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   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                 },
  51                 .underflow = {
  52                         [NF_IP_PRE_ROUTING] = 0,
  53                         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  54                         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  55                 },
  56         },
  57         .entries = {
  58                 IPT_STANDARD_INIT(NF_ACCEPT),   /* PRE_ROUTING */
  59                 IPT_STANDARD_INIT(NF_ACCEPT),   /* POST_ROUTING */
  60                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
  61         },
  62         .term = IPT_ERROR_INIT,                 /* ERROR */
  63 };
  64
  65 static struct xt_table nat_table = {
  66         .name           = "nat",
  67         .valid_hooks    = NAT_VALID_HOOKS,
  68         .lock           = RW_LOCK_UNLOCKED,
  69         .me             = THIS_MODULE,
  70         .af             = AF_INET,
  71 };
  72
  73 /* Source NAT */
  74 static unsigned int ipt_snat_target(struct sk_buff **pskb,
  75                                     const struct net_device *in,
  76                                     const struct net_device *out,
  77                                     unsigned int hooknum,
  78                                     const struct xt_target *target,
  79                                     const void *targinfo)
  80 {
  81         struct nf_conn *ct;
  82         enum ip_conntrack_info ctinfo;
  83         const struct nf_nat_multi_range_compat *mr = targinfo;
  84
  85         NF_CT_ASSERT(hooknum == NF_IP_POST_ROUTING);
  86
  87         ct = nf_ct_get(*pskb, &ctinfo);
  88
  89         /* Connection must be valid and new. */
  90         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  91                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  92         NF_CT_ASSERT(out);
  93
  94         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
  95 }
  96
  97 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
  98 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
  99 {
 100         static int warned = 0;
 101         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
 102         struct rtable *rt;
 103
 104         if (ip_route_output_key(&rt, &fl) != 0)
 105                 return;
 106
 107         if (rt->rt_src != srcip && !warned) {
 108                 printk("NAT: no longer support implicit source local NAT\n");
 109                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 110                        NIPQUAD(srcip), NIPQUAD(dstip));
 111                 warned = 1;
 112         }
 113         ip_rt_put(rt);
 114 }
 115
 116 static unsigned int ipt_dnat_target(struct sk_buff **pskb,
 117                                     const struct net_device *in,
 118                                     const struct net_device *out,
 119                                     unsigned int hooknum,
 120                                     const struct xt_target *target,
 121                                     const void *targinfo)
 122 {
 123         struct nf_conn *ct;
 124         enum ip_conntrack_info ctinfo;
 125         const struct nf_nat_multi_range_compat *mr = targinfo;
 126
 127         NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 128                      hooknum == NF_IP_LOCAL_OUT);
 129
 130         ct = nf_ct_get(*pskb, &ctinfo);
 131
 132         /* Connection must be valid and new. */
 133         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 134
 135         if (hooknum == NF_IP_LOCAL_OUT &&
 136             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 137                 warn_if_extra_mangle(ip_hdr(*pskb)->daddr,
 138                                      mr->range[0].min_ip);
 139
 140         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
 141 }
 142
 143 static bool ipt_snat_checkentry(const char *tablename,
 144                                 const void *entry,
 145                                 const struct xt_target *target,
 146                                 void *targinfo,
 147                                 unsigned int hook_mask)
 148 {
 149         struct nf_nat_multi_range_compat *mr = targinfo;
 150
 151         /* Must be a valid range */
 152         if (mr->rangesize != 1) {
 153                 printk("SNAT: multiple ranges no longer supported\n");
 154                 return false;
 155         }
 156         return true;
 157 }
 158
 159 static bool ipt_dnat_checkentry(const char *tablename,
 160                                 const void *entry,
 161                                 const struct xt_target *target,
 162                                 void *targinfo,
 163                                 unsigned int hook_mask)
 164 {
 165         struct nf_nat_multi_range_compat *mr = targinfo;
 166
 167         /* Must be a valid range */
 168         if (mr->rangesize != 1) {
 169                 printk("DNAT: multiple ranges no longer supported\n");
 170                 return false;
 171         }
 172         return true;
 173 }
 174
 175 unsigned int
 176 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 177 {
 178         /* Force range to this IP; let proto decide mapping for
 179            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 180            Use reply in case it's already been mangled (eg local packet).
 181         */
 182         __be32 ip
 183                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 184                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 185                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 186         struct nf_nat_range range
 187                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 188
 189         DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
 190                ct, NIPQUAD(ip));
 191         return nf_nat_setup_info(ct, &range, hooknum);
 192 }
 193
 194 unsigned int
 195 alloc_null_binding_confirmed(struct nf_conn *ct, unsigned int hooknum)
 196 {
 197         __be32 ip
 198                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 199                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 200                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 201         u_int16_t all
 202                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 203                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 204                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 205         struct nf_nat_range range
 206                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 207
 208         DEBUGP("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 209                ct, NIPQUAD(ip));
 210         return nf_nat_setup_info(ct, &range, hooknum);
 211 }
 212
 213 int nf_nat_rule_find(struct sk_buff **pskb,
 214                      unsigned int hooknum,
 215                      const struct net_device *in,
 216                      const struct net_device *out,
 217                      struct nf_conn *ct)
 218 {
 219         int ret;
 220
 221         ret = ipt_do_table(pskb, hooknum, in, out, &nat_table);
 222
 223         if (ret == NF_ACCEPT) {
 224                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 225                         /* NUL mapping */
 226                         ret = alloc_null_binding(ct, hooknum);
 227         }
 228         return ret;
 229 }
 230
 231 static struct xt_target ipt_snat_reg __read_mostly = {
 232         .name           = "SNAT",
 233         .target         = ipt_snat_target,
 234         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 235         .table          = "nat",
 236         .hooks          = 1 << NF_IP_POST_ROUTING,
 237         .checkentry     = ipt_snat_checkentry,
 238         .family         = AF_INET,
 239 };
 240
 241 static struct xt_target ipt_dnat_reg __read_mostly = {
 242         .name           = "DNAT",
 243         .target         = ipt_dnat_target,
 244         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 245         .table          = "nat",
 246         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 247         .checkentry     = ipt_dnat_checkentry,
 248         .family         = AF_INET,
 249 };
 250
 251 int __init nf_nat_rule_init(void)
 252 {
 253         int ret;
 254
 255         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 256         if (ret != 0)
 257                 return ret;
 258         ret = xt_register_target(&ipt_snat_reg);
 259         if (ret != 0)
 260                 goto unregister_table;
 261
 262         ret = xt_register_target(&ipt_dnat_reg);
 263         if (ret != 0)
 264                 goto unregister_snat;
 265
 266         return ret;
 267
 268  unregister_snat:
 269         xt_unregister_target(&ipt_snat_reg);
 270  unregister_table:
 271         ipt_unregister_table(&nat_table);
 272
 273         return ret;
 274 }
 275
 276 void nf_nat_rule_cleanup(void)
 277 {
 278         xt_unregister_target(&ipt_dnat_reg);
 279         xt_unregister_target(&ipt_snat_reg);
 280         ipt_unregister_table(&nat_table);
 281 }