xref: /openbmc/linux/net/ipv6/reassembly.c (revision 2efdaaaf) 
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 
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 
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 *
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 
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  */
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 
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 	__be16 frag_off;
328 	int iif, offset;
329 	u8 nexthdr;
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(0xFFF9))) {
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 		return 1;
356 	}
357 
358 	/* RFC 8200, Section 4.5 Fragment Header:
359 	 * If the first fragment does not include all headers through an
360 	 * Upper-Layer header, then that fragment should be discarded and
361 	 * an ICMP Parameter Problem, Code 3, message should be sent to
362 	 * the source of the fragment, with the Pointer field set to zero.
363 	 */
364 	nexthdr = hdr->nexthdr;
365 	offset = ipv6_skip_exthdr(skb, skb_transport_offset(skb), &nexthdr, &frag_off);
366 	if (offset >= 0) {
367 		/* Check some common protocols' header */
368 		if (nexthdr == IPPROTO_TCP)
369 			offset += sizeof(struct tcphdr);
370 		else if (nexthdr == IPPROTO_UDP)
371 			offset += sizeof(struct udphdr);
372 		else if (nexthdr == IPPROTO_ICMPV6)
373 			offset += sizeof(struct icmp6hdr);
374 		else
375 			offset += 1;
376 
377 		if (!(frag_off & htons(IP6_OFFSET)) && offset > skb->len) {
378 			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
379 					IPSTATS_MIB_INHDRERRORS);
380 			icmpv6_param_prob(skb, ICMPV6_HDR_INCOMP, 0);
381 			return -1;
382 		}
383 	}
384 
385 	iif = skb->dev ? skb->dev->ifindex : 0;
386 	fq = fq_find(net, fhdr->identification, hdr, iif);
387 	if (fq) {
388 		u32 prob_offset = 0;
389 		int ret;
390 
391 		spin_lock(&fq->q.lock);
392 
393 		fq->iif = iif;
394 		ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff,
395 				     &prob_offset);
396 
397 		spin_unlock(&fq->q.lock);
398 		inet_frag_put(&fq->q);
399 		if (prob_offset) {
400 			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
401 					IPSTATS_MIB_INHDRERRORS);
402 			/* icmpv6_param_prob() calls kfree_skb(skb) */
403 			icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
404 		}
405 		return ret;
406 	}
407 
408 	__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
409 	kfree_skb(skb);
410 	return -1;
411 
412 fail_hdr:
413 	__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
414 			IPSTATS_MIB_INHDRERRORS);
415 	icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb));
416 	return -1;
417 }
418 
419 static const struct inet6_protocol frag_protocol = {
420 	.handler	=	ipv6_frag_rcv,
421 	.flags		=	INET6_PROTO_NOPOLICY,
422 };
423 
424 #ifdef CONFIG_SYSCTL
425 
426 static struct ctl_table ip6_frags_ns_ctl_table[] = {
427 	{
428 		.procname	= "ip6frag_high_thresh",
429 		.maxlen		= sizeof(unsigned long),
430 		.mode		= 0644,
431 		.proc_handler	= proc_doulongvec_minmax,
432 	},
433 	{
434 		.procname	= "ip6frag_low_thresh",
435 		.maxlen		= sizeof(unsigned long),
436 		.mode		= 0644,
437 		.proc_handler	= proc_doulongvec_minmax,
438 	},
439 	{
440 		.procname	= "ip6frag_time",
441 		.maxlen		= sizeof(int),
442 		.mode		= 0644,
443 		.proc_handler	= proc_dointvec_jiffies,
444 	},
445 	{ }
446 };
447 
448 /* secret interval has been deprecated */
449 static int ip6_frags_secret_interval_unused;
450 static struct ctl_table ip6_frags_ctl_table[] = {
451 	{
452 		.procname	= "ip6frag_secret_interval",
453 		.data		= &ip6_frags_secret_interval_unused,
454 		.maxlen		= sizeof(int),
455 		.mode		= 0644,
456 		.proc_handler	= proc_dointvec_jiffies,
457 	},
458 	{ }
459 };
460 
461 static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
462 {
463 	struct ctl_table *table;
464 	struct ctl_table_header *hdr;
465 
466 	table = ip6_frags_ns_ctl_table;
467 	if (!net_eq(net, &init_net)) {
468 		table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);
