net/mac80211/mesh_pathtbl.c - pub/scm/linux/kernel/git/jesse/openvswitch - Git at Google

 /*
  * Copyright (c) 2008 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/spinlock.h>
 #include <linux/string.h>
 #include <net/mac80211.h>
 #include "ieee80211_i.h"
 #include "mesh.h"

 /* There will be initially 2^INIT_PATHS_SIZE_ORDER buckets */
 #define INIT_PATHS_SIZE_ORDER	2

 /* Keep the mean chain length below this constant */
 #define MEAN_CHAIN_LEN		2

 #define MPATH_EXPIRED(mpath) ((mpath->flags & MESH_PATH_ACTIVE) && \
 				time_after(jiffies, mpath->exp_time) && \
 				!(mpath->flags & MESH_PATH_FIXED))

 struct mpath_node {
 	struct hlist_node list;
 	struct rcu_head rcu;
 	/* This indirection allows two different tables to point to the same
 	 * mesh_path structure, useful when resizing
 	 */
 	struct mesh_path *mpath;
 };

 static struct mesh_table *mesh_paths;
 static struct mesh_table *mpp_paths; /* Store paths for MPP&MAP */

 /* This lock will have the grow table function as writer and add / delete nodes
  * as readers. When reading the table (i.e. doing lookups) we are well protected
  * by RCU
  */
 static DEFINE_RWLOCK(pathtbl_resize_lock);

 /**
  *
  * 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)
 {
 	rcu_assign_pointer(mpath->next_hop, sta);
 }


 /**
  * mesh_path_lookup - look up a path in the mesh path table
  * @dst: hardware address (ETH_ALEN length) of destination
  * @sdata: local subif
  *
  * 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(u8 *dst, struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath;
 	struct hlist_node *n;
 	struct hlist_head *bucket;
 	struct mesh_table *tbl;
 	struct mpath_node *node;

 	tbl = rcu_dereference(mesh_paths);

 	bucket = &tbl->hash_buckets[mesh_table_hash(dst, sdata, tbl)];
 	hlist_for_each_entry_rcu(node, n, bucket, list) {
 		mpath = node->mpath;
 		if (mpath->sdata == sdata &&
 				memcmp(dst, mpath->dst, ETH_ALEN) == 0) {
 			if (MPATH_EXPIRED(mpath)) {
 				spin_lock_bh(&mpath->state_lock);
 				if (MPATH_EXPIRED(mpath))
 					mpath->flags &= ~MESH_PATH_ACTIVE;
 				spin_unlock_bh(&mpath->state_lock);
 			}
 			return mpath;
 		}
 	}
 	return NULL;
 }

 struct mesh_path *mpp_path_lookup(u8 *dst, struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath;
 	struct hlist_node *n;
 	struct hlist_head *bucket;
 	struct mesh_table *tbl;
 	struct mpath_node *node;

 	tbl = rcu_dereference(mpp_paths);

 	bucket = &tbl->hash_buckets[mesh_table_hash(dst, sdata, tbl)];
 	hlist_for_each_entry_rcu(node, n, bucket, list) {
 		mpath = node->mpath;
 		if (mpath->sdata == sdata &&
 		    memcmp(dst, mpath->dst, ETH_ALEN) == 0) {
 			if (MPATH_EXPIRED(mpath)) {
 				spin_lock_bh(&mpath->state_lock);
 				if (MPATH_EXPIRED(mpath))
 					mpath->flags &= ~MESH_PATH_ACTIVE;
 				spin_unlock_bh(&mpath->state_lock);
 			}
 			return mpath;
 		}
 	}
 	return NULL;
 }


 /**
  * 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(int idx, struct ieee80211_sub_if_data *sdata)
 {
 	struct mpath_node *node;
 	struct hlist_node *p;
 	int i;
 	int j = 0;

 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		if (sdata && node->mpath->sdata != sdata)
 			continue;
 		if (j++ == idx) {
 			if (MPATH_EXPIRED(node->mpath)) {
 				spin_lock_bh(&node->mpath->state_lock);
 				if (MPATH_EXPIRED(node->mpath))
 					node->mpath->flags &= ~MESH_PATH_ACTIVE;
 				spin_unlock_bh(&node->mpath->state_lock);
 			}
 			return node->mpath;
 		}
 	}

 	return NULL;
 }

 /**
  * mesh_path_add - allocate and add a new path to the mesh path table
  * @addr: destination address of the path (ETH_ALEN length)
  * @sdata: local subif
  *
  * Returns: 0 on sucess
  *
  * State: the initial state of the new path is set to 0
  */
 int mesh_path_add(u8 *dst, struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath, *new_mpath;
 	struct mpath_node *node, *new_node;
 	struct hlist_head *bucket;
 	struct hlist_node *n;
 	int grow = 0;
 	int err = 0;
 	u32 hash_idx;

