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         u32 c;
  54
  55         net_get_random_once(&lowpan_frags.rnd, sizeof(lowpan_frags.rnd));
  56         c = jhash_3words(ieee802154_addr_hash(saddr),
  57                          ieee802154_addr_hash(daddr),
  58                          (__force u32)(tag + (d_size << 16)),
  59                          lowpan_frags.rnd);
  60
  61         return c & (INETFRAGS_HASHSZ - 1);
  62 }
  63
  64 static unsigned int lowpan_hashfn(const struct inet_frag_queue *q)
  65 {
  66         const struct lowpan_frag_queue *fq;
  67
  68         fq = container_of(q, struct lowpan_frag_queue, q);
  69         return lowpan_hash_frag(fq->tag, fq->d_size, &fq->saddr, &fq->daddr);
  70 }
  71
  72 static bool lowpan_frag_match(const struct inet_frag_queue *q, const void *a)
  73 {
  74         const struct lowpan_frag_queue *fq;
  75         const struct lowpan_create_arg *arg = a;
  76
  77         fq = container_of(q, struct lowpan_frag_queue, q);
  78         return  fq->tag == arg->tag && fq->d_size == arg->d_size &&
  79                 ieee802154_addr_equal(&fq->saddr, arg->src) &&
  80                 ieee802154_addr_equal(&fq->daddr, arg->dst);
  81 }
  82
  83 static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
  84 {
  85         const struct lowpan_create_arg *arg = a;
  86         struct lowpan_frag_queue *fq;
  87
  88         fq = container_of(q, struct lowpan_frag_queue, q);
  89
  90         fq->tag = arg->tag;
  91         fq->d_size = arg->d_size;
  92         fq->saddr = *arg->src;
  93         fq->daddr = *arg->dst;
  94 }
  95
  96 static void lowpan_frag_expire(unsigned long data)
  97 {
  98         struct frag_queue *fq;
  99         struct net *net;
 100
 101         fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
 102         net = container_of(fq->q.net, struct net, ieee802154_lowpan.frags);
 103
 104         spin_lock(&fq->q.lock);
 105
 106         if (fq->q.last_in & INET_FRAG_COMPLETE)
 107                 goto out;
 108
 109         inet_frag_kill(&fq->q, &lowpan_frags);
 110 out:
 111         spin_unlock(&fq->q.lock);
 112         inet_frag_put(&fq->q, &lowpan_frags);
 113 }
 114
 115 static inline struct lowpan_frag_queue *
 116 fq_find(struct net *net, const struct lowpan_frag_info *frag_info,
 117         const struct ieee802154_addr *src,
 118         const struct ieee802154_addr *dst)
 119 {
 120         struct inet_frag_queue *q;
 121         struct lowpan_create_arg arg;
 122         unsigned int hash;
 123         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 124                 net_ieee802154_lowpan(net);
 125
 126         arg.tag = frag_info->d_tag;
 127         arg.d_size = frag_info->d_size;
 128         arg.src = src;
 129         arg.dst = dst;
 130
 131         read_lock(&lowpan_frags.lock);
 132         hash = lowpan_hash_frag(frag_info->d_tag, frag_info->d_size, src, dst);
 133
 134         q = inet_frag_find(&ieee802154_lowpan->frags,
 135                            &lowpan_frags, &arg, hash);
 136         if (IS_ERR_OR_NULL(q)) {
 137                 inet_frag_maybe_warn_overflow(q, pr_fmt());
 138                 return NULL;
 139         }
 140         return container_of(q, struct lowpan_frag_queue, q);
 141 }
 142
 143 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
 144                              struct sk_buff *skb, const u8 frag_type)
 145 {
 146         struct sk_buff *prev, *next;
 147         struct net_device *dev;
 148         int end, offset;
 149
 150         if (fq->q.last_in & INET_FRAG_COMPLETE)
 151                 goto err;
 152
 153         offset = lowpan_cb(skb)->d_offset << 3;
 154         end = lowpan_cb(skb)->d_size;
 155
 156         /* Is this the final fragment? */
 157         if (offset + skb->len == end) {
 158                 /* If we already have some bits beyond end
 159                  * or have different end, the segment is corrupted.
 160                  */
 161                 if (end < fq->q.len ||
 162                     ((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len))
 163                         goto err;
 164                 fq->q.last_in |= INET_FRAG_LAST_IN;
 165                 fq->q.len = end;
 166         } else {
 167                 if (end > fq->q.len) {
 168                         /* Some bits beyond end -> corruption. */
 169                         if (fq->q.last_in & INET_FRAG_LAST_IN)
 170                                 goto err;
 171                         fq->q.len = end;
 172                 }
 173         }
 174
 175         /* Find out which fragments are in front and at the back of us
 176          * in the chain of fragments so far.  We must know where to put
 177          * this fragment, right?
