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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 <net/ip.h>
21#include <net/inetpeer.h>
22#include <net/secure_seq.h>
23
24/*
25 * Theory of operations.
26 * We keep one entry for each peer IP address. The nodes contains long-living
27 * information about the peer which doesn't depend on routes.
28 * At this moment this information consists only of ID field for the next
29 * outgoing IP packet. This field is incremented with each packet as encoded
30 * in inet_getid() function (include/net/inetpeer.h).
31 * At the moment of writing this notes identifier of IP packets is generated
32 * to be unpredictable using this code only for packets subjected
33 * (actually or potentially) to defragmentation. I.e. DF packets less than
34 * PMTU in size uses a constant ID and do not use this code (see
35 * ip_select_ident() in include/net/ip.h).
36 *
37 * Route cache entries hold references to our nodes.
38 * New cache entries get references via lookup by destination IP address in
39 * the avl tree. The reference is grabbed only when it's needed i.e. only
40 * when we try to output IP packet which needs an unpredictable ID (see
41 * __ip_select_ident() in net/ipv4/route.c).
42 * Nodes are removed only when reference counter goes to 0.
43 * When it's happened the node may be removed when a sufficient amount of
44 * time has been passed since its last use. The less-recently-used entry can
45 * also be removed if the pool is overloaded i.e. if the total amount of
46 * entries is greater-or-equal than the threshold.
47 *
48 * Node pool is organised as an AVL tree.
49 * Such an implementation has been chosen not just for fun. It's a way to
50 * prevent easy and efficient DoS attacks by creating hash collisions. A huge
51 * amount of long living nodes in a single hash slot would significantly delay
52 * lookups performed with disabled BHs.
53 *
54 * Serialisation issues.
55 * 1. Nodes may appear in the tree only with the pool lock held.
56 * 2. Nodes may disappear from the tree only with the pool lock held
57 * AND reference count being 0.
58 * 3. Global variable peer_total is modified under the pool lock.
59 * 4. struct inet_peer fields modification:
60 * avl_left, avl_right, avl_parent, avl_height: pool lock
61 * refcnt: atomically against modifications on other CPU;
62 * usually under some other lock to prevent node disappearing
63 * daddr: unchangeable
64 * ip_id_count: atomic value (no lock needed)
65 */
66
67static struct kmem_cache *peer_cachep __read_mostly;
68
69#define node_height(x) x->avl_height
70
71#define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
72#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
73static const struct inet_peer peer_fake_node = {
74 .avl_left = peer_avl_empty_rcu,
75 .avl_right = peer_avl_empty_rcu,
76 .avl_height = 0
77};
78
79struct inet_peer_base {
80 struct inet_peer __rcu *root;
81 seqlock_t lock;
82 int total;
83};
84
85static struct inet_peer_base v4_peers = {
86 .root = peer_avl_empty_rcu,
87 .lock = __SEQLOCK_UNLOCKED(v4_peers.lock),
88 .total = 0,
89};
90
91static struct inet_peer_base v6_peers = {
92 .root = peer_avl_empty_rcu,
93 .lock = __SEQLOCK_UNLOCKED(v6_peers.lock),
94 .total = 0,
95};
96
97#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
98
99/* Exported for sysctl_net_ipv4. */
100int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
101 * aggressively at this stage */
102int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
103int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */
104
105
106/* Called from ip_output.c:ip_init */
107void __init inet_initpeers(void)
108{
109 struct sysinfo si;
110
111 /* Use the straight interface to information about memory. */
112 si_meminfo(&si);
113 /* The values below were suggested by Alexey Kuznetsov
114 * <kuznet@ms2.inr.ac.ru>. I don't have any opinion about the values
115 * myself. --SAW
116 */
117 if (si.totalram <= (32768*1024)/PAGE_SIZE)
118 inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
119 if (si.totalram <= (16384*1024)/PAGE_SIZE)
120 inet_peer_threshold >>= 1; /* about 512KB */
121 if (si.totalram <= (8192*1024)/PAGE_SIZE)
122 inet_peer_threshold >>= 2; /* about 128KB */
123
124 peer_cachep = kmem_cache_create("inet_peer_cache",
125 sizeof(struct inet_peer),
126 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
127 NULL);
128
129}
130
131static int addr_compare(const struct inetpeer_addr *a,
132 const struct inetpeer_addr *b)
133{
134 int i, n = (a->family == AF_INET ? 1 : 4);
135
136 for (i = 0; i < n; i++) {
137 if (a->addr.a6[i] == b->addr.a6[i])
138 continue;
139 if (a->addr.a6[i] < b->addr.a6[i])
140 return -1;
141 return 1;
142 }
143
144 return 0;
145}
146
147#define rcu_deref_locked(X, BASE) \
148 rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))
149
150/*
151 * Called with local BH disabled and the pool lock held.
