Version:  2.0.40 2.2.26 2.4.37 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16

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

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