bat_iv_ogm.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 "translation-table.h"
#include "ring_buffer.h"
#include "originator.h"
#include "routing.h"
#include "gateway_common.h"
#include "gateway_client.h"
#include "hard-interface.h"
#include "send.h"
#include "bat_algo.h"

static struct batadv_neigh_node *
batadv_iv_ogm_neigh_new(struct batadv_hard_iface *hard_iface,
            const uint8_t *neigh_addr,
            struct batadv_orig_node *orig_node,
            struct batadv_orig_node *orig_neigh, __be32 seqno)
{
    struct batadv_neigh_node *neigh_node;

    neigh_node = batadv_neigh_node_new(hard_iface, neigh_addr,
                       ntohl(seqno));
    if (!neigh_node)
        goto out;

    INIT_LIST_HEAD(&neigh_node->bonding_list);

    neigh_node->orig_node = orig_neigh;
    neigh_node->if_incoming = hard_iface;

    spin_lock_bh(&orig_node->neigh_list_lock);
    hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list);
    spin_unlock_bh(&orig_node->neigh_list_lock);

out:
    return neigh_node;
}

static int batadv_iv_ogm_iface_enable(struct batadv_hard_iface *hard_iface)
{
    struct batadv_ogm_packet *batadv_ogm_packet;
    uint32_t random_seqno;
    int res = -ENOMEM;

    /* randomize initial seqno to avoid collision */
    get_random_bytes(&random_seqno, sizeof(random_seqno));
    atomic_set(&hard_iface->seqno, random_seqno);

    hard_iface->packet_len = BATADV_OGM_HLEN;
    hard_iface->packet_buff = kmalloc(hard_iface->packet_len, GFP_ATOMIC);

    if (!hard_iface->packet_buff)
        goto out;

    batadv_ogm_packet = (struct batadv_ogm_packet *)hard_iface->packet_buff;
    batadv_ogm_packet->header.packet_type = BATADV_IV_OGM;
    batadv_ogm_packet->header.version = BATADV_COMPAT_VERSION;
    batadv_ogm_packet->header.ttl = 2;
    batadv_ogm_packet->flags = BATADV_NO_FLAGS;
    batadv_ogm_packet->tq = BATADV_TQ_MAX_VALUE;
    batadv_ogm_packet->tt_num_changes = 0;
    batadv_ogm_packet->ttvn = 0;

    res = 0;

out:
    return res;
}

static void batadv_iv_ogm_iface_disable(struct batadv_hard_iface *hard_iface)
{
    kfree(hard_iface->packet_buff);
    hard_iface->packet_buff = NULL;
}

static void batadv_iv_ogm_iface_update_mac(struct batadv_hard_iface *hard_iface)
{
    struct batadv_ogm_packet *batadv_ogm_packet;

    batadv_ogm_packet = (struct batadv_ogm_packet *)hard_iface->packet_buff;
    memcpy(batadv_ogm_packet->orig,
           hard_iface->net_dev->dev_addr, ETH_ALEN);
    memcpy(batadv_ogm_packet->prev_sender,
           hard_iface->net_dev->dev_addr, ETH_ALEN);
}

static void
batadv_iv_ogm_primary_iface_set(struct batadv_hard_iface *hard_iface)
{
    struct batadv_ogm_packet *batadv_ogm_packet;

    batadv_ogm_packet = (struct batadv_ogm_packet *)hard_iface->packet_buff;
    batadv_ogm_packet->flags = BATADV_PRIMARIES_FIRST_HOP;
    batadv_ogm_packet->header.ttl = BATADV_TTL;
}

/* when do we schedule our own ogm to be sent */
static unsigned long
batadv_iv_ogm_emit_send_time(const struct batadv_priv *bat_priv)
{
    unsigned int msecs;

    msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
    msecs += (random32() % 2 * BATADV_JITTER);

    return jiffies + msecs_to_jiffies(msecs);
}

/* when do we schedule a ogm packet to be sent */
static unsigned long batadv_iv_ogm_fwd_send_time(void)
{
    return jiffies + msecs_to_jiffies(random32() % (BATADV_JITTER / 2));
}

/* apply hop penalty for a normal link */
static uint8_t batadv_hop_penalty(uint8_t tq,
                  const struct batadv_priv *bat_priv)
{
    int hop_penalty = atomic_read(&bat_priv->hop_penalty);
    int new_tq;

    new_tq = tq * (BATADV_TQ_MAX_VALUE - hop_penalty);
    new_tq /= BATADV_TQ_MAX_VALUE;

    return new_tq;
}

/* is there another aggregated packet here? */
static int batadv_iv_ogm_aggr_packet(int buff_pos, int packet_len,
                     int tt_num_changes)
{
    int next_buff_pos = 0;

    next_buff_pos += buff_pos + BATADV_OGM_HLEN;
    next_buff_pos += batadv_tt_len(tt_num_changes);

    return (next_buff_pos <= packet_len) &&
           (next_buff_pos <= BATADV_MAX_AGGREGATION_BYTES);
}

/* send a batman ogm to a given interface */
static void batadv_iv_ogm_send_to_if(struct batadv_forw_packet *forw_packet,
                     struct batadv_hard_iface *hard_iface)
{
    struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
    char *fwd_str;
    uint8_t packet_num;
    int16_t buff_pos;
    struct batadv_ogm_packet *batadv_ogm_packet;
    struct sk_buff *skb;
    uint8_t *packet_pos;

    if (hard_iface->if_status != BATADV_IF_ACTIVE)
        return;

    packet_num = 0;
    buff_pos = 0;
    packet_pos = forw_packet->skb->data;
    batadv_ogm_packet = (struct batadv_ogm_packet *)packet_pos;

    /* adjust all flags and log packets */
    while (batadv_iv_ogm_aggr_packet(buff_pos, forw_packet->packet_len,
                     batadv_ogm_packet->tt_num_changes)) {

        /* we might have aggregated direct link packets with an
         * ordinary base packet
         */
        if (forw_packet->direct_link_flags & BIT(packet_num) &&
            forw_packet->if_incoming == hard_iface)
            batadv_ogm_packet->flags |= BATADV_DIRECTLINK;
        else
            batadv_ogm_packet->flags &= ~BATADV_DIRECTLINK;

        if (packet_num > 0 || !forw_packet->own)
            fwd_str = "Forwarding";
        else
            fwd_str = "Sending own";

