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/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index f897841..5bb2847 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -36,6 +36,8 @@
  *	YOSHIFUJI Hideaki @USAGI	:	improved source address
  *						selection; consider scope,
  *						status etc.
+ *	Harout S. Hedeshian		:	procfs flag to toggle automatic
+ *						addition of prefix route
  */
 
 #include <linux/errno.h>
@@ -197,6 +199,7 @@
 	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
 	.disable_ipv6		= 0,
 	.accept_dad		= 1,
+	.accept_ra_prefix_route = 1,
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -231,6 +234,7 @@
 	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
 	.disable_ipv6		= 0,
 	.accept_dad		= 1,
+	.accept_ra_prefix_route = 1,
 };
 
 /* IPv6 Wildcard Address and Loopback Address defined by RFC2553 */
@@ -1908,8 +1912,10 @@
 				flags |= RTF_EXPIRES;
 				expires = jiffies_to_clock_t(rt_expires);
 			}
-			addrconf_prefix_route(&pinfo->prefix, pinfo->prefix_len,
-					      dev, expires, flags);
+			if (dev->ip6_ptr->cnf.accept_ra_prefix_route) {
+				addrconf_prefix_route(&pinfo->prefix,
+					pinfo->prefix_len, dev, expires, flags);
+			}
 		}
 		if (rt)
 			dst_release(&rt->dst);
@@ -4598,6 +4604,13 @@
 			.proc_handler   = proc_dointvec
 		},
 		{
+			.procname	= "accept_ra_prefix_route",
+			.data		= &ipv6_devconf.accept_ra_prefix_route,
+			.maxlen		= sizeof(int),
+			.mode		= 0644,
+			.proc_handler	= proc_dointvec,
+		},
+		{
 			/* sentinel */
 		}
 	},