1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Copyright (c) 2011 Florian Westphal <fw@strlen.de> |
4 | */ |
5 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
6 | #include <linux/module.h> |
7 | #include <linux/skbuff.h> |
8 | #include <linux/netdevice.h> |
9 | #include <linux/route.h> |
10 | #include <net/ip6_fib.h> |
11 | #include <net/ip6_route.h> |
12 | |
13 | #include <linux/netfilter/xt_rpfilter.h> |
14 | #include <linux/netfilter/x_tables.h> |
15 | |
16 | MODULE_LICENSE("GPL" ); |
17 | MODULE_AUTHOR("Florian Westphal <fw@strlen.de>" ); |
18 | MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match" ); |
19 | |
20 | static bool rpfilter_addr_unicast(const struct in6_addr *addr) |
21 | { |
22 | int addr_type = ipv6_addr_type(addr); |
23 | return addr_type & IPV6_ADDR_UNICAST; |
24 | } |
25 | |
26 | static bool rpfilter_addr_linklocal(const struct in6_addr *addr) |
27 | { |
28 | int addr_type = ipv6_addr_type(addr); |
29 | return addr_type & IPV6_ADDR_LINKLOCAL; |
30 | } |
31 | |
32 | static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb, |
33 | const struct net_device *dev, u8 flags) |
34 | { |
35 | struct rt6_info *rt; |
36 | struct ipv6hdr *iph = ipv6_hdr(skb); |
37 | bool ret = false; |
38 | struct flowi6 fl6 = { |
39 | .flowi6_iif = LOOPBACK_IFINDEX, |
40 | .flowi6_l3mdev = l3mdev_master_ifindex_rcu(dev), |
41 | .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK, |
42 | .flowi6_proto = iph->nexthdr, |
43 | .flowi6_uid = sock_net_uid(net, NULL), |
44 | .daddr = iph->saddr, |
45 | }; |
46 | int lookup_flags; |
47 | |
48 | if (rpfilter_addr_unicast(addr: &iph->daddr)) { |
49 | memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr)); |
50 | lookup_flags = RT6_LOOKUP_F_HAS_SADDR; |
51 | } else { |
52 | lookup_flags = 0; |
53 | } |
54 | |
55 | fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; |
56 | |
57 | if (rpfilter_addr_linklocal(addr: &iph->saddr)) { |
58 | lookup_flags |= RT6_LOOKUP_F_IFACE; |
59 | fl6.flowi6_oif = dev->ifindex; |
60 | } else if ((flags & XT_RPFILTER_LOOSE) == 0) |
61 | fl6.flowi6_oif = dev->ifindex; |
62 | |
63 | rt = (void *)ip6_route_lookup(net, fl6: &fl6, skb, flags: lookup_flags); |
64 | if (rt->dst.error) |
65 | goto out; |
66 | |
67 | if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST)) |
68 | goto out; |
69 | |
70 | if (rt->rt6i_flags & RTF_LOCAL) { |
71 | ret = flags & XT_RPFILTER_ACCEPT_LOCAL; |
72 | goto out; |
73 | } |
74 | |
75 | if (rt->rt6i_idev->dev == dev || |
76 | l3mdev_master_ifindex_rcu(dev: rt->rt6i_idev->dev) == dev->ifindex || |
77 | (flags & XT_RPFILTER_LOOSE)) |
78 | ret = true; |
79 | out: |
80 | ip6_rt_put(rt); |
81 | return ret; |
82 | } |
83 | |
84 | static bool |
85 | rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in) |
86 | { |
87 | return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK; |
88 | } |
89 | |
90 | static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) |
91 | { |
92 | const struct xt_rpfilter_info *info = par->matchinfo; |
93 | int saddrtype; |
94 | struct ipv6hdr *iph; |
95 | bool invert = info->flags & XT_RPFILTER_INVERT; |
96 | |
97 | if (rpfilter_is_loopback(skb, in: xt_in(par))) |
98 | return true ^ invert; |
99 | |
100 | iph = ipv6_hdr(skb); |
101 | saddrtype = ipv6_addr_type(addr: &iph->saddr); |
102 | if (unlikely(saddrtype == IPV6_ADDR_ANY)) |
103 | return true ^ invert; /* not routable: forward path will drop it */ |
104 | |
105 | return rpfilter_lookup_reverse6(net: xt_net(par), skb, dev: xt_in(par), |
106 | flags: info->flags) ^ invert; |
107 | } |
108 | |
109 | static int rpfilter_check(const struct xt_mtchk_param *par) |
110 | { |
111 | const struct xt_rpfilter_info *info = par->matchinfo; |
112 | unsigned int options = ~XT_RPFILTER_OPTION_MASK; |
113 | |
114 | if (info->flags & options) { |
115 | pr_info_ratelimited("unknown options\n" ); |
116 | return -EINVAL; |
117 | } |
118 | |
119 | if (strcmp(par->table, "mangle" ) != 0 && |
120 | strcmp(par->table, "raw" ) != 0) { |
121 | pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n" , |
122 | par->table); |
123 | return -EINVAL; |
124 | } |
125 | |
126 | return 0; |
127 | } |
128 | |
129 | static struct xt_match rpfilter_mt_reg __read_mostly = { |
130 | .name = "rpfilter" , |
131 | .family = NFPROTO_IPV6, |
132 | .checkentry = rpfilter_check, |
133 | .match = rpfilter_mt, |
134 | .matchsize = sizeof(struct xt_rpfilter_info), |
135 | .hooks = (1 << NF_INET_PRE_ROUTING), |
136 | .me = THIS_MODULE |
137 | }; |
138 | |
139 | static int __init rpfilter_mt_init(void) |
140 | { |
141 | return xt_register_match(target: &rpfilter_mt_reg); |
142 | } |
143 | |
144 | static void __exit rpfilter_mt_exit(void) |
145 | { |
146 | xt_unregister_match(target: &rpfilter_mt_reg); |
147 | } |
148 | |
149 | module_init(rpfilter_mt_init); |
150 | module_exit(rpfilter_mt_exit); |
151 | |