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   1 /*
   2  *      IPv6 fragment reassembly
   3  *      Linux INET6 implementation
   4  *
   5  *      Authors:
   6  *      Pedro Roque             <roque@di.fc.ul.pt>
   7  *
   8  *      $Id: reassembly.c,v 1.26 2001/03/07 22:00:57 davem Exp $
   9  *
  10  *      Based on: net/ipv4/ip_fragment.c
  11  *
  12  *      This program is free software; you can redistribute it and/or
  13  *      modify it under the terms of the GNU General Public License
  14  *      as published by the Free Software Foundation; either version
  15  *      2 of the License, or (at your option) any later version.
  16  */
  17
  18 /*
  19  *      Fixes:
  20  *      Andi Kleen      Make it work with multiple hosts.
  21  *                      More RFC compliance.
  22  *
  23  *      Horst von Brand Add missing #include <linux/string.h>
  24  *      Alexey Kuznetsov        SMP races, threading, cleanup.
  25  *      Patrick McHardy         LRU queue of frag heads for evictor.
  26  *      Mitsuru KANDA @USAGI    Register inet6_protocol{}.
  27  *      David Stevens and
  28  *      YOSHIFUJI,H. @USAGI     Always remove fragment header to
  29  *                              calculate ICV correctly.
  30  */
  31 #include <linux/errno.h>
  32 #include <linux/types.h>
  33 #include <linux/string.h>
  34 #include <linux/socket.h>
  35 #include <linux/sockios.h>
  36 #include <linux/jiffies.h>
  37 #include <linux/net.h>
  38 #include <linux/list.h>
  39 #include <linux/netdevice.h>
  40 #include <linux/in6.h>
  41 #include <linux/ipv6.h>
  42 #include <linux/icmpv6.h>
  43 #include <linux/random.h>
  44 #include <linux/jhash.h>
  45 #include <linux/skbuff.h>
  46
  47 #include <net/sock.h>
  48 #include <net/snmp.h>
  49
  50 #include <net/ipv6.h>
  51 #include <net/ip6_route.h>
  52 #include <net/protocol.h>
  53 #include <net/transp_v6.h>
  54 #include <net/rawv6.h>
  55 #include <net/ndisc.h>
  56 #include <net/addrconf.h>
  57 #include <net/inet_frag.h>
  58
  59 struct ip6frag_skb_cb
  60 {
  61         struct inet6_skb_parm   h;
  62         int                     offset;
  63 };
  64
  65 #define FRAG6_CB(skb)   ((struct ip6frag_skb_cb*)((skb)->cb))
  66
  67
  68 /*
  69  *      Equivalent of ipv4 struct ipq
  70  */
  71
  72 struct frag_queue
  73 {
  74         struct inet_frag_queue  q;
  75
  76         __be32                  id;             /* fragment id          */
  77         struct in6_addr         saddr;
  78         struct in6_addr         daddr;
  79
  80         int                     iif;
  81         unsigned int            csum;
  82         __u16                   nhoffset;
  83 };
  84
  85 struct inet_frags_ctl ip6_frags_ctl __read_mostly = {
  86         .high_thresh     = 256 * 1024,
  87         .low_thresh      = 192 * 1024,
  88         .timeout         = IPV6_FRAG_TIMEOUT,
  89         .secret_interval = 10 * 60 * HZ,
  90 };
  91
  92 static struct inet_frags ip6_frags;
  93
  94 int ip6_frag_nqueues(void)
  95 {
  96         return ip6_frags.nqueues;
  97 }
  98
  99 int ip6_frag_mem(void)
 100 {
 101         return atomic_read(&ip6_frags.mem);
 102 }
 103
 104 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
 105                           struct net_device *dev);
 106
 107 /*
 108  * callers should be careful not to use the hash value outside the ipfrag_lock
 109  * as doing so could race with ipfrag_hash_rnd being recalculated.
