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                 .data           = &init_net.nf_frag.frags.timeout,
  58                 .maxlen         = sizeof(unsigned int),
  59                 .mode           = 0644,
  60                 .proc_handler   = proc_dointvec_jiffies,
  61         },
  62         {
  63                 .procname       = "nf_conntrack_frag6_low_thresh",
  64                 .data           = &init_net.nf_frag.frags.low_thresh,
  65                 .maxlen         = sizeof(unsigned long),
  66                 .mode           = 0644,
  67                 .proc_handler   = proc_doulongvec_minmax,
  68                 .extra2         = &init_net.nf_frag.frags.high_thresh
  69         },
  70         {
  71                 .procname       = "nf_conntrack_frag6_high_thresh",
  72                 .data           = &init_net.nf_frag.frags.high_thresh,
  73                 .maxlen         = sizeof(unsigned long),
  74                 .mode           = 0644,
  75                 .proc_handler   = proc_doulongvec_minmax,
  76                 .extra1         = &init_net.nf_frag.frags.low_thresh
  77         },
  78         { }
  79 };
  80
  81 static int nf_ct_frag6_sysctl_register(struct net *net)
  82 {
  83         struct ctl_table *table;
  84         struct ctl_table_header *hdr;
  85
  86         table = nf_ct_frag6_sysctl_table;
  87         if (!net_eq(net, &init_net)) {
  88                 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
  89                                 GFP_KERNEL);
  90                 if (table == NULL)
  91                         goto err_alloc;
  92
  93                 table[0].data = &net->nf_frag.frags.timeout;
  94                 table[1].data = &net->nf_frag.frags.low_thresh;
  95                 table[1].extra2 = &net->nf_frag.frags.high_thresh;
  96                 table[2].data = &net->nf_frag.frags.high_thresh;
  97                 table[2].extra1 = &net->nf_frag.frags.low_thresh;
  98                 table[2].extra2 = &init_net.nf_frag.frags.high_thresh;
  99         }
 100
 101         hdr = register_net_sysctl(net, "net/netfilter", table);
 102         if (hdr == NULL)
 103                 goto err_reg;
 104
 105         net->nf_frag_frags_hdr = hdr;
 106         return 0;
 107
 108 err_reg:
 109         if (!net_eq(net, &init_net))
 110                 kfree(table);
 111 err_alloc:
 112         return -ENOMEM;
 113 }
 114
 115 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
 116 {
 117         struct ctl_table *table;
 118
 119         table = net->nf_frag_frags_hdr->ctl_table_arg;
 120         unregister_net_sysctl_table(net->nf_frag_frags_hdr);
 121         if (!net_eq(net, &init_net))
 122                 kfree(table);
 123 }
 124
 125 #else
 126 static int nf_ct_frag6_sysctl_register(struct net *net)
 127 {
 128         return 0;
 129 }
 130 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
 131 {
 132 }
 133 #endif
 134
 135 static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
 136                              struct sk_buff *prev_tail, struct net_device *dev);
 137
 138 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
 139 {
 140         return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
 141 }
 142
 143 static void nf_ct_frag6_expire(struct timer_list *t)
 144 {
 145         struct inet_frag_queue *frag = from_timer(frag, t, timer);
 146         struct frag_queue *fq;
 147         struct net *net;
 148
 149         fq = container_of(frag, struct frag_queue, q);
 150         net = container_of(fq->q.net, struct net, nf_frag.frags);
 151
 152         ip6frag_expire_frag_queue(net, fq);
 153 }
 154
 155 /* Creation primitives. */
 156 static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
 157                                   const struct ipv6hdr *hdr, int iif)
 158 {
 159         struct frag_v6_compare_key key = {
 160                 .id = id,
 161                 .saddr = hdr->saddr,
 162                 .daddr = hdr->daddr,
 163                 .user = user,
 164                 .iif = iif,
 165         };
 166         struct inet_frag_queue *q;
 167
 168         q = inet_frag_find(&net->nf_frag.frags, &key);
 169         if (!q)
 170                 return NULL;
 171
 172         return container_of(q, struct frag_queue, q);
 173 }
 174
 175
 176 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
 177                              const struct frag_hdr *fhdr, int nhoff)
 178 {
 179         unsigned int payload_len;
 180         struct net_device *dev;
 181         struct sk_buff *prev;
 182         int offset, end, err;
 183         u8 ecn;
 184
 185         if (fq->q.flags & INET_FRAG_COMPLETE) {
 186                 pr_debug("Already completed\n");
 187                 goto err;
 188         }
 189
 190         payload_len = ntohs(ipv6_hdr(skb)->payload_len);
 191
 192         offset = ntohs(fhdr->frag_off) & ~0x7;
 193         end = offset + (payload_len -
 194                         ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
 195
 196         if ((unsigned int)end > IPV6_MAXPLEN) {
 197                 pr_debug("offset is too large.\n");
 198                 return -EINVAL;
 199         }
 200
 201         ecn = ip6_frag_ecn(ipv6_hdr(skb));
 202
 203         if (skb->ip_summed == CHECKSUM_COMPLETE) {
 204                 const unsigned char *nh = skb_network_header(skb);
 205                 skb->csum = csum_sub(skb->csum,
 206                                      csum_partial(nh, (u8 *)(fhdr + 1) - nh,
 207                                                   0));
 208         }
 209
 210         /* Is this the final fragment? */
 211         if (!(fhdr->frag_off & htons(IP6_MF))) {
 212                 /* If we already have some bits beyond end
 213                  * or have different end, the segment is corrupted.
