netconf: advertise mc_forwarding status

This patch advertise the MC_FORWARDING status for IPv4 and IPv6.
This field is readonly, only multicast engine in the kernel updates it.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 22ae75d..28e0e62 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -469,6 +469,8 @@
 	/* type -1 is used for ALL */
 	if (type == -1 || type == NETCONFA_FORWARDING)
 		size += nla_total_size(4);
+	if (type == -1 || type == NETCONFA_MC_FORWARDING)
+		size += nla_total_size(4);
 
 	return size;
 }
@@ -496,6 +498,10 @@
 	if ((type == -1 || type == NETCONFA_FORWARDING) &&
 	    nla_put_s32(skb, NETCONFA_FORWARDING, devconf->forwarding) < 0)
 		goto nla_put_failure;
+	if ((type == -1 || type == NETCONFA_MC_FORWARDING) &&
+	    nla_put_s32(skb, NETCONFA_MC_FORWARDING,
+			devconf->mc_forwarding) < 0)
+		goto nla_put_failure;
 
 	return nlmsg_end(skb, nlh);
 
@@ -504,8 +510,8 @@
 	return -EMSGSIZE;
 }
 
-static void inet6_netconf_notify_devconf(struct net *net, int type, int ifindex,
-					 struct ipv6_devconf *devconf)
+void inet6_netconf_notify_devconf(struct net *net, int type, int ifindex,
+				  struct ipv6_devconf *devconf)
 {
 	struct sk_buff *skb;
 	int err = -ENOBUFS;