1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * IPv6 packet mangling table, a port of the IPv4 mangle table to IPv6
4  *
5  * Copyright (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
6  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
7  */
8 #include <linux/module.h>
9 #include <linux/netfilter_ipv6/ip6_tables.h>
10 #include <linux/slab.h>
11 #include <net/ipv6.h>
12 
13 MODULE_LICENSE("GPL");
14 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
15 MODULE_DESCRIPTION("ip6tables mangle table");
16 
17 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
18 			    (1 << NF_INET_LOCAL_IN) | \
19 			    (1 << NF_INET_FORWARD) | \
20 			    (1 << NF_INET_LOCAL_OUT) | \
21 			    (1 << NF_INET_POST_ROUTING))
22 
23 static int __net_init ip6table_mangle_table_init(struct net *net);
24 
25 static const struct xt_table packet_mangler = {
26 	.name		= "mangle",
27 	.valid_hooks	= MANGLE_VALID_HOOKS,
28 	.me		= THIS_MODULE,
29 	.af		= NFPROTO_IPV6,
30 	.priority	= NF_IP6_PRI_MANGLE,
31 	.table_init	= ip6table_mangle_table_init,
32 };
33 
34 static unsigned int
35 ip6t_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state, void *priv)
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 
43 	/* save source/dest address, mark, hoplimit, flowlabel, priority,  */
44 	memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
45 	memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
46 	mark = skb->mark;
47 	hop_limit = ipv6_hdr(skb)->hop_limit;
48 
49 	/* flowlabel and prio (includes version, which shouldn't change either */
50 	flowlabel = *((u_int32_t *)ipv6_hdr(skb));
51 
52 	ret = ip6t_do_table(skb, state, priv);
53 
54 	if (ret != NF_DROP && ret != NF_STOLEN &&
55 	    (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
56 	     !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
57 	     skb->mark != mark ||
58 	     ipv6_hdr(skb)->hop_limit != hop_limit ||
59 	     flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
60 		err = ip6_route_me_harder(state->net, state->sk, skb);
61 		if (err < 0)
62 			ret = NF_DROP_ERR(err);
63 	}
64 
65 	return ret;
66 }
67 
68 /* The work comes in here from netfilter.c. */
69 static unsigned int
70 ip6table_mangle_hook(void *priv, struct sk_buff *skb,
71 		     const struct nf_hook_state *state)
72 {
73 	if (state->hook == NF_INET_LOCAL_OUT)
74 		return ip6t_mangle_out(skb, state, priv);
75 	return ip6t_do_table(skb, state, priv);
76 }
77 
78 static struct nf_hook_ops *mangle_ops __read_mostly;
79 static int __net_init ip6table_mangle_table_init(struct net *net)
80 {
81 	struct ip6t_replace *repl;
82 	int ret;
83 
84 	repl = ip6t_alloc_initial_table(&packet_mangler);
85 	if (repl == NULL)
86 		return -ENOMEM;
87 	ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops);
88 	kfree(repl);
89 	return ret;
90 }
91 
92 static void __net_exit ip6table_mangle_net_pre_exit(struct net *net)
93 {
94 	ip6t_unregister_table_pre_exit(net, "mangle");
95 }
96 
97 static void __net_exit ip6table_mangle_net_exit(struct net *net)
98 {
99 	ip6t_unregister_table_exit(net, "mangle");
100 }
101 
102 static struct pernet_operations ip6table_mangle_net_ops = {
103 	.pre_exit = ip6table_mangle_net_pre_exit,
104 	.exit = ip6table_mangle_net_exit,
105 };
106 
107 static int __init ip6table_mangle_init(void)
108 {
109 	int ret;
110 
111 	mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
112 	if (IS_ERR(mangle_ops))
113 		return PTR_ERR(mangle_ops);
114 
115 	ret = register_pernet_subsys(&ip6table_mangle_net_ops);
116 	if (ret < 0) {
117 		kfree(mangle_ops);
118 		return ret;
119 	}
120 
121 	ret = ip6table_mangle_table_init(&init_net);
122 	if (ret) {
123 		unregister_pernet_subsys(&ip6table_mangle_net_ops);
124 		kfree(mangle_ops);
125 	}
126 	return ret;
127 }
128 
129 static void __exit ip6table_mangle_fini(void)
130 {
131 	unregister_pernet_subsys(&ip6table_mangle_net_ops);
132 	kfree(mangle_ops);
133 }
134 
135 module_init(ip6table_mangle_init);
136 module_exit(ip6table_mangle_fini);
137