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 /* RFC 3168 support :
  83  * We want to check ECN values of all fragments, do detect invalid combinations.
  84  * In ipq->ecn, we store the OR value of each ip4_frag_ecn() fragment value.
  85  */
  86 #define IPFRAG_ECN_NOT_ECT      0x01 /* one frag had ECN_NOT_ECT */
  87 #define IPFRAG_ECN_ECT_1        0x02 /* one frag had ECN_ECT_1 */
  88 #define IPFRAG_ECN_ECT_0        0x04 /* one frag had ECN_ECT_0 */
  89 #define IPFRAG_ECN_CE           0x08 /* one frag had ECN_CE */
  90
  91 static inline u8 ip4_frag_ecn(u8 tos)
  92 {
  93         return 1 << (tos & INET_ECN_MASK);
  94 }
  95
  96 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
  97  * Value : 0xff if frame should be dropped.
  98  *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
  99  */
 100 static const u8 ip4_frag_ecn_table[16] = {
 101         /* at least one fragment had CE, and others ECT_0 or ECT_1 */
 102         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]                      = INET_ECN_CE,
 103         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]                      = INET_ECN_CE,
 104         [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]   = INET_ECN_CE,
 105
 106         /* invalid combinations : drop frame */
 107         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
 108         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
 109         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
 110         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
 111         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
 112         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
 113         [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
 114 };
 115
 116 static struct inet_frags ip4_frags;
 117
 118 int ip_frag_nqueues(struct net *net)
 119 {
 120         return net->ipv4.frags.nqueues;
 121 }
 122
 123 int ip_frag_mem(struct net *net)
 124 {
 125         return atomic_read(&net->ipv4.frags.mem);
 126 }
 127
 128 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 129                          struct net_device *dev);
 130
 131 struct ip4_create_arg {
 132         struct iphdr *iph;
 133         u32 user;
 134 };
 135
 136 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
 137 {
 138         return jhash_3words((__force u32)id << 16 | prot,
 139                             (__force u32)saddr, (__force u32)daddr,
 140                             ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
 141 }
 142
 143 static unsigned int ip4_hashfn(struct inet_frag_queue *q)
 144 {
 145         struct ipq *ipq;
 146
 147         ipq = container_of(q, struct ipq, q);
 148         return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
 149 }
 150
 151 static bool ip4_frag_match(struct inet_frag_queue *q, void *a)
 152 {
 153         struct ipq *qp;
 154         struct ip4_create_arg *arg = a;
 155
 156         qp = container_of(q, struct ipq, q);
 157         return  qp->id == arg->iph->id &&
 158                 qp->saddr == arg->iph->saddr &&
 159                 qp->daddr == arg->iph->daddr &&
 160                 qp->protocol == arg->iph->protocol &&
 161                 qp->user == arg->user;
 162 }
 163
 164 /* Memory Tracking Functions. */
 165 static void frag_kfree_skb(struct netns_frags *nf, struct sk_buff *skb)
 166 {
 167         atomic_sub(skb->truesize, &nf->mem);
 168         kfree_skb(skb);
 169 }
 170
 171 static void ip4_frag_init(struct inet_frag_queue *q, void *a)
 172 {
 173         struct ipq *qp = container_of(q, struct ipq, q);
 174         struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
 175                                                frags);
 176         struct net *net = container_of(ipv4, struct net, ipv4);
 177
 178         struct ip4_create_arg *arg = a;
 179
 180         qp->protocol = arg->iph->protocol;
 181         qp->id = arg->iph->id;
 182         qp->ecn = ip4_frag_ecn(arg->iph->tos);
 183         qp->saddr = arg->iph->saddr;
 184         qp->daddr = arg->iph->daddr;
 185         qp->user = arg->user;
 186         qp->peer = sysctl_ipfrag_max_dist ?
 187                 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, 1) : NULL;
 188 }
 189
 190 static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
 191 {
 192         struct ipq *qp;
 193
 194         qp = container_of(q, struct ipq, q);
 195         if (qp->peer)
 196                 inet_putpeer(qp->peer);
 197 }
 198
 199
 200 /* Destruction primitives. */
 201
 202 static __inline__ void ipq_put(struct ipq *ipq)
 203 {
 204         inet_frag_put(&ipq->q, &ip4_frags);
 205 }
 206
 207 /* Kill ipq entry. It is not destroyed immediately,
 208  * because caller (and someone more) holds reference count.
