Version:  2.0.40 2.2.26 2.4.37 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 3.17

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         int             iif;
 79         unsigned int    rid;
 80         struct inet_peer *peer;
 81 };
 82 
 83 static inline u8 ip4_frag_ecn(u8 tos)
 84 {
 85         return 1 << (tos & INET_ECN_MASK);
 86 }
 87 
 88 static struct inet_frags ip4_frags;
 89 
 90 int ip_frag_mem(struct net *net)
 91 {
 92         return sum_frag_mem_limit(&net->ipv4.frags);
 93 }
 94 
 95 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 96                          struct net_device *dev);
 97 
 98 struct ip4_create_arg {
 99         struct iphdr *iph;
100         u32 user;
101 };
102 
103 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
104 {
105         net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
106         return jhash_3words((__force u32)id << 16 | prot,
107                             (__force u32)saddr, (__force u32)daddr,
108                             ip4_frags.rnd);
109 }
110 
111 static unsigned int ip4_hashfn(const struct inet_frag_queue *q)
112 {
113         const struct ipq *ipq;
114 
115         ipq = container_of(q, struct ipq, q);
116         return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
117 }
118 
119 static bool ip4_frag_match(const struct inet_frag_queue *q, const void *a)
120 {
121         const struct ipq *qp;
122         const struct ip4_create_arg *arg = a;
123 
124         qp = container_of(q, struct ipq, q);
125         return  qp->id == arg->iph->id &&
126                 qp->saddr == arg->iph->saddr &&
127                 qp->daddr == arg->iph->daddr &&
128                 qp->protocol == arg->iph->protocol &&
129                 qp->user == arg->user;
130 }
131 
132 static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
133 {
134         struct ipq *qp = container_of(q, struct ipq, q);
135         struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
136                                                frags);
137         struct net *net = container_of(ipv4, struct net, ipv4);
138 
139         const struct ip4_create_arg *arg = a;
140 
141         qp->protocol = arg->iph->protocol;
142         qp->id = arg->iph->id;
143         qp->ecn = ip4_frag_ecn(arg->iph->tos);
144         qp->saddr = arg->iph->saddr;
145         qp->daddr = arg->iph->daddr;
146         qp->user = arg->user;
147         qp->peer = sysctl_ipfrag_max_dist ?
148                 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, 1) : NULL;
149 }
150 
151 static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
152 {
153         struct ipq *qp;
154 
155         qp = container_of(q, struct ipq, q);
156         if (qp->peer)
157                 inet_putpeer(qp->peer);
158 }
159 
160 
161 /* Destruction primitives. */
162 
163 static __inline__ void ipq_put(struct ipq *ipq)
164 {
165         inet_frag_put(&ipq->q, &ip4_frags);
166 }
167 
168 /* Kill ipq entry. It is not destroyed immediately,
169  * because caller (and someone more) holds reference count.
170  */
171 static void ipq_kill(struct ipq *ipq)
172 {
173         inet_frag_kill(&ipq->q, &ip4_frags);
174 }
175 
176 /*
177  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
178  */
179 static void ip_expire(unsigned long arg)
180 {
181         struct ipq *qp;
182         struct net *net;
183 
184         qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
185         net = container_of(qp->q.net, struct net, ipv4.frags);
186 
187         spin_lock(&qp->q.lock);
188 
189         if (qp->q.flags & INET_FRAG_COMPLETE)
190                 goto out;
191 
192         ipq_kill(qp);
193         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
194 
195         if (!(qp->q.flags & INET_FRAG_EVICTED)) {
196                 struct sk_buff *head = qp->q.fragments;
197                 const struct iphdr *iph;
198                 int err;
199 
200                 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
201 
202                 if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
203                         goto out;
204 
205                 rcu_read_lock();
206                 head->dev = dev_get_by_index_rcu(net, qp->iif);
207                 if (!head->dev)
208                         goto out_rcu_unlock;
209 
210                 /* skb has no dst, perform route lookup again */
211                 iph = ip_hdr(head);
212                 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
213                                            iph->tos, head->dev);
214                 if (err)
215                         goto out_rcu_unlock;
216 
217                 /* Only an end host needs to send an ICMP
218                  * "Fragment Reassembly Timeout" message, per RFC792.
