xref: /openbmc/linux/net/ipv4/ip_fragment.c (revision f7d84fa7)
1 /*
2  * INET		An implementation of the TCP/IP protocol suite for the LINUX
3  *		operating system.  INET is implemented using the  BSD Socket
4  *		interface as the means of communication with the user level.
5  *
6  *		The IP fragmentation functionality.
7  *
8  * Authors:	Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
9  *		Alan Cox <alan@lxorguk.ukuu.org.uk>
10  *
11  * Fixes:
12  *		Alan Cox	:	Split from ip.c , see ip_input.c for history.
13  *		David S. Miller :	Begin massive cleanup...
14  *		Andi Kleen	:	Add sysctls.
15  *		xxxx		:	Overlapfrag bug.
16  *		Ultima          :       ip_expire() kernel panic.
17  *		Bill Hawes	:	Frag accounting and evictor fixes.
18  *		John McDonald	:	0 length frag bug.
19  *		Alexey Kuznetsov:	SMP races, threading, cleanup.
20  *		Patrick McHardy :	LRU queue of frag heads for evictor.
21  */
22 
23 #define pr_fmt(fmt) "IPv4: " fmt
24 
25 #include <linux/compiler.h>
26 #include <linux/module.h>
27 #include <linux/types.h>
28 #include <linux/mm.h>
29 #include <linux/jiffies.h>
30 #include <linux/skbuff.h>
31 #include <linux/list.h>
32 #include <linux/ip.h>
33 #include <linux/icmp.h>
34 #include <linux/netdevice.h>
35 #include <linux/jhash.h>
36 #include <linux/random.h>
37 #include <linux/slab.h>
38 #include <net/route.h>
39 #include <net/dst.h>
40 #include <net/sock.h>
41 #include <net/ip.h>
42 #include <net/icmp.h>
43 #include <net/checksum.h>
44 #include <net/inetpeer.h>
45 #include <net/inet_frag.h>
46 #include <linux/tcp.h>
47 #include <linux/udp.h>
48 #include <linux/inet.h>
49 #include <linux/netfilter_ipv4.h>
50 #include <net/inet_ecn.h>
51 #include <net/l3mdev.h>
52 
53 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
54  * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
55  * as well. Or notify me, at least. --ANK
56  */
57 static const char ip_frag_cache_name[] = "ip4-frags";
58 
59 struct ipfrag_skb_cb
60 {
61 	struct inet_skb_parm	h;
62 	int			offset;
63 };
64 
65 #define FRAG_CB(skb)	((struct ipfrag_skb_cb *)((skb)->cb))
66 
67 /* Describe an entry in the "incomplete datagrams" queue. */
68 struct ipq {
69 	struct inet_frag_queue q;
70 
71 	u32		user;
72 	__be32		saddr;
73 	__be32		daddr;
74 	__be16		id;
75 	u8		protocol;
76 	u8		ecn; /* RFC3168 support */
77 	u16		max_df_size; /* largest frag with DF set seen */
78 	int             iif;
79 	int             vif;   /* L3 master device index */
80 	unsigned int    rid;
81 	struct inet_peer *peer;
82 };
83 
84 static u8 ip4_frag_ecn(u8 tos)
85 {
86 	return 1 << (tos & INET_ECN_MASK);
87 }
88 
89 static struct inet_frags ip4_frags;
90 
91 int ip_frag_mem(struct net *net)
92 {
93 	return sum_frag_mem_limit(&net->ipv4.frags);
94 }
95 
96 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
97 			 struct net_device *dev);
98 
99 struct ip4_create_arg {
100 	struct iphdr *iph;
101 	u32 user;
102 	int vif;
103 };
104 
105 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
106 {
107 	net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
108 	return jhash_3words((__force u32)id << 16 | prot,
109 			    (__force u32)saddr, (__force u32)daddr,
110 			    ip4_frags.rnd);
111 }
112 
113 static unsigned int ip4_hashfn(const struct inet_frag_queue *q)
114 {
115 	const struct ipq *ipq;
116 
117 	ipq = container_of(q, struct ipq, q);
118 	return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
119 }
120 
121 static bool ip4_frag_match(const struct inet_frag_queue *q, const void *a)
122 {
123 	const struct ipq *qp;
124 	const struct ip4_create_arg *arg = a;
125 
126 	qp = container_of(q, struct ipq, q);
127 	return	qp->id == arg->iph->id &&
128 		qp->saddr == arg->iph->saddr &&
129 		qp->daddr == arg->iph->daddr &&
130 		qp->protocol == arg->iph->protocol &&
131 		qp->user == arg->user &&
132 		qp->vif == arg->vif;
133 }
134 
135 static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
136 {
137 	struct ipq *qp = container_of(q, struct ipq, q);
138 	struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
139 					       frags);
140 	struct net *net = container_of(ipv4, struct net, ipv4);
141 
142 	const struct ip4_create_arg *arg = a;
143 
144 	qp->protocol = arg->iph->protocol;
145 	qp->id = arg->iph->id;
146 	qp->ecn = ip4_frag_ecn(arg->iph->tos);
147 	qp->saddr = arg->iph->saddr;
148 	qp->daddr = arg->iph->daddr;
149 	qp->vif = arg->vif;
150 	qp->user = arg->user;
151 	qp->peer = q->net->max_dist ?
