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
rpfilter_addr_unicast(const struct in6_addr * addr)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
rpfilter_lookup_reverse6(const struct sk_buff * skb,const struct net_device * dev,u8 flags)29 static bool rpfilter_lookup_reverse6(const struct sk_buff *skb,
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 = {
36 .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
37 .flowi6_proto = iph->nexthdr,
38 .daddr = iph->saddr,
39 };
40 int lookup_flags;
41
42 if (rpfilter_addr_unicast(&iph->daddr)) {
43 memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
44 lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
45 } else {
46 lookup_flags = 0;
47 }
48
49 fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
50 if ((flags & XT_RPFILTER_LOOSE) == 0) {
51 fl6.flowi6_oif = dev->ifindex;
52 lookup_flags |= RT6_LOOKUP_F_IFACE;
53 }
54
55 rt = (void *) ip6_route_lookup(dev_net(dev), &fl6, lookup_flags);
56 if (rt->dst.error)
57 goto out;
58
59 if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
60 goto out;
61
62 if (rt->rt6i_flags & RTF_LOCAL) {
63 ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
64 goto out;
65 }
66
67 if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
68 ret = true;
69 out:
70 dst_release(&rt->dst);
71 return ret;
72 }
73
rpfilter_mt(const struct sk_buff * skb,struct xt_action_param * par)74 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
75 {
76 const struct xt_rpfilter_info *info = par->matchinfo;
77 int saddrtype;
78 struct ipv6hdr *iph;
79 bool invert = info->flags & XT_RPFILTER_INVERT;
80
81 if (par->in->flags & IFF_LOOPBACK)
82 return true ^ invert;
83
84 iph = ipv6_hdr(skb);
85 saddrtype = ipv6_addr_type(&iph->saddr);
86 if (unlikely(saddrtype == IPV6_ADDR_ANY))
87 return true ^ invert; /* not routable: forward path will drop it */
88
89 return rpfilter_lookup_reverse6(skb, par->in, info->flags) ^ invert;
90 }
91
rpfilter_check(const struct xt_mtchk_param * par)92 static int rpfilter_check(const struct xt_mtchk_param *par)
93 {
94 const struct xt_rpfilter_info *info = par->matchinfo;
95 unsigned int options = ~XT_RPFILTER_OPTION_MASK;
96
97 if (info->flags & options) {
98 pr_info("unknown options encountered");
99 return -EINVAL;
100 }
101
102 if (strcmp(par->table, "mangle") != 0 &&
103 strcmp(par->table, "raw") != 0) {
104 pr_info("match only valid in the \'raw\' "
105 "or \'mangle\' tables, not \'%s\'.\n", par->table);
106 return -EINVAL;
107 }
108
109 return 0;
110 }
111
112 static struct xt_match rpfilter_mt_reg __read_mostly = {
113 .name = "rpfilter",
114 .family = NFPROTO_IPV6,
115 .checkentry = rpfilter_check,
116 .match = rpfilter_mt,
117 .matchsize = sizeof(struct xt_rpfilter_info),
118 .hooks = (1 << NF_INET_PRE_ROUTING),
119 .me = THIS_MODULE
120 };
121
rpfilter_mt_init(void)122 static int __init rpfilter_mt_init(void)
123 {
124 return xt_register_match(&rpfilter_mt_reg);
125 }
126
rpfilter_mt_exit(void)127 static void __exit rpfilter_mt_exit(void)
128 {
129 xt_unregister_match(&rpfilter_mt_reg);
130 }
131
132 module_init(rpfilter_mt_init);
133 module_exit(rpfilter_mt_exit);
134