[PATCH 2/2] Interface group match

[Laszlo Attila Toth <panther@balabit.hu>]

Interface group values can be checked on both input and output interfaces.

Signed-off-by: Laszlo Attila Toth <panther@balabit.hu>
---
 include/linux/netfilter/xt_ifgroup.h |   18 ++++++
 net/netfilter/Kconfig                |   16 +++++
 net/netfilter/Makefile               |    1 +
 net/netfilter/xt_ifgroup.c           |  108 ++++++++++++++++++++++++++++++++++
 4 files changed, 143 insertions(+), 0 deletions(-)

diff --git a/include/linux/netfilter/xt_ifgroup.h b/include/linux/netfilter/xt_ifgroup.h
new file mode 100644
index 0000000..9ac75de
--- /dev/null
+++ b/include/linux/netfilter/xt_ifgroup.h
@@ -0,0 +1,18 @@
+#ifndef _XT_IFGROUP_H
+#define _XT_IFGROUP_H
+
+#define XT_IFGROUP_INVERT_IN	0x01
+#define XT_IFGROUP_INVERT_OUT	0x02
+#define XT_IFGROUP_MATCH_IN	0x04
+#define XT_IFGROUP_MATCH_OUT	0x08		
+
+struct xt_ifgroup_info {
+	u_int32_t in_group;
+	u_int32_t in_mask;
+	u_int32_t out_group;
+	u_int32_t out_mask;
+	u_int8_t flags;
+};
+
+#endif /*_XT_IFGROUP_H*/
+
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 3599770..0864e19 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -597,6 +597,22 @@ config NETFILTER_XT_MATCH_QUOTA
 	  If you want to compile it as a module, say M here and read
 	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
 
+config NETFILTER_XT_MATCH_IFGROUP
+	tristate '"ifgroup" interface group match support'
+	depends on NETFILTER_XTABLES
+	help
+	  Interface group matching allows you to match a packet by
+	  its incoming interface "group", settable using ip link set
+	  group
+
+	  Typical usage is to assign dynamic interfaces to a group
+	  when they come up using "ip link set group" and then match
+	  incoming packets with a rule like this:
+
+	    iptables -A INPUT -m ifgroup --if-group openvpn-rw1 -j LOG
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_MATCH_REALM
 	tristate  '"realm" match support'
 	depends on NETFILTER_XTABLES
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 0c054bf..da9ab07 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -77,3 +77,4 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_TCPMSS) += xt_tcpmss.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_PHYSDEV) += xt_physdev.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_U32) += xt_u32.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_HASHLIMIT) += xt_hashlimit.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_IFGROUP) += xt_ifgroup.o
diff --git a/net/netfilter/xt_ifgroup.c b/net/netfilter/xt_ifgroup.c
new file mode 100644
index 0000000..07c3acc
--- /dev/null
+++ b/net/netfilter/xt_ifgroup.c
@@ -0,0 +1,108 @@
+/*
+ * An x_tables match module to match interface groups
+ *
+ * (C) 2006,2007 Balazs Scheidler <bazsi@balabit.hu>,
+ *   Laszlo Attila Toth <panther@balabit.hu>
+ *
+ * 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 <linux/netfilter/xt_ifgroup.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Laszlo Attila Toth <panther@balabit.hu>");
+MODULE_DESCRIPTION("Xtables interface group matching module");
+MODULE_ALIAS("ipt_ifgroup");
+MODULE_ALIAS("ip6t_ifgroup");
+
+static bool ifgroup_match(const struct sk_buff *skb,
+			  const struct net_device *in,
+			  const struct net_device *out,
+			  const struct xt_match *match,
+			  const void *matchinfo,
+			  int offset,
+			  unsigned int protoff,
+			  bool *hotdrop)
+{
+#define FLAG_IS_SET(a,b)  ((a & b) == b)
+#define MATCH_IN  (((in->ifgroup & info->in_mask) == info->in_group) ^ FLAG_IS_SET(info->flags, XT_IFGROUP_INVERT_IN))
+#define MATCH_OUT (((out->ifgroup & info->out_mask) == info->out_group) ^ FLAG_IS_SET(info->flags, XT_IFGROUP_INVERT_OUT))
+
+	const struct xt_ifgroup_info *info = matchinfo;
+	bool verdict = false;
+	
+	if ((info->flags & XT_IFGROUP_MATCH_IN) && (info->flags & XT_IFGROUP_MATCH_OUT))
+		verdict = MATCH_IN && MATCH_OUT;
+	else if (info->flags & XT_IFGROUP_MATCH_IN)
+		verdict = MATCH_IN;
+	else if (info->flags & XT_IFGROUP_MATCH_OUT)
+		verdict = MATCH_OUT;
+	return verdict;
+}
+
+static bool ifgroup_checkentry(const char *tablename, const void *ip_void,
+			       const struct xt_match *match,
+			       void *matchinfo, unsigned int hook_mask)
+{
+	struct xt_ifgroup_info *info = matchinfo;
+
+	if (!(info->flags & (XT_IFGROUP_MATCH_IN|XT_IFGROUP_MATCH_OUT))) {
+		printk(KERN_ERR "xt_ifgroup: neither incoming nor "
+				"outgoing device selected\n");
+		return false;
+	}
+	if (hook_mask & (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_LOCAL_IN)
+	    && info->flags & XT_IFGROUP_MATCH_OUT) {
+		printk(KERN_ERR "xt_ifgroup: output device not valid in "
+				"PRE_ROUTING and INPUT\n");
+		return false;
+	}
+	if (hook_mask & (1 << NF_IP_POST_ROUTING | 1 << NF_IP_LOCAL_OUT)
+	    && info->flags & XT_IFGROUP_MATCH_IN) {
+		printk(KERN_ERR "xt_ifgroup: input device not valid in "
+				"POST_ROUTING and OUTPUT\n");
+		return false;
+	}
+	return true;
+}
+
+static struct xt_match xt_ifgroup_match[] __read_mostly  = {
+        {
+		.name		= "ifgroup",
+		.match		= ifgroup_match,
+		.checkentry	= ifgroup_checkentry,
+		.matchsize	= sizeof(struct xt_ifgroup_info),
+		.family		= AF_INET,
+		.me		= THIS_MODULE,
+	
+	},
+	{
+		.name		= "ifgroup",
+		.match		= ifgroup_match,
+		.checkentry	= ifgroup_checkentry,
+		.matchsize	= sizeof(struct xt_ifgroup_info),
+		.family		= AF_INET6,
+		.me		= THIS_MODULE,
+	},
+};
+
+static int __init xt_ifgroup_init(void)
+{
+	return xt_register_matches(xt_ifgroup_match, ARRAY_SIZE(xt_ifgroup_match));
+}
+
+static void __exit xt_ifgroup_fini(void)
+{
+	xt_unregister_matches(xt_ifgroup_match, ARRAY_SIZE(xt_ifgroup_match));
+}
+
+module_init(xt_ifgroup_init);
+module_exit(xt_ifgroup_fini);
-- 
1.5.2.5