summaryrefslogtreecommitdiff
path: root/net/netfilter/xt_hashlimit.c
blob: 9228ee0dc11a307a49d131e7f879c738351dcef5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
/*
 *	xt_hashlimit - Netfilter module to limit the number of packets per time
 *	separately for each hashbucket (sourceip/sourceport/dstip/dstport)
 *
 *	(C) 2003-2004 by Harald Welte <laforge@netfilter.org>
 *	Copyright © CC Computer Consultants GmbH, 2007 - 2008
 *
 * Development of this code was funded by Astaro AG, http://www.astaro.com/
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/list.h>
#include <linux/skbuff.h>
#include <linux/mm.h>
#include <linux/in.h>
#include <linux/ip.h>
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
#include <linux/ipv6.h>
#include <net/ipv6.h>
#endif

#include <net/net_namespace.h>
#include <net/netns/generic.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/xt_hashlimit.h>
#include <linux/mutex.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("Xtables: per hash-bucket rate-limit match");
MODULE_ALIAS("ipt_hashlimit");
MODULE_ALIAS("ip6t_hashlimit");

struct hashlimit_net {
	struct hlist_head	htables;
	struct proc_dir_entry	*ipt_hashlimit;
	struct proc_dir_entry	*ip6t_hashlimit;
};

static int hashlimit_net_id;
static inline struct hashlimit_net *hashlimit_pernet(struct net *net)
{
	return net_generic(net, hashlimit_net_id);
}

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

/* hash table crap */
struct dsthash_dst {
	union {
		struct {
			__be32 src;
			__be32 dst;
		} ip;
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
		struct {
			__be32 src[4];
			__be32 dst[4];
		} ip6;
#endif
	};
	__be16 src_port;
	__be16 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 */
	spinlock_t lock;
	unsigned long expires;		/* precalculated expiry time */
	struct {
		unsigned long prev;	/* last modification */
		u_int32_t credit;
		u_int32_t credit_cap, cost;
	} rateinfo;
	struct rcu_head rcu;
};

struct xt_hashlimit_htable {
	struct hlist_node node;		/* global list of all htables */
	int use;
	u_int8_t family;
	bool rnd_initialized;

	struct hashlimit_cfg1 cfg;	/* config */

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

	/* seq_file stuff */
	struct proc_dir_entry *pde;
	struct net *net;

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

static DEFINE_MUTEX(hashlimit_mutex);	/* protects htables list */
static struct kmem_cache *hashlimit_cachep __read_mostly;

static inline bool dst_cmp(const struct dsthash_ent *ent,
			   const struct dsthash_dst *b)
{
	return !memcmp(&ent->dst, b, sizeof(ent->dst));
}

static u_int32_t
hash_dst(const struct xt_hashlimit_htable *ht, const struct dsthash_dst *dst)
{
	u_int32_t hash = jhash2((const u32 *)dst,
				sizeof(*dst)/sizeof(u32),
				ht->rnd);
	/*
	 * Instead of returning hash % ht->cfg.size (implying a divide)
	 * we return the high 32 bits of the (hash * ht->cfg.size) that will
	 * give results between [0 and cfg.size-1] and same hash distribution,
	 * but using a multiply, less expensive than a divide
	 */
	return ((u64)hash * ht->cfg.size) >> 32;
}

static struct dsthash_ent *
dsthash_find(const struct xt_hashlimit_htable *ht,
	     const 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_rcu(ent, pos, &ht->hash[hash], node)
			if (dst_cmp(ent, dst)) {
				spin_lock(&ent->lock);
				return ent;
			}
	}
	return NULL;
}

