Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1894 insertions, 0 deletions

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
new file mode 100644
index 000000000..ddd3b4c70
--- /dev/null
+++ b/net/batman-adv/distributed-arp-table.c
@@ -0,0 +1,1894 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2011-2020  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[];
+};
+
+#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)
+{
+	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)
+{
+	if (!dat_entry)
+		return;
+
+	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 *(__force __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)
+{
+	u8 *dst = batadv_arp_hw_src(skb, hdr_size) + ETH_ALEN * 2 + 4;
+
+	return *(__force __be32 *)dst;
+}
+
+/**
+ * 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 = (__force 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)\n",
+			   &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)\n",
+		   &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\n", 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]\n",
+		   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\n");
+		break;
+	case BATADV_UNICAST_4ADDR:
+		batadv_dbg(BATADV_DBG_DAT, bat_priv,
+			   "* encapsulated within a UNICAST_4ADDR packet (src: %pM)\n",
+			   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\n");
+			break;
+		case BATADV_P_DAT_DHT_GET:
+			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DAT_DHT_GET\n");
+			break;
+		case BATADV_P_DAT_CACHE_REPLY:
+			batadv_dbg(BATADV_DBG_DAT, bat_priv,
+				   "* type: DAT_CACHE_REPLY\n");
+			break;
+		case BATADV_P_DATA:
+			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: DATA\n");
+			break;
+		default:
+			batadv_dbg(BATADV_DBG_DAT, bat_priv, "* type: Unknown (%u)!\n",
+				   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)\n",
+			   orig_addr);
+		break;
+	default:
+		batadv_dbg(BATADV_DBG_DAT, bat_priv,
+			   "* encapsulated within an unknown packet type (0x%x)\n",
+			   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\n",
+			   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\n", __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 a 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\n", &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;
+
+	INIT_DELAYED_WORK(&bat_priv->dat.work, batadv_dat_purge);
+	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):\n", net_dev->name);
+	seq_puts(seq,
+		 "          IPv4             MAC        VID   last-seen\n");
+
+	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\n",
+				   &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\n");
+		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\n",
+			   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.\n",
+			   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)\n",
+		   &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)\n",
+		   &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)\n",
+		   &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)\n",
+		   &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\n", &ip_dst);
+		goto out;
+	}
+
+	batadv_dbg(BATADV_DBG_DAT, bat_priv,
+		   "ARP Request for %pI4: fallback prevented\n", &ip_dst);
+	ret = true;
+
+out:
+	if (dat_entry)
+		batadv_dat_entry_put(dat_entry);
+	return ret;
+}