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 __inline__ void __ipq_unlink(struct ipq *qp)
 112 {
 113         hlist_del(&qp->q.list);
 114         list_del(&qp->q.lru_list);
 115         ip4_frags.nqueues--;
 116 }
 117
 118 static __inline__ void ipq_unlink(struct ipq *ipq)
 119 {
 120         write_lock(&ip4_frags.lock);
 121         __ipq_unlink(ipq);
 122         write_unlock(&ip4_frags.lock);
 123 }
 124
 125 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
 126 {
 127         return jhash_3words((__force u32)id << 16 | prot,
 128                             (__force u32)saddr, (__force u32)daddr,
 129                             ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
 130 }
 131
 132 static void ipfrag_secret_rebuild(unsigned long dummy)
 133 {
 134         unsigned long now = jiffies;
 135         int i;
 136
 137         write_lock(&ip4_frags.lock);
 138         get_random_bytes(&ip4_frags.rnd, sizeof(u32));
 139         for (i = 0; i < INETFRAGS_HASHSZ; i++) {
 140                 struct ipq *q;
 141                 struct hlist_node *p, *n;
 142
 143                 hlist_for_each_entry_safe(q, p, n, &ip4_frags.hash[i], q.list) {
 144                         unsigned int hval = ipqhashfn(q->id, q->saddr,
 145                                                       q->daddr, q->protocol);
 146
 147                         if (hval != i) {
 148                                 hlist_del(&q->q.list);
 149
 150                                 /* Relink to new hash chain. */
 151                                 hlist_add_head(&q->q.list, &ip4_frags.hash[hval]);
 152                         }
 153                 }
 154         }
 155         write_unlock(&ip4_frags.lock);
 156
 157         mod_timer(&ip4_frags.secret_timer, now + ip4_frags_ctl.secret_interval);
 158 }
 159
 160 /* Memory Tracking Functions. */
 161 static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
 162 {
 163         if (work)
 164                 *work -= skb->truesize;
 165         atomic_sub(skb->truesize, &ip4_frags.mem);
 166         kfree_skb(skb);
 167 }
 168
 169 static __inline__ void frag_free_queue(struct ipq *qp, int *work)
 170 {
 171         if (work)
 172                 *work -= sizeof(struct ipq);
 173         atomic_sub(sizeof(struct ipq), &ip4_frags.mem);
 174         kfree(qp);
 175 }
 176
 177 static __inline__ struct ipq *frag_alloc_queue(void)
 178 {
 179         struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC);
 180
 181         if (!qp)
 182                 return NULL;
 183         atomic_add(sizeof(struct ipq), &ip4_frags.mem);
 184         return qp;
 185 }
 186
 187
 188 /* Destruction primitives. */
 189
 190 /* Complete destruction of ipq. */
 191 static void ip_frag_destroy(struct ipq *qp, int *work)
 192 {
 193         struct sk_buff *fp;
 194
 195         BUG_TRAP(qp->q.last_in&COMPLETE);
 196         BUG_TRAP(del_timer(&qp->q.timer) == 0);
 197
 198         if (qp->peer)
 199                 inet_putpeer(qp->peer);
 200
 201         /* Release all fragment data. */
 202         fp = qp->q.fragments;
 203         while (fp) {
 204                 struct sk_buff *xp = fp->next;
 205
 206                 frag_kfree_skb(fp, work);
 207                 fp = xp;
 208         }
 209
 210         /* Finally, release the queue descriptor itself. */
 211         frag_free_queue(qp, work);
 212 }
 213
 214 static __inline__ void ipq_put(struct ipq *ipq, int *work)
 215 {
 216         if (atomic_dec_and_test(&ipq->q.refcnt))
 217                 ip_frag_destroy(ipq, work);
 218 }
 219
 220 /* Kill ipq entry. It is not destroyed immediately,
 221  * because caller (and someone more) holds reference count.
 222  */
 223 static void ipq_kill(struct ipq *ipq)
 224 {
 225         if (del_timer(&ipq->q.timer))
 226                 atomic_dec(&ipq->q.refcnt);
 227
 228         if (!(ipq->q.last_in & COMPLETE)) {
 229                 ipq_unlink(ipq);
 230                 atomic_dec(&ipq->q.refcnt);
 231                 ipq->q.last_in |= COMPLETE;
 232         }
 233 }
 234
 235 /* Memory limiting on fragments.  Evictor trashes the oldest
 236  * fragment queue until we are back under the threshold.
