Linux-2.6.12-rc2

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / ipv4 / netfilter / ipt_hashlimit.c

/* iptables match extension to limit the number of packets per second
 * seperately for each hashbucket (sourceip/sourceport/dstip/dstport)
 *
 * (C) 2003-2004 by Harald Welte <laforge@netfilter.org>
 *
 * $Id: ipt_hashlimit.c 3244 2004-10-20 16:24:29Z laforge@netfilter.org $
 *
 * Development of this code was funded by Astaro AG, http://www.astaro.com/
 *
 * based on ipt_limit.c by:
 * Jérôme de Vivie      <devivie@info.enserb.u-bordeaux.fr>
 * Hervé Eychenne       <eychenne@info.enserb.u-bordeaux.fr>
 * Rusty Russell        <rusty@rustcorp.com.au>
 *
 * The general idea is to create a hash table for every dstip and have a
 * seperate limit counter per tuple.  This way you can do something like 'limit
 * the number of syn packets for each of my internal addresses.
 *
 * Ideally this would just be implemented as a general 'hash' match, which would
 * allow us to attach any iptables target to it's hash buckets.  But this is
 * not possible in the current iptables architecture.  As always, pkttables for
 * 2.7.x will help ;)
 */
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/sctp.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/list.h>

#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_hashlimit.h>
#include <linux/netfilter_ipv4/lockhelp.h>

/* FIXME: this is just for IP_NF_ASSERRT */
#include <linux/netfilter_ipv4/ip_conntrack.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("iptables match for limiting per hash-bucket");

/* need to declare this at the top */
static struct proc_dir_entry *hashlimit_procdir;
static struct file_operations dl_file_ops;

/* hash table crap */

struct dsthash_dst {
        u_int32_t src_ip;
        u_int32_t dst_ip;
        /* ports have to be consecutive !!! */
        u_int16_t src_port;
        u_int16_t dst_port;
};

struct dsthash_ent {
        /* static / read-only parts in the beginning */
        struct hlist_node node;
        struct dsthash_dst dst;

        /* modified structure members in the end */
        unsigned long expires;          /* precalculated expiry time */
        struct {
                unsigned long prev;     /* last modification */
                u_int32_t credit;
                u_int32_t credit_cap, cost;
        } rateinfo;
};

struct ipt_hashlimit_htable {
        struct hlist_node node;         /* global list of all htables */
        atomic_t use;

        struct hashlimit_cfg cfg;       /* config */

        /* used internally */
        spinlock_t lock;                /* lock for list_head */
        u_int32_t rnd;                  /* random seed for hash */
        struct timer_list timer;        /* timer for gc */
        atomic_t count;                 /* number entries in table */

        /* seq_file stuff */
        struct proc_dir_entry *pde;

        struct hlist_head hash[0];      /* hashtable itself */
};

static DECLARE_LOCK(hashlimit_lock);    /* protects htables list */
static DECLARE_MUTEX(hlimit_mutex);     /* additional checkentry protection */
static HLIST_HEAD(hashlimit_htables);
static kmem_cache_t *hashlimit_cachep;

static inline int dst_cmp(const struct dsthash_ent *ent, struct dsthash_dst *b)
{
        return (ent->dst.dst_ip == b->dst_ip 
                && ent->dst.dst_port == b->dst_port
                && ent->dst.src_port == b->src_port
                && ent->dst.src_ip == b->src_ip);
}

static inline u_int32_t
hash_dst(const struct ipt_hashlimit_htable *ht, const struct dsthash_dst *dst)
{
        return (jhash_3words(dst->dst_ip, (dst->dst_port<<16 | dst->src_port), 
                             dst->src_ip, ht->rnd) % ht->cfg.size);
}

static inline struct dsthash_ent *
__dsthash_find(const struct ipt_hashlimit_htable *ht, struct dsthash_dst *dst)
{
        struct dsthash_ent *ent;
        struct hlist_node *pos;
        u_int32_t hash = hash_dst(ht, dst);

        if (!hlist_empty(&ht->hash[hash]))
                hlist_for_each_entry(ent, pos, &ht->hash[hash], node) {
                        if (dst_cmp(ent, dst)) {
                                return ent;
                        }
                }
        
        return NULL;
}

/* allocate dsthash_ent, initialize dst, put in htable and lock it */
static struct dsthash_ent *
__dsthash_alloc_init(struct ipt_hashlimit_htable *ht, struct dsthash_dst *dst)
{
        struct dsthash_ent *ent;

