net/ieee802154/6lowpan/reassembly.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*      6LoWPAN fragment reassembly
   3  *
   4  *      Authors:
   5  *      Alexander Aring         <aar@pengutronix.de>
   6  *
   7  *      Based on: net/ipv6/reassembly.c
   8  */
   9
  10 #define pr_fmt(fmt) "6LoWPAN: " fmt
  11
  12 #include <linux/net.h>
  13 #include <linux/list.h>
  14 #include <linux/netdevice.h>
  15 #include <linux/random.h>
  16 #include <linux/jhash.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/slab.h>
  19 #include <linux/export.h>
  20
  21 #include <net/ieee802154_netdev.h>
  22 #include <net/6lowpan.h>
  23 #include <net/ipv6_frag.h>
  24 #include <net/inet_frag.h>
  25 #include <net/ip.h>
  26
  27 #include "6lowpan_i.h"
  28
  29 static const char lowpan_frags_cache_name[] = "lowpan-frags";
  30
  31 static struct inet_frags lowpan_frags;
  32
  33 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
  34                              struct sk_buff *prev,  struct net_device *ldev);
  35
  36 static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
  37 {
  38         const struct frag_lowpan_compare_key *key = a;
  39
  40         BUILD_BUG_ON(sizeof(*key) > sizeof(q->key));
  41         memcpy(&q->key, key, sizeof(*key));
  42 }
  43
  44 static void lowpan_frag_expire(struct timer_list *t)
  45 {
  46         struct inet_frag_queue *frag = from_timer(frag, t, timer);
  47         struct frag_queue *fq;
  48
  49         fq = container_of(frag, struct frag_queue, q);
  50
  51         spin_lock(&fq->q.lock);
  52
  53         if (fq->q.flags & INET_FRAG_COMPLETE)
  54                 goto out;
  55
  56         inet_frag_kill(&fq->q);
  57 out:
  58         spin_unlock(&fq->q.lock);
  59         inet_frag_put(&fq->q);
  60 }
  61
  62 static inline struct lowpan_frag_queue *
  63 fq_find(struct net *net, const struct lowpan_802154_cb *cb,
  64         const struct ieee802154_addr *src,
  65         const struct ieee802154_addr *dst)
  66 {
  67         struct netns_ieee802154_lowpan *ieee802154_lowpan =
  68                 net_ieee802154_lowpan(net);
  69         struct frag_lowpan_compare_key key = {};
  70         struct inet_frag_queue *q;
  71
  72         key.tag = cb->d_tag;
  73         key.d_size = cb->d_size;
  74         key.src = *src;
  75         key.dst = *dst;
  76
  77         q = inet_frag_find(ieee802154_lowpan->fqdir, &key);
  78         if (!q)
  79                 return NULL;
  80
  81         return container_of(q, struct lowpan_frag_queue, q);
  82 }
  83
  84 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
  85                              struct sk_buff *skb, u8 frag_type)
  86 {
  87         struct sk_buff *prev_tail;
  88         struct net_device *ldev;
  89         int end, offset, err;
  90
  91         /* inet_frag_queue_* functions use skb->cb; see struct ipfrag_skb_cb
  92          * in inet_fragment.c
  93          */
  94         BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet_skb_parm));
  95         BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet6_skb_parm));
  96
  97         if (fq->q.flags & INET_FRAG_COMPLETE)
  98                 goto err;
  99
 100         offset = lowpan_802154_cb(skb)->d_offset << 3;
 101         end = lowpan_802154_cb(skb)->d_size;
 102
 103         /* Is this the final fragment? */
 104         if (offset + skb->len == end) {
 105                 /* If we already have some bits beyond end
 106                  * or have different end, the segment is corrupted.
