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