[Dnsmasq-discuss] prevent dnsmasq from releasing IPs

Simon Kelley simon at thekelleys.org.uk
Tue Jan 26 21:37:58 GMT 2016


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On 26/01/16 16:03, Neil Jerram wrote:
> On 26/01/16 15:09, Stefan Priebe - Profihost AG wrote:
>>> Am 26.01.2016 um 14:46 schrieb Simon Kelley
>>> <simon at thekelleys.org.uk>:
>>> 
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>>> 
>>> 
>>> 
>>>> On 26/01/16 13:42, Stefan Priebe - Profihost AG wrote: what
>>>> about writing and sending kill 1 / HUP?
>>> 
>>> No. The only only way to make that work would be to
>>> 
>>> 1) Stop dnsmasq with SIGTERM 2) modify the leases file 3)
>>> restart dnsmasq
>>> 
>>> 
>>> in that
>> Last idea isn't it possible to make the host static on add? If it
>> is which file should I use to add the mac  hostname IP
>> combination
> 
> FYI, at https://github.com/projectcalico/calico/issues/233 we have
> a long trail about what we think is the opposite problem.  Namely,
> that Dnsmasq will not reallocate an IP that should have been
> released, and whose old IP/MAC mapping has been removed from the
> 'host' config file. As you'll see if you read that trail, we
> thought this was caused by a problem in the delivery of the
> DHCP_RELEASE message to Dnsmasq, and hence Dnsmasq retaining a
> record of the old lease in its internal data.
> 
> Based on that, I'd expect that if you deliberately did something to
> stop the DHCP_RELEASE message from reaching Dnsmasq, Dnsmasq would
> then retain the old lease (which I believe is what you're asking
> for).

That's certainly true.
> 
> However, that understanding does seem to be contradicted by what
> Simon has said in this thread, and I would strongly assume that
> Simon is right - but perhaps there might still be some hint or
> useful information in that issue trail.
> 


I looks like the problem there is exactly as you say: dnsmasq is
failing to allocate an address because it has run out of free
addresses because addresses have been consumed by machine which are
now "dead" but did not release their address when they died, so the
address is unavailable until the lease period expires.


Cheers,

Simon.

> Regards, Neil
> 
> 
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