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 #include <linux/errno.h>
18 #include <linux/types.h>
19 #include <linux/string.h>
20 #include <linux/socket.h>
21 #include <linux/sockios.h>
22 #include <linux/jiffies.h>
23 #include <linux/net.h>
24 #include <linux/list.h>
25 #include <linux/netdevice.h>
26 #include <linux/in6.h>
27 #include <linux/ipv6.h>
28 #include <linux/icmpv6.h>
29 #include <linux/random.h>
30 #include <linux/slab.h>
31
32 #include <net/sock.h>
33 #include <net/snmp.h>
34 #include <net/inet_frag.h>
35
36 #include <net/ipv6.h>
37 #include <net/protocol.h>
38 #include <net/transp_v6.h>
39 #include <net/rawv6.h>
40 #include <net/ndisc.h>
41 #include <net/addrconf.h>
42 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
43 #include <linux/sysctl.h>
44 #include <linux/netfilter.h>
45 #include <linux/netfilter_ipv6.h>
46 #include <linux/kernel.h>
47 #include <linux/module.h>
48 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
49
50
51 struct nf_ct_frag6_skb_cb
52 {
53 struct inet6_skb_parm h;
54 int offset;
55 struct sk_buff *orig;
56 };
57
58 #define NFCT_FRAG6_CB(skb) ((struct nf_ct_frag6_skb_cb*)((skb)->cb))
59
60 struct nf_ct_frag6_queue
61 {
62 struct inet_frag_queue q;
63
64 __be32 id; /* fragment id */
65 u32 user;
66 struct in6_addr saddr;
67 struct in6_addr daddr;
68
69 unsigned int csum;
70 __u16 nhoffset;
71 };
72
73 static struct inet_frags nf_frags;
74 static struct netns_frags nf_init_frags;
75
76 #ifdef CONFIG_SYSCTL
77 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
78 {
79 .procname = "nf_conntrack_frag6_timeout",
80 .data = &nf_init_frags.timeout,
81 .maxlen = sizeof(unsigned int),
82 .mode = 0644,
83 .proc_handler = proc_dointvec_jiffies,
84 },
85 {
86 .procname = "nf_conntrack_frag6_low_thresh",
87 .data = &nf_init_frags.low_thresh,
88 .maxlen = sizeof(unsigned int),
89 .mode = 0644,
90 .proc_handler = proc_dointvec,
91 },
92 {
93 .procname = "nf_conntrack_frag6_high_thresh",
94 .data = &nf_init_frags.high_thresh,
95 .maxlen = sizeof(unsigned int),
96 .mode = 0644,
97 .proc_handler = proc_dointvec,
98 },
99 { }
100 };
101
102 static struct ctl_table_header *nf_ct_frag6_sysctl_header;
103 #endif
104
nf_hashfn(struct inet_frag_queue * q)105 static unsigned int nf_hashfn(struct inet_frag_queue *q)
106 {
107 const struct nf_ct_frag6_queue *nq;
108
109 nq = container_of(q, struct nf_ct_frag6_queue, q);
110 return inet6_hash_frag(nq->id, &nq->saddr, &nq->daddr, nf_frags.rnd);
111 }
112
nf_skb_free(struct sk_buff * skb)113 static void nf_skb_free(struct sk_buff *skb)
114 {
115 if (NFCT_FRAG6_CB(skb)->orig)
116 kfree_skb(NFCT_FRAG6_CB(skb)->orig);
117 }
118
119 /* Destruction primitives. */
120
fq_put(struct nf_ct_frag6_queue * fq)121 static __inline__ void fq_put(struct nf_ct_frag6_queue *fq)
122 {
123 inet_frag_put(&fq->q, &nf_frags);
124 }
125
126 /* Kill fq entry. It is not destroyed immediately,
127 * because caller (and someone more) holds reference count.
