text: /* Copyright (C) 2007-2017  B.A.T.M.A.N. contributors:
   *
   * Marek Lindner, Simon Wunderlich
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of version 2 of the GNU General Public
   * License as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, see <http://www.gnu.org/licenses/>.
   */
  
  #include "routing.h"
  #include "main.h"
  
  #include <linux/atomic.h>
  #include <linux/byteorder/generic.h>
  #include <linux/compiler.h>
  #include <linux/errno.h>
  #include <linux/etherdevice.h>
  #include <linux/if_ether.h>
  #include <linux/jiffies.h>
  #include <linux/kref.h>
  #include <linux/netdevice.h>
  #include <linux/printk.h>
  #include <linux/rculist.h>
  #include <linux/rcupdate.h>
  #include <linux/skbuff.h>
  #include <linux/spinlock.h>
  #include <linux/stddef.h>
  
  #include "bitarray.h"
  #include "bridge_loop_avoidance.h"
  #include "distributed-arp-table.h"
  #include "fragmentation.h"
  #include "hard-interface.h"
  #include "icmp_socket.h"
  #include "log.h"
  #include "network-coding.h"
  #include "originator.h"
  #include "packet.h"
  #include "send.h"
  #include "soft-interface.h"
  #include "tp_meter.h"
  #include "translation-table.h"
  #include "tvlv.h"
  
  static int batadv_route_unicast_packet(struct sk_buff *skb,
  				       struct batadv_hard_iface *recv_if);
  
  /**
   * _batadv_update_route - set the router for this originator
   * @bat_priv: the bat priv with all the soft interface information
   * @orig_node: orig node which is to be configured
   * @recv_if: the receive interface for which this route is set
   * @neigh_node: neighbor which should be the next router
   *
   * This function does not perform any error checks
   */
  static void _batadv_update_route(struct batadv_priv *bat_priv,
  				 struct batadv_orig_node *orig_node,
  				 struct batadv_hard_iface *recv_if,
  				 struct batadv_neigh_node *neigh_node)
  {
  	struct batadv_orig_ifinfo *orig_ifinfo;
  	struct batadv_neigh_node *curr_router;
  
  	orig_ifinfo = batadv_orig_ifinfo_get(orig_node, recv_if);
  	if (!orig_ifinfo)
  		return;
  
  	spin_lock_bh(&orig_node->neigh_list_lock);
  	/* curr_router used earlier may not be the current orig_ifinfo->router
  	 * anymore because it was dereferenced outside of the neigh_list_lock
  	 * protected region. After the new best neighbor has replace the current
  	 * best neighbor the reference counter needs to decrease. Consequently,
  	 * the code needs to ensure the curr_router variable contains a pointer
  	 * to the replaced best neighbor.
  	 */
  	curr_router = rcu_dereference_protected(orig_ifinfo->router, true);
  
  	/* increase refcount of new best neighbor */
  	if (neigh_node)
  		kref_get(&neigh_node->refcount);
  
  	rcu_assign_pointer(orig_ifinfo->router, neigh_node);
  	spin_unlock_bh(&orig_node->neigh_list_lock);
  	batadv_orig_ifinfo_put(orig_ifinfo);
  
  	/* route deleted */
  	if ((curr_router) && (!neigh_node)) {
  		batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
  			   "Deleting route towards: %pM\n", orig_node->orig);
  		batadv_tt_global_del_orig(bat_priv, orig_node, -1,
  					  "Deleted route towards originator");
  
  	/* route added */
  	} else if ((!curr_router) && (neigh_node)) {
  		batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
  			   "Adding route towards: %pM (via %pM)\n",
  			   orig_node->orig, neigh_node->addr);
  	/* route changed */
  	} else if (neigh_node && curr_router) {
  		batadv_dbg(BATADV_DBG_ROUTES, bat_priv,
  			   "Changing route towards: %pM (now via %pM - was via %pM)\n",
  			   orig_node->orig, neigh_node->addr,
  			   curr_router->addr);
  	}
  
  	/* decrease refcount of previous best neighbor */
  	if (curr_router)
  		batadv_neigh_node_put(curr_router);
  }
  
  /**
   * batadv_update_route - set the router for this originator
   * @bat_priv: the bat priv with all the soft interface information
   * @orig_node: orig node which is to be configured
   * @recv_if: the receive interface for which this route is set
   * @neigh_node: neighbor which should be the next router
   */
  void batadv_update_route(struct batadv_priv *bat_priv,
  			 struct batadv_orig_node *orig_node,
  			 struct batadv_hard_iface *recv_if,
  			 struct batadv_neigh_node *neigh_node)
  {
  	struct batadv_neigh_node *router = NULL;
  
  	if (!orig_node)
  		goto out;
  
  	router = batadv_orig_router_get(orig_node, recv_if);
  
  	if (router != neigh_node)
  		_batadv_update_route(bat_priv, orig_node, recv_if, neigh_node);
  
  out:
  	if (router)
  		batadv_neigh_node_put(router);
  }
  
  /**
   * batadv_window_protected - checks whether the host restarted and is in the
   *  protection time.
   * @bat_priv: the bat priv with all the soft interface information
   * @seq_num_diff: difference between the current/received sequence number and
   *  the last sequence number
   * @seq_old_max_diff: maximum age of sequence number not considered as restart
   * @last_reset: jiffies timestamp of the last reset, will be updated when reset
   *  is detected
   * @protection_started: is set to true if the protection window was started,
   *   doesn't change otherwise.
   *
   * Return:
   *  false if the packet is to be accepted.
   *  true if the packet is to be ignored.
   */
  bool batadv_window_protected(struct batadv_priv *bat_priv, s32 seq_num_diff,
  			     s32 seq_old_max_diff, unsigned long *last_reset,
  			     bool *protection_started)
  {
  	if (seq_num_diff <= -seq_old_max_diff ||
  	    seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE) {
  		if (!batadv_has_timed_out(*last_reset,
  					  BATADV_RESET_PROTECTION_MS))
  			return true;
  