152 		inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, arg->vif, 1) :
153 		NULL;
154 }
155 
156 static void ip4_frag_free(struct inet_frag_queue *q)
157 {
158 	struct ipq *qp;
159 
160 	qp = container_of(q, struct ipq, q);
161 	if (qp->peer)
162 		inet_putpeer(qp->peer);
163 }
164 
165 
166 /* Destruction primitives. */
167 
168 static void ipq_put(struct ipq *ipq)
169 {
170 	inet_frag_put(&ipq->q, &ip4_frags);
171 }
172 
173 /* Kill ipq entry. It is not destroyed immediately,
174  * because caller (and someone more) holds reference count.
175  */
176 static void ipq_kill(struct ipq *ipq)
177 {
178 	inet_frag_kill(&ipq->q, &ip4_frags);
179 }
180 
181 static bool frag_expire_skip_icmp(u32 user)
182 {
183 	return user == IP_DEFRAG_AF_PACKET ||
184 	       ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
185 					 __IP_DEFRAG_CONNTRACK_IN_END) ||
186 	       ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
187 					 __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
188 }
189 
190 /*
191  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
192  */
193 static void ip_expire(unsigned long arg)
194 {
195 	struct ipq *qp;
196 	struct net *net;
197 
198 	qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
199 	net = container_of(qp->q.net, struct net, ipv4.frags);
200 
201 	rcu_read_lock();
202 	spin_lock(&qp->q.lock);
203 
204 	if (qp->q.flags & INET_FRAG_COMPLETE)
205 		goto out;
206 
207 	ipq_kill(qp);
208 	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
209 
210 	if (!inet_frag_evicting(&qp->q)) {
211 		struct sk_buff *clone, *head = qp->q.fragments;
212 		const struct iphdr *iph;
213 		int err;
214 
215 		__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
216 
217 		if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
218 			goto out;
219 
220 		head->dev = dev_get_by_index_rcu(net, qp->iif);
221 		if (!head->dev)
222 			goto out;
223 
224 
225 		/* skb has no dst, perform route lookup again */
226 		iph = ip_hdr(head);
227 		err = ip_route_input_noref(head, iph->daddr, iph->saddr,
228 					   iph->tos, head->dev);
229 		if (err)
230 			goto out;
231 
232 		/* Only an end host needs to send an ICMP
233 		 * "Fragment Reassembly Timeout" message, per RFC792.
234 		 */
235 		if (frag_expire_skip_icmp(qp->user) &&
236 		    (skb_rtable(head)->rt_type != RTN_LOCAL))
237 			goto out;
238 
239 		clone = skb_clone(head, GFP_ATOMIC);
240 
241 		/* Send an ICMP "Fragment Reassembly Timeout" message. */
242 		if (clone) {
243 			spin_unlock(&qp->q.lock);
244 			icmp_send(clone, ICMP_TIME_EXCEEDED,
245 				  ICMP_EXC_FRAGTIME, 0);
246 			consume_skb(clone);
247 			goto out_rcu_unlock;
248 		}
249 	}
250 out:
251 	spin_unlock(&qp->q.lock);
252 out_rcu_unlock:
253 	rcu_read_unlock();
254 	ipq_put(qp);
255 }
256 
257 /* Find the correct entry in the "incomplete datagrams" queue for
258  * this IP datagram, and create new one, if nothing is found.