 	if (memcmp(dst, sdata->dev->dev_addr, ETH_ALEN) == 0)
 		/* never add ourselves as neighbours */
 		return -ENOTSUPP;

 	if (is_multicast_ether_addr(dst))
 		return -ENOTSUPP;

 	if (atomic_add_unless(&sdata->u.mesh.mpaths, 1, MESH_MAX_MPATHS) == 0)
 		return -ENOSPC;

 	err = -ENOMEM;
 	new_mpath = kzalloc(sizeof(struct mesh_path), GFP_KERNEL);
 	if (!new_mpath)
 		goto err_path_alloc;

 	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);
 	if (!new_node)
 		goto err_node_alloc;

 	read_lock(&pathtbl_resize_lock);
 	memcpy(new_mpath->dst, dst, ETH_ALEN);
 	new_mpath->sdata = sdata;
 	new_mpath->flags = 0;
 	skb_queue_head_init(&new_mpath->frame_queue);
 	new_node->mpath = new_mpath;
 	new_mpath->timer.data = (unsigned long) new_mpath;
 	new_mpath->timer.function = mesh_path_timer;
 	new_mpath->exp_time = jiffies;
 	spin_lock_init(&new_mpath->state_lock);
 	init_timer(&new_mpath->timer);

 	hash_idx = mesh_table_hash(dst, sdata, mesh_paths);
 	bucket = &mesh_paths->hash_buckets[hash_idx];

 	spin_lock(&mesh_paths->hashwlock[hash_idx]);

 	err = -EEXIST;
 	hlist_for_each_entry(node, n, bucket, list) {
 		mpath = node->mpath;
 		if (mpath->sdata == sdata && memcmp(dst, mpath->dst, ETH_ALEN) == 0)
 			goto err_exists;
 	}

 	hlist_add_head_rcu(&new_node->list, bucket);
 	if (atomic_inc_return(&mesh_paths->entries) >=
 		mesh_paths->mean_chain_len * (mesh_paths->hash_mask + 1))
 		grow = 1;

 	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	if (grow) {
 		struct mesh_table *oldtbl, *newtbl;

 		write_lock(&pathtbl_resize_lock);
 		oldtbl = mesh_paths;
 		newtbl = mesh_table_grow(mesh_paths);
 		if (!newtbl) {
 			write_unlock(&pathtbl_resize_lock);
 			return 0;
 		}
 		rcu_assign_pointer(mesh_paths, newtbl);
 		write_unlock(&pathtbl_resize_lock);

 		synchronize_rcu();
 		mesh_table_free(oldtbl, false);
 	}
 	return 0;

 err_exists:
 	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	kfree(new_node);
 err_node_alloc:
 	kfree(new_mpath);
 err_path_alloc:
 	atomic_dec(&sdata->u.mesh.mpaths);
 	return err;
 }


 int mpp_path_add(u8 *dst, u8 *mpp, struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath, *new_mpath;
 	struct mpath_node *node, *new_node;
 	struct hlist_head *bucket;
 	struct hlist_node *n;
 	int grow = 0;
 	int err = 0;
 	u32 hash_idx;


 	if (memcmp(dst, sdata->dev->dev_addr, ETH_ALEN) == 0)
 		/* never add ourselves as neighbours */
 		return -ENOTSUPP;

 	if (is_multicast_ether_addr(dst))
 		return -ENOTSUPP;

 	err = -ENOMEM;
 	new_mpath = kzalloc(sizeof(struct mesh_path), GFP_KERNEL);
 	if (!new_mpath)
 		goto err_path_alloc;

 	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);
 	if (!new_node)
 		goto err_node_alloc;

 	read_lock(&pathtbl_resize_lock);
 	memcpy(new_mpath->dst, dst, ETH_ALEN);
 	memcpy(new_mpath->mpp, mpp, ETH_ALEN);
 	new_mpath->sdata = sdata;
 	new_mpath->flags = 0;
 	skb_queue_head_init(&new_mpath->frame_queue);
 	new_node->mpath = new_mpath;
 	new_mpath->exp_time = jiffies;
 	spin_lock_init(&new_mpath->state_lock);

 	hash_idx = mesh_table_hash(dst, sdata, mpp_paths);
 	bucket = &mpp_paths->hash_buckets[hash_idx];

 	spin_lock(&mpp_paths->hashwlock[hash_idx]);

