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, id: 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(net1: net, net2: &init_net)) { |
76 | table = kmemdup(p: table, size: 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 | |
90 | hdr = register_net_sysctl_sz(net, path: "net/netfilter" , table, |
91 | ARRAY_SIZE(nf_ct_frag6_sysctl_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(net1: net, net2: &init_net)) |
100 | kfree(objp: 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(header: nf_frag->nf_frag_frags_hdr); |
112 | if (!net_eq(net1: net, net2: &init_net)) |
113 | kfree(objp: 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(net: 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(fqdir: nf_frag->fqdir, key: &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(ipv6h: 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(csum: skb->csum, |
196 | addend: csum_partial(buff: nh, len: (u8 *)(fhdr + 1) - nh, |
197 | sum: 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(q: &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, len: (u8 *) (fhdr + 1) - skb->data)) { |
239 | pr_debug("queue: message is too short.\n" ); |
240 | goto err; |
241 | } |
242 | if (pskb_trim_rcsum(skb, len: 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(q: &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_reason(skb, reason: SKB_DROP_REASON_DUP_FRAG); |
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.mono_delivery_time = skb->mono_delivery_time; |
268 | fq->q.meat += skb->len; |
269 | fq->ecn |= ecn; |
270 | if (payload_len > fq->q.max_size) |
271 | fq->q.max_size = payload_len; |
272 | add_frag_mem_limit(fqdir: fq->q.fqdir, val: skb->truesize); |
273 | |
274 | /* The first fragment. |
275 | * nhoffset is obtained from the first fragment, of course. |
276 | */ |
277 | if (offset == 0) { |
278 | fq->nhoffset = nhoff; |
279 | fq->q.flags |= INET_FRAG_FIRST_IN; |
280 | } |
281 | |
282 | if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && |
283 | fq->q.meat == fq->q.len) { |
284 | unsigned long orefdst = skb->_skb_refdst; |
285 | |
286 | skb->_skb_refdst = 0UL; |
287 | err = nf_ct_frag6_reasm(fq, skb, prev_tail: prev, dev); |
288 | skb->_skb_refdst = orefdst; |
289 | |
290 | /* After queue has assumed skb ownership, only 0 or |
291 | * -EINPROGRESS must be returned. |
292 | */ |
293 | return err ? -EINPROGRESS : 0; |
294 | } |
295 | |
296 | skb_dst_drop(skb); |
297 | skb_orphan(skb); |
298 | return -EINPROGRESS; |
299 | |
300 | insert_error: |
301 | inet_frag_kill(q: &fq->q); |
302 | err: |
303 | skb_dst_drop(skb); |
304 | return -EINVAL; |
305 | } |
306 | |
307 | /* |
308 | * Check if this packet is complete. |
309 | * |
310 | * It is called with locked fq, and caller must check that |
311 | * queue is eligible for reassembly i.e. it is not COMPLETE, |
312 | * the last and the first frames arrived and all the bits are here. |
313 | */ |
314 | static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb, |
315 | struct sk_buff *prev_tail, struct net_device *dev) |
316 | { |
317 | void *reasm_data; |
318 | int payload_len; |
319 | u8 ecn; |
320 | |
321 | inet_frag_kill(q: &fq->q); |
322 | |
323 | ecn = ip_frag_ecn_table[fq->ecn]; |
324 | if (unlikely(ecn == 0xff)) |
325 | goto err; |
326 | |
327 | reasm_data = inet_frag_reasm_prepare(q: &fq->q, skb, parent: prev_tail); |
328 | if (!reasm_data) |
329 | goto err; |
330 | |
331 | payload_len = -skb_network_offset(skb) - |
332 | sizeof(struct ipv6hdr) + fq->q.len - |
333 | sizeof(struct frag_hdr); |
334 | if (payload_len > IPV6_MAXPLEN) { |
335 | net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n" , |
336 | payload_len); |
337 | goto err; |
338 | } |
