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 static 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 static struct inet_frags ip4_frags;
  78
  79 int ip_frag_nqueues(struct net *net)
  80 {
  81         return net->ipv4.frags.nqueues;
  82 }
  83
  84 int ip_frag_mem(struct net *net)
  85 {
  86         return atomic_read(&net->ipv4.frags.mem);
  87 }
  88
  89 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
  90                          struct net_device *dev);
  91
  92 struct ip4_create_arg {
  93         struct iphdr *iph;
  94         u32 user;
  95 };
  96
  97 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
  98 {
  99         return jhash_3words((__force u32)id << 16 | prot,
 100                             (__force u32)saddr, (__force u32)daddr,
 101                             ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
 102 }
 103
 104 static unsigned int ip4_hashfn(struct inet_frag_queue *q)
 105 {
 106         struct ipq *ipq;
 107
 108         ipq = container_of(q, struct ipq, q);
 109         return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
 110 }
 111
 112 static int ip4_frag_match(struct inet_frag_queue *q, void *a)
 113 {
 114         struct ipq *qp;
 115         struct ip4_create_arg *arg = a;
 116
 117         qp = container_of(q, struct ipq, q);
 118         return (qp->id == arg->iph->id &&
 119                         qp->saddr == arg->iph->saddr &&
 120                         qp->daddr == arg->iph->daddr &&
 121                         qp->protocol == arg->iph->protocol &&
 122                         qp->user == arg->user);
 123 }
 124
 125 /* Memory Tracking Functions. */
 126 static __inline__ void frag_kfree_skb(struct netns_frags *nf,
 127                 struct sk_buff *skb, int *work)
 128 {
 129         if (work)
 130                 *work -= skb->truesize;
 131         atomic_sub(skb->truesize, &nf->mem);
 132         kfree_skb(skb);
 133 }
 134
 135 static void ip4_frag_init(struct inet_frag_queue *q, void *a)
 136 {
 137         struct ipq *qp = container_of(q, struct ipq, q);
 138         struct ip4_create_arg *arg = a;
 139
 140         qp->protocol = arg->iph->protocol;
 141         qp->id = arg->iph->id;
 142         qp->saddr = arg->iph->saddr;
 143         qp->daddr = arg->iph->daddr;
 144         qp->user = arg->user;
 145         qp->peer = sysctl_ipfrag_max_dist ?
 146                 inet_getpeer(arg->iph->saddr, 1) : NULL;
 147 }
 148
 149 static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
 150 {
 151         struct ipq *qp;
 152
 153         qp = container_of(q, struct ipq, q);
 154         if (qp->peer)
 155                 inet_putpeer(qp->peer);
 156 }
 157
 158
 159 /* Destruction primitives. */
 160
 161 static __inline__ void ipq_put(struct ipq *ipq)
 162 {
 163         inet_frag_put(&ipq->q, &ip4_frags);
 164 }
 165
 166 /* Kill ipq entry. It is not destroyed immediately,
 167  * because caller (and someone more) holds reference count.
 168  */
 169 static void ipq_kill(struct ipq *ipq)
 170 {
 171         inet_frag_kill(&ipq->q, &ip4_frags);
 172 }
 173
 174 /* Memory limiting on fragments.  Evictor trashes the oldest
 175  * fragment queue until we are back under the threshold.
 176  */
 177 static void ip_evictor(struct net *net)
 178 {
 179         int evicted;
 180
 181         evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags);
 182         if (evicted)
 183                 IP_ADD_STATS_BH(IPSTATS_MIB_REASMFAILS, evicted);
 184 }
 185
 186 /*
 187  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
 188  */
 189 static void ip_expire(unsigned long arg)
 190 {
 191         struct ipq *qp;
 192
 193         qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
 194
 195         spin_lock(&qp->q.lock);
 196
 197         if (qp->q.last_in & INET_FRAG_COMPLETE)
 198                 goto out;
 199
 200         ipq_kill(qp);
 201
 202         IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
 203         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 204
 205         if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
 206                 struct sk_buff *head = qp->q.fragments;
 207                 struct net *net;
 208
 209                 net = container_of(qp->q.net, struct net, ipv4.frags);
 210                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
 211                 if ((head->dev = dev_get_by_index(net, qp->iif)) != NULL) {
 212                         icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
 213                         dev_put(head->dev);
 214                 }
 215         }
 216 out:
 217         spin_unlock(&qp->q.lock);
 218         ipq_put(qp);
 219 }
 220
 221 /* Find the correct entry in the "incomplete datagrams" queue for
 222  * this IP datagram, and create new one, if nothing is found.