219                  */
220                 if (qp->user == IP_DEFRAG_AF_PACKET ||
221                     ((qp->user >= IP_DEFRAG_CONNTRACK_IN) &&
222                      (qp->user <= __IP_DEFRAG_CONNTRACK_IN_END) &&
223                      (skb_rtable(head)->rt_type != RTN_LOCAL)))
224                         goto out_rcu_unlock;
225 
226                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
227                 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
228 out_rcu_unlock:
229                 rcu_read_unlock();
230         }
231 out:
232         spin_unlock(&qp->q.lock);
233         ipq_put(qp);
234 }
235 
236 /* Find the correct entry in the "incomplete datagrams" queue for
237  * this IP datagram, and create new one, if nothing is found.
238  */
239 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
240 {
241         struct inet_frag_queue *q;
242         struct ip4_create_arg arg;
243         unsigned int hash;
244 
245         arg.iph = iph;
246         arg.user = user;
247 
248         hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
249 
250         q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
251         if (IS_ERR_OR_NULL(q)) {
252                 inet_frag_maybe_warn_overflow(q, pr_fmt());
253                 return NULL;
254         }
255         return container_of(q, struct ipq, q);
256 }
257 
258 /* Is the fragment too far ahead to be part of ipq? */
259 static inline int ip_frag_too_far(struct ipq *qp)
260 {
261         struct inet_peer *peer = qp->peer;
262         unsigned int max = sysctl_ipfrag_max_dist;
263         unsigned int start, end;
264 
265         int rc;
266 
267         if (!peer || !max)
268                 return 0;
269 
270         start = qp->rid;
271         end = atomic_inc_return(&peer->rid);
272         qp->rid = end;
273 
274         rc = qp->q.fragments && (end - start) > max;
275 
276         if (rc) {
277                 struct net *net;
278 
279                 net = container_of(qp->q.net, struct net, ipv4.frags);
280                 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
281         }
282 
283         return rc;
284 }
285 
286 static int ip_frag_reinit(struct ipq *qp)
287 {
288         struct sk_buff *fp;
289         unsigned int sum_truesize = 0;
290 
291         if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
292                 atomic_inc(&qp->q.refcnt);
293                 return -ETIMEDOUT;
294         }
295 
296         fp = qp->q.fragments;
297         do {
298                 struct sk_buff *xp = fp->next;
299 
300                 sum_truesize += fp->truesize;
301                 kfree_skb(fp);
302                 fp = xp;
303         } while (fp);
304         sub_frag_mem_limit(&qp->q, sum_truesize);
305 
306         qp->q.flags = 0;
307         qp->q.len = 0;
308         qp->q.meat = 0;
309         qp->q.fragments = NULL;
310         qp->q.fragments_tail = NULL;
311         qp->iif = 0;
312         qp->ecn = 0;
313 
314         return 0;
315 }
316 
317 /* Add new segment to existing queue. */
318 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
319 {
320         struct sk_buff *prev, *next;
321         struct net_device *dev;
322         int flags, offset;
323         int ihl, end;
324         int err = -ENOENT;
325         u8 ecn;
326 
327         if (qp->q.flags & INET_FRAG_COMPLETE)
328                 goto err;
329 
330         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
331             unlikely(ip_frag_too_far(qp)) &&
332             unlikely(err = ip_frag_reinit(qp))) {
333                 ipq_kill(qp);
334                 goto err;
335         }
336 
337         ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
338         offset = ntohs(ip_hdr(skb)->frag_off);
339         flags = offset & ~IP_OFFSET;
340         offset &= IP_OFFSET;
341         offset <<= 3;           /* offset is in 8-byte chunks */
342         ihl = ip_hdrlen(skb);
343 
344         /* Determine the position of this fragment. */
345         end = offset + skb->len - ihl;
346         err = -EINVAL;
347 
348         /* Is this the final fragment? */
349         if ((flags & IP_MF) == 0) {
350                 /* If we already have some bits beyond end
351                  * or have different end, the segment is corrupted.
