1 /*
2 * IPv6 fragment reassembly for connection tracking
3 *
4 * Copyright (C)2004 USAGI/WIDE Project
5 *
6 * Author:
7 * Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
8 *
9 * Based on: net/ipv6/reassembly.c
10 *
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version
14 * 2 of the License, or (at your option) any later version.
15 */
16
17 #define pr_fmt(fmt) "IPv6-nf: " fmt
18
19 #include <linux/errno.h>
20 #include <linux/types.h>
21 #include <linux/string.h>
22 #include <linux/socket.h>
23 #include <linux/sockios.h>
24 #include <linux/jiffies.h>
25 #include <linux/net.h>
26 #include <linux/list.h>
27 #include <linux/netdevice.h>
28 #include <linux/in6.h>
29 #include <linux/ipv6.h>
30 #include <linux/icmpv6.h>
31 #include <linux/random.h>
32 #include <linux/slab.h>
33
34 #include <net/sock.h>
35 #include <net/snmp.h>
36 #include <net/inet_frag.h>
37
38 #include <net/ipv6.h>
39 #include <net/protocol.h>
40 #include <net/transp_v6.h>
41 #include <net/rawv6.h>
42 #include <net/ndisc.h>
43 #include <net/addrconf.h>
44 #include <net/inet_ecn.h>
45 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
46 #include <linux/sysctl.h>
47 #include <linux/netfilter.h>
48 #include <linux/netfilter_ipv6.h>
49 #include <linux/kernel.h>
50 #include <linux/module.h>
51 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
52
53 static const char nf_frags_cache_name[] = "nf-frags";
54
55 struct nf_ct_frag6_skb_cb
56 {
57 struct inet6_skb_parm h;
58 int offset;
59 };
60
61 #define NFCT_FRAG6_CB(skb) ((struct nf_ct_frag6_skb_cb *)((skb)->cb))
62
63 static struct inet_frags nf_frags;
64
65 #ifdef CONFIG_SYSCTL
66 static int zero;
67
68 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
69 {
70 .procname = "nf_conntrack_frag6_timeout",
71 .data = &init_net.nf_frag.frags.timeout,
72 .maxlen = sizeof(unsigned int),
73 .mode = 0644,
74 .proc_handler = proc_dointvec_jiffies,
75 },
76 {
77 .procname = "nf_conntrack_frag6_low_thresh",
78 .data = &init_net.nf_frag.frags.low_thresh,
79 .maxlen = sizeof(unsigned int),
80 .mode = 0644,
81 .proc_handler = proc_dointvec_minmax,
82 .extra1 = &zero,
83 .extra2 = &init_net.nf_frag.frags.high_thresh
84 },
85 {
86 .procname = "nf_conntrack_frag6_high_thresh",
87 .data = &init_net.nf_frag.frags.high_thresh,
88 .maxlen = sizeof(unsigned int),
89 .mode = 0644,
90 .proc_handler = proc_dointvec_minmax,
91 .extra1 = &init_net.nf_frag.frags.low_thresh
92 },
93 { }
94 };
95
96 static int nf_ct_frag6_sysctl_register(struct net *net)
97 {
98 struct ctl_table *table;
99 struct ctl_table_header *hdr;
100
101 table = nf_ct_frag6_sysctl_table;
102 if (!net_eq(net, &init_net)) {
103 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
104 GFP_KERNEL);
105 if (table == NULL)
106 goto err_alloc;
107
108 table[0].data = &net->nf_frag.frags.timeout;
109 table[1].data = &net->nf_frag.frags.low_thresh;
110 table[1].extra2 = &net->nf_frag.frags.high_thresh;
111 table[2].data = &net->nf_frag.frags.high_thresh;
112 table[2].extra1 = &net->nf_frag.frags.low_thresh;
113 table[2].extra2 = &init_net.nf_frag.frags.high_thresh;
114 }
115
116 hdr = register_net_sysctl(net, "net/netfilter", table);
117 if (hdr == NULL)
118 goto err_reg;
119
120 net->nf_frag.sysctl.frags_hdr = hdr;
121 return 0;
122
123 err_reg:
124 if (!net_eq(net, &init_net))
125 kfree(table);
126 err_alloc:
127 return -ENOMEM;
128 }
129
130 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
131 {
