mac80211: mesh path table implementation

/*

 * 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/netdevice.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;

/* 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)

{

	__sta_info_get(sta);

	if (mpath->next_hop)

		sta_info_put(mpath->next_hop);

	mpath->next_hop = sta;

}

/**

 * mesh_path_lookup - look up a path in the mesh path table

 * @dst: hardware address (ETH_ALEN length) of destination

 * @dev: local interface

 *

 * 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 net_device *dev)

{

	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, dev, tbl)];

	hlist_for_each_entry_rcu(node, n, bucket, list) {

		mpath = node->mpath;

		if (mpath->dev == dev &&

				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

 * @dev: local interface

 *

 * 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 net_device *dev)

{

	struct mpath_node *node;

	struct hlist_node *p;

	int i;

	int j = 0;

	for_each_mesh_entry(mesh_paths, p, node, i)

		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)

 * @dev: local interface

 *

 * Returns: 0 on sucess

 *

 * State: the initial state of the new path is set to 0

 */

int mesh_path_add(u8 *dst, struct net_device *dev)

{

	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);

	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, 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.sta.mpaths, 1, MESH_MAX_MPATHS) == 0)

		return -ENOSPC;

	read_lock(&pathtbl_resize_lock);

	new_mpath = kzalloc(sizeof(struct mesh_path), GFP_KERNEL);

	if (!new_mpath) {

		atomic_dec(&sdata->u.sta.mpaths);

		err = -ENOMEM;

		goto endadd2;

	}

	memcpy(new_mpath->dst, dst, ETH_ALEN);

	new_mpath->dev = dev;

	new_mpath->flags = 0;

	skb_queue_head_init(&new_mpath->frame_queue);

	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);

	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, dev, 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->dev == dev && memcmp(dst, mpath->dst, ETH_ALEN)

				== 0) {

			err = -EEXIST;

			atomic_dec(&sdata->u.sta.mpaths);

			kfree(new_node);

			kfree(new_mpath);

			goto endadd;

		}

	}

	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;

endadd:

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

endadd2:

	read_unlock(&pathtbl_resize_lock);

	if (!err && 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 -ENOMEM;

		}

		rcu_assign_pointer(mesh_paths, newtbl);

		synchronize_rcu();

		mesh_table_free(oldtbl, false);

		write_unlock(&pathtbl_resize_lock);

	}

	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 net_device *dev = sta->dev;

	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),

					dev->broadcast, dev);

		} 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 ESTAB

 * to any other state, since ESTAB state is the only one that allows path

 * creation. This will happen before the sta can be freed (since we hold

 * a reference to it) so any reader in a rcu read block will be protected

 * against the plink dissapearing.

 */

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->dev);

	}

}

void mesh_path_flush(struct net_device *dev)

{

	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->dev == dev)

			mesh_path_del(mpath->dst, mpath->dev);

	}

}

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 =

		IEEE80211_DEV_TO_SUB_IF(node->mpath->dev);

	if (node->mpath->next_hop)

		sta_info_put(node->mpath->next_hop);

	atomic_dec(&sdata->u.sta.mpaths);

	kfree(node->mpath);

	kfree(node);

}

/**

 * mesh_path_del - delete a mesh path from the table

 *

 * @addr: dst address (ETH_ALEN length)

 * @dev: local interface

 *

 * Returns: 0 if succesful

 *

 * State: if the path is being resolved, the deletion will be postponed until

 * the path resolution completes or times out.

 */

int mesh_path_del(u8 *addr, struct net_device *dev)

{

	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, dev, 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->dev == dev &&

				memcmp(addr, mpath->dst, ETH_ALEN) == 0) {

			spin_lock_bh(&mpath->state_lock);

			if (mpath->flags & MESH_PATH_RESOLVING) {

				mpath->flags |= MESH_PATH_DELETE;

			} else {

				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

 * @dev: network device 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 net_device *dev)

{

	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);

	struct mesh_path *mpath;

	u32 dsn = 0;

	if (skb->pkt_type == PACKET_OTHERHOST) {

		struct ieee80211s_hdr *prev_meshhdr;

		int mshhdrlen;

		u8 *ra, *da;

		prev_meshhdr = ((struct ieee80211s_hdr *)skb->cb);

		mshhdrlen = ieee80211_get_mesh_hdrlen(prev_meshhdr);

		da = skb->data;

		ra = MESH_PREQ(skb);

		mpath = mesh_path_lookup(da, dev);

		if (mpath)

			dsn = ++mpath->dsn;

		mesh_path_error_tx(skb->data, cpu_to_le32(dsn), ra, dev);

	}

	kfree_skb(skb);

	sdata->u.sta.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 ieee80211_sub_if_data *sdata;

	struct sk_buff *skb;

	sdata = IEEE80211_DEV_TO_SUB_IF(mpath->dev);

	while ((skb = skb_dequeue(&mpath->frame_queue)) &&

			(mpath->flags & MESH_PATH_ACTIVE))

		mesh_path_discard_frame(skb, mpath->dev);

}

/**

 * 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);

	synchronize_rcu();

	if (free_leafs)

		kfree(mpath);

	kfree(node);

}

static void 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;

	node = hlist_entry(p, struct mpath_node, list);

	mpath = node->mpath;

	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);

	new_node->mpath = mpath;

	hash_idx = mesh_table_hash(mpath->dst, mpath->dev, newtbl);

	hlist_add_head(&new_node->list,

			&newtbl->hash_buckets[hash_idx]);

}

int mesh_pathtbl_init(void)

{

	mesh_paths = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);

	mesh_paths->free_node = &mesh_path_node_free;

	mesh_paths->copy_node = &mesh_path_node_copy;

	mesh_paths->mean_chain_len = MEAN_CHAIN_LEN;

	if (!mesh_paths)

		return -ENOMEM;

	return 0;

}

void mesh_path_expire(struct net_device *dev)

{

	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->dev != dev)

			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->dev);

		} else

			spin_unlock_bh(&mpath->state_lock);

	}

	read_unlock(&pathtbl_resize_lock);

}

void mesh_pathtbl_unregister(void)

{

	mesh_table_free(mesh_paths, true);

}