[Samba] Mac Clients Disconnect with: source3/smbd/service.c:1050(close_cnum) closed connection to service data

[Rowland penny]

On 18/10/2019 12:35, Louis Waweru via samba wrote:
> Hello,
>
> I have an issue where Macs running a wide range of OS versions all drop
> connections at seemingly random intervals, but usually after some long
> period of time less than 24 hours. The Windows clients keep their
> connections, however.
>
> I can test this in PowerShell with a loop like the following:
> PS C:\Users\louis> while($true) { Add-Content
> Z:\_smbcheck\windwows-client.txt $DT; Start-Sleep 10;  $DT = Get-Date; }
>
> This will run endlessly.
>
> Similar tests on different Mac clients, all connected to Ethernet on
> reliable network infrastructure will all fail within hours, and at
> different times:
> while sleep 10; do echo "Alive at: `date`" >>
> /Volumes/data/_smbcheck/macClientServerSigningOff; done
>
> while sleep 10; do echo "Alive at: `date`" >>
> /Volumes/data/_smbcheck/macClientServerSigningOn; done
>
> while sleep 10; do echo "Alive at: `date`" >>
> /Volumes/data/_smbcheck/macClientServerSMB2; done
>
> while sleep 10; do echo "Alive at: `date`" >>
> /Volumes/data/_smbcheck/macClientServerSMB3-Caffeinate; done
>
> etc...
>
> The Mac computers running these loops range from completely vanilla to
> having suggested tweaks found here and there.
>
> In the logs, the only indication of these events are the following:
>
> [2019/10/18 05:27:37.005650,  2] ../source3/smbd/service.c:1050(close_cnum)
>
> 10.11.12.13 (ipv4:10.11.23.13:57939) closed connection to service data
>
> The Mac clients don't all do this at the same time. It happens completely
> irregularly and not at fixed intervals.
>
> I've tried all the various possibilities in a Mac client's /etc/nsmb.conf
> to no avail:
>
> [default]
>
> protocol_vers_map=4
>
> signing_required=no
>
> I've set the most power aggressive energy settings, and even used caffeinate
> <https://github.com/newmarcel/KeepingYouAwake> to make sure the computer
> was always awake.
>
> I've tested a brand new NIC on the server, upgrading firmware on the
> server, building new versions of samba, reinstalling to Ubuntu 16.04 from
> 18.04 and upgrading to 18.10 and 19.04 hoping to find a version that didn't
> have the issue.
>
> How can I begin to diagnose this issue, assuming hardware is fine.
>
> In summary all hardware tests pass, and after testing with a new NIC, and
> the fact that Windows clients don't disconnect make me feel like it's a Mac
> issue, and there are countless threads on the Internet complaining about
> how Apple implemented SMB, but I'm hoping to learn what these log messages
> mean:
>
> [TimeStamp,  2] ../source3/smbd/service.c:1050(close_cnum)
>
> 10.11.12.13 (ipv4:10.11.23.13:57939) closed connection to service data
>
>
> Are they initiated on the client or server side?
>
>
> I am digging for a configuration fix, because there are actually a dozen
> other servers set up with the same provisioning protocol that don't have
> the issue.
>
>
> Example: smb.conf file:
>
> [global]
>
> workgroup = DEPT
>
> security = ads
>
> realm = DEPT.EXAMPLE.COM
>
> ;idmap backend = tdb
>
> ;idmap uid = 20000-299999
>
> ;idmap gid = 20000-299999
>
> idmap config DEPT:backend = rid
>
> idmap config DEPT:range = 10000-199999
>
> winbind enum users = yes
>
> winbind enum groups = yes
>
> winbind use default domain = yes
>
> winbind nested groups = yes
>
> winbind refresh tickets = yes
>
> winbind offline logon = true
>
> winbind expand groups = 1
>
> template homedir = /home/%U
>
> template shell = /bin/bash
>
> client use spnego = yes
>
> client ntlmv2 auth = yes
>
> log file = /var/log/samba/samba.log
>
> log level = 2
>
> ;obey pam restrictions = yes
>
> min protocol = SMB2
>
> client min protocol = SMB2
>
> inherit permissions = yes
>
> client ipc signing = auto
>
> ;wins support = yes
>
>
> [homes]
>
> available = yes
>
> comment = Home directories
>
> read only = No
>
> browseable = No
>
>
> [data]
>
> available = yes
>
> comment = Main data store for all users
>
> path = /data
>
> valid users = +DEPT\groupxusers
>
> force group = +DEPT\groupxusers
>
> writable = yes
>
> read only = no
>
>
> Comments in the above show things I have tried enabling and disabling.
>
> Higher log levels don't indicate anything before, between, or after:
>
> ../source3/smbd/service.c:1050(close_cnum)
>
> 10.11.12.13 (ipv4:10.11.23.13:57939) closed connection to service data
>
> Many thanks,
> Louis
>
The only problem with your smb.conf is that you haven't set up the 
'idmap config lines for the '*' domain, I would add:

idmap config * : backend = tdb

idmap config * : range = 3000-7999

I do not think this is your problem, I am fairly sure that Samba is only 
printing that debug message because you have 'log level = 2' in smb.conf 
and your Mac clients are closing the connections.

Rowland