net/ipv4/ip_fragment.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              The IP fragmentation functionality.
   7  *
   8  * Authors:     Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
   9  *              Alan Cox <alan@lxorguk.ukuu.org.uk>
  10  *
  11  * Fixes:
  12  *              Alan Cox        :       Split from ip.c , see ip_input.c for history.
  13  *              David S. Miller :       Begin massive cleanup...
  14  *              Andi Kleen      :       Add sysctls.
  15  *              xxxx            :       Overlapfrag bug.
  16  *              Ultima          :       ip_expire() kernel panic.
  17  *              Bill Hawes      :       Frag accounting and evictor fixes.
  18  *              John McDonald   :       0 length frag bug.
  19  *              Alexey Kuznetsov:       SMP races, threading, cleanup.
  20  *              Patrick McHardy :       LRU queue of frag heads for evictor.
  21  */
  22
  23 #define pr_fmt(fmt) "IPv4: " fmt
  24
  25 #include <linux/compiler.h>
  26 #include <linux/module.h>
  27 #include <linux/types.h>
  28 #include <linux/mm.h>
  29 #include <linux/jiffies.h>
  30 #include <linux/skbuff.h>
  31 #include <linux/list.h>
  32 #include <linux/ip.h>
  33 #include <linux/icmp.h>
  34 #include <linux/netdevice.h>
  35 #include <linux/jhash.h>
  36 #include <linux/random.h>
  37 #include <linux/slab.h>
  38 #include <net/route.h>
  39 #include <net/dst.h>
  40 #include <net/sock.h>
  41 #include <net/ip.h>
  42 #include <net/icmp.h>
  43 #include <net/checksum.h>
  44 #include <net/inetpeer.h>
  45 #include <net/inet_frag.h>
  46 #include <linux/tcp.h>
  47 #include <linux/udp.h>
  48 #include <linux/inet.h>
  49 #include <linux/netfilter_ipv4.h>
  50 #include <net/inet_ecn.h>
  51
  52 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
  53  * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
  54  * as well. Or notify me, at least. --ANK
  55  */
  56
  57 static int sysctl_ipfrag_max_dist __read_mostly = 64;
  58
  59 struct ipfrag_skb_cb
  60 {
  61         struct inet_skb_parm    h;
  62         int                     offset;
  63 };
  64
  65 #define FRAG_CB(skb)    ((struct ipfrag_skb_cb *)((skb)->cb))
  66
  67 /* Describe an entry in the "incomplete datagrams" queue. */
  68 struct ipq {
  69         struct inet_frag_queue q;
  70
  71         u32             user;
  72         __be32          saddr;
  73         __be32          daddr;
  74         __be16          id;
  75         u8              protocol;
  76         u8              ecn; /* RFC3168 support */
  77         int             iif;
  78         unsigned int    rid;
  79         struct inet_peer *peer;
  80 };
  81
  82 static inline u8 ip4_frag_ecn(u8 tos)
  83 {
  84         return 1 << (tos & INET_ECN_MASK);
  85 }
  86
  87 static struct inet_frags ip4_frags;
  88
  89 int ip_frag_nqueues(struct net *net)
  90 {
  91         return net->ipv4.frags.nqueues;
  92 }
  93
  94 int ip_frag_mem(struct net *net)
  95 {
  96         return sum_frag_mem_limit(&net->ipv4.frags);
  97 }
  98
  99 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 100                          struct net_device *dev);
 101
 102 struct ip4_create_arg {
 103         struct iphdr *iph;
 104         u32 user;
 105 };
 106
 107 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
 108 {
 109         net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
 110         return jhash_3words((__force u32)id << 16 | prot,
 111                             (__force u32)saddr, (__force u32)daddr,
 112                             ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
 113 }
 114
 115 static unsigned int ip4_hashfn(struct inet_frag_queue *q)
 116 {
 117         struct ipq *ipq;
 118
 119         ipq = container_of(q, struct ipq, q);
 120         return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
 121 }
 122
 123 static bool ip4_frag_match(struct inet_frag_queue *q, void *a)
 124 {
 125         struct ipq *qp;
 126         struct ip4_create_arg *arg = a;
 127
 128         qp = container_of(q, struct ipq, q);
 129         return  qp->id == arg->iph->id &&
 130                 qp->saddr == arg->iph->saddr &&
 131                 qp->daddr == arg->iph->daddr &&
 132                 qp->protocol == arg->iph->protocol &&
 133                 qp->user == arg->user;
 134 }
 135
 136 static void ip4_frag_init(struct inet_frag_queue *q, void *a)
 137 {
 138         struct ipq *qp = container_of(q, struct ipq, q);
 139         struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
 140                                                frags);
 141         struct net *net = container_of(ipv4, struct net, ipv4);
 142
 143         struct ip4_create_arg *arg = a;
 144
 145         qp->protocol = arg->iph->protocol;
 146         qp->id = arg->iph->id;
 147         qp->ecn = ip4_frag_ecn(arg->iph->tos);
 148         qp->saddr = arg->iph->saddr;
 149         qp->daddr = arg->iph->daddr;
 150         qp->user = arg->user;
 151         qp->peer = sysctl_ipfrag_max_dist ?
