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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/cache.h>
10#include <linux/module.h>
11#include <linux/types.h>
12#include <linux/slab.h>
13#include <linux/interrupt.h>
14#include <linux/spinlock.h>
15#include <linux/random.h>
16#include <linux/timer.h>
17#include <linux/time.h>
18#include <linux/kernel.h>
19#include <linux/mm.h>
20#include <linux/net.h>
21#include <linux/workqueue.h>
22#include <net/ip.h>
23#include <net/inetpeer.h>
24#include <net/secure_seq.h>
25
26/*
27 * Theory of operations.
28 * We keep one entry for each peer IP address. The nodes contains long-living
29 * information about the peer which doesn't depend on routes.
30 *
31 * Nodes are removed only when reference counter goes to 0.
32 * When it's happened the node may be removed when a sufficient amount of
33 * time has been passed since its last use. The less-recently-used entry can
34 * also be removed if the pool is overloaded i.e. if the total amount of
35 * entries is greater-or-equal than the threshold.
36 *
37 * Node pool is organised as an RB tree.
38 * Such an implementation has been chosen not just for fun. It's a way to
39 * prevent easy and efficient DoS attacks by creating hash collisions. A huge
40 * amount of long living nodes in a single hash slot would significantly delay
41 * lookups performed with disabled BHs.
42 *
43 * Serialisation issues.
44 * 1. Nodes may appear in the tree only with the pool lock held.
45 * 2. Nodes may disappear from the tree only with the pool lock held
46 * AND reference count being 0.
47 * 3. Global variable peer_total is modified under the pool lock.
48 * 4. struct inet_peer fields modification:
49 * rb_node: pool lock
50 * refcnt: atomically against modifications on other CPU;
51 * usually under some other lock to prevent node disappearing
52 * daddr: unchangeable
53 */
54
55static struct kmem_cache *peer_cachep __ro_after_init;
56
57void inet_peer_base_init(struct inet_peer_base *bp)
58{
59 bp->rb_root = RB_ROOT;
60 seqlock_init(&bp->lock);
61 bp->total = 0;
62}
63EXPORT_SYMBOL_GPL(inet_peer_base_init);
64
65#define PEER_MAX_GC 32
66
67/* Exported for sysctl_net_ipv4. */
68int inet_peer_threshold __read_mostly; /* start to throw entries more
69 * aggressively at this stage */
70int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
71int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
72
73/* Called from ip_output.c:ip_init */
74void __init inet_initpeers(void)
75{
76 u64 nr_entries;
77
78 /* 1% of physical memory */
79 nr_entries = div64_ul((u64)totalram_pages() << PAGE_SHIFT,
80 100 * L1_CACHE_ALIGN(sizeof(struct inet_peer)));
81
82 inet_peer_threshold = clamp_val(nr_entries, 4096, 65536 + 128);
83
84 peer_cachep = KMEM_CACHE(inet_peer, SLAB_HWCACHE_ALIGN | SLAB_PANIC);
85}
86
87/* Called with rcu_read_lock() or base->lock held */
88static struct inet_peer *lookup(const struct inetpeer_addr *daddr,
89 struct inet_peer_base *base,
90 unsigned int seq,
91 struct inet_peer *gc_stack[],
92 unsigned int *gc_cnt,
93 struct rb_node **parent_p,
94 struct rb_node ***pp_p)
95{
96 struct rb_node **pp, *parent, *next;
97 struct inet_peer *p;
98 u32 now;
99
100 pp = &base->rb_root.rb_node;
101 parent = NULL;
102 while (1) {
103 int cmp;
104
105 next = rcu_dereference_raw(*pp);
106 if (!next)
107 break;
108 parent = next;
109 p = rb_entry(parent, struct inet_peer, rb_node);
110 cmp = inetpeer_addr_cmp(daddr, &p->daddr);
111 if (cmp == 0) {
112 now = jiffies;
113 if (READ_ONCE(p->dtime) != now)
114 WRITE_ONCE(p->dtime, now);
115 return p;
116 }
117 if (gc_stack) {
118 if (*gc_cnt < PEER_MAX_GC)
119 gc_stack[(*gc_cnt)++] = p;
