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 struct lowpan_frag_info {
  34         __be16 d_tag;
  35         u16 d_size;
  36         u8 d_offset;
  37 };
  38
  39 static struct lowpan_frag_info *lowpan_cb(struct sk_buff *skb)
  40 {
  41         return (struct lowpan_frag_info *)skb->cb;
  42 }
  43
  44 static struct inet_frags lowpan_frags;
  45
  46 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq,
  47                              struct sk_buff *prev, struct net_device *dev);
  48
  49 static unsigned int lowpan_hash_frag(__be16 tag, u16 d_size,
  50                                      const struct ieee802154_addr *saddr,
  51                                      const struct ieee802154_addr *daddr)
  52 {
  53         net_get_random_once(&lowpan_frags.rnd, sizeof(lowpan_frags.rnd));
  54         return jhash_3words(ieee802154_addr_hash(saddr),
  55                             ieee802154_addr_hash(daddr),
  56                             (__force u32)(tag + (d_size << 16)),
  57                             lowpan_frags.rnd);
  58 }
  59
  60 static unsigned int lowpan_hashfn(const struct inet_frag_queue *q)
  61 {
  62         const struct lowpan_frag_queue *fq;
  63
  64         fq = container_of(q, struct lowpan_frag_queue, q);
  65         return lowpan_hash_frag(fq->tag, fq->d_size, &fq->saddr, &fq->daddr);
  66 }
  67
  68 static bool lowpan_frag_match(const struct inet_frag_queue *q, const void *a)
  69 {
  70         const struct lowpan_frag_queue *fq;
  71         const struct lowpan_create_arg *arg = a;
  72
  73         fq = container_of(q, struct lowpan_frag_queue, q);
  74         return  fq->tag == arg->tag && fq->d_size == arg->d_size &&
  75                 ieee802154_addr_equal(&fq->saddr, arg->src) &&
  76                 ieee802154_addr_equal(&fq->daddr, arg->dst);
  77 }
  78
  79 static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
  80 {
  81         const struct lowpan_create_arg *arg = a;
  82         struct lowpan_frag_queue *fq;
  83
  84         fq = container_of(q, struct lowpan_frag_queue, q);
  85
  86         fq->tag = arg->tag;
  87         fq->d_size = arg->d_size;
  88         fq->saddr = *arg->src;
  89         fq->daddr = *arg->dst;
  90 }
  91
  92 static void lowpan_frag_expire(unsigned long data)
  93 {
  94         struct frag_queue *fq;
  95         struct net *net;
  96
  97         fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
  98         net = container_of(fq->q.net, struct net, ieee802154_lowpan.frags);
  99
 100         spin_lock(&fq->q.lock);
 101
 102         if (fq->q.last_in & INET_FRAG_COMPLETE)
 103                 goto out;
 104
 105         inet_frag_kill(&fq->q, &lowpan_frags);
 106 out:
 107         spin_unlock(&fq->q.lock);
 108         inet_frag_put(&fq->q, &lowpan_frags);
 109 }
 110
 111 static inline struct lowpan_frag_queue *
 112 fq_find(struct net *net, const struct lowpan_frag_info *frag_info,
 113         const struct ieee802154_addr *src,
 114         const struct ieee802154_addr *dst)
 115 {
 116         struct inet_frag_queue *q;
 117         struct lowpan_create_arg arg;
 118         unsigned int hash;
 119         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 120                 net_ieee802154_lowpan(net);
 121
 122         arg.tag = frag_info->d_tag;
 123         arg.d_size = frag_info->d_size;
 124         arg.src = src;
 125         arg.dst = dst;
 126
 127         read_lock(&lowpan_frags.lock);
 128         hash = lowpan_hash_frag(frag_info->d_tag, frag_info->d_size, src, dst);
 129
 130         q = inet_frag_find(&ieee802154_lowpan->frags,
 131                            &lowpan_frags, &arg, hash);
 132         if (IS_ERR_OR_NULL(q)) {
 133                 inet_frag_maybe_warn_overflow(q, pr_fmt());
 134                 return NULL;
 135         }
 136         return container_of(q, struct lowpan_frag_queue, q);
 137 }
 138
 139 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
 140                              struct sk_buff *skb, const u8 frag_type)
 141 {
 142         struct sk_buff *prev, *next;
 143         struct net_device *dev;
 144         int end, offset;
 145
 146         if (fq->q.last_in & INET_FRAG_COMPLETE)
 147                 goto err;
 148
 149         offset = lowpan_cb(skb)->d_offset << 3;
 150         end = lowpan_cb(skb)->d_size;
 151
 152         /* Is this the final fragment? */
 153         if (offset + skb->len == end) {
 154                 /* If we already have some bits beyond end
 155                  * or have different end, the segment is corrupted.
