ip_fragment.c revision 5a0e3ad6af8660be21ca98a971cd00f331318c05 
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#include <linux/compiler.h>
24#include <linux/module.h>
25#include <linux/types.h>
26#include <linux/mm.h>
27#include <linux/jiffies.h>
28#include <linux/skbuff.h>
29#include <linux/list.h>
30#include <linux/ip.h>
31#include <linux/icmp.h>
32#include <linux/netdevice.h>
33#include <linux/jhash.h>
34#include <linux/random.h>
35#include <linux/slab.h>
36#include <net/route.h>
37#include <net/dst.h>
38#include <net/sock.h>
39#include <net/ip.h>
40#include <net/icmp.h>
41#include <net/checksum.h>
42#include <net/inetpeer.h>
43#include <net/inet_frag.h>
44#include <linux/tcp.h>
45#include <linux/udp.h>
46#include <linux/inet.h>
47#include <linux/netfilter_ipv4.h>
48
49/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
50 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
51 * as well. Or notify me, at least. --ANK
52 */
53
54static int sysctl_ipfrag_max_dist __read_mostly = 64;
55
56struct ipfrag_skb_cb
57{
58	struct inet_skb_parm	h;
59	int			offset;
60};
61
62#define FRAG_CB(skb)	((struct ipfrag_skb_cb *)((skb)->cb))
63
64/* Describe an entry in the "incomplete datagrams" queue. */
65struct ipq {
66	struct inet_frag_queue q;
67
68	u32		user;
69	__be32		saddr;
70	__be32		daddr;
71	__be16		id;
72	u8		protocol;
73	int             iif;
74	unsigned int    rid;
75	struct inet_peer *peer;
76};
77
78static struct inet_frags ip4_frags;
79
80int ip_frag_nqueues(struct net *net)
81{
82	return net->ipv4.frags.nqueues;
83}
84
85int ip_frag_mem(struct net *net)
86{
87	return atomic_read(&net->ipv4.frags.mem);
88}
89
90static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
91			 struct net_device *dev);
92
93struct ip4_create_arg {
94	struct iphdr *iph;
95	u32 user;
96};
97
98static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
99{
100	return jhash_3words((__force u32)id << 16 | prot,
101			    (__force u32)saddr, (__force u32)daddr,
102			    ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
103}
104
105static unsigned int ip4_hashfn(struct inet_frag_queue *q)
106{
107	struct ipq *ipq;
108
109	ipq = container_of(q, struct ipq, q);
110	return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
111}
112
113static int ip4_frag_match(struct inet_frag_queue *q, void *a)
114{
115	struct ipq *qp;
116	struct ip4_create_arg *arg = a;
117
118	qp = container_of(q, struct ipq, q);
119	return (qp->id == arg->iph->id &&
120			qp->saddr == arg->iph->saddr &&
121			qp->daddr == arg->iph->daddr &&
122			qp->protocol == arg->iph->protocol &&
123			qp->user == arg->user);
124}
125
126/* Memory Tracking Functions. */
127static __inline__ void frag_kfree_skb(struct netns_frags *nf,
128		struct sk_buff *skb, int *work)
129{
130	if (work)
131		*work -= skb->truesize;
132	atomic_sub(skb->truesize, &nf->mem);
133	kfree_skb(skb);
134}
135
136static void ip4_frag_init(struct inet_frag_queue *q, void *a)
137{
138	struct ipq *qp = container_of(q, struct ipq, q);
139	struct ip4_create_arg *arg = a;
140
141	qp->protocol = arg->iph->protocol;
142	qp->id = arg->iph->id;
143	qp->saddr = arg->iph->saddr;
144	qp->daddr = arg->iph->daddr;
145	qp->user = arg->user;
146	qp->peer = sysctl_ipfrag_max_dist ?
147		inet_getpeer(arg->iph->saddr, 1) : NULL;
148}
149
150static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
151{
152	struct ipq *qp;
153
154	qp = container_of(q, struct ipq, q);
155	if (qp->peer)
156		inet_putpeer(qp->peer);
157}
158
159
160/* Destruction primitives. */
161
162static __inline__ void ipq_put(struct ipq *ipq)
163{
164	inet_frag_put(&ipq->q, &ip4_frags);
165}
166
167/* Kill ipq entry. It is not destroyed immediately,
168 * because caller (and someone more) holds reference count.
169 */
170static void ipq_kill(struct ipq *ipq)
171{
172	inet_frag_kill(&ipq->q, &ip4_frags);
173}
174
175/* Memory limiting on fragments.  Evictor trashes the oldest
176 * fragment queue until we are back under the threshold.
