text: /*
   * Copyright (c) 2008, 2009 open80211s Ltd.
   * Author:     Luis Carlos Cobo <luisca@cozybit.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <linux/etherdevice.h>
  #include <linux/list.h>
  #include <linux/random.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/string.h>
  #include <net/mac80211.h>
  #include "wme.h"
  #include "ieee80211_i.h"
  #include "mesh.h"
  
  static void mesh_path_free_rcu(struct mesh_table *tbl, struct mesh_path *mpath);
  
  static u32 mesh_table_hash(const void *addr, u32 len, u32 seed)
  {
  	/* Use last four bytes of hw addr as hash index */
  	return jhash_1word(__get_unaligned_cpu32((u8 *)addr + 2), seed);
  }
  
  static const struct rhashtable_params mesh_rht_params = {
  	.nelem_hint = 2,
  	.automatic_shrinking = true,
  	.key_len = ETH_ALEN,
  	.key_offset = offsetof(struct mesh_path, dst),
  	.head_offset = offsetof(struct mesh_path, rhash),
  	.hashfn = mesh_table_hash,
  };
  
  static inline bool mpath_expired(struct mesh_path *mpath)
  {
  	return (mpath->flags & MESH_PATH_ACTIVE) &&
  	       time_after(jiffies, mpath->exp_time) &&
  	       !(mpath->flags & MESH_PATH_FIXED);
  }
  
  static void mesh_path_rht_free(void *ptr, void *tblptr)
  {
  	struct mesh_path *mpath = ptr;
  	struct mesh_table *tbl = tblptr;
  
  	mesh_path_free_rcu(tbl, mpath);
  }
  
  static struct mesh_table *mesh_table_alloc(void)
  {
  	struct mesh_table *newtbl;
  
  	newtbl = kmalloc(sizeof(struct mesh_table), GFP_ATOMIC);
  	if (!newtbl)
  		return NULL;
  
  	INIT_HLIST_HEAD(&newtbl->known_gates);
  	INIT_HLIST_HEAD(&newtbl->walk_head);
  	atomic_set(&newtbl->entries,  0);
  	spin_lock_init(&newtbl->gates_lock);
  	spin_lock_init(&newtbl->walk_lock);
  
  	return newtbl;
  }
  
  static void mesh_table_free(struct mesh_table *tbl)
  {
  	rhashtable_free_and_destroy(&tbl->rhead,
  				    mesh_path_rht_free, tbl);
  	kfree(tbl);
  }
  
  /**
   *
   * mesh_path_assign_nexthop - update mesh path next hop
   *
   * @mpath: mesh path to update
   * @sta: next hop to assign
   *
   * Locking: mpath->state_lock must be held when calling this function
   */
  void mesh_path_assign_nexthop(struct mesh_path *mpath, struct sta_info *sta)
  {
  	struct sk_buff *skb;
  	struct ieee80211_hdr *hdr;
  	unsigned long flags;
  
  	rcu_assign_pointer(mpath->next_hop, sta);
  
  	spin_lock_irqsave(&mpath->frame_queue.lock, flags);
  	skb_queue_walk(&mpath->frame_queue, skb) {
  		hdr = (struct ieee80211_hdr *) skb->data;
  		memcpy(hdr->addr1, sta->sta.addr, ETH_ALEN);
  		memcpy(hdr->addr2, mpath->sdata->vif.addr, ETH_ALEN);
  		ieee80211_mps_set_frame_flags(sta->sdata, sta, hdr);
  	}
  
  	spin_unlock_irqrestore(&mpath->frame_queue.lock, flags);
  }
  
  static void prepare_for_gate(struct sk_buff *skb, char *dst_addr,
  			     struct mesh_path *gate_mpath)
  {
  	struct ieee80211_hdr *hdr;
  	struct ieee80211s_hdr *mshdr;
  	int mesh_hdrlen, hdrlen;
  	char *next_hop;
  
  	hdr = (struct ieee80211_hdr *) skb->data;
  	hdrlen = ieee80211_hdrlen(hdr->frame_control);
  	mshdr = (struct ieee80211s_hdr *) (skb->data + hdrlen);
  
  	if (!(mshdr->flags & MESH_FLAGS_AE)) {
  		/* size of the fixed part of the mesh header */
  		mesh_hdrlen = 6;
  