 178          */
 179         prev = fq->q.fragments_tail;
 180         if (!prev || lowpan_cb(prev)->d_offset < lowpan_cb(skb)->d_offset) {
 181                 next = NULL;
 182                 goto found;
 183         }
 184         prev = NULL;
 185         for (next = fq->q.fragments; next != NULL; next = next->next) {
 186                 if (lowpan_cb(next)->d_offset >= lowpan_cb(skb)->d_offset)
 187                         break;  /* bingo! */
 188                 prev = next;
 189         }
 190
 191 found:
 192         /* Insert this fragment in the chain of fragments. */
 193         skb->next = next;
 194         if (!next)
 195                 fq->q.fragments_tail = skb;
 196         if (prev)
 197                 prev->next = skb;
 198         else
 199                 fq->q.fragments = skb;
 200
 201         dev = skb->dev;
 202         if (dev)
 203                 skb->dev = NULL;
 204
 205         fq->q.stamp = skb->tstamp;
 206         if (frag_type == LOWPAN_DISPATCH_FRAG1) {
 207                 /* Calculate uncomp. 6lowpan header to estimate full size */
 208                 fq->q.meat += lowpan_uncompress_size(skb, NULL);
 209                 fq->q.last_in |= INET_FRAG_FIRST_IN;
 210         } else {
 211                 fq->q.meat += skb->len;
 212         }
 213         add_frag_mem_limit(&fq->q, skb->truesize);
 214
 215         if (fq->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 216             fq->q.meat == fq->q.len) {
 217                 int res;
 218                 unsigned long orefdst = skb->_skb_refdst;
 219
 220                 skb->_skb_refdst = 0UL;
 221                 res = lowpan_frag_reasm(fq, prev, dev);
 222                 skb->_skb_refdst = orefdst;
 223                 return res;
 224         }
 225
 226         inet_frag_lru_move(&fq->q);
 227         return -1;
 228 err:
 229         kfree_skb(skb);
 230         return -1;
 231 }
 232
 233 /*      Check if this packet is complete.
 234  *      Returns NULL on failure by any reason, and pointer
 235  *      to current nexthdr field in reassembled frame.
 236  *
 237  *      It is called with locked fq, and caller must check that
 238  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 239  *      the last and the first frames arrived and all the bits are here.
 240  */
 241 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *prev,
 242                              struct net_device *dev)
 243 {
 244         struct sk_buff *fp, *head = fq->q.fragments;
 245         int sum_truesize;
 246
 247         inet_frag_kill(&fq->q, &lowpan_frags);
 248
 249         /* Make the one we just received the head. */
 250         if (prev) {
 251                 head = prev->next;
 252                 fp = skb_clone(head, GFP_ATOMIC);
 253
 254                 if (!fp)
 255                         goto out_oom;
 256
 257                 fp->next = head->next;
 258                 if (!fp->next)
 259                         fq->q.fragments_tail = fp;
 260                 prev->next = fp;
 261
 262                 skb_morph(head, fq->q.fragments);
 263                 head->next = fq->q.fragments->next;
 264
 265                 consume_skb(fq->q.fragments);
 266                 fq->q.fragments = head;
 267         }
 268
 269         /* Head of list must not be cloned. */
 270         if (skb_unclone(head, GFP_ATOMIC))
 271                 goto out_oom;
 272
 273         /* If the first fragment is fragmented itself, we split
 274          * it to two chunks: the first with data and paged part
 275          * and the second, holding only fragments.
