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         (*pskb)->nfcache |= NFC_UNKNOWN;
  77
  78         /* If we had a hardware checksum before, it's now invalid */
  79         if ((*pskb)->ip_summed == CHECKSUM_HW)
  80                 if (skb_checksum_help(*pskb, (out == NULL)))
  81                         return NF_DROP;
  82
  83         ct = ip_conntrack_get(*pskb, &ctinfo);
  84         /* Can't track?  It's not due to stress, or conntrack would
  85            have dropped it.  Hence it's the user's responsibilty to
  86            packet filter it out, or implement conntrack/NAT for that
  87            protocol. 8) --RR */
  88         if (!ct) {
  89                 /* Exception: ICMP redirect to new connection (not in
  90                    hash table yet).  We must not let this through, in
  91                    case we're doing NAT to the same network. */
  92                 if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) {
  93                         struct icmphdr _hdr, *hp;
  94
  95                         hp = skb_header_pointer(*pskb,
  96                                                 (*pskb)->nh.iph->ihl*4,
  97                                                 sizeof(_hdr), &_hdr);
  98                         if (hp != NULL &&
  99                             hp->type == ICMP_REDIRECT)
 100                                 return NF_DROP;
 101                 }
 102                 return NF_ACCEPT;
 103         }
 104
 105         /* Don't try to NAT if this packet is not conntracked */
 106         if (ct == &ip_conntrack_untracked)
 107                 return NF_ACCEPT;
 108
 109         switch (ctinfo) {
 110         case IP_CT_RELATED:
 111         case IP_CT_RELATED+IP_CT_IS_REPLY:
 112                 if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) {
 113                         if (!icmp_reply_translation(pskb, ct, maniptype,
 114                                                     CTINFO2DIR(ctinfo)))
 115                                 return NF_DROP;
 116                         else
 117                                 return NF_ACCEPT;
 118                 }
 119                 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
 120         case IP_CT_NEW:
 121                 info = &ct->nat.info;
 122
 123                 /* Seen it before?  This can happen for loopback, retrans,
 124                    or local packets.. */
 125                 if (!ip_nat_initialized(ct, maniptype)) {
 126                         unsigned int ret;
 127
 128                         /* LOCAL_IN hook doesn't have a chain!  */
 129                         if (hooknum == NF_IP_LOCAL_IN)
 130                                 ret = alloc_null_binding(ct, info, hooknum);
 131                         else
 132                                 ret = ip_nat_rule_find(pskb, hooknum,
 133                                                        in, out, ct,
 134                                                        info);
 135
 136                         if (ret != NF_ACCEPT) {
 137                                 return ret;
 138                         }
 139                 } else
 140                         DEBUGP("Already setup manip %s for ct %p\n",
 141                                maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
 142                                ct);
 143                 break;
 144
 145         default:
 146                 /* ESTABLISHED */
 147                 IP_NF_ASSERT(ctinfo == IP_CT_ESTABLISHED
 148                              || ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
 149                 info = &ct->nat.info;
 150         }
 151
 152         IP_NF_ASSERT(info);
 153         return nat_packet(ct, ctinfo, hooknum, pskb);
 154 }
 155
 156 static unsigned int
 157 ip_nat_in(unsigned int hooknum,
 158           struct sk_buff **pskb,
 159           const struct net_device *in,
 160           const struct net_device *out,
 161           int (*okfn)(struct sk_buff *))
 162 {
 163         u_int32_t saddr, daddr;
 164         unsigned int ret;
 165
 166         saddr = (*pskb)->nh.iph->saddr;
 167         daddr = (*pskb)->nh.iph->daddr;
 168
 169         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
 170         if (ret != NF_DROP && ret != NF_STOLEN
 171             && ((*pskb)->nh.iph->saddr != saddr
 172                 || (*pskb)->nh.iph->daddr != daddr)) {
 173                 dst_release((*pskb)->dst);
 174                 (*pskb)->dst = NULL;
 175         }
 176         return ret;
 177 }
 178
 179 static unsigned int
 180 ip_nat_out(unsigned int hooknum,
 181            struct sk_buff **pskb,
 182            const struct net_device *in,
 183            const struct net_device *out,
 184            int (*okfn)(struct sk_buff *))
 185 {
 186         /* root is playing with raw sockets. */
 187         if ((*pskb)->len < sizeof(struct iphdr)
 188             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
 189                 return NF_ACCEPT;
 190
 191         /* We can hit fragment here; forwarded packets get
 192            defragmented by connection tracking coming in, then
 193            fragmented (grr) by the forward code.
