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 struct inet_peer_base {
  86         struct inet_peer __rcu *root;
  87         seqlock_t       lock;
  88         int             total;
  89 };
  90
  91 static struct inet_peer_base v4_peers = {
  92         .root           = peer_avl_empty_rcu,
  93         .lock           = __SEQLOCK_UNLOCKED(v4_peers.lock),
  94         .total          = 0,
  95 };
  96
  97 static struct inet_peer_base v6_peers = {
  98         .root           = peer_avl_empty_rcu,
  99         .lock           = __SEQLOCK_UNLOCKED(v6_peers.lock),
 100         .total          = 0,
 101 };
 102
 103 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
 104
 105 /* Exported for sysctl_net_ipv4.  */
 106 int inet_peer_threshold __read_mostly = 65536 + 128;    /* start to throw entries more
 107                                          * aggressively at this stage */
 108 int inet_peer_minttl __read_mostly = 120 * HZ;  /* TTL under high load: 120 sec */
 109 int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;      /* usual time to live: 10 min */
 110
 111 static void inetpeer_gc_worker(struct work_struct *work)
 112 {
 113         struct inet_peer *p, *n;
 114         LIST_HEAD(list);
 115
 116         spin_lock_bh(&gc_lock);
 117         list_replace_init(&gc_list, &list);
 118         spin_unlock_bh(&gc_lock);
 119
 120         if (list_empty(&list))
 121                 return;
 122
 123         list_for_each_entry_safe(p, n, &list, gc_list) {
 124
 125                 if(need_resched())
 126                         cond_resched();
 127
 128                 if (p->avl_left != peer_avl_empty) {
 129                         list_add_tail(&p->avl_left->gc_list, &list);
 130                         p->avl_left = peer_avl_empty;
 131                 }
 132
 133                 if (p->avl_right != peer_avl_empty) {
 134                         list_add_tail(&p->avl_right->gc_list, &list);
 135                         p->avl_right = peer_avl_empty;
 136                 }
 137
 138                 n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
 139
 140                 if (!atomic_read(&p->refcnt)) {
 141                         list_del(&p->gc_list);
 142                         kmem_cache_free(peer_cachep, p);
 143                 }
 144         }
 145
 146         if (list_empty(&list))
 147                 return;
 148
 149         spin_lock_bh(&gc_lock);
 150         list_splice(&list, &gc_list);
 151         spin_unlock_bh(&gc_lock);
 152
 153         schedule_delayed_work(&gc_work, gc_delay);
 154 }
 155
 156 /* Called from ip_output.c:ip_init  */
 157 void __init inet_initpeers(void)
 158 {
 159         struct sysinfo si;
 160
 161         /* Use the straight interface to information about memory. */
 162         si_meminfo(&si);
 163         /* The values below were suggested by Alexey Kuznetsov
 164          * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
 165          * myself.  --SAW
 166          */
 167         if (si.totalram <= (32768*1024)/PAGE_SIZE)
 168                 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
 169         if (si.totalram <= (16384*1024)/PAGE_SIZE)
 170                 inet_peer_threshold >>= 1; /* about 512KB */
 171         if (si.totalram <= (8192*1024)/PAGE_SIZE)
 172                 inet_peer_threshold >>= 2; /* about 128KB */
 173
 174         peer_cachep = kmem_cache_create("inet_peer_cache",
 175                         sizeof(struct inet_peer),
 176                         0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
 177                         NULL);
 178
 179         INIT_DELAYED_WORK_DEFERRABLE(&gc_work, inetpeer_gc_worker);
 180 }
 181
 182 static int addr_compare(const struct inetpeer_addr *a,
 183                         const struct inetpeer_addr *b)
 184 {
 185         int i, n = (a->family == AF_INET ? 1 : 4);
 186
 187         for (i = 0; i < n; i++) {
 188                 if (a->addr.a6[i] == b->addr.a6[i])
 189                         continue;
 190                 if ((__force u32)a->addr.a6[i] < (__force u32)b->addr.a6[i])
 191                         return -1;
 192                 return 1;
 193         }
 194
 195         return 0;
 196 }
 197
 198 #define rcu_deref_locked(X, BASE)                               \
 199         rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
 200
 201 /*
 202  * Called with local BH disabled and the pool lock held.
