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Linux/net/ipv6/netfilter/ip6t_rpfilter.c

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

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