339 | |
340 | /* We have to remove fragment header from datagram and to relocate |
341 | * header in order to calculate ICV correctly. */ |
342 | skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0]; |
343 | memmove(skb->head + sizeof(struct frag_hdr), skb->head, |
344 | (skb->data - skb->head) - sizeof(struct frag_hdr)); |
345 | skb->mac_header += sizeof(struct frag_hdr); |
346 | skb->network_header += sizeof(struct frag_hdr); |
347 | |
348 | skb_reset_transport_header(skb); |
349 | |
350 | inet_frag_reasm_finish(q: &fq->q, head: skb, reasm_data, try_coalesce: false); |
351 | |
352 | skb->ignore_df = 1; |
353 | skb->dev = dev; |
354 | ipv6_hdr(skb)->payload_len = htons(payload_len); |
355 | ipv6_change_dsfield(ipv6h: ipv6_hdr(skb), mask: 0xff, value: ecn); |
356 | IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size; |
357 | IP6CB(skb)->flags |= IP6SKB_FRAGMENTED; |
358 | |
359 | /* Yes, and fold redundant checksum back. 8) */ |
360 | if (skb->ip_summed == CHECKSUM_COMPLETE) |
361 | skb->csum = csum_partial(buff: skb_network_header(skb), |
362 | len: skb_network_header_len(skb), |
363 | sum: skb->csum); |
364 | |
365 | fq->q.rb_fragments = RB_ROOT; |
366 | fq->q.fragments_tail = NULL; |
367 | fq->q.last_run_head = NULL; |
368 | |
369 | return 0; |
370 | |
371 | err: |
372 | inet_frag_kill(q: &fq->q); |
373 | return -EINVAL; |
374 | } |
375 | |
376 | /* |
377 | * find the header just before Fragment Header. |
378 | * |
379 | * if success return 0 and set ... |
380 | * (*prevhdrp): the value of "Next Header Field" in the header |
381 | * just before Fragment Header. |
382 | * (*prevhoff): the offset of "Next Header Field" in the header |
383 | * just before Fragment Header. |
384 | * (*fhoff) : the offset of Fragment Header. |
385 | * |
386 | * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c |
387 | * |
388 | */ |
389 | static int |
390 | find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff) |
391 | { |
392 | u8 nexthdr = ipv6_hdr(skb)->nexthdr; |
393 | const int netoff = skb_network_offset(skb); |
394 | u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr); |
395 | int start = netoff + sizeof(struct ipv6hdr); |
396 | int len = skb->len - start; |
397 | u8 prevhdr = NEXTHDR_IPV6; |
398 | |
399 | while (nexthdr != NEXTHDR_FRAGMENT) { |
400 | struct ipv6_opt_hdr hdr; |
401 | int hdrlen; |
402 | |
403 | if (!ipv6_ext_hdr(nexthdr)) { |
404 | return -1; |
405 | } |
406 | if (nexthdr == NEXTHDR_NONE) { |
407 | pr_debug("next header is none\n" ); |
408 | return -1; |
409 | } |
410 | if (len < (int)sizeof(struct ipv6_opt_hdr)) { |
411 | pr_debug("too short\n" ); |
412 | return -1; |
413 | } |
414 | if (skb_copy_bits(skb, offset: start, to: &hdr, len: sizeof(hdr))) |
415 | BUG(); |
416 | if (nexthdr == NEXTHDR_AUTH) |
417 | hdrlen = ipv6_authlen(&hdr); |
418 | else |
419 | hdrlen = ipv6_optlen(&hdr); |
420 | |
421 | prevhdr = nexthdr; |
422 | prev_nhoff = start; |
423 | |
424 | nexthdr = hdr.nexthdr; |
425 | len -= hdrlen; |
426 | start += hdrlen; |
427 | } |
428 | |
429 | if (len < 0) |
430 | return -1; |
431 | |
432 | *prevhdrp = prevhdr; |
433 | *prevhoff = prev_nhoff; |
434 | *fhoff = start; |
435 | |
436 | return 0; |
437 | } |
438 | |
439 | int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user) |
440 | { |
441 | u16 savethdr = skb->transport_header; |
442 | u8 nexthdr = NEXTHDR_FRAGMENT; |
443 | int fhoff, nhoff, ret; |
444 | struct frag_hdr *fhdr; |
445 | struct frag_queue *fq; |
446 | struct ipv6hdr *hdr; |
447 | u8 prevhdr; |
448 | |
449 | /* Jumbo payload inhibits frag. header */ |
450 | if (ipv6_hdr(skb)->payload_len == 0) { |
451 | pr_debug("payload len = 0\n" ); |
452 | return 0; |
453 | } |
