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   1 /*
   2  * IPv6 fragment reassembly for connection tracking
   3  *
   4  * Copyright (C)2004 USAGI/WIDE Project
   5  *
   6  * Author:
   7  *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
   8  *
   9  * Based on: net/ipv6/reassembly.c
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version
  14  * 2 of the License, or (at your option) any later version.
  15  */
  16
  17 #include <linux/config.h>
  18 #include <linux/errno.h>
  19 #include <linux/types.h>
  20 #include <linux/string.h>
  21 #include <linux/socket.h>
  22 #include <linux/sockios.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/net.h>
  25 #include <linux/list.h>
  26 #include <linux/netdevice.h>
  27 #include <linux/in6.h>
  28 #include <linux/ipv6.h>
  29 #include <linux/icmpv6.h>
  30 #include <linux/random.h>
  31 #include <linux/jhash.h>
  32
  33 #include <net/sock.h>
  34 #include <net/snmp.h>
  35
  36 #include <net/ipv6.h>
  37 #include <net/protocol.h>
  38 #include <net/transp_v6.h>
  39 #include <net/rawv6.h>
  40 #include <net/ndisc.h>
  41 #include <net/addrconf.h>
  42 #include <linux/sysctl.h>
  43 #include <linux/netfilter.h>
  44 #include <linux/netfilter_ipv6.h>
  45 #include <linux/kernel.h>
  46 #include <linux/module.h>
  47
  48 #if 0
  49 #define DEBUGP printk
  50 #else
  51 #define DEBUGP(format, args...)
  52 #endif
  53
  54 #define NF_CT_FRAG6_HIGH_THRESH 262144 /* == 256*1024 */
  55 #define NF_CT_FRAG6_LOW_THRESH 196608  /* == 192*1024 */
  56 #define NF_CT_FRAG6_TIMEOUT IPV6_FRAG_TIMEOUT
  57
  58 unsigned int nf_ct_frag6_high_thresh = 256*1024;
  59 unsigned int nf_ct_frag6_low_thresh = 192*1024;
  60 unsigned long nf_ct_frag6_timeout = IPV6_FRAG_TIMEOUT;
  61
  62 struct nf_ct_frag6_skb_cb
  63 {
  64         struct inet6_skb_parm   h;
  65         int                     offset;
  66         struct sk_buff          *orig;
  67 };
  68
  69 #define NFCT_FRAG6_CB(skb)      ((struct nf_ct_frag6_skb_cb*)((skb)->cb))
  70
  71 struct nf_ct_frag6_queue
  72 {
  73         struct nf_ct_frag6_queue        *next;
  74         struct list_head lru_list;              /* lru list member      */
  75
  76         __u32                   id;             /* fragment id          */
  77         struct in6_addr         saddr;
  78         struct in6_addr         daddr;
  79
  80         spinlock_t              lock;
  81         atomic_t                refcnt;
  82         struct timer_list       timer;          /* expire timer         */
  83         struct sk_buff          *fragments;
  84         int                     len;
  85         int                     meat;
  86         struct timeval          stamp;
  87         unsigned int            csum;
  88         __u8                    last_in;        /* has first/last segment arrived? */
  89 #define COMPLETE                4
  90 #define FIRST_IN                2
  91 #define LAST_IN                 1
  92         __u16                   nhoffset;
  93         struct nf_ct_frag6_queue        **pprev;
  94 };
  95
  96 /* Hash table. */
  97
  98 #define FRAG6Q_HASHSZ   64
  99
 100 static struct nf_ct_frag6_queue *nf_ct_frag6_hash[FRAG6Q_HASHSZ];
 101 static rwlock_t nf_ct_frag6_lock = RW_LOCK_UNLOCKED;
 102 static u32 nf_ct_frag6_hash_rnd;
 103 static LIST_HEAD(nf_ct_frag6_lru_list);
 104 int nf_ct_frag6_nqueues = 0;
 105
 106 static __inline__ void __fq_unlink(struct nf_ct_frag6_queue *fq)
 107 {
 108         if (fq->next)
 109                 fq->next->pprev = fq->pprev;
 110         *fq->pprev = fq->next;
 111         list_del(&fq->lru_list);
 112         nf_ct_frag6_nqueues--;
 113 }
 114
 115 static __inline__ void fq_unlink(struct nf_ct_frag6_queue *fq)
 116 {
 117         write_lock(&nf_ct_frag6_lock);
 118         __fq_unlink(fq);
 119         write_unlock(&nf_ct_frag6_lock);
 120 }
 121
 122 static unsigned int ip6qhashfn(u32 id, struct in6_addr *saddr,
 123                                struct in6_addr *daddr)
 124 {
 125         u32 a, b, c;
 126
 127         a = saddr->s6_addr32[0];
