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.mono_delivery_time = skb->mono_delivery_time;
198 fq->q.meat += skb->len;
199 fq->ecn |= ecn;
200 add_frag_mem_limit(fq->q.fqdir, skb->truesize);
201
202 fragsize = -skb_network_offset(skb) + skb->len;
203 if (fragsize > fq->q.max_size)
204 fq->q.max_size = fragsize;
205
206 /* The first fragment.
207 * nhoffset is obtained from the first fragment, of course.
208 */
209 if (offset == 0) {
210 fq->nhoffset = nhoff;
211 fq->q.flags |= INET_FRAG_FIRST_IN;
212 }
213
214 if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
215 fq->q.meat == fq->q.len) {
216 unsigned long orefdst = skb->_skb_refdst;
217
218 skb->_skb_refdst = 0UL;
219 err = ip6_frag_reasm(fq, skb, prev_tail, dev);
220 skb->_skb_refdst = orefdst;
221 return err;
222 }
223
224 skb_dst_drop(skb);
225 return -EINPROGRESS;
226
227 insert_error:
228 if (err == IPFRAG_DUP) {
229 kfree_skb(skb);
230 return -EINVAL;
231 }
232 err = -EINVAL;
233 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
234 IPSTATS_MIB_REASM_OVERLAPS);
235 discard_fq:
236 inet_frag_kill(&fq->q);
237 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
238 IPSTATS_MIB_REASMFAILS);
239 err:
240 kfree_skb(skb);
241 return err;
242 }
243
244 /*
245 * Check if this packet is complete.
246 *
247 * It is called with locked fq, and caller must check that
248 * queue is eligible for reassembly i.e. it is not COMPLETE,
249 * the last and the first frames arrived and all the bits are here.
250 */
ip6_frag_reasm(struct frag_queue * fq,struct sk_buff * skb,struct sk_buff * prev_tail,struct net_device * dev)251 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
252 struct sk_buff *prev_tail, struct net_device *dev)
253 {
254 struct net *net = fq->q.fqdir->net;
255 unsigned int nhoff;
256 void *reasm_data;
257 int payload_len;
258 u8 ecn;
259
260 inet_frag_kill(&fq->q);
261
262 ecn = ip_frag_ecn_table[fq->ecn];
263 if (unlikely(ecn == 0xff))
264 goto out_fail;
265
266 reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
267 if (!reasm_data)
268 goto out_oom;
269
270 payload_len = ((skb->data - skb_network_header(skb)) -
271 sizeof(struct ipv6hdr) + fq->q.len -
272 sizeof(struct frag_hdr));
273 if (payload_len > IPV6_MAXPLEN)
274 goto out_oversize;
275
276 /* We have to remove fragment header from datagram and to relocate
277 * header in order to calculate ICV correctly. */
278 nhoff = fq->nhoffset;
279 skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
280 memmove(skb->head + sizeof(struct frag_hdr), skb->head,
281 (skb->data - skb->head) - sizeof(struct frag_hdr));
282 if (skb_mac_header_was_set(skb))
283 skb->mac_header += sizeof(struct frag_hdr);
284 skb->network_header += sizeof(struct frag_hdr);
285
286 skb_reset_transport_header(skb);
287
288 inet_frag_reasm_finish(&fq->q, skb, reasm_data, true);
289
290 skb->dev = dev;
291 ipv6_hdr(skb)->payload_len = htons(payload_len);
292 ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
293 IP6CB(skb)->nhoff = nhoff;
294 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
295 IP6CB(skb)->frag_max_size = fq->q.max_size;
296
297 /* Yes, and fold redundant checksum back. 8) */
298 skb_postpush_rcsum(skb, skb_network_header(skb),
299 skb_network_header_len(skb));
300
301 rcu_read_lock();
302 __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
303 rcu_read_unlock();
304 fq->q.rb_fragments = RB_ROOT;
305 fq->q.fragments_tail = NULL;
306 fq->q.last_run_head = NULL;
307 return 1;
308
309 out_oversize:
310 net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
311 goto out_fail;
312 out_oom:
313 net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
314 out_fail:
315 rcu_read_lock();
316 __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
317 rcu_read_unlock();
318 inet_frag_kill(&fq->q);
319 return -1;
320 }
321
ipv6_frag_rcv(struct sk_buff * skb)322 static int ipv6_frag_rcv(struct sk_buff *skb)
323 {
324 struct frag_hdr *fhdr;
325 struct frag_queue *fq;
326 const struct ipv6hdr *hdr = ipv6_hdr(skb);
327 struct net *net = dev_net(skb_dst(skb)->dev);
328 u8 nexthdr;
329 int iif;
330
331 if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
332 goto fail_hdr;
333
334 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS);
335
336 /* Jumbo payload inhibits frag. header */
337 if (hdr->payload_len == 0)
338 goto fail_hdr;
339
340 if (!pskb_may_pull(skb, (skb_transport_offset(skb) +
341 sizeof(struct frag_hdr))))
342 goto fail_hdr;
343
344 hdr = ipv6_hdr(skb);
345 fhdr = (struct frag_hdr *)skb_transport_header(skb);
346
347 if (!(fhdr->frag_off & htons(IP6_OFFSET | IP6_MF))) {
348 /* It is not a fragmented frame */
349 skb->transport_header += sizeof(struct frag_hdr);
350 __IP6_INC_STATS(net,
351 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);
352
353 IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
354 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
355 IP6CB(skb)->frag_max_size = ntohs(hdr->payload_len) +
356 sizeof(struct ipv6hdr);
357 return 1;
358 }
359
360 /* RFC 8200, Section 4.5 Fragment Header:
361 * If the first fragment does not include all headers through an
362 * Upper-Layer header, then that fragment should be discarded and
363 * an ICMP Parameter Problem, Code 3, message should be sent to
364 * the source of the fragment, with the Pointer field set to zero.
