iptable_filter.c revision 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 
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 ipt_table packet_filter = {
78	.name		= "filter",
79	.valid_hooks	= FILTER_VALID_HOOKS,
80	.lock		= RW_LOCK_UNLOCKED,
81	.me		= THIS_MODULE
82};
83
84/* The work comes in here from netfilter.c. */
85static unsigned int
86ipt_hook(unsigned int hook,
87	 struct sk_buff **pskb,
88	 const struct net_device *in,
89	 const struct net_device *out,
90	 int (*okfn)(struct sk_buff *))
91{
92	return ipt_do_table(pskb, hook, in, out, &packet_filter, NULL);
93}
94
95static unsigned int
96ipt_local_out_hook(unsigned int hook,
97		   struct sk_buff **pskb,
98		   const struct net_device *in,
99		   const struct net_device *out,
100		   int (*okfn)(struct sk_buff *))
101{
102	/* root is playing with raw sockets. */
103	if ((*pskb)->len < sizeof(struct iphdr)
104	    || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
105		if (net_ratelimit())
106			printk("ipt_hook: happy cracking.\n");
107		return NF_ACCEPT;
108	}
109
110	return ipt_do_table(pskb, hook, in, out, &packet_filter, NULL);
111}
112
113static struct nf_hook_ops ipt_ops[] = {
114	{
115		.hook		= ipt_hook,
116		.owner		= THIS_MODULE,
117		.pf		= PF_INET,
118		.hooknum	= NF_IP_LOCAL_IN,
119		.priority	= NF_IP_PRI_FILTER,
120	},
121	{
122		.hook		= ipt_hook,
123		.owner		= THIS_MODULE,
124		.pf		= PF_INET,
125		.hooknum	= NF_IP_FORWARD,
126		.priority	= NF_IP_PRI_FILTER,
127	},
128	{
129		.hook		= ipt_local_out_hook,
130		.owner		= THIS_MODULE,
131		.pf		= PF_INET,
132		.hooknum	= NF_IP_LOCAL_OUT,
133		.priority	= NF_IP_PRI_FILTER,
134	},
135};
136
137/* Default to forward because I got too much mail already. */
138static int forward = NF_ACCEPT;
139module_param(forward, bool, 0000);
140
141static int __init init(void)
142{
143	int ret;
144
145	if (forward < 0 || forward > NF_MAX_VERDICT) {
146		printk("iptables forward must be 0 or 1\n");
147		return -EINVAL;
148	}
149
150	/* Entry 1 is the FORWARD hook */
151	initial_table.entries[1].target.verdict = -forward - 1;
152
153	/* Register table */
154	ret = ipt_register_table(&packet_filter, &initial_table.repl);
155	if (ret < 0)
156		return ret;
157
158	/* Register hooks */
159	ret = nf_register_hook(&ipt_ops[0]);
160	if (ret < 0)
161		goto cleanup_table;
162
163	ret = nf_register_hook(&ipt_ops[1]);
164	if (ret < 0)
165		goto cleanup_hook0;
166
167	ret = nf_register_hook(&ipt_ops[2]);
168	if (ret < 0)
169		goto cleanup_hook1;
170
171	return ret;
172
173 cleanup_hook1:
174	nf_unregister_hook(&ipt_ops[1]);
175 cleanup_hook0:
176	nf_unregister_hook(&ipt_ops[0]);
177 cleanup_table:
178	ipt_unregister_table(&packet_filter);
179
180	return ret;
181}
182
183static void __exit fini(void)
184{
185	unsigned int i;
186
187	for (i = 0; i < sizeof(ipt_ops)/sizeof(struct nf_hook_ops); i++)
188		nf_unregister_hook(&ipt_ops[i]);
189
190	ipt_unregister_table(&packet_filter);
191}
192
193module_init(init);
194module_exit(fini);
195