 110  */
 111 static unsigned int ip6qhashfn(__be32 id, struct in6_addr *saddr,
 112                                struct in6_addr *daddr)
 113 {
 114         u32 a, b, c;
 115
 116         a = (__force u32)saddr->s6_addr32[0];
 117         b = (__force u32)saddr->s6_addr32[1];
 118         c = (__force u32)saddr->s6_addr32[2];
 119
 120         a += JHASH_GOLDEN_RATIO;
 121         b += JHASH_GOLDEN_RATIO;
 122         c += ip6_frags.rnd;
 123         __jhash_mix(a, b, c);
 124
 125         a += (__force u32)saddr->s6_addr32[3];
 126         b += (__force u32)daddr->s6_addr32[0];
 127         c += (__force u32)daddr->s6_addr32[1];
 128         __jhash_mix(a, b, c);
 129
 130         a += (__force u32)daddr->s6_addr32[2];
 131         b += (__force u32)daddr->s6_addr32[3];
 132         c += (__force u32)id;
 133         __jhash_mix(a, b, c);
 134
 135         return c & (INETFRAGS_HASHSZ - 1);
 136 }
 137
 138 static unsigned int ip6_hashfn(struct inet_frag_queue *q)
 139 {
 140         struct frag_queue *fq;
 141
 142         fq = container_of(q, struct frag_queue, q);
 143         return ip6qhashfn(fq->id, &fq->saddr, &fq->daddr);
 144 }
 145
 146 /* Memory Tracking Functions. */
 147 static inline void frag_kfree_skb(struct sk_buff *skb, int *work)
 148 {
 149         if (work)
 150                 *work -= skb->truesize;
 151         atomic_sub(skb->truesize, &ip6_frags.mem);
 152         kfree_skb(skb);
 153 }
 154
 155 static inline void frag_free_queue(struct frag_queue *fq, int *work)
 156 {
 157         if (work)
 158                 *work -= sizeof(struct frag_queue);
 159         atomic_sub(sizeof(struct frag_queue), &ip6_frags.mem);
 160         kfree(fq);
 161 }
 162
 163 static inline struct frag_queue *frag_alloc_queue(void)
 164 {
 165         struct frag_queue *fq = kzalloc(sizeof(struct frag_queue), GFP_ATOMIC);
 166
 167         if(!fq)
 168                 return NULL;
 169         atomic_add(sizeof(struct frag_queue), &ip6_frags.mem);
 170         return fq;
 171 }
 172
 173 /* Destruction primitives. */
 174
 175 /* Complete destruction of fq. */
 176 static void ip6_frag_destroy(struct frag_queue *fq, int *work)
 177 {
 178         struct sk_buff *fp;
 179
 180         BUG_TRAP(fq->q.last_in&COMPLETE);
 181         BUG_TRAP(del_timer(&fq->q.timer) == 0);
 182
 183         /* Release all fragment data. */
 184         fp = fq->q.fragments;
 185         while (fp) {
 186                 struct sk_buff *xp = fp->next;
 187
 188                 frag_kfree_skb(fp, work);
 189                 fp = xp;
 190         }
 191
 192         frag_free_queue(fq, work);
 193 }
 194
 195 static __inline__ void fq_put(struct frag_queue *fq, int *work)
 196 {
 197         if (atomic_dec_and_test(&fq->q.refcnt))
 198                 ip6_frag_destroy(fq, work);
 199 }
 200
 201 /* Kill fq entry. It is not destroyed immediately,
 202  * because caller (and someone more) holds reference count.