 223  */
 224 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
 225 {
 226         struct inet_frag_queue *q;
 227         struct ip4_create_arg arg;
 228         unsigned int hash;
 229
 230         arg.iph = iph;
 231         arg.user = user;
 232
 233         read_lock(&ip4_frags.lock);
 234         hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
 235
 236         q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
 237         if (q == NULL)
 238                 goto out_nomem;
 239
 240         return container_of(q, struct ipq, q);
 241
 242 out_nomem:
 243         LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
 244         return NULL;
 245 }
 246
 247 /* Is the fragment too far ahead to be part of ipq? */
 248 static inline int ip_frag_too_far(struct ipq *qp)
 249 {
 250         struct inet_peer *peer = qp->peer;
 251         unsigned int max = sysctl_ipfrag_max_dist;
 252         unsigned int start, end;
 253
 254         int rc;
 255
 256         if (!peer || !max)
 257                 return 0;
 258
 259         start = qp->rid;
 260         end = atomic_inc_return(&peer->rid);
 261         qp->rid = end;
 262
 263         rc = qp->q.fragments && (end - start) > max;
 264
 265         if (rc) {
 266                 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 267         }
 268
 269         return rc;
 270 }
 271
 272 static int ip_frag_reinit(struct ipq *qp)
 273 {
 274         struct sk_buff *fp;
 275
 276         if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
 277                 atomic_inc(&qp->q.refcnt);
 278                 return -ETIMEDOUT;
 279         }
 280
 281         fp = qp->q.fragments;
 282         do {
 283                 struct sk_buff *xp = fp->next;
 284                 frag_kfree_skb(qp->q.net, fp, NULL);
 285                 fp = xp;
 286         } while (fp);
 287
 288         qp->q.last_in = 0;
 289         qp->q.len = 0;
 290         qp->q.meat = 0;
 291         qp->q.fragments = NULL;
 292         qp->iif = 0;
 293
 294         return 0;
 295 }
 296
 297 /* Add new segment to existing queue. */
 298 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 299 {
 300         struct sk_buff *prev, *next;
 301         struct net_device *dev;
 302         int flags, offset;
 303         int ihl, end;
 304         int err = -ENOENT;
 305
 306         if (qp->q.last_in & INET_FRAG_COMPLETE)
 307                 goto err;
 308
 309         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
 310             unlikely(ip_frag_too_far(qp)) &&
 311             unlikely(err = ip_frag_reinit(qp))) {
 312                 ipq_kill(qp);
 313                 goto err;
 314         }
 315
 316         offset = ntohs(ip_hdr(skb)->frag_off);
 317         flags = offset & ~IP_OFFSET;
 318         offset &= IP_OFFSET;
 319         offset <<= 3;           /* offset is in 8-byte chunks */
 320         ihl = ip_hdrlen(skb);
 321
 322         /* Determine the position of this fragment. */
 323         end = offset + skb->len - ihl;
 324         err = -EINVAL;
 325
 326         /* Is this the final fragment? */
 327         if ((flags & IP_MF) == 0) {
 328                 /* If we already have some bits beyond end
 329                  * or have different end, the segment is corrrupted.
 330                  */
 331                 if (end < qp->q.len ||
 332                     ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len))
 333                         goto err;
 334                 qp->q.last_in |= INET_FRAG_LAST_IN;
 335                 qp->q.len = end;
 336         } else {
 337                 if (end&7) {
 338                         end &= ~7;
 339                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 340                                 skb->ip_summed = CHECKSUM_NONE;
 341                 }
 342                 if (end > qp->q.len) {
 343                         /* Some bits beyond end -> corruption. */
 344                         if (qp->q.last_in & INET_FRAG_LAST_IN)
 345                                 goto err;
 346                         qp->q.len = end;
 347                 }
 348         }
 349         if (end == offset)
 350                 goto err;
 351
 352         err = -ENOMEM;
 353         if (pskb_pull(skb, ihl) == NULL)
 354                 goto err;
 355
 356         err = pskb_trim_rcsum(skb, end - offset);
 357         if (err)
 358                 goto err;
 359
 360         /* Find out which fragments are in front and at the back of us
 361          * in the chain of fragments so far.  We must know where to put
 362          * this fragment, right?
