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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
19MODULE_LICENSE("GPL");
20MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
21MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");
22
23static 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
29static bool rpfilter_addr_linklocal(const struct in6_addr *addr)
30{
31 int addr_type = ipv6_addr_type(addr);
32 return addr_type & IPV6_ADDR_LINKLOCAL;
33}
34
35static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
36 const struct net_device *dev, u8 flags)
37{
38 struct rt6_info *rt;
39 struct ipv6hdr *iph = ipv6_hdr(skb);
40 bool ret = false;
41 struct flowi6 fl6 = {
42 .flowi6_iif = LOOPBACK_IFINDEX,
43 .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
44 .flowi6_proto = iph->nexthdr,
45 .daddr = iph->saddr,
46 };
47 int lookup_flags;
48
49 if (rpfilter_addr_unicast(&iph->daddr)) {
50 memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
51 lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
52 } else {
53 lookup_flags = 0;
54 }
55
56 fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
57
58 if (rpfilter_addr_linklocal(&iph->saddr)) {
59 lookup_flags |= RT6_LOOKUP_F_IFACE;
60 fl6.flowi6_oif = dev->ifindex;
61 } else if ((flags & XT_RPFILTER_LOOSE) == 0)
62 fl6.flowi6_oif = dev->ifindex;
63
64 rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags);
65 if (rt->dst.error)
66 goto out;
67
68 if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
69 goto out;
70
71 if (rt->rt6i_flags & RTF_LOCAL) {
72 ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
73 goto out;
74 }
75
76 if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
77 ret = true;
78 out:
79 ip6_rt_put(rt);
80 return ret;
81}
82
83static bool
84rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
85{
86 return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
87}
88
89static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
90{
91 const struct xt_rpfilter_info *info = par->matchinfo;
92 int saddrtype;
93 struct ipv6hdr *iph;
94 bool invert = info->flags & XT_RPFILTER_INVERT;
95
96 if (rpfilter_is_loopback(skb, xt_in(par)))
97 return true ^ invert;
98
99 iph = ipv6_hdr(skb);
100 saddrtype = ipv6_addr_type(&iph->saddr);
101 if (unlikely(saddrtype == IPV6_ADDR_ANY))
102 return true ^ invert;
103
104 return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par),
105 info->flags) ^ invert;
106}
107
108static int rpfilter_check(const struct xt_mtchk_param *par)
109{
110 const struct xt_rpfilter_info *info = par->matchinfo;
111 unsigned int options = ~XT_RPFILTER_OPTION_MASK;
112
113 if (info->flags & options) {
114 pr_info_ratelimited("unknown options\n");
115 return -EINVAL;
116 }
117
118 if (strcmp(par->table, "mangle") != 0 &&
119 strcmp(par->table, "raw") != 0) {
120 pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n",
121 par->table);
122 return -EINVAL;
123 }
124
125 return 0;
126}
127
128static struct xt_match rpfilter_mt_reg __read_mostly = {
129 .name = "rpfilter",
130 .family = NFPROTO_IPV6,
131 .checkentry = rpfilter_check,
132 .match = rpfilter_mt,
133 .matchsize = sizeof(struct xt_rpfilter_info),
134 .hooks = (1 << NF_INET_PRE_ROUTING),
135 .me = THIS_MODULE
136};
137
138static int __init rpfilter_mt_init(void)
139{
140 return xt_register_match(&rpfilter_mt_reg);
141}
142
143static void __exit rpfilter_mt_exit(void)
144{
145 xt_unregister_match(&rpfilter_mt_reg);
146}
147
148module_init(rpfilter_mt_init);
149module_exit(rpfilter_mt_exit);
150
