net/ieee802154/6lowpan/reassembly.c

   1 /*      6LoWPAN fragment reassembly
   2  *
   3  *
   4  *      Authors:
   5  *      Alexander Aring         <aar@pengutronix.de>
   6  *
   7  *      Based on: net/ipv6/reassembly.c
   8  *
   9  *      This program is free software; you can redistribute it and/or
  10  *      modify it under the terms of the GNU General Public License
  11  *      as published by the Free Software Foundation; either version
  12  *      2 of the License, or (at your option) any later version.
  13  */
  14
  15 #define pr_fmt(fmt) "6LoWPAN: " fmt
  16
  17 #include <linux/net.h>
  18 #include <linux/list.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/random.h>
  21 #include <linux/jhash.h>
  22 #include <linux/skbuff.h>
  23 #include <linux/slab.h>
  24 #include <linux/export.h>
  25
  26 #include <net/ieee802154_netdev.h>
  27 #include <net/6lowpan.h>
  28 #include <net/ipv6.h>
  29 #include <net/inet_frag.h>
  30
  31 #include "6lowpan_i.h"
  32
  33 static const char lowpan_frags_cache_name[] = "lowpan-frags";
  34
  35 static struct inet_frags lowpan_frags;
  36
  37 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq,
  38                              struct sk_buff *prev, struct net_device *ldev);
  39
  40 static unsigned int lowpan_hash_frag(u16 tag, u16 d_size,
  41                                      const struct ieee802154_addr *saddr,
  42                                      const struct ieee802154_addr *daddr)
  43 {
  44         net_get_random_once(&lowpan_frags.rnd, sizeof(lowpan_frags.rnd));
  45         return jhash_3words(ieee802154_addr_hash(saddr),
  46                             ieee802154_addr_hash(daddr),
  47                             (__force u32)(tag + (d_size << 16)),
  48                             lowpan_frags.rnd);
  49 }
  50
  51 static unsigned int lowpan_hashfn(const struct inet_frag_queue *q)
  52 {
  53         const struct lowpan_frag_queue *fq;
  54
  55         fq = container_of(q, struct lowpan_frag_queue, q);
  56         return lowpan_hash_frag(fq->tag, fq->d_size, &fq->saddr, &fq->daddr);
  57 }
  58
  59 static bool lowpan_frag_match(const struct inet_frag_queue *q, const void *a)
  60 {
  61         const struct lowpan_frag_queue *fq;
  62         const struct lowpan_create_arg *arg = a;
  63
  64         fq = container_of(q, struct lowpan_frag_queue, q);
  65         return  fq->tag == arg->tag && fq->d_size == arg->d_size &&
  66                 ieee802154_addr_equal(&fq->saddr, arg->src) &&
  67                 ieee802154_addr_equal(&fq->daddr, arg->dst);
  68 }
  69
  70 static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
  71 {
  72         const struct lowpan_create_arg *arg = a;
  73         struct lowpan_frag_queue *fq;
  74
  75         fq = container_of(q, struct lowpan_frag_queue, q);
  76
  77         fq->tag = arg->tag;
  78         fq->d_size = arg->d_size;
  79         fq->saddr = *arg->src;
  80         fq->daddr = *arg->dst;
  81 }
  82
  83 static void lowpan_frag_expire(struct timer_list *t)
  84 {
  85         struct inet_frag_queue *frag = from_timer(frag, t, timer);
  86         struct frag_queue *fq;
  87         struct net *net;
  88
  89         fq = container_of(frag, struct frag_queue, q);
  90         net = container_of(fq->q.net, struct net, ieee802154_lowpan.frags);
  91
  92         spin_lock(&fq->q.lock);
  93
  94         if (fq->q.flags & INET_FRAG_COMPLETE)
  95                 goto out;
  96
  97         inet_frag_kill(&fq->q, &lowpan_frags);
  98 out:
  99         spin_unlock(&fq->q.lock);
 100         inet_frag_put(&fq->q, &lowpan_frags);
 101 }
 102
 103 static inline struct lowpan_frag_queue *
 104 fq_find(struct net *net, const struct lowpan_802154_cb *cb,
 105         const struct ieee802154_addr *src,
 106         const struct ieee802154_addr *dst)
 107 {
 108         struct inet_frag_queue *q;
 109         struct lowpan_create_arg arg;
 110         unsigned int hash;
 111         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 112                 net_ieee802154_lowpan(net);
 113
 114         arg.tag = cb->d_tag;