 203  */
 204 #define lookup(_daddr, _stack, _base)                           \
 205 ({                                                              \
 206         struct inet_peer *u;                                    \
 207         struct inet_peer __rcu **v;                             \
 208                                                                 \
 209         stackptr = _stack;                                      \
 210         *stackptr++ = &_base->root;                             \
 211         for (u = rcu_deref_locked(_base->root, _base);          \
 212              u != peer_avl_empty; ) {                           \
 213                 int cmp = addr_compare(_daddr, &u->daddr);      \
 214                 if (cmp == 0)                                   \
 215                         break;                                  \
 216                 if (cmp == -1)                                  \
 217                         v = &u->avl_left;                       \
 218                 else                                            \
 219                         v = &u->avl_right;                      \
 220                 *stackptr++ = v;                                \
 221                 u = rcu_deref_locked(*v, _base);                \
 222         }                                                       \
 223         u;                                                      \
 224 })
 225
 226 /*
 227  * Called with rcu_read_lock()
 228  * Because we hold no lock against a writer, its quite possible we fall
 229  * in an endless loop.
 230  * But every pointer we follow is guaranteed to be valid thanks to RCU.
 231  * We exit from this function if number of links exceeds PEER_MAXDEPTH
 232  */
 233 static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
 234                                     struct inet_peer_base *base)
 235 {
 236         struct inet_peer *u = rcu_dereference(base->root);
 237         int count = 0;
 238
 239         while (u != peer_avl_empty) {
 240                 int cmp = addr_compare(daddr, &u->daddr);
 241                 if (cmp == 0) {
 242                         /* Before taking a reference, check if this entry was
 243                          * deleted (refcnt=-1)
 244                          */
 245                         if (!atomic_add_unless(&u->refcnt, 1, -1))
 246                                 u = NULL;
 247                         return u;
 248                 }
 249                 if (cmp == -1)
 250                         u = rcu_dereference(u->avl_left);
 251                 else
 252                         u = rcu_dereference(u->avl_right);
 253                 if (unlikely(++count == PEER_MAXDEPTH))
 254                         break;
 255         }
 256         return NULL;
 257 }
 258
 259 /* Called with local BH disabled and the pool lock held. */
 260 #define lookup_rightempty(start, base)                          \
 261 ({                                                              \
 262         struct inet_peer *u;                                    \
 263         struct inet_peer __rcu **v;                             \
 264         *stackptr++ = &start->avl_left;                         \
 265         v = &start->avl_left;                                   \
 266         for (u = rcu_deref_locked(*v, base);                    \
 267              u->avl_right != peer_avl_empty_rcu; ) {            \
 268                 v = &u->avl_right;                              \
 269                 *stackptr++ = v;                                \
 270                 u = rcu_deref_locked(*v, base);                 \
 271         }                                                       \
 272         u;                                                      \
 273 })
 274
 275 /* Called with local BH disabled and the pool lock held.
 276  * Variable names are the proof of operation correctness.
 277  * Look into mm/map_avl.c for more detail description of the ideas.
