2 * Copyright (c) 2011 Florian Westphal <fw@strlen.de>
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.
8 * based on fib_frontend.c; Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/module.h>
12 #include <linux/skbuff.h>
13 #include <linux/netdevice.h>
16 #include <net/ip_fib.h>
17 #include <net/route.h>
19 #include <linux/netfilter/xt_rpfilter.h>
20 #include <linux/netfilter/x_tables.h>
22 MODULE_LICENSE("GPL");
23 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
24 MODULE_DESCRIPTION("iptables: ipv4 reverse path filter match");
26 /* don't try to find route from mcast/bcast/zeronet */
27 static __be32 rpfilter_get_saddr(__be32 addr)
29 if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr) ||
30 ipv4_is_zeronet(addr))
35 static bool rpfilter_lookup_reverse(struct net *net, struct flowi4 *fl4,
36 const struct net_device *dev, u8 flags)
38 struct fib_result res;
40 int ret __maybe_unused;
42 if (fib_lookup(net, fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE))
45 if (res.type != RTN_UNICAST) {
46 if (res.type != RTN_LOCAL || !(flags & XT_RPFILTER_ACCEPT_LOCAL))
50 #ifdef CONFIG_IP_ROUTE_MULTIPATH
51 for (ret = 0; ret < res.fi->fib_nhs; ret++) {
52 struct fib_nh *nh = &res.fi->fib_nh[ret];
54 if (nh->nh_dev == dev) {
60 if (FIB_RES_DEV(res) == dev)
63 return dev_match || flags & XT_RPFILTER_LOOSE;
66 static bool rpfilter_is_local(const struct sk_buff *skb)
68 const struct rtable *rt = skb_rtable(skb);
69 return rt && (rt->rt_flags & RTCF_LOCAL);
72 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
74 const struct xt_rpfilter_info *info;
75 const struct iphdr *iph;
79 info = par->matchinfo;
80 invert = info->flags & XT_RPFILTER_INVERT;
82 if (rpfilter_is_local(skb))
86 if (ipv4_is_zeronet(iph->saddr)) {
87 if (ipv4_is_lbcast(iph->daddr) ||
88 ipv4_is_local_multicast(iph->daddr))
92 flow.flowi4_iif = LOOPBACK_IFINDEX;
93 flow.daddr = iph->saddr;
94 flow.saddr = rpfilter_get_saddr(iph->daddr);
96 flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
97 flow.flowi4_tos = RT_TOS(iph->tos);
98 flow.flowi4_scope = RT_SCOPE_UNIVERSE;
100 return rpfilter_lookup_reverse(xt_net(par), &flow, xt_in(par), info->flags) ^ invert;
103 static int rpfilter_check(const struct xt_mtchk_param *par)
105 const struct xt_rpfilter_info *info = par->matchinfo;
106 unsigned int options = ~XT_RPFILTER_OPTION_MASK;
107 if (info->flags & options) {
108 pr_info("unknown options encountered");
112 if (strcmp(par->table, "mangle") != 0 &&
113 strcmp(par->table, "raw") != 0) {
114 pr_info("match only valid in the \'raw\' "
115 "or \'mangle\' tables, not \'%s\'.\n", par->table);
122 static struct xt_match rpfilter_mt_reg __read_mostly = {
124 .family = NFPROTO_IPV4,
125 .checkentry = rpfilter_check,
126 .match = rpfilter_mt,
127 .matchsize = sizeof(struct xt_rpfilter_info),
128 .hooks = (1 << NF_INET_PRE_ROUTING),
132 static int __init rpfilter_mt_init(void)
134 return xt_register_match(&rpfilter_mt_reg);
137 static void __exit rpfilter_mt_exit(void)
139 xt_unregister_match(&rpfilter_mt_reg);
142 module_init(rpfilter_mt_init);
143 module_exit(rpfilter_mt_exit);