120 } else if (unlikely(read_seqretry(&base->lock, seq))) {
121 break;
122 }
123 if (cmp == -1)
124 pp = &next->rb_left;
125 else
126 pp = &next->rb_right;
127 }
128 *parent_p = parent;
129 *pp_p = pp;
130 return NULL;
131}
132
133/* perform garbage collect on all items stacked during a lookup */
134static void inet_peer_gc(struct inet_peer_base *base,
135 struct inet_peer *gc_stack[],
136 unsigned int gc_cnt)
137{
138 int peer_threshold, peer_maxttl, peer_minttl;
139 struct inet_peer *p;
140 __u32 delta, ttl;
141 int i;
142
143 peer_threshold = READ_ONCE(inet_peer_threshold);
144 peer_maxttl = READ_ONCE(inet_peer_maxttl);
145 peer_minttl = READ_ONCE(inet_peer_minttl);
146
147 if (base->total >= peer_threshold)
148 ttl = 0; /* be aggressive */
149 else
150 ttl = peer_maxttl - (peer_maxttl - peer_minttl) / HZ *
151 base->total / peer_threshold * HZ;
152 for (i = 0; i < gc_cnt; i++) {
153 p = gc_stack[i];
154
155 delta = (__u32)jiffies - READ_ONCE(p->dtime);
156
157 if (delta < ttl || !refcount_dec_if_one(&p->refcnt))
158 gc_stack[i] = NULL;
159 }
160 for (i = 0; i < gc_cnt; i++) {
161 p = gc_stack[i];
162 if (p) {
163 rb_erase(&p->rb_node, &base->rb_root);
164 base->total--;
165 kfree_rcu(p, rcu);
166 }
167 }
168}
169
170/* Must be called under RCU : No refcount change is done here. */
171struct inet_peer *inet_getpeer(struct inet_peer_base *base,
172 const struct inetpeer_addr *daddr)
173{
174 struct inet_peer *p, *gc_stack[PEER_MAX_GC];
175 struct rb_node **pp, *parent;
176 unsigned int gc_cnt, seq;
177
178 /* Attempt a lockless lookup first.
179 * Because of a concurrent writer, we might not find an existing entry.
180 */
181 seq = read_seqbegin(&base->lock);
182 p = lookup(daddr, base, seq, NULL, &gc_cnt, &parent, &pp);
183
184 if (p)
185 return p;
186
187 /* retry an exact lookup, taking the lock before.
188 * At least, nodes should be hot in our cache.
189 */
190 parent = NULL;
191 write_seqlock_bh(&base->lock);
192
193 gc_cnt = 0;
194 p = lookup(daddr, base, seq, gc_stack, &gc_cnt, &parent, &pp);
195 if (!p) {
196 p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
197 if (p) {
198 p->daddr = *daddr;
199 p->dtime = (__u32)jiffies;
200 refcount_set(&p->refcnt, 1);
201 atomic_set(&p->rid, 0);
202 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
203 p->rate_tokens = 0;
204 p->n_redirects = 0;
205 /* 60*HZ is arbitrary, but chosen enough high so that the first
206 * calculation of tokens is at its maximum.
207 */
208 p->rate_last = jiffies - 60*HZ;
209
210 rb_link_node(&p->rb_node, parent, pp);
211 rb_insert_color(&p->rb_node, &base->rb_root);
212 base->total++;
213 }
214 }
215 if (gc_cnt)
216 inet_peer_gc(base, gc_stack, gc_cnt);
217 write_sequnlock_bh(&base->lock);
218
219 return p;
220}
221EXPORT_SYMBOL_GPL(inet_getpeer);
222
223void inet_putpeer(struct inet_peer *p)
224{
225 if (refcount_dec_and_test(&p->refcnt))
226 kfree_rcu(p, rcu);
227}
228
229/*
230 * Check transmit rate limitation for given message.
231 * The rate information is held in the inet_peer entries now.
232 * This function is generic and could be used for other purposes
233 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
234 *
235 * Note that the same inet_peer fields are modified by functions in
236 * route.c too, but these work for packet destinations while xrlim_allow
237 * works for icmp destinations. This means the rate limiting information
238 * for one "ip object" is shared - and these ICMPs are twice limited:
239 * by source and by destination.
240 *
241 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
242 * SHOULD allow setting of rate limits
243 *
244 * Shared between ICMPv4 and ICMPv6.
