net/ipv4/netfilter/nf_nat_core.c

   1 /* NAT for netfilter; shared with compatibility layer. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/types.h>
  13 #include <linux/timer.h>
  14 #include <linux/skbuff.h>
  15 #include <net/checksum.h>
  16 #include <net/icmp.h>
  17 #include <net/ip.h>
  18 #include <net/tcp.h>  /* For tcp_prot in getorigdst */
  19 #include <linux/icmp.h>
  20 #include <linux/udp.h>
  21 #include <linux/jhash.h>
  22
  23 #include <linux/netfilter_ipv4.h>
  24 #include <net/netfilter/nf_conntrack.h>
  25 #include <net/netfilter/nf_conntrack_core.h>
  26 #include <net/netfilter/nf_nat.h>
  27 #include <net/netfilter/nf_nat_protocol.h>
  28 #include <net/netfilter/nf_nat_core.h>
  29 #include <net/netfilter/nf_nat_helper.h>
  30 #include <net/netfilter/nf_conntrack_helper.h>
  31 #include <net/netfilter/nf_conntrack_l3proto.h>
  32 #include <net/netfilter/nf_conntrack_l4proto.h>
  33
  34 static DEFINE_SPINLOCK(nf_nat_lock);
  35
  36 static struct nf_conntrack_l3proto *l3proto __read_mostly;
  37
  38 /* Calculated at init based on memory size */
  39 static unsigned int nf_nat_htable_size __read_mostly;
  40 static int nf_nat_vmalloced;
  41
  42 static struct hlist_head *bysource __read_mostly;
  43
  44 #define MAX_IP_NAT_PROTO 256
  45 static const struct nf_nat_protocol *nf_nat_protos[MAX_IP_NAT_PROTO]
  46                                                 __read_mostly;
  47
  48 static inline const struct nf_nat_protocol *
  49 __nf_nat_proto_find(u_int8_t protonum)
  50 {
  51         return rcu_dereference(nf_nat_protos[protonum]);
  52 }
  53
  54 const struct nf_nat_protocol *
  55 nf_nat_proto_find_get(u_int8_t protonum)
  56 {
  57         const struct nf_nat_protocol *p;
  58
  59         rcu_read_lock();
  60         p = __nf_nat_proto_find(protonum);
  61         if (!try_module_get(p->me))
  62                 p = &nf_nat_unknown_protocol;
  63         rcu_read_unlock();
  64
  65         return p;
  66 }
  67 EXPORT_SYMBOL_GPL(nf_nat_proto_find_get);
  68
  69 void
  70 nf_nat_proto_put(const struct nf_nat_protocol *p)
  71 {
  72         module_put(p->me);
  73 }
  74 EXPORT_SYMBOL_GPL(nf_nat_proto_put);
  75
  76 /* We keep an extra hash for each conntrack, for fast searching. */
  77 static inline unsigned int
  78 hash_by_src(const struct nf_conntrack_tuple *tuple)
  79 {
  80         unsigned int hash;
  81
  82         /* Original src, to ensure we map it consistently if poss. */
  83         hash = jhash_3words((__force u32)tuple->src.u3.ip,
  84                             (__force u32)tuple->src.u.all,
  85                             tuple->dst.protonum, 0);
  86         return ((u64)hash * nf_nat_htable_size) >> 32;
  87 }
  88
  89 /* Is this tuple already taken? (not by us) */
  90 int
  91 nf_nat_used_tuple(const struct nf_conntrack_tuple *tuple,
  92                   const struct nf_conn *ignored_conntrack)
  93 {
  94         /* Conntrack tracking doesn't keep track of outgoing tuples; only
  95            incoming ones.  NAT means they don't have a fixed mapping,
  96            so we invert the tuple and look for the incoming reply.