128 */
fq_kill(struct nf_ct_frag6_queue * fq)129 static __inline__ void fq_kill(struct nf_ct_frag6_queue *fq)
130 {
131 inet_frag_kill(&fq->q, &nf_frags);
132 }
133
nf_ct_frag6_evictor(void)134 static void nf_ct_frag6_evictor(void)
135 {
136 local_bh_disable();
137 inet_frag_evictor(&nf_init_frags, &nf_frags);
138 local_bh_enable();
139 }
140
nf_ct_frag6_expire(unsigned long data)141 static void nf_ct_frag6_expire(unsigned long data)
142 {
143 struct nf_ct_frag6_queue *fq;
144
145 fq = container_of((struct inet_frag_queue *)data,
146 struct nf_ct_frag6_queue, q);
147
148 spin_lock(&fq->q.lock);
149
150 if (fq->q.last_in & INET_FRAG_COMPLETE)
151 goto out;
152
153 fq_kill(fq);
154
155 out:
156 spin_unlock(&fq->q.lock);
157 fq_put(fq);
158 }
159
160 /* Creation primitives. */
161
162 static __inline__ struct nf_ct_frag6_queue *
fq_find(__be32 id,u32 user,struct in6_addr * src,struct in6_addr * dst)163 fq_find(__be32 id, u32 user, struct in6_addr *src, struct in6_addr *dst)
164 {
165 struct inet_frag_queue *q;
166 struct ip6_create_arg arg;
167 unsigned int hash;
168
169 arg.id = id;
170 arg.user = user;
171 arg.src = src;
172 arg.dst = dst;
173
174 read_lock_bh(&nf_frags.lock);
175 hash = inet6_hash_frag(id, src, dst, nf_frags.rnd);
176
177 q = inet_frag_find(&nf_init_frags, &nf_frags, &arg, hash);
178 local_bh_enable();
179 if (q == NULL)
180 goto oom;
181
182 return container_of(q, struct nf_ct_frag6_queue, q);
183
184 oom:
185 return NULL;
186 }
187
188
nf_ct_frag6_queue(struct nf_ct_frag6_queue * fq,struct sk_buff * skb,const struct frag_hdr * fhdr,int nhoff)189 static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb,
190 const struct frag_hdr *fhdr, int nhoff)
191 {
192 struct sk_buff *prev, *next;
193 int offset, end;
194
195 if (fq->q.last_in & INET_FRAG_COMPLETE) {
196 pr_debug("Already completed\n");
197 goto err;
198 }
199
200 offset = ntohs(fhdr->frag_off) & ~0x7;
201 end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
202 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
203
204 if ((unsigned int)end > IPV6_MAXPLEN) {
205 pr_debug("offset is too large.\n");
206 return -1;
207 }
208
209 if (skb->ip_summed == CHECKSUM_COMPLETE) {
210 const unsigned char *nh = skb_network_header(skb);
211 skb->csum = csum_sub(skb->csum,
212 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
213 0));
214 }
215
216 /* Is this the final fragment? */
217 if (!(fhdr->frag_off & htons(IP6_MF))) {
218 /* If we already have some bits beyond end
219 * or have different end, the segment is corrupted.
220 */
221 if (end < fq->q.len ||
222 ((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len)) {
223 pr_debug("already received last fragment\n");
224 goto err;
225 }
226 fq->q.last_in |= INET_FRAG_LAST_IN;
227 fq->q.len = end;
228 } else {
229 /* Check if the fragment is rounded to 8 bytes.
230 * Required by the RFC.
231 */
232 if (end & 0x7) {
233 /* RFC2460 says always send parameter problem in
234 * this case. -DaveM
235 */
236 pr_debug("end of fragment not rounded to 8 bytes.\n");
237 return -1;
238 }
239 if (end > fq->q.len) {
240 /* Some bits beyond end -> corruption. */
241 if (fq->q.last_in & INET_FRAG_LAST_IN) {
242 pr_debug("last packet already reached.\n");
243 goto err;
244 }
245 fq->q.len = end;
246 }
247 }
248
249 if (end == offset)
250 goto err;
251
252 /* Point into the IP datagram 'data' part. */
253 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
254 pr_debug("queue: message is too short.\n");
255 goto err;
256 }
257 if (pskb_trim_rcsum(skb, end - offset)) {
258 pr_debug("Can't trim\n");
259 goto err;
260 }
261
262 /* Find out which fragments are in front and at the back of us
263 * in the chain of fragments so far. We must know where to put
264 * this fragment, right?
265 */
266 prev = fq->q.fragments_tail;
267 if (!prev || NFCT_FRAG6_CB(prev)->offset < offset) {
268 next = NULL;
269 goto found;
270 }
271 prev = NULL;
272 for (next = fq->q.fragments; next != NULL; next = next->next) {
273 if (NFCT_FRAG6_CB(next)->offset >= offset)
274 break; /* bingo! */
275 prev = next;
276 }
277
278 found:
279 /* RFC5722, Section 4:
280 * When reassembling an IPv6 datagram, if
281 * one or more its constituent fragments is determined to be an
282 * overlapping fragment, the entire datagram (and any constituent
283 * fragments, including those not yet received) MUST be silently
284 * discarded.