 237  */
 238 static void ip_evictor(void)
 239 {
 240         struct ipq *qp;
 241         struct list_head *tmp;
 242         int work;
 243
 244         work = atomic_read(&ip4_frags.mem) - ip4_frags_ctl.low_thresh;
 245         if (work <= 0)
 246                 return;
 247
 248         while (work > 0) {
 249                 read_lock(&ip4_frags.lock);
 250                 if (list_empty(&ip4_frags.lru_list)) {
 251                         read_unlock(&ip4_frags.lock);
 252                         return;
 253                 }
 254                 tmp = ip4_frags.lru_list.next;
 255                 qp = list_entry(tmp, struct ipq, q.lru_list);
 256                 atomic_inc(&qp->q.refcnt);
 257                 read_unlock(&ip4_frags.lock);
 258
 259                 spin_lock(&qp->q.lock);
 260                 if (!(qp->q.last_in&COMPLETE))
 261                         ipq_kill(qp);
 262                 spin_unlock(&qp->q.lock);
 263
 264                 ipq_put(qp, &work);
 265                 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 266         }
 267 }
 268
 269 /*
 270  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
 271  */
 272 static void ip_expire(unsigned long arg)
 273 {
 274         struct ipq *qp = (struct ipq *) arg;
 275
 276         spin_lock(&qp->q.lock);
 277
 278         if (qp->q.last_in & COMPLETE)
 279                 goto out;
 280
 281         ipq_kill(qp);
 282
 283         IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
 284         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 285
 286         if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) {
 287                 struct sk_buff *head = qp->q.fragments;
 288                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
 289                 if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {
 290                         icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
 291                         dev_put(head->dev);
 292                 }
 293         }
 294 out:
 295         spin_unlock(&qp->q.lock);
 296         ipq_put(qp, NULL);
 297 }
 298
 299 /* Creation primitives. */
 300
 301 static struct ipq *ip_frag_intern(struct ipq *qp_in)
 302 {
 303         struct ipq *qp;
 304 #ifdef CONFIG_SMP
 305         struct hlist_node *n;
 306 #endif
 307         unsigned int hash;
 308
 309         write_lock(&ip4_frags.lock);
 310         hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr,
 311                          qp_in->protocol);
 312 #ifdef CONFIG_SMP
 313         /* With SMP race we have to recheck hash table, because
 314          * such entry could be created on other cpu, while we
 315          * promoted read lock to write lock.
 316          */
 317         hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) {
 318                 if (qp->id == qp_in->id         &&
 319                     qp->saddr == qp_in->saddr   &&
 320                     qp->daddr == qp_in->daddr   &&
 321                     qp->protocol == qp_in->protocol &&
 322                     qp->user == qp_in->user) {
 323                         atomic_inc(&qp->q.refcnt);
 324                         write_unlock(&ip4_frags.lock);
 325                         qp_in->q.last_in |= COMPLETE;
 326                         ipq_put(qp_in, NULL);
 327                         return qp;
 328                 }
 329         }
 330 #endif
 331         qp = qp_in;
 332
 333         if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout))
 334                 atomic_inc(&qp->q.refcnt);
 335
 336         atomic_inc(&qp->q.refcnt);
 337         hlist_add_head(&qp->q.list, &ip4_frags.hash[hash]);
 338         INIT_LIST_HEAD(&qp->q.lru_list);
 339         list_add_tail(&qp->q.lru_list, &ip4_frags.lru_list);
 340         ip4_frags.nqueues++;
 341         write_unlock(&ip4_frags.lock);
 342         return qp;
 343 }
 344
 345 /* Add an entry to the 'ipq' queue for a newly received IP datagram. */
 346 static struct ipq *ip_frag_create(struct iphdr *iph, u32 user)
 347 {
 348         struct ipq *qp;
 349
 350         if ((qp = frag_alloc_queue()) == NULL)
 351                 goto out_nomem;
 352
 353         qp->protocol = iph->protocol;
 354         qp->q.last_in = 0;
 355         qp->id = iph->id;
 356         qp->saddr = iph->saddr;
 357         qp->daddr = iph->daddr;
 358         qp->user = user;
 359         qp->q.len = 0;
 360         qp->q.meat = 0;
 361         qp->q.fragments = NULL;
 362         qp->iif = 0;
 363         qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
 364
 365         /* Initialize a timer for this entry. */
 366         init_timer(&qp->q.timer);
 367         qp->q.timer.data = (unsigned long) qp;  /* pointer to queue     */
 368         qp->q.timer.function = ip_expire;               /* expire function      */
 369         spin_lock_init(&qp->q.lock);
 370         atomic_set(&qp->q.refcnt, 1);
 371
 372         return ip_frag_intern(qp);
 373
 374 out_nomem:
 375         LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
 376         return NULL;
 377 }
 378
 379 /* Find the correct entry in the "incomplete datagrams" queue for
 380  * this IP datagram, and create new one, if nothing is found.
