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 #include <linux/netfilter_ipv4/ip_tables.h>
  23 #include <linux/netfilter_ipv4/ip_nat.h>
  24 #include <linux/netfilter_ipv4/ip_nat_core.h>
  25 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 #define NAT_VALID_HOOKS ((1<<NF_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))
  34
  35 static struct
  36 {
  37         struct ipt_replace repl;
  38         struct ipt_standard entries[3];
  39         struct ipt_error term;
  40 } nat_initial_table __initdata
  41 = { { "nat", NAT_VALID_HOOKS, 4,
  42       sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  43       { [NF_IP_PRE_ROUTING] = 0,
  44         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  45         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  46       { [NF_IP_PRE_ROUTING] = 0,
  47         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  48         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  49       0, NULL, { } },
  50     {
  51             /* PRE_ROUTING */
  52             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  53                 0,
  54                 sizeof(struct ipt_entry),
  55                 sizeof(struct ipt_standard),
  56                 0, { 0, 0 }, { } },
  57               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  58                 -NF_ACCEPT - 1 } },
  59             /* POST_ROUTING */
  60             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  61                 0,
  62                 sizeof(struct ipt_entry),
  63                 sizeof(struct ipt_standard),
  64                 0, { 0, 0 }, { } },
  65               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  66                 -NF_ACCEPT - 1 } },
  67             /* LOCAL_OUT */
  68             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  69                 0,
  70                 sizeof(struct ipt_entry),
  71                 sizeof(struct ipt_standard),
  72                 0, { 0, 0 }, { } },
  73               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  74                 -NF_ACCEPT - 1 } }
  75     },
  76     /* ERROR */
  77     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  78         0,
  79         sizeof(struct ipt_entry),
  80         sizeof(struct ipt_error),
  81         0, { 0, 0 }, { } },
  82       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
  83           { } },
  84         "ERROR"
  85       }
  86     }
  87 };
  88
  89 static struct xt_table nat_table = {
  90         .name           = "nat",
  91         .valid_hooks    = NAT_VALID_HOOKS,
  92         .lock           = RW_LOCK_UNLOCKED,
  93         .me             = THIS_MODULE,
  94         .af             = AF_INET,
  95 };
  96
  97 /* Source NAT */
  98 static unsigned int ipt_snat_target(struct sk_buff **pskb,
  99                                     const struct net_device *in,
 100                                     const struct net_device *out,
 101                                     unsigned int hooknum,
 102                                     const struct xt_target *target,
 103                                     const void *targinfo)
 104 {
 105         struct ip_conntrack *ct;
 106         enum ip_conntrack_info ctinfo;
 107         const struct ip_nat_multi_range_compat *mr = targinfo;
 108
 109         IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
 110
 111         ct = ip_conntrack_get(*pskb, &ctinfo);
 112
 113         /* Connection must be valid and new. */
 114         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
 115                             || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
 116         IP_NF_ASSERT(out);
 117
 118         return ip_nat_setup_info(ct, &mr->range[0], hooknum);
 119 }
 120
 121 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
 122 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
 123 {
 124         static int warned = 0;
 125         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
 126         struct rtable *rt;
 127
 128         if (ip_route_output_key(&rt, &fl) != 0)
 129                 return;
 130
 131         if (rt->rt_src != srcip && !warned) {
 132                 printk("NAT: no longer support implicit source local NAT\n");
 133                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 134                        NIPQUAD(srcip), NIPQUAD(dstip));
 135                 warned = 1;
 136         }
 137         ip_rt_put(rt);
 138 }
 139
 140 static unsigned int ipt_dnat_target(struct sk_buff **pskb,
 141                                     const struct net_device *in,
 142                                     const struct net_device *out,
 143                                     unsigned int hooknum,
 144                                     const struct xt_target *target,
 145                                     const void *targinfo)
 146 {
 147         struct ip_conntrack *ct;
 148         enum ip_conntrack_info ctinfo;
 149         const struct ip_nat_multi_range_compat *mr = targinfo;
 150
 151         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
 152                      || hooknum == NF_IP_LOCAL_OUT);
 153
 154         ct = ip_conntrack_get(*pskb, &ctinfo);
 155
 156         /* Connection must be valid and new. */
 157         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 158
 159         if (hooknum == NF_IP_LOCAL_OUT
 160             && mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 161                 warn_if_extra_mangle((*pskb)->nh.iph->daddr,
 162                                      mr->range[0].min_ip);
 163
 164         return ip_nat_setup_info(ct, &mr->range[0], hooknum);
 165 }
 166
 167 static int ipt_snat_checkentry(const char *tablename,
 168                                const void *entry,
 169                                const struct xt_target *target,
 170                                void *targinfo,
 171                                unsigned int hook_mask)
 172 {
 173         struct ip_nat_multi_range_compat *mr = targinfo;
 174
 175         /* Must be a valid range */
 176         if (mr->rangesize != 1) {
 177                 printk("SNAT: multiple ranges no longer supported\n");
 178                 return 0;
 179         }
 180         return 1;
 181 }
 182
 183 static int ipt_dnat_checkentry(const char *tablename,
 184                                const void *entry,
 185                                const struct xt_target *target,
 186                                void *targinfo,
 187                                unsigned int hook_mask)
 188 {
 189         struct ip_nat_multi_range_compat *mr = targinfo;
 190
 191         /* Must be a valid range */
 192         if (mr->rangesize != 1) {
 193                 printk("DNAT: multiple ranges no longer supported\n");
 194                 return 0;
 195         }
 196         if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM) {
 197                 printk("DNAT: port randomization not 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         __be32 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         __be32 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 xt_target ipt_snat_reg = {
 265         .name           = "SNAT",
 266         .family         = AF_INET,
 267         .target         = ipt_snat_target,
 268         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 269         .table          = "nat",
 270         .hooks          = 1 << NF_IP_POST_ROUTING,
 271         .checkentry     = ipt_snat_checkentry,
 272 };
 273
 274 static struct xt_target ipt_dnat_reg = {
 275         .name           = "DNAT",
 276         .family         = AF_INET,
 277         .target         = ipt_dnat_target,
 278         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 279         .table          = "nat",
 280         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 281         .checkentry     = ipt_dnat_checkentry,
 282 };
 283
 284 int __init ip_nat_rule_init(void)
 285 {
 286         int ret;
 287
 288         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 289         if (ret != 0)
 290                 return ret;
 291         ret = xt_register_target(&ipt_snat_reg);
 292         if (ret != 0)
 293                 goto unregister_table;
 294
 295         ret = xt_register_target(&ipt_dnat_reg);
 296         if (ret != 0)
 297                 goto unregister_snat;
 298
 299         return ret;
 300
 301  unregister_snat:
 302         xt_unregister_target(&ipt_snat_reg);
 303  unregister_table:
 304         xt_unregister_table(&nat_table);
 305
 306         return ret;
 307 }
 308
 309 void ip_nat_rule_cleanup(void)
 310 {
 311         xt_unregister_target(&ipt_dnat_reg);
 312         xt_unregister_target(&ipt_snat_reg);
 313         ipt_unregister_table(&nat_table);
 314 }