tuntap: switch to use rtnl_dereference()

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / mac80211 / mesh_pathtbl.c

/*
 * 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"

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

int mesh_paths_generation;

/* This lock will have the grow table function as writer and add / delete nodes
 * as readers. RCU provides sufficient protection only when reading the table
 * (i.e. doing lookups).  Adding or adding or removing nodes requires we take
 * the read lock or we risk operating on an old table.  The write lock is only
 * needed when modifying the number of buckets a table.
 */
static DEFINE_RWLOCK(pathtbl_resize_lock);


static inline struct mesh_table *resize_dereference_mesh_paths(void)
{
        return rcu_dereference_protected(mesh_paths,
                lockdep_is_held(&pathtbl_resize_lock));
}

static inline struct mesh_table *resize_dereference_mpp_paths(void)
{
        return rcu_dereference_protected(mpp_paths,
                lockdep_is_held(&pathtbl_resize_lock));
}

/*
 * CAREFUL -- "tbl" must not be an expression,
 * in particular not an rcu_dereference(), since
 * it's used twice. So it is illegal to do
 *      for_each_mesh_entry(rcu_dereference(...), ...)
 */
#define for_each_mesh_entry(tbl, p, node, i) \
        for (i = 0; i <= tbl->hash_mask; i++) \
                hlist_for_each_entry_rcu(node, p, &tbl->hash_buckets[i], list)


static struct mesh_table *mesh_table_alloc(int size_order)
{
        int i;
        struct mesh_table *newtbl;

        newtbl = kmalloc(sizeof(struct mesh_table), GFP_ATOMIC);
        if (!newtbl)
                return NULL;

        newtbl->hash_buckets = kzalloc(sizeof(struct hlist_head) *
                        (1 << size_order), GFP_ATOMIC);

        if (!newtbl->hash_buckets) {
                kfree(newtbl);
                return NULL;
        }

        newtbl->hashwlock = kmalloc(sizeof(spinlock_t) *
                        (1 << size_order), GFP_ATOMIC);
        if (!newtbl->hashwlock) {
                kfree(newtbl->hash_buckets);
                kfree(newtbl);
                return NULL;
        }

        newtbl->size_order = size_order;
        newtbl->hash_mask = (1 << size_order) - 1;
        atomic_set(&newtbl->entries,  0);
        get_random_bytes(&newtbl->hash_rnd,
                        sizeof(newtbl->hash_rnd));
        for (i = 0; i <= newtbl->hash_mask; i++)
                spin_lock_init(&newtbl->hashwlock[i]);
        spin_lock_init(&newtbl->gates_lock);

        return newtbl;
}

static void __mesh_table_free(struct mesh_table *tbl)
{
        kfree(tbl->hash_buckets);
        kfree(tbl->hashwlock);
        kfree(tbl);
}

static void mesh_table_free(struct mesh_table *tbl, bool free_leafs)
{
        struct hlist_head *mesh_hash;
        struct hlist_node *p, *q;
        struct mpath_node *gate;
        int i;

        mesh_hash = tbl->hash_buckets;
        for (i = 0; i <= tbl->hash_mask; i++) {
                spin_lock_bh(&tbl->hashwlock[i]);
                hlist_for_each_safe(p, q, &mesh_hash[i]) {
                        tbl->free_node(p, free_leafs);
                        atomic_dec(&tbl->entries);
                }
                spin_unlock_bh(&tbl->hashwlock[i]);
        }
        if (free_leafs) {
                spin_lock_bh(&tbl->gates_lock);
                hlist_for_each_entry_safe(gate, p, q,
                                         tbl->known_gates, list) {
                        hlist_del(&gate->list);
                        kfree(gate);
                }
                kfree(tbl->known_gates);
                spin_unlock_bh(&tbl->gates_lock);
        }

