1 /*
2 * Copyright (c) 2011, 2012 Patrick McHardy <kaber@trash.net>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
11 #include <linux/ipv6.h>
12 #include <net/ipv6.h>
13 #include <linux/netfilter.h>
14 #include <linux/netfilter_ipv6.h>
15 #include <linux/netfilter_ipv6/ip6t_NPT.h>
16 #include <linux/netfilter/x_tables.h>
17
18 static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
19 {
20 struct ip6t_npt_tginfo *npt = par->targinfo;
21 struct in6_addr pfx;
22 __wsum src_sum, dst_sum;
23
24 if (npt->src_pfx_len > 64 || npt->dst_pfx_len > 64)
25 return -EINVAL;
26
27 /* Ensure that LSB of prefix is zero */
28 ipv6_addr_prefix(&pfx, &npt->src_pfx.in6, npt->src_pfx_len);
29 if (!ipv6_addr_equal(&pfx, &npt->src_pfx.in6))
30 return -EINVAL;
31 ipv6_addr_prefix(&pfx, &npt->dst_pfx.in6, npt->dst_pfx_len);
32 if (!ipv6_addr_equal(&pfx, &npt->dst_pfx.in6))
33 return -EINVAL;
34
35 src_sum = csum_partial(&npt->src_pfx.in6, sizeof(npt->src_pfx.in6), 0);
36 dst_sum = csum_partial(&npt->dst_pfx.in6, sizeof(npt->dst_pfx.in6), 0);
37
38 npt->adjustment = ~csum_fold(csum_sub(src_sum, dst_sum));
39 return 0;
40 }
41
42 static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt,
43 struct in6_addr *addr)
44 {
45 unsigned int pfx_len;
46 unsigned int i, idx;
47 __be32 mask;
48 __sum16 sum;
49
50 pfx_len = max(npt->src_pfx_len, npt->dst_pfx_len);
51 for (i = 0; i < pfx_len; i += 32) {
52 if (pfx_len - i >= 32)
53 mask = 0;
54 else
55 mask = htonl((1 << (i - pfx_len + 32)) - 1);
56
57 idx = i / 32;
58 addr->s6_addr32[idx] &= mask;
59 addr->s6_addr32[idx] |= ~mask & npt->dst_pfx.in6.s6_addr32[idx];
60 }
61
62 if (pfx_len <= 48)
63 idx = 3;
64 else {
65 for (idx = 4; idx < ARRAY_SIZE(addr->s6_addr16); idx++) {
66 if ((__force __sum16)addr->s6_addr16[idx] !=
67 CSUM_MANGLED_0)
68 break;
69 }
70 if (idx == ARRAY_SIZE(addr->s6_addr16))
71 return false;
72 }
73
74 sum = ~csum_fold(csum_add(csum_unfold((__force __sum16)addr->s6_addr16[idx]),
75 csum_unfold(npt->adjustment)));
76 if (sum == CSUM_MANGLED_0)
77 sum = 0;
78 *(__force __sum16 *)&addr->s6_addr16[idx] = sum;
79
80 return true;
81 }
82
83 static unsigned int
84 ip6t_snpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
85 {
86 const struct ip6t_npt_tginfo *npt = par->targinfo;
87
88 if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->saddr)) {
89 icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
90 offsetof(struct ipv6hdr, saddr));
91 return NF_DROP;
92 }
93 return XT_CONTINUE;
94 }
95
96 static unsigned int
97 ip6t_dnpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
98 {
99 const struct ip6t_npt_tginfo *npt = par->targinfo;
100
101 if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->daddr)) {
102 icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
103 offsetof(struct ipv6hdr, daddr));
104 return NF_DROP;
105 }
106 return XT_CONTINUE;
107 }
108
109 static struct xt_target ip6t_npt_target_reg[] __read_mostly = {
110 {
111 .name = "SNPT",
112 .table = "mangle",
113 .target = ip6t_snpt_tg,
114 .targetsize = sizeof(struct ip6t_npt_tginfo),
115 .checkentry = ip6t_npt_checkentry,
116 .family = NFPROTO_IPV6,
117 .hooks = (1 << NF_INET_LOCAL_IN) |
118 (1 << NF_INET_POST_ROUTING),
119 .me = THIS_MODULE,
120 },
121 {
122 .name = "DNPT",
123 .table = "mangle",
124 .target = ip6t_dnpt_tg,
125 .targetsize = sizeof(struct ip6t_npt_tginfo),
126 .checkentry = ip6t_npt_checkentry,
127 .family = NFPROTO_IPV6,
128 .hooks = (1 << NF_INET_PRE_ROUTING) |
129 (1 << NF_INET_LOCAL_OUT),
130 .me = THIS_MODULE,
131 },
132 };
133
134 static int __init ip6t_npt_init(void)
135 {
136 return xt_register_targets(ip6t_npt_target_reg,
137 ARRAY_SIZE(ip6t_npt_target_reg));
138 }
139
140 static void __exit ip6t_npt_exit(void)
141 {
142 xt_unregister_targets(ip6t_npt_target_reg,
143 ARRAY_SIZE(ip6t_npt_target_reg));
144 }
145
146 module_init(ip6t_npt_init);
147 module_exit(ip6t_npt_exit);
148
149 MODULE_LICENSE("GPL");
150 MODULE_DESCRIPTION("IPv6-to-IPv6 Network Prefix Translation (RFC 6296)");
151 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
152 MODULE_ALIAS("ip6t_SNPT");
153 MODULE_ALIAS("ip6t_DNPT");
154
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