// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2011 Florian Westphal <fw@strlen.de>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/netdevice.h>
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#include <linux/route.h>
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#include <net/ip6_fib.h>
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#include <net/ip6_route.h>
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#include <linux/netfilter/xt_rpfilter.h>
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#include <linux/netfilter/x_tables.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
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MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");
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static bool rpfilter_addr_unicast(const struct in6_addr *addr)
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{
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int addr_type = ipv6_addr_type(addr);
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return addr_type & IPV6_ADDR_UNICAST;
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}
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static bool rpfilter_addr_linklocal(const struct in6_addr *addr)
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{
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int addr_type = ipv6_addr_type(addr);
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return addr_type & IPV6_ADDR_LINKLOCAL;
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}
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static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
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const struct net_device *dev, u8 flags)
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{
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struct rt6_info *rt;
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struct ipv6hdr *iph = ipv6_hdr(skb);
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bool ret = false;
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struct flowi6 fl6 = {
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.flowi6_iif = LOOPBACK_IFINDEX,
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.flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
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.flowi6_proto = iph->nexthdr,
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.daddr = iph->saddr,
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};
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int lookup_flags;
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if (rpfilter_addr_unicast(&iph->daddr)) {
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memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
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lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
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} else {
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lookup_flags = 0;
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}
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fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
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if (rpfilter_addr_linklocal(&iph->saddr)) {
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lookup_flags |= RT6_LOOKUP_F_IFACE;
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fl6.flowi6_oif = dev->ifindex;
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/* Set flowi6_oif for vrf devices to lookup route in l3mdev domain. */
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} else if (netif_is_l3_master(dev) || netif_is_l3_slave(dev) ||
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(flags & XT_RPFILTER_LOOSE) == 0)
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fl6.flowi6_oif = dev->ifindex;
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rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags);
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if (rt->dst.error)
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goto out;
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if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
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goto out;
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if (rt->rt6i_flags & RTF_LOCAL) {
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ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
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goto out;
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}
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if (rt->rt6i_idev->dev == dev ||
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l3mdev_master_ifindex_rcu(rt->rt6i_idev->dev) == dev->ifindex ||
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(flags & XT_RPFILTER_LOOSE))
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ret = true;
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out:
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ip6_rt_put(rt);
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return ret;
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}
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static bool
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rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
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{
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return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
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}
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static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_rpfilter_info *info = par->matchinfo;
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int saddrtype;
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struct ipv6hdr *iph;
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bool invert = info->flags & XT_RPFILTER_INVERT;
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if (rpfilter_is_loopback(skb, xt_in(par)))
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return true ^ invert;
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iph = ipv6_hdr(skb);
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saddrtype = ipv6_addr_type(&iph->saddr);
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if (unlikely(saddrtype == IPV6_ADDR_ANY))
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return true ^ invert; /* not routable: forward path will drop it */
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return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par),
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info->flags) ^ invert;
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}
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static int rpfilter_check(const struct xt_mtchk_param *par)
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{
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const struct xt_rpfilter_info *info = par->matchinfo;
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unsigned int options = ~XT_RPFILTER_OPTION_MASK;
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if (info->flags & options) {
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pr_info_ratelimited("unknown options\n");
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return -EINVAL;
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}
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if (strcmp(par->table, "mangle") != 0 &&
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strcmp(par->table, "raw") != 0) {
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pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n",
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par->table);
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return -EINVAL;
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}
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return 0;
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}
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static struct xt_match rpfilter_mt_reg __read_mostly = {
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.name = "rpfilter",
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.family = NFPROTO_IPV6,
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.checkentry = rpfilter_check,
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.match = rpfilter_mt,
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.matchsize = sizeof(struct xt_rpfilter_info),
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.hooks = (1 << NF_INET_PRE_ROUTING),
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.me = THIS_MODULE
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};
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static int __init rpfilter_mt_init(void)
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{
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return xt_register_match(&rpfilter_mt_reg);
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}
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static void __exit rpfilter_mt_exit(void)
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{
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xt_unregister_match(&rpfilter_mt_reg);
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}
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module_init(rpfilter_mt_init);
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module_exit(rpfilter_mt_exit);
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