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/socket.h>
19 #include <linux/sockios.h>
20 #include <linux/jiffies.h>
21 #include <linux/net.h>
22 #include <linux/list.h>
23 #include <linux/netdevice.h>
24 #include <linux/in6.h>
25 #include <linux/ipv6.h>
26 #include <linux/icmpv6.h>
27 #include <linux/random.h>
28 #include <linux/slab.h>
29
30 #include <net/sock.h>
31 #include <net/snmp.h>
32 #include <net/ipv6_frag.h>
33
34 #include <net/protocol.h>
35 #include <net/transp_v6.h>
36 #include <net/rawv6.h>
37 #include <net/ndisc.h>
38 #include <net/addrconf.h>
39 #include <net/inet_ecn.h>
40 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
41 #include <linux/sysctl.h>
42 #include <linux/netfilter.h>
43 #include <linux/netfilter_ipv6.h>
44 #include <linux/kernel.h>
45 #include <linux/module.h>
46 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
47
48 static const char nf_frags_cache_name[] = "nf-frags";
49
50 static struct inet_frags nf_frags;
51
52 #ifdef CONFIG_SYSCTL
53
54 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
55 {
56 .procname = "nf_conntrack_frag6_timeout",
57 .data = &init_net.nf_frag.frags.timeout,
58 .maxlen = sizeof(unsigned int),
59 .mode = 0644,
60 .proc_handler = proc_dointvec_jiffies,
61 },
62 {
63 .procname = "nf_conntrack_frag6_low_thresh",
64 .data = &init_net.nf_frag.frags.low_thresh,
65 .maxlen = sizeof(unsigned long),
66 .mode = 0644,
67 .proc_handler = proc_doulongvec_minmax,
68 .extra2 = &init_net.nf_frag.frags.high_thresh
69 },
70 {
71 .procname = "nf_conntrack_frag6_high_thresh",
72 .data = &init_net.nf_frag.frags.high_thresh,
73 .maxlen = sizeof(unsigned long),
74 .mode = 0644,
75 .proc_handler = proc_doulongvec_minmax,
76 .extra1 = &init_net.nf_frag.frags.low_thresh
77 },
78 { }
79 };
80
81 static int nf_ct_frag6_sysctl_register(struct net *net)
82 {
83 struct ctl_table *table;
84 struct ctl_table_header *hdr;
85
86 table = nf_ct_frag6_sysctl_table;
87 if (!net_eq(net, &init_net)) {
88 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
89 GFP_KERNEL);
90 if (table == NULL)
91 goto err_alloc;
92
93 table[0].data = &net->nf_frag.frags.timeout;
94 table[1].data = &net->nf_frag.frags.low_thresh;
95 table[1].extra2 = &net->nf_frag.frags.high_thresh;
96 table[2].data = &net->nf_frag.frags.high_thresh;
97 table[2].extra1 = &net->nf_frag.frags.low_thresh;
98 table[2].extra2 = &init_net.nf_frag.frags.high_thresh;
99 }
100
101 hdr = register_net_sysctl(net, "net/netfilter", table);
102 if (hdr == NULL)
103 goto err_reg;
104
105 net->nf_frag_frags_hdr = hdr;
106 return 0;
107
108 err_reg:
109 if (!net_eq(net, &init_net))
110 kfree(table);
111 err_alloc:
112 return -ENOMEM;
113 }
114
115 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
116 {
117 struct ctl_table *table;
118
119 table = net->nf_frag_frags_hdr->ctl_table_arg;
120 unregister_net_sysctl_table(net->nf_frag_frags_hdr);
121 if (!net_eq(net, &init_net))
122 kfree(table);
123 }
124
125 #else
126 static int nf_ct_frag6_sysctl_register(struct net *net)
127 {
128 return 0;
129 }
130 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
131 {
132 }
133 #endif
134
135 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
136 struct sk_buff *prev_tail, struct net_device *dev);
137
138 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
139 {
140 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
141 }
142
143 static void nf_ct_frag6_expire(struct timer_list *t)
144 {
145 struct inet_frag_queue *frag = from_timer(frag, t, timer);
146 struct frag_queue *fq;
