter(bat_priv, BATADV_CNT_FORWARD);
        batadv_add_counter(bat_priv, BATADV_CNT_FORWARD_BYTES,
                           skb->len + ETH_HLEN);

        /* route it */
        if (batadv_send_skb_to_orig(skb, orig_node, recv_if))
                ret = NET_RX_SUCCESS;

out:
        if (neigh_node)
                batadv_neigh_node_free_ref(neigh_node);
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}

/**
 * batadv_reroute_unicast_packet - update the unicast header for re-routing
 * @bat_priv: the bat priv with all the soft interface information
 * @unicast_packet: the unicast header to be updated
 * @dst_addr: the payload destination
 *
 * Search the translation table for dst_addr and update the unicast header with
 * the new corresponding information (originator address where the destination
 * client currently is and its known TTVN)
 *
 * Returns true if the packet header has been updated, false otherwise
 */
static bool
batadv_reroute_unicast_packet(struct batadv_priv *bat_priv,
                              struct batadv_unicast_packet *unicast_packet,
                              uint8_t *dst_addr)
{
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_hard_iface *primary_if = NULL;
        bool ret = false;
        uint8_t *orig_addr, orig_ttvn;

        if (batadv_is_my_client(bat_priv, dst_addr)) {
                primary_if = batadv_primary_if_get_selected(bat_priv);
                if (!primary_if)
                        goto out;
                orig_addr = primary_if->net_dev->dev_addr;
                orig_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
        } else {
                orig_node = batadv_transtable_search(bat_priv, NULL, dst_addr);
                if (!orig_node)
                        goto out;

                if (batadv_compare_eth(orig_node->orig, unicast_packet->dest))
                        goto out;

                orig_addr = orig_node->orig;
                orig_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
        }

        /* update the packet header */
        memcpy(unicast_packet->dest, orig_addr, ETH_ALEN);
        unicast_packet->ttvn = orig_ttvn;

        ret = true;
out:
        if (primary_if)
                batadv_hardif_free_ref(primary_if);
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);

        return ret;
}

static int batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
                                     struct sk_buff *skb) {
        uint8_t curr_ttvn, old_ttvn;
        struct batadv_orig_node *orig_node;
        struct ethhdr *ethhdr;
        struct batadv_hard_iface *primary_if;
        struct batadv_unicast_packet *unicast_packet;
        int is_old_ttvn;

        /* check if there is enough data before accessing it */
        if (pskb_may_pull(skb, sizeof(*unicast_packet) + ETH_HLEN) < 0)
                return 0;

        /* create a copy of the skb (in case of for re-routing) to modify it. */
        if (skb_cow(skb, sizeof(*unicast_packet)) < 0)
                return 0;

        unicast_packet = (struct batadv_unicast_packet *)skb->data;
        ethhdr = (struct ethhdr *)(skb->data + sizeof(*unicast_packet));

        /* check if the destination client was served by this node and it is now
         * roaming. In this case, it means that the node has got a ROAM_ADV
         * message and that it knows the new destination in the mesh to re-route
         * the packet to
         */
        if (batadv_tt_local_client_is_roaming(bat_priv, ethhdr->h_dest)) {
                if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
                                                  ethhdr->h_dest))
                        net_ratelimited_function(batadv_dbg, BATADV_DBG_TT,
                                                 bat_priv,
                                                 "Rerouting unicast packet to %pM (dst=%pM): Local Roaming\n",
                                                 unicast_packet->dest,
                                                 ethhdr->h_dest);
                /* at this point the mesh destination should have been
                 * substituted with the originator address found in the global
                 * table. If not, let the packet go untouched anyway because
                 * there is nothing the node can do
                 */
                return 1;
        }

        /* retrieve the TTVN known by this node for the packet destination. This
         * value is used later to check if the node which sent (or re-routed
         * last time) the packet had an updated information or not
         */
        curr_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
        if (!batadv_is_my_mac(unicast_packet->dest)) {
                orig_node = batadv_orig_hash_find(bat_priv,
                                                  unicast_packet->dest);
                /* if it is not possible to find the orig_node representing the
                 * destination, the packet can immediately be dropped as it will
                 * not be possible to deliver it
                 */
                if (!orig_node)
                        return 0;

                curr_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
                batadv_orig_node_free_ref(orig_node);
        }