 381  */
 382 static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
 383 {
 384         __be16 id = iph->id;
 385         __be32 saddr = iph->saddr;
 386         __be32 daddr = iph->daddr;
 387         __u8 protocol = iph->protocol;
 388         unsigned int hash;
 389         struct ipq *qp;
 390         struct hlist_node *n;
 391
 392         read_lock(&ip4_frags.lock);
 393         hash = ipqhashfn(id, saddr, daddr, protocol);
 394         hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) {
 395                 if (qp->id == id                &&
 396                     qp->saddr == saddr  &&
 397                     qp->daddr == daddr  &&
 398                     qp->protocol == protocol &&
 399                     qp->user == user) {
 400                         atomic_inc(&qp->q.refcnt);
 401                         read_unlock(&ip4_frags.lock);
 402                         return qp;
 403                 }
 404         }
 405         read_unlock(&ip4_frags.lock);
 406
 407         return ip_frag_create(iph, user);
 408 }
 409
 410 /* Is the fragment too far ahead to be part of ipq? */
 411 static inline int ip_frag_too_far(struct ipq *qp)
 412 {
 413         struct inet_peer *peer = qp->peer;
 414         unsigned int max = sysctl_ipfrag_max_dist;
 415         unsigned int start, end;
 416
 417         int rc;
 418
 419         if (!peer || !max)
 420                 return 0;
 421
 422         start = qp->rid;
 423         end = atomic_inc_return(&peer->rid);
 424         qp->rid = end;
 425
 426         rc = qp->q.fragments && (end - start) > max;
 427
 428         if (rc) {
 429                 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 430         }
 431
 432         return rc;
 433 }
 434
 435 static int ip_frag_reinit(struct ipq *qp)
 436 {
 437         struct sk_buff *fp;
 438
 439         if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout)) {
 440                 atomic_inc(&qp->q.refcnt);
 441                 return -ETIMEDOUT;
 442         }
 443
 444         fp = qp->q.fragments;
 445         do {
 446                 struct sk_buff *xp = fp->next;
 447                 frag_kfree_skb(fp, NULL);
 448                 fp = xp;
 449         } while (fp);
 450
 451         qp->q.last_in = 0;
 452         qp->q.len = 0;
 453         qp->q.meat = 0;
 454         qp->q.fragments = NULL;
 455         qp->iif = 0;
 456
 457         return 0;
 458 }
 459
 460 /* Add new segment to existing queue. */
 461 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 462 {
 463         struct sk_buff *prev, *next;
 464         struct net_device *dev;
 465         int flags, offset;
 466         int ihl, end;
 467         int err = -ENOENT;
 468
 469         if (qp->q.last_in & COMPLETE)
 470                 goto err;
 471
 472         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
 473             unlikely(ip_frag_too_far(qp)) &&
 474             unlikely(err = ip_frag_reinit(qp))) {
 475                 ipq_kill(qp);
 476                 goto err;
 477         }
 478
 479         offset = ntohs(ip_hdr(skb)->frag_off);
 480         flags = offset & ~IP_OFFSET;
 481         offset &= IP_OFFSET;
 482         offset <<= 3;           /* offset is in 8-byte chunks */
 483         ihl = ip_hdrlen(skb);
 484
 485         /* Determine the position of this fragment. */
 486         end = offset + skb->len - ihl;
 487         err = -EINVAL;
 488
 489         /* Is this the final fragment? */
 490         if ((flags & IP_MF) == 0) {
 491                 /* If we already have some bits beyond end
 492                  * or have different end, the segment is corrrupted.
