ip6table_mangle.c revision b2907e501945d5d13326a6a7441c13e41cd0e799 
1/*
2 * IPv6 packet mangling table, a port of the IPv4 mangle table to IPv6
3 *
4 * Copyright (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
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_ipv6/ip6_tables.h>
13
14MODULE_LICENSE("GPL");
15MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
16MODULE_DESCRIPTION("ip6tables mangle table");
17
18#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
19			    (1 << NF_INET_LOCAL_IN) | \
20			    (1 << NF_INET_FORWARD) | \
21			    (1 << NF_INET_LOCAL_OUT) | \
22			    (1 << NF_INET_POST_ROUTING))
23
24static const struct xt_table packet_mangler = {
25	.name		= "mangle",
26	.valid_hooks	= MANGLE_VALID_HOOKS,
27	.me		= THIS_MODULE,
28	.af		= NFPROTO_IPV6,
29	.priority	= NF_IP6_PRI_MANGLE,
30};
31
32static unsigned int
33ip6t_local_out_hook(unsigned int hook,
34		   struct sk_buff *skb,
35		   const struct net_device *out,
36		   int (*okfn)(struct sk_buff *))
37{
38
39	unsigned int ret;
40	struct in6_addr saddr, daddr;
41	u_int8_t hop_limit;
42	u_int32_t flowlabel, mark;
43
44#if 0
45	/* root is playing with raw sockets. */
46	if (skb->len < sizeof(struct iphdr) ||
47	    ip_hdrlen(skb) < sizeof(struct iphdr)) {
48		if (net_ratelimit())
49			printk("ip6t_hook: happy cracking.\n");
50		return NF_ACCEPT;
51	}
52#endif
53
54	/* save source/dest address, mark, hoplimit, flowlabel, priority,  */
55	memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
56	memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
57	mark = skb->mark;
58	hop_limit = ipv6_hdr(skb)->hop_limit;
59
60	/* flowlabel and prio (includes version, which shouldn't change either */
61	flowlabel = *((u_int32_t *)ipv6_hdr(skb));
62
63	ret = ip6t_do_table(skb, hook, NULL, out,
64			    dev_net(out)->ipv6.ip6table_mangle);
65
66	if (ret != NF_DROP && ret != NF_STOLEN &&
67	    (memcmp(&ipv6_hdr(skb)->saddr, &saddr, sizeof(saddr)) ||
68	     memcmp(&ipv6_hdr(skb)->daddr, &daddr, sizeof(daddr)) ||
69	     skb->mark != mark ||
70	     ipv6_hdr(skb)->hop_limit != hop_limit))
71		return ip6_route_me_harder(skb) == 0 ? ret : NF_DROP;
72
73	return ret;
74}
75
76/* The work comes in here from netfilter.c. */
77static unsigned int
78ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
79		     const struct net_device *in, const struct net_device *out,
80		     int (*okfn)(struct sk_buff *))
81{
82	if (hook == NF_INET_LOCAL_OUT)
83		return ip6t_local_out_hook(hook, skb, out, okfn);
84	if (hook == NF_INET_POST_ROUTING)
85		return ip6t_do_table(skb, hook, in, out,
86				     dev_net(out)->ipv6.ip6table_mangle);
87	/* INPUT/FORWARD */
88	return ip6t_do_table(skb, hook, in, out,
89			     dev_net(in)->ipv6.ip6table_mangle);
90}
91
92static struct nf_hook_ops *mangle_ops __read_mostly;
93static int __net_init ip6table_mangle_net_init(struct net *net)
94{
95	struct ip6t_replace *repl;
96
97	repl = ip6t_alloc_initial_table(&packet_mangler);
98	if (repl == NULL)
99		return -ENOMEM;
100	net->ipv6.ip6table_mangle =
101		ip6t_register_table(net, &packet_mangler, repl);
102	kfree(repl);
103	if (IS_ERR(net->ipv6.ip6table_mangle))
104		return PTR_ERR(net->ipv6.ip6table_mangle);
105	return 0;
106}
107
108static void __net_exit ip6table_mangle_net_exit(struct net *net)
109{
110	ip6t_unregister_table(net, net->ipv6.ip6table_mangle);
111}
112
113static struct pernet_operations ip6table_mangle_net_ops = {
114	.init = ip6table_mangle_net_init,
115	.exit = ip6table_mangle_net_exit,
116};
117
118static int __init ip6table_mangle_init(void)
119{
120	int ret;
121
122	ret = register_pernet_subsys(&ip6table_mangle_net_ops);
123	if (ret < 0)
124		return ret;
125
126	/* Register hooks */
127	mangle_ops = xt_hook_link(&packet_mangler, ip6table_mangle_hook);
128	if (IS_ERR(mangle_ops)) {
129		ret = PTR_ERR(mangle_ops);
130		goto cleanup_table;
131	}
132
133	return ret;
134
135 cleanup_table:
136	unregister_pernet_subsys(&ip6table_mangle_net_ops);
137	return ret;
138}
139
140static void __exit ip6table_mangle_fini(void)
141{
142	xt_hook_unlink(&packet_mangler, mangle_ops);
143	unregister_pernet_subsys(&ip6table_mangle_net_ops);
144}
145
146module_init(ip6table_mangle_init);
147module_exit(ip6table_mangle_fini);
148