  		*last_reset = jiffies;
  		if (protection_started)
  			*protection_started = true;
  		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
  			   "old packet received, start protection\n");
  	}
  
  	return false;
  }
  
  bool batadv_check_management_packet(struct sk_buff *skb,
  				    struct batadv_hard_iface *hard_iface,
  				    int header_len)
  {
  	struct ethhdr *ethhdr;
  
  	/* drop packet if it has not necessary minimum size */
  	if (unlikely(!pskb_may_pull(skb, header_len)))
  		return false;
  
  	ethhdr = eth_hdr(skb);
  
  	/* packet with broadcast indication but unicast recipient */
  	if (!is_broadcast_ether_addr(ethhdr->h_dest))
  		return false;
  
  	/* packet with invalid sender address */
  	if (!is_valid_ether_addr(ethhdr->h_source))
  		return false;
  
  	/* create a copy of the skb, if needed, to modify it. */
  	if (skb_cow(skb, 0) < 0)
  		return false;
  
  	/* keep skb linear */
  	if (skb_linearize(skb) < 0)
  		return false;
  
  	return true;
  }
  
  /**
   * batadv_recv_my_icmp_packet - receive an icmp packet locally
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: icmp packet to process
   *
   * Return: NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
   * otherwise.
   */
  static int batadv_recv_my_icmp_packet(struct batadv_priv *bat_priv,
  				      struct sk_buff *skb)
  {
  	struct batadv_hard_iface *primary_if = NULL;
  	struct batadv_orig_node *orig_node = NULL;
  	struct batadv_icmp_header *icmph;
  	int res, ret = NET_RX_DROP;
  
  	icmph = (struct batadv_icmp_header *)skb->data;
  
  	switch (icmph->msg_type) {
  	case BATADV_ECHO_REPLY:
  	case BATADV_DESTINATION_UNREACHABLE:
  	case BATADV_TTL_EXCEEDED:
  		/* receive the packet */
  		if (skb_linearize(skb) < 0)
  			break;
  
  		batadv_socket_receive_packet(icmph, skb->len);
  		break;
  	case BATADV_ECHO_REQUEST:
  		/* answer echo request (ping) */
  		primary_if = batadv_primary_if_get_selected(bat_priv);
  		if (!primary_if)
  			goto out;
  
  		/* get routing information */
  		orig_node = batadv_orig_hash_find(bat_priv, icmph->orig);
  		if (!orig_node)
  			goto out;
  
  		/* create a copy of the skb, if needed, to modify it. */
  		if (skb_cow(skb, ETH_HLEN) < 0)
  			goto out;
  
  		icmph = (struct batadv_icmp_header *)skb->data;
  
  		ether_addr_copy(icmph->dst, icmph->orig);
  		ether_addr_copy(icmph->orig, primary_if->net_dev->dev_addr);
  		icmph->msg_type = BATADV_ECHO_REPLY;
  		icmph->ttl = BATADV_TTL;
  
  		res = batadv_send_skb_to_orig(skb, orig_node, NULL);
  		if (res == NET_XMIT_SUCCESS)
  			ret = NET_RX_SUCCESS;
  
  		/* skb was consumed */
  		skb = NULL;
  		break;
  	case BATADV_TP:
  		if (!pskb_may_pull(skb, sizeof(struct batadv_icmp_tp_packet)))
  			goto out;
  
  		batadv_tp_meter_recv(bat_priv, skb);
  		ret = NET_RX_SUCCESS;
  		/* skb was consumed */
  		skb = NULL;
  		goto out;
  	default:
  		/* drop unknown type */
  		goto out;
  	}
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  
  	kfree_skb(skb);
  
  	return ret;
  }
  
  static int batadv_recv_icmp_ttl_exceeded(struct batadv_priv *bat_priv,
  					 struct sk_buff *skb)
  {
  	struct batadv_hard_iface *primary_if = NULL;
  	struct batadv_orig_node *orig_node = NULL;
  	struct batadv_icmp_packet *icmp_packet;
  	int res, ret = NET_RX_DROP;
  
  	icmp_packet = (struct batadv_icmp_packet *)skb->data;
  
  	/* send TTL exceeded if packet is an echo request (traceroute) */
  	if (icmp_packet->msg_type != BATADV_ECHO_REQUEST) {
  		pr_debug("Warning - can't forward icmp packet from %pM to %pM: ttl exceeded\n",
  			 icmp_packet->orig, icmp_packet->dst);
  		goto out;
  	}
  
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)
  		goto out;
  
  	/* get routing information */
  	orig_node = batadv_orig_hash_find(bat_priv, icmp_packet->orig);
  	if (!orig_node)
  		goto out;
  
  	/* create a copy of the skb, if needed, to modify it. */
  	if (skb_cow(skb, ETH_HLEN) < 0)
  		goto out;
  
  	icmp_packet = (struct batadv_icmp_packet *)skb->data;
  
  	ether_addr_copy(icmp_packet->dst, icmp_packet->orig);
  	ether_addr_copy(icmp_packet->orig, primary_if->net_dev->dev_addr);
  	icmp_packet->msg_type = BATADV_TTL_EXCEEDED;
  	icmp_packet->ttl = BATADV_TTL;
  
  	res = batadv_send_skb_to_orig(skb, orig_node, NULL);
  	if (res == NET_RX_SUCCESS)
  		ret = NET_XMIT_SUCCESS;
  
