2 * xt_hashlimit - Netfilter module to limit the number of packets per time
3 * separately for each hashbucket (sourceip/sourceport/dstip/dstport)
5 * (C) 2003-2004 by Harald Welte <laforge@netfilter.org>
6 * Copyright © CC Computer Consultants GmbH, 2007 - 2008
8 * Development of this code was funded by Astaro AG, http://www.astaro.com/
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/module.h>
12 #include <linux/spinlock.h>
13 #include <linux/random.h>
14 #include <linux/jhash.h>
15 #include <linux/slab.h>
16 #include <linux/vmalloc.h>
17 #include <linux/proc_fs.h>
18 #include <linux/seq_file.h>
19 #include <linux/list.h>
20 #include <linux/skbuff.h>
24 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
25 #include <linux/ipv6.h>
29 #include <net/net_namespace.h>
30 #include <net/netns/generic.h>
32 #include <linux/netfilter/x_tables.h>
33 #include <linux/netfilter_ipv4/ip_tables.h>
34 #include <linux/netfilter_ipv6/ip6_tables.h>
35 #include <linux/netfilter/xt_hashlimit.h>
36 #include <linux/mutex.h>
38 MODULE_LICENSE("GPL");
39 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
40 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
41 MODULE_DESCRIPTION("Xtables: per hash-bucket rate-limit match");
42 MODULE_ALIAS("ipt_hashlimit");
43 MODULE_ALIAS("ip6t_hashlimit");
45 struct hashlimit_net {
46 struct hlist_head htables;
47 struct proc_dir_entry *ipt_hashlimit;
48 struct proc_dir_entry *ip6t_hashlimit;
51 static int hashlimit_net_id;
52 static inline struct hashlimit_net *hashlimit_pernet(struct net *net)
54 return net_generic(net, hashlimit_net_id);
57 /* need to declare this at the top */
58 static const struct file_operations dl_file_ops;
67 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
79 /* static / read-only parts in the beginning */
80 struct hlist_node node;
81 struct dsthash_dst dst;
83 /* modified structure members in the end */
85 unsigned long expires; /* precalculated expiry time */
87 unsigned long prev; /* last modification */
89 u_int32_t credit_cap, cost;
94 struct xt_hashlimit_htable {
95 struct hlist_node node; /* global list of all htables */
100 struct hashlimit_cfg1 cfg; /* config */
102 /* used internally */
103 spinlock_t lock; /* lock for list_head */
104 u_int32_t rnd; /* random seed for hash */
105 unsigned int count; /* number entries in table */
106 struct timer_list timer; /* timer for gc */
109 struct proc_dir_entry *pde;
112 struct hlist_head hash[0]; /* hashtable itself */
115 static DEFINE_MUTEX(hashlimit_mutex); /* protects htables list */
116 static struct kmem_cache *hashlimit_cachep __read_mostly;
118 static inline bool dst_cmp(const struct dsthash_ent *ent,
119 const struct dsthash_dst *b)
121 return !memcmp(&ent->dst, b, sizeof(ent->dst));
125 hash_dst(const struct xt_hashlimit_htable *ht, const struct dsthash_dst *dst)
127 u_int32_t hash = jhash2((const u32 *)dst,
128 sizeof(*dst)/sizeof(u32),
131 * Instead of returning hash % ht->cfg.size (implying a divide)
132 * we return the high 32 bits of the (hash * ht->cfg.size) that will
133 * give results between [0 and cfg.size-1] and same hash distribution,
134 * but using a multiply, less expensive than a divide
136 return ((u64)hash * ht->cfg.size) >> 32;
139 static struct dsthash_ent *
140 dsthash_find(const struct xt_hashlimit_htable *ht,
141 const struct dsthash_dst *dst)
143 struct dsthash_ent *ent;
144 struct hlist_node *pos;
145 u_int32_t hash = hash_dst(ht, dst);
147 if (!hlist_empty(&ht->hash[hash])) {
148 hlist_for_each_entry_rcu(ent, pos, &ht->hash[hash], node)
149 if (dst_cmp(ent, dst)) {
150 spin_lock(&ent->lock);
157 /* allocate dsthash_ent, initialize dst, put in htable and lock it */
158 static struct dsthash_ent *
159 dsthash_alloc_init(struct xt_hashlimit_htable *ht,
160 const struct dsthash_dst *dst)
162 struct dsthash_ent *ent;
164 spin_lock(&ht->lock);
165 /* initialize hash with random val at the time we allocate
