1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * IPv6 fragment reassembly for connection tracking
4 *
5 * Copyright (C)2004 USAGI/WIDE Project
6 *
7 * Author:
8 * Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
9 *
10 * Based on: net/ipv6/reassembly.c
11 */
12
13 #define pr_fmt(fmt) "IPv6-nf: " fmt
14
15 #include <linux/errno.h>
16 #include <linux/types.h>
17 #include <linux/string.h>
18 #include <linux/net.h>
19 #include <linux/netdevice.h>
20 #include <linux/ipv6.h>
21 #include <linux/slab.h>
22
23 #include <net/ipv6_frag.h>
24
25 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
26 #include <linux/sysctl.h>
27 #include <linux/netfilter.h>
28 #include <linux/netfilter_ipv6.h>
29 #include <linux/kernel.h>
30 #include <linux/module.h>
31 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
32 #include <net/netns/generic.h>
33
34 static const char nf_frags_cache_name[] = "nf-frags";
35
36 static unsigned int nf_frag_pernet_id __read_mostly;
37 static struct inet_frags nf_frags;
38
39 static struct nft_ct_frag6_pernet *nf_frag_pernet(struct net *net)
40 {
41 return net_generic(net, nf_frag_pernet_id);
42 }
43
44 #ifdef CONFIG_SYSCTL
45
46 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
47 {
48 .procname = "nf_conntrack_frag6_timeout",
49 .maxlen = sizeof(unsigned int),
50 .mode = 0644,
51 .proc_handler = proc_dointvec_jiffies,
52 },
53 {
54 .procname = "nf_conntrack_frag6_low_thresh",
55 .maxlen = sizeof(unsigned long),
56 .mode = 0644,
57 .proc_handler = proc_doulongvec_minmax,
58 },
59 {
60 .procname = "nf_conntrack_frag6_high_thresh",
61 .maxlen = sizeof(unsigned long),
62 .mode = 0644,
63 .proc_handler = proc_doulongvec_minmax,
64 },
65 { }
66 };
67
68 static int nf_ct_frag6_sysctl_register(struct net *net)
69 {
70 struct nft_ct_frag6_pernet *nf_frag;
71 struct ctl_table *table;
72 struct ctl_table_header *hdr;
73
74 table = nf_ct_frag6_sysctl_table;
75 if (!net_eq(net, &init_net)) {
76 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
77 GFP_KERNEL);
78 if (table == NULL)
79 goto err_alloc;
80 }
81
82 nf_frag = nf_frag_pernet(net);
83
84 table[0].data = &nf_frag->fqdir->timeout;
85 table[1].data = &nf_frag->fqdir->low_thresh;
86 table[1].extra2 = &nf_frag->fqdir->high_thresh;
87 table[2].data = &nf_frag->fqdir->high_thresh;
88 table[2].extra1 = &nf_frag->fqdir->low_thresh;
89 table[2].extra2 = &nf_frag->fqdir->high_thresh;
90
91 hdr = register_net_sysctl(net, "net/netfilter", table);
92 if (hdr == NULL)
93 goto err_reg;
94
95 nf_frag->nf_frag_frags_hdr = hdr;
96 return 0;
97
98 err_reg:
99 if (!net_eq(net, &init_net))
100 kfree(table);
101 err_alloc:
102 return -ENOMEM;
103 }
104
105 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
106 {
107 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
108 struct ctl_table *table;
109
110 table = nf_frag->nf_frag_frags_hdr->ctl_table_arg;
111 unregister_net_sysctl_table(nf_frag->nf_frag_frags_hdr);
112 if (!net_eq(net, &init_net))
113 kfree(table);
114 }
115
116 #else
117 static int nf_ct_frag6_sysctl_register(struct net *net)
118 {
119 return 0;
120 }
121 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
122 {
123 }
124 #endif
125
126 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
127 struct sk_buff *prev_tail, struct net_device *dev);
128
129 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
130 {
131 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
132 }
133
134 static void nf_ct_frag6_expire(struct timer_list *t)
135 {
136 struct inet_frag_queue *frag = from_timer(frag, t, timer);
137 struct frag_queue *fq;
138
139 fq = container_of(frag, struct frag_queue, q);
140
141 ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
142 }
143
144 /* Creation primitives. */
145 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
146 const struct ipv6hdr *hdr, int iif)
