Release 4.11 net/netfilter/xt_hashlimit.c

/*
 *      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>
 *      (C) 2006-2012 Patrick McHardy <kaber@trash.net>
 *      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 IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
#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 unsigned int hashlimit_net_id;


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

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/* need to declare this at the top */

static const struct file_operations dl_file_ops_v1;

static const struct file_operations dl_file_ops;

/* hash table crap */

struct dsthash_dst {
	union {
		struct {
			
__be32 src;
			
__be32 dst;
		} 
ip;
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
		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_int64_t credit;
		

u_int64_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_cfg2 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 delayed_work gc_work;

	/* seq_file stuff */
	
struct proc_dir_entry *pde;
	
const char *name;
	
struct net *net;

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


static int

cfg_copy(struct hashlimit_cfg2 *to, void *from, int revision)
{
	if (revision == 1) {
		struct hashlimit_cfg1 *cfg = (struct hashlimit_cfg1 *)from;

		to->mode = cfg->mode;
		to->avg = cfg->avg;
		to->burst = cfg->burst;
		to->size = cfg->size;
		to->max = cfg->max;
		to->gc_interval = cfg->gc_interval;
		to->expire = cfg->expire;
		to->srcmask = cfg->srcmask;
		to->dstmask = cfg->dstmask;
	} else if (revision == 2) {
		memcpy(to, from, sizeof(struct hashlimit_cfg2));
	} else {
		return -EINVAL;
	}

	return 0;
}

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142
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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));
}

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Harald Welte
26
68.42%
1
25.00%
Patrick McHardy
10
26.32%
1
25.00%
Jan Engelhardt
2
5.26%
2
50.00%
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38
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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 reciprocal_scale(hash, ht->cfg.size);
}

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Harald Welte
32
54.24%
1
25.00%
Eric Dumazet
18
30.51%
1
25.00%
Patrick McHardy
5
8.47%
1
25.00%
Daniel Borkmann
4
6.78%
1
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59
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static struct dsthash_ent *

dsthash_find(const struct xt_hashlimit_htable *ht,
	     const struct dsthash_dst *dst)
{
	struct dsthash_ent *ent;
	u_int32_t hash = hash_dst(ht, dst);

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

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Harald Welte
65
77.38%
2
33.33%
Eric Dumazet
11
13.10%
1
16.67%
jix@bugmachine.ca
4
4.76%
1
16.67%
Patrick McHardy
3
3.57%
1
16.67%
Jan Engelhardt
1
1.19%
1
16.67%
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84
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6
100.00%

/* 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, bool *race)
{
	struct dsthash_ent *ent;

	spin_lock(&ht->lock);

	/* Two or more packets may race to create the same entry in the
         * hashtable, double check if this packet lost race.
         */
	ent = dsthash_find(ht, dst);
	if (ent != NULL) {
		spin_unlock(&ht->lock);
		*race = true;
		return ent;
	}

	/* 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.. */
		net_err_ratelimited("max count of %u reached\n", ht->cfg.max);
		ent = NULL;
	} else
		ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
	if (ent) {
		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;
}

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Harald Welte
115
50.88%
2
18.18%
Eric Dumazet
41
18.14%
1
9.09%
Pablo Neira Ayuso
38
16.81%
1
9.09%
Patrick McHardy
22
9.73%
2
18.18%
Hagen Paul Pfeifer
6
2.65%
1
9.09%
Jan Engelhardt
3
1.33%
3
27.27%
Joe Perches
1
0.44%
1
9.09%
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226
100.00%
11
100.00%



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);
}

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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--;
}
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Harald Welte
30
75.00%
2
50.00%
Eric Dumazet
7
17.50%
1
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Patrick McHardy
3
7.50%
1
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40
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static void htable_gc(struct work_struct *work);



static int htable_create(struct net *net, struct hashlimit_cfg2 *cfg,
			 const char *name, u_int8_t family,
			 struct xt_hashlimit_htable **out_hinfo,
			 int revision)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
	struct xt_hashlimit_htable *hinfo;
	unsigned int size, i;
	int ret;

	if (cfg->size) {
		size = 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;
	*out_hinfo = hinfo;

	/* copy match config into hashtable config */
	ret = cfg_copy(&hinfo->cfg, (void *)cfg, 2);

	if (ret)
		return ret;

	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;
	hinfo->name = kstrdup(name, GFP_KERNEL);
	if (!hinfo->name) {
		vfree(hinfo);
		return -ENOMEM;
	}
	spin_lock_init(&hinfo->lock);

	hinfo->pde = proc_create_data(name, 0,
		(family == NFPROTO_IPV4) ?
		hashlimit_net->ipt_hashlimit : hashlimit_net->ip6t_hashlimit,
		(revision == 1) ? &dl_file_ops_v1 : &dl_file_ops,
		hinfo);
	if (hinfo->pde == NULL) {
		kfree(hinfo->name);
		vfree(hinfo);
		return -ENOMEM;
	}
	hinfo->net = net;