259  */
260 static struct ipq *ip_find(struct net *net, struct iphdr *iph,
261 			   u32 user, int vif)
262 {
263 	struct inet_frag_queue *q;
264 	struct ip4_create_arg arg;
265 	unsigned int hash;
266 
267 	arg.iph = iph;
268 	arg.user = user;
269 	arg.vif = vif;
270 
271 	hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
272 
273 	q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
274 	if (IS_ERR_OR_NULL(q)) {
275 		inet_frag_maybe_warn_overflow(q, pr_fmt());
276 		return NULL;
277 	}
278 	return container_of(q, struct ipq, q);
279 }
280 
281 /* Is the fragment too far ahead to be part of ipq? */
282 static int ip_frag_too_far(struct ipq *qp)
283 {
284 	struct inet_peer *peer = qp->peer;
285 	unsigned int max = qp->q.net->max_dist;
286 	unsigned int start, end;
287 
288 	int rc;
289 
290 	if (!peer || !max)
291 		return 0;
292 
293 	start = qp->rid;
294 	end = atomic_inc_return(&peer->rid);
295 	qp->rid = end;
296 
297 	rc = qp->q.fragments && (end - start) > max;
298 
299 	if (rc) {
300 		struct net *net;
301 
302 		net = container_of(qp->q.net, struct net, ipv4.frags);
303 		__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
304 	}
305 
306 	return rc;
307 }
308 
309 static int ip_frag_reinit(struct ipq *qp)
310 {
311 	struct sk_buff *fp;
312 	unsigned int sum_truesize = 0;
313 
314 	if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
315 		atomic_inc(&qp->q.refcnt);
316 		return -ETIMEDOUT;
317 	}
318 
319 	fp = qp->q.fragments;
320 	do {
321 		struct sk_buff *xp = fp->next;
322 
323 		sum_truesize += fp->truesize;
324 		kfree_skb(fp);
325 		fp = xp;
326 	} while (fp);
327 	sub_frag_mem_limit(qp->q.net, sum_truesize);
328 
329 	qp->q.flags = 0;
330 	qp->q.len = 0;
331 	qp->q.meat = 0;
332 	qp->q.fragments = NULL;
333 	qp->q.fragments_tail = NULL;
334 	qp->iif = 0;
335 	qp->ecn = 0;
336 
337 	return 0;
338 }
339 
340 /* Add new segment to existing queue. */
341 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
342 {
343 	struct sk_buff *prev, *next;
344 	struct net_device *dev;
345 	unsigned int fragsize;
346 	int flags, offset;
347 	int ihl, end;
348 	int err = -ENOENT;
349 	u8 ecn;
350 
351 	if (qp->q.flags & INET_FRAG_COMPLETE)
352 		goto err;
353 
354 	if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
355 	    unlikely(ip_frag_too_far(qp)) &&
356 	    unlikely(err = ip_frag_reinit(qp))) {
357 		ipq_kill(qp);
358 		goto err;
359 	}
360 
361 	ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
362 	offset = ntohs(ip_hdr(skb)->frag_off);
363 	flags = offset & ~IP_OFFSET;
364 	offset &= IP_OFFSET;
365 	offset <<= 3;		/* offset is in 8-byte chunks */
366 	ihl = ip_hdrlen(skb);
367 
368 	/* Determine the position of this fragment. */
369 	end = offset + skb->len - skb_network_offset(skb) - ihl;
370 	err = -EINVAL;
371 
372 	/* Is this the final fragment? */
373 	if ((flags & IP_MF) == 0) {
374 		/* If we already have some bits beyond end
375 		 * or have different end, the segment is corrupted.
376 		 */
377 		if (end < qp->q.len ||
378 		    ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
379 			goto err;
380 		qp->q.flags |= INET_FRAG_LAST_IN;
381 		qp->q.len = end;
382 	} else {
383 		if (end&7) {
384 			end &= ~7;
385 			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
386 				skb->ip_summed = CHECKSUM_NONE;
387 		}
388 		if (end > qp->q.len) {
389 			/* Some bits beyond end -> corruption. */
390 			if (qp->q.flags & INET_FRAG_LAST_IN)
391 				goto err;
392 			qp->q.len = end;
393 		}
394 	}
395 	if (end == offset)
396 		goto err;
397 
398 	err = -ENOMEM;
399 	if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
400 		goto err;
401 
402 	err = pskb_trim_rcsum(skb, end - offset);
403 	if (err)
404 		goto err;
405 
406 	/* Find out which fragments are in front and at the back of us
407 	 * in the chain of fragments so far.  We must know where to put
408 	 * this fragment, right?