152 */
153#define lookup(_daddr, _stack, _base) \
154({ \
155 struct inet_peer *u; \
156 struct inet_peer __rcu **v; \
157 \
158 stackptr = _stack; \
159 *stackptr++ = &_base->root; \
160 for (u = rcu_deref_locked(_base->root, _base); \
161 u != peer_avl_empty; ) { \
162 int cmp = addr_compare(_daddr, &u->daddr); \
163 if (cmp == 0) \
164 break; \
165 if (cmp == -1) \
166 v = &u->avl_left; \
167 else \
168 v = &u->avl_right; \
169 *stackptr++ = v; \
170 u = rcu_deref_locked(*v, _base); \
171 } \
172 u; \
173})
174
175/*
176 * Called with rcu_read_lock()
177 * Because we hold no lock against a writer, its quite possible we fall
178 * in an endless loop.
179 * But every pointer we follow is guaranteed to be valid thanks to RCU.
180 * We exit from this function if number of links exceeds PEER_MAXDEPTH
181 */
182static struct inet_peer *lookup_rcu(const struct inetpeer_addr *daddr,
183 struct inet_peer_base *base)
184{
185 struct inet_peer *u = rcu_dereference(base->root);
186 int count = 0;
187
188 while (u != peer_avl_empty) {
189 int cmp = addr_compare(daddr, &u->daddr);
190 if (cmp == 0) {
191 /* Before taking a reference, check if this entry was
192 * deleted (refcnt=-1)
193 */
194 if (!atomic_add_unless(&u->refcnt, 1, -1))
195 u = NULL;
196 return u;
197 }
198 if (cmp == -1)
199 u = rcu_dereference(u->avl_left);
200 else
201 u = rcu_dereference(u->avl_right);
202 if (unlikely(++count == PEER_MAXDEPTH))
203 break;
204 }
205 return NULL;
206}
207
208/* Called with local BH disabled and the pool lock held. */
209#define lookup_rightempty(start, base) \
210({ \
211 struct inet_peer *u; \
212 struct inet_peer __rcu **v; \
213 *stackptr++ = &start->avl_left; \
214 v = &start->avl_left; \
215 for (u = rcu_deref_locked(*v, base); \
216 u->avl_right != peer_avl_empty_rcu; ) { \
217 v = &u->avl_right; \
218 *stackptr++ = v; \
219 u = rcu_deref_locked(*v, base); \
220 } \
221 u; \
222})
223
224/* Called with local BH disabled and the pool lock held.
225 * Variable names are the proof of operation correctness.
226 * Look into mm/map_avl.c for more detail description of the ideas.
