[libvirt] Proposed: optionally enable dnsmasq logging

[Gene Czarcinski]

Note:  the solutions listed below will all work with dnsmasq-2.48.

Sometimes it is very difficult to determine what a dnsmasq problem is 
when it does not work as expected.  Dnsmasq has to options for logging: 
log-quiries and log-dhcp.  Either or both can be enabled. By default, 
neither is enabled.

1.  Add an option or options to libvirtd.conf which will enable the 
logging on all started dnsmasq processes.  While this is doable, it will 
also produce a great deal of syslog mesages if more than one dnsmasq 
process is running.

2.  Add an option to libvirtd.conf which will enable the solutions given 
below.  By default, it will not be enabled.

3.  Add dnsmasq parameter conf-dir= to specify a directory (under the 
same directory as the leases file) where the administrator/user can add 
a file which contains log-queries and/or log-dhcp.

4.  Add the dnsmasq parameter conf-file= to specify an additional 
configuration file.  This would be under the same directory as the 
leases file and have a name of something like: <network_name>.conf-2.  
If the file already existed, nothing would be done.  If the file did not 
exist, a zero-length file would be created.

Currently, I favor ether 4 or the combination of 4 and 2.

Note: dnsmasq would only read this secondary configuration file when it 
is started or restarted.

Comments?  Suggestions?  Whatever?

Gene