// SPDX-License-Identifier: GPL-2.0

  /* Copyright (C) 2011-2019  B.A.T.M.A.N. contributors:

   *
   * Antonio Quartulli

   */

  #include "distributed-arp-table.h"
  #include "main.h"

  #include <asm/unaligned.h>

  #include <linux/atomic.h>

  #include <linux/bitops.h>

  #include <linux/byteorder/generic.h>
  #include <linux/errno.h>
  #include <linux/etherdevice.h>

  #include <linux/gfp.h>

  #include <linux/if_arp.h>

  #include <linux/if_ether.h>

  #include <linux/if_vlan.h>

  #include <linux/in.h>

  #include <linux/ip.h>

  #include <linux/jiffies.h>
  #include <linux/kernel.h>

  #include <linux/kref.h>

  #include <linux/list.h>

  #include <linux/netlink.h>

  #include <linux/rculist.h>
  #include <linux/rcupdate.h>
  #include <linux/seq_file.h>
  #include <linux/skbuff.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/stddef.h>
  #include <linux/string.h>

  #include <linux/udp.h>

  #include <linux/workqueue.h>

  #include <net/arp.h>

  #include <net/genetlink.h>
  #include <net/netlink.h>
  #include <net/sock.h>
  #include <uapi/linux/batman_adv.h>

  #include "bridge_loop_avoidance.h"

  #include "hard-interface.h"

  #include "hash.h"

  #include "log.h"

  #include "netlink.h"

  #include "originator.h"
  #include "send.h"

  #include "soft-interface.h"

  #include "translation-table.h"

  #include "tvlv.h"

  enum batadv_bootpop {
  	BATADV_BOOTREPLY	= 2,
  };
  
  enum batadv_boothtype {
  	BATADV_HTYPE_ETHERNET	= 1,
  };
  
  enum batadv_dhcpoptioncode {
  	BATADV_DHCP_OPT_PAD		= 0,
  	BATADV_DHCP_OPT_MSG_TYPE	= 53,
  	BATADV_DHCP_OPT_END		= 255,
  };
  
  enum batadv_dhcptype {
  	BATADV_DHCPACK		= 5,
  };
  
  /* { 99, 130, 83, 99 } */
  #define BATADV_DHCP_MAGIC 1669485411
  
  struct batadv_dhcp_packet {
  	__u8 op;
  	__u8 htype;
  	__u8 hlen;
  	__u8 hops;
  	__be32 xid;
  	__be16 secs;
  	__be16 flags;
  	__be32 ciaddr;
  	__be32 yiaddr;
  	__be32 siaddr;
  	__be32 giaddr;
  	__u8 chaddr[16];
  	__u8 sname[64];
  	__u8 file[128];
  	__be32 magic;
  	__u8 options[0];
  };
  
  #define BATADV_DHCP_YIADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->yiaddr)
  #define BATADV_DHCP_CHADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->chaddr)

  static void batadv_dat_purge(struct work_struct *work);
  
  /**

   * batadv_dat_start_timer() - initialise the DAT periodic worker

   * @bat_priv: the bat priv with all the soft interface information
   */
  static void batadv_dat_start_timer(struct batadv_priv *bat_priv)
  {
  	INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
  	queue_delayed_work(batadv_event_workqueue, &bat_priv->dat.work,
  			   msecs_to_jiffies(10000));
  }
  
  /**

   * batadv_dat_entry_release() - release dat_entry from lists and queue for free

   *  after rcu grace period
   * @ref: kref pointer of the dat_entry
   */
  static void batadv_dat_entry_release(struct kref *ref)
  {
  	struct batadv_dat_entry *dat_entry;
  
  	dat_entry = container_of(ref, struct batadv_dat_entry, refcount);
  
  	kfree_rcu(dat_entry, rcu);
  }
  
  /**

   * batadv_dat_entry_put() - decrement the dat_entry refcounter and possibly

   *  release it
   * @dat_entry: dat_entry to be free'd

   */

  static void batadv_dat_entry_put(struct batadv_dat_entry *dat_entry)

  {

  	kref_put(&dat_entry->refcount, batadv_dat_entry_release);

  }
  
  /**

   * batadv_dat_to_purge() - check whether a dat_entry has to be purged or not

   * @dat_entry: the entry to check
   *

   * Return: true if the entry has to be purged now, false otherwise.

   */
  static bool batadv_dat_to_purge(struct batadv_dat_entry *dat_entry)
  {
  	return batadv_has_timed_out(dat_entry->last_update,
  				    BATADV_DAT_ENTRY_TIMEOUT);
  }
  
  /**

   * __batadv_dat_purge() - delete entries from the DAT local storage

   * @bat_priv: the bat priv with all the soft interface information
   * @to_purge: function in charge to decide whether an entry has to be purged or
   *	      not. This function takes the dat_entry as argument and has to
   *	      returns a boolean value: true is the entry has to be deleted,
   *	      false otherwise
   *

   * Loops over each entry in the DAT local storage and deletes it if and only if
   * the to_purge function passed as argument returns true.

   */
  static void __batadv_dat_purge(struct batadv_priv *bat_priv,
  			       bool (*to_purge)(struct batadv_dat_entry *))
  {
  	spinlock_t *list_lock; /* protects write access to the hash lists */
  	struct batadv_dat_entry *dat_entry;

  	struct hlist_node *node_tmp;

  	struct hlist_head *head;

  	u32 i;

  
  	if (!bat_priv->dat.hash)
  		return;
  
  	for (i = 0; i < bat_priv->dat.hash->size; i++) {
  		head = &bat_priv->dat.hash->table[i];
  		list_lock = &bat_priv->dat.hash->list_locks[i];
  
  		spin_lock_bh(list_lock);

  		hlist_for_each_entry_safe(dat_entry, node_tmp, head,

  					  hash_entry) {

  			/* if a helper function has been passed as parameter,

  			 * ask it if the entry has to be purged or not
  			 */
  			if (to_purge && !to_purge(dat_entry))
  				continue;

  			hlist_del_rcu(&dat_entry->hash_entry);

  			batadv_dat_entry_put(dat_entry);

  		}
  		spin_unlock_bh(list_lock);
  	}
  }
  
  /**

   * batadv_dat_purge() - periodic task that deletes old entries from the local
   *  DAT hash table

   * @work: kernel work struct
   */
  static void batadv_dat_purge(struct work_struct *work)
  {
  	struct delayed_work *delayed_work;
  	struct batadv_priv_dat *priv_dat;
  	struct batadv_priv *bat_priv;

  	delayed_work = to_delayed_work(work);

  	priv_dat = container_of(delayed_work, struct batadv_priv_dat, work);
  	bat_priv = container_of(priv_dat, struct batadv_priv, dat);
  
  	__batadv_dat_purge(bat_priv, batadv_dat_to_purge);
  	batadv_dat_start_timer(bat_priv);
  }
  
  /**

   * batadv_compare_dat() - comparing function used in the local DAT hash table

   * @node: node in the local table
   * @data2: second object to compare the node to
   *

   * Return: true if the two entries are the same, false otherwise.

   */

  static bool batadv_compare_dat(const struct hlist_node *node, const void *data2)

  {
  	const void *data1 = container_of(node, struct batadv_dat_entry,
  					 hash_entry);

  	return memcmp(data1, data2, sizeof(__be32)) == 0;

  }

  /**

   * batadv_arp_hw_src() - extract the hw_src field from an ARP packet

   * @skb: ARP packet
   * @hdr_size: size of the possible header before the ARP packet
   *

   * Return: the value of the hw_src field in the ARP packet.

   */

  static u8 *batadv_arp_hw_src(struct sk_buff *skb, int hdr_size)

  {

  	u8 *addr;

  	addr = (u8 *)(skb->data + hdr_size);

  	addr += ETH_HLEN + sizeof(struct arphdr);
  
  	return addr;
  }
  
  /**

   * batadv_arp_ip_src() - extract the ip_src field from an ARP packet

   * @skb: ARP packet
   * @hdr_size: size of the possible header before the ARP packet
   *

   * Return: the value of the ip_src field in the ARP packet.

