Merge tag 'ktest-v3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt...
[firefly-linux-kernel-4.4.55.git] / 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->total = 0;
76 }
77 EXPORT_SYMBOL_GPL(inet_peer_base_init);
78
79 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
80
81 /* Exported for sysctl_net_ipv4.  */
82 int inet_peer_threshold __read_mostly = 65536 + 128;    /* start to throw entries more
83                                          * aggressively at this stage */
84 int inet_peer_minttl __read_mostly = 120 * HZ;  /* TTL under high load: 120 sec */
85 int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;      /* usual time to live: 10 min */
86
87 static void inetpeer_gc_worker(struct work_struct *work)
88 {
89         struct inet_peer *p, *n, *c;
90         struct list_head list;
91
92         spin_lock_bh(&gc_lock);
93         list_replace_init(&gc_list, &list);
94         spin_unlock_bh(&gc_lock);
95
96         if (list_empty(&list))
97                 return;
98
99         list_for_each_entry_safe(p, n, &list, gc_list) {
100
101                 if (need_resched())
102                         cond_resched();
103
104                 c = rcu_dereference_protected(p->avl_left, 1);
105                 if (c != peer_avl_empty) {
106                         list_add_tail(&c->gc_list, &list);
107                         p->avl_left = peer_avl_empty_rcu;
108                 }
109
110                 c = rcu_dereference_protected(p->avl_right, 1);
111                 if (c != peer_avl_empty) {
112                         list_add_tail(&c->gc_list, &list);
113                         p->avl_right = peer_avl_empty_rcu;
114                 }
115
116                 n = list_entry(p->gc_list.next, struct inet_peer, gc_list);
117
118                 if (!atomic_read(&p->refcnt)) {
119                         list_del(&p->gc_list);
120                         kmem_cache_free(peer_cachep, p);
121                 }
122         }
123
124         if (list_empty(&list))
125                 return;
126
127         spin_lock_bh(&gc_lock);
128         list_splice(&list, &gc_list);
129         spin_unlock_bh(&gc_lock);
130
131         schedule_delayed_work(&gc_work, gc_delay);
132 }
133
134 /* Called from ip_output.c:ip_init  */
135 void __init inet_initpeers(void)
136 {
137         struct sysinfo si;
138
139         /* Use the straight interface to information about memory. */
140         si_meminfo(&si);
141         /* The values below were suggested by Alexey Kuznetsov
142          * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
143          * myself.  --SAW
144          */
145         if (si.totalram <= (32768*1024)/PAGE_SIZE)
146                 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
147         if (si.totalram <= (16384*1024)/PAGE_SIZE)
148                 inet_peer_threshold >>= 1; /* about 512KB */
149         if (si.totalram <= (8192*1024)/PAGE_SIZE)
150                 inet_peer_threshold >>= 2; /* about 128KB */
151
152         peer_cachep = kmem_cache_create("inet_peer_cache",
153                         sizeof(struct inet_peer),
154                         0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
155                         NULL);
156
157         INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker);
158 }
159
160 static int addr_compare(const struct inetpeer_addr *a,
161                         const struct inetpeer_addr *b)
162 {
163         int i, n = (a->family == AF_INET ? 1 : 4);
164
165         for (i = 0; i < n; i++) {
166                 if (a->addr.a6[i] == b->addr.a6[i])
167                         continue;
168                 if ((__force u32)a->addr.a6[i] < (__force u32)b->addr.a6[i])
169                         return -1;
170                 return 1;
171         }
172
173         return 0;
174 }
175
176 #define rcu_deref_locked(X, BASE)                               \
177         rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
178
179 /*
180  * Called with local BH disabled and the pool lock held.
181  */
182 #define lookup(_daddr, _stack, _base)                           \
183 ({                                                              \
184         struct inet_peer *u;                                    \
185         struct inet_peer __rcu **v;                             \
186                                                                 \
187         stackptr = _stack;                                      \
188         *stackptr++ = &_base->root;                             \
189         for (u = rcu_deref_locked(_base->root, _base);          \
190              u != peer_avl_empty;) {                            \
191                 int cmp = addr_compare(_daddr, &u->daddr);      \
192                 if (cmp == 0)                                   \
193                         break;                                  \
194                 if (cmp == -1)                                  \
195                         v = &u->avl_left;                       \
196                 else                                            \
197                         v = &u->avl_right;                      \
198                 *stackptr++ = v;                                \
199                 u = rcu_deref_locked(*v, _base);                \
200         }                                                       \
201         u;                                                      \
202 })
203
204 /*
205  * Called with rcu_read_lock()
206  * Because we hold no lock against a writer, its quite possible we fall
207  * in an endless loop.
