[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, 79 insertions, 0 deletions

diff --git a/net/netfilter/xt_realm.c b/net/netfilter/xt_realm.c
new file mode 100644
index 000000000000..2b7e1781d34d
--- /dev/null
+++ b/net/netfilter/xt_realm.c
@@ -0,0 +1,79 @@
+/* IP tables module for matching the routing realm
+ *
+ * $Id: ipt_realm.c,v 1.3 2004/03/05 13:25:40 laforge Exp $
+ *
+ * (C) 2003 by Sampsa Ranta <sampsa@netsonic.fi>
+ *
+ * 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/skbuff.h>
+#include <linux/netdevice.h>
+#include <net/route.h>
+
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter/xt_realm.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_AUTHOR("Sampsa Ranta <sampsa@netsonic.fi>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("X_tables realm match");
+MODULE_ALIAS("ipt_realm");
+
+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_realm_info *info = matchinfo;
+	struct dst_entry *dst = skb->dst;
+    
+	return (info->id == (dst->tclassid & info->mask)) ^ info->invert;
+}
+
+static int check(const char *tablename,
+                 const void *ip,
+                 void *matchinfo,
+                 unsigned int matchsize,
+                 unsigned int hook_mask)
+{
+	if (hook_mask
+	    & ~((1 << NF_IP_POST_ROUTING) | (1 << NF_IP_FORWARD) |
+	        (1 << NF_IP_LOCAL_OUT) | (1 << NF_IP_LOCAL_IN))) {
+		printk("xt_realm: only valid for POST_ROUTING, LOCAL_OUT, "
+		       "LOCAL_IN or FORWARD.\n");
+		return 0;
+	}
+	if (matchsize != XT_ALIGN(sizeof(struct xt_realm_info))) {
+		printk("xt_realm: invalid matchsize.\n");
+		return 0;
+	}
+	return 1;
+}
+
+static struct xt_match realm_match = {
+	.name		= "realm",
+	.match		= match, 
+	.checkentry	= check,
+	.me		= THIS_MODULE
+};
+
+static int __init init(void)
+{
+	return xt_register_match(AF_INET, &realm_match);
+}
+
+static void __exit fini(void)
+{
+	xt_unregister_match(AF_INET, &realm_match);
+}
+
+module_init(init);
+module_exit(fini);