[INET]: Move common fields from frag_queues in one place.
[linux-2.6.git] / net / ipv4 / ip_fragment.c
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  * Version:     $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
9  *
10  * Authors:     Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
11  *              Alan Cox <Alan.Cox@linux.org>
12  *
13  * Fixes:
14  *              Alan Cox        :       Split from ip.c , see ip_input.c for history.
15  *              David S. Miller :       Begin massive cleanup...
16  *              Andi Kleen      :       Add sysctls.
17  *              xxxx            :       Overlapfrag bug.
18  *              Ultima          :       ip_expire() kernel panic.
19  *              Bill Hawes      :       Frag accounting and evictor fixes.
20  *              John McDonald   :       0 length frag bug.
21  *              Alexey Kuznetsov:       SMP races, threading, cleanup.
22  *              Patrick McHardy :       LRU queue of frag heads for evictor.
23  */
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 <net/sock.h>
38 #include <net/ip.h>
39 #include <net/icmp.h>
40 #include <net/checksum.h>
41 #include <net/inetpeer.h>
42 #include <net/inet_frag.h>
43 #include <linux/tcp.h>
44 #include <linux/udp.h>
45 #include <linux/inet.h>
46 #include <linux/netfilter_ipv4.h>
47
48 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
49  * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
50  * as well. Or notify me, at least. --ANK
51  */
52
53 /* Fragment cache limits. We will commit 256K at one time. Should we
54  * cross that limit we will prune down to 192K. This should cope with
55  * even the most extreme cases without allowing an attacker to measurably
56  * harm machine performance.
57  */
58 int sysctl_ipfrag_high_thresh __read_mostly = 256*1024;
59 int sysctl_ipfrag_low_thresh __read_mostly = 192*1024;
60
61 int sysctl_ipfrag_max_dist __read_mostly = 64;
62
63 /* Important NOTE! Fragment queue must be destroyed before MSL expires.
64  * RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
65  */
66 int sysctl_ipfrag_time __read_mostly = IP_FRAG_TIME;
67
68 struct ipfrag_skb_cb
69 {
70         struct inet_skb_parm    h;
71         int                     offset;
72 };
73
74 #define FRAG_CB(skb)    ((struct ipfrag_skb_cb*)((skb)->cb))
75
76 /* Describe an entry in the "incomplete datagrams" queue. */
77 struct ipq {
78         struct inet_frag_queue q;
79
80         u32             user;
81         __be32          saddr;
82         __be32          daddr;
83         __be16          id;
84         u8              protocol;
85         int             iif;
86         unsigned int    rid;
87         struct inet_peer *peer;
88 };
89
90 /* Hash table. */
91
92 #define IPQ_HASHSZ      64
93
94 /* Per-bucket lock is easy to add now. */
95 static struct hlist_head ipq_hash[IPQ_HASHSZ];
96 static DEFINE_RWLOCK(ipfrag_lock);
97 static u32 ipfrag_hash_rnd;
98 static LIST_HEAD(ipq_lru_list);
99 int ip_frag_nqueues = 0;
100
101 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
102                          struct net_device *dev);
103
104 static __inline__ void __ipq_unlink(struct ipq *qp)
105 {
106         hlist_del(&qp->q.list);
107         list_del(&qp->q.lru_list);
108         ip_frag_nqueues--;
109 }
110
111 static __inline__ void ipq_unlink(struct ipq *ipq)
112 {
113         write_lock(&ipfrag_lock);
114         __ipq_unlink(ipq);
115         write_unlock(&ipfrag_lock);
116 }
117
118 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
119 {
120         return jhash_3words((__force u32)id << 16 | prot,
121                             (__force u32)saddr, (__force u32)daddr,
