mm: discard memblock data later

[linux/fpc-iii.git] / net / batman-adv / bat_v_ogm.c

/* Copyright (C) 2013-2016 B.A.T.M.A.N. contributors:
 *
 * Antonio Quartulli
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */

#include "bat_v_ogm.h"
#include "main.h"

#include <linux/atomic.h>
#include <linux/byteorder/generic.h>
#include <linux/errno.h>
#include <linux/etherdevice.h>
#include <linux/fs.h>
#include <linux/if_ether.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/random.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/stddef.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/workqueue.h>

#include "bat_algo.h"
#include "hard-interface.h"
#include "hash.h"
#include "log.h"
#include "originator.h"
#include "packet.h"
#include "routing.h"
#include "send.h"
#include "translation-table.h"
#include "tvlv.h"

/**
 * batadv_v_ogm_orig_get - retrieve and possibly create an originator node
 * @bat_priv: the bat priv with all the soft interface information
 * @addr: the address of the originator
 *
 * Return: the orig_node corresponding to the specified address. If such object
 * does not exist it is allocated here. In case of allocation failure returns
 * NULL.
 */
struct batadv_orig_node *batadv_v_ogm_orig_get(struct batadv_priv *bat_priv,
                                               const u8 *addr)
{
        struct batadv_orig_node *orig_node;
        int hash_added;

        orig_node = batadv_orig_hash_find(bat_priv, addr);
        if (orig_node)
                return orig_node;

        orig_node = batadv_orig_node_new(bat_priv, addr);
        if (!orig_node)
                return NULL;

        kref_get(&orig_node->refcount);
        hash_added = batadv_hash_add(bat_priv->orig_hash, batadv_compare_orig,
                                     batadv_choose_orig, orig_node,
                                     &orig_node->hash_entry);
        if (hash_added != 0) {
                /* remove refcnt for newly created orig_node and hash entry */
                batadv_orig_node_put(orig_node);
                batadv_orig_node_put(orig_node);
                orig_node = NULL;
        }

        return orig_node;
}

/**
 * batadv_v_ogm_start_timer - restart the OGM sending timer
 * @bat_priv: the bat priv with all the soft interface information
 */
static void batadv_v_ogm_start_timer(struct batadv_priv *bat_priv)
{
        unsigned long msecs;
        /* this function may be invoked in different contexts (ogm rescheduling
         * or hard_iface activation), but the work timer should not be reset
         */
        if (delayed_work_pending(&bat_priv->bat_v.ogm_wq))
                return;

        msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
        msecs += prandom_u32() % (2 * BATADV_JITTER);
        queue_delayed_work(batadv_event_workqueue, &bat_priv->bat_v.ogm_wq,
                           msecs_to_jiffies(msecs));
}

/**
 * batadv_v_ogm_send_to_if - send a batman ogm using a given interface
 * @skb: the OGM to send
 * @hard_iface: the interface to use to send the OGM
 */
static void batadv_v_ogm_send_to_if(struct sk_buff *skb,
                                    struct batadv_hard_iface *hard_iface)
{
        struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);

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

        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_broadcast_skb(skb, hard_iface);
}

/**
 * batadv_v_ogm_send - periodic worker broadcasting the own OGM
 * @work: work queue item
 */
static void batadv_v_ogm_send(struct work_struct *work)
{
        struct batadv_hard_iface *hard_iface;
        struct batadv_priv_bat_v *bat_v;
        struct batadv_priv *bat_priv;
        struct batadv_ogm2_packet *ogm_packet;
        struct sk_buff *skb, *skb_tmp;
        unsigned char *ogm_buff, *pkt_buff;
        int ogm_buff_len;
        u16 tvlv_len = 0;

        bat_v = container_of(work, struct batadv_priv_bat_v, ogm_wq.work);
        bat_priv = container_of(bat_v, struct batadv_priv, bat_v);

        if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING)
                goto out;

        ogm_buff = bat_priv->bat_v.ogm_buff;
        ogm_buff_len = bat_priv->bat_v.ogm_buff_len;
        /* tt changes have to be committed before the tvlv data is
         * appended as it may alter the tt tvlv container
         */
        batadv_tt_local_commit_changes(bat_priv);
        tvlv_len = batadv_tvlv_container_ogm_append(bat_priv, &ogm_buff,
                                                    &ogm_buff_len,
                                                    BATADV_OGM2_HLEN);

