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_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))
  28
  29 static struct
  30 {
  31         struct ipt_replace repl;
  32         struct ipt_standard entries[3];
  33         struct ipt_error term;
  34 } nat_initial_table __initdata = {
  35         .repl = {
  36                 .name = "nat",
  37                 .valid_hooks = NAT_VALID_HOOKS,
  38                 .num_entries = 4,
  39                 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  40                 .hook_entry = {
  41                         [NF_IP_PRE_ROUTING] = 0,
  42                         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  43                         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  44                 },
  45                 .underflow = {
  46                         [NF_IP_PRE_ROUTING] = 0,
  47                         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  48                         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  49                 },
  50         },
  51         .entries = {
  52                 IPT_STANDARD_INIT(NF_ACCEPT),   /* PRE_ROUTING */
  53                 IPT_STANDARD_INIT(NF_ACCEPT),   /* POST_ROUTING */
  54                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
  55         },
  56         .term = IPT_ERROR_INIT,                 /* ERROR */
  57 };
  58
  59 static struct xt_table nat_table = {
  60         .name           = "nat",
  61         .valid_hooks    = NAT_VALID_HOOKS,
  62         .lock           = RW_LOCK_UNLOCKED,
  63         .me             = THIS_MODULE,
  64         .af             = AF_INET,
  65 };
  66
  67 /* Source NAT */
  68 static unsigned int ipt_snat_target(struct sk_buff **pskb,
  69                                     const struct net_device *in,
  70                                     const struct net_device *out,
  71                                     unsigned int hooknum,
  72                                     const struct xt_target *target,
  73                                     const void *targinfo)
  74 {
  75         struct nf_conn *ct;
  76         enum ip_conntrack_info ctinfo;
  77         const struct nf_nat_multi_range_compat *mr = targinfo;
  78
  79         NF_CT_ASSERT(hooknum == NF_IP_POST_ROUTING);
  80
  81         ct = nf_ct_get(*pskb, &ctinfo);
  82
  83         /* Connection must be valid and new. */
  84         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  85                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  86         NF_CT_ASSERT(out);
  87
  88         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
  89 }
  90
  91 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
  92 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
  93 {
  94         static int warned = 0;
  95         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
  96         struct rtable *rt;
  97
  98         if (ip_route_output_key(&rt, &fl) != 0)
  99                 return;
 100
 101         if (rt->rt_src != srcip && !warned) {
 102                 printk("NAT: no longer support implicit source local NAT\n");
 103                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 104                        NIPQUAD(srcip), NIPQUAD(dstip));
 105                 warned = 1;
 106         }
 107         ip_rt_put(rt);
 108 }
 109
 110 static unsigned int ipt_dnat_target(struct sk_buff **pskb,
 111                                     const struct net_device *in,
 112                                     const struct net_device *out,
 113                                     unsigned int hooknum,
 114                                     const struct xt_target *target,
 115                                     const void *targinfo)
 116 {
 117         struct nf_conn *ct;
 118         enum ip_conntrack_info ctinfo;
 119         const struct nf_nat_multi_range_compat *mr = targinfo;
 120
 121         NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 122                      hooknum == NF_IP_LOCAL_OUT);
 123
 124         ct = nf_ct_get(*pskb, &ctinfo);
 125
 126         /* Connection must be valid and new. */
 127         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 128
 129         if (hooknum == NF_IP_LOCAL_OUT &&
 130             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 131                 warn_if_extra_mangle(ip_hdr(*pskb)->daddr,
 132                                      mr->range[0].min_ip);
 133
 134         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
 135 }
 136
 137 static bool ipt_snat_checkentry(const char *tablename,
 138                                 const void *entry,
 139                                 const struct xt_target *target,
 140                                 void *targinfo,
 141                                 unsigned int hook_mask)
 142 {
 143         struct nf_nat_multi_range_compat *mr = targinfo;
 144
 145         /* Must be a valid range */
 146         if (mr->rangesize != 1) {
 147                 printk("SNAT: multiple ranges no longer supported\n");
 148                 return false;
 149         }
 150         return true;
 151 }
 152
 153 static bool ipt_dnat_checkentry(const char *tablename,
 154                                 const void *entry,
 155                                 const struct xt_target *target,
 156                                 void *targinfo,
 157                                 unsigned int hook_mask)
 158 {
 159         struct nf_nat_multi_range_compat *mr = targinfo;
 160
 161         /* Must be a valid range */
 162         if (mr->rangesize != 1) {
 163                 printk("DNAT: multiple ranges no longer supported\n");
 164                 return false;
 165         }
 166         return true;
 167 }
 168
 169 unsigned int
 170 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 171 {
 172         /* Force range to this IP; let proto decide mapping for
 173            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 174            Use reply in case it's already been mangled (eg local packet).
 175         */
 176         __be32 ip
 177                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 178                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 179                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 180         struct nf_nat_range range
 181                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 182
 183         pr_debug("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
 184                  ct, NIPQUAD(ip));
 185         return nf_nat_setup_info(ct, &range, hooknum);
 186 }
 187
 188 unsigned int
 189 alloc_null_binding_confirmed(struct nf_conn *ct, unsigned int hooknum)
 190 {
 191         __be32 ip
 192                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 193                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 194                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 195         u_int16_t all
 196                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 197                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 198                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 199         struct nf_nat_range range
 200                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 201
 202         pr_debug("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 203                  ct, NIPQUAD(ip));
 204         return nf_nat_setup_info(ct, &range, hooknum);
 205 }
 206
 207 int nf_nat_rule_find(struct sk_buff **pskb,
 208                      unsigned int hooknum,
 209                      const struct net_device *in,
 210                      const struct net_device *out,
 211                      struct nf_conn *ct)
 212 {
 213         int ret;
 214
 215         ret = ipt_do_table(pskb, hooknum, in, out, &nat_table);
 216
 217         if (ret == NF_ACCEPT) {
 218                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 219                         /* NUL mapping */
 220                         ret = alloc_null_binding(ct, hooknum);
 221         }
 222         return ret;
 223 }
 224
 225 static struct xt_target ipt_snat_reg __read_mostly = {
 226         .name           = "SNAT",
 227         .target         = ipt_snat_target,
 228         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 229         .table          = "nat",
 230         .hooks          = 1 << NF_IP_POST_ROUTING,
 231         .checkentry     = ipt_snat_checkentry,
 232         .family         = AF_INET,
 233 };
 234
 235 static struct xt_target ipt_dnat_reg __read_mostly = {
 236         .name           = "DNAT",
 237         .target         = ipt_dnat_target,
 238         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 239         .table          = "nat",
 240         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 241         .checkentry     = ipt_dnat_checkentry,
 242         .family         = AF_INET,
 243 };
 244
 245 int __init nf_nat_rule_init(void)
 246 {
 247         int ret;
 248
 249         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 250         if (ret != 0)
 251                 return ret;
 252         ret = xt_register_target(&ipt_snat_reg);
 253         if (ret != 0)
 254                 goto unregister_table;
 255
 256         ret = xt_register_target(&ipt_dnat_reg);
 257         if (ret != 0)
 258                 goto unregister_snat;
 259
 260         return ret;
 261
 262  unregister_snat:
 263         xt_unregister_target(&ipt_snat_reg);
 264  unregister_table:
 265         ipt_unregister_table(&nat_table);
 266
 267         return ret;
 268 }
 269
 270 void nf_nat_rule_cleanup(void)
 271 {
 272         xt_unregister_target(&ipt_dnat_reg);
 273         xt_unregister_target(&ipt_snat_reg);
 274         ipt_unregister_table(&nat_table);
 275 }