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_addr_linklocal(const struct in6_addr * addr)29 static 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
rpfilter_lookup_reverse6(struct net * net,const struct sk_buff * skb,const struct net_device * dev,u8 flags)35 static 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 /* Set flowi6_oif for vrf devices to lookup route in l3mdev domain. */
62 } else if (netif_is_l3_master(dev) || netif_is_l3_slave(dev) ||
63 (flags & XT_RPFILTER_LOOSE) == 0)
64 fl6.flowi6_oif = dev->ifindex;
65
66 rt = (void *) ip6_route_lookup(net, &fl6, lookup_flags);
67 if (rt->dst.error)
68 goto out;
69
70 if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
71 goto out;
72
73 if (rt->rt6i_flags & RTF_LOCAL) {
74 ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
75 goto out;
76 }
77
78 if (rt->rt6i_idev->dev == dev ||
79 l3mdev_master_ifindex_rcu(rt->rt6i_idev->dev) == dev->ifindex ||
80 (flags & XT_RPFILTER_LOOSE))
81 ret = true;
82 out:
83 ip6_rt_put(rt);
84 return ret;
85 }
86
87 static bool
rpfilter_is_loopback(const struct sk_buff * skb,const struct net_device * in)88 rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
89 {
90 return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
91 }
92
rpfilter_mt(const struct sk_buff * skb,struct xt_action_param * par)93 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
94 {
95 const struct xt_rpfilter_info *info = par->matchinfo;
96 int saddrtype;
97 struct ipv6hdr *iph;
98 bool invert = info->flags & XT_RPFILTER_INVERT;
99
100 if (rpfilter_is_loopback(skb, xt_in(par)))
101 return true ^ invert;
102
103 iph = ipv6_hdr(skb);
104 saddrtype = ipv6_addr_type(&iph->saddr);
105 if (unlikely(saddrtype == IPV6_ADDR_ANY))
106 return true ^ invert; /* not routable: forward path will drop it */
107
108 return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par),
109 info->flags) ^ invert;
110 }
111
rpfilter_check(const struct xt_mtchk_param * par)112 static int rpfilter_check(const struct xt_mtchk_param *par)
113 {
114 const struct xt_rpfilter_info *info = par->matchinfo;
115 unsigned int options = ~XT_RPFILTER_OPTION_MASK;
116
117 if (info->flags & options) {
118 pr_info("unknown options encountered");
119 return -EINVAL;
120 }
121
122 if (strcmp(par->table, "mangle") != 0 &&
123 strcmp(par->table, "raw") != 0) {
124 pr_info("match only valid in the \'raw\' "
125 "or \'mangle\' tables, not \'%s\'.\n", par->table);
126 return -EINVAL;
127 }
128
129 return 0;
130 }
131
132 static struct xt_match rpfilter_mt_reg __read_mostly = {
133 .name = "rpfilter",
134 .family = NFPROTO_IPV6,
135 .checkentry = rpfilter_check,
136 .match = rpfilter_mt,
137 .matchsize = sizeof(struct xt_rpfilter_info),
138 .hooks = (1 << NF_INET_PRE_ROUTING),
139 .me = THIS_MODULE
140 };
141
rpfilter_mt_init(void)142 static int __init rpfilter_mt_init(void)
143 {
144 return xt_register_match(&rpfilter_mt_reg);
145 }
146
rpfilter_mt_exit(void)147 static void __exit rpfilter_mt_exit(void)
148 {
149 xt_unregister_match(&rpfilter_mt_reg);
150 }
151
152 module_init(rpfilter_mt_init);
153 module_exit(rpfilter_mt_exit);
154