        /* initialize hash with random val at the time we allocate
         * the first hashtable entry */
        if (!ht->rnd)
                get_random_bytes(&ht->rnd, 4);

        if (ht->cfg.max &&
            atomic_read(&ht->count) >= ht->cfg.max) {
                /* FIXME: do something. question is what.. */
                if (net_ratelimit())
                        printk(KERN_WARNING 
                                "ipt_hashlimit: max count of %u reached\n", 
                                ht->cfg.max);
                return NULL;
        }

        ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
        if (!ent) {
                if (net_ratelimit())
                        printk(KERN_ERR 
                                "ipt_hashlimit: can't allocate dsthash_ent\n");
                return NULL;
        }

        atomic_inc(&ht->count);

        ent->dst.dst_ip = dst->dst_ip;
        ent->dst.dst_port = dst->dst_port;
        ent->dst.src_ip = dst->src_ip;
        ent->dst.src_port = dst->src_port;

        hlist_add_head(&ent->node, &ht->hash[hash_dst(ht, dst)]);

        return ent;
}

static inline void 
__dsthash_free(struct ipt_hashlimit_htable *ht, struct dsthash_ent *ent)
{
        hlist_del(&ent->node);
        kmem_cache_free(hashlimit_cachep, ent);
        atomic_dec(&ht->count);
}
static void htable_gc(unsigned long htlong);

static int htable_create(struct ipt_hashlimit_info *minfo)
{
        int i;
        unsigned int size;
        struct ipt_hashlimit_htable *hinfo;

        if (minfo->cfg.size)
                size = minfo->cfg.size;
        else {
                size = (((num_physpages << PAGE_SHIFT) / 16384)
                         / sizeof(struct list_head));
                if (num_physpages > (1024 * 1024 * 1024 / PAGE_SIZE))
                        size = 8192;
                if (size < 16)
                        size = 16;
        }
        /* FIXME: don't use vmalloc() here or anywhere else -HW */
        hinfo = vmalloc(sizeof(struct ipt_hashlimit_htable)
                        + (sizeof(struct list_head) * size));
        if (!hinfo) {
                printk(KERN_ERR "ipt_hashlimit: Unable to create hashtable\n");
                return -1;
        }
        minfo->hinfo = hinfo;

        /* copy match config into hashtable config */
        memcpy(&hinfo->cfg, &minfo->cfg, sizeof(hinfo->cfg));
        hinfo->cfg.size = size;
        if (!hinfo->cfg.max)
                hinfo->cfg.max = 8 * hinfo->cfg.size;
        else if (hinfo->cfg.max < hinfo->cfg.size)
                hinfo->cfg.max = hinfo->cfg.size;

        for (i = 0; i < hinfo->cfg.size; i++)
                INIT_HLIST_HEAD(&hinfo->hash[i]);

        atomic_set(&hinfo->count, 0);
        atomic_set(&hinfo->use, 1);
        hinfo->rnd = 0;
        spin_lock_init(&hinfo->lock);
        hinfo->pde = create_proc_entry(minfo->name, 0, hashlimit_procdir);
        if (!hinfo->pde) {
                vfree(hinfo);
                return -1;
        }
        hinfo->pde->proc_fops = &dl_file_ops;
        hinfo->pde->data = hinfo;

        init_timer(&hinfo->timer);
        hinfo->timer.expires = jiffies + msecs_to_jiffies(hinfo->cfg.gc_interval);
        hinfo->timer.data = (unsigned long )hinfo;
        hinfo->timer.function = htable_gc;
        add_timer(&hinfo->timer);