 128         b = saddr->s6_addr32[1];
 129         c = saddr->s6_addr32[2];
 130
 131         a += JHASH_GOLDEN_RATIO;
 132         b += JHASH_GOLDEN_RATIO;
 133         c += nf_ct_frag6_hash_rnd;
 134         __jhash_mix(a, b, c);
 135
 136         a += saddr->s6_addr32[3];
 137         b += daddr->s6_addr32[0];
 138         c += daddr->s6_addr32[1];
 139         __jhash_mix(a, b, c);
 140
 141         a += daddr->s6_addr32[2];
 142         b += daddr->s6_addr32[3];
 143         c += id;
 144         __jhash_mix(a, b, c);
 145
 146         return c & (FRAG6Q_HASHSZ - 1);
 147 }
 148
 149 static struct timer_list nf_ct_frag6_secret_timer;
 150 int nf_ct_frag6_secret_interval = 10 * 60 * HZ;
 151
 152 static void nf_ct_frag6_secret_rebuild(unsigned long dummy)
 153 {
 154         unsigned long now = jiffies;
 155         int i;
 156
 157         write_lock(&nf_ct_frag6_lock);
 158         get_random_bytes(&nf_ct_frag6_hash_rnd, sizeof(u32));
 159         for (i = 0; i < FRAG6Q_HASHSZ; i++) {
 160                 struct nf_ct_frag6_queue *q;
 161
 162                 q = nf_ct_frag6_hash[i];
 163                 while (q) {
 164                         struct nf_ct_frag6_queue *next = q->next;
 165                         unsigned int hval = ip6qhashfn(q->id,
 166                                                        &q->saddr,
 167                                                        &q->daddr);
 168
 169                         if (hval != i) {
 170                                 /* Unlink. */
 171                                 if (q->next)
 172                                         q->next->pprev = q->pprev;
 173                                 *q->pprev = q->next;
 174
 175                                 /* Relink to new hash chain. */
 176                                 if ((q->next = nf_ct_frag6_hash[hval]) != NULL)
 177                                         q->next->pprev = &q->next;
 178                                 nf_ct_frag6_hash[hval] = q;
 179                                 q->pprev = &nf_ct_frag6_hash[hval];
 180                         }
 181
 182                         q = next;
 183                 }
 184         }
 185         write_unlock(&nf_ct_frag6_lock);
 186
 187         mod_timer(&nf_ct_frag6_secret_timer, now + nf_ct_frag6_secret_interval);
 188 }
 189
 190 atomic_t nf_ct_frag6_mem = ATOMIC_INIT(0);
 191
 192 /* Memory Tracking Functions. */
 193 static inline void frag_kfree_skb(struct sk_buff *skb)
 194 {
 195         atomic_sub(skb->truesize, &nf_ct_frag6_mem);
 196         if (NFCT_FRAG6_CB(skb)->orig)
 197                 kfree_skb(NFCT_FRAG6_CB(skb)->orig);
 198
 199         kfree_skb(skb);
 200 }
 201
 202 static inline void frag_free_queue(struct nf_ct_frag6_queue *fq)
 203 {
 204         atomic_sub(sizeof(struct nf_ct_frag6_queue), &nf_ct_frag6_mem);
 205         kfree(fq);
 206 }
 207
 208 static inline struct nf_ct_frag6_queue *frag_alloc_queue(void)
 209 {
 210         struct nf_ct_frag6_queue *fq = kmalloc(sizeof(struct nf_ct_frag6_queue), GFP_ATOMIC);
 211
 212         if (!fq)
 213                 return NULL;
 214         atomic_add(sizeof(struct nf_ct_frag6_queue), &nf_ct_frag6_mem);
 215         return fq;
 216 }
 217
 218 /* Destruction primitives. */
 219
 220 /* Complete destruction of fq. */
 221 static void nf_ct_frag6_destroy(struct nf_ct_frag6_queue *fq)
 222 {
 223         struct sk_buff *fp;
 224
 225         BUG_TRAP(fq->last_in&COMPLETE);
 226         BUG_TRAP(del_timer(&fq->timer) == 0);
 227
 228         /* Release all fragment data. */
 229         fp = fq->fragments;
 230         while (fp) {
 231                 struct sk_buff *xp = fp->next;
 232
 233                 frag_kfree_skb(fp);
 234                 fp = xp;
 235         }
 236
 237         frag_free_queue(fq);
 238 }
 239
 240 static __inline__ void fq_put(struct nf_ct_frag6_queue *fq)
 241 {
 242         if (atomic_dec_and_test(&fq->refcnt))
 243                 nf_ct_frag6_destroy(fq);
 244 }
 245
 246 /* Kill fq entry. It is not destroyed immediately,
 247  * because caller (and someone more) holds reference count.
