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 #include <linux/module.h>
12 #include <linux/netfilter_ipv4/ip_tables.h>
13 #include <linux/netdevice.h>
14 #include <linux/skbuff.h>
15 #include <net/sock.h>
16 #include <net/route.h>
17 #include <linux/ip.h>
18 #include <net/ip.h>
19
20 MODULE_LICENSE("GPL");
21 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
22 MODULE_DESCRIPTION("iptables mangle table");
23
24 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
25 (1 << NF_INET_LOCAL_IN) | \
26 (1 << NF_INET_FORWARD) | \
27 (1 << NF_INET_LOCAL_OUT) | \
28 (1 << NF_INET_POST_ROUTING))
29
30 /* Ouch - five different hooks? Maybe this should be a config option..... -- BC */
31 static struct
32 {
33 struct ipt_replace repl;
34 struct ipt_standard entries[5];
35 struct ipt_error term;
36 } initial_table __net_initdata = {
37 .repl = {
38 .name = "mangle",
39 .valid_hooks = MANGLE_VALID_HOOKS,
40 .num_entries = 6,
41 .size = sizeof(struct ipt_standard) * 5 + sizeof(struct ipt_error),
42 .hook_entry = {
43 [NF_INET_PRE_ROUTING] = 0,
44 [NF_INET_LOCAL_IN] = sizeof(struct ipt_standard),
45 [NF_INET_FORWARD] = sizeof(struct ipt_standard) * 2,
46 [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 3,
47 [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard) * 4,
48 },
49 .underflow = {
50 [NF_INET_PRE_ROUTING] = 0,
51 [NF_INET_LOCAL_IN] = sizeof(struct ipt_standard),
52 [NF_INET_FORWARD] = sizeof(struct ipt_standard) * 2,
53 [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 3,
54 [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard) * 4,
55 },
56 },
57 .entries = {
58 IPT_STANDARD_INIT(NF_ACCEPT), /* PRE_ROUTING */
59 IPT_STANDARD_INIT(NF_ACCEPT), /* LOCAL_IN */
60 IPT_STANDARD_INIT(NF_ACCEPT), /* FORWARD */
61 IPT_STANDARD_INIT(NF_ACCEPT), /* LOCAL_OUT */
62 IPT_STANDARD_INIT(NF_ACCEPT), /* POST_ROUTING */
63 },
64 .term = IPT_ERROR_INIT, /* ERROR */
65 };
66
67 static struct xt_table packet_mangler = {
68 .name = "mangle",
69 .valid_hooks = MANGLE_VALID_HOOKS,
70 .lock = RW_LOCK_UNLOCKED,
71 .me = THIS_MODULE,
72 .af = AF_INET,
73 };
74
75 /* The work comes in here from netfilter.c. */
76 static unsigned int
77 ipt_route_hook(unsigned int hook,
78 struct sk_buff *skb,
79 const struct net_device *in,
80 const struct net_device *out,
81 int (*okfn)(struct sk_buff *))
82 {
83 return ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_mangle);
84 }
85
86 static unsigned int
87 ipt_local_hook(unsigned int hook,
88 struct sk_buff *skb,
89 const struct net_device *in,
90 const struct net_device *out,
91 int (*okfn)(struct sk_buff *))
92 {
93 unsigned int ret;
94 const struct iphdr *iph;
95 u_int8_t tos;
96 __be32 saddr, daddr;
97 u_int32_t mark;
98
99 /* root is playing with raw sockets. */
100 if (skb->len < sizeof(struct iphdr)
101 || ip_hdrlen(skb) < sizeof(struct iphdr)) {
102 if (net_ratelimit())
103 printk("iptable_mangle: ignoring short SOCK_RAW "
104 "packet.\n");
105 return NF_ACCEPT;
106 }
107
108 /* Save things which could affect route */
109 mark = skb->mark;
110 iph = ip_hdr(skb);
111 saddr = iph->saddr;
112 daddr = iph->daddr;
113 tos = iph->tos;
114
115 ret = ipt_do_table(skb, hook, in, out, init_net.ipv4.iptable_mangle);
116 /* Reroute for ANY change. */
117 if (ret != NF_DROP && ret != NF_STOLEN && ret != NF_QUEUE) {
118 iph = ip_hdr(skb);
119
120 if (iph->saddr != saddr ||
121 iph->daddr != daddr ||
122 skb->mark != mark ||
123 iph->tos != tos)
124 if (ip_route_me_harder(skb, RTN_UNSPEC))
125 ret = NF_DROP;
126 }
127
128 return ret;
129 }
130
131 static struct nf_hook_ops ipt_ops[] __read_mostly = {
132 {
133 .hook = ipt_route_hook,
134 .owner = THIS_MODULE,
135 .pf = PF_INET,
136 .hooknum = NF_INET_PRE_ROUTING,
137 .priority = NF_IP_PRI_MANGLE,
138 },
139 {
140 .hook = ipt_route_hook,
141 .owner = THIS_MODULE,
142 .pf = PF_INET,
143 .hooknum = NF_INET_LOCAL_IN,
144 .priority = NF_IP_PRI_MANGLE,
145 },
146 {
147 .hook = ipt_route_hook,
148 .owner = THIS_MODULE,
149 .pf = PF_INET,
150 .hooknum = NF_INET_FORWARD,
151 .priority = NF_IP_PRI_MANGLE,
152 },
153 {
154 .hook = ipt_local_hook,
155 .owner = THIS_MODULE,
156 .pf = PF_INET,
157 .hooknum = NF_INET_LOCAL_OUT,
158 .priority = NF_IP_PRI_MANGLE,
159 },
160 {
161 .hook = ipt_route_hook,
162 .owner = THIS_MODULE,
163 .pf = PF_INET,
164 .hooknum = NF_INET_POST_ROUTING,
165 .priority = NF_IP_PRI_MANGLE,
166 },
167 };
168
169 static int __net_init iptable_mangle_net_init(struct net *net)
170 {
171 /* Register table */
172 net->ipv4.iptable_mangle =
173 ipt_register_table(net, &packet_mangler, &initial_table.repl);
174 if (IS_ERR(net->ipv4.iptable_mangle))
175 return PTR_ERR(net->ipv4.iptable_mangle);
176 return 0;
177 }
178
179 static void __net_exit iptable_mangle_net_exit(struct net *net)
180 {
181 ipt_unregister_table(net->ipv4.iptable_mangle);
182 }
183
184 static struct pernet_operations iptable_mangle_net_ops = {
185 .init = iptable_mangle_net_init,
186 .exit = iptable_mangle_net_exit,
187 };
188
189 static int __init iptable_mangle_init(void)
190 {
191 int ret;
192
193 ret = register_pernet_subsys(&iptable_mangle_net_ops);
194 if (ret < 0)
195 return ret;
196
197 /* Register hooks */
198 ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
199 if (ret < 0)
200 goto cleanup_table;
201
202 return ret;
203
204 cleanup_table:
205 unregister_pernet_subsys(&iptable_mangle_net_ops);
206 return ret;
207 }
208
209 static void __exit iptable_mangle_fini(void)
210 {
211 nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
212 unregister_pernet_subsys(&iptable_mangle_net_ops);
213 }
214
215 module_init(iptable_mangle_init);
216 module_exit(iptable_mangle_fini);
217
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