122                             ipfrag_hash_rnd) & (IPQ_HASHSZ - 1);
123 }
124
125 static struct timer_list ipfrag_secret_timer;
126 int sysctl_ipfrag_secret_interval __read_mostly = 10 * 60 * HZ;
127
128 static void ipfrag_secret_rebuild(unsigned long dummy)
129 {
130         unsigned long now = jiffies;
131         int i;
132
133         write_lock(&ipfrag_lock);
134         get_random_bytes(&ipfrag_hash_rnd, sizeof(u32));
135         for (i = 0; i < IPQ_HASHSZ; i++) {
136                 struct ipq *q;
137                 struct hlist_node *p, *n;
138
139                 hlist_for_each_entry_safe(q, p, n, &ipq_hash[i], q.list) {
140                         unsigned int hval = ipqhashfn(q->id, q->saddr,
141                                                       q->daddr, q->protocol);
142
143                         if (hval != i) {
144                                 hlist_del(&q->q.list);
145
146                                 /* Relink to new hash chain. */
147                                 hlist_add_head(&q->q.list, &ipq_hash[hval]);
148                         }
149                 }
150         }
151         write_unlock(&ipfrag_lock);
152
153         mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval);
154 }
155
156 atomic_t ip_frag_mem = ATOMIC_INIT(0);  /* Memory used for fragments */
157
158 /* Memory Tracking Functions. */
159 static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
160 {
161         if (work)
162                 *work -= skb->truesize;
163         atomic_sub(skb->truesize, &ip_frag_mem);
164         kfree_skb(skb);
165 }
166
167 static __inline__ void frag_free_queue(struct ipq *qp, int *work)
168 {
169         if (work)
170                 *work -= sizeof(struct ipq);
171         atomic_sub(sizeof(struct ipq), &ip_frag_mem);
172         kfree(qp);
173 }
174
175 static __inline__ struct ipq *frag_alloc_queue(void)
176 {
177         struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC);
178
179         if (!qp)
180                 return NULL;
181         atomic_add(sizeof(struct ipq), &ip_frag_mem);
182         return qp;
183 }
184
185
186 /* Destruction primitives. */
187
188 /* Complete destruction of ipq. */
189 static void ip_frag_destroy(struct ipq *qp, int *work)
190 {
191         struct sk_buff *fp;
192
193         BUG_TRAP(qp->q.last_in&COMPLETE);
194         BUG_TRAP(del_timer(&qp->q.timer) == 0);
195
196         if (qp->peer)
197                 inet_putpeer(qp->peer);
198
199         /* Release all fragment data. */
200         fp = qp->q.fragments;
201         while (fp) {
202                 struct sk_buff *xp = fp->next;
203
204                 frag_kfree_skb(fp, work);
205                 fp = xp;
206         }
207
208         /* Finally, release the queue descriptor itself. */
209         frag_free_queue(qp, work);
210 }
211
212 static __inline__ void ipq_put(struct ipq *ipq, int *work)
213 {
214         if (atomic_dec_and_test(&ipq->q.refcnt))
215                 ip_frag_destroy(ipq, work);
216 }
217
218 /* Kill ipq entry. It is not destroyed immediately,
219  * because caller (and someone more) holds reference count.
220  */
221 static void ipq_kill(struct ipq *ipq)
222 {
223         if (del_timer(&ipq->q.timer))
224                 atomic_dec(&ipq->q.refcnt);
225
226         if (!(ipq->q.last_in & COMPLETE)) {
227                 ipq_unlink(ipq);
228                 atomic_dec(&ipq->q.refcnt);
229                 ipq->q.last_in |= COMPLETE;
230         }
231 }
232
233 /* Memory limiting on fragments.  Evictor trashes the oldest
234  * fragment queue until we are back under the threshold.
