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  *
  30  *  Nodes are removed only when reference counter goes to 0.
  31  *  When it's happened the node may be removed when a sufficient amount of
  32  *  time has been passed since its last use.  The less-recently-used entry can
  33  *  also be removed if the pool is overloaded i.e. if the total amount of
  34  *  entries is greater-or-equal than the threshold.
  35  *
  36  *  Node pool is organised as an AVL tree.
  37  *  Such an implementation has been chosen not just for fun.  It's a way to
  38  *  prevent easy and efficient DoS attacks by creating hash collisions.  A huge
  39  *  amount of long living nodes in a single hash slot would significantly delay
  40  *  lookups performed with disabled BHs.
  41  *
  42  *  Serialisation issues.
  43  *  1.  Nodes may appear in the tree only with the pool lock held.
  44  *  2.  Nodes may disappear from the tree only with the pool lock held
  45  *      AND reference count being 0.
  46  *  3.  Global variable peer_total is modified under the pool lock.
  47  *  4.  struct inet_peer fields modification:
  48  *              avl_left, avl_right, avl_parent, avl_height: pool lock
  49  *              refcnt: atomically against modifications on other CPU;
  50  *                 usually under some other lock to prevent node disappearing
  51  *              daddr: unchangeable
  52  */
  53
  54 static struct kmem_cache *peer_cachep __read_mostly;
  55
  56 static LIST_HEAD(gc_list);
  57 static const int gc_delay = 60 * HZ;
  58 static struct delayed_work gc_work;
  59 static DEFINE_SPINLOCK(gc_lock);
  60
  61 #define node_height(x) x->avl_height
  62
  63 #define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
  64 #define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
  65 static const struct inet_peer peer_fake_node = {
  66         .avl_left       = peer_avl_empty_rcu,
  67         .avl_right      = peer_avl_empty_rcu,
  68         .avl_height     = 0
  69 };
  70
  71 void inet_peer_base_init(struct inet_peer_base *bp)
  72 {
  73         bp->root = peer_avl_empty_rcu;
  74         seqlock_init(&bp->lock);
  75         bp->flush_seq = ~0U;
  76         bp->total = 0;
  77 }
  78 EXPORT_SYMBOL_GPL(inet_peer_base_init);
  79
  80 static atomic_t v4_seq = ATOMIC_INIT(0);
  81 static atomic_t v6_seq = ATOMIC_INIT(0);
  82
  83 static atomic_t *inetpeer_seq_ptr(int family)
  84 {
  85         return (family == AF_INET ? &v4_seq : &v6_seq);
  86 }
  87
  88 static inline void flush_check(struct inet_peer_base *base, int family)
  89 {
  90         atomic_t *fp = inetpeer_seq_ptr(family);
  91
  92         if (unlikely(base->flush_seq != atomic_read(fp))) {
  93                 inetpeer_invalidate_tree(base);
  94                 base->flush_seq = atomic_read(fp);
  95         }
  96 }
  97
  98 void inetpeer_invalidate_family(int family)
  99 {
 100         atomic_t *fp = inetpeer_seq_ptr(family);
 101
 102         atomic_inc(fp);
 103 }
 104
 105 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
 106
 107 /* Exported for sysctl_net_ipv4.  */
 108 int inet_peer_threshold __read_mostly = 65536 + 128;    /* start to throw entries more
 109                                          * aggressively at this stage */
 110 int inet_peer_minttl __read_mostly = 120 * HZ;  /* TTL under high load: 120 sec */
 111 int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;      /* usual time to live: 10 min */
 112
 113 static void inetpeer_gc_worker(struct work_struct *work)
 114 {
 115         struct inet_peer *p, *n, *c;
 116         LIST_HEAD(list);
 117
 118         spin_lock_bh(&gc_lock);
 119         list_replace_init(&gc_list, &list);
 120         spin_unlock_bh(&gc_lock);
 121
 122         if (list_empty(&list))
 123                 return;
 124
 125         list_for_each_entry_safe(p, n, &list, gc_list) {
 126
 127                 if (need_resched())
 128                         cond_resched();
 129
 130                 c = rcu_dereference_protected(p->avl_left, 1);
 131                 if (c != peer_avl_empty) {
 132                         list_add_tail(&c->gc_list, &list);
 133                         p->avl_left = peer_avl_empty_rcu;
 134                 }
 135
 136                 c = rcu_dereference_protected(p->avl_right, 1);
 137                 if (c != peer_avl_empty) {
 138                         list_add_tail(&c->gc_list, &list);
 139                         p->avl_right = peer_avl_empty_rcu;
 140                 }
 141
 142                 n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
 143
 144                 if (!atomic_read(&p->refcnt)) {
 145                         list_del(&p->gc_list);
 146                         kmem_cache_free(peer_cachep, p);
 147                 }
 148         }
 149
 150         if (list_empty(&list))
 151                 return;
 152
 153         spin_lock_bh(&gc_lock);
 154         list_splice(&list, &gc_list);
 155         spin_unlock_bh(&gc_lock);
 156
 157         schedule_delayed_work(&gc_work, gc_delay);
 158 }
 159
 160 /* Called from ip_output.c:ip_init  */
 161 void __init inet_initpeers(void)
 162 {
 163         struct sysinfo si;
 164
 165         /* Use the straight interface to information about memory. */
 166         si_meminfo(&si);
 167         /* The values below were suggested by Alexey Kuznetsov
 168          * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
