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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 #define NAT_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  28                          (1 << NF_INET_POST_ROUTING) | \
  29                          (1 << NF_INET_LOCAL_OUT))
  30
  31 static struct
  32 {
  33         struct ipt_replace repl;
  34         struct ipt_standard entries[3];
  35         struct ipt_error term;
  36 } nat_initial_table __initdata = {
  37         .repl = {
  38                 .name = "nat",
  39                 .valid_hooks = NAT_VALID_HOOKS,
  40                 .num_entries = 4,
  41                 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  42                 .hook_entry = {
  43                         [NF_INET_PRE_ROUTING] = 0,
  44                         [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
  45                         [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  46                 },
  47                 .underflow = {
  48                         [NF_INET_PRE_ROUTING] = 0,
  49                         [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
  50                         [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  51                 },
  52         },
  53         .entries = {
  54                 IPT_STANDARD_INIT(NF_ACCEPT),   /* PRE_ROUTING */
  55                 IPT_STANDARD_INIT(NF_ACCEPT),   /* POST_ROUTING */
  56                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
  57         },
  58         .term = IPT_ERROR_INIT,                 /* ERROR */
  59 };
  60
  61 static struct xt_table nat_table = {
  62         .name           = "nat",
  63         .valid_hooks    = NAT_VALID_HOOKS,
  64         .lock           = RW_LOCK_UNLOCKED,
  65         .me             = THIS_MODULE,
  66         .af             = AF_INET,
  67 };
  68
  69 /* Source NAT */
  70 static unsigned int ipt_snat_target(struct sk_buff *skb,
  71                                     const struct net_device *in,
  72                                     const struct net_device *out,
  73                                     unsigned int hooknum,
  74                                     const struct xt_target *target,
  75                                     const void *targinfo)
  76 {
  77         struct nf_conn *ct;
  78         enum ip_conntrack_info ctinfo;
  79         const struct nf_nat_multi_range_compat *mr = targinfo;
  80
  81         NF_CT_ASSERT(hooknum == NF_INET_POST_ROUTING);
  82
  83         ct = nf_ct_get(skb, &ctinfo);
  84
  85         /* Connection must be valid and new. */
  86         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  87                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  88         NF_CT_ASSERT(out);
  89
  90         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
  91 }
  92
  93 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
  94 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
  95 {
  96         static int warned = 0;
  97         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
  98         struct rtable *rt;
  99
 100         if (ip_route_output_key(&rt, &fl) != 0)
 101                 return;
 102
 103         if (rt->rt_src != srcip && !warned) {
 104                 printk("NAT: no longer support implicit source local NAT\n");
 105                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 106                        NIPQUAD(srcip), NIPQUAD(dstip));
 107                 warned = 1;
 108         }
 109         ip_rt_put(rt);
 110 }
 111
 112 static unsigned int ipt_dnat_target(struct sk_buff *skb,
 113                                     const struct net_device *in,
 114                                     const struct net_device *out,
 115                                     unsigned int hooknum,
 116                                     const struct xt_target *target,
 117                                     const void *targinfo)
 118 {
 119         struct nf_conn *ct;
 120         enum ip_conntrack_info ctinfo;
 121         const struct nf_nat_multi_range_compat *mr = targinfo;
 122
 123         NF_CT_ASSERT(hooknum == NF_INET_PRE_ROUTING ||
 124                      hooknum == NF_INET_LOCAL_OUT);
 125
 126         ct = nf_ct_get(skb, &ctinfo);
 127
 128         /* Connection must be valid and new. */
 129         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 130
 131         if (hooknum == NF_INET_LOCAL_OUT &&
 132             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 133                 warn_if_extra_mangle(ip_hdr(skb)->daddr,
 134                                      mr->range[0].min_ip);
 135
 136         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
 137 }
 138
 139 static bool ipt_snat_checkentry(const char *tablename,
 140                                 const void *entry,
 141                                 const struct xt_target *target,
 142                                 void *targinfo,
 143                                 unsigned int hook_mask)
 144 {
 145         struct nf_nat_multi_range_compat *mr = targinfo;
 146
 147         /* Must be a valid range */
 148         if (mr->rangesize != 1) {
 149                 printk("SNAT: multiple ranges no longer supported\n");
 150                 return false;
 151         }
 152         return true;
 153 }
 154
 155 static bool ipt_dnat_checkentry(const char *tablename,
 156                                 const void *entry,
 157                                 const struct xt_target *target,
 158                                 void *targinfo,
 159                                 unsigned int hook_mask)
 160 {
 161         struct nf_nat_multi_range_compat *mr = targinfo;
 162
 163         /* Must be a valid range */
 164         if (mr->rangesize != 1) {
 165                 printk("DNAT: multiple ranges no longer supported\n");
 166                 return false;
 167         }
 168         return true;
 169 }
 170
 171 unsigned int
 172 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 173 {
 174         /* Force range to this IP; let proto decide mapping for
 175            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 176            Use reply in case it's already been mangled (eg local packet).
