http://gongdan.oss-cn-hangzhou.aliyuncs.com/market/cmISV/%E4%B8%8B%E8%BD%BD/2015-10-12/centos%206.5%2064%E4%BD%8DStrongswan5.3.2%2BOpenvpn2.3.8%20%2B%20FlexGW2.0.pdf?spm=5176.730006-cmjj006981.102.8.VrQAQu&file=centos%206.5%2064%E4%BD%8DStrongswan5.3.2%2BOpenvpn2.3.8%20%2B%20FlexGW2.0.pdf
http://www.newsharp.com.cn/net/product/IPSecVPN.htm