365 */
366 nexthdr = hdr->nexthdr;
367 if (ipv6frag_thdr_truncated(skb, skb_transport_offset(skb), &nexthdr)) {
368 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
369 IPSTATS_MIB_INHDRERRORS);
370 icmpv6_param_prob(skb, ICMPV6_HDR_INCOMP, 0);
371 return -1;
372 }
373
374 iif = skb->dev ? skb->dev->ifindex : 0;
375 fq = fq_find(net, fhdr->identification, hdr, iif);
376 if (fq) {
377 u32 prob_offset = 0;
378 int ret;
379
380 spin_lock(&fq->q.lock);
381
382 fq->iif = iif;
383 ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff,
384 &prob_offset);
385
386 spin_unlock(&fq->q.lock);
387 inet_frag_put(&fq->q);
388 if (prob_offset) {
389 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
390 IPSTATS_MIB_INHDRERRORS);
391 /* icmpv6_param_prob() calls kfree_skb(skb) */
392 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
393 }
394 return ret;
395 }
396
397 __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
398 kfree_skb(skb);
399 return -1;
400
401 fail_hdr:
402 __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
403 IPSTATS_MIB_INHDRERRORS);
404 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb));
405 return -1;
406 }
407
408 static const struct inet6_protocol frag_protocol = {
409 .handler = ipv6_frag_rcv,
410 .flags = INET6_PROTO_NOPOLICY,
411 };
412
413 #ifdef CONFIG_SYSCTL
414
415 static struct ctl_table ip6_frags_ns_ctl_table[] = {
416 {
417 .procname = "ip6frag_high_thresh",
418 .maxlen = sizeof(unsigned long),
419 .mode = 0644,
420 .proc_handler = proc_doulongvec_minmax,
421 },
422 {
423 .procname = "ip6frag_low_thresh",
424 .maxlen = sizeof(unsigned long),
425 .mode = 0644,
426 .proc_handler = proc_doulongvec_minmax,
427 },
428 {
429 .procname = "ip6frag_time",
430 .maxlen = sizeof(int),
431 .mode = 0644,
432 .proc_handler = proc_dointvec_jiffies,
433 },
434 { }
435 };
436
437 /* secret interval has been deprecated */
438 static int ip6_frags_secret_interval_unused;
439 static struct ctl_table ip6_frags_ctl_table[] = {
440 {
441 .procname = "ip6frag_secret_interval",
442 .data = &ip6_frags_secret_interval_unused,
443 .maxlen = sizeof(int),
444 .mode = 0644,
445 .proc_handler = proc_dointvec_jiffies,
446 },
447 { }
448 };
449
ip6_frags_ns_sysctl_register(struct net * net)450 static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
451 {
452 struct ctl_table *table;
453 struct ctl_table_header *hdr;
454
455 table = ip6_frags_ns_ctl_table;
456 if (!net_eq(net, &init_net)) {
457 table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);
458 if (!table)
459 goto err_alloc;
460
461 }
462 table[0].data = &net->ipv6.fqdir->high_thresh;
463 table[0].extra1 = &net->ipv6.fqdir->low_thresh;
464 table[1].data = &net->ipv6.fqdir->low_thresh;
465 table[1].extra2 = &net->ipv6.fqdir->high_thresh;
466 table[2].data = &net->ipv6.fqdir->timeout;
467
468 hdr = register_net_sysctl(net, "net/ipv6", table);
469 if (!hdr)
470 goto err_reg;
471
472 net->ipv6.sysctl.frags_hdr = hdr;
473 return 0;
474
475 err_reg:
476 if (!net_eq(net, &init_net))
477 kfree(table);
478 err_alloc:
479 return -ENOMEM;
480 }
481
ip6_frags_ns_sysctl_unregister(struct net * net)482 static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)
483 {
484 struct ctl_table *table;
485
486 table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
487 unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);
488 if (!net_eq(net, &init_net))
489 kfree(table);
490 }