 177         */
 178         __be32 ip
 179                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 180                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 181                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 182         struct nf_nat_range range
 183                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 184
 185         pr_debug("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
 186                  ct, NIPQUAD(ip));
 187         return nf_nat_setup_info(ct, &range, hooknum);
 188 }
 189
 190 unsigned int
 191 alloc_null_binding_confirmed(struct nf_conn *ct, unsigned int hooknum)
 192 {
 193         __be32 ip
 194                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 195                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 196                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 197         __be16 all
 198                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 199                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 200                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 201         struct nf_nat_range range
 202                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 203
 204         pr_debug("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 205                  ct, NIPQUAD(ip));
 206         return nf_nat_setup_info(ct, &range, hooknum);
 207 }
 208
 209 int nf_nat_rule_find(struct sk_buff *skb,
 210                      unsigned int hooknum,
 211                      const struct net_device *in,
 212                      const struct net_device *out,
 213                      struct nf_conn *ct)
 214 {
 215         int ret;
 216
 217         ret = ipt_do_table(skb, hooknum, in, out, &nat_table);
 218
 219         if (ret == NF_ACCEPT) {
 220                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 221                         /* NUL mapping */
 222                         ret = alloc_null_binding(ct, hooknum);
 223         }
 224         return ret;
 225 }
 226
 227 static struct xt_target ipt_snat_reg __read_mostly = {
 228         .name           = "SNAT",
 229         .target         = ipt_snat_target,
 230         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 231         .table          = "nat",
 232         .hooks          = 1 << NF_INET_POST_ROUTING,
 233         .checkentry     = ipt_snat_checkentry,
 234         .family         = AF_INET,
 235 };
 236
 237 static struct xt_target ipt_dnat_reg __read_mostly = {
 238         .name           = "DNAT",
 239         .target         = ipt_dnat_target,
 240         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 241         .table          = "nat",
 242         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 243         .checkentry     = ipt_dnat_checkentry,
 244         .family         = AF_INET,
 245 };
 246
 247 int __init nf_nat_rule_init(void)
 248 {
 249         int ret;
 250
 251         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 252         if (ret != 0)
 253                 return ret;
 254         ret = xt_register_target(&ipt_snat_reg);
 255         if (ret != 0)
 256                 goto unregister_table;
 257
 258         ret = xt_register_target(&ipt_dnat_reg);
 259         if (ret != 0)
 260                 goto unregister_snat;
 261
 262         return ret;
 263
 264  unregister_snat:
 265         xt_unregister_target(&ipt_snat_reg);
 266  unregister_table:
 267         ipt_unregister_table(&nat_table);
 268
 269         return ret;
 270 }
 271
 272 void nf_nat_rule_cleanup(void)
 273 {
 274         xt_unregister_target(&ipt_dnat_reg);
 275         xt_unregister_target(&ipt_snat_reg);
 276         ipt_unregister_table(&nat_table);
 277 }