Unnecessary error "X509 error" when client connects without SSL certificate

[renecannao]

• A clear description of the issue

If a client tries to establish an SSL connection without specifying any certificate, proxysql will log an error

• ProxySQL version

2.1.1 and newer.
But introduced in #3343

• OS version

Any

• The steps to reproduce the issue

Start proxysql with enabled SSL (for example running SET mysql-have_ssl='true'; load mysql variables to runtime; .
Then use any client to establish an SSL connection without certificate. For example:

mysql -u sbtest -psbtest -h 127.0.0.1 -P6033 --ssl-mode=required

• The full ProxySQL error log (default location: /var/lib/proxysql/proxysql.log)

The full error log is irrelevant.
The specific error message is:

2021-04-28 20:54:55 mysql_data_stream.cpp:189:do_ssl_handshake(): [ERROR] X509 error: no required certificate sent by client

Suggested changes:
The error here doesn't seem correct. The certificate is not required.
It should be replaced with a warning, and the warning itself should be toggled on or off using a new global variable.

[seikath]

I see the same error with self signed certificates

[renecannao]

Message will go away in the next release

[kasabov]

Just verified that the issue indeed disappears with version 2.3.2.