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