245 */
246#define XRLIM_BURST_FACTOR 6
247bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
248{
249 unsigned long now, token;
250 bool rc = false;
251
252 if (!peer)
253 return true;
254
255 token = peer->rate_tokens;
256 now = jiffies;
257 token += now - peer->rate_last;
258 peer->rate_last = now;
259 if (token > XRLIM_BURST_FACTOR * timeout)
260 token = XRLIM_BURST_FACTOR * timeout;
261 if (token >= timeout) {
262 token -= timeout;
263 rc = true;
264 }
265 peer->rate_tokens = token;
266 return rc;
267}
268EXPORT_SYMBOL(inet_peer_xrlim_allow);
269
270void inetpeer_invalidate_tree(struct inet_peer_base *base)
271{
272 struct rb_node *p = rb_first(&base->rb_root);
273
274 while (p) {
275 struct inet_peer *peer = rb_entry(p, struct inet_peer, rb_node);
276
277 p = rb_next(p);
278 rb_erase(&peer->rb_node, &base->rb_root);
279 inet_putpeer(peer);
280 cond_resched();
281 }
282
283 base->total = 0;
284}
285EXPORT_SYMBOL(inetpeer_invalidate_tree);
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
54static struct kmem_cache *peer_cachep __read_mostly;
55
56static LIST_HEAD(gc_list);
57static const int gc_delay = 60 * HZ;
58static struct delayed_work gc_work;
59static 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)
65static 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
71void 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}
77EXPORT_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. */
82int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
83 * aggressively at this stage */
84int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
85int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
86
87static 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 */
135void __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#define rcu_deref_locked(X, BASE) \
161 rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
162
163/*
164 * Called with local BH disabled and the pool lock held.
165 */
166#define lookup(_daddr, _stack, _base) \
167({ \
168 struct inet_peer *u; \
169 struct inet_peer __rcu **v; \
170 \
171 stackptr = _stack; \
172 *stackptr++ = &_base->root; \
173 for (u = rcu_deref_locked(_base->root, _base); \
174 u != peer_avl_empty;) { \
175 int cmp = inetpeer_addr_cmp(_daddr, &u->daddr); \
176 if (cmp == 0) \
177 break; \
178 if (cmp == -1) \
179 v = &u->avl_left; \
180 else \
181 v = &u->avl_right; \
182 *stackptr++ = v; \
183 u = rcu_deref_locked(*v, _base); \
184 } \
185 u; \
186})
187
188/*
189 * Called with rcu_read_lock()
190 * Because we hold no lock against a writer, its quite possible we fall
191 * in an endless loop.
192 * But every pointer we follow is guaranteed to be valid thanks to RCU.
193 * We exit from this function if number of links exceeds PEER_MAXDEPTH
194 */
195static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
196 struct inet_peer_base *base)
197{
198 struct inet_peer *u = rcu_dereference(base->root);
199 int count = 0;
200
201 while (u != peer_avl_empty) {
202 int cmp = inetpeer_addr_cmp(daddr, &u->daddr);
203 if (cmp == 0) {
204 /* Before taking a reference, check if this entry was
205 * deleted (refcnt=-1)
206 */
207 if (!atomic_add_unless(&u->refcnt, 1, -1))
208 u = NULL;
209 return u;
210 }
211 if (cmp == -1)
212 u = rcu_dereference(u->avl_left);
213 else
214 u = rcu_dereference(u->avl_right);
215 if (unlikely(++count == PEER_MAXDEPTH))
216 break;
217 }
218 return NULL;
219}
220
221/* Called with local BH disabled and the pool lock held. */
222#define lookup_rightempty(start, base) \
223({ \
224 struct inet_peer *u; \
225 struct inet_peer __rcu **v; \
226 *stackptr++ = &start->avl_left; \
227 v = &start->avl_left; \
228 for (u = rcu_deref_locked(*v, base); \
229 u->avl_right != peer_avl_empty_rcu;) { \
230 v = &u->avl_right; \
231 *stackptr++ = v; \
232 u = rcu_deref_locked(*v, base); \
233 } \
234 u; \
235})
236
237/* Called with local BH disabled and the pool lock held.
238 * Variable names are the proof of operation correctness.
239 * Look into mm/map_avl.c for more detail description of the ideas.
