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 if ((flags & XT_RPFILTER_LOOSE) == 0) { 52 fl6.flowi6_oif = dev->ifindex; 53 lookup_flags |= RT6_LOOKUP_F_IFACE; 54 } 55 56 rt = (void *) ip6_route_lookup(net, &fl6, lookup_flags); 57 if (rt->dst.error) 58 goto out; 59 60 if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST)) 61 goto out; 62 63 if (rt->rt6i_flags & RTF_LOCAL) { 64 ret = flags & XT_RPFILTER_ACCEPT_LOCAL; 65 goto out; 66 } 67 68 if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE)) 69 ret = true; 70 out: 71 ip6_rt_put(rt); 72 return ret; 73 } 74 75 static bool 76 rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in) 77 { 78 return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK; 79 } 80 81 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) 82 { 83 const struct xt_rpfilter_info *info = par->matchinfo; 84 int saddrtype; 85 struct ipv6hdr *iph; 86 bool invert = info->flags & XT_RPFILTER_INVERT; 87 88 if (rpfilter_is_loopback(skb, xt_in(par))) 89 return true ^ invert; 90 91 iph = ipv6_hdr(skb); 92 saddrtype = ipv6_addr_type(&iph->saddr); 93 if (unlikely(saddrtype == IPV6_ADDR_ANY)) 94 return true ^ invert; /* not routable: forward path will drop it */ 95 96 return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par), 97 info->flags) ^ invert; 98 } 99 100 static int rpfilter_check(const struct xt_mtchk_param *par) 101 { 102 const struct xt_rpfilter_info *info = par->matchinfo; 103 unsigned int options = ~XT_RPFILTER_OPTION_MASK; 104 105 if (info->flags & options) { 106 pr_info("unknown options encountered"); 107 return -EINVAL; 108 } 109 110 if (strcmp(par->table, "mangle") != 0 && 111 strcmp(par->table, "raw") != 0) { 112 pr_info("match only valid in the \'raw\' " 113 "or \'mangle\' tables, not \'%s\'.\n", par->table); 114 return -EINVAL; 115 } 116 117 return 0; 118 } 119 120 static struct xt_match rpfilter_mt_reg __read_mostly = { 121 .name = "rpfilter", 122 .family = NFPROTO_IPV6, 123 .checkentry = rpfilter_check, 124 .match = rpfilter_mt, 125 .matchsize = sizeof(struct xt_rpfilter_info), 126 .hooks = (1 << NF_INET_PRE_ROUTING), 127 .me = THIS_MODULE 128 }; 129 130 static int __init rpfilter_mt_init(void) 131 { 132 return xt_register_match(&rpfilter_mt_reg); 133 } 134 135 static void __exit rpfilter_mt_exit(void) 136 { 137 xt_unregister_match(&rpfilter_mt_reg); 138 } 139 140 module_init(rpfilter_mt_init); 141 module_exit(rpfilter_mt_exit); 142