| /* |
| * 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_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 = 0; |
| } else { |
| 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(&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); |