        bat_priv->bat_v.ogm_buff = ogm_buff;
        bat_priv->bat_v.ogm_buff_len = ogm_buff_len;

        skb = netdev_alloc_skb_ip_align(NULL, ETH_HLEN + ogm_buff_len);
        if (!skb)
                goto reschedule;

        skb_reserve(skb, ETH_HLEN);
        pkt_buff = skb_put(skb, ogm_buff_len);
        memcpy(pkt_buff, ogm_buff, ogm_buff_len);

        ogm_packet = (struct batadv_ogm2_packet *)skb->data;
        ogm_packet->seqno = htonl(atomic_read(&bat_priv->bat_v.ogm_seqno));
        atomic_inc(&bat_priv->bat_v.ogm_seqno);
        ogm_packet->tvlv_len = htons(tvlv_len);

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

                if (!kref_get_unless_zero(&hard_iface->refcount))
                        continue;

                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Sending own OGM2 packet (originator %pM, seqno %u, throughput %u, TTL %d) on interface %s [%pM]\n",
                           ogm_packet->orig, ntohl(ogm_packet->seqno),
                           ntohl(ogm_packet->throughput), ogm_packet->ttl,
                           hard_iface->net_dev->name,
                           hard_iface->net_dev->dev_addr);

                /* this skb gets consumed by batadv_v_ogm_send_to_if() */
                skb_tmp = skb_clone(skb, GFP_ATOMIC);
                if (!skb_tmp) {
                        batadv_hardif_put(hard_iface);
                        break;
                }

                batadv_v_ogm_send_to_if(skb_tmp, hard_iface);
                batadv_hardif_put(hard_iface);
        }
        rcu_read_unlock();

        consume_skb(skb);

reschedule:
        batadv_v_ogm_start_timer(bat_priv);
out:
        return;
}

/**
 * batadv_v_ogm_iface_enable - prepare an interface for B.A.T.M.A.N. V
 * @hard_iface: the interface to prepare
 *
 * Takes care of scheduling own OGM sending routine for this interface.
 *
 * Return: 0 on success or a negative error code otherwise
 */
int batadv_v_ogm_iface_enable(struct batadv_hard_iface *hard_iface)
{
        struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);

        batadv_v_ogm_start_timer(bat_priv);

        return 0;
}

/**
 * batadv_v_ogm_primary_iface_set - set a new primary interface
 * @primary_iface: the new primary interface
 */
void batadv_v_ogm_primary_iface_set(struct batadv_hard_iface *primary_iface)
{
        struct batadv_priv *bat_priv = netdev_priv(primary_iface->soft_iface);
        struct batadv_ogm2_packet *ogm_packet;

        if (!bat_priv->bat_v.ogm_buff)
                return;

        ogm_packet = (struct batadv_ogm2_packet *)bat_priv->bat_v.ogm_buff;
        ether_addr_copy(ogm_packet->orig, primary_iface->net_dev->dev_addr);
}

/**
 * batadv_v_forward_penalty - apply a penalty to the throughput metric forwarded
 *  with B.A.T.M.A.N. V OGMs
 * @bat_priv: the bat priv with all the soft interface information
 * @if_incoming: the interface where the OGM has been received
 * @if_outgoing: the interface where the OGM has to be forwarded to
 * @throughput: the current throughput
 *
 * Apply a penalty on the current throughput metric value based on the
 * characteristic of the interface where the OGM has been received. The return
 * value is computed as follows:
 * - throughput * 50%          if the incoming and outgoing interface are the
 *                             same WiFi interface and the throughput is above
 *                             1MBit/s
 * - throughput                if the outgoing interface is the default
 *                             interface (i.e. this OGM is processed for the
 *                             internal table and not forwarded)
 * - throughput * hop penalty  otherwise
 *
 * Return: the penalised throughput metric.
 */
static u32 batadv_v_forward_penalty(struct batadv_priv *bat_priv,
                                    struct batadv_hard_iface *if_incoming,
                                    struct batadv_hard_iface *if_outgoing,
                                    u32 throughput)
{
        int hop_penalty = atomic_read(&bat_priv->hop_penalty);
        int hop_penalty_max = BATADV_TQ_MAX_VALUE;

