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 */ 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. */ 155 static void unlink_from_unused(struct inet_peer *p) 156 { 157 spin_lock_bh(&unused_peers.lock); 158 list_del_init(&p->unused); 159 spin_unlock_bh(&unused_peers.lock); 160 } 161 162 static int addr_compare(const struct inetpeer_addr *a, 163 const struct inetpeer_addr *b) 164 { 165 int i, n = (a->family == AF_INET ? 1 : 4); 166 167 for (i = 0; i < n; i++) { 168 if (a->addr.a6[i] == b->addr.a6[i]) 169 continue; 170 if (a->addr.a6[i] < b->addr.a6[i]) 171 return -1; 172 return 1; 173 } 174 175 return 0; 176 } 177 178 #define rcu_deref_locked(X, BASE) \ 179 rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock)) 180 181 /* 182 * Called with local BH disabled and the pool lock held. 183 */ 184 #define lookup(_daddr, _stack, _base) \ 185 ({ \ 186 struct inet_peer *u; \ 187 struct inet_peer __rcu **v; \ 188 \ 189 stackptr = _stack; \ 190 *stackptr++ = &_base->root; \ 191 for (u = rcu_deref_locked(_base->root, _base); \ 192 u != peer_avl_empty; ) { \ 193 int cmp = addr_compare(_daddr, &u->daddr); \ 194 if (cmp == 0) \ 195 break; \ 196 if (cmp == -1) \ 197 v = &u->avl_left; \ 198 else \ 199 v = &u->avl_right; \ 200 *stackptr++ = v; \ 201 u = rcu_deref_locked(*v, _base); \ 202 } \ 203 u; \ 204 }) 205 206 static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv) 207 { 208 int cur, old = atomic_read(ptr); 209 210 while (old != u) { 211 *newv = old + a; 212 cur = atomic_cmpxchg(ptr, old, *newv); 213 if (cur == old) 214 return true; 215 old = cur; 216 } 217 return false; 218 } 219 220 /* 221 * Called with rcu_read_lock() 222 * Because we hold no lock against a writer, its quite possible we fall 223 * in an endless loop. 224 * But every pointer we follow is guaranteed to be valid thanks to RCU. 225 * We exit from this function if number of links exceeds PEER_MAXDEPTH 226 */ 227 static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr, 228 struct inet_peer_base *base, 229 int *newrefcnt) 230 { 231 struct inet_peer *u = rcu_dereference(base->root); 232 int count = 0; 233 234 while (u != peer_avl_empty) { 235 int cmp = addr_compare(daddr, &u->daddr); 236 if (cmp == 0) { 237 /* Before taking a reference, check if this entry was 238 * deleted, unlink_from_pool() sets refcnt=-1 to make 239 * distinction between an unused entry (refcnt=0) and 240 * a freed one. 241 */ 242 if (!atomic_add_unless_return(&u->refcnt, 1, -1, newrefcnt)) 243 u = NULL; 244 return u; 245 } 246 if (cmp == -1) 247 u = rcu_dereference(u->avl_left); 248 else 249 u = rcu_dereference(u->avl_right); 250 if (unlikely(++count == PEER_MAXDEPTH)) 251 break; 252 } 253 return NULL; 254 } 255 256 /* Called with local BH disabled and the pool lock held. */ 257 #define lookup_rightempty(start, base) \ 258 ({ \ 259 struct inet_peer *u; \ 260 struct inet_peer __rcu **v; \ 261 *stackptr++ = &start->avl_left; \ 262 v = &start->avl_left; \ 263 for (u = rcu_deref_locked(*v, base); \ 264 u->avl_right != peer_avl_empty_rcu; ) { \ 265 v = &u->avl_right; \ 266 *stackptr++ = v; \ 267 u = rcu_deref_locked(*v, base); \ 268 } \ 269 u; \ 270 }) 271 272 /* Called with local BH disabled and the pool lock held. 273 * Variable names are the proof of operation correctness. 274 * Look into mm/map_avl.c for more detail description of the ideas. 