  97
  98            We could keep a separate hash if this proves too slow. */
  99         struct nf_conntrack_tuple reply;
 100
 101         nf_ct_invert_tuplepr(&reply, tuple);
 102         return nf_conntrack_tuple_taken(&reply, ignored_conntrack);
 103 }
 104 EXPORT_SYMBOL(nf_nat_used_tuple);
 105
 106 /* If we source map this tuple so reply looks like reply_tuple, will
 107  * that meet the constraints of range. */
 108 static int
 109 in_range(const struct nf_conntrack_tuple *tuple,
 110          const struct nf_nat_range *range)
 111 {
 112         const struct nf_nat_protocol *proto;
 113         int ret = 0;
 114
 115         /* If we are supposed to map IPs, then we must be in the
 116            range specified, otherwise let this drag us onto a new src IP. */
 117         if (range->flags & IP_NAT_RANGE_MAP_IPS) {
 118                 if (ntohl(tuple->src.u3.ip) < ntohl(range->min_ip) ||
 119                     ntohl(tuple->src.u3.ip) > ntohl(range->max_ip))
 120                         return 0;
 121         }
 122
 123         rcu_read_lock();
 124         proto = __nf_nat_proto_find(tuple->dst.protonum);
 125         if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED) ||
 126             proto->in_range(tuple, IP_NAT_MANIP_SRC,
 127                             &range->min, &range->max))
 128                 ret = 1;
 129         rcu_read_unlock();
 130
 131         return ret;
 132 }
 133
 134 static inline int
 135 same_src(const struct nf_conn *ct,
 136          const struct nf_conntrack_tuple *tuple)
 137 {
 138         const struct nf_conntrack_tuple *t;
 139
 140         t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
 141         return (t->dst.protonum == tuple->dst.protonum &&
 142                 t->src.u3.ip == tuple->src.u3.ip &&
 143                 t->src.u.all == tuple->src.u.all);
 144 }
 145
 146 /* Only called for SRC manip */
 147 static int
 148 find_appropriate_src(const struct nf_conntrack_tuple *tuple,
 149                      struct nf_conntrack_tuple *result,
 150                      const struct nf_nat_range *range)
 151 {
 152         unsigned int h = hash_by_src(tuple);
 153         const struct nf_conn_nat *nat;
 154         const struct nf_conn *ct;
 155         const struct hlist_node *n;
 156
 157         rcu_read_lock();
 158         hlist_for_each_entry_rcu(nat, n, &bysource[h], bysource) {
 159                 ct = nat->ct;
 160                 if (same_src(ct, tuple)) {
 161                         /* Copy source part from reply tuple. */
 162                         nf_ct_invert_tuplepr(result,
 163                                        &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 164                         result->dst = tuple->dst;
 165
 166                         if (in_range(result, range)) {
 167                                 rcu_read_unlock();
 168                                 return 1;
 169                         }
 170                 }
 171         }
 172         rcu_read_unlock();
 173         return 0;
 174 }
 175
 176 /* For [FUTURE] fragmentation handling, we want the least-used
 177    src-ip/dst-ip/proto triple.  Fairness doesn't come into it.  Thus
 178    if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports
 179    1-65535, we don't do pro-rata allocation based on ports; we choose
 180    the ip with the lowest src-ip/dst-ip/proto usage.
 181 */
 182 static void
 183 find_best_ips_proto(struct nf_conntrack_tuple *tuple,
 184                     const struct nf_nat_range *range,
 185                     const struct nf_conn *ct,
 186                     enum nf_nat_manip_type maniptype)
 187 {
 188         __be32 *var_ipp;
 189         /* Host order */
 190         u_int32_t minip, maxip, j;
 191
 192         /* No IP mapping?  Do nothing. */
 193         if (!(range->flags & IP_NAT_RANGE_MAP_IPS))
 194                 return;
 195
 196         if (maniptype == IP_NAT_MANIP_SRC)
 197                 var_ipp = &tuple->src.u3.ip;
 198         else
 199                 var_ipp = &tuple->dst.u3.ip;
 200
 201         /* Fast path: only one choice. */
 202         if (range->min_ip == range->max_ip) {
 203                 *var_ipp = range->min_ip;
 204                 return;
 205         }
 206
 207         /* Hashing source and destination IPs gives a fairly even
 208          * spread in practice (if there are a small number of IPs
 209          * involved, there usually aren't that many connections
 210          * anyway).  The consistency means that servers see the same
 211          * client coming from the same IP (some Internet Banking sites
 212          * like this), even across reboots. */
 213         minip = ntohl(range->min_ip);
 214         maxip = ntohl(range->max_ip);
 215         j = jhash_2words((__force u32)tuple->src.u3.ip,
 216                          (__force u32)tuple->dst.u3.ip, 0);
 217         j = ((u64)j * (maxip - minip + 1)) >> 32;
 218         *var_ipp = htonl(minip + j);
 219 }
 220
 221 /* Manipulate the tuple into the range given.  For NF_INET_POST_ROUTING,
 222  * we change the source to map into the range.  For NF_INET_PRE_ROUTING
 223  * and NF_INET_LOCAL_OUT, we change the destination to map into the
 224  * range.  It might not be possible to get a unique tuple, but we try.
