splice: fix generic_file_splice_read() race with page invalidation

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

/*
 * 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)
{
        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
 * @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, 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 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 (dev && node->mpath->dev != dev)
                        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)
 * @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;

        new_mpath = kzalloc(sizeof(struct mesh_path), GFP_KERNEL);
        if (!new_mpath) {
                atomic_dec(&sdata->u.sta.mpaths);
                err = -ENOMEM;
                goto endadd2;
        }
        new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);
        if (!new_node) {
                kfree(new_mpath);
                atomic_dec(&sdata->u.sta.mpaths);
                err = -ENOMEM;
                goto endadd2;
        }

        read_lock(&pathtbl_resize_lock);
        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->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]);
        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);
                write_unlock(&pathtbl_resize_lock);

                synchronize_rcu();
                mesh_table_free(oldtbl, false);
        }
endadd2:
        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->sdata->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();
}
EXPORT_SYMBOL(mesh_plink_broken);

/**
 * 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->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);

        del_timer_sync(&node->mpath->timer);
        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
 */
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);
                        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);
}