147 struct net *net;
148
149 fq = container_of(frag, struct frag_queue, q);
150 net = container_of(fq->q.net, struct net, nf_frag.frags);
151
152 ip6frag_expire_frag_queue(net, fq);
153 }
154
155 /* Creation primitives. */
156 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
157 const struct ipv6hdr *hdr, int iif)
158 {
159 struct frag_v6_compare_key key = {
160 .id = id,
161 .saddr = hdr->saddr,
162 .daddr = hdr->daddr,
163 .user = user,
164 .iif = iif,
165 };
166 struct inet_frag_queue *q;
167
168 q = inet_frag_find(&net->nf_frag.frags, &key);
169 if (!q)
170 return NULL;
171
172 return container_of(q, struct frag_queue, q);
173 }
174
175
176 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
177 const struct frag_hdr *fhdr, int nhoff)
178 {
179 unsigned int payload_len;
180 struct net_device *dev;
181 struct sk_buff *prev;
182 int offset, end, err;
183 u8 ecn;
184
185 if (fq->q.flags & INET_FRAG_COMPLETE) {
186 pr_debug("Already completed\n");
187 goto err;
188 }
189
190 payload_len = ntohs(ipv6_hdr(skb)->payload_len);
191
192 offset = ntohs(fhdr->frag_off) & ~0x7;
193 end = offset + (payload_len -
194 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
195
196 if ((unsigned int)end > IPV6_MAXPLEN) {
197 pr_debug("offset is too large.\n");
198 return -EINVAL;
199 }
200
201 ecn = ip6_frag_ecn(ipv6_hdr(skb));
202
203 if (skb->ip_summed == CHECKSUM_COMPLETE) {
204 const unsigned char *nh = skb_network_header(skb);
205 skb->csum = csum_sub(skb->csum,
206 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
207 0));
208 }
209
210 /* Is this the final fragment? */
211 if (!(fhdr->frag_off & htons(IP6_MF))) {
212 /* If we already have some bits beyond end
213 * or have different end, the segment is corrupted.
214 */
215 if (end < fq->q.len ||
216 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
217 pr_debug("already received last fragment\n");
218 goto err;
219 }
220 fq->q.flags |= INET_FRAG_LAST_IN;
221 fq->q.len = end;
222 } else {
223 /* Check if the fragment is rounded to 8 bytes.
224 * Required by the RFC.
225 */
226 if (end & 0x7) {
227 /* RFC2460 says always send parameter problem in
228 * this case. -DaveM
229 */
230 pr_debug("end of fragment not rounded to 8 bytes.\n");
231 inet_frag_kill(&fq->q);
232 return -EPROTO;
233 }
234 if (end > fq->q.len) {
235 /* Some bits beyond end -> corruption. */
236 if (fq->q.flags & INET_FRAG_LAST_IN) {
237 pr_debug("last packet already reached.\n");
238 goto err;
239 }
240 fq->q.len = end;
241 }
242 }
243
244 if (end == offset)
245 goto err;
246
247 /* Point into the IP datagram 'data' part. */
248 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
249 pr_debug("queue: message is too short.\n");
250 goto err;
251 }
252 if (pskb_trim_rcsum(skb, end - offset)) {
253 pr_debug("Can't trim\n");
254 goto err;
255 }
256
257 /* Note : skb->rbnode and skb->dev share the same location. */
258 dev = skb->dev;
259 /* Makes sure compiler wont do silly aliasing games */
260 barrier();
261
262 prev = fq->q.fragments_tail;
263 err = inet_frag_queue_insert(&fq->q, skb, offset, end);
264 if (err) {
265 if (err == IPFRAG_DUP) {
266 /* No error for duplicates, pretend they got queued. */
267 kfree_skb(skb);
268 return -EINPROGRESS;
269 }
270 goto insert_error;
271 }
272
273 if (dev)
274 fq->iif = dev->ifindex;
275
276 fq->q.stamp = skb->tstamp;
277 fq->q.meat += skb->len;
278 fq->ecn |= ecn;
279 if (payload_len > fq->q.max_size)
280 fq->q.max_size = payload_len;
281 add_frag_mem_limit(fq->q.net, skb->truesize);
282
283 /* The first fragment.