 225  * At worst (or if we race), we will end up with a final duplicate in
 226  * __ip_conntrack_confirm and drop the packet. */
 227 static void
 228 get_unique_tuple(struct nf_conntrack_tuple *tuple,
 229                  const struct nf_conntrack_tuple *orig_tuple,
 230                  const struct nf_nat_range *range,
 231                  struct nf_conn *ct,
 232                  enum nf_nat_manip_type maniptype)
 233 {
 234         const struct nf_nat_protocol *proto;
 235
 236         /* 1) If this srcip/proto/src-proto-part is currently mapped,
 237            and that same mapping gives a unique tuple within the given
 238            range, use that.
 239
 240            This is only required for source (ie. NAT/masq) mappings.
 241            So far, we don't do local source mappings, so multiple
 242            manips not an issue.  */
 243         if (maniptype == IP_NAT_MANIP_SRC &&
 244             !(range->flags & IP_NAT_RANGE_PROTO_RANDOM)) {
 245                 if (find_appropriate_src(orig_tuple, tuple, range)) {
 246                         pr_debug("get_unique_tuple: Found current src map\n");
 247                         if (!nf_nat_used_tuple(tuple, ct))
 248                                 return;
 249                 }
 250         }
 251
 252         /* 2) Select the least-used IP/proto combination in the given
 253            range. */
 254         *tuple = *orig_tuple;
 255         find_best_ips_proto(tuple, range, ct, maniptype);
 256
 257         /* 3) The per-protocol part of the manip is made to map into
 258            the range to make a unique tuple. */
 259
 260         rcu_read_lock();
 261         proto = __nf_nat_proto_find(orig_tuple->dst.protonum);
 262
 263         /* Change protocol info to have some randomization */
 264         if (range->flags & IP_NAT_RANGE_PROTO_RANDOM) {
 265                 proto->unique_tuple(tuple, range, maniptype, ct);
 266                 goto out;
 267         }
 268
 269         /* Only bother mapping if it's not already in range and unique */
 270         if ((!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED) ||
 271              proto->in_range(tuple, maniptype, &range->min, &range->max)) &&
 272             !nf_nat_used_tuple(tuple, ct))
 273                 goto out;
 274
 275         /* Last change: get protocol to try to obtain unique tuple. */
 276         proto->unique_tuple(tuple, range, maniptype, ct);
 277 out:
 278         rcu_read_unlock();
 279 }
 280
 281 unsigned int
 282 nf_nat_setup_info(struct nf_conn *ct,
 283                   const struct nf_nat_range *range,
 284                   enum nf_nat_manip_type maniptype)
 285 {
 286         struct nf_conntrack_tuple curr_tuple, new_tuple;
 287         struct nf_conn_nat *nat;
 288         int have_to_hash = !(ct->status & IPS_NAT_DONE_MASK);
 289
 290         /* nat helper or nfctnetlink also setup binding */
 291         nat = nfct_nat(ct);
 292         if (!nat) {
 293                 nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
 294                 if (nat == NULL) {
 295                         pr_debug("failed to add NAT extension\n");
 296                         return NF_ACCEPT;
 297                 }
 298         }
 299
 300         NF_CT_ASSERT(maniptype == IP_NAT_MANIP_SRC ||
 301                      maniptype == IP_NAT_MANIP_DST);
 302         BUG_ON(nf_nat_initialized(ct, maniptype));
 303
 304         /* What we've got will look like inverse of reply. Normally
 305            this is what is in the conntrack, except for prior
 306            manipulations (future optimization: if num_manips == 0,
 307            orig_tp =
 308            conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple) */
 309         nf_ct_invert_tuplepr(&curr_tuple,
 310                              &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 311
 312         get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype);
 313
 314         if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) {
 315                 struct nf_conntrack_tuple reply;
 316
 317                 /* Alter conntrack table so will recognize replies. */
 318                 nf_ct_invert_tuplepr(&reply, &new_tuple);
 319                 nf_conntrack_alter_reply(ct, &reply);
 320
 321                 /* Non-atomic: we own this at the moment. */
 322                 if (maniptype == IP_NAT_MANIP_SRC)
