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  * Version:     $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
   9  *
  10  * Authors:     Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
  11  *              Alan Cox <Alan.Cox@linux.org>
  12  *
  13  * Fixes:
  14  *              Alan Cox        :       Split from ip.c , see ip_input.c for history.
  15  *              David S. Miller :       Begin massive cleanup...
  16  *              Andi Kleen      :       Add sysctls.
  17  *              xxxx            :       Overlapfrag bug.
  18  *              Ultima          :       ip_expire() kernel panic.
  19  *              Bill Hawes      :       Frag accounting and evictor fixes.
  20  *              John McDonald   :       0 length frag bug.
  21  *              Alexey Kuznetsov:       SMP races, threading, cleanup.
  22  *              Patrick McHardy :       LRU queue of frag heads for evictor.
  23  */
  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 <net/sock.h>
  38 #include <net/ip.h>
  39 #include <net/icmp.h>
  40 #include <net/checksum.h>
  41 #include <net/inetpeer.h>
  42 #include <net/inet_frag.h>
  43 #include <linux/tcp.h>
  44 #include <linux/udp.h>
  45 #include <linux/inet.h>
  46 #include <linux/netfilter_ipv4.h>
  47
  48 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
  49  * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
  50  * as well. Or notify me, at least. --ANK
  51  */
  52
  53 int sysctl_ipfrag_max_dist __read_mostly = 64;
  54
  55 struct ipfrag_skb_cb
  56 {
  57         struct inet_skb_parm    h;
  58         int                     offset;
  59 };
  60
  61 #define FRAG_CB(skb)    ((struct ipfrag_skb_cb*)((skb)->cb))
  62
  63 /* Describe an entry in the "incomplete datagrams" queue. */
  64 struct ipq {
  65         struct inet_frag_queue q;
  66
  67         u32             user;
  68         __be32          saddr;
  69         __be32          daddr;
  70         __be16          id;
  71         u8              protocol;
  72         int             iif;
  73         unsigned int    rid;
  74         struct inet_peer *peer;
  75 };
  76
  77 struct inet_frags_ctl ip4_frags_ctl __read_mostly = {
  78         /*
  79          * Fragment cache limits. We will commit 256K at one time. Should we
  80          * cross that limit we will prune down to 192K. This should cope with
  81          * even the most extreme cases without allowing an attacker to
  82          * measurably harm machine performance.
  83          */
  84         .high_thresh     = 256 * 1024,
  85         .low_thresh      = 192 * 1024,
  86
  87         /*
  88          * Important NOTE! Fragment queue must be destroyed before MSL expires.
  89          * RFC791 is wrong proposing to prolongate timer each fragment arrival
  90          * by TTL.
  91          */
  92         .timeout         = IP_FRAG_TIME,
  93         .secret_interval = 10 * 60 * HZ,
  94 };
  95
  96 static struct inet_frags ip4_frags;
  97
  98 int ip_frag_nqueues(void)
  99 {
 100         return ip4_frags.nqueues;
 101 }
 102
 103 int ip_frag_mem(void)
 104 {
 105         return atomic_read(&ip4_frags.mem);
 106 }
 107
 108 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 109                          struct net_device *dev);
 110
 111 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
 112 {
 113         return jhash_3words((__force u32)id << 16 | prot,
 114                             (__force u32)saddr, (__force u32)daddr,
 115                             ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
 116 }
 117
 118 static unsigned int ip4_hashfn(struct inet_frag_queue *q)
 119 {
 120         struct ipq *ipq;
 121
 122         ipq = container_of(q, struct ipq, q);
 123         return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
 124 }
 125
 126 /* Memory Tracking Functions. */
 127 static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
 128 {
 129         if (work)
 130                 *work -= skb->truesize;
 131         atomic_sub(skb->truesize, &ip4_frags.mem);
 132         kfree_skb(skb);
 133 }
 134
 135 static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
 136 {
 137         struct ipq *qp;
 138
 139         qp = container_of(q, struct ipq, q);
 140         if (qp->peer)
 141                 inet_putpeer(qp->peer);
 142         kfree(qp);
 143 }
 144
 145 static __inline__ struct ipq *frag_alloc_queue(void)
 146 {
 147         struct ipq *qp = kzalloc(sizeof(struct ipq), GFP_ATOMIC);
 148
 149         if (!qp)
 150                 return NULL;
 151         atomic_add(sizeof(struct ipq), &ip4_frags.mem);
 152         return qp;
 153 }
 154
 155
 156 /* Destruction primitives. */
 157
 158 static __inline__ void ipq_put(struct ipq *ipq)
 159 {
 160         inet_frag_put(&ipq->q, &ip4_frags);
 161 }
 162
 163 /* Kill ipq entry. It is not destroyed immediately,
 164  * because caller (and someone more) holds reference count.
