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Linux/net/ipv4/netfilter/iptable_filter.c

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  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 <linux/slab.h>
 17 #include <net/ip.h>
 18 
 19 MODULE_LICENSE("GPL");
 20 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
 21 MODULE_DESCRIPTION("iptables filter table");
 22 
 23 #define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
 24                             (1 << NF_INET_FORWARD) | \
 25                             (1 << NF_INET_LOCAL_OUT))
 26 static int __net_init iptable_filter_table_init(struct net *net);
 27 
 28 static const struct xt_table packet_filter = {
 29         .name           = "filter",
 30         .valid_hooks    = FILTER_VALID_HOOKS,
 31         .me             = THIS_MODULE,
 32         .af             = NFPROTO_IPV4,
 33         .priority       = NF_IP_PRI_FILTER,
 34         .table_init     = iptable_filter_table_init,
 35 };
 36 
 37 static unsigned int
 38 iptable_filter_hook(void *priv, struct sk_buff *skb,
 39                     const struct nf_hook_state *state)
 40 {
 41         if (state->hook == NF_INET_LOCAL_OUT &&
 42             (skb->len < sizeof(struct iphdr) ||
 43              ip_hdrlen(skb) < sizeof(struct iphdr)))
 44                 /* root is playing with raw sockets. */
 45                 return NF_ACCEPT;
 46 
 47         return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
 48 }
 49 
 50 static struct nf_hook_ops *filter_ops __read_mostly;
 51 
 52 /* Default to forward because I got too much mail already. */
 53 static bool forward __read_mostly = true;
 54 module_param(forward, bool, 0000);
 55 
 56 static int __net_init iptable_filter_table_init(struct net *net)
 57 {
 58         struct ipt_replace *repl;
 59         int err;
 60 
 61         if (net->ipv4.iptable_filter)
 62                 return 0;
 63 
 64         repl = ipt_alloc_initial_table(&packet_filter);
 65         if (repl == NULL)
 66                 return -ENOMEM;
 67         /* Entry 1 is the FORWARD hook */
 68         ((struct ipt_standard *)repl->entries)[1].target.verdict =
 69                 forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
 70 
 71         err = ipt_register_table(net, &packet_filter, repl, filter_ops,
 72                                  &net->ipv4.iptable_filter);
 73         kfree(repl);
 74         return err;
 75 }
 76 
 77 static int __net_init iptable_filter_net_init(struct net *net)
 78 {
 79         if (net == &init_net || !forward)
 80                 return iptable_filter_table_init(net);
 81 
 82         return 0;
 83 }
 84 
 85 static void __net_exit iptable_filter_net_exit(struct net *net)
 86 {
 87         if (!net->ipv4.iptable_filter)
 88                 return;
 89         ipt_unregister_table(net, net->ipv4.iptable_filter, filter_ops);
 90         net->ipv4.iptable_filter = NULL;
 91 }
 92 
 93 static struct pernet_operations iptable_filter_net_ops = {
 94         .init = iptable_filter_net_init,
 95         .exit = iptable_filter_net_exit,
 96 };
 97 
 98 static int __init iptable_filter_init(void)
 99 {
100         int ret;
101 
102         filter_ops = xt_hook_ops_alloc(&packet_filter, iptable_filter_hook);
103         if (IS_ERR(filter_ops))
104                 return PTR_ERR(filter_ops);
105 
106         ret = register_pernet_subsys(&iptable_filter_net_ops);
107         if (ret < 0)
108                 kfree(filter_ops);
109 
110         return ret;
111 }
112 
113 static void __exit iptable_filter_fini(void)
114 {
115         unregister_pernet_subsys(&iptable_filter_net_ops);
116         kfree(filter_ops);
117 }
118 
119 module_init(iptable_filter_init);
120 module_exit(iptable_filter_fini);
121 

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