 323                         ct->status |= IPS_SRC_NAT;
 324                 else
 325                         ct->status |= IPS_DST_NAT;
 326         }
 327
 328         /* Place in source hash if this is the first time. */
 329         if (have_to_hash) {
 330                 unsigned int srchash;
 331
 332                 srchash = hash_by_src(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 333                 spin_lock_bh(&nf_nat_lock);
 334                 /* nf_conntrack_alter_reply might re-allocate exntension aera */
 335                 nat = nfct_nat(ct);
 336                 nat->ct = ct;
 337                 hlist_add_head_rcu(&nat->bysource, &bysource[srchash]);
 338                 spin_unlock_bh(&nf_nat_lock);
 339         }
 340
 341         /* It's done. */
 342         if (maniptype == IP_NAT_MANIP_DST)
 343                 set_bit(IPS_DST_NAT_DONE_BIT, &ct->status);
 344         else
 345                 set_bit(IPS_SRC_NAT_DONE_BIT, &ct->status);
 346
 347         return NF_ACCEPT;
 348 }
 349 EXPORT_SYMBOL(nf_nat_setup_info);
 350
 351 /* Returns true if succeeded. */
 352 static bool
 353 manip_pkt(u_int16_t proto,
 354           struct sk_buff *skb,
 355           unsigned int iphdroff,
 356           const struct nf_conntrack_tuple *target,
 357           enum nf_nat_manip_type maniptype)
 358 {
 359         struct iphdr *iph;
 360         const struct nf_nat_protocol *p;
 361
 362         if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
 363                 return false;
 364
 365         iph = (void *)skb->data + iphdroff;
 366
 367         /* Manipulate protcol part. */
 368
 369         /* rcu_read_lock()ed by nf_hook_slow */
 370         p = __nf_nat_proto_find(proto);
 371         if (!p->manip_pkt(skb, iphdroff, target, maniptype))
 372                 return false;
 373
 374         iph = (void *)skb->data + iphdroff;
 375
 376         if (maniptype == IP_NAT_MANIP_SRC) {
 377                 csum_replace4(&iph->check, iph->saddr, target->src.u3.ip);
 378                 iph->saddr = target->src.u3.ip;
 379         } else {
 380                 csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip);
 381                 iph->daddr = target->dst.u3.ip;
 382         }
 383         return true;
 384 }
 385
 386 /* Do packet manipulations according to nf_nat_setup_info. */
 387 unsigned int nf_nat_packet(struct nf_conn *ct,
 388                            enum ip_conntrack_info ctinfo,
 389                            unsigned int hooknum,
 390                            struct sk_buff *skb)
 391 {
 392         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 393         unsigned long statusbit;
 394         enum nf_nat_manip_type mtype = HOOK2MANIP(hooknum);
 395
 396         if (mtype == IP_NAT_MANIP_SRC)
 397                 statusbit = IPS_SRC_NAT;
 398         else
 399                 statusbit = IPS_DST_NAT;
 400
 401         /* Invert if this is reply dir. */
 402         if (dir == IP_CT_DIR_REPLY)
 403                 statusbit ^= IPS_NAT_MASK;
 404
 405         /* Non-atomic: these bits don't change. */
 406         if (ct->status & statusbit) {
 407                 struct nf_conntrack_tuple target;
 408
 409                 /* We are aiming to look like inverse of other direction. */
 410                 nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 411
 412                 if (!manip_pkt(target.dst.protonum, skb, 0, &target, mtype))
 413                         return NF_DROP;
 414         }
 415         return NF_ACCEPT;
 416 }
 417 EXPORT_SYMBOL_GPL(nf_nat_packet);
 418
 419 /* Dir is direction ICMP is coming from (opposite to packet it contains) */
 420 int nf_nat_icmp_reply_translation(struct nf_conn *ct,
 421                                   enum ip_conntrack_info ctinfo,
 422                                   unsigned int hooknum,
 423                                   struct sk_buff *skb)
 424 {
 425         struct {
 426                 struct icmphdr icmp;
 427                 struct iphdr ip;
 428         } *inside;
 429         const struct nf_conntrack_l4proto *l4proto;
 430         struct nf_conntrack_tuple inner, target;
 431         int hdrlen = ip_hdrlen(skb);
 432         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 433         unsigned long statusbit;
 434         enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
 435