 165  */
 166 static void ipq_kill(struct ipq *ipq)
 167 {
 168         inet_frag_kill(&ipq->q, &ip4_frags);
 169 }
 170
 171 /* Memory limiting on fragments.  Evictor trashes the oldest
 172  * fragment queue until we are back under the threshold.
 173  */
 174 static void ip_evictor(void)
 175 {
 176         int evicted;
 177
 178         evicted = inet_frag_evictor(&ip4_frags);
 179         if (evicted)
 180                 IP_ADD_STATS_BH(IPSTATS_MIB_REASMFAILS, evicted);
 181 }
 182
 183 /*
 184  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
 185  */
 186 static void ip_expire(unsigned long arg)
 187 {
 188         struct ipq *qp = (struct ipq *) arg;
 189
 190         spin_lock(&qp->q.lock);
 191
 192         if (qp->q.last_in & COMPLETE)
 193                 goto out;
 194
 195         ipq_kill(qp);
 196
 197         IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
 198         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 199
 200         if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) {
 201                 struct sk_buff *head = qp->q.fragments;
 202                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
 203                 if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {
 204                         icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
 205                         dev_put(head->dev);
 206                 }
 207         }
 208 out:
 209         spin_unlock(&qp->q.lock);
 210         ipq_put(qp);
 211 }
 212
 213 /* Creation primitives. */
 214
 215 static struct ipq *ip_frag_intern(struct ipq *qp_in)
 216 {
 217         struct ipq *qp;
 218 #ifdef CONFIG_SMP
 219         struct hlist_node *n;
 220 #endif
 221         unsigned int hash;
 222
 223         write_lock(&ip4_frags.lock);
 224         hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr,
 225                          qp_in->protocol);
 226 #ifdef CONFIG_SMP
 227         /* With SMP race we have to recheck hash table, because
 228          * such entry could be created on other cpu, while we
 229          * promoted read lock to write lock.
 230          */
 231         hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) {
 232                 if (qp->id == qp_in->id         &&
 233                     qp->saddr == qp_in->saddr   &&
 234                     qp->daddr == qp_in->daddr   &&
 235                     qp->protocol == qp_in->protocol &&
 236                     qp->user == qp_in->user) {
 237                         atomic_inc(&qp->q.refcnt);
 238                         write_unlock(&ip4_frags.lock);
 239                         qp_in->q.last_in |= COMPLETE;
 240                         ipq_put(qp_in);
 241                         return qp;
 242                 }
 243         }
 244 #endif
 245         qp = qp_in;
 246
 247         if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout))
 248                 atomic_inc(&qp->q.refcnt);
 249
 250         atomic_inc(&qp->q.refcnt);
 251         hlist_add_head(&qp->q.list, &ip4_frags.hash[hash]);
 252         INIT_LIST_HEAD(&qp->q.lru_list);
 253         list_add_tail(&qp->q.lru_list, &ip4_frags.lru_list);
 254         ip4_frags.nqueues++;
 255         write_unlock(&ip4_frags.lock);
 256         return qp;
 257 }
 258
 259 /* Add an entry to the 'ipq' queue for a newly received IP datagram. */
 260 static struct ipq *ip_frag_create(struct iphdr *iph, u32 user)
 261 {
 262         struct ipq *qp;
 263
 264         if ((qp = frag_alloc_queue()) == NULL)
 265                 goto out_nomem;
 266
 267         qp->protocol = iph->protocol;
 268         qp->id = iph->id;
 269         qp->saddr = iph->saddr;
 270         qp->daddr = iph->daddr;
 271         qp->user = user;
 272         qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
 273
 274         /* Initialize a timer for this entry. */
 275         init_timer(&qp->q.timer);
 276         qp->q.timer.data = (unsigned long) qp;  /* pointer to queue     */
 277         qp->q.timer.function = ip_expire;               /* expire function      */
 278         spin_lock_init(&qp->q.lock);
 279         atomic_set(&qp->q.refcnt, 1);
 280
 281         return ip_frag_intern(qp);
 282
 283 out_nomem:
 284         LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
 285         return NULL;
 286 }
 287
 288 /* Find the correct entry in the "incomplete datagrams" queue for
 289  * this IP datagram, and create new one, if nothing is found.