        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "%s %spacket (originator %pM, seqno %u, TQ %d, TTL %d, IDF %s, ttvn %d) on interface %s [%pM]\n",
               fwd_str, (packet_num > 0 ? "aggregated " : ""),
               batadv_ogm_packet->orig,
               ntohl(batadv_ogm_packet->seqno),
               batadv_ogm_packet->tq, batadv_ogm_packet->header.ttl,
               (batadv_ogm_packet->flags & BATADV_DIRECTLINK ?
                "on" : "off"),
               batadv_ogm_packet->ttvn, hard_iface->net_dev->name,
               hard_iface->net_dev->dev_addr);

        buff_pos += BATADV_OGM_HLEN;
        buff_pos += batadv_tt_len(batadv_ogm_packet->tt_num_changes);
        packet_num++;
        packet_pos = forw_packet->skb->data + buff_pos;
        batadv_ogm_packet = (struct batadv_ogm_packet *)packet_pos;
    }

    /* create clone because function is called more than once */
    skb = skb_clone(forw_packet->skb, GFP_ATOMIC);
    if (skb) {
        batadv_inc_counter(bat_priv, BATADV_CNT_MGMT_TX);
        batadv_add_counter(bat_priv, BATADV_CNT_MGMT_TX_BYTES,
                   skb->len + ETH_HLEN);
        batadv_send_skb_packet(skb, hard_iface, batadv_broadcast_addr);
    }
}

/* send a batman ogm packet */
static void batadv_iv_ogm_emit(struct batadv_forw_packet *forw_packet)
{
    struct batadv_hard_iface *hard_iface;
    struct net_device *soft_iface;
    struct batadv_priv *bat_priv;
    struct batadv_hard_iface *primary_if = NULL;
    struct batadv_ogm_packet *batadv_ogm_packet;
    unsigned char directlink;
    uint8_t *packet_pos;

    packet_pos = forw_packet->skb->data;
    batadv_ogm_packet = (struct batadv_ogm_packet *)packet_pos;
    directlink = (batadv_ogm_packet->flags & BATADV_DIRECTLINK ? 1 : 0);

    if (!forw_packet->if_incoming) {
        pr_err("Error - can't forward packet: incoming iface not specified\n");
        goto out;
    }

    soft_iface = forw_packet->if_incoming->soft_iface;
    bat_priv = netdev_priv(soft_iface);

    if (forw_packet->if_incoming->if_status != BATADV_IF_ACTIVE)
        goto out;

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

    /* multihomed peer assumed
     * non-primary OGMs are only broadcasted on their interface
     */
    if ((directlink && (batadv_ogm_packet->header.ttl == 1)) ||
        (forw_packet->own && (forw_packet->if_incoming != primary_if))) {

        /* FIXME: what about aggregated packets ? */
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "%s packet (originator %pM, seqno %u, TTL %d) on interface %s [%pM]\n",
               (forw_packet->own ? "Sending own" : "Forwarding"),
               batadv_ogm_packet->orig,
               ntohl(batadv_ogm_packet->seqno),
               batadv_ogm_packet->header.ttl,
               forw_packet->if_incoming->net_dev->name,
               forw_packet->if_incoming->net_dev->dev_addr);

        /* skb is only used once and than forw_packet is free'd */
        batadv_send_skb_packet(forw_packet->skb,
                       forw_packet->if_incoming,
                       batadv_broadcast_addr);
        forw_packet->skb = NULL;

        goto out;
    }

    /* broadcast on every interface */
    rcu_read_lock();
    list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
        if (hard_iface->soft_iface != soft_iface)
            continue;

        batadv_iv_ogm_send_to_if(forw_packet, hard_iface);
    }
    rcu_read_unlock();

out:
    if (primary_if)
        batadv_hardif_free_ref(primary_if);
}

/* return true if new_packet can be aggregated with forw_packet */
static bool
batadv_iv_ogm_can_aggregate(const struct batadv_ogm_packet *new_bat_ogm_packet,
                struct batadv_priv *bat_priv,
                int packet_len, unsigned long send_time,
                bool directlink,
                const struct batadv_hard_iface *if_incoming,
                const struct batadv_forw_packet *forw_packet)
{
    struct batadv_ogm_packet *batadv_ogm_packet;
    int aggregated_bytes = forw_packet->packet_len + packet_len;
    struct batadv_hard_iface *primary_if = NULL;
    bool res = false;
    unsigned long aggregation_end_time;

    batadv_ogm_packet = (struct batadv_ogm_packet *)forw_packet->skb->data;
    aggregation_end_time = send_time;
    aggregation_end_time += msecs_to_jiffies(BATADV_MAX_AGGREGATION_MS);

    /* we can aggregate the current packet to this aggregated packet
     * if:
     *
     * - the send time is within our MAX_AGGREGATION_MS time
     * - the resulting packet wont be bigger than
     *   MAX_AGGREGATION_BYTES
     */
    if (time_before(send_time, forw_packet->send_time) &&
        time_after_eq(aggregation_end_time, forw_packet->send_time) &&
        (aggregated_bytes <= BATADV_MAX_AGGREGATION_BYTES)) {

        /* check aggregation compatibility
         * -> direct link packets are broadcasted on
         *    their interface only
         * -> aggregate packet if the current packet is
         *    a "global" packet as well as the base
         *    packet
         */
        primary_if = batadv_primary_if_get_selected(bat_priv);
        if (!primary_if)
            goto out;

        /* packets without direct link flag and high TTL
         * are flooded through the net
         */
        if ((!directlink) &&
            (!(batadv_ogm_packet->flags & BATADV_DIRECTLINK)) &&
            (batadv_ogm_packet->header.ttl != 1) &&

            /* own packets originating non-primary
             * interfaces leave only that interface
             */
            ((!forw_packet->own) ||
             (forw_packet->if_incoming == primary_if))) {
            res = true;
            goto out;
        }

        /* if the incoming packet is sent via this one
         * interface only - we still can aggregate
         */
        if ((directlink) &&
            (new_bat_ogm_packet->header.ttl == 1) &&
            (forw_packet->if_incoming == if_incoming) &&