   */
  static __be32 batadv_arp_ip_src(struct sk_buff *skb, int hdr_size)
  {
  	return *(__be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN);
  }
  
  /**

   * batadv_arp_hw_dst() - extract the hw_dst field from an ARP packet

   * @skb: ARP packet
   * @hdr_size: size of the possible header before the ARP packet
   *

   * Return: the value of the hw_dst field in the ARP packet.

   */

  static u8 *batadv_arp_hw_dst(struct sk_buff *skb, int hdr_size)

  {
  	return batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN + 4;
  }
  
  /**

   * batadv_arp_ip_dst() - extract the ip_dst field from an ARP packet

   * @skb: ARP packet
   * @hdr_size: size of the possible header before the ARP packet
   *

   * Return: the value of the ip_dst field in the ARP packet.

   */
  static __be32 batadv_arp_ip_dst(struct sk_buff *skb, int hdr_size)
  {
  	return *(__be32 *)(batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN * 2 + 4);
  }
  
  /**

   * batadv_hash_dat() - compute the hash value for an IP address

   * @data: data to hash
   * @size: size of the hash table
   *

   * Return: the selected index in the hash table for the given data.

   */

  static u32 batadv_hash_dat(const void *data, u32 size)

  {

  	u32 hash = 0;

  	const struct batadv_dat_entry *dat = data;

  	const unsigned char *key;

  	__be16 vid;

  	u32 i;

  
  	key = (const unsigned char *)&dat->ip;
  	for (i = 0; i < sizeof(dat->ip); i++) {
  		hash += key[i];
  		hash += (hash << 10);
  		hash ^= (hash >> 6);
  	}

  	vid = htons(dat->vid);
  	key = (__force const unsigned char *)&vid;

  	for (i = 0; i < sizeof(dat->vid); i++) {
  		hash += key[i];
  		hash += (hash << 10);
  		hash ^= (hash >> 6);
  	}

  
  	hash += (hash << 3);
  	hash ^= (hash >> 11);
  	hash += (hash << 15);
  
  	return hash % size;
  }
  
  /**

   * batadv_dat_entry_hash_find() - look for a given dat_entry in the local hash

   * table
   * @bat_priv: the bat priv with all the soft interface information
   * @ip: search key

   * @vid: VLAN identifier

   *

   * Return: the dat_entry if found, NULL otherwise.

   */
  static struct batadv_dat_entry *

  batadv_dat_entry_hash_find(struct batadv_priv *bat_priv, __be32 ip,
  			   unsigned short vid)

  {
  	struct hlist_head *head;

  	struct batadv_dat_entry to_find, *dat_entry, *dat_entry_tmp = NULL;

  	struct batadv_hashtable *hash = bat_priv->dat.hash;

  	u32 index;

  
  	if (!hash)
  		return NULL;

  	to_find.ip = ip;
  	to_find.vid = vid;
  
  	index = batadv_hash_dat(&to_find, hash->size);

  	head = &hash->table[index];
  
  	rcu_read_lock();

  	hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {

  		if (dat_entry->ip != ip)
  			continue;

  		if (!kref_get_unless_zero(&dat_entry->refcount))

  			continue;
  
  		dat_entry_tmp = dat_entry;
  		break;
  	}
  	rcu_read_unlock();
  
  	return dat_entry_tmp;
  }
  
  /**

   * batadv_dat_entry_add() - add a new dat entry or update it if already exists

   * @bat_priv: the bat priv with all the soft interface information
   * @ip: ipv4 to add/edit
   * @mac_addr: mac address to assign to the given ipv4

   * @vid: VLAN identifier

   */
  static void batadv_dat_entry_add(struct batadv_priv *bat_priv, __be32 ip,

  				 u8 *mac_addr, unsigned short vid)

  {
  	struct batadv_dat_entry *dat_entry;
  	int hash_added;

  	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip, vid);

  	/* if this entry is already known, just update it */
  	if (dat_entry) {
  		if (!batadv_compare_eth(dat_entry->mac_addr, mac_addr))

  			ether_addr_copy(dat_entry->mac_addr, mac_addr);

  		dat_entry->last_update = jiffies;
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,

  			   "Entry updated: %pI4 %pM (vid: %d)
  ",
  			   &dat_entry->ip, dat_entry->mac_addr,

  			   batadv_print_vid(vid));

  		goto out;
  	}
  
  	dat_entry = kmalloc(sizeof(*dat_entry), GFP_ATOMIC);
  	if (!dat_entry)
  		goto out;
  
  	dat_entry->ip = ip;

  	dat_entry->vid = vid;

  	ether_addr_copy(dat_entry->mac_addr, mac_addr);

  	dat_entry->last_update = jiffies;

  	kref_init(&dat_entry->refcount);

  	kref_get(&dat_entry->refcount);

  	hash_added = batadv_hash_add(bat_priv->dat.hash, batadv_compare_dat,

  				     batadv_hash_dat, dat_entry,

  				     &dat_entry->hash_entry);
  
  	if (unlikely(hash_added != 0)) {
  		/* remove the reference for the hash */

  		batadv_dat_entry_put(dat_entry);

  		goto out;
  	}

  	batadv_dbg(BATADV_DBG_DAT, bat_priv, "New entry added: %pI4 %pM (vid: %d)
  ",

  		   &dat_entry->ip, dat_entry->mac_addr, batadv_print_vid(vid));

  
  out:
  	if (dat_entry)

  		batadv_dat_entry_put(dat_entry);

  }

  #ifdef CONFIG_BATMAN_ADV_DEBUG
  
  /**

   * batadv_dbg_arp() - print a debug message containing all the ARP packet
   *  details

   * @bat_priv: the bat priv with all the soft interface information
   * @skb: ARP packet

   * @hdr_size: size of the possible header before the ARP packet
   * @msg: message to print together with the debugging information
   */
  static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,

  			   int hdr_size, char *msg)

  {
  	struct batadv_unicast_4addr_packet *unicast_4addr_packet;
  	struct batadv_bcast_packet *bcast_pkt;

  	u8 *orig_addr;

  	__be32 ip_src, ip_dst;
  
  	if (msg)
  		batadv_dbg(BATADV_DBG_DAT, bat_priv, "%s
  ", msg);
  
  	ip_src = batadv_arp_ip_src(skb, hdr_size);
  	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
  	batadv_dbg(BATADV_DBG_DAT, bat_priv,
  		   "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]
  ",
  		   batadv_arp_hw_src(skb, hdr_size), &ip_src,
  		   batadv_arp_hw_dst(skb, hdr_size), &ip_dst);

  	if (hdr_size < sizeof(struct batadv_unicast_packet))

  		return;

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

  	switch (unicast_4addr_packet->u.packet_type) {

  	case BATADV_UNICAST:
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "* encapsulated within a UNICAST packet
  ");
  		break;
  	case BATADV_UNICAST_4ADDR:
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "* encapsulated within a UNICAST_4ADDR packet (src: %pM)
  ",
  			   unicast_4addr_packet->src);
  		switch (unicast_4addr_packet->subtype) {
  		case BATADV_P_DAT_DHT_PUT:
  			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_PUT
  ");
  			break;
  		case BATADV_P_DAT_DHT_GET:
  			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_GET
  ");
  			break;
  		case BATADV_P_DAT_CACHE_REPLY:
  			batadv_dbg(BATADV_DBG_DAT, bat_priv,
  				   "* type: DAT_CACHE_REPLY
  ");
  			break;
  		case BATADV_P_DATA:
  			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DATA
  ");
  			break;
  		default:
  			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: Unknown (%u)!
  ",

  				   unicast_4addr_packet->u.packet_type);

  		}
  		break;
  	case BATADV_BCAST:
  		bcast_pkt = (struct batadv_bcast_packet *)unicast_4addr_packet;
  		orig_addr = bcast_pkt->orig;
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "* encapsulated within a BCAST packet (src: %pM)
  ",
  			   orig_addr);
  		break;
  	default:
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "* encapsulated within an unknown packet type (0x%x)
  ",

  			   unicast_4addr_packet->u.packet_type);

  	}
  }
  
  #else
  
  static void batadv_dbg_arp(struct batadv_priv *bat_priv, struct sk_buff *skb,

  			   int hdr_size, char *msg)

  {
  }
  
  #endif /* CONFIG_BATMAN_ADV_DEBUG */

  /**

   * batadv_is_orig_node_eligible() - check whether a node can be a DHT candidate

   * @res: the array with the already selected candidates
   * @select: number of already selected candidates
   * @tmp_max: address of the currently evaluated node
   * @max: current round max address
   * @last_max: address of the last selected candidate
   * @candidate: orig_node under evaluation
   * @max_orig_node: last selected candidate
   *

   * Return: true if the node has been elected as next candidate or false

   * otherwise.

