1 /*
2 * INETPEER - A storage for permanent information about peers
3 *
4 * This source is covered by the GNU GPL, the same as all kernel sources.
5 *
6 * Authors: Andrey V. Savochkin <saw@msu.ru>
7 */
8
9 #include <linux/module.h>
10 #include <linux/types.h>
11 #include <linux/slab.h>
12 #include <linux/interrupt.h>
13 #include <linux/spinlock.h>
14 #include <linux/random.h>
15 #include <linux/timer.h>
16 #include <linux/time.h>
17 #include <linux/kernel.h>
18 #include <linux/mm.h>
19 #include <linux/net.h>
20 #include <net/ip.h>
21 #include <net/inetpeer.h>
22
23 /*
24 * Theory of operations.
25 * We keep one entry for each peer IP address. The nodes contains long-living
26 * information about the peer which doesn't depend on routes.
27 * At this moment this information consists only of ID field for the next
28 * outgoing IP packet. This field is incremented with each packet as encoded
29 * in inet_getid() function (include/net/inetpeer.h).
30 * At the moment of writing this notes identifier of IP packets is generated
31 * to be unpredictable using this code only for packets subjected
32 * (actually or potentially) to defragmentation. I.e. DF packets less than
33 * PMTU in size uses a constant ID and do not use this code (see
34 * ip_select_ident() in include/net/ip.h).
35 *
36 * Route cache entries hold references to our nodes.
37 * New cache entries get references via lookup by destination IP address in
38 * the avl tree. The reference is grabbed only when it's needed i.e. only
39 * when we try to output IP packet which needs an unpredictable ID (see
40 * __ip_select_ident() in net/ipv4/route.c).
41 * Nodes are removed only when reference counter goes to 0.
42 * When it's happened the node may be removed when a sufficient amount of
43 * time has been passed since its last use. The less-recently-used entry can
44 * also be removed if the pool is overloaded i.e. if the total amount of
45 * entries is greater-or-equal than the threshold.
46 *
47 * Node pool is organised as an AVL tree.
48 * Such an implementation has been chosen not just for fun. It's a way to
49 * prevent easy and efficient DoS attacks by creating hash collisions. A huge
50 * amount of long living nodes in a single hash slot would significantly delay
51 * lookups performed with disabled BHs.
52 *
53 * Serialisation issues.
54 * 1. Nodes may appear in the tree only with the pool lock held.
55 * 2. Nodes may disappear from the tree only with the pool lock held
56 * AND reference count being 0.
57 * 3. Nodes appears and disappears from unused node list only under
58 * "inet_peer_unused_lock".
59 * 4. Global variable peer_total is modified under the pool lock.
60 * 5. struct inet_peer fields modification:
61 * avl_left, avl_right, avl_parent, avl_height: pool lock
62 * unused: unused node list lock
63 * refcnt: atomically against modifications on other CPU;
64 * usually under some other lock to prevent node disappearing
65 * dtime: unused node list lock
66 * daddr: unchangeable
67 * ip_id_count: atomic value (no lock needed)
68 */
69
70 static struct kmem_cache *peer_cachep __read_mostly;
71
72 #define node_height(x) x->avl_height
73
74 #define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
75 #define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
76 static const struct inet_peer peer_fake_node = {
77 .avl_left = peer_avl_empty_rcu,
78 .avl_right = peer_avl_empty_rcu,
79 .avl_height = 0
80 };
81
82 struct inet_peer_base {
83 struct inet_peer __rcu *root;
84 seqlock_t lock;
85 int total;
86 };
87
88 static struct inet_peer_base v4_peers = {
89 .root = peer_avl_empty_rcu,
90 .lock = __SEQLOCK_UNLOCKED(v4_peers.lock),
91 .total = 0,
92 };
93
94 static struct inet_peer_base v6_peers = {
95 .root = peer_avl_empty_rcu,
96 .lock = __SEQLOCK_UNLOCKED(v6_peers.lock),
97 .total = 0,
98 };
99
100 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
101
102 /* Exported for sysctl_net_ipv4. */
103 int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
104 * aggressively at this stage */
105 int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
106 int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
107 int inet_peer_gc_mintime __read_mostly = 10 * HZ;
108 int inet_peer_gc_maxtime __read_mostly = 120 * HZ;
109
110 static struct {
111 struct list_head list;
112 spinlock_t lock;
113 } unused_peers = {
114 .list = LIST_HEAD_INIT(unused_peers.list),
115 .lock = __SPIN_LOCK_UNLOCKED(unused_peers.lock),
116 };
117
118 static void peer_check_expire(unsigned long dummy);
119 static DEFINE_TIMER(peer_periodic_timer, peer_check_expire, 0, 0);
120
121
122 /* Called from ip_output.c:ip_init */
inet_initpeers(void)123 void __init inet_initpeers(void)
124 {
125 struct sysinfo si;
126
127 /* Use the straight interface to information about memory. */
128 si_meminfo(&si);
129 /* The values below were suggested by Alexey Kuznetsov
130 * <kuznet@ms2.inr.ac.ru>. I don't have any opinion about the values
131 * myself. --SAW
132 */
133 if (si.totalram <= (32768*1024)/PAGE_SIZE)
134 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
135 if (si.totalram <= (16384*1024)/PAGE_SIZE)
136 inet_peer_threshold >>= 1; /* about 512KB */
137 if (si.totalram <= (8192*1024)/PAGE_SIZE)
138 inet_peer_threshold >>= 2; /* about 128KB */
139
140 peer_cachep = kmem_cache_create("inet_peer_cache",
141 sizeof(struct inet_peer),
142 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
143 NULL);
144
145 /* All the timers, started at system startup tend
146 to synchronize. Perturb it a bit.
