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[mirror_ubuntu-bionic-kernel.git] / net / ipv4 / inet_fragment.c
1 /*
2 * inet fragments management
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version
7 * 2 of the License, or (at your option) any later version.
8 *
9 * Authors: Pavel Emelyanov <xemul@openvz.org>
10 * Started as consolidation of ipv4/ip_fragment.c,
11 * ipv6/reassembly. and ipv6 nf conntrack reassembly
12 */
13
14 #include <linux/list.h>
15 #include <linux/spinlock.h>
16 #include <linux/module.h>
17 #include <linux/timer.h>
18 #include <linux/mm.h>
19 #include <linux/random.h>
20 #include <linux/skbuff.h>
21 #include <linux/rtnetlink.h>
22 #include <linux/slab.h>
23
24 #include <net/sock.h>
25 #include <net/inet_frag.h>
26 #include <net/inet_ecn.h>
27
28 #define INETFRAGS_EVICT_BUCKETS 128
29 #define INETFRAGS_EVICT_MAX 512
30
31 /* don't rebuild inetfrag table with new secret more often than this */
32 #define INETFRAGS_MIN_REBUILD_INTERVAL (5 * HZ)
33
34 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
35 * Value : 0xff if frame should be dropped.
36 * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field
37 */
38 const u8 ip_frag_ecn_table[16] = {
39 /* at least one fragment had CE, and others ECT_0 or ECT_1 */
40 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE,
41 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
42 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
43
44 /* invalid combinations : drop frame */
45 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
46 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
47 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
48 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
49 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
50 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
51 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
52 };
53 EXPORT_SYMBOL(ip_frag_ecn_table);
54
55 static unsigned int
56 inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q)
57 {
58 return f->hashfn(q) & (INETFRAGS_HASHSZ - 1);
59 }
60
61 static bool inet_frag_may_rebuild(struct inet_frags *f)
62 {
63 return time_after(jiffies,
64 f->last_rebuild_jiffies + INETFRAGS_MIN_REBUILD_INTERVAL);
65 }
66
67 static void inet_frag_secret_rebuild(struct inet_frags *f)
68 {
69 int i;
70
71 write_seqlock_bh(&f->rnd_seqlock);
72
73 if (!inet_frag_may_rebuild(f))
74 goto out;
75
76 get_random_bytes(&f->rnd, sizeof(u32));
77
78 for (i = 0; i < INETFRAGS_HASHSZ; i++) {
79 struct inet_frag_bucket *hb;
80 struct inet_frag_queue *q;
81 struct hlist_node *n;
82
83 hb = &f->hash[i];
84 spin_lock(&hb->chain_lock);
85
86 hlist_for_each_entry_safe(q, n, &hb->chain, list) {
87 unsigned int hval = inet_frag_hashfn(f, q);
88
89 if (hval != i) {
90 struct inet_frag_bucket *hb_dest;
91
92 hlist_del(&q->list);
93
94 /* Relink to new hash chain. */
95 hb_dest = &f->hash[hval];
96
97 /* This is the only place where we take
98 * another chain_lock while already holding
99 * one. As this will not run concurrently,
100 * we cannot deadlock on hb_dest lock below, if its
101 * already locked it will be released soon since
102 * other caller cannot be waiting for hb lock
103 * that we've taken above.
