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/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 3ffd233..8be7623 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1057,6 +1057,13 @@
 	address.
 	Default: FALSE (enable IPv6 operation)
 
+	When this value is changed from 1 to 0 (IPv6 is being enabled),
+	it will dynamically create a link-local address on the given
+	interface and start Duplicate Address Detection, if necessary.
+
+	When this value is changed from 0 to 1 (IPv6 is being disabled),
+	it will dynamically delete all address on the given interface.
+
 accept_dad - INTEGER
 	Whether to accept DAD (Duplicate Address Detection).
 	0: Disable DAD