  		/* make room for the two extended addresses */
  		skb_push(skb, 2 * ETH_ALEN);
  		memmove(skb->data, hdr, hdrlen + mesh_hdrlen);
  
  		hdr = (struct ieee80211_hdr *) skb->data;
  
  		/* we preserve the previous mesh header and only add
  		 * the new addreses */
  		mshdr = (struct ieee80211s_hdr *) (skb->data + hdrlen);
  		mshdr->flags = MESH_FLAGS_AE_A5_A6;
  		memcpy(mshdr->eaddr1, hdr->addr3, ETH_ALEN);
  		memcpy(mshdr->eaddr2, hdr->addr4, ETH_ALEN);
  	}
  
  	/* update next hop */
  	hdr = (struct ieee80211_hdr *) skb->data;
  	rcu_read_lock();
  	next_hop = rcu_dereference(gate_mpath->next_hop)->sta.addr;
  	memcpy(hdr->addr1, next_hop, ETH_ALEN);
  	rcu_read_unlock();
  	memcpy(hdr->addr2, gate_mpath->sdata->vif.addr, ETH_ALEN);
  	memcpy(hdr->addr3, dst_addr, ETH_ALEN);
  }
  
  /**
   *
   * mesh_path_move_to_queue - Move or copy frames from one mpath queue to another
   *
   * This function is used to transfer or copy frames from an unresolved mpath to
   * a gate mpath.  The function also adds the Address Extension field and
   * updates the next hop.
   *
   * If a frame already has an Address Extension field, only the next hop and
   * destination addresses are updated.
   *
   * The gate mpath must be an active mpath with a valid mpath->next_hop.
   *
   * @mpath: An active mpath the frames will be sent to (i.e. the gate)
   * @from_mpath: The failed mpath
   * @copy: When true, copy all the frames to the new mpath queue.  When false,
   * move them.
   */
  static void mesh_path_move_to_queue(struct mesh_path *gate_mpath,
  				    struct mesh_path *from_mpath,
  				    bool copy)
  {
  	struct sk_buff *skb, *fskb, *tmp;
  	struct sk_buff_head failq;
  	unsigned long flags;
  
  	if (WARN_ON(gate_mpath == from_mpath))
  		return;
  	if (WARN_ON(!gate_mpath->next_hop))
  		return;
  
  	__skb_queue_head_init(&failq);
  
  	spin_lock_irqsave(&from_mpath->frame_queue.lock, flags);
  	skb_queue_splice_init(&from_mpath->frame_queue, &failq);
  	spin_unlock_irqrestore(&from_mpath->frame_queue.lock, flags);
  
  	skb_queue_walk_safe(&failq, fskb, tmp) {
  		if (skb_queue_len(&gate_mpath->frame_queue) >=
  				  MESH_FRAME_QUEUE_LEN) {
  			mpath_dbg(gate_mpath->sdata, "mpath queue full!\n");
  			break;
  		}
  
  		skb = skb_copy(fskb, GFP_ATOMIC);
  		if (WARN_ON(!skb))
  			break;
  
  		prepare_for_gate(skb, gate_mpath->dst, gate_mpath);
  		skb_queue_tail(&gate_mpath->frame_queue, skb);
  
  		if (copy)
  			continue;
  
  		__skb_unlink(fskb, &failq);
  		kfree_skb(fskb);
  	}
  
  	mpath_dbg(gate_mpath->sdata, "Mpath queue for gate %pM has %d frames\n",
  		  gate_mpath->dst, skb_queue_len(&gate_mpath->frame_queue));
  
  	if (!copy)
  		return;
  
  	spin_lock_irqsave(&from_mpath->frame_queue.lock, flags);
  	skb_queue_splice(&failq, &from_mpath->frame_queue);
  	spin_unlock_irqrestore(&from_mpath->frame_queue.lock, flags);
  }
  
  
  static struct mesh_path *mpath_lookup(struct mesh_table *tbl, const u8 *dst,
  				      struct ieee80211_sub_if_data *sdata)
  {
  	struct mesh_path *mpath;
  
  	mpath = rhashtable_lookup_fast(&tbl->rhead, dst, mesh_rht_params);
  
  	if (mpath && mpath_expired(mpath)) {
  		spin_lock_bh(&mpath->state_lock);
  		mpath->flags &= ~MESH_PATH_ACTIVE;
  		spin_unlock_bh(&mpath->state_lock);
  	}
  	return mpath;
  }
  
