IPv6: Add 'autoconf' and 'disable_ipv6' module parameters

Add 'autoconf' and 'disable_ipv6' parameters to the IPv6 module.

The first controls if IPv6 addresses are autoconfigured from
prefixes received in Router Advertisements.  The IPv6 loopback
(::1) and link-local addresses are still configured.

The second controls if IPv6 addresses are desired at all.  No
IPv6 addresses will be added to any interfaces.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 476d946..c662efa 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -169,6 +169,12 @@
 	__s32		accept_dad;
 	void		*sysctl;
 };
+
+struct ipv6_params {
+	__s32 disable_ipv6;
+	__s32 autoconf;
+};
+extern struct ipv6_params ipv6_defaults;
 #endif
 
 /* index values for the variables in ipv6_devconf */