On 09/23/2014 06:00 PM, Petr Spacek wrote:
On 22.9.2014 14:09, Petr Viktorin wrote:
On 09/22/2014 01:48 PM, Petr Spacek wrote:
On 22.9.2014 10:38, Martin Kosek wrote:
On 09/22/2014 10:31 AM, Petr Spacek wrote:
On 22.9.2014 10:14, Martin Kosek wrote:
On 09/19/2014 07:29 PM, Petr Viktorin wrote:
https://fedorahosted.org/freeipa/ticket/4551

See ticket & commit message for details.

Shouldn't we add a 1 sec sleep between tries? Wouldn't current
version just
hammer DNS server with as many DNS queries as it can send?

Oh yes, please add some time.sleep() call :-)

Wow, no idea how that slipped out. Thanks for the catch.

Also I would like to see more detailed message:
+        self.log.info('Waiting for hostname %s to be resolvable',
+                      self.replica_fqdn)

=> 'Waiting for hostname %s to be resolvable to A or AAAA record'

<bikeshed>

Really? Shouldn't term "resolvable" already have that covered? A good
software
should work on all network types, whether it is IPv4, IPv6 or IPv8.
So I
personally do not think we need to be that specific and can stick to
original
proposal.

I will agree with you if you post magic code which will work with DNS
records for IPv8 :-) The code is not going to work with IPv8 just
because we didn't mention 'A/AAAA' in the error message, A and AAAA
RRtypes are hardcoded in the code.

+1; we're checking A and AAAA so that's what we should say we're doing.

Is this wording OK?
Little NACK. (However, the wording is fine.)

Tcpdump revealed this:

IP vm-117.test.34067 > vm-133.test.domain: 38467+ A? vm-092.test. (51)
IP vm-133.test.domain > vm-117.test.34067: 38467 NXDomain* 0/1/0 (116)
IP vm-117.test.36006 > vm-133.test.domain: 20194+ A?
vm-092.test.ipa.example. (63)
IP vm-133.test.domain > vm-117.test.36006: 20194 NXDomain* 0/1/0 (143)
IP vm-117.test.51333 > vm-133.test.domain: 34027+ AAAA? vm-092.test. (51)
IP vm-133.test.domain > vm-117.test.51333: 34027 NXDomain* 0/1/0 (116)
IP vm-117.test.60373 > vm-133.test.domain: 45679+ AAAA?
vm-092.test.ipa.example. (63)

You can see that the query for each A/AAAA type is repeated twice, the
second time with 'ipa.example.' suffix.

This is caused by search list processing (search directive in
/etc/resolv.conf) and is highly undesirable. (Read this [1] e-mail if
you want to hear it from Paul Vixie.)

The fix is simple: You have to be sure that self.replica_fqdn is
actually absolute FQDN - with the trailing period.

Naive solution would be to use
dns_answer = resolver.query(self.replica_fqdn + '.', 'A', 'IN')
but I don't know if self.replica_fqdn variable can contain trailing
period or not.

Mbasti can show you more advanced code snippets using 'dns.name'.

[1]
https://lists.dns-oarc.net/pipermail/dns-operations/2014-September/012157.html

Does this version look good?


--
Petr³
From 95cb012079bf6ad83498cf113bcb78a8bcd61a07 Mon Sep 17 00:00:00 2001
From: Petr Viktorin <pvikt...@redhat.com>
Date: Fri, 19 Sep 2014 15:57:44 +0200
Subject: [PATCH] ipa-replica-prepare: Wait for the DNS entry to be resolvable

It takes some time after the DNS record is added until it propagates
to Bind. In automated installations, it might happen that
replica-install is attempted before the hostname is resolvable;
in that case the connection check would fail.

Wait for the name to be resolvable at the end of replica-prepare.
Mention that this can be interrupted (Ctrl+C).
Provide an option to skip the wait.

In case DNS is not managed by IPA, this reminds the admin of the necessary
configuration and checks their work, but it's possible to skip (either by
interrupting it interactively, or by the option).

https://fedorahosted.org/freeipa/ticket/4551
---
 ipaserver/install/ipa_replica_prepare.py | 48 ++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/ipaserver/install/ipa_replica_prepare.py b/ipaserver/install/ipa_replica_prepare.py
index c1ced3dcbcf9b619285347efff31ced335f397ce..1a10eed94907c66ee9629bb99a3144365a9387df 100644
--- a/ipaserver/install/ipa_replica_prepare.py
+++ b/ipaserver/install/ipa_replica_prepare.py
@@ -21,9 +21,12 @@
 import os
 import shutil
 import tempfile
+import time
 from optparse import OptionGroup
 from ConfigParser import SafeConfigParser
 
+import dns.resolver
+
 from ipaserver.install import certs, installutils, bindinstance, dsinstance
 from ipaserver.install.replication import enable_replication_version_checking
 from ipaserver.plugins.ldap2 import ldap2
@@ -64,6 +67,9 @@ def add_options(cls, parser):
         parser.add_option("--ca", dest="ca_file", default=paths.CACERT_P12,
             metavar="FILE",
             help="location of CA PKCS#12 file, default /root/cacert.p12")
+        parser.add_option('--no-wait-for-dns', dest='wait_for_dns',
+            action='store_false', default=True,
+            help="do not wait until the replica is resolvable in DNS")
 
         group = OptionGroup(parser, "SSL certificate options",
             "Only used if the server was installed using custom SSL certificates")
@@ -290,6 +296,8 @@ def run(self):
         if options.ip_address:
             self.add_dns_records()
 
+        self.wait_for_dns()
+
     def copy_ds_certificate(self):
         options = self.options
 
@@ -454,6 +462,46 @@ def add_dns_records(self):
                 raise admintool.ScriptError(
                     "Could not add reverse DNS record for the replica: %s" % e)
 
+    def check_dns(self, replica_fqdn):
+        """Return true if the replica hostname is resolvable"""
+        resolver = dns.resolver.Resolver()
+        exceptions = dns.resolver.NXDOMAIN, dns.resolver.NoAnswer
+
+        try:
+            dns_answer = resolver.query(replica_fqdn, 'A', 'IN')
+        except exceptions:
+            try:
+                dns_answer = resolver.query(replica_fqdn, 'AAAA', 'IN')
+            except exceptions:
+                return False
+
+        return True
+
+    def wait_for_dns(self):
+        options = self.options
+
+        # Make sure replica_fqdn has a trailing dot, so the
+        # 'search' directive in /etc/resolv.conf doesn't apply
+        replica_fqdn = self.replica_fqdn
+        if not replica_fqdn.endswith('.'):
+            replica_fqdn += '.'
+
+        if not options.wait_for_dns or self.check_dns(replica_fqdn):
+            self.log.debug('%s A/AAAA record resolvable', replica_fqdn)
+            return
+
+        self.log.info('Waiting for %s A or AAAA record to be resolvable',
+                      replica_fqdn)
+        print 'This can be safely interrupted (Ctrl+C)'
+
+        try:
+            while not self.check_dns(replica_fqdn):
+                time.sleep(1)
+        except KeyboardInterrupt:
+            self.log.info('Interrupted')
+        else:
+            self.log.debug('%s A/AAAA record resolvable', replica_fqdn)
+
     def copy_info_file(self, source, dest):
         """Copy a file into the info directory
 
-- 
1.9.3

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