   */
  static bool batadv_is_orig_node_eligible(struct batadv_dat_candidate *res,
  					 int select, batadv_dat_addr_t tmp_max,
  					 batadv_dat_addr_t max,
  					 batadv_dat_addr_t last_max,
  					 struct batadv_orig_node *candidate,
  					 struct batadv_orig_node *max_orig_node)
  {
  	bool ret = false;
  	int j;

  	/* check if orig node candidate is running DAT */

  	if (!test_bit(BATADV_ORIG_CAPA_HAS_DAT, &candidate->capabilities))

  		goto out;

  	/* Check if this node has already been selected... */
  	for (j = 0; j < select; j++)
  		if (res[j].orig_node == candidate)
  			break;
  	/* ..and possibly skip it */
  	if (j < select)
  		goto out;
  	/* sanity check: has it already been selected? This should not happen */
  	if (tmp_max > last_max)
  		goto out;
  	/* check if during this iteration an originator with a closer dht
  	 * address has already been found
  	 */
  	if (tmp_max < max)
  		goto out;
  	/* this is an hash collision with the temporary selected node. Choose
  	 * the one with the lowest address
  	 */

  	if (tmp_max == max && max_orig_node &&

  	    batadv_compare_eth(candidate->orig, max_orig_node->orig))

  		goto out;
  
  	ret = true;
  out:
  	return ret;
  }
  
  /**

   * batadv_choose_next_candidate() - select the next DHT candidate

   * @bat_priv: the bat priv with all the soft interface information
   * @cands: candidates array
   * @select: number of candidates already present in the array
   * @ip_key: key to look up in the DHT
   * @last_max: pointer where the address of the selected candidate will be saved
   */
  static void batadv_choose_next_candidate(struct batadv_priv *bat_priv,
  					 struct batadv_dat_candidate *cands,
  					 int select, batadv_dat_addr_t ip_key,
  					 batadv_dat_addr_t *last_max)
  {

  	batadv_dat_addr_t max = 0;
  	batadv_dat_addr_t tmp_max = 0;

  	struct batadv_orig_node *orig_node, *max_orig_node = NULL;
  	struct batadv_hashtable *hash = bat_priv->orig_hash;

  	struct hlist_head *head;
  	int i;
  
  	/* if no node is eligible as candidate, leave the candidate type as
  	 * NOT_FOUND
  	 */
  	cands[select].type = BATADV_DAT_CANDIDATE_NOT_FOUND;

  	/* iterate over the originator list and find the node with the closest

  	 * dat_address which has not been selected yet
  	 */
  	for (i = 0; i < hash->size; i++) {
  		head = &hash->table[i];
  
  		rcu_read_lock();

  		hlist_for_each_entry_rcu(orig_node, head, hash_entry) {

  			/* the dht space is a ring using unsigned addresses */

  			tmp_max = BATADV_DAT_ADDR_MAX - orig_node->dat_addr +
  				  ip_key;
  
  			if (!batadv_is_orig_node_eligible(cands, select,
  							  tmp_max, max,
  							  *last_max, orig_node,
  							  max_orig_node))
  				continue;

  			if (!kref_get_unless_zero(&orig_node->refcount))

  				continue;
  
  			max = tmp_max;
  			if (max_orig_node)

  				batadv_orig_node_put(max_orig_node);

  			max_orig_node = orig_node;
  		}
  		rcu_read_unlock();
  	}
  	if (max_orig_node) {
  		cands[select].type = BATADV_DAT_CANDIDATE_ORIG;
  		cands[select].orig_node = max_orig_node;
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "dat_select_candidates() %d: selected %pM addr=%u dist=%u
  ",
  			   select, max_orig_node->orig, max_orig_node->dat_addr,
  			   max);
  	}
  	*last_max = max;
  }
  
  /**

   * batadv_dat_select_candidates() - select the nodes which the DHT message has
   *  to be sent to

   * @bat_priv: the bat priv with all the soft interface information
   * @ip_dst: ipv4 to look up in the DHT

   * @vid: VLAN identifier

   *
   * An originator O is selected if and only if its DHT_ID value is one of three
   * closest values (from the LEFT, with wrap around if needed) then the hash
   * value of the key. ip_dst is the key.
   *

   * Return: the candidate array of size BATADV_DAT_CANDIDATE_NUM.

   */
  static struct batadv_dat_candidate *

  batadv_dat_select_candidates(struct batadv_priv *bat_priv, __be32 ip_dst,
  			     unsigned short vid)

  {
  	int select;
  	batadv_dat_addr_t last_max = BATADV_DAT_ADDR_MAX, ip_key;
  	struct batadv_dat_candidate *res;

  	struct batadv_dat_entry dat;

  
  	if (!bat_priv->orig_hash)
  		return NULL;

  	res = kmalloc_array(BATADV_DAT_CANDIDATES_NUM, sizeof(*res),
  			    GFP_ATOMIC);

  	if (!res)
  		return NULL;

  	dat.ip = ip_dst;

  	dat.vid = vid;

  	ip_key = (batadv_dat_addr_t)batadv_hash_dat(&dat,

  						    BATADV_DAT_ADDR_MAX);
  
  	batadv_dbg(BATADV_DBG_DAT, bat_priv,

  		   "%s(): IP=%pI4 hash(IP)=%u
  ", __func__, &ip_dst,

  		   ip_key);
  
  	for (select = 0; select < BATADV_DAT_CANDIDATES_NUM; select++)
  		batadv_choose_next_candidate(bat_priv, res, select, ip_key,
  					     &last_max);
  
  	return res;
  }
  
  /**

   * batadv_dat_forward_data() - copy and send payload to the selected candidates

   * @bat_priv: the bat priv with all the soft interface information
   * @skb: payload to send
   * @ip: the DHT key

   * @vid: VLAN identifier

   * @packet_subtype: unicast4addr packet subtype to use
   *

   * This function copies the skb with pskb_copy() and is sent as unicast packet
   * to each of the selected candidates.

   *

   * Return: true if the packet is sent to at least one candidate, false

   * otherwise.

   */

  static bool batadv_dat_forward_data(struct batadv_priv *bat_priv,
  				    struct sk_buff *skb, __be32 ip,
  				    unsigned short vid, int packet_subtype)

  {
  	int i;
  	bool ret = false;
  	int send_status;
  	struct batadv_neigh_node *neigh_node = NULL;
  	struct sk_buff *tmp_skb;
  	struct batadv_dat_candidate *cand;

  	cand = batadv_dat_select_candidates(bat_priv, ip, vid);

  	if (!cand)
  		goto out;
  
  	batadv_dbg(BATADV_DBG_DAT, bat_priv, "DHT_SEND for %pI4
  ", &ip);
  
  	for (i = 0; i < BATADV_DAT_CANDIDATES_NUM; i++) {
  		if (cand[i].type == BATADV_DAT_CANDIDATE_NOT_FOUND)
  			continue;

  		neigh_node = batadv_orig_router_get(cand[i].orig_node,
  						    BATADV_IF_DEFAULT);

  		if (!neigh_node)
  			goto free_orig;

  		tmp_skb = pskb_copy_for_clone(skb, GFP_ATOMIC);

  		if (!batadv_send_skb_prepare_unicast_4addr(bat_priv, tmp_skb,
  							   cand[i].orig_node,
  							   packet_subtype)) {

  			kfree_skb(tmp_skb);
  			goto free_neigh;
  		}

  		send_status = batadv_send_unicast_skb(tmp_skb, neigh_node);

  		if (send_status == NET_XMIT_SUCCESS) {
  			/* count the sent packet */
  			switch (packet_subtype) {
  			case BATADV_P_DAT_DHT_GET:
  				batadv_inc_counter(bat_priv,
  						   BATADV_CNT_DAT_GET_TX);
  				break;
  			case BATADV_P_DAT_DHT_PUT:
  				batadv_inc_counter(bat_priv,
  						   BATADV_CNT_DAT_PUT_TX);
  				break;
  			}

