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 pr_debug("Can't alloc new queue\n");
186 return NULL;
187 }
188
189
nf_ct_frag6_queue(struct nf_ct_frag6_queue * fq,struct sk_buff * skb,const struct frag_hdr * fhdr,int nhoff)190 static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb,
191 const struct frag_hdr *fhdr, int nhoff)
192 {
193 struct sk_buff *prev, *next;
194 int offset, end;
195
196 if (fq->q.last_in & INET_FRAG_COMPLETE) {
197 pr_debug("Already completed\n");
198 goto err;
199 }
200
201 offset = ntohs(fhdr->frag_off) & ~0x7;
202 end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
203 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
204
205 if ((unsigned int)end > IPV6_MAXPLEN) {
206 pr_debug("offset is too large.\n");
207 return -1;
208 }
209
210 if (skb->ip_summed == CHECKSUM_COMPLETE) {
211 const unsigned char *nh = skb_network_header(skb);
212 skb->csum = csum_sub(skb->csum,
213 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
214 0));
215 }
216
217 /* Is this the final fragment? */
218 if (!(fhdr->frag_off & htons(IP6_MF))) {
219 /* If we already have some bits beyond end
220 * or have different end, the segment is corrupted.
221 */
222 if (end < fq->q.len ||
223 ((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len)) {
224 pr_debug("already received last fragment\n");
225 goto err;
226 }
227 fq->q.last_in |= INET_FRAG_LAST_IN;
228 fq->q.len = end;
229 } else {
230 /* Check if the fragment is rounded to 8 bytes.
231 * Required by the RFC.
232 */
233 if (end & 0x7) {
234 /* RFC2460 says always send parameter problem in
235 * this case. -DaveM
236 */
237 pr_debug("end of fragment not rounded to 8 bytes.\n");
238 return -1;
239 }
240 if (end > fq->q.len) {
241 /* Some bits beyond end -> corruption. */
242 if (fq->q.last_in & INET_FRAG_LAST_IN) {
243 pr_debug("last packet already reached.\n");
244 goto err;
245 }
246 fq->q.len = end;
247 }
248 }
249
250 if (end == offset)
251 goto err;
252
253 /* Point into the IP datagram 'data' part. */
254 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
255 pr_debug("queue: message is too short.\n");
256 goto err;
257 }
258 if (pskb_trim_rcsum(skb, end - offset)) {
259 pr_debug("Can't trim\n");
260 goto err;
261 }
262
263 /* Find out which fragments are in front and at the back of us
264 * in the chain of fragments so far. We must know where to put
265 * this fragment, right?
266 */
267 prev = fq->q.fragments_tail;
268 if (!prev || NFCT_FRAG6_CB(prev)->offset < offset) {
269 next = NULL;
270 goto found;
271 }
272 prev = NULL;
273 for (next = fq->q.fragments; next != NULL; next = next->next) {
274 if (NFCT_FRAG6_CB(next)->offset >= offset)
275 break; /* bingo! */
276 prev = next;
277 }
278
279 found:
280 /* RFC5722, Section 4:
281 * When reassembling an IPv6 datagram, if
282 * one or more its constituent fragments is determined to be an
283 * overlapping fragment, the entire datagram (and any constituent
284 * fragments, including those not yet received) MUST be silently
285 * discarded.
286 */
287
288 /* Check for overlap with preceding fragment. */
289 if (prev &&
290 (NFCT_FRAG6_CB(prev)->offset + prev->len) > offset)
291 goto discard_fq;
292
293 /* Look for overlap with succeeding segment. */
294 if (next && NFCT_FRAG6_CB(next)->offset < end)
295 goto discard_fq;
296
297 NFCT_FRAG6_CB(skb)->offset = offset;
298
299 /* Insert this fragment in the chain of fragments. */
300 skb->next = next;
301 if (!next)
302 fq->q.fragments_tail = skb;
303 if (prev)
304 prev->next = skb;
305 else
306 fq->q.fragments = skb;
307
308 skb->dev = NULL;
309 fq->q.stamp = skb->tstamp;
310 fq->q.meat += skb->len;
311 atomic_add(skb->truesize, &nf_init_frags.mem);
312
313 /* The first fragment.