132 struct ctl_table *table;
133
134 table = net->nf_frag.sysctl.frags_hdr->ctl_table_arg;
135 unregister_net_sysctl_table(net->nf_frag.sysctl.frags_hdr);
136 if (!net_eq(net, &init_net))
137 kfree(table);
138 }
139
140 #else
141 static int nf_ct_frag6_sysctl_register(struct net *net)
142 {
143 return 0;
144 }
145 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
146 {
147 }
148 #endif
149
150 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
151 {
152 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
153 }
154
155 static unsigned int nf_hash_frag(__be32 id, const struct in6_addr *saddr,
156 const struct in6_addr *daddr)
157 {
158 net_get_random_once(&nf_frags.rnd, sizeof(nf_frags.rnd));
159 return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr),
160 (__force u32)id, nf_frags.rnd);
161 }
162
163
164 static unsigned int nf_hashfn(const struct inet_frag_queue *q)
165 {
166 const struct frag_queue *nq;
167
168 nq = container_of(q, struct frag_queue, q);
169 return nf_hash_frag(nq->id, &nq->saddr, &nq->daddr);
170 }
171
172 static void nf_ct_frag6_expire(unsigned long data)
173 {
174 struct frag_queue *fq;
175 struct net *net;
176
177 fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
178 net = container_of(fq->q.net, struct net, nf_frag.frags);
179
180 ip6_expire_frag_queue(net, fq, &nf_frags);
181 }
182
183 /* Creation primitives. */
184 static inline struct frag_queue *fq_find(struct net *net, __be32 id,
185 u32 user, struct in6_addr *src,
186 struct in6_addr *dst, int iif, u8 ecn)
187 {
188 struct inet_frag_queue *q;
189 struct ip6_create_arg arg;
190 unsigned int hash;
191
192 arg.id = id;
193 arg.user = user;
194 arg.src = src;
195 arg.dst = dst;
196 arg.iif = iif;
197 arg.ecn = ecn;
198
199 local_bh_disable();
200 hash = nf_hash_frag(id, src, dst);
201
202 q = inet_frag_find(&net->nf_frag.frags, &nf_frags, &arg, hash);
203 local_bh_enable();
204 if (IS_ERR_OR_NULL(q)) {
205 inet_frag_maybe_warn_overflow(q, pr_fmt());
206 return NULL;
207 }
208 return container_of(q, struct frag_queue, q);
209 }
210
211
212 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
213 const struct frag_hdr *fhdr, int nhoff)
214 {
215 struct sk_buff *prev, *next;
216 unsigned int payload_len;
217 int offset, end;
218 u8 ecn;
219
220 if (fq->q.flags & INET_FRAG_COMPLETE) {
221 pr_debug("Already completed\n");
222 goto err;
223 }
224
225 payload_len = ntohs(ipv6_hdr(skb)->payload_len);
226
227 offset = ntohs(fhdr->frag_off) & ~0x7;
228 end = offset + (payload_len -
229 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
230
231 if ((unsigned int)end > IPV6_MAXPLEN) {
232 pr_debug("offset is too large.\n");
233 return -1;
234 }
235
236 ecn = ip6_frag_ecn(ipv6_hdr(skb));
237
238 if (skb->ip_summed == CHECKSUM_COMPLETE) {
239 const unsigned char *nh = skb_network_header(skb);
240 skb->csum = csum_sub(skb->csum,
241 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
242 0));
243 }
244
245 /* Is this the final fragment? */
246 if (!(fhdr->frag_off & htons(IP6_MF))) {
247 /* If we already have some bits beyond end
248 * or have different end, the segment is corrupted.
249 */
250 if (end < fq->q.len ||
251 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
252 pr_debug("already received last fragment\n");
253 goto err;
254 }
255 fq->q.flags |= INET_FRAG_LAST_IN;
256 fq->q.len = end;
257 } else {
258 /* Check if the fragment is rounded to 8 bytes.
259 * Required by the RFC.
