/* flow.c: Generic flow cache.
 *
 * Copyright (C) 2003 Alexey N. Kuznetsov (kuznet@ms2.inr.ac.ru)
 * Copyright (C) 2003 David S. Miller (davem@redhat.com)
 */

#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 <asm/atomic.h>
#include <linux/security.h>

struct flow_cache_entry {
        struct flow_cache_entry *next;
        u16                     family;
        u8                      dir;
        u32                     genid;
        struct flowi            key;
        void                    *object;
        atomic_t                *object_ref;
};

atomic_t flow_cache_genid = ATOMIC_INIT(0);

static u32 flow_hash_shift;
#define flow_hash_size  (1 << flow_hash_shift)
static DEFINE_PER_CPU(struct flow_cache_entry **, flow_tables) = { NULL };

#define flow_table(cpu) (per_cpu(flow_tables, cpu))

static struct kmem_cache *flow_cachep __read_mostly;

static int flow_lwm, flow_hwm;

struct flow_percpu_info {
        int hash_rnd_recalc;
        u32 hash_rnd;
        int count;
};
static DEFINE_PER_CPU(struct flow_percpu_info, flow_hash_info) = { 0 };

#define flow_hash_rnd_recalc(cpu) \
        (per_cpu(flow_hash_info, cpu).hash_rnd_recalc)
#define flow_hash_rnd(cpu) \
        (per_cpu(flow_hash_info, cpu).hash_rnd)
#define flow_count(cpu) \
        (per_cpu(flow_hash_info, cpu).count)

static struct timer_list flow_hash_rnd_timer;

#define FLOW_HASH_RND_PERIOD    (10 * 60 * HZ)

struct flow_flush_info {
        atomic_t cpuleft;
        struct completion completion;
};
static DEFINE_PER_CPU(struct tasklet_struct, flow_flush_tasklets) = { NULL };

#define flow_flush_tasklet(cpu) (&per_cpu(flow_flush_tasklets, cpu))

static void flow_cache_new_hashrnd(unsigned long arg)
{
        int i;

        for_each_possible_cpu(i)
                flow_hash_rnd_recalc(i) = 1;

        flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
        add_timer(&flow_hash_rnd_timer);
}

static void flow_entry_kill(int cpu, struct flow_cache_entry *fle)
{
        if (fle->object)
                atomic_dec(fle->object_ref);
        kmem_cache_free(flow_cachep, fle);
        flow_count(cpu)--;
}

static void __flow_cache_shrink(int cpu, int shrink_to)
{
        struct flow_cache_entry *fle, **flp;
        int i;

        for (i = 0; i < flow_hash_size; i++) {
                int k = 0;

                flp = &flow_table(cpu)[i];
                while ((fle = *flp) != NULL && k < shrink_to) {
                        k++;
                        flp = &fle->next;
                }
                while ((fle = *flp) != NULL) {
                        *flp = fle->next;
                        flow_entry_kill(cpu, fle);
                }
        }
}

static void flow_cache_shrink(int cpu)
{
        int shrink_to = flow_lwm / flow_hash_size;

        __flow_cache_shrink(cpu, shrink_to);
}

static void flow_new_hash_rnd(int cpu)
{
        get_random_bytes(&flow_hash_rnd(cpu), sizeof(u32));
        flow_hash_rnd_recalc(cpu) = 0;

        __flow_cache_shrink(cpu, 0);
}

static u32 flow_hash_code(struct flowi *key, int cpu)
{
        u32 *k = (u32 *) key;

        return (jhash2(k, (sizeof(*key) / sizeof(u32)), flow_hash_rnd(cpu)) &
                (flow_hash_size - 1));
}

#if (BITS_PER_LONG == 64)
typedef u64 flow_compare_t;
#else
typedef u32 flow_compare_t;
#endif

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

        BUILD_BUG_ON(sizeof(struct flowi) % sizeof(flow_compare_t));

        k1 = (flow_compare_t *) key1;
        k1_lim = k1 + n_elem;

        k2 = (flow_compare_t *) key2;

