1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * IPv6 fragment reassembly
4 * Linux INET6 implementation
5 *
6 * Authors:
7 * Pedro Roque <roque@di.fc.ul.pt>
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
61 static const char ip6_frag_cache_name[] = "ip6-frags";
62
ip6_frag_ecn(const struct ipv6hdr * ipv6h)63 static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
64 {
65 return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
66 }
67
68 static struct inet_frags ip6_frags;
69
70 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
71 struct sk_buff *prev_tail, struct net_device *dev);
72
ip6_frag_expire(struct timer_list * t)73 static void ip6_frag_expire(struct timer_list *t)
74 {
75 struct inet_frag_queue *frag = from_timer(frag, t, timer);
76 struct frag_queue *fq;
77
78 fq = container_of(frag, struct frag_queue, q);
79
80 ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
81 }
82
83 static struct frag_queue *
fq_find(struct net * net,__be32 id,const struct ipv6hdr * hdr,int iif)84 fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif)
85 {
86 struct frag_v6_compare_key key = {
87 .id = id,
88 .saddr = hdr->saddr,
89 .daddr = hdr->daddr,
90 .user = IP6_DEFRAG_LOCAL_DELIVER,
91 .iif = iif,
92 };
93 struct inet_frag_queue *q;
94
95 if (!(ipv6_addr_type(&hdr->daddr) & (IPV6_ADDR_MULTICAST |
96 IPV6_ADDR_LINKLOCAL)))
97 key.iif = 0;
98
99 q = inet_frag_find(net->ipv6.fqdir, &key);
100 if (!q)
101 return NULL;
102
103 return container_of(q, struct frag_queue, q);
104 }
105
ip6_frag_queue(struct frag_queue * fq,struct sk_buff * skb,struct frag_hdr * fhdr,int nhoff,u32 * prob_offset)106 static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
107 struct frag_hdr *fhdr, int nhoff,
108 u32 *prob_offset)
109 {
110 struct net *net = dev_net(skb_dst(skb)->dev);
111 int offset, end, fragsize;
112 struct sk_buff *prev_tail;
113 struct net_device *dev;
114 int err = -ENOENT;
115 u8 ecn;
116
117 if (fq->q.flags & INET_FRAG_COMPLETE)
118 goto err;
119
120 err = -EINVAL;
121 offset = ntohs(fhdr->frag_off) & ~0x7;
122 end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
123 ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
124
125 if ((unsigned int)end > IPV6_MAXPLEN) {
126 *prob_offset = (u8 *)&fhdr->frag_off - skb_network_header(skb);
127 /* note that if prob_offset is set, the skb is freed elsewhere,
128 * we do not free it here.
129 */
130 return -1;
131 }
132
133 ecn = ip6_frag_ecn(ipv6_hdr(skb));
134
135 if (skb->ip_summed == CHECKSUM_COMPLETE) {
136 const unsigned char *nh = skb_network_header(skb);
137 skb->csum = csum_sub(skb->csum,
138 csum_partial(nh, (u8 *)(fhdr + 1) - nh,
139 0));
140 }
141
142 /* Is this the final fragment? */
143 if (!(fhdr->frag_off & htons(IP6_MF))) {
144 /* If we already have some bits beyond end
145 * or have different end, the segment is corrupted.
146 */
147 if (end < fq->q.len ||
148 ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
149 goto discard_fq;
150 fq->q.flags |= INET_FRAG_LAST_IN;
151 fq->q.len = end;
152 } else {
153 /* Check if the fragment is rounded to 8 bytes.
154 * Required by the RFC.
155 */
156 if (end & 0x7) {
157 /* RFC2460 says always send parameter problem in
158 * this case. -DaveM
159 */
160 *prob_offset = offsetof(struct ipv6hdr, payload_len);
161 return -1;
162 }
163 if (end > fq->q.len) {
164 /* Some bits beyond end -> corruption. */
165 if (fq->q.flags & INET_FRAG_LAST_IN)
166 goto discard_fq;
167 fq->q.len = end;
168 }
169 }
170
171 if (end == offset)
172 goto discard_fq;
173
174 err = -ENOMEM;
175 /* Point into the IP datagram 'data' part. */
176 if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data))
177 goto discard_fq;
178
179 err = pskb_trim_rcsum(skb, end - offset);
180 if (err)
181 goto discard_fq;
182
183 /* Note : skb->rbnode and skb->dev share the same location. */
184 dev = skb->dev;
185 /* Makes sure compiler wont do silly aliasing games */
186 barrier();
187
188 prev_tail = fq->q.fragments_tail;
189 err = inet_frag_queue_insert(&fq->q, skb, offset, end);
190 if (err)
191 goto insert_error;
192
193 if (dev)
194 fq->iif = dev->ifindex;
195
196 fq->q.stamp = skb->tstamp;
197 fq->q.meat += skb->len;
198 fq->ecn |= ecn;
199 add_frag_mem_limit(fq->q.fqdir, skb->truesize);
200
201 fragsize = -skb_network_offset(skb) + skb->len;
202 if (fragsize > fq->q.max_size)
203 fq->q.max_size = fragsize;
204
205 /* The first fragment.
