Strange DLZ issues

[Lars Hanke]

Following the last Debian Jessie update, my Samba attached bind ceased 
working. Since there was no Samba update, the DLZ libs were unchanged, 
as was the configuration.

I'm now running BIND 9.9.5-7-Debian, which imports zones from a Samba4 
installation. Actually, Samba is expected to only serve the forward 
zones, i.e. if I check the Samba AD, there are no reverse zones defined. 
But this is what I see when starting bind:

Dec 29 10:43:07 verdandi named[2763]: built with '--prefix=/usr' 
'--mandir=/usr/share/man' '--infodir=/usr/share/info' 
'--sysconfdir=/etc/bind' '--localstatedir=/var' '--enable-threads' 
'--enable-largefile' '--with-libtool' '--enable-shared' 
'--enable-static' '--with-openssl=/usr' '--with-gssapi=/usr' 
'--with-gnu-ld' '--with-geoip=/usr' '--with-atf=no' '--enable-ipv6' 
'--enable-rrl' '--enable-filter-aaaa' 'CFLAGS=-fno-strict-aliasing 
-fno-delete-null-pointer-checks -DDIG_SIGCHASE -O2'
Dec 29 10:43:07 verdandi named[2763]: 
----------------------------------------------------
Dec 29 10:43:07 verdandi named[2763]: BIND 9 is maintained by Internet 
Systems Consortium,
Dec 29 10:43:07 verdandi named[2763]: Inc. (ISC), a non-profit 501(c)(3) 
public-benefit
Dec 29 10:43:07 verdandi named[2763]: corporation.  Support and training 
for BIND 9 are
Dec 29 10:43:07 verdandi named[2763]: available at 
https://www.isc.org/support
Dec 29 10:43:07 verdandi named[2763]: 
----------------------------------------------------
Dec 29 10:43:07 verdandi named[2763]: adjusted limit on open files from 
4096 to 1048576
Dec 29 10:43:07 verdandi named[2763]: found 4 CPUs, using 4 worker threads
Dec 29 10:43:07 verdandi named[2763]: using 4 UDP listeners per interface
Dec 29 10:43:07 verdandi named[2763]: using up to 4096 sockets
Dec 29 10:43:07 verdandi named[2763]: loading configuration from 
'/etc/bind/named.conf'
Dec 29 10:43:07 verdandi named[2763]: reading built-in trusted keys from 
file '/etc/bind/bind.keys'
Dec 29 10:43:07 verdandi named[2763]: using default UDP/IPv4 port range: 
[1024, 65535]
Dec 29 10:43:07 verdandi named[2763]: using default UDP/IPv6 port range: 
[1024, 65535]
Dec 29 10:43:07 verdandi named[2763]: no IPv6 interfaces found
Dec 29 10:43:07 verdandi named[2763]: listening on IPv4 interface lo, 
127.0.0.1#53
Dec 29 10:43:07 verdandi named[2763]: listening on IPv4 interface eth0, 
172.16.10.17#53
Dec 29 10:43:07 verdandi named[2763]: generating session key for dynamic DNS
Dec 29 10:43:07 verdandi named[2763]: sizing zone task pool based on 22 
zones
Dec 29 10:43:07 verdandi named[2763]: Loading 'AD Zones' using driver dlopen
Dec 29 10:43:07 verdandi named[2763]: samba_dlz: started for DN 
DC=ad,DC=microsult,DC=de
Dec 29 10:43:07 verdandi named[2763]: samba_dlz: starting configure
Dec 29 10:43:07 verdandi named[2763]: zone 10.16.172.in-addr.arpa/NONE: 
has 0 SOA records
Dec 29 10:43:07 verdandi named[2763]: zone 10.16.172.in-addr.arpa/NONE: 
has no NS records
Dec 29 10:43:07 verdandi named[2763]: samba_dlz: Failed to configure 
zone '10.16.172.in-addr.arpa.'
Dec 29 10:43:07 verdandi named[2763]: loading configuration: bad zone
Dec 29 10:43:07 verdandi named[2763]: exiting (due to fatal error)
Dec 29 10:43:07 verdandi named[2763]: samba_dlz: shutting down

Okay, the reverse zone does not exist, but I could create it in Samba, 
which changes the game slightly:

Dec 29 10:31:12 verdandi named[2601]: samba_dlz: started for DN 
DC=ad,DC=microsult,DC=de
Dec 29 10:31:12 verdandi named[2601]: samba_dlz: starting configure
Dec 29 10:31:12 verdandi named[2601]: samba_dlz: configured writeable 
zone '10.16.172.in-addr.arpa.'
Dec 29 10:31:12 verdandi named[2601]: zone 1.16.172.in-addr.arpa/NONE: 
has 0 SOA records
Dec 29 10:31:12 verdandi named[2601]: zone 1.16.172.in-addr.arpa/NONE: 
has no NS records
Dec 29 10:31:12 verdandi named[2601]: samba_dlz: Failed to configure 
zone '1.16.172.in-addr.arpa.'
Dec 29 10:31:12 verdandi named[2601]: loading configuration: bad zone

Okay, another reverse zone. Let's iterate successful steps:

Dec 29 10:29:20 verdandi named[2522]: samba_dlz: started for DN 
DC=ad,DC=microsult,DC=de
Dec 29 10:29:20 verdandi named[2522]: samba_dlz: starting configure
Dec 29 10:29:20 verdandi named[2522]: samba_dlz: configured writeable 
zone '10.16.172.in-addr.arpa.'
Dec 29 10:29:20 verdandi named[2522]: samba_dlz: configured writeable 
zone '1.16.172.in-addr.arpa.'
Dec 29 10:29:20 verdandi named[2522]: samba_dlz: Failed to configure 
zone '10.16.172.in-addr.arpa'
Dec 29 10:29:20 verdandi named[2522]: loading configuration: already exists

Ooops! It fails on the zone added first! And what does it want to tell 
me by "already exists"?

Any ideas how to troubleshoot the issue?

Thanks for your help,
  - lars.