275 */ 276 static void peer_avl_rebalance(struct inet_peer __rcu **stack[], 277 struct inet_peer __rcu ***stackend, 278 struct inet_peer_base *base) 279 { 280 struct inet_peer __rcu **nodep; 281 struct inet_peer *node, *l, *r; 282 int lh, rh; 283 284 while (stackend > stack) { 285 nodep = *--stackend; 286 node = rcu_deref_locked(*nodep, base); 287 l = rcu_deref_locked(node->avl_left, base); 288 r = rcu_deref_locked(node->avl_right, base); 289 lh = node_height(l); 290 rh = node_height(r); 291 if (lh > rh + 1) { /* l: RH+2 */ 292 struct inet_peer *ll, *lr, *lrl, *lrr; 293 int lrh; 294 ll = rcu_deref_locked(l->avl_left, base); 295 lr = rcu_deref_locked(l->avl_right, base); 296 lrh = node_height(lr); 297 if (lrh <= node_height(ll)) { /* ll: RH+1 */ 298 RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */ 299 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */ 300 node->avl_height = lrh + 1; /* RH+1 or RH+2 */ 301 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */ 302 RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */ 303 l->avl_height = node->avl_height + 1; 304 RCU_INIT_POINTER(*nodep, l); 305 } else { /* ll: RH, lr: RH+1 */ 306 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */ 307 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */ 308 RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */ 309 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */ 310 node->avl_height = rh + 1; /* node: RH+1 */ 311 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */ 312 RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */ 313 l->avl_height = rh + 1; /* l: RH+1 */ 314 RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */ 315 RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */ 316 lr->avl_height = rh + 2; 317 RCU_INIT_POINTER(*nodep, lr); 318 } 319 } else if (rh > lh + 1) { /* r: LH+2 */ 320 struct inet_peer *rr, *rl, *rlr, *rll; 321 int rlh; 322 rr = rcu_deref_locked(r->avl_right, base); 323 rl = rcu_deref_locked(r->avl_left, base); 324 rlh = node_height(rl); 325 if (rlh <= node_height(rr)) { /* rr: LH+1 */ 326 RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */ 327 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */ 328 node->avl_height = rlh + 1; /* LH+1 or LH+2 */ 329 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */ 330 RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */ 331 r->avl_height = node->avl_height + 1; 332 RCU_INIT_POINTER(*nodep, r); 333 } else { /* rr: RH, rl: RH+1 */ 334 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */ 335 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */ 336 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */ 337 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */ 338 node->avl_height = lh + 1; /* node: LH+1 */ 339 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */ 340 RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */ 341 r->avl_height = lh + 1; /* r: LH+1 */ 342 RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */ 343 RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */ 344 rl->avl_height = lh + 2; 345 RCU_INIT_POINTER(*nodep, rl); 346 } 347 } else { 348 node->avl_height = (lh > rh ? lh : rh) + 1; 349 } 350 } 351 } 352 353 /* Called with local BH disabled and the pool lock held. */ 354 #define link_to_pool(n, base) \ 355 do { \ 356 n->avl_height = 1; \ 357 n->avl_left = peer_avl_empty_rcu; \ 358 n->avl_right = peer_avl_empty_rcu; \ 359 /* lockless readers can catch us now */ \ 360 rcu_assign_pointer(**--stackptr, n); \ 361 peer_avl_rebalance(stack, stackptr, base); \ 362 } while (0) 363 364 static void inetpeer_free_rcu(struct rcu_head *head) 365 { 366 kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu)); 367 } 368 369 /* May be called with local BH enabled. */ 370 static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base, 371 struct inet_peer __rcu **stack[PEER_MAXDEPTH]) 372 { 373 int do_free; 374 375 do_free = 0; 376 377 write_seqlock_bh(&base->lock); 378 /* Check the reference counter. It was artificially incremented by 1 379 * in cleanup() function to prevent sudden disappearing. If we can 380 * atomically (because of lockless readers) take this last reference, 381 * it's safe to remove the node and free it later. 382 * We use refcnt=-1 to alert lockless readers this entry is deleted. 