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_frag.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 void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
  41 {
  42         const struct frag_lowpan_compare_key *key = a;
  43
  44         BUILD_BUG_ON(sizeof(*key) > sizeof(q->key));
  45         memcpy(&q->key, key, sizeof(*key));
  46 }
  47
  48 static void lowpan_frag_expire(struct timer_list *t)
  49 {
  50         struct inet_frag_queue *frag = from_timer(frag, t, timer);
  51         struct frag_queue *fq;
  52
  53         fq = container_of(frag, struct frag_queue, q);
  54
  55         spin_lock(&fq->q.lock);
  56
  57         if (fq->q.flags & INET_FRAG_COMPLETE)
  58                 goto out;
  59
  60         inet_frag_kill(&fq->q);
  61 out:
  62         spin_unlock(&fq->q.lock);
  63         inet_frag_put(&fq->q);
  64 }
  65
  66 static inline struct lowpan_frag_queue *
  67 fq_find(struct net *net, const struct lowpan_802154_cb *cb,
  68         const struct ieee802154_addr *src,
  69         const struct ieee802154_addr *dst)
  70 {
  71         struct netns_ieee802154_lowpan *ieee802154_lowpan =
  72                 net_ieee802154_lowpan(net);
  73         struct frag_lowpan_compare_key key = {};
  74         struct inet_frag_queue *q;
  75
  76         key.tag = cb->d_tag;
  77         key.d_size = cb->d_size;
  78         key.src = *src;
  79         key.dst = *dst;
  80
  81         q = inet_frag_find(&ieee802154_lowpan->frags, &key);
  82         if (!q)
  83                 return NULL;
  84
  85         return container_of(q, struct lowpan_frag_queue, q);
  86 }
  87
  88 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
  89                              struct sk_buff *skb, u8 frag_type)
  90 {
  91         struct sk_buff *prev, *next;
  92         struct net_device *ldev;
  93         int end, offset;
  94
  95         if (fq->q.flags & INET_FRAG_COMPLETE)
  96                 goto err;
  97
  98         offset = lowpan_802154_cb(skb)->d_offset << 3;
  99         end = lowpan_802154_cb(skb)->d_size;
 100
 101         /* Is this the final fragment? */
 102         if (offset + skb->len == end) {
 103                 /* If we already have some bits beyond end
 104                  * or have different end, the segment is corrupted.
 105                  */
 106                 if (end < fq->q.len ||
 107                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
 108                         goto err;
 109                 fq->q.flags |= INET_FRAG_LAST_IN;
 110                 fq->q.len = end;
 111         } else {
 112                 if (end > fq->q.len) {
 113                         /* Some bits beyond end -> corruption. */
 114                         if (fq->q.flags & INET_FRAG_LAST_IN)
 115                                 goto err;
 116                         fq->q.len = end;
 117                 }
 118         }
 119
 120         /* Find out which fragments are in front and at the back of us
 121          * in the chain of fragments so far.  We must know where to put
 122          * this fragment, right?
