1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * inet fragments management
4 *
5 * Authors: Pavel Emelyanov <xemul@openvz.org>
6 * Started as consolidation of ipv4/ip_fragment.c,
7 * ipv6/reassembly. and ipv6 nf conntrack reassembly
8 */
9
10 #include <linux/list.h>
11 #include <linux/spinlock.h>
12 #include <linux/module.h>
13 #include <linux/timer.h>
14 #include <linux/mm.h>
15 #include <linux/random.h>
16 #include <linux/skbuff.h>
17 #include <linux/rtnetlink.h>
18 #include <linux/slab.h>
19 #include <linux/rhashtable.h>
20
21 #include <net/sock.h>
22 #include <net/inet_frag.h>
23 #include <net/inet_ecn.h>
24 #include <net/ip.h>
25 #include <net/ipv6.h>
26
27 /* Use skb->cb to track consecutive/adjacent fragments coming at
28 * the end of the queue. Nodes in the rb-tree queue will
29 * contain "runs" of one or more adjacent fragments.
30 *
31 * Invariants:
32 * - next_frag is NULL at the tail of a "run";
33 * - the head of a "run" has the sum of all fragment lengths in frag_run_len.
34 */
35 struct ipfrag_skb_cb {
36 union {
37 struct inet_skb_parm h4;
38 struct inet6_skb_parm h6;
39 };
40 struct sk_buff *next_frag;
41 int frag_run_len;
42 };
43
44 #define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
45
fragcb_clear(struct sk_buff * skb)46 static void fragcb_clear(struct sk_buff *skb)
47 {
48 RB_CLEAR_NODE(&skb->rbnode);
49 FRAG_CB(skb)->next_frag = NULL;
50 FRAG_CB(skb)->frag_run_len = skb->len;
51 }
52
53 /* Append skb to the last "run". */
fragrun_append_to_last(struct inet_frag_queue * q,struct sk_buff * skb)54 static void fragrun_append_to_last(struct inet_frag_queue *q,
55 struct sk_buff *skb)
56 {
57 fragcb_clear(skb);
58
59 FRAG_CB(q->last_run_head)->frag_run_len += skb->len;
60 FRAG_CB(q->fragments_tail)->next_frag = skb;
61 q->fragments_tail = skb;
62 }
63
64 /* Create a new "run" with the skb. */
fragrun_create(struct inet_frag_queue * q,struct sk_buff * skb)65 static void fragrun_create(struct inet_frag_queue *q, struct sk_buff *skb)
66 {
67 BUILD_BUG_ON(sizeof(struct ipfrag_skb_cb) > sizeof(skb->cb));
68 fragcb_clear(skb);
69
70 if (q->last_run_head)
71 rb_link_node(&skb->rbnode, &q->last_run_head->rbnode,
72 &q->last_run_head->rbnode.rb_right);
73 else
74 rb_link_node(&skb->rbnode, NULL, &q->rb_fragments.rb_node);
75 rb_insert_color(&skb->rbnode, &q->rb_fragments);
76
77 q->fragments_tail = skb;
78 q->last_run_head = skb;
79 }
80
81 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
82 * Value : 0xff if frame should be dropped.