 152                 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, 1) : NULL;
 153 }
 154
 155 static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
 156 {
 157         struct ipq *qp;
 158
 159         qp = container_of(q, struct ipq, q);
 160         if (qp->peer)
 161                 inet_putpeer(qp->peer);
 162 }
 163
 164
 165 /* Destruction primitives. */
 166
 167 static __inline__ void ipq_put(struct ipq *ipq)
 168 {
 169         inet_frag_put(&ipq->q, &ip4_frags);
 170 }
 171
 172 /* Kill ipq entry. It is not destroyed immediately,
 173  * because caller (and someone more) holds reference count.
 174  */
 175 static void ipq_kill(struct ipq *ipq)
 176 {
 177         inet_frag_kill(&ipq->q, &ip4_frags);
 178 }
 179
 180 /* Memory limiting on fragments.  Evictor trashes the oldest
 181  * fragment queue until we are back under the threshold.
 182  */
 183 static void ip_evictor(struct net *net)
 184 {
 185         int evicted;
 186
 187         evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags, false);
 188         if (evicted)
 189                 IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted);
 190 }
 191
 192 /*
 193  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
 194  */
 195 static void ip_expire(unsigned long arg)
 196 {
 197         struct ipq *qp;
 198         struct net *net;
 199
 200         qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
 201         net = container_of(qp->q.net, struct net, ipv4.frags);
 202
 203         spin_lock(&qp->q.lock);
 204
 205         if (qp->q.last_in & INET_FRAG_COMPLETE)
 206                 goto out;
 207
 208         ipq_kill(qp);
 209
 210         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
 211         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 212
 213         if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
 214                 struct sk_buff *head = qp->q.fragments;
 215                 const struct iphdr *iph;
 216                 int err;
 217
 218                 rcu_read_lock();
 219                 head->dev = dev_get_by_index_rcu(net, qp->iif);
 220                 if (!head->dev)
 221                         goto out_rcu_unlock;
 222
 223                 /* skb has no dst, perform route lookup again */
 224                 iph = ip_hdr(head);
 225                 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
 226                                            iph->tos, head->dev);
 227                 if (err)
 228                         goto out_rcu_unlock;
 229
 230                 /*
 231                  * Only an end host needs to send an ICMP
 232                  * "Fragment Reassembly Timeout" message, per RFC792.
 233                  */
 234                 if (qp->user == IP_DEFRAG_AF_PACKET ||
 235                     ((qp->user >= IP_DEFRAG_CONNTRACK_IN) &&
 236                      (qp->user <= __IP_DEFRAG_CONNTRACK_IN_END) &&
 237                      (skb_rtable(head)->rt_type != RTN_LOCAL)))
 238                         goto out_rcu_unlock;
 239
 240
 241                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
 242                 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
 243 out_rcu_unlock:
 244                 rcu_read_unlock();
 245         }
 246 out:
 247         spin_unlock(&qp->q.lock);
 248         ipq_put(qp);
 249 }
 250
 251 /* Find the correct entry in the "incomplete datagrams" queue for
 252  * this IP datagram, and create new one, if nothing is found.