 	err = -EEXIST;
 	hlist_for_each_entry(node, n, bucket, list) {
 		mpath = node->mpath;
 		if (mpath->sdata == sdata && memcmp(dst, mpath->dst, ETH_ALEN) == 0)
 			goto err_exists;
 	}

 	hlist_add_head_rcu(&new_node->list, bucket);
 	if (atomic_inc_return(&mpp_paths->entries) >=
 		mpp_paths->mean_chain_len * (mpp_paths->hash_mask + 1))
 		grow = 1;

 	spin_unlock(&mpp_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	if (grow) {
 		struct mesh_table *oldtbl, *newtbl;

 		write_lock(&pathtbl_resize_lock);
 		oldtbl = mpp_paths;
 		newtbl = mesh_table_grow(mpp_paths);
 		if (!newtbl) {
 			write_unlock(&pathtbl_resize_lock);
 			return 0;
 		}
 		rcu_assign_pointer(mpp_paths, newtbl);
 		write_unlock(&pathtbl_resize_lock);

 		synchronize_rcu();
 		mesh_table_free(oldtbl, false);
 	}
 	return 0;

 err_exists:
 	spin_unlock(&mpp_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	kfree(new_node);
 err_node_alloc:
 	kfree(new_mpath);
 err_path_alloc:
 	return err;
 }


 /**
  * 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 mesh_path *mpath;
 	struct mpath_node *node;
 	struct hlist_node *p;
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	int i;

 	rcu_read_lock();
 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		mpath = node->mpath;
 		spin_lock_bh(&mpath->state_lock);
 		if (mpath->next_hop == sta &&
 		    mpath->flags & MESH_PATH_ACTIVE &&
 		    !(mpath->flags & MESH_PATH_FIXED)) {
 			mpath->flags &= ~MESH_PATH_ACTIVE;
 			++mpath->dsn;
 			spin_unlock_bh(&mpath->state_lock);
 			mesh_path_error_tx(mpath->dst,
 					cpu_to_le32(mpath->dsn),
 					sdata->dev->broadcast, sdata);
 		} else
 		spin_unlock_bh(&mpath->state_lock);
 	}
 	rcu_read_unlock();
 }

 /**
  * 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 mesh_path *mpath;
 	struct mpath_node *node;
 	struct hlist_node *p;
 	int i;

 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		mpath = node->mpath;
 		if (mpath->next_hop == sta)
 			mesh_path_del(mpath->dst, mpath->sdata);
 	}
 }

 void mesh_path_flush(struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath;
 	struct mpath_node *node;
 	struct hlist_node *p;
 	int i;

 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		mpath = node->mpath;
 		if (mpath->sdata == sdata)
 			mesh_path_del(mpath->dst, mpath->sdata);
 	}
 }

 static void mesh_path_node_reclaim(struct rcu_head *rp)
 {
 	struct mpath_node *node = container_of(rp, struct mpath_node, rcu);
 	struct ieee80211_sub_if_data *sdata = node->mpath->sdata;

 	del_timer_sync(&node->mpath->timer);
 	atomic_dec(&sdata->u.mesh.mpaths);
 	kfree(node->mpath);
 	kfree(node);
 }

 /**
  * mesh_path_del - delete a mesh path from the table
  *
  * @addr: dst address (ETH_ALEN length)
  * @sdata: local subif
  *
  * Returns: 0 if succesful
  */
 int mesh_path_del(u8 *addr, struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath;
 	struct mpath_node *node;
 	struct hlist_head *bucket;
 	struct hlist_node *n;
 	int hash_idx;
 	int err = 0;

 	read_lock(&pathtbl_resize_lock);
 	hash_idx = mesh_table_hash(addr, sdata, mesh_paths);
 	bucket = &mesh_paths->hash_buckets[hash_idx];

 	spin_lock(&mesh_paths->hashwlock[hash_idx]);
 	hlist_for_each_entry(node, n, bucket, list) {
 		mpath = node->mpath;
 		if (mpath->sdata == sdata &&
 				memcmp(addr, mpath->dst, ETH_ALEN) == 0) {
 			spin_lock_bh(&mpath->state_lock);
 			mpath->flags |= MESH_PATH_RESOLVING;
 			hlist_del_rcu(&node->list);
 			call_rcu(&node->rcu, mesh_path_node_reclaim);
 			atomic_dec(&mesh_paths->entries);
 			spin_unlock_bh(&mpath->state_lock);
 			goto enddel;
 		}
 	}

 	err = -ENXIO;
 enddel:
 	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
 	read_unlock(&pathtbl_resize_lock);
 	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)
 {
 	struct sk_buff *skb;

 	while ((skb = skb_dequeue(&mpath->frame_queue)) &&
 			(mpath->flags & MESH_PATH_ACTIVE))
 		dev_queue_xmit(skb);
 }

