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