 253  */
 254 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
 255 {
 256         struct inet_frag_queue *q;
 257         struct ip4_create_arg arg;
 258         unsigned int hash;
 259
 260         arg.iph = iph;
 261         arg.user = user;
 262
 263         read_lock(&ip4_frags.lock);
 264         hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
 265
 266         q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
 267         if (IS_ERR_OR_NULL(q)) {
 268                 inet_frag_maybe_warn_overflow(q, pr_fmt());
 269                 return NULL;
 270         }
 271         return container_of(q, struct ipq, q);
 272 }
 273
 274 /* Is the fragment too far ahead to be part of ipq? */
 275 static inline int ip_frag_too_far(struct ipq *qp)
 276 {
 277         struct inet_peer *peer = qp->peer;
 278         unsigned int max = sysctl_ipfrag_max_dist;
 279         unsigned int start, end;
 280
 281         int rc;
 282
 283         if (!peer || !max)
 284                 return 0;
 285
 286         start = qp->rid;
 287         end = atomic_inc_return(&peer->rid);
 288         qp->rid = end;
 289
 290         rc = qp->q.fragments && (end - start) > max;
 291
 292         if (rc) {
 293                 struct net *net;
 294
 295                 net = container_of(qp->q.net, struct net, ipv4.frags);
 296                 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 297         }
 298
 299         return rc;
 300 }
 301
 302 static int ip_frag_reinit(struct ipq *qp)
 303 {
 304         struct sk_buff *fp;
 305         unsigned int sum_truesize = 0;
 306
 307         if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
 308                 atomic_inc(&qp->q.refcnt);
 309                 return -ETIMEDOUT;
 310         }
 311
 312         fp = qp->q.fragments;
 313         do {
 314                 struct sk_buff *xp = fp->next;
 315
 316                 sum_truesize += fp->truesize;
 317                 kfree_skb(fp);
 318                 fp = xp;
 319         } while (fp);
 320         sub_frag_mem_limit(&qp->q, sum_truesize);
 321
 322         qp->q.last_in = 0;
 323         qp->q.len = 0;
 324         qp->q.meat = 0;
 325         qp->q.fragments = NULL;
 326         qp->q.fragments_tail = NULL;
 327         qp->iif = 0;
 328         qp->ecn = 0;
 329
 330         return 0;
 331 }
 332
 333 /* Add new segment to existing queue. */
 334 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 335 {
 336         struct sk_buff *prev, *next;
 337         struct net_device *dev;
 338         int flags, offset;
 339         int ihl, end;
 340         int err = -ENOENT;
 341         u8 ecn;
 342
 343         if (qp->q.last_in & INET_FRAG_COMPLETE)
 344                 goto err;
 345
 346         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
 347             unlikely(ip_frag_too_far(qp)) &&
 348             unlikely(err = ip_frag_reinit(qp))) {
 349                 ipq_kill(qp);
 350                 goto err;
 351         }
 352
 353         ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
 354         offset = ntohs(ip_hdr(skb)->frag_off);
 355         flags = offset & ~IP_OFFSET;
 356         offset &= IP_OFFSET;
 357         offset <<= 3;           /* offset is in 8-byte chunks */
 358         ihl = ip_hdrlen(skb);
 359
 360         /* Determine the position of this fragment. */
 361         end = offset + skb->len - ihl;
 362         err = -EINVAL;
 363
 364         /* Is this the final fragment? */
 365         if ((flags & IP_MF) == 0) {
 366                 /* If we already have some bits beyond end
 367                  * or have different end, the segment is corrupted.
 368                  */
 369                 if (end < qp->q.len ||
 370                     ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len))
 371                         goto err;
 372                 qp->q.last_in |= INET_FRAG_LAST_IN;
 373                 qp->q.len = end;
 374         } else {
 375                 if (end&7) {
 376                         end &= ~7;
 377                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 378                                 skb->ip_summed = CHECKSUM_NONE;
 379                 }
 380                 if (end > qp->q.len) {
 381                         /* Some bits beyond end -> corruption. */
 382                         if (qp->q.last_in & INET_FRAG_LAST_IN)
 383                                 goto err;
 384                         qp->q.len = end;
 385                 }
 386         }
 387         if (end == offset)
 388                 goto err;
 389
 390         err = -ENOMEM;
 391         if (pskb_pull(skb, ihl) == NULL)
 392                 goto err;
 393
 394         err = pskb_trim_rcsum(skb, end - offset);
 395         if (err)
 396                 goto err;
 397
 398         /* Find out which fragments are in front and at the back of us
 399          * in the chain of fragments so far.  We must know where to put
 400          * this fragment, right?