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

	spin_lock(&ht->lock);
	/* initialize hash with random val at the time we allocate
	 * the first hashtable entry */
	if (unlikely(!ht->rnd_initialized)) {
		get_random_bytes(&ht->rnd, sizeof(ht->rnd));
		ht->rnd_initialized = true;
	}

	if (ht->cfg.max && ht->count >= ht->cfg.max) {
		/* FIXME: do something. question is what.. */
		if (net_ratelimit())
			pr_err("max count of %u reached\n", ht->cfg.max);
		ent = NULL;
	} else
		ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
	if (!ent) {
		if (net_ratelimit())
			pr_err("cannot allocate dsthash_ent\n");
	} else {
		memcpy(&ent->dst, dst, sizeof(ent->dst));
		spin_lock_init(&ent->lock);

		spin_lock(&ent->lock);
		hlist_add_head_rcu(&ent->node, &ht->hash[hash_dst(ht, dst)]);
		ht->count++;
	}
	spin_unlock(&ht->lock);
	return ent;
}

static void dsthash_free_rcu(struct rcu_head *head)
{
	struct dsthash_ent *ent = container_of(head, struct dsthash_ent, rcu);

	kmem_cache_free(hashlimit_cachep, ent);
}

static inline void
dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
{
	hlist_del_rcu(&ent->node);
	call_rcu_bh(&ent->rcu, dsthash_free_rcu);
	ht->count--;
}
static void htable_gc(unsigned long htlong);

static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo,
			 u_int8_t family)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
	struct xt_hashlimit_htable *hinfo;
	unsigned int size;
	unsigned int i;

	if (minfo->cfg.size) {
		size = minfo->cfg.size;
	} else {
		size = (totalram_pages << PAGE_SHIFT) / 16384 /
		       sizeof(struct list_head);
		if (totalram_pages > 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 xt_hashlimit_htable) +
	                sizeof(struct list_head) * size);
	if (hinfo == NULL)
		return -ENOMEM;
	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 == 0)
		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]);

	hinfo->use = 1;
	hinfo->count = 0;
	hinfo->family = family;
	hinfo->rnd_initialized = false;
	spin_lock_init(&hinfo->lock);

	hinfo->pde = proc_create_data(minfo->name, 0,
		(family == NFPROTO_IPV4) ?
		hashlimit_net->ipt_hashlimit : hashlimit_net->ip6t_hashlimit,
		&dl_file_ops, hinfo);
	if (hinfo->pde == NULL) {
		vfree(hinfo);
		return -ENOMEM;
	}
	hinfo->net = net;

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

	hlist_add_head(&hinfo->node, &hashlimit_net->htables);

	return 0;
}

static bool select_all(const struct xt_hashlimit_htable *ht,
		       const struct dsthash_ent *he)
{
	return 1;
}

static bool select_gc(const struct xt_hashlimit_htable *ht,
		      const struct dsthash_ent *he)
{
	return time_after_eq(jiffies, he->expires);
}

static void htable_selective_cleanup(struct xt_hashlimit_htable *ht,
			bool (*select)(const struct xt_hashlimit_htable *ht,
				      const struct dsthash_ent *he))
{
	unsigned int i;

	/* 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 xt_hashlimit_htable *ht = (struct xt_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 xt_hashlimit_htable *hinfo)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(hinfo->net);
	struct proc_dir_entry *parent;

	del_timer_sync(&hinfo->timer);

	if (hinfo->family == NFPROTO_IPV4)
		parent = hashlimit_net->ipt_hashlimit;
	else
		parent = hashlimit_net->ip6t_hashlimit;
	remove_proc_entry(hinfo->pde->name, parent);
	htable_selective_cleanup(hinfo, select_all);
	vfree(hinfo);
}

static struct xt_hashlimit_htable *htable_find_get(struct net *net,
						   const char *name,
						   u_int8_t family)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
	struct xt_hashlimit_htable *hinfo;
	struct hlist_node *pos;

	hlist_for_each_entry(hinfo, pos, &hashlimit_net->htables, node) {
		if (!strcmp(name, hinfo->pde->name) &&
		    hinfo->family == family) {
			hinfo->use++;
			return hinfo;
		}
	}
	return NULL;
}

static void htable_put(struct xt_hashlimit_htable *hinfo)
{
	mutex_lock(&hashlimit_mutex);
	if (--hinfo->use == 0) {
		hlist_del(&hinfo->node);
		htable_destroy(hinfo);
	}
	mutex_unlock(&hashlimit_mutex);
}

