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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * IPv6 fragment reassembly
4 * Linux INET6 implementation
5 *
6 * Authors:
7 * Pedro Roque <[email protected]>
8 *
9 * Based on: net/ipv4/ip_fragment.c
10 */
11
12/*
13 * Fixes:
14 * Andi Kleen Make it work with multiple hosts.
15 * More RFC compliance.
16 *
17 * Horst von Brand Add missing #include <linux/string.h>
18 * Alexey Kuznetsov SMP races, threading, cleanup.
19 * Patrick McHardy LRU queue of frag heads for evictor.
20 * Mitsuru KANDA @USAGI Register inet6_protocol{}.
21 * David Stevens and
22 * YOSHIFUJI,H. @USAGI Always remove fragment header to
23 * calculate ICV correctly.
24 */
25
26#define pr_fmt(fmt) "IPv6: " fmt
27
28#include <linux/errno.h>
29#include <linux/types.h>
30#include <linux/string.h>
31#include <linux/socket.h>
32#include <linux/sockios.h>
33#include <linux/jiffies.h>
34#include <linux/net.h>
35#include <linux/list.h>
36#include <linux/netdevice.h>
37#include <linux/in6.h>
38#include <linux/ipv6.h>
39#include <linux/icmpv6.h>
40#include <linux/random.h>
41#include <linux/jhash.h>
42#include <linux/skbuff.h>
43#include <linux/slab.h>
44#include <linux/export.h>
45#include <linux/tcp.h>
46#include <linux/udp.h>
47
48#include <net/sock.h>
49#include <net/snmp.h>
50
51#include <net/ipv6.h>
52#include <net/ip6_route.h>
53#include <net/protocol.h>
54#include <net/transp_v6.h>
55#include <net/rawv6.h>
56#include <net/ndisc.h>
57#include <net/addrconf.h>
58#include <net/ipv6_frag.h>
59#include <net/inet_ecn.h>
60
61static const char ip6_frag_cache_name[] = "ip6-frags";
62
63static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
64{
65 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
66}
67
68static struct inet_frags ip6_frags;
69
70static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
71 struct sk_buff *prev_tail, struct net_device *dev,
72 struct inet6_dev *idev, int *refs);
73
74static void ip6_frag_expire(struct timer_list *t)
75{
76 struct inet_frag_queue *frag = timer_container_of(frag, t, timer);
77 struct frag_queue *fq;
78
79 fq = container_of(frag, struct frag_queue, q);
80
81 ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
82}
83
84static struct frag_queue *
85fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif)
86{
87 struct frag_v6_compare_key key = {
88 .id = id,
89 .saddr = hdr->saddr,
90 .daddr = hdr->daddr,
91 .user = IP6_DEFRAG_LOCAL_DELIVER,
92 .iif = iif,
93 };
94 struct inet_frag_queue *q;
95
96 if (!(ipv6_addr_type(&hdr->daddr) & (IPV6_ADDR_MULTICAST |
97 IPV6_ADDR_LINKLOCAL)))
98 key.iif = 0;
99
100 q = inet_frag_find(net->ipv6.fqdir, &key);
101 if (!q)
102 return NULL;
103
104 return container_of(q, struct frag_queue, q);
105}
106
107static int ip6_frag_queue(struct net *net,
108 struct frag_queue *fq, struct sk_buff *skb,
109 struct frag_hdr *fhdr, int nhoff,
110 u32 *prob_offset, int *refs,
111 struct inet6_dev *idev)
112{
113 int offset, end, fragsize;
114 struct sk_buff *prev_tail;
115 struct net_device *dev;
116 int err = -ENOENT;
117 SKB_DR(reason);
118 u8 ecn;
119
120 /* If reassembly is already done, @skb must be a duplicate frag. */
121 if (fq->q.flags & INET_FRAG_COMPLETE) {
122 SKB_DR_SET(reason, DUP_FRAG);
123 goto err;
124 }
125
126 err = -EINVAL;
127 offset = ntohs(fhdr->frag_off) & ~0x7;
128 end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
129 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
130
131 if ((unsigned int)end > IPV6_MAXPLEN) {
132 *prob_offset = (u8 *)&fhdr->frag_off - skb_network_header(skb);
133 /* note that if prob_offset is set, the skb is freed elsewhere,
134 * we do not free it here.
