net/ipv6/addrconf: IPv6 tethering enhancement

Added new procfs flag to toggle the automatic addition of prefix
routes on a per device basis. The new flag is accept_ra_prefix_route.
Defaults to 1 as to not break existing behavior.

Change-Id: If25493890c7531c27f5b2c4855afebbbbf5d072a
CRs-Fixed: 504095
Signed-off-by: Harout Hedeshian <harouth@codeaurora.org>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 8260ef7..4effce6 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -172,6 +172,7 @@
 	__s32		disable_ipv6;
 	__s32		accept_dad;
 	__s32		force_tllao;
+	__s32		accept_ra_prefix_route;
 	void		*sysctl;
 };
 
@@ -213,6 +214,7 @@
 	DEVCONF_DISABLE_IPV6,
 	DEVCONF_ACCEPT_DAD,
 	DEVCONF_FORCE_TLLAO,
+	DEVCONF_ACCEPT_RA_PREFIX_ROUTE,
 	DEVCONF_MAX
 };