/* 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 / XT_HASHLIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;

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

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

static inline __be32 maskl(__be32 a, unsigned int l)
{
	return l ? htonl(ntohl(a) & ~0 << (32 - l)) : 0;
}

#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
static void hashlimit_ipv6_mask(__be32 *i, unsigned int p)
{
	switch (p) {
	case 0 ... 31:
		i[0] = maskl(i[0], p);
		i[1] = i[2] = i[3] = 0;
		break;
	case 32 ... 63:
		i[1] = maskl(i[1], p - 32);
		i[2] = i[3] = 0;
		break;
	case 64 ... 95:
		i[2] = maskl(i[2], p - 64);
		i[3] = 0;
		break;
	case 96 ... 127:
		i[3] = maskl(i[3], p - 96);
		break;
	case 128:
		break;
	}
}
#endif

static int
hashlimit_init_dst(const struct xt_hashlimit_htable *hinfo,
		   struct dsthash_dst *dst,
		   const struct sk_buff *skb, unsigned int protoff)
{
	__be16 _ports[2], *ports;
	u8 nexthdr;
	int poff;

	memset(dst, 0, sizeof(*dst));

	switch (hinfo->family) {
	case NFPROTO_IPV4:
		if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DIP)
			dst->ip.dst = maskl(ip_hdr(skb)->daddr,
			              hinfo->cfg.dstmask);
		if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SIP)
			dst->ip.src = maskl(ip_hdr(skb)->saddr,
			              hinfo->cfg.srcmask);

		if (!(hinfo->cfg.mode &
		      (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
			return 0;
		nexthdr = ip_hdr(skb)->protocol;
		break;
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	case NFPROTO_IPV6:
		if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DIP) {
			memcpy(&dst->ip6.dst, &ipv6_hdr(skb)->daddr,
			       sizeof(dst->ip6.dst));
			hashlimit_ipv6_mask(dst->ip6.dst, hinfo->cfg.dstmask);
		}
		if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SIP) {
			memcpy(&dst->ip6.src, &ipv6_hdr(skb)->saddr,
			       sizeof(dst->ip6.src));
			hashlimit_ipv6_mask(dst->ip6.src, hinfo->cfg.srcmask);
		}

		if (!(hinfo->cfg.mode &
		      (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
			return 0;
		nexthdr = ipv6_hdr(skb)->nexthdr;
		protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr);
		if ((int)protoff < 0)
			return -1;
		break;
#endif
	default:
		BUG();
		return 0;
	}

	poff = proto_ports_offset(nexthdr);
	if (poff >= 0) {
		ports = skb_header_pointer(skb, protoff + poff, sizeof(_ports),
					   &_ports);
	} else {
		_ports[0] = _ports[1] = 0;
		ports = _ports;
	}
	if (!ports)
		return -1;
	if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SPT)
		dst->src_port = ports[0];
	if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DPT)
		dst->dst_port = ports[1];
	return 0;
}

static bool
hashlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
	const struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
	struct xt_hashlimit_htable *hinfo = info->hinfo;
	unsigned long now = jiffies;
	struct dsthash_ent *dh;
	struct dsthash_dst dst;

	if (hashlimit_init_dst(hinfo, &dst, skb, par->thoff) < 0)
		goto hotdrop;

	rcu_read_lock_bh();
	dh = dsthash_find(hinfo, &dst);
	if (dh == NULL) {
		dh = dsthash_alloc_init(hinfo, &dst);
		if (dh == NULL) {
			rcu_read_unlock_bh();
			goto hotdrop;
		}
		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);
	} else {
		/* update expiration timeout */
		dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);
		rateinfo_recalc(dh, now);
	}