240 */
241static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
242 struct inet_peer __rcu ***stackend,
243 struct inet_peer_base *base)
244{
245 struct inet_peer __rcu **nodep;
246 struct inet_peer *node, *l, *r;
247 int lh, rh;
248
249 while (stackend > stack) {
250 nodep = *--stackend;
251 node = rcu_deref_locked(*nodep, base);
252 l = rcu_deref_locked(node->avl_left, base);
253 r = rcu_deref_locked(node->avl_right, base);
254 lh = node_height(l);
255 rh = node_height(r);
256 if (lh > rh + 1) { /* l: RH+2 */
257 struct inet_peer *ll, *lr, *lrl, *lrr;
258 int lrh;
259 ll = rcu_deref_locked(l->avl_left, base);
260 lr = rcu_deref_locked(l->avl_right, base);
261 lrh = node_height(lr);
262 if (lrh <= node_height(ll)) { /* ll: RH+1 */
263 RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */
264 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
265 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
266 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */
267 RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */
268 l->avl_height = node->avl_height + 1;
269 RCU_INIT_POINTER(*nodep, l);
270 } else { /* ll: RH, lr: RH+1 */
271 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
272 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
273 RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */
274 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
275 node->avl_height = rh + 1; /* node: RH+1 */
276 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */
277 RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */
278 l->avl_height = rh + 1; /* l: RH+1 */
279 RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */
280 RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */
281 lr->avl_height = rh + 2;
282 RCU_INIT_POINTER(*nodep, lr);
283 }
284 } else if (rh > lh + 1) { /* r: LH+2 */
285 struct inet_peer *rr, *rl, *rlr, *rll;
286 int rlh;
287 rr = rcu_deref_locked(r->avl_right, base);
288 rl = rcu_deref_locked(r->avl_left, base);
289 rlh = node_height(rl);
290 if (rlh <= node_height(rr)) { /* rr: LH+1 */
291 RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */
292 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
293 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
294 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */
295 RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */
296 r->avl_height = node->avl_height + 1;
297 RCU_INIT_POINTER(*nodep, r);
298 } else { /* rr: RH, rl: RH+1 */
299 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
300 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
301 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
302 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
303 node->avl_height = lh + 1; /* node: LH+1 */
304 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */
305 RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */
306 r->avl_height = lh + 1; /* r: LH+1 */
307 RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */
308 RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */
309 rl->avl_height = lh + 2;
310 RCU_INIT_POINTER(*nodep, rl);
311 }
312 } else {
313 node->avl_height = (lh > rh ? lh : rh) + 1;
314 }
315 }
316}
317
318/* Called with local BH disabled and the pool lock held. */
319#define link_to_pool(n, base) \
320do { \
321 n->avl_height = 1; \
322 n->avl_left = peer_avl_empty_rcu; \
323 n->avl_right = peer_avl_empty_rcu; \
324 /* lockless readers can catch us now */ \
325 rcu_assign_pointer(**--stackptr, n); \
326 peer_avl_rebalance(stack, stackptr, base); \
327} while (0)
328
329static void inetpeer_free_rcu(struct rcu_head *head)
330{
331 kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
332}
333
334static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
335 struct inet_peer __rcu **stack[PEER_MAXDEPTH])
336{
337 struct inet_peer __rcu ***stackptr, ***delp;
338
339 if (lookup(&p->daddr, stack, base) != p)
340 BUG();
341 delp = stackptr - 1; /* *delp[0] == p */
342 if (p->avl_left == peer_avl_empty_rcu) {
343 *delp[0] = p->avl_right;
344 --stackptr;
345 } else {
346 /* look for a node to insert instead of p */
347 struct inet_peer *t;
348 t = lookup_rightempty(p, base);
349 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
350 **--stackptr = t->avl_left;
351 /* t is removed, t->daddr > x->daddr for any
352 * x in p->avl_left subtree.
353 * Put t in the old place of p. */
354 RCU_INIT_POINTER(*delp[0], t);
355 t->avl_left = p->avl_left;
356 t->avl_right = p->avl_right;
357 t->avl_height = p->avl_height;
358 BUG_ON(delp[1] != &p->avl_left);
359 delp[1] = &t->avl_left; /* was &p->avl_left */
360 }
361 peer_avl_rebalance(stack, stackptr, base);
362 base->total--;
363 call_rcu(&p->rcu, inetpeer_free_rcu);
364}
365
366/* perform garbage collect on all items stacked during a lookup */
367static int inet_peer_gc(struct inet_peer_base *base,
368 struct inet_peer __rcu **stack[PEER_MAXDEPTH],
369 struct inet_peer __rcu ***stackptr)
370{
371 struct inet_peer *p, *gchead = NULL;
372 __u32 delta, ttl;
373 int cnt = 0;
374
375 if (base->total >= inet_peer_threshold)
376 ttl = 0; /* be aggressive */
377 else
378 ttl = inet_peer_maxttl
379 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
380 base->total / inet_peer_threshold * HZ;
381 stackptr--; /* last stack slot is peer_avl_empty */
382 while (stackptr > stack) {
383 stackptr--;
384 p = rcu_deref_locked(**stackptr, base);
385 if (atomic_read(&p->refcnt) == 0) {
386 smp_rmb();
387 delta = (__u32)jiffies - p->dtime;
388 if (delta >= ttl &&
389 atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
390 p->gc_next = gchead;
391 gchead = p;
392 }
393 }
394 }
395 while ((p = gchead) != NULL) {
396 gchead = p->gc_next;
397 cnt++;
398 unlink_from_pool(p, base, stack);
399 }
400 return cnt;
401}
402
403struct inet_peer *inet_getpeer(struct inet_peer_base *base,
404 const struct inetpeer_addr *daddr,
405 int create)
406{
407 struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
408 struct inet_peer *p;
409 unsigned int sequence;
410 int invalidated, gccnt = 0;
411
412 /* Attempt a lockless lookup first.
