release/src-rt/linux/linux-2.6/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 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 #define NAT_VALID_HOOKS ((1<<NF_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))
  34
  35 static struct
  36 {
  37         struct ipt_replace repl;
  38         struct ipt_standard entries[3];
  39         struct ipt_error term;
  40 } nat_initial_table __initdata = {
  41         .repl = {
  42                 .name = "nat",
  43                 .valid_hooks = NAT_VALID_HOOKS,
  44                 .num_entries = 4,
  45                 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  46                 .hook_entry = {
  47                         [NF_IP_PRE_ROUTING] = 0,
  48                         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  49                         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  50                 },
  51                 .underflow = {
  52                         [NF_IP_PRE_ROUTING] = 0,
  53                         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  54                         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
  55                 },
  56         },
  57         .entries = {
  58                 IPT_STANDARD_INIT(NF_ACCEPT),   /* PRE_ROUTING */
  59                 IPT_STANDARD_INIT(NF_ACCEPT),   /* POST_ROUTING */
  60                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
  61         },
  62         .term = IPT_ERROR_INIT,                 /* ERROR */
  63 };
  64
  65 static struct xt_table nat_table = {
  66         .name           = "nat",
  67         .valid_hooks    = NAT_VALID_HOOKS,
  68         .me             = THIS_MODULE,
  69         .af             = AF_INET,
  70 };
  71
  72 /* Source NAT */
  73 static unsigned int ipt_snat_target(struct sk_buff *skb,
  74                                     const struct net_device *in,
  75                                     const struct net_device *out,
  76                                     unsigned int hooknum,
  77                                     const struct xt_target *target,
  78                                     const void *targinfo)
  79 {
  80         struct nf_conn *ct;
  81         enum ip_conntrack_info ctinfo;
  82         const struct nf_nat_multi_range_compat *mr = targinfo;
  83
  84         NF_CT_ASSERT(hooknum == NF_IP_POST_ROUTING);
  85
  86         ct = nf_ct_get(skb, &ctinfo);
  87
  88         /* Connection must be valid and new. */
  89         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  90                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  91         NF_CT_ASSERT(out);
  92
  93         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
  94 }
  95
  96 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
  97 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
  98 {
  99         static int warned = 0;
 100         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
 101         struct rtable *rt;
 102
 103         if (ip_route_output_key(&rt, &fl) != 0)
 104                 return;
 105
 106         if (rt->rt_src != srcip && !warned) {
 107                 printk("NAT: no longer support implicit source local NAT\n");
 108                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 109                        NIPQUAD(srcip), NIPQUAD(dstip));
 110                 warned = 1;
 111         }
 112         ip_rt_put(rt);
 113 }
 114
 115 static unsigned int ipt_dnat_target(struct sk_buff *skb,
 116                                     const struct net_device *in,
 117                                     const struct net_device *out,
 118                                     unsigned int hooknum,
 119                                     const struct xt_target *target,
 120                                     const void *targinfo)
 121 {
 122         struct nf_conn *ct;
 123         enum ip_conntrack_info ctinfo;
 124         const struct nf_nat_multi_range_compat *mr = targinfo;
 125
 126         NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING ||
 127                      hooknum == NF_IP_LOCAL_OUT);
 128
 129         ct = nf_ct_get(skb, &ctinfo);
 130
 131         /* Connection must be valid and new. */
 132         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 133
 134         if (hooknum == NF_IP_LOCAL_OUT &&
 135             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 136                 warn_if_extra_mangle(ip_hdr(skb)->daddr,
 137                                      mr->range[0].min_ip);
 138
 139         return nf_nat_setup_info(ct, &mr->range[0], hooknum);
 140 }
 141
 142 static int ipt_snat_checkentry(const char *tablename,
 143                                const void *entry,
 144                                const struct xt_target *target,
 145                                void *targinfo,
 146                                unsigned int hook_mask)
 147 {
 148         struct nf_nat_multi_range_compat *mr = targinfo;
 149
 150         /* Must be a valid range */
 151         if (mr->rangesize != 1) {
 152                 printk("SNAT: multiple ranges no longer supported\n");
 153                 return 0;
 154         }
 155         return 1;
 156 }
 157
 158 static int ipt_dnat_checkentry(const char *tablename,
 159                                const void *entry,
 160                                const struct xt_target *target,
 161                                void *targinfo,
 162                                unsigned int hook_mask)
 163 {
 164         struct nf_nat_multi_range_compat *mr = targinfo;
 165
 166         /* Must be a valid range */
 167         if (mr->rangesize != 1) {
 168                 printk("DNAT: multiple ranges no longer supported\n");
 169                 return 0;
 170         }
 171         return 1;
 172 }
 173
 174 inline unsigned int
 175 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
 176 {
 177         /* Force range to this IP; let proto decide mapping for
 178            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 179            Use reply in case it's already been mangled (eg local packet).