208  * But every pointer we follow is guaranteed to be valid thanks to RCU.
209  * We exit from this function if number of links exceeds PEER_MAXDEPTH
210  */
211 static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
212                                     struct inet_peer_base *base)
213 {
214         struct inet_peer *u = rcu_dereference(base->root);
215         int count = 0;
216
217         while (u != peer_avl_empty) {
218                 int cmp = addr_compare(daddr, &u->daddr);
219                 if (cmp == 0) {
220                         /* Before taking a reference, check if this entry was
221                          * deleted (refcnt=-1)
222                          */
223                         if (!atomic_add_unless(&u->refcnt, 1, -1))
224                                 u = NULL;
225                         return u;
226                 }
227                 if (cmp == -1)
228                         u = rcu_dereference(u->avl_left);
229                 else
230                         u = rcu_dereference(u->avl_right);
231                 if (unlikely(++count == PEER_MAXDEPTH))
232                         break;
233         }
234         return NULL;
235 }
236
237 /* Called with local BH disabled and the pool lock held. */
238 #define lookup_rightempty(start, base)                          \
239 ({                                                              \
240         struct inet_peer *u;                                    \
241         struct inet_peer __rcu **v;                             \
242         *stackptr++ = &start->avl_left;                         \
243         v = &start->avl_left;                                   \
244         for (u = rcu_deref_locked(*v, base);                    \
245              u->avl_right != peer_avl_empty_rcu;) {             \
246                 v = &u->avl_right;                              \
247                 *stackptr++ = v;                                \
248                 u = rcu_deref_locked(*v, base);                 \
249         }                                                       \
250         u;                                                      \
251 })
252
253 /* Called with local BH disabled and the pool lock held.
254  * Variable names are the proof of operation correctness.
255  * Look into mm/map_avl.c for more detail description of the ideas.
256  */
257 static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
258                                struct inet_peer __rcu ***stackend,
259                                struct inet_peer_base *base)
260 {
261         struct inet_peer __rcu **nodep;
262         struct inet_peer *node, *l, *r;
263         int lh, rh;
264
265         while (stackend > stack) {
266                 nodep = *--stackend;
267                 node = rcu_deref_locked(*nodep, base);
268                 l = rcu_deref_locked(node->avl_left, base);
269                 r = rcu_deref_locked(node->avl_right, base);
270                 lh = node_height(l);
271                 rh = node_height(r);
272                 if (lh > rh + 1) { /* l: RH+2 */
273                         struct inet_peer *ll, *lr, *lrl, *lrr;
274                         int lrh;
275                         ll = rcu_deref_locked(l->avl_left, base);
276                         lr = rcu_deref_locked(l->avl_right, base);
277                         lrh = node_height(lr);
278                         if (lrh <= node_height(ll)) {   /* ll: RH+1 */
279                                 RCU_INIT_POINTER(node->avl_left, lr);   /* lr: RH or RH+1 */
280                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
281                                 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
282                                 RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
283                                 RCU_INIT_POINTER(l->avl_right, node);   /* node: RH+1 or RH+2 */
284                                 l->avl_height = node->avl_height + 1;
285                                 RCU_INIT_POINTER(*nodep, l);
286                         } else { /* ll: RH, lr: RH+1 */
287                                 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
288                                 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
289                                 RCU_INIT_POINTER(node->avl_left, lrr);  /* lrr: RH or RH-1 */
290                                 RCU_INIT_POINTER(node->avl_right, r);   /* r: RH */
291                                 node->avl_height = rh + 1; /* node: RH+1 */
292                                 RCU_INIT_POINTER(l->avl_left, ll);      /* ll: RH */
293                                 RCU_INIT_POINTER(l->avl_right, lrl);    /* lrl: RH or RH-1 */
294                                 l->avl_height = rh + 1; /* l: RH+1 */
295                                 RCU_INIT_POINTER(lr->avl_left, l);      /* l: RH+1 */
296                                 RCU_INIT_POINTER(lr->avl_right, node);  /* node: RH+1 */
297                                 lr->avl_height = rh + 2;
298                                 RCU_INIT_POINTER(*nodep, lr);
299                         }
300                 } else if (rh > lh + 1) { /* r: LH+2 */
301                         struct inet_peer *rr, *rl, *rlr, *rll;
302                         int rlh;
303                         rr = rcu_deref_locked(r->avl_right, base);
304                         rl = rcu_deref_locked(r->avl_left, base);
305                         rlh = node_height(rl);
306                         if (rlh <= node_height(rr)) {   /* rr: LH+1 */
307                                 RCU_INIT_POINTER(node->avl_right, rl);  /* rl: LH or LH+1 */
308                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