177 */
178static void ip_evictor(struct net *net)
179{
180	int evicted;
181
182	evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags);
183	if (evicted)
184		IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted);
185}
186
187/*
188 * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
189 */
190static void ip_expire(unsigned long arg)
191{
192	struct ipq *qp;
193	struct net *net;
194
195	qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
196	net = container_of(qp->q.net, struct net, ipv4.frags);
197
198	spin_lock(&qp->q.lock);
199
200	if (qp->q.last_in & INET_FRAG_COMPLETE)
201		goto out;
202
203	ipq_kill(qp);
204
205	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
206	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
207
208	if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
209		struct sk_buff *head = qp->q.fragments;
210
211		rcu_read_lock();
212		head->dev = dev_get_by_index_rcu(net, qp->iif);
213		if (!head->dev)
214			goto out_rcu_unlock;
215
216		/*
217		 * Only search router table for the head fragment,
218		 * when defraging timeout at PRE_ROUTING HOOK.
219		 */
220		if (qp->user == IP_DEFRAG_CONNTRACK_IN && !skb_dst(head)) {
221			const struct iphdr *iph = ip_hdr(head);
222			int err = ip_route_input(head, iph->daddr, iph->saddr,
223						 iph->tos, head->dev);
224			if (unlikely(err))
225				goto out_rcu_unlock;
226
227			/*
228			 * Only an end host needs to send an ICMP
229			 * "Fragment Reassembly Timeout" message, per RFC792.
230			 */
231			if (skb_rtable(head)->rt_type != RTN_LOCAL)
232				goto out_rcu_unlock;
233
234		}
235
236		/* Send an ICMP "Fragment Reassembly Timeout" message. */
237		icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
238out_rcu_unlock:
239		rcu_read_unlock();
240	}
241out:
242	spin_unlock(&qp->q.lock);
243	ipq_put(qp);
244}
245
246/* Find the correct entry in the "incomplete datagrams" queue for
247 * this IP datagram, and create new one, if nothing is found.
248 */
249static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
250{
251	struct inet_frag_queue *q;
252	struct ip4_create_arg arg;
253	unsigned int hash;
254
255	arg.iph = iph;
256	arg.user = user;
257
258	read_lock(&ip4_frags.lock);
259	hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
260
261	q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
262	if (q == NULL)
263		goto out_nomem;
264
265	return container_of(q, struct ipq, q);
266
267out_nomem:
268	LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
269	return NULL;
270}
271
272/* Is the fragment too far ahead to be part of ipq? */
273static inline int ip_frag_too_far(struct ipq *qp)
274{
275	struct inet_peer *peer = qp->peer;
276	unsigned int max = sysctl_ipfrag_max_dist;
277	unsigned int start, end;
278
279	int rc;
280
281	if (!peer || !max)
282		return 0;
283
284	start = qp->rid;
285	end = atomic_inc_return(&peer->rid);
286	qp->rid = end;
287
288	rc = qp->q.fragments && (end - start) > max;
289
290	if (rc) {
291		struct net *net;
292
293		net = container_of(qp->q.net, struct net, ipv4.frags);
294		IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
295	}
296
297	return rc;
298}
299
300static int ip_frag_reinit(struct ipq *qp)
301{
302	struct sk_buff *fp;
303
304	if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
305		atomic_inc(&qp->q.refcnt);
306		return -ETIMEDOUT;
307	}
308
309	fp = qp->q.fragments;
310	do {
311		struct sk_buff *xp = fp->next;
312		frag_kfree_skb(qp->q.net, fp, NULL);
313		fp = xp;
314	} while (fp);
315
316	qp->q.last_in = 0;
317	qp->q.len = 0;
318	qp->q.meat = 0;
319	qp->q.fragments = NULL;
320	qp->iif = 0;
321
322	return 0;
323}
324
325/* Add new segment to existing queue. */
326static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
327{
328	struct sk_buff *prev, *next;
329	struct net_device *dev;
330	int flags, offset;
331	int ihl, end;
332	int err = -ENOENT;
333
334	if (qp->q.last_in & INET_FRAG_COMPLETE)
335		goto err;
336
337	if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
338	    unlikely(ip_frag_too_far(qp)) &&
339	    unlikely(err = ip_frag_reinit(qp))) {
340		ipq_kill(qp);
341		goto err;
342	}
343
344	offset = ntohs(ip_hdr(skb)->frag_off);
345	flags = offset & ~IP_OFFSET;
346	offset &= IP_OFFSET;
347	offset <<= 3;		/* offset is in 8-byte chunks */
348	ihl = ip_hdrlen(skb);
349
350	/* Determine the position of this fragment. */
351	end = offset + skb->len - ihl;
352	err = -EINVAL;
353
354	/* Is this the final fragment? */
355	if ((flags & IP_MF) == 0) {
356		/* If we already have some bits beyond end
357		 * or have different end, the segment is corrrupted.