        /* Don't apply hop penalty in default originator table. */
        if (if_outgoing == BATADV_IF_DEFAULT)
                return throughput;

        /* Forwarding on the same WiFi interface cuts the throughput in half
         * due to the store & forward characteristics of WIFI.
         * Very low throughput values are the exception.
         */
        if ((throughput > 10) &&
            (if_incoming == if_outgoing) &&
            !(if_incoming->bat_v.flags & BATADV_FULL_DUPLEX))
                return throughput / 2;

        /* hop penalty of 255 equals 100% */
        return throughput * (hop_penalty_max - hop_penalty) / hop_penalty_max;
}

/**
 * batadv_v_ogm_forward - check conditions and forward an OGM to the given
 *  outgoing interface
 * @bat_priv: the bat priv with all the soft interface information
 * @ogm_received: previously received OGM to be forwarded
 * @orig_node: the originator which has been updated
 * @neigh_node: the neigh_node through with the OGM has been received
 * @if_incoming: the interface on which this OGM was received on
 * @if_outgoing: the interface to which the OGM has to be forwarded to
 *
 * Forward an OGM to an interface after having altered the throughput metric and
 * the TTL value contained in it. The original OGM isn't modified.
 */
static void batadv_v_ogm_forward(struct batadv_priv *bat_priv,
                                 const struct batadv_ogm2_packet *ogm_received,
                                 struct batadv_orig_node *orig_node,
                                 struct batadv_neigh_node *neigh_node,
                                 struct batadv_hard_iface *if_incoming,
                                 struct batadv_hard_iface *if_outgoing)
{
        struct batadv_neigh_ifinfo *neigh_ifinfo = NULL;
        struct batadv_orig_ifinfo *orig_ifinfo = NULL;
        struct batadv_neigh_node *router = NULL;
        struct batadv_ogm2_packet *ogm_forward;
        unsigned char *skb_buff;
        struct sk_buff *skb;
        size_t packet_len;
        u16 tvlv_len;

        /* only forward for specific interfaces, not for the default one. */
        if (if_outgoing == BATADV_IF_DEFAULT)
                goto out;

        orig_ifinfo = batadv_orig_ifinfo_new(orig_node, if_outgoing);
        if (!orig_ifinfo)
                goto out;

        /* acquire possibly updated router */
        router = batadv_orig_router_get(orig_node, if_outgoing);

        /* strict rule: forward packets coming from the best next hop only */
        if (neigh_node != router)
                goto out;

        /* don't forward the same seqno twice on one interface */
        if (orig_ifinfo->last_seqno_forwarded == ntohl(ogm_received->seqno))
                goto out;

        orig_ifinfo->last_seqno_forwarded = ntohl(ogm_received->seqno);

        if (ogm_received->ttl <= 1) {
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv, "ttl exceeded\n");
                goto out;
        }

        neigh_ifinfo = batadv_neigh_ifinfo_get(neigh_node, if_outgoing);
        if (!neigh_ifinfo)
                goto out;

        tvlv_len = ntohs(ogm_received->tvlv_len);

        packet_len = BATADV_OGM2_HLEN + tvlv_len;
        skb = netdev_alloc_skb_ip_align(if_outgoing->net_dev,
                                        ETH_HLEN + packet_len);
        if (!skb)
                goto out;

        skb_reserve(skb, ETH_HLEN);
        skb_buff = skb_put(skb, packet_len);
        memcpy(skb_buff, ogm_received, packet_len);

        /* apply forward penalty */
        ogm_forward = (struct batadv_ogm2_packet *)skb_buff;
        ogm_forward->throughput = htonl(neigh_ifinfo->bat_v.throughput);
        ogm_forward->ttl--;

        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                   "Forwarding OGM2 packet on %s: throughput %u, ttl %u, received via %s\n",
                   if_outgoing->net_dev->name, ntohl(ogm_forward->throughput),
                   ogm_forward->ttl, if_incoming->net_dev->name);

        batadv_v_ogm_send_to_if(skb, if_outgoing);

out:
        if (orig_ifinfo)
                batadv_orig_ifinfo_put(orig_ifinfo);
        if (router)
                batadv_neigh_node_put(router);
        if (neigh_ifinfo)
                batadv_neigh_ifinfo_put(neigh_ifinfo);
}