104 */
105 spin_lock_nested(&hb_dest->chain_lock,
106 SINGLE_DEPTH_NESTING);
107 hlist_add_head(&q->list, &hb_dest->chain);
108 spin_unlock(&hb_dest->chain_lock);
109 }
110 }
111 spin_unlock(&hb->chain_lock);
112 }
113
114 f->rebuild = false;
115 f->last_rebuild_jiffies = jiffies;
116 out:
117 write_sequnlock_bh(&f->rnd_seqlock);
118 }
119
120 static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
121 {
122 return q->net->low_thresh == 0 ||
123 frag_mem_limit(q->net) >= q->net->low_thresh;
124 }
125
126 static unsigned int
127 inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb)
128 {
129 struct inet_frag_queue *fq;
130 struct hlist_node *n;
131 unsigned int evicted = 0;
132 HLIST_HEAD(expired);
133
134 evict_again:
135 spin_lock(&hb->chain_lock);
136
137 hlist_for_each_entry_safe(fq, n, &hb->chain, list) {
138 if (!inet_fragq_should_evict(fq))
139 continue;
140
141 if (!del_timer(&fq->timer)) {
142 /* q expiring right now thus increment its refcount so
143 * it won't be freed under us and wait until the timer
144 * has finished executing then destroy it
145 */
146 atomic_inc(&fq->refcnt);
147 spin_unlock(&hb->chain_lock);
148 del_timer_sync(&fq->timer);
149 WARN_ON(atomic_read(&fq->refcnt) != 1);
150 inet_frag_put(fq, f);
151 goto evict_again;
152 }
153
154 fq->flags |= INET_FRAG_EVICTED;
155 hlist_del(&fq->list);
156 hlist_add_head(&fq->list, &expired);
157 ++evicted;
158 }
159
160 spin_unlock(&hb->chain_lock);
161
162 hlist_for_each_entry_safe(fq, n, &expired, list)
163 f->frag_expire((unsigned long) fq);
164
165 return evicted;
166 }
167
168 static void inet_frag_worker(struct work_struct *work)
169 {
170 unsigned int budget = INETFRAGS_EVICT_BUCKETS;
171 unsigned int i, evicted = 0;
172 struct inet_frags *f;
173
174 f = container_of(work, struct inet_frags, frags_work);
175
176 BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
177
178 local_bh_disable();
179
180 for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
181 evicted += inet_evict_bucket(f, &f->hash[i]);
182 i = (i + 1) & (INETFRAGS_HASHSZ - 1);
183 if (evicted > INETFRAGS_EVICT_MAX)
184 break;
185 }
186
187 f->next_bucket = i;
188
189 local_bh_enable();
190
191 if (f->rebuild && inet_frag_may_rebuild(f))
192 inet_frag_secret_rebuild(f);
193 }
194
195 static void inet_frag_schedule_worker(struct inet_frags *f)
196 {
197 if (unlikely(!work_pending(&f->frags_work)))
198 schedule_work(&f->frags_work);
199 }
200
201 int inet_frags_init(struct inet_frags *f)
202 {
203 int i;
204
205 INIT_WORK(&f->frags_work, inet_frag_worker);
206
207 for (i = 0; i < INETFRAGS_HASHSZ; i++) {
208 struct inet_frag_bucket *hb = &f->hash[i];
209
210 spin_lock_init(&hb->chain_lock);
211 INIT_HLIST_HEAD(&hb->chain);
212 }
213
214 seqlock_init(&f->rnd_seqlock);
215 f->last_rebuild_jiffies = 0;
216 f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
217 NULL);
218 if (!f->frags_cachep)
219 return -ENOMEM;
220
221 return 0;
222 }
223 EXPORT_SYMBOL(inet_frags_init);
224
225 void inet_frags_init_net(struct netns_frags *nf)
226 {
227 init_frag_mem_limit(nf);
228 }
229 EXPORT_SYMBOL(inet_frags_init_net);
230
231 void inet_frags_fini(struct inet_frags *f)
232 {
233 cancel_work_sync(&f->frags_work);
234 kmem_cache_destroy(f->frags_cachep);
235 }
236 EXPORT_SYMBOL(inet_frags_fini);
237
238 void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
239 {
240 unsigned int seq;
241 int i;
242
243 nf->low_thresh = 0;
244 local_bh_disable();
245
246 evict_again:
247 seq = read_seqbegin(&f->rnd_seqlock);
248
249 for (i = 0; i < INETFRAGS_HASHSZ ; i++)
250 inet_evict_bucket(f, &f->hash[i]);
251
252 if (read_seqretry(&f->rnd_seqlock, seq))
253 goto evict_again;
254
255 local_bh_enable();
256
257 percpu_counter_destroy(&nf->mem);
258 }
259 EXPORT_SYMBOL(inet_frags_exit_net);
260
261 static struct inet_frag_bucket *
262 get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
263 __acquires(hb->chain_lock)
264 {
265 struct inet_frag_bucket *hb;
266 unsigned int seq, hash;
267
268 restart:
269 seq = read_seqbegin(&f->rnd_seqlock);
270
271 hash = inet_frag_hashfn(f, fq);
272 hb = &f->hash[hash];
273
274 spin_lock(&hb->chain_lock);
275 if (read_seqretry(&f->rnd_seqlock, seq)) {
276 spin_unlock(&hb->chain_lock);
277 goto restart;
278 }
279
280 return hb;
281 }
282
283 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
284 {
285 struct inet_frag_bucket *hb;
286