166 * the first hashtable entry */
167 if (unlikely(!ht->rnd_initialized)) {
168 get_random_bytes(&ht->rnd, sizeof(ht->rnd));
169 ht->rnd_initialized = true;
172 if (ht->cfg.max && ht->count >= ht->cfg.max) {
173 /* FIXME: do something. question is what.. */
175 pr_err("max count of %u reached\n", ht->cfg.max);
178 ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
180 memcpy(&ent->dst, dst, sizeof(ent->dst));
181 spin_lock_init(&ent->lock);
183 spin_lock(&ent->lock);
184 hlist_add_head_rcu(&ent->node, &ht->hash[hash_dst(ht, dst)]);
187 spin_unlock(&ht->lock);
191 static void dsthash_free_rcu(struct rcu_head *head)
193 struct dsthash_ent *ent = container_of(head, struct dsthash_ent, rcu);
195 kmem_cache_free(hashlimit_cachep, ent);
199 dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
201 hlist_del_rcu(&ent->node);
202 call_rcu_bh(&ent->rcu, dsthash_free_rcu);
205 static void htable_gc(unsigned long htlong);
207 static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo,
210 struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
211 struct xt_hashlimit_htable *hinfo;
215 if (minfo->cfg.size) {
216 size = minfo->cfg.size;
218 size = (totalram_pages << PAGE_SHIFT) / 16384 /
219 sizeof(struct list_head);
220 if (totalram_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
225 /* FIXME: don't use vmalloc() here or anywhere else -HW */
226 hinfo = vmalloc(sizeof(struct xt_hashlimit_htable) +
227 sizeof(struct list_head) * size);
230 minfo->hinfo = hinfo;
232 /* copy match config into hashtable config */
233 memcpy(&hinfo->cfg, &minfo->cfg, sizeof(hinfo->cfg));
234 hinfo->cfg.size = size;
235 if (hinfo->cfg.max == 0)
236 hinfo->cfg.max = 8 * hinfo->cfg.size;
237 else if (hinfo->cfg.max < hinfo->cfg.size)
238 hinfo->cfg.max = hinfo->cfg.size;
240 for (i = 0; i < hinfo->cfg.size; i++)
241 INIT_HLIST_HEAD(&hinfo->hash[i]);
245 hinfo->family = family;
246 hinfo->rnd_initialized = false;
247 spin_lock_init(&hinfo->lock);
249 hinfo->pde = proc_create_data(minfo->name, 0,
250 (family == NFPROTO_IPV4) ?
251 hashlimit_net->ipt_hashlimit : hashlimit_net->ip6t_hashlimit,
252 &dl_file_ops, hinfo);
253 if (hinfo->pde == NULL) {
259 setup_timer(&hinfo->timer, htable_gc, (unsigned long)hinfo);
260 hinfo->timer.expires = jiffies + msecs_to_jiffies(hinfo->cfg.gc_interval);
261 add_timer(&hinfo->timer);
263 hlist_add_head(&hinfo->node, &hashlimit_net->htables);
268 static bool select_all(const struct xt_hashlimit_htable *ht,
269 const struct dsthash_ent *he)
274 static bool select_gc(const struct xt_hashlimit_htable *ht,
275 const struct dsthash_ent *he)
277 return time_after_eq(jiffies, he->expires);
280 static void htable_selective_cleanup(struct xt_hashlimit_htable *ht,
281 bool (*select)(const struct xt_hashlimit_htable *ht,
282 const struct dsthash_ent *he))
286 /* lock hash table and iterate over it */
287 spin_lock_bh(&ht->lock);
288 for (i = 0; i < ht->cfg.size; i++) {
289 struct dsthash_ent *dh;
290 struct hlist_node *pos, *n;
291 hlist_for_each_entry_safe(dh, pos, n, &ht->hash[i], node) {
292 if ((*select)(ht, dh))
293 dsthash_free(ht, dh);
296 spin_unlock_bh(&ht->lock);
299 /* hash table garbage collector, run by timer */
300 static void htable_gc(unsigned long htlong)
302 struct xt_hashlimit_htable *ht = (struct xt_hashlimit_htable *)htlong;
304 htable_selective_cleanup(ht, select_gc);
306 /* re-add the timer accordingly */
307 ht->timer.expires = jiffies + msecs_to_jiffies(ht->cfg.gc_interval);
308 add_timer(&ht->timer);
311 static void htable_destroy(struct xt_hashlimit_htable *hinfo)
313 struct hashlimit_net *hashlimit_net = hashlimit_pernet(hinfo->net);
314 struct proc_dir_entry *parent;
316 del_timer_sync(&hinfo->timer);
318 if (hinfo->family == NFPROTO_IPV4)
319 parent = hashlimit_net->ipt_hashlimit;
321 parent = hashlimit_net->ip6t_hashlimit;
322 remove_proc_entry(hinfo->pde->name, parent);
323 htable_selective_cleanup(hinfo, select_all);