 248  */
 249 static __inline__ void fq_kill(struct nf_ct_frag6_queue *fq)
 250 {
 251         if (del_timer(&fq->timer))
 252                 atomic_dec(&fq->refcnt);
 253
 254         if (!(fq->last_in & COMPLETE)) {
 255                 fq_unlink(fq);
 256                 atomic_dec(&fq->refcnt);
 257                 fq->last_in |= COMPLETE;
 258         }
 259 }
 260
 261 static void nf_ct_frag6_evictor(void)
 262 {
 263         struct nf_ct_frag6_queue *fq;
 264         struct list_head *tmp;
 265
 266         for (;;) {
 267                 if (atomic_read(&nf_ct_frag6_mem) <= nf_ct_frag6_low_thresh)
 268                         return;
 269                 read_lock(&nf_ct_frag6_lock);
 270                 if (list_empty(&nf_ct_frag6_lru_list)) {
 271                         read_unlock(&nf_ct_frag6_lock);
 272                         return;
 273                 }
 274                 tmp = nf_ct_frag6_lru_list.next;
 275                 fq = list_entry(tmp, struct nf_ct_frag6_queue, lru_list);
 276                 atomic_inc(&fq->refcnt);
 277                 read_unlock(&nf_ct_frag6_lock);
 278
 279                 spin_lock(&fq->lock);
 280                 if (!(fq->last_in&COMPLETE))
 281                         fq_kill(fq);
 282                 spin_unlock(&fq->lock);
 283
 284                 fq_put(fq);
 285         }
 286 }
 287
 288 static void nf_ct_frag6_expire(unsigned long data)
 289 {
 290         struct nf_ct_frag6_queue *fq = (struct nf_ct_frag6_queue *) data;
 291
 292         spin_lock(&fq->lock);
 293
 294         if (fq->last_in & COMPLETE)
 295                 goto out;
 296
 297         fq_kill(fq);
 298
 299 out:
 300         spin_unlock(&fq->lock);
 301         fq_put(fq);
 302 }
 303
 304 /* Creation primitives. */
 305
 306
 307 static struct nf_ct_frag6_queue *nf_ct_frag6_intern(unsigned int hash,
 308                                           struct nf_ct_frag6_queue *fq_in)
 309 {
 310         struct nf_ct_frag6_queue *fq;
 311
 312         write_lock(&nf_ct_frag6_lock);
 313 #ifdef CONFIG_SMP
 314         for (fq = nf_ct_frag6_hash[hash]; fq; fq = fq->next) {
 315                 if (fq->id == fq_in->id &&
 316                     !ipv6_addr_cmp(&fq_in->saddr, &fq->saddr) &&
 317                     !ipv6_addr_cmp(&fq_in->daddr, &fq->daddr)) {
 318                         atomic_inc(&fq->refcnt);
 319                         write_unlock(&nf_ct_frag6_lock);
 320                         fq_in->last_in |= COMPLETE;
 321                         fq_put(fq_in);
 322                         return fq;
 323                 }
 324         }
 325 #endif
 326         fq = fq_in;
 327
 328         if (!mod_timer(&fq->timer, jiffies + nf_ct_frag6_timeout))
 329                 atomic_inc(&fq->refcnt);
 330
 331         atomic_inc(&fq->refcnt);
 332         if ((fq->next = nf_ct_frag6_hash[hash]) != NULL)
 333                 fq->next->pprev = &fq->next;
 334         nf_ct_frag6_hash[hash] = fq;
 335         fq->pprev = &nf_ct_frag6_hash[hash];
 336         INIT_LIST_HEAD(&fq->lru_list);
 337         list_add_tail(&fq->lru_list, &nf_ct_frag6_lru_list);
