/* * Copyright (c) 2011 Florian Westphal * * 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. * * based on fib_frontend.c; Author: Alexey Kuznetsov, */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include MODULE_LICENSE("GPL"); MODULE_AUTHOR("Florian Westphal "); MODULE_DESCRIPTION("iptables: ipv4 reverse path filter match"); /* don't try to find route from mcast/bcast/zeronet */ static __be32 rpfilter_get_saddr(__be32 addr) { if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr) || ipv4_is_zeronet(addr)) return 0; return addr; } static bool rpfilter_lookup_reverse(struct net *net, struct flowi4 *fl4, const struct net_device *dev, u8 flags) { struct fib_result res; bool dev_match; int ret __maybe_unused; if (fib_lookup(net, fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE)) return false; if (res.type != RTN_UNICAST) { if (res.type != RTN_LOCAL || !(flags & XT_RPFILTER_ACCEPT_LOCAL)) return false; } dev_match = false; #ifdef CONFIG_IP_ROUTE_MULTIPATH for (ret = 0; ret < res.fi->fib_nhs; ret++) { struct fib_nh *nh = &res.fi->fib_nh[ret]; if (nh->nh_dev == dev) { dev_match = true; break; } } #else if (FIB_RES_DEV(res) == dev) dev_match = true; #endif return dev_match || flags & XT_RPFILTER_LOOSE; } static bool rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in) { return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK; } static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) { const struct xt_rpfilter_info *info; const struct iphdr *iph; struct flowi4 flow; bool invert; info = par->matchinfo; invert = info->flags & XT_RPFILTER_INVERT; if (rpfilter_is_loopback(skb, xt_in(par))) return true ^ invert; iph = ip_hdr(skb); if (ipv4_is_zeronet(iph->saddr)) { if (ipv4_is_lbcast(iph->daddr) || ipv4_is_local_multicast(iph->daddr)) return true ^ invert; } memset(&flow, 0, sizeof(flow)); flow.flowi4_iif = LOOPBACK_IFINDEX; flow.daddr = iph->saddr; flow.saddr = rpfilter_get_saddr(iph->daddr); flow.flowi4_mark = info->flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0; flow.flowi4_tos = RT_TOS(iph->tos); flow.flowi4_scope = RT_SCOPE_UNIVERSE; flow.flowi4_oif = l3mdev_master_ifindex_rcu(xt_in(par)); return rpfilter_lookup_reverse(xt_net(par), &flow, xt_in(par), 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_ratelimited("unknown options\n"); return -EINVAL; } if (strcmp(par->table, "mangle") != 0 && strcmp(par->table, "raw") != 0) { pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n", par->table); return -EINVAL; } return 0; } static struct xt_match rpfilter_mt_reg __read_mostly = { .name = "rpfilter", .family = NFPROTO_IPV4, .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);