  			/* packet sent to a candidate: return true */
  			ret = true;

  		}

  free_neigh:

  		batadv_neigh_node_put(neigh_node);

  free_orig:

  		batadv_orig_node_put(cand[i].orig_node);

  	}
  
  out:
  	kfree(cand);
  	return ret;
  }

  
  /**

   * batadv_dat_tvlv_container_update() - update the dat tvlv container after dat

   *  setting change
   * @bat_priv: the bat priv with all the soft interface information
   */
  static void batadv_dat_tvlv_container_update(struct batadv_priv *bat_priv)
  {
  	char dat_mode;
  
  	dat_mode = atomic_read(&bat_priv->distributed_arp_table);
  
  	switch (dat_mode) {
  	case 0:
  		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
  		break;
  	case 1:
  		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_DAT, 1,
  					       NULL, 0);
  		break;
  	}
  }
  
  /**

   * batadv_dat_status_update() - update the dat tvlv container after dat

   *  setting change
   * @net_dev: the soft interface net device
   */
  void batadv_dat_status_update(struct net_device *net_dev)
  {
  	struct batadv_priv *bat_priv = netdev_priv(net_dev);

  	batadv_dat_tvlv_container_update(bat_priv);
  }
  
  /**

   * batadv_dat_tvlv_ogm_handler_v1() - process incoming dat tvlv container

   * @bat_priv: the bat priv with all the soft interface information
   * @orig: the orig_node of the ogm
   * @flags: flags indicating the tvlv state (see batadv_tvlv_handler_flags)
   * @tvlv_value: tvlv buffer containing the gateway data
   * @tvlv_value_len: tvlv buffer length
   */
  static void batadv_dat_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
  					   struct batadv_orig_node *orig,

  					   u8 flags,
  					   void *tvlv_value, u16 tvlv_value_len)

  {
  	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)

  		clear_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);

  	else

  		set_bit(BATADV_ORIG_CAPA_HAS_DAT, &orig->capabilities);

  }
  
  /**

   * batadv_dat_hash_free() - free the local DAT hash table

   * @bat_priv: the bat priv with all the soft interface information
   */
  static void batadv_dat_hash_free(struct batadv_priv *bat_priv)
  {

  	if (!bat_priv->dat.hash)
  		return;

  	__batadv_dat_purge(bat_priv, NULL);
  
  	batadv_hash_destroy(bat_priv->dat.hash);
  
  	bat_priv->dat.hash = NULL;
  }
  
  /**

   * batadv_dat_init() - initialise the DAT internals

   * @bat_priv: the bat priv with all the soft interface information

   *
   * Return: 0 in case of success, a negative error code otherwise

   */
  int batadv_dat_init(struct batadv_priv *bat_priv)
  {
  	if (bat_priv->dat.hash)
  		return 0;
  
  	bat_priv->dat.hash = batadv_hash_new(1024);
  
  	if (!bat_priv->dat.hash)
  		return -ENOMEM;
  
  	batadv_dat_start_timer(bat_priv);

  	batadv_tvlv_handler_register(bat_priv, batadv_dat_tvlv_ogm_handler_v1,
  				     NULL, BATADV_TVLV_DAT, 1,
  				     BATADV_TVLV_HANDLER_OGM_CIFNOTFND);
  	batadv_dat_tvlv_container_update(bat_priv);

  	return 0;
  }
  
  /**

   * batadv_dat_free() - free the DAT internals

   * @bat_priv: the bat priv with all the soft interface information
   */
  void batadv_dat_free(struct batadv_priv *bat_priv)
  {

  	batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_DAT, 1);
  	batadv_tvlv_handler_unregister(bat_priv, BATADV_TVLV_DAT, 1);

  	cancel_delayed_work_sync(&bat_priv->dat.work);
  
  	batadv_dat_hash_free(bat_priv);
  }

  #ifdef CONFIG_BATMAN_ADV_DEBUGFS

  /**

   * batadv_dat_cache_seq_print_text() - print the local DAT hash table

   * @seq: seq file to print on
   * @offset: not used

   *
   * Return: always 0

   */
  int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset)
  {
  	struct net_device *net_dev = (struct net_device *)seq->private;
  	struct batadv_priv *bat_priv = netdev_priv(net_dev);
  	struct batadv_hashtable *hash = bat_priv->dat.hash;
  	struct batadv_dat_entry *dat_entry;
  	struct batadv_hard_iface *primary_if;

  	struct hlist_head *head;
  	unsigned long last_seen_jiffies;
  	int last_seen_msecs, last_seen_secs, last_seen_mins;

  	u32 i;

  
  	primary_if = batadv_seq_print_text_primary_if_get(seq);
  	if (!primary_if)
  		goto out;
  
  	seq_printf(seq, "Distributed ARP Table (%s):
  ", net_dev->name);

  	seq_puts(seq,
  		 "          IPv4             MAC        VID   last-seen
  ");

  
  	for (i = 0; i < hash->size; i++) {
  		head = &hash->table[i];
  
  		rcu_read_lock();

  		hlist_for_each_entry_rcu(dat_entry, head, hash_entry) {

  			last_seen_jiffies = jiffies - dat_entry->last_update;
  			last_seen_msecs = jiffies_to_msecs(last_seen_jiffies);
  			last_seen_mins = last_seen_msecs / 60000;
  			last_seen_msecs = last_seen_msecs % 60000;
  			last_seen_secs = last_seen_msecs / 1000;

  			seq_printf(seq, " * %15pI4 %pM %4i %6i:%02i
  ",

  				   &dat_entry->ip, dat_entry->mac_addr,

  				   batadv_print_vid(dat_entry->vid),

  				   last_seen_mins, last_seen_secs);
  		}
  		rcu_read_unlock();
  	}
  
  out:
  	if (primary_if)

  		batadv_hardif_put(primary_if);

  	return 0;
  }

  #endif

  
  /**

   * batadv_dat_cache_dump_entry() - dump one entry of the DAT cache table to a
   *  netlink socket
   * @msg: buffer for the message
   * @portid: netlink port

   * @cb: Control block containing additional options

   * @dat_entry: entry to dump
   *
   * Return: 0 or error code.
   */
  static int

  batadv_dat_cache_dump_entry(struct sk_buff *msg, u32 portid,
  			    struct netlink_callback *cb,

  			    struct batadv_dat_entry *dat_entry)
  {
  	int msecs;
  	void *hdr;

  	hdr = genlmsg_put(msg, portid, cb->nlh->nlmsg_seq,
  			  &batadv_netlink_family, NLM_F_MULTI,
  			  BATADV_CMD_GET_DAT_CACHE);

  	if (!hdr)
  		return -ENOBUFS;

  	genl_dump_check_consistent(cb, hdr);

  	msecs = jiffies_to_msecs(jiffies - dat_entry->last_update);
  
  	if (nla_put_in_addr(msg, BATADV_ATTR_DAT_CACHE_IP4ADDRESS,
  			    dat_entry->ip) ||
  	    nla_put(msg, BATADV_ATTR_DAT_CACHE_HWADDRESS, ETH_ALEN,
  		    dat_entry->mac_addr) ||
  	    nla_put_u16(msg, BATADV_ATTR_DAT_CACHE_VID, dat_entry->vid) ||
  	    nla_put_u32(msg, BATADV_ATTR_LAST_SEEN_MSECS, msecs)) {
  		genlmsg_cancel(msg, hdr);
  		return -EMSGSIZE;
  	}
  
  	genlmsg_end(msg, hdr);
  	return 0;
  }
  
  /**
   * batadv_dat_cache_dump_bucket() - dump one bucket of the DAT cache table to
   *  a netlink socket
   * @msg: buffer for the message
   * @portid: netlink port

   * @cb: Control block containing additional options
   * @hash: hash to dump
   * @bucket: bucket index to dump

