ipv6/netfilter/nf_conntrack_reasm.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * IPv6 fragment reassembly for connection tracking
   4  *
   5  * Copyright (C)2004 USAGI/WIDE Project
   6  *
   7  * Author:
   8  *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
   9  *
  10  * Based on: net/ipv6/reassembly.c
  11  */
  12
  13 #define pr_fmt(fmt) "IPv6-nf: " fmt
  14
  15 #include <linux/errno.h>
  16 #include <linux/types.h>
  17 #include <linux/string.h>
  18 #include <linux/net.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/ipv6.h>
  21 #include <linux/slab.h>
  22
  23 #include <net/ipv6_frag.h>
  24
  25 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  26 #include <linux/sysctl.h>
  27 #include <linux/netfilter.h>
  28 #include <linux/netfilter_ipv6.h>
  29 #include <linux/kernel.h>
  30 #include <linux/module.h>
  31 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  32 #include <net/netns/generic.h>
  33
  34 static const char nf_frags_cache_name[] = "nf-frags";
  35
  36 static unsigned int nf_frag_pernet_id __read_mostly;
  37 static struct inet_frags nf_frags;
  38
  39 static struct nft_ct_frag6_pernet *nf_frag_pernet(struct net *net)
  40 {
  41         return net_generic(net, nf_frag_pernet_id);
  42 }
  43
  44 #ifdef CONFIG_SYSCTL
  45
  46 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
  47         {
  48                 .procname       = "nf_conntrack_frag6_timeout",
  49                 .maxlen         = sizeof(unsigned int),
  50                 .mode           = 0644,
  51                 .proc_handler   = proc_dointvec_jiffies,
  52         },
  53         {
  54                 .procname       = "nf_conntrack_frag6_low_thresh",
  55                 .maxlen         = sizeof(unsigned long),
  56                 .mode           = 0644,
  57                 .proc_handler   = proc_doulongvec_minmax,
  58         },
  59         {
  60                 .procname       = "nf_conntrack_frag6_high_thresh",
  61                 .maxlen         = sizeof(unsigned long),
  62                 .mode           = 0644,
  63                 .proc_handler   = proc_doulongvec_minmax,
  64         },
  65         { }
  66 };
  67
  68 static int nf_ct_frag6_sysctl_register(struct net *net)
  69 {
  70         struct nft_ct_frag6_pernet *nf_frag;
  71         struct ctl_table *table;
  72         struct ctl_table_header *hdr;
  73
  74         table = nf_ct_frag6_sysctl_table;
  75         if (!net_eq(net, &init_net)) {
  76                 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
  77                                 GFP_KERNEL);
  78                 if (table == NULL)
  79                         goto err_alloc;
  80         }
  81
  82         nf_frag = nf_frag_pernet(net);
  83
  84         table[0].data   = &nf_frag->fqdir->timeout;
  85         table[1].data   = &nf_frag->fqdir->low_thresh;
  86         table[1].extra2 = &nf_frag->fqdir->high_thresh;
  87         table[2].data   = &nf_frag->fqdir->high_thresh;
  88         table[2].extra1 = &nf_frag->fqdir->low_thresh;
  89
  90         hdr = register_net_sysctl_sz(net, "net/netfilter", table,
  91                                      ARRAY_SIZE(nf_ct_frag6_sysctl_table));
  92         if (hdr == NULL)
  93                 goto err_reg;
  94
  95         nf_frag->nf_frag_frags_hdr = hdr;
  96         return 0;
  97
  98 err_reg:
  99         if (!net_eq(net, &init_net))
 100                 kfree(table);
 101 err_alloc:
 102         return -ENOMEM;
 103 }
 104
 105 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
 106 {
 107         struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
 108         struct ctl_table *table;
 109
 110         table = nf_frag->nf_frag_frags_hdr->ctl_table_arg;
