shadowsocks-rust

TODO

[x] add cache for DNS
[x] review unwrap, .ok()、unimplemented, unreachable
[x] check if there exists cannot decrypt log
[x] test with shadowsocks
[x] remove unnecessary clone ~~(maybe this is the cause of high CPU problem)~~
[x] find the reason of high CPU (5% ~ 20%)
[ ] response slow after fixed high CPU problem
[ ] finish all TODO items in source
[ ] handle the timeout situation of client
[ ] handle DNS error properly (e.g. remove caller or call resolve again)
[ ] review tcp_processor
[ ] refactor error handle