  /**
   * mesh_path_lookup - look up a path in the mesh path table
   * @sdata: local subif
   * @dst: hardware address (ETH_ALEN length) of destination
   *
   * Returns: pointer to the mesh path structure, or NULL if not found
   *
   * Locking: must be called within a read rcu section.
   */
  struct mesh_path *
  mesh_path_lookup(struct ieee80211_sub_if_data *sdata, const u8 *dst)
  {
  	return mpath_lookup(sdata->u.mesh.mesh_paths, dst, sdata);
  }
  
  struct mesh_path *
  mpp_path_lookup(struct ieee80211_sub_if_data *sdata, const u8 *dst)
  {
  	return mpath_lookup(sdata->u.mesh.mpp_paths, dst, sdata);
  }
  
  static struct mesh_path *
  __mesh_path_lookup_by_idx(struct mesh_table *tbl, int idx)
  {
  	int i = 0;
  	struct mesh_path *mpath;
  
  	hlist_for_each_entry_rcu(mpath, &tbl->walk_head, walk_list) {
  		if (i++ == idx)
  			break;
  	}
  
  	if (!mpath)
  		return NULL;
  
  	if (mpath_expired(mpath)) {
  		spin_lock_bh(&mpath->state_lock);
  		mpath->flags &= ~MESH_PATH_ACTIVE;
  		spin_unlock_bh(&mpath->state_lock);
  	}
  	return mpath;
  }
  
  /**
   * mesh_path_lookup_by_idx - look up a path in the mesh path table by its index
   * @idx: index
   * @sdata: local subif, or NULL for all entries
   *
   * Returns: pointer to the mesh path structure, or NULL if not found.
   *
   * Locking: must be called within a read rcu section.
   */
  struct mesh_path *
  mesh_path_lookup_by_idx(struct ieee80211_sub_if_data *sdata, int idx)
  {
  	return __mesh_path_lookup_by_idx(sdata->u.mesh.mesh_paths, idx);
  }
  
  /**
   * mpp_path_lookup_by_idx - look up a path in the proxy path table by its index
   * @idx: index
   * @sdata: local subif, or NULL for all entries
   *
   * Returns: pointer to the proxy path structure, or NULL if not found.
   *
   * Locking: must be called within a read rcu section.
   */
  struct mesh_path *
  mpp_path_lookup_by_idx(struct ieee80211_sub_if_data *sdata, int idx)
  {
  	return __mesh_path_lookup_by_idx(sdata->u.mesh.mpp_paths, idx);
  }
  
  /**
   * mesh_path_add_gate - add the given mpath to a mesh gate to our path table
   * @mpath: gate path to add to table
   */
  int mesh_path_add_gate(struct mesh_path *mpath)
  {
  	struct mesh_table *tbl;
  	int err;
  
  	rcu_read_lock();
  	tbl = mpath->sdata->u.mesh.mesh_paths;
  
  	spin_lock_bh(&mpath->state_lock);
  	if (mpath->is_gate) {
  		err = -EEXIST;
  		spin_unlock_bh(&mpath->state_lock);
  		goto err_rcu;
  	}
  	mpath->is_gate = true;
  	mpath->sdata->u.mesh.num_gates++;
  
  	spin_lock(&tbl->gates_lock);
  	hlist_add_head_rcu(&mpath->gate_list, &tbl->known_gates);
  	spin_unlock(&tbl->gates_lock);
  
  	spin_unlock_bh(&mpath->state_lock);
  
  	mpath_dbg(mpath->sdata,
  		  "Mesh path: Recorded new gate: %pM. %d known gates\n",
  		  mpath->dst, mpath->sdata->u.mesh.num_gates);
  	err = 0;
  err_rcu:
  	rcu_read_unlock();
  	return err;
  }
  
  /**
   * mesh_gate_del - remove a mesh gate from the list of known gates
   * @tbl: table which holds our list of known gates
   * @mpath: gate mpath
   */
  static void mesh_gate_del(struct mesh_table *tbl, struct mesh_path *mpath)
  {
  	lockdep_assert_held(&mpath->state_lock);
  	if (!mpath->is_gate)
  		return;
  
  	mpath->is_gate = false;
  	spin_lock_bh(&tbl->gates_lock);
  	hlist_del_rcu(&mpath->gate_list);
  	mpath->sdata->u.mesh.num_gates--;
  	spin_unlock_bh(&tbl->gates_lock);
  
  	mpath_dbg(mpath->sdata,
  		  "Mesh path: Deleted gate: %pM. %d known gates\n",
  		  mpath->dst, mpath->sdata->u.mesh.num_gates);
  }
  