 363          */
 364         prev = NULL;
 365         for (next = qp->q.fragments; next != NULL; next = next->next) {
 366                 if (FRAG_CB(next)->offset >= offset)
 367                         break;  /* bingo! */
 368                 prev = next;
 369         }
 370
 371         /* We found where to put this one.  Check for overlap with
 372          * preceding fragment, and, if needed, align things so that
 373          * any overlaps are eliminated.
 374          */
 375         if (prev) {
 376                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
 377
 378                 if (i > 0) {
 379                         offset += i;
 380                         err = -EINVAL;
 381                         if (end <= offset)
 382                                 goto err;
 383                         err = -ENOMEM;
 384                         if (!pskb_pull(skb, i))
 385                                 goto err;
 386                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 387                                 skb->ip_summed = CHECKSUM_NONE;
 388                 }
 389         }
 390
 391         err = -ENOMEM;
 392
 393         while (next && FRAG_CB(next)->offset < end) {
 394                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
 395
 396                 if (i < next->len) {
 397                         /* Eat head of the next overlapped fragment
 398                          * and leave the loop. The next ones cannot overlap.
 399                          */
 400                         if (!pskb_pull(next, i))
 401                                 goto err;
 402                         FRAG_CB(next)->offset += i;
 403                         qp->q.meat -= i;
 404                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 405                                 next->ip_summed = CHECKSUM_NONE;
 406                         break;
 407                 } else {
 408                         struct sk_buff *free_it = next;
 409
 410                         /* Old fragment is completely overridden with
 411                          * new one drop it.
 412                          */
 413                         next = next->next;
 414
 415                         if (prev)
 416                                 prev->next = next;
 417                         else
 418                                 qp->q.fragments = next;
 419
 420                         qp->q.meat -= free_it->len;
 421                         frag_kfree_skb(qp->q.net, free_it, NULL);
 422                 }
 423         }
 424
 425         FRAG_CB(skb)->offset = offset;
 426
 427         /* Insert this fragment in the chain of fragments. */
 428         skb->next = next;
 429         if (prev)
 430                 prev->next = skb;
 431         else
 432                 qp->q.fragments = skb;
 433
 434         dev = skb->dev;
 435         if (dev) {
 436                 qp->iif = dev->ifindex;
 437                 skb->dev = NULL;
 438         }
 439         qp->q.stamp = skb->tstamp;
 440         qp->q.meat += skb->len;
 441         atomic_add(skb->truesize, &qp->q.net->mem);
 442         if (offset == 0)
 443                 qp->q.last_in |= INET_FRAG_FIRST_IN;
 444
 445         if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 446             qp->q.meat == qp->q.len)
 447                 return ip_frag_reasm(qp, prev, dev);
 448
 449         write_lock(&ip4_frags.lock);
 450         list_move_tail(&qp->q.lru_list, &qp->q.net->lru_list);
 451         write_unlock(&ip4_frags.lock);
 452         return -EINPROGRESS;
 453
 454 err:
 455         kfree_skb(skb);
 456         return err;
 457 }
 458
 459
 460 /* Build a new IP datagram from all its fragments. */
 461
 462 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 463                          struct net_device *dev)
 464 {
 465         struct iphdr *iph;
 466         struct sk_buff *fp, *head = qp->q.fragments;
 467         int len;
 468         int ihlen;
 469         int err;
 470
 471         ipq_kill(qp);
 472
 473         /* Make the one we just received the head. */
 474         if (prev) {
 475                 head = prev->next;
 476                 fp = skb_clone(head, GFP_ATOMIC);
 477                 if (!fp)
 478                         goto out_nomem;
 479
 480                 fp->next = head->next;
 481                 prev->next = fp;
 482
 483                 skb_morph(head, qp->q.fragments);
 484                 head->next = qp->q.fragments->next;
 485
 486                 kfree_skb(qp->q.fragments);
 487                 qp->q.fragments = head;
 488         }
 489
 490         BUG_TRAP(head != NULL);
 491         BUG_TRAP(FRAG_CB(head)->offset == 0);
 492
 493         /* Allocate a new buffer for the datagram. */
