net/ipv4/netfilter/ip_nat_rule.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 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 #define ASSERT_READ_LOCK(x)
  23 #define ASSERT_WRITE_LOCK(x)
  24
  25 #include <linux/netfilter_ipv4/ip_tables.h>
  26 #include <linux/netfilter_ipv4/ip_nat.h>
  27 #include <linux/netfilter_ipv4/ip_nat_core.h>
  28 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  29 #include <linux/netfilter_ipv4/listhelp.h>
  30
  31 #if 0
  32 #define DEBUGP printk
  33 #else
  34 #define DEBUGP(format, args...)
  35 #endif
  36
  37 #define NAT_VALID_HOOKS ((1<<NF_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))
  38
  39 static struct
  40 {
  41         struct ipt_replace repl;
  42         struct ipt_standard entries[3];
  43         struct ipt_error term;
  44 } nat_initial_table __initdata
  45 = { { "nat", NAT_VALID_HOOKS, 4,
  46       sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  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       { [NF_IP_PRE_ROUTING] = 0,
  51         [NF_IP_POST_ROUTING] = sizeof(struct ipt_standard),
  52         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  53       0, NULL, { } },
  54     {
  55             /* PRE_ROUTING */
  56             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  57                 0,
  58                 sizeof(struct ipt_entry),
  59                 sizeof(struct ipt_standard),
  60                 0, { 0, 0 }, { } },
  61               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  62                 -NF_ACCEPT - 1 } },
  63             /* POST_ROUTING */
  64             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  65                 0,
  66                 sizeof(struct ipt_entry),
  67                 sizeof(struct ipt_standard),
  68                 0, { 0, 0 }, { } },
  69               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  70                 -NF_ACCEPT - 1 } },
  71             /* LOCAL_OUT */
  72             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  73                 0,
  74                 sizeof(struct ipt_entry),
  75                 sizeof(struct ipt_standard),
  76                 0, { 0, 0 }, { } },
  77               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  78                 -NF_ACCEPT - 1 } }
  79     },
  80     /* ERROR */
  81     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  82         0,
  83         sizeof(struct ipt_entry),
  84         sizeof(struct ipt_error),
  85         0, { 0, 0 }, { } },
  86       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
  87           { } },
  88         "ERROR"
  89       }
  90     }
  91 };
  92
  93 static struct ipt_table nat_table = {
  94         .name           = "nat",
  95         .valid_hooks    = NAT_VALID_HOOKS,
  96         .lock           = RW_LOCK_UNLOCKED,
  97         .me             = THIS_MODULE,
  98         .af             = AF_INET,
  99 };
 100
 101 /* Source NAT */
 102 static unsigned int ipt_snat_target(struct sk_buff **pskb,
 103                                     const struct net_device *in,
 104                                     const struct net_device *out,
 105                                     unsigned int hooknum,
 106                                     const struct ipt_target *target,
 107                                     const void *targinfo,
 108                                     void *userinfo)
 109 {
 110         struct ip_conntrack *ct;
 111         enum ip_conntrack_info ctinfo;
 112         const struct ip_nat_multi_range_compat *mr = targinfo;
 113
 114         IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
 115
 116         ct = ip_conntrack_get(*pskb, &ctinfo);
 117
 118         /* Connection must be valid and new. */
 119         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
 120                             || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
 121         IP_NF_ASSERT(out);
 122
 123         return ip_nat_setup_info(ct, &mr->range[0], hooknum);
 124 }
 125
 126 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
 127 static void warn_if_extra_mangle(u32 dstip, u32 srcip)
 128 {
 129         static int warned = 0;
 130         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
 131         struct rtable *rt;
 132
 133         if (ip_route_output_key(&rt, &fl) != 0)
 134                 return;
 135
 136         if (rt->rt_src != srcip && !warned) {
 137                 printk("NAT: no longer support implicit source local NAT\n");
 138                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
 139                        NIPQUAD(srcip), NIPQUAD(dstip));
 140                 warned = 1;
 141         }
 142         ip_rt_put(rt);
 143 }
 144
 145 static unsigned int ipt_dnat_target(struct sk_buff **pskb,
 146                                     const struct net_device *in,
 147                                     const struct net_device *out,
 148                                     unsigned int hooknum,
 149                                     const struct ipt_target *target,
 150                                     const void *targinfo,
 151                                     void *userinfo)
 152 {
 153         struct ip_conntrack *ct;
 154         enum ip_conntrack_info ctinfo;
 155         const struct ip_nat_multi_range_compat *mr = targinfo;
 156
 157         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
 158                      || hooknum == NF_IP_LOCAL_OUT);
 159
 160         ct = ip_conntrack_get(*pskb, &ctinfo);
 161
 162         /* Connection must be valid and new. */
 163         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
 164
 165         if (hooknum == NF_IP_LOCAL_OUT
 166             && mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