 111         unregister_net_sysctl_table(nf_frag->nf_frag_frags_hdr);
 112         if (!net_eq(net, &init_net))
 113                 kfree(table);
 114 }
 115
 116 #else
 117 static int nf_ct_frag6_sysctl_register(struct net *net)
 118 {
 119         return 0;
 120 }
 121 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
 122 {
 123 }
 124 #endif
 125
 126 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
 127                              struct sk_buff *prev_tail, struct net_device *dev);
 128
 129 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
 130 {
 131         return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
 132 }
 133
 134 static void nf_ct_frag6_expire(struct timer_list *t)
 135 {
 136         struct inet_frag_queue *frag = from_timer(frag, t, timer);
 137         struct frag_queue *fq;
 138
 139         fq = container_of(frag, struct frag_queue, q);
 140
 141         ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
 142 }
 143
 144 /* Creation primitives. */
 145 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
 146                                   const struct ipv6hdr *hdr, int iif)
 147 {
 148         struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
 149         struct frag_v6_compare_key key = {
 150                 .id = id,
 151                 .saddr = hdr->saddr,
 152                 .daddr = hdr->daddr,
 153                 .user = user,
 154                 .iif = iif,
 155         };
 156         struct inet_frag_queue *q;
 157
 158         q = inet_frag_find(nf_frag->fqdir, &key);
 159         if (!q)
 160                 return NULL;
 161
 162         return container_of(q, struct frag_queue, q);
 163 }
 164
 165
 166 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
 167                              const struct frag_hdr *fhdr, int nhoff)
 168 {
 169         unsigned int payload_len;
 170         struct net_device *dev;
 171         struct sk_buff *prev;
 172         int offset, end, err;
 173         u8 ecn;
 174
 175         if (fq->q.flags & INET_FRAG_COMPLETE) {
 176                 pr_debug("Already completed\n");
 177                 goto err;
 178         }
 179
 180         payload_len = ntohs(ipv6_hdr(skb)->payload_len);
 181
 182         offset = ntohs(fhdr->frag_off) & ~0x7;
 183         end = offset + (payload_len -
 184                         ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
 185
 186         if ((unsigned int)end > IPV6_MAXPLEN) {
 187                 pr_debug("offset is too large.\n");
 188                 return -EINVAL;
 189         }
 190
 191         ecn = ip6_frag_ecn(ipv6_hdr(skb));
 192
 193         if (skb->ip_summed == CHECKSUM_COMPLETE) {
 194                 const unsigned char *nh = skb_network_header(skb);
 195                 skb->csum = csum_sub(skb->csum,
 196                                      csum_partial(nh, (u8 *)(fhdr + 1) - nh,
 197                                                   0));
 198         }
 199
 200         /* Is this the final fragment? */
 201         if (!(fhdr->frag_off & htons(IP6_MF))) {
 202                 /* If we already have some bits beyond end
 203                  * or have different end, the segment is corrupted.
 204                  */
 205                 if (end < fq->q.len ||
 206                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
 207                         pr_debug("already received last fragment\n");
 208                         goto err;
 209                 }
 210                 fq->q.flags |= INET_FRAG_LAST_IN;
 211                 fq->q.len = end;
 212         } else {
 213                 /* Check if the fragment is rounded to 8 bytes.
 214                  * Required by the RFC.