  	/* skb was consumed */
  	skb = NULL;
  
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  
  	kfree_skb(skb);
  
  	return ret;
  }
  
  int batadv_recv_icmp_packet(struct sk_buff *skb,
  			    struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_icmp_header *icmph;
  	struct batadv_icmp_packet_rr *icmp_packet_rr;
  	struct ethhdr *ethhdr;
  	struct batadv_orig_node *orig_node = NULL;
  	int hdr_size = sizeof(struct batadv_icmp_header);
  	int res, ret = NET_RX_DROP;
  
  	/* drop packet if it has not necessary minimum size */
  	if (unlikely(!pskb_may_pull(skb, hdr_size)))
  		goto free_skb;
  
  	ethhdr = eth_hdr(skb);
  
  	/* packet with unicast indication but non-unicast recipient */
  	if (!is_valid_ether_addr(ethhdr->h_dest))
  		goto free_skb;
  
  	/* packet with broadcast/multicast sender address */
  	if (is_multicast_ether_addr(ethhdr->h_source))
  		goto free_skb;
  
  	/* not for me */
  	if (!batadv_is_my_mac(bat_priv, ethhdr->h_dest))
  		goto free_skb;
  
  	icmph = (struct batadv_icmp_header *)skb->data;
  
  	/* add record route information if not full */
  	if ((icmph->msg_type == BATADV_ECHO_REPLY ||
  	     icmph->msg_type == BATADV_ECHO_REQUEST) &&
  	    (skb->len >= sizeof(struct batadv_icmp_packet_rr))) {
  		if (skb_linearize(skb) < 0)
  			goto free_skb;
  
  		/* create a copy of the skb, if needed, to modify it. */
  		if (skb_cow(skb, ETH_HLEN) < 0)
  			goto free_skb;
  
  		ethhdr = eth_hdr(skb);
  		icmph = (struct batadv_icmp_header *)skb->data;
  		icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmph;
  		if (icmp_packet_rr->rr_cur >= BATADV_RR_LEN)
  			goto free_skb;
  
  		ether_addr_copy(icmp_packet_rr->rr[icmp_packet_rr->rr_cur],
  				ethhdr->h_dest);
  		icmp_packet_rr->rr_cur++;
  	}
  
  	/* packet for me */
  	if (batadv_is_my_mac(bat_priv, icmph->dst))
  		return batadv_recv_my_icmp_packet(bat_priv, skb);
  
  	/* TTL exceeded */
  	if (icmph->ttl < 2)
  		return batadv_recv_icmp_ttl_exceeded(bat_priv, skb);
  
  	/* get routing information */
  	orig_node = batadv_orig_hash_find(bat_priv, icmph->dst);
  	if (!orig_node)
  		goto free_skb;
  
  	/* create a copy of the skb, if needed, to modify it. */
  	if (skb_cow(skb, ETH_HLEN) < 0)
  		goto put_orig_node;
  
  	icmph = (struct batadv_icmp_header *)skb->data;
  
  	/* decrement ttl */
  	icmph->ttl--;
  
  	/* route it */
  	res = batadv_send_skb_to_orig(skb, orig_node, recv_if);
  	if (res == NET_XMIT_SUCCESS)
  		ret = NET_RX_SUCCESS;
  
  	/* skb was consumed */
  	skb = NULL;
  
  put_orig_node:
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  free_skb:
  	kfree_skb(skb);
  
  	return ret;
  }
  
  /**
   * batadv_check_unicast_packet - Check for malformed unicast packets
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: packet to check
   * @hdr_size: size of header to pull
   *
   * Check for short header and bad addresses in given packet.
   *
   * Return: negative value when check fails and 0 otherwise. The negative value
   * depends on the reason: -ENODATA for bad header, -EBADR for broadcast
   * destination or source, and -EREMOTE for non-local (other host) destination.
   */
  static int batadv_check_unicast_packet(struct batadv_priv *bat_priv,
  				       struct sk_buff *skb, int hdr_size)
  {
  	struct ethhdr *ethhdr;
  
  	/* drop packet if it has not necessary minimum size */
  	if (unlikely(!pskb_may_pull(skb, hdr_size)))
  		return -ENODATA;
  
  	ethhdr = eth_hdr(skb);
  
  	/* packet with unicast indication but non-unicast recipient */
  	if (!is_valid_ether_addr(ethhdr->h_dest))
  		return -EBADR;
  
  	/* packet with broadcast/multicast sender address */
  	if (is_multicast_ether_addr(ethhdr->h_source))
  		return -EBADR;
  