  /**
   * mesh_gate_num - number of gates known to this interface
   * @sdata: subif data
   */
  int mesh_gate_num(struct ieee80211_sub_if_data *sdata)
  {
  	return sdata->u.mesh.num_gates;
  }
  
  static
  struct mesh_path *mesh_path_new(struct ieee80211_sub_if_data *sdata,
  				const u8 *dst, gfp_t gfp_flags)
  {
  	struct mesh_path *new_mpath;
  
  	new_mpath = kzalloc(sizeof(struct mesh_path), gfp_flags);
  	if (!new_mpath)
  		return NULL;
  
  	memcpy(new_mpath->dst, dst, ETH_ALEN);
  	eth_broadcast_addr(new_mpath->rann_snd_addr);
  	new_mpath->is_root = false;
  	new_mpath->sdata = sdata;
  	new_mpath->flags = 0;
  	skb_queue_head_init(&new_mpath->frame_queue);
  	new_mpath->exp_time = jiffies;
  	spin_lock_init(&new_mpath->state_lock);
  	timer_setup(&new_mpath->timer, mesh_path_timer, 0);
  
  	return new_mpath;
  }
  
  /**
   * mesh_path_add - allocate and add a new path to the mesh path table
   * @dst: destination address of the path (ETH_ALEN length)
   * @sdata: local subif
   *
   * Returns: 0 on success
   *
   * State: the initial state of the new path is set to 0
   */
  struct mesh_path *mesh_path_add(struct ieee80211_sub_if_data *sdata,
  				const u8 *dst)
  {
  	struct mesh_table *tbl;
  	struct mesh_path *mpath, *new_mpath;
  
  	if (ether_addr_equal(dst, sdata->vif.addr))
  		/* never add ourselves as neighbours */
  		return ERR_PTR(-ENOTSUPP);
  
  	if (is_multicast_ether_addr(dst))
  		return ERR_PTR(-ENOTSUPP);
  
  	if (atomic_add_unless(&sdata->u.mesh.mpaths, 1, MESH_MAX_MPATHS) == 0)
  		return ERR_PTR(-ENOSPC);
  
  	new_mpath = mesh_path_new(sdata, dst, GFP_ATOMIC);
  	if (!new_mpath)
  		return ERR_PTR(-ENOMEM);
  
  	tbl = sdata->u.mesh.mesh_paths;
  	spin_lock_bh(&tbl->walk_lock);
  	mpath = rhashtable_lookup_get_insert_fast(&tbl->rhead,
  						  &new_mpath->rhash,
  						  mesh_rht_params);
  	if (!mpath)
  		hlist_add_head(&new_mpath->walk_list, &tbl->walk_head);
  	spin_unlock_bh(&tbl->walk_lock);
  
  	if (mpath) {
  		kfree(new_mpath);
  
  		if (IS_ERR(mpath))
  			return mpath;
  
  		new_mpath = mpath;
  	}
  
  	sdata->u.mesh.mesh_paths_generation++;
  	return new_mpath;
  }
  
  int mpp_path_add(struct ieee80211_sub_if_data *sdata,
  		 const u8 *dst, const u8 *mpp)
  {
  	struct mesh_table *tbl;
  	struct mesh_path *new_mpath;
  	int ret;
  
  	if (ether_addr_equal(dst, sdata->vif.addr))
  		/* never add ourselves as neighbours */
  		return -ENOTSUPP;
  
  	if (is_multicast_ether_addr(dst))
  		return -ENOTSUPP;
  
  	new_mpath = mesh_path_new(sdata, dst, GFP_ATOMIC);
  
  	if (!new_mpath)
  		return -ENOMEM;
  
  	memcpy(new_mpath->mpp, mpp, ETH_ALEN);
  	tbl = sdata->u.mesh.mpp_paths;
  