   * @idx_skip: How many entries to skip
   *
   * Return: 0 or error code.
   */
  static int

  batadv_dat_cache_dump_bucket(struct sk_buff *msg, u32 portid,
  			     struct netlink_callback *cb,
  			     struct batadv_hashtable *hash, unsigned int bucket,
  			     int *idx_skip)

  {
  	struct batadv_dat_entry *dat_entry;
  	int idx = 0;

  	spin_lock_bh(&hash->list_locks[bucket]);
  	cb->seq = atomic_read(&hash->generation) << 1 | 1;
  
  	hlist_for_each_entry(dat_entry, &hash->table[bucket], hash_entry) {

  		if (idx < *idx_skip)
  			goto skip;

  		if (batadv_dat_cache_dump_entry(msg, portid, cb, dat_entry)) {
  			spin_unlock_bh(&hash->list_locks[bucket]);

  			*idx_skip = idx;
  
  			return -EMSGSIZE;
  		}
  
  skip:
  		idx++;
  	}

  	spin_unlock_bh(&hash->list_locks[bucket]);

  
  	return 0;
  }
  
  /**
   * batadv_dat_cache_dump() - dump DAT cache table to a netlink socket
   * @msg: buffer for the message
   * @cb: callback structure containing arguments
   *
   * Return: message length.
   */
  int batadv_dat_cache_dump(struct sk_buff *msg, struct netlink_callback *cb)
  {
  	struct batadv_hard_iface *primary_if = NULL;
  	int portid = NETLINK_CB(cb->skb).portid;
  	struct net *net = sock_net(cb->skb->sk);
  	struct net_device *soft_iface;
  	struct batadv_hashtable *hash;
  	struct batadv_priv *bat_priv;
  	int bucket = cb->args[0];

  	int idx = cb->args[1];
  	int ifindex;
  	int ret = 0;
  
  	ifindex = batadv_netlink_get_ifindex(cb->nlh,
  					     BATADV_ATTR_MESH_IFINDEX);
  	if (!ifindex)
  		return -EINVAL;
  
  	soft_iface = dev_get_by_index(net, ifindex);
  	if (!soft_iface || !batadv_softif_is_valid(soft_iface)) {
  		ret = -ENODEV;
  		goto out;
  	}
  
  	bat_priv = netdev_priv(soft_iface);
  	hash = bat_priv->dat.hash;
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if || primary_if->if_status != BATADV_IF_ACTIVE) {
  		ret = -ENOENT;
  		goto out;
  	}
  
  	while (bucket < hash->size) {

  		if (batadv_dat_cache_dump_bucket(msg, portid, cb, hash, bucket,

  						 &idx))
  			break;
  
  		bucket++;
  		idx = 0;
  	}
  
  	cb->args[0] = bucket;
  	cb->args[1] = idx;
  
  	ret = msg->len;
  
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  
  	if (soft_iface)
  		dev_put(soft_iface);
  
  	return ret;
  }
  
  /**

   * batadv_arp_get_type() - parse an ARP packet and gets the type

   * @bat_priv: the bat priv with all the soft interface information
   * @skb: packet to analyse
   * @hdr_size: size of the possible header before the ARP packet in the skb
   *

   * Return: the ARP type if the skb contains a valid ARP packet, 0 otherwise.

   */

  static u16 batadv_arp_get_type(struct batadv_priv *bat_priv,
  			       struct sk_buff *skb, int hdr_size)

  {
  	struct arphdr *arphdr;
  	struct ethhdr *ethhdr;
  	__be32 ip_src, ip_dst;

  	u8 *hw_src, *hw_dst;
  	u16 type = 0;

  
  	/* pull the ethernet header */
  	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
  		goto out;
  
  	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
  
  	if (ethhdr->h_proto != htons(ETH_P_ARP))
  		goto out;
  
  	/* pull the ARP payload */
  	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN +
  				    arp_hdr_len(skb->dev))))
  		goto out;
  
  	arphdr = (struct arphdr *)(skb->data + hdr_size + ETH_HLEN);

  	/* check whether the ARP packet carries a valid IP information */

  	if (arphdr->ar_hrd != htons(ARPHRD_ETHER))
  		goto out;
  
  	if (arphdr->ar_pro != htons(ETH_P_IP))
  		goto out;
  
  	if (arphdr->ar_hln != ETH_ALEN)
  		goto out;
  
  	if (arphdr->ar_pln != 4)
  		goto out;
  
  	/* Check for bad reply/request. If the ARP message is not sane, DAT
  	 * will simply ignore it
  	 */
  	ip_src = batadv_arp_ip_src(skb, hdr_size);
  	ip_dst = batadv_arp_ip_dst(skb, hdr_size);
  	if (ipv4_is_loopback(ip_src) || ipv4_is_multicast(ip_src) ||

  	    ipv4_is_loopback(ip_dst) || ipv4_is_multicast(ip_dst) ||
  	    ipv4_is_zeronet(ip_src) || ipv4_is_lbcast(ip_src) ||
  	    ipv4_is_zeronet(ip_dst) || ipv4_is_lbcast(ip_dst))

  		goto out;

  	hw_src = batadv_arp_hw_src(skb, hdr_size);
  	if (is_zero_ether_addr(hw_src) || is_multicast_ether_addr(hw_src))
  		goto out;

  	/* don't care about the destination MAC address in ARP requests */

  	if (arphdr->ar_op != htons(ARPOP_REQUEST)) {
  		hw_dst = batadv_arp_hw_dst(skb, hdr_size);
  		if (is_zero_ether_addr(hw_dst) ||
  		    is_multicast_ether_addr(hw_dst))
  			goto out;
  	}

  	type = ntohs(arphdr->ar_op);
  out:
  	return type;
  }

  
  /**

   * batadv_dat_get_vid() - extract the VLAN identifier from skb if any

   * @skb: the buffer containing the packet to extract the VID from
   * @hdr_size: the size of the batman-adv header encapsulating the packet
   *

   * Return: If the packet embedded in the skb is vlan tagged this function
   * returns the VID with the BATADV_VLAN_HAS_TAG flag. Otherwise BATADV_NO_FLAGS
   * is returned.

   */
  static unsigned short batadv_dat_get_vid(struct sk_buff *skb, int *hdr_size)
  {
  	unsigned short vid;
  
  	vid = batadv_get_vid(skb, *hdr_size);
  
  	/* ARP parsing functions jump forward of hdr_size + ETH_HLEN.
  	 * If the header contained in the packet is a VLAN one (which is longer)
  	 * hdr_size is updated so that the functions will still skip the
  	 * correct amount of bytes.
  	 */
  	if (vid & BATADV_VLAN_HAS_TAG)
  		*hdr_size += VLAN_HLEN;
  
  	return vid;
  }
  
  /**

   * batadv_dat_arp_create_reply() - create an ARP Reply

   * @bat_priv: the bat priv with all the soft interface information
   * @ip_src: ARP sender IP
   * @ip_dst: ARP target IP
   * @hw_src: Ethernet source and ARP sender MAC
   * @hw_dst: Ethernet destination and ARP target MAC
   * @vid: VLAN identifier (optional, set to zero otherwise)
   *
   * Creates an ARP Reply from the given values, optionally encapsulated in a
   * VLAN header.
   *
   * Return: An skb containing an ARP Reply.
   */
  static struct sk_buff *
  batadv_dat_arp_create_reply(struct batadv_priv *bat_priv, __be32 ip_src,
  			    __be32 ip_dst, u8 *hw_src, u8 *hw_dst,
  			    unsigned short vid)
  {
  	struct sk_buff *skb;
  
  	skb = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_dst, bat_priv->soft_iface,
  			 ip_src, hw_dst, hw_src, hw_dst);
  	if (!skb)
  		return NULL;
  
  	skb_reset_mac_header(skb);
  
  	if (vid & BATADV_VLAN_HAS_TAG)
  		skb = vlan_insert_tag(skb, htons(ETH_P_8021Q),
  				      vid & VLAN_VID_MASK);
  
  	return skb;
  }
  
  /**

   * batadv_dat_snoop_outgoing_arp_request() - snoop the ARP request and try to

   * answer using DAT
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: packet to check
   *

   * Return: true if the message has been sent to the dht candidates, false

   * otherwise. In case of a positive return value the message has to be enqueued
   * to permit the fallback.