            /* packets from direct neighbors or
             * own secondary interface packets
             * (= secondary interface packets in general)
             */
            (batadv_ogm_packet->flags & BATADV_DIRECTLINK ||
             (forw_packet->own &&
              forw_packet->if_incoming != primary_if))) {
            res = true;
            goto out;
        }
    }

out:
    if (primary_if)
        batadv_hardif_free_ref(primary_if);
    return res;
}

/* create a new aggregated packet and add this packet to it */
static void batadv_iv_ogm_aggregate_new(const unsigned char *packet_buff,
                    int packet_len, unsigned long send_time,
                    bool direct_link,
                    struct batadv_hard_iface *if_incoming,
                    int own_packet)
{
    struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
    struct batadv_forw_packet *forw_packet_aggr;
    unsigned char *skb_buff;
    unsigned int skb_size;

    if (!atomic_inc_not_zero(&if_incoming->refcount))
        return;

    /* own packet should always be scheduled */
    if (!own_packet) {
        if (!batadv_atomic_dec_not_zero(&bat_priv->batman_queue_left)) {
            batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                   "batman packet queue full\n");
            goto out;
        }
    }

    forw_packet_aggr = kmalloc(sizeof(*forw_packet_aggr), GFP_ATOMIC);
    if (!forw_packet_aggr) {
        if (!own_packet)
            atomic_inc(&bat_priv->batman_queue_left);
        goto out;
    }

    if ((atomic_read(&bat_priv->aggregated_ogms)) &&
        (packet_len < BATADV_MAX_AGGREGATION_BYTES))
        skb_size = BATADV_MAX_AGGREGATION_BYTES + ETH_HLEN;
    else
        skb_size = packet_len + ETH_HLEN;

    forw_packet_aggr->skb = dev_alloc_skb(skb_size);
    if (!forw_packet_aggr->skb) {
        if (!own_packet)
            atomic_inc(&bat_priv->batman_queue_left);
        kfree(forw_packet_aggr);
        goto out;
    }
    skb_reserve(forw_packet_aggr->skb, ETH_HLEN);

    INIT_HLIST_NODE(&forw_packet_aggr->list);

    skb_buff = skb_put(forw_packet_aggr->skb, packet_len);
    forw_packet_aggr->packet_len = packet_len;
    memcpy(skb_buff, packet_buff, packet_len);

    forw_packet_aggr->own = own_packet;
    forw_packet_aggr->if_incoming = if_incoming;
    forw_packet_aggr->num_packets = 0;
    forw_packet_aggr->direct_link_flags = BATADV_NO_FLAGS;
    forw_packet_aggr->send_time = send_time;

    /* save packet direct link flag status */
    if (direct_link)
        forw_packet_aggr->direct_link_flags |= 1;

    /* add new packet to packet list */
    spin_lock_bh(&bat_priv->forw_bat_list_lock);
    hlist_add_head(&forw_packet_aggr->list, &bat_priv->forw_bat_list);
    spin_unlock_bh(&bat_priv->forw_bat_list_lock);

    /* start timer for this packet */
    INIT_DELAYED_WORK(&forw_packet_aggr->delayed_work,
              batadv_send_outstanding_bat_ogm_packet);
    queue_delayed_work(batadv_event_workqueue,
               &forw_packet_aggr->delayed_work,
               send_time - jiffies);

    return;
out:
    batadv_hardif_free_ref(if_incoming);
}

/* aggregate a new packet into the existing ogm packet */
static void batadv_iv_ogm_aggregate(struct batadv_forw_packet *forw_packet_aggr,
                    const unsigned char *packet_buff,
                    int packet_len, bool direct_link)
{
    unsigned char *skb_buff;
    unsigned long new_direct_link_flag;

    skb_buff = skb_put(forw_packet_aggr->skb, packet_len);
    memcpy(skb_buff, packet_buff, packet_len);
    forw_packet_aggr->packet_len += packet_len;
    forw_packet_aggr->num_packets++;

    /* save packet direct link flag status */
    if (direct_link) {
        new_direct_link_flag = BIT(forw_packet_aggr->num_packets);
        forw_packet_aggr->direct_link_flags |= new_direct_link_flag;
    }
}

static void batadv_iv_ogm_queue_add(struct batadv_priv *bat_priv,
                    unsigned char *packet_buff,
                    int packet_len,
                    struct batadv_hard_iface *if_incoming,
                    int own_packet, unsigned long send_time)
{
    /* _aggr -> pointer to the packet we want to aggregate with
     * _pos -> pointer to the position in the queue
     */
    struct batadv_forw_packet *forw_packet_aggr = NULL;
    struct batadv_forw_packet *forw_packet_pos = NULL;
    struct hlist_node *tmp_node;
    struct batadv_ogm_packet *batadv_ogm_packet;
    bool direct_link;
    unsigned long max_aggregation_jiffies;

    batadv_ogm_packet = (struct batadv_ogm_packet *)packet_buff;
    direct_link = batadv_ogm_packet->flags & BATADV_DIRECTLINK ? 1 : 0;
    max_aggregation_jiffies = msecs_to_jiffies(BATADV_MAX_AGGREGATION_MS);

    /* find position for the packet in the forward queue */
    spin_lock_bh(&bat_priv->forw_bat_list_lock);
    /* own packets are not to be aggregated */
    if ((atomic_read(&bat_priv->aggregated_ogms)) && (!own_packet)) {
        hlist_for_each_entry(forw_packet_pos, tmp_node,
                     &bat_priv->forw_bat_list, list) {
            if (batadv_iv_ogm_can_aggregate(batadv_ogm_packet,
                            bat_priv, packet_len,
                            send_time, direct_link,
                            if_incoming,
                            forw_packet_pos)) {
                forw_packet_aggr = forw_packet_pos;
                break;
            }
        }
    }

    /* nothing to aggregate with - either aggregation disabled or no
     * suitable aggregation packet found
     */
    if (!forw_packet_aggr) {
        /* the following section can run without the lock */
        spin_unlock_bh(&bat_priv->forw_bat_list_lock);