        /* check if the TTVN contained in the packet is fresher than what the
         * node knows
         */
        is_old_ttvn = batadv_seq_before(unicast_packet->ttvn, curr_ttvn);
        if (!is_old_ttvn)
                return 1;

        old_ttvn = unicast_packet->ttvn;
        /* the packet was forged based on outdated network information. Its
         * destination can possibly be updated and forwarded towards the new
         * target host
         */
        if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
                                          ethhdr->h_dest)) {
                net_ratelimited_function(batadv_dbg, BATADV_DBG_TT, bat_priv,
                                         "Rerouting unicast packet to %pM (dst=%pM): TTVN mismatch old_ttvn=%u new_ttvn=%u\n",
                                         unicast_packet->dest, ethhdr->h_dest,
                                         old_ttvn, curr_ttvn);
                return 1;
        }

        /* the packet has not been re-routed: either the destination is
         * currently served by this node or there is no destination at all and
         * it is possible to drop the packet
         */
        if (!batadv_is_my_client(bat_priv, ethhdr->h_dest))
                return 0;

        /* update the header in order to let the packet be delivered to this
         * node's soft interface
         */
        primary_if = batadv_primary_if_get_selected(bat_priv);
        if (!primary_if)
                return 0;

        memcpy(unicast_packet->dest, primary_if->net_dev->dev_addr, ETH_ALEN);

        batadv_hardif_free_ref(primary_if);

        unicast_packet->ttvn = curr_ttvn;

        return 1;
}

int batadv_recv_unicast_packet(struct sk_buff *skb,
                               struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_unicast_packet *unicast_packet;
        struct batadv_unicast_4addr_packet *unicast_4addr_packet;
        uint8_t *orig_addr;
        struct batadv_orig_node *orig_node = NULL;
        int hdr_size = sizeof(*unicast_packet);
        bool is4addr;

        unicast_packet = (struct batadv_unicast_packet *)skb->data;
        unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;

        is4addr = unicast_packet->header.packet_type == BATADV_UNICAST_4ADDR;
        /* the caller function should have already pulled 2 bytes */
        if (is4addr)
                hdr_size = sizeof(*unicast_4addr_packet);

        if (batadv_check_unicast_packet(skb, hdr_size) < 0)
                return NET_RX_DROP;

        if (!batadv_check_unicast_ttvn(bat_priv, skb))
                return NET_RX_DROP;

        /* packet for me */
        if (batadv_is_my_mac(unicast_packet->dest)) {
                if (is4addr) {
                        batadv_dat_inc_counter(bat_priv,
                                               unicast_4addr_packet->subtype);
                        orig_addr = unicast_4addr_packet->src;
                        orig_node = batadv_orig_hash_find(bat_priv, orig_addr);
                }

                if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb,
                                                          hdr_size))
                        goto rx_success;
                if (batadv_dat_snoop_incoming_arp_reply(bat_priv, skb,
                                                        hdr_size))
                        goto rx_success;

                batadv_interface_rx(recv_if->soft_iface, skb, recv_if, hdr_size,
                                    orig_node);

rx_success:
                if (orig_node)
                        batadv_orig_node_free_ref(orig_node);

                return NET_RX_SUCCESS;
        }

        return batadv_route_unicast_packet(skb, recv_if);
}

int batadv_recv_ucast_frag_packet(struct sk_buff *skb,
                                  struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_unicast_frag_packet *unicast_packet;
        int hdr_size = sizeof(*unicast_packet);
        struct sk_buff *new_skb = NULL;
        int ret;

        if (batadv_check_unicast_packet(skb, hdr_size) < 0)
                return NET_RX_DROP;

        if (!batadv_check_unicast_ttvn(bat_priv, skb))
                return NET_RX_DROP;

        unicast_packet = (struct batadv_unicast_frag_packet *)skb->data;

        /* packet for me */
        if (batadv_is_my_mac(unicast_packet->dest)) {

                ret = batadv_frag_reassemble_skb(skb, bat_priv, &new_skb);

                if (ret == NET_RX_DROP)
                        return NET_RX_DROP;

                /* packet was buffered for late merge */
                if (!new_skb)
                        return NET_RX_SUCCESS;

                if (batadv_dat_snoop_incoming_arp_request(bat_priv, new_skb,
                                                          hdr_size))
                        goto rx_success;
                if (batadv_dat_snoop_incoming_arp_reply(bat_priv, new_skb,
                                                        hdr_size))
                        goto rx_success;

                batadv_interface_rx(recv_if->soft_iface, new_skb, recv_if,
                                    sizeof(struct batadv_unicast_packet), NULL);

rx_success:
                return NET_RX_SUCCESS;
        }

        return batadv_route_unicast_packet(skb, recv_if);
}


int batadv_recv_bcast_packet(struct sk_buff *skb,
                             struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_bcast_packet *bcast_packet;
        struct ethhdr *ethhdr;
        int hdr_size = sizeof(*bcast_packet);
        int ret = NET_RX_DROP;
        int32_t seq_diff;

