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