net/ipv4/netfilter/iptable_filter.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  */
  12
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/netfilter_ipv4/ip_tables.h>
  16 #include <net/ip.h>
  17
  18 MODULE_LICENSE("GPL");
  19 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  20 MODULE_DESCRIPTION("iptables filter table");
  21
  22 #define FILTER_VALID_HOOKS ((1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | (1 << NF_IP_LOCAL_OUT))
  23
  24 static struct
  25 {
  26         struct ipt_replace repl;
  27         struct ipt_standard entries[3];
  28         struct ipt_error term;
  29 } initial_table __initdata
  30 = { { "filter", FILTER_VALID_HOOKS, 4,
  31       sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  32       { [NF_IP_LOCAL_IN] = 0,
  33         [NF_IP_FORWARD] = sizeof(struct ipt_standard),
  34         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  35       { [NF_IP_LOCAL_IN] = 0,
  36         [NF_IP_FORWARD] = sizeof(struct ipt_standard),
  37         [NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
  38       0, NULL, { } },
  39     {
  40             /* LOCAL_IN */
  41             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  42                 0,
  43                 sizeof(struct ipt_entry),
  44                 sizeof(struct ipt_standard),
  45                 0, { 0, 0 }, { } },
  46               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  47                 -NF_ACCEPT - 1 } },
  48             /* FORWARD */
  49             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  50                 0,
  51                 sizeof(struct ipt_entry),
  52                 sizeof(struct ipt_standard),
  53                 0, { 0, 0 }, { } },
  54               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  55                 -NF_ACCEPT - 1 } },
  56             /* LOCAL_OUT */
  57             { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  58                 0,
  59                 sizeof(struct ipt_entry),
  60                 sizeof(struct ipt_standard),
  61                 0, { 0, 0 }, { } },
  62               { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  63                 -NF_ACCEPT - 1 } }
  64     },
  65     /* ERROR */
  66     { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  67         0,
  68         sizeof(struct ipt_entry),
  69         sizeof(struct ipt_error),
  70         0, { 0, 0 }, { } },
  71       { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
  72           { } },
  73         "ERROR"
  74       }
  75     }
  76 };
  77
  78 static struct xt_table packet_filter = {
  79         .name           = "filter",
  80         .valid_hooks    = FILTER_VALID_HOOKS,
  81         .lock           = RW_LOCK_UNLOCKED,
  82         .me             = THIS_MODULE,
  83         .af             = AF_INET,
  84 };
  85
  86 /* The work comes in here from netfilter.c. */
  87 static unsigned int
  88 ipt_hook(unsigned int hook,
  89          struct sk_buff **pskb,
  90          const struct net_device *in,
  91          const struct net_device *out,
  92          int (*okfn)(struct sk_buff *))
  93 {
  94         return ipt_do_table(pskb, hook, in, out, &packet_filter);
  95 }
  96
  97 static unsigned int
  98 ipt_local_out_hook(unsigned int hook,
  99                    struct sk_buff **pskb,
 100                    const struct net_device *in,
 101                    const struct net_device *out,
 102                    int (*okfn)(struct sk_buff *))
 103 {
 104         /* root is playing with raw sockets. */
 105         if ((*pskb)->len < sizeof(struct iphdr)
 106             || ip_hdrlen(*pskb) < sizeof(struct iphdr)) {
 107                 if (net_ratelimit())
 108                         printk("ipt_hook: happy cracking.\n");
 109                 return NF_ACCEPT;
 110         }
 111
 112         return ipt_do_table(pskb, hook, in, out, &packet_filter);
 113 }
 114
 115 static struct nf_hook_ops ipt_ops[] = {
 116         {
 117                 .hook           = ipt_hook,
 118                 .owner          = THIS_MODULE,
 119                 .pf             = PF_INET,
 120                 .hooknum        = NF_IP_LOCAL_IN,
 121                 .priority       = NF_IP_PRI_FILTER,
 122         },
 123         {
 124                 .hook           = ipt_hook,
 125                 .owner          = THIS_MODULE,
 126                 .pf             = PF_INET,
 127                 .hooknum        = NF_IP_FORWARD,
 128                 .priority       = NF_IP_PRI_FILTER,
 129         },
 130         {
 131                 .hook           = ipt_local_out_hook,
 132                 .owner          = THIS_MODULE,
 133                 .pf             = PF_INET,
 134                 .hooknum        = NF_IP_LOCAL_OUT,
 135                 .priority       = NF_IP_PRI_FILTER,
 136         },
 137 };
 138
 139 /* Default to forward because I got too much mail already. */
 140 static int forward = NF_ACCEPT;
 141 module_param(forward, bool, 0000);
 142
 143 static int __init iptable_filter_init(void)
 144 {
 145         int ret;
 146
 147         if (forward < 0 || forward > NF_MAX_VERDICT) {
 148                 printk("iptables forward must be 0 or 1\n");
 149                 return -EINVAL;
 150         }
 151
 152         /* Entry 1 is the FORWARD hook */
 153         initial_table.entries[1].target.verdict = -forward - 1;
 154
 155         /* Register table */
 156         ret = ipt_register_table(&packet_filter, &initial_table.repl);
 157         if (ret < 0)
 158                 return ret;
 159
 160         /* Register hooks */
 161         ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 162         if (ret < 0)
 163                 goto cleanup_table;
 164
 165         return ret;
 166
 167  cleanup_table:
 168         ipt_unregister_table(&packet_filter);
 169         return ret;
 170 }
 171
 172 static void __exit iptable_filter_fini(void)
 173 {
 174         nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 175         ipt_unregister_table(&packet_filter);
 176 }
 177
 178 module_init(iptable_filter_init);
 179 module_exit(iptable_filter_fini);