383 */ 384 if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) { 385 struct inet_peer __rcu ***stackptr, ***delp; 386 if (lookup(&p->daddr, stack, base) != p) 387 BUG(); 388 delp = stackptr - 1; /* *delp[0] == p */ 389 if (p->avl_left == peer_avl_empty_rcu) { 390 *delp[0] = p->avl_right; 391 --stackptr; 392 } else { 393 /* look for a node to insert instead of p */ 394 struct inet_peer *t; 395 t = lookup_rightempty(p, base); 396 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t); 397 **--stackptr = t->avl_left; 398 /* t is removed, t->daddr > x->daddr for any 399 * x in p->avl_left subtree. 400 * Put t in the old place of p. */ 401 RCU_INIT_POINTER(*delp[0], t); 402 t->avl_left = p->avl_left; 403 t->avl_right = p->avl_right; 404 t->avl_height = p->avl_height; 405 BUG_ON(delp[1] != &p->avl_left); 406 delp[1] = &t->avl_left; /* was &p->avl_left */ 407 } 408 peer_avl_rebalance(stack, stackptr, base); 409 base->total--; 410 do_free = 1; 411 } 412 write_sequnlock_bh(&base->lock); 413 414 if (do_free) 415 call_rcu(&p->rcu, inetpeer_free_rcu); 416 else 417 /* The node is used again. Decrease the reference counter 418 * back. The loop "cleanup -> unlink_from_unused 419 * -> unlink_from_pool -> putpeer -> link_to_unused 420 * -> cleanup (for the same node)" 421 * doesn't really exist because the entry will have a 422 * recent deletion time and will not be cleaned again soon. 423 */ 424 inet_putpeer(p); 425 } 426 427 static struct inet_peer_base *family_to_base(int family) 428 { 429 return (family == AF_INET ? &v4_peers : &v6_peers); 430 } 431 432 static struct inet_peer_base *peer_to_base(struct inet_peer *p) 433 { 434 return family_to_base(p->daddr.family); 435 } 436 437 /* May be called with local BH enabled. */ 438 static int cleanup_once(unsigned long ttl, struct inet_peer __rcu **stack[PEER_MAXDEPTH]) 439 { 440 struct inet_peer *p = NULL; 441 442 /* Remove the first entry from the list of unused nodes. */ 443 spin_lock_bh(&unused_peers.lock); 444 if (!list_empty(&unused_peers.list)) { 445 __u32 delta; 446 447 p = list_first_entry(&unused_peers.list, struct inet_peer, unused); 448 delta = (__u32)jiffies - p->dtime; 449 450 if (delta < ttl) { 451 /* Do not prune fresh entries. */ 452 spin_unlock_bh(&unused_peers.lock); 453 return -1; 454 } 455 456 list_del_init(&p->unused); 457 458 /* Grab an extra reference to prevent node disappearing 459 * before unlink_from_pool() call. */ 460 atomic_inc(&p->refcnt); 461 } 462 spin_unlock_bh(&unused_peers.lock); 463 464 if (p == NULL) 465 /* It means that the total number of USED entries has 466 * grown over inet_peer_threshold. It shouldn't really 467 * happen because of entry limits in route cache. */ 468 return -1; 469 470 unlink_from_pool(p, peer_to_base(p), stack); 471 return 0; 472 } 473 474 /* Called with or without local BH being disabled. */ 475 struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create) 476 { 477 struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr; 478 struct inet_peer_base *base = family_to_base(daddr->family); 479 struct inet_peer *p; 480 unsigned int sequence; 481 int invalidated, newrefcnt = 0; 482 483 /* Look up for the address quickly, lockless. 484 * Because of a concurrent writer, we might not find an existing entry. 485 */ 486 rcu_read_lock(); 487 sequence = read_seqbegin(&base->lock); 488 p = lookup_rcu(daddr, base, &newrefcnt); 489 invalidated = read_seqretry(&base->lock, sequence); 490 rcu_read_unlock(); 491 492 if (p) { 493 found: /* The existing node has been found. 494 * Remove the entry from unused list if it was there. 495 */ 496 if (newrefcnt == 1) 497 unlink_from_unused(p); 498 return p; 499 } 500 501 /* If no writer did a change during our lookup, we can return early. */ 502 if (!create && !invalidated) 503 return NULL; 504 505 /* retry an exact lookup, taking the lock before. 