net/ipv4/netfilter/nf_nat_rule.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2006 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 <net/netfilter/nf_nat.h>
  24 #include <net/netfilter/nf_nat_core.h>
  25 #include <net/netfilter/nf_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         .repl = {
  42                 .name = "nat",
  43                 .valid_hooks = NAT_VALID_HOOKS,
  44                 .num_entries = 4,
  45                 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  46                 .hook_entry = {
  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                 .underflow = {
  51                         [NF_IP_PRE_ROUTING] = 0,
  52                         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  53                         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  54         },
  55         .entries = {
  56                 /* PRE_ROUTING */
  57                 {
  58                         .entry = {
  59                                 .target_offset = sizeof(struct ipt_entry),
  60                                 .next_offset = sizeof(struct ipt_standard),
  61                         },
  62                         .target = {
  63                                 .target = {
  64                                         .u = {
  65                                                 .target_size = IPT_ALIGN(sizeof(struct ipt_standard_target)),
  66                                         },
  67                                 },
  68                                 .verdict = -NF_ACCEPT - 1,
  69                         },
  70                 },
  71                 /* POST_ROUTING */
  72                 {
  73                         .entry = {
  74                                 .target_offset = sizeof(struct ipt_entry),
  75                                 .next_offset = sizeof(struct ipt_standard),
  76                         },
  77                         .target = {
  78                                 .target = {
  79                                         .u = {
  80                                                 .target_size = IPT_ALIGN(sizeof(struct ipt_standard_target)),
  81                                         },
  82                                 },
  83                                 .verdict = -NF_ACCEPT - 1,
  84                         },
  85                 },
  86                 /* LOCAL_OUT */
  87                 {
  88                         .entry = {
  89                                 .target_offset = sizeof(struct ipt_entry),
  90                                 .next_offset = sizeof(struct ipt_standard),
  91                         },
  92                         .target = {
  93                                 .target = {
  94                                         .u = {
  95                                                 .target_size = IPT_ALIGN(sizeof(struct ipt_standard_target)),
  96                                         },
  97                                 },
  98                                 .verdict = -NF_ACCEPT - 1,
  99                         },
 100                 },
 101         },
 102         /* ERROR */
 103         .term = {
 104                 .entry = {
 105                         .target_offset = sizeof(struct ipt_entry),
 106                         .next_offset = sizeof(struct ipt_error),
 107                 },
 108                 .target = {
 109                         .target = {
 110                                 .u = {
 111                                         .user = {
 112                                                 .target_size = IPT_ALIGN(sizeof(struct ipt_error_target)),
 113                                                 .name = IPT_ERROR_TARGET,
 114                                         },
 115                                 },
 116                         },
 117                         .errorname = "ERROR",
 118                 },
 119         }
 120 };
 121
 122 static struct xt_table nat_table = {
 123         .name           = "nat",
 124         .valid_hooks    = NAT_VALID_HOOKS,
 125         .lock           = RW_LOCK_UNLOCKED,
 126         .me             = THIS_MODULE,
 127         .af             = AF_INET,
 128 };
 129
 130 /* Source NAT */
 131 static unsigned int ipt_snat_target(struct sk_buff **pskb,
 132                                     const struct net_device *in,
 133                                     const struct net_device *out,
 134                                     unsigned int hooknum,
 135                                     const struct xt_target *target,
 136                                     const void *targinfo)
 137 {
 138         struct nf_conn *ct;
 139         enum ip_conntrack_info ctinfo;
 140         const struct nf_nat_multi_range_compat *mr = targinfo;
 141
 142         NF_CT_ASSERT(hooknum == NF_IP_POST_ROUTING);
 143
 144         ct = nf_ct_get(*pskb, &ctinfo);
 145
 146         /* Connection must be valid and new. */
 147         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
 148                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
 149         NF_CT_ASSERT(out);
 150
 151         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
 152 }
 153
 154 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
 155 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
 156 {
 157         static int warned = 0;
 158         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
 159         struct rtable *rt;
 160
 161         if (ip_route_output_key(&rt, &fl) != 0)
 162                 return;
 163
 164         if (rt->rt_src != srcip && !warned) {
 165                 printk("NAT: no longer support implicit source local NAT\n");
 166                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 167                        NIPQUAD(srcip), NIPQUAD(dstip));
 168                 warned = 1;
 169         }
 170         ip_rt_put(rt);
 171 }
 172
 173 static unsigned int ipt_dnat_target(struct sk_buff **pskb,
 174                                     const struct net_device *in,
 175                                     const struct net_device *out,
 176                                     unsigned int hooknum,
 177                                     const struct xt_target *target,
 178                                     const void *targinfo)
 179 {
 180         struct nf_conn *ct;