 276          */
 277         if (skb_has_frag_list(head)) {
 278                 struct sk_buff *clone;
 279                 int i, plen = 0;
 280
 281                 clone = alloc_skb(0, GFP_ATOMIC);
 282                 if (!clone)
 283                         goto out_oom;
 284                 clone->next = head->next;
 285                 head->next = clone;
 286                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 287                 skb_frag_list_init(head);
 288                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 289                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 290                 clone->len = head->data_len - plen;
 291                 clone->data_len = clone->len;
 292                 head->data_len -= clone->len;
 293                 head->len -= clone->len;
 294                 add_frag_mem_limit(&fq->q, clone->truesize);
 295         }
 296
 297         WARN_ON(head == NULL);
 298
 299         sum_truesize = head->truesize;
 300         for (fp = head->next; fp;) {
 301                 bool headstolen;
 302                 int delta;
 303                 struct sk_buff *next = fp->next;
 304
 305                 sum_truesize += fp->truesize;
 306                 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 307                         kfree_skb_partial(fp, headstolen);
 308                 } else {
 309                         if (!skb_shinfo(head)->frag_list)
 310                                 skb_shinfo(head)->frag_list = fp;
 311                         head->data_len += fp->len;
 312                         head->len += fp->len;
 313                         head->truesize += fp->truesize;
 314                 }
 315                 fp = next;
 316         }
 317         sub_frag_mem_limit(&fq->q, sum_truesize);
 318
 319         head->next = NULL;
 320         head->dev = dev;
 321         head->tstamp = fq->q.stamp;
 322
 323         fq->q.fragments = NULL;
 324         fq->q.fragments_tail = NULL;
 325
 326         return 1;
 327 out_oom:
 328         net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
 329         return -1;
 330 }
 331
 332 static int lowpan_get_frag_info(struct sk_buff *skb, const u8 frag_type,
 333                                 struct lowpan_frag_info *frag_info)
 334 {
 335         bool fail;
 336         u8 pattern = 0, low = 0;
 337
 338         fail = lowpan_fetch_skb(skb, &pattern, 1);
 339         fail |= lowpan_fetch_skb(skb, &low, 1);
 340         frag_info->d_size = (pattern & 7) << 8 | low;
 341         fail |= lowpan_fetch_skb(skb, &frag_info->d_tag, 2);
 342
 343         if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 344                 fail |= lowpan_fetch_skb(skb, &frag_info->d_offset, 1);
 345         } else {
 346                 skb_reset_network_header(skb);
 347                 frag_info->d_offset = 0;
 348         }
 349
 350         if (unlikely(fail))
 351                 return -EIO;
 352
 353         return 0;
 354 }
 355
 356 int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type)
 357 {
 358         struct lowpan_frag_queue *fq;
 359         struct net *net = dev_net(skb->dev);
 360         struct lowpan_frag_info *frag_info = lowpan_cb(skb);
 361         struct ieee802154_addr source, dest;
 362         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 363                 net_ieee802154_lowpan(net);
 364         int err;
 365
 366         source = mac_cb(skb)->source;
 367         dest = mac_cb(skb)->dest;
 368
 369         err = lowpan_get_frag_info(skb, frag_type, frag_info);
 370         if (err < 0)
 371                 goto err;
 372
 373         if (frag_info->d_size > ieee802154_lowpan->max_dsize)
 374                 goto err;
 375
 376         inet_frag_evictor(&ieee802154_lowpan->frags, &lowpan_frags, false);
 377
 378         fq = fq_find(net, frag_info, &source, &dest);
 379         if (fq != NULL) {
 380                 int ret;
 381
 382                 spin_lock(&fq->q.lock);
 383                 ret = lowpan_frag_queue(fq, skb, frag_type);
 384                 spin_unlock(&fq->q.lock);
 385
 386                 inet_frag_put(&fq->q, &lowpan_frags);
 387                 return ret;
 388         }
 389
 390 err:
 391         kfree_skb(skb);
 392         return -1;
 393 }
 394 EXPORT_SYMBOL(lowpan_frag_rcv);
 395
 396 #ifdef CONFIG_SYSCTL
 397 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 398         {
 399                 .procname       = "6lowpanfrag_high_thresh",
 400                 .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 401                 .maxlen         = sizeof(int),
 402                 .mode           = 0644,
 403                 .proc_handler   = proc_dointvec
 404         },
 405         {
 406                 .procname       = "6lowpanfrag_low_thresh",
 407                 .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 408                 .maxlen         = sizeof(int),
 409                 .mode           = 0644,
 410                 .proc_handler   = proc_dointvec
 411         },
 412         {
 413                 .procname       = "6lowpanfrag_time",
 414                 .data           = &init_net.ieee802154_lowpan.frags.timeout,
 415                 .maxlen         = sizeof(int),
 416                 .mode           = 0644,
 417                 .proc_handler   = proc_dointvec_jiffies,
 418         },
 419         {
 420                 .procname       = "6lowpanfrag_max_datagram_size",
 421                 .data           = &init_net.ieee802154_lowpan.max_dsize,
