netfilter: xtables: connlimit revision 1

This adds destination address-based selection. The old "inverse"
member is overloaded (memory-wise) with a new "flags" variable,
similar to how J.Park did it with xt_string rev 1. Since revision 0
userspace only sets flag 0x1, no great changes are made to explicitly
test for different revisions.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>

Documentation/feature-removal-schedule.txt

@@ -576,3 +576,10 @@ Why:	The functions have been superceded by cancel_delayed_work_sync()
 Who:	Tejun Heo <tj@kernel.org>
 
 ----------------------------
+
+What:	xt_connlimit rev 0
+When:	2012
+Who:	Jan Engelhardt <jengelh@medozas.de>
+Files:	net/netfilter/xt_connlimit.c
+
+----------------------------

include/linux/netfilter/xt_connlimit.h

@@ -3,6 +3,11 @@
 
 struct xt_connlimit_data;
 
+enum {
+	XT_CONNLIMIT_INVERT = 1 << 0,
+	XT_CONNLIMIT_DADDR  = 1 << 1,
+};
+
 struct xt_connlimit_info {
 	union {
 		union nf_inet_addr mask;
@@ -14,6 +19,13 @@ struct xt_connlimit_info {
 #endif
 	};
 	unsigned int limit, inverse;
+	union {
+		/* revision 0 */
+		unsigned int inverse;
+
+		/* revision 1 */
+		__u32 flags;
+	};
 
 	/* Used internally by the kernel */
 	struct xt_connlimit_data *data __attribute__((aligned(8)));

net/netfilter/xt_connlimit.c

@@ -193,10 +193,12 @@ connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
 
 	if (par->family == NFPROTO_IPV6) {
 		const struct ipv6hdr *iph = ipv6_hdr(skb);
-		memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
+		memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
+		       &iph->daddr : &iph->saddr, sizeof(addr.ip6));
 	} else {
 		const struct iphdr *iph = ip_hdr(skb);
-		addr.ip = iph->saddr;
+		addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ?
+			  iph->daddr : iph->saddr;
 	}
 
 	spin_lock_bh(&info->data->lock);
@@ -208,7 +210,8 @@ connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
 		/* kmalloc failed, drop it entirely */
 		goto hotdrop;
 
-	return (connections > info->limit) ^ info->inverse;
+	return (connections > info->limit) ^
+	       !!(info->flags & XT_CONNLIMIT_INVERT);
 
  hotdrop:
 	par->hotdrop = true;
@@ -266,25 +269,38 @@ static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
 	kfree(info->data);
 }
 
-static struct xt_match connlimit_mt_reg __read_mostly = {
-	.name       = "connlimit",
-	.revision   = 0,
-	.family     = NFPROTO_UNSPEC,
-	.checkentry = connlimit_mt_check,
-	.match      = connlimit_mt,
-	.matchsize  = sizeof(struct xt_connlimit_info),
-	.destroy    = connlimit_mt_destroy,
-	.me         = THIS_MODULE,
+static struct xt_match connlimit_mt_reg[] __read_mostly = {
+	{
+		.name       = "connlimit",
+		.revision   = 0,
+		.family     = NFPROTO_UNSPEC,
+		.checkentry = connlimit_mt_check,
+		.match      = connlimit_mt,
+		.matchsize  = sizeof(struct xt_connlimit_info),
+		.destroy    = connlimit_mt_destroy,
+		.me         = THIS_MODULE,
+	},
+	{
+		.name       = "connlimit",
+		.revision   = 1,
+		.family     = NFPROTO_UNSPEC,
+		.checkentry = connlimit_mt_check,
+		.match      = connlimit_mt,
+		.matchsize  = sizeof(struct xt_connlimit_info),
+		.destroy    = connlimit_mt_destroy,
+		.me         = THIS_MODULE,
+	},
 };
 
 static int __init connlimit_mt_init(void)
 {
-	return xt_register_match(&connlimit_mt_reg);
+	return xt_register_matches(connlimit_mt_reg,
+	       ARRAY_SIZE(connlimit_mt_reg));
 }
 
 static void __exit connlimit_mt_exit(void)
 {
-	xt_unregister_match(&connlimit_mt_reg);
+	xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
 }
 
 module_init(connlimit_mt_init);