Version:  2.0.40 2.2.26 2.4.37 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 4.3 4.4 4.5

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 #include <net/l3mdev.h>
 52 
 53 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
 54  * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
 55  * as well. Or notify me, at least. --ANK
 56  */
 57 
 58 static int sysctl_ipfrag_max_dist __read_mostly = 64;
 59 static const char ip_frag_cache_name[] = "ip4-frags";
 60 
 61 struct ipfrag_skb_cb
 62 {
 63         struct inet_skb_parm    h;
 64         int                     offset;
 65 };
 66 
 67 #define FRAG_CB(skb)    ((struct ipfrag_skb_cb *)((skb)->cb))
 68 
 69 /* Describe an entry in the "incomplete datagrams" queue. */
 70 struct ipq {
 71         struct inet_frag_queue q;
 72 
 73         u32             user;
 74         __be32          saddr;
 75         __be32          daddr;
 76         __be16          id;
 77         u8              protocol;
 78         u8              ecn; /* RFC3168 support */
 79         u16             max_df_size; /* largest frag with DF set seen */
 80         int             iif;
 81         int             vif;   /* L3 master device index */
 82         unsigned int    rid;
 83         struct inet_peer *peer;
 84 };
 85 
 86 static u8 ip4_frag_ecn(u8 tos)
 87 {
 88         return 1 << (tos & INET_ECN_MASK);
 89 }
 90 
 91 static struct inet_frags ip4_frags;
 92 
 93 int ip_frag_mem(struct net *net)
 94 {
 95         return sum_frag_mem_limit(&net->ipv4.frags);
 96 }
 97 
 98 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 99                          struct net_device *dev);
100 
101 struct ip4_create_arg {
102         struct iphdr *iph;
103         u32 user;
104         int vif;
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);
113 }
114 
115 static unsigned int ip4_hashfn(const struct inet_frag_queue *q)
116 {
117         const 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(const struct inet_frag_queue *q, const void *a)
124 {
125         const struct ipq *qp;
126         const 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                 qp->vif == arg->vif;
135 }
136 
137 static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
138 {
139         struct ipq *qp = container_of(q, struct ipq, q);
140         struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
141                                                frags);
142         struct net *net = container_of(ipv4, struct net, ipv4);
143 
144         const struct ip4_create_arg *arg = a;
145 
146         qp->protocol = arg->iph->protocol;
147         qp->id = arg->iph->id;
148         qp->ecn = ip4_frag_ecn(arg->iph->tos);
149         qp->saddr = arg->iph->saddr;
150         qp->daddr = arg->iph->daddr;
151         qp->vif = arg->vif;
152         qp->user = arg->user;
153         qp->peer = sysctl_ipfrag_max_dist ?
154                 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, arg->vif, 1) :
155                 NULL;
156 }
157 
158 static void ip4_frag_free(struct inet_frag_queue *q)
159 {
160         struct ipq *qp;
161 
162         qp = container_of(q, struct ipq, q);
163         if (qp->peer)
164                 inet_putpeer(qp->peer);
165 }
166 
167 
168 /* Destruction primitives. */
169 
170 static void ipq_put(struct ipq *ipq)
171 {
172         inet_frag_put(&ipq->q, &ip4_frags);
173 }
174 
175 /* Kill ipq entry. It is not destroyed immediately,
176  * because caller (and someone more) holds reference count.
177  */
178 static void ipq_kill(struct ipq *ipq)
179 {
180         inet_frag_kill(&ipq->q, &ip4_frags);
181 }
182 
183 static bool frag_expire_skip_icmp(u32 user)
184 {
185         return user == IP_DEFRAG_AF_PACKET ||
186                ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
187                                          __IP_DEFRAG_CONNTRACK_IN_END) ||
188                ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
189                                          __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
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.flags & INET_FRAG_COMPLETE)
206                 goto out;
207 
208         ipq_kill(qp);
209         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
210 
211         if (!inet_frag_evicting(&qp->q)) {
212                 struct sk_buff *head = qp->q.fragments;
213                 const struct iphdr *iph;
214                 int err;
215 
216                 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
217 
218                 if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
219                         goto out;
220 
221                 rcu_read_lock();
222                 head->dev = dev_get_by_index_rcu(net, qp->iif);
223                 if (!head->dev)
224                         goto out_rcu_unlock;
225 
226                 /* skb has no dst, perform route lookup again */
227                 iph = ip_hdr(head);
228                 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
229                                            iph->tos, head->dev);
230                 if (err)
231                         goto out_rcu_unlock;
232 
233                 /* Only an end host needs to send an ICMP
234                  * "Fragment Reassembly Timeout" message, per RFC792.