135 */
136 inet_frag_kill(&fq->q, refs);
137 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMFAILS);
138 return -1;
139 }
140
141 ecn = ip6_frag_ecn(ipv6_hdr(skb));
142
143 if (skb->ip_summed == CHECKSUM_COMPLETE) {
144 const unsigned char *nh = skb_network_header(skb);
145 skb->csum = csum_sub(skb->csum,
146 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
147 0));
148 }
149
150 /* Is this the final fragment? */
151 if (!(fhdr->frag_off & htons(IP6_MF))) {
152 /* If we already have some bits beyond end
153 * or have different end, the segment is corrupted.
154 */
155 if (end < fq->q.len ||
156 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
157 goto discard_fq;
158 fq->q.flags |= INET_FRAG_LAST_IN;
159 fq->q.len = end;
160 } else {
161 /* Check if the fragment is rounded to 8 bytes.
162 * Required by the RFC.
163 */
164 if (end & 0x7) {
165 /* RFC2460 says always send parameter problem in
166 * this case. -DaveM
167 */
168 *prob_offset = offsetof(struct ipv6hdr, payload_len);
169 inet_frag_kill(&fq->q, refs);
170 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMFAILS);
171 return -1;
172 }
173 if (end > fq->q.len) {
174 /* Some bits beyond end -> corruption. */
175 if (fq->q.flags & INET_FRAG_LAST_IN)
176 goto discard_fq;
177 fq->q.len = end;
178 }
179 }
180
181 if (end == offset)
182 goto discard_fq;
183
184 err = -ENOMEM;
185 /* Point into the IP datagram 'data' part. */
186 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data))
187 goto discard_fq;
188
189 err = pskb_trim_rcsum(skb, end - offset);
190 if (err)
191 goto discard_fq;
192
193 /* Note : skb->rbnode and skb->dev share the same location. */
194 dev = skb->dev;
195 /* Makes sure compiler wont do silly aliasing games */
196 barrier();
197
198 prev_tail = fq->q.fragments_tail;
199 err = inet_frag_queue_insert(&fq->q, skb, offset, end);
200 if (err)
201 goto insert_error;
202
203 if (dev)
204 fq->iif = dev->ifindex;
205
206 fq->q.stamp = skb->tstamp;
207 fq->q.tstamp_type = skb->tstamp_type;
208 fq->q.meat += skb->len;
209 fq->ecn |= ecn;
210 add_frag_mem_limit(fq->q.fqdir, skb->truesize);
211
212 fragsize = -skb_network_offset(skb) + skb->len;
213 if (fragsize > fq->q.max_size)
214 fq->q.max_size = fragsize;
215
216 /* The first fragment.
217 * nhoffset is obtained from the first fragment, of course.
218 */
219 if (offset == 0) {
220 fq->nhoffset = nhoff;
221 fq->q.flags |= INET_FRAG_FIRST_IN;
222 }
223
224 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
225 fq->q.meat == fq->q.len) {
226 unsigned long orefdst = skb->_skb_refdst;
227
228 skb->_skb_refdst = 0UL;
229 err = ip6_frag_reasm(fq, skb, prev_tail, dev, idev, refs);
230 skb->_skb_refdst = orefdst;
231 return err;
232 }
233
234 skb_dst_drop(skb);
235 return -EINPROGRESS;
236
237insert_error:
238 if (err == IPFRAG_DUP) {
239 SKB_DR_SET(reason, DUP_FRAG);
240 err = -EINVAL;
241 goto err;
242 }
243 err = -EINVAL;
244 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASM_OVERLAPS);
245discard_fq:
246 inet_frag_kill(&fq->q, refs);
247 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMFAILS);
248err:
249 kfree_skb_reason(skb, reason);
250 return err;
251}
252
253/*
254 * Check if this packet is complete.
