How to audit non LDAP connections?

Due to security/audits have moved most users to LDAP. Looking for a way
to tell if a connection is/is not going through LDAP.

Other than errors, such as bad password, have not found a way to tell if
a connection is using LDAP or postgresql internal authentication in the
logs. Tried going through different log variables and setting verbosity
to max and did not see any indication of LDAP connections.

Long term we plan to only allow remote connections through LDAP in
pg_hba.conf, but hoping to track down any connection that is not using
LDAP to have that converted in a controlled fashion vs flipping the
switch and seeing what breaks.

Postgres 9.3