 338         nf_ct_frag6_nqueues++;
 339         write_unlock(&nf_ct_frag6_lock);
 340         return fq;
 341 }
 342
 343
 344 static struct nf_ct_frag6_queue *
 345 nf_ct_frag6_create(unsigned int hash, u32 id, struct in6_addr *src,                                struct in6_addr *dst)
 346 {
 347         struct nf_ct_frag6_queue *fq;
 348
 349         if ((fq = frag_alloc_queue()) == NULL) {
 350                 DEBUGP("Can't alloc new queue\n");
 351                 goto oom;
 352         }
 353
 354         memset(fq, 0, sizeof(struct nf_ct_frag6_queue));
 355
 356         fq->id = id;
 357         ipv6_addr_copy(&fq->saddr, src);
 358         ipv6_addr_copy(&fq->daddr, dst);
 359
 360         init_timer(&fq->timer);
 361         fq->timer.function = nf_ct_frag6_expire;
 362         fq->timer.data = (long) fq;
 363         fq->lock = SPIN_LOCK_UNLOCKED;
 364         atomic_set(&fq->refcnt, 1);
 365
 366         return nf_ct_frag6_intern(hash, fq);
 367
 368 oom:
 369         return NULL;
 370 }
 371
 372 static __inline__ struct nf_ct_frag6_queue *
 373 fq_find(u32 id, struct in6_addr *src, struct in6_addr *dst)
 374 {
 375         struct nf_ct_frag6_queue *fq;
 376         unsigned int hash = ip6qhashfn(id, src, dst);
 377
 378         read_lock(&nf_ct_frag6_lock);
 379         for (fq = nf_ct_frag6_hash[hash]; fq; fq = fq->next) {
 380                 if (fq->id == id &&
 381                     !ipv6_addr_cmp(src, &fq->saddr) &&
 382                     !ipv6_addr_cmp(dst, &fq->daddr)) {
 383                         atomic_inc(&fq->refcnt);
 384                         read_unlock(&nf_ct_frag6_lock);
 385                         return fq;
 386                 }
 387         }
 388         read_unlock(&nf_ct_frag6_lock);
 389
 390         return nf_ct_frag6_create(hash, id, src, dst);
 391 }
 392
 393
 394 static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb,
 395                              struct frag_hdr *fhdr, int nhoff)
 396 {
 397         struct sk_buff *prev, *next;
 398         int offset, end;
 399
 400         if (fq->last_in & COMPLETE) {
 401                 DEBUGP("Allready completed\n");
 402                 goto err;
 403         }
 404
 405         offset = ntohs(fhdr->frag_off) & ~0x7;
 406         end = offset + (ntohs(skb->nh.ipv6h->payload_len) -
 407                         ((u8 *) (fhdr + 1) - (u8 *) (skb->nh.ipv6h + 1)));
 408
 409         if ((unsigned int)end > IPV6_MAXPLEN) {
 410                 DEBUGP("offset is too large.\n");
 411                 return -1;
 412         }
 413
 414         if (skb->ip_summed == CHECKSUM_HW)
 415                 skb->csum = csum_sub(skb->csum,
 416                                      csum_partial(skb->nh.raw,
 417                                                   (u8*)(fhdr + 1) - skb->nh.raw,
 418                                                   0));
 419
 420         /* Is this the final fragment? */
 421         if (!(fhdr->frag_off & htons(IP6_MF))) {
 422                 /* If we already have some bits beyond end
 423                  * or have different end, the segment is corrupted.
