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