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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11 #include <linux/types.h>
  12 #include <linux/ip.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/netfilter_ipv4.h>
  15 #include <linux/module.h>
  16 #include <linux/kmod.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/proc_fs.h>
  19 #include <linux/slab.h>
  20 #include <net/checksum.h>
  21 #include <net/route.h>
  22 #include <linux/bitops.h>
  23
  24 #include <linux/netfilter_ipv4/ip_tables.h>
  25 #include <net/netfilter/nf_nat.h>
  26 #include <net/netfilter/nf_nat_core.h>
  27 #include <net/netfilter/nf_nat_rule.h>
  28
  29 #define NAT_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  30                          (1 << NF_INET_POST_ROUTING) | \
  31                          (1 << NF_INET_LOCAL_OUT))
  32
  33 static const struct xt_table nat_table = {
  34         .name           = "nat",
  35         .valid_hooks    = NAT_VALID_HOOKS,
  36         .me             = THIS_MODULE,
  37         .af             = NFPROTO_IPV4,
  38 };
  39
  40 /* Source NAT */
  41 static unsigned int
  42 ipt_snat_target(struct sk_buff *skb, const struct xt_target_param *par)
  43 {
  44         struct nf_conn *ct;
  45         enum ip_conntrack_info ctinfo;
  46         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  47
  48         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
  49
  50         ct = nf_ct_get(skb, &ctinfo);
  51
  52         /* Connection must be valid and new. */
  53         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  54                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  55         NF_CT_ASSERT(par->out != NULL);
  56
  57         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
  58 }
  59
  60 static unsigned int
  61 ipt_dnat_target(struct sk_buff *skb, const struct xt_target_param *par)
  62 {
  63         struct nf_conn *ct;
  64         enum ip_conntrack_info ctinfo;
  65         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  66
  67         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
  68                      par->hooknum == NF_INET_LOCAL_OUT);
  69
  70         ct = nf_ct_get(skb, &ctinfo);
  71
  72         /* Connection must be valid and new. */
  73         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  74
  75         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
  76 }
  77
  78 static int ipt_snat_checkentry(const struct xt_tgchk_param *par)
  79 {
  80         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  81
  82         /* Must be a valid range */
  83         if (mr->rangesize != 1) {
  84                 pr_info("SNAT: multiple ranges no longer supported\n");
  85                 return -EINVAL;
  86         }
  87         return 0;
  88 }
  89
  90 static int ipt_dnat_checkentry(const struct xt_tgchk_param *par)
  91 {
  92         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  93
  94         /* Must be a valid range */
  95         if (mr->rangesize != 1) {
  96                 pr_info("DNAT: multiple ranges no longer supported\n");
  97                 return -EINVAL;
  98         }
  99         return 0;
 100 }
 101
 102 unsigned int
 103 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 104 {
 105         /* Force range to this IP; let proto decide mapping for
 106            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 107            Use reply in case it's already been mangled (eg local packet).
 108         */
 109         __be32 ip
 110                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 111                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 112                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 113         struct nf_nat_range range
 114                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 115
 116         pr_debug("Allocating NULL binding for %p (%pI4)\n", ct, &ip);
 117         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
 118 }
 119
 120 int nf_nat_rule_find(struct sk_buff *skb,
 121                      unsigned int hooknum,
 122                      const struct net_device *in,
 123                      const struct net_device *out,
 124                      struct nf_conn *ct)
 125 {
 126         struct net *net = nf_ct_net(ct);
 127         int ret;
 128
 129         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
 130
 131         if (ret == NF_ACCEPT) {
 132                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 133                         /* NUL mapping */
 134                         ret = alloc_null_binding(ct, hooknum);
 135         }
 136         return ret;
 137 }
 138
 139 static struct xt_target ipt_snat_reg __read_mostly = {
 140         .name           = "SNAT",
 141         .target         = ipt_snat_target,
 142         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 143         .table          = "nat",
 144         .hooks          = 1 << NF_INET_POST_ROUTING,
 145         .checkentry     = ipt_snat_checkentry,
 146         .family         = AF_INET,
 147 };
 148
 149 static struct xt_target ipt_dnat_reg __read_mostly = {
 150         .name           = "DNAT",
 151         .target         = ipt_dnat_target,
 152         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 153         .table          = "nat",
 154         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 155         .checkentry     = ipt_dnat_checkentry,
 156         .family         = AF_INET,
 157 };
 158
 159 static int __net_init nf_nat_rule_net_init(struct net *net)
 160 {
 161         struct ipt_replace *repl;
 162
 163         repl = ipt_alloc_initial_table(&nat_table);
 164         if (repl == NULL)
 165                 return -ENOMEM;
 166         net->ipv4.nat_table = ipt_register_table(net, &nat_table, repl);
 167         kfree(repl);
 168         if (IS_ERR(net->ipv4.nat_table))
 169                 return PTR_ERR(net->ipv4.nat_table);
 170         return 0;
 171 }
 172
 173 static void __net_exit nf_nat_rule_net_exit(struct net *net)
 174 {
 175         ipt_unregister_table(net, net->ipv4.nat_table);
 176 }
 177
 178 static struct pernet_operations nf_nat_rule_net_ops = {
 179         .init = nf_nat_rule_net_init,
 180         .exit = nf_nat_rule_net_exit,
 181 };
 182
 183 int __init nf_nat_rule_init(void)
 184 {
 185         int ret;
 186
 187         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
 188         if (ret != 0)
 189                 goto out;
 190         ret = xt_register_target(&ipt_snat_reg);
 191         if (ret != 0)
 192                 goto unregister_table;
 193
 194         ret = xt_register_target(&ipt_dnat_reg);
 195         if (ret != 0)
 196                 goto unregister_snat;
 197
 198         return ret;
 199
 200  unregister_snat:
 201         xt_unregister_target(&ipt_snat_reg);
 202  unregister_table:
 203         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 204  out:
 205         return ret;
 206 }
 207
 208 void nf_nat_rule_cleanup(void)
 209 {
 210         xt_unregister_target(&ipt_dnat_reg);
 211         xt_unregister_target(&ipt_snat_reg);
 212         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 213 }