![Florian Westphal](/assets/img/avatar_default.png)
The netfilter NAT core cannot deal with more than one NAT hook per hook location (prerouting, input ...), because the NAT hooks install a NAT null binding in case the iptables nat table (iptable_nat hooks) or the corresponding nftables chain (nft nat hooks) doesn't specify a nat transformation. Null bindings are needed to detect port collsisions between NAT-ed and non-NAT-ed connections. This causes nftables NAT rules to not work when iptable_nat module is loaded, and vice versa because nat binding has already been attached when the second nat hook is consulted. The netfilter core is not really the correct location to handle this (hooks are just hooks, the core has no notion of what kinds of side effects a hook implements), but its the only place where we can check for conflicts between both iptables hooks and nftables hooks without adding dependencies. So add nat annotation to hook_ops to describe those hooks that will add NAT bindings and then make core reject if such a hook already exists. The annotation fills a padding hole, in case further restrictions appar we might change this to a 'u8 type' instead of bool. iptables error if nft nat hook active: iptables -t nat -A POSTROUTING -j MASQUERADE iptables v1.4.21: can't initialize iptables table `nat': File exists Perhaps iptables or your kernel needs to be upgraded. nftables error if iptables nat table present: nft -f /etc/nftables/ipv4-nat /usr/etc/nftables/ipv4-nat:3:1-2: Error: Could not process rule: File exists table nat { ^^ Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
158 lines
3.9 KiB
C
158 lines
3.9 KiB
C
/*
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* Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Based on Rusty Russell's IPv4 NAT code. Development of IPv6 NAT
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* funded by Astaro.
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*/
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#include <linux/module.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter_ipv6.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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#include <linux/ipv6.h>
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#include <net/ipv6.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_core.h>
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#include <net/netfilter/nf_nat_l3proto.h>
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static int __net_init ip6table_nat_table_init(struct net *net);
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static const struct xt_table nf_nat_ipv6_table = {
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.name = "nat",
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.valid_hooks = (1 << NF_INET_PRE_ROUTING) |
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(1 << NF_INET_POST_ROUTING) |
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(1 << NF_INET_LOCAL_OUT) |
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(1 << NF_INET_LOCAL_IN),
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.me = THIS_MODULE,
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.af = NFPROTO_IPV6,
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.table_init = ip6table_nat_table_init,
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};
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static unsigned int ip6table_nat_do_chain(void *priv,
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struct sk_buff *skb,
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const struct nf_hook_state *state,
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struct nf_conn *ct)
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{
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return ip6t_do_table(skb, state, state->net->ipv6.ip6table_nat);
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}
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static unsigned int ip6table_nat_fn(void *priv,
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struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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return nf_nat_ipv6_fn(priv, skb, state, ip6table_nat_do_chain);
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}
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static unsigned int ip6table_nat_in(void *priv,
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struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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return nf_nat_ipv6_in(priv, skb, state, ip6table_nat_do_chain);
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}
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static unsigned int ip6table_nat_out(void *priv,
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struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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return nf_nat_ipv6_out(priv, skb, state, ip6table_nat_do_chain);
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}
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static unsigned int ip6table_nat_local_fn(void *priv,
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struct sk_buff *skb,
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const struct nf_hook_state *state)
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{
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return nf_nat_ipv6_local_fn(priv, skb, state, ip6table_nat_do_chain);
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}
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static const struct nf_hook_ops nf_nat_ipv6_ops[] = {
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/* Before packet filtering, change destination */
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{
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.hook = ip6table_nat_in,
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.pf = NFPROTO_IPV6,
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.nat_hook = true,
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.hooknum = NF_INET_PRE_ROUTING,
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.priority = NF_IP6_PRI_NAT_DST,
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},
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/* After packet filtering, change source */
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{
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.hook = ip6table_nat_out,
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.pf = NFPROTO_IPV6,
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.nat_hook = true,
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.hooknum = NF_INET_POST_ROUTING,
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.priority = NF_IP6_PRI_NAT_SRC,
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},
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/* Before packet filtering, change destination */
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{
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.hook = ip6table_nat_local_fn,
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.pf = NFPROTO_IPV6,
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.nat_hook = true,
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.hooknum = NF_INET_LOCAL_OUT,
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.priority = NF_IP6_PRI_NAT_DST,
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},
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/* After packet filtering, change source */
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{
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.hook = ip6table_nat_fn,
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.nat_hook = true,
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.pf = NFPROTO_IPV6,
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.hooknum = NF_INET_LOCAL_IN,
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.priority = NF_IP6_PRI_NAT_SRC,
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},
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};
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static int __net_init ip6table_nat_table_init(struct net *net)
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{
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struct ip6t_replace *repl;
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int ret;
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if (net->ipv6.ip6table_nat)
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return 0;
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repl = ip6t_alloc_initial_table(&nf_nat_ipv6_table);
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if (repl == NULL)
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return -ENOMEM;
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ret = ip6t_register_table(net, &nf_nat_ipv6_table, repl,
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nf_nat_ipv6_ops, &net->ipv6.ip6table_nat);
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kfree(repl);
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return ret;
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}
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static void __net_exit ip6table_nat_net_exit(struct net *net)
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{
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if (!net->ipv6.ip6table_nat)
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return;
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ip6t_unregister_table(net, net->ipv6.ip6table_nat, nf_nat_ipv6_ops);
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net->ipv6.ip6table_nat = NULL;
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}
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static struct pernet_operations ip6table_nat_net_ops = {
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.exit = ip6table_nat_net_exit,
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};
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static int __init ip6table_nat_init(void)
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{
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int ret = register_pernet_subsys(&ip6table_nat_net_ops);
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if (ret)
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return ret;
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ret = ip6table_nat_table_init(&init_net);
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if (ret)
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unregister_pernet_subsys(&ip6table_nat_net_ops);
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return ret;
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}
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static void __exit ip6table_nat_exit(void)
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{
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unregister_pernet_subsys(&ip6table_nat_net_ops);
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}
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module_init(ip6table_nat_init);
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module_exit(ip6table_nat_exit);
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MODULE_LICENSE("GPL");
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