Version:  2.0.40 2.2.26 2.4.37 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2

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

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