 215                  */
 216                 if (end & 0x7) {
 217                         /* RFC2460 says always send parameter problem in
 218                          * this case. -DaveM
 219                          */
 220                         pr_debug("end of fragment not rounded to 8 bytes.\n");
 221                         inet_frag_kill(&fq->q);
 222                         return -EPROTO;
 223                 }
 224                 if (end > fq->q.len) {
 225                         /* Some bits beyond end -> corruption. */
 226                         if (fq->q.flags & INET_FRAG_LAST_IN) {
 227                                 pr_debug("last packet already reached.\n");
 228                                 goto err;
 229                         }
 230                         fq->q.len = end;
 231                 }
 232         }
 233
 234         if (end == offset)
 235                 goto err;
 236
 237         /* Point into the IP datagram 'data' part. */
 238         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
 239                 pr_debug("queue: message is too short.\n");
 240                 goto err;
 241         }
 242         if (pskb_trim_rcsum(skb, end - offset)) {
 243                 pr_debug("Can't trim\n");
 244                 goto err;
 245         }
 246
 247         /* Note : skb->rbnode and skb->dev share the same location. */
 248         dev = skb->dev;
 249         /* Makes sure compiler wont do silly aliasing games */
 250         barrier();
 251
 252         prev = fq->q.fragments_tail;
 253         err = inet_frag_queue_insert(&fq->q, skb, offset, end);
 254         if (err) {
 255                 if (err == IPFRAG_DUP) {
 256                         /* No error for duplicates, pretend they got queued. */
 257                         kfree_skb_reason(skb, SKB_DROP_REASON_DUP_FRAG);
 258                         return -EINPROGRESS;
 259                 }
 260                 goto insert_error;
 261         }
 262
 263         if (dev)
 264                 fq->iif = dev->ifindex;
 265
 266         fq->q.stamp = skb->tstamp;
 267         fq->q.mono_delivery_time = skb->mono_delivery_time;
 268         fq->q.meat += skb->len;
 269         fq->ecn |= ecn;
 270         if (payload_len > fq->q.max_size)
 271                 fq->q.max_size = payload_len;
 272         add_frag_mem_limit(fq->q.fqdir, skb->truesize);
 273
 274         /* The first fragment.
 275          * nhoffset is obtained from the first fragment, of course.
 276          */
 277         if (offset == 0) {
 278                 fq->nhoffset = nhoff;
 279                 fq->q.flags |= INET_FRAG_FIRST_IN;
 280         }
 281
 282         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 283             fq->q.meat == fq->q.len) {
 284                 unsigned long orefdst = skb->_skb_refdst;
 285
 286                 skb->_skb_refdst = 0UL;
 287                 err = nf_ct_frag6_reasm(fq, skb, prev, dev);
 288                 skb->_skb_refdst = orefdst;
 289
 290                 /* After queue has assumed skb ownership, only 0 or
 291                  * -EINPROGRESS must be returned.
 292                  */
 293                 return err ? -EINPROGRESS : 0;
 294         }
 295
 296         skb_dst_drop(skb);
 297         skb_orphan(skb);
 298         return -EINPROGRESS;
 299
 300 insert_error:
 301         inet_frag_kill(&fq->q);
 302 err:
 303         skb_dst_drop(skb);
 304         return -EINVAL;
 305 }
 306
 307 /*
 308  *      Check if this packet is complete.
 309  *
 310  *      It is called with locked fq, and caller must check that
 311  *      queue is eligible for reassembly i.e. it is not COMPLETE,
 312  *      the last and the first frames arrived and all the bits are here.
 313  */
 314 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
 315                              struct sk_buff *prev_tail, struct net_device *dev)
 316 {
 317         void *reasm_data;
 318         int payload_len;
 319         u8 ecn;
 320
 321         inet_frag_kill(&fq->q);
 322
 323         ecn = ip_frag_ecn_table[fq->ecn];
 324         if (unlikely(ecn == 0xff))
 325                 goto err;
 326
 327         reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
 328         if (!reasm_data)
 329                 goto err;
 330
 331         payload_len = ((skb->data - skb_network_header(skb)) -
 332                        sizeof(struct ipv6hdr) + fq->q.len -
 333                        sizeof(struct frag_hdr));
 334         if (payload_len > IPV6_MAXPLEN) {
 335                 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
 336                                     payload_len);
 337                 goto err;
 338         }
 339
 340         /* We have to remove fragment header from datagram and to relocate
 341          * header in order to calculate ICV correctly. */
 342         skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0];
 343         memmove(skb->head + sizeof(struct frag_hdr), skb->head,
 344                 (skb->data - skb->head) - sizeof(struct frag_hdr));
 345         skb->mac_header += sizeof(struct frag_hdr);
 346         skb->network_header += sizeof(struct frag_hdr);
 347
 348         skb_reset_transport_header(skb);
 349
 350         inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
 351
 352         skb->ignore_df = 1;
 353         skb->dev = dev;
 354         ipv6_hdr(skb)->payload_len = htons(payload_len);
 355         ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
 356         IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
 357         IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
 358
 359         /* Yes, and fold redundant checksum back. 8) */
 360         if (skb->ip_summed == CHECKSUM_COMPLETE)
 361                 skb->csum = csum_partial(skb_network_header(skb),
 362                                          skb_network_header_len(skb),
 363                                          skb->csum);
 364
 365         fq->q.rb_fragments = RB_ROOT;
 366         fq->q.fragments_tail = NULL;
 367         fq->q.last_run_head = NULL;
 368
 369         return 0;
 370
 371 err:
 372         inet_frag_kill(&fq->q);
 373         return -EINVAL;
 374 }
 375
 376 /*
 377  * find the header just before Fragment Header.
