Linux 5.7.7

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

// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2007-2020  B.A.T.M.A.N. contributors:
 *
 * Marek Lindner, Simon Wunderlich
 */

#include "routing.h"
#include "main.h"

#include <linux/atomic.h>
#include <linux/byteorder/generic.h>
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/jiffies.h>
#include <linux/kref.h>
#include <linux/netdevice.h>
#include <linux/printk.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/stddef.h>
#include <uapi/linux/batadv_packet.h>

#include "bitarray.h"
#include "bridge_loop_avoidance.h"
#include "distributed-arp-table.h"
#include "fragmentation.h"
#include "hard-interface.h"
#include "icmp_socket.h"
#include "log.h"
#include "network-coding.h"
#include "originator.h"
#include "send.h"
#include "soft-interface.h"
#include "tp_meter.h"
#include "translation-table.h"
#include "tvlv.h"

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

/**
 * _batadv_update_route() - set the router for this originator
 * @bat_priv: the bat priv with all the soft interface information
 * @orig_node: orig node which is to be configured
 * @recv_if: the receive interface for which this route is set
 * @neigh_node: neighbor which should be the next router
 *
 * This function does not perform any error checks
 */
static void _batadv_update_route(struct batadv_priv *bat_priv,
                                 struct batadv_orig_node *orig_node,
                                 struct batadv_hard_iface *recv_if,
                                 struct batadv_neigh_node *neigh_node)
{
        struct batadv_orig_ifinfo *orig_ifinfo;
        struct batadv_neigh_node *curr_router;

        orig_ifinfo = batadv_orig_ifinfo_get(orig_node, recv_if);
        if (!orig_ifinfo)
                return;

        spin_lock_bh(&orig_node->neigh_list_lock);
        /* curr_router used earlier may not be the current orig_ifinfo->router
         * anymore because it was dereferenced outside of the neigh_list_lock
         * protected region. After the new best neighbor has replace the current
         * best neighbor the reference counter needs to decrease. Consequently,
         * the code needs to ensure the curr_router variable contains a pointer
         * to the replaced best neighbor.
         */
        curr_router = rcu_dereference_protected(orig_ifinfo->router, true);

        /* increase refcount of new best neighbor */
        if (neigh_node)
                kref_get(&neigh_node->refcount);

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

        /* 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);
        }

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

/**
 * batadv_update_route() - set the router for this originator
 * @bat_priv: the bat priv with all the soft interface information
 * @orig_node: orig node which is to be configured
 * @recv_if: the receive interface for which this route is set
 * @neigh_node: neighbor which should be the next router
 */
void batadv_update_route(struct batadv_priv *bat_priv,
                         struct batadv_orig_node *orig_node,
                         struct batadv_hard_iface *recv_if,
                         struct batadv_neigh_node *neigh_node)
{
        struct batadv_neigh_node *router = NULL;

        if (!orig_node)
                goto out;

        router = batadv_orig_router_get(orig_node, recv_if);

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

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

/**
 * batadv_window_protected() - checks whether the host restarted and is in the
 *  protection time.
 * @bat_priv: the bat priv with all the soft interface information
 * @seq_num_diff: difference between the current/received sequence number and
 *  the last sequence number
 * @seq_old_max_diff: maximum age of sequence number not considered as restart
 * @last_reset: jiffies timestamp of the last reset, will be updated when reset
 *  is detected
 * @protection_started: is set to true if the protection window was started,
 *   doesn't change otherwise.
 *
 * Return:
 *  false if the packet is to be accepted.
 *  true if the packet is to be ignored.
 */
bool batadv_window_protected(struct batadv_priv *bat_priv, s32 seq_num_diff,
                             s32 seq_old_max_diff, unsigned long *last_reset,
                             bool *protection_started)
{
        if (seq_num_diff <= -seq_old_max_diff ||
            seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE) {
                if (!batadv_has_timed_out(*last_reset,
                                          BATADV_RESET_PROTECTION_MS))
                        return true;

