openwrt: save cache to disk when reboot system

package/luci-compat/files/luci/i18n/smartdns.zh-cn.po

@@ -31,6 +31,9 @@ msgstr "绑定到设备"
 msgid "Bind Device Name"
 msgstr "绑定的设备名称"
 
+msgid "Cache Persist"
+msgstr "持久化缓存"
+
 msgid "Cache Size"
 msgstr "缓存大小"
 
@@ -502,6 +505,9 @@ msgstr ""
 "用于校验 TLS 服务器的有效性，数值为 Base64 编码的 SPKI 指纹，留空表示不验证 "
 "TLS 的合法性。"
 
+msgid "Write cache to disk on exit and load on startup."
+msgstr "退出时保存cache到磁盘，启动时加载。"
+
 msgid "domain list (/etc/smartdns/domain-set)"
 msgstr "域名列表（/etc/smartdns/domain-set）"
 

package/luci-compat/files/luci/model/cbi/smartdns/smartdns.lua

@@ -161,6 +161,14 @@ end
 o = s:taboption("advanced", Value, "cache_size", translate("Cache Size"), translate("DNS domain result cache size"))
 o.rempty      = true
 
+---- cache-persist;
+o = s:taboption("advanced", Flag, "cache_persist", translate("Cache Persist"), translate("Write cache to disk on exit and load on startup."))
+o.rmempty      = false;
+o.default     = o.enabled;
+o.cfgvalue    = function(...)
+    return Flag.cfgvalue(...) or "1"
+end
+
 -- cache-size
 o = s:taboption("advanced", Flag, "resolve_local_hostnames", translate("Resolve Local Hostnames"), translate("Resolve local hostnames by reading Dnsmasq lease file."))
 o.rmempty     = false