1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (c) 2011 Florian Westphal <fw@strlen.de>
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>
13 #include <linux/netfilter/xt_rpfilter.h>
14 #include <linux/netfilter/x_tables.h>
16 MODULE_LICENSE("GPL");
17 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
18 MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");
20 static bool rpfilter_addr_unicast(const struct in6_addr *addr)
22 int addr_type = ipv6_addr_type(addr);
23 return addr_type & IPV6_ADDR_UNICAST;
26 static bool rpfilter_addr_linklocal(const struct in6_addr *addr)
28 int addr_type = ipv6_addr_type(addr);
29 return addr_type & IPV6_ADDR_LINKLOCAL;
32 static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
33 const struct net_device *dev, u8 flags)
36 struct ipv6hdr *iph = ipv6_hdr(skb);
39 .flowi6_iif = LOOPBACK_IFINDEX,
40 .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
41 .flowi6_proto = iph->nexthdr,
46 if (rpfilter_addr_unicast(&iph->daddr)) {
47 memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
48 lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
53 fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
55 if (rpfilter_addr_linklocal(&iph->saddr)) {
56 lookup_flags |= RT6_LOOKUP_F_IFACE;
57 fl6.flowi6_oif = dev->ifindex;
58 } else if ((flags & XT_RPFILTER_LOOSE) == 0)
59 fl6.flowi6_oif = dev->ifindex;
61 rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags);
65 if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
68 if (rt->rt6i_flags & RTF_LOCAL) {
69 ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
73 if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
81 rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
83 return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
86 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
88 const struct xt_rpfilter_info *info = par->matchinfo;
91 bool invert = info->flags & XT_RPFILTER_INVERT;
93 if (rpfilter_is_loopback(skb, xt_in(par)))
97 saddrtype = ipv6_addr_type(&iph->saddr);
98 if (unlikely(saddrtype == IPV6_ADDR_ANY))
99 return true ^ invert; /* not routable: forward path will drop it */
101 return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par),
102 info->flags) ^ invert;
105 static int rpfilter_check(const struct xt_mtchk_param *par)
107 const struct xt_rpfilter_info *info = par->matchinfo;
108 unsigned int options = ~XT_RPFILTER_OPTION_MASK;
110 if (info->flags & options) {
111 pr_info_ratelimited("unknown options\n");
115 if (strcmp(par->table, "mangle") != 0 &&
116 strcmp(par->table, "raw") != 0) {
117 pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n",
125 static struct xt_match rpfilter_mt_reg __read_mostly = {
127 .family = NFPROTO_IPV6,
128 .checkentry = rpfilter_check,
129 .match = rpfilter_mt,
130 .matchsize = sizeof(struct xt_rpfilter_info),
131 .hooks = (1 << NF_INET_PRE_ROUTING),
135 static int __init rpfilter_mt_init(void)
137 return xt_register_match(&rpfilter_mt_reg);
140 static void __exit rpfilter_mt_exit(void)
142 xt_unregister_match(&rpfilter_mt_reg);
145 module_init(rpfilter_mt_init);
146 module_exit(rpfilter_mt_exit);