routing.c

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/* 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"

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_neigh_node *router = 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;

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

    batadv_send_skb_packet(skb, router->if_incoming, router->addr);
    ret = NET_RX_SUCCESS;

out:
    if (primary_if)
        batadv_hardif_free_ref(primary_if);
    if (router)
        batadv_neigh_node_free_ref(router);
    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_neigh_node *router = 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;

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

    batadv_send_skb_packet(skb, router->if_incoming, router->addr);
    ret = NET_RX_SUCCESS;

out:
    if (primary_if)
        batadv_hardif_free_ref(primary_if);
    if (router)
        batadv_neigh_node_free_ref(router);
    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;
    struct batadv_neigh_node *router = 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;

    router = batadv_orig_node_get_router(orig_node);
    if (!router)
        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 */
    batadv_send_skb_packet(skb, router->if_incoming, router->addr);
    ret = NET_RX_SUCCESS;

out:
    if (router)
        batadv_neigh_node_free_ref(router);
    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 (!atomic_inc_not_zero(&tmp_neigh_node->refcount))
            continue;

        /* if we don't have a router yet
         * or this one is better, choose it.
         */
        if ((!router) ||
            (tmp_neigh_node->tq_avg > router->tq_avg)) {
            /* decrement refcount of
             * previously selected router
             */
            if (router)
                batadv_neigh_node_free_ref(router);

            router = tmp_neigh_node;
            atomic_inc_not_zero(&router->refcount);
        }

        batadv_neigh_node_free_ref(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;
    struct ethhdr *ethhdr;

    /* drop packet if it has not necessary minimum size */
    if (unlikely(!pskb_may_pull(skb,
                    sizeof(struct batadv_roam_adv_packet))))
        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;

    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);

    /* Roaming phase starts: I have new information but the ttvn has not
     * been incremented yet. This flag will make me check all the incoming
     * packets for the correct destination.
     */
    bat_priv->tt.poss_change = true;

    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 */
    batadv_send_skb_packet(skb, neigh_node->if_incoming, neigh_node->addr);
    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;
}

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

    /* I could need to modify it */
    if (skb_cow(skb, sizeof(struct batadv_unicast_packet)) < 0)
        return 0;

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

    if (batadv_is_my_mac(unicast_packet->dest)) {
        tt_poss_change = bat_priv->tt.poss_change;
        curr_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
    } else {
        orig_node = batadv_orig_hash_find(bat_priv,
                          unicast_packet->dest);

        if (!orig_node)
            return 0;

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

    /* Check whether I have to reroute the packet */
    is_old_ttvn = batadv_seq_before(unicast_packet->ttvn, curr_ttvn);
    if (is_old_ttvn || tt_poss_change) {
        /* check if there is enough data before accessing it */
        if (pskb_may_pull(skb, sizeof(struct batadv_unicast_packet) +
                  ETH_HLEN) < 0)
            return 0;

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

        /* we don't have an updated route for this client, so we should
         * not try to reroute the packet!!
         */
        if (batadv_tt_global_client_is_roaming(bat_priv,
                               ethhdr->h_dest))
            return 1;

        orig_node = batadv_transtable_search(bat_priv, NULL,
                             ethhdr->h_dest);

        if (!orig_node) {
            if (!batadv_is_my_client(bat_priv, ethhdr->h_dest))
                return 0;
            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);
        } else {
            memcpy(unicast_packet->dest, orig_node->orig,
                   ETH_ALEN);
            curr_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
            batadv_orig_node_free_ref(orig_node);
        }

        batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
               "TTVN mismatch (old_ttvn %u new_ttvn %u)! Rerouting unicast packet (for %pM) to %pM\n",
               unicast_packet->ttvn, curr_ttvn, ethhdr->h_dest,
               unicast_packet->dest);

        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;
    int hdr_size = sizeof(*unicast_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;

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

    /* packet for me */
    if (batadv_is_my_mac(unicast_packet->dest)) {
        batadv_interface_rx(recv_if->soft_iface, skb, recv_if, hdr_size,
                    NULL);

        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;

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

    /* keep skb linear for crc calculation */
    if (skb_linearize(skb) < 0)
        goto out;

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

    /* check whether this has been sent by another originator before */
    if (batadv_bla_check_bcast_duplist(bat_priv, bcast_packet, skb->len))
        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;

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