  	spin_lock_bh(&tbl->walk_lock);
  	ret = rhashtable_lookup_insert_fast(&tbl->rhead,
  					    &new_mpath->rhash,
  					    mesh_rht_params);
  	if (!ret)
  		hlist_add_head_rcu(&new_mpath->walk_list, &tbl->walk_head);
  	spin_unlock_bh(&tbl->walk_lock);
  
  	if (ret)
  		kfree(new_mpath);
  
  	sdata->u.mesh.mpp_paths_generation++;
  	return ret;
  }
  
  
  /**
   * mesh_plink_broken - deactivates paths and sends perr when a link breaks
   *
   * @sta: broken peer link
   *
   * This function must be called from the rate control algorithm if enough
   * delivery errors suggest that a peer link is no longer usable.
   */
  void mesh_plink_broken(struct sta_info *sta)
  {
  	struct ieee80211_sub_if_data *sdata = sta->sdata;
  	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
  	static const u8 bcast[ETH_ALEN] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
  	struct mesh_path *mpath;
  
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(mpath, &tbl->walk_head, walk_list) {
  		if (rcu_access_pointer(mpath->next_hop) == sta &&
  		    mpath->flags & MESH_PATH_ACTIVE &&
  		    !(mpath->flags & MESH_PATH_FIXED)) {
  			spin_lock_bh(&mpath->state_lock);
  			mpath->flags &= ~MESH_PATH_ACTIVE;
  			++mpath->sn;
  			spin_unlock_bh(&mpath->state_lock);
  			mesh_path_error_tx(sdata,
  				sdata->u.mesh.mshcfg.element_ttl,
  				mpath->dst, mpath->sn,
  				WLAN_REASON_MESH_PATH_DEST_UNREACHABLE, bcast);
  		}
  	}
  	rcu_read_unlock();
  }
  
  static void mesh_path_free_rcu(struct mesh_table *tbl,
  			       struct mesh_path *mpath)
  {
  	struct ieee80211_sub_if_data *sdata = mpath->sdata;
  
  	spin_lock_bh(&mpath->state_lock);
  	mpath->flags |= MESH_PATH_RESOLVING | MESH_PATH_DELETED;
  	mesh_gate_del(tbl, mpath);
  	spin_unlock_bh(&mpath->state_lock);
  	del_timer_sync(&mpath->timer);
  	atomic_dec(&sdata->u.mesh.mpaths);
  	atomic_dec(&tbl->entries);
  	kfree_rcu(mpath, rcu);
  }
  
  static void __mesh_path_del(struct mesh_table *tbl, struct mesh_path *mpath)
  {
  	hlist_del_rcu(&mpath->walk_list);
  	rhashtable_remove_fast(&tbl->rhead, &mpath->rhash, mesh_rht_params);
  	mesh_path_free_rcu(tbl, mpath);
  }
  
  /**
   * mesh_path_flush_by_nexthop - Deletes mesh paths if their next hop matches
   *
   * @sta: mesh peer to match
   *
   * RCU notes: this function is called when a mesh plink transitions from
   * PLINK_ESTAB to any other state, since PLINK_ESTAB state is the only one that
   * allows path creation. This will happen before the sta can be freed (because
   * sta_info_destroy() calls this) so any reader in a rcu read block will be
   * protected against the plink disappearing.
   */
  void mesh_path_flush_by_nexthop(struct sta_info *sta)
  {
  	struct ieee80211_sub_if_data *sdata = sta->sdata;
  	struct mesh_table *tbl = sdata->u.mesh.mesh_paths;
  	struct mesh_path *mpath;
  	struct hlist_node *n;
  
  	spin_lock_bh(&tbl->walk_lock);
  	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
  		if (rcu_access_pointer(mpath->next_hop) == sta)
  			__mesh_path_del(tbl, mpath);
  	}
  	spin_unlock_bh(&tbl->walk_lock);
  }
  
  static void mpp_flush_by_proxy(struct ieee80211_sub_if_data *sdata,
  			       const u8 *proxy)
  {
  	struct mesh_table *tbl = sdata->u.mesh.mpp_paths;
  	struct mesh_path *mpath;
  	struct hlist_node *n;
  
  	spin_lock_bh(&tbl->walk_lock);
  	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
  		if (ether_addr_equal(mpath->mpp, proxy))
  			__mesh_path_del(tbl, mpath);
  	}
  	spin_unlock_bh(&tbl->walk_lock);
  }
  
  static void table_flush_by_iface(struct mesh_table *tbl)
  {
  	struct mesh_path *mpath;
  	struct hlist_node *n;
  
  	spin_lock_bh(&tbl->walk_lock);
  	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
  		__mesh_path_del(tbl, mpath);
  	}
  	spin_unlock_bh(&tbl->walk_lock);
  }
  
