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- /*
- * 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.
- */
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/netdevice.h>
- #include <linux/route.h>
- #include <net/ip6_fib.h>
- #include <net/ip6_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("Xtables: IPv6 reverse path filter match");
- static bool rpfilter_addr_unicast(const struct in6_addr *addr)
- {
- int addr_type = ipv6_addr_type(addr);
- return addr_type & IPV6_ADDR_UNICAST;
- }
- static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
- const struct net_device *dev, u8 flags)
- {
- struct rt6_info *rt;
- struct ipv6hdr *iph = ipv6_hdr(skb);
- bool ret = false;
- struct flowi6 fl6 = {
- .flowi6_iif = LOOPBACK_IFINDEX,
- .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
- .flowi6_proto = iph->nexthdr,
- .daddr = iph->saddr,
- };
- int lookup_flags;
- if (rpfilter_addr_unicast(&iph->daddr)) {
- memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
- lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
- } else {
- lookup_flags = 0;
- }
- fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
- if ((flags & XT_RPFILTER_LOOSE) == 0) {
- fl6.flowi6_oif = dev->ifindex;
- lookup_flags |= RT6_LOOKUP_F_IFACE;
- }
- rt = (void *) ip6_route_lookup(net, &fl6, lookup_flags);
- if (rt->dst.error)
- goto out;
- if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
- goto out;
- if (rt->rt6i_flags & RTF_LOCAL) {
- ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
- goto out;
- }
- if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
- ret = true;
- out:
- ip6_rt_put(rt);
- return ret;
- }
- static bool rpfilter_is_local(const struct sk_buff *skb)
- {
- const struct rt6_info *rt = (const void *) skb_dst(skb);
- return rt && (rt->rt6i_flags & RTF_LOCAL);
- }
- static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
- {
- const struct xt_rpfilter_info *info = par->matchinfo;
- int saddrtype;
- struct ipv6hdr *iph;
- bool invert = info->flags & XT_RPFILTER_INVERT;
- if (rpfilter_is_local(skb))
- return true ^ invert;
- iph = ipv6_hdr(skb);
- saddrtype = ipv6_addr_type(&iph->saddr);
- if (unlikely(saddrtype == IPV6_ADDR_ANY))
- return true ^ invert; /* not routable: forward path will drop it */
- return rpfilter_lookup_reverse6(par->net, skb, 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_IPV6,
- .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);
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