284 * nhoffset is obtained from the first fragment, of course.
285 */
286 if (offset == 0) {
287 fq->nhoffset = nhoff;
288 fq->q.flags |= INET_FRAG_FIRST_IN;
289 }
290
291 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
292 fq->q.meat == fq->q.len) {
293 unsigned long orefdst = skb->_skb_refdst;
294
295 skb->_skb_refdst = 0UL;
296 err = nf_ct_frag6_reasm(fq, skb, prev, dev);
297 skb->_skb_refdst = orefdst;
298
299 /* After queue has assumed skb ownership, only 0 or
300 * -EINPROGRESS must be returned.
301 */
302 return err ? -EINPROGRESS : 0;
303 }
304
305 skb_dst_drop(skb);
306 return -EINPROGRESS;
307
308 insert_error:
309 inet_frag_kill(&fq->q);
310 err:
311 skb_dst_drop(skb);
312 return -EINVAL;
313 }
314
315 /*
316 * Check if this packet is complete.
317 *
318 * It is called with locked fq, and caller must check that
319 * queue is eligible for reassembly i.e. it is not COMPLETE,
320 * the last and the first frames arrived and all the bits are here.
321 */
322 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
323 struct sk_buff *prev_tail, struct net_device *dev)
324 {
325 void *reasm_data;
326 int payload_len;
327 u8 ecn;
328
329 inet_frag_kill(&fq->q);
330
331 ecn = ip_frag_ecn_table[fq->ecn];
332 if (unlikely(ecn == 0xff))
333 goto err;
334
335 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
336 if (!reasm_data)
337 goto err;
338
339 payload_len = ((skb->data - skb_network_header(skb)) -
340 sizeof(struct ipv6hdr) + fq->q.len -
341 sizeof(struct frag_hdr));
342 if (payload_len > IPV6_MAXPLEN) {
343 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
344 payload_len);
345 goto err;
346 }
347
348 /* We have to remove fragment header from datagram and to relocate
349 * header in order to calculate ICV correctly. */
350 skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0];
351 memmove(skb->head + sizeof(struct frag_hdr), skb->head,
352 (skb->data - skb->head) - sizeof(struct frag_hdr));
353 skb->mac_header += sizeof(struct frag_hdr);
354 skb->network_header += sizeof(struct frag_hdr);
355
356 skb_reset_transport_header(skb);
357
358 inet_frag_reasm_finish(&fq->q, skb, reasm_data);
359
360 skb->ignore_df = 1;
361 skb->dev = dev;
362 ipv6_hdr(skb)->payload_len = htons(payload_len);
363 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
364 IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
365
366 /* Yes, and fold redundant checksum back. 8) */
367 if (skb->ip_summed == CHECKSUM_COMPLETE)
368 skb->csum = csum_partial(skb_network_header(skb),
369 skb_network_header_len(skb),
370 skb->csum);
371
372 fq->q.rb_fragments = RB_ROOT;
373 fq->q.fragments_tail = NULL;
374 fq->q.last_run_head = NULL;
375
376 return 0;
377
378 err:
379 inet_frag_kill(&fq->q);
380 return -EINVAL;
381 }
382
383 /*
384 * find the header just before Fragment Header.
385 *
386 * if success return 0 and set ...
387 * (*prevhdrp): the value of "Next Header Field" in the header
388 * just before Fragment Header.
389 * (*prevhoff): the offset of "Next Header Field" in the header
390 * just before Fragment Header.
391 * (*fhoff) : the offset of Fragment Header.