 209  */
 210 static void ipq_kill(struct ipq *ipq)
 211 {
 212         inet_frag_kill(&ipq->q, &ip4_frags);
 213 }
 214
 215 /* Memory limiting on fragments.  Evictor trashes the oldest
 216  * fragment queue until we are back under the threshold.
 217  */
 218 static void ip_evictor(struct net *net)
 219 {
 220         int evicted;
 221
 222         evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags, false);
 223         if (evicted)
 224                 IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted);
 225 }
 226
 227 /*
 228  * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
 229  */
 230 static void ip_expire(unsigned long arg)
 231 {
 232         struct ipq *qp;
 233         struct net *net;
 234
 235         qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
 236         net = container_of(qp->q.net, struct net, ipv4.frags);
 237
 238         spin_lock(&qp->q.lock);
 239
 240         if (qp->q.last_in & INET_FRAG_COMPLETE)
 241                 goto out;
 242
 243         ipq_kill(qp);
 244
 245         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
 246         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 247
 248         if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
 249                 struct sk_buff *head = qp->q.fragments;
 250                 const struct iphdr *iph;
 251                 int err;
 252
 253                 rcu_read_lock();
 254                 head->dev = dev_get_by_index_rcu(net, qp->iif);
 255                 if (!head->dev)
 256                         goto out_rcu_unlock;
 257
 258                 /* skb dst is stale, drop it, and perform route lookup again */
 259                 skb_dst_drop(head);
 260                 iph = ip_hdr(head);
 261                 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
 262                                            iph->tos, head->dev);
 263                 if (err)
 264                         goto out_rcu_unlock;
 265
 266                 /*
 267                  * Only an end host needs to send an ICMP
 268                  * "Fragment Reassembly Timeout" message, per RFC792.
 269                  */
 270                 if (qp->user == IP_DEFRAG_AF_PACKET ||
 271                     (qp->user == IP_DEFRAG_CONNTRACK_IN &&
 272                      skb_rtable(head)->rt_type != RTN_LOCAL))
 273                         goto out_rcu_unlock;
 274
 275
 276                 /* Send an ICMP "Fragment Reassembly Timeout" message. */
 277                 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
 278 out_rcu_unlock:
 279                 rcu_read_unlock();
 280         }
 281 out:
 282         spin_unlock(&qp->q.lock);
 283         ipq_put(qp);
 284 }
 285
 286 /* Find the correct entry in the "incomplete datagrams" queue for
 287  * this IP datagram, and create new one, if nothing is found.
 288  */
 289 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
 290 {
 291         struct inet_frag_queue *q;
 292         struct ip4_create_arg arg;
 293         unsigned int hash;
 294
 295         arg.iph = iph;
 296         arg.user = user;
 297
 298         read_lock(&ip4_frags.lock);
 299         hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
 300
 301         q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
 302         if (q == NULL)
 303                 goto out_nomem;
 304
 305         return container_of(q, struct ipq, q);
 306
 307 out_nomem:
 308         LIMIT_NETDEBUG(KERN_ERR pr_fmt("ip_frag_create: no memory left !\n"));
 309         return NULL;
 310 }
 311
 312 /* Is the fragment too far ahead to be part of ipq? */
 313 static inline int ip_frag_too_far(struct ipq *qp)
 314 {
 315         struct inet_peer *peer = qp->peer;
 316         unsigned int max = sysctl_ipfrag_max_dist;
 317         unsigned int start, end;
 318
 319         int rc;
 320
 321         if (!peer || !max)
 322                 return 0;
 323
 324         start = qp->rid;
 325         end = atomic_inc_return(&peer->rid);
 326         qp->rid = end;
 327
 328         rc = qp->q.fragments && (end - start) > max;
 329
 330         if (rc) {
 331                 struct net *net;
 332
 333                 net = container_of(qp->q.net, struct net, ipv4.frags);
 334                 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 335         }
 336
 337         return rc;
 338 }
 339
 340 static int ip_frag_reinit(struct ipq *qp)
 341 {
 342         struct sk_buff *fp;
 343
 344         if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
 345                 atomic_inc(&qp->q.refcnt);
 346                 return -ETIMEDOUT;
 347         }
 348
 349         fp = qp->q.fragments;
 350         do {
 351                 struct sk_buff *xp = fp->next;
 352                 frag_kfree_skb(qp->q.net, fp);
 353                 fp = xp;
 354         } while (fp);
 355
 356         qp->q.last_in = 0;
 357         qp->q.len = 0;
 358         qp->q.meat = 0;
 359         qp->q.fragments = NULL;
 360         qp->q.fragments_tail = NULL;
 361         qp->iif = 0;