 107                  */
 108                 if (end < fq->q.len ||
 109                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
 110                         goto err;
 111                 fq->q.flags |= INET_FRAG_LAST_IN;
 112                 fq->q.len = end;
 113         } else {
 114                 if (end > fq->q.len) {
 115                         /* Some bits beyond end -> corruption. */
 116                         if (fq->q.flags & INET_FRAG_LAST_IN)
 117                                 goto err;
 118                         fq->q.len = end;
 119                 }
 120         }
 121
 122         ldev = skb->dev;
 123         if (ldev)
 124                 skb->dev = NULL;
 125         barrier();
 126
 127         prev_tail = fq->q.fragments_tail;
 128         err = inet_frag_queue_insert(&fq->q, skb, offset, end);
 129         if (err)
 130                 goto err;
 131
 132         fq->q.stamp = skb->tstamp;
 133         fq->q.mono_delivery_time = skb->mono_delivery_time;
 134         if (frag_type == LOWPAN_DISPATCH_FRAG1)
 135                 fq->q.flags |= INET_FRAG_FIRST_IN;
 136
 137         fq->q.meat += skb->len;
 138         add_frag_mem_limit(fq->q.fqdir, skb->truesize);
 139
 140         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 141             fq->q.meat == fq->q.len) {
 142                 int res;
 143                 unsigned long orefdst = skb->_skb_refdst;
 144
 145                 skb->_skb_refdst = 0UL;
 146                 res = lowpan_frag_reasm(fq, skb, prev_tail, ldev);
 147                 skb->_skb_refdst = orefdst;
 148                 return res;
 149         }
 150         skb_dst_drop(skb);
 151
 152         return -1;
 153 err:
 154         kfree_skb(skb);
 155         return -1;
 156 }
 157
 158 /*      Check if this packet is complete.
 159  *
 160  *      It is called with locked fq, and caller must check that
 161  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 162  *      the last and the first frames arrived and all the bits are here.
 163  */
 164 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
 165                              struct sk_buff *prev_tail, struct net_device *ldev)
 166 {
 167         void *reasm_data;
 168
 169         inet_frag_kill(&fq->q);
 170
 171         reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
 172         if (!reasm_data)
 173                 goto out_oom;
 174         inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
 175
 176         skb->dev = ldev;
 177         skb->tstamp = fq->q.stamp;
 178         fq->q.rb_fragments = RB_ROOT;
 179         fq->q.fragments_tail = NULL;
 180         fq->q.last_run_head = NULL;
 181
 182         return 1;
 183 out_oom:
 184         net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
 185         return -1;
 186 }
 187
 188 static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
 189                                           lowpan_rx_result res)
 190 {
 191         switch (res) {
 192         case RX_QUEUED:
 193                 return NET_RX_SUCCESS;
 194         case RX_CONTINUE:
 195                 /* nobody cared about this packet */
 196                 net_warn_ratelimited("%s: received unknown dispatch\n",
 197                                      __func__);
 198
 199                 fallthrough;
 200         default:
 201                 /* all others failure */
 202                 return NET_RX_DROP;
 203         }
 204 }
 205
 206 static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
 207 {
 208         int ret;
 209
 210         if (!lowpan_is_iphc(*skb_network_header(skb)))
 211                 return RX_CONTINUE;
 212
 213         ret = lowpan_iphc_decompress(skb);
 214         if (ret < 0)
 215                 return RX_DROP;
 216
 217         return RX_QUEUED;
 218 }
 219
 220 static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
 221 {
 222         lowpan_rx_result res;
 223
 224 #define CALL_RXH(rxh)                   \
 225         do {                            \
 226                 res = rxh(skb); \
 227                 if (res != RX_CONTINUE) \
 228                         goto rxh_next;  \
 229         } while (0)
 230
 231         /* likely at first */
 232         CALL_RXH(lowpan_frag_rx_h_iphc);
 233         CALL_RXH(lowpan_rx_h_ipv6);
 234
 235 rxh_next:
 236         return lowpan_frag_rx_handlers_result(skb, res);
 237 #undef CALL_RXH
 238 }
 239
 240 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK        0x07
 241 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT       8
 242
 243 static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
 244                          struct lowpan_802154_cb *cb)
 245 {
 246         bool fail;
 247         u8 high = 0, low = 0;
 248         __be16 d_tag = 0;
 249
 250         fail = lowpan_fetch_skb(skb, &high, 1);
 251         fail |= lowpan_fetch_skb(skb, &low, 1);
 252         /* remove the dispatch value and use first three bits as high value
 253          * for the datagram size
 254          */
 255         cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
 256                 LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