  	/* not for me */
  	if (!batadv_is_my_mac(bat_priv, ethhdr->h_dest))
  		return -EREMOTE;
  
  	return 0;
  }
  
  /**
   * batadv_last_bonding_get - Get last_bonding_candidate of orig_node
   * @orig_node: originator node whose last bonding candidate should be retrieved
   *
   * Return: last bonding candidate of router or NULL if not found
   *
   * The object is returned with refcounter increased by 1.
   */
  static struct batadv_orig_ifinfo *
  batadv_last_bonding_get(struct batadv_orig_node *orig_node)
  {
  	struct batadv_orig_ifinfo *last_bonding_candidate;
  
  	spin_lock_bh(&orig_node->neigh_list_lock);
  	last_bonding_candidate = orig_node->last_bonding_candidate;
  
  	if (last_bonding_candidate)
  		kref_get(&last_bonding_candidate->refcount);
  	spin_unlock_bh(&orig_node->neigh_list_lock);
  
  	return last_bonding_candidate;
  }
  
  /**
   * batadv_last_bonding_replace - Replace last_bonding_candidate of orig_node
   * @orig_node: originator node whose bonding candidates should be replaced
   * @new_candidate: new bonding candidate or NULL
   */
  static void
  batadv_last_bonding_replace(struct batadv_orig_node *orig_node,
  			    struct batadv_orig_ifinfo *new_candidate)
  {
  	struct batadv_orig_ifinfo *old_candidate;
  
  	spin_lock_bh(&orig_node->neigh_list_lock);
  	old_candidate = orig_node->last_bonding_candidate;
  
  	if (new_candidate)
  		kref_get(&new_candidate->refcount);
  	orig_node->last_bonding_candidate = new_candidate;
  	spin_unlock_bh(&orig_node->neigh_list_lock);
  
  	if (old_candidate)
  		batadv_orig_ifinfo_put(old_candidate);
  }
  
  /**
   * batadv_find_router - find a suitable router for this originator
   * @bat_priv: the bat priv with all the soft interface information
   * @orig_node: the destination node
   * @recv_if: pointer to interface this packet was received on
   *
   * Return: the router which should be used for this orig_node on
   * this interface, or NULL if not available.
   */
  struct batadv_neigh_node *
  batadv_find_router(struct batadv_priv *bat_priv,
  		   struct batadv_orig_node *orig_node,
  		   struct batadv_hard_iface *recv_if)
  {
  	struct batadv_algo_ops *bao = bat_priv->algo_ops;
  	struct batadv_neigh_node *first_candidate_router = NULL;
  	struct batadv_neigh_node *next_candidate_router = NULL;
  	struct batadv_neigh_node *router, *cand_router = NULL;
  	struct batadv_neigh_node *last_cand_router = NULL;
  	struct batadv_orig_ifinfo *cand, *first_candidate = NULL;
  	struct batadv_orig_ifinfo *next_candidate = NULL;
  	struct batadv_orig_ifinfo *last_candidate;
  	bool last_candidate_found = false;
  
  	if (!orig_node)
  		return NULL;
  
  	router = batadv_orig_router_get(orig_node, recv_if);
  
  	if (!router)
  		return router;
  
  	/* only consider bonding for recv_if == BATADV_IF_DEFAULT (first hop)
  	 * and if activated.
  	 */
  	if (!(recv_if == BATADV_IF_DEFAULT && atomic_read(&bat_priv->bonding)))
  		return router;
  
  	/* bonding: loop through the list of possible routers found
  	 * for the various outgoing interfaces and find a candidate after
  	 * the last chosen bonding candidate (next_candidate). If no such
  	 * router is found, use the first candidate found (the previously
  	 * chosen bonding candidate might have been the last one in the list).
  	 * If this can't be found either, return the previously chosen
  	 * router - obviously there are no other candidates.
  	 */
  	rcu_read_lock();
  	last_candidate = batadv_last_bonding_get(orig_node);
  	if (last_candidate)
  		last_cand_router = rcu_dereference(last_candidate->router);
  
  	hlist_for_each_entry_rcu(cand, &orig_node->ifinfo_list, list) {
  		/* acquire some structures and references ... */
  		if (!kref_get_unless_zero(&cand->refcount))
  			continue;
  
  		cand_router = rcu_dereference(cand->router);
  		if (!cand_router)
  			goto next;
  
  		if (!kref_get_unless_zero(&cand_router->refcount)) {
  			cand_router = NULL;
  			goto next;
  		}
  
  		/* alternative candidate should be good enough to be
  		 * considered
  		 */
  		if (!bao->neigh.is_similar_or_better(cand_router,
  						     cand->if_outgoing, router,
  						     recv_if))
  			goto next;
  
  		/* don't use the same router twice */
  		if (last_cand_router == cand_router)
  			goto next;
  
  		/* mark the first possible candidate */
  		if (!first_candidate) {
  			kref_get(&cand_router->refcount);
  			kref_get(&cand->refcount);
  			first_candidate = cand;
  			first_candidate_router = cand_router;
  		}
  
  		/* check if the loop has already passed the previously selected
  		 * candidate ... this function should select the next candidate
  		 * AFTER the previously used bonding candidate.
  		 */
  		if (!last_candidate || last_candidate_found) {
  			next_candidate = cand;
  			next_candidate_router = cand_router;
  			break;
  		}
  
  		if (last_candidate == cand)
  			last_candidate_found = true;
  next:
  		/* free references */
  		if (cand_router) {
  			batadv_neigh_node_put(cand_router);
  			cand_router = NULL;
  		}
  		batadv_orig_ifinfo_put(cand);
  	}
  	rcu_read_unlock();
  
  	/* After finding candidates, handle the three cases:
  	 * 1) there is a next candidate, use that
  	 * 2) there is no next candidate, use the first of the list
  	 * 3) there is no candidate at all, return the default router
  	 */
  	if (next_candidate) {
  		batadv_neigh_node_put(router);
  
  		kref_get(&next_candidate_router->refcount);
  		router = next_candidate_router;
  		batadv_last_bonding_replace(orig_node, next_candidate);
  	} else if (first_candidate) {
  		batadv_neigh_node_put(router);
  
  		kref_get(&first_candidate_router->refcount);
  		router = first_candidate_router;
  		batadv_last_bonding_replace(orig_node, first_candidate);
  	} else {
  		batadv_last_bonding_replace(orig_node, NULL);
  	}
  
