/* Copyright (C) 2007-2013 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 "bridge_loop_avoidance.h"
#include "distributed-arp-table.h"
#include "network-coding.h"
#include "fragmentation.h"

#include <linux/if_vlan.h>

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

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, -1,
                                          "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;
}

/**
 * batadv_bonding_candidate_add - consider a new link for bonding mode towards
 *  the given originator
 * @bat_priv: the bat priv with all the soft interface information
 * @orig_node: the target node
 * @neigh_node: the neighbor representing the new link to consider for bonding
 *  mode
 */
void batadv_bonding_candidate_add(struct batadv_priv *bat_priv,
                                  struct batadv_orig_node *orig_node,
                                  struct batadv_neigh_node *neigh_node)
{
        struct batadv_algo_ops *bao = bat_priv->bat_algo_ops;
        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 (bao->bat_neigh_is_equiv_or_better(neigh_node, router))
                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,
                                 &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 = eth_hdr(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;
}

/**
 * batadv_recv_my_icmp_packet - receive an icmp packet locally
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: icmp packet to process
 *
 * Returns NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
 * otherwise.
 */
static int batadv_recv_my_icmp_packet(struct batadv_priv *bat_priv,
                                      struct sk_buff *skb)
{
        struct batadv_hard_iface *primary_if = NULL;
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_icmp_header *icmph;
        int res, ret = NET_RX_DROP;

        icmph = (struct batadv_icmp_header *)skb->data;

        switch (icmph->msg_type) {
        case BATADV_ECHO_REPLY:
        case BATADV_DESTINATION_UNREACHABLE:
        case BATADV_TTL_EXCEEDED:
                /* receive the packet */
                if (skb_linearize(skb) < 0)
                        break;

                batadv_socket_receive_packet(icmph, skb->len);
                break;
        case BATADV_ECHO_REQUEST:
                /* answer echo request (ping) */
                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, icmph->orig);
                if (!orig_node)
                        goto out;

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

                icmph = (struct batadv_icmp_header *)skb->data;

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

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

                break;
        default:
                /* drop unknown type */
                goto out;
        }
out:
        if (primary_if)
                batadv_hardif_free_ref(primary_if);
        if (orig_node)
                batadv_orig_node_free_ref(orig_node);
        return ret;
}

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

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

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

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

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

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

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

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

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

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


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

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

        ethhdr = eth_hdr(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(bat_priv, ethhdr->h_dest))
                goto out;

        icmph = (struct batadv_icmp_header *)skb->data;

        /* add record route information if not full */
        if ((icmph->msg_type == BATADV_ECHO_REPLY ||
             icmph->msg_type == BATADV_ECHO_REQUEST) &&
            (skb->len >= sizeof(struct batadv_icmp_packet_rr))) {
                if (skb_linearize(skb) < 0)
                        goto out;

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

                icmph = (struct batadv_icmp_header *)skb->data;
                icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmph;
                if (icmp_packet_rr->rr_cur >= BATADV_RR_LEN)
                        goto out;

                memcpy(&(icmp_packet_rr->rr[icmp_packet_rr->rr_cur]),
                       ethhdr->h_dest, ETH_ALEN);
                icmp_packet_rr->rr_cur++;
        }

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

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

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

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

        icmph = (struct batadv_icmp_header *)skb->data;

        /* decrement ttl */
        icmph->ttl--;

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

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

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

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

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

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

                router = tmp_neigh_node;
                break;
        }

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

        if (!router)
                goto out;

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

out:
        rcu_read_unlock();
        return router;
}

/**
 * batadv_find_ifalter_router - find the best of the remaining candidates which
 *  are not using this interface
 * @bat_priv: the bat priv with all the soft interface information
 * @primary_orig: the destination
 * @recv_if: the interface that the router returned by this function has to not
 *  use
 *
 * Returns the best candidate towards primary_orig that is not using recv_if.
 * Increases the returned neighbor's refcount
 */
static struct batadv_neigh_node *
batadv_find_ifalter_router(struct batadv_priv *bat_priv,
                           struct batadv_orig_node *primary_orig,
                           const struct batadv_hard_iface *recv_if)
{
        struct batadv_neigh_node *router = NULL, *first_candidate = NULL;
        struct batadv_algo_ops *bao = bat_priv->bat_algo_ops;
        struct batadv_neigh_node *tmp_neigh_node;

