[Samba] Certain systems can no longer access samba post upgrade to 4.3.9

[Jeremy Allison]

On Mon, Aug 29, 2016 at 11:41:53AM -0400, Jeff Hodge via samba wrote:
> During an ubuntu 14.04 update samba was updated from 4.1.6 to 4.3.9.  We
> had no problems with any windows system accessing the server prior to the
> upgrade to 4.3.9.  It seems to affect access to the entire samba server as
> no shares are able to be seen or accessed when trying to view \\servername
> or \\servname.domain.local
> 
> The "fix" seems to be to use the fully qualified name, but after a while
> that will stop working and you have to change to the short name and vice
> versa.  I am trying to correlate the times to see if there is a pattern,
> but no pattern has emerged yet.
> 
> What is odd is if the short name is failing and you change to fully
> qualified and the share comes up, you will then be able to use the short
> name to pull up the share after you have made the successful connection to
> the fully qualified name.
> 
> The one log entry that seems to identify systems with this issue is this,
> repeated over and over:
> 
> [2016/08/29 08:35:56.694436,  0]
> ../source3/param/loadparm.c:1460(canonicalize_servicename)
>   canonicalize_servicename: NULL source name!
> 
> [2016/08/29 08:35:57.694984,  0]
> ../source3/param/loadparm.c:1460(canonicalize_servicename)
>   canonicalize_servicename: NULL source name!
> 
> [2016/08/29 08:35:58.694495,  0]
> ../source3/param/loadparm.c:1460(canonicalize_servicename)
>   canonicalize_servicename: NULL source name!
> 
> The majority of our servers are not having any problems accessing the samba
> shares, but a few key high use systems are having this issue.
> 
> Has anyone seen this error and may have an idea what may be causing and
> possible system setting that may need to be changed/enabled in 4.3.9 to
> allow all systems to connect reliably?

Can you post your smb.conf, plus a debug level 10 log from one
of the machines having the problem ?