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 struct inet_frags lowpan_frags;
  34
  35 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq,
  36                              struct sk_buff *prev, struct net_device *dev);
  37
  38 static unsigned int lowpan_hash_frag(__be16 tag, u16 d_size,
  39                                      const struct ieee802154_addr *saddr,
  40                                      const struct ieee802154_addr *daddr)
  41 {
  42         u32 c;
  43
  44         net_get_random_once(&lowpan_frags.rnd, sizeof(lowpan_frags.rnd));
  45         c = jhash_3words(ieee802154_addr_hash(saddr),
  46                          ieee802154_addr_hash(daddr),
  47                          (__force u32)(tag + (d_size << 16)),
  48                          lowpan_frags.rnd);
  49
  50         return c & (INETFRAGS_HASHSZ - 1);
  51 }
  52
  53 static unsigned int lowpan_hashfn(struct inet_frag_queue *q)
  54 {
  55         struct lowpan_frag_queue *fq;
  56
  57         fq = container_of(q, struct lowpan_frag_queue, q);
  58         return lowpan_hash_frag(fq->tag, fq->d_size, &fq->saddr, &fq->daddr);
  59 }
  60
  61 bool lowpan_frag_match(struct inet_frag_queue *q, void *a)
  62 {
  63         struct lowpan_frag_queue *fq;
  64         struct lowpan_create_arg *arg = a;
  65
  66         fq = container_of(q, struct lowpan_frag_queue, q);
  67         return  fq->tag == arg->tag && fq->d_size == arg->d_size &&
  68                 ieee802154_addr_addr_equal(&fq->saddr, arg->src) &&
  69                 ieee802154_addr_addr_equal(&fq->daddr, arg->dst);
  70 }
  71 EXPORT_SYMBOL(lowpan_frag_match);
  72
  73 void lowpan_frag_init(struct inet_frag_queue *q, void *a)
  74 {
  75         struct lowpan_frag_queue *fq;
  76         struct lowpan_create_arg *arg = a;
  77
  78         fq = container_of(q, struct lowpan_frag_queue, q);
  79
  80         fq->tag = arg->tag;
  81         fq->d_size = arg->d_size;
  82         fq->saddr = *arg->src;
  83         fq->daddr = *arg->dst;
  84 }
  85 EXPORT_SYMBOL(lowpan_frag_init);
  86
  87 void lowpan_expire_frag_queue(struct frag_queue *fq, struct inet_frags *frags)
  88 {
  89         spin_lock(&fq->q.lock);
  90
  91         if (fq->q.last_in & INET_FRAG_COMPLETE)
  92                 goto out;
  93
  94         inet_frag_kill(&fq->q, frags);
  95 out:
  96         spin_unlock(&fq->q.lock);
  97         inet_frag_put(&fq->q, frags);
  98 }
  99 EXPORT_SYMBOL(lowpan_expire_frag_queue);
 100
 101 static void lowpan_frag_expire(unsigned long data)
 102 {
 103         struct frag_queue *fq;
 104         struct net *net;
 105
 106         fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
 107         net = container_of(fq->q.net, struct net, ieee802154_lowpan.frags);
 108
 109         lowpan_expire_frag_queue(fq, &lowpan_frags);
 110 }
 111
 112 static inline struct lowpan_frag_queue *
 113 fq_find(struct net *net, const struct ieee802154_frag_info *frag_info,
 114         const struct ieee802154_addr *src, const struct ieee802154_addr *dst)
 115 {
 116         struct inet_frag_queue *q;
 117         struct lowpan_create_arg arg;
 118         unsigned int hash;
 119
 120         arg.tag = frag_info->d_tag;
 121         arg.d_size = frag_info->d_size;
 122         arg.src = src;
 123         arg.dst = dst;
 124
 125         read_lock(&lowpan_frags.lock);
 126         hash = lowpan_hash_frag(frag_info->d_tag, frag_info->d_size, src, dst);
 127
 128         q = inet_frag_find(&net->ieee802154_lowpan.frags,
 129                            &lowpan_frags, &arg, hash);
 130         if (IS_ERR_OR_NULL(q)) {
 131                 inet_frag_maybe_warn_overflow(q, pr_fmt());
 132                 return NULL;
 133         }
 134         return container_of(q, struct lowpan_frag_queue, q);
 135 }
 136
 137 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
 138                              struct sk_buff *skb, const u8 frag_type)
 139 {
 140         struct sk_buff *prev, *next;
 141         struct net_device *dev;
 142         int end, offset;
 143
 144         if (fq->q.last_in & INET_FRAG_COMPLETE)
 145                 goto err;
 146
 147         offset = mac_cb(skb)->frag_info.d_offset << 3;
 148         end = mac_cb(skb)->frag_info.d_size;
 149
 150         /* Is this the final fragment? */
 151         if (offset + skb->len == end) {
 152                 /* If we already have some bits beyond end
 153                  * or have different end, the segment is corrupted.
