[NETFILTER]: x_tables: replace IPv4/IPv6 policy match by address family independant version

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 220 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index a8e5544..1740278 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -279,6 +279,16 @@ config NETFILTER_XT_MATCH_MARK
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NETFILTER_XT_MATCH_POLICY
+	tristate 'IPsec "policy" match support'
+	depends on NETFILTER_XTABLES && XFRM
+	help
+	  Policy matching allows you to match packets based on the
+	  IPsec policy that was used during decapsulation/will
+	  be used during encapsulation.
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_MATCH_PHYSDEV
 	tristate '"physdev" match support'
 	depends on NETFILTER_XTABLES && BRIDGE_NETFILTER
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 746172e..9558727 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_LENGTH) += xt_length.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_LIMIT) += xt_limit.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_MAC) += xt_mac.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_MARK) += xt_mark.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_POLICY) += xt_policy.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_PKTTYPE) += xt_pkttype.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_REALM) += xt_realm.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_SCTP) += xt_sctp.o
diff --git a/net/netfilter/xt_policy.c b/net/netfilter/xt_policy.c
new file mode 100644
index 0000000..1ec2208
--- /dev/null
+++ b/net/netfilter/xt_policy.c
@@ -0,0 +1,209 @@
+/* IP tables module for matching IPsec policy
+ *
+ * Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.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/kernel.h>
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/init.h>
+#include <net/xfrm.h>
+
+#include <linux/netfilter/xt_policy.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
+MODULE_DESCRIPTION("Xtables IPsec policy matching module");
+MODULE_LICENSE("GPL");
+
+static inline int
+xt_addr_cmp(const union xt_policy_addr *a1, const union xt_policy_addr *m,
+	    const union xt_policy_addr *a2, unsigned short family)
+{
+	switch (family) {
+	case AF_INET:
+		return (a1->a4.s_addr ^ a2->a4.s_addr) & m->a4.s_addr;
+	case AF_INET6:
+		return ipv6_masked_addr_cmp(&a1->a6, &m->a6, &a2->a6);
+	}
+	return 0;
+}
+
+static inline int
+match_xfrm_state(struct xfrm_state *x, const struct xt_policy_elem *e,
+		 unsigned short family)
+{
+#define MATCH_ADDR(x,y,z)	(!e->match.x ||			       \
+				 (xt_addr_cmp(&e->x, &e->y, z, family) \
+				  ^ e->invert.x))
+#define MATCH(x,y)		(!e->match.x || ((e->x == (y)) ^ e->invert.x))
+
+	return MATCH_ADDR(saddr, smask, (union xt_policy_addr *)&x->props.saddr) &&
+	       MATCH_ADDR(daddr, dmask, (union xt_policy_addr *)&x->id.daddr.a4) &&
+	       MATCH(proto, x->id.proto) &&
+	       MATCH(mode, x->props.mode) &&
+	       MATCH(spi, x->id.spi) &&
+	       MATCH(reqid, x->props.reqid);
+}
+
+static int
+match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info,
+		unsigned short family)
+{
+	const struct xt_policy_elem *e;
+	struct sec_path *sp = skb->sp;
+	int strict = info->flags & XT_POLICY_MATCH_STRICT;
+	int i, pos;
+
+	if (sp == NULL)
+		return -1;
+	if (strict && info->len != sp->len)
+		return 0;
+
+	for (i = sp->len - 1; i >= 0; i--) {
+		pos = strict ? i - sp->len + 1 : 0;
+		if (pos >= info->len)
+			return 0;
+		e = &info->pol[pos];
+
+		if (match_xfrm_state(sp->x[i].xvec, e, family)) {
+			if (!strict)
+				return 1;
+		} else if (strict)
+			return 0;
+	}
+
+	return strict ? 1 : 0;
+}
+
+static int
+match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info,
+		 unsigned short family)
+{
+	const struct xt_policy_elem *e;
+	struct dst_entry *dst = skb->dst;
+	int strict = info->flags & XT_POLICY_MATCH_STRICT;
+	int i, pos;
+
+	if (dst->xfrm == NULL)
+		return -1;
+
+	for (i = 0; dst && dst->xfrm; dst = dst->child, i++) {
+		pos = strict ? i : 0;
+		if (pos >= info->len)
+			return 0;
+		e = &info->pol[pos];
+
+		if (match_xfrm_state(dst->xfrm, e, family)) {
+			if (!strict)
+				return 1;
+		} else if (strict)
+			return 0;
+	}
+
+	return strict ? i == info->len : 0;
+}
+
+static int 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,
+                 int *hotdrop)
+{
+	const struct xt_policy_info *info = matchinfo;
+	int ret;
+
+	if (info->flags & XT_POLICY_MATCH_IN)
+		ret = match_policy_in(skb, info, match->family);
+	else
+		ret = match_policy_out(skb, info, match->family);
+
+	if (ret < 0)
+		ret = info->flags & XT_POLICY_MATCH_NONE ? 1 : 0;
+	else if (info->flags & XT_POLICY_MATCH_NONE)
+		ret = 0;
+
+	return ret;
+}
+
+static int checkentry(const char *tablename, const void *ip_void,
+                      const struct xt_match *match,
+                      void *matchinfo, unsigned int matchsize,
+                      unsigned int hook_mask)
+{
+	struct xt_policy_info *info = matchinfo;
+
+	if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) {
+		printk(KERN_ERR "xt_policy: neither incoming nor "
+		                "outgoing policy selected\n");
+		return 0;
+	}
+	/* hook values are equal for IPv4 and IPv6 */
+	if (hook_mask & (1 << NF_IP_PRE_ROUTING | 1 << NF_IP_LOCAL_IN)
+	    && info->flags & XT_POLICY_MATCH_OUT) {
+		printk(KERN_ERR "xt_policy: output policy not valid in "
+		                "PRE_ROUTING and INPUT\n");
+		return 0;
+	}
+	if (hook_mask & (1 << NF_IP_POST_ROUTING | 1 << NF_IP_LOCAL_OUT)
+	    && info->flags & XT_POLICY_MATCH_IN) {
+		printk(KERN_ERR "xt_policy: input policy not valid in "
+		                "POST_ROUTING and OUTPUT\n");
+		return 0;
+	}
+	if (info->len > XT_POLICY_MAX_ELEM) {
+		printk(KERN_ERR "xt_policy: too many policy elements\n");
+		return 0;
+	}
+	return 1;
+}
+
+static struct xt_match policy_match = {
+	.name		= "policy",
+	.family		= AF_INET,
+	.match		= match,
+	.matchsize	= sizeof(struct xt_policy_info),
+	.checkentry 	= checkentry,
+	.me		= THIS_MODULE,
+};
+
+static struct xt_match policy6_match = {
+	.name		= "policy",
+	.family		= AF_INET6,
+	.match		= match,
+	.matchsize	= sizeof(struct xt_policy_info),
+	.checkentry	= checkentry,
+	.me		= THIS_MODULE,
+};
+
+static int __init init(void)
+{
+	int ret;
+
+	ret = xt_register_match(AF_INET, &policy_match);
+	if (ret)
+		return ret;
+	ret = xt_register_match(AF_INET6, &policy6_match);
+	if (ret)
+		xt_unregister_match(AF_INET, &policy_match);
+	return ret;
+}
+
+static void __exit fini(void)
+{
+	xt_unregister_match(AF_INET6, &policy6_match);
+	xt_unregister_match(AF_INET, &policy_match);
+}
+
+module_init(init);
+module_exit(fini);
+MODULE_ALIAS("ipt_policy");
+MODULE_ALIAS("ip6t_policy");