  	/* cleanup of candidates */
  	if (first_candidate) {
  		batadv_neigh_node_put(first_candidate_router);
  		batadv_orig_ifinfo_put(first_candidate);
  	}
  
  	if (next_candidate) {
  		batadv_neigh_node_put(next_candidate_router);
  		batadv_orig_ifinfo_put(next_candidate);
  	}
  
  	if (last_candidate)
  		batadv_orig_ifinfo_put(last_candidate);
  
  	return router;
  }
  
  static int batadv_route_unicast_packet(struct sk_buff *skb,
  				       struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_orig_node *orig_node = NULL;
  	struct batadv_unicast_packet *unicast_packet;
  	struct ethhdr *ethhdr = eth_hdr(skb);
  	int res, hdr_len, ret = NET_RX_DROP;
  	unsigned int len;
  
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  
  	/* TTL exceeded */
  	if (unicast_packet->ttl < 2) {
  		pr_debug("Warning - can't forward unicast packet from %pM to %pM: ttl exceeded\n",
  			 ethhdr->h_source, unicast_packet->dest);
  		goto free_skb;
  	}
  
  	/* get routing information */
  	orig_node = batadv_orig_hash_find(bat_priv, unicast_packet->dest);
  
  	if (!orig_node)
  		goto free_skb;
  
  	/* create a copy of the skb, if needed, to modify it. */
  	if (skb_cow(skb, ETH_HLEN) < 0)
  		goto put_orig_node;
  
  	/* decrement ttl */
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  	unicast_packet->ttl--;
  
  	switch (unicast_packet->packet_type) {
  	case BATADV_UNICAST_4ADDR:
  		hdr_len = sizeof(struct batadv_unicast_4addr_packet);
  		break;
  	case BATADV_UNICAST:
  		hdr_len = sizeof(struct batadv_unicast_packet);
  		break;
  	default:
  		/* other packet types not supported - yet */
  		hdr_len = -1;
  		break;
  	}
  
  	if (hdr_len > 0)
  		batadv_skb_set_priority(skb, hdr_len);
  
  	len = skb->len;
  	res = batadv_send_skb_to_orig(skb, orig_node, recv_if);
  
  	/* translate transmit result into receive result */
  	if (res == NET_XMIT_SUCCESS) {
  		ret = NET_RX_SUCCESS;
  		/* skb was transmitted and consumed */
  		batadv_inc_counter(bat_priv, BATADV_CNT_FORWARD);
  		batadv_add_counter(bat_priv, BATADV_CNT_FORWARD_BYTES,
  				   len + ETH_HLEN);
  	}
  
  	/* skb was consumed */
  	skb = NULL;
  
  put_orig_node:
  	batadv_orig_node_put(orig_node);
  free_skb:
  	kfree_skb(skb);
  
  	return ret;
  }
  
  /**
   * batadv_reroute_unicast_packet - update the unicast header for re-routing
   * @bat_priv: the bat priv with all the soft interface information
   * @skb: unicast packet to process
   * @unicast_packet: the unicast header to be updated
   * @dst_addr: the payload destination
   * @vid: VLAN identifier
   *
   * Search the translation table for dst_addr and update the unicast header with
   * the new corresponding information (originator address where the destination
   * client currently is and its known TTVN)
   *
   * Return: true if the packet header has been updated, false otherwise
   */
  static bool
  batadv_reroute_unicast_packet(struct batadv_priv *bat_priv, struct sk_buff *skb,
  			      struct batadv_unicast_packet *unicast_packet,
  			      u8 *dst_addr, unsigned short vid)
  {
  	struct batadv_orig_node *orig_node = NULL;
  	struct batadv_hard_iface *primary_if = NULL;
  	bool ret = false;
  	u8 *orig_addr, orig_ttvn;
  
  	if (batadv_is_my_client(bat_priv, dst_addr, vid)) {
  		primary_if = batadv_primary_if_get_selected(bat_priv);
  		if (!primary_if)
  			goto out;
  		orig_addr = primary_if->net_dev->dev_addr;
  		orig_ttvn = (u8)atomic_read(&bat_priv->tt.vn);
  	} else {
  		orig_node = batadv_transtable_search(bat_priv, NULL, dst_addr,
  						     vid);
  		if (!orig_node)
  			goto out;
  
  		if (batadv_compare_eth(orig_node->orig, unicast_packet->dest))
  			goto out;
  
  		orig_addr = orig_node->orig;
  		orig_ttvn = (u8)atomic_read(&orig_node->last_ttvn);
  	}
  
  	/* update the packet header */
  	skb_postpull_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
  	ether_addr_copy(unicast_packet->dest, orig_addr);
  	unicast_packet->ttvn = orig_ttvn;
  	skb_postpush_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
  
  	ret = true;
  out:
  	if (primary_if)
  		batadv_hardif_put(primary_if);
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  
  	return ret;
  }
  
  static bool batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
  				      struct sk_buff *skb, int hdr_len)
  {
  	struct batadv_unicast_packet *unicast_packet;
  	struct batadv_hard_iface *primary_if;
  	struct batadv_orig_node *orig_node;
  	u8 curr_ttvn, old_ttvn;
  	struct ethhdr *ethhdr;
  	unsigned short vid;
  	int is_old_ttvn;
  
  	/* check if there is enough data before accessing it */
  	if (!pskb_may_pull(skb, hdr_len + ETH_HLEN))
  		return false;
  