260 */
261 if (end & 0x7) {
262 /* RFC2460 says always send parameter problem in
263 * this case. -DaveM
264 */
265 pr_debug("end of fragment not rounded to 8 bytes.\n");
266 return -1;
267 }
268 if (end > fq->q.len) {
269 /* Some bits beyond end -> corruption. */
270 if (fq->q.flags & INET_FRAG_LAST_IN) {
271 pr_debug("last packet already reached.\n");
272 goto err;
273 }
274 fq->q.len = end;
275 }
276 }
277
278 if (end == offset)
279 goto err;
280
281 /* Point into the IP datagram 'data' part. */
282 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
283 pr_debug("queue: message is too short.\n");
284 goto err;
285 }
286 if (pskb_trim_rcsum(skb, end - offset)) {
287 pr_debug("Can't trim\n");
288 goto err;
289 }
290
291 /* Find out which fragments are in front and at the back of us
292 * in the chain of fragments so far. We must know where to put
293 * this fragment, right?
294 */
295 prev = fq->q.fragments_tail;
296 if (!prev || NFCT_FRAG6_CB(prev)->offset < offset) {
297 next = NULL;
298 goto found;
299 }
300 prev = NULL;
301 for (next = fq->q.fragments; next != NULL; next = next->next) {
302 if (NFCT_FRAG6_CB(next)->offset >= offset)
303 break; /* bingo! */
304 prev = next;
305 }
306
307 found:
308 /* RFC5722, Section 4:
309 * When reassembling an IPv6 datagram, if
310 * one or more its constituent fragments is determined to be an
311 * overlapping fragment, the entire datagram (and any constituent
312 * fragments, including those not yet received) MUST be silently
313 * discarded.
314 */
315
316 /* Check for overlap with preceding fragment. */
317 if (prev &&
318 (NFCT_FRAG6_CB(prev)->offset + prev->len) > offset)
319 goto discard_fq;
320
321 /* Look for overlap with succeeding segment. */
322 if (next && NFCT_FRAG6_CB(next)->offset < end)
323 goto discard_fq;
324
325 NFCT_FRAG6_CB(skb)->offset = offset;
326
327 /* Insert this fragment in the chain of fragments. */
328 skb->next = next;
329 if (!next)
330 fq->q.fragments_tail = skb;
331 if (prev)
332 prev->next = skb;
333 else
334 fq->q.fragments = skb;
335
336 if (skb->dev) {
337 fq->iif = skb->dev->ifindex;
338 skb->dev = NULL;
339 }
340 fq->q.stamp = skb->tstamp;
341 fq->q.meat += skb->len;
342 fq->ecn |= ecn;
343 if (payload_len > fq->q.max_size)
344 fq->q.max_size = payload_len;
345 add_frag_mem_limit(fq->q.net, skb->truesize);
346
347 /* The first fragment.
348 * nhoffset is obtained from the first fragment, of course.
349 */
350 if (offset == 0) {
351 fq->nhoffset = nhoff;
352 fq->q.flags |= INET_FRAG_FIRST_IN;
353 }
354
355 return 0;
356
357 discard_fq:
358 inet_frag_kill(&fq->q, &nf_frags);
359 err:
360 return -1;
361 }
362
363 /*
364 * Check if this packet is complete.
365 *
366 * It is called with locked fq, and caller must check that
367 * queue is eligible for reassembly i.e. it is not COMPLETE,
368 * the last and the first frames arrived and all the bits are here.
369 *
370 * returns true if *prev skb has been transformed into the reassembled
371 * skb, false otherwise.
