- KAL : keep alive ("option http-keep-alive") which is the default mode : all
requests and responses are processed, and connections remain open but idle
between responses and new requests. 默认的保持连接方式
- TUN: tunnel ("option http-tunnel") : this was the default mode for versions
1.0 to 1.5-dev21 : only the first request and response are processed, and
everything else is forwarded with no analysis at all. This mode should not
be used as it creates lots of trouble with logging and HTTP processing. HTTP隧道方式
- PCL: passive close ("option httpclose") : exactly the same as tunnel mode,
but with "Connection: close" appended in both directions to try to make
both ends close after the first request/response exchange. 关闭方式
- SCL: server close ("option http-server-close") : the server-facing
connection is closed after the end of the response is received, but the
client-facing connection remains open. 服务端关闭方式
- FCL: forced close ("option forceclose") : the connection is actively closed
after the end of the response. 强制关闭方式