 278  */
 279 static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
 280                                struct inet_peer __rcu ***stackend,
 281                                struct inet_peer_base *base)
 282 {
 283         struct inet_peer __rcu **nodep;
 284         struct inet_peer *node, *l, *r;
 285         int lh, rh;
 286
 287         while (stackend > stack) {
 288                 nodep = *--stackend;
 289                 node = rcu_deref_locked(*nodep, base);
 290                 l = rcu_deref_locked(node->avl_left, base);
 291                 r = rcu_deref_locked(node->avl_right, base);
 292                 lh = node_height(l);
 293                 rh = node_height(r);
 294                 if (lh > rh + 1) { /* l: RH+2 */
 295                         struct inet_peer *ll, *lr, *lrl, *lrr;
 296                         int lrh;
 297                         ll = rcu_deref_locked(l->avl_left, base);
 298                         lr = rcu_deref_locked(l->avl_right, base);
 299                         lrh = node_height(lr);
 300                         if (lrh <= node_height(ll)) {   /* ll: RH+1 */
 301                                 RCU_INIT_POINTER(node->avl_left, lr);   /* lr: RH or RH+1 */
 302                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
 303                                 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
 304                                 RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
 305                                 RCU_INIT_POINTER(l->avl_right, node);   /* node: RH+1 or RH+2 */
 306                                 l->avl_height = node->avl_height + 1;
 307                                 RCU_INIT_POINTER(*nodep, l);
 308                         } else { /* ll: RH, lr: RH+1 */
 309                                 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
 310                                 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
 311                                 RCU_INIT_POINTER(node->avl_left, lrr);  /* lrr: RH or RH-1 */
 312                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
 313                                 node->avl_height = rh + 1; /* node: RH+1 */
 314                                 RCU_INIT_POINTER(l->avl_left, ll);      /* ll: RH */
 315                                 RCU_INIT_POINTER(l->avl_right, lrl);    /* lrl: RH or RH-1 */
 316                                 l->avl_height = rh + 1; /* l: RH+1 */
 317                                 RCU_INIT_POINTER(lr->avl_left, l);      /* l: RH+1 */
 318                                 RCU_INIT_POINTER(lr->avl_right, node);  /* node: RH+1 */
 319                                 lr->avl_height = rh + 2;
 320                                 RCU_INIT_POINTER(*nodep, lr);
 321                         }
 322                 } else if (rh > lh + 1) { /* r: LH+2 */
 323                         struct inet_peer *rr, *rl, *rlr, *rll;
 324                         int rlh;
 325                         rr = rcu_deref_locked(r->avl_right, base);
 326                         rl = rcu_deref_locked(r->avl_left, base);
 327                         rlh = node_height(rl);
 328                         if (rlh <= node_height(rr)) {   /* rr: LH+1 */
 329                                 RCU_INIT_POINTER(node->avl_right, rl);  /* rl: LH or LH+1 */
 330                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
 331                                 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
 332                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH+1 */
 333                                 RCU_INIT_POINTER(r->avl_left, node);    /* node: LH+1 or LH+2 */
 334                                 r->avl_height = node->avl_height + 1;
 335                                 RCU_INIT_POINTER(*nodep, r);
 336                         } else { /* rr: RH, rl: RH+1 */
 337                                 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
 338                                 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
 339                                 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
 340                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
 341                                 node->avl_height = lh + 1; /* node: LH+1 */
 342                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH */
 343                                 RCU_INIT_POINTER(r->avl_left, rlr);     /* rlr: LH or LH-1 */
 344                                 r->avl_height = lh + 1; /* r: LH+1 */
 345                                 RCU_INIT_POINTER(rl->avl_right, r);     /* r: LH+1 */
 346                                 RCU_INIT_POINTER(rl->avl_left, node);   /* node: LH+1 */
 347                                 rl->avl_height = lh + 2;
 348                                 RCU_INIT_POINTER(*nodep, rl);
 349                         }
 350                 } else {
 351                         node->avl_height = (lh > rh ? lh : rh) + 1;
 352                 }
 353         }
 354 }
 355
 356 /* Called with local BH disabled and the pool lock held. */
 357 #define link_to_pool(n, base)                                   \
 358 do {                                                            \
 359         n->avl_height = 1;                                      \
 360         n->avl_left = peer_avl_empty_rcu;                       \
 361         n->avl_right = peer_avl_empty_rcu;                      \
 362         /* lockless readers can catch us now */                 \
 363         rcu_assign_pointer(**--stackptr, n);                    \
 364         peer_avl_rebalance(stack, stackptr, base);              \
 365 } while (0)
 366
 367 static void inetpeer_free_rcu(struct rcu_head *head)
 368 {
 369         kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
 370 }
 371
 372 static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
 373                              struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 374 {
 375         struct inet_peer __rcu ***stackptr, ***delp;
 376
 377         if (lookup(&p->daddr, stack, base) != p)
 378                 BUG();
 379         delp = stackptr - 1; /* *delp[0] == p */
 380         if (p->avl_left == peer_avl_empty_rcu) {
 381                 *delp[0] = p->avl_right;
 382                 --stackptr;
 383         } else {
 384                 /* look for a node to insert instead of p */
 385                 struct inet_peer *t;
 386                 t = lookup_rightempty(p, base);
 387                 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
 388                 **--stackptr = t->avl_left;
 389                 /* t is removed, t->daddr > x->daddr for any
 390                  * x in p->avl_left subtree.
