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