        LOCK_BH(&hashlimit_lock);
        hlist_add_head(&hinfo->node, &hashlimit_htables);
        UNLOCK_BH(&hashlimit_lock);

        return 0;
}

static int select_all(struct ipt_hashlimit_htable *ht, struct dsthash_ent *he)
{
        return 1;
}

static int select_gc(struct ipt_hashlimit_htable *ht, struct dsthash_ent *he)
{
        return (jiffies >= he->expires);
}

static void htable_selective_cleanup(struct ipt_hashlimit_htable *ht,
                                int (*select)(struct ipt_hashlimit_htable *ht, 
                                              struct dsthash_ent *he))
{
        int i;

        IP_NF_ASSERT(ht->cfg.size && ht->cfg.max);

        /* lock hash table and iterate over it */
        spin_lock_bh(&ht->lock);
        for (i = 0; i < ht->cfg.size; i++) {
                struct dsthash_ent *dh;
                struct hlist_node *pos, *n;
                hlist_for_each_entry_safe(dh, pos, n, &ht->hash[i], node) {
                        if ((*select)(ht, dh))
                                __dsthash_free(ht, dh);
                }
        }
        spin_unlock_bh(&ht->lock);
}

/* hash table garbage collector, run by timer */
static void htable_gc(unsigned long htlong)
{
        struct ipt_hashlimit_htable *ht = (struct ipt_hashlimit_htable *)htlong;

        htable_selective_cleanup(ht, select_gc);

        /* re-add the timer accordingly */
        ht->timer.expires = jiffies + msecs_to_jiffies(ht->cfg.gc_interval);
        add_timer(&ht->timer);
}

static void htable_destroy(struct ipt_hashlimit_htable *hinfo)
{
        /* remove timer, if it is pending */
        if (timer_pending(&hinfo->timer))
                del_timer(&hinfo->timer);

        /* remove proc entry */
        remove_proc_entry(hinfo->pde->name, hashlimit_procdir);

        htable_selective_cleanup(hinfo, select_all);
        vfree(hinfo);
}

static struct ipt_hashlimit_htable *htable_find_get(char *name)
{
        struct ipt_hashlimit_htable *hinfo;
        struct hlist_node *pos;

        LOCK_BH(&hashlimit_lock);
        hlist_for_each_entry(hinfo, pos, &hashlimit_htables, node) {
                if (!strcmp(name, hinfo->pde->name)) {
                        atomic_inc(&hinfo->use);
                        UNLOCK_BH(&hashlimit_lock);
                        return hinfo;
                }
        }
        UNLOCK_BH(&hashlimit_lock);

        return NULL;
}

static void htable_put(struct ipt_hashlimit_htable *hinfo)
{
        if (atomic_dec_and_test(&hinfo->use)) {
                LOCK_BH(&hashlimit_lock);
                hlist_del(&hinfo->node);
                UNLOCK_BH(&hashlimit_lock);
                htable_destroy(hinfo);
        }
}


/* The algorithm used is the Simple Token Bucket Filter (TBF)
 * see net/sched/sch_tbf.c in the linux source tree
 */

/* Rusty: This is my (non-mathematically-inclined) understanding of
   this algorithm.  The `average rate' in jiffies becomes your initial
   amount of credit `credit' and the most credit you can ever have
   `credit_cap'.  The `peak rate' becomes the cost of passing the
   test, `cost'.

   `prev' tracks the last packet hit: you gain one credit per jiffy.
   If you get credit balance more than this, the extra credit is
   discarded.  Every time the match passes, you lose `cost' credits;
   if you don't have that many, the test fails.

   See Alexey's formal explanation in net/sched/sch_tbf.c.

