net/ipv4/inetpeer.c

   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 <linux/workqueue.h>
  21 #include <net/ip.h>
  22 #include <net/inetpeer.h>
  23 #include <net/secure_seq.h>
  24
  25 /*
  26  *  Theory of operations.
  27  *  We keep one entry for each peer IP address.  The nodes contains long-living
  28  *  information about the peer which doesn't depend on routes.
  29  *  At this moment this information consists only of ID field for the next
  30  *  outgoing IP packet.  This field is incremented with each packet as encoded
  31  *  in inet_getid() function (include/net/inetpeer.h).
  32  *  At the moment of writing this notes identifier of IP packets is generated
  33  *  to be unpredictable using this code only for packets subjected
  34  *  (actually or potentially) to defragmentation.  I.e. DF packets less than
  35  *  PMTU in size uses a constant ID and do not use this code (see
  36  *  ip_select_ident() in include/net/ip.h).
  37  *
  38  *  Route cache entries hold references to our nodes.
  39  *  New cache entries get references via lookup by destination IP address in
  40  *  the avl tree.  The reference is grabbed only when it's needed i.e. only
  41  *  when we try to output IP packet which needs an unpredictable ID (see
  42  *  __ip_select_ident() in net/ipv4/route.c).
  43  *  Nodes are removed only when reference counter goes to 0.
  44  *  When it's happened the node may be removed when a sufficient amount of
  45  *  time has been passed since its last use.  The less-recently-used entry can
  46  *  also be removed if the pool is overloaded i.e. if the total amount of
  47  *  entries is greater-or-equal than the threshold.
  48  *
  49  *  Node pool is organised as an AVL tree.
  50  *  Such an implementation has been chosen not just for fun.  It's a way to
  51  *  prevent easy and efficient DoS attacks by creating hash collisions.  A huge
  52  *  amount of long living nodes in a single hash slot would significantly delay
  53  *  lookups performed with disabled BHs.
  54  *
  55  *  Serialisation issues.
  56  *  1.  Nodes may appear in the tree only with the pool lock held.
  57  *  2.  Nodes may disappear from the tree only with the pool lock held
  58  *      AND reference count being 0.
  59  *  3.  Global variable peer_total is modified under the pool lock.
  60  *  4.  struct inet_peer fields modification:
  61  *              avl_left, avl_right, avl_parent, avl_height: pool lock
  62  *              refcnt: atomically against modifications on other CPU;
  63  *                 usually under some other lock to prevent node disappearing
  64  *              daddr: unchangeable
  65  *              ip_id_count: atomic value (no lock needed)
  66  */
  67
  68 static struct kmem_cache *peer_cachep __read_mostly;
  69
  70 static LIST_HEAD(gc_list);
  71 static const int gc_delay = 60 * HZ;
  72 static struct delayed_work gc_work;
  73 static DEFINE_SPINLOCK(gc_lock);
  74
  75 #define node_height(x) x->avl_height
  76
  77 #define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
  78 #define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
  79 static const struct inet_peer peer_fake_node = {
  80         .avl_left       = peer_avl_empty_rcu,
  81         .avl_right      = peer_avl_empty_rcu,
  82         .avl_height     = 0
  83 };
  84
  85 void inet_peer_base_init(struct inet_peer_base *bp)
  86 {
  87         bp->root = peer_avl_empty_rcu;
  88         seqlock_init(&bp->lock);
  89         bp->flush_seq = ~0U;
  90         bp->total = 0;
  91 }
  92 EXPORT_SYMBOL_GPL(inet_peer_base_init);
  93
  94 static atomic_t v4_seq = ATOMIC_INIT(0);
  95 static atomic_t v6_seq = ATOMIC_INIT(0);
  96
  97 static atomic_t *inetpeer_seq_ptr(int family)
  98 {
  99         return (family == AF_INET ? &v4_seq : &v6_seq);
 100 }
 101
 102 static inline void flush_check(struct inet_peer_base *base, int family)
 103 {
 104         atomic_t *fp = inetpeer_seq_ptr(family);
 105
 106         if (unlikely(base->flush_seq != atomic_read(fp))) {
 107                 inetpeer_invalidate_tree(base);
 108                 base->flush_seq = atomic_read(fp);
