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 flowi4 *fl4,
36 const struct net_device *dev, u8 flags)
38 struct fib_result res;
40 struct net *net = dev_net(dev);
41 int ret __maybe_unused;
43 if (fib_lookup(net, fl4, &res))
46 if (res.type != RTN_UNICAST) {
47 if (res.type != RTN_LOCAL || !(flags & XT_RPFILTER_ACCEPT_LOCAL))
51 #ifdef CONFIG_IP_ROUTE_MULTIPATH
52 for (ret = 0; ret < res.fi->fib_nhs; ret++) {
53 struct fib_nh *nh = &res.fi->fib_nh[ret];
55 if (nh->nh_dev == dev) {
61 if (FIB_RES_DEV(res) == dev)
64 if (dev_match || flags & XT_RPFILTER_LOOSE)
65 return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
69 static bool rpfilter_is_local(const struct sk_buff *skb)
71 const struct rtable *rt = skb_rtable(skb);
72 return rt && (rt->rt_flags & RTCF_LOCAL);
75 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
77 const struct xt_rpfilter_info *info;
78 const struct iphdr *iph;
82 info = par->matchinfo;
83 invert = info->flags & XT_RPFILTER_INVERT;
85 if (rpfilter_is_local(skb))
89 if (ipv4_is_multicast(iph->daddr)) {
90 if (ipv4_is_zeronet(iph->saddr))
91 return ipv4_is_local_multicast(iph->daddr) ^ invert;
94 flow.flowi4_iif = LOOPBACK_IFINDEX;
97 flow.daddr = iph->saddr;
98 flow.saddr = rpfilter_get_saddr(iph->daddr);
100 flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
101 flow.flowi4_tos = RT_TOS(iph->tos);
102 flow.flowi4_scope = RT_SCOPE_UNIVERSE;
104 return rpfilter_lookup_reverse(&flow, par->in, info->flags) ^ invert;
107 static int rpfilter_check(const struct xt_mtchk_param *par)
109 const struct xt_rpfilter_info *info = par->matchinfo;
110 unsigned int options = ~XT_RPFILTER_OPTION_MASK;
111 if (info->flags & options) {
112 pr_info("unknown options encountered");
116 if (strcmp(par->table, "mangle") != 0 &&
117 strcmp(par->table, "raw") != 0) {
118 pr_info("match only valid in the \'raw\' "
119 "or \'mangle\' tables, not \'%s\'.\n", par->table);
126 static struct xt_match rpfilter_mt_reg __read_mostly = {
128 .family = NFPROTO_IPV4,
129 .checkentry = rpfilter_check,
130 .match = rpfilter_mt,
131 .matchsize = sizeof(struct xt_rpfilter_info),
132 .hooks = (1 << NF_INET_PRE_ROUTING),
136 static int __init rpfilter_mt_init(void)
138 return xt_register_match(&rpfilter_mt_reg);
141 static void __exit rpfilter_mt_exit(void)
143 xt_unregister_match(&rpfilter_mt_reg);
146 module_init(rpfilter_mt_init);
147 module_exit(rpfilter_mt_exit);