255 *
256 * It is called with locked fq, and caller must check that
257 * queue is eligible for reassembly i.e. it is not COMPLETE,
258 * the last and the first frames arrived and all the bits are here.
259 */
260static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
261 struct sk_buff *prev_tail, struct net_device *dev,
262 struct inet6_dev *idev, int *refs)
263{
264 struct net *net = fq->q.fqdir->net;
265 unsigned int nhoff;
266 void *reasm_data;
267 int payload_len;
268 u8 ecn;
269
270 inet_frag_kill(&fq->q, refs);
271
272 ecn = ip_frag_ecn_table[fq->ecn];
273 if (unlikely(ecn == 0xff))
274 goto out_fail;
275
276 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
277 if (!reasm_data)
278 goto out_oom;
279
280 payload_len = -skb_network_offset(skb) -
281 sizeof(struct ipv6hdr) + fq->q.len -
282 sizeof(struct frag_hdr);
283 if (payload_len > IPV6_MAXPLEN)
284 goto out_oversize;
285
286 /* We have to remove fragment header from datagram and to relocate
287 * header in order to calculate ICV correctly. */
288 nhoff = fq->nhoffset;
289 skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
290 memmove(skb->head + sizeof(struct frag_hdr), skb->head,
291 (skb->data - skb->head) - sizeof(struct frag_hdr));
292 if (skb_mac_header_was_set(skb))
293 skb->mac_header += sizeof(struct frag_hdr);
294 skb->network_header += sizeof(struct frag_hdr);
295
296 skb_reset_transport_header(skb);
297
298 inet_frag_reasm_finish(&fq->q, skb, reasm_data, true);
299
300 skb->dev = dev;
301 ipv6_hdr(skb)->payload_len = htons(payload_len);
302 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
303 IP6CB(skb)->nhoff = nhoff;
304 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
305 IP6CB(skb)->frag_max_size = fq->q.max_size;
306
307 /* Yes, and fold redundant checksum back. 8) */
308 skb_postpush_rcsum(skb, skb_network_header(skb),
309 skb_network_header_len(skb));
310
311 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMOKS);
312 fq->q.rb_fragments = RB_ROOT;
313 fq->q.fragments_tail = NULL;
314 fq->q.last_run_head = NULL;
315 return 1;
316
317out_oversize:
318 net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
319 goto out_fail;
320out_oom:
321 net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
322out_fail:
323 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMFAILS);
324 inet_frag_kill(&fq->q, refs);
325 return -1;
326}
327
328static int ipv6_frag_rcv(struct sk_buff *skb)
329{
330 const struct ipv6hdr *hdr = ipv6_hdr(skb);
331 struct net *net = skb_dst_dev_net(skb);
332 struct inet6_dev *idev;
333 struct frag_hdr *fhdr;
334 struct frag_queue *fq;
335 u8 nexthdr;
336 int iif;
337
338 idev = skb->dev ? __in6_dev_stats_get(skb->dev, skb) : NULL;
339
340 if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
341 goto fail_hdr;
342
343 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMREQDS);
344
345 /* Jumbo payload inhibits frag. header */
346 if (hdr->payload_len == 0)
347 goto fail_hdr;
348
349 if (!pskb_may_pull(skb, (skb_transport_offset(skb) +
350 sizeof(struct frag_hdr))))
351 goto fail_hdr;
352
353 hdr = ipv6_hdr(skb);
354 fhdr = (struct frag_hdr *)skb_transport_header(skb);
355
356 if (!(fhdr->frag_off & htons(IP6_OFFSET | IP6_MF))) {
357 /* It is not a fragmented frame */
358 skb->transport_header += sizeof(struct frag_hdr);
359 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMOKS);
360
361 IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
362 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
363 IP6CB(skb)->frag_max_size = ntohs(hdr->payload_len) +
364 sizeof(struct ipv6hdr);
365 return 1;
366 }
367
368 /* RFC 8200, Section 4.5 Fragment Header:
369 * If the first fragment does not include all headers through an
370 * Upper-Layer header, then that fragment should be discarded and
371 * an ICMP Parameter Problem, Code 3, message should be sent to
372 * the source of the fragment, with the Pointer field set to zero.