 123          */
 124         prev = fq->q.fragments_tail;
 125         if (!prev ||
 126             lowpan_802154_cb(prev)->d_offset <
 127             lowpan_802154_cb(skb)->d_offset) {
 128                 next = NULL;
 129                 goto found;
 130         }
 131         prev = NULL;
 132         for (next = fq->q.fragments; next != NULL; next = next->next) {
 133                 if (lowpan_802154_cb(next)->d_offset >=
 134                     lowpan_802154_cb(skb)->d_offset)
 135                         break;  /* bingo! */
 136                 prev = next;
 137         }
 138
 139 found:
 140         /* Insert this fragment in the chain of fragments. */
 141         skb->next = next;
 142         if (!next)
 143                 fq->q.fragments_tail = skb;
 144         if (prev)
 145                 prev->next = skb;
 146         else
 147                 fq->q.fragments = skb;
 148
 149         ldev = skb->dev;
 150         if (ldev)
 151                 skb->dev = NULL;
 152
 153         fq->q.stamp = skb->tstamp;
 154         if (frag_type == LOWPAN_DISPATCH_FRAG1)
 155                 fq->q.flags |= INET_FRAG_FIRST_IN;
 156
 157         fq->q.meat += skb->len;
 158         add_frag_mem_limit(fq->q.net, skb->truesize);
 159
 160         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 161             fq->q.meat == fq->q.len) {
 162                 int res;
 163                 unsigned long orefdst = skb->_skb_refdst;
 164
 165                 skb->_skb_refdst = 0UL;
 166                 res = lowpan_frag_reasm(fq, prev, ldev);
 167                 skb->_skb_refdst = orefdst;
 168                 return res;
 169         }
 170
 171         return -1;
 172 err:
 173         kfree_skb(skb);
 174         return -1;
 175 }
 176
 177 /*      Check if this packet is complete.
 178  *      Returns NULL on failure by any reason, and pointer
 179  *      to current nexthdr field in reassembled frame.
 180  *
 181  *      It is called with locked fq, and caller must check that
 182  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 183  *      the last and the first frames arrived and all the bits are here.
 184  */
 185 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *prev,
 186                              struct net_device *ldev)
 187 {
 188         struct sk_buff *fp, *head = fq->q.fragments;
 189         int sum_truesize;
 190
 191         inet_frag_kill(&fq->q);
 192
 193         /* Make the one we just received the head. */
 194         if (prev) {
 195                 head = prev->next;
 196                 fp = skb_clone(head, GFP_ATOMIC);
 197
 198                 if (!fp)
 199                         goto out_oom;
 200
 201                 fp->next = head->next;
 202                 if (!fp->next)
 203                         fq->q.fragments_tail = fp;
 204                 prev->next = fp;
 205
 206                 skb_morph(head, fq->q.fragments);
 207                 head->next = fq->q.fragments->next;
 208
 209                 consume_skb(fq->q.fragments);
 210                 fq->q.fragments = head;
 211         }
 212
 213         /* Head of list must not be cloned. */
 214         if (skb_unclone(head, GFP_ATOMIC))
 215                 goto out_oom;
 216
 217         /* If the first fragment is fragmented itself, we split
 218          * it to two chunks: the first with data and paged part
 219          * and the second, holding only fragments.
 220          */
 221         if (skb_has_frag_list(head)) {
 222                 struct sk_buff *clone;
 223                 int i, plen = 0;
 224
 225                 clone = alloc_skb(0, GFP_ATOMIC);
 226                 if (!clone)
 227                         goto out_oom;
 228                 clone->next = head->next;
 229                 head->next = clone;
 230                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 231                 skb_frag_list_init(head);
 232                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 233                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 234                 clone->len = head->data_len - plen;
 235                 clone->data_len = clone->len;
 236                 head->data_len -= clone->len;
 237                 head->len -= clone->len;
 238                 add_frag_mem_limit(fq->q.net, clone->truesize);
 239         }
 240
 241         WARN_ON(head == NULL);
 242
 243         sum_truesize = head->truesize;
 244         for (fp = head->next; fp;) {
 245                 bool headstolen;
 246                 int delta;
 247                 struct sk_buff *next = fp->next;