 180         */
 181         __be32 ip
 182                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 183                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 184                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 185         struct nf_nat_range range
 186                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 187
 188         DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
 189                ct, NIPQUAD(ip));
 190         return nf_nat_setup_info(ct, &range, hooknum);
 191 }
 192
 193 unsigned int
 194 alloc_null_binding_confirmed(struct nf_conn *ct, unsigned int hooknum)
 195 {
 196         __be32 ip
 197                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 198                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
 199                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
 200         u_int16_t all
 201                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 202                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 203                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 204         struct nf_nat_range range
 205                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 206
 207         DEBUGP("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 208                ct, NIPQUAD(ip));
 209         return nf_nat_setup_info(ct, &range, hooknum);
 210 }
 211
 212 int nf_nat_rule_find(struct sk_buff *skb,
 213                      unsigned int hooknum,
 214                      const struct net_device *in,
 215                      const struct net_device *out,
 216                      struct nf_conn *ct)
 217 {
 218         int ret;
 219
 220         ret = ipt_do_table(skb, hooknum, in, out, &nat_table);
 221
 222         if (ret == NF_ACCEPT) {
 223                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
 224                         /* NUL mapping */
 225                         ret = alloc_null_binding(ct, hooknum);
 226         }
 227         return ret;
 228 }
 229
 230 static struct xt_target ipt_snat_reg = {
 231         .name           = "SNAT",
 232         .target         = ipt_snat_target,
 233         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 234         .table          = "nat",
 235         .hooks          = 1 << NF_IP_POST_ROUTING,
 236         .checkentry     = ipt_snat_checkentry,
 237         .family         = AF_INET,
 238 };
 239
 240 static struct xt_target ipt_dnat_reg = {
 241         .name           = "DNAT",
 242         .target         = ipt_dnat_target,
 243         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 244         .table          = "nat",
 245         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 246         .checkentry     = ipt_dnat_checkentry,
 247         .family         = AF_INET,
 248 };
 249
 250 int __init nf_nat_rule_init(void)
 251 {
 252         int ret;
 253
 254         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 255         if (ret != 0)
 256                 return ret;
 257         ret = xt_register_target(&ipt_snat_reg);
 258         if (ret != 0)
 259                 goto unregister_table;
 260
 261         ret = xt_register_target(&ipt_dnat_reg);
 262         if (ret != 0)
 263                 goto unregister_snat;
 264
 265         return ret;
 266
 267  unregister_snat:
 268         xt_unregister_target(&ipt_snat_reg);
 269  unregister_table:
 270         ipt_unregister_table(&nat_table);
 271
 272         return ret;
 273 }
 274
 275 void nf_nat_rule_cleanup(void)
 276 {
 277         xt_unregister_target(&ipt_dnat_reg);
 278         xt_unregister_target(&ipt_snat_reg);
 279         ipt_unregister_table(&nat_table);
 280 }