 /**
  * 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
  *
  * If the frame was beign forwarded from another MP, a PERR frame will be sent
  * to the precursor.
  *
  * Locking: the function must me called within a rcu_read_lock region
  */
 void mesh_path_discard_frame(struct sk_buff *skb,
 			     struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 	struct mesh_path *mpath;
 	u32 dsn = 0;

 	if (memcmp(hdr->addr4, sdata->dev->dev_addr, ETH_ALEN) != 0) {
 		u8 *ra, *da;

 		da = hdr->addr3;
 		ra = hdr->addr2;
 		mpath = mesh_path_lookup(da, sdata);
 		if (mpath)
 			dsn = ++mpath->dsn;
 		mesh_path_error_tx(skb->data, cpu_to_le32(dsn), ra, sdata);
 	}

 	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 withing 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)) &&
 			(mpath->flags & MESH_PATH_ACTIVE))
 		mesh_path_discard_frame(skb, mpath->sdata);
 }

 /**
  * 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->dsn = 0xffff;
 	mpath->metric = 0;
 	mpath->hop_count = 0;
 	mpath->exp_time = 0;
 	mpath->flags |= MESH_PATH_FIXED;
 	mesh_path_activate(mpath);
 	spin_unlock_bh(&mpath->state_lock);
 	mesh_path_tx_pending(mpath);
 }

 static void mesh_path_node_free(struct hlist_node *p, bool free_leafs)
 {
 	struct mesh_path *mpath;
 	struct mpath_node *node = hlist_entry(p, struct mpath_node, list);
 	mpath = node->mpath;
 	hlist_del_rcu(p);
 	if (free_leafs)
 		kfree(mpath);
 	kfree(node);
 }

 static int mesh_path_node_copy(struct hlist_node *p, struct mesh_table *newtbl)
 {
 	struct mesh_path *mpath;
 	struct mpath_node *node, *new_node;
 	u32 hash_idx;

 	new_node = kmalloc(sizeof(struct mpath_node), GFP_ATOMIC);
 	if (new_node == NULL)
 		return -ENOMEM;

 	node = hlist_entry(p, struct mpath_node, list);
 	mpath = node->mpath;
 	new_node->mpath = mpath;
 	hash_idx = mesh_table_hash(mpath->dst, mpath->sdata, newtbl);
 	hlist_add_head(&new_node->list,
 			&newtbl->hash_buckets[hash_idx]);
 	return 0;
 }

 int mesh_pathtbl_init(void)
 {
 	mesh_paths = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);
 	if (!mesh_paths)
 		return -ENOMEM;
 	mesh_paths->free_node = &mesh_path_node_free;
 	mesh_paths->copy_node = &mesh_path_node_copy;
 	mesh_paths->mean_chain_len = MEAN_CHAIN_LEN;

 	mpp_paths = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);
 	if (!mpp_paths) {
 		mesh_table_free(mesh_paths, true);
 		return -ENOMEM;
 	}
 	mpp_paths->free_node = &mesh_path_node_free;
 	mpp_paths->copy_node = &mesh_path_node_copy;
 	mpp_paths->mean_chain_len = MEAN_CHAIN_LEN;

 	return 0;
 }

 void mesh_path_expire(struct ieee80211_sub_if_data *sdata)
 {
 	struct mesh_path *mpath;
 	struct mpath_node *node;
 	struct hlist_node *p;
 	int i;

 	read_lock(&pathtbl_resize_lock);
 	for_each_mesh_entry(mesh_paths, p, node, i) {
 		if (node->mpath->sdata != sdata)
 			continue;
 		mpath = node->mpath;
 		spin_lock_bh(&mpath->state_lock);
 		if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
 		    (!(mpath->flags & MESH_PATH_FIXED)) &&
 			time_after(jiffies,
 			 mpath->exp_time + MESH_PATH_EXPIRE)) {
 			spin_unlock_bh(&mpath->state_lock);
 			mesh_path_del(mpath->dst, mpath->sdata);
 		} else
 			spin_unlock_bh(&mpath->state_lock);
 	}
 	read_unlock(&pathtbl_resize_lock);
 }

 void mesh_pathtbl_unregister(void)
 {
 	mesh_table_free(mesh_paths, true);
 	mesh_table_free(mpp_paths, true);
 }
	/*
	* Copyright (c) 2008 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/spinlock.h>
	#include <linux/string.h>
	#include <net/mac80211.h>
	#include "ieee80211_i.h"
	#include "mesh.h"

