net/ipv4/netfilter/ip_nat_standalone.c

   1 /* This file contains all the functions required for the standalone
   2    ip_nat module.
   3
   4    These are not required by the compatibility layer.
   5 */
   6
   7 /* (C) 1999-2001 Paul `Rusty' Russell
   8  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  */
  14
  15 /*
  16  * 23 Apr 2001: Harald Welte <laforge@gnumonks.org>
  17  *      - new API and handling of conntrack/nat helpers
  18  *      - now capable of multiple expectations for one master
  19  * */
  20
  21 #include <linux/config.h>
  22 #include <linux/types.h>
  23 #include <linux/icmp.h>
  24 #include <linux/ip.h>
  25 #include <linux/netfilter.h>
  26 #include <linux/netfilter_ipv4.h>
  27 #include <linux/module.h>
  28 #include <linux/skbuff.h>
  29 #include <linux/proc_fs.h>
  30 #include <net/ip.h>
  31 #include <net/checksum.h>
  32 #include <linux/spinlock.h>
  33
  34 #define ASSERT_READ_LOCK(x)
  35 #define ASSERT_WRITE_LOCK(x)
  36
  37 #include <linux/netfilter_ipv4/ip_nat.h>
  38 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  39 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
  40 #include <linux/netfilter_ipv4/ip_nat_core.h>
  41 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  42 #include <linux/netfilter_ipv4/ip_tables.h>
  43 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  44 #include <linux/netfilter_ipv4/listhelp.h>
  45
  46 #if 0
  47 #define DEBUGP printk
  48 #else
  49 #define DEBUGP(format, args...)
  50 #endif
  51
  52 #define HOOKNAME(hooknum) ((hooknum) == NF_IP_POST_ROUTING ? "POST_ROUTING"  \
  53                            : ((hooknum) == NF_IP_PRE_ROUTING ? "PRE_ROUTING" \
  54                               : ((hooknum) == NF_IP_LOCAL_OUT ? "LOCAL_OUT"  \
  55                                  : ((hooknum) == NF_IP_LOCAL_IN ? "LOCAL_IN"  \
  56                                     : "*ERROR*")))
  57
  58 static unsigned int
  59 ip_nat_fn(unsigned int hooknum,
  60           struct sk_buff **pskb,
  61           const struct net_device *in,
  62           const struct net_device *out,
  63           int (*okfn)(struct sk_buff *))
  64 {
  65         struct ip_conntrack *ct;
  66         enum ip_conntrack_info ctinfo;
  67         struct ip_nat_info *info;
  68         /* maniptype == SRC for postrouting. */
  69         enum ip_nat_manip_type maniptype = HOOK2MANIP(hooknum);
  70
  71         /* We never see fragments: conntrack defrags on pre-routing
  72            and local-out, and ip_nat_out protects post-routing. */
  73         IP_NF_ASSERT(!((*pskb)->nh.iph->frag_off
  74                        & htons(IP_MF|IP_OFFSET)));
  75
  76         /* If we had a hardware checksum before, it's now invalid */
  77         if ((*pskb)->ip_summed == CHECKSUM_HW)
  78                 if (skb_checksum_help(*pskb, (out == NULL)))
  79                         return NF_DROP;
  80
  81         ct = ip_conntrack_get(*pskb, &ctinfo);
  82         /* Can't track?  It's not due to stress, or conntrack would
  83            have dropped it.  Hence it's the user's responsibilty to
  84            packet filter it out, or implement conntrack/NAT for that
  85            protocol. 8) --RR */
  86         if (!ct) {
  87                 /* Exception: ICMP redirect to new connection (not in
  88                    hash table yet).  We must not let this through, in
  89                    case we're doing NAT to the same network. */
  90                 if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) {
  91                         struct icmphdr _hdr, *hp;
  92
  93                         hp = skb_header_pointer(*pskb,
  94                                                 (*pskb)->nh.iph->ihl*4,
  95                                                 sizeof(_hdr), &_hdr);
  96                         if (hp != NULL &&
  97                             hp->type == ICMP_REDIRECT)