 154                  */
 155                 if (end < fq->q.len ||
 156                     ((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len))
 157                         goto err;
 158                 fq->q.last_in |= INET_FRAG_LAST_IN;
 159                 fq->q.len = end;
 160         } else {
 161                 if (end > fq->q.len) {
 162                         /* Some bits beyond end -> corruption. */
 163                         if (fq->q.last_in & INET_FRAG_LAST_IN)
 164                                 goto err;
 165                         fq->q.len = end;
 166                 }
 167         }
 168
 169         /* Find out which fragments are in front and at the back of us
 170          * in the chain of fragments so far.  We must know where to put
 171          * this fragment, right?
 172          */
 173         prev = fq->q.fragments_tail;
 174         if (!prev || mac_cb(prev)->frag_info.d_offset <
 175                      mac_cb(skb)->frag_info.d_offset) {
 176                 next = NULL;
 177                 goto found;
 178         }
 179         prev = NULL;
 180         for (next = fq->q.fragments; next != NULL; next = next->next) {
 181                 if (mac_cb(next)->frag_info.d_offset >=
 182                     mac_cb(skb)->frag_info.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         inet_frag_lru_move(&fq->q);
 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 ieee802154_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 ieee802154_frag_info *frag_info = &mac_cb(skb)->frag_info;
 357         int err;
 358
 359         err = lowpan_get_frag_info(skb, frag_type, frag_info);
 360         if (err < 0)
 361                 goto err;
 362
 363         if (frag_info->d_size > net->ieee802154_lowpan.max_dsize)
 364                 goto err;
 365
 366         inet_frag_evictor(&net->ieee802154_lowpan.frags, &lowpan_frags, false);
 367
 368         fq = fq_find(net, frag_info, &mac_cb(skb)->sa, &mac_cb(skb)->da);
 369         if (fq != NULL) {
 370                 int ret;
 371                 spin_lock(&fq->q.lock);
 372                 ret = lowpan_frag_queue(fq, skb, frag_type);
 373                 spin_unlock(&fq->q.lock);
 374
 375                 inet_frag_put(&fq->q, &lowpan_frags);
 376                 return ret;
 377         }
 378
 379 err:
 380         kfree_skb(skb);
 381         return -1;
 382 }
 383 EXPORT_SYMBOL(lowpan_frag_rcv);
 384
 385 #ifdef CONFIG_SYSCTL
 386 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 387         {
 388                 .procname       = "6lowpanfrag_high_thresh",
 389                 .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 390                 .maxlen         = sizeof(int),
 391                 .mode           = 0644,
 392                 .proc_handler   = proc_dointvec
 393         },
 394         {
 395                 .procname       = "6lowpanfrag_low_thresh",
 396                 .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 397                 .maxlen         = sizeof(int),
 398                 .mode           = 0644,
 399                 .proc_handler   = proc_dointvec
 400         },
 401         {
 402                 .procname       = "6lowpanfrag_time",
 403                 .data           = &init_net.ieee802154_lowpan.frags.timeout,
 404                 .maxlen         = sizeof(int),
 405                 .mode           = 0644,
 406                 .proc_handler   = proc_dointvec_jiffies,
 407         },
 408         {
 409                 .procname       = "6lowpanfrag_max_datagram_size",
 410                 .data           = &init_net.ieee802154_lowpan.max_dsize,
 411                 .maxlen         = sizeof(int),
 412                 .mode           = 0644,
 413                 .proc_handler   = proc_dointvec
 414         },
 415         { }
 416 };
 417
 418 static struct ctl_table lowpan_frags_ctl_table[] = {
 419         {
 420                 .procname       = "6lowpanfrag_secret_interval",
 421                 .data           = &lowpan_frags.secret_interval,
 422                 .maxlen         = sizeof(int),
 423                 .mode           = 0644,
 424                 .proc_handler   = proc_dointvec_jiffies,
 425         },
 426         { }
 427 };
 428
 429 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 430 {
 431         struct ctl_table *table;
 432         struct ctl_table_header *hdr;
 433
 434         table = lowpan_frags_ns_ctl_table;