352                  */
353                 if (end < qp->q.len ||
354                     ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
355                         goto err;
356                 qp->q.flags |= INET_FRAG_LAST_IN;
357                 qp->q.len = end;
358         } else {
359                 if (end&7) {
360                         end &= ~7;
361                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
362                                 skb->ip_summed = CHECKSUM_NONE;
363                 }
364                 if (end > qp->q.len) {
365                         /* Some bits beyond end -> corruption. */
366                         if (qp->q.flags & INET_FRAG_LAST_IN)
367                                 goto err;
368                         qp->q.len = end;
369                 }
370         }
371         if (end == offset)
372                 goto err;
373 
374         err = -ENOMEM;
375         if (pskb_pull(skb, ihl) == NULL)
376                 goto err;
377 
378         err = pskb_trim_rcsum(skb, end - offset);
379         if (err)
380                 goto err;
381 
382         /* Find out which fragments are in front and at the back of us
383          * in the chain of fragments so far.  We must know where to put
384          * this fragment, right?
385          */
386         prev = qp->q.fragments_tail;
387         if (!prev || FRAG_CB(prev)->offset < offset) {
388                 next = NULL;
389                 goto found;
390         }
391         prev = NULL;
392         for (next = qp->q.fragments; next != NULL; next = next->next) {
393                 if (FRAG_CB(next)->offset >= offset)
394                         break;  /* bingo! */
395                 prev = next;
396         }
397 
398 found:
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                         sub_frag_mem_limit(&qp->q, free_it->truesize);
450                         kfree_skb(free_it);
451                 }
452         }
453 
454         FRAG_CB(skb)->offset = offset;
455 
456         /* Insert this fragment in the chain of fragments. */
457         skb->next = next;
458         if (!next)
459                 qp->q.fragments_tail = skb;
460         if (prev)
461                 prev->next = skb;
462         else
463                 qp->q.fragments = skb;
464 
465         dev = skb->dev;
466         if (dev) {
467                 qp->iif = dev->ifindex;
468                 skb->dev = NULL;
469         }
470         qp->q.stamp = skb->tstamp;
471         qp->q.meat += skb->len;
472         qp->ecn |= ecn;
473         add_frag_mem_limit(&qp->q, skb->truesize);
474         if (offset == 0)
475                 qp->q.flags |= INET_FRAG_FIRST_IN;
476 
477         if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
478             skb->len + ihl > qp->q.max_size)
479                 qp->q.max_size = skb->len + ihl;
480 
481         if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
482             qp->q.meat == qp->q.len) {
483                 unsigned long orefdst = skb->_skb_refdst;
484 
485                 skb->_skb_refdst = 0UL;
486                 err = ip_frag_reasm(qp, prev, dev);
487                 skb->_skb_refdst = orefdst;
488                 return err;
489         }
490 
491         skb_dst_drop(skb);
492         return -EINPROGRESS;
493 
494 err:
495         kfree_skb(skb);
496         return err;
497 }
498 
499 
500 /* Build a new IP datagram from all its fragments. */
501 
502 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
503                          struct net_device *dev)
504 {
505         struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
506         struct iphdr *iph;
507         struct sk_buff *fp, *head = qp->q.fragments;
508         int len;
509         int ihlen;
510         int err;
511         int sum_truesize;
512         u8 ecn;
513 
514         ipq_kill(qp);
515 
516         ecn = ip_frag_ecn_table[qp->ecn];
517         if (unlikely(ecn == 0xff)) {
518                 err = -EINVAL;
519                 goto out_fail;
520         }
521         /* Make the one we just received the head. */
522         if (prev) {
523                 head = prev->next;
524                 fp = skb_clone(head, GFP_ATOMIC);
