samba - Apr 2016 - Error "Failed to setup SPNEGO negTokenInit request" after Samba update to 2:4.3.8+dfsg-0ubuntu0.14.04.2

Hi,


I am running an Ubuntu 14.04 server with Samba configured to use Quest
Authentication Services for user authentication with an Active Directory
infrastructure. After an Samba upgrade from version
2:4.1.6+dfsg-1ubuntu2.14.04.13 to 2:4.3.8+dfsg-0ubuntu0.14.04.2, I am
facing the problem that none of the configured Samba shares is
accessible anymore.

The log contains the following entry:

	[2016/04/19 07:38:44.807461,  0]
	../source3/auth/auth_domain.c:184(domain_client_validate)
	domain_client_validate: Domain password server not available.

After raising the debug level, I can see the following log entry:

	[2016/04/20 18:49:24.264752,  1]
	../auth/gensec/spnego.c:664(gensec_spnego_create_negTokenInit)
	Failed to setup SPNEGO negTokenInit request:
	NT_STATUS_INTERNAL_ERROR

When I try to access a share, the following entries are showing up:

	[2016/04/20 18:51:30.913637,  3]
	../source3/libsmb/cliconnect.c:2173(cli_session_setup_done_spnego)
	SPNEGO login failed: Logon failure

	[2016/04/20 18:51:30.913675,  0]
	../source3/auth/auth_domain.c:184(domain_client_validate)
	domain_client_validate: Domain password server not available.

	[2016/04/20 18:51:30.913687,  2]
	../source3/auth/auth.c:315(auth_check_ntlm_password)
	check_ntlm_password:  Authentication for user [redacted] -> [redacted]
	FAILED with error NT_STATUS_LOGON_FAILURE

	[2016/04/20 18:51:30.913702,  2]
	../auth/gensec/spnego.c:708(gensec_spnego_server_negTokenTarg)
	SPNEGO login failed: NT_STATUS_LOGON_FAILURE

	[2016/04/20 18:51:30.914170,  3]
	../source3/smbd/server_exit.c:252(exit_server_common)
	Server exit (NT_STATUS_CONNECTION_RESET)


I have no clue how to trace the problem down/how to fix this issue. Any
support is appreciated.


Kind regards,
René