linux/net/ieee802154/6lowpan/reassembly.c
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   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 "6lowpan_i.h"
  32
  33static const char lowpan_frags_cache_name[] = "lowpan-frags";
  34
  35static struct inet_frags lowpan_frags;
  36
  37static int lowpan_frag_reasm(struct lowpan_frag_queue *fq,
  38                             struct sk_buff *prev, struct net_device *ldev);
  39
  40static unsigned int lowpan_hash_frag(u16 tag, u16 d_size,
  41                                     const struct ieee802154_addr *saddr,
  42                                     const struct ieee802154_addr *daddr)
  43{
  44        net_get_random_once(&lowpan_frags.rnd, sizeof(lowpan_frags.rnd));
  45        return jhash_3words(ieee802154_addr_hash(saddr),
  46                            ieee802154_addr_hash(daddr),
  47                            (__force u32)(tag + (d_size << 16)),
  48                            lowpan_frags.rnd);
  49}
  50
  51static unsigned int lowpan_hashfn(const struct inet_frag_queue *q)
  52{
  53        const struct lowpan_frag_queue *fq;
  54
  55        fq = container_of(q, struct lowpan_frag_queue, q);
  56        return lowpan_hash_frag(fq->tag, fq->d_size, &fq->saddr, &fq->daddr);
  57}
  58
  59static bool lowpan_frag_match(const struct inet_frag_queue *q, const void *a)
  60{
  61        const struct lowpan_frag_queue *fq;
  62        const struct lowpan_create_arg *arg = a;
  63
  64        fq = container_of(q, struct lowpan_frag_queue, q);
  65        return  fq->tag == arg->tag && fq->d_size == arg->d_size &&
  66                ieee802154_addr_equal(&fq->saddr, arg->src) &&
  67                ieee802154_addr_equal(&fq->daddr, arg->dst);
  68}
  69
  70static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
  71{
  72        const struct lowpan_create_arg *arg = a;
  73        struct lowpan_frag_queue *fq;
  74
  75        fq = container_of(q, struct lowpan_frag_queue, q);
  76
  77        fq->tag = arg->tag;
  78        fq->d_size = arg->d_size;
  79        fq->saddr = *arg->src;
  80        fq->daddr = *arg->dst;
  81}
  82
  83static void lowpan_frag_expire(unsigned long data)
  84{
  85        struct frag_queue *fq;
  86        struct net *net;
  87
  88        fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
  89        net = container_of(fq->q.net, struct net, ieee802154_lowpan.frags);
  90
  91        spin_lock(&fq->q.lock);
  92
  93        if (fq->q.flags & INET_FRAG_COMPLETE)
  94                goto out;
  95
  96        inet_frag_kill(&fq->q, &lowpan_frags);
  97out:
  98        spin_unlock(&fq->q.lock);
  99        inet_frag_put(&fq->q, &lowpan_frags);
 100}
 101
 102static inline struct lowpan_frag_queue *
 103fq_find(struct net *net, const struct lowpan_802154_cb *cb,
 104        const struct ieee802154_addr *src,
 105        const struct ieee802154_addr *dst)
 106{
 107        struct inet_frag_queue *q;
 108        struct lowpan_create_arg arg;
 109        unsigned int hash;
 110        struct netns_ieee802154_lowpan *ieee802154_lowpan =
 111                net_ieee802154_lowpan(net);
 112
 113        arg.tag = cb->d_tag;
 114        arg.d_size = cb->d_size;
 115        arg.src = src;
 116        arg.dst = dst;
 117
 118        hash = lowpan_hash_frag(cb->d_tag, cb->d_size, src, dst);
 119
 120        q = inet_frag_find(&ieee802154_lowpan->frags,
 121                           &lowpan_frags, &arg, hash);
 122        if (IS_ERR_OR_NULL(q)) {
 123                inet_frag_maybe_warn_overflow(q, pr_fmt());
 124                return NULL;
 125        }
 126        return container_of(q, struct lowpan_frag_queue, q);
 127}
 128
 129static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
 130                             struct sk_buff *skb, u8 frag_type)
 131{
 132        struct sk_buff *prev, *next;
 133        struct net_device *ldev;
 134        int end, offset;
 135
 136        if (fq->q.flags & INET_FRAG_COMPLETE)
 137                goto err;
 138
 139        offset = lowpan_802154_cb(skb)->d_offset << 3;
 140        end = lowpan_802154_cb(skb)->d_size;
 141
 142        /* Is this the final fragment? */
 143        if (offset + skb->len == end) {
 144                /* If we already have some bits beyond end
 145                 * or have different end, the segment is corrupted.
