net/ipv4/ip_fragment.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              The IP fragmentation functionality.
   8  *
   9  * Authors:     Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
  10  *              Alan Cox <alan@lxorguk.ukuu.org.uk>
  11  *
  12  * Fixes:
  13  *              Alan Cox        :       Split from ip.c , see ip_input.c for history.
  14  *              David S. Miller :       Begin massive cleanup...
  15  *              Andi Kleen      :       Add sysctls.
  16  *              xxxx            :       Overlapfrag bug.
  17  *              Ultima          :       ip_expire() kernel panic.
  18  *              Bill Hawes      :       Frag accounting and evictor fixes.
  19  *              John McDonald   :       0 length frag bug.
  20  *              Alexey Kuznetsov:       SMP races, threading, cleanup.
  21  *              Patrick McHardy :       LRU queue of frag heads for evictor.
  22  */
  23
  24 #define pr_fmt(fmt) "IPv4: " fmt
  25
  26 #include <linux/compiler.h>
  27 #include <linux/module.h>
  28 #include <linux/types.h>
  29 #include <linux/mm.h>
  30 #include <linux/jiffies.h>
  31 #include <linux/skbuff.h>
  32 #include <linux/list.h>
  33 #include <linux/ip.h>
  34 #include <linux/icmp.h>
  35 #include <linux/netdevice.h>
  36 #include <linux/jhash.h>
  37 #include <linux/random.h>
  38 #include <linux/slab.h>
  39 #include <net/route.h>
  40 #include <net/dst.h>
  41 #include <net/sock.h>
  42 #include <net/ip.h>
  43 #include <net/icmp.h>
  44 #include <net/checksum.h>
  45 #include <net/inetpeer.h>
  46 #include <net/inet_frag.h>
  47 #include <linux/tcp.h>
  48 #include <linux/udp.h>
  49 #include <linux/inet.h>
  50 #include <linux/netfilter_ipv4.h>
  51 #include <net/inet_ecn.h>
  52 #include <net/l3mdev.h>
  53
  54 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
  55  * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
  56  * as well. Or notify me, at least. --ANK
  57  */
  58 static const char ip_frag_cache_name[] = "ip4-frags";
  59
  60 /* Describe an entry in the "incomplete datagrams" queue. */
  61 struct ipq {
  62         struct inet_frag_queue q;
  63
  64         u8              ecn; /* RFC3168 support */
  65         u16             max_df_size; /* largest frag with DF set seen */
  66         int             iif;
  67         unsigned int    rid;
  68         struct inet_peer *peer;
  69 };
  70
  71 static u8 ip4_frag_ecn(u8 tos)
  72 {
  73         return 1 << (tos & INET_ECN_MASK);
  74 }
  75
  76 static struct inet_frags ip4_frags;
  77
  78 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
  79                          struct sk_buff *prev_tail, struct net_device *dev);
  80
  81
  82 static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
  83 {
  84         struct ipq *qp = container_of(q, struct ipq, q);
  85         struct net *net = q->fqdir->net;
  86
  87         const struct frag_v4_compare_key *key = a;
  88
  89         q->key.v4 = *key;
  90         qp->ecn = 0;
  91         qp->peer = q->fqdir->max_dist ?
  92                 inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif, 1) :
  93                 NULL;
  94 }
  95
  96 static void ip4_frag_free(struct inet_frag_queue *q)
  97 {
  98         struct ipq *qp;
  99
 100         qp = container_of(q, struct ipq, q);
 101         if (qp->peer)
 102                 inet_putpeer(qp->peer);
 103 }
 104
 105
 106 /* Destruction primitives. */
 107
 108 static void ipq_put(struct ipq *ipq)
 109 {
 110         inet_frag_put(&ipq->q);
 111 }
 112
 113 /* Kill ipq entry. It is not destroyed immediately,
 114  * because caller (and someone more) holds reference count.