 156                  */
 157                 if (end < fq->q.len ||
 158                     ((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len))
 159                         goto err;
 160                 fq->q.last_in |= INET_FRAG_LAST_IN;
 161                 fq->q.len = end;
 162         } else {
 163                 if (end > fq->q.len) {
 164                         /* Some bits beyond end -> corruption. */
 165                         if (fq->q.last_in & INET_FRAG_LAST_IN)
 166                                 goto err;
 167                         fq->q.len = end;
 168                 }
 169         }
 170
 171         /* Find out which fragments are in front and at the back of us
 172          * in the chain of fragments so far.  We must know where to put
 173          * this fragment, right?
 174          */
 175         prev = fq->q.fragments_tail;
 176         if (!prev || lowpan_cb(prev)->d_offset < lowpan_cb(skb)->d_offset) {
 177                 next = NULL;
 178                 goto found;
 179         }
 180         prev = NULL;
 181         for (next = fq->q.fragments; next != NULL; next = next->next) {
 182                 if (lowpan_cb(next)->d_offset >= lowpan_cb(skb)->d_offset)
 183                         break;  /* bingo! */
 184                 prev = next;
 185         }
 186
 187 found:
 188         /* Insert this fragment in the chain of fragments. */
 189         skb->next = next;
 190         if (!next)
 191                 fq->q.fragments_tail = skb;
 192         if (prev)
 193                 prev->next = skb;
 194         else
 195                 fq->q.fragments = skb;
 196
 197         dev = skb->dev;
 198         if (dev)
 199                 skb->dev = NULL;
 200
 201         fq->q.stamp = skb->tstamp;
 202         if (frag_type == LOWPAN_DISPATCH_FRAG1) {
 203                 /* Calculate uncomp. 6lowpan header to estimate full size */
 204                 fq->q.meat += lowpan_uncompress_size(skb, NULL);
 205                 fq->q.last_in |= INET_FRAG_FIRST_IN;
 206         } else {
 207                 fq->q.meat += skb->len;
 208         }
 209         add_frag_mem_limit(&fq->q, skb->truesize);
 210
 211         if (fq->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 212             fq->q.meat == fq->q.len) {
 213                 int res;
 214                 unsigned long orefdst = skb->_skb_refdst;
 215
 216                 skb->_skb_refdst = 0UL;
 217                 res = lowpan_frag_reasm(fq, prev, dev);
 218                 skb->_skb_refdst = orefdst;
 219                 return res;
 220         }
 221
 222         return -1;
 223 err:
 224         kfree_skb(skb);
 225         return -1;
 226 }
 227
 228 /*      Check if this packet is complete.
 229  *      Returns NULL on failure by any reason, and pointer
 230  *      to current nexthdr field in reassembled frame.
 231  *
 232  *      It is called with locked fq, and caller must check that
 233  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 234  *      the last and the first frames arrived and all the bits are here.
 235  */
 236 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *prev,
 237                              struct net_device *dev)
 238 {
 239         struct sk_buff *fp, *head = fq->q.fragments;
 240         int sum_truesize;
 241
 242         inet_frag_kill(&fq->q, &lowpan_frags);
 243
 244         /* Make the one we just received the head. */
 245         if (prev) {
 246                 head = prev->next;
 247                 fp = skb_clone(head, GFP_ATOMIC);
 248
 249                 if (!fp)
 250                         goto out_oom;
 251
 252                 fp->next = head->next;
 253                 if (!fp->next)
 254                         fq->q.fragments_tail = fp;
 255                 prev->next = fp;
 256
 257                 skb_morph(head, fq->q.fragments);
 258                 head->next = fq->q.fragments->next;
 259
 260                 consume_skb(fq->q.fragments);
 261                 fq->q.fragments = head;
 262         }
 263
 264         /* Head of list must not be cloned. */
 265         if (skb_unclone(head, GFP_ATOMIC))
 266                 goto out_oom;
 267
 268         /* If the first fragment is fragmented itself, we split
 269          * it to two chunks: the first with data and paged part
 270          * and the second, holding only fragments.
