net/ipv6/netfilter/nf_conntrack_reasm.c

   1 /*
   2  * IPv6 fragment reassembly for connection tracking
   3  *
   4  * Copyright (C)2004 USAGI/WIDE Project
   5  *
   6  * Author:
   7  *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
   8  *
   9  * Based on: net/ipv6/reassembly.c
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version
  14  * 2 of the License, or (at your option) any later version.
  15  */
  16
  17 #define pr_fmt(fmt) "IPv6-nf: " fmt
  18
  19 #include <linux/errno.h>
  20 #include <linux/types.h>
  21 #include <linux/string.h>
  22 #include <linux/socket.h>
  23 #include <linux/sockios.h>
  24 #include <linux/jiffies.h>
  25 #include <linux/net.h>
  26 #include <linux/list.h>
  27 #include <linux/netdevice.h>
  28 #include <linux/in6.h>
  29 #include <linux/ipv6.h>
  30 #include <linux/icmpv6.h>
  31 #include <linux/random.h>
  32 #include <linux/slab.h>
  33
  34 #include <net/sock.h>
  35 #include <net/snmp.h>
  36 #include <net/ipv6_frag.h>
  37
  38 #include <net/protocol.h>
  39 #include <net/transp_v6.h>
  40 #include <net/rawv6.h>
  41 #include <net/ndisc.h>
  42 #include <net/addrconf.h>
  43 #include <net/inet_ecn.h>
  44 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  45 #include <linux/sysctl.h>
  46 #include <linux/netfilter.h>
  47 #include <linux/netfilter_ipv6.h>
  48 #include <linux/kernel.h>
  49 #include <linux/module.h>
  50 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  51
  52 static const char nf_frags_cache_name[] = "nf-frags";
  53
  54 static struct inet_frags nf_frags;
  55
  56 #ifdef CONFIG_SYSCTL
  57
  58 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
  59         {
  60                 .procname       = "nf_conntrack_frag6_timeout",
  61                 .data           = &init_net.nf_frag.frags.timeout,
  62                 .maxlen         = sizeof(unsigned int),
  63                 .mode           = 0644,
  64                 .proc_handler   = proc_dointvec_jiffies,
  65         },
  66         {
  67                 .procname       = "nf_conntrack_frag6_low_thresh",
  68                 .data           = &init_net.nf_frag.frags.low_thresh,
  69                 .maxlen         = sizeof(unsigned long),
  70                 .mode           = 0644,
  71                 .proc_handler   = proc_doulongvec_minmax,
  72                 .extra2         = &init_net.nf_frag.frags.high_thresh
  73         },
  74         {
  75                 .procname       = "nf_conntrack_frag6_high_thresh",
  76                 .data           = &init_net.nf_frag.frags.high_thresh,
  77                 .maxlen         = sizeof(unsigned long),
  78                 .mode           = 0644,
  79                 .proc_handler   = proc_doulongvec_minmax,
  80                 .extra1         = &init_net.nf_frag.frags.low_thresh
  81         },
  82         { }
  83 };
  84
  85 static int nf_ct_frag6_sysctl_register(struct net *net)
  86 {
  87         struct ctl_table *table;
  88         struct ctl_table_header *hdr;
  89
  90         table = nf_ct_frag6_sysctl_table;
  91         if (!net_eq(net, &init_net)) {
  92                 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
  93                                 GFP_KERNEL);
  94                 if (table == NULL)
  95                         goto err_alloc;
  96
  97                 table[0].data = &net->nf_frag.frags.timeout;
  98                 table[1].data = &net->nf_frag.frags.low_thresh;
  99                 table[1].extra2 = &net->nf_frag.frags.high_thresh;
 100                 table[2].data = &net->nf_frag.frags.high_thresh;
 101                 table[2].extra1 = &net->nf_frag.frags.low_thresh;
 102                 table[2].extra2 = &init_net.nf_frag.frags.high_thresh;
 103         }
 104
 105         hdr = register_net_sysctl(net, "net/netfilter", table);
 106         if (hdr == NULL)
 107                 goto err_reg;
 108
 109         net->nf_frag_frags_hdr = hdr;
 110         return 0;
 111
 112 err_reg:
 113         if (!net_eq(net, &init_net))
 114                 kfree(table);
 115 err_alloc:
 116         return -ENOMEM;
 117 }
 118
 119 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
 120 {
 121         struct ctl_table *table;
 122
 123         table = net->nf_frag_frags_hdr->ctl_table_arg;
 124         unregister_net_sysctl_table(net->nf_frag_frags_hdr);
 125         if (!net_eq(net, &init_net))
 126                 kfree(table);
 127 }
 128
 129 #else
 130 static int nf_ct_frag6_sysctl_register(struct net *net)
 131 {
 132         return 0;
 133 }
 134 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
 135 {
 136 }
 137 #endif
 138
 139 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
 140                              struct sk_buff *prev_tail, struct net_device *dev);
 141
 142 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
 143 {
 144         return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
 145 }
 146
 147 static void nf_ct_frag6_expire(unsigned long data)
 148 {
 149         struct frag_queue *fq;
 150         struct net *net;
 151
 152         fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
