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                          (1 << NF_INET_LOCAL_IN))
  33
  34 static const struct xt_table nat_table = {
  35         .name           = "nat",
  36         .valid_hooks    = NAT_VALID_HOOKS,
  37         .me             = THIS_MODULE,
  38         .af             = NFPROTO_IPV4,
  39 };
  40
  41 /* Source NAT */
  42 static unsigned int
  43 ipt_snat_target(struct sk_buff *skb, const struct xt_action_param *par)
  44 {
  45         struct nf_conn *ct;
  46         enum ip_conntrack_info ctinfo;
  47         const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
  48
  49         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING ||
  50                      par->hooknum == NF_INET_LOCAL_IN);
  51
  52         ct = nf_ct_get(skb, &ctinfo);
  53
  54         /* Connection must be valid and new. */
  55         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  56                             ctinfo == IP_CT_RELATED_REPLY));
  57         NF_CT_ASSERT(par->out != NULL);
  58
  59         return nf_nat_setup_info(ct, &mr->range[0], NF_NAT_MANIP_SRC);
  60 }
  61
  62 static unsigned int
  63 ipt_dnat_target(struct sk_buff *skb, const struct xt_action_param *par)
  64 {
  65         struct nf_conn *ct;
  66         enum ip_conntrack_info ctinfo;
  67         const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
  68
  69         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
  70                      par->hooknum == NF_INET_LOCAL_OUT);
  71
  72         ct = nf_ct_get(skb, &ctinfo);
  73
  74         /* Connection must be valid and new. */
  75         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  76
  77         return nf_nat_setup_info(ct, &mr->range[0], NF_NAT_MANIP_DST);
  78 }
  79
  80 static int ipt_snat_checkentry(const struct xt_tgchk_param *par)
  81 {
  82         const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
  83
  84         /* Must be a valid range */
  85         if (mr->rangesize != 1) {
  86                 pr_info("SNAT: multiple ranges no longer supported\n");
  87                 return -EINVAL;
  88         }
  89         return 0;
  90 }
  91
  92 static int ipt_dnat_checkentry(const struct xt_tgchk_param *par)
  93 {
  94         const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
  95
  96         /* Must be a valid range */
  97         if (mr->rangesize != 1) {
  98                 pr_info("DNAT: multiple ranges no longer supported\n");
  99                 return -EINVAL;
 100         }
 101         return 0;
 102 }
 103
 104 static unsigned int
 105 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 106 {
 107         /* Force range to this IP; let proto decide mapping for
 108            per-proto parts (hence not NF_NAT_RANGE_PROTO_SPECIFIED).
 109         */
 110         struct nf_nat_ipv4_range range;
 111
 112         range.flags = 0;
 113         pr_debug("Allocating NULL binding for %p (%pI4)\n", ct,
 114                  HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC ?
 115                  &ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip :
 116                  &ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 117
 118         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
 119 }
 120
 121 int nf_nat_rule_find(struct sk_buff *skb,
 122                      unsigned int hooknum,
 123                      const struct net_device *in,
 124                      const struct net_device *out,
 125                      struct nf_conn *ct)
 126 {
 127         struct net *net = nf_ct_net(ct);
 128         int ret;
 129
 130         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
 131
 132         if (ret == NF_ACCEPT) {
 133                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 134                         /* NUL mapping */
 135                         ret = alloc_null_binding(ct, hooknum);
 136         }
 137         return ret;
 138 }
 139
 140 static struct xt_target ipt_snat_reg __read_mostly = {
 141         .name           = "SNAT",
 142         .target         = ipt_snat_target,
 143         .targetsize     = sizeof(struct nf_nat_ipv4_multi_range_compat),
 144         .table          = "nat",
 145         .hooks          = (1 << NF_INET_POST_ROUTING) | (1 << NF_INET_LOCAL_IN),
 146         .checkentry     = ipt_snat_checkentry,
 147         .family         = AF_INET,
 148 };
 149
 150 static struct xt_target ipt_dnat_reg __read_mostly = {
 151         .name           = "DNAT",
 152         .target         = ipt_dnat_target,
 153         .targetsize     = sizeof(struct nf_nat_ipv4_multi_range_compat),
 154         .table          = "nat",
 155         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 156         .checkentry     = ipt_dnat_checkentry,
 157         .family         = AF_INET,
 158 };
 159
 160 static int __net_init nf_nat_rule_net_init(struct net *net)
 161 {
 162         struct ipt_replace *repl;
 163
 164         repl = ipt_alloc_initial_table(&nat_table);
 165         if (repl == NULL)
 166                 return -ENOMEM;
 167         net->ipv4.nat_table = ipt_register_table(net, &nat_table, repl);
 168         kfree(repl);
 169         if (IS_ERR(net->ipv4.nat_table))
 170                 return PTR_ERR(net->ipv4.nat_table);
 171         return 0;
 172 }
 173
 174 static void __net_exit nf_nat_rule_net_exit(struct net *net)
 175 {
 176         ipt_unregister_table(net, net->ipv4.nat_table);
 177 }
 178
 179 static struct pernet_operations nf_nat_rule_net_ops = {
 180         .init = nf_nat_rule_net_init,
 181         .exit = nf_nat_rule_net_exit,
 182 };
 183
 184 int __init nf_nat_rule_init(void)
 185 {
 186         int ret;
 187
 188         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
 189         if (ret != 0)
 190                 goto out;
 191         ret = xt_register_target(&ipt_snat_reg);
 192         if (ret != 0)
 193                 goto unregister_table;
 194
 195         ret = xt_register_target(&ipt_dnat_reg);
 196         if (ret != 0)
 197                 goto unregister_snat;
 198
 199         return ret;
 200
 201  unregister_snat:
 202         xt_unregister_target(&ipt_snat_reg);
 203  unregister_table:
 204         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 205  out:
 206         return ret;
 207 }
 208
 209 void nf_nat_rule_cleanup(void)
 210 {
 211         xt_unregister_target(&ipt_dnat_reg);
 212         xt_unregister_target(&ipt_snat_reg);
 213         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 214 }