 401          */
 402         prev = qp->q.fragments_tail;
 403         if (!prev || FRAG_CB(prev)->offset < offset) {
 404                 next = NULL;
 405                 goto found;
 406         }
 407         prev = NULL;
 408         for (next = qp->q.fragments; next != NULL; next = next->next) {
 409                 if (FRAG_CB(next)->offset >= offset)
 410                         break;  /* bingo! */
 411                 prev = next;
 412         }
 413
 414 found:
 415         /* We found where to put this one.  Check for overlap with
 416          * preceding fragment, and, if needed, align things so that
 417          * any overlaps are eliminated.
 418          */
 419         if (prev) {
 420                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
 421
 422                 if (i > 0) {
 423                         offset += i;
 424                         err = -EINVAL;
 425                         if (end <= offset)
 426                                 goto err;
 427                         err = -ENOMEM;
 428                         if (!pskb_pull(skb, i))
 429                                 goto err;
 430                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 431                                 skb->ip_summed = CHECKSUM_NONE;
 432                 }
 433         }
 434
 435         err = -ENOMEM;
 436
 437         while (next && FRAG_CB(next)->offset < end) {
 438                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
 439
 440                 if (i < next->len) {
 441                         /* Eat head of the next overlapped fragment
 442                          * and leave the loop. The next ones cannot overlap.
 443                          */
 444                         if (!pskb_pull(next, i))
 445                                 goto err;
 446                         FRAG_CB(next)->offset += i;
 447                         qp->q.meat -= i;
 448                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 449                                 next->ip_summed = CHECKSUM_NONE;
 450                         break;
 451                 } else {
 452                         struct sk_buff *free_it = next;
 453
 454                         /* Old fragment is completely overridden with
 455                          * new one drop it.
 456                          */
 457                         next = next->next;
 458
 459                         if (prev)
 460                                 prev->next = next;
 461                         else
 462                                 qp->q.fragments = next;
 463
 464                         qp->q.meat -= free_it->len;
 465                         sub_frag_mem_limit(&qp->q, free_it->truesize);
 466                         kfree_skb(free_it);
 467                 }
 468         }
 469
 470         FRAG_CB(skb)->offset = offset;
 471
 472         /* Insert this fragment in the chain of fragments. */
 473         skb->next = next;
 474         if (!next)
 475                 qp->q.fragments_tail = skb;
 476         if (prev)
 477                 prev->next = skb;
 478         else
 479                 qp->q.fragments = skb;
 480
 481         dev = skb->dev;
 482         if (dev) {
 483                 qp->iif = dev->ifindex;
 484                 skb->dev = NULL;
 485         }
 486         qp->q.stamp = skb->tstamp;
 487         qp->q.meat += skb->len;
 488         qp->ecn |= ecn;
 489         add_frag_mem_limit(&qp->q, skb->truesize);
 490         if (offset == 0)
 491                 qp->q.last_in |= INET_FRAG_FIRST_IN;
 492
 493         if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
 494             skb->len + ihl > qp->q.max_size)
 495                 qp->q.max_size = skb->len + ihl;
 496
 497         if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 498             qp->q.meat == qp->q.len) {
 499                 unsigned long orefdst = skb->_skb_refdst;
 500
 501                 skb->_skb_refdst = 0UL;
 502                 err = ip_frag_reasm(qp, prev, dev);
 503                 skb->_skb_refdst = orefdst;
 504                 return err;
 505         }
 506
 507         skb_dst_drop(skb);
 508         inet_frag_lru_move(&qp->q);
 509         return -EINPROGRESS;
 510
 511 err:
 512         kfree_skb(skb);
 513         return err;
 514 }
 515
 516
 517 /* Build a new IP datagram from all its fragments. */
