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