        __mesh_table_free(tbl);
}

static int mesh_table_grow(struct mesh_table *oldtbl,
                           struct mesh_table *newtbl)
{
        struct hlist_head *oldhash;
        struct hlist_node *p, *q;
        int i;

        if (atomic_read(&oldtbl->entries)
                        < oldtbl->mean_chain_len * (oldtbl->hash_mask + 1))
                return -EAGAIN;

        newtbl->free_node = oldtbl->free_node;
        newtbl->mean_chain_len = oldtbl->mean_chain_len;
        newtbl->copy_node = oldtbl->copy_node;
        newtbl->known_gates = oldtbl->known_gates;
        atomic_set(&newtbl->entries, atomic_read(&oldtbl->entries));

        oldhash = oldtbl->hash_buckets;
        for (i = 0; i <= oldtbl->hash_mask; i++)
                hlist_for_each(p, &oldhash[i])
                        if (oldtbl->copy_node(p, newtbl) < 0)
                                goto errcopy;

        return 0;

errcopy:
        for (i = 0; i <= newtbl->hash_mask; i++) {
                hlist_for_each_safe(p, q, &newtbl->hash_buckets[i])
                        oldtbl->free_node(p, 0);
        }
        return -ENOMEM;
}

static u32 mesh_table_hash(u8 *addr, struct ieee80211_sub_if_data *sdata,
                           struct mesh_table *tbl)
{
        /* Use last four bytes of hw addr and interface index as hash index */
        return jhash_2words(*(u32 *)(addr+2), sdata->dev->ifindex, tbl->hash_rnd)
                & tbl->hash_mask;
}


/**
 *
 * 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);
        }

        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;

        BUG_ON(gate_mpath == from_mpath);
        BUG_ON(!gate_mpath->next_hop);

        __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, u8 *dst,
                                          struct ieee80211_sub_if_data *sdata)
{
        struct mesh_path *mpath;
        struct hlist_node *n;
        struct hlist_head *bucket;
        struct mpath_node *node;

        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 &&
                    ether_addr_equal(dst, mpath->dst)) {
                        if (MPATH_EXPIRED(mpath)) {
                                spin_lock_bh(&mpath->state_lock);
                                mpath->flags &= ~MESH_PATH_ACTIVE;
                                spin_unlock_bh(&mpath->state_lock);
                        }
                        return mpath;
                }
        }
        return NULL;
}

/**
 * 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)
{
        return mpath_lookup(rcu_dereference(mesh_paths), dst, sdata);
}

struct mesh_path *mpp_path_lookup(u8 *dst, struct ieee80211_sub_if_data *sdata)
{
        return mpath_lookup(rcu_dereference(mpp_paths), dst, sdata);
}


/**
 * 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 mesh_table *tbl = rcu_dereference(mesh_paths);
        struct mpath_node *node;
        struct hlist_node *p;
        int i;
        int j = 0;

        for_each_mesh_entry(tbl, 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);
                                node->mpath->flags &= ~MESH_PATH_ACTIVE;
                                spin_unlock_bh(&node->mpath->state_lock);
                        }
                        return node->mpath;
                }
        }

        return NULL;
}

/**
 * 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;
        struct mpath_node *gate, *new_gate;
        struct hlist_node *n;
        int err;

        rcu_read_lock();
        tbl = rcu_dereference(mesh_paths);

        hlist_for_each_entry_rcu(gate, n, tbl->known_gates, list)
                if (gate->mpath == mpath) {
                        err = -EEXIST;
                        goto err_rcu;
                }

        new_gate = kzalloc(sizeof(struct mpath_node), GFP_ATOMIC);
        if (!new_gate) {
                err = -ENOMEM;
                goto err_rcu;
        }

        mpath->is_gate = true;
        mpath->sdata->u.mesh.num_gates++;
        new_gate->mpath = mpath;
        spin_lock_bh(&tbl->gates_lock);
        hlist_add_head_rcu(&new_gate->list, tbl->known_gates);
        spin_unlock_bh(&tbl->gates_lock);
        rcu_read_unlock();
        mpath_dbg(mpath->sdata,
                  "Mesh path: Recorded new gate: %pM. %d known gates\n",
                  mpath->dst, mpath->sdata->u.mesh.num_gates);
        return 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
 *
 * Returns: 0 on success
 *
 * Locking: must be called inside rcu_read_lock() section
 */
static int mesh_gate_del(struct mesh_table *tbl, struct mesh_path *mpath)
{
        struct mpath_node *gate;
        struct hlist_node *p, *q;