392 *
393 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
394 *
395 */
396 static int
397 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
398 {
399 u8 nexthdr = ipv6_hdr(skb)->nexthdr;
400 const int netoff = skb_network_offset(skb);
401 u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
402 int start = netoff + sizeof(struct ipv6hdr);
403 int len = skb->len - start;
404 u8 prevhdr = NEXTHDR_IPV6;
405
406 while (nexthdr != NEXTHDR_FRAGMENT) {
407 struct ipv6_opt_hdr hdr;
408 int hdrlen;
409
410 if (!ipv6_ext_hdr(nexthdr)) {
411 return -1;
412 }
413 if (nexthdr == NEXTHDR_NONE) {
414 pr_debug("next header is none\n");
415 return -1;
416 }
417 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
418 pr_debug("too short\n");
419 return -1;
420 }
421 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
422 BUG();
423 if (nexthdr == NEXTHDR_AUTH)
424 hdrlen = (hdr.hdrlen+2)<<2;
425 else
426 hdrlen = ipv6_optlen(&hdr);
427
428 prevhdr = nexthdr;
429 prev_nhoff = start;
430
431 nexthdr = hdr.nexthdr;
432 len -= hdrlen;
433 start += hdrlen;
434 }
435
436 if (len < 0)
437 return -1;
438
439 *prevhdrp = prevhdr;
440 *prevhoff = prev_nhoff;
441 *fhoff = start;
442
443 return 0;
444 }
445
446 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
447 {
448 u16 savethdr = skb->transport_header;
449 int fhoff, nhoff, ret;
450 struct frag_hdr *fhdr;
451 struct frag_queue *fq;
452 struct ipv6hdr *hdr;
453 u8 prevhdr;
454
455 /* Jumbo payload inhibits frag. header */
456 if (ipv6_hdr(skb)->payload_len == 0) {
457 pr_debug("payload len = 0\n");
458 return 0;
459 }
460
461 if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
462 return 0;
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 int res;
496
497 net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
498 net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
499 net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
500 net->nf_frag.frags.f = &nf_frags;
501
502 res = inet_frags_init_net(&net->nf_frag.frags);
503 if (res < 0)
504 return res;
505 res = nf_ct_frag6_sysctl_register(net);
506 if (res < 0)
507 inet_frags_exit_net(&net->nf_frag.frags);
508 return res;
509 }
510
511 static void nf_ct_net_exit(struct net *net)
512 {
513 nf_ct_frags6_sysctl_unregister(net);
514 inet_frags_exit_net(&net->nf_frag.frags);
515 }
516
517 static struct pernet_operations nf_ct_net_ops = {
518 .init = nf_ct_net_init,
519 .exit = nf_ct_net_exit,
520 };
521
522 static const struct rhashtable_params nfct_rhash_params = {
523 .head_offset = offsetof(struct inet_frag_queue, node),
524 .hashfn = ip6frag_key_hashfn,
525 .obj_hashfn = ip6frag_obj_hashfn,
526 .obj_cmpfn = ip6frag_obj_cmpfn,
527 .automatic_shrinking = true,
528 };
529
530 int nf_ct_frag6_init(void)
531 {
532 int ret = 0;
533
534 nf_frags.constructor = ip6frag_init;
535 nf_frags.destructor = NULL;
536 nf_frags.qsize = sizeof(struct frag_queue);
537 nf_frags.frag_expire = nf_ct_frag6_expire;
538 nf_frags.frags_cache_name = nf_frags_cache_name;
539 nf_frags.rhash_params = nfct_rhash_params;
540 ret = inet_frags_init(&nf_frags);
541 if (ret)
542 goto out;
543 ret = register_pernet_subsys(&nf_ct_net_ops);
544 if (ret)
545 inet_frags_fini(&nf_frags);
546
547 out:
548 return ret;
549 }
550
551 void nf_ct_frag6_cleanup(void)
552 {
553 unregister_pernet_subsys(&nf_ct_net_ops);
554 inet_frags_fini(&nf_frags);
555 }
556
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