net/ipv6/reassembly.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      IPv6 fragment reassembly
   4  *      Linux INET6 implementation
   5  *
   6  *      Authors:
   7  *      Pedro Roque             <roque@di.fc.ul.pt>
   8  *
   9  *      Based on: net/ipv4/ip_fragment.c
  10  */
  11
  12 /*
  13  *      Fixes:
  14  *      Andi Kleen      Make it work with multiple hosts.
  15  *                      More RFC compliance.
  16  *
  17  *      Horst von Brand Add missing #include <linux/string.h>
  18  *      Alexey Kuznetsov        SMP races, threading, cleanup.
  19  *      Patrick McHardy         LRU queue of frag heads for evictor.
  20  *      Mitsuru KANDA @USAGI    Register inet6_protocol{}.
  21  *      David Stevens and
  22  *      YOSHIFUJI,H. @USAGI     Always remove fragment header to
  23  *                              calculate ICV correctly.
  24  */
  25
  26 #define pr_fmt(fmt) "IPv6: " fmt
  27
  28 #include <linux/errno.h>
  29 #include <linux/types.h>
  30 #include <linux/string.h>
  31 #include <linux/socket.h>
  32 #include <linux/sockios.h>
  33 #include <linux/jiffies.h>
  34 #include <linux/net.h>
  35 #include <linux/list.h>
  36 #include <linux/netdevice.h>
  37 #include <linux/in6.h>
  38 #include <linux/ipv6.h>
  39 #include <linux/icmpv6.h>
  40 #include <linux/random.h>
  41 #include <linux/jhash.h>
  42 #include <linux/skbuff.h>
  43 #include <linux/slab.h>
  44 #include <linux/export.h>
  45
  46 #include <net/sock.h>
  47 #include <net/snmp.h>
  48
  49 #include <net/ipv6.h>
  50 #include <net/ip6_route.h>
  51 #include <net/protocol.h>
  52 #include <net/transp_v6.h>
  53 #include <net/rawv6.h>
  54 #include <net/ndisc.h>
  55 #include <net/addrconf.h>
  56 #include <net/ipv6_frag.h>
  57 #include <net/inet_ecn.h>
  58
  59 static const char ip6_frag_cache_name[] = "ip6-frags";
  60
  61 static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
  62 {
  63         return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
  64 }
  65
  66 static struct inet_frags ip6_frags;
  67
  68 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
  69                           struct sk_buff *prev_tail, struct net_device *dev);
  70
  71 static void ip6_frag_expire(struct timer_list *t)
  72 {
  73         struct inet_frag_queue *frag = from_timer(frag, t, timer);
  74         struct frag_queue *fq;
  75         struct net *net;
  76
  77         fq = container_of(frag, struct frag_queue, q);
  78         net = container_of(fq->q.net, struct net, ipv6.frags);
  79
  80         ip6frag_expire_frag_queue(net, fq);
  81 }
  82
  83 static struct frag_queue *
  84 fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif)
  85 {
  86         struct frag_v6_compare_key key = {
  87                 .id = id,
  88                 .saddr = hdr->saddr,
  89                 .daddr = hdr->daddr,
  90                 .user = IP6_DEFRAG_LOCAL_DELIVER,
  91                 .iif = iif,
  92         };
  93         struct inet_frag_queue *q;
  94
  95         if (!(ipv6_addr_type(&hdr->daddr) & (IPV6_ADDR_MULTICAST |
  96                                             IPV6_ADDR_LINKLOCAL)))
  97                 key.iif = 0;
  98
  99         q = inet_frag_find(&net->ipv6.frags, &key);
 100         if (!q)
 101                 return NULL;
 102
 103         return container_of(q, struct frag_queue, q);
 104 }
 105
 106 static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
 107                           struct frag_hdr *fhdr, int nhoff,
 108                           u32 *prob_offset)
 109 {
 110         struct net *net = dev_net(skb_dst(skb)->dev);
 111         int offset, end, fragsize;
 112         struct sk_buff *prev_tail;
 113         struct net_device *dev;
 114         int err = -ENOENT;
 115         u8 ecn;
 116
 117         if (fq->q.flags & INET_FRAG_COMPLETE)
 118                 goto err;
 119
 120         err = -EINVAL;
 121         offset = ntohs(fhdr->frag_off) & ~0x7;
 122         end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
 123                         ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
 124
 125         if ((unsigned int)end > IPV6_MAXPLEN) {
 126                 *prob_offset = (u8 *)&fhdr->frag_off - skb_network_header(skb);
 127                 /* note that if prob_offset is set, the skb is freed elsewhere,
 128                  * we do not free it here.