 169          * myself.  --SAW
 170          */
 171         if (si.totalram <= (32768*1024)/PAGE_SIZE)
 172                 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
 173         if (si.totalram <= (16384*1024)/PAGE_SIZE)
 174                 inet_peer_threshold >>= 1; /* about 512KB */
 175         if (si.totalram <= (8192*1024)/PAGE_SIZE)
 176                 inet_peer_threshold >>= 2; /* about 128KB */
 177
 178         peer_cachep = kmem_cache_create("inet_peer_cache",
 179                         sizeof(struct inet_peer),
 180                         0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
 181                         NULL);
 182
 183         INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker);
 184 }
 185
 186 static int addr_compare(const struct inetpeer_addr *a,
 187                         const struct inetpeer_addr *b)
 188 {
 189         int i, n = (a->family == AF_INET ? 1 : 4);
 190
 191         for (i = 0; i < n; i++) {
 192                 if (a->addr.a6[i] == b->addr.a6[i])
 193                         continue;
 194                 if ((__force u32)a->addr.a6[i] < (__force u32)b->addr.a6[i])
 195                         return -1;
 196                 return 1;
 197         }
 198
 199         return 0;
 200 }
 201
 202 #define rcu_deref_locked(X, BASE)                               \
 203         rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
 204
 205 /*
 206  * Called with local BH disabled and the pool lock held.
 207  */
 208 #define lookup(_daddr, _stack, _base)                           \
 209 ({                                                              \
 210         struct inet_peer *u;                                    \
 211         struct inet_peer __rcu **v;                             \
 212                                                                 \
 213         stackptr = _stack;                                      \
 214         *stackptr++ = &_base->root;                             \
 215         for (u = rcu_deref_locked(_base->root, _base);          \
 216              u != peer_avl_empty; ) {                           \
 217                 int cmp = addr_compare(_daddr, &u->daddr);      \
 218                 if (cmp == 0)                                   \
 219                         break;                                  \
 220                 if (cmp == -1)                                  \
 221                         v = &u->avl_left;                       \
 222                 else                                            \
 223                         v = &u->avl_right;                      \
 224                 *stackptr++ = v;                                \
 225                 u = rcu_deref_locked(*v, _base);                \
 226         }                                                       \
 227         u;                                                      \
 228 })
 229
 230 /*
 231  * Called with rcu_read_lock()
 232  * Because we hold no lock against a writer, its quite possible we fall
 233  * in an endless loop.
 234  * But every pointer we follow is guaranteed to be valid thanks to RCU.
 235  * We exit from this function if number of links exceeds PEER_MAXDEPTH
 236  */
 237 static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
 238                                     struct inet_peer_base *base)
 239 {
 240         struct inet_peer *u = rcu_dereference(base->root);
 241         int count = 0;
 242
 243         while (u != peer_avl_empty) {
 244                 int cmp = addr_compare(daddr, &u->daddr);
 245                 if (cmp == 0) {
 246                         /* Before taking a reference, check if this entry was
 247                          * deleted (refcnt=-1)
 248                          */
 249                         if (!atomic_add_unless(&u->refcnt, 1, -1))
 250                                 u = NULL;
 251                         return u;
 252                 }
 253                 if (cmp == -1)
 254                         u = rcu_dereference(u->avl_left);
 255                 else
 256                         u = rcu_dereference(u->avl_right);
 257                 if (unlikely(++count == PEER_MAXDEPTH))
 258                         break;
 259         }
 260         return NULL;
 261 }
 262
 263 /* Called with local BH disabled and the pool lock held. */
 264 #define lookup_rightempty(start, base)                          \
 265 ({                                                              \
 266         struct inet_peer *u;                                    \
 267         struct inet_peer __rcu **v;                             \
 268         *stackptr++ = &start->avl_left;                         \
 269         v = &start->avl_left;                                   \
 270         for (u = rcu_deref_locked(*v, base);                    \
 271              u->avl_right != peer_avl_empty_rcu; ) {            \
 272                 v = &u->avl_right;                              \
 273                 *stackptr++ = v;                                \
 274                 u = rcu_deref_locked(*v, base);                 \
 275         }                                                       \
 276         u;                                                      \
 277 })
 278
 279 /* Called with local BH disabled and the pool lock held.
