Florian Westphal | 8f97339 | 2011-07-04 22:48:10 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2011 Florian Westphal <fw@strlen.de> |
| 3 | * |
| 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. |
| 7 | * |
| 8 | * based on fib_frontend.c; Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> |
| 9 | */ |
| 10 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 11 | #include <linux/module.h> |
| 12 | #include <linux/skbuff.h> |
| 13 | #include <linux/netdevice.h> |
| 14 | #include <linux/ip.h> |
| 15 | #include <net/ip.h> |
| 16 | #include <net/ip_fib.h> |
| 17 | #include <net/route.h> |
| 18 | |
| 19 | #include <linux/netfilter/xt_rpfilter.h> |
| 20 | #include <linux/netfilter/x_tables.h> |
| 21 | |
| 22 | MODULE_LICENSE("GPL"); |
| 23 | MODULE_AUTHOR("Florian Westphal <fw@strlen.de>"); |
| 24 | MODULE_DESCRIPTION("iptables: ipv4 reverse path filter match"); |
| 25 | |
| 26 | /* don't try to find route from mcast/bcast/zeronet */ |
| 27 | static __be32 rpfilter_get_saddr(__be32 addr) |
| 28 | { |
| 29 | if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr) || |
| 30 | ipv4_is_zeronet(addr)) |
| 31 | return 0; |
| 32 | return addr; |
| 33 | } |
| 34 | |
| 35 | static bool rpfilter_lookup_reverse(struct flowi4 *fl4, |
| 36 | const struct net_device *dev, u8 flags) |
| 37 | { |
| 38 | struct fib_result res; |
| 39 | bool dev_match; |
| 40 | struct net *net = dev_net(dev); |
| 41 | int ret __maybe_unused; |
| 42 | |
| 43 | if (fib_lookup(net, fl4, &res)) |
| 44 | return false; |
| 45 | |
| 46 | if (res.type != RTN_UNICAST) { |
| 47 | if (res.type != RTN_LOCAL || !(flags & XT_RPFILTER_ACCEPT_LOCAL)) |
| 48 | return false; |
| 49 | } |
| 50 | dev_match = false; |
| 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]; |
| 54 | |
| 55 | if (nh->nh_dev == dev) { |
| 56 | dev_match = true; |
| 57 | break; |
| 58 | } |
| 59 | } |
| 60 | #else |
| 61 | if (FIB_RES_DEV(res) == dev) |
| 62 | dev_match = true; |
| 63 | #endif |
| 64 | if (dev_match || flags & XT_RPFILTER_LOOSE) |
| 65 | return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST; |
| 66 | return dev_match; |
| 67 | } |
| 68 | |
| 69 | static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) |
| 70 | { |
| 71 | const struct xt_rpfilter_info *info; |
| 72 | const struct iphdr *iph; |
| 73 | struct flowi4 flow; |
| 74 | bool invert; |
| 75 | |
| 76 | info = par->matchinfo; |
| 77 | invert = info->flags & XT_RPFILTER_INVERT; |
| 78 | |
| 79 | if (par->in->flags & IFF_LOOPBACK) |
| 80 | return true ^ invert; |
| 81 | |
| 82 | iph = ip_hdr(skb); |
| 83 | if (ipv4_is_multicast(iph->daddr)) { |
| 84 | if (ipv4_is_zeronet(iph->saddr)) |
| 85 | return ipv4_is_local_multicast(iph->daddr) ^ invert; |
Florian Westphal | 8f97339 | 2011-07-04 22:48:10 +0100 | [diff] [blame] | 86 | } |
Pavel Emelyanov | feb645e | 2012-08-08 21:53:36 +0000 | [diff] [blame] | 87 | flow.flowi4_iif = LOOPBACK_IFINDEX; |
Florian Westphal | 8f97339 | 2011-07-04 22:48:10 +0100 | [diff] [blame] | 88 | flow.daddr = iph->saddr; |
| 89 | flow.saddr = rpfilter_get_saddr(iph->daddr); |
| 90 | flow.flowi4_oif = 0; |
| 91 | flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; |
| 92 | flow.flowi4_tos = RT_TOS(iph->tos); |
| 93 | flow.flowi4_scope = RT_SCOPE_UNIVERSE; |
| 94 | |
| 95 | return rpfilter_lookup_reverse(&flow, par->in, info->flags) ^ invert; |
| 96 | } |
| 97 | |
| 98 | static int rpfilter_check(const struct xt_mtchk_param *par) |
| 99 | { |
| 100 | const struct xt_rpfilter_info *info = par->matchinfo; |
| 101 | unsigned int options = ~XT_RPFILTER_OPTION_MASK; |
| 102 | if (info->flags & options) { |
| 103 | pr_info("unknown options encountered"); |
| 104 | return -EINVAL; |
| 105 | } |
| 106 | |
| 107 | if (strcmp(par->table, "mangle") != 0 && |
| 108 | strcmp(par->table, "raw") != 0) { |
| 109 | pr_info("match only valid in the \'raw\' " |
| 110 | "or \'mangle\' tables, not \'%s\'.\n", par->table); |
| 111 | return -EINVAL; |
| 112 | } |
| 113 | |
| 114 | return 0; |
| 115 | } |
| 116 | |
| 117 | static struct xt_match rpfilter_mt_reg __read_mostly = { |
| 118 | .name = "rpfilter", |
| 119 | .family = NFPROTO_IPV4, |
| 120 | .checkentry = rpfilter_check, |
| 121 | .match = rpfilter_mt, |
| 122 | .matchsize = sizeof(struct xt_rpfilter_info), |
| 123 | .hooks = (1 << NF_INET_PRE_ROUTING), |
| 124 | .me = THIS_MODULE |
| 125 | }; |
| 126 | |
| 127 | static int __init rpfilter_mt_init(void) |
| 128 | { |
| 129 | return xt_register_match(&rpfilter_mt_reg); |
| 130 | } |
| 131 | |
| 132 | static void __exit rpfilter_mt_exit(void) |
| 133 | { |
| 134 | xt_unregister_match(&rpfilter_mt_reg); |
| 135 | } |
| 136 | |
| 137 | module_init(rpfilter_mt_init); |
| 138 | module_exit(rpfilter_mt_exit); |