Authentication not working properly in case of compressed connection

[JavierJF]

Description

When trying to execute a query in a compressed connection, connection is dropped by proxysql, but in case of using --default-auth=mysql_native_password everything works as expected.

Version

Confirmed OSs:

Distributor ID: Ubuntu
Description:    Ubuntu 19.10
Release:        19.10
Codename:       eoan

ProxySQL version:

ProxySQL version 2.0.12-11-gd1032d12_DEBUG, codename Truls

Steps to reproduce the issue

1. Launch proxysql.
2. Try to execute a query to a mysql server, e.g: mysql -uroot -proot -h 127.0.0.1 -P6033 -C -e "select 1";

Relevant log info

After executing the given command, mysql client replies with:

ERROR 2013 (HY000): Lost connection to MySQL server during query

While proxysql shows that it has received an unknown command:

2020-05-14 19:37:40 MySQL_Session.cpp:3338:handler(): [ERROR] RECEIVED AN UNKNOWN COMMAND: 0 -- PLEASE REPORT A BUG

Full error log:

compress-auth.txt

[renecannao]

Reopening this, there is no full PR yet for 2.1.0