[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, 111 insertions, 0 deletions

diff --git a/net/netfilter/xt_string.c b/net/netfilter/xt_string.c
new file mode 100644
index 000000000000..7c7d5c8807d6
--- /dev/null
+++ b/net/netfilter/xt_string.c
@@ -0,0 +1,111 @@
+/* String matching match for iptables
+ * 
+ * (C) 2005 Pablo Neira Ayuso <pablo@eurodev.net>
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_string.h>
+#include <linux/textsearch.h>
+
+MODULE_AUTHOR("Pablo Neira Ayuso <pablo@eurodev.net>");
+MODULE_DESCRIPTION("IP tables string match module");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_string");
+MODULE_ALIAS("ip6t_string");
+
+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)
+{
+	struct ts_state state;
+	struct xt_string_info *conf = (struct xt_string_info *) matchinfo;
+
+	memset(&state, 0, sizeof(struct ts_state));
+
+	return (skb_find_text((struct sk_buff *)skb, conf->from_offset, 
+			     conf->to_offset, conf->config, &state) 
+			     != UINT_MAX) && !conf->invert;
+}
+
+#define STRING_TEXT_PRIV(m) ((struct xt_string_info *) m)
+
+static int checkentry(const char *tablename,
+		      const void *ip,
+		      void *matchinfo,
+		      unsigned int matchsize,
+		      unsigned int hook_mask)
+{
+	struct xt_string_info *conf = matchinfo;
+	struct ts_config *ts_conf;
+
+	if (matchsize != XT_ALIGN(sizeof(struct xt_string_info)))
+		return 0;
+
+	/* Damn, can't handle this case properly with iptables... */
+	if (conf->from_offset > conf->to_offset)
+		return 0;
+
+	ts_conf = textsearch_prepare(conf->algo, conf->pattern, conf->patlen,
+				     GFP_KERNEL, TS_AUTOLOAD);
+	if (IS_ERR(ts_conf))
+		return 0;
+
+	conf->config = ts_conf;
+
+	return 1;
+}
+
+static void destroy(void *matchinfo, unsigned int matchsize)
+{
+	textsearch_destroy(STRING_TEXT_PRIV(matchinfo)->config);
+}
+
+static struct xt_match string_match = {
+	.name 		= "string",
+	.match 		= match,
+	.checkentry	= checkentry,
+	.destroy 	= destroy,
+	.me 		= THIS_MODULE
+};
+static struct xt_match string6_match = {
+	.name 		= "string",
+	.match 		= match,
+	.checkentry	= checkentry,
+	.destroy 	= destroy,
+	.me 		= THIS_MODULE
+};
+
+static int __init init(void)
+{
+	int ret;
+
+	ret = xt_register_match(AF_INET, &string_match);
+	if (ret)
+		return ret;
+	ret = xt_register_match(AF_INET6, &string6_match);
+	if (ret)
+		xt_unregister_match(AF_INET, &string_match);
+
+	return ret;
+}
+
+static void __exit fini(void)
+{
+	xt_unregister_match(AF_INET, &string_match);
+	xt_unregister_match(AF_INET6, &string6_match);
+}
+
+module_init(init);
+module_exit(fini);