   */
  bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
  					   struct sk_buff *skb)
  {

  	u16 type = 0;

  	__be32 ip_dst, ip_src;

  	u8 *hw_src;

  	bool ret = false;
  	struct batadv_dat_entry *dat_entry = NULL;
  	struct sk_buff *skb_new;

  	struct net_device *soft_iface = bat_priv->soft_iface;

  	int hdr_size = 0;
  	unsigned short vid;

  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		goto out;

  	vid = batadv_dat_get_vid(skb, &hdr_size);
  
  	type = batadv_arp_get_type(bat_priv, skb, hdr_size);

  	/* If the node gets an ARP_REQUEST it has to send a DHT_GET unicast
  	 * message to the selected DHT candidates
  	 */
  	if (type != ARPOP_REQUEST)
  		goto out;

  	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REQUEST");

  	ip_src = batadv_arp_ip_src(skb, hdr_size);
  	hw_src = batadv_arp_hw_src(skb, hdr_size);
  	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

  	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);

  	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);

  	if (dat_entry) {

  		/* If the ARP request is destined for a local client the local
  		 * client will answer itself. DAT would only generate a
  		 * duplicate packet.
  		 *
  		 * Moreover, if the soft-interface is enslaved into a bridge, an
  		 * additional DAT answer may trigger kernel warnings about
  		 * a packet coming from the wrong port.
  		 */

  		if (batadv_is_my_client(bat_priv, dat_entry->mac_addr, vid)) {

  			ret = true;
  			goto out;
  		}

  		/* If BLA is enabled, only send ARP replies if we have claimed
  		 * the destination for the ARP request or if no one else of
  		 * the backbone gws belonging to our backbone has claimed the
  		 * destination.
  		 */
  		if (!batadv_bla_check_claim(bat_priv,
  					    dat_entry->mac_addr, vid)) {
  			batadv_dbg(BATADV_DBG_DAT, bat_priv,
  				   "Device %pM claimed by another backbone gw. Don't send ARP reply!",
  				   dat_entry->mac_addr);
  			ret = true;
  			goto out;
  		}

  		skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
  						      dat_entry->mac_addr,
  						      hw_src, vid);

  		if (!skb_new)
  			goto out;

  		skb_new->protocol = eth_type_trans(skb_new, soft_iface);

  		batadv_inc_counter(bat_priv, BATADV_CNT_RX);
  		batadv_add_counter(bat_priv, BATADV_CNT_RX_BYTES,
  				   skb->len + ETH_HLEN + hdr_size);

  
  		netif_rx(skb_new);
  		batadv_dbg(BATADV_DBG_DAT, bat_priv, "ARP request replied locally
  ");
  		ret = true;
  	} else {

  		/* Send the request to the DHT */

  		ret = batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
  					      BATADV_P_DAT_DHT_GET);

  	}
  out:
  	if (dat_entry)

  		batadv_dat_entry_put(dat_entry);

  	return ret;
  }
  
  /**

   * batadv_dat_snoop_incoming_arp_request() - snoop the ARP request and try to

   * answer using the local DAT storage
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: packet to check
   * @hdr_size: size of the encapsulation header
   *

   * Return: true if the request has been answered, false otherwise.

   */
  bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
  					   struct sk_buff *skb, int hdr_size)
  {

  	u16 type;

  	__be32 ip_src, ip_dst;

  	u8 *hw_src;

  	struct sk_buff *skb_new;

  	struct batadv_dat_entry *dat_entry = NULL;
  	bool ret = false;

  	unsigned short vid;

  	int err;

  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		goto out;

  	vid = batadv_dat_get_vid(skb, &hdr_size);

  	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
  	if (type != ARPOP_REQUEST)
  		goto out;
  
  	hw_src = batadv_arp_hw_src(skb, hdr_size);
  	ip_src = batadv_arp_ip_src(skb, hdr_size);
  	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

  	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REQUEST");

  	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);

  	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);

  	if (!dat_entry)
  		goto out;

  	skb_new = batadv_dat_arp_create_reply(bat_priv, ip_dst, ip_src,
  					      dat_entry->mac_addr, hw_src, vid);

  	if (!skb_new)
  		goto out;

  	/* To preserve backwards compatibility, the node has choose the outgoing
  	 * format based on the incoming request packet type. The assumption is
  	 * that a node not using the 4addr packet format doesn't support it.

  	 */
  	if (hdr_size == sizeof(struct batadv_unicast_4addr_packet))

  		err = batadv_send_skb_via_tt_4addr(bat_priv, skb_new,
  						   BATADV_P_DAT_CACHE_REPLY,

  						   NULL, vid);

  	else

  		err = batadv_send_skb_via_tt(bat_priv, skb_new, NULL, vid);

  	if (err != NET_XMIT_DROP) {

  		batadv_inc_counter(bat_priv, BATADV_CNT_DAT_CACHED_REPLY_TX);

  		ret = true;

  	}

  out:
  	if (dat_entry)

  		batadv_dat_entry_put(dat_entry);

  	if (ret)
  		kfree_skb(skb);
  	return ret;
  }
  
  /**

   * batadv_dat_snoop_outgoing_arp_reply() - snoop the ARP reply and fill the DHT

   * @bat_priv: the bat priv with all the soft interface information
   * @skb: packet to check
   */
  void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
  					 struct sk_buff *skb)
  {

  	u16 type;

  	__be32 ip_src, ip_dst;

  	u8 *hw_src, *hw_dst;

  	int hdr_size = 0;
  	unsigned short vid;

  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		return;

  	vid = batadv_dat_get_vid(skb, &hdr_size);
  
  	type = batadv_arp_get_type(bat_priv, skb, hdr_size);

  	if (type != ARPOP_REPLY)
  		return;

  	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing outgoing ARP REPLY");

  	hw_src = batadv_arp_hw_src(skb, hdr_size);
  	ip_src = batadv_arp_ip_src(skb, hdr_size);
  	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
  	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

  	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
  	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

  
  	/* Send the ARP reply to the candidates for both the IP addresses that

  	 * the node obtained from the ARP reply

  	 */

  	batadv_dat_forward_data(bat_priv, skb, ip_src, vid,
  				BATADV_P_DAT_DHT_PUT);
  	batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
  				BATADV_P_DAT_DHT_PUT);

  }

  /**

   * batadv_dat_snoop_incoming_arp_reply() - snoop the ARP reply and fill the
   *  local DAT storage only

   * @bat_priv: the bat priv with all the soft interface information
   * @skb: packet to check

   * @hdr_size: size of the encapsulation header

   *

   * Return: true if the packet was snooped and consumed by DAT. False if the

   * packet has to be delivered to the interface

   */
  bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
  					 struct sk_buff *skb, int hdr_size)
  {

  	struct batadv_dat_entry *dat_entry = NULL;

  	u16 type;

  	__be32 ip_src, ip_dst;

  	u8 *hw_src, *hw_dst;

  	bool dropped = false;

  	unsigned short vid;

  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		goto out;

  	vid = batadv_dat_get_vid(skb, &hdr_size);

  	type = batadv_arp_get_type(bat_priv, skb, hdr_size);
  	if (type != ARPOP_REPLY)
  		goto out;

  	batadv_dbg_arp(bat_priv, skb, hdr_size, "Parsing incoming ARP REPLY");

  
  	hw_src = batadv_arp_hw_src(skb, hdr_size);
  	ip_src = batadv_arp_ip_src(skb, hdr_size);
  	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
  	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

  	/* If ip_dst is already in cache and has the right mac address,
  	 * drop this frame if this ARP reply is destined for us because it's
  	 * most probably an ARP reply generated by another node of the DHT.
  	 * We have most probably received already a reply earlier. Delivering
  	 * this frame would lead to doubled receive of an ARP reply.
  	 */
  	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_src, vid);
  	if (dat_entry && batadv_compare_eth(hw_src, dat_entry->mac_addr)) {
  		batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP reply removed: ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; dat_entry: %pM-%pI4
  ",
  			   hw_src, &ip_src, hw_dst, &ip_dst,
  			   dat_entry->mac_addr,	&dat_entry->ip);
  		dropped = true;