235                  */
236                 if (frag_expire_skip_icmp(qp->user) &&
237                     (skb_rtable(head)->rt_type != RTN_LOCAL))
238                         goto out_rcu_unlock;
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 struct ipq *ip_find(struct net *net, struct iphdr *iph,
254                            u32 user, int vif)
255 {
256         struct inet_frag_queue *q;
257         struct ip4_create_arg arg;
258         unsigned int hash;
259 
260         arg.iph = iph;
261         arg.user = user;
262         arg.vif = vif;
263 
264         hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
265 
266         q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
267         if (IS_ERR_OR_NULL(q)) {
268                 inet_frag_maybe_warn_overflow(q, pr_fmt());
269                 return NULL;
270         }
271         return container_of(q, struct ipq, q);
272 }
273 
274 /* Is the fragment too far ahead to be part of ipq? */
275 static int ip_frag_too_far(struct ipq *qp)
276 {
277         struct inet_peer *peer = qp->peer;
278         unsigned int max = sysctl_ipfrag_max_dist;
279         unsigned int start, end;
280 
281         int rc;
282 
283         if (!peer || !max)
284                 return 0;
285 
286         start = qp->rid;
287         end = atomic_inc_return(&peer->rid);
288         qp->rid = end;
289 
290         rc = qp->q.fragments && (end - start) > max;
291 
292         if (rc) {
293                 struct net *net;
294 
295                 net = container_of(qp->q.net, struct net, ipv4.frags);
296                 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
297         }
298 
299         return rc;
300 }
301 
302 static int ip_frag_reinit(struct ipq *qp)
303 {
304         struct sk_buff *fp;
305         unsigned int sum_truesize = 0;
306 
307         if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
308                 atomic_inc(&qp->q.refcnt);
309                 return -ETIMEDOUT;
310         }
311 
312         fp = qp->q.fragments;
313         do {
314                 struct sk_buff *xp = fp->next;
315 
316                 sum_truesize += fp->truesize;
317                 kfree_skb(fp);
318                 fp = xp;
319         } while (fp);
320         sub_frag_mem_limit(qp->q.net, sum_truesize);
321 
322         qp->q.flags = 0;
323         qp->q.len = 0;
324         qp->q.meat = 0;
325         qp->q.fragments = NULL;
326         qp->q.fragments_tail = NULL;
327         qp->iif = 0;
328         qp->ecn = 0;
329 
330         return 0;
331 }
332 
333 /* Add new segment to existing queue. */
334 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
335 {
336         struct sk_buff *prev, *next;
337         struct net_device *dev;
338         unsigned int fragsize;
339         int flags, offset;
340         int ihl, end;
341         int err = -ENOENT;
342         u8 ecn;
343 
344         if (qp->q.flags & INET_FRAG_COMPLETE)
345                 goto err;
346 
347         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
348             unlikely(ip_frag_too_far(qp)) &&
349             unlikely(err = ip_frag_reinit(qp))) {
350                 ipq_kill(qp);
351                 goto err;
352         }
353 
354         ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
355         offset = ntohs(ip_hdr(skb)->frag_off);
356         flags = offset & ~IP_OFFSET;
357         offset &= IP_OFFSET;
358         offset <<= 3;           /* offset is in 8-byte chunks */
359         ihl = ip_hdrlen(skb);
360 
361         /* Determine the position of this fragment. */
362         end = offset + skb->len - skb_network_offset(skb) - ihl;
363         err = -EINVAL;
364 
365         /* Is this the final fragment? */
366         if ((flags & IP_MF) == 0) {
367                 /* If we already have some bits beyond end
368                  * or have different end, the segment is corrupted.