 109         }
 110 }
 111
 112 void inetpeer_invalidate_family(int family)
 113 {
 114         atomic_t *fp = inetpeer_seq_ptr(family);
 115
 116         atomic_inc(fp);
 117 }
 118
 119 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
 120
 121 /* Exported for sysctl_net_ipv4.  */
 122 int inet_peer_threshold __read_mostly = 65536 + 128;    /* start to throw entries more
 123                                          * aggressively at this stage */
 124 int inet_peer_minttl __read_mostly = 120 * HZ;  /* TTL under high load: 120 sec */
 125 int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;      /* usual time to live: 10 min */
 126
 127 static void inetpeer_gc_worker(struct work_struct *work)
 128 {
 129         struct inet_peer *p, *n, *c;
 130         LIST_HEAD(list);
 131
 132         spin_lock_bh(&gc_lock);
 133         list_replace_init(&gc_list, &list);
 134         spin_unlock_bh(&gc_lock);
 135
 136         if (list_empty(&list))
 137                 return;
 138
 139         list_for_each_entry_safe(p, n, &list, gc_list) {
 140
 141                 if (need_resched())
 142                         cond_resched();
 143
 144                 c = rcu_dereference_protected(p->avl_left, 1);
 145                 if (c != peer_avl_empty) {
 146                         list_add_tail(&c->gc_list, &list);
 147                         p->avl_left = peer_avl_empty_rcu;
 148                 }
 149
 150                 c = rcu_dereference_protected(p->avl_right, 1);
 151                 if (c != peer_avl_empty) {
 152                         list_add_tail(&c->gc_list, &list);
 153                         p->avl_right = peer_avl_empty_rcu;
 154                 }
 155
 156                 n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
 157
 158                 if (!atomic_read(&p->refcnt)) {
 159                         list_del(&p->gc_list);
 160                         kmem_cache_free(peer_cachep, p);
 161                 }
 162         }
 163
 164         if (list_empty(&list))
 165                 return;
 166
 167         spin_lock_bh(&gc_lock);
 168         list_splice(&list, &gc_list);
 169         spin_unlock_bh(&gc_lock);
 170
 171         schedule_delayed_work(&gc_work, gc_delay);
 172 }
 173
 174 /* Called from ip_output.c:ip_init  */
 175 void __init inet_initpeers(void)
 176 {
 177         struct sysinfo si;
 178
 179         /* Use the straight interface to information about memory. */
 180         si_meminfo(&si);
 181         /* The values below were suggested by Alexey Kuznetsov
 182          * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
 183          * myself.  --SAW
 184          */
 185         if (si.totalram <= (32768*1024)/PAGE_SIZE)
 186                 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
 187         if (si.totalram <= (16384*1024)/PAGE_SIZE)
 188                 inet_peer_threshold >>= 1; /* about 512KB */
 189         if (si.totalram <= (8192*1024)/PAGE_SIZE)
 190                 inet_peer_threshold >>= 2; /* about 128KB */
 191
 192         peer_cachep = kmem_cache_create("inet_peer_cache",
 193                         sizeof(struct inet_peer),
 194                         0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
 195                         NULL);
 196
 197         INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker);
 198 }
 199
 200 static int addr_compare(const struct inetpeer_addr *a,
 201                         const struct inetpeer_addr *b)
 202 {
 203         int i, n = (a->family == AF_INET ? 1 : 4);
 204
 205         for (i = 0; i < n; i++) {
 206                 if (a->addr.a6[i] == b->addr.a6[i])
 207                         continue;
 208                 if ((__force u32)a->addr.a6[i] < (__force u32)b->addr.a6[i])
 209                         return -1;
 210                 return 1;
 211         }
 212
 213         return 0;
 214 }
 215
 216 #define rcu_deref_locked(X, BASE)                               \
 217         rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
 218
 219 /*
 220  * Called with local BH disabled and the pool lock held.