 290  */
 291 static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
 292 {
 293         __be16 id = iph->id;
 294         __be32 saddr = iph->saddr;
 295         __be32 daddr = iph->daddr;
 296         __u8 protocol = iph->protocol;
 297         unsigned int hash;
 298         struct ipq *qp;
 299         struct hlist_node *n;
 300
 301         read_lock(&ip4_frags.lock);
 302         hash = ipqhashfn(id, saddr, daddr, protocol);
 303         hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) {
 304                 if (qp->id == id                &&
 305                     qp->saddr == saddr  &&
 306                     qp->daddr == daddr  &&
 307                     qp->protocol == protocol &&
 308                     qp->user == user) {
 309                         atomic_inc(&qp->q.refcnt);
 310                         read_unlock(&ip4_frags.lock);
 311                         return qp;
 312                 }
 313         }
 314         read_unlock(&ip4_frags.lock);
 315
 316         return ip_frag_create(iph, user);
 317 }
 318
 319 /* Is the fragment too far ahead to be part of ipq? */
 320 static inline int ip_frag_too_far(struct ipq *qp)
 321 {
 322         struct inet_peer *peer = qp->peer;
 323         unsigned int max = sysctl_ipfrag_max_dist;
 324         unsigned int start, end;
 325
 326         int rc;
 327
 328         if (!peer || !max)
 329                 return 0;
 330
 331         start = qp->rid;
 332         end = atomic_inc_return(&peer->rid);
 333         qp->rid = end;
 334
 335         rc = qp->q.fragments && (end - start) > max;
 336
 337         if (rc) {
 338                 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 339         }
 340
 341         return rc;
 342 }
 343
 344 static int ip_frag_reinit(struct ipq *qp)
 345 {
 346         struct sk_buff *fp;
 347
 348         if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout)) {
 349                 atomic_inc(&qp->q.refcnt);
 350                 return -ETIMEDOUT;
 351         }
 352
 353         fp = qp->q.fragments;
 354         do {
 355                 struct sk_buff *xp = fp->next;
 356                 frag_kfree_skb(fp, NULL);
 357                 fp = xp;
 358         } while (fp);
 359
 360         qp->q.last_in = 0;
 361         qp->q.len = 0;
 362         qp->q.meat = 0;
 363         qp->q.fragments = NULL;
 364         qp->iif = 0;
 365
 366         return 0;
 367 }
 368
 369 /* Add new segment to existing queue. */
 370 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 371 {
 372         struct sk_buff *prev, *next;
 373         struct net_device *dev;
 374         int flags, offset;
 375         int ihl, end;
 376         int err = -ENOENT;
 377
 378         if (qp->q.last_in & COMPLETE)
 379                 goto err;
 380
 381         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
 382             unlikely(ip_frag_too_far(qp)) &&
 383             unlikely(err = ip_frag_reinit(qp))) {
 384                 ipq_kill(qp);
 385                 goto err;
 386         }
 387
 388         offset = ntohs(ip_hdr(skb)->frag_off);
 389         flags = offset & ~IP_OFFSET;
 390         offset &= IP_OFFSET;
 391         offset <<= 3;           /* offset is in 8-byte chunks */
 392         ihl = ip_hdrlen(skb);
 393
 394         /* Determine the position of this fragment. */
 395         end = offset + skb->len - ihl;
 396         err = -EINVAL;
 397
 398         /* Is this the final fragment? */
 399         if ((flags & IP_MF) == 0) {
 400                 /* If we already have some bits beyond end
 401                  * or have different end, the segment is corrrupted.
