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TOMOYO Linux Cross Reference
Linux/net/netfilter/xt_hashlimit.c

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  1 /*
  2  *      xt_hashlimit - Netfilter module to limit the number of packets per time
  3  *      separately for each hashbucket (sourceip/sourceport/dstip/dstport)
  4  *
  5  *      (C) 2003-2004 by Harald Welte <laforge@netfilter.org>
  6  *      Copyright © CC Computer Consultants GmbH, 2007 - 2008
  7  *
  8  * Development of this code was funded by Astaro AG, http://www.astaro.com/
  9  */
 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>
 21 #include <linux/mm.h>
 22 #include <linux/in.h>
 23 #include <linux/ip.h>
 24 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 25 #include <linux/ipv6.h>
 26 #include <net/ipv6.h>
 27 #endif
 28 
 29 #include <net/net_namespace.h>
 30 #include <net/netns/generic.h>
 31 
 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>
 37 
 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");
 44 
 45 struct hashlimit_net {
 46         struct hlist_head       htables;
 47         struct proc_dir_entry   *ipt_hashlimit;
 48         struct proc_dir_entry   *ip6t_hashlimit;
 49 };
 50 
 51 static int hashlimit_net_id;
 52 static inline struct hashlimit_net *hashlimit_pernet(struct net *net)
 53 {
 54         return net_generic(net, hashlimit_net_id);
 55 }
 56 
 57 /* need to declare this at the top */
 58 static const struct file_operations dl_file_ops;
 59 
 60 /* hash table crap */
 61 struct dsthash_dst {
 62         union {
 63                 struct {
 64                         __be32 src;
 65                         __be32 dst;
 66                 } ip;
 67 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
 68                 struct {
 69                         __be32 src[4];
 70                         __be32 dst[4];
 71                 } ip6;
 72 #endif
 73         };
 74         __be16 src_port;
 75         __be16 dst_port;
 76 };
 77 
 78 struct dsthash_ent {
 79         /* static / read-only parts in the beginning */
 80         struct hlist_node node;
 81         struct dsthash_dst dst;
 82 
 83         /* modified structure members in the end */
 84         spinlock_t lock;
 85         unsigned long expires;          /* precalculated expiry time */
 86         struct {
 87                 unsigned long prev;     /* last modification */
 88                 u_int32_t credit;
 89                 u_int32_t credit_cap, cost;
 90         } rateinfo;
 91         struct rcu_head rcu;
 92 };
 93 
 94 struct xt_hashlimit_htable {
 95         struct hlist_node node;         /* global list of all htables */
 96         int use;
 97         u_int8_t family;
 98         bool rnd_initialized;
 99 
100         struct hashlimit_cfg1 cfg;      /* config */
101 
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 */
107 
108         /* seq_file stuff */
109         struct proc_dir_entry *pde;
110         struct net *net;
111 
112         struct hlist_head hash[0];      /* hashtable itself */
113 };
114 
115 static DEFINE_MUTEX(hashlimit_mutex);   /* protects htables list */
116 static struct kmem_cache *hashlimit_cachep __read_mostly;
117 
118 static inline bool dst_cmp(const struct dsthash_ent *ent,
119                            const struct dsthash_dst *b)
120 {
121         return !memcmp(&ent->dst, b, sizeof(ent->dst));
122 }
123 
124 static u_int32_t
125 hash_dst(const struct xt_hashlimit_htable *ht, const struct dsthash_dst *dst)
126 {
127         u_int32_t hash = jhash2((const u32 *)dst,
128                                 sizeof(*dst)/sizeof(u32),
129                                 ht->rnd);
130         /*
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
135          */
136         return ((u64)hash * ht->cfg.size) >> 32;
137 }
138 
139 static struct dsthash_ent *
140 dsthash_find(const struct xt_hashlimit_htable *ht,
141              const struct dsthash_dst *dst)
142 {
143         struct dsthash_ent *ent;
144         struct hlist_node *pos;
145         u_int32_t hash = hash_dst(ht, dst);
146 
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);
151                                 return ent;
152                         }
153         }
154         return NULL;
155 }
156 
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, bool *race)
161 {
162         struct dsthash_ent *ent;
163 
164         spin_lock(&ht->lock);
165 
166         /* Two or more packets may race to create the same entry in the
167          * hashtable, double check if this packet lost race.