 436         if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
 437                 return 0;
 438
 439         inside = (void *)skb->data + ip_hdrlen(skb);
 440
 441         /* We're actually going to mangle it beyond trivial checksum
 442            adjustment, so make sure the current checksum is correct. */
 443         if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
 444                 return 0;
 445
 446         /* Must be RELATED */
 447         NF_CT_ASSERT(skb->nfctinfo == IP_CT_RELATED ||
 448                      skb->nfctinfo == IP_CT_RELATED+IP_CT_IS_REPLY);
 449
 450         /* Redirects on non-null nats must be dropped, else they'll
 451            start talking to each other without our translation, and be
 452            confused... --RR */
 453         if (inside->icmp.type == ICMP_REDIRECT) {
 454                 /* If NAT isn't finished, assume it and drop. */
 455                 if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
 456                         return 0;
 457
 458                 if (ct->status & IPS_NAT_MASK)
 459                         return 0;
 460         }
 461
 462         pr_debug("icmp_reply_translation: translating error %p manip %u "
 463                  "dir %s\n", skb, manip,
 464                  dir == IP_CT_DIR_ORIGINAL ? "ORIG" : "REPLY");
 465
 466         /* rcu_read_lock()ed by nf_hook_slow */
 467         l4proto = __nf_ct_l4proto_find(PF_INET, inside->ip.protocol);
 468
 469         if (!nf_ct_get_tuple(skb,
 470                              ip_hdrlen(skb) + sizeof(struct icmphdr),
 471                              (ip_hdrlen(skb) +
 472                               sizeof(struct icmphdr) + inside->ip.ihl * 4),
 473                              (u_int16_t)AF_INET,
 474                              inside->ip.protocol,
 475                              &inner, l3proto, l4proto))
 476                 return 0;
 477
 478         /* Change inner back to look like incoming packet.  We do the
 479            opposite manip on this hook to normal, because it might not
 480            pass all hooks (locally-generated ICMP).  Consider incoming
 481            packet: PREROUTING (DST manip), routing produces ICMP, goes
 482            through POSTROUTING (which must correct the DST manip). */
 483         if (!manip_pkt(inside->ip.protocol, skb,
 484                        ip_hdrlen(skb) + sizeof(inside->icmp),
 485                        &ct->tuplehash[!dir].tuple,
 486                        !manip))
 487                 return 0;
 488
 489         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 490                 /* Reloading "inside" here since manip_pkt inner. */
 491                 inside = (void *)skb->data + ip_hdrlen(skb);
 492                 inside->icmp.checksum = 0;
 493                 inside->icmp.checksum =
 494                         csum_fold(skb_checksum(skb, hdrlen,
 495                                                skb->len - hdrlen, 0));
 496         }
 497
 498         /* Change outer to look the reply to an incoming packet
 499          * (proto 0 means don't invert per-proto part). */
 500         if (manip == IP_NAT_MANIP_SRC)
 501                 statusbit = IPS_SRC_NAT;
 502         else
 503                 statusbit = IPS_DST_NAT;
 504
 505         /* Invert if this is reply dir. */
 506         if (dir == IP_CT_DIR_REPLY)
 507                 statusbit ^= IPS_NAT_MASK;
 508
 509         if (ct->status & statusbit) {
 510                 nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 511                 if (!manip_pkt(0, skb, 0, &target, manip))
 512                         return 0;
 513         }
 514
 515         return 1;
 516 }
 517 EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
 518
 519 /* Protocol registration. */
 520 int nf_nat_protocol_register(const struct nf_nat_protocol *proto)
 521 {
 522         int ret = 0;
 523
 524         spin_lock_bh(&nf_nat_lock);
 525         if (nf_nat_protos[proto->protonum] != &nf_nat_unknown_protocol) {
 526                 ret = -EBUSY;
 527                 goto out;
 528         }
 529         rcu_assign_pointer(nf_nat_protos[proto->protonum], proto);
 530  out:
 531         spin_unlock_bh(&nf_nat_lock);
 532         return ret;
 533 }
 534 EXPORT_SYMBOL(nf_nat_protocol_register);
 535
 536 /* Noone stores the protocol anywhere; simply delete it. */