285 */
286
287 /* Check for overlap with preceding fragment. */
288 if (prev &&
289 (NFCT_FRAG6_CB(prev)->offset + prev->len) > offset)
290 goto discard_fq;
291
292 /* Look for overlap with succeeding segment. */
293 if (next && NFCT_FRAG6_CB(next)->offset < end)
294 goto discard_fq;
295
296 NFCT_FRAG6_CB(skb)->offset = offset;
297
298 /* Insert this fragment in the chain of fragments. */
299 skb->next = next;
300 if (!next)
301 fq->q.fragments_tail = skb;
302 if (prev)
303 prev->next = skb;
304 else
305 fq->q.fragments = skb;
306
307 skb->dev = NULL;
308 fq->q.stamp = skb->tstamp;
309 fq->q.meat += skb->len;
310 atomic_add(skb->truesize, &nf_init_frags.mem);
311
312 /* The first fragment.
313 * nhoffset is obtained from the first fragment, of course.
314 */
315 if (offset == 0) {
316 fq->nhoffset = nhoff;
317 fq->q.last_in |= INET_FRAG_FIRST_IN;
318 }
319 write_lock(&nf_frags.lock);
320 list_move_tail(&fq->q.lru_list, &nf_init_frags.lru_list);
321 write_unlock(&nf_frags.lock);
322 return 0;
323
324 discard_fq:
325 fq_kill(fq);
326 err:
327 return -1;
328 }
329
330 /*
331 * Check if this packet is complete.
332 * Returns NULL on failure by any reason, and pointer
333 * to current nexthdr field in reassembled frame.
334 *
335 * It is called with locked fq, and caller must check that
336 * queue is eligible for reassembly i.e. it is not COMPLETE,
337 * the last and the first frames arrived and all the bits are here.
338 */
339 static struct sk_buff *
nf_ct_frag6_reasm(struct nf_ct_frag6_queue * fq,struct net_device * dev)340 nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
341 {
342 struct sk_buff *fp, *op, *head = fq->q.fragments;
343 int payload_len;
344
345 fq_kill(fq);
346
347 WARN_ON(head == NULL);
348 WARN_ON(NFCT_FRAG6_CB(head)->offset != 0);
349
350 /* Unfragmented part is taken from the first segment. */
351 payload_len = ((head->data - skb_network_header(head)) -
352 sizeof(struct ipv6hdr) + fq->q.len -
353 sizeof(struct frag_hdr));
354 if (payload_len > IPV6_MAXPLEN) {
355 pr_debug("payload len is too large.\n");
356 goto out_oversize;
357 }
358
359 /* Head of list must not be cloned. */
360 if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) {
361 pr_debug("skb is cloned but can't expand head");
362 goto out_oom;
363 }
364
365 /* If the first fragment is fragmented itself, we split
366 * it to two chunks: the first with data and paged part
367 * and the second, holding only fragments. */
368 if (skb_has_frag_list(head)) {
369 struct sk_buff *clone;
370 int i, plen = 0;
371
372 clone = alloc_skb(0, GFP_ATOMIC);
373 if (clone == NULL)
374 goto out_oom;
375
376 clone->next = head->next;
377 head->next = clone;
378 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
379 skb_frag_list_init(head);
380 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
381 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
382 clone->len = clone->data_len = head->data_len - plen;
383 head->data_len -= clone->len;
384 head->len -= clone->len;
385 clone->csum = 0;
386 clone->ip_summed = head->ip_summed;
387
388 NFCT_FRAG6_CB(clone)->orig = NULL;
389 atomic_add(clone->truesize, &nf_init_frags.mem);
390 }
391
392 /* We have to remove fragment header from datagram and to relocate
393 * header in order to calculate ICV correctly. */
394 skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0];
395 memmove(head->head + sizeof(struct frag_hdr), head->head,
396 (head->data - head->head) - sizeof(struct frag_hdr));
397 head->mac_header += sizeof(struct frag_hdr);
398 head->network_header += sizeof(struct frag_hdr);
