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         u16 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(u16 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         __be16 d_tag = 0;
 334
 335         fail = lowpan_fetch_skb(skb, &pattern, 1);
 336         fail |= lowpan_fetch_skb(skb, &low, 1);
 337         frag_info->d_size = (pattern & 7) << 8 | low;
 338         fail |= lowpan_fetch_skb(skb, &d_tag, 2);
 339         frag_info->d_tag = ntohs(d_tag);
 340
 341         if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 342                 fail |= lowpan_fetch_skb(skb, &frag_info->d_offset, 1);
 343         } else {
 344                 skb_reset_network_header(skb);
 345                 frag_info->d_offset = 0;
 346         }
 347
 348         if (unlikely(fail))
 349                 return -EIO;
 350
 351         return 0;
 352 }
 353
 354 int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type)
 355 {
 356         struct lowpan_frag_queue *fq;
 357         struct net *net = dev_net(skb->dev);
 358         struct lowpan_frag_info *frag_info = lowpan_cb(skb);
 359         struct ieee802154_addr source, dest;
 360         int err;
 361
 362         source = mac_cb(skb)->source;
 363         dest = mac_cb(skb)->dest;
 364
 365         err = lowpan_get_frag_info(skb, frag_type, frag_info);
 366         if (err < 0)
 367                 goto err;
 368
 369         if (frag_info->d_size > IPV6_MIN_MTU) {
 370                 net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
 371                 goto err;
 372         }
 373
 374         fq = fq_find(net, frag_info, &source, &dest);
 375         if (fq != NULL) {
 376                 int ret;
 377
 378                 spin_lock(&fq->q.lock);
 379                 ret = lowpan_frag_queue(fq, skb, frag_type);
 380                 spin_unlock(&fq->q.lock);
 381
 382                 inet_frag_put(&fq->q, &lowpan_frags);
 383                 return ret;
 384         }
 385
 386 err:
 387         kfree_skb(skb);
 388         return -1;
 389 }
 390 EXPORT_SYMBOL(lowpan_frag_rcv);
 391
 392 #ifdef CONFIG_SYSCTL
 393 static int zero;
 394
 395 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 396         {
 397                 .procname       = "6lowpanfrag_high_thresh",
 398                 .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 399                 .maxlen         = sizeof(int),
 400                 .mode           = 0644,
 401                 .proc_handler   = proc_dointvec_minmax,
 402                 .extra1         = &init_net.ieee802154_lowpan.frags.low_thresh
 403         },
 404         {
 405                 .procname       = "6lowpanfrag_low_thresh",
 406                 .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 407                 .maxlen         = sizeof(int),
 408                 .mode           = 0644,
 409                 .proc_handler   = proc_dointvec_minmax,
 410                 .extra1         = &zero,
 411                 .extra2         = &init_net.ieee802154_lowpan.frags.high_thresh
 412         },
 413         {
 414                 .procname       = "6lowpanfrag_time",
 415                 .data           = &init_net.ieee802154_lowpan.frags.timeout,
 416                 .maxlen         = sizeof(int),
 417                 .mode           = 0644,
 418                 .proc_handler   = proc_dointvec_jiffies,
 419         },
 420         { }
 421 };
 422
 423 /* secret interval has been deprecated */
 424 static int lowpan_frags_secret_interval_unused;
 425 static struct ctl_table lowpan_frags_ctl_table[] = {
 426         {
 427                 .procname       = "6lowpanfrag_secret_interval",
 428                 .data           = &lowpan_frags_secret_interval_unused,
 429                 .maxlen         = sizeof(int),
 430                 .mode           = 0644,
 431                 .proc_handler   = proc_dointvec_jiffies,
 432         },
 433         { }
 434 };
 435
 436 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 437 {
 438         struct ctl_table *table;
 439         struct ctl_table_header *hdr;
 440         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 441                 net_ieee802154_lowpan(net);
 442
 443         table = lowpan_frags_ns_ctl_table;
 444         if (!net_eq(net, &init_net)) {
 445                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 446                                 GFP_KERNEL);
 447                 if (table == NULL)
 448                         goto err_alloc;
 449
 450                 table[0].data = &ieee802154_lowpan->frags.high_thresh;