525                 if (!fp)
526                         goto out_nomem;
527 
528                 fp->next = head->next;
529                 if (!fp->next)
530                         qp->q.fragments_tail = fp;
531                 prev->next = fp;
532 
533                 skb_morph(head, qp->q.fragments);
534                 head->next = qp->q.fragments->next;
535 
536                 consume_skb(qp->q.fragments);
537                 qp->q.fragments = head;
538         }
539 
540         WARN_ON(head == NULL);
541         WARN_ON(FRAG_CB(head)->offset != 0);
542 
543         /* Allocate a new buffer for the datagram. */
544         ihlen = ip_hdrlen(head);
545         len = ihlen + qp->q.len;
546 
547         err = -E2BIG;
548         if (len > 65535)
549                 goto out_oversize;
550 
551         /* Head of list must not be cloned. */
552         if (skb_unclone(head, GFP_ATOMIC))
553                 goto out_nomem;
554 
555         /* If the first fragment is fragmented itself, we split
556          * it to two chunks: the first with data and paged part
557          * and the second, holding only fragments. */
558         if (skb_has_frag_list(head)) {
559                 struct sk_buff *clone;
560                 int i, plen = 0;
561 
562                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
563                         goto out_nomem;
564                 clone->next = head->next;
565                 head->next = clone;
566                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
567                 skb_frag_list_init(head);
568                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
569                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
570                 clone->len = clone->data_len = head->data_len - plen;
571                 head->data_len -= clone->len;
572                 head->len -= clone->len;
573                 clone->csum = 0;
574                 clone->ip_summed = head->ip_summed;
575                 add_frag_mem_limit(&qp->q, clone->truesize);
576         }
577 
578         skb_push(head, head->data - skb_network_header(head));
579 
580         sum_truesize = head->truesize;
581         for (fp = head->next; fp;) {
582                 bool headstolen;
583                 int delta;
584                 struct sk_buff *next = fp->next;
585 
586                 sum_truesize += fp->truesize;
587                 if (head->ip_summed != fp->ip_summed)
588                         head->ip_summed = CHECKSUM_NONE;
589                 else if (head->ip_summed == CHECKSUM_COMPLETE)
590                         head->csum = csum_add(head->csum, fp->csum);
591 
592                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
593                         kfree_skb_partial(fp, headstolen);
594                 } else {
595                         if (!skb_shinfo(head)->frag_list)
596                                 skb_shinfo(head)->frag_list = fp;
597                         head->data_len += fp->len;
598                         head->len += fp->len;
599                         head->truesize += fp->truesize;
600                 }
601                 fp = next;
602         }
603         sub_frag_mem_limit(&qp->q, sum_truesize);
604 
605         head->next = NULL;
606         head->dev = dev;
607         head->tstamp = qp->q.stamp;
608         IPCB(head)->frag_max_size = qp->q.max_size;
609 
610         iph = ip_hdr(head);
611         /* max_size != 0 implies at least one fragment had IP_DF set */
612         iph->frag_off = qp->q.max_size ? htons(IP_DF) : 0;
613         iph->tot_len = htons(len);
614         iph->tos |= ecn;
615         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
616         qp->q.fragments = NULL;
617         qp->q.fragments_tail = NULL;
618         return 0;
619 
620 out_nomem:
621         LIMIT_NETDEBUG(KERN_ERR pr_fmt("queue_glue: no memory for gluing queue %p\n"),
622                        qp);
623         err = -ENOMEM;
624         goto out_fail;
625 out_oversize:
626         net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
627 out_fail:
628         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
629         return err;
630 }
631 