 167                 warn_if_extra_mangle((*pskb)->nh.iph->daddr,
 168                                      mr->range[0].min_ip);
 169
 170         return ip_nat_setup_info(ct, &mr->range[0], hooknum);
 171 }
 172
 173 static int ipt_snat_checkentry(const char *tablename,
 174                                const void *entry,
 175                                const struct ipt_target *target,
 176                                void *targinfo,
 177                                unsigned int targinfosize,
 178                                unsigned int hook_mask)
 179 {
 180         struct ip_nat_multi_range_compat *mr = targinfo;
 181
 182         /* Must be a valid range */
 183         if (mr->rangesize != 1) {
 184                 printk("SNAT: multiple ranges no longer supported\n");
 185                 return 0;
 186         }
 187         return 1;
 188 }
 189
 190 static int ipt_dnat_checkentry(const char *tablename,
 191                                const void *entry,
 192                                const struct ipt_target *target,
 193                                void *targinfo,
 194                                unsigned int targinfosize,
 195                                unsigned int hook_mask)
 196 {
 197         struct ip_nat_multi_range_compat *mr = targinfo;
 198
 199         /* Must be a valid range */
 200         if (mr->rangesize != 1) {
 201                 printk("DNAT: multiple ranges no longer supported\n");
 202                 return 0;
 203         }
 204         return 1;
 205 }
 206
 207 inline unsigned int
 208 alloc_null_binding(struct ip_conntrack *conntrack,
 209                    struct ip_nat_info *info,
 210                    unsigned int hooknum)
 211 {
 212         /* Force range to this IP; let proto decide mapping for
 213            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
 214            Use reply in case it's already been mangled (eg local packet).
 215         */
 216         u_int32_t ip
 217                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 218                    ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip
 219                    : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
 220         struct ip_nat_range range
 221                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
 222
 223         DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n", conntrack,
 224                NIPQUAD(ip));
 225         return ip_nat_setup_info(conntrack, &range, hooknum);
 226 }
 227
 228 unsigned int
 229 alloc_null_binding_confirmed(struct ip_conntrack *conntrack,
 230                              struct ip_nat_info *info,
 231                              unsigned int hooknum)
 232 {
 233         u_int32_t ip
 234                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 235                    ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip
 236                    : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
 237         u_int16_t all
 238                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
 239                    ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
 240                    : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
 241         struct ip_nat_range range
 242                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
 243
 244         DEBUGP("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
 245                conntrack, NIPQUAD(ip));
 246         return ip_nat_setup_info(conntrack, &range, hooknum);
 247 }
 248
 249 int ip_nat_rule_find(struct sk_buff **pskb,
 250                      unsigned int hooknum,
 251                      const struct net_device *in,
 252                      const struct net_device *out,
 253                      struct ip_conntrack *ct,
 254                      struct ip_nat_info *info)
 255 {
 256         int ret;
 257
 258         ret = ipt_do_table(pskb, hooknum, in, out, &nat_table, NULL);
 259
 260         if (ret == NF_ACCEPT) {
 261                 if (!ip_nat_initialized(ct, HOOK2MANIP(hooknum)))
 262                         /* NUL mapping */
 263                         ret = alloc_null_binding(ct, info, hooknum);
 264         }
 265         return ret;
 266 }
 267
 268 static struct ipt_target ipt_snat_reg = {
 269         .name           = "SNAT",
 270         .target         = ipt_snat_target,
 271         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 272         .table          = "nat",
 273         .hooks          = 1 << NF_IP_POST_ROUTING,
 274         .checkentry     = ipt_snat_checkentry,
 275 };
 276
 277 static struct ipt_target ipt_dnat_reg = {
 278         .name           = "DNAT",
 279         .target         = ipt_dnat_target,
 280         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 281         .table          = "nat",
 282         .hooks          = 1 << NF_IP_PRE_ROUTING,
 283         .checkentry     = ipt_dnat_checkentry,
 284 };
 285
 286 int __init ip_nat_rule_init(void)
 287 {
 288         int ret;
 289
 290         ret = ipt_register_table(&nat_table, &nat_initial_table.repl);
 291         if (ret != 0)
 292                 return ret;
 293         ret = ipt_register_target(&ipt_snat_reg);
 294         if (ret != 0)
 295                 goto unregister_table;
 296
 297         ret = ipt_register_target(&ipt_dnat_reg);
 298         if (ret != 0)
 299                 goto unregister_snat;
 300
 301         return ret;
 302
 303  unregister_snat:
 304         ipt_unregister_target(&ipt_snat_reg);
 305  unregister_table:
 306         ipt_unregister_table(&nat_table);
 307
 308         return ret;
 309 }
 310
 311 void ip_nat_rule_cleanup(void)
 312 {
 313         ipt_unregister_target(&ipt_dnat_reg);
 314         ipt_unregister_target(&ipt_snat_reg);
 315         ipt_unregister_table(&nat_table);
 316 }