 248
 249                 sum_truesize += fp->truesize;
 250                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 251                         kfree_skb_partial(fp, headstolen);
 252                 } else {
 253                         if (!skb_shinfo(head)->frag_list)
 254                                 skb_shinfo(head)->frag_list = fp;
 255                         head->data_len += fp->len;
 256                         head->len += fp->len;
 257                         head->truesize += fp->truesize;
 258                 }
 259                 fp = next;
 260         }
 261         sub_frag_mem_limit(fq->q.net, sum_truesize);
 262
 263         skb_mark_not_on_list(head);
 264         head->dev = ldev;
 265         head->tstamp = fq->q.stamp;
 266
 267         fq->q.fragments = NULL;
 268         fq->q.fragments_tail = NULL;
 269
 270         return 1;
 271 out_oom:
 272         net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
 273         return -1;
 274 }
 275
 276 static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
 277                                           lowpan_rx_result res)
 278 {
 279         switch (res) {
 280         case RX_QUEUED:
 281                 return NET_RX_SUCCESS;
 282         case RX_CONTINUE:
 283                 /* nobody cared about this packet */
 284                 net_warn_ratelimited("%s: received unknown dispatch\n",
 285                                      __func__);
 286
 287                 /* fall-through */
 288         default:
 289                 /* all others failure */
 290                 return NET_RX_DROP;
 291         }
 292 }
 293
 294 static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
 295 {
 296         int ret;
 297
 298         if (!lowpan_is_iphc(*skb_network_header(skb)))
 299                 return RX_CONTINUE;
 300
 301         ret = lowpan_iphc_decompress(skb);
 302         if (ret < 0)
 303                 return RX_DROP;
 304
 305         return RX_QUEUED;
 306 }
 307
 308 static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
 309 {
 310         lowpan_rx_result res;
 311
 312 #define CALL_RXH(rxh)                   \
 313         do {                            \
 314                 res = rxh(skb); \
 315                 if (res != RX_CONTINUE) \
 316                         goto rxh_next;  \
 317         } while (0)
 318
 319         /* likely at first */
 320         CALL_RXH(lowpan_frag_rx_h_iphc);
 321         CALL_RXH(lowpan_rx_h_ipv6);
 322
 323 rxh_next:
 324         return lowpan_frag_rx_handlers_result(skb, res);
 325 #undef CALL_RXH
 326 }
 327
 328 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK        0x07
 329 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT       8
 330
 331 static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
 332                          struct lowpan_802154_cb *cb)
 333 {
 334         bool fail;
 335         u8 high = 0, low = 0;
 336         __be16 d_tag = 0;
 337
 338         fail = lowpan_fetch_skb(skb, &high, 1);
 339         fail |= lowpan_fetch_skb(skb, &low, 1);
 340         /* remove the dispatch value and use first three bits as high value
 341          * for the datagram size
 342          */
 343         cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
 344                 LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
 345         fail |= lowpan_fetch_skb(skb, &d_tag, 2);
 346         cb->d_tag = ntohs(d_tag);
 347
 348         if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 349                 fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
 350         } else {
 351                 skb_reset_network_header(skb);
 352                 cb->d_offset = 0;
 353                 /* check if datagram_size has ipv6hdr on FRAG1 */
 354                 fail |= cb->d_size < sizeof(struct ipv6hdr);
 355                 /* check if we can dereference the dispatch value */
 356                 fail |= !skb->len;
 357         }
 358
 359         if (unlikely(fail))
 360                 return -EIO;
 361
 362         return 0;
 363 }
 364
 365 int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 366 {
 367         struct lowpan_frag_queue *fq;
 368         struct net *net = dev_net(skb->dev);
 369         struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
 370         struct ieee802154_hdr hdr = {};
 371         int err;
 372
 373         if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
 374                 goto err;
 375
 376         err = lowpan_get_cb(skb, frag_type, cb);
 377         if (err < 0)