235  */
236 static void ip_evictor(void)
237 {
238         struct ipq *qp;
239         struct list_head *tmp;
240         int work;
241
242         work = atomic_read(&ip_frag_mem) - sysctl_ipfrag_low_thresh;
243         if (work <= 0)
244                 return;
245
246         while (work > 0) {
247                 read_lock(&ipfrag_lock);
248                 if (list_empty(&ipq_lru_list)) {
249                         read_unlock(&ipfrag_lock);
250                         return;
251                 }
252                 tmp = ipq_lru_list.next;
253                 qp = list_entry(tmp, struct ipq, q.lru_list);
254                 atomic_inc(&qp->q.refcnt);
255                 read_unlock(&ipfrag_lock);
256
257                 spin_lock(&qp->q.lock);
258                 if (!(qp->q.last_in&COMPLETE))
259                         ipq_kill(qp);
260                 spin_unlock(&qp->q.lock);
261
262                 ipq_put(qp, &work);
263                 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
264         }
265 }
266
267 /*
268  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
269  */
270 static void ip_expire(unsigned long arg)
271 {
272         struct ipq *qp = (struct ipq *) arg;
273
274         spin_lock(&qp->q.lock);
275
276         if (qp->q.last_in & COMPLETE)
277                 goto out;
278
279         ipq_kill(qp);
280
281         IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
282         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
283
284         if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) {
285                 struct sk_buff *head = qp->q.fragments;
286                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
287                 if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {
288                         icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
289                         dev_put(head->dev);
290                 }
291         }
292 out:
293         spin_unlock(&qp->q.lock);
294         ipq_put(qp, NULL);
295 }
296
297 /* Creation primitives. */
298
299 static struct ipq *ip_frag_intern(struct ipq *qp_in)
300 {
301         struct ipq *qp;
302 #ifdef CONFIG_SMP
303         struct hlist_node *n;
304 #endif
305         unsigned int hash;
306
307         write_lock(&ipfrag_lock);
308         hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr,
309                          qp_in->protocol);
310 #ifdef CONFIG_SMP
311         /* With SMP race we have to recheck hash table, because
312          * such entry could be created on other cpu, while we
313          * promoted read lock to write lock.
314          */
315         hlist_for_each_entry(qp, n, &ipq_hash[hash], q.list) {
316                 if (qp->id == qp_in->id         &&
317                     qp->saddr == qp_in->saddr   &&
318                     qp->daddr == qp_in->daddr   &&
319                     qp->protocol == qp_in->protocol &&
320                     qp->user == qp_in->user) {
321                         atomic_inc(&qp->q.refcnt);
322                         write_unlock(&ipfrag_lock);
323                         qp_in->q.last_in |= COMPLETE;
324                         ipq_put(qp_in, NULL);
325                         return qp;
326                 }
327         }
328 #endif
329         qp = qp_in;
330
331         if (!mod_timer(&qp->q.timer, jiffies + sysctl_ipfrag_time))
332                 atomic_inc(&qp->q.refcnt);
333
334         atomic_inc(&qp->q.refcnt);
335         hlist_add_head(&qp->q.list, &ipq_hash[hash]);
336         INIT_LIST_HEAD(&qp->q.lru_list);
337         list_add_tail(&qp->q.lru_list, &ipq_lru_list);
338         ip_frag_nqueues++;
339         write_unlock(&ipfrag_lock);
340         return qp;
341 }
342
343 /* Add an entry to the 'ipq' queue for a newly received IP datagram. */
344 static struct ipq *ip_frag_create(struct iphdr *iph, u32 user)
345 {
346         struct ipq *qp;
347
348         if ((qp = frag_alloc_queue()) == NULL)
349                 goto out_nomem;
350
351         qp->protocol = iph->protocol;
352         qp->q.last_in = 0;
353         qp->id = iph->id;
354         qp->saddr = iph->saddr;
355         qp->daddr = iph->daddr;
356         qp->user = user;
357         qp->q.len = 0;
358         qp->q.meat = 0;
359         qp->q.fragments = NULL;
360         qp->iif = 0;
361         qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
362
363         /* Initialize a timer for this entry. */
364         init_timer(&qp->q.timer);
365         qp->q.timer.data = (unsigned long) qp;  /* pointer to queue     */
366         qp->q.timer.function = ip_expire;               /* expire function      */
367         spin_lock_init(&qp->q.lock);
368         atomic_set(&qp->q.refcnt, 1);
369
370         return ip_frag_intern(qp);
371
372 out_nomem:
373         LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
374         return NULL;
375 }
376
377 /* Find the correct entry in the "incomplete datagrams" queue for
378  * this IP datagram, and create new one, if nothing is found.