 362         qp->ecn = 0;
 363
 364         return 0;
 365 }
 366
 367 /* Add new segment to existing queue. */
 368 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
 369 {
 370         struct sk_buff *prev, *next;
 371         struct net_device *dev;
 372         int flags, offset;
 373         int ihl, end;
 374         int err = -ENOENT;
 375         u8 ecn;
 376
 377         if (qp->q.last_in & INET_FRAG_COMPLETE)
 378                 goto err;
 379
 380         if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
 381             unlikely(ip_frag_too_far(qp)) &&
 382             unlikely(err = ip_frag_reinit(qp))) {
 383                 ipq_kill(qp);
 384                 goto err;
 385         }
 386
 387         ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
 388         offset = ntohs(ip_hdr(skb)->frag_off);
 389         flags = offset & ~IP_OFFSET;
 390         offset &= IP_OFFSET;
 391         offset <<= 3;           /* offset is in 8-byte chunks */
 392         ihl = ip_hdrlen(skb);
 393
 394         /* Determine the position of this fragment. */
 395         end = offset + skb->len - ihl;
 396         err = -EINVAL;
 397
 398         /* Is this the final fragment? */
 399         if ((flags & IP_MF) == 0) {
 400                 /* If we already have some bits beyond end
 401                  * or have different end, the segment is corrupted.
 402                  */
 403                 if (end < qp->q.len ||
 404                     ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len))
 405                         goto err;
 406                 qp->q.last_in |= INET_FRAG_LAST_IN;
 407                 qp->q.len = end;
 408         } else {
 409                 if (end&7) {
 410                         end &= ~7;
 411                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 412                                 skb->ip_summed = CHECKSUM_NONE;
 413                 }
 414                 if (end > qp->q.len) {
 415                         /* Some bits beyond end -> corruption. */
 416                         if (qp->q.last_in & INET_FRAG_LAST_IN)
 417                                 goto err;
 418                         qp->q.len = end;
 419                 }
 420         }
 421         if (end == offset)
 422                 goto err;
 423
 424         err = -ENOMEM;
 425         if (pskb_pull(skb, ihl) == NULL)
 426                 goto err;
 427
 428         err = pskb_trim_rcsum(skb, end - offset);
 429         if (err)
 430                 goto err;
 431
 432         /* Find out which fragments are in front and at the back of us
 433          * in the chain of fragments so far.  We must know where to put
 434          * this fragment, right?
 435          */
 436         prev = qp->q.fragments_tail;
 437         if (!prev || FRAG_CB(prev)->offset < offset) {
 438                 next = NULL;
 439                 goto found;
 440         }
 441         prev = NULL;
 442         for (next = qp->q.fragments; next != NULL; next = next->next) {
 443                 if (FRAG_CB(next)->offset >= offset)
 444                         break;  /* bingo! */
 445                 prev = next;
 446         }
 447
 448 found:
 449         /* We found where to put this one.  Check for overlap with
 450          * preceding fragment, and, if needed, align things so that
 451          * any overlaps are eliminated.
 452          */
 453         if (prev) {
 454                 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
 455
 456                 if (i > 0) {
 457                         offset += i;
 458                         err = -EINVAL;
 459                         if (end <= offset)
 460                                 goto err;
 461                         err = -ENOMEM;
 462                         if (!pskb_pull(skb, i))
 463                                 goto err;
 464                         if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 465                                 skb->ip_summed = CHECKSUM_NONE;
 466                 }
 467         }
 468
 469         err = -ENOMEM;
 470
 471         while (next && FRAG_CB(next)->offset < end) {
 472                 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
 473
 474                 if (i < next->len) {
 475                         /* Eat head of the next overlapped fragment
 476                          * and leave the loop. The next ones cannot overlap.
 477                          */
 478                         if (!pskb_pull(next, i))
 479                                 goto err;
 480                         FRAG_CB(next)->offset += i;
 481                         qp->q.meat -= i;
 482                         if (next->ip_summed != CHECKSUM_UNNECESSARY)
 483                                 next->ip_summed = CHECKSUM_NONE;
 484                         break;
 485                 } else {
 486                         struct sk_buff *free_it = next;
 487
 488                         /* Old fragment is completely overridden with
 489                          * new one drop it.