 129                  */
 130                 return -1;
 131         }
 132
 133         ecn = ip6_frag_ecn(ipv6_hdr(skb));
 134
 135         if (skb->ip_summed == CHECKSUM_COMPLETE) {
 136                 const unsigned char *nh = skb_network_header(skb);
 137                 skb->csum = csum_sub(skb->csum,
 138                                      csum_partial(nh, (u8 *)(fhdr + 1) - nh,
 139                                                   0));
 140         }
 141
 142         /* Is this the final fragment? */
 143         if (!(fhdr->frag_off & htons(IP6_MF))) {
 144                 /* If we already have some bits beyond end
 145                  * or have different end, the segment is corrupted.
 146                  */
 147                 if (end < fq->q.len ||
 148                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
 149                         goto discard_fq;
 150                 fq->q.flags |= INET_FRAG_LAST_IN;
 151                 fq->q.len = end;
 152         } else {
 153                 /* Check if the fragment is rounded to 8 bytes.
 154                  * Required by the RFC.
 155                  */
 156                 if (end & 0x7) {
 157                         /* RFC2460 says always send parameter problem in
 158                          * this case. -DaveM
 159                          */
 160                         *prob_offset = offsetof(struct ipv6hdr, payload_len);
 161                         return -1;
 162                 }
 163                 if (end > fq->q.len) {
 164                         /* Some bits beyond end -> corruption. */
 165                         if (fq->q.flags & INET_FRAG_LAST_IN)
 166                                 goto discard_fq;
 167                         fq->q.len = end;
 168                 }
 169         }
 170
 171         if (end == offset)
 172                 goto discard_fq;
 173
 174         err = -ENOMEM;
 175         /* Point into the IP datagram 'data' part. */
 176         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data))
 177                 goto discard_fq;
 178
 179         err = pskb_trim_rcsum(skb, end - offset);
 180         if (err)
 181                 goto discard_fq;
 182
 183         /* Note : skb->rbnode and skb->dev share the same location. */
 184         dev = skb->dev;
 185         /* Makes sure compiler wont do silly aliasing games */
 186         barrier();
 187
 188         prev_tail = fq->q.fragments_tail;
 189         err = inet_frag_queue_insert(&fq->q, skb, offset, end);
 190         if (err)
 191                 goto insert_error;
 192
 193         if (dev)
 194                 fq->iif = dev->ifindex;
 195
 196         fq->q.stamp = skb->tstamp;
 197         fq->q.meat += skb->len;
 198         fq->ecn |= ecn;
 199         add_frag_mem_limit(fq->q.net, skb->truesize);
 200
 201         fragsize = -skb_network_offset(skb) + skb->len;
 202         if (fragsize > fq->q.max_size)
 203                 fq->q.max_size = fragsize;
 204
 205         /* The first fragment.
 206          * nhoffset is obtained from the first fragment, of course.
 207          */
 208         if (offset == 0) {
 209                 fq->nhoffset = nhoff;
 210                 fq->q.flags |= INET_FRAG_FIRST_IN;
 211         }
 212
 213         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 214             fq->q.meat == fq->q.len) {
 215                 unsigned long orefdst = skb->_skb_refdst;
 216
 217                 skb->_skb_refdst = 0UL;
 218                 err = ip6_frag_reasm(fq, skb, prev_tail, dev);
 219                 skb->_skb_refdst = orefdst;
 220                 return err;
 221         }
 222
 223         skb_dst_drop(skb);
 224         return -EINPROGRESS;
 225
 226 insert_error:
 227         if (err == IPFRAG_DUP) {
 228                 kfree_skb(skb);
 229                 return -EINVAL;
 230         }
 231         err = -EINVAL;
 232         __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
 233                         IPSTATS_MIB_REASM_OVERLAPS);
 234 discard_fq:
 235         inet_frag_kill(&fq->q);
 236         __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
 237                         IPSTATS_MIB_REASMFAILS);
 238 err:
 239         kfree_skb(skb);
 240         return err;
 241 }
 242
 243 /*
 244  *      Check if this packet is complete.