 146                 */
 147                if (end < fq->q.len ||
 148                    ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
 149                        goto err;
 150                fq->q.flags |= INET_FRAG_LAST_IN;
 151                fq->q.len = end;
 152        } else {
 153                if (end > fq->q.len) {
 154                        /* Some bits beyond end -> corruption. */
 155                        if (fq->q.flags & INET_FRAG_LAST_IN)
 156                                goto err;
 157                        fq->q.len = end;
 158                }
 159        }
 160
 161        /* Find out which fragments are in front and at the back of us
 162         * in the chain of fragments so far.  We must know where to put
 163         * this fragment, right?
 164         */
 165        prev = fq->q.fragments_tail;
 166        if (!prev ||
 167            lowpan_802154_cb(prev)->d_offset <
 168            lowpan_802154_cb(skb)->d_offset) {
 169                next = NULL;
 170                goto found;
 171        }
 172        prev = NULL;
 173        for (next = fq->q.fragments; next != NULL; next = next->next) {
 174                if (lowpan_802154_cb(next)->d_offset >=
 175                    lowpan_802154_cb(skb)->d_offset)
 176                        break;  /* bingo! */
 177                prev = next;
 178        }
 179
 180found:
 181        /* Insert this fragment in the chain of fragments. */
 182        skb->next = next;
 183        if (!next)
 184                fq->q.fragments_tail = skb;
 185        if (prev)
 186                prev->next = skb;
 187        else
 188                fq->q.fragments = skb;
 189
 190        ldev = skb->dev;
 191        if (ldev)
 192                skb->dev = NULL;
 193
 194        fq->q.stamp = skb->tstamp;
 195        if (frag_type == LOWPAN_DISPATCH_FRAG1)
 196                fq->q.flags |= INET_FRAG_FIRST_IN;
 197
 198        fq->q.meat += skb->len;
 199        add_frag_mem_limit(fq->q.net, skb->truesize);
 200
 201        if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 202            fq->q.meat == fq->q.len) {
 203                int res;
 204                unsigned long orefdst = skb->_skb_refdst;
 205
 206                skb->_skb_refdst = 0UL;
 207                res = lowpan_frag_reasm(fq, prev, ldev);
 208                skb->_skb_refdst = orefdst;
 209                return res;
 210        }
 211
 212        return -1;
 213err:
 214        kfree_skb(skb);
 215        return -1;
 216}
 217
 218/*      Check if this packet is complete.
 219 *      Returns NULL on failure by any reason, and pointer
 220 *      to current nexthdr field in reassembled frame.
 221 *
 222 *      It is called with locked fq, and caller must check that
 223 *      queue is eligible for reassembly i.e. it is not COMPLETE,
 224 *      the last and the first frames arrived and all the bits are here.
 225 */
 226static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *prev,
 227                             struct net_device *ldev)
 228{
 229        struct sk_buff *fp, *head = fq->q.fragments;
 230        int sum_truesize;
 231
 232        inet_frag_kill(&fq->q, &lowpan_frags);
 233
 234        /* Make the one we just received the head. */
 235        if (prev) {
 236                head = prev->next;
 237                fp = skb_clone(head, GFP_ATOMIC);
 238
 239                if (!fp)
 240                        goto out_oom;
 241
 242                fp->next = head->next;
 243                if (!fp->next)
 244                        fq->q.fragments_tail = fp;
 245                prev->next = fp;
 246
 247                skb_morph(head, fq->q.fragments);
 248                head->next = fq->q.fragments->next;
 249
 250                consume_skb(fq->q.fragments);
 251                fq->q.fragments = head;
 252        }
 253
 254        /* Head of list must not be cloned. */
 255        if (skb_unclone(head, GFP_ATOMIC))
 256                goto out_oom;
 257
 258        /* If the first fragment is fragmented itself, we split
 259         * it to two chunks: the first with data and paged part
 260         * and the second, holding only fragments.