147 {
148 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
149 struct frag_v6_compare_key key = {
150 .id = id,
151 .saddr = hdr->saddr,
152 .daddr = hdr->daddr,
153 .user = user,
154 .iif = iif,
155 };
156 struct inet_frag_queue *q;
157
158 q = inet_frag_find(nf_frag->fqdir, &key);
159 if (!q)
160 return NULL;
161
162 return container_of(q, struct frag_queue, q);
163 }
164
165
166 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
167 const struct frag_hdr *fhdr, int nhoff)
168 {
169 unsigned int payload_len;
170 struct net_device *dev;
171 struct sk_buff *prev;
172 int offset, end, err;
173 u8 ecn;
174
175 if (fq->q.flags & INET_FRAG_COMPLETE) {
176 pr_debug("Already completed\n");
177 goto err;
178 }
179
180 payload_len = ntohs(ipv6_hdr(skb)->payload_len);
181
182 offset = ntohs(fhdr->frag_off) & ~0x7;
183 end = offset + (payload_len -
184 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
185
186 if ((unsigned int)end > IPV6_MAXPLEN) {
187 pr_debug("offset is too large.\n");
188 return -EINVAL;
189 }
190
191 ecn = ip6_frag_ecn(ipv6_hdr(skb));
192
193 if (skb->ip_summed == CHECKSUM_COMPLETE) {
194 const unsigned char *nh = skb_network_header(skb);
195 skb->csum = csum_sub(skb->csum,
196 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
197 0));
198 }
199
200 /* Is this the final fragment? */
201 if (!(fhdr->frag_off & htons(IP6_MF))) {
202 /* If we already have some bits beyond end
203 * or have different end, the segment is corrupted.
204 */
205 if (end < fq->q.len ||
206 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
207 pr_debug("already received last fragment\n");
208 goto err;
209 }
210 fq->q.flags |= INET_FRAG_LAST_IN;
211 fq->q.len = end;
212 } else {
213 /* Check if the fragment is rounded to 8 bytes.
214 * Required by the RFC.
215 */
216 if (end & 0x7) {
217 /* RFC2460 says always send parameter problem in
218 * this case. -DaveM
219 */
220 pr_debug("end of fragment not rounded to 8 bytes.\n");
221 inet_frag_kill(&fq->q);
222 return -EPROTO;
223 }
224 if (end > fq->q.len) {
225 /* Some bits beyond end -> corruption. */
226 if (fq->q.flags & INET_FRAG_LAST_IN) {
227 pr_debug("last packet already reached.\n");
228 goto err;
229 }
230 fq->q.len = end;
231 }
232 }
233
234 if (end == offset)
235 goto err;
236
237 /* Point into the IP datagram 'data' part. */
238 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
239 pr_debug("queue: message is too short.\n");
240 goto err;
241 }
242 if (pskb_trim_rcsum(skb, end - offset)) {
243 pr_debug("Can't trim\n");
244 goto err;
245 }
246
247 /* Note : skb->rbnode and skb->dev share the same location. */
248 dev = skb->dev;
249 /* Makes sure compiler wont do silly aliasing games */
250 barrier();
251
252 prev = fq->q.fragments_tail;
253 err = inet_frag_queue_insert(&fq->q, skb, offset, end);
254 if (err) {
255 if (err == IPFRAG_DUP) {
256 /* No error for duplicates, pretend they got queued. */
257 kfree_skb(skb);
258 return -EINPROGRESS;
259 }
260 goto insert_error;
261 }
262
263 if (dev)
264 fq->iif = dev->ifindex;
265
266 fq->q.stamp = skb->tstamp;
267 fq->q.meat += skb->len;
268 fq->ecn |= ecn;
269 if (payload_len > fq->q.max_size)
270 fq->q.max_size = payload_len;
271 add_frag_mem_limit(fq->q.fqdir, skb->truesize);
272
273 /* The first fragment.
274 * nhoffset is obtained from the first fragment, of course.
275 */
276 if (offset == 0) {
277 fq->nhoffset = nhoff;
278 fq->q.flags |= INET_FRAG_FIRST_IN;
279 }
280
281 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
282 fq->q.meat == fq->q.len) {
283 unsigned long orefdst = skb->_skb_refdst;
284
285 skb->_skb_refdst = 0UL;
286 err = nf_ct_frag6_reasm(fq, skb, prev, dev);
287 skb->_skb_refdst = orefdst;
288
289 /* After queue has assumed skb ownership, only 0 or
290 * -EINPROGRESS must be returned.