 257         fail |= lowpan_fetch_skb(skb, &d_tag, 2);
 258         cb->d_tag = ntohs(d_tag);
 259
 260         if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 261                 fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
 262         } else {
 263                 skb_reset_network_header(skb);
 264                 cb->d_offset = 0;
 265                 /* check if datagram_size has ipv6hdr on FRAG1 */
 266                 fail |= cb->d_size < sizeof(struct ipv6hdr);
 267                 /* check if we can dereference the dispatch value */
 268                 fail |= !skb->len;
 269         }
 270
 271         if (unlikely(fail))
 272                 return -EIO;
 273
 274         return 0;
 275 }
 276
 277 int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 278 {
 279         struct lowpan_frag_queue *fq;
 280         struct net *net = dev_net(skb->dev);
 281         struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
 282         struct ieee802154_hdr hdr = {};
 283         int err;
 284
 285         if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
 286                 goto err;
 287
 288         err = lowpan_get_cb(skb, frag_type, cb);
 289         if (err < 0)
 290                 goto err;
 291
 292         if (frag_type == LOWPAN_DISPATCH_FRAG1) {
 293                 err = lowpan_invoke_frag_rx_handlers(skb);
 294                 if (err == NET_RX_DROP)
 295                         goto err;
 296         }
 297
 298         if (cb->d_size > IPV6_MIN_MTU) {
 299                 net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
 300                 goto err;
 301         }
 302
 303         fq = fq_find(net, cb, &hdr.source, &hdr.dest);
 304         if (fq != NULL) {
 305                 int ret;
 306
 307                 spin_lock(&fq->q.lock);
 308                 ret = lowpan_frag_queue(fq, skb, frag_type);
 309                 spin_unlock(&fq->q.lock);
 310
 311                 inet_frag_put(&fq->q);
 312                 return ret;
 313         }
 314
 315 err:
 316         kfree_skb(skb);
 317         return -1;
 318 }
 319
 320 #ifdef CONFIG_SYSCTL
 321
 322 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 323         {
 324                 .procname       = "6lowpanfrag_high_thresh",
 325                 .maxlen         = sizeof(unsigned long),
 326                 .mode           = 0644,
 327                 .proc_handler   = proc_doulongvec_minmax,
 328         },
 329         {
 330                 .procname       = "6lowpanfrag_low_thresh",
 331                 .maxlen         = sizeof(unsigned long),
 332                 .mode           = 0644,
 333                 .proc_handler   = proc_doulongvec_minmax,
 334         },
 335         {
 336                 .procname       = "6lowpanfrag_time",
 337                 .maxlen         = sizeof(int),
 338                 .mode           = 0644,
 339                 .proc_handler   = proc_dointvec_jiffies,
 340         },
 341         { }
 342 };
 343
 344 /* secret interval has been deprecated */
 345 static int lowpan_frags_secret_interval_unused;
 346 static struct ctl_table lowpan_frags_ctl_table[] = {
 347         {
 348                 .procname       = "6lowpanfrag_secret_interval",
 349                 .data           = &lowpan_frags_secret_interval_unused,
 350                 .maxlen         = sizeof(int),
 351                 .mode           = 0644,
 352                 .proc_handler   = proc_dointvec_jiffies,
 353         },
 354         { }
 355 };
 356
 357 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 358 {
 359         struct ctl_table *table;
 360         struct ctl_table_header *hdr;
 361         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 362                 net_ieee802154_lowpan(net);
 363         size_t table_size = ARRAY_SIZE(lowpan_frags_ns_ctl_table);
 364
 365         table = lowpan_frags_ns_ctl_table;
 366         if (!net_eq(net, &init_net)) {
 367                 table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 368                                 GFP_KERNEL);
 369                 if (table == NULL)
 370                         goto err_alloc;
 371
 372                 /* Don't export sysctls to unprivileged users */
 373                 if (net->user_ns != &init_user_ns) {
 374                         table[0].procname = NULL;
 375                         table_size = 0;
 376                 }
 377         }
 378
 379         table[0].data   = &ieee802154_lowpan->fqdir->high_thresh;
 380         table[0].extra1 = &ieee802154_lowpan->fqdir->low_thresh;
 381         table[1].data   = &ieee802154_lowpan->fqdir->low_thresh;
 382         table[1].extra2 = &ieee802154_lowpan->fqdir->high_thresh;
 383         table[2].data   = &ieee802154_lowpan->fqdir->timeout;
 384
 385         hdr = register_net_sysctl_sz(net, "net/ieee802154/6lowpan", table,
 386                                      table_size);
 387         if (hdr == NULL)
 388                 goto err_reg;
 389
 390         ieee802154_lowpan->sysctl.frags_hdr = hdr;
 391         return 0;
 392
 393 err_reg:
 394         if (!net_eq(net, &init_net))
 395                 kfree(table);
 396 err_alloc:
 397         return -ENOMEM;
 398 }
 399