147 */
148 peer_periodic_timer.expires = jiffies
149 + net_random() % inet_peer_gc_maxtime
150 + inet_peer_gc_maxtime;
151 add_timer(&peer_periodic_timer);
152 }
153
154 /* Called with or without local BH being disabled. */
unlink_from_unused(struct inet_peer * p)155 static void unlink_from_unused(struct inet_peer *p)
156 {
157 if (!list_empty(&p->unused)) {
158 spin_lock_bh(&unused_peers.lock);
159 list_del_init(&p->unused);
160 spin_unlock_bh(&unused_peers.lock);
161 }
162 }
163
addr_compare(const struct inetpeer_addr * a,const struct inetpeer_addr * b)164 static int addr_compare(const struct inetpeer_addr *a,
165 const struct inetpeer_addr *b)
166 {
167 int i, n = (a->family == AF_INET ? 1 : 4);
168
169 for (i = 0; i < n; i++) {
170 if (a->addr.a6[i] == b->addr.a6[i])
171 continue;
172 if (a->addr.a6[i] < b->addr.a6[i])
173 return -1;
174 return 1;
175 }
176
177 return 0;
178 }
179
180 #define rcu_deref_locked(X, BASE) \
181 rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
182
183 /*
184 * Called with local BH disabled and the pool lock held.
185 */
186 #define lookup(_daddr, _stack, _base) \
187 ({ \
188 struct inet_peer *u; \
189 struct inet_peer __rcu **v; \
190 \
191 stackptr = _stack; \
192 *stackptr++ = &_base->root; \
193 for (u = rcu_deref_locked(_base->root, _base); \
194 u != peer_avl_empty; ) { \
195 int cmp = addr_compare(_daddr, &u->daddr); \
196 if (cmp == 0) \
197 break; \
198 if (cmp == -1) \
199 v = &u->avl_left; \
200 else \
201 v = &u->avl_right; \
202 *stackptr++ = v; \
203 u = rcu_deref_locked(*v, _base); \
204 } \
205 u; \
206 })
207
208 /*
209 * Called with rcu_read_lock()
210 * Because we hold no lock against a writer, its quite possible we fall
211 * in an endless loop.
212 * But every pointer we follow is guaranteed to be valid thanks to RCU.
213 * We exit from this function if number of links exceeds PEER_MAXDEPTH
214 */
lookup_rcu(const struct inetpeer_addr * daddr,struct inet_peer_base * base)215 static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
216 struct inet_peer_base *base)
217 {
218 struct inet_peer *u = rcu_dereference(base->root);
219 int count = 0;
220
221 while (u != peer_avl_empty) {
222 int cmp = addr_compare(daddr, &u->daddr);
223 if (cmp == 0) {
224 /* Before taking a reference, check if this entry was
225 * deleted, unlink_from_pool() sets refcnt=-1 to make
226 * distinction between an unused entry (refcnt=0) and
227 * a freed one.
228 */
229 if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1)))
230 u = NULL;
231 return u;
232 }
233 if (cmp == -1)
234 u = rcu_dereference(u->avl_left);
235 else
236 u = rcu_dereference(u->avl_right);
237 if (unlikely(++count == PEER_MAXDEPTH))
238 break;
239 }
240 return NULL;
241 }
242
243 /* Called with local BH disabled and the pool lock held. */
244 #define lookup_rightempty(start, base) \
245 ({ \
246 struct inet_peer *u; \
247 struct inet_peer __rcu **v; \
248 *stackptr++ = &start->avl_left; \
249 v = &start->avl_left; \
250 for (u = rcu_deref_locked(*v, base); \
251 u->avl_right != peer_avl_empty_rcu; ) { \
252 v = &u->avl_right; \
253 *stackptr++ = v; \
254 u = rcu_deref_locked(*v, base); \
255 } \
256 u; \
257 })
258
259 /* Called with local BH disabled and the pool lock held.