314 * nhoffset is obtained from the first fragment, of course.
315 */
316 if (offset == 0) {
317 fq->nhoffset = nhoff;
318 fq->q.last_in |= INET_FRAG_FIRST_IN;
319 }
320 write_lock(&nf_frags.lock);
321 list_move_tail(&fq->q.lru_list, &nf_init_frags.lru_list);
322 write_unlock(&nf_frags.lock);
323 return 0;
324
325 discard_fq:
326 fq_kill(fq);
327 err:
328 return -1;
329 }
330
331 /*
332 * Check if this packet is complete.
333 * Returns NULL on failure by any reason, and pointer
334 * to current nexthdr field in reassembled frame.
335 *
336 * It is called with locked fq, and caller must check that
337 * queue is eligible for reassembly i.e. it is not COMPLETE,
338 * the last and the first frames arrived and all the bits are here.
339 */
340 static struct sk_buff *
nf_ct_frag6_reasm(struct nf_ct_frag6_queue * fq,struct net_device * dev)341 nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
342 {
343 struct sk_buff *fp, *op, *head = fq->q.fragments;
344 int payload_len;
345
346 fq_kill(fq);
347
348 WARN_ON(head == NULL);
349 WARN_ON(NFCT_FRAG6_CB(head)->offset != 0);
350
351 /* Unfragmented part is taken from the first segment. */
352 payload_len = ((head->data - skb_network_header(head)) -
353 sizeof(struct ipv6hdr) + fq->q.len -
354 sizeof(struct frag_hdr));
355 if (payload_len > IPV6_MAXPLEN) {
356 pr_debug("payload len is too large.\n");
357 goto out_oversize;
358 }
359
360 /* Head of list must not be cloned. */
361 if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) {
362 pr_debug("skb is cloned but can't expand head");
363 goto out_oom;
364 }
365
366 /* If the first fragment is fragmented itself, we split
367 * it to two chunks: the first with data and paged part
368 * and the second, holding only fragments. */
369 if (skb_has_frag_list(head)) {
370 struct sk_buff *clone;
371 int i, plen = 0;
372
373 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) {
374 pr_debug("Can't alloc skb\n");
375 goto out_oom;
376 }
377 clone->next = head->next;
378 head->next = clone;
379 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
380 skb_frag_list_init(head);
381 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
382 plen += skb_shinfo(head)->frags[i].size;
383 clone->len = clone->data_len = head->data_len - plen;
384 head->data_len -= clone->len;
385 head->len -= clone->len;
386 clone->csum = 0;
387 clone->ip_summed = head->ip_summed;
388
389 NFCT_FRAG6_CB(clone)->orig = NULL;
390 atomic_add(clone->truesize, &nf_init_frags.mem);
391 }
392
393 /* We have to remove fragment header from datagram and to relocate
394 * header in order to calculate ICV correctly. */
395 skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0];
396 memmove(head->head + sizeof(struct frag_hdr), head->head,
397 (head->data - head->head) - sizeof(struct frag_hdr));
398 head->mac_header += sizeof(struct frag_hdr);
399 head->network_header += sizeof(struct frag_hdr);
400
401 skb_shinfo(head)->frag_list = head->next;
402 skb_reset_transport_header(head);
403 skb_push(head, head->data - skb_network_header(head));
404
405 for (fp=head->next; fp; fp = fp->next) {
406 head->data_len += fp->len;
407 head->len += fp->len;
408 if (head->ip_summed != fp->ip_summed)
409 head->ip_summed = CHECKSUM_NONE;
410 else if (head->ip_summed == CHECKSUM_COMPLETE)
411 head->csum = csum_add(head->csum, fp->csum);