 115  */
 116 static void ipq_kill(struct ipq *ipq)
 117 {
 118         inet_frag_kill(&ipq->q);
 119 }
 120
 121 static bool frag_expire_skip_icmp(u32 user)
 122 {
 123         return user == IP_DEFRAG_AF_PACKET ||
 124                ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
 125                                          __IP_DEFRAG_CONNTRACK_IN_END) ||
 126                ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
 127                                          __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
 128 }
 129
 130 /*
 131  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
 132  */
 133 static void ip_expire(struct timer_list *t)
 134 {
 135         struct inet_frag_queue *frag = from_timer(frag, t, timer);
 136         const struct iphdr *iph;
 137         struct sk_buff *head = NULL;
 138         struct net *net;
 139         struct ipq *qp;
 140         int err;
 141
 142         qp = container_of(frag, struct ipq, q);
 143         net = qp->q.fqdir->net;
 144
 145         rcu_read_lock();
 146
 147         if (qp->q.fqdir->dead)
 148                 goto out_rcu_unlock;
 149
 150         spin_lock(&qp->q.lock);
 151
 152         if (qp->q.flags & INET_FRAG_COMPLETE)
 153                 goto out;
 154
 155         ipq_kill(qp);
 156         __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
 157         __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
 158
 159         if (!(qp->q.flags & INET_FRAG_FIRST_IN))
 160                 goto out;
 161
 162         /* sk_buff::dev and sk_buff::rbnode are unionized. So we
 163          * pull the head out of the tree in order to be able to
 164          * deal with head->dev.
 165          */
 166         head = inet_frag_pull_head(&qp->q);
 167         if (!head)
 168                 goto out;
 169         head->dev = dev_get_by_index_rcu(net, qp->iif);
 170         if (!head->dev)
 171                 goto out;
 172
 173
 174         /* skb has no dst, perform route lookup again */
 175         iph = ip_hdr(head);
 176         err = ip_route_input_noref(head, iph->daddr, iph->saddr,
 177                                            iph->tos, head->dev);
 178         if (err)
 179                 goto out;
 180
 181         /* Only an end host needs to send an ICMP
 182          * "Fragment Reassembly Timeout" message, per RFC792.
 183          */
 184         if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
 185             (skb_rtable(head)->rt_type != RTN_LOCAL))
 186                 goto out;
 187
 188         spin_unlock(&qp->q.lock);
 189         icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
 190         goto out_rcu_unlock;
 191
 192 out:
 193         spin_unlock(&qp->q.lock);
 194 out_rcu_unlock:
 195         rcu_read_unlock();
 196         kfree_skb(head);
 197         ipq_put(qp);
 198 }
 199
 200 /* Find the correct entry in the "incomplete datagrams" queue for
 201  * this IP datagram, and create new one, if nothing is found.
 202  */
 203 static struct ipq *ip_find(struct net *net, struct iphdr *iph,
 204                            u32 user, int vif)
 205 {
 206         struct frag_v4_compare_key key = {
 207                 .saddr = iph->saddr,
 208                 .daddr = iph->daddr,
 209                 .user = user,
 210                 .vif = vif,
 211                 .id = iph->id,
 212                 .protocol = iph->protocol,
 213         };
 214         struct inet_frag_queue *q;
 215
 216         q = inet_frag_find(net->ipv4.fqdir, &key);
 217         if (!q)
 218                 return NULL;
 219
 220         return container_of(q, struct ipq, q);
 221 }
 222
 223 /* Is the fragment too far ahead to be part of ipq? */
 224 static int ip_frag_too_far(struct ipq *qp)
 225 {
 226         struct inet_peer *peer = qp->peer;
 227         unsigned int max = qp->q.fqdir->max_dist;
 228         unsigned int start, end;
 229
 230         int rc;
 231
 232         if (!peer || !max)
 233                 return 0;
 234
 235         start = qp->rid;
 236         end = atomic_inc_return(&peer->rid);
 237         qp->rid = end;
 238
 239         rc = qp->q.fragments_tail && (end - start) > max;
 240
 241         if (rc)
 242                 __IP_INC_STATS(qp->q.fqdir->net, IPSTATS_MIB_REASMFAILS);
 243
 244         return rc;
 245 }
 246
 247 static int ip_frag_reinit(struct ipq *qp)
 248 {
 249         unsigned int sum_truesize = 0;
 250
 251         if (!mod_timer(&qp->q.timer, jiffies + qp->q.fqdir->timeout)) {
 252                 refcount_inc(&qp->q.refcnt);
 253                 return -ETIMEDOUT;
 254         }
 255
 256         sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments);
