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 27 static const struct xt_table packet_filter = { 28 .name = "filter", 29 .valid_hooks = FILTER_VALID_HOOKS, 30 .me = THIS_MODULE, 31 .af = NFPROTO_IPV4, 32 .priority = NF_IP_PRI_FILTER, 33 }; 34 35 static unsigned int 36 iptable_filter_hook(unsigned int hook, struct sk_buff *skb, 37 const struct net_device *in, const struct net_device *out, 38 int (*okfn)(struct sk_buff *)) 39 { 40 const struct net *net; 41 42 if (hook == NF_INET_LOCAL_OUT && 43 (skb->len < sizeof(struct iphdr) || 44 ip_hdrlen(skb) < sizeof(struct iphdr))) 45 /* root is playing with raw sockets. */ 46 return NF_ACCEPT; 47 48 net = dev_net((in != NULL) ? in : out); 49 return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter); 50 } 51 52 static struct nf_hook_ops *filter_ops __read_mostly; 53 54 /* Default to forward because I got too much mail already. */ 55 static bool forward = true; 56 module_param(forward, bool, 0000); 57 58 static int __net_init iptable_filter_net_init(struct net *net) 59 { 60 struct ipt_replace *repl; 61 62 repl = ipt_alloc_initial_table(&packet_filter); 63 if (repl == NULL) 64 return -ENOMEM; 65 /* Entry 1 is the FORWARD hook */ 66 ((struct ipt_standard *)repl->entries)[1].target.verdict = 67 forward ? -NF_ACCEPT - 1 : -NF_DROP - 1; 68 69 net->ipv4.iptable_filter = 70 ipt_register_table(net, &packet_filter, repl); 71 kfree(repl); 72 return PTR_RET(net->ipv4.iptable_filter); 73 } 74 75 static void __net_exit iptable_filter_net_exit(struct net *net) 76 { 77 ipt_unregister_table(net, net->ipv4.iptable_filter); 78 } 79 80 static struct pernet_operations iptable_filter_net_ops = { 81 .init = iptable_filter_net_init, 82 .exit = iptable_filter_net_exit, 83 }; 84 85 static int __init iptable_filter_init(void) 86 { 87 int ret; 88 89 ret = register_pernet_subsys(&iptable_filter_net_ops); 90 if (ret < 0) 91 return ret; 92 93 /* Register hooks */ 94 filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook); 95 if (IS_ERR(filter_ops)) { 96 ret = PTR_ERR(filter_ops); 97 unregister_pernet_subsys(&iptable_filter_net_ops); 98 } 99 100 return ret; 101 } 102 103 static void __exit iptable_filter_fini(void) 104 { 105 xt_hook_unlink(&packet_filter, filter_ops); 106 unregister_pernet_subsys(&iptable_filter_net_ops); 107 } 108 109 module_init(iptable_filter_init); 110 module_exit(iptable_filter_fini); 111