LXR linux/net/ipv4/netfilter/ipt

   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
  22MODULE_LICENSE("GPL");
  23MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
  24MODULE_DESCRIPTION("iptables: ipv4 reverse path filter match");
  25
  26/* don't try to find route from mcast/bcast/zeronet */
  27static __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
  35static bool rpfilter_lookup_reverse(struct net *net, struct flowi4 *fl4,
  36                                const struct net_device *dev, u8 flags)
  37{
  38        struct fib_result res;
  39        int ret __maybe_unused;
  40
  41        if (fib_lookup(net, fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE))
  42                return false;
  43
  44        if (res.type != RTN_UNICAST) {
  45                if (res.type != RTN_LOCAL || !(flags & XT_RPFILTER_ACCEPT_LOCAL))
  46                        return false;
  47        }
  48        return fib_info_nh_uses_dev(res.fi, dev) || flags & XT_RPFILTER_LOOSE;
  49}
  50
  51static bool
  52rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
  53{
  54        return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
  55}
  56
  57static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
  58{
  59        const struct xt_rpfilter_info *info;
  60        const struct iphdr *iph;
  61        struct flowi4 flow;
  62        bool invert;
  63
  64        info = par->matchinfo;
  65        invert = info->flags & XT_RPFILTER_INVERT;
  66
  67        if (rpfilter_is_loopback(skb, xt_in(par)))
  68                return true ^ invert;
  69
  70        iph = ip_hdr(skb);
  71        if (ipv4_is_zeronet(iph->saddr)) {
  72                if (ipv4_is_lbcast(iph->daddr) ||
  73                    ipv4_is_local_multicast(iph->daddr))
  74                        return true ^ invert;
  75        }
  76
  77        memset(&flow, 0, sizeof(flow));
  78        flow.flowi4_iif = LOOPBACK_IFINDEX;
  79        flow.daddr = iph->saddr;
  80        flow.saddr = rpfilter_get_saddr(iph->daddr);
  81        flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
  82        flow.flowi4_tos = RT_TOS(iph->tos);
  83        flow.flowi4_scope = RT_SCOPE_UNIVERSE;
  84
  85        return rpfilter_lookup_reverse(xt_net(par), &flow, xt_in(par), info->flags) ^ invert;
  86}
  87
  88static int rpfilter_check(const struct xt_mtchk_param *par)
  89{
  90        const struct xt_rpfilter_info *info = par->matchinfo;
  91        unsigned int options = ~XT_RPFILTER_OPTION_MASK;
  92        if (info->flags & options) {
  93                pr_info_ratelimited("unknown options\n");
  94                return -EINVAL;
  95        }
  96
  97        if (strcmp(par->table, "mangle") != 0 &&
  98            strcmp(par->table, "raw") != 0) {
  99                pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n",
 100                                    par->table);
 101                return -EINVAL;
 102        }
 103
 104        return 0;
 105}
 106
 107static struct xt_match rpfilter_mt_reg __read_mostly = {
 108        .name           = "rpfilter",
 109        .family         = NFPROTO_IPV4,
 110        .checkentry     = rpfilter_check,
 111        .match          = rpfilter_mt,
 112        .matchsize      = sizeof(struct xt_rpfilter_info),
 113        .hooks          = (1 << NF_INET_PRE_ROUTING),
 114        .me             = THIS_MODULE
 115};
 116
 117static int __init rpfilter_mt_init(void)
 118{
 119        return xt_register_match(&rpfilter_mt_reg);
 120}
 121
 122static void __exit rpfilter_mt_exit(void)
 123{
 124        xt_unregister_match(&rpfilter_mt_reg);
 125}
 126
 127module_init(rpfilter_mt_init);
 128module_exit(rpfilter_mt_exit);
 129