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

        return 0;
}

void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
                        flow_resolve_t resolver)
{
        struct flow_cache_entry *fle, **head;
        unsigned int hash;
        int cpu;

        local_bh_disable();
        cpu = smp_processor_id();

        fle = NULL;
        /* Packet really early in init?  Making flow_cache_init a
         * pre-smp initcall would solve this.  --RR */
        if (!flow_table(cpu))
                goto nocache;

        if (flow_hash_rnd_recalc(cpu))
                flow_new_hash_rnd(cpu);
        hash = flow_hash_code(key, cpu);

        head = &flow_table(cpu)[hash];
        for (fle = *head; fle; fle = fle->next) {
                if (fle->family == family &&
                    fle->dir == dir &&
                    flow_key_compare(key, &fle->key) == 0) {
                        if (fle->genid == atomic_read(&flow_cache_genid)) {
                                void *ret = fle->object;

                                if (ret)
                                        atomic_inc(fle->object_ref);
                                local_bh_enable();

                                return ret;
                        }
                        break;
                }
        }

        if (!fle) {
                if (flow_count(cpu) > flow_hwm)
                        flow_cache_shrink(cpu);

                fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC);
                if (fle) {
                        fle->next = *head;
                        *head = fle;
                        fle->family = family;
                        fle->dir = dir;
                        memcpy(&fle->key, key, sizeof(*key));
                        fle->object = NULL;
                        flow_count(cpu)++;
                }
        }

nocache:
        {
                int err;
                void *obj;
                atomic_t *obj_ref;

                err = resolver(net, key, family, dir, &obj, &obj_ref);

                if (fle && !err) {
                        fle->genid = atomic_read(&flow_cache_genid);

                        if (fle->object)
                                atomic_dec(fle->object_ref);

                        fle->object = obj;
                        fle->object_ref = obj_ref;
                        if (obj)
                                atomic_inc(fle->object_ref);
                }
                local_bh_enable();

                if (err)
                        obj = ERR_PTR(err);
                return obj;
        }
}

static void flow_cache_flush_tasklet(unsigned long data)
{
        struct flow_flush_info *info = (void *)data;
        int i;
        int cpu;

        cpu = smp_processor_id();
        for (i = 0; i < flow_hash_size; i++) {
                struct flow_cache_entry *fle;

                fle = flow_table(cpu)[i];
                for (; fle; fle = fle->next) {
                        unsigned genid = atomic_read(&flow_cache_genid);

                        if (!fle->object || fle->genid == genid)
                                continue;

                        fle->object = NULL;
                        atomic_dec(fle->object_ref);
                }
        }

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

static void flow_cache_flush_per_cpu(void *) __attribute__((__unused__));
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 = flow_flush_tasklet(cpu);
        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);
        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 __init flow_cache_cpu_prepare(int cpu)
{
        struct tasklet_struct *tasklet;
        unsigned long order;

        for (order = 0;
             (PAGE_SIZE << order) <
                     (sizeof(struct flow_cache_entry *)*flow_hash_size);
             order++)
                /* NOTHING */;

        flow_table(cpu) = (struct flow_cache_entry **)
                __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
        if (!flow_table(cpu))
                panic("NET: failed to allocate flow cache order %lu\n", order);

        flow_hash_rnd_recalc(cpu) = 1;
        flow_count(cpu) = 0;

        tasklet = flow_flush_tasklet(cpu);
        tasklet_init(tasklet, flow_cache_flush_tasklet, 0);
}

static int flow_cache_cpu(struct notifier_block *nfb,
                          unsigned long action,
                          void *hcpu)
{
        if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
                __flow_cache_shrink((unsigned long)hcpu, 0);
        return NOTIFY_OK;
}

static int __init flow_cache_init(void)
{
        int i;

        flow_cachep = kmem_cache_create("flow_cache",
                                        sizeof(struct flow_cache_entry),
                                        0, SLAB_PANIC,
                                        NULL);
        flow_hash_shift = 10;
        flow_lwm = 2 * flow_hash_size;
        flow_hwm = 4 * flow_hash_size;

        setup_timer(&flow_hash_rnd_timer, flow_cache_new_hashrnd, 0);
        flow_hash_rnd_timer.expires = jiffies + FLOW_HASH_RND_PERIOD;
        add_timer(&flow_hash_rnd_timer);

        for_each_possible_cpu(i)
                flow_cache_cpu_prepare(i);

        hotcpu_notifier(flow_cache_cpu, 0);
        return 0;
}

module_init(flow_cache_init);

EXPORT_SYMBOL(flow_cache_genid);
EXPORT_SYMBOL(flow_cache_lookup);