409 	 */
410 	prev = qp->q.fragments_tail;
411 	if (!prev || FRAG_CB(prev)->offset < offset) {
412 		next = NULL;
413 		goto found;
414 	}
415 	prev = NULL;
416 	for (next = qp->q.fragments; next != NULL; next = next->next) {
417 		if (FRAG_CB(next)->offset >= offset)
418 			break;	/* bingo! */
419 		prev = next;
420 	}
421 
422 found:
423 	/* We found where to put this one.  Check for overlap with
424 	 * preceding fragment, and, if needed, align things so that
425 	 * any overlaps are eliminated.
426 	 */
427 	if (prev) {
428 		int i = (FRAG_CB(prev)->offset + prev->len) - offset;
429 
430 		if (i > 0) {
431 			offset += i;
432 			err = -EINVAL;
433 			if (end <= offset)
434 				goto err;
435 			err = -ENOMEM;
436 			if (!pskb_pull(skb, i))
437 				goto err;
438 			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
439 				skb->ip_summed = CHECKSUM_NONE;
440 		}
441 	}
442 
443 	err = -ENOMEM;
444 
445 	while (next && FRAG_CB(next)->offset < end) {
446 		int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
447 
448 		if (i < next->len) {
449 			/* Eat head of the next overlapped fragment
450 			 * and leave the loop. The next ones cannot overlap.
451 			 */
452 			if (!pskb_pull(next, i))
453 				goto err;
454 			FRAG_CB(next)->offset += i;
455 			qp->q.meat -= i;
456 			if (next->ip_summed != CHECKSUM_UNNECESSARY)
457 				next->ip_summed = CHECKSUM_NONE;
458 			break;
459 		} else {
460 			struct sk_buff *free_it = next;
461 
462 			/* Old fragment is completely overridden with
463 			 * new one drop it.
464 			 */
465 			next = next->next;
466 
467 			if (prev)
468 				prev->next = next;
469 			else
470 				qp->q.fragments = next;
471 
472 			qp->q.meat -= free_it->len;
473 			sub_frag_mem_limit(qp->q.net, free_it->truesize);
474 			kfree_skb(free_it);
475 		}
476 	}
477 
478 	FRAG_CB(skb)->offset = offset;
479 
480 	/* Insert this fragment in the chain of fragments. */
481 	skb->next = next;
482 	if (!next)
483 		qp->q.fragments_tail = skb;
484 	if (prev)
485 		prev->next = skb;
486 	else
487 		qp->q.fragments = skb;
488 
489 	dev = skb->dev;
490 	if (dev) {
491 		qp->iif = dev->ifindex;
492 		skb->dev = NULL;
493 	}
494 	qp->q.stamp = skb->tstamp;
495 	qp->q.meat += skb->len;
496 	qp->ecn |= ecn;
497 	add_frag_mem_limit(qp->q.net, skb->truesize);
498 	if (offset == 0)
499 		qp->q.flags |= INET_FRAG_FIRST_IN;
500 
501 	fragsize = skb->len + ihl;
502 
503 	if (fragsize > qp->q.max_size)
504 		qp->q.max_size = fragsize;
505 
506 	if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
507 	    fragsize > qp->max_df_size)
508 		qp->max_df_size = fragsize;
509 
510 	if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
511 	    qp->q.meat == qp->q.len) {
512 		unsigned long orefdst = skb->_skb_refdst;
513 
514 		skb->_skb_refdst = 0UL;
515 		err = ip_frag_reasm(qp, prev, dev);
516 		skb->_skb_refdst = orefdst;
517 		return err;
518 	}
519 
520 	skb_dst_drop(skb);
521 	return -EINPROGRESS;
522 
523 err:
524 	kfree_skb(skb);
525 	return err;
526 }
527 
528 
529 /* Build a new IP datagram from all its fragments. */
530 
531 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
532 			 struct net_device *dev)
533 {