 203  */
 204 static __inline__ void fq_kill(struct frag_queue *fq)
 205 {
 206         inet_frag_kill(&fq->q, &ip6_frags);
 207 }
 208
 209 static void ip6_evictor(struct inet6_dev *idev)
 210 {
 211         struct frag_queue *fq;
 212         struct list_head *tmp;
 213         int work;
 214
 215         work = atomic_read(&ip6_frags.mem) - ip6_frags_ctl.low_thresh;
 216         if (work <= 0)
 217                 return;
 218
 219         while(work > 0) {
 220                 read_lock(&ip6_frags.lock);
 221                 if (list_empty(&ip6_frags.lru_list)) {
 222                         read_unlock(&ip6_frags.lock);
 223                         return;
 224                 }
 225                 tmp = ip6_frags.lru_list.next;
 226                 fq = list_entry(tmp, struct frag_queue, q.lru_list);
 227                 atomic_inc(&fq->q.refcnt);
 228                 read_unlock(&ip6_frags.lock);
 229
 230                 spin_lock(&fq->q.lock);
 231                 if (!(fq->q.last_in&COMPLETE))
 232                         fq_kill(fq);
 233                 spin_unlock(&fq->q.lock);
 234
 235                 fq_put(fq, &work);
 236                 IP6_INC_STATS_BH(idev, IPSTATS_MIB_REASMFAILS);
 237         }
 238 }
 239
 240 static void ip6_frag_expire(unsigned long data)
 241 {
 242         struct frag_queue *fq = (struct frag_queue *) data;
 243         struct net_device *dev = NULL;
 244
 245         spin_lock(&fq->q.lock);
 246
 247         if (fq->q.last_in & COMPLETE)
 248                 goto out;
 249
 250         fq_kill(fq);
 251
 252         dev = dev_get_by_index(&init_net, fq->iif);
 253         if (!dev)
 254                 goto out;
 255
 256         rcu_read_lock();
 257         IP6_INC_STATS_BH(__in6_dev_get(dev), IPSTATS_MIB_REASMTIMEOUT);
 258         IP6_INC_STATS_BH(__in6_dev_get(dev), IPSTATS_MIB_REASMFAILS);
 259         rcu_read_unlock();
 260
 261         /* Don't send error if the first segment did not arrive. */
 262         if (!(fq->q.last_in&FIRST_IN) || !fq->q.fragments)
 263                 goto out;
 264
 265         /*
 266            But use as source device on which LAST ARRIVED
 267            segment was received. And do not use fq->dev
 268            pointer directly, device might already disappeared.
 269          */
 270         fq->q.fragments->dev = dev;
 271         icmpv6_send(fq->q.fragments, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0, dev);
 272 out:
 273         if (dev)
 274                 dev_put(dev);
 275         spin_unlock(&fq->q.lock);
 276         fq_put(fq, NULL);
 277 }
 278
 279 /* Creation primitives. */
 280
 281
 282 static struct frag_queue *ip6_frag_intern(struct frag_queue *fq_in)
 283 {
 284         struct frag_queue *fq;
 285         unsigned int hash;
 286 #ifdef CONFIG_SMP
 287         struct hlist_node *n;
 288 #endif
 289
 290         write_lock(&ip6_frags.lock);
 291         hash = ip6qhashfn(fq_in->id, &fq_in->saddr, &fq_in->daddr);
 292 #ifdef CONFIG_SMP
 293         hlist_for_each_entry(fq, n, &ip6_frags.hash[hash], q.list) {
 294                 if (fq->id == fq_in->id &&
 295                     ipv6_addr_equal(&fq_in->saddr, &fq->saddr) &&
 296                     ipv6_addr_equal(&fq_in->daddr, &fq->daddr)) {
 297                         atomic_inc(&fq->q.refcnt);
 298                         write_unlock(&ip6_frags.lock);
 299                         fq_in->q.last_in |= COMPLETE;
 300                         fq_put(fq_in, NULL);
 301                         return fq;
 302                 }
 303         }
 304 #endif
 305         fq = fq_in;
 306
 307         if (!mod_timer(&fq->q.timer, jiffies + ip6_frags_ctl.timeout))
 308                 atomic_inc(&fq->q.refcnt);
 309
 310         atomic_inc(&fq->q.refcnt);
 311         hlist_add_head(&fq->q.list, &ip6_frags.hash[hash]);