 245  *
 246  *      It is called with locked fq, and caller must check that
 247  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 248  *      the last and the first frames arrived and all the bits are here.
 249  */
 250 static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *skb,
 251                           struct sk_buff *prev_tail, struct net_device *dev)
 252 {
 253         struct net *net = container_of(fq->q.net, struct net, ipv6.frags);
 254         unsigned int nhoff;
 255         void *reasm_data;
 256         int payload_len;
 257         u8 ecn;
 258
 259         inet_frag_kill(&fq->q);
 260
 261         ecn = ip_frag_ecn_table[fq->ecn];
 262         if (unlikely(ecn == 0xff))
 263                 goto out_fail;
 264
 265         reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
 266         if (!reasm_data)
 267                 goto out_oom;
 268
 269         payload_len = ((skb->data - skb_network_header(skb)) -
 270                        sizeof(struct ipv6hdr) + fq->q.len -
 271                        sizeof(struct frag_hdr));
 272         if (payload_len > IPV6_MAXPLEN)
 273                 goto out_oversize;
 274
 275         /* We have to remove fragment header from datagram and to relocate
 276          * header in order to calculate ICV correctly. */
 277         nhoff = fq->nhoffset;
 278         skb_network_header(skb)[nhoff] = skb_transport_header(skb)[0];
 279         memmove(skb->head + sizeof(struct frag_hdr), skb->head,
 280                 (skb->data - skb->head) - sizeof(struct frag_hdr));
 281         if (skb_mac_header_was_set(skb))
 282                 skb->mac_header += sizeof(struct frag_hdr);
 283         skb->network_header += sizeof(struct frag_hdr);
 284
 285         skb_reset_transport_header(skb);
 286
 287         inet_frag_reasm_finish(&fq->q, skb, reasm_data);
 288
 289         skb->dev = dev;
 290         ipv6_hdr(skb)->payload_len = htons(payload_len);
 291         ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
 292         IP6CB(skb)->nhoff = nhoff;
 293         IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
 294         IP6CB(skb)->frag_max_size = fq->q.max_size;
 295
 296         /* Yes, and fold redundant checksum back. 8) */
 297         skb_postpush_rcsum(skb, skb_network_header(skb),
 298                            skb_network_header_len(skb));
 299
 300         rcu_read_lock();
 301         __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMOKS);
 302         rcu_read_unlock();
 303         fq->q.rb_fragments = RB_ROOT;
 304         fq->q.fragments_tail = NULL;
 305         fq->q.last_run_head = NULL;
 306         return 1;
 307
 308 out_oversize:
 309         net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len);
 310         goto out_fail;
 311 out_oom:
 312         net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n");
 313 out_fail:
 314         rcu_read_lock();
 315         __IP6_INC_STATS(net, __in6_dev_stats_get(dev, skb), IPSTATS_MIB_REASMFAILS);
 316         rcu_read_unlock();
 317         inet_frag_kill(&fq->q);
 318         return -1;
 319 }
 320
 321 static int ipv6_frag_rcv(struct sk_buff *skb)
 322 {
 323         struct frag_hdr *fhdr;
 324         struct frag_queue *fq;
 325         const struct ipv6hdr *hdr = ipv6_hdr(skb);
 326         struct net *net = dev_net(skb_dst(skb)->dev);
 327         int iif;
 328
 329         if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
 330                 goto fail_hdr;
 331
 332         __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS);
 333
 334         /* Jumbo payload inhibits frag. header */
 335         if (hdr->payload_len == 0)
 336                 goto fail_hdr;
 337
 338         if (!pskb_may_pull(skb, (skb_transport_offset(skb) +
 339                                  sizeof(struct frag_hdr))))
 340                 goto fail_hdr;
 341
 342         hdr = ipv6_hdr(skb);
 343         fhdr = (struct frag_hdr *)skb_transport_header(skb);
 344
 345         if (!(fhdr->frag_off & htons(0xFFF9))) {
 346                 /* It is not a fragmented frame */
 347                 skb->transport_header += sizeof(struct frag_hdr);
 348                 __IP6_INC_STATS(net,
 349                                 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);