399
400 skb_shinfo(head)->frag_list = head->next;
401 skb_reset_transport_header(head);
402 skb_push(head, head->data - skb_network_header(head));
403
404 for (fp=head->next; fp; fp = fp->next) {
405 head->data_len += fp->len;
406 head->len += fp->len;
407 if (head->ip_summed != fp->ip_summed)
408 head->ip_summed = CHECKSUM_NONE;
409 else if (head->ip_summed == CHECKSUM_COMPLETE)
410 head->csum = csum_add(head->csum, fp->csum);
411 head->truesize += fp->truesize;
412 }
413 atomic_sub(head->truesize, &nf_init_frags.mem);
414
415 head->next = NULL;
416 head->dev = dev;
417 head->tstamp = fq->q.stamp;
418 ipv6_hdr(head)->payload_len = htons(payload_len);
419
420 /* Yes, and fold redundant checksum back. 8) */
421 if (head->ip_summed == CHECKSUM_COMPLETE)
422 head->csum = csum_partial(skb_network_header(head),
423 skb_network_header_len(head),
424 head->csum);
425
426 fq->q.fragments = NULL;
427 fq->q.fragments_tail = NULL;
428
429 /* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
430 fp = skb_shinfo(head)->frag_list;
431 if (fp && NFCT_FRAG6_CB(fp)->orig == NULL)
432 /* at above code, head skb is divided into two skbs. */
433 fp = fp->next;
434
435 op = NFCT_FRAG6_CB(head)->orig;
436 for (; fp; fp = fp->next) {
437 struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig;
438
439 op->next = orig;
440 op = orig;
441 NFCT_FRAG6_CB(fp)->orig = NULL;
442 }
443
444 return head;
445
446 out_oversize:
447 if (net_ratelimit())
448 printk(KERN_DEBUG "nf_ct_frag6_reasm: payload len = %d\n", payload_len);
449 goto out_fail;
450 out_oom:
451 if (net_ratelimit())
452 printk(KERN_DEBUG "nf_ct_frag6_reasm: no memory for reassembly\n");
453 out_fail:
454 return NULL;
455 }
456
457 /*
458 * find the header just before Fragment Header.
459 *
460 * if success return 0 and set ...
461 * (*prevhdrp): the value of "Next Header Field" in the header
462 * just before Fragment Header.
463 * (*prevhoff): the offset of "Next Header Field" in the header
464 * just before Fragment Header.
465 * (*fhoff) : the offset of Fragment Header.
466 *
467 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
468 *
469 */
470 static int
find_prev_fhdr(struct sk_buff * skb,u8 * prevhdrp,int * prevhoff,int * fhoff)471 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
472 {
473 u8 nexthdr = ipv6_hdr(skb)->nexthdr;
474 const int netoff = skb_network_offset(skb);
475 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
476 int start = netoff + sizeof(struct ipv6hdr);
477 int len = skb->len - start;
478 u8 prevhdr = NEXTHDR_IPV6;
479
480 while (nexthdr != NEXTHDR_FRAGMENT) {
481 struct ipv6_opt_hdr hdr;
482 int hdrlen;
483
484 if (!ipv6_ext_hdr(nexthdr)) {
485 return -1;
486 }
487 if (nexthdr == NEXTHDR_NONE) {
488 pr_debug("next header is none\n");
489 return -1;
490 }
491 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
492 pr_debug("too short\n");
493 return -1;
494 }
495 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
496 BUG();
497 if (nexthdr == NEXTHDR_AUTH)
498 hdrlen = (hdr.hdrlen+2)<<2;
499 else
500 hdrlen = ipv6_optlen(&hdr);
501
502 prevhdr = nexthdr;
503 prev_nhoff = start;
504
505 nexthdr = hdr.nexthdr;
506 len -= hdrlen;
507 start += hdrlen;
508 }
509
510 if (len < 0)
511 return -1;
512
513 *prevhdrp = prevhdr;
514 *prevhoff = prev_nhoff;
515 *fhoff = start;
516
517 return 0;
518 }
519
nf_ct_frag6_gather(struct sk_buff * skb,u32 user)520 struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user)
521 {
522 struct sk_buff *clone;
523 struct net_device *dev = skb->dev;
524 struct frag_hdr *fhdr;
