Fix isSubnet after netlink library changes

Author: devzbysiu

daemon/routes/netlink/retriever.go

@@ -163,7 +163,7 @@ func routeCmp(a netlink.Route, b netlink.Route) int {
 // isSubnet returns true if network contains whole range of subnet. Otherwise, returns false.
 func isSubnet(network, subnet *net.IPNet) bool {
 	// nil is treated as an IP with 0 prefix
-	if network == nil {
+	if network == nil || network.IP.Equal(net.IPv4zero) || network.IP.Equal(net.IPv6zero) {
 		return true
 	}
 	if subnet == nil {

daemon/routes/netlink/retriever_test.go

@@ -230,6 +230,8 @@ func TestIsSubnet(t *testing.T) {
 		{"IPv6 subnet outside network", "2001:db8::/32", "2001:db9::/48", false},
 		{"IPv6 subnet larger than network", "2001:db8::/48", "2001:db8::/32", false},
 		{"nil network (default route)", "", "192.168.1.0/24", true},
+		{"zero IPv4 network", "0.0.0.0/0", "192.168.1.0/24", true},
+		{"zero IPv6 network", "::/0", "192.168.1.0/24", true},
 		{"nil subnet", "192.168.1.0/24", "", false},
 	}