 350
 351                 IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
 352                 IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
 353                 return 1;
 354         }
 355
 356         iif = skb->dev ? skb->dev->ifindex : 0;
 357         fq = fq_find(net, fhdr->identification, hdr, iif);
 358         if (fq) {
 359                 u32 prob_offset = 0;
 360                 int ret;
 361
 362                 spin_lock(&fq->q.lock);
 363
 364                 fq->iif = iif;
 365                 ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff,
 366                                      &prob_offset);
 367
 368                 spin_unlock(&fq->q.lock);
 369                 inet_frag_put(&fq->q);
 370                 if (prob_offset) {
 371                         __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
 372                                         IPSTATS_MIB_INHDRERRORS);
 373                         /* icmpv6_param_prob() calls kfree_skb(skb) */
 374                         icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);
 375                 }
 376                 return ret;
 377         }
 378
 379         __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS);
 380         kfree_skb(skb);
 381         return -1;
 382
 383 fail_hdr:
 384         __IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),
 385                         IPSTATS_MIB_INHDRERRORS);
 386         icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb));
 387         return -1;
 388 }
 389
 390 static const struct inet6_protocol frag_protocol = {
 391         .handler        =       ipv6_frag_rcv,
 392         .flags          =       INET6_PROTO_NOPOLICY,
 393 };
 394
 395 #ifdef CONFIG_SYSCTL
 396
 397 static struct ctl_table ip6_frags_ns_ctl_table[] = {
 398         {
 399                 .procname       = "ip6frag_high_thresh",
 400                 .data           = &init_net.ipv6.frags.high_thresh,
 401                 .maxlen         = sizeof(unsigned long),
 402                 .mode           = 0644,
 403                 .proc_handler   = proc_doulongvec_minmax,
 404                 .extra1         = &init_net.ipv6.frags.low_thresh
 405         },
 406         {
 407                 .procname       = "ip6frag_low_thresh",
 408                 .data           = &init_net.ipv6.frags.low_thresh,
 409                 .maxlen         = sizeof(unsigned long),
 410                 .mode           = 0644,
 411                 .proc_handler   = proc_doulongvec_minmax,
 412                 .extra2         = &init_net.ipv6.frags.high_thresh
 413         },
 414         {
 415                 .procname       = "ip6frag_time",
 416                 .data           = &init_net.ipv6.frags.timeout,
 417                 .maxlen         = sizeof(int),
 418                 .mode           = 0644,
 419                 .proc_handler   = proc_dointvec_jiffies,
 420         },
 421         { }
 422 };
 423
 424 /* secret interval has been deprecated */
 425 static int ip6_frags_secret_interval_unused;
 426 static struct ctl_table ip6_frags_ctl_table[] = {
 427         {
 428                 .procname       = "ip6frag_secret_interval",
 429                 .data           = &ip6_frags_secret_interval_unused,
 430                 .maxlen         = sizeof(int),
 431                 .mode           = 0644,
 432                 .proc_handler   = proc_dointvec_jiffies,
 433         },
 434         { }
 435 };
 436
 437 static int __net_init ip6_frags_ns_sysctl_register(struct net *net)
 438 {
 439         struct ctl_table *table;
 440         struct ctl_table_header *hdr;
 441
 442         table = ip6_frags_ns_ctl_table;
 443         if (!net_eq(net, &init_net)) {
 444                 table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL);
 445                 if (!table)
 446                         goto err_alloc;
 447
 448                 table[0].data = &net->ipv6.frags.high_thresh;
 449                 table[0].extra1 = &net->ipv6.frags.low_thresh;
 450                 table[1].data = &net->ipv6.frags.low_thresh;
 451                 table[1].extra2 = &net->ipv6.frags.high_thresh;
 452                 table[2].data = &net->ipv6.frags.timeout;