168          */
169         ent = dsthash_find(ht, dst);
170         if (ent != NULL) {
171                 spin_unlock(&ht->lock);
172                 *race = true;
173                 return ent;
174         }
175 
176         /* initialize hash with random val at the time we allocate
177          * the first hashtable entry */
178         if (unlikely(!ht->rnd_initialized)) {
179                 get_random_bytes(&ht->rnd, sizeof(ht->rnd));
180                 ht->rnd_initialized = true;
181         }
182 
183         if (ht->cfg.max && ht->count >= ht->cfg.max) {
184                 /* FIXME: do something. question is what.. */
185                 net_err_ratelimited("max count of %u reached\n", ht->cfg.max);
186                 ent = NULL;
187         } else
188                 ent = kmem_cache_alloc(hashlimit_cachep, GFP_ATOMIC);
189         if (ent) {
190                 memcpy(&ent->dst, dst, sizeof(ent->dst));
191                 spin_lock_init(&ent->lock);
192 
193                 spin_lock(&ent->lock);
194                 hlist_add_head_rcu(&ent->node, &ht->hash[hash_dst(ht, dst)]);
195                 ht->count++;
196         }
197         spin_unlock(&ht->lock);
198         return ent;
199 }
200 
201 static void dsthash_free_rcu(struct rcu_head *head)
202 {
203         struct dsthash_ent *ent = container_of(head, struct dsthash_ent, rcu);
204 
205         kmem_cache_free(hashlimit_cachep, ent);
206 }
207 
208 static inline void
209 dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
210 {
211         hlist_del_rcu(&ent->node);
212         call_rcu_bh(&ent->rcu, dsthash_free_rcu);
213         ht->count--;
214 }
215 static void htable_gc(unsigned long htlong);
216 
217 static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo,
218                          u_int8_t family)
219 {
220         struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
221         struct xt_hashlimit_htable *hinfo;
222         unsigned int size;
223         unsigned int i;
224 
225         if (minfo->cfg.size) {
226                 size = minfo->cfg.size;
227         } else {
228                 size = (totalram_pages << PAGE_SHIFT) / 16384 /
229                        sizeof(struct list_head);
230                 if (totalram_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
231                         size = 8192;
232                 if (size < 16)
233                         size = 16;
234         }
235         /* FIXME: don't use vmalloc() here or anywhere else -HW */
236         hinfo = vmalloc(sizeof(struct xt_hashlimit_htable) +
237                         sizeof(struct list_head) * size);
238         if (hinfo == NULL)
239                 return -ENOMEM;
240         minfo->hinfo = hinfo;
241 
242         /* copy match config into hashtable config */
243         memcpy(&hinfo->cfg, &minfo->cfg, sizeof(hinfo->cfg));
244         hinfo->cfg.size = size;
245         if (hinfo->cfg.max == 0)
246                 hinfo->cfg.max = 8 * hinfo->cfg.size;
247         else if (hinfo->cfg.max < hinfo->cfg.size)
248                 hinfo->cfg.max = hinfo->cfg.size;
249 
250         for (i = 0; i < hinfo->cfg.size; i++)
251                 INIT_HLIST_HEAD(&hinfo->hash[i]);
252 
253         hinfo->use = 1;
254         hinfo->count = 0;
255         hinfo->family = family;
256         hinfo->rnd_initialized = false;
257         spin_lock_init(&hinfo->lock);
258 
259         hinfo->pde = proc_create_data(minfo->name, 0,
260                 (family == NFPROTO_IPV4) ?
