[libvirt] [PATCH] leaseshelper: add enhancements to support all events

Nehal J Wani nehaljw.kkd1 at gmail.com
Wed Jul 16 15:31:13 UTC 2014

>>      cmd = virCommandNew(dnsmasqCapsGetBinaryPath(caps));
>>      virCommandAddArgFormat(cmd, "--conf-file=%s", configfile);
>> -    virCommandAddArgFormat(cmd, "--dhcp-script=%s", leaseshelper_path);
>> +    virCommandAddArgFormat(cmd, "--dhcp-script=%s", pseudo_leaseshelper_path);
>> +    virCommandAddArgFormat(cmd, "--leasefile-ro");
> Does dnsmasq pass through the rest of the environment we pass to it at
> this point? The leaseshelper extracts quite a lot of stuff from the
> environment variables that are passed by dnsmasq. In case it does we
> could use an env variable to pass the interface name instead of linking
> the helper and using different names.

If I use the following line of code in the function
networkBuildDhcpDaemonCommandLine ...
setenv("VIR_BRIDGE_NAME", network->def->bridge, 1);
.. then yes, the helper program invoked by dnsmasq does get to see
this variable. (It does so in Fedora20). (Looks like I acted in haste,
should've waited for more replies on RFC, sigh)

So, in the next version that I will send, should I first make a
wrapper by the name virSetEnvBlockSUID for setenv, just like we have
virGetEnvBlockSUID for getenv?

> A second issue that comes into my mind is compatibility with already
> existing files. Does this work when you already have a lease file? (I
> didn't try it, I'm just asking).

If we use the --leasefile-ro option, then although this method will
work, but no, the lease file will *not* be read/written at all. So
even if an old one exists, its of no use.
But then again, the use of --leasefile-ro is mandatory, so that all
events are captured by our helper program. For example, renew of a

Nehal J Wani

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