这是一篇折腾文，一般人基本用不上，就当看个解题思路吧
设备hg255d 一款很能折腾的小路由器，便宜，耐玩（虽然针对pandorabox但是不同芯片，貌似路径还是不一样的，动手之前最好查清楚）
心血来潮想直接用路由器连接vpn，然后软件包搜索 openl2tp-full 提示
Downloading http://downloads.openwrt.org/snapshots/trunk/ralink/packages/base/Packages.gz.
Collected errors:
* opkg_download: Failed to download http://downloads.openwrt.org/snapshots/trunk/ralink/packages/base/Packages.gz, wget returned 8.
一桶乱搜，发现一个刷小米的同学提到了，配置文件中源的地址其实已经发生了变化，但是刷了的里面的并没有修改，所以导致的无法升级
/etc/opkg.conf
修改
src/gz 14.09_base http://downloads.openwrt.org/snapshots/trunk/ramips/rt305x/packages/base
src/gz 14.09_packages http://downloads.openwrt.org/snapshots/trunk/ramips/rt305x/packages/packages
src/gz 14.09_routing http://downloads.openwrt.org/snapshots/trunk/ramips/rt305x/packages/routing
src/gz 14.09_telephony http://downloads.openwrt.org/snapshots/trunk/ramips/rt305x/packages/telephony
src/gz 14.09_management http://downloads.openwrt.org/snapshots/trunk/ramips/rt305x/packages/management
# src/gz 14.09_oldpackages http://downloads.openwrt.org/snapshots/trunk/ramips/rt305x/packages/oldpackages
其实只是把ralink 换成了 ramips/rt305x
src/gz pandoraox_base http://downloads.openwrt.org.cn/PandoraBox/ralink/packages/base
src/gz pandoraox_packages http://downloads.openwrt.org.cn/PandoraBox/ralink/packages/packages
src/gz pandoraox_routing http://downloads.openwrt.org.cn/PandoraBox/ralink/packages/routing
src/gz pandoraox_telephony http://downloads.openwrt.org.cn/PandoraBox/ralink/packages/telephony
src/gz pandoraox_management http://downloads.openwrt.org.cn/PandoraBox/ralink/packages/management
src/gz pandoraox http://downloads.openwrt.org.cn/PandoraBox/ralink/packages/oldpackages
本来打算只是把源的链接改了，后来发现还有问题，索性换到国内源了
参考：
https://blog.phpgao.com/xiaomi_router_opkg.html
http://wayjam.me/post/two-problems-about-install-package-on-openwrt.md
http://wiki.openwrt.org/doc/howto/connect_by_l2tp
ps 这wordpress的代码段太难看了，但是我懒得折腾了