 181         enum ip_conntrack_info ctinfo;
 182         const struct nf_nat_multi_range_compat *mr = targinfo;
 183
 184         NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 185                      hooknum == NF_IP_LOCAL_OUT);
 186
 187         ct = nf_ct_get(*pskb, &ctinfo);
 188
 189         /* Connection must be valid and new. */
 190         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 191
 192         if (hooknum == NF_IP_LOCAL_OUT &&
 193             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 194                 warn_if_extra_mangle((*pskb)->nh.iph->daddr,
 195                                      mr->range[0].min_ip);
 196
 197         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
 198 }
 199
 200 static int ipt_snat_checkentry(const char *tablename,
 201                                const void *entry,
 202                                const struct xt_target *target,
 203                                void *targinfo,
 204                                unsigned int hook_mask)
 205 {
 206         struct nf_nat_multi_range_compat *mr = targinfo;
 207
 208         /* Must be a valid range */
 209         if (mr->rangesize != 1) {
 210                 printk("SNAT: multiple ranges no longer supported\n");
 211                 return 0;
 212         }
 213         return 1;
 214 }
 215
 216 static int ipt_dnat_checkentry(const char *tablename,
 217                                const void *entry,
 218                                const struct xt_target *target,
 219                                void *targinfo,
 220                                unsigned int hook_mask)
 221 {
 222         struct nf_nat_multi_range_compat *mr = targinfo;
 223
 224         /* Must be a valid range */
 225         if (mr->rangesize != 1) {
 226                 printk("DNAT: multiple ranges no longer supported\n");
 227                 return 0;
 228         }
 229         if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM) {
 230                 printk("DNAT: port randomization not supported\n");
 231                 return 0;
 232         }
 233         return 1;
 234 }
 235
 236 inline unsigned int
 237 alloc_null_binding(struct nf_conn *ct,
 238                    struct nf_nat_info *info,
 239                    unsigned int hooknum)
 240 {
 241         /* Force range to this IP; let proto decide mapping for
 242            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 243            Use reply in case it's already been mangled (eg local packet).
 244         */
 245         __be32 ip
 246                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 247                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 248                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 249         struct nf_nat_range range
 250                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 251
 252         DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
 253                ct, NIPQUAD(ip));
 254         return nf_nat_setup_info(ct, &range, hooknum);
 255 }
 256
 257 unsigned int
 258 alloc_null_binding_confirmed(struct nf_conn *ct,
 259                              struct nf_nat_info *info,
 260                              unsigned int hooknum)
 261 {
 262         __be32 ip
 263                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 264                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 265                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 266         u_int16_t all
 267                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 268                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 269                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 270         struct nf_nat_range range
 271                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 272
 273         DEBUGP("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 274                ct, NIPQUAD(ip));
 275         return nf_nat_setup_info(ct, &range, hooknum);
 276 }
 277
 278 int nf_nat_rule_find(struct sk_buff **pskb,
 279                      unsigned int hooknum,
 280                      const struct net_device *in,
 281                      const struct net_device *out,
 282                      struct nf_conn *ct,
 283                      struct nf_nat_info *info)
 284 {
 285         int ret;
 286
 287         ret = ipt_do_table(pskb, hooknum, in, out, &nat_table);
 288
 289         if (ret == NF_ACCEPT) {
 290                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 291                         /* NUL mapping */
 292                         ret = alloc_null_binding(ct, info, hooknum);
 293         }
 294         return ret;
 295 }
 296
 297 static struct xt_target ipt_snat_reg = {
 298         .name           = "SNAT",
 299         .target         = ipt_snat_target,
 300         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 301         .table          = "nat",
 302         .hooks          = 1 << NF_IP_POST_ROUTING,
 303         .checkentry     = ipt_snat_checkentry,
 304         .family         = AF_INET,
 305 };
 306
 307 static struct xt_target ipt_dnat_reg = {
 308         .name           = "DNAT",
 309         .target         = ipt_dnat_target,
 310         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 311         .table          = "nat",
 312         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 313         .checkentry     = ipt_dnat_checkentry,
 314         .family         = AF_INET,
 315 };
 316
 317 int __init nf_nat_rule_init(void)
 318 {
 319         int ret;
 320
 321         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 322         if (ret != 0)
 323                 return ret;
 324         ret = xt_register_target(&ipt_snat_reg);
 325         if (ret != 0)
 326                 goto unregister_table;
 327
 328         ret = xt_register_target(&ipt_dnat_reg);
 329         if (ret != 0)
 330                 goto unregister_snat;
 331
 332         return ret;
 333
 334  unregister_snat:
 335         xt_unregister_target(&ipt_snat_reg);
 336  unregister_table:
 337         ipt_unregister_table(&nat_table);
 338
 339         return ret;
 340 }
 341
 342 void nf_nat_rule_cleanup(void)
 343 {
 344         xt_unregister_target(&ipt_dnat_reg);
 345         xt_unregister_target(&ipt_snat_reg);
 346         ipt_unregister_table(&nat_table);
 347 }