83 * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field
84 */
85 const u8 ip_frag_ecn_table[16] = {
86 /* at least one fragment had CE, and others ECT_0 or ECT_1 */
87 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE,
88 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
89 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
90
91 /* invalid combinations : drop frame */
92 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
93 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
94 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
95 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
96 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
97 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
98 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
99 };
100 EXPORT_SYMBOL(ip_frag_ecn_table);
101
inet_frags_init(struct inet_frags * f)102 int inet_frags_init(struct inet_frags *f)
103 {
104 f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
105 NULL);
106 if (!f->frags_cachep)
107 return -ENOMEM;
108
109 refcount_set(&f->refcnt, 1);
110 init_completion(&f->completion);
111 return 0;
112 }
113 EXPORT_SYMBOL(inet_frags_init);
114
inet_frags_fini(struct inet_frags * f)115 void inet_frags_fini(struct inet_frags *f)
116 {
117 if (refcount_dec_and_test(&f->refcnt))
118 complete(&f->completion);
119
120 wait_for_completion(&f->completion);
121
122 kmem_cache_destroy(f->frags_cachep);
123 f->frags_cachep = NULL;
124 }
125 EXPORT_SYMBOL(inet_frags_fini);
126
127 /* called from rhashtable_free_and_destroy() at netns_frags dismantle */
inet_frags_free_cb(void * ptr,void * arg)128 static void inet_frags_free_cb(void *ptr, void *arg)
129 {
130 struct inet_frag_queue *fq = ptr;
131 int count;
132
133 count = del_timer_sync(&fq->timer) ? 1 : 0;
134
135 spin_lock_bh(&fq->lock);
136 if (!(fq->flags & INET_FRAG_COMPLETE)) {
137 fq->flags |= INET_FRAG_COMPLETE;
138 count++;
139 } else if (fq->flags & INET_FRAG_HASH_DEAD) {
140 count++;
141 }
142 spin_unlock_bh(&fq->lock);
143
144 if (refcount_sub_and_test(count, &fq->refcnt))
145 inet_frag_destroy(fq);
146 }
147
fqdir_work_fn(struct work_struct * work)148 static void fqdir_work_fn(struct work_struct *work)
149 {
150 struct fqdir *fqdir = container_of(work, struct fqdir, destroy_work);
151 struct inet_frags *f = fqdir->f;
152
153 rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL);
154
155 /* We need to make sure all ongoing call_rcu(..., inet_frag_destroy_rcu)
156 * have completed, since they need to dereference fqdir.
157 * Would it not be nice to have kfree_rcu_barrier() ? :)
158 */
159 rcu_barrier();
160
161 if (refcount_dec_and_test(&f->refcnt))
162 complete(&f->completion);
163
164 kfree(fqdir);
165 }
166
fqdir_init(struct fqdir ** fqdirp,struct inet_frags * f,struct net * net)167 int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net)
168 {
169 struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL);
170 int res;
171
172 if (!fqdir)
173 return -ENOMEM;
174 fqdir->f = f;
175 fqdir->net = net;
176 res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params);
177 if (res < 0) {
178 kfree(fqdir);
179 return res;
180 }
181 refcount_inc(&f->refcnt);
182 *fqdirp = fqdir;
183 return 0;
184 }
185 EXPORT_SYMBOL(fqdir_init);
186
fqdir_exit(struct fqdir * fqdir)187 void fqdir_exit(struct fqdir *fqdir)
188 {
189 INIT_WORK(&fqdir->destroy_work, fqdir_work_fn);
190 queue_work(system_wq, &fqdir->destroy_work);
191 }
192 EXPORT_SYMBOL(fqdir_exit);
193
inet_frag_kill(struct inet_frag_queue * fq)194 void inet_frag_kill(struct inet_frag_queue *fq)
195 {
196 if (del_timer(&fq->timer))
197 refcount_dec(&fq->refcnt);
198
199 if (!(fq->flags & INET_FRAG_COMPLETE)) {
200 struct fqdir *fqdir = fq->fqdir;
201
202 fq->flags |= INET_FRAG_COMPLETE;
203 rcu_read_lock();
204 /* The RCU read lock provides a memory barrier
205 * guaranteeing that if fqdir->dead is false then
206 * the hash table destruction will not start until
207 * after we unlock. Paired with inet_frags_exit_net().