        /* if we could not aggregate this packet with one of the others
         * we hold it back for a while, so that it might be aggregated
         * later on
         */
        if (!own_packet && atomic_read(&bat_priv->aggregated_ogms))
            send_time += max_aggregation_jiffies;

        batadv_iv_ogm_aggregate_new(packet_buff, packet_len,
                        send_time, direct_link,
                        if_incoming, own_packet);
    } else {
        batadv_iv_ogm_aggregate(forw_packet_aggr, packet_buff,
                    packet_len, direct_link);
        spin_unlock_bh(&bat_priv->forw_bat_list_lock);
    }
}

static void batadv_iv_ogm_forward(struct batadv_orig_node *orig_node,
                  const struct ethhdr *ethhdr,
                  struct batadv_ogm_packet *batadv_ogm_packet,
                  bool is_single_hop_neigh,
                  bool is_from_best_next_hop,
                  struct batadv_hard_iface *if_incoming)
{
    struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
    uint8_t tt_num_changes;

    if (batadv_ogm_packet->header.ttl <= 1) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv, "ttl exceeded\n");
        return;
    }

    if (!is_from_best_next_hop) {
        /* Mark the forwarded packet when it is not coming from our
         * best next hop. We still need to forward the packet for our
         * neighbor link quality detection to work in case the packet
         * originated from a single hop neighbor. Otherwise we can
         * simply drop the ogm.
         */
        if (is_single_hop_neigh)
            batadv_ogm_packet->flags |= BATADV_NOT_BEST_NEXT_HOP;
        else
            return;
    }

    tt_num_changes = batadv_ogm_packet->tt_num_changes;

    batadv_ogm_packet->header.ttl--;
    memcpy(batadv_ogm_packet->prev_sender, ethhdr->h_source, ETH_ALEN);

    /* apply hop penalty */
    batadv_ogm_packet->tq = batadv_hop_penalty(batadv_ogm_packet->tq,
                           bat_priv);

    batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
           "Forwarding packet: tq: %i, ttl: %i\n",
           batadv_ogm_packet->tq, batadv_ogm_packet->header.ttl);

    /* switch of primaries first hop flag when forwarding */
    batadv_ogm_packet->flags &= ~BATADV_PRIMARIES_FIRST_HOP;
    if (is_single_hop_neigh)
        batadv_ogm_packet->flags |= BATADV_DIRECTLINK;
    else
        batadv_ogm_packet->flags &= ~BATADV_DIRECTLINK;

    batadv_iv_ogm_queue_add(bat_priv, (unsigned char *)batadv_ogm_packet,
                BATADV_OGM_HLEN + batadv_tt_len(tt_num_changes),
                if_incoming, 0, batadv_iv_ogm_fwd_send_time());
}

static void batadv_iv_ogm_schedule(struct batadv_hard_iface *hard_iface)
{
    struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
    struct batadv_ogm_packet *batadv_ogm_packet;
    struct batadv_hard_iface *primary_if;
    int vis_server, tt_num_changes = 0;
    uint32_t seqno;
    uint8_t bandwidth;

    vis_server = atomic_read(&bat_priv->vis_mode);
    primary_if = batadv_primary_if_get_selected(bat_priv);

    if (hard_iface == primary_if)
        tt_num_changes = batadv_tt_append_diff(bat_priv,
                               &hard_iface->packet_buff,
                               &hard_iface->packet_len,
                               BATADV_OGM_HLEN);

    batadv_ogm_packet = (struct batadv_ogm_packet *)hard_iface->packet_buff;

    /* change sequence number to network order */
    seqno = (uint32_t)atomic_read(&hard_iface->seqno);
    batadv_ogm_packet->seqno = htonl(seqno);
    atomic_inc(&hard_iface->seqno);

    batadv_ogm_packet->ttvn = atomic_read(&bat_priv->tt.vn);
    batadv_ogm_packet->tt_crc = htons(bat_priv->tt.local_crc);
    if (tt_num_changes >= 0)
        batadv_ogm_packet->tt_num_changes = tt_num_changes;

    if (vis_server == BATADV_VIS_TYPE_SERVER_SYNC)
        batadv_ogm_packet->flags |= BATADV_VIS_SERVER;
    else
        batadv_ogm_packet->flags &= ~BATADV_VIS_SERVER;

    if (hard_iface == primary_if &&
        atomic_read(&bat_priv->gw_mode) == BATADV_GW_MODE_SERVER) {
        bandwidth = (uint8_t)atomic_read(&bat_priv->gw_bandwidth);
        batadv_ogm_packet->gw_flags = bandwidth;
    } else {
        batadv_ogm_packet->gw_flags = BATADV_NO_FLAGS;
    }

    batadv_slide_own_bcast_window(hard_iface);
    batadv_iv_ogm_queue_add(bat_priv, hard_iface->packet_buff,
                hard_iface->packet_len, hard_iface, 1,
                batadv_iv_ogm_emit_send_time(bat_priv));

    if (primary_if)
        batadv_hardif_free_ref(primary_if);
}

static void
batadv_iv_ogm_orig_update(struct batadv_priv *bat_priv,
              struct batadv_orig_node *orig_node,
              const struct ethhdr *ethhdr,
              const struct batadv_ogm_packet *batadv_ogm_packet,
              struct batadv_hard_iface *if_incoming,
              const unsigned char *tt_buff,
              int is_duplicate)
{
    struct batadv_neigh_node *neigh_node = NULL, *tmp_neigh_node = NULL;
    struct batadv_neigh_node *router = NULL;
    struct batadv_orig_node *orig_node_tmp;
    struct hlist_node *node;
    int if_num;
    uint8_t sum_orig, sum_neigh;
    uint8_t *neigh_addr;
    uint8_t tq_avg;

    batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
           "update_originator(): Searching and updating originator entry of received packet\n");

    rcu_read_lock();
    hlist_for_each_entry_rcu(tmp_neigh_node, node,
                 &orig_node->neigh_list, list) {
        neigh_addr = tmp_neigh_node->addr;
        if (batadv_compare_eth(neigh_addr, ethhdr->h_source) &&
            tmp_neigh_node->if_incoming == if_incoming &&
            atomic_inc_not_zero(&tmp_neigh_node->refcount)) {
            if (neigh_node)
                batadv_neigh_node_free_ref(neigh_node);
            neigh_node = tmp_neigh_node;
            continue;
        }