 221  */
 222 #define lookup(_daddr, _stack, _base)                           \
 223 ({                                                              \
 224         struct inet_peer *u;                                    \
 225         struct inet_peer __rcu **v;                             \
 226                                                                 \
 227         stackptr = _stack;                                      \
 228         *stackptr++ = &_base->root;                             \
 229         for (u = rcu_deref_locked(_base->root, _base);          \
 230              u != peer_avl_empty; ) {                           \
 231                 int cmp = addr_compare(_daddr, &u->daddr);      \
 232                 if (cmp == 0)                                   \
 233                         break;                                  \
 234                 if (cmp == -1)                                  \
 235                         v = &u->avl_left;                       \
 236                 else                                            \
 237                         v = &u->avl_right;                      \
 238                 *stackptr++ = v;                                \
 239                 u = rcu_deref_locked(*v, _base);                \
 240         }                                                       \
 241         u;                                                      \
 242 })
 243
 244 /*
 245  * Called with rcu_read_lock()
 246  * Because we hold no lock against a writer, its quite possible we fall
 247  * in an endless loop.
 248  * But every pointer we follow is guaranteed to be valid thanks to RCU.
 249  * We exit from this function if number of links exceeds PEER_MAXDEPTH
 250  */
 251 static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
 252                                     struct inet_peer_base *base)
 253 {
 254         struct inet_peer *u = rcu_dereference(base->root);
 255         int count = 0;
 256
 257         while (u != peer_avl_empty) {
 258                 int cmp = addr_compare(daddr, &u->daddr);
 259                 if (cmp == 0) {
 260                         /* Before taking a reference, check if this entry was
 261                          * deleted (refcnt=-1)
 262                          */
 263                         if (!atomic_add_unless(&u->refcnt, 1, -1))
 264                                 u = NULL;
 265                         return u;
 266                 }
 267                 if (cmp == -1)
 268                         u = rcu_dereference(u->avl_left);
 269                 else
 270                         u = rcu_dereference(u->avl_right);
 271                 if (unlikely(++count == PEER_MAXDEPTH))
 272                         break;
 273         }
 274         return NULL;
 275 }
 276
 277 /* Called with local BH disabled and the pool lock held. */
 278 #define lookup_rightempty(start, base)                          \
 279 ({                                                              \
 280         struct inet_peer *u;                                    \
 281         struct inet_peer __rcu **v;                             \
 282         *stackptr++ = &start->avl_left;                         \
 283         v = &start->avl_left;                                   \
 284         for (u = rcu_deref_locked(*v, base);                    \
 285              u->avl_right != peer_avl_empty_rcu; ) {            \
 286                 v = &u->avl_right;                              \
 287                 *stackptr++ = v;                                \
 288                 u = rcu_deref_locked(*v, base);                 \
 289         }                                                       \
 290         u;                                                      \
 291 })
 292
 293 /* Called with local BH disabled and the pool lock held.
 294  * Variable names are the proof of operation correctness.
 295  * Look into mm/map_avl.c for more detail description of the ideas.
