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- /*
- * 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 net *net, struct flowi4 *fl4,
- const struct net_device *dev, u8 flags)
- {
- struct fib_result res;
- bool dev_match;
- int ret __maybe_unused;
- if (fib_lookup(net, fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE))
- 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
- return dev_match || flags & XT_RPFILTER_LOOSE;
- }
- static bool rpfilter_is_local(const struct sk_buff *skb)
- {
- const struct rtable *rt = skb_rtable(skb);
- return rt && (rt->rt_flags & RTCF_LOCAL);
- }
- 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 (rpfilter_is_local(skb))
- 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 = LOOPBACK_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(par->net, &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);
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