/**
 * batadv_v_ogm_metric_update - update route metric based on OGM
 * @bat_priv: the bat priv with all the soft interface information
 * @ogm2: OGM2 structure
 * @orig_node: Originator structure for which the OGM has been received
 * @neigh_node: the neigh_node through with the OGM has been received
 * @if_incoming: the interface where this packet was received
 * @if_outgoing: the interface for which the packet should be considered
 *
 * Return:
 *  1  if the OGM is new,
 *  0  if it is not new but valid,
 *  <0 on error (e.g. old OGM)
 */
static int batadv_v_ogm_metric_update(struct batadv_priv *bat_priv,
                                      const struct batadv_ogm2_packet *ogm2,
                                      struct batadv_orig_node *orig_node,
                                      struct batadv_neigh_node *neigh_node,
                                      struct batadv_hard_iface *if_incoming,
                                      struct batadv_hard_iface *if_outgoing)
{
        struct batadv_orig_ifinfo *orig_ifinfo = NULL;
        struct batadv_neigh_ifinfo *neigh_ifinfo = NULL;
        bool protection_started = false;
        int ret = -EINVAL;
        u32 path_throughput;
        s32 seq_diff;

        orig_ifinfo = batadv_orig_ifinfo_new(orig_node, if_outgoing);
        if (!orig_ifinfo)
                goto out;

        seq_diff = ntohl(ogm2->seqno) - orig_ifinfo->last_real_seqno;

        if (!hlist_empty(&orig_node->neigh_list) &&
            batadv_window_protected(bat_priv, seq_diff,
                                    BATADV_OGM_MAX_AGE,
                                    &orig_ifinfo->batman_seqno_reset,
                                    &protection_started)) {
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Drop packet: packet within window protection time from %pM\n",
                           ogm2->orig);
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Last reset: %ld, %ld\n",
                           orig_ifinfo->batman_seqno_reset, jiffies);
                goto out;
        }

        /* drop packets with old seqnos, however accept the first packet after
         * a host has been rebooted.
         */
        if ((seq_diff < 0) && !protection_started)
                goto out;

        neigh_node->last_seen = jiffies;

        orig_node->last_seen = jiffies;

        orig_ifinfo->last_real_seqno = ntohl(ogm2->seqno);
        orig_ifinfo->last_ttl = ogm2->ttl;

        neigh_ifinfo = batadv_neigh_ifinfo_new(neigh_node, if_outgoing);
        if (!neigh_ifinfo)
                goto out;

        path_throughput = batadv_v_forward_penalty(bat_priv, if_incoming,
                                                   if_outgoing,
                                                   ntohl(ogm2->throughput));
        neigh_ifinfo->bat_v.throughput = path_throughput;
        neigh_ifinfo->bat_v.last_seqno = ntohl(ogm2->seqno);
        neigh_ifinfo->last_ttl = ogm2->ttl;

        if (seq_diff > 0 || protection_started)
                ret = 1;
        else
                ret = 0;
out:
        if (orig_ifinfo)
                batadv_orig_ifinfo_put(orig_ifinfo);
        if (neigh_ifinfo)
                batadv_neigh_ifinfo_put(neigh_ifinfo);

        return ret;
}

/**
 * batadv_v_ogm_route_update - update routes based on OGM
 * @bat_priv: the bat priv with all the soft interface information
 * @ethhdr: the Ethernet header of the OGM2
 * @ogm2: OGM2 structure
 * @orig_node: Originator structure for which the OGM has been received
 * @neigh_node: the neigh_node through with the OGM has been received
 * @if_incoming: the interface where this packet was received
 * @if_outgoing: the interface for which the packet should be considered
 *
 * Return: true if the packet should be forwarded, false otherwise
 */
static bool batadv_v_ogm_route_update(struct batadv_priv *bat_priv,
                                      const struct ethhdr *ethhdr,
                                      const struct batadv_ogm2_packet *ogm2,
                                      struct batadv_orig_node *orig_node,
                                      struct batadv_neigh_node *neigh_node,
                                      struct batadv_hard_iface *if_incoming,
                                      struct batadv_hard_iface *if_outgoing)
{
        struct batadv_neigh_node *router = NULL;
        struct batadv_orig_node *orig_neigh_node = NULL;
        struct batadv_neigh_node *orig_neigh_router = NULL;
        struct batadv_neigh_ifinfo *router_ifinfo = NULL, *neigh_ifinfo = NULL;
        u32 router_throughput, neigh_throughput;
        u32 router_last_seqno;
        u32 neigh_last_seqno;
        s32 neigh_seq_diff;
        bool forward = false;