 451                 table[0].extra1 = &ieee802154_lowpan->frags.low_thresh;
 452                 table[0].extra2 = &init_net.ieee802154_lowpan.frags.high_thresh;
 453                 table[1].data = &ieee802154_lowpan->frags.low_thresh;
 454                 table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;
 455                 table[2].data = &ieee802154_lowpan->frags.timeout;
 456
 457                 /* Don't export sysctls to unprivileged users */
 458                 if (net->user_ns != &init_user_ns)
 459                         table[0].procname = NULL;
 460         }
 461
 462         hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 463         if (hdr == NULL)
 464                 goto err_reg;
 465
 466         ieee802154_lowpan->sysctl.frags_hdr = hdr;
 467         return 0;
 468
 469 err_reg:
 470         if (!net_eq(net, &init_net))
 471                 kfree(table);
 472 err_alloc:
 473         return -ENOMEM;
 474 }
 475
 476 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 477 {
 478         struct ctl_table *table;
 479         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 480                 net_ieee802154_lowpan(net);
 481
 482         table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 483         unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 484         if (!net_eq(net, &init_net))
 485                 kfree(table);
 486 }
 487
 488 static struct ctl_table_header *lowpan_ctl_header;
 489
 490 static int __init lowpan_frags_sysctl_register(void)
 491 {
 492         lowpan_ctl_header = register_net_sysctl(&init_net,
 493                                                 "net/ieee802154/6lowpan",
 494                                                 lowpan_frags_ctl_table);
 495         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 496 }
 497
 498 static void lowpan_frags_sysctl_unregister(void)
 499 {
 500         unregister_net_sysctl_table(lowpan_ctl_header);
 501 }
 502 #else
 503 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 504 {
 505         return 0;
 506 }
 507
 508 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 509 {
 510 }
 511
 512 static inline int __init lowpan_frags_sysctl_register(void)
 513 {
 514         return 0;
 515 }
 516
 517 static inline void lowpan_frags_sysctl_unregister(void)
 518 {
 519 }
 520 #endif
 521
 522 static int __net_init lowpan_frags_init_net(struct net *net)
 523 {
 524         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 525                 net_ieee802154_lowpan(net);
 526
 527         ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 528         ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 529         ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
 530
 531         inet_frags_init_net(&ieee802154_lowpan->frags);
 532
 533         return lowpan_frags_ns_sysctl_register(net);
 534 }
 535
 536 static void __net_exit lowpan_frags_exit_net(struct net *net)
 537 {
 538         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 539                 net_ieee802154_lowpan(net);
 540
 541         lowpan_frags_ns_sysctl_unregister(net);
 542         inet_frags_exit_net(&ieee802154_lowpan->frags, &lowpan_frags);
 543 }
 544
 545 static struct pernet_operations lowpan_frags_ops = {
 546         .init = lowpan_frags_init_net,
 547         .exit = lowpan_frags_exit_net,
 548 };
 549
 550 int __init lowpan_net_frag_init(void)
 551 {
 552         int ret;
 553
 554         ret = lowpan_frags_sysctl_register();
 555         if (ret)
 556                 return ret;
 557
 558         ret = register_pernet_subsys(&lowpan_frags_ops);
 559         if (ret)
 560                 goto err_pernet;
 561
 562         lowpan_frags.hashfn = lowpan_hashfn;
 563         lowpan_frags.constructor = lowpan_frag_init;
 564         lowpan_frags.destructor = NULL;
 565         lowpan_frags.skb_free = NULL;
 566         lowpan_frags.qsize = sizeof(struct frag_queue);
 567         lowpan_frags.match = lowpan_frag_match;
 568         lowpan_frags.frag_expire = lowpan_frag_expire;
 569         lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
 570         ret = inet_frags_init(&lowpan_frags);
 571         if (ret)
 572                 goto err_pernet;
 573
 574         return ret;
 575 err_pernet:
 576         lowpan_frags_sysctl_unregister();
 577         return ret;
 578 }
 579
 580 void lowpan_net_frag_exit(void)
 581 {
 582         inet_frags_fini(&lowpan_frags);
 583         lowpan_frags_sysctl_unregister();
 584         unregister_pernet_subsys(&lowpan_frags_ops);
 585 }