309                                 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
310                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH+1 */
311                                 RCU_INIT_POINTER(r->avl_left, node);    /* node: LH+1 or LH+2 */
312                                 r->avl_height = node->avl_height + 1;
313                                 RCU_INIT_POINTER(*nodep, r);
314                         } else { /* rr: RH, rl: RH+1 */
315                                 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
316                                 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
317                                 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
318                                 RCU_INIT_POINTER(node->avl_left, l);    /* l: LH */
319                                 node->avl_height = lh + 1; /* node: LH+1 */
320                                 RCU_INIT_POINTER(r->avl_right, rr);     /* rr: LH */
321                                 RCU_INIT_POINTER(r->avl_left, rlr);     /* rlr: LH or LH-1 */
322                                 r->avl_height = lh + 1; /* r: LH+1 */
323                                 RCU_INIT_POINTER(rl->avl_right, r);     /* r: LH+1 */
324                                 RCU_INIT_POINTER(rl->avl_left, node);   /* node: LH+1 */
325                                 rl->avl_height = lh + 2;
326                                 RCU_INIT_POINTER(*nodep, rl);
327                         }
328                 } else {
329                         node->avl_height = (lh > rh ? lh : rh) + 1;
330                 }
331         }
332 }
333
334 /* Called with local BH disabled and the pool lock held. */
335 #define link_to_pool(n, base)                                   \
336 do {                                                            \
337         n->avl_height = 1;                                      \
338         n->avl_left = peer_avl_empty_rcu;                       \
339         n->avl_right = peer_avl_empty_rcu;                      \
340         /* lockless readers can catch us now */                 \
341         rcu_assign_pointer(**--stackptr, n);                    \
342         peer_avl_rebalance(stack, stackptr, base);              \
343 } while (0)
344
345 static void inetpeer_free_rcu(struct rcu_head *head)
346 {
347         kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
348 }
349
350 static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
351                              struct inet_peer __rcu **stack[PEER_MAXDEPTH])
352 {
353         struct inet_peer __rcu ***stackptr, ***delp;
354
355         if (lookup(&p->daddr, stack, base) != p)
356                 BUG();
357         delp = stackptr - 1; /* *delp[0] == p */
358         if (p->avl_left == peer_avl_empty_rcu) {
359                 *delp[0] = p->avl_right;
360                 --stackptr;
361         } else {
362                 /* look for a node to insert instead of p */
363                 struct inet_peer *t;
364                 t = lookup_rightempty(p, base);
365                 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
366                 **--stackptr = t->avl_left;
367                 /* t is removed, t->daddr > x->daddr for any
368                  * x in p->avl_left subtree.
369                  * Put t in the old place of p. */
370                 RCU_INIT_POINTER(*delp[0], t);
371                 t->avl_left = p->avl_left;
372                 t->avl_right = p->avl_right;
373                 t->avl_height = p->avl_height;
374                 BUG_ON(delp[1] != &p->avl_left);
375                 delp[1] = &t->avl_left; /* was &p->avl_left */
376         }
377         peer_avl_rebalance(stack, stackptr, base);
378         base->total--;
379         call_rcu(&p->rcu, inetpeer_free_rcu);
380 }
381
382 /* perform garbage collect on all items stacked during a lookup */
383 static int inet_peer_gc(struct inet_peer_base *base,
384                         struct inet_peer __rcu **stack[PEER_MAXDEPTH],
385                         struct inet_peer __rcu ***stackptr)
386 {
387         struct inet_peer *p, *gchead = NULL;
388         __u32 delta, ttl;
389         int cnt = 0;
390
391         if (base->total >= inet_peer_threshold)
392                 ttl = 0; /* be aggressive */
393         else
394                 ttl = inet_peer_maxttl
395                                 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
396                                         base->total / inet_peer_threshold * HZ;
397         stackptr--; /* last stack slot is peer_avl_empty */
398         while (stackptr > stack) {
399                 stackptr--;
400                 p = rcu_deref_locked(**stackptr, base);
401                 if (atomic_read(&p->refcnt) == 0) {
402                         smp_rmb();
403                         delta = (__u32)jiffies - p->dtime;
404                         if (delta >= ttl &&
405                             atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
406                                 p->gc_next = gchead;
407                                 gchead = p;
408                         }
409                 }
410         }
411         while ((p = gchead) != NULL) {
412                 gchead = p->gc_next;
413                 cnt++;
414                 unlink_from_pool(p, base, stack);
415         }
416         return cnt;
417 }
418
419 struct inet_peer *inet_getpeer(struct inet_peer_base *base,
420                                const struct inetpeer_addr *daddr,
421                                int create)
422 {
423         struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
424         struct inet_peer *p;
425         unsigned int sequence;
426         int invalidated, gccnt = 0;
427
428         /* Attempt a lockless lookup first.
