new file mode 100644
@@ -0,0 +1,23 @@
+#ifndef _XT_RPATH_H
+#define _XT_RPATH_H
+
+#include <linux/types.h>
+
+enum {
+ XT_RPFILTER_LOOSE = 1 << 0,
+ XT_RPFILTER_VALID_MARK = 1 << 1,
+ XT_RPFILTER_ACCEPT_LOCAL = 1 << 2,
+ XT_RPFILTER_INVERT = 1 << 3,
+#ifdef __KERNEL__
+ XT_RPFILTER_OPTION_MASK = XT_RPFILTER_LOOSE |
+ XT_RPFILTER_VALID_MARK |
+ XT_RPFILTER_ACCEPT_LOCAL |
+ XT_RPFILTER_INVERT,
+#endif
+};
+
+struct xt_rpfilter_info {
+ __u8 flags;
+};
+
+#endif
@@ -82,6 +82,16 @@ config IP_NF_MATCH_ECN
To compile it as a module, choose M here. If unsure, say N.
+config IP_NF_MATCH_RPFILTER
+ tristate '"rpfilter" reverse path filter match support'
+ depends on NETFILTER_ADVANCED
+ ---help---
+ This option allows you to match packets whose replies would
+ go out via the interface the packet came in.
+
+ To compile it as a module, choose M here. If unsure, say N.
+ The module will be called ipt_rpfilter.
+
config IP_NF_MATCH_TTL
tristate '"ttl" match support'
depends on NETFILTER_ADVANCED
@@ -50,6 +50,7 @@ obj-$(CONFIG_IP_NF_SECURITY) += iptable_security.o
# matches
obj-$(CONFIG_IP_NF_MATCH_AH) += ipt_ah.o
obj-$(CONFIG_IP_NF_MATCH_ECN) += ipt_ecn.o
+obj-$(CONFIG_IP_NF_MATCH_RPFILTER) += ipt_rpfilter.o
# targets
obj-$(CONFIG_IP_NF_TARGET_CLUSTERIP) += ipt_CLUSTERIP.o
new file mode 100644
@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 2011 Florian Westphal <fw@strlen.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * based on fib_frontend.c; Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/ip.h>
+#include <net/ip.h>
+#include <net/ip_fib.h>
+#include <net/route.h>
+
+#include <linux/netfilter/xt_rpfilter.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
+MODULE_DESCRIPTION("iptables: ipv4 reverse path filter match");
+
+/* don't try to find route from mcast/bcast/zeronet */
+static __be32 rpfilter_get_saddr(__be32 addr)
+{
+ if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr) ||
+ ipv4_is_zeronet(addr))
+ return 0;
+ return addr;
+}
+
+static bool rpfilter_lookup_reverse(struct flowi4 *fl4,
+ const struct net_device *dev, u8 flags)
+{
+ struct fib_result res;
+ bool dev_match;
+ struct net *net = dev_net(dev);
+ int ret __maybe_unused;
+
+ if (fib_lookup(net, fl4, &res))
+ return false;
+
+ if (res.type != RTN_UNICAST) {
+ if (res.type != RTN_LOCAL || !(flags & XT_RPFILTER_ACCEPT_LOCAL))
+ return false;
+ }
+ dev_match = false;
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+ for (ret = 0; ret < res.fi->fib_nhs; ret++) {
+ struct fib_nh *nh = &res.fi->fib_nh[ret];
+
+ if (nh->nh_dev == dev) {
+ dev_match = true;
+ break;
+ }
+ }
+#else
+ if (FIB_RES_DEV(res) == dev)
+ dev_match = true;
+#endif
+ if (dev_match || flags & XT_RPFILTER_LOOSE)
+ return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
+ return dev_match;
+}
+
+static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct xt_rpfilter_info *info;
+ const struct iphdr *iph;
+ struct flowi4 flow;
+ bool invert;
+
+ info = par->matchinfo;
+ invert = info->flags & XT_RPFILTER_INVERT;
+
+ if (par->in->flags & IFF_LOOPBACK)
+ return true ^ invert;
+
+ iph = ip_hdr(skb);
+ if (ipv4_is_multicast(iph->daddr)) {
+ if (ipv4_is_zeronet(iph->saddr))
+ return ipv4_is_local_multicast(iph->daddr) ^ invert;
+ flow.flowi4_iif = 0;
+ } else {
+ flow.flowi4_iif = dev_net(par->in)->loopback_dev->ifindex;
+ }
+
+ flow.daddr = iph->saddr;
+ flow.saddr = rpfilter_get_saddr(iph->daddr);
+ flow.flowi4_oif = 0;
+ flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
+ flow.flowi4_tos = RT_TOS(iph->tos);
+ flow.flowi4_scope = RT_SCOPE_UNIVERSE;
+
+ return rpfilter_lookup_reverse(&flow, par->in, info->flags) ^ invert;
+}
+
+static int rpfilter_check(const struct xt_mtchk_param *par)
+{
+ const struct xt_rpfilter_info *info = par->matchinfo;
+ unsigned int options = ~XT_RPFILTER_OPTION_MASK;
+ if (info->flags & options) {
+ pr_info("unknown options encountered");
+ return -EINVAL;
+ }
+
+ if (strcmp(par->table, "mangle") != 0 &&
+ strcmp(par->table, "raw") != 0) {
+ pr_info("match only valid in the \'raw\' "
+ "or \'mangle\' tables, not \'%s\'.\n", par->table);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static struct xt_match rpfilter_mt_reg __read_mostly = {
+ .name = "rpfilter",
+ .family = NFPROTO_IPV4,
+ .checkentry = rpfilter_check,
+ .match = rpfilter_mt,
+ .matchsize = sizeof(struct xt_rpfilter_info),
+ .hooks = (1 << NF_INET_PRE_ROUTING),
+ .me = THIS_MODULE
+};
+
+static int __init rpfilter_mt_init(void)
+{
+ return xt_register_match(&rpfilter_mt_reg);
+}
+
+static void __exit rpfilter_mt_exit(void)
+{
+ xt_unregister_match(&rpfilter_mt_reg);
+}
+
+module_init(rpfilter_mt_init);
+module_exit(rpfilter_mt_exit);