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 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
  90 static void warn_if_extra_mangle(struct net *net, __be32 dstip, __be32 srcip)
  91 {
  92         static int warned = 0;
  93         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
  94         struct rtable *rt;
  95
  96         if (ip_route_output_key(net, &rt, &fl) != 0)
  97                 return;
  98
  99         if (rt->rt_src != srcip && !warned) {
 100                 printk("NAT: no longer support implicit source local NAT\n");
 101                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 102                        NIPQUAD(srcip), NIPQUAD(dstip));
 103                 warned = 1;
 104         }
 105         ip_rt_put(rt);
 106 }
 107
 108 static unsigned int
 109 ipt_dnat_target(struct sk_buff *skb, const struct xt_target_param *par)
 110 {
 111         struct nf_conn *ct;
 112         enum ip_conntrack_info ctinfo;
 113         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 114
 115         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
 116                      par->hooknum == NF_INET_LOCAL_OUT);
 117
 118         ct = nf_ct_get(skb, &ctinfo);
 119
 120         /* Connection must be valid and new. */
 121         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 122
 123         if (par->hooknum == NF_INET_LOCAL_OUT &&
 124             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 125                 warn_if_extra_mangle(dev_net(par->out), ip_hdr(skb)->daddr,
 126                                      mr->range[0].min_ip);
 127
 128         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
 129 }
 130
 131 static bool ipt_snat_checkentry(const struct xt_tgchk_param *par)
 132 {
 133         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 134
 135         /* Must be a valid range */
 136         if (mr->rangesize != 1) {
 137                 printk("SNAT: multiple ranges no longer supported\n");
 138                 return false;
 139         }
 140         return true;
 141 }
 142
 143 static bool ipt_dnat_checkentry(const struct xt_tgchk_param *par)
 144 {
 145         const struct nf_nat_multi_range_compat *mr = par->targinfo;
 146
 147         /* Must be a valid range */
 148         if (mr->rangesize != 1) {
 149                 printk("DNAT: multiple ranges no longer supported\n");
 150                 return false;
 151         }
 152         return true;
 153 }
 154
 155 unsigned int
 156 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 157 {
 158         /* Force range to this IP; let proto decide mapping for
 159            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 160            Use reply in case it's already been mangled (eg local packet).
 161         */
 162         __be32 ip
 163                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 164                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 165                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 166         struct nf_nat_range range
 167                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 168
 169         pr_debug("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
 170                  ct, NIPQUAD(ip));
 171         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
 172 }
 173
 174 int nf_nat_rule_find(struct sk_buff *skb,
 175                      unsigned int hooknum,
 176                      const struct net_device *in,
 177                      const struct net_device *out,
 178                      struct nf_conn *ct)
 179 {
 180         struct net *net = nf_ct_net(ct);
 181         int ret;
 182
 183         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
 184
 185         if (ret == NF_ACCEPT) {
 186                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 187                         /* NUL mapping */
 188                         ret = alloc_null_binding(ct, hooknum);
 189         }
 190         return ret;
 191 }
 192
 193 static struct xt_target ipt_snat_reg __read_mostly = {
 194         .name           = "SNAT",
 195         .target         = ipt_snat_target,
 196         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 197         .table          = "nat",
 198         .hooks          = 1 << NF_INET_POST_ROUTING,
 199         .checkentry     = ipt_snat_checkentry,
 200         .family         = AF_INET,
 201 };
 202
 203 static struct xt_target ipt_dnat_reg __read_mostly = {
 204         .name           = "DNAT",
 205         .target         = ipt_dnat_target,
 206         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 207         .table          = "nat",
 208         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 209         .checkentry     = ipt_dnat_checkentry,
 210         .family         = AF_INET,
 211 };
 212
 213 static int __net_init nf_nat_rule_net_init(struct net *net)
 214 {
 215         net->ipv4.nat_table = ipt_register_table(net, &nat_table,
 216                                                  &nat_initial_table.repl);
 217         if (IS_ERR(net->ipv4.nat_table))
 218                 return PTR_ERR(net->ipv4.nat_table);
 219         return 0;
 220 }
 221
 222 static void __net_exit nf_nat_rule_net_exit(struct net *net)
 223 {
 224         ipt_unregister_table(net->ipv4.nat_table);
 225 }
 226
 227 static struct pernet_operations nf_nat_rule_net_ops = {
 228         .init = nf_nat_rule_net_init,
 229         .exit = nf_nat_rule_net_exit,
 230 };
 231
 232 int __init nf_nat_rule_init(void)
 233 {
 234         int ret;
 235
 236         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
 237         if (ret != 0)
 238                 goto out;
 239         ret = xt_register_target(&ipt_snat_reg);
 240         if (ret != 0)
 241                 goto unregister_table;
 242
 243         ret = xt_register_target(&ipt_dnat_reg);
 244         if (ret != 0)
 245                 goto unregister_snat;
 246
 247         return ret;
 248
 249  unregister_snat:
 250         xt_unregister_target(&ipt_snat_reg);
 251  unregister_table:
 252         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 253  out:
 254         return ret;
 255 }
 256
 257 void nf_nat_rule_cleanup(void)
 258 {
 259         xt_unregister_target(&ipt_dnat_reg);
 260         xt_unregister_target(&ipt_snat_reg);
 261         unregister_pernet_subsys(&nf_nat_rule_net_ops);
 262 }