[NETFILTER]: x_tables: add TRACE target

The TRACE target can be used to follow IP and IPv6 packets through
the ruleset.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Patrick NcHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/Kconfig

@@ -343,6 +343,18 @@ config NETFILTER_XT_TARGET_NOTRACK
 	  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_TARGET_TRACE
+	tristate  '"TRACE" target support'
+	depends on NETFILTER_XTABLES
+	depends on IP_NF_RAW || IP6_NF_RAW
+	help
+	  The TRACE target allows you to mark packets so that the kernel
+	  will log every rule which match the packets as those traverse
+	  the tables, chains, rules.
+
+	  If you want to compile it as a module, say M here and read
+	  <file:Documentation/modules.txt>.  If unsure, say `N'.
+
 config NETFILTER_XT_TARGET_SECMARK
 	tristate '"SECMARK" target support'
 	depends on NETFILTER_XTABLES && NETWORK_SECMARK

net/netfilter/Makefile

@@ -44,6 +44,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_MARK) += xt_MARK.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o

net/netfilter/xt_TRACE.c

@@ -0,0 +1,53 @@
+/* This is a module which is used to mark packets for tracing.
+ */
+#include <linux/module.h>
+#include <linux/skbuff.h>
+
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_TRACE");
+MODULE_ALIAS("ip6t_TRACE");
+
+static unsigned int
+target(struct sk_buff **pskb,
+       const struct net_device *in,
+       const struct net_device *out,
+       unsigned int hooknum,
+       const struct xt_target *target,
+       const void *targinfo)
+{
+	(*pskb)->nf_trace = 1;
+	return XT_CONTINUE;
+}
+
+static struct xt_target xt_trace_target[] = {
+	{
+		.name		= "TRACE",
+		.family		= AF_INET,
+		.target		= target,
+		.table		= "raw",
+		.me		= THIS_MODULE,
+	},
+	{
+		.name		= "TRACE",
+		.family		= AF_INET6,
+		.target		= target,
+		.table		= "raw",
+		.me		= THIS_MODULE,
+	},
+};
+
+static int __init xt_trace_init(void)
+{
+	return xt_register_targets(xt_trace_target,
+				   ARRAY_SIZE(xt_trace_target));
+}
+
+static void __exit xt_trace_fini(void)
+{
+	xt_unregister_targets(xt_trace_target, ARRAY_SIZE(xt_trace_target));
+}
+
+module_init(xt_trace_init);
+module_exit(xt_trace_fini);