        hlist_for_each_entry_safe(gate, p, q, tbl->known_gates, list)
                if (gate->mpath == mpath) {
                        spin_lock_bh(&tbl->gates_lock);
                        hlist_del_rcu(&gate->list);
                        kfree_rcu(gate, rcu);
                        spin_unlock_bh(&tbl->gates_lock);
                        mpath->sdata->u.mesh.num_gates--;
                        mpath->is_gate = false;
                        mpath_dbg(mpath->sdata,
                                  "Mesh path: Deleted gate: %pM. %d known gates\n",
                                  mpath->dst, mpath->sdata->u.mesh.num_gates);
                        break;
                }

        return 0;
}

/**
 * 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;
}

/**
 * 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 success
 *
 * 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 ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct ieee80211_local *local = sdata->local;
        struct mesh_table *tbl;
        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 (ether_addr_equal(dst, sdata->vif.addr))
                /* 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_ATOMIC);
        if (!new_mpath)
                goto err_path_alloc;

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

        read_lock_bh(&pathtbl_resize_lock);
        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_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);

        tbl = resize_dereference_mesh_paths();

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

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

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

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

        mesh_paths_generation++;

        spin_unlock(&tbl->hashwlock[hash_idx]);
        read_unlock_bh(&pathtbl_resize_lock);
        if (grow) {
                set_bit(MESH_WORK_GROW_MPATH_TABLE,  &ifmsh->wrkq_flags);
                ieee80211_queue_work(&local->hw, &sdata->work);
        }
        return 0;

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

static void mesh_table_free_rcu(struct rcu_head *rcu)
{
        struct mesh_table *tbl = container_of(rcu, struct mesh_table, rcu_head);

        mesh_table_free(tbl, false);
}

void mesh_mpath_table_grow(void)
{
        struct mesh_table *oldtbl, *newtbl;

        write_lock_bh(&pathtbl_resize_lock);
        oldtbl = resize_dereference_mesh_paths();
        newtbl = mesh_table_alloc(oldtbl->size_order + 1);
        if (!newtbl)
                goto out;
        if (mesh_table_grow(oldtbl, newtbl) < 0) {
                __mesh_table_free(newtbl);
                goto out;
        }
        rcu_assign_pointer(mesh_paths, newtbl);

        call_rcu(&oldtbl->rcu_head, mesh_table_free_rcu);

 out:
        write_unlock_bh(&pathtbl_resize_lock);
}

void mesh_mpp_table_grow(void)
{
        struct mesh_table *oldtbl, *newtbl;

        write_lock_bh(&pathtbl_resize_lock);
        oldtbl = resize_dereference_mpp_paths();
        newtbl = mesh_table_alloc(oldtbl->size_order + 1);
        if (!newtbl)
                goto out;
        if (mesh_table_grow(oldtbl, newtbl) < 0) {
                __mesh_table_free(newtbl);
                goto out;
        }
        rcu_assign_pointer(mpp_paths, newtbl);
        call_rcu(&oldtbl->rcu_head, mesh_table_free_rcu);

 out:
        write_unlock_bh(&pathtbl_resize_lock);
}

int mpp_path_add(u8 *dst, u8 *mpp, struct ieee80211_sub_if_data *sdata)
{
        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
        struct ieee80211_local *local = sdata->local;
        struct mesh_table *tbl;
        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 (ether_addr_equal(dst, sdata->vif.addr))
                /* 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_ATOMIC);
        if (!new_mpath)
                goto err_path_alloc;

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

        read_lock_bh(&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;
        init_timer(&new_mpath->timer);
        new_mpath->exp_time = jiffies;
        spin_lock_init(&new_mpath->state_lock);

        tbl = resize_dereference_mpp_paths();