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

        return false;
}

/**
 * batadv_check_management_packet() - Check preconditions for management packets
 * @skb: incoming packet buffer
 * @hard_iface: incoming hard interface
 * @header_len: minimal header length of packet type
 *
 * Return: true when management preconditions are met, false otherwise
 */
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 invalid sender address */
        if (!is_valid_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
 *
 * Return: 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;

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

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

                /* skb was consumed */
                skb = NULL;
                break;
        case BATADV_TP:
                if (!pskb_may_pull(skb, sizeof(struct batadv_icmp_tp_packet)))
                        goto out;

                batadv_tp_meter_recv(bat_priv, skb);
                ret = NET_RX_SUCCESS;
                /* skb was consumed */
                skb = NULL;
                goto out;
        default:
                /* drop unknown type */
                goto out;
        }
out:
        if (primary_if)
                batadv_hardif_put(primary_if);
        if (orig_node)
                batadv_orig_node_put(orig_node);

        kfree_skb(skb);

        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 res, 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;

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

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

        /* skb was consumed */
        skb = NULL;

out:
        if (primary_if)
                batadv_hardif_put(primary_if);
        if (orig_node)
                batadv_orig_node_put(orig_node);

        kfree_skb(skb);

        return ret;
}

/**
 * batadv_recv_icmp_packet() - Process incoming icmp packet
 * @skb: incoming packet buffer
 * @recv_if: incoming hard interface
 *
 * Return: NET_RX_SUCCESS on success or NET_RX_DROP in case of failure
 */
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 res, ret = NET_RX_DROP;

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

        ethhdr = eth_hdr(skb);

        /* packet with unicast indication but non-unicast recipient */
        if (!is_valid_ether_addr(ethhdr->h_dest))
                goto free_skb;

        /* packet with broadcast/multicast sender address */
        if (is_multicast_ether_addr(ethhdr->h_source))
                goto free_skb;

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

        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 free_skb;

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

                ethhdr = eth_hdr(skb);
                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 free_skb;

                ether_addr_copy(icmp_packet_rr->rr[icmp_packet_rr->rr_cur],
                                ethhdr->h_dest);
                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 free_skb;

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

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

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

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

        /* skb was consumed */
        skb = NULL;

put_orig_node:
        if (orig_node)
                batadv_orig_node_put(orig_node);
free_skb:
        kfree_skb(skb);

        return ret;
}

/**
 * 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.
 *
 * Return: 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 non-unicast recipient */
        if (!is_valid_ether_addr(ethhdr->h_dest))
                return -EBADR;

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

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

        return 0;
}

/**
 * batadv_last_bonding_get() - Get last_bonding_candidate of orig_node
 * @orig_node: originator node whose last bonding candidate should be retrieved
 *
 * Return: last bonding candidate of router or NULL if not found
 *
 * The object is returned with refcounter increased by 1.
 */
static struct batadv_orig_ifinfo *
batadv_last_bonding_get(struct batadv_orig_node *orig_node)
{
        struct batadv_orig_ifinfo *last_bonding_candidate;

        spin_lock_bh(&orig_node->neigh_list_lock);
        last_bonding_candidate = orig_node->last_bonding_candidate;

        if (last_bonding_candidate)
                kref_get(&last_bonding_candidate->refcount);
        spin_unlock_bh(&orig_node->neigh_list_lock);

        return last_bonding_candidate;
}

/**
 * batadv_last_bonding_replace() - Replace last_bonding_candidate of orig_node
 * @orig_node: originator node whose bonding candidates should be replaced
 * @new_candidate: new bonding candidate or NULL
 */
static void
batadv_last_bonding_replace(struct batadv_orig_node *orig_node,
                            struct batadv_orig_ifinfo *new_candidate)
{
        struct batadv_orig_ifinfo *old_candidate;

        spin_lock_bh(&orig_node->neigh_list_lock);
        old_candidate = orig_node->last_bonding_candidate;

        if (new_candidate)
                kref_get(&new_candidate->refcount);
        orig_node->last_bonding_candidate = new_candidate;
        spin_unlock_bh(&orig_node->neigh_list_lock);