358		 */
359		if (end < qp->q.len ||
360		    ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len))
361			goto err;
362		qp->q.last_in |= INET_FRAG_LAST_IN;
363		qp->q.len = end;
364	} else {
365		if (end&7) {
366			end &= ~7;
367			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
368				skb->ip_summed = CHECKSUM_NONE;
369		}
370		if (end > qp->q.len) {
371			/* Some bits beyond end -> corruption. */
372			if (qp->q.last_in & INET_FRAG_LAST_IN)
373				goto err;
374			qp->q.len = end;
375		}
376	}
377	if (end == offset)
378		goto err;
379
380	err = -ENOMEM;
381	if (pskb_pull(skb, ihl) == NULL)
382		goto err;
383
384	err = pskb_trim_rcsum(skb, end - offset);
385	if (err)
386		goto err;
387
388	/* Find out which fragments are in front and at the back of us
389	 * in the chain of fragments so far.  We must know where to put
390	 * this fragment, right?
391	 */
392	prev = NULL;
393	for (next = qp->q.fragments; next != NULL; next = next->next) {
394		if (FRAG_CB(next)->offset >= offset)
395			break;	/* bingo! */
396		prev = next;
397	}
398
399	/* We found where to put this one.  Check for overlap with
400	 * preceding fragment, and, if needed, align things so that
401	 * any overlaps are eliminated.
402	 */
403	if (prev) {
404		int i = (FRAG_CB(prev)->offset + prev->len) - offset;
405
406		if (i > 0) {
407			offset += i;
408			err = -EINVAL;
409			if (end <= offset)
410				goto err;
411			err = -ENOMEM;
412			if (!pskb_pull(skb, i))
413				goto err;
414			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
415				skb->ip_summed = CHECKSUM_NONE;
416		}
417	}
418
419	err = -ENOMEM;
420
421	while (next && FRAG_CB(next)->offset < end) {
422		int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
423
424		if (i < next->len) {
425			/* Eat head of the next overlapped fragment
426			 * and leave the loop. The next ones cannot overlap.
427			 */
428			if (!pskb_pull(next, i))
429				goto err;
430			FRAG_CB(next)->offset += i;
431			qp->q.meat -= i;
432			if (next->ip_summed != CHECKSUM_UNNECESSARY)
433				next->ip_summed = CHECKSUM_NONE;
434			break;
435		} else {
436			struct sk_buff *free_it = next;
437
438			/* Old fragment is completely overridden with
439			 * new one drop it.
440			 */
441			next = next->next;
442
443			if (prev)
444				prev->next = next;
445			else
446				qp->q.fragments = next;
447
448			qp->q.meat -= free_it->len;
449			frag_kfree_skb(qp->q.net, free_it, NULL);
450		}
451	}
452
453	FRAG_CB(skb)->offset = offset;
454
455	/* Insert this fragment in the chain of fragments. */
456	skb->next = next;
457	if (prev)
458		prev->next = skb;
459	else
460		qp->q.fragments = skb;
461
462	dev = skb->dev;
463	if (dev) {
464		qp->iif = dev->ifindex;
465		skb->dev = NULL;
466	}
467	qp->q.stamp = skb->tstamp;
468	qp->q.meat += skb->len;
469	atomic_add(skb->truesize, &qp->q.net->mem);
470	if (offset == 0)
471		qp->q.last_in |= INET_FRAG_FIRST_IN;
472
473	if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
474	    qp->q.meat == qp->q.len)
475		return ip_frag_reasm(qp, prev, dev);
476
477	write_lock(&ip4_frags.lock);
478	list_move_tail(&qp->q.lru_list, &qp->q.net->lru_list);
479	write_unlock(&ip4_frags.lock);
480	return -EINPROGRESS;
481
482err:
483	kfree_skb(skb);
484	return err;
485}
486
487
488/* Build a new IP datagram from all its fragments. */
489
490static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
491			 struct net_device *dev)
492{
493	struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
494	struct iphdr *iph;
495	struct sk_buff *fp, *head = qp->q.fragments;
496	int len;
497	int ihlen;
498	int err;
499
500	ipq_kill(qp);
501
502	/* Make the one we just received the head. */
503	if (prev) {
504		head = prev->next;
505		fp = skb_clone(head, GFP_ATOMIC);