 257         sub_frag_mem_limit(qp->q.fqdir, sum_truesize);
 258
 259         qp->q.flags = 0;
 260         qp->q.len = 0;
 261         qp->q.meat = 0;
 262         qp->q.rb_fragments = RB_ROOT;
 263         qp->q.fragments_tail = NULL;
 264         qp->q.last_run_head = NULL;
 265         qp->iif = 0;
 266         qp->ecn = 0;
 267
 268         return 0;
 269 }
 270
 271 /* Add new segment to existing queue. */
 272 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 273 {
 274         struct net *net = qp->q.fqdir->net;
 275         int ihl, end, flags, offset;
 276         struct sk_buff *prev_tail;
 277         struct net_device *dev;
 278         unsigned int fragsize;
 279         int err = -ENOENT;
 280         u8 ecn;
 281
 282         if (qp->q.flags & INET_FRAG_COMPLETE)
 283                 goto err;
 284
 285         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
 286             unlikely(ip_frag_too_far(qp)) &&
 287             unlikely(err = ip_frag_reinit(qp))) {
 288                 ipq_kill(qp);
 289                 goto err;
 290         }
 291
 292         ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
 293         offset = ntohs(ip_hdr(skb)->frag_off);
 294         flags = offset & ~IP_OFFSET;
 295         offset &= IP_OFFSET;
 296         offset <<= 3;           /* offset is in 8-byte chunks */
 297         ihl = ip_hdrlen(skb);
 298
 299         /* Determine the position of this fragment. */
 300         end = offset + skb->len - skb_network_offset(skb) - ihl;
 301         err = -EINVAL;
 302
 303         /* Is this the final fragment? */
 304         if ((flags & IP_MF) == 0) {
 305                 /* If we already have some bits beyond end
 306                  * or have different end, the segment is corrupted.
 307                  */
 308                 if (end < qp->q.len ||
 309                     ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
 310                         goto discard_qp;
 311                 qp->q.flags |= INET_FRAG_LAST_IN;
 312                 qp->q.len = end;
 313         } else {
 314                 if (end&7) {
 315                         end &= ~7;
 316                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 317                                 skb->ip_summed = CHECKSUM_NONE;
 318                 }
 319                 if (end > qp->q.len) {
 320                         /* Some bits beyond end -> corruption. */
 321                         if (qp->q.flags & INET_FRAG_LAST_IN)
 322                                 goto discard_qp;
 323                         qp->q.len = end;
 324                 }
 325         }
 326         if (end == offset)
 327                 goto discard_qp;
 328
 329         err = -ENOMEM;
 330         if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
 331                 goto discard_qp;
 332
 333         err = pskb_trim_rcsum(skb, end - offset);
 334         if (err)
 335                 goto discard_qp;
 336
 337         /* Note : skb->rbnode and skb->dev share the same location. */
 338         dev = skb->dev;
 339         /* Makes sure compiler wont do silly aliasing games */
 340         barrier();
 341
 342         prev_tail = qp->q.fragments_tail;
 343         err = inet_frag_queue_insert(&qp->q, skb, offset, end);
 344         if (err)
 345                 goto insert_error;
 346
 347         if (dev)
 348                 qp->iif = dev->ifindex;
 349
 350         qp->q.stamp = skb->tstamp;
 351         qp->q.meat += skb->len;
 352         qp->ecn |= ecn;
 353         add_frag_mem_limit(qp->q.fqdir, skb->truesize);
 354         if (offset == 0)
 355                 qp->q.flags |= INET_FRAG_FIRST_IN;
 356
 357         fragsize = skb->len + ihl;
 358
 359         if (fragsize > qp->q.max_size)
 360                 qp->q.max_size = fragsize;
 361
 362         if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
 363             fragsize > qp->max_df_size)
 364                 qp->max_df_size = fragsize;
 365
 366         if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 367             qp->q.meat == qp->q.len) {
 368                 unsigned long orefdst = skb->_skb_refdst;
 369
 370                 skb->_skb_refdst = 0UL;
 371                 err = ip_frag_reasm(qp, skb, prev_tail, dev);
 372                 skb->_skb_refdst = orefdst;
 373                 if (err)
 374                         inet_frag_kill(&qp->q);
 375                 return err;
 376         }
 377
 378         skb_dst_drop(skb);
 379         return -EINPROGRESS;
 380
 381 insert_error:
 382         if (err == IPFRAG_DUP) {
 383                 kfree_skb(skb);
 384                 return -EINVAL;