 261         */
 262        if (skb_has_frag_list(head)) {
 263                struct sk_buff *clone;
 264                int i, plen = 0;
 265
 266                clone = alloc_skb(0, GFP_ATOMIC);
 267                if (!clone)
 268                        goto out_oom;
 269                clone->next = head->next;
 270                head->next = clone;
 271                skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
 272                skb_frag_list_init(head);
 273                for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
 274                        plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
 275                clone->len = head->data_len - plen;
 276                clone->data_len = clone->len;
 277                head->data_len -= clone->len;
 278                head->len -= clone->len;
 279                add_frag_mem_limit(fq->q.net, clone->truesize);
 280        }
 281
 282        WARN_ON(head == NULL);
 283
 284        sum_truesize = head->truesize;
 285        for (fp = head->next; fp;) {
 286                bool headstolen;
 287                int delta;
 288                struct sk_buff *next = fp->next;
 289
 290                sum_truesize += fp->truesize;
 291                if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
 292                        kfree_skb_partial(fp, headstolen);
 293                } else {
 294                        if (!skb_shinfo(head)->frag_list)
 295                                skb_shinfo(head)->frag_list = fp;
 296                        head->data_len += fp->len;
 297                        head->len += fp->len;
 298                        head->truesize += fp->truesize;
 299                }
 300                fp = next;
 301        }
 302        sub_frag_mem_limit(fq->q.net, sum_truesize);
 303
 304        head->next = NULL;
 305        head->dev = ldev;
 306        head->tstamp = fq->q.stamp;
 307
 308        fq->q.fragments = NULL;
 309        fq->q.fragments_tail = NULL;
 310
 311        return 1;
 312out_oom:
 313        net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
 314        return -1;
 315}
 316
 317static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
 318                                          lowpan_rx_result res)
 319{
 320        switch (res) {
 321        case RX_QUEUED:
 322                return NET_RX_SUCCESS;
 323        case RX_CONTINUE:
 324                /* nobody cared about this packet */
 325                net_warn_ratelimited("%s: received unknown dispatch\n",
 326                                     __func__);
 327
 328                /* fall-through */
 329        default:
 330                /* all others failure */
 331                return NET_RX_DROP;
 332        }
 333}
 334
 335static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
 336{
 337        int ret;
 338
 339        if (!lowpan_is_iphc(*skb_network_header(skb)))
 340                return RX_CONTINUE;
 341
 342        ret = lowpan_iphc_decompress(skb);
 343        if (ret < 0)
 344                return RX_DROP;
 345
 346        return RX_QUEUED;
 347}
 348
 349static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
 350{
 351        lowpan_rx_result res;
 352
 353#define CALL_RXH(rxh)                   \
 354        do {                            \
 355                res = rxh(skb); \
 356                if (res != RX_CONTINUE) \
 357                        goto rxh_next;  \
 358        } while (0)
 359
 360        /* likely at first */
 361        CALL_RXH(lowpan_frag_rx_h_iphc);
 362        CALL_RXH(lowpan_rx_h_ipv6);
 363
 364rxh_next:
 365        return lowpan_frag_rx_handlers_result(skb, res);
 366#undef CALL_RXH
 367}
 368
 369#define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK        0x07
 370#define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT       8
 371
 372static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
 373                         struct lowpan_802154_cb *cb)
 374{
 375        bool fail;
 376        u8 high = 0, low = 0;
 377        __be16 d_tag = 0;
 378
 379        fail = lowpan_fetch_skb(skb, &high, 1);
 380        fail |= lowpan_fetch_skb(skb, &low, 1);
 381        /* remove the dispatch value and use first three bits as high value
 382         * for the datagram size
 383         */
 384        cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
 385                LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