 435         if (!net_eq(net, &init_net)) {
 436                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 437                                 GFP_KERNEL);
 438                 if (table == NULL)
 439                         goto err_alloc;
 440
 441                 table[0].data = &net->ieee802154_lowpan.frags.high_thresh;
 442                 table[1].data = &net->ieee802154_lowpan.frags.low_thresh;
 443                 table[2].data = &net->ieee802154_lowpan.frags.timeout;
 444                 table[2].data = &net->ieee802154_lowpan.max_dsize;
 445
 446                 /* Don't export sysctls to unprivileged users */
 447                 if (net->user_ns != &init_user_ns)
 448                         table[0].procname = NULL;
 449         }
 450
 451         hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 452         if (hdr == NULL)
 453                 goto err_reg;
 454
 455         net->ieee802154_lowpan.sysctl.frags_hdr = hdr;
 456         return 0;
 457
 458 err_reg:
 459         if (!net_eq(net, &init_net))
 460                 kfree(table);
 461 err_alloc:
 462         return -ENOMEM;
 463 }
 464
 465 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 466 {
 467         struct ctl_table *table;
 468
 469         table = net->ieee802154_lowpan.sysctl.frags_hdr->ctl_table_arg;
 470         unregister_net_sysctl_table(net->ieee802154_lowpan.sysctl.frags_hdr);
 471         if (!net_eq(net, &init_net))
 472                 kfree(table);
 473 }
 474
 475 static struct ctl_table_header *lowpan_ctl_header;
 476
 477 static int lowpan_frags_sysctl_register(void)
 478 {
 479         lowpan_ctl_header = register_net_sysctl(&init_net,
 480                                                 "net/ieee802154/6lowpan",
 481                                                 lowpan_frags_ctl_table);
 482         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 483 }
 484
 485 static void lowpan_frags_sysctl_unregister(void)
 486 {
 487         unregister_net_sysctl_table(lowpan_ctl_header);
 488 }
 489 #else
 490 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 491 {
 492         return 0;
 493 }
 494
 495 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 496 {
 497 }
 498
 499 static inline int lowpan_frags_sysctl_register(void)
 500 {
 501         return 0;
 502 }
 503
 504 static inline void lowpan_frags_sysctl_unregister(void)
 505 {
 506 }
 507 #endif
 508
 509 static int __net_init lowpan_frags_init_net(struct net *net)
 510 {
 511         net->ieee802154_lowpan.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 512         net->ieee802154_lowpan.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 513         net->ieee802154_lowpan.frags.timeout = IPV6_FRAG_TIMEOUT;
 514         net->ieee802154_lowpan.max_dsize = 0xFFFF;
 515
 516         inet_frags_init_net(&net->ieee802154_lowpan.frags);
 517
 518         return lowpan_frags_ns_sysctl_register(net);
 519 }
 520
 521 static void __net_exit lowpan_frags_exit_net(struct net *net)
 522 {
 523         lowpan_frags_ns_sysctl_unregister(net);
 524         inet_frags_exit_net(&net->ieee802154_lowpan.frags, &lowpan_frags);
 525 }
 526
 527 static struct pernet_operations lowpan_frags_ops = {
 528         .init = lowpan_frags_init_net,
 529         .exit = lowpan_frags_exit_net,
 530 };
 531
 532 int __init lowpan_net_frag_init(void)
 533 {
 534         int ret;
 535
 536         ret = lowpan_frags_sysctl_register();
 537         if (ret)
 538                 return ret;
 539
 540         ret = register_pernet_subsys(&lowpan_frags_ops);
 541         if (ret)
 542                 goto err_pernet;
 543
 544         lowpan_frags.hashfn = lowpan_hashfn;
 545         lowpan_frags.constructor = lowpan_frag_init;
 546         lowpan_frags.destructor = NULL;
 547         lowpan_frags.skb_free = NULL;
 548         lowpan_frags.qsize = sizeof(struct frag_queue);
 549         lowpan_frags.match = lowpan_frag_match;
 550         lowpan_frags.frag_expire = lowpan_frag_expire;
 551         lowpan_frags.secret_interval = 10 * 60 * HZ;
 552         inet_frags_init(&lowpan_frags);
 553
 554         return ret;
 555 err_pernet:
 556         lowpan_frags_sysctl_unregister();
 557         return ret;
 558 }
 559
 560 void lowpan_net_frag_exit(void)
 561 {
 562         inet_frags_fini(&lowpan_frags);
 563         lowpan_frags_sysctl_unregister();
 564         unregister_pernet_subsys(&lowpan_frags_ops);
 565 }