        orig_neigh_node = batadv_v_ogm_orig_get(bat_priv, ethhdr->h_source);
        if (!orig_neigh_node)
                goto out;

        orig_neigh_router = batadv_orig_router_get(orig_neigh_node,
                                                   if_outgoing);

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

        /* Mark the OGM to be considered for forwarding, and update routes
         * if needed.
         */
        forward = true;

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

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

        /* don't consider neighbours with worse throughput.
         * also switch route if this seqno is BATADV_V_MAX_ORIGDIFF newer than
         * the last received seqno from our best next hop.
         */
        if (router) {
                router_ifinfo = batadv_neigh_ifinfo_get(router, if_outgoing);
                neigh_ifinfo = batadv_neigh_ifinfo_get(neigh_node, if_outgoing);

                /* if these are not allocated, something is wrong. */
                if (!router_ifinfo || !neigh_ifinfo)
                        goto out;

                neigh_last_seqno = neigh_ifinfo->bat_v.last_seqno;
                router_last_seqno = router_ifinfo->bat_v.last_seqno;
                neigh_seq_diff = neigh_last_seqno - router_last_seqno;
                router_throughput = router_ifinfo->bat_v.throughput;
                neigh_throughput = neigh_ifinfo->bat_v.throughput;

                if ((neigh_seq_diff < BATADV_OGM_MAX_ORIGDIFF) &&
                    (router_throughput >= neigh_throughput))
                        goto out;
        }

        batadv_update_route(bat_priv, orig_node, if_outgoing, neigh_node);
out:
        if (router)
                batadv_neigh_node_put(router);
        if (orig_neigh_router)
                batadv_neigh_node_put(orig_neigh_router);
        if (orig_neigh_node)
                batadv_orig_node_put(orig_neigh_node);
        if (router_ifinfo)
                batadv_neigh_ifinfo_put(router_ifinfo);
        if (neigh_ifinfo)
                batadv_neigh_ifinfo_put(neigh_ifinfo);

        return forward;
}

/**
 * batadv_v_ogm_process_per_outif - process a batman v OGM for an outgoing if
 * @bat_priv: the bat priv with all the soft interface information
 * @ethhdr: the Ethernet header of the OGM2
 * @ogm2: OGM2 structure
 * @orig_node: Originator structure for which the OGM has been received
 * @neigh_node: the neigh_node through with the OGM has been received
 * @if_incoming: the interface where this packet was received
 * @if_outgoing: the interface for which the packet should be considered
 */
static void
batadv_v_ogm_process_per_outif(struct batadv_priv *bat_priv,
                               const struct ethhdr *ethhdr,
                               const struct batadv_ogm2_packet *ogm2,
                               struct batadv_orig_node *orig_node,
                               struct batadv_neigh_node *neigh_node,
                               struct batadv_hard_iface *if_incoming,
                               struct batadv_hard_iface *if_outgoing)
{
        int seqno_age;
        bool forward;

        /* first, update the metric with according sanity checks */
        seqno_age = batadv_v_ogm_metric_update(bat_priv, ogm2, orig_node,
                                               neigh_node, if_incoming,
                                               if_outgoing);

        /* outdated sequence numbers are to be discarded */
        if (seqno_age < 0)
                return;

        /* only unknown & newer OGMs contain TVLVs we are interested in */
        if ((seqno_age > 0) && (if_outgoing == BATADV_IF_DEFAULT))
                batadv_tvlv_containers_process(bat_priv, true, orig_node,
                                               NULL, NULL,
                                               (unsigned char *)(ogm2 + 1),
                                               ntohs(ogm2->tvlv_len));

        /* if the metric update went through, update routes if needed */
        forward = batadv_v_ogm_route_update(bat_priv, ethhdr, ogm2, orig_node,
                                            neigh_node, if_incoming,
                                            if_outgoing);