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

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

                if (router && bao->bat_neigh_cmp(tmp_neigh_node, router))
                        continue;

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

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

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

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

        rcu_read_unlock();
        return router;
}

/**
 * batadv_check_unicast_packet - Check for malformed unicast packets
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: packet to check
 * @hdr_size: size of header to pull
 *
 * Check for short header and bad addresses in given packet. Returns negative
 * value when check fails and 0 otherwise. The negative value depends on the
 * reason: -ENODATA for bad header, -EBADR for broadcast destination or source,
 * and -EREMOTE for non-local (other host) destination.
 */
static int batadv_check_unicast_packet(struct batadv_priv *bat_priv,
                                       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 -ENODATA;

        ethhdr = eth_hdr(skb);

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

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

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

        return 0;
}

/* 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(bat_priv, 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_unicast_packet *unicast_packet;
        struct ethhdr *ethhdr = eth_hdr(skb);
        int res, hdr_len, ret = NET_RX_DROP;

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

        /* TTL exceeded */
        if (unicast_packet->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;

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

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

        switch (unicast_packet->packet_type) {
        case BATADV_UNICAST_4ADDR:
                hdr_len = sizeof(struct batadv_unicast_4addr_packet);
                break;
        case BATADV_UNICAST:
                hdr_len = sizeof(struct batadv_unicast_packet);
                break;
        default:
                /* other packet types not supported - yet */
                hdr_len = -1;
                break;
        }

        if (hdr_len > 0)
                batadv_skb_set_priority(skb, hdr_len);

        res = batadv_send_skb_to_orig(skb, orig_node, recv_if);

        /* translate transmit result into receive result */
        if (res == NET_XMIT_SUCCESS) {
                /* skb was transmitted and consumed */
                batadv_inc_counter(bat_priv, BATADV_CNT_FORWARD);
                batadv_add_counter(bat_priv, BATADV_CNT_FORWARD_BYTES,
                                   skb->len + ETH_HLEN);

                ret = NET_RX_SUCCESS;
        } else if (res == NET_XMIT_POLICED) {
                /* skb was buffered and consumed */
                ret = NET_RX_SUCCESS;
        }

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

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

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

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

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

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

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

        return ret;
}

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

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

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

        unicast_packet = (struct batadv_unicast_packet *)skb->data;
        vid = batadv_get_vid(skb, hdr_len);
        ethhdr = (struct ethhdr *)(skb->data + hdr_len);

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

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

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

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

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

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

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

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

        batadv_hardif_free_ref(primary_if);

        unicast_packet->ttvn = curr_ttvn;

        return 1;
}

/**
 * batadv_recv_unhandled_unicast_packet - receive and process packets which
 *      are in the unicast number space but not yet known to the implementation
 * @skb: unicast tvlv packet to process
 * @recv_if: pointer to interface this packet was received on
 *
 * Returns NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
 * otherwise.
 */
int batadv_recv_unhandled_unicast_packet(struct sk_buff *skb,
                                         struct batadv_hard_iface *recv_if)
{
        struct batadv_unicast_packet *unicast_packet;
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        int check, hdr_size = sizeof(*unicast_packet);

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

        /* we don't know about this type, drop it. */
        unicast_packet = (struct batadv_unicast_packet *)skb->data;
        if (batadv_is_my_mac(bat_priv, unicast_packet->dest))
                return NET_RX_DROP;

        return batadv_route_unicast_packet(skb, recv_if);
}

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

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

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

        /* function returns -EREMOTE for promiscuous packets */
        check = batadv_check_unicast_packet(bat_priv, skb, hdr_size);

        /* Even though the packet is not for us, we might save it to use for
         * decoding a later received coded packet
         */
        if (check == -EREMOTE)
                batadv_nc_skb_store_sniffed_unicast(bat_priv, skb);

        if (check < 0)
                return NET_RX_DROP;
        if (!batadv_check_unicast_ttvn(bat_priv, skb, hdr_size))
                return NET_RX_DROP;