 493                  */
 494                 if (end < qp->q.len ||
 495                     ((qp->q.last_in & LAST_IN) && end != qp->q.len))
 496                         goto err;
 497                 qp->q.last_in |= LAST_IN;
 498                 qp->q.len = end;
 499         } else {
 500                 if (end&7) {
 501                         end &= ~7;
 502                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 503                                 skb->ip_summed = CHECKSUM_NONE;
 504                 }
 505                 if (end > qp->q.len) {
 506                         /* Some bits beyond end -> corruption. */
 507                         if (qp->q.last_in & LAST_IN)
 508                                 goto err;
 509                         qp->q.len = end;
 510                 }
 511         }
 512         if (end == offset)
 513                 goto err;
 514
 515         err = -ENOMEM;
 516         if (pskb_pull(skb, ihl) == NULL)
 517                 goto err;
 518
 519         err = pskb_trim_rcsum(skb, end - offset);
 520         if (err)
 521                 goto err;
 522
 523         /* Find out which fragments are in front and at the back of us
 524          * in the chain of fragments so far.  We must know where to put
 525          * this fragment, right?
 526          */
 527         prev = NULL;
 528         for (next = qp->q.fragments; next != NULL; next = next->next) {
 529                 if (FRAG_CB(next)->offset >= offset)
 530                         break;  /* bingo! */
 531                 prev = next;
 532         }
 533
 534         /* We found where to put this one.  Check for overlap with
 535          * preceding fragment, and, if needed, align things so that
 536          * any overlaps are eliminated.
 537          */
 538         if (prev) {
 539                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
 540
 541                 if (i > 0) {
 542                         offset += i;
 543                         err = -EINVAL;
 544                         if (end <= offset)
 545                                 goto err;
 546                         err = -ENOMEM;
 547                         if (!pskb_pull(skb, i))
 548                                 goto err;
 549                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 550                                 skb->ip_summed = CHECKSUM_NONE;
 551                 }
 552         }
 553
 554         err = -ENOMEM;
 555
 556         while (next && FRAG_CB(next)->offset < end) {
 557                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
 558
 559                 if (i < next->len) {
 560                         /* Eat head of the next overlapped fragment
 561                          * and leave the loop. The next ones cannot overlap.
 562                          */
 563                         if (!pskb_pull(next, i))
 564                                 goto err;
 565                         FRAG_CB(next)->offset += i;
 566                         qp->q.meat -= i;
 567                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 568                                 next->ip_summed = CHECKSUM_NONE;
 569                         break;
 570                 } else {
 571                         struct sk_buff *free_it = next;
 572
 573                         /* Old fragment is completely overridden with
 574                          * new one drop it.
 575                          */
 576                         next = next->next;
 577
 578                         if (prev)
 579                                 prev->next = next;
 580                         else
 581                                 qp->q.fragments = next;
 582
 583                         qp->q.meat -= free_it->len;
 584                         frag_kfree_skb(free_it, NULL);
 585                 }
 586         }
 587
 588         FRAG_CB(skb)->offset = offset;
 589
 590         /* Insert this fragment in the chain of fragments. */
 591         skb->next = next;
 592         if (prev)
 593                 prev->next = skb;
 594         else
 595                 qp->q.fragments = skb;
 596
 597         dev = skb->dev;
 598         if (dev) {
 599                 qp->iif = dev->ifindex;
 600                 skb->dev = NULL;
 601         }
 602         qp->q.stamp = skb->tstamp;
 603         qp->q.meat += skb->len;
 604         atomic_add(skb->truesize, &ip4_frags.mem);
 605         if (offset == 0)
 606                 qp->q.last_in |= FIRST_IN;
 607
 608         if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len)
 609                 return ip_frag_reasm(qp, prev, dev);
 610
 611         write_lock(&ip4_frags.lock);
 612         list_move_tail(&qp->q.lru_list, &ip4_frags.lru_list);
 613         write_unlock(&ip4_frags.lock);
 614         return -EINPROGRESS;
 615
 616 err:
 617         kfree_skb(skb);
 618         return err;
 619 }
 620
 621
 622 /* Build a new IP datagram from all its fragments. */
 623
 624 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 625                          struct net_device *dev)
 626 {
 627         struct iphdr *iph;
 628         struct sk_buff *fp, *head = qp->q.fragments;
 629         int len;
 630         int ihlen;