 378  *
 379  * if success return 0 and set ...
 380  * (*prevhdrp): the value of "Next Header Field" in the header
 381  *              just before Fragment Header.
 382  * (*prevhoff): the offset of "Next Header Field" in the header
 383  *              just before Fragment Header.
 384  * (*fhoff)   : the offset of Fragment Header.
 385  *
 386  * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
 387  *
 388  */
 389 static int
 390 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
 391 {
 392         u8 nexthdr = ipv6_hdr(skb)->nexthdr;
 393         const int netoff = skb_network_offset(skb);
 394         u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
 395         int start = netoff + sizeof(struct ipv6hdr);
 396         int len = skb->len - start;
 397         u8 prevhdr = NEXTHDR_IPV6;
 398
 399         while (nexthdr != NEXTHDR_FRAGMENT) {
 400                 struct ipv6_opt_hdr hdr;
 401                 int hdrlen;
 402
 403                 if (!ipv6_ext_hdr(nexthdr)) {
 404                         return -1;
 405                 }
 406                 if (nexthdr == NEXTHDR_NONE) {
 407                         pr_debug("next header is none\n");
 408                         return -1;
 409                 }
 410                 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
 411                         pr_debug("too short\n");
 412                         return -1;
 413                 }
 414                 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
 415                         BUG();
 416                 if (nexthdr == NEXTHDR_AUTH)
 417                         hdrlen = ipv6_authlen(&hdr);
 418                 else
 419                         hdrlen = ipv6_optlen(&hdr);
 420
 421                 prevhdr = nexthdr;
 422                 prev_nhoff = start;
 423
 424                 nexthdr = hdr.nexthdr;
 425                 len -= hdrlen;
 426                 start += hdrlen;
 427         }
 428
 429         if (len < 0)
 430                 return -1;
 431
 432         *prevhdrp = prevhdr;
 433         *prevhoff = prev_nhoff;
 434         *fhoff = start;
 435
 436         return 0;
 437 }
 438
 439 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 440 {
 441         u16 savethdr = skb->transport_header;
 442         u8 nexthdr = NEXTHDR_FRAGMENT;
 443         int fhoff, nhoff, ret;
 444         struct frag_hdr *fhdr;
 445         struct frag_queue *fq;
 446         struct ipv6hdr *hdr;
 447         u8 prevhdr;
 448
 449         /* Jumbo payload inhibits frag. header */
 450         if (ipv6_hdr(skb)->payload_len == 0) {
 451                 pr_debug("payload len = 0\n");
 452                 return 0;
 453         }
 454
 455         if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
 456                 return 0;
 457
 458         /* Discard the first fragment if it does not include all headers
 459          * RFC 8200, Section 4.5
 460          */
 461         if (ipv6frag_thdr_truncated(skb, fhoff, &nexthdr)) {
 462                 pr_debug("Drop incomplete fragment\n");
 463                 return 0;
 464         }
 465
 466         if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
 467                 return -ENOMEM;
 468
 469         skb_set_transport_header(skb, fhoff);
 470         hdr = ipv6_hdr(skb);
 471         fhdr = (struct frag_hdr *)skb_transport_header(skb);