 385         }
 386         err = -EINVAL;
 387         __IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
 388 discard_qp:
 389         inet_frag_kill(&qp->q);
 390         __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
 391 err:
 392         kfree_skb(skb);
 393         return err;
 394 }
 395
 396 static bool ip_frag_coalesce_ok(const struct ipq *qp)
 397 {
 398         return qp->q.key.v4.user == IP_DEFRAG_LOCAL_DELIVER;
 399 }
 400
 401 /* Build a new IP datagram from all its fragments. */
 402 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
 403                          struct sk_buff *prev_tail, struct net_device *dev)
 404 {
 405         struct net *net = qp->q.fqdir->net;
 406         struct iphdr *iph;
 407         void *reasm_data;
 408         int len, err;
 409         u8 ecn;
 410
 411         ipq_kill(qp);
 412
 413         ecn = ip_frag_ecn_table[qp->ecn];
 414         if (unlikely(ecn == 0xff)) {
 415                 err = -EINVAL;
 416                 goto out_fail;
 417         }
 418
 419         /* Make the one we just received the head. */
 420         reasm_data = inet_frag_reasm_prepare(&qp->q, skb, prev_tail);
 421         if (!reasm_data)
 422                 goto out_nomem;
 423
 424         len = ip_hdrlen(skb) + qp->q.len;
 425         err = -E2BIG;
 426         if (len > 65535)
 427                 goto out_oversize;
 428
 429         inet_frag_reasm_finish(&qp->q, skb, reasm_data,
 430                                ip_frag_coalesce_ok(qp));
 431
 432         skb->dev = dev;
 433         IPCB(skb)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
 434
 435         iph = ip_hdr(skb);
 436         iph->tot_len = htons(len);
 437         iph->tos |= ecn;
 438
 439         /* When we set IP_DF on a refragmented skb we must also force a
 440          * call to ip_fragment to avoid forwarding a DF-skb of size s while
 441          * original sender only sent fragments of size f (where f < s).
 442          *
 443          * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
 444          * frag seen to avoid sending tiny DF-fragments in case skb was built
 445          * from one very small df-fragment and one large non-df frag.
 446          */
 447         if (qp->max_df_size == qp->q.max_size) {
 448                 IPCB(skb)->flags |= IPSKB_FRAG_PMTU;
 449                 iph->frag_off = htons(IP_DF);
 450         } else {
 451                 iph->frag_off = 0;
 452         }
 453
 454         ip_send_check(iph);
 455
 456         __IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
 457         qp->q.rb_fragments = RB_ROOT;
 458         qp->q.fragments_tail = NULL;
 459         qp->q.last_run_head = NULL;
 460         return 0;
 461
 462 out_nomem:
 463         net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
 464         err = -ENOMEM;
 465         goto out_fail;
 466 out_oversize:
 467         net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr);
 468 out_fail:
 469         __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
 470         return err;
 471 }
 472
 473 /* Process an incoming IP datagram fragment. */
 474 int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
 475 {
 476         struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
 477         int vif = l3mdev_master_ifindex_rcu(dev);
 478         struct ipq *qp;
 479
 480         __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
 481         skb_orphan(skb);
 482
 483         /* Lookup (or create) queue header */
 484         qp = ip_find(net, ip_hdr(skb), user, vif);
 485         if (qp) {
 486                 int ret;
 487
 488                 spin_lock(&qp->q.lock);
 489
 490                 ret = ip_frag_queue(qp, skb);
 491
 492                 spin_unlock(&qp->q.lock);
 493                 ipq_put(qp);
 494                 return ret;
 495         }
 496
 497         __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
 498         kfree_skb(skb);
 499         return -ENOMEM;
 500 }
 501 EXPORT_SYMBOL(ip_defrag);
 502
 503 struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
 504 {
 505         struct iphdr iph;
 506         int netoff;
 507         u32 len;
 508
 509         if (skb->protocol != htons(ETH_P_IP))
 510                 return skb;
 511
 512         netoff = skb_network_offset(skb);
 513
 514         if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
 515                 return skb;
 516
 517         if (iph.ihl < 5 || iph.version != 4)
 518                 return skb;
 519
 520         len = ntohs(iph.tot_len);
 521         if (skb->len < netoff + len || len < (iph.ihl * 4))
 522                 return skb;
 523