379  */
380 static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
381 {
382         __be16 id = iph->id;
383         __be32 saddr = iph->saddr;
384         __be32 daddr = iph->daddr;
385         __u8 protocol = iph->protocol;
386         unsigned int hash;
387         struct ipq *qp;
388         struct hlist_node *n;
389
390         read_lock(&ipfrag_lock);
391         hash = ipqhashfn(id, saddr, daddr, protocol);
392         hlist_for_each_entry(qp, n, &ipq_hash[hash], q.list) {
393                 if (qp->id == id                &&
394                     qp->saddr == saddr  &&
395                     qp->daddr == daddr  &&
396                     qp->protocol == protocol &&
397                     qp->user == user) {
398                         atomic_inc(&qp->q.refcnt);
399                         read_unlock(&ipfrag_lock);
400                         return qp;
401                 }
402         }
403         read_unlock(&ipfrag_lock);
404
405         return ip_frag_create(iph, user);
406 }
407
408 /* Is the fragment too far ahead to be part of ipq? */
409 static inline int ip_frag_too_far(struct ipq *qp)
410 {
411         struct inet_peer *peer = qp->peer;
412         unsigned int max = sysctl_ipfrag_max_dist;
413         unsigned int start, end;
414
415         int rc;
416
417         if (!peer || !max)
418                 return 0;
419
420         start = qp->rid;
421         end = atomic_inc_return(&peer->rid);
422         qp->rid = end;
423
424         rc = qp->q.fragments && (end - start) > max;
425
426         if (rc) {
427                 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
428         }
429
430         return rc;
431 }
432
433 static int ip_frag_reinit(struct ipq *qp)
434 {
435         struct sk_buff *fp;
436
437         if (!mod_timer(&qp->q.timer, jiffies + sysctl_ipfrag_time)) {
438                 atomic_inc(&qp->q.refcnt);
439                 return -ETIMEDOUT;
440         }
441
442         fp = qp->q.fragments;
443         do {
444                 struct sk_buff *xp = fp->next;
445                 frag_kfree_skb(fp, NULL);
446                 fp = xp;
447         } while (fp);
448
449         qp->q.last_in = 0;
450         qp->q.len = 0;
451         qp->q.meat = 0;
452         qp->q.fragments = NULL;
453         qp->iif = 0;
454
455         return 0;
456 }
457
458 /* Add new segment to existing queue. */
459 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
460 {
461         struct sk_buff *prev, *next;
462         struct net_device *dev;
463         int flags, offset;
464         int ihl, end;
465         int err = -ENOENT;
466
467         if (qp->q.last_in & COMPLETE)
468                 goto err;
469
470         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
471             unlikely(ip_frag_too_far(qp)) &&
472             unlikely(err = ip_frag_reinit(qp))) {
473                 ipq_kill(qp);
474                 goto err;
475         }
476
477         offset = ntohs(ip_hdr(skb)->frag_off);
478         flags = offset & ~IP_OFFSET;
479         offset &= IP_OFFSET;
480         offset <<= 3;           /* offset is in 8-byte chunks */
481         ihl = ip_hdrlen(skb);
482
483         /* Determine the position of this fragment. */
484         end = offset + skb->len - ihl;
485         err = -EINVAL;
486
487         /* Is this the final fragment? */
488         if ((flags & IP_MF) == 0) {
489                 /* If we already have some bits beyond end
490                  * or have different end, the segment is corrrupted.