291 */
292 return err ? -EINPROGRESS : 0;
293 }
294
295 skb_dst_drop(skb);
296 return -EINPROGRESS;
297
298 insert_error:
299 inet_frag_kill(&fq->q);
300 err:
301 skb_dst_drop(skb);
302 return -EINVAL;
303 }
304
305 /*
306 * Check if this packet is complete.
307 *
308 * It is called with locked fq, and caller must check that
309 * queue is eligible for reassembly i.e. it is not COMPLETE,
310 * the last and the first frames arrived and all the bits are here.
311 */
312 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
313 struct sk_buff *prev_tail, struct net_device *dev)
314 {
315 void *reasm_data;
316 int payload_len;
317 u8 ecn;
318
319 inet_frag_kill(&fq->q);
320
321 ecn = ip_frag_ecn_table[fq->ecn];
322 if (unlikely(ecn == 0xff))
323 goto err;
324
325 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
326 if (!reasm_data)
327 goto err;
328
329 payload_len = ((skb->data - skb_network_header(skb)) -
330 sizeof(struct ipv6hdr) + fq->q.len -
331 sizeof(struct frag_hdr));
332 if (payload_len > IPV6_MAXPLEN) {
333 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
334 payload_len);
335 goto err;
336 }
337
338 /* We have to remove fragment header from datagram and to relocate
339 * header in order to calculate ICV correctly. */
340 skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0];
341 memmove(skb->head + sizeof(struct frag_hdr), skb->head,
342 (skb->data - skb->head) - sizeof(struct frag_hdr));
343 skb->mac_header += sizeof(struct frag_hdr);
344 skb->network_header += sizeof(struct frag_hdr);
345
346 skb_reset_transport_header(skb);
347
348 inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
349
350 skb->ignore_df = 1;
351 skb->dev = dev;
352 ipv6_hdr(skb)->payload_len = htons(payload_len);
353 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
354 IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
355 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
356
357 /* Yes, and fold redundant checksum back. 8) */
358 if (skb->ip_summed == CHECKSUM_COMPLETE)
359 skb->csum = csum_partial(skb_network_header(skb),
360 skb_network_header_len(skb),
361 skb->csum);
362
363 fq->q.rb_fragments = RB_ROOT;
364 fq->q.fragments_tail = NULL;
365 fq->q.last_run_head = NULL;
366
367 return 0;
368
369 err:
370 inet_frag_kill(&fq->q);
371 return -EINVAL;
372 }
373
374 /*
375 * find the header just before Fragment Header.
376 *
377 * if success return 0 and set ...
378 * (*prevhdrp): the value of "Next Header Field" in the header
379 * just before Fragment Header.
380 * (*prevhoff): the offset of "Next Header Field" in the header
381 * just before Fragment Header.
382 * (*fhoff) : the offset of Fragment Header.
383 *
384 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
385 *
386 */
387 static int
388 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
389 {
390 u8 nexthdr = ipv6_hdr(skb)->nexthdr;
391 const int netoff = skb_network_offset(skb);
392 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
393 int start = netoff + sizeof(struct ipv6hdr);
394 int len = skb->len - start;
395 u8 prevhdr = NEXTHDR_IPV6;
396
397 while (nexthdr != NEXTHDR_FRAGMENT) {
398 struct ipv6_opt_hdr hdr;
399 int hdrlen;
400
401 if (!ipv6_ext_hdr(nexthdr)) {
402 return -1;
403 }
404 if (nexthdr == NEXTHDR_NONE) {
405 pr_debug("next header is none\n");
406 return -1;
407 }
408 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
409 pr_debug("too short\n");
410 return -1;
411 }
412 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
413 BUG();
414 if (nexthdr == NEXTHDR_AUTH)
415 hdrlen = ipv6_authlen(&hdr);
416 else
417 hdrlen = ipv6_optlen(&hdr);
418
419 prevhdr = nexthdr;
420 prev_nhoff = start;
421
422 nexthdr = hdr.nexthdr;
423 len -= hdrlen;
424 start += hdrlen;
425 }