  	/* create a copy of the skb (in case of for re-routing) to modify it. */
  	if (skb_cow(skb, sizeof(*unicast_packet)) < 0)
  		return false;
  
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  	vid = batadv_get_vid(skb, hdr_len);
  	ethhdr = (struct ethhdr *)(skb->data + hdr_len);
  
  	/* check if the destination client was served by this node and it is now
  	 * roaming. In this case, it means that the node has got a ROAM_ADV
  	 * message and that it knows the new destination in the mesh to re-route
  	 * the packet to
  	 */
  	if (batadv_tt_local_client_is_roaming(bat_priv, ethhdr->h_dest, vid)) {
  		if (batadv_reroute_unicast_packet(bat_priv, skb, unicast_packet,
  						  ethhdr->h_dest, vid))
  			batadv_dbg_ratelimited(BATADV_DBG_TT,
  					       bat_priv,
  					       "Rerouting unicast packet to %pM (dst=%pM): Local Roaming\n",
  					       unicast_packet->dest,
  					       ethhdr->h_dest);
  		/* at this point the mesh destination should have been
  		 * substituted with the originator address found in the global
  		 * table. If not, let the packet go untouched anyway because
  		 * there is nothing the node can do
  		 */
  		return true;
  	}
  
  	/* retrieve the TTVN known by this node for the packet destination. This
  	 * value is used later to check if the node which sent (or re-routed
  	 * last time) the packet had an updated information or not
  	 */
  	curr_ttvn = (u8)atomic_read(&bat_priv->tt.vn);
  	if (!batadv_is_my_mac(bat_priv, unicast_packet->dest)) {
  		orig_node = batadv_orig_hash_find(bat_priv,
  						  unicast_packet->dest);
  		/* if it is not possible to find the orig_node representing the
  		 * destination, the packet can immediately be dropped as it will
  		 * not be possible to deliver it
  		 */
  		if (!orig_node)
  			return false;
  
  		curr_ttvn = (u8)atomic_read(&orig_node->last_ttvn);
  		batadv_orig_node_put(orig_node);
  	}
  
  	/* check if the TTVN contained in the packet is fresher than what the
  	 * node knows
  	 */
  	is_old_ttvn = batadv_seq_before(unicast_packet->ttvn, curr_ttvn);
  	if (!is_old_ttvn)
  		return true;
  
  	old_ttvn = unicast_packet->ttvn;
  	/* the packet was forged based on outdated network information. Its
  	 * destination can possibly be updated and forwarded towards the new
  	 * target host
  	 */
  	if (batadv_reroute_unicast_packet(bat_priv, skb, unicast_packet,
  					  ethhdr->h_dest, vid)) {
  		batadv_dbg_ratelimited(BATADV_DBG_TT, bat_priv,
  				       "Rerouting unicast packet to %pM (dst=%pM): TTVN mismatch old_ttvn=%u new_ttvn=%u\n",
  				       unicast_packet->dest, ethhdr->h_dest,
  				       old_ttvn, curr_ttvn);
  		return true;
  	}
  
  	/* the packet has not been re-routed: either the destination is
  	 * currently served by this node or there is no destination at all and
  	 * it is possible to drop the packet
  	 */
  	if (!batadv_is_my_client(bat_priv, ethhdr->h_dest, vid))
  		return false;
  
  	/* update the header in order to let the packet be delivered to this
  	 * node's soft interface
  	 */
  	primary_if = batadv_primary_if_get_selected(bat_priv);
  	if (!primary_if)
  		return false;
  
  	/* update the packet header */
  	skb_postpull_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
  	ether_addr_copy(unicast_packet->dest, primary_if->net_dev->dev_addr);
  	unicast_packet->ttvn = curr_ttvn;
  	skb_postpush_rcsum(skb, unicast_packet, sizeof(*unicast_packet));
  
  	batadv_hardif_put(primary_if);
  
  	return true;
  }
  
  /**
   * batadv_recv_unhandled_unicast_packet - receive and process packets which
   *	are in the unicast number space but not yet known to the implementation
   * @skb: unicast tvlv packet to process
   * @recv_if: pointer to interface this packet was received on
   *
   * Return: NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
   * otherwise.
   */
  int batadv_recv_unhandled_unicast_packet(struct sk_buff *skb,
  					 struct batadv_hard_iface *recv_if)
  {
  	struct batadv_unicast_packet *unicast_packet;
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	int check, hdr_size = sizeof(*unicast_packet);
  
  	check = batadv_check_unicast_packet(bat_priv, skb, hdr_size);
  	if (check < 0)
  		goto free_skb;
  
  	/* we don't know about this type, drop it. */
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  	if (batadv_is_my_mac(bat_priv, unicast_packet->dest))
  		goto free_skb;
  
  	return batadv_route_unicast_packet(skb, recv_if);
  
  free_skb:
  	kfree_skb(skb);
  	return NET_RX_DROP;
  }
  
  int batadv_recv_unicast_packet(struct sk_buff *skb,
  			       struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_unicast_packet *unicast_packet;
  	struct batadv_unicast_4addr_packet *unicast_4addr_packet;
  	u8 *orig_addr, *orig_addr_gw;
  	struct batadv_orig_node *orig_node = NULL, *orig_node_gw = NULL;
  	int check, hdr_size = sizeof(*unicast_packet);
  	enum batadv_subtype subtype;
  	struct ethhdr *ethhdr;
  	int ret = NET_RX_DROP;
  	bool is4addr, is_gw;
  
  	unicast_packet = (struct batadv_unicast_packet *)skb->data;
  	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
  	ethhdr = eth_hdr(skb);
  
  	is4addr = unicast_packet->packet_type == BATADV_UNICAST_4ADDR;
  	/* the caller function should have already pulled 2 bytes */
  	if (is4addr)
  		hdr_size = sizeof(*unicast_4addr_packet);
  
