[libvirt] dnsmasq-248 (CentOS/RHEL) compatibility

Gene Czarcinski gene at czarc.net
Fri Nov 2 13:50:30 UTC 2012

On 11/02/2012 09:22 AM, Daniel P. Berrange wrote:
> On Fri, Nov 02, 2012 at 08:57:04AM -0400, Gene Czarcinski wrote:
>> There are currently three significant libvirt patches I am involved with:
>> 1. Change so that dnsmasq parameters are in a conf file instead of
>> on the command line.
>> 2. A small patch to add dnsmasq parameter interface=
>> 3. A significant patch to add DHCPv6 support to libvirt.
>> A concern has been raised about the compatibility of my patches with
>> dnsmasq-2.48 which is the version on CentOS 6 and RHEL 6.  While
>> something like libvirt-1.0.0 is not officially supported, there is a
>> strong desire not to get in the way of individuals back-porting it.
>> Plan A:  Install CentOS 6.3 into a virtual guest.  Apparently, the
>> current virt-manager has some problems running CentOS 6.3.  Since I
>> was here to drain a swap, I decided not to go after this alligator.
>> Plan B:  Get a the src.rpm for dnsmasq-2.48 from CentOS and build it
>> on Fedora 17.  Then, using a Fedora 17  virtual guest, downgrade
>> install dnsmasq-2.48 on it.
>> I then took four of my virtual dnsmasq conf-files than I use,
>> slightly modify them to use interface=eth2 and common pid,
>> hostsfile, addnhosts, and leases files.  I then fed each of these
>> configuration files to dnsmasq-2.48.  Everything worked except for
>> the one which had an IPv6 dhcp-range specified.  That was not
>> surprising dnsmasq-2.48 only supports IPv6 for dns.
>> If someone has some additional tests they would like run, please say so.
>> My recommendation:  Incorporate my patches [when I finish the DHCPv6
>> one and resubmit the others].  Add (somewhere?) a warning to
>> backporters that they will need to update their dnsmasq packages to
>> actually do DHCPv6 but otherwise, earlier versions such as
>> dnsmasq-2.48 will be compatible.
> If it is merely a case that RHEL-6 users won't be able to take
> advantage of new IPv6 related features, then this is fine for
> us. When we talk about compatibility all we're worried about
> is existing users loosing existing features.  If they want
> new features, it is perfectly reasonable to require them to
> upgrade
A position I agree with 100%.

As a matter of fact, you need dnsmasq-2.64 or dnsmasq-2.63 with a couple 
small patches to use DHCPv6 at all.  Without these patches, it just does 
not work.


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