 391                  * Put t in the old place of p. */
 392                 RCU_INIT_POINTER(*delp[0], t);
 393                 t->avl_left = p->avl_left;
 394                 t->avl_right = p->avl_right;
 395                 t->avl_height = p->avl_height;
 396                 BUG_ON(delp[1] != &p->avl_left);
 397                 delp[1] = &t->avl_left; /* was &p->avl_left */
 398         }
 399         peer_avl_rebalance(stack, stackptr, base);
 400         base->total--;
 401         call_rcu(&p->rcu, inetpeer_free_rcu);
 402 }
 403
 404 static struct inet_peer_base *family_to_base(int family)
 405 {
 406         return family == AF_INET ? &v4_peers : &v6_peers;
 407 }
 408
 409 /* perform garbage collect on all items stacked during a lookup */
 410 static int inet_peer_gc(struct inet_peer_base *base,
 411                         struct inet_peer __rcu **stack[PEER_MAXDEPTH],
 412                         struct inet_peer __rcu ***stackptr)
 413 {
 414         struct inet_peer *p, *gchead = NULL;
 415         __u32 delta, ttl;
 416         int cnt = 0;
 417
 418         if (base->total >= inet_peer_threshold)
 419                 ttl = 0; /* be aggressive */
 420         else
 421                 ttl = inet_peer_maxttl
 422                                 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
 423                                         base->total / inet_peer_threshold * HZ;
 424         stackptr--; /* last stack slot is peer_avl_empty */
 425         while (stackptr > stack) {
 426                 stackptr--;
 427                 p = rcu_deref_locked(**stackptr, base);
 428                 if (atomic_read(&p->refcnt) == 0) {
 429                         smp_rmb();
 430                         delta = (__u32)jiffies - p->dtime;
 431                         if (delta >= ttl &&
 432                             atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
 433                                 p->gc_next = gchead;
 434                                 gchead = p;
 435                         }
 436                 }
 437         }
 438         while ((p = gchead) != NULL) {
 439                 gchead = p->gc_next;
 440                 cnt++;
 441                 unlink_from_pool(p, base, stack);
 442         }
 443         return cnt;
 444 }
 445
 446 struct inet_peer *inet_getpeer(const struct inetpeer_addr *daddr, int create)
 447 {
 448         struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
 449         struct inet_peer_base *base = family_to_base(daddr->family);
 450         struct inet_peer *p;
 451         unsigned int sequence;
 452         int invalidated, gccnt = 0;
 453
 454         /* Attempt a lockless lookup first.
 455          * Because of a concurrent writer, we might not find an existing entry.
 456          */
 457         rcu_read_lock();
 458         sequence = read_seqbegin(&base->lock);
 459         p = lookup_rcu(daddr, base);
 460         invalidated = read_seqretry(&base->lock, sequence);
 461         rcu_read_unlock();
 462
 463         if (p)
 464                 return p;
 465
 466         /* If no writer did a change during our lookup, we can return early. */
 467         if (!create && !invalidated)
 468                 return NULL;
 469
 470         /* retry an exact lookup, taking the lock before.
 471          * At least, nodes should be hot in our cache.