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

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

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

rx_success:
                if (orig_node)
                        batadv_orig_node_free_ref(orig_node);

                return NET_RX_SUCCESS;
        }

        return batadv_route_unicast_packet(skb, recv_if);
}

/**
 * batadv_recv_unicast_tvlv - receive and process unicast tvlv packets
 * @skb: unicast tvlv packet to process
 * @recv_if: pointer to interface this packet was received on
 * @dst_addr: the payload destination
 *
 * Returns NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
 * otherwise.
 */
int batadv_recv_unicast_tvlv(struct sk_buff *skb,
                             struct batadv_hard_iface *recv_if)
{
        struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
        struct batadv_unicast_tvlv_packet *unicast_tvlv_packet;
        unsigned char *tvlv_buff;
        uint16_t tvlv_buff_len;
        int hdr_size = sizeof(*unicast_tvlv_packet);
        int ret = NET_RX_DROP;

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

        /* the header is likely to be modified while forwarding */
        if (skb_cow(skb, hdr_size) < 0)
                return NET_RX_DROP;

        /* packet needs to be linearized to access the tvlv content */
        if (skb_linearize(skb) < 0)
                return NET_RX_DROP;

        unicast_tvlv_packet = (struct batadv_unicast_tvlv_packet *)skb->data;

        tvlv_buff = (unsigned char *)(skb->data + hdr_size);
        tvlv_buff_len = ntohs(unicast_tvlv_packet->tvlv_len);

        if (tvlv_buff_len > skb->len - hdr_size)
                return NET_RX_DROP;

        ret = batadv_tvlv_containers_process(bat_priv, false, NULL,
                                             unicast_tvlv_packet->src,
                                             unicast_tvlv_packet->dst,
                                             tvlv_buff, tvlv_buff_len);

        if (ret != NET_RX_SUCCESS)
                ret = batadv_route_unicast_packet(skb, recv_if);

        return ret;
}

/**
 * batadv_recv_frag_packet - process received fragment
 * @skb: the received fragment
 * @recv_if: interface that the skb is received on
 *
 * This function does one of the three following things: 1) Forward fragment, if
 * the assembled packet will exceed our MTU; 2) Buffer fragment, if we till
 * lack further fragments; 3) Merge fragments, if we have all needed parts.
 *
 * Return NET_RX_DROP if the skb is not consumed, NET_RX_SUCCESS otherwise.
 */
int batadv_recv_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_orig_node *orig_node_src = NULL;
        struct batadv_frag_packet *frag_packet;
        int ret = NET_RX_DROP;

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

        frag_packet = (struct batadv_frag_packet *)skb->data;
        orig_node_src = batadv_orig_hash_find(bat_priv, frag_packet->orig);
        if (!orig_node_src)
                goto out;

        /* Route the fragment if it is not for us and too big to be merged. */
        if (!batadv_is_my_mac(bat_priv, frag_packet->dest) &&
            batadv_frag_skb_fwd(skb, recv_if, orig_node_src)) {
                ret = NET_RX_SUCCESS;
                goto out;
        }

        batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_RX);
        batadv_add_counter(bat_priv, BATADV_CNT_FRAG_RX_BYTES, skb->len);

        /* Add fragment to buffer and merge if possible. */
        if (!batadv_frag_skb_buffer(&skb, orig_node_src))
                goto out;

        /* Deliver merged packet to the appropriate handler, if it was
         * merged
         */
        if (skb)
                batadv_batman_skb_recv(skb, recv_if->net_dev,
                                       &recv_if->batman_adv_ptype, NULL);

        ret = NET_RX_SUCCESS;

out:
        if (orig_node_src)
                batadv_orig_node_free_ref(orig_node_src);

        return ret;
}

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 = eth_hdr(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(bat_priv, ethhdr->h_source))
                goto out;

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

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

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

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

        if (!orig_node)
                goto out;

        spin_lock_bh(&orig_node->bcast_seqno_lock);

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

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

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

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

        spin_unlock_bh(&orig_node->bcast_seqno_lock);

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

        batadv_skb_set_priority(skb, sizeof(struct batadv_bcast_packet));

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

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

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

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

rx_success:
        ret = NET_RX_SUCCESS;
        goto out;

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