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 __net_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 const struct xt_table packet_filter = {
  57         .name           = "filter",
  58         .valid_hooks    = FILTER_VALID_HOOKS,
  59         .me             = THIS_MODULE,
  60         .af             = NFPROTO_IPV4,
  61         .priority       = NF_IP_PRI_FILTER,
  62 };
  63
  64 static unsigned int
  65 iptable_filter_hook(unsigned int hook, struct sk_buff *skb,
  66                     const struct net_device *in, const struct net_device *out,
  67                     int (*okfn)(struct sk_buff *))
  68 {
  69         const struct net *net;
  70
  71         if (hook == NF_INET_LOCAL_OUT &&
  72             (skb->len < sizeof(struct iphdr) ||
  73              ip_hdrlen(skb) < sizeof(struct iphdr)))
  74                 /* root is playing with raw sockets. */
  75                 return NF_ACCEPT;
  76
  77         net = dev_net((in != NULL) ? in : out);
  78         return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter);
  79 }
  80
  81 static struct nf_hook_ops *filter_ops __read_mostly;
  82
  83 /* Default to forward because I got too much mail already. */
  84 static int forward = NF_ACCEPT;
  85 module_param(forward, bool, 0000);
  86
  87 static int __net_init iptable_filter_net_init(struct net *net)
  88 {
  89         /* Register table */
  90         net->ipv4.iptable_filter =
  91                 ipt_register_table(net, &packet_filter, &initial_table.repl);
  92         if (IS_ERR(net->ipv4.iptable_filter))
  93                 return PTR_ERR(net->ipv4.iptable_filter);
  94         return 0;
  95 }
  96
  97 static void __net_exit iptable_filter_net_exit(struct net *net)
  98 {
  99         ipt_unregister_table(net, net->ipv4.iptable_filter);
 100 }
 101
 102 static struct pernet_operations iptable_filter_net_ops = {
 103         .init = iptable_filter_net_init,
 104         .exit = iptable_filter_net_exit,
 105 };
 106
 107 static int __init iptable_filter_init(void)
 108 {
 109         int ret;
 110
 111         if (forward < 0 || forward > NF_MAX_VERDICT) {
 112                 printk("iptables forward must be 0 or 1\n");
 113                 return -EINVAL;
 114         }
 115
 116         /* Entry 1 is the FORWARD hook */
 117         initial_table.entries[1].target.verdict = -forward - 1;
 118
 119         ret = register_pernet_subsys(&iptable_filter_net_ops);
 120         if (ret < 0)
 121                 return ret;
 122
 123         /* Register hooks */
 124         filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
 125         if (IS_ERR(filter_ops)) {
 126                 ret = PTR_ERR(filter_ops);
 127                 goto cleanup_table;
 128         }
 129
 130         return ret;
 131
 132  cleanup_table:
 133         unregister_pernet_subsys(&iptable_filter_net_ops);
 134         return ret;
 135 }
 136
 137 static void __exit iptable_filter_fini(void)
 138 {
 139         xt_hook_unlink(&packet_filter, filter_ops);
 140         unregister_pernet_subsys(&iptable_filter_net_ops);
 141 }
 142
 143 module_init(iptable_filter_init);
 144 module_exit(iptable_filter_fini);