Discussion:
[Dnsmasq-discuss] localdomain non-responsive without edns on ubuntu 14.04
Justin Karneges
2016-02-12 17:44:15 UTC
Permalink
Hi list,

I noticed a weird issue on Ubuntu 14.04, which installs dnsmasq 2.68. If I
try to look up an A record for a non-existent host within the "localdomain"
domain without edns, the server is unresponsive.

In other words, these commands all get a response from 127.0.0.1 in some
way (NXDOMAIN or empty) :

dig nosuchhost.localdomain
dig nosuchhost.foo
dig nosuchhost
dig nosuchhost.foo +noedns
dig nosuchhost +noedns

whereas, this command hangs:

dig nosuchhost.localdomain +noedns

; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> nosuchhost.localdomain +noedns
;; global options: +cmd
;; connection timed out; no servers could be reached

This issue does not appear to be present in Ubuntu 15.10, which uses
dnsmasq 2.75.

Was this a bug in dnsmasq that was fixed? Or a configuration difference
between the two OS versions?

Thanks,
Justin
Simon Kelley
2016-02-13 17:12:49 UTC
Permalink
I'm running 14.04 and just tried that experiment. I can't see any
difference in behaviour. In each case the query gets passed on to the
upstream nameserver, so I guess that the effect might originate there.




Cheers,

Simon
Post by Justin Karneges
Hi list,
I noticed a weird issue on Ubuntu 14.04, which installs dnsmasq 2.68. If I
try to look up an A record for a non-existent host within the "localdomain"
domain without edns, the server is unresponsive.
In other words, these commands all get a response from 127.0.0.1 in some
dig nosuchhost.localdomain
dig nosuchhost.foo
dig nosuchhost
dig nosuchhost.foo +noedns
dig nosuchhost +noedns
dig nosuchhost.localdomain +noedns
; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> nosuchhost.localdomain +noedns
;; global options: +cmd
;; connection timed out; no servers could be reached
This issue does not appear to be present in Ubuntu 15.10, which uses
dnsmasq 2.75.
Was this a bug in dnsmasq that was fixed? Or a configuration difference
between the two OS versions?
Thanks,
Justin
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Justin Karneges
2016-02-14 00:52:26 UTC
Permalink
Thanks for your reply, Simon.

I'm using tcpdump to monitor src/dest port 53. I can see a request packet
being sent to 127.0.0.1:53 and then another sent to 127.0.1.1:53 which
doesn't respond. It turns out there are two dnsmasq services running, and
the first is forwarding to the second. However, I don't see any traffic
after this, which suggests that the second dnsmasq (the one listening on
127.0.1.1) isn't forwarding the request to whatever upstream nameserver is
behind it. So I think this is a dnsmasq issue?
Post by Simon Kelley
I'm running 14.04 and just tried that experiment. I can't see any
difference in behaviour. In each case the query gets passed on to the
upstream nameserver, so I guess that the effect might originate there.
Cheers,
Simon
Post by Justin Karneges
Hi list,
I noticed a weird issue on Ubuntu 14.04, which installs dnsmasq 2.68. If
I
Post by Justin Karneges
try to look up an A record for a non-existent host within the
"localdomain"
Post by Justin Karneges
domain without edns, the server is unresponsive.
In other words, these commands all get a response from 127.0.0.1 in some
dig nosuchhost.localdomain
dig nosuchhost.foo
dig nosuchhost
dig nosuchhost.foo +noedns
dig nosuchhost +noedns
dig nosuchhost.localdomain +noedns
; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> nosuchhost.localdomain +noedns
;; global options: +cmd
;; connection timed out; no servers could be reached
This issue does not appear to be present in Ubuntu 15.10, which uses
dnsmasq 2.75.
Was this a bug in dnsmasq that was fixed? Or a configuration difference
between the two OS versions?
Thanks,
Justin
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