 271          */
 272         if (skb_has_frag_list(head)) {
 273                 struct sk_buff *clone;
 274                 int i, plen = 0;
 275
 276                 clone = alloc_skb(0, GFP_ATOMIC);
 277                 if (!clone)
 278                         goto out_oom;
 279                 clone->next = head->next;
 280                 head->next = clone;
 281                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 282                 skb_frag_list_init(head);
 283                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 284                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 285                 clone->len = head->data_len - plen;
 286                 clone->data_len = clone->len;
 287                 head->data_len -= clone->len;
 288                 head->len -= clone->len;
 289                 add_frag_mem_limit(&fq->q, clone->truesize);
 290         }
 291
 292         WARN_ON(head == NULL);
 293
 294         sum_truesize = head->truesize;
 295         for (fp = head->next; fp;) {
 296                 bool headstolen;
 297                 int delta;
 298                 struct sk_buff *next = fp->next;
 299
 300                 sum_truesize += fp->truesize;
 301                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 302                         kfree_skb_partial(fp, headstolen);
 303                 } else {
 304                         if (!skb_shinfo(head)->frag_list)
 305                                 skb_shinfo(head)->frag_list = fp;
 306                         head->data_len += fp->len;
 307                         head->len += fp->len;
 308                         head->truesize += fp->truesize;
 309                 }
 310                 fp = next;
 311         }
 312         sub_frag_mem_limit(&fq->q, sum_truesize);
 313
 314         head->next = NULL;
 315         head->dev = dev;
 316         head->tstamp = fq->q.stamp;
 317
 318         fq->q.fragments = NULL;
 319         fq->q.fragments_tail = NULL;
 320
 321         return 1;
 322 out_oom:
 323         net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
 324         return -1;
 325 }
 326
 327 static int lowpan_get_frag_info(struct sk_buff *skb, const u8 frag_type,
 328                                 struct lowpan_frag_info *frag_info)
 329 {
 330         bool fail;
 331         u8 pattern = 0, low = 0;
 332
 333         fail = lowpan_fetch_skb(skb, &pattern, 1);
 334         fail |= lowpan_fetch_skb(skb, &low, 1);
 335         frag_info->d_size = (pattern & 7) << 8 | low;
 336         fail |= lowpan_fetch_skb(skb, &frag_info->d_tag, 2);
 337
 338         if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 339                 fail |= lowpan_fetch_skb(skb, &frag_info->d_offset, 1);
 340         } else {
 341                 skb_reset_network_header(skb);
 342                 frag_info->d_offset = 0;
 343         }
 344
 345         if (unlikely(fail))
 346                 return -EIO;
 347
 348         return 0;
 349 }
 350
 351 int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type)
 352 {
 353         struct lowpan_frag_queue *fq;
 354         struct net *net = dev_net(skb->dev);
 355         struct lowpan_frag_info *frag_info = lowpan_cb(skb);
 356         struct ieee802154_addr source, dest;
 357         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 358                 net_ieee802154_lowpan(net);
 359         int err;
 360
 361         source = mac_cb(skb)->source;
 362         dest = mac_cb(skb)->dest;
 363
 364         err = lowpan_get_frag_info(skb, frag_type, frag_info);
 365         if (err < 0)
 366                 goto err;
 367
 368         if (frag_info->d_size > ieee802154_lowpan->max_dsize)
 369                 goto err;
 370
 371         fq = fq_find(net, frag_info, &source, &dest);
 372         if (fq != NULL) {
 373                 int ret;
 374
 375                 spin_lock(&fq->q.lock);
 376                 ret = lowpan_frag_queue(fq, skb, frag_type);
 377                 spin_unlock(&fq->q.lock);
 378
 379                 inet_frag_put(&fq->q, &lowpan_frags);
 380                 return ret;
 381         }
 382
 383 err:
 384         kfree_skb(skb);
 385         return -1;
 386 }
 387 EXPORT_SYMBOL(lowpan_frag_rcv);
 388
 389 #ifdef CONFIG_SYSCTL
 390 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 391         {
 392                 .procname       = "6lowpanfrag_high_thresh",
 393                 .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 394                 .maxlen         = sizeof(int),
 395                 .mode           = 0644,
 396                 .proc_handler   = proc_dointvec
 397         },
 398         {
 399                 .procname       = "6lowpanfrag_low_thresh",
 400                 .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 401                 .maxlen         = sizeof(int),
 402                 .mode           = 0644,
 403                 .proc_handler   = proc_dointvec
 404         },
 405         {
 406                 .procname       = "6lowpanfrag_time",
 407                 .data           = &init_net.ieee802154_lowpan.frags.timeout,
 408                 .maxlen         = sizeof(int),
 409                 .mode           = 0644,
 410                 .proc_handler   = proc_dointvec_jiffies,
 411         },
 412         {
 413                 .procname       = "6lowpanfrag_max_datagram_size",
 414                 .data           = &init_net.ieee802154_lowpan.max_dsize,
 415                 .maxlen         = sizeof(int),
