diff options
Diffstat (limited to 'net/ipv4/netfilter/ipt_rpfilter.c')
| -rw-r--r-- | net/ipv4/netfilter/ipt_rpfilter.c | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c new file mode 100644 index 000000000..ded5bef02 --- /dev/null +++ b/net/ipv4/netfilter/ipt_rpfilter.c @@ -0,0 +1,126 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (c) 2011 Florian Westphal <fw@strlen.de> + * + * based on fib_frontend.c; Author: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru> + */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/netdevice.h> +#include <linux/ip.h> +#include <net/ip.h> +#include <net/ip_fib.h> +#include <net/route.h> + +#include <linux/netfilter/xt_rpfilter.h> +#include <linux/netfilter/x_tables.h> + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Florian Westphal <fw@strlen.de>"); +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; + + 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; + } + return fib_info_nh_uses_dev(res.fi, dev) || 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 = iph->tos & IPTOS_RT_MASK; + flow.flowi4_scope = RT_SCOPE_UNIVERSE; + flow.flowi4_l3mdev = l3mdev_master_ifindex_rcu(xt_in(par)); + flow.flowi4_uid = sock_net_uid(xt_net(par), NULL); + + 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); |