[Dnsmasq-discuss] What if external DNS unreachable or timed out

[Nikolay P]

Thank you.

Well it looks like dnsmasq does not cache. When I send SIGUSR1 to dnsmasq (with log-queries option enabled) it returns list of cache which consists of one entry - 127.0.0.1 (flags 4FRI H). This is despite the fact that I performed dozen of queries just before.

Log file looks like:

query[A] host.domain from 127.0.0.1
forwarded host.domain to 10.0.0.1
reply host.domain is 10.0.10.10
query[A] host.domain from 127.0.0.1
forwarded host.domain to 10.0.0.1
reply host.domain is 10.0.10.10
query[A] host.domain from 127.0.0.1
forwarded host.domain to 10.0.0.1
reply host.domain is 10.0.10.10

10.0.0.1 is my internal DNS server (it is authoritative for domain "domain")

Is there known list of issues which can force dnsmasq not to cache replies? Otherwise I have no idea where to dig.


----- Original Message -----
From: "/dev/rob0" <rob0 at gmx.co.uk>
To: dnsmasq-discuss at lists.thekelleys.org.uk
Sent: Thursday, February 12, 2015 10:13:40 PM GMT -05:00 US/Canada Eastern
Subject: Re: [Dnsmasq-discuss] What if external DNS unreachable or timed out

On Thu, Feb 12, 2015 at 08:43:20PM -0500, Nikolay P wrote:
> I am wondering what will happen if none of the external DNS servers 
> are reachable or suddenly (for any reason) a DNS query to external 
> servers timed out. Will Dnsmasq reply to the client's request from 
> cache? Assume that this particular query is performed frequently 
> and it should be in Dnsmasq cache.

If the record is cached, dnsmasq is not going to ask an upstream 
nameserver.  If a query is made to an upstream nameserver, that means 
the record is NOT in the cache.

Then if the upstream query times out or otherwise fails, that's what 
dnsmasq will tell the client.

> So, will the Dnsmasq reply to the client's request from cache if 
> none of the external servers replied?

No, it wasn't cached.
-- 
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