 296  */
 297 static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
 298                                struct inet_peer __rcu ***stackend,
 299                                struct inet_peer_base *base)
 300 {
 301         struct inet_peer __rcu **nodep;
 302         struct inet_peer *node, *l, *r;
 303         int lh, rh;
 304
 305         while (stackend > stack) {
 306                 nodep = *--stackend;
 307                 node = rcu_deref_locked(*nodep, base);
 308                 l = rcu_deref_locked(node->avl_left, base);
 309                 r = rcu_deref_locked(node->avl_right, base);
 310                 lh = node_height(l);
 311                 rh = node_height(r);
 312                 if (lh > rh + 1) { /* l: RH+2 */
 313                         struct inet_peer *ll, *lr, *lrl, *lrr;
 314                         int lrh;
 315                         ll = rcu_deref_locked(l->avl_left, base);
 316                         lr = rcu_deref_locked(l->avl_right, base);
 317                         lrh = node_height(lr);
 318                         if (lrh <= node_height(ll)) {   /* ll: RH+1 */
 319                                 RCU_INIT_POINTER(node->avl_left, lr);   /* lr: RH or RH+1 */
 320                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
 321                                 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
 322                                 RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
 323                                 RCU_INIT_POINTER(l->avl_right, node);   /* node: RH+1 or RH+2 */
 324                                 l->avl_height = node->avl_height + 1;
 325                                 RCU_INIT_POINTER(*nodep, l);
 326                         } else { /* ll: RH, lr: RH+1 */
 327                                 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
 328                                 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
 329                                 RCU_INIT_POINTER(node->avl_left, lrr);  /* lrr: RH or RH-1 */
 330                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
 331                                 node->avl_height = rh + 1; /* node: RH+1 */
 332                                 RCU_INIT_POINTER(l->avl_left, ll);      /* ll: RH */
 333                                 RCU_INIT_POINTER(l->avl_right, lrl);    /* lrl: RH or RH-1 */
 334                                 l->avl_height = rh + 1; /* l: RH+1 */
 335                                 RCU_INIT_POINTER(lr->avl_left, l);      /* l: RH+1 */
 336                                 RCU_INIT_POINTER(lr->avl_right, node);  /* node: RH+1 */
 337                                 lr->avl_height = rh + 2;
 338                                 RCU_INIT_POINTER(*nodep, lr);
 339                         }
 340                 } else if (rh > lh + 1) { /* r: LH+2 */
 341                         struct inet_peer *rr, *rl, *rlr, *rll;
 342                         int rlh;
 343                         rr = rcu_deref_locked(r->avl_right, base);
 344                         rl = rcu_deref_locked(r->avl_left, base);
 345                         rlh = node_height(rl);
 346                         if (rlh <= node_height(rr)) {   /* rr: LH+1 */
 347                                 RCU_INIT_POINTER(node->avl_right, rl);  /* rl: LH or LH+1 */
 348                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
 349                                 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
 350                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH+1 */
 351                                 RCU_INIT_POINTER(r->avl_left, node);    /* node: LH+1 or LH+2 */
 352                                 r->avl_height = node->avl_height + 1;
 353                                 RCU_INIT_POINTER(*nodep, r);
 354                         } else { /* rr: RH, rl: RH+1 */
 355                                 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
 356                                 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
 357                                 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
 358                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
 359                                 node->avl_height = lh + 1; /* node: LH+1 */
 360                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH */
 361                                 RCU_INIT_POINTER(r->avl_left, rlr);     /* rlr: LH or LH-1 */
 362                                 r->avl_height = lh + 1; /* r: LH+1 */
 363                                 RCU_INIT_POINTER(rl->avl_right, r);     /* r: LH+1 */
 364                                 RCU_INIT_POINTER(rl->avl_left, node);   /* node: LH+1 */
 365                                 rl->avl_height = lh + 2;
 366                                 RCU_INIT_POINTER(*nodep, rl);
 367                         }
 368                 } else {
 369                         node->avl_height = (lh > rh ? lh : rh) + 1;
 370                 }
 371         }
 372 }
 373
 374 /* Called with local BH disabled and the pool lock held. */
 375 #define link_to_pool(n, base)                                   \
 376 do {                                                            \
 377         n->avl_height = 1;                                      \
 378         n->avl_left = peer_avl_empty_rcu;                       \
 379         n->avl_right = peer_avl_empty_rcu;                      \
 380         /* lockless readers can catch us now */                 \
 381         rcu_assign_pointer(**--stackptr, n);                    \
 382         peer_avl_rebalance(stack, stackptr, base);              \
 383 } while (0)
 384
 385 static void inetpeer_free_rcu(struct rcu_head *head)
 386 {
 387         kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
 388 }
 389
 390 static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
 391                              struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 392 {
 393         struct inet_peer __rcu ***stackptr, ***delp;
 394
 395         if (lookup(&p->daddr, stack, base) != p)
 396                 BUG();
 397         delp = stackptr - 1; /* *delp[0] == p */
 398         if (p->avl_left == peer_avl_empty_rcu) {
 399                 *delp[0] = p->avl_right;
 400                 --stackptr;
 401         } else {
 402                 /* look for a node to insert instead of p */
 403                 struct inet_peer *t;
 404                 t = lookup_rightempty(p, base);
 405                 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
 406                 **--stackptr = t->avl_left;
 407                 /* t is removed, t->daddr > x->daddr for any
 408                  * x in p->avl_left subtree.
