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e26f9a48 FW |
1 | /* |
2 | * Copyright (c) 2011 Florian Westphal <fw@strlen.de> | |
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 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
9 | #include <linux/module.h> | |
10 | #include <linux/skbuff.h> | |
11 | #include <linux/netdevice.h> | |
12 | #include <linux/route.h> | |
13 | #include <net/ip6_fib.h> | |
14 | #include <net/ip6_route.h> | |
15 | ||
16 | #include <linux/netfilter/xt_rpfilter.h> | |
17 | #include <linux/netfilter/x_tables.h> | |
18 | ||
19 | MODULE_LICENSE("GPL"); | |
20 | MODULE_AUTHOR("Florian Westphal <fw@strlen.de>"); | |
21 | MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match"); | |
22 | ||
23 | static bool rpfilter_addr_unicast(const struct in6_addr *addr) | |
24 | { | |
25 | int addr_type = ipv6_addr_type(addr); | |
26 | return addr_type & IPV6_ADDR_UNICAST; | |
27 | } | |
28 | ||
686c9b50 | 29 | static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb, |
e26f9a48 FW |
30 | const struct net_device *dev, u8 flags) |
31 | { | |
32 | struct rt6_info *rt; | |
33 | struct ipv6hdr *iph = ipv6_hdr(skb); | |
34 | bool ret = false; | |
35 | struct flowi6 fl6 = { | |
e374c618 | 36 | .flowi6_iif = LOOPBACK_IFINDEX, |
e26f9a48 FW |
37 | .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK, |
38 | .flowi6_proto = iph->nexthdr, | |
39 | .daddr = iph->saddr, | |
40 | }; | |
41 | int lookup_flags; | |
42 | ||
43 | if (rpfilter_addr_unicast(&iph->daddr)) { | |
44 | memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr)); | |
45 | lookup_flags = RT6_LOOKUP_F_HAS_SADDR; | |
46 | } else { | |
47 | lookup_flags = 0; | |
48 | } | |
49 | ||
50 | fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; | |
51 | if ((flags & XT_RPFILTER_LOOSE) == 0) { | |
52 | fl6.flowi6_oif = dev->ifindex; | |
53 | lookup_flags |= RT6_LOOKUP_F_IFACE; | |
54 | } | |
55 | ||
686c9b50 | 56 | rt = (void *) ip6_route_lookup(net, &fl6, lookup_flags); |
e26f9a48 FW |
57 | if (rt->dst.error) |
58 | goto out; | |
59 | ||
60 | if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST)) | |
61 | goto out; | |
62 | ||
63 | if (rt->rt6i_flags & RTF_LOCAL) { | |
64 | ret = flags & XT_RPFILTER_ACCEPT_LOCAL; | |
65 | goto out; | |
66 | } | |
67 | ||
68 | if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE)) | |
69 | ret = true; | |
70 | out: | |
94e187c0 | 71 | ip6_rt_put(rt); |
e26f9a48 FW |
72 | return ret; |
73 | } | |
74 | ||
f83a7ea2 FW |
75 | static bool rpfilter_is_local(const struct sk_buff *skb) |
76 | { | |
77 | const struct rt6_info *rt = (const void *) skb_dst(skb); | |
78 | return rt && (rt->rt6i_flags & RTF_LOCAL); | |
79 | } | |
80 | ||
e26f9a48 FW |
81 | static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) |
82 | { | |
83 | const struct xt_rpfilter_info *info = par->matchinfo; | |
84 | int saddrtype; | |
85 | struct ipv6hdr *iph; | |
86 | bool invert = info->flags & XT_RPFILTER_INVERT; | |
87 | ||
f83a7ea2 | 88 | if (rpfilter_is_local(skb)) |
e26f9a48 FW |
89 | return true ^ invert; |
90 | ||
91 | iph = ipv6_hdr(skb); | |
92 | saddrtype = ipv6_addr_type(&iph->saddr); | |
93 | if (unlikely(saddrtype == IPV6_ADDR_ANY)) | |
94 | return true ^ invert; /* not routable: forward path will drop it */ | |
95 | ||
686c9b50 | 96 | return rpfilter_lookup_reverse6(par->net, skb, par->in, info->flags) ^ invert; |
e26f9a48 FW |
97 | } |
98 | ||
99 | static int rpfilter_check(const struct xt_mtchk_param *par) | |
100 | { | |
101 | const struct xt_rpfilter_info *info = par->matchinfo; | |
102 | unsigned int options = ~XT_RPFILTER_OPTION_MASK; | |
103 | ||
104 | if (info->flags & options) { | |
105 | pr_info("unknown options encountered"); | |
106 | return -EINVAL; | |
107 | } | |
108 | ||
109 | if (strcmp(par->table, "mangle") != 0 && | |
110 | strcmp(par->table, "raw") != 0) { | |
111 | pr_info("match only valid in the \'raw\' " | |
112 | "or \'mangle\' tables, not \'%s\'.\n", par->table); | |
113 | return -EINVAL; | |
114 | } | |
115 | ||
116 | return 0; | |
117 | } | |
118 | ||
119 | static struct xt_match rpfilter_mt_reg __read_mostly = { | |
120 | .name = "rpfilter", | |
121 | .family = NFPROTO_IPV6, | |
122 | .checkentry = rpfilter_check, | |
123 | .match = rpfilter_mt, | |
124 | .matchsize = sizeof(struct xt_rpfilter_info), | |
125 | .hooks = (1 << NF_INET_PRE_ROUTING), | |
126 | .me = THIS_MODULE | |
127 | }; | |
128 | ||
129 | static int __init rpfilter_mt_init(void) | |
130 | { | |
131 | return xt_register_match(&rpfilter_mt_reg); | |
132 | } | |
133 | ||
134 | static void __exit rpfilter_mt_exit(void) | |
135 | { | |
136 | xt_unregister_match(&rpfilter_mt_reg); | |
137 | } | |
138 | ||
139 | module_init(rpfilter_mt_init); | |
140 | module_exit(rpfilter_mt_exit); |