	if (dh->rateinfo.credit >= dh->rateinfo.cost) {
		/* below the limit */
		dh->rateinfo.credit -= dh->rateinfo.cost;
		spin_unlock(&dh->lock);
		rcu_read_unlock_bh();
		return !(info->cfg.mode & XT_HASHLIMIT_INVERT);
	}

	spin_unlock(&dh->lock);
	rcu_read_unlock_bh();
	/* default match is underlimit - so over the limit, we need to invert */
	return info->cfg.mode & XT_HASHLIMIT_INVERT;

 hotdrop:
	par->hotdrop = true;
	return false;
}

static int hashlimit_mt_check(const struct xt_mtchk_param *par)
{
	struct net *net = par->net;
	struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
	int ret;

	/* Check for overflow. */
	if (info->cfg.burst == 0 ||
	    user2credits(info->cfg.avg * info->cfg.burst) <
	    user2credits(info->cfg.avg)) {
		pr_info("overflow, try lower: %u/%u\n",
			info->cfg.avg, info->cfg.burst);
		return -ERANGE;
	}
	if (info->cfg.gc_interval == 0 || info->cfg.expire == 0)
		return -EINVAL;
	if (info->name[sizeof(info->name)-1] != '\0')
		return -EINVAL;
	if (par->family == NFPROTO_IPV4) {
		if (info->cfg.srcmask > 32 || info->cfg.dstmask > 32)
			return -EINVAL;
	} else {
		if (info->cfg.srcmask > 128 || info->cfg.dstmask > 128)
			return -EINVAL;
	}

	mutex_lock(&hashlimit_mutex);
	info->hinfo = htable_find_get(net, info->name, par->family);
	if (info->hinfo == NULL) {
		ret = htable_create(net, info, par->family);
		if (ret < 0) {
			mutex_unlock(&hashlimit_mutex);
			return ret;
		}
	}
	mutex_unlock(&hashlimit_mutex);
	return 0;
}

static void hashlimit_mt_destroy(const struct xt_mtdtor_param *par)
{
	const struct xt_hashlimit_mtinfo1 *info = par->matchinfo;

	htable_put(info->hinfo);
}

static struct xt_match hashlimit_mt_reg[] __read_mostly = {
	{
		.name           = "hashlimit",
		.revision       = 1,
		.family         = NFPROTO_IPV4,
		.match          = hashlimit_mt,
		.matchsize      = sizeof(struct xt_hashlimit_mtinfo1),
		.checkentry     = hashlimit_mt_check,
		.destroy        = hashlimit_mt_destroy,
		.me             = THIS_MODULE,
	},
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	{
		.name           = "hashlimit",
		.revision       = 1,
		.family         = NFPROTO_IPV6,
		.match          = hashlimit_mt,
		.matchsize      = sizeof(struct xt_hashlimit_mtinfo1),
		.checkentry     = hashlimit_mt_check,
		.destroy        = hashlimit_mt_destroy,
		.me             = THIS_MODULE,
	},
#endif
};

/* PROC stuff */
static void *dl_seq_start(struct seq_file *s, loff_t *pos)
	__acquires(htable->lock)
{
	struct xt_hashlimit_htable *htable = s->private;
	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 xt_hashlimit_htable *htable = s->private;
	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)
	__releases(htable->lock)
{
	struct xt_hashlimit_htable *htable = s->private;
	unsigned int *bucket = (unsigned int *)v;

	if (!IS_ERR(bucket))
		kfree(bucket);
	spin_unlock_bh(&htable->lock);
}

static int dl_seq_real_show(struct dsthash_ent *ent, u_int8_t family,
				   struct seq_file *s)
{
	int res;

	spin_lock(&ent->lock);
	/* recalculate to show accurate numbers */
	rateinfo_recalc(ent, jiffies);

