zones: add Zone.SetGateway() to set one by ID

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/zones/zones.go

@@ -44,6 +44,31 @@ func (z *Zone) ForEachMachine(fn func(*Machine) bool) {
 	}
 }
 
+// SetGateway configures a machine to be the zone's ring0 gateway
+func (z *Zone) SetGateway(gatewayID int, enabled bool) error {
+	var err error
+	var found bool
+
+	z.ForEachMachine(func(p *Machine) bool {
+		if p.ID == gatewayID {
+			found = true
+			err = p.SetGateway(enabled)
+
+			return true
+		}
+		return false
+	})
+
+	switch {
+	case err != nil:
+		return err
+	case !found:
+		return fs.ErrNotExist
+	default:
+		return nil
+	}
+}
+
 // Zones represents all zones in a cluster
 type Zones struct {
 	dir      fs.FS