Smack: secmark support for netfilter

Smack uses CIPSO to label internet packets and thus provide
for access control on delivery of packets. The netfilter facility
was not used to allow for Smack to work properly without netfilter
configuration. Smack does not need netfilter, however there are
cases where it would be handy.

As a side effect, the labeling of local IPv4 packets can be optimized
and the handling of local IPv6 packets is just all out better.

The best part is that the netfilter tools use "contexts" that
are just strings, and they work just as well for Smack as they
do for SELinux.

All of the conditional compilation for IPv6 was implemented
by Rafal Krypa <r.krypa@samsung.com>

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
diff --git a/security/smack/Kconfig b/security/smack/Kconfig
index b065f97..271adae 100644
--- a/security/smack/Kconfig
+++ b/security/smack/Kconfig
@@ -28,3 +28,15 @@
 	  access rule set once the behavior is well understood.
 	  This is a superior mechanism to the oft abused
 	  "permissive" mode of other systems.
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_SMACK_NETFILTER
+	bool "Packet marking using secmarks for netfilter"
+	depends on SECURITY_SMACK
+	depends on NETWORK_SECMARK
+	depends on NETFILTER
+	default n
+	help
+	  This enables security marking of network packets using
+	  Smack labels.
+	  If you are unsure how to answer this question, answer N.