206 * nhoffset is obtained from the first fragment, of course.
207 */
208 if (offset == 0) {
209 fq->nhoffset = nhoff;
210 fq->q.flags |= INET_FRAG_FIRST_IN;
211 }
212
213 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
214 fq->q.meat == fq->q.len) {
215 unsigned long orefdst = skb->_skb_refdst;
216
217 skb->_skb_refdst = 0UL;
218 err = ip6_frag_reasm(fq, skb, prev_tail, dev);
219 skb->_skb_refdst = orefdst;
220 return err;
221 }
222
223 skb_dst_drop(skb);
224 return -EINPROGRESS;
225
226 insert_error:
227 if (err == IPFRAG_DUP) {
228 kfree_skb(skb);
229 return -EINVAL;
230 }
231 err = -EINVAL;
232 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
233 IPSTATS_MIB_REASM_OVERLAPS);
234 discard_fq:
235 inet_frag_kill(&fq->q);
236 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
237 IPSTATS_MIB_REASMFAILS);
238 err:
239 kfree_skb(skb);
240 return err;
241 }
242
243 /*
244 * Check if this packet is complete.
245 *
246 * It is called with locked fq, and caller must check that
247 * queue is eligible for reassembly i.e. it is not COMPLETE,
248 * the last and the first frames arrived and all the bits are here.
249 */
ip6_frag_reasm(struct frag_queue * fq,struct sk_buff * skb,struct sk_buff * prev_tail,struct net_device * dev)250 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
251 struct sk_buff *prev_tail, struct net_device *dev)
252 {
253 struct net *net = fq->q.fqdir->net;
254 unsigned int nhoff;
255 void *reasm_data;
256 int payload_len;
257 u8 ecn;
258
259 inet_frag_kill(&fq->q);
260
261 ecn = ip_frag_ecn_table[fq->ecn];
262 if (unlikely(ecn == 0xff))
263 goto out_fail;
264
265 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
266 if (!reasm_data)
267 goto out_oom;
268
269 payload_len = ((skb->data - skb_network_header(skb)) -
270 sizeof(struct ipv6hdr) + fq->q.len -
271 sizeof(struct frag_hdr));
272 if (payload_len > IPV6_MAXPLEN)
273 goto out_oversize;
274
275 /* We have to remove fragment header from datagram and to relocate
276 * header in order to calculate ICV correctly. */
277 nhoff = fq->nhoffset;
278 skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
279 memmove(skb->head + sizeof(struct frag_hdr), skb->head,
280 (skb->data - skb->head) - sizeof(struct frag_hdr));
281 if (skb_mac_header_was_set(skb))
282 skb->mac_header += sizeof(struct frag_hdr);
283 skb->network_header += sizeof(struct frag_hdr);
284
285 skb_reset_transport_header(skb);
286
287 inet_frag_reasm_finish(&fq->q, skb, reasm_data, true);
288
289 skb->dev = dev;
290 ipv6_hdr(skb)->payload_len = htons(payload_len);
291 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
292 IP6CB(skb)->nhoff = nhoff;
293 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
294 IP6CB(skb)->frag_max_size = fq->q.max_size;
295
296 /* Yes, and fold redundant checksum back. 8) */
297 skb_postpush_rcsum(skb, skb_network_header(skb),
298 skb_network_header_len(skb));
299
300 rcu_read_lock();
301 __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
302 rcu_read_unlock();
303 fq->q.rb_fragments = RB_ROOT;
304 fq->q.fragments_tail = NULL;
305 fq->q.last_run_head = NULL;
306 return 1;
307
308 out_oversize:
309 net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
310 goto out_fail;
311 out_oom:
312 net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
313 out_fail:
314 rcu_read_lock();
315 __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
316 rcu_read_unlock();
317 inet_frag_kill(&fq->q);
318 return -1;
319 }
320
ipv6_frag_rcv(struct sk_buff * skb)321 static int ipv6_frag_rcv(struct sk_buff *skb)
322 {
323 struct frag_hdr *fhdr;
324 struct frag_queue *fq;
325 const struct ipv6hdr *hdr = ipv6_hdr(skb);
326 struct net *net = dev_net(skb_dst(skb)->dev);
327 u8 nexthdr;
328 int iif;
329
330 if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
331 goto fail_hdr;
332
333 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS);
334
335 /* Jumbo payload inhibits frag. header */
336 if (hdr->payload_len == 0)
337 goto fail_hdr;
338
339 if (!pskb_may_pull(skb, (skb_transport_offset(skb) +
340 sizeof(struct frag_hdr))))
341 goto fail_hdr;
342
343 hdr = ipv6_hdr(skb);
344 fhdr = (struct frag_hdr *)skb_transport_header(skb);
345
346 if (!(fhdr->frag_off & htons(0xFFF9))) {
347 /* It is not a fragmented frame */
348 skb->transport_header += sizeof(struct frag_hdr);
349 __IP6_INC_STATS(net,
350 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);
351
352 IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
353 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
354 return 1;
355 }
356
357 /* RFC 8200, Section 4.5 Fragment Header:
358 * If the first fragment does not include all headers through an
359 * Upper-Layer header, then that fragment should be discarded and
360 * an ICMP Parameter Problem, Code 3, message should be sent to
361 * the source of the fragment, with the Pointer field set to zero.