   To get the maximum range, we multiply by this factor (ie. you get N
   credits per jiffy).  We want to allow a rate as low as 1 per day
   (slowest userspace tool allows), which means
   CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32 ie.
*/
#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))

/* Repeated shift and or gives us all 1s, final shift and add 1 gives
 * us the power of 2 below the theoretical max, so GCC simply does a
 * shift. */
#define _POW2_BELOW2(x) ((x)|((x)>>1))
#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)

#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)

/* Precision saver. */
static inline u_int32_t
user2credits(u_int32_t user)
{
        /* If multiplying would overflow... */
        if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
                /* Divide first. */
                return (user / IPT_HASHLIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;

        return (user * HZ * CREDITS_PER_JIFFY) / IPT_HASHLIMIT_SCALE;
}

static inline void rateinfo_recalc(struct dsthash_ent *dh, unsigned long now)
{
        dh->rateinfo.credit += (now - xchg(&dh->rateinfo.prev, now)) 
                                        * CREDITS_PER_JIFFY;
        if (dh->rateinfo.credit > dh->rateinfo.credit_cap)
                dh->rateinfo.credit = dh->rateinfo.credit_cap;
}

static inline int get_ports(const struct sk_buff *skb, int offset, 
                            u16 ports[2])
{
        union {
                struct tcphdr th;
                struct udphdr uh;
                sctp_sctphdr_t sctph;
        } hdr_u, *ptr_u;

        /* Must not be a fragment. */
        if (offset)
                return 1;

        /* Must be big enough to read ports (both UDP and TCP have
           them at the start). */
        ptr_u = skb_header_pointer(skb, skb->nh.iph->ihl*4, 8, &hdr_u); 
        if (!ptr_u)
                return 1;

        switch (skb->nh.iph->protocol) {
                case IPPROTO_TCP:
                        ports[0] = ptr_u->th.source;
                        ports[1] = ptr_u->th.dest;
                        break;
                case IPPROTO_UDP:
                        ports[0] = ptr_u->uh.source;
                        ports[1] = ptr_u->uh.dest;
                        break;
                case IPPROTO_SCTP:
                        ports[0] = ptr_u->sctph.source;
                        ports[1] = ptr_u->sctph.dest;
                        break;
                default:
                        /* all other protocols don't supprot per-port hash
                         * buckets */
                        ports[0] = ports[1] = 0;
                        break;
        }

        return 0;
}


static int
hashlimit_match(const struct sk_buff *skb,
                const struct net_device *in,
                const struct net_device *out,
                const void *matchinfo,
                int offset,
                int *hotdrop)
{
        struct ipt_hashlimit_info *r = 
                ((struct ipt_hashlimit_info *)matchinfo)->u.master;
        struct ipt_hashlimit_htable *hinfo = r->hinfo;
        unsigned long now = jiffies;
        struct dsthash_ent *dh;
        struct dsthash_dst dst;

        /* build 'dst' according to hinfo->cfg and current packet */
        memset(&dst, 0, sizeof(dst));
        if (hinfo->cfg.mode & IPT_HASHLIMIT_HASH_DIP)
                dst.dst_ip = skb->nh.iph->daddr;
        if (hinfo->cfg.mode & IPT_HASHLIMIT_HASH_SIP)
                dst.src_ip = skb->nh.iph->saddr;
        if (hinfo->cfg.mode & IPT_HASHLIMIT_HASH_DPT
            ||hinfo->cfg.mode & IPT_HASHLIMIT_HASH_SPT) {
                u_int16_t ports[2];
                if (get_ports(skb, offset, ports)) {
                        /* We've been asked to examine this packet, and we
                          can't.  Hence, no choice but to drop. */
                        *hotdrop = 1;
                        return 0;
                }
                if (hinfo->cfg.mode & IPT_HASHLIMIT_HASH_SPT)
                        dst.src_port = ports[0];
                if (hinfo->cfg.mode & IPT_HASHLIMIT_HASH_DPT)
                        dst.dst_port = ports[1];
        } 

        spin_lock_bh(&hinfo->lock);
        dh = __dsthash_find(hinfo, &dst);
        if (!dh) {
                dh = __dsthash_alloc_init(hinfo, &dst);