506 * At least, nodes should be hot in our cache. 507 */ 508 write_seqlock_bh(&base->lock); 509 p = lookup(daddr, stack, base); 510 if (p != peer_avl_empty) { 511 newrefcnt = atomic_inc_return(&p->refcnt); 512 write_sequnlock_bh(&base->lock); 513 goto found; 514 } 515 p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL; 516 if (p) { 517 p->daddr = *daddr; 518 atomic_set(&p->refcnt, 1); 519 atomic_set(&p->rid, 0); 520 atomic_set(&p->ip_id_count, secure_ip_id(daddr->addr.a4)); 521 p->tcp_ts_stamp = 0; 522 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW; 523 p->rate_tokens = 0; 524 p->rate_last = 0; 525 p->pmtu_expires = 0; 526 p->pmtu_orig = 0; 527 memset(&p->redirect_learned, 0, sizeof(p->redirect_learned)); 528 INIT_LIST_HEAD(&p->unused); 529 530 531 /* Link the node. */ 532 link_to_pool(p, base); 533 base->total++; 534 } 535 write_sequnlock_bh(&base->lock); 536 537 if (base->total >= inet_peer_threshold) 538 /* Remove one less-recently-used entry. */ 539 cleanup_once(0, stack); 540 541 return p; 542 } 543 544 static int compute_total(void) 545 { 546 return v4_peers.total + v6_peers.total; 547 } 548 EXPORT_SYMBOL_GPL(inet_getpeer); 549 550 /* Called with local BH disabled. */ 551 static void peer_check_expire(unsigned long dummy) 552 { 553 unsigned long now = jiffies; 554 int ttl, total; 555 struct inet_peer __rcu **stack[PEER_MAXDEPTH]; 556 557 total = compute_total(); 558 if (total >= inet_peer_threshold) 559 ttl = inet_peer_minttl; 560 else 561 ttl = inet_peer_maxttl 562 - (inet_peer_maxttl - inet_peer_minttl) / HZ * 563 total / inet_peer_threshold * HZ; 564 while (!cleanup_once(ttl, stack)) { 565 if (jiffies != now) 566 break; 567 } 568 569 /* Trigger the timer after inet_peer_gc_mintime .. inet_peer_gc_maxtime 570 * interval depending on the total number of entries (more entries, 571 * less interval). */ 572 total = compute_total(); 573 if (total >= inet_peer_threshold) 574 peer_periodic_timer.expires = jiffies + inet_peer_gc_mintime; 575 else 576 peer_periodic_timer.expires = jiffies 577 + inet_peer_gc_maxtime 578 - (inet_peer_gc_maxtime - inet_peer_gc_mintime) / HZ * 579 total / inet_peer_threshold * HZ; 580 add_timer(&peer_periodic_timer); 581 } 582 583 void inet_putpeer(struct inet_peer *p) 584 { 585 local_bh_disable(); 586 587 if (atomic_dec_and_lock(&p->refcnt, &unused_peers.lock)) { 588 list_add_tail(&p->unused, &unused_peers.list); 589 p->dtime = (__u32)jiffies; 590 spin_unlock(&unused_peers.lock); 591 } 592 593 local_bh_enable(); 594 } 595 EXPORT_SYMBOL_GPL(inet_putpeer); 596 597 /* 598 * Check transmit rate limitation for given message. 599 * The rate information is held in the inet_peer entries now. 600 * This function is generic and could be used for other purposes 601 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov. 602 * 603 * Note that the same inet_peer fields are modified by functions in 604 * route.c too, but these work for packet destinations while xrlim_allow 605 * works for icmp destinations. This means the rate limiting information 606 * for one "ip object" is shared - and these ICMPs are twice limited: 607 * by source and by destination. 608 * 609 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate 610 * SHOULD allow setting of rate limits 611 * 612 * Shared between ICMPv4 and ICMPv6. 613 */ 614 #define XRLIM_BURST_FACTOR 6 615 bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout) 616 { 617 unsigned long now, token; 618 bool rc = false; 619 620 if (!peer) 621 return true; 622 623 token = peer->rate_tokens; 624 now = jiffies; 625 token += now - peer->rate_last; 626 peer->rate_last = now; 627 if (token > XRLIM_BURST_FACTOR * timeout) 628 token = XRLIM_BURST_FACTOR * timeout; 629 if (token >= timeout) { 630 token -= timeout; 631 rc = true; 632 } 633 peer->rate_tokens = token; 634 return rc; 635 } 636 EXPORT_SYMBOL(inet_peer_xrlim_allow); 637