 386        fail |= lowpan_fetch_skb(skb, &d_tag, 2);
 387        cb->d_tag = ntohs(d_tag);
 388
 389        if (frag_type == LOWPAN_DISPATCH_FRAGN) {
 390                fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
 391        } else {
 392                skb_reset_network_header(skb);
 393                cb->d_offset = 0;
 394                /* check if datagram_size has ipv6hdr on FRAG1 */
 395                fail |= cb->d_size < sizeof(struct ipv6hdr);
 396                /* check if we can dereference the dispatch value */
 397                fail |= !skb->len;
 398        }
 399
 400        if (unlikely(fail))
 401                return -EIO;
 402
 403        return 0;
 404}
 405
 406int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
 407{
 408        struct lowpan_frag_queue *fq;
 409        struct net *net = dev_net(skb->dev);
 410        struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
 411        struct ieee802154_hdr hdr;
 412        int err;
 413
 414        if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
 415                goto err;
 416
 417        err = lowpan_get_cb(skb, frag_type, cb);
 418        if (err < 0)
 419                goto err;
 420
 421        if (frag_type == LOWPAN_DISPATCH_FRAG1) {
 422                err = lowpan_invoke_frag_rx_handlers(skb);
 423                if (err == NET_RX_DROP)
 424                        goto err;
 425        }
 426
 427        if (cb->d_size > IPV6_MIN_MTU) {
 428                net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
 429                goto err;
 430        }
 431
 432        fq = fq_find(net, cb, &hdr.source, &hdr.dest);
 433        if (fq != NULL) {
 434                int ret;
 435
 436                spin_lock(&fq->q.lock);
 437                ret = lowpan_frag_queue(fq, skb, frag_type);
 438                spin_unlock(&fq->q.lock);
 439
 440                inet_frag_put(&fq->q, &lowpan_frags);
 441                return ret;
 442        }
 443
 444err:
 445        kfree_skb(skb);
 446        return -1;
 447}
 448
 449#ifdef CONFIG_SYSCTL
 450static int zero;
 451
 452static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 453        {
 454                .procname       = "6lowpanfrag_high_thresh",
 455                .data           = &init_net.ieee802154_lowpan.frags.high_thresh,
 456                .maxlen         = sizeof(int),
 457                .mode           = 0644,
 458                .proc_handler   = proc_dointvec_minmax,
 459                .extra1         = &init_net.ieee802154_lowpan.frags.low_thresh
 460        },
 461        {
 462                .procname       = "6lowpanfrag_low_thresh",
 463                .data           = &init_net.ieee802154_lowpan.frags.low_thresh,
 464                .maxlen         = sizeof(int),
 465                .mode           = 0644,
 466                .proc_handler   = proc_dointvec_minmax,
 467                .extra1         = &zero,
 468                .extra2         = &init_net.ieee802154_lowpan.frags.high_thresh
 469        },
 470        {
 471                .procname       = "6lowpanfrag_time",
 472                .data           = &init_net.ieee802154_lowpan.frags.timeout,
 473                .maxlen         = sizeof(int),
 474                .mode           = 0644,
 475                .proc_handler   = proc_dointvec_jiffies,
 476        },
 477        { }
 478};
 479
 480/* secret interval has been deprecated */
 481static int lowpan_frags_secret_interval_unused;
 482static struct ctl_table lowpan_frags_ctl_table[] = {
 483        {
 484                .procname       = "6lowpanfrag_secret_interval",
 485                .data           = &lowpan_frags_secret_interval_unused,
 486                .maxlen         = sizeof(int),
 487                .mode           = 0644,
 488                .proc_handler   = proc_dointvec_jiffies,
 489        },
 490        { }
 491};
 492
 493static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 494{
 495        struct ctl_table *table;
 496        struct ctl_table_header *hdr;
 497        struct netns_ieee802154_lowpan *ieee802154_lowpan =
 498                net_ieee802154_lowpan(net);
 499
 500        table = lowpan_frags_ns_ctl_table;
 501        if (!net_eq(net, &init_net)) {
 502                table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
 503                                GFP_KERNEL);
 504                if (table == NULL)
 505                        goto err_alloc;
 506