 312         INIT_LIST_HEAD(&fq->q.lru_list);
 313         list_add_tail(&fq->q.lru_list, &ip6_frags.lru_list);
 314         ip6_frags.nqueues++;
 315         write_unlock(&ip6_frags.lock);
 316         return fq;
 317 }
 318
 319
 320 static struct frag_queue *
 321 ip6_frag_create(__be32 id, struct in6_addr *src, struct in6_addr *dst,
 322                 struct inet6_dev *idev)
 323 {
 324         struct frag_queue *fq;
 325
 326         if ((fq = frag_alloc_queue()) == NULL)
 327                 goto oom;
 328
 329         fq->id = id;
 330         ipv6_addr_copy(&fq->saddr, src);
 331         ipv6_addr_copy(&fq->daddr, dst);
 332
 333         init_timer(&fq->q.timer);
 334         fq->q.timer.function = ip6_frag_expire;
 335         fq->q.timer.data = (long) fq;
 336         spin_lock_init(&fq->q.lock);
 337         atomic_set(&fq->q.refcnt, 1);
 338
 339         return ip6_frag_intern(fq);
 340
 341 oom:
 342         IP6_INC_STATS_BH(idev, IPSTATS_MIB_REASMFAILS);
 343         return NULL;
 344 }
 345
 346 static __inline__ struct frag_queue *
 347 fq_find(__be32 id, struct in6_addr *src, struct in6_addr *dst,
 348         struct inet6_dev *idev)
 349 {
 350         struct frag_queue *fq;
 351         struct hlist_node *n;
 352         unsigned int hash;
 353
 354         read_lock(&ip6_frags.lock);
 355         hash = ip6qhashfn(id, src, dst);
 356         hlist_for_each_entry(fq, n, &ip6_frags.hash[hash], q.list) {
 357                 if (fq->id == id &&
 358                     ipv6_addr_equal(src, &fq->saddr) &&
 359                     ipv6_addr_equal(dst, &fq->daddr)) {
 360                         atomic_inc(&fq->q.refcnt);
 361                         read_unlock(&ip6_frags.lock);
 362                         return fq;
 363                 }
 364         }
 365         read_unlock(&ip6_frags.lock);
 366
 367         return ip6_frag_create(id, src, dst, idev);
 368 }
 369
 370
 371 static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
 372                            struct frag_hdr *fhdr, int nhoff)
 373 {
 374         struct sk_buff *prev, *next;
 375         struct net_device *dev;
 376         int offset, end;
 377
 378         if (fq->q.last_in & COMPLETE)
 379                 goto err;
 380
 381         offset = ntohs(fhdr->frag_off) & ~0x7;
 382         end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
 383                         ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
 384
 385         if ((unsigned int)end > IPV6_MAXPLEN) {
 386                 IP6_INC_STATS_BH(ip6_dst_idev(skb->dst),
 387                                  IPSTATS_MIB_INHDRERRORS);
 388                 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 389                                   ((u8 *)&fhdr->frag_off -
 390                                    skb_network_header(skb)));
 391                 return -1;
 392         }
 393
 394         if (skb->ip_summed == CHECKSUM_COMPLETE) {
 395                 const unsigned char *nh = skb_network_header(skb);
 396                 skb->csum = csum_sub(skb->csum,
 397                                      csum_partial(nh, (u8 *)(fhdr + 1) - nh,
 398                                                   0));
 399         }
 400
 401         /* Is this the final fragment? */
 402         if (!(fhdr->frag_off & htons(IP6_MF))) {
 403                 /* If we already have some bits beyond end
 404                  * or have different end, the segment is corrupted.
 405                  */
 406                 if (end < fq->q.len ||
 407                     ((fq->q.last_in & LAST_IN) && end != fq->q.len))
 408                         goto err;
 409                 fq->q.last_in |= LAST_IN;
 410                 fq->q.len = end;
 411         } else {
 412                 /* Check if the fragment is rounded to 8 bytes.
 413                  * Required by the RFC.