 631         int err;
 632
 633         ipq_kill(qp);
 634
 635         /* Make the one we just received the head. */
 636         if (prev) {
 637                 head = prev->next;
 638                 fp = skb_clone(head, GFP_ATOMIC);
 639
 640                 if (!fp)
 641                         goto out_nomem;
 642
 643                 fp->next = head->next;
 644                 prev->next = fp;
 645
 646                 skb_morph(head, qp->q.fragments);
 647                 head->next = qp->q.fragments->next;
 648
 649                 kfree_skb(qp->q.fragments);
 650                 qp->q.fragments = head;
 651         }
 652
 653         BUG_TRAP(head != NULL);
 654         BUG_TRAP(FRAG_CB(head)->offset == 0);
 655
 656         /* Allocate a new buffer for the datagram. */
 657         ihlen = ip_hdrlen(head);
 658         len = ihlen + qp->q.len;
 659
 660         err = -E2BIG;
 661         if (len > 65535)
 662                 goto out_oversize;
 663
 664         /* Head of list must not be cloned. */
 665         err = -ENOMEM;
 666         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
 667                 goto out_nomem;
 668
 669         /* If the first fragment is fragmented itself, we split
 670          * it to two chunks: the first with data and paged part
 671          * and the second, holding only fragments. */
 672         if (skb_shinfo(head)->frag_list) {
 673                 struct sk_buff *clone;
 674                 int i, plen = 0;
 675
 676                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
 677                         goto out_nomem;
 678                 clone->next = head->next;
 679                 head->next = clone;
 680                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 681                 skb_shinfo(head)->frag_list = NULL;
 682                 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
 683                         plen += skb_shinfo(head)->frags[i].size;
 684                 clone->len = clone->data_len = head->data_len - plen;
 685                 head->data_len -= clone->len;
 686                 head->len -= clone->len;
 687                 clone->csum = 0;
 688                 clone->ip_summed = head->ip_summed;
 689                 atomic_add(clone->truesize, &ip4_frags.mem);
 690         }
 691
 692         skb_shinfo(head)->frag_list = head->next;
 693         skb_push(head, head->data - skb_network_header(head));
 694         atomic_sub(head->truesize, &ip4_frags.mem);
 695
 696         for (fp=head->next; fp; fp = fp->next) {
 697                 head->data_len += fp->len;
 698                 head->len += fp->len;
 699                 if (head->ip_summed != fp->ip_summed)
 700                         head->ip_summed = CHECKSUM_NONE;
 701                 else if (head->ip_summed == CHECKSUM_COMPLETE)
 702                         head->csum = csum_add(head->csum, fp->csum);
 703                 head->truesize += fp->truesize;
 704                 atomic_sub(fp->truesize, &ip4_frags.mem);
 705         }
 706
 707         head->next = NULL;
 708         head->dev = dev;
 709         head->tstamp = qp->q.stamp;
 710
 711         iph = ip_hdr(head);
 712         iph->frag_off = 0;
 713         iph->tot_len = htons(len);
 714         IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
 715         qp->q.fragments = NULL;
 716         return 0;
 717
 718 out_nomem:
 719         LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
 720                               "queue %p\n", qp);
 721         goto out_fail;
 722 out_oversize:
 723         if (net_ratelimit())
 724                 printk(KERN_INFO
 725                         "Oversized IP packet from %d.%d.%d.%d.\n",
 726                         NIPQUAD(qp->saddr));
 727 out_fail:
 728         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 729         return err;
 730 }
 731
 732 /* Process an incoming IP datagram fragment. */
 733 int ip_defrag(struct sk_buff *skb, u32 user)
 734 {
 735         struct ipq *qp;
 736
 737         IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
 738
 739         /* Start by cleaning up the memory. */
 740         if (atomic_read(&ip4_frags.mem) > ip4_frags_ctl.high_thresh)
 741                 ip_evictor();
 742
 743         /* Lookup (or create) queue header */
 744         if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {
 745                 int ret;
 746
 747                 spin_lock(&qp->q.lock);
 748
 749                 ret = ip_frag_queue(qp, skb);
 750
 751                 spin_unlock(&qp->q.lock);
 752                 ipq_put(qp, NULL);
 753                 return ret;
 754         }
 755
 756         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 757         kfree_skb(skb);
 758         return -ENOMEM;
 759 }
 760
 761 void __init ipfrag_init(void)
 762 {
 763         init_timer(&ip4_frags.secret_timer);
 764         ip4_frags.secret_timer.function = ipfrag_secret_rebuild;
 765         ip4_frags.secret_timer.expires = jiffies + ip4_frags_ctl.secret_interval;
 766         add_timer(&ip4_frags.secret_timer);
 767
 768         ip4_frags.ctl = &ip4_frags_ctl;
 769         inet_frags_init(&ip4_frags);
 770 }
 771
 772 EXPORT_SYMBOL(ip_defrag);