260 * Variable names are the proof of operation correctness.
261 * Look into mm/map_avl.c for more detail description of the ideas.
262 */
peer_avl_rebalance(struct inet_peer __rcu ** stack[],struct inet_peer __rcu *** stackend,struct inet_peer_base * base)263 static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
264 struct inet_peer __rcu ***stackend,
265 struct inet_peer_base *base)
266 {
267 struct inet_peer __rcu **nodep;
268 struct inet_peer *node, *l, *r;
269 int lh, rh;
270
271 while (stackend > stack) {
272 nodep = *--stackend;
273 node = rcu_deref_locked(*nodep, base);
274 l = rcu_deref_locked(node->avl_left, base);
275 r = rcu_deref_locked(node->avl_right, base);
276 lh = node_height(l);
277 rh = node_height(r);
278 if (lh > rh + 1) { /* l: RH+2 */
279 struct inet_peer *ll, *lr, *lrl, *lrr;
280 int lrh;
281 ll = rcu_deref_locked(l->avl_left, base);
282 lr = rcu_deref_locked(l->avl_right, base);
283 lrh = node_height(lr);
284 if (lrh <= node_height(ll)) { /* ll: RH+1 */
285 RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */
286 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
287 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
288 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */
289 RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */
290 l->avl_height = node->avl_height + 1;
291 RCU_INIT_POINTER(*nodep, l);
292 } else { /* ll: RH, lr: RH+1 */
293 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
294 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
295 RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */
296 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
297 node->avl_height = rh + 1; /* node: RH+1 */
298 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */
299 RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */
300 l->avl_height = rh + 1; /* l: RH+1 */
301 RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */
302 RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */
303 lr->avl_height = rh + 2;
304 RCU_INIT_POINTER(*nodep, lr);
305 }
306 } else if (rh > lh + 1) { /* r: LH+2 */
307 struct inet_peer *rr, *rl, *rlr, *rll;
308 int rlh;
309 rr = rcu_deref_locked(r->avl_right, base);
310 rl = rcu_deref_locked(r->avl_left, base);
311 rlh = node_height(rl);
312 if (rlh <= node_height(rr)) { /* rr: LH+1 */
313 RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */
314 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
315 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
316 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */
317 RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */
318 r->avl_height = node->avl_height + 1;
319 RCU_INIT_POINTER(*nodep, r);
320 } else { /* rr: RH, rl: RH+1 */
321 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
322 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
323 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
324 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
325 node->avl_height = lh + 1; /* node: LH+1 */
326 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */
327 RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */
328 r->avl_height = lh + 1; /* r: LH+1 */
329 RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */
330 RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */
331 rl->avl_height = lh + 2;
332 RCU_INIT_POINTER(*nodep, rl);
333 }
334 } else {
335 node->avl_height = (lh > rh ? lh : rh) + 1;
336 }
337 }
338 }
339
340 /* Called with local BH disabled and the pool lock held. */
341 #define link_to_pool(n, base) \
342 do { \
343 n->avl_height = 1; \
344 n->avl_left = peer_avl_empty_rcu; \
345 n->avl_right = peer_avl_empty_rcu; \
346 /* lockless readers can catch us now */ \
347 rcu_assign_pointer(**--stackptr, n); \
348 peer_avl_rebalance(stack, stackptr, base); \
349 } while (0)
350
inetpeer_free_rcu(struct rcu_head * head)351 static void inetpeer_free_rcu(struct rcu_head *head)
352 {
353 kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
354 }
355
356 /* May be called with local BH enabled. */
unlink_from_pool(struct inet_peer * p,struct inet_peer_base * base,struct inet_peer __rcu ** stack[PEER_MAXDEPTH])357 static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
358 struct inet_peer __rcu **stack[PEER_MAXDEPTH])
359 {
360 int do_free;
361
362 do_free = 0;
363
364 write_seqlock_bh(&base->lock);
365 /* Check the reference counter. It was artificially incremented by 1
366 * in cleanup() function to prevent sudden disappearing. If we can
367 * atomically (because of lockless readers) take this last reference,
368 * it's safe to remove the node and free it later.
