git.oblomov.eu Git - linux-2.6/blob - 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 #include <linux/module.h>
  12 #include <linux/netfilter_ipv4/ip_tables.h>
  13 #include <linux/netdevice.h>
  14 #include <linux/skbuff.h>
  15 #include <net/sock.h>
  16 #include <net/route.h>
  17 #include <linux/ip.h>
  18 #include <net/ip.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  22 MODULE_DESCRIPTION("iptables mangle table");
  23
  24 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
  25                             (1 << NF_INET_LOCAL_IN) | \
  26                             (1 << NF_INET_FORWARD) | \
  27                             (1 << NF_INET_LOCAL_OUT) | \
  28                             (1 << NF_INET_POST_ROUTING))
  29
  30 /* Ouch - five different hooks? Maybe this should be a config option..... -- BC */
  31 static struct
  32 {
  33         struct ipt_replace repl;
  34         struct ipt_standard entries[5];
  35         struct ipt_error term;
  36 } initial_table __initdata = {
  37         .repl = {
  38                 .name = "mangle",
  39                 .valid_hooks = MANGLE_VALID_HOOKS,
  40                 .num_entries = 6,
  41                 .size = sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),
  42                 .hook_entry = {
  43                         [NF_INET_PRE_ROUTING]   = 0,
  44                         [NF_INET_LOCAL_IN]      = sizeof(struct ipt_standard),
  45                         [NF_INET_FORWARD]       = sizeof(struct ipt_standard) * 2,
  46                         [NF_INET_LOCAL_OUT]     = sizeof(struct ipt_standard) * 3,
  47                         [NF_INET_POST_ROUTING]  = sizeof(struct ipt_standard) * 4,
  48                 },
  49                 .underflow = {
  50                         [NF_INET_PRE_ROUTING]   = 0,
  51                         [NF_INET_LOCAL_IN]      = sizeof(struct ipt_standard),
  52                         [NF_INET_FORWARD]       = sizeof(struct ipt_standard) * 2,
  53                         [NF_INET_LOCAL_OUT]     = sizeof(struct ipt_standard) * 3,
  54                         [NF_INET_POST_ROUTING]  = sizeof(struct ipt_standard) * 4,
  55                 },
  56         },
  57         .entries = {
  58                 IPT_STANDARD_INIT(NF_ACCEPT),   /* PRE_ROUTING */
  59                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_IN */
  60                 IPT_STANDARD_INIT(NF_ACCEPT),   /* FORWARD */
  61                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
  62                 IPT_STANDARD_INIT(NF_ACCEPT),   /* POST_ROUTING */
  63         },
  64         .term = IPT_ERROR_INIT,                 /* ERROR */
  65 };
  66
  67 static struct xt_table __packet_mangler = {
  68         .name           = "mangle",
  69         .valid_hooks    = MANGLE_VALID_HOOKS,
  70         .lock           = RW_LOCK_UNLOCKED,
  71         .me             = THIS_MODULE,
  72         .af             = AF_INET,
  73 };
  74 static struct xt_table *packet_mangler;
  75
  76 /* The work comes in here from netfilter.c. */
  77 static unsigned int
  78 ipt_route_hook(unsigned int hook,
  79          struct sk_buff *skb,
  80          const struct net_device *in,
  81          const struct net_device *out,
  82          int (*okfn)(struct sk_buff *))
  83 {
  84         return ipt_do_table(skb, hook, in, out, packet_mangler);
  85 }
  86
  87 static unsigned int
  88 ipt_local_hook(unsigned int hook,
  89                    struct sk_buff *skb,
  90                    const struct net_device *in,
  91                    const struct net_device *out,
  92                    int (*okfn)(struct sk_buff *))
  93 {
  94         unsigned int ret;
  95         const struct iphdr *iph;
  96         u_int8_t tos;
  97         __be32 saddr, daddr;
  98         u_int32_t mark;
  99
 100         /* root is playing with raw sockets. */
 101         if (skb->len < sizeof(struct iphdr)
 102             || ip_hdrlen(skb) < sizeof(struct iphdr)) {
 103                 if (net_ratelimit())
 104                         printk("iptable_mangle: ignoring short SOCK_RAW "
 105                                "packet.\n");
 106                 return NF_ACCEPT;
 107         }
 108
 109         /* Save things which could affect route */
 110         mark = skb->mark;
 111         iph = ip_hdr(skb);
 112         saddr = iph->saddr;
 113         daddr = iph->daddr;
 114         tos = iph->tos;
 115
 116         ret = ipt_do_table(skb, hook, in, out, packet_mangler);
 117         /* Reroute for ANY change. */
 118         if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE) {
 119                 iph = ip_hdr(skb);
 120
 121                 if (iph->saddr != saddr ||
 122                     iph->daddr != daddr ||
 123                     skb->mark != mark ||
 124                     iph->tos != tos)
 125                         if (ip_route_me_harder(skb, RTN_UNSPEC))
 126                                 ret = NF_DROP;
 127         }
 128
 129         return ret;
 130 }
 131
 132 static struct nf_hook_ops ipt_ops[] __read_mostly = {
 133         {
 134                 .hook           = ipt_route_hook,
 135                 .owner          = THIS_MODULE,
 136                 .pf             = PF_INET,
 137                 .hooknum        = NF_INET_PRE_ROUTING,
 138                 .priority       = NF_IP_PRI_MANGLE,
 139         },
 140         {
 141                 .hook           = ipt_route_hook,
 142                 .owner          = THIS_MODULE,
 143                 .pf             = PF_INET,
 144                 .hooknum        = NF_INET_LOCAL_IN,
 145                 .priority       = NF_IP_PRI_MANGLE,
 146         },
 147         {
 148                 .hook           = ipt_route_hook,
 149                 .owner          = THIS_MODULE,
 150                 .pf             = PF_INET,
 151                 .hooknum        = NF_INET_FORWARD,
 152                 .priority       = NF_IP_PRI_MANGLE,
 153         },
 154         {
 155                 .hook           = ipt_local_hook,
 156                 .owner          = THIS_MODULE,
 157                 .pf             = PF_INET,
 158                 .hooknum        = NF_INET_LOCAL_OUT,
 159                 .priority       = NF_IP_PRI_MANGLE,
 160         },
 161         {
 162                 .hook           = ipt_route_hook,
 163                 .owner          = THIS_MODULE,
 164                 .pf             = PF_INET,
 165                 .hooknum        = NF_INET_POST_ROUTING,
 166                 .priority       = NF_IP_PRI_MANGLE,
 167         },
 168 };
 169
 170 static int __init iptable_mangle_init(void)
 171 {
 172         int ret;
 173
 174         /* Register table */
 175         packet_mangler = ipt_register_table(&init_net, &__packet_mangler,
 176                                             &initial_table.repl);
 177         if (IS_ERR(packet_mangler))
 178                 return PTR_ERR(packet_mangler);
 179
 180         /* Register hooks */
 181         ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 182         if (ret < 0)
 183                 goto cleanup_table;
 184
 185         return ret;
 186
 187  cleanup_table:
 188         ipt_unregister_table(packet_mangler);
 189         return ret;
 190 }
 191
 192 static void __exit iptable_mangle_fini(void)
 193 {
 194         nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 195         ipt_unregister_table(packet_mangler);
 196 }
 197
 198 module_init(iptable_mangle_init);
 199 module_exit(iptable_mangle_fini);