 414                  */
 415                 if (end & 0x7) {
 416                         /* RFC2460 says always send parameter problem in
 417                          * this case. -DaveM
 418                          */
 419                         IP6_INC_STATS_BH(ip6_dst_idev(skb->dst),
 420                                          IPSTATS_MIB_INHDRERRORS);
 421                         icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 422                                           offsetof(struct ipv6hdr, payload_len));
 423                         return -1;
 424                 }
 425                 if (end > fq->q.len) {
 426                         /* Some bits beyond end -> corruption. */
 427                         if (fq->q.last_in & LAST_IN)
 428                                 goto err;
 429                         fq->q.len = end;
 430                 }
 431         }
 432
 433         if (end == offset)
 434                 goto err;
 435
 436         /* Point into the IP datagram 'data' part. */
 437         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data))
 438                 goto err;
 439
 440         if (pskb_trim_rcsum(skb, end - offset))
 441                 goto err;
 442
 443         /* Find out which fragments are in front and at the back of us
 444          * in the chain of fragments so far.  We must know where to put
 445          * this fragment, right?
 446          */
 447         prev = NULL;
 448         for(next = fq->q.fragments; next != NULL; next = next->next) {
 449                 if (FRAG6_CB(next)->offset >= offset)
 450                         break;  /* bingo! */
 451                 prev = next;
 452         }
 453
 454         /* We found where to put this one.  Check for overlap with
 455          * preceding fragment, and, if needed, align things so that
 456          * any overlaps are eliminated.
 457          */
 458         if (prev) {
 459                 int i = (FRAG6_CB(prev)->offset + prev->len) - offset;
 460
 461                 if (i > 0) {
 462                         offset += i;
 463                         if (end <= offset)
 464                                 goto err;
 465                         if (!pskb_pull(skb, i))
 466                                 goto err;
 467                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 468                                 skb->ip_summed = CHECKSUM_NONE;
 469                 }
 470         }
 471
 472         /* Look for overlap with succeeding segments.
 473          * If we can merge fragments, do it.
 474          */
 475         while (next && FRAG6_CB(next)->offset < end) {
 476                 int i = end - FRAG6_CB(next)->offset; /* overlap is 'i' bytes */
 477
 478                 if (i < next->len) {
 479                         /* Eat head of the next overlapped fragment
 480                          * and leave the loop. The next ones cannot overlap.
 481                          */
 482                         if (!pskb_pull(next, i))
 483                                 goto err;
 484                         FRAG6_CB(next)->offset += i;    /* next fragment */
 485                         fq->q.meat -= i;
 486                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 487                                 next->ip_summed = CHECKSUM_NONE;
 488                         break;
 489                 } else {
 490                         struct sk_buff *free_it = next;
 491
 492                         /* Old fragment is completely overridden with
 493                          * new one drop it.
 494                          */
 495                         next = next->next;
 496
 497                         if (prev)
 498                                 prev->next = next;
 499                         else
 500                                 fq->q.fragments = next;
 501
 502                         fq->q.meat -= free_it->len;
 503                         frag_kfree_skb(free_it, NULL);
 504                 }
 505         }
 506
 507         FRAG6_CB(skb)->offset = offset;
 508
 509         /* Insert this fragment in the chain of fragments. */
 510         skb->next = next;
 511         if (prev)
 512                 prev->next = skb;
 513         else
 514                 fq->q.fragments = skb;
 515
 516         dev = skb->dev;
 517         if (dev) {
 518                 fq->iif = dev->ifindex;
 519                 skb->dev = NULL;
 520         }
 521         fq->q.stamp = skb->tstamp;
 522         fq->q.meat += skb->len;
 523         atomic_add(skb->truesize, &ip6_frags.mem);
 524
 525         /* The first fragment.
 526          * nhoffset is obtained from the first fragment, of course.
 527          */
 528         if (offset == 0) {
 529                 fq->nhoffset = nhoff;
 530                 fq->q.last_in |= FIRST_IN;
 531         }
 532
 533         if (fq->q.last_in == (FIRST_IN | LAST_IN) && fq->q.meat == fq->q.len)
 534                 return ip6_frag_reasm(fq, prev, dev);
 535
 536         write_lock(&ip6_frags.lock);
 537         list_move_tail(&fq->q.lru_list, &ip6_frags.lru_list);
 538         write_unlock(&ip6_frags.lock);
 539         return -1;
 540
 541 err:
 542         IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_REASMFAILS);
 543         kfree_skb(skb);
 544         return -1;
 545 }
 546
 547 /*
 548  *      Check if this packet is complete.