 214                  */
 215                 if (end < fq->q.len ||
 216                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
 217                         pr_debug("already received last fragment\n");
 218                         goto err;
 219                 }
 220                 fq->q.flags |= INET_FRAG_LAST_IN;
 221                 fq->q.len = end;
 222         } else {
 223                 /* Check if the fragment is rounded to 8 bytes.
 224                  * Required by the RFC.
 225                  */
 226                 if (end & 0x7) {
 227                         /* RFC2460 says always send parameter problem in
 228                          * this case. -DaveM
 229                          */
 230                         pr_debug("end of fragment not rounded to 8 bytes.\n");
 231                         inet_frag_kill(&fq->q);
 232                         return -EPROTO;
 233                 }
 234                 if (end > fq->q.len) {
 235                         /* Some bits beyond end -> corruption. */
 236                         if (fq->q.flags & INET_FRAG_LAST_IN) {
 237                                 pr_debug("last packet already reached.\n");
 238                                 goto err;
 239                         }
 240                         fq->q.len = end;
 241                 }
 242         }
 243
 244         if (end == offset)
 245                 goto err;
 246
 247         /* Point into the IP datagram 'data' part. */
 248         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
 249                 pr_debug("queue: message is too short.\n");
 250                 goto err;
 251         }
 252         if (pskb_trim_rcsum(skb, end - offset)) {
 253                 pr_debug("Can't trim\n");
 254                 goto err;
 255         }
 256
 257         /* Note : skb->rbnode and skb->dev share the same location. */
 258         dev = skb->dev;
 259         /* Makes sure compiler wont do silly aliasing games */
 260         barrier();
 261
 262         prev = fq->q.fragments_tail;
 263         err = inet_frag_queue_insert(&fq->q, skb, offset, end);
 264         if (err)
 265                 goto insert_error;
 266
 267         if (dev)
 268                 fq->iif = dev->ifindex;
 269
 270         fq->q.stamp = skb->tstamp;
 271         fq->q.meat += skb->len;
 272         fq->ecn |= ecn;
 273         if (payload_len > fq->q.max_size)
 274                 fq->q.max_size = payload_len;
 275         add_frag_mem_limit(fq->q.net, skb->truesize);
 276
 277         /* The first fragment.
 278          * nhoffset is obtained from the first fragment, of course.
 279          */
 280         if (offset == 0) {
 281                 fq->nhoffset = nhoff;
 282                 fq->q.flags |= INET_FRAG_FIRST_IN;
 283         }
 284
 285         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
 286             fq->q.meat == fq->q.len) {
 287                 unsigned long orefdst = skb->_skb_refdst;
 288
 289                 skb->_skb_refdst = 0UL;
 290                 err = nf_ct_frag6_reasm(fq, skb, prev, dev);
 291                 skb->_skb_refdst = orefdst;
 292                 return err;
 293         }
 294
 295         skb_dst_drop(skb);
 296         return -EINPROGRESS;
 297
 298 insert_error:
 299         if (err == IPFRAG_DUP)
 300                 goto err;
 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);
 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
 358         /* Yes, and fold redundant checksum back. 8) */
 359         if (skb->ip_summed == CHECKSUM_COMPLETE)
 360                 skb->csum = csum_partial(skb_network_header(skb),
 361                                          skb_network_header_len(skb),
 362                                          skb->csum);
 363
 364         fq->q.rb_fragments = RB_ROOT;
 365         fq->q.fragments_tail = NULL;
 366         fq->q.last_run_head = NULL;
 367
 368         return 0;
 369
 370 err:
 371         inet_frag_kill(&fq->q);
 372         return -EINVAL;
 373 }
 374
 375 /*
 376  * find the header just before Fragment Header.
 377  *
 378  * if success return 0 and set ...
 379  * (*prevhdrp): the value of "Next Header Field" in the header
 380  *              just before Fragment Header.
 381  * (*prevhoff): the offset of "Next Header Field" in the header
 382  *              just before Fragment Header.
 383  * (*fhoff)   : the offset of Fragment Header.
