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

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On 07/16/14 17:31, Nehal J Wani wrote:
>>>      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)

I wanted to reply to that but I was a bit busy and didn't manage to do
it soon enough.

We have wrappers for running a separate command with a env variable
virCommandAddEnv*... you can use easily for this.


> 
> 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?

No, please use the API mentioned above

> 
>> 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
> lease.

My concerns are whether this will work in the case you already used the
leases helper as the patch is adding a few fields to the stored format.

> 
> 
> Regards,
> Nehal J Wani
> 

Peter

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