                if (!dh) {
                        /* enomem... don't match == DROP */
                        if (net_ratelimit())
                                printk(KERN_ERR "%s: ENOMEM\n", __FUNCTION__);
                        spin_unlock_bh(&hinfo->lock);
                        return 0;
                }

                dh->expires = jiffies + msecs_to_jiffies(hinfo->cfg.expire);

                dh->rateinfo.prev = jiffies;
                dh->rateinfo.credit = user2credits(hinfo->cfg.avg * 
                                                        hinfo->cfg.burst);
                dh->rateinfo.credit_cap = user2credits(hinfo->cfg.avg * 
                                                        hinfo->cfg.burst);
                dh->rateinfo.cost = user2credits(hinfo->cfg.avg);

                spin_unlock_bh(&hinfo->lock);
                return 1;
        }

        /* update expiration timeout */
        dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);

        rateinfo_recalc(dh, now);
        if (dh->rateinfo.credit >= dh->rateinfo.cost) {
                /* We're underlimit. */
                dh->rateinfo.credit -= dh->rateinfo.cost;
                spin_unlock_bh(&hinfo->lock);
                return 1;
        }

        spin_unlock_bh(&hinfo->lock);

        /* default case: we're overlimit, thus don't match */
        return 0;
}

static int
hashlimit_checkentry(const char *tablename,
                     const struct ipt_ip *ip,
                     void *matchinfo,
                     unsigned int matchsize,
                     unsigned int hook_mask)
{
        struct ipt_hashlimit_info *r = matchinfo;

        if (matchsize != IPT_ALIGN(sizeof(struct ipt_hashlimit_info)))
                return 0;

        /* Check for overflow. */
        if (r->cfg.burst == 0
            || user2credits(r->cfg.avg * r->cfg.burst) < 
                                        user2credits(r->cfg.avg)) {
                printk(KERN_ERR "ipt_hashlimit: Overflow, try lower: %u/%u\n",
                       r->cfg.avg, r->cfg.burst);
                return 0;
        }

        if (r->cfg.mode == 0 
            || r->cfg.mode > (IPT_HASHLIMIT_HASH_DPT
                          |IPT_HASHLIMIT_HASH_DIP
                          |IPT_HASHLIMIT_HASH_SIP
                          |IPT_HASHLIMIT_HASH_SPT))
                return 0;

        if (!r->cfg.gc_interval)
                return 0;
        
        if (!r->cfg.expire)
                return 0;

        /* This is the best we've got: We cannot release and re-grab lock,
         * since checkentry() is called before ip_tables.c grabs ipt_mutex.  
         * We also cannot grab the hashtable spinlock, since htable_create will 
         * call vmalloc, and that can sleep.  And we cannot just re-search
         * the list of htable's in htable_create(), since then we would
         * create duplicate proc files. -HW */
        down(&hlimit_mutex);
        r->hinfo = htable_find_get(r->name);
        if (!r->hinfo && (htable_create(r) != 0)) {
                up(&hlimit_mutex);
                return 0;
        }
        up(&hlimit_mutex);

        /* Ugly hack: For SMP, we only want to use one set */
        r->u.master = r;

        return 1;
}

static void
hashlimit_destroy(void *matchinfo, unsigned int matchsize)
{
        struct ipt_hashlimit_info *r = (struct ipt_hashlimit_info *) matchinfo;

        htable_put(r->hinfo);
}

static struct ipt_match ipt_hashlimit = { 
        .name = "hashlimit", 
        .match = hashlimit_match, 
        .checkentry = hashlimit_checkentry, 
        .destroy = hashlimit_destroy,
        .me = THIS_MODULE 
};

/* PROC stuff */

static void *dl_seq_start(struct seq_file *s, loff_t *pos)
{
        struct proc_dir_entry *pde = s->private;
        struct ipt_hashlimit_htable *htable = pde->data;
        unsigned int *bucket;

        spin_lock_bh(&htable->lock);
        if (*pos >= htable->cfg.size)
                return NULL;

        bucket = kmalloc(sizeof(unsigned int), GFP_ATOMIC);
        if (!bucket)
                return ERR_PTR(-ENOMEM);