491                  */
492                 if (end < qp->q.len ||
493                     ((qp->q.last_in & LAST_IN) && end != qp->q.len))
494                         goto err;
495                 qp->q.last_in |= LAST_IN;
496                 qp->q.len = end;
497         } else {
498                 if (end&7) {
499                         end &= ~7;
500                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
501                                 skb->ip_summed = CHECKSUM_NONE;
502                 }
503                 if (end > qp->q.len) {
504                         /* Some bits beyond end -> corruption. */
505                         if (qp->q.last_in & LAST_IN)
506                                 goto err;
507                         qp->q.len = end;
508                 }
509         }
510         if (end == offset)
511                 goto err;
512
513         err = -ENOMEM;
514         if (pskb_pull(skb, ihl) == NULL)
515                 goto err;
516
517         err = pskb_trim_rcsum(skb, end - offset);
518         if (err)
519                 goto err;
520
521         /* Find out which fragments are in front and at the back of us
522          * in the chain of fragments so far.  We must know where to put
523          * this fragment, right?
524          */
525         prev = NULL;
526         for (next = qp->q.fragments; next != NULL; next = next->next) {
527                 if (FRAG_CB(next)->offset >= offset)
528                         break;  /* bingo! */
529                 prev = next;
530         }
531
532         /* We found where to put this one.  Check for overlap with
533          * preceding fragment, and, if needed, align things so that
534          * any overlaps are eliminated.
535          */
536         if (prev) {
537                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
538
539                 if (i > 0) {
540                         offset += i;
541                         err = -EINVAL;
542                         if (end <= offset)
543                                 goto err;
544                         err = -ENOMEM;
545                         if (!pskb_pull(skb, i))
546                                 goto err;
547                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
548                                 skb->ip_summed = CHECKSUM_NONE;
549                 }
550         }
551
552         err = -ENOMEM;
553
554         while (next && FRAG_CB(next)->offset < end) {
555                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
556
557                 if (i < next->len) {
558                         /* Eat head of the next overlapped fragment
559                          * and leave the loop. The next ones cannot overlap.
560                          */
561                         if (!pskb_pull(next, i))
562                                 goto err;
563                         FRAG_CB(next)->offset += i;
564                         qp->q.meat -= i;
565                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
566                                 next->ip_summed = CHECKSUM_NONE;
567                         break;
568                 } else {
569                         struct sk_buff *free_it = next;
570
571                         /* Old fragment is completely overridden with
572                          * new one drop it.
573                          */
574                         next = next->next;
575
576                         if (prev)
577                                 prev->next = next;
578                         else
579                                 qp->q.fragments = next;
580
581                         qp->q.meat -= free_it->len;
582                         frag_kfree_skb(free_it, NULL);
583                 }
584         }
585
586         FRAG_CB(skb)->offset = offset;
587
588         /* Insert this fragment in the chain of fragments. */
589         skb->next = next;
590         if (prev)
591                 prev->next = skb;
592         else
593                 qp->q.fragments = skb;
594
595         dev = skb->dev;
596         if (dev) {
597                 qp->iif = dev->ifindex;
598                 skb->dev = NULL;
599         }
600         qp->q.stamp = skb->tstamp;
601         qp->q.meat += skb->len;
602         atomic_add(skb->truesize, &ip_frag_mem);
603         if (offset == 0)
604                 qp->q.last_in |= FIRST_IN;
605
606         if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len)
607                 return ip_frag_reasm(qp, prev, dev);
608
609         write_lock(&ipfrag_lock);
610         list_move_tail(&qp->q.lru_list, &ipq_lru_list);
611         write_unlock(&ipfrag_lock);
612         return -EINPROGRESS;
613
614 err:
615         kfree_skb(skb);
616         return err;
617 }
618
619
620 /* Build a new IP datagram from all its fragments. */
621
622 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
623                          struct net_device *dev)
624 {
625         struct iphdr *iph;
626         struct sk_buff *fp, *head = qp->q.fragments;
627         int len;
628         int ihlen;
629         int err;