429          * Because of a concurrent writer, we might not find an existing entry.
430          */
431         rcu_read_lock();
432         sequence = read_seqbegin(&base->lock);
433         p = lookup_rcu(daddr, base);
434         invalidated = read_seqretry(&base->lock, sequence);
435         rcu_read_unlock();
436
437         if (p)
438                 return p;
439
440         /* If no writer did a change during our lookup, we can return early. */
441         if (!create && !invalidated)
442                 return NULL;
443
444         /* retry an exact lookup, taking the lock before.
445          * At least, nodes should be hot in our cache.
446          */
447         write_seqlock_bh(&base->lock);
448 relookup:
449         p = lookup(daddr, stack, base);
450         if (p != peer_avl_empty) {
451                 atomic_inc(&p->refcnt);
452                 write_sequnlock_bh(&base->lock);
453                 return p;
454         }
455         if (!gccnt) {
456                 gccnt = inet_peer_gc(base, stack, stackptr);
457                 if (gccnt && create)
458                         goto relookup;
459         }
460         p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
461         if (p) {
462                 p->daddr = *daddr;
463                 atomic_set(&p->refcnt, 1);
464                 atomic_set(&p->rid, 0);
465                 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
466                 p->rate_tokens = 0;
467                 /* 60*HZ is arbitrary, but chosen enough high so that the first
468                  * calculation of tokens is at its maximum.
469                  */
470                 p->rate_last = jiffies - 60*HZ;
471                 INIT_LIST_HEAD(&p->gc_list);
472
473                 /* Link the node. */
474                 link_to_pool(p, base);
475                 base->total++;
476         }
477         write_sequnlock_bh(&base->lock);
478
479         return p;
480 }
481 EXPORT_SYMBOL_GPL(inet_getpeer);
482
483 void inet_putpeer(struct inet_peer *p)
484 {
485         p->dtime = (__u32)jiffies;
486         smp_mb__before_atomic();
487         atomic_dec(&p->refcnt);
488 }
489 EXPORT_SYMBOL_GPL(inet_putpeer);
490
491 /*
492  *      Check transmit rate limitation for given message.
493  *      The rate information is held in the inet_peer entries now.
494  *      This function is generic and could be used for other purposes
495  *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
496  *
497  *      Note that the same inet_peer fields are modified by functions in
498  *      route.c too, but these work for packet destinations while xrlim_allow
499  *      works for icmp destinations. This means the rate limiting information
500  *      for one "ip object" is shared - and these ICMPs are twice limited:
501  *      by source and by destination.
502  *
503  *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
504  *                        SHOULD allow setting of rate limits
505  *
506  *      Shared between ICMPv4 and ICMPv6.
507  */
508 #define XRLIM_BURST_FACTOR 6
509 bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
510 {
511         unsigned long now, token;
512         bool rc = false;
513
514         if (!peer)
515                 return true;
516
517         token = peer->rate_tokens;
518         now = jiffies;
519         token += now - peer->rate_last;
520         peer->rate_last = now;
521         if (token > XRLIM_BURST_FACTOR * timeout)
522                 token = XRLIM_BURST_FACTOR * timeout;
523         if (token >= timeout) {
524                 token -= timeout;
525                 rc = true;
526         }
527         peer->rate_tokens = token;
528         return rc;
529 }
530 EXPORT_SYMBOL(inet_peer_xrlim_allow);
531
532 static void inetpeer_inval_rcu(struct rcu_head *head)
533 {
534         struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
535
536         spin_lock_bh(&gc_lock);
537         list_add_tail(&p->gc_list, &gc_list);
538         spin_unlock_bh(&gc_lock);
539
540         schedule_delayed_work(&gc_work, gc_delay);
541 }
542
543 void inetpeer_invalidate_tree(struct inet_peer_base *base)
544 {
545         struct inet_peer *root;
546
547         write_seqlock_bh(&base->lock);
548
549         root = rcu_deref_locked(base->root, base);
550         if (root != peer_avl_empty) {
551                 base->root = peer_avl_empty_rcu;
552                 base->total = 0;
553                 call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
554         }
555
556         write_sequnlock_bh(&base->lock);
557 }
558 EXPORT_SYMBOL(inetpeer_invalidate_tree);