 518
 519 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 520                          struct net_device *dev)
 521 {
 522         struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
 523         struct iphdr *iph;
 524         struct sk_buff *fp, *head = qp->q.fragments;
 525         int len;
 526         int ihlen;
 527         int err;
 528         int sum_truesize;
 529         u8 ecn;
 530
 531         ipq_kill(qp);
 532
 533         ecn = ip_frag_ecn_table[qp->ecn];
 534         if (unlikely(ecn == 0xff)) {
 535                 err = -EINVAL;
 536                 goto out_fail;
 537         }
 538         /* Make the one we just received the head. */
 539         if (prev) {
 540                 head = prev->next;
 541                 fp = skb_clone(head, GFP_ATOMIC);
 542                 if (!fp)
 543                         goto out_nomem;
 544
 545                 fp->next = head->next;
 546                 if (!fp->next)
 547                         qp->q.fragments_tail = fp;
 548                 prev->next = fp;
 549
 550                 skb_morph(head, qp->q.fragments);
 551                 head->next = qp->q.fragments->next;
 552
 553                 consume_skb(qp->q.fragments);
 554                 qp->q.fragments = head;
 555         }
 556
 557         WARN_ON(head == NULL);
 558         WARN_ON(FRAG_CB(head)->offset != 0);
 559
 560         /* Allocate a new buffer for the datagram. */
 561         ihlen = ip_hdrlen(head);
 562         len = ihlen + qp->q.len;
 563
 564         err = -E2BIG;
 565         if (len > 65535)
 566                 goto out_oversize;
 567
 568         /* Head of list must not be cloned. */
 569         if (skb_unclone(head, GFP_ATOMIC))
 570                 goto out_nomem;
 571
 572         /* If the first fragment is fragmented itself, we split
 573          * it to two chunks: the first with data and paged part
 574          * and the second, holding only fragments. */
 575         if (skb_has_frag_list(head)) {
 576                 struct sk_buff *clone;
 577                 int i, plen = 0;
 578
 579                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
 580                         goto out_nomem;
 581                 clone->next = head->next;
 582                 head->next = clone;
 583                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 584                 skb_frag_list_init(head);
 585                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 586                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 587                 clone->len = clone->data_len = head->data_len - plen;
 588                 head->data_len -= clone->len;
 589                 head->len -= clone->len;
 590                 clone->csum = 0;
 591                 clone->ip_summed = head->ip_summed;
 592                 add_frag_mem_limit(&qp->q, clone->truesize);
 593         }
 594
 595         skb_push(head, head->data - skb_network_header(head));
 596
 597         sum_truesize = head->truesize;
 598         for (fp = head->next; fp;) {
 599                 bool headstolen;
 600                 int delta;
 601                 struct sk_buff *next = fp->next;
 602
 603                 sum_truesize += fp->truesize;
 604                 if (head->ip_summed != fp->ip_summed)
 605                         head->ip_summed = CHECKSUM_NONE;
 606                 else if (head->ip_summed == CHECKSUM_COMPLETE)
 607                         head->csum = csum_add(head->csum, fp->csum);
 608
 609                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 610                         kfree_skb_partial(fp, headstolen);
 611                 } else {
 612                         if (!skb_shinfo(head)->frag_list)
 613                                 skb_shinfo(head)->frag_list = fp;
 614                         head->data_len += fp->len;
 615                         head->len += fp->len;
 616                         head->truesize += fp->truesize;
 617                 }
 618                 fp = next;
 619         }
 620         sub_frag_mem_limit(&qp->q, sum_truesize);
 621
 622         head->next = NULL;
 623         head->dev = dev;
 624         head->tstamp = qp->q.stamp;
 625         IPCB(head)->frag_max_size = qp->q.max_size;
 626
 627         iph = ip_hdr(head);
 628         /* max_size != 0 implies at least one fragment had IP_DF set */