 549  *      Returns NULL on failure by any reason, and pointer
 550  *      to current nexthdr field in reassembled frame.
 551  *
 552  *      It is called with locked fq, and caller must check that
 553  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 554  *      the last and the first frames arrived and all the bits are here.
 555  */
 556 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
 557                           struct net_device *dev)
 558 {
 559         struct sk_buff *fp, *head = fq->q.fragments;
 560         int    payload_len;
 561         unsigned int nhoff;
 562
 563         fq_kill(fq);
 564
 565         /* Make the one we just received the head. */
 566         if (prev) {
 567                 head = prev->next;
 568                 fp = skb_clone(head, GFP_ATOMIC);
 569
 570                 if (!fp)
 571                         goto out_oom;
 572
 573                 fp->next = head->next;
 574                 prev->next = fp;
 575
 576                 skb_morph(head, fq->q.fragments);
 577                 head->next = fq->q.fragments->next;
 578
 579                 kfree_skb(fq->q.fragments);
 580                 fq->q.fragments = head;
 581         }
 582
 583         BUG_TRAP(head != NULL);
 584         BUG_TRAP(FRAG6_CB(head)->offset == 0);
 585
 586         /* Unfragmented part is taken from the first segment. */
 587         payload_len = ((head->data - skb_network_header(head)) -
 588                        sizeof(struct ipv6hdr) + fq->q.len -
 589                        sizeof(struct frag_hdr));
 590         if (payload_len > IPV6_MAXPLEN)
 591                 goto out_oversize;
 592
 593         /* Head of list must not be cloned. */
 594         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
 595                 goto out_oom;
 596
 597         /* If the first fragment is fragmented itself, we split
 598          * it to two chunks: the first with data and paged part
 599          * and the second, holding only fragments. */
 600         if (skb_shinfo(head)->frag_list) {
 601                 struct sk_buff *clone;
 602                 int i, plen = 0;
 603
 604                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
 605                         goto out_oom;
 606                 clone->next = head->next;
 607                 head->next = clone;
 608                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 609                 skb_shinfo(head)->frag_list = NULL;
 610                 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
 611                         plen += skb_shinfo(head)->frags[i].size;
 612                 clone->len = clone->data_len = head->data_len - plen;
 613                 head->data_len -= clone->len;
 614                 head->len -= clone->len;
 615                 clone->csum = 0;
 616                 clone->ip_summed = head->ip_summed;
 617                 atomic_add(clone->truesize, &ip6_frags.mem);
 618         }
 619
 620         /* We have to remove fragment header from datagram and to relocate
 621          * header in order to calculate ICV correctly. */
 622         nhoff = fq->nhoffset;
 623         skb_network_header(head)[nhoff] = skb_transport_header(head)[0];
 624         memmove(head->head + sizeof(struct frag_hdr), head->head,
 625                 (head->data - head->head) - sizeof(struct frag_hdr));
 626         head->mac_header += sizeof(struct frag_hdr);
 627         head->network_header += sizeof(struct frag_hdr);
 628
 629         skb_shinfo(head)->frag_list = head->next;
 630         skb_reset_transport_header(head);
 631         skb_push(head, head->data - skb_network_header(head));
 632         atomic_sub(head->truesize, &ip6_frags.mem);
 633
 634         for (fp=head->next; fp; fp = fp->next) {
 635                 head->data_len += fp->len;
 636                 head->len += fp->len;
 637                 if (head->ip_summed != fp->ip_summed)
 638                         head->ip_summed = CHECKSUM_NONE;
 639                 else if (head->ip_summed == CHECKSUM_COMPLETE)
 640                         head->csum = csum_add(head->csum, fp->csum);
 641                 head->truesize += fp->truesize;
