LXR linux/net/ipv6/netfilter/ip6t

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (c) 2011 Florian Westphal <fw@strlen.de>
   4 */
   5#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   6#include <linux/module.h>
   7#include <linux/skbuff.h>
   8#include <linux/netdevice.h>
   9#include <linux/route.h>
  10#include <net/ip6_fib.h>
  11#include <net/ip6_route.h>
  12
  13#include <linux/netfilter/xt_rpfilter.h>
  14#include <linux/netfilter/x_tables.h>
  15
  16MODULE_LICENSE("GPL");
  17MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
  18MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");
  19
  20static bool rpfilter_addr_unicast(const struct in6_addr *addr)
  21{
  22        int addr_type = ipv6_addr_type(addr);
  23        return addr_type & IPV6_ADDR_UNICAST;
  24}
  25
  26static bool rpfilter_addr_linklocal(const struct in6_addr *addr)
  27{
  28        int addr_type = ipv6_addr_type(addr);
  29        return addr_type & IPV6_ADDR_LINKLOCAL;
  30}
  31
  32static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
  33                                     const struct net_device *dev, u8 flags)
  34{
  35        struct rt6_info *rt;
  36        struct ipv6hdr *iph = ipv6_hdr(skb);
  37        bool ret = false;
  38        struct flowi6 fl6 = {
  39                .flowi6_iif = LOOPBACK_IFINDEX,
  40                .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
  41                .flowi6_proto = iph->nexthdr,
  42                .daddr = iph->saddr,
  43        };
  44        int lookup_flags;
  45
  46        if (rpfilter_addr_unicast(&iph->daddr)) {
  47                memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
  48                lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
  49        } else {
  50                lookup_flags = 0;
  51        }
  52
  53        fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
  54
  55        if (rpfilter_addr_linklocal(&iph->saddr)) {
  56                lookup_flags |= RT6_LOOKUP_F_IFACE;
  57                fl6.flowi6_oif = dev->ifindex;
  58        /* Set flowi6_oif for vrf devices to lookup route in l3mdev domain. */
  59        } else if (netif_is_l3_master(dev) || netif_is_l3_slave(dev) ||
  60                  (flags & XT_RPFILTER_LOOSE) == 0)
  61                fl6.flowi6_oif = dev->ifindex;
  62
  63        rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags);
  64        if (rt->dst.error)
  65                goto out;
  66
  67        if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
  68                goto out;
  69
  70        if (rt->rt6i_flags & RTF_LOCAL) {
  71                ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
  72                goto out;
  73        }
  74
  75        if (rt->rt6i_idev->dev == dev ||
  76            l3mdev_master_ifindex_rcu(rt->rt6i_idev->dev) == dev->ifindex ||
  77            (flags & XT_RPFILTER_LOOSE))
  78                ret = true;
  79 out:
  80        ip6_rt_put(rt);
  81        return ret;
  82}
  83
  84static bool
  85rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
  86{
  87        return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
  88}
  89
  90static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
  91{
  92        const struct xt_rpfilter_info *info = par->matchinfo;
  93        int saddrtype;
  94        struct ipv6hdr *iph;
  95        bool invert = info->flags & XT_RPFILTER_INVERT;
  96
  97        if (rpfilter_is_loopback(skb, xt_in(par)))
  98                return true ^ invert;
  99
 100        iph = ipv6_hdr(skb);
 101        saddrtype = ipv6_addr_type(&iph->saddr);
 102        if (unlikely(saddrtype == IPV6_ADDR_ANY))
 103                return true ^ invert; /* not routable: forward path will drop it */
 104
 105        return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par),
 106                                        info->flags) ^ invert;
 107}
 108
 109static int rpfilter_check(const struct xt_mtchk_param *par)
 110{
 111        const struct xt_rpfilter_info *info = par->matchinfo;
 112        unsigned int options = ~XT_RPFILTER_OPTION_MASK;
 113
 114        if (info->flags & options) {
 115                pr_info_ratelimited("unknown options\n");
 116                return -EINVAL;
 117        }
 118
 119        if (strcmp(par->table, "mangle") != 0 &&
 120            strcmp(par->table, "raw") != 0) {
 121                pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n",
 122                                    par->table);
 123                return -EINVAL;
 124        }
 125
 126        return 0;
 127}
 128
 129static struct xt_match rpfilter_mt_reg __read_mostly = {
 130        .name           = "rpfilter",
 131        .family         = NFPROTO_IPV6,
 132        .checkentry     = rpfilter_check,
 133        .match          = rpfilter_mt,
 134        .matchsize      = sizeof(struct xt_rpfilter_info),
 135        .hooks          = (1 << NF_INET_PRE_ROUTING),
 136        .me             = THIS_MODULE
 137};
 138
 139static int __init rpfilter_mt_init(void)
 140{
 141        return xt_register_match(&rpfilter_mt_reg);
 142}
 143
 144static void __exit rpfilter_mt_exit(void)
 145{
 146        xt_unregister_match(&rpfilter_mt_reg);
 147}
 148
 149module_init(rpfilter_mt_init);
 150module_exit(rpfilter_mt_exit);
 151