 494         ihlen = ip_hdrlen(head);
 495         len = ihlen + qp->q.len;
 496
 497         err = -E2BIG;
 498         if (len > 65535)
 499                 goto out_oversize;
 500
 501         /* Head of list must not be cloned. */
 502         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
 503                 goto out_nomem;
 504
 505         /* If the first fragment is fragmented itself, we split
 506          * it to two chunks: the first with data and paged part
 507          * and the second, holding only fragments. */
 508         if (skb_shinfo(head)->frag_list) {
 509                 struct sk_buff *clone;
 510                 int i, plen = 0;
 511
 512                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
 513                         goto out_nomem;
 514                 clone->next = head->next;
 515                 head->next = clone;
 516                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 517                 skb_shinfo(head)->frag_list = NULL;
 518                 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
 519                         plen += skb_shinfo(head)->frags[i].size;
 520                 clone->len = clone->data_len = head->data_len - plen;
 521                 head->data_len -= clone->len;
 522                 head->len -= clone->len;
 523                 clone->csum = 0;
 524                 clone->ip_summed = head->ip_summed;
 525                 atomic_add(clone->truesize, &qp->q.net->mem);
 526         }
 527
 528         skb_shinfo(head)->frag_list = head->next;
 529         skb_push(head, head->data - skb_network_header(head));
 530         atomic_sub(head->truesize, &qp->q.net->mem);
 531
 532         for (fp=head->next; fp; fp = fp->next) {
 533                 head->data_len += fp->len;
 534                 head->len += fp->len;
 535                 if (head->ip_summed != fp->ip_summed)
 536                         head->ip_summed = CHECKSUM_NONE;
 537                 else if (head->ip_summed == CHECKSUM_COMPLETE)
 538                         head->csum = csum_add(head->csum, fp->csum);
 539                 head->truesize += fp->truesize;
 540                 atomic_sub(fp->truesize, &qp->q.net->mem);
 541         }
 542
 543         head->next = NULL;
 544         head->dev = dev;
 545         head->tstamp = qp->q.stamp;
 546
 547         iph = ip_hdr(head);
 548         iph->frag_off = 0;
 549         iph->tot_len = htons(len);
 550         IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
 551         qp->q.fragments = NULL;
 552         return 0;
 553
 554 out_nomem:
 555         LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
 556                               "queue %p\n", qp);
 557         err = -ENOMEM;
 558         goto out_fail;
 559 out_oversize:
 560         if (net_ratelimit())
 561                 printk(KERN_INFO
 562                         "Oversized IP packet from " NIPQUAD_FMT ".\n",
 563                         NIPQUAD(qp->saddr));
 564 out_fail:
 565         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 566         return err;
 567 }
 568
 569 /* Process an incoming IP datagram fragment. */
 570 int ip_defrag(struct sk_buff *skb, u32 user)
 571 {
 572         struct ipq *qp;
 573         struct net *net;
 574
 575         IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
 576
 577         net = skb->dev ? dev_net(skb->dev) : dev_net(skb->dst->dev);
 578         /* Start by cleaning up the memory. */
 579         if (atomic_read(&net->ipv4.frags.mem) > net->ipv4.frags.high_thresh)
 580                 ip_evictor(net);
 581
 582         /* Lookup (or create) queue header */
 583         if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
 584                 int ret;
 585
 586                 spin_lock(&qp->q.lock);
 587
 588                 ret = ip_frag_queue(qp, skb);
 589
 590                 spin_unlock(&qp->q.lock);
 591                 ipq_put(qp);
 592                 return ret;
 593         }
 594
 595         IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
 596         kfree_skb(skb);
 597         return -ENOMEM;
 598 }
 599
 600 #ifdef CONFIG_SYSCTL
 601 static int zero;
 602
 603 static struct ctl_table ip4_frags_ctl_table[] = {
 604         {
 605                 .ctl_name       = NET_IPV4_IPFRAG_HIGH_THRESH,
 606                 .procname       = "ipfrag_high_thresh",
 607                 .data           = &init_net.ipv4.frags.high_thresh,
 608                 .maxlen         = sizeof(int),
 609                 .mode           = 0644,
 610                 .proc_handler   = &proc_dointvec
 611         },
 612         {
 613                 .ctl_name       = NET_IPV4_IPFRAG_LOW_THRESH,
 614                 .procname       = "ipfrag_low_thresh",
 615                 .data           = &init_net.ipv4.frags.low_thresh,
