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