632 /* Process an incoming IP datagram fragment. */
633 int ip_defrag(struct sk_buff *skb, u32 user)
634 {
635         struct ipq *qp;
636         struct net *net;
637 
638         net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev);
639         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
640 
641         /* Lookup (or create) queue header */
642         if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
643                 int ret;
644 
645                 spin_lock(&qp->q.lock);
646 
647                 ret = ip_frag_queue(qp, skb);
648 
649                 spin_unlock(&qp->q.lock);
650                 ipq_put(qp);
651                 return ret;
652         }
653 
654         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
655         kfree_skb(skb);
656         return -ENOMEM;
657 }
658 EXPORT_SYMBOL(ip_defrag);
659 
660 struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
661 {
662         struct iphdr iph;
663         u32 len;
664 
665         if (skb->protocol != htons(ETH_P_IP))
666                 return skb;
667 
668         if (!skb_copy_bits(skb, 0, &iph, sizeof(iph)))
669                 return skb;
670 
671         if (iph.ihl < 5 || iph.version != 4)
672                 return skb;
673 
674         len = ntohs(iph.tot_len);
675         if (skb->len < len || len < (iph.ihl * 4))
676                 return skb;
677 
678         if (ip_is_fragment(&iph)) {
679                 skb = skb_share_check(skb, GFP_ATOMIC);
680                 if (skb) {
681                         if (!pskb_may_pull(skb, iph.ihl*4))
682                                 return skb;
683                         if (pskb_trim_rcsum(skb, len))
684                                 return skb;
685                         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
686                         if (ip_defrag(skb, user))
687                                 return NULL;
688                         skb_clear_hash(skb);
689                 }
690         }
691         return skb;
692 }
693 EXPORT_SYMBOL(ip_check_defrag);
694 
695 #ifdef CONFIG_SYSCTL
696 static int zero;
697 
698 static struct ctl_table ip4_frags_ns_ctl_table[] = {
699         {
700                 .procname       = "ipfrag_high_thresh",
701                 .data           = &init_net.ipv4.frags.high_thresh,
702                 .maxlen         = sizeof(int),
703                 .mode           = 0644,
704                 .proc_handler   = proc_dointvec_minmax,
705                 .extra1         = &init_net.ipv4.frags.low_thresh
706         },
707         {
708                 .procname       = "ipfrag_low_thresh",
709                 .data           = &init_net.ipv4.frags.low_thresh,
710                 .maxlen         = sizeof(int),
711                 .mode           = 0644,
712                 .proc_handler   = proc_dointvec_minmax,
713                 .extra1         = &zero,
714                 .extra2         = &init_net.ipv4.frags.high_thresh
715         },
716         {
717                 .procname       = "ipfrag_time",
718                 .data           = &init_net.ipv4.frags.timeout,
719                 .maxlen         = sizeof(int),
720                 .mode           = 0644,
721                 .proc_handler   = proc_dointvec_jiffies,
722         },
723         { }
724 };
725 
726 /* secret interval has been deprecated */
727 static int ip4_frags_secret_interval_unused;
728 static struct ctl_table ip4_frags_ctl_table[] = {
729         {
730                 .procname       = "ipfrag_secret_interval",
731                 .data           = &ip4_frags_secret_interval_unused,
732                 .maxlen         = sizeof(int),
733                 .mode           = 0644,
734                 .proc_handler   = proc_dointvec_jiffies,
735         },
736         {
737                 .procname       = "ipfrag_max_dist",
738                 .data           = &sysctl_ipfrag_max_dist,
739                 .maxlen         = sizeof(int),
740                 .mode           = 0644,
741                 .proc_handler   = proc_dointvec_minmax,
742                 .extra1         = &zero
743         },
744         { }
745 };
746 
747 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
748 {
