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 #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 __net_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(nat_table.lock),
  65         .me             = THIS_MODULE,
  66         .af             = AF_INET,
  67 };
  68
  69 /* Source NAT */
  70 static unsigned int
  71 ipt_snat_target(struct sk_buff *skb, const struct xt_target_param *par)
  72 {
  73         struct nf_conn *ct;
  74         enum ip_conntrack_info ctinfo;
  75         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  76
  77         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
  78
  79         ct = nf_ct_get(skb, &ctinfo);
  80
  81         /* Connection must be valid and new. */
  82         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  83                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  84         NF_CT_ASSERT(par->out != NULL);
  85
  86         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
  87 }
  88
  89 static unsigned int
  90 ipt_dnat_target(struct sk_buff *skb, const struct xt_target_param *par)
  91 {
  92         struct nf_conn *ct;
  93         enum ip_conntrack_info ctinfo;
  94         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  95
  96         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
  97                      par->hooknum == NF_INET_LOCAL_OUT);
  98
  99         ct = nf_ct_get(skb, &ctinfo);
 100
 101         /* Connection must be valid and new. */
 102         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 103
 104         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
 105 }
 106
 107 static bool ipt_snat_checkentry(const struct xt_tgchk_param *par)
 108 {
 109         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 110
 111         /* Must be a valid range */
 112         if (mr->rangesize != 1) {
 113                 printk("SNAT: multiple ranges no longer supported\n");
 114                 return false;
 115         }
 116         return true;
 117 }
 118
 119 static bool ipt_dnat_checkentry(const struct xt_tgchk_param *par)
 120 {
 121         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 122
 123         /* Must be a valid range */
 124         if (mr->rangesize != 1) {
 125                 printk("DNAT: multiple ranges no longer supported\n");
 126                 return false;
 127         }
 128         return true;
 129 }
 130
 131 unsigned int
 132 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 133 {
 134         /* Force range to this IP; let proto decide mapping for
 135            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 136            Use reply in case it's already been mangled (eg local packet).
 137         */
 138         __be32 ip
 139                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 140                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 141                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 142         struct nf_nat_range range
 143                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 144
 145         pr_debug("Allocating NULL binding for %p (%pI4)\n", ct, &ip);
 146         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
 147 }
 148
 149 int nf_nat_rule_find(struct sk_buff *skb,
 150                      unsigned int hooknum,
 151                      const struct net_device *in,
 152                      const struct net_device *out,
 153                      struct nf_conn *ct)
 154 {
 155         struct net *net = nf_ct_net(ct);
 156         int ret;
 157
 158         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
 159
 160         if (ret == NF_ACCEPT) {
 161                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 162                         /* NUL mapping */
 163                         ret = alloc_null_binding(ct, hooknum);
 164         }
 165         return ret;
 166 }
 167
 168 static struct xt_target ipt_snat_reg __read_mostly = {
 169         .name           = "SNAT",
 170         .target         = ipt_snat_target,
 171         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 172         .table          = "nat",
 173         .hooks          = 1 << NF_INET_POST_ROUTING,
 174         .checkentry     = ipt_snat_checkentry,
 175         .family         = AF_INET,
 176 };
 177
 178 static struct xt_target ipt_dnat_reg __read_mostly = {
 179         .name           = "DNAT",
 180         .target         = ipt_dnat_target,
 181         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 182         .table          = "nat",
 183         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 184         .checkentry     = ipt_dnat_checkentry,
 185         .family         = AF_INET,
 186 };
 187
 188 static int __net_init nf_nat_rule_net_init(struct net *net)
 189 {
 190         net->ipv4.nat_table = ipt_register_table(net, &nat_table,
 191                                                  &nat_initial_table.repl);
 192         if (IS_ERR(net->ipv4.nat_table))
 193                 return PTR_ERR(net->ipv4.nat_table);
 194         return 0;
 195 }
 196
 197 static void __net_exit nf_nat_rule_net_exit(struct net *net)
 198 {
 199         ipt_unregister_table(net->ipv4.nat_table);
 200 }
 201
 202 static struct pernet_operations nf_nat_rule_net_ops = {
 203         .init = nf_nat_rule_net_init,
 204         .exit = nf_nat_rule_net_exit,
 205 };
 206
 207 int __init nf_nat_rule_init(void)
 208 {
 209         int ret;
 210
 211         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
 212         if (ret != 0)
 213                 goto out;
 214         ret = xt_register_target(&ipt_snat_reg);
 215         if (ret != 0)
 216                 goto unregister_table;
 217
 218         ret = xt_register_target(&ipt_dnat_reg);
 219         if (ret != 0)
 220                 goto unregister_snat;
 221
 222         return ret;
 223
 224  unregister_snat:
 225         xt_unregister_target(&ipt_snat_reg);
 226  unregister_table:
 227         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 228  out:
 229         return ret;
 230 }
 231
 232 void nf_nat_rule_cleanup(void)
 233 {
 234         xt_unregister_target(&ipt_dnat_reg);
 235         xt_unregister_target(&ipt_snat_reg);
 236         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 237 }