327 static struct xt_hashlimit_htable *htable_find_get(struct net *net,
331 struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
332 struct xt_hashlimit_htable *hinfo;
333 struct hlist_node *pos;
335 hlist_for_each_entry(hinfo, pos, &hashlimit_net->htables, node) {
336 if (!strcmp(name, hinfo->pde->name) &&
337 hinfo->family == family) {
345 static void htable_put(struct xt_hashlimit_htable *hinfo)
347 mutex_lock(&hashlimit_mutex);
348 if (--hinfo->use == 0) {
349 hlist_del(&hinfo->node);
350 htable_destroy(hinfo);
352 mutex_unlock(&hashlimit_mutex);
355 /* The algorithm used is the Simple Token Bucket Filter (TBF)
356 * see net/sched/sch_tbf.c in the linux source tree
359 /* Rusty: This is my (non-mathematically-inclined) understanding of
360 this algorithm. The `average rate' in jiffies becomes your initial
361 amount of credit `credit' and the most credit you can ever have
362 `credit_cap'. The `peak rate' becomes the cost of passing the
365 `prev' tracks the last packet hit: you gain one credit per jiffy.
366 If you get credit balance more than this, the extra credit is
367 discarded. Every time the match passes, you lose `cost' credits;
368 if you don't have that many, the test fails.
370 See Alexey's formal explanation in net/sched/sch_tbf.c.
372 To get the maximum range, we multiply by this factor (ie. you get N
373 credits per jiffy). We want to allow a rate as low as 1 per day
374 (slowest userspace tool allows), which means
375 CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32 ie.
377 #define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
379 /* Repeated shift and or gives us all 1s, final shift and add 1 gives
380 * us the power of 2 below the theoretical max, so GCC simply does a
382 #define _POW2_BELOW2(x) ((x)|((x)>>1))
383 #define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
384 #define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
385 #define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
386 #define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
387 #define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
389 #define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
391 /* Precision saver. */
392 static u32 user2credits(u32 user)
394 /* If multiplying would overflow... */
395 if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
397 return (user / XT_HASHLIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
399 return (user * HZ * CREDITS_PER_JIFFY) / XT_HASHLIMIT_SCALE;
402 static void rateinfo_recalc(struct dsthash_ent *dh, unsigned long now)
404 dh->rateinfo.credit += (now - dh->rateinfo.prev) * CREDITS_PER_JIFFY;
405 if (dh->rateinfo.credit > dh->rateinfo.credit_cap)
406 dh->rateinfo.credit = dh->rateinfo.credit_cap;
407 dh->rateinfo.prev = now;
410 static inline __be32 maskl(__be32 a, unsigned int l)
412 return l ? htonl(ntohl(a) & ~0 << (32 - l)) : 0;
415 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
416 static void hashlimit_ipv6_mask(__be32 *i, unsigned int p)
420 i[0] = maskl(i[0], p);
421 i[1] = i[2] = i[3] = 0;
424 i[1] = maskl(i[1], p - 32);
428 i[2] = maskl(i[2], p - 64);
432 i[3] = maskl(i[3], p - 96);
441 hashlimit_init_dst(const struct xt_hashlimit_htable *hinfo,
442 struct dsthash_dst *dst,
443 const struct sk_buff *skb, unsigned int protoff)
445 __be16 _ports[2], *ports;
449 memset(dst, 0, sizeof(*dst));
451 switch (hinfo->family) {
453 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DIP)
454 dst->ip.dst = maskl(ip_hdr(skb)->daddr,
456 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SIP)
457 dst->ip.src = maskl(ip_hdr(skb)->saddr,
460 if (!(hinfo->cfg.mode &
461 (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
463 nexthdr = ip_hdr(skb)->protocol;
465 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
470 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DIP) {
471 memcpy(&dst->ip6.dst, &ipv6_hdr(skb)->daddr,
472 sizeof(dst->ip6.dst));
