flow.c

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/* flow.c: Generic flow cache.
 *
 * Copyright (C) 2003 Alexey N. Kuznetsov ([email protected])
 * Copyright (C) 2003 David S. Miller ([email protected])
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/completion.h>
#include <linux/percpu.h>
#include <linux/bitops.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/mutex.h>
#include <net/flow.h>
#include <linux/atomic.h>
#include <linux/security.h>

struct flow_cache_entry {
    union {
        struct hlist_node   hlist;
        struct list_head    gc_list;
    } u;
    struct net          *net;
    u16             family;
    u8              dir;
    u32             genid;
    struct flowi            key;
    struct flow_cache_object    *object;
};

struct flow_cache_percpu {
    struct hlist_head       *hash_table;
    int             hash_count;
    u32             hash_rnd;
    int             hash_rnd_recalc;
    struct tasklet_struct       flush_tasklet;
};

struct flow_flush_info {
    struct flow_cache       *cache;
    atomic_t            cpuleft;
    struct completion       completion;
};

struct flow_cache {
    u32             hash_shift;
    struct flow_cache_percpu __percpu *percpu;
    struct notifier_block       hotcpu_notifier;
    int             low_watermark;
    int             high_watermark;
    struct timer_list       rnd_timer;
};

atomic_t flow_cache_genid = ATOMIC_INIT(0);
EXPORT_SYMBOL(flow_cache_genid);
static struct flow_cache flow_cache_global;
static struct kmem_cache *flow_cachep __read_mostly;

static DEFINE_SPINLOCK(flow_cache_gc_lock);
static LIST_HEAD(flow_cache_gc_list);

#define flow_cache_hash_size(cache) (1 << (cache)->hash_shift)
#define FLOW_HASH_RND_PERIOD        (10 * 60 * HZ)

static void flow_cache_new_hashrnd(unsigned long arg)
{
    struct flow_cache *fc = (void *) arg;
    int i;

    for_each_possible_cpu(i)
        per_cpu_ptr(fc->percpu, i)->hash_rnd_recalc = 1;

    fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
    add_timer(&fc->rnd_timer);
}

static int flow_entry_valid(struct flow_cache_entry *fle)
{
    if (atomic_read(&flow_cache_genid) != fle->genid)
        return 0;
    if (fle->object && !fle->object->ops->check(fle->object))
        return 0;
    return 1;
}

static void flow_entry_kill(struct flow_cache_entry *fle)
{
    if (fle->object)
        fle->object->ops->delete(fle->object);
    kmem_cache_free(flow_cachep, fle);
}

static void flow_cache_gc_task(struct work_struct *work)
{
    struct list_head gc_list;
    struct flow_cache_entry *fce, *n;

    INIT_LIST_HEAD(&gc_list);
    spin_lock_bh(&flow_cache_gc_lock);
    list_splice_tail_init(&flow_cache_gc_list, &gc_list);
    spin_unlock_bh(&flow_cache_gc_lock);

    list_for_each_entry_safe(fce, n, &gc_list, u.gc_list)
        flow_entry_kill(fce);
}
static DECLARE_WORK(flow_cache_gc_work, flow_cache_gc_task);

static void flow_cache_queue_garbage(struct flow_cache_percpu *fcp,
                     int deleted, struct list_head *gc_list)
{
    if (deleted) {
        fcp->hash_count -= deleted;
        spin_lock_bh(&flow_cache_gc_lock);
        list_splice_tail(gc_list, &flow_cache_gc_list);
        spin_unlock_bh(&flow_cache_gc_lock);
        schedule_work(&flow_cache_gc_work);
    }
}

static void __flow_cache_shrink(struct flow_cache *fc,
                struct flow_cache_percpu *fcp,
                int shrink_to)
{
    struct flow_cache_entry *fle;
    struct hlist_node *entry, *tmp;
    LIST_HEAD(gc_list);
    int i, deleted = 0;

    for (i = 0; i < flow_cache_hash_size(fc); i++) {
        int saved = 0;

        hlist_for_each_entry_safe(fle, entry, tmp,
                      &fcp->hash_table[i], u.hlist) {
            if (saved < shrink_to &&
                flow_entry_valid(fle)) {
                saved++;
            } else {
                deleted++;
                hlist_del(&fle->u.hlist);
                list_add_tail(&fle->u.gc_list, &gc_list);
            }
        }
    }

    flow_cache_queue_garbage(fcp, deleted, &gc_list);
}

static void flow_cache_shrink(struct flow_cache *fc,
                  struct flow_cache_percpu *fcp)
{
    int shrink_to = fc->low_watermark / flow_cache_hash_size(fc);

