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 const 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 const struct xt_table nat_table = {
  62         .name           = "nat",
  63         .valid_hooks    = NAT_VALID_HOOKS,
  64         .me             = THIS_MODULE,
  65         .af             = NFPROTO_IPV4,
  66 };
  67
  68 /* Source NAT */
  69 static unsigned int
  70 ipt_snat_target(struct sk_buff *skb, const struct xt_target_param *par)
  71 {
  72         struct nf_conn *ct;
  73         enum ip_conntrack_info ctinfo;
  74         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  75
  76         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
  77
  78         ct = nf_ct_get(skb, &ctinfo);
  79
  80         /* Connection must be valid and new. */
  81         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  82                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  83         NF_CT_ASSERT(par->out != NULL);
  84
  85         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
  86 }
  87
  88 static unsigned int
  89 ipt_dnat_target(struct sk_buff *skb, const struct xt_target_param *par)
  90 {
  91         struct nf_conn *ct;
  92         enum ip_conntrack_info ctinfo;
  93         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  94
  95         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
  96                      par->hooknum == NF_INET_LOCAL_OUT);
  97
  98         ct = nf_ct_get(skb, &ctinfo);
  99
 100         /* Connection must be valid and new. */
 101         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 102
 103         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
 104 }
 105
 106 static bool ipt_snat_checkentry(const struct xt_tgchk_param *par)
 107 {
 108         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 109
 110         /* Must be a valid range */
 111         if (mr->rangesize != 1) {
 112                 printk("SNAT: multiple ranges no longer supported\n");
 113                 return false;
 114         }
 115         return true;
 116 }
 117
 118 static bool ipt_dnat_checkentry(const struct xt_tgchk_param *par)
 119 {
 120         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 121
 122         /* Must be a valid range */
 123         if (mr->rangesize != 1) {
 124                 printk("DNAT: multiple ranges no longer supported\n");
 125                 return false;
 126         }
 127         return true;
 128 }
 129
 130 unsigned int
 131 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 132 {
 133         /* Force range to this IP; let proto decide mapping for
 134            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 135            Use reply in case it's already been mangled (eg local packet).
 136         */
 137         __be32 ip
 138                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 139                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 140                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 141         struct nf_nat_range range
 142                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 143
 144         pr_debug("Allocating NULL binding for %p (%pI4)\n", ct, &ip);
 145         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
 146 }
 147
 148 int nf_nat_rule_find(struct sk_buff *skb,
 149                      unsigned int hooknum,
 150                      const struct net_device *in,
 151                      const struct net_device *out,
 152                      struct nf_conn *ct)
 153 {
 154         struct net *net = nf_ct_net(ct);
 155         int ret;
 156
 157         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
 158
 159         if (ret == NF_ACCEPT) {
 160                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 161                         /* NUL mapping */
 162                         ret = alloc_null_binding(ct, hooknum);
 163         }
 164         return ret;
 165 }
 166
 167 static struct xt_target ipt_snat_reg __read_mostly = {
 168         .name           = "SNAT",
 169         .target         = ipt_snat_target,
 170         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 171         .table          = "nat",
 172         .hooks          = 1 << NF_INET_POST_ROUTING,
 173         .checkentry     = ipt_snat_checkentry,
 174         .family         = AF_INET,
 175 };
 176
 177 static struct xt_target ipt_dnat_reg __read_mostly = {
 178         .name           = "DNAT",
 179         .target         = ipt_dnat_target,
 180         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 181         .table          = "nat",
 182         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 183         .checkentry     = ipt_dnat_checkentry,
 184         .family         = AF_INET,
 185 };
 186
 187 static int __net_init nf_nat_rule_net_init(struct net *net)
 188 {
 189         net->ipv4.nat_table = ipt_register_table(net, &nat_table,
 190                                                  &nat_initial_table.repl);
 191         if (IS_ERR(net->ipv4.nat_table))
 192                 return PTR_ERR(net->ipv4.nat_table);
 193         return 0;
 194 }
 195
 196 static void __net_exit nf_nat_rule_net_exit(struct net *net)
 197 {
 198         ipt_unregister_table(net, net->ipv4.nat_table);
 199 }
 200
 201 static struct pernet_operations nf_nat_rule_net_ops = {
 202         .init = nf_nat_rule_net_init,
 203         .exit = nf_nat_rule_net_exit,
 204 };
 205
 206 int __init nf_nat_rule_init(void)
 207 {
 208         int ret;
 209
 210         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
 211         if (ret != 0)
 212                 goto out;
 213         ret = xt_register_target(&ipt_snat_reg);
 214         if (ret != 0)
 215                 goto unregister_table;
 216
 217         ret = xt_register_target(&ipt_dnat_reg);
 218         if (ret != 0)
 219                 goto unregister_snat;
 220
 221         return ret;
 222
 223  unregister_snat:
 224         xt_unregister_target(&ipt_snat_reg);
 225  unregister_table:
 226         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 227  out:
 228         return ret;
 229 }
 230
 231 void nf_nat_rule_cleanup(void)
 232 {
 233         xt_unregister_target(&ipt_dnat_reg);
 234         xt_unregister_target(&ipt_snat_reg);
 235         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 236 }