  98                                 return NF_DROP;
  99                 }
 100                 return NF_ACCEPT;
 101         }
 102
 103         /* Don't try to NAT if this packet is not conntracked */
 104         if (ct == &ip_conntrack_untracked)
 105                 return NF_ACCEPT;
 106
 107         switch (ctinfo) {
 108         case IP_CT_RELATED:
 109         case IP_CT_RELATED+IP_CT_IS_REPLY:
 110                 if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) {
 111                         if (!icmp_reply_translation(pskb, ct, maniptype,
 112                                                     CTINFO2DIR(ctinfo)))
 113                                 return NF_DROP;
 114                         else
 115                                 return NF_ACCEPT;
 116                 }
 117                 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
 118         case IP_CT_NEW:
 119                 info = &ct->nat.info;
 120
 121                 /* Seen it before?  This can happen for loopback, retrans,
 122                    or local packets.. */
 123                 if (!ip_nat_initialized(ct, maniptype)) {
 124                         unsigned int ret;
 125
 126                         /* LOCAL_IN hook doesn't have a chain!  */
 127                         if (hooknum == NF_IP_LOCAL_IN)
 128                                 ret = alloc_null_binding(ct, info, hooknum);
 129                         else
 130                                 ret = ip_nat_rule_find(pskb, hooknum,
 131                                                        in, out, ct,
 132                                                        info);
 133
 134                         if (ret != NF_ACCEPT) {
 135                                 return ret;
 136                         }
 137                 } else
 138                         DEBUGP("Already setup manip %s for ct %p\n",
 139                                maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
 140                                ct);
 141                 break;
 142
 143         default:
 144                 /* ESTABLISHED */
 145                 IP_NF_ASSERT(ctinfo == IP_CT_ESTABLISHED
 146                              || ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
 147                 info = &ct->nat.info;
 148         }
 149
 150         IP_NF_ASSERT(info);
 151         return nat_packet(ct, ctinfo, hooknum, pskb);
 152 }
 153
 154 static unsigned int
 155 ip_nat_in(unsigned int hooknum,
 156           struct sk_buff **pskb,
 157           const struct net_device *in,
 158           const struct net_device *out,
 159           int (*okfn)(struct sk_buff *))
 160 {
 161         u_int32_t saddr, daddr;
 162         unsigned int ret;
 163
 164         saddr = (*pskb)->nh.iph->saddr;
 165         daddr = (*pskb)->nh.iph->daddr;
 166
 167         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
 168         if (ret != NF_DROP && ret != NF_STOLEN
 169             && ((*pskb)->nh.iph->saddr != saddr
 170                 || (*pskb)->nh.iph->daddr != daddr)) {
 171                 dst_release((*pskb)->dst);
 172                 (*pskb)->dst = NULL;
 173         }
 174         return ret;
 175 }
 176
 177 static unsigned int
 178 ip_nat_out(unsigned int hooknum,
 179            struct sk_buff **pskb,
 180            const struct net_device *in,
 181            const struct net_device *out,
 182            int (*okfn)(struct sk_buff *))
 183 {
 184         /* root is playing with raw sockets. */
 185         if ((*pskb)->len < sizeof(struct iphdr)
 186             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
 187                 return NF_ACCEPT;
 188
 189         /* We can hit fragment here; forwarded packets get
 190            defragmented by connection tracking coming in, then
 191            fragmented (grr) by the forward code.