 280  * Variable names are the proof of operation correctness.
 281  * Look into mm/map_avl.c for more detail description of the ideas.
 282  */
 283 static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
 284                                struct inet_peer __rcu ***stackend,
 285                                struct inet_peer_base *base)
 286 {
 287         struct inet_peer __rcu **nodep;
 288         struct inet_peer *node, *l, *r;
 289         int lh, rh;
 290
 291         while (stackend > stack) {
 292                 nodep = *--stackend;
 293                 node = rcu_deref_locked(*nodep, base);
 294                 l = rcu_deref_locked(node->avl_left, base);
 295                 r = rcu_deref_locked(node->avl_right, base);
 296                 lh = node_height(l);
 297                 rh = node_height(r);
 298                 if (lh > rh + 1) { /* l: RH+2 */
 299                         struct inet_peer *ll, *lr, *lrl, *lrr;
 300                         int lrh;
 301                         ll = rcu_deref_locked(l->avl_left, base);
 302                         lr = rcu_deref_locked(l->avl_right, base);
 303                         lrh = node_height(lr);
 304                         if (lrh <= node_height(ll)) {   /* ll: RH+1 */
 305                                 RCU_INIT_POINTER(node->avl_left, lr);   /* lr: RH or RH+1 */
 306                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
 307                                 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
 308                                 RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
 309                                 RCU_INIT_POINTER(l->avl_right, node);   /* node: RH+1 or RH+2 */
 310                                 l->avl_height = node->avl_height + 1;
 311                                 RCU_INIT_POINTER(*nodep, l);
 312                         } else { /* ll: RH, lr: RH+1 */
 313                                 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
 314                                 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
 315                                 RCU_INIT_POINTER(node->avl_left, lrr);  /* lrr: RH or RH-1 */
 316                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
 317                                 node->avl_height = rh + 1; /* node: RH+1 */
 318                                 RCU_INIT_POINTER(l->avl_left, ll);      /* ll: RH */
 319                                 RCU_INIT_POINTER(l->avl_right, lrl);    /* lrl: RH or RH-1 */
 320                                 l->avl_height = rh + 1; /* l: RH+1 */
 321                                 RCU_INIT_POINTER(lr->avl_left, l);      /* l: RH+1 */
 322                                 RCU_INIT_POINTER(lr->avl_right, node);  /* node: RH+1 */
 323                                 lr->avl_height = rh + 2;
 324                                 RCU_INIT_POINTER(*nodep, lr);
 325                         }
 326                 } else if (rh > lh + 1) { /* r: LH+2 */
 327                         struct inet_peer *rr, *rl, *rlr, *rll;
 328                         int rlh;
 329                         rr = rcu_deref_locked(r->avl_right, base);
 330                         rl = rcu_deref_locked(r->avl_left, base);
 331                         rlh = node_height(rl);
 332                         if (rlh <= node_height(rr)) {   /* rr: LH+1 */
 333                                 RCU_INIT_POINTER(node->avl_right, rl);  /* rl: LH or LH+1 */
 334                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
 335                                 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
 336                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH+1 */
 337                                 RCU_INIT_POINTER(r->avl_left, node);    /* node: LH+1 or LH+2 */
 338                                 r->avl_height = node->avl_height + 1;
 339                                 RCU_INIT_POINTER(*nodep, r);
 340                         } else { /* rr: RH, rl: RH+1 */
 341                                 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
 342                                 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
 343                                 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
 344                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
 345                                 node->avl_height = lh + 1; /* node: LH+1 */
 346                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH */
 347                                 RCU_INIT_POINTER(r->avl_left, rlr);     /* rlr: LH or LH-1 */
 348                                 r->avl_height = lh + 1; /* r: LH+1 */
 349                                 RCU_INIT_POINTER(rl->avl_right, r);     /* r: LH+1 */
