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