369                  */
370                 if (end < qp->q.len ||
371                     ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
372                         goto err;
373                 qp->q.flags |= INET_FRAG_LAST_IN;
374                 qp->q.len = end;
375         } else {
376                 if (end&7) {
377                         end &= ~7;
378                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
379                                 skb->ip_summed = CHECKSUM_NONE;
380                 }
381                 if (end > qp->q.len) {
382                         /* Some bits beyond end -> corruption. */
383                         if (qp->q.flags & INET_FRAG_LAST_IN)
384                                 goto err;
385                         qp->q.len = end;
386                 }
387         }
388         if (end == offset)
389                 goto err;
390 
391         err = -ENOMEM;
392         if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
393                 goto err;
394 
395         err = pskb_trim_rcsum(skb, end - offset);
396         if (err)
397                 goto err;
398 
399         /* Find out which fragments are in front and at the back of us
400          * in the chain of fragments so far.  We must know where to put
401          * this fragment, right?
402          */
403         prev = qp->q.fragments_tail;
404         if (!prev || FRAG_CB(prev)->offset < offset) {
405                 next = NULL;
406                 goto found;
407         }
408         prev = NULL;
409         for (next = qp->q.fragments; next != NULL; next = next->next) {
410                 if (FRAG_CB(next)->offset >= offset)
411                         break;  /* bingo! */
412                 prev = next;
413         }
414 
415 found:
416         /* We found where to put this one.  Check for overlap with
417          * preceding fragment, and, if needed, align things so that
418          * any overlaps are eliminated.
419          */
420         if (prev) {
421                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
422 
423                 if (i > 0) {
424                         offset += i;
425                         err = -EINVAL;
426                         if (end <= offset)
427                                 goto err;
428                         err = -ENOMEM;
429                         if (!pskb_pull(skb, i))
430                                 goto err;
431                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
432                                 skb->ip_summed = CHECKSUM_NONE;
433                 }
434         }
435 
436         err = -ENOMEM;
437 
438         while (next && FRAG_CB(next)->offset < end) {
439                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
440 
441                 if (i < next->len) {
442                         /* Eat head of the next overlapped fragment
443                          * and leave the loop. The next ones cannot overlap.
444                          */
445                         if (!pskb_pull(next, i))
446                                 goto err;
447                         FRAG_CB(next)->offset += i;
448                         qp->q.meat -= i;
449                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
450                                 next->ip_summed = CHECKSUM_NONE;
451                         break;
452                 } else {
453                         struct sk_buff *free_it = next;
454 
455                         /* Old fragment is completely overridden with
456                          * new one drop it.
457                          */
458                         next = next->next;
459 
460                         if (prev)
461                                 prev->next = next;
462                         else
463                                 qp->q.fragments = next;
464 
465                         qp->q.meat -= free_it->len;
466                         sub_frag_mem_limit(qp->q.net, free_it->truesize);
467                         kfree_skb(free_it);
468                 }
469         }
470 
471         FRAG_CB(skb)->offset = offset;
472 
473         /* Insert this fragment in the chain of fragments. */
474         skb->next = next;
475         if (!next)
476                 qp->q.fragments_tail = skb;
477         if (prev)
478                 prev->next = skb;
479         else
480                 qp->q.fragments = skb;
481 
482         dev = skb->dev;
483         if (dev) {
484                 qp->iif = dev->ifindex;
485                 skb->dev = NULL;
486         }
487         qp->q.stamp = skb->tstamp;
488         qp->q.meat += skb->len;
489         qp->ecn |= ecn;
490         add_frag_mem_limit(qp->q.net, skb->truesize);
491         if (offset == 0)
492                 qp->q.flags |= INET_FRAG_FIRST_IN;
493 
494         fragsize = skb->len + ihl;
495 
496         if (fragsize > qp->q.max_size)
497                 qp->q.max_size = fragsize;
498 