        if (old_candidate)
                batadv_orig_ifinfo_put(old_candidate);
}

/**
 * batadv_find_router() - find a suitable router for this originator
 * @bat_priv: the bat priv with all the soft interface information
 * @orig_node: the destination node
 * @recv_if: pointer to interface this packet was received on
 *
 * Return: the router which should be used for this orig_node on
 * this interface, or NULL if not available.
 */
struct batadv_neigh_node *
batadv_find_router(struct batadv_priv *bat_priv,
                   struct batadv_orig_node *orig_node,
                   struct batadv_hard_iface *recv_if)
{
        struct batadv_algo_ops *bao = bat_priv->algo_ops;
        struct batadv_neigh_node *first_candidate_router = NULL;
        struct batadv_neigh_node *next_candidate_router = NULL;
        struct batadv_neigh_node *router, *cand_router = NULL;
        struct batadv_neigh_node *last_cand_router = NULL;
        struct batadv_orig_ifinfo *cand, *first_candidate = NULL;
        struct batadv_orig_ifinfo *next_candidate = NULL;
        struct batadv_orig_ifinfo *last_candidate;
        bool last_candidate_found = false;

        if (!orig_node)
                return NULL;

        router = batadv_orig_router_get(orig_node, recv_if);

        if (!router)
                return router;

        /* only consider bonding for recv_if == BATADV_IF_DEFAULT (first hop)
         * and if activated.
         */
        if (!(recv_if == BATADV_IF_DEFAULT && atomic_read(&bat_priv->bonding)))
                return router;

        /* bonding: loop through the list of possible routers found
         * for the various outgoing interfaces and find a candidate after
         * the last chosen bonding candidate (next_candidate). If no such
         * router is found, use the first candidate found (the previously
         * chosen bonding candidate might have been the last one in the list).
         * If this can't be found either, return the previously chosen
         * router - obviously there are no other candidates.
         */
        rcu_read_lock();
        last_candidate = batadv_last_bonding_get(orig_node);
        if (last_candidate)
                last_cand_router = rcu_dereference(last_candidate->router);

        hlist_for_each_entry_rcu(cand, &orig_node->ifinfo_list, list) {
                /* acquire some structures and references ... */
                if (!kref_get_unless_zero(&cand->refcount))
                        continue;

                cand_router = rcu_dereference(cand->router);
                if (!cand_router)
                        goto next;

                if (!kref_get_unless_zero(&cand_router->refcount)) {
                        cand_router = NULL;
                        goto next;
                }

                /* alternative candidate should be good enough to be
                 * considered
                 */
                if (!bao->neigh.is_similar_or_better(cand_router,
                                                     cand->if_outgoing, router,
                                                     recv_if))
                        goto next;

                /* don't use the same router twice */
                if (last_cand_router == cand_router)
                        goto next;

                /* mark the first possible candidate */
                if (!first_candidate) {
                        kref_get(&cand_router->refcount);
                        kref_get(&cand->refcount);
                        first_candidate = cand;
                        first_candidate_router = cand_router;
                }

                /* check if the loop has already passed the previously selected
                 * candidate ... this function should select the next candidate
                 * AFTER the previously used bonding candidate.
                 */
                if (!last_candidate || last_candidate_found) {
                        next_candidate = cand;
                        next_candidate_router = cand_router;
                        break;
                }

                if (last_candidate == cand)
                        last_candidate_found = true;
next:
                /* free references */
                if (cand_router) {
                        batadv_neigh_node_put(cand_router);
                        cand_router = NULL;
                }
                batadv_orig_ifinfo_put(cand);
        }
        rcu_read_unlock();

        /* After finding candidates, handle the three cases:
         * 1) there is a next candidate, use that
         * 2) there is no next candidate, use the first of the list
         * 3) there is no candidate at all, return the default router
         */
        if (next_candidate) {
                batadv_neigh_node_put(router);

                kref_get(&next_candidate_router->refcount);
                router = next_candidate_router;
                batadv_last_bonding_replace(orig_node, next_candidate);
        } else if (first_candidate) {
                batadv_neigh_node_put(router);

                kref_get(&first_candidate_router->refcount);
                router = first_candidate_router;
                batadv_last_bonding_replace(orig_node, first_candidate);
        } else {
                batadv_last_bonding_replace(orig_node, NULL);
        }

