[Samba] Duplicate PDC SRV records in DNS and can't delete the wrong one with samba-tool

[Rowland Penny]

On 13/03/2023 20:58, Norbert Hanke via samba wrote:
> Hi,
> 
> I transferred FSMO roles from my DC2 to my DC1, and that looks ok from
> samba-tool point of view:
> 
> # samba-tool fsmo show
> ldb_wrap open of secrets.ldb
> SchemaMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> InfrastructureMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> RidAllocationMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> PdcEmulationMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> DomainNamingMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> DomainDnsZonesMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> ForestDnsZonesMasterRole owner: CN=NTDS
> Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=ad,DC=mydomain,DC=tld
> 
> 
> But in DNS I now have 2 SRV entries for the PDC role:
> 
> # host -t SRV _ldap._tcp.pdc._msdcs.ad.mydomain.tld dc1.ad.mydomain.tld
> Using domain server:
> Name: dc1.ad.mydomain.tld
> Address: 10.88.1.8#53
> Aliases:
> 
> _ldap._tcp.pdc._msdcs.ad.mydomain.tld has SRV record 0 100 389
> dc2.ad.mydomain.tld.
> _ldap._tcp.pdc._msdcs.ad.mydomain.tld has SRV record 0 100 389
> dc1.ad.mydomain.tld.
> 
> 
> samba-tool also sees 2 records:
> 
> # samba-tool dns query dc1.ad.mydomain.tld _msdcs.ad.mydomain.tld
> _tcp.pdc SRV
> Using binding ncacn_ip_tcp:dc1.ad.mydomain.tld[,sign]
> resolve_lmhosts: Attempting lmhosts lookup for name
> dc1.ad.mydomain.tld<0x20>
> resolve_lmhosts: Attempting lmhosts lookup for name
> dc1.ad.mydomain.tld<0x20>
>    Name=, Records=0, Children=0
>    Name=_ldap, Records=2, Children=0
>      SRV: dc2.ad.mydomain.tld. (389, 0, 100) (flags=f0, serial=458, 
> ttl=900)
>      SRV: dc1.ad.mydomain.tld. (389, 0, 100) (flags=f0, serial=458, 
> ttl=900)
> 
> 
> That is wrong: the record with dc2 should not exist and I would expect
> it gets deleted and the one with dc1 created while transferring the fsmo
> role.

You can expect has much as you like, but there is no code to remove the 
dns record. ;-)

> 
> I tried to manually delete the wrong record but that does not work:
> 
> # samba-tool dns delete dc1.ad.mydomain.tld _msdcs.ad.mydomain.tld
> _tcp.pdc SRV 'dc2.ad.mydomain.tld 389 0 100'

Wrong name, it is _ldap._tcp.pdc

> Using binding ncacn_ip_tcp:dc1.ad.mydomain.tld[,sign]
> resolve_lmhosts: Attempting lmhosts lookup for name
> dc1.ad.mydomain.tld<0x20>
> resolve_lmhosts: Attempting lmhosts lookup for name
> dc1.ad.mydomain.tld<0x20>
> ERROR: Record does not exist; record could not be deleted.
> zone[_msdcs.ad.mydomain.tld] name[_tcp.pdc]
>    File "/usr/lib/python3/dist-packages/samba/netcmd/dns.py", line 1223,
> in run
> dns_conn.DnssrvUpdateRecord2(dnsserver.DNS_CLIENT_VERSION_LONGHORN,
> 
> Is this a bug, or am I doing something wrong? Any help is appreciated.

Yes, it s a bug (a known bug). No, you are not doing anything wrong 
(other than using the wrong name when trying to delete the incorrect 
record).

Rowland