261                 hashlimit_net->ipt_hashlimit : hashlimit_net->ip6t_hashlimit,
262                 &dl_file_ops, hinfo);
263         if (hinfo->pde == NULL) {
264                 vfree(hinfo);
265                 return -ENOMEM;
266         }
267         hinfo->net = net;
268 
269         setup_timer(&hinfo->timer, htable_gc, (unsigned long)hinfo);
270         hinfo->timer.expires = jiffies + msecs_to_jiffies(hinfo->cfg.gc_interval);
271         add_timer(&hinfo->timer);
272 
273         hlist_add_head(&hinfo->node, &hashlimit_net->htables);
274 
275         return 0;
276 }
277 
278 static bool select_all(const struct xt_hashlimit_htable *ht,
279                        const struct dsthash_ent *he)
280 {
281         return 1;
282 }
283 
284 static bool select_gc(const struct xt_hashlimit_htable *ht,
285                       const struct dsthash_ent *he)
286 {
287         return time_after_eq(jiffies, he->expires);
288 }
289 
290 static void htable_selective_cleanup(struct xt_hashlimit_htable *ht,
291                         bool (*select)(const struct xt_hashlimit_htable *ht,
292                                       const struct dsthash_ent *he))
293 {
294         unsigned int i;
295 
296         /* lock hash table and iterate over it */
297         spin_lock_bh(&ht->lock);
298         for (i = 0; i < ht->cfg.size; i++) {
299                 struct dsthash_ent *dh;
300                 struct hlist_node *pos, *n;
301                 hlist_for_each_entry_safe(dh, pos, n, &ht->hash[i], node) {
302                         if ((*select)(ht, dh))
303                                 dsthash_free(ht, dh);
304                 }
305         }
306         spin_unlock_bh(&ht->lock);
307 }
308 
309 /* hash table garbage collector, run by timer */
310 static void htable_gc(unsigned long htlong)
311 {
312         struct xt_hashlimit_htable *ht = (struct xt_hashlimit_htable *)htlong;
313 
314         htable_selective_cleanup(ht, select_gc);
315 
316         /* re-add the timer accordingly */
317         ht->timer.expires = jiffies + msecs_to_jiffies(ht->cfg.gc_interval);
318         add_timer(&ht->timer);
319 }
320 
321 static void htable_destroy(struct xt_hashlimit_htable *hinfo)
322 {
323         struct hashlimit_net *hashlimit_net = hashlimit_pernet(hinfo->net);
324         struct proc_dir_entry *parent;
325 
326         del_timer_sync(&hinfo->timer);
327 
328         if (hinfo->family == NFPROTO_IPV4)
329                 parent = hashlimit_net->ipt_hashlimit;
330         else
331                 parent = hashlimit_net->ip6t_hashlimit;
332 
333         if(parent != NULL)
334                 remove_proc_entry(hinfo->pde->name, parent);
335 
336         htable_selective_cleanup(hinfo, select_all);
337         vfree(hinfo);
338 }
339 
340 static struct xt_hashlimit_htable *htable_find_get(struct net *net,
341                                                    const char *name,
342                                                    u_int8_t family)
343 {
344         struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
345         struct xt_hashlimit_htable *hinfo;
346         struct hlist_node *pos;
347 
348         hlist_for_each_entry(hinfo, pos, &hashlimit_net->htables, node) {
349                 if (!strcmp(name, hinfo->pde->name) &&
350                     hinfo->family == family) {
351                         hinfo->use++;
352                         return hinfo;
353                 }
354         }
355         return NULL;
356 }
357 
358 static void htable_put(struct xt_hashlimit_htable *hinfo)
359 {
360         mutex_lock(&hashlimit_mutex);
361         if (--hinfo->use == 0) {
362                 hlist_del(&hinfo->node);
363                 htable_destroy(hinfo);
364         }
365         mutex_unlock(&hashlimit_mutex);
366 }
367 
368 /* The algorithm used is the Simple Token Bucket Filter (TBF)
369  * see net/sched/sch_tbf.c in the linux source tree
370  */
371 
372 /* Rusty: This is my (non-mathematically-inclined) understanding of
373    this algorithm.  The `average rate' in jiffies becomes your initial
374    amount of credit `credit' and the most credit you can ever have
375    `credit_cap'.  The `peak rate' becomes the cost of passing the
376    test, `cost'.
377 
378    `prev' tracks the last packet hit: you gain one credit per jiffy.
379    If you get credit balance more than this, the extra credit is
380    discarded.  Every time the match passes, you lose `cost' credits;
381    if you don't have that many, the test fails.
382 
383    See Alexey's formal explanation in net/sched/sch_tbf.c.
384 
385    To get the maximum range, we multiply by this factor (ie. you get N
386    credits per jiffy).  We want to allow a rate as low as 1 per day
387    (slowest userspace tool allows), which means
388    CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32 ie.
389 */
390 #define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
391 
392 /* Repeated shift and or gives us all 1s, final shift and add 1 gives
393  * us the power of 2 below the theoretical max, so GCC simply does a
394  * shift. */
395 #define _POW2_BELOW2(x) ((x)|((x)>>1))
396 #define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
397 #define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
398 #define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
399 #define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
400 #define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
401 
402 #define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
403 
404 /* in byte mode, the lowest possible rate is one packet/second.
