net/ipv4/netfilter/ip_nat_rule.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 /* Everything about the rules for NAT. */
  10 #include <linux/types.h>
  11 #include <linux/ip.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/netfilter_ipv4.h>
  14 #include <linux/module.h>
  15 #include <linux/kmod.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/proc_fs.h>
  18 #include <net/checksum.h>
  19 #include <net/route.h>
  20 #include <linux/bitops.h>
  21
  22 #define ASSERT_READ_LOCK(x)
  23 #define ASSERT_WRITE_LOCK(x)
  24
  25 #include <linux/netfilter_ipv4/ip_tables.h>
  26 #include <linux/netfilter_ipv4/ip_nat.h>
  27 #include <linux/netfilter_ipv4/ip_nat_core.h>
  28 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  29 #include <linux/netfilter_ipv4/listhelp.h>
  30
  31 #if 0
  32 #define DEBUGP printk
  33 #else
  34 #define DEBUGP(format, args...)
  35 #endif
  36
  37 #define NAT_VALID_HOOKS ((1<<NF_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))
  38
  39 static struct
  40 {
  41         struct ipt_replace repl;
  42         struct ipt_standard entries[3];
  43         struct ipt_error term;
  44 } nat_initial_table __initdata
  45 = { { "nat", NAT_VALID_HOOKS, 4,
  46       sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  47       { [NF_IP_PRE_ROUTING] = 0,
  48         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  49         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  50       { [NF_IP_PRE_ROUTING] = 0,
  51         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  52         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  53       0, NULL, { } },
  54     {
  55             /* PRE_ROUTING */
  56             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  57                 0,
  58                 sizeof(struct ipt_entry),
  59                 sizeof(struct ipt_standard),
  60                 0, { 0, 0 }, { } },
  61               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  62                 -NF_ACCEPT - 1 } },
  63             /* POST_ROUTING */
  64             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  65                 0,
  66                 sizeof(struct ipt_entry),
  67                 sizeof(struct ipt_standard),
  68                 0, { 0, 0 }, { } },
  69               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  70                 -NF_ACCEPT - 1 } },
  71             /* LOCAL_OUT */
  72             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  73                 0,
  74                 sizeof(struct ipt_entry),
  75                 sizeof(struct ipt_standard),
  76                 0, { 0, 0 }, { } },
  77               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  78                 -NF_ACCEPT - 1 } }
  79     },
  80     /* ERROR */
  81     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  82         0,
  83         sizeof(struct ipt_entry),
  84         sizeof(struct ipt_error),
  85         0, { 0, 0 }, { } },
  86       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
  87           { } },
  88         "ERROR"
  89       }
  90     }
  91 };
  92
  93 static struct ipt_table nat_table = {
  94         .name           = "nat",
  95         .valid_hooks    = NAT_VALID_HOOKS,
  96         .lock           = RW_LOCK_UNLOCKED,
  97         .me             = THIS_MODULE,
  98         .af             = AF_INET,
  99 };
 100
 101 /* Source NAT */
 102 static unsigned int ipt_snat_target(struct sk_buff **pskb,
 103                                     const struct net_device *in,
 104                                     const struct net_device *out,
 105                                     unsigned int hooknum,
 106                                     const struct ipt_target *target,
 107                                     const void *targinfo)
 108 {
 109         struct ip_conntrack *ct;
 110         enum ip_conntrack_info ctinfo;
 111         const struct ip_nat_multi_range_compat *mr = targinfo;
 112
 113         IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
 114
 115         ct = ip_conntrack_get(*pskb, &ctinfo);
 116
 117         /* Connection must be valid and new. */
 118         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
 119                             || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
 120         IP_NF_ASSERT(out);
 121
 122         return ip_nat_setup_info(ct, &mr->range[0], hooknum);
 123 }
 124
 125 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
 126 static void warn_if_extra_mangle(u32 dstip, u32 srcip)
 127 {
 128         static int warned = 0;
 129         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
 130         struct rtable *rt;
 131
 132         if (ip_route_output_key(&rt, &fl) != 0)
 133                 return;
 134
 135         if (rt->rt_src != srcip && !warned) {
 136                 printk("NAT: no longer support implicit source local NAT\n");
 137                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 138                        NIPQUAD(srcip), NIPQUAD(dstip));
 139                 warned = 1;
 140         }
 141         ip_rt_put(rt);
 142 }
 143
 144 static unsigned int ipt_dnat_target(struct sk_buff **pskb,
 145                                     const struct net_device *in,
 146                                     const struct net_device *out,
 147                                     unsigned int hooknum,
 148                                     const struct ipt_target *target,
 149                                     const void *targinfo)
 150 {
 151         struct ip_conntrack *ct;
 152         enum ip_conntrack_info ctinfo;
 153         const struct ip_nat_multi_range_compat *mr = targinfo;
 154
 155         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
 156                      || hooknum == NF_IP_LOCAL_OUT);
 157
 158         ct = ip_conntrack_get(*pskb, &ctinfo);
 159