 629         iph->frag_off = qp->q.max_size ? htons(IP_DF) : 0;
 630         iph->tot_len = htons(len);
 631         iph->tos |= ecn;
 632         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
 633         qp->q.fragments = NULL;
 634         qp->q.fragments_tail = NULL;
 635         return 0;
 636
 637 out_nomem:
 638         LIMIT_NETDEBUG(KERN_ERR pr_fmt("queue_glue: no memory for gluing queue %p\n"),
 639                        qp);
 640         err = -ENOMEM;
 641         goto out_fail;
 642 out_oversize:
 643         net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
 644 out_fail:
 645         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 646         return err;
 647 }
 648
 649 /* Process an incoming IP datagram fragment. */
 650 int ip_defrag(struct sk_buff *skb, u32 user)
 651 {
 652         struct ipq *qp;
 653         struct net *net;
 654
 655         net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev);
 656         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
 657
 658         /* Start by cleaning up the memory. */
 659         ip_evictor(net);
 660
 661         /* Lookup (or create) queue header */
 662         if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
 663                 int ret;
 664
 665                 spin_lock(&qp->q.lock);
 666
 667                 ret = ip_frag_queue(qp, skb);
 668
 669                 spin_unlock(&qp->q.lock);
 670                 ipq_put(qp);
 671                 return ret;
 672         }
 673
 674         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 675         kfree_skb(skb);
 676         return -ENOMEM;
 677 }
 678 EXPORT_SYMBOL(ip_defrag);
 679
 680 struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
 681 {
 682         struct iphdr iph;
 683         u32 len;
 684
 685         if (skb->protocol != htons(ETH_P_IP))
 686                 return skb;
 687
 688         if (!skb_copy_bits(skb, 0, &iph, sizeof(iph)))
 689                 return skb;
 690
 691         if (iph.ihl < 5 || iph.version != 4)
 692                 return skb;
 693
 694         len = ntohs(iph.tot_len);
 695         if (skb->len < len || len < (iph.ihl * 4))
 696                 return skb;
 697
 698         if (ip_is_fragment(&iph)) {
 699                 skb = skb_share_check(skb, GFP_ATOMIC);
 700                 if (skb) {
 701                         if (!pskb_may_pull(skb, iph.ihl*4))
 702                                 return skb;
 703                         if (pskb_trim_rcsum(skb, len))
 704                                 return skb;
 705                         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 706                         if (ip_defrag(skb, user))
 707                                 return NULL;
 708                         skb_clear_hash(skb);
 709                 }
 710         }
 711         return skb;
 712 }
 713 EXPORT_SYMBOL(ip_check_defrag);
 714
 715 #ifdef CONFIG_SYSCTL
 716 static int zero;
 717
 718 static struct ctl_table ip4_frags_ns_ctl_table[] = {
 719         {
 720                 .procname       = "ipfrag_high_thresh",
 721                 .data           = &init_net.ipv4.frags.high_thresh,
 722                 .maxlen         = sizeof(int),
 723                 .mode           = 0644,
 724                 .proc_handler   = proc_dointvec
 725         },
 726         {
 727                 .procname       = "ipfrag_low_thresh",
 728                 .data           = &init_net.ipv4.frags.low_thresh,
 729                 .maxlen         = sizeof(int),
 730                 .mode           = 0644,
 731                 .proc_handler   = proc_dointvec
 732         },
 733         {
 734                 .procname       = "ipfrag_time",
 735                 .data           = &init_net.ipv4.frags.timeout,
 736                 .maxlen         = sizeof(int),
 737                 .mode           = 0644,
 738                 .proc_handler   = proc_dointvec_jiffies,
 739         },
 740         { }
 741 };
 742
 743 static struct ctl_table ip4_frags_ctl_table[] = {
 744         {
 745                 .procname       = "ipfrag_secret_interval",
 746                 .data           = &ip4_frags.secret_interval,
 747                 .maxlen         = sizeof(int),
 748                 .mode           = 0644,
 749                 .proc_handler   = proc_dointvec_jiffies,
 750         },
 751         {