 616                 .maxlen         = sizeof(int),
 617                 .mode           = 0644,
 618                 .proc_handler   = &proc_dointvec
 619         },
 620         {
 621                 .ctl_name       = NET_IPV4_IPFRAG_TIME,
 622                 .procname       = "ipfrag_time",
 623                 .data           = &init_net.ipv4.frags.timeout,
 624                 .maxlen         = sizeof(int),
 625                 .mode           = 0644,
 626                 .proc_handler   = &proc_dointvec_jiffies,
 627                 .strategy       = &sysctl_jiffies
 628         },
 629         {
 630                 .ctl_name       = NET_IPV4_IPFRAG_SECRET_INTERVAL,
 631                 .procname       = "ipfrag_secret_interval",
 632                 .data           = &ip4_frags.secret_interval,
 633                 .maxlen         = sizeof(int),
 634                 .mode           = 0644,
 635                 .proc_handler   = &proc_dointvec_jiffies,
 636                 .strategy       = &sysctl_jiffies
 637         },
 638         {
 639                 .procname       = "ipfrag_max_dist",
 640                 .data           = &sysctl_ipfrag_max_dist,
 641                 .maxlen         = sizeof(int),
 642                 .mode           = 0644,
 643                 .proc_handler   = &proc_dointvec_minmax,
 644                 .extra1         = &zero
 645         },
 646         { }
 647 };
 648
 649 static int ip4_frags_ctl_register(struct net *net)
 650 {
 651         struct ctl_table *table;
 652         struct ctl_table_header *hdr;
 653
 654         table = ip4_frags_ctl_table;
 655         if (net != &init_net) {
 656                 table = kmemdup(table, sizeof(ip4_frags_ctl_table), GFP_KERNEL);
 657                 if (table == NULL)
 658                         goto err_alloc;
 659
 660                 table[0].data = &net->ipv4.frags.high_thresh;
 661                 table[1].data = &net->ipv4.frags.low_thresh;
 662                 table[2].data = &net->ipv4.frags.timeout;
 663                 table[3].mode &= ~0222;
 664                 table[4].mode &= ~0222;
 665         }
 666
 667         hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table);
 668         if (hdr == NULL)
 669                 goto err_reg;
 670
 671         net->ipv4.frags_hdr = hdr;
 672         return 0;
 673
 674 err_reg:
 675         if (net != &init_net)
 676                 kfree(table);
 677 err_alloc:
 678         return -ENOMEM;
 679 }
 680
 681 static void ip4_frags_ctl_unregister(struct net *net)
 682 {
 683         struct ctl_table *table;
 684
 685         table = net->ipv4.frags_hdr->ctl_table_arg;
 686         unregister_net_sysctl_table(net->ipv4.frags_hdr);
 687         kfree(table);
 688 }
 689 #else
 690 static inline int ip4_frags_ctl_register(struct net *net)
 691 {
 692         return 0;
 693 }
 694
 695 static inline void ip4_frags_ctl_unregister(struct net *net)
 696 {
 697 }
 698 #endif
 699
 700 static int ipv4_frags_init_net(struct net *net)
 701 {
 702         /*
 703          * Fragment cache limits. We will commit 256K at one time. Should we
 704          * cross that limit we will prune down to 192K. This should cope with
 705          * even the most extreme cases without allowing an attacker to
 706          * measurably harm machine performance.
 707          */
 708         net->ipv4.frags.high_thresh = 256 * 1024;
 709         net->ipv4.frags.low_thresh = 192 * 1024;
 710         /*
 711          * Important NOTE! Fragment queue must be destroyed before MSL expires.
 712          * RFC791 is wrong proposing to prolongate timer each fragment arrival
 713          * by TTL.
 714          */
 715         net->ipv4.frags.timeout = IP_FRAG_TIME;
 716
 717         inet_frags_init_net(&net->ipv4.frags);
 718
 719         return ip4_frags_ctl_register(net);
 720 }
 721
 722 static void ipv4_frags_exit_net(struct net *net)
 723 {
 724         ip4_frags_ctl_unregister(net);
 725         inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
 726 }
 727
 728 static struct pernet_operations ip4_frags_ops = {
 729         .init = ipv4_frags_init_net,
 730         .exit = ipv4_frags_exit_net,
 731 };
 732
 733 void __init ipfrag_init(void)
 734 {
 735         register_pernet_subsys(&ip4_frags_ops);
 736         ip4_frags.hashfn = ip4_hashfn;
 737         ip4_frags.constructor = ip4_frag_init;
 738         ip4_frags.destructor = ip4_frag_free;
 739         ip4_frags.skb_free = NULL;
 740         ip4_frags.qsize = sizeof(struct ipq);
 741         ip4_frags.match = ip4_frag_match;
 742         ip4_frags.frag_expire = ip_expire;
 743         ip4_frags.secret_interval = 10 * 60 * HZ;
 744         inet_frags_init(&ip4_frags);
 745 }
 746
 747 EXPORT_SYMBOL(ip_defrag);