372 */
373 static bool
374 nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *prev, struct net_device *dev)
375 {
376 struct sk_buff *fp, *head = fq->q.fragments;
377 int payload_len;
378 u8 ecn;
379
380 inet_frag_kill(&fq->q, &nf_frags);
381
382 WARN_ON(head == NULL);
383 WARN_ON(NFCT_FRAG6_CB(head)->offset != 0);
384
385 ecn = ip_frag_ecn_table[fq->ecn];
386 if (unlikely(ecn == 0xff))
387 return false;
388
389 /* Unfragmented part is taken from the first segment. */
390 payload_len = ((head->data - skb_network_header(head)) -
391 sizeof(struct ipv6hdr) + fq->q.len -
392 sizeof(struct frag_hdr));
393 if (payload_len > IPV6_MAXPLEN) {
394 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
395 payload_len);
396 return false;
397 }
398
399 /* Head of list must not be cloned. */
400 if (skb_unclone(head, GFP_ATOMIC))
401 return false;
402
403 /* If the first fragment is fragmented itself, we split
404 * it to two chunks: the first with data and paged part
405 * and the second, holding only fragments. */
406 if (skb_has_frag_list(head)) {
407 struct sk_buff *clone;
408 int i, plen = 0;
409
410 clone = alloc_skb(0, GFP_ATOMIC);
411 if (clone == NULL)
412 return false;
413
414 clone->next = head->next;
415 head->next = clone;
416 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
417 skb_frag_list_init(head);
418 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
419 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
420 clone->len = clone->data_len = head->data_len - plen;
421 head->data_len -= clone->len;
422 head->len -= clone->len;
423 clone->csum = 0;
424 clone->ip_summed = head->ip_summed;
425
426 add_frag_mem_limit(fq->q.net, clone->truesize);
427 }
428
429 /* morph head into last received skb: prev.
430 *
431 * This allows callers of ipv6 conntrack defrag to continue
432 * to use the last skb(frag) passed into the reasm engine.
433 * The last skb frag 'silently' turns into the full reassembled skb.
434 *
435 * Since prev is also part of q->fragments we have to clone it first.
436 */
437 if (head != prev) {
438 struct sk_buff *iter;
439
440 fp = skb_clone(prev, GFP_ATOMIC);
441 if (!fp)
442 return false;
443
444 fp->next = prev->next;
445
446 iter = head;
447 while (iter) {
448 if (iter->next == prev) {
449 iter->next = fp;
450 break;
451 }
452 iter = iter->next;
453 }
454
455 skb_morph(prev, head);
456 prev->next = head->next;
457 consume_skb(head);
458 head = prev;
459 }
460
461 /* We have to remove fragment header from datagram and to relocate
462 * header in order to calculate ICV correctly. */
463 skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0];
464 memmove(head->head + sizeof(struct frag_hdr), head->head,
465 (head->data - head->head) - sizeof(struct frag_hdr));
466 head->mac_header += sizeof(struct frag_hdr);
467 head->network_header += sizeof(struct frag_hdr);
468
469 skb_shinfo(head)->frag_list = head->next;
470 skb_reset_transport_header(head);
471 skb_push(head, head->data - skb_network_header(head));
472
473 for (fp = head->next; fp; fp = fp->next) {
474 head->data_len += fp->len;
475 head->len += fp->len;
476 if (head->ip_summed != fp->ip_summed)
477 head->ip_summed = CHECKSUM_NONE;
478 else if (head->ip_summed == CHECKSUM_COMPLETE)
479 head->csum = csum_add(head->csum, fp->csum);
480 head->truesize += fp->truesize;
481 }
482 sub_frag_mem_limit(fq->q.net, head->truesize);
483
484 head->ignore_df = 1;
485 head->next = NULL;
486 head->dev = dev;
487 head->tstamp = fq->q.stamp;
488 ipv6_hdr(head)->payload_len = htons(payload_len);
489 ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn);
490 IP6CB(head)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
491
492 /* Yes, and fold redundant checksum back. 8) */
493 if (head->ip_summed == CHECKSUM_COMPLETE)
494 head->csum = csum_partial(skb_network_header(head),
495 skb_network_header_len(head),
496 head->csum);
497
498 fq->q.fragments = NULL;
499 fq->q.fragments_tail = NULL;
500
501 return true;
502 }
503
504 /*
505 * find the header just before Fragment Header.
506 *
507 * if success return 0 and set ...
508 * (*prevhdrp): the value of "Next Header Field" in the header
509 * just before Fragment Header.
510 * (*prevhoff): the offset of "Next Header Field" in the header
511 * just before Fragment Header.
512 * (*fhoff) : the offset of Fragment Header.