 153         net = container_of(fq->q.net, struct net, nf_frag.frags);
 154
 155         ip6frag_expire_frag_queue(net, fq);
 156 }
 157
 158 /* Creation primitives. */
 159 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
 160                                   const struct ipv6hdr *hdr, int iif)
 161 {
 162         struct frag_v6_compare_key key = {
 163                 .id = id,
 164                 .saddr = hdr->saddr,
 165                 .daddr = hdr->daddr,
 166                 .user = user,
 167                 .iif = iif,
 168         };
 169         struct inet_frag_queue *q;
 170
 171         q = inet_frag_find(&net->nf_frag.frags, &key);
 172         if (!q)
 173                 return NULL;
 174
 175         return container_of(q, struct frag_queue, q);
 176 }
 177
 178
 179 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
 180                              const struct frag_hdr *fhdr, int nhoff)
 181 {
 182         unsigned int payload_len;
 183         struct net_device *dev;
 184         struct sk_buff *prev;
 185         int offset, end, err;
 186         u8 ecn;
 187
 188         if (fq->q.flags & INET_FRAG_COMPLETE) {
 189                 pr_debug("Already completed\n");
 190                 goto err;
 191         }
 192
 193         payload_len = ntohs(ipv6_hdr(skb)->payload_len);
 194
 195         offset = ntohs(fhdr->frag_off) & ~0x7;
 196         end = offset + (payload_len -
 197                         ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
 198
 199         if ((unsigned int)end > IPV6_MAXPLEN) {
 200                 pr_debug("offset is too large.\n");
 201                 return -EINVAL;
 202         }
 203
 204         ecn = ip6_frag_ecn(ipv6_hdr(skb));
 205
 206         if (skb->ip_summed == CHECKSUM_COMPLETE) {
 207                 const unsigned char *nh = skb_network_header(skb);
 208                 skb->csum = csum_sub(skb->csum,
 209                                      csum_partial(nh, (u8 *)(fhdr + 1) - nh,
 210                                                   0));
 211         }
 212
 213         /* Is this the final fragment? */
 214         if (!(fhdr->frag_off & htons(IP6_MF))) {
 215                 /* If we already have some bits beyond end
 216                  * or have different end, the segment is corrupted.
 217                  */
 218                 if (end < fq->q.len ||
 219                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
 220                         pr_debug("already received last fragment\n");
 221                         goto err;
 222                 }
 223                 fq->q.flags |= INET_FRAG_LAST_IN;
 224                 fq->q.len = end;
 225         } else {
 226                 /* Check if the fragment is rounded to 8 bytes.
 227                  * Required by the RFC.
 228                  */
 229                 if (end & 0x7) {
 230                         /* RFC2460 says always send parameter problem in
 231                          * this case. -DaveM
 232                          */
 233                         pr_debug("end of fragment not rounded to 8 bytes.\n");
 234                         inet_frag_kill(&fq->q);
 235                         return -EPROTO;
 236                 }
 237                 if (end > fq->q.len) {
 238                         /* Some bits beyond end -> corruption. */
 239                         if (fq->q.flags & INET_FRAG_LAST_IN) {
 240                                 pr_debug("last packet already reached.\n");
 241                                 goto err;
 242                         }
 243                         fq->q.len = end;
 244                 }
 245         }
 246
 247         if (end == offset)
 248                 goto err;
 249
 250         /* Point into the IP datagram 'data' part. */
 251         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
 252                 pr_debug("queue: message is too short.\n");
 253                 goto err;
 254         }
 255         if (pskb_trim_rcsum(skb, end - offset)) {
 256                 pr_debug("Can't trim\n");
 257                 goto err;
 258         }
 259
 260         /* Note : skb->rbnode and skb->dev share the same location. */
 261         dev = skb->dev;
 262         /* Makes sure compiler wont do silly aliasing games */
 263         barrier();
 264
 265         prev = fq->q.fragments_tail;
 266         err = inet_frag_queue_insert(&fq->q, skb, offset, end);
 267         if (err) {
 268                 if (err == IPFRAG_DUP) {
 269                         /* No error for duplicates, pretend they got queued. */
 270                         kfree_skb(skb);
 271                         return -EINPROGRESS;
 272                 }
 273                 goto insert_error;
 274         }
 275
 276         if (dev)
 277                 fq->iif = dev->ifindex;
 278
 279         fq->q.stamp = skb->tstamp;
 280         fq->q.meat += skb->len;
 281         fq->ecn |= ecn;
 282         if (payload_len > fq->q.max_size)
 283                 fq->q.max_size = payload_len;
 284         add_frag_mem_limit(fq->q.net, skb->truesize);
 285
 286         /* The first fragment.