373 */
374 nexthdr = hdr->nexthdr;
375 if (ipv6frag_thdr_truncated(skb, skb_network_offset(skb) + sizeof(struct ipv6hdr), &nexthdr)) {
376 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
377 icmpv6_param_prob(skb, ICMPV6_HDR_INCOMP, 0);
378 return -1;
379 }
380
381 iif = skb->dev ? skb->dev->ifindex : 0;
382 rcu_read_lock();
383 fq = fq_find(net, fhdr->identification, hdr, iif);
384 if (fq) {
385 u32 prob_offset = 0;
386 int ret, refs = 0;
387
388 spin_lock(&fq->q.lock);
389
390 fq->iif = iif;
391 ret = ip6_frag_queue(net, fq, skb, fhdr, IP6CB(skb)->nhoff,
392 &prob_offset, &refs, idev);
393
394 spin_unlock(&fq->q.lock);
395 rcu_read_unlock();
396 inet_frag_putn(&fq->q, refs);
397 if (prob_offset) {
398 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
399 /* icmpv6_param_prob() calls kfree_skb(skb) */
400 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
401 }
402 return ret;
403 }
404 rcu_read_unlock();
405
406 __IP6_INC_STATS(net, idev, IPSTATS_MIB_REASMFAILS);
407 kfree_skb(skb);
408 return -1;
409
410fail_hdr:
411 __IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
412 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb));
413 return -1;
414}
415
416static const struct inet6_protocol frag_protocol = {
417 .handler = ipv6_frag_rcv,
418 .flags = INET6_PROTO_NOPOLICY,
419};
420
421#ifdef CONFIG_SYSCTL
422
423static struct ctl_table ip6_frags_ns_ctl_table[] = {
424 {
425 .procname = "ip6frag_high_thresh",
426 .maxlen = sizeof(unsigned long),
427 .mode = 0644,
428 .proc_handler = proc_doulongvec_minmax,
429 },
430 {
431 .procname = "ip6frag_low_thresh",
432 .maxlen = sizeof(unsigned long),
433 .mode = 0644,
434 .proc_handler = proc_doulongvec_minmax,
435 },
436 {
437 .procname = "ip6frag_time",
438 .maxlen = sizeof(int),
439 .mode = 0644,
440 .proc_handler = proc_dointvec_jiffies,
441 },
442};
443
444/* secret interval has been deprecated */
445static int ip6_frags_secret_interval_unused;
446static struct ctl_table ip6_frags_ctl_table[] = {
447 {
448 .procname = "ip6frag_secret_interval",
449 .data = &ip6_frags_secret_interval_unused,
450 .maxlen = sizeof(int),
451 .mode = 0644,
452 .proc_handler = proc_dointvec_jiffies,
453 },
454};
455
456static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
457{
458 struct ctl_table *table;
459 struct ctl_table_header *hdr;
460
461 table = ip6_frags_ns_ctl_table;
462 if (!net_eq(net, &init_net)) {
463 table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);
464 if (!table)
465 goto err_alloc;
466
467 }
468 table[0].data = &net->ipv6.fqdir->high_thresh;
469 table[0].extra1 = &net->ipv6.fqdir->low_thresh;
470 table[1].data = &net->ipv6.fqdir->low_thresh;
471 table[1].extra2 = &net->ipv6.fqdir->high_thresh;
472 table[2].data = &net->ipv6.fqdir->timeout;
473
474 hdr = register_net_sysctl_sz(net, "net/ipv6", table,
475 ARRAY_SIZE(ip6_frags_ns_ctl_table));
476 if (!hdr)
477 goto err_reg;
478
479 net->ipv6.sysctl.frags_hdr = hdr;
480 return 0;
481
482err_reg:
483 if (!net_eq(net, &init_net))
484 kfree(table);
485err_alloc:
486 return -ENOMEM;
487}
488
489static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)
490{
491 const struct ctl_table *table;