208 */
209 if (!fqdir->dead) {
210 rhashtable_remove_fast(&fqdir->rhashtable, &fq->node,
211 fqdir->f->rhash_params);
212 refcount_dec(&fq->refcnt);
213 } else {
214 fq->flags |= INET_FRAG_HASH_DEAD;
215 }
216 rcu_read_unlock();
217 }
218 }
219 EXPORT_SYMBOL(inet_frag_kill);
220
inet_frag_destroy_rcu(struct rcu_head * head)221 static void inet_frag_destroy_rcu(struct rcu_head *head)
222 {
223 struct inet_frag_queue *q = container_of(head, struct inet_frag_queue,
224 rcu);
225 struct inet_frags *f = q->fqdir->f;
226
227 if (f->destructor)
228 f->destructor(q);
229 kmem_cache_free(f->frags_cachep, q);
230 }
231
inet_frag_rbtree_purge(struct rb_root * root)232 unsigned int inet_frag_rbtree_purge(struct rb_root *root)
233 {
234 struct rb_node *p = rb_first(root);
235 unsigned int sum = 0;
236
237 while (p) {
238 struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);
239
240 p = rb_next(p);
241 rb_erase(&skb->rbnode, root);
242 while (skb) {
243 struct sk_buff *next = FRAG_CB(skb)->next_frag;
244
245 sum += skb->truesize;
246 kfree_skb(skb);
247 skb = next;
248 }
249 }
250 return sum;
251 }
252 EXPORT_SYMBOL(inet_frag_rbtree_purge);
253
inet_frag_destroy(struct inet_frag_queue * q)254 void inet_frag_destroy(struct inet_frag_queue *q)
255 {
256 struct fqdir *fqdir;
257 unsigned int sum, sum_truesize = 0;
258 struct inet_frags *f;
259
260 WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
261 WARN_ON(del_timer(&q->timer) != 0);
262
263 /* Release all fragment data. */
264 fqdir = q->fqdir;
265 f = fqdir->f;
266 sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments);
267 sum = sum_truesize + f->qsize;
268
269 call_rcu(&q->rcu, inet_frag_destroy_rcu);
270
271 sub_frag_mem_limit(fqdir, sum);
272 }
273 EXPORT_SYMBOL(inet_frag_destroy);
274
inet_frag_alloc(struct fqdir * fqdir,struct inet_frags * f,void * arg)275 static struct inet_frag_queue *inet_frag_alloc(struct fqdir *fqdir,
276 struct inet_frags *f,
277 void *arg)
278 {
279 struct inet_frag_queue *q;
280
281 q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
282 if (!q)
283 return NULL;
284
285 q->fqdir = fqdir;
286 f->constructor(q, arg);
287 add_frag_mem_limit(fqdir, f->qsize);
288
289 timer_setup(&q->timer, f->frag_expire, 0);
290 spin_lock_init(&q->lock);
291 refcount_set(&q->refcnt, 3);
292
293 return q;
294 }
295
inet_frag_create(struct fqdir * fqdir,void * arg,struct inet_frag_queue ** prev)296 static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir,
297 void *arg,
298 struct inet_frag_queue **prev)
299 {
300 struct inet_frags *f = fqdir->f;
301 struct inet_frag_queue *q;
302
303 q = inet_frag_alloc(fqdir, f, arg);
304 if (!q) {
305 *prev = ERR_PTR(-ENOMEM);
306 return NULL;
307 }
308 mod_timer(&q->timer, jiffies + fqdir->timeout);
309
310 *prev = rhashtable_lookup_get_insert_key(&fqdir->rhashtable, &q->key,
311 &q->node, f->rhash_params);
312 if (*prev) {
313 q->flags |= INET_FRAG_COMPLETE;
314 inet_frag_kill(q);
315 inet_frag_destroy(q);
316 return NULL;
317 }
318 return q;
319 }
320
321 /* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
inet_frag_find(struct fqdir * fqdir,void * key)322 struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key)
323 {
324 struct inet_frag_queue *fq = NULL, *prev;
325
326 if (!fqdir->high_thresh || frag_mem_limit(fqdir) > fqdir->high_thresh)
327 return NULL;
328
329 rcu_read_lock();
330
331 prev = rhashtable_lookup(&fqdir->rhashtable, key, fqdir->f->rhash_params);
332 if (!prev)
333 fq = inet_frag_create(fqdir, key, &prev);
334 if (!IS_ERR_OR_NULL(prev)) {
335 fq = prev;
336 if (!refcount_inc_not_zero(&fq->refcnt))
337 fq = NULL;
338 }
339 rcu_read_unlock();
340 return fq;
341 }
342 EXPORT_SYMBOL(inet_frag_find);
343
inet_frag_queue_insert(struct inet_frag_queue * q,struct sk_buff * skb,int offset,int end)344 int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb,
345 int offset, int end)
346 {
347 struct sk_buff *last = q->fragments_tail;
348
349 /* RFC5722, Section 4, amended by Errata ID : 3089
350 * When reassembling an IPv6 datagram, if
351 * one or more its constituent fragments is determined to be an
352 * overlapping fragment, the entire datagram (and any constituent
353 * fragments) MUST be silently discarded.