 524         if (ip_is_fragment(&iph)) {
 525                 skb = skb_share_check(skb, GFP_ATOMIC);
 526                 if (skb) {
 527                         if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) {
 528                                 kfree_skb(skb);
 529                                 return NULL;
 530                         }
 531                         if (pskb_trim_rcsum(skb, netoff + len)) {
 532                                 kfree_skb(skb);
 533                                 return NULL;
 534                         }
 535                         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 536                         if (ip_defrag(net, skb, user))
 537                                 return NULL;
 538                         skb_clear_hash(skb);
 539                 }
 540         }
 541         return skb;
 542 }
 543 EXPORT_SYMBOL(ip_check_defrag);
 544
 545 #ifdef CONFIG_SYSCTL
 546 static int dist_min;
 547
 548 static struct ctl_table ip4_frags_ns_ctl_table[] = {
 549         {
 550                 .procname       = "ipfrag_high_thresh",
 551                 .maxlen         = sizeof(unsigned long),
 552                 .mode           = 0644,
 553                 .proc_handler   = proc_doulongvec_minmax,
 554         },
 555         {
 556                 .procname       = "ipfrag_low_thresh",
 557                 .maxlen         = sizeof(unsigned long),
 558                 .mode           = 0644,
 559                 .proc_handler   = proc_doulongvec_minmax,
 560         },
 561         {
 562                 .procname       = "ipfrag_time",
 563                 .maxlen         = sizeof(int),
 564                 .mode           = 0644,
 565                 .proc_handler   = proc_dointvec_jiffies,
 566         },
 567         {
 568                 .procname       = "ipfrag_max_dist",
 569                 .maxlen         = sizeof(int),
 570                 .mode           = 0644,
 571                 .proc_handler   = proc_dointvec_minmax,
 572                 .extra1         = &dist_min,
 573         },
 574         { }
 575 };
 576
 577 /* secret interval has been deprecated */
 578 static int ip4_frags_secret_interval_unused;
 579 static struct ctl_table ip4_frags_ctl_table[] = {
 580         {
 581                 .procname       = "ipfrag_secret_interval",
 582                 .data           = &ip4_frags_secret_interval_unused,
 583                 .maxlen         = sizeof(int),
 584                 .mode           = 0644,
 585                 .proc_handler   = proc_dointvec_jiffies,
 586         },
 587         { }
 588 };
 589
 590 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
 591 {
 592         struct ctl_table *table;
 593         struct ctl_table_header *hdr;
 594
 595         table = ip4_frags_ns_ctl_table;
 596         if (!net_eq(net, &init_net)) {
 597                 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
 598                 if (!table)
 599                         goto err_alloc;
 600
 601         }
 602         table[0].data   = &net->ipv4.fqdir->high_thresh;
 603         table[0].extra1 = &net->ipv4.fqdir->low_thresh;
 604         table[1].data   = &net->ipv4.fqdir->low_thresh;
 605         table[1].extra2 = &net->ipv4.fqdir->high_thresh;
 606         table[2].data   = &net->ipv4.fqdir->timeout;
 607         table[3].data   = &net->ipv4.fqdir->max_dist;
 608
 609         hdr = register_net_sysctl(net, "net/ipv4", table);
 610         if (!hdr)
 611                 goto err_reg;
 612
 613         net->ipv4.frags_hdr = hdr;
 614         return 0;
 615
 616 err_reg:
 617         if (!net_eq(net, &init_net))
 618                 kfree(table);
 619 err_alloc:
 620         return -ENOMEM;
 621 }
 622
 623 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
 624 {
 625         struct ctl_table *table;
 626
 627         table = net->ipv4.frags_hdr->ctl_table_arg;
 628         unregister_net_sysctl_table(net->ipv4.frags_hdr);
 629         kfree(table);
 630 }
 631
 632 static void __init ip4_frags_ctl_register(void)
 633 {
 634         register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
 635 }
 636 #else
 637 static int ip4_frags_ns_ctl_register(struct net *net)
 638 {
 639         return 0;
 640 }
 641
 642 static void ip4_frags_ns_ctl_unregister(struct net *net)
 643 {
 644 }
 645
 646 static void __init ip4_frags_ctl_register(void)
 647 {
 648 }
 649 #endif
 650
 651 static int __net_init ipv4_frags_init_net(struct net *net)
 652 {
 653         int res;
 654
 655         res = fqdir_init(&net->ipv4.fqdir, &ip4_frags, net);
 656         if (res < 0)
 657                 return res;
 658         /* Fragment cache limits.