405  * credit_cap is used as a counter that tells us how many times we can
406  * refill the "credits available" counter when it becomes empty.
407  */
408 #define MAX_CPJ_BYTES (0xFFFFFFFF / HZ)
409 #define CREDITS_PER_JIFFY_BYTES POW2_BELOW32(MAX_CPJ_BYTES)
410 
411 static u32 xt_hashlimit_len_to_chunks(u32 len)
412 {
413         return (len >> XT_HASHLIMIT_BYTE_SHIFT) + 1;
414 }
415 
416 /* Precision saver. */
417 static u32 user2credits(u32 user)
418 {
419         /* If multiplying would overflow... */
420         if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
421                 /* Divide first. */
422                 return (user / XT_HASHLIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
423 
424         return (user * HZ * CREDITS_PER_JIFFY) / XT_HASHLIMIT_SCALE;
425 }
426 
427 static u32 user2credits_byte(u32 user)
428 {
429         u64 us = user;
430         us *= HZ * CREDITS_PER_JIFFY_BYTES;
431         return (u32) (us >> 32);
432 }
433 
434 static void rateinfo_recalc(struct dsthash_ent *dh, unsigned long now, u32 mode)
435 {
436         unsigned long delta = now - dh->rateinfo.prev;
437         u32 cap;
438 
439         if (delta == 0)
440                 return;
441 
442         dh->rateinfo.prev = now;
443 
444         if (mode & XT_HASHLIMIT_BYTES) {
445                 u32 tmp = dh->rateinfo.credit;
446                 dh->rateinfo.credit += CREDITS_PER_JIFFY_BYTES * delta;
447                 cap = CREDITS_PER_JIFFY_BYTES * HZ;
448                 if (tmp >= dh->rateinfo.credit) {/* overflow */
449                         dh->rateinfo.credit = cap;
450                         return;
451                 }
452         } else {
453                 dh->rateinfo.credit += delta * CREDITS_PER_JIFFY;
454                 cap = dh->rateinfo.credit_cap;
455         }
456         if (dh->rateinfo.credit > cap)
457                 dh->rateinfo.credit = cap;
458 }
459 
460 static void rateinfo_init(struct dsthash_ent *dh,
461                           struct xt_hashlimit_htable *hinfo)
462 {
463         dh->rateinfo.prev = jiffies;
464         if (hinfo->cfg.mode & XT_HASHLIMIT_BYTES) {
465                 dh->rateinfo.credit = CREDITS_PER_JIFFY_BYTES * HZ;
466                 dh->rateinfo.cost = user2credits_byte(hinfo->cfg.avg);
467                 dh->rateinfo.credit_cap = hinfo->cfg.burst;
468         } else {
469                 dh->rateinfo.credit = user2credits(hinfo->cfg.avg *
470                                                    hinfo->cfg.burst);
471                 dh->rateinfo.cost = user2credits(hinfo->cfg.avg);
472                 dh->rateinfo.credit_cap = dh->rateinfo.credit;
473         }
474 }
475 
476 static inline __be32 maskl(__be32 a, unsigned int l)
477 {
478         return l ? htonl(ntohl(a) & ~0 << (32 - l)) : 0;
479 }
480 
481 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
482 static void hashlimit_ipv6_mask(__be32 *i, unsigned int p)
483 {
484         switch (p) {
485         case 0 ... 31:
486                 i[0] = maskl(i[0], p);
487                 i[1] = i[2] = i[3] = 0;
488                 break;
489         case 32 ... 63:
490                 i[1] = maskl(i[1], p - 32);
491                 i[2] = i[3] = 0;
492                 break;
493         case 64 ... 95:
494                 i[2] = maskl(i[2], p - 64);
495                 i[3] = 0;
496                 break;
497         case 96 ... 127:
498                 i[3] = maskl(i[3], p - 96);
499                 break;
500         case 128:
501                 break;
502         }
503 }
504 #endif
505 
506 static int
507 hashlimit_init_dst(const struct xt_hashlimit_htable *hinfo,
508                    struct dsthash_dst *dst,
509                    const struct sk_buff *skb, unsigned int protoff)
510 {
511         __be16 _ports[2], *ports;
512         u8 nexthdr;
513         int poff;
514 
515         memset(dst, 0, sizeof(*dst));
516 
517         switch (hinfo->family) {
518         case NFPROTO_IPV4:
519                 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DIP)
520                         dst->ip.dst = maskl(ip_hdr(skb)->daddr,
521                                       hinfo->cfg.dstmask);