 350                                 RCU_INIT_POINTER(rl->avl_left, node);   /* node: LH+1 */
 351                                 rl->avl_height = lh + 2;
 352                                 RCU_INIT_POINTER(*nodep, rl);
 353                         }
 354                 } else {
 355                         node->avl_height = (lh > rh ? lh : rh) + 1;
 356                 }
 357         }
 358 }
 359
 360 /* Called with local BH disabled and the pool lock held. */
 361 #define link_to_pool(n, base)                                   \
 362 do {                                                            \
 363         n->avl_height = 1;                                      \
 364         n->avl_left = peer_avl_empty_rcu;                       \
 365         n->avl_right = peer_avl_empty_rcu;                      \
 366         /* lockless readers can catch us now */                 \
 367         rcu_assign_pointer(**--stackptr, n);                    \
 368         peer_avl_rebalance(stack, stackptr, base);              \
 369 } while (0)
 370
 371 static void inetpeer_free_rcu(struct rcu_head *head)
 372 {
 373         kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
 374 }
 375
 376 static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
 377                              struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 378 {
 379         struct inet_peer __rcu ***stackptr, ***delp;
 380
 381         if (lookup(&p->daddr, stack, base) != p)
 382                 BUG();
 383         delp = stackptr - 1; /* *delp[0] == p */
 384         if (p->avl_left == peer_avl_empty_rcu) {
 385                 *delp[0] = p->avl_right;
 386                 --stackptr;
 387         } else {
 388                 /* look for a node to insert instead of p */
 389                 struct inet_peer *t;
 390                 t = lookup_rightempty(p, base);
 391                 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
 392                 **--stackptr = t->avl_left;
 393                 /* t is removed, t->daddr > x->daddr for any
 394                  * x in p->avl_left subtree.
 395                  * Put t in the old place of p. */
 396                 RCU_INIT_POINTER(*delp[0], t);
 397                 t->avl_left = p->avl_left;
 398                 t->avl_right = p->avl_right;
 399                 t->avl_height = p->avl_height;
 400                 BUG_ON(delp[1] != &p->avl_left);
 401                 delp[1] = &t->avl_left; /* was &p->avl_left */
 402         }
 403         peer_avl_rebalance(stack, stackptr, base);
 404         base->total--;
 405         call_rcu(&p->rcu, inetpeer_free_rcu);
 406 }
 407
 408 /* perform garbage collect on all items stacked during a lookup */
 409 static int inet_peer_gc(struct inet_peer_base *base,
 410                         struct inet_peer __rcu **stack[PEER_MAXDEPTH],
 411                         struct inet_peer __rcu ***stackptr)
 412 {
 413         struct inet_peer *p, *gchead = NULL;
 414         __u32 delta, ttl;
 415         int cnt = 0;
 416
 417         if (base->total >= inet_peer_threshold)
 418                 ttl = 0; /* be aggressive */
 419         else
 420                 ttl = inet_peer_maxttl
 421                                 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
 422                                         base->total / inet_peer_threshold * HZ;
 423         stackptr--; /* last stack slot is peer_avl_empty */
 424         while (stackptr > stack) {
 425                 stackptr--;
 426                 p = rcu_deref_locked(**stackptr, base);
 427                 if (atomic_read(&p->refcnt) == 0) {
 428                         smp_rmb();
 429                         delta = (__u32)jiffies - p->dtime;
 430                         if (delta >= ttl &&
 431                             atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
 432                                 p->gc_next = gchead;
 433                                 gchead = p;
 434                         }
 435                 }
 436         }
 437         while ((p = gchead) != NULL) {
 438                 gchead = p->gc_next;
 439                 cnt++;
 440                 unlink_from_pool(p, base, stack);
 441         }
 442         return cnt;
 443 }
 444
 445 struct inet_peer *inet_getpeer(struct inet_peer_base *base,
 446                                const struct inetpeer_addr *daddr,
 447                                int create)
 448 {
 449         struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
 450         struct inet_peer *p;
 451         unsigned int sequence;
 452         int invalidated, gccnt = 0;
 453
 454         flush_check(base, daddr->family);
 455
 456         /* Attempt a lockless lookup first.
 457          * Because of a concurrent writer, we might not find an existing entry.