 659          *
 660          * The fragment memory accounting code, (tries to) account for
 661          * the real memory usage, by measuring both the size of frag
 662          * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
 663          * and the SKB's truesize.
 664          *
 665          * A 64K fragment consumes 129736 bytes (44*2944)+200
 666          * (1500 truesize == 2944, sizeof(struct ipq) == 200)
 667          *
 668          * We will commit 4MB at one time. Should we cross that limit
 669          * we will prune down to 3MB, making room for approx 8 big 64K
 670          * fragments 8x128k.
 671          */
 672         net->ipv4.fqdir->high_thresh = 4 * 1024 * 1024;
 673         net->ipv4.fqdir->low_thresh  = 3 * 1024 * 1024;
 674         /*
 675          * Important NOTE! Fragment queue must be destroyed before MSL expires.
 676          * RFC791 is wrong proposing to prolongate timer each fragment arrival
 677          * by TTL.
 678          */
 679         net->ipv4.fqdir->timeout = IP_FRAG_TIME;
 680
 681         net->ipv4.fqdir->max_dist = 64;
 682
 683         res = ip4_frags_ns_ctl_register(net);
 684         if (res < 0)
 685                 fqdir_exit(net->ipv4.fqdir);
 686         return res;
 687 }
 688
 689 static void __net_exit ipv4_frags_pre_exit_net(struct net *net)
 690 {
 691         fqdir_pre_exit(net->ipv4.fqdir);
 692 }
 693
 694 static void __net_exit ipv4_frags_exit_net(struct net *net)
 695 {
 696         ip4_frags_ns_ctl_unregister(net);
 697         fqdir_exit(net->ipv4.fqdir);
 698 }
 699
 700 static struct pernet_operations ip4_frags_ops = {
 701         .init           = ipv4_frags_init_net,
 702         .pre_exit       = ipv4_frags_pre_exit_net,
 703         .exit           = ipv4_frags_exit_net,
 704 };
 705
 706
 707 static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed)
 708 {
 709         return jhash2(data,
 710                       sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
 711 }
 712
 713 static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed)
 714 {
 715         const struct inet_frag_queue *fq = data;
 716
 717         return jhash2((const u32 *)&fq->key.v4,
 718                       sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
 719 }
 720
 721 static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
 722 {
 723         const struct frag_v4_compare_key *key = arg->key;
 724         const struct inet_frag_queue *fq = ptr;
 725
 726         return !!memcmp(&fq->key, key, sizeof(*key));
 727 }
 728
 729 static const struct rhashtable_params ip4_rhash_params = {
 730         .head_offset            = offsetof(struct inet_frag_queue, node),
 731         .key_offset             = offsetof(struct inet_frag_queue, key),
 732         .key_len                = sizeof(struct frag_v4_compare_key),
 733         .hashfn                 = ip4_key_hashfn,
 734         .obj_hashfn             = ip4_obj_hashfn,
 735         .obj_cmpfn              = ip4_obj_cmpfn,
 736         .automatic_shrinking    = true,
 737 };
 738
 739 void __init ipfrag_init(void)
 740 {
 741         ip4_frags.constructor = ip4_frag_init;
 742         ip4_frags.destructor = ip4_frag_free;
 743         ip4_frags.qsize = sizeof(struct ipq);
 744         ip4_frags.frag_expire = ip_expire;
 745         ip4_frags.frags_cache_name = ip_frag_cache_name;
 746         ip4_frags.rhash_params = ip4_rhash_params;
 747         if (inet_frags_init(&ip4_frags))
 748                 panic("IP: failed to allocate ip4_frags cache\n");
 749         ip4_frags_ctl_register();
 750         register_pernet_subsys(&ip4_frags_ops);
 751 }