522                 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SIP)
523                         dst->ip.src = maskl(ip_hdr(skb)->saddr,
524                                       hinfo->cfg.srcmask);
525 
526                 if (!(hinfo->cfg.mode &
527                       (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
528                         return 0;
529                 nexthdr = ip_hdr(skb)->protocol;
530                 break;
531 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
532         case NFPROTO_IPV6:
533         {
534                 __be16 frag_off;
535 
536                 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DIP) {
537                         memcpy(&dst->ip6.dst, &ipv6_hdr(skb)->daddr,
538                                sizeof(dst->ip6.dst));
539                         hashlimit_ipv6_mask(dst->ip6.dst, hinfo->cfg.dstmask);
540                 }
541                 if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SIP) {
542                         memcpy(&dst->ip6.src, &ipv6_hdr(skb)->saddr,
543                                sizeof(dst->ip6.src));
544                         hashlimit_ipv6_mask(dst->ip6.src, hinfo->cfg.srcmask);
545                 }
546 
547                 if (!(hinfo->cfg.mode &
548                       (XT_HASHLIMIT_HASH_DPT | XT_HASHLIMIT_HASH_SPT)))
549                         return 0;
550                 nexthdr = ipv6_hdr(skb)->nexthdr;
551                 protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr, &frag_off);
552                 if ((int)protoff < 0)
553                         return -1;
554                 break;
555         }
556 #endif
557         default:
558                 BUG();
559                 return 0;
560         }
561 
562         poff = proto_ports_offset(nexthdr);
563         if (poff >= 0) {
564                 ports = skb_header_pointer(skb, protoff + poff, sizeof(_ports),
565                                            &_ports);
566         } else {
567                 _ports[0] = _ports[1] = 0;
568                 ports = _ports;
569         }
570         if (!ports)
571                 return -1;
572         if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_SPT)
573                 dst->src_port = ports[0];
574         if (hinfo->cfg.mode & XT_HASHLIMIT_HASH_DPT)
575                 dst->dst_port = ports[1];
576         return 0;
577 }
578 
579 static u32 hashlimit_byte_cost(unsigned int len, struct dsthash_ent *dh)
580 {
581         u64 tmp = xt_hashlimit_len_to_chunks(len);
582         tmp = tmp * dh->rateinfo.cost;
583 
584         if (unlikely(tmp > CREDITS_PER_JIFFY_BYTES * HZ))
585                 tmp = CREDITS_PER_JIFFY_BYTES * HZ;
586 
587         if (dh->rateinfo.credit < tmp && dh->rateinfo.credit_cap) {
588                 dh->rateinfo.credit_cap--;
589                 dh->rateinfo.credit = CREDITS_PER_JIFFY_BYTES * HZ;
590         }
591         return (u32) tmp;
592 }
593 
594 static bool
595 hashlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
596 {
597         const struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
598         struct xt_hashlimit_htable *hinfo = info->hinfo;
599         unsigned long now = jiffies;
600         struct dsthash_ent *dh;
601         struct dsthash_dst dst;
602         bool race = false;
603         u32 cost;
604 
605         if (hashlimit_init_dst(hinfo, &dst, skb, par->thoff) < 0)
606                 goto hotdrop;
607 
608         rcu_read_lock_bh();
609         dh = dsthash_find(hinfo, &dst);
610         if (dh == NULL) {
611                 dh = dsthash_alloc_init(hinfo, &dst, &race);
612                 if (dh == NULL) {
613                         rcu_read_unlock_bh();
614                         goto hotdrop;
615                 } else if (race) {
616                         /* Already got an entry, update expiration timeout */
617                         dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);
618                         rateinfo_recalc(dh, now, hinfo->cfg.mode);
619                 } else {
620                         dh->expires = jiffies + msecs_to_jiffies(hinfo->cfg.expire);
621                         rateinfo_init(dh, hinfo);
622                 }