        /* cleanup of candidates */
        if (first_candidate) {
                batadv_neigh_node_put(first_candidate_router);
                batadv_orig_ifinfo_put(first_candidate);
        }

        if (next_candidate) {
                batadv_neigh_node_put(next_candidate_router);
                batadv_orig_ifinfo_put(next_candidate);
        }

        if (last_candidate)
                batadv_orig_ifinfo_put(last_candidate);

        return router;
}

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;
        unsigned int len;

        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 free_skb;
        }

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

        if (!orig_node)
                goto free_skb;

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

        /* 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);

        len = skb->len;
        res = batadv_send_skb_to_orig(skb, orig_node, recv_if);

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

        /* skb was consumed */
        skb = NULL;

put_orig_node:
        batadv_orig_node_put(orig_node);
free_skb:
        kfree_skb(skb);

        return ret;
}

/**
 * batadv_reroute_unicast_packet() - update the unicast header for re-routing
 * @bat_priv: the bat priv with all the soft interface information
 * @skb: unicast packet to process
 * @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)
 *
 * Return: true if the packet header has been updated, false otherwise
 */
static bool
batadv_reroute_unicast_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
                              struct batadv_unicast_packet *unicast_packet,
                              u8 *dst_addr, unsigned short vid)
{
        struct batadv_orig_node *orig_node = NULL;
        struct batadv_hard_iface *primary_if = NULL;
        bool ret = false;
        u8 *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 = (u8)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 = (u8)atomic_read(&orig_node->last_ttvn);
        }

        /* update the packet header */
        skb_postpull_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
        ether_addr_copy(unicast_packet->dest, orig_addr);
        unicast_packet->ttvn = orig_ttvn;
        skb_postpush_rcsum(skb, unicast_packet, sizeof(*unicast_packet));

        ret = true;
out:
        if (primary_if)
                batadv_hardif_put(primary_if);
        if (orig_node)
                batadv_orig_node_put(orig_node);

        return ret;
}

static bool 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;
        u8 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))
                return false;

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

        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, skb, unicast_packet,
                                                  ethhdr->h_dest, vid))
                        batadv_dbg_ratelimited(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 true;
        }

        /* 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 = (u8)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 false;

                curr_ttvn = (u8)atomic_read(&orig_node->last_ttvn);
                batadv_orig_node_put(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 true;

        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, skb, unicast_packet,
                                          ethhdr->h_dest, vid)) {
                batadv_dbg_ratelimited(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 true;
        }

        /* 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 false;

        /* 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 false;

        /* update the packet header */
        skb_postpull_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
        ether_addr_copy(unicast_packet->dest, primary_if->net_dev->dev_addr);
        unicast_packet->ttvn = curr_ttvn;
        skb_postpush_rcsum(skb, unicast_packet, sizeof(*unicast_packet));

        batadv_hardif_put(primary_if);

        return true;
}

/**
 * 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
 *
 * Return: 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)
                goto free_skb;

        /* 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))
                goto free_skb;

        return batadv_route_unicast_packet(skb, recv_if);

free_skb:
        kfree_skb(skb);
        return NET_RX_DROP;
}

/**
 * batadv_recv_unicast_packet() - Process incoming unicast packet
 * @skb: incoming packet buffer
 * @recv_if: incoming hard interface
 *
 * Return: NET_RX_SUCCESS on success or NET_RX_DROP in case of failure
 */
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;
        u8 *orig_addr, *orig_addr_gw;
        struct batadv_orig_node *orig_node = NULL, *orig_node_gw = NULL;
        int check, hdr_size = sizeof(*unicast_packet);
        enum batadv_subtype subtype;
        int ret = NET_RX_DROP;
        bool is4addr, is_gw;

        unicast_packet = (struct batadv_unicast_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)
                goto free_skb;
        if (!batadv_check_unicast_ttvn(bat_priv, skb, hdr_size))
                goto free_skb;

