iptable_filter.c revision e60a13e030867078f3c9fef8dca6cd8a5b883478 
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
17MODULE_LICENSE("GPL");
18MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
19MODULE_DESCRIPTION("iptables filter table");
20
21#define FILTER_VALID_HOOKS ((1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | (1 << NF_IP_LOCAL_OUT))
22
23static struct
24{
25	struct ipt_replace repl;
26	struct ipt_standard entries[3];
27	struct ipt_error term;
28} initial_table __initdata
29= { { "filter", FILTER_VALID_HOOKS, 4,
30      sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
31      { [NF_IP_LOCAL_IN] = 0,
32	[NF_IP_FORWARD] = sizeof(struct ipt_standard),
33	[NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
34      { [NF_IP_LOCAL_IN] = 0,
35	[NF_IP_FORWARD] = sizeof(struct ipt_standard),
36	[NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
37      0, NULL, { } },
38    {
39	    /* LOCAL_IN */
40	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
41		0,
42		sizeof(struct ipt_entry),
43		sizeof(struct ipt_standard),
44		0, { 0, 0 }, { } },
45	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
46		-NF_ACCEPT - 1 } },
47	    /* FORWARD */
48	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
49		0,
50		sizeof(struct ipt_entry),
51		sizeof(struct ipt_standard),
52		0, { 0, 0 }, { } },
53	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
54		-NF_ACCEPT - 1 } },
55	    /* LOCAL_OUT */
56	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
57		0,
58		sizeof(struct ipt_entry),
59		sizeof(struct ipt_standard),
60		0, { 0, 0 }, { } },
61	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
62		-NF_ACCEPT - 1 } }
63    },
64    /* ERROR */
65    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
66	0,
67	sizeof(struct ipt_entry),
68	sizeof(struct ipt_error),
69	0, { 0, 0 }, { } },
70      { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
71	  { } },
72	"ERROR"
73      }
74    }
75};
76
77static struct xt_table packet_filter = {
78	.name		= "filter",
79	.valid_hooks	= FILTER_VALID_HOOKS,
80	.lock		= RW_LOCK_UNLOCKED,
81	.me		= THIS_MODULE,
82	.af		= AF_INET,
83};
84
85/* The work comes in here from netfilter.c. */
86static unsigned int
87ipt_hook(unsigned int hook,
88	 struct sk_buff **pskb,
89	 const struct net_device *in,
90	 const struct net_device *out,
91	 int (*okfn)(struct sk_buff *))
92{
93	return ipt_do_table(pskb, hook, in, out, &packet_filter);
94}
95
96static unsigned int
97ipt_local_out_hook(unsigned int hook,
98		   struct sk_buff **pskb,
99		   const struct net_device *in,
100		   const struct net_device *out,
101		   int (*okfn)(struct sk_buff *))
102{
103	/* root is playing with raw sockets. */
104	if ((*pskb)->len < sizeof(struct iphdr)
105	    || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
106		if (net_ratelimit())
107			printk("ipt_hook: happy cracking.\n");
108		return NF_ACCEPT;
109	}
110
111	return ipt_do_table(pskb, hook, in, out, &packet_filter);
112}
113
114static struct nf_hook_ops ipt_ops[] = {
115	{
116		.hook		= ipt_hook,
117		.owner		= THIS_MODULE,
118		.pf		= PF_INET,
119		.hooknum	= NF_IP_LOCAL_IN,
120		.priority	= NF_IP_PRI_FILTER,
121	},
122	{
123		.hook		= ipt_hook,
124		.owner		= THIS_MODULE,
125		.pf		= PF_INET,
126		.hooknum	= NF_IP_FORWARD,
127		.priority	= NF_IP_PRI_FILTER,
128	},
129	{
130		.hook		= ipt_local_out_hook,
131		.owner		= THIS_MODULE,
132		.pf		= PF_INET,
133		.hooknum	= NF_IP_LOCAL_OUT,
134		.priority	= NF_IP_PRI_FILTER,
135	},
136};
137
138/* Default to forward because I got too much mail already. */
139static int forward = NF_ACCEPT;
140module_param(forward, bool, 0000);
141
142static int __init iptable_filter_init(void)
143{
144	int ret;
145
146	if (forward < 0 || forward > NF_MAX_VERDICT) {
147		printk("iptables forward must be 0 or 1\n");
148		return -EINVAL;
149	}
150
151	/* Entry 1 is the FORWARD hook */
152	initial_table.entries[1].target.verdict = -forward - 1;
153
154	/* Register table */
155	ret = ipt_register_table(&packet_filter, &initial_table.repl);
156	if (ret < 0)
157		return ret;
158
159	/* Register hooks */
160	ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
161	if (ret < 0)
162		goto cleanup_table;
163
164	return ret;
165
166 cleanup_table:
167	ipt_unregister_table(&packet_filter);
168	return ret;
169}
170
171static void __exit iptable_filter_fini(void)
172{
173	nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
174	ipt_unregister_table(&packet_filter);
175}
176
177module_init(iptable_filter_init);
178module_exit(iptable_filter_fini);
179