623         } else {
624                 /* update expiration timeout */
625                 dh->expires = now + msecs_to_jiffies(hinfo->cfg.expire);
626                 rateinfo_recalc(dh, now, hinfo->cfg.mode);
627         }
628 
629         if (info->cfg.mode & XT_HASHLIMIT_BYTES)
630                 cost = hashlimit_byte_cost(skb->len, dh);
631         else
632                 cost = dh->rateinfo.cost;
633 
634         if (dh->rateinfo.credit >= cost) {
635                 /* below the limit */
636                 dh->rateinfo.credit -= cost;
637                 spin_unlock(&dh->lock);
638                 rcu_read_unlock_bh();
639                 return !(info->cfg.mode & XT_HASHLIMIT_INVERT);
640         }
641 
642         spin_unlock(&dh->lock);
643         rcu_read_unlock_bh();
644         /* default match is underlimit - so over the limit, we need to invert */
645         return info->cfg.mode & XT_HASHLIMIT_INVERT;
646 
647  hotdrop:
648         par->hotdrop = true;
649         return false;
650 }
651 
652 static int hashlimit_mt_check(const struct xt_mtchk_param *par)
653 {
654         struct net *net = par->net;
655         struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
656         int ret;
657 
658         if (info->cfg.gc_interval == 0 || info->cfg.expire == 0)
659                 return -EINVAL;
660         if (info->name[sizeof(info->name)-1] != '\0')
661                 return -EINVAL;
662         if (par->family == NFPROTO_IPV4) {
663                 if (info->cfg.srcmask > 32 || info->cfg.dstmask > 32)
664                         return -EINVAL;
665         } else {
666                 if (info->cfg.srcmask > 128 || info->cfg.dstmask > 128)
667                         return -EINVAL;
668         }
669 
670         if (info->cfg.mode & ~XT_HASHLIMIT_ALL) {
671                 pr_info("Unknown mode mask %X, kernel too old?\n",
672                                                 info->cfg.mode);
673                 return -EINVAL;
674         }
675 
676         /* Check for overflow. */
677         if (info->cfg.mode & XT_HASHLIMIT_BYTES) {
678                 if (user2credits_byte(info->cfg.avg) == 0) {
679                         pr_info("overflow, rate too high: %u\n", info->cfg.avg);
680                         return -EINVAL;
681                 }
682         } else if (info->cfg.burst == 0 ||
683                     user2credits(info->cfg.avg * info->cfg.burst) <
684                     user2credits(info->cfg.avg)) {
685                         pr_info("overflow, try lower: %u/%u\n",
686                                 info->cfg.avg, info->cfg.burst);
687                         return -ERANGE;
688         }
689 
690         mutex_lock(&hashlimit_mutex);
691         info->hinfo = htable_find_get(net, info->name, par->family);
692         if (info->hinfo == NULL) {
693                 ret = htable_create(net, info, par->family);
694                 if (ret < 0) {
695                         mutex_unlock(&hashlimit_mutex);
696                         return ret;
697                 }
698         }
699         mutex_unlock(&hashlimit_mutex);
700         return 0;
701 }
702 
703 static void hashlimit_mt_destroy(const struct xt_mtdtor_param *par)
704 {
705         const struct xt_hashlimit_mtinfo1 *info = par->matchinfo;
706 
707         htable_put(info->hinfo);
708 }
709 
710 static struct xt_match hashlimit_mt_reg[] __read_mostly = {
711         {
712                 .name           = "hashlimit",
713                 .revision       = 1,
714                 .family         = NFPROTO_IPV4,
715                 .match          = hashlimit_mt,
716                 .matchsize      = sizeof(struct xt_hashlimit_mtinfo1),
717                 .checkentry     = hashlimit_mt_check,
718                 .destroy        = hashlimit_mt_destroy,
719                 .me             = THIS_MODULE,
720         },
721 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
722         {
723                 .name           = "hashlimit",
724                 .revision       = 1,
725                 .family         = NFPROTO_IPV6,
726                 .match          = hashlimit_mt,
727                 .matchsize      = sizeof(struct xt_hashlimit_mtinfo1),