  	/* function returns -EREMOTE for promiscuous packets */
  	check = batadv_check_unicast_packet(bat_priv, skb, hdr_size);
  
  	/* Even though the packet is not for us, we might save it to use for
  	 * decoding a later received coded packet
  	 */
  	if (check == -EREMOTE)
  		batadv_nc_skb_store_sniffed_unicast(bat_priv, skb);
  
  	if (check < 0)
  		goto free_skb;
  	if (!batadv_check_unicast_ttvn(bat_priv, skb, hdr_size))
  		goto free_skb;
  
  	/* packet for me */
  	if (batadv_is_my_mac(bat_priv, unicast_packet->dest)) {
  		/* If this is a unicast packet from another backgone gw,
  		 * drop it.
  		 */
  		orig_addr_gw = ethhdr->h_source;
  		orig_node_gw = batadv_orig_hash_find(bat_priv, orig_addr_gw);
  		if (orig_node_gw) {
  			is_gw = batadv_bla_is_backbone_gw(skb, orig_node_gw,
  							  hdr_size);
  			batadv_orig_node_put(orig_node_gw);
  			if (is_gw) {
  				batadv_dbg(BATADV_DBG_BLA, bat_priv,
  					   "%s(): Dropped unicast pkt received from another backbone gw %pM.\n",
  					   __func__, orig_addr_gw);
  				goto free_skb;
  			}
  		}
  
  		if (is4addr) {
  			subtype = unicast_4addr_packet->subtype;
  			batadv_dat_inc_counter(bat_priv, subtype);
  
  			/* Only payload data should be considered for speedy
  			 * join. For example, DAT also uses unicast 4addr
  			 * types, but those packets should not be considered
  			 * for speedy join, since the clients do not actually
  			 * reside at the sending originator.
  			 */
  			if (subtype == BATADV_P_DATA) {
  				orig_addr = unicast_4addr_packet->src;
  				orig_node = batadv_orig_hash_find(bat_priv,
  								  orig_addr);
  			}
  		}
  
  		if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb,
  							  hdr_size))
  			goto rx_success;
  		if (batadv_dat_snoop_incoming_arp_reply(bat_priv, skb,
  							hdr_size))
  			goto rx_success;
  
  		batadv_interface_rx(recv_if->soft_iface, skb, hdr_size,
  				    orig_node);
  
  rx_success:
  		if (orig_node)
  			batadv_orig_node_put(orig_node);
  
  		return NET_RX_SUCCESS;
  	}
  
  	ret = batadv_route_unicast_packet(skb, recv_if);
  	/* skb was consumed */
  	skb = NULL;
  
  free_skb:
  	kfree_skb(skb);
  
  	return ret;
  }
  
  /**
   * batadv_recv_unicast_tvlv - receive and process unicast tvlv packets
   * @skb: unicast tvlv packet to process
   * @recv_if: pointer to interface this packet was received on
   *
   * Return: NET_RX_SUCCESS if the packet has been consumed or NET_RX_DROP
   * otherwise.
   */
  int batadv_recv_unicast_tvlv(struct sk_buff *skb,
  			     struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_unicast_tvlv_packet *unicast_tvlv_packet;
  	unsigned char *tvlv_buff;
  	u16 tvlv_buff_len;
  	int hdr_size = sizeof(*unicast_tvlv_packet);
  	int ret = NET_RX_DROP;
  
  	if (batadv_check_unicast_packet(bat_priv, skb, hdr_size) < 0)
  		goto free_skb;
  
  	/* the header is likely to be modified while forwarding */
  	if (skb_cow(skb, hdr_size) < 0)
  		goto free_skb;
  
  	/* packet needs to be linearized to access the tvlv content */
  	if (skb_linearize(skb) < 0)
  		goto free_skb;
  
  	unicast_tvlv_packet = (struct batadv_unicast_tvlv_packet *)skb->data;
  
  	tvlv_buff = (unsigned char *)(skb->data + hdr_size);
  	tvlv_buff_len = ntohs(unicast_tvlv_packet->tvlv_len);
  
  	if (tvlv_buff_len > skb->len - hdr_size)
  		goto free_skb;
  
  	ret = batadv_tvlv_containers_process(bat_priv, false, NULL,
  					     unicast_tvlv_packet->src,
  					     unicast_tvlv_packet->dst,
  					     tvlv_buff, tvlv_buff_len);
  
  	if (ret != NET_RX_SUCCESS) {
  		ret = batadv_route_unicast_packet(skb, recv_if);
  		/* skb was consumed */
  		skb = NULL;
  	}
  
  free_skb:
  	kfree_skb(skb);
  
  	return ret;
  }
  
  /**
   * batadv_recv_frag_packet - process received fragment
   * @skb: the received fragment
   * @recv_if: interface that the skb is received on
   *
   * This function does one of the three following things: 1) Forward fragment, if
   * the assembled packet will exceed our MTU; 2) Buffer fragment, if we till
   * lack further fragments; 3) Merge fragments, if we have all needed parts.
   *
   * Return: NET_RX_DROP if the skb is not consumed, NET_RX_SUCCESS otherwise.
   */
  int batadv_recv_frag_packet(struct sk_buff *skb,
  			    struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_orig_node *orig_node_src = NULL;
  	struct batadv_frag_packet *frag_packet;
  	int ret = NET_RX_DROP;
  
  	if (batadv_check_unicast_packet(bat_priv, skb,
  					sizeof(*frag_packet)) < 0)
  		goto free_skb;
  
  	frag_packet = (struct batadv_frag_packet *)skb->data;
  	orig_node_src = batadv_orig_hash_find(bat_priv, frag_packet->orig);
  	if (!orig_node_src)
  		goto free_skb;
  
  	skb->priority = frag_packet->priority + 256;
  
