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.

CRs-Fixed: 435320
Change-Id: If25493890c7531c27f5b2c4855afebbbbf5d072a
Acked-by: Harout S. Hedeshian <harouth@qti.qualcomm.com>
Signed-off-by: Tianyi Gou <tgou@codeaurora.org>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: Tejaswi Tanikella <tejaswit@codeaurora.org>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 140d05f..a5c1ff3 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -240,6 +240,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
 	.use_oif_addrs_only	= 0,
 	.ignore_routes_with_linkdown = 0,
 	.keep_addr_on_down	= 0,
+	.accept_ra_prefix_route = 1,
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -288,6 +289,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 	.use_oif_addrs_only	= 0,
 	.ignore_routes_with_linkdown = 0,
 	.keep_addr_on_down	= 0,
+	.accept_ra_prefix_route = 1,
 };
 
 /* Check if link is ready: is it up and is a valid qdisc available */
@@ -2607,8 +2609,11 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
 				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);
+			}
 		}
 		ip6_rt_put(rt);
 	}
@@ -6125,6 +6130,13 @@ static const struct ctl_table addrconf_sysctl[] = {
 
 	},
 	{
+		.procname	= "accept_ra_prefix_route",
+		.data		= &ipv6_devconf.accept_ra_prefix_route,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
 		/* sentinel */
 	}
 };