412 head->truesize += fp->truesize;
413 }
414 atomic_sub(head->truesize, &nf_init_frags.mem);
415
416 head->next = NULL;
417 head->dev = dev;
418 head->tstamp = fq->q.stamp;
419 ipv6_hdr(head)->payload_len = htons(payload_len);
420
421 /* Yes, and fold redundant checksum back. 8) */
422 if (head->ip_summed == CHECKSUM_COMPLETE)
423 head->csum = csum_partial(skb_network_header(head),
424 skb_network_header_len(head),
425 head->csum);
426
427 fq->q.fragments = NULL;
428 fq->q.fragments_tail = NULL;
429
430 /* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
431 fp = skb_shinfo(head)->frag_list;
432 if (fp && NFCT_FRAG6_CB(fp)->orig == NULL)
433 /* at above code, head skb is divided into two skbs. */
434 fp = fp->next;
435
436 op = NFCT_FRAG6_CB(head)->orig;
437 for (; fp; fp = fp->next) {
438 struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig;
439
440 op->next = orig;
441 op = orig;
442 NFCT_FRAG6_CB(fp)->orig = NULL;
443 }
444
445 return head;
446
447 out_oversize:
448 if (net_ratelimit())
449 printk(KERN_DEBUG "nf_ct_frag6_reasm: payload len = %d\n", payload_len);
450 goto out_fail;
451 out_oom:
452 if (net_ratelimit())
453 printk(KERN_DEBUG "nf_ct_frag6_reasm: no memory for reassembly\n");
454 out_fail:
455 return NULL;
456 }
457
458 /*
459 * find the header just before Fragment Header.
460 *
461 * if success return 0 and set ...
462 * (*prevhdrp): the value of "Next Header Field" in the header
463 * just before Fragment Header.
464 * (*prevhoff): the offset of "Next Header Field" in the header
465 * just before Fragment Header.
466 * (*fhoff) : the offset of Fragment Header.
467 *
468 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
469 *
470 */
471 static int
find_prev_fhdr(struct sk_buff * skb,u8 * prevhdrp,int * prevhoff,int * fhoff)472 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
473 {
474 u8 nexthdr = ipv6_hdr(skb)->nexthdr;
475 const int netoff = skb_network_offset(skb);
476 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
477 int start = netoff + sizeof(struct ipv6hdr);
478 int len = skb->len - start;
479 u8 prevhdr = NEXTHDR_IPV6;
480
481 while (nexthdr != NEXTHDR_FRAGMENT) {
482 struct ipv6_opt_hdr hdr;
483 int hdrlen;
484
485 if (!ipv6_ext_hdr(nexthdr)) {
486 return -1;
487 }
488 if (nexthdr == NEXTHDR_NONE) {
489 pr_debug("next header is none\n");
490 return -1;
491 }
492 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
493 pr_debug("too short\n");
494 return -1;
495 }
496 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
497 BUG();
498 if (nexthdr == NEXTHDR_AUTH)
499 hdrlen = (hdr.hdrlen+2)<<2;
500 else
501 hdrlen = ipv6_optlen(&hdr);
502
503 prevhdr = nexthdr;
504 prev_nhoff = start;
505
506 nexthdr = hdr.nexthdr;
507 len -= hdrlen;
508 start += hdrlen;
509 }
510
511 if (len < 0)
512 return -1;
513
514 *prevhdrp = prevhdr;
515 *prevhoff = prev_nhoff;
516 *fhoff = start;
517
518 return 0;
519 }
520
nf_ct_frag6_gather(struct sk_buff * skb,u32 user)521 struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user)
522 {
523 struct sk_buff *clone;
524 struct net_device *dev = skb->dev;
525 struct frag_hdr *fhdr;
526 struct nf_ct_frag6_queue *fq;
527 struct ipv6hdr *hdr;
528 int fhoff, nhoff;
529 u8 prevhdr;
530 struct sk_buff *ret_skb = NULL;
531
532 /* Jumbo payload inhibits frag. header */
533 if (ipv6_hdr(skb)->payload_len == 0) {
