aboutsummaryrefslogtreecommitdiffstats
path: root/net/ipv4/netfilter/iptable_mangle.c
blob: 4e7998beda635970bacb483dae78052180d649c8 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
/*
 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
 *
 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Extended to all five netfilter hooks by Brad Chapman & Harald Welte
 */
#include <linux/module.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/route.h>
#include <linux/ip.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("iptables mangle table");

#define MANGLE_VALID_HOOKS ((1 << NF_IP_PRE_ROUTING) | \
			    (1 << NF_IP_LOCAL_IN) | \
			    (1 << NF_IP_FORWARD) | \
			    (1 << NF_IP_LOCAL_OUT) | \
			    (1 << NF_IP_POST_ROUTING))

/* Ouch - five different hooks? Maybe this should be a config option..... -- BC */
static struct
{
	struct ipt_replace repl;
	struct ipt_standard entries[5];
	struct ipt_error term;
} initial_table __initdata
= { { "mangle", MANGLE_VALID_HOOKS, 6,
      sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),
      { [NF_IP_PRE_ROUTING] 	= 0,
	[NF_IP_LOCAL_IN] 	= sizeof(struct ipt_standard),
	[NF_IP_FORWARD] 	= sizeof(struct ipt_standard) * 2,
	[NF_IP_LOCAL_OUT] 	= sizeof(struct ipt_standard) * 3,
	[NF_IP_POST_ROUTING] 	= sizeof(struct ipt_standard) * 4 },
      { [NF_IP_PRE_ROUTING] 	= 0,
	[NF_IP_LOCAL_IN] 	= sizeof(struct ipt_standard),
	[NF_IP_FORWARD] 	= sizeof(struct ipt_standard) * 2,
	[NF_IP_LOCAL_OUT] 	= sizeof(struct ipt_standard) * 3,
	[NF_IP_POST_ROUTING]	= sizeof(struct ipt_standard) * 4 },
      0, NULL, { } },
    {
	    /* PRE_ROUTING */
	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
		0,
		sizeof(struct ipt_entry),
		sizeof(struct ipt_standard),
		0, { 0, 0 }, { } },
	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
		-NF_ACCEPT - 1 } },
	    /* LOCAL_IN */
 	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
		0,
		sizeof(struct ipt_entry),
		sizeof(struct ipt_standard),
		0, { 0, 0 }, { } },
	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
		-NF_ACCEPT - 1 } },
	    /* FORWARD */
 	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
		0,
		sizeof(struct ipt_entry),
		sizeof(struct ipt_standard),
		0, { 0, 0 }, { } },
	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
		-NF_ACCEPT - 1 } },
	    /* LOCAL_OUT */
	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
		0,
		sizeof(struct ipt_entry),
		sizeof(struct ipt_standard),
		0, { 0, 0 }, { } },
	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
		-NF_ACCEPT - 1 } },
	    /* POST_ROUTING */
	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
		0,
		sizeof(struct ipt_entry),
		sizeof(struct ipt_standard),
		0, { 0, 0 }, { } },
	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
		-NF_ACCEPT - 1 } },
    },
    /* ERROR */
    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
	0,
	sizeof(struct ipt_entry),
	sizeof(struct ipt_error),
	0, { 0, 0 }, { } },
      { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
	  { } },
	"ERROR"
      }
    }
};

static struct ipt_table packet_mangler = {
	.name		= "mangle",
	.valid_hooks	= MANGLE_VALID_HOOKS,
	.lock		= RW_LOCK_UNLOCKED,
	.me		= THIS_MODULE,
	.af		= AF_INET,
};

/* The work comes in here from netfilter.c. */
static unsigned int
ipt_route_hook(unsigned int hook,
	 struct sk_buff **pskb,
	 const struct net_device *in,
	 const struct net_device *out,
	 int (*okfn)(struct sk_buff *))
{
	return ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
}

static unsigned int
ipt_local_hook(unsigned int hook,
		   struct sk_buff **pskb,
		   const struct net_device *in,
		   const struct net_device *out,
		   int (*okfn)(struct sk_buff *))
{
	unsigned int ret;
	u_int8_t tos;
	u_int32_t saddr, daddr;
	unsigned long nfmark;

	/* root is playing with raw sockets. */
	if ((*pskb)->len < sizeof(struct iphdr)
	    || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
		if (net_ratelimit())
			printk("ipt_hook: happy cracking.\n");
		return NF_ACCEPT;
	}

	/* Save things which could affect route */
	nfmark = (*pskb)->nfmark;
	saddr = (*pskb)->nh.iph->saddr;
	daddr = (*pskb)->nh.iph->daddr;
	tos = (*pskb)->nh.iph->tos;

	ret = ipt_do_table(pskb, hook, in, out, &packet_mangler, NULL);
	/* Reroute for ANY change. */
	if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE
	    && ((*pskb)->nh.iph->saddr != saddr
		|| (*pskb)->nh.iph->daddr != daddr
#ifdef CONFIG_IP_ROUTE_FWMARK
		|| (*pskb)->nfmark != nfmark
#endif
		|| (*pskb)->nh.iph->tos != tos))
		return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;

	return ret;
}

static struct nf_hook_ops ipt_ops[] = {
	{
		.hook		= ipt_route_hook,
		.owner		= THIS_MODULE,
		.pf		= PF_INET,
		.hooknum	= NF_IP_PRE_ROUTING, 
		.priority	= NF_IP_PRI_MANGLE,
	},
	{
		.hook		= ipt_route_hook,
		.owner		= THIS_MODULE,
		.pf		= PF_INET,
		.hooknum	= NF_IP_LOCAL_IN,
		.priority	= NF_IP_PRI_MANGLE,
	},
	{
		.hook		= ipt_route_hook,
		.owner		= THIS_MODULE,
		.pf		= PF_INET,
		.hooknum	= NF_IP_FORWARD,
		.priority	= NF_IP_PRI_MANGLE,
	},
	{
		.hook		= ipt_local_hook,
		.owner		= THIS_MODULE,
		.pf		= PF_INET,
		.hooknum	= NF_IP_LOCAL_OUT,
		.priority	= NF_IP_PRI_MANGLE,
	},
	{
		.hook		= ipt_route_hook,
		.owner		= THIS_MODULE,
		.pf		= PF_INET,
		.hooknum	= NF_IP_POST_ROUTING,
		.priority	= NF_IP_PRI_MANGLE,
	},
};

static int __init iptable_mangle_init(void)
{
	int ret;

	/* Register table */
	ret = ipt_register_table(&packet_mangler, &initial_table.repl);
	if (ret < 0)
		return ret;

	/* Register hooks */
	ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
	if (ret < 0)
		goto cleanup_table;

	return ret;

 cleanup_table:
	ipt_unregister_table(&packet_mangler);
	return ret;
}

static void __exit iptable_mangle_fini(void)
{
	nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
	ipt_unregister_table(&packet_mangler);
}

module_init(iptable_mangle_init);
module_exit(iptable_mangle_fini);