 402                  */
 403                 if (end < qp->q.len ||
 404                     ((qp->q.last_in & LAST_IN) && end != qp->q.len))
 405                         goto err;
 406                 qp->q.last_in |= LAST_IN;
 407                 qp->q.len = end;
 408         } else {
 409                 if (end&7) {
 410                         end &= ~7;
 411                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 412                                 skb->ip_summed = CHECKSUM_NONE;
 413                 }
 414                 if (end > qp->q.len) {
 415                         /* Some bits beyond end -> corruption. */
 416                         if (qp->q.last_in & LAST_IN)
 417                                 goto err;
 418                         qp->q.len = end;
 419                 }
 420         }
 421         if (end == offset)
 422                 goto err;
 423
 424         err = -ENOMEM;
 425         if (pskb_pull(skb, ihl) == NULL)
 426                 goto err;
 427
 428         err = pskb_trim_rcsum(skb, end - offset);
 429         if (err)
 430                 goto err;
 431
 432         /* Find out which fragments are in front and at the back of us
 433          * in the chain of fragments so far.  We must know where to put
 434          * this fragment, right?
 435          */
 436         prev = NULL;
 437         for (next = qp->q.fragments; next != NULL; next = next->next) {
 438                 if (FRAG_CB(next)->offset >= offset)
 439                         break;  /* bingo! */
 440                 prev = next;
 441         }
 442
 443         /* We found where to put this one.  Check for overlap with
 444          * preceding fragment, and, if needed, align things so that
 445          * any overlaps are eliminated.
 446          */
 447         if (prev) {
 448                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
 449
 450                 if (i > 0) {
 451                         offset += i;
 452                         err = -EINVAL;
 453                         if (end <= offset)
 454                                 goto err;
 455                         err = -ENOMEM;
 456                         if (!pskb_pull(skb, i))
 457                                 goto err;
 458                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 459                                 skb->ip_summed = CHECKSUM_NONE;
 460                 }
 461         }
 462
 463         err = -ENOMEM;
 464
 465         while (next && FRAG_CB(next)->offset < end) {
 466                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
 467
 468                 if (i < next->len) {
 469                         /* Eat head of the next overlapped fragment
 470                          * and leave the loop. The next ones cannot overlap.
 471                          */
 472                         if (!pskb_pull(next, i))
 473                                 goto err;
 474                         FRAG_CB(next)->offset += i;
 475                         qp->q.meat -= i;
 476                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 477                                 next->ip_summed = CHECKSUM_NONE;
 478                         break;
 479                 } else {
 480                         struct sk_buff *free_it = next;
 481
 482                         /* Old fragment is completely overridden with
 483                          * new one drop it.
 484                          */
 485                         next = next->next;
 486
 487                         if (prev)
 488                                 prev->next = next;
 489                         else
 490                                 qp->q.fragments = next;
 491
 492                         qp->q.meat -= free_it->len;
 493                         frag_kfree_skb(free_it, NULL);
 494                 }
 495         }
 496
 497         FRAG_CB(skb)->offset = offset;
 498
 499         /* Insert this fragment in the chain of fragments. */
 500         skb->next = next;
 501         if (prev)
 502                 prev->next = skb;
 503         else
 504                 qp->q.fragments = skb;
 505
 506         dev = skb->dev;
 507         if (dev) {
 508                 qp->iif = dev->ifindex;
 509                 skb->dev = NULL;
 510         }
 511         qp->q.stamp = skb->tstamp;
 512         qp->q.meat += skb->len;
 513         atomic_add(skb->truesize, &ip4_frags.mem);
 514         if (offset == 0)
 515                 qp->q.last_in |= FIRST_IN;
 516
 517         if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len)
 518                 return ip_frag_reasm(qp, prev, dev);
 519
 520         write_lock(&ip4_frags.lock);
 521         list_move_tail(&qp->q.lru_list, &ip4_frags.lru_list);
 522         write_unlock(&ip4_frags.lock);
 523         return -EINPROGRESS;
 524
 525 err:
 526         kfree_skb(skb);
 527         return err;
 528 }
 529
 530
 531 /* Build a new IP datagram from all its fragments. */
 532
 533 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 534                          struct net_device *dev)
 535 {
 536         struct iphdr *iph;
 537         struct sk_buff *fp, *head = qp->q.fragments;