        /* if the routes have been processed correctly, check and forward */
        if (forward)
                batadv_v_ogm_forward(bat_priv, ogm2, orig_node, neigh_node,
                                     if_incoming, if_outgoing);
}

/**
 * batadv_v_ogm_aggr_packet - checks if there is another OGM aggregated
 * @buff_pos: current position in the skb
 * @packet_len: total length of the skb
 * @tvlv_len: tvlv length of the previously considered OGM
 *
 * Return: true if there is enough space for another OGM, false otherwise.
 */
static bool batadv_v_ogm_aggr_packet(int buff_pos, int packet_len,
                                     __be16 tvlv_len)
{
        int next_buff_pos = 0;

        next_buff_pos += buff_pos + BATADV_OGM2_HLEN;
        next_buff_pos += ntohs(tvlv_len);

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

/**
 * batadv_v_ogm_process - process an incoming batman v OGM
 * @skb: the skb containing the OGM
 * @ogm_offset: offset to the OGM which should be processed (for aggregates)
 * @if_incoming: the interface where this packet was receved
 */
static void batadv_v_ogm_process(const struct sk_buff *skb, int ogm_offset,
                                 struct batadv_hard_iface *if_incoming)
{
        struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
        struct ethhdr *ethhdr;
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_hardif_neigh_node *hardif_neigh = NULL;
        struct batadv_neigh_node *neigh_node = NULL;
        struct batadv_hard_iface *hard_iface;
        struct batadv_ogm2_packet *ogm_packet;
        u32 ogm_throughput, link_throughput, path_throughput;

        ethhdr = eth_hdr(skb);
        ogm_packet = (struct batadv_ogm2_packet *)(skb->data + ogm_offset);

        ogm_throughput = ntohl(ogm_packet->throughput);

        batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                   "Received OGM2 packet via NB: %pM, IF: %s [%pM] (from OG: %pM, seqno %u, troughput %u, TTL %u, V %u, tvlv_len %u)\n",
                   ethhdr->h_source, if_incoming->net_dev->name,
                   if_incoming->net_dev->dev_addr, ogm_packet->orig,
                   ntohl(ogm_packet->seqno), ogm_throughput, ogm_packet->ttl,
                   ogm_packet->version, ntohs(ogm_packet->tvlv_len));

        /* If the troughput metric is 0, immediately drop the packet. No need to
         * create orig_node / neigh_node for an unusable route.
         */
        if (ogm_throughput == 0) {
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Drop packet: originator packet with troughput metric of 0\n");
                return;
        }

        /* require ELP packets be to received from this neighbor first */
        hardif_neigh = batadv_hardif_neigh_get(if_incoming, ethhdr->h_source);
        if (!hardif_neigh) {
                batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
                           "Drop packet: OGM via unknown neighbor!\n");
                goto out;
        }

        orig_node = batadv_v_ogm_orig_get(bat_priv, ogm_packet->orig);
        if (!orig_node)
                return;

        neigh_node = batadv_neigh_node_get_or_create(orig_node, if_incoming,
                                                     ethhdr->h_source);
        if (!neigh_node)
                goto out;

        /* Update the received throughput metric to match the link
         * characteristic:
         *  - If this OGM traveled one hop so far (emitted by single hop
         *    neighbor) the path throughput metric equals the link throughput.
         *  - For OGMs traversing more than hop the path throughput metric is
         *    the smaller of the path throughput and the link throughput.
         */
        link_throughput = ewma_throughput_read(&hardif_neigh->bat_v.throughput);
        path_throughput = min_t(u32, link_throughput, ogm_throughput);
        ogm_packet->throughput = htonl(path_throughput);

        batadv_v_ogm_process_per_outif(bat_priv, ethhdr, ogm_packet, orig_node,
                                       neigh_node, if_incoming,
                                       BATADV_IF_DEFAULT);

        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 != bat_priv->soft_iface)
                        continue;

                if (!kref_get_unless_zero(&hard_iface->refcount))
                        continue;

                batadv_v_ogm_process_per_outif(bat_priv, ethhdr, ogm_packet,
                                               orig_node, neigh_node,
                                               if_incoming, hard_iface);

                batadv_hardif_put(hard_iface);
        }
        rcu_read_unlock();
out:
        if (orig_node)
                batadv_orig_node_put(orig_node);
        if (neigh_node)
                batadv_neigh_node_put(neigh_node);
        if (hardif_neigh)
                batadv_hardif_neigh_put(hardif_neigh);
}