  /**
   * mesh_path_flush_by_iface - Deletes all mesh paths associated with a given iface
   *
   * This function deletes both mesh paths as well as mesh portal paths.
   *
   * @sdata: interface data to match
   *
   */
  void mesh_path_flush_by_iface(struct ieee80211_sub_if_data *sdata)
  {
  	table_flush_by_iface(sdata->u.mesh.mesh_paths);
  	table_flush_by_iface(sdata->u.mesh.mpp_paths);
  }
  
  /**
   * table_path_del - delete a path from the mesh or mpp table
   *
   * @tbl: mesh or mpp path table
   * @sdata: local subif
   * @addr: dst address (ETH_ALEN length)
   *
   * Returns: 0 if successful
   */
  static int table_path_del(struct mesh_table *tbl,
  			  struct ieee80211_sub_if_data *sdata,
  			  const u8 *addr)
  {
  	struct mesh_path *mpath;
  
  	spin_lock_bh(&tbl->walk_lock);
  	mpath = rhashtable_lookup_fast(&tbl->rhead, addr, mesh_rht_params);
  	if (!mpath) {
  		spin_unlock_bh(&tbl->walk_lock);
  		return -ENXIO;
  	}
  
  	__mesh_path_del(tbl, mpath);
  	spin_unlock_bh(&tbl->walk_lock);
  	return 0;
  }
  
  
  /**
   * mesh_path_del - delete a mesh path from the table
   *
   * @addr: dst address (ETH_ALEN length)
   * @sdata: local subif
   *
   * Returns: 0 if successful
   */
  int mesh_path_del(struct ieee80211_sub_if_data *sdata, const u8 *addr)
  {
  	int err;
  
  	/* flush relevant mpp entries first */
  	mpp_flush_by_proxy(sdata, addr);
  
  	err = table_path_del(sdata->u.mesh.mesh_paths, sdata, addr);
  	sdata->u.mesh.mesh_paths_generation++;
  	return err;
  }
  
  /**
   * mesh_path_tx_pending - sends pending frames in a mesh path queue
   *
   * @mpath: mesh path to activate
   *
   * Locking: the state_lock of the mpath structure must NOT be held when calling
   * this function.
   */
  void mesh_path_tx_pending(struct mesh_path *mpath)
  {
  	if (mpath->flags & MESH_PATH_ACTIVE)
  		ieee80211_add_pending_skbs(mpath->sdata->local,
  				&mpath->frame_queue);
  }
  
  /**
   * mesh_path_send_to_gates - sends pending frames to all known mesh gates
   *
   * @mpath: mesh path whose queue will be emptied
   *
   * If there is only one gate, the frames are transferred from the failed mpath
   * queue to that gate's queue.  If there are more than one gates, the frames
   * are copied from each gate to the next.  After frames are copied, the
   * mpath queues are emptied onto the transmission queue.
   */
  int mesh_path_send_to_gates(struct mesh_path *mpath)
  {
  	struct ieee80211_sub_if_data *sdata = mpath->sdata;
  	struct mesh_table *tbl;
  	struct mesh_path *from_mpath = mpath;
  	struct mesh_path *gate;
  	bool copy = false;
  
  	tbl = sdata->u.mesh.mesh_paths;
  
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(gate, &tbl->known_gates, gate_list) {
  		if (gate->flags & MESH_PATH_ACTIVE) {
  			mpath_dbg(sdata, "Forwarding to %pM\n", gate->dst);
  			mesh_path_move_to_queue(gate, from_mpath, copy);
  			from_mpath = gate;
  			copy = true;
  		} else {
  			mpath_dbg(sdata,
  				  "Not forwarding to %pM (flags %#x)\n",
  				  gate->dst, gate->flags);
  		}
  	}
  
  	hlist_for_each_entry_rcu(gate, &tbl->known_gates, gate_list) {
  		mpath_dbg(sdata, "Sending to %pM\n", gate->dst);
  		mesh_path_tx_pending(gate);
  	}
  	rcu_read_unlock();
  
  	return (from_mpath == mpath) ? -EHOSTUNREACH : 0;
  }
  
  /**
   * mesh_path_discard_frame - discard a frame whose path could not be resolved
   *
   * @skb: frame to discard
   * @sdata: network subif the frame was to be sent through
   *
   * Locking: the function must me called within a rcu_read_lock region
   */
  void mesh_path_discard_frame(struct ieee80211_sub_if_data *sdata,
  			     struct sk_buff *skb)
  {
  	kfree_skb(skb);
  	sdata->u.mesh.mshstats.dropped_frames_no_route++;
  }
  