 490                          */
 491                         next = next->next;
 492
 493                         if (prev)
 494                                 prev->next = next;
 495                         else
 496                                 qp->q.fragments = next;
 497
 498                         qp->q.meat -= free_it->len;
 499                         frag_kfree_skb(qp->q.net, free_it);
 500                 }
 501         }
 502
 503         FRAG_CB(skb)->offset = offset;
 504
 505         /* Insert this fragment in the chain of fragments. */
 506         skb->next = next;
 507         if (!next)
 508                 qp->q.fragments_tail = skb;
 509         if (prev)
 510                 prev->next = skb;
 511         else
 512                 qp->q.fragments = skb;
 513
 514         dev = skb->dev;
 515         if (dev) {
 516                 qp->iif = dev->ifindex;
 517                 skb->dev = NULL;
 518         }
 519         qp->q.stamp = skb->tstamp;
 520         qp->q.meat += skb->len;
 521         qp->ecn |= ecn;
 522         atomic_add(skb->truesize, &qp->q.net->mem);
 523         if (offset == 0)
 524                 qp->q.last_in |= INET_FRAG_FIRST_IN;
 525
 526         if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
 527             skb->len + ihl > qp->q.max_size)
 528                 qp->q.max_size = skb->len + ihl;
 529
 530         if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 531             qp->q.meat == qp->q.len)
 532                 return ip_frag_reasm(qp, prev, dev);
 533
 534         write_lock(&ip4_frags.lock);
 535         list_move_tail(&qp->q.lru_list, &qp->q.net->lru_list);
 536         write_unlock(&ip4_frags.lock);
 537         return -EINPROGRESS;
 538
 539 err:
 540         kfree_skb(skb);
 541         return err;
 542 }
 543
 544
 545 /* Build a new IP datagram from all its fragments. */
 546
 547 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
 548                          struct net_device *dev)
 549 {
 550         struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
 551         struct iphdr *iph;
 552         struct sk_buff *fp, *head = qp->q.fragments;
 553         int len;
 554         int ihlen;
 555         int err;
 556         int sum_truesize;
 557         u8 ecn;
 558
 559         ipq_kill(qp);
 560
 561         ecn = ip4_frag_ecn_table[qp->ecn];
 562         if (unlikely(ecn == 0xff)) {
 563                 err = -EINVAL;
 564                 goto out_fail;
 565         }
 566         /* Make the one we just received the head. */
 567         if (prev) {
 568                 head = prev->next;
 569                 fp = skb_clone(head, GFP_ATOMIC);
 570                 if (!fp)
 571                         goto out_nomem;
 572
 573                 fp->next = head->next;
 574                 if (!fp->next)
 575                         qp->q.fragments_tail = fp;
 576                 prev->next = fp;
 577
 578                 skb_morph(head, qp->q.fragments);
 579                 head->next = qp->q.fragments->next;
 580
 581                 consume_skb(qp->q.fragments);
 582                 qp->q.fragments = head;
 583         }
 584
 585         WARN_ON(head == NULL);
 586         WARN_ON(FRAG_CB(head)->offset != 0);
 587
 588         /* Allocate a new buffer for the datagram. */
 589         ihlen = ip_hdrlen(head);
 590         len = ihlen + qp->q.len;
 591
 592         err = -E2BIG;
 593         if (len > 65535)
 594                 goto out_oversize;
 595
 596         /* Head of list must not be cloned. */
 597         if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
 598                 goto out_nomem;
 599
 600         /* If the first fragment is fragmented itself, we split
 601          * it to two chunks: the first with data and paged part
 602          * and the second, holding only fragments. */
 603         if (skb_has_frag_list(head)) {
 604                 struct sk_buff *clone;
 605                 int i, plen = 0;
 606
 607                 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
 608                         goto out_nomem;
 609                 clone->next = head->next;
 610                 head->next = clone;
 611                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 612                 skb_frag_list_init(head);
 613                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 614                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 615                 clone->len = clone->data_len = head->data_len - plen;
 616                 head->data_len -= clone->len;
 617                 head->len -= clone->len;
 618                 clone->csum = 0;
 619                 clone->ip_summed = head->ip_summed;
 620                 atomic_add(clone->truesize, &qp->q.net->mem);
 621         }
 622
 623         skb_push(head, head->data - skb_network_header(head));