        if (is_duplicate)
            continue;

        spin_lock_bh(&tmp_neigh_node->lq_update_lock);
        batadv_ring_buffer_set(tmp_neigh_node->tq_recv,
                       &tmp_neigh_node->tq_index, 0);
        tq_avg = batadv_ring_buffer_avg(tmp_neigh_node->tq_recv);
        tmp_neigh_node->tq_avg = tq_avg;
        spin_unlock_bh(&tmp_neigh_node->lq_update_lock);
    }

    if (!neigh_node) {
        struct batadv_orig_node *orig_tmp;

        orig_tmp = batadv_get_orig_node(bat_priv, ethhdr->h_source);
        if (!orig_tmp)
            goto unlock;

        neigh_node = batadv_iv_ogm_neigh_new(if_incoming,
                             ethhdr->h_source,
                             orig_node, orig_tmp,
                             batadv_ogm_packet->seqno);

        batadv_orig_node_free_ref(orig_tmp);
        if (!neigh_node)
            goto unlock;
    } else
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Updating existing last-hop neighbor of originator\n");

    rcu_read_unlock();

    orig_node->flags = batadv_ogm_packet->flags;
    neigh_node->last_seen = jiffies;

    spin_lock_bh(&neigh_node->lq_update_lock);
    batadv_ring_buffer_set(neigh_node->tq_recv,
                   &neigh_node->tq_index,
                   batadv_ogm_packet->tq);
    neigh_node->tq_avg = batadv_ring_buffer_avg(neigh_node->tq_recv);
    spin_unlock_bh(&neigh_node->lq_update_lock);

    if (!is_duplicate) {
        orig_node->last_ttl = batadv_ogm_packet->header.ttl;
        neigh_node->last_ttl = batadv_ogm_packet->header.ttl;
    }

    batadv_bonding_candidate_add(orig_node, neigh_node);

    /* if this neighbor already is our next hop there is nothing
     * to change
     */
    router = batadv_orig_node_get_router(orig_node);
    if (router == neigh_node)
        goto update_tt;

    /* if this neighbor does not offer a better TQ we won't consider it */
    if (router && (router->tq_avg > neigh_node->tq_avg))
        goto update_tt;

    /* if the TQ is the same and the link not more symmetric we
     * won't consider it either
     */
    if (router && (neigh_node->tq_avg == router->tq_avg)) {
        orig_node_tmp = router->orig_node;
        spin_lock_bh(&orig_node_tmp->ogm_cnt_lock);
        if_num = router->if_incoming->if_num;
        sum_orig = orig_node_tmp->bcast_own_sum[if_num];
        spin_unlock_bh(&orig_node_tmp->ogm_cnt_lock);

        orig_node_tmp = neigh_node->orig_node;
        spin_lock_bh(&orig_node_tmp->ogm_cnt_lock);
        if_num = neigh_node->if_incoming->if_num;
        sum_neigh = orig_node_tmp->bcast_own_sum[if_num];
        spin_unlock_bh(&orig_node_tmp->ogm_cnt_lock);

        if (sum_orig >= sum_neigh)
            goto update_tt;
    }

    batadv_update_route(bat_priv, orig_node, neigh_node);

update_tt:
    /* I have to check for transtable changes only if the OGM has been
     * sent through a primary interface
     */
    if (((batadv_ogm_packet->orig != ethhdr->h_source) &&
         (batadv_ogm_packet->header.ttl > 2)) ||
        (batadv_ogm_packet->flags & BATADV_PRIMARIES_FIRST_HOP))
        batadv_tt_update_orig(bat_priv, orig_node, tt_buff,
                      batadv_ogm_packet->tt_num_changes,
                      batadv_ogm_packet->ttvn,
                      ntohs(batadv_ogm_packet->tt_crc));

    if (orig_node->gw_flags != batadv_ogm_packet->gw_flags)
        batadv_gw_node_update(bat_priv, orig_node,
                      batadv_ogm_packet->gw_flags);

    orig_node->gw_flags = batadv_ogm_packet->gw_flags;

    /* restart gateway selection if fast or late switching was enabled */
    if ((orig_node->gw_flags) &&
        (atomic_read(&bat_priv->gw_mode) == BATADV_GW_MODE_CLIENT) &&
        (atomic_read(&bat_priv->gw_sel_class) > 2))
        batadv_gw_check_election(bat_priv, orig_node);

    goto out;

unlock:
    rcu_read_unlock();
out:
    if (neigh_node)
        batadv_neigh_node_free_ref(neigh_node);
    if (router)
        batadv_neigh_node_free_ref(router);
}

static int batadv_iv_ogm_calc_tq(struct batadv_orig_node *orig_node,
                 struct batadv_orig_node *orig_neigh_node,
                 struct batadv_ogm_packet *batadv_ogm_packet,
                 struct batadv_hard_iface *if_incoming)
{
    struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
    struct batadv_neigh_node *neigh_node = NULL, *tmp_neigh_node;
    struct hlist_node *node;
    uint8_t total_count;
    uint8_t orig_eq_count, neigh_rq_count, neigh_rq_inv, tq_own;
    unsigned int neigh_rq_inv_cube, neigh_rq_max_cube;
    int tq_asym_penalty, inv_asym_penalty, ret = 0;
    unsigned int combined_tq;

    /* find corresponding one hop neighbor */
    rcu_read_lock();
    hlist_for_each_entry_rcu(tmp_neigh_node, node,
                 &orig_neigh_node->neigh_list, list) {

        if (!batadv_compare_eth(tmp_neigh_node->addr,
                    orig_neigh_node->orig))
            continue;

        if (tmp_neigh_node->if_incoming != if_incoming)
            continue;

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

        neigh_node = tmp_neigh_node;
        break;
    }
    rcu_read_unlock();

    if (!neigh_node)
        neigh_node = batadv_iv_ogm_neigh_new(if_incoming,
                             orig_neigh_node->orig,
                             orig_neigh_node,
                             orig_neigh_node,
                             batadv_ogm_packet->seqno);

    if (!neigh_node)
        goto out;

    /* if orig_node is direct neighbor update neigh_node last_seen */
    if (orig_node == orig_neigh_node)
        neigh_node->last_seen = jiffies;

    orig_node->last_seen = jiffies;

