Version:  2.6.34 2.6.35 2.6.36 2.6.37 2.6.38 2.6.39 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

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

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us