473 hashlimit_ipv6_mask(dst->ip6.dst, hinfo->cfg.dstmask);
475 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SIP) {
476 memcpy(&dst->ip6.src, &ipv6_hdr(skb)->saddr,
477 sizeof(dst->ip6.src));
478 hashlimit_ipv6_mask(dst->ip6.src, hinfo->cfg.srcmask);
481 if (!(hinfo->cfg.mode &
482 (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
484 nexthdr = ipv6_hdr(skb)->nexthdr;
485 protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr, &frag_off);
486 if ((int)protoff < 0)
496 poff = proto_ports_offset(nexthdr);
498 ports = skb_header_pointer(skb, protoff + poff, sizeof(_ports),
501 _ports[0] = _ports[1] = 0;
506 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SPT)
507 dst->src_port = ports[0];
508 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DPT)
509 dst->dst_port = ports[1];
514 hashlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
516 const struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
517 struct xt_hashlimit_htable *hinfo = info->hinfo;
518 unsigned long now = jiffies;
519 struct dsthash_ent *dh;
520 struct dsthash_dst dst;
522 if (hashlimit_init_dst(hinfo, &dst, skb, par->thoff) < 0)
526 dh = dsthash_find(hinfo, &dst);
528 dh = dsthash_alloc_init(hinfo, &dst);
530 rcu_read_unlock_bh();
533 dh->expires = jiffies + msecs_to_jiffies(hinfo->cfg.expire);
534 dh->rateinfo.prev = jiffies;
535 dh->rateinfo.credit = user2credits(hinfo->cfg.avg *
537 dh->rateinfo.credit_cap = dh->rateinfo.credit;
538 dh->rateinfo.cost = user2credits(hinfo->cfg.avg);
540 /* update expiration timeout */
541 dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);
542 rateinfo_recalc(dh, now);
545 if (dh->rateinfo.credit >= dh->rateinfo.cost) {
546 /* below the limit */
547 dh->rateinfo.credit -= dh->rateinfo.cost;
548 spin_unlock(&dh->lock);
549 rcu_read_unlock_bh();
550 return !(info->cfg.mode & XT_HASHLIMIT_INVERT);
553 spin_unlock(&dh->lock);
554 rcu_read_unlock_bh();
555 /* default match is underlimit - so over the limit, we need to invert */
556 return info->cfg.mode & XT_HASHLIMIT_INVERT;
563 static int hashlimit_mt_check(const struct xt_mtchk_param *par)
565 struct net *net = par->net;
566 struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
569 /* Check for overflow. */
570 if (info->cfg.burst == 0 ||
571 user2credits(info->cfg.avg * info->cfg.burst) <
572 user2credits(info->cfg.avg)) {
573 pr_info("overflow, try lower: %u/%u\n",
574 info->cfg.avg, info->cfg.burst);
577 if (info->cfg.gc_interval == 0 || info->cfg.expire == 0)
579 if (info->name[sizeof(info->name)-1] != '\0')
581 if (par->family == NFPROTO_IPV4) {
582 if (info->cfg.srcmask > 32 || info->cfg.dstmask > 32)
585 if (info->cfg.srcmask > 128 || info->cfg.dstmask > 128)
589 mutex_lock(&hashlimit_mutex);
590 info->hinfo = htable_find_get(net, info->name, par->family);
591 if (info->hinfo == NULL) {
592 ret = htable_create(net, info, par->family);
594 mutex_unlock(&hashlimit_mutex);
598 mutex_unlock(&hashlimit_mutex);
602 static void hashlimit_mt_destroy(const struct xt_mtdtor_param *par)
604 const struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
606 htable_put(info->hinfo);
609 static struct xt_match hashlimit_mt_reg[] __read_mostly = {
613 .family = NFPROTO_IPV4,
614 .match = hashlimit_mt,
615 .matchsize = sizeof(struct xt_hashlimit_mtinfo1),
616 .checkentry = hashlimit_mt_check,
617 .destroy = hashlimit_mt_destroy,
620 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
624 .family = NFPROTO_IPV6,
625 .match = hashlimit_mt,
626 .matchsize = sizeof(struct xt_hashlimit_mtinfo1),
627 .checkentry = hashlimit_mt_check,
628 .destroy = hashlimit_mt_destroy,
635 static void *dl_seq_start(struct seq_file *s, loff_t *pos)
636 __acquires(htable->lock)
638 struct xt_hashlimit_htable *htable = s->private;
639 unsigned int *bucket;
641 spin_lock_bh(&htable->lock);
642 if (*pos >= htable->cfg.size)
645 bucket = kmalloc(sizeof(unsigned int), GFP_ATOMIC);
647 return ERR_PTR(-ENOMEM);
