[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables

This monster-patch tries to do the best job for unifying the data
structures and backend interfaces for the three evil clones ip_tables,
ip6_tables and arp_tables.  In an ideal world we would never have
allowed this kind of copy+paste programming... but well, our world
isn't (yet?) ideal.

o introduce a new x_tables module
o {ip,arp,ip6}_tables depend on this x_tables module
o registration functions for tables, matches and targets are only
  wrappers around x_tables provided functions
o all matches/targets that are used from ip_tables and ip6_tables
  are now implemented as xt_FOOBAR.c files and provide module aliases
  to ipt_FOOBAR and ip6t_FOOBAR
o header files for xt_matches are in include/linux/netfilter/,
  include/linux/netfilter_{ipv4,ipv6} contains compatibility wrappers
  around the xt_FOOBAR.h headers

Based on this patchset we're going to further unify the code,
gradually getting rid of all the layer 3 specific assumptions.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 188 insertions, 0 deletions

diff --git a/net/netfilter/xt_helper.c b/net/netfilter/xt_helper.c
new file mode 100644
index 00000000000..38b6715e1db
--- /dev/null
+++ b/net/netfilter/xt_helper.c
@@ -0,0 +1,188 @@
+/* iptables module to match on related connections */
+/*
+ * (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
+ *
+ * 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.
+ *
+ *   19 Mar 2002 Harald Welte <laforge@gnumonks.org>:
+ *   		 - Port to newnat infrastructure
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter.h>
+#if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
+#include <linux/netfilter_ipv4/ip_conntrack.h>
+#include <linux/netfilter_ipv4/ip_conntrack_core.h>
+#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
+#else
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_conntrack_helper.h>
+#endif
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_helper.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
+MODULE_DESCRIPTION("iptables helper match module");
+MODULE_ALIAS("ipt_helper");
+MODULE_ALIAS("ip6t_helper");
+
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(format, args...)
+#endif
+
+#if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
+static int
+match(const struct sk_buff *skb,
+      const struct net_device *in,
+      const struct net_device *out,
+      const void *matchinfo,
+      int offset,
+      unsigned int protoff,
+      int *hotdrop)
+{
+	const struct xt_helper_info *info = matchinfo;
+	struct ip_conntrack *ct;
+	enum ip_conntrack_info ctinfo;
+	int ret = info->invert;
+	
+	ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
+	if (!ct) {
+		DEBUGP("xt_helper: Eek! invalid conntrack?\n");
+		return ret;
+	}
+
+	if (!ct->master) {
+		DEBUGP("xt_helper: conntrack %p has no master\n", ct);
+		return ret;
+	}
+
+	read_lock_bh(&ip_conntrack_lock);
+	if (!ct->master->helper) {
+		DEBUGP("xt_helper: master ct %p has no helper\n", 
+			exp->expectant);
+		goto out_unlock;
+	}
+
+	DEBUGP("master's name = %s , info->name = %s\n", 
+		ct->master->helper->name, info->name);
+
+	if (info->name[0] == '\0')
+		ret ^= 1;
+	else
+		ret ^= !strncmp(ct->master->helper->name, info->name, 
+		                strlen(ct->master->helper->name));
+out_unlock:
+	read_unlock_bh(&ip_conntrack_lock);
+	return ret;
+}
+
+#else /* CONFIG_IP_NF_CONNTRACK */
+
+static int
+match(const struct sk_buff *skb,
+      const struct net_device *in,
+      const struct net_device *out,
+      const void *matchinfo,
+      int offset,
+      unsigned int protoff,
+      int *hotdrop)
+{
+	const struct xt_helper_info *info = matchinfo;
+	struct nf_conn *ct;
+	enum ip_conntrack_info ctinfo;
+	int ret = info->invert;
+	
+	ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
+	if (!ct) {
+		DEBUGP("xt_helper: Eek! invalid conntrack?\n");
+		return ret;
+	}
+
+	if (!ct->master) {
+		DEBUGP("xt_helper: conntrack %p has no master\n", ct);
+		return ret;
+	}
+
+	read_lock_bh(&nf_conntrack_lock);
+	if (!ct->master->helper) {
+		DEBUGP("xt_helper: master ct %p has no helper\n", 
+			exp->expectant);
+		goto out_unlock;
+	}
+
+	DEBUGP("master's name = %s , info->name = %s\n", 
+		ct->master->helper->name, info->name);
+
+	if (info->name[0] == '\0')
+		ret ^= 1;
+	else
+		ret ^= !strncmp(ct->master->helper->name, info->name, 
+		                strlen(ct->master->helper->name));
+out_unlock:
+	read_unlock_bh(&nf_conntrack_lock);
+	return ret;
+}
+#endif
+
+static int check(const char *tablename,
+		 const void *inf,
+		 void *matchinfo,
+		 unsigned int matchsize,
+		 unsigned int hook_mask)
+{
+	struct xt_helper_info *info = matchinfo;
+
+	info->name[29] = '\0';
+
+	/* verify size */
+	if (matchsize != XT_ALIGN(sizeof(struct xt_helper_info)))
+		return 0;
+
+	return 1;
+}
+
+static struct xt_match helper_match = {
+	.name		= "helper",
+	.match		= &match,
+	.checkentry	= &check,
+	.me		= THIS_MODULE,
+};
+static struct xt_match helper6_match = {
+	.name		= "helper",
+	.match		= &match,
+	.checkentry	= &check,
+	.me		= THIS_MODULE,
+};
+
+static int __init init(void)
+{
+	int ret;
+	need_conntrack();
+
+	ret = xt_register_match(AF_INET, &helper_match);
+	if (ret < 0)
+		return ret;
+
+	ret = xt_register_match(AF_INET6, &helper6_match);
+	if (ret < 0)
+		xt_unregister_match(AF_INET, &helper_match);
+
+	return ret;
+}
+
+static void __exit fini(void)
+{
+	xt_unregister_match(AF_INET, &helper_match);
+	xt_unregister_match(AF_INET6, &helper6_match);
+}
+
+module_init(init);
+module_exit(fini);
+