    /* find packet count of corresponding one hop neighbor */
    spin_lock_bh(&orig_node->ogm_cnt_lock);
    orig_eq_count = orig_neigh_node->bcast_own_sum[if_incoming->if_num];
    neigh_rq_count = neigh_node->real_packet_count;
    spin_unlock_bh(&orig_node->ogm_cnt_lock);

    /* pay attention to not get a value bigger than 100 % */
    if (orig_eq_count > neigh_rq_count)
        total_count = neigh_rq_count;
    else
        total_count = orig_eq_count;

    /* if we have too few packets (too less data) we set tq_own to zero
     * if we receive too few packets it is not considered bidirectional
     */
    if (total_count < BATADV_TQ_LOCAL_BIDRECT_SEND_MINIMUM ||
        neigh_rq_count < BATADV_TQ_LOCAL_BIDRECT_RECV_MINIMUM)
        tq_own = 0;
    else
        /* neigh_node->real_packet_count is never zero as we
         * only purge old information when getting new
         * information
         */
        tq_own = (BATADV_TQ_MAX_VALUE * total_count) /  neigh_rq_count;

    /* 1 - ((1-x) ** 3), normalized to TQ_MAX_VALUE this does
     * affect the nearly-symmetric links only a little, but
     * punishes asymmetric links more.  This will give a value
     * between 0 and TQ_MAX_VALUE
     */
    neigh_rq_inv = BATADV_TQ_LOCAL_WINDOW_SIZE - neigh_rq_count;
    neigh_rq_inv_cube = neigh_rq_inv * neigh_rq_inv * neigh_rq_inv;
    neigh_rq_max_cube = BATADV_TQ_LOCAL_WINDOW_SIZE *
                BATADV_TQ_LOCAL_WINDOW_SIZE *
                BATADV_TQ_LOCAL_WINDOW_SIZE;
    inv_asym_penalty = BATADV_TQ_MAX_VALUE * neigh_rq_inv_cube;
    inv_asym_penalty /= neigh_rq_max_cube;
    tq_asym_penalty = BATADV_TQ_MAX_VALUE - inv_asym_penalty;

    combined_tq = batadv_ogm_packet->tq * tq_own * tq_asym_penalty;
    combined_tq /= BATADV_TQ_MAX_VALUE * BATADV_TQ_MAX_VALUE;
    batadv_ogm_packet->tq = combined_tq;

    batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
           "bidirectional: orig = %-15pM neigh = %-15pM => own_bcast = %2i, real recv = %2i, local tq: %3i, asym_penalty: %3i, total tq: %3i\n",
           orig_node->orig, orig_neigh_node->orig, total_count,
           neigh_rq_count, tq_own,
           tq_asym_penalty, batadv_ogm_packet->tq);

    /* if link has the minimum required transmission quality
     * consider it bidirectional
     */
    if (batadv_ogm_packet->tq >= BATADV_TQ_TOTAL_BIDRECT_LIMIT)
        ret = 1;

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

/* processes a batman packet for all interfaces, adjusts the sequence number and
 * finds out whether it is a duplicate.
 * returns:
 *   1 the packet is a duplicate
 *   0 the packet has not yet been received
 *  -1 the packet is old and has been received while the seqno window
 *     was protected. Caller should drop it.
 */
static int
batadv_iv_ogm_update_seqnos(const struct ethhdr *ethhdr,
                const struct batadv_ogm_packet *batadv_ogm_packet,
                const struct batadv_hard_iface *if_incoming)
{
    struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
    struct batadv_orig_node *orig_node;
    struct batadv_neigh_node *tmp_neigh_node;
    struct hlist_node *node;
    int is_duplicate = 0;
    int32_t seq_diff;
    int need_update = 0;
    int set_mark, ret = -1;
    uint32_t seqno = ntohl(batadv_ogm_packet->seqno);
    uint8_t *neigh_addr;
    uint8_t packet_count;

    orig_node = batadv_get_orig_node(bat_priv, batadv_ogm_packet->orig);
    if (!orig_node)
        return 0;

    spin_lock_bh(&orig_node->ogm_cnt_lock);
    seq_diff = seqno - orig_node->last_real_seqno;

    /* signalize caller that the packet is to be dropped. */
    if (!hlist_empty(&orig_node->neigh_list) &&
        batadv_window_protected(bat_priv, seq_diff,
                    &orig_node->batman_seqno_reset))
        goto out;

    rcu_read_lock();
    hlist_for_each_entry_rcu(tmp_neigh_node, node,
                 &orig_node->neigh_list, list) {

        is_duplicate |= batadv_test_bit(tmp_neigh_node->real_bits,
                        orig_node->last_real_seqno,
                        seqno);

        neigh_addr = tmp_neigh_node->addr;
        if (batadv_compare_eth(neigh_addr, ethhdr->h_source) &&
            tmp_neigh_node->if_incoming == if_incoming)
            set_mark = 1;
        else
            set_mark = 0;

        /* if the window moved, set the update flag. */
        need_update |= batadv_bit_get_packet(bat_priv,
                             tmp_neigh_node->real_bits,
                             seq_diff, set_mark);

        packet_count = bitmap_weight(tmp_neigh_node->real_bits,
                         BATADV_TQ_LOCAL_WINDOW_SIZE);
        tmp_neigh_node->real_packet_count = packet_count;
    }
    rcu_read_unlock();

    if (need_update) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "updating last_seqno: old %u, new %u\n",
               orig_node->last_real_seqno, seqno);
        orig_node->last_real_seqno = seqno;
    }

    ret = is_duplicate;

out:
    spin_unlock_bh(&orig_node->ogm_cnt_lock);
    batadv_orig_node_free_ref(orig_node);
    return ret;
}

static void batadv_iv_ogm_process(const struct ethhdr *ethhdr,
                  struct batadv_ogm_packet *batadv_ogm_packet,
                  const unsigned char *tt_buff,
                  struct batadv_hard_iface *if_incoming)
{
    struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
    struct batadv_hard_iface *hard_iface;
    struct batadv_orig_node *orig_neigh_node, *orig_node;
    struct batadv_neigh_node *router = NULL, *router_router = NULL;
    struct batadv_neigh_node *orig_neigh_router = NULL;
    int has_directlink_flag;
    int is_my_addr = 0, is_my_orig = 0, is_my_oldorig = 0;
    int is_broadcast = 0, is_bidirect;
    bool is_single_hop_neigh = false;
    bool is_from_best_next_hop = false;
    int is_duplicate, sameseq, simlar_ttl;
    uint32_t if_incoming_seqno;
    uint8_t *prev_sender;