    __flow_cache_shrink(fc, fcp, shrink_to);
}

static void flow_new_hash_rnd(struct flow_cache *fc,
                  struct flow_cache_percpu *fcp)
{
    get_random_bytes(&fcp->hash_rnd, sizeof(u32));
    fcp->hash_rnd_recalc = 0;
    __flow_cache_shrink(fc, fcp, 0);
}

static u32 flow_hash_code(struct flow_cache *fc,
              struct flow_cache_percpu *fcp,
              const struct flowi *key,
              size_t keysize)
{
    const u32 *k = (const u32 *) key;
    const u32 length = keysize * sizeof(flow_compare_t) / sizeof(u32);

    return jhash2(k, length, fcp->hash_rnd)
        & (flow_cache_hash_size(fc) - 1);
}

/* I hear what you're saying, use memcmp.  But memcmp cannot make
 * important assumptions that we can here, such as alignment.
 */
static int flow_key_compare(const struct flowi *key1, const struct flowi *key2,
                size_t keysize)
{
    const flow_compare_t *k1, *k1_lim, *k2;

    k1 = (const flow_compare_t *) key1;
    k1_lim = k1 + keysize;

    k2 = (const flow_compare_t *) key2;

    do {
        if (*k1++ != *k2++)
            return 1;
    } while (k1 < k1_lim);

    return 0;
}

struct flow_cache_object *
flow_cache_lookup(struct net *net, const struct flowi *key, u16 family, u8 dir,
          flow_resolve_t resolver, void *ctx)
{
    struct flow_cache *fc = &flow_cache_global;
    struct flow_cache_percpu *fcp;
    struct flow_cache_entry *fle, *tfle;
    struct hlist_node *entry;
    struct flow_cache_object *flo;
    size_t keysize;
    unsigned int hash;

    local_bh_disable();
    fcp = this_cpu_ptr(fc->percpu);

    fle = NULL;
    flo = NULL;

    keysize = flow_key_size(family);
    if (!keysize)
        goto nocache;

    /* Packet really early in init?  Making flow_cache_init a
     * pre-smp initcall would solve this.  --RR */
    if (!fcp->hash_table)
        goto nocache;

    if (fcp->hash_rnd_recalc)
        flow_new_hash_rnd(fc, fcp);

    hash = flow_hash_code(fc, fcp, key, keysize);
    hlist_for_each_entry(tfle, entry, &fcp->hash_table[hash], u.hlist) {
        if (tfle->net == net &&
            tfle->family == family &&
            tfle->dir == dir &&
            flow_key_compare(key, &tfle->key, keysize) == 0) {
            fle = tfle;
            break;
        }
    }

    if (unlikely(!fle)) {
        if (fcp->hash_count > fc->high_watermark)
            flow_cache_shrink(fc, fcp);

        fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
        if (fle) {
            fle->net = net;
            fle->family = family;
            fle->dir = dir;
            memcpy(&fle->key, key, keysize * sizeof(flow_compare_t));
            fle->object = NULL;
            hlist_add_head(&fle->u.hlist, &fcp->hash_table[hash]);
            fcp->hash_count++;
        }
    } else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
        flo = fle->object;
        if (!flo)
            goto ret_object;
        flo = flo->ops->get(flo);
        if (flo)
            goto ret_object;
    } else if (fle->object) {
            flo = fle->object;
            flo->ops->delete(flo);
            fle->object = NULL;
    }

nocache:
    flo = NULL;
    if (fle) {
        flo = fle->object;
        fle->object = NULL;
    }
    flo = resolver(net, key, family, dir, flo, ctx);
    if (fle) {
        fle->genid = atomic_read(&flow_cache_genid);
        if (!IS_ERR(flo))
            fle->object = flo;
        else
            fle->genid--;
    } else {
        if (flo && !IS_ERR(flo))
            flo->ops->delete(flo);
    }
ret_object:
    local_bh_enable();
    return flo;
}
EXPORT_SYMBOL(flow_cache_lookup);

static void flow_cache_flush_tasklet(unsigned long data)
{
    struct flow_flush_info *info = (void *)data;
    struct flow_cache *fc = info->cache;
    struct flow_cache_percpu *fcp;
    struct flow_cache_entry *fle;
    struct hlist_node *entry, *tmp;
    LIST_HEAD(gc_list);
    int i, deleted = 0;