 115         arg.d_size = cb->d_size;
 116         arg.src = src;
 117         arg.dst = dst;
 118
 119         hash = lowpan_hash_frag(cb->d_tag, cb->d_size, src, dst);
 120
 121         q = inet_frag_find(&ieee802154_lowpan->frags,
 122                            &lowpan_frags, &arg, hash);
 123         if (IS_ERR_OR_NULL(q)) {
 124                 inet_frag_maybe_warn_overflow(q, pr_fmt());
 125                 return NULL;
 126         }
 127         return container_of(q, struct lowpan_frag_queue, q);
 128 }
 129
 130 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
 131                              struct sk_buff *skb, u8 frag_type)
 132 {
 133         struct sk_buff *prev, *next;
 134         struct net_device *ldev;
 135         int end, offset;
 136
 137         if (fq->q.flags & INET_FRAG_COMPLETE)
 138                 goto err;
 139
 140         offset = lowpan_802154_cb(skb)->d_offset << 3;
 141         end = lowpan_802154_cb(skb)->d_size;
 142
 143         /* Is this the final fragment? */
 144         if (offset + skb->len == end) {
 145                 /* If we already have some bits beyond end
 146                  * or have different end, the segment is corrupted.
 147                  */
 148                 if (end < fq->q.len ||
 149                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
 150                         goto err;
 151                 fq->q.flags |= INET_FRAG_LAST_IN;
 152                 fq->q.len = end;
 153         } else {
 154                 if (end > fq->q.len) {
 155                         /* Some bits beyond end -> corruption. */
 156                         if (fq->q.flags & INET_FRAG_LAST_IN)
 157                                 goto err;
 158                         fq->q.len = end;
 159                 }
 160         }
 161
 162         /* Find out which fragments are in front and at the back of us
 163          * in the chain of fragments so far.  We must know where to put
 164          * this fragment, right?
 165          */
 166         prev = fq->q.fragments_tail;
 167         if (!prev ||
 168             lowpan_802154_cb(prev)->d_offset <
 169             lowpan_802154_cb(skb)->d_offset) {
 170                 next = NULL;
 171                 goto found;
 172         }
 173         prev = NULL;
 174         for (next = fq->q.fragments; next != NULL; next = next->next) {
 175                 if (lowpan_802154_cb(next)->d_offset >=
 176                     lowpan_802154_cb(skb)->d_offset)
 177                         break;  /* bingo! */
 178                 prev = next;
 179         }
 180
 181 found:
 182         /* Insert this fragment in the chain of fragments. */
 183         skb->next = next;
 184         if (!next)
 185                 fq->q.fragments_tail = skb;
 186         if (prev)
 187                 prev->next = skb;
 188         else
 189                 fq->q.fragments = skb;
 190
 191         ldev = skb->dev;
 192         if (ldev)
 193                 skb->dev = NULL;
 194
 195         fq->q.stamp = skb->tstamp;
 196         if (frag_type == LOWPAN_DISPATCH_FRAG1)
 197                 fq->q.flags |= INET_FRAG_FIRST_IN;
 198
 199         fq->q.meat += skb->len;
 200         add_frag_mem_limit(fq->q.net, skb->truesize);
 201
 202         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 203             fq->q.meat == fq->q.len) {
 204                 int res;
 205                 unsigned long orefdst = skb->_skb_refdst;
 206
 207                 skb->_skb_refdst = 0UL;
 208                 res = lowpan_frag_reasm(fq, prev, ldev);
 209                 skb->_skb_refdst = orefdst;
 210                 return res;
 211         }
 212
 213         return -1;
 214 err:
 215         kfree_skb(skb);
 216         return -1;
 217 }
 218
 219 /*      Check if this packet is complete.
 220  *      Returns NULL on failure by any reason, and pointer
 221  *      to current nexthdr field in reassembled frame.
 222  *
 223  *      It is called with locked fq, and caller must check that
 224  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 225  *      the last and the first frames arrived and all the bits are here.
