CIFS authentication failure when mounting DFS shares

Issue

• Error message "Permission denied" is returned when attempting to mount a DFS share from a Windows Active Directory domain:

# mount --verbose -t cifs //my_domain.com/DFS_root/dirA/dirB/dirC /mnt/my_mountpoint -o user=my_username,domain=MYDOMAIN,sec=ntlmi  
Password:  

 mount.cifs kernel mount options: unc=//my_domain.comDFS_root,ip=1.2.3.4,ver=1,rw,user=my_username,domain=MYDOMAIN,sec=ntlmi,prefixpath=dirA/dirB/dirC,pass=********  
 mount error 13 = Permission denied  
 Refer to the mount.cifs(8) manual page (e.g.man mount.cifs)

• The CIFS kernel module complains about unexpected SMB signatures:

 Nov  7 13:54:32 <kern.err> my_hostname kernel:  CIFS VFS: Unexpected SMB signature  
 Nov  7 13:54:32 <kern.notice> my_hostname kernel: Status code returned 0xc000006d NT_STATUS_LOGON_FAILURE  
 Nov  7 13:54:32 <kern.err> my_hostname kernel:  CIFS VFS: Send error in SessSetup = -13  
 Nov  7 13:54:32 <kern.err> my_hostname kernel:  CIFS VFS: cifs_mount failed w/return code = -13