netfilter: nf_tables: convert built-in tables/chains to chain types

This patch converts built-in tables/chains to chain types that
allows you to deploy customized table and chain configurations from
userspace.

After this patch, you have to specify the chain type when
creating a new chain:

 add chain ip filter output { type filter hook input priority 0; }
                              ^^^^ ------

The existing chain types after this patch are: filter, route and
nat. Note that tables are just containers of chains with no specific
semantics, which is a significant change with regards to iptables.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 86 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/nft_chain_route_ipv4.c b/net/ipv4/netfilter/nft_chain_route_ipv4.c
new file mode 100644
index 000000000000..6b84e097b8fc
--- /dev/null
+++ b/net/ipv4/netfilter/nft_chain_route_ipv4.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
+ * Copyright (c) 2012 Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter/nfnetlink.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/route.h>
+#include <net/ip.h>
+
+static unsigned int nf_route_table_hook(const struct nf_hook_ops *ops,
+					struct sk_buff *skb,
+					const struct net_device *in,
+					const struct net_device *out,
+					int (*okfn)(struct sk_buff *))
+{
+	unsigned int ret;
+	u32 mark;
+	__be32 saddr, daddr;
+	u_int8_t tos;
+	const struct iphdr *iph;
+
+	/* root is playing with raw sockets. */
+	if (skb->len < sizeof(struct iphdr) ||
+	    ip_hdrlen(skb) < sizeof(struct iphdr))
+		return NF_ACCEPT;
+
+	mark = skb->mark;
+	iph = ip_hdr(skb);
+	saddr = iph->saddr;
+	daddr = iph->daddr;
+	tos = iph->tos;
+
+	ret = nft_do_chain(ops, skb, in, out, okfn);
+	if (ret != NF_DROP && ret != NF_QUEUE) {
+		iph = ip_hdr(skb);
+
+		if (iph->saddr != saddr ||
+		    iph->daddr != daddr ||
+		    skb->mark != mark ||
+		    iph->tos != tos)
+			if (ip_route_me_harder(skb, RTN_UNSPEC))
+				ret = NF_DROP;
+	}
+	return ret;
+}
+
+static struct nf_chain_type nft_chain_route_ipv4 = {
+	.family		= NFPROTO_IPV4,
+	.name		= "route",
+	.type		= NFT_CHAIN_T_ROUTE,
+	.hook_mask	= (1 << NF_INET_LOCAL_OUT),
+	.fn		= {
+		[NF_INET_LOCAL_OUT]	= nf_route_table_hook,
+	},
+	.me		= THIS_MODULE,
+};
+
+static int __init nft_chain_route_init(void)
+{
+	return nft_register_chain_type(&nft_chain_route_ipv4);
+}
+
+static void __exit nft_chain_route_exit(void)
+{
+	nft_unregister_chain_type(&nft_chain_route_ipv4);
+}
+
+module_init(nft_chain_route_init);
+module_exit(nft_chain_route_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
+MODULE_ALIAS_NFT_CHAIN(AF_INET, "route");