 287          * nhoffset is obtained from the first fragment, of course.
 288          */
 289         if (offset == 0) {
 290                 fq->nhoffset = nhoff;
 291                 fq->q.flags |= INET_FRAG_FIRST_IN;
 292         }
 293
 294         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 295             fq->q.meat == fq->q.len) {
 296                 unsigned long orefdst = skb->_skb_refdst;
 297
 298                 skb->_skb_refdst = 0UL;
 299                 err = nf_ct_frag6_reasm(fq, skb, prev, dev);
 300                 skb->_skb_refdst = orefdst;
 301
 302                 /* After queue has assumed skb ownership, only 0 or
 303                  * -EINPROGRESS must be returned.
 304                  */
 305                 return err ? -EINPROGRESS : 0;
 306         }
 307
 308         skb_dst_drop(skb);
 309         return -EINPROGRESS;
 310
 311 insert_error:
 312         inet_frag_kill(&fq->q);
 313 err:
 314         skb_dst_drop(skb);
 315         return -EINVAL;
 316 }
 317
 318 /*
 319  *      Check if this packet is complete.
 320  *
 321  *      It is called with locked fq, and caller must check that
 322  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 323  *      the last and the first frames arrived and all the bits are here.
 324  */
 325 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
 326                              struct sk_buff *prev_tail, struct net_device *dev)
 327 {
 328         void *reasm_data;
 329         int payload_len;
 330         u8 ecn;
 331
 332         inet_frag_kill(&fq->q);
 333
 334         ecn = ip_frag_ecn_table[fq->ecn];
 335         if (unlikely(ecn == 0xff))
 336                 goto err;
 337
 338         reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
 339         if (!reasm_data)
 340                 goto err;
 341
 342         payload_len = ((skb->data - skb_network_header(skb)) -
 343                        sizeof(struct ipv6hdr) + fq->q.len -
 344                        sizeof(struct frag_hdr));
 345         if (payload_len > IPV6_MAXPLEN) {
 346                 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
 347                                     payload_len);
 348                 goto err;
 349         }
 350
 351         /* We have to remove fragment header from datagram and to relocate
 352          * header in order to calculate ICV correctly. */
 353         skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0];
 354         memmove(skb->head + sizeof(struct frag_hdr), skb->head,
 355                 (skb->data - skb->head) - sizeof(struct frag_hdr));
 356         skb->mac_header += sizeof(struct frag_hdr);
 357         skb->network_header += sizeof(struct frag_hdr);
 358
 359         skb_reset_transport_header(skb);
 360
 361         inet_frag_reasm_finish(&fq->q, skb, reasm_data);
 362
 363         skb->ignore_df = 1;
 364         skb->dev = dev;
 365         ipv6_hdr(skb)->payload_len = htons(payload_len);
 366         ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
 367         IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
 368
 369         /* Yes, and fold redundant checksum back. 8) */
 370         if (skb->ip_summed == CHECKSUM_COMPLETE)
 371                 skb->csum = csum_partial(skb_network_header(skb),
 372                                          skb_network_header_len(skb),
 373                                          skb->csum);
 374
 375         fq->q.fragments = NULL;
 376         fq->q.rb_fragments = RB_ROOT;
 377         fq->q.fragments_tail = NULL;
 378         fq->q.last_run_head = NULL;
 379
 380         return 0;
 381
 382 err:
 383         inet_frag_kill(&fq->q);
 384         return -EINVAL;
 385 }
 386
 387 /*
 388  * find the header just before Fragment Header.
 389  *
 390  * if success return 0 and set ...
 391  * (*prevhdrp): the value of "Next Header Field" in the header
 392  *              just before Fragment Header.
 393  * (*prevhoff): the offset of "Next Header Field" in the header
 394  *              just before Fragment Header.
 395  * (*fhoff)   : the offset of Fragment Header.