728                 .checkentry     = hashlimit_mt_check,
729                 .destroy        = hashlimit_mt_destroy,
730                 .me             = THIS_MODULE,
731         },
732 #endif
733 };
734 
735 /* PROC stuff */
736 static void *dl_seq_start(struct seq_file *s, loff_t *pos)
737         __acquires(htable->lock)
738 {
739         struct xt_hashlimit_htable *htable = s->private;
740         unsigned int *bucket;
741 
742         spin_lock_bh(&htable->lock);
743         if (*pos >= htable->cfg.size)
744                 return NULL;
745 
746         bucket = kmalloc(sizeof(unsigned int), GFP_ATOMIC);
747         if (!bucket)
748                 return ERR_PTR(-ENOMEM);
749 
750         *bucket = *pos;
751         return bucket;
752 }
753 
754 static void *dl_seq_next(struct seq_file *s, void *v, loff_t *pos)
755 {
756         struct xt_hashlimit_htable *htable = s->private;
757         unsigned int *bucket = (unsigned int *)v;
758 
759         *pos = ++(*bucket);
760         if (*pos >= htable->cfg.size) {
761                 kfree(v);
762                 return NULL;
763         }
764         return bucket;
765 }
766 
767 static void dl_seq_stop(struct seq_file *s, void *v)
768         __releases(htable->lock)
769 {
770         struct xt_hashlimit_htable *htable = s->private;
771         unsigned int *bucket = (unsigned int *)v;
772 
773         if (!IS_ERR(bucket))
774                 kfree(bucket);
775         spin_unlock_bh(&htable->lock);
776 }
777 
778 static int dl_seq_real_show(struct dsthash_ent *ent, u_int8_t family,
779                                    struct seq_file *s)
780 {
781         int res;
782         const struct xt_hashlimit_htable *ht = s->private;
783 
784         spin_lock(&ent->lock);
785         /* recalculate to show accurate numbers */
786         rateinfo_recalc(ent, jiffies, ht->cfg.mode);
787 
788         switch (family) {
789         case NFPROTO_IPV4:
790                 res = seq_printf(s, "%ld %pI4:%u->%pI4:%u %u %u %u\n",
791                                  (long)(ent->expires - jiffies)/HZ,
792                                  &ent->dst.ip.src,
793                                  ntohs(ent->dst.src_port),
794                                  &ent->dst.ip.dst,
795                                  ntohs(ent->dst.dst_port),
796                                  ent->rateinfo.credit, ent->rateinfo.credit_cap,
797                                  ent->rateinfo.cost);
798                 break;
799 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
800         case NFPROTO_IPV6:
801                 res = seq_printf(s, "%ld %pI6:%u->%pI6:%u %u %u %u\n",
802                                  (long)(ent->expires - jiffies)/HZ,
803                                  &ent->dst.ip6.src,
804                                  ntohs(ent->dst.src_port),
805                                  &ent->dst.ip6.dst,
806                                  ntohs(ent->dst.dst_port),
807                                  ent->rateinfo.credit, ent->rateinfo.credit_cap,
808                                  ent->rateinfo.cost);
809                 break;
810 #endif
811         default:
812                 BUG();
813                 res = 0;
814         }
815         spin_unlock(&ent->lock);
816         return res;
817 }
818 
819 static int dl_seq_show(struct seq_file *s, void *v)
820 {
821         struct xt_hashlimit_htable *htable = s->private;
822         unsigned int *bucket = (unsigned int *)v;
823         struct dsthash_ent *ent;
824         struct hlist_node *pos;
825 
826         if (!hlist_empty(&htable->hash[*bucket])) {
827                 hlist_for_each_entry(ent, pos, &htable->hash[*bucket], node)
828                         if (dl_seq_real_show(ent, htable->family, s))
829                                 return -1;
830         }
831         return 0;
832 }
833 
834 static const struct seq_operations dl_seq_ops = {
835         .start = dl_seq_start,
836         .next  = dl_seq_next,
837         .stop  = dl_seq_stop,
838         .show  = dl_seq_show
839 };
840 
841 static int dl_proc_open(struct inode *inode, struct file *file)
842 {
843         int ret = seq_open(file, &dl_seq_ops);
844 
