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Subject[PATCH] RFC3514 packet filtering
   This patch provides an RFC3514 filter for iptables. This is the
kernel half of the patch, against 2.6.5-rc3.

Please cc: replies to me -- I'm having some trouble subscribing to
linux-kernel at the moment.

Hugo.

diff -uNr linux-2.6/include/linux/netfilter_ipv4/ipt_evil.h linux-2.6-ipt-evil/include/linux/netfilter_ipv4/ipt_evil.h
--- linux-2.6/include/linux/netfilter_ipv4/ipt_evil.h 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-ipt-evil/include/linux/netfilter_ipv4/ipt_evil.h 2004-03-15 22:05:34.268945232 +0000
@@ -0,0 +1,7 @@
+#ifndef _IPT_EVIL_H
+#define _IPT_EVIL_H
+
+struct ipt_evil_info {
+ int invert;
+};
+#endif /*_IPT_EVIL_H*/
diff -uNr linux-2.6/include/net/ip.h linux-2.6-ipt-evil/include/net/ip.h
--- linux-2.6/include/net/ip.h 2003-09-08 19:50:16.000000000 +0000
+++ linux-2.6-ipt-evil/include/net/ip.h 2004-03-15 20:43:33.349763049 +0000
@@ -71,6 +71,7 @@

/* IP flags. */
#define IP_CE 0x8000 /* Flag: "Congestion" */
+#define IP_EVIL 0x8000 /* Flag: "Evil" (RFC 3514) */
#define IP_DF 0x4000 /* Flag: "Don't Fragment" */
#define IP_MF 0x2000 /* Flag: "More Fragments" */
#define IP_OFFSET 0x1FFF /* "Fragment Offset" part */
diff -uNr linux-2.6/net/ipv4/netfilter/Kconfig linux-2.6-ipt-evil/net/ipv4/netfilter/Kconfig
--- linux-2.6/net/ipv4/netfilter/Kconfig 2004-03-15 21:47:01.353917514 +0000
+++ linux-2.6-ipt-evil/net/ipv4/netfilter/Kconfig 2004-03-15 20:56:08.577655525 +0000
@@ -274,6 +274,15 @@

To compile it as a module, choose M here. If unsure, say N.

+config IP_NF_MATCH_EVIL
+ tristate "Evil bit match support"
+ depends on IP_NF_IPTABLES
+ help
+ Matches the "Evil" bit in the IP header. See RFC 3514 for
+ details.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
# The targets
config IP_NF_FILTER
tristate "Packet filtering"
diff -uNr linux-2.6/net/ipv4/netfilter/Makefile linux-2.6-ipt-evil/net/ipv4/netfilter/Makefile
--- linux-2.6/net/ipv4/netfilter/Makefile 2003-09-08 19:49:57.000000000 +0000
+++ linux-2.6-ipt-evil/net/ipv4/netfilter/Makefile 2004-03-15 20:59:18.934937734 +0000
@@ -66,6 +66,8 @@

obj-$(CONFIG_IP_NF_MATCH_PHYSDEV) += ipt_physdev.o

+obj-$(CONFIG_IP_NF_MATCH_EVIL) += ipt_evil.o
+
# targets
obj-$(CONFIG_IP_NF_TARGET_REJECT) += ipt_REJECT.o
obj-$(CONFIG_IP_NF_TARGET_TOS) += ipt_TOS.o
diff -uNr linux-2.6/net/ipv4/netfilter/ipt_evil.c linux-2.6-ipt-evil/net/ipv4/netfilter/ipt_evil.c
--- linux-2.6/net/ipv4/netfilter/ipt_evil.c 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-ipt-evil/net/ipv4/netfilter/ipt_evil.c 2004-03-15 21:16:21.991019291 +0000
@@ -0,0 +1,67 @@
+/* (C) 2004 Hugo Mills <hugo@carfax.org.uk>
+ * Structure copied/stolen from ipt_pkttype.c
+ *
+ * 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/if_ether.h>
+#include <linux/if_packet.h>
+#include <net/ip.h>
+
+#include <linux/netfilter_ipv4/ipt_evil.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Hugo Mills <hugo@carfax.org.uk>");
+MODULE_DESCRIPTION("IP tables match to match on evil bit (RFC 3514)");
+
+static int match(const struct sk_buff *skb,
+ const struct net_device *in,
+ const struct net_device *out,
+ const void *matchinfo,
+ int offset,
+ int *hotdrop)
+{
+ const struct ipt_evil_info *info = matchinfo;
+
+ if(skb->nh.iph->frag_off & __constant_htons(IP_EVIL))
+ return !info->invert;
+
+ return info->invert;
+}
+
+static int checkentry(const char *tablename,
+ const struct ipt_ip *ip,
+ void *matchinfo,
+ unsigned int matchsize,
+ unsigned int hook_mask)
+{
+ if (matchsize != IPT_ALIGN(sizeof(struct ipt_evil_info)))
+ return 0;
+
+ return 1;
+}
+
+static struct ipt_match evil_match = {
+ .name = "evil",
+ .match = &match,
+ .checkentry = &checkentry,
+ .me = THIS_MODULE,
+};
+
+static int __init init(void)
+{
+ return ipt_register_match(&evil_match);
+}
+
+static void __exit fini(void)
+{
+ ipt_unregister_match(&evil_match);
+}
+
+module_init(init);
+module_exit(fini);

--
--- Hugo Mills - <hugo@soton.ac.uk> - ECS at Southampton University ---
--- Comb-e-chem project: http://www.combechem.org/ ---
Quantum Mechanics: The dreams stuff is made of
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