 537 void nf_nat_protocol_unregister(const struct nf_nat_protocol *proto)
 538 {
 539         spin_lock_bh(&nf_nat_lock);
 540         rcu_assign_pointer(nf_nat_protos[proto->protonum],
 541                            &nf_nat_unknown_protocol);
 542         spin_unlock_bh(&nf_nat_lock);
 543         synchronize_rcu();
 544 }
 545 EXPORT_SYMBOL(nf_nat_protocol_unregister);
 546
 547 /* Noone using conntrack by the time this called. */
 548 static void nf_nat_cleanup_conntrack(struct nf_conn *ct)
 549 {
 550         struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
 551
 552         if (nat == NULL || nat->ct == NULL)
 553                 return;
 554
 555         NF_CT_ASSERT(nat->ct->status & IPS_NAT_DONE_MASK);
 556
 557         spin_lock_bh(&nf_nat_lock);
 558         hlist_del_rcu(&nat->bysource);
 559         spin_unlock_bh(&nf_nat_lock);
 560 }
 561
 562 static void nf_nat_move_storage(void *new, void *old)
 563 {
 564         struct nf_conn_nat *new_nat = new;
 565         struct nf_conn_nat *old_nat = old;
 566         struct nf_conn *ct = old_nat->ct;
 567
 568         if (!ct || !(ct->status & IPS_NAT_DONE_MASK))
 569                 return;
 570
 571         spin_lock_bh(&nf_nat_lock);
 572         new_nat->ct = ct;
 573         hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
 574         spin_unlock_bh(&nf_nat_lock);
 575 }
 576
 577 static struct nf_ct_ext_type nat_extend __read_mostly = {
 578         .len            = sizeof(struct nf_conn_nat),
 579         .align          = __alignof__(struct nf_conn_nat),
 580         .destroy        = nf_nat_cleanup_conntrack,
 581         .move           = nf_nat_move_storage,
 582         .id             = NF_CT_EXT_NAT,
 583         .flags          = NF_CT_EXT_F_PREALLOC,
 584 };
 585
 586 static int __init nf_nat_init(void)
 587 {
 588         size_t i;
 589         int ret;
 590
 591         need_ipv4_conntrack();
 592
 593         ret = nf_ct_extend_register(&nat_extend);
 594         if (ret < 0) {
 595                 printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
 596                 return ret;
 597         }
 598
 599         /* Leave them the same for the moment. */
 600         nf_nat_htable_size = nf_conntrack_htable_size;
 601
 602         bysource = nf_ct_alloc_hashtable(&nf_nat_htable_size,
 603                                          &nf_nat_vmalloced);
 604         if (!bysource) {
 605                 ret = -ENOMEM;
 606                 goto cleanup_extend;
 607         }
 608
 609         /* Sew in builtin protocols. */
 610         spin_lock_bh(&nf_nat_lock);
 611         for (i = 0; i < MAX_IP_NAT_PROTO; i++)
 612                 rcu_assign_pointer(nf_nat_protos[i], &nf_nat_unknown_protocol);
 613         rcu_assign_pointer(nf_nat_protos[IPPROTO_TCP], &nf_nat_protocol_tcp);
 614         rcu_assign_pointer(nf_nat_protos[IPPROTO_UDP], &nf_nat_protocol_udp);
 615         rcu_assign_pointer(nf_nat_protos[IPPROTO_ICMP], &nf_nat_protocol_icmp);
 616         spin_unlock_bh(&nf_nat_lock);
 617
 618         /* Initialize fake conntrack so that NAT will skip it */
 619         nf_conntrack_untracked.status |= IPS_NAT_DONE_MASK;
 620
 621         l3proto = nf_ct_l3proto_find_get((u_int16_t)AF_INET);
 622
 623         BUG_ON(nf_nat_seq_adjust_hook != NULL);
 624         rcu_assign_pointer(nf_nat_seq_adjust_hook, nf_nat_seq_adjust);
 625         return 0;
 626
 627  cleanup_extend:
 628         nf_ct_extend_unregister(&nat_extend);
 629         return ret;
 630 }
 631
 632 /* Clear NAT section of all conntracks, in case we're loaded again. */
 633 static int clean_nat(struct nf_conn *i, void *data)
 634 {
 635         struct nf_conn_nat *nat = nfct_nat(i);
 636
 637         if (!nat)
 638                 return 0;
 639         memset(nat, 0, sizeof(*nat));
 640         i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK | IPS_SEQ_ADJUST);
 641         return 0;
 642 }
 643
 644 static void __exit nf_nat_cleanup(void)
 645 {
 646         nf_ct_iterate_cleanup(&clean_nat, NULL);
 647         synchronize_rcu();
 648         nf_ct_free_hashtable(bysource, nf_nat_vmalloced, nf_nat_htable_size);
 649         nf_ct_l3proto_put(l3proto);
 650         nf_ct_extend_unregister(&nat_extend);
 651         rcu_assign_pointer(nf_nat_seq_adjust_hook, NULL);
 652         synchronize_net();
 653 }
 654
 655 MODULE_LICENSE("GPL");
 656
 657 module_init(nf_nat_init);
 658 module_exit(nf_nat_cleanup);