 642                 atomic_sub(fp->truesize, &ip6_frags.mem);
 643         }
 644
 645         head->next = NULL;
 646         head->dev = dev;
 647         head->tstamp = fq->q.stamp;
 648         ipv6_hdr(head)->payload_len = htons(payload_len);
 649         IP6CB(head)->nhoff = nhoff;
 650
 651         /* Yes, and fold redundant checksum back. 8) */
 652         if (head->ip_summed == CHECKSUM_COMPLETE)
 653                 head->csum = csum_partial(skb_network_header(head),
 654                                           skb_network_header_len(head),
 655                                           head->csum);
 656
 657         rcu_read_lock();
 658         IP6_INC_STATS_BH(__in6_dev_get(dev), IPSTATS_MIB_REASMOKS);
 659         rcu_read_unlock();
 660         fq->q.fragments = NULL;
 661         return 1;
 662
 663 out_oversize:
 664         if (net_ratelimit())
 665                 printk(KERN_DEBUG "ip6_frag_reasm: payload len = %d\n", payload_len);
 666         goto out_fail;
 667 out_oom:
 668         if (net_ratelimit())
 669                 printk(KERN_DEBUG "ip6_frag_reasm: no memory for reassembly\n");
 670 out_fail:
 671         rcu_read_lock();
 672         IP6_INC_STATS_BH(__in6_dev_get(dev), IPSTATS_MIB_REASMFAILS);
 673         rcu_read_unlock();
 674         return -1;
 675 }
 676
 677 static int ipv6_frag_rcv(struct sk_buff **skbp)
 678 {
 679         struct sk_buff *skb = *skbp;
 680         struct frag_hdr *fhdr;
 681         struct frag_queue *fq;
 682         struct ipv6hdr *hdr = ipv6_hdr(skb);
 683
 684         IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_REASMREQDS);
 685
 686         /* Jumbo payload inhibits frag. header */
 687         if (hdr->payload_len==0) {
 688                 IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_INHDRERRORS);
 689                 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 690                                   skb_network_header_len(skb));
 691                 return -1;
 692         }
 693         if (!pskb_may_pull(skb, (skb_transport_offset(skb) +
 694                                  sizeof(struct frag_hdr)))) {
 695                 IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_INHDRERRORS);
 696                 icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 697                                   skb_network_header_len(skb));
 698                 return -1;
 699         }
 700
 701         hdr = ipv6_hdr(skb);
 702         fhdr = (struct frag_hdr *)skb_transport_header(skb);
 703
 704         if (!(fhdr->frag_off & htons(0xFFF9))) {
 705                 /* It is not a fragmented frame */
 706                 skb->transport_header += sizeof(struct frag_hdr);
 707                 IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_REASMOKS);
 708
 709                 IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
 710                 return 1;
 711         }
 712
 713         if (atomic_read(&ip6_frags.mem) > ip6_frags_ctl.high_thresh)
 714                 ip6_evictor(ip6_dst_idev(skb->dst));
 715
 716         if ((fq = fq_find(fhdr->identification, &hdr->saddr, &hdr->daddr,
 717                           ip6_dst_idev(skb->dst))) != NULL) {
 718                 int ret;
 719
 720                 spin_lock(&fq->q.lock);
 721
 722                 ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff);
 723
 724                 spin_unlock(&fq->q.lock);
 725                 fq_put(fq, NULL);
 726                 return ret;
 727         }
 728
 729         IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_REASMFAILS);
 730         kfree_skb(skb);
 731         return -1;
 732 }
 733
 734 static struct inet6_protocol frag_protocol =
 735 {
 736         .handler        =       ipv6_frag_rcv,
 737         .flags          =       INET6_PROTO_NOPOLICY,
 738 };
 739
 740 void __init ipv6_frag_init(void)
 741 {
 742         if (inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT) < 0)
 743                 printk(KERN_ERR "ipv6_frag_init: Could not register protocol\n");
 744
 745         ip6_frags.ctl = &ip6_frags_ctl;
 746         ip6_frags.hashfn = ip6_hashfn;
 747         inet_frags_init(&ip6_frags);
 748 }