MySQL  8.0.16
Source Code Documentation
Protocol::AuthSwitchRequest:

Authentication method Switch Request Packet

If both server and the client support CLIENT_PLUGIN_AUTH capability, server can send this packet tp ask client to use another authentication method.

Payload
TypeNameDescription
int<1> 0xFE (254) status tag
string[NUL] plugin name name of the client authentication plugin to switch to
string[EOF] plugin provided data Initial authentication data for that client plugin
Returns
Protocol::AuthSwitchResponse: or closing the connection.
See also
send_plugin_request_packet(), client_mpvio_read_packet()