Set MULTI_RESULTS and MULTI_STATEMENTS MySQL client CAP

[smallinsky]

What

Preset CLIENT_MULTI_RESULTS and CLIENT_MULTI_STATEMENTS client capabilities when connecting to mysql instance.

Why

Those caps requested and set to conn.SetCapability() https://github.com/gravitational/go-mysql/blob/smallinsky/v1.5.0-teleport.1/client/auth.go#L181 function to take effect.

capability |= c.ccaps&CLIENT_MULTI_STATEMENTS | c.ccaps&CLIENT_MULTI_RESULTS |

[jakule]

@smallinsky Any reason why we hardcode the options instead of forwarding them from the client? AFAIR we're already doing something similar with Postgres, so it shouldn't be hard to implement.

[smallinsky]

Any reason why we hardcode the options instead of forwarding them from the client? AFAIR we're already doing something similar with Postgres, so it shouldn't be hard to implement.

The client cap are obtained in teleport proxy where connection to upstream server is done in teleport db agent. Teleport agent and proxy speaks raw TCP thus right now the only way to propagate client capability is to encode them in client TLS identity.
In Progres case the capability are propagated by StartupMessage message that are send for db client thought teleport proxy and can be received by db agent. In mysql the client/server capabilities are propagated in MySQL Handshake so there is no easy way just forward them.

[github-actions]

@smallinsky See the table below for backport results.

Branch	Result
branch/v8	Failed
branch/v9	Failed