	/* There will be initially 2^INIT_PATHS_SIZE_ORDER buckets */
	#define INIT_PATHS_SIZE_ORDER 2

	/* Keep the mean chain length below this constant */
	#define MEAN_CHAIN_LEN 2

	#define MPATH_EXPIRED(mpath) ((mpath->flags & MESH_PATH_ACTIVE) && \
	time_after(jiffies, mpath->exp_time) && \
	!(mpath->flags & MESH_PATH_FIXED))

	struct mpath_node {
	struct hlist_node list;
	struct rcu_head rcu;
	/* This indirection allows two different tables to point to the same
	* mesh_path structure, useful when resizing
	*/
	struct mesh_path *mpath;
	};

	static struct mesh_table *mesh_paths;
	static struct mesh_table mpp_paths; / Store paths for MPP&MAP */

	/* This lock will have the grow table function as writer and add / delete nodes
	* as readers. When reading the table (i.e. doing lookups) we are well protected
	* by RCU
	*/
	static DEFINE_RWLOCK(pathtbl_resize_lock);

	/**
	*
	* 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)
	{
	rcu_assign_pointer(mpath->next_hop, sta);
	}


	/**
	* mesh_path_lookup - look up a path in the mesh path table
	* @dst: hardware address (ETH_ALEN length) of destination
	* @sdata: local subif
	*
	* 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(u8 dst, struct ieee80211_sub_if_data *sdata)
	{
	struct mesh_path *mpath;
	struct hlist_node *n;
	struct hlist_head *bucket;
	struct mesh_table *tbl;
	struct mpath_node *node;

	tbl = rcu_dereference(mesh_paths);

	bucket = &tbl->hash_buckets[mesh_table_hash(dst, sdata, tbl)];
	hlist_for_each_entry_rcu(node, n, bucket, list) {
	mpath = node->mpath;
	if (mpath->sdata == sdata &&
	memcmp(dst, mpath->dst, ETH_ALEN) == 0) {
	if (MPATH_EXPIRED(mpath)) {
	spin_lock_bh(&mpath->state_lock);
	if (MPATH_EXPIRED(mpath))
	mpath->flags &= ~MESH_PATH_ACTIVE;
	spin_unlock_bh(&mpath->state_lock);
	}
	return mpath;
	}
	}
	return NULL;
	}

	struct mesh_path mpp_path_lookup(u8 dst, struct ieee80211_sub_if_data *sdata)
	{
	struct mesh_path *mpath;
	struct hlist_node *n;
	struct hlist_head *bucket;
	struct mesh_table *tbl;
	struct mpath_node *node;

	tbl = rcu_dereference(mpp_paths);

	bucket = &tbl->hash_buckets[mesh_table_hash(dst, sdata, tbl)];
	hlist_for_each_entry_rcu(node, n, bucket, list) {
	mpath = node->mpath;
	if (mpath->sdata == sdata &&
	memcmp(dst, mpath->dst, ETH_ALEN) == 0) {
	if (MPATH_EXPIRED(mpath)) {
	spin_lock_bh(&mpath->state_lock);
	if (MPATH_EXPIRED(mpath))
	mpath->flags &= ~MESH_PATH_ACTIVE;
	spin_unlock_bh(&mpath->state_lock);
	}
	return mpath;
	}
	}
	return NULL;
	}


	/**
	* 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(int idx, struct ieee80211_sub_if_data sdata)
	{
	struct mpath_node *node;
	struct hlist_node *p;
	int i;
	int j = 0;

	for_each_mesh_entry(mesh_paths, p, node, i) {
	if (sdata && node->mpath->sdata != sdata)
	continue;
	if (j++ == idx) {
	if (MPATH_EXPIRED(node->mpath)) {
	spin_lock_bh(&node->mpath->state_lock);
	if (MPATH_EXPIRED(node->mpath))
	node->mpath->flags &= ~MESH_PATH_ACTIVE;
	spin_unlock_bh(&node->mpath->state_lock);
	}
	return node->mpath;
	}
	}

	return NULL;
	}

	/**
	* mesh_path_add - allocate and add a new path to the mesh path table
	* @addr: destination address of the path (ETH_ALEN length)
	* @sdata: local subif
	*
	* Returns: 0 on sucess
	*
	* State: the initial state of the new path is set to 0
	*/
	int mesh_path_add(u8 dst, struct ieee80211_sub_if_data sdata)
	{
	struct mesh_path mpath, new_mpath;
	struct mpath_node node, new_node;
	struct hlist_head *bucket;
	struct hlist_node *n;
	int grow = 0;
	int err = 0;
	u32 hash_idx;

	if (memcmp(dst, sdata->dev->dev_addr, ETH_ALEN) == 0)
	/* never add ourselves as neighbours */
	return -ENOTSUPP;

	if (is_multicast_ether_addr(dst))
	return -ENOTSUPP;

	if (atomic_add_unless(&sdata->u.mesh.mpaths, 1, MESH_MAX_MPATHS) == 0)
	return -ENOSPC;

	err = -ENOMEM;
	new_mpath = kzalloc(sizeof(struct mesh_path), GFP_KERNEL);
	if (!new_mpath)
	goto err_path_alloc;

