[Dnsmasq-discuss] Dealing with a unstable/slow upstream DNS

Joachim Berdal Haga jobh at simula.no
Fri Oct 4 12:23:27 BST 2013


On 4 October 2013 12:32, Simon Kelley <simon at thekelleys.org.uk> wrote:
> On 04/10/13 08:56, Joachim Berdal Haga wrote:

>> Is it possible to instruct dnsmasq to not forward AAAA requests
>> when the A record is deduced from /etc/hosts (or vice versa)?
>
> No, but you're not the first person to ask for this feature. I've been
> hesitant to add it because it introduces a form of pollution into the DNS
> that will make deploying IPv6 more difficult.


Indeed. One could argue that /etc/hosts already overrides upstream
DNS, so the pollution is already there. And it makes a certain sense
to let /etc/hosts be authoritative for a given host name. But the IPv6
transition is hard enough already. I certainly won't press for this.


>> Is it possible to instruct dnsmasq to refresh its
>> cache while replying immediately with the already cached record? Either
>> optimistically (when the entry will soon expire) or lazily (when the entry
>> has just expired).
>
> No again. I once saw a patch to dnsmasq that did this for a number of
> configured domains. You can't really do it for all domains, since it will
> make the cache grow without bound - one a domain is in you can't ever lose
> it again.

My thought was not to do this automatically, but only when the record
is requested by a client. If this request happens within a
configurable time window (say the last minute before expiry), the
record is refreshed asynchronously. This would at most double the
cache size (if every record is refreshed once but not used again
afterwards).

Regards,
Joachim.



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