534 	struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
535 	struct iphdr *iph;
536 	struct sk_buff *fp, *head = qp->q.fragments;
537 	int len;
538 	int ihlen;
539 	int err;
540 	u8 ecn;
541 
542 	ipq_kill(qp);
543 
544 	ecn = ip_frag_ecn_table[qp->ecn];
545 	if (unlikely(ecn == 0xff)) {
546 		err = -EINVAL;
547 		goto out_fail;
548 	}
549 	/* Make the one we just received the head. */
550 	if (prev) {
551 		head = prev->next;
552 		fp = skb_clone(head, GFP_ATOMIC);
553 		if (!fp)
554 			goto out_nomem;
555 
556 		fp->next = head->next;
557 		if (!fp->next)
558 			qp->q.fragments_tail = fp;
559 		prev->next = fp;
560 
561 		skb_morph(head, qp->q.fragments);
562 		head->next = qp->q.fragments->next;
563 
564 		consume_skb(qp->q.fragments);
565 		qp->q.fragments = head;
566 	}
567 
568 	WARN_ON(!head);
569 	WARN_ON(FRAG_CB(head)->offset != 0);
570 
571 	/* Allocate a new buffer for the datagram. */
572 	ihlen = ip_hdrlen(head);
573 	len = ihlen + qp->q.len;
574 
575 	err = -E2BIG;
576 	if (len > 65535)
577 		goto out_oversize;
578 
579 	/* Head of list must not be cloned. */
580 	if (skb_unclone(head, GFP_ATOMIC))
581 		goto out_nomem;
582 
583 	/* If the first fragment is fragmented itself, we split
584 	 * it to two chunks: the first with data and paged part
585 	 * and the second, holding only fragments. */
586 	if (skb_has_frag_list(head)) {
587 		struct sk_buff *clone;
588 		int i, plen = 0;
589 
590 		clone = alloc_skb(0, GFP_ATOMIC);
591 		if (!clone)
592 			goto out_nomem;
593 		clone->next = head->next;
594 		head->next = clone;
595 		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
596 		skb_frag_list_init(head);
597 		for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
598 			plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
599 		clone->len = clone->data_len = head->data_len - plen;
600 		head->data_len -= clone->len;
601 		head->len -= clone->len;
602 		clone->csum = 0;
603 		clone->ip_summed = head->ip_summed;
604 		add_frag_mem_limit(qp->q.net, clone->truesize);
605 	}
606 
607 	skb_shinfo(head)->frag_list = head->next;
608 	skb_push(head, head->data - skb_network_header(head));
609 
610 	for (fp=head->next; fp; fp = fp->next) {
611 		head->data_len += fp->len;
612 		head->len += fp->len;
613 		if (head->ip_summed != fp->ip_summed)
614 			head->ip_summed = CHECKSUM_NONE;
615 		else if (head->ip_summed == CHECKSUM_COMPLETE)
616 			head->csum = csum_add(head->csum, fp->csum);
617 		head->truesize += fp->truesize;
618 	}
619 	sub_frag_mem_limit(qp->q.net, head->truesize);
620 
621 	head->next = NULL;
622 	head->dev = dev;
623 	head->tstamp = qp->q.stamp;
624 	IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
625 
626 	iph = ip_hdr(head);
627 	iph->tot_len = htons(len);
628 	iph->tos |= ecn;
629 
630 	/* When we set IP_DF on a refragmented skb we must also force a
631 	 * call to ip_fragment to avoid forwarding a DF-skb of size s while
632 	 * original sender only sent fragments of size f (where f < s).
633 	 *
634 	 * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
635 	 * frag seen to avoid sending tiny DF-fragments in case skb was built
636 	 * from one very small df-fragment and one large non-df frag.