	INIT_DEFERRABLE_WORK(&hinfo->gc_work, htable_gc);
	queue_delayed_work(system_power_efficient_wq, &hinfo->gc_work,
			   msecs_to_jiffies(hinfo->cfg.gc_interval));

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

	return 0;
}

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Harald Welte
257
58.28%
2
9.09%
Vishwanath Pai
49
11.11%
2
9.09%
Al Viro
36
8.16%
1
4.55%
Alexey Dobriyan
30
6.80%
1
4.55%
Patrick McHardy
27
6.12%
4
18.18%
Jan Engelhardt
21
4.76%
6
27.27%
Eric Dumazet
9
2.04%
1
4.55%
Denis V. Lunev
5
1.13%
2
9.09%
Andrew Morton
4
0.91%
1
4.55%
Jan Beulich
2
0.45%
1
4.55%
Tobias Klauser
1
0.23%
1
4.55%
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441
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22
100.00%



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

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Jan Engelhardt
12
57.14%
1
33.33%
Harald Welte
6
28.57%
1
33.33%
Alexey Dobriyan
3
14.29%
1
33.33%
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21
100.00%
3
100.00%



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

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Jan Engelhardt
24
85.71%
1
33.33%
Alexey Dobriyan
3
10.71%
1
33.33%
Harald Welte
1
3.57%
1
33.33%
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28
100.00%
3
100.00%



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;

	for (i = 0; i < ht->cfg.size; i++) {
		struct dsthash_ent *dh;
		struct hlist_node *n;

		spin_lock_bh(&ht->lock);
		hlist_for_each_entry_safe(dh, n, &ht->hash[i], node) {
			if ((*select)(ht, dh))
				dsthash_free(ht, dh);
		}
		spin_unlock_bh(&ht->lock);
		cond_resched();
	}
}

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Jan Engelhardt
85
75.22%
2
33.33%
Harald Welte
13
11.50%
1
16.67%
Eric Dumazet
12
10.62%
1
16.67%
Patrick McHardy
2
1.77%
1
16.67%
Alexey Dobriyan
1
0.88%
1
16.67%
Total
113
100.00%
6
100.00%



static void htable_gc(struct work_struct *work)
{
	struct xt_hashlimit_htable *ht;

	ht = container_of(work, struct xt_hashlimit_htable, gc_work.work);

	htable_selective_cleanup(ht, select_gc);

	queue_delayed_work(system_power_efficient_wq,
			   &ht->gc_work, msecs_to_jiffies(ht->cfg.gc_interval));
}

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Jan Engelhardt
28
50.00%
2
50.00%
Eric Dumazet
24
42.86%
1
25.00%
Harald Welte
4
7.14%
1
25.00%
Total
56
100.00%
4
100.00%



static void htable_remove_proc_entry(struct xt_hashlimit_htable *hinfo)
{
	struct hashlimit_net *hashlimit_net = hashlimit_pernet(hinfo->net);
	struct proc_dir_entry *parent;

	if (hinfo->family == NFPROTO_IPV4)
		parent = hashlimit_net->ipt_hashlimit;
	else
		parent = hashlimit_net->ip6t_hashlimit;

	if (parent != NULL)
		remove_proc_entry(hinfo->name, parent);
}

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Jan Engelhardt
47
73.44%
2
40.00%
Harald Welte
9
14.06%
1
20.00%
Vitaly E. Lavrov
6
9.38%
1
20.00%
Sergey Popovich
2
3.12%
1
20.00%
Total
64
100.00%
5
100.00%



static void htable_destroy(struct xt_hashlimit_htable *hinfo)
{
	cancel_delayed_work_sync(&hinfo->gc_work);
	htable_remove_proc_entry(hinfo);
	htable_selective_cleanup(hinfo, select_all);
	kfree(hinfo->name);
	vfree(hinfo);
}

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Sergey Popovich
21
48.84%
1
16.67%
Jan Engelhardt
8
18.60%
2
33.33%
Al Viro
7
16.28%
1
16.67%
Harald Welte
5
11.63%
1
16.67%
Eric Dumazet
2
4.65%
1
16.67%
Total
43
100.00%
6
100.00%



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;

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

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Jan Engelhardt
68
88.31%
2
40.00%
Harald Welte
5
6.49%
1
20.00%
Patrick McHardy
3
3.90%
1
20.00%
Denis V. Lunev
1
1.30%
1
20.00%
Total
77
100.00%
5
100.00%



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);
}

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Jan Engelhardt
31
65.96%
2
50.00%
Harald Welte
15
31.91%
1
25.00%
Alexey Dobriyan
1
2.13%
1
25.00%
Total
47
100.00%
4
100.00%

/* 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_v1 (0xFFFFFFFF / (HZ*60*60*24))

#define MAX_CPJ (0xFFFFFFFFFFFFFFFFULL / (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_BELOW64(x) (_POW2_BELOW32(x)|_POW2_BELOW32((x)>>32))