454 | |
455 | if (find_prev_fhdr(skb, prevhdrp: &prevhdr, prevhoff: &nhoff, fhoff: &fhoff) < 0) |
456 | return 0; |
457 | |
458 | /* Discard the first fragment if it does not include all headers |
459 | * RFC 8200, Section 4.5 |
460 | */ |
461 | if (ipv6frag_thdr_truncated(skb, start: fhoff, nexthdrp: &nexthdr)) { |
462 | pr_debug("Drop incomplete fragment\n" ); |
463 | return 0; |
464 | } |
465 | |
466 | if (!pskb_may_pull(skb, len: fhoff + sizeof(*fhdr))) |
467 | return -ENOMEM; |
468 | |
469 | skb_set_transport_header(skb, offset: fhoff); |
470 | hdr = ipv6_hdr(skb); |
471 | fhdr = (struct frag_hdr *)skb_transport_header(skb); |
472 | |
473 | fq = fq_find(net, id: fhdr->identification, user, hdr, |
474 | iif: skb->dev ? skb->dev->ifindex : 0); |
475 | if (fq == NULL) { |
476 | pr_debug("Can't find and can't create new queue\n" ); |
477 | return -ENOMEM; |
478 | } |
479 | |
480 | spin_lock_bh(lock: &fq->q.lock); |
481 | |
482 | ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff); |
483 | if (ret == -EPROTO) { |
484 | skb->transport_header = savethdr; |
485 | ret = 0; |
486 | } |
487 | |
488 | spin_unlock_bh(lock: &fq->q.lock); |
489 | inet_frag_put(q: &fq->q); |
490 | return ret; |
491 | } |
492 | EXPORT_SYMBOL_GPL(nf_ct_frag6_gather); |
493 | |
494 | static int nf_ct_net_init(struct net *net) |
495 | { |
496 | struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); |
497 | int res; |
498 | |
499 | res = fqdir_init(fqdirp: &nf_frag->fqdir, f: &nf_frags, net); |
500 | if (res < 0) |
501 | return res; |
502 | |
503 | nf_frag->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH; |
504 | nf_frag->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH; |
505 | nf_frag->fqdir->timeout = IPV6_FRAG_TIMEOUT; |
506 | |
507 | res = nf_ct_frag6_sysctl_register(net); |
508 | if (res < 0) |
509 | fqdir_exit(fqdir: nf_frag->fqdir); |
510 | return res; |
511 | } |
512 | |
513 | static void nf_ct_net_pre_exit(struct net *net) |
514 | { |
515 | struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); |
516 | |
517 | fqdir_pre_exit(fqdir: nf_frag->fqdir); |
518 | } |
519 | |
520 | static void nf_ct_net_exit(struct net *net) |
521 | { |
522 | struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net); |
523 | |
524 | nf_ct_frags6_sysctl_unregister(net); |
525 | fqdir_exit(fqdir: nf_frag->fqdir); |
526 | } |
527 | |
528 | static struct pernet_operations nf_ct_net_ops = { |
529 | .init = nf_ct_net_init, |
530 | .pre_exit = nf_ct_net_pre_exit, |
531 | .exit = nf_ct_net_exit, |
532 | .id = &nf_frag_pernet_id, |
533 | .size = sizeof(struct nft_ct_frag6_pernet), |
534 | }; |
535 | |
536 | static const struct rhashtable_params nfct_rhash_params = { |
537 | .head_offset = offsetof(struct inet_frag_queue, node), |
538 | .hashfn = ip6frag_key_hashfn, |
539 | .obj_hashfn = ip6frag_obj_hashfn, |
540 | .obj_cmpfn = ip6frag_obj_cmpfn, |
541 | .automatic_shrinking = true, |
542 | }; |
543 | |
544 | int nf_ct_frag6_init(void) |
545 | { |
546 | int ret = 0; |
547 | |
548 | nf_frags.constructor = ip6frag_init; |
549 | nf_frags.destructor = NULL; |
550 | nf_frags.qsize = sizeof(struct frag_queue); |
551 | nf_frags.frag_expire = nf_ct_frag6_expire; |
552 | nf_frags.frags_cache_name = nf_frags_cache_name; |
553 | nf_frags.rhash_params = nfct_rhash_params; |
554 | ret = inet_frags_init(&nf_frags); |
555 | if (ret) |
556 | goto out; |
557 | ret = register_pernet_subsys(&nf_ct_net_ops); |
558 | if (ret) |
559 | inet_frags_fini(&nf_frags); |
560 | |
561 | out: |
562 | return ret; |
563 | } |
564 | |
565 | void nf_ct_frag6_cleanup(void) |
566 | { |
567 | unregister_pernet_subsys(&nf_ct_net_ops); |
568 | inet_frags_fini(&nf_frags); |
569 | } |
570 | |