369 * We use refcnt=-1 to alert lockless readers this entry is deleted.
370 */
371 if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {
372 struct inet_peer __rcu ***stackptr, ***delp;
373 if (lookup(&p->daddr, stack, base) != p)
374 BUG();
375 delp = stackptr - 1; /* *delp[0] == p */
376 if (p->avl_left == peer_avl_empty_rcu) {
377 *delp[0] = p->avl_right;
378 --stackptr;
379 } else {
380 /* look for a node to insert instead of p */
381 struct inet_peer *t;
382 t = lookup_rightempty(p, base);
383 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
384 **--stackptr = t->avl_left;
385 /* t is removed, t->daddr > x->daddr for any
386 * x in p->avl_left subtree.
387 * Put t in the old place of p. */
388 RCU_INIT_POINTER(*delp[0], t);
389 t->avl_left = p->avl_left;
390 t->avl_right = p->avl_right;
391 t->avl_height = p->avl_height;
392 BUG_ON(delp[1] != &p->avl_left);
393 delp[1] = &t->avl_left; /* was &p->avl_left */
394 }
395 peer_avl_rebalance(stack, stackptr, base);
396 base->total--;
397 do_free = 1;
398 }
399 write_sequnlock_bh(&base->lock);
400
401 if (do_free)
402 call_rcu(&p->rcu, inetpeer_free_rcu);
403 else
404 /* The node is used again. Decrease the reference counter
405 * back. The loop "cleanup -> unlink_from_unused
406 * -> unlink_from_pool -> putpeer -> link_to_unused
407 * -> cleanup (for the same node)"
408 * doesn't really exist because the entry will have a
409 * recent deletion time and will not be cleaned again soon.
410 */
411 inet_putpeer(p);
412 }
413
family_to_base(int family)414 static struct inet_peer_base *family_to_base(int family)
415 {
416 return (family == AF_INET ? &v4_peers : &v6_peers);
417 }
418
peer_to_base(struct inet_peer * p)419 static struct inet_peer_base *peer_to_base(struct inet_peer *p)
420 {
421 return family_to_base(p->daddr.family);
422 }
423
424 /* May be called with local BH enabled. */
cleanup_once(unsigned long ttl,struct inet_peer __rcu ** stack[PEER_MAXDEPTH])425 static int cleanup_once(unsigned long ttl, struct inet_peer __rcu **stack[PEER_MAXDEPTH])
426 {
427 struct inet_peer *p = NULL;
428
429 /* Remove the first entry from the list of unused nodes. */
430 spin_lock_bh(&unused_peers.lock);
431 if (!list_empty(&unused_peers.list)) {
432 __u32 delta;
433
434 p = list_first_entry(&unused_peers.list, struct inet_peer, unused);
435 delta = (__u32)jiffies - p->dtime;
436
437 if (delta < ttl) {
438 /* Do not prune fresh entries. */
439 spin_unlock_bh(&unused_peers.lock);
440 return -1;
441 }
442
443 list_del_init(&p->unused);
444
445 /* Grab an extra reference to prevent node disappearing
446 * before unlink_from_pool() call. */
447 atomic_inc(&p->refcnt);
448 }
449 spin_unlock_bh(&unused_peers.lock);
450
451 if (p == NULL)
452 /* It means that the total number of USED entries has
453 * grown over inet_peer_threshold. It shouldn't really
454 * happen because of entry limits in route cache. */
455 return -1;
456
457 unlink_from_pool(p, peer_to_base(p), stack);
458 return 0;
459 }
460
461 /* Called with or without local BH being disabled. */
inet_getpeer(struct inetpeer_addr * daddr,int create)462 struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
463 {
464 struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
465 struct inet_peer_base *base = family_to_base(daddr->family);
466 struct inet_peer *p;
467 unsigned int sequence;
468 int invalidated;
469
470 /* Look up for the address quickly, lockless.
471 * Because of a concurrent writer, we might not find an existing entry.
472 */
473 rcu_read_lock();
474 sequence = read_seqbegin(&base->lock);
475 p = lookup_rcu(daddr, base);
476 invalidated = read_seqretry(&base->lock, sequence);
477 rcu_read_unlock();
478
479 if (p) {
480 /* The existing node has been found.
481 * Remove the entry from unused list if it was there.
482 */
483 unlink_from_unused(p);
484 return p;
485 }
486
487 /* If no writer did a change during our lookup, we can return early. */
488 if (!create && !invalidated)
489 return NULL;
490
491 /* retry an exact lookup, taking the lock before.
492 * At least, nodes should be hot in our cache.