 409                  * Put t in the old place of p. */
 410                 RCU_INIT_POINTER(*delp[0], t);
 411                 t->avl_left = p->avl_left;
 412                 t->avl_right = p->avl_right;
 413                 t->avl_height = p->avl_height;
 414                 BUG_ON(delp[1] != &p->avl_left);
 415                 delp[1] = &t->avl_left; /* was &p->avl_left */
 416         }
 417         peer_avl_rebalance(stack, stackptr, base);
 418         base->total--;
 419         call_rcu(&p->rcu, inetpeer_free_rcu);
 420 }
 421
 422 /* perform garbage collect on all items stacked during a lookup */
 423 static int inet_peer_gc(struct inet_peer_base *base,
 424                         struct inet_peer __rcu **stack[PEER_MAXDEPTH],
 425                         struct inet_peer __rcu ***stackptr)
 426 {
 427         struct inet_peer *p, *gchead = NULL;
 428         __u32 delta, ttl;
 429         int cnt = 0;
 430
 431         if (base->total >= inet_peer_threshold)
 432                 ttl = 0; /* be aggressive */
 433         else
 434                 ttl = inet_peer_maxttl
 435                                 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
 436                                         base->total / inet_peer_threshold * HZ;
 437         stackptr--; /* last stack slot is peer_avl_empty */
 438         while (stackptr > stack) {
 439                 stackptr--;
 440                 p = rcu_deref_locked(**stackptr, base);
 441                 if (atomic_read(&p->refcnt) == 0) {
 442                         smp_rmb();
 443                         delta = (__u32)jiffies - p->dtime;
 444                         if (delta >= ttl &&
 445                             atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
 446                                 p->gc_next = gchead;
 447                                 gchead = p;
 448                         }
 449                 }
 450         }
 451         while ((p = gchead) != NULL) {
 452                 gchead = p->gc_next;
 453                 cnt++;
 454                 unlink_from_pool(p, base, stack);
 455         }
 456         return cnt;
 457 }
 458
 459 struct inet_peer *inet_getpeer(struct inet_peer_base *base,
 460                                const struct inetpeer_addr *daddr,
 461                                int create)
 462 {
 463         struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
 464         struct inet_peer *p;
 465         unsigned int sequence;
 466         int invalidated, gccnt = 0;
 467
 468         flush_check(base, daddr->family);
 469
 470         /* Attempt a lockless lookup first.
 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                 return p;
 481
 482         /* If no writer did a change during our lookup, we can return early. */
 483         if (!create && !invalidated)
 484                 return NULL;
 485
 486         /* retry an exact lookup, taking the lock before.
 487          * At least, nodes should be hot in our cache.
