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) MUST_BE_READ_LOCKED(&ip_nat_lock)
  35 #define ASSERT_WRITE_LOCK(x) MUST_BE_WRITE_LOCKED(&ip_nat_lock)
  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         switch (ctinfo) {
 106         case IP_CT_RELATED:
 107         case IP_CT_RELATED+IP_CT_IS_REPLY:
 108                 if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) {
 109                         if (!icmp_reply_translation(pskb, ct, maniptype,
 110                                                     CTINFO2DIR(ctinfo)))
 111                                 return NF_DROP;
 112                         else
 113                                 return NF_ACCEPT;
 114                 }
 115                 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
 116         case IP_CT_NEW:
 117                 info = &ct->nat.info;
 118
 119                 /* Seen it before?  This can happen for loopback, retrans,
 120                    or local packets.. */
 121                 if (!ip_nat_initialized(ct, maniptype)) {
 122                         unsigned int ret;
 123
 124                         /* LOCAL_IN hook doesn't have a chain!  */
 125                         if (hooknum == NF_IP_LOCAL_IN)
 126                                 ret = alloc_null_binding(ct, info, hooknum);
 127                         else
 128                                 ret = ip_nat_rule_find(pskb, hooknum,
 129                                                        in, out, ct,
 130                                                        info);
 131
 132                         if (ret != NF_ACCEPT) {
 133                                 return ret;
 134                         }
 135                 } else
 136                         DEBUGP("Already setup manip %s for ct %p\n",
 137                                maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
 138                                ct);
 139                 break;
 140
 141         default:
 142                 /* ESTABLISHED */
 143                 IP_NF_ASSERT(ctinfo == IP_CT_ESTABLISHED
 144                              || ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
 145                 info = &ct->nat.info;
 146         }
 147
 148         IP_NF_ASSERT(info);
 149         return nat_packet(ct, ctinfo, hooknum, pskb);
 150 }
 151
 152 static unsigned int
 153 ip_nat_in(unsigned int hooknum,
 154           struct sk_buff **pskb,
 155           const struct net_device *in,
 156           const struct net_device *out,
 157           int (*okfn)(struct sk_buff *))
 158 {
 159         u_int32_t saddr, daddr;
 160         unsigned int ret;
 161
 162         saddr = (*pskb)->nh.iph->saddr;
 163         daddr = (*pskb)->nh.iph->daddr;
 164
 165         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
 166         if (ret != NF_DROP && ret != NF_STOLEN
 167             && ((*pskb)->nh.iph->saddr != saddr
 168                 || (*pskb)->nh.iph->daddr != daddr)) {
 169                 dst_release((*pskb)->dst);
 170                 (*pskb)->dst = NULL;
 171         }
 172         return ret;
 173 }
 174
 175 static unsigned int
 176 ip_nat_out(unsigned int hooknum,
 177            struct sk_buff **pskb,
 178            const struct net_device *in,
 179            const struct net_device *out,
 180            int (*okfn)(struct sk_buff *))
 181 {
 182         /* root is playing with raw sockets. */
 183         if ((*pskb)->len < sizeof(struct iphdr)
 184             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
 185                 return NF_ACCEPT;
 186
 187         /* We can hit fragment here; forwarded packets get
 188            defragmented by connection tracking coming in, then
 189            fragmented (grr) by the forward code.