	switch (family) {
	case NFPROTO_IPV4:
		res = seq_printf(s, "%ld %pI4:%u->%pI4:%u %u %u %u\n",
				 (long)(ent->expires - jiffies)/HZ,
				 &ent->dst.ip.src,
				 ntohs(ent->dst.src_port),
				 &ent->dst.ip.dst,
				 ntohs(ent->dst.dst_port),
				 ent->rateinfo.credit, ent->rateinfo.credit_cap,
				 ent->rateinfo.cost);
		break;
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	case NFPROTO_IPV6:
		res = seq_printf(s, "%ld %pI6:%u->%pI6:%u %u %u %u\n",
				 (long)(ent->expires - jiffies)/HZ,
				 &ent->dst.ip6.src,
				 ntohs(ent->dst.src_port),
				 &ent->dst.ip6.dst,
				 ntohs(ent->dst.dst_port),
				 ent->rateinfo.credit, ent->rateinfo.credit_cap,
				 ent->rateinfo.cost);
		break;
#endif
	default:
		BUG();
		res = 0;
	}
	spin_unlock(&ent->lock);
	return res;
}

static int dl_seq_show(struct seq_file *s, void *v)
{
	struct xt_hashlimit_htable *htable = s->private;
	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, htable->family, s))
				return -1;
	}
	return 0;
}

static const 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)->data;
	}
	return ret;
}

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

static int __net_init hashlimit_proc_net_init(struct net *net)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);

	hashlimit_net->ipt_hashlimit = proc_mkdir("ipt_hashlimit", net->proc_net);
	if (!hashlimit_net->ipt_hashlimit)
		return -ENOMEM;
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	hashlimit_net->ip6t_hashlimit = proc_mkdir("ip6t_hashlimit", net->proc_net);
	if (!hashlimit_net->ip6t_hashlimit) {
		proc_net_remove(net, "ipt_hashlimit");
		return -ENOMEM;
	}
#endif
	return 0;
}

static void __net_exit hashlimit_proc_net_exit(struct net *net)
{
	proc_net_remove(net, "ipt_hashlimit");
#if defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
	proc_net_remove(net, "ip6t_hashlimit");
#endif
}

static int __net_init hashlimit_net_init(struct net *net)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);

	INIT_HLIST_HEAD(&hashlimit_net->htables);
	return hashlimit_proc_net_init(net);
}

static void __net_exit hashlimit_net_exit(struct net *net)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);

	BUG_ON(!hlist_empty(&hashlimit_net->htables));
	hashlimit_proc_net_exit(net);
}

static struct pernet_operations hashlimit_net_ops = {
	.init	= hashlimit_net_init,
	.exit	= hashlimit_net_exit,
	.id	= &hashlimit_net_id,
	.size	= sizeof(struct hashlimit_net),
};

static int __init hashlimit_mt_init(void)
{
	int err;

	err = register_pernet_subsys(&hashlimit_net_ops);
	if (err < 0)
		return err;
	err = xt_register_matches(hashlimit_mt_reg,
	      ARRAY_SIZE(hashlimit_mt_reg));
	if (err < 0)
		goto err1;

	err = -ENOMEM;
	hashlimit_cachep = kmem_cache_create("xt_hashlimit",
					    sizeof(struct dsthash_ent), 0, 0,
					    NULL);
	if (!hashlimit_cachep) {
		pr_warning("unable to create slab cache\n");
		goto err2;
	}
	return 0;

err2:
	xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
err1:
	unregister_pernet_subsys(&hashlimit_net_ops);
	return err;

}

static void __exit hashlimit_mt_exit(void)
{
	xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
	unregister_pernet_subsys(&hashlimit_net_ops);

	rcu_barrier_bh();
	kmem_cache_destroy(hashlimit_cachep);
}

module_init(hashlimit_mt_init);
module_exit(hashlimit_mt_exit);