	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);
	if (!new_node)
	goto err_node_alloc;

	read_lock(&pathtbl_resize_lock);
	memcpy(new_mpath->dst, dst, ETH_ALEN);
	new_mpath->sdata = sdata;
	new_mpath->flags = 0;
	skb_queue_head_init(&new_mpath->frame_queue);
	new_node->mpath = new_mpath;
	new_mpath->timer.data = (unsigned long) new_mpath;
	new_mpath->timer.function = mesh_path_timer;
	new_mpath->exp_time = jiffies;
	spin_lock_init(&new_mpath->state_lock);
	init_timer(&new_mpath->timer);

	hash_idx = mesh_table_hash(dst, sdata, mesh_paths);
	bucket = &mesh_paths->hash_buckets[hash_idx];

	spin_lock(&mesh_paths->hashwlock[hash_idx]);

	err = -EEXIST;
	hlist_for_each_entry(node, n, bucket, list) {
	mpath = node->mpath;
	if (mpath->sdata == sdata && memcmp(dst, mpath->dst, ETH_ALEN) == 0)
	goto err_exists;
	}

	hlist_add_head_rcu(&new_node->list, bucket);
	if (atomic_inc_return(&mesh_paths->entries) >=
	mesh_paths->mean_chain_len * (mesh_paths->hash_mask + 1))
	grow = 1;

	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
	read_unlock(&pathtbl_resize_lock);
	if (grow) {
	struct mesh_table oldtbl, newtbl;

	write_lock(&pathtbl_resize_lock);
	oldtbl = mesh_paths;
	newtbl = mesh_table_grow(mesh_paths);
	if (!newtbl) {
	write_unlock(&pathtbl_resize_lock);
	return 0;
	}
	rcu_assign_pointer(mesh_paths, newtbl);
	write_unlock(&pathtbl_resize_lock);

	synchronize_rcu();
	mesh_table_free(oldtbl, false);
	}
	return 0;

	err_exists:
	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
	read_unlock(&pathtbl_resize_lock);
	kfree(new_node);
	err_node_alloc:
	kfree(new_mpath);
	err_path_alloc:
	atomic_dec(&sdata->u.mesh.mpaths);
	return err;
	}


	int mpp_path_add(u8 dst, u8 mpp, struct ieee80211_sub_if_data *sdata)
	{
	struct mesh_path mpath, new_mpath;
	struct mpath_node node, new_node;
	struct hlist_head *bucket;
	struct hlist_node *n;
	int grow = 0;
	int err = 0;
	u32 hash_idx;


	if (memcmp(dst, sdata->dev->dev_addr, ETH_ALEN) == 0)
	/* never add ourselves as neighbours */
	return -ENOTSUPP;

	if (is_multicast_ether_addr(dst))
	return -ENOTSUPP;

	err = -ENOMEM;
	new_mpath = kzalloc(sizeof(struct mesh_path), GFP_KERNEL);
	if (!new_mpath)
	goto err_path_alloc;

	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);
	if (!new_node)
	goto err_node_alloc;

	read_lock(&pathtbl_resize_lock);
	memcpy(new_mpath->dst, dst, ETH_ALEN);
	memcpy(new_mpath->mpp, mpp, ETH_ALEN);
	new_mpath->sdata = sdata;
	new_mpath->flags = 0;
	skb_queue_head_init(&new_mpath->frame_queue);
	new_node->mpath = new_mpath;
	new_mpath->exp_time = jiffies;
	spin_lock_init(&new_mpath->state_lock);

	hash_idx = mesh_table_hash(dst, sdata, mpp_paths);
	bucket = &mpp_paths->hash_buckets[hash_idx];

	spin_lock(&mpp_paths->hashwlock[hash_idx]);

	err = -EEXIST;
	hlist_for_each_entry(node, n, bucket, list) {
	mpath = node->mpath;
	if (mpath->sdata == sdata && memcmp(dst, mpath->dst, ETH_ALEN) == 0)
	goto err_exists;
	}