    /* Silently drop when the batman packet is actually not a
     * correct packet.
     *
     * This might happen if a packet is padded (e.g. Ethernet has a
     * minimum frame length of 64 byte) and the aggregation interprets
     * it as an additional length.
     *
     * TODO: A more sane solution would be to have a bit in the
     * batadv_ogm_packet to detect whether the packet is the last
     * packet in an aggregation.  Here we expect that the padding
     * is always zero (or not 0x01)
     */
    if (batadv_ogm_packet->header.packet_type != BATADV_IV_OGM)
        return;

    /* could be changed by schedule_own_packet() */
    if_incoming_seqno = atomic_read(&if_incoming->seqno);

    if (batadv_ogm_packet->flags & BATADV_DIRECTLINK)
        has_directlink_flag = 1;
    else
        has_directlink_flag = 0;

    if (batadv_compare_eth(ethhdr->h_source, batadv_ogm_packet->orig))
        is_single_hop_neigh = true;

    batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
           "Received BATMAN packet via NB: %pM, IF: %s [%pM] (from OG: %pM, via prev OG: %pM, seqno %u, ttvn %u, crc %u, changes %u, td %d, TTL %d, V %d, IDF %d)\n",
           ethhdr->h_source, if_incoming->net_dev->name,
           if_incoming->net_dev->dev_addr, batadv_ogm_packet->orig,
           batadv_ogm_packet->prev_sender,
           ntohl(batadv_ogm_packet->seqno), batadv_ogm_packet->ttvn,
           ntohs(batadv_ogm_packet->tt_crc),
           batadv_ogm_packet->tt_num_changes, batadv_ogm_packet->tq,
           batadv_ogm_packet->header.ttl,
           batadv_ogm_packet->header.version, has_directlink_flag);

    rcu_read_lock();
    list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
        if (hard_iface->if_status != BATADV_IF_ACTIVE)
            continue;

        if (hard_iface->soft_iface != if_incoming->soft_iface)
            continue;

        if (batadv_compare_eth(ethhdr->h_source,
                       hard_iface->net_dev->dev_addr))
            is_my_addr = 1;

        if (batadv_compare_eth(batadv_ogm_packet->orig,
                       hard_iface->net_dev->dev_addr))
            is_my_orig = 1;

        if (batadv_compare_eth(batadv_ogm_packet->prev_sender,
                       hard_iface->net_dev->dev_addr))
            is_my_oldorig = 1;

        if (is_broadcast_ether_addr(ethhdr->h_source))
            is_broadcast = 1;
    }
    rcu_read_unlock();

    if (batadv_ogm_packet->header.version != BATADV_COMPAT_VERSION) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: incompatible batman version (%i)\n",
               batadv_ogm_packet->header.version);
        return;
    }

    if (is_my_addr) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: received my own broadcast (sender: %pM)\n",
               ethhdr->h_source);
        return;
    }

    if (is_broadcast) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: ignoring all packets with broadcast source addr (sender: %pM)\n",
               ethhdr->h_source);
        return;
    }

    if (is_my_orig) {
        unsigned long *word;
        int offset;
        int32_t bit_pos;
        int16_t if_num;
        uint8_t *weight;

        orig_neigh_node = batadv_get_orig_node(bat_priv,
                               ethhdr->h_source);
        if (!orig_neigh_node)
            return;

        /* neighbor has to indicate direct link and it has to
         * come via the corresponding interface
         * save packet seqno for bidirectional check
         */
        if (has_directlink_flag &&
            batadv_compare_eth(if_incoming->net_dev->dev_addr,
                       batadv_ogm_packet->orig)) {
            if_num = if_incoming->if_num;
            offset = if_num * BATADV_NUM_WORDS;

            spin_lock_bh(&orig_neigh_node->ogm_cnt_lock);
            word = &(orig_neigh_node->bcast_own[offset]);
            bit_pos = if_incoming_seqno - 2;
            bit_pos -= ntohl(batadv_ogm_packet->seqno);
            batadv_set_bit(word, bit_pos);
            weight = &orig_neigh_node->bcast_own_sum[if_num];
            *weight = bitmap_weight(word,
                        BATADV_TQ_LOCAL_WINDOW_SIZE);
            spin_unlock_bh(&orig_neigh_node->ogm_cnt_lock);
        }

        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: originator packet from myself (via neighbor)\n");
        batadv_orig_node_free_ref(orig_neigh_node);
        return;
    }

    if (is_my_oldorig) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: ignoring all rebroadcast echos (sender: %pM)\n",
               ethhdr->h_source);
        return;
    }

    if (batadv_ogm_packet->flags & BATADV_NOT_BEST_NEXT_HOP) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: ignoring all packets not forwarded from the best next hop (sender: %pM)\n",
               ethhdr->h_source);
        return;
    }

    orig_node = batadv_get_orig_node(bat_priv, batadv_ogm_packet->orig);
    if (!orig_node)
        return;

    is_duplicate = batadv_iv_ogm_update_seqnos(ethhdr, batadv_ogm_packet,
                           if_incoming);

    if (is_duplicate == -1) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: packet within seqno protection time (sender: %pM)\n",
               ethhdr->h_source);
        goto out;
    }

    if (batadv_ogm_packet->tq == 0) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: originator packet with tq equal 0\n");
        goto out;
    }

    router = batadv_orig_node_get_router(orig_node);
    if (router)
        router_router = batadv_orig_node_get_router(router->orig_node);

    if ((router && router->tq_avg != 0) &&
        (batadv_compare_eth(router->addr, ethhdr->h_source)))
        is_from_best_next_hop = true;

    prev_sender = batadv_ogm_packet->prev_sender;
    /* avoid temporary routing loops */
    if (router && router_router &&
        (batadv_compare_eth(router->addr, prev_sender)) &&
        !(batadv_compare_eth(batadv_ogm_packet->orig, prev_sender)) &&
        (batadv_compare_eth(router->addr, router_router->addr))) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: ignoring all rebroadcast packets that may make me loop (sender: %pM)\n",
               ethhdr->h_source);
        goto out;
    }