 192
 193            In future: If we have nfct != NULL, AND we have NAT
 194            initialized, AND there is no helper, then we can do full
 195            NAPT on the head, and IP-address-only NAT on the rest.
 196
 197            I'm starting to have nightmares about fragments.  */
 198
 199         if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 200                 *pskb = ip_ct_gather_frags(*pskb, IP_DEFRAG_NAT_OUT);
 201
 202                 if (!*pskb)
 203                         return NF_STOLEN;
 204         }
 205
 206         return ip_nat_fn(hooknum, pskb, in, out, okfn);
 207 }
 208
 209 static unsigned int
 210 ip_nat_local_fn(unsigned int hooknum,
 211                 struct sk_buff **pskb,
 212                 const struct net_device *in,
 213                 const struct net_device *out,
 214                 int (*okfn)(struct sk_buff *))
 215 {
 216         u_int32_t saddr, daddr;
 217         unsigned int ret;
 218
 219         /* root is playing with raw sockets. */
 220         if ((*pskb)->len < sizeof(struct iphdr)
 221             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
 222                 return NF_ACCEPT;
 223
 224         saddr = (*pskb)->nh.iph->saddr;
 225         daddr = (*pskb)->nh.iph->daddr;
 226
 227         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
 228         if (ret != NF_DROP && ret != NF_STOLEN
 229             && ((*pskb)->nh.iph->saddr != saddr
 230                 || (*pskb)->nh.iph->daddr != daddr))
 231                 return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
 232         return ret;
 233 }
 234
 235 static unsigned int
 236 ip_nat_adjust(unsigned int hooknum,
 237               struct sk_buff **pskb,
 238               const struct net_device *in,
 239               const struct net_device *out,
 240               int (*okfn)(struct sk_buff *))
 241 {
 242         struct ip_conntrack *ct;
 243         enum ip_conntrack_info ctinfo;
 244
 245         ct = ip_conntrack_get(*pskb, &ctinfo);
 246         if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
 247                 DEBUGP("ip_nat_standalone: adjusting sequence number\n");
 248                 if (!ip_nat_seq_adjust(pskb, ct, ctinfo))
 249                         return NF_DROP;
 250         }
 251         return NF_ACCEPT;
 252 }
 253
 254 /* We must be after connection tracking and before packet filtering. */
 255
 256 /* Before packet filtering, change destination */
 257 static struct nf_hook_ops ip_nat_in_ops = {
 258         .hook           = ip_nat_in,
 259         .owner          = THIS_MODULE,
 260         .pf             = PF_INET,
 261         .hooknum        = NF_IP_PRE_ROUTING,
 262         .priority       = NF_IP_PRI_NAT_DST,
 263 };
 264
 265 /* After packet filtering, change source */
 266 static struct nf_hook_ops ip_nat_out_ops = {
 267         .hook           = ip_nat_out,
 268         .owner          = THIS_MODULE,
 269         .pf             = PF_INET,
 270         .hooknum        = NF_IP_POST_ROUTING,
 271         .priority       = NF_IP_PRI_NAT_SRC,
 272 };
 273
 274 /* After conntrack, adjust sequence number */
 275 static struct nf_hook_ops ip_nat_adjust_out_ops = {
 276         .hook           = ip_nat_adjust,
 277         .owner          = THIS_MODULE,
 278         .pf             = PF_INET,
 279         .hooknum        = NF_IP_POST_ROUTING,
 280         .priority       = NF_IP_PRI_NAT_SEQ_ADJUST,
 281 };
 282
 283 /* Before packet filtering, change destination */
 284 static struct nf_hook_ops ip_nat_local_out_ops = {
 285         .hook           = ip_nat_local_fn,
 286         .owner          = THIS_MODULE,
 287         .pf             = PF_INET,
 288         .hooknum        = NF_IP_LOCAL_OUT,
 289         .priority       = NF_IP_PRI_NAT_DST,
 290 };
 291
 292 /* After packet filtering, change source for reply packets of LOCAL_OUT DNAT */