	hlist_add_head_rcu(&new_node->list, bucket);
	if (atomic_inc_return(&mpp_paths->entries) >=
	mpp_paths->mean_chain_len * (mpp_paths->hash_mask + 1))
	grow = 1;

	spin_unlock(&mpp_paths->hashwlock[hash_idx]);
	read_unlock(&pathtbl_resize_lock);
	if (grow) {
	struct mesh_table oldtbl, newtbl;

	write_lock(&pathtbl_resize_lock);
	oldtbl = mpp_paths;
	newtbl = mesh_table_grow(mpp_paths);
	if (!newtbl) {
	write_unlock(&pathtbl_resize_lock);
	return 0;
	}
	rcu_assign_pointer(mpp_paths, newtbl);
	write_unlock(&pathtbl_resize_lock);

	synchronize_rcu();
	mesh_table_free(oldtbl, false);
	}
	return 0;

	err_exists:
	spin_unlock(&mpp_paths->hashwlock[hash_idx]);
	read_unlock(&pathtbl_resize_lock);
	kfree(new_node);
	err_node_alloc:
	kfree(new_mpath);
	err_path_alloc:
	return err;
	}


	/**
	* 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 mesh_path *mpath;
	struct mpath_node *node;
	struct hlist_node *p;
	struct ieee80211_sub_if_data *sdata = sta->sdata;
	int i;

	rcu_read_lock();
	for_each_mesh_entry(mesh_paths, p, node, i) {
	mpath = node->mpath;
	spin_lock_bh(&mpath->state_lock);
	if (mpath->next_hop == sta &&
	mpath->flags & MESH_PATH_ACTIVE &&
	!(mpath->flags & MESH_PATH_FIXED)) {
	mpath->flags &= ~MESH_PATH_ACTIVE;
	++mpath->dsn;
	spin_unlock_bh(&mpath->state_lock);
	mesh_path_error_tx(mpath->dst,
	cpu_to_le32(mpath->dsn),
	sdata->dev->broadcast, sdata);
	} else
	spin_unlock_bh(&mpath->state_lock);
	}
	rcu_read_unlock();
	}

	/**
	* 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 mesh_path *mpath;
	struct mpath_node *node;
	struct hlist_node *p;
	int i;

	for_each_mesh_entry(mesh_paths, p, node, i) {
	mpath = node->mpath;
	if (mpath->next_hop == sta)
	mesh_path_del(mpath->dst, mpath->sdata);
	}
	}

	void mesh_path_flush(struct ieee80211_sub_if_data *sdata)
	{
	struct mesh_path *mpath;
	struct mpath_node *node;
	struct hlist_node *p;
	int i;

	for_each_mesh_entry(mesh_paths, p, node, i) {
	mpath = node->mpath;
	if (mpath->sdata == sdata)
	mesh_path_del(mpath->dst, mpath->sdata);
	}
	}

	static void mesh_path_node_reclaim(struct rcu_head *rp)
	{
	struct mpath_node *node = container_of(rp, struct mpath_node, rcu);
	struct ieee80211_sub_if_data *sdata = node->mpath->sdata;

	del_timer_sync(&node->mpath->timer);
	atomic_dec(&sdata->u.mesh.mpaths);
	kfree(node->mpath);
	kfree(node);
	}

	/**
	* mesh_path_del - delete a mesh path from the table
	*
	* @addr: dst address (ETH_ALEN length)
	* @sdata: local subif
	*
	* Returns: 0 if succesful
	*/
	int mesh_path_del(u8 addr, struct ieee80211_sub_if_data sdata)
	{
	struct mesh_path *mpath;
	struct mpath_node *node;
	struct hlist_head *bucket;
	struct hlist_node *n;
	int hash_idx;
	int err = 0;

	read_lock(&pathtbl_resize_lock);
	hash_idx = mesh_table_hash(addr, sdata, mesh_paths);
	bucket = &mesh_paths->hash_buckets[hash_idx];

	spin_lock(&mesh_paths->hashwlock[hash_idx]);
	hlist_for_each_entry(node, n, bucket, list) {
	mpath = node->mpath;
	if (mpath->sdata == sdata &&
	memcmp(addr, mpath->dst, ETH_ALEN) == 0) {
	spin_lock_bh(&mpath->state_lock);
	mpath->flags \|= MESH_PATH_RESOLVING;
	hlist_del_rcu(&node->list);
	call_rcu(&node->rcu, mesh_path_node_reclaim);
	atomic_dec(&mesh_paths->entries);
	spin_unlock_bh(&mpath->state_lock);
	goto enddel;
	}
	}

	err = -ENXIO;
	enddel:
	spin_unlock(&mesh_paths->hashwlock[hash_idx]);
	read_unlock(&pathtbl_resize_lock);
	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)
	{
	struct sk_buff *skb;

	while ((skb = skb_dequeue(&mpath->frame_queue)) &&
	(mpath->flags & MESH_PATH_ACTIVE))
	dev_queue_xmit(skb);
	}