 160         /* Connection must be valid and new. */
 161         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 162
 163         if (hooknum == NF_IP_LOCAL_OUT
 164             && mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 165                 warn_if_extra_mangle((*pskb)->nh.iph->daddr,
 166                                      mr->range[0].min_ip);
 167
 168         return ip_nat_setup_info(ct, &mr->range[0], hooknum);
 169 }
 170
 171 static int ipt_snat_checkentry(const char *tablename,
 172                                const void *entry,
 173                                const struct ipt_target *target,
 174                                void *targinfo,
 175                                unsigned int hook_mask)
 176 {
 177         struct ip_nat_multi_range_compat *mr = targinfo;
 178
 179         /* Must be a valid range */
 180         if (mr->rangesize != 1) {
 181                 printk("SNAT: multiple ranges no longer supported\n");
 182                 return 0;
 183         }
 184         return 1;
 185 }
 186
 187 static int ipt_dnat_checkentry(const char *tablename,
 188                                const void *entry,
 189                                const struct ipt_target *target,
 190                                void *targinfo,
 191                                unsigned int hook_mask)
 192 {
 193         struct ip_nat_multi_range_compat *mr = targinfo;
 194
 195         /* Must be a valid range */
 196         if (mr->rangesize != 1) {
 197                 printk("DNAT: multiple ranges no longer supported\n");
 198                 return 0;
 199         }
 200         return 1;
 201 }
 202
 203 inline unsigned int
 204 alloc_null_binding(struct ip_conntrack *conntrack,
 205                    struct ip_nat_info *info,
 206                    unsigned int hooknum)
 207 {
 208         /* Force range to this IP; let proto decide mapping for
 209            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 210            Use reply in case it's already been mangled (eg local packet).
 211         */
 212         u_int32_t ip
 213                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 214                    ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip
 215                    : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
 216         struct ip_nat_range range
 217                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 218
 219         DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n", conntrack,
 220                NIPQUAD(ip));
 221         return ip_nat_setup_info(conntrack, &range, hooknum);
 222 }
 223
 224 unsigned int
 225 alloc_null_binding_confirmed(struct ip_conntrack *conntrack,
 226                              struct ip_nat_info *info,
 227                              unsigned int hooknum)
 228 {
 229         u_int32_t ip
 230                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 231                    ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip
 232                    : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
 233         u_int16_t all
 234                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 235                    ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 236                    : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 237         struct ip_nat_range range
 238                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 239
 240         DEBUGP("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 241                conntrack, NIPQUAD(ip));
 242         return ip_nat_setup_info(conntrack, &range, hooknum);
 243 }
 244
 245 int ip_nat_rule_find(struct sk_buff **pskb,
 246                      unsigned int hooknum,
 247                      const struct net_device *in,
 248                      const struct net_device *out,
 249                      struct ip_conntrack *ct,
 250                      struct ip_nat_info *info)
 251 {
 252         int ret;
 253
 254         ret = ipt_do_table(pskb, hooknum, in, out, &nat_table);
 255
 256         if (ret == NF_ACCEPT) {
 257                 if (!ip_nat_initialized(ct, HOOK2MANIP(hooknum)))
 258                         /* NUL mapping */
 259                         ret = alloc_null_binding(ct, info, hooknum);
 260         }
 261         return ret;
 262 }
 263
 264 static struct ipt_target ipt_snat_reg = {
 265         .name           = "SNAT",
 266         .target         = ipt_snat_target,
 267         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 268         .table          = "nat",
 269         .hooks          = 1 << NF_IP_POST_ROUTING,
 270         .checkentry     = ipt_snat_checkentry,
 271 };
 272
 273 static struct ipt_target ipt_dnat_reg = {
 274         .name           = "DNAT",
 275         .target         = ipt_dnat_target,
 276         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 277         .table          = "nat",
 278         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 279         .checkentry     = ipt_dnat_checkentry,
 280 };
 281
 282 int __init ip_nat_rule_init(void)
 283 {
 284         int ret;
 285
 286         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 287         if (ret != 0)
 288                 return ret;
 289         ret = ipt_register_target(&ipt_snat_reg);
 290         if (ret != 0)
 291                 goto unregister_table;
 292
 293         ret = ipt_register_target(&ipt_dnat_reg);
 294         if (ret != 0)
 295                 goto unregister_snat;
 296
 297         return ret;
 298
 299  unregister_snat:
 300         ipt_unregister_target(&ipt_snat_reg);
 301  unregister_table:
 302         ipt_unregister_table(&nat_table);
 303
 304         return ret;
 305 }
 306
 307 void ip_nat_rule_cleanup(void)
 308 {
 309         ipt_unregister_target(&ipt_dnat_reg);
 310         ipt_unregister_target(&ipt_snat_reg);
 311         ipt_unregister_table(&nat_table);
 312 }