 507                table[0].data = &ieee802154_lowpan->frags.high_thresh;
 508                table[0].extra1 = &ieee802154_lowpan->frags.low_thresh;
 509                table[0].extra2 = &init_net.ieee802154_lowpan.frags.high_thresh;
 510                table[1].data = &ieee802154_lowpan->frags.low_thresh;
 511                table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;
 512                table[2].data = &ieee802154_lowpan->frags.timeout;
 513
 514                /* Don't export sysctls to unprivileged users */
 515                if (net->user_ns != &init_user_ns)
 516                        table[0].procname = NULL;
 517        }
 518
 519        hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
 520        if (hdr == NULL)
 521                goto err_reg;
 522
 523        ieee802154_lowpan->sysctl.frags_hdr = hdr;
 524        return 0;
 525
 526err_reg:
 527        if (!net_eq(net, &init_net))
 528                kfree(table);
 529err_alloc:
 530        return -ENOMEM;
 531}
 532
 533static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
 534{
 535        struct ctl_table *table;
 536        struct netns_ieee802154_lowpan *ieee802154_lowpan =
 537                net_ieee802154_lowpan(net);
 538
 539        table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
 540        unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
 541        if (!net_eq(net, &init_net))
 542                kfree(table);
 543}
 544
 545static struct ctl_table_header *lowpan_ctl_header;
 546
 547static int __init lowpan_frags_sysctl_register(void)
 548{
 549        lowpan_ctl_header = register_net_sysctl(&init_net,
 550                                                "net/ieee802154/6lowpan",
 551                                                lowpan_frags_ctl_table);
 552        return lowpan_ctl_header == NULL ? -ENOMEM : 0;
 553}
 554
 555static void lowpan_frags_sysctl_unregister(void)
 556{
 557        unregister_net_sysctl_table(lowpan_ctl_header);
 558}
 559#else
 560static inline int lowpan_frags_ns_sysctl_register(struct net *net)
 561{
 562        return 0;
 563}
 564
 565static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
 566{
 567}
 568
 569static inline int __init lowpan_frags_sysctl_register(void)
 570{
 571        return 0;
 572}
 573
 574static inline void lowpan_frags_sysctl_unregister(void)
 575{
 576}
 577#endif
 578
 579static int __net_init lowpan_frags_init_net(struct net *net)
 580{
 581        struct netns_ieee802154_lowpan *ieee802154_lowpan =
 582                net_ieee802154_lowpan(net);
 583
 584        ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 585        ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 586        ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
 587
 588        inet_frags_init_net(&ieee802154_lowpan->frags);
 589
 590        return lowpan_frags_ns_sysctl_register(net);
 591}
 592
 593static void __net_exit lowpan_frags_exit_net(struct net *net)
 594{
 595        struct netns_ieee802154_lowpan *ieee802154_lowpan =
 596                net_ieee802154_lowpan(net);
 597
 598        lowpan_frags_ns_sysctl_unregister(net);
 599        inet_frags_exit_net(&ieee802154_lowpan->frags, &lowpan_frags);
 600}
 601
 602static struct pernet_operations lowpan_frags_ops = {
 603        .init = lowpan_frags_init_net,
 604        .exit = lowpan_frags_exit_net,
 605};
 606
 607int __init lowpan_net_frag_init(void)
 608{
 609        int ret;
 610
 611        ret = lowpan_frags_sysctl_register();
 612        if (ret)
 613                return ret;
 614
 615        ret = register_pernet_subsys(&lowpan_frags_ops);
 616        if (ret)
 617                goto err_pernet;
 618
 619        lowpan_frags.hashfn = lowpan_hashfn;
 620        lowpan_frags.constructor = lowpan_frag_init;
 621        lowpan_frags.destructor = NULL;
 622        lowpan_frags.qsize = sizeof(struct frag_queue);
 623        lowpan_frags.match = lowpan_frag_match;
 624        lowpan_frags.frag_expire = lowpan_frag_expire;
 625        lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
 626        ret = inet_frags_init(&lowpan_frags);
 627        if (ret)
 628                goto err_pernet;
 629
 630        return ret;
 631err_pernet:
 632        lowpan_frags_sysctl_unregister();
 633        return ret;
 634}
 635
 636void lowpan_net_frag_exit(void)
 637{
 638        inet_frags_fini(&lowpan_frags);
 639        lowpan_frags_sysctl_unregister();
 640        unregister_pernet_subsys(&lowpan_frags_ops);
 641}
 642