  	/* Route the fragment if it is not for us and too big to be merged. */
  	if (!batadv_is_my_mac(bat_priv, frag_packet->dest) &&
  	    batadv_frag_skb_fwd(skb, recv_if, orig_node_src)) {
  		/* skb was consumed */
  		skb = NULL;
  		ret = NET_RX_SUCCESS;
  		goto put_orig_node;
  	}
  
  	batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_RX);
  	batadv_add_counter(bat_priv, BATADV_CNT_FRAG_RX_BYTES, skb->len);
  
  	/* Add fragment to buffer and merge if possible. */
  	if (!batadv_frag_skb_buffer(&skb, orig_node_src))
  		goto put_orig_node;
  
  	/* Deliver merged packet to the appropriate handler, if it was
  	 * merged
  	 */
  	if (skb) {
  		batadv_batman_skb_recv(skb, recv_if->net_dev,
  				       &recv_if->batman_adv_ptype, NULL);
  		/* skb was consumed */
  		skb = NULL;
  	}
  
  	ret = NET_RX_SUCCESS;
  
  put_orig_node:
  	batadv_orig_node_put(orig_node_src);
  free_skb:
  	kfree_skb(skb);
  
  	return ret;
  }
  
  int batadv_recv_bcast_packet(struct sk_buff *skb,
  			     struct batadv_hard_iface *recv_if)
  {
  	struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
  	struct batadv_orig_node *orig_node = NULL;
  	struct batadv_bcast_packet *bcast_packet;
  	struct ethhdr *ethhdr;
  	int hdr_size = sizeof(*bcast_packet);
  	int ret = NET_RX_DROP;
  	s32 seq_diff;
  	u32 seqno;
  
  	/* drop packet if it has not necessary minimum size */
  	if (unlikely(!pskb_may_pull(skb, hdr_size)))
  		goto free_skb;
  
  	ethhdr = eth_hdr(skb);
  
  	/* packet with broadcast indication but unicast recipient */
  	if (!is_broadcast_ether_addr(ethhdr->h_dest))
  		goto free_skb;
  
  	/* packet with broadcast/multicast sender address */
  	if (is_multicast_ether_addr(ethhdr->h_source))
  		goto free_skb;
  
  	/* ignore broadcasts sent by myself */
  	if (batadv_is_my_mac(bat_priv, ethhdr->h_source))
  		goto free_skb;
  
  	bcast_packet = (struct batadv_bcast_packet *)skb->data;
  
  	/* ignore broadcasts originated by myself */
  	if (batadv_is_my_mac(bat_priv, bcast_packet->orig))
  		goto free_skb;
  
  	if (bcast_packet->ttl < 2)
  		goto free_skb;
  
  	orig_node = batadv_orig_hash_find(bat_priv, bcast_packet->orig);
  
  	if (!orig_node)
  		goto free_skb;
  
  	spin_lock_bh(&orig_node->bcast_seqno_lock);
  
  	seqno = ntohl(bcast_packet->seqno);
  	/* check whether the packet is a duplicate */
  	if (batadv_test_bit(orig_node->bcast_bits, orig_node->last_bcast_seqno,
  			    seqno))
  		goto spin_unlock;
  
  	seq_diff = seqno - orig_node->last_bcast_seqno;
  
  	/* check whether the packet is old and the host just restarted. */
  	if (batadv_window_protected(bat_priv, seq_diff,
  				    BATADV_BCAST_MAX_AGE,
  				    &orig_node->bcast_seqno_reset, NULL))
  		goto spin_unlock;
  
  	/* mark broadcast in flood history, update window position
  	 * if required.
  	 */
  	if (batadv_bit_get_packet(bat_priv, orig_node->bcast_bits, seq_diff, 1))
  		orig_node->last_bcast_seqno = seqno;
  
  	spin_unlock_bh(&orig_node->bcast_seqno_lock);
  
  	/* check whether this has been sent by another originator before */
  	if (batadv_bla_check_bcast_duplist(bat_priv, skb))
  		goto free_skb;
  
  	batadv_skb_set_priority(skb, sizeof(struct batadv_bcast_packet));
  
  	/* rebroadcast packet */
  	batadv_add_bcast_packet_to_list(bat_priv, skb, 1, false);
  
  	/* don't hand the broadcast up if it is from an originator
  	 * from the same backbone.
  	 */
  	if (batadv_bla_is_backbone_gw(skb, orig_node, hdr_size))
  		goto free_skb;
  
  	if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb, hdr_size))
  		goto rx_success;
  	if (batadv_dat_snoop_incoming_arp_reply(bat_priv, skb, hdr_size))
  		goto rx_success;
  
  	/* broadcast for me */
  	batadv_interface_rx(recv_if->soft_iface, skb, hdr_size, orig_node);
  
  rx_success:
  	ret = NET_RX_SUCCESS;
  	goto out;
  
  spin_unlock:
  	spin_unlock_bh(&orig_node->bcast_seqno_lock);
  free_skb:
  	kfree_skb(skb);
  out:
  	if (orig_node)
  		batadv_orig_node_put(orig_node);
  	return ret;
  }
  