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

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

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

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

        spin_unlock(&tbl->hashwlock[hash_idx]);
        read_unlock_bh(&pathtbl_resize_lock);
        if (grow) {
                set_bit(MESH_WORK_GROW_MPP_TABLE,  &ifmsh->wrkq_flags);
                ieee80211_queue_work(&local->hw, &sdata->work);
        }
        return 0;

err_exists:
        spin_unlock(&tbl->hashwlock[hash_idx]);
        read_unlock_bh(&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_table *tbl;
        static const u8 bcast[ETH_ALEN] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
        struct mesh_path *mpath;
        struct mpath_node *node;
        struct hlist_node *p;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
        int i;
        __le16 reason = cpu_to_le16(WLAN_REASON_MESH_PATH_DEST_UNREACHABLE);

        rcu_read_lock();
        tbl = rcu_dereference(mesh_paths);
        for_each_mesh_entry(tbl, p, node, i) {
                mpath = node->mpath;
                if (rcu_dereference(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->u.mesh.mshcfg.element_ttl,
                                        mpath->dst, cpu_to_le32(mpath->sn),
                                        reason, bcast, sdata);
                }
        }
        rcu_read_unlock();
}

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);
}

/* needs to be called with the corresponding hashwlock taken */
static void __mesh_path_del(struct mesh_table *tbl, struct mpath_node *node)
{
        struct mesh_path *mpath;
        mpath = node->mpath;
        spin_lock(&mpath->state_lock);
        mpath->flags |= MESH_PATH_RESOLVING;
        if (mpath->is_gate)
                mesh_gate_del(tbl, mpath);
        hlist_del_rcu(&node->list);
        call_rcu(&node->rcu, mesh_path_node_reclaim);
        spin_unlock(&mpath->state_lock);
        atomic_dec(&tbl->entries);
}

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

        rcu_read_lock();
        read_lock_bh(&pathtbl_resize_lock);
        tbl = resize_dereference_mesh_paths();
        for_each_mesh_entry(tbl, p, node, i) {
                mpath = node->mpath;
                if (rcu_dereference(mpath->next_hop) == sta) {
                        spin_lock(&tbl->hashwlock[i]);
                        __mesh_path_del(tbl, node);
                        spin_unlock(&tbl->hashwlock[i]);
                }
        }
        read_unlock_bh(&pathtbl_resize_lock);
        rcu_read_unlock();
}

static void table_flush_by_iface(struct mesh_table *tbl,
                                 struct ieee80211_sub_if_data *sdata)
{
        struct mesh_path *mpath;
        struct mpath_node *node;
        struct hlist_node *p;
        int i;

        WARN_ON(!rcu_read_lock_held());
        for_each_mesh_entry(tbl, p, node, i) {
                mpath = node->mpath;
                if (mpath->sdata != sdata)
                        continue;
                spin_lock_bh(&tbl->hashwlock[i]);
                __mesh_path_del(tbl, node);
                spin_unlock_bh(&tbl->hashwlock[i]);
        }
}

/**
 * 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)
{
        struct mesh_table *tbl;

        rcu_read_lock();
        read_lock_bh(&pathtbl_resize_lock);
        tbl = resize_dereference_mesh_paths();
        table_flush_by_iface(tbl, sdata);
        tbl = resize_dereference_mpp_paths();
        table_flush_by_iface(tbl, sdata);
        read_unlock_bh(&pathtbl_resize_lock);
        rcu_read_unlock();
}

/**
 * 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(u8 *addr, struct ieee80211_sub_if_data *sdata)
{
        struct mesh_table *tbl;
        struct mesh_path *mpath;
        struct mpath_node *node;
        struct hlist_head *bucket;
        struct hlist_node *n;
        int hash_idx;
        int err = 0;

        read_lock_bh(&pathtbl_resize_lock);
        tbl = resize_dereference_mesh_paths();
        hash_idx = mesh_table_hash(addr, sdata, tbl);
        bucket = &tbl->hash_buckets[hash_idx];

        spin_lock(&tbl->hashwlock[hash_idx]);
        hlist_for_each_entry(node, n, bucket, list) {
                mpath = node->mpath;
                if (mpath->sdata == sdata &&
                    ether_addr_equal(addr, mpath->dst)) {
                        __mesh_path_del(tbl, node);
                        goto enddel;
                }
        }

