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_INET_LOCAL_IN) | \
  23                             (1 << NF_INET_FORWARD) | \
  24                             (1 << NF_INET_LOCAL_OUT))
  25
  26 static struct
  27 {
  28         struct ipt_replace repl;
  29         struct ipt_standard entries[3];
  30         struct ipt_error term;
  31 } initial_table __initdata = {
  32         .repl = {
  33                 .name = "filter",
  34                 .valid_hooks = FILTER_VALID_HOOKS,
  35                 .num_entries = 4,
  36                 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
  37                 .hook_entry = {
  38                         [NF_INET_LOCAL_IN] = 0,
  39                         [NF_INET_FORWARD] = sizeof(struct ipt_standard),
  40                         [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
  41                 },
  42                 .underflow = {
  43                         [NF_INET_LOCAL_IN] = 0,
  44                         [NF_INET_FORWARD] = sizeof(struct ipt_standard),
  45                         [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
  46                 },
  47         },
  48         .entries = {
  49                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_IN */
  50                 IPT_STANDARD_INIT(NF_ACCEPT),   /* FORWARD */
  51                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
  52         },
  53         .term = IPT_ERROR_INIT,                 /* ERROR */
  54 };
  55
  56 static struct xt_table packet_filter = {
  57         .name           = "filter",
  58         .valid_hooks    = FILTER_VALID_HOOKS,
  59         .lock           = RW_LOCK_UNLOCKED,
  60         .me             = THIS_MODULE,
  61         .af             = AF_INET,
  62 };
  63
  64 /* The work comes in here from netfilter.c. */
  65 static unsigned int
  66 ipt_hook(unsigned int hook,
  67          struct sk_buff *skb,
  68          const struct net_device *in,
  69          const struct net_device *out,
  70          int (*okfn)(struct sk_buff *))
  71 {
  72         return ipt_do_table(skb, hook, in, out, &packet_filter);
  73 }
  74
  75 static unsigned int
  76 ipt_local_out_hook(unsigned int hook,
  77                    struct sk_buff *skb,
  78                    const struct net_device *in,
  79                    const struct net_device *out,
  80                    int (*okfn)(struct sk_buff *))
  81 {
  82         /* root is playing with raw sockets. */
  83         if (skb->len < sizeof(struct iphdr) ||
  84             ip_hdrlen(skb) < sizeof(struct iphdr)) {
  85                 if (net_ratelimit())
  86                         printk("iptable_filter: ignoring short SOCK_RAW "
  87                                "packet.\n");
  88                 return NF_ACCEPT;
  89         }
  90
  91         return ipt_do_table(skb, hook, in, out, &packet_filter);
  92 }
  93
  94 static struct nf_hook_ops ipt_ops[] = {
  95         {
  96                 .hook           = ipt_hook,
  97                 .owner          = THIS_MODULE,
  98                 .pf             = PF_INET,
  99                 .hooknum        = NF_INET_LOCAL_IN,
 100                 .priority       = NF_IP_PRI_FILTER,
 101         },
 102         {
 103                 .hook           = ipt_hook,
 104                 .owner          = THIS_MODULE,
 105                 .pf             = PF_INET,
 106                 .hooknum        = NF_INET_FORWARD,
 107                 .priority       = NF_IP_PRI_FILTER,
 108         },
 109         {
 110                 .hook           = ipt_local_out_hook,
 111                 .owner          = THIS_MODULE,
 112                 .pf             = PF_INET,
 113                 .hooknum        = NF_INET_LOCAL_OUT,
 114                 .priority       = NF_IP_PRI_FILTER,
 115         },
 116 };
 117
 118 /* Default to forward because I got too much mail already. */
 119 static int forward = NF_ACCEPT;
 120 module_param(forward, bool, 0000);
 121
 122 static int __init iptable_filter_init(void)
 123 {
 124         int ret;
 125
 126         if (forward < 0 || forward > NF_MAX_VERDICT) {
 127                 printk("iptables forward must be 0 or 1\n");
 128                 return -EINVAL;
 129         }
 130
 131         /* Entry 1 is the FORWARD hook */
 132         initial_table.entries[1].target.verdict = -forward - 1;
 133
 134         /* Register table */
 135         ret = ipt_register_table(&packet_filter, &initial_table.repl);
 136         if (ret < 0)
 137                 return ret;
 138
 139         /* Register hooks */
 140         ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 141         if (ret < 0)
 142                 goto cleanup_table;
 143
 144         return ret;
 145
 146  cleanup_table:
 147         ipt_unregister_table(&packet_filter);
 148         return ret;
 149 }
 150
 151 static void __exit iptable_filter_fini(void)
 152 {
 153         nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 154         ipt_unregister_table(&packet_filter);
 155 }
 156
 157 module_init(iptable_filter_init);
 158 module_exit(iptable_filter_fini);