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

        /* packet for me */
        if (batadv_is_my_mac(bat_priv, unicast_packet->dest)) {
                /* If this is a unicast packet from another backgone gw,
                 * drop it.
                 */
                orig_addr_gw = eth_hdr(skb)->h_source;
                orig_node_gw = batadv_orig_hash_find(bat_priv, orig_addr_gw);
                if (orig_node_gw) {
                        is_gw = batadv_bla_is_backbone_gw(skb, orig_node_gw,
                                                          hdr_size);
                        batadv_orig_node_put(orig_node_gw);
                        if (is_gw) {
                                batadv_dbg(BATADV_DBG_BLA, bat_priv,
                                           "%s(): Dropped unicast pkt received from another backbone gw %pM.\n",
                                           __func__, orig_addr_gw);
                                goto free_skb;
                        }
                }

                if (is4addr) {
                        unicast_4addr_packet =
                                (struct batadv_unicast_4addr_packet *)skb->data;
                        subtype = unicast_4addr_packet->subtype;
                        batadv_dat_inc_counter(bat_priv, subtype);

                        /* Only payload data should be considered for speedy
                         * join. For example, DAT also uses unicast 4addr
                         * types, but those packets should not be considered
                         * for speedy join, since the clients do not actually
                         * reside at the sending originator.
                         */
                        if (subtype == BATADV_P_DATA) {
                                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_dat_snoop_incoming_dhcp_ack(bat_priv, skb, hdr_size);

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

rx_success:
                if (orig_node)
                        batadv_orig_node_put(orig_node);

                return NET_RX_SUCCESS;
        }

        ret = batadv_route_unicast_packet(skb, recv_if);
        /* skb was consumed */
        skb = NULL;

free_skb:
        kfree_skb(skb);

        return ret;
}

/**
 * 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
 *
 * Return: 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;
        u16 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)
                goto free_skb;

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

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

        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)
                goto free_skb;

        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);
                /* skb was consumed */
                skb = NULL;
        }

free_skb:
        kfree_skb(skb);

        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 free_skb;

        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 free_skb;

        skb->priority = frag_packet->priority + 256;

        /* 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)) {
                /* skb was consumed */
                skb = NULL;
                ret = NET_RX_SUCCESS;
                goto put_orig_node;
        }

        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 put_orig_node;

        /* 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);
                /* skb was consumed */
                skb = NULL;
        }

        ret = NET_RX_SUCCESS;

put_orig_node:
        batadv_orig_node_put(orig_node_src);
free_skb:
        kfree_skb(skb);

        return ret;
}

/**
 * batadv_recv_bcast_packet() - Process incoming broadcast packet
 * @skb: incoming packet buffer
 * @recv_if: incoming hard interface
 *
 * Return: NET_RX_SUCCESS on success or NET_RX_DROP in case of failure
 */
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;
        s32 seq_diff;
        u32 seqno;

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

        ethhdr = eth_hdr(skb);

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

        /* packet with broadcast/multicast sender address */
        if (is_multicast_ether_addr(ethhdr->h_source))
                goto free_skb;

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

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

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

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

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

        if (!orig_node)
                goto free_skb;

        spin_lock_bh(&orig_node->bcast_seqno_lock);

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

        seq_diff = 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,
                                    BATADV_BCAST_MAX_AGE,
                                    &orig_node->bcast_seqno_reset, NULL))
                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 = 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 free_skb;

        batadv_skb_set_priority(skb, sizeof(struct batadv_bcast_packet));

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

        /* 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 free_skb;

        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_dat_snoop_incoming_dhcp_ack(bat_priv, skb, hdr_size);

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

rx_success:
        ret = NET_RX_SUCCESS;
        goto out;

spin_unlock:
        spin_unlock_bh(&orig_node->bcast_seqno_lock);
free_skb:
        kfree_skb(skb);
out:
        if (orig_node)
                batadv_orig_node_put(orig_node);
        return ret;
}