493 */
494 write_seqlock_bh(&base->lock);
495 p = lookup(daddr, stack, base);
496 if (p != peer_avl_empty) {
497 atomic_inc(&p->refcnt);
498 write_sequnlock_bh(&base->lock);
499 /* Remove the entry from unused list if it was there. */
500 unlink_from_unused(p);
501 return p;
502 }
503 p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
504 if (p) {
505 p->daddr = *daddr;
506 atomic_set(&p->refcnt, 1);
507 atomic_set(&p->rid, 0);
508 atomic_set(&p->ip_id_count, secure_ip_id(daddr->addr.a4));
509 p->tcp_ts_stamp = 0;
510 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
511 p->rate_tokens = 0;
512 p->rate_last = 0;
513 p->pmtu_expires = 0;
514 p->pmtu_orig = 0;
515 memset(&p->redirect_learned, 0, sizeof(p->redirect_learned));
516 INIT_LIST_HEAD(&p->unused);
517
518
519 /* Link the node. */
520 link_to_pool(p, base);
521 base->total++;
522 }
523 write_sequnlock_bh(&base->lock);
524
525 if (base->total >= inet_peer_threshold)
526 /* Remove one less-recently-used entry. */
527 cleanup_once(0, stack);
528
529 return p;
530 }
531
compute_total(void)532 static int compute_total(void)
533 {
534 return v4_peers.total + v6_peers.total;
535 }
536 EXPORT_SYMBOL_GPL(inet_getpeer);
537
538 /* Called with local BH disabled. */
peer_check_expire(unsigned long dummy)539 static void peer_check_expire(unsigned long dummy)
540 {
541 unsigned long now = jiffies;
542 int ttl, total;
543 struct inet_peer __rcu **stack[PEER_MAXDEPTH];
544
545 total = compute_total();
546 if (total >= inet_peer_threshold)
547 ttl = inet_peer_minttl;
548 else
549 ttl = inet_peer_maxttl
550 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
551 total / inet_peer_threshold * HZ;
552 while (!cleanup_once(ttl, stack)) {
553 if (jiffies != now)
554 break;
555 }
556
557 /* Trigger the timer after inet_peer_gc_mintime .. inet_peer_gc_maxtime
558 * interval depending on the total number of entries (more entries,
559 * less interval). */
560 total = compute_total();
561 if (total >= inet_peer_threshold)
562 peer_periodic_timer.expires = jiffies + inet_peer_gc_mintime;
563 else
564 peer_periodic_timer.expires = jiffies
565 + inet_peer_gc_maxtime
566 - (inet_peer_gc_maxtime - inet_peer_gc_mintime) / HZ *
567 total / inet_peer_threshold * HZ;
568 add_timer(&peer_periodic_timer);
569 }
570
inet_putpeer(struct inet_peer * p)571 void inet_putpeer(struct inet_peer *p)
572 {
573 local_bh_disable();
574
575 if (atomic_dec_and_lock(&p->refcnt, &unused_peers.lock)) {
576 list_add_tail(&p->unused, &unused_peers.list);
577 p->dtime = (__u32)jiffies;
578 spin_unlock(&unused_peers.lock);
579 }
580
581 local_bh_enable();
582 }
583 EXPORT_SYMBOL_GPL(inet_putpeer);
584
585 /*
586 * Check transmit rate limitation for given message.
587 * The rate information is held in the inet_peer entries now.
588 * This function is generic and could be used for other purposes
589 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
590 *
591 * Note that the same inet_peer fields are modified by functions in
592 * route.c too, but these work for packet destinations while xrlim_allow
593 * works for icmp destinations. This means the rate limiting information
594 * for one "ip object" is shared - and these ICMPs are twice limited:
595 * by source and by destination.
596 *
597 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
598 * SHOULD allow setting of rate limits
599 *
600 * Shared between ICMPv4 and ICMPv6.
601 */
602 #define XRLIM_BURST_FACTOR 6
inet_peer_xrlim_allow(struct inet_peer * peer,int timeout)603 bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
604 {
605 unsigned long now, token;
606 bool rc = false;
607
608 if (!peer)
609 return true;
610
611 token = peer->rate_tokens;
612 now = jiffies;
613 token += now - peer->rate_last;
614 peer->rate_last = now;
615 if (token > XRLIM_BURST_FACTOR * timeout)
616 token = XRLIM_BURST_FACTOR * timeout;
617 if (token >= timeout) {
618 token -= timeout;
619 rc = true;
620 }
621 peer->rate_tokens = token;
622 return rc;
623 }
624 EXPORT_SYMBOL(inet_peer_xrlim_allow);
625