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 16 MODULE_LICENSE("GPL"); 17 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>"); 18 MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match"); 19 20 static 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 26 static 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 32 static 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 .flowi6_l3mdev = l3mdev_master_ifindex_rcu(dev), 41 .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK, 42 .flowi6_proto = iph->nexthdr, 43 .flowi6_uid = sock_net_uid(net, NULL), 44 .daddr = iph->saddr, 45 }; 46 int lookup_flags; 47 48 if (rpfilter_addr_unicast(&iph->daddr)) { 49 memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr)); 50 lookup_flags = RT6_LOOKUP_F_HAS_SADDR; 51 } else { 52 lookup_flags = 0; 53 } 54 55 fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; 56 57 if (rpfilter_addr_linklocal(&iph->saddr)) { 58 lookup_flags |= RT6_LOOKUP_F_IFACE; 59 fl6.flowi6_oif = dev->ifindex; 60 } else if ((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 || (flags & XT_RPFILTER_LOOSE)) 76 ret = true; 77 out: 78 ip6_rt_put(rt); 79 return ret; 80 } 81 82 static bool 83 rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in) 84 { 85 return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK; 86 } 87 88 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) 89 { 90 const struct xt_rpfilter_info *info = par->matchinfo; 91 int saddrtype; 92 struct ipv6hdr *iph; 93 bool invert = info->flags & XT_RPFILTER_INVERT; 94 95 if (rpfilter_is_loopback(skb, xt_in(par))) 96 return true ^ invert; 97 98 iph = ipv6_hdr(skb); 99 saddrtype = ipv6_addr_type(&iph->saddr); 100 if (unlikely(saddrtype == IPV6_ADDR_ANY)) 101 return true ^ invert; /* not routable: forward path will drop it */ 102 103 return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par), 104 info->flags) ^ invert; 105 } 106 107 static int rpfilter_check(const struct xt_mtchk_param *par) 108 { 109 const struct xt_rpfilter_info *info = par->matchinfo; 110 unsigned int options = ~XT_RPFILTER_OPTION_MASK; 111 112 if (info->flags & options) { 113 pr_info_ratelimited("unknown options\n"); 114 return -EINVAL; 115 } 116 117 if (strcmp(par->table, "mangle") != 0 && 118 strcmp(par->table, "raw") != 0) { 119 pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n", 120 par->table); 121 return -EINVAL; 122 } 123 124 return 0; 125 } 126 127 static struct xt_match rpfilter_mt_reg __read_mostly = { 128 .name = "rpfilter", 129 .family = NFPROTO_IPV6, 130 .checkentry = rpfilter_check, 131 .match = rpfilter_mt, 132 .matchsize = sizeof(struct xt_rpfilter_info), 133 .hooks = (1 << NF_INET_PRE_ROUTING), 134 .me = THIS_MODULE 135 }; 136 137 static int __init rpfilter_mt_init(void) 138 { 139 return xt_register_match(&rpfilter_mt_reg); 140 } 141 142 static void __exit rpfilter_mt_exit(void) 143 { 144 xt_unregister_match(&rpfilter_mt_reg); 145 } 146 147 module_init(rpfilter_mt_init); 148 module_exit(rpfilter_mt_exit); 149