491
492 static struct ctl_table_header *ip6_ctl_header;
493
ip6_frags_sysctl_register(void)494 static int ip6_frags_sysctl_register(void)
495 {
496 ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",
497 ip6_frags_ctl_table);
498 return ip6_ctl_header == NULL ? -ENOMEM : 0;
499 }
500
ip6_frags_sysctl_unregister(void)501 static void ip6_frags_sysctl_unregister(void)
502 {
503 unregister_net_sysctl_table(ip6_ctl_header);
504 }
505 #else
ip6_frags_ns_sysctl_register(struct net * net)506 static int ip6_frags_ns_sysctl_register(struct net *net)
507 {
508 return 0;
509 }
510
ip6_frags_ns_sysctl_unregister(struct net * net)511 static void ip6_frags_ns_sysctl_unregister(struct net *net)
512 {
513 }
514
ip6_frags_sysctl_register(void)515 static int ip6_frags_sysctl_register(void)
516 {
517 return 0;
518 }
519
ip6_frags_sysctl_unregister(void)520 static void ip6_frags_sysctl_unregister(void)
521 {
522 }
523 #endif
524
ipv6_frags_init_net(struct net * net)525 static int __net_init ipv6_frags_init_net(struct net *net)
526 {
527 int res;
528
529 res = fqdir_init(&net->ipv6.fqdir, &ip6_frags, net);
530 if (res < 0)
531 return res;
532
533 net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
534 net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
535 net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;
536
537 res = ip6_frags_ns_sysctl_register(net);
538 if (res < 0)
539 fqdir_exit(net->ipv6.fqdir);
540 return res;
541 }
542
ipv6_frags_pre_exit_net(struct net * net)543 static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
544 {
545 fqdir_pre_exit(net->ipv6.fqdir);
546 }
547
ipv6_frags_exit_net(struct net * net)548 static void __net_exit ipv6_frags_exit_net(struct net *net)
549 {
550 ip6_frags_ns_sysctl_unregister(net);
551 fqdir_exit(net->ipv6.fqdir);
552 }
553
554 static struct pernet_operations ip6_frags_ops = {
555 .init = ipv6_frags_init_net,
556 .pre_exit = ipv6_frags_pre_exit_net,
557 .exit = ipv6_frags_exit_net,
558 };
559
560 static const struct rhashtable_params ip6_rhash_params = {
561 .head_offset = offsetof(struct inet_frag_queue, node),
562 .hashfn = ip6frag_key_hashfn,
563 .obj_hashfn = ip6frag_obj_hashfn,
564 .obj_cmpfn = ip6frag_obj_cmpfn,
565 .automatic_shrinking = true,
566 };
567
ipv6_frag_init(void)568 int __init ipv6_frag_init(void)
569 {
570 int ret;
571
572 ip6_frags.constructor = ip6frag_init;
573 ip6_frags.destructor = NULL;
574 ip6_frags.qsize = sizeof(struct frag_queue);
575 ip6_frags.frag_expire = ip6_frag_expire;
576 ip6_frags.frags_cache_name = ip6_frag_cache_name;
577 ip6_frags.rhash_params = ip6_rhash_params;
578 ret = inet_frags_init(&ip6_frags);
579 if (ret)
580 goto out;
581
582 ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT);
583 if (ret)
584 goto err_protocol;
585
586 ret = ip6_frags_sysctl_register();
587 if (ret)
588 goto err_sysctl;
589
590 ret = register_pernet_subsys(&ip6_frags_ops);
591 if (ret)
592 goto err_pernet;
593
594 out:
595 return ret;
596
597 err_pernet:
598 ip6_frags_sysctl_unregister();
599 err_sysctl:
600 inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
601 err_protocol:
602 inet_frags_fini(&ip6_frags);
603 goto out;
604 }
605
ipv6_frag_exit(void)606 void ipv6_frag_exit(void)
607 {
608 ip6_frags_sysctl_unregister();
609 unregister_pernet_subsys(&ip6_frags_ops);
610 inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
611 inet_frags_fini(&ip6_frags);
612 }
613