[Samba] Strange problem samba+winbind+AD - transport endpoint is not connected

[Nacho del Rey]

Hi there

Yesterday at job we had a poltergeist with radius + winbind & samba in a
linux box with authentication against an Active Directory (Windows 2012)

The AD is formed by 3 windows servers. The linux box has a connection
established against one of them thru port 445. Then this server downs and a
bunch of messages like the following are shown in /var/log/messages

May 19 16:40:59 pv4il0168 winbindd[18357]: cm_prepare_connection:
getpeername failed with: Transport endpoint is not connected

An execution of the following command

[PRO] [root@pv4il0168 samba]# wbinfo -t
checking the trust secret for domain XXXXXX via RPC calls failed
error code was NT_STATUS_DOMAIN_CONTROLLER_NOT_FOUND (0xc0000233)
failed to call wbcCheckTrustCredentials: WBC_ERR_AUTH_ERROR
Could not check secret

There was no way to reestablish connections against AD restarting samba &
winbind services.. no way

After 3 hours investigating with a 'debug level = 10' in samba, I tried do
a net cache flush and it worked

10 min later we can reproduce the problem (each time the server where samba
was connected went down, the problem appeared) and the solutions was the
same.

Finally we decide to do a net ads leave and net ads join and so far, the
system is working like a charm

The question is, does anyone know any problem/bug related to this strange
behaviour?

Connections, DNS, permissions, etc were fine. The linux box have been
working properly for months

Thanks in advance

Nacho.
------------------------------------------------------------------------------------------
Data:

[PRO] [root@pv4il0168 samba]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.4 (Santiago)

samba4-libs-4.0.0-55.el6.rc4.x86_64
samba-common-3.6.9-151.el6_4.1.x86_64
samba-3.6.9-151.el6_4.1.x86_64
samba-winbind-clients-3.6.9-151.el6_4.1.x86_64
samba-winbind-3.6.9-151.el6_4.1.x86_64

smb.conf

[global]

workgroup = XXXXXXX
server string = RADIUS
log file = /var/log/samba/log.%m
max log size = 50
security = ads
realm = XXXXXXX.NET
password server = ldapofi.yyyyyyy.net
idmap uid = 10000-20000
idmap gid = 10000-20000
load printers = no
cups options = raw
printcap name = /etc/printcap
printing = lprng

/etc/krb5.conf

[realms]
XXXXXX.NET = {
kdc = pv4iw0001.xxxxxx.net
kdc = pv4iw0002.xxxxxx.net
admin_server = pv4iw0001.xxxxxx.net
admin_server = pv4iw0002.xxxxxx.net
default_domain = xxxxxx.net


debug

[2015/05/19 12:59:25.021104, 10] libsmb/namequery.c:89(saf_store)
saf_store: domain = [XXXXX], server = [PV4IW0001.XXXXX.net], expire =
[1432034065]
[2015/05/19 12:59:25.021127, 10]
lib/gencache.c:183(gencache_set_data_blob) Adding cache entry with key =
SAF/DOMAIN/XXXXX and timeout = Tue May 19 13:14:25 2015 (900 seconds
ahead)
[2015/05/19 12:59:25.021164, 10] libsmb/namequery.c:89(saf_store)
saf_store: domain = [XXXXX.NET], server = [PV4IW0001.XXXXX.net], expire =
[1432034065]
[2015/05/19 12:59:25.021186, 10]
lib/gencache.c:183(gencache_set_data_blob) Adding cache entry with key =
SAF/DOMAIN/XXXXX.NET and timeout = Tue May 19 13:14:25 2015 (900 seconds
ahead)
[2015/05/19 12:59:25.021237, 10]
winbindd/winbindd_cm.c:802(cm_prepare_connection) cm_prepare_connection:
connecting to DC PV4IW0001.XXXXX.net for domain XXXXX [2015/05/19
12:59:25.021289, 0] winbindd/winbindd_cm.c:835(cm_prepare_connection)
cm_prepare_connection: getpeername failed with: Transport endpoint is not
connected
[2015/05/19 12:59:25.021549, 10]
lib/gencache.c:183(gencache_set_data_blob) Adding cache entry with key =
NEG_CONN_CACHE/XXXXX,PV4IW0001.XXXXX.net and timeout = Tue May 19 12:59:55
2015 (30 seconds ahead)
[2015/05/19 12:59:25.021591, 9]
libsmb/conncache.c:189(add_failed_connection_entry)
add_failed_connection_entry: added domain XXXXX (PV4IW0001.XXXXX.net) to
failed conn cache
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