 472          */
 473         write_seqlock_bh(&base->lock);
 474 relookup:
 475         p = lookup(daddr, stack, base);
 476         if (p != peer_avl_empty) {
 477                 atomic_inc(&p->refcnt);
 478                 write_sequnlock_bh(&base->lock);
 479                 return p;
 480         }
 481         if (!gccnt) {
 482                 gccnt = inet_peer_gc(base, stack, stackptr);
 483                 if (gccnt && create)
 484                         goto relookup;
 485         }
 486         p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
 487         if (p) {
 488                 p->daddr = *daddr;
 489                 atomic_set(&p->refcnt, 1);
 490                 atomic_set(&p->rid, 0);
 491                 atomic_set(&p->ip_id_count,
 492                                 (daddr->family == AF_INET) ?
 493                                         secure_ip_id(daddr->addr.a4) :
 494                                         secure_ipv6_id(daddr->addr.a6));
 495                 p->tcp_ts_stamp = 0;
 496                 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
 497                 p->rate_tokens = 0;
 498                 p->rate_last = 0;
 499                 p->pmtu_expires = 0;
 500                 p->pmtu_orig = 0;
 501                 memset(&p->redirect_learned, 0, sizeof(p->redirect_learned));
 502                 INIT_LIST_HEAD(&p->gc_list);
 503
 504                 /* Link the node. */
 505                 link_to_pool(p, base);
 506                 base->total++;
 507         }
 508         write_sequnlock_bh(&base->lock);
 509
 510         return p;
 511 }
 512 EXPORT_SYMBOL_GPL(inet_getpeer);
 513
 514 void inet_putpeer(struct inet_peer *p)
 515 {
 516         p->dtime = (__u32)jiffies;
 517         smp_mb__before_atomic_dec();
 518         atomic_dec(&p->refcnt);
 519 }
 520 EXPORT_SYMBOL_GPL(inet_putpeer);
 521
 522 /*
 523  *      Check transmit rate limitation for given message.
 524  *      The rate information is held in the inet_peer entries now.
 525  *      This function is generic and could be used for other purposes
 526  *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
 527  *
 528  *      Note that the same inet_peer fields are modified by functions in
 529  *      route.c too, but these work for packet destinations while xrlim_allow
 530  *      works for icmp destinations. This means the rate limiting information
 531  *      for one "ip object" is shared - and these ICMPs are twice limited:
 532  *      by source and by destination.
 533  *
 534  *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
 535  *                        SHOULD allow setting of rate limits
 536  *
 537  *      Shared between ICMPv4 and ICMPv6.
 538  */
 539 #define XRLIM_BURST_FACTOR 6
 540 bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
 541 {
 542         unsigned long now, token;
 543         bool rc = false;
 544
 545         if (!peer)
 546                 return true;
 547
 548         token = peer->rate_tokens;
 549         now = jiffies;
 550         token += now - peer->rate_last;
 551         peer->rate_last = now;
 552         if (token > XRLIM_BURST_FACTOR * timeout)
 553                 token = XRLIM_BURST_FACTOR * timeout;
 554         if (token >= timeout) {
 555                 token -= timeout;
 556                 rc = true;
 557         }
 558         peer->rate_tokens = token;
 559         return rc;
 560 }
 561 EXPORT_SYMBOL(inet_peer_xrlim_allow);
 562
 563 void inetpeer_invalidate_tree(int family)
 564 {
 565         struct inet_peer *old, *new, *prev;
 566         struct inet_peer_base *base = family_to_base(family);
 567
 568         write_seqlock_bh(&base->lock);
 569
 570         old = base->root;
 571         if (old == peer_avl_empty_rcu)
 572                 goto out;
 573
 574         new = peer_avl_empty_rcu;
 575
 576         prev = cmpxchg(&base->root, old, new);
 577         if (prev == old) {
 578                 base->total = 0;
 579                 spin_lock(&gc_lock);
 580                 list_add_tail(&prev->gc_list, &gc_list);
 581                 spin_unlock(&gc_lock);
 582                 schedule_delayed_work(&gc_work, gc_delay);
 583         }
 584
 585 out:
 586         write_sequnlock_bh(&base->lock);
 587 }
 588 EXPORT_SYMBOL(inetpeer_invalidate_tree);