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