 194
 195            In future: If we have nfct != NULL, AND we have NAT
 196            initialized, AND there is no helper, then we can do full
 197            NAPT on the head, and IP-address-only NAT on the rest.
 198
 199            I'm starting to have nightmares about fragments.  */
 200
 201         if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 202                 *pskb = ip_ct_gather_frags(*pskb, IP_DEFRAG_NAT_OUT);
 203
 204                 if (!*pskb)
 205                         return NF_STOLEN;
 206         }
 207
 208         return ip_nat_fn(hooknum, pskb, in, out, okfn);
 209 }
 210
 211 static unsigned int
 212 ip_nat_local_fn(unsigned int hooknum,
 213                 struct sk_buff **pskb,
 214                 const struct net_device *in,
 215                 const struct net_device *out,
 216                 int (*okfn)(struct sk_buff *))
 217 {
 218         u_int32_t saddr, daddr;
 219         unsigned int ret;
 220
 221         /* root is playing with raw sockets. */
 222         if ((*pskb)->len < sizeof(struct iphdr)
 223             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
 224                 return NF_ACCEPT;
 225
 226         saddr = (*pskb)->nh.iph->saddr;
 227         daddr = (*pskb)->nh.iph->daddr;
 228
 229         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
 230         if (ret != NF_DROP && ret != NF_STOLEN
 231             && ((*pskb)->nh.iph->saddr != saddr
 232                 || (*pskb)->nh.iph->daddr != daddr))
 233                 return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
 234         return ret;
 235 }
 236
 237 static unsigned int
 238 ip_nat_adjust(unsigned int hooknum,
 239               struct sk_buff **pskb,
 240               const struct net_device *in,
 241               const struct net_device *out,
 242               int (*okfn)(struct sk_buff *))
 243 {
 244         struct ip_conntrack *ct;
 245         enum ip_conntrack_info ctinfo;
 246
 247         ct = ip_conntrack_get(*pskb, &ctinfo);
 248         if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
 249                 DEBUGP("ip_nat_standalone: adjusting sequence number\n");
 250                 if (!ip_nat_seq_adjust(pskb, ct, ctinfo))
 251                         return NF_DROP;
 252         }
 253         return NF_ACCEPT;
 254 }
 255
 256 /* We must be after connection tracking and before packet filtering. */
 257
 258 /* Before packet filtering, change destination */
 259 static struct nf_hook_ops ip_nat_in_ops = {
 260         .hook           = ip_nat_in,
 261         .owner          = THIS_MODULE,
 262         .pf             = PF_INET,
 263         .hooknum        = NF_IP_PRE_ROUTING,
 264         .priority       = NF_IP_PRI_NAT_DST,
 265 };
 266
 267 /* After packet filtering, change source */
 268 static struct nf_hook_ops ip_nat_out_ops = {
 269         .hook           = ip_nat_out,
 270         .owner          = THIS_MODULE,
 271         .pf             = PF_INET,
 272         .hooknum        = NF_IP_POST_ROUTING,
 273         .priority       = NF_IP_PRI_NAT_SRC,
 274 };
 275
 276 /* After conntrack, adjust sequence number */
 277 static struct nf_hook_ops ip_nat_adjust_out_ops = {
 278         .hook           = ip_nat_adjust,
 279         .owner          = THIS_MODULE,
 280         .pf             = PF_INET,
 281         .hooknum        = NF_IP_POST_ROUTING,
 282         .priority       = NF_IP_PRI_NAT_SEQ_ADJUST,
 283 };
 284
 285 /* Before packet filtering, change destination */
 286 static struct nf_hook_ops ip_nat_local_out_ops = {
 287         .hook           = ip_nat_local_fn,
 288         .owner          = THIS_MODULE,
 289         .pf             = PF_INET,
 290         .hooknum        = NF_IP_LOCAL_OUT,