630
631         ipq_kill(qp);
632
633         /* Make the one we just received the head. */
634         if (prev) {
635                 head = prev->next;
636                 fp = skb_clone(head, GFP_ATOMIC);
637
638                 if (!fp)
639                         goto out_nomem;
640
641                 fp->next = head->next;
642                 prev->next = fp;
643
644                 skb_morph(head, qp->q.fragments);
645                 head->next = qp->q.fragments->next;
646
647                 kfree_skb(qp->q.fragments);
648                 qp->q.fragments = head;
649         }
650
651         BUG_TRAP(head != NULL);
652         BUG_TRAP(FRAG_CB(head)->offset == 0);
653
654         /* Allocate a new buffer for the datagram. */
655         ihlen = ip_hdrlen(head);
656         len = ihlen + qp->q.len;
657
658         err = -E2BIG;
659         if (len > 65535)
660                 goto out_oversize;
661
662         /* Head of list must not be cloned. */
663         err = -ENOMEM;
664         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
665                 goto out_nomem;
666
667         /* If the first fragment is fragmented itself, we split
668          * it to two chunks: the first with data and paged part
669          * and the second, holding only fragments. */
670         if (skb_shinfo(head)->frag_list) {
671                 struct sk_buff *clone;
672                 int i, plen = 0;
673
674                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
675                         goto out_nomem;
676                 clone->next = head->next;
677                 head->next = clone;
678                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
679                 skb_shinfo(head)->frag_list = NULL;
680                 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
681                         plen += skb_shinfo(head)->frags[i].size;
682                 clone->len = clone->data_len = head->data_len - plen;
683                 head->data_len -= clone->len;
684                 head->len -= clone->len;
685                 clone->csum = 0;
686                 clone->ip_summed = head->ip_summed;
687                 atomic_add(clone->truesize, &ip_frag_mem);
688         }
689
690         skb_shinfo(head)->frag_list = head->next;
691         skb_push(head, head->data - skb_network_header(head));
692         atomic_sub(head->truesize, &ip_frag_mem);
693
694         for (fp=head->next; fp; fp = fp->next) {
695                 head->data_len += fp->len;
696                 head->len += fp->len;
697                 if (head->ip_summed != fp->ip_summed)
698                         head->ip_summed = CHECKSUM_NONE;
699                 else if (head->ip_summed == CHECKSUM_COMPLETE)
700                         head->csum = csum_add(head->csum, fp->csum);
701                 head->truesize += fp->truesize;
702                 atomic_sub(fp->truesize, &ip_frag_mem);
703         }
704
705         head->next = NULL;
706         head->dev = dev;
707         head->tstamp = qp->q.stamp;
708
709         iph = ip_hdr(head);
710         iph->frag_off = 0;
711         iph->tot_len = htons(len);
712         IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
713         qp->q.fragments = NULL;
714         return 0;
715
716 out_nomem:
717         LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
718                               "queue %p\n", qp);
719         goto out_fail;
720 out_oversize:
721         if (net_ratelimit())
722                 printk(KERN_INFO
723                         "Oversized IP packet from %d.%d.%d.%d.\n",
724                         NIPQUAD(qp->saddr));
725 out_fail:
726         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
727         return err;
728 }
729
730 /* Process an incoming IP datagram fragment. */
731 int ip_defrag(struct sk_buff *skb, u32 user)
732 {
733         struct ipq *qp;
734
735         IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
736
737         /* Start by cleaning up the memory. */
738         if (atomic_read(&ip_frag_mem) > sysctl_ipfrag_high_thresh)
739                 ip_evictor();
740
741         /* Lookup (or create) queue header */
742         if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {
743                 int ret;
744
745                 spin_lock(&qp->q.lock);
746
747                 ret = ip_frag_queue(qp, skb);
748
749                 spin_unlock(&qp->q.lock);
750                 ipq_put(qp, NULL);
751                 return ret;
752         }
753
754         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
755         kfree_skb(skb);
756         return -ENOMEM;
757 }
758
759 void __init ipfrag_init(void)
760 {
761         ipfrag_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
762                                  (jiffies ^ (jiffies >> 6)));
763
764         init_timer(&ipfrag_secret_timer);
765         ipfrag_secret_timer.function = ipfrag_secret_rebuild;
766         ipfrag_secret_timer.expires = jiffies + sysctl_ipfrag_secret_interval;
767         add_timer(&ipfrag_secret_timer);
768 }
769
770 EXPORT_SYMBOL(ip_defrag);