354 *
355 * Duplicates, however, should be ignored (i.e. skb dropped, but the
356 * queue/fragments kept for later reassembly).
357 */
358 if (!last)
359 fragrun_create(q, skb); /* First fragment. */
360 else if (last->ip_defrag_offset + last->len < end) {
361 /* This is the common case: skb goes to the end. */
362 /* Detect and discard overlaps. */
363 if (offset < last->ip_defrag_offset + last->len)
364 return IPFRAG_OVERLAP;
365 if (offset == last->ip_defrag_offset + last->len)
366 fragrun_append_to_last(q, skb);
367 else
368 fragrun_create(q, skb);
369 } else {
370 /* Binary search. Note that skb can become the first fragment,
371 * but not the last (covered above).
372 */
373 struct rb_node **rbn, *parent;
374
375 rbn = &q->rb_fragments.rb_node;
376 do {
377 struct sk_buff *curr;
378 int curr_run_end;
379
380 parent = *rbn;
381 curr = rb_to_skb(parent);
382 curr_run_end = curr->ip_defrag_offset +
383 FRAG_CB(curr)->frag_run_len;
384 if (end <= curr->ip_defrag_offset)
385 rbn = &parent->rb_left;
386 else if (offset >= curr_run_end)
387 rbn = &parent->rb_right;
388 else if (offset >= curr->ip_defrag_offset &&
389 end <= curr_run_end)
390 return IPFRAG_DUP;
391 else
392 return IPFRAG_OVERLAP;
393 } while (*rbn);
394 /* Here we have parent properly set, and rbn pointing to
395 * one of its NULL left/right children. Insert skb.
396 */
397 fragcb_clear(skb);
398 rb_link_node(&skb->rbnode, parent, rbn);
399 rb_insert_color(&skb->rbnode, &q->rb_fragments);
400 }
401
402 skb->ip_defrag_offset = offset;
403
404 return IPFRAG_OK;
405 }
406 EXPORT_SYMBOL(inet_frag_queue_insert);
407
inet_frag_reasm_prepare(struct inet_frag_queue * q,struct sk_buff * skb,struct sk_buff * parent)408 void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb,
409 struct sk_buff *parent)
410 {
411 struct sk_buff *fp, *head = skb_rb_first(&q->rb_fragments);
412 struct sk_buff **nextp;
413 int delta;
414
415 if (head != skb) {
416 fp = skb_clone(skb, GFP_ATOMIC);
417 if (!fp)
418 return NULL;
419 FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag;
420 if (RB_EMPTY_NODE(&skb->rbnode))
421 FRAG_CB(parent)->next_frag = fp;
422 else
423 rb_replace_node(&skb->rbnode, &fp->rbnode,
424 &q->rb_fragments);
425 if (q->fragments_tail == skb)
426 q->fragments_tail = fp;
427 skb_morph(skb, head);
428 FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag;
429 rb_replace_node(&head->rbnode, &skb->rbnode,
430 &q->rb_fragments);
431 consume_skb(head);
432 head = skb;
433 }
434 WARN_ON(head->ip_defrag_offset != 0);
435
436 delta = -head->truesize;
437
438 /* Head of list must not be cloned. */
439 if (skb_unclone(head, GFP_ATOMIC))
440 return NULL;
441
442 delta += head->truesize;
443 if (delta)
444 add_frag_mem_limit(q->fqdir, delta);
445
446 /* If the first fragment is fragmented itself, we split
447 * it to two chunks: the first with data and paged part
448 * and the second, holding only fragments.