/**
 * batadv_v_ogm_packet_recv - OGM2 receiving handler
 * @skb: the received OGM
 * @if_incoming: the interface where this OGM has been received
 *
 * Return: NET_RX_SUCCESS and consume the skb on success or returns NET_RX_DROP
 * (without freeing the skb) on failure
 */
int batadv_v_ogm_packet_recv(struct sk_buff *skb,
                             struct batadv_hard_iface *if_incoming)
{
        struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
        struct batadv_ogm2_packet *ogm_packet;
        struct ethhdr *ethhdr = eth_hdr(skb);
        int ogm_offset;
        u8 *packet_pos;
        int ret = NET_RX_DROP;

        /* did we receive a OGM2 packet on an interface that does not have
         * B.A.T.M.A.N. V enabled ?
         */
        if (strcmp(bat_priv->algo_ops->name, "BATMAN_V") != 0)
                return NET_RX_DROP;

        if (!batadv_check_management_packet(skb, if_incoming, BATADV_OGM2_HLEN))
                return NET_RX_DROP;

        if (batadv_is_my_mac(bat_priv, ethhdr->h_source))
                return NET_RX_DROP;

        ogm_packet = (struct batadv_ogm2_packet *)skb->data;

        if (batadv_is_my_mac(bat_priv, ogm_packet->orig))
                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);

        ogm_offset = 0;
        ogm_packet = (struct batadv_ogm2_packet *)skb->data;

        while (batadv_v_ogm_aggr_packet(ogm_offset, skb_headlen(skb),
                                        ogm_packet->tvlv_len)) {
                batadv_v_ogm_process(skb, ogm_offset, if_incoming);

                ogm_offset += BATADV_OGM2_HLEN;
                ogm_offset += ntohs(ogm_packet->tvlv_len);

                packet_pos = skb->data + ogm_offset;
                ogm_packet = (struct batadv_ogm2_packet *)packet_pos;
        }

        ret = NET_RX_SUCCESS;
        consume_skb(skb);

        return ret;
}

/**
 * batadv_v_ogm_init - initialise the OGM2 engine
 * @bat_priv: the bat priv with all the soft interface information
 *
 * Return: 0 on success or a negative error code in case of failure
 */
int batadv_v_ogm_init(struct batadv_priv *bat_priv)
{
        struct batadv_ogm2_packet *ogm_packet;
        unsigned char *ogm_buff;
        u32 random_seqno;

        bat_priv->bat_v.ogm_buff_len = BATADV_OGM2_HLEN;
        ogm_buff = kzalloc(bat_priv->bat_v.ogm_buff_len, GFP_ATOMIC);
        if (!ogm_buff)
                return -ENOMEM;

        bat_priv->bat_v.ogm_buff = ogm_buff;
        ogm_packet = (struct batadv_ogm2_packet *)ogm_buff;
        ogm_packet->packet_type = BATADV_OGM2;
        ogm_packet->version = BATADV_COMPAT_VERSION;
        ogm_packet->ttl = BATADV_TTL;
        ogm_packet->flags = BATADV_NO_FLAGS;
        ogm_packet->throughput = htonl(BATADV_THROUGHPUT_MAX_VALUE);

        /* randomize initial seqno to avoid collision */
        get_random_bytes(&random_seqno, sizeof(random_seqno));
        atomic_set(&bat_priv->bat_v.ogm_seqno, random_seqno);
        INIT_DELAYED_WORK(&bat_priv->bat_v.ogm_wq, batadv_v_ogm_send);

        return 0;
}

/**
 * batadv_v_ogm_free - free OGM private resources
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_v_ogm_free(struct batadv_priv *bat_priv)
{
        cancel_delayed_work_sync(&bat_priv->bat_v.ogm_wq);

        kfree(bat_priv->bat_v.ogm_buff);
        bat_priv->bat_v.ogm_buff = NULL;
        bat_priv->bat_v.ogm_buff_len = 0;
}