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