 378                 goto err;
 379
 380         if (frag_type == LOWPAN_DISPATCH_FRAG1) {
 381                 err = lowpan_invoke_frag_rx_handlers(skb);
 382                 if (err == NET_RX_DROP)
 383                         goto err;
 384         }
 385
 386         if (cb->d_size > IPV6_MIN_MTU) {
 387                 net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
 388                 goto err;
 389         }
 390
 391         fq = fq_find(net, cb, &hdr.source, &hdr.dest);
 392         if (fq != NULL) {
 393                 int ret;
 394
 395                 spin_lock(&fq->q.lock);
 396                 ret = lowpan_frag_queue(fq, skb, frag_type);
 397                 spin_unlock(&fq->q.lock);
 398
 399                 inet_frag_put(&fq->q);
 400                 return ret;
 401         }
 402
 403 err:
 404         kfree_skb(skb);
 405         return -1;
 406 }
 407
 408 #ifdef CONFIG_SYSCTL
 409
 410 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 411         {
 412                 .procname       = "6lowpanfrag_high_thresh",
 413                 .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 414                 .maxlen         = sizeof(unsigned long),
 415                 .mode           = 0644,
 416                 .proc_handler   = proc_doulongvec_minmax,
 417                 .extra1         = &init_net.ieee802154_lowpan.frags.low_thresh
 418         },
 419         {
 420                 .procname       = "6lowpanfrag_low_thresh",
 421                 .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 422                 .maxlen         = sizeof(unsigned long),
 423                 .mode           = 0644,
 424                 .proc_handler   = proc_doulongvec_minmax,
 425                 .extra2         = &init_net.ieee802154_lowpan.frags.high_thresh
 426         },
 427         {
 428                 .procname       = "6lowpanfrag_time",
 429                 .data           = &init_net.ieee802154_lowpan.frags.timeout,
 430                 .maxlen         = sizeof(int),
 431                 .mode           = 0644,
 432                 .proc_handler   = proc_dointvec_jiffies,
 433         },
 434         { }
 435 };
 436
 437 /* secret interval has been deprecated */
 438 static int lowpan_frags_secret_interval_unused;
 439 static struct ctl_table lowpan_frags_ctl_table[] = {
 440         {
 441                 .procname       = "6lowpanfrag_secret_interval",
 442                 .data           = &lowpan_frags_secret_interval_unused,
 443                 .maxlen         = sizeof(int),
 444                 .mode           = 0644,
 445                 .proc_handler   = proc_dointvec_jiffies,
 446         },
 447         { }
 448 };
 449
 450 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 451 {
 452         struct ctl_table *table;
 453         struct ctl_table_header *hdr;
 454         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 455                 net_ieee802154_lowpan(net);
 456
 457         table = lowpan_frags_ns_ctl_table;
 458         if (!net_eq(net, &init_net)) {
 459                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 460                                 GFP_KERNEL);
 461                 if (table == NULL)
 462                         goto err_alloc;
 463
 464                 table[0].data = &ieee802154_lowpan->frags.high_thresh;
 465                 table[0].extra1 = &ieee802154_lowpan->frags.low_thresh;
 466                 table[1].data = &ieee802154_lowpan->frags.low_thresh;
 467                 table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;
 468                 table[2].data = &ieee802154_lowpan->frags.timeout;
 469
 470                 /* Don't export sysctls to unprivileged users */
 471                 if (net->user_ns != &init_user_ns)
 472                         table[0].procname = NULL;
 473         }
 474
 475         hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 476         if (hdr == NULL)
 477                 goto err_reg;
 478
 479         ieee802154_lowpan->sysctl.frags_hdr = hdr;
 480         return 0;
 481
 482 err_reg:
 483         if (!net_eq(net, &init_net))
 484                 kfree(table);
 485 err_alloc:
 486         return -ENOMEM;
 487 }
 488
 489 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 490 {
 491         struct ctl_table *table;
 492         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 493                 net_ieee802154_lowpan(net);
 494
 495         table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 496         unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 497         if (!net_eq(net, &init_net))