506		if (!fp)
507			goto out_nomem;
508
509		fp->next = head->next;
510		prev->next = fp;
511
512		skb_morph(head, qp->q.fragments);
513		head->next = qp->q.fragments->next;
514
515		kfree_skb(qp->q.fragments);
516		qp->q.fragments = head;
517	}
518
519	WARN_ON(head == NULL);
520	WARN_ON(FRAG_CB(head)->offset != 0);
521
522	/* Allocate a new buffer for the datagram. */
523	ihlen = ip_hdrlen(head);
524	len = ihlen + qp->q.len;
525
526	err = -E2BIG;
527	if (len > 65535)
528		goto out_oversize;
529
530	/* Head of list must not be cloned. */
531	if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
532		goto out_nomem;
533
534	/* If the first fragment is fragmented itself, we split
535	 * it to two chunks: the first with data and paged part
536	 * and the second, holding only fragments. */
537	if (skb_has_frags(head)) {
538		struct sk_buff *clone;
539		int i, plen = 0;
540
541		if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
542			goto out_nomem;
543		clone->next = head->next;
544		head->next = clone;
545		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
546		skb_frag_list_init(head);
547		for (i=0; i<skb_shinfo(head)->nr_frags; i++)
548			plen += skb_shinfo(head)->frags[i].size;
549		clone->len = clone->data_len = head->data_len - plen;
550		head->data_len -= clone->len;
551		head->len -= clone->len;
552		clone->csum = 0;
553		clone->ip_summed = head->ip_summed;
554		atomic_add(clone->truesize, &qp->q.net->mem);
555	}
556
557	skb_shinfo(head)->frag_list = head->next;
558	skb_push(head, head->data - skb_network_header(head));
559	atomic_sub(head->truesize, &qp->q.net->mem);
560
561	for (fp=head->next; fp; fp = fp->next) {
562		head->data_len += fp->len;
563		head->len += fp->len;
564		if (head->ip_summed != fp->ip_summed)
565			head->ip_summed = CHECKSUM_NONE;
566		else if (head->ip_summed == CHECKSUM_COMPLETE)
567			head->csum = csum_add(head->csum, fp->csum);
568		head->truesize += fp->truesize;
569		atomic_sub(fp->truesize, &qp->q.net->mem);
570	}
571
572	head->next = NULL;
573	head->dev = dev;
574	head->tstamp = qp->q.stamp;
575
576	iph = ip_hdr(head);
577	iph->frag_off = 0;
578	iph->tot_len = htons(len);
579	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
580	qp->q.fragments = NULL;
581	return 0;
582
583out_nomem:
584	LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
585			      "queue %p\n", qp);
586	err = -ENOMEM;
587	goto out_fail;
588out_oversize:
589	if (net_ratelimit())
590		printk(KERN_INFO "Oversized IP packet from %pI4.\n",
591			&qp->saddr);
592out_fail:
593	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
594	return err;
595}
596
597/* Process an incoming IP datagram fragment. */
598int ip_defrag(struct sk_buff *skb, u32 user)
599{
600	struct ipq *qp;
601	struct net *net;
602
603	net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev);
604	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
605
606	/* Start by cleaning up the memory. */
607	if (atomic_read(&net->ipv4.frags.mem) > net->ipv4.frags.high_thresh)
608		ip_evictor(net);
609
610	/* Lookup (or create) queue header */
611	if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
612		int ret;
613
614		spin_lock(&qp->q.lock);
615
616		ret = ip_frag_queue(qp, skb);
617
618		spin_unlock(&qp->q.lock);
619		ipq_put(qp);
620		return ret;
621	}
622
623	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
624	kfree_skb(skb);
625	return -ENOMEM;
626}
627
628#ifdef CONFIG_SYSCTL
629static int zero;
630
631static struct ctl_table ip4_frags_ns_ctl_table[] = {
632	{
633		.procname	= "ipfrag_high_thresh",
634		.data		= &init_net.ipv4.frags.high_thresh,
635		.maxlen		= sizeof(int),
636		.mode		= 0644,
637		.proc_handler	= proc_dointvec
638	},
639	{
640		.procname	= "ipfrag_low_thresh",