499         if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
500             fragsize > qp->max_df_size)
501                 qp->max_df_size = fragsize;
502 
503         if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
504             qp->q.meat == qp->q.len) {
505                 unsigned long orefdst = skb->_skb_refdst;
506 
507                 skb->_skb_refdst = 0UL;
508                 err = ip_frag_reasm(qp, prev, dev);
509                 skb->_skb_refdst = orefdst;
510                 return err;
511         }
512 
513         skb_dst_drop(skb);
514         return -EINPROGRESS;
515 
516 err:
517         kfree_skb(skb);
518         return err;
519 }
520 
521 
522 /* Build a new IP datagram from all its fragments. */
523 
524 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
525                          struct net_device *dev)
526 {
527         struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
528         struct iphdr *iph;
529         struct sk_buff *fp, *head = qp->q.fragments;
530         int len;
531         int ihlen;
532         int err;
533         u8 ecn;
534 
535         ipq_kill(qp);
536 
537         ecn = ip_frag_ecn_table[qp->ecn];
538         if (unlikely(ecn == 0xff)) {
539                 err = -EINVAL;
540                 goto out_fail;
541         }
542         /* Make the one we just received the head. */
543         if (prev) {
544                 head = prev->next;
545                 fp = skb_clone(head, GFP_ATOMIC);
546                 if (!fp)
547                         goto out_nomem;
548 
549                 fp->next = head->next;
550                 if (!fp->next)
551                         qp->q.fragments_tail = fp;
552                 prev->next = fp;
553 
554                 skb_morph(head, qp->q.fragments);
555                 head->next = qp->q.fragments->next;
556 
557                 consume_skb(qp->q.fragments);
558                 qp->q.fragments = head;
559         }
560 
561         WARN_ON(!head);
562         WARN_ON(FRAG_CB(head)->offset != 0);
563 
564         /* Allocate a new buffer for the datagram. */
565         ihlen = ip_hdrlen(head);
566         len = ihlen + qp->q.len;
567 
568         err = -E2BIG;
569         if (len > 65535)
570                 goto out_oversize;
571 
572         /* Head of list must not be cloned. */
573         if (skb_unclone(head, GFP_ATOMIC))
574                 goto out_nomem;
575 
576         /* If the first fragment is fragmented itself, we split
577          * it to two chunks: the first with data and paged part
578          * and the second, holding only fragments. */
579         if (skb_has_frag_list(head)) {
580                 struct sk_buff *clone;
581                 int i, plen = 0;
582 
583                 clone = alloc_skb(0, GFP_ATOMIC);
584                 if (!clone)
585                         goto out_nomem;
586                 clone->next = head->next;
587                 head->next = clone;
588                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
589                 skb_frag_list_init(head);
590                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
591                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
592                 clone->len = clone->data_len = head->data_len - plen;
593                 head->data_len -= clone->len;
594                 head->len -= clone->len;
595                 clone->csum = 0;
596                 clone->ip_summed = head->ip_summed;
597                 add_frag_mem_limit(qp->q.net, clone->truesize);
598         }
599 
600         skb_shinfo(head)->frag_list = head->next;
601         skb_push(head, head->data - skb_network_header(head));
602 
603         for (fp=head->next; fp; fp = fp->next) {
604                 head->data_len += fp->len;
605                 head->len += fp->len;
606                 if (head->ip_summed != fp->ip_summed)
607                         head->ip_summed = CHECKSUM_NONE;
608                 else if (head->ip_summed == CHECKSUM_COMPLETE)
609                         head->csum = csum_add(head->csum, fp->csum);
610                 head->truesize += fp->truesize;
611         }
612         sub_frag_mem_limit(qp->q.net, head->truesize);
613 
614         head->next = NULL;
615         head->dev = dev;
616         head->tstamp = qp->q.stamp;
617         IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
618 
619         iph = ip_hdr(head);
620         iph->tot_len = htons(len);
621         iph->tos |= ecn;
622 
623         /* When we set IP_DF on a refragmented skb we must also force a
624          * call to ip_fragment to avoid forwarding a DF-skb of size s while
625          * original sender only sent fragments of size f (where f < s).
626          *
627          * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
628          * frag seen to avoid sending tiny DF-fragments in case skb was built
629          * from one very small df-fragment and one large non-df frag.
