Added DB SharedNode model to support sharing nodes

db.go

@@ -44,6 +44,11 @@ func (h *Headscale) initDB() error {
 		return err
 	}
 
+	err = db.AutoMigrate(&SharedNode{})
+	if err != nil {
+		return err
+	}
+
 	err = h.setValue("db_version", dbVersion)
 	return err
 }

sharing_nodes.go

@@ -0,0 +1,37 @@
+package headscale
+
+import "gorm.io/gorm"
+
+const errorSameNamespace = Error("Destination namespace same as origin")
+const errorNodeAlreadyShared = Error("Node already shared to this namespace")
+
+// Sharing is a join table to support sharing nodes between namespaces
+type SharedNode struct {
+	gorm.Model
+	MachineID   uint64
+	Machine     Machine
+	NamespaceID uint
+	Namespace   Namespace
+}
+
+// ShareNodeInNamespace adds a machine as a shared node to a namespace
+func (h *Headscale) ShareNodeInNamespace(m *Machine, ns *Namespace) error {
+	if m.NamespaceID == ns.ID {
+		return errorSameNamespace
+	}
+
+	sn := SharedNode{}
+	if err := h.db.Where("machine_id = ? AND namespace_id", m.ID, ns.ID).First(&sn).Error; err == nil {
+		return errorNodeAlreadyShared
+	}
+
+	sn = SharedNode{
+		MachineID:   m.ID,
+		Machine:     *m,
+		NamespaceID: ns.ID,
+		Namespace:   *ns,
+	}
+	h.db.Save(&sn)
+
+	return nil
+}