        err = -ENXIO;
enddel:
        mesh_paths_generation++;
        spin_unlock(&tbl->hashwlock[hash_idx]);
        read_unlock_bh(&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)
{
        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 hlist_node *n;
        struct mesh_table *tbl;
        struct mesh_path *from_mpath = mpath;
        struct mpath_node *gate = NULL;
        bool copy = false;
        struct hlist_head *known_gates;

        rcu_read_lock();
        tbl = rcu_dereference(mesh_paths);
        known_gates = tbl->known_gates;
        rcu_read_unlock();

        if (!known_gates)
                return -EHOSTUNREACH;

        hlist_for_each_entry_rcu(gate, n, known_gates, list) {
                if (gate->mpath->sdata != sdata)
                        continue;

                if (gate->mpath->flags & MESH_PATH_ACTIVE) {
                        mpath_dbg(sdata, "Forwarding to %pM\n", gate->mpath->dst);
                        mesh_path_move_to_queue(gate->mpath, from_mpath, copy);
                        from_mpath = gate->mpath;
                        copy = true;
                } else {
                        mpath_dbg(sdata,
                                  "Not forwarding %p (flags %#x)\n",
                                  gate->mpath, gate->mpath->flags);
                }
        }

        hlist_for_each_entry_rcu(gate, n, known_gates, list)
                if (gate->mpath->sdata == sdata) {
                        mpath_dbg(sdata, "Sending to %pM\n", gate->mpath->dst);
                        mesh_path_tx_pending(gate->mpath);
                }

        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 sk_buff *skb,
                             struct ieee80211_sub_if_data *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 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(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->sn = 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) {
                del_timer_sync(&mpath->timer);
                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)
{
        struct mesh_table *tbl_path, *tbl_mpp;
        int ret;

        tbl_path = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);
        if (!tbl_path)
                return -ENOMEM;
        tbl_path->free_node = &mesh_path_node_free;
        tbl_path->copy_node = &mesh_path_node_copy;
        tbl_path->mean_chain_len = MEAN_CHAIN_LEN;
        tbl_path->known_gates = kzalloc(sizeof(struct hlist_head), GFP_ATOMIC);
        if (!tbl_path->known_gates) {
                ret = -ENOMEM;
                goto free_path;
        }
        INIT_HLIST_HEAD(tbl_path->known_gates);


        tbl_mpp = mesh_table_alloc(INIT_PATHS_SIZE_ORDER);
        if (!tbl_mpp) {
                ret = -ENOMEM;
                goto free_path;
        }
        tbl_mpp->free_node = &mesh_path_node_free;
        tbl_mpp->copy_node = &mesh_path_node_copy;
        tbl_mpp->mean_chain_len = MEAN_CHAIN_LEN;
        tbl_mpp->known_gates = kzalloc(sizeof(struct hlist_head), GFP_ATOMIC);
        if (!tbl_mpp->known_gates) {
                ret = -ENOMEM;
                goto free_mpp;
        }
        INIT_HLIST_HEAD(tbl_mpp->known_gates);

        /* Need no locking since this is during init */
        RCU_INIT_POINTER(mesh_paths, tbl_path);
        RCU_INIT_POINTER(mpp_paths, tbl_mpp);

        return 0;

free_mpp:
        mesh_table_free(tbl_mpp, true);
free_path:
        mesh_table_free(tbl_path, true);
        return ret;
}

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

        rcu_read_lock();
        tbl = rcu_dereference(mesh_paths);
        for_each_mesh_entry(tbl, p, node, i) {
                if (node->mpath->sdata != sdata)
                        continue;
                mpath = node->mpath;
                if ((!(mpath->flags & MESH_PATH_RESOLVING)) &&
                    (!(mpath->flags & MESH_PATH_FIXED)) &&
                     time_after(jiffies, mpath->exp_time + MESH_PATH_EXPIRE))
                        mesh_path_del(mpath->dst, mpath->sdata);
        }
        rcu_read_unlock();
}

void mesh_pathtbl_unregister(void)
{
        /* no need for locking during exit path */
        mesh_table_free(rcu_dereference_protected(mesh_paths, 1), true);
        mesh_table_free(rcu_dereference_protected(mpp_paths, 1), true);
}