227 */
228static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
229 struct inet_peer __rcu ***stackend,
230 struct inet_peer_base *base)
231{
232 struct inet_peer __rcu **nodep;
233 struct inet_peer *node, *l, *r;
234 int lh, rh;
235
236 while (stackend > stack) {
237 nodep = *--stackend;
238 node = rcu_deref_locked(*nodep, base);
239 l = rcu_deref_locked(node->avl_left, base);
240 r = rcu_deref_locked(node->avl_right, base);
241 lh = node_height(l);
242 rh = node_height(r);
243 if (lh > rh + 1) { /* l: RH+2 */
244 struct inet_peer *ll, *lr, *lrl, *lrr;
245 int lrh;
246 ll = rcu_deref_locked(l->avl_left, base);
247 lr = rcu_deref_locked(l->avl_right, base);
248 lrh = node_height(lr);
249 if (lrh <= node_height(ll)) { /* ll: RH+1 */
250 RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */
251 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
252 node->avl_height = lrh + 1; /* RH+1 or RH+2 */
253 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */
254 RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */
255 l->avl_height = node->avl_height + 1;
256 RCU_INIT_POINTER(*nodep, l);
257 } else { /* ll: RH, lr: RH+1 */
258 lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
259 lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
260 RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */
261 RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
262 node->avl_height = rh + 1; /* node: RH+1 */
263 RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */
264 RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */
265 l->avl_height = rh + 1; /* l: RH+1 */
266 RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */
267 RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */
268 lr->avl_height = rh + 2;
269 RCU_INIT_POINTER(*nodep, lr);
270 }
271 } else if (rh > lh + 1) { /* r: LH+2 */
272 struct inet_peer *rr, *rl, *rlr, *rll;
273 int rlh;
274 rr = rcu_deref_locked(r->avl_right, base);
275 rl = rcu_deref_locked(r->avl_left, base);
276 rlh = node_height(rl);
277 if (rlh <= node_height(rr)) { /* rr: LH+1 */
278 RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */
279 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
280 node->avl_height = rlh + 1; /* LH+1 or LH+2 */
281 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */
282 RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */
283 r->avl_height = node->avl_height + 1;
284 RCU_INIT_POINTER(*nodep, r);
285 } else { /* rr: RH, rl: RH+1 */
286 rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
287 rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
288 RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
289 RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
290 node->avl_height = lh + 1; /* node: LH+1 */
291 RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */
292 RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */
293 r->avl_height = lh + 1; /* r: LH+1 */
294 RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */
295 RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */
296 rl->avl_height = lh + 2;
297 RCU_INIT_POINTER(*nodep, rl);
298 }
299 } else {
300 node->avl_height = (lh > rh ? lh : rh) + 1;
301 }
302 }
303}
304
305/* Called with local BH disabled and the pool lock held. */
306#define link_to_pool(n, base) \
307do { \
308 n->avl_height = 1; \
309 n->avl_left = peer_avl_empty_rcu; \
310 n->avl_right = peer_avl_empty_rcu; \
311 /* lockless readers can catch us now */ \
312 rcu_assign_pointer(**--stackptr, n); \
313 peer_avl_rebalance(stack, stackptr, base); \
314} while (0)
315
316static void inetpeer_free_rcu(struct rcu_head *head)
317{
318 kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
319}
320
321static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
322 struct inet_peer __rcu **stack[PEER_MAXDEPTH])
323{
324 struct inet_peer __rcu ***stackptr, ***delp;
325
326 if (lookup(&p->daddr, stack, base) != p)
327 BUG();
328 delp = stackptr - 1; /* *delp[0] == p */
329 if (p->avl_left == peer_avl_empty_rcu) {
330 *delp[0] = p->avl_right;
331 --stackptr;
332 } else {
333 /* look for a node to insert instead of p */
334 struct inet_peer *t;
335 t = lookup_rightempty(p, base);
336 BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
337 **--stackptr = t->avl_left;
338 /* t is removed, t->daddr > x->daddr for any
339 * x in p->avl_left subtree.
340 * Put t in the old place of p. */
341 RCU_INIT_POINTER(*delp[0], t);
342 t->avl_left = p->avl_left;
343 t->avl_right = p->avl_right;
344 t->avl_height = p->avl_height;
345 BUG_ON(delp[1] != &p->avl_left);
346 delp[1] = &t->avl_left; /* was &p->avl_left */
347 }
348 peer_avl_rebalance(stack, stackptr, base);
349 base->total--;
350 call_rcu(&p->rcu, inetpeer_free_rcu);
351}
352
353static struct inet_peer_base *family_to_base(int family)
354{
355 return family == AF_INET ? &v4_peers : &v6_peers;
356}
357
358/* perform garbage collect on all items stacked during a lookup */
359static int inet_peer_gc(struct inet_peer_base *base,
360 struct inet_peer __rcu **stack[PEER_MAXDEPTH],
361 struct inet_peer __rcu ***stackptr)
362{
363 struct inet_peer *p, *gchead = NULL;
364 __u32 delta, ttl;
365 int cnt = 0;
366
367 if (base->total >= inet_peer_threshold)
368 ttl = 0; /* be aggressive */
369 else
370 ttl = inet_peer_maxttl
371 - (inet_peer_maxttl - inet_peer_minttl) / HZ *
372 base->total / inet_peer_threshold * HZ;
373 stackptr--; /* last stack slot is peer_avl_empty */
374 while (stackptr > stack) {
375 stackptr--;
376 p = rcu_deref_locked(**stackptr, base);
377 if (atomic_read(&p->refcnt) == 0) {
378 smp_rmb();
379 delta = (__u32)jiffies - p->dtime;
380 if (delta >= ttl &&
381 atomic_cmpxchg(&p->refcnt, 0, -1) == 0) {
382 p->gc_next = gchead;
383 gchead = p;
384 }
385 }
386 }
387 while ((p = gchead) != NULL) {
388 gchead = p->gc_next;
389 cnt++;
390 unlink_from_pool(p, base, stack);
391 }
392 return cnt;
393}
394
395struct inet_peer *inet_getpeer(const struct inetpeer_addr *daddr, int create)
396{
397 struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
398 struct inet_peer_base *base = family_to_base(daddr->family);
399 struct inet_peer *p;
400 unsigned int sequence;
401 int invalidated, gccnt = 0;
402
403 /* Attempt a lockless lookup first.