 293 static struct nf_hook_ops ip_nat_local_in_ops = {
 294         .hook           = ip_nat_fn,
 295         .owner          = THIS_MODULE,
 296         .pf             = PF_INET,
 297         .hooknum        = NF_IP_LOCAL_IN,
 298         .priority       = NF_IP_PRI_NAT_SRC,
 299 };
 300
 301 /* After conntrack, adjust sequence number */
 302 static struct nf_hook_ops ip_nat_adjust_in_ops = {
 303         .hook           = ip_nat_adjust,
 304         .owner          = THIS_MODULE,
 305         .pf             = PF_INET,
 306         .hooknum        = NF_IP_LOCAL_IN,
 307         .priority       = NF_IP_PRI_NAT_SEQ_ADJUST,
 308 };
 309
 310
 311 static int init_or_cleanup(int init)
 312 {
 313         int ret = 0;
 314
 315         need_ip_conntrack();
 316
 317         if (!init) goto cleanup;
 318
 319         ret = ip_nat_rule_init();
 320         if (ret < 0) {
 321                 printk("ip_nat_init: can't setup rules.\n");
 322                 goto cleanup_nothing;
 323         }
 324         ret = ip_nat_init();
 325         if (ret < 0) {
 326                 printk("ip_nat_init: can't setup rules.\n");
 327                 goto cleanup_rule_init;
 328         }
 329         ret = nf_register_hook(&ip_nat_in_ops);
 330         if (ret < 0) {
 331                 printk("ip_nat_init: can't register in hook.\n");
 332                 goto cleanup_nat;
 333         }
 334         ret = nf_register_hook(&ip_nat_out_ops);
 335         if (ret < 0) {
 336                 printk("ip_nat_init: can't register out hook.\n");
 337                 goto cleanup_inops;
 338         }
 339         ret = nf_register_hook(&ip_nat_adjust_in_ops);
 340         if (ret < 0) {
 341                 printk("ip_nat_init: can't register adjust in hook.\n");
 342                 goto cleanup_outops;
 343         }
 344         ret = nf_register_hook(&ip_nat_adjust_out_ops);
 345         if (ret < 0) {
 346                 printk("ip_nat_init: can't register adjust out hook.\n");
 347                 goto cleanup_adjustin_ops;
 348         }
 349         ret = nf_register_hook(&ip_nat_local_out_ops);
 350         if (ret < 0) {
 351                 printk("ip_nat_init: can't register local out hook.\n");
 352                 goto cleanup_adjustout_ops;;
 353         }
 354         ret = nf_register_hook(&ip_nat_local_in_ops);
 355         if (ret < 0) {
 356                 printk("ip_nat_init: can't register local in hook.\n");
 357                 goto cleanup_localoutops;
 358         }
 359         return ret;
 360
 361  cleanup:
 362         nf_unregister_hook(&ip_nat_local_in_ops);
 363  cleanup_localoutops:
 364         nf_unregister_hook(&ip_nat_local_out_ops);
 365  cleanup_adjustout_ops:
 366         nf_unregister_hook(&ip_nat_adjust_out_ops);
 367  cleanup_adjustin_ops:
 368         nf_unregister_hook(&ip_nat_adjust_in_ops);
 369  cleanup_outops:
 370         nf_unregister_hook(&ip_nat_out_ops);
 371  cleanup_inops:
 372         nf_unregister_hook(&ip_nat_in_ops);
 373  cleanup_nat:
 374         ip_nat_cleanup();
 375  cleanup_rule_init:
 376         ip_nat_rule_cleanup();
 377  cleanup_nothing:
 378         return ret;
 379 }
 380
 381 static int __init init(void)
 382 {
 383         return init_or_cleanup(1);
 384 }
 385
 386 static void __exit fini(void)
 387 {
 388         init_or_cleanup(0);
 389 }
 390
 391 module_init(init);
 392 module_exit(fini);
 393
 394 EXPORT_SYMBOL(ip_nat_setup_info);
 395 EXPORT_SYMBOL(ip_nat_protocol_register);
 396 EXPORT_SYMBOL(ip_nat_protocol_unregister);
 397 EXPORT_SYMBOL_GPL(ip_nat_proto_find_get);
 398 EXPORT_SYMBOL_GPL(ip_nat_proto_put);
 399 EXPORT_SYMBOL(ip_nat_cheat_check);
 400 EXPORT_SYMBOL(ip_nat_mangle_tcp_packet);
 401 EXPORT_SYMBOL(ip_nat_mangle_udp_packet);
 402 EXPORT_SYMBOL(ip_nat_used_tuple);
 403 EXPORT_SYMBOL(ip_nat_follow_master);
 404 MODULE_LICENSE("GPL");