  /**
   * mesh_path_flush_pending - free the pending queue of a mesh path
   *
   * @mpath: mesh path whose queue has to be freed
   *
   * Locking: the function must me called within a rcu_read_lock region
   */
  void mesh_path_flush_pending(struct mesh_path *mpath)
  {
  	struct sk_buff *skb;
  
  	while ((skb = skb_dequeue(&mpath->frame_queue)) != NULL)
  		mesh_path_discard_frame(mpath->sdata, skb);
  }
  
  /**
   * mesh_path_fix_nexthop - force a specific next hop for a mesh path
   *
   * @mpath: the mesh path to modify
   * @next_hop: the next hop to force
   *
   * Locking: this function must be called holding mpath->state_lock
   */
  void mesh_path_fix_nexthop(struct mesh_path *mpath, struct sta_info *next_hop)
  {
  	spin_lock_bh(&mpath->state_lock);
  	mesh_path_assign_nexthop(mpath, next_hop);
  	mpath->sn = 0xffff;
  	mpath->metric = 0;
  	mpath->hop_count = 0;
  	mpath->exp_time = 0;
  	mpath->flags = MESH_PATH_FIXED | MESH_PATH_SN_VALID;
  	mesh_path_activate(mpath);
  	spin_unlock_bh(&mpath->state_lock);
  	ewma_mesh_fail_avg_init(&next_hop->mesh->fail_avg);
  	/* init it at a low value - 0 start is tricky */
  	ewma_mesh_fail_avg_add(&next_hop->mesh->fail_avg, 1);
  	mesh_path_tx_pending(mpath);
  }
  
  int mesh_pathtbl_init(struct ieee80211_sub_if_data *sdata)
  {
  	struct mesh_table *tbl_path, *tbl_mpp;
  	int ret;
  
  	tbl_path = mesh_table_alloc();
  	if (!tbl_path)
  		return -ENOMEM;
  
  	tbl_mpp = mesh_table_alloc();
  	if (!tbl_mpp) {
  		ret = -ENOMEM;
  		goto free_path;
  	}
  
  	rhashtable_init(&tbl_path->rhead, &mesh_rht_params);
  	rhashtable_init(&tbl_mpp->rhead, &mesh_rht_params);
  
  	sdata->u.mesh.mesh_paths = tbl_path;
  	sdata->u.mesh.mpp_paths = tbl_mpp;
  
  	return 0;
  
  free_path:
  	mesh_table_free(tbl_path);
  	return ret;
  }
  
  static
  void mesh_path_tbl_expire(struct ieee80211_sub_if_data *sdata,
  			  struct mesh_table *tbl)
  {
  	struct mesh_path *mpath;
  	struct hlist_node *n;
  
  	spin_lock_bh(&tbl->walk_lock);
  	hlist_for_each_entry_safe(mpath, n, &tbl->walk_head, walk_list) {
  		if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
  		    (!(mpath->flags & MESH_PATH_FIXED)) &&
  		     time_after(jiffies, mpath->exp_time + MESH_PATH_EXPIRE))
  			__mesh_path_del(tbl, mpath);
  	}
  	spin_unlock_bh(&tbl->walk_lock);
  }
  
  void mesh_path_expire(struct ieee80211_sub_if_data *sdata)
  {
  	mesh_path_tbl_expire(sdata, sdata->u.mesh.mesh_paths);
  	mesh_path_tbl_expire(sdata, sdata->u.mesh.mpp_paths);
  }
  
  void mesh_pathtbl_unregister(struct ieee80211_sub_if_data *sdata)
  {
  	mesh_table_free(sdata->u.mesh.mesh_paths);
  	mesh_table_free(sdata->u.mesh.mpp_paths);
  }
  