534 pr_debug("payload len = 0\n");
535 return skb;
536 }
537
538 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
539 return skb;
540
541 clone = skb_clone(skb, GFP_ATOMIC);
542 if (clone == NULL) {
543 pr_debug("Can't clone skb\n");
544 return skb;
545 }
546
547 NFCT_FRAG6_CB(clone)->orig = skb;
548
549 if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) {
550 pr_debug("message is too short.\n");
551 goto ret_orig;
552 }
553
554 skb_set_transport_header(clone, fhoff);
555 hdr = ipv6_hdr(clone);
556 fhdr = (struct frag_hdr *)skb_transport_header(clone);
557
558 if (atomic_read(&nf_init_frags.mem) > nf_init_frags.high_thresh)
559 nf_ct_frag6_evictor();
560
561 fq = fq_find(fhdr->identification, user, &hdr->saddr, &hdr->daddr);
562 if (fq == NULL) {
563 pr_debug("Can't find and can't create new queue\n");
564 goto ret_orig;
565 }
566
567 spin_lock_bh(&fq->q.lock);
568
569 if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) {
570 spin_unlock_bh(&fq->q.lock);
571 pr_debug("Can't insert skb to queue\n");
572 fq_put(fq);
573 goto ret_orig;
574 }
575
576 if (fq->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
577 fq->q.meat == fq->q.len) {
578 ret_skb = nf_ct_frag6_reasm(fq, dev);
579 if (ret_skb == NULL)
580 pr_debug("Can't reassemble fragmented packets\n");
581 }
582 spin_unlock_bh(&fq->q.lock);
583
584 fq_put(fq);
585 return ret_skb;
586
587 ret_orig:
588 kfree_skb(clone);
589 return skb;
590 }
591
nf_ct_frag6_output(unsigned int hooknum,struct sk_buff * skb,struct net_device * in,struct net_device * out,int (* okfn)(struct sk_buff *))592 void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
593 struct net_device *in, struct net_device *out,
594 int (*okfn)(struct sk_buff *))
595 {
596 struct sk_buff *s, *s2;
597
598 for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
599 nf_conntrack_put_reasm(s->nfct_reasm);
600 nf_conntrack_get_reasm(skb);
601 s->nfct_reasm = skb;
602
603 s2 = s->next;
604 s->next = NULL;
605
606 NF_HOOK_THRESH(NFPROTO_IPV6, hooknum, s, in, out, okfn,
607 NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
608 s = s2;
609 }
610 nf_conntrack_put_reasm(skb);
611 }
612
nf_ct_frag6_init(void)613 int nf_ct_frag6_init(void)
614 {
615 nf_frags.hashfn = nf_hashfn;
616 nf_frags.constructor = ip6_frag_init;
617 nf_frags.destructor = NULL;
618 nf_frags.skb_free = nf_skb_free;
619 nf_frags.qsize = sizeof(struct nf_ct_frag6_queue);
620 nf_frags.match = ip6_frag_match;
621 nf_frags.frag_expire = nf_ct_frag6_expire;
622 nf_frags.secret_interval = 10 * 60 * HZ;
623 nf_init_frags.timeout = IPV6_FRAG_TIMEOUT;
624 nf_init_frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
625 nf_init_frags.low_thresh = IPV6_FRAG_LOW_THRESH;
626 inet_frags_init_net(&nf_init_frags);
627 inet_frags_init(&nf_frags);
628
629 #ifdef CONFIG_SYSCTL
630 nf_ct_frag6_sysctl_header = register_sysctl_paths(nf_net_netfilter_sysctl_path,
631 nf_ct_frag6_sysctl_table);
632 if (!nf_ct_frag6_sysctl_header) {
633 inet_frags_fini(&nf_frags);
634 return -ENOMEM;
635 }
636 #endif
637
638 return 0;
639 }
640
nf_ct_frag6_cleanup(void)641 void nf_ct_frag6_cleanup(void)
642 {
643 #ifdef CONFIG_SYSCTL
644 unregister_sysctl_table(nf_ct_frag6_sysctl_header);
645 nf_ct_frag6_sysctl_header = NULL;
646 #endif
647 inet_frags_fini(&nf_frags);
648
649 nf_init_frags.low_thresh = 0;
650 nf_ct_frag6_evictor();
651 }
652