Currently, when LDAP operations are issued, it's assumed that any errors will immediately be returned synchronously as a result of calling the operation's method on nsLDAPOperation (eg SimpleBind()).

However, it's a network operation, so there are lots of things that can go wrong after this point. But there is currently no way to notify the calling code that something has gone wrong.
This will become more acute as more of the LDAP work goes async (required for Bug 1576364, to get the secure LDAP working again).

I think the way forward is to add an onLDAPError() method to nsILDAPMessageListener.

I don't think there are too many places to change - a search for onLDAPInit shows the listeners. There'll likely be some extra work to propagate and handle errors in the address-book LDAP code too.

Fixed by work over in Bug 1659947:
https://hg.mozilla.org/comm-central/rev/44e81d98aeb6