 453         }
 454
 455         hdr = register_net_sysctl(net, "net/ipv6", table);
 456         if (!hdr)
 457                 goto err_reg;
 458
 459         net->ipv6.sysctl.frags_hdr = hdr;
 460         return 0;
 461
 462 err_reg:
 463         if (!net_eq(net, &init_net))
 464                 kfree(table);
 465 err_alloc:
 466         return -ENOMEM;
 467 }
 468
 469 static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net)
 470 {
 471         struct ctl_table *table;
 472
 473         table = net->ipv6.sysctl.frags_hdr->ctl_table_arg;
 474         unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);
 475         if (!net_eq(net, &init_net))
 476                 kfree(table);
 477 }
 478
 479 static struct ctl_table_header *ip6_ctl_header;
 480
 481 static int ip6_frags_sysctl_register(void)
 482 {
 483         ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6",
 484                         ip6_frags_ctl_table);
 485         return ip6_ctl_header == NULL ? -ENOMEM : 0;
 486 }
 487
 488 static void ip6_frags_sysctl_unregister(void)
 489 {
 490         unregister_net_sysctl_table(ip6_ctl_header);
 491 }
 492 #else
 493 static int ip6_frags_ns_sysctl_register(struct net *net)
 494 {
 495         return 0;
 496 }
 497
 498 static void ip6_frags_ns_sysctl_unregister(struct net *net)
 499 {
 500 }
 501
 502 static int ip6_frags_sysctl_register(void)
 503 {
 504         return 0;
 505 }
 506
 507 static void ip6_frags_sysctl_unregister(void)
 508 {
 509 }
 510 #endif
 511
 512 static int __net_init ipv6_frags_init_net(struct net *net)
 513 {
 514         int res;
 515
 516         net->ipv6.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 517         net->ipv6.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 518         net->ipv6.frags.timeout = IPV6_FRAG_TIMEOUT;
 519         net->ipv6.frags.f = &ip6_frags;
 520
 521         res = inet_frags_init_net(&net->ipv6.frags);
 522         if (res < 0)
 523                 return res;
 524
 525         res = ip6_frags_ns_sysctl_register(net);
 526         if (res < 0)
 527                 inet_frags_exit_net(&net->ipv6.frags);
 528         return res;
 529 }
 530
 531 static void __net_exit ipv6_frags_exit_net(struct net *net)
 532 {
 533         ip6_frags_ns_sysctl_unregister(net);
 534         inet_frags_exit_net(&net->ipv6.frags);
 535 }
 536
 537 static struct pernet_operations ip6_frags_ops = {
 538         .init = ipv6_frags_init_net,
 539         .exit = ipv6_frags_exit_net,
 540 };
 541
 542 static const struct rhashtable_params ip6_rhash_params = {
 543         .head_offset            = offsetof(struct inet_frag_queue, node),
 544         .hashfn                 = ip6frag_key_hashfn,
 545         .obj_hashfn             = ip6frag_obj_hashfn,
 546         .obj_cmpfn              = ip6frag_obj_cmpfn,
 547         .automatic_shrinking    = true,
 548 };
 549
 550 int __init ipv6_frag_init(void)
 551 {
 552         int ret;
 553
 554         ip6_frags.constructor = ip6frag_init;
 555         ip6_frags.destructor = NULL;
 556         ip6_frags.qsize = sizeof(struct frag_queue);
 557         ip6_frags.frag_expire = ip6_frag_expire;
 558         ip6_frags.frags_cache_name = ip6_frag_cache_name;
 559         ip6_frags.rhash_params = ip6_rhash_params;
 560         ret = inet_frags_init(&ip6_frags);
 561         if (ret)
 562                 goto out;
 563
 564         ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 565         if (ret)
 566                 goto err_protocol;
 567
 568         ret = ip6_frags_sysctl_register();
 569         if (ret)
 570                 goto err_sysctl;
 571
 572         ret = register_pernet_subsys(&ip6_frags_ops);
 573         if (ret)
 574                 goto err_pernet;
 575
 576 out:
 577         return ret;
 578
 579 err_pernet:
 580         ip6_frags_sysctl_unregister();
 581 err_sysctl:
 582         inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 583 err_protocol:
 584         inet_frags_fini(&ip6_frags);
 585         goto out;
 586 }
 587
 588 void ipv6_frag_exit(void)
 589 {
 590         inet_frags_fini(&ip6_frags);
 591         ip6_frags_sysctl_unregister();
 592         unregister_pernet_subsys(&ip6_frags_ops);
 593         inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 594 }