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 .daddr = iph->saddr, 44 }; 45 int lookup_flags; 46 47 if (rpfilter_addr_unicast(&iph->daddr)) { 48 memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr)); 49 lookup_flags = RT6_LOOKUP_F_HAS_SADDR; 50 } else { 51 lookup_flags = 0; 52 } 53 54 fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; 55 56 if (rpfilter_addr_linklocal(&iph->saddr)) { 57 lookup_flags |= RT6_LOOKUP_F_IFACE; 58 fl6.flowi6_oif = dev->ifindex; 59 } else if ((flags & XT_RPFILTER_LOOSE) == 0) 60 fl6.flowi6_oif = dev->ifindex; 61 62 rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags); 63 if (rt->dst.error) 64 goto out; 65 66 if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST)) 67 goto out; 68 69 if (rt->rt6i_flags & RTF_LOCAL) { 70 ret = flags & XT_RPFILTER_ACCEPT_LOCAL; 71 goto out; 72 } 73 74 if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE)) 75 ret = true; 76 out: 77 ip6_rt_put(rt); 78 return ret; 79 } 80 81 static bool 82 rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in) 83 { 84 return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK; 85 } 86 87 static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) 88 { 89 const struct xt_rpfilter_info *info = par->matchinfo; 90 int saddrtype; 91 struct ipv6hdr *iph; 92 bool invert = info->flags & XT_RPFILTER_INVERT; 93 94 if (rpfilter_is_loopback(skb, xt_in(par))) 95 return true ^ invert; 96 97 iph = ipv6_hdr(skb); 98 saddrtype = ipv6_addr_type(&iph->saddr); 99 if (unlikely(saddrtype == IPV6_ADDR_ANY)) 100 return true ^ invert; /* not routable: forward path will drop it */ 101 102 return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par), 103 info->flags) ^ invert; 104 } 105 106 static int rpfilter_check(const struct xt_mtchk_param *par) 107 { 108 const struct xt_rpfilter_info *info = par->matchinfo; 109 unsigned int options = ~XT_RPFILTER_OPTION_MASK; 110 111 if (info->flags & options) { 112 pr_info_ratelimited("unknown options\n"); 113 return -EINVAL; 114 } 115 116 if (strcmp(par->table, "mangle") != 0 && 117 strcmp(par->table, "raw") != 0) { 118 pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n", 119 par->table); 120 return -EINVAL; 121 } 122 123 return 0; 124 } 125 126 static struct xt_match rpfilter_mt_reg __read_mostly = { 127 .name = "rpfilter", 128 .family = NFPROTO_IPV6, 129 .checkentry = rpfilter_check, 130 .match = rpfilter_mt, 131 .matchsize = sizeof(struct xt_rpfilter_info), 132 .hooks = (1 << NF_INET_PRE_ROUTING), 133 .me = THIS_MODULE 134 }; 135 136 static int __init rpfilter_mt_init(void) 137 { 138 return xt_register_match(&rpfilter_mt_reg); 139 } 140 141 static void __exit rpfilter_mt_exit(void) 142 { 143 xt_unregister_match(&rpfilter_mt_reg); 144 } 145 146 module_init(rpfilter_mt_init); 147 module_exit(rpfilter_mt_exit); 148