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: 435320
Acked-by: Harout S. Hedeshian <harouth@qti.qualcomm.com>
Signed-off-by: Tianyi Gou <tgou@codeaurora.org>
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 5aecb48..2d4a6db 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1098,6 +1098,11 @@
 	Functional default: enabled if accept_ra is enabled.
 			    disabled if accept_ra is disabled.
 
+accept_ra_prefix_route - BOOLEAN
+	Set the prefix route for the autoconfigured interface address
+
+	Functional default: enabled
+
 accept_redirects - BOOLEAN
 	Accept Redirects.