 538         int len;
 539         int ihlen;
 540         int err;
 541
 542         ipq_kill(qp);
 543
 544         /* Make the one we just received the head. */
 545         if (prev) {
 546                 head = prev->next;
 547                 fp = skb_clone(head, GFP_ATOMIC);
 548
 549                 if (!fp)
 550                         goto out_nomem;
 551
 552                 fp->next = head->next;
 553                 prev->next = fp;
 554
 555                 skb_morph(head, qp->q.fragments);
 556                 head->next = qp->q.fragments->next;
 557
 558                 kfree_skb(qp->q.fragments);
 559                 qp->q.fragments = head;
 560         }
 561
 562         BUG_TRAP(head != NULL);
 563         BUG_TRAP(FRAG_CB(head)->offset == 0);
 564
 565         /* Allocate a new buffer for the datagram. */
 566         ihlen = ip_hdrlen(head);
 567         len = ihlen + qp->q.len;
 568
 569         err = -E2BIG;
 570         if (len > 65535)
 571                 goto out_oversize;
 572
 573         /* Head of list must not be cloned. */
 574         err = -ENOMEM;
 575         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
 576                 goto out_nomem;
 577
 578         /* If the first fragment is fragmented itself, we split
 579          * it to two chunks: the first with data and paged part
 580          * and the second, holding only fragments. */
 581         if (skb_shinfo(head)->frag_list) {
 582                 struct sk_buff *clone;
 583                 int i, plen = 0;
 584
 585                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
 586                         goto out_nomem;
 587                 clone->next = head->next;
 588                 head->next = clone;
 589                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 590                 skb_shinfo(head)->frag_list = NULL;
 591                 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
 592                         plen += skb_shinfo(head)->frags[i].size;
 593                 clone->len = clone->data_len = head->data_len - plen;
 594                 head->data_len -= clone->len;
 595                 head->len -= clone->len;
 596                 clone->csum = 0;
 597                 clone->ip_summed = head->ip_summed;
 598                 atomic_add(clone->truesize, &ip4_frags.mem);
 599         }
 600
 601         skb_shinfo(head)->frag_list = head->next;
 602         skb_push(head, head->data - skb_network_header(head));
 603         atomic_sub(head->truesize, &ip4_frags.mem);
 604
 605         for (fp=head->next; fp; fp = fp->next) {
 606                 head->data_len += fp->len;
 607                 head->len += fp->len;
 608                 if (head->ip_summed != fp->ip_summed)
 609                         head->ip_summed = CHECKSUM_NONE;
 610                 else if (head->ip_summed == CHECKSUM_COMPLETE)
 611                         head->csum = csum_add(head->csum, fp->csum);
 612                 head->truesize += fp->truesize;
 613                 atomic_sub(fp->truesize, &ip4_frags.mem);
 614         }
 615
 616         head->next = NULL;
 617         head->dev = dev;
 618         head->tstamp = qp->q.stamp;
 619
 620         iph = ip_hdr(head);
 621         iph->frag_off = 0;
 622         iph->tot_len = htons(len);
 623         IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
 624         qp->q.fragments = NULL;
 625         return 0;
 626
 627 out_nomem:
 628         LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
 629                               "queue %p\n", qp);
 630         goto out_fail;
 631 out_oversize:
 632         if (net_ratelimit())
 633                 printk(KERN_INFO
 634                         "Oversized IP packet from %d.%d.%d.%d.\n",
 635                         NIPQUAD(qp->saddr));
 636 out_fail:
 637         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 638         return err;
 639 }
 640
 641 /* Process an incoming IP datagram fragment. */
 642 int ip_defrag(struct sk_buff *skb, u32 user)
 643 {
 644         struct ipq *qp;
 645
 646         IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
 647
 648         /* Start by cleaning up the memory. */
 649         if (atomic_read(&ip4_frags.mem) > ip4_frags_ctl.high_thresh)
 650                 ip_evictor();
 651
 652         /* Lookup (or create) queue header */
 653         if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {
 654                 int ret;
 655
 656                 spin_lock(&qp->q.lock);
 657
 658                 ret = ip_frag_queue(qp, skb);
 659
 660                 spin_unlock(&qp->q.lock);
 661                 ipq_put(qp);
 662                 return ret;
 663         }
 664
 665         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 666         kfree_skb(skb);
 667         return -ENOMEM;
 668 }
 669
 670 void __init ipfrag_init(void)
 671 {
 672         ip4_frags.ctl = &ip4_frags_ctl;
 673         ip4_frags.hashfn = ip4_hashfn;
 674         ip4_frags.destructor = ip4_frag_free;
 675         ip4_frags.skb_free = NULL;
 676         ip4_frags.qsize = sizeof(struct ipq);
 677         inet_frags_init(&ip4_frags);
 678 }
 679
 680 EXPORT_SYMBOL(ip_defrag);