 384  *
 385  * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
 386  *
 387  */
 388 static int
 389 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
 390 {
 391         u8 nexthdr = ipv6_hdr(skb)->nexthdr;
 392         const int netoff = skb_network_offset(skb);
 393         u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
 394         int start = netoff + sizeof(struct ipv6hdr);
 395         int len = skb->len - start;
 396         u8 prevhdr = NEXTHDR_IPV6;
 397
 398         while (nexthdr != NEXTHDR_FRAGMENT) {
 399                 struct ipv6_opt_hdr hdr;
 400                 int hdrlen;
 401
 402                 if (!ipv6_ext_hdr(nexthdr)) {
 403                         return -1;
 404                 }
 405                 if (nexthdr == NEXTHDR_NONE) {
 406                         pr_debug("next header is none\n");
 407                         return -1;
 408                 }
 409                 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
 410                         pr_debug("too short\n");
 411                         return -1;
 412                 }
 413                 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
 414                         BUG();
 415                 if (nexthdr == NEXTHDR_AUTH)
 416                         hdrlen = (hdr.hdrlen+2)<<2;
 417                 else
 418                         hdrlen = ipv6_optlen(&hdr);
 419
 420                 prevhdr = nexthdr;
 421                 prev_nhoff = start;
 422
 423                 nexthdr = hdr.nexthdr;
 424                 len -= hdrlen;
 425                 start += hdrlen;
 426         }
 427
 428         if (len < 0)
 429                 return -1;
 430
 431         *prevhdrp = prevhdr;
 432         *prevhoff = prev_nhoff;
 433         *fhoff = start;
 434
 435         return 0;
 436 }
 437
 438 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 439 {
 440         u16 savethdr = skb->transport_header;
 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         if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
 457                 return -ENOMEM;
 458
 459         skb_set_transport_header(skb, fhoff);
 460         hdr = ipv6_hdr(skb);
 461         fhdr = (struct frag_hdr *)skb_transport_header(skb);
 462
 463         skb_orphan(skb);
 464         fq = fq_find(net, fhdr->identification, user, hdr,
 465                      skb->dev ? skb->dev->ifindex : 0);
 466         if (fq == NULL) {
 467                 pr_debug("Can't find and can't create new queue\n");
 468                 return -ENOMEM;
 469         }
 470
 471         spin_lock_bh(&fq->q.lock);
 472
 473         ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
 474         if (ret == -EPROTO) {
 475                 skb->transport_header = savethdr;
 476                 ret = 0;
 477         }
 478
 479         /* after queue has assumed skb ownership, only 0 or -EINPROGRESS
 480          * must be returned.
 481          */
 482         if (ret)
 483                 ret = -EINPROGRESS;
 484
 485         spin_unlock_bh(&fq->q.lock);
 486         inet_frag_put(&fq->q);
 487         return ret;
 488 }
 489 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
 490
 491 static int nf_ct_net_init(struct net *net)
 492 {
 493         int res;
 494
 495         net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
 496         net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
 497         net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
 498         net->nf_frag.frags.f = &nf_frags;
 499
 500         res = inet_frags_init_net(&net->nf_frag.frags);
 501         if (res < 0)
 502                 return res;
 503         res = nf_ct_frag6_sysctl_register(net);
 504         if (res < 0)
 505                 inet_frags_exit_net(&net->nf_frag.frags);
 506         return res;
 507 }
 508
 509 static void nf_ct_net_exit(struct net *net)
 510 {
 511         nf_ct_frags6_sysctl_unregister(net);
 512         inet_frags_exit_net(&net->nf_frag.frags);
 513 }
 514
 515 static struct pernet_operations nf_ct_net_ops = {
 516         .init = nf_ct_net_init,
 517         .exit = nf_ct_net_exit,
 518 };
 519
 520 static const struct rhashtable_params nfct_rhash_params = {
 521         .head_offset            = offsetof(struct inet_frag_queue, node),
 522         .hashfn                 = ip6frag_key_hashfn,
 523         .obj_hashfn             = ip6frag_obj_hashfn,
 524         .obj_cmpfn              = ip6frag_obj_cmpfn,
 525         .automatic_shrinking    = true,
 526 };
 527
 528 int nf_ct_frag6_init(void)
 529 {
 530         int ret = 0;
 531
 532         nf_frags.constructor = ip6frag_init;
 533         nf_frags.destructor = NULL;
 534         nf_frags.qsize = sizeof(struct frag_queue);
 535         nf_frags.frag_expire = nf_ct_frag6_expire;
 536         nf_frags.frags_cache_name = nf_frags_cache_name;
 537         nf_frags.rhash_params = nfct_rhash_params;
 538         ret = inet_frags_init(&nf_frags);
 539         if (ret)
 540                 goto out;
 541         ret = register_pernet_subsys(&nf_ct_net_ops);
 542         if (ret)
 543                 inet_frags_fini(&nf_frags);
 544
 545 out:
 546         return ret;
 547 }
 548
 549 void nf_ct_frag6_cleanup(void)
 550 {
 551         unregister_pernet_subsys(&nf_ct_net_ops);
 552         inet_frags_fini(&nf_frags);
 553 }