469 		if (!table)
470 			goto err_alloc;
471 
472 	}
473 	table[0].data	= &net->ipv6.fqdir->high_thresh;
474 	table[0].extra1	= &net->ipv6.fqdir->low_thresh;
475 	table[1].data	= &net->ipv6.fqdir->low_thresh;
476 	table[1].extra2	= &net->ipv6.fqdir->high_thresh;
477 	table[2].data	= &net->ipv6.fqdir->timeout;
478 
479 	hdr = register_net_sysctl(net, "net/ipv6", table);
480 	if (!hdr)
481 		goto err_reg;
482 
483 	net->ipv6.sysctl.frags_hdr = hdr;
484 	return 0;
485 
486 err_reg:
487 	if (!net_eq(net, &init_net))
488 		kfree(table);
489 err_alloc:
490 	return -ENOMEM;
491 }
492 
493 static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)
494 {
495 	struct ctl_table *table;
496 
497 	table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
498 	unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);
499 	if (!net_eq(net, &init_net))
500 		kfree(table);
501 }
502 
503 static struct ctl_table_header *ip6_ctl_header;
504 
505 static int ip6_frags_sysctl_register(void)
506 {
507 	ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",
508 			ip6_frags_ctl_table);
509 	return ip6_ctl_header == NULL ? -ENOMEM : 0;
510 }
511 
512 static void ip6_frags_sysctl_unregister(void)
513 {
514 	unregister_net_sysctl_table(ip6_ctl_header);
515 }
516 #else
517 static int ip6_frags_ns_sysctl_register(struct net *net)
518 {
519 	return 0;
520 }
521 
522 static void ip6_frags_ns_sysctl_unregister(struct net *net)
523 {
524 }
525 
526 static int ip6_frags_sysctl_register(void)
527 {
528 	return 0;
529 }
530 
531 static void ip6_frags_sysctl_unregister(void)
532 {
533 }
534 #endif
535 
536 static int __net_init ipv6_frags_init_net(struct net *net)
537 {
538 	int res;
539 
540 	res = fqdir_init(&net->ipv6.fqdir, &ip6_frags, net);
541 	if (res < 0)
542 		return res;
543 
544 	net->ipv6.fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
545 	net->ipv6.fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
546 	net->ipv6.fqdir->timeout = IPV6_FRAG_TIMEOUT;
547 
548 	res = ip6_frags_ns_sysctl_register(net);
549 	if (res < 0)
550 		fqdir_exit(net->ipv6.fqdir);
551 	return res;
552 }
553 
554 static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
555 {
556 	fqdir_pre_exit(net->ipv6.fqdir);
557 }
558 
559 static void __net_exit ipv6_frags_exit_net(struct net *net)
560 {
561 	ip6_frags_ns_sysctl_unregister(net);
562 	fqdir_exit(net->ipv6.fqdir);
563 }
564 
565 static struct pernet_operations ip6_frags_ops = {
566 	.init		= ipv6_frags_init_net,
567 	.pre_exit	= ipv6_frags_pre_exit_net,
568 	.exit		= ipv6_frags_exit_net,
569 };
570 
571 static const struct rhashtable_params ip6_rhash_params = {
572 	.head_offset		= offsetof(struct inet_frag_queue, node),
573 	.hashfn			= ip6frag_key_hashfn,
574 	.obj_hashfn		= ip6frag_obj_hashfn,
575 	.obj_cmpfn		= ip6frag_obj_cmpfn,
576 	.automatic_shrinking	= true,
577 };
578 
579 int __init ipv6_frag_init(void)
580 {
581 	int ret;
582 
583 	ip6_frags.constructor = ip6frag_init;
584 	ip6_frags.destructor = NULL;
585 	ip6_frags.qsize = sizeof(struct frag_queue);
586 	ip6_frags.frag_expire = ip6_frag_expire;
587 	ip6_frags.frags_cache_name = ip6_frag_cache_name;
588 	ip6_frags.rhash_params = ip6_rhash_params;
589 	ret = inet_frags_init(&ip6_frags);
590 	if (ret)
591 		goto out;
592 
593 	ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT);
594 	if (ret)
595 		goto err_protocol;
596 
597 	ret = ip6_frags_sysctl_register();
598 	if (ret)
599 		goto err_sysctl;
600 
601 	ret = register_pernet_subsys(&ip6_frags_ops);
602 	if (ret)
603 		goto err_pernet;
604 
605 out:
606 	return ret;
607 
608 err_pernet:
609 	ip6_frags_sysctl_unregister();
610 err_sysctl:
611 	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
612 err_protocol:
613 	inet_frags_fini(&ip6_frags);
614 	goto out;
615 }
616 
617 void ipv6_frag_exit(void)
618 {
619 	ip6_frags_sysctl_unregister();
620 	unregister_pernet_subsys(&ip6_frags_ops);
621 	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
622 	inet_frags_fini(&ip6_frags);
623 }
624