 226  */
 227 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *prev,
 228                              struct net_device *ldev)
 229 {
 230         struct sk_buff *fp, *head = fq->q.fragments;
 231         int sum_truesize;
 232
 233         inet_frag_kill(&fq->q, &lowpan_frags);
 234
 235         /* Make the one we just received the head. */
 236         if (prev) {
 237                 head = prev->next;
 238                 fp = skb_clone(head, GFP_ATOMIC);
 239
 240                 if (!fp)
 241                         goto out_oom;
 242
 243                 fp->next = head->next;
 244                 if (!fp->next)
 245                         fq->q.fragments_tail = fp;
 246                 prev->next = fp;
 247
 248                 skb_morph(head, fq->q.fragments);
 249                 head->next = fq->q.fragments->next;
 250
 251                 consume_skb(fq->q.fragments);
 252                 fq->q.fragments = head;
 253         }
 254
 255         /* Head of list must not be cloned. */
 256         if (skb_unclone(head, GFP_ATOMIC))
 257                 goto out_oom;
 258
 259         /* If the first fragment is fragmented itself, we split
 260          * it to two chunks: the first with data and paged part
 261          * and the second, holding only fragments.
 262          */
 263         if (skb_has_frag_list(head)) {
 264                 struct sk_buff *clone;
 265                 int i, plen = 0;
 266
 267                 clone = alloc_skb(0, GFP_ATOMIC);
 268                 if (!clone)
 269                         goto out_oom;
 270                 clone->next = head->next;
 271                 head->next = clone;
 272                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 273                 skb_frag_list_init(head);
 274                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 275                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 276                 clone->len = head->data_len - plen;
 277                 clone->data_len = clone->len;
 278                 head->data_len -= clone->len;
 279                 head->len -= clone->len;
 280                 add_frag_mem_limit(fq->q.net, clone->truesize);
 281         }
 282
 283         WARN_ON(head == NULL);
 284
 285         sum_truesize = head->truesize;
 286         for (fp = head->next; fp;) {
 287                 bool headstolen;
 288                 int delta;
 289                 struct sk_buff *next = fp->next;
 290
 291                 sum_truesize += fp->truesize;
 292                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 293                         kfree_skb_partial(fp, headstolen);
 294                 } else {
 295                         if (!skb_shinfo(head)->frag_list)
 296                                 skb_shinfo(head)->frag_list = fp;
 297                         head->data_len += fp->len;
 298                         head->len += fp->len;
 299                         head->truesize += fp->truesize;
 300                 }
 301                 fp = next;
 302         }
 303         sub_frag_mem_limit(fq->q.net, sum_truesize);
 304
 305         head->next = NULL;
 306         head->dev = ldev;
 307         head->tstamp = fq->q.stamp;
 308
 309         fq->q.fragments = NULL;
 310         fq->q.fragments_tail = NULL;
 311
 312         return 1;
 313 out_oom:
 314         net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
 315         return -1;
 316 }
 317
 318 static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
 319                                           lowpan_rx_result res)
 320 {
 321         switch (res) {
 322         case RX_QUEUED:
 323                 return NET_RX_SUCCESS;
 324         case RX_CONTINUE:
 325                 /* nobody cared about this packet */
 326                 net_warn_ratelimited("%s: received unknown dispatch\n",
 327                                      __func__);
 328
 329                 /* fall-through */
 330         default:
 331                 /* all others failure */
 332                 return NET_RX_DROP;
 333         }
 334 }
 335
 336 static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
 337 {
 338         int ret;
 339
 340         if (!lowpan_is_iphc(*skb_network_header(skb)))
 341                 return RX_CONTINUE;
 342
 343         ret = lowpan_iphc_decompress(skb);
 344         if (ret < 0)
 345                 return RX_DROP;
 346
 347         return RX_QUEUED;
 348 }
 349
 350 static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
 351 {
 352         lowpan_rx_result res;
 353
 354 #define CALL_RXH(rxh)                   \
 355         do {                            \
 356                 res = rxh(skb); \
 357                 if (res != RX_CONTINUE) \
 358                         goto rxh_next;  \
 359         } while (0)
 360
 361         /* likely at first */
 362         CALL_RXH(lowpan_frag_rx_h_iphc);
 363         CALL_RXH(lowpan_rx_h_ipv6);
 364
 365 rxh_next:
 366         return lowpan_frag_rx_handlers_result(skb, res);
 367 #undef CALL_RXH
 368 }