    fcp = this_cpu_ptr(fc->percpu);
    for (i = 0; i < flow_cache_hash_size(fc); i++) {
        hlist_for_each_entry_safe(fle, entry, tmp,
                      &fcp->hash_table[i], u.hlist) {
            if (flow_entry_valid(fle))
                continue;

            deleted++;
            hlist_del(&fle->u.hlist);
            list_add_tail(&fle->u.gc_list, &gc_list);
        }
    }

    flow_cache_queue_garbage(fcp, deleted, &gc_list);

    if (atomic_dec_and_test(&info->cpuleft))
        complete(&info->completion);
}

static void flow_cache_flush_per_cpu(void *data)
{
    struct flow_flush_info *info = data;
    int cpu;
    struct tasklet_struct *tasklet;

    cpu = smp_processor_id();
    tasklet = &per_cpu_ptr(info->cache->percpu, cpu)->flush_tasklet;
    tasklet->data = (unsigned long)info;
    tasklet_schedule(tasklet);
}

void flow_cache_flush(void)
{
    struct flow_flush_info info;
    static DEFINE_MUTEX(flow_flush_sem);

    /* Don't want cpus going down or up during this. */
    get_online_cpus();
    mutex_lock(&flow_flush_sem);
    info.cache = &flow_cache_global;
    atomic_set(&info.cpuleft, num_online_cpus());
    init_completion(&info.completion);

    local_bh_disable();
    smp_call_function(flow_cache_flush_per_cpu, &info, 0);
    flow_cache_flush_tasklet((unsigned long)&info);
    local_bh_enable();

    wait_for_completion(&info.completion);
    mutex_unlock(&flow_flush_sem);
    put_online_cpus();
}

static void flow_cache_flush_task(struct work_struct *work)
{
    flow_cache_flush();
}

static DECLARE_WORK(flow_cache_flush_work, flow_cache_flush_task);

void flow_cache_flush_deferred(void)
{
    schedule_work(&flow_cache_flush_work);
}

static int __cpuinit flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
{
    struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
    size_t sz = sizeof(struct hlist_head) * flow_cache_hash_size(fc);

    if (!fcp->hash_table) {
        fcp->hash_table = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
        if (!fcp->hash_table) {
            pr_err("NET: failed to allocate flow cache sz %zu\n", sz);
            return -ENOMEM;
        }
        fcp->hash_rnd_recalc = 1;
        fcp->hash_count = 0;
        tasklet_init(&fcp->flush_tasklet, flow_cache_flush_tasklet, 0);
    }
    return 0;
}

static int __cpuinit flow_cache_cpu(struct notifier_block *nfb,
              unsigned long action,
              void *hcpu)
{
    struct flow_cache *fc = container_of(nfb, struct flow_cache, hotcpu_notifier);
    int res, cpu = (unsigned long) hcpu;
    struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);

    switch (action) {
    case CPU_UP_PREPARE:
    case CPU_UP_PREPARE_FROZEN:
        res = flow_cache_cpu_prepare(fc, cpu);
        if (res)
            return notifier_from_errno(res);
        break;
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
        __flow_cache_shrink(fc, fcp, 0);
        break;
    }
    return NOTIFY_OK;
}

static int __init flow_cache_init(struct flow_cache *fc)
{
    int i;

    fc->hash_shift = 10;
    fc->low_watermark = 2 * flow_cache_hash_size(fc);
    fc->high_watermark = 4 * flow_cache_hash_size(fc);

    fc->percpu = alloc_percpu(struct flow_cache_percpu);
    if (!fc->percpu)
        return -ENOMEM;

    for_each_online_cpu(i) {
        if (flow_cache_cpu_prepare(fc, i))
            goto err;
    }
    fc->hotcpu_notifier = (struct notifier_block){
        .notifier_call = flow_cache_cpu,
    };
    register_hotcpu_notifier(&fc->hotcpu_notifier);

    setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
            (unsigned long) fc);
    fc->rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
    add_timer(&fc->rnd_timer);

    return 0;

err:
    for_each_possible_cpu(i) {
        struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
        kfree(fcp->hash_table);
        fcp->hash_table = NULL;
    }

    free_percpu(fc->percpu);
    fc->percpu = NULL;

    return -ENOMEM;
}

static int __init flow_cache_init_global(void)
{
    flow_cachep = kmem_cache_create("flow_cache",
                    sizeof(struct flow_cache_entry),
                    0, SLAB_PANIC, NULL);

    return flow_cache_init(&flow_cache_global);
}

module_init(flow_cache_init_global);