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 /* Ouch - five different hooks? Maybe this should be a config option..... -- BC */
  33 static struct
  34 {
  35         struct ipt_replace repl;
  36         struct ipt_standard entries[5];
  37         struct ipt_error term;
  38 } initial_table __initdata
  39 = { { "mangle", MANGLE_VALID_HOOKS, 6,
  40       sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),
  41       { [NF_IP_PRE_ROUTING]     = 0,
  42         [NF_IP_LOCAL_IN]        = sizeof(struct ipt_standard),
  43         [NF_IP_FORWARD]         = sizeof(struct ipt_standard) * 2,
  44         [NF_IP_LOCAL_OUT]       = sizeof(struct ipt_standard) * 3,
  45         [NF_IP_POST_ROUTING]    = sizeof(struct ipt_standard) * 4 },
  46       { [NF_IP_PRE_ROUTING]     = 0,
  47         [NF_IP_LOCAL_IN]        = sizeof(struct ipt_standard),
  48         [NF_IP_FORWARD]         = sizeof(struct ipt_standard) * 2,
  49         [NF_IP_LOCAL_OUT]       = sizeof(struct ipt_standard) * 3,
  50         [NF_IP_POST_ROUTING]    = sizeof(struct ipt_standard) * 4 },
  51       0, NULL, { } },
  52     {
  53             /* PRE_ROUTING */
  54             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  55                 0,
  56                 sizeof(struct ipt_entry),
  57                 sizeof(struct ipt_standard),
  58                 0, { 0, 0 }, { } },
  59               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  60                 -NF_ACCEPT - 1 } },
  61             /* LOCAL_IN */
  62             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  63                 0,
  64                 sizeof(struct ipt_entry),
  65                 sizeof(struct ipt_standard),
  66                 0, { 0, 0 }, { } },
  67               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  68                 -NF_ACCEPT - 1 } },
  69             /* FORWARD */
  70             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  71                 0,
  72                 sizeof(struct ipt_entry),
  73                 sizeof(struct ipt_standard),
  74                 0, { 0, 0 }, { } },
  75               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  76                 -NF_ACCEPT - 1 } },
  77             /* LOCAL_OUT */
  78             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  79                 0,
  80                 sizeof(struct ipt_entry),
  81                 sizeof(struct ipt_standard),
  82                 0, { 0, 0 }, { } },
  83               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  84                 -NF_ACCEPT - 1 } },
  85             /* POST_ROUTING */
  86             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  87                 0,
  88                 sizeof(struct ipt_entry),
  89                 sizeof(struct ipt_standard),
  90                 0, { 0, 0 }, { } },
  91               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  92                 -NF_ACCEPT - 1 } },
  93     },
  94     /* ERROR */
  95     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  96         0,
  97         sizeof(struct ipt_entry),
  98         sizeof(struct ipt_error),
  99         0, { 0, 0 }, { } },
 100       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
 101           { } },
 102         "ERROR"
 103       }
 104     }
 105 };
 106
 107 static struct ipt_table packet_mangler = {
 108         .name           = "mangle",
 109         .valid_hooks    = MANGLE_VALID_HOOKS,
 110         .lock           = RW_LOCK_UNLOCKED,
 111         .me             = THIS_MODULE,
 112 };
 113
 114 /* The work comes in here from netfilter.c. */
 115 static unsigned int
 116 ipt_route_hook(unsigned int hook,
 117          struct sk_buff **pskb,
 118          const struct net_device *in,
 119          const struct net_device *out,
 120          int (*okfn)(struct sk_buff *))
 121 {
 122         return ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
 123 }
 124
 125 static unsigned int
 126 ipt_local_hook(unsigned int hook,
 127                    struct sk_buff **pskb,
 128                    const struct net_device *in,
 129                    const struct net_device *out,
 130                    int (*okfn)(struct sk_buff *))
 131 {
 132         unsigned int ret;
 133         u_int8_t tos;
 134         u_int32_t saddr, daddr;
