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 
16 MODULE_LICENSE("GPL");
17 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
18 MODULE_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 
26 static int __net_init ip6table_mangle_table_init(struct net *net);
27 
28 static const struct xt_table packet_mangler = {
29 	.name		= "mangle",
30 	.valid_hooks	= MANGLE_VALID_HOOKS,
31 	.me		= THIS_MODULE,
32 	.af		= NFPROTO_IPV6,
33 	.priority	= NF_IP6_PRI_MANGLE,
34 	.table_init	= ip6table_mangle_table_init,
35 };
36 
37 static unsigned int
38 ip6t_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
39 {
40 	unsigned int ret;
41 	struct in6_addr saddr, daddr;
42 	u_int8_t hop_limit;
43 	u_int32_t flowlabel, mark;
44 	int err;
45 
46 	/* save source/dest address, mark, hoplimit, flowlabel, priority,  */
47 	memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
48 	memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
49 	mark = skb->mark;
50 	hop_limit = ipv6_hdr(skb)->hop_limit;
51 
52 	/* flowlabel and prio (includes version, which shouldn't change either */
53 	flowlabel = *((u_int32_t *)ipv6_hdr(skb));
54 
55 	ret = ip6t_do_table(skb, state, state->net->ipv6.ip6table_mangle);
56 
57 	if (ret != NF_DROP && ret != NF_STOLEN &&
58 	    (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
59 	     !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
60 	     skb->mark != mark ||
61 	     ipv6_hdr(skb)->hop_limit != hop_limit ||
62 	     flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
63 		err = ip6_route_me_harder(state->net, skb);
64 		if (err < 0)
65 			ret = NF_DROP_ERR(err);
66 	}
67 
68 	return ret;
69 }
70 
71 /* The work comes in here from netfilter.c. */
72 static unsigned int
73 ip6table_mangle_hook(void *priv, struct sk_buff *skb,
74 		     const struct nf_hook_state *state)
75 {
76 	if (state->hook == NF_INET_LOCAL_OUT)
77 		return ip6t_mangle_out(skb, state);
78 	return ip6t_do_table(skb, state, state->net->ipv6.ip6table_mangle);
79 }
80 
81 static struct nf_hook_ops *mangle_ops __read_mostly;
82 static int __net_init ip6table_mangle_table_init(struct net *net)
83 {
84 	struct ip6t_replace *repl;
85 	int ret;
86 
87 	if (net->ipv6.ip6table_mangle)
88 		return 0;
89 
90 	repl = ip6t_alloc_initial_table(&packet_mangler);
91 	if (repl == NULL)
92 		return -ENOMEM;
93 	ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops,
94 				  &net->ipv6.ip6table_mangle);
95 	kfree(repl);
96 	return ret;
97 }
98 
99 static void __net_exit ip6table_mangle_net_exit(struct net *net)
100 {
101 	if (!net->ipv6.ip6table_mangle)
102 		return;
103 
104 	ip6t_unregister_table(net, net->ipv6.ip6table_mangle, mangle_ops);
105 	net->ipv6.ip6table_mangle = NULL;
106 }
107 
108 static struct pernet_operations ip6table_mangle_net_ops = {
109 	.exit = ip6table_mangle_net_exit,
110 };
111 
112 static int __init ip6table_mangle_init(void)
113 {
114 	int ret;
115 
116 	mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
117 	if (IS_ERR(mangle_ops))
118 		return PTR_ERR(mangle_ops);
119 
120 	ret = register_pernet_subsys(&ip6table_mangle_net_ops);
121 	if (ret < 0) {
122 		kfree(mangle_ops);
123 		return ret;
124 	}
125 
126 	ret = ip6table_mangle_table_init(&init_net);
127 	if (ret) {
128 		unregister_pernet_subsys(&ip6table_mangle_net_ops);
129 		kfree(mangle_ops);
130 	}
131 	return ret;
132 }
133 
134 static void __exit ip6table_mangle_fini(void)
135 {
136 	unregister_pernet_subsys(&ip6table_mangle_net_ops);
137 	kfree(mangle_ops);
138 }
139 
140 module_init(ip6table_mangle_init);
141 module_exit(ip6table_mangle_fini);
142