  	}

  	/* Update our internal cache with both the IP addresses the node got
  	 * within the ARP reply
  	 */

  	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
  	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

  	if (dropped)
  		goto out;

  	/* If BLA is enabled, only forward ARP replies if we have claimed the
  	 * source of the ARP reply or if no one else of the same backbone has
  	 * already claimed that client. This prevents that different gateways
  	 * to the same backbone all forward the ARP reply leading to multiple
  	 * replies in the backbone.
  	 */
  	if (!batadv_bla_check_claim(bat_priv, hw_src, vid)) {
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "Device %pM claimed by another backbone gw. Drop ARP reply.
  ",
  			   hw_src);
  		dropped = true;
  		goto out;
  	}

  	/* if this REPLY is directed to a client of mine, let's deliver the
  	 * packet to the interface
  	 */

  	dropped = !batadv_is_my_client(bat_priv, hw_dst, vid);
  
  	/* if this REPLY is sent on behalf of a client of mine, let's drop the
  	 * packet because the client will reply by itself
  	 */
  	dropped |= batadv_is_my_client(bat_priv, hw_src, vid);

  out:

  	if (dropped)

  		kfree_skb(skb);

  	if (dat_entry)
  		batadv_dat_entry_put(dat_entry);

  	/* if dropped == false -> deliver to the interface */
  	return dropped;

  }
  
  /**

   * batadv_dat_check_dhcp_ipudp() - check skb for IP+UDP headers valid for DHCP
   * @skb: the packet to check
   * @ip_src: a buffer to store the IPv4 source address in
   *
   * Checks whether the given skb has an IP and UDP header valid for a DHCP
   * message from a DHCP server. And if so, stores the IPv4 source address in
   * the provided buffer.
   *
   * Return: True if valid, false otherwise.
   */
  static bool
  batadv_dat_check_dhcp_ipudp(struct sk_buff *skb, __be32 *ip_src)
  {
  	unsigned int offset = skb_network_offset(skb);
  	struct udphdr *udphdr, _udphdr;
  	struct iphdr *iphdr, _iphdr;
  
  	iphdr = skb_header_pointer(skb, offset, sizeof(_iphdr), &_iphdr);
  	if (!iphdr || iphdr->version != 4 || iphdr->ihl * 4 < sizeof(_iphdr))
  		return false;
  
  	if (iphdr->protocol != IPPROTO_UDP)
  		return false;
  
  	offset += iphdr->ihl * 4;
  	skb_set_transport_header(skb, offset);
  
  	udphdr = skb_header_pointer(skb, offset, sizeof(_udphdr), &_udphdr);
  	if (!udphdr || udphdr->source != htons(67))
  		return false;
  
  	*ip_src = get_unaligned(&iphdr->saddr);
  
  	return true;
  }
  
  /**
   * batadv_dat_check_dhcp() - examine packet for valid DHCP message
   * @skb: the packet to check
   * @proto: ethernet protocol hint (behind a potential vlan)
   * @ip_src: a buffer to store the IPv4 source address in
   *
   * Checks whether the given skb is a valid DHCP packet. And if so, stores the
   * IPv4 source address in the provided buffer.
   *
   * Caller needs to ensure that the skb network header is set correctly.
   *
   * Return: If skb is a valid DHCP packet, then returns its op code
   * (e.g. BOOTREPLY vs. BOOTREQUEST). Otherwise returns -EINVAL.
   */
  static int
  batadv_dat_check_dhcp(struct sk_buff *skb, __be16 proto, __be32 *ip_src)
  {
  	__be32 *magic, _magic;
  	unsigned int offset;
  	struct {
  		__u8 op;
  		__u8 htype;
  		__u8 hlen;
  		__u8 hops;
  	} *dhcp_h, _dhcp_h;
  
  	if (proto != htons(ETH_P_IP))
  		return -EINVAL;
  
  	if (!batadv_dat_check_dhcp_ipudp(skb, ip_src))
  		return -EINVAL;
  
  	offset = skb_transport_offset(skb) + sizeof(struct udphdr);
  	if (skb->len < offset + sizeof(struct batadv_dhcp_packet))
  		return -EINVAL;
  
  	dhcp_h = skb_header_pointer(skb, offset, sizeof(_dhcp_h), &_dhcp_h);
  	if (!dhcp_h || dhcp_h->htype != BATADV_HTYPE_ETHERNET ||
  	    dhcp_h->hlen != ETH_ALEN)
  		return -EINVAL;
  
  	offset += offsetof(struct batadv_dhcp_packet, magic);
  
  	magic = skb_header_pointer(skb, offset, sizeof(_magic), &_magic);
  	if (!magic || get_unaligned(magic) != htonl(BATADV_DHCP_MAGIC))
  		return -EINVAL;
  
  	return dhcp_h->op;
  }
  
  /**
   * batadv_dat_get_dhcp_message_type() - get message type of a DHCP packet
   * @skb: the DHCP packet to parse
   *
   * Iterates over the DHCP options of the given DHCP packet to find a
   * DHCP Message Type option and parse it.
   *
   * Caller needs to ensure that the given skb is a valid DHCP packet and
   * that the skb transport header is set correctly.
   *
   * Return: The found DHCP message type value, if found. -EINVAL otherwise.
   */
  static int batadv_dat_get_dhcp_message_type(struct sk_buff *skb)
  {
  	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
  	u8 *type, _type;
  	struct {
  		u8 type;
  		u8 len;
  	} *tl, _tl;
  
  	offset += sizeof(struct batadv_dhcp_packet);
  
  	while ((tl = skb_header_pointer(skb, offset, sizeof(_tl), &_tl))) {
  		if (tl->type == BATADV_DHCP_OPT_MSG_TYPE)
  			break;
  
  		if (tl->type == BATADV_DHCP_OPT_END)
  			break;
  
  		if (tl->type == BATADV_DHCP_OPT_PAD)
  			offset++;
  		else
  			offset += tl->len + sizeof(_tl);
  	}
  
  	/* Option Overload Code not supported */
  	if (!tl || tl->type != BATADV_DHCP_OPT_MSG_TYPE ||
  	    tl->len != sizeof(_type))
  		return -EINVAL;
  
  	offset += sizeof(_tl);
  
  	type = skb_header_pointer(skb, offset, sizeof(_type), &_type);
  	if (!type)
  		return -EINVAL;
  
  	return *type;
  }
  
  /**
   * batadv_dat_get_dhcp_yiaddr() - get yiaddr from a DHCP packet
   * @skb: the DHCP packet to parse
   * @buf: a buffer to store the yiaddr in
   *
   * Caller needs to ensure that the given skb is a valid DHCP packet and
   * that the skb transport header is set correctly.
   *
   * Return: True on success, false otherwise.
   */
  static bool batadv_dat_dhcp_get_yiaddr(struct sk_buff *skb, __be32 *buf)
  {
  	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
  	__be32 *yiaddr;
  
  	offset += offsetof(struct batadv_dhcp_packet, yiaddr);
  	yiaddr = skb_header_pointer(skb, offset, BATADV_DHCP_YIADDR_LEN, buf);
  
  	if (!yiaddr)
  		return false;
  
  	if (yiaddr != buf)
  		*buf = get_unaligned(yiaddr);
  
  	return true;
  }
  
  /**
   * batadv_dat_get_dhcp_chaddr() - get chaddr from a DHCP packet
   * @skb: the DHCP packet to parse
   * @buf: a buffer to store the chaddr in
   *
   * Caller needs to ensure that the given skb is a valid DHCP packet and
   * that the skb transport header is set correctly.
   *
   * Return: True on success, false otherwise
   */
  static bool batadv_dat_get_dhcp_chaddr(struct sk_buff *skb, u8 *buf)
  {
  	unsigned int offset = skb_transport_offset(skb) + sizeof(struct udphdr);
  	u8 *chaddr;
  
  	offset += offsetof(struct batadv_dhcp_packet, chaddr);
  	chaddr = skb_header_pointer(skb, offset, BATADV_DHCP_CHADDR_LEN, buf);
  
