net/ipv4/netfilter/iptable_mangle.c

   1 /*
   2  * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
   3  *
   4  * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
   5  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * Extended to all five netfilter hooks by Brad Chapman & Harald Welte
  12  */
  13 #include <linux/config.h>
  14 #include <linux/module.h>
  15 #include <linux/netfilter_ipv4/ip_tables.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/skbuff.h>
  18 #include <net/sock.h>
  19 #include <net/route.h>
  20 #include <linux/ip.h>
  21
  22 MODULE_LICENSE("GPL");
  23 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  24 MODULE_DESCRIPTION("iptables mangle table");
  25
  26 #define MANGLE_VALID_HOOKS ((1 << NF_IP_PRE_ROUTING) | \
  27                             (1 << NF_IP_LOCAL_IN) | \
  28                             (1 << NF_IP_FORWARD) | \
  29                             (1 << NF_IP_LOCAL_OUT) | \
  30                             (1 << NF_IP_POST_ROUTING))
  31
  32 /* Standard entry. */
  33 struct ipt_standard
  34 {
  35         struct ipt_entry entry;
  36         struct ipt_standard_target target;
  37 };
  38
  39 struct ipt_error_target
  40 {
  41         struct ipt_entry_target target;
  42         char errorname[IPT_FUNCTION_MAXNAMELEN];
  43 };
  44
  45 struct ipt_error
  46 {
  47         struct ipt_entry entry;
  48         struct ipt_error_target target;
  49 };
  50
  51 /* Ouch - five different hooks? Maybe this should be a config option..... -- BC */
  52 static struct
  53 {
  54         struct ipt_replace repl;
  55         struct ipt_standard entries[5];
  56         struct ipt_error term;
  57 } initial_table __initdata
  58 = { { "mangle", MANGLE_VALID_HOOKS, 6,
  59       sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),
  60       { [NF_IP_PRE_ROUTING]     = 0,
  61         [NF_IP_LOCAL_IN]        = sizeof(struct ipt_standard),
  62         [NF_IP_FORWARD]         = sizeof(struct ipt_standard) * 2,
  63         [NF_IP_LOCAL_OUT]       = sizeof(struct ipt_standard) * 3,
  64         [NF_IP_POST_ROUTING]    = sizeof(struct ipt_standard) * 4 },
  65       { [NF_IP_PRE_ROUTING]     = 0,
  66         [NF_IP_LOCAL_IN]        = sizeof(struct ipt_standard),
  67         [NF_IP_FORWARD]         = sizeof(struct ipt_standard) * 2,
  68         [NF_IP_LOCAL_OUT]       = sizeof(struct ipt_standard) * 3,
  69         [NF_IP_POST_ROUTING]    = sizeof(struct ipt_standard) * 4 },
  70       0, NULL, { } },
  71     {
  72             /* PRE_ROUTING */
  73             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  74                 0,
  75                 sizeof(struct ipt_entry),
  76                 sizeof(struct ipt_standard),
  77                 0, { 0, 0 }, { } },
  78               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  79                 -NF_ACCEPT - 1 } },
  80             /* LOCAL_IN */
  81             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  82                 0,
  83                 sizeof(struct ipt_entry),
  84                 sizeof(struct ipt_standard),
  85                 0, { 0, 0 }, { } },
  86               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  87                 -NF_ACCEPT - 1 } },
  88             /* FORWARD */
  89             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  90                 0,
  91                 sizeof(struct ipt_entry),
  92                 sizeof(struct ipt_standard),
  93                 0, { 0, 0 }, { } },
  94               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  95                 -NF_ACCEPT - 1 } },
  96             /* LOCAL_OUT */
  97             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  98                 0,
  99                 sizeof(struct ipt_entry),
 100                 sizeof(struct ipt_standard),
 101                 0, { 0, 0 }, { } },
 102               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
 103                 -NF_ACCEPT - 1 } },
 104             /* POST_ROUTING */
 105             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
 106                 0,
 107                 sizeof(struct ipt_entry),
 108                 sizeof(struct ipt_standard),
 109                 0, { 0, 0 }, { } },
 110               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
 111                 -NF_ACCEPT - 1 } },
 112     },
 113     /* ERROR */
 114     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
 115         0,
 116         sizeof(struct ipt_entry),
 117         sizeof(struct ipt_error),
 118         0, { 0, 0 }, { } },
 119       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
 120           { } },
 121         "ERROR"
 122       }
 123     }
 124 };
 125
 126 static struct ipt_table packet_mangler = {
 127         .name           = "mangle",
 128         .table          = &initial_table.repl,
 129         .valid_hooks    = MANGLE_VALID_HOOKS,
 130         .lock           = RW_LOCK_UNLOCKED,
 131         .me             = THIS_MODULE,