 624
 625         sum_truesize = head->truesize;
 626         for (fp = head->next; fp;) {
 627                 bool headstolen;
 628                 int delta;
 629                 struct sk_buff *next = fp->next;
 630
 631                 sum_truesize += fp->truesize;
 632                 if (head->ip_summed != fp->ip_summed)
 633                         head->ip_summed = CHECKSUM_NONE;
 634                 else if (head->ip_summed == CHECKSUM_COMPLETE)
 635                         head->csum = csum_add(head->csum, fp->csum);
 636
 637                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 638                         kfree_skb_partial(fp, headstolen);
 639                 } else {
 640                         if (!skb_shinfo(head)->frag_list)
 641                                 skb_shinfo(head)->frag_list = fp;
 642                         head->data_len += fp->len;
 643                         head->len += fp->len;
 644                         head->truesize += fp->truesize;
 645                 }
 646                 fp = next;
 647         }
 648         atomic_sub(sum_truesize, &qp->q.net->mem);
 649
 650         head->next = NULL;
 651         head->dev = dev;
 652         head->tstamp = qp->q.stamp;
 653         IPCB(head)->frag_max_size = qp->q.max_size;
 654
 655         iph = ip_hdr(head);
 656         /* max_size != 0 implies at least one fragment had IP_DF set */
 657         iph->frag_off = qp->q.max_size ? htons(IP_DF) : 0;
 658         iph->tot_len = htons(len);
 659         iph->tos |= ecn;
 660         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
 661         qp->q.fragments = NULL;
 662         qp->q.fragments_tail = NULL;
 663         return 0;
 664
 665 out_nomem:
 666         LIMIT_NETDEBUG(KERN_ERR pr_fmt("queue_glue: no memory for gluing queue %p\n"),
 667                        qp);
 668         err = -ENOMEM;
 669         goto out_fail;
 670 out_oversize:
 671         net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
 672 out_fail:
 673         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 674         return err;
 675 }
 676
 677 /* Process an incoming IP datagram fragment. */
 678 int ip_defrag(struct sk_buff *skb, u32 user)
 679 {
 680         struct ipq *qp;
 681         struct net *net;
 682
 683         net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev);
 684         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
 685
 686         /* Start by cleaning up the memory. */
 687         ip_evictor(net);
 688
 689         /* Lookup (or create) queue header */
 690         if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
 691                 int ret;
 692
 693                 spin_lock(&qp->q.lock);
 694
 695                 ret = ip_frag_queue(qp, skb);
 696
 697                 spin_unlock(&qp->q.lock);
 698                 ipq_put(qp);
 699                 return ret;
 700         }
 701
 702         IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
 703         kfree_skb(skb);
 704         return -ENOMEM;
 705 }
 706 EXPORT_SYMBOL(ip_defrag);
 707
 708 struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
 709 {
 710         const struct iphdr *iph;
 711         u32 len;
 712
 713         if (skb->protocol != htons(ETH_P_IP))
 714                 return skb;
 715
 716         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 717                 return skb;
 718
 719         iph = ip_hdr(skb);
 720         if (iph->ihl < 5 || iph->version != 4)
 721                 return skb;
 722         if (!pskb_may_pull(skb, iph->ihl*4))
 723                 return skb;
 724         iph = ip_hdr(skb);
 725         len = ntohs(iph->tot_len);
 726         if (skb->len < len || len < (iph->ihl * 4))
 727                 return skb;
 728
 729         if (ip_is_fragment(ip_hdr(skb))) {
 730                 skb = skb_share_check(skb, GFP_ATOMIC);
 731                 if (skb) {
 732                         if (pskb_trim_rcsum(skb, len))
 733                                 return skb;
 734                         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 735                         if (ip_defrag(skb, user))
 736                                 return NULL;
 737                         skb->rxhash = 0;
 738                 }
 739         }
 740         return skb;
 741 }
 742 EXPORT_SYMBOL(ip_check_defrag);
 743
 744 #ifdef CONFIG_SYSCTL
 745 static int zero;
 746
 747 static struct ctl_table ip4_frags_ns_ctl_table[] = {
 748         {
 749                 .procname       = "ipfrag_high_thresh",
 750                 .data           = &init_net.ipv4.frags.high_thresh,
 751                 .maxlen         = sizeof(int),
 752                 .mode           = 0644,
 753                 .proc_handler   = proc_dointvec
 754         },
 755         {