 369
 370 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK        0x07
 371 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT       8
 372
 373 static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
 374                          struct lowpan_802154_cb *cb)
 375 {
 376         bool fail;
 377         u8 high = 0, low = 0;
 378         __be16 d_tag = 0;
 379
 380         fail = lowpan_fetch_skb(skb, &high, 1);
 381         fail |= lowpan_fetch_skb(skb, &low, 1);
 382         /* remove the dispatch value and use first three bits as high value
 383          * for the datagram size
 384          */
 385         cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
 386                 LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
 387         fail |= lowpan_fetch_skb(skb, &d_tag, 2);
 388         cb->d_tag = ntohs(d_tag);
 389
 390         if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 391                 fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
 392         } else {
 393                 skb_reset_network_header(skb);
 394                 cb->d_offset = 0;
 395                 /* check if datagram_size has ipv6hdr on FRAG1 */
 396                 fail |= cb->d_size < sizeof(struct ipv6hdr);
 397                 /* check if we can dereference the dispatch value */
 398                 fail |= !skb->len;
 399         }
 400
 401         if (unlikely(fail))
 402                 return -EIO;
 403
 404         return 0;
 405 }
 406
 407 int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 408 {
 409         struct lowpan_frag_queue *fq;
 410         struct net *net = dev_net(skb->dev);
 411         struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
 412         struct ieee802154_hdr hdr;
 413         int err;
 414
 415         if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
 416                 goto err;
 417
 418         err = lowpan_get_cb(skb, frag_type, cb);
 419         if (err < 0)
 420                 goto err;
 421
 422         if (frag_type == LOWPAN_DISPATCH_FRAG1) {
 423                 err = lowpan_invoke_frag_rx_handlers(skb);
 424                 if (err == NET_RX_DROP)
 425                         goto err;
 426         }
 427
 428         if (cb->d_size > IPV6_MIN_MTU) {
 429                 net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
 430                 goto err;
 431         }
 432
 433         fq = fq_find(net, cb, &hdr.source, &hdr.dest);
 434         if (fq != NULL) {
 435                 int ret;
 436
 437                 spin_lock(&fq->q.lock);
 438                 ret = lowpan_frag_queue(fq, skb, frag_type);
 439                 spin_unlock(&fq->q.lock);
 440
 441                 inet_frag_put(&fq->q, &lowpan_frags);
 442                 return ret;
 443         }
 444
 445 err:
 446         kfree_skb(skb);
 447         return -1;
 448 }
 449
 450 #ifdef CONFIG_SYSCTL
 451 static int zero;
 452
 453 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 454         {
 455                 .procname       = "6lowpanfrag_high_thresh",
 456                 .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 457                 .maxlen         = sizeof(int),
 458                 .mode           = 0644,
 459                 .proc_handler   = proc_dointvec_minmax,
 460                 .extra1         = &init_net.ieee802154_lowpan.frags.low_thresh
 461         },
 462         {
 463                 .procname       = "6lowpanfrag_low_thresh",
 464                 .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 465                 .maxlen         = sizeof(int),
 466                 .mode           = 0644,
 467                 .proc_handler   = proc_dointvec_minmax,
 468                 .extra1         = &zero,
 469                 .extra2         = &init_net.ieee802154_lowpan.frags.high_thresh
 470         },
 471         {
 472                 .procname       = "6lowpanfrag_time",
 473                 .data           = &init_net.ieee802154_lowpan.frags.timeout,
 474                 .maxlen         = sizeof(int),
 475                 .mode           = 0644,
 476                 .proc_handler   = proc_dointvec_jiffies,
 477         },
 478         { }
 479 };
 480
 481 /* secret interval has been deprecated */
 482 static int lowpan_frags_secret_interval_unused;
 483 static struct ctl_table lowpan_frags_ctl_table[] = {
 484         {
 485                 .procname       = "6lowpanfrag_secret_interval",
 486                 .data           = &lowpan_frags_secret_interval_unused,
 487                 .maxlen         = sizeof(int),
 488                 .mode           = 0644,
 489                 .proc_handler   = proc_dointvec_jiffies,
 490         },
 491         { }
 492 };
 493
 494 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 495 {
 496         struct ctl_table *table;
 497         struct ctl_table_header *hdr;
 498         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 499                 net_ieee802154_lowpan(net);
 500
 501         table = lowpan_frags_ns_ctl_table;