 190
 191            In future: If we have nfct != NULL, AND we have NAT
 192            initialized, AND there is no helper, then we can do full
 193            NAPT on the head, and IP-address-only NAT on the rest.
 194
 195            I'm starting to have nightmares about fragments.  */
 196
 197         if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 198                 *pskb = ip_ct_gather_frags(*pskb, IP_DEFRAG_NAT_OUT);
 199
 200                 if (!*pskb)
 201                         return NF_STOLEN;
 202         }
 203
 204         return ip_nat_fn(hooknum, pskb, in, out, okfn);
 205 }
 206
 207 static unsigned int
 208 ip_nat_local_fn(unsigned int hooknum,
 209                 struct sk_buff **pskb,
 210                 const struct net_device *in,
 211                 const struct net_device *out,
 212                 int (*okfn)(struct sk_buff *))
 213 {
 214         u_int32_t saddr, daddr;
 215         unsigned int ret;
 216
 217         /* root is playing with raw sockets. */
 218         if ((*pskb)->len < sizeof(struct iphdr)
 219             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
 220                 return NF_ACCEPT;
 221
 222         saddr = (*pskb)->nh.iph->saddr;
 223         daddr = (*pskb)->nh.iph->daddr;
 224
 225         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
 226         if (ret != NF_DROP && ret != NF_STOLEN
 227             && ((*pskb)->nh.iph->saddr != saddr
 228                 || (*pskb)->nh.iph->daddr != daddr))
 229                 return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
 230         return ret;
 231 }
 232
 233 /* We must be after connection tracking and before packet filtering. */
 234
 235 /* Before packet filtering, change destination */
 236 static struct nf_hook_ops ip_nat_in_ops = {
 237         .hook           = ip_nat_in,
 238         .owner          = THIS_MODULE,
 239         .pf             = PF_INET,
 240         .hooknum        = NF_IP_PRE_ROUTING,
 241         .priority       = NF_IP_PRI_NAT_DST,
 242 };
 243
 244 /* After packet filtering, change source */
 245 static struct nf_hook_ops ip_nat_out_ops = {
 246         .hook           = ip_nat_out,
 247         .owner          = THIS_MODULE,
 248         .pf             = PF_INET,
 249         .hooknum        = NF_IP_POST_ROUTING,
 250         .priority       = NF_IP_PRI_NAT_SRC,
 251 };
 252
 253 /* Before packet filtering, change destination */
 254 static struct nf_hook_ops ip_nat_local_out_ops = {
 255         .hook           = ip_nat_local_fn,
 256         .owner          = THIS_MODULE,
 257         .pf             = PF_INET,
 258         .hooknum        = NF_IP_LOCAL_OUT,
 259         .priority       = NF_IP_PRI_NAT_DST,
 260 };
 261
 262 /* After packet filtering, change source for reply packets of LOCAL_OUT DNAT */
 263 static struct nf_hook_ops ip_nat_local_in_ops = {
 264         .hook           = ip_nat_fn,
 265         .owner          = THIS_MODULE,
 266         .pf             = PF_INET,
 267         .hooknum        = NF_IP_LOCAL_IN,
 268         .priority       = NF_IP_PRI_NAT_SRC,
 269 };
 270
 271 static int init_or_cleanup(int init)
 272 {
 273         int ret = 0;
 274
 275         need_ip_conntrack();
 276
 277         if (!init) goto cleanup;
 278
 279         ret = ip_nat_rule_init();
 280         if (ret < 0) {
 281                 printk("ip_nat_init: can't setup rules.\n");
 282                 goto cleanup_nothing;
 283         }
 284         ret = ip_nat_init();
 285         if (ret < 0) {
 286                 printk("ip_nat_init: can't setup rules.\n");
 287                 goto cleanup_rule_init;
 288         }
 289         ret = nf_register_hook(&ip_nat_in_ops);
 290         if (ret < 0) {
 291                 printk("ip_nat_init: can't register in hook.\n");
 292                 goto cleanup_nat;
 293         }
 294         ret = nf_register_hook(&ip_nat_out_ops);
 295         if (ret < 0) {
 296                 printk("ip_nat_init: can't register out hook.\n");
 297                 goto cleanup_inops;
 298         }
 299         ret = nf_register_hook(&ip_nat_local_out_ops);
 300         if (ret < 0) {
 301                 printk("ip_nat_init: can't register local out hook.\n");
 302                 goto cleanup_outops;
 303         }
 304         ret = nf_register_hook(&ip_nat_local_in_ops);
 305         if (ret < 0) {
 306                 printk("ip_nat_init: can't register local in hook.\n");
 307                 goto cleanup_localoutops;
 308         }
 309         return ret;
 310
 311  cleanup:
 312         nf_unregister_hook(&ip_nat_local_in_ops);
 313  cleanup_localoutops:
 314         nf_unregister_hook(&ip_nat_local_out_ops);
 315  cleanup_outops:
 316         nf_unregister_hook(&ip_nat_out_ops);
 317  cleanup_inops:
 318         nf_unregister_hook(&ip_nat_in_ops);
 319  cleanup_nat:
 320         ip_nat_cleanup();
 321  cleanup_rule_init:
 322         ip_nat_rule_cleanup();
 323  cleanup_nothing:
 324         MUST_BE_READ_WRITE_UNLOCKED(&ip_nat_lock);
 325         return ret;
 326 }
 327
 328 static int __init init(void)
 329 {
 330         return init_or_cleanup(1);
 331 }
 332
 333 static void __exit fini(void)
 334 {
 335         init_or_cleanup(0);
 336 }
 337
 338 module_init(init);
 339 module_exit(fini);
 340
 341 EXPORT_SYMBOL(ip_nat_setup_info);
 342 EXPORT_SYMBOL(ip_nat_protocol_register);
 343 EXPORT_SYMBOL(ip_nat_protocol_unregister);
 344 EXPORT_SYMBOL(ip_nat_cheat_check);
 345 EXPORT_SYMBOL(ip_nat_mangle_tcp_packet);
 346 EXPORT_SYMBOL(ip_nat_mangle_udp_packet);
 347 EXPORT_SYMBOL(ip_nat_used_tuple);
 348 EXPORT_SYMBOL(ip_nat_follow_master);
 349 MODULE_LICENSE("GPL");