 424                  */
 425                 if (end < fq->len ||
 426                     ((fq->last_in & LAST_IN) && end != fq->len)) {
 427                         DEBUGP("already received last fragment\n");
 428                         goto err;
 429                 }
 430                 fq->last_in |= LAST_IN;
 431                 fq->len = end;
 432         } else {
 433                 /* Check if the fragment is rounded to 8 bytes.
 434                  * Required by the RFC.
 435                  */
 436                 if (end & 0x7) {
 437                         /* RFC2460 says always send parameter problem in
 438                          * this case. -DaveM
 439                          */
 440                         DEBUGP("the end of this fragment is not rounded to 8 bytes.\n");
 441                         return -1;
 442                 }
 443                 if (end > fq->len) {
 444                         /* Some bits beyond end -> corruption. */
 445                         if (fq->last_in & LAST_IN) {
 446                                 DEBUGP("last packet already reached.\n");
 447                                 goto err;
 448                         }
 449                         fq->len = end;
 450                 }
 451         }
 452
 453         if (end == offset)
 454                 goto err;
 455
 456         /* Point into the IP datagram 'data' part. */
 457         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
 458                 DEBUGP("queue: message is too short.\n");
 459                 goto err;
 460         }
 461         if (end-offset < skb->len) {
 462                 if (pskb_trim(skb, end - offset)) {
 463                         DEBUGP("Can't trim\n");
 464                         goto err;
 465                 }
 466                 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 467                         skb->ip_summed = CHECKSUM_NONE;
 468         }
 469
 470         /* Find out which fragments are in front and at the back of us
 471          * in the chain of fragments so far.  We must know where to put
 472          * this fragment, right?
 473          */
 474         prev = NULL;
 475         for (next = fq->fragments; next != NULL; next = next->next) {
 476                 if (NFCT_FRAG6_CB(next)->offset >= offset)
 477                         break;  /* bingo! */
 478                 prev = next;
 479         }
 480
 481         /* We found where to put this one.  Check for overlap with
 482          * preceding fragment, and, if needed, align things so that
 483          * any overlaps are eliminated.
 484          */
 485         if (prev) {
 486                 int i = (NFCT_FRAG6_CB(prev)->offset + prev->len) - offset;
 487
 488                 if (i > 0) {
 489                         offset += i;
 490                         if (end <= offset) {
 491                                 DEBUGP("overlap\n");
 492                                 goto err;
 493                         }
 494                         if (!pskb_pull(skb, i)) {
 495                                 DEBUGP("Can't pull\n");
 496                                 goto err;
 497                         }
 498                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 499                                 skb->ip_summed = CHECKSUM_NONE;
 500                 }
 501         }
 502
 503         /* Look for overlap with succeeding segments.
 504          * If we can merge fragments, do it.
 505          */
 506         while (next && NFCT_FRAG6_CB(next)->offset < end) {
 507                 /* overlap is 'i' bytes */
 508                 int i = end - NFCT_FRAG6_CB(next)->offset;
 509
 510                 if (i < next->len) {
 511                         /* Eat head of the next overlapped fragment
 512                          * and leave the loop. The next ones cannot overlap.
 513                          */
 514                         DEBUGP("Eat head of the overlapped parts.: %d", i);
 515                         if (!pskb_pull(next, i))
 516                                 goto err;
 517
 518                         /* next fragment */
 519                         NFCT_FRAG6_CB(next)->offset += i;
 520                         fq->meat -= i;
 521                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 522                                 next->ip_summed = CHECKSUM_NONE;
 523                         break;
 524                 } else {
 525                         struct sk_buff *free_it = next;
 526
 527                         /* Old fragmnet is completely overridden with
 528                          * new one drop it.
 529                          */
 530                         next = next->next;
 531
 532                         if (prev)
 533                                 prev->next = next;
 534                         else
 535                                 fq->fragments = next;
 536
 537                         fq->meat -= free_it->len;
 538                         frag_kfree_skb(free_it);
 539                 }
 540         }
 541
 542         NFCT_FRAG6_CB(skb)->offset = offset;
 543
 544         /* Insert this fragment in the chain of fragments. */
 545         skb->next = next;
 546         if (prev)
 547                 prev->next = skb;
 548         else
 549                 fq->fragments = skb;
 550
 551         skb->dev = NULL;
 552         skb_get_timestamp(skb, &fq->stamp);
 553         fq->meat += skb->len;
 554         atomic_add(skb->truesize, &nf_ct_frag6_mem);
 555
 556         /* The first fragment.