 132 };
 133
 134 /* The work comes in here from netfilter.c. */
 135 static unsigned int
 136 ipt_route_hook(unsigned int hook,
 137          struct sk_buff **pskb,
 138          const struct net_device *in,
 139          const struct net_device *out,
 140          int (*okfn)(struct sk_buff *))
 141 {
 142         return ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
 143 }
 144
 145 static unsigned int
 146 ipt_local_hook(unsigned int hook,
 147                    struct sk_buff **pskb,
 148                    const struct net_device *in,
 149                    const struct net_device *out,
 150                    int (*okfn)(struct sk_buff *))
 151 {
 152         unsigned int ret;
 153         u_int8_t tos;
 154         u_int32_t saddr, daddr;
 155         unsigned long nfmark;
 156
 157         /* root is playing with raw sockets. */
 158         if ((*pskb)->len < sizeof(struct iphdr)
 159             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
 160                 if (net_ratelimit())
 161                         printk("ipt_hook: happy cracking.\n");
 162                 return NF_ACCEPT;
 163         }
 164
 165         /* Save things which could affect route */
 166         nfmark = (*pskb)->nfmark;
 167         saddr = (*pskb)->nh.iph->saddr;
 168         daddr = (*pskb)->nh.iph->daddr;
 169         tos = (*pskb)->nh.iph->tos;
 170
 171         ret = ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
 172         /* Reroute for ANY change. */
 173         if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE
 174             && ((*pskb)->nh.iph->saddr != saddr
 175                 || (*pskb)->nh.iph->daddr != daddr
 176                 || (*pskb)->nfmark != nfmark
 177                 || (*pskb)->nh.iph->tos != tos))
 178                 return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
 179
 180         return ret;
 181 }
 182
 183 static struct nf_hook_ops ipt_ops[] = {
 184         {
 185                 .hook           = ipt_route_hook,
 186                 .owner          = THIS_MODULE,
 187                 .pf             = PF_INET,
 188                 .hooknum        = NF_IP_PRE_ROUTING,
 189                 .priority       = NF_IP_PRI_MANGLE,
 190         },
 191         {
 192                 .hook           = ipt_route_hook,
 193                 .owner          = THIS_MODULE,
 194                 .pf             = PF_INET,
 195                 .hooknum        = NF_IP_LOCAL_IN,
 196                 .priority       = NF_IP_PRI_MANGLE,
 197         },
 198         {
 199                 .hook           = ipt_route_hook,
 200                 .owner          = THIS_MODULE,
 201                 .pf             = PF_INET,
 202                 .hooknum        = NF_IP_FORWARD,
 203                 .priority       = NF_IP_PRI_MANGLE,
 204         },
 205         {
 206                 .hook           = ipt_local_hook,
 207                 .owner          = THIS_MODULE,
 208                 .pf             = PF_INET,
 209                 .hooknum        = NF_IP_LOCAL_OUT,
 210                 .priority       = NF_IP_PRI_MANGLE,
 211         },
 212         {
 213                 .hook           = ipt_route_hook,
 214                 .owner          = THIS_MODULE,
 215                 .pf             = PF_INET,
 216                 .hooknum        = NF_IP_POST_ROUTING,
 217                 .priority       = NF_IP_PRI_MANGLE,
 218         },
 219 };
 220
 221 static int __init init(void)
 222 {
 223         int ret;
 224
 225         /* Register table */
 226         ret = ipt_register_table(&packet_mangler);
 227         if (ret < 0)
 228                 return ret;
 229
 230         /* Register hooks */
 231         ret = nf_register_hook(&ipt_ops[0]);
 232         if (ret < 0)
 233                 goto cleanup_table;
 234
 235         ret = nf_register_hook(&ipt_ops[1]);
 236         if (ret < 0)
 237                 goto cleanup_hook0;
 238
 239         ret = nf_register_hook(&ipt_ops[2]);
 240         if (ret < 0)
 241                 goto cleanup_hook1;
 242
 243         ret = nf_register_hook(&ipt_ops[3]);
 244         if (ret < 0)
 245                 goto cleanup_hook2;
 246
 247         ret = nf_register_hook(&ipt_ops[4]);
 248         if (ret < 0)
 249                 goto cleanup_hook3;
 250
 251         return ret;
 252
 253  cleanup_hook3:
 254         nf_unregister_hook(&ipt_ops[3]);
 255  cleanup_hook2:
 256         nf_unregister_hook(&ipt_ops[2]);
 257  cleanup_hook1:
 258         nf_unregister_hook(&ipt_ops[1]);
 259  cleanup_hook0:
 260         nf_unregister_hook(&ipt_ops[0]);
 261  cleanup_table:
 262         ipt_unregister_table(&packet_mangler);
 263
 264         return ret;
 265 }
 266
 267 static void __exit fini(void)
 268 {
 269         unsigned int i;
 270
 271         for (i = 0; i < sizeof(ipt_ops)/sizeof(struct nf_hook_ops); i++)
 272                 nf_unregister_hook(&ipt_ops[i]);
 273
 274         ipt_unregister_table(&packet_mangler);
 275 }
 276
 277 module_init(init);
 278 module_exit(fini);