637 	 */
638 	if (qp->max_df_size == qp->q.max_size) {
639 		IPCB(head)->flags |= IPSKB_FRAG_PMTU;
640 		iph->frag_off = htons(IP_DF);
641 	} else {
642 		iph->frag_off = 0;
643 	}
644 
645 	ip_send_check(iph);
646 
647 	__IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
648 	qp->q.fragments = NULL;
649 	qp->q.fragments_tail = NULL;
650 	return 0;
651 
652 out_nomem:
653 	net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
654 	err = -ENOMEM;
655 	goto out_fail;
656 out_oversize:
657 	net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
658 out_fail:
659 	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
660 	return err;
661 }
662 
663 /* Process an incoming IP datagram fragment. */
664 int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
665 {
666 	struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
667 	int vif = l3mdev_master_ifindex_rcu(dev);
668 	struct ipq *qp;
669 
670 	__IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
671 	skb_orphan(skb);
672 
673 	/* Lookup (or create) queue header */
674 	qp = ip_find(net, ip_hdr(skb), user, vif);
675 	if (qp) {
676 		int ret;
677 
678 		spin_lock(&qp->q.lock);
679 
680 		ret = ip_frag_queue(qp, skb);
681 
682 		spin_unlock(&qp->q.lock);
683 		ipq_put(qp);
684 		return ret;
685 	}
686 
687 	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
688 	kfree_skb(skb);
689 	return -ENOMEM;
690 }
691 EXPORT_SYMBOL(ip_defrag);
692 
693 struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
694 {
695 	struct iphdr iph;
696 	int netoff;
697 	u32 len;
698 
699 	if (skb->protocol != htons(ETH_P_IP))
700 		return skb;
701 
702 	netoff = skb_network_offset(skb);
703 
704 	if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
705 		return skb;
706 
707 	if (iph.ihl < 5 || iph.version != 4)
708 		return skb;
709 
710 	len = ntohs(iph.tot_len);
711 	if (skb->len < netoff + len || len < (iph.ihl * 4))
712 		return skb;
713 
714 	if (ip_is_fragment(&iph)) {
715 		skb = skb_share_check(skb, GFP_ATOMIC);
716 		if (skb) {
717 			if (!pskb_may_pull(skb, netoff + iph.ihl * 4))
718 				return skb;
719 			if (pskb_trim_rcsum(skb, netoff + len))
720 				return skb;
721 			memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
722 			if (ip_defrag(net, skb, user))
723 				return NULL;
724 			skb_clear_hash(skb);
725 		}
726 	}
727 	return skb;
728 }
729 EXPORT_SYMBOL(ip_check_defrag);
730 
731 #ifdef CONFIG_SYSCTL
732 static int zero;
733 
734 static struct ctl_table ip4_frags_ns_ctl_table[] = {
735 	{
736 		.procname	= "ipfrag_high_thresh",
737 		.data		= &init_net.ipv4.frags.high_thresh,
738 		.maxlen		= sizeof(int),
739 		.mode		= 0644,
740 		.proc_handler	= proc_dointvec_minmax,
741 		.extra1		= &init_net.ipv4.frags.low_thresh
742 	},
743 	{
744 		.procname	= "ipfrag_low_thresh",
745 		.data		= &init_net.ipv4.frags.low_thresh,
746 		.maxlen		= sizeof(int),
747 		.mode		= 0644,
748 		.proc_handler	= proc_dointvec_minmax,
749 		.extra1		= &zero,
750 		.extra2		= &init_net.ipv4.frags.high_thresh
751 	},
752 	{
753 		.procname	= "ipfrag_time",
754 		.data		= &init_net.ipv4.frags.timeout,
755 		.maxlen		= sizeof(int),
756 		.mode		= 0644,
757 		.proc_handler	= proc_dointvec_jiffies,
758 	},
759 	{
760 		.procname	= "ipfrag_max_dist",
761 		.data		= &init_net.ipv4.frags.max_dist,
762 		.maxlen		= sizeof(int),
763 		.mode		= 0644,
764 		.proc_handler	= proc_dointvec_minmax,
765 		.extra1		= &zero
766 	},
767 	{ }
768 };
769 
770 /* secret interval has been deprecated */
771 static int ip4_frags_secret_interval_unused;
772 static struct ctl_table ip4_frags_ctl_table[] = {
773 	{
774 		.procname	= "ipfrag_secret_interval",
775 		.data		= &ip4_frags_secret_interval_unused,
776 		.maxlen		= sizeof(int),
777 		.mode		= 0644,