 291         .priority       = NF_IP_PRI_NAT_DST,
 292 };
 293
 294 /* After packet filtering, change source for reply packets of LOCAL_OUT DNAT */
 295 static struct nf_hook_ops ip_nat_local_in_ops = {
 296         .hook           = ip_nat_fn,
 297         .owner          = THIS_MODULE,
 298         .pf             = PF_INET,
 299         .hooknum        = NF_IP_LOCAL_IN,
 300         .priority       = NF_IP_PRI_NAT_SRC,
 301 };
 302
 303 /* After conntrack, adjust sequence number */
 304 static struct nf_hook_ops ip_nat_adjust_in_ops = {
 305         .hook           = ip_nat_adjust,
 306         .owner          = THIS_MODULE,
 307         .pf             = PF_INET,
 308         .hooknum        = NF_IP_LOCAL_IN,
 309         .priority       = NF_IP_PRI_NAT_SEQ_ADJUST,
 310 };
 311
 312
 313 static int init_or_cleanup(int init)
 314 {
 315         int ret = 0;
 316
 317         need_ip_conntrack();
 318
 319         if (!init) goto cleanup;
 320
 321         ret = ip_nat_rule_init();
 322         if (ret < 0) {
 323                 printk("ip_nat_init: can't setup rules.\n");
 324                 goto cleanup_nothing;
 325         }
 326         ret = ip_nat_init();
 327         if (ret < 0) {
 328                 printk("ip_nat_init: can't setup rules.\n");
 329                 goto cleanup_rule_init;
 330         }
 331         ret = nf_register_hook(&ip_nat_in_ops);
 332         if (ret < 0) {
 333                 printk("ip_nat_init: can't register in hook.\n");
 334                 goto cleanup_nat;
 335         }
 336         ret = nf_register_hook(&ip_nat_out_ops);
 337         if (ret < 0) {
 338                 printk("ip_nat_init: can't register out hook.\n");
 339                 goto cleanup_inops;
 340         }
 341         ret = nf_register_hook(&ip_nat_adjust_in_ops);
 342         if (ret < 0) {
 343                 printk("ip_nat_init: can't register adjust in hook.\n");
 344                 goto cleanup_outops;
 345         }
 346         ret = nf_register_hook(&ip_nat_adjust_out_ops);
 347         if (ret < 0) {
 348                 printk("ip_nat_init: can't register adjust out hook.\n");
 349                 goto cleanup_adjustin_ops;
 350         }
 351         ret = nf_register_hook(&ip_nat_local_out_ops);
 352         if (ret < 0) {
 353                 printk("ip_nat_init: can't register local out hook.\n");
 354                 goto cleanup_adjustout_ops;;
 355         }
 356         ret = nf_register_hook(&ip_nat_local_in_ops);
 357         if (ret < 0) {
 358                 printk("ip_nat_init: can't register local in hook.\n");
 359                 goto cleanup_localoutops;
 360         }
 361         return ret;
 362
 363  cleanup:
 364         nf_unregister_hook(&ip_nat_local_in_ops);
 365  cleanup_localoutops:
 366         nf_unregister_hook(&ip_nat_local_out_ops);
 367  cleanup_adjustout_ops:
 368         nf_unregister_hook(&ip_nat_adjust_out_ops);
 369  cleanup_adjustin_ops:
 370         nf_unregister_hook(&ip_nat_adjust_in_ops);
 371  cleanup_outops:
 372         nf_unregister_hook(&ip_nat_out_ops);
 373  cleanup_inops:
 374         nf_unregister_hook(&ip_nat_in_ops);
 375  cleanup_nat:
 376         ip_nat_cleanup();
 377  cleanup_rule_init:
 378         ip_nat_rule_cleanup();
 379  cleanup_nothing:
 380         return ret;
 381 }
 382
 383 static int __init init(void)
 384 {
 385         return init_or_cleanup(1);
 386 }
 387
 388 static void __exit fini(void)
 389 {
 390         init_or_cleanup(0);
 391 }
 392
 393 module_init(init);
 394 module_exit(fini);
 395
 396 EXPORT_SYMBOL(ip_nat_setup_info);
 397 EXPORT_SYMBOL(ip_nat_protocol_register);
 398 EXPORT_SYMBOL(ip_nat_protocol_unregister);
 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");