 557          * nhoffset is obtained from the first fragment, of course.
 558          */
 559         if (offset == 0) {
 560                 fq->nhoffset = nhoff;
 561                 fq->last_in |= FIRST_IN;
 562         }
 563         write_lock(&nf_ct_frag6_lock);
 564         list_move_tail(&fq->lru_list, &nf_ct_frag6_lru_list);
 565         write_unlock(&nf_ct_frag6_lock);
 566         return 0;
 567
 568 err:
 569         return -1;
 570 }
 571
 572 /*
 573  *      Check if this packet is complete.
 574  *      Returns NULL on failure by any reason, and pointer
 575  *      to current nexthdr field in reassembled frame.
 576  *
 577  *      It is called with locked fq, and caller must check that
 578  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 579  *      the last and the first frames arrived and all the bits are here.
 580  */
 581 static struct sk_buff *
 582 nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
 583 {
 584         struct sk_buff *fp, *op, *head = fq->fragments;
 585         int    payload_len;
 586
 587         fq_kill(fq);
 588
 589         BUG_TRAP(head != NULL);
 590         BUG_TRAP(NFCT_FRAG6_CB(head)->offset == 0);
 591
 592         /* Unfragmented part is taken from the first segment. */
 593         payload_len = (head->data - head->nh.raw) - sizeof(struct ipv6hdr) + fq->len - sizeof(struct frag_hdr);
 594         if (payload_len > IPV6_MAXPLEN) {
 595                 DEBUGP("payload len is too large.\n");
 596                 goto out_oversize;
 597         }
 598
 599         /* Head of list must not be cloned. */
 600         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) {
 601                 DEBUGP("skb is cloned but can't expand head");
 602                 goto out_oom;
 603         }
 604
 605         /* If the first fragment is fragmented itself, we split
 606          * it to two chunks: the first with data and paged part
 607          * and the second, holding only fragments. */
 608         if (skb_shinfo(head)->frag_list) {
 609                 struct sk_buff *clone;
 610                 int i, plen = 0;
 611
 612                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) {
 613                         DEBUGP("Can't alloc skb\n");
 614                         goto out_oom;
 615                 }
 616                 clone->next = head->next;
 617                 head->next = clone;
 618                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 619                 skb_shinfo(head)->frag_list = NULL;
 620                 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
 621                         plen += skb_shinfo(head)->frags[i].size;
 622                 clone->len = clone->data_len = head->data_len - plen;
 623                 head->data_len -= clone->len;
 624                 head->len -= clone->len;
 625                 clone->csum = 0;
 626                 clone->ip_summed = head->ip_summed;
 627
 628                 NFCT_FRAG6_CB(clone)->orig = NULL;
 629                 atomic_add(clone->truesize, &nf_ct_frag6_mem);
 630         }
 631
 632         /* We have to remove fragment header from datagram and to relocate
 633          * header in order to calculate ICV correctly. */
 634         head->nh.raw[fq->nhoffset] = head->h.raw[0];
 635         memmove(head->head + sizeof(struct frag_hdr), head->head,
 636                 (head->data - head->head) - sizeof(struct frag_hdr));
 637         head->mac.raw += sizeof(struct frag_hdr);
 638         head->nh.raw += sizeof(struct frag_hdr);
 639
 640         skb_shinfo(head)->frag_list = head->next;
 641         head->h.raw = head->data;
 642         skb_push(head, head->data - head->nh.raw);
 643         atomic_sub(head->truesize, &nf_ct_frag6_mem);
 644
 645         for (fp=head->next; fp; fp = fp->next) {
 646                 head->data_len += fp->len;
 647                 head->len += fp->len;
 648                 if (head->ip_summed != fp->ip_summed)
 649                         head->ip_summed = CHECKSUM_NONE;
 650                 else if (head->ip_summed == CHECKSUM_HW)