525 struct nf_ct_frag6_queue *fq;
526 struct ipv6hdr *hdr;
527 int fhoff, nhoff;
528 u8 prevhdr;
529 struct sk_buff *ret_skb = NULL;
530
531 /* Jumbo payload inhibits frag. header */
532 if (ipv6_hdr(skb)->payload_len == 0) {
533 pr_debug("payload len = 0\n");
534 return skb;
535 }
536
537 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
538 return skb;
539
540 clone = skb_clone(skb, GFP_ATOMIC);
541 if (clone == NULL) {
542 pr_debug("Can't clone skb\n");
543 return skb;
544 }
545
546 NFCT_FRAG6_CB(clone)->orig = skb;
547
548 if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) {
549 pr_debug("message is too short.\n");
550 goto ret_orig;
551 }
552
553 skb_set_transport_header(clone, fhoff);
554 hdr = ipv6_hdr(clone);
555 fhdr = (struct frag_hdr *)skb_transport_header(clone);
556
557 if (atomic_read(&nf_init_frags.mem) > nf_init_frags.high_thresh)
558 nf_ct_frag6_evictor();
559
560 fq = fq_find(fhdr->identification, user, &hdr->saddr, &hdr->daddr);
561 if (fq == NULL) {
562 pr_debug("Can't find and can't create new queue\n");
563 goto ret_orig;
564 }
565
566 spin_lock_bh(&fq->q.lock);
567
568 if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) {
569 spin_unlock_bh(&fq->q.lock);
570 pr_debug("Can't insert skb to queue\n");
571 fq_put(fq);
572 goto ret_orig;
573 }
574
575 if (fq->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
576 fq->q.meat == fq->q.len) {
577 ret_skb = nf_ct_frag6_reasm(fq, dev);
578 if (ret_skb == NULL)
579 pr_debug("Can't reassemble fragmented packets\n");
580 }
581 spin_unlock_bh(&fq->q.lock);
582
583 fq_put(fq);
584 return ret_skb;
585
586 ret_orig:
587 kfree_skb(clone);
588 return skb;
589 }
590
nf_ct_frag6_output(unsigned int hooknum,struct sk_buff * skb,struct net_device * in,struct net_device * out,int (* okfn)(struct sk_buff *))591 void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
592 struct net_device *in, struct net_device *out,
593 int (*okfn)(struct sk_buff *))
594 {
595 struct sk_buff *s, *s2;
596
597 for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
598 nf_conntrack_put_reasm(s->nfct_reasm);
599 nf_conntrack_get_reasm(skb);
600 s->nfct_reasm = skb;
601
602 s2 = s->next;
603 s->next = NULL;
604
605 NF_HOOK_THRESH(NFPROTO_IPV6, hooknum, s, in, out, okfn,
606 NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
607 s = s2;
608 }
609 nf_conntrack_put_reasm(skb);
610 }
611
nf_ct_frag6_init(void)612 int nf_ct_frag6_init(void)
613 {
614 nf_frags.hashfn = nf_hashfn;
615 nf_frags.constructor = ip6_frag_init;
616 nf_frags.destructor = NULL;
617 nf_frags.skb_free = nf_skb_free;
618 nf_frags.qsize = sizeof(struct nf_ct_frag6_queue);
619 nf_frags.match = ip6_frag_match;
620 nf_frags.frag_expire = nf_ct_frag6_expire;
621 nf_frags.secret_interval = 10 * 60 * HZ;
622 nf_init_frags.timeout = IPV6_FRAG_TIMEOUT;
623 nf_init_frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
624 nf_init_frags.low_thresh = IPV6_FRAG_LOW_THRESH;
625 inet_frags_init_net(&nf_init_frags);
626 inet_frags_init(&nf_frags);
627
628 #ifdef CONFIG_SYSCTL
629 nf_ct_frag6_sysctl_header = register_sysctl_paths(nf_net_netfilter_sysctl_path,
630 nf_ct_frag6_sysctl_table);
631 if (!nf_ct_frag6_sysctl_header) {
632 inet_frags_fini(&nf_frags);
633 return -ENOMEM;
634 }
635 #endif
636
637 return 0;
638 }
639
nf_ct_frag6_cleanup(void)640 void nf_ct_frag6_cleanup(void)
641 {
642 #ifdef CONFIG_SYSCTL
643 unregister_sysctl_table(nf_ct_frag6_sysctl_header);
644 nf_ct_frag6_sysctl_header = NULL;
645 #endif
646 inet_frags_fini(&nf_frags);
647
648 nf_init_frags.low_thresh = 0;
649 nf_ct_frag6_evictor();
650 }
651