ipv6: add missing netconf notif when 'all' is updated

BugLink: https://bugs.launchpad.net/bugs/1878232

commit d26c638c upstream.

The 'default' value was not advertised.

Fixes: f3a1bfb1 ("rtnl/ipv6: use netconf msg to advertise forwarding status")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/ipv6/addrconf.c

@@ -771,7 +771,14 @@ static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int newf)
 	}
 
 	if (p == &net->ipv6.devconf_all->forwarding) {
+		int old_dflt = net->ipv6.devconf_dflt->forwarding;
+
 		net->ipv6.devconf_dflt->forwarding = newf;
+		if ((!newf) ^ (!old_dflt))
+			inet6_netconf_notify_devconf(net, NETCONFA_FORWARDING,
+						     NETCONFA_IFINDEX_DEFAULT,
+						     net->ipv6.devconf_dflt);
+
 		addrconf_forward_change(net, newf);
 		if ((!newf) ^ (!old))
 			inet6_netconf_notify_devconf(net, NETCONFA_FORWARDING,