 135         unsigned long nfmark;
 136
 137         /* root is playing with raw sockets. */
 138         if ((*pskb)->len < sizeof(struct iphdr)
 139             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
 140                 if (net_ratelimit())
 141                         printk("ipt_hook: happy cracking.\n");
 142                 return NF_ACCEPT;
 143         }
 144
 145         /* Save things which could affect route */
 146         nfmark = (*pskb)->nfmark;
 147         saddr = (*pskb)->nh.iph->saddr;
 148         daddr = (*pskb)->nh.iph->daddr;
 149         tos = (*pskb)->nh.iph->tos;
 150
 151         ret = ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
 152         /* Reroute for ANY change. */
 153         if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE
 154             && ((*pskb)->nh.iph->saddr != saddr
 155                 || (*pskb)->nh.iph->daddr != daddr
 156 #ifdef CONFIG_IP_ROUTE_FWMARK
 157                 || (*pskb)->nfmark != nfmark
 158 #endif
 159                 || (*pskb)->nh.iph->tos != tos))
 160                 return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
 161
 162         return ret;
 163 }
 164
 165 static struct nf_hook_ops ipt_ops[] = {
 166         {
 167                 .hook           = ipt_route_hook,
 168                 .owner          = THIS_MODULE,
 169                 .pf             = PF_INET,
 170                 .hooknum        = NF_IP_PRE_ROUTING,
 171                 .priority       = NF_IP_PRI_MANGLE,
 172         },
 173         {
 174                 .hook           = ipt_route_hook,
 175                 .owner          = THIS_MODULE,
 176                 .pf             = PF_INET,
 177                 .hooknum        = NF_IP_LOCAL_IN,
 178                 .priority       = NF_IP_PRI_MANGLE,
 179         },
 180         {
 181                 .hook           = ipt_route_hook,
 182                 .owner          = THIS_MODULE,
 183                 .pf             = PF_INET,
 184                 .hooknum        = NF_IP_FORWARD,
 185                 .priority       = NF_IP_PRI_MANGLE,
 186         },
 187         {
 188                 .hook           = ipt_local_hook,
 189                 .owner          = THIS_MODULE,
 190                 .pf             = PF_INET,
 191                 .hooknum        = NF_IP_LOCAL_OUT,
 192                 .priority       = NF_IP_PRI_MANGLE,
 193         },
 194         {
 195                 .hook           = ipt_route_hook,
 196                 .owner          = THIS_MODULE,
 197                 .pf             = PF_INET,
 198                 .hooknum        = NF_IP_POST_ROUTING,
 199                 .priority       = NF_IP_PRI_MANGLE,
 200         },
 201 };
 202
 203 static int __init init(void)
 204 {
 205         int ret;
 206
 207         /* Register table */
 208         ret = ipt_register_table(&packet_mangler, &initial_table.repl);
 209         if (ret < 0)
 210                 return ret;
 211
 212         /* Register hooks */
 213         ret = nf_register_hook(&ipt_ops[0]);
 214         if (ret < 0)
 215                 goto cleanup_table;
 216
 217         ret = nf_register_hook(&ipt_ops[1]);
 218         if (ret < 0)
 219                 goto cleanup_hook0;
 220
 221         ret = nf_register_hook(&ipt_ops[2]);
 222         if (ret < 0)
 223                 goto cleanup_hook1;
 224
 225         ret = nf_register_hook(&ipt_ops[3]);
 226         if (ret < 0)
 227                 goto cleanup_hook2;
 228
 229         ret = nf_register_hook(&ipt_ops[4]);
 230         if (ret < 0)
 231                 goto cleanup_hook3;
 232
 233         return ret;
 234
 235  cleanup_hook3:
 236         nf_unregister_hook(&ipt_ops[3]);
 237  cleanup_hook2:
 238         nf_unregister_hook(&ipt_ops[2]);
 239  cleanup_hook1:
 240         nf_unregister_hook(&ipt_ops[1]);
 241  cleanup_hook0:
 242         nf_unregister_hook(&ipt_ops[0]);
 243  cleanup_table:
 244         ipt_unregister_table(&packet_mangler);
 245
 246         return ret;
 247 }
 248
 249 static void __exit fini(void)
 250 {
 251         unsigned int i;
 252
 253         for (i = 0; i < sizeof(ipt_ops)/sizeof(struct nf_hook_ops); i++)
 254                 nf_unregister_hook(&ipt_ops[i]);
 255
 256         ipt_unregister_table(&packet_mangler);
 257 }
 258
 259 module_init(init);
 260 module_exit(fini);