287 hb = get_frag_bucket_locked(fq, f);
288 hlist_del(&fq->list);
289 spin_unlock(&hb->chain_lock);
290 }
291
292 void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
293 {
294 if (del_timer(&fq->timer))
295 atomic_dec(&fq->refcnt);
296
297 if (!(fq->flags & INET_FRAG_COMPLETE)) {
298 fq_unlink(fq, f);
299 atomic_dec(&fq->refcnt);
300 fq->flags |= INET_FRAG_COMPLETE;
301 }
302 }
303 EXPORT_SYMBOL(inet_frag_kill);
304
305 static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f,
306 struct sk_buff *skb)
307 {
308 if (f->skb_free)
309 f->skb_free(skb);
310 kfree_skb(skb);
311 }
312
313 void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f)
314 {
315 struct sk_buff *fp;
316 struct netns_frags *nf;
317 unsigned int sum, sum_truesize = 0;
318
319 WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
320 WARN_ON(del_timer(&q->timer) != 0);
321
322 /* Release all fragment data. */
323 fp = q->fragments;
324 nf = q->net;
325 while (fp) {
326 struct sk_buff *xp = fp->next;
327
328 sum_truesize += fp->truesize;
329 frag_kfree_skb(nf, f, fp);
330 fp = xp;
331 }
332 sum = sum_truesize + f->qsize;
333 sub_frag_mem_limit(q, sum);
334
335 if (f->destructor)
336 f->destructor(q);
337 kmem_cache_free(f->frags_cachep, q);
338 }
339 EXPORT_SYMBOL(inet_frag_destroy);
340
341 static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
342 struct inet_frag_queue *qp_in,
343 struct inet_frags *f,
344 void *arg)
345 {
346 struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
347 struct inet_frag_queue *qp;
348
349 #ifdef CONFIG_SMP
350 /* With SMP race we have to recheck hash table, because
351 * such entry could have been created on other cpu before
352 * we acquired hash bucket lock.
353 */
354 hlist_for_each_entry(qp, &hb->chain, list) {
355 if (qp->net == nf && f->match(qp, arg)) {
356 atomic_inc(&qp->refcnt);
357 spin_unlock(&hb->chain_lock);
358 qp_in->flags |= INET_FRAG_COMPLETE;
359 inet_frag_put(qp_in, f);
360 return qp;
361 }
362 }
363 #endif
364 qp = qp_in;
365 if (!mod_timer(&qp->timer, jiffies + nf->timeout))
366 atomic_inc(&qp->refcnt);
367
368 atomic_inc(&qp->refcnt);
369 hlist_add_head(&qp->list, &hb->chain);
370
371 spin_unlock(&hb->chain_lock);
372
373 return qp;
374 }
375
376 static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf,
377 struct inet_frags *f,
378 void *arg)
379 {
380 struct inet_frag_queue *q;
381
382 if (frag_mem_limit(nf) > nf->high_thresh) {
383 inet_frag_schedule_worker(f);
384 return NULL;
385 }
386
387 q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
388 if (q == NULL)
389 return NULL;
390
391 q->net = nf;
392 f->constructor(q, arg);
393 add_frag_mem_limit(q, f->qsize);
394
395 setup_timer(&q->timer, f->frag_expire, (unsigned long)q);
396 spin_lock_init(&q->lock);
397 atomic_set(&q->refcnt, 1);
398
399 return q;
400 }
401
402 static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
403 struct inet_frags *f,
404 void *arg)
405 {
406 struct inet_frag_queue *q;
407
408 q = inet_frag_alloc(nf, f, arg);
409 if (q == NULL)
410 return NULL;
411
412 return inet_frag_intern(nf, q, f, arg);
413 }
414
415 struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
416 struct inet_frags *f, void *key,
417 unsigned int hash)
418 {
419 struct inet_frag_bucket *hb;
420 struct inet_frag_queue *q;
421 int depth = 0;
422
423 if (frag_mem_limit(nf) > nf->low_thresh)
424 inet_frag_schedule_worker(f);
425
426 hash &= (INETFRAGS_HASHSZ - 1);
427 hb = &f->hash[hash];
428
429 spin_lock(&hb->chain_lock);
430 hlist_for_each_entry(q, &hb->chain, list) {
431 if (q->net == nf && f->match(q, key)) {
432 atomic_inc(&q->refcnt);
433 spin_unlock(&hb->chain_lock);
434 return q;
435 }
436 depth++;
437 }
438 spin_unlock(&hb->chain_lock);
439
440 if (depth <= INETFRAGS_MAXDEPTH)
441 return inet_frag_create(nf, f, key);
442
443 if (inet_frag_may_rebuild(f)) {
444 if (!f->rebuild)
445 f->rebuild = true;
446 inet_frag_schedule_worker(f);
447 }
448
449 return ERR_PTR(-ENOBUFS);
450 }
451 EXPORT_SYMBOL(inet_frag_find);
452
453 void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
454 const char *prefix)
455 {
456 static const char msg[] = "inet_frag_find: Fragment hash bucket"
457 " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH)
458 ". Dropping fragment.\n";
459
460 if (PTR_ERR(q) == -ENOBUFS)
461 LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg);
462 }
463 EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);