 416                 .mode           = 0644,
 417                 .proc_handler   = proc_dointvec
 418         },
 419         { }
 420 };
 421
 422 static struct ctl_table lowpan_frags_ctl_table[] = {
 423         {
 424                 .procname       = "6lowpanfrag_secret_interval",
 425                 .data           = &lowpan_frags.secret_interval,
 426                 .maxlen         = sizeof(int),
 427                 .mode           = 0644,
 428                 .proc_handler   = proc_dointvec_jiffies,
 429         },
 430         { }
 431 };
 432
 433 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 434 {
 435         struct ctl_table *table;
 436         struct ctl_table_header *hdr;
 437         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 438                 net_ieee802154_lowpan(net);
 439
 440         table = lowpan_frags_ns_ctl_table;
 441         if (!net_eq(net, &init_net)) {
 442                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 443                                 GFP_KERNEL);
 444                 if (table == NULL)
 445                         goto err_alloc;
 446
 447                 table[0].data = &ieee802154_lowpan->frags.high_thresh;
 448                 table[1].data = &ieee802154_lowpan->frags.low_thresh;
 449                 table[2].data = &ieee802154_lowpan->frags.timeout;
 450                 table[3].data = &ieee802154_lowpan->max_dsize;
 451
 452                 /* Don't export sysctls to unprivileged users */
 453                 if (net->user_ns != &init_user_ns)
 454                         table[0].procname = NULL;
 455         }
 456
 457         hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 458         if (hdr == NULL)
 459                 goto err_reg;
 460
 461         ieee802154_lowpan->sysctl.frags_hdr = hdr;
 462         return 0;
 463
 464 err_reg:
 465         if (!net_eq(net, &init_net))
 466                 kfree(table);
 467 err_alloc:
 468         return -ENOMEM;
 469 }
 470
 471 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 472 {
 473         struct ctl_table *table;
 474         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 475                 net_ieee802154_lowpan(net);
 476
 477         table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 478         unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 479         if (!net_eq(net, &init_net))
 480                 kfree(table);
 481 }
 482
 483 static struct ctl_table_header *lowpan_ctl_header;
 484
 485 static int lowpan_frags_sysctl_register(void)
 486 {
 487         lowpan_ctl_header = register_net_sysctl(&init_net,
 488                                                 "net/ieee802154/6lowpan",
 489                                                 lowpan_frags_ctl_table);
 490         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 491 }
 492
 493 static void lowpan_frags_sysctl_unregister(void)
 494 {
 495         unregister_net_sysctl_table(lowpan_ctl_header);
 496 }
 497 #else
 498 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 499 {
 500         return 0;
 501 }
 502
 503 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 504 {
 505 }
 506
 507 static inline int lowpan_frags_sysctl_register(void)
 508 {
 509         return 0;
 510 }
 511
 512 static inline void lowpan_frags_sysctl_unregister(void)
 513 {
 514 }
 515 #endif
 516
 517 static int __net_init lowpan_frags_init_net(struct net *net)
 518 {
 519         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 520                 net_ieee802154_lowpan(net);
 521
 522         ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 523         ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 524         ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
 525         ieee802154_lowpan->max_dsize = 0xFFFF;
 526
 527         inet_frags_init_net(&ieee802154_lowpan->frags);
 528
 529         return lowpan_frags_ns_sysctl_register(net);
 530 }
 531
 532 static void __net_exit lowpan_frags_exit_net(struct net *net)
 533 {
 534         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 535                 net_ieee802154_lowpan(net);
 536
 537         lowpan_frags_ns_sysctl_unregister(net);
 538         inet_frags_exit_net(&ieee802154_lowpan->frags, &lowpan_frags);
 539 }
 540
 541 static struct pernet_operations lowpan_frags_ops = {
 542         .init = lowpan_frags_init_net,
 543         .exit = lowpan_frags_exit_net,
 544 };
 545
 546 int __init lowpan_net_frag_init(void)
 547 {
 548         int ret;
 549
 550         ret = lowpan_frags_sysctl_register();
 551         if (ret)
 552                 return ret;
 553
 554         ret = register_pernet_subsys(&lowpan_frags_ops);
 555         if (ret)
 556                 goto err_pernet;
 557
 558         lowpan_frags.hashfn = lowpan_hashfn;
 559         lowpan_frags.constructor = lowpan_frag_init;
 560         lowpan_frags.destructor = NULL;
 561         lowpan_frags.skb_free = NULL;
 562         lowpan_frags.qsize = sizeof(struct frag_queue);
 563         lowpan_frags.match = lowpan_frag_match;
 564         lowpan_frags.frag_expire = lowpan_frag_expire;
 565         lowpan_frags.secret_interval = 10 * 60 * HZ;
 566         inet_frags_init(&lowpan_frags);
 567
 568         return ret;
 569 err_pernet:
 570         lowpan_frags_sysctl_unregister();
 571         return ret;
 572 }
 573
 574 void lowpan_net_frag_exit(void)
 575 {
 576         inet_frags_fini(&lowpan_frags);
 577         lowpan_frags_sysctl_unregister();
 578         unregister_pernet_subsys(&lowpan_frags_ops);
 579 }