362 */
363 nexthdr = hdr->nexthdr;
364 if (ipv6frag_thdr_truncated(skb, skb_transport_offset(skb), &nexthdr)) {
365 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
366 IPSTATS_MIB_INHDRERRORS);
367 icmpv6_param_prob(skb, ICMPV6_HDR_INCOMP, 0);
368 return -1;
369 }
370
371 iif = skb->dev ? skb->dev->ifindex : 0;
372 fq = fq_find(net, fhdr->identification, hdr, iif);
373 if (fq) {
374 u32 prob_offset = 0;
375 int ret;
376
377 spin_lock(&fq->q.lock);
378
379 fq->iif = iif;
380 ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff,
381 &prob_offset);
382
383 spin_unlock(&fq->q.lock);
384 inet_frag_put(&fq->q);
385 if (prob_offset) {
386 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
387 IPSTATS_MIB_INHDRERRORS);
388 /* icmpv6_param_prob() calls kfree_skb(skb) */
389 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
390 }
391 return ret;
392 }
393
394 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
395 kfree_skb(skb);
396 return -1;
397
398 fail_hdr:
399 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
400 IPSTATS_MIB_INHDRERRORS);
401 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb));
402 return -1;
403 }
404
405 static const struct inet6_protocol frag_protocol = {
406 .handler = ipv6_frag_rcv,
407 .flags = INET6_PROTO_NOPOLICY,
408 };
409
410 #ifdef CONFIG_SYSCTL
411
412 static struct ctl_table ip6_frags_ns_ctl_table[] = {
413 {
414 .procname = "ip6frag_high_thresh",
415 .maxlen = sizeof(unsigned long),
416 .mode = 0644,
417 .proc_handler = proc_doulongvec_minmax,
418 },
419 {
420 .procname = "ip6frag_low_thresh",
421 .maxlen = sizeof(unsigned long),
422 .mode = 0644,
423 .proc_handler = proc_doulongvec_minmax,
424 },
425 {
426 .procname = "ip6frag_time",
427 .maxlen = sizeof(int),
428 .mode = 0644,
429 .proc_handler = proc_dointvec_jiffies,
430 },
431 { }
432 };
433
434 /* secret interval has been deprecated */
435 static int ip6_frags_secret_interval_unused;
436 static struct ctl_table ip6_frags_ctl_table[] = {
437 {
438 .procname = "ip6frag_secret_interval",
439 .data = &ip6_frags_secret_interval_unused,
440 .maxlen = sizeof(int),
441 .mode = 0644,
442 .proc_handler = proc_dointvec_jiffies,
443 },
444 { }
445 };
446
ip6_frags_ns_sysctl_register(struct net * net)447 static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
448 {
449 struct ctl_table *table;
450 struct ctl_table_header *hdr;
451
452 table = ip6_frags_ns_ctl_table;
453 if (!net_eq(net, &init_net)) {
454 table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);
455 if (!table)
456 goto err_alloc;
457
458 }
459 table[0].data = &net->ipv6.fqdir->high_thresh;
460 table[0].extra1 = &net->ipv6.fqdir->low_thresh;
461 table[1].data = &net->ipv6.fqdir->low_thresh;
462 table[1].extra2 = &net->ipv6.fqdir->high_thresh;
463 table[2].data = &net->ipv6.fqdir->timeout;
464
465 hdr = register_net_sysctl(net, "net/ipv6", table);
466 if (!hdr)
467 goto err_reg;
468
469 net->ipv6.sysctl.frags_hdr = hdr;
470 return 0;
471
472 err_reg:
473 if (!net_eq(net, &init_net))
474 kfree(table);
475 err_alloc:
476 return -ENOMEM;
477 }
478
ip6_frags_ns_sysctl_unregister(struct net * net)479 static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)
480 {
481 struct ctl_table *table;
482
483 table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
484 unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);
485 if (!net_eq(net, &init_net))
486 kfree(table);
487 }