 472
 473         fq = fq_find(net, fhdr->identification, user, hdr,
 474                      skb->dev ? skb->dev->ifindex : 0);
 475         if (fq == NULL) {
 476                 pr_debug("Can't find and can't create new queue\n");
 477                 return -ENOMEM;
 478         }
 479
 480         spin_lock_bh(&fq->q.lock);
 481
 482         ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
 483         if (ret == -EPROTO) {
 484                 skb->transport_header = savethdr;
 485                 ret = 0;
 486         }
 487
 488         spin_unlock_bh(&fq->q.lock);
 489         inet_frag_put(&fq->q);
 490         return ret;
 491 }
 492 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
 493
 494 static int nf_ct_net_init(struct net *net)
 495 {
 496         struct nft_ct_frag6_pernet *nf_frag  = nf_frag_pernet(net);
 497         int res;
 498
 499         res = fqdir_init(&nf_frag->fqdir, &nf_frags, net);
 500         if (res < 0)
 501                 return res;
 502
 503         nf_frag->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
 504         nf_frag->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
 505         nf_frag->fqdir->timeout = IPV6_FRAG_TIMEOUT;
 506
 507         res = nf_ct_frag6_sysctl_register(net);
 508         if (res < 0)
 509                 fqdir_exit(nf_frag->fqdir);
 510         return res;
 511 }
 512
 513 static void nf_ct_net_pre_exit(struct net *net)
 514 {
 515         struct nft_ct_frag6_pernet *nf_frag  = nf_frag_pernet(net);
 516
 517         fqdir_pre_exit(nf_frag->fqdir);
 518 }
 519
 520 static void nf_ct_net_exit(struct net *net)
 521 {
 522         struct nft_ct_frag6_pernet *nf_frag  = nf_frag_pernet(net);
 523
 524         nf_ct_frags6_sysctl_unregister(net);
 525         fqdir_exit(nf_frag->fqdir);
 526 }
 527
 528 static struct pernet_operations nf_ct_net_ops = {
 529         .init           = nf_ct_net_init,
 530         .pre_exit       = nf_ct_net_pre_exit,
 531         .exit           = nf_ct_net_exit,
 532         .id             = &nf_frag_pernet_id,
 533         .size           = sizeof(struct nft_ct_frag6_pernet),
 534 };
 535
 536 static const struct rhashtable_params nfct_rhash_params = {
 537         .head_offset            = offsetof(struct inet_frag_queue, node),
 538         .hashfn                 = ip6frag_key_hashfn,
 539         .obj_hashfn             = ip6frag_obj_hashfn,
 540         .obj_cmpfn              = ip6frag_obj_cmpfn,
 541         .automatic_shrinking    = true,
 542 };
 543
 544 int nf_ct_frag6_init(void)
 545 {
 546         int ret = 0;
 547
 548         nf_frags.constructor = ip6frag_init;
 549         nf_frags.destructor = NULL;
 550         nf_frags.qsize = sizeof(struct frag_queue);
 551         nf_frags.frag_expire = nf_ct_frag6_expire;
 552         nf_frags.frags_cache_name = nf_frags_cache_name;
 553         nf_frags.rhash_params = nfct_rhash_params;
 554         ret = inet_frags_init(&nf_frags);
 555         if (ret)
 556                 goto out;
 557         ret = register_pernet_subsys(&nf_ct_net_ops);
 558         if (ret)
 559                 inet_frags_fini(&nf_frags);
 560
 561 out:
 562         return ret;
 563 }
 564
 565 void nf_ct_frag6_cleanup(void)
 566 {
 567         unregister_pernet_subsys(&nf_ct_net_ops);
 568         inet_frags_fini(&nf_frags);
 569 }