 396  *
 397  * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
 398  *
 399  */
 400 static int
 401 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
 402 {
 403         u8 nexthdr = ipv6_hdr(skb)->nexthdr;
 404         const int netoff = skb_network_offset(skb);
 405         u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
 406         int start = netoff + sizeof(struct ipv6hdr);
 407         int len = skb->len - start;
 408         u8 prevhdr = NEXTHDR_IPV6;
 409
 410         while (nexthdr != NEXTHDR_FRAGMENT) {
 411                 struct ipv6_opt_hdr hdr;
 412                 int hdrlen;
 413
 414                 if (!ipv6_ext_hdr(nexthdr)) {
 415                         return -1;
 416                 }
 417                 if (nexthdr == NEXTHDR_NONE) {
 418                         pr_debug("next header is none\n");
 419                         return -1;
 420                 }
 421                 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
 422                         pr_debug("too short\n");
 423                         return -1;
 424                 }
 425                 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
 426                         BUG();
 427                 if (nexthdr == NEXTHDR_AUTH)
 428                         hdrlen = (hdr.hdrlen+2)<<2;
 429                 else
 430                         hdrlen = ipv6_optlen(&hdr);
 431
 432                 prevhdr = nexthdr;
 433                 prev_nhoff = start;
 434
 435                 nexthdr = hdr.nexthdr;
 436                 len -= hdrlen;
 437                 start += hdrlen;
 438         }
 439
 440         if (len < 0)
 441                 return -1;
 442
 443         *prevhdrp = prevhdr;
 444         *prevhoff = prev_nhoff;
 445         *fhoff = start;
 446
 447         return 0;
 448 }
 449
 450 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 451 {
 452         u16 savethdr = skb->transport_header;
 453         int fhoff, nhoff, ret;
 454         struct frag_hdr *fhdr;
 455         struct frag_queue *fq;
 456         struct ipv6hdr *hdr;
 457         u8 prevhdr;
 458
 459         /* Jumbo payload inhibits frag. header */
 460         if (ipv6_hdr(skb)->payload_len == 0) {
 461                 pr_debug("payload len = 0\n");
 462                 return 0;
 463         }
 464
 465         if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
 466                 return 0;
 467
 468         if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
 469                 return -ENOMEM;
 470
 471         skb_set_transport_header(skb, fhoff);
 472         hdr = ipv6_hdr(skb);
 473         fhdr = (struct frag_hdr *)skb_transport_header(skb);
 474
 475         skb_orphan(skb);
 476         fq = fq_find(net, fhdr->identification, user, hdr,
 477                      skb->dev ? skb->dev->ifindex : 0);
 478         if (fq == NULL) {
 479                 pr_debug("Can't find and can't create new queue\n");
 480                 return -ENOMEM;
 481         }
 482
 483         spin_lock_bh(&fq->q.lock);
 484
 485         ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
 486         if (ret == -EPROTO) {
 487                 skb->transport_header = savethdr;
 488                 ret = 0;
 489         }
 490
 491         spin_unlock_bh(&fq->q.lock);
 492         inet_frag_put(&fq->q);
 493         return ret;
 494 }
 495 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
 496
 497 static int nf_ct_net_init(struct net *net)
 498 {
 499         int res;
 500
 501         net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 502         net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 503         net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
 504         net->nf_frag.frags.f = &nf_frags;
 505
 506         res = inet_frags_init_net(&net->nf_frag.frags);
 507         if (res < 0)
 508                 return res;
 509         res = nf_ct_frag6_sysctl_register(net);
 510         if (res < 0)
 511                 inet_frags_exit_net(&net->nf_frag.frags);
 512         return res;
 513 }
 514
 515 static void nf_ct_net_exit(struct net *net)
 516 {
 517         nf_ct_frags6_sysctl_unregister(net);
 518         inet_frags_exit_net(&net->nf_frag.frags);
 519 }
 520
 521 static struct pernet_operations nf_ct_net_ops = {
 522         .init = nf_ct_net_init,
 523         .exit = nf_ct_net_exit,
 524 };
 525
 526 static const struct rhashtable_params nfct_rhash_params = {
 527         .head_offset            = offsetof(struct inet_frag_queue, node),
 528         .hashfn                 = ip6frag_key_hashfn,
 529         .obj_hashfn             = ip6frag_obj_hashfn,
 530         .obj_cmpfn              = ip6frag_obj_cmpfn,
 531         .automatic_shrinking    = true,
 532 };
 533
 534 int nf_ct_frag6_init(void)
 535 {
 536         int ret = 0;
 537
 538         nf_frags.constructor = ip6frag_init;
 539         nf_frags.destructor = NULL;
 540         nf_frags.qsize = sizeof(struct frag_queue);
 541         nf_frags.frag_expire = nf_ct_frag6_expire;
 542         nf_frags.frags_cache_name = nf_frags_cache_name;
 543         nf_frags.rhash_params = nfct_rhash_params;
 544         ret = inet_frags_init(&nf_frags);
 545         if (ret)
 546                 goto out;
 547         ret = register_pernet_subsys(&nf_ct_net_ops);
 548         if (ret)
 549                 inet_frags_fini(&nf_frags);
 550
 551 out:
 552         return ret;
 553 }
 554
 555 void nf_ct_frag6_cleanup(void)
 556 {
 557         unregister_pernet_subsys(&nf_ct_net_ops);
 558         inet_frags_fini(&nf_frags);
 559 }