426
427 if (len < 0)
428 return -1;
429
430 *prevhdrp = prevhdr;
431 *prevhoff = prev_nhoff;
432 *fhoff = start;
433
434 return 0;
435 }
436
437 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
438 {
439 u16 savethdr = skb->transport_header;
440 u8 nexthdr = NEXTHDR_FRAGMENT;
441 int fhoff, nhoff, ret;
442 struct frag_hdr *fhdr;
443 struct frag_queue *fq;
444 struct ipv6hdr *hdr;
445 u8 prevhdr;
446
447 /* Jumbo payload inhibits frag. header */
448 if (ipv6_hdr(skb)->payload_len == 0) {
449 pr_debug("payload len = 0\n");
450 return 0;
451 }
452
453 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
454 return 0;
455
456 /* Discard the first fragment if it does not include all headers
457 * RFC 8200, Section 4.5
458 */
459 if (ipv6frag_thdr_truncated(skb, fhoff, &nexthdr)) {
460 pr_debug("Drop incomplete fragment\n");
461 return 0;
462 }
463
464 if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
465 return -ENOMEM;
466
467 skb_set_transport_header(skb, fhoff);
468 hdr = ipv6_hdr(skb);
469 fhdr = (struct frag_hdr *)skb_transport_header(skb);
470
471 skb_orphan(skb);
472 fq = fq_find(net, fhdr->identification, user, hdr,
473 skb->dev ? skb->dev->ifindex : 0);
474 if (fq == NULL) {
475 pr_debug("Can't find and can't create new queue\n");
476 return -ENOMEM;
477 }
478
479 spin_lock_bh(&fq->q.lock);
480
481 ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
482 if (ret == -EPROTO) {
483 skb->transport_header = savethdr;
484 ret = 0;
485 }
486
487 spin_unlock_bh(&fq->q.lock);
488 inet_frag_put(&fq->q);
489 return ret;
490 }
491 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
492
493 static int nf_ct_net_init(struct net *net)
494 {
495 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
496 int res;
497
498 res = fqdir_init(&nf_frag->fqdir, &nf_frags, net);
499 if (res < 0)
500 return res;
501
502 nf_frag->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
503 nf_frag->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
504 nf_frag->fqdir->timeout = IPV6_FRAG_TIMEOUT;
505
506 res = nf_ct_frag6_sysctl_register(net);
507 if (res < 0)
508 fqdir_exit(nf_frag->fqdir);
509 return res;
510 }
511
512 static void nf_ct_net_pre_exit(struct net *net)
513 {
514 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
515
516 fqdir_pre_exit(nf_frag->fqdir);
517 }
518
519 static void nf_ct_net_exit(struct net *net)
520 {
521 struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
522
523 nf_ct_frags6_sysctl_unregister(net);
524 fqdir_exit(nf_frag->fqdir);
525 }
526
527 static struct pernet_operations nf_ct_net_ops = {
528 .init = nf_ct_net_init,
529 .pre_exit = nf_ct_net_pre_exit,
530 .exit = nf_ct_net_exit,
531 .id = &nf_frag_pernet_id,
532 .size = sizeof(struct nft_ct_frag6_pernet),
533 };
534
535 static const struct rhashtable_params nfct_rhash_params = {
536 .head_offset = offsetof(struct inet_frag_queue, node),
537 .hashfn = ip6frag_key_hashfn,
538 .obj_hashfn = ip6frag_obj_hashfn,
539 .obj_cmpfn = ip6frag_obj_cmpfn,
540 .automatic_shrinking = true,
541 };
542
543 int nf_ct_frag6_init(void)
544 {
545 int ret = 0;
546
547 nf_frags.constructor = ip6frag_init;
548 nf_frags.destructor = NULL;
549 nf_frags.qsize = sizeof(struct frag_queue);
550 nf_frags.frag_expire = nf_ct_frag6_expire;
551 nf_frags.frags_cache_name = nf_frags_cache_name;
552 nf_frags.rhash_params = nfct_rhash_params;
553 ret = inet_frags_init(&nf_frags);
554 if (ret)
555 goto out;
556 ret = register_pernet_subsys(&nf_ct_net_ops);
557 if (ret)
558 inet_frags_fini(&nf_frags);
559
560 out:
561 return ret;
562 }
563
564 void nf_ct_frag6_cleanup(void)
565 {
566 unregister_pernet_subsys(&nf_ct_net_ops);
567 inet_frags_fini(&nf_frags);
568 }
569
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