    /* if sender is a direct neighbor the sender mac equals
     * originator mac
     */
    if (is_single_hop_neigh)
        orig_neigh_node = orig_node;
    else
        orig_neigh_node = batadv_get_orig_node(bat_priv,
                               ethhdr->h_source);

    if (!orig_neigh_node)
        goto out;

    orig_neigh_router = batadv_orig_node_get_router(orig_neigh_node);

    /* drop packet if sender is not a direct neighbor and if we
     * don't route towards it
     */
    if (!is_single_hop_neigh && (!orig_neigh_router)) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: OGM via unknown neighbor!\n");
        goto out_neigh;
    }

    is_bidirect = batadv_iv_ogm_calc_tq(orig_node, orig_neigh_node,
                        batadv_ogm_packet, if_incoming);

    batadv_bonding_save_primary(orig_node, orig_neigh_node,
                    batadv_ogm_packet);

    /* update ranking if it is not a duplicate or has the same
     * seqno and similar ttl as the non-duplicate
     */
    sameseq = orig_node->last_real_seqno == ntohl(batadv_ogm_packet->seqno);
    simlar_ttl = orig_node->last_ttl - 3 <= batadv_ogm_packet->header.ttl;
    if (is_bidirect && (!is_duplicate || (sameseq && simlar_ttl)))
        batadv_iv_ogm_orig_update(bat_priv, orig_node, ethhdr,
                      batadv_ogm_packet, if_incoming,
                      tt_buff, is_duplicate);

    /* is single hop (direct) neighbor */
    if (is_single_hop_neigh) {

        /* mark direct link on incoming interface */
        batadv_iv_ogm_forward(orig_node, ethhdr, batadv_ogm_packet,
                      is_single_hop_neigh,
                      is_from_best_next_hop, if_incoming);

        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Forwarding packet: rebroadcast neighbor packet with direct link flag\n");
        goto out_neigh;
    }

    /* multihop originator */
    if (!is_bidirect) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: not received via bidirectional link\n");
        goto out_neigh;
    }

    if (is_duplicate) {
        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
               "Drop packet: duplicate packet received\n");
        goto out_neigh;
    }

    batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
           "Forwarding packet: rebroadcast originator packet\n");
    batadv_iv_ogm_forward(orig_node, ethhdr, batadv_ogm_packet,
                  is_single_hop_neigh, is_from_best_next_hop,
                  if_incoming);

out_neigh:
    if ((orig_neigh_node) && (!is_single_hop_neigh))
        batadv_orig_node_free_ref(orig_neigh_node);
out:
    if (router)
        batadv_neigh_node_free_ref(router);
    if (router_router)
        batadv_neigh_node_free_ref(router_router);
    if (orig_neigh_router)
        batadv_neigh_node_free_ref(orig_neigh_router);

    batadv_orig_node_free_ref(orig_node);
}

static int batadv_iv_ogm_receive(struct sk_buff *skb,
                 struct batadv_hard_iface *if_incoming)
{
    struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
    struct batadv_ogm_packet *batadv_ogm_packet;
    struct ethhdr *ethhdr;
    int buff_pos = 0, packet_len;
    unsigned char *tt_buff, *packet_buff;
    bool ret;
    uint8_t *packet_pos;

    ret = batadv_check_management_packet(skb, if_incoming, BATADV_OGM_HLEN);
    if (!ret)
        return NET_RX_DROP;

    /* did we receive a B.A.T.M.A.N. IV OGM packet on an interface
     * that does not have B.A.T.M.A.N. IV enabled ?
     */
    if (bat_priv->bat_algo_ops->bat_ogm_emit != batadv_iv_ogm_emit)
        return NET_RX_DROP;

    batadv_inc_counter(bat_priv, BATADV_CNT_MGMT_RX);
    batadv_add_counter(bat_priv, BATADV_CNT_MGMT_RX_BYTES,
               skb->len + ETH_HLEN);

    packet_len = skb_headlen(skb);
    ethhdr = (struct ethhdr *)skb_mac_header(skb);
    packet_buff = skb->data;
    batadv_ogm_packet = (struct batadv_ogm_packet *)packet_buff;

    /* unpack the aggregated packets and process them one by one */
    do {
        tt_buff = packet_buff + buff_pos + BATADV_OGM_HLEN;

        batadv_iv_ogm_process(ethhdr, batadv_ogm_packet, tt_buff,
                      if_incoming);

        buff_pos += BATADV_OGM_HLEN;
        buff_pos += batadv_tt_len(batadv_ogm_packet->tt_num_changes);

        packet_pos = packet_buff + buff_pos;
        batadv_ogm_packet = (struct batadv_ogm_packet *)packet_pos;
    } while (batadv_iv_ogm_aggr_packet(buff_pos, packet_len,
                       batadv_ogm_packet->tt_num_changes));

    kfree_skb(skb);
    return NET_RX_SUCCESS;
}

static struct batadv_algo_ops batadv_batman_iv __read_mostly = {
    .name = "BATMAN_IV",
    .bat_iface_enable = batadv_iv_ogm_iface_enable,
    .bat_iface_disable = batadv_iv_ogm_iface_disable,
    .bat_iface_update_mac = batadv_iv_ogm_iface_update_mac,
    .bat_primary_iface_set = batadv_iv_ogm_primary_iface_set,
    .bat_ogm_schedule = batadv_iv_ogm_schedule,
    .bat_ogm_emit = batadv_iv_ogm_emit,
};

int __init batadv_iv_init(void)
{
    int ret;

    /* batman originator packet */
    ret = batadv_recv_handler_register(BATADV_IV_OGM,
                       batadv_iv_ogm_receive);
    if (ret < 0)
        goto out;

    ret = batadv_algo_register(&batadv_batman_iv);
    if (ret < 0)
        goto handler_unregister;

    goto out;

handler_unregister:
    batadv_recv_handler_unregister(BATADV_IV_OGM);
out:
    return ret;
}