749         struct ctl_table *table;
750         struct ctl_table_header *hdr;
751 
752         table = ip4_frags_ns_ctl_table;
753         if (!net_eq(net, &init_net)) {
754                 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
755                 if (table == NULL)
756                         goto err_alloc;
757 
758                 table[0].data = &net->ipv4.frags.high_thresh;
759                 table[0].extra1 = &net->ipv4.frags.low_thresh;
760                 table[0].extra2 = &init_net.ipv4.frags.high_thresh;
761                 table[1].data = &net->ipv4.frags.low_thresh;
762                 table[1].extra2 = &net->ipv4.frags.high_thresh;
763                 table[2].data = &net->ipv4.frags.timeout;
764 
765                 /* Don't export sysctls to unprivileged users */
766                 if (net->user_ns != &init_user_ns)
767                         table[0].procname = NULL;
768         }
769 
770         hdr = register_net_sysctl(net, "net/ipv4", table);
771         if (hdr == NULL)
772                 goto err_reg;
773 
774         net->ipv4.frags_hdr = hdr;
775         return 0;
776 
777 err_reg:
778         if (!net_eq(net, &init_net))
779                 kfree(table);
780 err_alloc:
781         return -ENOMEM;
782 }
783 
784 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
785 {
786         struct ctl_table *table;
787 
788         table = net->ipv4.frags_hdr->ctl_table_arg;
789         unregister_net_sysctl_table(net->ipv4.frags_hdr);
790         kfree(table);
791 }
792 
793 static void ip4_frags_ctl_register(void)
794 {
795         register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
796 }
797 #else
798 static inline int ip4_frags_ns_ctl_register(struct net *net)
799 {
800         return 0;
801 }
802 
803 static inline void ip4_frags_ns_ctl_unregister(struct net *net)
804 {
805 }
806 
807 static inline void ip4_frags_ctl_register(void)
808 {
809 }
810 #endif
811 
812 static int __net_init ipv4_frags_init_net(struct net *net)
813 {
814         /* Fragment cache limits.
815          *
816          * The fragment memory accounting code, (tries to) account for
817          * the real memory usage, by measuring both the size of frag
818          * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
819          * and the SKB's truesize.
820          *
821          * A 64K fragment consumes 129736 bytes (44*2944)+200
822          * (1500 truesize == 2944, sizeof(struct ipq) == 200)
823          *
824          * We will commit 4MB at one time. Should we cross that limit
825          * we will prune down to 3MB, making room for approx 8 big 64K
826          * fragments 8x128k.
827          */
828         net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
829         net->ipv4.frags.low_thresh  = 3 * 1024 * 1024;
830         /*
831          * Important NOTE! Fragment queue must be destroyed before MSL expires.
832          * RFC791 is wrong proposing to prolongate timer each fragment arrival
833          * by TTL.
834          */
835         net->ipv4.frags.timeout = IP_FRAG_TIME;
836 
837         inet_frags_init_net(&net->ipv4.frags);
838 
839         return ip4_frags_ns_ctl_register(net);
840 }
841 
842 static void __net_exit ipv4_frags_exit_net(struct net *net)
843 {
844         ip4_frags_ns_ctl_unregister(net);
845         inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
846 }
847 
848 static struct pernet_operations ip4_frags_ops = {
849         .init = ipv4_frags_init_net,
850         .exit = ipv4_frags_exit_net,
851 };
852 
853 void __init ipfrag_init(void)
854 {
855         ip4_frags_ctl_register();
856         register_pernet_subsys(&ip4_frags_ops);
857         ip4_frags.hashfn = ip4_hashfn;
858         ip4_frags.constructor = ip4_frag_init;
859         ip4_frags.destructor = ip4_frag_free;
860         ip4_frags.skb_free = NULL;
861         ip4_frags.qsize = sizeof(struct ipq);
862         ip4_frags.match = ip4_frag_match;
863         ip4_frags.frag_expire = ip_expire;
864         ip4_frags.frags_cache_name = ip_frag_cache_name;
865         if (inet_frags_init(&ip4_frags))
866                 panic("IP: failed to allocate ip4_frags cache\n");
867 }
868 

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