	/**
	* 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
	*
	* If the frame was beign forwarded from another MP, a PERR frame will be sent
	* to the precursor.
	*
	* Locking: the function must me called within a rcu_read_lock region
	*/
	void mesh_path_discard_frame(struct sk_buff *skb,
	struct ieee80211_sub_if_data *sdata)
	{
	struct ieee80211_hdr hdr = (struct ieee80211_hdr ) skb->data;
	struct mesh_path *mpath;
	u32 dsn = 0;

	if (memcmp(hdr->addr4, sdata->dev->dev_addr, ETH_ALEN) != 0) {
	u8 ra, da;

	da = hdr->addr3;
	ra = hdr->addr2;
	mpath = mesh_path_lookup(da, sdata);
	if (mpath)
	dsn = ++mpath->dsn;
	mesh_path_error_tx(skb->data, cpu_to_le32(dsn), ra, sdata);
	}

	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 withing 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)) &&
	(mpath->flags & MESH_PATH_ACTIVE))
	mesh_path_discard_frame(skb, mpath->sdata);
	}

	/**
	* 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->dsn = 0xffff;
	mpath->metric = 0;
	mpath->hop_count = 0;
	mpath->exp_time = 0;
	mpath->flags \|= MESH_PATH_FIXED;
	mesh_path_activate(mpath);
	spin_unlock_bh(&mpath->state_lock);
	mesh_path_tx_pending(mpath);
	}

	static void mesh_path_node_free(struct hlist_node *p, bool free_leafs)
	{
	struct mesh_path *mpath;
	struct mpath_node *node = hlist_entry(p, struct mpath_node, list);
	mpath = node->mpath;
	hlist_del_rcu(p);
	if (free_leafs)
	kfree(mpath);
	kfree(node);
	}

	static int mesh_path_node_copy(struct hlist_node p, struct mesh_table newtbl)
	{
	struct mesh_path *mpath;
	struct mpath_node node, new_node;
	u32 hash_idx;

	new_node = kmalloc(sizeof(struct mpath_node), GFP_ATOMIC);
	if (new_node == NULL)
	return -ENOMEM;

	node = hlist_entry(p, struct mpath_node, list);
	mpath = node->mpath;
	new_node->mpath = mpath;
	hash_idx = mesh_table_hash(mpath->dst, mpath->sdata, newtbl);
	hlist_add_head(&new_node->list,
	&newtbl->hash_buckets[hash_idx]);
	return 0;
	}

	int mesh_pathtbl_init(void)
	{
	mesh_paths = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);
	if (!mesh_paths)
	return -ENOMEM;
	mesh_paths->free_node = &mesh_path_node_free;
	mesh_paths->copy_node = &mesh_path_node_copy;
	mesh_paths->mean_chain_len = MEAN_CHAIN_LEN;

	mpp_paths = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);
	if (!mpp_paths) {
	mesh_table_free(mesh_paths, true);
	return -ENOMEM;
	}
	mpp_paths->free_node = &mesh_path_node_free;
	mpp_paths->copy_node = &mesh_path_node_copy;
	mpp_paths->mean_chain_len = MEAN_CHAIN_LEN;

	return 0;
	}

	void mesh_path_expire(struct ieee80211_sub_if_data *sdata)
	{
	struct mesh_path *mpath;
	struct mpath_node *node;
	struct hlist_node *p;
	int i;

	read_lock(&pathtbl_resize_lock);
	for_each_mesh_entry(mesh_paths, p, node, i) {
	if (node->mpath->sdata != sdata)
	continue;
	mpath = node->mpath;
	spin_lock_bh(&mpath->state_lock);
	if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
	(!(mpath->flags & MESH_PATH_FIXED)) &&
	time_after(jiffies,
	mpath->exp_time + MESH_PATH_EXPIRE)) {
	spin_unlock_bh(&mpath->state_lock);
	mesh_path_del(mpath->dst, mpath->sdata);
	} else
	spin_unlock_bh(&mpath->state_lock);
	}
	read_unlock(&pathtbl_resize_lock);
	}

	void mesh_pathtbl_unregister(void)
	{
	mesh_table_free(mesh_paths, true);
	mesh_table_free(mpp_paths, true);
	}