 400 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 401 {
 402         struct ctl_table *table;
 403         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 404                 net_ieee802154_lowpan(net);
 405
 406         table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 407         unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 408         if (!net_eq(net, &init_net))
 409                 kfree(table);
 410 }
 411
 412 static struct ctl_table_header *lowpan_ctl_header;
 413
 414 static int __init lowpan_frags_sysctl_register(void)
 415 {
 416         lowpan_ctl_header = register_net_sysctl(&init_net,
 417                                                 "net/ieee802154/6lowpan",
 418                                                 lowpan_frags_ctl_table);
 419         return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 420 }
 421
 422 static void lowpan_frags_sysctl_unregister(void)
 423 {
 424         unregister_net_sysctl_table(lowpan_ctl_header);
 425 }
 426 #else
 427 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 428 {
 429         return 0;
 430 }
 431
 432 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 433 {
 434 }
 435
 436 static inline int __init lowpan_frags_sysctl_register(void)
 437 {
 438         return 0;
 439 }
 440
 441 static inline void lowpan_frags_sysctl_unregister(void)
 442 {
 443 }
 444 #endif
 445
 446 static int __net_init lowpan_frags_init_net(struct net *net)
 447 {
 448         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 449                 net_ieee802154_lowpan(net);
 450         int res;
 451
 452
 453         res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
 454         if (res < 0)
 455                 return res;
 456
 457         ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
 458         ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
 459         ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
 460
 461         res = lowpan_frags_ns_sysctl_register(net);
 462         if (res < 0)
 463                 fqdir_exit(ieee802154_lowpan->fqdir);
 464         return res;
 465 }
 466
 467 static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
 468 {
 469         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 470                 net_ieee802154_lowpan(net);
 471
 472         fqdir_pre_exit(ieee802154_lowpan->fqdir);
 473 }
 474
 475 static void __net_exit lowpan_frags_exit_net(struct net *net)
 476 {
 477         struct netns_ieee802154_lowpan *ieee802154_lowpan =
 478                 net_ieee802154_lowpan(net);
 479
 480         lowpan_frags_ns_sysctl_unregister(net);
 481         fqdir_exit(ieee802154_lowpan->fqdir);
 482 }
 483
 484 static struct pernet_operations lowpan_frags_ops = {
 485         .init           = lowpan_frags_init_net,
 486         .pre_exit       = lowpan_frags_pre_exit_net,
 487         .exit           = lowpan_frags_exit_net,
 488 };
 489
 490 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
 491 {
 492         return jhash2(data,
 493                       sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
 494 }
 495
 496 static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
 497 {
 498         const struct inet_frag_queue *fq = data;
 499
 500         return jhash2((const u32 *)&fq->key,
 501                       sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
 502 }
 503
 504 static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
 505 {
 506         const struct frag_lowpan_compare_key *key = arg->key;
 507         const struct inet_frag_queue *fq = ptr;
 508
 509         return !!memcmp(&fq->key, key, sizeof(*key));
 510 }
 511
 512 static const struct rhashtable_params lowpan_rhash_params = {
 513         .head_offset            = offsetof(struct inet_frag_queue, node),
 514         .hashfn                 = lowpan_key_hashfn,
 515         .obj_hashfn             = lowpan_obj_hashfn,
 516         .obj_cmpfn              = lowpan_obj_cmpfn,
 517         .automatic_shrinking    = true,
 518 };
 519
 520 int __init lowpan_net_frag_init(void)
 521 {
 522         int ret;
 523
 524         lowpan_frags.constructor = lowpan_frag_init;
 525         lowpan_frags.destructor = NULL;
 526         lowpan_frags.qsize = sizeof(struct frag_queue);
 527         lowpan_frags.frag_expire = lowpan_frag_expire;
 528         lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
 529         lowpan_frags.rhash_params = lowpan_rhash_params;
 530         ret = inet_frags_init(&lowpan_frags);
 531         if (ret)
 532                 goto out;
 533
 534         ret = lowpan_frags_sysctl_register();
 535         if (ret)
 536                 goto err_sysctl;
 537
 538         ret = register_pernet_subsys(&lowpan_frags_ops);
 539         if (ret)
 540                 goto err_pernet;
 541 out:
 542         return ret;
 543 err_pernet:
 544         lowpan_frags_sysctl_unregister();
 545 err_sysctl:
 546         inet_frags_fini(&lowpan_frags);
 547         return ret;
 548 }
 549
 550 void lowpan_net_frag_exit(void)
 551 {
 552         lowpan_frags_sysctl_unregister();
 553         unregister_pernet_subsys(&lowpan_frags_ops);
 554         inet_frags_fini(&lowpan_frags);
 555 }