 458          */
 459         rcu_read_lock();
 460         sequence = read_seqbegin(&base->lock);
 461         p = lookup_rcu(daddr, base);
 462         invalidated = read_seqretry(&base->lock, sequence);
 463         rcu_read_unlock();
 464
 465         if (p)
 466                 return p;
 467
 468         /* If no writer did a change during our lookup, we can return early. */
 469         if (!create && !invalidated)
 470                 return NULL;
 471
 472         /* retry an exact lookup, taking the lock before.
 473          * At least, nodes should be hot in our cache.
 474          */
 475         write_seqlock_bh(&base->lock);
 476 relookup:
 477         p = lookup(daddr, stack, base);
 478         if (p != peer_avl_empty) {
 479                 atomic_inc(&p->refcnt);
 480                 write_sequnlock_bh(&base->lock);
 481                 return p;
 482         }
 483         if (!gccnt) {
 484                 gccnt = inet_peer_gc(base, stack, stackptr);
 485                 if (gccnt && create)
 486                         goto relookup;
 487         }
 488         p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
 489         if (p) {
 490                 p->daddr = *daddr;
 491                 atomic_set(&p->refcnt, 1);
 492                 atomic_set(&p->rid, 0);
 493                 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
 494                 p->rate_tokens = 0;
 495                 /* 60*HZ is arbitrary, but chosen enough high so that the first
 496                  * calculation of tokens is at its maximum.
 497                  */
 498                 p->rate_last = jiffies - 60*HZ;
 499                 INIT_LIST_HEAD(&p->gc_list);
 500
 501                 /* Link the node. */
 502                 link_to_pool(p, base);
 503                 base->total++;
 504         }
 505         write_sequnlock_bh(&base->lock);
 506
 507         return p;
 508 }
 509 EXPORT_SYMBOL_GPL(inet_getpeer);
 510
 511 void inet_putpeer(struct inet_peer *p)
 512 {
 513         p->dtime = (__u32)jiffies;
 514         smp_mb__before_atomic_dec();
 515         atomic_dec(&p->refcnt);
 516 }
 517 EXPORT_SYMBOL_GPL(inet_putpeer);
 518
 519 /*
 520  *      Check transmit rate limitation for given message.
 521  *      The rate information is held in the inet_peer entries now.
 522  *      This function is generic and could be used for other purposes
 523  *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
 524  *
 525  *      Note that the same inet_peer fields are modified by functions in
 526  *      route.c too, but these work for packet destinations while xrlim_allow
 527  *      works for icmp destinations. This means the rate limiting information
 528  *      for one "ip object" is shared - and these ICMPs are twice limited:
 529  *      by source and by destination.
 530  *
 531  *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
 532  *                        SHOULD allow setting of rate limits
 533  *
 534  *      Shared between ICMPv4 and ICMPv6.
 535  */
 536 #define XRLIM_BURST_FACTOR 6
 537 bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
 538 {
 539         unsigned long now, token;
 540         bool rc = false;
 541
 542         if (!peer)
 543                 return true;
 544
 545         token = peer->rate_tokens;
 546         now = jiffies;
 547         token += now - peer->rate_last;
 548         peer->rate_last = now;
 549         if (token > XRLIM_BURST_FACTOR * timeout)
 550                 token = XRLIM_BURST_FACTOR * timeout;
 551         if (token >= timeout) {
 552                 token -= timeout;
 553                 rc = true;
 554         }
 555         peer->rate_tokens = token;
 556         return rc;
 557 }
 558 EXPORT_SYMBOL(inet_peer_xrlim_allow);
 559
 560 static void inetpeer_inval_rcu(struct rcu_head *head)
 561 {
 562         struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
 563
 564         spin_lock_bh(&gc_lock);
 565         list_add_tail(&p->gc_list, &gc_list);
 566         spin_unlock_bh(&gc_lock);
 567
 568         schedule_delayed_work(&gc_work, gc_delay);
 569 }
 570
 571 void inetpeer_invalidate_tree(struct inet_peer_base *base)
 572 {
 573         struct inet_peer *root;
 574
 575         write_seqlock_bh(&base->lock);
 576
 577         root = rcu_deref_locked(base->root, base);
 578         if (root != peer_avl_empty) {
 579                 base->root = peer_avl_empty_rcu;
 580                 base->total = 0;
 581                 call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
 582         }
 583
 584         write_sequnlock_bh(&base->lock);
 585 }
 586 EXPORT_SYMBOL(inetpeer_invalidate_tree);