 498                 kfree(table);
 499 }
 500
 501 static struct ctl_table_header *lowpan_ctl_header;
 502
 503 static int __init lowpan_frags_sysctl_register(void)
 504 {
 505         lowpan_ctl_header = register_net_sysctl(&init_net,
 506                                                 "net/ieee802154/6lowpan",
 507                                                 lowpan_frags_ctl_table);
 508         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 509 }
 510
 511 static void lowpan_frags_sysctl_unregister(void)
 512 {
 513         unregister_net_sysctl_table(lowpan_ctl_header);
 514 }
 515 #else
 516 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 517 {
 518         return 0;
 519 }
 520
 521 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 522 {
 523 }
 524
 525 static inline int __init lowpan_frags_sysctl_register(void)
 526 {
 527         return 0;
 528 }
 529
 530 static inline void lowpan_frags_sysctl_unregister(void)
 531 {
 532 }
 533 #endif
 534
 535 static int __net_init lowpan_frags_init_net(struct net *net)
 536 {
 537         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 538                 net_ieee802154_lowpan(net);
 539         int res;
 540
 541         ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 542         ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 543         ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
 544         ieee802154_lowpan->frags.f = &lowpan_frags;
 545
 546         res = inet_frags_init_net(&ieee802154_lowpan->frags);
 547         if (res < 0)
 548                 return res;
 549         res = lowpan_frags_ns_sysctl_register(net);
 550         if (res < 0)
 551                 inet_frags_exit_net(&ieee802154_lowpan->frags);
 552         return res;
 553 }
 554
 555 static void __net_exit lowpan_frags_exit_net(struct net *net)
 556 {
 557         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 558                 net_ieee802154_lowpan(net);
 559
 560         lowpan_frags_ns_sysctl_unregister(net);
 561         inet_frags_exit_net(&ieee802154_lowpan->frags);
 562 }
 563
 564 static struct pernet_operations lowpan_frags_ops = {
 565         .init = lowpan_frags_init_net,
 566         .exit = lowpan_frags_exit_net,
 567 };
 568
 569 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
 570 {
 571         return jhash2(data,
 572                       sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
 573 }
 574
 575 static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
 576 {
 577         const struct inet_frag_queue *fq = data;
 578
 579         return jhash2((const u32 *)&fq->key,
 580                       sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
 581 }
 582
 583 static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
 584 {
 585         const struct frag_lowpan_compare_key *key = arg->key;
 586         const struct inet_frag_queue *fq = ptr;
 587
 588         return !!memcmp(&fq->key, key, sizeof(*key));
 589 }
 590
 591 static const struct rhashtable_params lowpan_rhash_params = {
 592         .head_offset            = offsetof(struct inet_frag_queue, node),
 593         .hashfn                 = lowpan_key_hashfn,
 594         .obj_hashfn             = lowpan_obj_hashfn,
 595         .obj_cmpfn              = lowpan_obj_cmpfn,
 596         .automatic_shrinking    = true,
 597 };
 598
 599 int __init lowpan_net_frag_init(void)
 600 {
 601         int ret;
 602
 603         lowpan_frags.constructor = lowpan_frag_init;
 604         lowpan_frags.destructor = NULL;
 605         lowpan_frags.qsize = sizeof(struct frag_queue);
 606         lowpan_frags.frag_expire = lowpan_frag_expire;
 607         lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
 608         lowpan_frags.rhash_params = lowpan_rhash_params;
 609         ret = inet_frags_init(&lowpan_frags);
 610         if (ret)
 611                 goto out;
 612
 613         ret = lowpan_frags_sysctl_register();
 614         if (ret)
 615                 goto err_sysctl;
 616
 617         ret = register_pernet_subsys(&lowpan_frags_ops);
 618         if (ret)
 619                 goto err_pernet;
 620 out:
 621         return ret;
 622 err_pernet:
 623         lowpan_frags_sysctl_unregister();
 624 err_sysctl:
 625         inet_frags_fini(&lowpan_frags);
 626         return ret;
 627 }
 628
 629 void lowpan_net_frag_exit(void)
 630 {
 631         inet_frags_fini(&lowpan_frags);
 632         lowpan_frags_sysctl_unregister();
 633         unregister_pernet_subsys(&lowpan_frags_ops);
 634 }