413 * Because of a concurrent writer, we might not find an existing entry.
414 */
415 rcu_read_lock();
416 sequence = read_seqbegin(&base->lock);
417 p = lookup_rcu(daddr, base);
418 invalidated = read_seqretry(&base->lock, sequence);
419 rcu_read_unlock();
420
421 if (p)
422 return p;
423
424 /* If no writer did a change during our lookup, we can return early. */
425 if (!create && !invalidated)
426 return NULL;
427
428 /* retry an exact lookup, taking the lock before.
429 * At least, nodes should be hot in our cache.
430 */
431 write_seqlock_bh(&base->lock);
432relookup:
433 p = lookup(daddr, stack, base);
434 if (p != peer_avl_empty) {
435 atomic_inc(&p->refcnt);
436 write_sequnlock_bh(&base->lock);
437 return p;
438 }
439 if (!gccnt) {
440 gccnt = inet_peer_gc(base, stack, stackptr);
441 if (gccnt && create)
442 goto relookup;
443 }
444 p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
445 if (p) {
446 p->daddr = *daddr;
447 atomic_set(&p->refcnt, 1);
448 atomic_set(&p->rid, 0);
449 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
450 p->rate_tokens = 0;
451 /* 60*HZ is arbitrary, but chosen enough high so that the first
452 * calculation of tokens is at its maximum.
453 */
454 p->rate_last = jiffies - 60*HZ;
455 INIT_LIST_HEAD(&p->gc_list);
456
457 /* Link the node. */
458 link_to_pool(p, base);
459 base->total++;
460 }
461 write_sequnlock_bh(&base->lock);
462
463 return p;
464}
465EXPORT_SYMBOL_GPL(inet_getpeer);
466
467void inet_putpeer(struct inet_peer *p)
468{
469 p->dtime = (__u32)jiffies;
470 smp_mb__before_atomic();
471 atomic_dec(&p->refcnt);
472}
473EXPORT_SYMBOL_GPL(inet_putpeer);
474
475/*
476 * Check transmit rate limitation for given message.
477 * The rate information is held in the inet_peer entries now.
478 * This function is generic and could be used for other purposes
479 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
480 *
481 * Note that the same inet_peer fields are modified by functions in
482 * route.c too, but these work for packet destinations while xrlim_allow
483 * works for icmp destinations. This means the rate limiting information
484 * for one "ip object" is shared - and these ICMPs are twice limited:
485 * by source and by destination.
486 *
487 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
488 * SHOULD allow setting of rate limits
489 *
490 * Shared between ICMPv4 and ICMPv6.
491 */
492#define XRLIM_BURST_FACTOR 6
493bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
494{
495 unsigned long now, token;
496 bool rc = false;
497
498 if (!peer)
499 return true;
500
501 token = peer->rate_tokens;
502 now = jiffies;
503 token += now - peer->rate_last;
504 peer->rate_last = now;
505 if (token > XRLIM_BURST_FACTOR * timeout)
506 token = XRLIM_BURST_FACTOR * timeout;
507 if (token >= timeout) {
508 token -= timeout;
509 rc = true;
510 }
511 peer->rate_tokens = token;
512 return rc;
513}
514EXPORT_SYMBOL(inet_peer_xrlim_allow);
515
516static void inetpeer_inval_rcu(struct rcu_head *head)
517{
518 struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
519
520 spin_lock_bh(&gc_lock);
521 list_add_tail(&p->gc_list, &gc_list);
522 spin_unlock_bh(&gc_lock);
523
524 schedule_delayed_work(&gc_work, gc_delay);
525}
526
527void inetpeer_invalidate_tree(struct inet_peer_base *base)
528{
529 struct inet_peer *root;
530
531 write_seqlock_bh(&base->lock);
532
533 root = rcu_deref_locked(base->root, base);
534 if (root != peer_avl_empty) {
535 base->root = peer_avl_empty_rcu;
536 base->total = 0;
537 call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
538 }
539
540 write_sequnlock_bh(&base->lock);
541}
542EXPORT_SYMBOL(inetpeer_invalidate_tree);