net: ipv6: check route protocol when deleting routes

BugLink: http://bugs.launchpad.net/bugs/1687629

commit c2ed1880 upstream.

The protocol field is checked when deleting IPv4 routes, but ignored for
IPv6, which causes problems with routing daemons accidentally deleting
externally set routes (observed by multiple bird6 users).

This can be verified using `ip -6 route del <prefix> proto something`.
Signed-off-by: Mantas Mikulėnas <grawity@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

net/ipv6/route.c

@@ -2084,6 +2084,8 @@ static int ip6_route_del(struct fib6_config *cfg)
 				continue;
 			if (cfg->fc_metric && cfg->fc_metric != rt->rt6i_metric)
 				continue;
+			if (cfg->fc_protocol && cfg->fc_protocol != rt->rt6i_protocol)
+				continue;
 			dst_hold(&rt->dst);
 			read_unlock_bh(&table->tb6_lock);