On 09/13/2013 09:29 AM, Petr Spacek wrote:
Hello list,

Jan Pazdziora <jpazdzi...@redhat.com> proposed that 'ipa dns*' commands should do some sanity checking/waiting after the record is added to LDAP.

I think that it could be valuable and I would like to get opinions from freeipa-devel list.


+1!

=== The problem ===
ipa dnsrecord-add and similar commands add the data to LDAP, but it doesn't mean that the data are *immediately* resolvable via DNS protocol. Note that data from LDAP are *asynchronously* read and processed by Named and the time when records are available is not predictable.

A mismatch between LDAP can be caused by some connection problem between DNS and LDAP servers, LDAP or DNS server restart, or simply by a bug in DNS<->LDAP synchronization code. (This is becomming more and more important if we consider the whole DNSSEC effort and related re-factoring.)

My experience is that users are very confused if the ipa dnsrecord-add command says 'record added' but it is still not available via DNS. It is really hard to debug when you see the problem first 10 times :-)


=== The proposal ===
1. Let FreeIPA framework to change DNS data in LDAP as we do now.
2. After each change, do DNS queries for changed record and wait until the new data are available.

IMHO it is very cheap operation (in usual cases 1 DNS packet back and forth) and it would save a lot of headaches to users and support.

We should make sure that we do not wait indefinitely here in case there's something else wrong with the named.

We could wait for DNS data to be made available up to small reasonable timeout. If the check succeeds, we can output "Verified: Yes" along with the usual ipa dns(whatever) command output. Otherwise, we could print out "Verified: No"

$ ipa dnszone-add $AD_DOMAIN --name-server=advm.$AD_DOMAIN --admin-email="hostmaster@$AD_DOMAIN.com" --force --forwarder=$AD_IP --forward-policy=only --ip-address=$AD_IP

  Zone name: tbad.ipa.com
  Authoritative nameserver: advm.tbad.ipa.com
  Administrator e-mail address: hostmaster.tbad.ipa.com.com.
  SOA serial: 1378285614
  SOA refresh: 3600
  SOA retry: 900
  SOA expire: 1209600
  SOA minimum: 3600
BIND update policy: grant DOM007.TBAD.IPA.COM krb5-self * A; grant DOM007.TBAD.IPA.COM krb5-self * AAAA; grant
                      DOM007.TBAD.IPA.COM krb5-self * SSHFP;
  Active zone: TRUE
  Dynamic update: FALSE
  Allow query: any;
  Allow transfer: none;
  Zone forwarders: 192.168.122.20
  Forward policy: only
  Verified: Yes

However, it would be nice to print out "Verified: No" in a somewhat emphasized manner. I created the following ticket:

https://fedorahosted.org/freeipa/ticket/3930


This will naturally catch the case where named crashes after the change etc.


=== Expected outcome ===
There will not be any failure like this:


We debugged this with Petr few days ago as part of CI testing for trusts, I'll just provide detailed explanation here:

$ ipa-adtrust-install

Ipa-adtrust-install restarts Directory Server as one of the installation steps. Named looses connection to the LDAP server and
by default reconnects in 60 seconds.


$ ipa dnszone-add $AD_DOMAIN --name-server=advm.$AD_DOMAIN --admin-email="hostmaster@$AD_DOMAIN.com" --force --forwarder=$AD_IP --forward-policy=only --ip-address=$AD_IP
      Zone name: dom123.example.com
      [...]


Ipa dnszone-add writes to LDAP and reports success.

$ ipa trust-add --type=ad DOM123.EXAMPLE.COM --admin Administrator --password
    Password for ad...@dom123.example.com:
    ipa: ERROR: Cannot find specified domain or server name


Named is unable to find the domain, since the connection is down.


--
Tomas Babej
Associate Software Engeneer | Red Hat | Identity Management
RHCE | Brno Site | IRC: tbabej | freeipa.org

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