653 static void *dl_seq_next(struct seq_file *s, void *v, loff_t *pos)
655 struct xt_hashlimit_htable *htable = s->private;
656 unsigned int *bucket = (unsigned int *)v;
659 if (*pos >= htable->cfg.size) {
666 static void dl_seq_stop(struct seq_file *s, void *v)
667 __releases(htable->lock)
669 struct xt_hashlimit_htable *htable = s->private;
670 unsigned int *bucket = (unsigned int *)v;
674 spin_unlock_bh(&htable->lock);
677 static int dl_seq_real_show(struct dsthash_ent *ent, u_int8_t family,
682 spin_lock(&ent->lock);
683 /* recalculate to show accurate numbers */
684 rateinfo_recalc(ent, jiffies);
688 res = seq_printf(s, "%ld %pI4:%u->%pI4:%u %u %u %u\n",
689 (long)(ent->expires - jiffies)/HZ,
691 ntohs(ent->dst.src_port),
693 ntohs(ent->dst.dst_port),
694 ent->rateinfo.credit, ent->rateinfo.credit_cap,
697 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
699 res = seq_printf(s, "%ld %pI6:%u->%pI6:%u %u %u %u\n",
700 (long)(ent->expires - jiffies)/HZ,
702 ntohs(ent->dst.src_port),
704 ntohs(ent->dst.dst_port),
705 ent->rateinfo.credit, ent->rateinfo.credit_cap,
713 spin_unlock(&ent->lock);
717 static int dl_seq_show(struct seq_file *s, void *v)
719 struct xt_hashlimit_htable *htable = s->private;
720 unsigned int *bucket = (unsigned int *)v;
721 struct dsthash_ent *ent;
722 struct hlist_node *pos;
724 if (!hlist_empty(&htable->hash[*bucket])) {
725 hlist_for_each_entry(ent, pos, &htable->hash[*bucket], node)
726 if (dl_seq_real_show(ent, htable->family, s))
732 static const struct seq_operations dl_seq_ops = {
733 .start = dl_seq_start,
739 static int dl_proc_open(struct inode *inode, struct file *file)
741 int ret = seq_open(file, &dl_seq_ops);
744 struct seq_file *sf = file->private_data;
745 sf->private = PDE(inode)->data;
750 static const struct file_operations dl_file_ops = {
751 .owner = THIS_MODULE,
752 .open = dl_proc_open,
755 .release = seq_release
758 static int __net_init hashlimit_proc_net_init(struct net *net)
760 struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
762 hashlimit_net->ipt_hashlimit = proc_mkdir("ipt_hashlimit", net->proc_net);
763 if (!hashlimit_net->ipt_hashlimit)
765 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
766 hashlimit_net->ip6t_hashlimit = proc_mkdir("ip6t_hashlimit", net->proc_net);
767 if (!hashlimit_net->ip6t_hashlimit) {
768 proc_net_remove(net, "ipt_hashlimit");
775 static void __net_exit hashlimit_proc_net_exit(struct net *net)
777 proc_net_remove(net, "ipt_hashlimit");
778 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
779 proc_net_remove(net, "ip6t_hashlimit");
783 static int __net_init hashlimit_net_init(struct net *net)
785 struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
787 INIT_HLIST_HEAD(&hashlimit_net->htables);
788 return hashlimit_proc_net_init(net);
791 static void __net_exit hashlimit_net_exit(struct net *net)
793 struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
795 BUG_ON(!hlist_empty(&hashlimit_net->htables));
796 hashlimit_proc_net_exit(net);
799 static struct pernet_operations hashlimit_net_ops = {
800 .init = hashlimit_net_init,
801 .exit = hashlimit_net_exit,
802 .id = &hashlimit_net_id,
803 .size = sizeof(struct hashlimit_net),
806 static int __init hashlimit_mt_init(void)
810 err = register_pernet_subsys(&hashlimit_net_ops);
813 err = xt_register_matches(hashlimit_mt_reg,
814 ARRAY_SIZE(hashlimit_mt_reg));
819 hashlimit_cachep = kmem_cache_create("xt_hashlimit",
820 sizeof(struct dsthash_ent), 0, 0,
822 if (!hashlimit_cachep) {
823 pr_warning("unable to create slab cache\n");
829 xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
831 unregister_pernet_subsys(&hashlimit_net_ops);
836 static void __exit hashlimit_mt_exit(void)
838 xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
839 unregister_pernet_subsys(&hashlimit_net_ops);
842 kmem_cache_destroy(hashlimit_cachep);
845 module_init(hashlimit_mt_init);
846 module_exit(hashlimit_mt_exit);