488
489 static struct ctl_table_header *ip6_ctl_header;
490
ip6_frags_sysctl_register(void)491 static int ip6_frags_sysctl_register(void)
492 {
493 ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",
494 ip6_frags_ctl_table);
495 return ip6_ctl_header == NULL ? -ENOMEM : 0;
496 }
497
ip6_frags_sysctl_unregister(void)498 static void ip6_frags_sysctl_unregister(void)
499 {
500 unregister_net_sysctl_table(ip6_ctl_header);
501 }
502 #else
ip6_frags_ns_sysctl_register(struct net * net)503 static int ip6_frags_ns_sysctl_register(struct net *net)
504 {
505 return 0;
506 }
507
ip6_frags_ns_sysctl_unregister(struct net * net)508 static void ip6_frags_ns_sysctl_unregister(struct net *net)
509 {
510 }
511
ip6_frags_sysctl_register(void)512 static int ip6_frags_sysctl_register(void)
513 {
514 return 0;
515 }
516
ip6_frags_sysctl_unregister(void)517 static void ip6_frags_sysctl_unregister(void)
518 {
519 }
520 #endif
521
ipv6_frags_init_net(struct net * net)522 static int __net_init ipv6_frags_init_net(struct net *net)
523 {
524 int res;
525
526 res = fqdir_init(&net->ipv6.fqdir, &ip6_frags, net);
527 if (res < 0)
528 return res;
529
530 net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
531 net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
532 net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;
533
534 res = ip6_frags_ns_sysctl_register(net);
535 if (res < 0)
536 fqdir_exit(net->ipv6.fqdir);
537 return res;
538 }
539
ipv6_frags_pre_exit_net(struct net * net)540 static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
541 {
542 fqdir_pre_exit(net->ipv6.fqdir);
543 }
544
ipv6_frags_exit_net(struct net * net)545 static void __net_exit ipv6_frags_exit_net(struct net *net)
546 {
547 ip6_frags_ns_sysctl_unregister(net);
548 fqdir_exit(net->ipv6.fqdir);
549 }
550
551 static struct pernet_operations ip6_frags_ops = {
552 .init = ipv6_frags_init_net,
553 .pre_exit = ipv6_frags_pre_exit_net,
554 .exit = ipv6_frags_exit_net,
555 };
556
557 static const struct rhashtable_params ip6_rhash_params = {
558 .head_offset = offsetof(struct inet_frag_queue, node),
559 .hashfn = ip6frag_key_hashfn,
560 .obj_hashfn = ip6frag_obj_hashfn,
561 .obj_cmpfn = ip6frag_obj_cmpfn,
562 .automatic_shrinking = true,
563 };
564
ipv6_frag_init(void)565 int __init ipv6_frag_init(void)
566 {
567 int ret;
568
569 ip6_frags.constructor = ip6frag_init;
570 ip6_frags.destructor = NULL;
571 ip6_frags.qsize = sizeof(struct frag_queue);
572 ip6_frags.frag_expire = ip6_frag_expire;
573 ip6_frags.frags_cache_name = ip6_frag_cache_name;
574 ip6_frags.rhash_params = ip6_rhash_params;
575 ret = inet_frags_init(&ip6_frags);
576 if (ret)
577 goto out;
578
579 ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT);
580 if (ret)
581 goto err_protocol;
582
583 ret = ip6_frags_sysctl_register();
584 if (ret)
585 goto err_sysctl;
586
587 ret = register_pernet_subsys(&ip6_frags_ops);
588 if (ret)
589 goto err_pernet;
590
591 out:
592 return ret;
593
594 err_pernet:
595 ip6_frags_sysctl_unregister();
596 err_sysctl:
597 inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
598 err_protocol:
599 inet_frags_fini(&ip6_frags);
600 goto out;
601 }
602
ipv6_frag_exit(void)603 void ipv6_frag_exit(void)
604 {
605 ip6_frags_sysctl_unregister();
606 unregister_pernet_subsys(&ip6_frags_ops);
607 inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
608 inet_frags_fini(&ip6_frags);
609 }
610