 502         if (!net_eq(net, &init_net)) {
 503                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 504                                 GFP_KERNEL);
 505                 if (table == NULL)
 506                         goto err_alloc;
 507
 508                 table[0].data = &ieee802154_lowpan->frags.high_thresh;
 509                 table[0].extra1 = &ieee802154_lowpan->frags.low_thresh;
 510                 table[0].extra2 = &init_net.ieee802154_lowpan.frags.high_thresh;
 511                 table[1].data = &ieee802154_lowpan->frags.low_thresh;
 512                 table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;
 513                 table[2].data = &ieee802154_lowpan->frags.timeout;
 514
 515                 /* Don't export sysctls to unprivileged users */
 516                 if (net->user_ns != &init_user_ns)
 517                         table[0].procname = NULL;
 518         }
 519
 520         hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 521         if (hdr == NULL)
 522                 goto err_reg;
 523
 524         ieee802154_lowpan->sysctl.frags_hdr = hdr;
 525         return 0;
 526
 527 err_reg:
 528         if (!net_eq(net, &init_net))
 529                 kfree(table);
 530 err_alloc:
 531         return -ENOMEM;
 532 }
 533
 534 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 535 {
 536         struct ctl_table *table;
 537         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 538                 net_ieee802154_lowpan(net);
 539
 540         table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 541         unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 542         if (!net_eq(net, &init_net))
 543                 kfree(table);
 544 }
 545
 546 static struct ctl_table_header *lowpan_ctl_header;
 547
 548 static int __init lowpan_frags_sysctl_register(void)
 549 {
 550         lowpan_ctl_header = register_net_sysctl(&init_net,
 551                                                 "net/ieee802154/6lowpan",
 552                                                 lowpan_frags_ctl_table);
 553         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 554 }
 555
 556 static void lowpan_frags_sysctl_unregister(void)
 557 {
 558         unregister_net_sysctl_table(lowpan_ctl_header);
 559 }
 560 #else
 561 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 562 {
 563         return 0;
 564 }
 565
 566 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 567 {
 568 }
 569
 570 static inline int __init lowpan_frags_sysctl_register(void)
 571 {
 572         return 0;
 573 }
 574
 575 static inline void lowpan_frags_sysctl_unregister(void)
 576 {
 577 }
 578 #endif
 579
 580 static int __net_init lowpan_frags_init_net(struct net *net)
 581 {
 582         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 583                 net_ieee802154_lowpan(net);
 584         int res;
 585
 586         ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 587         ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 588         ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
 589
 590         res = inet_frags_init_net(&ieee802154_lowpan->frags);
 591         if (res < 0)
 592                 return res;
 593         res = lowpan_frags_ns_sysctl_register(net);
 594         if (res < 0)
 595                 inet_frags_exit_net(&ieee802154_lowpan->frags, &lowpan_frags);
 596         return res;
 597 }
 598
 599 static void __net_exit lowpan_frags_exit_net(struct net *net)
 600 {
 601         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 602                 net_ieee802154_lowpan(net);
 603
 604         lowpan_frags_ns_sysctl_unregister(net);
 605         inet_frags_exit_net(&ieee802154_lowpan->frags, &lowpan_frags);
 606 }
 607
 608 static struct pernet_operations lowpan_frags_ops = {
 609         .init = lowpan_frags_init_net,
 610         .exit = lowpan_frags_exit_net,
 611 };
 612
 613 int __init lowpan_net_frag_init(void)
 614 {
 615         int ret;
 616
 617         ret = lowpan_frags_sysctl_register();
 618         if (ret)
 619                 return ret;
 620
 621         ret = register_pernet_subsys(&lowpan_frags_ops);
 622         if (ret)
 623                 goto err_pernet;
 624
 625         lowpan_frags.hashfn = lowpan_hashfn;
 626         lowpan_frags.constructor = lowpan_frag_init;
 627         lowpan_frags.destructor = NULL;
 628         lowpan_frags.qsize = sizeof(struct frag_queue);
 629         lowpan_frags.match = lowpan_frag_match;
 630         lowpan_frags.frag_expire = lowpan_frag_expire;
 631         lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
 632         ret = inet_frags_init(&lowpan_frags);
 633         if (ret)
 634                 goto err_pernet;
 635
 636         return ret;
 637 err_pernet:
 638         lowpan_frags_sysctl_unregister();
 639         return ret;
 640 }
 641
 642 void lowpan_net_frag_exit(void)
 643 {
 644         inet_frags_fini(&lowpan_frags);
 645         lowpan_frags_sysctl_unregister();
 646         unregister_pernet_subsys(&lowpan_frags_ops);
 647 }