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 struct xt_table packet_filter = {
  57         .name           = "filter",
  58         .valid_hooks    = FILTER_VALID_HOOKS,
  59         .me             = THIS_MODULE,
  60         .af             = AF_INET,
  61 };
  62
  63 /* The work comes in here from netfilter.c. */
  64 static unsigned int
  65 ipt_local_in_hook(unsigned int hook,
  66                   struct sk_buff *skb,
  67                   const struct net_device *in,
  68                   const struct net_device *out,
  69                   int (*okfn)(struct sk_buff *))
  70 {
  71         return ipt_do_table(skb, hook, in, out,
  72                             dev_net(in)->ipv4.iptable_filter);
  73 }
  74
  75 static unsigned int
  76 ipt_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         return ipt_do_table(skb, hook, in, out,
  83                             dev_net(in)->ipv4.iptable_filter);
  84 }
  85
  86 static unsigned int
  87 ipt_local_out_hook(unsigned int hook,
  88                    struct sk_buff *skb,
  89                    const struct net_device *in,
  90                    const struct net_device *out,
  91                    int (*okfn)(struct sk_buff *))
  92 {
  93         /* root is playing with raw sockets. */
  94         if (skb->len < sizeof(struct iphdr) ||
  95             ip_hdrlen(skb) < sizeof(struct iphdr))
  96                 return NF_ACCEPT;
  97         return ipt_do_table(skb, hook, in, out,
  98                             dev_net(out)->ipv4.iptable_filter);
  99 }
 100
 101 static struct nf_hook_ops ipt_ops[] __read_mostly = {
 102         {
 103                 .hook           = ipt_local_in_hook,
 104                 .owner          = THIS_MODULE,
 105                 .pf             = PF_INET,
 106                 .hooknum        = NF_INET_LOCAL_IN,
 107                 .priority       = NF_IP_PRI_FILTER,
 108         },
 109         {
 110                 .hook           = ipt_hook,
 111                 .owner          = THIS_MODULE,
 112                 .pf             = PF_INET,
 113                 .hooknum        = NF_INET_FORWARD,
 114                 .priority       = NF_IP_PRI_FILTER,
 115         },
 116         {
 117                 .hook           = ipt_local_out_hook,
 118                 .owner          = THIS_MODULE,
 119                 .pf             = PF_INET,
 120                 .hooknum        = NF_INET_LOCAL_OUT,
 121                 .priority       = NF_IP_PRI_FILTER,
 122         },
 123 };
 124
 125 /* Default to forward because I got too much mail already. */
 126 static int forward = NF_ACCEPT;
 127 module_param(forward, bool, 0000);
 128
 129 static int __net_init iptable_filter_net_init(struct net *net)
 130 {
 131         /* Register table */
 132         net->ipv4.iptable_filter =
 133                 ipt_register_table(net, &packet_filter, &initial_table.repl);
 134         if (IS_ERR(net->ipv4.iptable_filter))
 135                 return PTR_ERR(net->ipv4.iptable_filter);
 136         return 0;
 137 }
 138
 139 static void __net_exit iptable_filter_net_exit(struct net *net)
 140 {
 141         ipt_unregister_table(net->ipv4.iptable_filter);
 142 }
 143
 144 static struct pernet_operations iptable_filter_net_ops = {
 145         .init = iptable_filter_net_init,
 146         .exit = iptable_filter_net_exit,
 147 };
 148
 149 static int __init iptable_filter_init(void)
 150 {
 151         int ret;
 152
 153         if (forward < 0 || forward > NF_MAX_VERDICT) {
 154                 printk("iptables forward must be 0 or 1\n");
 155                 return -EINVAL;
 156         }
 157
 158         /* Entry 1 is the FORWARD hook */
 159         initial_table.entries[1].target.verdict = -forward - 1;
 160
 161         ret = register_pernet_subsys(&iptable_filter_net_ops);
 162         if (ret < 0)
 163                 return ret;
 164
 165         /* Register hooks */
 166         ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 167         if (ret < 0)
 168                 goto cleanup_table;
 169
 170         return ret;
 171
 172  cleanup_table:
 173         unregister_pernet_subsys(&iptable_filter_net_ops);
 174         return ret;
 175 }
 176
 177 static void __exit iptable_filter_fini(void)
 178 {
 179         nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
 180         unregister_pernet_subsys(&iptable_filter_net_ops);
 181 }
 182
 183 module_init(iptable_filter_init);
 184 module_exit(iptable_filter_fini);