        *bucket = *pos;
        return bucket;
}

static void *dl_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
        struct proc_dir_entry *pde = s->private;
        struct ipt_hashlimit_htable *htable = pde->data;
        unsigned int *bucket = (unsigned int *)v;

        *pos = ++(*bucket);
        if (*pos >= htable->cfg.size) {
                kfree(v);
                return NULL;
        }
        return bucket;
}

static void dl_seq_stop(struct seq_file *s, void *v)
{
        struct proc_dir_entry *pde = s->private;
        struct ipt_hashlimit_htable *htable = pde->data;
        unsigned int *bucket = (unsigned int *)v;

        kfree(bucket);

        spin_unlock_bh(&htable->lock);
}

static inline int dl_seq_real_show(struct dsthash_ent *ent, struct seq_file *s)
{
        /* recalculate to show accurate numbers */
        rateinfo_recalc(ent, jiffies);

        return seq_printf(s, "%ld %u.%u.%u.%u:%u->%u.%u.%u.%u:%u %u %u %u\n",
                        (long)(ent->expires - jiffies)/HZ,
                        NIPQUAD(ent->dst.src_ip), ntohs(ent->dst.src_port),
                        NIPQUAD(ent->dst.dst_ip), ntohs(ent->dst.dst_port),
                        ent->rateinfo.credit, ent->rateinfo.credit_cap,
                        ent->rateinfo.cost);
}

static int dl_seq_show(struct seq_file *s, void *v)
{
        struct proc_dir_entry *pde = s->private;
        struct ipt_hashlimit_htable *htable = pde->data;
        unsigned int *bucket = (unsigned int *)v;
        struct dsthash_ent *ent;
        struct hlist_node *pos;

        if (!hlist_empty(&htable->hash[*bucket]))
                hlist_for_each_entry(ent, pos, &htable->hash[*bucket], node) {
                        if (dl_seq_real_show(ent, s)) {
                                /* buffer was filled and unable to print that tuple */
                                return 1;
                        }
                }
        
        return 0;
}

static struct seq_operations dl_seq_ops = {
        .start = dl_seq_start,
        .next  = dl_seq_next,
        .stop  = dl_seq_stop,
        .show  = dl_seq_show
};

static int dl_proc_open(struct inode *inode, struct file *file)
{
        int ret = seq_open(file, &dl_seq_ops);

        if (!ret) {
                struct seq_file *sf = file->private_data;
                sf->private = PDE(inode);
        }
        return ret;
}

static struct file_operations dl_file_ops = {
        .owner   = THIS_MODULE,
        .open    = dl_proc_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release
};

static int init_or_fini(int fini)
{
        int ret = 0;

        if (fini)
                goto cleanup;

        if (ipt_register_match(&ipt_hashlimit)) {
                ret = -EINVAL;
                goto cleanup_nothing;
        }

        hashlimit_cachep = kmem_cache_create("ipt_hashlimit",
                                            sizeof(struct dsthash_ent), 0,
                                            0, NULL, NULL);
        if (!hashlimit_cachep) {
                printk(KERN_ERR "Unable to create ipt_hashlimit slab cache\n");
                ret = -ENOMEM;
                goto cleanup_unreg_match;
        }

        hashlimit_procdir = proc_mkdir("ipt_hashlimit", proc_net);
        if (!hashlimit_procdir) {
                printk(KERN_ERR "Unable to create proc dir entry\n");
                ret = -ENOMEM;
                goto cleanup_free_slab;
        }

        return ret;

cleanup:
        remove_proc_entry("ipt_hashlimit", proc_net);
cleanup_free_slab:
        kmem_cache_destroy(hashlimit_cachep);
cleanup_unreg_match:
        ipt_unregister_match(&ipt_hashlimit);
cleanup_nothing:
        return ret;
        
}

static int __init init(void)
{
        return init_or_fini(0);
}

static void __exit fini(void)
{
        init_or_fini(1);
}

module_init(init);
module_exit(fini);