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