[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>
diff --git a/net/netfilter/xt_length.c b/net/netfilter/xt_length.c
new file mode 100644
index 0000000..ab6c710
--- /dev/null
+++ b/net/netfilter/xt_length.c
@@ -0,0 +1,98 @@
+/* Kernel module to match packet length. */
+/* (C) 1999-2001 James Morris <jmorros@intercode.com.au>
+ *
+ * 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 <net/ip.h>
+
+#include <linux/netfilter/xt_length.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
+MODULE_DESCRIPTION("IP tables packet length matching module");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_length");
+MODULE_ALIAS("ip6t_length");
+
+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_length_info *info = matchinfo;
+ u_int16_t pktlen = ntohs(skb->nh.iph->tot_len);
+
+ return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
+}
+
+static int
+match6(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_length_info *info = matchinfo;
+ u_int16_t pktlen = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr);
+
+ return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
+}
+
+static int
+checkentry(const char *tablename,
+ const void *ip,
+ void *matchinfo,
+ unsigned int matchsize,
+ unsigned int hook_mask)
+{
+ if (matchsize != XT_ALIGN(sizeof(struct xt_length_info)))
+ return 0;
+
+ return 1;
+}
+
+static struct xt_match length_match = {
+ .name = "length",
+ .match = &match,
+ .checkentry = &checkentry,
+ .me = THIS_MODULE,
+};
+static struct xt_match length6_match = {
+ .name = "length",
+ .match = &match6,
+ .checkentry = &checkentry,
+ .me = THIS_MODULE,
+};
+
+static int __init init(void)
+{
+ int ret;
+ ret = xt_register_match(AF_INET, &length_match);
+ if (ret)
+ return ret;
+ ret = xt_register_match(AF_INET6, &length6_match);
+ if (ret)
+ xt_unregister_match(AF_INET, &length_match);
+
+ return ret;
+}
+
+static void __exit fini(void)
+{
+ xt_unregister_match(AF_INET, &length_match);
+ xt_unregister_match(AF_INET6, &length6_match);
+}
+
+module_init(init);
+module_exit(fini);