  	if (!chaddr)
  		return false;
  
  	if (chaddr != buf)
  		memcpy(buf, chaddr, BATADV_DHCP_CHADDR_LEN);
  
  	return true;
  }
  
  /**
   * batadv_dat_put_dhcp() - puts addresses from a DHCP packet into the DHT and
   *  DAT cache
   * @bat_priv: the bat priv with all the soft interface information
   * @chaddr: the DHCP client MAC address
   * @yiaddr: the DHCP client IP address
   * @hw_dst: the DHCP server MAC address
   * @ip_dst: the DHCP server IP address
   * @vid: VLAN identifier
   *
   * Adds given MAC/IP pairs to the local DAT cache and propagates them further
   * into the DHT.
   *
   * For the DHT propagation, client MAC + IP will appear as the ARP Reply
   * transmitter (and hw_dst/ip_dst as the target).
   */
  static void batadv_dat_put_dhcp(struct batadv_priv *bat_priv, u8 *chaddr,
  				__be32 yiaddr, u8 *hw_dst, __be32 ip_dst,
  				unsigned short vid)
  {
  	struct sk_buff *skb;
  
  	skb = batadv_dat_arp_create_reply(bat_priv, yiaddr, ip_dst, chaddr,
  					  hw_dst, vid);
  	if (!skb)
  		return;
  
  	skb_set_network_header(skb, ETH_HLEN);
  
  	batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid);
  	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

  	batadv_dat_forward_data(bat_priv, skb, yiaddr, vid,
  				BATADV_P_DAT_DHT_PUT);
  	batadv_dat_forward_data(bat_priv, skb, ip_dst, vid,
  				BATADV_P_DAT_DHT_PUT);

  	consume_skb(skb);

  	batadv_dbg(BATADV_DBG_DAT, bat_priv,
  		   "Snooped from outgoing DHCPACK (server address): %pI4, %pM (vid: %i)
  ",
  		   &ip_dst, hw_dst, batadv_print_vid(vid));
  	batadv_dbg(BATADV_DBG_DAT, bat_priv,
  		   "Snooped from outgoing DHCPACK (client address): %pI4, %pM (vid: %i)
  ",
  		   &yiaddr, chaddr, batadv_print_vid(vid));
  }
  
  /**
   * batadv_dat_check_dhcp_ack() - examine packet for valid DHCP message
   * @skb: the packet to check
   * @proto: ethernet protocol hint (behind a potential vlan)
   * @ip_src: a buffer to store the IPv4 source address in
   * @chaddr: a buffer to store the DHCP Client Hardware Address in
   * @yiaddr: a buffer to store the DHCP Your IP Address in
   *
   * Checks whether the given skb is a valid DHCPACK. And if so, stores the
   * IPv4 server source address (ip_src), client MAC address (chaddr) and client
   * IPv4 address (yiaddr) in the provided buffers.
   *
   * Caller needs to ensure that the skb network header is set correctly.
   *
   * Return: True if the skb is a valid DHCPACK. False otherwise.
   */
  static bool
  batadv_dat_check_dhcp_ack(struct sk_buff *skb, __be16 proto, __be32 *ip_src,
  			  u8 *chaddr, __be32 *yiaddr)
  {
  	int type;
  
  	type = batadv_dat_check_dhcp(skb, proto, ip_src);
  	if (type != BATADV_BOOTREPLY)
  		return false;
  
  	type = batadv_dat_get_dhcp_message_type(skb);
  	if (type != BATADV_DHCPACK)
  		return false;
  
  	if (!batadv_dat_dhcp_get_yiaddr(skb, yiaddr))
  		return false;
  
  	if (!batadv_dat_get_dhcp_chaddr(skb, chaddr))
  		return false;
  
  	return true;
  }
  
  /**
   * batadv_dat_snoop_outgoing_dhcp_ack() - snoop DHCPACK and fill DAT with it
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: the packet to snoop
   * @proto: ethernet protocol hint (behind a potential vlan)
   * @vid: VLAN identifier
   *
   * This function first checks whether the given skb is a valid DHCPACK. If
   * so then its source MAC and IP as well as its DHCP Client Hardware Address
   * field and DHCP Your IP Address field are added to the local DAT cache and
   * propagated into the DHT.
   *
   * Caller needs to ensure that the skb mac and network headers are set
   * correctly.
   */
  void batadv_dat_snoop_outgoing_dhcp_ack(struct batadv_priv *bat_priv,
  					struct sk_buff *skb,
  					__be16 proto,
  					unsigned short vid)
  {
  	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
  	__be32 ip_src, yiaddr;
  
  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		return;
  
  	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
  		return;
  
  	batadv_dat_put_dhcp(bat_priv, chaddr, yiaddr, eth_hdr(skb)->h_source,
  			    ip_src, vid);
  }
  
  /**
   * batadv_dat_snoop_incoming_dhcp_ack() - snoop DHCPACK and fill DAT cache
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: the packet to snoop
   * @hdr_size: header size, up to the tail of the batman-adv header
   *
   * This function first checks whether the given skb is a valid DHCPACK. If
   * so then its source MAC and IP as well as its DHCP Client Hardware Address
   * field and DHCP Your IP Address field are added to the local DAT cache.
   */
  void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv,
  					struct sk_buff *skb, int hdr_size)
  {
  	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
  	struct ethhdr *ethhdr;
  	__be32 ip_src, yiaddr;
  	unsigned short vid;
  	__be16 proto;
  	u8 *hw_src;
  
  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		return;
  
  	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
  		return;
  
  	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
  	skb_set_network_header(skb, hdr_size + ETH_HLEN);
  	proto = ethhdr->h_proto;
  
  	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
  		return;
  
  	hw_src = ethhdr->h_source;
  	vid = batadv_dat_get_vid(skb, &hdr_size);
  
  	batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid);
  	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
  
  	batadv_dbg(BATADV_DBG_DAT, bat_priv,
  		   "Snooped from incoming DHCPACK (server address): %pI4, %pM (vid: %i)
  ",
  		   &ip_src, hw_src, batadv_print_vid(vid));
  	batadv_dbg(BATADV_DBG_DAT, bat_priv,
  		   "Snooped from incoming DHCPACK (client address): %pI4, %pM (vid: %i)
  ",
  		   &yiaddr, chaddr, batadv_print_vid(vid));
  }
  
  /**

   * batadv_dat_drop_broadcast_packet() - check if an ARP request has to be
   *  dropped (because the node has already obtained the reply via DAT) or not

   * @bat_priv: the bat priv with all the soft interface information
   * @forw_packet: the broadcast packet
   *

   * Return: true if the node can drop the packet, false otherwise.

   */
  bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
  				      struct batadv_forw_packet *forw_packet)
  {

  	u16 type;

  	__be32 ip_dst;
  	struct batadv_dat_entry *dat_entry = NULL;
  	bool ret = false;

  	int hdr_size = sizeof(struct batadv_bcast_packet);
  	unsigned short vid;

  	if (!atomic_read(&bat_priv->distributed_arp_table))
  		goto out;

  	/* If this packet is an ARP_REQUEST and the node already has the
  	 * information that it is going to ask, then the packet can be dropped
  	 */

  	if (batadv_forw_packet_is_rebroadcast(forw_packet))

  		goto out;

  	vid = batadv_dat_get_vid(forw_packet->skb, &hdr_size);
  
  	type = batadv_arp_get_type(bat_priv, forw_packet->skb, hdr_size);

  	if (type != ARPOP_REQUEST)
  		goto out;

  	ip_dst = batadv_arp_ip_dst(forw_packet->skb, hdr_size);
  	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid);

  	/* check if the node already got this entry */
  	if (!dat_entry) {
  		batadv_dbg(BATADV_DBG_DAT, bat_priv,
  			   "ARP Request for %pI4: fallback
  ", &ip_dst);
  		goto out;
  	}
  
  	batadv_dbg(BATADV_DBG_DAT, bat_priv,
  		   "ARP Request for %pI4: fallback prevented
  ", &ip_dst);
  	ret = true;
  
  out:
  	if (dat_entry)

  		batadv_dat_entry_put(dat_entry);

  	return ret;
  }