 651                         head->csum = csum_add(head->csum, fp->csum);
 652                 head->truesize += fp->truesize;
 653                 atomic_sub(fp->truesize, &nf_ct_frag6_mem);
 654         }
 655
 656         head->next = NULL;
 657         head->dev = dev;
 658         skb_set_timestamp(head, &fq->stamp);
 659         head->nh.ipv6h->payload_len = htons(payload_len);
 660
 661         /* Yes, and fold redundant checksum back. 8) */
 662         if (head->ip_summed == CHECKSUM_HW)
 663                 head->csum = csum_partial(head->nh.raw, head->h.raw-head->nh.raw, head->csum);
 664
 665         fq->fragments = NULL;
 666
 667         /* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
 668         fp = skb_shinfo(head)->frag_list;
 669         if (NFCT_FRAG6_CB(fp)->orig == NULL)
 670                 /* at above code, head skb is divided into two skbs. */
 671                 fp = fp->next;
 672
 673         op = NFCT_FRAG6_CB(head)->orig;
 674         for (; fp; fp = fp->next) {
 675                 struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig;
 676
 677                 op->next = orig;
 678                 op = orig;
 679                 NFCT_FRAG6_CB(fp)->orig = NULL;
 680         }
 681
 682         return head;
 683
 684 out_oversize:
 685         if (net_ratelimit())
 686                 printk(KERN_DEBUG "nf_ct_frag6_reasm: payload len = %d\n", payload_len);
 687         goto out_fail;
 688 out_oom:
 689         if (net_ratelimit())
 690                 printk(KERN_DEBUG "nf_ct_frag6_reasm: no memory for reassembly\n");
 691 out_fail:
 692         return NULL;
 693 }
 694
 695 /*
 696  * find the header just before Fragment Header.
 697  *
 698  * if success return 0 and set ...
 699  * (*prevhdrp): the value of "Next Header Field" in the header
 700  *              just before Fragment Header.
 701  * (*prevhoff): the offset of "Next Header Field" in the header
 702  *              just before Fragment Header.
 703  * (*fhoff)   : the offset of Fragment Header.
 704  *
 705  * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
 706  *
 707  */
 708 static int
 709 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
 710 {
 711         u8 nexthdr = skb->nh.ipv6h->nexthdr;
 712         u8 prev_nhoff = (u8 *)&skb->nh.ipv6h->nexthdr - skb->data;
 713         int start = (u8 *)(skb->nh.ipv6h+1) - skb->data;
 714         int len = skb->len - start;
 715         u8 prevhdr = NEXTHDR_IPV6;
 716
 717         while (nexthdr != NEXTHDR_FRAGMENT) {
 718                 struct ipv6_opt_hdr hdr;
 719                 int hdrlen;
 720
 721                 if (!ipv6_ext_hdr(nexthdr)) {
 722                         return -1;
 723                 }
 724                 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
 725                         DEBUGP("too short\n");
 726                         return -1;
 727                 }
 728                 if (nexthdr == NEXTHDR_NONE) {
 729                         DEBUGP("next header is none\n");
 730                         return -1;
 731                 }
 732                 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
 733                         BUG();
 734                 if (nexthdr == NEXTHDR_AUTH)
 735                         hdrlen = (hdr.hdrlen+2)<<2;
 736                 else
 737                         hdrlen = ipv6_optlen(&hdr);
 738
 739                 prevhdr = nexthdr;
 740                 prev_nhoff = start;
 741
 742                 nexthdr = hdr.nexthdr;
 743                 len -= hdrlen;
 744                 start += hdrlen;
 745         }
 746
 747         if (len < 0)
 748                 return -1;
 749
 750         *prevhdrp = prevhdr;
 751         *prevhoff = prev_nhoff;
 752         *fhoff = start;
 753
 754         return 0;
 755 }
 756
 757 struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb)
 758 {
 759         struct sk_buff *clone;
 760         struct net_device *dev = skb->dev;
 761         struct frag_hdr *fhdr;
 762         struct nf_ct_frag6_queue *fq;
 763         struct ipv6hdr *hdr;