        /* drop packet if it has not necessary minimum size */
        if (unlikely(!pskb_may_pull(skb, hdr_size)))
                goto out;

        ethhdr = (struct ethhdr *)skb_mac_header(skb);

        /* packet with broadcast indication but unicast recipient */
        if (!is_broadcast_ether_addr(ethhdr->h_dest))
                goto out;

        /* packet with broadcast sender address */
        if (is_broadcast_ether_addr(ethhdr->h_source))
                goto out;

        /* ignore broadcasts sent by myself */
        if (batadv_is_my_mac(ethhdr->h_source))
                goto out;

        bcast_packet = (struct batadv_bcast_packet *)skb->data;

        /* ignore broadcasts originated by myself */
        if (batadv_is_my_mac(bcast_packet->orig))
                goto out;

        if (bcast_packet->header.ttl < 2)
                goto out;

        orig_node = batadv_orig_hash_find(bat_priv, bcast_packet->orig);

        if (!orig_node)
                goto out;

        spin_lock_bh(&orig_node->bcast_seqno_lock);

        /* check whether the packet is a duplicate */
        if (batadv_test_bit(orig_node->bcast_bits, orig_node->last_bcast_seqno,
                            ntohl(bcast_packet->seqno)))
                goto spin_unlock;

        seq_diff = ntohl(bcast_packet->seqno) - orig_node->last_bcast_seqno;

        /* check whether the packet is old and the host just restarted. */
        if (batadv_window_protected(bat_priv, seq_diff,
                                    &orig_node->bcast_seqno_reset))
                goto spin_unlock;

        /* mark broadcast in flood history, update window position
         * if required.
         */
        if (batadv_bit_get_packet(bat_priv, orig_node->bcast_bits, seq_diff, 1))
                orig_node->last_bcast_seqno = ntohl(bcast_packet->seqno);

        spin_unlock_bh(&orig_node->bcast_seqno_lock);

        /* check whether this has been sent by another originator before */
        if (batadv_bla_check_bcast_duplist(bat_priv, skb))
                goto out;

        /* rebroadcast packet */
        batadv_add_bcast_packet_to_list(bat_priv, skb, 1);

        /* don't hand the broadcast up if it is from an originator
         * from the same backbone.
         */
        if (batadv_bla_is_backbone_gw(skb, orig_node, hdr_size))
                goto out;

        if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb, hdr_size))
                goto rx_success;
        if (batadv_dat_snoop_incoming_arp_reply(bat_priv, skb, hdr_size))
                goto rx_success;

        /* broadcast for me */
        batadv_interface_rx(recv_if->soft_iface, skb, recv_if, hdr_size,
                            orig_node);

rx_success:
        ret = NET_RX_SUCCESS;
        goto out;

spin_unlock:
        spin_unlock_bh(&orig_node->bcast_seqno_lock);
out:
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}

int batadv_recv_vis_packet(struct sk_buff *skb,
                           struct batadv_hard_iface *recv_if)
{
        struct batadv_vis_packet *vis_packet;
        struct ethhdr *ethhdr;
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        int hdr_size = sizeof(*vis_packet);

        /* keep skb linear */
        if (skb_linearize(skb) < 0)
                return NET_RX_DROP;

        if (unlikely(!pskb_may_pull(skb, hdr_size)))
                return NET_RX_DROP;

        vis_packet = (struct batadv_vis_packet *)skb->data;
        ethhdr = (struct ethhdr *)skb_mac_header(skb);

        /* not for me */
        if (!batadv_is_my_mac(ethhdr->h_dest))
                return NET_RX_DROP;

        /* ignore own packets */
        if (batadv_is_my_mac(vis_packet->vis_orig))
                return NET_RX_DROP;

        if (batadv_is_my_mac(vis_packet->sender_orig))
                return NET_RX_DROP;

        switch (vis_packet->vis_type) {
        case BATADV_VIS_TYPE_SERVER_SYNC:
                batadv_receive_server_sync_packet(bat_priv, vis_packet,
                                                  skb_headlen(skb));
                break;

        case BATADV_VIS_TYPE_CLIENT_UPDATE:
                batadv_receive_client_update_packet(bat_priv, vis_packet,
                                                    skb_headlen(skb));
                break;

        default:        /* ignore unknown packet */
                break;
        }

        /* We take a copy of the data in the packet, so we should
         * always free the skbuf.
         */
        return NET_RX_DROP;
}