[libvirt] [PATCH] additional parameter needed for dnsmasq

[Gene Czarcinski]

On 08/21/2012 11:04 AM, Daniel P. Berrange wrote:
> On Tue, Aug 21, 2012 at 10:43:44AM -0400, Gene Czarcinski wrote:
>> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=849787
>>
>> As currently configured, dnsmasq for a virtual network will pass
>> some queries upstream toward the Internet.  This includes AAAA and
>> MX queries as well a A queries when dnsmasq cannot answer for that
>> name.  This is occurring whether a domain name is specified or not.
>> The problem is that dnsmasq will, by default, forward all queries
>> unless "local=" is specified.  I cannot envision a situation where
>> such queries should be forwarded.
>>
>> See the bugzilla report for more info.  While I did a lot of testing
>> to figure out the problem and what needed to be done to fix it, I am
>> unable to actually rebuild the libvirt rpm in my environment.
>>
>> The solution is the following patch:
>>
>> diff -uNr libvirt-0.9.11.4.orig/src/network/bridge_driver.c
>> libvirt-0.9.11.4/src/network/bridge_driver.c
>> --- libvirt-0.9.11.4.orig/src/network/bridge_driver.c    2012-06-15
>> 14:23:21.000000000 -0400
>> +++ libvirt-0.9.11.4/src/network/bridge_driver.c    2012-08-21
>> 09:03:17.387602485 -0400
>> @@ -491,7 +491,13 @@
>>       virCommandAddArgList(cmd, "--strict-order",
>> "--bind-interfaces", NULL);
>>
>>       if (network->def->domain)
>> -        virCommandAddArgList(cmd, "--domain", network->def->domain, NULL);
>> +//        virCommandAddArgList(cmd, "--domain",
>> network->def->domain, NULL);
>> +    virCommandAddArgFormat(cmd,
>> +                "--domain %s --local=/%s/",
>> +                network->def->domain,
>> +                network->def->domain);
>> +    else
>> +        virCommandAddArg(cmd, "--local=");
>>
>>       if (pidfile)
>>           virCommandAddArgPair(cmd, "--pid-file", pidfile);
>
> Since this changes the code that generates dnsmasq args, you'll
> also need to update the tests/networkxml2argvdata/ data files
> to take account of your new additions.
>
>
And here I thought it was just a tiny patch.  When I get thinks 
finalized, there will be an update to the tests also.

But, the patch itself is not good.  For example, for no domain 
specified, instead of "--local=", it should be "--local-//".  And then 
with the domain specified, this just does not work for some reason 
dnsmasq has errors starting.

I must say that I believe that whoever chose to use dnsmasq definitely 
made the right choice.  However, I wich it was easier to change and test 
new parameter seetings for dnsmasq rather than having it in the code.

So that I do not have to go through a lot of code changes, I am testing 
with two virtual guests.  The first has two NICs one connected to the 
default network and a second to a private network with dnsmasq (dns and 
dhcp) for the private network.  The second guest is on the private 
network and tests the various setups for dnsmasq.

My initial simplified test used the /etc/dnsmasq.conf and supplied some 
additional parameters that I had not realized.  My testing is not 
attempting to create a situation similar to that for libvirtd which has 
everything specified on the command-line.

Any comments, suggestions will be appreciated.

Gene