#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)

#define POW2_BELOW64(x) ((_POW2_BELOW64(x)>>1) + 1)


#define CREDITS_PER_JIFFY POW2_BELOW64(MAX_CPJ)

#define CREDITS_PER_JIFFY_v1 POW2_BELOW32(MAX_CPJ_v1)

/* in byte mode, the lowest possible rate is one packet/second.
 * credit_cap is used as a counter that tells us how many times we can
 * refill the "credits available" counter when it becomes empty.
 */

#define MAX_CPJ_BYTES (0xFFFFFFFF / HZ)

#define CREDITS_PER_JIFFY_BYTES POW2_BELOW32(MAX_CPJ_BYTES)



static u32 xt_hashlimit_len_to_chunks(u32 len)
{
	return (len >> XT_HASHLIMIT_BYTE_SHIFT) + 1;
}

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/* Precision saver. */


static u64 user2credits(u64 user, int revision)
{
	u64 scale = (revision == 1) ?
		XT_HASHLIMIT_SCALE : XT_HASHLIMIT_SCALE_v2;
	u64 cpj = (revision == 1) ?
		CREDITS_PER_JIFFY_v1 : CREDITS_PER_JIFFY;

	/* Avoid overflow: divide the constant operands first */
	if (scale >= HZ * cpj)
		return div64_u64(user, div64_u64(scale, HZ * cpj));

	return user * div64_u64(HZ * cpj, scale);
}

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Alban Browaeys
33
44.59%
1
16.67%
Vishwanath Pai
25
33.78%
2
33.33%
Jan Engelhardt
15
20.27%
2
33.33%
Florian Westphal
1
1.35%
1
16.67%
Total
74
100.00%
6
100.00%



static u32 user2credits_byte(u32 user)
{
	u64 us = user;
	us *= HZ * CREDITS_PER_JIFFY_BYTES;
	return (u32) (us >> 32);
}

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53.33%
1
50.00%
Florian Westphal
14
46.67%
1
50.00%
Total
30
100.00%
2
100.00%



static void rateinfo_recalc(struct dsthash_ent *dh, unsigned long now,
			    u32 mode, int revision)
{
	unsigned long delta = now - dh->rateinfo.prev;
	u64 cap, cpj;

	if (delta == 0)
		return;

	dh->rateinfo.prev = now;

	if (mode & XT_HASHLIMIT_BYTES) {
		u64 tmp = dh->rateinfo.credit;
		dh->rateinfo.credit += CREDITS_PER_JIFFY_BYTES * delta;
		cap = CREDITS_PER_JIFFY_BYTES * HZ;
		if (tmp >= dh->rateinfo.credit) {/* overflow */
			dh->rateinfo.credit = cap;
			return;
		}
	} else {
		cpj = (revision == 1) ?
			CREDITS_PER_JIFFY_v1 : CREDITS_PER_JIFFY;
		dh->rateinfo.credit += delta * cpj;
		cap = dh->rateinfo.credit_cap;
	}
	if (dh->rateinfo.credit > cap)
		dh->rateinfo.credit = cap;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Florian Westphal
84
52.83%
1
25.00%
Jan Engelhardt
55
34.59%
2
50.00%
Vishwanath Pai
20
12.58%
1
25.00%
Total
159
100.00%
4
100.00%



static void rateinfo_init(struct dsthash_ent *dh,
			  struct xt_hashlimit_htable *hinfo, int revision)
{
	dh->rateinfo.prev = jiffies;
	if (hinfo->cfg.mode & XT_HASHLIMIT_BYTES) {
		dh->rateinfo.credit = CREDITS_PER_JIFFY_BYTES * HZ;
		dh->rateinfo.cost = user2credits_byte(hinfo->cfg.avg);
		dh->rateinfo.credit_cap = hinfo->cfg.burst;
	} else {
		dh->rateinfo.credit = user2credits(hinfo->cfg.avg *
						   hinfo->cfg.burst, revision);
		dh->rateinfo.cost = user2credits(hinfo->cfg.avg, revision);
		dh->rateinfo.credit_cap = dh->rateinfo.credit;
	}
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Florian Westphal
124
94.66%
2
66.67%
Vishwanath Pai
7
5.34%
1
33.33%
Total
131
100.00%
3
100.00%



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

Contributors
Person
Tokens
Prop
Commits
CommitProp
Jan Engelhardt
34
94.44%
2
66.67%
Harald Welte
2
5.56%
1
33.33%
Total
36
100.00%
3
100.00%

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)


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;
	}
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Jan Engelhardt
142
94.67%
2
40.00%
Harald Welte
5
3.33%
1
20.00%
Patrick McHardy
3
2.00%
2
40.00%
Total
150
100.00%
5
100.00%

#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 IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
	case NFPROTO_IPV6:
	{
		__be16 frag_off;

		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, &frag_off);
		if ((int)protoff <