641		.data		= &init_net.ipv4.frags.low_thresh,
642		.maxlen		= sizeof(int),
643		.mode		= 0644,
644		.proc_handler	= proc_dointvec
645	},
646	{
647		.procname	= "ipfrag_time",
648		.data		= &init_net.ipv4.frags.timeout,
649		.maxlen		= sizeof(int),
650		.mode		= 0644,
651		.proc_handler	= proc_dointvec_jiffies,
652	},
653	{ }
654};
655
656static struct ctl_table ip4_frags_ctl_table[] = {
657	{
658		.procname	= "ipfrag_secret_interval",
659		.data		= &ip4_frags.secret_interval,
660		.maxlen		= sizeof(int),
661		.mode		= 0644,
662		.proc_handler	= proc_dointvec_jiffies,
663	},
664	{
665		.procname	= "ipfrag_max_dist",
666		.data		= &sysctl_ipfrag_max_dist,
667		.maxlen		= sizeof(int),
668		.mode		= 0644,
669		.proc_handler	= proc_dointvec_minmax,
670		.extra1		= &zero
671	},
672	{ }
673};
674
675static int __net_init ip4_frags_ns_ctl_register(struct net *net)
676{
677	struct ctl_table *table;
678	struct ctl_table_header *hdr;
679
680	table = ip4_frags_ns_ctl_table;
681	if (!net_eq(net, &init_net)) {
682		table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
683		if (table == NULL)
684			goto err_alloc;
685
686		table[0].data = &net->ipv4.frags.high_thresh;
687		table[1].data = &net->ipv4.frags.low_thresh;
688		table[2].data = &net->ipv4.frags.timeout;
689	}
690
691	hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table);
692	if (hdr == NULL)
693		goto err_reg;
694
695	net->ipv4.frags_hdr = hdr;
696	return 0;
697
698err_reg:
699	if (!net_eq(net, &init_net))
700		kfree(table);
701err_alloc:
702	return -ENOMEM;
703}
704
705static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
706{
707	struct ctl_table *table;
708
709	table = net->ipv4.frags_hdr->ctl_table_arg;
710	unregister_net_sysctl_table(net->ipv4.frags_hdr);
711	kfree(table);
712}
713
714static void ip4_frags_ctl_register(void)
715{
716	register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table);
717}
718#else
719static inline int ip4_frags_ns_ctl_register(struct net *net)
720{
721	return 0;
722}
723
724static inline void ip4_frags_ns_ctl_unregister(struct net *net)
725{
726}
727
728static inline void ip4_frags_ctl_register(void)
729{
730}
731#endif
732
733static int __net_init ipv4_frags_init_net(struct net *net)
734{
735	/*
736	 * Fragment cache limits. We will commit 256K at one time. Should we
737	 * cross that limit we will prune down to 192K. This should cope with
738	 * even the most extreme cases without allowing an attacker to
739	 * measurably harm machine performance.
740	 */
741	net->ipv4.frags.high_thresh = 256 * 1024;
742	net->ipv4.frags.low_thresh = 192 * 1024;
743	/*
744	 * Important NOTE! Fragment queue must be destroyed before MSL expires.
745	 * RFC791 is wrong proposing to prolongate timer each fragment arrival
746	 * by TTL.
747	 */
748	net->ipv4.frags.timeout = IP_FRAG_TIME;
749
750	inet_frags_init_net(&net->ipv4.frags);
751
752	return ip4_frags_ns_ctl_register(net);
753}
754
755static void __net_exit ipv4_frags_exit_net(struct net *net)
756{
757	ip4_frags_ns_ctl_unregister(net);
758	inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
759}
760
761static struct pernet_operations ip4_frags_ops = {
762	.init = ipv4_frags_init_net,
763	.exit = ipv4_frags_exit_net,
764};
765
766void __init ipfrag_init(void)
767{
768	ip4_frags_ctl_register();
769	register_pernet_subsys(&ip4_frags_ops);
770	ip4_frags.hashfn = ip4_hashfn;
771	ip4_frags.constructor = ip4_frag_init;
772	ip4_frags.destructor = ip4_frag_free;
773	ip4_frags.skb_free = NULL;
774	ip4_frags.qsize = sizeof(struct ipq);
775	ip4_frags.match = ip4_frag_match;
776	ip4_frags.frag_expire = ip_expire;
777	ip4_frags.secret_interval = 10 * 60 * HZ;
778	inet_frags_init(&ip4_frags);
779}
780
781EXPORT_SYMBOL(ip_defrag);
782