 422                 .maxlen         = sizeof(int),
 423                 .mode           = 0644,
 424                 .proc_handler   = proc_dointvec
 425         },
 426         { }
 427 };
 428
 429 static struct ctl_table lowpan_frags_ctl_table[] = {
 430         {
 431                 .procname       = "6lowpanfrag_secret_interval",
 432                 .data           = &lowpan_frags.secret_interval,
 433                 .maxlen         = sizeof(int),
 434                 .mode           = 0644,
 435                 .proc_handler   = proc_dointvec_jiffies,
 436         },
 437         { }
 438 };
 439
 440 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 441 {
 442         struct ctl_table *table;
 443         struct ctl_table_header *hdr;
 444         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 445                 net_ieee802154_lowpan(net);
 446
 447         table = lowpan_frags_ns_ctl_table;
 448         if (!net_eq(net, &init_net)) {
 449                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 450                                 GFP_KERNEL);
 451                 if (table == NULL)
 452                         goto err_alloc;
 453
 454                 table[0].data = &ieee802154_lowpan->frags.high_thresh;
 455                 table[1].data = &ieee802154_lowpan->frags.low_thresh;
 456                 table[2].data = &ieee802154_lowpan->frags.timeout;
 457                 table[3].data = &ieee802154_lowpan->max_dsize;
 458
 459                 /* Don't export sysctls to unprivileged users */
 460                 if (net->user_ns != &init_user_ns)
 461                         table[0].procname = NULL;
 462         }
 463
 464         hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 465         if (hdr == NULL)
 466                 goto err_reg;
 467
 468         ieee802154_lowpan->sysctl.frags_hdr = hdr;
 469         return 0;
 470
 471 err_reg:
 472         if (!net_eq(net, &init_net))
 473                 kfree(table);
 474 err_alloc:
 475         return -ENOMEM;
 476 }
 477
 478 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 479 {
 480         struct ctl_table *table;
 481         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 482                 net_ieee802154_lowpan(net);
 483
 484         table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 485         unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 486         if (!net_eq(net, &init_net))
 487                 kfree(table);
 488 }
 489
 490 static struct ctl_table_header *lowpan_ctl_header;
 491
 492 static int lowpan_frags_sysctl_register(void)
 493 {
 494         lowpan_ctl_header = register_net_sysctl(&init_net,
 495                                                 "net/ieee802154/6lowpan",
 496                                                 lowpan_frags_ctl_table);
 497         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 498 }
 499
 500 static void lowpan_frags_sysctl_unregister(void)
 501 {
 502         unregister_net_sysctl_table(lowpan_ctl_header);
 503 }
 504 #else
 505 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 506 {
 507         return 0;
 508 }
 509
 510 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 511 {
 512 }
 513
 514 static inline int lowpan_frags_sysctl_register(void)
 515 {
 516         return 0;
 517 }
 518
 519 static inline void lowpan_frags_sysctl_unregister(void)
 520 {
 521 }
 522 #endif
 523
 524 static int __net_init lowpan_frags_init_net(struct net *net)
 525 {
 526         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 527                 net_ieee802154_lowpan(net);
 528
 529         ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 530         ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 531         ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
 532         ieee802154_lowpan->max_dsize = 0xFFFF;
 533
 534         inet_frags_init_net(&ieee802154_lowpan->frags);
 535
 536         return lowpan_frags_ns_sysctl_register(net);
 537 }
 538
 539 static void __net_exit lowpan_frags_exit_net(struct net *net)
 540 {
 541         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 542                 net_ieee802154_lowpan(net);
 543
 544         lowpan_frags_ns_sysctl_unregister(net);
 545         inet_frags_exit_net(&ieee802154_lowpan->frags, &lowpan_frags);
 546 }
 547
 548 static struct pernet_operations lowpan_frags_ops = {
 549         .init = lowpan_frags_init_net,
 550         .exit = lowpan_frags_exit_net,
 551 };
 552
 553 int __init lowpan_net_frag_init(void)
 554 {
 555         int ret;
 556
 557         ret = lowpan_frags_sysctl_register();
 558         if (ret)
 559                 return ret;
 560
 561         ret = register_pernet_subsys(&lowpan_frags_ops);
 562         if (ret)
 563                 goto err_pernet;
 564
 565         lowpan_frags.hashfn = lowpan_hashfn;
 566         lowpan_frags.constructor = lowpan_frag_init;
 567         lowpan_frags.destructor = NULL;
 568         lowpan_frags.skb_free = NULL;
 569         lowpan_frags.qsize = sizeof(struct frag_queue);
 570         lowpan_frags.match = lowpan_frag_match;
 571         lowpan_frags.frag_expire = lowpan_frag_expire;
 572         lowpan_frags.secret_interval = 10 * 60 * HZ;
 573         inet_frags_init(&lowpan_frags);
 574
 575         return ret;
 576 err_pernet:
 577         lowpan_frags_sysctl_unregister();
 578         return ret;
 579 }
 580
 581 void lowpan_net_frag_exit(void)
 582 {
 583         inet_frags_fini(&lowpan_frags);
 584         lowpan_frags_sysctl_unregister();
 585         unregister_pernet_subsys(&lowpan_frags_ops);
 586 }