630          */
631         if (qp->max_df_size == qp->q.max_size) {
632                 IPCB(head)->flags |= IPSKB_FRAG_PMTU;
633                 iph->frag_off = htons(IP_DF);
634         } else {
635                 iph->frag_off = 0;
636         }
637 
638         ip_send_check(iph);
639 
640         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
641         qp->q.fragments = NULL;
642         qp->q.fragments_tail = NULL;
643         return 0;
644 
645 out_nomem:
646         net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
647         err = -ENOMEM;
648         goto out_fail;
649 out_oversize:
650         net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
651 out_fail:
652         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
653         return err;
654 }
655 
656 /* Process an incoming IP datagram fragment. */
657 int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
658 {
659         struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
660         int vif = l3mdev_master_ifindex_rcu(dev);
661         struct ipq *qp;
662 
663         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
664         skb_orphan(skb);
665 
666         /* Lookup (or create) queue header */
667         qp = ip_find(net, ip_hdr(skb), user, vif);
668         if (qp) {
669                 int ret;
670 
671                 spin_lock(&qp->q.lock);
672 
673                 ret = ip_frag_queue(qp, skb);
674 
675                 spin_unlock(&qp->q.lock);
676                 ipq_put(qp);
677                 return ret;
678         }
679 
680         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
681         kfree_skb(skb);
682         return -ENOMEM;
683 }
684 EXPORT_SYMBOL(ip_defrag);
685 
686 struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
687 {
688         struct iphdr iph;
689         int netoff;
690         u32 len;
691 
692         if (skb->protocol != htons(ETH_P_IP))
693                 return skb;
694 
695         netoff = skb_network_offset(skb);
696 
697         if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
698                 return skb;
699 
700         if (iph.ihl < 5 || iph.version != 4)
701                 return skb;
702 
703         len = ntohs(iph.tot_len);
704         if (skb->len < netoff + len || len < (iph.ihl * 4))
705                 return skb;
706 
707         if (ip_is_fragment(&iph)) {
708                 skb = skb_share_check(skb, GFP_ATOMIC);
709                 if (skb) {
710                         if (!pskb_may_pull(skb, netoff + iph.ihl * 4))
711                                 return skb;
712                         if (pskb_trim_rcsum(skb, netoff + len))
713                                 return skb;
714                         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
715                         if (ip_defrag(net, skb, user))
716                                 return NULL;
717                         skb_clear_hash(skb);
718                 }
719         }
720         return skb;
721 }
722 EXPORT_SYMBOL(ip_check_defrag);
723 
724 #ifdef CONFIG_SYSCTL
725 static int zero;
726 
727 static struct ctl_table ip4_frags_ns_ctl_table[] = {
728         {
729                 .procname       = "ipfrag_high_thresh",
730                 .data           = &init_net.ipv4.frags.high_thresh,
731                 .maxlen         = sizeof(int),
732                 .mode           = 0644,
733                 .proc_handler   = proc_dointvec_minmax,
734                 .extra1         = &init_net.ipv4.frags.low_thresh
735         },
736         {
737                 .procname       = "ipfrag_low_thresh",
738                 .data           = &init_net.ipv4.frags.low_thresh,
739                 .maxlen         = sizeof(int),
740                 .mode           = 0644,
741                 .proc_handler   = proc_dointvec_minmax,
742                 .extra1         = &zero,
743                 .extra2         = &init_net.ipv4.frags.high_thresh
744         },
745         {
746                 .procname       = "ipfrag_time",
747                 .data           = &init_net.ipv4.frags.timeout,
748                 .maxlen         = sizeof(int),
749                 .mode           = 0644,
750                 .proc_handler   = proc_dointvec_jiffies,
751         },
752         { }
753 };
754 
755 /* secret interval has been deprecated */
756 static int ip4_frags_secret_interval_unused;
757 static struct ctl_table ip4_frags_ctl_table[] = {
758         {
759                 .procname       = "ipfrag_secret_interval",
760                 .data           = &ip4_frags_secret_interval_unused,
761                 .maxlen         = sizeof(int),