 756                 .procname       = "ipfrag_low_thresh",
 757                 .data           = &init_net.ipv4.frags.low_thresh,
 758                 .maxlen         = sizeof(int),
 759                 .mode           = 0644,
 760                 .proc_handler   = proc_dointvec
 761         },
 762         {
 763                 .procname       = "ipfrag_time",
 764                 .data           = &init_net.ipv4.frags.timeout,
 765                 .maxlen         = sizeof(int),
 766                 .mode           = 0644,
 767                 .proc_handler   = proc_dointvec_jiffies,
 768         },
 769         { }
 770 };
 771
 772 static struct ctl_table ip4_frags_ctl_table[] = {
 773         {
 774                 .procname       = "ipfrag_secret_interval",
 775                 .data           = &ip4_frags.secret_interval,
 776                 .maxlen         = sizeof(int),
 777                 .mode           = 0644,
 778                 .proc_handler   = proc_dointvec_jiffies,
 779         },
 780         {
 781                 .procname       = "ipfrag_max_dist",
 782                 .data           = &sysctl_ipfrag_max_dist,
 783                 .maxlen         = sizeof(int),
 784                 .mode           = 0644,
 785                 .proc_handler   = proc_dointvec_minmax,
 786                 .extra1         = &zero
 787         },
 788         { }
 789 };
 790
 791 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
 792 {
 793         struct ctl_table *table;
 794         struct ctl_table_header *hdr;
 795
 796         table = ip4_frags_ns_ctl_table;
 797         if (!net_eq(net, &init_net)) {
 798                 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
 799                 if (table == NULL)
 800                         goto err_alloc;
 801
 802                 table[0].data = &net->ipv4.frags.high_thresh;
 803                 table[1].data = &net->ipv4.frags.low_thresh;
 804                 table[2].data = &net->ipv4.frags.timeout;
 805         }
 806
 807         hdr = register_net_sysctl(net, "net/ipv4", table);
 808         if (hdr == NULL)
 809                 goto err_reg;
 810
 811         net->ipv4.frags_hdr = hdr;
 812         return 0;
 813
 814 err_reg:
 815         if (!net_eq(net, &init_net))
 816                 kfree(table);
 817 err_alloc:
 818         return -ENOMEM;
 819 }
 820
 821 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
 822 {
 823         struct ctl_table *table;
 824
 825         table = net->ipv4.frags_hdr->ctl_table_arg;
 826         unregister_net_sysctl_table(net->ipv4.frags_hdr);
 827         kfree(table);
 828 }
 829
 830 static void ip4_frags_ctl_register(void)
 831 {
 832         register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
 833 }
 834 #else
 835 static inline int ip4_frags_ns_ctl_register(struct net *net)
 836 {
 837         return 0;
 838 }
 839
 840 static inline void ip4_frags_ns_ctl_unregister(struct net *net)
 841 {
 842 }
 843
 844 static inline void ip4_frags_ctl_register(void)
 845 {
 846 }
 847 #endif
 848
 849 static int __net_init ipv4_frags_init_net(struct net *net)
 850 {
 851         /*
 852          * Fragment cache limits. We will commit 256K at one time. Should we
 853          * cross that limit we will prune down to 192K. This should cope with
 854          * even the most extreme cases without allowing an attacker to
 855          * measurably harm machine performance.
 856          */
 857         net->ipv4.frags.high_thresh = 256 * 1024;
 858         net->ipv4.frags.low_thresh = 192 * 1024;
 859         /*
 860          * Important NOTE! Fragment queue must be destroyed before MSL expires.
 861          * RFC791 is wrong proposing to prolongate timer each fragment arrival
 862          * by TTL.
 863          */
 864         net->ipv4.frags.timeout = IP_FRAG_TIME;
 865
 866         inet_frags_init_net(&net->ipv4.frags);
 867
 868         return ip4_frags_ns_ctl_register(net);
 869 }
 870
 871 static void __net_exit ipv4_frags_exit_net(struct net *net)
 872 {
 873         ip4_frags_ns_ctl_unregister(net);
 874         inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
 875 }
 876
 877 static struct pernet_operations ip4_frags_ops = {
 878         .init = ipv4_frags_init_net,
 879         .exit = ipv4_frags_exit_net,
 880 };
 881
 882 void __init ipfrag_init(void)
 883 {
 884         ip4_frags_ctl_register();
 885         register_pernet_subsys(&ip4_frags_ops);
 886         ip4_frags.hashfn = ip4_hashfn;
 887         ip4_frags.constructor = ip4_frag_init;
 888         ip4_frags.destructor = ip4_frag_free;
 889         ip4_frags.skb_free = NULL;
 890         ip4_frags.qsize = sizeof(struct ipq);
 891         ip4_frags.match = ip4_frag_match;
 892         ip4_frags.frag_expire = ip_expire;
 893         ip4_frags.secret_interval = 10 * 60 * HZ;
 894         inet_frags_init(&ip4_frags);
 895 }