ip6table_mangle.c revision 58e35d1471287c59b9749fb82f04c628c36b9994 
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#include <linux/slab.h>
14#include <net/ipv6.h>
15
16MODULE_LICENSE("GPL");
17MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
18MODULE_DESCRIPTION("ip6tables mangle table");
19
20#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
21			    (1 << NF_INET_LOCAL_IN) | \
22			    (1 << NF_INET_FORWARD) | \
23			    (1 << NF_INET_LOCAL_OUT) | \
24			    (1 << NF_INET_POST_ROUTING))
25
26static const struct xt_table packet_mangler = {
27	.name		= "mangle",
28	.valid_hooks	= MANGLE_VALID_HOOKS,
29	.me		= THIS_MODULE,
30	.af		= NFPROTO_IPV6,
31	.priority	= NF_IP6_PRI_MANGLE,
32};
33
34static unsigned int
35ip6t_mangle_out(struct sk_buff *skb, const struct net_device *out)
36{
37	unsigned int ret;
38	struct in6_addr saddr, daddr;
39	u_int8_t hop_limit;
40	u_int32_t flowlabel, mark;
41	int err;
42#if 0
43	/* root is playing with raw sockets. */
44	if (skb->len < sizeof(struct iphdr) ||
45	    ip_hdrlen(skb) < sizeof(struct iphdr)) {
46		net_warn_ratelimited("ip6t_hook: happy cracking\n");
47		return NF_ACCEPT;
48	}
49#endif
50
51	/* save source/dest address, mark, hoplimit, flowlabel, priority,  */
52	memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
53	memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
54	mark = skb->mark;
55	hop_limit = ipv6_hdr(skb)->hop_limit;
56
57	/* flowlabel and prio (includes version, which shouldn't change either */
58	flowlabel = *((u_int32_t *)ipv6_hdr(skb));
59
60	ret = ip6t_do_table(skb, NF_INET_LOCAL_OUT, NULL, out,
61			    dev_net(out)->ipv6.ip6table_mangle);
62
63	if (ret != NF_DROP && ret != NF_STOLEN &&
64	    (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
65	     !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
66	     skb->mark != mark ||
67	     ipv6_hdr(skb)->hop_limit != hop_limit ||
68	     flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
69		err = ip6_route_me_harder(skb);
70		if (err < 0)
71			ret = NF_DROP_ERR(err);
72	}
73
74	return ret;
75}
76
77/* The work comes in here from netfilter.c. */
78static unsigned int
79ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
80		     const struct net_device *in, const struct net_device *out,
81		     int (*okfn)(struct sk_buff *))
82{
83	if (hook == NF_INET_LOCAL_OUT)
84		return ip6t_mangle_out(skb, out);
85	if (hook == NF_INET_POST_ROUTING)
86		return ip6t_do_table(skb, hook, in, out,
87				     dev_net(out)->ipv6.ip6table_mangle);
88	/* INPUT/FORWARD */
89	return ip6t_do_table(skb, hook, in, out,
90			     dev_net(in)->ipv6.ip6table_mangle);
91}
92
93static struct nf_hook_ops *mangle_ops __read_mostly;
94static int __net_init ip6table_mangle_net_init(struct net *net)
95{
96	struct ip6t_replace *repl;
97
98	repl = ip6t_alloc_initial_table(&packet_mangler);
99	if (repl == NULL)
100		return -ENOMEM;
101	net->ipv6.ip6table_mangle =
102		ip6t_register_table(net, &packet_mangler, repl);
103	kfree(repl);
104	return PTR_RET(net->ipv6.ip6table_mangle);
105}
106
107static void __net_exit ip6table_mangle_net_exit(struct net *net)
108{
109	ip6t_unregister_table(net, net->ipv6.ip6table_mangle);
110}
111
112static struct pernet_operations ip6table_mangle_net_ops = {
113	.init = ip6table_mangle_net_init,
114	.exit = ip6table_mangle_net_exit,
115};
116
117static int __init ip6table_mangle_init(void)
118{
119	int ret;
120
121	ret = register_pernet_subsys(&ip6table_mangle_net_ops);
122	if (ret < 0)
123		return ret;
124
125	/* Register hooks */
126	mangle_ops = xt_hook_link(&packet_mangler, ip6table_mangle_hook);
127	if (IS_ERR(mangle_ops)) {
128		ret = PTR_ERR(mangle_ops);
129		goto cleanup_table;
130	}
131
132	return ret;
133
134 cleanup_table:
135	unregister_pernet_subsys(&ip6table_mangle_net_ops);
136	return ret;
137}
138
139static void __exit ip6table_mangle_fini(void)
140{
141	xt_hook_unlink(&packet_mangler, mangle_ops);
142	unregister_pernet_subsys(&ip6table_mangle_net_ops);
143}
144
145module_init(ip6table_mangle_init);
146module_exit(ip6table_mangle_fini);
147