449 */
450 if (skb_has_frag_list(head)) {
451 struct sk_buff *clone;
452 int i, plen = 0;
453
454 clone = alloc_skb(0, GFP_ATOMIC);
455 if (!clone)
456 return NULL;
457 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
458 skb_frag_list_init(head);
459 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
460 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
461 clone->data_len = head->data_len - plen;
462 clone->len = clone->data_len;
463 head->truesize += clone->truesize;
464 clone->csum = 0;
465 clone->ip_summed = head->ip_summed;
466 add_frag_mem_limit(q->fqdir, clone->truesize);
467 skb_shinfo(head)->frag_list = clone;
468 nextp = &clone->next;
469 } else {
470 nextp = &skb_shinfo(head)->frag_list;
471 }
472
473 return nextp;
474 }
475 EXPORT_SYMBOL(inet_frag_reasm_prepare);
476
inet_frag_reasm_finish(struct inet_frag_queue * q,struct sk_buff * head,void * reasm_data,bool try_coalesce)477 void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head,
478 void *reasm_data, bool try_coalesce)
479 {
480 struct sk_buff **nextp = (struct sk_buff **)reasm_data;
481 struct rb_node *rbn;
482 struct sk_buff *fp;
483 int sum_truesize;
484
485 skb_push(head, head->data - skb_network_header(head));
486
487 /* Traverse the tree in order, to build frag_list. */
488 fp = FRAG_CB(head)->next_frag;
489 rbn = rb_next(&head->rbnode);
490 rb_erase(&head->rbnode, &q->rb_fragments);
491
492 sum_truesize = head->truesize;
493 while (rbn || fp) {
494 /* fp points to the next sk_buff in the current run;
495 * rbn points to the next run.
496 */
497 /* Go through the current run. */
498 while (fp) {
499 struct sk_buff *next_frag = FRAG_CB(fp)->next_frag;
500 bool stolen;
501 int delta;
502
503 sum_truesize += fp->truesize;
504 if (head->ip_summed != fp->ip_summed)
505 head->ip_summed = CHECKSUM_NONE;
506 else if (head->ip_summed == CHECKSUM_COMPLETE)
507 head->csum = csum_add(head->csum, fp->csum);
508
509 if (try_coalesce && skb_try_coalesce(head, fp, &stolen,
510 &delta)) {
511 kfree_skb_partial(fp, stolen);
512 } else {
513 fp->prev = NULL;
514 memset(&fp->rbnode, 0, sizeof(fp->rbnode));
515 fp->sk = NULL;
516
517 head->data_len += fp->len;
518 head->len += fp->len;
519 head->truesize += fp->truesize;
520
521 *nextp = fp;
522 nextp = &fp->next;
523 }
524
525 fp = next_frag;
526 }
527 /* Move to the next run. */
528 if (rbn) {
529 struct rb_node *rbnext = rb_next(rbn);
530
531 fp = rb_to_skb(rbn);
532 rb_erase(rbn, &q->rb_fragments);
533 rbn = rbnext;
534 }
535 }
536 sub_frag_mem_limit(q->fqdir, sum_truesize);
537
538 *nextp = NULL;
539 skb_mark_not_on_list(head);
540 head->prev = NULL;
541 head->tstamp = q->stamp;
542 }
543 EXPORT_SYMBOL(inet_frag_reasm_finish);
544
inet_frag_pull_head(struct inet_frag_queue * q)545 struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q)
546 {
547 struct sk_buff *head, *skb;
548
549 head = skb_rb_first(&q->rb_fragments);
550 if (!head)
551 return NULL;
552 skb = FRAG_CB(head)->next_frag;
553 if (skb)
554 rb_replace_node(&head->rbnode, &skb->rbnode,
555 &q->rb_fragments);
556 else
557 rb_erase(&head->rbnode, &q->rb_fragments);
558 memset(&head->rbnode, 0, sizeof(head->rbnode));
559 barrier();
560
561 if (head == q->fragments_tail)
562 q->fragments_tail = NULL;
563
564 sub_frag_mem_limit(q->fqdir, head->truesize);
565
566 return head;
567 }
568 EXPORT_SYMBOL(inet_frag_pull_head);
569