404 * Because of a concurrent writer, we might not find an existing entry.
405 */
406 rcu_read_lock();
407 sequence = read_seqbegin(&base->lock);
408 p = lookup_rcu(daddr, base);
409 invalidated = read_seqretry(&base->lock, sequence);
410 rcu_read_unlock();
411
412 if (p)
413 return p;
414
415 /* If no writer did a change during our lookup, we can return early. */
416 if (!create && !invalidated)
417 return NULL;
418
419 /* retry an exact lookup, taking the lock before.
420 * At least, nodes should be hot in our cache.
421 */
422 write_seqlock_bh(&base->lock);
423relookup:
424 p = lookup(daddr, stack, base);
425 if (p != peer_avl_empty) {
426 atomic_inc(&p->refcnt);
427 write_sequnlock_bh(&base->lock);
428 return p;
429 }
430 if (!gccnt) {
431 gccnt = inet_peer_gc(base, stack, stackptr);
432 if (gccnt && create)
433 goto relookup;
434 }
435 p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
436 if (p) {
437 p->daddr = *daddr;
438 atomic_set(&p->refcnt, 1);
439 atomic_set(&p->rid, 0);
440 atomic_set(&p->ip_id_count,
441 (daddr->family == AF_INET) ?
442 secure_ip_id(daddr->addr.a4) :
443 secure_ipv6_id(daddr->addr.a6));
444 p->tcp_ts_stamp = 0;
445 p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
446 p->rate_tokens = 0;
447 p->rate_last = 0;
448 p->pmtu_expires = 0;
449 p->pmtu_orig = 0;
450 memset(&p->redirect_learned, 0, sizeof(p->redirect_learned));
451
452
453 /* Link the node. */
454 link_to_pool(p, base);
455 base->total++;
456 }
457 write_sequnlock_bh(&base->lock);
458
459 return p;
460}
461EXPORT_SYMBOL_GPL(inet_getpeer);
462
463void inet_putpeer(struct inet_peer *p)
464{
465 p->dtime = (__u32)jiffies;
466 smp_mb__before_atomic_dec();
467 atomic_dec(&p->refcnt);
468}
469EXPORT_SYMBOL_GPL(inet_putpeer);
470
471/*
472 * Check transmit rate limitation for given message.
473 * The rate information is held in the inet_peer entries now.
474 * This function is generic and could be used for other purposes
475 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
476 *
477 * Note that the same inet_peer fields are modified by functions in
478 * route.c too, but these work for packet destinations while xrlim_allow
479 * works for icmp destinations. This means the rate limiting information
480 * for one "ip object" is shared - and these ICMPs are twice limited:
481 * by source and by destination.
482 *
483 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
484 * SHOULD allow setting of rate limits
485 *
486 * Shared between ICMPv4 and ICMPv6.
487 */
488#define XRLIM_BURST_FACTOR 6
489bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
490{
491 unsigned long now, token;
492 bool rc = false;
493
494 if (!peer)
495 return true;
496
497 token = peer->rate_tokens;
498 now = jiffies;
499 token += now - peer->rate_last;
500 peer->rate_last = now;
501 if (token > XRLIM_BURST_FACTOR * timeout)
502 token = XRLIM_BURST_FACTOR * timeout;
503 if (token >= timeout) {
504 token -= timeout;
505 rc = true;
506 }
507 peer->rate_tokens = token;
508 return rc;
509}
510EXPORT_SYMBOL(inet_peer_xrlim_allow);