Another systemd-resolved problem in 17.04

[Karl Auer]

On Wed, 2017-06-21 at 18:07 -0400, Tom H wrote:
> Jun 21 09:54:38 t470 systemd-resolved[961]: Using DNS server
> > fe80::1e74:dff:fe9d:5b1c%3 for transaction 37661.
> resolved is querying the wrong server because "fe80::..." is an ipv6
> link-local address.

Maybe, but not necessarily. In small networks the local DNS server is
often on the same link. Of course, if it is not listening on all
addresses it may not respond when queried on that address. It's not
clear (to me, but I'm not that familiar with systemd messages) whether
that "REFUSED" is a DNS failure or a failure to reach the server. That
is, was it that the DNS server heard the query and refused to answer,
or was the connection refused?

You should be able to do this to find out:

   dig daisy.ubuntu.com @fe80::1e74:dff:fe9d:5b1c%3

This is what I get when I use my local nameserver's link local address,
actual address truncated:

kauer at kt:~$ dig +short daisy.ubuntu.com @fe80::xxxx%wlan0
162.213.33.133
162.213.33.164

If the nameserver is listening, but refusing to serve you, you'll get a
response with a REFUSED status. Don't use "+short" or you won't see it:

kauer at kt:~$ dig daisy.ubuntu.com @dns1.ethz.ch
[...]
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 33381
;; flags: qr rd ra; QUERY: 0, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
[...]

If the nameserver is not there or not listening on that address, you'll
get a timeout like this:

kauer at kt:~$ dig +short daisy.ubuntu.com @fe80::xxxx%wlan0
;; connection timed out; no servers could be reached

Regards, K.

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Karl Auer (kauer at biplane.com.au)
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