778 		.proc_handler	= proc_dointvec_jiffies,
779 	},
780 	{ }
781 };
782 
783 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
784 {
785 	struct ctl_table *table;
786 	struct ctl_table_header *hdr;
787 
788 	table = ip4_frags_ns_ctl_table;
789 	if (!net_eq(net, &init_net)) {
790 		table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
791 		if (!table)
792 			goto err_alloc;
793 
794 		table[0].data = &net->ipv4.frags.high_thresh;
795 		table[0].extra1 = &net->ipv4.frags.low_thresh;
796 		table[0].extra2 = &init_net.ipv4.frags.high_thresh;
797 		table[1].data = &net->ipv4.frags.low_thresh;
798 		table[1].extra2 = &net->ipv4.frags.high_thresh;
799 		table[2].data = &net->ipv4.frags.timeout;
800 		table[3].data = &net->ipv4.frags.max_dist;
801 	}
802 
803 	hdr = register_net_sysctl(net, "net/ipv4", table);
804 	if (!hdr)
805 		goto err_reg;
806 
807 	net->ipv4.frags_hdr = hdr;
808 	return 0;
809 
810 err_reg:
811 	if (!net_eq(net, &init_net))
812 		kfree(table);
813 err_alloc:
814 	return -ENOMEM;
815 }
816 
817 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
818 {
819 	struct ctl_table *table;
820 
821 	table = net->ipv4.frags_hdr->ctl_table_arg;
822 	unregister_net_sysctl_table(net->ipv4.frags_hdr);
823 	kfree(table);
824 }
825 
826 static void __init ip4_frags_ctl_register(void)
827 {
828 	register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
829 }
830 #else
831 static int ip4_frags_ns_ctl_register(struct net *net)
832 {
833 	return 0;
834 }
835 
836 static void ip4_frags_ns_ctl_unregister(struct net *net)
837 {
838 }
839 
840 static void __init ip4_frags_ctl_register(void)
841 {
842 }
843 #endif
844 
845 static int __net_init ipv4_frags_init_net(struct net *net)
846 {
847 	int res;
848 
849 	/* Fragment cache limits.
850 	 *
851 	 * The fragment memory accounting code, (tries to) account for
852 	 * the real memory usage, by measuring both the size of frag
853 	 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
854 	 * and the SKB's truesize.
855 	 *
856 	 * A 64K fragment consumes 129736 bytes (44*2944)+200
857 	 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
858 	 *
859 	 * We will commit 4MB at one time. Should we cross that limit
860 	 * we will prune down to 3MB, making room for approx 8 big 64K
861 	 * fragments 8x128k.
862 	 */
863 	net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
864 	net->ipv4.frags.low_thresh  = 3 * 1024 * 1024;
865 	/*
866 	 * Important NOTE! Fragment queue must be destroyed before MSL expires.
867 	 * RFC791 is wrong proposing to prolongate timer each fragment arrival
868 	 * by TTL.
869 	 */
870 	net->ipv4.frags.timeout = IP_FRAG_TIME;
871 
872 	net->ipv4.frags.max_dist = 64;
873 
874 	res = inet_frags_init_net(&net->ipv4.frags);
875 	if (res)
876 		return res;
877 	res = ip4_frags_ns_ctl_register(net);
878 	if (res)
879 		inet_frags_uninit_net(&net->ipv4.frags);
880 	return res;
881 }
882 
883 static void __net_exit ipv4_frags_exit_net(struct net *net)
884 {
885 	ip4_frags_ns_ctl_unregister(net);
886 	inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
887 }
888 
889 static struct pernet_operations ip4_frags_ops = {
890 	.init = ipv4_frags_init_net,
891 	.exit = ipv4_frags_exit_net,
892 };
893 
894 void __init ipfrag_init(void)
895 {
896 	ip4_frags_ctl_register();
897 	register_pernet_subsys(&ip4_frags_ops);
898 	ip4_frags.hashfn = ip4_hashfn;
899 	ip4_frags.constructor = ip4_frag_init;
900 	ip4_frags.destructor = ip4_frag_free;
901 	ip4_frags.qsize = sizeof(struct ipq);
902 	ip4_frags.match = ip4_frag_match;
903 	ip4_frags.frag_expire = ip_expire;
904 	ip4_frags.frags_cache_name = ip_frag_cache_name;
905 	if (inet_frags_init(&ip4_frags))
906 		panic("IP: failed to allocate ip4_frags cache\n");
907 }
908