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