 488          */
 489         write_seqlock_bh(&base->lock);
 490 relookup:
 491         p = lookup(daddr, stack, base);
 492         if (p != peer_avl_empty) {
 493                 atomic_inc(&p->refcnt);
 494                 write_sequnlock_bh(&base->lock);
 495                 return p;
 496         }
 497         if (!gccnt) {
 498                 gccnt = inet_peer_gc(base, stack, stackptr);
 499                 if (gccnt && create)
 500                         goto relookup;
 501         }
 502         p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
 503         if (p) {
 504                 p->daddr = *daddr;
 505                 atomic_set(&p->refcnt, 1);
 506                 atomic_set(&p->rid, 0);
 507                 atomic_set(&p->ip_id_count,
 508                                 (daddr->family == AF_INET) ?
 509                                         secure_ip_id(daddr->addr.a4) :
 510                                         secure_ipv6_id(daddr->addr.a6));
 511                 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
 512                 p->rate_tokens = 0;
 513                 /* 60*HZ is arbitrary, but chosen enough high so that the first
 514                  * calculation of tokens is at its maximum.
 515                  */
 516                 p->rate_last = jiffies - 60*HZ;
 517                 INIT_LIST_HEAD(&p->gc_list);
 518
 519                 /* Link the node. */
 520                 link_to_pool(p, base);
 521                 base->total++;
 522         }
 523         write_sequnlock_bh(&base->lock);
 524
 525         return p;
 526 }
 527 EXPORT_SYMBOL_GPL(inet_getpeer);
 528
 529 void inet_putpeer(struct inet_peer *p)
 530 {
 531         p->dtime = (__u32)jiffies;
 532         smp_mb__before_atomic_dec();
 533         atomic_dec(&p->refcnt);
 534 }
 535 EXPORT_SYMBOL_GPL(inet_putpeer);
 536
 537 /*
 538  *      Check transmit rate limitation for given message.
 539  *      The rate information is held in the inet_peer entries now.
 540  *      This function is generic and could be used for other purposes
 541  *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
 542  *
 543  *      Note that the same inet_peer fields are modified by functions in
 544  *      route.c too, but these work for packet destinations while xrlim_allow
 545  *      works for icmp destinations. This means the rate limiting information
 546  *      for one "ip object" is shared - and these ICMPs are twice limited:
 547  *      by source and by destination.
 548  *
 549  *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
 550  *                        SHOULD allow setting of rate limits
 551  *
 552  *      Shared between ICMPv4 and ICMPv6.
 553  */
 554 #define XRLIM_BURST_FACTOR 6
 555 bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
 556 {
 557         unsigned long now, token;
 558         bool rc = false;
 559
 560         if (!peer)
 561                 return true;
 562
 563         token = peer->rate_tokens;
 564         now = jiffies;
 565         token += now - peer->rate_last;
 566         peer->rate_last = now;
 567         if (token > XRLIM_BURST_FACTOR * timeout)
 568                 token = XRLIM_BURST_FACTOR * timeout;
 569         if (token >= timeout) {
 570                 token -= timeout;
 571                 rc = true;
 572         }
 573         peer->rate_tokens = token;
 574         return rc;
 575 }
 576 EXPORT_SYMBOL(inet_peer_xrlim_allow);
 577
 578 static void inetpeer_inval_rcu(struct rcu_head *head)
 579 {
 580         struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
 581
 582         spin_lock_bh(&gc_lock);
 583         list_add_tail(&p->gc_list, &gc_list);
 584         spin_unlock_bh(&gc_lock);
 585
 586         schedule_delayed_work(&gc_work, gc_delay);
 587 }
 588
 589 void inetpeer_invalidate_tree(struct inet_peer_base *base)
 590 {
 591         struct inet_peer *root;
 592
 593         write_seqlock_bh(&base->lock);
 594
 595         root = rcu_deref_locked(base->root, base);
 596         if (root != peer_avl_empty) {
 597                 base->root = peer_avl_empty_rcu;
 598                 base->total = 0;
 599                 call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
 600         }
 601
 602         write_sequnlock_bh(&base->lock);
 603 }
 604 EXPORT_SYMBOL(inetpeer_invalidate_tree);