 764         int fhoff, nhoff;
 765         u8 prevhdr;
 766         struct sk_buff *ret_skb = NULL;
 767
 768         /* Jumbo payload inhibits frag. header */
 769         if (skb->nh.ipv6h->payload_len == 0) {
 770                 DEBUGP("payload len = 0\n");
 771                 return skb;
 772         }
 773
 774         if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
 775                 return skb;
 776
 777         clone = skb_clone(skb, GFP_ATOMIC);
 778         if (clone == NULL) {
 779                 DEBUGP("Can't clone skb\n");
 780                 return skb;
 781         }
 782
 783         NFCT_FRAG6_CB(clone)->orig = skb;
 784
 785         if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) {
 786                 DEBUGP("message is too short.\n");
 787                 goto ret_orig;
 788         }
 789
 790         clone->h.raw = clone->data + fhoff;
 791         hdr = clone->nh.ipv6h;
 792         fhdr = (struct frag_hdr *)clone->h.raw;
 793
 794         if (!(fhdr->frag_off & htons(0xFFF9))) {
 795                 DEBUGP("Invalid fragment offset\n");
 796                 /* It is not a fragmented frame */
 797                 goto ret_orig;
 798         }
 799
 800         if (atomic_read(&nf_ct_frag6_mem) > nf_ct_frag6_high_thresh)
 801                 nf_ct_frag6_evictor();
 802
 803         fq = fq_find(fhdr->identification, &hdr->saddr, &hdr->daddr);
 804         if (fq == NULL) {
 805                 DEBUGP("Can't find and can't create new queue\n");
 806                 goto ret_orig;
 807         }
 808
 809         spin_lock(&fq->lock);
 810
 811         if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) {
 812                 spin_unlock(&fq->lock);
 813                 DEBUGP("Can't insert skb to queue\n");
 814                 fq_put(fq);
 815                 goto ret_orig;
 816         }
 817
 818         if (fq->last_in == (FIRST_IN|LAST_IN) && fq->meat == fq->len) {
 819                 ret_skb = nf_ct_frag6_reasm(fq, dev);
 820                 if (ret_skb == NULL)
 821                         DEBUGP("Can't reassemble fragmented packets\n");
 822         }
 823         spin_unlock(&fq->lock);
 824
 825         fq_put(fq);
 826         return ret_skb;
 827
 828 ret_orig:
 829         kfree_skb(clone);
 830         return skb;
 831 }
 832
 833 void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
 834                         struct net_device *in, struct net_device *out,
 835                         int (*okfn)(struct sk_buff *))
 836 {
 837         struct sk_buff *s, *s2;
 838
 839         for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
 840                 nf_conntrack_put_reasm(s->nfct_reasm);
 841                 nf_conntrack_get_reasm(skb);
 842                 s->nfct_reasm = skb;
 843
 844                 s2 = s->next;
 845                 NF_HOOK_THRESH(PF_INET6, hooknum, s, in, out, okfn,
 846                                NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
 847                 s = s2;
 848         }
 849         nf_conntrack_put_reasm(skb);
 850 }
 851
 852 int nf_ct_frag6_kfree_frags(struct sk_buff *skb)
 853 {
 854         struct sk_buff *s, *s2;
 855
 856         for (s = NFCT_FRAG6_CB(skb)->orig; s; s = s2) {
 857
 858                 s2 = s->next;
 859                 kfree_skb(s);
 860         }
 861
 862         kfree_skb(skb);
 863
 864         return 0;
 865 }
 866
 867 int nf_ct_frag6_init(void)
 868 {
 869         nf_ct_frag6_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
 870                                    (jiffies ^ (jiffies >> 6)));
 871
 872         init_timer(&nf_ct_frag6_secret_timer);
 873         nf_ct_frag6_secret_timer.function = nf_ct_frag6_secret_rebuild;
 874         nf_ct_frag6_secret_timer.expires = jiffies
 875                                            + nf_ct_frag6_secret_interval;
 876         add_timer(&nf_ct_frag6_secret_timer);
 877
 878         return 0;
 879 }
 880
 881 void nf_ct_frag6_cleanup(void)
 882 {
 883         del_timer(&nf_ct_frag6_secret_timer);
 884         nf_ct_frag6_evictor();
 885 }