492
493 table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
494 unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);
495 if (!net_eq(net, &init_net))
496 kfree(table);
497}
498
499static struct ctl_table_header *ip6_ctl_header;
500
501static int ip6_frags_sysctl_register(void)
502{
503 ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",
504 ip6_frags_ctl_table);
505 return ip6_ctl_header == NULL ? -ENOMEM : 0;
506}
507
508static void ip6_frags_sysctl_unregister(void)
509{
510 unregister_net_sysctl_table(ip6_ctl_header);
511}
512#else
513static int ip6_frags_ns_sysctl_register(struct net *net)
514{
515 return 0;
516}
517
518static void ip6_frags_ns_sysctl_unregister(struct net *net)
519{
520}
521
522static int ip6_frags_sysctl_register(void)
523{
524 return 0;
525}
526
527static void ip6_frags_sysctl_unregister(void)
528{
529}
530#endif
531
532static int __net_init ipv6_frags_init_net(struct net *net)
533{
534 int res;
535
536 res = fqdir_init(&net->ipv6.fqdir, &ip6_frags, net);
537 if (res < 0)
538 return res;
539
540 net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
541 net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
542 net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;
543
544 res = ip6_frags_ns_sysctl_register(net);
545 if (res < 0)
546 fqdir_exit(net->ipv6.fqdir);
547 return res;
548}
549
550static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
551{
552 fqdir_pre_exit(net->ipv6.fqdir);
553}
554
555static void __net_exit ipv6_frags_exit_net(struct net *net)
556{
557 ip6_frags_ns_sysctl_unregister(net);
558 fqdir_exit(net->ipv6.fqdir);
559}
560
561static struct pernet_operations ip6_frags_ops = {
562 .init = ipv6_frags_init_net,
563 .pre_exit = ipv6_frags_pre_exit_net,
564 .exit = ipv6_frags_exit_net,
565};
566
567static const struct rhashtable_params ip6_rhash_params = {
568 .head_offset = offsetof(struct inet_frag_queue, node),
569 .hashfn = ip6frag_key_hashfn,
570 .obj_hashfn = ip6frag_obj_hashfn,
571 .obj_cmpfn = ip6frag_obj_cmpfn,
572 .automatic_shrinking = true,
573};
574
575int __init ipv6_frag_init(void)
576{
577 int ret;
578
579 ip6_frags.constructor = ip6frag_init;
580 ip6_frags.destructor = NULL;
581 ip6_frags.qsize = sizeof(struct frag_queue);
582 ip6_frags.frag_expire = ip6_frag_expire;
583 ip6_frags.frags_cache_name = ip6_frag_cache_name;
584 ip6_frags.rhash_params = ip6_rhash_params;
585 ret = inet_frags_init(&ip6_frags);
586 if (ret)
587 goto out;
588
589 ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT);
590 if (ret)
591 goto err_protocol;
592
593 ret = ip6_frags_sysctl_register();
594 if (ret)
595 goto err_sysctl;
596
597 ret = register_pernet_subsys(&ip6_frags_ops);
598 if (ret)
599 goto err_pernet;
600
601out:
602 return ret;
603
604err_pernet:
605 ip6_frags_sysctl_unregister();
606err_sysctl:
607 inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
608err_protocol:
609 inet_frags_fini(&ip6_frags);
610 goto out;
611}
612
613void ipv6_frag_exit(void)
614{
615 ip6_frags_sysctl_unregister();
616 unregister_pernet_subsys(&ip6_frags_ops);
617 inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
618 inet_frags_fini(&ip6_frags);
619}