zones: introduce Zone.GatewayIDs()

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

pkg/zones/zones.go

@@ -125,6 +125,19 @@ func (z *Zone) SetGateway(gatewayID int, enabled bool) error {
 	}
 }
 
+// GatewayIDs returns the list of IDs of machines that act as ring0 gateways
+func (z *Zone) GatewayIDs() ([]int, int) {
+	var out []int
+	z.ForEachMachine(func(p *Machine) bool {
+		if p.IsGateway() {
+			out = append(out, p.ID)
+		}
+		return false
+	})
+
+	return out, len(out)
+}
+
 // Zones represents all zones in a cluster
 type Zones struct {
 	dir      fs.FS