 752                 .procname       = "ipfrag_max_dist",
 753                 .data           = &sysctl_ipfrag_max_dist,
 754                 .maxlen         = sizeof(int),
 755                 .mode           = 0644,
 756                 .proc_handler   = proc_dointvec_minmax,
 757                 .extra1         = &zero
 758         },
 759         { }
 760 };
 761
 762 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
 763 {
 764         struct ctl_table *table;
 765         struct ctl_table_header *hdr;
 766
 767         table = ip4_frags_ns_ctl_table;
 768         if (!net_eq(net, &init_net)) {
 769                 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
 770                 if (table == NULL)
 771                         goto err_alloc;
 772
 773                 table[0].data = &net->ipv4.frags.high_thresh;
 774                 table[1].data = &net->ipv4.frags.low_thresh;
 775                 table[2].data = &net->ipv4.frags.timeout;
 776
 777                 /* Don't export sysctls to unprivileged users */
 778                 if (net->user_ns != &init_user_ns)
 779                         table[0].procname = NULL;
 780         }
 781
 782         hdr = register_net_sysctl(net, "net/ipv4", table);
 783         if (hdr == NULL)
 784                 goto err_reg;
 785
 786         net->ipv4.frags_hdr = hdr;
 787         return 0;
 788
 789 err_reg:
 790         if (!net_eq(net, &init_net))
 791                 kfree(table);
 792 err_alloc:
 793         return -ENOMEM;
 794 }
 795
 796 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
 797 {
 798         struct ctl_table *table;
 799
 800         table = net->ipv4.frags_hdr->ctl_table_arg;
 801         unregister_net_sysctl_table(net->ipv4.frags_hdr);
 802         kfree(table);
 803 }
 804
 805 static void ip4_frags_ctl_register(void)
 806 {
 807         register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
 808 }
 809 #else
 810 static inline int ip4_frags_ns_ctl_register(struct net *net)
 811 {
 812         return 0;
 813 }
 814
 815 static inline void ip4_frags_ns_ctl_unregister(struct net *net)
 816 {
 817 }
 818
 819 static inline void ip4_frags_ctl_register(void)
 820 {
 821 }
 822 #endif
 823
 824 static int __net_init ipv4_frags_init_net(struct net *net)
 825 {
 826         /* Fragment cache limits.
 827          *
 828          * The fragment memory accounting code, (tries to) account for
 829          * the real memory usage, by measuring both the size of frag
 830          * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
 831          * and the SKB's truesize.
 832          *
 833          * A 64K fragment consumes 129736 bytes (44*2944)+200
 834          * (1500 truesize == 2944, sizeof(struct ipq) == 200)
 835          *
 836          * We will commit 4MB at one time. Should we cross that limit
 837          * we will prune down to 3MB, making room for approx 8 big 64K
 838          * fragments 8x128k.
 839          */
 840         net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
 841         net->ipv4.frags.low_thresh  = 3 * 1024 * 1024;
 842         /*
 843          * Important NOTE! Fragment queue must be destroyed before MSL expires.
 844          * RFC791 is wrong proposing to prolongate timer each fragment arrival
 845          * by TTL.
 846          */
 847         net->ipv4.frags.timeout = IP_FRAG_TIME;
 848
 849         inet_frags_init_net(&net->ipv4.frags);
 850
 851         return ip4_frags_ns_ctl_register(net);
 852 }
 853
 854 static void __net_exit ipv4_frags_exit_net(struct net *net)
 855 {
 856         ip4_frags_ns_ctl_unregister(net);
 857         inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
 858 }
 859
 860 static struct pernet_operations ip4_frags_ops = {
 861         .init = ipv4_frags_init_net,
 862         .exit = ipv4_frags_exit_net,
 863 };
 864
 865 void __init ipfrag_init(void)
 866 {
 867         ip4_frags_ctl_register();
 868         register_pernet_subsys(&ip4_frags_ops);
 869         ip4_frags.hashfn = ip4_hashfn;
 870         ip4_frags.constructor = ip4_frag_init;
 871         ip4_frags.destructor = ip4_frag_free;
 872         ip4_frags.skb_free = NULL;
 873         ip4_frags.qsize = sizeof(struct ipq);
 874         ip4_frags.match = ip4_frag_match;
 875         ip4_frags.frag_expire = ip_expire;
 876         ip4_frags.secret_interval = 10 * 60 * HZ;
 877         inet_frags_init(&ip4_frags);
 878 }