When persistent connections were used, it was possible that the injection
of COM_CHANGE_USER statements caused a crash when a DCB in the wrong state
was accessed.
For MySQL protocol modules, the `data` member of the client DCB points to
the shared session data, a MYSQL_session struct, but for sessions in the
persistent pool, it points to NULL. The boolean, `was_persistent`, tells
whether a DCB was just taken from the pool or it has been in use.
The `was_persistent` status wasn't properly reset for connections that
were put into the pool which caused a COM_CHANGE_USER statement to be
injected for stale connections in the pool which caused a crash when the
NULL `data` member was accessed.
When a persistent connection is taken from the pool, the state is reset
with a COM_CHANGE_USER on the next write. This allows reuse of persistent
connections without having to worry about the state of the MySQL session.
In a subsequent change, the includes of server/core/*.c will be
cleaned up, and if there is a common set of include files, needed
by most, then a server/core/maxscale/core.h that includes those
will be introduced.
The general purpose stuff in skygw_utils.h was moved to utils.h
and the corresponding implementation from skygw_utils.cc to utils.c.
Includes updated accordingly.
Skygw_utils.h is now only used by log_manager and by mlist, which
is only used by log_manager. Consequently, skygw_utils.h was moved
to server/maxscale.
Utils.h needs a separate overhaul.
- STRERROR_BUFLEN moved to cdefs.h and renamed to MXS_STRERROR_BUFLEN.
Better would be to provide a 'const char* mxs_strerror(int errno)'
that would have a thread specific buffer for the error message.
- MIN and MAX also moved to defs.h as MXS_MIN and MXS_MAX.
- Now only mlist.h of the headers depend upon skygw_utils.h.
- Headers now to be included as <maxscale/xyz.h>
- First step, no cleanup of headers has been made. Only moving
from one place to another + necessary modifications.
The first message exchange between the server and the client will almost
always contain the same data. If the server is going to change
authentication methods, it will send an AuthSwitchRequest packet instead
of the OK/ERR packet that it would normally send. Only after this point
the authenticator modules actually need to do something.
In the case of the default 'mysql_native_password' plugin, the only thing
that the plugin needs to do is to check whether the server responded with
an OK packet.
The MySQLCommon library contains functions used by both the protocol and
authenticator modules. The contents of the modutil.c file could also be
moved to this file if the functions in that file are only used by modules
and not the core.