762                 .mode           = 0644,
763                 .proc_handler   = proc_dointvec_jiffies,
764         },
765         {
766                 .procname       = "ipfrag_max_dist",
767                 .data           = &sysctl_ipfrag_max_dist,
768                 .maxlen         = sizeof(int),
769                 .mode           = 0644,
770                 .proc_handler   = proc_dointvec_minmax,
771                 .extra1         = &zero
772         },
773         { }
774 };
775 
776 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
777 {
778         struct ctl_table *table;
779         struct ctl_table_header *hdr;
780 
781         table = ip4_frags_ns_ctl_table;
782         if (!net_eq(net, &init_net)) {
783                 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
784                 if (!table)
785                         goto err_alloc;
786 
787                 table[0].data = &net->ipv4.frags.high_thresh;
788                 table[0].extra1 = &net->ipv4.frags.low_thresh;
789                 table[0].extra2 = &init_net.ipv4.frags.high_thresh;
790                 table[1].data = &net->ipv4.frags.low_thresh;
791                 table[1].extra2 = &net->ipv4.frags.high_thresh;
792                 table[2].data = &net->ipv4.frags.timeout;
793 
794                 /* Don't export sysctls to unprivileged users */
795                 if (net->user_ns != &init_user_ns)
796                         table[0].procname = NULL;
797         }
798 
799         hdr = register_net_sysctl(net, "net/ipv4", table);
800         if (!hdr)
801                 goto err_reg;
802 
803         net->ipv4.frags_hdr = hdr;
804         return 0;
805 
806 err_reg:
807         if (!net_eq(net, &init_net))
808                 kfree(table);
809 err_alloc:
810         return -ENOMEM;
811 }
812 
813 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
814 {
815         struct ctl_table *table;
816 
817         table = net->ipv4.frags_hdr->ctl_table_arg;
818         unregister_net_sysctl_table(net->ipv4.frags_hdr);
819         kfree(table);
820 }
821 
822 static void __init ip4_frags_ctl_register(void)
823 {
824         register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
825 }
826 #else
827 static int ip4_frags_ns_ctl_register(struct net *net)
828 {
829         return 0;
830 }
831 
832 static void ip4_frags_ns_ctl_unregister(struct net *net)
833 {
834 }
835 
836 static void __init ip4_frags_ctl_register(void)
837 {
838 }
839 #endif
840 
841 static int __net_init ipv4_frags_init_net(struct net *net)
842 {
843         int res;
844 
845         /* Fragment cache limits.
846          *
847          * The fragment memory accounting code, (tries to) account for
848          * the real memory usage, by measuring both the size of frag
849          * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
850          * and the SKB's truesize.
851          *
852          * A 64K fragment consumes 129736 bytes (44*2944)+200
853          * (1500 truesize == 2944, sizeof(struct ipq) == 200)
854          *
855          * We will commit 4MB at one time. Should we cross that limit
856          * we will prune down to 3MB, making room for approx 8 big 64K
857          * fragments 8x128k.
858          */
859         net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
860         net->ipv4.frags.low_thresh  = 3 * 1024 * 1024;
861         /*
862          * Important NOTE! Fragment queue must be destroyed before MSL expires.
863          * RFC791 is wrong proposing to prolongate timer each fragment arrival
864          * by TTL.
865          */
866         net->ipv4.frags.timeout = IP_FRAG_TIME;
867 
868         res = inet_frags_init_net(&net->ipv4.frags);
869         if (res)
870                 return res;
871         res = ip4_frags_ns_ctl_register(net);
872         if (res)
873                 inet_frags_uninit_net(&net->ipv4.frags);
874         return res;
875 }
876 
877 static void __net_exit ipv4_frags_exit_net(struct net *net)
878 {
879         ip4_frags_ns_ctl_unregister(net);
880         inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
881 }
882 
883 static struct pernet_operations ip4_frags_ops = {
884         .init = ipv4_frags_init_net,
885         .exit = ipv4_frags_exit_net,
886 };
887 
888 void __init ipfrag_init(void)
889 {
890         ip4_frags_ctl_register();
891         register_pernet_subsys(&ip4_frags_ops);
892         ip4_frags.hashfn = ip4_hashfn;
893         ip4_frags.constructor = ip4_frag_init;
894         ip4_frags.destructor = ip4_frag_free;
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 

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