513 *
514 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
515 *
516 */
517 static int
518 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
519 {
520 u8 nexthdr = ipv6_hdr(skb)->nexthdr;
521 const int netoff = skb_network_offset(skb);
522 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
523 int start = netoff + sizeof(struct ipv6hdr);
524 int len = skb->len - start;
525 u8 prevhdr = NEXTHDR_IPV6;
526
527 while (nexthdr != NEXTHDR_FRAGMENT) {
528 struct ipv6_opt_hdr hdr;
529 int hdrlen;
530
531 if (!ipv6_ext_hdr(nexthdr)) {
532 return -1;
533 }
534 if (nexthdr == NEXTHDR_NONE) {
535 pr_debug("next header is none\n");
536 return -1;
537 }
538 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
539 pr_debug("too short\n");
540 return -1;
541 }
542 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
543 BUG();
544 if (nexthdr == NEXTHDR_AUTH)
545 hdrlen = (hdr.hdrlen+2)<<2;
546 else
547 hdrlen = ipv6_optlen(&hdr);
548
549 prevhdr = nexthdr;
550 prev_nhoff = start;
551
552 nexthdr = hdr.nexthdr;
553 len -= hdrlen;
554 start += hdrlen;
555 }
556
557 if (len < 0)
558 return -1;
559
560 *prevhdrp = prevhdr;
561 *prevhoff = prev_nhoff;
562 *fhoff = start;
563
564 return 0;
565 }
566
567 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
568 {
569 struct net_device *dev = skb->dev;
570 int fhoff, nhoff, ret;
571 struct frag_hdr *fhdr;
572 struct frag_queue *fq;
573 struct ipv6hdr *hdr;
574 u8 prevhdr;
575
576 /* Jumbo payload inhibits frag. header */
577 if (ipv6_hdr(skb)->payload_len == 0) {
578 pr_debug("payload len = 0\n");
579 return 0;
580 }
581
582 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
583 return 0;
584
585 if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
586 return -ENOMEM;
587
588 skb_set_transport_header(skb, fhoff);
589 hdr = ipv6_hdr(skb);
590 fhdr = (struct frag_hdr *)skb_transport_header(skb);
591
592 skb_orphan(skb);
593 fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr,
594 skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));
595 if (fq == NULL) {
596 pr_debug("Can't find and can't create new queue\n");
597 return -ENOMEM;
598 }
599
600 spin_lock_bh(&fq->q.lock);
601
602 if (nf_ct_frag6_queue(fq, skb, fhdr, nhoff) < 0) {
603 ret = -EINVAL;
604 goto out_unlock;
605 }
606
607 /* after queue has assumed skb ownership, only 0 or -EINPROGRESS
608 * must be returned.
609 */
610 ret = -EINPROGRESS;
611 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
612 fq->q.meat == fq->q.len &&
613 nf_ct_frag6_reasm(fq, skb, dev))
614 ret = 0;
615
616 out_unlock:
617 spin_unlock_bh(&fq->q.lock);
618 inet_frag_put(&fq->q, &nf_frags);
619 return ret;
620 }
621 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
622
623 static int nf_ct_net_init(struct net *net)
624 {
625 net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
626 net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
627 net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
628 inet_frags_init_net(&net->nf_frag.frags);
629
630 return nf_ct_frag6_sysctl_register(net);
631 }
632
633 static void nf_ct_net_exit(struct net *net)
634 {
635 nf_ct_frags6_sysctl_unregister(net);
636 inet_frags_exit_net(&net->nf_frag.frags, &nf_frags);
637 }
638
639 static struct pernet_operations nf_ct_net_ops = {
640 .init = nf_ct_net_init,
641 .exit = nf_ct_net_exit,
642 };
643
644 int nf_ct_frag6_init(void)
645 {
646 int ret = 0;
647
648 nf_frags.hashfn = nf_hashfn;
649 nf_frags.constructor = ip6_frag_init;
650 nf_frags.destructor = NULL;
651 nf_frags.qsize = sizeof(struct frag_queue);
652 nf_frags.match = ip6_frag_match;
653 nf_frags.frag_expire = nf_ct_frag6_expire;
654 nf_frags.frags_cache_name = nf_frags_cache_name;
655 ret = inet_frags_init(&nf_frags);
656 if (ret)
657 goto out;
658 ret = register_pernet_subsys(&nf_ct_net_ops);
659 if (ret)
660 inet_frags_fini(&nf_frags);
661
662 out:
663 return ret;
664 }
665
666 void nf_ct_frag6_cleanup(void)
667 {
668 unregister_pernet_subsys(&nf_ct_net_ops);
669 inet_frags_fini(&nf_frags);
670 }
671
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