845         if (!ret) {
846                 struct seq_file *sf = file->private_data;
847                 sf->private = PDE(inode)->data;
848         }
849         return ret;
850 }
851 
852 static const struct file_operations dl_file_ops = {
853         .owner   = THIS_MODULE,
854         .open    = dl_proc_open,
855         .read    = seq_read,
856         .llseek  = seq_lseek,
857         .release = seq_release
858 };
859 
860 static int __net_init hashlimit_proc_net_init(struct net *net)
861 {
862         struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
863 
864         hashlimit_net->ipt_hashlimit = proc_mkdir("ipt_hashlimit", net->proc_net);
865         if (!hashlimit_net->ipt_hashlimit)
866                 return -ENOMEM;
867 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
868         hashlimit_net->ip6t_hashlimit = proc_mkdir("ip6t_hashlimit", net->proc_net);
869         if (!hashlimit_net->ip6t_hashlimit) {
870                 proc_net_remove(net, "ipt_hashlimit");
871                 return -ENOMEM;
872         }
873 #endif
874         return 0;
875 }
876 
877 static void __net_exit hashlimit_proc_net_exit(struct net *net)
878 {
879         struct xt_hashlimit_htable *hinfo;
880         struct hlist_node *pos;
881         struct proc_dir_entry *pde;
882         struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
883 
884         /* recent_net_exit() is called before recent_mt_destroy(). Make sure
885          * that the parent xt_recent proc entry is is empty before trying to
886          * remove it.
887          */
888         mutex_lock(&hashlimit_mutex);
889         pde = hashlimit_net->ipt_hashlimit;
890         if (pde == NULL)
891                 pde = hashlimit_net->ip6t_hashlimit;
892 
893         hlist_for_each_entry(hinfo, pos, &hashlimit_net->htables, node)
894                 remove_proc_entry(hinfo->pde->name, pde);
895 
896         hashlimit_net->ipt_hashlimit = NULL;
897         hashlimit_net->ip6t_hashlimit = NULL;
898         mutex_unlock(&hashlimit_mutex);
899 
900         proc_net_remove(net, "ipt_hashlimit");
901 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
902         proc_net_remove(net, "ip6t_hashlimit");
903 #endif
904 }
905 
906 static int __net_init hashlimit_net_init(struct net *net)
907 {
908         struct hashlimit_net *hashlimit_net = hashlimit_pernet(net);
909 
910         INIT_HLIST_HEAD(&hashlimit_net->htables);
911         return hashlimit_proc_net_init(net);
912 }
913 
914 static void __net_exit hashlimit_net_exit(struct net *net)
915 {
916         hashlimit_proc_net_exit(net);
917 }
918 
919 static struct pernet_operations hashlimit_net_ops = {
920         .init   = hashlimit_net_init,
921         .exit   = hashlimit_net_exit,
922         .id     = &hashlimit_net_id,
923         .size   = sizeof(struct hashlimit_net),
924 };
925 
926 static int __init hashlimit_mt_init(void)
927 {
928         int err;
929 
930         err = register_pernet_subsys(&hashlimit_net_ops);
931         if (err < 0)
932                 return err;
933         err = xt_register_matches(hashlimit_mt_reg,
934               ARRAY_SIZE(hashlimit_mt_reg));
935         if (err < 0)
936                 goto err1;
937 
938         err = -ENOMEM;
939         hashlimit_cachep = kmem_cache_create("xt_hashlimit",
940                                             sizeof(struct dsthash_ent), 0, 0,
941                                             NULL);
942         if (!hashlimit_cachep) {
943                 pr_warning("unable to create slab cache\n");
944                 goto err2;
945         }
946         return 0;
947 
948 err2:
949         xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
950 err1:
951         unregister_pernet_subsys(&hashlimit_net_ops);
952         return err;
953 
954 }
955 
956 static void __exit hashlimit_mt_exit(void)
957 {
958         xt_unregister_matches(hashlimit_mt_reg, ARRAY_SIZE(hashlimit_mt_reg));
959         unregister_pernet_subsys(&hashlimit_net_ops);
960 
961         rcu_barrier_bh();
962         kmem_cache_destroy(hashlimit_cachep);
963 }
964 
965 module_init(hashlimit_mt_init);
966 module_exit(hashlimit_mt_exit);
967 

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